Effects of KrF excimer laser irradiation on human dental enamel

Spectra of human dental enamel was recorded in the 200-400 nm UV region. It showed the weak band at 280 nm which were present in enamel protein. Excimer laser are gas lasers which emit light with photochemical decomposition. The wavelength depends on the 248 nm with krypton-fluoride. The enamel surfaces of extracted human teeth were exposed to KrF excimer laser by an energy density range from 29.6 to 3200 J/cm2. The purpose of this study was to investigate the changes with photo chemical reaction in enamel by light microscopy, SEM and X ray diffraction method. Results of analyses suggested that the observed changes of enamel exposed to this laser were the alpha and beta-tricalcium phosphate (TCP) phase in small amounts. No histological changes were observed in grain boundaries of cross sectioned lased enamel under light microscopy. The SEM examination revealed a roughened surface with bubble formation at 800-3200 J/cm2. SEM of etched enamel surface with 0.1 N HCl after laser irradiation at 400-800 J/cm2 showed the extension along the length of the rods. At 1600-3200 J/cm2, there appeared to be a melting of prism structures, because of conversion of photon energy into thermal energy. These results showed the KrF excimer laser irradiation to dental enamel might be a new type of treatment modality and diagnosis in preventive dentistry.     

Effect of Nd: YAG laser on titanium dental implants studied by AFM

Bacterial contamination of dental implants is considered the main cause of implant failure. Recently, the laser treatment of the implant surface has been proposed as an useful method for decontamination. In such a view, the present study was conducted to investigate the effects of a Nd:YAG laser on the surface morphology of a titanium dental implant by means of an atomic force microscope. We demonstrated that, when the pulse energy of the laser was kept below 30 mJ, independently from the pulse rate, the laser-treated specimens exhibited a qualitatively similar surface morphology when compared to the untreated titanium implants, suggesting that the implant surface was unaffected by the treatment, in these particular conditions. We also found that, by cooling the implant surface with an air flow? during laser irradiation, the mean temperature of the implant was maintained under 37 degrees C. All these data taken together suggest the possibility to use Nd:YAG laser for the treatment of failing dental implants.     

Penetration depth into dental casting alloys by Nd:YAG laser

This study investigated the effect of laser-beam welding conditions [voltage (V) and spot diameter (mm)] on the penetration depth into dental casting alloys. Castings (3.0 mm x 8.0 mm x 50 mm) were prepared from the metals used in this study: commercially pure titanium (CP Ti), Ti-6Al-4V, Ti-6Al-7Nb, cobalt-chromium alloy (Co-Cr) and Type IV gold alloy. Two cast blocks of each metal were butted against one another at the 8.0 x 50-mm surfaces. They were then welded at their interface under the following conditions: voltage of 160-340 V, spot diameter of 0.4-1.6 mm, and pulse duration of 10 ms. After laser welding, the blocks were separated, and the penetration depth into each alloy was measured. The data were analyzed with the use of ANOVA at the p < 0.05 level of significance. The penetration depths were as follows: CP Ti (0.29-6.45 mm), Ti-6Al-4V (0.32-5.24 mm), Ti-6Al-7Nb (0.34-5.65 mm), Co-Cr (0.24-6.15 mm), and Type IV gold alloy (0.12-5.22 mm). The voltage and spot diameter affected the penetration depth into the metals tested. When the voltage increased and the spot diameter decreased, the penetration depth increased for each metal. Selecting suitable conditions for laser welding to obtain sufficient penetration depth for the optimal thickness of the metal is important when welding prostheses.     

A histochemical study of the regeneration process after injury by pulsed Nd:YAG laser irradiation of root canals

Histological changes of rat dental pulp cells were followed after injury. The regeneration process after 3, 6 and 10 days was monitored. Mandibular incisors were irradiated with a pulsed Nd:YAG laser at 2 W and 20 pulses per sec (pps) for 5 sec and the pulp was examined histologically and immunohistochemically for TGF-beta1. Eruption of the developing tooth was disturbed for a short period only. Rapid formation of osteodentin was observed. After 3 days, a zone of fibrodentin matrix as well as newly formed vessels were found. Afterwards, regenerative dentin formation was observed accompanied by the formation of a layer of odontoblast-like cells in the damaged area. Immunohistochemical staining of TGF-beta1 showed that positivity was present in small tissue areas beneath the mantle dentin, the zone of fibrodentin matrix and odontoblast-like cells. These results indicate that pulsed Nd:YAG laser irradiation of rat incisor pulp induces formation of osteodentin, and TGF-beta1 plays a role during regeneration.     

