Micro-computed tomographic characterisation of root dentin translucency in different age scales of aging individuals

Dental age estimation is an important niche in forensic odontology in cases of human identification. As dental hard tissues are resistant to degradation, they act as excellent age indicators for dental age estimation. Root dentin translucency is known to be strongly correlated with dental age and has been chosen as the sole parameter in multiple dental age estimation studies. Current dental age estimation studies based on root dentin translucency are focused on the length and area of translucency which, in some instances, require destructive tooth sectioning. As forensic odontology requires teeth to be preserved for legal and investigative purposes, destructive methods such as tooth sectioning are unfavourable. Micro-computed tomography (micro-CT) is a non-destructive, high-resolution imaging technique that allows for the development of accurate three-dimensional models and the acquisition of quantitative data. This study aims: (i) to develop and propose a method to 3-dimensionally visualise and quantify volumetric root dentin translucency (vRDT) via micro-CT, (ii) to determine vRDT of different age groups in the Malaysian Malay population based on micro-CT grey value, (iii) to determine the volumetric pulp chamber to whole tooth (vPCWT) of different age groups in the Malaysian Malay population via micro-CT, and (iv) to formulate novel dental age estimation formulas based on vRDT and vPCWT. 144 single-rooted male and female mandibular premolars of known chronological age from the Malay population were scanned using micro-CT scanner (XSlicer SMX-6000, Shimadzu). The X-ray source was operated at a voltage of 160 kV and a current of 100 µA, whilst analyses were performed using the open-source software FIJI/ImageJ. Results show that the micro-CT-generated grey-scale values are capable of visualising the distinctive butterfly-shaped pattern seen in physiological sclerotic dentin sections that represents the visual root dentin translucency effect, as well as generating distinctive grey values for dentin, enamel and the pulp chamber. Via the collection of adult premolars of known age, general population and sex specific dental age estimation models were constructed based on the calculated ratio of root dentin transluceny to root (rRDTR) and ratio of pulp chamber to whole tooth without enamel (rPCWT). Regression analyses using the generated data showed positive correlation when compared against known chronological age. The rRDTR parameter alone (males, R2 = 0.69; females, R2 = 0.667; mixed sex, R2 = 0.676), had a comparable accuracy to that of rPCWT parameter alone (males, R2 = 0.715; females, R2 = 0.72; mixed sex, R2 = 0.701). A combination of rRDTR and rPCWT generated an improved dental age estimation accuracy (males, R2 = 0.787; females, R2 = 0.823; mixed sex, R2 = 0.797). Though this novel method is in its infancy, it opens the avenue for future accurate non-destructive dental age estimation studies. Further work is needed to improve on dental hard tissue visualisation and chronological age correlation across different populations.