Irradiation of human dental tissues with CO2-, Nd:YAG-, and CO2-Nd:YAG combination laser

Abstract— Extracted third molars were used to study the effect of Nd:YAG laser irradiation combined with CO₂ laser beam on dental hard tissues. The specimens were studied with SEM after lasing and the size of the impact areas and beam penetration into enamel and dentin were planimetrically analyzed. High-energy CO₂ laser (e.g. 10 s irradiation with 10 W output energy) penetrated all enamel and dentin. The simultaneous addition of Nd:YAG irradiation to the CO₂ beam was found to increase the effect of CO₂ laser, while Nd:YAG irradiation alone, used with equivalent energy densities, did not cause any effect on enamel surface. Thus, Nd:YAG laser was found to potentiate statistically significantly the effect of CO₂ irradiation, but the morphologic alterations on dental hard tissues, such as crater formation at the beam focus site, appeared to be due to CO₂ irradiation alone.     

Effect of Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs laser irradiation on surface properties of endosseous dental implants

PURPOSE: To analyze potential surface alterations in endosseous dental implants induced by irradiation with common dental lasers. MATERIALS AND METHODS: Sandblasted and acid-etched, plasma-sprayed, hydroxyapatite-coated, and smooth titanium discs were irradiated using Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs lasers at various power settings. The specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Results: In an energy-dependent manner, the pulsed YAG lasers induced partial melting, cracking, and crater formation on all 4 surfaces. Within the energy range applied, the CO2 laser caused surface alterations on the hydroxyapatite and plasma coatings as well as in the acid-etched surface. GaAIAs laser irradiation did not damage any of the surfaces. Energy dispersive spectroscopy revealed an altered chemical compound of the surfaces with regard to titanium, oxygen, and silicon. DISCUSSION: The clinical application of most common dental laser systems can induce implant surface alterations. Relevant factors are not only the laser system and power setting, but also the application system. CONCLUSION: The results of the study indicate that Nd:YAG and Ho:YAG lasers are not suitable for use in decontamination of implant surfaces, irrespective of the power output. With the Er:YAG and CO2 laser, the power output must be limited so as to avoid surface damage. The GaAIAs laser seems to be safe as far as possible surface alterations are concerned.     

The pulsed Nd:YAG dental laser: review of clinical applications.

Since the first demonstration of a laser in 1960, numerous applications of this unique form of energy have been developed for the manufacturing, electronic, consumer and medical industries. Recent technological innovations have permitted development of lasers appropriate for use in the dental operatory. The carbon dioxide laser has been used for soft tissue surgery; the Nd:YAG laser has both soft and hard tissue applications. Advantages of laser treatment over conventional methods include minimal cellular destruction and tissue swelling, hemostasis, increased visualization of surgical sites and reduced post-operative pain. Additionally, it is possible to perform many procedures without needing anesthesia. Soft tissue clinical applications of the Nd:YAG laser include gingivectomies, gingivoplasties, operculectomies, biopsies, incising and draining procedures, frenectomies and treatment of aphthous ulcers; hard tissue clinical applications include vaporizing decay, etching enamel and dentin, desensitizing exposed root structure and creating temporary analgesia. As both clinical experiences and scientific investigations expand, possible future applications of the dental laser may well include development of new dental adhesives and composite systems, new methods for managing caries and new endodontic treatments. With its numerous benefits, the laser is having a positive impact on patients and the dental team.     

脉冲Nd:YAG激光照射后牙髓碱性磷酸酶的活性

目的 :探讨脉冲Nd :YAG激光照射后牙髓碱性磷酸酶 (ALP)的活性。方法 :选择 4条健康的本地杂种犬 ,进行牙齿过敏模型制备 ,随机分为 3组 ,分别给予 :33J/cm2 、5 6J/cm2 、111J/cm2 激光照射 ,按照即刻、3d、7d和 1月 4个时间段处死试验犬 ,实验牙经过固定、脱钙后 ,进行组织切片、染色、光镜观察、灰度值分级。结果 :3组激光能量照射后 ,牙髓成牙本质细胞均有染色 ,以 3d、7d染色较深 ,1月后染色变浅 ,ALP活性降低 ,接近正常牙髓细胞水平。结论 :在本实验条件下 ,牙髓成牙本质细胞碱性磷酸酶活性在不同的观察期相差显著 (P <0 .0 1) ,与激光能量无关 (P >0 .0 5 )。     

