The greater palatine foramen (GPF) serves as a pathway for the greater palatine nerve and larger palatine vessels. The greater palatine foramen is a significant anatomical feature that holds importance for dentists, maxillofacial surgeons, and plastic surgeons. The foramen is important because it serves as the entry point for the palatine canal, allowing access to the pterygopalatine ganglion [1]. Minor oral operations, periodontics, and general dentistry commonly employ the technique of blocking the greater palatine nerve, which provides sensory innervation to the posterior region of the hard palate through the greater palatine foramen (GPF). Moreover, the GPF region functions as a source of soft tissue grafts [2]. Hard palate grafting is a widely used and effective technique in oculoplasty operations for reconstructing the eyelid and socket. It is mostly the larger palatine vessels that supply blood to the mucoperiosteum of the hard palate. These vessels are a branch of the descending palatine artery that comes from the maxillary artery. These arteries emerge via the greater palatine foramen [3, 4]. As a result, it is very important to fully comprehend the greater palatine foramen (GPF) and its possible deviations when taking out oral mucoperiosteal grafts for reconstructive procedures involving the urethra and lips. To achieve deep anesthesia, it is necessary to accurately identify the precise anatomical position of the GPF for nerve block. Researchers hold different opinions regarding the precise location of the greater palatine foramen. Some suggest that it is situated near the lateral border of the hard palate [5], while others argue that it is positioned opposite the last molar [6], in relation to the second molar [7], or the third molar [2, 8, 9]. There are also suggestions that the foramen can be located anywhere between the maxillary second and third molars [10, 11]. However, additional landmarks are necessary for patients who still have an unerupted third molar. For these patients, measuring the distance from other prominent bony structures such as the mid-maxillary suture and the posterior border of the hard palate can be beneficial. This study aims to investigate the anatomical variations of the greater palatine foramen in adult skulls of the North Indian population and to assess its clinical significance, particularly concerning maxillofacial surgical procedures and dental interventions.

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 Jannayak Karpoori Thakur Medical College and Hospital, Madhepura, Bihar, and also from different medical colleges in the Bihar state of India, that belong to the North Indian population. 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, senile skulls with alveolar bone resorption, and juvenile skulls.

The following parameters were studied:

1. Non-Metric Parameters:

• Shape of the Graeter Palatine Foramen (GPF): It was recorded as oval, round, or irregular.
• Location of the Graeter Palatine Foramen (GPF): In reference to maxillary molar teeth.
• Direction of the opening of Graeter Palatine Foramen (GPF) on the palate: To determine the direction of the opening of the foramen on the palate, a needle was placed into the Greater Palatine Foramen (GPF). The directions were documented as anteromedial, anterior, and anterolateral.
• Lesser Palatine Foramen (LPF): The presence and number of the lesser palatine foramen (LPF) were also observed and recorded.

    B. Non-Metric Parameters:

• The perpendicular distance from the medial wall of the Greater Palatine Foramen (GPF) to the midline maxillary suture (MMS).
• The distance from the back wall of the GPF to the back edge of the hard palate (PBHP).

Figure 1: Showing the distance between the greater palatine foramen and midline maxillary suture.

Figure 2: Showing the distance between the greater palatine foramen and the posterior border of the hard palate.

The measurements were conducted bilaterally and directly on the dry skulls using a digital Vernier caliper with a precision of 0.1 mm. The measurements were meticulously conducted by a sole observer to eliminate any potential inter-observer discrepancies.

Statistical Analysis:

The metric parameters recorded on both sides were subjected to statistical analysis using the Statistical Package for Social Sciences (SPSS, version 24.0) and Excel 2019. A Student's t-test was conducted. The mean and standard deviation were computed for the ranges of each parameter. A p-value was calculated to evaluate the statistical significance of the observations.

The shape of the greater palatine foramen was oval in the anteroposterior direction in 72% of cases, round in 21%, and irregular in 7% [Table 1]. In the irregular cases, there was a lingula-like projection, similar to what is seen in the mandibular foramen, extending from the postero-lateral border of the greater palatine foramen. Regarding its relation to the maxillary molars, the greater palatine foramen was located opposite the second maxillary molar in 16% of cases, between the second and third molars in 10% of cases, and opposite the third molar in 74% of cases. This distribution was consistent on both sides [Table 2]. The opening of the greater palatine foramen on the palate was directed anteromedially in 70% of cases, anteriorly in 19%, and anterolaterally in 11% [Table 3]. The lesser palatine foramen was present in all skulls except three, which lacked it on the left side. A single lesser palatine foramen was seen in 43% of cases, double foramina in 38%, and three foramina in 16% of skulls [Table 4].

