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.     

Er:YAG激光照射对牙本质粘结强度的影响

目的探讨Er:YAG激光照射对牙本质粘结强度的影响。方法选取离体磨牙或前磨牙40颗,随机分为4组:A:酸蚀(35%磷酸)组;B:Er:YAG激光组;C:Er:YAG激光+磷酸酸蚀组;D:空白对照组。每组随机选取2颗制备成3 mm厚的牙本质盘,相应预处理后扫描电镜观察;每组剩余8颗牙制备统一标准粘结面,相应预处理后与树脂粘结测量剪切粘结强度。结果扫描电镜结果显示牙本质面经相应预处理后发生明显改变;统计分析结果显示A组剪切粘结强度最大(16.03±6.56)MPa,其次为C组(13.21±6.08)MPa,两组间差异无统计学意义(P>0.05);D组剪切粘结强度最低(4.52±1.02)MPa,与B组(7.91±4.56)MPa比较差异无统计学意义(P>0.05),与A、C组比较差异有统计学意义(P<0.05)。结论 Er:YAG激光照射联合磷酸酸蚀较单纯Er:YAG激光照射可提高牙本质剪切粘结强度。     

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。     

Er:YAG激光照射后釉质结构和成分变化的研究

目的:观察Er:YAG激光不同能量和照射时间对釉质表面形态和成分的影响。方法:处理后的104个釉质样本随机抽取8个为C组(空白对照组),剩余部分随机分为A(照射10 s)和B(照射20 s)两大实验组,其中每一大组再随机分为6个小组,分别用Er:YAG激光以1～6 W不同能量进行照射。照射后体视显微镜测量A、B两组凹坑的直径和深度,能量色散型X射线荧光光谱(EDX)测定3组的Ca、P含量和其比值的变化。结果:1～6 W不同能量照射20 s(B组)的凹坑直径和深度均明显大于照射10 s(A组)各能量组,差异均有统计学意义(P<0.05);A、B两组实验组的Ca、P含量均明显高于空白对照组,差异有统计学意义(P<0.05);空白组和两实验组的Ca/P比值差均无统计学差异(P>0.05)。结论:在Er:YAG激光一定能量的照射下,釉质的结构和成分均会产生一定的变化。     

Er：YAG激光在龈下楔状缺损治疗中的临床应用

目的评价Er：YAG激光在治疗龈下楔状缺损中的应用。方法选择有两个洞缘位于龈下1mm～2mm的楔状缺损患牙的患者共20例。对照组以车针预备窝洞,电刀切除牙龈的方法进行牙体预备,实验组以Er：YAG激光预备窝洞并同时切除牙龈的方法完成预备。以VAS评分记录术中不舒适程度,术后随访12个月检查充填体情况。结果试验组VAS平均值为42.3±12.1,对照组VAS平均值为61.1±17.0,两组间差异有显著性（P〈0.01）。术后1周,对照组有1例发生龈退缩。12个月,试验组和对照组分别有2例和3例出现边缘不密合和边缘着色（P〉0.05）。结论激光行龈下楔状缺损牙体预备的方法可以有效减轻术中不适,对充填体质量无副作用。     

Influence of Er:YAG laser irradiation distance on the bond strength of a restorative system to enamel

OBJECTIVES: The aim of the present study was to investigate in vitro the effect of Er:YAG laser on bonding to enamel, varying the irradiation distance. METHOD: Tensile bond strength of an adhesive restorative system to non-irradiated and irradiated enamel surfaces was evaluated. Thirty caries-free human third molars were sectioned in mesio-distal direction and embedded in acrylic resin. Enamel was flattened, and a 3-mm-diameter bonding area was demarcated. Specimens were randomly assigned into six groups: groups I-V were treated with the Er:YAG laser (80 mJ/2 Hz), varying the irradiation distance (11, 12 mm-focused, 14, 16 and 17 mm, respectively), followed by 35% phosphoric acid etching. Control group (VI) received treatment with phosphoric acid alone. Single Bond adhesive system was applied on the conditioned enamel, and composite resin cones, bonded to enamel, were fabricated with Z250. After storage, samples were tested in tensile to failure (50 kgf and 0.5 mm/min). RESULTS: Means in MPa were: I-9.67 (+/-3.44); II-13.29 (+/-2.65); III-13.33 (+/-2.22); IV-14.87 (+/-3.58); V-16.43 (+/-4.52); VI-22.90 (+/-3.03). ANOVA and Tukey test revealed statistically significant decrease of bond strength in group I (P < 0.05). Groups II-IV presented similar results, as did groups IV and V. Control group (VI) yielded the best overall performance (P < 0.05). CONCLUSION: Er:YAG laser irradiation adversely affected adhesion to enamel. However, bond strength was influenced by the irradiation distance, thus being stronger with the increase of distance to the target tissue.     

