The disease caused by COVID-19 was named severe acute respiratory syndrome (SARS-COV-2). As of January 14, 2024, there were 774.29 million cases worldwide and 7.02 million deaths. In Yucatan, Mexico, as of June 25, 2023, 145,910 cases of infection and 7,038 deaths were recorded. Due to its rapid spread and the declaration of quarantine, the pandemic impacted stress levels in the general population, primarily due to the fear of death [1]. The COVID-19 pandemic is responsible for many deaths around the world and for psychological problems. This pandemic is a reality that humanity had to face and combat as a process of survival and adaptation, thus becoming a challenge that led to stress [2].

Consequently, stress is considered an inevitable phenomenon and has been defined as a mental state that arises when humans face physical or psychological difficulties. It can also be described as a process in which the environment overwhelms an organism’s ability to adapt, leading to biopsychosocial changes that put individuals at risk of illness. Adaptation to new circumstances in life is a process that can either succeed or fail. When such adaptation is complicated and does not result in a positive outcome, stress is reflected as a cause that leads to deterioration or fatigue in the body and/or mind [3,4].

Relational or interactional stress symptoms primarily manifest as social isolation, along with distrust towards others. It is common to observe a constantly defensive attitude, leading to problems with family, friends, partners and coworkers, among others [5].

Furthermore, regarding reactivity to stress, women self-report higher levels of subjective distress in response to an acute stressor. However, they have reported using coping strategies, such as verbally expressing their emotions regarding certain circumstances6. In this regard, stress in pregnant women is defined as the imbalance a woman feels when she cannot cope with demands, which she expresses both behaviorally and physiologically. Studies have shown that when a pregnant woman is depressed, anxious, or stressed, as a result there is a higher probability that the baby will experience adverse effects on its neurological development, as well as a high risk of emotional, behavioral, and cognitive problems [4].

Consequently, the COVID-19 pandemic challenges society in various ways, specifically for pregnant women who face extraordinary concerns, such as the unknown risks for themselves and their baby in case of infection, restrictions on prenatal classes and hospital visits [2].

These stressful situations can contribute to bruxism, defined as the involuntary, unconscious, and excessive grinding of the teeth. It involves strong contact between the occlusal surfaces (occlusal faces in the posterior teeth and incisal edges in the anterior teeth) of both dental arches. Its diagnosis is a challenge for the treating dentist, as it is generally based on patient self-reports that are questionnaires and dental clinical history and, as a complement, intraoral clinical examination. Such self-reports are useful to assess the possible activity, frequency, intensity, and duration of bruxism [7].

In many cases, bruxism is mild and does not require treatment, but severe bruxism causes significant damage to the teeth and the following symptoms: tooth pain, dental hyperalgesia, headache, trigeminal neuralgia; as well as myalgia, tension, and fatigue in the masticatory muscles. Persistent orofacial muscle pain (POMP) associated with myofascial pain has traditionally been related to hyperactivity or abnormal contraction of the masticatory muscles [8,9].

The above leads us to the aim of this study to associate Covid 19 pandemic stress with bruxism symptoms in Pregnant Women at the Maternal and Child Hospital of Yucatan, Mexico. During the period from September to November 2023.

Sample: This was an exploratory cross-sectional study in which 354 pregnant women from the “Hospital Materno Infantil de Yucatan, Mexico”, participated during 2023.  The surveys were conducted in the early hours of the morning: from 6 to 9 a.m., they were surveyed personally by a single previously trained researcher, to standardize the explanation of the questionnaires and answer the questions asked by the pregnant women. The questionnaires were carried out with prior authorization from the hospital authorities, the Bioethics Committee, and the patients who signed or provided a digital fingerprint on the informed and voluntary consent letter based on the ethical guidelines on the Helsinki Declaration. They were provided with an identity form (sociodemographic data) where they were asked to indicate their age, the trimester of pregnancy they were in, and whether they spoke Spanish, Maya, or both, since they came from different communities in the state of Yucatan, where there is a significant Mayan population as well as from the city.

Measuring instruments: The “Inventario SISCO del Estrés de Pandemia (ISEP)” questionnaire was applied, which was originally developed and validated in Mexico by Barraza-Macías A, [10] and later validated in Argentina by Caccia et al, [11]. Barraza-Macías [10]’ ISEP showed a Cronbach’s alpha reliability of .90; its items exhibited high homogeneity and unidirectionality, and the overall inventory reported a three-factor structure (stressors, symptoms, and coping strategies) that explained 62% of the variance. Caccia et al.'s version obtained Cronbach’s alpha reliability ranging from .86 to .91 [11]. This instrument could be administered individually or collectively, and in the present research, it was decided to be administered individually to each pregnant patient. It consisted of fifteen Likert-type items, with six response options ranging from "not at all" (0) to "a lot" (5). It was divided into three sections: the first corresponded to stressors, the second to symptoms or reactions, and the third to coping strategies.

