Effetto della contaminazione ematica sul distacco di tre differenti tipi di brackets autoleganti: studio sperimentale in vitro

Objectives

To assess the effect of blood contamination on the bonding and bond-failure site of 3 different types of self-ligating bracket.

Materials and methods

Two hundred forty bovine permanent mandibular incisors were randomly divided into 12 groups, each containing 20 specimens. Three different self-ligating brackets (Smart Clip - 3 M Unitek, Monrovia, California, USA; Damon - Ormco, Glendora, California, USA; and Quick - Forestadent, Pforzheim, Germania) were bonded to the teeth with Orthosolo primer (Ormco, Glendora, California, USA) and Trasbond XT composite (3 M Unitek, Monrovia, California, USA). Bonding was tested under different surface enamel conditions: dry, contaminated with blood before priming, contaminated with blood after priming, and contaminated with blood before and after priming. After bonding, all samples were stored in distilled water at room temperature for 24 hours. Shear bond strength was then evaluated with a universal testing machine (Mod. 4301, Instron Corp., Canton, Massachussets, USA). After bond failure, the bracket bases and the enamel surfaces were examined under an optical microscope (Stereomicroscope SR, Zeiss, Oberkochen, Germany) at 10 x magnification, and the amount of adhesive left on the enamel surface was rated with the adhesive remnant index (ARI). All the data were statistically analyzed (Chi-square test; level of significance p < 0.05).

Results and conclusions

ARIs of 2 were more frequent among samples bonded to dry enamel, whereas samples bonded to blood-contaminated enamel (before, after, or before and after priming) exhibited a higher frequency of ARI 0. However, there were no significant differences between the ARI scores for the 3 conditions of contaminated enamel or for those related to the 3 types of self-ligating brackets tested.     

Effect of water contamination on the shear bond strength of self-ligating brackets

PurposeThe aim of the present study is to evaluate the effect of water contamination on the shear bond strength (SBS) and adhesive remnant index (ARI) score of self-ligating brackets.Materials and methodsOne conventional bracket and three different self-ligating brackets were bonded onto 160 bovine permanent mandibular incisors, divided randomly into 8 groups. For each type of bracket, 20 samples were bonded on dry enamel and 20 after water contamination. After 24 h, all specimens were tested for SBS using an Instron Universal Testing Machine, and ARI scores were evaluated.ResultsAll groups showed clinically adequate SBSs. Quick brackets bonded onto dry enamel showed significantly higher SBSs than all other groups tested, whereas the lowest shear strength values were recorded for Step, Quick, and Damon 3MX brackets bonded onto contaminated enamel and for Damon 3MX onto dry enamel. Frequency distribution of ARI Scores showed a prevalence of ARI “2” and “3” for all the groups tested.ConclusionsWater contamination reduces the SBS of self-ligating brackets, but significant differences have been found only for Quick brackets. All groups showed a significant higher frequency of ARI Score of “2” and “3”.     

A randomized clinical trial comparing ‘one-step’ and ‘two-step’ orthodontic bonding systems

Abstract

Objective: The primary objective of this prospective 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 randomized controlled clinical trial. Thirty-four patients were bonded, each being randomly 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 mandibular 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.     

Effect of a self-etching primer on shear bond strength of adhesive precoated brackets in vivo

