Critical analysis of diagnostic tools for the temporomandibular joint

Data regarding the prevalence of TMD fall within a very wide range. Different diagnostic tools used by researchers, inclusion criteria, age of participants or an influence of coexisting diseases are recognized as essential factors [3].

The first reference to the frequency of occurrence of TMD was made in the early 1970s [4,5]. Currently estimates fall within the range of between 20 and 25% of the general population [4,5].

Further studies with the development of specific diagnostic tools have resulted in reported occurrence rates at 5% [4], 3–4% [6], 6–7% [5], 2–4% [3], 8.4% [7] or 15.6–16.2% [8] for patients who required an intervention due to the intensity of their symptoms. Two studies describing native populations can be found in the Polish literature. Despite the fact that authors used the same diagnostic criteria, they showed different results, i.e. 48.9% [9] and 26.5% [10].

The development and spread of the RDC/TMD questionnaire has allowed researchers to compare their results, which directly influenced epidemiology data update both for the eneral population and patients with TMD symptoms.

The research revealed disc pathology in 11.4% [11] in the general population and 41.1% in TMD patients. Other studies showed TMJ disorders in 56.4% of the general population, 42% of whom had a disc problem [12]. In general, the literature shows a higher prevalence of TMD in women than men (a proportion of 3-4:1) [10,11,13,14]. There is a common agreement among researchers that the peak period of TMD occurs between the ages of 20 to 40 [15,16].

An interesting phenomenon of pathology coexistence was observed in the literature, i.e. disc and muscle or muscle and joint disorders. The rate of its occurrence ranged from 26.5% [10] to 38% [9] or even 64.3% of tested population [15].

The aim of the current study is to review selected tools used for diagnosing TMD and to assess their diagnostic value as well as to present the RDC/TMD questionnaire as the most complex tool for both scientific research and clinical practice.

Methods measuring the range of motion (ROM) of the TMJ play a primary role among quantitative tools because they can depict the trajectory of the mandible and describe its kinematics. These devices can be divided into two groups – simple devices used in a clinical setting and more advanced tools designed for scientific research. Simple methods include rulers (e.g. TheraBite® ruler) [17] or calipers (manual or electronic ones) [18,19]. The fact that they are quick and easy to use is a definite advantage especially in clinical practice when measuring both abduction and lateral mandible movements (mediotrusion and laterotrusion) [18,19]. Good validity of these procedures has been demonstrated in the literature [18].

More recent advanced devices for TMJ ROM measurements use technology that depicts a three-dimensional trajectory of mandible movements, which allows us to draw the Posselt diagram. Motion capture devices that have these features include: WinJawZebris®, Virtual Facebow®, KaVoARCUSdigma®, or Condylocomp® LR3. Because of their versatility and accuracy of 0.1mm [21] these devices are widely used in scientific research [22-28]. The main hindrance is a high purchase and operating cost.

Another aspect of TMJ diagnostics is pain measurement. Subjective levels of pain are most often tested with Visual Analogue Scale (VAS) or Numeric Pain Rating Scale (NRS) [18,29].

Although algometry is considered to be an objective method, it was not used very often [30,31].

Assessment of joint crepitus occurrence and intensity was based on history, palpation and auscultation with a stethoscope [32]. Research evaluating those two methods in the context of disc disorders detection showed poor reliability and high percentage of false positive results [33].

Based on the aforementioned results, researchers sought alternative tools for obkectively evaluating crepitus, thus the introduction of vibroarthrography (VAG).

VAG is a qualitative method used for all synovial joints. It is based on vibroacoustic signal registration, generated by a relative movement of bones within the joint. So far it has been demonstrated that hyaline cartilage present in healthy joints has the ability to minimize the level of friction expressed by the coefficient of kinetic friction (~0.002–0.004). The described phenomenon ensures optimal quality of movement and low vibroacoustic signal emission. Any changes compromising the biomechanical environment inside the joint lead to deterioration in its arthrokinematics (i.e. joint play) manifested in magnifying signal intensity.

Joint Vibration Analysis (JVA) together with compatible software (BioPAK Measurement System, Bioresearch Inc., Milwaukee, USA) is the most common vibroacoustic device used for TMJ [33,35-39].

When analyzing the issue of measurement and registration repeatability, it has to be emphasized that contrary results have been published over the years [33,36,38-40].

