Relationship between Jawbone Mineral Density and Number of Remaining Teeth

Objectives: In spite of some investigators demonstrating significant association between jawbone mineral density and tooth loss, other studies have failed to find this association. The biggest problem is difficulty in standardization of criteria. The purpose of this study was to evaluate whether jawbone mineral density measured by mandibular cortex condition influenced number of remaining teeth in older people. Methods: 126 subjects (67 men, 59 women) participated in this study. All of them were 77 years old. Four dentists measured number of remaining teeth. Jawbone mineral density was evaluated by Mandibular Cortical Index (MCI) on dental panoramic radiograph. Inferior cortex was detected on both sides of mandible, distally from mental foramen. Subjects were classified into three groups (C1: normal, C2: mild/moderate erosion, C3: severe erosion). After controlling for gender, multiple linear regression analysis was performed to assess the relationship between jawbone mineral density by MCI (1: normal, 2: not normal) and number of remaining teeth. Results: Mean numbers of remaining teeth were 19.5±8.5 for C1, 14.8±8.2 for C2 and 13.2±10.3 for C3. Significant greater loss of teeth was found in C2 (p<0.01) and C3 (p<0.01) compared with C1 by Scheffe-multiple-comparison test. Furthermore, jawbone mineral density was significantly associated with number of remaining teeth by multiple linear regression analysis (p<0.001, b=-0.356, R²=0.093). According to several studies, bone mineral density of mandibular cortex at distance of mental foramen wasn't affected by alveolar bone resorption caused by tooth loss. Conclusions: This study suggested that decline of jawbone mineral density influenced tooth loss in older people. This study was supported by grant-in-aid from the Ministry of Health and Welfare of Japan.