In this study we aimed to determine the prevalence of bruxism and investigate the relationship between occlusal factors, irritating tooth conditions and bruxism among 3-6-year-old preschool children in Isfahan.
Different techniques have been suggested to record bruxism in epidemiologic studies.27
One technique is the evaluation of dental attrition, from direct visual observations of the mouth,28
from dental study casts,29
or from occlusal appliances. However, it is very difficult to be sure if bruxism is a result of parafunctional or functional habits.30
Since the occlusal surfaces are worn physiologically in the deciduous dentition, the accuracy of the use of dental attrition is controversial.23
Another remarkable point is the timing of attrition because there is a risk of recording no bruxism when the subjects have recently developed bruxism and may not indicate attrition.23
The same risk exists when bruxism process has been stopped, though attrition is observed.31
Also, dental wear can be caused by many factors other than bruxism.32
Therefore, in this study the bruxism history was obtained by a combination of methods and interviews of the children and clinical examinations by the clinician.
The prevalence of bruxism in the literature varies from 7% to 88% in children34
and from 5% to 15% in adults.35
This diversity is probably due to different methodologies of studies.
The prevalence of bruxism in a study by Chiefetzet al,33
in which data was collected only via a questionnaire was reported 38% in children. In addition, Zenari et al36
reported a high occurrence (55.3%) of bruxism that was assessed by the parent's report.
However, in other studies that assessed bruxism with both questionnaire and child’s report, the prevalence of bruxism was lower, e.g. 15.9% in a study by Fonseca et al,20
13.27% by Egermark-Erikson et al,37
and 12.6% by Demir et al.24
In this study, the prevalence of bruxism was 12.75%, similar to the results of studies by Demir et al24
and Egermark-Erikson et al.37
Consistent with other studies, no statistically significant gender effect was found on the prevalence of bruxism in the present study.24,36,37
Several studies have shown a relationship between occlusal factors and bruxism in permanent dentition but there are a few studies evaluating the relationship between occlusal factors and bruxism in primary dentition.
Henrikson et al38
reported that bruxism was higher in the Class II malocclusion group when compared with the normal group, suggesting a relationship between parafunctional habits and orthodontic malocclusion. Nilner21
studied the relationship between occlusal factors and bruxism and reported statistically significant correlations between Class II and Class III molar relationships and bruxism.
Carlsson et al39
indicated that Angle Class II malocclusion and tooth wear in childhood predicted increased tooth wear in adulthood.
In contrast to the results discussed above, a number of investigators have reported that occlusal factors are not involved in the etiology of bruxism. They found no statistically significant relationship between any type of morphologic malocclusion and tooth clenching and grinding.23-25,40,41
It was shown in this study that two types of primary molar relationships (the mesial step and flash terminal plane) were significantly related to bruxism, which is in contrast to the results of a study by Sari et al23
They found no difference between any type of primary molar relationship and bruxism.
In another study, Nilner21
examined the relationship between occlusal factors and bruxism in 309 adolescents. A statistically significant correlation was reported between deep bite, clenching and dental wear.
Sari et al23
reported statistically significant relationship between an overjet of ˃6 mm, negative overjet, overbite, open bite, and bruxism in permanent dentition.
In this study no relationship was found between bruxism and anterior and posterior open bite and crossbite, in contrast to the results of studies by Miamoto C et al42
and José Pereira et al,43
indicating that posterior crossbite is directly associated with clinical manifestations of bruxism.
The relationship between irritating tooth conditions and bruxism has not been evaluated in other studies. In the present research, significant relationships were found between bruxism and food impaction, tooth caries, tooth pain, and sharp tooth edges.
Our findings indicate the importance of regular and accurate oral examination for early diagnosis of any tooth decays in children every three months, leading to the prevention of dental pain and food impaction.
By preventing such irritating causes, one can impede the process of bruxism and thus, its adverse consequences on a children’s life quality. Further longitudinal studies with larger sample sizes are recommended to assess whether there is a relationship between occlusal factors and bruxism.