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Effect of Crystallization Firing on Marginal Gap of CAD/CAM Fabricated Lithium Disilicate Crowns
Author(s) -
Gold Steven A.,
Ferracane Jack L.,
da Costa Juliana
Publication year - 2018
Publication title -
journal of prosthodontics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.902
H-Index - 60
eISSN - 1532-849X
pISSN - 1059-941X
DOI - 10.1111/jopr.12638
Subject(s) - cerec , leucite , materials science , crown (dentistry) , ceramic , lithium disilicate , crystallization , dental porcelain , glass ceramic , composite material , dentistry , chemistry , medicine , organic chemistry
Purpose To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite‐reinforced glass‐ceramic (IPS Empress CAD) blocks (LG), and lithium‐disilicate (IPS e.max CAD) blocks before (LD‐B), and after (LD‐A) crystallization firing. Materials and Methods A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full‐coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite‐reinforced glass‐ceramic blocks (n = 5) and lithium‐disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (μm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite‐reinforced glass‐ceramic crowns and the lithium‐disilicate crowns before and after crystallization firing. Results were analyzed by two‐way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05). Results The overall mean marginal gaps (μm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD‐B = 42.9 ± 12.2, and LD‐A = 57.2 ± 16.0. The marginal gaps for LG and LD‐B were not significantly different, but both were significantly less than for LD‐A. Conclusions The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium‐disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process. Clinical Relevance : The marginal gap of CAD/CAM‐fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.