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30 I I special _ transparent teeth _Since the early days of dentistry, dentists have exploredthemorphologyoftheinternalrootanatomy. From the pre-X-ray period to the technology-driven present, the study and examination of the root-canal system has become an obsession for endodontists. Several methods such as radiographic1 and histolo- gicalexaminations,2–3 cross-andlongitudinalsection- ing,4 and root-clearing techniques, to name a few, werewidelyusedinthepast.Today,differentcomput- erised tomography studies5 and observations under dental operating microscopes6 are performed to light up the dark confines of the dental pulp. _The tooth-clearing technique Over the last 100 years, the tooth-clearing tech- nique was utilised in human dental pulp morphology studies, as it provides a 3-D view of the pulp cavity in relation to the exterior of the teeth and allows a thoroughexaminationofthepulpchambersandroot canals.7–9 It was also utilised in the study of apical leakage.10 Today, the clearing technique remains usefulonlyasateachingandresearchtool,withlittle or no clinical applicability.11 In 1913, Hermann Prinz successfully cleared teeth using the protocol proposed by Spaltholz in 1906.12 Okumura performed in-depth studies of the pulp anatomy and classified the canals according to their distribution and prevalence.13 In order to simplify the canal system visually, he injected ink into the pulp cavity.13 Samples can also be stained with Haema- toxylin and Eosin, which are largely used to colour histological preparations. Compared with other procedures such as radiographic and histological examinations, the tooth-clearing technique has the following advantages: _retains the original form of the root; _enables the observation of minute details of the root-canal morphology; _is inexpensive; _samples can be conserved for a long time; and _is easy to perform. roots4_2010 Transparent teeth: Apowerful educational tool Author_ Dr Sergio Rosler, Argentina Fig. 1 Fig. 2 Fig. 3