ESEM and AFM analysis of human dentine irradiated with femtosecond laser pulses

Different approaches for painless, fast and localized laser treatment of dental hard tissue is a subject of continuing research for the scientists. Studies of dentine ablation with Er:YAG and Ho:YAG lasers have indicated several weaknesses of the surface preparation process expressed in melting, fissuring and slow material removal rates. Some modifications of these systems (Er, Cr:YSGG) were introduced in dental practice in combination with water spray in order to enhance the surface preparation by cooling the ablated region and increasing the ablation rate. This paper investigates the surface morphology and structure of dentine after ablation with ultra-short pulses using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM). A chirped pulse amplification (CPA) Ti:Sapphire laser is used, with an operating wavelength centered on 800 nm , pulse duration 25 fs and maximum repetition rate of 1 KHz. The laser induced damage is characterized over the fluence range 1.1-2.1 J /cm². The results demonstrate that it is possible with selected parameters to obtain efficient dentine femtosecond ablation. The surface is examined for the presence of collateral damage and the ablation threshold fluence of dentine is evaluated. The influence of the variation of different parameters like number of laser pulses and laser fluence, and comparison of their efficiency are analyzed.