الفهرس 
Aim of the StudyOnly 14 pages are availabe for public view
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Abstract
Removable partial denture (Rpd) frameworks are traditionally fabricated from chrome Cobalt (co-cr). However co-cr RPDs have several disadvantages. They are esthetically unacceptable, and induce increased stresses on the abutments and residual ridge due to the weight of the material, metallic taste and allergic reactions. Thus several thermoplastic materials were introduced to be used for Rpd construction to overcome the draw backs of the metallic frameworks.
Bio-HPP (high performance polymer) is biocompatible and has good mechanical properties. It also has high resistance and chemical stability. Moreover the modulus of elasticity of Bio-HPP is (4GP), thus it is similar to bone which reduces stresses transferred to the abutmens. The white color of the Bio-HPP makes it highly esthetic.
The use of computer-aided design and manufacturing (CAD/CAM) technology in fabrication of Rpds is an alternative for the conventional casting technique. Digital surveying of the scanned casts and subsequent designing and production of restorations by milling technology allow easy fabrication. Also CAD/CAM technology prevents operator variations and improves quality control in dental laboratories.
This study was done to compare between stresses induced by removable partial denture framework made from conventional chrome cobalt using lost wax technique and Bio-HPP material using CAD/CAM technique, by strain gauge.
This in-vitro study was applied on a Kennedy class I educational mandibular stone model. The abutments were the 2nd premolars bilaterally. Rest seat preparations were made in the far zone in the 2nd premolars bilaterally. Cingulum rest seats were prepared in the canines bilaterally to receive the additional rest for indirect retention. A plastic index was fabricated by using a vacuum sheet, for construction of artificial mucosa using mucosa stimulating material.
The 3shape D850 desktop scanner was used to scan the model. A space for mucosa stimulating material was created on the virtual cast. A 2 typically acrylic models were 3D printed, mucosa simulating material (Multisil mask-bredent-UK) was injected into the plastic index then the index was adapted to the acrylic cast.
Twenty removable partial denture frameworks were fabricated from two differental materials: group I: 10 PRD frameworks were fabricated from Bio-HPP group II: 10 RPD framework were fabricated from Co- Cr.
Strain values were recorded distal to the last abutment and at the distal part of the ridge for the 2 groups by the strain gauge device.
During bilateral load application t test show statically significant difference in the amount of strain recorded, in group I it was higher on the ridge than on the abutment. While in group II the strain on the abutment was higher than that on the ridge. The results of independent t test showed statically significant difference. It was higher on abutment in group II than group I, but on the ridge it was high in group I compered to group II. During unilateral load application, the results were similar however group I showed higher strain on abutments than group I.