Claudia Restrepo-Serna,Efraim Winocur
Sleep bruxism in children, from evidence to the clinic. A systematic review
sleep bruxism,children,anxiety,sugar,screen time,obstructive sleep apnea,sleep architecture
Objectives The present paper aims to systematically review the literature published from 2015 to 2023 on bruxism in children with the aim to compilate the best available evidence. Materials and Methods A systematic search in the National Library of Medicine's PubMed, Medline (EBSCO), SCOPUS, and Google Scholar databases was performed to identify all studies on humans assessing genetic, biopsychosocial, and sleep factors assessed with any different approach for sleep bruxism (SB) in children and its interventions. The selected articles were assessed independently by the two authors according to a structured reading of the article's format (PICO). The quality of the articles was evaluated using Quality Assessments Tool for Experimental Bruxism Studies (Qu-ATEBS) and the JBI critical appraisal tools. Results A total of 16 articles were included for discussion in the review and grouped into questionnaire/parental-report (n = 7), SB assessment through parental report of SB and clinical examination (n = 4), and instrumental assessment (n = 5) studies. The total quality scores evaluated with STROBE and Qu-ATEBS were high for all included papers. However, in general, there was no control of bias strategies and there was no control group in the intervention studies. Conclusions Investigations based on self-report, clinical, and instrumental bruxism assessment showed a positive association with genetics, quality of life aspects (school and emotional functions and overuse of screen-time), mother anxiety and family conformation, diet, alteration in sleep behaviors and architecture, and sleep breathing disorders. Additionally, the literature presents options to increase airway patency and, thus, reduce the occurrence of SB. Tooth wear was not found to be a major sign of SB in children. However, methods of SB assessment are heterogeneous and hamper a reliable comparison of the results.
Sleep bruxism in children, from evidence to the clinic. A systematic review

The present paper aims to systematically review the literature published from 2015 to 2023 on bruxism in children with the aim to compilate the best available evidence.

A systematic search in the National Library of Medicine's PubMed, Medline (EBSCO), SCOPUS, and Google Scholar databases was performed to identify all studies on humans assessing genetic, biopsychosocial, and sleep factors assessed with any different approach for sleep bruxism (SB) in children and its interventions. The selected articles were assessed independently by the two authors according to a structured reading of the article's format (PICO). The quality of the articles was evaluated using Quality Assessments Tool for Experimental Bruxism Studies (Qu-ATEBS) and the JBI critical appraisal tools.

A total of 16 articles were included for discussion in the review and grouped into questionnaire/parental-report (n = 7), SB assessment through parental report of SB and clinical examination (n = 4), and instrumental assessment (n = 5) studies. The total quality scores evaluated with STROBE and Qu-ATEBS were high for all included papers. However, in general, there was no control of bias strategies and there was no control group in the intervention studies.

Investigations based on self-report, clinical, and instrumental bruxism assessment showed a positive association with genetics, quality of life aspects (school and emotional functions and overuse of screen-time), mother anxiety and family conformation, diet, alteration in sleep behaviors and architecture, and sleep breathing disorders. Additionally, the literature presents options to increase airway patency and, thus, reduce the occurrence of SB. Tooth wear was not found to be a major sign of SB in children. However, methods of SB assessment are heterogeneous and hamper a reliable comparison of the results.

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible during sleep (1). The concept of bruxism shifted from a disorder to a motor activity that may even have potential protective relevance (2, 3). The etiology of SB is multifactorial (4) and includes biological, psychosocial, and lifestyle factors. According to gene analysis studies (5, 6) and studies among individuals of the same family (7), SB is explained by both environmental and genetic factors (8, 9). Moreover, an imbalance in certain neurotransmitters in the central nervous system (e.g., dopamine and serotonin) play a role in the genesis of masticatory muscle activity (MMA) and SB (10). This imbalance is related to lifestyle factors, like consumption of added sugar and screen-time overuse (11), and psychosocial factors, such as anxiety, depression, and stress, which have also been demonstrated to increase risk for SB (12, 13). Additionally, health issues like breathing disorders (14) and Gastroesophageal Reflux Disease (GERD) (15) have also been suggested as predictors of SB. Studies that follow cohorts to assess SB are scarce, which hampers the possibility of establishing a cause-consequence relationship. SB could be a transitory activity related to positive consequences in most of the cases (such as reducing cortisol levels during positive stress situations), but in some cases is the symptom of situations that can even compromise the patient's life (obstructive sleep apnea). In this last point, following subjects over time without undergoing intervention for the underlying condition is not viable due to ethical concerns. Variations in the conception and assessment of SB, population characteristics, and research methodologies among different studies might partially contribute to the inconsistent results. Due to these reasons, clinicians lack enough tools to update and apply an adequate evidence-based dentistry regarding bruxism in children. Therefore, this review aimed to compile the best available evidence about bruxism in children over the last seven years and give evidence-based recommendations for pediatric healthcare givers to treat bruxism in the clinic. The question we aim to answer is, “What is the evidence that supports the assessment and intervention of sleep bruxism in children?”

