Shear bond strength after multiple bracket bonding with or without repeated etching

The purpose of the study was to measure the in vitro shear bond strength (SBS) of metal brackets after multiple bonding and debonding with and without repeated etching. One hundred and twenty extracted premolars were divided into three equal groups. In group 1, the brackets were bonded and debonded three times with repeated enamel etching and in groups 2 and 3 without repeated etching. In group 2, all composite remnants were removed before bonding, while in group 3, the remnants were levelled. Analysis of variance was used to determine significant differences in SBS with Bonferroni adjustment for the multiple testing procedures. The results showed that in group 1, the mean SBS was 11.69 MPa (SD 2.65) at the first, 14.30 MPa (SD 2.69) at the second, and 12.19 MPa (SD 2.26) at the third debonding. In group 2, SBS decreased from 12.57 MPa (SD 2.54) to below 8.0 MPa. In group 3, SBS remained constant from the first (11.93 MPa; SD 2.14) to the second (12.06 MPa; SD 1.65) debonding and only decreased significantly to 9.74 MPa (SD 1.80) at the third debonding. Less composite remained on the teeth after each debonding sequence. This was characterized by a shift from adhesive remnant index (ARI) scores 2 and 3 after the first debonding to ARI scores 1 and 2 after the second debonding to predominantly scores 0 and 1 after the third debonding. After bracket loss and levelling of composite remnants, the SBS is sufficient for application of orthodontic forces. Repeated etching may involve a higher risk of enamel tear-outs during debonding.     

不同再粘接方法对托槽粘接效果的影响

目的评价托槽再粘接过程中酸蚀对再粘接效果的影响,比较传统两步法和自酸蚀一步法对再粘接效果的影响。方法收集40颗由于正畸治疗需要拔除的上颌第二前磨牙,随机分成4组。分别运用传统两步法(组1和组2)和自酸蚀一步法(组3和组4)进行首次托槽粘接。然后再去托槽,进行牙面处理,各组分别用相同的粘接剂重新粘接,其中组2和组4粘接前无酸蚀。再粘接后24h,对40颗牙进行剪切粘接强度(SBS)以及粘接剂剩余指数(ARI)的检测,并在扫描电镜下对牙釉质面进行观察。结果按组1-组4的顺序,其平均SBS值分别为14.18、6.57、11.90和5.91 MPa。其中组1与组2、组3与组4之间的差异有统计学意义(P<0.05);而组1与组3、组2与组4之间无统计学差异(P>0.05)。ARI指数在组1与组2之间差异具有统计学意义(P<0.05);其它各组间无统计学差异(P>0.05)。扫描电镜照片显示:组1与组2的釉质面上有大面积以及较深的沟裂;组3与组4釉质上有相对较浅的小凹。结论在本试验条件下:①再粘接过程中未经酸蚀也可获得临床所需的粘接强度,且牙釉质面比再次酸蚀者破坏范围相对较小;②传统两步法与自酸蚀一步法所获的托槽再粘接强度以及粘接剂剩余指数无明显差异。     

Effects of a fluoride-containing casein phosphopeptide-amorphous calcium phosphate complex on the shear bond strength of orthodontic brackets

