The adhesion, orientation, and proliferation of human gingival fibroblasts was studied on electropolished (elpTi), etched (etchTi), and sandblasted (sblTi) titanium surfaces. The texture, chemical state, and composition of the titanium surfaces were analyzed using a surface tracing instrument and electron spectroscopy for chemical analysis. Considerable differences were evident in the surface texture and chemical composition of the differently treated titanium plates. Electropolishing produced the smoothest and cleanest surface. Human gingival fibroblasts attached, spread, and proliferated on all titanium surfaces. However, cells on elpTi exhibited an extremely flat morphology and seemed to form cellular bridges with adjacent cells, whereas the etchTi and sblTi surfaces harbored both round and flat cells with many long processes. Cells on elpTi appeared to grow in thick layers with no specific orientation, whereas on etchTi surfaces they were migrating along the parallel, irregular minor grooves caused by mechanical polishing, and on sblTi surfaces they seemed to grow in clusters. Stress-fiber type actin bundles and vinculin-containing focal adhesions were present in cells spreading on elpTi and etchTi surfaces but not in cells spreading on sblTi surfaces. Cell shape, orientation, and proliferation appear to depend on the texture of the titanium surface and probably also on the properties of the oxide layer and adjacent bulk material. Our findings suggest that smooth or finely grooved titanium surfaces could be optimal in implants adjacent to soft tissues as they support the attachment and growth of human gingival fibroblasts.

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Clinical studies indicate that soft tissue responses around dental implants vary, depending on the material used. It is therefore also possible that there are differences in how epithelial cells attach to various biomaterial surfaces. We studied the adhesion of cultured epithelial cells to five different dental material surfaces and to glass. The efficacy of adhesion was evaluated by using scanning electron microscopy (SEM) and immunofluorescence microscopy (IF) with antibodies to vinculin and alpha(6)beta(4) integrin, two cell surface molecules that are functional in epithelial cell adhesion. Our results indicate that epithelial cells adhere and spread more avidly on metallic surfaces (titanium, Ti(6)Al(4)V titanium alloy, dental gold alloy) than on ceramic surfaces (dental porcelain, aluminum oxide). As revealed by SEM, cells on metallic surfaces had a flattened morphology and formed multicellular islands. On porcelain and aluminum oxide most cells were round and adhesion occurred as single cells. Surface coverage was over twofold on metallic surfaces as compared to ceramic surfaces. IF of cells grown on metallic surfaces revealed vinculin in well-organized focal contacts and alpha(6)beta(4) integrin in punctate patterns typical of prehemidesmosomes. On porcelain and aluminum oxide surfaces the cells were mostly round and showed less well-organized adhesion complexes. Our results indicate that smooth metallic biomaterial surfaces are optimal for epithelial cell adhesion and spreading. These findings may have clinical implications in the design of transgingival implant structures.

The effect of elimination of crystalline leucite on porcelain bonding to Ti was studied. The thermal expansion coefficient of low-fusing dental porcelain was decreased by eliminating the crystalline leucite phase. As a result, minimal thermal mismatch and better bonding between Ti and porcelain were obtained. [

Adherence of porcelain on titanium and possible bonding mechanisms were studied. The main variables were surface roughness, firing time and vacuum level. Adherence was greatly affected by the degree of surface roughness. The bond strength for Al,O,-blasted rough surfaces was superior to those ground by S i c paper or polished. The fracture was partly cohesive for the Al,O,-blasted surfaces as a result of mechanical interlocking. For smoother surfaces fracture occurred adhesively. Increased firing time and reduced vacuum level decreased the bond strength when mechanical interlocking was weak. This was most likely related to poor adherence of the interfacial oxide layer to the titanium substrate.

Abstract:Clinical studies indicate that soft tissue responses around dental implants vary, depending on the material used. It is therefore also possible that there are differences in how epithelial cells attach to various biomaterial surfaces. We studied the adhesion of cultured epithelial cells to five different dental material surfaces and to glass. The efficacy of adhesion was evaluated by using scanning electron microscopy (SEM) and immunofluorescence microscopy (IF) with antibodies to vinculin and ␣ 6 ␤ 4 integrin, two cell surface molecules that are functional in epithelial cell adhesion. Our results indicate that epithelial cells adhere and spread more avidly on metallic surfaces (titanium, Ti 6 Al 4 V titanium alloy, dental gold alloy) than on ceramic surfaces (dental porcelain, aluminum oxide). As revealed by SEM, cells on metallic surfaces had a flattened morphology and formed multicellular islands. On porcelain and aluminum oxide most cells were round and adhesion occurred as single cells. Surface coverage was over twofold on metallic surfaces as compared to ceramic surfaces. IF of cells grown on metallic surfaces revealed vinculin in well-organized focal contacts and ␣ 6 ␤ 4 integrin in punctate patterns typical of prehemidesmosomes. On porcelain and aluminum oxide surfaces the cells were mostly round and showed less wellorganized adhesion complexes. Our results indicate that smooth metallic biomaterial surfaces are optimal for epithelial cell adhesion and spreading. These findings may have clinical implications in the design of transgingival implant structures.

The effect of small In additions on oxide structure and porcelain adherence to Au-Pd alloys was studied. In was oxidized internally as In203. No uniform external oxide layer could be seen. Small In addition (1 at%) did not have any detectable effect on porcelain adherence (~12 MPa), whereas higher In concentration (5 at%) caused significant increase in bond strength (~,26 MPa). This increase was probably a result of higher In203 concentration at the surface. IntroductionPd-containing alloys have become recognized as alternatives to high-Au and non-precious alloys for metal-ceramic restorations. The main reasons for the popularity of palladium alloys are good corrosion and tarnish resistance along with acceptable biocompatibility and the price of Pd, which is approximately one-half of that for Au. Pd-rich alloys suitable for metal-ceramic restorations can be roughly divided into following groups: Au-Pd-, Pd-Co-, Pd-Cuand Pd-Ag-based alloys [1]. Considering the physical properties, processing characterics and the amount of precious metal components, the Au-Pd-system is very attractive because of the excellent compromise between these three factors [2].The importance of the oxide layer on the bonding of metal to porcelain is generally accepted for all kinds of metal-ceramic materials. The theory of glass/metalbonding was largely developed by Pask [3][4][5]. He postulated that chemical bonding across the interface is achieved by having therodynamically stable equilibrium in the interfacial zone and having both phases saturated with an oxide of the substrate metal. The oxide layer formed on metal by preoxidation is supposed to be dissolved by molten glass. The chemical bonding is maximized when a monomolecular oxide layer remains at the interface. The importance of oxide adherence to its alloy substrate has been emphasized by Mackert [6,7], who found a correlation between oxide adherence and porcelain adherence to metal. The dental noble alloys are normally alloyed by base metals like In, Sn and Ga, which form an oxide layer on the alloy. Accumulation of oxidizing elements within a few micrometres of the metal/porcelain interface has been reported in several studies [8-t3], in which concentration profiles of alloy components over a metal/porcelain interface were measured by electron microprobe. Such data are generally found to support the theory that chemical bonding mechanisms are controlled by oxidizing metal components. More de-

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