We have developed an experimental model to help identify and characterize factors necessary for periodontal connective tissue attachment formation on dental implants. In this pilot study, we report the effect of autogenous periodontal cell grafts, with and without the a pplication of enamel matrix derivative (EMD), on the implant-connective tissue interface. Periodontal ligament (PDL) and gingival connective tissue (GCT) cultures were established from an adult minipig. Implants were placed in osteotomies prepared with exaggerated countersinks that served as recipient sites for autogenous cell grafts in bilateral edentulated posterior mandibular sextants. In addition, 1 side received an application of EMD before placement of the autogenous cell grafts. A bioabsorbable membrane covering the coronal portion of the implants was placed before closure. After 8 weeks, quantitative histomorphometric and qualitative light microscopic analyses revealed that the implants that received gelatin vehicle alone were surrounded by bone, whereas the implants that received GCT cell grafts were mostly surrounded by fibrous connective tissue. In contrast, implants that received PDL cells without the application of EMD demonstrated good bone contact, but strands of epithelium were observed in the implant-connective tissue interface. Implants that received PDL cells and EMD also had good bone contact but without evidence of epithelium. A cementum-like interface was not observed in any of the groups. Results of this pilot study suggest that EMD and the type of cell populations present in the implant wound-healing environment may alter the implant-connective tissue interface.

The periodontal ligament has the potential to regenerate a complete periodontal connective tissue attachment, starting with the deposition of cementum, on pathologically exposed root surfaces as well as several materials including titanium oxide. However, most commonly used dental materials result in a fibrous encapsulation or a chronic inflammatory response after periodontal wound healing rather than the formation of a periodontal connective tissue attachment. Recently, an extract of porcine enamel matrix (Emdogain(R), EMD) has been reported inductive of cementum formation in both in vivo and in vitro studies. The aim of this study was to determine the effect of EMD, when applied to materials previously reported not supportive of periodontal connective tissue formation, on the periodontal connective tissue-material interface obtained with these materials in vivo. Bilateral osteotomies were performed on the mandible of a Yucatan minipig exposing the buccal root surface of four premolars. A series of four preparations were placed in each root surface that were subsequently filled with calcium hydroxide, gutta percha, mineral trioxide aggregate (MTA), or left unfilled. One side, in addition, received an application of EMD prior to surgical closure. A bioabsorbable surgical barrier membrane was placed over the osteotomy sites to exclude gingival connective tissue from the wound-healing environment. The mucoperiosteal flaps were then readapted and sutured in position. The animal was euthanized 10 weeks after the procedure, block sections obtained and prepared for light microscopy. Results demonstrated complete regeneration of alveolar bone and periodontal ligament in all four teeth from the EMD-treated side. Fibers from the periodontal ligament were observed to insert into a mineralized matrix consistent with cementum on all four root preparations. In contrast, massive root resorption without regeneration of alveolar bone was found on all teeth from the side not treated with EMD. The results of this pilot study suggest that the application of EMD to material surfaces that normally do not support periodontal connective tissue attachment formation can alter the type of periodontal connective tissue interface obtained with these materials.