Symptoms and signs of temporomandibular disorders among elderly Vietnamese

Abstract

Background:

To assess the prevalence of the symptoms and signs of temporomandibular disorders (TMDs) and determine the prevalence of TMDs among elderly Vietnamese aged 65–74 years old.

Methods:

A cross-sectional study was conducted among 258 participants aged 65–74 years old (128 females and 130 males) using two strategies for TMD diagnosis: a clinical examination of the temporomandibular joint and its associated structures using the Diagnostic Criteria for Temporomandibular Disorders Axis I; and a set of 14 questions regarding TMD symptoms to obtain anamnestic data.

Results:

The prevalence of TMD symptoms was: headache 49.6%; temporomandibular joint noise 28.0%; orofacial pain 25.2%; jaw locking 3.1%; 62.5% of participants had at least one TMD symptom. Headaches were more prevalent in females than males (p=0.009) and rural than urban residents (p<0.001). The most frequent signs were temporomandibular joint crepitus (50.4%), clicking (48.1%) and mouth-opening deviation (37.6%). Temporomandibular joint crepitus and mouth-opening deviation were more frequent among rural than urban (p=0.024 and p<0.001, respectively). TMD was found in 56.6% of the total sample. Of the TMD sufferers, 37.6% were diagnosed with disc displacement, 34.9% with degenerative joint disease, 3.5% with myalgia and 1.2% with arthralgia.

Conclusions:

More than half of elderly Vietnamese have at least one TMD symptom. TMD sounds were the most common clinical sign of TMD. There were no differences between the genders or place of residence and TMD diagnosis. Disc displacement and degenerative joint disease were most prevalent among elderly Vietnamese.

Keywords

Diagnosis elderly temporomandibular joint disorders temporomandibular joint

Background

Temporomandibular disorders (TMDs) are associated with functional disturbances of the masticatory system.^1–4 The prevalence of TMDs varies among general populations, with muscle disorders affecting about 12.6–34.0% of people, disc displacement 6.2–41.5% and degenerative joint disease 5.3–34.2%; rates depend on the ethnicity of the population, the sampling design and criteria, and the methods used for collecting information.^1,3,5–7

TMD symptoms have been considered most prevalent among the middle-aged, but they also occur in 40% of elderly populations, with approximately 20% of the latter reporting at least two subjective TMD symptoms.^1,6,8 Several studies have indicated that the symptoms of TMD such as headaches, temporomandibular joint noises and orofacial pain are mostly observed among the elderly.^6,9–11 The consequences of TMD include reduced chewing ability and effects upon people’s daily activities and quality of life.^11–13

Previous investigations demonstrated that 60% of older people have at least one clinical sign of TMD.^3,8 Clicking and crepitus of the temporomandibular joint (TMJ) were found in 25% of an elderly population aged 60–80 years old;³ restricted mandibular range of motion has been significantly associated with aging; masticatory muscle tenderness also causes a decline in oral health among the elderly.^3,8,12,14,15 Moreover, the elderly are most vulnerable to tooth loss and alteration to functional occlusion, which are known risk factors of TMD.^10,16,17 A shortened dental arch due to missing teeth decreases masticatory function and is attributed to muscle tenderness.^18,19

TMD diagnosis is based on the comprehensive examination of symptoms and signs. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I has been widely applied in epidemiological studies.² Recently, Schiffman et al. modified the RDC/TMD to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), because the validity of the RDC/TMD was found to be below the target sensitivity level of 70% and specificity level of 95% due to a lack of several criteria of diagnosing TMD.⁴

In addition, data on TMD among aging populations is insufficient, especially among those aged 65–74 years old, a representative group of the elderly population for oral health surveys according to the World Health Organization criteria. To the best of our knowledge, no epidemiological study has reported the signs and symptoms of TMD among the elderly in Vietnam, a country where 9,000,000 people are aged over 60 years old, and 68% of the elderly live in rural areas. Thus, we aimed with this cross-sectional epidemiological study to assess the prevalence the clinical signs and symptoms of TMD, and determine the prevalence of TMD among elderly Vietnamese aged 65–74 years old.

Methods

Study sample size

This cross-sectional study involved examining the oral health status of elderly people aged 65–74 years old living in and around Danang City, Vietnam. The sample size (300 participants) was calculated to a 90% confidence level; by assuming a 50% prevalence of any oral disease among elderly Vietnamese; this gave an acceptable error margin of 5%.

