dental erosion is defined as loss of tooth structure by acid dissolution without the involvement of bacteria . it is an increasing problem in today s society , because of the changing lifestyle and nutrition . numerous reports in literature indicate that the prevalence of dental erosion seems to be rising dramatically in young populations , with varying data from 11 to 100% in different countries [ 1 - 3 ] . the results of the national survey in iceland showed that the frequency of dental erosion among 15 year - olds doubled when compared to the 12 year - old children . pathogenesis mechanism of dental erosion is based on dissociation of hydroxyapatite and on impaired mineralization of the dental hard tissue due to long and frequent effect of acids . for the erosion to progress , the solution ph level has to be below 5.5 for enamel and below 6.0 for dentine . a number of external or internal causes can be responsible for the ph drop at tooth surfaces ; however development of the erosive process depends on the interplay of different biological , behavioural and chemical factors involved in it . most often reported risk factors of dental erosion are digestive and eating disorders ( gerd , regurgitation , bulimia , anorexia etc . ) as well as frequent consumption of acidic drinks and beverages . occupation and sports can add to development of erosive wear in some patients as well . amongst those , there might be individuals exposed to acids at the working place ( pharmaceutical enterprise , wine tasting etc . ) or , individuals engaged in heavy physical activity and using acidic sports drinks to compensate dehydration . a particular group of athletes is people who spend much time in pool water such as swimmers , water polo players and divers . the water ph level can decrease from 7.4 to 4 over night because of inadequate buffering of hcl when gas chlorination system is used . chlorine can also be added to pool water as sodium hypochlorite ( naocl ) , which has an alkaline ph and , thus , limited erosion potential . a case study by dawes et al . , reported about a complete loss of enamel by acid erosion , particularly from the anterior teeth in a person who swam daily for two weeks in an improperly chlorinated swimming pool . in several epidemiological studies , the prevalence of dental erosion among swimmers varied between 26% to 90% of swim team members . thus , the purpose of the present study was to estimate the prevalence of dental erosion among the different age groups of regular swimmers ; and to analyze correlation of dental erosion with their sport regimen and other potential risk factors of erosive tooth wear . the study population consisted of 12 - 25 year - old participants practicing swimming regularly in the swimming pools of kaunas , lithuania . in total , there are 5 swimming pools in kaunas ( kaunas swimming school with 3 swimming pools , lithuanian sports university - 1 swimming pool and kaunas center sport school - 1 swimming pool ) . all swimmers of the selected age , who practice in kaunas swimming pools , were invited to take part in the study . however , 50 swimmers of kaunas center sport school , and 12 swimmers from kaunas swimming school and lithuanian sports university were not interested to participate . the participants were informed about the purposes of the study and the informed consent was obtained . the bioethics committee at lithuanian university of health sciences provided ethical approval for the study ( bec - of-321 , bec - of-322 ) . the data were collected during may and june of 2013 . of the total of 194 of 12 - 25 year - old regular swimmers in kaunas , the participants were divided in two groups according to their age : 12 - 17 year - olds ( group 1 ) and 18 - 25 year - olds ( group 2 ) . there were 76 swimmers ( 50 males , 26 females ) in group 1 , and 56 swimmers ( 34 males , 22 females ) in group 2 , respectively . all participants went through a clinical dental examination at the premises of the swimming pools , using a portable dental unit equipped with fibre - optic operation light , compressed air and a suction device ( dentronic , aarhus , denmark ) , and standard dental instruments for oral inspection ( dental mirror and dental explorer ) . the occlusal , facial and labial surfaces of all teeth were examined for dental erosion , using lussi index   ( table 1 ) . the intra - examiner reliability was tested by repeating the examinations of 20 participants ( 10% of the study population ) , within the 2 days interval between the examinations . cohen s kappa was calculated at 0.91 representing good agreement for reproducibility of erosion . comparison of the study groups according to gender , swimming training time , and hours spent per week in a swimming pool 
