Evaluation of Shear Bond Strength of Different Concentrations Floriated Phosphoric Acid

Objectives: To evaluate the effect of adding the sodium fluoride to different phosphoric acid concentrations on Shear Bond Strength (SBS) of orthodontics brackets bonded to enamel surface. Methods: Forty eight freshly extracted human premolar for orthodontic purposes, were collected, and were randomly divided into four Groups. G1 etched by 37% Phosphoric acid for 30 s, G2 etched by 25% Phosphoric acid for 30 s, G 3 etched by 37% fluoridated Phosphoric acid (0.863% F-) for 30 s, G4 etched by fluoridated 25 % Phosphoric acid (0.694% F-) for 30s. Stainless steel metal brackets (Forestadent Company-sprint-Brackets) were bonded to teeth using self curing composite (system–RMO/ mono-lok2 bonding). A Universal Testing Machine (Testometric M350-5KN, UK) was used to measure SBS, 24 hours after bonding, and the force applied to the ligature groove between bracket base and wings. Data were analyzed using OneWay ANOVA with Tukey post-hoc test (p ≤ 0.05). Results: The mean SBSs were 14.97 MPa, 15.47MPa, 13.09 MPa and 11.16MPa for Groups 1-4 respectively. Significant differences in shear bond strengths were shown between Groups 2 and 4. Significance: The results suggested that the using mixed phosphoric acid 37% with NaF gel 1.23% for 30 s (0.863%F-) have no effect on SBS and may have a clinical application in the prevention of demineralization or caries surrounding and under orthodontic brackets bonded to enamel. Nevertheless, mixed phosphoric acid 25% with NaF% gel (0.694% F-) results to reducing SBS it may have a clinical application.