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Spectrophotometric analysis of two All-Ceramic materials. Varun Singh Barath University of Cologne, Germany. Dilemma. Esthetic Dentistry. Since ancient times – teeth have been an integral part of the face Animal teeth and Ivory– all carved in the form of human teeth

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Spectrophotometric analysis of two all ceramic materials l.jpg

Spectrophotometric analysis of two All-Ceramic materials

Varun Singh Barath

University of Cologne, Germany



Esthetic dentistry l.jpg
Esthetic Dentistry

  • Since ancient times – teeth have been an integral part of the face

  • Animal teeth and Ivory– all carved in the form of human teeth

  • Early 16th Century – Mineral teeth



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Esthetic Dentistry

  • Metal Ceramic restorations – 4 decades ago were the “State of Art”

  • All-Ceramic restorations – advancements in last decade have made them popular

    • Increase in strength

    • Better biocompatiblity

    • Excellent optical properties


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  • PART 1: Spectrophotometric analysis of two All-Ceramic materials with the effect of the background shade on the final shade

  • PART 2: Proposed Model for Color Prediction using Kubelka-Munk theory and Artificial Neural Networks


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Spectrophotometric analysis of two All-Ceramic materials with the effect of the background shade on the final shade


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Some aspects of Color with the effect of the background shade on the final shade

  • Color is the perception of light by the mind in response to a stimuli from the eye

  • It is a visual sensation

  • Different colors have different wavelengths

  • Visible part of the spectrum 380 – 750 nm


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Some aspects of Color with the effect of the background shade on the final shade


Color systems l.jpg
Color systems with the effect of the background shade on the final shade

  • Numerical representation of Color

  • International Commission of Illumination (Commission Internationale de l’Eclairage).

  • Important colorimetric systems are RGB, XYZ, CIELAB, CMC, Munsell system, to name a few


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CIELAB system with the effect of the background shade on the final shade

Courtesy: Handprint media


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CIELAB system with the effect of the background shade on the final shade

  • Estd. 1976 (by the International Commission of Illumination (Commission Internationale de l’Eclairage))

  • L* - vertical, achromatic coordinate

    0 (black) to 100 (white);

  • a* - horizontal, green/red coordinate,

    -80 (green) to +80 (red);

  • b* - horizontal, blue/yellow coordinate

    -80 (blue) to +80 (yellow);


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CIELAB system with the effect of the background shade on the final shade

Courtesy: Handprint media


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CIELAB system with the effect of the background shade on the final shade

  • C - saturation, representing the difference of a specific color in relation to gray color of the same lightness

  • H° - hue is represented in the ab plane

    H=0° corresponds to red color,

    H=90° corresponds to yellow,

    H=180° corresponds to green,

    H=270° corresponds to blue color


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Experimental Design with the effect of the background shade on the final shade

  • Aim: to study the effect of background shade on the final shade of All-Ceramic Systems (In-Ceram Alumina, Empress2)

  • Shades chosen: lighter than the lightest, darker than the darkest and one from the middle

  • Luting Agents: ZnPO4 , GIC, RLA

  • Background: Standard black and white


Armamentarium l.jpg
Armamentarium with the effect of the background shade on the final shade

  • Ceramic samples as clinical units

In-Ceram Alumina, 1,0 mm

In-Ceram Alumina, 1,4 mm

Empress 2, 1,4 mm


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Armamentarium with the effect of the background shade on the final shade

  • Cements


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Armamentarium with the effect of the background shade on the final shade

  • Micrometer (Mitutoyo, Japan)


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Armamentarium with the effect of the background shade on the final shade

  • Sample Preparation (Simulating a clinical All-Ceramic restoration)


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Armamentarium with the effect of the background shade on the final shade

  • Spectrophotometer (Dr. Lange GmBH, Berlin, Germany)

Spectral Range: 380 – 720nm

Viewing Geometry: d/8°


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Armamentarium with the effect of the background shade on the final shade

  • Standard Black and White Backgrounds


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Formula for color difference with the effect of the background shade on the final shade

  • ∆E = [(L w– L b)2 + (a w– a b)2 + (b w– b b)2] ½

  • ∆L = L w– L b

  • ∆a = a w– a b

  • ∆b = b w– bb


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Clinically significant color differences with the effect of the background shade on the final shade

  • ∆E > 3.7 : Very Poor match (Johnston and Kao, 1989)

  • ∆E > 2 : Clinically not acceptable (Touati et al, 1993)

  • ∆E ≤ 2 : Clinically acceptable (O‘Brien et al, 1990)

  • ∆E < 1 : Not appriciable (Kuehni and Marcus, 1990)


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Results with the effect of the background shade on the final shade


Empress2 l l.jpg
Empress2 ∆L with the effect of the background shade on the final shade


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Empress2 ∆a with the effect of the background shade on the final shade


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Empress2 ∆b with the effect of the background shade on the final shade


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Empress2 ∆E with the effect of the background shade on the final shade


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Inceram Alumina ∆l 1,40mm with the effect of the background shade on the final shade


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Inceram Alumina ∆a 1,40mm with the effect of the background shade on the final shade


Inceram alumina b 1 40mm l.jpg
Inceram Alumina ∆b 1,40mm with the effect of the background shade on the final shade


Inceram alumina e 1 40mm l.jpg
Inceram Alumina ∆E 1,40mm with the effect of the background shade on the final shade


