Six male Beagle dogs (~ 1.5 years old), weighting between 13 and 15 kg, were used in the present study. All animals were acclimatized in the experimental animal care facility of Federal University of Uberlândia for 2 weeks previously to the experimental procedures and randomly pair-housed in standard shelters (1 × 1.5 m kennel) to allow environmental enrichment (i.e., variety of toys, daily group play sessions, resistance running, and training) at the ambient temperature of 22 °C, under controlled humidity and 12-h circadian rhythm. The diet consisted of hard pellet and water ad libitum. The animal caretakers were blind to the experimental groups. The level of pain, distress, or suffering was daily assessed during the observation period to ensure the welfare of the animals. Aiming to guarantee selection blindness during the experimental allocation, the groups were systematically coded by a third person and the first implant to be placed in each tibia was randomly assigned. Sample size was calculated based on information in previous studies using the dog tibia model to allow evaluation of possible differences in bone-to-implant contact between groups. The surgical procedures and the histological/histomorphometrical outcomes of the study have been reported elsewhere [31].

Briefly, two pairs of implants (10 mm × 4 mm, L × Ø) from each of the experimental groups were placed under copious sterile saline irrigation and with a torque of about 45 N cm (last drill 3.5 mm Ø) in each proximal tibia of the animals (total no. of implants 48). Implants were placed with an alternating fashion in terms of medio-distal positioning with the first group chosen at random and surgeries were staged between left and right tibia to provide 2 and 4 weeks of healing times, i.e., 12 implants per group and per observation time. The first implant was inserted ca. 2 cm below the femoral-tibial-patellar joint line at the central medial-lateral portion of the proximal tibiae (Fig. 1). The following implants were placed in a distal direction with inter-implant distances of 1 cm along the central region of the bone until the tibia patellar joint. Implants were furnished with cover screws and then soft tissues were sutured in layers for primary intention healing. Postoperative pain and infection control was provided for 7 days. The animals were euthanized under sedation with an anesthesia overdose, and the upper third of the tibias was retrieved. The specimens were fixed in 10% buffered formalin solution and half of them were allocated to histomorphometric analysis and the other half to biomechanical analysis, reported herein.