Defense Date

2006

Document Type

Thesis

Degree Name

Master of Science

Department

Orthodontics

First Advisor

Dr. Eser Tüfekçi

Abstract

In vitro bond strength studies are of great importance and interest since they allow the prediction of clinical success of orthodontic adhesives. There are many studies that have investigated bond strength values of bonding systems. However, due to the variation in the materials and methods employed, it is very difficult and often impossible to make comparisons among data. The use of a substrate as an alternate to enamel for mechanical tests would minimize these variables and reduce the challenges faced with in vitro bond strength tests. The purpose of this study was to investigate the suitability of Macor as a substrate for bond strength testing of orthodontic adhesives. Macor samples were custom prepared in a shape similar to that of a human maxillary premolar. The groups tested were: Group 1: acid-etched with 9.6% hydrofluoric acid (HFA) for 60 seconds; Group 2: acid-etched with 9.6% HFA for 90 seconds; Group 3: acid-etched with 9.6% HFA for 120 seconds; Group 4: surface roughened with silicon carbide (Sic); and control group: human premolars etched with 37% phosphoric acid. Following surface preparation, samples were primed and brackets were bonded using Transbond XT (3MlUnitek). Mounted samples were stored in water for 24 hours at 37OC until mechanical testing. Brackets were debonded in the shear mode using an Instron Universal Testing Machine and the force at debond was recorded. The nature of adhesive bond failure among the groups was also compared using an adhesive remnant index (ARI). One-way ANOVA and Weibull analysis statistical tests were used to evaluate and compare the groups. Sample surfaces were analyzed under the light microscope to determine the mode of bond failure for ARI. The Kruskall-Wallis test was used to determine differences in the ARI scores. There were statistically significant differences in shear bond strengths among the enamel and Macor groups (p 0.05). The shear bond strength values of the Macor groups were significantly lower than those of the enamel control group, (p < 0.05). ARI scores were significantly different between the groups (p 10.0001); Macor samples treated with hydrofluoric acid had more adhesive remaining on their surfaces than those in the control and Sic groups. Based on the results of this study, Macor may not be a suitable substrate for bond strength testing in orthodontics.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

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