Stability changes of miniscrew implants over time

Abstract

Purpose: To quantify in vivo changes in miniscrew implant (MSI) stability over time using resonance frequency analysis, and to determine if pilot holes and placement sites affect changes in MSI stability. Materials and Methods: Twenty-two self-tapping MSIs (1.6 mm wide and 9 mm long) were placed in the maxillae of 2 adult beagle dogs (20 months old). The Osstell Mentor was used to measure the implant stability quotient (ISQ) weekly for 8 weeks. A split-mouth design was used to evaluate the effects of 1.1-mm wide, 3-mm deep pilot holes. Results: The MSIs that failed showed significantly (P , .05) greater decreases in ISQ values during the first 3 weeks than the MSIs that remained stable. All of the MSIs that failed (41%) had been placed in nonkeratinized tissue. MSIs that remained stable throughout the study also showed significant decreases in ISQ values during the first 3 weeks, followed by increases during the fourth and fifth weeks. Changes in ISQ values of MSIs inserted into bone with and without pilot holes were comparable (P . .05). Conclusion: Stability of unloaded MSIs decreased during the first 3 weeks and increased thereafter. Although the effects of pilot holes on stability could not be confirmed, placement of MSIs into nonkeratinized tissue negatively affected their stability and increased the likelihood of failures. (Angle Orthod. 2011;81:994-1000.)

Mini-implant stability at the initial healing period: A clinical pilot study

“…They investigated a subsequent increase of ISQ values. A similar result was found by Ure et al 15 for mini-implants in an animal study.…”

“…Since there were no respective data obtained from humans available, sample size calculation in this prospective study was based on the results of an animal study with a similar design. 15 Even though four patients dropped out of the study, there was still a sufficient number of patients (19 patients) who could be examined during the healing period. The choice of statistical methods was based on a test for normal distribution for small sample sizes.…”

“…Due to the fact that of this study there was no publication available investigating the stability changes of mini-implants in humans, we had to resort to data obtained from a study on stability changes in beagle dogs. 15 In this pilot study, modified mini-implants were used to allow RFA using SmartPegs. The changes found in ISQ values and standard deviations over a 3-week period after insertion through keratinized tissue were chosen as a basis for sample size calculation for this study.…”

Primary failure rate for 1680 extra-alveolar mandibular buccal shelf mini-screws placed in movable mucosa or attached gingiva

“…[26][27][28] Failure is common in the posterior mandible, typically occurring in the first few weeks, so primary stability is the critical factor for clinical success. [29][30][31] Attempts to improve primary stability include smaller diameter pilot holes, 23 sites with increased cortical bone thickness and density, [29][30][31][32] and a self-drilling protocol. 33,34 Bone quality is particularly important for orthodontic miniscrews because they are retained by mechanical locking rather than osseointegration.…”

Histomorphometric evaluation of the bone surrounding orthodontic miniscrews according to their adjacent root proximity

“…Orthodontic miniscrews achieve partial osseointegration from 3 weeks after insertion; this increases the removal difficulty 2. Furthermore, it was reported that there was no significant difference in miniscrew stability between immediate loading with a 250 g load and delayed loading,1415 although some researchers have recommended delayed loading (from 3 weeks to 3 months) 1617. Accordingly, we intended to determine how the amount of bone surrounding an orthodontic miniscrew changes as the miniscrew approaches their adjacent tooth root, with mild orthodontic force load.…”