Dental implant installation in the upper posterior region, an accurate diagnosis and a better understanding of bone remodeling in the area may be valuable for optimum treatment planning. Currently, cone-beam computed tomography (CBCT) is a common diagnostic tool that supports three-dimensional (3D) imaging and provides thin, detailed sections to assess the relationship between the maxillary sinus floor and the alveolar bone ridge. Although this method reduces the overlapping of anatomical structures and enables a better assessment, a few studies used CBCT to analyze sinus floor pneumatization in the posterior maxilla [1,2,7-9]. The purpose of this study was to determine the amount of sinus pneumatization after the extraction of maxillary teeth in the premolar and molar regions associated with the maxillary sinus via the evaluation of panoramic views.
In spite of common belief, only a few studies have described the phenomenon of pneumatization of the maxillary sinus [2,4,9-11]. Previous studies that were conducted by assessing panoramic radiographs or repeated radiographs have demonstrated the potential for differences in scale and/or mismatching, which might arise from comparing two different panoramic radiographs with differences in terms of the machine, the software, or the patient’s position or posture .
Pachota et al. investigated the bone level changes in the molar region after the extraction of premolars and molars. The measurements were evaluated in panoramic views. The lines passing through the lower sinus border parallel to the Frankfort horizontal plane and passing through the spina nasalis anterior were taken as reference lines to measure vertical changes in the bone [13-15]. The spina nasalis anterior was also taken as a reference point by Yua-Hoa et al. to measure changes in the bone at the maxillary sinus on panoramic views . The spina nasalis anterior is located at the midline of the maxilla. It is the point least affected by differences in head position and magnification on panoramic views. The spina nasalis anterior was taken as a reference point due to these aforementioned radiographic features.
Sharan et al. also investigated the relationship between tooth extraction and sinus pneumatization. Excessive sinus expansion was observed after the extraction of second molars in their study . A few previous studies have also shown close proximity between the second molar root ends and the maxillary sinus border. Extracting the second molar can cause cortical bone fractures between the root end and the maxillary sinus. Thus, the extraction of second maxillary molars is considered to cause excessive sinus pneumatization [2,7-9]. In the present study, greater sinus pneumatization was observed after the extraction of first molars. Additionally, sinus expansion was commonly observed after 2nd molar extraction. In a study by Sharan et al., greater sinus pneumatization was observed after the extraction of teeth that elevated the sinus floor . These findings are similar to ours. Additionally, greater sinus expansion was observed after the removal of teeth related to periapical lesions. No significant differences were observed with the removal of teeth that were directly associated with the maxillary sinus. These findings are consistent with those of studies by Wehrbein and Deidrichs [2,4]. At a minimum, 6 months are needed for the extraction socket to heal. Postextraction pneumatization occurs in the first 4 to 6 months before bone maturation. After 6 months, sinus pneumatization is less extensive sinus pneumatization occurs. .
In contrast, our study shows rapid sinus expansion in the first 6 months. Therefore, preprosthetic treatments, such as dental implant surgery, should be performed in the first 6 months after extractions in the molar region. Otherwise, additional procedures, likesuch as sinus elevation and grafting, might be needed.
Extensive sinus expansion occurred in cases of the extraction of more than one tooth in the same area. At sites of multiple extractions, bone resistance is reduced, and severe sinus pneumatization can occur . After extraction, adjacent teeth transport the occlusal forces to the extraction socket. This force transmission to the alveolar bone has been considered to reduce the amount of sinus expansion . This may be the reason why in our study, we found greater sinus expansion after the extraction of first upper molars than 2nd upper molars.
Immediate grafting of the extraction socket can be performed using particulate bone graft materials or bone substitutes with a barrier membrane or tissue engineering procedures to maintain the alveolar bone volume and height via osteoconductive or osteoinductive effects. These methods could prevent maxillary sinus pneumatization related to posterior tooth extraction. Levi et al. suggested that sinus pneumatization following maxillary posterior tooth extraction could be reduced by alveoler ridge preservation (ARP) procedures . A systematic review by van der Weijden and colleagues reported a mean alveolar bone height change of 3–12 months after extraction without ARP which can be effective to significantly decrease the vertical and horizontal alveolar bone dimensional changes .
There are a few limitations to the present study. One of these is the use of panoramic radiographs to measure changes in alveolar ridge and maxillary sinus dimensions. Although reference points were used to superimpose different radiographs, the use of cone-beam computerized tomography (CBCT) could verify sinus pneumatization changes. Second, pneumatization was associated with various factors except for tooth extraction in the maxillary posterior region. We evaluated only the correlation between tooth extraction and pneumatization with a small sample size. Further studies including CBCT examinations and larger sample sizes should be conducted to evaluate different factors and confirm these findings.