Effect of Three Different Protocols of Low-Level Laser Therapy on Thyroid Hormone Production After Dental Implant Placement in an Experimental Rabbit Model

Abstract

Objective: The purpose of this study was to assess the systemic effects of low-level laser therapy (LLLT) on thyroid gland function and, consequently, calcium regulation -as measured by serum triiodothyronine (T3), thyroxine (T4), and free calcium levels -when administered after dental implant placement in a rabbit model. Background data: Protocols for the use of laser therapy in several clinical procedures are currently under investigation, as not all of the actions and systemic effects of laser irradiation have been clearly established. Materials and methods: Forty male adult New Zealand rabbits were distributed across five groups of eight animals each: two control groups (C-I and C-II) of unirradiated animals, and three experimental groups (E-5, E-10, and E-20), each exposed to a distinct dose of gallium-aluminum-arsenide (GaAlAs) laser [k = 830 nm, 50 mW, continuous wave (CW)] every 48 h for a total of seven sessions. The total dose per session was 5 J/cm 2 in E-5, 10 J/cm 2 in E-10, and 20 J/cm 2 in E-20. Animals in C-II and all experimental groups underwent surgical extraction of the mandibular left incisor followed by immediate placement of an osseointegrated implant (Nanotite Ò , Biomet 3i TM ) into the socket. Animals in group C-I served as an absolute control for T3, T4, and calcium measurements. The level of significance was set at 5% ( p £ 0.05). Results: ANOVA with Tukey's posthoc test revealed significant differences in T3 and calcium levels among experimental groups, as well as significant within-group differences in T3, T4, and calcium levels over time. Conclusions: Although not reaching abnormal values, LLLT applied to the mandible influenced thyroid function in this model.

Histomorphometric Assessment of the Influence of Low-Level Laser Therapy on Peri-Implant Tissue Healing in the Rabbit Mandible

“…High doses of potassium chloride exert cardiotoxic effects that quickly cause cardiac arrest, and its intravenous administration in unconscious animals or animals under general anesthesia is considered an acceptable procedure to induce cardiac arrest or death in animal experimentation. 21,22 All rabbits were in good nutritional status at the time of euthanasia.…”

Under the spotlight: mechanisms of photobiomodulation concentrating on blue and green light

“…Nonetheless, a growing number of observations suggests that specific wavelengths of electromagnetic radiation spanning the visible to near infra-red spectrum (400-1100nm) could lead to photo-physical and photochemical effects that can modulate major biological processes to achieve therapeutic goals such as cellular proliferation, mitochondrial function and inflammatory signalling (5) in various eukaryotic organisms, including humans. The majority of the literature reports the beneficial therapeutic effects of red and near infrared light (red: ~600-750, NIR: ~750-1100nm) in promoting tissue healing and reducing inflammation (6)(7)(8)(9)(10)(11)(12)(13)(14). Nevertheless, controversy still surrounds the application of PBM in practice, due to the lack of knowledge concerning how PBM elicits its molecular effects and also a poor understanding of photophysics and radiometric parameters which affect repeatability and reliability (15).…”

Phototherapeutic Effect of Low‐Level Laser on Thyroid Gland of Gamma‐Irradiated Rats

“…Several studies have reported that LLLT did not protect the thyroid in different animals . On the other hand, other studies found that LLLT had a significant impact on serum T3 and T4, which differed by time and dose , these biomodulatory effects of laser may also occur remotely from the site of irradiation .…”

“…Low‐level laser therapy has been used for nearly 50 years to enhance tissue healing and to relieve pain, inflammation and swelling. Recently it has become apparent that LLLT can also be effective if delivered to normal cells or tissue before the actual insult or trauma, in a preconditioning mode . Although the mechanism of action of LLLT is still not fully understood, much information is now known concerning the short and long‐term effects of LLLT on cells and tissues .…”