Effects on shear bond strength and the enamel surface with an enamel bonding agent.

INTRODUCTION: The purpose of this study was to evaluate the shear bond strength of orthodontic brackets and the effect of an enamel bonding agent (EBA) on enamel surface after debonding. METHODS: Seventy-five extracted maxillary premolars were collected and randomly divided into 3 groups of 25. The enamel cracks were surveyed with a stereomicroscope. In the first group, 1 layer of EBA was applied before the adhesive resin. In the second group, 2 layers of EBA were used; in the third group, no EBA was used. Bonding was followed by incubation for 48 hours at 37 degrees C and thermocycling for 1000 cycles. Debonding was performed with a shear force. The surfaces of the teeth were evaluated, and the length, depth, direction of cracks, and adhesive remnants on the enamel surface were recorded. Data were analyzed by using analysis of variance and paired samples t tests. RESULTS: There were no significant differences between the shear bond strengths (P = 0.341) of the 3 groups, or in the direction, length, and depth of the cracks before and after debonding (P > 0.05). There was a significant increase in the number of cracks after debonding in the 3 groups (P < 0.05). The evaluation of adhesive remaining on the surface of the teeth indicated that most bond failures occurred at the resin-bracket interface. CONCLUSIONS: The use of EBA does not enhance bond strength or provide greater protection to the enamel surface during debonding.

Enamel cracks and ceramic bracket failure during debonding in vitro.

OBJECTIVE: To test the null hypothesis that no difference in bracket failure characteristics is noted when use of a new ceramic bracket debonding instrument is compared with the use of conventional pliers. MATERIALS AND METHODS: Thirty maxillary premolars were randomly assigned to one of two groups. In group 1, Clarity collapsible ceramic brackets (3M Unitek, Monrovia, Calif) were debonded with the use of conventional Utility/Weingart (3M Unitek, Monrovia, Calif) pliers. In group 2, Clarity brackets were debonded with a new Debonding Instrument (3M Unitek). For all teeth, the same bracket bonding system was used. Following debonding, teeth and brackets were examined under 10x magnification for assessment of bracket failure (fracture) and of residual adhesive on the enamel surface. Enamel surfaces were visualized with transillumination prior to bonding and after removal of the residual adhesive, so the effect of the debonding forces could be determined. RESULTS: The results of Adhesive Remnant Index comparisons indicated that a statistically significant difference (chi2 = 8.73; P = .013) in bond failure patterns was apparent when the two groups were compared. Brackets debonded with the new instrument showed a greater tendency for the adhesive to be removed from the tooth during debonding. CONCLUSIONS: The hypothesis is rejected. Although the incidence of enamel damage following debonding was similar in the two groups, the use of the new Debonding Instrument decreased the incidence of bracket fracture.

A new premixed self-etch adhesive for bonding orthodontic brackets.

OBJECTIVE: To determine if a new premixed self-etch adhesive can be used to successfully bond orthodontic brackets to enamel. MATERIALS AND METHODS: Forty human molars were cleaned, mounted, and randomly divided into two groups. In group 1, 20 teeth were conditioned using the self-etching primer Transbond Plus (3M Unitek, Monrovia, Calif). In group 2, 20 teeth were conditioned using a new premixed self-etching adhesive, AdheSE One (Ivoclar Vivadent Inc, Amherst, NY). Both groups were bonded using brackets precoated with a composite adhesive. The teeth were debonded within half an hour following initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10x magnifications to determine the amount of residual adhesive remaining on the tooth. A Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the Chi-square test was used to compare the adhesive remnant index (ARI) scores for the two adhesive systems. RESULTS: The mean SBS of the brackets bonded to the teeth using AdhesSE One was 3.6 +/- 1.3 MPa and was significantly lower (t = 2.80, P = .01) than the SBS of the brackets bonded using Transbond Plus (x = 5.9 +/- 3.2 MPa). The comparisons of the ARI scores between the two groups (chi2 = 19.26) indicated that bracket failure mode was also significantly different (P < .001), with more adhesive remaining on the teeth bonded using Transbond Plus. CONCLUSIONS: The SBS of the new premixed self-etching adhesive needs to be increased for it to be successfully used for bonding orthodontic brackets.

Effect of self-etchant pH on the shear bond strength of orthodontic brackets.

