Effects of Implant/Tissue Support of Dentures on Muscle Effort

Objectives: Improvements in masticatory performance have been found with the provision of maxillary and mandibular overdentures and fully implant-supported dentures compared to conventional dentures. The purpose of this study was to determine if the increased implant support of maxillary and mandibular prostheses significantly alters the muscle effort and jaw movements needed to achieve the improvements in masticatory.

Methods: Masseter EMG activity and jaw movements were recorded during standardized masticatory performance tests on the right and left chewing sides for 16 edentulous male participants with complete conventional dentures (CD) that subsequently were treated with maxillary and mandibular overdentures retained by two osseointegrated anterior implants splinted with a Hadar bar (IOD), followed by a mandibular fixed bridge supported by 5-6 implants and an implant-supported (6 implants) maxillary overdenture (ISD). Tests were completed with the original CDs, four months after delivery of the IODs and four months after delivery of the implant-supported dentures. Statistical comparisons were made for the change in EMG activity and jaw movements between denture conditions with ANOVAs for each of two foods, peanuts and carrots.

Results: Mean ipsilateral EMG activity (μVs) with CDs for peanuts (12.7+/-4.8) and carrots (12.4+/-4.3) were comparable (p>0.79) to scores with IOD (13.2+/-4.3; 12.3+/-4.2) and ISD (13.5+/-4.8; 12.4+/-4.1). Contralateral total and peak EMG activity for both muscles did not differ across denture conditions (p>0.42). Mean masseter contraction duration for carrots was significantly longer with CD compared to IOD and ISD (ipsilateral, F=6.1;p=0.006; contralateral, F=4.8;p=0.016). No significant differences were found in vertical, lateral and anterior/posterior jaw movements between denture conditions (p>0.53).

Conclusions: While both overdentures and fully implant-supported dentures produced significant improvement in masticatory performance compared to the original CDs, no additional muscle effort was utilized to achieve the superior performance.

Supported by DVA Medical Research Service.