Effects of Er:YAG laser and Nd:YAG laser treatment on the root canal dentin of human teeth: a SEM study

The objective of the study was to observe the morphological changes on root canal dentin after Er:YAG laser and Nd:YAG laser treatment. Twenty-one teeth biomechanically prepared were divided into three groups with seven teeth of each. Group A was unlased as a control. In group B, Er:YAG laser and in group C, Nd:YAG laser was applied to the root canal dentin. The roots were split longitudinally and examined using a scanning electron microscopy for the evaluation of debris, smear layer, and recrystallization. There was no statistically significant difference between the groups. This study indicates that laser beam is not effective in removing debris and smear layer.     

Effects of Er:YAG and Nd:YAG laser irradiation on radicular dentine permeability using different irrigating solutions

BACKGROUND AND OBJECTIVES: To evaluate the effect of Er:YAG and Nd:YAG laser on radicular dentine permeability when using distilled and deionized water and 1% NaClO as irrigating solutions. STUDY DESIGN/MATERIALS AND METHODS: Thirty human maxillary canines were divided randomly into six groups. The root canals were instrumented with K files and the step-back technique. Group I, irrigation with distilled and deionized water; Group II, irrigation with 1% NaClO; Group III, irrigation with distilled and deionized water and Er:YAG laser application (140 mJ input, 61 mJ output 15 Hz, 300 pulses, and 42 J); Group IV, irrigation with 1% NaClO and Er:YAG laser application (same parameters as Group III); Group V, irrigation with distilled and deionized water and Nd:YAG laser application (150 mJ, 15 Hz, 2,25 W); Group VI, irrigation with 1% NaClO and Nd:YAG laser application (same parameters as Group V). During laser application the teeth were always filled with the irrigating solution. The tip was withdrawn gently in helicoidal movement from the apex to the cervical portion. The teeth were processed for histochemical evaluation. RESULTS: The Tukey test showed that the cervical and middle thirds were statistically similar (P > 0.05) and significantly greater than the apical third (P < 0.05). The Scheffé test showed significantly greater dentine permeability in root canals in which water and Er:YAG laser were used and were significantly different from the other treatments (P < 0.05). CONCLUSIONS: The use of distilled and deionized water and Er:YAG laser showed the greater increase of dentine permeability. The use of 1% NaClO with Nd:YAG laser, distilled, and deionized water with Nd:YAG laser and the use of water increased dentine permeability less than the other groups. The use of 1% NaClO with and without Er:YAG laser application were positioned intermediately among the treatments.     

Evaluation of Nd:YAG laser on partial oxygen saturation of pulpal blood in anterior hypersensitive teeth

Dentine hypersensitivity has of long been known to be a common clinical problem in dental practices. Lasers have recently come to play a prominent role in the treatment of this disorder. They might, however, cause dental pulp damage. This study was conducted to evaluate the effect of Nd:yttrium-aluminum-garnet (YAG) laser on partial oxygen saturation of pulpal blood in sensitive anterior teeth. In this clinical trial, 65 hypersensitive teeth were selected and randomly allocated to two groups. The study group involved Nd:YAG laser treatment, while no treatment was employed for the control group. Using a pulse oximetry system, evaluations were preformed of the partial oxygen saturation in the pulpal blood before, immediately after, 1 week after, and 1 month after the treatment. The results were analyzed using the SPSS software and repeated-measures analysis of variance and paired-samples t tests. The mean partial oxygen saturation of the blood was found to be 85.4% in the study group, which was not significantly different from that of the control group. No significant differences were observed in the control group between the means obtained from pretreatment and post-treatment intervals (P > 0.05). The Post-treatment partial oxygen saturation mean rose to 89.3% (P = 0.001) and remained constant throughout the following week after it. However, no significant differences were found between the pretreatment partial oxygen saturation mean and the same measurement 1 month after treatment (P = 0.702). Nd:YAG laser therapy for dentine desensitization of anterior teeth caused no persistent changes in the partial oxygen saturation of pulpal blood. It may, therefore, be concluded that the diffusion of heat induced by the Nd:YAG laser into the pulp within the limit of the desensitization parameters cause no irreversible damages in the dental pulp.     

