Sequential Bone Response to Immediately Loaded Mini-Implants, in vivo Study

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0925-BB03-07

Sequential Bone Response to Immediately Loaded Mini-Implants, in vivo Study Glaucio Serra Guimarães1,2, Liliane Siqueira de Morais1,2, Carlos Nelson Elias2, and Marc Andre Meyers1 1 Mechanical and Aerospace Engineering, UCSD, 7564 Charmant drive # 1826, San Diego, California, 92122 2 Mechanical and Materials Science, Military Institute of Engineering, Rio de Janeiro, Rio de Janeiro, 22290-270, Brazil ABSTRACT Ti-6Al-4V alloy mini-implants were inserted in rabbit’s tibiae and immediately loaded with 1 N. The healing process was analyzed by SEM in the assessment periods of 1, 4, and 12 weeks. Results showed that the tissues formed after 12 weeks were different between loaded and unloaded groups, but both of them were mechanically stable. The compression and traction areas in the loaded group did not present difference between each other. This investigation showed that the immediate load affected the healing process of the bone-implant interfacial tissue, without compromising its stability. INTRODUCTION Osseointegrated titanium implants are an excellent alternative to traditional orthodontic anchorage methodologies, and they are a necessity when dental elements lack in quantity or quality, when extraoral devices are impractical, or when noncompliance during treatment is likely. In orthodontics, the mini-implants can be used to anchor different movements and are becoming widely used. They have few limitations related to the site of implantation, the insertion surgical procedure is relatively simple, and the control of direction and quantity of the force is easy. These improvements were possible due to the decrease of the implant size, but these changes can result on significant alterations at the bone-implant interface. Commercially pure titanium (c. p. Ti) is widely used as dental implant material because of its suitable mechanical properties and excellent biocompatibility [1,2]. However, c. p. Ti orthodontic mini-implants have high rate of fracture during insertion and removal procedures, because of their small size. The Ti-6Al-4V can be used to overcome this disadvantage. To simplify the mini-implant methodology they have to be loaded as fast as possible, decreasing the treatment time. The purpose of this work was to analyze the bone healing reactions of immediately loaded Ti-6Al-4V mini-implants by SEM observation, after 1, 4, and 12 weeks. IN VIVO EXPERIMENTAL DETAILS Twelve Ti-6Al-4V alloy mini-implants (Conexão Sistemas e Próteses, São Paulo, Brazil) were used. The mini-implants had a cylindrical screw design with 2.0 mm in diameter, 6.0 mm in length, and a hexagonal shaped head. The mini-implants were machined by turning, cleaned, passivated with nitric acid (HNO3), and sterilized with Co radiation. No implant surface treatment was made to change their roughness (Fig. 1). Ni-Ti closed coils spring were used to load (1N) the mini-implants.

Six-month-old male New Zealand rabbits, weighting 3.0 to 3.5 kgf, were used in the present research. The surgical procedures were common to all animals and cons