The rat esophagus: ultrastructure and radiological aspects of tissue response after 1320 nm Nd:YAG laser irradiation.

Morphological tissue response towards laser treatment was investigated in the esophagi of adult Wistar rats by light- and transmission electron microscopy. The specimens were fixed by perfusion immediately, 2 days and 14 days after laser treatment in order to assess different stages of the healing process. The epithelium of the lasercentre was completely destroyed in the immediate group. The connective tissue showed damaged cells, fused collagenous fibres and occluded blood vessels. Smooth muscle cells presented a vacuolated sarcoplasm and pycnotic nuclei. The cross striation of skeletal muscle cells had disappeared and their nuclei were karyolytic. In a distance of 4 mm from the lasercentre all wall tissues had an almost normal appearance. After 2 days the morphological feature of the lasercentre was the same as in the immediate group. In a distance of 2 mm some layers of flat and intact epithelial cells were observed below the necrotic epithelium. The adjacent connective tissue was infiltrated by inflammatory cells. After 14 days the formation of granulation tissue had caused an occlusion of the lumen in the lasercentre. In a distance of 2 mm the lumen was patent and the wall tissues had been partly restored. As the rat esophagus serves as a model for esophagotracheal fistulae in newborn children we assume the 1320 nm Nd:YAG laser to be a possible application in occlusion of these fistulae.     

Nd：YAG泪道激光成形术治疗泪道阻塞的体会

目的 探讨应用泪道激光治疗泪道阻塞的方法及疗效。方法 应用Nd：YAG泪道激光仪按泪道探通方法连续击射阻塞部位。用抗生素和丝裂霉素C混合液冲洗畅通后植入义管，每周冲洗一次，1月后拔管。结果共治疗53例60眼，随访1～3月。治愈57眼占95％，好转2眼占3．33％，无效1眼仍有溢脓，1月后行泪囊鼻腔吻合术治愈。结论 激光泪道成形术治疗泪总管、鼻泪管阻塞及泪囊炎，方法简单、疗效满意。     

Functional state of myocardium after transmyocardial revascularization with Nd:YAG laser

Providing a better perfusion of the myocardium, transmyocardial revascularization with an Nd:YAG laser improves cardiac function and general condition of patients with ischemic heart disease. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 8, pp. 204–206, August, 1997     

Cell viability in optical tweezers: high power red laser diode versus Nd:YAG laser

Viability of cultivated Chinese hamster ovary cells in optical tweezers was measured after exposure to various light doses of red high power laser diodes (lambda = 670-680 nm) and a Nd:yttrium-aluminum-garnet laser (lambda = 1064 nm). When using a radiant exposure of 2.4 GJ/cm2, a reduction of colony formation up to a factor 2 (670-680 nm) or 1.6 (1064 nm) as well as a delay of cell growth were detected in comparison with nonirradiated controls. In contrast, no cell damage was found at an exposure of 340 MJ/cm2 for both wavelengths, and virtually no lethal damage at 1 GJ/cm2 applied at 1064 nm. Cell viabilities were correlated with fluorescence excitation spectra and with literature data of wavelength dependent cloning efficiencies. Fluorescence excitation maxima of the coenzymes NAD(P)H and flavins were detected at 365 and 450 nm, respectively. This is half of the wavelengths of the maxima of cell inactivation, suggesting that two-photon absorption by these coenzymes may contribute to cellular damage. Two-photon excitation of NAD(P)H and flavins may also affect cell viability after exposure to 670-680 nm, whereas one-photon excitation of water molecules seems to limit cell viability at 1064 nm.     

