The hard palate, an essential part of the skull, is formed by the horizontal plates of the palatine bone, the pre-maxilla, and the palatine processes of the maxilla. It acts as a barrier between the nasal cavity above and the oral cavity below, featuring an arched shape that varies in depth and width, being widest in the molar area [1]. The larger palatine foramen and the smaller palatine foramina are found in the back portion of the hard palate [2]. People commonly acknowledge the significance of morphometry and palate morphology in forensic dentistry. The hard palate is a reliable structure for identifying people in cases where the skull has been destroyed or decomposed because of its position inside the oral cavity, making it unlikely to be damaged after trauma [3]. Skull measurements play a vital role in forensic and anthropological studies for identifying age, size, and ethnic background [3, 4]. An awareness of the normal anatomical features of the hard palate is necessary for procedures such as nasogastric intubation, nasal pharyngoscopy, and associated equipment [5]. Palatal measurements are essential for planning treatments for orthodontic issues, orthognathic surgeries, maxillary dental implants, and procedures like cleft palate surgery [6]. Precise measurements of the hard palate metric are especially useful for prosthetic restoration and denture fabrication [7-9]. Despite previous studies on the hard palate [10–14], our region has not adequately researched the minor palatine foramina and its link to surrounding landmarks. The information gathered from this study can serve as a baseline for future anthropometrics, dentistry, forensic sciences, and anatomical studies. This study aimed to measure the hard palate's morphometric characteristics in dried human cranium bones from the North Indian population.

This cross-sectional study was conducted on fifty dry adult skulls of unidentified gender. These human-dried skull bones were obtained from the Department of Anatomy of Nalanda Medical College, Patna Bihar, and also from different medical colleges in the Bihar state of India.

The study included only adult skulls that were fully complete and suitable for detailed observation, with an intact base of the skull, especially in the front and middle areas. This study excluded skulls with major deformities of the hard palate, severe damage, disease-related fractures, broken parts, or healed fractures.

Figure 1: Hard palate displaying key landmarks for measurement.

A digital Vernier caliper with 0.01 mm precision was used for all measurements. The hard palate's morphometry was measured as follows:

1. Hard palate length: The palatine length is measured as the distance from the orale at the front to the posterior nasal spine at the back (from point F to G in Figure 1). The orale is the point situated at the front end of the incisive suture, between the sockets of the two central maxillary incisors.
2. Hard palate breadth: The separation between the inner borders of the upper second molar sockets, as shown in Figure 1 from point K to L.
3. Hard palate height: The distance between the endomolaria and the palate.
4. The Palatine Index (PI): We classified the PI using the techniques developed by Hassanali and Mwaniki [15]. The percentage ratio of palatine width to palatine length can be calculated using the following formula:

Palatine Index (PI) = (Breadth/Length) x 100.

According to the Palatine Index (PI) measurements, palates can be categorized as leptostaphyline, mesostaphyline, or brachystaphyline.

• Type 1: A narrow palate with an index of approximately 79.9% is classified as the Leptostaphyline (L) type.
• Type 2: Mesostaphyline (M): Index 80–84.9%; intermediate palate.
• Type 3: Brachystaphyline (B): Index ≥85%; broad palate.

100. Palatine height index (PHI): We computed the palatal height index using the following formula: Palatine height index (PHI) = Palatal height/Breadth X 100.

Based on this calculation, the hard palates were classified into three types [15]:

• Type 1: Chemostaphyline, characterized by a low palate with an index of ≤27.9%.
• Type 2: Orthostaphyline, characterized by an intermediate palate with an index ranging from 28% to 39.9%.
• Type 3: Hypsistaphyline, characterized by a high or deep palate with an index of ≥40%.

One observer took all the measurements to prevent inter-observer bias. The measurements and information gathered will help to explain the hard palate's morphometry. Studies in the fields of forensics, anatomy, dentistry, and anthropometry can utilize these data.

Statistical Analysis: We assessed the collected data using the Statistical Package for Social Sciences (SPSS, version 24.0) and Excel 2019. We determined the metric parameters using the mean, standard deviation, and range.

In the current study, the average palatine length, width, and height were 45.95 ± 4.05 mm, 32.51 ± 2.83 mm, and 10.93 ± 2.32 mm, respectively. The mean values for the palatine index and the palatine height index were 70.78 ± 7.66 mm and 33.88 ± 7.68 mm, respectively. According to the palatine index, the most common type of hard palate was leptostaphyline (88%), followed by mesostaphyline (8%), with brachystaphyline (4%) being the least frequent. In terms of the palatine height index, orthostaphyline (54%) was the most frequent, followed by chemostaphyline (26%), with hypsistaphyline (20%) being the least common [Table and Figures 1, 2, and 3].

