Self-reported frequency of temporomandibular disorders among undergraduate students at Taibah University.

OBJECTIVES: This study aimed to evaluate the prevalence and severity of temporomandibular joint (TMJ) disorders among undergraduate students. In addition, the severity of TMD was examined in terms of its relationship with gender, age and field of study.
METHODS: A total of 439 undergraduate students of both genders (age range: 20-27 years) who were studying at various colleges at Taibah University were invited to participate in this study. Each student was provided with a questionnaire, and the significance and purpose of the study were explained. The data were collected using Fonseca's questionnaire, an instrument that assessed the demographic characteristics of the students and included ten key questions. The severity of TMD was categorized as no, mild, moderate or severe. The data were analysed using SPSS Version 22 (IBM, Illinois, USA). The chi-square test was used to compare the data from different groups and to determine whether the differences were statistically significant.
RESULTS: Of those who were invited, 78 students did not return the questionnaires, whereas another 11 were excluded due to their submitting an incomplete questionnaire. A majority of the students reported no TMD (46.7%) or mild TMD (42.7%). A moderate level of TMD was reported by 8.8% of students. Only 1.7% of students reported severe TMD. No significant differences were observed in the severity of TMD in terms of student age or field of study.
CONCLUSION: TMD is more prevalent among female students than male students. However, its occurrence is not affected by the age and field of study of the student.

Introduction

The temporomandibular joint (TMJ) is a bilateral joint of the mandibular condyles to the skull (temporal bone). It plays a functional role of moving the lower jaw during speech and mastication. Temporomandibular disorders (TMD) are commonly associated with myofascial and joint pain on opening and closing the mouth. Due to the complexity of aetiological factors and management, TMD represented a matter of great concern for dental practitioners.2, 3 Several aetiological factors have been attributed to TMD, including traumatic injuries. In addition, TMD is commonly related to changes in dental occlusion, including the alignment of the upper and lower teeth that affect maxilla-mandibular position and functioning. Many factors such as oral habits, fatigued masticatory muscles and premature loss of natural teeth have been linked to the disorder. Other important aetiological factors include emotional stress and high anxiety levels as well as stress-related symptoms, taking into consideration the high incidence of exposure to stressful life events that emphasize the contribution of such psychological parameters in the situation.7, 8

Previous studies of various populations have reported a high prevalence of TMD. For instance, the presence of one or more TMD signs has been reported in more than 50% of non-patients, with the presence of at least one symptom being reported among more than 30% of subjects.9, 10 In addition to being higher, the prevalence varied across various populations. For example, as many as 75% of residents of Riyadh, KSA had TMD signs and symptoms. Additionally, approximately 49.9% of German residents and 44.4% of Dutch residents were found to have TMD. It has been reported that TMD occurred more frequently among individuals in stressful situations compared to individuals who were not in stressful situations. Undergraduate students at a university or college are more prone to stressful conditions. It has been reported that university students are more likely to have a high risk of anxiety- and depression-related clinical disorders. The high academic load may lead to subsequent stress and changes in a student's lifestyle. In addition to changes in their attitude and behaviour, such situations may adversely affect their mental health and mood and eventually increase their risk of depression.

Many studies have been published on different prevalence rates of TMD due to issues such as variations in study design and use of non-standardized diagnostic methods. The prevalence of TMD with the associated complex anatomic features has put it in a diagnostically challenging category that is occasionally classified as a secondary headache disorder.

The symptoms of TMD worsen over time; therefore, early diagnosis and timely management are important. Given the relationship between TMD and mental stress, it was hypothesized that TMD would be frequent among undergraduate university students who were studying in various fields. Currently, there are no published articles on this relationship among undergraduate students at Taibah University. The current study aimed to evaluate the frequency and severity of TMD among undergraduate students.

Materials and Methods

Study design

This cross-sectional study evaluated the prevalence of TMD among full-time undergraduate students using Fonseca's questionnaire. The questionnaire was originally developed by Fonseca et al. and has been used in various studies15, 20, 21 to assess TMD and related symptoms. The study protocol was reviewed and approved by the research ethics committee at Taibah University College of Dentistry (Ref #: TUCODREC/20151006/ZAFAR). A total of 439 male and female students (age range: 20–27 years) from various disciplines (dentistry, engineering, medicine and pharmacy) were invited to participate. Each student was provided with the questionnaire and instructions explaining the significance and purpose of the study. Each participant returned the completed questionnaire to the investigators at their convenience. Participants with a history of previous orthodontic treatment and neurological or musculoskeletal disorders were excluded.