The participants were selected using a multistage stratified random sampling method based on demographic characteristics. Danang consists of six urban districts and two rural districts. First, three urban districts and one rural district were randomly chosen. Next, lists of elderly residents were obtained from Community Unions for Older Adults, into which all citizens aged 65–74 years old are incorporated. Finally, participants from each selected urban (50 subjects) and rural district (150 subjects) were randomly sampled and stratified according to gender and age groups (male:female ratio = 1:1; age group 65–69:70–74 ratio = 1:1). The sample selection is shown in Figure 1.

Figure 1.

Flow chart of the multistage stratified random sampling method used to select elderly participants aged 65–74 years old living in Danang, Vietnam.

Data collection

The selected participants: were able to answer questions about TMD symptoms; had no previous orthognathic or plastic surgery; had no history of TMJ trauma. Participants were examined for the status of their masticatory muscles and TMJs at local health centres or the dental clinic of the Danang University of Medical Technology and Pharmacy. The examination procedure was conducted via two strategies for the specific diagnosis of TMD using the DC/TMD Axis I.⁴

Written informed consent that explained temporomandibular examination procedures was obtained from each participant. First, the participant was asked about any history of pain in the orofacial area, headaches, jaw joint noises and any locking of the jaw while opening or closing their mouth. Second, an examination of the clinical signs of TMD was performed as follows: (1) confirming orofacial pain and headache locations; (2) measuring incisal relations; (3) evaluating the symmetry of mouth opening pattern; (4) measuring range of mandibular movement and determining the location of pain during mandibular movements; (5) identifying any clicking and crepitus of the TMJ during mandibular movements; (6) determining joint locking status; and (7) defining muscle and TMJ pain during palpation.

Diagnosis criteria included pain-related TMD, disc displacement, and degenerative joint disease. Pain related TMD consists of myalgia and arthralgia. Diagnosis of myalgia was based on the confirmation of pain in the masticatory muscle area, for example, pain from jaw opening or during masticatory muscle palpation. Arthralgia was confirmed by pain of the TMJ, for example, pain from the vertical/horizontal movement of the jaw or during palpation.

Disc displacement was confirmed by jaw joint noises as detected by the participant, and TMJ clicks during vertical mandibular movements as determined by the examiner, or in cases where the patient had jaw locking in the closed position that interfered with mastication. The degenerative joint disease was clinically diagnosed by a combination of jaw joint noises as detected by the participant, and TMJ crepitus as identified by the examination during mandibular movement.

A pilot study of a group of 25 elderly people was performed to calibrate the examiner and train two dental students to deliver the questionnaire and record the subjects’ answers on an assessment form. The first author conducted all clinical temporomandibular examinations. Ten per cent of the total sample were re-examined after three days to test the reliability of the examiner. The calculated Kappa-values were above 0.85, indicating a high degree of intra-examiner and inter-examination reliability.

This study was approved by the Human Research Ethics Committee of Danang University of Medical Technology and Pharmacy (No. 523/CN-DHKTYDDN), and performed in accordance with the World Medical Association’s Helsinki Declaration.

Statistical methods

Data entry and statistical analysis were performed using SPSS Statistics for Windows, Version 17.0 (SPSS Inc., Chicago, Illinois, USA). Percentages were calculated for the prevalence of symptoms, clinical signs and diagnosis criteria. Correlations between gender and/or place of residence, and the symptoms, clinical signs and diagnostic criteria of TMD were analysed using a Chi-square test. A confidence level of 95% and a two-sided p-value of <0.05 were considered statistically significant.

Results

Of the 300 elderly aged 65–74 years old, 42 subjects failed to participate in the study (Figure 1). The final sample consisted of 258 subjects, of which 128 were female (49.6%) and 130 male (50.4%), 46.7% subjects lived in rural areas and 53.3% in urban areas (Figure 1).

Among the 258 elderly participants, 62.5% had at least one symptom of TMD. TMD occurred more frequently among rural than urban residents (p<0.001). The most prevalent symptoms were headaches (49.6%), jaw joint noises (28.0%) and orofacial pain (25.2%); jaw locking was 3.1%. Significant differences related to headaches were found between the genders (p=0.009) and residency types (p<0.001); jaw joint noises were more frequent among rural (59.2%) than urban residents (40.8%, p=0.014). There was a near-significant higher prevalence of orofacial pain among females than males (p=0.053; Table 1).

Table 1.

Prevalence of TMD symptoms according to gender and place of residence (N=258).

