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Purpose: This study was an in in-vitro study conducted to compare the stress distribution pattern in implant retained maxillary obturators with three different attachment systems with the aid of three dimensional finite element analysis.Methods: CT scan was made for a patient with hemi-maxillectomy defect. The CT scan file was exported to a personal computer with Materialize Mimics 10.01 program (Materialize, interactive medical image (Materialize Leuven, Belgium). Mimics were utilized to modify the CT scan of the maxilla to construct 3-D model with Solid Works, Concord, Massachusetts, USA) for finite element stress analysis. All components of the models were constructed thereafter, superimposed till construction of maxillary obturator models. Three implants were inserted in the alveolar bone on the intact side. Ball & Nova-lock locator/ bar attachment systems were simulated according to their structural configurations. A static load of 100 N load was applied vertically & obliquely on the defect side. ANSYS program (Canonsburg, PA, USA) was utilized to solve the problems, The resultant Von Misses stresses in bone surrounding implants were evaluated and compared in the 3 studied models.Results: The highest Von Misses stresses were found in cortical bony layers around the implant adjacent to defect & the least stresses at the area of 3rd implant. Nova-lock retained implant obturtors had recorded the least Von Misses stresses (20. 479 &21.675 Mpa) in comparison to Ball (40.762 & 41.488 Mpa) & locator bar attachment systems (43.526 & 47.203 Mpa) under vertical & oblique load application respectively. All models had shown the highest stresses on oblique load application on the defect side.Conclusions: Within the limitations of this study various conclusions could be drawn: The load direction has more important role than the attachment type in stress distribution pattern in implant retained maxillary obturators.Nova- lock attachment system may induce the least stresses onto implant/ bone interface followed by Ball & locator bar attachment systems.The Locator/ bar attachment may allow better stress distribution in implant retained maxillary obturators than other Bar systems.

Background: Accuracy of implant placement using computer designed surgical guides ascompared to conventional laboratory-processed guides has been investigated by many researchers.However there are no published articles on the effect of placing dental implants using computerdesignedguides on bone height changes around the implants as compared to those placed usingconventional guides.Purpose: The aim of this study was to compare between bone height changes around dentalimplants placed using stereolithographic surgical guides versus conventional guides in completelyedentulous patients rehabilitated with 2-implant supported mandibular overdentures opposed byconventional maxillary complete dentures.Methods: This parallel randomized controlled trial (RCT) included 14 participants (age rangingfrom 50-60) with a mean age of 56.7 years who were selected based on specific inclusion criteria.Conventional maxillary and mandibular compete dentures were constructed for all participants whowere then randomly divided into two equal groups (7 participants in each). All participants receivedtwo implants, 3.5 mm in width and 10 mm in length, in the mandibular inter-foraminal areas(canine region). However implants in Group I (Control) were placed using a conventional surgicalguide while implants in Group II (Experimental Group) were placed using a stereolithographicsurgical guide. After implants’ osseointegration, all participants received ball attachment- retainedmandibular overdentures. Bone height changes around the installed implants were evaluated withthe aid of cone beam computed tomography (CBCT) scans. Measurements were recorded threetimes at 0 months, 6 months and 12 months after overdenture insertion and the changes werecalculated and statistically analysed. Statistical significance was set at 5 %.Results: All participants attended all follow up visits with no drop outs. None of the implantswas lost presenting a 100% survival rate for both groups. After 6 months post-insertion, the meanbone loss was 0.32mm and 0.31mm for groups I and II respectively. After 12 months post- insertion,mean bone loss reached 0.61mm and 0.49mm for groups I and II respectively. There were nostatistically significant differences between the two groups at both (6 and 12 months) follow-upperiods.Conclusion: Bone height changes around implants placed with stereolithographic surgicalguides versus conventional guides were statistically insignificant with no relevant superiority ofone guide over the other. Both surgical guides provided clinically successful implant treatment witha 100% survival rate for both groups during the one-year follow-up period.

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