Periodontal and peri-implant wound healing following laser therapy.

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Histological and SEM analysis of root cementum following irradiation with Er:YAG and CO2 lasers.

Recently, the Er:YAG and CO(2) lasers have been applied in periodontal therapy. However, the characteristics of laser-irradiated root cementum have not been fully analyzed. The aim of this study was to precisely analyze the alterations of root cementum treated with the Er:YAG and the CO(2) lasers, using non-decalcified thin histological sections. Eleven cementum plates were prepared from extracted human teeth. Pulsed Er:YAG laser contact irradiation was performed in a line at 40 mJ/pulse (14.2 J/cm(2)/pulse) and 25 Hz (1.0 W) under water spray. Continuous CO(2) laser irradiation was performed in non-contact mode at 1.0 W, and ultrasonic instrumentation was performed as a control. The treated samples were subjected to stereomicroscopy, scanning electron microscopy (SEM), light microscopy and SEM energy dispersive X-ray spectroscopy (SEM-EDS). The Er:YAG laser-treated cementum showed minimal alteration with a whitish, slightly ablated surface, whereas CO(2) laser treatment resulted in distinct carbonization. SEM analysis revealed characteristic micro-irregularities of the Er:YAG-lased surface and the melted, resolidified appearance surrounded by major and microcracks of the CO(2)-lased surface. Histological analysis revealed minimal thermal alteration and structural degradation of the Er:YAG laser-irradiated cementum with an affected layer of approximately 20-µm thickness, which partially consisted of two distinct affected layers. The CO(2)-lased cementum revealed multiple affected layers showing different structures/staining with approximately 140 µm thickness. Er:YAG laser irradiation used with water cooling resulted in minimal cementum ablation and thermal changes with a characteristic microstructure of the superficial layer. In contrast, CO(2) laser irradiation produced severely affected distinct multiple layers accompanied by melting and carbonization.

In vitro studies of the ablation mechanism of periodontopathic bacteria and decontamination effect on periodontally diseased root surfaces by erbium:yttrium-aluminum-garnet laser.

The erbium:yttrium-aluminum-garnet (Er:YAG) laser is now increasingly used in periodontal therapy. The purpose of this study was to investigate the effect of Er:YAG laser irradiation on the morphology of periodontopathic bacteria and to compare the bacterial elimination effect of the laser and the ultrasonic scaler on diseased root surfaces in vitro. Colonies of Porphyromonas gingivalis were exposed to a single-pulse Er:YAG laser at 40 mJ and were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also, 20 pairs of periodontally diseased root surfaces with subgingival calculi of freshly extracted teeth were treated by Er:YAG laser scaling at 40 mJ/pulse (14.2 J/cm(2) per pulse) and 10 Hz with water spray or ultrasonic scaling, or were not treated. The efficiency of each treatment was determined as the area treated per second, and the treated surfaces were examined by SEM. The material scraped from the treated root surfaces was cultured in aerobic and anaerobic conditions, and the numbers of colony forming units (CFUs) were compared. SEM and TEM showed that the Er:YAG laser had easily ablated the bacterial colony, leaving an ablation spot with a crater and the surrounding affected area showing melted branch-like structures. The laser irradiation was as equally effective and efficient as the ultrasonic scaler in performing root surface debridement. The CFUs after laser treatment were significantly fewer than those after ultrasonic scaling in aerobic and anaerobic culture conditions. Er:YAG laser ablates periodontopathic bacteria with thermal vaporization, and its bacterial elimination effect on the diseased root surfaces appears to be superior to that of the ultrasonic scaler.

Hindlimb withdrawal reflexes evoked by Er:YAG laser and scalpel incisions in rats.

