College of Dental Medicine Student Theses, Dissertations and Capstones

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Dentistry

Department

College of Dental Medicine

Publication Date / Copyright Date

2014

Publisher

Nova Southeastern University

Abstract

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Objective: The objectives of this study were 1) to evaluate the effect of enamel deproteinization on the shear bond strength (SBS) of orthodontic brackets bonded with a resin modified glass-ionomer (RMGI) adhesive and a composite resin, 2) to determine the mode of bond failure according to the adhesive remnant index (ARI) and 3) to evaluate the effect of these adhesives in the prevention of white spot lesions (WSLs). Background: WSLs are a concern for orthodontic patients. RMGI orthodontic adhesives are capable of absorbing fluoride from the oral environment and releasing it continuously over time, however, they are not frequently used as they exhibit low SBS. Techniques such as non-invasive enamel deproteinization with 5.25% sodium hypochlorite prior to acid etching rid the surface of organic components and have the potential to enhance the etching pattern. Methods: Eighty-eight extracted bovine incisors were randomly divided into two groups. 48 incisors in group (A) underwent SBS testing, through debonding of brackets with the Universal Testing Machine and subsequent measurement of the ARI. 40 incisors in group (B) underwent demineralization testing by measuring the depth of WSLs formed after exposure to an acidic challenge for 96 hours. In groups A and B, the teeth were divided to have brackets bonded with GC Fuji ORTHO LC adhesive or Transbond XT adhesive and a self-etching primer. Each adhesive group had an experimental group receiving the intervention of enamel deproteinization prior to etching and bonding and a control group. Results: The highest mean SBS was observed in the Transbond XT control group (12.48 ± 6.23 MPa) and the lowest mean SBS was observed in the Fuji ORTHO experimental group (5.49 ± 2.97 MPa). ANOVA and Post-Hoc Tukey tests revealed statistically significant differences (p<0.05) in the SBS of both Fuji ORTHO groups compared to the Transbond XT control group. A significantly greater percentage of Transbond XT control teeth had an ARI score of 0 and a greater percentage of Fuji ORTHO experimental teeth had an ARI score of 3. The Transbond XT experimental group had the largest average demineralization lesions (62.97 ± 10.95 micrometers). The smallest lesion depths were found in the Fuji ORTHO groups, with an average of 7.74 micrometers in the experimental group and 6.57 micrometers in the control group. ANOVA and Post-Hoc Tukey tests revealed significant differences (p<0.001) in the depth of white spot lesions when comparing both composite resin groups to each other, and when each glass ionomer group was compared to each composite resin group. Conclusions: Enamel deproteinization did not increase the SBS of orthodontic brackets bonded with either Fuji ORTHO adhesive or Transbond XT adhesive. However, according to the ARI, more bond failures occurred at the bracket-adhesive interface in the Fuji ORTHO experimental group. Also, both Fuji ORTHO adhesive groups showed greater protection against enamel demineralization, when compared to the Transbond XT adhesive groups.

Disciplines

Dentistry

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