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.     

The effects of CO2 laser and Nd:YAG with and without water/air surface cooling on tooth root structure: correlation between FTIR spectroscopy and histology

Morphologic and chemical characterization of root surfaces treated with either the CO₂, laser, Nd:YAG, or Nd:YAG with water/air surface cooling (Nd:YAG-C) was completed using scanning electron microscopy (SEM) and FTIR photoacoustic spectroscopy (FTIR/PAS). Specimens for morphologic analysis consisted of 20 extracted single rooted teeth unaffected by periodontal disease. The specimens were exposed at varying energy densities to a single pass of the laser. SEM examination revealed, for all lasers, a direct correlation between increasing energy densities and depth of tissue ablation and width of tissue damage. The Nd:YAG-C required higher energy densities than either the CO₂ or Nd:YAG lasers to achieve the same relative depth of tissue ablation. Regardless of energy density, and in contrast with other laser types, areas treated with the Nd:YAG-C did not exhibit collateral zones of heat damage. Specimens for spectroscopic examination consisted of 12 disks, 6x2 mm, cut from debrided root surfaces of extracted, unerupted human molars. The spectral results indicate a substantial reduction in the absorption bands attributable to protein and an additional band at 2015 cm^-1 in specimens exposed to the Nd:YAG without water. In the presence of water/air coolant, the band at 2015 cm^-1 appears only at a substanially higher energy density. The spectra of the CO₂ treated specimens, with the char layer present, show a significant reduction in the protein bands and additional bands at 2015 and 2200 cm^-1, that are tentatively assigned to the cyanamide and cyanate ions, respectively. These results suggest a reaction of the organic matrix and mineral with laser exposure.     

Healing of rat mouth mucosa after irradiation with CO2, Nd:YAG, and CO2-Nd:YAG combination lasers

The healing process of wounds made by a combination laser was studied in 90 rats. The laser system enabled both separate and combined use of CO₂, and Nd:YAG laser irradiations. The laser wounds and the control excision wounds made by alligator forceps appeared on both sides of the tongue. Specimens from the wound sites were taken immediately, 6 h, and 1, 2, 4, 7, 11, 21, 28, and 42 days after surgery. The wound-healing process was studied by macroscopic evaluation before preparing the specimens for light microscopy. Some dilferences were noted in the wound-healing process among the three groups into which the experimental animals were divided. Tissue coagulation damage was most extensive in the Nd:YAG laser sites, where it was observed in its full extent 4 days after surgery. Epithelial cells were seen to begin to proliferate in all the wounds 6 h after surgery. Re-epithelialization was completed by between 7 (CO₂) and 21 days (Nd:YAG) at all the wound sites. The inflammatory cell infiltration was more prominent in the Nd:YAG and the CO_rNd:YAG combination laser wounds than in the COi and excision wounds during healing. Tissue regeneration occurred faster with less contraction in the combination CO₂-Nd:YAG wounds than in Nd:YAG wounds. The best macroscopic healing result was seen in the CO₂, wound sites. The combination laser was effective both at cutting and at coagulating tissue. Combining the CO₂ and Nd:YAG laser irradiation into one beam resulted in a greater incision depth than what could have been expected from using the two lasers separately.     

Enamel surface roughness analysis after laser ablation and acid-etching

Laser-roughened enamel surfaces have been shown to provide for greater acid-resistance and enhanced restorative material/enamel bond strength. Extracted tooth enamel was irradiated with several lasers: CO₂/Nd:YAG (CW), CO₂ (RSP), Nd:YAG (CW), Nd:YAG (Q-switched), Argon (CW), and Ar:F excimer. Additional teeth were acid-etched. Energy densities were standardized at 25-47 J/cm² for all mediums. Surface profile analyses were conducted with a profilometer to determine the amount of enamel surface roughness. The acid-etched samples exhibited both a greater amount of surface roughness and a qualitatively different type of enamel surface morphology than the laser-treated specimens. Independent use of the CO₂ and Nd:YAG beams exhibited a moderate amount of roughness, while the coaxial CO₂/Nd:YAG beam displayed surface roughness approaching that of the acid-etch samples. Different laser mediums produce enamel surface morphologies that are characteristic of a variety of inherent lasing parameters.     

