Effect of Nd:YAG laser combined with fluoride on the prevention of primary tooth enamel demineralization

Most studies dealing with the caries preventive action of Nd:YAG laser have been done in permanent teeth and studies on primary teeth are still lacking. The aim of this study was to evaluate in vitro the effect of Nd:YAG laser combined or not with fluoride sources on the acid resistance of primary tooth enamel after artificial caries induction by assessing longitudinal microhardness and demineralization depth. Sixty enamel blocks obtained from the buccal/lingual surface of exfoliated human primary molars were coated with nail polish/wax, leaving only a 9 mm2 area exposed on the outer enamel surface, and randomly assigned to 6 groups (n=10) according to the type of treatment: C-control (no treatment); APF: 1.23% acidulated phosphate fluoride gel; FV: 5% fluoride varnish; L: Nd:YAG laser 0.5 W/10 Hz in contact mode; APFL: fluoride gel + laser; FVL: fluoride varnish + laser. After treatment, the specimens were subjected to a des-remineralization cycle for induction of artificial caries lesions. Longitudinal microhardness data (%LMC) were analyzed by the Kruskal-Wallis test and demineralization depth data were analyzed by oneway ANOVA and Fisher's LSD test (á=0.05). APFL and APF groups presented the lowest percentage of microhardness change (p<0.05). Demineralization depth was smaller in all treated groups compared with the untreated control. In conclusion, Nd:YAG laser combined or not with fluoride gel/varnish was not more effective than fluoride alone to prevent enamel demineralization within the experimental period.     

Nd: YAG激光在口腔医学中的应用

近年来,激光作为一种辅助手段已被广泛应用于口腔疾病的治疗中。Nd: YAG激光操作方便,使用安全,治疗后的创面不会产生结痂区,术后反应轻微,患者舒适度高。本文简要介绍了Nd: YAG激光在口腔硬组织与软组织治疗方面的应用,口腔硬组织方面的治疗包括窝洞预备、酸蚀、根管预备和消毒、牙本质脱敏治疗等,口腔软组织方面的治疗包括辅助牙周基础治疗、牙龈美学治疗、口内软组织切除治疗等。Nd: YAG激光治疗为这些口腔常见治疗手段提供了多样化选择,是口腔临床医生诊疗的重要辅助手段。     

脉冲Nd:YAG激光辅助极固宁脱敏剂治疗老年牙本质过敏症的临床研究

目的：研究脉冲Nd：YAG激光辅助极固宁脱敏剂治疗老年牙本质过敏症的临床效果。方法：实验组用脉冲Nd：YAG激光1W（30mJ／cm^2、15Hz）照射120sec后，涂擦极固宁脱敏剂3次;对照组强采用极固宁脱敏剂3次。结果：实验组即刻、3个月及6个月有效率分别为87．29％、81．36％和75．42％，对照组的有效率为79．09％、63．64％和52．73％。即刻两组差异无屁著性（P〉0．05），而3个月、6个月差异有显著性（P〈0．01）。结论：脉冲Nd：YAG激光辅助极固宁脱敏荆治疗老年牙本质过敏症是一种高效、作用持久、使用安全的方法。     

