Temporomandibular joints disorders (TMDs) prevalence and their relation to anxiety in dental students

Introduction

Temporomandibular joint disorders (TMDs) are a very common group of musculoskeletal disorders affecting the temporomandibular joint (TMJ) and the face causing pain. They are considered a significant public health burden in approximately 5% to 12% of the general population (National Institute of Dental and Craniofacial Research 2018, July). Painful TMD has a direct impact on the person’s quality of life and daily activity (Schiffman, Ohrbach et al. 2014). The TMD has a multifactorial pathogenesis in which it involves physiological and/or psychological factors like emotional distresses. Chronic parafunctional habits can cause repetitive trauma to the masticatory system, which may result in painful TMD episodes (Schiffman, Ohrbach et al. 2014). Parafunctional habits including but not limited to bruxing and clenching are known to have a critical role in aggravation and progression of TMD (Chisnoiu, Picos et al. 2015). Furthermore, psychosocial distress is also considered an important comorbidity contributing to TMD (Schiffman, Ohrbach et al. 2014). Some individuals, when exposed to stressful situations, tend to activate the stomatognathic system by clenching or grinding their teeth and increasing masticatory muscle contraction in order to relieve their stress. This increased masseter activation during stress and decrease in a relaxing situation was highly associated with the presence of TMD in individuals under more stress (Calixtre, Gruninger et al. 2014).

Many studies have looked into the psychological stress among university students and its impact on student’s academic achievement and well-being. High prevalence of mental issues between university students was reported (Adlaf, Gliksman et al. 2001). Stallman et al evaluated mental stress among Australian universities students and found a high prevalence of mental health problems (19.2 %) and subsyndromal symptoms (67.4%) which were significantly higher than those of the general population (Stallman 2010). This supports that university student population live under more stress than the general population. Thus, the prevalence of TMDs is relatively high among university students of different specialties.

Binoleil et al, assessed the prevalence of headaches and painful TMDs and examined the relationship between TMDs, headaches, and depression rates among dental and medical students. They reported higher depression scores in patients with painful TMD compared to patients without TMD (Benoliel, Sela et al. 2011). Furthermore, the relationship between stress level and painful TMD in students of health science was supported in few more studies locally (Alkhudhairy, Al Ramel et al. 2018) and internationally where stress played an important role in TMD progression (Monteiro, Zuim et al. 2011, Wieckiewicz, Grychowska et al. 2014).

The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was first proposed in 1992 and has been used widely as diagnostic protocol for TMD research (Dworkin and LeResche 1992). However, more research was done over the years to improve its validity and clinical utility. In 2014, an evidence-based new Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) was published and was considered a valid and reliable screening tool for use in clinical and research settings and included important modifications to the original RDC/TMD (Schiffman, Ohrbach et al. 2014). An acceptable sensitivity and specificity for a definitive diagnosis are considered as sensitivity ≥ 70% and specificity ≥ 95%. DC/TMD has diagnostic algorithms used to diagnose the most common pain-related TMD and most common intra-articular disorders (Schiffman, Ohrbach et al. 2014). The Axis I diagnostic algorithm consists of two parts; a self-report instrument where it is used for pain screening. The second part is used for TMJ clinical examination. The DC/TMD Axis II protocol included instruments to evaluate pain behavior, psychological status, and psychosocial functioning (Schiffman, Ohrbach et al. 2014).

To the best of our knowledge, the prevalence of TMDs among Umm al-Qura University (UQU) dental students has not been evaluated. In this study, we aimed to determine the prevalence of TMDs in UQU dental students using Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Also, to examine the relation between anxiety, self-reported bruxism and TMDs among UQU dental students.

Methods

This cross-sectional study was approved from Umm Al-Qura University (UQU), College of Dentistry Institutional Review Board (IRB) # (98-18). This study took place at collage of Dental Medicine Umm al Qura University. Data were collected between July 2019 and December 2019.

Results

A total of 304 electronic questionnaires were sent via email to all dental students at Umm al-Qura university who were between 2^nd year to the internship with a total of 6 academic years. A total of 240 questionnaires were completed and returned with a compliance rate of 78.9% (Homeida 2022). The demographics of respondents from the pain screening questionnaire can be found in Table 1.

Prevalence of TMDs among dental students

All the responders who reported TMD pain or symptoms (n=119) were invited for a TMJ examination. A total of 93 (78%) subjects presented for clinical assessment. The demographics of the subjects received the clinical examination are presented in Table 1. During TMJ clinical examination, more than half of the subjects 64.5% (n=60) had temporomandibular disorders (TMDs), while only 35.4% (n=33) students had normal TMJ findings at the time of the examination.

