Original article
Shear bond strength of orthodontic brackets bonded with a modified 1-step etchant-and-primer technique

https://doi.org/10.1016/S0889-5406(03)00404-9Get rights and content

Abstract

When bonding orthodontic brackets to enamel, most orthodontists use a conventional technique of etching tooth enamel with phosphoric acid, placing a hydrophilic primer on the etched, rinsed, and dried surface, then bonding the bracket with an adhesive resin composite. New systems simultaneously etch and prime the tooth surface in preparation for bonding. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to enamel with a conventional, multistep adhesive system and a self-etching primer adhesive system. In addition, a third group was included in which the air dispersion step in the self-etching primer system was omitted. Brackets were bonded to 108 extracted human molars according to 1 of 3 experimental protocols—group 1: conventional multistep adhesive (n = 36); group 2: self-etching primer system (n = 36); group 3: self-etching primer system without air dispersion (n = 36). Specimens were loaded to failure in a universal testing machine (Instron, Canton, Mass). Mean shear bond strengths in megapascals (standard deviation) were 11.3 (2.2), 11.9 (3.2), and 8.2 (2.8) for groups 1, 2, and 3, respectively. Data were subjected to 1-way analysis of variance at α = .05. The mean shear bond strength of the self-etching primer group in which the air dispersion step was omitted was significantly less than in the other 2 groups (P < .001). However, there was no difference in mean shear bond strength between the conventional, multistep adhesive system and the self-etching primer system when the primer was dispersed correctly (P = .34).

Section snippets

Material and methods

A total of 108 recently extracted third molars with no cracks, hypoplastic areas, or visible caries were collected for the study. The roots of the teeth were embedded in autopolymerizing orthodontic resin (Dentsply International, York, Pa) with the anatomic crowns exposed and stored in 0.5% chloramine-T. The specimens were placed in an artificial saliva solution (Roxane Laboratories, Columbus, Ohio) maintained at 37°C for a week before the orthodontic bonding procedure. The teeth were polished

Results

Results are summarized in the Table. One-way ANOVA detected a significant difference between groups (P < .001). Student t tests identified which groups were different. Group 3 specimens (self-etching primer system with the air dispersion step omitted) were found to have significantly less mean shear bond strength than the other 2 groups (P < .001). There was no evidence to suggest a difference in mean shear bond strength between groups 1 and 2 (P = .34).

Discussion

Etching tooth enamel with phosphoric acid creates surface microporosities and irregularities into which low-viscosity resins can readily flow. This formation of mechanical retention by cured resin on phosphoric acid-etched enamel has been the major factor responsible for the enamel adhesion of resin-based composite.14

Self-etching primers are relatively recent innovations that simultaneously act as etchant and primer. Self-etching primers are not rinsed off the surface of the teeth. Instead, all

Conclusions

Under the conditions of this study, there was no difference in the shear bond strength of orthodontic brackets bonded to teeth with a self-etching primer or a conventional, multistep bonding procedure. However, a significant decrease in shear bond strength was discovered when the self-etching primer solution was not air-thinned according to the manufacturer's directions. The omission of this step resulted in statistically lower shear bond strengths than in the other 2 groups.

References (25)

  • J. Perdiagao et al.

    Effects of a self-etching primer on enamel shear bond strengths and SEM morphology

    Am J Dent

    (1997)
  • J.C. Hoos

    Clinical findings using a self-etching primer

    Dent Today

    (1999)
  • Cited by (0)

    The views expressed in this article are those of the authors and do not reflect the official policy of the Department of Defense or other departments of the United States government.

    View full text