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).     

In vitro shearing force testing of two seventh generation self-etching primers

Objective: The purpose of this study was to evaluate the in vitro shearing force performance of orthodontic attachments using two self-etching primers (SEPs): iBOND and G-Bond. Design: In vitro, laboratory study. Material and methods: One hundred and eighty human molars were randomly divided into four groups and again into three sub-groups with 15 teeth each. Teeth were bonded with a stainless steel button (GAC International,Bohemia, NY, USA) using Transbond XT adhesive composite. The bonding agents were iBOND, G-Bond, Transbond Plus SEP and Transbond XT primer. Shearing force tests were carried out immediately, and at 24 hours and 3 months using a universal testing machine. Force to debond (N) and Adhesive Remnant Index (ARI) scores were evaluated and compared. Results: Transbond XT primer required a higher immediate (P<0·05)force to debond when compared to the Transbond Plus SEP, iBOND and G-Bond.After 24 hours, mean force to debond for Transbond XT primer and Transbond Plus SEP showed significant increases. At 3 months, all four bonding agents demonstrated force levels to debond that were not significantly different from one another. Furthermore, comparison of ARI scores indicated a significant difference between the groups at all time points. Conclusions: iBOND and G-Bond may well sufficiently with stand the alignment and occlusal forces imparted by light archwires during immediate archwire tie-in and over the initial levelling and alignment phase.     

Effect of water and saliva contamination on shear bond strength of brackets bonded with conventional, hydrophilic, and self-etching primers

This study assessed the effect of water and saliva contamination on the shear bond strength and bond failure site of 3 different orthodontic primers (Transbond XT, Transbond Moisture Insensitive Primer, and Transbond Plus Self Etching Primer; 3M Unitek, Monrovia, Calif) used with a light-cured composite resin (Transbond XT). Bovine permanent mandibular incisors (315) were randomly divided into 21 groups (15 in each group). Each primer-adhesive combination was tested under 7 different enamel surface conditions: (1) dry, (2) water application before priming, (3) water application after priming, (4) water application before and after priming, (5) saliva application before priming, (6) saliva application after priming, and (7) saliva application before and after priming. Stainless steel brackets were bonded in each test group with composite resin. After bonding, all samples were stored in distilled water at room temperature for 24 hours and then tested for shear bond strength. Noncontaminated enamel surfaces had the highest bond strengths for conventional, hydrophilic, and self-etching primers, which produced the same strength values. In most contaminated conditions, the self-etching primer had higher strength values than either the hydrophilic or conventional primers. The self-etching primer was the least influenced by water and saliva contamination, except when moistening occurred after the recommended 3-second air burst. No significant differences in debond locations were found among the groups bonded with the self-etching primer under the various enamel conditions.     

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.     

Thermocycling effects on shear bond strength of a self-etching primer

OBJECTIVE: To determine the effects of thermocycling on shear bond strengths (SBSs) of a self-etching primer (SEP) after 0, 2000, and 5000 thermal cycles. MATERIALS AND METHODS: Brackets were bonded to bovine incisors with two etching protocols. In the control group (conventional method) teeth were etched with 37% phosphoric acid. In the experimental group, an SEP (Transbond Plus) was applied as recommended by the manufacturer. Brackets were bonded with light-cure adhesive paste (Transbond XT) and light cured for 20 seconds in both groups. The SBSs were measured after water storage at 37 degrees C for 24 hours, after 2000 and 5000 cycles of thermocycling between 5 degrees C and 55 degrees C. Bond failure location was determined with the Adhesive Remnant Index (ARI). RESULTS: In the control group, SBSs did not show any significant differences among 0, 2000, and 5000 thermal cycles. However, in group SEP, SBSs decreased with 2000 and 5000 thermal cycles, and these decreases were significantly different from no thermocyling (P < .001). A significant difference was observed between ARI scores of the control group with 5000 thermal cycles and group SEP with no thermal cycles (P < .003). In addition, a significant difference was found between group SEP with no thermocycling and with 5000 thermal cycles (P < .003). CONCLUSION: The results of this study indicate that the SEP (Transbond Plus) provides clinically acceptable bond strength values compared with the conventional method after thermocycling.     

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.     

