Influence of post and core materials on distortion around 4-unit zirconia bridge margins

Abstract

The purpose of this study was to evaluate the surface strain of zirconia fixed partial denture frameworks and their abutment roots when restored with two types of post and core materials. Artificial mandibular first premolars and second molars were used as the abutment teeth. Posts and cores were of two types: resin composite with glass fiber posts (RC) and cast platinum gold alloy (MC). The cores and 4-unit zirconia frameworks were bonded to the specimens. Static loading was applied to the occlusal surfaces, and the surface strain of the frameworks and roots (distal premolar and mesial molar) was measured by strain gauge method. Premolar root showed a significantly higher magnitude of principal strain than molar root. RC showed a significantly higher magnitude of principal strain than MC. The results suggest that MC restrain the surface strain compared to RC when the missing teeth are replaced by a 4-unit zirconia framework.

Effect of frame design on the fracture strength of a zirconia crown and porcelain-faced crown

“…Zirconia has garnered much attention as a restoration material. Zirconia is needed because it has superior biocompatibility compared to metal and has better aesthetics than a metal frame [6][7][8][9] . A clinical problem with this technique is the chipping of, and damage inflicted upon, the porcelain facing the zirconia crown due to occlusal force.…”

The effects of post and core material combination on the surface strain of the 4-unit zirconia fixed partial denture margins

“…In contrast, some studies 17,18) have reported that the Young's modulus of the zirconia framework is greater than that of metal framework, which may help in preventing the fracture of the porcelain veneer. However, few studies 21) have evaluated both post and core materials and framework materials. The difference in the Young's modulus between the abutment teeth and the FPD framework on stress distribution has not been clarified.…”

“…A previous study led by Inagaki et al 21) investigated the surface strain of zirconia FPD frameworks and the roots of the abutment teeth when the missing posterior teeth were replaced by a 4-unit Y-TZP framework, and when the abutment teeth were additionally restored with two types of post and core materials. The study reported that high surface strain was detected, particularly at the premolar abutment, and that the cast post and core system played a role in limiting the magnitude of surface strain on the framework.…”

“…The stress distributions of endodontically treated teeth can be analyzed with a variety of methods: finite element analysis (FEA) 3,5,22) , photoelastic methods 20) and by using strain gauges 19,[21][22][23] . FEA and photoelastic methods evaluate the stress distribution within the models based on the mechanical properties of the material.…”

“…Dentists must determine which type of post and core materials would be suitable for the abutment teeth of the FPD to ensure a good prognosis. In a previous report 21) on FPDs, the stress concentration varied depending on the type of post and core material used and the type of abutment tooth, whereby the abutment teeth were restored with the same type of post and core materials. However, dentists should consider the stress distribution when each abutment tooth is restored, as there are different types of post and core materials that demonstrate different behaviors in a clinical setting, resulting in a more complicated stress distribution.…”