The purpose of this study was to investigate the effects of enamel pre-treatment with a new fluoride-containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) complex on the shear bond strength (SBS) of brackets bonded with etch-and-rinse or self-etching adhesive systems. The material comprised 66 extracted human premolars randomly divided into six equal groups with respect to the enamel pre-treatment and adhesive system employed: 1. No pre-treatment and brackets bonded with the etch-and-rinse adhesive system (Transbond XT). 2. Pre-treatment with fluoride-containing CPP-ACP paste (MI Paste Plus) and Transbond XT. 3. Pre-treatment with non-fluoride CPP-ACP paste (MI Paste) and Transbond XT.4. No pre-treatment and brackets bonded with the self-etching adhesive system (Transbond Plus). 5 and 6. Enamel pre-treated as for groups 2 and 3, respectively, and the Transbond Plus. Bonded specimens were subjected to thermal cycling (×1000) before SBS testing. The residual adhesive on the enamel surface was evaluated after debonding with the adhesive remnant index (ARI). Data evaluation was made using one-way analysis of variance and Tukey test for SBS results, and Kruskal-Wallis test for ARI results. The results showed that enamel pre-treatment with either fluoride or non-fluoride CPP-ACP paste had no significant effect on the SBS of the self-etching adhesive system (P > 0.05). Enamel pre-treatment with non-fluoride CPP-ACP in group 3 significantly reduced the SBS of the etch-and-rinse adhesive (P < 0.001), while pre-treatment with fluoride-containing CPP-ACP paste (groups 2 and 5) did not affect debonding values (P > 0.05). The fluoride-containing CPP-ACP did not compromise the SBS of brackets bonded with the tested etch-and-rinse and self-etching systems, but its non-fluoride version significantly decreased the SBS of the etch-and-rinse adhesive system.     

An in vitro comparison of the shear bond strength of a resin-reinforced glass ionomer cement and a composite adhesive for bonding orthodontic brackets

The shear bond strength (SBS) of a light-cured, resin-reinforced glass ionomer and a composite adhesive in combination with a self-etching primer was compared after different setting times to evaluate when orthodontic wires could be placed. Additionally, the fracture site after debonding was assessed using the Adhesive Remnant Index (ARI). Eighty freshly extracted human premolars were used. Twenty teeth were randomly assigned to each of four groups: (1) brackets bonded with Transbond XT with a Transbond Plus etching primer and debonded within 5 minutes; (2) brackets bonded with Fuji Ortho LC and debonded within 5 minutes; (3) brackets bonded as for group 1 and debonded within 15 minutes; (4) brackets bonded as for group 2 and debonded within 15 minutes. The SBS of each sample was determined with an Instron machine. The mean SBS were, respectively: (1) 8.8 +/- 2 MPa; (2) 6.6 +/- 2.5 MPa; (3) 11 +/- 1.6 MPa and (4) 9.6 +/- 1.6 MPa. Interpolating the cumulative fracture probability by means of a Weibull analysis, the 10 per cent probabilities of fracture for the groups were found to be attained for shear stresses of 6.1, 3.1, 8.3 and 7.1 MPa, respectively. Chi-square testing of the ARI scores revealed that the nature of the remnant did not vary significantly with time, but the type of bonding material could generally be distinguished in leaving more or less than 10 per cent of bonding material on the tooth. After debonding, the Transbond system was likely to leave adhesive on at least 10 per cent of the bonded area of the tooth. The present findings indicate that brackets bonded with either Transbond XT in combination with Transbond Plus etching primer and Fuji Ortho LC had adequate bond strength at 5 minutes and were even stronger 15 minutes after initial bonding.     

不同处理方法对托槽再黏结强度的影响

目的:比较不同处理方法对金属托槽再黏结强度的影响。方法:选择40颗离体前磨牙为实验对象,随机分为4组。粘结托槽后,选择3组剥离托槽,采用磨除、烧灼、喷砂3种不同托槽底板处理后予以再次黏结,经体外pH循环30 d后,测定托槽的抗剪切强度。采用SPSS 13.0软件包对所得数据进行单因素方差分析。另选取试样通过扫描电镜观察托槽底板的形态及结构。结果:4组间有显著差异,托槽烧灼再黏结组与其他各组间有显著差异,其余各组两两相比,均无显著性差异。结论:托槽底板残留黏结剂经磨除或喷砂处理,可获得与初次黏结相近的黏结强度。     

Evaluation of failure characteristics and bond strength after ceramic and polycarbonate bracket debonding: effect of bracket base silanization

