الفهرس 
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Abstract
This study aimed to propose a decision-making rationale on the need for CBCT scans before dentoalveolar surgery in the posterior maxilla since the previous researchers failed to reach an agreement concerning this point. The impact of this study on the dental field is reducing the dose and cost of CBCT images on patients undergoing surgical procedures in the maxillary molar region.
CBCT and digital periapical images for 23 patients, with a total of 342 maxillary molar roots, were acquired and investigated carefully to evaluate the accuracy of digital periapical images in showing the sinus-root relation compared to CBCT. A scoring system was implemented represented in Score 1: root apex placed outside the sinus, Score 2: root apex just contacting the sinus floor and Score3: root apex is projected into the sinus. Furtherly three periapical features were investigated for each root: A= Interruption of the sinus floor B= Discontinuity of lamina dura and C= Upward bending of the sinus floor to envelop the root partially or completely.
Three tests were used to evaluate the reliability of digital periapical images in assessing sinus-root relation compared to CBCT. McNemar-Bowker Test revealed significant difference between both imaging modalities. Fleiss’s Kappa test reported the reliability of periapical technique in showing sinus-root relation especially when the root is placed outside the sinus. In terms of accuracy, sensitivity and specificity, digital periapical images are considered accurate by 73 %, sensitive by 88% and specific by 63%.
Regarding the three periapical features, the presence of any of the features strongly suggests the intrusion of root into the sinus. However, the absence of any of these features does not ensure that the root is placed outside the sinus. Except for the interruption of lamina dura which is the only feature that can indicate both intrusion and extrusion of the root from the sinus.
The total number of roots located outside the sinus was 121 with 35.3%, while those contacting the sinus floor was 80 with 23.3% and those intruded the sinus were 141 with 41.2%. The percentage of intrusion of the roots into the sinus in males was significantly higher (56.9%) than females (42.9%) (P=0.01).
The probability of root intrusion in the left molars (54.2%) was non-significantly (p=0.067) higher than that of the right side (44.3%). As for the type of tooth, the second molar showed the highest probability of root intrusion into the sinus (55.3%) followed by the third molars (52.6%) then the first molars (40.9). According to the type of root, the mesiobuccal root showed the highest probability of intrusion into the sinus (50.9%) followed by the palatal root (49.1%) then the distobuccal root (47.4%). However, the difference in both type of tooth and type of root was statistically non-significant (p=0.051 and 0.869 respectively).