odontoma , the complex type is a tumor - like malformation in which all the dental tissues are represented , although in a more or less disorganized pattern . it is one of the most common odontogenic tumors with the relative frequency that varies between 5% and 30% . the active growth phase of the complex odontoma is during the formation of the dentition ; with preponderance of the cases diagnosed during the second decade of life . the posterior portion of the mandible is the most frequent site of occurrence followed by anterior maxilla . clinically , it presents as slow growing , expanding lesion ; majority of them being asymptomatic , often an incidental finding on a radiograph or diagnosed through failure of eruption of adjacent permanent teeth . radiographically , the lesion commences as a well - defined radiolucency with progressive deposition of radio - opaque material of a nodular nature . exposure of the tumor through the oral mucosa is an exception ; that may be accompanied by pain , infection associated with suppuration or inflammation of the adjacent soft tissues . in view of its exception , a case of complex odontoma in a 22-year - old male patient , with an apparent eruption in maxillary posterior segment associated with agenesis of maxillary second molar and impacted third molar is reported herewith . a 22-year - old apparently healthy male patient reported to the out - patient department , m.m college of dental sciences and research , mullana ( haryana , india ) , for the evaluation of a malformed tooth with respect to the left maxillary posterior region with 7 months of evolution . intraoral examination revealed a solitary , yellowish tooth - like mass measuring 2 cm  3 cm at the level of alveolar ridge distal to the left maxillary first molar . on palpation , the mass was hard in consistency , nontender , had irregular surface and exhibited no mobility . the lesion was asymptomatic with no infection or ulceration of the surrounding mucosa [ figure 1a and b ] . ( a and b ) intra - oral aspect of the erupted odontoma ( arrows ) ( c - f ) preoperative radiographs depicting a dense radio - opaque mass distal to 26 , associated with the crown of impacted 28 ( arrows ) to establish the precise location of the lesion , and its relation to the surrounding anatomical structures ; complementary studies were requested including intraoral periapical view , computed tomography scan and three dimensional reconstruction scan . these revealed uniformly dense , irregular radio - opaque mass surrounded by a corticated border , located distal to the erupted 26 , associated with agenesis of 27 and impacted 28 , seen in close approximation to the tumor [ figure 1c  f ] . in view of these findings , informed consent was obtained from the patient . under general anesthesia , access to the tumor was achieved through intraoral approach and the retrieved specimen was examined histologically . grossly , the specimen appeared as yellowish calcified mass with rough surface ; showing no resemblance to any tooth of the normal series . microscopic examination of the decalcified sections stained with hematoxylin and eosin revealed a disordered mixture of dental tissues enclosing clefts that contained mature enamel , lost during decalcification [ figure 2 ] ; suggestive of complex odontoma . the postoperative course was uneventful , with no evidence of clinical and radiological recurrence during 6 months follow - up period . photomicrograph of the decalcified section reveals disordered mixture of dental tissues and clefts occupied by enamel before decalcification ( h and e ) the etiology is uncertain ; but proposed reasons include local trauma , hereditary anomalies ( gardner 's syndrome , hermann 's syndrome , basal cell nevous syndrome ) , odontoblastic hyperactivity , infection , persistence of portion of dental lamina between the tooth germs or inheritance through a mutant gene or interference , possibly postnatally with the genetic control of tooth development . recurrent infection following eruption has been reported , but no such findings were observed in the present case , with the lesion being completely asymptomatic . the reason for eruption is ascribed to the eruptive forces of the apparently impacted teeth . however , in case of missing tooth ; alveolar bone remodeling , sequestration of the overlying bone or reactive growth of the capsule surrounding an odontoma , may contribute to this phenomenon . the suggested reasons for the eruption of odontoma do fit well with respect to the present case . further , the mechanism of eruption differs from that of normal tooth eruption ; attributed to the absence of periodontal ligament and root in odontoma . therefore , the force required to move the odontoma is not linked to the contractility of the fibroblasts , as in the case of teeth . most odontomas ( 70% ) are associated with pathological anomalies that include devitalization , malformation , aplasia , malposition and impaction of the neighboring teeth . in the present case , the erupted odontoma was associated with aplasia of the maxillary second molar and impaction of the maxillary third molar ; a unique finding . the radiographic characteristics are usually diagnostic . however , during its development , complex odontoma may resemble ameloblastic fibroma or fibro - odontoma ; or may be confused with an osteoma or other highly calcified bone lesions . conservative surgical enucleation is considered to be the treatment of choice in most cases of complex odontoma . as , these are often associated with impacted teeth , the possibility of eruption of the impacted tooth , after a presumed obstructive odontoma has been surgically removed is an important issue . in children , the impacted permanent teeth , depending on the age of the child and the tooth development , may be left to erupt spontaneously or may be guided to occlusion via orthodontic traction . in any case , follow - up is essential following odontoma excision . however , in the present case , the associated impacted tooth was removed along with the tumor taking into consideration that it was severely malpositioned with no possibility to erupt . in those cases , where an impacted tooth is not involved , immediate surgical intervention is not absolutely necessary , considering the high accuracy of the radiographic diagnosis , and the very limited potential of the odontomas . since , odontomas represent a large proportion of jaw tumors , therefore , sound knowledge of their characteristics is necessary for establishment of proper diagnosis and management . although , these have strictly limited growth potential ; the mass should be enucleated surgically as a potential source of obstruction to erupting teeth or as a possible focus for infection .
complex odontomas , hamartomas of aborted tooth development , mainly occur in posterior part of the mandible and rarely erupt into the oral cavity . 
 the spontaneous eruption may be associated with pain , inflammation of adjacent soft tissues or recurrent infection . 
 the present case of complex odontoma is of particular interest due to its apparent eruption in the maxillary posterior segment , its association with agenesis of the second molar and impacted third molar ; with the lesion being completely asymptomatic .