Six-month bracket survival with a self-etch adhesive

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). MATERIALS 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 materials. 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 materials. 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.     

Effect of saliva on shear bond strength of an orthodontic adhesive used with moisture-insensitive and self-etching primers.

The purpose of this study was to investigate the effect of saliva contamination on the shear bond strength of an orthodontic adhesive used with Transbond Moisture-Insensitive Primer (MIP, 3M Unitek, Monrovia, Calif) and Transbond Plus Self-Etching Primer (SEP, 3M Unitek). Hydrophobic Transbond XT primer (XT, 3M Unitek) was used as a control. A total of 162 extracted premolars were collected and divided equally into 9 groups of 18 teeth each, and brackets were bonded with Transbond XT adhesive (3M Unitek) under different experimental conditions: (1) control: etch/dry/XT, (2) etch/dry/MIP, (3) etch/dry/MIP/wet (saliva)/MIP, (4) etch/wet/MIP, (5) etch/wet/MIP/wet/MIP, (6) dry/SEP, (7) dry/SEP/wet/SEP, (8) wet/SEP, and (9) wet/SEP/wet/SEP. Shear bond strength of each sample was examined with a testing machine. The results showed that the control group had the highest mean shear bond strength (group 1, 21.3 +/- 6.8 MPa), followed by the MIP group in a dry field (group 2, 20.7 +/- 5.0 MPa). No significant difference was found between groups 1 and 2. Groups 3 through 9 had similar mean strengths, ranging from 12.7 to 15.0 MPa (P >.05), which were significantly lower than in groups 1 and 2 (P <.05). There was no significant difference in bond-failure site among the 9 groups. It was concluded that (1) Transbond XT adhesive with Transbond XT primer and MIP in a dry field yields similar bond strengths, which are greater than all other groups, (2) saliva contamination significantly lowers the bond strength of Transbond MIP, (3) saliva has no effect on the bond strength of Transbond SEP, (4) Transbond XT adhesive with Transbond MIP and SEP might have clinically acceptable bond strengths in either dry or wet fields.     

Scanning electron microscopy evaluation of the bonding mechanism of a self-etching primer on enamel

The aim of this study was to analyze the effect of a self-etching primer (Transbond Plus SEP, 3M Unitek, Monrovia, Calif), developed for orthodontic use, in the regularity and depth of adhesive infiltration in the enamel of human permanent teeth and to compare it with phosphoric acid using scanning electron microscopy (SEM). Thirty premolars were divided in two groups of 15 each: group 1(control)-phosphoric acid + Transbond XT Primer (3M Unitek) and group 2- Transbond Plus SEP. Transbond XT Adhesive Paste (3M Unitek) was used in both groups for bracket bonding. All products were used according to the manufacturer's instructions. Dental fragments were decalcified, and for micromorphologic observation of the adhesive penetration in enamel, the resin replicas, remnant at the base of the brackets, were covered with a thin gold layer and examined by SEM. Three calibrated examiners evaluated the photomicrographs and gave scores from 0 = without penetration to 2 = deep penetration. The Mann Whitney U-test (P < .0001) showed a statistical difference between the two groups. The results demonstrated that the SEP was more conservative and produced a smaller amount of demineralization and less penetration of adhesive in the enamel surfaces when compared with the conventional phosphoric acid system.     

Long-term clinical evaluation of bracket failure with a self-etching primer: a randomized controlled trial

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: Prospective randomized 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.     

Clinical bond failure rates of adhesive precoated self-ligating brackets using a self-etching primer

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).Materials and Methods:Fifty-seven patients with complete permanent dentition were included in this study. A total of 1140 APC self-ligating brackets (3M Unitek, Monrovia, Calif) were bonded using a split-mouth design. For each patient, SEP (Transbond Plus SEP, 3M 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.     

