Fracture resistance of ceramic brackets to arch wire torsional force / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. METHODS: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x0.027-inch stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. RESULTS: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. CONCLUSION: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.

Evaluation of friction of esthetic brackets according to different bracket-wire angulations / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate how the friction that occurs during the sliding movement of the archwire through esthetic brackets is differently affected by bracket materials, slot designs, and tip angulations of the archwire. METHODS: Eight types of brackets with 0.018 inch slots (composite: Brillant (BR); composite with metal slot: Spirit MB (SP); ceramic: Inspire (IN), Signature (SI), Cristaline V (CR); ceramic with metal slot: Clarity (CL), Luxi II (LU); and metal bracket: Integra (IT)), and placed into groups of 20 brackets in each group, were tested in artificial saliva with 0.018 inch stainless steel wire. The wire tip angulations were given as 0, 4 and 8 degrees. RESULTS: CR group significantly showed the lowest frictional force with all wire tip angulations of 0, 4, and 8 degrees. IN significantly showed the highest frictional force (p < 0.001). BR (polyoxymethylene) had significantly less frictional force than SP (polycarbonate) (p < 0.001) and showed no significant difference between metal brackets. Friction was increased as the wire tip angulations were increased, but no notches were observed on any parts of the archwire. CONCLUSIONS: According to the results of this study, esthetic brackets are superior or similar to SS brackets from a frictional point of view.