Significance of radiographic temporomandibular degenerative joint disease findings

Abstract

The field of orthodontics has seen a recent increase in the number of patients over the age of 50 seeking treatment and also an increase in the use of cone beam technology. Similar to other joints in the body, the temporomandibular joint (TMJ) is associated with age-related degeneration. However, unlike other joints, degeneration of the TMJ is rarely symptomatic and when there is pain, it is usually self-limiting. In this article, we will review: a) the incidence and prevalence of TMJ degenerative diseases, b) similarities and differences of TMJ vs knee degenerative diseases, and c) current treatment recommendations for TMJ degenerative diseases. In the vast majority of people, radiographic evidence of TMJ degeneration is an incidental finding. Future longitudinal research is needed to follow the natural course of TMJ degenerative patients.

Introduction

The number of adult patients receiving orthodontic treatment is increasing, particularly in those over the age of 65. [1] The majority of adults seeking orthodontic treatment choose to undergo clear aligner therapy. [2] Recently, Align Technology has allowed cone beams to be integrated with intraoral scans to predict tooth/root movements more accurately using clear aligners. [3] Since temporomandibular joint degeneration is an age-related disease that can be detected by cone beam scans, orthodontists may have an increased number of patients seeking routine orthodontic treatment that have radiographic evidence of temporomandibular joint degeneration.

Epidemiology of TMJ

Temporomandibular disorder (TMD) is the overarching term used to describe several clinical conditions involving the facial masticatory musculature, the temporomandibular joint (TMJ), and the surrounding hard and soft tissue structures. [4] Symptoms associated with TMD often vary in both severity and phenotype. With the exclusion of odontogenic-related orofacial pain, TMD is the most common cause of orofacial pain. It is reported that TMD currently affects 5-12% of the United States population. [5] The literature has described TMD diagnosis in three main categories: muscle disorders, disc disorders, and joint disorders. [6] Currently, the diagnostic criteria for TMD includes evidence-based assessment through use of the Diagnostic Criteria for TMD (DC/TMD) or the Research Diagnostic Criteria for TMD (RDC/TMD). [5] These diagnostic tools further classify TMD into 12 common temporomandibular disorders. [7]

There are numerous potential risk factors for TMJ disorder. The prevalence of TMD is higher in females than in males, with reports occurring more frequently and with greater severity among the female gender. [8] A systematic review and meta-analysis performed by Bueno et al. suggests that females have a 2x increased risk for development of TMD compared to men. It has also been determined that patient populations seeking treatment for TMD are more predominantly composed of women. [9, 10] The gender distribution seen in TMD coincides with other musculoskeletal conditions, showing high female prevalence compared to males. [9]

TMD is seen over a wide age range of individuals. It was previously thought that TMD predominantly afflicted individuals ages 20-40 years old. [11, 12]. However, a well-known, prospective multicenter clinical trial known as the OPPERA study (Orofacial Pain: Prospective Evaluation and Risk Assessment) evaluated the multifactorial influences that contribute to the development of temporomandibular joint disorders. [13] This research estimates that 4% of TMD-free adults ages 18-44 develop a clinically confirmed painful first-onset symptom of TMD. Additionally, this study also shows that the annual incidence of TMD associated with pain symptoms increases with age. [7, 13] Recent large sample studies now show peak prevalence of TMD in older individuals ages 45-64 [14, 15], supporting that TMD is present across a wide age range.

When specifically considering the elderly population, it is necessary to address degenerative joint disease. In previous literature, TMJ degeneration has been subdivided into osteoarthritis and osteoarthrosis, the differentiating term being based on the presence or absence of the clinical symptom of pain. [16] TMJ osteoarthritis was originally defined as the presence of TMJ degeneration with reports of symptomatic pain, whereas TMJ osteoarthrosis was defined as evidence of TMJ degeneration without experiencing clinical symptoms of pain. [16] However, this subdivision between TMJ osteoarthritis and osteoarthrosis is not commonly used in recent literature. Often, the current research uses the terms TMJ degeneration and TMJ osteoarthritis interchangeably.

