Temporomandibular Joint Disorders and Pain Confounders: An Awareness Study

Abstract

Objectives

Temporomandibular disorders (TMD) are the most common nonodontogenic cause of orofacial pain, leading to morbidity and impairment. TMD presents a diagnostic challenge due to many aetiologies that exhibit comparable symptoms and refer pain to the temporomandibular joint (TMJ) region. Patients may be referred to dental specialists without accounting for all pain sources. This study aims to identify radiographic confounders (RCs) that can be mistaken for TMD in patients undergoing TMJ assessment using cone-beam computed tomography (CBCT).

Materials and Methods

A review of 369 CBCT oral maxillofacial radiology reports of the TMJ acquired between July 2020 and June 2023 was completed. Pertinent RCs were classified as endodontic lesions, impacted dentition, sinus pathologies, root fractures, soft tissue calcifications, and others. The chi-squared test assessed the significance of the relationship between RCs and patient variables.

Results

A total of 283 RCs were identified in 202 of the 369 cases (54.7%). The most frequent findings included sinus abnormalities (32.5%), endodontic lesions (15.2%), impacted dentition (12.7%), and elongated/calcified stylohyoid process (9.2%). Significant associations were found between sinus pathologies with TMD signs (P = .009) and gender (P = .001).

Conclusion

Our results indicate that RCs that mimic TMD-related symptoms are prevalent in patients referred for TMJ CBCT imaging.

Clinical Relevance

Clinicians should be aware of these RCs when diagnosing complaints related to the TMJ. We recommend clinicians first obtain dental clearance and investigate all other potential sources of a patient's complaint before initiating referrals to avoid unnecessary costs and delays in patient care.

Introduction

Temporomandibular disorders (TMD) describe a diverse group of conditions that affect the temporomandibular joint (TMJ) complex and its associated structures in approximately 31% of the adult and 11% of the paediatric population.¹ TMD represents the most common nondental cause of facial pain, and the updated diagnostic criteria/TMD guidelines (DC/TMD) have divided the common TMD diagnosis into 12 categories.^1,2 Common pain-related TMDs include myalgia and arthralgia, where patients exhibit a history of pain involving the jaw or surrounding muscles aggravated by function.² Pain originates within the masticatory and cervical muscles for myalgia. In arthralgia, pain is derived from the joint directly, and a comprehensive clinical examination will elicit repeatable and familiar pain upon palpation of the lateral poles of the condyles or during maximal opening or excursive movements. Patients diagnosed with headaches attributed to TMD will present with complaints of a headache in the temple area aggravated by jaw function. Other common TMD diagnoses include internal derangement, degenerative joint disease, and subluxation. In addition to TMD, other orofacial pain conditions, including trigeminal neuropathic pain, can also lead to chronic facial pain conditions.³ Management of TMD costs approximately $4 billion annually in the United States.⁴

Obtaining a detailed history of the patient's presenting symptoms and performing a thorough examination are the primary methods to establish the initial clinical orofacial pain/TMD diagnosis.^5,6 Subsequent detailed radiographic investigations are often required to evaluate the hard and soft tissues of the TMJ to validate clinical findings or narrow down the differential diagnosis. Traditionally, magnetic resonance imaging (MRI) is the primary imaging modality used for TMJ investigation due to its ability to investigate both hard and soft tissue of the joint with higher interobserver reliability than 2-D modalities.⁷ However, patient access to MRI may be limited due to the long waiting list and the prioritization of more urgent cases over most TMD cases. This issue is particularly relevant in countries with public health systems, such as Canada.⁸ Alternatively, cone-beam computed tomography (CBCT) is a cost-effective modality for TMJ assessment, offering excellent diagnostic quality and accuracy for bone evaluation. Furthermore, its widespread availability in dental offices, along with easy and timely access to nearby facilities equipped with this technology, enhances its utility in clinical practice.^6,9,10 CBCT can effectively detect subtle osseous changes of the TMJ with higher sensitivity than conventional radiographs and even with more reliability than MRI for assessing bony pathologies including osteoarthritis.^6,7 In addition, CBCT imaging can also provide a thorough assessment of the dentition and surrounding tissues to detect existing pathologies that may mimic TMD symptoms.⁶ CBCT is very limited in its ability to image soft tissues of the TMJ; hence, MRI remains the preferred modality for assessing the TMJ's soft tissue pathologies.^6,7

