The effect of setting-up of artificial teeth in the neutral zone on EMG and Occlusal force equilibration in mandibular two implant overdentures

Purpose: This study was conducted to evaluate the effect of neutral zone concept on EMG
& % occlusal force distribution in mandibular implant overdentures.
Methodology: Twelve completely edentulous patients were selected from the out-patient clinic, Faculty of Dentistry, Beni-suef University. Patients were randomly divided into Group (I) & (II) according to the way of artificial teeth set-up in the complete dentures. Group (I): Patients had received mandibular two implant overdenture constructed with the artificial teeth set-up over the crest of ridge. Group (II): Patients had received mandibular two implant overdenture constructed according to the neutral zone concept.
Two implants were installed in areas of mandibular canines according to the two stage surgical protocol. Ball attachments were inserted onto the implants after osseointegration. The previously constructed dentures were used for direct pick up procedures. Dentures of both groups were inserted into the patients’ mouth.
Evaluation of EMG: Evaluation of EMG activity of the Masseter and Temporalis muscles was evaluated during clenching, chewing of soft food, chewing of hard food at denture insertion and one month after.
Evaluation of Occlusal force Equilibration: The % of occlusal force distribution was evaluated for the dentures in the two studied groups with the aid of T-Scan device at insertion after occlusal adjustment by the articulating paper; two weeks after denture insertion and one month after T- scan analysis.
Conclusions: Within the limitation of the present study the following was concluded
Implant overdentures constructed with Neutral Zone concept may have better occlusal force distribution on the denture surfaces and better EMG records than dentures with the conventional set-up of teeth.