Er:YAG激光预处理对牙本质-全瓷粘结剪切强度影响的体外研究

目的研究Er:YAG激光预处理牙本质对牙本质与全瓷粘结剪切强度的影响,以期为Er:YAG激光在临床的应用提供参考。方法选择新鲜拔除的完整第三磨牙80颗,根据表面处理方法不同随机分为5组,每组颊面标记为ABCDE,舌面标记为abcde。A/a:Er:YAG激光光照+Optibond Versa/Adper Easy One组;B/b:Er:YAG激光光照+35%磷酸酸蚀+Optibond Solo Plus/Adper Single Bond 2组;C/c:Er:YAG光照能量密度15.73 J/cm~2/31.46 J/cm~2组;D/d:Optibond Versa/Adper Easy One粘结剂组;E/e:35%磷酸酸蚀+Optibond Solo Plus/Adper Single Bond 2组。计算机设计制作牙制作直径3 mm厚2 mm IPS e.max PressⅡ瓷块,常规粘结后制作剪切试件并测剪切粘结强度,电子显微镜下观察断裂类型。SPSS20.0统计学分析软件分别对实验数据进行单因素方差分析和χ~2检验,对实验数据进行两两比较。结果 Er:YAG激光光照与全酸蚀粘结剂联合组剪切强度(23.01±4.41/25.37±3.96)MPa,显著高于其他组,差异有统计学意义(P<0.05)。结论不同厂家的全酸蚀粘结剂联合Er:YAG激光预处理牙面均能够有效提高牙本质与全瓷的粘接强度。     

Er：YAG激光在龋病治疗时消除疼痛疗效观察

目的：探讨Er:YAG激光在龋病治疗中的止痛效果。方法：使用Er:YAG激光治疗9例龋齿、观察临床效果及疼痛情况。结果：治疗过程中实验组患者疼痛得分平均为0．22且均未麻醉,而牙钻组疼痛得分平均为1．6,且2例进行麻醉。结论Er:YAG激光可以较好地解决龋齿治疗中的疼痛问题。     

点阵Er:YAG激光照射兔口腔黏膜后的组织学变化

目的: 研究点阵Er:YAG激光照射口腔黏膜后的组织学变化。方法: 使用Er:YAG激光照射家兔口腔黏膜,应用H-E、Masson、弹性纤维染色方法,评估照射后1、2、4周黏膜上皮厚度、固有层胶原纤维和弹性纤维含量。采用SPSS19.0软件包对实验结果进行统计学分析。结果: 点阵Er:YAG照射后,黏膜损伤区仅限黏膜上皮内,3~7 d后完全愈合,不遗留色素及瘢痕,黏膜上皮厚度显著增加（P<0.05）,固有层胶原纤维、弹性纤维含量显著增加（P<0.05）。点阵Er:YAG激光照射家兔口腔黏膜损伤小、愈合快,黏膜上皮重构,黏膜固有层胶原变性、收缩。结论: 点阵Er:YAG激光照射口腔黏膜后,胶原纤维及弹性纤维增生、重组,黏膜收紧,弹性增加。     

Immunohistochemical study on pulpal response in rat molars after cavity preparation by Er:YAG laser

