The effect of swimming on oral health status: competitive versus non-competitive athletes

ABSTRACT Young swimmers are particularly susceptible to the onset of oral diseases. Objective To evaluate the oral health status in young competitive and non-competitive swimmers, involving an assessment of salivary cariogenic bacteria and secretory IgA (S-IgA) concentration. Material and Methods Before training sessions (T1), 54 competitive and 69 non-competitive swimmers had the following parameters assessed: decayed, missing, and filled teeth (DMFT), Plaque Index (PlI), and Gingival Index (GI). At T1 and after training sessions (T2), stimulated saliva was collected and microbiological and immunological analyses were performed. Results Competitive swimmers trained 2.02±0.09 hours 5 times a week, while non-competitive swimmers trained 2.03±0.18 hours a week. A total of 14.7% of competitive swimmers suffered dental trauma related to sports. Only 11.76% of the competitive swimmers took a daily dose of fluoride, against 32.65% of non-competitive swimmers (p=0.029). Neither group followed an established diet or presented statistically significant differences in terms of nutritional supplement drink and chocolate intake. There were statistically significant differences in terms of oral hygiene. No significant difference in clinical indexes (DMFT, PlI, and GI) was present. S. mutans was harbored by 18.6% of competitive and the 32.2% of non-competitive swimmers. S. sobrinus was detected in 22.03% of competitive and 91.6% of non-competitive swimmers (p<0.05). S. sanguinis was found only in the saliva of competitive swimmers. The average S-IgA of competitive swimmers decreased significantly at T2 (p<0.05). The pool water had a daily average pH of 7.22. Conclusions Microbial markers, immune status and sporting characteristics are important for establishing guidelines for management of training load in order to minimize physical stress and the risk of oral infection.


INTRODUCTION
High performance standards are required for athletes, especially for swimmers, who must be totally healthy individuals. Dental diseases harm quality of life and have a negative impact on selfesteem, eating ability, and health, causing pain, anxiety, and impaired social functioning 4,11,18. Relatively little information is available on the correlation between the performance of swimming at a competitive level and tooth decay occurrence 14 . Dental caries is a lifetime disease that depends on biological factors present within the saliva and dental plaque. Dental plaque favors the emergence of mutans streptococci and Lactobacillus spp., which are capable of rapidly fermenting dietary carbohydrates and lowering the pH to the extent can occur 12,22,23 . The concentration of cariogenic bacteria levels within saliva and plaque determine if caries will occur 24 .
Many different agents protect the tooth surface against developing caries. Secretory IgA (S-IgA) constitutes the main immunoglobulin isotype found defense against pathogens which colonize or invade the oral cavity. As part of innate immunity, S-IgA is considered the best indicator of mucosal immunity and acts by preventing microbial pathogens from entering the body via mucosal surfaces, which are mainly responsible for infections of the upper respiratory tract 27,28 . Several studies have demonstrated that practicing different sports, in particular swimming, at a competitive level, leads to a decrease in S-IgA levels associated with an increased incidence of upper respiratory tract infections in professional athletes 9,21,24,28,29 .
The purpose of the present study was to evaluate the oral health of hard and soft tissues and the prevalence of caries in young selected competitive and non-competitive swimmers, by assessing salivary cariogenic bacteria and concentration of salivary IgA, both before and after training sessions. An additional objective was to monitor the water pH of the swimming pool during the day to assess its potential role in erosion.

Study population
The study population was composed of 123 subjects: 54 competitive swimmers (test group) and 69 non-competitive swimmers (control group), 58 females and 65 males. There was no difference between test and control group with respect to age ( Table 1). The swimmers (test and control) attended the swimming pools of Chieti and Francavilla al Mare (CH) (Italy) with different training amounts of time (competitive: 2.02±0.09 hours 5 days a week; noncompetitive: 2.03±0.18 hours one day a week). All athletes started swimming four years before (4.17±0.27). We discovered that the competitive swimmers trained for the same amount of hours in the swimming pools because the Italian competition rules, edited by the Swimming Italian Federation (FIN), divide the athletes by age and the ones in the same category have an identical training program. belong to the same Society and thus they have the same trainers. The non-competitive swimmers were voluntarily enrolled in the study but had to meet some parameters (training for four years, not belonging to a Sport Society, and not having a planned training program). Parental informed consent was obtained for all patients before they were examined (Privacy Law DL 196/2003). The selected subjects participated voluntarily in the study. In this study, the approval from the Ethics Committee was not required since the research protocol was based on a clinical protocol previously approved by the Department for medical use.
The following inclusion criteria were considered: Absence of systemic diseases that could affect the immune response or that could condition bacterial colonization.
No use of antibiotics for three months prior to the beginning of the study.
No orthodontic therapy. Dental care not in progress. A self-administered questionnaire was used to obtain data concerning hours and frequency of weekly training, complete pathological history, history of hard and soft tissues of the oral cavity, family history, oral hygiene practices, fluoride intake, and eating habits (supplements consumed and dietary information such as intake of drinks, fruit juices, and consumption of chocolates).

