PALATAL RUGAE PATTERNS IN THE SERBIAN POPULATION

Establishing the gender of a dead person is one of the main aspects in forensic medicine, especially in cases of massive diseasters. Palatal rugae have been related with specific racial groups and are said to be useful in sex determination. One hundred pre-orthodontic plaster casts, equally distributed between males and females with an age range of 15-30 years, were examined for different rugae patterns by the Thomas classification. The total number of rugae was not significantly gender linked. According to size, the primary type of rugae was dominant in both males and females.Wavy and curved patterns of rugae were the most common, both in males and females. There was a significant sex difference in the circular and converging types which was higher in males and females, respectively.


INTRODUCTION
The characteristics of the rugae pattern have been the subject of numerous investigations by anthropologists, biologists, orthodontists and forensic experts (Thomas and Kotze, 1983;English et al., 1988;Almeida et al., 1995;Kapali et al., 1997).Palatal rugae refer to the ridges on the anterior part of the palatal mucosa, each side of the median palatine raphe and behind the incisive papilla (Thomas and Kotze, 1983).Palatal rugae develop in the third month of intrauterine life as localized regions of epithelial proliferation and thickening even before the elevation of the palatal shelves (Amasaki et al., 2003).Later, fibroblasts and collagen fibers accumulate in the connective tissue beneath the thickened epithelium and attain a distinctive orientation (Hauser et al., 1989).
Palatal rugae are stable topographical structures in the oral cavity (Thomas and Kotze,1983;English et al., 1988;Abou et al., 1998;Limson and Julian, 2004;Caldas et al., 2007), and neither diseases, chemical agents or trauma change the form of palatal rugae which are protected from inside the oral cavity (English et al., 1988).).Rugae are unique to each individual, and Thomas and Kotze (1983) stated that palatal rugae are similar to finger prints.Henceforth it was suggested that rugae could be used to establish an individual's identity (English et al.et al., 1988;Muthusubramanian et al., 2005;Bansode and Kulkarni, 2009;Jain and Chowdhary, 2013;Bhullar et al., 2011;Indira et al. 2012), however, researchers have disagreed as to whether or not legal identification could be based solely on palatal rugae (Robison et al., 1998;Caldas et al., 2007).Given that there are differences in the appearance of certain rugae patterns in a population (Shetty et al., 2005;Paliwal et al., 2010;Gondivkar et al., 2011), it is necessary to establish certain rugae parameters so that identification would be more reliable.At present no such standards have been determined for the Serbian population.Therefore, this study was an attempt to determine the number and predominant pattern of rugae in the Serbian population.

MATERIALS AND METHODS
The sample for the present study consisted of 100 dental casts (50 males and 50 females).All the subjects were Serbs, healthy individuals free of congenital abnormalities, inflammation, trauma or orthodontic treatment.The classification used to describe the rugae patterns was based on those described by Thomas and Kotze (1983).This classification takes into consideration the number, length, shape and unification of rugae.The shapes are classified into curved, wavy, straight and circular; curved are crescent shaped and curved gently; wavy describes rugae with a slight curve at the origin or termination of a curved rugae; straight rugae run directly from their origin to termination; circular rugaeform a definite continuous ring.The rugae were classified based on their length as follows: primary >5mm, secondary 3-5mm, fragmentary <3mm.Unification considers rugae that (i) converge where two rugae originate away from the center and unite towards it, while (ii) diverging rugae originate from the center and diverge away from it.Rugae were plotted in black pen on the model, and identification was performed using a magnifying glass.The measurement was performed with a digital nonius (Mitutoyo, Tokyo) by one examiner.

RESULTS AND DISCUSSION
Investigators have implied that palatal rugae are unique to each individual and can be used successfully in human identification.The determination of sex is important in cases of major disasters where bodies are often mutilated beyond recognition, and identification of the sex of victims builds the biological profile of unidentified human remains (Bharath et al, 2011).Thomas and Kotze (1983) studied the rugae patterns of six South African populations to analyze the interracial differences.They found that rugae were unique to each ethnic group and that they can be used in genetic research.Hauser et al., (1989) compared the rugae pattern of Swazi and Greek populations and found definite differences between the two populations.Considering that there are differences in specific populations, it is necessary to determine specific population palatal rugae patterns.
The present study did not show any significant differences in the number of rugae between the sexes in the Serbian population (Table 1).No significant difference in the length of rugae was found between the sexes.(Table 2).Table 3 gives the descriptive statistics of different types of rugae categorized by gender.The wavy and curved patterns of rugae were found to be the most common both in males and in females.There was also a significant gender difference in the circular type, which was more frequently present in males, whereas the frequency of the converging type was higher in females.
In the present study the commonest palatal rugae shapes were wavy and curved compared with sinous and curved observed in Caucasian and aboriginal Australians (Kapali et al.,,1997), and in two Indian populations (Preethy et al., 2007) and Chileans (Hermosilla et al., 2009).In addition, circular rugae were present, although they constituted less than 5% of the total shapes of rugae.The circular and converging patterns of rugae were found to be statistically different in the sexes.This means that sex prediction based on rugae is more reliable when the converging and circular types of rugae are used (Saraf et al., 2011).In the study of Preethi et al., (2007) on Western and South Indian populations, the circular group was found to be absent.Eboh (2012) reported that the dominant rugae form among the Urhobo ethnic group was followed by the sinuous type.Santos and Caldas (2011) reported that there are no differences in shape of palatal rugae between Portuguese males and females.Fahmi et al., (2001) found that females had more converging type than males and males had more circular rugae.

CONCLUSIONS
The palatal rugae pattern of the investigated Serbs was characterized by the presence of primary rugae in most individuals, that mainly assumed wavy and curved shapes.There was also a significant gender difference in the circular type which was higher in males and in the converging type which was higher in females.When compared with the results from other studies, it is clear that the palatal rugae pattern can be set for different ethnic groups.This small sample justifies further work on a larger sample to confirm these findings.
Table3.Number of rugae and the mean value for males and females