This systematic review was registered in PROSPERO.

On March 25 2023, a literature review was performed based on a search in PubMed, Medline (EBSCO), SCOPUS, and Google Scholar databases for articles on SB in children and its etiology, assessment, and intervention. The search was filtered to include only papers published from 2015 to 2023 in the English language. The keywords used in the search strategy for each database are included in Table 1. The article screening included two phases: title and abstracts screening, and full-text review. First, all identified titles and abstracts were independently screened by the two authors. The inclusion criteria were: (a) studies on child human subjects (age 0–18 years); (b) studies dealing with SB, evaluated by parental-report [e.g., reporting of sleep tooth-grinding sound (STG) by questionnaire or interview] and/or clinical inspection (e.g., tooth wear, Linea Alba, and/or masticatory muscle pain), and/or instrumental assessment (e.g., scoring of SB episodes based on polysomnography (PSG), polygraphy, or Electromyography (EMG)); and (c) studies having the following designs: observational studies, controlled clinical trials, or randomized controlled clinical trials. The exclusion criteria were: (a) studies on animals; (b) studies on adults; (c) publication types such as editorials, letters, legal cases, interviews, and conference abstracts; (d) studies in which the assessment of SB and/or the outcome measures were not performed with calibrated/validated instruments and/or techniques; (e) studies including children with neurodevelopmental disorders; and (f) retrospective design. Full texts of eligible studies were only obtained when both reviewers were in consensus. Lack of agreement between the reviewers was resolved by discussion between both investigators.

The selected articles were read and assessed independently by the two authors according to a PICO (Population-Exposure-Comparison-Outcome) structured strategy. The population (P) is described in terms of sample size, inclusion criteria, and demographic characteristics. The intervention (I) concerns information on the study design, assessment approach, and measurement of variables. The comparison (C) includes data on the control group depending on the study design (i.e., individuals without SB). The outcome (O) is reported in terms of the possible relationship between different biopsychosocial and lifestyle variables and SB in children. The main conclusion of each study was also included. The PRISMA checklist for systematic reviews was followed.

Strengthening the Reporting of Observational studies in Epidemiology (STROBE) (16) was used for the quality assessment of case-control and cross-sectional studies. STROBE score, defined as the number of the 22 STROBE items adequately reported divided by the number of applicable items, expressed as a percentage, was determined for the quality assessment of the studies. The 13 STROBE items with several questions (2–15 questions per item, online supplementary) were considered adequately reported when at least 50% of their questions had “yes” answers (after exclusion of the “not applicable” components). Those studies dealing with intervention of sleep bruxism in children were evaluated with the Quality Assessments Tool for Experimental Bruxism Studies (Qu-ATEBS) (17). A score between 0 and 50 was considered low quality and a score between 51 and 70 was considered high quality. Only studies with a score above 50% in STROBE and above 51 in Qu-ATEBS were included in this systematic review.

Title and abstract reading led to the exclusion of 143 irrelevant articles. The full text was obtained of the remaining 27 articles. Of these, 14 were excluded for not fulfilling the inclusion criteria, so that 13 articles were selected for inclusion in the review. Two more papers were added to the review by searching the reference lists of two previous papers (18, 19). Thus, a total of 16 articles were included in the review. Table 2 includes the list of articles and the reason for exclusion from the review after reading the full text. Based on the type of assessment of SB, the selected articles were then divided into three categories: SB assessment by means of parental report (n = 7), SB assessment through parental report of SB and clinical examination (n = 4), and instrumental assessment (n = 5). The flow diagram for the inclusion of the studies is presented in Figure 1. The total quality scores evaluated with STROBE for all included papers with cross-sectional, case-control, and epidemiological studies were high. In general, there was no control of bias strategies. The total quality scores evaluated with Qu-ATEBS were high for the two included papers. However, in general, there was no control of bias and there was no control group in the intervention studies.