Ultrastructural changes of human dentin after irradiation by Nd:YAG laser

BACKGROUND AND OBJECTIVE: The use of Nd:YAG laser has been proposed for endodontic treatment. However, its ability to reduce dentin permeability, which is important for the success of root canal treatment, remains controversial. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human dentin. The parameters were: pulse energy (100 mJ), rate (10 pps), and total irradiation time (4 seconds). The crystalline phases, electron diffraction patterns, morphology, and microstructure of specimens after laser irradiation were observed by dark-field emission transmission electron microscope (TEM). RESULTS: Three ultrastructural zones could be delineated in the dentin: (1) an outer zone with an ordered columnar structure composed of hydroxyapatite and beta-tricalcium phosphate, (2) an intermediate zone composed of an amorphous substance (about 40-70 nm in diameter), and (3) an inner zone of well-crystallized hydroxyapatite grains. These three zones were free of pores or voids. CONCLUSIONS: Our study demonstrated that laser-irradiation might be used to reduce dentin permeability.     

Use of Nd:YAG laser in pancreatic resections with duodenal preservation in the dog

The trend in recent years for treatment of pancreatic carcinoma and occasionally for pancreatitis has been towards total pancreatectomy. The pancreas is also now being harvested for transplantation. Any operative technique that can reduce operating time, blood loss, and associated morbidity and mortality would be of tremendous advantage. The aim of this study was to undertake a total pancreatectomy using the Nd:YAG laser (wavelength 1,060 nm) with a helium neon laser (wavelength 628 nm) incorporated to provide a marker beam. The laser beam was passed into a 400 micron flexible glass fiber enclosed in a 2.5 mm polyethylene cannula, which also served as a conduit for coaxial CO2. The laser was operated in a continuous wave mode, and the fiber exit beam had a divergence of 10 degrees. For photocoagulation and tissue vaporization, peak powers of 50 W were used with 0.5-1 sec pulses. The total pancreatectomy using the Nd:YAG laser was performed in eight dogs, and ten dogs undergoing the conventional operative procedure served as controls. The findings indicate that the Nd:YAG laser could be used effectively and safely. The operating time was considerably diminished (P less than 0.01); the number of ligatures used was smaller; blood loss, graft survival, and duodenal viability were similar. The Nd:YAG laser offers a new therapeutic modality in the performance of tedious and often difficult pancreatic surgery.     

强脉冲光与Nd:YAG激光面部非剥脱除皱疗效比较分析

目的　比较强脉冲光与Nd :YAG激光在非剥脱面部除皱中的疗效与安全性。方法　 6 4例要求面部非剥脱除皱患者随机等分为两组 ,皆为FitzpatrickⅢ～Ⅳ型皮肤。一组接受 4次 6 4 0nm强脉冲光治疗 ,另一组接受 4次10 6 4nmNd :YAG激光治疗 ,治疗间隔 2周。分别于每次治疗后及最后一次治疗 2 ,4 ,8,12 ,2 4周后随访治疗效果。结果　治疗 2 4周后患者主观满意程度 (计分 1～ 10 )有明显差别。皮肤皱纹改善客观指标亦有明显差别。主要并发症是皮肤水疱及红斑现象。结论　 6 4 0nm强脉冲光与Nd :YAG激光皆有非剥脱除皱作用 ,6 4 0nm强脉冲光的疗效明显优于Nd :YAG激光 ,但并发症较多     

Q开关Nd:YAG美肤激光治疗太田痣317例

目的:观察Q开关Nd:YAG激光系统治疗太田痣的疗效和安全性。方法:应用Q开关Nd:YAG激光仪对317例太田痣患者进行皮损区的多次照射治疗。治疗间隔时间2～3个月,根据皮损不同颜色、部位、年龄及治疗经验选择不同能量和光斑大小。结果:治疗次数与疗效成正比相关,治疗次数越多,效果越好。接受治疗≤5次时,儿童临床效果较成人好;远期疗效儿童组与成人组相同。结论:Q开关Nd:YAG激光治疗太田痣安全有效,预后好。     

Q开关Nd：YAG激光治疗太田痣1496例疗效分析

目的：回顾性分析Q开关Nd：YAG激光治疗仪治疗太田痣的疗效和安全性。方法：分析2006年3月～2011年3月笔者科室运用Q开关激光仪治疗1496例太田痣患者的临床疗效,根据治疗前后照片进行对比分析。结果：1496例太田痣经4～10次治疗,痊愈1311例,显效132例,有效53例,总有效率为100%。12例出现一过性色素沉着,所有患者均未出现严重不良反应。结论：Q开关Nd：YAG激光治疗太田痣安全、有效,治疗次数与疗效成正比相关,治疗次数越多,效果越好。     