While Er:YAG laser systems are in extensive use for caries removal and cavity preparation, the effects of such treatment on pulp tissue remain unclear. This study evaluates these systems using immunohistochemical methods and compares the results with information gained from treatment using conventional burs. Cervical cavities were prepared in the upper first molars of rats, using either an Er:YAG laser or a conventional tungsten-carbide bur. At intervals of 5 min, 6 h, 12 h, 1 d, 3 d and 7 d after cavity preparation, the teeth were processed for immunohistochemical analyses of tissue non-specific alkaline phosphatase, OX6-positive major histocompatibility complex class II antigen-expressing cells and PGP 9.5-immunoreactive nerve fibers. DNA fragmentation was detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. Tissue non-specific alkaline phosphatase was observed mainly in the subodontoblastic layer under the cavity lesion, from 5 min, in both groups. The immunoreactivity was more pronounced in the laser group, but by 7 d no significant differences were recognizable. At 12 h, TUNEL-positive cells were detected around the odontoblastic layer in both groups. From 3 d to 7 d, a limited number of positive cells were still visible in the group that underwent standard treatment. Clear similarities in the distribution patterns of OX6-immunopositive cells and PGP 9.5-immunoreactive nerve fibers were also noted. From 12 h to 1 d, OX6-positive cells accumulated along the pulp-dentin border, extending their processes into the dentinal tubules. Numerous bead-like PGP 9.5-immunoreactive nerve fibers were observed under the odontoblastic layer at 7 d. These results demonstrated that there was no appreciable difference in the manner in which pulp tissue responded to treatment with either Er:YAG laser or a conventional drill. This would seem to indicate the usefulness of the Er:YAG laser system in the removal of caries and cavity preparation.     

Microleakage of class V resin composite restorations after conventional and Er:YAG laser preparation

This in vitro study compared the microleakage of Class V resin composite restorations at bevelled enamel/composite and dentin/composite interfaces following Er:YAG laser (pre-treatment modalities: laser-etching and/or acid-etching) or conventional preparation and acid-etch, in association with two resin composite formulations and their three-step adhesive system. Class V cavities with conventional bevel produced on the lingual and buccal surfaces of eighty extracted caries- and restoration-free human teeth, were assigned to eight groups: cavities were or Er:YAG-lased and acid-etched (groups 1 and 5); or Er:YAG-lased, laser-etched and acid-etched (groups 2 and 6); or Er:YAG-lased and only laser-etched (groups 3 and 7); or cut by dental drill at high-speed and acid-etched (groups 4 and 8). The specimens were restored with Optibond FL+Herculite XRV (groups 1, 2, 3 and 4) or with Scotchbond MP+Z 100 (groups 5, 6, 7 and 8), stored in distilled water at 37 degrees C for 24 h, thermocycled 1500 times between 5 and 55 degrees C, placed in a 2% aqueous solution of methylene blue for 24 h at 37 degrees C, embedded in resin and sectioned. Microleakage was assessed according to the depth of dye penetration along the restoration. There were statistically significant differences between occlusal and cervical regions for all groups (P<0.01) except for groups 3 and 7. Pair-wise comparison of groups showed that acid-etch is advocated when using resin composite in Er:YAG-lased Class V cavities; the seal at enamel margins in Er:YAG-lased and laser-etched cavities depended on the resin composite formulation and corresponding adhesive (P<0.05).     

Assessing microleakage of different class V restorations after Er:YAG laser and bur preparation

This study assessed in vitro marginal leakage of class V cavities prepared by turbine and Er:YAG laser and restored with different materials. Sixty cavities with enamel and dentine margins were prepared and assigned to six groups: I, II, III by turbine and IV, V, VI by Er:YAG laser. The following restorative systems were used: groups I and IV: Bond 1 + Alert; II and V: Fuji II LC; III and VI: SBMP + Dispersalloy. After finishing, specimens were thermocycled for 8 h and 45 min (500 cycles), isolated, immersed in a 0.2% Rhodamine B solution, sectioned oro-facially and analysed for leakage. The dye penetration means (%) were: occlusal I: 10.09 (+/- 21.28), II: 3.25 (+/- 10.27), III: 0, IV: 41.77 (+/- 42.48), V: 23.37 (+/- 33.79), VI: 12.66 (+/- 24.06); cervical I: 16.49 (+/- 26.67), II: 4.34 (+/- 13.71), III: 0, IV: 37.71 (+/- 30.47), V: 39.56 (+/- 43.35) and VI: 72.53 (+/- 37.79). The use of Er:YAG laser for cavity preparation yielded higher degree of marginal leakage, as compared with the use of conventional air-turbine. The enamel interface provided better marginal sealing, comparing with dentine/cementum margin. As to the cavity preparation device (i.e. laser or bur), the analysis of the results showed that bonded amalgam and Fuji II LC provided less infiltration, than Alert. On the other hand, for lased cavities, Alert provided the best results, similar to those of Fuji II LC and superior to those reached by bonded amalgam.     

