Prevalence and risk indicators of non-carious cervical lesions in male footballers

Non-carious cervical lesions (NCCLs) are defined as the loss of dental hard tissue at the cementoenamel junction (CEJ) region without the action of microorganisms or inflammatory processes. These lesions vary from shallow saucer-shaped grooves to deep wedge-shaped defects and can occur sub- or supragingival at facial, lingual, and/or interproximal surfaces. Although this oral disease has a high incidence and prevalence regardless of age, gender, social, economic, and cultural conditions, it has been increasingly associated with people’s lifestyles and youths [1‐5]. NCCLs have a multifactorial etiology, including mechanical stress (tension), erosion (chemical degradation), and friction. Risk factors such as teeth clenching, premature or eccentric contacts, overbrushing, and acidic beverages intake modulate the evolution of NCCLs according to their intensity, duration, and frequency.

The combination of factors seems relevant in the formation of NCCLs and mechanical stress is observed in most cases [6]. Individuals with lifestyles that enhance this peculiar interaction between tension, erosion, and friction are more vulnerable to NCCLs [7]. The intense physical exercises and high workloads that athletes are constantly submitted to increase the risk of body and dental trauma [8]. The fluid and electrolytes lost through sweat may cause dehydration and reduce the salivary flow rate. A dry mouth without the protection of saliva combined with acidic sports beverages intake significantly contributes to dental erosion [8‐10]. Therefore, this study aimed to determine the prevalence of NCCLs in footballers and to address potential risk indicators.

Most of the participants had a high level of education (58.1%), more than two years of a sports activity (62.8%), and more than 1 h of daily training (55.8%). Only 11.6% of the participants reported football as their exclusive occupation. Approximately 79% of the participants reported to use conventional toothpaste, 27.9% used to brush their teeth immediately after meals, 30.2% reported to have dry mouth, 11.6% reported gastroesophageal reflux, 23.2% used medication, 9.3% reported to drink lemon water while fasting, 74.4% reported parafunctional habits, 27.9% reported TMJ pain, 79% presented tooth sensitivity and 30.2% reported previous orthodontic treatment. The majority of the participants (81.4%) presented Angle Class I malocclusion and 41.9% presented an altered bite. The NCCLs were diagnosed in 39.5% of the participants. The footballers that reported up to 1 h of daily training had a significantly higher prevalence of NCCLs than those that trained for more than 1 h per day (p = 0.028) (Table 1).

The bivariate analysis revealed that the footballers that trained up to 1 h per day (PR 2.32 [1.05–5.11]; p = 0.038) and those who consumed lemon water while fasting (PR 2.5 [1.67–3.75]; p < 0.001) showed a significant association with the development of NCCLs. The multivariate analysis with adjusted values revealed a significant association between NCCLs and up to 1 h of daily training (PR 3.35 [1.18–9.49]; p = 0.023), lemon water intake while fasting (PR 8.10 [2.19–29.90]; p = 0.002), use of desensitizing toothpaste (PR 5.30 [1.63–16.96]; p = 0.004), presence of tooth sensitivity (PR 2.53 [1.31–4.88]; p = 0.006), and previous orthodontic treatment (PR 3.11 [1.48–6.50]; p = 0.003) (Table 2).

Occlusal/incisal wear was more frequently observed in anterior teeth (39.7%) and canines (29.1%) followed by premolars (16.3%) and molars (10.9%). The same trend was observed for tooth sensitivity evaluations: anterior teeth (21–24.5%), canines (24.4–23.3-%), premolars (18.1–21.1%), and molars (16.8–15.6%) (Table 3).

NCCLs were diagnosed in 8% of the teeth examined (94 of 1167). These lesions were more frequently found in premolars (16.9%), in the upper arch (8.8%), and on the right side (9.9%). The NCCLs were predominantly shallow (< 1 mm depth) and diagnosed in premolars (15.8%). The lesions of moderate depth (1–2 mm) were only observed in premolars (0.9%) and molars (0.9%). Class V restorations were more frequently observed in molars (2%) (Table 3).