TMD symptoms	Totaln (%)	Gender (%)		p-value^a	Residence (%)		p-value^a
TMD symptoms	Totaln (%)	Female	Male	p-value^a	Rural	Urban	p-value^a
Orofacial pain	65 (25.2)	60.0	40.0	0.053	47.7	52.3	0.882
Headache	128 (49.6)	57.8	42.2	0.009^*	59.4	40.6	<0.001^*
Jaw joint noises	71 (28.0)	54.9	45.1	0.256	59.2	40.8	0.014^*
Locking jaw	8 (3.1)	62.5	37.5	0.497	62.5	37.5	0.481
At least one symptom	158 (62.5)	51.9	48.1	0.249	56.3	43.7	<0.001^*

Chi-square test.

Significant.

TMD: temporomandibular disorder.

Table 2 shows that the most frequent clinical sign of TMD was TMJ sounds (69.0%), including crepitus (50.4%) and clicking (48.1%). Mouth-opening deviation occurred among 37.6% of the subjects. TMJ crepitus and deviation of mouth-opening pattern were significantly associated with rural residence (p=0.024 and p<0.001, respectively). TMJ tenderness was found among 16.3% of the sample, and females were more likely to have experienced TMJ tenderness (p<0.05). Overall, 25.6% of the subjects had at least one clinical sign of muscle tenderness, including tenderness of the temporalis (15.5%), masseter (14.7%) and lateral pterygoid (14.0%) muscles. Masseter tenderness significantly differed by gender (p=0.031) and type of residency (p=0.030). Likewise, lateral pterygoid tenderness was associated with rural residence (p=0.028).

Table 2.

Prevalence of TMD signs according to gender and place of residence (N=258).

TMD sign	Totaln (%)	Gender (%)		p-value^a	Residence (%)		p-value^a
TMD sign	Totaln (%)	Female	Male	p-value^a	Rural	Urban	p-value^a
Mouth-opening
Deviation	97 (37.6)	54.1	45.9	0.316	67.0	33.0	<0.001^*
Limitation (<40mm)	25 (9.7)	60.0	40.0	0.256	48.0	52.0	0.938
TMJ sounds
Clicking	124 (48.1)	48.4	51.6	0.705	48.4	51.6	0.645
Crepitus	130 (50.4)	50.8	49.2	0.708	53.8	46.2	0.024^*
At least one TMJ sound	178 (69.0)	48.3	51.7	0.534	50.0	50.0	0.137
TMJ pain
Lateral TMJ pole palpation	41 (15.9)	70.7	29.3	0.003^*	58.5	41.5	0.103
Around TMJ pole palpation	40 (15.5)	70.0	30.0	0.049^*	62.5	37.5	0.031^*
At least one sign of TMJ pain	42 (16.3)	71.4	28.6	0.002^*	59.5	40.5	0.073
Muscle pain
Temporalis	39 (15.5)	57.9	42.1	0.269	60.5	39.5	0.068
Masseter	38 (14.7)	65.8	34.2	0.031^*	63.2	36.8	0.030^*
Posterior mandibular	10 (3.9)	80.0	20.0	0.059	70.0	30.0	0.197
Submandibular	7 (2.7)	71.4	28.6	0.279	42.9	57.1	1.000
Lateral pterygoid	36 (14.0)	58.3	41.7	0.259	63.9	36.1	0.028^*
At least one sign of muscle pain	65 (25.6)	58.5	41.5	0.099	61.5	38.5	0.006

Chi-square test.

Significant.

TMD: temporomandibular disorder; TMJ: temporomandibular joint.

Table 3 shows that 37.6% of the elderly were diagnosed with disc displacement, 34.9% with degenerative joint disease, 3.5% with myalgia and 1.2% with arthralgia. Overall, TMD occurred among 56.6% of the total sample. There were no significant differences in terms of gender or residency among the diagnosis criteria (p>0.05).

Table 3.

DC/TMD Axis I diagnoses among elderly Vietnamese according to gender and place of residence (N=258).

Diagnosis criteria	Totaln (%)	Gender (%)		p-value^a	Residence (%)		p-value^a
Diagnosis criteria	Totaln (%)	Female	Male	p-value^a	Rural	Urban	p-value^a
Myalgia	9 (3.5)	77.8	22.2	0.101^b	77.8	22.2	0.088^b
Arthralgia	3 (1.2)	66.7	33.3	0.621^b	33.3	66.7	1.000^b
Disc displacement	97 (37.6)	45.4	54.6	0.289	49.5	50.5	0.518
Degenerative joint disease	88 (34.9)	52.2	47.8	0.725	54.5	45.5	0.077
At least TMD	146 (56.6)	51.4	48.6	0.696	51.4	48.6	0.061

Chi-square test.

