Abstract
Purpose
The study aims at finding the incidence of temporo-mandibular joint disorders (TMDs) in a non-patient population and relates their association with psychological distress and parafunctional habits.
Materials and Methods
A DC/TMD questionnaire and DASS-21 scale survey were completed by selected participants followed by clinical examination of TMDs symptoms in sample population.
Results
A study sample of 855 participants revealed 36.65% population with various TMDs symptoms, while 63.5% population had no TMDs symptoms. 50.8% study participants were men, and 49.2% were women. Of all affected population, 16.2% had pain-related TMDs, 12.39% had intra-articular TMDs symptoms, and 8.07% had TMJ pain associated with pain or dysfunction. For all TMDs symptoms groups, the strongest correlations were for depression, while no significant associations were observed with parafunctional habits in all groups.
Conclusions
Overall psychological distress and anxiety increased the prospects of TMDs symptoms. Clinical factors like muscle tenderness, crossbite and deep vertical overlap seem to be significant etiological factors, while angle molar relationship and parafunctional habits do not seem to be significant etiologic factors in TMDs.
Keywords: Temporo, Mandibular joint, TMDs, Psychological, Distress, Anxiety, Parafunctional habits, Incidence of tmds
Introduction
Temporo-mandibular disorders (TMDs) are a combination of musculoskeletal and neuromuscular problems involving pain, dysfunction, and degeneration of the temporo-mandibular joints, masticatory muscles, and contiguous structures [1]. The etiology of TMDs includes structural abnormalities, stress-induced muscle hyperactivity, and overloading from trauma. The role of occlusal factors remains unclear, perhaps because of varying adaptive capacities among individuals [2].
About 60–70% of the general population has at least one sign of temporo-mandibular joint dysfunction, but only one out of four individuals is aware of these symptoms and reports them to a specialist [3]. Understanding the etiology of TMDs is extremely important in identifying and avoiding potential pathologic factors [3].
The contemporary benchmark for the protocolized assessment and diagnosis of TMDs is the diagnostic criteria for TMDs (DC/TMD) [4]. Based on these criteria, common TMDs conditions can be categorized into pain-related and intra-articular TMJ disorders. Accordingly, TMDs features can also be classified into pain-related, intra-articular, and combined TMDs symptoms.
Investigations have described high levels of psychosocial impairment and a high prevalence of psychological disorders in a TMDs patient population. Their presence is said to be related to chronic pain and has important implications at the therapeutic level. Therefore, an assessment of psychosocial factors is a fundamental step during the diagnostic process of TMDs patients [5].
The aim of this study was to find out the incidence of TMDs, the related occlusal/clinical presentations and their association with psychological distress in a non-patient population.
Materials and Methods
Study participants
The study participants were recruited from Sudha Rustagi Dental college and research institute using convenience sampling method. All the participants were 18 years or older in age. After ethical approval from the institutional review board, informed consent was obtained before undergoing any clinical examination and completing a survey consisting of demographic information, the DC/TMD Symptom Questionnaire (SQ) and Depression, Anxiety, and Stress Scales-21 (DASS-21).
Inclusion criteria- Patients with the absence of history of any past traumatic injury to head and neck region, the absence of history of any cognitive impairments, and the absence of history of any past orthodontic therapy were included in the study.
Exclusion criteria- Patients with history of any psychiatric treatments, history of any past traumatic injury to head and neck region, history of past orthodontic therapy, and incomplete questionnaires were excluded from the study.
Measures
The SQ is a critical component of the DC/TMD and provides the needed history for making specific TMD Axis I (physical) diagnosis [1]. It comprises of 14 items concerning masticatory muscle/TMJ pain, headaches attributed to TMDs, TMJ sounds, closed and open locking. TMJ disorders were further stratified into a total of six possible symptom groups: No TMDs (NT), pain-related TMDs (TP), TMJ sounds (TS), TMJ dysfunction (TD), TMJ pain plus TMJ sounds (PS), and finally TMJ pain plus TMJ dysfunction (PD).
Psycho-emotional distress was evaluated using the DASS-21 which comprises 21 items with seven questions offered for each emotional state. Responses were scored on a 4 point scale varying from 0 = did not apply to me at all to 3 = applied to me very much, or most of the time. The total DASS score, which indicates overall psychological distress, was computed by summing all scores. Greater total and subscale scores denote higher levels of psycho-emotional distress.
