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

2015

Publisher

Nova Southeastern University. College of Dental Medicine.

Abstract

Objectives: The purpose of this in-vitro study was to evaluate the effects of three different surface preparation methods on the shear bond strength of orthodontic brackets bonded to zirconia and determine the most appropriate method. Methods: 45 zirconia and 30 leucite-reinforced porcelain mandibular premolar crowns were divided into 5 groups and received the following surface preparations: 37% phosphoric acid and non-hydrolyzed silane, 4% hydrofluoric acid and hydrolyzed silane, microetch with 50μ Al 2 O3 particles. A universal adhesive primer containing MDP was applied and the brackets were bonded with a bis-GMA composite resin. Shear bond strength (SBS) at bond failure and ARI score were recorded. Results: There was a statistically significant difference among the studied groups for the SBS. The highest mean SBS (11.03 MPA) was recorded for the zirconia/microetch group, and the lowest SBS (3.49 MPa) for the zirconia/phosphoric acid group. The leucite-reinforced porcelain/ hydrofluoric acid group had significantly more fractures than any other debond pattern. The zirconia/hydrofluoric acid group was the only one with a SBS (8.08 MPa) that fell within the recommended range of 6-8 MPa. This group also had a favorable debond pattern with most composite remaining on the bracket.

Conclusions: Important consideration should be given to the surface preparation of porcelain and zirconia prior to bonding orthodontic attachments. Phosphoric acid etch is not an adequate surface preparation when bonding to zirconia. Hydrofluoric acid is not suitable when bonding to leucite-reinforced porcelain, as it is associated with a higher rate of surface fracture. Microetch with 50μ Al 2 O3 particles in combination with an MDP containing universal adhesive primer provided optimal mean shear bond strength, along with favorable debond patterns when bonding to zirconia. Hydrofluoric acid etch in combination with a silane and a universal primer containing MDP provided acceptable shear bond strength to zirconia. This protocol was not significantly different from zirconia prepared with microetch and either method can be successfully employed.

Disciplines

Dental Materials | Dentistry

Keywords

Applied sciences, Health and environmental sciences, Bond strength, Brackets, Orthodontic, Surface preparation, Zirconia

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