Epidemiology of Temporomandibular Disorder
in the General Population: a Systematic Review
Joseph Ryan1, Rahena Akhter2*, Nur Hassan1, Glen Hilton1, James Wickham1 and Soichiro Ibaragi3
1Charles Sturt University, Australia
2University of Sydney, Australia
3Department of Oral and Maxillofacial Surgery Okayama University Hospital, Japan
Submission: February 01, 2019; Published: February 19, 2019
*Corresponding author: Dr. Rahena Akhter BDS, ADC (Melb.), PhD (Japan), Postdoc (Australia) Senior Lecturer, Cariology, Discipline of Tooth Conservation Faculty of Dentistry, The University of Sydney C24 Westmead Hospital, Level 1 WCOH, Westmead, New South Wales, Australia
How to cite this article: Joseph R, Rahena A, N Hassan, Glen H, James W, et al . Epidemiology of Temporomandibular Disorder in the General
Population: a Systematic Review. Adv Dent & Oral Health. 2019; 10(3): 555787.
The present paper aims to review the epidemiological literature regarding temporomandibular disorder (TMD) in order to determine which subgroups of the general population are more likely to suffer from TMD and why this might be the case. A literature search from the National Library of Medicine’s PubMed Database for relevant papers was conducted with pre-determined inclusion and exclusion criteria. Chosen articles that fulfilled the search criteria were compiled in tables and quality graded according to the QUADAS tool. A total of 42 articles were included and grouped into gender, age and psychological influences on TMD. It was found that TMD is the most common orofacial pain condition of non-dental origin. From the studies assessed, a two-to four-fold higher prevalence of TMD in women was noted with the prevalence peaking between the ages of 25-45. The higher prevalence rates for women indicated that possible biological, psychological, and/or social factors associated with the female gender increased the risk of TMD. It is evident that TMD is a significant and increasingly prevalent disorder found within the general population that appears more commonly in women and more common during the reproductive years. The available data highlights the need for further research on etiologic factors associated with TMD.
In recent times temporomandibular disorders (TMD) has been identified as a frequent pathological disorder and awareness of this has amplified within the general population. TMD is a term encompassing a broad range of related pathologies of the temporomandibular joint (TMJ) involving the masticatory muscles and associated structures. TMD is characterized by symptoms such as muscle tenderness, TMJ sounds, deviations or restrictions in the mandibular range of motion and associated headaches .
The prevalence of TMD has been comprehensively studied over the years, however, multiple difficulties (differing levels of skill between examiners, inconsistencies in judgments and research bias) arise when evaluating the results from a wide range of literature. The exact etiology of TMD has for many years been the center of debate, therefore many propose a multifactorial cause for the disorder. These have included, stress [2-9], age [10-14], gender [15-18], occlusion , parafunction [6,8], airway compromise  and psychological and psychosocial factors [2,7,21-23]. Furthermore, systemic problems such as rheumatoid arthritis, inflammatory conditions, ankylosing spondylitis and lupus [1,4,24] have also been implicated.
Epidemiological studies in multiple countries (America, Sweden, Netherlands, Finland, Pakistan, India, Italy, Iran, Denmark, Brazil, United-Kingdom and Canada) have outlined a substantial prevalence of orofacial pain symptoms in the adult population, showing that approximately 5-60% of the population suffers from at least one of the signs of TMD [25-27]. The aim of this review is to analyze the epidemiological literature in order to determine which subgroups of the population are more likely to suffer from TMD and why this maybe the case.
An electronic literature search of the US National Library of Medicine (PubMed) database and the Charles Sturt University Library was conducted (Figure 1). This review was restricted to full reports no older than 1995 on human subjects with letters, editorials and abstracts being excluded. Observational studies (cross-sectional surveys, cohorts and longitudinal studies) and previously published literature reviews were included. Epidemiological studies where subjects were representative of the general population were also included but studies were excluded when it was not possible to identify the source of the population. The protocol of this systematic review complies with
PRISMA guidelines for reporting systematic reviews.
For the complete search strategy, electronic databases were
queried (Table 1). Two internet sources were used to search for
suitable papers that fulfilled the study purpose. These sources
comprised the National library of Medicine, Washington, D. C
(MEDLING- Pubmed) and the Charles Sturt University Library
Data base. Both databases were searched for eligible studies up
to an including August 2015. The designed search started was
developed to include any systematic reviews, or population based
studies on the epidemiology of TMD. All the reference lists were
hand searched for further published work that could possible
meet the eligibility criteria of the study.