Removal of gutta-percha from root canals using an Nd:YAG laser

AIM: To examine the use of an Nd:YAG laser in removing gutta-percha fillings from root canals when used in conjunction with eucalyptol, dimethylformamide (DMF) or no solvent. METHODOLOGY: Root-canal fillings (sealer and gutta-percha) were removed with laser irradiation of 20 Hz/1.5 W from 30 roots randomly divided in three groups. In group 1, the solvent was eucalyptol; in group 2, the solvent was DMF; and in group 3, no solvent was used. Laser irradiation was performed until the temperature measured on the root surface increased by 4 degrees C over room temperature. The treatment was deemed complete when the apical foramen was reached with the optical fibre and a reamer. The samples were split longitudinally, and the area of remaining gutta-percha on the root-canal walls was determined with the aid of a computer program. The total number of laser pulses to achieve length and the highest temperature recorded was determined for each tooth. The results were statistically analysed using Student's t-test (P < 0.05) for independent samples. RESULTS: The average temperature increase in group 1 was 9.17 +/- 0.56 degrees C; in group 2, 9.56 +/- 0.28 degrees C; and in group 3, 8.29 +/- 0.41 degrees C. The shortest time to achieve length was in group 3 (6.4 +/- 0.49 min), then in group 1 (6.7 +/- 0.85 min) and group 2 (7.05 +/- 0.79 min). The area of remaining gutta-percha was the largest in group 2 (6.13 +/- 5.76%), whilst the smallest was for group 3 (4.69 +/- 4.03%), but the difference was not statistically significant. The number of pulses was not statistically significant between the groups. CONCLUSIONS: Use of an Nd:YAG laser alone is capable of softening gutta-percha. The addition of solvents did not improve the retreatment, either in terms of the time required for the procedure or in terms of the area of remaining gutta-percha on root-canal walls.     

Trauma from instrumentation after non-surgical periodontal treatment with ultrasonic scalers and Nd:YAG laser

Abstract

Objective. Periodontal therapies aimed at altering the progression of periodontal diseases must include meticulous mechanical debridement during both the non-surgical and the surgical phases of periodontal treatment. The aim of this study was to evaluate and compare the immediate effect of trauma from instrumentation on clinical attachment level after non-surgical periodontal treatment with ultrasonic scalers and a Nd:YAG laser. Materials and methods. Twenty-four patients with untreated chronic periodontitis, presenting probing depths of 4–6 mm on anterior teeth, upper and lower, were entered into the study. The selected teeth were probed with a pressure-controlled probe, guided by stents. Each quadrant was randomly allocated in a split-mouth design either to treatment with Nd:YAG laser using an energy of 1W, 100mj, 1064nm (test group) or to periodontal treatment using ultrasonic scalers (control group). Clinical parameters, including plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD) and probing attachment level (PAL) were acquired prior to and immediately after treatment. Results. Statistical analysis demonstrated no differences between groups at baseline for all parameters (p > 0.05). Immediately after treatment, the control group showed a greater PAL loss than the test group (p < 0.05). For the control group, there were statistically significant differences between PAL immediately before and after treatment (p < 0.05), but not test group (p > 0.05). Conclusions. Within the limits of the present study, it may be concluded that non-surgical periodontal treatment with ultrasonic scalers causes a mean immediate attachment loss of 0.68 mm and that a Nd:YAG laser seems to reduce significantly the trauma the instrumentation produced.     

Nd：YAG激光治疗牙本质过敏症

用Ｎｄ：ＹＡＧ激光治疗仪治疗由磨损引起的典型牙本质过敏症患者８８例，２００个牙。用自体同名牙常规硝酸银液脱敏作对照，表明：激光组和对照组即刻有效率均在９０％以上，３个月后，激光组有效率仍保持在９８％，而对照组有效率则下降至５０％左右，二者有显著性差异（Ｐ＜０．０１）。说明Ｎｄ：ＹＡＧ激光治疗牙本质过敏症的近期疗效是肯定的，效果维持时间长于常规脱敏，并初步探讨了激光作用机理、远期疗效、照射能量、时间、牙本质厚度等之间的关系     

Nd: YAG laser irradiation in root canal disinfection

Abstract The purpose of this study was to assess the efficacy of Nd:YAG laser irradiation in disinfecting the root canal system. Seventy-five teeth were uniformly instrumented and sterilized, and their root canals were infected for 60 min with an overnight culture of Enterococcus faecalis in Tryptic Soy Broth. The teeth were divided into 6 groups: 1 - non-infected controls; 2 - infected controls; 3 - infected, laser treated; 4 - infected, laser dummy (dye only); 5 - infected, laser dummy (dye and air-water spray); 6 - infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal shavings removed for a post-treatment culture. Quantitative analysis of bacteria surviving the various treatments were performed, and the bacterial counts for each group were compared. SEM analysis of teeth split longitudinally was used to illustrate the effect of treatment on the smear layer and on surface bacteria. Nd:YAG laser irradiation (group 3) significantly reduced the number of bacteria while NaOCl irrigation (group 6) effectively disinfected the canals.     

