Conservative therapy of non carious cervical lesion (NCCL): original method

AIM: The process of twisting has been used for decades to fabricate stainless steel instruments, but it was previously thought to be an impractical method for nickel-titanium (Ni-Ti) instrument manufacture A manufacturing method of twisting Nickel-Titanium wire to produce Ni-Ti files has been recently developed: the twisted files (TF). Theoretically, this new manufacturing process should overcome the problems associated with a grinding process, which previously limited instrument strength. Since TF manufacturing process is new and different from grinding, the aim of the present study was to evaluate the effects of a final deoxidation process (Deox) on torsional resistance of TF instruments. METHODS: Testing was performed in accordance with the International Standard (ISO 3630-1) by comparing 20 TF instruments versus 20 TF prototype instruments produced without the final deoxidation process. Data were collected and statistically analyzed (t-test). RESULTS: Results show that TF instruments withstood 90% more torque (max. torque) than TF prototype instruments manufactured without the deoxidation process (88.7 vs. 53.3 g/cm). This difference was found to be statistically significant at the 0.05 level of significance. CONCLUSION: Since design and dimensions of tested instruments were the same, the deoxidation process could be the only explanation of the improvement in torsional resistance.