1. R. Walraven, R.E.J. Sladek, I.E. Kieft, E. Stoffels, P.J.A. Tielbeek Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands E-mail: R.E.J.Sladek@tue.nl Investigation of possibilities for plasma treatment of dental caries 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). 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). Conclusions little temperature increase mineralised matrix not damaged ‘So far so good’ Conclusions little temperature increase mineralised matrix not damaged ‘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. 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. 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. 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. 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. 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. Results It has been verified that there is only little temperature increase (1 – 5 °C) in the gas (Figure 4) and even less in dental tissue. First x-ray measurements showed no damage to the mineralised matrix. Under extreme conditions the matrix showed cracks (Figure 5). Results It has been verified that there is only little temperature increase (1 – 5 °C) in the gas (Figure 4) and even less in dental tissue. First x-ray measurements showed no damage to the mineralised matrix. Under extreme conditions the matrix showed cracks (Figure 5). Temperature measurements Temperature measurements were made by use of a thermo-couple. The thermo-couple is inserted into the box via a rubber plug (Figure 2). Three types of temperature measurements were performed: 1) Temperature of gas (dry) 2) Temperature of PBS (wet) 3) Temperature inside tooth (inside root canal) Effect of plasma on mineralised matrix Tooth samples have been exposed to the plasma under various conditions (power, exposure time). After treatment these samples as well as untreated control samples were analysed by x- ray. Temperature measurements Temperature measurements were made by use of a thermo-couple. The thermo-couple is inserted into the box via a rubber plug (Figure 2). Three types of temperature measurements were performed: 1) Temperature of gas (dry) 2) Temperature of PBS (wet) 3) Temperature inside tooth (inside root canal) Effect of plasma on mineralised matrix Tooth samples have been exposed to the plasma under various conditions (power, exposure time). After treatment these samples as well as untreated control samples were analysed by x- ray. A B Figure 4: Typical temperature measurement of gas (dry). Figure 5: X-ray of crack formed in mineralised matrix. A = root canal; B = mineralised matrix. Figure 1: Dental cavity Figure 2: Experimental set-up. Figure 3: A scheme of the experimental set-up. Experimental set-up RF-driven ‘plasma needle’ Tungsten 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 parametersGas He RF frequency 9-14 MHz Power dissipated in plasma < 0.2 W Voltage  350 V The closed box (not vacuum-tight) shown in Figure 2 is filled with Helium at a flow rate of 2 l/min. Experimental set-up RF-driven ‘plasma needle’ Tungsten 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 parametersGas He RF frequency 9-14 MHz Power dissipated in plasma < 0.2 W Voltage  350 V The closed box (not vacuum-tight) shown in Figure 2 is filled with Helium at a flow rate of 2 l/min.