INTRODUCTION:

Forensic odontology is a specialty in dentistry which occupies a primary niche within the total spectrum of methods applied to medicolegal identification. Forensic odontology is a branch of dentistry which deals with the appropriate handling and examination of dental evidence and with the proper evaluation and presentation of dental findings in the interest of justice. [1][2]

Human characteristics such as fingerprints, DNA, and dental records are the most frequent identification techniques in forensic medicine. [3][4] In circumstances where it is difficult to identify a dead person by fingerprints or dental records, palatal rugae could be an alternative as they possess unique characteristics.

Therefore, for human identification, palatal rugae (as well as lip grooves) can be utilized successfully. [4]

Rugae or plica palatine are the anatomical folds located on the anterior palate behind the incisive papillae. Palatal rugae are formed from the lateral mem- brane of the incisive papilla in the third month of intra- uterine life and are present from birth in the anterior third of the palatal mucosa. [5][6] They show various configurations and are completely unique in every individual due to their design and structure, similar to fingerprints. [7]

Palatoscopy or palatal rugoscopy is the study of palatal rugae to establish a person's identity. This palatal rugoscopy was first proposed in 1932 by a Spanish investigator, Trobo Hermosa. [8] Palatal rugae is selected in forensics as it is relevant for human identification due to its internal position, stability, perennity [9] i.e., it persists throughout life. It is used in various fields such as sex determination, orthodontics and forensic odontology. [10]

The most challenging situations in forensic odontostomatology are mass disasters, where the forensic dentist is usually confronted with charred human remains or heavily decomposed or fragmented bodies; the rugae are in a position to resist trauma, high temperatures and decomposition. [11] It has been suggested that changes in the length of rugae with age result from underlying palatal growth. [6][12][13]However, the anterior rugae do not increase in length after 10 years of age. [14] Other qualitative characteristics such as shape, direction and unification remain stable throughout life. Despite the lack of an universal system of describing palatal rugae patterns qualitatively and quantitatively, their uniqueness to individuals has been recognized in forensic science as providing a potentially reliable source of identification. [15]

The objective of the study was to investigate the role of palatal rugae in personal identification.

MATERIALS AND METHODS:

This study was conducted at the Department of Oral Medicine and Radiology, Saveetha Dental College, Chennai. The study population consisted of 100 healthy subjects, 50 males and 50 females were randomly selected. All subjects were of Indian origin, aged 20 years and above. All subjects were healthy, free of congenital abnormalities and had no history of orthodontic treatment.

An irreversible hydrocolloid was used as an impression material on an appropriate perforated metal tray for maxillary arch for all subjects. Impressions were made and poured with type III dental stone. All casts were free of air bubbles and voids.

The palatal rugae patterns were highlighted using a graphite pencil on the cast and were analyzed following the classification of Martin dos Santos (1983). [4]

The classification indicates the following:

One Initial rugae: the most anterior rugae on the right side is represented by a capital letter Several complementary rugae: the other right rugae are represented by numbers One sub-initial rugae: the most anterior rugae on the left side is represented by a capital letter Several sub-complimentary rugae: the other left rugae are represented by numbers.

Table 1: Martin dos santos’ palatal rugae classification

Rugae type	Anterior position	Other positions
Point	P	0
Line	L	1
Curve	C	2
Angle	A	3
Circle	O	4
Sinuous	S	5
Bifurcated	B	6
Trifurcated	T	7
Interrupt	I	8
Anomaly	An	9

Figure 1: Palatal Rugae Forms

RESULTS:

The 100 dental stone casts examined showed different palatal rugae patterns. Each individual had an unique rugae pattern.

Curve form (34%) of rugae was the most common in both males and females whereas none of the casts exhibited the point form of rugae. Following the curve form, the sinuous form was common in males and line form was common in females.

Figure 2: Distribution of forms of palatal rugae patterns

Figure 3: Distribution of forms of palatal rugae patterns among males and females

DISCUSSION:

Determination of sex is the key analysis that forensic investigators perform in order to construct the biological profile of human remains. [16] Sex determination in forensic odontology can be done by either on morphological analysis or molecular analysis. Morphological variations linking to sex can be done on either hard or soft tissue. [17][18]

Routinely, teeth and bones are used for sex determination in forensics but in cases of their absence in identification, mucosal tissues are important since these structures provide interesting data for identification. The key factors which make palatal rugae one of the investigative tools in forensics are its internal position, stability, perennity etc. [9] Application of palatal rugae patterns to personal identification was first suggested by Allen in 1889. [19]

The present study was carried out to study the rugae pattern in an Indian population and to differentiate the rugae patterns between the males and females, which may be an additional method of differentiating the sexes.

In our present study, we did not find any single specific pattern alone in an individual but appeared as a mixture of varying forms. Curve forms predominated were most commonly observed which was consistent with the results of Pretty et al, Ohtani et al. and Indira et al. who also observed different palatal rugae patterns. [20][21][22]

We observed that curve form was most common which is consistent with the findings of the study by Indira et al. and Nayak et al. in an Indian population. It can therefore be concluded that certain rugae shapes are specific to particular population and may also have utility in population differentiation. [22][23]

In this study, on comparing rugae pattern of males and females, curve and sinuous forms were found to be higher in males while the curve and line forms were higher in females which was similar to the study by Indira et al. and Kumar A et al. [22][24]

In light of these results, we strongly suggest that palatal rugae pattern can be used in forensic investigation for antemortem and post-mortem identification. Further studies should be conducted on individuals of different populations. Also, a standard and uniform protocol needs to be put forth for the collection, recording and computerized analysis of the palatal rugae.

CONCLUSION:

Palatal rugae revealed a specific pattern among males and females. Its internal position, antemortem resistance, uniqueness, and regional variation provide a potentially reliable source of identification to the researchers.

However, these interpretations are precluded by the small sample size and further research work on larger samples and application of advanced statistical methods is required to validate its use in forensic application.

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Received on 21.07.2019 Modified on 25.08.2019

Research J. Pharm. and Tech 2020; 13(2):575-577.

DOI: 10.5958/0974-360X.2020.00108.0