INTRODUCTION: Self-etching primers (SEPs) have been used successfully during bonding to reduce technique sensitivity while minimizing the etching of enamel. Although serving the same purpose, SEPs differ in acidity and aggressiveness. Thus, the purpose of this study was to determine whether the pH of SEPs affects the shear bond strength of orthodontic brackets. METHODS: Forty-five molars were cleaned, mounted, and randomly divided into 3 groups with different SEPs: in group 1 (control), 15 orthodontic brackets were bonded to the teeth with Transbond Plus (3M Unitek, Monrovia, Calif) with a pH of about 1.0; in group 2, 15 brackets were bonded with Adper Prompt L-Pop (3M ESPE, St Paul, Minn) with a pH of 0.9 to 1.0; in group 3, 15 brackets were bonded with Clearfil S3 Bond (Kuraray America, New York, NY), with a pH of 2.7. All teeth were bonded with Transbond XT paste (3M Unitek). The teeth were debonded within half an hour after initial bonding by using a universal testing machine. The residual adhesive on each tooth was evaluated. ANOVA was used to compare the shear bond strength (SBS) of the 3 groups, and the chi-square test was used to compare the adhesive remnant index (ARI) scores for the 3 groups. RESULTS: ANOVA indicated significant differences between the groups. The Duncan multiple range test indicated that Clearfil S3 Bond produced a significantly stronger mean SBS (6.5 +/- 1.9 MPa) than the Transbond Plus system (mean, 4.2 +/- 1.9 MPa). No significant differences were seen between the SBS of the brackets bonded with Adper (mean, 5.9 +/- 3.4 MPa) and the other 2 groups. The comparisons of the ARI scores between the 3 groups indicated that bracket failure mode was not significantly different. CONCLUSIONS: The SEP with the highest pH (least acidic), Clearfil S3 Bond, bonded brackets successfully and with the strongest SBS; this suggests that the pH of the SEP is not the primary determinant of the SBS. The clinician should be aware that some SEPs can leave the enamel surface healthier after debonding.

Relative esthetic importance of orthodontic and color abnormalities.

OBJECTIVE: To assess the relative importance of an orthodontic esthetic index, dental fluorosis and nonfluoride opacities, with respect to parents' satisfaction with their children's dental esthetics. MATERIALS AND METHODS: Dental examinations of Iowa Fluoride Study participants assessed fluorosis and nonfluoride opacities in the mixed dentition. Dental casts of 200 randomly selected subjects were scored using the Dental Aesthetic Index (DAI) criteria. Parent satisfaction was assessed via multiple items on a questionnaire. Associations were evaluated using logistic regression. RESULTS: Nineteen percent of parents were somewhat or very dissatisfied with their children's dental esthetics. Overall DAI score was positively associated with dissatisfaction (P < .001), as was fluorosis (P = .003). CONCLUSIONS: In addition to changes related to DAI scores, parent esthetic satisfaction decreased with the presence of fluorosis. Dental professionals should address both the issues of tooth positioning and color aberration with respect to dental esthetics.

Shear bond strength of a new high fluoride release glass ionomer adhesive.

OBJECTIVE: To determine the shear bond strength of a new resin glass ionomer adhesive with higher fluoride release properties when bonding orthodontic brackets. MATERIALS AND METHODS: Sixty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into three groups according to the enamel conditioner/etchant and adhesive used. Group I: 20 teeth conditioned with 10% polyacrylic acid and brackets bonded with the new glass ionomer adhesive. Group II: 20 teeth conditioned with 37% phosphoric acid and brackets bonded with the new glass ionomer adhesive. Group III (control): 20 teeth etched with 37% phosphoric acid and brackets bonded with a composite adhesive. RESULTS: The results of the analysis of variance comparing the three experimental groups (F = 10.294) indicated the presence of significant differences between the three groups (P = .0001). The shear bond strengths were significantly lower in the two groups bonded with the new glass ionomer adhesive whether conditioned with polyacrylic acid ( x = 3.2 +/- 1.8 MPa) or phosphoric acid (x = 2.3 +/- 1.1 MPa), while the mean shear bond strength of the composite adhesive was 5.2 +/- 2.9 MPa. CONCLUSIONS: Although the increased fluoride release from the new glass ionomer has the potential of decreasing decalcification around orthodontic brackets, the shear bond strength of the material is relatively low.

Effects of buccal shields on mandibular dental arch parameters: a clinical and cephalometric study.

