The integration of orthodontic miniscrews under mechanical loading: a pre-clinical study in rabbit.
BACKGROUND
Orthodontic miniscrews are an increasingly popular choice to achieve absolute anchorage. The temporary use of miniscrews and their recent introduction have limited the debate over the biological aspect of the materials to that of the surface that permeates the field of dental implants. The aim of the present study was to investigate the integration of grade 5 titanium mini-implants with machined or sand blasted acid etched surface (SAE) under mechanical load in a rabbit tibia model of implant integration.


METHODS
A total of 64 miniscrews (Ti6Al4V) of 1.5 mm diameter and 6.5 mm length were inserted in the proximal medial surface of each tibia in eight male rabbits aged 6 months. Each tibia received four miniscrews. A 100 g nickel-titanium coil spring (Neosentalloy) was applied between two miniscrews along the main axis while two miniscrews were left unloaded. The removal torque was measured for loaded and unloaded miniscrews after 12 weeks. Two miniscrews were harvested for histology.


RESULTS
Removal torque was significantly higher for SAE mini-implants than for machined screws, under both loading conditions. Although no difference in bone to implant contact was observed among the groups, cortical area significantly decreased with both surfaces under loading.


CONCLUSIONS
Our data indicate that SAE miniscrews have higher bone retention than MA miniscrews, although the effects of mechanical loading of these devices on cortical bone require further investigations.
Department of Biomedical, Biotechnological and Translational Science, University of Parma.
B Giuliano
BG
Maino
Department of Biomedical, Biotechnological and Translational Science, University of Parma.
Alberto
A
Di Blasio
Private practice.
Davide
D
Spadoni
Department of Veterinary Science, University of Parma, Italy.
Francesca
F
Ravanetti
Department of Biomedical, Biotechnological and Translational Science, University of Parma.
Carlo
C
Galli
Department of Veterinary Science, University of Parma, Italy.
Antonio
A
Cacchioli
Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Switzerland.
Christos
C
Katsaros
Department of Biomedical, Biotechnological and Translational Science, University of Parma.
Mauro
M
Gandolfini
D000497:Alloys; D000818:Animals; D001863:Bone Screws; D015921:Dental Implants; D008297:Male; D009532:Nickel; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016348:Osseointegration / Q000502:physiology*; D011817:Rabbits; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000601:surgery; D014025:Titanium; D019415:Torque
D000497:Alloys; D015921:Dental Implants; C040654:titanium nickelide; C031462:titanium alloy (TiAl6V4); D009532:Nickel; D014025:Titanium