Journal of Lasers in Medical Sciences

Dentin hypersensitivity (DH) is a relatively common painful condition among dental problems. Although many studies have been performed regarding the diagnosis and treatment of DH, dental practitioners are still confused about the definite diagnosis and treatment.The use of lasers as a treatment for dentin hypersensitivity was first introduced in 1985. Laser treatment in dentin hypersensitivity is an interesting and controversial issue and many investigations have been done on its mechanism of action, advantages, and unclear points. The present literature review tries to go over the definition, diagnosis, etiology, predisposing factors, various laser types in the treatment of DH alone or in combination with topical desensitizing agents. Since a certain treatment has not yet introduced for dentin hypersensitivity, a combination of laser therapy and topical desensitizing factors, can increase the success of the treatment compared with either treatments alone.

Removal of smear layer and disinfection of canals are important objectives of teeth root canal cleaning. In order to achieve this purpose, rinsing substances, intra canal drugs as well as ultrasound are used. Today, use of laser to remove smear layer and to disinfect root canals has increasingly attracted the attentions. Till now different lasers such as CO2, Nd:YAG, Er:YAG, Er,Cr:YSGG have been used for debris and smear removal from the canals. Numerous studies have shown that Er:YAG is the most appropriate laser for intra canal debris and smear removal. In addition different laser wavelengths have been used directly or as an adjunctive to disinfect canals. Laser light can penetrate areas of canals where irrigating and disinfecting solutions cannot reach, like secondary canals and deep dentinal tubules and also can eliminate microorganisms. Different studies have confirmed the penetration of Nd:YAG laser in deep dentin and reduction of microorganisms penetration. But studies on comparison of antibacterial effects of Nd:YAG laser with sodium hypochlorite showed effectiveness of both, with a better effect for sodium hypochlorite. Studies performed in relation with anti-microbial effects of Diode laser with various parameters show that this laser can be effective in reducing intra canal bacterial count and penetration in the depth of 500 microns in dentin. In studies performed on Diode laser in combination with canal irrigating solutions such as sodium hypochlorite and oxygenated water better results were obtained. Although studies on disinfection by the Erbium laser family show that use of this laser alone can be effective in disinfecting canals, studies evaluating the disinfecting effects of this laser and different concentrations of sodium hypochlorite show that the latter alone is more effective in disinfecting canals. And better results were obtained when Erbium laser was used in combination with sodium hypochlorite irrigating solution in canals. Results of the aforementioned articles indicate that this laser is effective in combination with a rinsing solution such as sodium hypochlorite.

Results from studies including several types of the different Er:YAG, Ho:YAG, Nd:YAG, Er,Cr:YSGG lasers in disinfecting canals showed that all wavelengths used in disinfection for different thicknesses of dentin were efficacious without damaging thermal effect. Considering that use of different lasers in canals can be accompanied with temperature increase which can sometimes lead to damages to teeth and surrounding tissues, thus the use of photochemical phenomenon for elimination of microorganisms have attracted attention of many researchers. Studies in this field imply the efficacy of this method in reducing canal bacterial count and recommend its use as an adjunctive after biomechanical preparation of canals. Results from performed studies show removal of intra canal debris and smear layer by different lasers and particularly the Erbium laser family. Furthermore various laser wavelengths, particularly of Diode and Nd:YAG lasers can be effective in reducing intra canal microbial count. Maximum effect is obtained when laser light is used in canals in combination with sodium hypochlorite irrigating substance in appropriate concentration. Therefore use of laser energy can improve success rate of root canal treatments.

INTRODUCTION: Lasers, light emitting diodes (LEDs) and super luminous diodes (SLDs) are widely used to treat selected musculoskeletal, integumentary and neurological conditions. The mechanisms underlying the reported treatment effects of light therapy are unclear and the physiologic effect of light on a variety of tissues, particularly neurological, is mostly unknown. A few researchers have reported on the effects of lasers and to a lesser extent infrared LEDs on nerve conduction in superficial nerves, but there is little evidence of the effects of SLDs and red LEDs on conduction parameters of peripheral nerves. The purpose of this study was to examine the effects of a light therapy generated by cluster probe containing an array of infrared super luminous and red light emitting diodes on superficial radial nerve conduction.

