i. Gemination, fusion and concrescence

ii. Accessory cusps

iii. Ectopic enamel

iv. Taurodontism

v. Dilaceration

vi. Supernumerary roots.

• Gemination is a developmental anomaly that refers to division of single tooth germ into incomplete or complete formation of two teeth.

• Crowns may be partially or totally separated from each other.

• Roots are fused and single root canal is present within the root.

• The structure is usually one with two completely or incompletely separated crowns that have a single root and a root canal.

• The condition is seen in both deciduous and permanent dentition,with a higher frequency in the anterior and maxillary region.

• Fusion is defined as single enlarged tooth or joined tooth in which the tooth count reveals a missing tooth when the anomalous tooth is counted as one.

• One of the most important criteria for fusion is the fused tooth must exhibit confluent dentine.

• Both permanent and deciduous dentition are affected in case of fusion, although it is more common in deciduous teeth.

• Fusion can be complete or incomplete and its extent will depend on stage of odontogenesis at which fusion takes place.

• The incisor teeth are more frequently affected in both the dentitions.

• Concrescence is defined as union of two adjacent teeth by cementum only without confluence of the underlying dentine.

• It is the type of fusion, which is limited only to the roots of teeth and it occurs after the root formation of involved teeth is completed.

• Aetiology: Concrescence may be developmental or postinflammatory or due to traumatic injury.

• Common between maxillary second molar and unerupted third molar.

a. Cusp of Carabelli

b. Talon cusp

c. Dens invaginatous (dens in dente)

d. Dens evaginatous

• Present on mesiopalatal cusp of maxillary first molars.

• An analogous accessory cusp is seen occasionally on the mesiobuccal cusp of a mandibular permanent or deciduous molar known as protostylid.

• Talon cusp is an anomalous projection resembling eagle’s talon projects lingually from cingulum area of permanent incisors.

• A developmental groove is present at the site, where this projection meets with the lingual surface of tooth.

• This groove is prone to caries, so it should be removed. If pulp exposure is present then endodontic therapy is done.

• Found in association with ‘Rubinstein–Taybi syndrome’.

• Dens in dente is a developmental variation, which arises as a result of enamel epithelial invagination of the crown surface before calcification.

• Several causes of this condition are: it is because of focal growth proliferation and focal growth retardation that takes place in certain areas of tooth bud, increased localized external pressure.

• After calcification it appears as accentuation of lingual pit.

• Teeth most frequently involved are maxillary lateral and maxillary central incisors.

• Radiographic features

• Treatment

• Dens evaginatus is a developmental condition appears as an accessory cusp or globule of enamel on occlusal surface between buccal and lingual cusps of premolars unilaterally or bilaterally.

• This is opposite of invagination. That means, there occurs extrusion of the dental papilla outwards into the enamel organ.

• Clinical findings:

• Treatment consists of extraction of the tooth.

• Enamel pearls

• Cervical enamel extensions

• Predisposes to development of buccal bifurcation cysts.

• Taurodontism is a dental anomaly in which the body of the tooth is enlarged at the expense of roots.

• A specialized or retrograde character

• A primitive pattern

• An atavistic feature

• Mendelian recessive trait

• A mutation

• Associated with Klinefelter syndrome

• It is due to failure of Hertwig epithelial root sheath to invaginate at proper horizontal level.

• It may affect both deciduous and permanent dentition, but more common in permanent dentition.

• Molars are commonly affected.

• Tooth morphology is normal.

• Enlarged and rectangular pulp chamber is present.

• No constriction of pulp at cervical area.

• Roots are very short.

• Furcation is present just above root apex.

• No treatment is required.

• Dilaceration refers to angulation or curve in root or crown of tooth.

• Angulation is caused due to trauma to the tooth during formative stage of tooth.

• Curve is present at apical, middle or at cervical portion depending on the portion which is forming at the time of trauma.

• Occlusal trauma in deciduous tooth may also cause dilaceration of permanent tooth.

• More common in the maxillary anterior region.

• Significance: Tooth with bent root is difficult to extract.

• One or more extra roots may be present in tooth.

• Usually single rooted teeth such as mandibular cuspids and bicuspids are involved.

• Third molars of both jaws also present one or more extra roots.

• Internal resorption is also known as chronic perforating hyperplasia of pulp, odontoclastoma or pink tooth of mummery.

• It is an unusual form of resorption that begins centrally within the pulp, apparently initiated by a peculiar inflammatory hyperplasia of the pulp.

• Idiopathic

• No early clinical signs and symptoms.

• Tooth may show pink spot (pink tooth) when more of dentine is resorbed from one area of the crown, leaving a covering of translucent enamel.

• It appears as a pink area due to vascular pulp visible through the translucent enamel.

• Pink spot appears as round or ovoid area of radiolucency in the central portion of the tooth.

• If condition is discovered before perforation of crown, root canal therapy may be carried out.

• Once perforation has occurred, extraction of tooth is the treatment.

• Dens invaginatus is otherwise known as dens in dente or gestant odontoma.

• It is a developmental variation that arises as a result of enamel epithelial invagination of the crown surface before calcification.

• It is an enamel lined surface invagination of crown or root.

• It is because of focal growth proliferation and focal growth retardation that takes place in certain areas of tooth bud due to increased localized external pressure.

• Coronal form is formed by the infolding of enamel organ in to dental papilla, while radicular form is produced due to invagination of Hertwig root sheath.