Thyroid hormones may influence cortical bone healing around titanium implants: A histometric study in rats

Background: The aim of the present study was to evaluate, by histometric analysis, the influence of the thyroid hormones, triiodothyronine (T(3)) and thyroxine (T(4)), on bone healing around titanium implants inserted in rat tibiae. Methods: Forty-two male Wistar rats were randomly assigned to the experimental groups: G1 = healthy animals (control; N = 15); G2 hypothyroidism (N = 13); and G3 = hyperthyroidism (N 14). Once alterations were confirmed by total serum levels of T3 and T4, one screw-shaped titanium implant was placed in the rat tibiae. Sixty days later, the animals were sacrificed, and undecalcified sections were obtained. Bone-to-implant contact (BIC), bone area within the limits of the implant threads, and bone density in a 500-mu m-wide zone lateral to the implant were obtained separately for the cortical (zone A) and cancellous (zone B) bone regions. Results: Intergroup analysis demonstrated that thyroid hormones may significantly affect cortical bone healing around titanium implants. Hyperthyroidism significantly increased the area of newly formed bone in zone A (P<0.05), whereas hypothyroidism significantly decreased the area of newly formed bone and bone density around the implant in zone A (P<0.05) compared to the healthy group. In addition, hyperthyroidism significantly increased BIC extension in zone A compared to hypothyroidism (P