Gender-Specific Variations in Greater Palatine Foramen Anatomy: Insights from CBCT Scans in the North Cyprus Population

Introduction

The palatine bone’s horizontal plate and the maxilla’s palatine process form the hard palate. The greater palatine canal (GPC) is an anatomical passageway in the posterior part of the hard palate that houses the greater and lesser palatine nerves and palatine artery extending into the hard palate. It is a significant landmark of the hard palate because it contains crucial vascular and nerve fibers and acts as an anatomical bridge linking the oral cavity with the pterygopalatine fossa (PF) [1]. Within the PF are the maxillary artery and its branches, venous vessels corresponding veins accompany the arteries and drain into the pterygoid plexus of veins, the maxillary nerve and branches, and the pterygopalatine ganglion. The maxillary nerve is a pure sensory nerve that supplies the maxillary teeth, the soft tissues of the hard and soft palate, the nose, the upper lip, the maxillary sinus, and several surrounding structures [2]. The sphenopalatine nerve, a significant branch of the maxillary nerve, connects with the Meckel sphenopalatine ganglion via small nerve rami, giving rise to various terminal branches such as the upper nasal nerves, nasopalatine nerve, and the anterior, middle, and posterior palatine nerves [1,3]. Initially, the palatine nerves travel together from the pterygopalatine fossa via the greater palatine canal. Within the lower portion of the canal, the lesser palatine nerves (LPNs) diverge from the greater palatine nerve (GPN) and traverse their canal within the pyramidal process. Exiting through the lesser palatine foramina (LPF), the LPNs supply innervation to the soft palate, palatine tonsil, and uvula [4]. The greater palatine neurovascular bundle exits in the vault of the hard palate via the greater palatine foramen (GPF), supplying the palatine mucosa and the periodontal tissue of the posterior teeth and extends forward in a groove nearly to the incisor teeth where it connects with branches of the nasopalatine bundle [5,6].

Studies on dry skulls have shown that the GPF is generally located around the second and third molars [6]. Typically, clinicians use teeth as indirect guides to find the GPF, often referencing the palatal side of the second molar.

The greater palatine artery (GPA) begins its journey in the pterygopalatine fossa, branching off from the descending palatine artery. It traverses the GPC before exiting the fossa. Initially widest at its emergence from the fossa, the diameter of the GPA diminishes progressively as it moves towards the incisive foramen. The majority of its branches are distributed in the premolar region, with a preference towards the alveolar aspect rather than the hard palate [6].

GPA is also a critical anatomical structure in the practices of plastic surgeons, ear, nose, and throat doctors specialists (ENT), and dentists. For example, GPA damage can occur in downward fractures of the maxilla or other surgical procedures such as osteotomy of the medial and lateral maxillary sinus walls, pterygomaxillary separation, endoscopic medial maxillectomy, and pterygopalatine fossa infiltration [7].

The GPA’s location and the palatal mucosa’s thickness determine the size of subepithelial connective tissue grafts. GPA damage may cause prolonged intraoperative bleeding and postoperative wound healing complications due to impaired blood flow [8,9]. Clinicians choose to increase the effectiveness and safety of these procedures by optimally determining the position, angle, and length of the needle used for intervention according to the location of GPF in the oral cavity [9,10].

The GPF’s location can vary, but it is generally identifiable by palpating the palate opposite the third maxillary molar teeth. Viveka et al [11] revealed that using multiple anatomical reference points, such as the incisive foramen, the midline maxillary suture, and the second and third maxillary molars, simplifies the identification of the GPF. Proper identification of the GPF allows for the visualization of arterial pulsations, confirming the location of the GPA [10,12].

Blocking the maxillary nerve is essential for various clinical and surgical procedures involving maxillary injuries and fractures, particularly in the maxillary sinus, nasal region, posterior maxillary teeth, or palatine mucosa [13,14]. In maxillofacial surgery, it is routine to use local anesthesia by blocking the maxillary division of the trigeminal nerve or its branches. This is typically done via the greater palatine foramen, allowing access to the palatine canal that houses the palatine nerves and vessels [15]. GPN block is one of the local anesthesia methods used since it was first described in 1927 [16]. GPN block is the most frequently used technique for maxillary nerve blocks. It is applied in all palatal procedures requiring substantial palatal anesthesia, such as periodontal and maxillary surgery, including maxillary sinus interventions, abscess drainage, and oral surgeries. Potential complications include proptosis, narrowing of the ophthalmic arteries, spread of infection to the skull, intravascular injection, nasopharynx penetration, and nerve tissue damage [17,18]. Therefore, it is vital to thoroughly understand the location, anatomy, and average length of the GPC to avoid these complications.