Histologic evaluation of the pulsed Nd:YAG laser for laser lipolysis

BACKGROUND AND OBJECTIVES: Laser lipoplasty with pulsed Nd:YAG laser, widely used in Europe and Latin America, has recently been introduced in Japan and the USA. We report histologic analyses of the effects of the laser on human fat tissue. STUDY DESIGN/MATERIALS AND METHODS: Freshly excised human skin and subcutaneous fat were irradiated with the pulsed Nd:YAG laser (SmartLipo, DEKA, Italy). A 1,064 nm laser at 40 Hz and 150 mJ and 100 microseconds-long pulses were used. Methods of exposure were the same as in the clinical application. In the control group, the specimens were cannulated by the handpiece without irradiation. The tissue was studied by scanning electron microscopy and hematoxylin eosin staining. RESULTS: Scanning electron microscopy after irradiation showed greater destruction of human adipocytes than in the control. Degenerated cell membrane, vaporization, liquefaction, carbonization, and heat-coagulated collagen fibers were observed. CONCLUSIONS: Our study showed that the SmartLipo appeared to be histologically effective for destruction of human fat tissue.     

Clinical application of the Nd:YAG laser endoscopy

We report here our clinical experiences with Nd:YAG laser therapy, and evaluate the results of this treatment. From July 1980 to December 1981, we carried out endoscopic laser treatment for 31 patients with 33 lesions. Bleeding gastric ulcers except stomal ulcers were treated successfully. For mucosal lesions of the stomach, Nd:YAG laser irradiation was effective in extirpating them. In advanced gastric cancers, symptoms of cardiac stenosis could be relieved in 80% of the cases. Endoscopic laser therapy was also effective in 80% of postoperative stenosis in the gastrointestinal tract. It is concluded that endoscopic irradiation with the Nd:YAG laser is useful for hemostasis and also for the treatment of malignant tumors and stenosis of the gastrointestinal tract.     

Micro-shear bond strength of Er:YAG-laser-treated dentin

This study tested if dentin adhesion is affected by Er:YAG laser. Ninety dentin disks were divided in groups (n = 10): G1, control; G2, Er:YAG laser 150 mJ, 90 degrees contact, 38.8 J/cm(2); G3, Er:YAG laser 70 mJ, 90 degrees contact, 18.1 J/cm(2); G4, Er:YAG laser 150 mJ, 90 degrees non-contact, 1.44 J/cm(2); G5, Er:YAG laser 70 mJ, 90 degrees non-contact, 0.67 J/cm(2); G6, Er:YAG laser 150 mJ, 45 degrees contact, 37.5 J/cm(2); G7, Er:YAG laser 70 mJ, 45 degrees contact, 17.5 J/cm(2); G8, Er:YAG laser 150 mJ, 45 degrees non-contact, 1.55 J/cm(2); and G9, Er:YAG laser 70 mJ, 45 degrees non-contact, 0.72 J/cm(2). Bonding procedures were carried out and the micro-shear-bond strength (MSBS) test was performed. The adhesive surfaces were analyzed under SEM. Two-way ANOVA and multiple comparison tests revealed that MSBS was significantly influenced by the laser irradiation (p < 0.05). Mean values (MPa) of the MSBS test were: G1 (44.97 +/- 6.36), G2 (23.83 +/- 2.46), G3 (30.26 +/- 2.57), G4 (35.29 +/- 3.74), G5 (41.90 +/- 4.95), G6 (27.48 +/- 2.11), G7 (34.61 +/- 2.91), G8 (37.16 +/- 1.96), and G9 (41.74 +/- 1.60). It was concluded that the Er:YAG laser can constitute an alternative tool for dentin treatment before bonding procedures.     