Patients seeking treatment for pain arising near the TMJ region can have an extensive list of provisional diagnoses due to the number of possible causes of orofacial pain that can mimic TMD.¹¹ For instance, odontogenic pain can present as a sharp pain reproducible by function that refers to the TMJ area. Similarly, patients often report symptoms of facial fullness and pressure along that zygomatic region for sinus-related pain that can coincide with symptoms of some TMD entities.¹² It is estimated that 75% of orofacial pain complaints are due to odontogenic sources.^13,14 Under this circumstance, it can be easy for general dentists and other primary care clinicians to falsely attribute orofacial pain to TMJ-related pain and initiate referrals to dental specialists without first accounting for other possible aetiologies of the patient's pain complaint.

To our knowledge, no large-scale studies have determined the radiographic confounders (RCs) that may be implicated in causing symptoms that mimic TMD-related orofacial pain in TMJ through CBCT scans. Hence, this study aims to fill the knowledge gap in identifying the common clinically relevant RCs that can be mistaken for TMD-related orofacial pain in patients who were referred for a TMJ CBCT assessment. Therefore, our objective is to raise awareness that different aetiologies of orofacial pain exist, and they may be directly causing or contributing to symptoms that can mimic TMD pain. This may ultimately lead to improved diagnosis and subsequent treatment of these patients. In addition to providing insight to dentists, this information can also inform the broader medical community, including physicians and nurses who may represent the primary contact point for TMD patients.

Methods

This retrospective study received approval from the Human Research Ethics Board at the University of Alberta Pro00129205. This study followed the STROBE guidelines for reporting observational studies.

A pool of available CBCT images and associated oral and maxillofacial radiology (OMFR) reports were obtained from all patients who were referred for CBCT assessment of the TMJ from July 2020 to June 2023 at the School of Dentistry and the Oral Medicine Clinic of the University of Alberta and a private practice located in Edmonton, Canada. CBCT scans taken for other reasons were excluded from this study. All CBCT images and interpretive reports were interpreted and generated by board-certified Oral and Maxillofacial Radiologists.

From the OMFR reports and requisition forms, demographic data was recorded along with the field of view (FOV) of the CBCT scans, whether the patient presented with TMD symptoms at the time of imaging, and the resulting TMJ provisional radiographic diagnosis. When alternative radiographic provisional diagnoses were provided for the two joints in the same patient, only the more severe diagnosis was recorded. Subsequently, each OMFR report was reviewed for the presence or absence of each category of possible RC and manually entered into a standardized data collection template.

Statistical analysis

Descriptive characteristics of the data (means, standard deviations, and ranges) and the frequencies of each RC and TMJ findings category were calculated. The demographic characteristics of each patient were tabulated. We examined whether statistically significant relationships or associations exist between variables, such as RCs, FOV sizes, symptoms, and TMJ findings. To analyse categorical data and test the significance of the associations, the Chi-square was used to determine whether observed results differed significantly from expected results. The prevalence of positive findings in each category was calculated as a total of the population sample. Data analysis was performed with the Statistical Package for Social Sciences (SPSS, version 23, IBM). A P value less than .05 was deemed statistically significant.

Results

A total of 369 CBCT images and OMFR reports were reviewed, and a total of 738 TMJs were investigated. Of the 369 patients, 246 (66.7%) were female and 123 (33.3%) were male, with an average age of 36.4 years (SD = 17.1 years) at the time of imaging between the age of 3 months and 87 years. Cases with either positive TMD signs or symptoms referred to TMJ specialists accounted for 93.2% of the study population. Patients with no relevant clinical information represented 24.9% of the total cases and likely had displayed TMD signs and symptoms which prompted their referral. Meanwhile, 6.8% of the patients exhibited no TMD symptoms at the time of imaging. The FOV most frequently used for image acquisition was large (75.1%), followed by small, restricted for the condyles only (10.8%), and medium FOV in 14.1% of the scans.

Fig. 1, Fig. 2 show the TMJ provisional radiographic diagnoses provided in the OMFR reports divided by signs and symptoms of TMD and by gender. The most common radiographic diagnosis was degenerative joint disease (32.8%). Notably, a considerable number of OMFR reports (11.9%) found that both joints were of normal anatomy, and 28.2% exhibited condylar remodelling, a physiologic change of the joints in response to increased functional load.

