Background: Implants placed immediately after tooth extraction offer several advantages, but many authors have reported problems in filling the residual gap between the implant and the socket walls. Barrier and grafting techniques have been tested and yield varying results, so it has been suggested that the timing of implant placement may be important for success. The aim of thi study was to analyze bone healing and coronal bone remodeling around 35 implants, 20 placed immediately after tooth removal and 15 placed 6 to 8 weeks after extraction. Methods: All the implants were submerged and placed within the alveoli confines, leaving circumferential defects because the implants did not contact the bone at their coronal aspects; stabilization was achieved in the bone apically. After implant placement the mean distance from buccal bone to lingual bone was 10 mm (SD 1.522) for immediate implants and 8.86 mm (SD 2,356) for delayed implants. No membrane or filling materials were used. Primary flap closure was accomplished in all cases. Results: At second stage surgery all peri-implant defects were filled, and the mean distance from buccal bone to lingual bone was 8.1 mm (SD 1.334) for immediate implants and 5.8 mm (SD 1.265) for delayed implants. This pattern of coronal bone remodeling, showing a narrowing of the bucco-lingual width, was clinically similar for the two groups, although it should be noted that the delayed implants exhibited smaller buccolingual bone width already at the first measurement: it can be speculated that early remodeling may start immediately after tooth extraction and continue, non-uniformly, even after delayed implant placement. Conclusions: This study suggests that circumferential defects could heal clinically without any guided bone regeneration (GBR) in both experimental groups and that the procedure was virtually free from complications in the postoperative period, probably because of the absence of barrier membranes and /or grafting materials. Histologically, peri-implant defects of over 1.5 mm heal by connective tissue apposition, rather than by direct bone-to-implant contact but clinically this healing may be very successfu. No histological analysis was carried out in the present study, but even the largest residual gaps were filled with hard tissue that could not be probed. Thus such outcomes can be considered clinically successful. The different rate of bone remodeling around immediate or delayed implants could have implications fort he preferred timing of implant placement in sites of high esthetic concern. Key words:Bone regeneration; bone remodeling; dental implants, immediate; peri-implants; wound healing.
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