KHOẢNG XƯƠNG SAU RĂNG HÀM LỚN THỨ HAI HÀM DƯỚI Ở TƯƠNG QUAN XƯƠNG LOẠI I VỚI CÁC KIỂU MẶT KHÁC NHAU THEO CHIỀU ĐỨNG TRÊN PHIM CONEBEAM CT

Abstract

Objectives: To evaluate the mandibular retromolar space in skeletal class I patients with different vertical facial types using Cone-beam computed tomography (CBCT). Subjects and methods: A case series study was conducted on 86 skeletal class I patients (aged 18-47 years). Patients were categorized into hypodivergent, normodivergent, and hyperdivergent groups based on their vertical face types. Mandibular retromolar space was measured distally at four planes (0 mm, 2 mm, 4 mm and 6 mm from the cement-enamel joint (CEJ)) along the sagittal line and molar cuspal line, respectively. Results: In the sagittal plane, at the slice 2mm from the CEJ, the largest retromolar space of the mandibular second molar was found in the hypodivergent group (7.41±2.59 mm), followed by the normodivergent group, and was smallest in the hyperdivergent group (4.79±1.87 mm). A similar trend was also observed at the 4 mm slice from the CEJ. At the plane 6mm from the CEJ, the largest retromolar space was found in the normodivergent group (8.70±1.89 mm) and the smallest in the hyperdivergent group (5.61±1.59 mm). On the occlusal plane, the mandibular second molar retromolar space at the 6mm slice from the CEJ was largest in the normodivergent group (9.88±2.43 mm) and smallest in the hyperdivergent group (6.89±3.11 mm). In the normodivergent group, patients with normally erupted third molars had a significantly larger retromolar space on the occlusal plane compared to those with impacted third molars at the 0mm, 2mm and 4 mm slices from the CEJ. Conclusion: The vertical facial pattern and the eruption pattern of the mandibular third molar were factors influencing the mandibular retromolar space. The mean mandibular retromolar space was smallest in the hyperdivergent group, larger in the normodivergent group and hypodivergent group. Hyperdivergent patients have the smallest retromolar space, so distalization in this group should be carefully considered.