The Photoelastic Study Of The Stress Distribution On The Supporting Tissues Of KennedyⅠ Edentulous Restored By Removable Partial Dentures With Different Frameworks Of Vitallium

Bilateral distal-extension edentulous is more common in dentition defect.At present, RPD is the traditional method to restore distal-extensionedentulous.It has many advantages, such as grinding less teeth,convenience andlow-price,make it more popular in patients. But because of the limit in theproperty of the traditional RPD materials, if inappropriate in design, the strengthfocus on the abutment,give the higher torque to the abutment, and will injure it,then,influence the masticatory efficiency.If adopt more flexible and morescattered design, the property of the material can not be competent, so, inclinical,it exist certain limit in using.How to improve the material and thedesign,project reasonable RPD, reduce the torque to the abutment, improve themasticatory efficiency, turn into a significant problem. Vitallium,a alloy,contain higher Co、Cr and Mo,has higher surrender and higher extension,can resist broken better,and has higher elasticity,so it can be desighed moreflexible. Vitallium is a good medium in transmit stress, so it is considered to besuit to splitting design. But,these all basis on clinical observation, lack offorceful evidence of experiment. This experiment adopt Three dimensionalphotoelastic frozen section method, adopt Vitallium and CoCr alloy,use RPIand splitting designs, manufacture four removable partial dentures.To study thestress distribution on the supporting tissues of Kennedy ClassⅠ edentulous. Inorder to provide basis for the application of casting frame flexible denture.Objective:Adopt Vitallium and CoCr alloy,use RPI and splitting designs,manufacture four removable partial dentures, restore Kennedy ClassⅠedentulous. Three dimensional photoelastic frozen section method was used tostudy the stress distribution on the supporting tissues of Kennedy ClassⅠremovable partial dentures with the four forms and to compared with eachother，in order to check the advantage of the new material and the newdesign,and then to provide basis for the application of casting frame flexibledenture．Materials and Methods:This experiment adopt Vitallium and CoCr alloy,use RPI and splittingdesigns, manufacture four removable partial dentures, restore mandible bilateraldistal-extension edentulous.Adopt three dimensional photoelastic frozen sectionmethod, establish the photoelastic model,observe the colour streak,calculatethe stress, study the stress distribution on the supporting tissues of mandible bilateral distal-extension edentulous with the four removable partial dentures.Results:1. This experiment established the photoelastic model. The photoelasticmodel manufactured is transparent and without first stress, The proportion is1.36:1;0.00027among elastic modulus of difierent materials to make themodel,and is reflect the basic consistency with actual tissues. The model canmeet the requirements of the experiment,can be used to analysis the stressdistribution on the abutment and the supporting tissues.2. The material streak value is12.24N/mm for photoelastic teeth and11.36N/mm for alveolar bone.3. Stress loaded on the posterior teeth bilaterally, on the condition of thesame material, the stress to distal of the abutment: the metal frameworkremovable partial denture with splitting＜the metal framework removablepartial denture with RPI; on the condition of the same design, the stress todistal of the abutment: the metal framework removable partial denture withVitallium＜the metal framework removable partial denture with CoCr alloy;there is a interaction between the material and the design, the metal frameworkremovable partial denture with Vitallium and splitting exhibits the lower stressto distal of the abutment.Conclusion:Among Kennedy class Ⅰremovable partial dentures,the metal frameworkremovable partial denture with Vitallium and splitting exhibits better stresspattern，reduce the torque to the abutment，protect the abutment， and shouldbe considered as a preferable design.