What can human experimental pain models teach us about clinical TMD?

Human experimental pain (HEP) models applied to the orofacial area have been widely used over the last decades and several reviews are available on the interaction between HEP and jaw-motor function. In this selective review some of the possibilities and limitations with HEP models are discussed based on the current experience with HEP models. For example, it is appropriate to consider how closely HEP models may mimic the clinical phenomenon, i.e., do they represent a reasonable "proxy" of temporomandibular disorders (TMD) and what can HEP models offer for the understanding of jaw-motor function in relation to painful TMD conditions. Finally, are there any clinical implications of the knowledge derived from HEP studies? This present review suggests that HEP models, indeed, are valuable and can provide clinically relevant information by serving as a bridge between basic animal experiments and studies in pain populations; however, there are several caveats to this suggestion which needs to be acknowledged.     

What skeletal and dental characteristics do TMD patients have in common?

The purpose of this study was to determine if there are any common skeletal or dental characteristics among TMD patients that may be of diagnostic value. Thirty charts of orthodontic patients with pretreatmentTMD symptoms were selected at random.Gender, age, sex, ethnicity, SNA, SNB, ANB,Wits, interincisal angle, missing teeth, prior orthodontic treatment, crossbites, Angle's Class and maxillary and mandibular length were tabulated and analyzed for patterns. The results revealed a clear pattern of excessive mandibular length relative to maxillary length.     

Glutamate-evoked jaw muscle pain as a model of persistent myofascial TMD pain?

OBJECTIVE: Compare pain-related measures and psychosocial variables between glutamate-evoked jaw muscle pain in healthy subjects (HS) and patients with persistent myofascial temporomandibular disorder (TMD) pain. DESIGN: Forty-seven female HS and 10 female patients with persistent myofascial TMD pain participated. The HS received an injection of glutamate into the masseter muscle to model persistent myofascial TMD pain. Participants filled out a coping strategies questionnaire (CSQ), the symptom checklist 90 (SCL-90) and McGill pain questionnaire (MPQ). Pain intensity was assessed on an electronic visual analogue scale (VAS). Pain-drawing areas, numerical rating scale (NRS) scores of unpleasantness, pressure pain thresholds (PPTs) and pressure pain tolerance (PPTOL) were measured. Unpaired t-tests and correlation tests were used for analyses. RESULTS: The groups were significantly different when comparing the CSQ scores of control, decrease, diverting attention, increase of behavioural activities and somatization. The peak VAS pain, NRS of unpleasantness and MPQ scores were not significantly different between groups, but PPT and PPTOL were significantly lower in the TMD patients. Significant positive correlations were found in the TMD patients between peak VAS pain and CSQ catastrophizing score and SCL-90 somatization. The scores of PPTs and PPTOLs, in patients showed positive correlations with CSQ reinterpreting pain sensations scores and PPTs correlated with CSQ praying/hoping scores. CONCLUSIONS: Glutamate-evoked pain responses in HS and persistent myofascial TMD pain have similar sensory-discriminative and affective-unpleasantness components but differ in psychosocial features. This study suggests that experimental designs based on glutamate injection into muscle can provide an appropriate model for elucidating persistent myofascial pain conditions.