Generalizations regarding the process and phenomenon of osseointegration. Part II. In vitro studies.

In this review, the appropriate use of cell culture to evaluate substrate effects on osteoblast behavior during the process of osseointegration has been considered in the context of existing reports. The interactions of osteoblasts with different substrates can be measured in terms of cytotoxicity, attachment, proliferation, and differentiation. The osteoblast culture systems that produce an osteoblast matrix opposing implant material substrates provide one model for evaluating the implant-bone interface. Alterations in osteoblast behavior at different culture substrates may reflect clinical determinants of bone formation at these substrates in vivo; however, cell responses in vitro have not been compared or correlated with in vivo outcomes. Legitimate interpretations of in vitro experiments are discussed in terms of practical, technical, and biologic limitations presented by the cell culture approach. Cell culture provides access to molecular and cellular information that fosters nanostructural engineering approaches to implant design and significant hypotheses to be tested in vivo. In this way, cell culture offers unique insights into the process and phenomenon of osseointegration.

Spatiotemporal assessment of fetal bovine osteoblast culture differentiation indicates a role for BSP in promoting differentiation.

Fetal bovine mandible-derived osteoblasts were cultured for the purpose of obtaining a spatiotemporal assessment of bone matrix protein expression during in vitro differentiation. The results obtained from electron microscopic, immunohistological, biochemical, and molecular biological analyses indicated that these primary cultured osteoblasts produce an abundant extracellular matrix which mineralizes during a 14-day culture period. During this process, a restricted, spatiotemporal pattern of bone sialoprotein expression was indicated by immunohistological and molecular evaluations. To test the possibility that bone sialoprotein promoted the continued morphodifferentiation of osteoblastic cells, cultures were grown in the presence of anti-bone sialoprotein antibodies known to interfere with cell-bone sialoprotein attachment. Compared with cultures grown in the presence of normal rabbit serum (1:150), cultures grown in the media containing anti-bone sialoprotein antibody (1:150) failed to mineralize as demonstrated by von Kossa staining and failed to express osteocalcin and osteopontin as shown by the reverse transcription polymerase chain reaction. These results contribute to the growing evidence that bone sialoprotein is an important determinant of osteoblast differentiation and bone formation. Matrix protein-cell interactions may be examined using this spatiotemporally defined model.

Generalizations regarding the process and phenomenon of osseointegration. Part I. In vivo studies.

The clinical success of endosseous implants is associated with the formation and maintenance of bone at implant surfaces. Histologic analyses have indicated that bone formation at a variety of implant surfaces is a continuous process that supports long-term functional integration. Based on in vivo observations, several generalizations have been derived regarding the nature of the interface. Experimental descriptions indicate that the implantbone interface may be characterized in spatial and temporal terms as discontinuous. Biomechanical tests of the bone associations with implants demonstrate that the chemical composition and the surface topography of the implant influence the rate and extent of bone formation at implant surfaces. The precise character and functional attributes of this interface are the focus of this investigation. Many technical difficulties are associated with its structural and chemical characterization in vivo. Despite the technically difficult nature of this type of analysis and the limitations of current histologic examinations and biomechanical tests, in vivo models of osseointegration are necessary experimental tools for the continued empirical development of clinical implant applications.

Preliminary comparison of mineralizing multilayer cultures formed by primary fetal bovine mandibular osteoblasts grown on titanium, hydroxyapatite, and glass substrates.

Bone formation at implant surfaces may be directly influenced by effects of the implant material on osteoblast behavior. Cell culture models of osteoblast physiology may be used to investigate the interaction of osteoblastic cells with various surfaces. In this study, primary cultured fetal bovine mandibular osteoblastic cells were cultured on titanium, ceramic hydroxyapatite, and glass coverslip surfaces to allow for the comparison of the mineralizing matrix elaborated by osteoblasts grown on different implant material surfaces. Morphologic and immunohistochemical analysis revealed the similar formation of multilayered, mineralizing cultures on these three surfaces. The qualitative similarity of the matrix formed on these culture surfaces may reflect similar qualitative in vivo responses of bone to titanium and hydroxyapatite implants.

Correlative microscopic investigation of the interface between titanium alloy and the osteoblast-osteoblast matrix using mineralizing cultures of primary fetal bovine mandibular osteoblasts.

In this study, the primary culture of bovine mandibular osteoblast cells in a microculture assay has been used to further investigate the interaction of mineralizing osteoblast cultures with implant surfaces by using correlative microscopic techniques. Rapid differentiation and mineralization of osteoblast cultures grown on titanium alloy surfaces was observed. The successful short-term culture of mineralizing mandibular osteoblasts on titanium alloy surfaces occurred without the formation of a tenacious adhesive interface between the alloplastic material and the multilayered cell culture.