The searched studies titles and abstracts were screened
for eligible papers. If the papers title or abstract were deemed
eligible the paper was selected for further reading. If eligibility
aspects were cited in the title, the abstract was read in detail to
screen for appropriateness. After selection, the full papers were
read in detail. The papers that satisfied the selection criteria were
processed for data extraction.
The chosen studies included in this review were assessed
using the QUADAS tool  with each included study being rated
as high, moderate or low quality according to the pre-specified
criteria which can be found in the appendix (Table 2).
After examination of the full text articles, 42 articles were
chosen for inclusion in the literature review (Figure 1). It was
noted that when reviewing the epidemiology of TMD in the
general population there seemed to be three main recurring
influences (gender, age and emotional/psychosocial status) on
TMD, which guided the decision to split the review into these
three main influences. Therefore, the studies included in the
review were grouped into gender influence (N=19) age influence
(N=14) and psychological influence (N=18) on the epidemiology
of temporomandibular disorders in the general population.
The results were tabulated into three tables with each table
summarizing the findings from the chosen studies according
to these three main influences on TMD. Note that some studies,
which were assessed, did overlap with these influences and thus
may be found in multiple tables.
Of the selected 42 articles assessed there were no articles
to be found of high quality, 28 to be found of moderate quality
and 14 to be found of low quality. Elements that weakened the
quality of evidence included: study limitations, inconsistency, and
indirectness. Study limitations were recorded if there was any sign
of publication bias, insufficient statistical analysis, uncertainty
about blinding of the outcome assessor or any associated
limitation in the methods of the study. If a single predictor or a
method model was not validated indirectness was recorded.
Inconsistency was recorded if there was a large variability in the
results or if confidence intervals were wide. One study limitation
that was taken into consideration is that many studies deem that
any one symptom of TMD is enough to diagnose a subject with
TMD. In this review at least two symptoms or a single painful
symptom was required for inclusion in the review.
A summary of the studies with their quality of evidence and
associated weaknesses and strengths are presented in Tables 3-5.
The general prevalence of orofacial pain symptoms in the
adult population is substantial, with many studies claiming that
approximately half of the population suffers from at least one of
the signs of TMD [8,9,24,29-33]. A randomized population study
carried out in Germany which looked at 7,008 subjects showed
that half of the subjects had one or more clinical signs of TMD
. Studies assessed in this review showed the prevalence of
signs and symptoms of TMD in the general population varied
greatly, ranging from 1% to 75%, when established on clinical
evaluation, and 6% to 75% when based on pain questionnaires
only [8,9,24,29-34]. It is possible that such differences stem from
the disparities in the population studies, or as a result of the
different methods and clinical criteria used in the various studies.
These differing prevalence figures on reported TMD symptoms
can be seen in the various investigations, reflecting differences
in study populations, definitions, inclusion and exclusion criteria
and methodology used (Table 6) . Epidemiological studies of
TMD have reported further difficulties in creating a standardized
pattern in the distribution of the disease, as well as standardizing
the definition of TMD.
When reviewing the literature, it was found that there are
three main factors that should be considered when looking at the
epidemiology of TMD. These include gender, age and emotional
or psychosocial status. We will explore the significance of these 3
major influences further in order to determine which subgroups
of the population are more likely to suffer from TMD and why this
maybe the case.
In general, it was determined from the studies selected for
this review that women suffer more from TMD than men. This
is consistent with many of the previous studies [26,27]. A study
conducted on university students in Brazil found that 68% of
all subjects exhibited some degree of disorder with 43.7% of
subjects exhibiting audible TMJ sounds . In this study the
prevalence of TMD in women was almost four times greater than
men. Many studies observed similar results and found that TMD
seems to be far more prevalent in the female population (Table
3) [16,17,19,31,33,34,36-39]. Among all the studies analyzed only
two studies did not find any statistically significant differences
between males and females (Table 3) [9,40] Of these two studies
one of them was deemed to be of limited quality as no clinical
evaluation was carried out on any of the subjects .
