Is trabecular bone related to primary stability of miniscrews?
OBJECTIVE
To compare the primary stability of miniscrews inserted into bone blocks of different bone mineral densities (BMDs) with and without cortical bone, and investigate whether some trabecular properties could influence primary stability.


METHODS
Fifty-two bone blocks were extracted from fresh bovine pelvic bone. Four groups were created based on bone type (iliac or pubic region) and presence or absence of cortical bone. Specimens were micro-computed tomography imaged to evaluate trabecular thickness, trabecular number, trabecular separation, bone volume density (BV/TV), BMD, and cortical thickness. Miniscrews 1.4 mm in diameter and 6 mm long were inserted into the bone blocks, and primary stability was evaluated by insertion torque (IT), mini-implant mobility (PTV), and pull-out strength (PS).


RESULTS
Intergroup comparison showed lower levels of primary stability when the BMD of trabecular bone was lower and in the absence of cortical bone (P≤.05). The Pearson correlation test showed correlation between trabecular number, trabecular thickness, BV/TV, trabecular BMD, total BMD, and IT, PTV, and PS. There was correlation between cortical thickness and IT and PS (P≤.05).


CONCLUSIONS
Cancellous bone plays an important role in primary stability of mini-implants in the presence or absence of cortical bone.
a  PhD Student, Department of Pedodontics and Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Mariana
M
Marquezan
Inayá
I
Lima
Ricardo Tadeu
RT
Lopes
Eduardo Franzotti
EF
Sant'Anna
Margareth Maria Gomes
MM
de Souza
D019412:Anatomy, Cross-Sectional / Q000379:methods; D000818:Animals; D015519:Bone Density / Q000502:physiology; D001863:Bone Screws; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000601:surgery; D002417:Cattle; D003799:Dental Stress Analysis / Q000295:instrumentation; D017886:Durapatite / Q000737:chemistry; D007085:Ilium / Q000601:surgery; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation; D009967:Orthodontic Appliances; D011630:Pubic Bone / Q000601:surgery; D013314:Stress, Mechanical; D019415:Torque; D055114:X-Ray Microtomography / Q000379:methods
D017886:Durapatite