Treatment of dentin hypersensitivity by Nd:YAG laser

BACKGROUND, AIMS: Promising results using Nd:YAG laser against dentin hypersensitivity have been reported. The aim of this double-blind, controlled, split-mouth designed clinical trial was to assess the effect of a single Nd:YAG laser application on alleviating hypersensitivity. METHODS/RESULTS: Seventeen subjects participated in the study. Each of them had two teeth treated; one with the laser activated and one with nonactivated (placebo), for 2 min The assessment of pain was performed by a VAS, after an air blast at baseline immediately after treatment, at 1 week, 4 weeks and 16 weeks. Mean values of VAS for test and control teeth were compared by paired t-test (alpha = 0.05). The results showed mean baseline VAS values of 6.59 (+/- 1.65) and 6.14(+/- 1.95) for test and control teeth, respectively. Immediately after treatment, these values decreased to 4.09(+/- 2.28) and 3.89(+/- 2.11), respectively. After 1 week, 4 weeks and 16 weeks the mean values for test and control teeth were 3.85 +/- 2.36, 4.03 +/- 1.95, 3.60 +/- 2.66, and 4.44 +/- 2.56, 3.41 +/- 2.30, 3.42 +/- 2.30, respectively. There were no statistically significant differences between test and control at any time. However, both groups improved significantly (P < 0.05) from baseline to immediately after application, and at 1 week, 4 weeks and 16 weeks, respectively. The changes that occurred between immediately after application and 1 week, 4 weeks and 16 weeks, respectively, were not statistically significant. CONCLUSION: It is concluded that the effect of treatment of hypersensitive teeth with Nd:YAG laser is not different from placebo. The observed effects seem to last for at least 16 weeks.     

Morphology, chemical structure and diffusion processes of root surface after Er:YAG and Nd:YAG laser irradiation

OBJECTIVES: The aim of this in vitro study was to evaluate the effects of Er:YAG and Nd:YAG lasers on morphology, chemical structure and diffusion processes of the root surface. MATERIAL AND METHODS: 60 root samples were irradiated for 1 min each either with 60 mJ/p, 80 mJ/p and 100 mJ/p using Er:YAG laser or with 0.5W, 1.0W and 1.5W using Nd:YAG laser. Scanning electron microscopy (SEM) was used to determine the morphology, infrared (IR) spectroscopy to assess the alterations in chemical structure and one dimensional electron paramagnetic resonance imaging (1-D EPRI) was used to estimate the diffusion coefficients in dental root samples. RESULTS: Er:YAG laser treatment resulted in deep crater formation with exposed dentin. Morphological alterations of root surface after Nd:YAG laser irradiation included cracks, crater formation, meltdown of the root mineral and resolidified porous globules formation. Er:YAG laser failed to alter the intensity of Amide peaks I, II or III. In contrast, treatment with Nd:YAG laser, using the highest power setting of 1.5W, reduced the intensity of Amide peak II and III in comparison to the control. The diffusion coefficients were increased significantly in all Er:YAG and Nd:YAG treated root samples. CONCLUSION: This study demonstrated that Er:YAG laser influences only on morphology and diffusion processes of root surfaces, while Nd:YAG laser also alters the chemical structure of root proteins.     