Seven studies investigated the association between parental-reported SB and lifestyle, habits, psychological and stress aspects, tooth wear, and the effect of two interventions (direct and indirect) for SB in children (Table 3). Study designs were strongly heterogeneous, based on the evaluation of SB either in non-patient children (e.g., school students or pediatric patients attending dental clinics of universities for conservative care) or in case-control groups of SB. Methodological differences were also evident from the strategy to assess SB as well as from the outcome measures established in each investigation. All the studies were based on a cross-sectional assessment, except for the two intervention studies. The authors used parental reports based on the Children's Sleep Habits Questionnaire (CSHQ) (34–36, 39) and the Self-Administered Questionnaire for Mother (38) and one used only the report included in the criteria of the American Academy of Sleep Medicine (AASM) (37). As for the results, six papers found a statistically significant association between SB and breathing disorders and parasomnias (35), forgetting things and feeling afraid or scared (36), and overuse of screen time and added sugar (34). Demographic characteristics were found not to affect the frequency of SB in children (35, 36) and tooth wear was not found to be significantly associated with the frequency of SB in children with mixed dentition (39). The paper dealing with palatal expansion on SB in children (40) showed reduction of parental-reported SB within the time of the study, but did not present long-term results.

Four investigations calculated the correlation of SB evaluated by means of parental report and clinical examination (tooth wear, Linea Alba, etc.) with genetics and family function (Table 4). All studies except one (44) were based on a case-control design (41–43) with comparison groups of SB vs. non-SB in children. The authors used parental reports of SB and a comprehensive clinical assessment (41, 42) or parental-reported SB and presence of tooth wear (43, 44) to evaluate bruxism. The two studies dealing with genetics found certain polymorphisms of Dopamine and Serotonin associated with bruxism (p < 0.05) (41, 42). Another study concluded that nail-biting and mother's and children's stress increase the odds of having SB (OR > 2; p < 0.02) (43). Finally, one study determined that the prevalence of SB among individuals with tonsil hypertrophy, restricted tongue mobility, and nasal obstruction was 90.9% (p < 0.05) (44).

One study evaluated the accuracy of PSG as a tool to assess SB in children (45), another determined the correlation between an EMG device (Grindcare measure) and PSG to evaluate SB/MMA in children (46), and two more evaluated the sleep architecture and physiology in children with SB (47, 48). One last investigation observed the effect of a Mandibular Advancement Device (MAD) to reduce SB by means of the BiteStrip® EMG device and obstructive sleep apnea by means of the ApneaLinkTM Plus in children (49) (Table 5). Subjects were recruited either among patients of a medical hospital (49) or university dental clinics (45–47). The assessment of SB with portable devices used in both studies with EMG for in-home recording were based on single-channel recording (46, 49). In one study, the researchers placed the EMG surface electrode (Grindcare measure) on the temporal muscle for five nights (46) and, in the other one, the BiteStrip® (49) was placed in the masseter muscle for 60 nights. All studies were based on a dichotomous assessment of presence/absence of bruxism, based on a cutoff threshold of two or four EMG episodes per hour of sleep (45–49), even though in one study, the number of EMG events were considered as a continuous variable (48). As for the findings, two studies did not retrieve any significant associations between SB/MMA and parental-reported SB (45) or between EMG for in-home recording with the Grindcare Measure and SB/MMA in the PSG recordings (46). Regarding the behavior of sleep in children with SB, sleep architecture and sleep MMA in the different stages of sleep significantly differed between children with and without SB. In sleep cycles, SB children showed more frequent MMA in all sleep stages than controls, while cyclic changes in cortical and autonomic activities did not significantly differ between the two groups. In SB children, MMA was the most prevalent in nREM stage 3 and was associated with increases in cortical beta activity and arousal. More than 70% of MMA occurred with cortical and motor arousals (47). Regarding treatment, one study evaluated the effect of a mandibular advancement device (MAD) for the treatment of obstructive sleep apnea syndrome (OSAS) in pediatric patients and one of the outcome measures of that study was the reduction of SB, which went from moderate to absent in 12 of 18 patients (49).

