In situ gelling drug delivery systems for periodontal anaesthesia.
In this thesis local anaesthetic formulations based on PEO-PPO-PEO block copolymers (PEO and PPO being poly(ethylene oxide) and poly(propylene oxide), respectively) or nonionic cellulose ethers undergoing temperature- or dilution-induced thickening were investigated. The aim of the work was to develop formulations which can be easily administered to the periodontal pocket, stay at the application site, give a fast onset of anaesthesia and have a duration sufficient to perform periodontal scaling procedures. Emulsions, (mixed) micellar solutions and microemulsions fulfilling the requirements stated above were achieved by combining the active ingredients lidocaine and prilocaine with the nonionic block copolymers Lutrol® F127 and Lutrol® F68. The critical micellisation and gelation temperatures of the systems were found to be interconnected and influenced by the total polymer concentration and the polymer mixture composition, as well as the presence of cosolutes and pH. A low-viscous isotropic phase that turns into a high-viscous hexagonal phase as the water content increases was found by combining Lutrol® F68, water, a eutectic mixture of lidocaine and prilocaine and Akoline MCM. The system has a slower release rate compared to the microemulsion formulation which might make it suitable for indications where a longer duration is needed. Finally, a temperature-induced gelling system was achieved by adding lidocaine and prilocaine to mixtures of ethyl(hydroxyethyl)cellulose (EHEC) and sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB) or myristoylcholine bromide systems at, or just below, the surfactant concentration found to give a maximum viscosity increase at room temperature. In particular, the myristoylcholine bromide system may be interesting considering its antibacterial properties and biodegradability.
Oral mucosal analgesia quantitatively assessed by argon laser-induced thresholds and single-evoked vertex potentials.
The aim of this study is to quantitate the efficacy of a new topical anesthetic applied to the oral mucosa. Nociceptive pinprick thresholds and single-evoked vertex potentials (VP) elicited by high-intensity argon laser stimuli are used as measures of analgesia. After 5 minutes of occlusion (Orahesive Oral Bandages, ConvaTec) with a eutectic mixture of local anesthetics (EMLA cream, Astra), nociceptive pinprick thresholds on the tongue and gingiva are higher than those taken during nonocclusion. In a double blind-placebo controlled experiment, VPs were elicited every 1 minute for 19 minutes by single laser stimuli applied to the mucosa of the lower lip. After occlusion with EMLA cream for 3 minutes, VPs were significantly reduced when compared to those with placebo cream. One minute after removal of the EMLA cream, the spectral power of the single-evoked VP decreased significantly by 63.3%, the root-mean-square amplitude decreased by 42.7%, and the subjective pain perception (estimated on visual analogue scales) decreased by 88%. A significant reduction in single-evoked VPs was detected until 13 minutes after the removal of the EMLA cream. Oral mucosal analgesia may be quantitated by argon laser-induced nociceptive pinprick thresholds and single-evoked VPs.
Numerical Simulation of Induction Heating Process of Continuous Casting Slab
Compared with traditional blazing furnace, the Continuous Casting-Direct Rolling is an advanced manufacturing steel technology, which can reduce energy waste, decrease pollution and enhance efficiency. The characteristics of steels during induction heating are complex, the change of material properties with temperature makes exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite difference analysis) is selected to numerically model the induction heating process in this paper. The mathematic model coupling with electromagnetic field and thermal field was established, and it was solved by finite difference method (FDM), thus the slab temperature distribution and its variation with time were obtained, and the characteristics in whole induction heating process were studied. To validate the program feasible, the results were evaluated and compared with experiment results, which showed that the simulation results are reliable and effective. The skin effect in heating process from the two results was studied and demonstrated, the temperature change caused by different parameters such as the induced power intensity and the corner radian were also presented, which indicate that the slab temperature can be heated uniformly through adjusting these parameters, thus the continuous casting slab can meet the rolling requirement.