Data collection

The data were collected using a questionnaire that included items designed to obtain the demographic data of students (name, age, sex and discipline) and ten key questions (Table 1) derived from Fonseca's questionnaire. For each key question, the participants were given three options (yes, sometimes, no). Each “yes” response was scored as 10, each “sometimes” response was scored as 5, and each “no” response was scored as 0. Hence, the collective score of each questionnaire ranged from 0 to 100. Incomplete and partially completed questionnaires were excluded. A clinical index was described on the basis of collective score of key questions (Table 1). TMD severity was categorized as no TMD (0–15), mild TMD (20–40), moderate TMD (45–65) and severe TMD (70–100). The frequency and severity of TMD were compared in terms of students' gender, age and college.

Table 1

Key questions in Fonseca's questionnaire and classification of TMD severity.

	Fonseca's key question	Yes	Sometimes	No
1.	Do you feel that it is difficult to open your mouth?
2.	Do you feel that right and left movement of your jaw is difficult?
3.	Do you feel muscular pain and feel tired while chewing?
4.	Do you have headaches frequently?
5.	Do you feel stiffness in your neck?
6.	Do you feel pain in your ears or TMJ?
7.	Do you hear any sounds of the TMJ clicking while chewing or opening your mouth?
8.	Do you grind or clench your teeth?
9.	Do you feel that your teeth do not articulate properly?
10.	Do you feel that you are a tense or nervous person?

Statistical analysis

The data were analysed using SPSS Version 22 (IBM, Illinois, USA). To compare the various groups for statistical significance, the chi-square test was used. When interpreting the data, a P-value <0.05 was considered to be significant.

Results

A total of 439 students were invited to participate in this study. Of these participants, 78 students did not return the questionnaire, whereas another 11 were excluded due to their submitting an incomplete questionnaire. Hence, the results of this study are based on the data from 351 students (79.9% response rate) who returned a completed questionnaire. This included 200 (57%) male and 151 (43%) female undergraduate students. A majority of the students reported no TMD (46.7%) or mild TMD (42.7%). The frequency of mild TMD was 45.7% in female students, which was higher than in male students (40.5%); however, the difference was not statistically significant (P > 0.05). Moderate TMD was reported by 8.8% of students, whereas severe TMD was reported by only 1.7% of students (Table 2). Although the frequency of moderate and severe TMD was slightly higher in female students, there were no statistically significant differences by gender (df = 3, Χ2 = 2.66, P > 0.05).

Table 2

Distribution and severity of TMD among university students assessed using Fonseca's questionnaire.

TMD degree	Male	Female	Total
No TMD	98 (49)	66 (43.7)	164 (46.7)
Mild TMD	81 (40.5)	69 (45.7)	150 (42.7)
Moderate TMD	19 (9.5)	12 (8)	31 (8.8)
Severe TMD	2 (1)	4 (2.6)	6 (1.7)
Total	200 (100)	151 (100)	351 (100)

The data are shown in numbers and percentages (parentheses).

The data were further compared in relation to the age group of students (Table 3). Although the participants' responses varied, collectively, the frequency of no and mild TMD was 91.1%, 86.2% and 90% for students in the ≤21, 22–24 and 25–27 age groups, respectively. There was no significant difference based on age (P > 0.05). In contrast, severe TMD was reported in 1.8% of students aged ≤21 years and 1.7% of students aged 22–24 years, which was significantly higher than the frequency of severe TMD reported in students who were 25–27 years of age (0%) (df = 6, Χ2 = 12.87, P < 0.05). While comparing the frequency of TMD among students in various colleges (Table 4), 2.6% of students in the college of dentistry and 2.4% of students in the college of pharmacy reported severe TMD, which was higher than the proportion of students in the college of medicine (1%) and college of engineering (0%). The frequency of moderate TMD was highest among engineering students (17.6%), followed by dentistry students (10.6%) and pharmacy students (7.7%). A majority of participants (82% or more) reported no or mild TMD, regardless of their discipline. There was no significant difference in no or mild TMD among students in various disciplines (P > 0.05).

Table 3

Distribution and severity of TMD among university students in various age groups.

TMD degree	<21	22–24	25–27	Total
No TMD	116 (51.6)	41 (35.3)	7 (70)	164 (46.7)
Mild TMD	89 (39.5)	59 (50.9)	2 (20)	150 (42.7)
Moderate TMD	16 (7.1)	14 (12.1)	1 (10)	31 (8.8)
Severe TMD	4 (1.8)	2 (1.7)	0 (0)	6 (1.7)
Total	225 (100)	116 (100)	10 (100)	351 (100)

The data are shown in numbers and percentages (parentheses).

