Light transmittance of CAD/CAM ceramics with different shades and thicknesses and microhardness of the underlying light-cured resin cement

Abstract

ObjectivesThe aim of this in vitro study was to evaluate the effects of the thickness and shade of 3 types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials.Materials and MethodsA total of 120 specimens of 2 shades (A1 and A3) and 2 thicknesses (1 and 2 mm) were fabricated using VITA Mark II (VM; VITA Zahnfabrik), IPS e.max CAD (IE; IvoclarVivadent), and VITA Suprinity (VS; VITA Zahnfabrik) (n = 10 per subgroup). The amount of light transmission through the ceramic specimens was measured by a radiometer (Optilux, Kerr). Light-cured resin cement samples (Choice 2, Bisco) were fabricated in a Teflon mold and activated through the various ceramics with different shades and thicknesses using an LED unit (Bluephase, IvoclarVivadent). In the control group, the resin cement sample was directly light-cured without any ceramic. Vickers microhardness indentations were made on the resin surfaces (KoopaPazhoohesh) after 24 hours of dark storage in a 37°C incubator. Data were analyzed using analysis of variance followed by the Tukey post hoc test (α = 0.05).ResultsCeramic thickness and shade had significant effects on light transmission and the microhardness of all specimens (p < 0.05). The mean values of light transmittance and microhardness of the resin cement in the VM group were significantly higher than those observed in the IE and VS groups. The lowest microhardness was observed in the VS group, due to the lowest level of light transmission (p < 0.05).ConclusionGreater thickness and darker shades of the 3 types of CAD/CAM ceramics significantly decreased the microhardness of the underlying resin cement.

Effect of thickness of CAD/CAM materials on light transmission and resin cement polymerization using a blue light‐emitting diode light‐curing unit

“…This increases the number of encounters between the light beam and the crystal boundaries, resulting in higher scattering and, thus, lower light transmission 14,15 . Similar to a previous study, more light was transmitted through the feldspathic ceramic than all other ceramics, especially through 1.5 and 2.0 mm 17 . The needle‐shaped lithium disilicate and lithium silicate crystals 26,27 may cause more light scattering compared to feldspathic ceramic, which has lower crystalline content 26 .…”

Effect of the thickness of CAD‐CAM materials on the shear bond strength of light‐polymerized resin cement

“…This result can be attributed to the amount of light passing through ceramic materials. Previous studies have shown that the light intensity weakens with the increasing ceramic layer thickness [43, 44] even if the ceramics are selected as highly translucent [15]. Considering the results of the current study, it can be speculated that higher bond strength values are achievable with reduced ceramic thickness.…”

Transmittance of lithium disilicate ceramic of different thicknesses and opacities with different curing units

“…Glass matrix ceramics (GMCs) are preferred when the main goals are esthetic results and stable micro-mechanical and chemical adhesive interaction with composite resin luting materials [3][4][5][6] . Among GMCs lithium disilicate (LDS) based ceramics have gained popularity recently, due mainly to their versatility, with an indication range that goes from veneers to three-piece bridges in premolar areas and implant-supported single crowns 7,8 . LDS restorations can be made either by traditional heat-pressing procedure or through a digital workflow and milling process (CAD-CAM).…”

“…LDS restorations can be made either by traditional heat-pressing procedure or through a digital workflow and milling process (CAD-CAM). There are key differences in crystal distribution, shape and size between pressed and CAD-CAM restorations, all of which are prone to affect the transmittance of the structure 8,9 . One of the most important factors related to clinical success of glass ceramics is the achievement of durable bonding between dental tissues and the restorative unit through a composite-based luting material (CBLM) of adequate mechanical properties 10 .…”

“…The amount of radiant energy that is lost whilst being transmitted through a ceramic restoration" depends on ceramic composition, structure, quality and quantity of the crystalline phase, thickness, shade and porosity, among other factors 14,17 . This reduction results in less energy being absorbed by the initiator system of the luting composite and thus, a lower degree of conversion and lower mechanical and chemical properties, biological compatibility and bond strength 8 . Light transmittance for successful activation of composite luting materials depends not only on the characteristics of the restorative materials, but also the quality of the irradiated light.…”