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studies concerning the epidemiology in dentistry have showed that dental caries and periodontal diseases are the most prevalent pathologies that affect the oral cavity .
previous studies performed by american researchers had suggested that dental caries was the main reason for teeth extraction , and other studies accomplished in new zealand , sweden , and even in brazil confirmed that caries may lead to tooth mortality [ 15 ] . on the other hand , some studies suggested that periodontal disease was the most prevalent reason that leads to tooth loss .
thus , controversial findings could be explained by differences in the characteristics of the study population , immunological and genetic factors , cultural beliefs , and socioeconomic characteristics , among others .
immunological and genetic reasons are some of the contributory factors that may explain why some populations exposed to the same bacterial etiologic factors did not develop similar pathological conditions [ 6 , 7 ] .  
populations with poorer socioeconomic conditions have shown higher prevalence and extent of teeth mortality , which increases with aging [ 810 ] .
the prevalence , extent , and risk indicators for tooth loss were studied in a representative brazilian population , showing that 94% of the subjects had experienced tooth loss .
the authors verified a tooth mortality mean of 11.2 , ranging from 5.5 to 20.2 teeth in subjects from 30 to 39 years old and 60 + years age groups , respectively ; gender , socioeconomic status , cigarette smoking , caries experience , and attachment loss were important risk indicators .   on the other hand , a decline in the tooth loss can be verified in developed countries in the last years [ 7 , 11 , 12 ] , which can be explained by preventive programs and higher accessibility to the oral health care that have been decreasing the extractions [ 13 , 14 ] .
brazil is a country in development progress ( underdeveloped ) , and some studies verified the prevalence of tooth extractions in brazilians [ 4 , 810 , 15 , 16 ] , but few of them have verified the reasons for the tooth mortality in this population .
thus , the aim of this study was to describe the epidemiological data of the prevalence and reasons for teeth extractions in a convenience sample of brazilians .
this study was approved by the ethics committee in human of araraquara dental school ( unesp  process number 45/99 ) .
a review of 800 clinical records was performed to select 439 patients with tooth loss from 1999 up to 2002 in dental clinics at state university of so paulo ( unesp ) , araraquara city , brazil ( sudeste region ) . from the 800 clinical records ,
361 subjects were excluded by x - ray absence or absence of specifications of the reasons for tooth mortality , and 439 patients were enrolled in this study . from these 439 patients , 800 teeth with x - ray and specifications of reasons for tooth loss
the clinical records were evaluated considering the gender and the age groups . additionally , the prevalence of tooth loss was evaluated by reasons of extractions and type of teeth ( molars , premolars , incisors and canines ) .
the reasons for teeth mortality were adapted based on cahen et al .   as follows : ( 1 ) caries : it is properly caries ; ( 2 ) endodontic problems , such as pulp inflammation , necrosis , or even tooth fracture ; ( 3 ) periodontal diseases : tooth extraction by periodontal attachment loss ; ( 4 ) eruption problems : tooth loss by dental impacation ; ( 5 ) prosthetics : indication for extraction by prosthetic reasons ; ( 6 ) trauma : extractions by external trauma ; ( 7 ) orthodontics : tooth extraction by orthodontic indications ; ( 8) occlusal problems : extractions by occlusal dysfunction , such as extrusion ; ( 9 ) other reasons : any other determined reasons , such as iatrogenic factors .
a single examiner accomplished the clinical records assessment , and data was described in a proper form .  
chi - square statistics (  ) were applied , considering p < 0.05 as a statistical significant difference . adjusted residual chi - square (  )
was calculated , considering 1.96 (  = 0.05 ) and 2.573 (  = 0.01 ) .

 table 1 shows the data collected from 1999 to 2002 , the number of subjects , and teeth included in this study .
the number of subjects according to age groups and gender ratio can be verified in table 2 , that shows a similar prevalence of tooth loss between gender in all age groups ( p = 0.67 ) .  
table 3 shows that the groups with range from 35 to 44 years , 45 to 54 years , and 55 to 64 years revealed significantly greater number of teeth extractions than other age groups ( p < 0.0001 ) .
the anterior teeth loss increased with aging and the extractions of premolars and molars decreased with aging , while the tooth mortality of premolar and molar were higher in younger people ( table 4 ) .
the results showed that caries and periodontal diseases were statistically significant reasons for tooth loss when compared to the other factors ( p < 0.0001 ; table 5 ) .  
table 6 shows that caries was the most prevalent reason for tooth mortality among young and adults up to 44 years old , while the periodontal disease was the main reason for extractions from 45 years old until range of 81 years .