Table 4

Distribution and severity of TMD among university students based on their college.

TMD degree	College of Engineering	College of Dentistry	College of Medicine	College of Pharmacy	Total
No TMD	14 (27.5)	53 (43.1)	70 (70.7)	27 (34.6)	164 (46.7)
Mild TMD	28 (54.9)	54 (43.9)	25 (25.3)	43 (55.1)	150 (42.7)
Moderate TMD	9 (17.6)	13 (10.6)	3 (3)	6 (7.7)	31 (8.8)
Severe TMD	0 (0)	3 (2.4)	1 (1)	2 (2.6)	6 (1.7)
Total	51 (100)	123 (100)	99 (100)	78 (100)	351 (100)

The data are shown in numbers and percentages (parentheses).

Table 5 compares the responses of participants using a factorial design based on age and discipline as variables. For any college, few students (1–4%) fell into the age group 25–27 years; consequently, the TMD results from the younger age groups (≤21 years and 22–24 years) are discussed. In the college of engineering, there was no significant difference based on the age of participants. In contrast, in all the other colleges (medicine, dentistry and pharmacy), a significantly higher number of participants in the ≤21 age group reported no TMD than in the 22–24 age group (Table 5). In terms of mild TMD, there was a non-significant difference among the participants in both age groups in all colleges. The only exception was the college of medicine, as students reported a significantly higher percentage of mild TMD in the ≤21 age group (23.2%) than the 22–24 age group (1%). Although the percentages of participants in all the colleges fluctuated in terms of moderate and severe TMD, there were no significant differences among the various age groups.

Table 5

Distribution and severity of TMD among university students by age and college.

TMD	College of Engineering			College of Dentistry			College of Medicine			College of Pharmacy			Total
Age	<21	22–24	25–27	<21	22–24	25–27	<21	22–24	25–27	<21	22–24	25–27
No TMD	7 (13.7)	6 (11.8)	1 (2)	35 (28.5)	15 (12.2)	3 (2.4)	59 (59.6)	9 (9.1)	2 (2)	15 (19.2)	11 (14.1)	1 (1.3)	164 (46.7)
Mild	15 (29.4)	13 (25.5)	0 (0)	24 (19.5)	29 (23.6)	1 (0.8)	23 (23.2)	1 (1)	1 (1)	27 (34.6)	16 (20.5)	0 (0)	150 (42.7)
Moderate	5 (9.8)	4 (7.8)	0 (0)	5 (4.1)	7 (5.7)	1 (0.8)	2 (2)	1 (1)	0 (0)	4 (5.1)	2 (2.6)	0 (0)	31 (8.8)
Severe	0 (0)	0 (0)	0 (0)	2 (1.6)	1 (0.8)	0 (0)	1 (1)	0 (0)	0 (0)	1 (1.3)	1 (1.3)	0 (0)	6 (1.7)
Total	27 (52.9)	23 (45.1)	1 (2)	66 (53.7)	52 (42.3)	5 (4)	85 (85.9)	11 (11.1)	3 (3)	47 (60.2)	30 (38.5)	1 (1.3)	351 (100)
	51 (100)			123 (100)			99 (100)			78 (100)			351 (100)

The data are shown in numbers and percentages (parentheses); significant P-value <0.05.

Discussion

The current study reported the frequency and severity of TMD among undergraduate students at Taibah University using Fonseca's questionnaire. The response rate of participants (79.9%) was satisfactory and higher than rates reported in previous studies of various populations.15, 20, 21 Well-planned survey studies with a high response rate are believed to be important research tools. Although a lower response rate (43%) shows evidence of a minimum non-response bias, a higher response rate (more than 70%) is believed to eliminate the risk of bias.24, 25, 26 The higher response rate in this study is attributed to the fact that the questionnaire were delivered and received in person. The delivery method of questionnaires affects the response rate. For instance, a relatively poor response rate has been linked to web-based surveys.27, 28, 29

Fonseca's questionnaire developed by Fonseca et al. and has been used in various studies15, 20, 21 to assess TMD symptoms. It has been found to be a useful tool due to its benefits. For example, it is easy, quick and cost-effective. In addition, it is considered to be a highly valid method for assessing TMD severity. In the current study, 53.3% of participants were categorized as having mild, moderate or severe TMD, which are within the range of TMD frequencies reported in previous studies using Fonseca's questionnaire.15, 20, 21 In terms of gender, a higher proportion of female students (56.3%) reported mild, moderate or severe TMD compared to male students (49%). This finding is consistent with that of Nomura et al., who also reported a higher risk of TMD in females compared to males.

