The effect of heat treatment on sliding mechanics of stainless steel orthodontic wires

Aim: The aim of this study was to evaluate the effect of heat treatment (tempering) on the sliding mechanics of stainless steel Chrome Nickel (CrNi) orthodontic wires. Methods: A universal testing machine EMIC DL 2000 was used at a speed of 10 mm/minute for reading-out the sliding strength and friction between brackets and wires, by simulating the sliding mechanics in a fixed orthodontic appliance. The results were submitted to ANOVA variance test for statistical analysis at the level of 5% (p<0.05). Results: The results indicated that depending on the type of bracket, wire and type of treatment, the groups without heat treatment showed higher mean static friction values, except for groups with CrNi GAC wire and conventional brackets, which showed no significant difference with and without heat treatment; and the group with self-ligated brackets and CrNi GAC wires that showed the lowest mean static friction values with heat treatment. Conclusion: The heat treatment reduced the static friction values on CrNi Morelli wires for any combination of brackets (conventional and self-ligated types) and commercial brands. For the CrNi GAC wires, there was a reduction in friction values only in the combination with In-Ovation R/GAC self-ligated brackets

Assessment of Extruded Debris in Primary Molars Comparing Manual and Reciprocating Instrumentation

Objective: To compare the amount of extruded debris in primary molars after manual instrumentation or WaveOne system. Material and Methods: Twenty-five primary molar roots with mild and moderate root angulation (between 10 to 20º), having at least two thirds of root length, no pathological reabsorption (internal or external) or furcation perforation, were selected for this study. Roots were standardized at 6 mm in length, inserted and stabilized in individual acrylic resin blocks with random distribution into two groups: G1 (n=12): Instrumentation with crown-down manual technique; and G2 (n=13): instrumentation with WaveOne system. Blocks with roots were weighed before and after instrumentation, allowing the calculation of extruded debris using both mechanical preparations. Data analysis was performed by Bioestat 4.0 statistical software using Mann Whitney test. Results: The mean weight of extruded debris in manual instrumentation and WaveOne system have no significant difference (p=0.8704). Conclusion: Manual crown-down instrumentation or WaveOne system does not influence the amount of extruded debris after mechanical preparation, suggesting that both techniques were effective in canals clean causing similar extrused debris, however more studies with largest sample should be done to better validate this evidence.