Background: The morphological characteristics of the alveolar bone thickness between the maxillary sinus and root ca nal tips of the premolars and molars is important for dental implant and orthodontic treatment. The hypotheses formulated were that there would be differences in the morphological characteristics of the alveolar bone at various tooth positions in the posterior maxilla and that age and sex would not influence the findings. This study may provide useful information for dental implant and mini-implant treatment, so as to help lead to successful treatment outcomes. Aim: To evaluate the vertical relationship between the maxillary sinus and molar teeth using cone beam computed to mography (CBCT). Materials and Methods: The study design was retrospective study. We selected 30 CBCT images that were taken in the Central Dental Hospital, Mongolian National University Medical Sciences (MNUMS), between 2021 and 2023. We collected all images according to the inclusion and exclusion criteria. We used Full CBCT (16cm*8cm) images using the target sampling method. The all CBCT images (85kW, 7mA) were obtained with HDX, WILL (DENTRI, Seoul, Korea) using OnDemand3D (CyberMed. Seoul. Korea). The vertical relationship between the maxillary sinus and the maxillary molars was classified into 5 categories according to Kwak’s classification. The study was approved by the Research Ethics Committee of MNUMS. Statistical analyses were done by IBM SPSS version 27 software. Results: A total of 202 maxillary premolars and molars were examined using CBCT images, and were taken in 30 pa tients. The patient group consisted of 12 men and 18 women with an average age of 26.87 years (range, 16–42 years). In the maxillary first premolars: Class I was 77.4%, Class II was 13.2%, Class V was 9.4%, Classes III and IV were not observed. In the maxillary second premolars: Class I was 44.8%, Class V was 37.9%, Class II was 17.2%. In the maxillary f irst molars: Class V was 62.3%, Class I was 24.4%, Class II was 6.7%, Class III was 4.4%, Class IV was 2.2%. In the maxillary second molars: Class V was 63.1%, Class I was 23.9%, Class II was 6.5%, Class III was 6.5%. When examining the distance from the apex of the root of the molars to the floor of the maxillary sinus, the distance between the root of the buccal side of the second molar was the smallest, 0.67±1.36mm, and the distance between the root of the first premolar was the furthest, 5.14±4.32mm (p<0.01). Conclusion Among the maxillary posterior teeth, the second molar was positioned closest to the floor of the maxillary si nus, whereas the first premolar was located at the greatest distance. Regarding the maxillary molars, Type V characterized by root protrusion into the floor of the maxillary sinus was the most frequently observed configuration. Conversely, for the premolars, Type I defined by a distinct separation from the sinus floor was the predominant anatomical relationship.

Background: Reconstruction of mandibular and maxillary defects resulting from malignant tumors has remained a complex challenge in recent years. Defects caused by tumors—as well as trauma, inflammatory diseases, and congenital anomalies—lead to impaired essential functions such as mastication, swallowing, and speech. Prior to the 1950s, reconstruction of maxillofacial hard tissue was not commonly performed. Instead, metal plates were used to reestablish bony continuity, and surrounding tissues were utilized to close soft tissue defects, without effectively restoring function. With modern advances in three-dimensional (3D) virtual planning, it is now possible to accurately plan free bone flaps for reconstructing jaw defects. During surgery, manually bending reconstruction plates to fit donor bone precisely is often not feasible. Preoperative 3D planning allows for precise fabrication of surgical guides and fixation plates, improving accuracy and significantly reducing operative time. Additionally, incorporating dental implant planning into the reconstruction process facilitates restoration of both structural and functional outcomes. Aim: To evaluate the outcomes of mandibular defect reconstruction using scapular free flaps in Mongolia and explore potential approaches to optimize the technique. Materials and Methods: This was a case study series. Data from reconstructive surgeries performed at the National Cancer Center of Mongolia, Central Dental Hospital, and the Mongolia-Japan Hospital were collected. Variables included patient age and sex, etiology of the mandibular defect, size of the scapular bone segment, operative time, ischemia time of the free flap, number of vascular anastomoses performed, and pedicle length. For 3D planning, CT scans of the patient's head and lower limb (slice thickness <1 cm) were used to generate 3D models via the 3D Slicer software. Cutting guides for the mandible and scapula (ASIGA), as well as the reconstruction models (AMS), were printed using a 3D printer. Results: A total of 400 free flap reconstructions were performed during the study period. Of these, 29 cases involved reconstruction of mandibular defects using scapular free flaps. The mean age of patients was 40.0 ± 18.3 years, with 52% (15 patients) being female. The etiologies of the defects included malignant tumors (13 cases, 45%), benign tumors (6 cases, 21%), and pre-existing defects (10 cases, 34%). In one case, tumor resection and mandibular reconstruction were performed using 3D planning. The total operative time was 9 hours and 30 minutes, and the ischemia time was 2 hours and 40 minutes. Conclusion Between 2012 and 2025, a total of 29 mandibular reconstructions using scapular free flaps were performed in Mongolia. Traditional reconstruction methods were associated with prolonged ischemia time. The use of 3D surgical planning has shown potential in significantly reducing ischemia time and improving surgical outcomes.