An Investigation into the Use of a Single Component Self-etching Primer Adhesive System for Orthodontic Bonding: A Randomized Controlled Clinical Trial A randomised clinical trial to investigate bond failure rates using a self-etching primer. An in vivo investigation into bond failure rates with a new self-etching primer system. Six and 12 months' evaluation of a self-etching primer versus two-stage etch and prime for orthodontic bonding: a randomized clinical trial. Clinical bond failure rates of adhesive precoated self-ligating brackets using a self-etching primer. A comparative in vivo assessment of the long-term failure rate of 2 self-etching primers. Effect of saliva contamination on bracket failure with a self-etching primer: a prospective controlled clinical trial. A Randomized Clinical Trial Comparing ‘One-Step’ and ‘Two-Step’ Orthodontic Bonding Systems Eighteen-month bracket survival rate: conventional versus self-etch adhesive. Six-month bracket failure rate evaluation of a self-etching primer. Long-Term Clinical Evaluation of Bracket Failure with a Self-Etching Primer: A Randomized Controlled Trial A randomized, controlled clinical trial of one-step self-etching adhesive systems in non-carious cervical lesions. An 18-months' evaluation of self-etch and etch & rinse adhesive in non-carious cervical lesions Clinical performance of a self-etching adhesive at 18 months. Bond failure rates with a self-etching primer: a randomized controlled trial. Total-etch versus self-etch adhesive: effect on postoperative sensitivity. Six-month bracket survival with a self-etch adhesive.
Objective This study assessed the in vivo bond failure of the single component orthodontic self-etching primer system , Ideal 1 ( GAC Orthodontic Products ) and compared it with the conventional acid etching using a conventional 37 % o-phosphoric acid , rinsing and drying regimen when bonding stainless steel orthodontic brackets to enamel . Design Prospect i ve r and omized , controlled clinical trial . Setting Orthodontic Department , Bristol Dental School . Material and methods Twenty consecutive patients undergoing upper and lower fixed orthodontic treatment entered this cross-mouth control study . Diagonally opposite quadrants were r and omly allocated to either the self-etching primer group or the conventional etching group . A total of 339 teeth were bonded with Ideal 1 light-cured adhesive . Bond failures and locus of bond failure were then recorded at 1 , 6 and 12 months . Results Significantly more bond failures occurred at each of the 3 time intervals , 1 , 6 and 12 months , where the enamel was pretreated with the Ideal I self-etching primer , than when the enamel was treated with the conventional etchant , 37 % o-phosphoric acid . With the latter the cumulative bond failure rates were 3.0 , 5.3 and 14.8 % , respectively . With the self-etching primer the cumulative failure rates were 29.4 , 56.5 and 72.4 % . Conclusion The study found that enamel pre-treatment with the Ideal 1 self-etching primer system prior to orthodontic bonding results in an unacceptably high bond failure rate when compared with conventional enamel acid etching This clinical trial evaluated , over a 12-month period , the performance of brackets bonded to teeth etched and primed with Transbond Plus Self-Etching Primer ( SEP ) when compared with a conventional separate two-step etch and primer system .  Thirty-nine r and omly selected patients requiring fixed appliance therapy were entered into the study . R and om allocation of each etching system , along with a ' split-mouth cross-quadrant ' design was used . A total of 661 brackets were placed by two operators . The failure and survival rates of the brackets were determined for age and gender of the patients , each etching system , operator , mode of failure , tooth position in the dental arch , and number of manipulations prior to curing the adhesive . Statistical analysis showed that SEP had a significantly higher bond failure rate ( 11.2 per cent ) than the conventional etch and primer system ( 3.9 per cent ) at the P = 0.001 level . Cox 's proportional hazards regression showed the conventional etch and primer system to have a 60 per cent reduced chance of bracket failure over a 12-month observation period , while males had a 2.4 times increased risk compared with females . The predominant mode of failure was at the composite enamel interface for the SEP , while for the conventional etch and primer system , it was within the composite adhesive . No statistically significant differences were found for the failure rate with respect to the age of the patient , operator , tooth location , or the number of manipulations of the bracket . This in vivo study showed that brackets bonded using SEP had an increased clinical bond failure rate compared with the conventional , separate , etch and prime system Self-etching primers have recently been introduced to simplify the orthodontic bonding process . The aim of this study was to compare the effectiveness of such a product with conventional 2-stage etching and priming with 37 % o-phosphoric acid and a conventional unfilled primer .  