Matthias Kreisler

Effect of diode laser irradiation on root surfaces in vitro.

OBJECTIVE The objective of this study was to evaluate possible morphological alterations of root surfaces after GaAlAs-diode laser (809 nm) irradiation under standardized in vitro conditions. MATERIALS AND METHODS Root specimens obtained from extracted periodontally diseased teeth were scaled and root planed with curettes followed by air-powder abrasive treatment prior to lasing. The variable parameters were power output (0.5-2.5 W) and exposure time (10-30 sec per specimen). Additionally, the effect of a saline solution and a human blood film on the root surface was investigated. The root segments were analyzed by means of a reflected light microscope. Photographs before and after irradiation were taken and evaluated. The scale of carbonization was quantified using a grid laid over the photographs. Specimens with distinct morphological changes were analyzed with a scanning electron microscope. RESULTS Lasing dry specimens and specimens moistened with saline resulted in no detectable alterations, irrespective of irradiation time and power output applied. Depending on different settings, irradiation caused severe damages to the root surface when segments were covered by a thin blood film. Irradiation at a power output of 1 Watt and below had barely any negative effect on the root surface, whereas lasing at 1.5, 2.0, and 2.5 Watt resulted in partial or total carbonizations of the root samples. The angle of irradiation had a significant effect on the scale of the root surface damage (Mann-Whitney U test,p < 0.05). CONCLUSION The diode laser may cause damage to periodontal hard tissues if irradiation parameters are not adequate.

Low-level 809 nm GaAlAs laser irradiation increases the proliferation rate of human laryngeal carcinoma cells in vitro.

The aim of the study was to investigate the effect of low-level 809 nm laser irradiation on the proliferation rate of human larynx carcinoma cells in vitro. Epithelial tumor cells were obtained from a laryngeal carcinoma and cultured under standard conditions. For laser treatment the cells were spread on 96-well tissue culture plates. Sixty-six cell cultures were irradiated with an 809 nm GaAlAs laser. Another 66 served as controls. Power output was 10 mW(cw) and the time of exposure 75–300 s per well, corresponding to an energy fluence of 1.96–7.84 J/cm2. Subsequent to laser treatment, the cultures were incubated for 72 h. The proliferation rate was determined by means of fluorescence activity of a redox indicator (Alamar Blue Assay) added to the cultures immediately after the respective treatment. The indicator is reduced by metabolic activity related to cellular growth. Proliferation was determined up to 72 h after laser application. The irradiated cells revealed a considerably higher proliferation activity. The differences were highly significant up to 72 h after irradiation (Mann–Whitney U test, p < 0.001). A cellular responsiveness of human laryngeal carcinoma cells to low-level laser irradiation is obvious. The cell line is therefore suitable for basic research investigations concerning the biological mechanisms of LLLT on cells.

Clinical evaluation of a modified marginal sulcular incision technique in endodontic surgery.

The authors evaluated periodontal parameters following apical surgery using a new marginal sulcular incision. In 65 cases, surgical access was achieved by means of a sulcular incision technique without the involvement of the adjacent periodontia and the interproximal papillae and in 33 cases by means of a submarginal trapezoidal technique. Periodontal parameters (probing pocket depth, gingival recession, clinical attachment loss, and tooth mobility [periotest]) were recorded at baseline and after 6 months. Scar formation and the loss of papilla height were evaluated photographically. No significant changes in the attachment level and no loss of papilla height were found in either group. A slight gingival recession (0.2 +/- 0.4 mm) corresponding to the decrease in pocket depths occurred on the buccal aspect with the sulcular incision. Tooth mobility was significantly increased in both groups immediately and 6 months after surgery. Scar formation was more unfavorable with the submarginal incision.

Temperature elevations in endosseous dental implants and the peri-implant bone during diode-laser-assisted surface decontamination

The aim of the study was to investigate temperature elevations in the implant surface and the peri-implant bone during simulated surface decontamination of endosseous dental implants with an 809 nm semiconductor laser. Stepped cylinder implants were inserted into bone blocks cut from resected pig femurs. An artificial peri-implant bone defect provided access for the irradiation of the implant surface. A 600 micron optic fiber was used at a distance of 0.5 mm from the implant surface. Power output varied between 0.5 and 2.5 W in the cw-mode. Power density was between 176.9 and 884.6 Wcm-2. The bone block was placed into a 37 degree(s)C water bath in order to simulate in vivo thermal conductivity and diffusitivity of heat. Temperature elevations during irradiation were registered by means of K-Type thermocouples and a short wave thermocamera. In a time and energy-dependant manner, the critical threshold of 47 degree(s)C was exceeded in the peri-implant bone. Surface peak temperatures in the focus of up to 427.8 degree(s)C were observed. Implant surface decontamination with an 809 nm GaAlAs laser must be limited to a maximum of 10 s at an energy density below 350 wcm-2 to ensure a safe clinical treatment.