Flexural Strength of Resin Core Build-Up Materials: Correlation to Root Dentin Shear Bond Strength and Pull-Out Force.

Masao Irie,Takuya Matsumoto,Goro Nishigawa,Kumiko Yoshihara,Yukinori Maruo

doi:10.3390/polym12122947

Abstract

The aims of this study were to investigate the effects of root dentin shear bond strength and pull-out force of resin core build-up materials on flexural strength immediately after setting, after one-day water storage, and after 20,000 thermocycles. Eight core build-up and three luting materials were investigated, using 10 specimens (n = 10) per subgroup. At three time periods—immediately after setting, after one-day water storage, and after 20,000 thermocycles, shear bond strengths to root dentin and pull-out forces were measured. Flexural strengths were measured using a 3-point bending test. For all core build-up and luting materials, the mean data of flexural strength, shear bond strength and pull-out force were the lowest immediately after setting. After one-day storage, almost all the materials yielded their highest results. A weak, but statistically significant, correlation was found between flexural strength and shear bond strength (r = 0.508, p = 0.0026, n = 33). As the pull-out force increased, the flexural strength of core build-up materials also increased (r = 0.398, p = 0.0218, n = 33). Multiple linear regression analyses were conducted using these three independent factors of flexural strength, pull-out force and root dentin shear bond strength, which showed this relationship: Flexural strength = 3.264 × Shear bond strength + 1.533 × Pull out force + 10.870, p = 0.002). For all the 11 core build-up and luting materials investigated immediately after setting, after one-day storage and after 20,000 thermocycles, their shear bond strengths to root dentin and pull-out forces were correlated to the flexural strength in core build-up materials. It was concluded that the flexural strength results of the core build-up material be used in research and quality control for the predictor of the shear bond strength to the root dentin and the retentive force of the post.

Highlights

An endodontically-treated tooth presents a higher risk of biomechanical failure than a vital tooth.An appropriate restoration for endodontically–treated teeth is guided by both strength and esthetics.Posts are generally used to restore missing tooth structure and pulpless teeth [1], and new tooth-colored posts have improved the esthetics of teeth restored with posts and cores [2,3]
For all the three time periods, ESTECORE showed the highest values among all the core build-up materials
It is thought that flexural strength is a significant important mechanical property of resin core build-up and luting materials

Summary

Introduction

An appropriate restoration for endodontically–treated teeth is guided by both strength and esthetics. Posts are generally used to restore missing tooth structure and pulpless teeth [1], and new tooth-colored posts have improved the esthetics of teeth restored with posts and cores [2,3]. To ensure the durability of endodontically–treated teeth, it is extremely important that posts are optimally bonded to reduce debonding, long-term sorption and solubility, and fracture risks [4,5,6]. A core build-up system usually comprises a post, and it restores the tooth to the extent necessary to support a crown or an abutment tooth. A core build-up material, such as resin composite, is a restoration placed in a badly broken-down tooth to restore the bulk of the tooth’s coronal portion

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