Experience with the Nd:YAG laser in the treatment of keloid scars

Numerous therapeutic modalities have been espoused for the treatment of keloids. In the laboratory, great strides have been made in understanding the connective tissue pathobiology that underlies this problem. Unfortunately, no consistent treatment has been found to prevent the development of surface overhealing. Moreover, all forms of therapy designed to treat this condition have produced inconsistent results. This article documents the use of the Nd:YAG laser in the treatment of 20 patients with keloid scars. Candidates for the study included patients with no previous therapy and those who had prior treatment with steroids and/or surgery with no improvement. Although the use of Nd:YAG laser for keloids continues to be investigational, our results appear promising. Success of therapy was judged by softening and flattening of the scar. Laboratory studies provide a basis for understanding the possible effect of connective tissue metabolism with the Nd:YAG.     

可调脉宽倍频Nd：YAG激光和点阵CO_2激光综合治疗瘢痕的临床应用

目的：探讨综合应用可调脉宽倍频Nd：YAG532nm激光和点阵CO2激光分别治疗面颈部早期红色瘢痕和晚期浅表性瘢痕的临床效果。方法：采用可调脉宽倍频Nd：YAG 532nm波长激光治疗面颈部红色增生期瘢痕,采用点阵CO2激光治疗面颈部浅表性瘢痕,并且根据疗效评定标准对治疗效果进行评价。结果：98个早期红色增生期瘢痕每次经激光治疗后症状和体征都减轻,4次治疗后手术切口条形瘢痕的总有效率为100%,显效率为96%,挫伤及烧烫伤后片状瘢痕的总有效率为91%,显效率为70%。80例浅表性瘢痕一次治疗后的总显效率为65%。结论：综合应用可调脉宽倍频Nd：YAG532nm激光和点阵CO2激光分别治疗面颈部早期增生性瘢痕和晚期浅表性瘢痕的治疗方案可行,值得临床推广应用。     

Efficacy and safety of Nd:YAG laser alone compared with combined Nd:YAG laser with intralesional steroid or botulinum toxin A in the treatment of hypertrophic scars

Lasers in Medical Science - The aim of this study is to evaluate the efficacy and safety of Nd:YAG laser alone or in combination with intralesional injection of botulinum toxin type A or...     

Nd:YAG laser irradiation of an eye model: experimental analysis

This work reviews a series of experiments performed on an eye model to study physical effect relevant for a safe and effective use of the Q-switched Nd:YAG laser in ophthalmic microsurgery. The breakdown probability per laser pulse has been found to depend exponentially on the reciprocal laser field. This indicates that, as in transparent solids, electron avalanche ionization is likely the main mechanism for optical breakdown in liquids. Shielding of the retina, by the laser-induced plasma, is not very effective, but an appreciable degree of shielding is present, in burst operation, even after membrane disruption. A backscattered beam, which presents the typical properties of stimulated Brillouin scattering, has been observed in the eye model, with a threshold of approximately 5 X 10(9) W/cm2. This beam, which presents an irregular spatial structure with peaks of irradiance well above the average value, may produce damage of the internal wall of the cornea.     

Temperature rise in biological tissue during Nd:YAG laser irradiation

Few data are available about temperature distribution in tissue during Nd:YAG laser irradiation. To study the heat distribution that produces tissue coagulation, we used a thermographic camera aimed orthogonally to the laser beam axis to obtain thermal maps. Immediately after surgical resection, specimens of human stomach were irradiated near the resected edge, and the heat emitted sideways was detected by an infrared image system. A magnifying lens mounted on the camera enabled us to obtain 0.1 mm spatial resolution of the isothermic curves. The thermal analysis showed that the maximum depth where the increase in temperature reached 25 degrees C (corresponding to a coagulation temperature of about 60 degrees C) was never greater than 3 mm, irrespective of the power and exposure time used. Moreover, the bidimensional thermal maps showed that the temperature did not decrease in a purely exponential fashion along the beam axis, but reached a maximum at about 1 mm beneath the surface. This fact, which confirms the decrepitation theorem, could explain the explosion inside the tissues observed in surgical application of the Nd:YAG laser.     