The aim of this study was to evaluate the influence of a self-etching primer (SEP) (Transbond Plus SEP, 3M Unitek, Monrovia, Calif) on shear bond strength of adhesive uncoated and precoated Victory brackets (3M Unitek). The sample group consisted of 23 patients, with four premolars each, equally divided in four different groups. Brackets were bonded in vivo by the same operator using a split-mouth random technique: group 1, 37% phosphoric acid + primer + composite + conventional Victory bracket; group 2, 37% phosphoric acid + primer + precoated Victory bracket; group 3, SEP + composite + conventional bracket; group 4, SEP + precoated bracket. After 30 days, premolars were extracted for orthodontic reasons and a Universal Instron Machine was used to apply an occlusal shear force directly to the enamel-bracket interface at a speed of 0.5 mm/min. The groups were compared using two-way analysis of variance. Mean results and standard deviation for the groups were: group 1 = 11.60 +/- 2.65 Mpa, group 2 = 9.79 +/- 2.71 Mpa, group 3 = 10.75 +/- 2.67 Mpa, and group 4 = 10.31+/- 2.70 Mpa. No difference was observed between the conventional etching and primer or SEP (P = .948). However, significant differences in bond strength were present between the uncoated and precoated brackets (P = .032). Considering the values required to withstand normal orthodontic forces (8-9 Mpa), it could be concluded that the SEP combined with adhesive precoated brackets showed adequate shear bond strength and may be suitable for clinical use.     

Self-etching primers: is prophylactic pumicing necessary? A randomized clinical trial

The purpose of this clinical trial was to determine whether pumice prophylaxis is required before the use of a self-etching primer (SEP). A total of 30 patients undergoing treatment with full upper and lower fixed appliances were recruited into this randomized cross-mouth controlled trial. In all cases, stainless steel orthodontic brackets were bonded using Transbondtrade mark XT adhesive after pretreatment of the enamel surface using a new SEP. Diagonally opposite quadrants of the mouth were randomly assigned to have the enamel either pumiced or not pumiced before the use of a SEP. Bond failures, along with the adhesive remnant index (ARI) scores, were recorded at 6 and 12 months into treatment. The data were subsequently analyzed in terms of odds ratio and associated 95% confidence interval. Because of the very high bond failure rates of 55.5% for the no-pumice group and 33.2% for the pumice group, patient recruitment ceased at only 14 patients. Although the bond failure rates were unacceptably high in both groups, pumicing was found to have a clinically and statistically significant effect on reducing clinical bond failure rates. The ARI scores in all cases were 0, indicating that no adhesive remained on the enamel surface at bond failure. The significance of this trial is that pumicing before the use of an SEP is to be recommended, although the SEP used in this study cannot be recommended for clinical use.     

Effect of using a new cyanoacrylate adhesive on the shear bond strength of orthodontic brackets.

During bonding of orthodontic brackets to enamel, conventional adhesive systems use three different agents: an enamel conditioner, a primer solution, and an adhesive resin. A unique characteristic of some new bonding systems is that they need neither a priming agent nor a curing light to bond brackets. Such an approach should be more cost-effective for the clinician and indirectly also for the patient. The purpose of this study was to determine the effects of using a cyanoacrylate adhesive on the shear bond strength of orthodontic brackets and on the bracket/adhesive failure mode. The brackets were bonded to extracted human teeth according to one of two protocols. Group 1: Teeth were etched with 37% phosphoric acid. After applying the primer, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and were light-cured for 20 seconds. Group 2: Teeth were etched with 35% phosphoric acid. The brackets were then bonded with Smartbond (Gestenco International, G?thenburg, Sweden). The present in vitro findings indicated that the use of the cyanoacrylate adhesive to bond orthodontic brackets to the enamel surface did not result in a significantly different (P = .24) shear bond force (mean = 5.8 +/- 2.4 MPa) as compared to the control group (mean = 5.2 +/- 2.9 MPa). The comparison of the Adhesive Remnant Index scores indicated that there was significantly (P = .006) less residual adhesive remaining on the tooth with the cyanoacrylate than on the tooth with the conventional adhesive system. In conclusion, the new adhesive has the potential to be used to bond orthodontic brackets while reducing the total bonding time.     

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

Abstract

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^TM 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^TM 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^TM 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^TM 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.     

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.     

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.     

