Post-treatment changes in permanent retention  

Abstract

OBJECTIVES While permanent retention is today the method of choice to stabilize orthodontic treatment outcomes, recent studies have increasingly reported posttreatment changes in tooth position during permanent retention. We conducted this study to analyze changes in the anterior mandible, whether the changes follow an underlying movement pattern, and, aiming for a preventive strategy, whether any risk factors could be identified comparing findings with the pretreatment situations. METH-ODS We included 30 patients who had worn fixed Twistflex retainers (UK 3-3) extending from canine to canine in the mandible. Casts reflecting the intraoral situations before orthodontic treatment (T0), directly after completion of active therapy (T1), and 6 months later (T2) were scanned and superimposed using Imageware Surfacer software. Posttreatment changes (T2-T1) of tooth position within the retainer block were analyzed on 3D virtual models and were compared to pretreatment (T0) and treatment-related (T1-T0) findings to identify potential risk factors. RESULTS Almost all analyzed patients revealed three-dimensional changes in tooth position within the retainer block. Comparing these movements, we repeatedly found rotated retainer blocks in labio-oral direction, while the center of rotation was located at the first incisors. This pattern was associated with intercanine expansion and excessive overjet correction during orthodontic treatment. The canines underwent the most pronounced (rotational and translational) movements. CONCLUSIONS In general permanent lingual retainers are safe but in special clinical cases retainers can induce undesired tooth movement. Risk factors seem to be intercanine expansion and excessive overjet correction during orthodontic treatment. In specific cases an additional retention device might be needed. AbstractObjectives. While permanent retention is today frequently the method of choice to stabilize orthodontic treatment outcomes, recent studies have increasingly reported posttreatment changes in tooth position during permanent retention. We conducted this study to analyze such changes in the anterior mandible, whether these follow an underlying movement pattern, and, aiming for a preventive strategy, whether any risk factors could be identified by comparing findings to the pretreatment situations. Methods.We included 30 patients who had worn a fixed Twistflex retainer extending from canine to canine in the mandible. Casts reflecting the intraoral situations before orthodontic treatment (T0), directly upon completion of active therapy (T1), and 6 months into retention (T2) were scanned and superposed using Imageware Surfacer software. Posttreatment changes (T2−T1) in tooth position inside the retainer block were analyzed on 3D virtual models and were compared to pretreatment (T0) and treatment-related (T1−T0) findings to identify potential risk factors.Results. Almost all patients revealed three-dimensional changes in tooth position within the retainer block. On comparing these movements...

Retention und digitale Entwicklung

“…Wird bei ausgeprägten Platzdefiziten eine forcierte Erweiterung des Zahnbogens angestrebt, kann dies ein Stabilitätsrisiko für die kieferorthopädische Behandlung darstellen [11]. So sollte -unter Abwägung der therapeutischen Ziele -bei einem Missverhältnis zwischen Zahn-und Kiefergröße eine Extraktionsmaßnahme aus Stabilitätsgründen in Erwägung gezogen werden.…”

“…Die genaue Ätiologie scheint hier noch nicht abschließend geklärt zu sein, jedoch wird als mögliche Ursache u. a. ein nicht passives Einbringen des Retainerdrahtes aufgeführt [30]. Eigene Daten konnten zeigen, dass Zahnbewegungen während einer festsitzenden Retention vermehrt auftraten, wenn vorweg therapeutisch eine Vergrößerung der interkaninen Distanz im Unterkiefer und eine ausgeprägte Reduktion des Overjets stattgefunden hatte [11]. In solchen Fällen wird es als empfehlenswert angesehen, den festsitzenden Retainer mit einer herausnehmbaren Apparatur zu kombinieren.…”

3D-analysis of unwanted tooth movements despite bonded orthodontic retainers: a pilot study

“…However, unexpected tooth movements despite intact bonded retainers may occur [ 11 , 15 – 24 ]. Some articles on this subject are however case reports or small case series; thus, information regarding the incidence of such side effects is rare and ranges between 1.1 and 43.3% of the patients [ 11 , 16 , 19 ]. In some questionnaire-based survey studies, unwanted side effects were reported by 56.7 to 100% of respondent orthodontists, however only a small number of patients were involved [ 4 , 5 , 7 ].…”

“…Different patterns of unwanted tooth movements have been described: torque differences between two adjacent incisors, opposite torque of canines, and increased buccal or lingual inclination of single canines [ 11 , 16 , 19 , 22 , 23 ]. These movements are classified as newly developed posttreatment malocclusion rather than relapse, because they show no similarities to the pretreatment malocclusion [ 11 , 16 , 22 ].…”

“…Such movements are attributed to an activation/distortion of the retainer wire, with the underlying mechanisms being yet unknown. Until now, only two studies have investigated this subject systematically for the lower jaw [ 19 , 22 ]. Kucera and Marek [ 22 ] screened a total of 3500 patients at their annual retention recall and reported that 1.1% of them were affected by unwanted tooth movements.…”