Fisher’s exact test.

DC/TMD: Diagnostic Criteria for Temporomandibular Disorders.

Discussion

Our main finding was a high prevalence of TMDs among an elderly Vietnamese population. TMD symptoms occurred among 62.5% of the sample. This result was much higher compared with elderly populations in Sweden (18%),¹⁰ Brazil (35.8%)⁶ and Nigeria (17.4%).²⁰ Previous investigations have indicated that symptoms of TMD tend to decrease with age;^6,7,9 nevertheless, TMD symptoms were more frequent among elderly Vietnamese compared with the middle-aged and young adults of other studies.^9,21

Headache was a symptom closely related to TMDs, with half of the elderly Vietnamese studied suffering from headaches. This result was higher than a study conducted in Brazil (38.5%),¹ lower than another in Croatia (61.2%),¹⁴ but in line with a finding in Hong Kong (52.6%).¹² Previous studies have reported that headaches are more common in females than males,^10,22 which is also consistent with our study. A headache has been considered a protective mechanism against adverse changes in weather.²³ Our participants are living in a tropical monsoon climate area of high temperature and humidity. In addition, women often have a lower threshold to the pain response compared with men. This could explain the high rate of headache associated with females in our study.

Rural residency is a risk indicator of TMD symptoms related to headaches and jaw joint noises. A previous study conducted in Danang indicated an influence of social factors on the psychology of the elderly.²⁴ This study concluded that rural residents suffered more worries compared with urban residents. Therefore, this psychological problem might be considered a factor of influence on the TMD symptoms that were found among elderly Vietnamese.

Regarding signs of TMD, masticatory muscle tenderness was found in 25.6% of elderly Vietnamese. Our finding was similar to that observed by Sipilä et al. in Finland,¹⁸ but lower than the finding of Camacho et al. in Brazil¹ and higher than levels reported from Germany by Schmitter et al.⁸ and from Turkey by Nekora-Azak el al.⁹ Females and rural residents seemed to be closely associated with a sign of masseter tenderness in the current study. This is because women express fatigue in the mastication muscle more frequently compared with men,^9,22 and rural residency is related to the risk of edentulism, which causes impaired masticatory performance.^15,25 Our study found that muscle tenderness occurred more often in the temporalis, masseter and lateral pterygoid muscles than in the posterior mandibular and submandibular regions. This finding was expected because the hyperactivity of the main masticatory muscles often cause tenderness and has been associated with TMDs.²⁶

In the current study, TMJ tenderness (16.3%) was found to be more frequent in females than males, and this observation was consistent with other studies.^3,22 Among the same age group, TMJ tenderness has been found to be as low as 4% among Germans³ and as high as 27% in Brazilians.¹ The disagreement of the current study may be related to TMJ palpation techniques of the DC/TMD method. In our study, 0.5–1.0 kg pressure palpation for the lateral pole was used for assessing the TMJ tenderness.⁴

TMD sounds were the most prevalent sign of TMD among elderly Vietnamese. Our study discovered that TMJ clicking and crepitus occurred in 48.1% and 51.0% of the subjects respectively. This result was relatively high compared with studies conducted in Brazil (33%)¹ and Finland (38%).⁸ In addition, no significant difference in the prevalence of TMJ sounds was found in terms of gender in the current study, our findings contrasting with those of Gesch et al. and Troeltzsch et al., who demonstrated that females are much more likely to experience TMD sounds than males.^3,27 TMJ sounds are probably a result of alterations to the tissues within the capsule of the TMJ condyle and one of signs of TMJ degeneration that has been known as an age-related disease.

The assessment of TMD is also based on the clinical sign of the mouth-opening pattern. In our study, a mouth-opening deviation occurred in 37.6% of the elderly, and 9.7% had a mouth-opening limit of ≤40mm. A similar study showed that 7.9% of elderly Japanese exhibited restricted mouth opening,¹⁷ and another study has reported that the elderly have impaired maximal jaw opening capacities compared with other age groups.⁸ It is likely that disorders of mouth-opening patterns result from muscle incorporation or joint immobility due to intra-capsular joint disorder.²⁸

In the current study, a total of 56.6% of elderly Vietnamese were affected by TMD. This finding is in line with studies conducted in Mexico²⁹ and Brazil.¹ We found that gender was not a significant factor in the current study; this is in contrast to another study that found TMD to be higher in females than males.³ It should be recognized that TMD is comparatively prevalent among elderly Vietnamese.

