The implantable cardioverter defibrillator (ICD) is used for the treatment of patients with severe arrhythmia. These implantable medical devices such as the implantable pacemaker and ICD are affected by electromagnetic interference (EMI). EMI is an unwanted disturbance that affects electrical circuits due to either electromagnetic conduction or electromagnetic radiation emitted from an external source to implantable medical devices. Recently, opportunities for using laser equipment in many kinds of dental treatments have been increasing. It has been reported that the dental laser could cause EMI with an implantable pacemaker. However, the effects of a dental laser on ICD have not been reported. Therefore, we examined whether the dental laser might cause incorrect operation of ICD by using Irnich's human body model.
The purpose of this study was to compare the pain-relieving effects of pulsed Nd:YAG laser irradiation with topical anesthetic application during placement of a rubber dam clamp. Twenty-two students, aged 22 to 31 years (mean 24.05), who had not experienced either endodontic or cervical restorative treatment of first permanent molars, participated in this study. In this study, the same tooth for the same patient was tested three times every week. The following were the conditions of each site: 1) control site: no pretreatment before placement of the rubber dam clamp, 2) topical anesthetic site: application of topical anesthetic 60 seconds before placement of the rubber dam clamp and wash-out by three-way syringe water, 3) Nd:YAG laser irradiation site: Nd:YAG laser irradiation before placement of the rubber dam clamp. The irradiation conditions were 120 mJ, 1.2 W, 10 pps, and irradiation time was 30 sec twice. The efficacy of pain-relief was assessed by visual analogue scale (VAS) at the start, before placement of the rubber dam clamp, after placement of the rubber dam clamp, and until 20 minutes at 2-minute intervals. The clamp was removed 14 minutes after the start. Pain-relieving effects were also examined by questionnaire. The VAS levels of both placement and removal of the rubber dam clamp were high for all sites. On placement of the rubber dam clamp, the VAS level with Nd:YAG laser irradiation was statistically significantly lower than with no preparation (P<0.05: Wilcoxon signed-ranks test). During placement of the rubber dam clamp, the VAS level with Nd:YAG laser irradiation and topical anesthetic application were statistically significantly lower than with no preparation (P<0.05: Wilcoxon signed-ranks test).
This study proposes a method of measuring the dynamic force induced by laser irradiation on the human tooth. The dynamic load induced in a specimen by using elastic wave propagation in a long aluminum-alloy bar was measured. The laser-induced stress intensity was evaluated from the dynamic strain which was measured by semiconductor strain gauges attached to the long bar. In addition, the process of laser irradiation to the hard tissue surface was observed with an ultrahigh-speed video camera. Carbon powder and titanium dioxide powder were applied to the dentin surface so as to effectively absorb the laser beam. The results showed that the hard tissue surface was flashed during the laser irradiation, and the melted tissues continued to scatter in the direction perpendicular to the tissue surface in a mushroom-like wave. The measured dynamic stress induced on the surface increased with the increase of laser energy and was closely related to the prepared cavity on the surface. The titanium dioxide powder more effectively induced stress than the carbon powder. The induced dynamic stress for eliminating a unit volume of hard tissue was 0.03 Pa/mm3.
Recently, many studies have been performed on the Er:YAG laser to expand its clinical use. This investigation aimed to evaluate the effects of varying parameters of Er:YAG laser irradiation on human dentin surfaces using contact probes for intracanal use. Dentin plates were prepared from palatal roots of human maxillary first molars. An Er:YAG laser (Erwin AdvErL, Morita, Kyoto, Japan) was irradiated at 30 mJ through a sharp-end-type contact probe designed for intracanal use (R200T, Morita, Kyoto, Japan), and a flat-end-type contact probe (R200F, Morita, Kyoto, Japan). The repetition rates of applied pulses were 5, 10, and 25 pps. Distances to the samples were 0, 100, 200, 400, 800 and 1200 μm. R200T probes were used for the experimental group (n=5), and R200F probes for the control (n=5). Touching the end of the contact probes from the surface of dentin plates horizontally or perpendicularly, each laser pulse was delivered under water spray cooling (0.05 ml/s) for 10 seconds. After the laser irradiation, samples were stained with rhodamine 123, and observed by confocal laser microscopy (CLSM) to measure the depths and widths of the cavities. The samples were also observed by scanning electron microscopy (SEM) to evaluate the laser-irradiated surfaces, and the following results were obtained. When the samples were irradiated horizontally, the cavities prepared with R200T were significantly deeper than those with R200F, and the diameters of cavities with R200T were larger than those prepared with R200F (2-way ANOVA, Tukey-Kramer test, p < 0.05). When the samples were irradiated perpendicularly to the plates, the cavities with R200T were significantly shallower than those with R200F. No significant difference was found between the diameters of cavities with R200T and R200F (p > 0.05, 2-way ANOVA, Tukey-Kramer test). SEM observation showed the cavities with R200T were of crescent-moon shape when the plates were irradiated horizontally, while those with R200T were of circular shape when the plates were irradiated perpendicularly. There was no obvious smear layer, crack, carbonization or fusion in any of the samples. Taken together, the distance between the probe end and the dentin surface should be minimized to ablate dentin effectively with contact probes for intracanal use. Since the contact probes for intracanal use could destroy the root apex, lasing conditions should be strictly controlled.
Dental implant therapy is invariably accompanied by peri-implantitis, and while there have been many reports on how to treat this problem, none of the methods has been sufficiently effective so far. Furthermore, it is nearly impossible to disinfect surfaces such as TiUnite® that promote osteoconduction once they have become infected, and an effective way to do this is essential. We proposed and discussed an effective method to disinfect implant surfaces of TiUnite® using an Er:YAG laser. The laser can strip away a thin layer of the TiUnite® surface leaving a new, uncontaminated surface. This clinical report suggests that this novel method by Er:YAG laser would be helpful for treating peri-implantitis.