Severe corneal ulcerations, causing major keratolysis with large perforation of the cornea or extending to the limbal region, are an ophthalmic emergency. In these cases, a larger corneoscleral graft can be transplanted to restore tectonic integrity, alleviate pain, save vision, and prevent loss of the eye. Chart review of 34 patients with a corneoscleral graft ≥9.5 mm was conducted. Primary endpoints of the study were tectonic stability defined as no need for another keratoplasty or enucleation. In addition, visual acuity, postoperative complications, and secondary procedures were analyzed. In total, 12 patients (35%) were female. The mean age at transplantation was 65 ± 19 years. The underlying disease was a perforated infectious corneal ulcer in 30 cases (88%). Mean follow up was 675 ± 789 days. Tectonic stability at the end of the follow-up was maintained with a probability of 56% in a Kaplan–Meier analysis. Another penetrating keratoplasty was necessary in six cases (17%) and enucleation in five cases (15%). A corneoscleral transplant remains a viable treatment option to prevent enucleation in severe keratolysis. In our study, this was possible in about half of the cases. Postoperative complications, secondary surgeries, and markedly reduced visual acuity put the advantages into perspective. Severe corneal ulcers, especially in the setting of microbial keratitis, that cause extensive keratolysis with perforation of more than a portion of the cornea or extending to or beyond the limbus, are ophthalmic emergencies . In thesEven if the eye would otherwise have been lost, larger grafts carry a high potential for complications . In addiAlthough corneoscleral transplantation is a rare procedure and has known disadvantages, it can rescue end-stage ocular disease in some patients and is used for this purpose . In the This is a retrospective, longitudinal single-center study of 34 patients who received a corneoscleral grafts of ≥9.5 mm for perforated corneal ulcers at the Department of Ophthalmology between 1 January 2010 and 9 January 2022. This retrospective analysis was approved by the ethics committee of the University of Ulm  and adhered to the tenets of the Declaration of Helsinki. Data were extracted from charts. Thirty-four patients were identified with perforated corneal ulcers so severe and extensive that only a corneoscleral graft ≥ 9.5 mm could salvage the eye. Graft size ranged from 9.5 to 14 mm with a mean size of 11.6 ± 1.4 mm. Of these patients, 12 (35%) were female. The mean age at transplantation was 65 ± 19 years. The underlying disease was infectious in 30 cases (88%). One case was Acanthamoeba (3%), three cases were fungal (9%), and five cases were herpes simplex (15%). Five non-infectious causes (15%) included chemical burns, exposure keratopathy, and neurotrophic keratopathy. The mean graft size was 10.8 ± 1.2 mm.Written informed consent was obtained for the procedure and to ensure understanding of the poor prognosis and regular follow-up. Surgery was performed under general anesthesia by six different experienced surgeons. The planned step-by-step procedure was as follows but was regularly modified for individual approach and management of complications: (1) Sterile draping and disinfection with povidone iodine, taking into account any perforation. (2) A surgical compass was used to determine the diameter of the patient’s corneoscleral tissue to be removed. (3) The graft was marked with a corneal radial keratotomy marker. (4) The donor graft was prepared prior to any surgery on the recipient eye. (5) The diameter of the donor graft was 0.5-1 mm larger than the diameter of the tissue to be removed from the recipient. (6) The donor graft was placed on a plastic block, taking care not to desiccate the endothelium. (7) A central corneoscleral button was sutured. (8) The corneoscleral button was placed in surgical viscoelastic. (9) A cell culture medium swab was taken. (10) The conjunctiva was opened and moved away from the limbal region to expose 360° of the paralimbal sclera. (11) Bleeding during dissection was stopped with an electrocautery device. (12) The recipient was marked with a corneal radial keratotomy marker. (13) A Flieringa scleral fixation ring was sutured to the sclera at 4 equidistant points with 7-0 silk sutures. (14) The recipient eye was opened by paracentesis or entered through a perforation site and a viscosurgical device was injected into the anterior chamber. (15) Removal of the recipient corneoscleral tissue requires an individualized approach. The following considerations were made on a case-by-case basis to remove lytic tissue while maintaining the best possible function: (a) A round trephine was always used, often in combination with an ophthalmic crescent blade and round corneoscleral scissors. (b) To preserve the iridocorneal angle structures and avoid choroidal exposure, the sclera was not trephined in full thickness. A scleral lamella was removed manually with a crescent blade in a planned thickness of approximately 400 µm to create a scleral ledge. (c) The graft was sometimes decentered to preserve the limbal region. (d) Electrocautery is often necessary but causes tissue contraction. (16) The donor graft was attached with four cardinal sutures and secured with multiple 8-0 to 10-0 nylon sutures . (17) All suture knots were buried. (18) The Flieringa scleral fixation ring and viscoelastic were removed. (19) Sutures were replaced if graft–host junction leakage was detected. (20) Balanced salt solution and intracameral cefuroxime were injected. (21) The conjunctiva was approximated to the limbus with 9.0 absorbable sutures. (22) The eye was patched. Postoperative topical therapy varied depending on the underlying disease, but usually included prednisolone and antibiotics. Lubrication was also prescribed. Due to the size of the grafts, the transplantation of scleral tissue and the resulting high risk of graft rejection, oral immunosuppression was prescribed in all cases. Postoperative weight-adjusted prednisolone and/or mycophenolate mofetil 1 g was administered orally twice daily.The primary endpoint of the study was tectonic stability. Maintaining tectonic stability after the initial surgery was further defined as not requiring additional penetrating keratoplasty or enucleation. If no additional surgery was required to maintain tectonic stability, the initial surgery was defined as successful. Secondary endpoints were final visual acuity excluding the 5 enucleations and complications and secondary surgeries.Patients were regularly followed up in the outpatient clinic at appropriate intervals. Patients were readmitted to the inpatient clinic in case of complications or loss of tectonic stability. Medical history, intraocular pressure, corrected visual acuity, a comprehensive slit-lamp examination and the treatment plan were recorded at each follow-up visit. Grafts were evaluated for complications, such as re-infection, graft rejection, hypotony, or secondary glaucoma. Underlying conditions, both infectious and non-infectious, such as neurotrophic or exposure keratopathy were also treated as appropriate.p-value < 0.05.Statistical analysis was performed using unpaired t-test for parametric data or the Mann–Whitney test for nonparametric data. Graft survival was analyzed via simple Kaplan–Meier survival analysis. This was performed using GraphPad Prism (version 9). Statistical significance was set at a The primary endpoint of the study was tectonic stability, defined by the need for additional penetrating keratoplasty or enucleation. Using this definition, the proportion of eyes with a probability of tectonic stability at the end of follow-up was 56% as estimated via Kaplan–Meier analysis . Reasonsp = 0.0005).Concurrent with the procedure, all patients received intensive topical treatment tailored to their underlying disease and needs. All patients were treated with topical prednisolone 1%. In addition, systemic immunosuppressants, antivirals, and antibiotics were used, as well as contact lenses when appropriate for non-infectious epithelial defects. Because corneoscleral transplantation can be a difficult procedure and is often performed in very severe cases, the risk of postoperative complications is significant. During our mean follow-up of 675 ± 789 days, several complications were observed. The most common complication was epithelial defect in 13 cases (38%), followed by postoperative intraocular pressure decompensation in 12 cases (35%), and recurrent infection in 9 cases (26%). Postoperative hypotony occurred in five cases (15%). Oral immunosuppressive therapy was used as recommended in 22 cases (65%) and rejection occurred in 10 cases (29%). Graft size seemed to play an important role as the graft size of patients with graft rejection was significantly larger than the graft size of patients without rejection in our cohort  had a final visual acuity of hand movements or worse, 7 (24%) had a final visual acuity of counting fingers to 1.0 logMAR, and 5 (17%) had a final visual acuity of <1.0 logMAR. In general, visual acuity was poor, but there was one notable exception among our patients. The patient had a transplantation due to a severe fusarium-related perforated corneal ulcer. The graft was completely clear with a visual acuity of 0.3 logMAR after 8 years without systemic immunosuppression .When postoperative problems could not be managed by appropriate adjustment of local therapy, surgery was performed . Repeat The treatment of extensive corneal ulcers causing severe keratolysis with perforation of more than a portion of the cornea and extending to or beyond the limbus remains a challenge. In these cases, a corneoscleral transplantation is a treatment option to preserve the eye. In our study, this was possible in approximately half of the cases. Postoperative complications, secondary surgeries, and significantly reduced visual acuity put the advantages into perspective.p = 0.45). Regarding tectonic stability in severe infections, in another study of 60 large grafts, 7 eyes underwent regrafting, 7 eyes developed phthisis bulbi, and a tectonic outcome was achieved in 80% of cases, which was slightly higher than in our study [There are few studies that comment on the development of visual acuity, and the general impression is that tectonic stability is what can be expected from the procedure . Some auur study . In anotur study . The difur study . RegardiElevated intraocular pressure is a common complication after corneoscleral transplantation, so intraocular pressure must be monitored regularly as it can lead to glaucoma. The postoperative use of steroids can also lead to increased intraocular pressure. The current report and previous studies are in agreement regarding the increase in intraocular pressure. In our study, 34% of patients suffered from increased pressure, while another group reported 57% . ScleralIn general, it is difficult to comment on the average survival of corneoscleral grafts due to the lack of precise information in the published studies and the high variance of the study population between the different studies. In addition, the definition of tectonic stability also varies between studies. The mean survival of corneoscleral grafts ranges from 24 months  to 20 moThere are reports describing both long-term graft survival. For example, a corneoscleral graft was used for 18 years with excellent visual results . AnotherThe most frequently reported postoperative complication in our study was a persistent epithelial defect. This may be due to the fact that most grafts were larger than 10 mm, and, therefore, some allogeneic limbal tissue was transplanted and later rejected, or that the recipient’s limbus was altered either by the surgery or by the severe inflammatory conditions prior to surgery. Donor keratolimbal tissue has been shown to promote corneal epithelial healing in severe ocular surface disease . ImmunosThe immune privilege of the cornea guarantees the high graft survival rates observed in low-risk keratoplasty . UnfortuLamellar keratoplasty techniques, such as large deep anterior lamellar keratoplasty, may be an interesting technique for large keratolysis with descemetocele, for example in severe herpetic keratitis. One case report showed a healthy graft and relatively clear interfaces 6 months after surgery . AnotherLimitations of the study are related to the rarity of the procedure and the disease treated. These include the retrospective nature of this study and the lack of a control group. Data had to be obtained from clinical records. Surgery was performed by different surgeons with different follow-up times. Future studies with larger numbers of patients are needed to further specify when corneoscleral transplantation should be performed and what strategies should be used to allow long-term graft survival and, thus, preserve the integrity of the globe.Severe corneal ulceration is a serious threat to visual acuity and often results in loss of tectonic stability and ultimately of the eye. Corneoscleral grafts represent a treatment option to achieve tectonic stability and prevent enucleation in these cases. In this study with a large cohort of 34 patients, the integrity of the otherwise lost globe was preserved in more than half of the cases. Prognosis of visual acuity is guarded, except for notable exceptions, and is not the primary goal of treatment.


