Temporomandibular disorder (TMD) is a collective term for various clinical problems involving the masticatory muscles and/or temporomandibular joints (TMJs) and associated structures[1] with the following characteristics: (a) pain in the TMJ, periauricular area, or masticatory muscles; (b) TMJ noises during mandibular movement; and (c) deviations or restrictions in the range of motion of the mandible[2]. Following the odontogenic pain, TMD is one of the most prevalent sources of discomfort in the oral and maxillofacial areas[3].

Several studies have reported that signs and symptoms of TMD generally occurred between ages 20 and 40 years[4,5] but rarely in growing children[6]. However, the TMD prevalence in children and adolescents has been increasing worldwide; its signs and symptoms in young patients appear to be as frequent as in adults[7,8], and its related pain has also been reported in children and adolescents[6].

TMD typically causes pain, dysfunction, and distress in affected patients[9]. It can last for long periods and may induce irreversible facial musculature and jaw changes, although its long-term effects have not been fully elucidated[10]. Furthermore, TMD negatively affects children’ s oral health-related quality of life[11]. Therefore, early diagnosis of TMD is crucial to minimize its effects on the growth and development of children, despite the difficulties encountered during its diagnosis and treatment in young patients.

Since TMD in children and adolescents has not been extensively studied, this review aims to provide its overview and describe its diagnosis and treatment for pediatric dentists who are responsible for their overall oral health.

The TMD prevalence is not yet well understood in children and adolescents compared to adults. Studies that only used some questions or a questionnaire to assess TMD reported that its prevalence varied from 5.1% to 36.9% in adolescents aged 13 years and older[8,11-13]. In other studies that used clinical examination with a questionnaire, the prevalence also highly differed, ranging from 5.73% to 68%[14,15], and regardless of varying methodology and population, a prevalence rate of >20% has been reported[6,16-18]. In Korea, the 2010 National Oral Health Survey reported that the prevalence of TMD in Korean children and adolescents was 13.0%[19] and that few children younger than 10 years have also been diagnosed with TMD[20]. However, these prevalence rates may be underestimated because TMD is not typically considered a pediatric problem, and children tend not to visit clinics for TMD symptoms[18].

Consistent with adults, TMD tended to be more prevalent in females than males among children and adolescents[13,21,22]. The gender difference is insignificant at a young age but becomes evident with growth, showing considerable differences in late adolescence[23]. This gender difference might be caused by hormonal changes and physiologic variables[7] and might be associated with social factors, differences in pain sensitivity, as well as the tendency for females to seek TMD treatment more than males[18].

TMD is commonly diagnosed based on signs and symptoms, with TMJ noise (clicking, popping, or crepitus) being the most common clinical sign, followed by TMJ pain and masticatory muscle pain[2,19]. Impaired mandibular movement, limited mouth opening, headache, periauricular pain, facial pain, and jaw tenderness during jaw movement also commonly occur[16,24]. These signs and symptoms can be observed in all age groups and are usually mild, and their progression to severe pain and dysfunction is rare in young patients[25].

Meanwhile, headache was significantly associated with painful TMD[26], and some studies have reported that painful TMD was associated with emotional and somatic malfunctioning and promoted aggressive behaviors in young patients[27,28]. Moreover, some factors associated with pain from TMD becoming chronic are as follows: females with myogenous TMD, increasing age at presentation, graded chronic pain scale score of 3 or 4, higher pain intensity, higher pain interference, more widespread non-specific symptoms or higher number of pain locations, and concurrent psychiatric diagnosis or mood disturbance such as depression, anxiety, and anger[3]. Indeed, the longer the pain persists, the higher the risk of developing and intensifying cognitive, psychosocial, and behavioral factors. This can increase pain sensitivity and likelihood of persistent pain and decrease the chance of success with standard treatments[29].

Recent scientific developments have emphasized the etiology of TMD away from a biomedical paradigm and toward a more intricate multifactorial biopsychosocial model considering the biological, psychological, and social factors[30]. TMD in children and adolescents is also associated with multifactorial etiologies, with several risk factors interacting differently at the individual level[31]. These factors are classified as predisposing, initiating, and perpetuating based on their role in TMD progression[3]. Structural, metabolic, and psychological conditions negatively affecting the masticatory system are considered predisposing factors because they can increase the risk of developing TMD. The initiating factors result in the onset of TMD and are associated with trauma, occlusal interference, or repetitive adverse loading of the masticatory system. Parafunction, hormonal, immunological, or psychological factors are considered perpetuating factors because they can sustain the condition, and these perpetuating factors may be closely related to any predisposing and initiating factors[23].

