Effectiveness of Ultraviolet Light on Sterilization of Conventional Orthodontic Metal Brackets - An In-vitro study

Abstract

Introduction: Infection control is critical in dentistry, as orthodontic appliances (brackets, wires, elastics) can harbour microorganisms that may be transmitted if not sterilized prior to use. Studies have shown that new orthodontic brackets received from manufacturers often carry bacterial contamination. Ultraviolet-C (UV-C) light with wavelength 100–280 nm is a potent germicidal method that inactivates microbes via DNA damage and offers a dry, residue-free sterilization option without heat-related warping. However, the optimal UV-C exposure time for fully sterilizing orthodontic brackets is unclear.

Objectives: To evaluate and compare the antimicrobial effectiveness of UV-C irradiation on conventional orthodontic metal brackets at exposure times of 5, 10, and 15 minutes.

Methods: Forty new, unused maxillary premolar metal brackets (0.022″ MBT prescription) were randomly assigned to four groups (n=10 each): Group 1, control (no sterilization); Group 2, UV-C exposure for 5 minutes; Group 3, UV-C exposure for 10 minutes; Group 4, UV-C exposure for 15 minutes. UV-C irradiation was applied using a bench-top UV-C sterilizer. After treatment, each bracket was aseptically placed on a blood agar plate and incubated at 37 °C for 72 hours. The primary outcome was the presence or absence of bacterial colony growth on each plate. Data was analysed with the Chi-square test (significance at p ≤ 0.05).

Results: In the control group (no sterilization), 10 of 10 brackets (100%) showed microbial growth. After 5 minutes of UV-C, 8 of 10 brackets (80%) showed growth. After 10 minutes, 6 of 10 (60%) showed growth. After 15 minutes, only 2 of 10 brackets (20%) showed growth. The differences among groups were statistically significant (Chi-square p < 0.001). Increasing UV-C exposure time correlated with a marked reduction in bacterial contamination.

Conclusions: UV-C irradiation significantly reduced microbial load on orthodontic metal brackets in vitro in a time-dependent manner. Fifteen minutes of UV-C exposure achieved the greatest sterilization. These results support UV-C as a rapid, heat-free method for disinfecting orthodontic brackets prior to clinical use.