Assessment of suitability of natural hard tissue educational preparations by advanced estimates of their optical properties

Background. Educational simulation using synthetic organ phantoms becomes very popular in training of wide range medical professionals. However, in some cases only specially processed natural hard tissue preparations could help to gain particular valuable skills for future practices. One of major features of such preparations is translucency enabling comprehensive control of the educational process, e.g., instrument manipulations. Aim. The aim of this study was to elaborate a method for evaluation of optical properties of the preparations enabling assessment of its suitability and optimisation of the preparation process. Methods. This particular study was designed to compare optical properties of natural teeth preparations made using two chemical methods – a) the traditional, using methyl ester of salicylic acid, giving satisfactory results, but toxic, vs b) using benzyl benzoate and benzyl alcohol, from the first impression giving also satisfactory results, but being much less toxic. Translucent light images of 32 teeth were captured using a collimated white light source and a digital camera (C-P8, Optika, Italy), with the teeth positioned on a dental glass slab. A small piece of prosthodontic impression material (A-silicone Elite Transparent, Zhermack, Italy) was placed nearby to normalise exposure and white balance across all images. The optical properties of tooth translucency were analysed using custom-made image processing algorithms in the MatLab environment. The algorithm segmented the apical part of each tooth using superpixel technique. Optical properties of segmented apical part of each tooth were estimated in HSV colour scheme. Results. We did not find any statistical difference in optical properties of apical parts prepared by both methods. Statistical analysis (Mann–Whitney U test, p > 0.2) showed no significant difference in hue, saturation, nor in value between the two groups. Conclusions. The optical properties of the translucent teeth prepared by both methods were similar, so we advise to use less toxic method using benzyl benzoate and benzyl alcohol. The principle of evaluation of optical properties could be used also for assessment of other tissues and other processing methods.