The objective of this review was to compilate the best available evidence about SB in children from the last seven years and to give evidence-based recommendations for pediatric healthcare givers to treat bruxism in the clinic. The results showed that there is available literature using only parental-report of SB as well as parental-report and clinical symptoms of SB (e.g., tooth wear, Linea Alba, impressions in the mucosa and tongue, headaches, and orofacial pain on awakening, chewing and/or opening, and tenderness and pain on the temporal and masseter muscles during bilateral palpation) and SB/PSG. Epidemiological as well as case-control and intervention studies were found. The investigations dealt with genetics, sleep behaviors and architecture, lifestyle and habits, and quality of life, diet, and assessment of reliability of diagnostic tools and parental reports of SB. The experimental studies addressed the intervention of SB from its origin, evaluating the effect of two types of orthopedic devices (e.g., McNamara and MAD) to reduce the obstruction of the airway aiming to reduce parental-reported SB and SB episodes. Below, each of the topics found in the review will be discussed.

According to the results of this review, there is an association between SB and expression of certain polymorphisms (41) of Dopamine and Serotonin, which are related to coping strategies, the regulation of the wake-sleep cycle and the regulation of hunger and satiety (50). Regarding the Dopaminergic genes, the DRD2, DRD3, and DRD5 receptors (51, 52) represent a predisposing genetic pattern for SB in adults, but DRD2 and catechol-o-methyltransferase (COMT) have been related to SB in children (42), as shown in this review. COMT and DRD2 are associated with disruption of the reward system in the brain (53), stress, authoritarian parenting patterns (54), and deleterious changes in the quality of life (55) of children. These patterns, in turn, have also been recognized in children with SB at the school stage (34, 36). As will be mentioned later in this review, SB has a close relationship with OSA. In this regard, in adults, the DRD1 rs686 may indicate a predisposition to BS caused by obstructive sleep apnea and or hypopnea (OSA), and the HTR2A rs2770304 polymorphism could contribute to the association between SB and OSA (56). In this review of the literature, these polymorphisms were not related to SB in children. Further studies are necessary to determine the relationship between the genetic factors associated both with respiratory disturbances (e.g., OSA) and SB in children.

Two studies were included in this review that deal with sleep architecture of SB in children (47, 48). One showed that SB was more frequent in nREM 3 (47), while the other indicated that sleep architecture of children with SB was more affected in REM than in nREM sleep (48). This is in agreement with the results of a previous investigation that found that the episodes of SB occur primarily during nREM 2 and during REM sleep (57). In the three studies (47, 48, 57), a relevant percentage of bruxism episodes were associated with arousal. Additionally, within the limitations of the study, Restrepo et al. (48) demonstrated that the odds of high masticatory muscle activity related to SB increased when there was high sleep onset latency, short sleep duration, short REM sleep duration, and high microarousals/hour during REM sleep. A significant correlation between SB and snoring has been supported by several studies in children (35, 44). Although studies have suggested concomitant occurrence of SB in individuals with OSA, a narrow upper airway, rather than an obstruction of the upper airway, could be a factor contributing to the relationship between snoring and SB in children (58). OSA and its relationship to sleep bruxism is related to an arousal response that is often generated by hypoxemia and respiratory difficulty that triggers a serotoninergic neuronal reaction (56). At the end of an apneic event, frequent snoring, mumbling, gasping, and or STG occur (59). It is imperative to recognize these symptoms early, as children with SB can have a high likelihood of showing problematic daytime behavior that can also be frequently associated with sleep problems (60). Thus, evaluating the upper airway and using other diagnostic tools such as cephalograms and panoramic x-rays to determine airway dimensions and/or obstruction is mandatory in the dental room to search for a transdisciplinary assessment and intervention. GERD acidifies the gastric tract and causes contraction of the airway, triggering SB/MMA in order to increase the buffer capacity by stimulating the salivary glands (61). Bruxism patients who experience GERD for extensive periods of time are prone to severe tooth wear. Gastric juice has greater erosive effects on both enamel and dentin (62) compared to acids from diet (63). This may be the reason why, when excluding from studies children with GERD, increasing frequency of SB was not correlated with the severity of tooth wear, as demonstrated in one of the articles included in this review (39). According to this evidence, it is mandatory to change the procedures to determine the origin of tooth wear and rethinking tooth wear as a diagnostic criterion to assess SB in children.

