Introduction

The term “bruxism” has undergone a drastic evolution in recent years. The condition has been associated with dental clenching and parasomnias and has even been considered a predisposing or protective against certain conditions. More recently, it has been linked to muscle contraction events. Functionally, it is also defined as a collective term for parafunctional movements outside the physiological range of chewing movements.^1,2) It can also cause various signs and symptoms, including masseter muscle hypertrophy, tooth wear, fracture or failure of restorations and dental implants, tooth sensitivity or pain, muscle or joint involvement, and temporomandibular joint (TMJ) disc displacements.³ Tooth clenching is of great concern, given its multiple clinical implications.⁴⁾ In recent years, the definition of “bruxism” has been modified mainly to unify the diffuse and heterogeneous criteria prevailing in the professional and research communities. Therefore, a recent international consensus of experts defined bruxism as “repetitive masticatory muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible.”⁵ For this reason, most of the works published in the last five years base their research designs on this definition.^6,7

For several decades, studies on bruxism focused on what happened during sleep. However, this changed as a result of international expert consensus. Experts recommended that single definition of bruxism should no longer be used in favor of two separate definitions considering the circadian manifestations of the phenomenon: sleep and wakefulness.⁸⁾ Awake bruxism (AB) is a masticatory muscle activity occurring during wakefulness that is characterized by repetitive or sustained tooth contact and/or by bracing or thrusting the mandible, and sleep bruxism (SB) is a masticatory muscle activity during sleep characterized as rhythmic (phasic) or non-rhythmic (tonic).^5,9)

Some authors state that bruxism prevalence is between 22% and 31%.^10,11 According to Manfredini et al.,¹⁰ bruxism is not related to gender, and it tends to decrease with age. In Uruguay, a study including 2,800 people on the prevalence of temporomandibular disorders (TMD) and bruxism revealed that 30% of the participants reported feeling they had slept clenching their teeth. Additionally, approximately 72% had parafunctional tooth wear facets.¹²

Some studies have shown a potential association between bruxism, anxiety, and stress in college students.^13-15 According to Carvallo and Mouthéz,¹⁶ there is a positive correlation between bruxism and anxiety. Thus, one of the manifestations of stress is bruxism, the gnashing and clenching of teeth without a functional purpose with variable frequency in the general population.¹⁷ In this regard, a study showed that 68% of university students are stressed and that awake bruxism was detected in over half the sample (52.1%).¹⁸⁾ In addition, moderate to severe bruxism is a warning sign regarding oral health, since tooth wear, loss of restorations/teeth, and muscle and/or joint pain may occur, affecting health and quality of life.^19-22)

Several studies agree that university students suffer high levels of stress and anxiety daily, confirming the association between stress and bruxism. There has been increased incidence of bruxism in the last decades.^21-23) A study conducted in Finland on a sample of 4,403 students at the University of Applied Sciences also showed that bruxism and TMDs are prevalent in university students.²⁴⁾ However, no studies have yet analyzed the problem of bruxism among physical education students. This degree may include very specific strength, power, and resistance training activities. This could lead us to think that this student population may behave differently from other university students regarding psychological stress, anxiety, or bruxism, among other factors.

In this context, this study aimed to use self-reporting to explore teeth clenching and factors associated with AB, such as stress and anxiety in undergraduate physical education students at Universidad de la República, Uruguay.

Materials and methods

Results

The sample included 178 students, with a mean age of 24 (minimum 18 and maximum 34). A total of 68% of students said they knew what bruxism was. Thirty-three percent reported having bruxism, of which 14% claimed to have been clinically diagnosed. Of the volunteers, 6% were undergoing treatment with an oral device (Figure 1).

Figure 1: Reported bruxism 

Age and perceived bruxism

Figure 2: Age and reported bruxism 

Seventeen percent of the volunteers aged between 18 and 25 (70% of the sample) self-reported bruxism. Of the remaining 30% (26 and 34 years), 25% self-reported bruxism (Figure 2).

Sex and perceived bruxism

Forty-nine percent of the sample was female, and the remaining 51% was male. Additionally, 43% of the female participants reported bruxism, and only 26% of the male participants reported it (Figure 3).

Figure 3: Sex and perceived bruxism 

Anxiety, stress, and perceived bruxism

Regarding anxiety and stress, 28% of the volunteers who reported anxiety also reported bruxism. As for the volunteers who reported suffering from stress, 11% also reported bruxism (Figure 4).