Effect of a self-etch primer/adhesive on the shear bond strength of orthodontic brackets

Conventional adhesive systems use 3 different agents (an enamel conditioner, a primer solution, and an adhesive resin) during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single product. Combining conditioning and priming saves time and should be more cost-effective to the clinician and, indirectly, to the patient. The purpose of this study was to determine the effects of the use of a self-etch primer on the shear bond strength of orthodontic brackets and on the bracket/adhesive failure mode. Brackets were bonded to extracted human teeth according to 1 of 2 protocols. In the control group, teeth were etched with 37% phosphoric acid. After the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In the experimental group, a self-etch acidic primer (ESPE Dental AG, Seefeld, Germany) was placed on the enamel for 15 seconds and gently evaporated with air, as suggested by the manufacturer. The brackets were then bonded with Transbond XT as in the first group. The present in vitro findings indicate that the use of a self-etch primer to bond orthodontic brackets to the enamel surface resulted in a significantly (P = .004) lower, but clinically acceptable, shear bond force (mean, 7.1 +/- 4.4 MPa) as compared with the control group (mean, 10.4 +/- 2.8 MPa). The comparison of the adhesive remnant index scores indicated that there was significantly (P = .006) more residual adhesive remaining on the teeth that were treated with the new self-etch primer than on those teeth that were bonded with the use of the conventional adhesive system.     

A comparison of shear bond strength and debonding characteristics of conventional, moisture-insensitive, and self-etching primers in vitro

Bond failure is often attributed to moisture contamination. To overcome this commonly encountered problem, materials have been developed that are hydrophilic and that are believed to offer better bond strength in moisture-contaminated environment. Shear bond strength was compared among three materials: conventional Transbond XT primer (3M Unitek), moisture-insensitive primer (MIP, 3M Unitek), and self-etch primer (Transbond plus, 3M Unitek). Bond strength was tested under laboratory conditions with brackets bonded on both dry enamel and enamel contaminated with natural saliva. Self-etch primer showed maximum bond strength under both dry and wet conditions. Conventional primer was comparable with the former under dry conditions but did not offer clinically adequate bond strength in cases of moisture contamination. Both MIP and self-etch primer showed adequate bond strength superior to that of conventional primer in case of moisture contamination. All primers showed typical debonding characteristics of separation at the bracket-adhesive interface or within the adhesive itself, with the exception of the conventional primer used with moisture-contaminated enamel.     

An in-vitro investigation into the use of a single component self-etching primer adhesive system for orthodontic bonding: a pilot study

OBJECTIVE: This pilot study assessed force to debond (N); time, and site of bond failure of a single component self-etching primer (SEP) and adhesive system, Ideal 1 (GAC International Inc., USA) and compared it with the conventional acid etch and rinse regimen using 37% o-phosphoric acid solution and either Transbond XT (3M Unitek) or Ideal 1 adhesive. DESIGN: In vitro laboratory study. SETTING: Bristol Dental Hospital, UK. Sept 2003-Sept 2004. MATERIAL AND METHODS: Nine groups of 20 premolars were bonded using metal orthodontic brackets using three protocols: (1) 37% o-phosphoric acid etch and Transbond XT adhesive; (2) 37% o-phosphoric acid and Ideal 1 adhesive; (3) Ideal 1 SEP and Ideal 1 adhesive. Force to debond and locus of bond failure were determined at three time intervals. RESULTS: Enamel pre-treatment prior to bonding, namely SEP versus conventional etching had no significant effect on the median force to debond with the Ideal 1 adhesive. Similarly, when the enamel was conventionally etched, the adhesive type, namely Ideal 1 or Transbond XT, had no significant effect on the measured force to debond. However, there appeared to be differences in the locus of bond failure: failure predominated at the enamel/adhesive interface for the Transbond XT conventional etch group and at adhesive/bracket interface for the Ideal 1 SEP and adhesive group and the Ideal 1 adhesive conventional etch group. CONCLUSION: These results suggested that the complete Ideal 1 SEP and adhesive system might be successful in vivo leading therefore to a clinical trial. However, implications for clean up time are discussed and improvements to in vitro study designs are advised.     

Six-month bracket failure rate evaluation of a self-etching primer

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, randomized, 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.     

Comparison of the shear bond strength of 2 self-etch primer/adhesive systems.