In procedures such as surgery for maxillary bone fractures, maxillary sinus surgery, palatal tumor resection, palatal abscess incision, and periodontal surgery, which require frequent use of posterior palatal block anesthesia, accurate determination of the anatomical location of the GPF is of critical importance for ENT specialists, plastic surgeons, and dentists [19].

Previous studies have indicated that the GPF’s location can vary based on age, sex, and racial differences [20]. A meta-analysis of 23 studies by Tomaszewska et al found that the GPF is most commonly situated opposite the maxillary third molar [21]. The other critical landmarks for determining the GPF’s position are the mid-maxillary suture (MMS), posterior nasal spine (PNS), and alveolar crest.

Cone beam computed tomography (CBCT) images consist of reformatted slices of bone, avoiding issues of magnification and overlapping of adjacent structures. As a result, they produce much clearer images that accurately represent bony landmarks [22].

Therefore, this study aimed to evaluate the anatomical position of the greater palatine foramen in 93 women and 67 men at a single center in Cyprus using cone beam computed tomography.

Material and Methods

STUDY DESIGN AND SAMPLE SELECTION:

The study obtained authorization from the Research and Ethics Committee (EKK23-24/005/11), aligning with the principles outlined in the 1964 Helsinki Declaration, subsequent amendments, or similar ethical guidelines. It also adhered to the moral standards set by the institutional and national research committees regarding all human participant procedures. Additionally, informed consent was secured from all individuals participating in the study.

A retrospective analysis was conducted on 160 randomly chosen CBCT scans sourced from the records of a private dental imaging center in Nicosia. Before this study, CBCT scans had been utilized for various purposes, including implant surgeries, orthodontic assessments, and evaluation of impacted teeth.

The study involved analyzing CBCT records from individuals aged 18 years and above. Only artifact-free images with excellent quality, providing a clear visualization of the maxilla and allowing full observation of both maxillofacial planes, were considered for inclusion. Patients with severe malocclusion, craniofacial anomalies, cleft lip-palate, history of orthognathic surgery, or maxillofacial trauma were excluded from the study.

CBCT IMAGE ACQUISITION:

The scans were performed using CBCT radiography with the Newtom GO 3D/2D system (Quantitive Radiology s.r.l., Verona, Italy). The scanning parameters were set at 90 kVp, 24 seconds, 4 mA, with a voxel size of 0.3 mm, and a field of view of 10×10 cm.

RADIOLOGICAL ASSESSMENT:

The horizontal and vertical diameters of the right GPF (RGPF) and left GPF (LGPF) were measured in the axial sections in millimeters (Figure 1).

The distance from the midpoint of the GPF to the incisive foramen (GPF-IF), the distance from the midpoint of the GPF to the posterior nasal spine (GPF-PNS) and anterior nasal spine (GPF-ANS), and the nearest perpendicular distance from the midpoint of the GPF to the mid-maxillary suture (GPF-MMS) were measured in the axial sections in millimeters (Figure 2).

The positioning of the GPF relative to the upper molars was evaluated as the 3rd molar and 2nd molar region. The morphology of the right-left GPF was classified as round, ovoid, and slit (Figure 3). The number of LPFs was also evaluated.

STATISTICAL ANALYSIS:

The data obtained from the measurements were transferred to SPSS, where sex and shape were classified nominally. After defining the database, frequency analysis was performed to determine the distribution by sex. Descriptive statistics were used to determine minimum age, maximum age, mean age, and range values for the distribution of patients according to age, in addition to the mean and standard deviation values of the descriptive statistical values of the right and left measurement parameters, skewness and kurtosis distributions of the measurements were calculated in the decision-making process regarding normality. Since the right-side measurement parameters were distributed within the range of ±1.5 regarding skewness and kurtosis, they provided normality. In the measurement parameters on the left side, except for the LGPF vertical diameter, LGPF distance to the incisive foramen, and the number of LGF parameters, the other parameters showed skewness and kurtosis outside the normal distribution range. We examined the LGPF vertical diameter and LGPF distance to the incisive foramen and number of lesser LGFs have high values in skewness and kurtosis, Kolmogorov-Smirnov and Shapiro-Wilk scores, as well as histogram distributions, showing that these 3 parameters were not normally distributed. In this context, in the comparisons in terms of sex, an independent samples t test was used except for the 3 parameters mentioned above.