Twenty consecutive patients having orthodontic bonds placed were selected to participate in this cross-mouth control study . Diagonally opposite quadrants were r and omly allocated to either the self-etching primer group or the conventional etching and priming group . A total of 364 teeth were bonded with a light-cured diacrylate adhesive ; bond failures were then monitored over 6 months . There were 20 bond failures ( 10.99 % ) in the self-etching primer group and 9 bond failures ( 4.95 % ) in the conventional etch and priming group over this period . The results were analyzed with the McNemar test and 95 % confidence interval . The difference between the failure proportions was -0.06 with an associated 95 % confidence interval of -0.121 to 0.001 . This study produced weak evidence to suggest that bond failures with a self-etching primer will be higher than those with conventional etching and priming . This increased likelihood of bond failure must be weighed against the time advantage of the self-etching primer when used at the initial bonding appointment The aim of the study was to compare the mean clinical chair-side time required for bracket bonding and the mean bond failure rate at 6 and 12 months of stainless steel brackets with a micro-etched base bonded with a light-cured composite using a self-etching primer ( SEP ) or a two-stage etch and prime system .  Fifty-one subjects who required upper and /or lower pre-adjusted edgewise fixed appliances were recruited in a single centre r and omized clinical trial . The trial was a single-blind design , involving a within-patient comparison of the two bonding systems with each patient r and omly allocated the two bonding systems for each side of the mouth ( all teeth except molars ) . The two bonding techniques used were st and ardized throughout the trial and all bracket bonding was performed by a single operator . Bonding time was recorded using a digital timer . The bond failure rate of a strictly paired sample was recorded at 6 and 12 months for each patient . The mean bracket bonding time per patient with the SEP was significantly less than that with the two-stage bonding system ( mean difference 24.9 seconds ; 95 per cent confidence interval 22.1 - 27.7 seconds ; paired t-test P < 0.001 ) . The overall bond failure rates at 6 and 12 months with the SEP were 0.8 and 1.6 per cent , respectively , and for the two-stage etch and prime 1.1 and 3.1 per cent , respectively . At 6 months , the mean bond failure rate per patient with the SEP was 0.81 per cent and with the two-stage bonding system 0.96 per cent ( P = 0.87 ; Wilcoxon signed rank test ) . At 12 months , the mean bond failure rate with the SEP per patient was 1.54 per cent and with the two-stage bonding system 2.78 per cent ( P = 0.33 ; Wilcoxon signed rank test ) . The mean bracket bonding time with the SEP per patient was significantly shorter than that of the two-stage bonding system ( P < 0.001 ) . The difference between the overall bond failure rate and the mean bond failure rate per patient for the two bonding systems was not statistically nor clinical ly significant at 6 and 12 months ( P = 1.00 and P = 0.125 , respectively ; McNemar 's test ) OBJECTIVE To comparatively assess the failure rate of adhesive precoated ( APC ) self-ligating metal brackets bonded with two different enamel surface preparation techniques : self-etching primer ( SEP ) and conventional two-step etch and primer method ( CM ) . MATERIAL S AND METHODS Fifty-seven patients with complete permanent dentition were included in this study . A total of 1140 APC self-ligating brackets ( 3 M Unitek , Monrovia , Calif ) were bonded using a split-mouth design . For each patient , SEP ( Transbond Plus SEP , 3 M Unitek ) and CM ( 37 % phosphoric acid ) were used in alternate quadrants . All brackets were bonded by the same investigator after pumicing and rinsing of all of the teeth . The number , site , and date of first-time bracket failures were monitored throughout orthodontic treatment ( mean , 22 months ) . The survival rates of the brackets were estimated by Kaplan-Meier and log-rank tests ( P < .05 ) . The adhesive remnant index was used to determine the bond failure interface . RESULTS The bond failure rates were 2.97 % and 2.18 % for the CM and SEP , respectively . No statistically significant difference in failure rates was found between the groups . The bond failure sites were predominantly at the enamel-adhesive interface in both groups . CONCLUSION This long-term in vivo study showed that the combined use of SEP