The lip bumper is a vestibular functional appliance designed to extend bilaterally between the mandibular buccal tubes and contact the inner surface of the lower lip and cheeks. It functions to eliminate the pressure on the incisors, canines, and premolars, and to transmit distally directed forces to the molars. The purpose of this study was to evaluate the short-term effects of the buccal shield modification of the lip bumper design on various mandibular dental arch parameters, as well as on the inclination of the mandibular incisors. Included in the present study were 44 consecutively treated patients, consisting of 29 females and 15 males from a private orthodontic practice. Student and paired t tests were used to evaluate the changes over time for the various measurements. The results indicated a significant (P < .0001) increase in all arch parameters measured. The greatest mean expansion was observed at the first (5.0 +/- 2.2 mm) and second (3.4 +/- 2.2 mm) premolar width measurements. Less expansion occurred in the intercanine (2.4 +/- 2.0 mm) and intermolar (2.4 +/- 2.6 mm) arch widths. Arch length increased on average 1.6 +/- 2.1 mm. These were significantly (P <.0001) greater than the normal age-related changes in the corresponding parameters.

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

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

A self-conditioner for resin-modified glass ionomers in bonding orthodontic brackets.

OBJECTIVE: To evaluate a new self-etch conditioner used with resin-modified glass ionomers (RMGIs) in bonding orthodontic brackets. MATERIALS AND METHODS: Sixty human molars were cleaned, mounted, and randomly divided into three groups. In group 1 (control), 20 orthodontic brackets were bonded to teeth using Transbond Plus Self-etching Primer; in group 2, 20 brackets were bonded using an RMGI with a 10% polyacrylic acid conditioner. In group 3, 20 brackets were bonded using Fuji Ortho LC with a new no-rinse self-conditioner for RMGIs. The same bracket type was used on all groups. The teeth were debonded in shear mode using a universal testing machine, and the amount of residual adhesive remaining on each tooth was evaluated. Analysis of variance was used to compare the shear bond strength (SBS), and the chi(2) test was used to compare the Adhesive Remnant Index (ARI) scores. RESULTS: There were no significant differences in the SBS (P = .556) between the groups. The mean SBS for Transbond Plus was 8.6 +/- 2.6 MPa, for Fuji Ortho LC using 10% polyacrylic acid 9.1 +/- 4.6 MPa, and for Fuji Ortho LC using GC Self-conditioner 9.9 +/- 4.1 MPa. The comparisons of the ARI scores between the three groups (chi(2) = 35.5) indicated that bracket failure mode was significantly different (P < .001), with more adhesive remaining on the teeth bonded using Transbond. CONCLUSIONS: The new self-etch conditioner can be used with an RMGI to successfully bond brackets. In addition, brackets bonded with Fuji Ortho LC resulted in less residual adhesive remaining on the teeth.

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.

Evaluation of a new nano-filled restorative material for bonding orthodontic brackets.

AIM: To compare the shear bond strength of a nano-hybrid restorative material, Grandio (Voco, Cuxhaven, Germany), to that of a traditional adhesive material (Transbond XT; 3M Unitek, Monrovia, CA, USA) when bonding orthodontic brackets. MATERIAL AND METHODS: Forty teeth were randomly divided into 2 groups: 20 teeth were bonded with the Transbond adhesive system and the other 20 teeth with the Grandio restorative system, following manufacturer's instructions. Student t test was used to compare the shear bond strength of the 2 systems. Significance was predetermined at P 5 .05. RESULTS: The t test comparisons (t = 0.55) of the shear bond strength between the 2 adhesives indicated the absence of a significant (P = .585) difference. The mean shear bond strength for Grandio was 4.1 +/- 2.6 MPa and that for Transbond XT was 4.6 +/- 3.2 MPa. During debonding, 3 of 20 brackets (15%) bonded with Grandio failed without registering any force on the Zwick recording. None of the brackets bonded with Transbond XT had a similar failure mode. CONCLUSIONS: The newly introduced nano-filled composite materials can potentially be used to bond orthodontic brackets to teeth if its consistency can be more flowable to readily adhere to the bracket base.

Shear bond strength comparison of two adhesive systems following thermocycling. A new self-etch primer and a resin-modified glass ionomer.

