Abstract 
Sialolithiasis is the most common pathology affecting the salivary glands. The submandibular gland is most commonly affected. Sialoliths typically causes pain and swelling in the affected gland. They usually range in size from 1 to 10 mm, while those larger than 15 mm are considered rare. The exact etiology of sialolith formation remains unknown. We report the case of a 62-year-old patient with submandibular gland sialolith, that was incidentally discovered during imaging performed for dental implant planning. Remarkably, the patient was completely asymptomatic, despite the stone being giant in all three dimensions. Cone-Beam Computed Tomography (CBCT) of the mandible revealed a radiopaque lesion posterior to the mandibular Body, measuring approximately 2.8×1.8×2 cm. The sialolith was successfully removed using a minimally invasive transoral sialolithotomy.
Keywords: Dental implants, Mandible, Pain, Salivary gland calculi,
Spiral cone-beam computed tomography, Submandibular gland

Introduction
Sialolithiasis is the most common pathology of salivary glands (1). It is characterized by obstruction of salivary flow due to a calculus, which is accompanied by pain, swelling, and inflammation of the affected gland (2).
Sialolithiasis affects approximately 1% of the general population (3), most commonly between the third and sixth decades of life (2,4). Men are affected twice as often as women, and the condition rarely occurs in children (5,6). More than 80% of the sialoliths occur in the submandibular gland (6-8), whereas 5-20% are found in the parotid gland (8,9), and only 1-2% in sublingual and minor salivary glands (6,9). Sialolith formation is less common in intraglandular locations compared to intraductal locations (5). Submandibular calculi are mainly formed in Wharton’s duct, whereas parotid stones are usually located in the gland parenchyma (9). Sialolithiasis is more likely to occur in the submandibular gland due to its anatomical position requiring drainage against gravity, alkaline pH and high viscosity of its saliva, higher mineral content, and the long, tortuous, and narrow orifice of its ductal system (5). Although the size of sialoliths is variable, most (88%) are less than 10 mm (6).
The diagnosis can easily be made through a detailed history and clinical examination, especially in the presence of a large sialolith. However, imaging can be helpful, particularly for small stones that are difficult to detect by palpation (10). Conventional radiography, digital subtraction sialography, ultrasonography, computed tomography, and Magnetic Resonance (MR) sialography are imaging modalities that can be utilized to investigate salivary calculi (3). Sialoliths of the submandibular gland are typically recognized as radiopaque formations on plain radiographs and appear as radiolucent filling defects on sialography (5). In the literature, sialoliths measuring more than 15 mm in their maximum dimension are referred to as “giant”. Giant sialoliths, also called megaliths have been rarely reported (5,10). This report presents a rare case of an asymptomatic giant sialolith of the submandibular gland, measuring 2.90 cm in its maximum dimension.

Case presentation
A 62-year-old male patient with a medical history of hypertension and diabetes mellitus was referred to our clinic for evaluation of an oral lesion, that was incidentally detected during imaging conducted for dental implant planning. Remarkably, the patient was completely asymptomatic, despite the considerable size of the lesion. He presented to us solely upon the recommendation of his dentist.
Intraoral clinical examination through bimanual palpation revealed a stony hard, non-tender mass located in the floor of the mouth, measuring approximately 3.5×3.5 cm in size. No swelling or bulging was observed on extraoral examination (Figure 1). However, a mild elevation was noted in the left floor of the mouth (Figure 2), which was not perceived by the patient. A saliva milking test demonstrated a slightly reduced volume of saliva with normal coloration. The test did not provoke any discomfort or pain. Panoramic radiography revealed a well-defined radiopaque mass superimposed over the left posterior body of the mandible, in proximity to the first and second mandibular molars, measuring approximately 3.5×3.2 cm (Figure 3).
A provisional diagnosis of sialolithiasis was considered.
Cone-Beam Computed Tomography (CBCT) of the mandible revealed a radiopaque lesion posterior to and near the mandibular body, measuring approximately 2.8×1.8×2 cm (Figure 4). Ultrasonography of the left submandibular gland, with and without Doppler study, was performed. It showed a normal-sized left submandibular gland with mild heterogenicity and a calcified sialolith (anteroposterior size:2.07 cm). No abnormal vascularization was observed on color Doppler ultrasonography. Based on clinical and radiographic findings, a differential diagnosis of left submandibular duct sialolithiasis was proposed. Laboratory investigations revealed an HbA1c level of 6.7% and blood pressure was measured at 135/85 mmHg. Under local anesthesia, the sialolith was removed via a minimally invasive transoral sialolithotomy. The excised stone measured 2.90×1.90
×2.18 cm (Figure 5).

Discussion
Sialolithiasis is the most common cause of major salivary gland swelling (11). It refers to the formation of calculi within the salivary glands or their ducts (10). The composition of sialoliths can vary depending on the relative concentrations of organic and inorganic components (12). Although the exact pathogenesis remains unclear, it is widely accepted that sialoliths form via the deposition of calcium-rich salts around a central nidus. This nidus may consist of desquamated epithelial cells, foreign bodies, bacteria or their degradation products (13).
It has also been suggested that food debris or bacteria from the oral cavity can migrate into the salivary ducts and initiate stone formation (14). Salivary stones are composed of both organic and inorganic materials, including calcium carbonates and phosphates, cellular debris, glycoproteins, and mucopolysaccharides. Typically, the core of the stone is composed predominantly of organic matter, whereas the peripheral layers are mostly inorganic (15). Sialolith usually causes pain and swelling in the affected salivary gland with symptoms ranging from very mild to very severe (6). In the present case, despite the presence of a giant sialolith, the patient was completely asymptomatic and unaware of its existence (Table 1).

Table 1. Comparative table of various cases of giant submandibular sialolithiasis with different characteristics and teatments

Abbations: F, female; M, male.

Prolonged obstruction in the absence of infection can eventually lead to glandular atrophy, loss of secretory
function and subsequent fibrosis (16). Therefore, surgical treatment is recommended even in asymptomatic patients to prevent potential future complications. Sialolithiasis is most commonly observed between the third and sixth decades of life (2,4). Consistent with the typical age range, the present case involved a 62-year-old man. Some studies suggested that systemic diseases, medications, smoking, and alcohol consumption play no or only a limited role in the development of salivary stones (17). Sialoliths typically range in size from 1 to 10 mm with an average of 6 to 9 mm. Stones larger than 15 mm are considered rare (18). In present case, the sialolith measured 29 mm, placing it within the rare “giant sialolith” category.
The primary goal in treating giant sialoliths is to restore normal salivary flow. Treatment options for submandibular sialoliths include interventional sialendoscopy, intraoral stone removal, and gland resection. The appropriate method depends on the stone’s location, size, and number (5). Stones located within 2 cm of the duct orifice may be removed intraorally, as indicated in the present case; whereas those located posteriorly in the duct or within the gland may necessitate submandibular sialoadenectomy (4).

Acknowledgement
The authors would like to thank the staff of the Faculty of Dentistry of Shahid Beheshti University for their extraordinary support in this research project. Verbal informed consent was obtained from the patient for publication of the case details and accompanying images.

Conflict of Interest
There was no conflict of interest in this manuscript.