Fig. 1.

TMJ provisional radiographic diagnosis of the cases.

Fig. 2.

Association of TMJ CBCT provisional diagnosis and signs and symptoms of TMD.

A total of 283 RCs to the TMD pain diagnosis were identified in this sample population, representing an average rate of 0.77 radiographic findings per patient. Out of the entire group, 167 patients (45.3%) had no relevant radiographic TMD confounders. It was found that the most common categories of RC present in this population included sinus abnormalities (32.5%), endodontic lesions (15.2%), impacted dentition (12.7%), elongated/calcified styloid process (9.2%), and dental root fractures (6.0%).

Table 1, Table 2 demonstrate the significance of the relationship between case variables and the presence of each type of RC. Notably, a significant relationship was also found between the gender of the patient (P = .001) and whether the patient exhibited signs and symptoms of TMD (P = .009) with sinus abnormalities.

Table 1.

The frequency of confounders to the TMD pain diagnosis by gender.

Variables		Male		Female		Total		x2 value; df = 1	P value
		N	%	N	%	N	%
Impacted dentition	No	105	85.4	217	88.2	322	87.3	0.597	.440
	Yes	18	14.6	29	11.8	47	12.7
Sinus pathology	No	69	56.1	180	73.2	249	67.5	10.892	.001*
	Yes	54	43.9	66	26.8	120	32.5
Periapical pathology	No	101	82.1	212	86.2	313	84.8	1.053	.305
	Yes	22	17.9	34	13.8	56	15.2
Previous traumatic condylar fracture	No	121	98.4	246	100.0	367	99.5	4.022	.045*
	Yes	2	1.6	-	-	2	0.5
Root fracture and residual root tips	No	116	94.3	231	93.9	347	94.0	0.024	.876
	Yes	7	5.7	15	6.1	22	6.0
Calcified Stylohyoid process	No	112	91.1	223	90.7	335	90.8	0.016	.899
	Yes	11	8.9	23	9.3	34	9.2
Other soft tissue calcifications	No	122	99.2	245	99.6	367	99.5	0.251	.616
	Yes	1	0.8	1	0.4	2	0.5

Chi-square test: NS: P > .05; not significant; *P < .05; significant.

Table 2.

The frequency of confounders to the TMD pain diagnosis

Variables		Symptoms and signs of TMD						x2 value; df = 1	P value
		No		Yes		Total
		N	%	N	%	N	%
Impacted dentition	No	23	92.0	299	86.9	322	87.3	0.541	.462
	Yes	2	8.0	45	13.1	47	12.7
Sinus pathology	No	11	44.0	238	69.2	249	67.5	6.737	.009*
	Yes	14	56.0	106	30.8	120	32.5
Periapical pathology	No	23	92.0	290	84.3	313	84.8	1.073	.300
	Yes	2	8.0	54	15.7	56	15.2
Previous traumatic condylar fracture	No	25	100.0	342	99.4	367	99.5	0.146	.702
	Yes	-	-	2	0.6	2	0.5
Root Fracture and residual root tips	No	23	92.0	324	94.2	347	94.0	0.199	.656
	Yes	2	8.0	20	5.8	22	6.0
Calcified Stylohyoid process	No	22	88.0	313	91.0	335	90.8	0.249	.618
	Yes	3	12.0	31	9.0	34	9.2
Other soft tissue calcifications	No	25	100.0	342	99.4	367	99.5	0.146	.702
	Yes	-	-	2	0.6	2	0.5

Chi-square test: NS: P > .05; not significant; *P < .05; significant.

Discussion

This study found that RCs are common among patients referred for a CBCT assessment of the TMJ. Of the total number of patients, 54% of the scans had at least one RC. The discovery of these RCs in a patient suffering from TMD is worthy of attention. This is especially critical when patients present with characteristics that we have identified to be significantly associated with the presence of RCs. Many of these incidental radiographic findings can produce symptoms that coincide with or contribute to orofacial pain derived from the TMJs. In fact, multiple RCs that we have identified are capable of directly causing pain that closely resembles that of TMD.