Figure 4: Anxiety, stress, and self-reported bruxism 

Associated factors and perceived bruxism

As for factors associated with bruxism, 21% reported tooth wear, 20.2% reported clenching their teeth during the day, and 6% described suffering from stiffness and tension in the jaw. Twenty-one percent reported their teeth made noises at night and 15 % had orofacial pain. Additionally, 4% reported having a locked jaw upon awakening, and 40% woke up feeling tired (Figure 5).

Figure 5: Factors associated with bruxism 

Discussion

This study found no associations between age and bruxism in university physical education students. This result agrees with previous studies conducted on a young population,^18,25,26 but does not coincide with the study by Emodi Perlman et al.,²⁷ who observed a correlation between awake bruxism and age. These differences probably occured because the studies have heterogeneous methodological designs.

Women presented a higher percentage of self-reported bruxism than men. This agrees with previous studies stating that bruxism is higher in women than in men.¹² In addition, disorders related to the function of the masticatory system, as well as TMDs, tend to be more frequent in women.²⁸⁾ However, this association has not been verified for awake bruxism.^18,25,27) The findings of this work regarding the coexistence of bruxism and anxiety in university students agree with other studies that demonstrate the significant association between self-reported waking bruxism and anxiety.^26,29,31) Likewise, another study observed that students with bruxism are more predisposed to anxiety.^18,30 These findings support modern changes in diagnostic and therapeutic paradigms as we migrate from a purely mechanistic model to a bio-psycho-social model that considers emotional factors.

Regarding stress and bruxism, some studies indicate that people who self-report bruxism are more likely to develop this parafunction when stress is a risk factor.^29,32 These findings are consistent with our own: there is a significant correlation between waking bruxism and stress. Another factor frequently associated with bruxism is tiredness. ^33-35 We observed that 39.8% of university students reported waking up tired. All these factors could cause neuromuscular alterations and an increased likelihood of TMDs.²² Similarly, tooth clenching increases with stress experienced mainly during the day and exam periods.¹⁶ As a result, students are affected and suffer from anxiety and stress.¹³

A study conducted among engineering students, in which moderate stress predominated, found evidence of tooth wear.¹⁹ These data agree with our study that reported 21.3% dental attrition. However, tooth wear may not be considered a determinant of bruxism, as it may be caused by diet, age, and other factors.^13,36,37 In addition, patients suffering from clenching bruxism tend not to wear down their teeth. According to Machado et al.,³⁸ bruxism sufferers are those with dental wear in at least one tooth, associated with teeth clenching/grinding, since bruxism can increase tooth enamel wear. However, at first, the teeth may not show signs of wear.³⁹⁾ This makes it challenging to diagnose bruxism in young people. Also, on clinical examination, wear facets may indicate a previous history of bruxism, and the condition may no longer exist at the time of examination.¹³⁾

Another critical sign of bruxism is teeth grinding,³⁹ considered a major contributing factor in TMDs.⁴⁰⁾ In this study, 20.2% of the volunteers had perceived teeth clenching during the day in the previous two months and 21% upon awakening (or that they were awakened) by teeth noises (grinding) while sleeping. Both teeth grinding and clenching are related to muscle hyperactivity.¹⁷⁾ This may be due to the overexertion of the masticatory muscles. This effort leads to other symptoms associated with bruxism that include jaw pain and pain in the facial muscles due to the effort made by these muscles.⁴¹⁾ During hyperfunction, the muscles may present painful symptoms⁴⁰ or even radiated pain, such as pain in the head.^13,20,42 This agrees with our results: 15.1% reported orofacial pain (Figure 5). In addition, 61% reported daily stiffness and strains (Figure 5). Regarding students’ perception, 33% reported bruxism (Figure 1), which agrees with a study that determined the prevalence (33.9%) of awake bruxism through self-reporting.²⁵⁾ It is also consistent with a systematic review of self-reported studies which presents a 22.1-31% AB prevalence in people who reported having suffered this parafunction frequently in the last six months.¹⁰

Conclusions

This study analyzes the situation of university physical education students regarding awake bruxism for the first time. It has found a high prevalence and a significant association between self-reported bruxism and females. These preliminary results suggest the need for more extensive studies to explore potential causal factors specific to this university degree. They might be linked to strength or resistance physical activity, stress, and anxiety.