OBJECTIVE: In this study, we assessed the magnitudes of nociceptive withdrawal reflexes evoked by skin and muscle incisions made with steel scalpel and erbium:yttrium-aluminum-garnet (Er:YAG) laser. BACKGROUND DATA: A few studies have suggested that laser incisions would be less painful than conventional scalpel incisions. METHODS: Twenty adult male Sprague-Dawley rats were used. Under light barbiturate anesthesia, graded incisions were made into the plantar surface of the animals' hindpaws. Electromyographic (EMG) recordings from a hamstring muscle were used to estimate the nociceptive response. RESULTS: The mean amplitude of EMG activity was significantly higher during incisions made with steel scalpel than with any of the laser irradiation parameters. All laser irradiation parameters produced similar nociceptive responses. CONCLUSION: Er:YAG laser incisions may be less painful, albeit considerably slower, than scalpel incisions. Laser incisional pain would be more closely related to the mechanical rather than the thermal effect of laser ablation.

Antinociceptive effect of Er:YAG laser irradiation in the orofacial formalin test.

Low-power, soft, or low-level laser irradiation has been successfully used to provide analgesia in injured or diseased tissues. In this study, we tested the possible antinociceptive effect of laser irradiation when applied to a normal tissue before the onset of a painful stimulus. Male Wistar rats (350-380 g) were used. A 1.5% formalin solution (50 microL s.c., diluted in saline) was injected into the right upper lip of the test animals (n = 9) immediately after 10 min of low-power Er:YAG laser irradiation (wavelength: 2.94 microm; energy: 0.1 J/cm(2)/pulse at 10 Hz). Control animals (n = 9) were restrained for 10 min without laser application. The nociceptive response, i.e., the amount of time the rats spent rubbing the formalin injected area, was measured by an investigator blind to whether the animals had been laser irradiated or not. On laser irradiated rats, significantly less nociceptive behavior was observed only during the late phase (12-39 min) of the test. This result is similar to that reported for nonsteroid antiinflammatory drugs (NSAIDs) and other peripherally acting antiinflammatory agents. We conclude that low-power laser irradiation have a tonic antinociceptive effect on inflammatory pain even when applied before tissue injury.

Scanning electron microscopy and Fourier transformed infrared spectroscopy analysis of bone removal using Er:YAG and CO2 lasers.

BACKGROUND: A thorough analysis of laser-ablated bone tissue is required before applying the technique to osseous surgery. In this study, we examine the morphological features and chemical composition of the bone surface after Er:YAG and CO2 lasers ablation. METHODS: Six Wistar rats were used. An Er:YAG laser was used for ablation at an output energy of 100 mJ/pulse and a pulse rate of 10 Hz (1 W). Continuous CO2 laser irradiation was performed at an output energy of 1 W. Sites drilled using a conventional micromotor were used as controls. Analysis using scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) spectroscopy was performed. RESULTS: Er:YAG laser ablation produced a groove with similar dimensions to that produced by bur drilling, whereas the CO2 laser produced only a charred line with minimal tissue removal. SEM observations revealed that the groove produced by the Er:YAG laser had well-defined edges and a smear layer-free surface with a characteristically rough appearance and with entrapped fibrin-like tissue. The melting and carbonization produced by the CO2 laser were not observed on sites irradiated by the Er:YAG laser. FTIR spectroscopy revealed that the chemical composition of the bone surface after Er:YAG laser ablation was much the same as that following bur drilling. The production of toxic substances that occurred after CO2 laser irradiation was not observed following Er:YAG laser irradiation or bur drilling. CONCLUSION: These results suggest that the use of Er:YAG laser ablation may become an alternative method for oral and periodontal osseous surgery.

Histological and TEM examination of early stages of bone healing after Er:YAG laser irradiation.

