despite the vast literature reporting the prevalence of oral and maxillofacial diseases in the last decades , few studies have focused on biopsied lesions in the pediatric population . when comparing the occurrence of lesions in the pediatric population , variations regarding the age , prevalence and geographic distribution have been found . in brazil , only two studies carried out in the states of minas gerais7 and so paulo10 reported data about biopsied oral pediatric lesions in brazil . since that geographic distribution is a source of variation , the occurrence of lesions in pediatric patients in other parts of the country may be a relevant topic to be investigated . in this study , we performed a survey of oral and maxillofacial biopsies from children aged 0 to 14 years in a southern city of brazil . this study had the approval of the research ethics committee of the federal university of pelotas . the biopsies files from the center of diagnosis of oral diseases ( cddb ) of the dental school of the federal university of pelotas , were retrieved and those related to pediatric patients aged 0 to 14 years , during the period comprised between january 1983 and december 2002 , were selected . for the oral and maxillofacial lesions detected , data regarding to location , histopathological features , age and gender were evaluated . biopsies were then ranked under 13 categories , as follow : 

 hyperplastic / reactionary lesions : pyogenic granuloma , inflammatory fibrous hyperplasia , peripheral giant cell granuloma , peripheral ossifying fibroma , lymphoid hyperplasia , gingival hyperplasia , pulp polyp , parulis . benign neoplasms : fibroma , squamous papilloma , nevus , hemangioma , giant cell fibroma , lymphangioma , neurofibroma , congenital epulis , vascular hamartoma , lipoma , common wart . oral mucosa lesions : unspecific inflammatory process , acanthosis , hyperkeratosis , hematoma , foreign body granulomatous inflammation . cystic lesions : periapical cyst , paradental cyst , residual cyst , dentigerous cyst , eruption cyst , unclassified cysts of odontogenic origin , epidermoid cyst , median lingual cyst , pilar cyst , incisive canal cyst . odontogenic tumors : odontoma , keratocystic odontogenic tumor , ameloblastoma , myxoma , ameloblastic fibrodentinoma . bone pathologies : giant cell central granuloma , aneurysmal bone cyst , traumatic bone cyst , fibrous dysplasia , exostosis , central ossifying fibroma , massive osteolysis , ossifying periostitis , cherubism , reaction bone tissue , bone sequestrum . salivary gland lesions : mucocele , ranula , sialolithiasis , sialocyst , adenomatoid hyperplasia , pleomorphic adenoma , myoepithelioma . malignant neoplasms : rhabdomyosarcoma , langerhans cell histiocytosis , burkitt 's lymphoma , neuroblastoma , nevoid basal cell carcinoma . dental alterations : dens in dente , fusion , mesiodens , dental malformation , external dental resorption , pulp nodules , pulp necrosis , ankylosis.inconclusive diagnoses 
 
 hyperplastic / reactionary lesions : pyogenic granuloma , inflammatory fibrous hyperplasia , peripheral giant cell granuloma , peripheral ossifying fibroma , lymphoid hyperplasia , gingival hyperplasia , pulp polyp , parulis . benign neoplasms : fibroma , squamous papilloma , nevus , hemangioma , giant cell fibroma , lymphangioma , neurofibroma , congenital epulis , vascular hamartoma , lipoma , common wart . oral mucosa lesions : unspecific inflammatory process , acanthosis , hyperkeratosis , hematoma , foreign body granulomatous inflammation . cystic lesions : periapical cyst , paradental cyst , residual cyst , dentigerous cyst , eruption cyst , unclassified cysts of odontogenic origin , epidermoid cyst , median lingual cyst , pilar cyst , incisive canal cyst . odontogenic tumors : odontoma , keratocystic odontogenic tumor , ameloblastoma , myxoma , ameloblastic fibrodentinoma . bone pathologies : giant cell central granuloma , aneurysmal bone cyst , traumatic bone cyst , fibrous dysplasia , exostosis , central ossifying fibroma , massive osteolysis , ossifying periostitis , cherubism , reaction bone tissue , bone sequestrum . salivary gland lesions : mucocele , ranula , sialolithiasis , sialocyst , adenomatoid hyperplasia , pleomorphic adenoma , myoepithelioma . malignant neoplasms : rhabdomyosarcoma , langerhans cell histiocytosis , burkitt 's lymphoma , neuroblastoma , nevoid basal cell carcinoma . healthy tissues and teeth : pericoronal follicle , healthy tissue , natal tooth . 
