Torus mandibularis

Torus mandibularis is a benign, non-neoplastic bony exostosis (hyperostosis) arising on the lingual surface of the mandibular body, above the mylohyoid line.[1][2] It is one of the most common developmental osseous anomalies of the oral cavity and carries no malignant potential.[3][4] Etiology is multifactorial, involving a genetic predisposition — thought to follow an autosomal dominant pattern with variable penetrance — modulated by environmental and biomechanical factors, particularly parafunctional occlusal stress such as bruxism.[2][3][5] Finite element analysis demonstrates stress concentration in the lingual premolar region during parafunctional loading, especially in individuals with square-shaped mandibles.[5] An embryological anlage at the site of Meckel's cartilage bending above the developing mylohyoid muscle has been proposed as a developmental precursor.[1] Radiographically, torus mandibularis presents as a well-defined, homogeneously radiopaque mass superimposed on the premolar root apices on conventional imaging. Most cases require no treatment; surgical excision is reserved for functional or prosthodontic indications.[4][6]

• Torus mandibularis (plural: tori mandibulares) is the accepted term in current oral pathology and radiology literature.[3][7]
• Commonly abbreviated TM in clinical and epidemiological studies.[8][9]
• The lesion is classified among oral tori and exostoses — localized, non-neoplastic bony outgrowths of the jaws. It is not included in the WHO classification of odontogenic and maxillofacial bone tumors, as it is considered a developmental anatomic variant rather than a neoplasm.[2][10][11]
• The term mandibular exostosis has been used interchangeably in some literature, though exostosis more precisely refers to bony overgrowths on the alveolar process (buccal or lingual), whereas torus mandibularis designates the specific lingual body protuberance above the mylohyoid line. This distinction is inconsistently applied, and the terms overlap in older publications.[2]

• Prevalence varies widely by population, ranging from approximately 5% to over 60%, with the highest frequencies in circumpolar and northern-latitude populations and the lowest near the equator.[2][12]
• In clinical dental populations, reported prevalence typically ranges from 12% to 40%.[6][9]
• Sex distribution: a slight male predominance is generally reported, in contrast to torus palatinus, which favors females.[3][7]
• Age: tori typically become clinically apparent in early to middle adulthood and may enlarge slowly over decades. Some data suggest prevalence is highest in younger adults and inversely related to age, possibly reflecting resorption or tooth loss in older cohorts.[4][9]
• Laterality: bilateral presentation occurs in approximately 80% of cases; unilateral tori are the minority.[3][8]
• Dentition: presence of teeth is strongly correlated with torus expression; edentulous individuals show markedly lower prevalence, supporting a biomechanical contribution.[2]

Presentation and symptoms

• Torus mandibularis is characteristically an asymptomatic, firm, bony-hard, sessile swelling on the lingual aspect of the mandibular body, most commonly in the premolar region.[2][4]
• The overlying mucosa is thin, poorly vascularized, and normal in color.[2]
• Most tori are discovered incidentally during routine dental examination or radiographic survey.[4][13]

Morphology

• Shape is classified as flat, spindle, nodular, or lobular.[14]
• Size is variable; most are less than 2 cm in greatest dimension, though large tori may nearly meet in the midline of the floor of the mouth.[6][8]

Complications and red flags

• Large tori may interfere with speech, mastication, oral hygiene, or seating of removable dental prostheses.[4][6]
• The thin mucosal covering is susceptible to chronic traumatic ulceration from food, denture flanges, or tongue entrapment between bilateral tori.[6]
• Rapid enlargement, pain, mucosal fixation, or paresthesia are not features of torus mandibularis and should prompt consideration of an alternative diagnosis such as osteoma or malignancy.[15][16]

Location and distribution

• Torus mandibularis arises on the lingual cortex of the mandibular body, above the mylohyoid line and below the alveolar crest, characteristically in the premolar region.[2][9]
• Bilateral involvement is the rule; when unilateral, the torus still occupies the same premolar-to-canine zone.[3][8]
• Extension from the canine region distally toward the molar area is common in larger tori.[2]

Periphery and shape

• The periphery is well-defined and corticated, blending smoothly with the adjacent lingual cortical plate.[9][17]
• On panoramic and periapical radiographs, the torus projects as a homogeneously radiopaque mass superimposed on the roots of the premolars (and occasionally canines), with its inferior margin above the mylohyoid line.[17][18]
• Shape on cross-sectional imaging mirrors the clinical morphology: flat (broad-based, low-profile), spindle (elongated ridge), nodular (single dome), or lobular (multiple rounded lobes).[14]
• Lobulated tori with mediolateral extension of 4 mm or more are the most reliably detected on conventional radiographs; smaller or flat tori may be radiographically occult.[17]

Internal architecture

• Internal density is uniformly radiopaque, composed predominantly of dense cortical (lamellar) bone with minimal or no medullary component.[9][19]
• CT analysis confirms that tori are composed almost entirely of cortical bone, with a mean cortical thickness of approximately 7 mm in medium-sized tori.[9]
• No internal radiolucency, mixed density, or ground-glass pattern is expected; such findings should raise concern for an alternative diagnosis.