Permeability, morphologic and temperature changes of canal dentine walls induced by Nd: YAG, CO2 and argon lasers

The permeability, temperature and morphologic changes of the wall of the root canal induced by Nd:YAG, CO₂ and argon lasers were studied. The changes were evaluated according to the presence or absence of a smear layer. Root canals of 140 human single-rooted teeth were enlarged using a step-back technique. Permeability was evaluated by the extent of methylene blue dye penetration into the tubules. Temperature changes were measured using a thermovision system, and morphological changes were evaluated by scanning electron microscopy. Laser energy was delivered into the canal by means of a flexible optical fibre or metal tip. There were statistically significant differences in permeability between Iased groups with and without a smear layer in the cervical third of the root canal following lasing. In the middle third of the root canal, all three laser types induced permeability increases in groups with a smear layer. In the apical third, statistically significantly decreases in permeability were observed among C02 laser and Nd:YAG compared with control group (P<0.01). Rises in temperature ranged from a minimum of +10.1 °C (CO₂ laser) to a maximum of +54.8 °C (argon laser). All three laser devices appeared capable of producing a glazed-like surface and craters.     

Nd：YAG激光去除陶瓷托槽对兔牙髓组织的影响

目的应用Nd：YAG激光,观察在不同功率、时间等参数下,激光照射辅助去除陶瓷托槽后兔牙髓的组织学变化。方法选择新西兰长耳白兔20只,将其4颗前牙作为实验用牙齿,常规黏结陶瓷托槽。左上前牙机械去黏结,作为对照组;其余3颗牙齿采用激光去黏结,右上前牙激光能量为3 W、3 s（A组）,左下前牙能量为2 W、5 s（B组）,右下前牙能量为5 W、2 s（C组）。去黏结后5 min、1 d、3 d、1周和1月后处死动物,每次处死4只,拔除前牙,制作兔牙髓组织切片。结果与对照组相比,经不同能量激光照射后5 min,兔牙髓组织均出现轻度毛细血管扩张。1 d后,A、B组出现中度毛细血管扩张;C组除有中度毛细血管扩张外,还伴有少量炎细胞浸润。3 d后,B组牙髓症状消失;A组牙髓症状减轻,仍有轻度毛细血管扩张;C组有毛细血管扩张、出血,并伴有炎细胞浸润。1周后,A组毛细血管扩张减轻,基本恢复正常;C组症状仍很明显。1月后,A组牙髓症状消失,C组仍有轻度毛细血管扩张。结论采用能量为3 W、3 s的Nd：YAG激光去除陶瓷托槽,兔牙髓组织不会出现不可逆的组织学变化。     

Nd：YAG激光用于狗牙直接盖髓术的实验研究

目的：观察Ｎｄ：ＹＡＧ激光照射暴露牙髓后的盖髓术疗效。方法：用肉眼和组织学切片法。结果：１０７个狗牙露髓面用３个不同参数（１５９２ｍＪ／ｍｍ２、３１８５ｍＪ／ｍｍ２、４７７７ｍＪ／ｍｍ２）Ｎｄ：ＹＡＧ激光照射５ｓ后用氢氧化钙盖髓，与单纯氢氧化钙组比较，发现：低能量Ｎｄ：ＹＡＧ激光有刺激照射区和侧方修复性牙本质形成、促进创伤愈合作用，而高能量Ｎｄ：ＹＡＧ激光照射则可能引起牙髓变性坏死。结论：低能量Ｎｄ：ＹＡＧ激光有一定的促进创伤愈合作用，但在Ｎｄ：ＹＡＧ激光用于照射露髓面牙髓前，还应该对促进牙本质桥形成的Ｎｄ：ＹＡＧ激光照射条件进行更详细研究。     

