Assessment of the Greater Palatine Foramen Position in an Indian Population

A Cone-Beam Computed Tomography Study

Abstract

Background: 

During minor dental surgical procedures, the greater palatine nerve block is commonly utilized to achieve anesthesia. The greater palatine nerve and arteries are transmitted through the greater palatine foramen (GPF). Furthermore, this region serves as a soft-tissue donor site. The goal of this research was to interpret the location of the GPF and its diameter in an Indian population by utilizing cone-beam computed tomography (CBCT).

Materials and Methods: 

The position of GPF relative to the maxillary molars was estimated by utilizing 120 CBCT scans. Furthermore, the GPF's diameter and distance between the mid-palatine suture and the alveolar ridge were also determined.

Results: 

Of the 120 GPFs examined, 102 were found to be in the third molar region. The GPF's distance from the mid-palatine suture and alveolar ridge was 14.01 ± 1.12 mm and 6.74 ± 1.95 mm, respectively. The mean anteroposterior diameter was 3.43 ± 0.3 mm. On considering the age group ≤45 years, the GPF's average distance from the mid-palatine suture (14.35 ± 1.10 mm) and alveolar ridge (7.87 ± 2.09 mm) was significantly higher than >45 years (P = 0.0329 and P < 0.0001, respectively). All the measurements were significantly higher in males.

Conclusion: 

The location of GPF is variable but more closely related to the third molar. Sound knowledge of the GPF anatomy is crucial for an effective nerve block and also for preventing complications.

INTRODUCTION

The greater palatine foramen (GPF) is an opening located posteriorly to the hard palate, which is produced by the connection between the greater palatine sulcus of the palatine bone and the maxillary bone.[¹] The greater palatine nerve and the descending palatine artery are transmitted to the palate through this foramen.[²] Furthermore, it provides innervation to the mucosal membrane, gums, and palatine glands situated on the roof of the mouth.[³] The greater palatine nerve block is frequently utilized to achieve anesthesia for surgeries including the maxillary molars, nasal region, and maxillary sinus.[⁴] The inability to accurately locate the GPF can lead to the failure of anesthesia[⁵] and also increase the possibility of accidental injury to the greater palatine nerve and vessels.[⁶]

Another clinical application is the mucogingival surgical procedures that require the harvest of a soft-tissue graft from the palate.[⁷⁸] By making an incision through the palatal mucosa, the graft is harvested from the area extending from the molar to the premolar region. The possibility of injuring the greater palatine artery while harvesting the graft from the palate has sparked widespread concern. Therefore, to reduce the risk of hemorrhages and anesthetic failure, a comprehensive study of the anatomical landmarks including the variations of the GPF is required.[⁷⁸⁹]

Unfortunately, the commonly described guidelines for locating the GPF, as being palatally to the second molar,[¹⁰] near the second molar and third molar,[¹¹] adjacent to the palatal suture's lateral border, etc.[¹²] are frequently inaccurate. Furthermore, several anatomical examinations on dry skulls have shown that GPF is located in the third molar region.[⁶⁹¹³] However, there is a wide variation in its reported prevalence ranging from 47% to as high as 92% showing a significant disparity in the results.[⁶¹⁰] A major limitation of these studies is that the gender is often not known and hence one cannot distinguish between the males and females making the applicability of the results questionable.[¹⁴¹⁵]

Recent advances in radiographic imaging, particularly cone-beam computed tomography (CBCT) and computed tomography (CT) grant a more precise evaluation of the anatomic structures.[⁵] Few studies have utilized CT and CBCT to evaluate the dimensions of GPF.[²⁴¹⁰] However, to the best of our knowledge, the studies utilizing CBCT to analyze the GPF in the Indian population are sparse. Hence, the goal of this research was to determine and to locate the GPF and its diameter in an Indian population using CBCT.

MATERIALS AND METHODS

Study sample

The research was conducted in the department of Periodontics and Implantology in our institute in the period of March 2020–September 2021. The study protocol got approval by the Institutional Ethics Committee and complied with the Helsinki Declaration of 1975 as revised in 2013. Overall, 120 CBCT scans from patients aged 20 to 60 years old were evaluated. These patients were advised CBCT imaging mostly for dental implant treatment planning, intrabony defects, and impacted third molar extractions. The study included high-quality CBCT images. The presence of three upper molars on both sides and individuals aged 20–60 years were the study's inclusion criteria. The images were excluded if there was a fracture in the upper jaw, missing posterior teeth, or any pathological lesions involving the upper jaw.

All images were analyzed by two examiners SR and SD. For assessing the intraexaminer variance, each examiner measured randomly selected 50 CBCT images twice at an interval of at least 1 month. All patients provided written informed consent for the images to be used in scientific research. The trial received its registration with the Clinical Trial Registry of India (Ref No: CTRI/2021/07/045729).

Image analysis by radiography

The CBCT (Orthophos® XG 3D/Ceph, Sirona Dental Systems GmbH, Germany, at kVp = 84 and mA = 16) scans were analyzed using commercially available CBCT software.