The scoring was based on an average of the total items, and for each dimension. That is, the natural sum of the items was divided by the total number of questions (fifteen). Finally, the score was transferred to a 0–100 scale, using a direct proportion to obtain percentages, resulting in the following stress levels: 1%–20% (very mild level); 21%–40% (mild level); 41%–60% (moderate level); 61%–80% (strong level); 81%–100% (very strong level).

For the measurement of bruxism symptoms, the Self-Reported Bruxism Questionnaire (CBA) by Cruz-Fierro N et al, [12] was used. The reliability of the instrument was evaluated with a Cronbach’s alpha of .88, suggesting that the eleven items have adequate internal consistency. These items are rated on a Likert scale with five possible responses: 1 (not at all), 2 (little), 3 (regular), 4 (moderate), and 5 (a lot). As part of the CBA scoring, bruxism symptom scores could range from 1 to 55, yielding the following probable score ranges: 0–18: unlikely bruxism symptoms; 19–24: probable bruxism symptoms; and 25 or higher: definitive bruxism symptoms.

Statistical Analysis: Variables related to determining the frequencies of bruxism and pandemic stress levels were analyzed using descriptive statistics through absolute and relative frequency tables. This approach was replicated in specific analyses, where results were stratified according to the trimester of pregnancy or age group by dividing the analyses by groups. However, to determine the statistical significance of the identified trends, a non-parametric correlation analysis between the variables age and trimester with stress and bruxism levels was performed using Spearman’s test. This was because both age groups and trimesters were ordinal variables. Additionally, to examine the relationship between stress levels and bruxism, a non-parametric Spearman correlation was performed again since none of the variables showed a normal distribution. To control the effect of age group or trimester, the analysis was repeated using partial correlation. For all these analyses, a significance level of 0.05 was used.

The 354 pregnant patients had an age range between 10 and 49 years, a mean age of 24 ± 6.25 years, a median of 23, and a mode of 22 years. The most frequent age group was 20 to 24 years, comprising 33.1% (n = 117) of the sample, followed by the group of 25 to 29 years with 23.2% (n = 82) and the range of 15 to 19 years with 20.9% (n = 74). The vast majority, 95.2% (n = 337), were in the third trimester of pregnancy, while less than 1% (n = 2) were in the first trimester. Regarding language, 92.7% (n = 328) spoke only Spanish, and 7.3% (n = 26) were bilingual (speaking both Maya and Spanish).

The levels of pandemic stress due to COVID-19 were determined, revealing relatively high stress levels; approximately 70.6% of the participants presented stress levels ranging from moderate (27.4%), strong (29.9%), and very strong (13.3%).

On the other hand, during the first trimester, stress levels ranged from mild to moderate, while in the second trimester, strong levels were observed. In the third trimester, some patients even experienced very strong stress levels (Figure 1). Although an increase in stress levels was identified as the trimester advanced, this relationship was not statistically significant (rho = 0.042; p = 0.435).

Figure 1: Prevalence of Stress Levels in 354 Patients by Pregnancy Trimester.

Furthermore, stress levels in relation to the age group, as detailed in Table 1, showed that very strong stress levels were more noticeable as age increased, while very mild levels were more common among younger patients. A statistically significant, albeit weak and positive, relationship was revealed (rho = 0.170; p = 0.001). This finding indicated that older patients experienced higher stress levels during the pandemic.

Table 1:  Prevalence of Stress Levels among 354 Pregnant Women by Age Group.

Additionally, an evaluation of the prevalence of bruxism symptom levels was carried out. Results indicated that, overall, participants exhibited low levels of bruxism symptoms, that is, 81.1% had unlikely symptoms, 9.9% had probable symptoms, and 9% presented definitive bruxism symptoms.

Similarly, an analysis was conducted to determine whether the prevalence of bruxism symptoms showed any distinctive pattern according to the trimester of pregnancy. In Figure 2, it was indicated that patients in the first trimester did not exhibit bruxism symptom indicators; however, those in the second trimester already showed probable bruxism symptoms, while only those in the third trimester presented definitive bruxism symptoms. Nonetheless, examining this relationship indicated that this pattern was not statistically significant (rho = 0.017; p = 0.376).

Figure 2: Prevalence of Bruxism Symptom Levels in 354 Patients, According to the Trimester of Pregnancy.

An analysis of the relationship between bruxism symptoms and age was also carried out in a similar manner as with stress levels. The results presented in Table 2 showed mixed findings, as no clear pattern was observed beyond the fact that the presence of unlikely bruxism symptoms was the most prevalent across all age groups. This was confirmed by the Spearman non-parametric correlation, which indicated the absence of a statistically significant correlation between the variables (rho = 0.056; p = 0.295).