The clinical examination included Angles’ molar classification; vertical and horizontal overlap; the presence/absence of anterior and/or posterior crossbite; range of protrusive and laterotrusive movements (marked as restricted if range of movement without pain recorded at less than 4 mm) and mouth opening; tooth wear (marked as 0,1,2,3 depending upon the defect with reference of Smith and Knight tooth wear index); and pain/tenderness in muscles of mastication (determined by digital palpation of TMJ and muscles and scored 0,1,2,3 as not present, mild pain, distinct pain, body withdrawal and observable palpebral reflex, respectively).
Results
A total of 902 individuals were invited to contribute to the study out of which 47 individuals were excluded, resulting in a final sample of 855 individuals.
The study sample comprised of 49.20% men and 50.80% women.
While 63.50% reported no TMDs manifestations, 36.65% experienced various TMDs symptoms. Table 1 shows the gender distribution and frequencies of the various TMDs symptoms. Pain-related, intra-articular, and combined TMDs symptoms were present in 16.02, 12.39 and 8.07% of the participants, respectively. While the intra-articular TMDs symptoms (IT) group comprised of 6.54% with TMJ sounds and 5.84% with TMJ dysfunction, the combined TMDs symptoms (CT) group consisted of 5.14% with TMDs pain plus TMJ sounds and 2.92% with TMDs pain plus TMJ dysfunction.
Table 1.
Gender distribution of various TMD symptom sub-groups
| Tmdcategory and abbreviations | Sex | Total | ||||
|---|---|---|---|---|---|---|
| Males | Females | |||||
| No tmd symptom | NT | N | 276 | 267 | 543 | |
| % | 66.5% | 60.7% | 63.5% | |||
| Pain-related tmd symptom | TP | N | 75 | 62 | 137 | |
| % | 18.1% | 14.1% | 16.0% | |||
| Intra-articular tmd symptoms (IT) N = 106 | Tmj sounds | TS | N | 29 | 27 | 56 |
| % | 7.0% | 6.1% | 6.5% | |||
| Tmj dysfunction | TD | N | 15 | 35 | 50 | |
| % | 3.6% | 8.0% | 5.8% | |||
| Combined tmd symptoms (CT) N = 89 | Tmd pain plus tmj sounds | PS | N | 15 | 29 | 44 |
| % | 3.6% | 6.6% | 5.1% | |||
| Tmd pain plus tmj dysfunction | PD | N | 5 | 20 | 25 | |
| % | 1.2% | 4.5% | 2.9% | |||
| Total | N | 415 | 440 | 855 | ||
| % | 48.53% | 51.46% | 100.0% | |||
| Chi square, pa value | 22.197, 0.0001* sig | |||||
achi square test, level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Tables 2 and 3 reflect the mean/median DASS-21 scores for the various TMDs symptom groups and subgroups. Among the four symptom groups, significant differences in total DASS (CT > IT > TP > NT), depression (CT > IT > TP > NT), anxiety (CT > IT > TP > NT), and stress (CT > IT > TP > NT) were noted for PD (P < 0.005). For all TMDs symptom groups, the strongest correlations were observed for depression (rs =—0.52–0.65) with painful TMDs symptoms yielding greater associations (Tables 4, 5, 6, 7).
Table 2.
