Comparison of Veneer Preparation Design and Fracture Strength
Uniformed Services University of the Health Sciences Bethesda United States
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Background Aesthetic dentistry has been advocated by dentists since the early twentieth century, its limitations solely based upon the materials and methods to securely retain porcelain restorations to tooth structure. With the advent of a safe and predictable method to directly bond ceramic materials to enamel tooth structure, a number of methodologies have been advocated that preserve and maintain maximum tooth structure while achieving both the desired aesthetic results and longevity of the restorations. The purpose of this study is to compare the fracture strengths of two most popular and oft promoted preparation designs and determine which is the superior product. Methods A total of fifty samples were fabricated from ivorine teeth replicating tooth number 8 maxillary right central incisor divided into two groups twenty-five samples based upon the Butt-Joint veneer preparation and twenty-five samples based on the Prepless veneer design. A Sirona CADCAM system was employed to scan and mill lithium disilicate eMax veneer restorations for the ivorine teeth. The restorations were subsequently cemented with resin cement onto each ivorine tooth and then placed at 135 degrees into a brass jig to simulate normal position. Each sample was placed on an Instron device and then loaded at 0.5mmmin until failure occurred. An ANOVA analysis was then utilized to review the data. Results The mean load at break N for the Prepless Peneer group was 344.47 SD 4.18, mean for Butt-Joint preparation M 603.46, SD 189.67. Mean modulus MPa of the Prepless veneer group M 74.69, SD 7.70 was greater than the mean of the Butt-Joint preparation samples M 44.45, SD 15.52. Significant differences were found between the preparations for both extension at maximum load F1, 48 4.49, p 0.04, p 2 0.09 and extension at break F1, 48 4.47, p 0.04, p 2 0.09.
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