重症牙本质过敏牙Nd：YAG激光照射后的SEM观察

用脉冲Ｎｄ：ＹＡＧ牙科激光照射３个新鲜离体的重症牙本质过敏牙３０ｍＪ、８０ｍＪ，脉冲数１０／ｓ，１ｍｉｎ，并涂布２％甲紫液。ＳＥＭ显示：照射３０ｍＪ者，牙本质小管口部分或完全封闭，表面密度明显提高，出现＂弹坑＂样结构；照射８０ｍＪ者，牙本质小管口模糊，出现不规则均质化物质；涂布２％甲紫液照射３０ｍＪ区的大部分牙本质小管口封闭，表面密度提高，出现均质化物质和＂弹坑＂样结构，所有的照射区都未发现微裂。提示：牙本质小管口的封闭和牙本质表面的溶融是牙本质过敏症激光脱敏的形态学变化。２％甲紫液可作为该激光的光敏剂使用。     

脉冲Nd:YAG激光照射对犬牙髓的影响

目的：探讨Nd：YAG激光对牙髓的安全阈值。方法：选择4条健康的本地杂种犬，先进行过敏模型制备，随机分为3组，分别给予：33J／cm^2、56J／cm^2和111J／cm^2激光照射，按照即刻、3d、7d、1个月4个时间段处死试验犬，实验牙经过固定、脱钙后，进行组织切片、光镜观察、病理分级。结果：牙髓反应均在3级以下，随激光照射能量的升高牙髓组织病理变化明显。在33～56J／cm^2之间，牙髓组织正常或反应轻微。结论：应用Nd：YAG激光进行牙齿过敏治疗时，其热效应可能对牙髓组织产生影响，33～56J／cm^2的激光能量不会对牙髓组织产生损害，能量较高将导致牙髓组织炎症，所以33～56J／cm^2的能量密度应为进行当次牙齿过敏治疗的安全阈值。     

Nd:YAG激光对猴牙牙髓的影响

目的：观察Nd：YAG激光对猴牙牙髓的影响，比较牙面涂布60g／L美蓝和经常规硝酸银脱敏后对激光照射效果的影响情况。方法：以1592、3185、4777mJ／mm^23种能量水平的Nd：YAG激光照射3只猴的30个牙面，用组织病理学方法观察牙髓变化情况。结果：1592mJ／mm^2照射组，不论牙面经何种处理，牙髓反应均与对照组相似，为0级；3185mJ／mm^2照射组，牙髓出现轻度改变；大能量、高频率的4777mJ／mm^2照射则出现广泛性成牙本质细胞变性、坏死。照射面色素的存在增加了激光对牙髓的刺激，氨硝酸银加丁香油酚还原成银沉淀，隔绝了外界刺激对牙本质和牙髓的影响，同样参数的Nd：YAG激光造成的牙髓损害在3组中最小。结论：大能量Nd：YAG激光可造成牙髓组织损伤性反应，照射面经不同的处理可影响Nd：YAG激光的照射效果。     

Effects of Nd: YAG laser, air-abrasion and acid-etching on human enamel and dentin

The effects of the Nd:YAG laser, air-abrasion and acid-etching systems on mineral content and surface morphology of cut dentin and enamel were examined in 10 extracted human teeth. Enamel specimens were lased for two seconds at a fluence of 0.75 J and a frequency of 15 Hz, air-abraded for two seconds with 50 micron Al-oxide and etched for 60 seconds with 37% ortho-phosphoric acid. Dentinal specimens were subjected to the same procedure for half the time. Untreated areas of the same specimens served as the control. Morphologically, the lased dentin showed an apparently melted surface with partial obstruction of the dentin tubules, as well as cracks along the lased surface. Air-abrasion created very irregular surfaces on enamel and dentin. Dentin tubules were observed on the acid-etched dentin samples but not the air-abraded surfaces. The Nd:YAG laser created the most surface irregularity on both enamel and dentin. Laser treatment appeared to alter the chemical structure and surface morphology of the dentin and enamel.     

