Effect of Sagital Incisal Guidance Inclination on the Condylar Movements and EMG Activity in Masticatory Muscles

Kakiyama Hirofumi, Takei Junji, Shimizu Shinichiro, Matsumoto Atsushi, Hanashima Miwa, Sato Sadao

doi:10.14399/jacd1999.24.66

We examined the effect of different inclinations of anterior incisal guidance on functional condylar movements (open/close, protrusion/retrusion, laterotrusion, anterior grinding, speaking, and mastication) and on the electromyographic (EMG) activity in the anterior part of the temporalis, the masseter, and the anterior belly of the diagastric muscle. The subject was a 37-year-old male whose upper four anterior teeth were planed to prepare them to receive a new prosthodontic appliance. The axiographic condylar movements showed that there were no significant changes in functional movements except in speaking and in masticating. For both of these functions, we observed a transverse displacement and reduced movement when the incisal guidance was steep. We analyzed a set of EMGs and observed that the activity of the anterior belly of the digastric muscle increased in the event incisal guidance was more than 15° steeper than the sagital condylar inclination (SCI) . Functional condylar movements and the EMG activity were relatively stable and the patient was comfortable when the incisal guidance was 10° steeper than the SCI. Based on these findings, we concluded that the incisal-guidance angle should be about 10° steeper than the SCI.

Effect of Sagital Incisal Guidance Inclination on the Condylar Movements and EMG Activity in Masticatory Muscles

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