OBJECTIVE: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. METHODS: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a 0.017 x 0.025-in wire in the 0.018-in slots and a 0.019 x 0.025-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey's post-hoc test at the 95% confidence level (alpha = 0.05) were also used for statistical analyses. RESULTS: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (micro = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (micro = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (micro = 0.85). CONCLUSIONS: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.
Aluminum Oxide ; Ceramics ; Friction* ; Orthodontic Brackets* ; Stainless Steel

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al2O3), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel–titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al2O3 , TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel–titanium archwire with Al2O3 reduced the coefficients of friction (CoFs) for the bracket–archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al2O3 and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket–archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al2O3 coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions Our findings suggest that the CoFs for metal bracket–archwire combinations used in orthodontic treatment can be decreased by coating with Al2O3 and TiN thin films.

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al2O3), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel–titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al2O3 , TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel–titanium archwire with Al2O3 reduced the coefficients of friction (CoFs) for the bracket–archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al2O3 and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket–archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al2O3 coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions Our findings suggest that the CoFs for metal bracket–archwire combinations used in orthodontic treatment can be decreased by coating with Al2O3 and TiN thin films.