This study evaluated the accuracy of marginal and internal fit between the all-ceramic crowns manufactured by a conventional double-layer computer-aided design/computer-aided manufacturing (CAD/CAM) system and a single-layer system. Ten standardized crowns were fabricated from each of these two systems: conventional double-layer CAD/CAM system (Procera) and a single-layer system (Cerec 3D). The copings and completed crowns were seated on the abutments by a special device that facilitated uniform loading, and the marginal discrepancies were measured. Internal gaps were also measured using a low-viscosity silicone material. Marginal discrepancies of Procera copings were significantly smaller than those of Procera crowns and Cerec 3D crowns (p<0.05), but Procera crowns and Cerec 3D crowns did not differ significantly from each other (p>0.05). On internal gaps, Cerec 3D crowns showed significantly larger internal gaps than Procera copings and crowns (p<0.05). Within the limitations of this study, the single-layer system demonstrated acceptable marginal and internal fit.
Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal. Specimens were chemically washed for 2 min in a 1:1:1.5 (vol.%) mixture of 48 %HF, 60 %HNO 3 and distilled water. The specimens were then chemically treated with a solution containing 97 %H 2 SO 4 and 30 %H 2 O 2 at the ratio of 1:1 (vol.%) at 40 o C for 1 h, and subsequently heat-treated at 400 o C for 1 h. All the specimens were immersed in HBSS with pH 7.4 at 36.5 o C for 15 d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28 d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a solution of H 2 SO 4 and H 2 O 2 . The average roughness was 2.175 Pm after chemical surface treatment. The amorphous titania was subsequently transformed into anatase by heat treatment at 400 o C for 1 h. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 47.1 Pm in the chemically treated Ti, and 52.2, 168.7 and 101.9 Pm, respectively, in the untreated commercial pure Ti, aluminum and stainless steel 316L.
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