Journal of Lasers in Medical Sciences

Lasers in dentistry began to gain popularity in the 1990s. Lasers in dentistry are used as a treatment tool or as an adjunct tool. By using the laser in the field of dentistry, the main goal is to overcome the disadvantages, which are currently being experienced in conventional dental treatment procedures. Many specialties in dentistry including oral surgery, implants, oral medicine, periodontics, pediatrics, and operative use the current new laser technology. The ability of lasers to provide minimally invasive procedures with less discomfort to the patient has been useful in the patient delivery system in dental practice. This article describes in brief on the uses of lasers in oral mucosal lesions.

Distraction osteogenesis (DO) is a surgical procedure to increase bone height in different body parts. DO includes a surgical incision, wherein the bone is cut and a device is installed for further separation of the two ends by gradual unscrewing of the device screw. New bone gradually forms and fills the gap, and the bone height increases as such.
Photobiomodulation (PBM) or low-level laser therapy (LLLT) enhances the formation of soft and hard tissue such as bone and can, therefore, accelerate the process of DO and shorten the duration of different surgical phases of DO such as latency, activation, and consolidation.
Different laser types with variable exposure settings and protocols have been used for this purpose. The gallium-aluminum-arsenide (GaAlAs) diode laser is the most commonly used laser type for LLLT. This study reviews 18 published articles on the effects of LLLT on DO and summarizes their findings to further elucidate this topic.

Introduction: Laser therapy is known as an efficient approach in dermatology surgery. CO2 laser therapy is a gold standard treatment in skin surgery. This study aimed to evaluate the interferons change after CO2 laser surgery

Methods: Significant differentially-expressed genes (DEGs) of arm skin after 7 days of treatment by the CO2 laser relative to the controls are downloaded from Gene Expression Omnibus (GEO) and are included in the protein-protein interaction network via a STRING database (an application of Cytoscape software). The central DEGs were identified and enriched via gene ontology by using Clue GO software.  

Results: A network including 78 DEGs and 100 neighbors was constructed and STAT1, MX1, ISG15, OAS1, IFIT1, IRF8, OASL, OAS2, and RSAD2 as hubs and STAT1, PTPRC, MX1, IRF8, ISG15, IL6, RORC, SAMSN1, and IFIT1 as bottlenecks were introduced. The cytokine-mediated signaling pathway, interferon gamma signaling, hepatitis C, interferon alpha/beta signaling, and the type I interferon signaling pathway were identified as five clusters of biological terms which are related to the central nodes.

Conclusion: It can be concluded that the cytokine-mediated signaling pathway is the major pathway that is dysregulated after laser application in the treated skin.

Introduction: Recently, infrared lasers (wavelengths larger than 1100 nm) have been applied to stimulate neural tissues. Infrared neural stimulation (INS) has some advantages over conventional electric stimulation, including contact-free delivery, spatial precision, and lack of stimulation artifacts. In this study and based on a photothermal mechanism, we applied the heat diffusion equation to study temperature variation of a biological phantom during INS. In addition, the impact of laser parameters on spatially localized heating induced by two different infrared wavelengths were studied.

Method: We studied the localization of INS inside a phantom similar to cortical neural tissue. First, we analytically solved the heat diffusion equation to study the distribution of temperature inside this phantom. Then, the accuracy of analytical results was verified by heating the phantom using amplitude-modulated infrared lasers (lambda= 1450 and 1500 nm, the energy between 2 and 5 mJ and pulse duration up to 20 ms). The laser light was directed to sample by a multimode optical fiber (NA=0.22, Core size= 200 microns). Finally, the impacts of laser properties on the spatial resolution of infrared heating were discerned.

Result: In order to verify analytical results, we measured the maximum temperatures of the phantom during illumination of lasers and compared them with analytical results. The analytical results were in agreement with the experimental results. The effects of laser beam properties such as pulse duration, energy and repetition rate frequency on the spatial resolution were investigated. The results indicated that the spatial resolution of INS can be smaller than one millimeter.

Conclusion: Here, the influences of laser properties on the localization of INS inside a biological phantom were studied. These results can be applied to improve the spatial selectivity of the peripheral nerve interface.

Introduction:One of the primary goals of pulpectomy is to decrease the sum total of microorganisms and disinfect the tooth root canal system. To achieve this, mechanical preparation, irrigation, disinfection and obturation of the root canal is necessary. The present study was set out to evaluate the difference in the antibacterial efficacy of primary teeth root canals either irrigated with Chlorhexidine,Saline,and Sodium hypochlorite or irradiated with a Soft tissue Diode Laser(980nm, Photon Plus, Zolar Tech &Mfg Co. Inc, Ontario, Canada).