Starch nanoparticles (SNPs) are generally defined as starch grains smaller than 600–1000 nm produced from a series of physical, chemical, or biologically modified starches. Many studies have reported the preparation and modification of SNPs, which are mostly based on the traditional “top-down” strategy. The preparation process generally has problems with process complexity, long reaction periods, low yield, high energy consumption, poor repeatability, etc. A “bottom-up” strategy, such as an anti-solvent method, is proven to be suitable for the preparation of SNPs, and they are synthesized with small particle size, good repeatability, a low requirement on equipment, simple operation, and great development potential. The surface of raw starch contains a large amount of hydroxyl and has a high degree of hydrophilicity, while SNP is a potential emulsifier for food and non-food applications. Starch is a natural biological polymer, which is synthesized by plant photosynthesis and a series of complex biochemical reactions, widely present in various types of plant crops, and it is the second-largest biomass in nature after cellulose . Starch Pickering emulsions refer to emulsions stabilized by ultrafine solid particles . StudiesConcentrations . TherefoStarch-based Pickering emulsion, as a degradable and nontoxic carrier, has become a hot topic. It is possible that the modified starch based on Pickering emulsion could be presented as promising culture substrates for various biomedical applications due to its lack of significant detrimental effect on cell adhesion . NanoparTherefore, this paper reviews the preparation methods of starch nanoparticles and the stability mechanism of Pickering emulsion, and introduces the application of starch nanoparticles in emulsion.Chemically, starch is polymerized by D-glucose residues linked by α-1,4-glycoside bonds and α-1,6-glycoside bonds. According to the different links, the starch molecules can be divided into amylose and amylopectin. The former is a linear polysaccharide formed by the α-1,4-glycoside bond and a small amount (<1%) α-1,6-glycosidic bond polymerization, and the latter is a large number of side chains linked by α-1,4-glycoside bonds through 5% to 6% of the α-1,6-glycoside bond to the main chain to form a branched polysaccharide . This isThe amylopectin content of most proto-starches is as high as 70~80%, so the amylopectin molecular model is significant for the molecular structure levels of starch. It is suggested that amylopectin molecules can be divided into A-chain , B-chain , and C-chain (main chain). The chain structure is based on the B-chain as a medium, respectively, linked to the inner A-chain and outer B-chain through α-1,6-glycosidic bonds to form a cluster structure. An amylopectin molecule has only one C-chain and one reducing end. The A-chain and B-chain form double helices in their respective extending directions.Recently, there are two theories for describing the arrangement of amylopectin C-chains. As shown in The crystal form of starch can be determined by the X-ray diffraction pattern. As shown in In addition, the introduction of hydrophobic guest molecules induces a single V-shaped helical structure between starch molecules and guest molecules. Based on the size of the guest molecule, its interaction with the glucose unit will directly determine the form of the hydrophobic cavity that embeds the starch molecule, and then form V-6, V-7, and V-8 helical structures composed of 6, 7, and 8 glucosyl units in a spiral cycle .In recent years, the dominant model is the multi-level starch structure. According to this theory, starch particles are formed by onion-like growth rings with a thickness of 120–500 nm growing from inside to outside. The growth rings are composed of structural units (Blocklets). According to the arrangement density of Blocklets, growth rings are divided into semi-crystalline growth rings and amorphous growth rings, which are alternately arranged similar to a shell . Based oAccording to the different production paths, the preparation methods of the SNP can be divided into “top-down” and “bottom-up”. Where “top-down” refers to the technology of gradually pulverizing and deagglomerating raw starch into nano-sized particles from macroscopic bulky aggregates by a series of physical and chemical means. The traditional method of preparing nano-sized starch mainly carries out micro-structure level scale deagglomerating on large particles of raw starch by physical and chemical methods such as acid hydrolysis, high-pressure homogenization, reaction extrusion, and grinding, thereby generating submicron and nano-sized SNPs . Based oGenerally, physical preparation technologies of SNP mainly involve extrusion, grinding, and high-pressure homogenization. Wherein the extrusion method is a technology that feeds the raw materials of the prepared starch-water-crosslinker mixture into a high-temperature and high-pressure environment, then gelatinization and rupture occur after mechanical shearing by the screw . Song etAmong biochemical methods, the acid hydrolysis method is the most widely used. As the crystalline lamellae of starch have strong acid resistance, the amorphous regions of starch will be acidolyzed preferentially. Therefore, the final hydrolysis product of nano-starch prepared by acidolyzation is starch nanocrystals (SNC) with high crystallinity. Jiang et al.  used waxIn general, the single “top-down” method is not enough to achieve satisfactory results, it needs to be combined with other methods. However, the synergistic use of methods still cannot solve defects such as complicated processes, long reaction cycles, and irregular product morphology completely. More importantly, due to the differences in specific production equipment and process parameters, the physicochemical properties of the products obtained by the “top-down” method mostly lack stability and are difficult to replicate.The “bottom-up” method can be understood as a generalization of all SNPs prepared by the self-assembly approach, which refers to the transformation of native starch into the molecular state under certain conditions, and the re-nucleation of starch molecules to generate SNPs by adjusting the physical and chemical parameters of the system ,39,40. SThe antisolvent method is an excellent “bottom-up” type nanoparticle preparation technology proposed by Fessi et al.  in 1989.Nano-starch has high biocompatibility and bioaccessibility, and its nano-scale size can promote the accurate delivery of active ingredients in the human body, which is conducive to improving bioavailability. It is an excellent bio-based carrier ,57. In rSNPs can also be used as fillers in composite materials to improve the mechanical strength and biodegradability of materials . DulariaThe surface of raw starch contains a large number of hydroxyl, and it has a high degree of hydrophilicity and cannot be used as a stabilizer for Pickering emulsion, which requires hydrophobic modification. Emulsification tests implied that octenyl succinic starch ester was an effective emulsifier for the stabilization of oil-in-water emulsions. At present, the research on starch-based emulsifiers focuses on the modification of hydrophobic groups. The Octenyl succinic anhydride (OSA) modification is one of the most widely used hydrophobic modification strategies for food-grade starch, based on the principle of OSA grafting of starch molecules through esterification reaction under alkaline conditions  Figure . HoweverDue to the poor emulsifying ability of raw starch, starch, and another bio-based emulsifier can be combined to stabilize the emulsion through a synergistic effect  Figure . Li et aAlthough the starch-based emulsifier can improve the stability of the emulsion under certain conditions, the combined emulsifier has great limitations. On the one hand, the emulsifying effect of the combined emulsifier easily fluctuates with the changes in the physical and chemical environment of the system. For example, the changes in temperature or pH result in the denaturation and precipitation of protein, and thus the loss of emulsifying ability ,74. On tA study showed that reducing the size of starch particles was conducive to the formation of emulsion with smaller droplet sizes, and improved the storage stability of the emulsion . Lu et aA study showed that compared with proteins and lipids, the structural changes caused by heat-induced starch gelatinization might improve the stability of the emulsion . TherefoDue to the small size of starch nanoparticles, it has high dispersibility and is easy to gelatinize during processing. It has the tendency of spontaneous agglomeration due to the high surface energy. Therefore, the size effect of starch nanoparticles varies in different environments, which directly affects their emulsifying ability. So far, there is still a lack of systematic discussion on the structure-activity relationship between the nano-structure of starch nanoparticles and their emulsion stability. Through the comprehensive investigation of the relationship between the nano-size effect of starch nanoparticles and their functional characteristics, as well as improving the performance by modifying starch nanoparticles and binding them with food-grade components such as fiber and protein, it is of great significance to give full play to the advantages of starch nanoparticles in practical applications.