Nd:YAG激光辅助去除陶瓷托槽对托槽的粘接强度及髓腔温度影响的研究

目的　研究国产DL-200型计算机控制脉冲Nd:YAG口腔激光机去除陶瓷托槽的最佳技术参数。方法　观察未使用激光照射组,以及激光功率5 W、照射时间2 s组,功率3 W、照射时间3 s组和功率2 W、照射时间5 s 组,3种参数下激光对陶瓷托槽的粘接强度及髓腔温度的影响。结果　①激光照射后可以显著降低陶瓷托槽的粘接强度,约降低50%,4组间的平均粘接强度差异有统计学意义(P<0·001);②激光照射后各组髓腔温度均升高,各组温度升高有统计学意义(P<0·001),激光功率3 W、照射时间3 s组髓腔温度只升高3·65℃,较其他两组低。结论　国产DL-200型计算机控制脉冲Nd:YAG口腔科激光治疗机激光照射后可以显著降低陶瓷托槽的粘接强度,去除陶瓷托槽的最佳参数是激光功率3 W、照射时间3 s,这一能量不会明显升高牙髓温度。     

Post-operative symptoms and healing after endodontic treatment of infected teeth using pulsed Nd: YAG laser

Abstract— Forty-four teeth in 38 patients, diagnosed with chronic apical periodontitis, were endodontically treated. Root canals were shaped using a step-back technique with 5% NaOCl and 3% H₂O₂ as irrigants. In half of the teeth the canal terminus was irradiated with pulsed Nd:YAG laser (1 W, 15 pps, 1 s). All canals were then obturated with laterally condensed gutta-percha points and sealer, and final radiographs were obtained. Occurrence of spontaneous pain was recorded 1 day after treatment. Percussion pain was recorded after 1 week, and then at 3 and 6 months after treatment. Radiographic follow-up was performed at 3 and 6 months. Percussion pain was significantly less ( P >0.05) in the laser-treated group than in the control group, both 1 week and 3 months after treatment. Other differences between the groups were not significant. These results suggested that the clinical application of pulsed Nd: YAG laser might be advantageous for the treatment of infected root canals.     

Prospective study of two retrograde endodontic apical preparations with and without the use of CO2 laser

Abstract— This article covers a 4-year study that reports 320 cases in which endodontic surgery was performed for residual apical lesions or lesions that could not be treated in a conventional way. Four groups of 80 teeth each were formed and they were followed up after a 12-month interval. The first group comprised cases treated with a micro bur, retrograde filling and IRM; the second, cases treated at the apical and radicular portions with a CO₂ laser; the third, cases in which the retrograde cavity was prepared with an ultrasonic device instead of a micro bur; and the fourth group comprised cases treated in a similar way to the second group, i.e., cases treated at the apical and radicular portions, but with a CO₂ laser instead of a micro bur. After 12 months, the results showed a better prognosis with ultrasonic treatment. Regardless of technique, the CO₂ laser did not improve the healing process.     

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。     

A histopathological study of the morphological changes at the apical seat and in the periapical region after irradiation with a pulsed Nd:YAG laser

In this study, the effects of pulsed Nd:YAG laser irradiation on the apical seat and periapical region of instrumented root canals were investigated. One hundred and ninety-two teeth, including incisors and molars (239 root canals), in 18 healthy adult beagle dogs were used. After extirpation of the pulp under anaesthesia, each root canal was shaped up to at least a size 40 K-file, and then laser irradiated using the following parameters: 1 W, 15 pps for 2, 3, and 4 s; 2 W, 15 pps for 2 s. The effectiveness of debris removal and carbonization on the root canal walls immediately laser irradiation were examined and inflammation of the periapical region at 1, 2, and 4 weeks after laser irradiation was examined using light microscopy. Effective debris removal was observed in most cases in the laser-treated groups and was dependent on irradiated energy. Carbonization was observed in the irradiated root canals except at the parameter of 1 W for 2 s. Periapical inflammation was observed at 1 W for 2 s to the same extent as in the control group (P > 0.01). These results suggest that the pulsed Nd:YAG laser is useful for debris removal with no adverse effects immediately after extirpation of the pulp if appropriate parameters are selected.     

