Effects of coronal substrates and water storage on the microhardness of a resin cement used for luting ceramic crowns

Abstract

Composite resin and metallic posts are the materials most employed for reconstruction of teeth presenting partial or total destruction of crowns. Resin-based cements have been widely used for cementation of ceramic crowns. The success of cementation depends on the achievement of adequate cement curing.ObjectivesTo evaluate the microhardness of Variolink® II (Ivoclar Vivadent, Schaan, Liechtenstein), used for cementing ceramic crowns onto three different coronal substrate preparations (dentin, metal, and composite resin), after 7 days and 3 months of water storage. The evaluation was performed along the cement line in the cervical, medium and occlusal thirds on the buccal and lingual aspects, and on the occlusal surface. Material and MethodsThirty molars were distributed in three groups (N=10) according to the type of coronal substrate: Group D- the prepared surfaces were kept in dentin; Groups M (metal) and R (resin)- the crowns were sectioned at the level of the cementoenamel junction and restored with metallic cast posts or resin build-up cores, respectively. The crowns were fabricated in ceramic IPS e.max® Press (Ivoclar Vivadent, Schaan, Liechtenstein) and luted with Variolink II. After 7 days of water storage, 5 specimens of each group were sectioned in buccolingual direction for microhardness measurements. The other specimens (N=5) were kept stored in deionized water at 37ºC for three months, followed by sectioning and microhardness measurements. ResultsData were first analyzed by three-way ANOVA that did not reveal significant differences between thirds and occlusal surface (p=0.231). Two-way ANOVA showed significant effect of substrates (p<0.001) and the Tukey test revealed that microhardness was significantly lower when crowns were cemented on resin cores and tested after 7 days of water storage (p=0.007). ConclusionThe type of material employed for coronal reconstruction of preparations for prosthetic purposes may influence the cement properties.

Comprehensive micro-mechanical characterization of experimental direct core build-up resin composites with different amounts of filler contents

“…The restoration of endodontically treated or severely broken down teeth, which in most cases are mechanically compromised, is required to compensate for the considerable bulk loss of hard tissues. There are many studies that have focused on the restoration of teeth after endodontic procedures 1,2) . A core build-up is a restoration that facilitates a subsequent extracoronal restoration.…”

Bond performance of “Touch and Cure” adhesives on resin core systems

“…The restoration of endodontically treated teeth has been studied extensively 1,2) . Endodontically treated teeth have traditionally been restored with metal cores 2) .…”

“…Endodontically treated teeth have traditionally been restored with metal cores 2) . However, because of a much higher modulus of elasticity than the supporting dentine, this mismatch in modulus could lead to stress concentration and root fractures 3) .…”

Study of lumineers' interfaces by means of optical coherence tomography

“…The retention of ceramic laminates depends mainly on the enamel adhesive bond strength and ceramics. Adherence with the glaze probably determines the success of this type of restoration because the clamping force to the ceramic exceeds that obtained in enamel [25,26,27]. Layton, Clarke and Walton says that the outcomes may prove clinically acceptable with time, but evidence remains lacking and the use of these materials for veneers remains still experimental [3].…”

“…The authors claim that the thickness should be a determining factor of the bond strength, related to the stress distribution, the relationship between this factor and the shear strength and tension [27,28,29]. In the present study it may be noted a lack of uniformity in the internal structure of the laminate, resulting in variations in the cement thickness, which may have been originated during the fabrication process, Which certainly contributes to the formation of air pockets and crevices, which as it was found, increase with time and culminate in the detachment of the restoration or its fracture as a result of creating an weak area arising from a discontinuity in the bondline.…”