Options for diagnostic testing and dental treatment are not the same as recommendations that a dentist may make, but recommendations are generated from options.

As an analogy, I live approximately four miles from my office. There are three ways to get from my home to my office. One way, the shortest route, involves four left turns, climbing the steepest hill in our county on a one-lane road, descending a very steep grade, and passing through a school zone and four traffic lights. A second route involves five right turns, passing through two school zones, and 12 traffic lights — most of which can usually be passed through without stopping if a speed of 37 mph is maintained, except when school zones are active. A third route, the fastest, involves two right turns, six traffic lights that are not coordinated, two left turns, a school zone, and three miles of interstate driving.

Each of these three routes will get a person to my office within about two minutes of the other two, and they are all options. However, if I am giving a person directions to my office from my home, my recommendation will be based on my knowledge of the person’s navigation abilities and driving skills, my personal preference, and my knowledge of current local factors like construction or traffic during that time of day. Some might consider my recommendation about how to get to my office from my home to be evidence-based.

In dentistry, many options are available for any given treatment based on a diagnosis and also for assisting in making a diagnosis, but best practice is to make evidence-based and ethical recommendations that are supported by current peer-reviewed literature, are in the best interest of the patient from a beneficial and cost effective perspective, create the least amount of risk for the patient in consideration of emotional and physical factors, and are based in part on the clinician’s experience and skillset.

When ordering any diagnostic test, the ethical clinician should always ask, ‘What will I gain from this test that will significantly affect my treatment plan?’

Once dentists make a diagnosis about teeth, we tend to have a very good understanding about treatment options. For example, if a tooth is significantly damaged due to fracture or decay, we understand the options available: heroic direct restoration with composite or amalgam, lithium disilicate crown, full or layered zirconia crown, cast metal or milled titanium crown, porcelain-fused-to-metal crown, onlays of various materials, etc. If a tooth has a small interproximal carious lesion requiring restoration, we have several options available to us: amalgam, composite resin, gold inlay, ceramic inlay, resin inlay, etc. After a discussion with the patient about their desires and the options available to him or her, we make a recommendation based on our diagnosis, saying something like, “Of the options available, I recommend _____ therapy in your situation because …”

We tend to get into a quagmire when we are confronted with making appropriate recommendations for diagnostic tests, especially since modern science has provided many reliable options for diagnostic testing.

The following is a scenario in which I was caught in a significant predicament several years ago when I recommended a saliva test to identify whether or not a patient had been exposed to a particular virus that has been shown to cause oropharyngeal cancer1. In fact, it was a very good test; it tested quite accurately for the presence of the HPV virus strains that cause cervical and oropharyngeal cancer. However, the problem with administering the test at that time was that there was no direction as to what to tell a patient who received positive test results.

Since it was well-known in the literature that the substantial majority of otherwise healthy patients exposed to this particular virus naturally cleared it from their systems within 90 days, even if the recommended protocol to retest the patient after 90 days if a positive finding was found, there was still not adequate information about what to do with a repeated positive test. Theoretically, it was reasonably possible that an otherwise healthy person could be in an ongoing sexual relationship with an individual who was a carrier of HPV, which is quite ubiquitous in society; therefore, patients who naturally cleared infections of the virus might be repeatedly reinoculated with the virus on an ongoing basis, which would result in repeated positive tests; or, a repeated positive test could indicate a persistent infection in the absence of a precancerous or cancerous lesion.

Furthermore, in the absence of a physical lesion, how would one treat a known HPV infection since there is no medication to treat it? In fact, positive tests create social and ethical problems because the testing clinician is ethically bound to disclose the results of the test, even if positive, but then we can really give no further recommendations or guidance with what to do with that information. In fact, I had one patient whose marriage was ruined because of a positive HPV test because she blamed her husband for cheating on her and giving her the virus from the person with whom she assumed he was cheating. Whether that was the case or not, I have no idea.