Artificial saliva contamination effects on bond strength of self-etching primers

OBJECTIVE: To test the hypothesis that there is no difference in the bond strength with or without contamination with artificial saliva when using two different self-etching primers (Transbond Plus and iBond) in comparison with a conventional acid-etching method (37% phosphoric acid and Transbond XT) for bonding of orthodontic brackets. MATERIALS AND METHODS: One hundred fifty extracted human premolars were randomly allocated to six different groups, with 25 teeth in each group. Orthodontic metal brackets (APC II, Victory Twin 22 UNIV) were used. For contamination, a saliva replacement (Ptyalin) was applied. After contamination the surface was air-dried for 5 seconds and the bonding procedure continued. The bonded teeth were stored in deionized water at 37 degrees C for 30 days and then thermocycled for 24 hours before debonding with a universal testing machine. The load was recorded at bond failure. The location of adhesive failure was determined under magnification using the adhesive remnant index (ARI). RESULTS: Clinically acceptable bond strengths were found for all primers used in this study. The contamination by saliva significantly decreased the bond strength when using the conventional acid-etching method (t = 0.0001). Self-etching primers were less influenced by saliva contamination. There was no significant difference in the ARI score among the groups (P > .05). CONCLUSIONS: Saliva contamination significantly decreased the bond strength when the conventional acid-etching method was used. The self-etching primers were influenced the least. The bond strengths achieved for the self-etching primers and the conventional etching method after saliva contamination were not significantly different.     

粘结时间对微蚀刻底托槽粘结强度的影响

目的:对比微蚀刻底托槽粘结后不同时间的粘结强度,寻找合适的力的加载时机。方法:随机挑选对称性拔除上下颌第一前磨牙正畸患者30例,分为A、B、C三组进行全口微蚀刻底托槽粘结,分别在粘结后5 min,30 min,60min进行弓丝结扎,统计患者第一次复诊时托槽脱落率。将30例患者拔除的上颌第一前磨牙60颗,随机分成1～6组,每组10颗。1～6组离体牙粘结微蚀刻底直丝托槽,分别在粘结后5 min,10 min,15 min,30 min,60 min,24 h进行抗剪切强度(SBS)测定,并统计粘结剂残留指数(ARI),扫描电镜观察托槽粘结前后底板形貌。结果:微蚀刻底托槽在体外粘结后24 h抗剪切强度达到最大。结论:微蚀刻底托槽的粘结强度能够满足临床需要,临床医师可在托槽粘结后5 min进行力的加载。     

Bond strength comparison of moisture-insensitive primers.

The objective of this in vitro bonding study was to evaluate the effectiveness of 2 moisture-insensitive primers, Assure (Reliance Orthodontic Products, Itasca, Ill) and MIP (3M Unitek, Monrovia, Calif) compared with a control hydrophobic primer, Transbond XT (3M Unitek). Six groups of 40 premolars were acid etched and bonded using metal orthodontic brackets with the following in vitro protocols: (1) Transbond XT primer and adhesive applied to a noncontaminated surface; (2) Assure primer applied after saliva contamination; (3) MIP primer applied after saliva contamination; (4) Assure primer reapplied after saliva contamination; (5) MIP reapplied after saliva contamination; and (6) Assure adhesive applied after saliva contamination of the primer. All bonded specimens were stored in deionized water at 37 degrees C for 30 days and thermocycled for 24 hours before debonding. Brackets were debonded using a shear-peel load on a testing machine, bond strength was measured in megapascals, and bond failure was analyzed by using the adhesive remnant index. In vitro shear-peel bond strengths were acceptable for all groups, and the bond strengths for Assure and MIP were not significantly affected by saliva contamination. The mean shear-peel bond strength of the control (14.82 MPa) was significantly higher (P <.001) than the contaminated groups with the exception of MIP group 5 (14.02 MPa). The values of the Assure primer and adhesive were less than the MIP primer and its respective adhesive; however, the hydrophilic Assure adhesive resin applied to a saliva-contaminated surface had acceptable bond strength. Bond failure analysis (adhesive remnant index) mainly showed adhesive bond failures. An increased frequency of enamel fractures at debond was noted, with the control group (1) and the MIP groups (3 and 5) having 22.5%, 12.5%, and 15%, respectively. The Assure groups had no enamel fractures.     

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.     

Effects of blood contamination on the shear bond strengths of conventional and hydrophilic primers.