应用Nd:YAG激光防龋的研究进展

Nd:YAG激光因能改变牙齿硬组织的表面形态、改变釉质和牙本质的晶体结构、促进牙齿硬组织对氟的吸收而被应用于预防龋病。本文着重就Nd:YAG激光对牙体硬组织的作用，对牙齿硬组织吸氟能力的影响以及对牙髓的影响等方面的研究进展作一综述。     

Microhardness of Nd:YAG laser irradiated enamel surfaces

Several studies have been conducted in order to verify effects of laser irradiation on dental structures. However, different settings and methods employed have led to inconclusive results. The aim of this study was to evaluate the effects of several settings of Nd:YAG laser irradiation on enamel microhardness. Fifteen groups of 10 human third molars each were submitted to Vickers microhardness indentations prior to and after laser irradiation. The data were submitted to the t-test for dependent samples (P < 0.05) for statistical evaluation. Lower total delivered energy (under 30 J) resulted in no statistically significant difference of microhardness between irradiated and non-irradiated samples, whereas higher energy settings decreased enamel surface microhardness significantly. This can be due to the significant temperature rise during irradiation. Thus, we conclude that laser irradiation, under the conditions of this study, is not suitable for improving enamel properties, because of decreased microhardness of irradiated samples.     

脉冲Nd:YAG激光照射牙本质后与复合树脂粘结的初步研究

目的 :筛选脉冲Nd :YAG激光应用于牙本质粘结的最佳输出参数 ,并与传统的表面处理方法进行对照 ,探讨脉冲Nd :YAG激光的应用前景。方法 :选取 3 5个新鲜健康的离体人前磨牙 ,随机分成 5组 ,分别用 5组激光剂量照射牙本质表面 ,复合树脂粘结 ,测定抗拉粘结强度。另选取 2 7个离体牙 ,随机分成 3组 :激光组 (前面筛选的 )、磷酸酸蚀组和 10 3液组。每组随机抽取 2个样本 ,垂直于粘结界面剖开 ,扫描电镜观察粘结界面的形态学 ;其余样本用于测定抗拉粘结强度 ,并观察断面的形态学改变。结果 :当激光输出参数为 1W、15Hz时 ,抗拉粘结强度最高〔( 5 .74± 2 .86)MPa〕。在对比研究中 ,激光组的抗拉粘结强度均值最高 ,但与其它 2组无统计学差异 (P >0 .0 5 )。界面与断面结果 ,激光组的混合层最厚 ( 10～ 3 0 μm) ,激光组和 10 3液组断面残留的复合树脂明显多于酸蚀组。结论 :脉冲Nd :YAG激光作为牙本质表面处理方法的最佳输出参数为 1W、15Hz ,但抗拉粘结强度与 10 3液组和磷酸酸蚀组无显著性差异     

Nd:YAG激光去除根管内充填材料效果的研究

目的通过测定根管内充填材料的清除率和根管外壁温度的变化,评价不同功率Nd:YAG激光去除根管内充填材料的效果。方法选取临床拔除的40颗单根管离体上颌中切牙,常规镍钛锉根管预备、热牙胶充填根管后,随机均分为A、B、C实验组和D对照组,分别采用1.0,1.5,2.0 W的Nd:YAG激光及Protaper D3再治疗锉去除根管内充填材料,同时测量根管外壁的温度变化。各样本在处理前后分别采用mimics软件将口腔颌面锥形束CT(CBCT)的扫描数据进行处理,计算出实验前根管内充填材料体积、处理后剩余充填材料体积及根管充填材料清除率。结果 A、B、C、D四组根管充填材料清除率分别为80.49%、89.82%、78.09%、21.09%,除A组与C组比较无统计学差异外,其他组间两两比较均有统计学差异(P<0.05);A、B、C、D四组根管外壁温度升高均值分别为5.28、6.48、7.73、0.80℃,A、B、C组均与D组有统计学差异(P<0.05)。结论Nd:YAG激光能够有效去除根管内充填材料,参数设置为频率20 Hz,功率1.5 W,SP模式的Nd:YAG激光根管充填材料清除率高,根管外壁温度较再治疗锉明显升高,但在牙周可耐受范围以内。     

