Diammine silver fluoride has been used for preventive therapy of dental caries in pediatric dentistry. However, dental caries are often difficult to identify by visual inspection. Recently, a laser fluorescence system (DIAGNOdent®) has been developed. This laser system has higher diagnostic validity for the detection and quantification of varied lesions than an electronic caries monitor, and it has higher measurement reproducibility. The aim of this study was to evaluate the ability of the laser diagnosis system to detect caries after diammine silver fluoride application. Eight extracted teeth, which had occlusal dental caries as judged by visual inspection, were studied. A total 28 points were evaluated on the experimental teeth. DIAGNOdent® values were measured before, immediately after, and at 1, 2, 5, and 7 days after drug application. The DIAGNOdent® values were statistically decreased after treatment with diammine silver fluoride for all of the experimental teeth. These results suggested that DIAGNOdent® was not able to detect the carious state after diammine silver fluoride application, however results were revealed reflected fluorescence on carious lesion, and statement of drug applications.
The purpose of this study was to investigate the effects of phosphoric acid on tensile bond strength of composite resin to Er: YAG laser (The KaVo K. E. Y Laser® 1242)-irradiated enamel. Twenty-one extracted human incisors were used. Flat enamel surfaces were prepared and irradiated with an Er: YAG laser at 4Hz and 200mJ, with water colling. The teeth were divided into 3 groups--Group 1: no acid etch./Single Bond and Z100/3M (nSB); Group 2: acid etch for 15sec. Single bond and Z100 (SB); Group 3: acid etch for 60sec./Single Bond and Z100 (60SB). The restoratives were applied in a plastic mold with a bond diameter of 2.4mm. Tensile bond strengths were determined after storage in a moisture box at 37°C for 24hours (n=7). The surfaces of specimens were observed by SEM. The results (MPa±SD) were as follows: nSB 4.2±1.7; SB 7.5±2.7; 605B 9.1±3.2. A one-way ANOVA revealed significant differences of bond strength values by the surface treatment methods (p<0.05). From the results of tensile bond strengths, it can be concluded that the application of phosphoric acid improved the tensile bond strength of composite resin to the Er: YAG laser-irradiated enamel. SEM observation showed that some enamel influence by Er: YAG laser irradiation remained, even if it was etched with 35% phosphoric acid.
Tuning a laser wavelength to a stretching vibration of specific biomolecules, has some advantages for ablation of hard tissue and surface modification induced by photothermal or photo-mechanical interaction. In this paper, a tunable, pulsed, TEA CO2 laser was used to lase 9.45μm, which is the stretching vibration of phosphoric acid in hydroxyapatite. Dried cow dentine was irradiated to the CO2 laser of 36W/cm2. As results, laser irradiation shortened the peak wavelength of the dentine surface from 9.76μm to 8.93μm. The atomic ratio of Ca/P was changed from 1.4 to 1.9. These results showed the potential ability of a 9.45μm CO2 laser for ablating and modification of the dentine surface.
The Er: YAG laser system is applied either as a more comfortable alternative to conventional mechanical cavity preparation, or as an adjunctive method performed at the same time. However, discoloration of the dentin margin of the cervical cavity could be a problem. The purpose of this study was to evaluate the improvement of resin bond strength to Er: YAG laser-irradiated dentin with mechanical processing. Extracted bovine dentins were cut at the cervix, ground the exposed coronal dentins from 180-up to 600-grid SiC paper disc, and the ground surfaces were then uniformly irradiated with the Er: YAG laser. The laser-treated surface was then stained with a caries detector. The stained region was removed with mechanical dentin-surface processing (with a hand excavator, an ultrasonic scaler, and a dental polishing brush). After processing, the surface was etched with an aqueous solution of 10% citric acid/3% ferric chloride (10-3). A PMMA rod was bonded to the etched dentins with 4-META/MMA-TBB resin (Super Bond C & B). The bonded teeth were then cross-sectioned to make 2.0-mm-thick bonded dentin slabs, which were trimmed to prepare a miniaturized dumbbell-shaped specimens. After storage in water at 37°C for one day, the tensile bond strength was measured, and we evaluated the fracture mode after the tensile testing, by scanning electron microscopy (SEM). All of the teeth from which the stained region detected by the caries detector had been removed, had superior bond strength compared with non-processed teeth in which the stained region was left intact. In particular, cohesive failure in resin was observed in the groups in which the stained region was removed with the dental polishing brush or the ultrasonic scaler, by SEM evaluation. These results suggested that removal of the Er: YAG laser-affected dentin surface with a dental polishing brush or an ultrasonic scaler can resultin a good dentin surface for resin bonding.
Neodymium: YAG (Nd: YAG) laser therapy is performed for oral lesions. During the period from June 1992 to March 2000, we treated 69 oral lesions (31 males, 38 females) with a contact Nd: YAG laser in the operating room of the Department of Dentistry and Oral and Maxillofacial Surgery of Hamamatsu University School of Medicine. The lesions were 51 cases of squamous cell carcinoma, 2 of adenoid cystic carcinoma, 8 of leukoplakia, 5 of benign tumors, 2 of inflammatory diseases, and one of scarring. The lesions of 65 cases were resected by the Nd: YAG laser. The wounds of 26 of those cases were not sutured, and the patients did not complain of any severe symptoms. The wound healing was prolonged, at 3-5 weeks. The Nd: YAG laser has a hemostatic effect and an analgesic effect for a malignant tumor and a lesion with a strong tendency to bleed. The wound after treatment with an Nd: YAG laser recovers without suturing or skin grafting.