الفهرس 
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Abstract
The aim of this study is to evaluate the effect of splinting of the abutment teeth on stress distribution around dental implant supporting mandibular distal extension base removable partial denture retained by extra coronal attachments using a three-dimensional finite element analysis.
Conclusion
Within the limitations of this 3D finite element stress analysis study, the following conclusions could be drawn:
1. Oblique loading generates much more stresses than vertical loading.
2. Splinting the primary abutment to the adjacent tooth redirects stress from the bone crest to the apical areas of both teeth.
3. Splinting produces more homogenous distribution of stresses at the supporting structures without areas of great concentrations.
Summary
The present study was planned to evaluate the effect of splinting of the abutment teeth on stress distribution around supporting structures as well as dental implant in bilateral distal extension RPDs. The implants were used to support mandibular distal extension base RPD that was retained by extra coronal attachments. The stress distributions were evaluated using a three-dimensional Finite element analysis (FEA).
FEA has become an increasingly useful tool for the prediction of the effects of stress on the implant and its surrounding bone. Compared with other mathematical methods, FEA is considered more accurate in analyzing the stress distribution in tissues with complicated structures such as human alveolar bone. In the present study, more accurate analysis model was constructed by using actual patient’s data and a study model.
This model represented a case of mandibular Kennedy class I partially edentulous situation. The last standing natural abutment was the 1st premolar bilaterally. An implant was drawn to support the simulated RPD at the area of 2nd molar. An extracoronal attachment was used to retain the RPD to the natural abutment.
Two identical models were created; one with the 1st premolar splinted with the canine. The other model represented non-splinted condition.
Two loading conditions were tested; vertical and oblique, using a 150N distributed at the central fossae and vertical slopes of buccal cusps of artificial teeth.
Meshing, running the analysis and collection of results were carried out.
The results showed the following tendencies:
The placement of an implant in the distal area to support a RPD decreases the stresses exerted by the denture to the abutments and supporting tissues. The effect of implant placement is more important in cases of non splinted model as it shares greater stresses than splinted designs.
Oblique loading produces higher stress concentrations than vertical in all models as it has the greatest effect on the terminal abutments, implants and supporting structures in comparison with vertical loads.
Splinting the main abutment to the adjacent tooth might be beneficial as it produces more favorable stress distribution and can tolerate non axial loading.
In splinted models; the effective sharing of loads between the implant and the abutment of the loaded side, and the limited denture base movement that needs less cross-arch stabilization result in dramatic decrease in stresses provided by the RPD for the non loaded side.
The denture base movement is increased in non splinted model hence produces more stresses at the non-loaded side and highlights the importance of cross-arch retention and stabilization.
Conclusion
Within the limitations of this 3D finite element stress analysis study, the following conclusions could be drawn:
1. Oblique loading generates much more stresses than vertical loading.
2. Splinting the primary abutment to the adjacent tooth redirects stress from the bone crest to the apical areas of both teeth.
3. Splinting produces more homogenous distribution of stresses at the supporting structures without areas of great concentrations.
4. Even with using implant to support the distal extension RPD; splinting the natural abutments would be the design of choice.