Er:YAG laser modification of root canal dentine: influence of pulse duration,repetitive irradiation and water spray

. The aim of this study was to determine the effects of varying parameters of Er:YAG laser irradiation with and without water spray cooling on root canal dentine in vitro. After horizontally removing tooth crowns from extracted human teeth, roots were axially sectioned into thin slices, exposing the root canal surface. An Er:YAG laser delivered 10–30 J/cm² into a 0.4-mm diameter laser spot on the root canal surface. Single pulses of different lengths (80–280 μs) were applied with and without water spray cooling/irrigation, and sequences of three pulses at a repetition rate of 30 Hz were applied at selected pulse parameters. The irradiated samples were investigated using both confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). At most irradiation conditions, the root canal dentine surface was ablated. Three-dimensional images from CLSM revealed that the cavity walls were not smooth. Depths of the cavities revealed significant differences between the cavities. No debris was observed at the surface of cavities at any irradiation condition. Strong melting and recrystallisation, or unusually flat surfaces with open dentinal tubules were obtained with sequences of three pulses without water cooling. CLSM is an effective tool for investigation of laser effects on root canal dentine. By varying the irradiation conditions, the Er:YAG laser can induce different modifications of root canal surface, which may be very interesting for root canal preparation. Paper received 23 November 2001; accepted after revision 3 January 2002.     

Repetitive Er:YAG laser irradiation of human skin: a histological evaluation

BACKGROUND AND OBJECTIVE: Deep coagulation of skin collagen by Er:YAG laser repetitive pulses has been predicted by previous theoretical models and later demonstrated on animal skin. The goal of this study was to determine the effect of repetitive Er:YAG laser pulses on human skin and its response to this treatment. STUDY DESIGN/MATERIALS AND METHODS: Lid skin of six female volunteers with blepharochalasis has been treated with laser at day 0, 7, and 21 before elective surgery-blepharoplasty. The treated skin was excised as part of the procedure and prepared for further histological examination. We used a 2,940 nm Er:YAG laser (Fidelis M320A by Fotona) with 'smooth' mode parameters: fluence from 0.50 to 2.00 J/cm2; six pulses per packet; 550 microsecond/pulse, 250 millisecond/packet; single pass, no overlapping; spot size 5 mm; repetition rate 20 Hz. RESULTS: We observed deep collagen denaturation at laser fluences of 1.25 J/cm2 and over; epidermal damage was proportional to fluence with total coagulation of the epidermal layer at fluences of 1.75 J/cm2 and over. At day 7 after laser treatment we observed a complete regeneration of the epidermal layer and a regeneration zone within the dermis with prominent infiltration of CD68+ monocytes/macrophages. At day 21 after laser treatment we observed collagen remodeling and (myo-)fibroblast proliferation at tissue depths of up to 240 microm. CONCLUSIONS: Repetitive Er:YAG laser irradiation is effective in deep denaturation and remodeling of human skin collagen in vivo, with less epidermal damage compared to standard Er:YAG laser skin resurfacing.     

Treatment of rhinophyma with Er:YAG laser

BACKGROUND AND OBJECTIVE: Rhinophyma is a benign, disfiguring disorder of the nose which presents the end stage of acne rosacea, and can also occasionally result in nasal airway obstruction. We describe the first series of patients treated with Erbium laser. STUDY DESIGN/MATERIALS AND METHODS: Severe-to-moderate rhinophyma in six patients were treated at our institution between 1995 and 1996, using the Erbium:YAG (Erb:YAG) laser. RESULTS: All patients achieved marked cosmetic improvement, with no complications. Post-operative healing time was seven to fourteen days-significantly shorter than similar other modalities. CONCLUSIONS: The Erbium laser provides very accurate tissue ablation and allows the sculpturing of the hypertrophied areas, offering good cosmetic results, with a very short healing period as shown in our study.     