METHODS: This was a single blind, randomized controlled trial conducted in an academic clinical laboratory. Thirty-two healthy participants (mean age = 25 years) were randomized to a treatment group or a placebo group. The treatment group received light irradiation through the application of a cluster probe containing 32 infrared (880nm) SLDs and 4 red (660nm) LEDs for 30 seconds at a dose of 6 J/cm2 to each of the two 5 cm2 segments of skin overlying the superficial radial nerve. The placebo group received identical set-up without the application of light irradiation. Negative peak latency (NPL) and conduction velocity (NCV) for the superficial radial nerve were measured before treatment and for 10-minutes following treatment at 2-minute intervals. Skin temperature was monitored throughout.

RESULTS: No significant differences between groups and over time for NPL, NCV, or temperature difference scores were identified. However, a significant increase in skin temperature was measured over time at each time point compared to baseline

CONCLUSION: Light irradiation using a cluster probe containing infrared super luminous and red light emitting diodes does not impact the neurophysiological properties of the superficial radial nerve.

INTRODUCTION: Implant bed preparation with laser is taken into consideration owing to the increased interest in use of lasers in hard tissue surgery. The purpose of this study is to determine the deviations in the position and inclination between the planned and prepared implant beds with Erbium, Chromium doped Yttrium Scandium Gallium Garnet (Er,Cr: YSGG) laser using stereolithographic (SLA) surgical guides.

METHODS: After 3-dimensional (3D) imaging of six sheep lower jaws, computed tomography (CT) images were transformed into 3D models. Locations of implant beds were determined on these models. Two implant beds in each half jaw were prepared with an Er,Cr:YSGG laser system and a conventional drilling method using a total of 12 SLA surgical guides. A new CT was taken to analyze the deviation values between planned and prepared implant beds. Finally, a software program was used to superimpose the images on 3D models, then the laser and conventional drilling groups were compared.

RESULTS: Differences of mean angular deviations between the planned and prepared implant beds were 5.17±4.91° in the laser group and 2.02±1.94° in the conventional drilling group. The mean coronal deviation values were found to be 0.48±0.25 mm and 0.23±0.14 mm in the laser group and conventional drilling group, respectively. While the mean deviation at the apex between the planned and prepared implant beds were 0.70±0.26 mm and 0.26±0.08, the mean vertical deviations were 0.06±0.15 mm and 0.02±0.05 mm for the laser group and the conventional drilling group, respectively.

CONCLUSION: It is possible to prepare an implant bed properly with the aid of Er,Cr:YSGG laser by using SLA surgical guide.

INTRODUCTION: Solar lentigines are among commonest cosmetic problems. There are many topical therapies suggested to treat these lesions including cryotherapy, chemical peeling with tri chloro acetic acid (TCA) and laser therapy with q-switched lasers as well as long pulsed lasers. Considering possible treatment side effects (PIH, scar) with cryotherapy and peeling in Iranian patients (darker skin types) it seems necessary to try to find alternative measures. The aim of the present study was to evaluate effect of long pulsed dye laser (LPDL) on lentigines via an objective method (computerized dermoscopy).

METHODS: Patients with pathologically confirmed lentigines were selected if they agreed to participate in the study,were not treated before, hadn’t history of psoriasis, vitiligo, scar formation and were not pregnant. Letigines were dermoscopied before and after treatment with PDL (V-beam, 595nm, Candela Corp. Wayland, USA) using fluence of 10 joules, without DCD (dynamic cooling device) via extra compress lens provided with laser system. The resulting figures were compared by two academic unrelated dermatologists as well as by computerized analysis. Post laser side effects were treated with topical antibiotics and mild topical steroids. Patients were followed for six months after the end of the study to determine the rate of recurrence via dermoscopy of sites of previous lesions and also delayed side effects.

RESULTS: A total of 21 patients with the same number of lesions, were included in the study. Mean age of patients was 54.2 years (±23.3) ranging from 39 to 71 years. Included patients were 18 females and three males. From 21 treated lesions, 11 were located on the hands and 10 on the face. Comparing before and after photographs taken through dermoscopy system, revealed that approximately 57% of patients had more than 75% improvement. Mean pigment analysis score (calculated by computerized dermoscope software) was respectively 8 and 2 before and after PDL therapy, showing noticeable decrease in pigment density of lesions. Side effects were mild erythema and local irritation responding to topical mild steroids. No hypo or persistent hyper pigmentation or other delayed side effects was seen after six months follow up. One patient experienced transient hyper pigmentation of treatment site after treatment. During six months follow up, no recurrences were seen.

