Effect of three different protocols of low-level laser therapy on thyroid hormone production after dental implant placement in an experimental rabbit model.

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 [λ=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(®), Biomet 3i(™)) 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 post-hoc 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.