Effect of extended application time of universal adhesives on bond strength of brackets and enamel integrity

May Anny Alves Fraga,Daniela Feu Rosa Kroeff De Souza Laignier Laignier,Licia Pacheco Teixeira,Juliana Malacarne-Zanon,Américo Bortolazzo Correr,Carolina Sandra Yamashita Garfias

doi:10.33448/rsd-v10i13.20832

Abstract

The objective of this study to evaluate the effect of universal adhesives application time to enamel through shear bond strength (SBS), adhesive remnant index (ARI), and morphological enamel integrity. Bovine incisors were divided into four groups according to bonding system protocol (n=20): (1) conventional etch-and-rise adhesive – Transbond XT Primer (P-XT); (2) one-step self-etching adhesive – Transbond Self Etching Primer (T-SEP); (3) one universal adhesive – Single Bond Universal, which were rubbed for 20s (SBU-20) or (4) 40s (SBU-40). Transbond XT composite was used to bond the brackets to enamel. SBS was evaluated in a universal test machine at 0.5mm/minute. ARI was determined under x12.5 magnification and enamel damage was evaluated through scanning electron microscope (SEM) after debonding (n=10). SBS data were compared using one-way ANOVA and Tukey’s test. The Kruskal–Wallis test was used to compare the ARI scores (α =0.05). The P-XT and T-SEP groups showed significantly higher bond strength than SBU-20 and SBU-40 (p<0.05). The ARI was similar for all groups (p>0.05). SEM showed enamel damage only in T-SEP and P-XT groups. Conventional ‘etch and rinse’ and ‘self-etch’ adhesives had the highest shear bond strength, but they were associated with more enamel damage compared to universal adhesives. The application of universal adhesives with the time recommended by the manufacturer — ensure satisfactory bond strength and enamel integrity.

Highlights

It is essential that dental adhesives used to bond orthodontic brackets to enamel provide enough bond strength between them to prevent spontaneous dislodgments during treatment
It was not observed a significant difference between the groups according to the adhesive remnant index (ARI) distribution (Figure 1, KruskalWallis test, P = 0,062)
scanning electron microscope (SEM) analysis showed that enamel damage was detected in Transbond Self Etching Primer (T-s; (manufacturer recommendationE) tching Primer (SEP)) (Figure 2) and Primer XT (P-XT) (Figure 3) groups

Summary

Introduction

It is essential that dental adhesives used to bond orthodontic brackets to enamel provide enough bond strength between them to prevent spontaneous dislodgments during treatment. Adhesives should not induce damage to the enamel surface when removed (Lamper et al, 2014). Excessive forces on removing the orthodontic brackets may cause enamel damage (Meeran, 2013), as in, it is recommended that resin materials used on brackets bonding should stay adhered to the teeth surface after its intentional removal. Values of 6 MPa and 8 MPa have been reported to be suitable to tolerate masticatory forces as well as to preserve dental structure during brackets’ removal (Alshahrani et al, 2018). Bond strength values higher than 12 MPa revealed a 70%

Methods

Results

Conclusion