Optical-fiber-based laser-induced breakdown spectroscopy for detection of early caries.

Shuhei Sasazawa,Yuji Matsuura,Satoko Kakino

doi:10.1117/1.jbo.20.6.065002

Abstract

A laser-induced breakdown spectroscopy (LIBS) system targeting for the in vivo analysis of tooth enamel is described. The system is planned to enable real-time analysis of teeth during laser dental treatment by utilizing a hollow optical fiber that transmits both Q-switched Nd:YAG laser light for LIBS and infrared Er:YAG laser light for tooth ablation. The sensitivity of caries detection was substantially improved by expanding the spectral region under analysis to ultraviolet (UV) light and by focusing on emission peaks of Zn in the UV region. Subsequently, early caries were distinguished from healthy teeth with accuracy rates above 80% in vitro.

Highlights

Visual observation and contact methods using a dental probe have been applied for diagnosing dental caries, they sometimes lead to misdiagnosis and pain in patients
We describe our expansion of the spectral region under analysis to ultraviolet (UV) light to improve the sensitivity of caries detection, and we show that early caries can be detected at high accuracy by analyzing the emission peaks of zinc (Zn) using UV light
By using a hollow optical fiber for delivery of the laser light to the sample surface, the system is capable of both diagnosis based on laser-induced breakdown spectroscopy (LIBS) and caries removal because the hollow optical fibers deliver high-powered infrared laser light for tooth ablation as well.[23,24]

Summary

Introduction

Visual observation and contact methods using a dental probe have been applied for diagnosing dental caries, they sometimes lead to misdiagnosis and pain in patients. To improve diagnostic accuracy and to avoid causing pain, many noncontact methods based on the radiation of electromagnetic waves have been developed. Digital imaging fiber-optic transillumination[2] and other methods based on fluorescence observation, such as quantitative light-induced fluorescence[2,3] and infrared-laser or visible lightinduced fluorescence,[4,5] have been well established. Some groups have proposed to use diagnosis methods based on fluorescence observation,[6] photoacoustic signals,[7,8] and infrared spectra[8,9,10] for feedback controlling of laser ablation of dental tissues. A definitive method has not appeared yet, Chan et al.[11] and Alexander and Fried[12] succeeded in selectively removing dental composite from teeth surfaces by using spectral feedback.[11,12] They focused on the difference in concentration of calcium between dental composites and dental hard tissues

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Conclusion