Mean (standard deviation) and median (interquartile range) total and subscale of DASS-21 scores for various TMD symptoms groups
| N | Mean | Std. Deviation | Median | Minimum | Maximum | Chi square, pb value | Post hoc c | ||
|---|---|---|---|---|---|---|---|---|---|
| DASSS | NT | 543.00 | 17.65 | 8.18 | 18 | 4.00 | 36.00 | 196, 0.0001*, sig | NT < TP,TS < TD,PS < PD |
| TP | 137.00 | 25.85 | 9.27 | 27 | 4.00 | 64.00 | |||
| TS | 56.00 | 27.68 | 9.55 | 27 | 16.00 | 69.00 | |||
| TD | 50.00 | 32.92 | 6.87 | 31 | 20.00 | 56.00 | |||
| PS | 44.00 | 38.27 | 18.12 | 32 | 17.00 | 74.00 | |||
| PD | 25.00 | 49.68 | 16.40 | 47 | 27.00 | 77.00 | |||
| D | NT | 543.00 | 5.72 | 2.46 | 6 | 2.00 | 11.00 | 399.590, 0.0001*, sig | NT < TP < TS,TD < PS < PD |
| TP | 137.00 | 8.88 | 3.32 | 9 | 2.00 | 21.00 | |||
| TS | 56.00 | 10.57 | 2.88 | 10 | 6.00 | 22.00 | |||
| TD | 50.00 | 11.36 | 3.73 | 11 | 6.00 | 25.00 | |||
| PS | 44.00 | 14.59 | 5.06 | 13 | 10.00 | 26.00 | |||
| PD | 25.00 | 17.32 | 5.10 | 16 | 10.00 | 27.00 | |||
| A | NT | 542.00 | 6.30 | 3.99 | 5 | 0.00 | 13.00 | 72.370, 0.0001*, sig | NT < TP,TS < TD,PS < PD |
| TP | 137.00 | 8.44 | 3.10 | 9 | 2.00 | 16.00 | |||
| TS | 56.00 | 8.18 | 2.77 | 8 | 2.00 | 19.00 | |||
| TD | 50.00 | 9.30 | 2.05 | 9 | 5.00 | 17.00 | |||
| PS | 44.00 | 9.48 | 5.13 | 9 | 2.00 | 19.00 | |||
| PD | 25.00 | 13.16 | 4.25 | 12 | 7.00 | 19.00 | |||
| S | NT | 543.00 | 5.64 | 3.64 | 5 | 0.00 | 15.00 | 184.108, 0.0001*, sig | NT < TP < TS,PS < PD |
| TP | 137.00 | 8.53 | 4.66 | 9 | 0.00 | 27.00 | |||
| TS | 56.00 | 8.93 | 5.54 | 9 | 0.00 | 28.00 | |||
| TD | 50.00 | 12.26 | 3.77 | 12 | 4.00 | 21.00 | |||
| PS | 44.00 | 14.20 | 8.66 | 11 | 4.00 | 32.00 | |||
| PD | 25.00 | 19.20 | 7.76 | 19 | 6.00 | 31.00 |
bKruskal–Wallis test, cMann–Whitney U test (post hoc comparison), level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Table 3.
Mean (standard deviation) and median (interquartile range) total and subscale of DASS-21 scores for various TMD symptoms groups
| N | Mean | Std. Deviation | Median | Minimum | Maximum | Chi square, pa value | Post hocb | ||
|---|---|---|---|---|---|---|---|---|---|
| DASSS | NT | 543 | 17.648 | 8.1786 | 18 | 4.0 | 36.0 | 273.804, 0.0001*, sig | NT < TP < IT < CT |
| TP | 137 | 25.847 | 9.2735 | 27 | 4.0 | 64.0 | |||
| IT | 106 | 30.151 | 8.7601 | 28 | 16.0 | 69.0 | |||
| CT | 69 | 42.406 | 18.2502 | 37 | 17.0 | 77.0 | |||
| D | NT | 543 | 5.720 | 2.4606 | 6 | 2.0 | 11.0 | 399.590, 0.0001*, sig | NT < TP < IT < CT |
| TP | 137 | 8.876 | 3.3176 | 9 | 2.0 | 21.0 | |||
| IT | 106 | 10.943 | 3.3147 | 10 | 6.0 | 25.0 | |||
| CT | 69 | 15.580 | 5.2086 | 14 | 10.0 | 27.0 | |||
| A | NT | 541 | 6.311 | 3.9800 | 5 | 0.0 | 13.0 | 72.370, 0.0001*, sig | NT < TP, IT < CT |
| TP | 137 | 8.438 | 3.1009 | 9 | 2.0 | 16.0 | |||
| IT | 106 | 8.708 | 2.5108 | 9 | 2.0 | 19.0 | |||
| CT | 69 | 10.812 | 5.1200 | 10 | 2.0 | 19.0 | |||
| S | NT | 543 | 5.641 | 3.6450 | 5 | 0.0 | 15.0 | 184.108, 0.0001*, sig | NT < TP < IT < CT |
| TP | 137 | 8.533 | 4.6622 | 9 | 0.0 | 27.0 | |||
| IT | 106 | 10.500 | 5.0526 | 9 | 0.0 | 28.0 | |||
| CT | 69 | 16.014 | 8.6305 | 14 | 4.0 | 32.0 | |||
aKruskal–Wallis test, bWhitney U test (post hoc comparison), level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Table 4.
