Spectrophotometric analysis of two all ceramic materials l.jpg
Sponsored Links
This presentation is the property of its rightful owner.
1 / 58

Spectrophotometric analysis of two All-Ceramic materials PowerPoint PPT Presentation


  • 128 Views
  • Uploaded on
  • Presentation posted in: General

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

Download Presentation

Spectrophotometric analysis of two All-Ceramic materials

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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

  • Early 16th Century – Mineral teeth


John Greenwood


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


  • 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


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


Some aspects of Color

  • 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


Some aspects of Color


Color systems

  • 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


CIELAB system

Courtesy: Handprint media


CIELAB system

  • 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);


CIELAB system

Courtesy: Handprint media


CIELAB system

  • 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


Experimental Design

  • 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

  • Ceramic samples as clinical units

In-Ceram Alumina, 1,0 mm

In-Ceram Alumina, 1,4 mm

Empress 2, 1,4 mm


Armamentarium

  • Cements


Armamentarium

  • Micrometer (Mitutoyo, Japan)


Armamentarium

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


Armamentarium

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

Spectral Range: 380 – 720nm

Viewing Geometry: d/8°


Armamentarium

  • Standard Black and White Backgrounds


Formula for color difference

  • ∆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


Clinically significant color differences

  • ∆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)


Results


Empress2 ∆L


Empress2 ∆a


Empress2 ∆b


Empress2 ∆E


Inceram Alumina ∆l 1,40mm


Inceram Alumina ∆a 1,40mm


Inceram Alumina ∆b 1,40mm


Inceram Alumina ∆E 1,40mm


Inceram Alumina ∆l 1,00mm


Inceram Alumina ∆a 1,00mm


Inceram Alumina ∆b 1,00mm


Inceram Alumina ∆E 1,00mm


Correlation:∆Lwb and ∆Ebcwc(of translucency with the color change due to luting agent)

  • Pearsons correlation (r):

    Compolute = 0.13p = 0.38 0.21 ±0.05mm

    GIC = 0.05p = 0.76 0.24 ±0.04mm

    ZnPO = 0.82p = 0.00 0.24 ±0.10mm


Cements: ZnPO, GIC, RLA


Cements: ZnPO, GIC, RLA


Conclusions

  • 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)


Conclusions

  • 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


Conclusions

  • 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


Future Work

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


Kubelka-Munk theory

  • 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 theory

  • 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

  • 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)

  • 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 (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.........................


Artificial Neural Network (ANN)

Threshold Logical Unit


Artificial Neural Network

Feed forward fully connected back propagation algorithm for weight adjustments


CIELab for ANN ??

  • ADVANTAGES:

    • Easier access to CIELab data

    • Already existing databases

  • DISADVANTAGES:

    • More experimental work required

    • Does not predict the reflectance spectra at various thickness


Software engineeringWaterfall Model


ColPres (Color Prescription)

  • Development of an algorithm

  • Development of test Database (MySQL)

  • Testing the algorithm

  • Development of a Complete Database (MySQL)

  • Full implementaion of the algorithm (Java)


Clinical Implication of ColPres

ShadeEye-NCC™


Clinical Implication of ColPres


Million dollar Smile


Thank you for your attention.


  • Login