Journal of clinical laser medicine & surgery最新文献

Objective: In order to evaluate the effects of pulsed continuous wave (CW) laser and detect the role of wound healing in rats using both pulsed and CW 635-nm low-level laser therapy (LLLT), a pilot study was undertaken.

Background data: Some acceleration effects of wound healing on animals were found after treatment using various lasers with CW. There are other reports, however, using pulsed CW laser to evaluate the effects of wound healing in rats.

Materials and methods: An elliptic wound was created aseptically with a scalpel on the shaved back of the rats after anesthesia. The rats treated were restrained in a Plexiglas cage without anesthesia during the laser irradiation period. An Erchonia pulse laser (635 nm) was used in the experiment. The laser beam was delivered through an expander. The percentage of relative wound healing was calculated.

Results: The percentage of relative wound healing was 4.32 in 100 Hz, 3.21 in 200 Hz, 3.83 in 300 Hz, 2.22 in 400 Hz, 1.73 in 500 Hz and 4.81 in CW.

Conclusion: LLLT using pulsed, CW laser at the appropriate dosimetry and frequency can provide acceleration in wound healing in rats. The 100-Hz frequency had a better effect than other pulse frequencies used in the study. The effects of treatment using CW laser was higher than pulse frequency. The frequency of pulsed CW laser was not found to increase wound healing in rats compared with normal CW laser, as reported in our previous studies.

Objective: The aim of this in vitro study was to investigate the antibacterial depth effect of continuous wave laser irradiation with a wavelength of 980 nm in the root canal wall dentin of bovine teeth.

Background data: The long-term success of an endodontic therapy often fails due to remaining bacteria in the root canal or dentin tubules, which cannot be sufficiently eliminated through the classical root canal preparation technique nor through rinsing solutions.

Materials and methods: A total of 102 slices of bovine root dentin of different thicknesses (100, 300 and 500 micro m) were prepared. The samples were inoculated from one side with 5 micro L of an enterococcus faecalis suspension of defined concentration. Four slices per slice thickness served as a control group; the rest of the 30 slices per thickness were subjected to laser irradiation - 10 each of these slices were irradiated with distal outputs of 1.75, 2.3, and 2.8 Watts (W). After drying them for 30 sec, the back of the inoculated dentin slice was irradiated for 32 seconds with a 200- micro m fiber optical waveguide under constant movement of the fibers. The remaining bacteria were then detached in NaCl under vibration. The eluate produced by this was - taking account of the degree of dilution - plated out on sheep blood agar plates. After 24 h of incubation, the grown bacterial colonies were able to be counted out and evaluated. By doing so, they were compared with the non-irradiated, but otherwise identically treated control group.

Results: With a slice thickness of 100 micro m, the 980-nm diode laser achieved a maximum bacterial reduction of 95% at 1.75 W, 96% at 2.3 W, and 97% at 2.8 W. With a slice thickness of 300 micro m, a maximum of 77% of the bacteria was destroyed at 1.75 W, 87% at 2.3 W, and 89% at 2.8 W. The maximum bacterial reduction with a slice thickness of 500 micro m was 57% at 1.75 W, 66% at 2.3 W, and 86% at 2.8 W.

Conclusion: The results of this research show that the 980-nm diode laser can eliminate bacteria that have immigrated deep into the dentin, thus being able to increase the success rate in endodontic therapy.

Objective: The aim of the present study was to assess the clinical usefulness of laser surgery for oral leukoplakia.

Background: Recurrence and/or malignanT transformation of oral leukoplakia have occasionally been observed following laser surgery. It is reported that the rate of recurrence was 7.7-38.1%, while malignant transformation was 2.6-9%.

Materials and methods: A total of 154 oral leukoplakias from 116 patients were treated in our department. Comparisons with the rate of recurrence, malignant transformation and clinical futures, epithelial dysplasia, location, and treatment procedure were examined. To evaluate recurrence and malignant transformation, the cases were restricted to those with a minimum follow-up of 6 months.

Results: A total of 97 lesions fulfilled this criterion. The rate of recurrence had no association with the location or the epithelial dysplasia, although it differed with the treatment procedure. The rate of recurrence in laser surgery was approximately 29%. Malignant transformation was observed in four of 97 lesions. They were observed in 13.6% of tongue cases and 1.8% of gingival cases. Three of four lesions were treated with excision surgery, and the remaining one treated with laser vaporization. Only 1.2% malignant transformation in laser surgery was revealed.

Conclusion: Laser excision is suitable for leukoplakia cases on non-keratinized epithelia (i.e., the tongue and buccal mucosa), while laser vaporization is suitable for the gingival cases. Management of oral leukoplakia prevents not only recurrence and malignant transformation, but also postoperative dysfunction. We believe that laser surgery is an excellent procedure.

Objective: The purpose of this study was to determine the effect of CO2 laser irradiation in the prevention of pit and fissure caries in immature molars with covering opercula.

Background data: In pediatric dentistry, it is not unusual to find partially erupted immature permanent teeth, especially with opercula. Conventional dental caries prevention is not effective in these cases because of the immaturity of tooth substance and the presence of the opercula, which accumulate a substantial amount of plaque.

