Expanded Casting Post-core Have Influence On Retentive Force Of The Premolar Post Crown

bjective: Through the production of expanded castingpost-corefrom different length and diameter expansion, to observe expandedcasting post and corehave influence on. Explore the best length and diameterto strengthen retentive force of the premolar post crown, then to analysisfurther of the expanded casting post-corein place have the influence on thestress distribution of root. Methods: This subject mainly used the vitro model,vitro extracted teeth from the body and vitro organic glass model to researchthe control group and the experimental group, each group of10samples foraverage. According to the root, roots and root neck the groups were dividedinto three3different parts; according to every part of the length of1mm and2mm in the expansion was divided into two groups; each inflation lengthaccording to the expansion diameter of0.1,0.2,0.3mm was divided into threegroups,finally each group10samples for average.Through statistical softwarefor statistical analysis, obtains the correlation among retention of force andinflation place and inflation amount, then to find out the best position and theexpansion of inflation. The experimental group and the control group weredivided from healthy teeth in devices for root making model, according to bestinflation amount and part on the above to make expanded casting post-core,then to analysis two groups of difference retention force comparatively. Thelast using of macroscopic observation guaranteed that really have no root babbling fold and crack. Result:1. The root of the neck, middle, pointed of12experimental group from three experiment group were compared with thecontrol group, retention of the force is statistically significant differences, andits retention power higher than the control group.2. Diameter increase in thesame time, the length of post-core with comparison between1mm and2mm,root in the neck, middle,pointed on experiment group in retention of forcewere no statistical significance differences.3. post-core in both scope length,to increase diameter between0.1mm and0.2mm with comparison of root inthe neck, middle, pointed, on experiment group in retention of the force wasstatistically significant differences, the greater the diameter increases, thegreater the retention of forces increased.4. When post-core of length anddiameter in increased at the same time, the neck, middle, pointed root ongroups with comparison, retention force was statistically significant.5.Choose apex inflation range of1mm, diameter increased0.1mm and controlgroup from the body with comparison of bending was no significancedifferences. Conclusion: The expansion of post-core can increase retention ofthe force, and retention of the force of increasing has nothing to do with theinflation place and length range, the retention of force increased with inflation.Expansion increases risk to root fracture, the expansion amount increasespossibility to root fold, the apex less than inflation of root neck.