If the design and funding of an epidemiologic study provide an opportunity to conduct clinical examinations of subjects, cases can be defined on the basis of clinical signs, or on the basis of a combination of clinical signs and symptom report.

There are a number of classification schemes used in epidemiologic studies of TMD that incorporate clinical signs, including:

• The Helkimo Index (Helkimo, 1974);
• The Craniomandibular Index (CMI, Friction and Shiffman, 1986); and
• The Research Diagnostic Criteria for TMD (RDC/TMD, Dworkin and LeResche, 1992).

The Helkimo Index and the CMI produce summary scores for the severity of clinical signs, and thus a cut-off score must be decided on in order to formulate a case definition if one of these measures is used.

The RDC/TMD takes a different approach. Subjects are assigned specific TMD diagnoses (e.g. myofascial pain, arthralgia) if particular combinations of signs and symptoms are present (i.e. there are algorithms for diagnosis). The scheme is non hierarchical, so subjects can receive more than one diagnosis. The RDC/TMD also provides standardized examination criteria of known reliability, so that findings from different studies using the RDC/TMD can be directly compared.

Table 12.1 below lists the clinical signs on which case definitions are most often based, along with estimates of the level of reliability of measurement that can be achieved by trained and calibrated examiners assessing each of these signs.

A thorough review of the issues involved in diagnosis and classification of TMD is beyond the scope of this chapter. These are discussed elsewhere (Drangsholt and LeResche, 1999).

Page 17 of 44
Previous Section

Next Section