Distribution of sites of muscle tenderness for various TMD symptom sub-groups
| NT | TP | TS | TD | PS | PD | P value | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| N | % | N | % | N | % | N | % | N | % | N | % | |||
| Masseter | None | 538 | 99.08 | 121 | 88.32 | 43 | 76.79 | 40 | 80 | 29 | 65.91 | 17 | 68 | 0.0001*, Sig |
| Unilateral | 5 | 0.92 | 14 | 10.22 | 11 | 19.64 | 8 | 16 | 10 | 22.73 | 5 | 20 | ||
| Bilateral | 0 | 0.00 | 2 | 1.46 | 2 | 3.57 | 2 | 4 | 5 | 11.36 | 3 | 12 | ||
| Temporalis | None | 541 | 99.63 | 134 | 97.81 | 51 | 91.07 | 39 | 78 | 36 | 81.82 | 20 | 80 | 0.0001*, Sig |
| Unilateral | 2 | 0.37 | 3 | 2.19 | 5 | 8.93 | 8 | 16 | 8 | 18.18 | 5 | 20 | ||
| Bilateral | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | 3 | 6 | 0 | 0.00 | 0 | 0 | ||
| Medial Pterygoid | None | 537 | 98.90 | 135 | 98.54 | 52 | 92.86 | 46 | 92 | 42 | 95.45 | 20 | 80 | 0.0001*, Sig |
| Unilateral | 4 | 0.74 | 2 | 1.46 | 3 | 5.36 | 4 | 8 | 2 | 4.55 | 5 | 20 | ||
| Bilateral | 2 | 0.37 | 0 | 0.00 | 1 | 1.79 | 0 | 0 | 0 | 0.00 | 0 | 0 | ||
| Lateral pterygoid | None | 532 | 97.97 | 120 | 87.59 | 43 | 76.79 | 34 | 68 | 31 | 70.45 | 12 | 48 | 0.0001*, Sig |
| Unilateral | 10 | 1.84 | 17 | 12.41 | 10 | 17.86 | 9 | 18 | 11 | 25.00 | 6 | 24 | ||
| Bilateral | 1 | 0.18 | 0 | 0.00 | 3 | 5.36 | 7 | 14 | 2 | 4.55 | 7 | 28 | ||
| Temporal tendon | None | 538 | 99.08 | 136 | 99.27 | 55 | 98.21 | 42 | 84 | 37 | 84.09 | 15 | 60 | 0.0001*, Sig |
| Unilateral | 5 | 0.92 | 1 | 0.73 | 1 | 1.79 | 8 | 16 | 6 | 13.64 | 9 | 36 | ||
| Bilateral | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | 0 | 0 | 1 | 2.27 | 1 | 4 | ||
achi square test, level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Table 5.
