Teeth

💡Abnormalities in Number

These conditions involve congenital absence of teeth due to disturbances in tooth development.

Most commonly missing teeth

1. Third molars.
2. Mandibular second premolars.
3. Maxillary lateral incisors.

Associated conditions

• Ectodermal dysplasia.
• Down syndrome.
• Cleft lip and/or palate.
• Rieger syndrome.
• Other genetic disturbances of odontogenesis.

FCPS tip: Third molars are the teeth most commonly missing congenitally. Do not confuse congenital absence with extraction or failure of eruption.

Supernumerary teeth (hyperdontia)

Supernumerary teeth are additional teeth beyond the normal complement.

Types

Mesiodens

• The most common supernumerary tooth.
• Usually occurs in the maxillary midline.
• May be conical or resemble a normal tooth.
• Can delay eruption or displace permanent incisors.
• Approximately 90% are reported in the maxilla in the source.

Associated syndromes

💡Abnormalities of Eruption

Delayed eruption

Delayed eruption occurs when a tooth emerges later than expected for the relevant developmental stage.

Clinical approach: Determine whether the tooth is developmentally absent, delayed, impacted or obstructed. Clinical examination and radiographs help distinguish these possibilities.

💡Natal and neonatal teeth

Complications and management

• Assess tooth mobility and aspiration risk.
• Check whether feeding is impaired.
• Look for ulceration of the ventral tongue, known as Riga–Fede disease.
• Extraction may be indicated if the tooth is excessively mobile, poses an aspiration risk or causes significant traumatic ulceration.
• Stable teeth without complications may be monitored.

Exam tip: Natal = at birth; neonatal = within 30 days after birth.

💡Defects of Enamel Structure

💡Amelogenesis imperfecta (AI)

Amelogenesis imperfecta is a group of inherited conditions affecting enamel formation. It may involve primary and permanent teeth, while dentin is generally structurally normal.

Classification

Key differences

Hypoplastic AI

• Quantitative defect: too little enamel is formed.
• Enamel is thin, but may be relatively hard.
• Pitting and grooves may be present.

Hypocalcified AI

• Qualitative defect: enamel mineralization is poor.
• Enamel is soft and breaks down readily.
• Often has a yellow-brown appearance.

Hypomaturation AI

• Enamel matrix is present but maturation is incomplete.
• Enamel may appear mottled, opaque or snow-capped.
• It is often softer than normal enamel.

Inheritance

AI may be autosomal dominant, autosomal recessive or X-linked, depending on the subtype and gene involved.

Management

• Prevent sensitivity and further enamel breakdown.
• Restore function and aesthetics.
• Use full-coverage restorations when indicated.
• Provide preventive care and monitor occlusion and tooth wear.

FCPS memory rule:

• Hypoplastic = thin enamel.
• Hypocalcified = soft enamel.
• Hypomaturation = mottled/opaque enamel.

💡Dentinogenesis imperfecta (DI)

Dentinogenesis imperfecta is an inherited dentin disorder, classically associated with abnormal dentin formation and opalescent teeth.

Types

Clinical features

• Amber, blue-gray or opalescent tooth discoloration.
• Bulbous crowns.
• Cervical constriction.
• Enamel may fracture because of poor underlying dentin support.
• Rapid wear of exposed dentin.

Radiographic features

• Bulbous crowns.
• Short or narrowed roots in many cases.
• Pulp chambers and root canals may become partially or completely obliterated.
• Type III may show very large pulp chambers, sometimes described as shell teeth.

Genetics

• Classically associated with mutations affecting DSPP, the dentin sialophosphoprotein gene, in types II and III.

Management

• Protect teeth against attrition and fracture.
• Use suitable full-coverage restorations when required.
• Emphasize prevention and early intervention.
• Consider the difficulty of endodontic treatment when pulp chambers are obliterated.

MCQ tip: Opalescent teeth + bulbous crowns + obliterated pulp chambers = dentinogenesis imperfecta.

