Abstract
To evaluate torque loss a week after insertion, both in an in vivo and an in vitro experimental setup were designed. In the in vivo setup a total of 29 miniscrews were placed in 20 patients who underwent orthodontic treatment. Maximum insertion torque (MIT) was evaluated at insertion time (T1). A week later, insertion torque was measured again by applying a quarter turn (T2); no load was applied on the screw during the first week. In the in vitro setup a total of 20 miniscrews were placed in pig rib bone samples. MIT was evaluated at insertion time (T1). Bone samples were kept in saline solution and controlled environment for a week during which the solution was refreshed every day. Afterwards, torque was measured again by applying a quarter turn (T2). The comparison of MIT over time was done calculating the percentage difference of the torque values between pre- and post-treatment and using the parametric two independent samples t-test or the non-parametric Mann–Whitney test. After a week unloaded miniscrews showed a mean loss of rotational torque of 36.3% and 40.9% in in vitro and in in vivo conditions, respectively. No statistical differences were found between the two different setups. Torque loss was observed after the first week in both study models; in vitro experimental setup provided a reliable study model for studying torque variation during the first week after insertion.
Highlights
In the in vivo setup a total of 29 miniscrews were placed in 20 patients who underwent orthodontic treatment
Maximum insertion torque (MIT) was evaluated at insertion time (T1)
Most of orthodontic treatment plans require some form of anchorage
Summary
Most of orthodontic treatment plans require some form of anchorage. A variety of intra-and extra-oral appliances are used for this purpose, but these treatment mechanics cannot always guarantee “absolute” anchorage and outcomes frequently depend on the collaboration of patients. Different approaches exist to obtain measurements of miniscrew connection with the bone, among these maximum insertion torque (MIT), resonance frequency analysis (RFA), and maximal removal torque (MRT) [8 - 10]. Stability is compromised during the first week after implant insertion [11] as a result of active bone remodeling in the peri-implant tissues. This process is identical to the normal wound healing phases of bone and includes necrosis of the traumatized area and subsequent bone reabsorption. Osteogenesis begins within the first week following implant insertion
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