Effect of topical fluoride on microshear bond strength of primary enamel to composite, microhardness of enamel and its surface morphology: An in vitro study.

Mina Biria,Narges Panahandeh,Seyedeh Mahsa Sheikh-Al-Eslamian,Sajedeh Namaei Ghasemi

doi:10.15171/joddd.2019.046

Abstract

Background. This in vitro study aimed to evaluate the microshear bond strength (μSBS), microhardness and morphological characteristics of primary enamel after treating with sodium fluoride (NaF) and acidulated phosphate fluoride (APF). Methods. Forty-eight primary canines were cut into mesial and distal sections and assigned to five groups randomly: group 1 (immersed in saliva as a control), group 2 (treated with NAF and immersed in saliva for 30 minutes), group 3 (treated with APF and immersed in saliva for 30 minutes), group 4 (treated with NAF and immersed in saliva for 10 days), and group 5 (treated with APF and immersed in saliva for 10 days). Composite resin (Filtek Z250) was bonded on the specimens (n=15) for measuring the μSBS. After storage in 37°C artificial saliva for 24 hours, µSBS and Vickers hardness tests (10 readings) were performed. The data were analyzed using one-way ANOVA and Kolmogorov-Smirnov, Levene’s and Tukey HSD tests (P<0.05). Morphological analysis of enamel and modes of failure were carried out under a scanning electron microscope (SEM) on two remaining specimens. Results. Significant differences in μSBS were only noted between groups 2 and 4 (P=0.024). Group 3 showed a significant decrease in hardness after storage in artificial saliva (P<0.001), with a significantly lower hardness than the other groups (P<0.001). The SEM observations showed irregular particles in groups 3 and 5; uniform, smooth and thin coats were seen in groups 2 and 4. Conclusion. Fluoride therapy with NaF and APF gels prior to restorative treatments had no adverse effects on the microshear bond strength.

Highlights

Fluoride therapy is a commonly used method for caries prevention in children and adults, which enhances remineralization.[1,2] Different methods of fluoride therapy include daily use of fluoride mouthwashes, application of fluoride gels and use of fluoride varnishes in the dental office.[3,4]In pediatric dentistry, fluoride therapy is often performed as the first treatment procedure in the first dental visit of patients and prior to other procedures
Fluoride therapy with NaF and acidulated phosphate fluoride (APF) gels prior to restorative treatments had no adverse effects on the microshear bond strength
Our findings showed a decrease in the bond strength of composite resin to primary enamel immediately after fluoride application

Summary

Introduction

Fluoride therapy is often performed as the first treatment procedure in the first dental visit of patients and prior to other procedures In such cases, the possible adverse effects of fluoride therapy on the properties of restorative materials are often a concern for many clinicians. It was reported that teeth with fluorosis have lower bond strength to orthodontic brackets compared to normal enamel.[7] In contrast, some studies have shown that fluoridated toothpastes have no significant effects on bond strength.[8]. This in vitro study aimed to evaluate the microshear bond strength (μSBS), microhardness and morphological characteristics of primary enamel after treating with sodium fluoride (NaF) and acidulated phosphate fluoride (APF)

Objectives

Methods

Results

Discussion

Conclusion