A small percentage of patients (6.8%) did not demonstrate any signs or symptoms of TMD when the scans were taken. However, the radiographic examination was justified for reasons including assessing condylar position for orthodontic assessment or if the patient had a history of trauma to the jaws or was previously diagnosed with TMD that is currently asymptomatic. More concerningly, 24.9% of referring clinicians did not include any relevant clinical information when requesting a joint assessment. In accordance with Canadian guidelines for prescribing radiographic examinations, it is critical for the prescribing clinician to include pertinent clinical information when requesting for imaging studies to be completed.^10,15 This is important both for justification and for optimization purposes to minimize ionizing radiation exposure, adhering to the principles of ALARA and ALADA which is the standard of care.^6,15 Additionally, clinical information is essential for TMD cases and must be included in the referral for advanced imaging (CBCT or MRI) to ensure proper evaluation and interpretation of the results. At the same time, this information permits the radiologist to consider lower-dose alternatives for joint evaluations and to optimize image acquisition parameters for the best diagnostic images – a consideration that is even more critical when dealing with paediatric patients suspected of TMD. Clinicians should be more aware of the importance of a detailed clinical examination and include any potentially useful information on their requisition forms for future referrals.

There is limited literature on the prevalence of these RCs in CBCTs that focuses on identifying confounding entities that can mimic TMD-related pain. One study by Cağlayan and Tozoğlu¹⁶ assessed the prevalence of incidental findings in CBCTs taken for various diagnostic properties, and their study inadvertently evaluated a subset of our RCs. Out of the 85 CBCT images taken specifically to assess the TMJ, the authors found signs of mucositis (25.9%), impacted third molars (31.8%), and endodontic pathology (5.9%) of the patients in this sample population. However, the authors failed to connect these findings to TMD and did not discuss how this finding can be related to managing this patient population. Indeed, this still demonstrates that clinically relevant confounders exist and are relatively common in patients suspected of TMD who were subsequently sent for further joint assessment. By contrast, the prevalence of RCs in our study is considerably higher for sinus abnormalities (32.5%), lower for impacted dentition (12.7%), and higher for endodontic lesions (15.2%). The differences may be attributable primarily to differences in the demographics of the group, the sample population size, the CBCT FOVs, and the location of the study being carried out compared to the present study population. Furthermore, our study included more categories of RCs relevant to causing orofacial pain compared to the previous study.

Endodontic lesions – In this study, endodontic problems were the second most common RCs, representing 15.2% of all identified confounders. Teeth with symptomatic pulpal or periapical conditions can cause sharp and shooting pain that is reproducible or worsened by mastication and can refer to the TMJ area.^11,17 Falace et al¹⁸ revealed that 89.8% of study participants with posterior teeth diagnosed with pulpal or periapical pathology had referred pain. Furthermore, 74.7% of those patients experiencing referred pain also reported extraoral pain, which often involved the jaws and TMJ region. Interestingly, 79.5% of RCs of endodontic concerns were found in posterior teeth in the present study, which suggests that a considerable proportion of these endodontic findings may have resulted in or contributed to pain-mimicking TMDs. Apical widening of the periodontal ligaments can be induced by occlusal trauma, where pain or tenderness can be triggered by routine mastication.^19,20 Moreover, widening of the periodontal ligament space can often be the first sign of an endodontic infection and an early indicator of periapical inflammation.^19,21 Other less commonly seen aetiologies can include neoplastic lesions of the jaw and jaw osteonecrosis, which typically involve jaw pain.^19,22,23 Internal and external cervical resorption cases are usually asymptomatic.^24,25 However, they can result in pain in advanced cases of severe resorption, leading to perforation of the remaining tooth structure. This was the case in this study, where an OMR report identified advanced cervical resorption associated with periapical pathology and, therefore, likely to exhibit orofacial pain. Endodontic pain is unlikely to be well understood or acknowledged by physicians during facial pain assessments.