Materials and methods: The CO2 laser was used on 22 immature erupting molars with opercula. In each case, we first cut the operculum with a CO2 laser in a 2- or 3-watt continuous mode. Then, the occlusal surface was irradiated spot by spot along the pits and fissures of the molar using a CO2 laser in a 2-watt pulsed mode with 0.2 sec of irradiation time (average power, 0.3 watt; pulse width, 10 msec; repetition time, 15 Hz; energy density, 15 J/cm2). Each of the studied teeth was clinically examined for dental caries for 3 years.

Results: It took less than 2 min to cut the operculum, and there was no bleeding. The irradiation imparted acid resistance to the teeth without any discomfort to the patients. The patients did not complain of any pain after the procedure. Only two of the studied teeth developed dental caries during the observation period.

Conclusion: We conclude that a CO2 laser might be an effective mode of treatment in the prevention of pit and fissure caries in partially erupted permanent molars covered with opercula.

Objective: Near infrared Raman spectroscopy (RS) was used to monitor, in vitro, the degree of conversion (DC) of composite resins (Z100, 3M), photoactivated by both the halogen lamp and the argon laser beam.

Background data: Several methods were used to study the alterations of composite resins. Vibration methods such as RS allow a precise assessment of the depth of polymerization and the degree of conversion of composite resins.

Materials and methods: Sixty circular blocks of resin (7 mm x 2.5 mm) were cured using a halogen light source (n=30, lambda=400-500 nm, power density=478 mW/cm2) or an argon laser beam (n=30, lambda=488 nm, power density=625 mW/cm2) using the same irradiation time (5, 10, 20, 30, 40, and 60 sec). The directly irradiated (top) and the non-irradiated (bottom) surfaces were analyzed immediately after curing by Raman spectroscopy.

Results: The Raman results show systematic changes of the relative intensities between the peaks at 1610 (aromatic C=C stretching mode) and the 1640 cm(-1) (methacrylate C=C stretching mode), as a function of irradiation time. After 60 sec of irradiation time, the maximum degree of conversion reached for the samples cured either by the argon laser or halogen lamp was 66.4% and 62.2%, respectively.

Conclusion: The argon laser was more effective and showed better biocompatibility, with less residual monomer in the bottom (2.5 mm). These results show that RS can be used as an effective method to study the degree of conversion of composite resins.

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.

Objective: The aim of this study was to evaluate the usefulness of low-level laser therapy (LLLT) for the control of painful stomatitis in patients with hand-foot-and-mouth disease (HFMD).

Background data: LLLT has been successfully applied to various painful oral mucosal diseases, although there have been few reports on LLLT for HFMD patients.

Materials and methods: Through a randomized double-blind placebo controlled trial, the painful period of HFMD stomatitis was compared between the LLLT group (n=11) and the placebo LLLT one (n=9), which had similar clinical backgrounds. The LLLT parameters supplied were as follows: wavelength of 830 nm, power of 30 mW, frequency of 30 Hz, and energy output of 1.1 J/cm2. Acceptability and safety of the treatment were also evaluated.

Results: The painful period was shorter in the LLLT group (4.0 +/- 1.3 days) than in the placebo LLLT one (6.7 +/- 1.6 days) with a statistically significant difference (p<0.005). The treatment was judged acceptable for 90.0% (18 of 20) of patients. No adverse events were observed in any cases.

Conclusion: LLLT is a useful method to control HFMD stomatitis by shortening the painful period, with its high acceptability and lack of adverse events.

Objective: The purpose of this work is to study the temperature rise and potential thermal damage caused during ablation of human dentine using a super pulsed carbon dioxide laser of 9.6-microm wavelength, equipped with a water-cooling spray and scanner system.

Background data: There have been no reports on thermal effects of super pulsed CO2 laser of 9.6 microm wavelength on human dentine recently.

Materials and methods: Two different types of samples were investigated to yield data most consistent with a typical clinical situation. Human dentine slices and crown segments were studied at a drilling depth of 1.0 +/- 0.1 mm and 2.5 +/- 0.5 mm, respectively. A control group treated with a conventional hand piece was compared to four laser groups with settings varying from 2 to 8 W.

Results: In the laser group demonstrating the highest elevation in temperature of the four studied, dentine slices lased at 2 W for 15 sec showed a mean temperature rise of less than 1.68 degrees C at an ablation rate of 0.86 +/- 0.08 mm. Conventional drilling with a comparable ablation rate of 0.76 +/- 0.59 mm resulted in a mean rise of 2.87 degrees C. The laser groups of crown segments revealed a constant decrease in temperature. SEM observations were lacking the typical morphological changes seen in earlier studies, specifically extensive melting, charring or cracking.

Conclusion: A maximum rise of mean temperature to 1.68 degrees C in closest vicinity to the pulpal chamber and the morphological unaltered dentine surfaces demonstrate the safe and tissue preserving character of the superpulsed 9.6 microm CO2 laser. The laser caused an even lower temperature rise than conventional drilling. Moreover, the laser showed acceptable efficacy with ablation rates that did not significantly differ from the conventional dental drill.