Rugae dimensions and their significance in forensic dentistry.

BACKGROUND: The palatal rugae are the ridges situated in the anterior part of the palatal mucosa, are unique to each individual, and can establish individual's identity. AIMS: To establish the reliability of using the palatal rugae dimensions in identifying the different ethnic groups. SETTINGS AND
DESIGN: Many studies have established the reliability of using the palatal rugae patterns in identifying the different ethnic groups. However, no studies have been reported in the English language literature that uses the rugae dimensions to identify the different ethnic groups.
MATERIALS AND METHODS: A total of 60 subjects aged between 18-30 years comprising of 30 Kannada speaking and 30 Malayalam speaking individuals, with 15 males and 15 females, in each were considered for the study. The rugae patterns of these patients were traced on dental casts obtained with alginate impressions. A digital caliper was used to measure the different dimensions of the palatal rugae. STASTICAL ANALYSIS: Statistical analysis was carried out using the unpaired 't' test. RESULTS AND
CONCLUSION: The present study showed a significant difference in the palatal rugae dimensions among the Karnataka and Kerala individuals.

Introduction

The palatal rugae are ridges situated in the anterior part of the palatal mucosa on each side of the medial palatal raphae and behind the incisive papilla. The pattern of orientation typical for the individual is formed by the 12th to 14th week of intrauterine life and remains stable from this time throughout the life until the oral mucosa degenerates at death, with exceptions for those patients who have undergone orthodontic treatment.[1] The palatal rugae possess unique characteristics that could be used in paternity identification and in circumstances where identification of an individual by fingerprint or dental record comparison is difficult. In this case, palatal rugae may be considered as an alternative source of comparative material.[2] The palatal rugae are permanent (except in the individuals who have undergone orthodontic treatment), unique to each individual and can establish identity through discrimination.[34] There seems to be a significant association between the rugae form and ethnicity; if a particular rugae pattern could be established for different ethnic groups, it would be an easy assignment for the forensic odontologist to help in the identification of an individual.

Various studies have been done to establish the reliability of using the palatal rugae patterns in the identification of different ethnic groups. Though, the rugae pattern is unique to individuals, interpretation of the rugae pattern is subjective. A subjective parameter considered for any analysis usually gives rise to inter-observer variability. To know the ethnic background in the English language literature, no studies have been done using objective parameters or palatal rugae.

The purpose of this article is to analyze if there are any significant differences in dimensions of palatine rugae between the Kanada speaking and Malayalam speaking groups and between the males and females.

Materials and Methods

A total of 60 subjects aged between 18–30 years comprising of 30 Kannada speaking and 30 Malayalam speaking, with each group including 15 males and 15 females were considered for the study. The patients with complete set of dentition were considered in the study. The study sample was divided into four groups: (i) The Karnataka boys, (ii) the Karnataka girls, (iii) the Kerala boys and (iv) the Kerala girls. Since, this is an institution-based study, the number of subjects available for the Kerala boys group were limited. The study being comparative in nature, it required equal number of subjects in each group. Thus, the uniformity of the subjects was maintained for each group by selecting 15 random subjects for each group. The patients with systemic illness, orthodontic therapy, patients with palatal prosthesis and cleft lip or cleft palate patients were excluded from the study. The prevalence of Class II malocclusion is known to be higher among the Malayalam speaking. This group was used along with the Kannada speaking to compare and ascertain, if there would be any influence of the Class II malocclusion on the palatal rugae dimensions.

The procedures followed were in accordance with the ethical standards of the institutional committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 2000. The subjects were briefly explained about the study and written informed consent was obtained. The subjects were asked to rinse the oral cavity and alginate impressions of the maxillary jaw were made by an experienced prosthodontist. The rugae patterns were traced on dental casts obtained with alginate impressions. A digital caliper was used to measure the dimension of the palatal rugae [Figure 1]. The following dimensions were noted by meticulous examination of each cast.

Figure 1

Digital vernier calipers

A-B distance: This is the distance between the most anterior point on the incisive papilla and the most medial point of the first primary rugae [Figure 2]

Figure 2

The three reference points considered for the study (A, B and C) to calculate the A-B, A–C and B–C distances

A-C distance: This is the distance between the most anterior point on the incisive papilla and the most medial point of the last primary rugae [Figure 2]

B-C distance: This is the distance between the medial points of the first and the last primary rugae. This distance is calculated by subtracting the A-B distance from the A-C distance [Figure 2].

The dimensions were measured on right and the left sides and the average of the two measurements was considered for the study. Statistical analysis was carried out using the unpaired t test. The Statistical Package for the Social Sciences (SPSS) software was used for the statistical analysis. P value less than 0.05 was considered significant.

