Friction Force Between the TiN and non-TiN Coated Metal Brackets

Objective: Orthodontic metal bracket can be corroded in oral environment. The purpose of the present study was to compare the friction force between the non coated metal bracket and titanium nitride (TiN) coated metal bracket after electrochemical corrosion.

Methods: Total 40 metal brackets were used in present study. Experimental group contained twenty metal brackets which were coated with TiN by performing it under conditions of 400-W rf power, 13-mPa argon gas pressure, 53-mPa nitrogen gas pressure, and -1-kV bias voltage. The rest twenty metal brackets were as control group. The half of each group metal brackets were corroded by elelctrochemistry method in fluoride contained mouth rinse. The elastic modulus were used to ligate the bracket and archwire. The friction force were recorded on an EZ-test machine (Shimadazu, Tokyo, Japan) with a crosshead speed of 10mm per minute over a 5-mm stretch of 0.019x0.025 inches stainless steel archwire. Statistic and kinetic friction force were analyzed and one way ANOVA was used to test for significant difference. Results: The results showed that the friction force was higher on non TiN coated bracket group (p<0.05) in non corrosion status. The friction force was higher on TiN coated group (p<0.05) in corrosion status.

Conclusions: The TiN coated metal bracket do not reduce the friction force. The irregular bracket morphology might cause uneven TiN coating on bracket which result in more rough surface of metal bracket. This roughen surface cause the high friction force between wire and bracket.