Quality of life (QoL) is emerging as an important outcome measure in the current medical literature, but available data on its relationship with SB in children are still scarce. As stated before, polymorphisms in DRD2 related to bruxism phenotypes in children (42) is a genetic variation in the dopamine receptor D2 (DRD2) that may alter dopamine signaling and modify the rewarding effects of food (64) and videogame playing (65) and could explain the relationship between SB, sugar, and screen overuse (34). The consumption of added sugar and excessive screen-time is increasing worldwide (66), increasing the prevalence of sleep problems (67, 68), psychosocial disorders (69, 70), lack of cortisol homeostasis (71), depression and hostility, and Attention Deficit Hyperactivity Disorder-related symptoms (72). All these issues have also been associated with SB in children (35). On the same hand, alterations in QoL have been associated with SB in children, particularly effects on working memory and emotional regulation (36). Excessive screen-time and added sugar consumption are also risk factors for the same QoL issues (73, 74).

Anxiety in childhood is a frequent occurrence (75). However, it is underdiagnosed because of diverse symptomatology according to the different phases of development. Additionally, the concept of education is changing, and family structure and parenting style are also changing. Parenting requires spending a lot of time and resources on caring for and nurturing children (75). In addition, the unavailability of educational resources, the comparison between peers, and the lack of parenting experience increase parents' and children's tension and anxiety. Mothers have the highest influence on children, as they have the most contact with them (75). This may be the reason why studies have found that there is a correlation between mothers' and children's emotions. As a matter of fact, one of the studies included in this review (43) found that elevated anxiety levels of mothers increase the risk of having SB in children. Additionally, the same study found nail-biting as a predictor of SB and proposed that this could be a consequence of anxiety (43). This is the main reason why it is so important to evaluate the children's relationship with their mothers and the rest of their families when addressing SB in children in the clinic.

The two investigations that were included in this review regarding intervention were focused on improving airway patency (40, 49) in order to reduce the mechanism that triggers SB in children. Other studies evaluating strategies to treat anxiety, psychological issues, and parafunctional habits associated with SB were not included in this review, even though they are extremely necessary. The study by Giannasi et al. (40) evaluated the parental reports of SB before and after palatal expansion with the McNamara device to increase nasal volume and airflow. The other investigation (49) increased oropharynx dimensions by using MAD in children with respiratory disturbances and the measurement of SB was made with PSG (49). In both cases, the report of SB and SB/MMA decreased.

The quality of studies about bruxism in children varies widely. All studies included in this systematic review were well-conducted, using appropriate study designs and methods. However, there are limitations, such as small sample sizes, lack of appropriate control groups and control of bias, and unclear measures of outcomes. Additionally, there is a lack of consensus about the assessment and treatment of bruxism in children, which leads to variability in study results. One of the main challenges in conducting studies about SB in children is the difficulty in diagnosing the condition. Bruxism is often identified by parental reports of grinding or clenching teeth during sleep and/or clinical examination, but even the reports and clinical examination are not standardized or accurate in identifying the condition. Another challenge is the lack of consensus about the etiology of bruxism. Some studies suggest that it is related to psychological factors, such as anxiety or stress, while others point to quality of life, lifestyle and habits, diet, or other medical conditions. This variability in etiology can make it challenging to design studies that adequately control for confounding factors and is difficult to review the studies to synthetize the evidence. Despite these challenges, there have been several well-conducted studies on SB in children that provide insights into the prevalence, risk factors, outcomes, and intervention of the condition. These studies have highlighted the importance of paying attention to what is generating SB and intervening when necessary. However, more high-quality studies are needed to better understand the underlying mechanisms, risk factors, and effective interventions for bruxism in children. Future studies should strive to use appropriate study designs and methods, include appropriate controls and measures, and use consistent definitions and diagnostic criteria to improve the quality and comparability of study findings.

Sleep bruxism is a symptom of underlying health, biopsychosocial, lifestyle, and diet conditions of children and their families. According to the findings in this review, methods of SB assessment are heterogeneous and hamper a reliable comparison of the results. However, with the available literature, it is possible to propose a flowchart based on an algorithm to assess and intervene with SB in the clinic (Figure 2). This algorithm contains the main variables that have been studied regarding SB in children and proposes a transdisciplinary approach.