Impacted dentition – This study found that impacted dentition was the third most common category of RCs seen on CBCT imaging of the joints, accounting for 12.7% of cases. Only 6.4% of the presenting impacted dentition in the current study were associated with clinical pericoronitis of third molars. When impacted dentition is associated with pericoronitis, patients may experience tenderness near the posterior mandible region and radiating pain to the ear and TMJ area.26, 27, 28 Patients with acute or severe pericoronitis may have limited mouth opening, headaches, and swallowing difficulties. Additionally, even though most of the impacted dentition in the study did not show any pathology detectable by CBCT, patients with impacted dentition may still experience pain symptoms. The percentage of symptomatic impacted third molars varied among different studies in the literature. It is reported that pain and trismus were present in 39% and 10% of the patients, respectively.²⁹ In another study, 68.29% of impacted mandibular third molars were symptomatic.³⁰ Although most cases of impacted dentition in our study did not show associated changes detectable by CBCT, it is likely that some proportion of these patients experience clinical symptoms. Under this circumstance, clinicians should be careful not to attribute pain to TMJ without considering the possibility of impacted dentition as the source of pain, as it can be a common occurrence.

Sinus pathologies – The prevalence of incidental findings of the sinus is high in the literature.^16,31 Coincidentally, this category of RC represented the most prevalent category in the current study (32.5%). Sinusitis is the symptomatic inflammation of the sinus.^32,33 In acute sinusitis, facial feelings of fullness, pressure, or pain are one of the three diagnostic criteria of the condition. Furthermore, referred pain to the maxillary dentition can often be an important clue to making the correct diagnosis. In chronic sinusitis, symptoms of pressure, fullness, and congestion of the face and zygomatic arch region remain high at 70% to 85%. Other relevant clinical presentations can similarly include referred odontogenic pain and headache. Odontogenic mucositis is common and can be associated with odontogenic pathologies that in turn act as a confounder to the TMD-related pain diagnosis.³⁴ The relationship of periapical lesions with orofacial pain has been previously discussed and hence clinicians must be diligent about this common incidental finding prior to initiating referrals.

Root fracture and residual root tips – In our study, we identified 22 cases of dental root fractures. The fractured tooth may be symptomatic and present with mobility and elicit a painful response when the patient bites down during normal chewing.³⁵ Additionally, one study reported that up to 37.5% of anterior teeth with root fractures eventually develop pulpal necrosis.³⁶ In the same study, 16% of the fractured teeth had to be ultimately extracted due to apical periodontitis and/or severe resorption of the surrounding alveolar bone. In a study involving both symptomatic and asymptomatic retained root tips, 14.5% of extracted root tips were histologically associated with rarefying osteitis, which can produce symptoms of endodontic infection that have been previously discussed.³⁷ Although these types of RCs are often considered asymptomatic, they can potentially cause orofacial pain. Complaints of pain upon biting down and referred pain to the TMJ region can sometimes mislead unwary clinicians into thinking that odontogenic pain is due to an undiagnosed TMD.

Soft tissue calcifications – In our study population, we found that 9.2% of the patients had stylohyoid ligament calcifications or elongations. However, it is estimated that only 4% of patients with elongated styloid processes are symptomatic; known as Eagle syndrome.³⁸ The most common symptom is neck pain that is difficult to pinpoint but can also include pain that radiates to the TMJ/ear and worsens with head rotations.^39,40 Other symptoms include headache, pain along the distribution of cranial nerves, tinnitus and pain on mastication. Under this circumstance, the presence of referred pain to the TMJ and neck can make it challenging for clinicians to differentiate the pain from TMD-related pain.

As an awareness study, we have identified and highlighted the most prevalent RCs that can lead clinicians to mistakenly investigate TMJ in search of an explanation for the patient's pain complaint. Many entities can cause pain in the TMJ area, refer pain to the joint, or be aggravated by normal mastication. This creates a diagnostic challenge for not only dentists but also nurses, primary care physicians, and other clinicians who are often the first point of contact for patients with orofacial pain. Fortunately, all the RCs that we have identified exhibit other signs and symptoms or radiographic features that can help a prudent clinician narrow down the differential diagnosis.

