Light transmission through porcelain

Peixoto, Rogéli T.R.C.; Paulinelli, Vanessa Maria F.; Sander, Herbert H.; Lanza, Marcos D.; Cury, Luiz Alberto; Poletto, Luiz Thadeu A.

doi:10.1016/j.dental.2006.11.025

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Volume 23, Issue 11 , Pages 1363-1368, November 2007

Light transmission through porcelain

Rogéli T.R.C. Peixoto
- Department of Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
- Corresponding author at: Rua Miradouro, 40/101, Bairro Sion, 30.310-640 Belo Horizonte, Minas Gerais, Brazil. Tel.: +55 31 3287 7973; fax: +55 31 3287 7973.
Vanessa Maria F. Paulinelli
- Department of Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
Herbert H. Sander
- Department of Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
Marcos D. Lanza
- Department of Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
Luiz Alberto Cury
- Department of Optical Physics, Federal University of Minas Gerais, Belo Horizonte, Brazil
Luiz Thadeu A. Poletto
- Department of Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil

Received 13 May 2006; received in revised form 7 July 2006; accepted 16 November 2006.

Abstract

Objective

This study evaluates the effect of shade and thickness of porcelain in light transmission.

Methods

One hundred and twenty-eight disks of Duceram^® porcelain were made to combine four different thicknesses (1.5; 2.0; 3.0; 4.0mm) and eight shades (A₁; A₄; B₁; B₄; C₁; C₄; D₂; D₄). A digital power meter (Newport Optical Power Meter^®) was used to measure light transmission. The porcelain transmission coefficient was calculated using Lambert–Beer law, t_c=Ce^−αd, where t_c is the transmission coefficient, C the contribution factor of the reflection coefficient, e a constant, α the absorption coefficient and d is the sample thickness.

Results

The transmission coefficients did not vary statistically in relation to the two visible light-curing units studied. From all the samples, the colors A₁ and D₂, thickness 1.5mm, presented the highest percentages of transmission (8%) and the shades, A₄, B₄ and C₄, thickness 4mm, the lowest (0.5%). The relationship between the Naperian logarithm of the transmission coefficient and the samples thickness followed the Lambert–Beer law. The linear adjustment of the experimental points of the two variables, showed the absorption coefficient (α) and the constant value related to the reflection (C) of each porcelain shade. The reflection coefficient values of all shades did not vary statistically among themselves.

Significance

For most shades there was a significant decrease in light transmission as the sample porcelain thickness increased. For the same thickness most shades presented statistical difference between the transmission coefficients. However, the larger the thickness, the higher the number of shades which, statistically, showed no difference.

Keywords: Light transmission, Porcelain, Ceramics, Lambert–Beer law, Polymerization, Photo-polymerization, Porcelain shades, Transmission coefficient, Absorption coefficient, Reflection coefficient, Dental material