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

Abstract

The use of osseointegrated titanium implants has been related like an excellent alternative to traditional orthodontic anchorage methodologies, and they are a necessity when dental elements lack quantity or quality, when extraoral devices are impractical, or when noncompliance during treatment is likely. In orthodontics, the implants can be use to anchor different movements. However, conventional dental implants can only be placed in limited areas such as the retromolar or the edentulous areas. Another limitation has been the direction of the force application and conventional dental implants are troublesome for patients because of the severity of the surgery, the discomfort of the initial healing, and the difficulty of oral hygiene. Due to these factors, mini-implants became widely used. They have little limitations related to the local of implantation, the surgical procedure of insertion is relatively simple and the control of direction and quantify of the force is simple to be done. These improvements were obtained due to decrease of the size, but these changes could result on significant changes to the bone-implant interface. Since, the orthodontic treatment has to be done as fast as possible. The purpose of this work is to analyze the bone healing reactions to immediately loaded mini-implant of titanium alloy grade 4 by histological, fluorescent and SEM observation, by histomorphometric analysis and by removal torque test. Material and method: Seventy two mini-implants were inserted in eighteen New Zealand rabbits. Four mini-implants were put in the right tibiae of each rabbit and two of then were loaded immediately with 100 gf. Subcutaneous injections of fluorescent labels were administrated in defined periods. The animals were euthanized after 1, 4 and 12 weeks, performing three time analysis and the tibias were dissected and prepared to microcopy analysis and to removal torque test. Results: The results indicated that all the mini-implants remained stable during experimental time. The SEM findings indicated no differences between load and unload group in one and four weeks period, although, the 12 weeks loaded group demonstrated more mature bone formation than the unload group in the same time. These findings suggest that the force can be applied after insertion of the mini-implant without compromises their stability.