Mier [33] indicated high subjectivity of vibroacoustic signal analysis as a direct cause of poor reliability among examiners. Furthermore, he showed a trend in the field of interest where many authors described technologies of signal recording; however, only one paper assessed VAG accuracy, while none of them rated their diagnostic value.

On the other hand, Zhang et al. [36] and Bakalczuk et al. [38] clearly showed VAG reliability to be good and excellent based on Intraclass Correlation Coefficient (ICC) – 0.75 and 0.738–0.907, respectively. The authors agreed on the need for further studies regarding diagnostic value of VAG and identification of characteristic waveforms for different subgroups of TMD patients.

Sharma et al. [39] published a systematic review which analyzed diagnostic value of JVA device in the context of TMJ pathologies detection. Most of the fifteen papers included in the review presented methodology limitations which prevented the authors from demonstrating strong enough evidence about JVA as a reliable diagnostic tool.

In another study, Sharma et al. [40] avoided the methodological mistakes identifies in their 2013 paper. The researchers obtained excellent reliability and marked JVA’s diagnostic validity as high. They also proposed a composite score, which can be used to discriminate between normal and displaced disc position.

The selection of imaging types is mostly based on the potentially problematic structure. Recommendations for imaging are grouped by the following pathologies [41,42,43,44]:

• •

  disc – MRI, USG, arthrography

• •

  joint (arthritis or arthrosis) – CT, X-ray (dental panoramic radiograph).

The international RDC-TMD Consortium proposed interpretation guidelines for both unification purposes and also as an attempt to objectify the clinical reasoning process.

The findings of numerous studies have demonstrated that CT is the best tool for joint imaging (ĸ=0.71), whereas radiography was the poorest technique (ĸ=0.16) [41]. MRI is the best method for disc pathologies detection (ĸ=0.78– 0.94) [41], which has been confirmed by a number of other studies [42,43,44].

Further studies showed the necessity for further evaluation and update of these guidelines (especially for the disc) regarding their influence on the pathology, diagnostic value and the cost of the procedure [45].

Ultrasound (US) has been shown to be useful as a supplemental examination especially in non-standard cases. Its validity and specificity is considered as good to excellent. Dynamic examination performance is its biggest advantage [46].

Strøm et al. [47] presented a similar conclusion regarding US as a supplemental method, claiming that the obtained results cannot be treated as decisive when excluding disc pathology compared to MRI.

Quality of life (QOL) issues can be tested on three levels – general, characteristic of the disease and characteristic of the dysfunctional organ.

The literature shows a relatively small number of questionnaires measuring QOL on the general level. The Oral Health Related Quality of Life (OHRQoL) is the most commonly used questionnaire regarding oral cavity health in TMD population. The authors demonstrated that TMD patients suffered from lower QOL significantly more often than their controlled peers [48,49,50,51].

According to the World Health Organization (WHO), health is defined as a state of complete physical, mental and social well being and not merely the absence of disease or infirmity. OHRQoL measures the influence of oral health on the aforementioned aspects of health in general.

Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) is an example of a questionnaire targeted at specific diseases i.e. temporomandibular disorders. The classification was proposed by the International RDC-TMD Consortium for the needs of scientific research in dentistry (International Association for Dental Research). The role of RDC/TMD is to recognize patient’s symptoms and assign them to one of two axis (groups of pathologies). RDC/TMD questionnaire will be described in more detail later in this paper.

Jaw Functional Limitation Scale (JFLS) [52,53] with its two versions (8 and 20 items) as well as Mandibular Function Impairment Questionnaire (MFIQ) [54] are examples of organ-specific questionnaires.

JFLS-20 consists of 20 questions regarding three groups of activities – chewing, range of motion in the sagittal plane and verbal/emotional expression [53,55]. There is no official translation nor cultural adaptation of this tool in Poland.

MFIQ is made up of 17 questions assessing subjective perception of the effects of mandible dysfunction on such activities as speech, food and drink intake, laughing or yawning. The patient’s task is to mark a level of difficulty on a five-step scale, where the total score indicates severity of dysfunction from severe, through moderate to low.

Chinese and Portuguese authors who translated and culturally adapted MFIQ reported its diagnostic value as good and excellent [56,57]. As in the case of JFLS–20, official translation or cultural adaptation does not exist in Poland.

Less frequently used questionnaires are as follows: Fonseca’s Questionnaire, Helkimo Index, Symptom Intensity Scale (SIS) or TMD Disability Index (Steigerwaldi Maher). Most of them have been replaced by RDC/TMD, which is the most complex and researched protocol available for TMD.