No abstract

No abstract

Objective: To explore the changes in nickel-titanium (NiTi) archwires after exposure to fluoride-containing acetic acid solutions. Materials and methods: Preformed rectangular NiTi wires were immersed in either an acidulated fluoride solution, a neutral fluoride solution or distilled water (control) for 1.5 hours at 37°C. After immersion, the unloading force values at four deflection points were measured by three-point bending test. Scanning electron microscopy and X-ray diffraction analysis were also performed to characterize the effects of the fluoride exposure on the wire. Results: Unloading force values of NiTi orthodontic wires were significantly decreased after exposure to both fluoride solutions (p < 0.001). Corrosive changes in surface topography were observed for both fluoride solutions. Wires exposed to acidic fluoride appeared as more severely affected. X-ray diffraction analysis showed no change in crystal lattice of NiTi wires in both solutions. Conclusion: The results suggest that using topical fluoride agents with NiTi wire could decrease the functional unloading mechanical properties of the wire and contribute to prolonged orthodontic treatment.

No abstract

The increasing demand for a more esthetic metal bonded appliance has led to a reduction in the size of the brackets and their bases. The reduction of bracket size improves esthetics and produces a more easily cleansed appliance. This reduction results in less base surface area available for bonding with the concomitant clinical reality of increased debonding rates.Objectives: To compare the shear bond strength and to evaluate and compare the surface design characteristics (mesh type, mesh wire size) of different commercially available direct bonding metal brackets. Materials and methods:Maxillary first premolar brackets of six different manufacturing companies were bonded on freshly extracted human premolars preserved in artificial saliva, with the same adhesive and then debonded using a universal testing machine. The bracket bases were also examined under the scanning electron microscope (SEM). Results:The bond strength obtained with different commercially available bracket bases was stastically variable. The size of bracket bases influenced the shear bond strength values. The mesh size and its configuration also affect the bond strength. Conclusion:Gemini brackets provided the best bond strengths clinically, followed by Mini Diagonali, Nu-Edge, Mini Twin, Mini Diamond and the Sapphire brackets in decreasing order as measured using the Weibull analysis.