Introduction

Torus Palatinus (TP) is an anatomical variation where an individual grows a painless, bony, benign exostosis on the roof of their mouth, located on the hard palate (median palatine suture).¹ It is asymptomatic, a slow-growing protrusion that can differ in size and shape. It is more common in specific populations which could have genetic or environmental influences. For instance, specific gene variants influence bone formation within the palatal process of the maxillary bone. Genetic predisposition is caused by autosomal dominant inheritance.² It is commonly benign and has an unknown aetiology and can vary widely in phenotypic expression.³ It is more common in certain ethnic groups such as Asians, Inuit, and Scandinavian populations. However, East Asian populations typically exhibit the highest prevalence, followed by Europeans and then individuals of West African ancestry.¹ Furthermore, diagnosis of Torus Palatinus can also depend on sex and ancestry, even within the same ethnic groups. It is generally more common in females than males across diverse populations, suggesting a strong hereditary component; moreover, environmental factors such as diet and mechanical stress may also contribute.⁴

Clinical aspects

Torus Palatinus is oval with long sagittal projection and normal gingival appearance. The surgical approach depended on size and morphology.⁵ Treatment is not required unless it interferes with oral function, or prosthetic appliance placement or becomes ulcerated due to trauma. During dental practice, Torus Palatinus can interfere with and complicate the fitting of dentures, as the bony prominence may cause discomfort or an improper fit.⁶

Therefore, oral surgery is a common option for this complication for the removal of protrusions before certain procedures. Additionally, its presence can sometimes be mistaken for pathological growths, requiring differential diagnosis to rule out other conditions. Understanding the prevalence and variations of TP can aid clinicians in patient education and treatment planning, particularly in populations with a higher predisposition.⁴

Embryological and developmental aspects

Torus Palatinus originates from neural crest-derived mesenchymal cells, which contribute to the formation of craniofacial bones, including the hard palate.⁷ It can occur during embryonic development. The cells can migrate and differentiate under the influence of genetic and environmental factors, ultimately leading to the formation of the palatine bone. 

Torus Palatinus development is polygenic, with a strong hereditary component, as it frequently runs in families.⁸ However, the environment can influence the development, such as masticatory stress, diet, and parafunctional habits that contribute to its formation and growth. 

Ossification of the hard palate begins during fetal development and continues postnatally, with Torus Palatinus typically emerging in late childhood or early adulthood. Growth patterns are generally slow and progressive, often stabilising in adulthood. While the exact mechanisms remain unclear, Torus Palatinus likely results from a combination of genetic predisposition and mechanical stimulation over time.

Gross anatomy of the torus palatinus

Torus Palatinus is always located in this central position with differences between the size, shape, and surface texture among individuals. Torus Palatinus can range from small, barely noticeable protrusions to large growths that extend across the palate, sometimes interfering with oral functions.⁹ The surface texture may be smooth or irregular, depending on its developmental pattern.

Based on morphology, Torus Palatinus is classified into four main types:¹⁰

1. Flat – the flat torus is a broad, thick bony growth that creates a flat or slightly raised smooth area on both sides of the midline of the hard palate. It disrupts the natural arch of the mouth’s roof and has a wide base without a stalk. This condition is considered a type of excessive bone growth (hyperostosis) in the palatal region. It is covered by a thin, pale layer of mucosa and, due to its hardness, can make it difficult to fit and retain a full denture
2. Nodular – The nodular torus consists of small bony protrusions (exostoses) that usually appear on both sides of the palate. When these protuberances merge closely, they can form a single swelling. However, the overlying mucosa often retains grooves that reveal their multiple origins. If the growth continues, it may develop into the lobular type
3. Spindle-shaped – The spindle-shaped torus forms a ridge on either side of the midline of the hard palate, with a groove marking its dual bony origin. Its length varies, often stretching from the papilla palatina to the back of the hard palate, widening in the middle and gradually tapering off at the end. It may represent an early stage of the lobular type
4. Lobulated – The lobular torus forms a large, overhanging bony swelling, caused by the continuous growth and expansion. Sometimes, it can extend across the entire palate, even reaching the alveolar process on the sides¹¹

Genetic and mechanical factors can influence morphology. For instance, occlusal forces and masticatory stress, contribute to differences in presentation among individuals.