OBJECTIVE: To compare the effects of a standardized thermocycling protocol on the shear bond strength (SBS) of two adhesive systems: a resin-modified glass ionomer and a composite resin used with a new self-etching primer. MATERIALS AND METHODS: Forty human molars were cleaned, mounted, and randomly divided into two groups. In group 1, brackets were bonded to the teeth using Fuji Ortho LC adhesive, and in group 2, the Transbond Plus system was used. The teeth were stored in water at 37 degrees C for 24 hours, thermocycled between 5 and 55 degrees C, and debonded using a universal testing machine. The enamel surface was examined under 10x magnification to determine the amount of residual adhesive remaining on the tooth. Student's t-test was used to compare the SBS and the chi-square test was used to compare the adhesive remnant index (ARI) scores. RESULTS: The mean SBS for the brackets bonded using the Fuji Ortho LC was 6.4 +/- 4.5 MPa, and the mean SBS for the Transbond Plus system was 6.1 +/- 3.2 MPa. The result of the t-test comparisons (t = 0.207) indicated that there was no significant difference (P = .837) between the two groups. The comparisons of the ARI scores (chi(2) = 0.195) indicated that bracket failure mode was not significantly different (P = .907) between the two adhesives. CONCLUSION: Although SBS and ARI scores were not significantly different for the two adhesives, clinicians need to take into consideration the other properties of the adhesives before using them.

An evaluation of buccal shield treatment. A clinical and cephalometric study.

OBJECTIVE: To evaluate the short-term effects of the buccal shield modification of the lip-bumper design and on various mandibular dental arch parameters and to determine whether the changes in arch widths are due to the tipping or bodily movements of the teeth involved. MATERIALS AND METHODS: This study included 45 consecutively treated patients (29 girls and 16 boys) from a private orthodontic practice. Student's and paired t-tests were used to test the null hypothesis of no change over time for the various measurements. Linear regression analyses were used to determine whether treatment time was a significant predictor of arch width expansion. Significance for all statistical tests was predetermined at P < or = .05. RESULTS: Student's t-test results indicated the presence of a significant (P < .0001) increase in all the arch parameters measured. The greatest mean expansion was observed at the first (5.0 +/- 2.2 mm) and second (3.4 +/- 2.2 mm) premolar width measurements. The changes in arch width parameters were significantly (P < .0001) greater than the normal age-related changes in the corresponding parameters. There was no significant difference between arch width expansion of the occlusal vs gingival levels, indicating a bodily and not tipping movement. Only 30% of the lower incisors demonstrated an increase in their proclination beyond normal values. CONCLUSION: When using the buccal shield appliance, the mandibular arch width parameters can be expanded in the mixed dentition with bodily movement of teeth. The expanded arch width dimensions are greater than what would be expected as a result of normal growth.

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

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

Changes in the prevalence of nonnutritive sucking patterns in the first 8 years of life.

INTRODUCTION: The purposes of the study were to determine prospectively the duration of nonnutritive sucking behaviors of children between 1 and 8 years of age and the effect of persistent habits on selected occlusal characteristics in the late deciduous dentition. METHODS: Sucking behavior data were initially collected from 797 children who were followed longitudinally from birth; the data came from periodic questionnaires completed by the parents. In addition, study models were obtained for 372 children at 4 to 5 years of age and assessed for posterior crossbite, anterior open bite, and overjet. The subjects were grouped according to the duration and type of habit (pacifier or digit, for less than 12 months or more than 48 months). Children with nonnutritive sucking of less than 12 months were further grouped according to the duration of breast-feeding. The McNemar nonparametric test was used to compare the changes in the incidence and effect of the habits with time. RESULTS: There was a significant (P = .001) decrease in the incidence of pacifier habits between 1 and 5 years of age, from 40% to 1%. There was a significant (P = .01) decrease in the incidence of digit habits between 1 and 4 years of age, from 31% to 12%. Between 4 and 7 years of age, the decrease in the incidence reached a plateau--ie, the decrease continued but at a slower rate. Between 7 and 8 years of age, there was an additional significant (P = .008) decrease in the incidence of digit habits, but 4% of the children were, to various extents, still sucking fingers. Children who had pacifier or digit habits lasting less than 12 months did not have significantly different occlusal characteristics than children who were breast-fed for 6 to 12 months. Prolonged pacifier and digit habits caused significant changes in the occlusal characteristics in the late deciduous dentition, and the effects of pacifier habits were different from those of digit sucking. CONCLUSIONS: To intercept the development of crossbites and functional shifts, the developing occlusion should be observed in the deciduous dentition in children with prolonged digit or pacifier habits. The transverse occlusal relationship, particularly in pacifier-sucking children, should be evaluated between 2 and 3 years of age. If there are interfering contacts of the deciduous canines, the parents should be instructed to reduce pacifier-sucking time, and appropriate treatment should be rendered, if required.

