Palatal rugoscopy as an adjunct for sex determination in forensic odontology (Sri Ganganagar population): A cross-sectional study of 100 subjects.

Introduction: Palatorugoscopy is the term used to study the rugae patterns. The word rugae came from the Greek word seam. Moreover, it relates the crisscrossing or joining or stitching of the parts of two biological structures during fetal differentiation. The aim of this study is to determine the gender difference in rugae pattern with regard to length, number, shape, unification and direction in the population of Sri Ganganagar, Rajasthan. Objective: The objective is to determine the gender difference in rugae pattern with regard to length, number, shape, unification and direction; to investigate the difference in division of rugae in males and females and to compare rugae pattern in males and females of different age group. Materials and
Methods: This study included 100 subjects, in which 50 were males (Group A) and other 50 were females (Group B). After the formation of primary cast, all quantitative as well as qualitative characteristics of palatal rugae patterns were recorded. Mainly, two classifications were used in this study, Thomas et al. and Kapali et al. Statistical Analysis: Student t-test was used, and "P" value of <0.05 was considered statistically significant.
Results: A statistically significant value was found in left-sided palatal rugae patterns depending upon the size, where we found that primary rugae were more in males. On comparing the angulation of palatal rugae patterns of left-sided rugae, a statistically significant value was found among the negative angulation which was higher in male subjects. Next, while comparing the angulation of palatal rugae of right side, we found a statistically significant value among zero (perpendicular rugae), which was more in male population. On comparing the unification of right-sided rugae patterns, we found that divergent rugae were more in male subjects.
Conclusion: Palatal rugae patterns act as individualistic, and are unique patterns, and are helpful in determining the human gender. Further, more studies are required on palatal rugae patterns used in forensics on large population scale. Copyright:

INTRODUCTION

According to the Federation Dentaire Internationale, forensic dentistry is the branch of dentistry which works for exact assessment and inspection of dental proofs, and helps in conservation and detection of records for proper fairness in decision.[1]

The study of palatal rugae for evaluating human specification and naming is defined as palatoscopy.[2] The word rugae came from the Greek word seam. Moreover, it relates the crisscrossing or stitching of the parts of two biological structures during fetal differentiation.[3] Design and placement of palatal rugae patterns are organized between the 12th and 14th weeks of intrauterine phase, and this alignment lasts for whole life unless the soft tissue decays afterward decease.[4]

Epithelial–mesenchymal interchange is the factor which controls and expands the dimensions of rugae patterns, and along with this, some molecules are also identified during growing.[5] Acids, chemicals, injuries, wounds, eruption and dropping of teeth or life-threatening conditions do not alter or affect the configuration of palatal rugae patterns.[6] Rugae are useful in recognition methods due to their simplicity, accuracy and cost-effectiveness.[7] Hence, with these features, palatal rugae patterns are one of the specific postmortem proofs.

The present study is conducted to determine the gender difference in rugae pattern with regard to length, number, shape, unification and direction in the population of Sri Ganganagar, Rajasthan.

MATERIALS AND METHODS

Candidates were selected from the Outpatient Department of Maharaja Ganga Singh Dental College and Research Centre, Sri Ganganagar, Rajasthan. This study included 100 subjects, in which 50 were males (Group A) and other 50 were females (Group B). Sample size was correctly distributed within the age group 30–70 years.

After the settlement of the patient on the dental chair, mixing of alginate impression material was carried out. Measured amount of powder and water was added into the bowl and mixed in the figure-of-eight motion up to 1 min. Quickly after mixing of alginate material, maxillary impression tray was filled with the material and instantly inserted into the patient's mouth. Impression tray was stationary and immobile during the setting of impression material. After taking maxillary impression, suddenly primary cast was made with the use of dental stone.

After the formation of primary cast, all quantitative as well as qualitative characteristics of palatal rugae patterns were recorded.

Mainly, two classifications were used in this study, Thomas et al. and Kapali et al.[8]

Parameters are as follows [Figure 1]:

Figure 1

Tracing palatal rugae

Length of palatal rugae was measured with the use of manual Vernier caliper (primary rugae, secondary rugae and fragmental rugae)

Unification: Meeting point of two different rugae patterns at the same place may be at starting or terminal point of rugae (convergent and divergent rugae)

Shape: Curved, wavy, straight and circular

Angulation or direction: Angle formed between the line joining starting and terminal portion of palatal rugae and it must be perpendicular to the median raphe (forwardly directed, backwardly directed and perpendicular rugae)

Number of palatal rugae was evaluated.

Statistical analysis

Findings were recorded, tabulated and subjected to statistical analysis.

Student's t-test was used. “P” value of < 0.05 was considered statistically significant.

