[Measurement of proximal enamel thickness of 182 permanent teeth]

Objective: To measure the proximal enamel thickness (PET) at the mesial and distal contact areas of the permanent teeth and to provide a reference for interproximal enamel reduction (IPR). Methods: From May 2016 to February 2018, 182 isolated permanent teeth were collected and screened from patients who underwent extraction at Department of Oral and Maxillofacial Surgery, Capital Medical University School of Stomatology. These teeth were extracted for orthodontic purpose or due to severe periodontitis. The patients having teeth extracted were all Beijing residents, Han nationality, and aged (39.5±10.6) years. Ninety percent of the teeth came from patients under 50 years old. These teeth were classified according to different tooth type. The mesial and distal contact areas of these teeth were marked with fluid resin. The isolated teeth were scanned using micro-CT and the enamel thickness was measured and analyzed. The parameters measured included mesial PET (PETm), distal PET (PETd), the distance from mesial contact area to occlusal plane (CAm-OP), the distance from distal contact area to occlusal plane (CAd-OP), the distance from mesial contact area to the cementoenamel junction (CAm-CEJ), the distance from distal contact area to cementoenamel junction (CAd-CEJ) and tooth width (TWmd). Results: The PET gradually increased from the anterior tooth area [(0.63±0.16) mm] to the molar area [(1.46±0.25) mm]. The sum of the PET from the second molar to the contralateral second molar in the maxillary dentition was 31.60 mm, and that of the PET from the second molar to the contralateral second molar in the mandibular dentition was 29.68 mm. The contact areas were located on the occlusal third of the proximal walls of anterior teeth and the middle third of the proximal walls of posterior teeth. The PET were positively correlated with the tooth width between the mesial and distal contact areas (P<0.05). Conclusions: The PET was thinner in the incisor area and thicker in the molar area. IPR should be carried out close to the occlusal side of the proximal walls in anterior teeth and the cementoenamel junction side of the proximal walls in posterior teeth.