ASSESSMENT OF TEMPOROMANDIBULAR JOINT SOUNDS IN CHILDREN WITH BRUXISM Avaliação dos ruídos da articulação temporomandibular em crianças com bruxismo

Conflito de interesses: inexistente (TMJ)1,2. Bruxism can also have behavioral and psychological effects3. The consequences of bruxism to the TMJ are directly related to the changes that occur in the masticatory muscles. Pain and discomfort in this joint are the main complaints of affected individuals, along with difficulty chewing, uncoordinated jaw movements, joint luxation, degenerative alterations in the joint, restricted/deviated mandibular movements and joint sounds4,5. Studies have demonstrated sounds in the TMJ are frequent in children with temporomandibular disorder (TMD)6-9. However, there is little evidence of this sign in children with bruxism. Moreover, divergent findings are reported regarding the relationship between TMD and bruxism in this population9.  INTRODUCTION


INTRODUCTION
Bruxism (clenching and/or grinding of one's teeth) is often found in children and adolescents.This habit can have harmful effects on the teeth, periodontium, masticatory muscles and temporomandibular joint ABSTRACT Purpose: the aim of the present study was to determine whether between bruxism is associated with joint sounds in children.Methods: children aged six to nine years were recruited from the pediatric clinic of the School of Dentistry of Nove de Julho University (Brazil).Twenty-one children with bruxism and 27 children without this disorder (control group) were selected.The evaluation was performed by a previously trained examiner who was blinded to the allocation of the groups and involved manual palpation as well as lateral and dorsal extra-auricular auscultation of the temporomandibular joints with the aid of a stethoscope for the determination of joint sounds, differentiating a click/pop from crepitation.At least three readings were performed on each child.Descriptive statistics were conducted and the chi-square test was used to test the strength of associations between variables, with the level of significance set to 5% (p < 0.05).Results: a total of 37.5% (n = 18) of the sample exhibited some type of joint sound.Among these children, 72.2% (n = 13) exhibited a click/pop and 27.8% (n = 5) exhibited crepitation.Of the 18 children who presented some typical noise, 66,7% (n=12) were also bruxism.A statistically significant association was found between joint sounds and bruxism.No association was found between joints sounds and gender.However, a significant association was found with regard to age, as a greater percentage of children at six years of age had no joint sounds.Conclusion: the present data demonstrate an association between bruxism and joint sounds in children.

KEYWORDS: Bruxism; Temporomandibular Joint; Child; Noise
The clinical evaluation was performed by a single examiner who had undergone a training exercise.The examiner was blinded to the allocation of the children to the different groups.The analysis of joint sounds involved a lateral and dorsal extra-auricular exam for the occurrence of a click/pop and crepitus.Manual palpation of both TMJs was performed, along with auscultation with the aid of a stethoscope.The participant was asked to open and close his/her mouth several times upon verbal commands ("open" and "close") given by the examiner to determine the absence or presence of joints sounds and classify the type of sound in affirmative cases.Each child performed the different movements at least three times.When one or more signs were detected by auscultation, the child was classified as positive for joint sounds.
Manual palpation of the masticatory muscles and the evaluation of the TMJ followed the recommendations of Pertes and Gross 12 .Palpation was performed as a complement to the clinical evaluation for the analysis of muscle conditions.
Statistical analysis was conducted using the SPSS version 20.0 (IBM, USA).Descriptive analyses were carried out for all variables.The chi-square test was used to test the association between joint sounds/type and the other variables (bruxism, age and sex).The level of significance was set to 5% (p < 0.05) for all analyses.
A statistically significant association was found between joint sounds and bruxism, as 66.7% of the children with joint sounds (n = 12) also had bruxism (Table 1).No association was found between joints sounds and sex.However, a significant association was found with regard to age, as a greater percentage of children at six years of age had no joint sounds (Table 2).
Joint sounds are classified as a single, explosive noise (click or pop) or a continuous grating noise (crepitus) that occurs when the mouth is opened and/or closed.There is consensus in the literature that clicks are generally the result of the impact between the mandibular condyle and the temporal component of the TMJ after its rapid passage through the posterior band of the joint disc. 10repitus is found in more advanced stages of TMD and is generally associated with a degenerative condition 10 .
Considering the consequences of these aspects to the TMJ, the aim of the present study was to investigate the possible relationship between bruxism and joint sounds in children.The results could allow the establishment of measures aimed at preventing damage to the TMJ.