What I do know is that the HPV test was the initiating factor. Incidentally, that was more than five years ago, the patient still is my patient and she has not developed any concerning lesions to date. So, here is the question: Just because a test is accurate, what are we able to do with the information it provides? Furthermore, will the benefit gained from a diagnostic test justify the expense to the patient? In other words, is there a favorable cost-benefit ratio?

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One of the scenarios we face in the field of orofacial pain, specifically when it comes to diagnosing temporomandibular joint disorders, is which diagnostic options to recommend. Some clinicians strongly recommend cone beam computed tomography for any patient with suspected TMJ disorders. Others strongly recommend an MRI with a variety of protocols and in varying joint positions. Still others believe that basic panoramic radiographs are adequate. The challenge is that all of these are good diagnostic tests for specific purposes, and each provides different information.

For example, soft tissue, along with hard tissue, is best viewed with an MRI, but it requires multiple lengthy series (approximately 30 minutes for each image) that can be enhanced with injectable dye and typically are much more costly than other imaging modalities available to evaluate the TMJ. Hard tissues in three dimensions are viewed with good resolution with CBCT and CT (computed tomography) images. CBCT has the benefit of lower radiation exposure than CT (some even coming close to the same dosage as conventional panoramic radiographs) and the convenience of being available in many dental offices and is often less financially burdensome to the patient. Panoramic radiographs are adequate screening images to evaluate for gross remodeling at a lower radiation dosage than CBCT and CT images. In fact, as I learned when considering accepting a position to evaluate veterans for combat-related TMJ disorders for benefit determination, panoramic radiographs are used as the standard diagnostic imaging for the U.S. military.

A CBCT view showing how three-dimensional evaluation of hard tissue also provides hints about disc position in TMJ cases
Figure 1: CBCT allows three-dimensional evaluation of hard tissue and gives hints about disc position. Note the frontal, sagittal, and coronal views of the condyle in the glenoid fossa. The “beaking” that represents initial osteophyte formation in the right TMJ (red arrow) and the remodeling of the left articular eminence (blue arrow) and condyle (yellow arrow) that are suggestive of degenerative joint disease. The joint space in the right TMJ is of relatively normal width, which may suggest that the disc is grossly in the appropriate orientation (green arrow) while the asymmetric appearance the left joint space likely suggests disc displacement.

When ordering any diagnostic test, the ethical clinician should always ask, “What will I gain from this test that will significantly affect my treatment plan?” Advanced imaging modalities are best used to confirm or rule out clinical diagnoses so an effective treatment plan may be developed.

Since there is strong evidence supporting the notion that the majority of TMJ disorders are self-limiting, treatment should be directed toward managing clinical symptoms rather than findings based solely on imaging2. For instance, for the majority of TMJ disorders, the first line of treatment should entail non-invasive therapies such as physical self-regulation techniques, physical therapy, full-arch occlusal orthotic appliances with shallow guidance, anti-inflammatory medications, etc2.

This protocol is conservative and commonly employed, regardless of imaging findings. In fact, properly performed clinical exams are actually quite reliable for diagnosing significant TMJ disorders when compared with MRI as a standard, with high sensitivity (a diagnosis actually is as clinically diagnosed based on MRI findings — true positive) and high specificity (the patient does not have a diagnosis based MRI confirmation — true negative3).

For common TMJ disorders2:

  • Disc displacement with reduction: sensitivity = .34; specificity = .92. (A clinical click does not necessarily indicate that a disc reduces, but if there is no click there is likely no displacement.)
  • Disc displacement with reduction with intermittent locking: sensitivity = .38; specificity = .92.(A clinical click does not necessarily indicate reduction, but if there is no locking and no clicking there is likely no displacement.)
  • Disc displacement without reduction with limited opening — “closed lock:” sensitivity = .80; specificity = .97 (Clinical findings are likely accurate for displaced disc.)
  • Disc displacement without reduction without limited opening: sensitivity = .54; specificity = .79. (Disc can be displaced without limited range of motion and no click.)