Effects on teeth and adjacent structures

• Tori do not cause root resorption, tooth displacement, or widening of the periodontal ligament space.[17][20]
• The lamina dura and periodontal ligament space of adjacent teeth remain intact.
• The mandibular canal is not displaced.
• On panoramic radiographs, the superimposition of the torus over the premolar roots may mimic a periapical radiopacity; correlation with clinical examination or an occlusal radiograph resolves this ambiguity.[17][18]

Growth pattern and cortical involvement

• Growth is very slow, typically over years to decades, and may stabilize or even regress after tooth loss.[2][9]
• The torus expands the lingual cortex without disrupting cortical continuity; periosteal reaction and cortical destruction are absent.

Variants

• Unilateral torus: occurs in a minority of cases; imaging features are otherwise identical to bilateral tori.[2][3]
• Large confluent tori: bilateral tori may extend posteriorly and medially to nearly meet in the midline, creating a shelf-like radiopacity across the anterior mandibular body on occlusal or axial views.[6]
• Multiple discrete lobules: lobular tori may present as several separate radiopaque nodules along the lingual surface, each with well-corticated margins.[14][17]
• CBCT is useful when conventional radiographs are ambiguous — cross-sectional slices confirm the lingual cortical origin, delineate the three-dimensional extent for presurgical planning, and exclude involvement of the mandibular canal or tooth roots.[9][21]

Torus mandibularis is usually diagnosed clinically by its characteristic location, bilateral symmetry, bony hardness, and normal overlying mucosa. Radiographic differential considerations arise primarily when the lesion is unilateral, unusually large, or detected incidentally on panoramic imaging without clinical correlation.

The highest-risk diagnostic pitfall is misidentifying a unilateral, enlarging osteoma or low-grade osteosarcoma as a torus. Any lingual mandibular mass that is unilateral, rapidly enlarging, painful, or associated with paresthesia, cortical destruction, or periosteal reaction warrants further imaging and biopsy rather than observation.[15][16]

• Torus mandibularis is composed of lamellar Haversian bone in the vast majority of cases, with a dense cortical architecture and minimal trabecular component.[4][19]
• A distinctive feature is asymmetric bone remodeling within the Haversian canals: osteoid seams are deposited on the side facing the free torus surface, while Howship's lacunae with active osteoclasts line the opposite (deep) side. This pattern has been proposed as a histological feature that may help differentiate tori from other exostoses.[19]
• The mineral apposition rate is high both at the torus surface and within the canals, consistent with active, ongoing remodeling.[19]
• The overlying mucosa is thin, composed of keratinized stratified squamous epithelium with sparse lamina propria and limited vascularity.[2]
• No iron or aluminum deposits are identified histochemically, distinguishing tori from metabolic bone disease.[19]

Radiologic–pathologic correlation

The uniformly radiopaque, corticated appearance on imaging corresponds directly to the dense lamellar cortical bone seen histologically. The absence of a medullary or trabecular component in most tori explains the lack of internal radiolucency on any imaging modality.[9][19]

Indications for treatment

• The majority of mandibular tori require no treatment and are managed by observation alone.[4][7]
• Surgical excision is indicated when tori:
  • Interfere with fabrication or seating of removable dental prostheses[6][7]
  • Cause chronic mucosal ulceration or recurrent trauma[6]
  • Impair speech, mastication, or oral hygiene[4]
  • Are needed as a source of autogenous cortical bone graft for periodontal or implant surgery[6][7]

Surgical technique

• Standard removal involves a lingual full-thickness mucoperiosteal flap with excision using a high-speed rotary handpiece and osteotomes.[6]
• Alternative methods include piezoelectric surgery and Er:YAG laser; clinical outcomes and healing are comparable, though laser techniques require longer operative time.[6]

Complications

• Surgery in the floor of the mouth carries risk of significant hemorrhage and potential airway compromise, which may necessitate hospital admission.[6]
• Lingual nerve injury is a recognized risk of lingual mandibular surgery and should be discussed during informed consent.[25][26]

Recurrence and prognosis

• Recurrence after surgical removal is uncommon but documented, with regrowth reported as late as 11–14 years postoperatively.[6][27]
• Prognosis is excellent; torus mandibularis has no malignant potential and no systemic health consequences.[3][4]
• Periodic clinical observation is appropriate for asymptomatic tori; routine radiographic follow-up is not required.[13]