Early events associated with periodontal connective tissue attachment formation on titanium and hydroxyapatite surfaces

Endosseous dental implants can support at least three types of biomaterial/ connective tissue interfaces: osseointegration, fibro-osseous integration, and periodontal connective tissue attachment. Although a periodontal connec tive tissue attachment offers distinct advantages, only osseointegration an d fibro-osseous integration are at present clinically achievable. Recent st udies indicate a periodontal regeneration-competent cell population and an appropriate biomaterial substrate both are required for periodontal connect ive attachment formation on biomaterial surfaces. We therefore have develop ed an in vitro model to characterize the effects of various biomaterial sub strates on the early events of periodontal connective tissue attachment for mation. Primary cultures of periodontal ligament and gingival connective ti ssue cells were cultured on uncoated (control) and coated (titanium- and hy droxyapatite-coated) tissue culture plastic, and the level of cell prolifer ation, collagen, and noncollagen protein synthesis, alkaline phosphatase ac tivity, and expression of a 42 kD cementum extracellular matrix protein wer e measured over 5, 7, and 9 days in culture. While all three substrates sup ported cell attachment, proliferation, and protein synthesis, only uncoated and titanium-coated tissue culture plastic supported expression of the cem entum extracellular matrix protein after 9 days of culture. In addition, th e levels of cell proliferation and collagen and noncollagen protein synthes is for cells grown on hydroxyapatite-coated surfaces lagged behind cells cu ltured on the control or titanium-coated surfaces at each of the three time points. These data suggest that biomaterial substrates markedly can influe nce the temporal sequence of extracellular matrix proteins associated with periodontal connective tissue attachment formation. In addition to surface composition (titanium versus hydroxyapatite), surface properties (e.g., top ography) also may have an effect on periodontal connective tissue attachmen t formation. This model may be of use in designing biomaterials to support the formation of periodontal connective tissue attachment in vivo. (C) 1999 John Wiley & Sons, Inc.