Histological structure of Torus Palatinus

Epithelial features

Keratinised stratified squamous epithelium tissue covers the Torus Palatinus, which aids with the protection against mechanical stress from mastication. The thickness of the epithelium varies, with greater keratinisation and epithelial thickness observed in individuals with higher masticatory forces. Rete ridges are small extensions of the outer skin layer that grow into the underlying tissue. They often develop in response to repeated pressure or friction, helping the skin stay firmly attached and providing extra support.¹²

Connective tissue

Under the outer layer of tissue (epithelium), a strong, fibrous layer provides support. This layer contains special cells (fibroblasts), collagen fibres, and blood vessels that help deliver nutrients. It also connects to the periosteum, a tissue that helps with bone growth and repair.¹³

Bone composition

The primary component that Torus Palatinus is made up of is lamellar bone and woven bone in some regions, especially in areas that are actively growing. This is strong and rigid, as it is made up of dense cortical bone. Furthermore, the presence of Haversian systems allows vascular supply and nutrient diffusion.¹⁴

Histopathological considerations

Torus Palatinus is a benign, non-inflammatory bony exostosis, with minimal or no inflammatory cell infiltration under normal conditions. However, if the overlying mucosa becomes stressed. For example, there can be localised inflammation and secondary infection due to mechanical irritation from mastication or prosthetic appliances, which allows neutrophils, lymphocytes, and macrophages to infiltrate.¹

However, the tissue surface of the Torus Palatinus can develop sores if exposed to repeated pressure, especially in people with thin or delicate tissue that covers the mucosal area.¹⁵ Hence, exposing underlying layers such as connective tissue increases the likelihood of developing infections, for instance, bacterial or fungal.

Unlike softer areas of the mouth, such as the soft palate or inner cheeks, Torus Palatinus has very little fat or glandular tissue. Its connective tissue is dense and mainly supports the overlying skin and bone rather than producing fluids.¹⁶

Functional and clinical implications

Role in oral biomechanics and force distribution

A critical role Torus Palatinus plays in oral biomechanics, where it is associated with distributing masticatory forces across the hard palate.¹⁷ This can reduce the stress on individual teeth and provide more support for the palate, especially when chewing.

Impact on prosthetic dentistry

The clinical concern, people with Torus Palatinus get their prosthetic dentistry impacted, like denture fabrication and fitting. Having a Torus Palatinus can result in an uneven surface which can make it difficult to achieve proper adaptation of a maxillary denture.⁶

By having Torus Palatinus, the denture may be improperly fit; therefore, leading to mucosal ulceration caused by the pressure exerted. In serious situations, surgical reduction (torus reduction surgery) can be necessary before denture placement to ensure a stable and comfortable fit.

Rare pathological transformations

Although Torus Palatinus is a harmless anatomical variation, rare complications can occur. Osteomyelitis is an infection of the bone which can develop following trauma, ulceration, or invasive dental procedures, particularly in immunocompromised individuals.¹⁸

Furthermore, conditions such as bone tumours or fibrous dysplasia can sometimes mimic Torus Palatinus. This would require careful differential diagnosis through imaging and histopathological analysis. However, malignant transformation is extremely rare, any sudden changes in size, shape, or associated symptoms should prompt further evaluation.

Summary

Torus Palatinus is a painless bony benign exostosis. It can be characterised by histological features such as keratinised stratified squamous epithelium, which is a dense fibrous connective tissue layer, and an underlying highly mineralised lamellar bone structure with Haversian systems and bone marrow spaces.

In clinical circumstances, Torus Palatinus is typically asymptomatic but can impact prosthetic dentistry, especially in denture fabrication, which can be prone to mechanical irritation and ulceration. Though rare, pathological transformations such as osteomyelitis or fibrous dysplasia should be considered in cases of sudden changes or persistent symptoms.

Future research should be considered, especially focusing on genetic and developmental mechanisms underlying Torus Palatinus formation, particularly on factors such as ethnic variations and sex.