Objective: Implant designs that can stimulate and integrate with an epithelial wound-healing process may significantly enhance the efficacy of dental implants. Here, we evaluated the potential of "step-type" implant systems to improve the sealing between the peri-implant epithelium (PIE) and the implant surface, and investigated the effect of implant structure on PIE down-growth. Materials and methods: Right maxillary first molars were extirpated from rats and implanted with either a straight-type or a step-type implant varying in step height and/or width (N s: 0.8mm height, 0.1mm width; W s: 0.8mm height, 0.2mm width; H s: 0.4mm height, 0.1mm width). Maxillae were harvested at various time points over 16 weeks to evaluate laminin-5 distribution as an indicator of wound healing and PIE formation, horse-radish peroxidase (HRP) penetration as a measurement of epithelial sealing, and PIE down-growth formation. Results: In all implant models, the PIE formed from the oral sulcular epithelium and spread apically along the implant surface. In the W s group, HRP penetration was detected only in the coronal region of the PIE at 4 weeks, whereas in the straight-type, it was observed in the apical region and the connective tissue. At 16 weeks, the W s implants exhibited markedly less PIE down-growth than the Con, N s or H s implants, and were equivalent to that observed in natural teeth. Conclusion: The step-type implant system may have the potential for improving epithelial sealing at the tissue-implant interface, as well as reducing apical PIE down-growth, thus enhancing dental implant efficacy.
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