The purpose of this study was to investigate whether number of non-vital teeth was an indicator of tooth loss during maintenance. Thirty-three general practitioners provided data on 321 patients undergoing maintenance over 10 years. The number of present teeth (PT), smoking status, level of bone loss, number of non-vital teeth, and reason for tooth loss during that period were investigated. Multiple logistic regression was performed to identify whether the number of non-vital teeth was associated with tooth loss. The average number of lost teeth was 1.07±1.82; that of PT at baseline was 24.4±3.9; and that of non-vital teeth at baseline was 5.4±4.5. Multiple logistic regression revealed a significant association between >8 non-vital teeth and tooth loss during maintenance (odds ratio [OR]: 2.40; 95% confidence interval [CI]: 1.18-4.87). It also demonstrated relationships between >8 non-vital teeth and root fracture or caries (OR: 3.90; 95%CI: 1.68-9.03 or OR: 2.85, 95%CI: 1.14-7.10, respectively). The number of non-vital teeth was associated with tooth loss during maintenance. The results suggest that patients with many non-vital teeth before commencement of maintenance are particularly at risk of tooth loss due to root fracture or caries. Therefore, the number of non-vital teeth offers a useful indicator of potential tooth loss.
Keywords: Endodontically treated teeth; Maintenance; Non-vital teeth; Permanent teeth; Risk factors.