Masking Ability of Subtractively and Additively Manufactured Dental Ceramic Restorations: A Systematic Review.

Objective: To conduct a systematic review on the masking ability of subtractively and additively manufactured dental ceramics.

Materials and methods: The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The electronic search was carried out through MEDLINE, Scopus, and Website of Science databases with a date restriction being from 2001 onwards. Publications in English, in vitro studies, and studies regarding the evaluation of the masking ability of crown materials that were subtractively and additively manufactured were included.

Results: Out of 619 eligible articles, 13 were included. A thickness of 1.5 mm for lithium disilicate (LD) resulted in a dramatic decrease in ∆E_ab/∆E₀₀ across all substrates compared to a 1 mm thickness. Low-translucent LD appeared to have the best masking ability regardless of the shade of the try-in paste. Layering flowable composite over the substrates improved masking ability. Darker substrates were the hardest to mask no matter the type of restorative material, try-in paste used, and layering technique. Bilayered restorative materials proved to be superior to monolithic materials regarding masking ability.

Conclusion: Increasing the thickness of subtractively manufactured ceramics materials improves the masking ability. 1.5 mm thickness is found to provide the best masking ability for most ceramic materials. Darker substrates prove to be difficult to mask in comparison to lighter substrates and require either thicker materials and/or more opaque cements. Bilayered crowns are recommended for achieving optimal masking while preserving tooth structure. Despite the increasing demand, there is no study available on 3D-printed (additively manufactured) restoration's masking ability.

Clinical significance: This review provides a comparison of masking abilities of multiple subtractively manufactured ceramic materials and highlight the lack of current knowledge on additively manufactured crown materials. It also emphasizes the importance of having a universal approach to interpreting and communicating color changes between collaborative dental professionals to ensure the same shade predictions. In addition, when masking darker shades, clinicians should be aware that alternative material choice or clinical and technical procedures are essential.