Er：YAG激光和Nd：YAG激光联合应用治疗口腔均质型白斑

目的：探讨Er：YAG激光和Nd：YAG激光联合应用治疗口腔均质型白斑的临床疗效。方法：应用Er：YAG激光和Nd：YAG激光联合治疗均质型白斑31例,根据病损面积、患者的疼痛状况调整激光参数。治疗间隔时间1个月。结果：本组31例白斑治愈14例,显效14例,有效3例,治愈率45．1％,有效率90．3％。结论：Er：YAG激光和Nd：YAG激光联合应用治疗口腔均质型白斑临床疗效好,不良反应小,是治疗口腔均质型白斑的有效方法之一。     

Enamel diffusion modulated by Er:YAG laser (Part 1)--FRAP

Several studies have demonstrated the caries protective effect of lasers by strengthening enamel crystalline structure. However, the effect of laser on enamel diffusion (ED) remains unclear.     

Er：YAG激光切除牙根断面的扫描电镜观察

目的对Er：YAG激光切除的牙根断面进行扫描电镜研究,并通过对比超声金刚砂尖以及高速涡轮金刚砂车针切除牙根断面的不同表面状态,为Er：YAG激光应用于临床根尖切除术提供依据。方法将30颗上颌中切牙随机分为3组（Er：YAG激光切除组、超声金刚砂尖切除组、高速涡轮金刚砂车针切除组）,分别使用Er：YAG激光、超声金刚砂尖以及高速涡轮金刚砂车针在距离根尖3 mm处进行牙根切除。使用扫描电镜观察3组牙根断面残屑及玷污层、牙本质小管开放、裂隙以及器械切割痕迹情况。结果Er：YAG激光切除组和超声金刚砂尖切除组牙根断面有少量残屑、玷污层,并有牙本质小管开放;高速涡轮金刚砂车针切除组牙根断面有大量残屑及玷污层,没有牙本质小管开放。高速涡轮金刚砂车针切除组中能看到大量裂隙出现,超声金刚砂尖切除组中可见裂隙出现,而Er:YAG激光切除组中几乎没有裂隙出现。高速涡轮金刚砂车针切除组和超声金刚砂尖切除组牙根断面的表面粗糙并有明显切割痕迹,而Er：YAG激光切除组牙根表面没有切割痕迹,较为平滑。结论Er：YAG激光应用于根尖切除具有一定的优势,其牙根断面组织形态学方面的表现明显优于超声金刚砂尖和高速涡轮金刚砂车针。     

Efficacy of subgingival calculus removal with Er:YAG laser compared to mechanical debridement: an in situ study

OBJECTIVES: The aim of the present study was to compare the effectiveness of subgingival calculus removal from periodontally involved root surfaces with an Er:YAG laser compared to hand instrumentation in situ. METHODS: The mesial and distal surfaces of 30 single-rooted teeth with untreated periodontitis were treated either by hand instrumentation (scaling and root planing (SRP)) or by Er:YAG laser irradiation with the aim of achieving a calculus-free root surface. Subgingival plaque samples were obtained before and immediately after treatment for microbiological evaluation by culture and DNA probe analysis. The teeth were extracted and the residual calculus was measured by means of digitized planimetry. The morphology of the root surface was evaluated by scanning electron microscopy, and undecalcified sections were analyzed to determine residual calculus and the extent of cementum removal following both treatments. RESULTS: Following laser irradiation, 68.4+/-14.4% of the root surface was calculus free in contrast to 93.9+/-3.7% after SRP when both treatments were performed for the same time (2:15+/-1:00 min). If laser irradiation was allowed twice the time used for hand instrumentation, 83.3+/-5.7% of the root surface was devoid of calculus. The effectiveness of both treatments was not related to initial probing depth. The histologic evaluation showed that after SRP 73.2% of root dentin was completely denuded from cementum, while only a minimal cementum reduction was apparent after laser irradiation. Both treatment modalities resulted in a similar reduction of periodontopathogens. DISCUSSION: The present investigation could demonstrate the in vivo capability of the Er:YAG laser to remove calculus from periodontally involved root surfaces, although the effectiveness did not reach that achieved by hand instrumentation. The lack of cementum removal in contrast to SRP may qualify the laser as an alternative approach during supportive periodontal therapy.     

