[The influence of the relationship between the root apex of the posterior teeth and the maxillary sinus floor on the thickness of the maxillary sinus mucosa].

PURPOSE

To measure and analyze the thickness of the maxillary sinus mucosa under different relationships between the maxillary posterior teeth apex and the maxillary sinus floor on cone beam CT (CBCT).

METHODS

A total of 987 patients requiring implant surgery due to dentition defect or loss were selected from Ruijin Hospital, Shanghai Jiao Tong University School of Medicine from January 2020 to December 2022. The maxillary posterior teeth most closely related to the maxillary sinus were observed on CBCT, the tooth position and root apex were recorded, and the vertical distance between the apex of the posterior tooth and the base of the maxillary sinus was measured. According to the distance between the root apex and the maxillary sinus floor, the posterior teeth were divided into three categories: Class Ⅰ: the distance between the root apex and the maxillary sinus floor (d ＞0 mm); Class Ⅱ : the root apex was attached to the maxillary sinus floor and the cortical bone of the maxillary sinus floor was continuous (d=0 mm); Class Ⅲ : apical protrusion into the maxillary sinus floor(d＜0 mm). The thickness of the thickest part of the maxillary sinus floor mucosa was measured. The distance between the root and the maxillary sinus floor and the thickness of the maxillary sinus mucosa were compared under different root-sinus floor relationship, and the correlation analysis was performed. SPSS 26.0 software package was used to analyze the data.

RESULTS

Among the 1974 maxillary sinuses of 987 patients, there were 450 maxillary sinuses with Class I relationship between the posterior root apex and the maxillary sinus floor, while 126 (28%) of the maxillary second molar proximal root and the maxillary sinus floor were the most closely related. In ClassⅠrelationship, the average distance from root to the maxillary sinus floor was (2.9±2.7) mm, and the average thickness of the maxillary sinus mucosa was (2.9±4.0) mm. There was no correlation between the distance from root to the maxillary sinus floor and the thickness of the maxillary sinus mucosa. There were 808 maxillary sinuses with ClassⅡ relationship between the posterior root apex and the maxillary sinus floor, among which 132 (16.3%) maxillary first molars had the closest relationship with the maxillary sinus floor. In Class Ⅱ relationship, the average thickness of the maxillary sinus mucosa was (3.0±4.6) mm. There were 249 maxillary sinuses with Class Ⅲ relationship between the posterior tooth root apex and the maxillary sinus floor, among which 87 (34.9%) palatal roots of the maxillary first molar were the most closely related to the maxillary sinus floor. The average distance from the root to the maxillary sinus floor was (-1.9±-1.4) mm, and the average thickness of maxillary sinus mucosa was (2.4±4.9) mm. There was a positive correlation between them (r=0.18, P=0.004).

CONCLUSIONS

The most common relationship between the posterior maxillary tooth apex and the maxillary sinus floor is Class Ⅱ. The palatal root of the first molar is most closely related to the maxillary sinus floor, the mesiobuccal root of the second molar ranks second. The thickness of the maxillary sinus mucosa varies on the relationship between the different maxillary posterior teeth apex and the maxillary sinus floor. The average thickness of the maxillary sinus mucosa in Class Ⅲ is thicker than Class Ⅱ and Class I. In Class Ⅲ, as the distance from the apices to the maxillary sinus floor increases, the thickness of maxillary sinus mucosa increases.