**3.6 Dens in dente (dens invaginatus)**

The 'dens in dente' is a developmental variant that is believed to come from an invagination in the tooth crown's surface prior to calcification. Prior to the calcification of the dental tissues, there is histologically observed deepening or invagination of the enamel organ into the dental papilla [5].

Clinical: The tooth's labial face is frequently bulbous. Conical or asymmetrical crown shapes are both possible. Dental infolding is a rare clinical occurrence. Rarely, primary teeth may be impacted.

Radiological: It can be identified as a pear-shaped invagination of enamel and dentin that has a close resemblance to the pulp in depth and a tight constriction at the aperture on the surface of the tooth. The tooth appears to be 'inverted' (**Figure 4**).

## **3.7 Dens evaginatus**

The dens evaginatus is a developmental condition that appears clinically as an accessory cusp or a globule of enamel on the occlusal surface between the buccal and lingual cusps of premolars, unilaterally or bilaterally, although it has been reported to occur rarely on molars, cuspids and incisors.

Schulze [6] distinguished the following five types of DE for posterior teeth by the location of the tubercle.

1.A cone-like enlargement of the lingual cusp.

2.A tubercle on the inclined plane of the lingual cusp.

3.A cone-like enlargement of the buccal cusp.

4.A tubercle on the inclined plane of the buccal cusp.

5.A tubercle arising from the occlusal surface obliterating the central groove.

Clinical: It appears as a tubercle of enamel on occlusal surface of the affected tooth. Polyp-like protuberance in central groove on lingual ridge of buccal cusp is seen.

Radiological: Occlusal surface has tuberculated appearance.

#### **3.8 Enamel pearl**

Heterotopic presence of enamel in the form of a globule is called enamel pearl. It is usually found on the root surface.

Clinical: It appears as a yellowish white, spherical structure adherent to the furcation area of the root surface. The diameter ranges from 1 mm to 3 mm.

Radiological: It appears as smooth, round and well-defined radiopacity present along the root surface. Radiodensity is same as that of the enamel.

#### **3.9 Taurodontism**

It is characterised by clinical and anatomical crown of normal shape and size, an elongated body and short roots with longitudinally enlarged pulp chambers [7].

Clinical: Affected teeth tend to be rectangular and exhibit pulp chambers with a dramatically increased apico-occlusal height and a bifurcation close to the apex [7, 8].

Radiological: Pulp chamber is extremely large with much greater apico-occlusal height than normal. Extensions of rectangular pulp chamber occur into elongated body of the tooth [7]. Pulp lacks the usual constriction at the cervix of tooth. The root and root canals are exceedingly short. There is also increased dimension between cementoenamel junction and furcation.

#### **3.10 Supernumerary roots**

Teeth that are normally single-rooted exhibit two roots.

Clinical: They develop as slender outgrowths at the centre of furcation area of molar teeth.

Radiological: If the bifurcation produces two distinct apices and these are arranged as one mesial to the other, then it will be seen on the radiographs. If the two apices are on the labial and lingual side, they may get superimposed on each other appearing as a bulbous root, which may mimic hypercementosis.

### **4. Developmental disturbances in structure of teeth**

Amelogenesis imperfect: A complex collection of diseases known as amelogenesis imperfecta shows developmental changes in the enamel's structure when no underlying systemic problem is present.

Inaccuracies in hypoplastic amelogenesis.

Pits that range in size from a pinhead to a pea are dispersed around the teeth's surface. The pits can be placed in rows or columns and are more noticeable on the buccal surfaces of the teeth.

Localised pattern: Linear depressions and horizontal rows of pits can be seen on the affected teeth. The affected region is typically found in the middle third of the buccal surfaces of the teeth. Typically, neither the incisal edge nor the occlusal surface is impacted.

All teeth have an enamel that is thin, firm, shiny, and has an autosomal dominant smooth pattern. There is lack of the proper enamel thickness.

Radiographs exhibit a thin peripheral outline of radiodense enamel. Unerupted teeth, often undergoing resorption, may be seen.

Enamel agenesis: A total lack of enamel formation. The teeth are the shape and colour of the dentin, with a yellow-brown hue, open contact points and crowns that taper towards the incisal-occlusal surface. The surface of the dentin is rough, and an anterior open bite is seen frequently.