The objectives of this study were to evaluate the effect of silanization on the failure type and shear-peel bond strength (SBS) of ceramic and polycarbonate brackets, and to determine the type of failure when debonded with either a universal testing machine or orthodontic pliers. Silanized and non-silanized ceramic and polycarbonate brackets (N = 48, n = 24 per bracket type) were bonded to extracted caries-free human maxillary central incisors using an alignment apparatus under a weight of 750 g. All bonded specimens were thermocycled 1000 times (5-55 degrees C). Half of the specimens from each group were debonded with a universal testing machine (1 mm/minute) to determine the SBS and the other half by an operator using orthodontic debonding pliers. Failure types of the enamel surface and the bracket base were identified both from visual inspection and digital photographs using the adhesive remnant index (ARI) and base remnant index (BRI). As-received ceramic brackets showed significantly higher bond strength values (11.5 +/- 4.1 MPa) than polycarbonate brackets [6.3 +/- 2.7 MPa; (P = 0.0077; analysis of variance (ANOVA)]. Interaction between bracket types and silanization was not significant (P = 0.4408). Silanization did not significantly improve the mean SBS results either for the ceramic or polycarbonate brackets (12.9 +/- 3.7 and 6.3 +/- 2.7 MPa, respectively; P = 0.4044; two-way ANOVA, Tukey-Kramer adjustment). There was a significant difference between groups in ARI scores for ceramic (P = 0.0991) but not polycarbonate (P = 0.3916; Kruskall-Wallis) brackets. BRI values did not vary significantly for ceramic (P = 0.1476) or polycarbonate (P = 0.0227) brackets. Failure type was not significantly different when brackets were debonded with a universal testing machine or with orthodontic debonding pliers. No enamel damage was observed in any of the groups.     

不同正畸粘接系统在托槽再粘接中的应用评价

目的：检测使用不同正畸粘接系统再粘接托槽对其剪切粘接强度的影响,以探讨提高临床再粘接效率的方法。方法：选择60颗正畸减数的恒双尖牙,依据不同粘接系统随机分为3组：津京釉质粘接剂（A组）、TransbondXT光固化粘接系统（B组）及Transbond自酸蚀粘接系统（C组）。所有样本均先用津京釉质粘接剂粘接托槽,24h后去除托槽重新粘接新托槽,测量3组托槽再粘接的剪切强度及粘接剂残留指数（AdhesiveRemnantIndex,ARI）。结果：3组托槽再粘接剪切强度分别为（8．615±2．460）MPa、（8．807±1．801）MPa及（8．144±3．023）MPa,组间剪切强度差异无显著性;ARI评分表明：C组牙面上残留的粘接剂明显少于其他两组。结论：采用自酸蚀粘接系统再粘接托槽的剪切强度与其它两种粘接系统相当,并且去除托槽后牙面残留粘接剂较少。     

树脂修饰化玻璃离子托槽粘结剂粘结强度的体外研究

目的：评估一种树脂修饰化的玻璃离子托槽粘结剂在牙面不同处理方式和环境下的两次粘结后的剪切强度情况。方法：将新近拔除的105颗上颌第一前磨牙随机均分成7组,按照说明书的要求完成托槽的粘结。对照组牙面用37%的磷酸处理后,用光固化复合树脂粘结剂（3M,Transbond XT）粘结。其它6组牙面分别在37%的磷酸、GC处理剂（GC Self-Conditioner）、和不做任何处理的条件下,分别在干燥和湿润的环境下用树脂修饰化的玻璃离子（RMGIC;Fuji ORTHO LC,GC Corporation,Tokyo,Japan）粘结,所有牙齿均选用同种托槽。托槽粘结24 h后,在万能测力机下以1 mm/min的速度卸载,并记录下数值。除去牙面和托槽底面多余粘结剂后,重复上述过程。每次卸载后检查牙釉质损坏情况。结果：对照组两次剪切强度有较小的差异,其它GC玻璃离子粘结剂组两次剪切强度没有统计学意义。GC粘结剂不做任何处理组在干燥和湿润的环境下其剪切强度存在明显的差异。干燥环境下,37%的磷酸和GC处理剂处理后,GC粘结剂组两次卸载后的牙釉质均出现不同程度的釉裂或釉质脱落。结论：这种树脂修饰化的玻璃离子粘结剂可以在多种条件下用于托槽的粘结。     

