The aim of this study was to develop a dental implant that is surrounded by periodontal ligament and has an attachment with the ligament in the alveolar socket. After rat maxillary left first molars (ULMI) were extracted, titanium implants which were handmade to be nearly the same size as natural teeth were inserted into the extraction sockets and the support function and structure of newly-formed connective tissue between the implants and alveolar bone were examined.
Male Wistar rats, aged 41~43 days, were used. Under general anesthesia, ULM1 was extracted, and a ULM1-shaped titanium implant was placed into the socket. Mobility of the implant was assessed every week after placement. The tensile strength of the peri-implant connective tissue was measured by extracting the implant from its socket using a materials testing machine. The extracted implants and natural teeth were subjected to scanning electron microscopy to assess their surface characteristics. At 7, 14, 21, and 28 days after placement, rats were sacrificed, and newly-formed peri-implant connective tissue was analyzed with microcomputed tomography (MCT), light microscopy, and polarizing microscopy.
Immediately after placement, the average mobility of the implants was M3. Thereafter, the mobility gradually decreased and became less than M0.3 after 14 days.The tensile strength of the newly-formed peri-implant tissue was low at day 14, but increased markedly at day 28. The mean value at day 28 was 68% of that for the natural tooth. On the surfaces of the extracted implants and natural teeth, collagen fiber bundles, cementoblast-like cells and surrounding amorphous tissue, as in natural teeth, were observed. MCT scans revealed the presence of a periodontal ligament-like radiolucent area between the implants and alveolar bone. Histologically, after one week cementoblast-like cells were seen on the surface of the implants, collagen fiber bundles being seen running perpendicular to the surface of the implants near the alveolar process. After two weeks, extracellular matrix and calcified structures were observed adjacent to the implant surfaces in the middle and apical root levels. Some collagen fibers were aligned parallel to the implant surfaces while the other fibers connected the alveolar bone to the implant as in the periodontal ligament of natural teeth.
These findings suggested that the remaining periodontal ligament adhering to the surface of extraction sockets may induce the formation and attachment of new connective tissue on the implant surface which is similar to the normal support function and structure of periodontal ligament.
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