الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
While many studies had focused on the topic of implant-assisted overdentures in the edentulous mandible, few rare studies related implants cavity preparation and placement to mandible weakening. Therefore, the current study was conducted to compare inconsistent sample and the differences in fracture resistance, maximum failure load, maximum displacement and fracture locations between fully intact mandibular replicas and replicas where one, two or three implants were inserted.
Materials & methods
Thirty-two (32) Mild atrophic completely edentulous polyurethane replicas were used throughout the experiment that was held in the Department of Prosthodontics, Faculty of Dentistry, Alexandria University and City of scientific research in New Borg Arab. These replicas were divided into 4 groups:
Group-I : Included unaltered eight fully intact replicas representing control group acting as a reference.
Group-II : Included eight replicas where only single symphyseal implant was placed representing single implant group.
Group-III : Included eight replicas with inserted double implants in canine area representing double implant group.
Group-IV : Included eight replicas with inserted triple implants (two implants in premolar area, one implant in symphysis) representing triple implant group.
Summary, Conclusion and Recommendations
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Prosthetic management
For all polyurethane replicas, mandibular complete dentures were constructed. Then, completely guided surgical guide were fabricated to act as a guide for implant placement.
In each group, each polyurethane replica had subjected to the following investigations:
Vertical loads were simulated by universal testing machine under conditions simulating trauma, with a compression force acting laterally on the ramus of the mandible with displacement rate up of 5 mm/min until failure.
Fracture locations, maximum load and displacement to failure were categorized and collected. Scanning electron microscope was utilized to evaluate the changes in the implant surfaces in fracture sites.
Results:
The results of the present study showed that:
1- Evaluation of maximum load where the structure integrity of mandibular replicas failed:
The results of this study revealed that there was a statistically insignificant difference in maximal load between control group and single implant group.
2- Evaluation of Maximum Displacement till the structure integrity of mandibular replicas failed:
The results of this study revealed that there were insignificant differences in maximal displacement across all mandible groups
3- Evaluation of fracture locations:
The results of this study revealed that break locations were significantly different across all mandible groups
4- Evaluation of Scanning Electron Microscope Pictures:
Pictures of scanning electron microscope (SEM) indicated that all the dummy implants surfaces were surrounded by polyurethane foam particles anchored to the implant surface.