Among the teeth with shallow NCCLs (< 1 mm), 83% did not present occlusal/incisal wear and 17% presented wear only in enamel. Occlusal/incisal wear was not observed in those teeth with moderate NCCL (1–2 mm depth) (Table 4). Therefore, the relationship between occlusal/incisal tooth wear and NCCLs depth was not significant (p = 0.077).

The most frequent morphological characteristics of the NCCLs were: rounded shape (65%), shallow depth (94%), coronal to the CEJ (52%), supragingival (52%), without sclerotic dentin (98%), and smooth texture (99%). Figure 1 shows the morphological aspects of some NCCLs.

The laboratory assays of participants with or without NCCLs revealed regular salivary flow (higher than 0.7 ml/min), neutral pH, and buffering capacity above 5.5. All participants presented similar amounts of Ca, Na, and K ions, and their level of cortisol remained bellow 20.3 nmol/l. Therefore, none of the salivary analyses indicated significant differences.

This study diagnosed a remarkable prevalence of NCCLs in footballers and revealed the daily training time as an important risk indicator. The NCCLs were diagnosed in 39.5% of the participants, while the data in the literature varies from 5 to 85% due to different types of participants (specific subgroups of the general population) combined with the lack of method standardization [2, 16]. For instance, a study involving Brazilians between 40 to 60 years old reported NCCLs prevalence of 67% while a population from 35 to 74 years old in China presented a prevalence of 81.3% [17, 18]. However, a recent clinical trial with patients between 18 and 40 years old treated for NCCLs and cervical dentin hypersensitivity at a Brazilian university revealed a prevalence of 88.1% and also suggested an increasing distribution of NCCLs among youths [1]. Other studies reported prevalence ratios below 53% [19‐23].

The bivariate regression analysis revealed that daily training time is a dominant risk indicator for the development of NCCLs. The fact that footballers that reported only up to 1 h of daily training presented more NCCLs may be related to poor physical conditioning. Therefore, the footballers that trained more than 1 h per day seem to better withstand the intensity and directions of the loads that teeth are subjected to. Similarly, Antunes et al. observed that the training time of Brazilian amateur runners represented a risk factor for dental erosion [22]. Approximately 52% of the runners that expended only up to 1 h during training presented tooth erosion, while the rate decreased to 38 and 9.5% for those runners that trained up to 2 and 3 h, respectively. In addition to good physical conditioning, individuals dedicated to long training times possibly take better healthcare. The intake of lemon water while fasting was significantly associated with NCCLs. Acids of either exogenous (some fruits and juices, carbonated soft drinks, acidic sports beverages, alcoholic drinks, some medications, and occupational factors such as chlorine used in swimming pools) or endogenous origin (gastric juice) contribute to dental erosion and consequently to the development of NCCLs [24‐29].

The multivariate regression analysis significantly associated the prevalence of NCCLs with several variables (daily training time, lemon water intake while fasting, use of desensitizing toothpaste, tooth sensitivity, and previous orthodontic treatment), which confirms that the combination of factors is more relevant in the development of these lesions [1, 7].

Our findings reinforce that the indiscriminate use of desensitizing toothpaste without professional follow-up impairs the early diagnosis of NCCLs since the painful symptoms are masked and the individual does not seek appropriate treatment. The presence of tooth sensitivity allows proper NCCL diagnosis and its association with other variables favors the development of the lesions [30].

Although orthodontic treatment induces stress in the cervical region of teeth, the intensity of the force applied by orthodontic appliances should not exceed the intrinsic tensile and compression strength of dental structures [31, 32]. Spini assessed the cervical tension of premolars through finite element analysis and extensiometry and concluded that the accumulation of tension and deformity was higher in teeth with NCCL and previously subjected to orthodontics [33]. In our study, the significant association between orthodontic treatment and NCCLs may be explained by the excessive forces that teeth were subjected during successive years and caused structural losses of enamel and alveolar bone. The increasing prevalence of NCCLs among youths represents novel information to the literature. However, it was observed that most participants did not have their orthodontic treatment completed.

