Reliability of measuring active mandibular excursion using a new tool: the Mandibular Excursiometer.

Measurement tools improve the reliability and validity of measurement. The purpose of this study was to test the intrarater and interrater reliability of a new instrument, the Mandibular Excursiometer, for measuring mandibular excursion on the X and Y axis in the coronal plane during active opening. Two raters measured 12 volunteers. Four ratio, three nominal, and one ordinal scale measurements were analyzed using percent agreement. The Mandibular Excursiometer had high intrarater reliability for vertical opening (100%) and for the categorization of the presence or absence and direction of lateral deviation at the maximum point during opening (92-100%). Overall, moderate intrarater reliability existed for the quantity of lateral deviation at the maximum point during opening (66-83%), presence and direction of deflection (66-83%), presence of deviation or deflection during opening (66-83%), and in which third of opening the maximum point of lateral deviation occurred (66-83%). Moderate interrater reliability existed for vertical opening (75%) and for the classification of presence and direction of lateral deviation at the maximum point during opening (91%). All other measurements had low reliability. The Mandibular Excursiometer had higher intrarater and interrater reliability for measuring deviation and deflection during active mandibular opening than observation alone, based on a comparison with the literature. This measurement can assist in documenting progress while treating patients with TMJ disorders.