All the dimensions were measured by a single investigator who meticulously examined each cast and noted the measurements. The intra-observer calibration was carried by examining 10 casts from each group at two different intervals. The intra k value at two different moments was 0.8.

Results

The A–B dimensions: The mean of A–B dimensions showed significant statistical difference among the Karnataka boys and Kerala boys [Table 1] and among the Kerala boys and girls [Table 2]. However, their mean dimensions were statistically not significant among the Karnataka and Kerala girls [Table 3] and among the Karnataka boys and girls [Table 4]

Table 1

Mean palatal rugae dimensions among Karnataka boys and Kerala boys at A-B distance

Table 2

Mean palatal rugae dimensions among Kerala boys and Kerala girls at A-B distance

Table 3

Mean palatal rugae dimensions among Karnataka girls and Kerala girls at A-B distance

Table 4

Mean palatal rugae dimensions among Karnataka boys and Karnataka girls at A-B distance

The A–C dimensions: The A–C dimensions showed highly significant statistical differences between the Karnataka and Kerala boys [Table 5], among the Karnataka and Kerala girls [Table 6], and among the Karnataka boys and girls [Table 7] and among the Kerala boys and girls [Table 8]

Table 5

Mean palatal rugae dimensions among Karnataka boys and Kerala boys at A-C distance

Table 6

Mean palatal rugae dimensions among Karnataka girls and Kerala girls at A-C distance

Table 7

Mean palatal rugae dimensions among Karnataka boys and Karnataka girls at A-C distance

Table 8

Mean palatal rugae dimensions among Kerala boys and Kerala girls at A-C distance

The B–C dimensions: There was a highly significant statistical difference between the B–C dimensions among the Karnataka and Kerala boys [Table 9], among the Karnataka and Kerala girls [Table 10], and among the Karnataka boys and girls [Table 11] and among the Kerala boys and girls [Table 12].

Table 9

Mean palatal rugae dimensions among Karnataka boys and Kerala boys at B-C distance

Table 10

Mean palatal rugae dimensions among Karnataka girls and Kerala girls at B-C distance

Table 11

Mean palatal rugae dimensions among Karnataka boys and Karnataka girls at B-C distance

Table 12

Mean palatal rugae dimensions among Kerala boys and Kerala girls at B-C distance

Discussion

Various classification systems have been proposed for the rugae patterns.[567891011] Thomas CJ and Kotze proposed the reference points to measure the rugae pattern dimensions.[12] Various studies have been done to correlate the rugae pattern with the different ethnic groups. Kotrashetti VS et al. compared rugae pattern among the Karnataka and Maharashtra population with the help of regression analysis.[13] Their study gave a predictive value of 70%. Kallianpur S et al. carried out an anthropometric analysis of facial height, arch length, and palatal rugae. Their study concluded that the Indian and Nepalese have similar anthropometric characteristics with regard to facial height. However, arch length and palatal rugae characteristics vary between the two different ethnic groups.[14] Shetty DK et al. carried a comparison of palatal rugae patterns in Kodava and Malayalam speaking population of South India, and found a significant difference between Malayalam speaking and Kodavas for wavy and unification pattern. Significant difference between sexes for straight rugae pattern among Malayalam speaking was also seen. They concluded that the differences in rugae shape between the two populations may be attributed to genetic factors and recent shared ancestry has probably rendered their differences to moderate levels.[15] A study investigated the morphology and individuality of palatal rugae among Jordanians. The predominant types of palatal rugae were primary, anterior, and wavy. This study provides evidence that the individuality of palatal rugae is not limited to certain ethnicity or population; but is more likely, a worldwide phenomenon.[16]

In the present study, the palatal rugae dimensions have been analyzed using the three dimensions namely: A–B, A–C and B–C. The study showed that Karnataka boys had statistically significant, greater A–B, A–C and B-C dimensions compared to the Kerala boys. The Karnataka boys also had a greater A–C and B–C dimensions as compared with the Karnataka girls. Whereas, the Kerala girls had greater A–B, A–C and B–C dimensions as compared to the Kerala boys. The Kerala girls also had a greater A–C and B–C dimensions as compared with the Karnataka girls.

Summary and Conclusion

The present study showed a significant difference in the palatal rugae dimensions among the Karnataka and the Kerala boys, with the Karnataka boys having greater dimensions. The Kerala girls showed greater palatal rugae dimensions as compared to the Karnataka girls and Kerala boys. Since the study is first of its kind, many more studies in this regard could establish the reliability of using the palatal rugae dimensions in recognizing the different ethnic groups and in forensic identification.