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

First Advisor

Cristina Garcia-Godoy

Date of original Performance / Presentation

January 2021

Publication Date / Copyright Date

1-1-2021

Abstract

Introduction: The goal of orthodontic treatment is to enhance smile esthetics while improving dental health. However, patients undergoing orthodontic treatment are subject to enamel demineralization, or white spot lesions (WSLs). Inadequacies in maintaining proper oral hygiene, paired with plaque-retentive orthodontic appliances, contribute to the formation of WSLs. These lesions serve as the beginning of the decay process, caused by subsurface mineral loss beneath an intact layer of sound enamel. The initial approach in the management of WSLs should focus on prevention. Preventive measures include topical fluoride application, as well as laser irradiation. CO2 laser irradiation has been proposed as a conservative approach to alter the surface morphology of enamel to increase its acid-resistance and minimize the harmful effects of demineralization. Although the benefits of fluoride are well-known, its potential synergistic effects with other preventive measures continue to be explored. It has been suggested that combined therapy with topical fluoride application and laser irradiation may have a synergistic effect on inhibition of enamel demineralization. Thus, the goal of this study is to assess the preventative effects of CO2 laser irradiation and acidulated phosphate fluoride (APF) gel, alone and in conjunction, on inhibiting enamel demineralization. Methods: 80 bovine incisors were used in this study. All incisors were standardized by flattening the facial surface, followed by application of an acid-resistant varnish except for an exposed window delineated by adhesive tape. The teeth were mounted and randomly assigned to one of four groups of 20 teeth. Baseline microhardness values were recorded for all teeth using Vicker’s microhardness testing. The groups consisted of: Group 1: control (untreated) (C), Group 2: 1.23% APF gel applied alone for 4 min (F), Group 3: CO2 laser alone (L), Group 4: CO2 laser followed by 1.23% APF gel applied for 4 min (L+F). Following the assigned treatment, all teeth were placed in a demineralizing solution for 6 hrs. After demineralization, Vicker’s microhardness testing and polarized light microscopy was performed. Results: Analysis of variance (ANOVA) demonstrated a significant effect of the different treatments on microhardness at the p<0.05 level for the three groups [F(3,76)= 41.03, p=<0.0001]. Post-hoc analysis using Tukey’s HSD indicated that the decrease in microhardness was significantly greater in group 1 (C) than group 2 (F) (p<0.0001), group 1 (C) than group 4 (L+F) (p<0.0001), group 3 (L) than group 2 (F) (p<0.0001), and group 3 (L) than group 4 (L+F) (p<0.0001). ANOVA also demonstrated a significant effect of the different treatments on demineralization depth at the p<.05 level for the three conditions [F(3, 68) = 5.78, p = .001]. Post-hoc analysis using Tukey’s HSD indicated that demineralization depth was significantly greater in group 1 (C) than group 2 (F) (p=0.042), group 1 (C) than group 4 (L+F) (p=0.018), group 3 (L) than group 2 (F) (p=0.028), and group 3 (L) than group 4 (L+F) (p=0.011). Conclusions: Groups treated with 1.23% APF gel (groups 2 and 4) resisted enamel microhardness decrease and showed the smallest demineralization depths. When treated with CO2 laser alone, enamel microhardness and demineralization depth were not significantly different than the control group. There was no synergistic effect between 1.23% APF gel application and CO2 laser irradiation at the laser parameters that were used. Topical fluoride application remains one of the most effective preventive measures against enamel demineralization.

Disciplines

Dentistry

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