The sites that were measured are specified in the image below (Fig. 1). The most posterior and anterior aspects of the visible maxillary sinus were measured. The ½ point along with the ¼ and ¾ points were then selected, and the measurements of the mucosal thickening were then completed at these three sites. The thickest portion of the mucosa was also measured if it did not coincide with one of the three earlier measurements. Post implant placement radiographs were analyzed to locate the area where the implant was placed, and this area was then estimated on the CBCT and the thickness of the alveolus was measured there.

Outcome analyses included the overall implant survival rate and percentage of mucosal thickening at different sites. The associations between the amount of mucosal thickening and the recorded variables, including patients’ systemic conditions and dental history, were estimated by linear mixed models. Adjustment for potential inter-variable influence using regression analysis was also performed. A p value of 0.05 was used as the level of significance. All the statistical analyses were calculated using a computer program (SAS Institute Inc. 2011. Base SAS® 9.3 Procedures Guide, Cary, NC).