optical properties of different dental ceramics

1. 2- Glass ceramics
• Glass reinforced with lithium disilicate or leucite or fluorapatite
• Semi translucent systems superior translucency and more strength than
porcelains

3. • Leucite reinforced 35-60% crystals
• Lithium disilicate 65% crystals
• Lithium disilicate’s translucency can be adjusted by varying the
crystallization heat treatment. Thus HT ceramic exhibits crystals of (1.5
x 0.8 mm) in a glassy matrix, whereas LT ceramic exhibits smaller
crystals (0.8 x 0.2 mm) interlocked in a high density matrix.

4. Translucency of glass ceramics

5. 3-Polycrystalline
ceramics

6. Structure of Polycrystalline
Ceramics

7. • The band gap of undoped
tetragonal zirconia is 3.0-4.5
eV (413-275 nm) and this
increases to 5.2-6.0 eV (238-
206 nm) when doped with 3
mol% yttria which means that
zirconia should be
transparent BUT???
Zirconia has high scattering
coefficient

8. • Allow more light
transmission compared to
PFM
• Grain boundaries and
porosities cause light
scattering
• Intragranular and
intergranular pores

10. • Feldspathic glass matrix has a
refractive index of 1.5
• Partially stabilized zirconia has a
refractive index of 2.4
• Fully stabilized tetragonal
zirconia’s refractive index is 2.2
• Cubic zirconia has a refractive
index of 2

11. Birefringence
• Double refraction due to passing
through anisotropic crystals

12. Best optical properties are achieved by
• Decreasing the porosities (esp. intragranular) using pore scavengers
• Decreasing grain boundaries and interfaces between phases
• Decreasing birefringence (isotropic grain arrangement)
• Increasing grain size
• Avoiding pores and grains of sizes similar to the wavelengths of visible
light (e.g. Alumina)
• Avoiding rough surface finish

16. Factors affecting color
• Natural dentin color
• Luting agent
• Material thickness
• Particle size
• Firing temperature
• Doping agents

17. 1-Natural
Dentin color
• Normal tooth,
discolored or
treated with post
and core

18. 2-Luting agent
• Shade of luting agent has 5% effect
• Use highly translucent universal shade resin
cement
• The development of improved optical
properties (e.g., more translucent zirconia)
not only enhances the aesthetic quality but
also improves the photopolymerization of
the resin cement

19. 3-Material thickness
• The thickness of the body porcelain layer determines the color
obtained with a given opaque porcelain
• Increasing the thickness of a ceramic material decreases the
degree of translucency due to less transmission
• Enamel like structures should be more incisally and proximally

20. 4-Particle size

21. Ceramic
nanoparticles
• Nanocrystalline
ceramics have a grain
size of about 50 nm,
which is significantly
less than the
wavelength range of
visible light resulting
in higher transmission

22. 5-Firing techniques
Repeated firing and high firing temperatures can cause pigment
breakdown
Repeated
Firing
Pressure during sintering increases densification and decreases the
pores thus improving translucencyPressure
Spark plasma sintering (SPS) at 1200 C and vacuum to obtain dense
ceramicsSPS
Light transmission can be improved by air annealing at 750 C as it fills
the oxygen vacancies with atmospheric oxygenAnnealing
Low temp. presintering of zirconia creates small crystals with small
pores while high temp. produces large grains with intragranular poresPresintering
Microwave sintering results in reduced porosity and a uniform
grain size distribution
Microwave

23. 6- Doping agents
• Yittrium is a pore scavenger reducing
intragranular porosity
• lanthanum dopant completely dissolves in the
zirconia, which results in a finer microstructure
free of precipitation by secondary phases (no
boundaries nor scattering)
• Fe doped ceramics has lower refractive index,
less oxygen vacancies and less porosities
• Pr doped have lower oxygen vacancies as
praseodymium can be both tri and tetravalent

24. Recent
advances
1- Multilayered blocks

25. 2- Zirconia reinforced glass ceramics

26. 3- VITA Ambria

27. 4- Porcelain
Blocks

29. 5- Shade choice app

30. References
• Raptis NV, Michalakis KX, Hirayama H. Optical behavior of current ceramic systems. International
Journal of Periodontics & Restorative Dentistry. 2006 Jan 1;26(1).
• Babu PJ, Alla RK, Alluri VR, Datla SR, Konakanchi A. Dental ceramics: Part I–An overview of
composition, structure and properties. Am J Mater Eng Technol. 2015;3(1):13-8.
• Bergmann CP, Stumpf A. Dental ceramics. Biomaterials. 2013:9-13.
• Shahmiri R, Standard OC, Hart JN, Sorrell CC. Optical properties of zirconia ceramics for esthetic
dental restorations: A systematic review. The Journal of prosthetic dentistry. 2018 Jan 1;119(1):36-46.
• Volpato C, Philippi A, Petter C, Fredel M. Ceramic materials and color in dentistry. INTECH Open Access
Publisher; 2010 Sep 28.
• Shahmiri RA, Standard OC, Hart JN, Sorrell CC. A Review of the Characteristics and Optimization of
Optical Properties of Zirconia Ceramics for Aesthetic Dental Restorations. International Journal of
Biomedical and Biological Engineering. 2017 Oct 2;11(8):499-507.

31. References
• Ahmed WM, Troczynski T, McCullagh AP, Wyatt CC, Carvalho RM. The influence of altering sintering protocols on
the optical and mechanical properties of zirconia: A review. Journal of Esthetic and Restorative Dentistry. 2019
Sep;31(5):423-30.
• Arena A, Prete F, Rambaldi E, Bignozzi MC, Monaco C, Di Fiore A, Chevalier J. Nanostructured Zirconia-Based
Ceramics and Composites in Dentistry: A State-of-the-Art Review. Nanomaterials. 2019 Oct;9(10):1393.
• Bashir M, Riaz S, Naseem S. Fe 3 O 4 stabilized zirconia: structural, mechanical and optical properties. Journal of
Sol-Gel Science and Technology. 2015 May 1;74(2):281-9.
• Della Bona A, Nogueira AD, Pecho OE. Optical properties of CAD–CAM ceramic systems. Journal of dentistry. 2014
Sep 1;42(9):1202-9.
• Vanini L, Mangani FM. Determination and communication of color using the five color dimensions of teeth. Practical
Periodontics and Aesthetic Dentistry. 2001 Jan;13(1):19-26.
• https://glidewelldental.com/education/inclusive-dental-implant-magazine/volume-2-issue-4/understanding-zirconia-
crown-esthetics-and-optical-properties/
• https://www.vita-zahnfabrik.com/en/VITA-Zahnfabrik-This-is-how-prosthetics-are-made-88384.html

32. THANK YOU