Anchorage value of surgical titanium screws in orthodontic tooth movement

Influence of Insertion Site on the Failure Rates of Orthodontic Miniscrews

“…The 18.4% failure rate we report in this study falls within the range of many other studies [5,8,12,[15][16][17]. No definitive effect has been identified to date between the insertion site and final outcomes.…”

“…We also attempted to insert down to at least 5 mm, however our results seem to indicate that, with miniscrews in the palatal maxilla, either greater insertion depths are necessary, or we somehow failed to achieve the desired minimum insertion depth of 5 mm in every patient. Higher failure rates in the palatal maxilla have been reported [1,8]. As in animal studies, the palatal mucosa's thickness and concomitant long lever arm were suspected as having caused overloading of the bone and a subsequent screw loosening [1,2].…”

“…On the other hand, permanent tongue load may be a factor behind the high failure rate of palatally-inserted miniscrews, a risk factor already described [14], and other authors report a failure rate of 22% for miniscrews inserted in the palatal maxilla [8], although they also suspected influence by tongue pressure. Permanent tongue pressure may be the cause of premature screw loosening due to less osseous support, especially when shorter miniscrews are used.…”

“…Die in der vorliegenden Studie ermittelte Misserfolgsrate von 18,4% liegt im Bereich zahlreicher anderer Untersuchungen [5,8,12,[15][16][17]. Ein möglicher Einfluss des Insertionsortes auf die Ergebnisse konnte bislang noch nicht eindeutig geklärt werden.…”

Optimal force magnitude loaded to orthodontic microimplants: A finite element analysis

“…Liou et al 7 found significant screw displacement after applying immediate forces of 400 g. Others found displacement to occur at even lower force levels. 8,9 Wang et al 10 found that screw displacement was not correlated with force magnitudes of 200 g to 425 g and that beyond this range, other consequences might ensue. When an excessive load is applied, partly osseointegrated microimplants can become extremely mobile and eventually fail.…”