Effects of Nd:YAG laser pulpotomy on human primary molars

The purpose of this study was to compare the effects of Nd:YAG laser pulpotomy to formocresol pulpotomy on human primary teeth. Patients with a primary tooth that required pulpotomy because of pulpal exposure to caries, were selected for this study. After removal of coronal pulpal tissue, Nd:YAG laser at 2 W, 20 Hz, 100 mJ or a 1:5 dilution of formocresol was introduced into the canal orifice for complete hemostasis. IRM paste was then placed over the pulp stump, and the tooth was restored either with composite resin or stainless steel crown. Sixty-eight teeth were treated with Nd:YAG laser and followed up for 6 to 64 months. Clinical success was achieved in 66 out of the 68 teeth (97 %), and 94.1 % were radiographically successful. In the control group, 69 primary molars were treated with formocresol and followed up for 9 to 66 months; 85.5 and 78.3% achieved clinical and radiographic success, respectively. The success rate of Nd:YAG laser pulpotomy was significantly higher than that of formocresol pulpotomy. The permanent successors of the laser-treated teeth erupted without any complications.     

Effects of the Nd:YAG dental laser on plasma-sprayed and hydroxyapatite-coated titanium dental implants: surface alteration and attempted sterilization.

The Nd:YAG dental laser has been recommended for a number of applications, including the decontamination or sterilization of surfaces of dental implants that are diseased or failing. The effects of laser irradiation in vitro (1) on the surface properties of plasma-sprayed titanium and plasma-sprayed hydroxyapatite-coated titanium dental implants, and (2) on the potential to sterilize those surfaces after contamination with spores of Bacillus subtilis have been examined. Surface effects were examined by scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction after laser irradiation at 0.3, 2.0, and 3.0 W using either contact or noncontact handpieces. Controls received no laser irradiation. Melting, loss of porosity, and other surface alterations were observed on both types of implants, even with the lowest power setting. For the sterilization study, both types of implants were first sterilized by exposure to ethylene oxide and then contaminated with spores of B subtilis. After laser irradiation, the implants were transferred to sterile growth medium and incubated. Laser irradiation did not sterilize either type of implant. The spore-contaminated implants in the control group were successfully sterilized with ethylene oxide.     

Phase, compositional, and morphological changes of human dentin after Nd:YAG laser treatment

Although techniques for repairing root fracture have been proposed, the prognosis is generally poor. If the fusion of a root fracture by laser is possible, it will offer an alternative to extraction. Our group has attempted to use lasers to fuse a low melting-point bioactive glass to fractured dentin. This report is focused on the phase, compositional, and morphological changes observed by means of X-ray diffractometer, Fourier transforming infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy in human dentin after exposure to Nd:YAG laser. The irradiation energies were from 150 mJ/ pulse-10 pps-4 s to 150 mJ/pulse-30 pps-4 s. After exposure to Nd:YAG laser, dentin showed four peaks on the X-ray diffractometer that corresponding to a-tricalcium phosphate (TCP) and beta-TCP at 20 = 30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. The peaks of a-TCP and beta-TCP gradually increased in intensity with the elevation of irradiation energy. In Fourier transforming infrared analysis, two absorption bands at 2200 cm(-1) and 2015 cm(-1) could be traced on dentin treated by Nd:YAG laser with the irradiation energies beyond 150 mJ/pulse-10 pps-4 s. The energy dispersive X-ray results showed that the calcium/phosphorus ratios of the irradiated area proportionally increased with the elevation of irradiation energy. The laser energies of 150 mJ/ pulse-30 pps-4 s and 150 mJ/pulse-20 pps-4 s could result in the a-TCP formation and collagen breakdown. However, the formation of glass-like melted substances without a-TCP at the irradiated site was induced by the energy output of 150 mJ/ pulse-10 pps-4 s. Scanning electron micrographs also revealed that the laser energy of 150 mJ/ pulse-10 pps-4 s was sufficient to prompt melting and recrystallization of dentin crystals without cracking. Therefore, we suggest that the irradiation energy of Nd:YAG laser used to fuse a low melting-point bioactive glass to dentin is 150 mJ/ pulse-10 pps-4 s.     