In the elderly population, radiographic evidence shows that 45-70% of individuals over the age 65 have signs of TMJ degeneration. [17-20] However, the increase in radiographic evidence of TMJ degeneration does not correspond to symptomatic disease and patients seeking treatment. [20] A large cross-sectional study performed by Lövgren et al. further evaluated the prevalence of temporomandibular pain using a self-reported questionnaire and found that fewer than 6% of people over the age of 65 have self-reported TMJ pain. [15]

Evaluation of Radiographic TMJ Osteoarthritis (TMJ-OA) and Self-Reported TMD Symptoms: A Single Center Experience

The distinction between radiographic findings and symptomatic self-reporting is seen in the literature, illustrating that with age, self-reported TMJ pain decreases and evidence of radiographic TMJ-OA increases. [15, 20] However, the mystery remains as to why there can be evidence of TMJ degeneration without accompanying symptomatic disease in aging individuals. In support of TMJ degenerative disease not corresponding with pain, we recently evaluated cone beam evidence of TMD-OA and compared it to self-reported TMD in 88 patients at Columbia University College of Dental Medicine. This was part of a larger study examing age-related changes in the mandibular bone, which was approved by the Columbia University Irving Medical Center Institutional Review Board. Written informed consent was obtained from all study subjects. Inclusion criteria was a) ages 35-70 and exclusion criteria were a) history of bisphosphonate or other osteoporosis therapy, b) current oral contraceptive, hormone replacement therapy (HRT), or testosterone supplementation and c) currently pregnant or nursing. Participants were recruited from the general dental clinic through IRB-approved flyers and the RecruitMe website. All participants were given a validated brief TMD screening questionnaire consisting of 6 questions that evaluated the current state and history of orofacial pain and whether pain is provoked by certain jaw activities. [21] High-resolution CBCT images of the left and right mandibular condyles were taken by a Planmeca ProMax 3D Classic CBCT scanner (84kVp, 6.2mA, 12s scan time).

We initially identified 88 patients with a total of 176 CBCT scans for screening. We excluded 20 patients (20 bilateral CBCT scans) and 16 unilateral CBCT scans because of motion artifacts in the analysis, leaving a total of 68 unique participants with 120 CBCT scans of the mandibular condyle. Anonymized scans were graded independently by two examiners who regularly see CBCT images and were blinded to clinical information. Examiners were calibrated using CBCT images randomly selected from the samples and following the scoring system. [22] On completion of these observations, a diagnosis was made based on the worst score from three evaluations, categorizing the joint as normal, indeterminate, or affected with osteoarthritis (OA). [22] Inter-examiner agreement was determined by consensus when a discrepancy occurred between the two examiners.

The mean age of the 88 study participants (66 women and 22 men) was 51.84+/− 10.02 years old and there were 10 women who had self-reported TMD. None of the participants with Radiographic TMJ-OA had self-reported TMD and in the 10 participants with self-reported TMD, 95% of their scans had no evidence of radiographic TMJ-OA. Table 1, Figure 1

Table 1.

Statistical data for patient cohort demographics, self-reported TMD, no self-reported TMD, CBCT analysis and TMJ-OA status scans.

	Total (n=88)	No Self- Reported TMD	Self Reported TMD	p- value
Age	51.84 (10.02)	51.97 (10.02)	50.80 (10.45)	0.94
Sex
Female	N=66	N=56	N=10	0.152
Male	N=22	N=22	N=0
Race
Black	37 (42.0%)	32 (41.0%)	5 (50.0%)	0.86
Non-Black	51 (58.0%)	46 (59.0%)	5 (50.0%)
Ethnicity
Hispanic	47 (53.4%)	41 (52.6%)	6 (60.0%)	0.906
Non-Hispanic	41 (46.5%)	37 (47.4%)	4 (40.0%)
Smoking	16 (18.2%)	14 (17.9%)	2 (2.6%)	0.989
Diabetes Mellitus	5 (5.7%)	4 (5.1%)	1 (1.3%)	0.822
CBCT Analysis
Number of readable TMJ	N=68 participants/120 scans	N=58 participants/101 scans	N=10 participants/19 scans
TMJ-OA status Scans
No Osteoarthritis	79 (65.8%)	61 (60.40%)	18 (94.74%)	0.078
Indeterminate for Osteoarthritis	36 (30.0%)	35 (34.65%)	1 (5.26%)
Osteoarthritis	5 (4.2%)	5 (4.95%)	0 (0.00%)

Figure 1-.

