ABSTRACT
Statement of the Problem: Some studies have reported the bond strength to be significantly lower in fluorotic enamels than the non-fluorosed
Purpose: The purpose of this study was to evaluate the shear bond strength of metallic brackets to non-fluorosed and fluorosed teeth after different enamel conditioning
Materials and Method: A total of 176 freshly extracted human premolars [88 nonfluorosed and 88 fluorosed teeth] were used in this study for bonding the metallic brackets. Teeth with moderate fluorosis were used according to Thylstrup and Fejereskov index [TFI]. Eighty non-fluorosed and 80 fluorosed teeth [TFI=4-6] were randomly divided into 8 equal groups of 20 teeth each. The remaining 16 teeth were used for scanning electron microscopy observation. The enamel surface was conditioned by 4 methods: acid etching for 30 sec, acid etching for 120 sec, air abrasion followed by acid etching, and Er: YAG laser etching followed by acid etching. The morphology of etching patterns in different groups was studied under scanning electron microscope
Results: The shear bond strength of fluorosed teeth to the brackets was significantly lower than non-fluorosed ones [p= 0.003]. The shear bond strength of laser-acid groups in both non-fluorosed and fluorosed teeth was significantly lower than other groups [p< 0.001]. Weibull analysis indicated that the chance of failure under the applied force was different between fluorosed and non-fluorosed group. The scanning electron microscope observations revealed that the fluorosed teeth treated with phosphoric acid had fewer irregularities compared to non-fluorosed teeth. The most irregularities were detected in the teeth conditioned with phosphoric acid for 120 seconds
Conclusion: Fluorotic enamel adversely affects the bond strength of orthodontic brackets. None of the conditioning methods tested in this study could significantly improve shear bond strength of metallic brackets. Er: YAG laser conditioning followed by acid further reduced the bond strength in non-fluorosed and fluorosed teeth