Conventional adhesive systems use 3 different agents-an enamel conditioner, a primer solution, and an adhesive resin for bonding orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single application. Combining conditioning and priming saves time and should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to assess and compare the effects of mix and no-mix self-etch primers/bonding systems on the shear bond strengths of orthodontic brackets. The brackets were bonded to extracted human molars according to the following protocols. In group I, a self-etch acidic primer/adhesive system, Transbond Plus (3M Unitek, Monrovia, Calif), was applied on the enamel surface as suggested by the manufacturer; it has 2 components that must be mixed before use. The brackets were then bonded with Transbond XT and light-cured for 20 seconds. In group II, a no-mix self-etch bracket adhesive system, Ideal 1 (GAG International, Islandia, NY), was applied to the teeth as suggested by the manufacturer. The self-etch primer has 1 component that does not need to be mixed before use. The brackets were then bonded with the adhesive and light-cured for 20 seconds. The in vitro findings indicated that the shear bond strength comparisons (t = 0.681) of the 2 adhesive systems were not significantly different (P =.501). The mean shear bond strength of the 2-component acid etch primer was 5.9 +/- 2.7 MPa, and the mean for the 1-component system was 6.6 +/- 3.2 MPa. The clinician should consider the bond strength and the ease of application of the various components of the bracket bonding systems available on the market.     

Effects of self-etching primer on shear bond strength of orthodontic brackets at different debond times

OBJECTIVE: To evaluate the effect of a self-etching primer on shear bond strengths (SBS) at the different debond times of 5, 15, 30, and 60 minutes and 24 hours. MATERIALS AND METHODS: Brackets were bonded to human premolars with different etching protocols. In the control group (conventional method [CM]) teeth were etched with 37% phosphoric acid. In the study group, a self-etching primer (SEP; Transbond Plus Self Etching Primer; 3M Unitek, Monrovia, Calif) was applied as recommended by the manufacturer. Brackets were bonded with light-cure adhesive paste (Transbond XT; 3M Unitek) and light-cured for 20 seconds in both groups. The shear bond test was performed at the different debond times of 5, 15, 30 and 60 minutes and 24 hours. RESULTS: Lowest SBS was attained with a debond time of 5 minutes for the CM group (9.51 MPa) and the SEP group (8.97 MPa). Highest SBS was obtained with a debond time of 24 hours for the CM group (16.82 MPa) and the SEP group (19.11 MPa). Statistically significant differences between the two groups were not observed for debond times of 5, 15, 30, or 60 minutes. However, the SBS values obtained at 24 hours were significantly different (P < .001). CONCLUSIONS: Adequate SBS was obtained with self-etching primer during the first 60 minutes (5, 15, 30 and 60 minutes) when compared with the conventional method. It is reliable to load the bracket 5 minutes after bonding using self-etching primer (Transbond Plus) with the light-cure adhesive (Transbond XT).     

Failure rate of self-ligating and edgewise brackets bonded with conventional acid etching and a self-etching primer: a prospective in vivo study

The purpose of this study was to comparatively assess the failure rate of self-ligating and edgewise brackets bonded with a self-etching adhesive and conventional phosphoric acid in patients followed for 12 months of active treatment. Sixty-two patients with complete permanent dentitions, similar treatment plans, and mechanotherapy were selected for the study. GAC Microarch edgewise brackets and ORMCO Damon2 brackets were bonded using a split mouth design, using the 3M Transbond Plus Self-etching primer (SEP) and Transbond XT paste; and conventional acid etching, with Orthosolo primer and Enlight paste, applied at an alternate sequence so that the adhesives were equally distributed on the maxillary and mandibular right and left quadrants. Data analysis was conducted with the use of logistic regression modeling. No difference in failure incidence was noted for either bracket-adhesive and mandibular or maxillary arch combinations, whereas a statistically significant difference was shown for right-sided appliances. On the basis of the results of this study, bonding of self-ligating brackets with SEP does not demonstrate higher probability for failure relative to standard bonding procedures and conventional brackets.     

Effect of a fluoride-releasing self-etch acidic primer on the shear bond strength of orthodontic brackets

Conventional adhesive systems use three different agents--an enamel conditioner, a primer solution, and an adhesive resin--during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single application. Combining conditioning and priming saves time and should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to assess and compare the effects of self-etching primers, including a fluoride-releasing primer, on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human teeth according to one of four protocols. In group 1 (control), teeth were etched with 37% phosphoric acid; after the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In group 2, a self-etch acidic primer (3M ESPE, St Paul, Minn) was applied as suggested by the manufacturer, and the brackets were then bonded with Transbond XT as in the first group. In group 3, an experimental self-etch primer EXL #547 (3M ESPE) was applied to the teeth as suggested by the manufacturer, and the brackets were then bonded as in groups 1 and 2. In group 4, a fluoride-releasing self-etch primer, One-Up Bond F (J. Mortia, USA Inc. Irvine, Calif) that also has a novel dye-sensitized photo polymerization initiator system was applied as suggested by the manufacturer, and the brackets were then bonded as in the other groups. The present in vitro findings indicated that the shear bond strengths of the four groups were significantly different (P = .001). Duncan multiple range tests indicated that One-Up Bond F (mean +/- SD strength, 5.1+/-2.5 MPa) and Prompt L-Pop (strength, 7.1+/-4.4 MPa) had significantly lower shear bond strengths than both the EXL #547 self-etch primer (strength, 9.7+/-3.7 MPa) or the phosphoric acid etch and the conventional adhesive system (strength, 10.4+/-2.8 MPa).     