Nd:YAG激光、CO2激光局部治疗轻型复发性阿弗他溃疡短期疗效比较研究

目的:比较Nd:YAG激光和CO2激光治疗轻型复发性阿弗他溃疡短期临床疗效。方法:选取68例临床上确诊为轻型复发性阿弗他溃疡的患者,随机分为2组,其中Nd:YAG激光治疗组和CO₂激光治疗组各34例。治疗周期3~5 d。应用视觉模拟评分法(VAS)及DP分级法评估并比较两组短期疗效。结果 :在激光照射后的第1天、第2天和第3天分别记录两组疼痛指数减少值,其中Nd:YAG激光减少值为:(3.27±0.24)、(4.23±0.26)和(5.60±0.27);CO₂激光组为(2.56±0.27)、(3.40±0.30)和(4.20±0.28),Nd:YAG激光组疼痛指数减少更明显(P<0.05);激光照射治疗后Nd:YAG激光组及CO2激光组的平均溃疡期分别为(4.07±0.82) d和(5.12±0.26) d,差异具有统计学意义(P<0.05),Nd:YAG激光组及CO₂激光组总有效率分别为100.0%和90.0%,差异具有统计学意义(P<0.05);同时治疗过程中Nd:YAG激光组患者无明显不适反应,而CO₂激光组有6例对疼痛感到紧张,有7例对气味较敏感。结论:Nd:YAG激光治疗MiRAU的疗效优于CO₂激光,且舒适度较好。     

Scanning electron microscopic and immunocytochemical studies of contraction during secondary C02 laser wound healing in rat tongue mucosa

An experimental model was established in which the decrease in surface area of CO₂ laser wounds on rat tongues was measured during the healing process. Scanning electron microscopy was used to measure and delineate the outlines of the initial wounds and those of the residual wounds. A 50% decrease in the surface area of the wounds was observed 10 days after surgery during the healing process. At day 30, the scar surface area was less than 10% (7.4%) of the wound surface area at day 2. This contrasts with studies reported elsewhere where only minimal contraction was observed during the healing of CO₂ laser wounds. Immunoperoxidase techniques revealed that three different phenotypes of myofibroblasts were present inside the healing area, expressing vimentin, actin and desmin. These persisted until day 30 after CO₂ irradiation.     

Kr:F准分子激光对牙体硬组织的热效应研究

目的：评价Kr:F准分子激光照射牙齿后，对牙体硬组织的影响。方法；通过测量Kr:F准分子激光照射后牙齿硬组织的温度，并与Nd:YAG激光照射组进行比较。结果：10s,60s时，Kr:F准分子激光组牙齿硬组织的温度升高值明显低于Nd：YAG激光照射组（P＜0．01）。在照射10s-60s时间内，Kr:F准分子激光照射后牙齿硬组织的温度变化值也明显低于Nd:YAG激光照射组（P＜0．01）。结论：Kr:F准分子激光牙齿产热较少。     

Nd: YAG激光对牙根面结构及变异链球菌黏附的影响

目的 研究不同功率的水冷Nd: YAG激光照射治疗对牙根面结构及变异链球菌黏附的影响。方法 将因重度慢性牙周炎拔除的离体牙分为4组,均进行手工刮治和根面平整,制备牙根片,激光1、2、3组分别用功率为4、6、8 W的水冷Nd: YAG激光照射处理60 s,对照组不作处理。用扫描电子显微镜（SEM）观察各组根片的表面结构。将变异链球菌接种于各组牙根片表面并进行培养,计数各组根片表面细菌的黏附量（CFU·mL-1）;同时用SEM观察对照组及激光2组根面的细菌黏附情况。结果 SEM观察根片表面结构,激光组较对照组牙根表面的玷污层、碎屑及菌斑样物质附着减少,但裂隙增多。3个激光组牙根表面的细菌黏附量均少于对照组（P<0.05）,而不同功率的激光组之间的差异无统计学意义（P>0.05）。SEM观察细菌黏附情况,激光2组表面的细菌黏附量明显少于对照组。结论 与单纯刮治相比,刮治后进行水冷Nd: YAG激光治疗能清除牙根表面的玷污层、碎屑及菌斑样物质,并能减少变异链球菌的黏附,但激光会导致牙根表面出现裂隙。本实验中,6 W为激光最佳功率,既能较好地去除牙根表面的玷污层和碎屑等,又能较好地控制激光对根面的热损害程度。     