This systematic review and meta-analysis aimed to evaluate the effect of different surface treatments on the shear bond strength (SBS) values between zirconia and resin cement compared to untreated specimens. The effects of various surface treatments on the bond strength between zirconia and resin cement were investigated by searching relevant articles on PubMed, ScienceDirect, and Google Scholar databases. A total of 13 studies that met the inclusion and exclusion criteria and addressed the research question were selected for statistical analysis. The studies were evaluated for heterogeneity, and a meta-analysis was performed.In total, 13 in vitro studies were included in accordance with the eligibility criteria. All 13 studies consistently demonstrated that silica coating yielded the highest SBS, followed by sandblasting and laser treatments. The meta-analysis using a random-effect model indicated a significant intergroup comparison, except for a few studies.Among the three treatments examined, the silica coating of zirconia was identified as the most effective in enhancing the bond strength between zirconia and resin cement. Further controlled laboratory and clinical studies are necessary to validate these findings and explore additional factors that may influence the effects of these surface treatments. The successful outcome of polycrystalline ceramic restorations in clinical settings relies on the proper adhesion of dental elements. Adequate adhesion plays a crucial role in preventing microleakage, achieving better marginal adaptation, and increasing retention and fracture resistance . Over tiZirconia stands out from other dental ceramics due to its unique characteristic of transformation toughening . When puThe structural stabilization of zirconia by yttria results in a significant proportion of metastable tetragonal phase. This metastable tetragonal phase strengthens and toughens the structure by a localized transformation to the monoclinic phase when tensile stresses develop at crack tips. The resulting volume expansion adjacent to the crack tips produces a high local compressive stress around the crack tips, which increases the localized fracture toughness and inhibits the potential for crack propagation. The phenomenon of transformation toughening increases the flexural and tensile fracture resistance of stabilized zirconia prostheses and presumably the survival probabilities of zirconia-based restorations. The capability of stress-bearing of zirconia is directly proportional to transformation toughening. The mechanical properties, such as flexural strength and fracture resistance, are also greater than traditional ceramics.However, a major concern associated with zirconia is the process of luting or bonding, as it lacks a silane phase and is not susceptible to etching with hydrofluoric acid, unlike glass ceramics ,6. In th2), and erbium, chromium-doped yttrium, scandium, gallium and garnet  to condition ceramic surfaces before luting. Laser surface treatments have been found to increase the surface roughness, wettability, and SBS of the resin cement [Many authors have explored air-particle abrasion, also known as sandblasting, as a surface treatment method for zirconia. This technique involves roughening the zirconia surface, which increases surface area and enhances surface energy, resulting in improved micromechanical retention. However, it is important to note that the metastable nature of tetragonal zirconia can be affected by grit blasting, leading to a transition from the tetragonal to a monoclinic structure . This stn cement . A studyn cement .2O3) particles to remove contaminants and create micro-roughness. Subsequently, the surface is subjected to airborne particle abrasion with aluminum trioxide particles modified by silica. The blasting pressure causes the silica-coated alumina particles to embed onto the ceramic surface, facilitating a chemical change induced by the silica [Another method that has shown promising results is the tribochemical deposition of silica on the zirconia surface using air-blasting equipment. In this technique, the ceramic surface is initially abraded with aluminum oxide  ceramic a challenge. This systematic review and meta-analysis was performed to evaluate different surface treatments of zirconia and their effect on the SBS values between the Y-TZP and resin cement compared to untreated specimens. The null hypothesis is that no significant difference will be found in the SBS values between the treated and untreated specimens.MethodologySourcesAn electronic search was conducted to identify relevant articles published in the English language between 2000 and July 2020. The search was performed using databases such as PubMed, ScienceDirect, and Google Scholar. The search strategy employed a combination of Medical Subject Headings (MeSH) terms and keywords including “Zirconia surface treatment,” “All ceramic surface treatment,” “Bond strength of zirconia to resin cement,” “Bond strength of all ceramic to resin cement,” “Bond strength of zirconia to luting cement,” and “Bond strength of all ceramic to luting cement.”Selection of StudiesThe review process was conducted in two phases. In the first phase, the titles and abstracts obtained from the database search were screened by two authors to determine their relevance to the study. The full text of the abstracts that met the inclusion criteria was then obtained and evaluated. Any inconsistencies or disagreements were resolved through discussion between the authors or with the input of a third author.Following the initial phase of the review process, a manual search was conducted on the selected articles as well as their references. In the second stage, the articles gathered were screened based on predefined inclusion and exclusion criteria. Relevant articles were identified and selected for further analysis and data extraction. Duplicates and articles lacking sufficient necessary data were excluded by the two authors, with any disagreements resolved through the suggestions of a third author.During the article selection process, the inclusion criteria consisted of studies focusing on surface treatments such as laser, sandblasting with 50-micron alumina, and silica coating, along with the measurement of SBS. Additionally, studies with a sample size exceeding 150 were included. Conversely, review articles, studies published in Chinese, those with a sample size of less than 150, and articles assessing tensile strength were excluded from the analysis. The aim was to gather relevant studies that specifically examined the effects of these surface treatments on SBS.ResultsThe initial electronic database search across PubMed/MEDLINE, ScienceDirect, and Google Scholar yielded a total of 2,809 titles. Following the screening of abstracts, 1,182 articles were identified as relevant and subsequently evaluated by two independent reviewers. Of the initial selection, 1,627 articles were deemed unrelated to the study and excluded. Through a thorough examination and discussions among the reviewers, 276 articles were chosen for full-text evaluation. After applying pre-screening, inclusion, and exclusion criteria and addressing the specific research question, a final set of 13 studies remained for further analysis  specimens were treated with sandblasting, 330 (24.16%) with lasers, and 418 (30.61%) with silica coating. Each reviewer independently selected these specimens for inclusion in the final meta-analysis. We established a database into which we entered the information extracted from each article . The impact of these particles on the ceramic surface results in the deposition of a thin silica film. Silicatization not only creates micro-roughness on the surface but also chemically modifies it, thereby enhancing its bonding properties .2 lasers to enhance the adhesion between resin cement and zirconia [2 and resin cement are contradictory. The null hypothesis formulated in this study was rejected, as a significant difference in SBS values was observed between the luting cement and the treated and untreated surfaces. The results favored the surface-treated groups, indicating that the surface treatments had a positive impact on SBS.Different authors have explored the use of Er:YAG or COzirconia . This teThe studies included in this meta-analysis were in vitro, prospective, cross-sectional studies. These studies investigated the effects of different surface treatments on all-ceramic or zirconia materials. Six studies compared the sandblasting or air abrasion technique with silica coating ,20,23,24This systematic review and meta-analysis of in vitro studies suggests several key findings regarding the surface treatment of Zirconia. First, it was observed that such treatment significantly improves the SBS between zirconia and resin cement. Among the different treatment methods investigated, silica coating demonstrated the highest SBS, followed by sandblasting and lasers. The use of hydrofluoric acid etching and silane treatment is not effective for zirconia. Lasers as an alternative surface treatment method have gained interest due to their potential to reduce the negative impact of grit-blasting on the performance of zirconia restorations. However, further studies are needed to confirm these findings and investigate the long-term effects of different surface treatments on the performance of zirconia restorations.