The ablation threshold of Er:YAG and Er:YSGG laser radiation in dental enamel

. The scientific investigation of fundamental problems plays a decisive role in understanding the mode of action and the consequences of the use of lasers on biological material. One of these fundamental aspects is the investigation of the ablation threshold of various laser wavelengths in dental enamel. Knowledge of the relationships and influencing factors in the laser ablation of hard tooth tissue constitutes the basis for use in patients and the introduction of new indications. The present paper examines the ablation threshold of an Er:YAG laser (λ=2.94 μm) and an Er:YSGG laser (λ=2.79 μm) in human dental enamel. To this end, 130 enamel samples were taken from wisdom teeth and treated with increasing energy densities of 2–40 J/cm². The sample material was mounted and irradiated on an automated linear micropositioner. Treatment was performed with a pulse duration of τ_P(FWHM)≈150 μs and a pulse repetition rate of 5 Hz for both wavelengths. The repetition rate of the laser and the feed rate of the micropositioner resulted in overlapping of the single pulses. The surface changes were assessed by means of reflected light and scanning electron microscopy. On the basis of the results, it was possible to identify an energy density range as the ablation threshold for both the Er:YAG and the Er:YSGG laser. With the Er:YAG laser, the transition was found in an energy density range of 9–11 J/cm². The range for the Er:YSGG laser was slightly higher at 10–14 J/cm². Paper received 15 May 2001; accepted after revision 14 January 2002. Correspondence to: Dr Christian Apel, Department of Conservative Dentistry, Periodontology and Preventive Dentistry, University of Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany. Tel.: +49 241 8089088; Fax: +49 241 8888468; e-mail: capel@post.klinikum.rwth-aachen.de     

Preliminary study of the Nd:YAG laser in canine partial nephrectomy

Partial nephrectomy is effective in the treatment of segmental renal disease but hemostasis remains a challenge. In this preliminary investigation the Nd:YAG laser was used alone or as an adjunct to the scalpel in partial nephrectomies to determine if hemostasis could be improved. A technique of 100-W laser transection with occlusion of the renal artery was effective for partial nephrectomy and achieved complete hemostasis. Conditions of patent renal artery flow or renal cooling were associated with a reduction in necrosis depth with 100-W laser partial nephrectomies. All techniques were compatible with survival over the 5-day study period.     

Nd:YAG laser clinical assisted in class II furcation treatment

The Nd:YAG laser efficacy associated with conventional treatment for bacterial reduction has been investigated throughout literature. The purpose of this study was to evaluate the bacterial reduction after Nd:YAG laser irradiation associated with scaling and root planning in class II furcation defects in patients with chronic periodontitis. Thirty-four furcation lesions were selected from 17 subjects. The control group received conventional treatment, and the experimental group received the same treatment followed by Nd:YAG laser irradiation (100 mJ/pulse; 15 Hz; 1.5 W, 60 s, 141.5 J/cm²). Both treatments resulted in improvements of most clinical parameters. A significant reduction of colony forming unit (CFU) of total bacteria number was observed in both groups. The highest reduction was noted in the experimental group immediately after the treatment. The number of dark pigmented bacteria and the percentage of patients with Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans reduced immediately after the treatment and returned to values close to the initial ones 6 weeks after the baseline for both groups. The Nd:YAG laser associated with conventional treatment promoted significant bacterial reduction in class II furcation immediately after irradiation, although this reduction was not observed 6 weeks after the baseline.     

Measurement of the elastic modulus of porcine septal cartilage specimens following Nd: YAG laser treatment

Laser cartilage reshaping is a temperature-dependent process that results in stress relaxation with subsequent formation of a new and stable specimen geometry. The objective of this study was to quantitatively measure changes in the elastic moduli of porcine cartilage following laser heating. The elastic modulus of porcine nasal septal cartilage specimen (25 × 5 × 2 mm) was measured before and after Nd: YAG laser (=1.32 m, 21.22 W/cm²) irradiation and following rehydration in saline solution. Specimens were secured in a single beam cantilever configuration and displaced using a calibrated thin beam load cell attached to a motorised micropositioner. Elastic modulus was calculated using elastic beam theory. Measurements were recorded before and immediately after laser heating, and following rehydration in saline solution (40 minutes, 25 °C). Specimens heated in saline (100 °C and then re-hydrated) were used as controls to determine the effect of total thermal denaturation. The calculated moduli before and after irradiation were 4.86 ± .145 MPa and 1.166 ± .055 MPa respectively. Following rehydration in saline, the modulus returned to near-baseline values (5.119 ± .163 MPa). In contrast, elasticity remained lower in specimens boiled and re-hydrated (3.25 ± .130 MPa). These findings suggest that cartilage matrix does not undergo complete thermal denaturation during laser reshaping, given the return in tissue properties with rehydration.     