Table 1: Showing the incidence of the different shapes of the greater palatine foramen (GPF)

Table 2: Showing the incidence of the different positions of the greater palatine foramen (GPF) in reference to the maxillary molar 

Table 3: Showing the direction of the opening of the greater palatine foramen (GPF) onto the hard palate

Table 4: Showing the presence and absence of the lesser palatine foramen (LPF) in the hard palate

The mean distance of greater palatine foramen (GPF) to midline maxillary suture (MMS) was 12.99 mm with a standard deviation of 1.54 on the right side and 13.11 mm with a standard deviation of 1.18 on the left side. The mean distance of greater palatine foramen to the posterior border of the hard palate (PBHP) was 2.97 mm with a standard deviation of 1.12 on the right side and 3.02 mm on the left side with a standard deviation of 1.08. On applying the student t-test  no significant difference was observed in the values of distance from greater palatine foramen (GPF) to Midline maxillary suture (MMS)  and posterior border of the hard palate  on the right and left side as p>0.05  [Table 5]

Table 5: Showing the different morphometric observations of the greater palatine foramen

The landmarks used in the present study to locate the GPF can be readily reached in a patient. The study found that the shape of the GPF was oval and elongated in the anteroposterior direction in 72% of instances, round in 21% of cases, and irregular in 7% of cases. A lingular projection was observed arising from the postero-lateral boundary in the irregular foramina, accounting for 7% of the total. The existence of these protrusions could potentially cause blockage and hinder the needle's flow during drug injection. A slender and skeletal protrusion, originating from the back edge, has previously been documented [9]. There has been a divergent opinion regarding the positioning of the GPF in reference to the molar teeth. The study found that the most common placement of the greater palatine foramen was between the second and third molars [12]. Similar findings were seen in studies conducted on Chinese skulls [13]. The predominant position of the maxillary third molar was documented in East Indian, Negroid, Nigerian, Iraqi, Indian, Brazilian, and Kenyan skulls [14-21]. In this study, it was found that 76% of the detected larger palatine foramen were positioned opposite the 3rd molar tooth. This finding is consistent with previous investigations, particularly those conducted on Indian skulls. It is crucial to consider the orientation of the greater palatine canal while inserting a probe into the greater palatine foramen to administer injections. In 70 percent of cases, the opening of the larger palatine foramen on both sides of the palate was directed anteromedially. In 19% of cases, it was directed anteriorly, while in 11% of cases, it was directed anterolaterally. Prior studies [4,18,21] have also observed that it is predominantly directed anteromedially. According to Wang et al. [13], a study on Chinese skulls revealed that the opening was oriented anteriorly in 90.5% of the skulls, whereas it was oriented vertically in 9.5% of the skulls. This variance could potentially account for the sporadic challenges found when trying to put the needle's tip into the GPF and pterygopalatine canal [22]. Racial disparities may account for the discrepancy in occurrence. The number of minor palatine foramen ranged from one to three, or perhaps none, in three skulls on the left side. Prior research has indicated that between two and five lesser palatine foramina (LPF) were found in 40% of the examined skulls [21]. Additionally, one LPF was seen in 62.5% of the skulls [23], while no LPF was present in 4% of the skulls [18]. If there are no minor palatine foramina, it is suggested that the lesser palatine nerve and arteries may also emerge from the greater palatine foramen [18]. The study found that the average distance between the greater palatine foramen and the palatine suture is 12.99 mm on the right side and 13.11 mm on the left side. The results are lower compared to those obtained by other researchers who conducted studies in China [13], Nigeria [15], and Iraq [18], where they found the measurements to be between 15 mm and 16 mm. Nevertheless, research conducted on South Indian skulls [15,19] revealed that the average measurement was approximately 14.6 mm, which is smaller than the measurements observed in Chinese and Nigerian skulls. The variability in the position of the foramen may be attributed to the formation of sutures between the maxilla and the palatine bone. The anteroposterior dimension of the palate expands when the posterior teeth emerge [22]. The current investigation was carried out using skulls of North Indian descent. Hence, the disparity can be ascribed to racial and ethnic variables. Nevertheless, all investigations have successfully shown symmetry between the right and left sides. No statistically significant difference was observed in the distance between the greater palatine foramen (GPF) and the posterior border of the hard palate (PBHP) on the right and left sides, with a p-value greater than 0.05. This conclusion is consistent with the results of previous researchers [15,19-20], who reported a range of 3.39 to 3.58 mm. Nevertheless, all research confirmed the presence of symmetry between the right and left sides. Therefore, it is clear from previous and current research that there are ethnic differences in the size and shape of the greater palatine foramen. Additionally, it is worth noting that the bilateral symmetry of the greater palatine foramen on both sides of each skull is particularly noteworthy [4]. Considering the significant significance of the precise location of the larger palatine foramen, the findings of this study will aid in characterizing variations in the position of the greater palatine foramen. In addition to administering anaesthesia during dental surgeries, understanding the location of the greater palatine foramen is crucial for determining the appropriate area of the palate from which to harvest sub-epithelial connective tissue grafts (SCTG) for palatal mucosa grafting. The size of the graft that can be obtained is determined by the position of the greater palatine neurovascular bundle. As the study only focused on adult skulls and ignored senile and juvenile skulls, the applicability of these findings in children, such as after primary cleft palate surgery, is restricted. Further research is needed to investigate this in the future.

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 study concluded that the third molar, when present, can serve as a reliable landmark for localizing the greater palatine foramen (GPF) for nerve block anesthesia during maxillary and reconstructive surgeries. However, due to potential periodontal disease or impaction, the third molar may not be present in all patients. In such cases, the mean distance of the GPF from the midline maxillary suture and the posterior border of the hard palate can be used as reliable metrics. The GPF exhibits bilateral symmetry and is usually directed anteromedially in the North Indian population. This study also aids in localizing the greater palatine artery during palatal graft harvesting, emphasizing the need for caution to avoid damaging the GPF neurovascular bundle around the third molar region.

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