The biological effects of different LED wavelengths in the health field. A review / Os efeitos biológicos de diferentes comprimentos de onda de LED na área da saúde. Uma revisão

Introduction: the use of light emitting diodes (LED) in domestic and public vias have increased in the last 20 years. In addition, the LED light has been used as a light source for medical applications. Objective: since humans are increasingly exposed to LEDs, there is an urgency to investigate the possible biological effects on tissues caused by this exposure. So, researchers have been focused their investigations in the application of this light in the health field. Material and method: in this review, a search in important databases was performed on the biological effects caused after application of different LED light protocols in in vitro and in vivo studies. Result: although most published papers have shown positive results, some of them reported negative biological effects of light LEDs technology on humans' cells/tissues. Conclusion: therefore, the comprehension of the biological effects caused by light LEDs will provide a better assessment of the risks involved using this technology.

Introdução: o uso de diodos emissores de luz ("LED") em vias domésticas e públicas tem aumentado nos últimos 20 anos. Além disso, a luz LED tem sido usada para aplicações médicas. Objetivo: pelo fato de seres humanos estarem cada vez mais expostos aos LEDs, há urgência em investigar os possíveis efeitos biológicos nos tecidos causados por esta exposição. Assim, pesquisadores têm focado suas investigações no uso desta luz na área da saúde. Material e método: nesta revisão foi realizada uma pesquisa em bancos de dados conceituados sobre os efeitos biológicos causados após aplicação de diferentes protocolos de luz LED em estudos in vitro e in vivo. Resultado: embora a maioria dos artigos publicados tenham mostrado resultados positivos, alguns deles relataram efeitos biológicos negativos da tecnologia de LEDs nas células/tecidos humanos. Conclusão: portanto, a compreensão dos efeitos biológicos causados pela luz LED proporcionará uma melhor avaliação dos riscos envolvidos no uso desta tecnologia.

Selection of light sources and radiation parameters in photodynamic therapy for skin diseases / 中华皮肤科杂志

Photodynamic therapy (PDT) is the first-line treatment of some intractable skin diseases, such as actinic keratosis, condyloma acuminatum and moderate to severe acne vulgaris. In clinical practice, radiation parameters and light sources are important for the efficacy of PDT. This review focuses on the selection of radiation parameters and light sources for PDT in terms of the wavelength and type of light sources and dose of radiation, and summarizes research progress in new light sources for PDT.

Advances in the application of photodynamic therapy to root canal disinfection / 口腔疾病防治

@#In recent years, many researchers have devoted themselves to the application of photodynamic therapy (PDT) in root canal disinfection, as conventional root canal disinfection methods have failed to achieve the optimal effect. Some clinicians have also applied PDT to root canal disinfection. PDT is expected to have a better effect than traditional root canal disinfection. This paper reviews the research progress on the mechanism, effect, influencing factors and limitations of PDT in root canal disinfection. Current research suggests that differences in the type and status of the bacteria, photosensitizers, light sources, operating environment and methods all affect the efficacy of root canal disinfection of PDT. Most of the research into PDT for root canal disinfection finds that it is effective, nontoxic, advantageous to dental pulp regeneration and comfortable for the patient, as well as lacking an excitant; however, its bactericidal effect is inferior to that of sodium hypochlorite. At present, it cannot replace traditional chemical washing but is a promising auxiliary method. The design of the photosensitizer, the energy dose of the light source and the optimal irradiation time need to be determined by further experiments, and more clinical verification is needed before its application in root canal therapy.

Research progress in metronomic photodynamic therapy / 国际生物医学工程杂志

Metronomic photodynamic therapy (mPDT) is a new type of photodynamic therapy (PDT) that has received much attention in recent years. It has a similar therapeutic mechanism to traditional PDT, i.e. the photosensitizer is irradiated by visible light irradiation with a specific wavelength, and tissue oxygen photochemical reactions produce cytotoxic reactive oxygen species (ROS) that selectively kill rapidly proliferating tumor cells. Unlike traditional PDT, the photosensitizer and light in mPDT are continuously transmitted at a low time and at a low rate, and the specificity of tumor treatment is enhanced by apoptosis. In this paper, the current researches on the in vitro and in vivo effects and mechanisms of mPDT, as well as the research status of photosensitizers and light sources for in vivo research, were reviewed, with a view to understanding the existing mPDT technology and providing reference for the further studies. This review paper can provide a basic for promoting the clinical research and application of mPDT.

