Impact of Zirconia Coping Overlapped by Lithium Disilicate on Esthetic Outcome: A Systematic Review

This systematic review aims to evaluate the impact of a zirconia coping veneered or overlapped by lithium disilicate ceramic on the esthetic and mechanical outcomes of dental restorations. A systematic search of PubMed, Medline, Embase, and the Cochrane Library was conducted for articles published between January 2014 and January 2023. Inclusion criteria encompassed primary studies investigating the aesthetic outcome of restorations with a zirconia coping layered with lithium disilicate. The review included 13 studies (10 in vitro, three clinical) after screening, data extraction, and risk of bias assessment. The findings indicate a predominantly favorable consensus, with 10 studies supporting the bilayered approach. This combination leverages the high strength of zirconia and the superior aesthetics of lithium disilicate, demonstrating excellent fracture resistance, clinical success rates, and patient satisfaction in the short to medium term. Key factors influencing aesthetics include the ability to polish zirconia-reinforced lithium silicate (ZLS) to a high gloss and the critical role of cement shade on the final color. However, some studies reported less favorable outcomes, including higher plaque accumulation compared to monolithic zirconia and potentially higher flexural strength for traditional lithium disilicate over some ZLS materials. The zirconia coping and lithium disilicate veneer combination is a viable and aesthetically promising treatment modality. It offers a favorable balance of strength and aesthetics, though the results are technique-sensitive and influenced by material processing. The promising in-vitro and short-term clinical data necessitate confirmation through well-designed, long-term clinical trials to definitively establish the clinical longevity and aesthetic stability of these restorations.