The possibility of dowel removal by pulsed Nd:YAG laser irradiation

BACKGROUND AND OBJECTIVES: Nd:YAG laser is one of the popularly used laser, in dentistry for treatment and technologic processing. Removal of dowel from root canal is very troublesome at endodontic retreatment. This study aimed to examine the possibility and efficiency of dowel removal from the root canal using the Nd:YAG laser in vitro. STUDY DESIGN/MATERIALS AND METHODS: Irradiation time and energies required for complete removal of the dowel set in the root canal using the laser were measured. The dowel ablation was observed by contact microradiographs (CMRs). The surface of the root canal after lasing was observed by a scanning electron microscope (SEM). RESULTS: A significant difference existed in irradiation times and energies to remove dowels among various combinations of metal and cement (P < 0.05). The CMRs showed that both dowel and dentin were ablated, and the SEM observation demonstrated that root canal surface was melted. CONCLUSIONS: The Nd:YAG laser irradiation could remove set dowels from the root canal.     

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND AND OBJECTIVE: The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining. RESULTS: The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality. CONCLUSION: Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.     

Ultrastructural changes of human dentin after irradiation by Nd:YAG laser

BACKGROUND AND OBJECTIVE: The use of Nd:YAG laser has been proposed for endodontic treatment. However, its ability to reduce dentin permeability, which is important for the success of root canal treatment, remains controversial. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human dentin. The parameters were: pulse energy (100 mJ), rate (10 pps), and total irradiation time (4 seconds). The crystalline phases, electron diffraction patterns, morphology, and microstructure of specimens after laser irradiation were observed by dark-field emission transmission electron microscope (TEM). RESULTS: Three ultrastructural zones could be delineated in the dentin: (1) an outer zone with an ordered columnar structure composed of hydroxyapatite and beta-tricalcium phosphate, (2) an intermediate zone composed of an amorphous substance (about 40-70 nm in diameter), and (3) an inner zone of well-crystallized hydroxyapatite grains. These three zones were free of pores or voids. CONCLUSIONS: Our study demonstrated that laser-irradiation might be used to reduce dentin permeability.     

Clinical experience with the Nd:YAG laser

This study presents the results and complications of 389 patientswho were treated with the Nd:YAG laser between September 1982 and November 1983 with at least a six-month follow-up. The majority of patients had a secondary discission of the posterior capsule. Other procedures included vitreolysis, iridotomy, pupilloplasty, synechialysis, intraocular suture cutting, cutting of intraocular lens haptics, and removal of anterior pseudophakic pigmented precipitates. We have purposely avoided performing preoperative laser anterior capsulotomies and have been unsuccessful in reopening freshly sealed trabeculectomy sites. The visual acuity improved in 83.1% of patients. No statistically significant difference in visual outcome was detected in relation to the time interval between surgery and Nd:YAG laser treatment. The most common adverse finding was an increase in intraocular pressure, which occurred to some degree in 63% of patients. Rare complications included cystoid macular edema and retinal detachment. No statistical correlation between these complications and preexisting conditions or intraoperative variables could be found.     

Treatment of atrophic scars with Er:YAG laser: our experience

Laser resurfacing is a new method to treat atrophic scars. The pulsed erbium YAG laser has been shown to be effective in the treatment of this variations of the skin texture secondary to a lot of conditions. Er:YAG laser allows precise epidermal ablation with minimal thermal injury to surrounding tissues. The goal of this study was to evaluate the effectiveness of the Er:YAG laser in the treatment of atrophic scars with multiple applications. In agreement with previously reported studies our results show that multiple treatments with erbium YAG laser are safe and effective to improve atrophic scars.     

Long-term effect of pulsed Nd:YAG laser irradiation on cultured human periodontal fibroblasts

BACKGROUND AND OBJECTIVES: The purpose of this study was to investigate the long-term effect of Nd:YAG laser irradiation on cultured human periodontal fibroblasts (hPF). STUDY DESIGN/MATERIALS AND METHODS: The cultured hPF were irradiated by pulsed Nd:YAG laser. The power delivery was 50 mJ x 10 pps (pulse per second) with irradiation duration 60, 120, 180, or 240 seconds. The viability and collagen content of laser-irradiated hPF were assessed on day 5 after laser treatment. Light microscope and transmission electron microscope (TEM) were used to observe cytomorphological change. The irradiated hPF cultured in mineralizing medium for 28 days were examined by alizarin red S and Von Kossa stain. RESULTS: The cellular viability and collagen content of hPF decreased after Nd:YAG laser irradiation. Cell damage was noted with retraction of cellular processes, loss of normal architecture, and lysis of some cells. However, survived hPF proliferated and migrated to the cell-debris-associated deposits. The electron-dense cytoplasm and amorphous organelles in laser-damaged cells was revealed by TEM. In vitro mineralization was demonstrated in the long-term laser-irradiated hPF cultured in mineralizing medium. CONCLUSION: Nd:YAG laser irradiation induced partial loss of cellular viability and collagen content. The co-existence of viable cells and progressive degeneration of laser-damaged cells was associated with the in vitro mineralization of hPF.     