Due to its poor toughness and hydrophilicity, the application of polylactic acid (PLA) in the field of absorbent sanitary materials is restricted. A butenediol vinyl alcohol copolymer (BVOH) was used to improve PLA via melt blending. The morphology, molecular structure, crystallization, thermal stability, tensile property, and hydrophilicity of PLA/BVOH composites with different mass ratios were investigated. The results show that the PLA/BVOH composites possessed a two-phase structure with good interfacial adhesion. The BVOH could effectively blend into PLA without a chemical reaction. The addition of the BVOH promoted the crystallization of PLA, improved the perfection of the crystalline region, and increased the glass transition temperature and melting temperature of PLA in the heating process. Moreover, the thermal stability of PLA was markedly improved by adding the BVOH. The addition of the BVOH also had a significant effect on the tensile property of the PLA/BVOH composites. When the content of the BVOH was 5 wt.%, the elongation at the break of the PLA/BVOH composites could reach 9.06% (increased by 76.3%). In addition, the hydrophilicity of PLA was also significantly improved, and the water contact angles decreased with the increase in the BVOH content and time. When the content of the BVOH was 10 wt.%, the water contact angle could reach 37.3° at 60 s, suggesting good hydrophilicity. With the intensification of the aging population, the consumption of absorbent sanitary products for adults continues to grow. At present, the main raw material source of absorbent sanitary products is ES (ethylene propylene side by side) fiber, which is a polyolefin fiber derived from petroleum. The application of disposable absorbent sanitary products provides comfort, health, and convenience to people. However, the nonbiodegradability and non-renewability of ES fibers have led to serious white pollution due to the billions of products consumed annually ,2. In adTo overcome these problems, researchers have developed new polymetric materials that can be biodegraded and obtained from renewable resources ,10,11. ANonetheless, some inherent defects, such as poor toughness, low heat resistance, easy hydrolysis, a slow crystallization rate, and poor hydrophilicity, have limited the range of applications ,19,20. MThe absorbent sanitary products prepared by ES fibers need to be modified in a hydrophilic manner to meet comfort requirements. Therefore, the poor hydrophilicity of PLA seriously restricts its application in absorbent sanitary products, which also needs to be significantly improved. The hydrophilic modification of PLA can be mainly divided into blending modification and surface modification ,28,29,30It is well-known that melt blending modification is a handy, effective, and environmentally friendly method that can improve the hydrophilicity of PLA, but the difficulty is to screen out the suitable hydrophilic modifier, which can be well dispersed in a PLA matrix and have good compatibility with PLA. Poly  (PVOH), which is a biodegradable, biocompatible, inexpensive, hydrophilic, and highly flexible polymer, has been used to improve the toughness and hydrophilicity of PLA by melt blending. The addition of PVOH can promote the hydrophilicity of PLA, but the immiscibility of PLA and PVOH degrades other properties .A butenediol vinyl alcohol copolymer (BVOH) is composed of butenediol and vinyl alcohol monomers and is a new, multifunctional, environmentally friendly material that combines moldability and water-soluble biodegradability  31,32,3,332,33. x composites are shown in x composites exhibit a clear two-phase structure (sea–island structure). The main component of PLA forms the continuous phase (sea phase), and the minor component of the BVOH forms the dispersed phase (island phase). It is evident that the BVOH can uniformly disperse in the PLA matrix with different contents in the particle state. In The morphologies of the fracture with liquid nitrogen of PLABFurthermore, it can be observed that there is no obvious boundary between the interface of the two phases when the BVOH content is equal to or less than 5 wt.%, as shown by the red scissors, indicating that the BVOH has good compatibility with the PLA component when the BVOH content is low . This caMoreover, the void spaces throughout the fracture surface caused by the BVOH being pulled out of the PLA matrix can be observed in x composites. For pure PLA, the peak at 1748 cm−1 can be attributed to the stretching vibration of symmetric C=O. The peak at 1452 cm−1 belongs to the asymmetric bending deformation of -CH3. The peak at 1358 cm−1 can be attributed to the stretching vibration of -CH and asymmetric deformation of crystalline -CH3. The peaks at 1180 and 1081 cm−1 belong to the stretching vibration of C-O-C. The small peaks at 2996 and 2948 cm−1 can be assigned to the asymmetric and symmetric stretching vibration of -CH3, respectively. Moreover, a small band that can be attributed to the hydroxyl groups can also be detected at ~3358 cm−1 [−1, -CH2 asymmetric and symmetric stretching bands at 2918 and 2851 cm−1, C-OH stretching bands at 1452 and 1088 cm−1, and a C-C stretching band at 1249 cm−1. Moreover, the small weak peak at 1652 cm−1 can be assigned to the terminal C=C stretching vibration. It needs to be pointed out that a peak at 1735 cm−1 can be observed in the FTIR spectrum of the BVOH, which can be attributed to the stretching vibration of C=O [358 cm−1 ,36. Meanx composites, and there are no absorption bands of new functional groups in the composites. Therefore, PLA and the BVOH physically blend without generating new chemical functional groups during the preparation process. Additionally, it can be found that the hydroxyl band of the PLABx composites increases in intensity with the increase in the BVOH content. This can be attributed to the contribution of hydroxyl groups in the BVOH. Moreover, it can be observed that the hydroxyl band of the PLABx composites shifts towards smaller wavenumbers by increasing the BVOH content, which indicates that hydrogen bonding occurs between the terminal hydroxyl groups of PLA and the hydroxyl groups of the BVOH [In the BVOH ,36.x composites are shown in x composites derived from DSC curves are listed in cX) is calculated based on the following equation:mH is the melting enthalpy of the samples, ΔccH is cold crystallization enthalpy, ΔfH is the melting enthalpy of 100% crystalline PLA (93 J/g) [The melting and crystallization curves of the pure PLA, BVOH, and PLAB(93 J/g) , and x igT) in the reheating and cooling curves can both be detected, and the crystallization exothermic peak and melting endothermic peak are obvious, indicating that the BVOH is a crystalline polymer. In cH) is only 0.02 J/g, which also indicates that the vast majority of macromolecules in pure PLA are in the amorphous region. In the cooling curve of the BVOH, a glass transition temperature at 62.3 °C, and an obvious crystallization peak at 129.4 °C can be observed. Moreover, with the increase in the BVOH content, the crystallization exothermic peak becomes obvious, the temperature of the crystalline peaks (cT) shifts to low temperatures, and the ΔcH gradually increases. This phenomenon indicates that adding the BVOH can improve the crystallinity of PLA due to the high cT (129.4 °C) because the crystal grains of the BVOH can supply nucleation sites as a nucleating agent to promote the crystallization of PLA [gcT) also moves towards low temperatures, which shows that the motility of PLA macromolecules is enhanced in the cooling process. When the content of the BVOH reaches 10 wt.%, two crystallization peaks at 97.9 and 124.2 °C can be observed from the cooling curves, which can be attributed to the PLA component and the BVOH component, respectively.In n of PLA ,38. Morex composites exhibit glass transition, cold crystallization, and subsequent melting in the reheating process. The appearance of cold crystallization peaks indicates that incompletely crystallized chains exist in the PLA matrix. In the reheating curve of the BVOH, a glass transition temperature of 73.1 °C and an obvious melting peak at 179.8 °C can be observed. Moreover, with the addition of the BVOH, the glass transition temperature in the reheating process (gT−h) moves towards high temperatures. This indicates that the PLABx composites have a more thermally stable structure than pure PLA, which further exhibits that PLA and the BVOH are compatible. This phenomenon can be attributed to two factors. First, the crystallization of the BVOH in the cooling process can promote the crystallization of PLA, which can make the PLA macromolecular chain arrangement change from a disordered structure to an ordered structure. Therefore, it takes more heat to make the macromolecular chains move during the heating process. Second, the gT of the BVOH is much higher than that of PLA, so the BVOH molecular chains in the glassy state can hinder the movement of PLA macromolecular chains [In r chains ,38.ccT) moves towards high temperatures and ΔccH decreases with the addition of the BVOH. This can be explained by the fact that the movement restriction of the PLA macromolecular chains by the BVOH results in an increase in ccT. Moreover, the decrease in ΔccH can be attributed to the larger crystallization region and a higher degree of crystal perfection in PLABx composites because of the promoting effect of the BVOH on the crystallization of PLA in the cooling process. Thus, pure PLA needs more crystal enthalpy to perfect the crystals than the PLABx composites. The increase in melting temperature (mT), ΔmH, and cX by adding the BVOH can also be crystalline and is explained by this reason. Moreover, it needs to be pointed out that there is only one melting peak in the reheating curves, which also illustrates the good compatibility of PLA and the BVOH.Furthermore, it can also be observed that the cold crystallization temperature (x composites are shown in 5%T), the maximum rate of decomposition (maxT), and the end of decomposition (endT) are summarized in x composites exhibit a two-stage degradation. In 5%T of the PLABx composites is improved due to the addition of the BVOH, while the 5%T of the PLABx composites decreases with the increase in BVOH content but is still higher than that of pure PLA. Moreover, the maximum rate of decomposition in the first stage (max1T) of PLA is also improved by adding the BVOH but decreases with the increases in the BVOH content. These phenomena indicate that adding the BVOH can improve the thermal stability of PLA. Moreover, the maximum rate of decomposition in the second stage (max2T) of the PLABx composites increases with the increase in the BVOH content.The thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) curves of the BVOH, pure PLA, and PLABx composites are shown in x composites are shown in x composites still exhibit brittle fractures. The tensile stress of the PLABx composites first increases and then decreases with the increase in the BVOH content. The tensile stress of pure PLA is 53.4 MPa, and the tensile stress of PLAB3 composites can reach 65.9 MPa, with an increase of 23.4%. This can be attributed to the increase in crystallinity and the improvement in the perfection of the crystalline region due to the addition of the BVOH. The tensile stress begins to decrease when the BVOH content is higher than 5%. This may be due to the stress concentration caused by the increasing difference in the BVOH particle size. Moreover, the elongation at the break of the PLABx composites also first increases and then decreases with the increase in the BVOH content. The elongation at the break of pure PLA is only 5.23%, and the elongation at the break of PLAB5 composites can reach 9.06%, with an increase of 73.2%. This may be attributed to the good dispersion and compatibility of the BVOH in the PLA matrix.The stress–strain curves of the BVOH, pure PLA, and PLABx composites. In x composites also decrease with the increase in the BVOH content. The WCA of the PLAB10 composite is 72.3° when the contact time is 0 s. This can be attributed to the good hydrophilicity of the BVOH due to a large number of hydroxyl groups. Furthermore, the WCAs of the PLABx composites also decrease with the increase in time, and the degree of decline is much greater than that of pure PLA. The WCA of the PLAB10 composite is only 37.3° when the contact time is 60 s, which indicates much better hydrophilicity than pure PLA. This can be explained by the fact that the large number of hydroxyl groups in the BVOH can make it dissolve in water. The water molecules can be diffused and wetted on the surface of the PLABx composites, and the WCA on the surface of the PLABx composites is reduced.The water contact angles (WCAs) are used to characterize the hydrophilicity of the PLABTM Biopolymer 6100D, thermoplastic fiber-grade resin, with a specific gravity of 1.24 g/cm3) was supplied by Nature Works LLC . Butenediol vinyl alcohol copolymer (BVOH)  was purchased from BASF (China) Co., Ltd. . All materials were dried in a vacuum oven before use to remove residual moisture and thus prevent hydrolysis during processing.Polylactic acid (PLA)  and then melt blended using an SISZ-10A counter-rotating twin-screw extruder . The screw extruder adopted conical twin screws that were the meshing type and inward counter-rotating. The screw diameter was 10/25 mm from the small end diameter to the big end diameter. The screw length was 190 mm, and the screw length–diameter ratio was 19:1. The maximum screw speed could reach 51 rpm. Melt blending continued for 3 min with a screw speed of 30 rpm. The temperature from the feed zone to the nozzle was 185, 190, 190, and 190 °C, respectively. The PLA/BVOH composites are denoted herein as PLABThe specimens used for the tensile tests were manufactured by an SZS-20 injection-molding machine . The injection temperature was 200 °C, and the mold temperature was 65 °C. The pressure holding time was 5 s, and the cooling time was 30 s with an injection pressure of 25 MPa. Before the injection, the blends were dried in a vacuum oven at 80 °C for 12 h. Moreover, pure PLA pellets were also subjected to the same melt blending and injection treatment to obtain the same thermal history as the blends.