2011 Volume 22 Issue 1 Pages 16-20
Selective caries removal is one of the most required applications of lasers in dentistry. The objective of this study was to regulate the laser irradiation effect precisely and to develop a technique for selectively removing carious dentin for the next laser dentistry using the specific absorption in the 6 μm wavelength range. To prepare a carious dentin model, a bovine dentin disc was soaked in lactic acid solution to demineralize the surface of the disc. A nanosecond pulsed laser with a wavelength of 6.02 μm, which corresponds to the absorption band called amide I, was used as the light source for treatment. The pulse width and repetition rate were 5 ns and 10 Hz. At average power densities below 15 W/cm2, removal of sound dentin was not observed. For demineralized dentin, tissue removal was observed at the average power density of 15 W/cm2 from the irradiation time of 1 s. The removal continued to the surface of sound dentin, and stopped at the boundary between the sound dentin and demineralized dentin. Our group has estimated that the major cause of the selective removal shown in this study is the difference of mechanical properties between sound and demineralized dentin, due to the difference in hydroxyapatite (HAP) content rate. In conclusion, 6.02 μm is a promising laser wavelength for selective caries removal without serious side effects on sound dentin. In the near future, the development of extremely-compact laser devices will pave the way for minimal invasive laser treatment in dental clinics.
