***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The use of low levels of visible or near infrared light for reducing pain , inflammation and edema , promoting healing of wounds , deeper tissues and nerves , and preventing cell death and tissue damage has been known for over forty years since the invention of lasers . Despite many reports of positive findings from experiments conducted in vitro , in animal models and in r and omized controlled clinical trials , LLLT remains controversial in mainstream medicine . The biochemical mechanisms underlying the positive effects are incompletely understood , and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength , fluence , power density , pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones . A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light . The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response . This review will cover the molecular and cellular mechanisms in LLLT , and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response The aim of this study was to evaluate the pain sensation that orthodontic patients experience when elastic separators are placed between molars and premolars and to determine the degree of analgesic efficacy of low-level laser therapy ( LLLT ) compared to a placebo treatment . The study was conducted with 20 volunteers who were fitted with elastic separators between the maxillary molars and premolars . One quadrant was r and omly chosen to be irradiated with an 830-nm laser , 100 mW , beam diameter of 7 mm , 250 mW/cm2 applied for 20 s per point ( 5 J/cm2 ) . Three points were irradiated in the buccal face and three were irradiated in the palate . The same procedure was applied in the contralateral quadrant with a placebo light . A visual analogue scale was used to assess pain 5 min , 6 h , 24 h , 48 h , and 72 h after placement of the separators . Maximum pain occurred 6–24 h after placement of the elastic separators . Pain intensity was significantly lower in the laser-treated quadrant ( mean , 7.7 mm ) than in the placebo-treated quadrant ( mean , 14.14 mm ; p = 0.0001 ) . LLLT at these parameters can reduce pain in patients following placement of orthodontic rubber separators This study was design ed to investigate the effects of low-intensity laser therapy ( LILT ) on periodontal ligament ( PDL ) remodeling during relapse and retention after the completion of orthodontic movement . The maxillary central incisors ( n = 104 ) of the 52 rats were r and omly divided into five groups according to the treatment modality : baseline control group without any intervention ( n = 8) ; relapse group without retainer after tooth movement ( n = 24 ) ; retention group with fixed retainer after tooth movement ( n = 24 ) ; lased relapse group without retainer after tooth movement and LILT ( n = 24 ) ; lased retention group with retainer after tooth movement and LILT ( n = 24 ) . LILT was daily performed using a gallium – aluminum – arsenide diode laser in a biostimulation mode : wavelength of 780 nm , continuous waves at 70 mW output power , a preset low intensity of 1.75 W/cm2 in contact mode , result ing in energy dose of 5 J/cm2 per irradiation for 3 s. The animals were euthanized on days 1 , 3 , and 7 after removal of the orthodontic appliance . Real-time RT-PCR was performed for quantitative analysis of matrix metalloproteinases mRNA expression . Immunoreactivities of collagen and tissue inhibitor of metalloproteinase were observed on the compression and tension sides . LILT significantly facilitated the expression of five tested MMP mRNAs in both relapse and retention groups . TIMP-1 immunoreactivity was inhibited by LILT in both groups , whereas Col-I immunoreactivity was increased by LILT only in the retention group . These results indicate that LILT would act differently on the stability after orthodontic treatment according to additional retainer wearing or not . LILT when combined with a retainer on the moved teeth may shorten the retention period by accelerating periodontal remodeling in the new tooth position , whereas , LILT on the moved teeth left without any retainer would rather increase the rate of relapse after treatment The effects of fiberotomy were evaluated in alleviating dental relapse of incisors after orthodontic treatment . The study sample consisted of 23 patients with crowded maxillary and m and ibular incisors before orthodontic treatment . The amount of initial crowding was determined according to Little 's irregularity index . Fiberotomy procedures were performed on 11 of the patients 1 week before debonding . The other 12 subjects served as the control group . All patients wore Hawley retainers . Lateral cephalometric headfilms and dental casts of the patients were taken at the beginning ( T1 ) and at the end ( T2 ) of treatment , 6 months into the retention phase ( T3 ) , and 1 year after orthodontic treatment ( T4 ) . Significant increase of irregularity index was noted in the control group at T3 and T4 for both maxillary and m and ibular anterior segments ( P < .05 , P < .01 ) . Meanwhile , in the group where circumferential supracrestal fiberotomy was performed , no significant increase of the irregularity index was noted OBJECTIVE The aim of the study was to determine whether low-level laser therapy ( LLLT ) has an analgesic effect in patients with recurrent aphthous stomatitis ( RAS ) . STUDY DESIGN A r and omized single-blinded placebo-controlled trial was conducted with LLLT ( wavelength , 809 nm ; power , 60 mW ; pulse frequency , 1800 Hz ; duration , 80 seconds per treatment ; dose , 6.3 J/cm(2 ) ) in 40 patients with RAS . The intervention group was treated with LLLT on 3 occasions , with a 1-day interval . The control group was treated similarly , without any laser power .  Pain perception ( visual analog scale [ VAS ] rating ) and patients ' experience of eating , drinking , and brushing teeth was registered . RESULTS VAS rating decreased ( day 0 until day 2 ) from 84.7 to 31.5 ( LLLT ) and from 81.7 to 76.1 ( placebo ) ( P < .0001 ) . LLLT also relieved the difficulty of drinking , eating , and brushing teeth . CONCLUSIONS LLLT reduced the pain and the inconvenience of eating , drinking , and brushing teeth for patients with RAS , compared with placebo Low level laser therapy ( LLLT ) has been shown to produce analgesic effects in many clinical applications . The aim of this clinical study was to test the efficacy of LLLT in controlling  orthodontic postadjustment pain . Thirty-nine volunteers were selected for this study that used a double-blind design with placebo control . Elastomeric separators were placed at the proximal contacts of one premolar in each quadrant of the dentition to induce orthodontic pain . The tip of a 30 mW gallium-arsenide-aluminium ( 830 nm ) diode laser probe was then placed at the buccal gingiva and directed at the middle third of the root . Three different treatment duration s of 15 , 30 , and 60 seconds and one placebo treatment of 30 seconds were tested within each subject . The study was conducted over 5 days , and the visual analogue scale ( VAS ) was used to quantify the pain experienced by the subjects before and after laser applications for each day . Analysis of the VAS median scores showed that teeth exposed to laser treatment had lower levels of pain as compared with those with the placebo treatment . However , nonparametric statistical analysis of the data showed that the differences between treatments and placebo within each subject were not statistically significant 
    Output:
    
According to the results of our systematic review , the effect of LLLT on relapse of corrected tooth rotations is related to energy density .
Namely , low energy density seems to promote relapse , while high energy density might alleviate the relapse .