−1 range.The morphology of the composites was observed by a GeminiSEM 300 scanning electron microscope (SEM)  at 3 kV with a cryo-fracture surface coating with a thin gold layer. A Nicolet-10 Fourier transform infrared spectrometer (FT-IR)  was used to examine the chemical structures of the composites in the 4000–400 cmx composites were evaluated from the second test step.The thermal properties of the composites were determined using a DSC-3 differential scanning calorimetric (DSC) . All samples were vacuum-dried at 80 °C for 12 h before the DSC test. The samples were subjected to a thermal cycle. In the first step, samples (5~8 mg) were heated from 25 to 210 °C with a heating rate of 10 °C/min and kept at that temperature for 3 min to eliminate the heat history. In the second step, the samples were examined from 30 to 210 °C with a heating and cooling rate of 20 °C/min. All tests were performed in a nitrogen atmosphere (50 mL/min). The thermal parameters for the crystallization and melting behavior of PLABTGA/DSC 3+ thermogravimetric analyzer (TGA)  was used to observe the thermal stability of the composites. The tests were performed in a nitrogen atmosphere (50 mL/min) at temperatures of up to 800 °C at a 10 °C/min heating rate.Tensile properties of the composites were analyzed using an EZ-SX tensile tester  with a 50 kN load cell according to the ASTM D638 with a loading speed of 5 mm/min. The testing of each sample was repeated at least five times, and the results were averagedThe water contact angles (WCAs) were measured using an OSA 60 video contact angle analyzer at 25 °C and 60% relative humidity. Deionized water was used as test liquid, and the volume of test drops was 5 μL. The average value was obtained by a multi-point test.x composites composed of PLA and a BVOH were successfully prepared by simple melt blending using a twin-screw extruder. The PLABx composites exhibited a clear “sea-island” two-phase structure with good compatibility and interface adhesion between the PLA and BVOH phases when the BVOH content was low. The FTIR analysis shows that PLA and the BVOH experienced physical melt blending without generating new chemical functional groups. However, hydrogen bonding occurred between the hydroxyl groups of PLA and the BVOH. Moreover, the addition of the BVOH promoted the crystallization of PLA in the cooling process but hindered the movement of PLA macromolecular chains in the heating process. The thermal stability of PLA was also improved by adding the BVOH. The brittle fracture of PLA was not changed with the addition of the BVOH during the tensile test, but the elongation at the break still exhibited a significant increase. Furthermore, the hydrophilicity of PLA was significantly improved by adding the BVOH, and the hydrophilicity of PLA became better with the extension of time. As a consequence, the addition of the BVOH improved the toughness and hydrophilicity of PLA.In this paper, PLAB


A challenge for these libraries is to efficiently check if a proposed molecule is present. Here we propose and study Bloom filters for testing if a molecule is present in a set using either string or fingerprint representations. Bloom filters are small enough to hold billions of molecules in just a few GB of memory and check membership in sub milliseconds. We found string representations can have a false positive rate below 1% and require significantly less storage than using fingerprints. Canonical SMILES with Bloom filters with the simple FNV (Fowler-Noll-Voll) hashing function provide fast and accurate membership tests with small memory requirements. We provide a general implementation and specific filters for detecting if a molecule is purchasable, patented, or a natural product according to existing databases at  With the growing scale of molecular screening, which now involves searching through billions of chemical structures, the processing times for querying extensive compound datasets have significantly increased , 2. To am) bit array to represent n elements, employing k hash functions to map each element to k positions within the array [The Bloom filter, a space-efficient and probabilistic data structure, was designed to ascertain whether an element belongs to a specific set. First proposed by Burton H. Bloom , this dahe array –5. This Originally applied in dictionaries and spell checkers , 6, BlooTraditionally, molecules have been represented using structure-based fingerprints . In thisThis study explores the use of Bloom filters in molecular databases. Although, we refer alternative data structures that offer functionalities that can either mitigate some limitations of Bloom filters or serve entirely different objectives. For example, Cuckoo filters  provide A Bloom filter is initialized with an m-length bit vector, with all positions set to zero, and employs k independent hashing functions. These hashing functions generate k values ranging from 0 to m−1, which correspond to the positions in the bit vector where a ”1” will be assigned. The hashing functions must exhibit the following characteristics : (1) QuiBloom filters enable the addition of new members but do not support individual removals. The filter can be queried to determine if a particular element has been added previously. However, this simplicity comes with certain drawbacks, such as the potential for two or more elements to be hashed to the same position in the Bloom filter . As a result, removing an element (by changing its positions from one to zero) could inadvertently affect other members with overlapping positions. This issue underscores the importance of randomness in hashing functions, often referred to as the avalanche effect. Figures For more comprehensive information on Bloom filter functionality, theoretical limits, and optimal implementation, refer to the existing literature. –5, 24A’ represents an element being hashed, Using the described method, the number of generated hashing functions can be selected depending on the number of elements to add (n), the bloom filter size in bits (M), and the pre-stablished false positive rate  , as wellTo assess false positive rates in each filter with different sizes, a fifty-fifty split was performed. The first half was added to empty filters, followed by membership testing in the second half. Any molecules from the second half classified as part of the set were counted as false positives.An evaluation was conducted to compare the speed of Bloom filters and traditional methods in searching for elements within a dataset (using the dataset’s native API).All six possible fingerprint combinations across eight distinct orders of magnitude for the Bloom filter and string hash implementations were examined. Figure As illustrated in Fig. Message Digest and FNV hashing (7 & 8) of strings yielded nearly identical and seemingly smooth curves, suggesting a well-randomized hashing of the elements. In contrast, other methods exhibit a “noisy” pattern, which serves as evidence of inadequate randomization. By design, these alternative methods are not highly randomized, as similar molecules tend to have comparable chemical fingerprints. This characteristic is the basis for their use in numerous optimization methods, as they can measure the distance between molecules. Consequently, their performance is suboptimal, as similar molecules have a higher likelihood of collisions within the Bloom filter.In terms of the time required for Bloom filters to verify whether a molecule is part of a set or not, Fig. We demonstrate that string hashing (FNV and MD4–5) for Bloom filters outperform and approximate the theoretical limit of these structures, confirming that strings are sufficient for molecule storage. Even taking into account the time spent on canonicalizing SMILES, Bloom filter retrieval is still more than two orders of magnitudes faster than using an internet search. We also show that FNV, despite its simplicity and speed, is as effective as MD5. Employing other string representations, such as InChI and SELFIES, is expected to yield similar results. Potential applications for the Bloom filter are to quickly determine if a molecule is purchasable in ZINC, patente


The editorial core group of Epidemiology and Health Services: Journal of the Brazilian National Health System (RESS) extends its thanks to the ad hoc reviewers listed below, for their collaboration and commitment in their careful evaluation of its manuscripts in 2022, which contributed greatly to the qualification, independence and ethical rigor of the journal


The SEM micrographs revealed that the addition of hydrocolloids to starch leads to the formation of denser gels with smaller pores. The water absorption of starch pastes was improved in the presence of gums, and samples containing 0.3% almond gum had the highest water absorption. The rapid visco analyzer (RVA) data showed that the incorporation of gums significantly affected the pasting properties by increasing the pasting time, pasting temperature, peak viscosity, final viscosity, and setback and decreasing breakdown. In all the pasting parameters, the changes caused by almond gum were more obvious. Based on TPA measurements, hydrocolloids were able to improve the textural properties of starch gels, such as firmness and gumminess but decreased the cohesiveness, and springiness was not affected by the incorporation of gums. Moreover, the freeze–thaw stability of starch was enhanced by the inclusion of gums, and almond gum exhibited better performance.In this study, the influence of different levels (0.1, 0.2, and 0.3%  Amylose accounts for approximately 20–30%, while amylopectin accounts for approximately 70–80% of starch granules. The properties of wheat starch determine the quality of flour-based products such as bread, noodles, pasta, cakes, cookies, etc. Additionally, functional properties such as water absorption, emulsion stabilization, pasting, and gelation have changed wheat starch into a unique hydrocolloid with several applications in food products. However, native wheat starch has inherent properties such as poor resistance to thermal and shear stresses, tendency to retrogradation, instability in cold–storage, sensitivity to freezing and acids, and relatively low water absorption capacity and paste viscosity. These properties deteriorate the quality of food products and prevent the extensive application of native starch in the food industry. In order to take advantage of starch and enhance its applications in processed food products, its functional properties can be modified by different methods such as chemical, enzymatic and physical treatments [Starch is the main constituent of wheat flour and is considered a major source of energy in the human diet. Wheat starch is the third most used starch in the world after corn and cassava starches which is stored in water-insoluble granules with semi-crystalline structures. It is a mixture of two polymers of D-glucose, a linear α-→4 linkedeatments ,6.Amygdalus scoparia Spach shrubs which are mostly grown in central regions of Iran [Amygdalus communis L.) are a member of Rosaceae family that grows in the Mediterranean region, southwest Asia, and the Middle East [The effects of hydrocolloid incorporation on the physicochemical and nutritional properties of starch have been investigated extensively. The effects of gum Arabic (GA) on tapioca starch (TS) were investigated by Singh et al. . They fo of Iran . Persian of Iran . Propert of Iran . Almondsdle East . The trudle East . This hydle East . Howeverdle East . Since wThe influence of gums on the water absorption of wheat starch is given in p ˂ 0.05) increased the peak viscosity, which indicates that the water absorption of starch was increased in the presence of gums. The highest peak viscosity was observed in samples with 0.3% almond gum, which is in line with the results of the water absorption test  that contained 7% moisture, 0.44% fat, 0.38% protein, and 0.13% ash (determined by the approved methods of the AACC . The totw/v) were prepared by incorporating starch with distilled water or gum solutions. The suspensions were prepared with a magnetic stirrer . The samples were heated in a water bath at 95 °C for 30 min under constant agitation (200 rpm) and then cooled to ambient temperature and centrifuged  at 700 g for 20 min. The separated water was removed, and the sediment was weighed to determine the water absorption with the following equation:Water absorption was determined by the method described by Rahimi et al. . In brieg for 15 min, and the released water from each paste was weighed, and syneresis (%) was quantified by the following equation:The freeze–thaw stability of starch pastes was measured according to the method described by Tarahi et al. . The wheThe pasting properties of wheat starch-gum composites were determined by using a rapid visco analyzer (RVA) . 3.5 g of starch powder was added to 25 g of water or gums solutions  in an RVA canister and inserted into the instrument. The slurry was heated at 50 °C for 1 min, then heated to 95 °C and kept at 95 °C for 2.7 min, and then cooled to 50 °C at the rate of 5 °C/min. The paddle rotation speed was 960 rpm for the first 10 s and then reached 160 rpm. Pasting parameters, including pasting temperature, pasting time, peak viscosity, breakdown, setback, and final viscosity, were determined from the RVA curves.The pastes obtained from the RVA were transferred into Plexiglas molds , covered to avoid moisture loss, and stored at 4 °C for 24 h before textural measurements. Gels were removed from holders, and texture profile analysis (TPA) was performed using a texture analyzer  with a cylindrical probe (35 mm diameter). The gel mixtures were compressed to 25% of their original height at a crosshead speed of 0.25 mm/s. Textural parameters such as hardness (maximum force required for a 25% compression in the first compression cycle), cohesiveness (the ratio between the area under the second peak and the area under the first peak), springiness (the height that the starch gels recovered during the time between the end of the first compression cycle and the start of the second compression cycle), and gumminess (hardness × cohesiveness) were obtained from time-force curves using the Texture Exponent Lite software (version 5.1.1.0) .The microstructure of the starch-gum composite gels was studied using a scanning electron microscope . The samples were freeze-dried . Cross sections of samples were prepared by a sharp knife and coated with gold in a sputter coater . The micrographs were taken under vacuum conditions with an accelerating voltage of 15 kV and 300× magnification.The statistical analysis of the experimental data was performed by one-way analysis of variance (ANOVA) at a confidence level of 0.05. The means were compared using Duncan’s multiple range test at a significance level of 0.05 with SPSS statistical software version 16.