CONCLUSION: In conclusion, PDL is a safe and effective option to treat lentigines if applied properly using compression method, especially in Iranian patients. However, further studies with larger sample size are required to confirm these results.

INTRODUCTION: The use of laser for cavity preparation or conditioning of dentin and enamel surfaces as an alternative for dental tissue acid-etch have increased in recent years. The aim of this in vitro study was to compare microleakage at enamel-composite and dentincomposite interfaces following Erbium-Doped Yttrium Aluminum Garnet(Er:YAG) laser conditioning or acid-etching of enamel and dentin, hybridized with different bonding systems.

METHODS: Class V cavities were prepared on the lingual and buccal surfaces of 50 recently extracted intact human posterior teeth with occlusal margin in the enamel and gingival margin in the dentin. The cavities were randomly assigned to five groups: group1:conditioned with laser (Energy=120mJ, Frequency=10Hz, Pulse duration=100μs for Enamel and Energy=80mJ, Frequency=10Hz, Pulse duration=100μs for Dentin) + Optibond FL, group2:conditioned with laser + etching with 35% phosphoric acid + Optibond FL, group3:conditioned with laser + Clearfil SE Bond, group 4 (control):acid etched with 35% phosphoric acid + Optibond FL, group 5 (control): Clearfil SE Bond. All cavities were restored using Point 4 composite resin. All samples were stored in distilled water at 37°c for 24 h, then were thermocycled for 500 cycles and immersed in 50% silver nitrate solution for 24 h. The teeth were sectioned bucco-lingually to evaluate the dye penetration. Kruskal-Wallis & Mann-Whitney tests were used for statistical analysis.

RESULTS: In occlusal margins, the least microleakage showed in groups 2, 4 and 5. The maximum microleakage was observed in group 3 (P=0.009). In gingival margins, the least microleakage was recorded in group2, while the most microleakage was found in group 5 (P=0.001). Differences between 5 study groups were statistically significant (P<0.05). The microleakage scores were higher at the gingival margins.

CONCLUSION: The use of the Er:YAG laser for conditioning with different dentin adhesive systems influenced the marginal sealing of composite resin restorations.

INTRODUCTION: The aim of this study was to investigate the morphological changes of human dentin after Erbium-Doped Yttrium Aluminum Garnet (Er:YAG), Carbon Dioxide (CO2) laser-irradiation and acid-etching by means of scanning electron microscopic (SEM)

METHODS: 9 extracted human third molars were used in this study. The teeth were divided in three groups: first group, CO2 laser with power of 1.5 w and frequency of 80 Hz; second group, Er:YAG laser with output power of 1.5 W frequency of 10 Hz, very short pulse withwater and air spray was applied; and third group, samples were prepared by acid-etching 37% for 15 sec and rinsed with air-water spray for 20 sec. Then, the samples were prepared for SEM examination.

RESULTS: Melting and cracks can be observed in CO2 laser but in Er:YAG laser cleaned ablated surfaces and exposed dentinal tubules, without smear layer was seen.

CONCLUSION: It can be concluded that Er:YAG laser can be an alternative technique for surface treatment and can be considered as safe as the conventional methods. But CO2 laser has some thermal side effects which make this device unsuitable for this purpose. 

INTRODUCTION: Laser surgery as an alternative for conventional surgical procedure has gained special attention. Using Carbon Dioxide (CO2) laser has some benefits like less post-operative pain, swelling and infection, decrease in risk of metastasis and edema, and less bleeding providing dry sites for surgery.

CASE REPORT: A 12 years old boy with lingual frenum with indication for excision was referred to the laser department of Tehran University of medical sciences dental school. CO2 laser was used with 10600 nm wavelength, 1.5 W output power, 100 Hz frequency and 400 μsec pulse duration in non-contact mode.

RESULTS: The result of using CO2 laser was dry and bloodless field during operation, no post operative swelling, no pain or discomfort, with normal healing process.

CONCLUSION: We suggest and stimulate the use of CO2 laser for soft tissue surgery because of elimination of suture, convenient coagulation, time saving, patients’ comfort and easy manipulation.