Spectrophotometric examination of monolithic zirconia materials

Abstract

Introduction: Patients’ demand for perfectly esthetic restorations is unstoppably increasing, however creating naturallooking crowns and FPDs is highly affected by the experience of the dental technician even in the present day. This problem is even more complicated if the abutment is discolored (e.g. obturated). Using modern dental ceramic materials, such as zirconia, it’s essential to know the physical (mechanical and optical) properties of the selected material to achieve the best result. Purpose: The purpose of this in vitro study of Semmelweis University Department of Prosthodontics and Budapest University of Technology and Economics Department of Atomic Physics was to examine specific optical properties of coloured and uncoloured monolithic zirconia materials considering thickness, try-in pastes and substrates of different colours using a spectrophotometer. Materials and methods: Zirconia specimens (A2P1, WHITE, Erran Tech) in 5 different thicknesses (with the thickness range of 0.5–2.5 mm), six types of substrate materials (VITA Simulate), three types of metal substrates and three types of try-in pastes (Variolink Esthetic Try-In Paste, Ivoclar Vivadent) were used in this study. Measurements were carried out at Budapest University of Technology and Economics with a PerkinElmer LAMBDA 1050 UV/Vis/NIR spectrophotometer. Colour differences (ΔE) were calculated using CIEDE2000 formula. Results: Mean of ΔE values of 0.5 mm thick A2P1 specimens was xΔE = 4.10 (σΔE = 2.91); that of specimens having thickness of 2.5 mm was xΔE = 1.88 (σΔE = 0.67). Mean of ΔE values of 0.5 mm thick WHITE specimens was xΔE = 6.40 (σΔE = 2.75); that of specimens having thickness of 2.5 mm was xΔE = 5.46 (σΔE = 0.79). Discussion: The substrate colour and the thickness of zirconia affects the optical results – with special regard to colour perceptibility and acceptability – as well as the shade of the try-in paste under 2 mm ceramic thickness. ΔE values of WHITE specimens are less influenced by the thickness of the ceramic layer, than ΔE values of A2P1 zirconia. Conclusions: Coloured (A2P1) and uncoloured (WHITE) zirconia materials show both similarities and discrepancies in behaviour, i.e. spectral reflectance and ΔE. Using monolithic coloured A2P1 zirconia of a proper thickness to restore discolored teeth can provide the opportunity to modify or mask the original toothshade.

Keywords

• ceramic
• monolithic
• zirconia
• color
• spectrophotometry
• prosthodontics