Our study did not find a significant association between endodontically treated teeth and mucosal thickening. Though this finding is consistent with some previously published studies, other studies did report an association. These discrepant findings could be the result of different inclusion criteria in the study design. Since our study did not include any patients with radiographic signs of pulpal pathoses, these data suggest that successful root canal treatment without signs of apical radiolucency should not be considered as a risk indicator of future mucosal thickening. On the other hand, it has been reported that the presence of apical periodontitis is related to sinus mucosal thickening, which should alert clinicians when planning future implant-related procedures. Because periapical infections are considered a multifactorial entity, they should be carefully evaluated and treated to ensure a favorable implant treatment outcome. In addition, the influence of a periapical scar of dense collagen tissue, formed after conventional root canal treatment, on implant treatment outcomes has not yet been fully explored. Therefore, additional future investigations are needed to examine these unresolved issues.

Although residual alveolar ridge height has been associated with sinus mucosal thickening, our study did not find a significant association between these two parameters. Acharya et al. reported that lower available bone height in the subsinus region was related to thickened sinus membranes within an Asian-Indian and Hong Kong-based Chinese population. Differences in the ethnic composition and geographic location of this population might explain the different findings compared to our study, which was primarily comprised of a Caucasian cohort in North America. Also, in their study, the majority of patients (80.53%) had some degree of periodontal disease, which might have directly influenced their outcome analysis. Since residual bone height depends highly on the rate of bone remodeling and sinus pneumatization after tooth extraction, future prospective clinical trials are needed to investigate the relationship between changes in maxillary sinus dimension and mucosal thickness.