Fusion
Fusion is a developmental anomaly where two separate tooth germs unite during odontogenesis, resulting in a single enlarged tooth structure. The union may occur at any stage of tooth development and can be complete (involving enamel, dentin, and cementum) or incomplete (involving only root structures). This condition is more prevalent in the anterior region and primary dentition. Clinical significance includes aesthetic concerns, periodontal complications due to excessive crown width, and complex endodontic anatomy. Note: The tooth count is reduced by one when fusion occurs unless fusion involves a supernumerary tooth.
Gemination
Gemination represents an attempt at division of a single tooth germ, resulting in a bifid crown with a single root canal system. Unlike fusion, the tooth count remains normal when the anomalous tooth is counted as one. It predominantly affects the anterior region and primary dentition. Clinical management focuses on aesthetic rehabilitation and prevention of periodontal complications due to excessive crown width.
The term double teeth (also called composite odontoma) refers to any tooth-like structure presenting as an apparent union of two dental units. This encompasses both fusion and gemination, which often cannot be differentiated clinically. The primary clinical significance lies in aesthetic concerns, spacing issues, and increased susceptibility to periodontal disease due to irregular crown morphology and cervical defects. Radiographic examination is essential for proper diagnosis and treatment planning.
- Differential diagnosis between fusion and gemination can be aided by the “two tooth rule”: count the anomalous tooth as one; a reduced total count indicates fusion, while a normal count suggests gemination.
- Root canal treatment of fused teeth requires careful assessment of the complex internal anatomy, often necessitating cone beam computed tomography (CBCT) for proper visualization.
- The presence of these anomalies may indicate the need for genetic counseling, as some forms are associated with developmental syndromes.
Dens evaginatus
Dens evaginatus is an ectopic tubercle composed of enamel and dentin, typically projecting from the occlusal surface of posterior teeth or lingual surface of anterior teeth. It results from abnormal proliferation and folding of the inner enamel epithelium during bell stage. Clinical significance includes premature occlusal contacts, tubercle fracture leading to pulp exposure, and potential periapical pathology. Most commonly affects premolars in Asian populations.
Dens invaginatus (also called dens in dente) represents a developmental malformation characterized by the invagination of enamel organ into the dental papilla prior to calcification. Oehlers classification describes three types:
- Type I: Invagination confined to crown, not extending beyond CEJ
- Type II: Invagination extends below CEJ, remains within root as blind sac
- Type III: Invagination penetrates through root forming second apical or lateral foramen
Clinical significance includes increased caries susceptibility, pulpal involvement, and complex endodontic treatment needs. Most commonly affects maxillary lateral incisors. - Prophylactic sealing of the invagination in dens invaginatus is recommended immediately after eruption to prevent pulpal complications.
Clinical Considerations For Dens Invaginatus:
- Early detection and prophylactic treatment
- Possible need for combined surgical-endodontic approach
- Regular monitoring for caries development
- Complex restoration requirements
Taurodontism
Taurodontism is a developmental disturbance characterized by vertical enlargement of the pulp chamber with apical displacement of the pulpal floor and furcation area. The term derives from “taurus” (bull) due to the bull-like appearance of affected teeth.
Most commonly affects permanent molars. The clinical crown appears normal, but the body of the tooth is elongated and the roots are shortened. Three forms are recognized based on severity: hypotaurodont (mild), mesotaurodont (moderate), and hypertaurodont (severe). Clinical significance includes complex endodontic treatment due to altered pulpal anatomy and challenges in furcation management. Note: Radiographic examination is essential for diagnosis as the clinical crown appears normal.
Taurodontism may be associated with several syndromes including Down syndrome, Klinefelter syndrome, and tricho-dento-osseous syndrome.
Clinical Considerations For Taurodontism:
- Modified endodontic access design
- Special attention to working length determination
- Complex obturation techniques required
- Careful furcation management in periodontal therapy
Concrescence describes a developmental or post-developmental union of two adjacent teeth by cementum only. This condition most frequently involves maxillary molars, particularly second and third molars. Clinical significance primarily relates to extraction difficulties, as separation of concrescent teeth may lead to unplanned extraction of the adjacent tooth.
Dilaceration describes an abrupt deviation of the root or crown from the normal axial alignment, resulting in an angular bend. The condition may occur due to:
- Trauma to primary predecessor tooth
- Developmental disturbance
- Mechanical interference during development
- Ectopic positioning of tooth germ
Clinical significance primarily relates to:
- Extraction difficulties
- Endodontic treatment complexity
- Potential impaction
- Challenges in orthodontic alignment
- CBCT imaging is often necessary for proper treatment planning in cases of severe dilaceration or complex dens invaginatus.
Clinical Considerations for Dilaceration:
- Careful treatment planning for extraction
- Modified endodontic access and instrumentation
- Special consideration in orthodontic treatment
- Possible surgical intervention for severely affected teeth
