Elsevier

Dental Materials

Volume 26, Issue 7, July 2010, Pages e205-e210
Dental Materials

Pilot in vivo image spectro-photometric evaluation of optical properties of pure enamel and enamel–dentin complex

https://doi.org/10.1016/j.dental.2010.03.006Get rights and content

Abstract

Objectives

The aim of this in vivo study is to investigate the L*a*b*and the opacity (CR) of front teeth by means of an image spectrophotometer and to evaluate the eventual influence of the background color on the results. The second aim is to investigate if there is a relationship between tea, coffee, red wine drinking habits or smoking habits of the test subjects and tooth color.

Methods

A novel image based spectro-photometric approach was developed and applied on a Swiss Army recruits group quantifying L*a*b* of pure enamel as well as of enamel–dentin complex against black and white background together with CR.

Results

When 2 mm thick pure enamel was considered, the values obtained were (mean (SD)) L*(76.3 (3.4)), a*(3.4 (1.2)) and b*(17.2 (2.45)) against white background and L*(63.5 (4.2)), a*(0.8 (1.3)) and b*(10.7 (2.7)) against black background. The opacity (CR) of 2 mm thick pure enamel was (64.4 (0.1)).

When 3 mm thick enamel–dentin complex was considered, the values obtained were L*(79.0 (2.6)), a*(3.9 (1.3)) and b*(20.4 (3.0)) against a white background and L*(74.9 (3.0)), a*(1.8 (1.2)) and b*(16.7 (3.1)) against a black background. The opacity (CR) of 3 mm thick enamel–dentin complex was (87.4 (0.1)).

Significance

The application of this method on a larger group of subjects of different ages may serve as a database for a more exact characterization of optical properties of natural enamel and dentin.

Introduction

The need for imperceptible esthetic restorations is steadily increasing due to the rise of very demanding patients [1]. In modern society, in fact, esthetic is one of the major pillars and dental appearance is an important factor, especially in front teeth. In the modern trend of minimal invasiveness, veneers and crowns are only indicated when acceptable esthetic results cannot be reached by the direct restorative approach, i.e. the use of free-hand bonded composite restorations.

Even if composite resins have proved to give satisfactory results in the hands of excellent practitioners, the invisible restoration is still a chimera for the majority of dentists. Besides the restorations’ shape, a proper color match is of main importance and it is difficult to achieve with today's composites. There is, in fact, an evident mismatch between shades of available restorative materials [2] and teeth. Furthermore a large part of the available composites still sticks to the Vita shade guide where the shade selection is done by mixing the color information of enamel and dentin. Due to this outdated concept the majority of epidemiologic tooth color studies have been done by measuring the color of the entire tooth. This approach has already been criticized and shade selection based on the separate choice of enamel and dentin color has been proposed [3], [4], [5]. Anyway, no study has, so far, tried to measure in vivo on a larger number of subjects the optical properties of enamel and dentin. The only few available data in this field are, in fact, available from in vitro measurements [6], [7] and limited to a low number of samples.

The aim of this in vivo study is therefore to investigate the L*a*b*, value and opacity (CR) of front teeth by means of an image spectrophotometer and to evaluate the eventual influence of the background color on the results. The second aim is to investigate if there is a relationship between tea, coffee, red wine drinking habits or smoking habits of the test subjects and tooth color.

Section snippets

Materials and methods

62 randomly chosen recruits from the Swiss Army coming from the German Swiss region in the age of 20–21 years gave their written informed consensus for a spectro-photometric analysis and the stone reproduction through a polysiloxane impression of their upper central incisors. Only patients with intact vital upper central incisors without malformations and significant intrinsic colorations, fissures or restorations were included into the study.

After answering a questionnaire on their drinking

Results

When the 2 mm thick pure enamel was considered, the values obtained were L*(76.3 (3.4)), a*(3.4 (1.2)) and b*(17.2 (2.5)) against a white background and L*(63.5 (4.2)), a*(0.8 (1.3)) and b*(10.7 (2.7)) against a black background. The opacity (CR) of 2 mm pure enamel was (64.4 (0.1)).

When the 3 mm thick enamel–dentin complex was considered, the values obtained were L*(79.0 (2.6)), a*(3.9 (1.3)) and b*(20.4 (3.0)) against a white background and, L*(74.9 (3.0)), a*(1.8 (1.2)) and b*(16.7 (3.1))

Discussion

Only little is known about quantitative optical properties of vital teeth of a specific population in their natural surrounding. This is especially true if specific data are required for enamel and for enamel-dentin complex. Optical properties of enamel and dentin, in fact, have only been measured in vitro on a very limited number of samples [5]. Clinical studies on a larger group of patients are scarce and only basic color of the entire tooth has been measured in these studies so far [10], [11]

Conclusions

In this in vivo study L*a*b*, and opacity (CR) of a young population of recruits in the Swiss Army were evaluated. The influence of background on the results was significant while only a marginal influence of the drinking habits (only tea showed to decrease L* values in pure enamel when analyzed against black background) could be found.

Future studies with higher number of subjects of different range of age and of different origins are needed in order to confirm the present data and to be able

Acknowledgements

This study was supported in part by the SSO research fund no. 221. The authors are grateful to the Swiss Army and Mr Vaglion for the permission of performing this study.

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