الفهرس 
COVEROnly 14 pages are availabe for public view
 |  | from | 105 |  |  |
| | | from | 105 | | |
Abstract
This study was conducted to compare between three removable partial denture designs rehabilitating lower bilateral distal extension cases with an isolated abutment using strain gauge analysis method.
Three identical heat cured acrylic resin models were constructed representing Kennedy class I modification 1 with isolated lower right 2nd premolar. The models used for this study were fabricated to simulate as much as possible the natural conditions.
The abutment teeth of each model were prepared according to the treatment modality as follows:
-Model 1 :
Mesial and distal rest seat preparations were carried out on the right isolated 2nd premolar to serve as an abutment for the removable partial denture.
Occlusal rest seat was prepared mesial to 2nd premolar on left side to receive the principal occlusal rest. Another occlusal rest seat distal to left 1st premolar and cingulum rest seat on the right canine were prepared to receive an auxillary rests to act as indirect retainers.
- Model 2:
The right isolated 2nd premolar was modified by reduction into a dome shape (about 1mm above the free gingiva) to serve as an overdenture abutment. Principal and auxillary rest seat preparations were carried out on the right canine and the left 1st and 2nd premolars as in the 1st model.
-Model 3:
The abutment teeth of the modification area were reduced following the principles of tooth reduction to receive a fixed bridge connecting the isolated 2nd premolar to the canine mesial to the modification space.
Occlusal rest seat was prepared mesial to 2nd premolar on left side to receive the principal occlusal rest. Another occlusal rest seat distal to left 1st premolar was prepared to receive an auxillary occlusal rest to act as indirect retainer.
Three partial dentures were constructed on the three acrylic models. The components of the RPDs of the three models were the same, combined denture bases, lingual bar as major connector, two auxiliary rests one on the right canine and the other on the distal aspect of the left 1st premolar and RPI clasps as direct retainers.
For the right isolated 2nd premolar, two strain gauges were installed 1mm mesial and distal to its socket. One strain gauge was also installed 1mm distal to the socket of the free end saddle abutment on the left side. Two strain gauges were installed bilaterally on the buccal slope of second molar area of the free end saddles.
Unilateral and bilateral loads up to 100 Newtons (N) were applied by the Universal testing machine. The strains developed at the 5 strain gauges were recorded using multichannel strain-meter. Once the load was completely applied, the microstrain readings were transferred to microstrain units from the multichannel strain-meter.
The means of the last 10 microstrain recorded values before the sudden DROP for the five strain gauges of each model were collected, tabulated and statistically analyzed.
The results revealed that, more stresses were induced in the supporting structures of the isolated abutment tooth in model 1 (conventional RPD design), followed by model 2 (overdenture design). However the least amount of stresses transmitted to the isolated abutment were recorded with model 3(fixed bridge design).
Model 1 (conventional RPD design) transmitted the least amount of stresses to the residual supporting ridge, followed by model 2 (overdenture design). However, Model 3(fixed bridge design) transmitted the highest stress values to the supporting ridge.