Since magnetic resonance imaging is the most accurate test for radiographically assessing the position of the disc and the treatment plans for the majority of TMJ disorders are similar until maximum symptom relief occurs, why would the astute clinician not order an MRI series for every patient with a concern about a TMJ disorder?

The question is an ethical one: What is the cost-benefit ratio? MRI scans are typically much more expensive than CT and CBCT scans. If contrast dye is used, then there is a risk of allergic reaction to the injected dye. The time for an MRI procedure is lengthy, which requires the patient to be postured awkwardly for lengthy periods of time, which can be detrimental to an injured joint and painful musculature.

The informed consent discussion should involve all options available for diagnostic imaging, including the risks and benefits, as well as what information will or will not be gained that will likely direct the treatment and affect the treatment plan.

If the patient suffers from claustrophobia, or if the patient contains any magnetic metals, then an MRI may be contraindicated. Since the financial burden is often great for MRI, the anticipated benefit from this diagnostic testing modality must be great. While a clinician certainly would not technically be wrong in ordering an MRI, the reality is that MRI is not absolutely indicated in many, if not most, TMJ disorders. Furthermore, the results provided by the image rarely alter the conservative nature of the treatment being considered for implementation.

Fortunately, there are respected groups of clinicians much smarter than me who have established guidelines for the diagnosis of TMJ disorders. Specialists in the field of orofacial pain, for example, who are credentialed by the American Board of Orofacial Pain through psychometric testing and recognized by the American Board of Dental Specialties, tend to prefer the guidelines for diagnosis of TMDs as described by the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD4). The American Board of Orofacial Pain and Academy of Orofacial Pain, as well as many orofacial pain residency programs, use the Diagnostic Criteria for Temporomandibular Disorders as a standard for diagnosis of common TMDs.

The DC/TMD calls for an MRI when confirmation of a clinical diagnosis is required; for example, prior to surgical intervention or in cases that do not respond favorably to non-surgical therapy like physical self-regulation and self-care therapy, anti-inflammatory medications, orthotic therapy, physical therapy, etc. It also supports CBCT for confirmation of a diagnosis of degenerative joint disease when crepitus is present during the clinical examination.

Furthermore, the American Society of Temporomandibular Joint Surgeons lists the following as indications for MRI5:

  1. Evaluation of dysfunctional TMJ after unsuccessful conservative therapy for at least four weeks with bite splint and anti-inflammatory medication.
  2. Pre-operative evaluation of dysfunctional TMJ in candidates for orthognathic surgery.
  3. Evaluation of locked jaw.(Active)
  4. Persistent TMJ dysfunction after surgical repair.

Undoubtedly, an MRI will provide a more accurate diagnosis of the physical joint condition than a clinical exam alone. In fact, 80% of symptomatic TMJs referred for an MRI will show a displaced disc, and 15% of painful joints will show effusion (more fluid than asymptomatic joints) of the joint. Nearly a third of those 15% with effusion (fluid like lymph, blood, etc.) will even have bone marrow changes6, 7. Incidentally, about 37% of totally asymptomatic joints that are quiet clinically have been shown to have displaced discs on an MRI2.

Regarding CBCT and panoramic radiographs, it is best practice to follow the ALARA (As Low as Reasonably Achievable) Principle. Minimally, a good panoramic radiograph is indicated. However, a panoramic radiograph only shows gross osseous remodeling. If this is the only option that your patient can afford or that is available to you, then this may be the only image necessary in the absence of symptoms.

With the availability of low-dose CBCT imaging today that sometimes enables very good imaging in three dimensions with radiation dosages that come very close to conventional panoramic radiographs, CBCT provides excellent information about the health of the condyles at a relatively low cost. Of course, neither a panoramic radiograph nor CBCT will show soft tissue detail like an MRI will, but if there is clearly degenerative joint change seen on either of these images, this is meaningful information.