Assessment of the location of the greater palatine foramen

The location of GPF in relation to the maxillary molars was assessed using the axial reconstruction of the CBCT image. The foramen's position was determined by drawing five tangents parallel to the middle of and interproximally along the second and third maxillary molars, in the following manner [Figure 1a]:

Figure 1: assessment of GPF location in relation to maxillary molars on the axial reconstruction. (a) The primary axial reconstruction. (b) The axial section is used to determine the position. GPF = Greater palatine foramen

1. Presence of the GPF between the medial face and center of the second maxillary molar.
2. Presence of the GPF between the center and distal face of the second maxillary molar.
3. Presence of the GPF between the medial face and center of the third maxillary molar.
4. Presence of the GPF between the center and distal face of the maxillary third molar.
5. Presence of the GPF distally of the third molar.

The overlap of the previously drawn tangents with the GPF at a new depth of axial reconstruction suggesting the exact position of the foramen was noted and recorded [Figure 1b].

Distance of the greater palatine foramen from mid-palatine suture and alveolar ridge

The extent of GPF from the mid-palatine suture was measured on the axial reconstructions. A line was drawn perpendicular extending from the center of the GPF to the mid-palatine suture and the distance was measured [Figure 2]. For measuring the extent of the GPF to the alveolar ridge, axial reconstruction was used. In the depth of the maxillary molars, a tangent to the alveolar ridge was drawn [Figure 3a]. The distance present between the alveolar ridge and the medial wall of the GPF was measured by drawing a line perpendicular to this tangent in the depth of the GPF [Figure 3b].

Figure 2: assessment of the distance of GPF from the mid-palatine suture on axial reconstruction. GPF = Greater palatine foramen

Figure 3: assessment of the distance of GPF from the alveolar ridge on axial reconstruction. (a) The primary axial reconstruction. (b) The axial section is used to determine the distance from the alveolar ridge to the medial wall of GPF. GPF = Greater palatine foramen

Measurement of the greater palatine foramen's diameter

The mediolateral diameter of GPF was measured in the axial section [Figure 4].

Figure 4: assessment of the mediolateral diameter of the GPF on axial reconstruction. GPF = Greater palatine foramen

All the measurements were done using the measurement tools of the CBCT software.

Statistical analysis

All the measurements were continuous and reported in terms of mean and SD. The intra and interexaminer reproducibility determination was done using the Intraclass Correlation Coefficient (ICC). Statistical analysis was carried out by means of descriptive and inferential statistics using Chi-square test and Student's unpaired t-test. The SPSS version 20.0 (IBM Corp, Armonk, USA) was used and P < 0.05 was considered statistically significant.

RESULTS

This study evaluated a total of 120 CBCT scans (59 males and 58 females). Table 1 shows descriptive statistics for the study population's demographic characteristics. As evidenced by P > 0.05, the mean age of males and females, as well as the gender distribution, differed insignificantly. The intraexaminer reproducibility coefficient for the measurement of the different parameters was 0.97 (SR) and 0.95 (SD) demonstrating high measurement agreement between the two examiners. Furthermore, the interexaminer reproducibility coefficient found for the first set of measurements was 0.963, demonstrating excellent agreement between the two examiners regarding the measurements.

Table 1: Demographic characteristics of the individuals

The anatomic position of the GPF differed significantly throughout the group studied. The GPF was discovered to be most commonly positioned between the center and the medial face of the maxillary third molar in 57% of the total images, followed by 28% between the center and the distal face of the maxillary third molar. The occurrence of GPF was distal to the third molar in 4% of the instances and in the remaining 11% of the images, it was found to be located between the middle and the distal face of the second molar. No CBCT scan showed the presence of GPF between the middle and the center of the maxillary second molar. Out of the total 120 GPFs that were examined, 102 were identified to be associated with the maxillary third molar area.

The GPF was located at a mean distance of 14.01 ± 1.12 mm and 6.74 ± 1.95 mm, respectively, from the mid-palatine suture and the alveolar ridge. According to the results of the research, the mean mediolateral diameter of the GPF was 3.43 ± 0.33 mm. The correlation between the distance of GPF from the alveolar ridge and mid-palatine suture and its diameter with age and gender has been demonstrated in Table 2. The age group ≤45 years demonstrated the mean distances of the GPF from the mid-palatine suture and the alveolar ridge to be 14.35 ± 1.10 mm and 7.87 ± 2.09 mm, respectively, whereas it was 13.90 ± 1.14 mm and 5.68 ± 1.14 mm, respectively, in the age group >45 years and these differences were significant (P = 0.0329, P < 0.0001, respectively). Similarly, the mean diameter of the GPF was found to be significantly high in ≤45 years in comparison to those >45 years but the difference could not reach a statistical significance (P = 0.4318). When the mean distances of the GPF between the mid-palatine suture and the alveolar ridge, as well as its mean diameter, were compared between the two genders, the values were substantially higher in the males (P < 0.0001).

