23 October 2019

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Wear of CAD-CAM ceramic single crowns and opposing natural teeth: glass matrix vs resin matrix

Lara Figini

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Contemporary computer-aided design and manufacturing (CAD/CAM) systems involve a wide range of dental restoration indications such as inlays, onlays, laminate veneers, partial and all-ceramic crowns, fixed dental prostheses (FDP), removable dentures, working model fabrication, maxillofacial prostheses as well as implant superstructures, reducing costs and laboratory related consequences.
Materials for aesthetic restorations can be ceramic with glass matrix or hybrid with resin matrix. In dentistry, a restorative material should be durable against heavy occlusal loads while not causing an undesired wear on the opposing dentition. Physiological and pathological conditions such as mastication and parafunctional occlusion may cause wear of the restoratives as well as the opposing dental tissues leading to a loss in tooth anatomy.         

Materials and Methods     
In a clinical study published on the Journal of Advance Prosthodontics April 2019 the authors investigated wear amount of single molar crowns, made from four different restoratives, and opposing natural teeth through computerized fabrication techniques using 3D image alignment. A total of 24 single crowns (N = 24 patients, age range: 18 - 50) were made from lithium disilicate (IPS E-max CAD), lithium silicate and zirconia based (Vita Suprinity CAD), resin matrix ceramic material (Cerasmart, GC), and dual matrix (Vita Enamic CAD) blocks. After digital impressions (Cerec 3D Bluecam, DentsplySirona), the crowns were designed and manufactured (Cerec 3, DentsplySirona). A dual-curing resin cement was used for cementation (Variolink Esthetic DC, Ivoclar). Then, measurement and recording of crowns and the opposing enamel surfaces with the intraoral scanner were made as well as at the third and sixth month follow-ups. All measurements were superimposed with a software (David-Laserscanner, V3.10.4). Statistical analysis was accomplished by Repeated Measures for ANOVA (SPSS 21) at = .05 significance level.  

Results  
After 6 months, insignificant differences of the glass matrix and resin matrix materials for restoration/enamel wear were observed (P>.05). While there were no significant differences between the glass matrix groups (P>.05), significant differences between the resin matrix group materials.  

Conclusions  
From the data of this study, which must be confirmed in other similar studies, it can be concluded that glass matrix materials showed less wear both on their own and opposing enamel surfaces than resin matrix ceramic materials.     
Especially in bruxist patients or in patients with occlusions that predispose to wear it is advisable to  prefers ceramic materials with a glass matrix for single crowns with CAD-CAM as these materials are less subject to wear and less weary for opposing natural teeth in a 6 months follow-up. 

For additional informations:  In vivo wear determination of novel CAD / CAM ceramic crowns by using 3D alignment.