Methods: 60 primary teeth of children requiring pulpectomy were divided into 4 groups of 15 each, Group 1 (2% Chlorhexidine), Group 2 (1 % Sodium hypochlorite), Group 3 (Laser irradiation) and Group 4 (Saline). Pulp tissue was extirpated from the canals and the samples were collected using sterile absorbent paper points. After cleaning and shaping, the root canals of the teeth in each group were irrigated usingsodium hypochlorite, chlorhexidine, and saline or were irradiated with the laser. The samples were obtained again and sent for microbiological examination.

Results – The Colony Forming Unit counts from pre-disinfection sample served as a baseline for comparisons throughout the study. The mean bacterial colony counts of all the isolated bacteria reduced after irrigation or irradiation. Intergroup comparisons showed no significant difference when Groups 1, 2, and 3 were compared to each other(p>0.05).However, a significant difference was seen when Groups 1, 2, 3 were compared to Group 4(p<0.05).

Conclusion: 2% Chlorhexidine, 1% Sodium hypochlorite and Laser irradiation succeeded in reducing the root canal infection. Hence, diode laser irradiation may be a possible supplement to existing protocols for disinfecting the root canal system.

Introduction: Some studies have shown that laser irradiation on unpolymerized adhesives can improve composite-dentin adhesion. The aim of the present study was to evaluate the effect of the Diode laser (810 nm) on the microleakage of multi-mode adhesive systems at enamel and dentin margins of composite restorations.

Methods: Classic Class V boxes were prepared on 48 sound premolar teeth and randomly divided into six groups (n=16). In the control groups, Scotch bond U(SBC), G-Premio (GBC), and Ambar U (AMC) were used by a self-etch mode. In the test groups (SBL, GBL, ABL), the 810 nm Diode laser was irradiated (1 Watt) for 10 seconds before the polymerization of the adhesive. The Boxes were restored by the resin composite. After finishing and polishing, the samples were thermocycled (5℃ to55℃) for 1000 cycles and then immersed in 0.1% Methylene blue dye (48 hours). Dye penetration through the gingival and occlusal margins was measured by Stereomicroscope. The data were analyzed at the 5% significance level using Kruskal-Wallis and Mann-Whitney U tests.

Results: Significant differences were found between the control and test groups (p<0.05). The occlusal margins of the SBL and GBL groups and the cervical margin of the SBL group exhibited the lowest microleakage (p<0.05). The AM control group showed maximum microleakage at cervical and occlusal margins.

Conclusions: The irradiation of the 810 nm Diode laser on the unpolymerized universal adhesive systems in a self-etch mode caused a significant reduction in enamel and dentin marginal microleakage of composite restorations.

Introduction: Today the use of electromagnetic waves has dramatically increased in modern industrial societies. This study aimed to investigate the effect of prenatal exposure to 2.4 GHz wireless frequency on forelimb development in an NMRI mouse in vivo.

Methods: A total of 21 female mice weighing 25-30 g were included in the present study. They were randomly assigned to three groups, namely control (n=7), sham (n=7), and experimental (n=7). After mating, the experimental group was exposed to 2.4 GHz radio frequency at a distance of 20-30 cm from the device, 4 h per day until the delivery. The sham group was placed at a distance of 20-30 cm from the device every day without exposure to electromagnetic waves, and the control group had a pregnancy period without any stress and electromagnetic wave exposure. After giving birth, the forelimbs were isolated from the infants and examined by stereological studies and RT-PCR for the evaluation of osteocalcin and RUNX2 gene expression.

Results: Although, at first glance, there was no macroscopic teratogen effect in forelimbs in all groups, via a stereological method, we showed that bone and cartilage volume decreased in the experimental group compared to the other groups. We also found that the experimental group had lower expression of the osteocalcin and RUNX2 gene than the control and sham groups did. However, there were no significant differences between the control and sham groups in terms of bone and cartilage volume and gene expression.

Conclusion: Although teratogen effect of prenatal exposure to 2.4 GHz radio frequency on forelimbs was not demonstrated macroscopically, further studies showed negative effects on the forelimb bone, cartilage volume, and gene expression.   

Introduction: Erosion is an important cause of tooth mineral loss. The combined use of lasers and fluoride has been introduced as a novel modality for the prevention of enamel demineralization. This study aimed to assess the effect of Er:YAG laser combined with fluoride application on primary and permanent enamel resistance to erosion.