other reasons for teeth extractions can be verified as follows : iatrogenic factors ( 9.9 ) , eruption problems ( 6.4 ) , orthodontics ( 5.7 ) , prosthetic indication ( 3.6 ) , trauma ( 2.6 ) , and occlusion problems ( 1.1 ) .
it can be seen in table 6 that tooth mortality for some reasons such as orthodontic , occlusal problems , and other reasons was significantly higher ( p < 0.0001 ) among younger , and by prosthetic reasons was significantly higher in older people ( p < 0.0001 ) .
our data showed that the number of male and female subjects with tooth loss was similar among all age groups .
conversely , the study by barbato et al .   verified higher prevalence of tooth mortality in women than in men .
other studies assessed the tooth mortality among the urban and rural adult population of dharwad district ( india ) in 1223 subjects ( 685 urban and 538 rural ) and found that females compared to males had higher tooth loss .
moreover , our findings showed that the age group between 35 to 44 years old presented a mean tooth loss of 2.3 , which was lower than the mean of 11 verified in the other study .
this difference could be explained by the sample size of the studies , which was of 439 brazilians in our sample and a major population of 13.431 brazilians in the study by barbato et al . .
our findings showed that among adolescents aged from 15 to 19 years , the prevalence of tooth extraction was 8.0% , while in a greater population of 16.833 brazilian adolescents it was 38.9% .
probably this difference could also be related to the sample size of the studies that is too discrepant .
the results in the present study demonstrated higher missing teeth for premolars ( 43.1 to 51.6% ) and molars ( 48.4 to 51.0% ) among the youngest subjects ( 15 to 24 years ) , and the dental caries was the main reason for teeth extractions ( 67.2% ) .
our findings are in agreement with previous studies that have demonstrated that the first molars were the most prevalent missing teeth in brazilian younger people [ 9 , 15 , 19 ] .
barbato and peres   found more than 55% of missing first molars , and dental caries experiences were found in 92.71% of all teeth lost .
other studies also suggested that the first molars were the most frequently missing teeth in subjects aged from 14 to 29   and from 13 to 16 years .  
the caries ( 38.4% ) and periodontal disease ( 32.3% ) were the most prevalent conditions for tooth mortality in the present study with similar prevalence .
conversely , other study on brazilians suggested that the main reason for tooth extraction was the caries ( 70.3% ) and not the periodontal disease ( 15.1% ) , but this study showed findings of a small sample with 404 teeth extracted . in a caribbean population 
antigua , viagnarajah   also suggested that caries was the main reason for tooth extraction ( 61.6% ) , and the periodontal disease was the next more frequent reason for tooth loss ( 29.9% ) .  
our results showed that periodontal disease was more prevalent among older subjects over 40 years of age .
some studies are in agreement with our findings , showing that periodontitis became the most prevalent reason for tooth mortality in people near 40 years old [ 10 , 2026 ] .
in addition , other reasons for teeth extractions were found in the present study as follows : iatrogenic factors ( 9.9% ) , eruption problems ( 6.4% ) , orthodontics ( 5.7% ) , prosthetic indication ( 3.6% ) , trauma ( 2.6% ) , and occlusal problems ( 1.1% ) .
caldas   also evaluated other reasons for extractions in 404 teeth , such as prosthetic reasons ( 6.4% ) , third molar - eruption disorders ( 3.7% ) , orthodontic reasons ( 2.5% ) , and trauma or patients request ( 1% ) , which showed lower prevalence than the caries and periodontal disease .  
considering that few studies evaluated reasons for teeth losses in brazilians , our retrospective study may be useful in clinical dentistry and used as baseline data regarding prevalence and reasons for teeth extractions in other populations ; moreover , other prospective studies might be performed .
within the limits of this study , it can be suggested that some reasons for tooth loss were age dependent , but the caries and the periodontal diseases were the main reasons for tooth mortality in this brazilian sample .
purpose . to evaluate the prevalence and reasons for teeth extractions in a sample from a dental clinic in brazil 
 . methods . 
 the prevalence of teeth mortality was analyzed by gender , age , tooth type and reasons for extraction on 800 teeth of 439 subjects , whose data was collected in clinical records in a convenience sample . results . 
 the groups with range from 35 to 44 years , 45 to 54 years and 55 to 64 years revealed significantly greater number of teeth extractions than other age groups ( p < 0.0001 ) . 
 the anterior teeth loss increased significantly with aging , while the tooth mortality of premolar and molar were higher in younger people . 
 the caries was the more prevalent reason for tooth mortality among young and adults up to 44 years old , while the periodontal disease was the main reason for extractions from 45 years old until range of 81 years ( p < 0.0001 ) . 
 conclusions . 
 it can be suggested that some reasons for tooth loss were age - dependent , but the caries and the periodontal diseases were the main reasons for tooth mortality in this brazilian sample .