The purpose of this study was to assess the effect of blood contamination on the shear bond strength and failure site of 2 orthodontic primers (Transbond XT and Transbond MIP; 3M/Unitek, Monrovia, Calif) when used with adhesive-precoated brackets (APC II brackets; 3M/Unitek). One hundred twenty bovine permanent mandibular incisors were randomly divided into 8 groups; each group contained 15 specimens. Each primer-adhesive combination was tested under a different enamel surface condition: dry, blood contamination before priming, blood contamination after priming, or blood contamination before and after priming. Stainless steel APC II brackets were bonded to the teeth. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. Noncontaminated enamel surfaces had the highest bond strengths for both conventional and hydrophilic primers; their values were almost the same. Under blood-contaminated conditions, both primers showed significantly lower shear bond strengths. For each type of primer, no significant differences were reported among the blood-contaminated groups. Significant differences in debond locations were found among the groups bonded with the 2 primers under the various enamel surface conditions. Blood contamination of enamel during the bonding procedure of conventional and hydrophilic primers significantly lowers their bond strength values and might produce a bond strength that is not clinically adequate.     

Effect of blood contamination on shear bond strength of brackets bonded with conventional and self-etching primers.

This study assessed the effect of blood contamination on the shear bond strength and bond failure site of 2 different orthodontic primers (Transbond XT and Transbond Plus Self-Etching Primer, both from 3M Unitek, Monrovia, Calif) used with adhesive-precoated brackets. Four different enamel surface conditions were tested: (1) dry, (2) blood contamination before priming, (3) blood contamination after priming, and (4) blood contamination before and after priming. Noncontaminated enamel surfaces had the highest bond strengths for both conventional and self-etching primers, which produced almost the same strength values. Under blood-contaminated conditions, both primers showed significantly reduced shear bond strengths. For the conventional primer, no significant differences were reported among the blood-contaminated groups, whereas when the self-etching primer was used, condition 4 reduced significantly the bond strength values. Significant differences in debond locations were found among the groups bonded with the 2 primers under the various enamel surface conditions.     

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.     

Effect of saliva contamiination on the shear bond strength of orthodontic brackets bonded with a self-etching primer

This study evaluates the effect of saliva contamination at different stages of the bonding brackets procedure using the self-etching primer Adper Prompt L-Pop (3M ESPE, Minneapolis, Minn) and the resin orthodontic adhesive system Transbond XT (3M). A total of 70 brackets were bonded to human extracted premolars, which were divided into four groups: group 1, uncontaminated (control); group 2, saliva application before priming; group 3, saliva application after priming; and group 4, saliva application before and after priming. Shear bond strength was measured with a universal test machine. The adhesive remnant on the tooth after debonding was determined using image analysis equipment. Significant differences were only observed between group 1 (12.42 +/- 3.27) and groups 2 (9.93 +/- 4.50) and 4 (9.59 +/- 2.92) (P < .05). Concerning the adhesive remnant, no significant differences were found between the groups evaluated (P > .05).     

A comparison of shear-peel band strengths of 5 orthodontic cements

The objective of this study was to compare the shear-peel band strength of 5 orthodontic cements using both factory and in-office micro-etched bands. The 5 orthodontic cements evaluated were a zinc phosphate (Fleck's Cement), 2 resin-modified glass ionomer cements (RMGI)(3M Multicure glass ionomer and Optiband), and 2 polyacid-modified composite resin cements (PMCR)(Transbond Plus and Ultra Band Lok). Salivary contamination was examined with a polyacid-modified composite resin (Transbond Plus). Two hundred and eighty extracted human molar teeth were embedded in resin blocks and each was randomly assigned to the following 7 groups: 6 groups with factory etched bands, 5 cement groups and salivary contaminated group, and 1 in-office micro-etched group. The cemented teeth were put in deionized water at 37 degrees C for 30 days and thermocycled for 24 hours. The force required to break the cement bond was used as a measure of shear-peel band retention. With the use of an Instron testing machine, a shear-peel load was applied to each cemented band. Data were analyzed with a one-way analysis of variance (ANOVA) with a Tukey test for the multiple comparisons. The RMGIs and PMCRs demonstrated significantly greater shear-peel band strengths compared to the zinc phosphate cement. No statistically significant differences were noted between the RMGI cement and PMCR cements and within the RMGI groups, however, there was a statistically significant difference within the PMCR groups. Significantly lower band strengths were noted with the saliva contaminated PMCR cement group (Transbond Plus) and the inpractice sandblasted PMCR group. Both RMGIs and PMCRs were found to demonstrate favorable banding qualities. The lower band strength with saliva-contaminated bands suggests that moisture control is critical when using a PMCR. The variability noted in the in-office micro-etched bands might be technique related.     