Methods: Eighty enamel specimens of permanent (n=40) and primary (n=40) molars were prepared and randomly assigned to four groups:  C —control (no pretreatment), F—acidulated phosphate fluoride (APF) gel, ­­­­­FL—APF gel application followed by Er:YAG laser irradiation, and LF—Er:YAG laser irradiation followed by the application of APF gel . The specimens were then submitted to pH cycling using Coca-Cola (pH=2.4). Enamel micro-hardness was measured using the Vickers micro-hardness tester before pretreatment and after the erosive process. The collected data were analyzed using the Kolmogorov-Smirnov test, two-way ANOVA and repeated measures ANOVA.

Results: The micro-hardness of both permanent and primary enamel significantly decreased after the erosive process (P<0.05). In the permanent enamel specimens, the greatest reduction in micro-hardness was noted in groups C and F, while the least reduction was noted in group FL. However, these differences were not statistically significant (P>0.05). In the primary enamel specimens, the greatest reduction in micro-hardness was noted in groups C and LF, while the least reduction was noted in group F. These differences were not statistically significant (P>0.05).

Conclusion: Within the limitations of this study, Er:YAG laser irradiation combined with fluoride application could not prevent erosion in permanent and primary enamel during the erosive process.

Introduction: The aim of this present study was to investigate the effect of different surface treatments of a hybrid ceramic, Vita Enamic (VE), on the micro-tensile bond strength (µ-TBS) to a resin cement.

Materials and methods: 10 blocks (3×10×8 mm)were retrieved from the original blocks and divided into five groups according to the different surface treatment performed: Groups 1: 35% Acid phosphoric for 60 seconds (PA); group 2: Sandblasting with 50µm Al₂O₃ particles for 10 seconds (SB); groups 3: 9.5% hydrofluoric acid for 60 seconds(HF), group 4: Er:YAG laser (2 W,10 Hz) (ER1), group 4: Er:YAG laser (3 W, 10 Hz) (ER2). All treated surfaces were salinizedand the blocks with similar surface treatments were bonded together using a dual cured resin cement and light cured. After 24-hour storage in water, blocks were cut into beams(1mm²). Half of the specimens in each group(n=16) were tested immediately and the rest were subjected to thermocycling between 5°C and 55°C for 6000 cycles before µ-TBS test at a crosshead speed of 0.5 mm/min. The data were analyzed using two-way ANOVA and Tukey HSD tests considering 0.05 as significance level. The failure mode was evaluated using a stereomicroscope.

Result: µ-TBSwas clearly influenced by surface treatment methods(P˂0.001) and thermocycling significantly decreased the bond strength values in all groups (P=0.007). The highest value (66.07 MPa±11.3) was obtained for HF groups with no thermocycling and the lowest values were observed in laser groups with no significant difference among different irradiation parameters. Adhesive failure was mainly observed in PA and SB groups while mixed failure was predominantly shown in laser and HF groups.

Conclusion: This study demonstrates that surface treatment of VE with HF and salinization can improve the bond strength to a dual cured resin cement and Er:YAG laser irradiation with the evaluated parameters  did not promote adhesion of the resin cement to VE.

Introduction: Microleakage has been reported to cause dentin hypersensitivity because of the passage of bacteria and their products through the restoration-tooth interface and is one of the main reasons for replacement of restorations. CO2 laser can be used for treatment of dentin hypersensitivity. Thus, this study aimed to evaluate in vitro the microleakage in composite restorations following surface pretreatment with acid etching and CO2 laser.

Methods: Twelve human caries-free primary molars were selected. Class II cavities were prepared on occlusal mesial and occlusal distal surfaces. Specimens were randomly divided into four groups (n = 6): Group 1 (G1) – 37% phosphoric acid gel etching + Beautiful-Bulk Restorative – Giomer (Shofu Inc); Group 2 (G2) – 37% phosphoric acid gel etching + SDR Bulk-Fill Flow (Dentsply); Group 3 (G3) – CO2 laser irradiation + Beautiful-Bulk Restorative – Giomer (Shofu Inc); Group 4 (G4) – CO2 laser irradiation + SDR Bulk-Fill Flow (Dentsply). Surfaces were restored with bonding agent (Natural Bond DE, DFL). Specimens were cut longitudinally and immersed in 0.5% methylene blue solution for 4 hours. Microleakage scores were assessed under a magnifying glass at x3,5 and qualitatively analyzed by scanning electron microscope (SEM). Data were analyzed using nonparametric Wilcoxon test (P < 0.05).

