# A New Design for Switched-Mode Dental Iontophoresis System Using a Dual-Return Probe
## 4 Results and Discussion
cycle rate decreases, the change in the iontophoresis current due to skin polarization decreases, whereas the time required for iontophoresis treatment increases. The iontophoresis average current changes obtained depending on the 3 V DC voltage at different frequencies between 0 and 1 kHz for the SMDIS and CDIS methods are shown in Figure 14. It is seen that the average current changes with frequency obtained for the SMDIS and CDIS methods are similar to each other for both prototypes. Figure 14: Average iontophoresis current changes depending on the applied DC voltage (3 V) with different frequencies using the SMDIS and CDIS. Figure 13: Average iontophoresis current changes depending on the applied DC voltage (3 V, 1 kHz) pulse values with different duty cycle rates using the SMDIS and CDIS. In the third stage of the experimental study, the comparison of the waveforms obtained with the oscilloscope for 3 V DC (1 kHz, 50%) applied to Prototype-I using the CDIS and SMDIS methods is shown in Figure 15. The oscilloscope contains two signals obtained from channels A and B, as well as waveforms for the sum of these two signals as M = A + B. In Figure 15a, the classically applied continuous DC (3 V) from channels A and B and the resulting M sum are shown. In Figure 15b, the applied pulse DC (3 V, 1 kHz, 50%) and the obtained M sum are seen. According to the new method, the applied pulse DC (3 V, 1 kHz, 50%) and the obtained M sum value are shown in Figure 15c by switching with a 180-degree phase shift from channels A and B. In the newly developed SMDIS, a continuous DC-like iontophoresis current can be applied to the DH region by switching the return probes to provide depolarization and complement each other with pulse currents in different paths. Depending on the timer resolution of the microcontroller used in the system, current spikes occur during the transit times between the RP-A and RP-B return channels. The effect of these current spikes on the system is negligible. If desired, by using a faster microcontroller and increasing the timer resolution value, current spikes occurring during the transit times between the RP-A and RP-B return channels can be eliminated. In the fourth stage of the experimental study, the change in treatment durations required for dental iontophoresis application depending on the desired treatment dose is examined. In general, as the amount of current applied to the tooth increases in the iontophoresis process, the electrical charge that allows the delivery of the solution to the deeper tissues of the tooth also increases and the treatment duration for the desired treatment dose decreases inversely proportionally. When the patient's pain threshold is taken into account, the treatment durations required for the new and classical methods according to the peak current value that can be applied are compared. The comparison of treatment durations depending on the desired 0-100 mC treatment dose for the peak current (250 uA, 1 kHz, 50%) applied to Prototype-I using the CDIS and SMDIS methods is shown in Figure 16. Here, it can be inferred that in an iontophoresis treatment application with a peak value of 250 uA depending on the patient's pain threshold, the treatment durations required for the desired treatment dose in the SMDIS Pulse DC and CDIS Continuous DC methods are approximately half that of the CDIS Pulse DC method. The SMDIS pulse DC method can deliver the average DC current obtained with the CDIS pulse DC, which has been proven by clinical studies, with a lower peak current. By this method, since more average DC current can be delivered with the same peak current depending on the patient's pain threshold for iontophoresis treatment, the desired treatment dose is provided in a shorter time in the SMDIS pulse DC method. Figure 15: Comparison of iontophoresis current waveforms depending on the applied DC voltage (3 V, 1 kHz, 50%) using the SMDIS and CDIS.