1093 Int. J. Morphol., 28(4):1093-1096, 2010. Sex Chromatin in Dental Pulp. Performance of Diagnosis Test and Gold Standard Generation Cromatina Sexual en Pulpa Dental. Rendimiento de la Prueba Diagnóstica y Generación del Gold Standard Iván Suazo Galdames; Ignacio Roa Henríquez & Mario Cantín L. SUAZO, G. I.; ROA, H. I. & CANTÍN, L. M. Sex chromatin in dental pulp. Performance of diagnosis test and gold standard generation. Int. J. Morphol., 28(4):1093-1096, 2010. SUMMARY: The sex chromatin or Barr body is a condensation of chromatin present at the nucleus of cells in female individuals. Their observation is possible in different cell types and is used for the rapid diagnosis of biological sex. The observation of this condensation in cells of the pulp tissue can be useful in the forensic diagnosis of sex, primarily because of the protection it give dental hard tissues, but its diagnostic value has not been tested. The purpose of this study is to analyze the diagnostic value of the observation of sex chromatin in cells of the pulp tissue. We used 40 premolars and third molars—20 from men with a mean age of 20.6 years (SD 8.8) and 20 from women with a mean age of 20.4 years (SD 7.4). The pulp was obtained from teeth extracted and localized 50 cells per plate. The presence of a cell with visible Barr body was considered positive for women. With these results, we evaluated the diagnostic performance of the test. The performance of the test was 100%; of the 50 cells observed per plate, mean Barr bodies positive cells was 20.4 (SD 0.44) in female samples. There was no positive cell in preparations of male subjects. The diagnostic test observation of sex chromatin in dental pulp is a reliable test for sex determination. This study provides a gold standard for performance assessment in which the teeth have suffered extreme physical conditions, such as incineration and dumping. KEY WORDS: Sex chromatin; Barr chromatin; Sex determination; Forensic dentistry. INTRODUCTION Sex determination in forensic medicine is considered one of the first and most important steps. This is usually done with a simple observation of the internal and external physical sexual characteristics. However, the problem arises in determining the sex of skeletons, especially when having only segments or isolated teeth. Tooth enamel is the hardest tissue in the body, and the teeth remain intact after death, thus making them useful for forensic identification of sex with respect to morphological characteristics (Haga, 1959; Gonda, 1959; Garm, 1964) and soft tissues (Das et al., 2004). In 1949, Barr and Bertram determined that there was a difference between male and female cells. They found that, in female cells, there was a small chromatin condensation at the nuclei of nerve cells of cats (Barr et al., 1950). This condensation (Barr chromatin or Barr body) also has been found in bone cells (Vernino & Laskin, 1960), cells of the retina (Teplitz, 1965), and oral mucosal cells (Dixon & Torr, 1956). The presence of sex chromatin or Barr bodies in den- tal tissues has been registered, but the results have been mixed regarding their share and postmortem time required for proper identification (Seno & Ishizu, 1973; Whittaker et al., 1975). Furthermore, there is no gold standard to assess its diagnostic value in different climatic conditions, burial conditions, and exposure to physical agents, such as heat and humidity. Against this background, the purpose of this study is to evaluate the diagnostic performance of Barr body observation for sex determination in healthy teeth, thus establishing a gold standard to evaluate its diagnostic per- formance variations in different situations. Universidad de Talca, Chile. Financing: Proyecto DIUTALCA VAC493