University of São Paulo: Use of violet LED light increases efficiency of gel tooth whitening

The use of violet LED light increases the efficiency of tooth whitening with gel performed by dentists, points out research from the Faculty of Dentistry (FO) of USP. According to the study, carried out in the laboratory and also with patients, the light allows the gel to stay in contact with the teeth for less time, without altering the whitening result and reducing the sensitivity of patients. The results are presented in an article published in the scientific journal Photodiagnosis and Photodynamic Therapy , published on the internet on February 3rd.

“The objective of the research was to test in a laboratory way, that is, in vitro , and then in a clinical way, that is, in vivo , the effects of violet LED light on in-office tooth whitening. Normally, for whitening, 37% hydrogen peroxide gel is applied on the teeth for about 30 to 45 minutes”, reports dentist Bruno Baciega, one of the authors of the article.

“Inside the teeth there is a living tissue, innervated and vascularized, called the pulp, which, like the rest of the human body, has a normal temperature, around 36 degrees Celsius ( o C). The lasers used in the past for whitening caused a lot of heating of the tooth and, consequently, of the intrapulpal temperature, that is, inside the pulp”, says Bachiega to Jornal da USP . “Raising the intrapulpal temperature excessively is like a person with a high, uncontrolled fever, in which case a root canal treatment is necessary.”

In addition to laboratory tests, the technique was applied to 120 patients, of which 60 were analyzed for the study. “In the laboratory, intrapulpal temperature variation, microhardness, adhesion resistance and color change were evaluated with the isolated LED light and associated with different protocols”, describes Bachiega. “Clinically, we evaluated the color change with the protocols that had the best in vitro results and the patient-reported sensitivity.”

Lower temperature, less sensitivity
According to the dentist, the laboratory study found that, thanks to the light triggering mechanism, the temperature variation does not exceed 1.5 o C, being safe. “About microhardness and adhesion resistance of the gel, we did not find statistically significant differences”, he points out. “In the case of in vitro color change , the protocols associating gel and violet LED light were statistically similar to the conventional protocol without light.”


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In the clinical study, the same results were verified on temperature variation, adhesion resistance and color of the gel obtained in the laboratory. “However, patients undergoing the protocol with violet LED light reported less sensitivity than the conventional group, which performed bleaching without the use of light”, highlights Bachiega. “The only downside to using just the gel is sensitivity. With the hybrid technique, using violet LED light, we apply the gel on the tooth for only 15 minutes, that is, half the conventional time, but with the same result. This may be one of the reasons why patients report lower sensitivity, but to prove this hypothesis we need further studies.”

According to the researcher, the violet LED is still very expensive and the conventional whitening technique is very cheap. “Although it is already on the market, the method still needs to be further studied and clinically tested, in order to obtain more scientific basis to indicate it”, he concludes.


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