Inceram alumina l 1 00mm l.jpg
Inceram Alumina ∆l 1,00mm with the effect of the background shade on the final shade


Inceram alumina a 1 00mm l.jpg
Inceram Alumina ∆a 1,00mm with the effect of the background shade on the final shade


Inceram alumina b 1 00mm l.jpg
Inceram Alumina ∆b 1,00mm with the effect of the background shade on the final shade


Inceram alumina e 1 00mm l.jpg
Inceram Alumina ∆E 1,00mm with the effect of the background shade on the final shade


Correlation l wb and e bcwc of translucency with the color change due to luting agent l.jpg
Correlation with the effect of the background shade on the final shade:∆Lwb and ∆Ebcwc(of translucency with the color change due to luting agent)

  • Pearsons correlation (r):

    Compolute = 0.13 p = 0.38 0.21 ±0.05 mm

    GIC = 0.05 p = 0.76 0.24 ±0.04 mm

    ZnPO = 0.82 p = 0.00 0.24 ±0.10 mm


Cements znpo gic rla l.jpg
Cements with the effect of the background shade on the final shade: ZnPO, GIC, RLA


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Cements with the effect of the background shade on the final shade: ZnPO, GIC, RLA


Conclusions l.jpg
Conclusions with the effect of the background shade on the final shade

  • All-Ceramics due to their translucency have an effect of the luting agents and background shade (dentine/discolored tooth/post) on the final shade

  • The two All-Ceramics examined showed a shift in the the ∆a values due to black background (shift towards red) (reflection curves at various wavelengths to be investigated)


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Conclusions with the effect of the background shade on the final shade

  • As ceramic thickness increases the effect of luting agent and background decreases

  • Depending on the luting agent the background shade can be partially masked

  • Luting agents have an effect on the final color


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Conclusions with the effect of the background shade on the final shade

  • The outcome of the ceramic restorations cannot be predicted with accuracy

  • Not only the color, that is percieved by the eye is important but also the optical properties of the materials shoud be studied for predicting the outcome of the all ceramic restorations


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Future Work with the effect of the background shade on the final shade

Model for Color Prediction using Kubelka-Munk theory and Artificial Neural Networks for all ceramic restorations


Kubelka munk theory l.jpg
Kubelka-Munk theory with the effect of the background shade on the final shade

  • color mixing model which describes the reflectance and transmittance of a color sample with respect to the absorption and scattering spectra of the material

  • mathematical model used to describe the reflectance

  • considers the absorption and scattering in a colored sample of fixed thickness


Kubelka munk theory46 l.jpg
Kubelka-Munk theory with the effect of the background shade on the final shade

  • four factors:

    • an absorption spectrum K(λ )

    • a scattering spectrum S(λ)

    • the sample thickness X

    • the reflectance spectrum of the substrate or backing Rp(λ )


Kubelka munk km theory l.jpg
Kubelka-Munk (KM) theory with the effect of the background shade on the final shade

  • Has been used to measure the reflectance of All-Ceramic materials (Miyagawa and Powers, (1982); Woolsey, G. D., W. M. Johnston, et al. (1984); Cook and McAree, (1985); ......................................... Davis, B. K., W. M. Johnston, et al. (1994))

  • “The data on the absorption/scattering coefficient ratio (K/S values) at certain wavelengths are necessary for the creation of a computer database and as well as for the computer color prescription”(Paravina R.D, (1999) )


Artificial neural network ann l.jpg
Artificial Neural Network with the effect of the background shade on the final shade(ANN)

  • The ANN technology is a computer system solution with a surprising capacity to learn from input data

  • computer-based algorithms which are modeled on the structure and behaviour of neurons in the human brain and can be trained to recognize and categorize complex patterns.


Artificial neural network ann49 l.jpg
Artificial Neural Network with the effect of the background shade on the final shade(ANN)

  • Neural networks are well suited for data mining tasks due to their ability to model complex, multi-dimensional data

  • Some applications of ANN.

    Stock market prediction

    Weather prediciton

    Speech recognition

    Face recognition.........................


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Artificial Neural Network with the effect of the background shade on the final shade(ANN)

Threshold Logical Unit


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Artificial Neural Network with the effect of the background shade on the final shade

Feed forward fully connected back propagation algorithm for weight adjustments


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CIELab for ANN ?? with the effect of the background shade on the final shade

  • ADVANTAGES:

    • Easier access to CIELab data

    • Already existing databases

  • DISADVANTAGES:

    • More experimental work required

    • Does not predict the reflectance spectra at various thickness


Software engineering waterfall model l.jpg
Software engineering with the effect of the background shade on the final shadeWaterfall Model


Colpres color prescription l.jpg
ColPres (Color Prescription) with the effect of the background shade on the final shade

  • Development of an algorithm

  • Development of test Database (MySQL)

  • Testing the algorithm

  • Development of a Complete Database (MySQL)

  • Full implementaion of the algorithm (Java)


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Clinical Implication of ColPres with the effect of the background shade on the final shade

ShadeEye-NCC™


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Clinical Implication of ColPres with the effect of the background shade on the final shade


Million dollar smile l.jpg
Million dollar Smile with the effect of the background shade on the final shade


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Thank you for your attention. with the effect of the background shade on the final shade


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