脉冲Nd:YAG激光用于磨损牙复合树脂粘接修复的临床观察

目的评价脉冲Nd：YAG激光联合自酸蚀粘接系统修复后牙面磨损的临床疗效。方法对15例患者的38颗后牙面磨损进行修复,要求每例患者至少有2颗磨牙或前磨牙有相似病损,试验组使用脉冲Nd：YAG激光联合AdperPromptL-Pop自酸蚀粘接剂,对照组直接使用AdperPromptL-Pop自酸蚀粘接剂,修复树脂为Z350光固化复合树脂,以改良美国公共卫生署标准评价修复后1、6、12个月的疗效。结果 12个月时试验组成功率为94.44%,对照组成功率为61.11%,2组的差异有统计学意义（P〈0.05）。1个月时试验组的牙髓牙本质反应好于对照组,差异有统计学意义（P〈0.05）;12个月时试验组的固位、边缘密合性好于对照组,差异有统计学意义（P〈0.05）。结论脉冲Nd：YAG激光处理后牙面磨损区可以提高光固化复合树脂与牙面的自酸蚀粘接力,降低术后敏感。     

脉冲Nd:YAG激光根管内照射对狗牙尖周组织的影响

目的：观察脉冲Ｎｄ：ＹＡＧ激光根管内照射对狗牙尖周组织的影响。方法;组织学切片法和超薄切片法。结果;２．１Ｗ,１４０ｍＪ,１５Ｈｚ的脉冲;Ｎｄ：ＹＡＧ激光根管内照射２５ｓ,对尖周组织产生了明显的损伤,并延缓了尖周病变的愈合。１．２Ｗ,８０ｍＪ,１５Ｈｚ的脉冲Ｎｄ;ＹＡＧ激光根管内照射２５ｓ,对尖周组织产生的损伤明显轻于传统根管治疗,有利于尖周病变的愈合。     

Clinical, radiographic, and histopathologic evaluation of Nd:YAG laser pulpotomy on human primary teeth

The purpose of this study was to compare clinical, radiographic, and histopathologic effects of Nd:YAG laser pulpotomy to formocresol pulpotomy on human primary teeth. Patients with at least two vital primary molar teeth that required pulpotomy, because of pulpal exposure to caries, were selected for this study. After hemorrhage control, complete hemostasis into the canal orifice was achieved by exposure to Nd:YAG laser (1064 nm) and an He-Ne laser (the aiming beam of the Nd:YAG laser) in noncontact mode at 2 W, 20 Hz, 100 mJ, or was achieved by applying 1:5 dilution of formocresol. Forty-two teeth in two groups were to be followed up clinically and radiographic at 1, 3, 6, 9, and 12 months. Eighteen teeth planned for serial extractions were selected for histopathologic study. The teeth were extracted at 7 and 60 days. The teeth in the laser group had a clinical success rate of 85.71% and a radiographic success rate 71.42% at 12 months. The teeth in the formocresol group had a clinical and radiographic success rate of 90.47% at 12 months. There were no statistically significant differences between laser and formocresol group with regard to both clinical and radiographic success rates. There was a statistically significant difference between 7- and 60-day laser groups with regard to inflammatory cell response criteria. Dentin bridge was absent in all samples. No stained bacteria were observed in any of these samples. In conclusion, Nd:YAG laser may be considered as an alternative to formocresol for pulpotomies in primary teeth.     

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激光联合平阳霉素对兔耳静脉作用效应的研究

目的：探讨Nd：YAG激光联合平阳霉素（PYM）对兔耳静脉血管的作用效应。方法：健康新西兰白兔37只（74侧耳）随机分为A、B、C、D4组,A、B、C每组各12只,其中A组（实验组）每只兔耳注射PYM溶液0．3ml（浓度：4mg／ml）,第7d后于注射段行Nd：YAG激光扫描照射（能量密度为2547．8J／cm^2）;B、C组（对照组）分别给予PYM注射、Nd：YAG激光扫描照射;D组（空白组）1只。A、B、C组于第1d、3d、7d、14d、21d、28d各取4只兔耳静脉组织行光镜观察,取第14d、28d组织行透射电镜观察。结果：①光镜下：A组与B组比较,14d、21d、28d的静脉损伤程度有显著性差异（P〈0．05）：A组与C组比较,7d、14d、21d、28d的静脉损伤程度有显著性差异（p〈0．05）。②电镜下：A组与B、C组比较,28d时仍可见内皮细胞水肿,内膜肿胀及附壁血栓。结论：Nd：YAG激光联合平阳霉素较单一处理对兔耳静脉的损伤程度重、损伤作用时间长。