Behavioral and clinical aspects associated with probable sleep bruxism in early childhood

Bruxismo do sono; desgaste dentário. Although many studies are being out with sleep bruxism, the literature points to a lack of studies with methodological quality in children. Objective: To evaluate the behavioral and clinical aspects associated with probable in early childhood. Material 6


INTRODUCTION
Defined as the repetitive movement of the mandibular muscles, the bruxism is characterized by the grinding and/or clenching of the teeth, which can occur while the individual is awake, known as awake bruxism, or during sleep, known as sleep bruxism 1 . The etiology is complex and multifactorial 2,3 , including biological factors (neurotransmitters, sleep alarms), psychological (stress, anxiety, personality) and exogenous (nicotine, alcohol, drugs, medications) 4,5 .
Different methods are used for the diagnosis; however, only the polysomnographic examination can confirm the presence of bruxism, this method is considered the gold standard [6][7][8] . Therefore, for conducting epidemiological studies with sleep bruxism in children, this method is not viable 9 . The American Academy of Sleep Medicine (AASM) considers that the reports of parents/caregivers or the self-report of teeth grinding, are quite reliable and sufficient for use in epidemiological studies 8,[10][11][12] . For this reason, the report of the parents/caregivers can be an essential complaint to the dental surgeon, so that he may, in due course, investigate further 6,13 .
Based on the literature, tooth wear seems to be a classic sign in confirmed cases of sleep bruxism, affecting mainly the incisal of anterior and occlusal of posterior teeth at different levels of severity. However, tooth wear in primary teeth is still much discussed since physiological wear is a common clinical situation 8,14,15 . Sleep bruxism can be considered multifactorial; the information such as location and conditions in which children sleep can explain the quality of sleep and, consequently, their parents/caregivers' observation of the habit of grinding their teeth 12 . Based on this information, the study hypothesis was that clinical variables evaluated and those related to sleep behavior are associated with the report of teeth grinding. Therefore, this study aimed to evaluate the behavioral and clinical aspects associated with probable sleep bruxism in early childhood.

MATERIAL AND METHOD
The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines were followed for the preparation and guidance of this study. This study was approved by the Human Research Ethics Committee (CAAE 01797118.3.0000.5385). Parents/caregivers and their children were invited and informed about the objective of the study and guaranteed the confidentiality of the collected data; in addition, they were informed that participation was entirely voluntary. After agreeing to participate in the study, the parents/guardians signed the free and informed consent form, and the children, the free and informed consent form. Data collection took place between March and June 2018. The parents received a questionnaire before the start of clinical data collection. Dental clinical examinations were carried out with the children inside the school.

Participants
A cross-sectional study was carried out with children from 4 to 6 years old, in the primary dentition stage, of both sexes, enrolled in municipal schools, and who did not have physical/mental impairment that would hinder their participation, previously authorized by parents/caregivers and who agreed to participate. The minimum sample was calculated based on a previous study 12 , considering the prevalence of bruxism in the unexposed group of 22.3%, test power of 80%, confidence level of 95%, and minimum odds ratio detectable of 2.0, resulting in a minimum number of 350 participants.

Non-clinical Data Collection
To assess the probable sleep bruxism, the parents/guardians responded if their children had gnashed their teeth during sleep in the past 30 days, causing the parents/caregivers to hear the noises 12,16,17 . Also, the parents/guardians answered questions related to their children's sleep behavior, about where their children slept, whether they were close to their parents' dormitory, whether their children slept with the door open or closed and whether they slept with lights on based on the American Academy of Sleep Medicine criteria ( Figure 1  A pilot study was carried out with 16 parents/caregivers to test the methodology. There was no need for adaptation, as the participants did not report any difficulty in understanding them. Pilot study participants were excluded and did not enter the main study.

