S. R. Prabhu - Handbook of Oral Pathology and Oral Medicine

Cone beam computed tomography (CBCT) precisely defines the location of the tooth and its proximity to vital anatomical structures such as the nasal floor and nasopalatine canal

History

Clinical examination

Radiography

Extraction in most cases

Microdontia: size of the tooth unusually smaller than average

Macrodontia: size of the tooth unusually larger than average

Differences in prevalence rates exist

Approximate prevalence in general population:1.58% for microdontia0.03% for macrodontiaMicrodontia in maxillary lateral incisors (‘peg laterals’) is common (0.8–8.4%)

Maternal influences, genetic and environmental factors.

Deciduous teeth are affected more due to intrauterine maternal influences

Permanent teeth are affected more due to environmental factors Figure 1.3 Microdontia: maxillary left lateral incisor (‘peg lateral’) is cone shaped and smaller than average for lateral incisor(source: by kind permission of Professor Charles Dunlap, Kansas City, USA).

Generalized microdontia involving all teeth is extremely rare

Generalized macrodontia is rare: often seen in pituitary gigantism

Generalized microdontia may be a feature of Down syndrome and pituitary dwarfism

Microdontia may be associated with hypodontia

Macrodontia may be associated with hyperdontia

Microdontia is more frequent in females

Macrodontia is more frequent in males

Maxillary lateral incisor is commonly involved in microdontia (peg lateral; Figure 1.3)

Isolated microdontia is frequently seen in third molars

Isolated macrodontia is occasionally seen in incisors, canines, second premolars and third molars (fused and geminated teeth to be differentiated from macrodontia)

History

Clinical examination

For macrodontia, radiography is useful to rule out gemination or fusion

No treatment is required unless for aesthetic purposes.

Porcelain crown for peg lateral is often used

Gemination: attempt at a single tooth bud to divide, resulting in a tooth with bifid crown and a common root and root canal (clinically seen as double teeth)

Fusion: union of two normally separated tooth buds resulting in a joined tooth with confluent dentine (clinically seen as double teeth) and separate root canals

Concrescence: union of two teeth by cementum without confluence of dentine

Varies; approximate prevalence rates are:Gemination: 0.22%Fusion: 0.19%Concrescence: 0.8% in permanent teeth and 0.2–3.7% in deciduous teeth

Gemination and fusion: evolution, trauma, heredity and environmental factors

Concrescence: inflammation around roots

Tooth count:Individuals with gemination have a normal tooth count. Clinically seen as double teeth but radiograph shows common root canal ( Figure 1.4a,b)Individuals with fusion show a missing tooth due to the union of two teeth. Clinically seen as a large tooth crown ( Figure 1.4c)Individuals with concrescence have a normal tooth count. Roots of two teeth are joined by cementum ( Figure 1.4d)

Gemination: more common in the maxilla

Fusion: more common in the mandible

Concrescence: common in posterior maxillary region. Often, second molar roots are joined with adjacent impacted third molar roots

Gemination and fusion in deciduous teeth may cause crowding, abnormal spacing or delayed eruption of permanent teeth

Gemination: common root, common root canal

Fusion: separate roots and root canals

Concrescence: roots joined at cementum of two adjoining teeth. CBCT is useful for concrescence (gives a three‐dimensional image)

History

Clinical examination

Radiography

Depends on patient requirement

Usually not indicated unless symptomatic due to other causes, such as extensive caries, periodontal pathology or interference with tooth eruption Figure 1.4 (a) Gemination; mandibular right incisors show gemination. Note the presence of all incisors. (b) Radiograph of bilateral gemination in maxillary central incisors. Note incisal notch and common root and root canal. (c) Fusion; shows left maxillary lateral incisor fused with the central incisor. (d) Concrescence; roots of two teeth are joined by cementum.(sources: a–c, by kind permission of Professor Charles Dunlap, Kansas City, USA); d, by kind permission of Dental Press Publishing, Brazil.)

Taurodontism refers to an enlarged pulp chamber, apical displacement of the pulpal floor and no constriction at the level of the cementoenamel junction

Dilaceration refers to abnormal angulation or bend in the root

Range:Taurodontism: 0.5–4.6% in general populationDilaceration: 0.3–15% in general population

Taurodontism:Failure of Hertwig's epithelial root sheath diaphragm to invaginate at the proper horizontal levelNo genetic association

Dilaceration:IdiopathicInjury that displaces the calcified portion of the tooth germ from the uncalcified portion resulting in an abnormal angle of the root

Taurodontism:May be unilateral or bilateralPermanent teeth are frequently affectedNo gender predilectionMay occur as a part of syndromes such as Klinefelter syndrome, Mohr syndrome and McCune–Albright syndromeIncreased frequency in patients with cleft lip, cleft palate and those with hypodontia.Increased chances of pulp exposure in decayed teeth with taurodontismDegree of taurodontism:hypotaurodontism (mild form)mesotaurodontism (moderate form)hypertaurodontism (severe form)

Dilaceration:Mandibular third molars are frequently involved followed by maxillary second premolars and mandibular second molarsRare in deciduous dentitionAsymptomatic in most casesAssociated with syndromes (e.g. Ehlers–Danlos syndrome)

Taurodontism:Commonly detected on routine radiographyInvolved teeth presume a rectangular shapeThe pulp chamber is exceedingly large with a greater apical–occlusal height than normalThe tooth lacks the usual constriction at the cervical regionRoots are exceedingly short and trifurcation or bifurcation may be seen a few millimetres above the apices of the roots ( Figure 1.5a)

Dilaceration:Radiographically, detected as mesial or distal bend in the root ( Figure 1.5b)Periodontal ligament space is normalDetected on routine radiography Figure 1.5 (a)Taurodontism of the mandibular first molar shows abnormally large pulp chamber and short roots. (b) Dilaceration of an extracted tooth shows abnormal bend in the roots.(source: by kind permission of Professor Charles Dunlap, Kansas City, USA.)

Taurodontism:No specific treatment required