These higher prevalence rates for women indicate that possible
biological, psychological, and/or social factors associated with
the female gender, increases the risk of TMD. One hypothesized
reason for women suffering a higher prevalence of TMD is
the physiological variances of the female, including hormonal
variations, different characteristics of the connective tissue, and
brain function and structure [8,34,41].
The greatest peak in the development of symptoms is apparent
between 20 and 40 years of age, or during the reproductive period.
Thus, it has been claimed, that the prevalent patterns of TMD may
be affected by reproductive hormones . The occurrence and
severity of TMD pain has been said to be like that of migraine,
where hormonal factors are also thought to account for some of
the gender difference in prevalence rates .
On another note, one study has confirmed that there is many
estrogen and progesterone receptors within the intra-articular
cartilage in women with TMD . Recently, locally synthesized
estrogens have been found and demonstrated to contribute
greatly to the function of cartilage . Since the 1990s, the
impact of estrogen deficiency on the development of TMD has also
been researched [42,43] demonstrating, at least in rats and mice,
that substantial alterations, such as the thickness of TMJ cartilage,
flattened condyles, decreasing volume of subchondral bone, and
general degenerative signs were observed after ovariectomy .
One study found that a drop in estrogen levels may be associated
with changes in specific neurotransmitters believed responsible
for the cause or potentiation headaches and TMD . Studies
however have additionally presented possible correlations
between increases in estrogen levels and a subsequent increase
in TMD symptoms [15-18]. Another possible mechanism by which
estrogen can modulate pain levels, is via a direct effect on the
expression and properties of ion channels in TMJ neurons .
This can lead to the neurons becoming more sensitized resulting
in a lowered action potential threshold.
Other studies have discovered gender differences in brain
structure and its possible connection with pain manifestation.
For example, it has been noted that in many cases women have
smaller hippocampal volumes when compared to men, and such
patients report more severe acute or chronic pain.
Several cross-sectional studies have demonstrated that the
overall prevalence of TMD is significantly higher in the 20-40 year
age group when compared with other age brackets [11,31,39,44].
The overall prevalence of TMD in children and adolescents differs
greatly between multiple studies (Table 4) [1,10,11,13,14,19,29,
32,33,35,38,39,44]. The reason for the disparity in results when
looking at the younger population in relation to TMD like other
pain conditions is the fact that many of the questionnaires and
examinations are tailored to the adult population. Children often
have difficulty in understanding some of the questionnaires and
can be confused by the examinations. Research looking at TMD
in over 1000 young children (3-7 years) found that 14% of males
and 18% of females suffered from TMD [1,37]. A study of 4724
children in Sweden aged 5-17 years showed 25% of participants
experienced one or more TMD symptoms .
One study has claimed that TMD prevalence was inversely
proportional to age . This study also found that prevalence varies with socio economic status, race and particularly Hispanic
ethnicity . Another study, investigating if there is a tendency
for TMD-related symptoms to decrease with age, found the
prevalence to be lower among the over 80-year-old subjects when
compared with the over 70-year-old subjects of both sexes .
A further study in 2010 found that at least two distinct age peaks
(30s and 50s) are identifiable within the population suffering
from TMD .
Multiple studies found that TMD shares significant
association with levels of anxiety and depression (Table 5) [2,5-
9,21,23,24,30,31,34,45,46]. Of all studies reviewed, only three
found no association between emotional and psychosocial
influences on TMD [3,4,12] with one of the studies having only 19
subjects , whilst the remaining two used sole questionnaires to
gauge TMD and chronic pain conditions [3,12]. A study in 2003
 reported that all the individuals with moderate and severe
TMD suffered from high emotional stress. The significance of
psychological factors, such as increased anxiety, depression, and
stress has been accentuated in literature describing the etiology
of TMD and oral parafunctions [8,9,24,30,34,46]. A recent study
investigating the significant role of psycho-emotional factors in the
development of TMD, found that easily excitable and emotionally
burdened persons suffered significantly more often from TMD and
oral parafunctions .
