mesenchyme cell layer remains throughout life, this can respond, as a result of ‘irritation’, to produce new tissue. Therefore, it is not uncommon for a patient who presents with osteoarthrosis of the TMJ to enter a phase of acute symptoms followed by a plateau stage followed by improvement of symptoms as remodelling and resurfacing of the condyle progress.
The clinical symptoms of osteoarthrosis include pain localised to the joint and limited movement which is worse with function. The clinical joint sound is crepitation, which is a grating or crunching sound from the joint that indicates a loss of the smooth articular surfaces. Crepitation can emanate from the articulating surfaces or the disc.
Disc displacement
A further pathological change is related to disc displacement (DD) if the intra‐articular disc is anteromedially displaced. The highly innervated posterior part of the bilaminar zone, which contains elastic fibers can, with the passage of time, undergo morphological changes that render this part of the disc more fibrous. It has been reported that cartilaginous changes can also occur in this situation, which is associated with long‐standing DD when the initial symptoms would have included pain due to compression of this innervated tissue. The pain gradually diminishes as the tissue undergoes the aforementioned morphological changes of conversion from innervated elastic to less innervated fibrous tissue.
Myofascial pain
In the case of myofascial pain, there is no readily demonstrable histopathology.
Diagnoses of TMDs
There is a multitude of classifications based upon the aetiology, clinical signs and symptoms, or anatomy; all have their weaknesses. Those classification systems that define the different kinds of TMD and utilize the history and examination provide the most help to the general dental practitioner as well as to the researcher.
The gold standard classification system for research is currently the TMD research diagnostic criteria (RDC/TMD).
This is a dual axis classification of TMD pain in a research tool which aims to provide a more rational, scientific basis for TMD diagnosis.
Axis 1: a set of opertionalised RDC for use in evaluating and investigating masticatory muscle pain, DD and degenerative diseases of the TMJ.
Axis 2: a set of operational RDC to assess chronic pain, dysfunction, depression, non‐specific physical symptoms, and orofacial disability.
The RDC categorise TMD criteria into three groups according to the common factors among conditions.
GROUP I: Muscle disorders
1 I.a Myofascial painCriteria: Reported pain in masticatory musclesPain on palpation in at least three sites, one of them at least in the same side of the reported pain.
2 I.b Myofascial pain with limited openingCriteria: Myofascial painPain‐free unassisted opening <40 mm and passive stretch ≥5 mm.
GROUP II: DDs
1 II.a DD with reductionCriteria: No pain in the jointReproducible click on excursion with either opening or closing clickWith click on opening and closing (unless excursive click confirmed):Click on opening occurs at ≥5 mm interincisal distance than on closingClicks eliminated by protrusive opening
2 II.b DD without reduction with limited openingCriteria: History of locking or catching that interfered with eatingAbsence of TMJ clickingUnassisted opening (even painful) ≤35 mm and passive stretch ≤4 mmContralateral excursion <7 mm or uncorrected ipsilateral deviation on opening
3 II.c DD without reduction without limited openingCriteria: History of locking or catching that interfered with eatingThe presence of TMJ sounds excluding DDR clickingUnassisted opening (even painful) >35 mm and passive stretch >4 mmContralateral excursion ≥7 mm 5. Optional imaging (Arthrography or MRI) to confirm DD
GROUP III: Other common joint disorders
1 III.a ArthralgiaPain and tenderness/no crepitationCriteria: Pain on TMJ palpation either laterally or intra auricularSelf‐reported joint pain with or without jaw movementAbsence of crepitus, and possibility of clicking
2 III.b OsteoarthritisInflammatory conditionPainCrepitation and/or changes on radiographCriteria: Pain as for arthralgiaCrepitus on any movement or radiographic evidence of joint changes
3 III.c OsteoarthrosisDegenerative disorderNo painCrepitation and/or changes on radiographCriteria: Crepitus on any movement or radiographic evidence of joint changesNo reported joint pain nor pain on any movement
Further Reading
1 Avery, J. (2006). Essential of Oral Histology and Embryology: A Clinical Approach, 3nde. St Louis, MO: Mosby.
2 Gage, J.P. (1989). Mechanisms of disc displacement in the temporomandibular joint. Aust Dent J 34: 427–436.
3 Gray, R.J., Davies, S.J., and Quayle, A.A. (1994). A clinical approach to temporomandibular disorders. 1. Classification and functional anatomy. Br Dent J 176: 429–435.
4 Rees, L.A. (1954). The structure and function of the mandibular joint. J Br Dent AssocXCVI: 126–133.
5 Schiffman, E., Ohrbach, R., Truelove, E. et al. (2014). Diagnostic criteria for temporomandibular disorders (DC/TMD) for clinical and research applications: recommendations of the international RDC/TMD consortium network and orofacial pain special interest group. J Oral Facial Pain Headache 28: 6–27.
3 Articulatory System Examination
Range of movement
Examination of the range of movement involves examining the interincisal opening, both pain‐free and maximum (Figure 3.1) and lateral excursions of the mandible.
Figure 3.1 Measurement of incisal opening.
(M. Ziad Al‐Ani, Robin J.M. Gray.)