Transscleral contact cyclophotocoagulation with Nd:YAG laser CW: experimental study on rabbit eyes

The authors suggest a new type of transscleral cyclophotocoagulation by using the Nd:YAG laser. This was done by bringing fibre optics into contact with the sclera. The study illustrates the macroscopic, histologic and scanning electron microscopic changes produced on the ciliary body of rabbit eyes with this technique. The actual possibility and the future prospect of applying this method to the human eye still remain to be investigated.     

Reaction of myocardial mast cells during neoangiogenesis induced by YAG:Nd laser

Time course of morphofunctional changes in myocardial mast cells of Wistar rats irradiated with a YAG:Nd laser is studied. Mast cells were detected on serial sections by toluidine blue staining. A drastic increase in mast cell degranulation around the laser channel was observed on days 1–20 of experiment. Mast cell degranulation may be the first stage in neoangiogenesis in the myocardium in response to laser injury. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 7, pp. 116–118, July, 1998     

On the wear mechanism of human dental enamel

The mechanisms and controlling factors in human enamel wear are not fully understood yet. To address this problem, we have used focused ion beam (FIB) milling and field emission scanning electron microscopy (FESEM) to investigate the processes taking place below the wear surface of enamel specimens from in vitro wear tests. These reveal the generation of subsurface cracks during wear of enamel. An analysis of published qualitative and quantitative experimental wear results for enamel as well as for ceramics shows the similarities of the wear processes taking place under similar contact conditions, despite the differences that exist between these two materials. It is shown that, for the considered conditions, fracture under elastic contact is responsible for enamel wear.     

Nd:YAG激光治疗儿童后发障的临床观察

目的探讨Nd:YAG激光治疗儿童后发障的时机、效果及并发症。方法用Nd:YAG激光对65例87眼儿童后发障患者进行治疗。结果术后视力提高1行者7眼,占8%;提高2行者20眼,占22.9%;提高3行及以上者54眼,占62%;术后视力未提高者6眼,占6.8%。结论Nd:YAG激光治疗儿童后发障是一种安全有效的方法,并应尽早进行。     

激光泪道成形术治疗泪道阻塞的临床观察

目的 观察激光泪道成形术治疗泪道阻塞的效果及复发病例再次激光联合插管治疗的效果。方法 采用Nd：YAG激光泪道成形术治疗泪道阻塞102例。132眼。对复发病例。再次行激光联合插管治疗。结果 113眼一次治愈，有效9眼。术后10眼复发，再次行激光联合插管治疗，7眼治愈，3眼未愈。本组总治愈率90．9％，有效率97．7％。结论 Nd：YAG激光泪道成形术治疗泪道阻塞操作简单，安全有效，复发病例联合插管治疗可以提高治愈率。     

Correlates of enamel hypoplasia with human dental reduction

Human dental reduction has been manifested in evolutionary and secular trends, but it is not known to what degree each of these complementary processes contributes to changes in tooth size. Enamel hypoplasia is a marker of developmental stress that is often found to be of greater frequency and severity in populations undergoing dental size reduction. In order to test the developmental association of enamel hypoplasia with tooth size, measurements of bucco-lingual and mesio-distal diameters were taken on teeth of 54 black male skulls from southern Africa. Those dentitions that exhibited incisal enamel hypoplasia were significantly reduced in size as compared to those showing no signs of developmental stress. A distinct pattern of reduction emerged: the bucco-lingual diameters of the I¹, I², P³, P⁴, M¹, and M² were significantly reduced, whereas the mesio-distal diameters of only the I² and M² decreased in size. The I² and M² showed the greatest degree of reduction despite the lack of macroscopic enamel hypoplasia on the M². Application of the data to the variety of dental reduction patterns evinced in modern and ancient populations indicates that factors including tooth shape, developmental timing of stress, and genetic determinants of tooth size must be considered in order to partition evolutionary and secular trends in the dentition.     

Nd:YAG laser radiation modifies the proteolytic resistance of rat liver tissue proteins

Central Research Laboratory, Department of Laryngo-Otorhinology, Academician I. P. Pavlov First Leningrad Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR N. P. Bekhtereva.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 2, pp. 217–219, February, 1991.     

