Keiko Yokoyama

Root surface temperature increase during Er:YAG laser irradiation of root canals.

The authors measured the temperature of the root surface during root canal preparation using Er:YAG laser irradiation and evaluated the thermal effect on the periodontal region. Twenty extracted human teeth with single roots were divided into two groups of 10. These were irradiated using an Er: YAG laser at 2 Hz and 136 to 184 or 170 to 230 mJ/pulse for 1 min with a water spray. The temperature of the root surface was monitored using thermocouples throughout the procedure. The teeth were longitudinally bisected and observed by stereoscopy and scanning electron microscopy. The temperature on the root surface increased by less than 6 degrees C at the apical area and by less than 3 degrees C at the central area. A morphological evaluation revealed no carbonization or melting. These results suggest that the thermal effect on periodontal tissues during root canal preparation using an Er: YAG laser at less than 230 mJ/pulse for 1 min is minimal.

Effects of Erbium, Chromium : YSGG laser irradiation on root surface : Morphological and atomic analytical studies

OBJECTIVE The purpose of this study was to investigate the morphological and atomic changes on the root surface by stereoscopy, field emission-scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (SEM-EDX) after erbium, chromium:yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser irradiation in vitro. SUMMARY BACKGROUND DATA There have been few reports on morphological and atomic analytical study on root surface by Er,Cr:YSGG laser irradiation. METHODS Eighteen extracted human premolar and molar teeth were irradiated on root surfaces at a vertical position with water-air spray by an Er,Cr:YSGG laser at the parameter of 5.0 W and 20 Hz for 5 sec while moving. The samples were then morphologically observed by stereoscopy and FE-SEM and examined atomic-analytically by SEM-EDX. RESULTS Craters having rough but clean surfaces and no melting or carbonization were observed in the samples. An atomic analytical examination showed that the calcium ratio to phosphorus showed no significant changes between the control and irradiated areas (p > 0.01). CONCLUSIONS These results showed that the Er,Cr:YSGG laser has a good cutting effect on root surface and causes no burning or melting after laser irradiation.

Clinical application of the erbium: YAG laser for apicoectomy

Recently, an Er:YAG laser has attracted attention because of the possibility of cutting hard tissues with extremely small thermal effects. In this article, we report 8 cases (13 teeth) of apicoectomy using Er:YAG laser. All procedures were performed without using an air turbine or an electric drill. Although the cutting speed of this laser was slightly slower than ordinary methods, its clinical application for apicoectomy has many advantages including absence of discomfort and vibration, less chance for contamination of the surgical site, and reduced risk of trauma to adjacent tissue.

Apical Leakage of Obturated Canals Prepared by Er:YAG Laser

The present study evaluates the degree of apical leakage in vitro after root canal preparation using Er:YAG laser irradiation followed by obturation. Twenty-four single-rooted teeth were divided into 2 groups of 12. One group served as a control and these root canals were conventionally prepared up to a #50K file. The other group was prepared by Er:YAG laser irradiation at parameters of 2 Hz and 170 to 230 mJ/pulse. After obturation the teeth were immersed in a vacuum flask containing 0.6% rhodamine for 48 h, longitudinally bisected, and observed by stereoscopy and scanning electron microscopy. The degree of apical leakage from an apical stop was measured and statistical analysis was performed. The degree of apical leakage from the teeth prepared by laser was not significantly less than that from control teeth (p > 0.01). Morphological findings showed that contact between the root canal walls and obturated materials was hermetic in both groups, but canal walls prepared by laser were rough and irregular. These results show that root canal preparation by laser does not affect apical leakage after obturation compared with leakage in canals prepared using the conventional method.

Histopathological changes in dental pulp irradiated by Er:YAG laser : a preliminary report on laser pulpotomy

OBJECTIVE The effects of Er:YAG laser irradiation on the pulp tissue during a pulpotomy procedure were evaluated histopathologically. BACKGROUND DATA The effects on pulp tissue during laser pulpotomy using Er:YAG laser irradiation are not clear. MATERIALS AND METHODS Sixty mesial root canals of mandibular first molars in rats were divided into four groups. In three of these groups, root canals were irradiated using an Er:YAG laser at 2 Hz and 34, 68, and 102 mJ/pulse for 15 sec. Non-irradiated canals served as controls. The effects of laser irradiation on the remaining pulp tissue and periodontal tissues were evaluated at 0 days, 2 days, and 1 week after irradiation under light microscopy. RESULTS At 1 week after treatment, no inflammation or resorption was observed in any cases in the control or 34 mJ/pulse-irradiated groups. However, moderate to severe inflammation was observed in 9 of 10 cases (90%) in the 68 and 102 mJ/pulse-irradiated groups. CONCLUSION These results suggest that effects on pulp tissues during a pulpotomy procedure by Er:YAG laser irradiation are minimal, if appropriate parameters are selected, and this is a potential therapy for pulpotomy of human teeth.

