INTRODUCTION
Odontomas are the most common benign odontogenic tumors of the jaws ; however , they are considered to be odontogenic hamartomas and not true neoplastic lesions [ 1-4 ] . Histologically , they have odontogenic epithelium and ectomesenchyme with dental hard tissue formation . The exact etiology is unknown , but genetics , infection and trauma have been proposed to contribute to their pathogenesis [ 1 , 3 , 5 , 6 ] . They are associated with several familial syndromes like Hermann syndrome , Gardner syndrome , cleidocranial dysostosis and familial adenomatous polyposis [ 7 , 8 ] .
Odontomas are pediatric tumors , and are commonly diagnosed on radiographs taken to investigate delayed eruption , malpositioning of an erupting tooth and overt retained teeth or as an incidental finding during routine dental radiographic examination [ 2-4 , 9 , 10 ] . There is no gender predilection [ 1 , 3 , 11-13 ] . They are usually asymptomatic , slowly growing and are seen in the tooth-bearing area of the jaws . At full maturity the size is usually 1-2 cm in diameter , but tumors up to 6 cm in size have been reported [ 1 ] . Radiographically , odontomas manifest as a dense radiopacity surrounded by radiolucent rim with a corticated border . Surgical removal is the treatment of choice for odontoma as they may continue to enlarge or pose problems to the adjacent teeth .
CLASSIFICATION
The radiographic , gross , and histologic features of odontomas assist in their classification .
COMPOUND ODONTOMA
This is the most common form of odontoma , which is usually seen in the maxillary anterior region [ 1 , 4 , 9 , 11 , 14 ] . Grossly , they resemble multiple miniature tooth-like structures ( Fig . 1 ). Radiographically , multiple radiopacities resembling rudimentary teeth ( denticles ) surrounded by a radiolucent rim with a thin corticated border is seen ( Fig . 2A ). Histologically , compound odontomas have all components of dental hard tissue arranged in a regular pattern , exhibiting tiny tooth form with some pulp tissue in the middle ( Fig . 3A ).
COMPLEX ODONTOMA
Complex odontomas are usually located in the mandibular posterior region [ 1 , 4 , 9 , 11 , 14 ] . This is the form of odontoma that can uncommonly be associated with other lesions [ 15-18 ] . Radiographically , it appears as a dense irregular amorphous mass surrounded by a radiolucent rim with a thin corticated border ( Fig . 2B ). Histologically , the dental hard tissue components ( enamel , dentin and cementum ) are arranged in a haphazard pattern ( Fig . 3B ).
CHALLENGES
Odontomas are known to have adverse effects on adjacent teeth by causing delayed eruption of teeth , impaction of the adjacent teeth , displacement of teeth , overt retention of teeth , root resorption , widening of follicular space from retention , and subsequently giving rise to inflammation or cyst formation within the jaw [ 1-4 , 9 , 11-14 , 16 , 18 ] . They are associated with congenital absence of a tooth [ 11 ] . Odontomas may also erupt into the oral cavity [ 14 , 19-21 ] . Uncommonly , odontomas have no effect on the adjacent teeth when they are not along the path of eruption of any tooth , making their detection more difficult . The permanent dentition is more frequently affected than the deciduous dentition by odontomas [ 4 , 9 , 11 , 13 ] .
Radiographically , there are other lesions which have a close resemblance to odontomas or maybe associated with them , resulting in radiographic misdiagnosis . Ameloblastic fibro-odontoma ( Fig . 4A ), is an uncommon odontogenic tumor with histologic features of both ameloblastic fibroma admixed with an odontoma . Radiographically , it resembles a complex odontoma within the follicular space of an impacted or malformed tooth . Ameloblastic fibro-odontomas are usually found in children and adolescents , they have been associated with blocking the path of an erupting teeth [ 1 ] . Calcifying cystic odontogenic tumor with odontoma ( Fig . 4B ), may exhibit aggressive features such as root resorption and expansile bone destruction which should help in the differentiation [ 1 ] . Thus , histologic evaluation is important for odontomas .
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