Antibacterial activity and debonding force of different lingual retainers bonded with conventional composite and nanoparticle containing composite: An in vitro study

Abstract

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.

Keywords: ARI score; Antibacterial activity; Debonding force; Lingual retainer; TiO(2) composite.