| Conflicting evidence has found that oral implant outcomes may be related to age- and site-specific aspects of jawbone condition. An observational historical study examined relationships between oral implant outcomes and age- and site-specific aspects of jawbone condition. Matched groups of older and younger adults, each with 45 complete or partial prostheses, demonstrated no significant difference in either their cumulative oral implant success over 4 to 17 years, 92% survival for the older group compared to 87% for the younger group, or in the mean annual crestal bone loss associated with their complete prostheses, both with less than 0.05 mm/year of bone loss after the first year of function. However, the younger fixed mandibular prostheses had significantly faster bone loss (0.047 mm/year) after the fourth year of function compared to the matched older subgroup (0.005 mm/year). Using the Lekholm and Zarb (1985) (LZ) classification, neither jawbone quantity nor quality were different between these subgroups. However, the older subgroup had been edentulous significantly longer (25.0 years) than the younger subgroup (13.6 years). The resulting supposition implies an increased susceptibility to bone loss for shorter periods of edentulism. Multivariate analysis of implant outcomes among 139 complete implant prostheses in 130 consecutively treated patients over 4 to 17 years suggested that implant success was related, albeit inconsistently, to jawbone condition, such that better survival was predicted with better LZ jawbone quantity and quality, and that crestal bone behaviour was best predicted by the number of years of edentulism, such that mean annual bone loss after the first year of function was predicted to range from 0.08 mm/year among sites edentulous 6 months at implant placement to 0.01 mm/year among sites edentulous 30 years at implant placement. Facilitating this work, the validity and intra-observer reliability of the LZ classification were found to be acceptable for research purposes. Inter-observer reliability of the LZ classification was found to be fair at best. To improve future implant outcomes research, a concurrent study demonstrated excellent validity and reliability using quantitative computed tomography for assessment of the cancellous bone mineral density of jawbone. |