Relationship between self-reported TMD and radiographic evidence of temporomandibular joint osteoarthritis

Our results are similar to a larger urban study, in which they found 35% of study participants had radiographic TMD, yet only 10% had TMJ self-reported pain in a sample of 159 people over the age of 65. [20] In another study, they found that 21 out of 30 people over 70 years old had MRI radiographic evidence of TMJ degeneration, but only one of them complained of TMJ pain. [19] Furthermore, in a large Korean study of greater than 1000 participants, they found no correlation between radiographic evidence of TMJ degeneration and pain. [23]

TMJ Osteoarthritis vs Knee Osteoarthritis

Despite the similarities between osteoarthritis of TMJ and knee, notable differences exist between the two, especially in their radiographic presentation and natural progression. In the knee, there is higher correlation of radiographic evidence and pain than in the TMJ, as approximately 50-60% of people with radiographic OA report pain [24]. A person’s pain perception with osteoarthritis in relationship to radiographic evidence is difficult to study, because it is a subjective experience and unique to each person. One way to control for this variable is to conduct a within-subject study in which the knees are discordant (one knee feels pain while the other is symptom-free) and to compare the difference in radiographic osteoarthritis staging. Within-subject studies have shown a very strong relationship between pain and radiographic evidence of OA, with an odds ratio greater than 70 in a person feeling pain in a knee with severe radiographic evidence of OA, compared to feeling no pain in the knee with no radiographic evidence of OA. [25, 26] We are unaware of any within-subject studies examining radiographic evidence of TMJ degeneration and pain, which are needed in order to further clarify of the nature of their intricate relationship.

Natural History of TMJ-OA vs Knee-OA

Pain from TMJ-OA is self-limiting with over 70% of patients having no pain after 1 year. [27] [28] Radiographic evidence of TMJ-OA also usually shows improvement in the joints with fewer than 20% of patients showing a worsened progression after 2 years [29] and 8 years [30]. There does not appear to be any longitudinal relationship between pain and radiographic TMJ degeneration in people diagnosed with TMJ-OA. In one study of 30 people who were diagnosed with TMJ-OA, 74% of the joints no longer showed any pain after 1 year, which was not associated in any improvements of their radiographic TMJ degeneration. [27] This contrasts with what is seen within the knee. In a recent systemic review, it was shown that after approximately 5 years, knee-OA had a steady pain trajectory in 85% of the patients, 8% of patients experienced pain reduction, and 7% of patients experienced pain worsening. [31] Additionally, in people with early symptomatic OA, changes in radiographic OA over 4-5 years were correlated to worsening of pain and function. [32, 33]

Cellular Repair of Osteoarthritic Joints

In joints with osteoathritis (including the TMJ and knee), carilage cells lose their post-mitotic, diferentiated, chondrocyte phenotype and enter an ectopic endochondral ossification (EO)-like state of proliferation along with abnormal hypertrophic differentiation. [34] This causes increased degeneration of the cartilage as a result of degrading enzymes produced by the hypertrophic chondrocytes and focal calcifications in the cartilage deep zones. [35] TMJ-OA is also associated with an endochondral ossification (EO)-like state of proliferation along with abnormal hypertrophic differentiation. [36] However, unlike the articular cartilage, the mandibular condylar cartilage undergoes endochondral ossification during normal growth [37] and some authors suggest that this occurs as normal remodeling in old age in humans. [38]

The promotion of endochondral ossification of the mandibular condyle is the biological basis for orthodontic functional appliances in children and adolescents. [39] It has also been suggested that adults treated with functional appliances have reactivation of the mandibular condylar endochondral-hypertrophic chondrocyte pathway. [40] Therefore, reactivation of endochondral ossification may represent a naturally occurring repair response in the TMJ, but a pathological response in the knee articular cartilage, which does not undergo endochondral ossification during growth. This may explain the self-limiting nature of TMJ-OA pain and the improvement in radiographic evidence of TMJ degeneration seen in most patients with TMJ-OA, but rarely, if ever, seen in radiographic knee osteoarthritis. Future single cell gene expression studies are needed to determine the similarities and differences between endochondral ossification during growth and OA-repair in the temporomandibular joint to elucidate if it is pathological or a repair response.

