International Journal of Science and Research (IJSR) ISSN: 2319-7064 SJIF (2019): 7.583 Volume 10 Issue 3, March 2021 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Bar Versus Locator Implant Assisted Maxillary Overdentures Opposing Two Implants Retained Mandible Overdentures: A Study of Chewing Efficiency and Electromyographic Activity Adel M. Ahmed 1 , Ahmed A. Habib 2 , Radwa M.K.Emera 3 , Abdallah M.I.Salem 4 , Mohamed T. El-sayed 5 1 PhD candidate, Prosthodontics Department of Prosthodontics, Faculty of Dentistry – Mansoura University 2 Professor of Prosthodontics Department of Prosthodontics, Faculty of Dentistry – Mansoura University 3 Associate Professor of Prosthodontics Department of Prosthodontics, Faculty of Dentistry – Mansoura University 4 Lecturer of Removable Prosthodontics, Faculty of Dentistry, Mansoura University 5 Lecturer of Neurology, Department of neurology, Faculty of Medicine Mansoura University Abstract: Two implants retained mandibular overdenture opposing conventional maxillary complete denture may induce a combination syndrome, implant supported maxillary overdenture was indicated to avoid this phenomena. Selection of splint or solitary attachment for this issue is a matter of debate.This study aimed to compare and evaluate chewing efficiency and electromyographic activity of patients wearing implant assisted maxillary overdentures by bar versus locator attachments opposing two implants retained mandibular over dentures. Six completely edentulous healthy male patients were selected for this study .After three months of conventional complete denture construction, the electromyographic (EMG) activity of masseter muscle and chewing efficiency measured by unmixed fractions of (UF) of double colored chewing gum were evaluated(Group I): ( control group). Two implants were installed bilaterally in the mandibular canines areas; and four implants were installed in the maxilla. After the osseointegeration period, bar assisted maxillary overdenture was constructed against mandibular locator retained overdenture and the (UF) and EMG were evaluated after three months (Group II) . After two weeks resting period, the bar attachments in was replaced by locator attachments (Group III) and the evaluation was done after three months of denture insertion. After two weeks resting period , the bar in group II was replaced by locator and the locator in group III was replaced be bar attachment to evaluate the (UF) and EMG after three months of replacement.Statistically significant difference in (UF) and ( EMG) activity of masseter muscle between implant assisted overdenture and conventional complete denture groups. 2- A statistically insignificant difference in(UF) and ( EMG) activity of masseter muscle between bar and locator assisted maxillary overdentures. Four implant assisted maxillary overdentures opposed by two implant retained mandibular overdentures significantly improve the chewing efficiency and EMG activity of masseter muscle compared with conventional complete dentures regardless the attachment design( splint bar or solitary locator) used for the maxillary overdenture. Keywords: Chewing Efficiency, Electromyographic, Attachments, Overdentures 1. Introduction Poor retention and stability of conventional complete dentures impedes adequate oral function, lowers bite forces and changes in the masticatory functions have been reported widely[1].Owing to the reduced surface areas of supporting tissues and the inherent compromised retention and stability of conventional mandibular complete denture, two implants retained mandibular overdenture is considered the minimal standard of care to provide stable and retentive denture that can improve oral function and patient satisfaction. Patients wearing mandibular two implant-retained prostheses opposed to maxillary conventional complete dentures may face degenerative tissue changes similarly seen in the classic combination syndrome [2-4]. These changes include: loosening of the maxillary denture, loss of posterior occlusion, increased anterior occlusal pressure and anterior maxillary bone loss with flabby tissue formation [5- 7]. The mandibular implants encourage the patients to incise anteriorly with maximum bite force creating a similar biomechanical situation to the distal extension removable partial denture [2]. In such situations, it is recommended to assist the maxillary denture with four implants to resist these undesirable effects. Two attachment systems are recommended for the four implants assisted maxillary overdenture including; the splint bar and solitary attachments. Splint bar provides greater retention and stability, resists lateral and rotational movement, enabling better force balance by its splinting effect and can correct implant disparalellisms [6]. Locator solitary attachments are widely used due to low profile height [7], self-alignment, dual retention mechanism (inner and outer) [8] and correction of problems related to implant angulation [7, 8]. In addition, repair and replacement are easy and fast [7]. When attachments used for implant overdentures, the activity of masseter muscle significantly were increased [9].It was agreed that improvement of oral function depends on the degree of retention and stability of the denture which are directly related to the design of the attachment system [10, 11]. Abdelhamid et al [11], observed statistically Paper ID: SR21313111532 DOI: 10.21275/SR21313111532 908