A histopathological study of the effects of pulsed Nd:YAG laser irradiation on infected root canals in dogs.

The effects of pulsed Nd:YAG laser irradiation during root canal treatment of infected teeth were investigated histopathologically in dogs. One hundred and eight teeth with a single root in 15 healthy adult beagle strain dogs were used in this study. After inducing infected teeth, each root canal was shaped with up to at least a #40 K-file; then, after coating with black ink, the canal was irradiated using the following parameters: 1 W, 30 pps, for 1 and 2 s, and 2 W, 30 pps, for 2 s. The degree of inflammation of the periapical regions at 2, 4, and 8 wk was examined histopathologically by light microscopy. Inflammation of the periapical regions in the laser-treated groups was significantly less than that in the control group at 4 and 8 wk (p < 0.05). These results suggest that pulsed Nd:YAG laser is useful for root canal treatment of infected teeth, if appropriate parameters are selected.     

脉冲Nd:YAG激光根管内照射与牙根表面温度变化的关系

目的:探讨不同剂量的脉冲Nd:YAG激光根管内照射与牙根表面温度变化的关系及影响因素。方法:108颗离体单根管牙处理后分为3组。A组为同剂量激光根管内照射不同牙位的牙;B、C两组分别在15 Hz和20 Hz频率下分7种功率根管内照射,B组根管壁涂增效剂后再照射,测牙根表面中部的温度;C组加测根表面下部的温度。结果:¹同剂量激光根管内照射,下切牙较上切牙、尖牙和前磨牙根面温度显著升高(P<0101)。º20 Hz和15 Hz 照射组随激光功率增大牙根表面温度升高。»根管壁涂增效剂后各功率激光照射后根面升温显著增加(P< 0101)。¼同剂量激光照射,根尖部较根管中部温度升高更多。结论:在一定范围内,脉冲Nd:YAG激光根管内照射,牙根表面温度变化随功率、频率增大而增加;牙位和增效剂等对牙根表面温度变化有不同程度影响。     

The effect of an Nd–YAG pulsed laser on the cleaning of the root canal and the formation of a fused apical plug

A Neodyminium-yttrium aluminium garnet (Nd–YAG) pulsed laser was used in vitro to determine whether various laser energy levels from 0.75 W to 1.7 W at 15 pulses s^?1 (pps) were able to (i) remove debris from the walls of prepared root canals (ii) remove pulpal tissue from unprepared canals and (iii) create a fused apical plug from dentine chips, hydroxyapatite (HAP) or low-fusing dental porcelain. Single-rooted teeth were sectioned at the amelocemental junction and the crowns discarded. The root canals of 50 teeth were prepared chemomechanically and allocated to four groups of 10 teeth for laser treatment. One group was left unlased as a control. After lasing, the teeth were split longitudinally, stained and examined for residual debris. Results showed that there was no statistically significant difference between the groups (P < 0.05). A further 20 teeth were not prepared and lased in the coronal one-third of the root canal at different energy levels; five teeth were not lased. The teeth were split and examined as previously. The results showed that lasing cleaned the coronal part of the root canal almost completely of pulpal tissue. In the final part of the study laser energy was applied to dentine chips, HAP and low-fusing procelain in an attempt to produce a fused apical plug. The laser was unable to melt the dentine chips but some hardening of HAP occurred when combined with blue food-colouring, with or without glycerine, at energy levels of 1.0 W, at 15 pps for 30 s. Superficial hardening of low-fusing porcelain occurred at 1.0 W, 15 pps for 30 s which increased when 1.5 W was applied at 15 pps for 30s.     

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.     

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

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.     

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。     

Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study

Abstract— The purposes of the study were to observe the morphological changes on root canal walls after instrumentation and irrigation, and assess the efficacy of conventional cleansing procedures and the effectiveness of Er:YAG laser in removing debris and smear layer from the root canal walls. Thirty-six endodontically treated human mandibular incisor teeth with single root canals were bisected longitudinally and divided into three groups of 12 teeth. Group 1 (Gl) was left unlased as a control. The teeth of group 2 (G2) and group 3 (G3) were irradiated by Er:YAG laser (laser parameters were set at 1 W, 100 mJ/pulse and 10 Hz) for 3 s and 5 s. The teeth were prepared for scanning electron microscope study. Control specimens showed debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. These results suggested that Er:YAG laser irradiation had an efficient cleaning effect on the prepared root canal walls.     

