Effective laser ablation of enamel and dentine without thermal side effects

Abstract

We present a feasibility study into laser treating dental materials by using femtosecond pulses generated by a titanium:sapphire laser system which consisted of an oscillator and a regenerative amplifier. The pulse duration was varied between 200 fs and 2 ps. The observed energy thresholds for the ablation process of dentine and enamel were clearly smaller than those observed when longer pulse durations were used. The consequence of this observation is a lower thermal load within the vicinity of the radiated area. Thus no thermal damage or mechanical damage, such as cracks, were produced during the laser treatment. Commercially available femtosecond laser systems can produce ablation rates in healthy and in-vitro demineralized dental material 2 mm3 per min and 6-16 mm3 per min, respectively. These values are an order of magnitude larger than those produced by picosecond laser systems at the same time pulse energy and pulse repetition rate. The brightness of the plasma spark generated by the laser treatment depended on the dimineralization of the teeth. This may allow online control of the laser treatment.

Laser-induced breakdown spectroscopy: a tool for real-time, in vitro and in vivo identification of carious teeth

“…In recent years research groups particularly in Germany have shown that the use of femto-second lasers may present an alternative to classical mechanical drilling techniques to realise contactless drills in dentistry [2,11,12]. While intriguingly elegant, femto-second laser drilling still experiences problems with ablation efficiency [11,12].…”

“…While intriguingly elegant, femto-second laser drilling still experiences problems with ablation efficiency [11,12]. For example, some dentists utilise Er:YAG lasers [12,13], which were recently approved by the US Food and Drug Administration (FDA) for use on human subjects [14]. Er:YAG lasers have greater efficiency than other, presently available femto-second laser systems.…”

“…Er:YAG lasers have greater efficiency than other, presently available femto-second laser systems. However, drill areas treated by Er:YAG lasers occasionally contain long fissures that arise due to sudden vaporisation of the water in the tooth tissue [11,12,15]. This may result in rough tooth surfaces with deep cracks, up to 300 μm; their presence and extent were detected using dye penetration tests [2].…”

“…To use the spectroscopic analysis of laser-induced plasmas, to obtain information about the caries – state of dental tissue, was first suggested by Niemz [2] and Kohns [12]. Their studies involved only the spectroscopic investigation of spectral lines of calcium (intensity and line width).…”

Influence of femtosecond laser treatment on shear bond strength of composite resin bonding to human dentin under simulated pulpal pressure

“…A main advantage of ultrashort laser pulses is the ablation of tissue with negligible heat damage, thus creating structures with minimal damage to the surrounding tissue enabling better SBS. 6,7 In 2004, Weigl et al 8 reported on cavities generated with a chirped-pulse amplification Ti:sapphire fs-laser in extracted teeth. This method resulted in extremely precise cavity preparations with sharp margins, free of chipping, no smear-layer, and open dentinal tubuli.…”