TMD is a complex multifactorial condition that may be initiated by factors such as malocclusion, parafunctional habits (lip biting, bruxism) and psychological factors, including anxiety or stress.31, 32, 33 Stress and parafunctional habits are well known factors that are associated with TMD symptoms in university students.15, 31 Additionally, a number of studies7, 20, 21 has been conducted to evaluate the frequency and severity of symptoms associated with TMD. It has been reported previously that patients with no mental stress report a lower frequency of TMD compared to patients who are experiencing stress.7, 14 The stress level of university students can fluctuate, for example, during examination time or as deadlines approach. For instance, Nomura et al. reported that a significant number of students with TMD (76.7%) considered themselves to be tense, whereas 71.6% of them were clenching or grinding their teeth. The conditions that affect TMD such as bruxism and clenching and grinding of teeth are directly associated with emotional stress.34, 35

This study compared the severity of TMD among students in various age groups. The severity of TMD varied to some extent; however, there was no significant difference in terms of moderate and severe TMD among the age groups. Although ageing can be a factor that affects the severity of TMD, the age groups in this study had a narrow distribution range (3 years); therefore, they did not show any significant differences. Gray et al. assessed the frequency and severity of TMD in elderly patients who were wearing complete dentures. Interestingly, despite the population, the frequency of no TMD (56.8%) was not much different than that presented in studies15, 21 conducted on undergraduate students. Similarly, comparable results have been reported for mild (40%), moderate (1.87%) and severe (1.26%) TMD. These finding are suggestive of and advocate for the excellent remodelling of TMJ structures and adaptability of soft tissues. Although complex changes during the loss of natural dentition and prosthesis wear significantly change the orientation of temporomandibular tissues, TMJ adapts accordingly, thereby preventing severe TMD.

While comparing the students in various colleges, the frequency and severity of TMD was distributed randomly. Moreover, there was no significant difference among engineering, dentistry and pharmacy students. These results are consistent with those of a previous study in which no statistically significant differences were reported among dentistry, pharmacy, medical and physiotherapy students in terms of TMD severity. This can be attributed to the fact that, regardless of the course of study, students have variable socioeconomic backgrounds and lifestyles. The only exception in this study was that medical students had a significantly lower (29.3%) frequency of TMD compared to students in any other discipline. There is no possible scientific explanation for this finding.

It is evident from the results of this study and discussion of relevant earlier studies that a significant proportion of undergraduate university students may suffer from TMD or aggravating factors. It is important to mention that earlier diagnosis and treatment planning can prevent irreversible damage to the TMJ and improve the prognosis. On the other hand, delayed diagnosis results in irreversible tissue derangement and ankyloses and requires surgical interventions. Due to the complex nature and multifactorial aetiology, the diagnosis of TMD is challenging. The simplification and standardization of clinical history tools may help clinicians to diagnose TMD at earlier stages. The main limitation of the current study is that the results are based on a small sample of undergraduate students with a narrow age range (20–27 years). The questionnaires were distributed among students simultaneously (two weeks after the start of the 1st term), and completed questionnaires were collected within two weeks. It was ensured that there was no stress due to examinations, academic pressure or coursework during the data collection period. However, mental stress due to reasons such as academic pressure, examinations, meeting deadlines or personal circumstances is likely to affect TMD and warrants further investigation. In contrast, the stress level, lifestyle and socioeconomic status of the general population differ compared to university students. Hence, the prevalence and frequency of TMD reported in this study may differ for the general population and require more studies with larger samples.

Conclusions

TMD frequently occurs in undergraduate students at Taibah University, as a majority of them reported related signs. TMD is relatively more prevalent among female students. The severity of TMD is not affected by the age and field of study of the students at Taibah University. There is a need for more studies to establish a correlation between the prevalence of TMD in students and the general public.

Authors' contributions

MSZ conceived and designed the study, conducted the research and provided the research materials. WMF and NT collected, organized and interpreted the data. MSZ and ZK wrote the initial and final drafts of the article. ZK critically reviewed the manuscript. AHK performed the data analysis and statistical interpretation and wrote part of the results section. All the authors have critically reviewed and approved the final draft and are responsible for the content and similarity index of the manuscript.

Conflict of interest

The authors have no conflict of interest to declare.