💡Dentin dysplasia

Dentin dysplasia is an inherited dentin disorder characterized by abnormal root or pulp development. The crown appearance may be relatively normal, particularly in the classic root form.

Management

• Prevent caries and pulpal infection.
• Monitor tooth mobility and periapical health.
• Endodontic treatment may be difficult, particularly in Type I, because of abnormal or obliterated canals.

Exam tip: Dentin dysplasia Type I = short roots; Type II = thistle-tube-shaped pulp chambers in permanent teeth.

💡Regional odontodysplasia — “Ghost teeth”

Regional odontodysplasia is an uncommon developmental disturbance affecting several dental tissues in a localized region.

Clinical features

• Usually affects a limited area or quadrant.
• Delayed eruption.
• Small, malformed teeth.
• Enamel, dentin, cementum and pulp are affected.
• Maxillary involvement is more common than mandibular involvement.

Radiographic features

The teeth have a characteristic ghost-like appearance due to poor mineralization and reduced radiographic density.

Management

• Monitor eruption and tooth development.
• Prevent infection and preserve teeth where feasible.
• Extraction may be needed for nonrestorable or infected teeth.
• Treatment is individualized according to function, infection, aesthetics and the patient's age.

FCPS tip: Ghost teeth = regional odontodysplasia, involving all dental tissues in a localized region

💡Environmental Defects of Enamel

Environmental insults during tooth development may cause localized or generalized enamel abnormalities. The clinical appearance depends on the timing, severity and duration of the insult.

Comparison table

💡Dental fluorosis

Fluorosis develops when excessive fluoride exposure occurs while enamel is forming.

Features

• Usually diffuse and relatively symmetrical.
• Mild disease produces white lines or cloudy opacities.
• More severe disease may produce brown discoloration, pitting and enamel breakdown.
• Dean's index is used to classify the severity of dental fluorosis.

Exam tip: Fluorosis is generally diffuse; a single localized enamel defect suggests another cause.

💡Turner tooth

A Turner tooth is a permanent tooth with a localized developmental enamel defect caused by infection or trauma involving its primary predecessor.

MCQ tip: Primary tooth periapical infection followed by a defective permanent successor = Turner tooth.

💡Molar–incisor hypomineralization (MIH)

MIH is a qualitative enamel defect affecting one or more first permanent molars, with or without involvement of permanent incisors.

• Demarcated white, cream, yellow or brown opacities.
• Enamel may fracture after eruption.
• Teeth may be sensitive.
• Caries risk can be increased because affected enamel breaks down.

Remember: MIH is a hypomineralization defect, not simply a quantitative absence of enamel.

💡Tetracycline staining

Tetracyclines can bind to mineralizing tissues and cause intrinsic discoloration during tooth development.

• Color ranges from yellow to gray-brown.
• Fluorescence may be seen under ultraviolet light.
• Risk depends on the specific drug, timing and exposure.
• Avoid tetracycline-class drugs during pregnancy and in young children when safer appropriate alternatives are available.

Dental exam tip: Distinguish intrinsic tetracycline staining from superficial extrinsic stains.

💡Odontomas

Odontomas are developmental odontogenic lesions composed of dental tissues. They are commonly regarded as hamartomas rather than true neoplasms.

Types of odontoma

Compound odontoma

• Composed of multiple small tooth-like structures, called denticles.
• Commonly located in the anterior maxilla.
• May prevent eruption of a permanent tooth.
• Often detected incidentally on radiographs.

Complex odontoma

• Composed of a disorganized mass of enamel, dentin and other dental tissues.
• Commonly associated with posterior jaw regions, particularly the mandible.
• May delay eruption or cause local expansion.

Radiographic appearance

Management

• Surgical removal when indicated, particularly if eruption is obstructed or pathology is suspected.
• Histopathological assessment where appropriate.
• Follow-up to assess eruption and healing.
• Recurrence is generally uncommon after complete removal.

FCPS tip: Compound odontoma resembles multiple miniature teeth; complex odontoma resembles an irregular radiopaque mass.