The contraction of the pulp chamber with secondary dentin apposition is a significant morphological dental age predictor in adults. The aim of this study is to evaluate the applicability of Kvaal's method and pulp/tooth volume ratio on cone-beam computed tomography (CBCT) images and develop a valid method for the Turkish adult population. In this study, 211 single-rooted teeth, extracted for orthodontic and periodontal reasons, of 134 patients with ages ranging from 16 to 71 years, were used. Each sample was scanned using CBCT. According to the reported technique (Kvaal's method), teeth were analysed on CBCT images. Additionally, pulp/tooth volume ratio was calculated using ITK-SNAP 3.4.0 software. The relationship between age and morphological variables was calculated by the Pearson correlation coefficient. Multiple linear regression models were established for each tooth, age as dependent variable, and morphological variables as independent variables. The determination of coefficients of the Kvaal's modified regression models were found in a range from 0.296 to 0.550. The pulp volume and the pulp/tooth volume ratio showed statistically significant differences between age groups (p < 0,001). Pulp volume and pulp/tooth volume ratio is a significant index for age. Linear measurement and ratios on CBCT images were insufficient estimates of the age of the Turkish population.