Introduction

Bruxism is defined as the “repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible.This can occur either during sleep or during wakefulness.

The occurrence of bruxism is more common in children and it decreases with age and is less common in adults [1, 2]. According to Manfredini et al. [2] the prevalence of the bruxism in children across the globe ranges from 3.5 to 40.6%, and does not show gender preference. In the recent times, bruxism has become one of increasing concern among children as it has a negative impact on quality of life. As a result of mechanical grinding either during night or day time, bruxism in children leads to tooth wear, tooth mobility, tongue/cheek indentation, masticatory muscle hypertrophy [3-5] temporomandibular disorder s[6], headaches [7], palatal changes and masticatory muscle pain or fatigue breathing disorders during sleep [8-10]. Functional disturbances of the masticatory system are found to be common in children aged between 7 and 14 years with 64% experiencing pain on muscle palpation and 39% experiencing pain on TMJ palpation [11].

In addition due to axial forces generated in children with bruxism, it acts as an adjuvant force causing progression of destructive periodontal disease in children [12]. The parafunctional habit also contributes to the development of false Class III, acceler¬ated root resorption of deciduous teeth and changes in the chronology of permanent teeth eruption and promotion of dental crowding [13]. Thus, this habit should be diagnosed and managed as early as possible [13]. Though studies have indicated a relation between bruxism and respiratory alterations [9, 10, 14] the effect of Bruxism on orofacial maturity and speech are still not well established. The numerous changes in the orofacial region due to grinding of teeth, calls for an early diagnosis and management of bruxism in children.

The various oral manifestations due to bruxism in children must be assessed by the dentists to arrive at a more accurate diagnosis of bruxism. Since, there is a lack of uniformity and standardization of criteria to assess the signs and symptoms of bruxism in children, a systematic and critical analysis of current literature is essential to obtain precise data of craniofacial features of children with bruxism.

The objective of this systematic review is to systematically evaluate the craniofacial changes associated with bruxism in children.

Materials and Methods

The present systematic review was registered in PROSPERO (CRD42018108124). The authors also followed the recommendations of the PRISMA statement during formulation of systematic review14. The PECO methodology was utilized to formulate the research question which was “To identify the craniofacial manifestations of children aged between 3 to 17 years with bruxism.”.

Search Strategy

An electronic search of the following databases which includes PubMed, ScienceDirect, Google Scholar and Cochrane were performed till Dec 2018. And a hand search of reference list in the selected articles were performed to recognize publications if not identified by electronic search. Articles only in English language were considered for inclusion in the systematic review. Case series and observational studies of the craniofacial features in children with bruxism aged between 3 to 17 years were included for review. Review studies that included both narrative and systematic reviews, letters to the editor, case reports, animal studies, studies without age discrimination, studies involving children with special health care needs were excluded from the review.

The following search strategy was used :((((((Children) OR Kids) OR younger age)) AND ((((Grinding of teeth) OR Sleep bruxism) OR Tooth clenching) OR Bruxism))) AND (((((((((((((((Tooth wear) AND Occlusal wear) AND Attrition of teeth)) OR (((anterior crossbite) OR posterior crossbite) OR transverse occlusal relationships)) OR Periodontal disease) OR Masseter muscle activity) OR Facial pain) OR Bone loss) OR Periodontitis) OR Gingivitis) OR Palatal morphology) OR Sensitivity of teeth) OR Head ache) OR (((Temporomandibular Joint pain) OR TMJ pain) OR Temporomandibular joint disorder)).

The initial list of articles, assessed by title and abstract, was submitted for review by two independent reviewers (MSN, DG) who applied inclusion criteria and exclusion criteria to determine the final sample. Should there be disagreement between the results of reviewers, a third reviewer (JM) was called in for consensus.

A total of 223 potentially relevant records were found: 219 articles from PubMed, 8 publications from Scopus, 8 publications from WEB OF SCIENCE, none form Cochrane Library, 13 publications from google scholar. After the duplicate references were removed, a total of 219 studies were available for further analysis. Based on titles and abstracts verification 11 articles were selected for the systematic review.

Data Extraction

Following data was extracted for the selected 11 studies: author names, year of publication, total sample size, sample sex, sample age, diagnosis of bruxism, classification of bruxism, according to the period that occurred and the pattern, occlusal characteristics, palatal morphology, transverse relationship, temporomandibular joint disorders, drooling of saliva, masticatory muscle hyperactivity. (Table 1)

Diagnostic Criteria of Bruxism

The diagnosis of bruxism was made by parents or guardians in most of the studies and 2 used clinical examination. Despite the wide variety of diagnostic forms for bruxism, 30% used the American Academy of Sleep Medicine 15 criteria and the other questionnaires were prepared by authors or used questionnaires from previous studies [16]. New Castle Ottawa Scale was used to assess the quality of the studies [17]. (Table 2 and Table 3)

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Study selection

Study characteristics

Edward V. Kuch (1979) [19] is a case control study showed 15.5% children out of 358 children showing bruxism. When compared with the controls there was no significant difference in the eight psychological traits evaluated namely conformity, masculinity femininity, maturity, aggression, inhibition, activity level, sleep disturbance and somatization.

C. C. RESTREPO (2008) [20] is a case control study comparing 23 children with bruxism with 23 controls for changes in form of palate in sagittal, frontal and horizontal plane. There was a statistically significant difference in the sagittal plane between bruxers and non-bruxers.

BahmanSeraj (2010) [21] is a cross-sectional descriptive study carried out on 600 children aged 4-12 years. This was a questionnaire based study which found 26.2% of prevalence for bruxism in the population. The present study reveals drooling as the most common sleep disorder in children with bruxism. In addition, the prevalence of bruxism was higher in children with temporomandibular disorder.

