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Statement of the problem: The use of narrow diameter implant to retain an implant overdenture could be the treatment of choice to restore resorbed mandibular ridge, however its success or failure depends on the amount of stresses transferred to the surrounding bone via the selected attachment system. The goal of this study was to evaluate the stress distribution around two narrow- diameter titanium-zirconium implants retaining mandibular overdenture with novel Novaloc attachment system in comparison with traditional locator attachment using 3 D finite element analysisMaterials and methods: Two 3D finite element models were prepared simulating completely edentulous mandibular ridge with complete overdentures supported by two narrow diameter implants in the canine region. Model 1,represented implants with locator attachment while Model 2, represented implants with Novaloc attachment. The models’ components were created on a commercial CAD/CAM package then imported to finite element software. Load of 100 N was applied on molar area of the mandible vertically and oblique Load of 50 N at 30o and 45o angle. Results: Within the limitations of this research, similar deformations and stresses distributions were reported in the bone and implant complex with a little more stresses in the Novaloc system. All values found were within acceptable physiological limits of the studied parts. Stress received by the PEEK matrix of the Novaloc attachment was significantly less than that of the locator nylon cap. Conclusion: Within the limitations of this in-vitro study it may be concluded that locator attachments may provide little less stress on the bone and implant complex in implant retained overdenture than did the Novaloc attachment. However, the lifetime of the flexible caps may be longer for Novaloc system in comparison to locator ones.

Purpose: Success and safety of dental implants requires accurate treatment planning andprecise implant placement. There should be no deviation between the virtually planned implantposition and the actual implant position after the implant installation regardless the technique ofconstruction of the surgical-guide. So this study was to evaluate and compare the accuracy of twodifferent CAD/CAM surgical guides in placement of all-on-4 implants. Materials and methods:A prospective randomized controlled double blind clinical study was carried out, in which twentyfour implants were placed in 6 edentulous patients. Patients were randomly allocated into one of thetwo groups: control group where surgeries were done using digital light processing (DLP) surgicalguidesand study group where implants were placed using selective laser sintering (SLS) surgicalguides.Each patient received 4 implants in the anterior part of the mandible, 2 axial implants in thecenter and 2 tilted implants at the distal ends. CBCT were taken to the implants after the surgery andthe actual implant positions were compared to the planned implant position. The deviation betweenthe planned and actual implant positions were compared between the 2 techniques of surgical guideconstructions. Results: The results of comparison between the two groups showed a statisticallysignificant difference for all comparisons, with the SLS fabricated guides showing higher deviationfrom control than those fabricated by the DLP printer.Conclusion: Although the computer manufactured surgical guides simplifies surgery and helpin optimal implant placement, there is still evidence of degree of deviation from the planned implantspositions in both of the surgical guides, particularly the SLS fabricated guides so a safety zone so asafety zone is recommended during planning to avoid to avoid critical anatomical structures.

Objective: The purpose of this RCL was to evaluate bone height changes around hybrid implants in three implant- retained mandibular overdenture with locator attachment.Materials & Methods: Ten completely edentulous male patients were enrolled in this study. Preoperative Cone beam computed tomography (CBCT) had been made to evaluate bone height & density in areas for implant installation. Patients had received three hybrid implants installed in midline & mandibular canine areas following flapless technique. Implants were early loaded; two weeks after implant installation. Overdentures were functionally fitted onto the locator attachment of the hybrid implants by direct pick-up technique.Evaluation: Bone height changes were evaluated with the aid of CBCT at the time of implants’ loading, six months and twelve months later. Mesial & distal crestal bone heights were calculated from reconstructed corrected sagittal views.Results: The results had revealed that there was no significant difference in peri-implant bone level throughout the follow-up periods on comparing the three implant sites. However, there was slightly higher bone resorption around the distal implants than the midline ones.Conclusions Three implant retained overdentures with locator attachments may preserve peri-implant bone in the anterior mandibular area. Midline implant in three implant overdentures may not be subjected to more stresses than the two distal implants