A comparative assessment of bracket survival and adhesive removal time using flash-free or conventional adhesive for orthodontic bracket bonding: A split-mouth randomized controlled clinical trial

Objectives:To compare bracket survival and adhesive removal time between a flash-free and a conventional adhesive for orthodontic bracket bonding.Materials and Methods:Forty-five consecutive patients had their maxillary incisors, canines, and premolars bonded with ceramic brackets using a flash-free adhesive (APC Flash-Free Adhesive, 3M Unitek, Monrovia, Calif) on one side and a conventional adhesive (APCII Adhesive, 3M Unitek) on the other side. The side allocation was randomized. Bracket failure was recorded at 4-week intervals. The adhesive remnant index (ARI) was scored on debond and adhesive removal timed to the nearest second. The primary outcome was adhesive removal time per quadrant. Secondary outcomes were bracket failure rate, time to first-time failure of a bracket, and ARI score on debond. Paired t-tests were used to compare adhesive removal times and ARI scores between the adhesives with P < .05 considered statistically significant.Results:Bracket failure rates were 4.3% for the flash-free adhesive and 1.9% for the conventional adhesive, with mean times to first-time failure of 31 weeks for the flash-free adhesive and 42 weeks for the conventional adhesive; neither failure rates nor times to first failure were significantly different. Although the flash-free adhesive left significantly more adhesive on the tooth surface after debonding, the adhesive removal times were 22.2% shorter than with the conventional adhesive.Conclusions:Bracket survival with the flash-free adhesive was equivalent to the conventional adhesive when ceramic brackets were bonded. Adhesive removal was significantly faster when using the flash-free adhesive, which may result in time savings of more than 20% compared with the conventional adhesive.     

Shear bond strength and residual adhesive after orthodontic bracket debonding

OBJECTIVE: To compare the shear bond strength and determine the area of residual adhesive on teeth after the debonding of brackets bonded with two types of orthodontic adhesives. These were a resin-modified glass ionomer cement (RMGIC; Fuji ORTHO LC, GC Corporation, Tokyo, Japan) and a resin applied as a precoated bracket (APC bracket, 3M Unitek GmbH, Seefeld, Germany). MATERIALS AND METHODS: A total of 60 premolar teeth were randomly divided into two groups, and brackets were bonded according to the manufacturers' instructions. In group 1, the teeth were conditioned using 10% polyacrylic acid, and the brackets were bonded using Fuji Ortho LC in wet condition. In group 2, the teeth were etched using 37% phosphoric acid, and the APC brackets were bonded. Bond strength was measured using a testing instrument (2000S, Lloyds Instruments, Fareham, England) at a crosshead speed of 1 mm/min, and the residual adhesive was quantified using a three-dimensional laser scanning instrument. RESULTS: The Mann-Whitney test showed that the median bond strength of group 1 was significantly lower than that of group 2 (P < .001). A Pearson chi-square test of the Adhesive Remnant Index (ARI) revealed a significant difference among the groups tested. All the adhesives in group 1 failed at the enamel/adhesive interface (100%), whereas group 2 exhibited cohesive failure of the adhesive (90%). CONCLUSIONS: The bond strength values obtained with the RMGIC were above the minimum values suggested in the literature to achieve a clinically effective adhesion in orthodontics.     

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.     

Shear bond strength of composite,glass ionomer,and acidic primer adhesive systems