Effect of applying a sustained force during bonding orthodontic brackets on the adhesive layer and on shear bond strength

The objective of this research was to investigate the effect of applying a sustained seating force during bonding on the adhesive layer and on shear bond strength (SBS) of orthodontic brackets. Forty human premolars divided into two groups were included in the study. Stainless steel brackets were bonded to the premolars with Transbond XT light cure adhesive and Transbond Plus Self Etch Primer (SEP). The brackets in both groups were subjected to an initial seating force of 300 g for 3 seconds, sufficient to position the bracket. The seating force was maintained throughout the 40 seconds of light curing in group 2. SBS was tested 24 hours after bracket bonding with a shear blade using an Instron testing unit at a crosshead speed of 2 mm/minute. A Student's t-test was used to compare the bond strength of the two groups and a chi-square test to compare the frequencies of the adhesive remnant index (ARI) scores. The mean SBS was significantly different between the two groups (P=0.025). The bond strength was higher (mean 8.15±0.89 MPa) in group 2 compared with group 1 (mean 7.39±1.14 MPa). There was no significant difference (P=0.440) in the ARI scores between the two groups. Applying a sustained seating force during orthodontic bracket bonding improves bond strength but does not change the distribution of the ARI scores.     

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.     

An in vitro comparative assessment of different enamel contaminants during bracket bonding

In orthodontics, adhesive failures can occur because of saliva contamination during bonding. However, most in vitro studies concerning bond strength of saliva-contaminated enamel disregard the influence of temperature changes in a wet environment. The aim of the present study was to compare the influence of saliva, blood and etching gel remnant contamination on shear bond strength (SBS) after thermocycling. After etching of extracted human third molars (n = 80), a conventional primer (Transbond XT) and a moisture-insensitive primer (Transbond MIP) were evaluated using the adhesive, Transbond XT, under dry conditions and after contamination with saliva, blood and etching gel remnants. To simulate temperature changes and the moisture of saliva in the oral cavity, all samples were thermocycled (6,000 x 5 degrees C/55 degrees C) in a mastication device before SBS testing. A Mann-Whitney U test was used to determine statistical differences. Under dry conditions Transbond XT and Transbond MIP showed no significant difference in SBS. However, clinically unacceptable (P = 0.005) bond strength was observed using Transbond XT after saliva and blood contamination. In wet conditions only Transbond MIP showed sufficient bond strength. If contamination during bonding is expected, a hydrophilic primer should be used. Under dry conditions hydrophilic or hydrophobic primers could be applied. Blood contamination seems to be a more serious problem for bond strength than saliva or etching gel contamination.     

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.     

Bracket bond strength and cariostatic potential of an experimental resin adhesive system containing Portland cement

Abstract Objective: To determine if a new experimental resin-based material containing Portland cement (PC) can help prevent enamel caries while providing adequate shear bond strength (SBS). Materials and Methods: Brackets were bonded to human premolars with experimental resin-based adhesive pastes composed of three weight rations of resin and PC powder (PC 30, 7∶3; PC 50, 5∶5; PC 70, 3∶7; n = 7). Self-etching primer (SEP) adhesive (Transbond Plus) and resin-modified glass ionomer cement (RMGIC) adhesive (Fuji Ortho FC Automix) were used for comparison. All of the bonded teeth were subjected to alternating immersion in demineralizing (pH?4.55) and remineralizing (pH?6.8) solutions for 14?days. The SBS for each sample was examined, and the Adhesive Remnant Index (ARI) score was calculated. The hardness and elastic modulus of the enamel were determined by a nanoindenter at 20 equidistant depths from the external surface at 100?μm from the bracket edge. Data were compared by one-way analysis of variance and a chi-square test. Results: PC 50 and PC 70 showed significantly greater SBS than Fuji Ortho FC Automix, although Transbond Plus showed significantly greater SBS than other bonding systems. No significant difference in the ARI category was observed among the five groups. For specimens bonded with PC 50 and PC 70, the hardness and elastic modulus values in most locations were equivalent to those of Fuji Ortho FC Automix. Conclusions: Experimental resin-based bonding material containing PC provides adequate SBS and a caries-preventive effect equivalent to that of the RMGIC adhesive system.