口腔インプラントの生存に関する疫学調査：オッセオインテグレーションの獲得と維持からみた評価

抄録

Successful application of osseointegrated dental implants for functional reconstruction of edentulous and partially edentulous jaws has been well documented in many clinical studies. However, most of the studies have focused on implant survival after insertion of the superstructures.
The purpose of this follow-up study was to separately investigate acquisition and maintenance of osseointegration in relation to the risk factors for osseodisintegration. The subjects were a consecutive series of patients in whom osseointegrated dental implants had been installed at Okayama University Dental Hospital from February 1990 to September 2000. Acquisition and maintenance of osseointegration were clinically assessed by 4 calibrated examiners in a follow-up period (from April to September 2000) using the criteria described by Zarb and Albrektsson(1988). Troubles of the superstructures were also assessed by oral examination and/or clinical record inspection in the follow-up period.
Two hundred sixty-two implants (82 maxillary and 180 mandibular implants) had been placed in 98 patients (46 males and 52 females, mean age 54.7 years). Among them,89 superstructures supported by 188 dental implants (55 maxillary and 133 mandibular implants) were installed in 74 patients (35 males and 39 females, mean age 56.0 years) at the time of follow-up. The mean functional time of the superstructures was 3.2＋/-2.8 years (1 month to 10 years).
Rate of successful acquisition of osseointegration in the consecutively installed maxillary implants (81.7%)was significantly lower than that in the mandible implants(96.1%)(chi-square test:p＜0.01).On the other hand, Kaplan-Meier analyses with an intention-to-treat concept revealed no significant difference in the cumulative survival rates between maxilla and mandible as 96.4 and 94.0%, respectively (Log-rank test:p=0.99). Older age and smoking behavior significantly contributed to the unsuccessful acquisition of osseointegration, while length and diameter of implants, age, sex, smoking and diabetes had no statistically significant influence on the cumulative survival rates of the dental implants after installation of the super structures (e.g., after acquisition of osseointegration). These results reconfirm the previously reported finding that implants placed in the mandible can acquire osseointegration more easily than those in the maxilla. Meanwhile, once the implants acquire osseointegration, prognosis of the implants is relatively promising regardless of the placement location.