The Mann-Whitney U test was used to compare the 3 parameters that did not show normal distribution according to sex. All analyses were evaluated according to a difference level of 0.05. In addition, the Pearson chi-square test was used to compare the distribution of the shapes in terms of sex.

Results

THE DISTRIBUTION OF PATIENTS:

Within the scope of the study, 58.1% (n=93) of the 160 patients were female and 41.9% (n=67) were male. The patients’ ages ranged between 18 and 73. The mean age of 160 patients was 46.6 years and the standard deviation was 11.6 years.

ASSESSMENT OF THE DIAMETERS OF GREATER PALATINE FORAMEN:

The mean values of the right side parameters were RGPF horizontal diameter 2.06 mm (±.66), RGPF vertical diameter 5.25 mm (±1.61), RGPF-mid-maxillary suture 15.66 mm (±1.41), RGPF-posterior nasal spine 16.64 mm (±1.46), RGPF-anterior nasal spine 47.1 mm (±3.43), and RGPF-incisive foramen 36.3 mm (±2.92).

The mean values of the left side parameters were LGPF 2.23 mm (±0.76), LGPF vertical diameter 5.39 mm (±2.07), LGPF-midaxillary suture 15.67 mm (±1.55), LGPF-posterior nasal spine 16.34 mm (±1.43), LGPF-anterior nasal spine 46.71 mm (±3.29), and LGPF-incisive foramen 36.25 mm (±3.28).

COMPARISON OF MORPHOMETRIC PARAMETERS WITH SEX:

Table 1 illustrates a comparison of parameters based on sex. A significant difference was observed in the right and left GPF measurements, with male mean measurements surpassing those of females (P<0.05). Specifically, in the right GPF, the vertical diameter, the distance between right GPF and mid-maxillary suture, the distance between right GPF and posterior nasal spine, and the distance between RGPF and anterior nasal spine among males were significantly greater than those among females (P<0.05). Nevertheless, the number of lesser PFs exhibited no significant sex-based difference (P>0.05). Regarding the distance RGPF-LGPF difference, the mean among males was significantly greater than that among females (P<0.05). The number of LPFs ranged from 1 to 5.

SHAPES OF GREATER PALATINE FORAMEN:

When analyzing the distribution of right GPF shapes, an ovoid shape was observed in 30.1% of women and 38.8% of men, showing a similar distribution. Similarly, a round shape was present in 8.6% of women and 3% of men within right GPF shape distributions. Moreover, a slit shape was observed in 61.3% of women and 58.2% of men, demonstrating closely matched distributions. Despite a slight variance in round shape percentages, the distributions of ovoid and slit shapes in RGPF were remarkably similar, with no significant difference observed (P>0.05) (Table 2).

Upon analyzing the distribution of left GFP shapes, an ovoid shape was noted in 31.2% of women and 44.8% of men. A round shape was observed in 7.5% of women and 4.5% of men, while a slit shape in LGFP was seen in 61.3% of women and 50.7% of men. However, upon considering the count numbers, it became evident that the figures were closely distributed, with no significant difference according to the chi-square test (P>0.05) (Table 2).

COMPARISON OF THE DIAMETERS OF GREATER PALATINE FORAMEN:

Table 3 illustrates the comparison of measurements for the right and left sides. In the measurement of the horizontal diameter of the GPF, a significant difference was observed between the right and left sides, with the left side having a significantly larger diameter (P<0.05) and the mean horizontal diameter of the left side was 0.17063 mm wider than the right side.

POSITION OF GREATER PALATINE FORAMEN:

Positioning of the GPF was evaluated relative to the molar teeth, showing that the GPF was predominantly situated in the third molar region (96.25% for the right side and 96.9% for the left side). Subsequently, it was observed that only 3.75% of the right GPF localized in the second molar region, while for the left side, only 3.1% localized in the second molar region.

Discussion

In the present study, we examined the anatomical characteristics of the greater palatine foramen across various CBCT scans, and a morphometric comparison of the GPF and maxillary anatomy based on sex was performed. Our results showed a significant difference in the right versus left GPF measurements, with male mean morphometric measurements surpassing those of females (P<0.05). There was no significant sex-based difference except for the number of lesser PFs (P>0.05). The distributions of shapes in GPF showed no significant difference in terms of sex (P>0.05). Slit shape had the highest percentage among the patients. In terms of the position of GPF, the GPF was predominantly situated in the third molar region (96.25% for the right side and 96.9% for the left side). According to the comparison of the right and left sides, the left side’s greater palatine foramen showed a significantly larger diameter than the right side (P<0.05)

A precise understanding of the anatomy of the GPF and GPC is essential to prevent damage to the GPA and GPN during various anesthetic, dental, or surgical procedures. Additionally, proper identification of the GPF enables the visualization of arterial pulsations, confirming the location of the GPA.