Interception of lymphatic drainage by Nd:YAG laser irradiation in rat urinary bladder

Lymphatic drainage can be demonstrated by colloidal indian ink injection. A small intramural indian ink spot in the bladder dome is separated from the rest of the rat urinary bladder by encircling transmural Neodymium-YAG (Nd:YAG) laser irradiation. In untreated animals there is an ink flow via the lymphatic vessels to the regional lymph nodes within several hours. In treated animals, after laser irradiation, the indian ink remains in the bladder dome and a penetration of the irradiated area cannot be found by macroscopic and histologic examination. Indian ink will be found in the regional lymph nodes after the ninth day of absorption of the coagulation necrosis and recanalisation of the intercepted lymphatics. Evidence for the interception of the lymphatic drainage is demonstrated by the distinctly delayed ink flow and the injected ink's remaining in the irradiated area. From this, we conclude that Nd:YAG laser irradiation is especially suitable for tumor coagulation, since simultaneous interception of lymphatic drainage will inhibit the spreading of tumor cells.     

Effects of Er:YAG and Nd:YAG laser irradiation on radicular dentine permeability using different irrigating solutions

BACKGROUND AND OBJECTIVES: To evaluate the effect of Er:YAG and Nd:YAG laser on radicular dentine permeability when using distilled and deionized water and 1% NaClO as irrigating solutions. STUDY DESIGN/MATERIALS AND METHODS: Thirty human maxillary canines were divided randomly into six groups. The root canals were instrumented with K files and the step-back technique. Group I, irrigation with distilled and deionized water; Group II, irrigation with 1% NaClO; Group III, irrigation with distilled and deionized water and Er:YAG laser application (140 mJ input, 61 mJ output 15 Hz, 300 pulses, and 42 J); Group IV, irrigation with 1% NaClO and Er:YAG laser application (same parameters as Group III); Group V, irrigation with distilled and deionized water and Nd:YAG laser application (150 mJ, 15 Hz, 2,25 W); Group VI, irrigation with 1% NaClO and Nd:YAG laser application (same parameters as Group V). During laser application the teeth were always filled with the irrigating solution. The tip was withdrawn gently in helicoidal movement from the apex to the cervical portion. The teeth were processed for histochemical evaluation. RESULTS: The Tukey test showed that the cervical and middle thirds were statistically similar (P > 0.05) and significantly greater than the apical third (P < 0.05). The Scheffé test showed significantly greater dentine permeability in root canals in which water and Er:YAG laser were used and were significantly different from the other treatments (P < 0.05). CONCLUSIONS: The use of distilled and deionized water and Er:YAG laser showed the greater increase of dentine permeability. The use of 1% NaClO with Nd:YAG laser, distilled, and deionized water with Nd:YAG laser and the use of water increased dentine permeability less than the other groups. The use of 1% NaClO with and without Er:YAG laser application were positioned intermediately among the treatments.     

Intraocular microsurgery with a picosecond Nd:YAG laser

We investigated the use of picosecond Nd:YAG laser pulses for intraocular microsurgery. With a pulse duration of 100 picoseconds, only 70 μJ of pulse energy is required to consistently produce optical breakdown in the deep vitreous. This pulse energy is nearly two orders of magnitude less than the typical pulse energies used in conventional (nanosecond) photodisruptors. The reduced pulse energy results in a smaller zone of tissue damage, an important consideration when operating close to the retina or other sensitive ocular structures. Efficient cutting action is achieved by applying multiple pulses at a moderately high repetition rate of 50–200 Hz. An in vitro model was developed to assess axial confinement of picosecond photodisruption. In vivo vitreous membrane surgery was performed in experimental rabbit eyes to demonstrate a potential clinical application of picosecond laser—induced optical breakdown. © 1994 Wiley-Liss, inc.