Brandini et al. [19] and Kolak et al. [20] evaluated men and women with a similar age range and diagnosed NCCLs in 13.2 and 3.1% of teeth, respectively. In comparison with the abovementioned studies, our prevalence of NCCLs in the examined teeth remained in the intermediate percentage level of 8% and the lesions were more frequently found in upper premolars. It is a consensus in the literature that premolars present the highest prevalence of NCCLs due to an unfavorable crown-root proportion and the thin buccal bone plate. These features result in a high-stress concentration in the cervical region during eccentric mandibular movements, particularly in the case of group disocclusion [1, 17, 19, 20, 34‐37].

The diagnosed NCCLs in this study were predominantly shallow, rounded, supragingival, and without sclerotic dentin, which characterizes them as initial lesions [38]. However, many participants also presented white spots at the cervical teeth outline that does not extend to the root in case of gingival recession. The white color does not change whether the enamel is wet or dry and the concentration varies from diffuse to a well-defined horizontal line. Considering that the footballers are constantly subjected to either tension or mechanical stress, we diagnosed these spots as cracks. This is supported by the concept of striations, which were defined as irregular horizontal enamel bands in the cervical region affected by molecular decomposition (molecular slips or Luder lines) [39]. Lee and Eakles [40] stated that when hydroxyapatite crystals are ruptured, the spaces are filled with water molecules from saliva that impair chemical bonds between crystals and the tooth becomes more vulnerable to mechanical and erosive damages. The water penetration into the dental structure may explain such a whitish aspect and the different shades may be related to the crack depth.

Posterior teeth showed the highest and lowest frequencies of tooth sensitivity and occlusal wear, respectively. Interestingly, the opposite trend was observed for incisors and canines; however, no correlation was found. The different number of participants with or without NCCLs figures as a limitation of this study that reduces the statistical efficiency.

The relationship between the occlusal/incisal wear and NCCL depth was inverse. Among the 94 teeth with NCCLs, 79 did not present occlusal/incisal wear, and 15 presented exclusive enamel wear. Senna et al. [41] conducted a systematic review on the association between NCCLs and occlusion and suggested that occlusal wear is a nature’s way to eliminate occlusal disturbances. The authors also reported that NCCLs develop before or during the establishment of occlusal wear when the teeth are subjected to occlusal stress. Despite the role of tension in the development of NCCLs, an inversive relationship was observed in our study since footballers with NCCLs showed little or no occlusal/incisal wear.

It was observed that the incidence of positive sensitivity in premolars (18.1 to 21.1%) was higher than the incidence of NCCLs (16.9%). We concluded that tooth sensitivity combined with the presence of white spots (cracks induced by stress) in many participants is symptoms/signs of initial NCCL.

The laboratory assays indicated normal salivary parameters in those participants with NCCLs; therefore, these lesions seem related to excessive mechanical stress and not to erosive factors such as acidic beverages or brushing immediately after meals. Fullagar et al. reported that footballers possess limited nutrition and hydration practices [42]. The level of cortisol of all participants was found normal. Although cortisol is regarded as a stress biomarker, the level of anxiety in footballers varies greatly depending on their physical performance [43‐45]. After evaluating both trained and untrained men, Rimmele et al. reported that physical activity may provide a protective effect against disorders related to stress since it regulates the level of cortisol [46].

Despite the symptoms/signs of initial NCCLs, the examined footballers need preventive or even curative treatment to control the progression of the lesions. Moreover, periodic follow-ups of their salivary and nutritional conditions are important to dental health. Due regard must be given to the daily training time as an important risk indicator of NCCLs development since the contemporary lifestyle of youths includes intensive physical exercises and frequent intake of acidic sports beverages. Therefore, clinicians must investigate and guide patients to reduce the risk of NCCLs development.

The prevalence of NCCLs among footballers was remarkable. The premolars were the most affected teeth and presented symptoms/signs of initial lesions. The daily training time was a dominant risk indicator of NCCLs development. These lesions were also significantly associated with several indicators (daily training time, lemon water intake while fasting, use of desensitizing toothpaste, tooth sensitivity, and previous orthodontic treatment). Footballers presented adequate salivary parameters and cortisol levels.