Date of Award

Spring 2000

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Dentistry

First Advisor

Dhuru, Virendra B.

Second Advisor

Kittleson, Russell T.

Third Advisor

Bradley, Thomas G.

Abstract

The purpose of this study was to determine the effects of multiple pumice prophies, acid etchings, and enamel reconditionings on the shear bond strength and shear rebond strength of orthodontic brackets using two different adhesives. Its purpose also included determining if there was a difference in the shear bond and shear rebond strengths between a traditional composite resin adhesive and a poly-acid modified composite resin adhesive. Brackets were bonded, with one of the two adhesives, to extracted human premolars and then debonded with a shear force in the Instron Universal Testing Machine. The enamel surface was then reconditioned with a 12-fluted tungsten carbide finishing bur in a high speed handpiece to remove the bulk of adhesive and then the same bur in a slow speed handpiece for finishing. This was followed by a coarse pumice prophy and the rebonding of a new bracket. The same debonding procedure was then conducted. Both adhesive groups were then reconditioned, rebonded, and debonded again following the same procedures as the previous steps. Therefore data was collected for three debondings of each specimen in both adhesive groups. The data was then evaluated to determine any differences in the shear bond strengths over the three bonds and debonds for the two adhesives. The results showed 1) No statistically significant difference between the shear bond strength values obtained for specimens bonded within the Transbond XT group, or within the the Ultra Band-Lok group over the three debonds (p< 0.05); 2) A very highly significant difference (p< 0.001) between the initial shear bond strength of Transbond XT and the second bonding shear bond strength of Ultra Band-Lok; 3) Rebond shear bond strengths indicating that the use of the 12-fluted bur when used in the high speed handpiece and the same bur in a slow speed handpiece followed by a coarse pumice cleaning is a viable option for the reconditioning of the enamel surface when rebonding with a new bracket; 4) Both Transbond XT and Ultra Band-Lok are capable of producing shear bond and shear rebond strengths that are similar and capable of withstanding applied forces of mastication.

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