the abuse of illicit drugs such as opiates is a worldwide problem for both the users and society . drug abuse is linked with a number of diseases , including hiv and hbv infections and other communicable diseases , and many drug addicts die of either the drug itself or complications from use everyday . in china , the number of drug addicts is estimated to be more than 1,160,000 in 2005 , and 78.3% of them are heroin users . there is an urgent need for a better health care aiming at prevention and treatment of drug addiction . methadone maintenance treatment for the management of opioid dependence is a substitution therapy that requires daily dosing with methadone solution under close monitoring by clinic staff . methadone treatment allows for the patients to decrease or completely stop their use of illegal drugs and drug - related high - risk behaviors . by the end of 2008 , there were over 500 methadone maintenance treatment clinics , and 95,000 users receiving treatment in mainland china . in sichuan province alone , the number of illegal drug users who have received this treatment is over 5000 . published studies have shown that the oral health of drug addicts is poorer than that of the general population [ 46 ] . for former heroin users who have received or are receiving methadone treatment , the prevalence rates of caries and periodontal diseases are higher than that in the general population . there are a number of reasons for this , including a lack of concern about oral health by the patients due to their altered mental state , damage due to the illicit drugs or methadone , or differing oral health care needs for other reasons ( eg , poverty or dietary problems ) . there is an urgent need for effective approaches to monitoring , preventing and treating oral health problems among these individuals . although the harmful effects of drug abuse on general and mental health have been well - documented , the information about the oral health status of former heroin users receiving methadone treatment in china is generally lacking . this study was designed to investigate and analyze the oral health status of former heroin users treated with methadone in chengdu , the capital of sichuan province in southwestern china . we speculate that the information obtained can then be used to better prevent and treat various oral health issues among this population . we recruited 445 former heroin users , including 317 males and 128 females , who were receiving methadone treatment in chengdu . the mean age of these subjects was 35.21 years , ranging from 20 to 59 years old . oral health examinations using a portable dental chair were carried out using the optical fiber projection plane dental reflector and community periodontal index ( cpi ) probe according to the who basic oral health survey methods ( version 4 , 1997 ) . the decayed / filled teeth index ( dft ) was used to record decayed teeth ( dt ) and filled teeth ( ft ) , and the presence of decayed root ( d - root ) , residual roots , missing teeth ( mt ) , and dental prosthetic restoration were also recorded . because of the poor periodontal health of the former heroin users , it was difficult to determine whether the missing teeth were a result of caries or periodontal disease . for this reason , the status of missing teeth was listed separately from the caries status , which was reflected by the prevalence rate of decayed and filled teeth and the mean decayed and filled teeth score . while all 32 teeth in the oral cavity were examined in this investigation for patients who had them in order to accurately reflect the teeth and dentition status , the missing teeth rate was determined excluding the third molars because of variations in tooth eruption . the consistency of df and periodontal examinations were evaluated , and the kappa values were 0.87 and 0.85 , respectively . a database of the results was set up , and the data were analyzed by  test , independent t - test , or single factor analysis of variance , as appropriate , using spss 12.0 software . we recruited 445 former heroin users , including 317 males and 128 females , who were receiving methadone treatment in chengdu . the mean age of these subjects was 35.21 years , ranging from 20 to 59 years old . oral health examinations using a portable dental chair were carried out using the optical fiber projection plane dental reflector and community periodontal index ( cpi ) probe according to the who basic oral health survey methods ( version 4 , 1997 ) . the decayed / filled teeth index ( dft ) was used to record decayed teeth ( dt ) and filled teeth ( ft ) , and the presence of decayed root ( d - root ) , residual roots , missing teeth ( mt ) , and dental prosthetic restoration were also recorded . because of the poor periodontal health of the former heroin users , it was difficult to determine whether the missing teeth were a result of caries or periodontal disease . for this reason , the status of missing teeth was