Disc displacement with reduction was the most frequent diagnosis 38.7%(n=36) followed by local myalgia 32.25% (n=30) and arthralgia 16.1% (n=15) (Figure 1). Interestingly, 29% (n=27) students had more than one diagnosis and coexistence of disc displacement with reduction and local myalgia was found to be the most frequent combination in 19.3% (n=18) students (Table 3). Overall, the diagnosis of TMD was significantly higher in the female students compared to the male students (P≤0.022). Both, pain-related disorders and intra-articular disorders were significantly higher in females with (P=0.027) and (P=0.024), respectively. Also, disc displacement with reduction showed a significant increase with the higher academic year (P≤0.01).

Figure 1. Percentage of dental students presenting with DC/TMD Diagnosis.

DC/TMD: Diagnostic Criteria for Temporomandibular Disorders.

Table 3. Gender based distribution of TMDs, Anxiety scale and history of bruxism.

	Female N (%)	Male N (%)	Total N (%)
Total number of participants	45 (48.3)	48 (51.6)	93 (100)
Bruxism	28 (30)	10 (10.7)	38 (40.8)
TMDs
Normal TMJ findings	12 (12.9)	21 (22.5)	33 (35.4)
Disc displacement with reduction	22 (23.6)	14 (15)	38.7 (36)
Local myalgia	16 (17)	14 (15)	32.2 (30)
Myofascial pain	11 (11.8)	1 (1)	12.9 (12)
Arthralgia	5 (5.3)	10 (10.7)	16.1 (15)
Headache attributed to TMD	4 (4)	0	4.3 (4)
Disc displacement with reduction with intermittent locking	3 (3)	0	3 (3)
Myofascial pain with referral	1 (1)	0	1 (1)
Disc displacement without reduction with limited opening	1 (1)	0	1 (1)
PHQ-4
Mild	16 (17)	4 (4)	20 (21.5)
Moderate to severe	20 (21.5)	1 (1)	21 (22.5)

Anxiety and depression scale and history of parafunctional habits

In total, 41 participants (44.09%) reported a positive response to the anxiety and depression scale. In which, 48.7% (n=20) had a mild score and 51% (n=21) had moderate to severe anxiety score (Table 3). Of the 41 subjects with a positive response to PHQ-4, 31 (73%) had been diagnosed with a painful TMDs. Moderate to severe anxiety was significantly associated with TMDs (P=0.006).

Overall, 40% of the participants (n=38) reported a parafunctional habit. Out of 38 (71%) with a history of bruxism, 27 had TMDs. Self-reported history of bruxism was significantly associated with TMDs in all students (P≤0.01).

Both the history of bruxism and the level of anxiety were significantly related (P=0.0002) and also significantly higher in females than males (P≤0.01). Besides, the anxiety level and history of bruxism significantly increased with higher academic years (P≤0.05). Those high scores of anxieties and bruxism were reversed in the internship year (Figure 2).

Figure 2. History of bruxism and anxiety levels significantly increased with higher academic years and declined in internship year.

Discussion

The present study found that half of UQU dental students reported at least one TMD symptom. Moreover, the clinical examination found that 64% were diagnosed with at least one TMJ disorder and about 30% (one- third) had multiple diagnoses. Bruxism and high anxiety levels were related to TMDs in this student population.

Evidence suggests that TMD is a common complain among students. The prevalence of TMD reported by this study is higher than what has been reported by other studies in Saudi universities which ranged between 25-39% (Alkhudhairy, Al Ramel et al. 2018, Srivastava, Shrivastava et al. 2021). Studies that addressed general university Saudi students also reported TMD prevalence of 20 to 50% (Zulqarnain, Khan et al. 1998, Habib, Al Rifaiy et al. 2015, Zwiri and Al-Omiri 2016, Srivastava, Shrivastava et al. 2021). All the above-mentioned studies with the exception of Srivastava et al. relied on self-administered questioners to identify subjects with TMDs and did not include TMJ clinical examination to confirm the diagnosis as the present study which may explain the difference in prevalence. When RDC/TMD algorithm was used to estimate the prevalence of TMD, 30 to 36% of dental students were found to have TMD (Fernandes Azevedo, Camara-Souza et al. 2018, Lövgren, Österlund et al. 2018). The present study used RDC/TMD pain screener to identify the subject with possible TMJ symptoms first, then, only those with positive responses to the pain screener were examined clinically for TMD diagnosis and that may explain the higher prevalence of TMDs.

Disc displacement with reduction was the most prevalent TMD disorder followed by myalgia. This finding concurs with a systematic review in which disc displacement of TMJ was highly prevalent TMD in the general population with prevalence ranging from 18 to 35% (Naeije, Te Veldhuis et al. 2013). Also, the finding of the increasing prevalence of disc displacement with age in this study is in alignment with other studies were disc displacement with reduction develops during childhood and adolescence and it’s prevalence levels off towards adulthood (Marpaung, van Selms et al. 2019, Sankuratri, Verma et al. 2021). Although myalgia was the reported as the commonest diagnosed condition in some studies (Srivastava, Shrivastava et al. 2021), it was the second most prevalence condition in this study. On the other hand, females had a higher prevalence of TMDs compared to males. This findings was in alignment with other studies (Bagis, Ayaz et al. 2012, Naeije, Te Veldhuis et al. 2013, Wieckiewicz, Grychowska et al. 2014, de Melo Junior, Aroucha et al. 2019, Xie, Lin et al. 2019, Sankuratri, Verma et al. 2021, Srivastava, Shrivastava et al. 2021). Interestingly, 30% of the subjects had more than one TMDs diagnosis. Similar finding were reported by Azevedo 2018 et al (Fernandes Azevedo, Camara-Souza et al. 2018) which highlights the importance of diagnosis and early management of TMDs.

