Marginal Bone Level Change around Implants supporting Full Arch Zirconia Fixed Prostheses

The primary aim of this retrospective study was to assess the change in marginal bone level around implants supporting full-arch implant-supported monolithic zirconia prostheses after a minimum service period of one year. The secondary aim was to identify potential predictors of marginal bone loss. All prostheses were delivered at the UIC College of Dentistry Prosthodontic clinic between January 2010 and June 2020. To measure marginal bone change, periapical radiographs taken at prosthesis delivery and at last follow-up visit, were obtained from the Axium electronic health record. Calibration and measurement of radiographs using ImageJ software (U. S. National Institutes of Health, Bethesda, Maryland, USA), ensured accuracy and consistency. A subsample of participant clinical records from a previous retrospective study of zirconia prostheses conducted in the Department of Restorative Dentistry provided the radiographs. Evaluation of potential predictors of peri-implant marginal bone loss included maxillary or mandibular arch, implant number, implant position, follow-up time, and implant manufacturer. Descriptive data for mean peri-implant marginal bone change, stratified by the potential predictors above, were calculated and presented in table format. The statistical analysis utilized a generalized estimating equation (GEE) modeling approach, which accounted for the hierarchical nature of the data (implants within prostheses). The final model included the variables of arch, implant angle, implant number, implant position, and follow-up time. The predictors above showed little evidence of association with marginal bone changes, with the exception of follow-up time. For mesial bone change measurements, the follow-up interval of 5-8 years, compared to 1-3 years, yielded a marginal bone loss of 0.265mm, 95% confidence interval (CI) of .0027 to 0.50, and a p value of 0.029. Although a null effect of implant angulation on mesial marginal bone change cannot be ruled out, the null value is near the upper confidence limit, and the change in the direction of mean bone level change is slight (-0.110mm, 95% CI [-0.224, 0.004], p= 0.059). All other estimates are consistent with the null hypothesis. All observed mean bone level changes were within published levels for clinical acceptability.