listed separately from the caries status , which was reflected by the prevalence rate of decayed and filled teeth and the mean decayed and filled teeth score . while all 32 teeth in the oral cavity were examined in this investigation for patients who had them in order to accurately reflect the teeth and dentition status , the missing teeth rate was determined excluding the third molars because of variations in tooth eruption . the consistency of df and periodontal examinations were evaluated , and the kappa values were 0.87 and 0.85 , respectively . a database of the results was set up , and the data were analyzed by  test , independent t - test , or single factor analysis of variance , as appropriate , using spss 12.0 software . the mean age of these subjects was 35.21 , ranging from 20 to 59 years old . eleven , 290 , 136 and 8 people had middle school , high school , college , and postgraduate education , respectively . the duration of illicit drug use ranged from 1 year to 32 years , and the duration of methadone treatment ranged from 1 to 15 months . the daily dosage of methadone was 8150 ml , which was adjusted daily , and the mean maintenance dosage was 40 ml . there were 329 smokers in this study ( 272 males and 57 females ) , and 334 subjects ( 227 males and 107 females ) brushed their teeth ( once or twice ) everyday . only 10.11% of subjects ( 30 males and 15 females ) had received dental treatment in the past year , 11 subjects had a tooth or teeth extracted , 27 subjects had a tooth filled and 7 subjects had dental prosthetic restoration performed . the detailed prevalence and scores of dft , grouped by sex , are shown in table 1 . as a general trend , females had higher ( worse ) prevalence / scores than the males , which is similar to the results of the chinese general population . the mean scores reflecting the presence of decayed teeth and decayed / filled teeth of female subjects was higher than male subjects ( table 1 , p<0.05 ) . as determined by the  test , the prevalence rate of decayed teeth and decayed / filled teeth of female subjects was higher than for males ( table 1 , p<0.05 ) . the dft scores were related to sex and the duration of drug abuse by linear regression ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone maintenance therapy ) . as shown in table 2 , we also observed ( by  test and single - factor analysis of variance ) that the prevalence of missing teeth increased as the age of subjects increased ( table 2 , p<0.05 ) . the prevalence of decayed roots for all subjects was 21.80% , the mean decayed root score was 0.62 , the residual root prevalence was 42.02% , and the mean residual root score was 1.06 . the prevalence of decayed root and of residual roots in women was significantly higher than that in men as determined by  and independent t - tests ( p<0.05 ) ( table 3 ) . the decayed root scores and the residual root scores related to sex and the duration of drug abuse by linear regression ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone therapy ) . in addition , there were a total of 38 patients who had dental prosthetic restoration . twenty subjects had fixed dental prosthetic restoration , and 18 subjects had removable prosthesis . the total overall rate of dental prosthetic restoration was 8.54% of the patients . there are no differences in this parameter between women and men . the distributions of the cpi scores of 0 , 1 , 2 , 3 , and 4 were 0% , 2.92% , 66.29% , 27.64% , and 2.70% , respectively . the cpi scores related to the sex , age and the duration of drug abuse by bivariate correlations ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone therapy ) . the overall frequency of gingival bleeding in all the subjects was 99.55% , the frequency of dental calculus was 96.63% , the frequency of shallow pocket was 30.34% , and the frequency of deep periodontal pocket was 2.70% . for the prevalence of gingival bleeding , there were no differences between men and women or among various age groups ( table 4 ) . as determined using the  test , the prevalence of calculus deposition , presence of shallow periodontal pockets , and presence of deep periodontal pockets were higher in men than women ( p<0.05 ) ( table 4 ) . the prevalence of calculus formation and the incidence of shallow and deep periodontal pockets increased with the age of the subjects ( p<0.05 ) ( table 4 ) . additionally , the dental calculus average section count in all the subjects treated with methadone was 3.99 , and the dental calculus average section count in males and females were 4.23 and 3.37 , respectively . the dental calculus average section count in subjects in men was larger than in women ( all p<0.05 ) . the dental calculus average section count of subjects , separated by age ( < 35 , 3544 , > 45 ) , were 3.49 , 4.37 , and 4.44 , respectively . the mean age of these subjects was 35.21 , ranging from 20 to 59 years old . eleven , 290 , 136 and 8 people had middle school , high school , college , and postgraduate education , respectively . the duration of illicit drug use ranged from 1 year to 32 years , and the duration of methadone treatment ranged from 1 to 15 months . the daily dosage of methadone was 8150 ml , which was adjusted daily , and the mean maintenance dosage was 40 ml . there were 329 smokers in this study ( 272 males and 57 females ) , and 334 subjects ( 227 males and 107 females ) brushed their teeth ( once or twice ) everyday . only 10.11% of subjects ( 30 males and 15 females ) had received dental treatment in the past year , 11 subjects had a tooth or teeth extracted , 27 subjects had a tooth filled and 7 subjects had dental prosthetic restoration performed . the detailed prevalence and scores of dft , grouped by sex , are shown in table 1 . as a general trend , females had higher ( worse ) prevalence / scores than the males , which is similar to the results of the chinese general population . the mean scores reflecting the presence of decayed teeth and decayed / filled teeth of female subjects was higher than male subjects ( table 1 , p<0.05 ) . as determined by the  test , the prevalence rate of decayed teeth and decayed / filled teeth of female subjects was higher than for males ( table 1 , p<0.05 ) . the dft scores were related to sex and the duration of drug abuse by linear regression ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone maintenance therapy ) . as shown in table 2 , women and men had differing prevalences of missing teeth . we also observed ( by  test and single - factor analysis of variance ) that the prevalence of missing teeth increased as the age of subjects increased ( table 2 , p<0.05 ) . the prevalence of decayed roots for all subjects was 21.80% , the mean decayed root score was 0.62 , the residual root prevalence was 42.02% , and the mean residual root score was 1.06 . the prevalence of decayed root and of residual roots in women was significantly higher than that in men as determined by  and independent t - tests ( p<0.05 ) ( table 3 ) . the decayed root scores and the residual root scores related to sex and the duration of drug abuse by linear regression ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone therapy ) . in addition , there were a total of 38 patients who had dental prosthetic restoration . twenty subjects had fixed dental prosthetic restoration , and 18 subjects had removable prosthesis . the total overall rate of dental prosthetic restoration was 8.54% of the patients . there are no differences in this parameter between women and men . the distributions of the cpi scores of 0 , 1 , 2 , 3 , and 4 were 0% , 2.92% , 66.29% , 27.64% , and 2.70% , respectively . the cpi scores related to the sex , age and the duration of drug abuse by bivariate correlations ( p<0.05 ) ( including education , occupation , sex , age , duration of drug abuse and methadone therapy ) . the overall frequency of gingival bleeding in all the subjects was 99.55% , the frequency of dental calculus was 96.63% , the frequency of shallow pocket was 30.34% , and the frequency of deep periodontal pocket was 2.70% . for the prevalence of gingival bleeding , there were no differences between men and women or among various age groups ( table 4 ) . as determined using the  test , the prevalence of calculus deposition , presence of shallow periodontal pockets , and presence of deep periodontal pockets were higher in men than women ( p<0.05 ) ( table 4 ) . the prevalence of calculus formation and the incidence of shallow and deep periodontal pockets increased with the age of the subjects ( p<0.05 ) ( table 4 ) . additionally , the dental calculus average section count in all the subjects treated with methadone was 3.99 , and the dental calculus average section count in males and females were 4.23 and 3.37 , respectively . the dental calculus average section count in subjects in men was larger than in women ( all p<0.05 ) . the dental calculus average section count of subjects , separated by age ( < 35 , 3544 , > 45 ) , were 3.49 , 4.37 , and 4.44 , respectively . there are a number of possible reasons for the poor oral health of the former heroin users . firstly , overall awareness of oral health care in this population is low , and few of the subjects regularly brushed their teeth the recommended two times per day . it has also been reported that the intake of sugar by drug addicts is higher than by the general population . additionally , the use of many medications is associated with xerostomia , and it has been shown that the amount of saliva produced by drug abusers is decreased , creating a favorable environment for the formation of plaque and eventual dental caries . thus , the illicit drug abuse and methadone treatment both could lead to xerostomia , which is associated with dental caries . although the effect of methadone itself on the formation of caries has not been demonstrated , it has been reported that the methadone was not sugar - free   and the ph of a 