Early shear bond strength of a one-step self-adhesive on orthodontic brackets

OBJECTIVE: The purpose of this study was to determine whether a self-adhesive universal cement, RelyX Unicem (3M ESPE, Seefeld, Germany), can be used successfully to bond orthodontic brackets to enamel. MATERIALS AND METHODS: Forty human molars were cleaned, mounted, and randomly divided into two groups: 20 orthodontic brackets were bonded to teeth using RelyX Unicem, and 20 brackets were bonded using the Transbond XT (3M Unitex, Monrovia, Calif) adhesive system. The teeth were debonded within 30 minutes after initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10x magnification to determine the amount of residual adhesive remaining on the tooth. Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the chi-square test was used to compare the Adhesive Remnant Index (ARI) scores for the two adhesive systems. RESULTS: The mean SBS of the brackets bonded using the RelyX Unicem was 3.7 +/- 2.1 MPa and was significantly lower (t = 2.07, P = .048) than the SBS of the brackets bonded with the Transbond system (x = 5.97 +/- 4.2 MPa). The comparisons of the ARI scores between the two groups (chi(2) = 17.4) indicated that bracket failure mode was significantly different (P = .002) with more adhesive remaining on the teeth bonded with Transbond XT. CONCLUSIONS: The SBS of the self-adhesive universal cement needs to be increased for it to be successfully used for bonding orthodontic brackets.     

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??Objective    To evaluate the bond strength of two-base brackets ??analyse the bracket base remnant and the effect on enamel surface after brackets were removed. Methods    The laser-structured base??n = 20??and cast-structured base??n = 20??brackets were bonded on the surfaces of extracted maxillary premolars and the SBS??TBS tested. Premolar brackets were from patients who finished orthodontic treatment ??laser-structured base??n = 71??cast- structured base??n = 71??.  ARI was recorded in all bracket bases and some bases were chosen randomly and analysed by scanning electron microscope??SEM??. Results    The SBS and ARI of laser-structured base brackets were higher than cast-structured base brackets??but the TBS was lower??P < 0.05??. Each bracket base remnant was found to have Ca element. Conclusion    The bond strengths of the two brackets are enough for clinical application??enamel damage occurs during removing.     

Influence of Adhesives and Methods of Enamel Pretreatment on the Shear Bond Strength of Orthodontic Brackets

Aim

The objective of present study was to examine influence of adhesives and methods of enamel pretreatment on the shear bond strength (SBS) of orthodontic brackets. The adhesives used were resin-reinforced glass ionomer cements-GIC (Fuji Ortho LC) and composite resin (Transbond XT).

Material and Methods

The experimental sample consisted of 80 extracted human first premolars. The sample was divided into four equal groups, and the metal brackets were bonded with different enamel pretreatments by using two adhesives: group A-10% polyacrylic acid; Fuji Ortho LC, group B–37% phosphoric acid; Fuji Ortho LC, group C–self etching primer; Transbond XT, group D–37% phosphoric acid, primer; Transbond XT. SBS of brackets was measured. After debonding of brackets, the adhesive remnant index (ARI) was evaluated.

Results

After the statistical analysis of the collected data was performed (ANOVA; Sheffe post-hoc test), the results showed that significantly lower SBS of the group B was found in relation to the groups C (p=0.031) and D (p=0.026). The results of ARI were similar in all testing groups and it was not possible to determine any statistically significant difference of the ARI (Chi- square test) between all four experimental groups.

