An improved statistical method for the racial classification of man by means of palatal rugae

doi:10.1016/0003-9969(87)90028-8

Archives of Oral Biology

Volume 32, Issue 4, 1987, Pages 315-317

https://doi.org/10.1016/0003-9969(87)90028-8 Get rights and content

Abstract

A classification of human ruga pattern disclosed interracial differences between six population groups. The conventional statistical procedures of linear and quadratic discriminant function and nearest neighbour-point-method delivered overall correct classification figures of 49.2, 45.3 and 29.1 per cent respectively. The jackknife-classification matrix for the kernel-function method delivered an overall percentage correctly classified of 61.1 per cent with an individual group figure range correctly classified of 37–100 per cent. Although computationally elaborate, this technique has led to new insights into the data compared with parametric methods.

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La rugoscopie
Chir. dent. Fr.
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Variable kernel density estimation in discriminant analysis
D.J. Hand
E. Parzen
On estimation of a probability density function and mode
Ann. Math. Statist.
(1962)

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Cited by (28)

Patterns of palatal rugae in the adult Egyptian population
2016, Egyptian Journal of Forensic Sciences
Citation Excerpt :
Personal identification represents one of the major issues in forensic odontology since dental identification can be used as the sole method for postmortem identification due to the high resistance of dental tissue to adverse conditions such as fire, trauma and decomposition.1 Palatal rugae are irregular transverse ridges of the mucosa in the anterior third of the palate, radiating from the palatine raphae behind the incisive papillae.2 They are formed in the early intrauterine life during the period from 12th to 14th week and remain stable throughout the person’s life,3 not undergoing any changes, except for increase in the length as a process of normal growth.4
Rugoscopy refers to the study of palatal rugae in order to establish a personal identity. A significant association has been found between rugae forms and ethnicity which may represent a valuable finding in forensic medicine. The present study was aimed to analyze the pattern of palatal rugae in the adult Egyptian population and to examine for any sex differences. A total of 108 pre-orthodontic dental casts were enrolled in this study (54 males and 54 females) in the age group of 18–35 years. The pattern of palatal rugae regarding the number, size and shape of rugae was identified according to the classification made by Kapali et al. Primary rugae type showed the highest frequency while the most frequent shape was the wavy shape, followed by the straight shape. The predominant direction of palatal rugae was the forward direction. Also, the converging form of unification was found to be more prevalent than the diverging form. No significant difference was found between males and females except for the curved shape that was significantly greater among females. This study showed a specific rugae pattern in the studied adult Egyptian population when compared to other populations’ patterns that are reported in the literature.
Morphological study of the palatal rugae in western Indian population
2011, Journal of Forensic and Legal Medicine
Citation Excerpt :
Transverse palatine folds or palatal rugae (PR), are asymmetrical and irregular elevations of the mucosa located in the anterior third of the palate, made from the lateral membrane of the incisive papilla, arranged in transverse direction from palatine raphe located in the midsagittal plane. These formations have been used in medicolegal identification processes because their individual morphological characteristics are stable over time.1 Palatine rugae can be used as internal dental-cast reference points for quantification of tooth migration in cases of orthodontic treatment.2
The aim of this study was to identify and compare the different morphological rugae patterns in males and females of western Indian population, which may be an additional method of identification in cases of crimes or aircraft accidents. A total of 108 plaster casts, equally distributed between the sexes and belonging to similar age-group, were examined for different biometric characteristics of the palatal rugae including number, shape, length, direction and unification and their incidence recorded. Association between these rugae biometric characteristics and sex were tested using chi-square analysis and statistical descriptors were identified for each of these parameters using the SPSS 15.0. The study revealed a statistically significant difference in the total number of rugae between the two sexes (P = 0.000). The different types of rugae between the males and females were statistically compared. The female showed a highly significant difference in the sinuous (P = 0.002) and primary type (P = 0.000) while the male had a significant difference in the unification (P = 0.005). The predominant direction of the rugae was found to be forward relative to backward. It may be concluded that the rugae pattern can be an additional method of differentiation between the male and female in conjunction with the other methods such as visual, fingerprints, and dental characteristics in forensic sciences.