Disc displacement (37.6%) and degenerative joint disease (34.9%) were the most frequent types of TMD among the elderly Vietnamese studied, whereas only a few of them were diagnosed with myalgia or arthralgia (3.5% and 1.2%, respectively). This substantial difference was due to the diagnosing algorithm of the DC/TMD. In this case, disc displacement and degenerative joint disease were diagnosed from TMJ sounds (present in 69.0% of the sample), while myalgia and arthralgia were diagnosed from symptoms of orofacial pain (25.2%). Our results were consistent with the data obtained by a study conducted in Mexico, where such a biased distribution of sub-group diagnosis types of TMD among an elderly general population was also found, with 2.6% having myalgia, 1.9% arthralgia and 26% disc displacement.²⁹

A meta-analysis of TMD data showed an overall 9.7% prevalence for myofascial pain, 11.4% for disc displacement and only 2.6% for arthralgia among general populations with a mean age range of 23–46 years old.⁷ Our finding of a high prevalence of disc displacement was expected for a group aged 65–74 years old, because the consequence of losing teeth is a decline in occlusion support and a change in mandibular functional movements during mastication, with the head of the condyle adapting to such dysfunction by changing the trajectory of TMJ movement.^30,31

The high prevalence of TMD among elderly Vietnamese shows the burden of TMD to the oral health care programme in Vietnam, where the density of dentistry personnel per 10,000 population is estimated to be 0.05 for rural and 0.74 for urban residents. Therefore, the elderly often lack the opportunity to visit a dentist for examinations and services that prevent TMJ disorders. TMD includes a wide range of disorders, and an accurate diagnosis is critical for successful treatment. TMD treatments such as physical therapy, splint or medicine have effect in reducing TMJ pain, TMJ sounds and restricted jaw mobility. TMJ surgery should be also recommended for an aggravated TMD case. A shortcoming of our study was that assessment of the risk factors of TMD has not been carried out yet. The management of TMDs should be assessed in future studies.

Conclusions

More than half of elderly Vietnamese suffer from at least one TMD symptom. TMD sounds were the most prevalent TMD clinical sign. Disc displacement and degenerative joint disease were most prevalent according to the DC/TMD Axis I among the elderly Vietnamese community. The information we obtained may be helpful in assessing the necessary implication for early diagnosis of TMD to prevent future TMD-related complications.

Footnotes

Declaration of conflicting interests

The authors declare that there is no conflict of interest.

Funding

This work was supported by the Estonian Science Foundation (grant number 9255), the Estonian Research Council (grant number IUT 20–46) and the European Social Fund’s Doctoral Studies and Internationalisation Programme, DoRa, which is carried out by Foundation Archimedes.

References

Camacho

JGDD

Oltramari-Navarro

PVP

Navarro

et al . Signs and symptoms of temporomandibular disorders in the elderly. Codas 2014; 26: 76–80.

Dworkin

LeResche

Research diagnostic criteria for temporomandibular disorders: Review, criteria, examinations and specifications, critique. J Craniomandib Disord Facial Oral Pain 1992; 6: 301–355.

Gesch

Bernhardt

Alte

et al . Prevalence of signs and symptoms of temporomandibular disorders in an urban and rural German population: Results of a population-based Study of Health in Pomerania. Quintessence Int 2004; 35: 143–150.

Schiffman

Ohrbach

Truelove

et al . Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) for clinical and research applications: Recommendations of the International RDC/TMD Consortium Network and Orofacial Pain Special Interest Group. J Oral Facial Pain Headache 2014; 28: 6–27.

Feteih

RM.

Signs and symptoms of temporomandibular disorders and oral parafunctions in urban Saudi Arabian adolescents: A research report. Head Face Med 2006; 2: 25.

Gonçalves

DAG

Dal Fabbro

Campos

JADB

et al . Symptoms of temporomandibular disorders in the population: An epidemiological study. J Orofac Pain 2010; 24: 270–278.

Manfredini

Guarda-Nardini

Winocur

et al . Research diagnostic criteria for temporomandibular disorders: A systematic review of axis I epidemiologic findings. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011; 112: 453–462.

Schmitter

Rammelsberg

Hassel

The prevalence of signs and symptoms of temporomandibular disorders in very old subjects. J Oral Rehabil 2005; 32: 467–473.