  all participants responded to an anonymous questionnaire related to the most common risk factors of dental erosion . the questions in the questionnaire covered background information about the respondent s age and gender as well as about training time and hours spent per week in a swimming pool ( one hour was considered as one training ) ; feeling of dental hypersensitivity ; bruxism and other related disorders and symptoms ( gerd , increased acidity of the stomach , frequent vomiting , dry mouth ) ; regular intake of acidic medicines such as vitamin c and acetylsalicylic acid ; carbonated soft drinks and sport drinks consumption . the quality of water in the pools was estimated based on the data provided by the pool workers ( water monitoring is performed twice a day ) . the parameters of water quality varied between the set limits of water ph 7 - 7.5 , and chlorine concentration 0.5 - 2 mg / l . the data were analyzed by means of spss software ( spss 20.0 for windows ) . the sample size calculation was based on paniotto formula that resulted in the minimum of 130 individuals to participate in the survey . the data were described using mean ( m ) values , standard deviation ( sd ) , 95% confidence intervals ( ci ) . the distribution and qualitative variables were compared by chi - square (  ) test . depending on the sample size , fisher s exact test ( for small samples ) and asymptomatic  were applied . prognostic values of the selected risk factors expressed as odds ratios ( or ) and confidence intervals ( 95 % ci ) , were estimated by means of univariate binary logistic regression analysis . to verify the statistical hypotheses , the significance level of 0.05 was chosen . group 1 comprised 76 individuals of age 12 - 17 years , and group 2 - 56 individuals of age 18 - 25 years , respectively . swimming training duration and the participants age had significant positive correlation ( kendall correlation analysis , r = 0.65 , p < 0.001 ) , meaning that older participants had attended swimming for a longer period . however , the swimmers in group 2 spent significantly less hours per week in the swimming pool as compared to the swimmers in group 1 ( table 2 ) . 
 the prevalence of dental erosion according to swimming training duration and hours spent per week in a swimming pool dental erosion was observed in 296 surfaces ( 1.4% of the total number of surfaces examined ) . the mean value of the surfaces affected by dental erosion in the total study group was 6.31 ( 4.37 ) . the lesions were distributed mainly on the labial and oral surfaces of the anterior teeth and premolars , no signs of erosion were observed on the molar teeth . the prevalence of dental erosion was 25% ( 19 individuals ) in group 1 , significantly lower than the estimated 50% ( 28 individuals ) in group 2 . the prevalence of dental erosion according to swimming training duration and hours spent per week in a swimming pool is shown in table 3 . the prevalence of dental erosion according to swimming training duration and hours spent per week in a swimming pool 
 
  = chi - square test ; d.f . the distribution of dental erosion according to gender , did not differ significantly among the females and males , although a tendency of higher prevalence of eroded dental surfaces among the male participants was observed : in 33% ( n = 16 ) of the girls and 37% ( n = 31 ) of the boys ( p = 0.68 ) . respectively , in group 1 : 23% ( n = 6 ) of the girls and 26% ( n = 13 ) of the boys ( p = 0.78 ) ; in group 2 : 46% ( n = 10 ) of the girls and 53% ( n = 18 ) of the boys ( p = 0.58 ) . figure 1 shows that some of the well known risk factors of dental erosion were highly prevalent among the study participants : about half of all swimmers indicated drinking carbonated soft drinks daily , and almost one third of the swimmers indicated drinking sport drinks on the daily basis . as shown in table 4 , the presence of dental erosion was significantly associated with swimmers age and training duration . the 18 - 25 year - old participants and those who practiced swimming for more than 10 years had 3 times greater risk to develop dental erosion than the younger swimmers ( 12 - 17 year - olds ) and those who practiced swimming less than 10 years . among all participants , there was no significant difference in the prevalence of dental hypersensitivity neither between two study groups nor between females and males . a very weak correlation between the reported dental hypersensitivity and presence of dental erosion ( r = 1.124 , p = 0.124 ) was estimated . only 23% of those who presented with dental erosion , reported about hypersensitivity as well . of all participants , 13% complained about dental hypersensitivity with no dental erosion recorded . the reported prevalence of the potential risk factors of the erosive dental wear among the study participants . univariate binary logistic regression analysis of the prevalence of dental erosion , with respect to the selected risk factors 
 