Table 1: Showing different metric parameters and indices of the hard palate

Figure 1: Showing comparison between the mean of different parameters of the hard palate

Table 2: Showing the classification of the hard palate according to the palatine index

Figure 2: Showing the prevalence of different types of the hard palate according to palatine index

Table 3: Showing the classification of the hard palate according to the palatine height index

Figure 3: Showing the prevalence of different types of the hard palate according to palatine height index

In this work, we obtained and examined morphometric characteristics crucial for identifying the race of the human skull. They are also helpful for maxillary nerve block in maxillo-facial surgeries, orthodontic procedures, and surgical correction of cleft palates. According to earlier research, mouth-breathing children had a narrower hard palate than nose-breathing children. In children whose mouths breathe often, there was also an increase in the depth of the hard palate in the canine teeth. As a result, a quantitative evaluation of the dimensions of the hard palate would aid in the detection of morphological alterations [12]. The study found that the mean length of the hard palate was 45.95 ± 4.05 mm. The results of this investigation were in strong agreement with the findings of previous studies conducted by Kaur A. et al. (46.16 mm) [16], D'Souza AS et al. (49.13 mm) [10], Jotania B. et al. (49.73 mm) [11], and Rao MJ et al. (49.87 mm) [12]. The investigation revealed that the mean palatal breadth measured 32.51 ± 2.83 mm. The measurement was smaller than the measurements published by D'Souza AS et al. (40.4 mm) [10], Jotania B et al. (37.75 mm) [11], Shalaby SA et al. (38 mm) [13], and Sarilita E et al. (38.68 mm) [14]. However, it was similar to the measurements reported by Kaur A et al. (33.01 mm) [16] and Rao MJ et al. (34.42 mm) [12].

In our investigation, the average height of the palate was found to be 10.93 ± 2.32 mm. This measurement is consistent with the findings of previous studies conducted by Sarilita E. et al. (11.8 mm) [14], Kaur A. et al. (11.06 mm) [16], and Shalaby SA et al. (11.5 mm) [13]. This study's palatal classification classified 88% of the skulls examined as leptostaphyline, 8% as mesostaphyline, and 4% as brachystaphyline. The results of this study did not align with the findings of D'Souza AS et al. (37.5% leptostaphyline) [10], Jotania B et al. (70% leptostaphyline) [11], and Rao MJ et al. (95% leptostaphyline) [12]. Nevertheless, their findings were in line with the research conducted by Kaur A et al. (83% leptostaphyline) [16] and Sarilita E et al. (84% leptostaphyline) [14]. In the present study, the analysis categorized the palatal height as orthostaphyline in 54% of instances, hypsistaphyline in 20% of cases, and chemostaphyline in 26% of cases. While the outcomes of Sarilita E et al. [14] and D'Souza AS et al. [10] were not consistent with the findings of the present investigation, they were most similar to the observations obtained by Shalaby SA et al. [13] and Kaur A et al. [16]. In their study, Gangrade et al. [17] discovered that the average palatal length in male skulls was 54.59 mm, while in female skulls it was 52.44 mm. The palatal breadth in male and female skulls was measured to be 38.49 and 35.89 mm, respectively. Statistical analysis revealed that male skulls had considerably greater palatal length and breadth compared to female skulls. Sexual dimorphism is observed in both the mean palate length and breadth. This discovery aligns with the findings of Bigoni et al. [18], who observed notable disparities between sexes in the palate area. Sumati et al. [19] found that among the five hard palate factors, the size of the palate was the most accurate indicator of sex. Using these variables, they were able to properly classify the gender of individuals in 70% of their sample from the North Indian population. Comprehending the palatine index is essential as research has demonstrated a connection between a high and narrow palate and several medical conditions, such as Apert syndrome, Turner's syndrome, Marfan syndrome, and Franceschetti-Collins syndrome. Shalaby et al. conducted a statistical analysis using logistic regression to examine the five characteristics of the hard palate. They found that external palate breadth was the most effective determinant of sex [13]. According to Gangrade et al. [17], the width of the external palate alone was sufficient to accurately categorize 66.7% of the sample size. Furthermore, the palate's morphometric properties have practical applications in forensic dentistry. Because the oral cavity provides protection, the palatal and dental structures are less susceptible to heat-related stresses and damage. This enables the identification of particular persons and the estimation of their biological sex, even in cases where there has been a significant loss of bodily tissue [20,21].

Study limitations: The age and sex of the skull bones were not examined because the information was not accessible. Additionally, as the results are unique to the North Indian population, more research across various ethnic groups and geographic regions is necessary to generalize the study's findings.

The findings from this study are valuable for medical sciences, dentistry, and anthropometry. A thorough understanding of the hard palate's anatomy is crucial for various applications, such as performing specific surgical procedures on the hard and soft palate, conducting anthropological research, and creating complete maxillary dentures for patients without teeth. This knowledge also aids in the ethnic and racial classification of skulls. Oral and maxillofacial surgeons can benefit from knowing the palatal index when performing surgeries to correct cleft palates or lips.

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