Table 2: Prevalence of Bruxism Symptom Levels in 354 Pregnant Women by Age Group.

Finally, the relationship between the level of bruxism symptoms and the level of stress experienced during the pandemic was examined. As shown in Figure 3, the results indicated a statistically significant, directly proportional relationship, although weak in intensity, between both variables (rho = 0.223; p < 0.001). This meant that pregnant women who experienced higher stress levels during the pandemic also more frequently manifested symptoms associated with bruxism.

Figure 3: Correlation between Stress Levels and Bruxism Symptoms in 354 Pregnant Women.

This relationship was subjected to additional analysis, controlling the effects of age and trimester, considering the previously identified association with stress. This control was achieved through partial Spearman correlation. The results again confirmed the significance of the correlation and even suggested a slightly stronger relationship (rho = 0.271; p < 0.001) after eliminating potential confounding effects, thereby strengthening the evidence of a clear connection between stress levels and bruxism symptoms in pregnant women.

Dominguez-Mejías M, et al., [13] assert that the pandemic has exacerbated the likelihood of developing psychological disturbances during pregnancy, a period of increased vulnerability. In a study by Awad-Sirhan N, et al., [14] levels of anxiety and stress during the pandemic are evaluated, showing that this period imposed additional stress on pregnant women, highlighting the need to address the psychological well-being of this population to avoid health damages resulting from this condition [13,14].

Based on the SISCO Inventory used in the present study, stress levels in pregnant women are identified according to their trimester. The results show that approximately 70% of pregnant women exhibit stress levels ranging from moderate to very strong. Lopez-Morales H, et al., performed a study in Argentina in 2021, comparing the psychopathological consequences of the pandemic between pregnant and non-pregnant women. Like the present study, higher levels of stress, anxiety, and depression are recorded in the third trimester [15].

Furthermore, stress levels according to age are evaluated using the SISCO Inventory. The American Association of Retired Persons (AARP) maintains that as age increases, an individual reacts to stress with greater intensity, and the health consequences can be more detrimental, with a longer recovery time after these episodes. Their survey reveals that 38% of people aged 40 or older report feeling extremely stressed. This supports the result obtained in this study, which determines that higher age is associated with higher stress levels [16].

On the other hand, the prevalence of unlikely, probable, or definitive bruxism symptoms is determined using the Self-Reported Bruxism Questionnaire (CBA). In 81.1% of the population, unlikely symptoms of bruxism are recorded, while 9% of the patients perceive definitive bruxism symptoms. In a study by Mu-Galvez B, et al., patients’ recognition of signs and symptoms of bruxism during the pandemic is evaluated, concluding that there is a lack of awareness about the condition even if they might be suffering from it. This is supported by references from Hernandez-Reyes B, et al., cited by Mu-Galvez B, et al., who confirm the difficulty in identifying bruxism in its early stages due to a lack of understanding of its meaning and effects [17].

Also, Diaz-Gomez et al., cited by Mu-Galvez B, et al., argue that 100% of the population may experience bruxism at some point in their lives without being aware of it, so self-reported studies might not capture the full presence of the condition [17].

Rodríguez R, a maxillofacial surgeon, affirms that stress can cause bruxism. His study shows that bruxism is present in 60% of adults between 30 and 59 years of age. He points out that treatment must be strictly multidisciplinary between psychiatry and dentistry. Moreover, in most cases, its detection is not perceived by the patient. Therefore, even though only 9% of participants in the present study reported definitive bruxism symptoms, as previously mentioned, there is a high possibility that a large portion of the study population may suffer from this condition without being aware of it [18].

In a study by Aucar-Lopez J, et al., which explored the relationship between stress and bruxism in medical science students, over 50% are diagnosed with bruxism, with the most affected being those in the medical program, who exhibit more frequent bruxism symptoms such as muscle pain, referred dental clenching, and joint pain, which are definitive bruxism symptoms [19].

From this information, it is concluded that psychological factors such as anxiety, stress, fear, and frustration are directly related to muscular hyperactivity and can be part of the etiology of bruxism, serving as a promoting factor for this condition, in agreement with the results of the present study that show a statistically significant, directly proportional relationship  in which patients with higher stress levels during the pandemic more frequently manifest symptoms associated with bruxism¹⁹.

It is hoped that this research will have a positive impact on the scientific community and be useful for further investigation into the subject. Based on the conclusions, a comprehensive approach addressing both symptoms and clinical signs is suggested to obtain a complete analysis of the condition. Furthermore, it is crucial to raise patient awareness about the importance of preventive consultations so that oral diseases can be detected and be halted before they progress.

Acknowledgments
To the Maternal and Child Hospital of Yucatan, Mexico. Also, to all the women that collaborated with this study. 

Data availability

Datasets related to this article will be available upon request to the corresponding author.

Conflict of interests

No potential conflict of interest was reported by the authors.

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