Clinical Data Collection
Clinically, intra and extra oral exams were performed, which verified the presence of lip sealing, clicking, marks on the jugal and lateral mucosa of the tongue 18 . Lip sealing was assessed visually, observing whether or not the child's lips were sealed. The presence of marks on the jugal mucosa at the time the teeth touched and on the side of the tongue was assessed with the help of a wooden spatula. To assess the presence of clicking on the temporomandibular joint, the child was instructed to perform maximum opening, followed by closing 18 . For data analysis, the clinical characteristics evaluated were dichotomized in presence and absence.
Dental wear was assessed using the criteria recommended by the Basic Erosive Wear Examination (BEWE), where a scoring system is used to check the most severely affected surface of a sextant. The scores considered were: (0) no loss of surface; (1) initial loss of texture of the enamel surface; (2) less than 50% loss of surface or (3) loss of more than 50% of surface 19 . In the present study, tooth wear was classified based on the highest score present in the oral cavity, and dichotomized in the absence (scores 0 and 1) and presence (scores 2 and 3) 19 .

Statistical Analysis
An absolute frequency distribution table of the studied independent variables was built. To perform the logistic regression analysis, the report of teeth grinding was considered as a dependent variable of this study (presence and absence); simple logistic regression analyzes were performed, estimating the gross odds ratio with the respective 95% confidence intervals. Variables with P < 0.20 at each level were tested in multilevel multiple logistic regression models, with those with P ≤ 0.05 remaining in the model, estimating the adjusted odds ratios with the respective 95% confidence intervals.

RESULT
This study had the participation of 371 children, with an average age of 5.  Table 2 shows the analysis of the associations of the variables analyzed with the presence of teeth grinding. It was possible to observe that children with the presence of tooth wear are 1.53 (1.00-2.31) times more likely to grind their teeth (P < 0.05). There was no significant association with the other variables analyzed (P > 0.05).

DISCUSSION
Based on previous studies, the prevalence of sleep bruxism in children varies from 3.5% to 40.6% 11,12 . In our study, based on the parents' report, 42.4% of the children gnashed their teeth while sleeping. The findings' difference is due to the methodology used since the current systematic reviews highlight the lack of studies with adequate methodological quality for assessing bruxism and its associated factors in children 9,17 . Thus, the lack of standardization can produce different results, compromising comparisons between studies 20 .
The literature highlights that parents/caregivers' approach or self-report about grinding their teeth is the most used form 9,14 . Also, studies on sleep bruxism have found that tooth wear is a more common clinical consequence of bruxism of sleep 8,21,22 ; however, in primary dentition, due to the lower degree of mineralization of the teeth, the presence of physiological wear is widespread 8 . Therefore, the present study considers the presence of tooth wear, only in the most graves, to exclude physiological wear 15 . Our main finding was that children with severe dental wear were more likely to grind their teeth, a result that is contrary to the previous study, which does not consider only the most severe wear 12 .
Sleep is a complex physiological process influenced by intrinsic, biological properties, temperament, expectations, cultural norms and environmental conditions, such as light, is directly linked to the human clock and sleep pathophysiology 16,23,24 . Variables such as sleeping with lights on are significant since this habit can interfere with sleep quality 12 ; however, our results did not find any association with the report of teeth grinding, and the literature has shown conflicting results about this association 16,17 . On the other hand, information about the proximity in which parents/caregivers sleep with their children, and whether the door remains open or closed could interfere with the observation of parents/caregivers; however, in the present study, there was no association between these variables, collaborating with the result of a previous study 16 . Despite the lack of association between sleep bruxism and the absence of lip sealing, there was no association between variables. Also, the literature recognizes that the presence of sleep bruxism is often associated with other respiratory disorders related to sleep, such as mouth breathing and sleep apnea 7,18 .
One of the biggest challenges for epidemiological studies on bruxism in children today is still the lack of standardization of the methodology 9 . Based on the literature, factors such as headache, muscle pain, low sleep quality, psychological factors, respiratory problems, and behavioral problems may be associated with sleep bruxism and may influence the development of comorbidities in the individual 6,11,15,[25][26][27] . As with any pathology, it is essential to diagnose and intervene early, even with little concrete information, if identified, it is possible to intervene and consequently eliminate or reduce the impact on the child's life.