New evaluation method by microfocus radiograph CT for 3D assessment of internal adaptation of all-ceramic crowns.

The aim of this study was to evaluate the effectiveness of the microfocus radiograph CT system in examining the adaptation of all-ceramic crowns three-dimensionally and non-destructively. The computed tomograms of the crown and abutment model were filmed by microfocus radiograph CT. Using a volumetric rendering software, images of gaps were extracted and reconstructed three-dimensionally, and their volume data analyzed. In order to compare this method with the conventional method, fitness test silicone paste was sandwiched between the abutment and all-ceramic crown. Adaptation of the crown on the abutment model was then observed non-destructively and three-dimensionally. Furthermore, the gaps could be analyzed in any arbitrary position. Concerning mean gap thickness, there was significant differences between the two measurement methods. However, it was very slight. We therefore concluded that the microfocus radiograph CT system is well positioned to be an extremely effective method in examining the adaptation of all-ceramic crowns.

Strength and elastic modulus of fiber-reinforced composites used for fabricating FPDs.

PURPOSE: The purpose of this study was to examine the flexural strength and elastic modulus of a new fiber-reinforced composite used for the fabrication of inlay-retained fixed partial dentures (FPD). MATERIALS AND METHODS: A total of six materials were used: Vectris, FibreKor, and an experimental material, BR-100, were the types of glass fiber preimpregnated with resin used for making the frameworks; Targis, Sculpture, and Estenia were used as the veneering composites. Five specimens of each material were prepared. Flexural strength and elastic modulus were determined using the three-point bending test. In addition, laminate specimens were fabricated by combination of the veneering composite and framework materials (Targis/Vectris, Sculpture/FibreKor, and Estenia/BR-100), and fracture loads of these specimens were determined. Laminate specimens were fabricated with three different framework thicknesses for Estenia/BR-100. RESULTS: Estenia had the greatest strength and highest modulus of elasticity of the veneering composites. All three framework materials had flexural strength values (567 to 686 MPa) more than three times as great as those of the veneering composites (132 to 193 MPa). Of the laminate specimens, the Estenia/BR-100 with a framework thickness of 1.0 mm had a fracture load more than 50% greater than Targis/Vectris and Sculpture/FibreKor. CONCLUSION: The combination of the experimental framework material BR-100 and the composite Estenia showed higher fracture loads than the other combinations tested.