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Plasma treatment of dental caries R.E.J. Sladek, R. Walraven, E. Stoffels, P.J.A. Tielbeek, R.A. Koolhoven Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands E-mail: [email protected] Dental caries In dentistry dental cavities (Figure 1) as a result of caries are a major problem. Cavities in teeth can be cleaned and/or sterilised by mechanically drilling or laser techniques. In both methods heating or vibrations can take place and this can be painful for the patient (heating and vibrations can irritate the nerve). Goal Our goal is to find a less destructive (no fractures) and less painful approach to clean dental cavities. This may be done by use of a non-thermal atmospheric plasma. Temperature measurements Temperature measurements will be made during plasma treatment. The thermo sensor (pt-100) is inserted into the pulp chamber like in Figure 5 and the temperature is recorded. Also a temperature distribution model in Matlab® is made. The model is compared to the experiment. According to Zach and Cohen, an increase in intra-pulpal temperature below 2.2 C fall within the safe range of thermal stress. Dental plaque experiment Plasma treatment on dental plaque will be investigated ex-vivo by confocal microscopy (CLSM) and vital fluorescence techniques. Plaque is collected on enamel slabs. The slabs are inserted into acrylic splints worn by participants. Figure 1: Dental cavity (left), caries (right). Why plasma? Plasma is an efficient source of various radicals, capable of bacterial decontamination, while it operates at room temperature and does not cause bulk destruction of the tissue. The advantage of this novel tissue-saving treatment is that it is superficial and that the plasma can easily penetrate the cavity, which is not possible with lasers. Also the use of plasmas is relatively cheap compared to the use of lasers. dual coupler matching network Figure 6: CLSM vital-stained 2-day-old plaque on Enamel. Thickness up to 32 m. Magnification x500. (Netuschil et al. 1998) Results RF amplifier power meter Figure 5: Radiograph of electrical thermistor implanted within the pulp chamber (Miserendino et al. 1989). function generator It has been verified that there is only little temperature increase (1 – 5 °C) in the gas and even less in dental tissue. First x-ray measurements showed no damage to the mineralised matrix. grounded box glass tube plasma metal wire gas inlet Figure 2: Experimental set-up (closed not-vacuum tight box). Figure 3: A scheme of the experimental set-up. Figure 4: Portable plasma needle. Experimental set-up RF- driven ‘plasma needle’ in closed (not vacuum-tight) box (Figure 2) Wire (0,3 mm ) in a glass tube (Figure 2 and 3). Because of the glass tube, the plasma stays at the tip of the needle. Experimental parameters Gas He (2 l/min) RF frequency 9-14 MHz Power dissipated in plasma 0.2 W Voltage 300 -500 V Prototype of portable plasma needle (Figure 4) Under development (is working!, see Figure 8 ) Figure 7: Temperature distribution in Figure 8: cylinder of dentine (rplasma=1 mm, Qin=2000 J/m2 . s). Conclusions • little temperature increase • ‘So far so good’ Future plans Dental plaque experiments In the near future we will investigate the efficiency of plasma-aided destruction of bacteria present in dental plaque using a standard bacterial viability kit.