Student Theses, Dissertations and Capstones

Document Type

Thesis - NSU Access Only

Degree Name

Master of Science (M.S.) in Dentistry

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Department

College of Dental Medicine

Publication Date / Copyright Date

12-2011

Publisher

Nova Southeastern University

Abstract

Introduction: Orthodontic treatment may cause an increased accumulation of cariogenic bacteria. An orthodontic resin with antibacterial properties may inhibit bacterial growth around the brackets. The aims of this in-vitro study were to compare the antibacterial and mechanical properties of the newly introduced orthodontic resin containing selenium with a standard resin and a resin modified glass ionomer (RMGI). Methods: Three orthodontic materials were tested (SeLECTDefense; TransbondXT, Fuji Ortho-LC). The antibacterial properties of these materials were evaluated by studying the bacterial growth in liquid media (BG) and agar diffusion (AD) tests. In the BG testing, 100 adhesive discs (3mmx2mm) were created of each material. Five discs were then placed into each vial containing 0.5ml of brain-heart-infusion broth and 2.5µl of streptococcus mutans (MS)(n=20). Following incubation (37°C, 24hours), the vials were placed in a Spectrophotomoter (Genesys 20) at 600 nm to determine bacterial growth by measuring the optical density (OD). In the AG testing, agar plates were inoculated with 100µl of MS in brain heart infusion agar. Fifteen adhesive discs (6mmx2mm) of each material were prepared and placed into groups of five on 3 agar plates. Following incubation (37°C, 48 hours), the agar plates were visually inspected for zones of bacterial inhibition. The mechanical properties were evaluated using shear bond strength testing (SBS) and an adhesive remnant index scoring (ARI). Sixty human premolars were randomly assorted into groups of 20 for each material (n=20). The brackets were bonded following the manufacturers' instructions. Debonding was performed using a universal testing device (Instron)(crossheadspeed 5mm/min). The mode of failure was evaluated using a stereomicroscope (OlympusSZX7) and scored 0-to-3 for remaining adhesive on enamel. Results were statistically analyzed using Welsch's ANOVA, One way ANOVA, Tukey's Kramer and Tukey's HSD tests. Results: In BG, the resin containing selenium (SD) promoted more bacterial growth (OD=0.427) compared to the standard resin (XT) (OD= 0.222) and RMGI (OD=0.275). In AD, no zones of inhibition were observed which means that no antibacterial agent was released from any of the orthodontic adhesives. In SBS, SD (11.63±2.07MPa) showed statistically lower bond strength than XT (15.16±4.68MPa) but both resins were in the clinically acceptable range. RMGI (6.03±3.95MPa) showed a statistically lower bond strength at a clinically unacceptable degree. Debonding was mostly at the bracket-adhesive interface for SD (ARI=2&3) meaning that most of the adhesive remained on the enamel. In XT and RMGI groups, debonding occurred mostly at the adhesive-enamel interfaces (ARI=0&1). Conclusion: Within the limitations of this in vitro study, the resin containing selenium did not show any favorable antibacterial properties in comparison to the other materials. None of the materials, including fluoride-releasing RMGI, caused bacterial inhibition in their surroundings. The resin containing selenium showed clinically acceptable but statistically lower bond strength as compared to standard resin but its mode of failure was more favorable because most of the adhesive remained on enamel.

Disciplines

Dental Materials | Dentistry | Orthodontics and Orthodontology

Keywords

Health and environmental sciences, Adhesive remnant index, Antibacterial activity, Selenium, Shear bond strength

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