Differences in the palatal rugae shape in two populations of India
2007, Archives of Oral Biology
Citation Excerpt :
The drawback of step-wise discriminant function is that it may treat discrete variables as continuous. Therefore, a non-parametric discriminant procedure based on the principle of density estimation and using the kernel function method is preferred, utilising which a marked improvement in race identification was obtained.16 As an analogy, we can expect better differentiation of the two Indian populations from rugae shape using non-parametric discriminant functions.
The aim of the study was to investigate differences in the shape of the palatal rugae in two populations of India and develop discriminant function to identify the populations based on rugae shape.
Thirty plaster casts from each population group, equally distributed between the sexes and belonging to similar age-group, were examined for rugae shape (straight, wavy, curved, unification and circular) and their incidence recorded. Association between rugae shape and population as well as rugae shape and sex were tested using chi-square analysis and discriminant function developed using SPSS 10.0 statistical package.
Wavy and curved were the most prevalent rugae shape in both groups, followed by straight rugae. Unifications were few in number while circular rugae were not observed. Chi-square analysis for association between rugae shape and population groups showed significant differences in straight and curved forms. No significant sex differences were observed. Three rugae shapes – straight, wavy and curved – contributed to the discriminant function which enabled population identification with an accuracy of 70%.
Palatal rugae shape revealed significant differences between the two Indian populations and also confirmed previous reports of lack of sex dimorphism. Discriminant function analysis allowed moderate differentiation of the populations and it is inferred that discrete variables such as rugae shape are better suited for the purpose than continuous variables such as rugae length. However, these interpretations are precluded by the small sample size and further work on larger samples is required to validate the findings.
Establishing identity using cheiloscopy and palatoscopy
2007, Forensic Science International
Citation Excerpt :
In fact, these authors found it legitimate to base identification upon their comparison [45], allowing for human identification even in extreme circumstances [62]. As with lips, interracial differences in palatoscopy can also be established [51,63–66]. However, to reach definitive conclusions, more studies should be carried out.
Establishing a person's identity can be a very difficult process. Dental, fingerprint and DNA comparisons are probably the most common techniques used in this context, allowing fast and secure identification processes. However, since they cannot always be used, sometimes it is necessary to apply different and less known techniques. In this paper, the authors describe two unusual techniques: cheiloscopy and palatoscopy. It is known that due to their special features, both lip grooves and palatal rugae can be used successfully in human identification. This paper reviews the techniques of cheiloscopy and palatoscopy, and describes the different classifications and their advantages and limitations.
The pattern of palatal rugae in submucous cleft palates and isolated cleft palates
1994, British Journal of Plastic Surgery
The early diagnosis of submucous cleft palate is important. In children too young to tolerate nasendoscopy and videofluoroscopy the diagnosis depends on the clinical history and intraoral examination. We have studied the pattern of the hard palate rugae to investigate their possible diagnostic significance.
Maxillary dental casts were obtained from 16 patients with submucous cleft palate, 17 patients with isolated clefts of the secondary palate, and 10 non-cleft controls. The hard palate mucosa had a unique feature in 14 (87.5%) of the submucous cleft palates: one or more of the palate rugae curved towards the region of the bony notch in the posterior border of the hard palate. The 2 cases without this rugae pattern did not have a detectable bony notch. In 100% of the isolated cleft palate cases, one or more of the rugae curved towards the anterior end of the cleft. This feature was not seen in any of the non-cleft controls. We consider this rugae pattern to be an additional diagnostic feature of submucous cleft palate.
Clinical comparative study on the accuracy of palatal rugae in models obtained by different impression materials and intraoral scanning
2024, Clinical Oral Investigations

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Short communicationAn improved statistical method for the racial classification of man by means of palatal rugae

Abstract

La rugoscopie

Chir. dent. Fr.

Variable kernel density estimation in discriminant analysis

On estimation of a probability density function and mode

Ann. Math. Statist.

Short communication
An improved statistical method for the racial classification of man by means of palatal rugae