Najat M. A. Farsi, BDS, MS
Faculty of Dentistry, King Abdulaziz University, Jeddah

Interest in pediatric temporomandibular dysfunction (TMD) is increasing. Many studies on TMD prevalence among children in Western countries are available. This study aimed to assess the prevalence of TMD signs among randomly selected female Saudi children aged 6 to 14 years and to evaluate the effect, if any, of their emotional states on the development of TMD. The children (n = 696) underwent an examination which consisted of palpation of temporomandibular joints and associated musculature for tenderness, determination of the maximal vertical opening and deviation of the mandible upon opening. Results showed that 17.1% of the children had at least one sign of TMD with joint sounds being the most frequent sign (13.9%). Restricted mouth opening was second in frequency (7.6%). Deviation upon opening as well as muscle tenderness to palpation were found infrequently. The prevalence of TMD is lower in the Saudi children than in some Caucasian populations. The results further revealed that children with nervous emotional states had a greater risk of developing signs of TMD than calm children. Therefore, it is suggested that emotional factors should be taken in consideration when treating these children.
 

Interest in pediatric temporomandibular dys- function (TMD) is increasing, as younger patients are being diagnosed and treated for the disorder. Many studies on TMD prevalence in children populations in Western countries are available.^1-11  These studies show that the prevalence of TMD seems to vary among different populations and ethnic groups. The etiology of TMD in children and adolescents has also been shown to be multifactorial.¹²¹⁶ Malocclusion, oral parafunctions and emotional states are the factors mostly investigated in adults.¹⁷¹⁹ Few studies reported higher pre- valence of TMD in children with traits of nervousness and anxiety.¹⁴-¹⁵²⁰ However, the importance of the emotional states in children as an etiological factor for TMD continues to be an important area of investigation.

In Saudi children, one study is available on the prevalence of TMD in children with primary dentition.²¹ There is lack of information regar- ding prevalence of TMD in the different age groups, predisposing factors as well as age of onset of TMD. Such information is important in determining whether early childhood problems can predispose patients to temporomandibular growth abnormalities. The purposes of this study were to record the prevalence of TMD among Saudi female children with mixed dentition and to evaluate the relationship between emotional states and development of TMD in the examined population.

Subjects

Examinations were performed on 696 Saudi female children with mixed dentition from age 6 to 14 years. The subjects were collected from eight girls' primary schools in Jeddah City. The city was divided into four geographical areas (North, South, East and West) and two schools were randomly selected from each area. In each school, four classes were randomly selected from grades 2 to 6. All the children with mixed dentition in each class were included in the study.

Examination

The examination and recording were made by three experienced faculty members. Prior to the study, the examiners were trained in temporo- mandibular examination criteria of previous studies⁹-²²-²³ and calibrated to acceptable levels of reliability for assessing the variables covered by the examination. All the subjects were examined at the schools using two chairs. Examination was done while the child was seated upright during the examination. The clinical examination included the following aspects:

Questionnaire

After the examination, a questionnaire was sent to the parents to collect information regarding psychological qualities of the children. The parents were asked to classify the children into the following categories: calm, nervous or not applicable.

The Chi-Square Test was used for analysis of correlations and differences between groups for the recorded variables. Fisher Exact Test was used for comparison whenever the comparable groups have a sample size smaller than five. P value of < 0.05 was regarded as significant.
 

Table 1 shows the distribution of different signs of TMD in the examined children. To make a more meaningful comparison, the children were divided into three groups: 6-8, 9-11 and 12 to 14 years of age. The prevalence of dys- function as determined by the presence of one or more of the five cardinal signs was 17.1% in the entire population. The prevalence increased slightly from the youngest age group (16.6%) to the oldest age group (18.9%). This difference was not statistically significant.

Joint sounds were the most prevalent sign among the children. Clicking was overwhel- mingly the most common joint sound produced by 88 (12.6%) children. Crepitus was detected in 9 (1.3%) children. Although not statistically significant, joint sounds were observed at a higher frequency in the oldest age group compared to the youngest age group; and no crepitus was observed in the youngest age group. Restricted mouth opening was second in frequency (7.6%). The prevalence of this sign showed statistically significant difference between the youngest (12.9%) and the oldest (5.7%) age groups. (X²= 1.78, df - 2, P=0.03). Joint tenderness was third in frequency. It occurred more frequently in the oldest age group than in the youngest group. This diffe- rence was marginally significant (P < 0.06). Deviation upon opening was found infrequently (2.4%) as was muscle tenderness to palpation (1.0%). It was not possible to measure the maximal opening for some children who had no anterior teeth due to normal exfoliation process and they were excluded from this part of the study. The maximal opening values found ranged from 31 mm to 54 mm with a mean value (±SD) of 49.1 mm ± 5.2. The means of maximal opening gradually increased with age as shown in Fig. 1. After excluding the children with missing anterior teeth (n = 144), restricted opening was recorded in 7.6% of the remaining sample.

