title: Thyroid hormones may influence cortical bone healing around titanium implants: a histometric study in rats.
abstract: 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 T(3) and T(4), 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-microm-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 <0.05).
  
  
  CONCLUSIONS
  Thyroid hormones may influence the healing process in the cortical bone around titanium implants placed in rats, whereas cancellous bone seems to be less sensitive to changes in T(3) and T(4) serum levels.
authors.affiliation: Department of Prosthodontics and Periodontics, Division of Periodontics, School of Dentistry at Piracicaba, State University of Campinas, Avenida Limeira 901, Areião, Piracicaba, SP, Brazil. dsfeitosa@yahoo.com
authors.forename: Daniela da Silva
authors.initials: Dda S
authors.lastname: Feitosa
authors.forename: Beatriz de Brito
authors.initials: Bde B
authors.lastname: Bezerra
authors.forename: Gláucia Maria Bovi
authors.initials: GM
authors.lastname: Ambrosano
authors.forename: Francisco Humberto
authors.initials: FH
authors.lastname: Nociti
authors.forename: Márcio Zaffalon
authors.initials: MZ
authors.lastname: Casati
authors.forename: Enilson Antônio
authors.initials: EA
authors.lastname: Sallum
authors.forename: Sérgio
authors.initials: S
authors.lastname: de Toledo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015519:Bone Density / Q000502:physiology; D001861:Bone Regeneration / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D004195:Disease Models, Animal; D006980:Hyperthyroidism / Q000097:blood / Q000503:physiopathology*; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology*; D008297:Male; D016348:Osseointegration / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000097:blood / Q000502:physiology*; D013977:Tibia / Q000601:surgery; D014025:Titanium; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology*; D014945:Wound Healing / Q000502:physiology*
chemical_list: D015921:Dental Implants; D014284:Triiodothyronine; D014025:Titanium; D013974:Thyroxine