Nd:YAG激光和Er:YAG激光对根管内粪肠球菌杀灭效果的研究

［摘要］ 目的 观察Nd:YAG激光、Er:YAG激光及两者联用对根管内粪肠球菌的杀灭效果。方法 选取离体牙建立粪肠球菌感染模型,随机分为五组：A组：生理盐水组;B组：1%次氯酸钠溶液组;C组：Nd:YAG激光组;D组：Er:YAG激光组;E组：Nd:YAG激光+Er:YAG激光组。通过细菌培养和扫描电镜观察对比各组的杀菌效果。结果 细菌培养和扫描电镜结果显示：A组杀菌率最低,B组杀菌率最高,E组次高。除C组和D组间杀菌率相近外（P>0.05）,各组间均有统计学差异（P<0.05）。结论 Nd:YAG激光和Er:YAG激光均有一定的根管杀菌效果,两者联用效果更佳,可作为传统消毒方法的补充。     

Short-term treatment of periapical lesion of anterior tooth affected by microleakage using Nd:YAG laser. Case report

Tooth-colored restorations are the first choice for anterior restorations. However, microleakage is a significant problem at the margins of anterior cavities restored with resin composites. Microleakage can cause pulpal irritation and periapical inflammation. Today, laser irradiation is used frequently for dental treatments. Nd:YAG laser has been used successfully in endodontic treatments. A 17-year-old male presented to our clinic with a maxillary right lateral incisor that resulted in microleakage of an old composite resin restoration. Clinical examination revealed swelling and abcess formation on the palatal mucosa. The radiographic examination was performed and an inflammation around the apex was diagnosed. Root canal preparation, canal sterilization by Nd:YAG laser and root canal filling were performed at the same visit. The patient was observed for two months. In the case presented here, short-term treatment of a periapical lesion of an anterior tooth affected by microleakage using the Nd:YAG laser is discussed.     

Nd: YAG laser for debonding ceramic orthodontic brackets.

INTRODUCTION: The purpose of this study was to develop an effective method for debonding ceramic orthodontic brackets with a high-peak power Nd:YAG laser. METHODS: Two types of ceramic brackets (single crystal and polycrystalline) were bonded to mandibular bovine teeth with 2 types of bonding resins (4-META/MMA and Bis-GMA). The laser was applied to 2 points on each bracket, each with a 1-pulse-per-second shot. Bond strength and thermal effects of the laser on the dentin surface were assessed at 3 laser energy levels: 1.0, 2.0, and 3.0 joules (J). Shear tests were performed on the irradiated test group and on a nonirradiated control group. ANOVA was used to determine significant differences. RESULTS: The shear test (P < .05) showed that every specimen in the 2.0-J and 3.0-J groups underwent a significant decrease in bonding strength compared with the nonirradiated group. However, the 1.0-J group did not exhibit any such difference. In the 2 former groups, laser irradiation alone was sufficient to debond some specimens. No significant difference was found between bonding resins. The maximum temperature rise measured on the pulpal walls at the lasing points was 5.1 degrees C. CONCLUSIONS: The application of a high-peak power Nd:YAG laser at 2.0 J or more is effective for debonding ceramic brackets.     

Nd:YAG laser ablation and acid resistance of enamel

The acid resistance of Nd:YAG laser-ablated enamel surfaces was studied by evaluating crystal structure, mineral distribution, and fluorescence radiance and image in the present study. For comparison, 37% phosphoric acid etching was performed. The formation of beta-tricalcium phosphate (beta-TCP) was confirmed in the laser-ablated surface. The Ca/P ratio increased after ablation due to mineral re-distribution. In contrast, the Ca/P ratio decreased after acid etching due to mineral loss. The laser-ablated enamels showed a smaller increase of fluorescence radiances and less clear laser confocal scanning microscope images than those observed in the acid-etched enamels. The former suggests a minimized mineral loss. The Nd:YAG laser irradiation will enhance the acid resistance and retard the carious progression in enamel.