A randomized control clinical trial investigating orthodontic bond failure rates when using Orthosolo universal bond enhancer compared to a conventional bonding primer

OBJECTIVE: This study assessed the in vivo bond failure rates of orthodontic brackets bonded using Orthosolo universal bond enhancer and compared it with the conventional bonding primer, Transbond XT. DESIGN: This was a single centre randomized controlled clinical study. SETTING: Department of Child Dental Health, Bristol Dental Hospital, Bristol, UK. MATERIALS AND METHODS: Thirty-three consecutive patients undergoing fixed orthodontic appliance therapy were included in this study. Using a split-mouth design, diagonally opposite quadrants were randomly allocated a primer, either Orthosolo universal bond enhancer (Ormco, Orange, CA, USA) or Transbond XT primer (3M Unitek, Monrovia, CA, USA). A total of 555 teeth were bonded using a conventional acid-etch technique. 277 received Orthosolo as their primer and 278 received the Transbond XT primer. Bond failures and their positions were recorded at six months. RESULTS: There was an overall bond failure rate of 1.26%. Four brackets failed in the Orthosolo group (0.72%) and three failed in the Transbond XT group (0.54%). CONCLUSION: There was no clinical or statistically significant difference in the in vivo bond failure rates between orthodontic brackets bonded using either Orthosolo universal bond enhancer or the conventional Transbond XT primer.     

Self-etching primer and a non-rinse conditioner versus phosphoric acid: alternative methods for bonding brackets

The objective of this study was to evaluate the effectiveness of a self-etching primer, Transbond Plus Self Etching Primer (TSEP, 3M Unitek), and a non-rinse conditioner (NRC, Dentsply DeTrey) for bonding brackets, compared with the acid-etch technique. The brackets were bonded to extracted premolars using Transbond XT (3M Unitek). One of the following three conditioning protocols were used: (1) 37 per cent phosphoric acid (n = 25), (2) TSEP (n = 25), and (3) NRC (n = 15). Shear bond strength (SBS) was measured with a universal testing machine. The adhesive remaining after debonding was determined using image analysis equipment. Scanning electron microscope (SEM) observations were also carried out on 12 premolars to observe the enamel surfaces. No significant differences were observed in SBS between the three groups (P = 0.56). TSEP and NRC left significantly less adhesive on the tooth than the traditional acid-etch technique (P = 0.004 and P = 0.000, respectively). NRC left significantly less adhesive than TSEP (P = 0.001). SEM observations showed that NRC produced a less aggressive etch pattern than TSEP, and that the etching effect of TSEP approximated that of phosphoric acid.     

Effect of loading mode on bond strength of orthodontic brackets bonded with 2 systems.

INTRODUCTION: A new orthodontic bracket bonding method or material invariably spawns bond strength studies examining the efficacy of the innovation. The primary purpose of this project was to ascertain whether the mode of in-vitro bracket debonding used in a study affects the measured bond strength. The secondary aim was to compare the bond strengths of 2 different bonding systems. METHODS: Flattened stainless steel orthodontic brackets were bonded to flattened bovine enamel with a resin composite bonding agent (Transbond XT, 3M Unitek, Monrovia, Calif). The enamel was prepared with traditional acid etching and priming (37% phosphoric acid gel and Transbond XT Primer, 3M Unitek) or a single-step method (Transbond Plus, 3M Unitek) that combined etching and priming. Cement thickness was kept constant, and bonding was done under controlled temperature and humidity. Brackets were debonded in shear-peel, tension, or torsion. RESULTS: When tested in shear-peel mode, traditional etching and priming produced a stronger bond than the single-step self-etch system. When tested in tension, the traditional bond was weaker than the single-step bond, and when tested in torsion, the bond strengths were similar. CONCLUSIONS: Bond strength can vary depending on the method of testing. Claims of clinical efficacy might not be valid.     