Individual variation in tooth-size/ arch-length changes from the primary to permanent dentitions.

AIM: To determine the individual variation in the maxillary and mandibular tooth-size/arch-length relationships after the complete eruption of the primary dentition (mean age, 4.0 years) and at the time of eruption of the second permanent molars (mean age, 13.3 years). METHODS: Records of 32 males and 27 females were evaluated. Each subject had a clinically acceptable occlusion; that is, a normal molar and canine relationship at the time of eruption of the primary and permanent teeth. In addition, each subject had a complete set of data at the 2 stages of dental development. These selection criteria limited the number of subjects in this investigation to 59. The mesiodistal diameter of all primary teeth and their permanent successors, as well as various dental arch length parameters were measured in the primary and permanent dentitions. A total of 60 parameters were measured or calculated. RESULTS: The findings from the present investigation indicated that of the total sample of 59 male and female subjects observed on a longitudinal basis, 29 (49%) maintained their relative tooth-size/arch-length relationship ranking in the 2 dentitions, while 30 (51%) changed to either a more favorable or less favorable relationship in the permanent dentition. CONCLUSIONS: The cases with the lower ranking of tooth-size/arch-length relationship in the primary dentition, 50% maintained their relatively lower rank in the permanent dentition, while the other 50% changed to a relatively more favorable rank in the permanent dentition. There is a similar probability for maintaining the same ranking in the primary and permanent dentitions in the mandibular arch (51%), as in the maxillary arch (49%). The clinical implications of the findings are discussed.

Fluoride release rate from an orthodontic sealant and its clinical implications.

The objectives were to measure the rate and amount of fluoride ions released from the sealant over a period of 17 weeks and to determine whether the fluoride-releasing sealant has a recharging ability when fluoride ions are reintroduced into the environment. Disc-shaped specimens were prepared from two types of sealants: (1) 10 discs were made using a fluoride-releasing sealant and (2) 10 discs were made of a nonfluoride adhesive primer (control). An ion analyzer was used to measure the fluoride release using a fluoride ion-specific combination electrode. The results of the repeated measure analysis (F = 7.76) indicated that the fluoride-containing sealant released fluoride ions into the solution in sustained but significantly (P = .014) decreasing rates from a high of 0.074 +/- 0.04 ppm/week/mm2 in the first week to a low of 0.015 +/- 0.017 ppm/week/mm2 at the end of the 17th week. Furthermore, the Pro Seal discs had the ability to be recharged with fluoride ions introduced from a foaming solution of acidulated phosphate fluoride. The mean fluoride release rate one week after recharging was 0.354 +/- 0.095 ppm/week/mm2 and decreased to 0.014 +/- 0.009 ppm/week/mm2 after eight weeks. The control sealant showed no significant fluoride release and was unable to absorb the fluoride ions available in the solution. The fluoride-containing sealant Pro Seal released fluoride ions in sustained but significantly decreasing amounts. The Pro Seal discs had the ability to be recharged with fluoride ions.

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

Orthodontic brackets 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 combine the conditioning, priming, and adhesive agents into a single application. The purpose of this study was to assess and compare the effects of using one-step and two-step self-etch primer/adhesive systems on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human molars according to one of two protocols. Group I (control): a two-step self-etch acidic primer/adhesive system was used, Transbond Plus was applied to the enamel surface as suggested by the manufacturer. The brackets were bonded with Transbond XT and light cured for 20 seconds. Group II: a one-step self-etch, self-adhesive resin cement system, Maxcem, was applied directly to the bracket. The self-etch primer/adhesive is made of two components that mix automatically during application. The brackets were then light cured for 20 seconds. The mean shear bond strength of the two-step acid-etch primer/adhesive was 5.9 +/- 2.7 Mpa and the mean for the one-step system was 3.1 +/- 1.7 MPa. The in vitro findings of this study indicated that the shear bond strengths (t = 3.79) of the two adhesive systems were significantly different (P = .001). One-step adhesive systems could potentially be advantageous for orthodontic purposes if their bond strength can be improved.