Proliferating trichilemmal tumours (PTT) are defined by a benign squamous cell proliferation inside a trichilemmal cystic (TC) cavity. A possible explanation of this proliferative phenomenon within the cyst may be molecular alterations in genes associated to cell proliferation, which can be induced by ultraviolet radiation. Among other genes, alterations on TP53 and DNA mismatch repair proteins (MMR) may be involved in the cellular proliferation observed in PTT. Based on this assumption, but also taking into account the close relationship between the sebaceous ducts and the external root sheath where TC develop, a MMR, a p53 expression assessment and a TP53 study were performed in a series of 5 PTT cases, including a giant one. We failed to demonstrate a MMR disorder on studied PTT, but we agree with previous results suggesting increased p53 expression in these tumours, particularly in proliferative areas. TP53 alteration was confirmed with FISH technique, demonstrating TP53 deletion in most cells.

Introduction: The European Union has established specific directives concerning radiological protection which are obligatory for member States. In addition, all Spanish dental clinics with radiological equipment are required to have an annual quality control check. Objective: To analyze the effect of new European legislation on dental radiological practice in Spain and to determine whether it has resulted in lower doses being administered to patients. Material and Methods: A total of 10,171 official radiological quality control reports on Spanish dental clinics, covering 16 autonomous regions, were studied following the passing of Royal Decree 2071/1995 on quality criteria in radiodiagnostic installations. The reports, compiled by U.T.P.R Asigma S.A., a company authorised by the Nuclear Safety Council, cover the years 1996 to 2003, which has enabled us to monitor the evolution of radiological procedures in dental clinics over a seven year period. Results: According to the reports for 2003, 77.3 % of clinics complied with EU requirements, using equipment of 70 kVp, 8 mA, 1.5 mm Al filters, with a collimator length of 20 cm. However, non-compliance was detected in approximately a third (30.8%) of the equipment inspected: alterations in the kilovoltage used, exposure time, performance of the tubing, dosage, linearity/intensity of current and acoustic-luminous signal 6.86%. The mean skin dose reached 3.11 mGy for patients who received an x-ray of an upper molar, representing a decrease of 18% over the seven years studied. Conclusion: there has obviously been a general improvement in the parameters studied, but only 77.3% of the installations complied fully with official EU regulations concerning dental radiological protection.