Table 2: Relationship of demographic parameters with the distance of greater palatine foramen from the alveolar ridge and mid-palatine suture and greater palatine foramen diameter

DISCUSSION

Considering the extensive use of the greater palatine nerve block in dentistry, it is necessary to have comprehensive information regarding the anatomy of the GPF and requires the founding of an exact reference point. The studies that have evaluated the position of this foramen show varied results.[¹⁷⁹¹⁶] Furthermore, the results seem to differ among the different ethnic races.[⁹¹⁰¹⁷]

This study investigated the anatomical location of the GPF relative to the maxillary molar teeth and showed the GPF to be most typically associated with the third molars in 85% of the instances. Only 4% were seen distal to the third molars; in 11% of the cases, GPF was found to be medially located to the third molar and none was located medial to the second molar. In a previous study involving the Brazilian population, the GPF was found to be associated with the third molars in 92% of the cases. In addition, no GPF was identified medial to the second molar.[¹⁰] These findings are very similar to our study. However, a study conducted on the dry skulls of the Nigerian population showed the presence of GPF medially to the third molars in 48% of the studied cases and contrary to the findings of our study, it demonstrated that 13% of the GPFs are present medial to the maxillary second molar.[¹] Yet another anatomic study in the Indian population demonstrated the GPF to be present opposite to the third molar in 74.6% of cases; in 24.2%, it was present between the third molar and the second molar; in 0.8% of cases, it was distal to the third molar and opposite to the second molar in 0.4% of the cases.[⁹] These findings are in accordance with those of our study. Majority of the studies in the literature report more than 70% of the GPFs are associated with the third molar region.[¹³] Our findings of a lesser GPF predilection distal to the third molar (4%) are comparable to the findings of most previous research, which were found to be 5%,[¹⁰] 2.9%,[¹] and 7%,[¹⁶] respectively.

In our study, the mid-palatine suture and alveolar ridge were used as reference landmarks to assess the GPF location. The distance of GPF from these landmarks can be used to ascertain its position precisely before the greater palatine nerve block and plan the incision for harvesting the soft-tissue graft from the palate. This research demonstrated the mean distance of the GPF from the midline to be 14.01 ± 1.12 mm which is in accordance with several other studies.[¹⁸¹⁹] However, a few studies have reported comparatively lesser distances.[¹⁴²⁰] When the alveolar ridge was used as a landmark for measuring the distance of the GPF, it was found to be 6.74 ± 1.95 mm which is consistent with the findings of Ikuta et al.[¹⁰] who reported the mean distance of 8 mm from the GPF to Alveolar ridge (AR).

The GPF's mean diameter was found to be 3.43 ± 0.33 mm which is consistent with earlier research.[²¹²²] A systematic review of the morphometric analysis of the greater palatine canal reported the GPF diameter to be in the range of 4.5–5.3 mm which further supports the results of our study.[¹⁴] However, a study conducted on a Lebanese population has demonstrated a higher diameter of the GPF.[¹⁷]

Our findings demonstrated an inverse relationship of age with the distance of GPF from the Mid-palatine suture (MMP) and the Alveolar ridge as well as the diameter suggesting a greater diameter and distance of the GPF from the MMP and AR in younger individuals and vice versa. This finding can be justified by the fact that the bone mass decreases with age and there is progressive atrophy of the maxilla, thereby bringing about numerous changes in its structure and construction.[²³] Although the diameter of the GPF could not reach statistical significance when compared between the two age groups, the reason could be measurement error or an inadequate number of cases in the two age subgroups.

Furthermore, the data of this study revealed a significant sexual dimorphism with significantly greater morphometric values of the GPF in males as compared to females and can be supported by the fact that there is enormous variability in the size and shape of the craniofacial complex between the genders.[²⁴²⁵²⁶] The size of the skull is relatively larger in males as compared to females.[²⁴] This finding is in accordance with the previous reports that have shown smaller dimensions of GPF in females.[^3141527]

The majority of research on the location of the GPF has been conducted on dry skulls with finite information about the patient's age, sex, or ethnicity. This study used CBCT which provided additional information on age, gender, and ethnicity. Since CBCT is gaining increased popularity, images are more readily available and a larger sample can be studied. Furthermore, it provides subjects with specific, predetermined characteristics and allows precise measurements. Since it is crucial to find the most precise position of the GPF for several maxillary surgical procedures, the observations made in this research will be beneficial to clinicians. In the absence of the maxillary third molar, the mid-palatine suture and the alveolar ridge can be used as a reference to locate the GPF. Therefore, it is quite clear that a combination of the above measurements can help to trace the GPF accurately.

However, further research is needed to substantiate these findings, and future studies involving a larger sample are required to determine variations in the length and opening of the greater palatine canal.

CONCLUSION

The findings of this investigation show that the GPF was commonly associated with the maxillary third molar. In addition, in the absence of a third molar or in edentulous patients, the mid-palatine suture and the alveolar ridge can be used as anatomic references to determine the position of the GPF. The diameter and the extent of the GPF from these landmarks are influenced by age and are greater in younger individuals and subsequently reduce. There are significant differences in these dimensions between the males and females with higher values reported in the males.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.