Prevalence of crossbites (anterior & posterior) and angle molar relationship for various TMD symptom sub-groups
| NT | TP | TS | TD | PS | PD | P value | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| N | % | N | % | N | % | N | % | N | % | N | % | |||
| Angle molar relationship: right | None | 12 | 2.21 | 2 | 1.46 | 0 | 0.00 | 2 | 4 | 0 | 0.00 | 1 | 4 | 0.970, NS |
| Class I | 436 | 80.29 | 114 | 83.21 | 46 | 82.14 | 38 | 76 | 37 | 84.09 | 21 | 84 | ||
| Class II | 88 | 16.21 | 19 | 13.87 | 10 | 17.86 | 9 | 18 | 6 | 13.64 | 3 | 12 | ||
| Class III | 7 | 1.29 | 2 | 1.46 | 0 | 0.00 | 1 | 2 | 1 | 2.27 | 0 | 0 | ||
| Angle molar relationship: left | None | 12 | 2.21 | 4 | 2.92 | 0 | 0.00 | 2 | 4 | 1 | 2.27 | 1 | 4 | 0.948, NS |
| Class I | 450 | 82.87 | 113 | 82.48 | 46 | 82.14 | 39 | 78 | 33 | 75.00 | 22 | 88 | ||
| Class II | 74 | 13.63 | 18 | 13.14 | 10 | 17.86 | 8 | 16 | 9 | 20.45 | 2 | 8 | ||
| Class III | 7 | 1.29 | 2 | 1.46 | 0 | 0.00 | 1 | 2 | 1 | 2.27 | 0 | 0 | ||
| Crossbite: anterior | ABSENT | 525 | 96.69 | 135 | 98.54 | 55 | 98.21 | 50 | 100 | 42 | 95.45 | 23 | 92 | 0.330, NS |
| PRESENT | 18 | 3.31 | 2 | 1.46 | 1 | 1.79 | 0 | 0 | 2 | 4.55 | 2 | 8 | ||
| Crossbite: posterior: right | ABSENT | 528 | 97.24 | 135 | 98.54 | 56 | 100.00 | 49 | 98 | 41 | 93.18 | 22 | 88 | 0.023*, sig |
| PRESENT | 15 | 2.76 | 2 | 1.46 | 0 | 0.00 | 1 | 2 | 3 | 6.82 | 3 | 12 | ||
| Crossbite: posterior: left | ABSENT | 532 | 97.97 | 137 | 100.00 | 56 | 100 | 55 | 110 | 44 | 100.00 | 23 | 92 | 0.030*, sig |
| PRESENT | 11 | 2.03 | 0 | 0.00 | 0 | 0.00 | 0 | 0 | 0 | 0.00 | 2 | 8 | ||
achi square test, level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Table 6.
Mean (standard deviation) and interquartile range of overjet, overbite, protrusive, lateral and mouth opening for various TMD symptoms groups
| N | Mean | Std. Deviation | Minimum | Maximum | P value | ||
|---|---|---|---|---|---|---|---|
| OVERJET | NT | 543 | 1.9678 | 1.01800 | 1.00 | 6.00 | 0.264, NS |
| TP | 137 | 1.9416 | 1.04154 | 1.00 | 6.00 | ||
| TS | 56 | 1.8661 | .80052 | 1.00 | 4.00 | ||
| TD | 50 | 2.1400 | 1.20391 | 1.00 | 6.00 | ||
| PS | 44 | 1.6932 | .71703 | 1.00 | 4.00 | ||
| PD | 25 | 2.2000 | 1.43614 | 1.00 | 6.00 | ||
| OVERBITE | NT | 543 | 2.349 | .7360 | 1.0 | 5.0 | 0.000*, Sig |
| TP | 137 | 2.321 | .7735 | 1.0 | 5.0 | NT, TP, TS < TD < PS < PD | |
| TS | 56 | 2.321 | .6355 | 1.0 | 4.0 | ||
| TD | 50 | 2.656 | .8450 | 1.0 | 5.2 | ||
| PS | 44 | 2.748 | .8148 | 1.0 | 5.0 | ||
| PD | 25 | 3.144 | .9832 | 1.5 | 4.7 | ||
| PROTRUSIVE | NT | 387 | 2.9251 | .98542 | 1.00 | 4.00 | 0.744, NS |
| TP | 92 | 2.8804 | 1.02542 | 1.00 | 4.00 | ||
| TS | 50 | 3.0600 | .91272 | 1.00 | 4.00 | ||
| TD | 31 | 3.0000 | .96609 | 1.00 | 4.00 | ||
| PS | 33 | 2.7273 | 1.09752 | 1.00 | 4.00 | ||
| PD | 15 | 3.0000 | .75593 | 2.00 | 4.00 | ||
| LATERAL | NT | 296 | 4.6284 | 4.94071 | 2.00 | 36.00 | 0.758, NS |
| TP | 71 | 4.3521 | 3.87703 | 2.00 | 36.00 | ||
| TS | 38 | 4.7105 | 5.26029 | 2.00 | 36.00 | ||
| TD | 25 | 4.9600 | 6.49667 | 2.00 | 36.00 | ||
| PS | 25 | 4.0400 | .73485 | 3.00 | 5.00 | ||
| PD | 10 | 6.8000 | 10.28267 | 2.00 | 36.00 | ||
| MOUTH OPENING | NT | 543 | 38.5746 | 5.75943 | 0.00 | 52.00 | 0.491, NS |
| TP | 137 | 38.9051 | 5.10462 | 0.00 | 52.00 | ||
| TS | 56 | 37.1964 | 5.77902 | 0.00 | 46.00 | ||
| TD | 50 | 38.7800 | 6.82818 | 0.00 | 52.00 | ||
| PS | 44 | 39.0227 | 3.52723 | 33.00 | 46.00 | ||
| PD | 25 | 37.8000 | 9.08754 | 0.00 | 52.00 | ||
aOne way ANOVA test, level of significance set at p < 0.05
ns: non-significant, sig: significant, *: statistically significant
Table 7.