Analysis of hyperpigmentation and hypopigmentation after Er:YAG laser skin resurfacing

BACKGROUND AND OBJECTIVES: Pigmentary disorders--such as hyperpigmentation and hypopigmentation, are devastating complications of erbium:yttrium-aluminum-garnet (Er:YAG) laser resurfacing. This study was undertaken to assess the clinical and histopathologic features of hyperpigmentation and hypopigmentation following Er:YAG laser resurfacing, especially in darker skin. STUDY DESIGN/MATERIALS AND METHODS: One hundred and ninety patients (skin phototypes III and above), treated with Er:YAG lasers--short-pulsed and modulated (variable-pulsed and dual-mode) Er:YAG lasers--for skin resurfacing were recruited. The clinical features of hyperpigmentation and hypopigmentation were evaluated retrospectively using medical charts and serial photographs. For histopathologic examinations, skin biopsies were performed in three patients at hyperpigmentation sites and in four patients at hypopigmentation sites. RESULTS: Hyperpigmentation was observed in 38.4% of the patients. Mean onset and duration were 3.5 and 7.2 weeks, and then it has faded away within 16 weeks in 93.2% of cases. Hypopigmentation was observed in 13.7% of the patients; its mean onset was 2 months after treatment, and it faded within 1 year in 85% of cases. The incidences and mean durations of these side effects were more intense and longer in patients treated with short-pulsed, variable-pulsed, and dual-mode Er:YAG lasers, in increasing order. In terms of histopathologic examinations, melanin amounts in the epidermal basal layer were observed to vary. CONCLUSIONS: Hyperpigmentation and hypopigmentation are frequent complications of Er:YAG laser resurfacing. Long pulse duration-induced thermal damage seems to be the most important factor in terms of the induction of pigmentary disorders.     

Shear bond strength of self-etching adhesive systems to Er:YAG-laser-prepared dentin

This study was conducted to compare the shear bond strengths of composite resin bonded to Er:YAG laser or bur-prepared dentin surfaces using three self-etching adhesive systems. The occlusal surfaces of 120 human third molars were ground flat to expose dentin. The dentin was prepared using either a carbide bur or an Er:YAG laser at 350 mJ/pulse and 10 Hz (fluence, 44.5 J/cm²). Three different self-etching adhesive systems were applied: iBond™, Xeno III™ and Clearfil SE Bond™. Rods of composite resin were bonded to dentin surfaces and shear bond tests were carried out. Both dentin surfaces after debonding and resin rods were observed using a scanning electron microscope. When the Xeno III™ was used, no difference was observed on shear bond strength values when bur and Er:YAG laser were compared. When using iBond™ and Clearfil SE Bond™, bond strength values measured on Er:YAG-laser-prepared surfaces were lower than those observed on bur-prepared surfaces. The absence of smear layer formation during the preparation of the dentin by the Er:YAG laser did not improve the adhesion values of self-etching adhesive systems.     

Scanning electron microscopic evaluation of resin-dentin interface after Er:YAG laser preparation

BACKGROUND AND OBJECTIVES: The aim of this study was to observe the morphological characteristics of dentin-resin interfaces when a composite resin was bonded to Er:YAG laser irradiated dentin. STUDY DESIGN/MATERIALS AND METHODS: Human dentin surfaces were divided into three equal areas. One third was prepared using a carbide bur and etched with phosphoric acid, the second third was conditioned using an Er:YAG laser, the third one was irradiated and etched. A hybrid composite resin was bonded on dentin surfaces using a single-component adhesive system. Longitudinal sections were exposed to 5 N HCl then to 1% NaOCl. The thickness of the hybrid layer and the dimensions of the resin tags were measured using scanning electron microscopy (SEM) pictures and an image analysis software. RESULTS: When acid etching was performed, a hybrid layer as well as the characteristic funnel-shaped resin tags were observed. When Er:YAG laser was used alone, no hybrid layer could be detected. The resin tags appeared thinner and exhibited a cylindrical shape. CONCLUSIONS: The acid pre-treatment of the irradiated surface allowed both the seal of the dentinal surface and the increase of the diameter of the resin tags.     

The Nd:YAG laser in neurological surgery

The Nd:YAG laser has been applied in microneuro-surgery and has been found to be quite effective in removing had and hemorrhagic tumors such as meningiomas, tumors of the deep skull base, or tumors deep in the ventricle. Another indication for the use of the Nd:YAG laser is to open the thick sellar floor in transsphenoidal operations.