Influence of a Retentive Shoulder Design to Prevent Early Failure of Three Core Build-Ups.

Esteban D Bonilla,Marc Hayashi,Cassio Do Nascimento,Cornelis H Pameijer,Vinicius Pedrazzi,Franklin Garcia-Godoy,Christine Khabbaz,Brian C Bonilla

doi:10.1590/0103-6440201902874

Abstract

This study evaluated the influence of a retentive shoulder design to prevent early failure of three resin composite build-ups on molars. Ninety-six intact extracted human maxillary third molars were assigned to two groups (n=48) based on occlusal, buccal cusps only and all cusps reduction. The groups were divided into two subgroups: pin retained and non-pin retained build-ups resulting in four groups (n=24), according the cusps reduction: pin retained/partial, pin retained/complete, non-pin retained/partial, non-pin retained/complete. Occlusal reduction was 3 mm with a semi-lunar retentive shoulder of 3 mm and an axial wall height of 1.5 mm. Groups were restored using a microhybrid, flowable or titanium reinforced resin composite. Modified self-curing acrylic resin provisional crowns were fabricated, cemented with non-eugenol temporary cement and thermal cycled. An instron machine applied tension to the provisional crowns parallel to the long axis of the tooth until dislodgement. A three-way analysis of variance was conducted on the influence of the variables on the retention of the core build-up. Ninety-three build-ups were retained under tensile load, while three core build-ups without pins were dislodged. Three-way analysis of variance showed no statistically significant difference between core build-ups using a retentive shoulder and pin retained core build-ups when tested under tensile load. With the advent of adhesive systems, increased surface area and retentive shoulder design can provide a retentive core foundation to prevent early failures of core build-ups during indirect restoration fabrication which will contribute to the longevity of final restorations.

Highlights

A variety of restorative materials and techniques have been used to fabricate core build-ups on vital posterior teeth that are to be restored with an indirect restoration [1,2,3]
Resistance of core build-ups without pins was directly related to the amount of remaining dentin, which corroborated the findings of other studies [20,21]
In order to provide a coronal core foundation for indirect restorations in cases of extensive loss of coronal structure, additional retentive features are required such as pins or auxiliary retentive preparation designs

Summary

Introduction

A variety of restorative materials and techniques have been used to fabricate core build-ups on vital posterior teeth that are to be restored with an indirect restoration [1,2,3]. There is a lack of evidence supporting specific techniques to prevent early failures of resin build-ups on compromised vital posterior teeth [15,16]. The retentive shoulder design is intended for use on vital molars exhibiting extensive loss of sound tooth structure, such as two or three major cusps, which require a build-up prior to crown fabrication. The aim of this in vitro study was to evaluate the influence of a retentive shoulder design to prevent early failure of three resin composite build-ups under tensile forces. If the null hypothesis is proven the need for the use of pins for retention can mostly be avoided, reducing inherent risks of root perforation or pulp exposure

Material and Methods

Results

Discussion

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