and the APC bracket system can be used effectively for bonding brackets after pumicing the enamel surfaces in clinical orthodontics INTRODUCTION The purpose of this study was to comparatively assess the failure rate of brackets bonded with 2 self-etching adhesives after 14 months of treatment . METHODS Twenty-two patients with complete permanent dentitions , and similar treatment plans and mechanotherapies , were selected for the study . Four hundred twenty-three brackets were bonded by using a split-mouth design , with Transbond Plus Self-Etching Primer ( 3 M Unitek , Monrovia , Calif ) or One-Step Self-Etching Primer ( Reliance , Itasca , Ill ) . These self-etching primers were applied alternately so that they were equally distributed on the maxillary and m and ibular right and left quadrants . RESULTS Failure rates were recorded for 14 months and analyzed with the chi-square test at alpha = 0.05 level of significance . Overall total failure rates were 0.94 % , for Transbond Plus and 8.10 % for One-Step . Although significantly more failures were found for the m and ibular arch , no difference was identified in failure rate between anterior and posterior teeth . The results of this study suggest that care should be taken in ensuring the compatibility of retainers with adhesives INTRODUCTION The aim of this study was to evaluate in vivo the effect of saliva contamination at different stages of the bonding procedure on the bond failure rate and the adhesive remaining on teeth after debonding brackets bonded with a hydrophilic self-etching primer ( Transbond Plus self-etching primer [ TSEP ] , 3 M Unitek , Monrovia , Calif ) . METHODS This was a prospect i ve controlled clinical trial . The sample consisted of 46 patients with similar treatment plans and mechanotherapies . Stainless steel brackets ( n = 531 ) were bonded with TSEP . The patients were divided into 2 groups : contamination with saliva before TSEP application and contamination with saliva after TSEP application . In both groups , saliva was applied in a split-mouth design . Diagonally opposite quadrants were allocated to either the contaminated group ( contamination before [ 153 teeth ] or after [ 115 teeth ] TSEP application ) or to the uncontaminated control group ( 263 teeth ) . Recording of failed brackets involved only first-time failures , and the observation period was a minimum of 6 months . RESULTS The chi-squared test showed no significant differences ( P = 0.11 ) in bracket failures between the groups . Kaplan-Meier survival analysis detected no significant differences in the survival rates between the 3 groups ( P = 0.51 ) . Most bond failures occurred during the first 3 months . In all 3 groups , the adhesive remaining on teeth after debonding tended to be less than half . CONCLUSIONS These findings suggest that saliva contamination before or after application of self-etching primer does not increase the clinical risk of bond failure Objective The primary objective of this prospect i ve clinical trial was to assess the clinical bond failure rates of orthodontic brackets bonded using a self-etching primer ( SEP ) , compared with brackets bonded using a conventional acid-etched technique with control adhesive ( Transbond ™ ) . A secondary aim was to investigate whether characteristics of the operator , patient or tooth bonded had any influence on bracket failure . Design Single-centre r and omized controlled clinical trial . Thirty-four patients were bonded , each being r and omly assigned to either the test or control adhesive . Setting NHS Hospital Orthodontic Department , Chester , UK . Subjects Orthodontic patients requiring fixed appliance treatment . Main outcome measures Bond failure . Main outcome results Failure rates over the initial 6-month period were 2.0 % ( Transbond ™ ) and 1.7 % ( SEP ) with no statistically significant difference between the two groups . Over the duration of the fixed appliance treatment , bond failure rates increased , but remained acceptable at 7.4 % ( TB ) and 7.0 % ( SEP ) , respectively . When operator , patient and tooth characteristics were analysed , only the bracket location was found to be significant . Maxillary brackets were more likely to fail than m and ibular brackets ( RR 0.47 % ; 95 % CI 0.22 , 1.03 ) . The failure rate for brackets in our study was low when compared with previous studies . Conclusions Both the acid-etched control and self-etching primer in combination with adhesive pre-coated brackets were successful for clinical bonding . Their combined failure rate was lower than that reported in similar trials The aim of this study was to evaluate , over an 18-month period , the clinical performance of a self-etch adhesive [ Transbond Plus Self Etching Primer ( SEP ) , 3 M Unitek ] compared with a conventional adhesive that employs the etch- and -rinse approach ( Transbond XT , 3 M Unitek ) . One operator , using the straight-wire technique , bonded 567 metallic brackets to the teeth of 30 patients ( age range 12 - 18 years ) in a way that patients acted as self-control . The brackets were bonded following the manufacturers ' instructions except for the fact that the self-etch system was brushed for a longer time than recommended ( 10 - 15 seconds ) since previous investigations have reported that prolonged application times can improve the bonding efficacy of self-etch systems to enamel . The failure modes were visually classified into : adhesive-enamel , adhesive-bracket , and cohesive failure . The survival rates of the brackets were estimated by Kaplan-Meier and log-rank test ( P < 0.05 ) . The failure rates of the self-etch and conventional adhesives were 15.6 and 17.6 per cent , respectively . No significant differences in the survival rate were observed between the material s ( P > 0.05 ) . Most of the failures were cohesive and at the adhesive-enamel interface . There was no difference in the fracture debonding mode . These findings indicate that Transbond Plus SEP can be safely used for orthodontic brackets since the survival rates are similar to the conventional Transbond XT The aim of this study was to compare the clinical performance of a self-etching primer ( SEP ) with a conventional two-step etch and primer [ conventional method ( CM ) ] . The chair time required for bonding was also evaluated . Thirty-seven patients ( 14 males and 23 females ) with a mean age of 16 years 5 months were included in the study . Six hundred and seventy-two brackets were bonded by one operator using a split-mouth design , with either SEP ( Transbond Plus ) or CM ( Transbond XT ) . Bracket failure rates were estimated with respect to bonding procedure , dental arch , type of tooth ( incisor , canine , and premolar ) , and gender . The results were evaluated using the chi-square test . The survival rate of the brackets was estimated with Kaplan-Meier analysis . Bracket survival distributions with respect to bonding procedure , dental arch , type of tooth , and patient gender were compared with a log-rank test . Bond failure interface was determined with the adhesive remnant index ( ARI ) . The failure rates were 0.6 per cent for both bonding procedures . The failure and survival rates did not show significant differences between the bonding procedures , upper and lower dental arches , or gender . However , premolar brackets displayed a higher bond failure rate and a lower survival rate than incisor and canine brackets ( P < 0.05 ) . The mean bracket bonding time per tooth with SEP was significantly shorter than with CM ( P < 0.001 ) . No significant difference was observed for the ARI scores ( P > 0.05 ) . The results of this in vivo , r and omized , cross-mouth clinical trial demonstrated a high survival rate with Transbond Plus . This finding indicates that  SEP  can be effectively used for bonding of orthodontic brackets Objective A long-term comparison of the failure rates of orthodontic brackets bonded with either a self-etching primer ( SEP ) or conventional etch and primer ( AE ) . Design Prospect i ve r and omized controlled clinical trial . Setting UK district general hospital with one operator , 2003–6 . Participants Hospital waiting list patients needing fixed appliances ( n=60 ) . Method  Experimental ( SEP ) group patients ( n=30 ) received pre-adjusted edgewise brackets ( n=438 ) bonded with Transbond Plus following manufacturer 's instructions .  Control ( AE ) group patients ( n=30 , brackets n=433 ) were bonded using a 15-second conventional etch and primer ( Transbond XT ) . In both groups brackets were light-cured for 20 seconds . First-time bond failures were recorded with the time of failure . Bracket bonding time was recorded . All patients were followed to the end or discontinuation of treatment . Results Bracket failure rates : SEP=4.8 % , AE=3.5 % , P=0.793 . Mean placement time per bracket ( seconds ) : SEP=75.5 ( ±6.7 ; 95 % CI=72.9 , 78.0 ) , AE=97.7 ( ±9.1 ; 95 % CI=94.3 , 101.2 ) P=0.000 . Conclusion There was no difference in the failure rates of brackets bonded with either Transbond Plus SEP or conventional AE using Transbond XT paste . Bonding with SEP was significantly faster than using conventional AE PURPOSE To evaluate the clinical effectiveness of two different one-step self-etching adhesives . METHODS Two single-step self-etching adhesive systems , Clearfil Tri-S Bond and G-Bond , were evaluated . As a control , a two-step self-etching adhesive system , Clearfil SE Bond , was used . The teeth to be restored were r and omly assigned . The resin composite used to restore the teeth was Clearfil AP-X. The three adhesive systems were evaluated by Modified USPHS at baseline , 3 months , 6 months , and 12 months . The evaluation