Dental clearance is essential before referring to an Oral Medicine specialist. A comprehensive clinical examination of the dentition can reveal suspicious teeth with pulpitis or large decay that may be causing unexplained orofacial pain. By conducting pulp testing and taking a periapical radiograph, the offending tooth can often be accurately identified with confidence. Moreover, impacted third molars or elongated stylohyoid or cervical ligaments can be conveniently visualized and evaluated using a panoramic radiograph. Additionally, root fractures typically occur with concurrent trauma. In such cases, taking a detailed dental and medical history of the patient, conducting a thorough clinical examination, prescribing appropriate conventional radiographs, and evaluating any potential sources of pain with additional tests proves to be invaluable. On the other hand, if a patient was referred for evaluation of the TMJ and later revealed that their orofacial pain was caused by an entity unrelated to the joint, consequences in terms of costs, delays to treatment, and unnecessary suffering can be significant. A recent survey of the Oral Medicine Clinic at the University of Alberta revealed that, on average, patients travelled 55 km and experienced a wait time of 105.5 days to attend the Clinic.⁴¹ Therefore, referrals made without first prudently eliminating other sources of pain place a considerable burden on the patient and can risk damaging the patient-practitioner relationship and trust. As a result, it is critically important for clinicians to be more aware of these potential RCs to improve patient satisfaction, support a higher quality of life, and reduce unnecessary medical expenses.

Medium or large FOV CBCT is generally used for TMJ imaging, when justified by trauma history and facial asymmetry, capturing structures beyond the usual focus on the oropharynx region by a general dental clinician. For instance, scans of the nasopharynx may reveal various incidental findings including carcinomas and lymphomas, where late detection can result in serious consequences.⁴² Consequently, it is strongly advisable to send all CBCT scans for a comprehensive interpretive report completed by an OMFR. This will ensure accurate review of the imaging volume and detection of incidental findings that may be pertinent to patient care. Ultimately this will lead to reduced misdiagnosis, better patient outcomes, and reduce liability on the treating dentist who may not have the background of a formally trained radiologist. While CBCT is increasingly available in dental clinics and offers valuable information for treatment planning of impacted teeth, extraction of high-risk teeth, and management of complex endodontic cases, its use must be indication-driven.^6,43 CBCT evaluation of TMJs has limitations concerning soft tissue assessment. Therefore, MRI remains the reference standard for articular disc displacement evaluation, and it should be the modality of choice when a clinical examination suggests a possible soft tissue etiology.⁶ CBCT should not be used as a screening tool as it offers limited assistance in managing the two most common TMDs – musculoskeletal conditions and articular disc displacements.^6,44 As a result, patient must first undergo a thorough clinical examination, ideally by a clinician with expertise in TMD such as a dental specialist, before being referred to CBCT or any advanced imaging modality. This recommendation is particularly important for children, who are more vulnerable to risks associated with exposure to ionizing radiation, including for medical purposes.⁴⁵

It is important to emphasize that the results of this study cannot be generalized, and its limitations should be considered. We calculated the prevalence of the RCs based on a retrospective analysis of the data from a population base with unique demographics primarily located in one Canadian city. Furthermore, the availability of clinical information is inconsistent since a sizable portion of the referring clinician did not include complete clinical information on their CBCT requisitions.

Further research on the prevalence of RCs in cases associated with trauma, such as motor vehicle accidents will assist clinicians dealing with these incidents and the various medical-legal implications this entails. In addition, more research on the cost of TMD management in Canada will help highlight the condition's considerable impact on individual patients and society. Lastly, additional data regarding the percentage of total cost for the management of TMD that can be attributed to unnecessary investigations and consultations will urge clinicians, insurance companies, and other stakeholders to be more aware of this problem and develop a more efficient protocol for investigating orofacial pain patients suspected of TMD.

Dentists and other primary care providers need to be aware of the high possibility of RCs when assessing patients with orofacial pain that resembles TMD. Additionally, the limitations of CBCT imaging for TMJ evaluation and the consideration of requiring an MRI for soft tissue evaluation should be considered. If imaging of the joints is necessary, we reemphasize that clinical examination and medical history review must precede any imaging investigation, as necessary to rule out other potential sources of pain. Upon referring the patient for imaging, the clinician should provide clinical information to the radiologist to ensure the proper acquisition parameters and interpretation of the results.

Conclusion

By examining all TMJ CBCT scans taken in the past 3 years, the results demonstrated that RCs are common in patients suspected of TMD and that most of the patients had at least one potential confounder revealed in their CBCT scans interpretive reports. The most prevalent RCs we have identified include sinus abnormalities, endodontic lesions, impacted dentition, and soft tissue calcifications. In conclusion, clinicians need to be vigilant of RCs to avoid unnecessary investigations and to maintain patient trust.

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.