 dental alterations : dens in dente , fusion , mesiodens , dental malformation , external dental resorption , pulp nodules , pulp necrosis , ankylosis . inconclusive diagnoses data were recorded and analyzed by descriptive statistics using the spss statistical package ( spss inc . this study had the approval of the research ethics committee of the federal university of pelotas . the biopsies files from the center of diagnosis of oral diseases ( cddb ) of the dental school of the federal university of pelotas , were retrieved and those related to pediatric patients aged 0 to 14 years , during the period comprised between january 1983 and december 2002 , were selected . for the oral and maxillofacial lesions detected , data regarding to location , histopathological features , age and gender were evaluated . biopsies were then ranked under 13 categories , as follow : 

 hyperplastic / reactionary lesions : pyogenic granuloma , inflammatory fibrous hyperplasia , peripheral giant cell granuloma , peripheral ossifying fibroma , lymphoid hyperplasia , gingival hyperplasia , pulp polyp , parulis . benign neoplasms : fibroma , squamous papilloma , nevus , hemangioma , giant cell fibroma , lymphangioma , neurofibroma , congenital epulis , vascular hamartoma , lipoma , common wart . oral mucosa lesions : unspecific inflammatory process , acanthosis , hyperkeratosis , hematoma , foreign body granulomatous inflammation . cystic lesions : periapical cyst , paradental cyst , residual cyst , dentigerous cyst , eruption cyst , unclassified cysts of odontogenic origin , epidermoid cyst , median lingual cyst , pilar cyst , incisive canal cyst . odontogenic tumors : odontoma , keratocystic odontogenic tumor , ameloblastoma , myxoma , ameloblastic fibrodentinoma . bone pathologies : giant cell central granuloma , aneurysmal bone cyst , traumatic bone cyst , fibrous dysplasia , exostosis , central ossifying fibroma , massive osteolysis , ossifying periostitis , cherubism , reaction bone tissue , bone sequestrum . salivary gland lesions : mucocele , ranula , sialolithiasis , sialocyst , adenomatoid hyperplasia , pleomorphic adenoma , myoepithelioma . malignant neoplasms : rhabdomyosarcoma , langerhans cell histiocytosis , burkitt 's lymphoma , neuroblastoma , nevoid basal cell carcinoma . dental alterations : dens in dente , fusion , mesiodens , dental malformation , external dental resorption , pulp nodules , pulp necrosis , ankylosis.inconclusive diagnoses 
 
 hyperplastic / reactionary lesions : pyogenic granuloma , inflammatory fibrous hyperplasia , peripheral giant cell granuloma , peripheral ossifying fibroma , lymphoid hyperplasia , gingival hyperplasia , pulp polyp , parulis . benign neoplasms : fibroma , squamous papilloma , nevus , hemangioma , giant cell fibroma , lymphangioma , neurofibroma , congenital epulis , vascular hamartoma , lipoma , common wart . oral mucosa lesions : unspecific inflammatory process , acanthosis , hyperkeratosis , hematoma , foreign body granulomatous inflammation . cystic lesions : periapical cyst , paradental cyst , residual cyst , dentigerous cyst , eruption cyst , unclassified cysts of odontogenic origin , epidermoid cyst , median lingual cyst , pilar cyst , incisive canal cyst . odontogenic tumors : odontoma , keratocystic odontogenic tumor , ameloblastoma , myxoma , ameloblastic fibrodentinoma . bone pathologies : giant cell central granuloma , aneurysmal bone cyst , traumatic bone cyst , fibrous dysplasia , exostosis , central ossifying fibroma , massive osteolysis , ossifying periostitis , cherubism , reaction bone tissue , bone sequestrum . salivary gland lesions : mucocele , ranula , sialolithiasis , sialocyst , adenomatoid hyperplasia , pleomorphic adenoma , myoepithelioma . malignant neoplasms : rhabdomyosarcoma , langerhans cell histiocytosis , burkitt 's lymphoma , neuroblastoma , nevoid basal cell carcinoma . healthy tissues and teeth : pericoronal follicle , healthy tissue , natal tooth . 
 dental alterations : dens in dente , fusion , mesiodens , dental malformation , external dental resorption , pulp nodules , pulp necrosis , ankylosis . data were recorded and analyzed by descriptive statistics using the spss statistical package ( spss inc . throughout the study period , 9,465 biopsies were performed , 625 ( 6.6% ) being from pediatric patients . figure 1 shows the patient distribution for age groups and the prevalence of cases in ages between 7 and 14 years ( 89.0% ) . maxilla was the most commonly affected site , followed by the mandibular region , and the lower lip ( figure 2 ) . the most common conditions diagnosed individually were mucocele ( 17.2% ) , pericoronal follicle ( 9.1% ) , and dentigerous cyst ( 8.6% ) ( figure 3 ) . regarding the diagnosis categories , the largest number of cases represented the salivary gland lesions , cystic lesions , and healthy tissues / teeth groups , in this order ( table 1 ) . mucocele was also the most common condition ( 89.2% ) in the salivary gland lesion category . dentigerous cyst was the most frequent condition in the cystic lesion group ( 46.1% ) , followed by periapical cyst ( 36.7% ) . fibroma was the most prevalent lesion in the benign neoplasm group , followed by squamous papilloma , nevus , and hemangioma ( figure 4 ) . malignant lesions were rarely diagnosed , corresponding to 1.2% of the total sample size ( table 2 ) . previous studies2,5,8 investigating the occurrence of oral and maxillofacial lesions in pediatric patients showed that the number of pediatric biopsies generally accounts for less than 10% of all cases referred to histopathology services . similar prevalence was observed , in the present study , since 6.6% of the total number of biopsies was conducted in children aged 7 to 14 years . recently , jones and franklin4 performed a retrospective investigation of oral and maxillofacial pathologies