Effects of Nd: YAG laser irradiation on the root canal wall dentin of human teeth: a SEM study

The purpose of this study was to observe the morphological and histological changes on the root canal walls after Nd:YAG laser application. Twenty vital, recently extracted single-rooted human teeth were used for this study. Root canals were cleaned and shaped by a conventional step-back technique--by means of k files up to a 20 k-file type at working length--and subsequently shaped by Ni-Ti root-canal rotary instrumentation up to 30/06 and irrigated with 2.5% hypochlorite solution. Ten teeth (control group) were left unlased, while the other ten teeth were irradiated with Nd:YAG laser by means of a 320 microns fibre inserted in the root canal at 1 mm from the apex with a power of 1.5 Watt and a frequency of 15 pps for five seconds in retraction with rotating movements. The control specimen showed debris and smear layer on the root canal surface obscuring the dentin tubules. The root canal walls irradiated with Nd:YAG laser showed a clear glazed surface, some open dentinal tubules and some surface craters with cracks. Such results confirm that smear layer and debris are removable with Nd:YAG laser, however clearing all root canal walls is still difficult and, if the energy level and duration of application are inadequate, a certain degree of thermal damage and morphological changes in dentin structure are observable.     

Dentin strain induced by laser irradiation

The purpose of this study was to investigate the strain and temperature change in dentin induced by laser irradiation of human root canals with or without water cooling. Twenty-eight palatal roots of extracted human maxillary first molars were used. The strain in dentin was measured using strain gauges fixed on the apical third of the buccal root surface. The temperature change of the root dentin was monitored using thermocouples embedded into dentin near the apex. The root canal was irradiated with Er:YAG or Nd:YAG laser at an output of 1 W (100 mJ, 10 pps) for 5 s. The tip of the irradiation fibre was located 2.0 mm from the root apex. With water cooling, the mean maximum strain induced by Er:YAG laser was significantly lower than that by Nd:YAG laser (P < 0.05). However, without water cooling, no significant difference between the two lasers (P > 0.05) was found. The results suggest that the strain induced by Er:YAG laser irradiation in dentin with water cooling may be minimal, but there still might be a risk of root micro-fracture if cooling is not sufficient.     

Effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals: an electrochemical study

AIM: The purpose of this laboratory study was to evaluate the effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals using an electrochemical method. METHODOLOGY: Forty extracted single-rooted teeth were selected and the anatomic crown of each tooth was removed. The specimens were randomly divided into four groups. In group 1, the root canals were prepared with K-files and irradiated with Nd:YAG laser (5 W, 20 Hz) via a 300 microns optical fibre. Then the root canals were obturated with laterally condensed gutta-percha and Pulp Canal Sealer EWT. In group 2, the root canals were treated with the same method as those of group 1 but without laser irradiation. In group 3, the root canals were prepared with ProFiles, laser irradiated and then obturated with vertically condensed gutta-percha and Pulp Canal Sealer EWT. In group 4, the root canals were treated with the same method as those of group 3 but without laser irradiation. The electric resistance between standard and experimental electrodes in the canals was measured over a period of 10 days. RESULTS: At 2 h, groups 1 and 3 irradiated with laser had significantly less apical leakage than group 2 (P < 0.05). After 10 days, group 4 had the highest leakage, followed by groups 2, 1 and 3; the differences between the groups was statistically significant (P < 0.05). CONCLUSIONS: Laser irradiation following root canal preparation reduced apical leakage following root canal obturation.     

超声波预备根管与Nd：YAG激光照射后根管牙本质的SEM研究

目的：评价超声预备根管及Ｎｄ：ＹＡＧ 激光照射根管壁后,根管内壁的清洁度和管壁牙本质微结构的变化。方法：１２ 个离体成人上前牙分为４ 组制备根管：手用器械、超声根管治疗仪、手用器械＋ Ｎｄ：ＹＡＧ 激光照射、超声波＋ Ｎｄ：ＹＡＧ 激光照射,扫描电镜下观察并照像记录。结果：手用扩锉预备的根管内壁有涂层污染和病理组织残留;超声波预备后根管内壁清洁、涂层消除,牙本质小管口开放;手用器械或超声制备后辅以适当能量激光照射的管内壁牙本质小管口封闭,管间牙本质熔融,并形成空泡状结晶。结论：超声波预备根管可达到理想的清洁效果,但牙本质小管口开放易造成根管术后渗漏。而Ｎｄ：ＹＡＧ 激光照射有利于封闭牙本质小管口,减少根尖孔渗漏,还具有封闭根管内壁死腔的作用。     