Insufficient research has been conducted in the literature assessing the performance of zirconia and polyetheretherketone (PEEK) crowns in relation to the essential requirements of successful restorations, such as fracture resistance or margin adaptation. The purpose of this study was to evaluate the effect of the coping materials zirconia or PEEK with different fabrication techniques on the vertical marginal gap and fracture resistance of posterior crowns with composite veneering.n = 18) restoring mandibular first molar were fabricated from zirconia , milled PEEK (PEEK CAD)  and pressed PEEK (PEEK Press)  six specimens each (n = 6). The copings were veneered with high impact polymer composite (HIPC) material . The vertical marginal gap was captured under a magnification of 40X. Five equidistant marks on each surface of the die distinguished the points of measurement for a total of 20 readings per sample. The analysis was completed using an image analysis system . The specimens were loaded to failure at a crosshead speed of 1 mm/min and the load at failure was recorded to measure the fracture resistance.Ceramic copings (p < 0.001). However, the results of fracture resistance showed no significant difference (p = 0.06) with 1687.47 ± 253.29 N, 2156.82 ± 407.64 N, 2436.72 ± 725.93 N for zirconia, PEEK CAD, and Press, respectively. The significance level was p < 0.05.The marginal gap was analyzed using one-way ANOVA followed by Tukey’s post hoc test. Fracture resistance was analyzed using Welch one-way ANOVA followed by the Games-Howell post hoc test. Marginal gap values showed a significant difference between the tested groups, with zirconia having significantly lower gap values (48.67 ± 11.98 µm) than both the PEEK CAD (108.00 ± 20.08 µm) and Press groups (108.00 ± 25.10 µm) (Zirconia framework crowns have a smaller vertical marginal gap than milled and pressed PEEK crowns. Crowns fabricated from zirconia, PEEK CAD, or PEEK Press frameworks and veneered with composite resin have comparable fracture resistance lower than the maximum biting force in the posterior region.Posterior crowns with zirconia frameworks are preferred over milled and pressed PEEK frameworks regarding margin adaptation, although all can safely survive the maximum occlusal forces without fracture. Recently, developments in dental materials and technologies have given rise to a huge boost in the fabrication of indirect dental restorations , 2. Comp3) and low modulus of elasticity (3–4 GPa) close to those of human bone [On the other hand, polyetheretherketone (PEEK) is a semicrystalline linear polycyclic aromatic polymer developed in 1978 . PEEK shman bone –16. All man bone .Different methods can be used to process PEEK. One option is to vacuum-press the material in a dental technical laboratory. PEEK utilized for this purpose is either in granular form or industrially prepressed pellets. Another choice is milling utilizing CAD/CAM technology, in which milled PEEK blanks are industrially pressed using predetermined conditions such as pressure, temperature, and time .Excellent optical and mechanical qualities have been made achievable by improvements in adhesive technology and newer composite resins. Composite resin veneering can be used to support and enhance ceramic crowns . In regaMarginal adaptation is crucial in determining how well a restoration performs over the long run. To prevent wear of the luting cement, a marginal adaptation value in clinical situations for ceramic restorations of up to 120 µm was considered acceptable . Poor maMoreover, the most frequent cause for replacing dental prostheses is fracture. Therefore, it is crucial to assess a dental material's fracture resistance before employing it as a long-term permanent restoration in different clinical conditions .The use of zirconia, pressed and milled PEEK crowns has been established in fixed prosthodontics. However, the performance of crowns regarding fundamental criteria of successful restorations, such as margin adaptation or fracture resistance, has not been adequately investigated in the literature. Therefore, this study aimed to assess the effect of the coping materials zirconia or PEEK with different techniques of fabrication, PEEK CAD or press, on the vertical marginal gap and fracture resistance of posterior crowns with composite veneering. The null hypothesis was that neither the material type nor the PEEK fabrication technique affects the restoration’s marginal adaptation or fracture resistance.n = 18) were considered adequate in this study and divided into three groups according to the type of material and technique of fabrication of the PEEK coping; zirconia, milled PEEK CAD, and PEEK press six samples each (n = 6). A study overview is shown in Fig. A power analysis test was conducted  based on the results of a previous study , and a s○C for 2 h in a sintering furnace . The milled wax patterns were transformed into PEEK by lost wax and heat pressing procedures. The wax patterns were sprued and invested with phosphate-bonded investment material . After preheating, PEEK granules  were pressed using a press device . Crowns were divested after cooling with the aid of a blasting device  utilizing 110 μm alumina particles at 3 bar pressure before finishing and polishing following the manufacturer’s instructions combining a rubber polisher with polishing paste.A mandibular first molar typodont tooth was fixed with the aid of a parallelometer  in a self-cured acrylic resin base  in an upright position. The top surface of the acrylic resin was 2 mm apical to the cervical line of the tooth. After the complete setting of the base, the tooth was prepared to receive an all-ceramic crown. The criteria of the preparation were a 1 mm deep chamfer finish line and a 1.5 mm occlusal clearance. A laboratory diamond abrasive bur with a round tip and 6° taper angle attached to a milling surveyor  was used for the axial preparation. A digital impression was produced by scanning the prepared tooth after spraying it with titanium dioxide powder using a dental lab scanner . Full anatomical crowns were designed using designing software  to have axial and occlusal dimensions of 1.5 mm followed by virtual reduction to attain 0.5 mm minimum thickness of the coping framework using digital cutback technique. The spacer thickness for cement was set at 50 µm starting 1 mm from the finish line margin. The designed files were imported to the 5-axis milling machine  for milling of six zirconia , six PEEK copings , and six wax patterns to be later employed for manufacturing the PEEK pressed group. The zirconia copings were then sintered according to the manufacturer’s instructions at 15302O3 powder at 2.5 bar and 3 cm distance. The HIPC composite veneers for all groups and PEEK frameworks were conditioned using PMMA and composite primer  and light cured for 90 s using bre lux Power light curing Unit 2  (intensity: 220 mW/cm2) at a wavelength between 370–500 nm for 90 s. Zirconia frameworks were conditioned after sandblasting using metal and ceramic primer  and cured for 90 s. Veneers were cemented to frameworks with dual-cure composite adhesive cement  and cured for 180 s. Excess material was removed, and samples were finished and polished using a Visio.lign finishing and polishing tool kit .The frameworks were individually scanned and superimposed with the full anatomical design to subtract the veneering parts that were later milled in high impact polymer composite (HIPC) , and a spacer of 50 µm was assigned for cement space between the framework and veneering Fig. . All fraThe vertical marginal gap was captured using a hand-held digital microscope with a built-in camera fitted on a precision microscopic stand  and connected to a personal computer using a magnification of 40X. Before initiating the measurements, the microscope's calibration instructions were accurately performed. The vertical gap was calculated as the distance between the finishing line's outermost margin and the restoration's most exterior cervical edge  at the sAll measurements and the analysis of all photos were conducted by the same researcher (M.E) for standardization purposes.The STL file of the digital impression captured previously for the prepared abutment was used to print a resin  abutment with the exact same dimensions using a 3D printer . Later and after post curing, the resin die was invested and cast to fabricate a cobalt-chromium metal tooth model. The metal die was fixed in a self-cured acrylic resin base  in an upright position. The crowns were checked on the die to ensure that they had the exact same fit as on the typodont prepared abutment. In the universal testing machine, each specimen from the three tested groups was placed individually on the metal die and held in place by the holder in the lower compartment of the machine before being loaded compressively at a crosshead speed of 1 mm/min. A vertically movable rod with a 5 mm-diameter semispherical head was positioned directly over the occlusal surface in the central fossa to ensure a uniform distribution of stresses. The value associated with the first break in the loaded specimen served as the failure load or fracture resistance value. As soon as the load dropped by 30% from the maximum load, the load at failure was confirmed and recorded in Newtons Fig. .Fig. 4FrThe data obtained from both vertical marginal gap distance measurements and fracture resistance testing were collected, tabulated, and then subjected to statistical analysis.p < 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.2.3 for Windows [Numerical data are presented as the mean, standard deviation (SD), median and interquartile range (IQR). Shapiro‒Wilk's test was used to test for normality. The homogeneity of variances was tested using Levene's test. Data were normally distributed, but the homogeneity assumption was violated in fracture resistance data, so they were analyzed using Welch one-way ANOVA followed by the Games-Howell post hoc test. Marginal gap values were analyzed using one-way ANOVA followed by Tukey’s post hoc test. The significance level was set at  Windows .p < 0.001). However, the results of intergroup comparisons of fracture resistance values presented in Table p = 0.06).Descriptive statistics for marginal gap values and fracture resistance are presented in Table Regarding the mode of failure