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Statement of problem:The improvement of the oral function of implant retained mandibular overdentures may depend on the degree of retention and stability of the denture and thus on the type of attachment.Purpose of the study: The aim of the study was to evaluate of the effect of two different attachment designs with different resiliency of implant retained mandibular overdentures on the masticatory function.Methods: Twelve completely edentulous patients were selected for the study each patient received two interforaminal implants in the canine areas of the mandible using standardized two-stage surgical technique. Implants were left unloaded for three months. Six of the patients received implant overdenture with ball and socket attachment first then the same denture was modified to receive positioner attachment. The other six patients received the implant overdenture with positioner first then the same denture was modified to receive ball and socket. Muscle activity and maximum muscle activity of both temporalis and masseter muscles were recorded during chewing cake, peanut and during clenching with using the electromyography.Results: Muscle activity and maximum muscle activity showed higher results with the positioner attachment in both masseter and temporalis muscles although the difference was not statistically significant. Masseter muscle showed higher results in both types of the attachments. Conclusion:The positioner attachment might be selected over Ball & Socket attachment when designing a two implant retained mandibular overdentures since it is more superior from the masticatory function point of view.

INTRODUCTION: Implant assisted prostheses provide a higher degree of patient satisfaction than traditional prostheses. However, severe atrophy of the edentulous maxilla and maxillary sinus pneumatization may reduce the available bone in the posterior region for a safe and reliable implant-supported dental rehabilitation. Tilted implants in the anterior region of the maxilla were suggested to be useful in the treatment of posterior atrophic edentulous maxilla that allows the use of longer implants to gain more stability. This may preclude the use of conventional Implant overdenture abutments, requiring the use of divergence correcting attachments. OBJECTIVES: The aim of the present study was to clinically evaluate the effect of the use of Smart Box accompanied with OT Equator attachment in retaining the inclined implant assisted overdenture for atrophic maxilla. MATERIALS AND METHODS: Ten patients with posterior atrophic maxilla and partially dentate mandible with posterior occlusal stops were allocated for this study. For each patient, an implant assisted maxillary overdenture was fabricated using minimally invasive flapless surgical technique. Four implants were placed while the most anterior implants were axial and the most posterior implants divergent to 25 degrees using CAD/CAM surgical guide. The implants were loaded immediately by OT EQUATOR and smart box attachment retained maxillary overdenture. Each patient was evaluated clinically at the final prosthesis insertion (baseline), three, six and nine months post insertion. Modified gingival index (MGI), Clinical attachment Level (CAL) and Peri-implant probing depth (PIPD) are the clinical parameters that were evaluated. RESULTS: MGI, CAL and PIPD revealed significant increase in both tilted and axial groups throughout the evaluation period intervals. Tilted implants group showed significantly greater increase in all parameters when compared with the axial group. CONCLUSIONS: Within the limitations of this study, it can be concluded that combination of axial and tilted implant assisted overdenture is a predictable treatment option in case of severely atrophic posterior maxillae.