OBJECTIVE: The aim of this study was to analyze the early healing process of bone tissue irradiated by Er:YAG laser and compare it with that treated by mechanical drilling and CO(2) laser. BACKGROUND DATA: Er:YAG laser has a great potential for cutting hard tissues as it is capable of ablation with less thermal damage. METHODS: Twenty-four male Wistar rats were used for this study. The calvarial bone of rats was exposed and straight grooves were prepared by Er:YAG laser, mechanical bur and continuous wave CO(2) laser. Four rats each were sacrificed at six time points: 10 min, 6 and 24 h and 3, 7, and 14 days post-surgery. Sections were prepared for light and transmission electron microscopic (TEM) observations. RESULTS: Compared to mechanical bur and CO(2) groups, the inflammatory cell infiltration adjacent to the irradiated bone surface, fibroblastic reaction, and revascularization were more pronounced in the Er:YAG laser-irradiated tissues. A cell-rich granulation tissue with fibroblasts and osteoblasts was predominant in 7-day specimens of Er:YAG laser group. Histopathological analysis of 14-day specimens in the Er:YAG group also revealed significantly greater new bone formation, compared with the mechanical bur and CO(2) laser groups. CONCLUSIONS: Initial bone healing following Er:YAG laser irradiation occurred faster than that after mechanical bur and CO(2) laser. Er:YAG laser treatment may be advantageous for wound healing of bone tissue, presumably by providing a favorable surface for cell attachment.

Comparison of jaw-opening reflexes evoked by Er:YAG laser versus scalpel incisions in rats.

OBJECTIVE: Anecdotal remarks suggest that incisions in oral soft tissue would be less painful if performed with laser rather than with scalpel, but such an argument remains to be scientifically validated. STUDY DESIGN: Twelve rats received graded incisions to lip, gingiva, mucosa, and tongue with either a pulsed Er:YAG laser (65 mJ/pulse at 10 Hz) or a stainless steel scalpel. The amplitude of the jaw-opening reflex, as measured by the digastric muscle electromyogram, was used to quantify the nociceptive response evoked by the surgical incisions. RESULTS: Except for lip, mean reflex amplitudes evoked by laser were significantly smaller (P < .05) than those evoked by scalpel in all other incision sites. CONCLUSION: Er:YAG laser surgery may be less painful and therefore require less use of anesthesia and sedation than conventional scalpel surgery in oral soft tissue procedures.

Ultrastructural analysis of bone tissue irradiated by Er:YAG Laser.

BACKGROUND AND OBJECTIVES: The use of erbium:yttrium aluminum garnet (Er:YAG) laser has been suggested for bone ablation, however, little is known about the nature of the tissue after irradiation. This study was aimed to analyze the ultrastructure of bone tissue treated with Er:YAG laser, as compared to those treated with CO(2) laser and bur drilling. STUDY DESIGN/MATERIALS AND METHODS: Parietal bones of Wistar rats were treated and analyzed by light microscopy, transmission electron microscopy (TEM), electron diffraction analysis and energy dispersive X-ray spectroscopy (SEM-EDX). RESULTS: This study demonstrated that Er:YAG laser irradiation resulted in a very thin changed layer of approximately 30 microm thickness, which consisted of two distinct sub-layers: a superficial, greatly altered layer and a deep, less affected layer. CONCLUSIONS: The major changes found on bone surface after Er:YAG laser irradiation consisted of micro-cracking, disorganization, and slight recrystallization of the original apatites and reduction of surrounding organic matrix.

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.

Effects of low power Er:YAG laser on the tooth pulp-evoked jaw-opening reflex.

BACKGROUND AND OBJECTIVES: Analgesic properties of laser irradiation have been of great interest in the field of dentistry. This study aimed at evaluating the analgesic effects of the Er:YAG laser system in rats during and after laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: A pulsed Er:YAG laser was applied to the oral mucosa of the mandibular incisor at an energy density of approximately 0.1 J/cm(2)/pulse for 10 minutes at 10 Hz, and the integrated digastric muscle electromyogram in tooth pulp-evoked jaw-opening reflex was used as an index of the nociceptive response. RESULTS: Significant reflex suppression was observed 10 minutes after laser irradiation. The reflex amplitude started to return to its original level about 45 minutes after cessation of laser irradiation. CONCLUSIONS: The Er:YAG laser used at low output levels presented inhibitory effects on the tooth pulp-evoked jaw-opening reflex, suggesting that this laser system may be of use for pain control during various dental treatments.