Clareamento com peróxido de hidrogênio a 35% ativado por diversas fontes de energia: análise térmica e microdureza do esmalte / Bleaching with 35% hydrogen peroxide active for several light souces, thermal and enamel microhardness analyses

O objetivo do presente estudo foi avaliar in vitro a variação de temperatura e a microdureza Knoop superficial do esmalte durante o processo de clareamento dental com peróxido de hidrogênio a 35% sob irradiação da luz halógena com o comprimento de onda de 400 a 500nm (HL), luz emitida por diodo com comprimento de onda de 460 de 480 (LED) e laser de diodo (DL) de alta intensidade e comprimento de onda de 810nm, em dentes humanos extraídos. Inicialmente investigou-se a variação de temperatura superficial através da termografia de infravermelho e a temperatura do interior da câmara pulpar por meio de termopares em incisivos inferiores humanos, quando submetidos ao clareamento dental com peróxido de hidrogênio a 35% nas cores vermelha (HP) e verde (HPM) irradiados por: HL e LED. Quatro grupos (n=10) foram divididos de acordo com o gel clareador e a fonte de luz. Os resultados foram submetidos à análise de variância e teste de Tukey (p < 0,05). Os valores médios e desvios padrão do aumento de temperatura dentro da câmara pulpar com a HL foram de 4.4 ± 2.1 °C para HP, e 4.5 ± 1.2 °C para HPM; enquanto que nos grupos usando LED, foram 1.4 ± 0.3 °C para HP, e 1.5 ± 0.2 °C para HPM. Para todas as temperaturas superficiais a variação máxima dos grupos irradiados com HL foi 6.5 ± 1.5 °C para HP, e 7.5 ± 1.1 °C usando HPM; enquanto para os grupos usando LED, foram 2.8 ± 0.7 °C usando HP, e 3 ± 0.8 °C para HPM. Não houve diferença estatística entre o aumento da temperatura pulpar e superficial entre os grupos usando os diferentes géis (p < 0,05). As médias de temperatura foram significativamente maiores para os grupos usando HL quando comparados com aqueles irradiados com LED (p < 0,05). Ainda foi investigada a variação de temperatura superficial e assim determinado o tempo de demora para ser atingida a variação crítica de temperatura (5,5 °C para câmara pulpar e 10 °C para o periodonto). Quarenta e cinco incisivos inferiores humanos foram divididos em 3 grupos e submetidos ao clareamento dental com HP ativado por fontes HP, LED e DL respectivamente. As médias de temperatura e desvios padrão do aumento da temperatura intrapulpar foram para o HL 6.47 ± 2.78 °C, para o DL foram 15.34 ± 8.81 °C e 1.90 ± 0.97 °C para LED. A temperatura superficial para a HL foi 9.13 ± 2.19 °C, para o DL foi 25.66 ± 18.89 °C e 2.58 ± 1.40 °C para LED. A média de temperatura foi significativamente (teste de Tukey p > 0,05) maior para o grupo irradiado com DL se comparado como irradiado com HL e LED. Aplicando-se os limites inferiores do intervalo de confiança a 95% foi encontrado um tempo de aplicação de 38,68 segundos para a HL e 4,38 segundos para DL. A fonte de luz LED não atingiu as temperaturas críticas para a polpa nem para o periodonto, mesmo quando irradia da por 360 segundos. Investigou-se também a microdureza do esmalte durante o clareamento dental com peróxido de hidrogênio a 35%, sob irradiação de fontes HL, LED e DL. Cento e cinco blocos obtidos de terceiros molares inclusos tiveram a superfície de esmalte planificada e foram feitas medidas iniciais de microdureza Knoop com a carga de 25g por 5s. Procedeu-se o tratamento clareador com HP: Grupo A, B e C ativados por HL, LED e DL respectivamente; grupo D, E e F tratados apenas com HP pelos mesmo tempos dos grupos A, B e C, respectivamente, e o grupo G (controle) foi mantido apenas em saliva artificial pelo mesmo período dos outros grupos experimentais. As médias percentuais de dureza e desvio padrão obtidos foram: A: 97,8 ± 13,1; B: 95,5 ± 12,7; C: 84,2 ± 13,6; D: 128,6 ± 20,5; E: 133,9 ± 14,2; F: 123,9 ± 14,2; G: 129,8 ± 18,.8. A análise estatíticas (Tukey p < 0,05) mostrou que as médias percentuais de microdureza dos grupos irradiados pelas fontes de luz são significativamente menores que dos grupos não irradiados. Além disso, os grupos não irradiados mostraram que a saliva artificial foi capaz de aumentar a microdureza durante o tempo de armazenagem. Segundo a análise térmica os resultados sugerem que o LED pode ser usado com segurança para os tecidos pulpar e periodontal quando usados os parâmetros desse trabalho, já a HL e o DL necessitam de maiores cuidados. Considerando as limitações desse estudo, a microdureza do esmalte foi diminuída quando as fontes de luz foram utilizadas durante o processo de clareamento e a saliva artificial foi capaz de aumentar a microdureza quando nenhuma luz foi irradiada.

