[Histological and histomorphometric results of implantation of dental implants by early and late implantation].

In this study, a histologic and histomorphometric analysis of delayed and immediate-placed implants was performed. An implantation of 16 self-cutting conical titanium screw implants was carried out in 8 beagle dogs. Of these implants, 8 were placed immediately after extraction of the second premolar and 8 implants were placed after 6 months of healing after extraction. For dynamic histomorphometry, fluorochrome bone markers were injected at two different times prior to euthanasia. The specimens were examined macroscopically and microscopically 8 months after implantation. A histologic, dynamic, and static histomorphometry was performed with the aid of different computer programs. A mean surface of osseointegration of 75.7% and a mean soft tissue implant contact surface of 24.2% was seen in immediate-placed implants. For delayed implantation, an osseointegrated surface of 80.7% and a soft tissue covering of 19.3% was examined. The fibrogenic structures in the cervical implant part were more dense and there were more adhesive epithelial elements (hemidesmosomes) around delayed implants. The result of the dynamic and static histomorphometry showed no significant differences in the two groups (P < 0.1). In conclusion, it can be stated that a new steady-state of the soft and hard tissue around dental implants was seen 8 months after implant insertion in both groups. There was a pseudoankylotic healing in the osseous part. The lower level of osseointegration in immediate-placed implants was caused by early resorption of bone in the crestal part. Thus, a larger part of the implant was surrounded by soft tissue and a long epithelial attachment resulted.