Results: Scores prevailed between 0 and 2, however, no statistically significant difference was found among the groups (P = 0.05).

Conclusion: It could be concluded that all composite resins bulk fill did not show significant difference among them regarding microleakage using either CO2 laser or 37% phosphoric acid etching.

Introduction:

This study aimed to characterize immune and endothelial cells, myofibroblasts and pericytes, and positive cells for hedgehog proteins in late tissue repair of rats skin wounds treated with 670 nm photobiomodulation therapy (PBMT).

Methods:

A blind experimental study was conducted, in order to assess the effect of PBMT in later stages of healing, with emphasis on neoangiogenesis, immune cells and Hedgehog signaling. Forty Wistar rats were allocated randomly in two groups; control and treated with a diode GaAlAs laser (9 mW, 670 nm, 0.031 W/cm², spot size of 0.28 cm², fluence of 4 J/ cm2 applied every other day, until a total dose of 16 J/cm2 was achieved). Standardized skin wounds were performed and the animals were euthanized at 14, 21, 28 and 35 days. Tissue sections were subjected to hematoxylin-eosin and immunohistochemistry for CD31, NG2, smooth muscle alpha actin, CD8, CD68, Ptch, Gli-2 and Ihh. All histomorphometric data were statistically analyzed and significance level was at P < 0.05.

Results:

At late stages of wound healing, neoangiogenesis persisted as revealed for the number of CD31+ cells (P = 0.016) and NG2+ and smooth muscle alpha actin positive pericytes (P = 0.025), for both experimental groups. By day 21, laser-treated group had decreased CD68+ cells (P = 0.032) and increased CD8+ (P=0.038). At remodeling stage, there were positive cells for the hedgehog signaling pathway family which seemed to be activated.

Conclusion: 

These data suggest that photobiomodulation therapy was able to modulate extracellular matrix remodelling even at the later stages of wound healing.

Introduction: Transcranial near-infrared photobiomodulation (NIR-PBM) is a new noninvasive procedure which transcranially applies a near-infrared wavelength to the scalp with a laser or a light-emitting diode (LED) source. Improvement in the neurological or psychological symptoms has been reported following light irradiation. However, to our knowledge, there is no study to investigate the effects of transcranial NIR-PBM on motor performance directly. Therefore, the objective of this study was to investigate the short-term effects of transcranial NIR-PBM on motor performance in healthy human subjects.

Methods: In this experimental single-blind randomized clinical trial study, 56 right-handed healthy participants, whose ages ranged from 18 to 30, were randomly assigned to (1) Real transcranial NIR-PBMC3 group (n=14), (2) Sham transcranial NIR-PBMC3 group (n=14), (3) Real transcranial NIR-PBMC4 group (n=14), and (4) Sham transcranial NIR-PBMC4 group (n=14). We applied the 808 nm laser with irradiation energy density of 60 J/cm2 and power density of 200 mw/cm2 to the C3 or C4 points of the scalp. The number of finger taps as an indicator of motor performance was assessed by the finger-tapping test (FTT) before and after irradiation of transcranial NIR-PBM on the corresponding points of the scalp for 5 minutes.

Results: The results showed that the number of finger taps in both right and left hands following the use of transcranial NIR-PBM in the real transcranial NIR-PBMC3 group significantly increased (P < 0.05).

Conclusion: We concluded that using transcranial NIR-PBM with a laser source on C3 point of the motor cortex in right-handed healthy people can increase the number of finger taps in both hands as an indicator of motor performance improvement.

Introduction: A deep burn ulcer, especially in areas with sensory-motor dysfunction, is hard to cure.

Case Report: The patient was a 20-year-old paraplegic girl with a grade 3 necrotic burn ulcer for 3 weeks. We used a fractional Co2 laser along with chemical debridement with trichloroacetic acid (TCA 80%) and low-level laser therapy (LLLT) with a 808 nm infrared laser, 6 J/cm2 for the necrotic area, and a 650 nm red laser, 2 J/cm2 for the open wound area. Complete healing occurred after 25 sessions without surgery.

Conclusion: Laser debridement along with LLLT and TCA administration may be useful to treat necrotic ulcers without surgery.

Introduction: Orofacial paresthesia is due to trauma to the neural structure of a particular nerve. In dentistry alterations caused by nerve damage in most cases are presented with transient symptomatology. However, it has been agreed by several authors that persistent inferior alveolar sensory aberrations for more than 6 months leave some degree of disability or are considered permanent. The objective of the present study is to report the clinical case of a young patient submitted to low-level laser therapy for the treatment of paresthesia of the inferior alveolar nerve after removal of a complex odontoma in the posterior region of the mandible.