Radiographs demonstrate no peripheral enamel overlying the dentin.

#### **4.1 Hypomaturation amelogenesis imperfecta**

Pigmented pattern: The surface enamel is mottled and agar brown. The enamel often fractures from the underlying dentin and is soft enough to be punctured by a dental explorer.

X-linked pattern: The deciduous teeth are opaque white with a translucent mottling; the permanent teeth are opaque yellow-white and may darken with age. Focal areas of brown discoloration may develop within the white opaque enamel [9].

Snow-capped patterns: A zone of white opaque enamel on the incisal or occlusal one quarter to one-third of the crown.

#### **4.2 Hypocalcified amelogenesis imperfecta**

On radiographs, the teeth show a thin radiopaque enamel outline around the periphery. Unruptured teeth showing signs of resorption are common.

Both dentitions have diffuse thin, smooth and glossy enamel in an X-linked pattern. Open contact points and crown preparation shapes are common in teeth. Brown to golden brown is the range of colour.

An outline of radiopaque enamel can be seen on radiographs.

Rough surface: The enamel is thin and firm and has a rough pattern. Similar to the smooth forms, the teeth have open contact sites and taper towards the incisal-occlusal surface. From white to bright white, the colour varies.

Clinical: On eruption, the enamel is yellow-brown or orange, but it often becomes stained brown to black and exhibits rapid calculus apposition.

A thin radiopaque enamel outline around the teeth's periphery can be seen on radiographs. Unruptured teeth that are showing resorption are common.

Thin, shiny, smooth enamel is diffused in both dentitions with an X-linked pattern. There are exposed contact sites and the teeth frequently resemble crown preparations. Brown to yellow-brown are the different shades.

Enamel that is radiopaque can be seen around the edges on radiographs.

The enamel has a rough surface and is thin and firm. The teeth display open contact points and taper towards the incisal-occlusal surface just like in the smooth forms. White to yellow-white can be seen throughout the spectrum.

Radiological: the density of the enamel and dentin are similar. Before eruption the teeth are normal in shape; however, after a period of function much of the cuspal enamel is lost, with the occlusal surface becoming the most irregular (**Figure 5**) [10].

#### **4.3 Dentinogenesis imperfecta**

Both deciduous and permanent teeth are affected by the autosomal dominant syndrome known as dentinegenesis imperfecta [11, 12].

Clinical: Affected teeth have large crowns, grey to yellowish brown colour, and constricted cervical areas give them a 'tulip' form.

**Figure 5.** *Courtesy: JSS Dental College, clinical picture of amelogenesis imperfecta.*

Radiologically, the teeth appear to be solid and devoid of root canals and pulp chambers. Because enamel is easily fractured, exposed dentin has rapid attrition. The teeth feature narrow roots, bulbous crowns, cervical constriction, and early pulp chamber and root canal obliteration.

Dentition with enamel that is normal in thickness, dentin that is incredibly thin and pulps that are noticeably enlarged is dentin dysplasia.

It is a rare disturbance of dentin formation, characterised by normal but atypical dentin formation, with abnormal pulp morphology.

Clinical:

Type I (radicular). Both dentitions are affected, although the teeth appear clinically normal in morphologic appearance and colour. Occasionally, there may be a slight amber translucency. However, the teeth characteristically exhibit extreme mobility and are commonly exfoliated prematurely or after only minor trauma as a result of their abnormally short roots.

Type II (coronal): The deciduous teeth have the same yellow, brown or bluish-grey opalescent appearance as seen in dentinogenesis imperfect [12].

Radiological:

Type I (radicular): In both dentitions, the roots are short, blunt, conical or similarly malformed. In the deciduous teeth, the pulp chambers and root canals are usually completely obliterated, while in the permanent dentition, a crescent-shaped pulpal remnant may still be seen in the pulp chamber.

Type II (coronal): Bulbous crowns, cervical constriction, thin roots, and early obliteration of the pulp. The permanent teeth demonstrate normal clinical coloration; however, radiographically, the pulp chambers exhibit significant enlargement and apical extension. This altered pulpal anatomy has been described as thistle tube shaped or flame shaped (**Figure 6**).