根管内Nd:YAG激光照射后对根尖周组织的作用

目的：观察激光在根管内照射后对根尖周组织的作用。方法：选3只小型猪,全麻下将乳前磨牙开髓、抽髓、根管扩大后,激光照射30秒,做常规根管充填。对照组为常规根管充填。1天、3天、7天和15天后观察根尖周组织的变化。结果：激光照射后1天,根周膜血管充血、轻度炎症,对照组只有根尖周膜充血。激光组织反应比对照组稍重。激光照射后3天和7天,少数病例根周组织有轻度的刺激与对照组的病理表现相近。激光照射后15天部分标本根周膜正常,部分标本有轻度炎症反应,与对照组结果基本相似。结论：本激光照射条件对根尖周组织没有明显损伤作用,可供临床应用时参考。     

根管内Nd:YAG激光照射后对根尖周组织的作用

目的:观察激光在根管内照射后对根尖周组织的作用.方法:选3只小型猪,全麻下将乳前磨牙开髓、抽髓,根管扩大后,激光照射30秒,做常规根管充填.对照组为常规根管充填.1天、3天、7天和15天后观察根尖周组织的变化.结果:激光照射后1天,根周膜血管充血、轻度炎症,对照组只有根尖周膜充血.激光组组织反应比对照组稍重.激光照射后3天和7天,少数病例根周组织有轻度的刺激与对照组的病理表现相近.激光照射后15天部分标本根周膜正常,部分标本有轻度炎症反应,与对照组结果基本相似.结论:本激光照射条件对根尖周组织没有明显损伤作用,可供临床应用时参考.     

根管治疗中应用Nd:YAG 激光的扫描电镜观察

目的 探讨Nd：YAG激光在根管治疗中的应用。方法 选用28个离体单根牙，随机分为4组。对照组不做处理。常规组进行根管扩大和根管冲洗，激光组经根管扩大后，用Nd：YAG激光1．5W，20pps分别照射15s和30s，并用扫描电镜观察。结果 激光照射15s组玷污层被去除，牙本质小管封闭和半封闭。激光照射30s组牙本质过分熔融，牙本质小管口开放。结论 Nd：YAG激光在根管治疗中的应用是可行的。     

Temperature elevation on the root surface during Nd:YAG laser irradiation in the root canal.

Nd:YAG lasers have been suggested as a potential tool in endodontic therapy because of their sterilizing and sealing effects on the dentinal tubules. However, the generation of heat in the root canal by laser irradiation may produce potentially harmful effects on adjacent tissues. The purpose of this study was to evaluate the temperature elevation on the root surface when Nd:YAG laser was irradiated in the root canal. The apical third area of 90 single-rooted teeth were irradiated with normal pulsed Nd:YAG laser (50, 80, 100, 150, and 200 mJ/pulse; 20, 25, and 30 pulses/s). The temperature elevation was measured and recorded on the root surface simultaneously. The temperature elevation did not exceed 10 degrees C only when the laser energy output was below 100 mJ/pulse and under 20 pulses/s.     

Nd:YAG 激光在直接盖髓术中的应用

目的 :观察研究脉冲Nd :YAG激光照射在直接盖髓术中的作用。方法 :选择门诊意外露髓的患者 10 0例 ,随机分为对照组和试验组。对照组采用传统的氢氧化钙直接盖髓术。试验组首先用脉冲Nd :YAG激光 (设置激光脉冲频率为 2 0Hz ,每脉冲能量 40mJ)照射穿髓孔区 5s,再以氢氧化钙封闭穿髓孔。病人于术后 2周、6月、12月分别复诊检查牙髓活力情况 ,记录盖髓术成功率。结果 :12月复诊时对照组成功率 76 % ,试验组成功率 92 % ,统计学分析两者有显著性差异。结论 :适当能量的Nd :YAG激光照射有助于直接盖髓术的成功。脉冲Nd :YAG激光不仅具有清除穿髓孔区牙体组织碎屑、使暴露的牙体组织表面凝固止血、对穿髓孔区灭菌消毒等功能 ,还具有促进牙髓组织细胞再生修复的作用。     