analysis, all zirconia and PEEK CAD samples showed catastrophic fracture of the coping and veneering Figs.  and 8, wThe null hypothesis was partially accepted, as there was no significant difference between the fracture resistance of crowns fabricated from the tested framework materials. However, there was a significant difference between the tested groups regarding marginal gap distance, with zirconia samples having significantly lower gap values than the PEEK CAD and press groups.All this study’s vertical marginal gap values, however, fell within acceptable limits. According to the authors, vertical marginal gaps for fixed dental prostheses (FDPs) < 120 µm were considered clinically acceptable . Others To avoid the effects of uncontrolled finger pressure or overfilling the crown with cement, which may result in an uneven flow of cement with some axial walls having a thick layer and the opposite walls having a thinner layer, the assessment of marginal discrepancy was carried out in our study before cementation . For in Direct microscopic examination was implemented in this study as it was considered less time-consuming than other methods and less likely to lead to the accumulation of errors that may arise from many steps and ultimately affect the accuracy of results .In the present study, the mean marginal gap values were 48.67 ± 11.98 µm for the zirconia group, 108.00 ± 20.08 µm for the PEEK CAD group, and 108.00 ± 25.10 µm for the PEEK Press group. As fully sintered zirconia demonstrated marginal discrepancy values ranging between 60.4 and 110.1 µm, while partially sintered zirconia showed marginal discrepancy values between 24.6 and 65 µm, the results of this study were considered within the range established by previous studies –38.Zeighamie et al.  comparedBaran et al.  comparedMeshreky et al.  evaluateThe degree of a material's stiffness and its capacity for internal and marginal adaptability have been found to be positively correlated. The zirconia material has a bending strength of 1250 MPa, whereas high-performance polymers are known to have bending values equivalent to those of dentin. In light of these results, the zirconia group's improved marginal and internal adaptation in the current investigation can be attributed to the material's enhanced stability during milling compared to high-performance polymers .Moreover, these findings might be due to PEEK's semicrystalline structure, which includes fillers entrapped in a resin matrix yielding a greater marginal gap during manufacturing than zirconia, which has a polycrystalline structure .Our study results are not in agreement with Park JY et al.  and HossMostafa et al.  evaluateAdditionally, the impact of various manufacturing methods on the marginal precision of PEEK single-crown copings was examined by Attia et al. . The aveThe peripheral and internal fit of copings made of PEEK and zirconia were assessed by Beuer et al.  There waMakky et al.  assessedSokkary et al.  assessedIn one study , stereomRegarding fracture resistance, there was no significant difference between the fracture resistance of crowns fabricated from zirconia, PEEK CAD and press groups, with all showing higher fracture load than the maximum biting force (800 – 1000 N) . The optThe results could also be attributed to the physical and chemical structure dissimilarity of zirconia and veneering composite compared to PEEK substructure veneered with a similarly based polymer composite veneering .These findings were consistent with a previous study concluding that the composite veneered PEEK crown group recorded higher fracture resistance values at 1327.18 ± 44.03 N, followed by zirconia veneered with composite crowns (1196.94 ± 52.10. N), which is consistent with the results of the current study . AnotherOn the other hand, our study results disagree with those of Tartuk et al. , who comRegarding the mode of failure analysis, in a previous study , FDPs maThe validity of comparing the results of the present study and those obtained in prior investigations is hindered by factors including the wide range of manufacturing techniques, the use of different materials and designs of master models, different numbers of restoration units, number of sample sizes, the study design (in vitro or in vivo), different measurement sites for margin measurements, different die materials used in fracture testing and the use of different cement thickness values , 46.Future studies with aging by chewing simulation or thermocycling are needed since specimens in this study were not aged and considered among the limitations. Furthermore, clinical research is also required to back up the application of PEEK for long-term treatments.Zirconia framework crowns have less vertical marginal gap than PEEK regardless of its fabrication technique, with all falling within the clinically acceptable range of < 120 µm.The technique of fabrication of PEEK with milling or pressing did not affect the vertical marginal gap of posterior crowns.Crowns fabricated from zirconia, PEEK CAD, or PEEK Press frameworks and veneered with composite resin have comparable fracture resistance lower than the maximum biting force in the posterior region.Composite veneered crowns fabricated from zirconia and PEEK CAD fail by complete fracture of the coping and veneering, while PEEK Press copings survive the applied load and show fracture and separation of the veneering composite.


Zirconia, a crystalline oxide of zirconium, holds good mechanical, optical, and biological properties. The metal-free restorations, mostly consisting of all-ceramic/zirconia restorations, are becoming popular restorative materials in restorative and prosthetic dentistry choices for aesthetic and biological reasons. Dental zirconia has increased over the past years producing wide varieties of zirconia for prosthetic restorations in dentistry. At present, literature is lacking on the recent zirconia biomaterials in dentistry. Currently, no article has the latest information on the various zirconia biomaterials in dentistry. Hence, the aim of this article is to present an overview of recent dental zirconia biomaterials and tends to classify the recent zirconia biomaterials in dentistry. This article is useful for dentists, dental technicians, prosthodontists, academicians, and researchers in the field of dental zirconia. FurtherProper bonding between the zirconia restoration and the tooth is important for the longevity of the prosthetic restoration . ZirconiDental zirconia has increased over the past years producing wide varieties of zirconia for prosthetic restorations in dentistry. Although some researchers have studied zirconia and classified dental zirconia in the past,  the currArticles on advances in dental zirconia ceramic were searched from January 1989 to December 2022 using Google Scholar, MEDLINE/PubMed, Web of Science, and ScienceDirect resources. Research and review articles in the English language were only included in this review. A total of 79 articles were selected and included in this review. Editorials, Letters to the Editor, and Case Reports were excluded from this review.2O3) to zirconia stabilizes the tetragonal phase  in the crystal lattice. This doping of zirconia results in partially stabilized zirconia (PSZ) , cerium (Ce), calcium (Ca), magnesium (Mg), etc. to make it stable at room temperature . The addal phase . Followial phase . Yttria-ia (PSZ) .zirconia polycrystal) are of various types based on the yttria content:  is added to the zirconia to produce ceria in tetragonal stabilized zirconia (Ce-TZP).At present multilayer (M) zirconia has been introduced. Similarly, M3Y is highly translucent and M6Y is super highly translucent . Some suZirconia is a stable restorative biomaterial. Dental zirconia is resistant to acid erosive attacks in the mouth although some erosive agents may have a negative effect on the surface roughness . It has Zirconia has the highest hardness among the various restorative materials used in dentistry . Its fleThe fracture strength of a zirconia implant is influenced by its design, composition, and kind of abutment preparation . The 1-pZirconia is supposed to cause the opposing teeth to wear. But smooth and well-polished zirconia does not cause tooth wear. Abrasive wear on the occlusal part of zirconia restoration affects the opposing teeth or restoration . When thZirconia is an esthetic biomaterial, but its translucency is slightly less compared to the glass-ceramics. To maintain the translucency of the zirconia and glass-ceramic prostheses, suitable luting cement should be used . The addZirconia has greater radio-opacity compared to aluminum and titanium. This is due to its intrinsically high density and effective atoms which can obtain high-contrast radiographic images useful for diagnosis . Speed sin vivo  and found no cytotoxicity. Similarly, 2 and found that its wettability was substantially enhanced by oxygen plasma treatment for maintaining a stable hydrophilicity surface. Water droplets can wet the hydrophilic zirconia surface (low contact angle) and this wetting condition that is suitable for oil-water separation is achieved by engineering the surface chemistry and surface roughness characteristics  . ZirconiSince there are various ceramic materials in the market and it is often confusion regarding choosing the material. Hence, the authors would like to categorize the zirconia materials based on their composition, and an indication of the commercially available zirconia materials –5.Finally, this review article provides updated information on the various dental types of zirconia used in dentistry. As this review does not use the PICO method, this review can be extended to do a more extensive review following the PICOS method.Zirconia can be of various types based on the yttria content, uniform or hybrid composition, monochromatic or polychromatic, and monolayer or multilayer. Increased yttria content in zirconia results in higher translucency but reduces the strength. Zirconia with lower yttria content  has better mechanical properties and less translucency whereas 3Y-TZP (3 mole % Y-TZP) with increased yttria content  has more translucency but presents lower mechanical properties. Speed sintering of zirconia has resulted in higher flexural strength and regular sintering of zirconia has shown bigger gain sizes and more translucency.