Treatment Approaches to TMJ Degenerative Joint Diseases

Temporomandibular joint osteoarthritis (TMJ-OA) is a degenerative condition characterized by joint inflammation, which can cause significant pain and functional impairment. [4, 41] Traditional conservative treatment approaches for TMJ-OA involve nonsurgical methods such as occlusal splints, non-steroidal anti-inflammatory drugs (NSAIDs), and arthrocentesis, while end-stage TMD treatment involves surgical temporomandibular joint replacement. Although this field has been studied, a recently published systematic review highlighted the need for further quality research in order to compare the efficacy of different noninvasive treatment interventions. This is due to many studies having non-uniform patient selection, differing diagnostic criteria, diverse treatment/assessment protocols, and varying methods of measuring interventions [42].

Occlusal Splints

Within the spectrum of conservative treatments, occlusal splints are often prescribed to treat TMJ-OA, but the evidence of their relative effectiveness in clinical use is inconclusive. A recent review summarized that while the precise mechanisms responsible for the clinical outcomes of occlusal splints are not fully understood, splints can be a good option for noninvasive treatment in selected individuals [43]. The types of splints that can be used include stabilization appliances of both hard and soft acrylic (produces comfortable jaw positions which reduces TMJ loading), anterior positioning appliances (positions the TMJ in a therapeutic position for healing and symptom relief), and anterior bite appliances (temporarily prevents habitual tooth contact thereby reducing acute symptoms) [44].

A retrospective study conducted by Ok et al compared condylar bone changes in patients with temporomandibular joint osteoarthritis who received stabilization splint (SS) therapy to those who did not and discovered that the SS group exhibited higher bone formation in the anterior condyle and more frequent cortical thickening in various sections compared to the non-SS group, suggesting that SS therapy led to favorable bone remodeling in the anterior condylar head division for TMJ-OA patients. [45] This finding is confirmed by Musa et al, who in their retrospective clinical study found that SS therapy increased condyle bone density in those with TMJ arthalgia [46]. Kim et al assessed 3-dimensional bony changes in the mandibular condyle of temporomandibular joint osteoarthritis patients treated with SS therapy and concluded that SS treatment led to both bone resorption and formation, resulting in morphological changes in the condyle head. [47] Lei et al investigated the impact of anterior repositioning splints (ARS) on osseous condylar changes in adolescents/young adults with early-stage degenerative joint disease of the temporomandibular joint, finding that ARS led to significantly higher occurrence of condylar repair and regeneration compared to conservative therapy without ARS, and that the splint group had a lower incidence of progressive TMJ degeneration. [48] Sato et al compared the clinical symptoms and TMJ tomograms before and after bite plane treatment, showing significant improvements in TMJ pain and mouth opening limitation, with a notable occurrence of TMJ remodeling observed in the observation period. [49]

However, in the study conducted by Truelove et al, they randomized 200 subjects with painful TMD into three groups receiving different treatments: usual conservative treatment (UT), UT plus a conventional flat-plane hard acrylic splint (HS), and UT plus a soft vinyl splint (SS) and the results showed no significant differences among the groups in pain levels or TMD symptoms, suggesting that traditional splint therapy offered no advantage over low-cost soft vinyl splint therapy or even self-care treatment without splint therapy. [50] Taken together, it appears that occlusal splints have an overall positive therapeutic effect in Temporomandibular Joint Disorders, but further studies are needed to determine the relative effectiveness of each appliance in clinical use. [51]

Pharmacotherapy

Pharmacological interventions can also contribute to the conservative treatment approach, provided they are used with care. Current research suggests that Non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and hyaluronate injections are effective for TMD joint pain. [52]

NSAIDs exert their therapeutic effects by inhibiting the activity of cyclooxygenase-2 (COX-2). [53] The study by Ta et al evaluated the efficacy of an NSAID in treating clinical TMD with joint pain and found that over 80% of patients had at least a 50% pain reduction over the six-week study duration. [54]

In a two-year follow-up study by Sato et al, they found that over 80% of patients treated with hyaluronate injections had a successful treatment outcome (defined as 35mm+ of maximum mouth opening and an absence of TMJ pain). [55] A recently conducted umbrella review of systematic reviews confirmed that intraarticular hyaluronate injections have positive results in terms of functional improvement and pain reduction. [56]