RESULTS

In our study, we found statistically significant value in left-sided palatal rugae patterns depending upon the size, where we found the mean value of primary rugae size (length) in male participants to be higher (3.62 ± 0.67) as compared to female participants (3.1 ± 0.77) [Table 1]

Table 1

The comparison of size among male and female participants on the basis of primary, secondary and fragmentary (left-sided palatal rugae patterns)

Group	N	Mean±SD	T	P
Primary
Female	50	3.1±0.67	−3.560	0.001*
Male	50	3.62±0.77
Secondary
Female	50	0.24±0.47	1.131	0.261
Male	50	0.14±0.40
Fragmentary
Female	50	0.0±0.00	-	-
Male	50	0.0±0.00

*Statistically significant (P<0.05). n: Number of participants, SD: Standard deviation, t: Student t-test

On comparing the angulation of palatal rugae patterns of left-sided rugae, a statistically significant value was found among the negative angulation which was having higher mean value in male subjects (1.36 ± 1.17) than females (0.9 ± 0.83) [Table 2]

Table 2

Comparison of angulation among males and females on the basis of positive, negative and zero (left-sided palatal rugae patterns)

Group	N	Mean±SD	T	P
Positive
Female	50	1.42±0.97	0.090	0.928
Male	50	1.4±1.22
Negative
Female	50	0.9±0.83	−2.254	0.026*
Male	50	1.36±1.17
Zero
Female	50	1.14±1.03	0.623	0.535
Male	50	1.02±0.89

*Statistically significant. n: Number of participants, SD: Standard deviation, t: Student t-test

Next, while comparing the angulation of palatal rugae of right side, we found a statistically significant value with respect to zero angulation (perpendicular rugae), with mean value more in females (0.92 ± 0.82) than males (0.56 ± 0.61) [Table 3]

Table 3

Comparison of angulation among males and females on the basis of angulation (right-sided palatal rugae patterns)

	Group	N	Mean±SD	t	P
Positive	Female	50	1.08±0.87	−0.738	0.463
	Male	50	1.22±1.01
Negative	Female	50	1.6±1.17	−0.533	0.595
	Male	50	1.72±1.06
Zero	Female	50	0.92±0.82	2.471	0.015*
	Male	50	0.56±0.61

*Statistically significant. n: Number of participants, SD: Standard deviation, t: Student t-test

On comparing the unification of right-sided rugae patterns, we found divergent rugae of higher mean value in males (0.56 ± 0.64) than females (0.3 ± 0.46) with statistically significant value [Table 4]

Table 4

Comparison among the male and female participants on the basis of unification (right-sided palatal rugae patterns)

Group	n	Mean±SD	t	P
Convergent
Female	50	0.04±0.19795	0.581	0.563
Male	50	0.02±0.14142
Divergent
Female	50	0.3000±0.46291	−2.318	0.023*
Male	50	0.5600±0.64397

*Statistically significant. n: Number of participants, SD: Standard deviation, t: Student t-test

In addition, on comparing the variables between males and females in general (taking left- and right-sided palatal rugae simultaneously), we found statistically significant values for size (length) of primary rugae (mean value in males 3.57 ± 0.08 higher than females 3.32 ± 0.81) and size of secondary rugae (mean value in males 1.83 ± 1.98 higher than females 0.19 ± 0.44), shape (straight; mean value in females 0.36 ± 0.68 higher than males 0.20 ± 0.42) and divergent unification (mean value in males 0.49 ± 0.57 higher than females 0.29 ± 0.45) [Table 5].

Table 5

Comparison of variables among males and females

Variables	Groups	Mean±SD	t	Significant
Number	Female	3.5100±0.88186	−1.117	0.265
	Male	3.6400±0.75905
Size
Primary	Female	3.3200±0.81501	−2.348	0.020*
	Male	3.5700±0.68542
Secondary	Female	0.1900±0.44256	−8.102	0.000*
	Male	1.8367±1.98288
Fragmental	Female	0.0000±0.00000
	Male	0.0000±0.00000
Angulation
Positive	Female	1.4100±1.10184	0.699	0.485
	Male	1.3000±1.12367
Negative	Female	1.2500±1.07661	−1.856	0.065
	Male	1.5400±1.13191
Zero	Female	0.9500±0.84537	1.379	0.170
	Male	0.7900±0.79512
Shape
Curved	Female	1.7800±1.01085	0.215	0.830
	Male	1.7500±0.95743
Wavy	Female	1.0900±0.81767	−0.765	0.445
	Male	1.1800±0.84543
Straight	Female	0.3600±0.68931	1.974	0.050*
	Male	0.2000±0.42640
Circular	Female	0.0100±0.10000	−0.579	0.563
	Male	0.0200±0.14071
Unification
Convergent	Female	0.0300±0.17145	0.451	0.653
	Male	0.0200±0.14071
Divergent	Female	0.2900±0.45605	−2.719	0.007*
	Male	0.4900±0.57726

*Statistically significant. SD: Standard deviation, t: Student t-test

DISCUSSION

In human-made as well as in natural disasters (mass casualties), dental records are highly useful for human identification, as finger records are not precise in each condition. The philosophy behind this is that postmortem dental records can be compared with the same person's antemortem record for identification along with the use of models and photographic views. Various methods are available for the recognition of humans such as determination of gender, blood grouping, age estimation, weighting, dental records, dactyloscopy and anthropometry. A palatal rugae pattern study (palatorugoscopy) is one of them as palatal rugae patterns are extremely distinctive and isolated in each and every human being.[8]

These patterns do not undergo any positional, locational and functional change in complete lifespan of person. The utilization of patterns in forensic odontology is because of its cost-effective and convenient procedure for analysis, along with other profitable points of rugae.[9]

In our study, we examined and studied the rugae length, number, shape, size, unification and direction on both the sides (left and right) of midpalatal suture of both male and female groups. Many differences were present between both the genders.

