| Summary: | Indiana University-Purdue University Indianapolis (IUPUI) === Background: Traditionally, zirconia has been used as a core material for allceramic
crowns that are later covered by a more esthetic veneering layer. Recently, new
zirconia materials with higher translucency commonly referred to as the “full contour
zirconia” have been introduced with the aim to allow dentist to fabricate entire allceramic
crown from the material with acceptable esthetic and mechanical functions
without the need for veneering. However, there is little information in the literature
regarding the translucency of full contour zirconia and the degree of conversion of resin
cement underneath the full contour zirconia. Objectives: 1) To investigate the
translucency parameter (TP) of recently marketed full contour zirconia and compare that
to traditional zirconia and lithium disilicate glass ceramic (LDGC) at different
thicknesses. 2) To evaluate the degree of conversion (DC) of the resin cement through
different thicknesses of the full contour zirconia, traditional zirconia and LDGC.
Alternative hypothesis: The new generation zirconia at the clinically recommended
thickness has lower translucency than that of LDGC and higher than that of non-veneered
traditional zirconia. In addition, DC of resin cement under full contour zirconia is lower
than that of LDGC and higher than that of traditional zirconia. Methods: 150 ceramic
specimens (12 x12 mm with thickness of 1-2 mm for LDGC and Zirconia) were divided
into 6 groups according to the type of material, as follow: LDGC (IPS e-max CAD),
Traditional Zirconia (CAP QZ), full contour zirconia (CAP FZ, Zirlux, Bruxzir, KDZ
Bruxer). The TP for materials at various thicknesses were measured by a
spectrophotometer (CM-2600D). The DC of the light curing resin cement (Variolink II)
underneath the ceramic disks was measured by FTIR. Result: All full contour zirconia
has lower translucency parameter and light transmission than LDGC. The translucency
parameter decreases with increasing thickness of any type of ceramic. There were no
significant differences in the degree of conversion of resin cement among the type of
ceramic disc, except Bruxzir. The correlation of TP between various thicknesses and the
types of ceramic materials was established by a regression analysis.
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