الفهرس 
INTORDUCTIONOnly 14 pages are availabe for public view
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Abstract
Summary& Conclusions
The objective of this study was to evaluate the relative effect of different design modalities; Implant length, Implant diameter and rigid or non-rigid connector on stress distribution of Tooth-implant and Implant-implant supported fixed prostheses. The stress distributions were evaluated using a three-dimensional finite element analysis (FEA). The relevant results were validated clinically.
FEA has become an increasingly useful tool for the prediction 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 Finite Element model was constructed by using actual patient’s data.
Twenty 3-D models simulation of Kennedy class II situations were constructed. Models were divided into four groups, different diametersand lengths were allowed for the distal implant at the site of the second mandibular molar.
The first group represented Tooth-implant supporting FPD with rigid connector. The second group represented Tooth-implant supporting FPD with non- rigid connector. The third group represented Implant-implant supporting FPD with rigid connector.Finally, the fourth group represented Implant-implant supporting FPD with non-rigid connector.
An occlusal load of 100 N was applied over the central fossa of the second premolar, first molar and the second molar of the three unit restoration for each of the 20 models.
Meshing, running the analysis and collection of results were carried out.
The present study demonstrated that theeffect of four investigated factors (diameter, length, connector type and Tooth-implant or Implant-implant supported FPD) on stress distribution in five different areas (FPD, mesial implant, distal implant, cancellous bone and 2nd premolar) is likely to be interrelated.
The effect of the four variables cannot be analyzed independently of the others.
Within the limitations of the present FEA study, the following conclusions were provided:
• With either Tooth-implant or Implant-implant supported FPD, non-rigid connectors showed higher stress than rigid connectors. Within the Tooth-implant FPD design, rigid connector reduced the stress induced in FPD by (36.4%), furthermore within the Implant-implant design, the rigid connector reduced the stress induced in FPD by (15.1%).
• With either rigid or non-rigid connector Tooth-implant design showed significant highest mean stress. Implant-implant design with the rigid or non-rigid connector showed reduction of stress by (75.2%) and (81.4%) respectively within the FPD.
• In case of stress in mesial abutment (second premolar or mesial implant) there was no significant difference with either type of connector. Nevertheless the Implant-implant design succeeded in reducing the stress within the mesial abutment by (1.65%).
• In case of stress in cancellous bone around the second premolar and mesial implant, the type of connector showed no significant difference. On the contrary Tooth-implant design succeeded in the reduction of stress by (45.8%) around the premolar. This was due to the fact that the periodontal ligament around the premolar reduced the stress transmitted to the cancellous bone.
• Increase of distal implant diameter to 4.7 mm and 5.7 mm reduced the stress within the distal implant by (55.6%) and (79.2%) respectively. In addition, same increase of implant diameter reduced the stress in cancellous bone around distal implant by (5.22%) and (12.77%) respectively.
• Increase in distal implant length to 11.5 mm reduced the stress within the distal implant by (6%) further increase in length to 13 mm increased the stress by (6.2%). Equally, increase in the implant length to 11.5 mm reduced the stress in cancellous bone by (0.67%), further increase in length to 13 mm increased the stress in cancellous bone by (30%).
• In the light of our findings, increase in diameter of implant was directly proportional with the reduction of stress; moderate increase in the length of the implant resulted in reduction of stress. On the contrary, large increase in the length of the implant without increase in diameter induced torque and increased stress.
• Moreover, according to our investigation with either Tooth-implant or Implant-implant designs, rigid forms of connections should be used.
The aim of the clinical study was radiographic evaluation of bone density and alveolar bone height around implants and premolars in Tooth-implant supported FPD with rigid connector versus Implant-implant supported FPD with rigid connector.
The present study included eight patients (six males and two females) with missing 1st and 2nd mandibular molars, the terminal abutment was either second premolar (group I) or First premolar (group II).
Implant fixtures were inserted at the site of the 2nd molar in case of (group I) or the site of 2nd premolar and 2nd molar in case of (group II) using two – stage surgical technique.
After three months, second stage surgery was performed and gingival formers were placed for two weeks to allow for proper soft tissue healing and contour.
Three months between implant insertion and loading was allowed for proper healing and Osseointegration. Then, transfer coping impression technique was used with addition silicone impression material for impression taking.
group I received a 3 unit FPD with rigid connection, supported by natural prepared tooth mesially and by implant distally.
group II received a 3 unit FPD with rigid connection, supported by free standing implants, at the site of 2nd premolar and 2nd molar respectively.
Patients were evaluated by CBCT radiographs to measure the bone density, and the vertical bone length from the crest of the alveolar ridge to the implant tip.
Bone density and vertical bone length were recorded at intervals: Immediately after FPD cementation, after 3 months and after 6 months.
Based on the findings of this clinical study, the following conclusions were drawn:
• No significant difference in bone density or in vertical bone loss was reported between Tooth–implant supported FPD and Implant – implant supported FPD.
• There was a slight increase in the mean bone density in Implant-implant supported FPD after 3 months as well as after 6 months; accordingly, and in agreement with the our FEA results, the Implant-implant supported FPD is the primary therapy of choice in partially dentate patients. On the other hand, Tooth-implant supported FPD is a successful alternative treatment as there was no significant difference concerning alveolar bone loss.