Morphological analysis of cementum and root dentin after Er:YAG laser irradiation

BACKGROUND AND OBJECTIVES: To investigate the morphology of cementum and root dentin after Er:YAG laser irradiation with and without water coolant, compared to that after CO(2) laser irradiation and an untreated surface. STUDY DESIGN/MATERIALS AND METHODS: Ten extracted healthy human teeth were used. Er:YAG and CO(2) lasers were applied with energy outputs of 0.4 W, with and without coolant and 0.5 W, without coolant, respectively. Scanning electron microscopy (SEM) analysis was performed at high and ultra-high magnifications. RESULTS: The surface of cementum was micro-irregular with numerous projections while that of dentin appeared scaly after Er:YAG laser irradiation. Unlike after CO(2) laser treatment, no major melting or cracking was observed with Er:YAG laser treatment. The use of water spray produced fine micro-irregularities without attached debris. Ultra-high magnification revealed similar microparticles-composed aspects for both cementum and dentin. However, the more porous structure of the surface was observed after Er:YAG laser irradiation without water spray. CONCLUSIONS: Cementum and root dentin presented distinct micro-roughness after Er:YAG laser irradiation, possibly due to structural differences in the original tissue. However, under ultra-high magnifications, both cementum and dentin presented similar characteristics of the irradiated surface. In addition, the use of water spray during laser irradiation minimized thermal effects and resulted in a cleaner and less porous surface.     

Modulating the Er:YAG laser

BACKGROUND AND OBJECTIVES: In the past 2 years, there has been some controversy about the optimal laser system, or combination of systems, for cutaneous resurfacing. Initially, it seemed that the Er:YAG laser would have significant advantages over the CO(2) laser. In practice, some of those who jumped early onto the Er:YAG bandwagon have been unimpressed with the degree of skin tightening that can be achieved with this system. Also, the excessive bleeding induced by the Er:YAG lasers prevented deeper vaporization. During the past 18 months, three new "modulated" Er:YAG lasers have been produced that are said to be able to achieve CO(2) laser-like effects, while maintaining the Er:YAG laser advantages. The purpose of this article is to examine these new systems and to discuss their potential benefits, if any, over the "conventional" Er:YAG lasers, and the CO(2) lasers. STUDY DESIGN/MATERIALS AND METHODS: The author has collected data from his own experience and that of his colleagues in the department of dermatology at University of California at San Francisco. The author has used all three types of modulated Er:YAG laser on patients presenting for cosmetic laser resurfacing and the treatment of many benign conditions over an 18-month period. RESULTS: All three modulated forms of Er:YAG lasers have been demonstrated to provide better coagulation than the conventional Er:YAG lasers. The Derma-K and the Contour Er:YAG lasers were able to induce tissue contraction/desiccation similar to the CO(2) laser. The author and his colleagues have induced only two cases of permanent hypopigmentation in over 50 cases during the past 18 months while using the Er:YAG laser, significantly less than might be expected with the CO(2) lasers. CONCLUSIONS: If a laser surgeon is happy with the results obtained with a high-energy, short-pulse CO(2) laser, then there seems little reason to consider changing to an Er:YAG laser. The modulated Er:YAG lasers have definite advantages over the conventional Er:YAG lasers. They exhibit better control of hemostasis and can ablate tissue to a greater depth than the conventional Er:YAG lasers. The Er:YAG lasers might induce less permanent hypopigmentation than the CO(2) lasers.     

Calcium solubility of dental enamel following sub-ablative Er:YAG and Er:YSGG laser irradiation in vitro

BACKGROUND AND OBJECTIVE: The objective of the present study was to investigate the effect of sub-ablative Er:YAG (lambda = 2.94 microm) and Er:YSGG (lambda = 2.79 microm) laser radiation on the acid solubility of dental enamel. The influence of fluoride application prior to laser irradiation was additionally evaluated. STUDY DESIGN/MATERIALS AND METHODS: To this end, 294 enamel specimens were prepared from bovine teeth and divided into 14 groups of 21 specimens each. The enamel samples were irradiated in their groups with the Er:YAG and the Er:YSGG laser, using energy densities of 4, 6, and 8 J/cm(2) in each case. Irradiation was additionally repeated in the same way on specimens, which had previously been immersed in 1% sodium fluoride solution for 15 minutes. One group was left untreated and served as a control group. A further group was not irradiated, but only immersed in the 1% fluoride solution for 15 minutes. The enamel specimens were demineralised for 24 hours in an acetate buffer solution. The calcium content in the demineralisation solution was subsequently determined with the aid of atomic absorption spectrometry. RESULTS: The results indicate a decline in calcium solubility after laser irradiation. Compared to the control group, a 20% lower calcium content was detected in the demineralisation solution after irradiation with the Er:YSGG laser at 8 J/cm(2). The difference between the laser-irradiated groups and the untreated control group was, however, not statistically significant. A significantly lower calcium content was found in the demineralisation solution after fluoridation of the specimens. Additional laser radiation had no further effect on this result. CONCLUSIONS: In summary, it can be stated that, although the erbium laser wavelengths apparently have the potential to increase acid resistance, their application solely for caries prevention would not appear to be sensible under the prevailing conditions.     

