CLINICAL-EVALUATION OF 2-PIECE APATITE DENTAL IMPLANTS IN 189 CASES

A two-piece apatite implant composed of a titanium abutment and a tita nium tubular root portion cemented to an outer dense hydroxyapatite (D -HAP) tubular shell by resin cement has been authorized as High Advanc ed Medical Technology (H.M.A.T.) and applied since December 1987. We w ill show the success rate and the evaluation of the implants applied t hrough May 1992. A successful implant was considered as one that provi des functional comfort with no mobility and the absence of surrounding mucosal inflammation. The number of implants applied during the last 4.5 years was 810 pieces in 189 cases with an overall success rate of 92.5% for the 704 implants with abutment. The extirpation rate has no clear linear association with the duration of the implant or with the patient's age. Most of the extirpations resulted from cases where the patient used a provisional denture during the bone healing period, the time between implantation and abutment cementation. Extirpation rate of implant was high in cases using large maxillary provisional denture s with ten or more missing teeth. It is believed that all implant case s in which large dentures were used frequently contributed to the exti rpation. These observations led us to suggest that provisional denture s may be harmful to the implant. When we shifted from the traditional method to the Delay Method 2.5 years ago, no incidence of extirpation was experienced in the mandible, even with the use of provisional dent ures. In the maxilla, the Delay Method proved to be effective without the provisional denture. However, the results of the Delay Method with provisional dentures remains to be evaluated. The reason is that too few cases were encountered with large missing teeth to suffice for our observation. This Delay Method (named by us) consists of delaying the insertion of the implant for approximately 2 months after the first s ocket preparation, until the bone tissue activity has risen. After som e adjustment in the prepared socket, the implant is then inserted duri ng the second surgical procedure. We therefore consider this method of potential benefit over the traditional method.