In order to standardize the measurements for each sinus, each scan was carefully oriented in the axial, coronal, and sagittal plane. In the axial plane, a horizontal line from the right and left zygoma was chosen as the standard. Orienting the hard palate horizontally was the standard in the coronal plane as well as in the sagittal plane. The specific teeth that were to be replaced by implants were then located by reviewing each patient’s chart, and the area of implant placement was located in the CBCT. To select the appropriate slice in the sagittal view to measure the mucosal thickening, the vertical line in the axial view was placed in the center of the alveolus where the future implant was to be placed. The appropriate sagittal view was then obtained and measurements of the mucosal thickening were performed. Each measurement was completed with the brightness and contrast set at 50%, and the zoom function was utilized to better visualize the soft tissue.

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.

Statistical analysis

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).