Out of 696 parents who received the questionnaires; only 404 (58%) responded. On the basis of the responses, the children were divided into two groups: (1) subjects rated as calm (N = 190), and (2) subjects rated as tense or nervous (N = 208). Responses from six parents whose answers didnt fall in these two categories were excluded from the analysis.

Table 2 reveals the distribution of the different signs of TMD among the two emotional status groups. Using Fisher Exact Test, the differences in the prevalence of TMJ between the two groups was statistically significant (P = .007). TMJ tenderness occurs more frequently in the nervous than in the calm group. Statistically significant differences between the two groups were not found with respect to other signs of TMD.
 

The sample of the present study consisted of randomly selected Saudi female children aged 6-14 years old in the mixed dentition period. While strong differences in the prevalence of TMD were noted between races,¹¹ most of the studies reported no significant differences in TMD between the sexes.⁵⁶-¹¹²⁴ Therefore, although the results are from female subjects only, they can be compared to these previous studies. One or more signs of TMD were observed in 17.1% of the total sample which is much lower than the findings of some earlier studies.⁵'⁶⁸¹⁰ The prevalence of at least one sign increased slightly with age, in agreement with many of the studies done on different age groups.⁴⁵ Alamoudi et al²¹ found a prevalence of   16.5% for TMD in Saudi children with primary dentition. The author's results of 17.1% therefore suggest an increase in prevalence from primary to mixed dentition. Morphological changes of the TMJ and jaw development as well as occlusal changes may be responsible for these observations. TMJ sound were the most frequently observed sign with significantly more cases in clicking than crepitus. These results are in accordance with data published by earlier authors.⁶'⁷¹⁰ Sounds occurred in 13.1% of the younger group and in 15.1% of the older ones. These results are consistent with that of Williamson¹ and Ogura⁷ (Table 3), are slightly higher than the figures by Nilner² and Brandt³ but much lower than Gazit,⁶ Grosfeld⁴ and Kritsineli¹⁰ who used a stethoscope to detect joint sound. Dworkin et al²⁵ used digital palpation and a stethoscope to detect joint sound and reported that detecting specific joint sound using a stethoscope resulted in un- acceptable reliability. Okeson and O'Donnell²⁶ in their temporomandibular evaluation work- shop considered the use of stethoscope to be of questionable value since it may magnify insignificant joint sounds.

TMJ tenderness in the present sample is lower than the reports of the studies, which included samples of older age groups.¹-⁴-⁶ Limited mouth opening was recorded in 7.6% of the present sample in which 40 mm was considered the lower limit of maximal opening for children with mixed dentition as suggested by Okeson and O'Donnell.²⁶ The prevalence of restricted opening in the present study is relatively high in comparison to the studies that considered 35 mm as the lower limit.²-⁴'¹⁰ The average mea- surement of the amplitude of opening (49.1 mm) is relatively lower than the average data of the same age group published by Grosfeld⁴ (51. 8mm) and Vanderas¹⁵ (54.8 mm). Restricted opening was significantly more apparent among the younger age group than the older one which could be due to inability of children younger than 8 years old to open as wide as the older ones. Therefore, for this age group (6-8 years) the lower limit of physiologic function could be placed at 35 mm.

The recording of deviation on opening was recorded at approximately the midpoint of maximal opening since some children open with their mandible following S-shaped trajectories and yet reach the maximal opening in an undeviated position.²² In the present investigation, this sign of dysfunction occurred less than what other studies reported earlier. (Table 3)

Several authors reported that psychological stressors cause increased muscle activity and that TMD patients respond to stressors with increased and prolonged masticatory muscle tension.²⁷²⁹ This study showed statistically significant differences in the prevalence of TMJ tenderness between the calm and nervous children. The present findings agree closely with that reported by Vanderas.¹⁵ The fact that no statistically significant differences related to TMJ sounds or dysfunction in the mandibular movement were found between the two groups might be explained by the mechanisms through which the emotional factors act on the masticatory system. It is suggested that pain and dysfunction arise from increased muscle tension caused by emotional factors.³⁰-³¹ The tender- ness among the nervous group in this study might not be severe enough to cause deflection of the mandible or restriction of the mandibular movements. Furthermore, high adaptability of the masticatory system of the young children could mask the development of other signs of dysfunction among the nervous group.
 

The results of this study showed that the prevalence of TMD among female Saudi chil- dren is relatively lower than in Western children with joint sound being the most frequent sign. The present findings also suggest that children in emotional states run a greater risk of deve- loping TMD signs.