Conclusion

The conclusion is that the use of composite resins material with appropriate enamel pretreatment according to manufacturer’s recommendation is the “gold standard” for brackets bonding for fixed orthodontic appliances.Key words: orthodontic brackets, shear strength, adhesive, enamel preparation     

喷砂技术对牙釉质和正畸托槽间黏结强度的影响

目的 观察牙釉质和托槽底板用喷砂技术表面处理后与复合树脂黏结的效果.方法 80颗人类前磨牙随机分为4组,均采用复合树脂黏结托槽.对照组(A组)根据产品使用说明黏结;喷砂组对托槽底部(B组)、釉质表面(C组)分别喷砂或同时(D组)进行喷砂处理后再做常规黏结.记录抗剪切强度和残留黏合剂指数(ARI).结果 酸蚀前用喷砂机对牙釉质和托槽底板表面分别进行喷砂处理的D组与A组、B组、C组之间的总体剪切强度和ARI记分差异有统计学意义. A组与B组、C组; B组与D组两两比较的剪切强度差异没有统计学意义.托槽底板和牙釉质表面同时经喷砂处理后获得了较高的黏结强度和较低的ARI记分.结论 对托槽底板和牙釉质表面同时喷吵处理可提高两者间黏结强度.     

不同方法处理脱落托槽后其抗剪切强度对比研究

目的 观察正畸托槽脱落后再次黏结时托槽底板的不同处理方法对抗剪切强度的影响。方法 选择40颗离体人前磨牙,随机分成4组,每组10个样本,托槽均使用3M UNITEK transbond XT光敏树脂正畸黏结剂黏结。处理方法分别为更换新托槽组（简称更新组）;磨除底板残胶组（简称磨除组）;托槽底板喷砂处理组（简称喷砂组）;氯仿溶液浸泡溶解托槽底板上的黏结剂组（简称氯仿浸润组）。各样本均采用万能测试机进行剪切强度试验,记录每组抗剪切强度数值的变化并观察ARI指数（牙面残留黏结剂指数）。结果 磨除组、喷砂组抗剪切强度增强,氯仿浸泡组抗剪切强度则减弱,三者间均有统计学差异。结论 黏结脱落托槽时可采用磨除法或喷砂法对脱落托槽底板进行处理。     

Shear bond strength of rebonded brackets after removal of adhesives with Er,Cr:YSGG laser

This study was conducted to examine the bond strength of rebonded orthodontic brackets after adhesive residuals on the surface of the bracket bases were removed by Er,Cr:YSGG lasers. Seventy-six brackets bonded to premolars with a self-etching primer adhesive system were equally divided into four groups after the first debonding with the bracket bases (Group 1) untreated, and treated by (Group 2) Er,Cr:YSGG laser, (Group 3) sandblaster, and (Group 4) Er,Cr:YSGG laser/sandblaster. The treated brackets were rebonded to the new premolars in the same manner as the first-stage experiment. The shear bond strengths were measured, with the bonding/debonding procedures repeated once after the first debonding, and the bracket/adhesive failure modes were evaluated after each debonding. The treated bracket base surfaces were observed under a scanning electron microscopy (SEM). The mean rebond strengths were significantly lower in group 1 than in other groups, and there were no significant differences between the other groups. The mean initial bond strength was significantly higher than the mean rebond strength in group 1 but there was no significant difference between the two in the other three groups. Failures at the bracket-adhesive interface occurred frequently at second debonding in group 1. Under the SEM, residual adhesive was removed from the bracket bases by Er,Cr:YSGG laser, while adhesive remnant was seen underneath the meshwork of the bracket bases and microroughness appeared on the meshwork after sandblasting. Er,Cr:YSGG laser certainly could serve the purpose of promoting the use of recycled orthodontic brackets.     

Comparison of shear bond strengths of orthodontic brackets bonded with flowable composites

This study evaluated the shear bond strengths of orthodontic brackets bonded to human premolars using five different combinations of flowable composites and one-step self-etching adhesives (n=12): (1) Adper Easy Bond+Filtek Supreme XT Flow; (2) Futurabond NR+Grandio Flow; (3) Clearfil S3 Bond+Clearfil Majesty Flow; (4) AdheSE One+Tetric EvoFlow; and (5) Transbond Plus Self Etching Primer+Transbond XT Light Cure Adhesive. After shear bond strength testing, adhesive remnant index (ARI) scores were given according to the amount of adhesive and resin remaining on the brackets. On shear bond strength, there were no statistically significant differences between Groups 2 and 4 and between Groups 3 and 5 (p>0.05). On ARI scores, the predominant ARI scores in Groups 1, 2, 3, and 5 were 4, 2, 5, and 4 respectively; in Group 4, they were 0 and 4. Results showed that some combinations of flowable composites and self-etching adhesives might not be suitable for orthodontic use due to their low shear bond strengths and high ARI scores -with the latter signaling the risk of damaging the enamel surface during debonding.     