Preparation of Root Canal Orifices by Er:YAG Laser Irradiation: In Vitro and Clinical Observations

OBJECTIVE The purpose of the present study was to evaluate the effectiveness of Er:YAG laser irradiation for preparation of root canal orifices in extracted human teeth and several clinical cases. BACKGROUND DATA Few studies with sufficient data have been conducted in this area. MATERIALS AND METHODS Orifices of 42 extracted human teeth were prepared by conventional methods using a Peeso reamer or Er:YAG laser device at 250 mJ/pulse and 8 Hz. In the clinical study, the orifices of 11 teeth from 11 patients with irreversible pulpitis were prepared by Er:YAG laser irradiation at 160 mJ/pulse and 8 Hz. Teeth were carefully irradiated using non-contact methods. Evaluation was performed by visual inspection, stereoscopy, radiography, and scanning electron microscopy (SEM). In addition, the efficiency of using the Er:YAG laser was evaluated. RESULTS In the in vitro study, canal orifices were clearly exposed by laser irradiation in all specimens. In 31 of 36 teeth (86%), orifices were successfully prepared without ledge formation or perforation. SEM observations revealed that irradiated surfaces were slightly rough and scaly, but essentially free from debris and smear layer. In the clinical study, orifices were successfully prepared in 10 of 11 teeth (91%), and no ledge formation or perforation was observed. CONCLUSION These results suggest that the preparation of root canal orifices by Er:YAG laser irradiation may be useful in most cases, if appropriate parameters are selected.

Preventive effect of tooth fracture by pulsed Nd:YAG laser irradiation with diamine silver fluoride solution.

OBJECTIVE The purpose of the present study was to evaluate the preventive effect of pulsed Nd:YAG laser irradiation with 38% diamine silver fluoride [Ag(NH3)2F] solution for the fracture of endodontically treated teeth in vitro. BACKGROUND DATA There have been no reports on the preventive effect of tooth fracture using Nd:YAG laser with Ag(NH3)2F solution. MATERIALS AND METHODS Twenty-eight human extracted teeth were used in this study. The teeth were randomly classified into four groups: control group, where tooth surfaces were not submitted to any treatment; group 1, where tooth surfaces were coated with 38% Ag(NH3)2F solution; group 2, where tooth surfaces were coated with Ag(NH3)2F solution and irradiated by pulsed Nd:YAG laser for 2 sec; and group 3, where tooth surfaces were coated with Ag(NH3)2F solution and irradiated by pulsed Nd:YAG laser for 10 sec. After preparation, shear tests were performed and the maximum load for the fracture was measured. Results were analyzed using the Scheffe test, and difference at p < 0.05 was considered significant. RESULTS The failure load for group 2 (mean, 182.5 kg) had the highest mean value and differed significantly from those for the control group (mean, 146.3 kg) and group 1 (mean, 147.1 kg; p < 0.05). The failure loads for groups 1 and 3 (mean, 150.0 kg) did not differ significantly from that for the control group (p > 0.05). CONCLUSION The results show that the application of 38% Ag(NH3)2F solution followed by pulsed Nd:YAG laser irradiation for 2 sec is useful for prevention of tooth fracture at endodontically treated teeth.

Histopathological study of the effects of Er:YAG laser irradiation on root canals in rats

The thermal effects of Er:YAG laser irradiation on the periodontal region during root canal preparation were evaluated using rats histopathologically. One hundred mesial root canals of mandibular first molars in rats were divided into four groups. In three of these groups, root canals were irradiated using an Er:YAG laser at 2 Hz and 34, 68, and 102 mJ/pulse for 30 s. Nonirradiated canals served as controls. The effects of laser irradiation on the periodontal tissues along the root surface and apical area were evaluated at 0, 2 days, 1, 2, and 4 weeks after irradiation under light microscopy. At 4 weeks after treatment, no inflammation or resorption was observed in any case in the control or 34 mJ/pulse-irradiated groups. However, moderate to severe inflammation with resorption of root surface was observed in four of five cases (80%) in the 102 mJ/pulse-irradiated group, which was significantly different from the control (P<0.01). These results suggest that thermal effects on periodontal tissues during root canal preparation by Er:YAG laser irradiation after pulpectomy are minimal, if appropriate parameters are selected.