In the hard palate, the GPA runs forward near the alveolar ridge. The greater palatine nerve travels in a groove located medial to the artery, separated by a noticeable crest that clinicians can use to find both structures [10]. An accurate understanding of the GPA’s location and size is crucial to prevent its injury, which is essential for pre-surgical evaluation and to avoid surgical and post-surgical complications.

The GPA is a critical anatomical structure in the practices of plastic surgeons, ENT specialists, and dentists. For example, GPA damage can occur in downward fractures of the maxilla or other surgical procedures such as osteotomy of the medial and lateral maxillary sinus walls, pterygomaxillary separation, endoscopic medial maxillectomy [12], and pterygopalatine fossa infiltration [11]. Clinicians choose to increase the effectiveness and safety of these procedures by optimally determining the position, angle, and length of the needle used for pterygopalatine fossa infiltration according to the location of anatomical structures, such as the GPF in the oral cavity [16].

The average horizontal diameter of the GPF is 2.06 mm. This mean value is slightly lower than in previous studies [7,23,24]. This can be attributed to the differences in the ethnicity of the subjects’ populations. The average vertical diameter of the GPF is 5.25 mm, which resembles the results of Tassoker et al [20]. We found that male patients showed significantly higher diameters of GPF. The findings of Aoun et al [24] and Aoun et al [25] et al resemble our results; on the other hand, Ikuta et al [7] could not find any significant difference between males and females.

The mean value of the distance between ANS and GPF is 47.1 mm. On both sides, males’ GPFs were positioned farther from the anterior nasal spine (ANS) than females’ GPFs. This result is consistent with those of Fonseka et al [23] and Rapado-González et al [12].

GPF-PNS was found to be 16.4 mm, which is consistent with previous studies [23,26]. Like our results, Bahşi et al [26] found significant differences between sexes.

Alotaibi et al [27] stated that the GPF-IF distance is significantly higher in males, and this finding resembles our result. On the other hand, Bahşi et al [26] stated that there is no difference between sexes regarding GPF-IF. The mean distance of GPF-IF is consistent with previous studies [20,23].

Ikuta et al [7], Fonseka et al [23], and Aout et al [24] stated that the average distance between the GPF and the mid-maxillary suture was 16.23 mm, 15.2 mm, and 15.3 mm, respectively, similar to our findings. However, unlike our results, Ikuta et al [7] and Fonseka et al [23] found no significant correlation between mid-maxillary suture and GPF. This can be attributed to differences in the ethnicity of patients.

Previous research [27] has shown LPFs ranging from 1 to 5, with most studies reporting 1 or 2 LPFs and not finding any significant difference in terms of sex, like our study. However, this study frequently observed 2 LPFs, and no instances of LPF absence were noted.

Tomaszewska et al [21] asserted that the upper molars were the most reliable points for identifying the GPF. The outcomes of this research were consistent with previously reported results in the literature [12,20,26,28]; the GPF was most located at the level of the third molar.

Fonseka et al [23] stated that the right side GPF appeared larger than the left side in both sexes. On the other hand, it was reported that the right GPF-mid-maxillary suture distance is more than the left side [24]. These findings are different from our outcomes. We only found significant differences in the diameter of the left side’s greater palatine foramen, which showed a significantly larger diameter than the right side. This can be attributed to the different ethnicities.

According to the shape of GPF, Rapado-González et al [12] stated that the most prevalent shape of GPF was the oval shape, and the least prevalent shape was the slit shape. On the other hand, Taşsöker et al [20] reported that while the oval shape was the most pervasive, the round shape was detected as the least prevalent shape like our results.

The current research is limited by its small sample size and needs more exploration into how age impacts the width of the greater and lesser palatine foramen.

Conclusions

There is a significant difference in the average distance from the anterior nasal spine, posterior nasal spine, mid-maxillary suture, and incisive foramen to the GPF on both the left and right sides, as well as in the size of the GPF, between males and females. However, we did not find a strong association between sex and the alignment of the GPF concerning the molars on either side. Recognizing these variations can enhance clinical planning and reduce the risk of complications.