Journal of Lasers in Medical Sciences

Low level lasers, cold or soft lasers:

These lasers do not produce thermal effects on tissues and induce photoreactions in cellsthrough light stimulation which is called photobiostimulation. Power of these lasers is usually under 250mW.

The main point differentiating low level lasers and high power ones is the activation of photochemical reactions without heat formation. The most important factor to achieve this light characteristic in lasers is not their power, but their power density for each surface unit (i.e cm2). Density lower than 670mW/cm2, can induce the stimulatory effects of low level lasers without thermal effects.

Low level lasers (therapeutic) used today as treatment adjunctive devices in medicine and dentistry. Numerous studies have been performed on the applications of low level lasers in patient pain reduction. Mechanisms of pain reduction with therapeutic lasers and their application are expressed, and the studies realized in this field are presented.

Low Level Laser Therapy (LLLT) uses a light source that generates extremely pure light, of a single wavelength1. The effect is not thermal, but rather related to photochemical reactions in the cells. LLLT was introduced as an alternative non-invasive treatment for OA about 10 years ago, but its effectiveness is still controversial2. A Cochrane review of LLLT in osteoarthritis included five trials, and concluded that despite some positive findings, the meta-analysis lacked data on how LLLT effectiveness was affected by the important factors of wavelength, treatment duration of LLLT, dosage, and site of application over nerves instead of joints1,3,4,5,6,7. A different review2 addresses some of these issues in a wider range of trials, and is broadly positive, if limited by numbers.

Introduction: Failure of teeth to erupt from gingival tissues at usual developmental time is called delayed tooth eruption (DTE). Delayed tooth eruption lead to prolonged fixed orthodontic treatment and its eventual complications. The purpose of the present study was to evaluate the effect of laser-assisted (808 nm) surgical uncovering, on the tooth emergence and orthodontic treatment of DTE.

Methods: A total of 16 orthodontic patients were included in this study and were equally assigned to an experimental and a control group. Subjects for experiment consisted of eight patients (6 girls and 2 boys) with a mean age of 14±0.9 years. All patients exhibited delayed second premolar eruption. The laser wavelength was 810 nm and it was set in a continuous wave mode at a power output of 1.6 watt with a 0.3-mm diameter fiber tip. When the target tissue was sufficiently anesthetized, the tip was directed at an angle of 10 to 20 degrees to the tissue (light contact mode); and was applied continuously for approximately 12 Seconds until an acceptable tooth exposure area was visible. The facial axis of the clinical crown (FACC) line represents the most prominent portion of the facial central lobe for premolars. All orthodontic brackets are aligned along this reference and are located on FA (Facial Axis) point. The standard for adequate tooth eruption was the accessibility of facial axis of the clinical crown (FACC) for bonding the brackets. Data gathered from the patients were statistically surveyed and compared by means of Tukey’s Test and Analysis of Variance (ANOVA).

Results: All patients showed good gingival status, no significant bleeding during or immediately after the surgery, and acceptable level of healing after laser surgery. The biologic width of the teeth was preserved and no violation of this important periodontal parameter was observed. The average time for accessing the FA point in experimental group was 11±1.1 weeks and the mentioned period was increased to 25±1.8 weeks in control group. The data analysis showed that in patients with DTE, laser intervention significantly accelerated tooth eruption (P < 0.05).

Conclusion: Laser-assisted surgical removal of the fibrous tissue over erupting premolars (DTE) with appropriate irradiation parameters appears to be a promising adjunct to orthodontic treatment for bringing the premolar to the aligned and leveled dental arch.

Introduction: Recent use of lasers for porcelain surface treatment for adhesion of brackets to restorations has not only showed some promising results, but is also accompanied with less undesirable effects among other advantages. The purpose of this study is the comparative electron microscope evaluation of feldspathic porcelain surfaces under irradiation by Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) with different powers (0.75, 1.5 and 2W) via the acid etching with hydrofluoric acid (HF) technique.

Methods: The glazed porcelain samples were obtained by duplicating labial surfaces of maxillary central incisor teeth. The specimens were randomly treated by 4 different methods. Group1 was etched with hydrofluoric acid 9.6%. Samples in group 2 to 4 were also irradiated by Nd:YAG laser with different powers: 0.75, 1.5 and 2W. Then the samples were prepared for evaluation by scanning electron microscope (SEM).