On comparing the length of palatal rugae patterns on left side (primary, secondary and fragmentary) in both male and female groups, we noticed that in the male population, the length (primary rugae) (P = 0.001) was more as compared to female population. Furthermore, length primary rugae (P = 0.020) and secondary rugae (P = 0.000) were more in males than females when compared in general that is taking left- and right-sided palatal rugae simultaneously. This is in accordance with a study conducted by Balgi et al. in 2019.[10]

This may be attributed to the fact that the length of palatal rugae undergoes a change, when changes occur in palatal bone with the increasing age of individual.[11] Reason behind more primary rugae length in males than females was higher arch length in male subjects as compared to the females.[1112]

On comparing the angulation (positive, negative and zero) of rugae patterns between both male and female subjects of left side of midpalatal suture, we found that negative angulation (left sided) in males was higher than females (P = 0.026) which is in accordance with a study conducted by Pramanik et al. in 2019[13] and Ahmed and Hamid in 2015.[14]

In the early intrauterine life,formation and development of palatal rugae occurs at a localized region due to epithelial thickening. Afterward, in the connective tissue beneath the proliferated epithelium, gathering of collagen fibers as well fibroblasts occurs, which further leads into a definite orientation of palatal rugae. Unique orientation of palatal rugae occurs because of the movement of collagen fibers anteroposterior across the basement area of each rugae pattern. At last, it is believed that such changes occur under the influence of genes.[151617]

On comparing the angulation of palatal rugae between the males and females on the right side of palate, we found that while comparing among those with zero angulation (perpendicular rugae), the mean of female participants was found to be higher than males (P = 0.015). Similar findings were obtained by Shrestha et al. in 2017[11] and Pramanik et al. in 2019.[13]

Zero angulated rugae are those which have perpendicular directions. Moreover, this may be because, during the development of human embryo, the palatal rugae which are thick and leading occupy the large dimension of palatal structure. The inclination, orientation and direction of palatal rugae are established in intrauterine life by the accumulation of running fibers (collagen fibers) over the foundation of palatal rugae patterns in the direction of anteroposterior turns and in concentric loops. Moreover, in embryogenesis, several variations also occur because of genetical factors.[18]

On comparing the unification of rugae patterns among both genders (male and female) of right side, divergent unification was more in males than females (P = 0.023). Furthermore, divergent unification was found to be more in males than females when taking into consideration both right- and left-sided palatal rugae simultaneously. Similar results were obtained by Thabitha et al. in 2015,[8] Kalyani et al. in 2016,[19] Bharath et al. in 2011[20] and Dr. Nagrale et al. in 2021[21] in their study.

This may be attributed as, in the embryo of mice, it has been demonstrated that on the fibroblast growth factor (FGF) and Sonic hedgehog signaling, activator–inhibitor system is dependent, in turn which further results in systematic generation of palatal rugae patterns in the specified growth areas in the growing palate. In mice, the absence of palatal rugae occurs, if loss of role related with FGF-10 or FGF-2. On the other side, in humans, the morphology of palatal rugae patterns is more complex than mouse, and the foundational mechanisms are probably to be maintained at the level of molecular genetics.[22]

On comparing the shape of palatal rugae patterns between the males and females taking into consideration both right- and left-sided rugae simultaneously, straight-shaped rugae were found more in females than males (P = 0.050), curved and wavy rugae more in males (P < 0.05) which is in accordance with studies done by Nallamilli et al. in 2015,[23] Azab et al. in 2016[17] and Selvamani et al. 2015.[24] Discrepancy in shapes of palatal rugae with respect to gender differentiation may be precisely studied by considering larger sample size.

CONCLUSION

In our study, we found a statistically significant value in left-sided palatal rugae patterns depending upon the size, where we found that primary rugae were more in males. However, on comparing the angulation of palatal rugae patterns of left-sided rugae, a statistically significant value was found among the negative angulation which was higher in male subjects. Next, while comparing the angulation of palatal rugae of right side, we found a statistically significant value among zero (perpendicular rugae), which was more in male population. On comparing the unification of right-sided rugae patterns, we found that divergent rugae were more in male subjects. With these findings, we can conclude that palatal rugae patterns act as individualistic, and are unique patterns, and are helpful in determining the human gender.

Further, more studies are required on palatal rugae patterns used in forensics on large population scale.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.