Anterior temporalis and masseter muscle activity with different centric relation locating methods: A randomized cross-over trial

The aim of the study was to evaluate anterior temporalis and masseter muscle activity and patient satisfaction after using the Leaf Gauge (LG), Lucia Jig (LJ), and Anterior Deprogrammer (AD) to locate centric relation (CR) in healthy adults. The research question was: "Which of the investigated CR locating methods will yield the lowest muscle activity, and the highest patient satisfaction score?". Thirty healthy adults were randomly allocated to three sequences for implementing tested methods, with a 24-hour wash-out period. Surface electromyography (Myowise) measured muscle activity at rest (R), maximum intercuspal position (MIP), and after locating CR. Patient satisfaction was assessed using a visual analogue scale (VAS) and a questionnaire. Friedman's test followed by Dunn's test compared muscle activity and VAS scores between methods (α = 0.05). Inter-method comparison showed no significant differences in anterior temporalis activity. Intra-method comparison showed that CR muscle activity was lower than MIP but higher than rest for all methods (P < 0.001 for right, left, and bilateral means). For masseter muscle activity, AD showed significantly lower muscle activity compared to LG and LJ. LJ and AD activity at CR was comparable to rest and significantly lower than MIP. LJ was rated the most comfortable, while LG presented the least comfort (P = 0.018). AD and LJ effectively reduced muscle activity when used to locate CR. LJ is simple and comfortable for healthy adults, while LG has limited versatility. Low muscle activity while locating CR is essential, as elevated muscle activity might compress the articular disc and alter the position. clinicaltrials.gov Identifier: NCT06095856, registration date: 2023-10-11.