1% water solution of methadone is 4.55.5 , suggesting that taking methadone could increase oral acidity , thus increasing the rate of caries . it has also been shown that the immune function of methadone patients decreases , with lower levels of igg , igm , and especially iga , the decrease of which may result in an increased rate of caries   compared to the general population . it is also possible that the concentration of microelements in the oral cavity may have changed , influencing the capacity of teeth to resist acid . in this study , the reason may be that the duration of using methadone was short , the longest only15 months , but the oral status did relate to the duration of drug abuse . caries prevalence and mean caries score increase with increasing age ; however , we did not observe any significant differences between groups based on age . by linear regression , the caries scores only related to sex and the duration of drug abuse . nevertheless , there was a tendency toward an increase in the prevalence and score of missing teeth as subject age increased . the detection rates of gingival bleeding , calculus , and shallow pockets and deep periodontal pockets in the former heroin users treated with methadone in chengdu were higher than in the general adult population in the same area . the cpi index was used in this periodontal examination . because only the worst condition was recorded in every zone , some periodontal conditions may have been overestimated , especially the probing bleeding , which may have been overestimated by as much as 50% . however , other reports have indicated that gingival bleeding was observed in most illegal drug users . thus , while there may have been some overestimation in this investigation , the periodontal condition of the subjects was poorer than the general population . earlier studies have shown that periodontal health continues declining with the duration of illegal drug use . in this study , in addition to local factors ( the presence of bacterial plaques and dental calculi ) , systemic factors also influence periodontal health . because heroin contains a number of noxious substances , it is likely that the drug can injure oral tissues following systemic administration . heroin has been demonstrated to induce disorders of the endocrine system , which could change the reaction of the periodontium to the drug stimulus , possibly increasing its destruction . drug abuse can also damage the humoral and cellular immunity , further exacerbating the periodontal disease . the dental calculus average section count is often used to evaluate the overall status of oral hygiene . in this investigation , the dental calculus average section count of men was higher than that of women , which explains the poorer periodontal status of the men . in this investigation , we discovered that the oral status of former heroin users in chengdu was poorer than the general population in the same area . there was a significant increase in various markers of dental and periodontal diseases in these subjects . the majority of carious teeth were untreated and the majority of missing teeth were not repaired . the frequency of missing teeth likely accounted for the lower values compared to other reports . a large number of carious retained roots were observed , demonstrating a high level of unmet dental treatment need . the west china dental hospital , located in chengdu , is the most famous dental hospital in china and has many dental clinics that offer dental treatment to all , including methadone users . this is likely because the former heroin users have a little expendable income and can not pay the fee for dental treatment . furthermore , their chaotic lifestyle makes them unlikely to practice good oral hygiene , and the illicit drug use may have masked the pain caused by the caries or residual root . since almost all of the subjects were from disadvantaged groups , it is hoped that this investigation will provide the necessary data to serve as an impetus for increasing programs that can help them improve their oral health . dentists should understand the dental emergency of methadone users . to provide better dental services for the methadone users , dentists teach them the importance of oral health , teach them brushing and oral self - care , check their oral status regularly and without charge and , and encourage them to take care of their teeth and see a dentist when needed . additionally , we suggest the government should establish a dental clinic in the methadone treatment clinic to provide basic dental care ( eg , filling teeth , root canal treatment , cleaning teeth , extracting teeth ) without charge or for a very low fee . we conclude that the oral health status among the studied former heroin users in chengdu is poorer compared to the general population . dentists should provide this population with basic dental care for free or charge only a small fee , as well as teaching them self - care .