A 2-year electromyographic study of patients with an immediate complete upper and a partial lower denture

A longitudinal electromyographic (EMG) investigation was performed on thirty subjects provided with an immediate complete upper and a partial lower denture. Electromyographic recordings in maximal clench, light tapping and postural position were obtained from the anterior temporal and masseter muscles before final extractions and 7 weeks, 6 months, 1 year and 2 years after denture insertion. The maximal clench activity of the jaw closing muscles showed an average tendency to decrease upon insertion of the dentures, but thereafter significant increases in mean voltages were observed during the first year of denture wear. During the second year no significant changes in EMG clenching force were noted. At the 2-year stage most of the muscles showed significantly greater clench activity than at the post-insertion stage, but did not exceed the pre-extraction level. The jaw muscle activity in light tapping showed no significant mean changes during the observation period. The postural activity tended to decrease during the period of denture wear, the decrease being significant for some of the muscles at the 2-year stage.