Carra MC, Huynh N (2011) [22] is a case control study where 604 children seeking orthodontic treatment were evaluated for bruxism and compared with controls for jaw muscle fatigue, headache and loud breathing during sleep. This study shows sleep and wake time bruxism to be associated with signs and symptoms suggestive of TMDs and sleep and behavioral problems.

Maryam Ghafournia (2012) [23] is a case control study who examined 400 children and divided them into bruxers and non-bruxers. This study found statistically significant changes in the bruxers and occlusal relationship such as flush terminal plane, mesial step, anterior and posterior crossbite.

Emodi Perlman (2012) [24] is a cohort study assessed 559 children for parafunctional habits and its association with anamnestic and clinical findings of TMD and possible impact of stressful life on the parafunctional habit. The present study showed stressful life showing increased association with the prevalence of parafunctional habits, however, bruxism was not associated with anamnestic and clinical findings of TMDs.

Tatiana Helena Junqueira (2012) [25] is a cohort study showing children with headache and restless sleep showed higher chance of presenting with bruxism. Children with bruxism showed higher prevalence of mesial step relationship.

Ana Carla Raphaelli Nahás-Scocate (2014) is a cross-sectional study which examined 873 children through questionnaire and clinical examination for bruxism and its corresponding effects on the occlusal characteristics in the transverse directions. This study showed 28.8% prevalence of bruxism habit, however, there was no significant difference between bruxers and prevalence of crossbites.

B.deL.Lucas (2014 [18] is a case control study which compared muscle activity between bruxers and non-bruxers. This study found no significant increase in the muscle activity in children with presence of bruxism.

Nashalie Andrade de Alencar (2016) [28] is a case control study that reported 34 children with bruxism compared with 32 nonbruxers. The outcomes of the child’s routine during the day, during sleep and awakening, headache frequency, temporomandibular joint (TMJ), and hearing impairments were assessed using questionnaire. In addition, electromyography was done to assess the activity of facial muscles. There was a positive association between bruxism and nightmares, snoring, orofacial pain and headache.

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Carolina CarvalhoBortoletto (2017) [29] is a cohort study conducted on 103 children aged 3-6 years. The present study evaluates the presence of sleep bruxism using the criteria given by American Academy of Sleep Medicine and the quality of sleep was evaluated using questionnaires. 47.6% of children showed sleep bruxism with 3.25 fold children more likely to be present with headache. This study does not report presence of headache associated with clenching teeth in the morning.

Discussion

Bruxism is an oral habit which is characterized by habitual clenching and grinding of teeth. It is associated with severe wear of the dentition as well as affects muscle and joint apparatus. In addition, it increases the risk of traumatic dental injuries and increases the progression of the periodontal diseases.

Bruxism is a Para-functional habit that possesses a multifactorial etiology. Its cause is related to genetics, premature occlusal interference, psychological and behavioral factors, increased overjet, overbite, open bite and crossbite. In addition Temporomandibular Joint disorder is also associated with the etiology of bruxism. These craniofacial factors are the cause as well as effect of the bruxism. Hence, the present systematic review evaluates the effect on craniofacial factors associated with bruxism.

The present systematic review includes 11 studies based on the pre-determined inclusion and exclusion criteria. These studies were either cohort studies or case control studies.

For cohort and cross-sectional studies the outcome was assessed using questionnaires which assessed the history and characteristics of the habit. In addition these studies also reported the prevalence of bruxism among the population. These characteristics of bruxism were co-related with the occlusal features in the dental arch. In addition ASSM criteria was also used to evaluate the pain and tenderness in the temporomandibular joints associated with bruxism which was co-related with presence of occlusal facets.

The outcome for case control studies, ASSM criteria was used. This compared outcomes between the children with bruxism and children without bruxism. Another study by B.deL.Lucas [18] used the EMG of masticatory muscles and compared with morphologic occlusion between the children with bruxism and children without bruxism. Nashalie Andrade de Alencar used both AASM criteria as well as EMG in addition to presence or absence of headache compared with occlusal factors between children with bruxism and children without bruxism. In study by Carra MC, Huynh N4 the craniofacial changes were evaluated based on the presence of overjet, overbite, crossbites and facial profiles between children with bruxism and children without bruxism.

The included studies showed prevalence of bruxism from 30- 47.6% varying among different populations. According to Edward V .Kuch, [19] wear facets were observed in children with bruxism. In addition to wear facets, pain and tenderness in the masticatory muscle and increased headache was reported in children with bruxism. This was a contradictory finding in another study by B.deL.Lucas who reported no significant difference in pain and tenderness of masticatory muscles and headache between children with bruxism and those without. Another contradictory report was found between the occlusal relationship in children with bruxism. A study by Maryam Ghafournia [23] reported higher number of mesial step relationship in children with bruxism as compared to the study by Tatiana Helena Junqueira [25] reported no significant difference between children with bruxism and their terminal relationships. In addition, a study by C. C. RESTREPO [20] reported children with bruxism to have high arch palate as a craniofacial abnormality. Also, studies by Carra MC, Huynh N4 and Ana Carla Raphaelli Nahás-Scocate [27] reported children with bruxism to have increased presence of crossbites.

Since there is a contradictory result from different studies regarding the outcomes of terminal relationship and presence of muscle tenderness, pain and headache, further studies giving a more definitive insight to these outcomes should be conducted. A major limitation of the present systematic review is that it selects article evaluating only the effect on craniofacial structures. Bruxism being a multifactorial disorder, incorporating more etiological factors and multiple outcomes can give an overall outlook to the parafunctional habit.