Calcium phosphate coatings obtained by Nd:YAG laser cladding: physicochemical and biologic properties

The plasma spray (PS) technique is the most popular method commercially in use to produce calcium phosphate (CaP) coatings to promote fixation and osteointegration of the cementless prosthesis. Nevertheless, PS has some disadvantages, such as the poor coating-to-substrate adhesion, low mechanical strength, and brittleness of the coating. In order to overcome the drawbacks of plasma spraying, we introduce in this work a new method to apply a CaP coating on a Ti alloy using a well-known technique in the metallurgical field: laser surface cladding. The physicochemical characterization of the coatings has been carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The biologic properties of the coatings have been assessed in vitro with human osteoblast-like MG-63 cells. The overall results of this study affirm that the Nd:YAG laser cladding technique is a promising method in the biomedical field.     

Studies on dental fluoride-releasing polymers IV: Fluoridation of human enamel by fluoride-containing sealant

An experimental fluoride-containing acrylic sealant was prepared using methacryloyl fluoride-methyl methacrylate copolymer as powder component. The in vitro fluoride acquisition by human enamel coated with the sealant after 11, 21, 41 and 84 days of incubation in a phosphate buffer of pH7 at 37°C was determined. Fluoride penetration and uptake were increased by prolonging the exposure time of enamel to the sealant. Most of the fluoride retained in enamel was found to be present as fluorapatite. The discharge of fluoride in the sealant was about 12% of initial load after 84 days of immersion.     

Effect of Kr :F excimer irradiation on the bond between sealant and enamel

Since the invention of Ruby laserby Maiman in1 960 s,many kinds of lasers areused widely in dentistry.It has been proved that laser irradiation can produce acid-etching like surface,thus strengthen the bond of material to enamel.But the heatgenerated during irradiation produces damage on dental pulp,which limits the laserapplications on dental hard surfaces.　　In1 990 s,a new type of Excimer laser with little thermal side effects seems topoint out an alternative way of laser treatment in den…     

Treatment of pseudofolliculitis barbae in very dark skin with a long pulse Nd:YAG laser

BACKGROUND: Pseudofolliculitis barbae affects some individuals with coarse curly hair. Currently available treatment modalities are often ineffective. In some studies, lasers have been shown to be potentially helpful in mitigating disease severity by reducing the number and/or thickness of hair shafts. METHODS: This was a side-by-side interventional study conducted at a military tertiary medical facility. The study group included 26 patients (skin types IV, V, and VI) referred from primary care physicians with a diagnosis of pseudofolliculitis barbae refractory to medical therapy. A neodymium YAG laser was used to treat one half of the neck. One month later, shaving bumps were counted and compared to their preoperative levels on both sides. RESULTS: Mean postoperative papule counts were 11.6 +/- 6 (SD) and 30.1 +/- 19 (SD) on the treated side and untreated sides, respectively. CONCLUSION: Neodymium YAG laser treatment represents a safe and effective option for reducing papule formation in patients with pseudofolliculitis barbae.     

强脉冲光联合Nd:YAG激光治疗黄褐斑疗效观察

目的:探讨强脉冲光联合Nd:YAG激光治疗黄褐斑的疗效。方法:60例患者按治疗方法不同分成3组:强脉冲光组、Nd:YAG激光组、联合组（强脉冲光联合Nd:YAG激光组）,每组20例患者,观察3组患者疗效和副作用。结果:3组之间疗效两两比较采用Mann-Whitney秩和检验,强脉冲光组和激光组疗效无显著差异,而联合组疗效显著好于强脉冲光组（Z=7.123, P=0.024）和激光组（Z=6.024, P=0.030）。3组患者治疗后均无出现色素沉着加重、色素脱失病等不良反应。强脉冲光组和激光组的满意度无显著差异,而联合组的满意度显著好于强脉冲光组（Z=7.361, P=0.029）和激光组（Z=6.831, P=0.027）。结论:强脉冲光联合Nd:YAG激光治疗黄褐斑是一种安全有效的治疗方法,值得临床推广。