Distribution of tooth wear index according to TMD groups
| Tooth wear index | Total | |||||||
|---|---|---|---|---|---|---|---|---|
| .00 | 1.00 | 2.00 | 3.00 | 4.00 | ||||
| Tmdcategory | NT | n | 357 | 163 | 10 | 11 | 2 | 543 |
| % | 65.7% | 30% | 1.8% | 2.0% | 0.4% | 100.0% | ||
| TP | n | 89 | 40 | 4 | 3 | 1 | 137 | |
| % | 65.0% | 29.2% | 2.9% | 2.2% | 0.7% | 100.0% | ||
| TS | n | 33 | 16 | 3 | 1 | 3 | 56 | |
| % | 58.9% | 28.6% | 5.4% | 1.8% | 5.4% | 100.0% | ||
| TD | n | 33 | 16 | 1 | 0 | 0 | 50 | |
| % | 66.0% | 32% | 2.0% | 0.0% | 0.0% | 100.0% | ||
| PS | n | 27 | 14 | 3 | 0 | 0 | 44 | |
| % | 61.4% | 31.9% | 6.8% | 0.0% | 0.0% | 100.0% | ||
| PD | n | 18 | 5 | 1 | 1 | 0 | 25 | |
| % | 72.0% | 20% | 4.0% | 4.0% | 0.0% | 100.0% | ||
| Total | n | 557 | 254 | 22 | 16 | 6 | 855 | |
| % | 65.1% | 29.7 | 2.6% | 1.9% | 0.7% | 100.0% | ||
| P value | 0.091,NS | |||||||
Among TMDs symptom groups, significant findings in relation to muscle tenderness were noted (P < 0.005). Lateral pterygoid (83%) > Masseter (67%) > Temporalis (34%) > Temporal tendon (32%) > Medial pterygoid (23%). (CT > IT > TP > NT).
Crossbite- Anterior crossbite was present in 25 individuals (2.59%), while posterior crossbite was present in 24 individuals (2.81%) and 13 individuals (1.52%) on right and left side, respectively.
No significant differences in any of the study groups were noted in relation to tooth wear, Grade 0 (65.1%), Grade 1 (29.7%), Grade 2 (2.6%), Grade 3 (1.9%), Grade 4 (0.7%).
Angles’ classification- Class 1 molar relation- 692 individuals (80.94%) had Class 1 molar relation on right side, 703 individuals (82.22%) had Class 1 molar relation on left side.
Class 2- 135 individuals (15.79%) had Class 2 molar relation on right side, and 121 individuals (14.15%) had Class 2 molar relation on left side.
Class 3- 11 individuals (1.29%) had Class 3 molar relation bilaterally.
No correlation was observed pertaining to Angle’s classification.
Discussion
TMDs are a group of conditions potentially associated with significant psychological distress, psychosocial impairment and behavioral upset [6, 7].
The aim of this study was to investigate the association of TMDs with psychological distress using the DASS-21 scale, the psychometric properties of which are widely documented and it had been employed for assessing PD in prior TMDs work [8, 9].
Moreover, this study ascertains the correlation of these findings with the clinical factors which may play an important role in the etiology of TMDs [10].
Suvinen TI et al. [11] and Dworkin SF et al. [12] in their studies have observed that patients with TMDs have similar psychological profiles and psychological dysfunction as other chronic musculoskeletal pain disorders, such as tension-type headache and back or arthritic pain. In our study on association of TMDs with psychological distress, strong correlations were observed for TMDs and depression for all TMDs symptom groups with painful TMDs symptoms groups yielding greater associations.