Results: Etching quality from a porosity point of view was similar for group2 and HF group. Laser with power of 0.75W has little potential to create mechanical porosity.

Conclusion: In regard of the results of this study, it is possible to benefit from Nd:YAG laser with appropriate parameters for surface conditioning.

Introduction: Tonsillectomy is among commonest otorhinolaryngologic surgeries. Many methods have been used to control post surgical pain, but despite it, pain is still one of the problems related to this operation. Recently, due to the non invasiveness of low level lasers, this modality has attracted attention. The purpose of this study is to evaluate the effects of low level laser irradiation at the end of surgery on reduction of pain after tonsillectomy in adults.

Methods: In a clinical trial, 60 adult patients, candidates for tonsillectomy were randomly assigned to two groups, A and B, and both groups were anesthetized similarly by the same technique. At the end of surgery, in the case group, the tonsils’ bed were irradiated by infrared laser with 980nm wavelength, 100Hz, 4J/cm2 from the infra mandibular angle. In the controlgroup, the tonsils’ bed had laser therapy with a turned off probe.

Follow ing laser treatment, the patients were reversed and extubated and consciousness achieved, pain and odynophagia were assessed at 2, 4, 6, 8, 12 and 24h post surgery based on visual analog scale for pain (VAS) and analgesic consumption.

Results: In the laser group frequency of patients with pain sensation in each evaluated hour was lower than in the control group. The amount of pain decrease and analgesic consumption reduction was significantly higher in patients who received laser (P=0.01).

Conclusion: Based on the results of this study, use of low level lasers is effective in reducing tonsillectomy post surgical pain in adults.

Introduction: The purpose of this study was to investigate the effect of 6W power Carbon Dioxide Laser (CO2) on the biologic compatibility of the Sandblasting with large grit and acid etching (SLA) titanium discs through studying of the Sarcoma Osteogenic (SaOS-2) human osteoblast-like cells viability.

Methods: Sterilized titanium discs were used together with SaOS-2 human osteoblast-like cells. 6 sterilized SLA titanium discs of the experimental group were exposed to irradiation by CO2 laser with a power of 6W and 10.600nm wavelength, at fixed frequency of 80Hz during 45 seconds in both pulse and non-contact settings. SaOS-2 human osteoblast-like cells were incubated under 37° C in humid atmosphere (95% weather, 5% CO2) for 72 hours. MTT test was performed to measure the ratio level of cellular proliferation.

Results: The results indicated that at 570nm wavelength, the 6W CO2 laser power have not affected the cellular viability.

Conclusion: CO2 laser in 6w power has had no effect on the biologic compatibility of the SLA titanium surface

Introduction: The aim of this study was to evaluate and compare the Scanning electron microscope (SEM) of indirect composite conditioned by Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser, Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) laserand Carbon Dioxide (CO2) laser.

Methods: 18 indirect composite blocks (GC Gradia DA2, Japan) with 15 × 10 × 10 mm dimensions were made. The bonding surface of these blocks were polished, then the samples were divided into six groups as follow: Er:YAG laser with output power of 0.5 W and frequency of 10 Hz, Nd:YAG laser with output power of 0.25, 0.5 W and frequency of 10 Hz, CO2 laser with output power of 0.5 W and frequency of 10 Hz and 5 Hz, and no treatment. Then, the surfaces were evaluated by SEM.

Results: Irregularities were observed in Er:YAG laser samples compared to control group that produced suitable retention for adhesion of cements. Nd:YAG and CO2 lasers showed melting areas.

Conclusion: Among different lasers, Er:YAG laser can be used as an alternative technique for surface treatment of indirect composites.

Introduction: Several treatment options have been introduced for removal of gingival hyperplasic lesions, but using diode lasers have many advantages such as less bleeding, time saving, better shaping, improved healing and less complication for the patients.

Case: A 15-year-old girl with multiple fibroma-like lesions in the oral cavity, who had a medical history of tuberous sclerosis, was selected for gingivoplasty treatment with 810nm diode laser.

Result: A perfect shaping was obtained after removal of the whole lesion in one session and no recurrence was observed in 6 months.

Conclusion: Using laser in the treatment of oral lesions leads to excellent wound healing along with excellent functional results.