Clinical monitoring and saliva collection
Before training sessions (T1), each patient was clinically evaluated. The number of decayed, assess the prevalence of caries according to World Health Organization (WHO) criteria. The Silness & Löe Plaque Index (PlI) and the Löe & Silness periodontal status, respectively.
In addition, an oral examination of intraoral mucosa was performed and the presence/absence of bad habits, malocclusion, and parafunctional habits was assessed.
Before (T1) and after training sessions (T2), saliva was collected with paraffin-chewing stimulation. The saliva samples were immediately placed on ice and transferred to the laboratories for was transferred to a microcentrifuge tube and used for microbiological analysis. The remainder of the by centrifugation at 10,000 Xg for 15 min at 4°C and frozen at -20°C for the titration of salivary IgA. The sizes of the PCR products were estimated from the electrophoretic migration of products relative to a 100-base-ladder marker (Amersham Pharmacia Biotech, AB, Uppsala, Sweden).

DNA extraction from saliva samples
The titration of salivary IgA was performed by using LC-examination Partigen immunodiffusion

Swimming pool water collection
Samples of swimming pool water (10 ml) were also collected in test tubes at regular intervals throughout the day and sent to the laboratory for pH evaluation. pH values were analyzed by a pHmeter

Statistical analysis
The Wilkoxon matched-pairs signed-rank test was used for the statistical analysis. All p-values

RESULTS
The demographic and clinical characteristics of the studied populations are presented in Table  1 and Table 3. The competitive swimmers trained 2.02±0.09 hours 5 times a week and the noncompetitive swimmers 2.03±0.18 hours a week. Age and gender were similar in the two groups. While 14.7% of competitive swimmers had suffered dental trauma related to sports, there were no cases in the control group. Only 11.76% of the against 32.65% of non-competitive swimmers, with Data concerning the dietary habits showed that neither group followed an established diet and that their nutritional supplement drink and chocolate between the two groups were observed. The most frequently reported by the study population were nail biting, sleep bruxism, and atypical swallowing.

DISCUSSION
The exercise involved in routine sport practice exposes athletes to the onset of numerous diseases. A number of factors, including the levels of competition and of exposure, can affect the higher or lower incidence. For this reason the present study considered two groups of swimmers attending the same environment (same pools) and same years of practice (4.17±0.27), but with different training loads. Results from this study indicated that athletes engaged in swimming at a competitive level, with more hours of training in pool water, had a higher incidence of dental stains and trauma. Dental injuries associated with various types of sports have often been described in literature 6,10,19,30 .
The incidence of dental stains was higher in competitive swimmers compared to non-competitive ones. Although the difference was not statistically et al. 11 (2000), by the chemical used to disinfect the pool water in both swimming pools analyzed and by the time spent inside swimming pools and order to permit contact between water and dental surfaces. In this study, the amount of training time of the competitive swimmers (2.02±0.09 hours 5 times a week) falls under the condition mentioned by Escartin, et al 11 (2000) of more than 6 hours of training per week as the time necessary to increase the risk of dental stains. Although the values are much lower than those reported by Escartinet, al 11 (2000) (prevalence of Dental Stains (DS) of 60.2% in the swimmers), it is possible to state that competitive swimmers had a high risk of developing extrinsic dental stains.
Competitive swimmers had a low prevalence of parafunctional behaviors. The most frequent oral habits reported by non-competitive swimmers were nail biting, sleep bruxism, and atypical swallowing, with an incidence similar to those reported in young adolescents in the literature 15 .
Data concerning the dietary habits showed that in both groups, because of the age of the or competitions. Intake of nutritional supplement different from non-competitive swimmers. Dental erosion is a further potential problem associated with sports drinks 1,5,14 . This study showed no potential problems related to the consumption of these beverages, as demonstrated by low dental erosion frequency.
Some authors believe that if the pH of the water in the pool decreases below that of saliva, erosions on the dental enamel may occur 3,18 . In this study, the waters of the pools showed a daily pH of 7.2, thereby meeting the required pH values ranging from 7.20 to 9.0 and having little or no effect on swimmers in relation to the development of erosions (2% vs 1%).
In this study, after training, there was a of salivary IgA levels of selected swimmers. S-IgA average values before and after training were in non-competitive swimmers. The results of this bouts of exercise reduced S-IgA levels in a variety of endurance sports, including swimming 7, 8,16,25,28 . These results contrasted with some authors who indicated that there are no differences in salivary concentrations of S-IgA between athletes and non-athletes, except when athletes are engaged in heavy training 13,25 . Several studies demonstrated that S-IgA concentration changes and in particular an absolute concentration of less than 40 mg/L was reported to relate to increased Upper Respiratory Tract Infection (URTI) incidence in athletes 28 . Therefore, since S-IgA acts as a marker of mucosal immunity, this study showed that its decline could Therefore, the results suggested that the time of training was the period characterized by the least intensive salivary functions and physiologic responses as a decrease in the salivary level of IgA. Swimming at competitive levels determined higher S-IgA average values, both before and after training, than for non-competitive swimmers. A low number of competitive swimmers harbored cariogenic microorganisms in their saliva; on the contrary, they showed a higher frequency of "protective" bacteria as S. sanguinis, associated of active caries. Several studies 2,20 reported that the oral health of those who practice the sport at a competitive level was harmed, with a high incidence of oral problems such as caries, trauma, etc. The difference from the results of this study was the age of the examined subjects, proving it is crucial to avoid the problems described in the literature by implementing a prevention program. CONCLUSIONS microbial risk markers, including mutans streptococci. Non-microbial caries risk factors included visible plaque, child age, race, salivary and pool water pH, and eating habits. Furthermore, mucosal immune status and sport characteristics (intensity, duration and frequency of training) are considered useful for establishing guidelines for nutritional support and management of training load. In this way, it would be possible to minimize physical stress and subsequently the risk for oral infection.