脉冲Nd:YAG激光照射剂量对牙周组织中SOD、MDA含量的影响

目的:探讨脉冲Nd:YAG激光不同照射剂量对大鼠实验性牙周炎牙周组织中超氧化物歧化酶(SOD)、丙二醛(MDA)含量的影响.方法:健康Sprague-Dawley大鼠共56只,随机分为7组,其中1组作为正常对照组,6组建立大鼠牙周炎动物模型.按照分组给予不同剂量激光照射,末次治疗24 h后测量牙周临床指标.采用分光光度仪测定大鼠牙周组织中SOD、MDA的含量.结果:实验剂量范围内,1.5 W、2.0 W 20 pps剂量组SOD含量较未照射组(P组)显著增高(P＜0.05).1.5 W、2.0 W、2.5 W 20 pps组较P组MDA活性均显著降低(P＜0.05).结论:在1.5～2.0 W 20 pps剂量范围内,采用脉冲Nd:YAG激光牙周袋内照射能有效增加牙周组织中SOD含量,减少MDA含量,起到治疗牙周炎的作用.     

Evaluation of the bactericidal effect of Er,Cr:YSGG, and Nd:YAG lasers in experimentally infected root canals

The aim of this study was to evaluate the bactericidal effect of the Er,Cr:YSGG laser and the Nd:YAG laser in experimentally infected root canals. Sixty single-rooted teeth with straight canals were selected. After preparation and sterilization, the specimens were inoculated with Enterococcus faecalis for 3 weeks. After irradiation by lasers, the number of bacteria in each root canal was examined. The Er,Cr:YSGG laser gave a reduction of 77% after irradiation at 1 W and 96% at 1.5 W, but there was no significant difference (p > 0.05). The Nd:YAG laser gave a reduction of 97% at 1 W and 98% at 1.5 W, and there was no significant difference (p > 0.05). Compared with the Er,Cr:YSGG laser, the Nd:YAG laser is more effective (p < 0.05). In conclusion, both lasers systems have a significant bactericidal effect in infected root canals, and the Nd:YAG laser is more effective than the Er,Cr:YSGG laser.     

Ex vivo study of the adhesion of an epoxy-based sealer to human dentine submitted to irradiation with Er : YAG and Nd : YAG lasers

AIM: To evaluate the adhesion of an epoxy-based sealer to human dentine submitted to irradiation with Er : YAG or Nd : YAG laser at various parameters. METHODOLOGY: Ninety maxillary canine teeth were sectioned transversely at the cemento-enamel junction and at the root tip to leave an 8-mm-long cylinder. The tooth specimen was centred in a metallic ring (16 mm diameter and 8 mm height) and embedded in acrylic resin. The root canals were prepared using a low-speed handpiece and a conical diamond bur, which was attached to a paralleling device. This bur was lowered to a depth previously determined by a silicone stop. Specimens were divided into nine groups: group I, dentine was treated with 2 mL of 17% EDTAC for 5 min. Groups II-V were irradiated with Er : YAG laser at the following parameters: group II - 8 Hz and 200 mJ input (120 mJ output); group III - 8 Hz and 400 mJ input (240 mJ output); group IV - 16 Hz and 200 mJ input (120 mJ output); group V - 16 Hz and 400 mJ input (240 mJ output). Groups VI-IX were irradiated with Nd : YAG laser at the following parameters: group VI - 10 Hz and 1 W input (0.4 W output); group VII - 10 Hz and 2 W input (0.8 W output); group VIII - 15 Hz and 1 W input (0.4 W output); group IX - 15 Hz and 2 W input (0.8 W output). The root canals were filled with an epoxy-based root canal sealer and submitted to a push-out test. RESULTS: Statistical analysis showed significant differences (P < 0.01) between Er : YAG and Nd : YAG laser treatments at the higher frequencies compared with 17% EDTAC. Greater adhesion values were obtained for groups IV and V (Er : YAG laser) and groups VIII and IX (Nd : YAG laser), which were statistically different from groups II and III (Er : YAG laser) and groups VI and VII (Nd : YAG laser). Treatment with only 17% EDTAC had the lowest adhesion values. CONCLUSIONS: An increase in frequency, independent of power settings, of the lasers used in this study increased adhesion of an epoxy-based root canal sealer.     

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。