consisted of retention rate , color match , marginal discoloration ( interfacial staining ) , marginal adaptation ( integrity ) , wear , post-operative sensitivity , caries recurrence , and other failures . Changes over time and across groups were evaluated statistically using generalized estimating equations . RESULTS During the 12-month study period , no statistical differences were observed among the three groups ( P > 0.05 ) in retention rate , color match , marginal discoloration ( interfacial staining ) , marginal adaptation ( integrity ) . No wear , post-operative sensitivity , caries recurrence , or other failures were detected in any groups . The two one-step self-etching adhesives tested showed good clinical performance at the end of 12 months Objective . In this intra-individual comparison ( an 18-months ' r and omized , controlled prospect i ve study ) , we evaluated the clinical performance of one self-etch and one “ etch & rinse ” adhesive in non-carious cervical lesions . Methods . Twenty-five patients with at least two pairs of similar-sized non-carious cervical lesions participated . Seventy-eight restorations were placed ; 39 with etch & rinse ( Single-Bond ) and 39 with self-etch ( Adper Prompt ) . Both adhesives were combined with the microfilled resin composite Filtek-A110 . The restorations were evaluated at baseline , 6 , 12 , and 18 months according to slightly modified USPHS criteria . Statistical differences between the adhesives was tested with McNemar 's test and clinical degradation over time for each material with the Fisher exact test ( α=0.05 ) . Results . Thirty pairs were evaluated at 12 and 18 months . Two self-etch restorations were lost after 18 months . Nine Adper Prompt and four Single-Bond restorations scored bravo for marginal adaptation at 18 months ( p<0.05 ) . Nine Adper Prompt and three Single-Bond restorations scored bravo for marginal discoloration ( p<0.05 ) . Conclusions . Both adhesive systems showed acceptable clinical retention rates according to the ADA full acceptance criteria for enamel-bonding systems in class V non-carious lesions . The self-etch adhesive showed a faster progressive marginal degradation PURPOSE To test the null hypothesis that beveling and /or etching enamel would not affect the 18-month clinical performance of the self-etching adhesive Clearfil SE Bond ( CSEB ) in noncarious cervical lesions ( NCCL ) . METHODS With Institutional Review Board approval , 34 patients were enrolled in this study . A total of 120 NCCL was selected and assigned to four groups : ( 1 ) CSEB was applied without any cavity preparation ; ( 2 ) CSEB was applied after beveling enamel ; ( 3 ) CSEB was applied after etching enamel for 15 seconds with 35 % phosphoric acid ; ( 4 ) CSEB was applied after beveling and etching enamel . A microfilled composite resin was used for all restorations . RESULTS At 6 months after initial placement , 120 restorations ( a 100 % recall rate ) were evaluated . At 18 months , 87 restorations ( a 72.5 % recall rate ) were available for evaluation . A survival rate of 100 % was measured for all groups at both 6 and 18 months . Sensitivity to air decreased significantly only for Group 3 ( no bevel+acid etch ) from baseline to 18 months without statistical changes from 6 months to 18 months . None of the other parameters result ed in significant differences for any of the four groups . However , when data were pooled , both the overall marginal discoloration and the overall marginal adaptation were significantly worse at 18 months than at baseline , while sensitivity to air decreased significantly from baseline to 18 months . The 18-month survival rate of the self-etching adhesive Clearfil SE Bond was not improved by enamel bevel or by enamel etching . Both overall marginal adaptation and overall marginal discoloration were worse at 18 months than at baseline . INTRODUCTION The purpose of this clinical trial was to evaluate over a 12-month period the performance of a self-etching system ( SEP ) ( Transbond Plus SEP , 3 M Unitek , Monrovia , Calif ) compared with a conventional multi-step system ( TBXT ) ( Transbond XT , 3 M Unitek ) . METHODS Twenty-eight r and omly selected patients were included in this study . They were r and omly assigned to either the TBXT or the SEP group . A total of 548 brackets were bonded according to the manufacturer 's instructions with Transbond XT adhesive paste ( 3 M Unitek ) . The survival rates of brackets were estimated with the Kaplan-Meier analysis . Bracket survival distributions for bonding procedure , tooth location , dental arch , and patient sex were compared with the log-rank test . RESULTS The failure rates of the TBXT and SEP groups were 4.78 % and 6.88 % , respectively . No significant differences in the survival rates were observed between the bonding procedures ( P = 0.311 ) . When tooth location , dental arch , and sex were analyzed , only tooth location was significant . Posterior brackets were more likely to fail than anterior brackets ( P = 0.013 ) . CONCLUSIONS Both systems had low bond failure rates and are adequate for orthodontic bonding needs BACKGROUND Self-etching adhesives are believed to prevent postoperative sensitivity when used under posterior resin-based composite restorations . The authors tested a twofold hypothesis : a self-etch , or SE , adhesive would result in less postoperative sensitivity than a total-etch , or TE , adhesive ; an SE adhesive would result in poorer enamel marginal integrity than a TE adhesive . METHODS Patients were selected on the basis of requiring Class I and II restorations in molars and premolars . The authors placed 30 restorations with the SE material ( Clearfil SE Bond , Kuraray America , New York ) and 36 restorations with Prime & Bond NT ( Dentsply Caulk , Milford , Del. ) , which uses 34 percent phosphoric acid to etch enamel and dentin simultaneously . Preparations were of st and ard design , with all margins in enamel without beveling . Upon rubber dam isolation , the authors conditioned the enamel and dentin walls with the self-etching primer ( for Clearfil SE Bond ) or etched with the proprietary 34 percent phosphoric acid ( for Prime & Bond NT ) , followed by application of the corresponding dentin adhesive . Teeth were restored with the proprietary hybrid resin-based composite indicated for posterior restorations : Clearfil AP-X for Clearfil SE Bond or Esthet-X Micro Matrix Restorative for Prime & Bond NT . The restored teeth were evaluated preoperatively and at two weeks , eight weeks and six months postoperatively for sensitivity to cold ( ice ) , air and masticatory forces , as well as for marginal discoloration . RESULTS Analysis of variance revealed no statistically significant differences in postoperative sensitivity between the SE and TE material s at any recall time . Marginal discoloration was rated as " absent " for all restorations at six months . Only one tooth displayed sensitivity to occlusal forces at six months . CONCLUSION The SE adhesive did not differ from the TE adhesive in regard to sensitivity and marginal discoloration . CLINICAL IMPLICATION S Postoperative sensitivity may depend on the restorative technique rather than on the type of dentin adhesive used OBJECTIVE To evaluate , over a 6-month period , the clinical performance of a self-etch adhesive ( Transbond Plus Self-Etching ) compared with a conventional adhesive that uses the etch and rinse approach ( Transbond XT ) . MATERIAL S AND METHODS One operator , using the straight-wire technique , placed 567 metallic brackets in 30 patients ( age range 12 - 18 years ) such that homologous teeth from the same arch received different material s. The brackets were bonded following the manufacturer 's instruction except for the fact that the self-etch system was brushed for a longer time than recommended ( 10 - 15 seconds ) . The failure modes were visually classified into three modes : adhesive-enamel , adhesive-bracket , and cohesive failure . The survival rate of the brackets was estimated by Kaplan-Meier and log-rank test ( P < .05 ) . RESULTS The failure rates of the conventional and self-etch  [ corrected ] adhesives  were 10.6 % and 7.4 % , respectively . The failure rate of the conventional system was 0.43 [ corrected ] times greater than that of the self-etch system . The self-etch adhesive showed a higher survival rate compared with the conventional system ( P < .05 ) . Most of the failures were cohesive and at the adhesive-enamel surface . No difference in the fracture debonding mode was observed for the material s. CONCLUSIONS These findings indicate that the self-etch Transbond Plus Self-Etching can be safely used for orthodontic brackets because it provides higher survival rates than does the conventional Transbond XT
There was insufficient evidence to assess the effect of bonding modality on demineralization rates .
CONCLUSIONS There is weak evidence indicating higher odds of failure with self-etch primer than acid etch over 12 months in orthodontic patients , and there is strong evidence that a self-etch primer is likely to result in a modest time savings ( 8 minutes for full bonding ) compared with acid etch
INTRODUCTION The use of self-etch primers has increased steadily because of their time savings and greater simplicity ; however , overall benefits and potential disadvantages and harms have not been assessed systematic ally .
In this study , we review ed r and omized controlled trials to assess the risk of attachment failure , bonding time , and demineralization adjacent to attachments between 1-stage ( self-etch ) and 2-stage ( acid etch ) bonding in orthodontic patients over a minimum follow-up period of 12 months .