Evaluating the efficiency of caries removal using an Er:YAG laser driven by fluorescence feedback control

Caries lesions in dental hard tissues autofluoresce when exposed to light of certain wavelengths, whereas sound tissues do not, and this can be used as an in vitro histological marker for dental caries. Detection of autofluorescence is the basis of KaVo DIAGNOdent™ technology, and provides objective feedback control of laser-stimulated ablation of dental caries for the KaVo Key Laser 3™. This Er:YAG laser operates at 2940nm wavelength, and is effective at removal of infected dental hard tissues. Micro-computed tomography (micro-CT) allows the non-invasive investigation of three-dimensional structures and analysis of mineral density profiles of dentine following laser ablation.

To evaluate removal of infected, demineralised dentine by Er:YAG irradiation with a laser feedback mechanism, using micro-CT.

27 carious teeth (1 control) and 1 sound tooth, treated with the KaVo Key Laser 3™ using a KaVo™ non-contact 2060 handpiece at specific feedback settings, were examined using a Skyscan 1172 Micro-CT, to observe the efficiency of demineralised dentine removal. Grey scale images obtained were colour rendered to assist detection of demineralised tissue if present.

Complete removal of demineralised tissue occurred with laser-stimulated ablation under feedback control at values of 7 and 8 when measured by micro-CT. At greater values, removal of demineralised dentine was incomplete.

Examination of dental tissues by micro-CT allowed determination of the efficiency of Er:YAG laser-stimulated ablation. Feedback control of the KaVo Key Laser 3™ appeared to operate like a cut-off switch when infected dentine was eliminated, at a threshold of between 6 and 7.