METHODS
An observational, descriptive, cross-sectional trial was conducted with a convenience sample of 48 children in the mixed dentition phase.This study received approval from the Human Research Ethics Committee of the university under process number nº 228.746.All legal guardians received clarifications regarding the objectives and procedures and signed a statement of informed consent agreeing to the participation of their children in compliance with Resolution 196/96 of the Brazilian National Health Board.
The participants were recruited from the pediatric clinic of the School of Dentistry of University Nove de Julho (Brazil) and were allocated to two groups: Group I -21 children with some sign or symptom of bruxism based on the criteria of the American Academy of Sleep Medicine: 11 parental report of clenching and/or grinding of the teeth and incisal and/or occlusal tooth wear; Group II -27 randomly selected children with no signs or symptoms of bruxism.For both groups, an additional inclusion criterion was the presence of the first permanent molars in the Angle Class I occlusal relationship.The exclusion criteria were neurological disorder, currently undergoing orthodontic treatment, malocclusion (open bite, crossbite or crowding), facial asymmetry and systemic adverse health condition.

DISCUSSION
Signs and symptoms of TMD can develop in childhood, the prevalence and severity of which tend to increase with age 13 .Considerable variability is found in the prevalence of bruxism in children depending on the method used for the diagnosis of this condition 14 .However, Serra-Negra et al. 1 found that at least 35.3% of a sample of Brazilian children had some sign of bruxism.Garcia et al 15 .report a prevalence rate of 40% in preschool children aged three to six years, 17% among those aged six and seven years and 24% among those aged eight and nine years.In the present study, the prevalence rate of bruxism was 43.7%.
Bruxism is characterized by clenching and/ or grinding one's teeth, which leads to incisal or occlusal tooth wear 16 .However, divergent findings are reported regarding joint sounds in individuals with bruxism.In the present study, a significant association was found between these two conditions.This association may be explained by the parafunctional activity, which is common in children and alters the movements of the jaw and its functions.
Okeson 16 found that many children were aware of sounds in the TMJ, which were confirmed by clinical exams.In other studies, the authors report an increase in the frequency of joint sounds with the greater degree of severity of bruxism 17 and that joint sounds are a significant predictor of TMD 18 .Epidemiological studies and an investigation or symptoms of TMD.The clicking sound occurs due to changes in the location of the joint disc in the fossa of the temporal bone, indicating that the disc was in a forward position and returned to its correct position during the vertical movement of the jaw 9 .Studies have demonstrated that crepitus is related to the progression of the anterior displacement of the disc, with internal derangement of the TMJ in severe cases 9,10,16 .Crepitus occurs in cases of osteoarthrosis of the TMJ, which explains the low prevalence of this joint noise in the present sample.

CONCLUSION
The present findings demonstrate an association between bruxism and joint sounds in children.Lower prevalence rates of joint sounds were found in children aged six and seven years in comparison to those aged eight and nine years.This finding suggests that joint sounds in children with bruxism may be associated with the progression and severity of symptoms.involving a convenience sample suggest a strong relationship between bruxism and TMD 19 .Petit et al. 20 report that the prevalence of bruxism increases significantly with age.Huang et al. 21suggest that sleep bruxism may be one of the factors of TMD.Molina et al. 22 found an association between selfreported bruxism and sounds in the TMJ.According to Morrow et al. 23 , TMD often results in pain, joint sounds and limited condyle movements when opening and closing the mouth.Sounds in the TMJ is a frequently reported symptom and a clinically proven sign in epidemiological investigations 24 .Joint sounds are related to structural and/or functional changes in the biomechanics of the TMJ and can even be indicative of degeneration of the joint 9,10,25 .

Table 2 -Distribution of joints sounds according to sex and age
a χ 2 test = 6.146 *statistically significant (p < 0.05) Chi-square test for evaluation of association between joint sounds and variables sex and age