Shade match comparison of CAD-CAM single crowns to a lithium disilicate crown

To assess the shade match ability of four varieties of all-ceramic crowns to a neighboring bilayered lithium disilicate crown.

A dentiform was used to fabricate a bilayered lithium disilicate crown on the maxillary right central incisor, following the anatomy and shade of a selected natural tooth. Two crowns (one full-contour, one cutback) were then designed on a prepared maxillary left central incisor, following the contour of the neighboring crown. The designed crowns were used to manufacture monolithic lithium disilicate, bilayered lithium disilicate, bilayered zirconia, and monolithic zirconia crowns, 10 each. An intraoral scanner and a spectrophotometer were used to assess the frequency of matched shades and to calculate the color difference (ΔE) between the two central incisors at the incisal, middle, and cervical thirds. Kruskal-Wallis and two-way ANOVA were used to compare the frequency of matched shades and ΔE values, respectively (α = 0.05).

There was no significant (p > 0.05) difference in frequencies of matched shades for each group at the three sites; except bilayered lithium disilicate crowns. Bilayered lithium disilicate crowns had significantly (p < 0.05) higher match frequency than monolithic zirconia at the middle third. The ΔE value was not significantly (p > 0.05) different among the groups at the cervical third. However, monolithic zirconia had significantly (p < 0.05) higher ΔE values than bilayered lithium disilicate and zirconia at the incisal and middle thirds.

Bilayered lithium disilicate and zirconia appeared to most closely match the shade of an existing bilayered lithium disilicate crown.