 statistically significant , univariate binary logistic regression analysis . the purpose of the present study was to explore possible correlations of the swimming regimen and the selected risk factors of dental erosion among the regular swimmers in kaunas , lithuania . in all swimming pools of kaunas the results showed that 25% of the 12 - 17 year - old participants had dental erosion , whereas the prevalence of dental erosion amongst the 18 - 25 year - olds was 50% . the prevalence of dental erosion did not correlate with the duration of swimming and time spent per week in pool , in both age groups of the participants . all lesions of dental erosion were valuated as grade 1 according to lussi index , the same results were found in a similar study by buczkowska - radliska et al . . there are numerous reports in the literature indicating that people who spend a lot of time in a swimming pool such as swimmers , water polo players , divers have an elevated risk to develop dental erosion [ 10 - 14,18 - 21 ] . however , development of dental erosion was mainly showed in studies performed in gas chlorinated pools . on the contrary , in the countries where sodium hypochlorite disinfection method is used for disinfection of pool water only 0.14% pools had ph level lower than 5.5 , which is a critical value with respect to decalcification of dental tissues . low ph of pool water is not exclusively responsible for the dental hydroxyapatite dissolution process , but the concentration of ions with respect to the saturation of dental hydroxyapatite , especially calcium and phosphate , may also be involved . long - term exposure to the pool water undersaturated with respect to hydroxyapatite could be responsible for erosive damage of dental tissues , particularly in the labial surfaces of teeth . labial erosions were found more frequently in males , who practiced long swimming sessions and an aggressive style of swimming , involving increased agitation ( e.g. , when a swimmer is swishing water in the mouth ) . another report   suggested that even in properly maintained gas - chlorinated swimming pools basic salivary parameters ( salivary flow rate , concentration of minerals in saliva ) of the swimmers might be altered thus contributing to enamel dissolution high intake of sports drinks during exercise , coupled with xerostomia from dehydration , may lead to the possibility of erosive damage to teeth as well . swimmers also experience physiological decrease of saliva flow because of body s dehydration during training . the effect of sport drinks , possible low swimming pool water ph and undersaturation of hydroxyapatite minerals accumulates and possibly increases the risk of dental erosion . the small sample size did not allow us to find any significant correlations with other potential risk factors of dental erosion , such as reflux , increased acidity of the stomach , dry mouth , regular intake of acidic medicines ( vitamin c , acetylsalicylic acid ) , or consumption of carbonated beverages and sport drinks . however , the reported prevalence of daily consumption of the soft drinks was high amongst the study participants . considering the fact that there was no correlation with the swimmer s time ( number of hours ) spent in swimming pools , it seems that a cumulative effect of various factors , related to the lifestyle of young people , might have occurred . further research involving larger study samples would be beneficial in order to estimate the severity of dental erosion among different population groups in lithuania . the prevalence of dental erosion of very low degree among the regular swimmers of kaunas city was high and significantly related with age . double estimates were found in 18 - 25 year - old swimmers as compared to their 12 - 17 year - old colleagues . the authors would like to thank irena nedzelskien ( lithuanian university of health sciences , faculty of odontology , department of dental and oral pathology ) for her help in statistical analysis and to the swimming schools and all the participants who participated in this survey .
abstractobjectivesto determine prevalence of dental erosion among competitive swimmers in kaunas , the second largest city in lithuania.material and methodsthe study was designed as a cross - sectional survey , with a questionnaire and clinical examination protocols . 
 the participants were 12 - 25 year - old swimmers regularly practicing in the swimming pools of kaunas . 
 of the total of 132 participants there were 76 ( 12 - 17 year - old ) and 56 ( 18 - 25 year - old ) individuals ; in groups 1 and 2 , respectively . 
 participants were examined for dental erosion , using a portable dental unit equipped with fibre - optic light , compressed air and suction , and standard dental instruments for oral inspection . 
 lussi index was applied for recording dental erosion . 
 the completed questionnaires focused on the common erosion risk factors were returned by all participants.resultsdental erosion was found in 25% of the 12 - 17 year - olds , and in 50% of 18 - 25 years - olds . 
 mean value of the surfaces with erosion was 6.31 ( sd 4.37 ) . 
 all eroded surfaces were evaluated as grade 1 . 
 swimming training duration and the participants age correlated positively ( kendall correlation , r = 0.65 , p < 0.001 ) , meaning that older swimmers had practiced for longer period . 
 no significant correlation between occurrence of dental erosion and the analyzed risk factors ( gastroesophageal reflux disease , frequent vomiting , dry mouth , regular intake of acidic medicines , carbonated drinks ) was found in both study groups.conclusionsprevalence of dental erosion of very low degree was high among the regular swimmers in kaunas , and was significantly related to swimmers age .