The temporomandibular opening index (TOI) in patients with closed lock anda control group with no temporomandibular disorders (TMD): an initial study

Mandibular movement may be assessed by measuring maximum mouth opening. Thi s is a linear measurement from the maxillary to the mandibular incisal edge and is affected by gender, age and ramus length. It cannot be used to clas sify patients. The temporomandibular opening index (TOI) appears to be inde pendent of these variables and has been shown to differ for different categ ories of patients with temporomandibular disorders (TMD). This study examin ed the TOI in a group of 11 patients with closed lock and a control group o f 11 individuals with no signs or symptoms of TMD. The group with closed lo ck had a significantly different TOI from that of the control group (P < 0. 001) according to the Mann-Whitney U-test. This suggests that the TOI may h ave greater diagnostic value than linear mouth opening.