The purpose of this study was to determine the shear bond strengths of orthodontic brackets bonded with one of three methods: (1) a glass ionomer adhesive with a 20% polyacrylic acid enamel conditioner; (2) a composite resin adhesive used with 37% phosphoric acid etchant and a conventional primer; or (3) the same composite resin used with an acidic primer that combines the etchant with the primer in one application. The brackets were bonded to the teeth according to one of three protocols. Group I teeth were etched with 37% phosphoric acid and bonded with Transbond XT (3M Unitek, Monrovia, Calif) following the manufacturer’s instructions. Group I acted as the control group. Group II teeth were etched with an acidic primer (Clearfil Liner Bond 2. J.C. Moritta Kuraway, Japan) that contains both the acid (Phenyl-P) and the primer (HEMA and dimethacrylate) and was placed on the enamel for 30 seconds; the adhesive used to bond the brackets was Transbond XT as in Group I. Group III teeth were etched with 20% polyacrylic acid and the brackets were bonded with Fuji Bond LC (G.C. America, Chicago, Ill). A steel rod with one flattened end was attached to the crosshead of a Zwick test machine (Zwick GmbH & Co, Ulm, Germany). An occlusogingival load was applied to the bracket, producing a shear force at the bracket-tooth interface. The results indicated that the resin/phosphoric acid adhesive system (control group) provided the strongest shear bond strength x̄ = 10.4 ± 2.8 MPa). The glass ionomer adhesive system provided a significantly lower bond strength (x̄ = 6.5 ± 1.9 MPa). The least shear bond strength was present when the acidic primer was used with an orthodontic adhesive (x̄ = 2.8 ± 1.9 MPa). In the present study, the use of either a fluoride-releasing glass ionomer or an acidic primer in combination with an available orthodontic composite adhesive resulted in a significantly reduced shear bond strength when compared with that of the conventional composite resin adhesive system. At the present time, the orthodontist and the patient are better served by using phosphoric acid/composite resin adhesive system or other equivalent systems that provide a clinically reliable bond strength between the bracket, the adhesive, and the enamel surface. (Am J Orthod Dentofacial Orthop 1999;115:24-8)     

A randomized clinical trial comparing 'one-step' and 'two-step' orthodontic bonding systems

OBJECTIVE: The primary objective of this prospective 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 randomized controlled clinical trial. Thirty-four patients were bonded, each being randomly 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 mandibular 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.     

Reconditioning of self-ligating brackets: A shear bond strength study

Objective:To test the null hypothesis that there is no significant difference in the shear bond strength (SBS) and Adhesive Remnant Index (ARI) scores of new vs reconditioned self-ligating brackets.Materials and Methods:One hundred and twenty permanent extracted bovine teeth were embedded in resin blocks. Three different new and reconditioned self-ligating orthodontic brackets (Smart Clip [3M Unitek]; Quick [Forestadent]; and Damon3MX [Ormco]) were tested. Scanning electron microphotographs of the different new (groups 1, 3, and 5) and reconditioned (groups 2, 4, and 6) bracket bases were taken before starting the experiments. Brackets were then bonded to the teeth using an orthodontic adhesive and were then tested in shear mode using an Instron Universal Testing Machine. ARI scores were then recorded. Statistical analysis was performed to determine significant differences in SBS and ARI Scores.Results:Smart Clip and Damon3MX reconditioned brackets showed significantly lower SBS than did new ones. On the contrary, Quick reconditioned brackets showed significantly higher SBS than did new ones. No significant differences in ARI scores were found after the reconditioning process for the three different brackets tested.Conclusion:The in-office reconditioning procedure alters the SBS of self-ligating brackets, although SBS values still remain clinically acceptable.     

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.     

A randomised clinical trial to investigate bond failure rates using a self-etching primer

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 randomly selected patients requiring fixed appliance therapy were entered into the study. Random 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.     

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.     

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).     

Shear bond strength of a mechanically retained ceramic bracket

The failure under shear loading of mechanically retained ceramic brackets bonded to enamel was investigated. One light-activated dual-cure and two no-mix self-cure adhesives were compared to all Adhesive Pre-coated bracket (APC). The results indicated that the ceramic bracket bonded with the light-activated dual-cure adhesive had a significantly higher mean shear bond strength than the other adhesive systems. All adhesive systems usually failed cohesively with adhesive remaining attached to the bracket and enamel surfaces. There was no significant difference in failure site. There was a significant difference in the amount of adhesive remaining attached to the enamel surface. The light-activated dual-cure adhesive and Adhesive Pre-coated brackets failed in 50% and 80% of instances respectively, with less than 10% of the adhesive remaining attached to the enamel surface. Self-cure adhesives failed usually with 10-90% of the adhesive remaining attached to the enamel surface. There were no instances of enamel damage. Three cases of bracket fracture occurred, one of these being associated with the highest recorded bond strength.