Panoramic radiographs that provide two-dimensional screening views of the temporomandibular joints, which highlight severe degenerative changes of the condyles seen bilaterally and the radiopacity in the left joint space.
Figure 2: Panoramic radiographs provide two-dimensional screening views of the temporomandibular joints. Note the severe degenerative changes of the condyles seen bilaterally and the radiopacity in the left joint space. This patient was diagnosed with synovial chondromatosis, a rare TMJ disorder that ultimately resulted in bilateral joint replacement surgery.

Furthermore, basing a diagnosis and subsequent treatment plan solely on the clinical and/or radiographic presentation of the TMJ and/or surrounding musculature alone follows the model of care centered on structure and function that gives no consideration to many of the other factors contributing to the pain, such as stress, emotion, compromised descending pain inhibition pathways, etc. A more current approach being embraced by many orofacial pain specialists in dentistry and chronic pain specialists in the medical arena is the more inclusive and robust biopsychosocial model of care in which the psychological and social signs and symptoms of the patient are considered along with the physical aspects of an orofacial pain case4, 8.

For example, past case reports and anecdotal observations that disc displacements are an etiologic factor leading to degenerative joint disease have not been confirmed by randomized clinical studies. In fact, the orofacial pain community has embraced the evidence-based concept that osseous changes of the joint occur independently of the disc placement and that exact radiographic diagnosis of the disc position is unlikely to affect the prognosis of most TMJ disorders. In fact, the etiology of most cases of TMJ disorders is multifactorial.

If there was strong scientific evidence to support that soft tissue injury leads to osseous change, then the argument for early MRI studies would be much stronger; however, this is not currently the case. A CBCT, CT, or even panoramic radiograph that shows degenerative condylar changes, however, may alter the prognosis of the case because bone remodeling has already occurred. It may also reflect the ability of a patient to redistribute excessive loading in order to protect against injury or damage.

An MRI shows soft tissue and bony anatomy of the TMJ with a disc that is displaced and deformed.
Figure 3: An MRI shows soft tissue and bony anatomy of the TMJ. In this case, the disc is displaced and deformed (yellow arrow). The condyle (green arrow) shows signs of remodeling. The superior belly of the lateral pterygoid muscle is seen attached to the displaced disc (blue arrow), and the inferior belly of the lateral pterygoid muscle is clearly seen (purple arrow9).

The informed consent discussion should involve all options available for diagnostic imaging, including the risks and benefits, as well as what information will or will not be gained that will likely direct the treatment and affect the treatment plan. The prognosis discussion in most TMJ disorders should simply include informing the patient that the joint has undergone changes and that it will never be the same as it was previously.

The fact that there is always a chance for degenerative joint changes is the same as for any other patient and should always be a part of the informed consent discussion; in fact, all human joints undergo various levels of degeneration with age, which is one of the reasons that we get shorter as we age. However, it is also important to point out that TMJ disorders tend to be self-limiting except in rare situations.

In summary, there is a difference between an option and a recommendation. In my opinion, supported by the positions of the American Academy of Orofacial Pain and the American Society of Temporomandibular Joint Surgeons, recommendations for advanced diagnostic testing should only be a consideration when the information gained will directly affect treatment planning and confirm or rule out a clinical diagnosis. When indicated, CBCT imaging can be a valuable diagnostic aid that offers more valuable information than a panoramic screening two-dimensional radiograph.

When non-invasive therapy fails to provide adequate reduction of symptoms, MRI for detailed soft tissue evaluation should be considered10. As ethical clinicians, dentists need to consider the economic and biological costs of diagnostic testing as it relates to the expected benefit to the patient and the anticipated impact it will have on treatment planning.

Kevin D. Huff, D.D.S., M.A.G.D., is a diplomate of the American Board of Orofacial Pain. He is a member of Spear Visiting Faculty, a moderator on the Spear Talk online forum and a contributor to Spear Digest.


  1. Huff, KD. Ethical Considerations and Decision-Making Methodology for Integrating Oral Mucosal Screening. Greater New York Dental Meeting. Manhattan, NY. November 27, 2011.
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