Porcelain-veneered zirconia (PVZ) restorations are increasingly used due to their optimal esthetics and high strength. However, chipping of porcelain limits the application of PVZ restorations. The aim of this study was to assess the shear bond strength (SBS) of colored and sandblasted zirconia to ceramic veneers fabricated by the pressing and layering techniques. μm alumina particles (S), and (III) coloring (C). Each group was subsequently divided into two subgroups according to the porcelain-veneering technique: (I) layering (L) and (II) pressing (P). The specimens underwent 10,000 thermal cycles between 5 and 55°C, and their biaxial SBS was measured in an electromechanical universal test machine (0.5 mm/min with 2.5 kN load cell). The failure mode was also assessed under a stereomicroscope. Three samples were randomly selected from each subgroup (n = 18) for examination of zirconia-phase transformation by X-ray diffraction (XRD). Two-way and one-way ANOVA followed by the post hoc Tukey test were used to analyze statistical differences among the groups and subgroups (α = 0.05).  Sixty cubic zirconia specimens (10 × 10 × 2 mm) were assigned to three groups according to their surface treatment: (I) control, (II) sandblasting with 50 P < 0.01).  The sandblasted zirconia with press porcelain (SP) subgroup showed the highest (24.40 ± 8.16 MPa) and the colored zirconia with press porcelain (CP) subgroup showed the lowest (13.76 ±3.62 MPa) SBS. All failures were cohesive. Rate of phase transformation in layered porcelain was significantly lower than that in pressed porcelain ( The sandblasted group showed the highest and the colored group showed the lowest SBS; the layered group showed higher SBS than the pressed group. Application of all-ceramic restorations has greatly increased in the recent years due to the increasing attention to esthetics . The priSeveral parameters may affect the bond strength of zirconia to porcelain such as porcelain thickness , porcelaThe results regarding the technique of porcelain veneering on SBS are also conflicting. Ishibe et al.  and KanaThe crystalline structure of zirconia has three phases of monoclinic, cubic, and tetragonal. Several studies –22 conclConsidering all the above, literature is controversial regarding the effects of porcelain-veneering technique, extrinsic pigmentation (coloring) of zirconia, and its sandblasting on SBS, and phase transformation of PVZ restorations. Thus, the purpose of this study was to evaluate the effect of zirconia surface treatments (coloring and sandblasting) and porcelain-veneering techniques (pressing and layering) on SBS of zirconia to porcelain and phase transformation of zirconia. The null hypotheses tested in this study were (I) different surface treatments (sandblasting and coloring) would have no significant effect on SBS of zirconia to porcelain or phase transformation of zirconia, and (II) the veneering technique (pressing or layering) would have no significant effect on SBS and phase transformation of zirconia.Sixty cubic zirconia specimens (10 × 10 × 2 mm) were fabricated from VITA YZ T blanks. They were designed with a CAD/CAM machine and milled by Imes Icore 450i milling machine  according to Juntavee et al. .n = 20): (I) control group without any surface treatment, (II) sandblasting (S) with 50 μm alumina (Al2O3) particles, and (III) coloring (C) with VITA In-Ceram YZ coloring liquid. Before sintering, group C specimens were immersed in the coloring liquid for 2 min according to the manufacturer's instructions. Next, all specimens were sintered in a furnace  with this procedure: to reach 900°C in 10 min then 900 to 1530°C in 5 min and finally held in 1530°C for 120 min with standard cooling. After sintering, the S group specimens were sandblasted with 50 μm alumina (Al2O3) particles with 0.2 MPa pressure for 10 s at 10 mm distance.The milled zirconia specimens were randomly assigned to three groups (n = 10):Conventional layering technique with VITA VM9 by using a silicon index measuring 4 mm × 4 mm × 2 mm. For calibration of layered specimens, the layering process was performed by only one technician for all specimens.Pressed technique with VITA PM9: each zirconia specimen was weighed before and after wax-up to determine the required amount of PM9 porcelain. Then, the cubic wax index (designed with STL file output) measuring 4 mm × 4 mm × 2 mm was placed on the zirconia specimens and invested with VITA PM investment material with 10 mm distance from the ring walls. To remove the wax pattern, the invested ring was placed in an oven. After wax burnout, the rings were immediately transferred from the preheating oven to the press furnace. The porcelain was injected into the mold in DP3000 Ivoclar furnace .First, the milled zirconia specimens were cleaned with 10% isopropyl alcohol  in an ulAll specimens underwent thermocycling  for 10,000 cycles between 5 and 55°C with a dwell time of 20 s and a transfer time of 10 s.Fixed specimens underwent the SBS test in an electromechanical universal testing machine  with a 2.5 kN load cell and 0.5 mm/min crosshead speed . SBS calThe mode of failure was assessed under a stereomicroscope equipped with a digital camera  at ×16 magnification , and clan = 18). The remaining porcelain was removed with 11% hydrofluoric acid rubbed on the surface by a microbrush. The X-ray settings included 1.54 nm wavelength, 2θ = 26–38°, 40 kV, 30 mA, 0.04° step size, and 8 s time for each step .Data were analyzed by SPSS version 20 . Two-way ANOVA and Tukey test were used to analyze the effect of surface treatments and porcelain-veneering techniques on SBS and zirconia-phase transformation. One-way ANOVA followed by the Tukey test were used to analyze significant differences in each veneering group. Independent P < 0.01, t-test to analyze the effect of veneering technique on SBS in each treatment group, and one-way ANOVA was applied to analyze the effect of surface treatment on SBS in each veneering technique.According to two-way ANOVA, the interaction effect of porcelain-veneering technique and zirconia treatment on SBS was significant . One-way ANOVA showed a significant difference among surface treatments in the pressed veneering group (P < 0.01). Independent Stereomicroscopic examination showed cohesive failure in the veneering ceramic in all specimens in all groups.P < 0.01) but the effect of zirconia treatment on phase transformation was not significant ; next, each group was divided into two subgroups according to the porcelain-veneering technique (pressed and layered). The specimens were evaluated in terms of SBS, mode of failure, and zirconia-phase transformation.P > 0.05). Similarly, Kim et al. [μm alumina particles with 0.4 MPa pressure for 10 s for sandblasting. Also, Ghaffari et al. [μm alumina particles with 3.5 bar pressure for 5 s. Thus, it appears that sandblasting with larger alumina particles and higher pressure may increase the SBS. In a study by Okada et al. [Sandblasting and coloring of zirconia had no significant effect on SBS of zirconia to layered porcelain  in the present study. Thus, it may be concluded that the pressed veneering technique is more affected by the zirconia surface treatment; however, further studies are required to better elucidate this topic. Ebadian et al. [μm alumina particles and 0.4 MPa pressure and coloring had no significant effect on SBS of zirconia to pressed porcelain in comparison with the control group. This difference may be due to the fact that they did not perform thermocycling in their study. Variations in the brand of products used may also explain the differences in the results.Sandblasting and coloring of zirconia had a significant effect on SBS of zirconia to pressed porcelain (n et al.  showed tn et al.  stated tThe pressing and layering–veneering techniques in the control group had no significant effect on SBS. Porcelain-veneering techniques had a significant effect on SBS except in the control group in studies by Ishibe et al.  and KanaAll failures was cohesive within the porcelain in the present study, which was similar to the results of Ebadian et al.  and Roy With respect to zirconia-phase transformation, the present results indicated that the first null hypothesis of the study was accepted, since sandblasting had no significant effect on phase transformation of zirconia. Also Inokoshi et al.  and OkadAlso, coloring of zirconia specimens had no significant effect on phase transformation of zirconia. Similarly, Tuncel et al.  stated tIn terms of zirconia-phase transformation, the second null hypothesis was rejected since the layering–veneering technique caused significantly lower percentage of phase transformation. However, Juntavee et al.  reportedThe results of SBS and phase transformation percentage were not completely correlated with each other, but it should be noted that a significant difference was observed between the CP and CL groups in both SBS and zirconia-phase transformation. Therefore, it may be concluded that by increasing the percentage of zirconia-phase transformation from tetragonal to monoclinic, the SBS also decreases. However, more studies are needed in this regard.Considering the limitations of this study, further studies with a larger sample size are required to find possibly significant differences. Also, future studies should perform cyclic loading, and use different particle sizes for sandblasting and different zirconia and ceramic brands. Furthermore, crown-shaped specimens should be used in future studies to better simulate the clinical setting.Sandblasting and coloring of zirconia had no significant effect on zirconia-phase transformation.SBS in colored zirconia depends on the veneering technique.SBS in pressed veneering technique depends on the type of zirconia surface treatment.The layering veneering technique caused lower percentage of phase transformation.Considering the limitations of this in vitro study, the following results were obtained:Further studies are required to investigate the effect of different veneering techniques, specially the pressed technique, on biaxial strength of PVZ restorations, and the effect of different factors on phase transformation of zirconia. Also, the effect of these factors should be assessed in vivo to better understand the zirconia behavior.