18 May 2023

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Color stability: CAD/CAM versus traditional resin-based composite

By Lorenzo Breschi and Annamaria Forte

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Introduction 

Through the progress of computer aided technology, many advances have been made in dentistry: new materials have been developed for CAD/CAM restorations, such as glass ceramics, zirconia, and composites, allowing clinicians the choice of different mechanical and optical properties. Although the use of direct resin-based composite (RBC) restorations is broad and can provide reliable and esthetic results, the higher mechanical properties and color stability of CAD/CAM restorations, due to the higher degree of conversion that can be obtained with extra-oral curing, have expanded their use in clinical practice. 

CAD/CAM composite blocks (CCB) offer higher quality compared to RBCs used in a conventional manual procedure in both direct and indirect restorations. Indeed, the temperature and/or high-pressure polymerization employed for CAD/CAM materials maximize polymer cross-linking and, therefore, increase their mechanical properties. 

One of the limits of RBCs is the propensity to color change in the long term. Color instability can be related to intrinsic (i.e., resin matrix, fillers, polymerization initiators) or extrinsic factors (i.e., absorption of pigments contained in food or drinks). This characteristic is of relevant importance because of the high increasing request for aesthetic dental restorations. 

For this reason, a systematic review of the current literature was recently conducted to investigate the color stability of CCBs when submitted to artificial staining. 

Materials and methods

A systematic search was performed on different databases (Embase, Medline, Scopus, Web of Science). Of the 378 initially retrieved articles, 19 were included in this review. Seventeen different CCBs submitted to different artificial staining by liquid protocols, including coffee, red wine, tea, and cola were investigated. CCBs exceeded clinical acceptability thresholds for color shift in 18 out of 19 studies, with a significantly higher color stability than conventional hybrid resin-based composites (RBCs), and a significantly lower color stability than ceramic materials. When compared with other materials, CCBs immersed in coffee solutions showed a significantly higher color change than lithium disilicate, zirconia-reinforced lithium silicate hybrid ceramic, and felspathic ceramic. CCBs immersed in red wine showed a significantly higher color change than zirconia-reinforced lithium silicate, hybrid ceramic, and felspathic ceramic. Conversely, CCBs showed higher color stability when compared with hybrid resin composites for direct restorations.

The identified differences in CCBs in color stability can be attributed to the material’s composition, but also to the heterogeneity of staining procedures. 

Conclusions

Based on the results of this systematic review, the results showed that resin-based blocks for CAD/CAM procedures possess higher color stability than direct or indirect (laboratory) RBCs. However, CCBs showed lower color stability than ceramic materials. Materials’ compositions, the type of staining media and the finishing/polishing procedures may influence the color stability of CCBs. 

Paolone G, Mandurino M, De Palma F, Mazzitelli C, Scotti N, Breschi L, Gherlone E, Cantatore G, Vichi A. "Color Stability of Polymer-Based Composite CAD/CAM Blocks: A Systematic Review." Polymers (Basel). 2023 Jan 16;15(2):464. doi: 10.3390/polym15020464.