Masking Ability of Monolithic and Layered Zirconia Crowns on Discolored Substrates

Abstract

There is scarce information on the colorimetric behavior of monolithic and layered zirconia crowns in combination with various abutment colors. This study evaluated the masking ability on discolored substrates of monolithic and layered zirconia crowns. Anterior crowns were fabricated using 3Y-TZP zirconia and layering ceramic and divided into three groups: monolithic (ML), bi-layer (BL), and tri-layer (TL). The crowns were placed over eleven substrates (ND1-ND9, zirconia, metal), and CIE L*, a*, b*, C*, and h° color coordinates were measured in the cervical, middle, and incisal areas with a spectrophotometer. Masking ability was calculated using the color difference formula, and values were interpreted according to the perceptibility and acceptability thresholds. Data were analyzed statistically (α = 0.001). The L* coordinate was not significantly different between BL and TL crowns, regardless of the measurement area or substrate (p ≥ 0.001). In the middle area, the L* coordinate of the ML group was statistically different from the BL and TL groups only for zirconia and metal substrates, while in the incisal area, only for ND7 and metal substrates. The a* coordinate was significantly different between the ML and layered crowns for all measurement areas and substrates (except zirconia). The b* and C* coordinates differed significantly between the groups only in the cervical area (p < 0.001). The ML crown had better masking ability than the BL and TL crowns. However, the color differences for ML crowns were below the acceptability threshold for ND2, ND3, and ND7 substrates in the cervical and middle areas and below perceptibility threshold only for the incisal area. The lowest masking ability of the crowns was found for ND9 and metal substrates in all measurement areas.

The effect of Phytosphingosine and bioactive glass-ceramics in preventing dental enamel erosion

“…It is important to assess the clinical significance of the color differences comparing the findings with the visual 50:50% perceptibility and acceptability thresholds. The results are irrelevant unless these parameters are used for clinically interpret the significant effect of the proposed treatments on the enamel color 42 .…”

Four‐point flexural strength and microtensile bond strength of digitally and conventionally veneered zirconia

“…Natural zirconia is highly opaque, which is an advantage in case of tooth-related discoloration, but for aesthetic restorations ceramic veneers are used to ensure better aesthetics [2]. Although, monolithic zirconia restorations have been used commonly, studies are continuing on the identification of the more advantageous type of all-ceramic restoration in terms of color, aesthetics and mechanical properties [3,4]. In veneered zirconia restorations which are exposed to contact forces and flexure in the mouth, the adhesive and mechanical relationship between the substructure and the veneer affects the success of the restorations [1].…”

Advanced Materials for Oral Application

“…Its lack of translucency has been overcome by the latest generations of 3Y-TZP zirconia, with improved properties and wider indications for both monolithic and veneered restorations. The study by Gasparik et al [ 10 ] aimed to evaluate the masking ability of 1 mm thick monolithic and veneered zirconia crowns on different discolored substrates. Its importance lies in the fact that treating tooth discoloration is challenging, and a successful outcome relies on the material’s ability to hide the discolored substrate, as well as matching the color of neighboring teeth.…”

“…The color measurements were performed using a non-contact dental spectrophotometer in the cervical, middle, and incisal portion of each crown. Despite the fact that the color coordinates of monolithic and veneered crowns were significantly different on all substrates, none of the 1 mm thick 3Y-TZP zirconia crowns showed sufficient masking ability on moderately or severely discolored substrates [ 10 ].…”