RESUMEN
BACKGROUND: To evaluate the antibacterial activity and debonding force of retainers bonded with conventional and nanoparticle (TiO2) containing composite. METHODOLOGY: Antibacterial activity was tested against Streptococcus mutans and Lactobacillus acidophilus using disk agar diffusion, biofilm inhibition, and eluted components tests. For the eluted components test, colony counts of bacteria were tested on 0, 3, and 30 days. Three different retainers were bonded to the lingual surface of extracted lower incisors using conventional and 1% TiO2 composite. Samples were divided as follows: Group 1: 1a, stainless steel retainer (Bond-a-Braid) with conventional composite, and 1b, stainless steel retainer with nanoparticle composite; Group 2: 2a, titanium retainer with conventional composite, and 2b, titanium retainer with nanoparticle composite; Group 3: 3a, fiber-reinforced retainer (Interlig) with conventional composite, and 3b, fiber-reinforced retainer with nanoparticle composite. The Instron stereomicroscope was used to test debonding force and failure sites respectively. RESULTS: In the disk agar diffusion test, TiO2 composite has shown more inhibition zones. Biofilm inhibition test showed a significant decrease in colony counts of both organisms in the TiO2 group. The eluted component test showed a significant decrease in colony counts from day 0 to day 30 in the TiO2 group compared with the control group. The highest debonding force was observed in stainless steel retainers with conventional composite, and lowest in fiber-reinforced composite retainers with TiO2 composite, with no significant difference in Adhesive Remnant Index scores. CONCLUSION: The TiO2 composite group showed greater antibacterial activity without compromising the bond strength, which was statistically significant. Compared with other groups, stainless steel wires bonded with conventional composite showed the highest debonding force.