Desensitizing effects of an Er:YAG laser on hypersensitive dentine

AIM: The aim of the present study was to evaluate and compare the desensitizing effects of an Er:YAG laser (KEY II(R), KaVo, Germany) and Dentin Protector (Vivadent, Germany) on cervically exposed hypersensitive dentine. METHOD: A group of 30 patients showing a total of 104 contralateral pairs of hypersensitive and caries-free teeth was selected and randomly allocated in a split-mouth design to either (1) Er:YAG laser (80 mJ/pulse, 3 Hz), or (2) the application of Dentin Protector (polyurethane-isocyanate 22.5%; methylenechloride 77.5%) whereat one pair served as an untreated control in each patient. The degree of sensitivity to a thermal stimulus was determined qualitatively with an evaporative stimulus defined as a 3-s air blast at a distance of 2 mm from each site to be tested. A qualitative registration of the degree of discomfort was determined according to an arbitrary pain scale in 4 degrees. Recordings were assessed before treatment, immediately after, 1 week, 2 and 6 months after treatment by 1 blinded examiner. RESULTS: Both treatment forms resulted in significant improvements of discomfort immediately after and 1 week post treatment. After 2 months, the discomfort in the Dentin Protector(R) group increased up to 65% of the baseline score and even up to 90% after 6 months, whereas the effect of the laser remained at the same level that was achieved immediately after treatment. The differences immediately after, 1 week, 2 and 6 months post treatment between both groups were statistically high significant (p< or =0.001; respectively). Compared to the untreated control group, both treatment forms resulted in a significant reduction of discomfort at each follow-up examination. CONCLUSION: It was concluded that desensitizing of hypersensitive dentine with an Er:YAG laser is effective and the maintenance of the positive result was more prolonged than with Dentin Protector.     

Compositional analysis of root cementum and dentin after Er:YAG laser irradiation compared with CO2 lased and intact roots using Fourier transformed infrared spectroscopy

The present study examines the dental root after Er:YAG laser irradiation, compared with CO2 lased and non-treated surfaces, using Fourier Transformed Infrared (FTIR) spectroscopy. Freshly extracted human teeth were irradiated by Er:YAG laser at an energy output of 40 mJ/pulse, 10 Hz (0.4 watts), with or without water coolant, and by CO2 laser at an energy output of 0.5 watts in continuous wave mode without coolant. The surfaces were chalky and smooth after irradiation by Er:YAG laser with water coolant, were charred and irregular after irradiation by Er:YAG laser without water coolant, and were completely carbonized after CO2 laser irradiation. The FTIR profiles from samples of the surfaces that were irradiated by Er:YAG laser with water coolant were similar to those from non-treated samples, except for a slight decrease on the OH and amide bands, which are mainly related to organic components. This decrease was observed to be extreme after CO2 laser irradiation and moderate after Er:YAG laser irradiation without coolant. The formation of new bands showing toxic substances was observed to a large extent after CO2 laser irradiation and to a smaller extent after Er:YAG laser irradiation without water coolant. In contrast, no such bands were detected after Er:YAG laser irradiation with water coolant. The present results show that these laser treatments selectively ablated more organic components than inorganic components and that Er:YAG laser irradiation with water coolant did not cause major compositional changes or chemically deleterious changes in either root cementum or dentin.