within a 30-year period . those authors verified that biopsies in patients aged between 0 and 16 years represented 8.2% of all cases reported . other authors found percentages of pediatric biopsies varied between 11 and 13% of the total number of cases3,6,9 . these higher values probably appear as consequence of setting a higher upper age threshold for the referred casuistic . in the present findings , a higher concentration of specimens from older children sousa , et al.10 also observed a higher occurrence of lesions in children between 9 and 14 years of age . regarding the prevalence in genders the evaluated material comprised a wide spectrum of lesions , which ranged from inflammatory processes to malignant tumors . additionally , a considerable part of the sample was formed by healthy tissues , especially by the pericoronal follicle ( 9.2% ) . the files reviewed in this study showed that mucocele as the most common of all lesions ( 17.2% ) , followed by dentigerous cyst ( 8.6% ) and unspecific inflammatory process ( 7.0% ) . taken together , these lesions accounted for 42.1% of the total number of biopsies in children . likewise , several authors2,9,10 have considered the mucus extravasation phenomenon as the most frequent lesion in children . mucocele also appears among one of the main conditions diagnosed in pediatric populations in a previous review of the most common labial lesions1 . maia , et al.7 ranked follicular cyst , fibrous hyperplasia , mucocele , and pericoronal follicle as the most frequent conditions diagnosed in their study . another point that that should be highlighted is the characterization of the difference between dentigerous cyst and pericoronal follicle . regarding this topic , many studies are based on radiographic investigations , which are susceptible to observer 's bias , sparking off diagnostic controversies . also , the classification criteria are usually different for each study , which leads to discrepant results . considering the salivary gland lesion group , when all neoplastic lesions are considered , odontoma occurrence was higher than that observed of fibroma , which represented 28% of all nonodontogenic benign neoplasms . however , if odontogenic origin of benign neoplasms is taken in account as a parameter for tumor classification , odontoma would still be ranked ahead of all other tumors recorded in the present study . in this aspect , our data are corroborated by those of tomizawa , et al.11 , who performed a retrospective study of lesions in japanese children . in their analysis , regarding benign neoplasms , fibroma was the most prevalent diagnosed condition , followed by squamous papilloma , nevus , and hemangioma . therefore , hemangioma occurrence might be even higher than the number of cases reported herein . on the other hand , the number of malignant lesions was very small in our study , corresponding to only 8 cases ( 1.2% of the biopsies ) . similar results have been reported by jones and franklin4 , who detected malignity in 1% of the all analyzed biopsies . additionally , the most commonly affected sites were the maxilla , mandible , lower lip , and gingiva . maaita , et al.6 mentioned the mandible and the lip as the most prevalent sites , while das and das3 found a higher prevalence in the periodontium and the lip . another essential aspect to be addressed while analyzing our data is the existence of variations in the prevalence of typical lesions of any given population group . moreover , it is worth mentioning that the data retrieved in the present study do not reproduce the prevalence of oral and maxillofacial lesions diagnosed by dentists in the clinical practice , since some pathologies , like herpes , aphthous ulcerations and even hemangioma , are diagnosed based on clinical features , while the present study included biopsied lesions exclusively . generally , the results of the present study are in line with those reported in the literature concerning the most prevalent lesions in the pediatric population . most detected lesions were benign , and malignant lesions were diagnosed in a very small part of the whole sample . the epidemiologic survey of oral and maxillofacial lesions biopsied in children is important to determine lesion prevalence in different geographic areas . this type of study also contributes with the characterization of lesion specificities in the pediatric population , providing to general dentists and pediatric dentists a solid background for diagnosis and treatment of the entities .
despite the large number of published cases about oral and maxillofacial pediatric lesions , the literature is scarce on epidemiological studies regarding the prevalence of these entities . 
 this study retrieved oral and maxillofacial pediatric lesions from the center of diagnosis of oral diseases ( cddb ) at the dental school of the federal university of pelotas ( ufpel ) , comprising a 20-year period ( 1983 - 2002 ) . from the total of 9,465 biopsies received in this period , 625 ( 6.6% ) were from children aged 0 to 14 years . 
 regardless of the histopathological diagnosis , patient data referring to lesion location , sex and age were collected . 
 diagnoses were grouped in 13 categories . as much as 89% of the cases occurred in patients aged 7 to 14 years ( 53% in females and 47% in males ) . 
 mucocele ( 17.2% ) was the most common type of lesion , followed by dentigerous cyst ( 8.6% ) . 
 in the category of odontogenic tumors , odontoma was the most frequent lesion ( 64.2% ) . 
 malignant lesions were observed in a small section of the sample ( 1.2% ) . 
 generally , the results of the present study are in line with those reported in the literature concerning the most prevalent lesions in the pediatric population . 
 most lesions were benign , and malignant lesions were diagnosed in a very small part of the sample .