Methods: Twenty-four hours after the surgical procedure the patient started the low-level laser therapy with the following parameters: 100 mW of potency, 140 J/cm² of energy density, 4 J of energy per application point, 40 seconds of application per point and 0.028 cm² of spot area. For this particular case, the technique of alternation of laser wavelengths was used, in the first session of which visible red of 660 nm was applied, followed by near-infrared of 808 nm and so on.

Results: In the first session, the score on the visual analog scale (VAS) was “3”. In the tenth and last sessions, the patient reported a VAS “9”.

Conclusions: It seems that the early initiation of the low-level laser therapy favors a better outcome in cases like the one presented in this paper. The technique of alternation of laser wavelengths between sessions seems to have some role in the outcome possibly because of the constant stimulation of different chromophores along the treatment course. These two factors need further confirmation and validation through randomized clinical trials.

Focal myositis (FM) is a rare inflammatory myopathy characterized by a painful swelling of a skeletal muscle. The lower limb is the most common site for FM, but it has also been reported in the abdomen, forearm, neck, and tongue musculature. Some conservative treatments such as non-steroidal anti-inflammatory drugs, physiotherapy, and steroids can relieve muscle pain and its minor complications. This report describes a patient who had shoulder pain and was diagnosed with FM in the left trapezius muscle with an excellent response to high-intensity laser therapy.

Introduction: Free gingival grafting is among the most foreseeing procedures for increasing the zone of keratinized attached gingiva and enhancing soft tissue around the teeth and dental implants. Nowadays low-level laser therapy (LLLT) is a promising approach in providing patients with more pleasing results in terms of esthetics and comfort. This study aims to investigate the effects of LLLT on gingival recessions treated with free gingival graft (FGG).

Methods: This case series was conducted on 12 individuals requiring a bilateral gingival graft in the mandibular region. There was a 30-day interval between the two operations. The test side was selected randomly and irradiated by a low-level laser (LLL) just before surgery. The patients did not know which side was irradiated. LLLT was applied to the donors’ as well as recipients’ site immediately after the operation and 48 hours later. The patients were instructed to record their post-operative pain in a visual analogue scale (VAS) 3 and 24 hours and 7 days after the surgical procedure. The clinical photographs were taken immediately and 30 days after surgical treatment were graded by three experienced periodontists for color matching to adjacent tissues.

Results: Ten individuals could finish the study. The test group presented significantly better shade matching and wound healing at the palatal donor site on days 7, 14 and 21. There was a significant reduction in postoperative pain after 24 hours (P = 0.007). No statistically significant difference was found between both groups in terms of clinical periodontal indices.

Conclusion: LLLT could reduce post-operative pain 24 hours after surgical treatment. Furthermore, the application of LLLT could improve the donors’ site healing and the recipients’ site color matching.

Introduction: Basal cell carcinoma (BCC) is the most prevalent form of non-melanoma skin cancer commonly arising in elderly patients. Currently, many laser systems are applied for the treatment of BCC. However, up to the present, there have been several reports concerning ocular side effects due to the laser procedure in the borders of the periorbital area. This determines the feasibility of testing new laser surgical modes for the management of periorbital BCC. This stuay aimed to estimate both the efficacy, the early post-radiated side effects and long-term outcomes of the CVL treatment of periorbital BCC.

Methods: Two men and 6 women aged 50 to 77 years were diagnosed with periorbital BCC according to the data of both the clinical evaluation and histological examination of the tissue samples taken from the involved area. Six months after the laser treatment, the histological examination of skin samples from the borderline of the irradiated area was made again. All patients were followed for 24 months after the laser treatment of BCC. The laser treatment was administered during one session of copper vapor laser (CVL) (Yakhroma-Med model). The treatment included CVL radiation with a wavelength of 511 nm and 578 nm, in the ratio of 3:2. The power level was set up to 3 W, and the exposure time was equal from 200 to 600 ms. The pulse duration accounted for 15 ns. The diameter of the light spot on the skin surface amounted to 1 mm.

Results: Dual-wavelengths CVL treatment of periorbital BCC provided a complete elimination of malignant cells and dysplastic vessels during one procedure. The duration of skin healing amounted to 2-4 weeks. There were neither ocular injuries or pronounced skin side effects nor relapses within 24 months after the laser procedure.

Conclusion: CVL treatment of periorbital BCC provides relevant cosmetic results without ocular injuries and relapses.