TMDs symptoms, especially pain, are also discussed as being a causative or intensifying factor in the development of depression and psychic diseases [3].
Ferrando M et al. [13] have confirmed that patients with myofascial pain or myofascial pain associated with arthralgia, arthritis or osteoarthritis present more advanced stages of depression and somatization than those diagnosed with disk displacement.
A. U. Yap et al. [1] among other similar studies found women to be at about two times greater risk of experiencing pain-related and combined TMDs symptoms than men [1]. Our study observed a greater percentage of female participants affected by TMDs. Thus, the distribution of TMDs symptoms was in significantly higher proportion with women as presented in earlier studies [1, 10].
The gender difference in TMDs expression has been explained by fluctuating hormone levels, socio-cultural factors, as well as variances in psycho-emotional distress, symptom sensitivity, reporting, and treatment-seeking. [10]
The existing data cannot determine the exact role of occlusal factors in TMDs, especially in Indian population where such studies on clinical factors have not been performed. Factors like parafunctional habits, malocclusion, deep vertical bite, muscle tenderness, etc., may play important roles in development of TMDs.
Parafunctions are defined as impaired or altered functions of temporo-mandibular joint [3]. Of these teeth clenching and bruxism have been extensively studied as possible risk factors for TMDs. The association between bruxism and TMDs symptoms is based on the theory according to which the repeated overuse of TMJ determines functional abnormalities [14].
Huang et al. [15] assessed a group of patients diagnosed with myofascial pain (n = 97), arthralgia (n = 20) and combined myofascial pain and arthralgia (n = 157), identifying a strong correlation between tooth clenching and the presence of myofascial pain. There was no significant association of tooth wear with TMDs symptom groups in our study suggesting no role of parafunctional habits as an etiological factor for TMDs.
Although malocclusion has been considered an etiologic factor in patients with TMDs [16–20], several studies have reported that specific angle classes of malocclusion may not be etiologically significant. [21–24] Our study revealed no significant findings in relation to angles’ molar classification and TMDs although malocclusion still may play an important role in development of TMDs as angle’s molar classification only assesses the molar relationship.
As per the previous studies done on children and teenagers, crossbites never contributed as a causative factor in development of TMD [25], but unilateral crossbites may induce asymmetric muscle activity[26, 27] and geometrically alter condyle-fossa relationships [28, 29].
In our study, posterior crossbite was found as a significant finding in TMD cases and could be considered as an etiological factor for the same.
Patients included in the study also had statistically significant association with vertical overlap when considering TMDs. Williamson [30] also cited the high prevalence of deep bites in a pre-orthodontic adolescent population along with clicking or pain. Even Lieberman MA et al. [25] and Heloe B et al. [31] showed statistically significant association between vertical overlap of 5 mm or more and TMJ dysfunction in general population of children and teenagers.
Muscle tenderness is a common clinical finding associated with malocclusion and TMDs. In previous studies by A.G. Pullinger et al., lateral pterygoid region was found to be mostly associated with TMDs while medial pterygoid region being least common. [2, 32]
Our study found lateral pterygoid region being the most common site of tenderness which corroborated with other studies as well [32–35].
In a previous study, Gross and Gale [33] attempted to control for palpation pressure and their selection of 3 pounds elicited 8.8% moderate to severe responses. They assumed that potential patients would respond to this degree of pressure, whereas healthy individuals would not while other studies, including this one, that used palpation techniques for trigger points as described by Travel and Simons [36] may apparently use stronger pressure therefore resulting in higher percentage of affected population with muscle tenderness.
Conclusion
Overall psychological distress and anxiety seem to increase the prospects of pain-related and intra-articular/combined TMDs symptoms, respectively.
On the other hand, clinical factors like muscle tenderness, crossbites and vertical overlap seem to be significant etiological factors in TMDs, while angles’ molar relationship and parafunctional habits do not seem to be a significant finding.
Understanding and identifying the etiology of TMDs are important in avoiding potential pathologic factors, and therefore, oral and maxillofacial surgery specialist may play an important role in help avoiding such TMDs by early diagnosis and treatment.
Limitations
Due to exclusion of patients with partially edentulous ridges means potential patients with TMDs were excluded from our study.
Declarations
Conflict of Interest
No conflict of interest between authors.
Footnotes
Publisher's Note
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References
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