The psycho-emotional element considerably influences the TMD occurrence, associated with the effects of other physical health-related variables, such as systemic disorders, malocclusions, tooth loss, traumas, and microtrauma[7]. Patients with psychological problems such as anxiety, stress, feelings of sadness, somatization, and life dissatisfaction frequently perceive the muscular component of TMD[12,27,32], and adolescents with TMD pain had significantly greater sensitivity to pleasant and aversive somatic stimuli than the controls[33]. TMD coexists with various other conditions, including back or spine pain, chronic fatigue syndrome, spastic colons, sleep problems, migraines, and arthritis[34]. Conversely, a cohort study also demonstrated that patients with high self-esteem had less tendency to develop TMD[35].

Students have been reported to experience greater stress than the general population and are far more likely to have TMD and oral dysfunction. Exams, presenting research papers, the desire to become independent, financial difficulties, studying in an uncomfortable posture, and poor academic performance can be potential stressors[36]. Furthermore, TMD can be influenced by the environment in children and adolescents, and the family environment is significantly important. Painful TMD was reportedly associated with living with divorced or single parents[37], and parental depression during their children’s childhood was associated with pain-related TMD during early adulthood[38].

A functional mandibular overload variable, especially bruxism, is a major cause of TMD not only in adults but also in children and adolescents[25]. Bruxism is defined as the habitual or involuntary, nonfunctional forceful contact between the occlusal surfaces of maxillary and mandibular teeth, and is known to have multifactorial causes, including morphologic, psychologic, and pathophysiologic factors[25]. It may also be caused by the immaturity of the masticatory neuromuscular system[39]. Sleep bruxism typically occurs at 1 year of age, and tooth grinding during sleep declines linearly with age, from 14% in children to 8% in adults to 3% in the older population aged >60 years[25]. Therefore, juvenile bruxism is thought to be self-limiting and not to progress to adult bruxism[40], and no study has supported any kind of therapeutic options for bruxism in children[41]. However, it can also induce complications such as dental attrition, headache, TMJ dysfunction, and masticatory muscle soreness[42,43], and other oral habits such as the nails, lips, or object biting and general oral habits have also been reportedly associated with TMD[21,44,45]. Furthermore, parafunction prevention during early childhood is thought to be helpful to decrease TMD problems[46].

Other possible causal factors for TMD occurrence in children are occlusal interference and instability during mixed and young permanent dentition[47]. However, some studies have reported that these occlusal factors were only weakly associated with TMD signs and symptoms, and a lateral forced bite between the intercuspal contact position and retruded contact position in young patients could be potential local risk factors in TMD development[23]. In these positions, the articular fluid compression during condyle translation can induce the TMJ sound, such as clicking, without disc displacement, or pain, which is different from that of adults. The prevalence of TMJ noise seems to increase from primary to permanent dentition and is believed to be associated with prolonged muscle tension causing intracapsular changes and TMJ sound in older individuals[48]. TMJ noise in children and adolescents can also be caused by temporary disc contour incompatibility because of differential growth rates and calcification[49].

Malocclusion was formerly thought as one of the primary etiological impacts of TMD signs and symptoms; however, the importance of TMD malocclusion has been recently decreasing[7]. Some studies found an association between them[47,50], whereas other studies revealed no association[51,52]. Although no strong association was established, the most common malocclusions associated with TMD were excessive overjet, posterior crossbite, deep and open bites, and Angle classes II and III[1,4]. Aberrant occlusal contacts in patients with malocclusion may have an impact on how the condyle and fossa are connected. Furthermore, the asymmetrical activation of the masticatory muscles caused by different tooth contacts on the right and left sides may overload on one side more than the other[1,53]. In addition, patients with the dolichofacial type of craniofacial morphology demonstrated a tendency for the occurrence of masticatory muscle tenderness; however, any particular trait cannot be considered as predictive factors for TMJ dysfunction[31,54].

Studies evaluated the relationship between orthodontic treatment and TMD and revealed that traditional orthodontic interventions did not significantly contribute to the development or exacerbation of TMJ-related issues[30,35,55], although the TMD prevalence of patients seeking orthodontic treatment was high, with many individuals presenting the signs/symptoms of painful TMD[4]. More specifically, orthodontic or functional treatments targeting skeletal class II and class III malocclusions have not increased the TMD risk during the treatment phase, nor decreased TMD risk after completing the treatment[1]. For fixed orthodontic treatments with premolar extractions, posterior condylar positioning was observed posttreatment, but they did not demonstrate a higher prevalence of disc displacement[56]. Intermaxillary elastics in fixed orthodontic treatment increased the strain on the TMJ, particularly in class II patients, and clear aligners and orthodontic retainers increased the electromyographic activity in masticatory muscles. However, the potential relationship between this increased strain and development of TMD signs and symptoms remains unknown[57-59]. Nonetheless, it is noteworthy that certain conventional orthodontic techniques that disregard the functional occlusion principles have been remarkably identified as potential initiators and perpetuators of TMD[1,60].