It has been demonstrated that emotional stress increases
the activity of the masticatory muscles leading to teeth clenching
and producing resultant circulatory changes in the mastication
muscles, which can consequently result in issues such as TMD
A remarkable, and yet worrying finding, suggests that
regularly used antidepressants, known as selective serotonin
reuptake inhibitors, may contribute to the cause of headaches
and muscle pain . A study showed that the development of
bruxism was coupled with the appearance of neuroleptic-induced
akathisia which occurs as a side-effect of antipsychotic drug
treatment . Evidence is showing that in many cases, repressed
or unsettled and unresolved emotional problems play a key role
in the continuation of TMD. These unresolved emotions generate
stress, which may form obstructions and reduced flow of peptide
signals that help preserve function at the cellular level, leading to
dysfunction and pathology .
Among the many controversies related to TMD, it has been
established that the approximation of the overall prevalence of
TMD in the general population has varied significantly. It was noted
that older studies found smaller percentage of the population
suffered from TMD when compared to the more recent studies
. Table 4 in the appendix, which has studies that were excluded
due mainly to their age, outlines the changing prevalence over the
years. These results also show the broad range of prevalent factors
reached due to the limitations addressed previously. There does,
however, appear to be an increase in people suffering from TMD
in the general population as can be seen from some of the more
recent population studies [9,11,32,33,36]. A large longitudinal
cross-sectional study was carried out to look at possible trends in
the prevalence of TMD symptoms in an adult population over two
decades, from 1983 to 2003 . This study found a statistically
significant increase in TMD prevalence over the 20 year period.
According to the study TMD symptoms increased over the 20-year
period from 27% to 38%. It was found that 10.5% of the study
population suffered from severe TMD symptoms in 1983 and in
2003 this increased to 16%. The study also found the incidence
of headaches was more than twice as high as it was 20 years
prior. From the literature, we can thus reasonably assume that the
percentage of the population suffering from TMD is on the rise.
The present review article shows that there is a large
percentage of the population suffering from TMD, younger females
and those suffering from depression and/or anxiety. It was seen
that the prevalence of TMD signs and symptoms is consistent with
much of the literature about the distribution of the symptoms
according to age and gender. Many of the authors consider
that using any single symptom as suggestive of TMD may lack
specificity. When assessing the prevalence of four or more TMD
symptoms, or what some authors considered severe TMD, many
studies found approximately 10% of the population were affected
[24,32,35,38,39]. However simply outlining several symptoms as
a way of correlating the severity of TMD has its many limitations.
These issues are what makes the study of the epidemiology of
TMD so difficult and it is why as mentioned previously that in this
review at least two symptoms or a single painful symptom was
There are multiple difficulties faced when looking at the
prevalence and epidemiology of TMD, several of which include
examiners with differing levels of skill, knowledge and experience,
inconsistencies in judgments and research bias. Another major
issue in determining the overall prevalence of TMD within a
population is that the division between disease and non-disease
is not always clear. Further to this, the overall conception of
TMD is unclear to most clinicians, as it is a collective term, which
incorporates numerous clinical pathologies or disorders that
involve the TMJ and its associated structures.
TMD constitutes several pathologies rather than just one
condition, with comparable signs and symptoms. Considerations
in the complicated interrelationships between the TMJ, teeth,
muscles, cervical spine, autonomic nervous system and the
higher centers of the brain in temporomandibular disorders
are essential. Such an unusual classification and description of
a group of disorders that affect such a vast amount of people in
the population effectively assures misunderstandings from the
perspective of epidemiology and research into this subject.
From this review we can conclude that TMD is the most
common orofacial pain condition of non-dental origin. However,
the actual TMD prevalence at the population level is a matter
of debate. This review did however outline that, the prevalence
peaks between the ages of 25-45, women suffer more than men
and added psychosocial issues lead to a greater prevalence and
intensity of TMD symptoms. It was also noted that there seems
to be an increase in TMD prevalence in the general population
over recent decades. Additional repeated population-based
investigations covering extended time periods would help add
important information in these areas and further validate the
findings. Also established, is the significance of a TMJ assessment
in the overall examination of the patient, especially at a young age.
Recognizing a potential TMD problem at an early stage may allow
intervention to avoid further complications. Future studies should
be adequately sized for accurate determination of the prevalence
and detection of important associated factors. Data on potential
risk factors and cofounders such as age, gender and emotional/
psychosocial status should also be collected and adjusted for in
the statistical analysis of future studies.
We would like to sincerely thank Professor Greg Murray, The
University of Sydney and Professor Manabu Morita, Okayama
University, Japan for their kind assistance in the review of the