Chemo-mechanical characterization of carious dentine using Raman microscopy and Knoop microhardness.

M Alturki,G Koller,A Banerjee,U Almhöjd

doi:10.1098/rsos.200404

Abstract

One of the aims in the clinical operative management of dental carious lesions is to remove selectively the highly infected and structurally denatured dentine tissue, while retaining the deeper, repairable affected and intact, healthy tissues for long-term mechanical strength. The present study examined the correlation of chemical functional groups and the microhardness through the different depths of a carious lesion using Raman spectroscopy and Knoop microhardness testing. The null hypothesis investigated was that there was no correlation between Raman peak ratios (amide I : phosphate ν1) and equivalent Knoop microhardness measurements. Ten freshly extracted human permanent teeth with carious dentine lesions were sectioned and examined using high-resolution Raman microscopy. The ratio of absorbency at the amide I and phosphate bands were calculated from 139 scan points through the depth of the lesions and correlated with 139 juxtaposed Knoop microhardness indentations. The results indicated a high correlation (p < 0.01) between the peak ratio and the equivalent Knoop hardness within carious dentine lesions. This study concluded that Raman spectroscopy can be used as a non-invasive analytical technology for in vitro studies to discriminate the hardness of carious dentine layers using the peak ratio as an alternative to the invasive, mechanical Knoop hardness test.

Highlights

In the contemporary minimally invasive (MI) approach to the operative caries management of active cavitated carious lesions, it is recommended to remove selectively only the superficial, highly bacterially contaminated and denatured zone of tissue that is clinically wet, soft and sticky––the caries-infected dentine
The most common carious dentine management techniques are mechanical in nature, ranging from diagnostics through to surgical intervention
The null hypothesis investigated was that there was no correlation between Raman peak ratios and Knoop microhardness measurements

Summary

Introduction

In the contemporary minimally invasive (MI) approach to the operative caries management of active cavitated carious lesions, it is recommended to remove selectively only the superficial, highly bacterially contaminated and denatured zone of tissue that is clinically wet, soft and sticky––the caries-infected dentine. The remaining deeper caries-affected tissues can be healed and repaired by the dentine-pulp complex and can be retained and sealed off using bio-interactive restorative materials. This surgical procedure preserves more dental tissue and improves the long-term survival of the dentine-pulp complex. The transition between these two histologically different zones of tissue, is rather diffuse and difficult to identify clinically, which leads to subjectivity between operators and often unnecessary excessive removal of tooth tissue. The hardness test has a major drawback in that it is an invasive, low-resolution test that damages samples, often precluding any further analysis of the tissues [11]

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