Corticosteroids can be administered directly into the TMJ, taken orally, or applied topically. [57]. The study by Arabshahi found that almost 80% of patients treated with corticosteroid treatment had complete resolution of TMJ pain. [58] The use of intraarticular corticosteroid injection should be reserved for therapy-refractory cases and administered as a single injection. [59]

Arthrocentesis

A systematic review conducted by Guarda-Nardini et al found that TMJ arthrocentesis improves jaw function and pain reduction in patients diagnosed with TMJ-OA. [60] The systematic review by Derwich et al reached the same conclusion, and furthermore found that arthrocentesis is effective alone in improving jaw function and reducing pain, and supplemental injections of hyaluronic acid and corticosteroids do not improve the final treatment outcome [61]. This is supported in the systematic review by Thorpe et al, finding that arthrocentesis was statistically significant in increasing maximum mouth opening and borderline superior for pain reduction when compared to other conservative therapies [62]. Interestingly, the Guarda-Nardini et al review findings suggest that the type of treatment intervention, the baseline presence of MRI effusion, and the specific Axis I diagnosis (TMD pain assessment) are not important predictors of treatment effectiveness, meaning that predictors of treatment outcome might be more patient-related than disease-related. Future efforts to identify predictors of treatment outcome should focus on the patient more than the disease. [60]

TMJ Replacement Surgery

Generally, TMJ replacement surgery is performed on joints that have undergone significant structural and functional deterioration, often leading to substantial chronic pain, limited jaw movement, and compromised quality of life. [63] [64] Diagnosis and treatment decisions are typically made based on a combination of clinical evaluation, imaging studies (such as MRI or CT scans), and patient-reported symptoms. [63] Patients experiencing severe TMJ degeneration often require comprehensive evaluation and may be candidates for TMJ replacement surgery to alleviate their symptoms and improve their quality of life.

TMJ replacement prostheses can either be stock or custom-made. Stock prostheses are cost-effective and readily available but may require bony preparation, posing potential challenges during surgery. Custom prostheses are tailored to the patient's anatomy, minimizing bone preparation, shortening operative time, and enhancing osseointegration. [63] However, they are more expensive and require comprehensive surgical planning.

The outcomes of TMJ replacement are controversial. One review article analyzed pain levels before and after surgery and found a significant reduction in pain in the first month following surgery. [65] However, in a long-term prospective study, only 50% of patients reported a reduction in subjective pain. [66] Additionally, in a retrospective study with an average follow-up duration of 40.1 months, 1 out of 5 patients reported chronic postoperative pain. [67] There are fewer long-term studies to support the success of TMJ replacement surgery in comparison to that of total knee replacement surgery. In contrast, knee joint replacement is highly effective, with 80% of total knee replacement recipients experiencing significant pain relief up to 90% and lasting 20 years. [68]

Conclusion:

Unlike in the knee, there is a very questionable relationship between structure, function, and pain in the TMJ. Fewer than 20% of people with radiographic evidence of TMJ-OA have symptoms, while over 50% of patients with radiographic knee OA are symptomatic. Conservative treatments improve both symptoms and radiographic evidence of degeneration in 60-75% of people with TMJ-OA, while 80% of patients still have persistent symptoms in the knee following conservative therapies. TMJ replacement has less than a 50% success rate over 10 years, while in the knee, 80% of patients show a reduction in pain symptoms and 90% of joint replacements last over 20 years.

Temporomandibular joint degenerative disease in the vast majority of people is self-limiting and radiographic evidence of degeneration is usually not associated with pain. There is a desperate need for longitudinal pain and imaging studies in people with temporomandibular joint osteoarthritis and within-subject studies on people with unilateral TMJ-OA to determine the intricacies of the relationship between structure and pain. In addition, studies are needed to characterize endochondral ossification during TMJ osteoarthritis and compare it to what occurs during natural growth. Treatment efforts for TMJ-OA may be better suited for symptom relief rather than restoration of function.

Figure 2-.

Comparison of the knee vs TMJ osteoarthritis for treatment and radiographic evidence of degeneration