Comparison of bond strength between simple foil mesh and laser-structured base retention brackets.

The aims of the current study were to evaluate the bond strength of a new metallic orthodontic bracket with a laser structured base (Discovery, Dentaurum, Ispringen, Germany), and its effects on the site of bond failure and on the behavior of the enamel after debonding. One hundred and twenty recently extracted human premolars were bonded with 1 of 2 types of mechanical interlock base metal brackets: a standard system with a simple foil mesh pad (Minitrim, Dentaurum) and the Discovery bracket. A resin-based, chemically activated bonding system, No-mix (Dentaurum), was used as the adhesive system in this trial. The teeth were immersed in normal saline solution at 37 degrees C for 7 days before debonding and were randomly assigned to different subgroups. A testing machine was used to evaluate tensile and fatigue bond strengths for both brackets. After debonding, the amount of residual adhesive on the bracket and enamel detachment were assessed according to the adhesive remnant index (ARI) and the enamel detachment index (EDI) with a scanning electron microscope and an energy dispersive X-ray spectrometer. The scores obtained from the ARI and the EDI showed that the laser structured base brackets had a significantly higher bond strength (mean +/- SD: 17.1 +/- 0.7 MPa) that was 2 times higher than that observed with the simple foil mesh brackets (mean +/- SD: 8.7 +/- 1.4 MPa) (P <.001). Bond failure with the laser structured base was at the enamel-adhesive interface with an ARI score of 3 in 80% of the teeth, and bond failure with the simple foil mesh base was at the bracket-adhesive interface with an ARI score of 0 in 75% of the teeth. A small area, with less than 10% of the enamel damaged (1 on the EDI) and 1.5 microm in thickness, was observed for both brackets. The laser structured base bracket's bond strength was double that of the simple foil mesh bracket but was equally safe and did not induce significant enamel detachment.     

Bonding with self-etching primers--pumice or pre-etch? An in vitro study

The purpose of this study was to compare the shear bond strengths (SBSs) of orthodontic brackets bonded with self-etching primer (SEP) using different enamel surface preparations. A two-by-two factorial study design was used. Sixty human premolars were harvested, cleaned, and randomly assigned to four groups (n = 15 per group). Teeth were bathed in saliva for 48 hours to form a pellicle. Treatments were assigned as follows: group 1 was pumiced for 10 seconds and pre-etched for 5 seconds with 37 per cent phosphoric acid before bonding with SEP (Transbond Plus). Group 2 was pumiced for 10 seconds before bonding. Group 3 was pre-etched for 5 seconds before bonding. Group 4 had no mechanical or chemical preparation before bonding. All teeth were stored in distilled water for 24 hours at 37°C before debonding. The SBS values and adhesive remnant index (ARI) score were recorded. The SBS values (± 1 SD) for groups 1-4 were 22.9 ± 6.6, 16.1 ± 7.3, 36.2 ± 8.2, and 13.1 ± 10.1 MPa, respectively. Two-way analysis of variance and subsequent contrasts showed statistically significant differences among treatment groups. ARI scores indicated the majority of adhesive remained on the bracket for all four groups. Pre-etching the bonding surface for 5 seconds with 37 per cent phosphoric acid, instead of pumicing, when using SEPs to bond orthodontic brackets, resulted in greater SBSs.     