Previous cross-sectional studies reported a significant increase in anxiety and depression scores among medical and dental students in different Saudi universities (Inam 2007, Aboalshamat, Hou et al. 2015, Basudan, Binanzan et al. 2017). In this study, 44% of the students with TMD symptoms reported a positive response to the PHQ-4 with half of them classified as having moderate to severe anxiety. Female dental students had a higher PHQ-4 mean score than male students which was in agreement with similar studies done on Saudi dental students (Inam 2007, Al-Saleh, Al-Madi et al. 2010, Benoliel, Sela et al. 2011, Al-Sowygh 2013). Overall, the rate of anxiety in women has been reported to be higher than men (Kessler, Sonnega et al. 1995, Steel, Marnane et al. 2014, Xie, Lin et al. 2019). This could be explained by the slower processing in neurotransmitter serotonin which has a critical role in anxiety and depression. Besides, women are more sensitive to specific hormone such as corticotropin-releasing factor which has an important role in stress response (Bangasser, Curtis et al. 2010).

The majority of those students who showed moderate to severe levels of anxiety and depression were diagnosed with painful TMDs on clinical examination and therefore, anxiety was found to be related to TMDs. Other studies have conflicting results. stress and anxiety were positively associated with TMD in university students in general and dental students in particular (Ton, Mota et al. 2020, Jaiswal and Deshpande 2021). While Azevedo et al found no association between anxiety and TMD (Fernandes Azevedo, Camara-Souza et al. 2018). Anxiety and stress in dental students can be caused by many external factors like exams, clinical requirements and academic assignments. This study was conducted during the academic year which could contribute to the higher prevalence of anxiety and TMDs.

In comparison to the general population, TMD prevalence ranges between 5–35% (Nadershah 2019, Schiffman et al. 2014). However, none of those studies reported on the association of TMD with stress, anxiety or phycological factors in general population. In general, anxiety disordered have been reported in 35% of chronic pain patients compared to only 18% of the general population (Poleshuck et al. 2009). In addition, Reissmann et al. compared patients diagnosed with TMD and general population without TMD related pain and reported that Trait anxiety is significantly associated with diagnoses of TMD pain. One point increase in the State-Trait Anxiety Inventory score related to an increase of the odds for pain-related TMD by the factor 1.04 (Reissmann et al. 2014). A similar finding reported by kmeid et al. were TMDs was significantly associated with depression, anxiety, and stress among Lebanese population (Kmeid et al. 2020).

In general, oral parafunctional habits are known as a major contributor to TMDs and play an important role in its progression (Chisnoiu, Picos et al. 2015). In the present study, self-reported bruxism was significantly associated with TMDs. This finding concurs similar findings in Swedish dental students in which participants with TMD reported significantly higher oral parafunctional habits (Lövgren, Österlund et al. 2018). Moreover, the results of this study are in accordance with Jaiswal et al, where they reported significant relationship between TMDs and parafunctional habits in Indian dental students (Jaiswal and Deshpande 2021).

History of bruxism and anxiety levels were found to be higher among the senior dental students at UQU. Similar findings were reported by other studies in which a statistical significant relationship between anxiety and the para-functional habit was revealed (Paterson, Lamb et al. 1995, Ahlberg, Lobbezoo et al. 2013). Most individuals who have anxiety disorders tend to relieve their stress by clenching and/or grinding their teeth and contracting masticatory muscle which leads to activation of the stomatognathic system (Calixtre, Gruninger et al. 2014). This increase in stress levels among final-years students can be due to more participants from those two academic years. However, it can be also explained by the higher clinical demands and more workload during these final clinical years. Declining of both bruxism and anxiety parameters was noted in participants from the internship year where there is a significant decrease in academic load and clinical requirements. Similar findings were reported by Ahuja (Ahuja, Ranjan et al. 2018).

Limitation of the study

This is a cross-sectional study in which only association between variables is detected. Longitudinal studies are needed to prove causation. The absence of a control group for anxiety screening was regarded as a limitation for this study, as no clinical examination nor depression score was done for the participants who denied TMD pain or symptoms. Also, a comparison of TMDs prevalence with age-matched general population (non-dental students) was not considered in this study and it is recommended for future research projects.

Conclusions

TMDs is highly prevalent among dental students. Disc displacement with reduction was the most predominant one. Greater prevalence was observed among females and higher academic years. Bruxism and anxiety were associated with painful TMDs.

Data availability