CBCT-Based Evaluation of External Root Morphology of Maxillary Third Molars in a Yemeni Population

Background Maxillary third molars exhibit high variability in root number, length, and curvature, which complicates extraction and potential endodontic treatment.[16, 18, 19, 25] Cone-beam computed tomography (CBCT) allows three-dimensional assessment of external root morphology and its relationship to the maxillary sinus, which is critical for risk-aware treatment planning.[13, 14, 17] Data on maxillary third molar morphology in Yemeni populations remain limited. Methods This retrospective cross-sectional CBCT study evaluated 320 maxillary third molars from Yemeni patients aged 20–65 years who attended three private dental radiology centers in Sana’a, Yemen. CBCT scans were acquired using a Green CBCT scanner (PHT-60CFO, Vatech, Korea; 5×5 cm field of view, voxel size 120 µm³).[13, 14] Images were analyzed in Ez3D-i software in axial, coronal, and sagittal planes. For each tooth, the number of roots, root length, external root curvature (angle, level, direction), root separation versus fusion, distance from root apices to the maxillary sinus floor, and pulp-chamber-related distances (occlusal surface to roof, roof to floor, floor to furcation) were recorded, following published CBCT protocols.[1–3, 13] Teeth with caries, open apices, apical pathology, developmental anomalies, periodontal bone loss, previous endodontic treatment, or image artefacts were excluded. Descriptive statistics and inferential tests (Chi-square and independent t-tests, α = 0.05) were performed using SPSS v28. Results Of 320 maxillary third molars (179 females, 55.9%; 141 males, 44.1%; mean age 30.62 ± 9.26 years), 15.6% had one root, 9.1% had two roots, 68.8% had three roots, and 6.5% had four roots. Overall, 41.6% of teeth presented with separated roots and 42.8% with fused roots; 15.6% were single-rooted. Mean root lengths ranged from 17.12 ± 2.53 mm for single-rooted teeth to 18.62 ± 1.99 mm for the mesiobuccal root in four-rooted teeth; palatal roots tended to be the longest across configurations. Root curvature was predominantly mild to moderate and most frequently located in the middle third for buccal roots and the apical third for palatal roots, with distal curvature being the most common direction. Regarding sinus relationship, 54.69% of roots were outside the maxillary sinus, 19.37% were in contact with the sinus floor, and 25.94% protruded into the sinus cavity. Mean pulp-chamber distances were 4.34 mm from occlusal surface to chamber roof, 3.04 mm from roof to floor, and 2.60 mm from floor to furcation. A significant association was observed between gender and number of roots, with males more frequently exhibiting two-rooted teeth and females more frequently showing three-rooted teeth (p < 0.05). Conclusions In this Yemeni sample, maxillary third molars were predominantly three-rooted with variable curvature and a high frequency of roots in close proximity to, or protruding into, the maxillary sinus.[16, 18, 19] These findings highlight the importance of pre-operative CBCT assessment before surgical extraction or complex restorative/endodontic procedures involving maxillary third molars. Population-specific knowledge of external root morphology can support individualized risk assessment and safer, more predictable clinical outcomes.[16, 18–20]