Influence of self-etchant application time on bracket shear bond strength

OBJECTIVE: To determine the influence of self-etching primer (SEP) application time on the shear bond strength of orthodontic brackets. MATERIALS AND METHODS: Forty human molars were cleaned, mounted, and randomly divided into two groups. The same SEP, adhesive, and brackets were used in both groups. Twenty teeth were conditioned following the manufacturers' recommendations by rubbing the SEP on the enamel surface for 3 to 5 seconds. The remaining 20 teeth were conditioned using the same SEP, but the application time was increased to 15 seconds. The teeth were debonded within half an hour following initial bonding using a universal testing machine. After debonding, the amount of residual adhesive remaining on the tooth was determined. Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the chi2 test was used to compare the Adhesive Remnant Index (ARI) scores for the two adhesive systems. RESULTS: The mean SBS of the brackets bonded to the teeth subjected to the SEP for 3 to 5 seconds was 8.0+/-4.6 MPa and was not significantly different (t=-0.69, P=.494) from the SBS of the brackets bonded using a 15-second SEP application time (x=8.9+/-3.4 MPa). The comparisons of the ARI scores between the two groups (chi2=2.16) indicated that bracket failure mode was not significantly different (P=.340) for both groups, and most failures were at the bracket-adhesive interface. CONCLUSION: The present findings indicate that increasing the SEP application from 3 to 5 seconds to 15 seconds does not result in a significant increase in SBS.     

Repeated bonding of fixed retainer increases the risk of enamel fracture

The aim of this study was to investigate the influences of repeated bonding, using 2 different orthodontic adhesive systems, on the shear bond strength (SBS) and the enamel surface morphology. Sixty premolars were divided into 2 groups (n = 30), and either Transbond XT (T group) or Fuji Ortho LC (F group) adhesives were used. SBS was measured 24 h after bonding, using a universal testing machine. Then, the enamel surfaces were investigated and the mode of failure was described using adhesive remnant index (ARI) scores. After each debonding, 10 teeth from each group were examined by scanning electron microscopy to determine the penetration of adhesives, the length of resin tags, and the state of the enamel surface. The other teeth were subjected to two more bonding/debonding procedures. In T group, the second debonding sequences had significantly higher bond strengths than the other sequences. The length of resin tags was greatest in the second debonding sequence, although there was no significant difference. In F group, the SBS increased with further rebonding and the failure mode tended towards cohesive failure. In both groups, the ARI scores increased with rebonding. Enamel loss could have occurred with both adhesives, although the surfaces appeared unchanged to the naked eye. From this study, we suggest that enamel damage caused by repeated bonding is of concern. To prevent bond failure, we should pay attention to the adhesion method used for bondable retainers.     

Clinical acceptability of two self-etch adhesive resins for the bonding of orthodontic brackets to enamel

Abstract

Objective: To determine whether two self-adhesive resin cements, Clearfil SA and RelyX, can be used to successfully bond orthodontic brackets to enamel.

Materials and methods: Seventy extracted premolars were custom mounted, cleaned and randomly divided into three groups. In group 1 (control), orthodontic brackets were bonded to 25 premolars using the Transbond Plus and Transbond XT two step adhesive systerm adhesive. In group 2, brackets were bonded to 25 premolars using Clearfil SA. In group 3, brackets were bonded to 20 premolars using RelyX. The brackets were debonded using a universal testing machine and shear bond strengths recorded. After debonding, each tooth was examined under 20× magnification to evaluate the residual adhesive remaining. An ANOVA with Duncan’s Multiple Range Test was used to determine whether there were significant differences in shear bond strength between the groups. A Kruskal–Wallis Test and a Bonferroni multiple comparison procedure were used to compare the bond failure modes (adhesive remnant index scores) between the groups.

Results: The mean shear bond strengths for the brackets bonded using Clearfil SA and RelyX were 5·930±1·840 and 3·334±1·953 MPa, respectively. Both were significantly lower than that for the brackets bonded using Transbond (7·875±3·611 MPa). Both self-etch adhesive resin cement groups showed a greater incidence of bracket failure at the enamel/adhesive interface while the Transbond group showed a higher incidence at the bracket/adhesive interface.

Conclusions: The shear bond strengths of the self-etch adhesive resin cements may be inadequate to successfully bond orthodontic brackets to enamel.