Nekora-Azak

Evlioglu

Ordulu

et al . Prevalence of symptoms associated with temporomandibular disorders in a Turkish population. J Oral Rehabil 2006; 33: 81–84.

10.

Osterberg

Carlsson

GE.

Relationship between symptoms of temporomandibular disorders and dental status, general health and psychosomatic factors in two cohorts of 70-year-old subjects. Gerodontology 2007; 24: 129–135.

11.

Silva

Brandão

Faleiros

et al . Temporo-mandibular disorders are an important comorbidity of migraine and may be clinically difficult to distinguish them from tension-type headache. Arq Neuropsiquiatr 2014; 72: 99–103.

12.

Luo

McMillan

Wong

MCM

et al . Orofacial pain conditions and impact on quality of life in community-dwelling elderly people in Hong Kong. J Orofac Pain 2007; 21: 63–71.

13.

Voog

Alstergren

Leibur

et al . Impact of temporomandibular joint pain on activities of daily living in patients with rheumatoid arthritis. Acta Odontol Scand 2003; 61: 278–282.

14.

Badel

Simunković

Marotti

et al . Study of temporomandibular joint disorder in older patients by magnetic resonance imaging. Gerodontology 2012; 29: 735–741.

15.

Ikebe

Matsuda

Kagawa

et al . Masticatory performance in older subjects with varying degrees of tooth loss. J Dent 2012; 40: 71–76.

16.

Ciancaglini

Gherlone

Redaelli

et al . The distribution of occlusal contacts in the intercuspal position and temporomandibular disorder. J Oral Rehabil 2002; 29: 1082–1090.

17.

Ikebe

Hazeyama

Iwase

et al . Association of symptomless TMJ sounds with occlusal force and masticatory performance in older adults. J Oral Rehabil 2008; 35: 317–323.

18.

Sipilä

Näpänkangas

Könönen

et al . The role of dental loss and denture status on clinical signs of temporomandibular disorders. J Oral Rehabil 2013; 40: 15–23.

19.

Witter

Kreulen

Mulder

et al . Signs and symptoms related to temporomandibular disorders – follow-up of subjects with shortened and complete dental arches. J Dent 2007; 35: 521–527.

20.

Taiwo

Kolude

Akinmoladun

Oral mucosal lesions and temporomandibular joint impairment of elderly people in the South East Local Government Area of Ibadan. Gerodontology 2009; 26: 219–224.

21.

Rutkiewicz

Könönen

Suominen-Taipale

et al . Occurrence of clinical signs of temporomandibular disorders in adult Finns. J Orofac Pain 2006; 20: 208–217.

22.

Ferreira

CLP

Silva

MAMR

Felício

CM.

Signs and symptoms of temporomandibular disorders in women and men. Codas 2016; 28: 17–21.

23.

Prince

Rapoport

Sheftell

et al . The effect of weather on headache. Headache 2004; 44: 596–602.

24.

Leggett

Zarit

Nguyen

et al . The influence of social factors and health on depressive symptoms and worry: A study of older Vietnamese adults. Aging Ment Health 2012; 16: 780–786.

25.

Nguyen

Voog-Oras

Jagomägi

et al . Tooth loss and risk factors among elderly Vietnamese. Stoma Edu J 2016; 3: 126–131.

26.

Pedroni

de Oliveira

Bérzin

Pain characteristics of temporomandibular disorder: A pilot study in patients with cervical spine dysfunction. J Appl Oral Sci 2006; 14: 388–392.

27.

Troeltzsch

Cronin

et al . Prevalence and association of headaches, temporomandibular joint disorders, and occlusal interferences. J Prosthet Dent 2011; 105: 410–417.

28.

Mathew

Sholapurkar

Pai

KM.

Condylar changes and its association with age, TMD, and dentition status: A cross-sectional study. Int J Dent 2011; 2011: 413639.

29.

Wiese

Svensson

Bakke

et al . Association between temporomandibular joint symptoms, signs, and clinical diagnosis using the RDC/TMD and radiographic findings in temporomandibular joint tomograms. J Orofac Pain 2008; 22: 239–251.

30.

Murrieta

Alvarado

Valdez

et al . Prevalence of temporomandibular joint disorders in a Mexican elderly group. J Oral Res 2016; 5: 13-18.

31.

Felício

Melchior

Silva

MAMR

et al . Masticatory performance in adults related to temporomandibular disorder and dental occlusion. Pro Fono 2007; 19: 151–158.