Nd：YAG激光在狗牙切髓术中的应用

目的：观察Ｎｄ：ＹＡＧ激光照射狗牙牙髓后的变化，了解Ｎｄ：ＹＡＧ激光照射条件与牙髓反应的关系。方法：肉眼及组织病理学切片法。结果：接受每秒１０个脉冲、输出能量５０ｍＪ照射的牙，术后早期，创伤牙髓的愈合优于对照组；术后２８ｄ及８４ｄ有程度不同的牙本质桥形成，根部牙髓无明显异常，组织学疗效评价均成功。大能量Ｎｄ：ＹＡＧ激光用于切髓术有较强的损伤作用。结论：Ｎｄ：ＹＡＧ具有一定的促进创伤愈合作用     

Laser application in non-surgical periodontal therapy: a systematic review

Objectives: The primary aim was to address the following focused question: What is the clinical effect of laser application compared with mechanical debridement in non-surgical periodontal therapy in patients with chronic periodontitis? A secondary aim was to survey the relevant literature in relation to safety of laser applications.
Material and Methods: Electronic databases of the PubMed and the Cochrane Library were searched and completed by manual searches up to December 2007.
Results: Following screening, 12 publications (11 studies) were eligible for the review. A meta-analysis could not be performed due to the heterogeneity of the studies. The results from a narrative synthesis indicate that Er:YAG laser monotherapy resulted in similar clinical outcomes, both in the short and the long term (up to 24 months), compared with mechanical debridement. There is insufficient evidence to support the clinical application of either CO₂, Nd:YAG, Nd:YAP, or different diode laser wavelengths.
Conclusions: The Er:YAG laser seems to possess characteristics most suitable for the non-surgical treatment of chronic periodontitis. Research conducted so far has indicated that its safety and effects might be expected to be within the range reported for conventional mechanical debridement. However, the evidence from the evaluated studies is weak.     

Morphologic study of Nd:YAG laser usage in treatment of dentinal hypersensitivity

Our previous in vitro study indicated that Nd:YAG laser irradiation on dentin could melt normal dentin surface and close the exposed dentinal tubule orifices without creating surface cracks. This study evaluated the morphologic changes of hypersensitive dentin after Nd:YAG laser irradiation. Thirty patients with clinically diagnosed cervical dentin hypersensitive teeth were treated with a Nd:YAG laser of 30 mJ intensity at 10 pulses per second for 2 min. An impression of the sensitive area was taken before and after laser treatment and then examined with a scanning electron microscope. The impression of the dentin surface after Nd:YAG laser treatment showed no protrusive rods, in contrast with the presence of numerous rods before laser irradiation. Because protrusive rods are a measure of open dentinal tubules, we interpret these data to support the hypothesis that Nd:YAG laser irradiation at specifications of 30 mJ, 10 pulses per second, and 2 min can be used to seal the exposed dentinal tubules.     

Nd:YAG激光对牙齿根尖封闭效应的微渗漏研究

目的 探讨Nd:YAG(掺钕钇铝石榴石)激光在牙髓病和根尖周病治疗方面的临床应用。方法 应用低能量连续Nd:YAG激光对新鲜离体牙进行不同能量及方式的照射，结合微渗漏实验对激光照射后的牙齿根尖封闭效应进行评估。结果 Nd:YAG激光无论经根管外还是于根管内照射根尖孔，均可显著减少根尖微渗漏。结论 Nd:YAG激光在促进根尖封闭方面具有显著效果，为探讨牙髓病及根尖周病的新疗法提供了理论及实验依据。