The objective of this in vitro study was to evaluate the variation of temperature and Knoop microhardness on enamel surface during the bleaching process whith 35% hydrogen peroxide under irradiation by halogen light whit the wavelength of 400 to 500nm (HL), LED whit the wavelength of 460 to 480nm and high intensity diode laser LED whit the wavelength of 810nm (LD) on extracted human teeth. Initially were investigated the variation of surface temperature (infrared thermography) and the temperature of the interior of the pulp chamber (thermocouples) in human mandibular incisors when subjected to dental bleaching with 35% hydrogen peroxide in the colors red (HP) and green(HPM) irradiated by: HL and LED. Four groups (n = 10) were divided according to the bleaching gel and light source. The results were submitted to the analysis of variance and Tukey test (p < 0.05). The mean values and standard deviations of the temperature increase inside the chamber pulp with HL were 4.4 ± 2.1 °C using HP and 4.5 ± 1.2 °C using HPM; while in LED groups, were 1.4 ± 0.3 °C to HP, and 1.5 ± 0.2 °C using HPM. For all surface temperatures, the maximum variation of the groups irradiated with HL was 6.5 ± 1.5 °C to HP and 7.5 ± 1.1 °C using HPM; while for the groups using LED, were 2.8° ± 0.7 °C using HP, and 3 ± 0.8 °C for HPM. There were no statistical difference between the increase of pulp and superficial temperature between groups using the various gels (p < 0.05). Mean temperatures were significantly higher for groups using HL compared with those irradiated with LED (p < 0.05). Was investigated the variation of surface temperature and thus given the time-delay to hit the critical variation of temperature (5.5 °C for the pulp chamber and 10 °C for periodontal). Forty-five human inferior incisors were divided into 3 groups and submitted to dental bleaching using HP and activated by HL, LED and DL sources respectively. The mean and standard deviation of the increase of pulpal temperature were 6.47 ± 2.78 °C for HL; 15.34 ± 8.81 °C for DL and 1.90 ± 0.97 °C for LED. The surface temperature for HL was 9.13 ± 2.19 °C, for DL was 25.66 ± 18.89 °C and for LED was 2.58 ± 1.40 °C. The mean temperature was significantly (Tukey test, p > 0.05) higher for the group irradiated by DL as compared as groups irradiated by HL and LED. Applying the lower limits of the confidence interval to 95% was found a time of 38.68 seconds for HL and 4.38 seconds for DL. The LED light source not reached the critical temperature for pulp or the periodontal, even when irradiated by 360 seconds. It was also investigated the dental enamel microhardness during the bleaching with hydrogen peroxide to 35%, under irradiation of HL, LED and DL sources. One hundred and five blocks were obtained from third molars, the enamel surface were planned and were made initial measures of Knoop microhardness with the burden of 25g per 5s. Then, the bleaching treatment with HP was made: A, B and C groups activated by HL, LED and DL respectively; D, E and F groups treated only with HP for the same time used on A, B and C groups, respectively, and G Group (control) was maintained only in artificial saliva for the same period of the other experimental groups. The average percentage of hardness and standard deviations obtained were: A: 97,8 ± 13,1; B: 95,5 ± 12,7; C: 84,2 ± 13,6; D: 128,6 ± 20,5; E: 133,9 ± 14,2; F: 123,9 ± 14,2; G: 129,8 ± 18,8. The statistical analysis (Tukey p < 0.05) showed that the mean percentage of microhardness for the groups irradiated by the light sources are significantly lower than the non-irradiated groups. Moreover, the non-irradiated groups showed that the artificial saliva was able to increase the microhardness during the time of storage. According to the thermal analysis, results suggest that the LED can be used safely for the pulp and periodontal tissue when used the parameters of this work. But the HL and DL require greater care. Considering the limitations of this study, the microhardness of the enamel was reduced when the light sources were used during the bleaching process and artificial saliva was able to increase the microhardness when no light was irradiated.