TMD is a serious public health issue because it is the primary reason for nondental orofacial pain[1,7] and the second most prevalent musculoskeletal problem behind chronic low back pain[61]. Several studies reported that TMD symptoms were significantly associated with poor oral health-related quality of life, low sleep quality, frequent sick leave from school, and pain chronicity in children and adolescents[11,62,63], and pain chronicity commonly causes reduced physical, social, and psychological functioning in young patients[64].

TMD is thought to potentially cause abnormal facial growth in growing children and adolescents. Studies have identified that open bite or hyperdivergent developmental patterns were associated with degenerative TMJ disorders and that this association is possibly caused by the early onset of TMD, revealing abnormal condyle development[1]. Degenerative joint disorders were thought to be associated with a mandibular ramus deficiency, a larger gonial angle, a clockwise mandibular rotation, a retrognathic appearance, and a vertically elongated facial pattern, resulting in a skeletal class II relation[31]. Besides the degenerative disorder, the anterior disc displacement without reduction may also be associated with the worsening of skeletal class II and mandibular asymmetry in skeletal open bite[65].

Patients with facial skeletal asymmetries have a higher incidence of TMD[66]. The shift of menton was found to be significantly associated with TMJ disc position on magnetic resonance imaging (MRI), with more deviation to the side with disc displacement[67]. Unilateral anterior disc displacement of the TMJ observed in adolescents can result in mandibular asymmetry, especially on the same side[68]. Conversely, mandibular asymmetry has also been described as a contributing factor to TMD, emphasizing the close relationship between function and morphology[69].

In 1992, Dworkin and LeResche developed the Research Diagnostic Criteria for TMDs (RDC/TMDs) as a standard tool for clinical research, aimed at enhancing the consistency of TMD studies conducted worldwide[36]. The RDC/TMD protocol consists of two axes based on the biopsychosocial model of TMD etiology[18]. Axis I deals with the physical properties of TMD, whereas Axis II refers to the psychological components. In 2014, TMD experts agreed to establish an expert-based DC/TMD to compensate for the slightly low validity of Axis I in RDC/TMD and finalize the new Axis I diagnostic algorithm and new Axis II instruments[29]. This assessment protocol can be used in both clinical and research settings and establishes a systematic approach to diagnosing TMD[70]. It has four major components: (1) The history and clinical examination, including the collection of a comprehensive medical history, assessing the patient’s symptoms, and performing a physical examination. During examination, the clinician assesses signs and symptoms associated with TMD, including jaw muscle tenderness, pain during jaw movement, jaw clicking, and range of motion changes. (2) Imaging studies, like X-rays, computed tomography (CT), and MRI, which are important to diagnose TMD, as they can detect structural abnormalities or degenerative changes in the TMJ and surrounding tissues. Panoramic radiographs detect gross hard tissue changes but are not sufficiently sensitive to diagnose degenerative changes. CT imaging detects bony abnormalities within the TMJ with high sensitivity, and MRI can visualize the soft tissues, specifically the TMJ disc position and contours (Fig. 1)[71]. (3) Psychological testing can promote understanding of psychological factors that may influence the patient’s symptoms. (4) The laboratory test can be used to rule out other systemic conditions that may cause the patient’s symptoms. Since diagnosing TMD is highly complex, the clinicians must integrate information obtained from DC/TMD to make an appropriate diagnosis; however, they should not rely solely on DC/TMD[18].

DC/TMD includes the following 12 common TMDs: myalgia and its three subtypes (local myalgia, myofascial pain with spreading, and myofascial pain with referral), arthralgia, headache attributed to TMD, four disc displacement disorders (disc displacement with reduction, disc displacement with reduction with intermittent locking, disc displacement without reduction with limited opening, and disc displacement without reduction without limited opening), degenerative joint disease, and subluxation. The diagnostic criteria for each TMD are shown in Tables 1 - 9[29]. Disc displacement, degenerative joint disease, and subluxation can be diagnosed using imaging examination results in addition to history taking and clinical examination. The International Network for Orofacial Pain and Related Disorders methodology, formerly known as the International RDC/TMD Consortium Network, establishes the clinical examination protocol[72].