Bactericidal effects of two parameters of Er:YAG laser intracanal irradiation: ex-vivo study

The success of endodontic treatment depends on the complete elimination of microorganisms from the root canal system, thus the search for new procedures to eliminate them is justified. The aim of this study was to assess bacterial reduction after intracanal irradiation with the Er:YAG laser. The canals of 70 extracted human maxillary canines were prepared up to file #40 using 1% NaOCl, irrigated with 17% EDTA, and then washed with physiological solution activated by ultrasound. The roots were sterilized by autoclaving, inoculated with 10?μl of a suspension containing 1.5?×?10(8) CFU/ml of Enterococcus faecalis ATCC 29212 and incubated at 37°C for 72?h. The canals were irradiated with the Er:YAG laser using two energy settings: 60?mJ and 15?Hz, and 100?mJ and 10?Hz. The remaining bacteria were counted immediately and 48?h after laser irradiation. The results showed a high bacterial reduction at both time points. With 60?mJ and 15?Hz there was an immediate reduction of 99.73% and the reduction was 77.02% after 48?h, and with 100?mJ and 10?Hz there was an immediate reduction of 99.95% and the reduction was 84.52% after 48?h. Although the best results were observed with 100?mJ of energy, the difference between the two settings was not statistically significant. The count performed 48?h after irradiation showed that E. faecalis were able to survive, and can grow even from small numbers.     

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.     

Removal of organic debris with Er:YAG laser irradiation and microleakage of fissures sealants in vitro

The current study was conducted to improve fissure sealing by pre-treatment with Er:YAG laser irradiation in order to remove organic debris. The surface morphology, surface roughness of fissure cavities, and the degree of microleakage after laser treatment were compared with those after bristle brush treatment in vitro. Sixty extracted human teeth were used in this study. The teeth were randomly divided into two groups of 30 each. Artificial fissures were prepared in all teeth into which artificial organic debris was placed. The debris in 30 teeth of one group was removed by means of Er:YAG laser system and the remaining 30 teeth were cleaned using a bristle brush with prophylaxis paste. Surface morphology and surface roughness of were analyzed in ten samples from each group by color laser three-dimensional (3D) microscopy and by scanning electron microscopic examination. The remaining samples were then filled with sealant and subjected to a microleakage test under thermocycling. Statistical analysis was performed using the Mann-Whitney U test; a value of p?相似文献   

Histological examination of experimentally infected root canals after preparation by Er:YAG laser irradiation

The influence of Er:YAG laser irradiation on periodontal tissues along the root surface and apical region during root canal preparation was histologically evaluated using experimentally infected root canals of rats. Eighty experimentally mesial infected root canals of mandibular first molars in rats were divided into four groups. In three groups, root canals were irradiated using an Er:YAG laser at 2 Hz with 34, 68, or 102 mJ/pulse for 30 s. Non-irradiated canals served as controls. The influence of laser irradiation on periodontal tissues along the root surface and apical area was evaluated histologically under light microscopy at 0 (immediately after), 1, 2, 4, and 8 weeks after irradiation. At all periods, no inflammation or resorption on the root surfaces caused by laser irradiation was observed in any cases in the control or 34 mJ/pulse-irradiated groups. However, mild to severe inflammation with resorption of root surfaces was observed in some cases in the 68- and 102-mJ/pulse-irradiated groups. No significant difference was apparent between control and laser-irradiated groups at the apical area for all experimental periods (p > 0.05). These results suggest that thermal influences on periodontal tissues of experimentally infected root canals during root canal preparation by Er:YAG laser irradiation are minimal if appropriate parameters are selected. Er:YAG laser irradiation is thus a potential therapy for human infected root canals.