The effect of modifying the self-etchant bonding protocol on the shear bond strength of orthodontic brackets

OBJECTIVE: To compare the shear bond strength (SBS) of orthodontic brackets when the self-etching primer (SEP) and the bracket adhesive are light cured either separately or simultaneously. MATERIALS AND METHODS: Seventy-five human molars were randomly divided into five equal groups. Brackets precoated with Transbond XT composite adhesive were used. The five protocols were: Group 1 (control), the SEP Transbond Plus was applied, brackets placed, and adhesive light cured for 20 seconds; Group 2, SEP Adper Prompt L-Pop was applied, light cured, brackets placed, and light cured; Group 3, the same SEP as in Group 2 was used, however, the SEP and bracket adhesive were light cured together; Group 4, SEP Clearfil S3 Bond was applied, light cured, brackets placed, and light cured; and Group 5, the same SEP as in group 4 was used, however, the SEP and the adhesive were light cured together. The teeth were debonded using a universal testing machine, and the enamel was examined for residual adhesive. Analysis of variance was used to compare the SBS. RESULTS: The SBS of Clearfil S3 Bond after one light cure and two light cures were significantly greater than the bonds of brackets using Transbond Plus. Brackets bonded using Adper Prompt L-Pop after one light cure and two light cures were not significantly different from the other groups. The groups did not differ significantly in their bracket failure modes. CONCLUSION: Only one light curing application is needed to successfully bond brackets when using SEPs and adhesives. This approach can potentially reduce technique sensitivity as well as chair time.     

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.     

Direct bonding with precoated brackets and self-etching primers

PURPOSE: To evaluate the shear bond strength and the adhesive remnant on the tooth after the debonding of APC Plus precoated brackets, when conditioning the enamel with phosphoric acid and Transbond Plus Self Etching Primer (TSEP), in comparison with uncoated brackets bonded with Transbond XT. METHODS: The brackets were bonded to extracted premolars, which were divided into three groups: (1) Acid/Transbond XT, (2) Acid/ APC Plus and (3) TSEP/APC Plus. Shear bond strength was measured using a universal test machine. The crosshead speed was 1 mm/minute. The adhesive remnant on the tooth was quantified using an image analysis equipment. RESULTS: No significant differences were found in the bond strengths of the three groups evaluated (P> 0.05). The two groups in which APC Plus system was used left significantly less adhesive on the tooth than Transbond XT. TSEP/APC Plus left significantly less adhesive than Acid/APC Plus (P< 0.017).     

Bond strength comparison of 2 self-etching primers over a 3-month storage period

The purpose of this in vitro study was to evaluate the shear-peel bond strength of 2 self-etching primer systems, Transbond Plus (3M/ Unitek, Monrovia, Calif) and First Step (Reliance Orthodontic Products, Itasca, Ill), with their respective adhesives, and compare them with a control adhesive system (Transbond XT, 3M/ Unitek) over a 3-month period. Two hundred seventy extracted human premolars were obtained and randomly divided into 9 groups of 30 teeth. Metal orthodontic brackets were bonded to the enamel, and each adhesive group was stored for 24 horrs (T1), 30 days (T2), or 3 months (T3) in deionized water at 37 degrees C. All bonded specimens were thermocycled at 10 degrees C and 50 degrees C for 24 hours before debonding. Brackets were debonded by using a shear-peel load on a testing machine at a cross-head speed of 2 mm/min. Bond failure was also evaluated. The shear-peel bond strengths of the 3 bonding systems were clinically acceptable with the possible exception of First Step at 30-day storage. Repeated measures analysis of variance showed a statistically significant (P < .0001) difference in mean bond strengths between the 3 adhesive systems. The shear-peel bond strength of the adhesives over the 3 time intervals showed statistically significant (P = .005) changes. In each group, there were statistically significant differences in shear-peel bond strength between time intervals T1-T2 and T2-T3 for Transbond Plus and T2-T3 for First Step. The change in mean shear-peel bond strength of the 3 adhesives demonstrated a consistent pattern of behavior over the 3 storage intervals. The lowest mean shear-peel bond strength values were noted at the 30-day storage. Bond failure analysis (adhesive remnant index) demonstrated mainly cohesive bond failures.