In vitro stimulation of human gingival epithelial cell attachment to dentin by surface conditioning

Background: Chemical root conditioning is widely used to improve the outcom e of regenerative periodontal therapies by favoring the attachment of the r egenerated periodontal structures. Although the effect of root conditioning on periodontal mesenchymal cells is well documented, very little is known about its potential effect on the re-formation of the junctional epithelium , a crucial event for the protection of the wound. The goal of the present study was to test in vitro the consequences of dentin conditioning with cit ric acid or minocycline on the attachment kinetics and morphology of human gingival keratinocytes (HGK). Methods: The attachment kinetics of HGK to samples of powdered human dentin (particle size 44 to 76 mu m) were examined by use of H-3-labeled cells. T he morphology of attached epithelial cells was then determined by scanning electron microscopy (SEM). Results: When the initial adhesion kinetics of cells on untreated dentin we re tested, the percentage of attached HGK proved to be dependent on the num ber of plated cells and the time of incubation (from 0 to 12 hours). Condit ioning the dentin by 3% citric acid or by minocycline-HCl (at 0.01, 0.1, or 2.5%) significantly increased (P < 0.005) keratinocyte attachment beyond 6 hours, without notable differences between the 2 substances at any concent ration. The attachment kinetics of HGK preincubated for 24 hours by 10 mu g /ml minocyline-HCl on untreated dentin was found to be similar to that obse rved for non-preincubated cells. These results are in agreement with the SE M observations: indeed, the surface conditioning of dentin significantly mo dified the morphology of attached HGK, whereas the preincubation of these c ells with minocyline-HCl did not. Conclusions: These results suggest that minocycline-HCl does not exert a di rect effect on human gingival epithelial cells. In contrast, conditioning t he dentin by citric acid or by minocycline stimulates the attachment of HGK , which could lead to a rapid periodontal healing by favoring the re-format ion of a junctional epithelium.