DC/TMD is designed for adult patients and is difficult to apply directly to children and adolescents because the ability to report past and future pain experiences is influenced by age and developmental stage[73]. Parents can help provide proxy reports; however, their observations can be somewhat distanced from the child’s actual experience. Thus, the comprehensive and short forms of DC/TMD can be applied to children aged 6 - 9 years and adolescents aged 10 - 19 years, using an age-specific version of the questionnaire for screening TMD and general health, with shortened clinical examination procedures and simplified language[63,74]. The results for the comprehensive and short form DC/TMD are the same in both child and adolescent versions, except for the results of lateral and protrusive mandibular movements, as shown in Table 3, 4, and 8.

TMD should be managed correctly and promptly in the young age group to minimize its impact. However, only very little research has been conducted on the treatment methods for TMD in children and adolescents, and systematic reviews and published guidelines reported widely varied therapeutic recommendations for TMD. The treatment goals are to restore function, reduce pain, minimize aggravating or contributing factors, and enhance the quality of life, and effective early management of acute TMD can prevent the potential onset of chronic pain[71].

In patients with disc displacement with reduction, many patients may not experience pain and only exhibit TMJ clicking sounds, and no treatment is generally necessary aside from reassurance and explanation. For other diagnoses, conservative and reversible therapies are known to effectively alleviate most TMD signs and symptoms in patients, including children and adolescents[75]. Irreversible therapies such as occlusal adjustments, orthodontics, and surgery are not recommended in growing patients.

Nonsurgical TMD management consists of a combination of patient education, a homecare plan, physical therapy, occlusal appliance therapy, and pharmacotherapy[75]. Patient education involves explanation of the following information to patients and parents in simple and clear language: (1) the nature of the disorder; (2) initiating, predisposing, and perpetuating factors; (3) TMJ anatomy; (4) treatment modalities; and (5) treatment goals. Homecare plan consists of (1) dietary habit modification (e.g., avoidance of chewing hard food), (2) application of cold and/or warm compresses, (3) avoidance of habits overloading the masticatory muscles and TMJ (e.g., chewing gum or pencils, clenching, and other parafunctional habits), and (4) maintenance of the jaw in resting position with teeth apart and relaxed masticatory muscles. Physical therapy is a noninvasive and conservative therapy to relieve musculoskeletal pain and restore function by modifying the sensory input, reducing inflammation, increasing the range of motion of the jaw, promoting tissue repair and regeneration, and aiding the reestablishment of oral motor function[76]. The types of physical therapy include manual manipulation, massage, TMJ distraction and mobilization, therapeutic exercises, coolant therapy with spray and stretch, ultrasound therapy, and transcutaneous electrical nerve stimulation.

Occlusal appliance therapy utilizes customized acrylic devices that typically fit onto the maxillary teeth to reduce TMJ pain, increase jaw movement range, and improve the joint function[75]. The most common types are stabilization appliances, anterior positioning appliances, and anterior bite appliances[77]. An occlusal appliance combined with brief information is an effective treatment for myofascial pain according to DC/TMD in adolescents[78,79]. Relaxation and home training can also be effective; however, adolescents are more motivated to use occlusal appliances than relaxation and home training[79]. No studies have evaluated the effectiveness of treatment in children with primary and mixed dentition, and clinicians should consider the potential negative consequences for younger patients[9].

Pharmacotherapy aimed to reduce pain and improve function. In adults, medications such as nonsteroidal anti-inflammatory drugs, acetaminophen, corticosteroids, hyaluronic acid, and adjunctive agents such as muscle relaxants, antidepressants, and benzodiazepines are commonly used[75]. Current studies do not recommend the use of opioids to manage chronic TMD, and data on the use of medications for managing TMJ disorders in children are limited[71].

Acute TMD can be managed with patient education and pharmacotherapy with nonsteroidal anti-inflammatory drugs; however, chronic TMD may require a multimodal approach including physical therapy, behavior evaluation, and pharmacotherapy[71]. Psychological factors can not only trigger TMD but also perpetuate and affect its long-term prognosis. Therefore, psychological distress management has been reported to alleviate TMD symptoms, signs, and chronic pain[80,81]. Furthermore, better treatment outcomes have been observed in adolescents with chronic pain when depression is treated early[82].

The prevalence of TMD in children and adolescents is high, exceeding 20%, and predominantly occurs in girls. It has multifactorial etiologies, with several risk factors interacting differently at the individual level. TMD is associated with poor oral health-related quality of life and abnormal facial growth. TMD in young patients is diagnosed using the DC/TMD assessment protocol, and TMD can be effectively managed with conservative therapies, such as patient education, home care, physical therapy, occlusal appliance therapy, and pharmacotherapy.

Pediatric dentists are in a unique position to detect TMD in children and adolescents early because they conduct regular checkups for this age group. Not only performing routine oral examinations, they can also conduct clinical assessments to screen TMD and take detailed histories, enabling them to identify TMD early and reduce complications that may arise from its chronic progression in growing children and adolescents.