Long-Term stability of the correction of the unilateral posterior crossbite

The aim of this retrospective odontometric study was to evaluate the stability of orthodontically corrected<br>unilateral crossbite. This was done by comparing the long-term therapeutic results of patients treated either with rapid maxillary expansion (RME) or with slow expansion devices in the early (mean age: 7.2 years) or in the late mixed dentition (mean age: 9.9 years).<br>One hundred patients were selected from the files of the Department of Orthodontics, School of Dental<br>Medicine, Albert-Ludwig-University, Freiburg i.Br., Germany.<br>Patients’ selection was based on standardized conditions: Maxillary expansion had to be performed either with a removable expansion plate (n= 50), or with a rapid maxillary expansion technique (RME) using a tissue-borne, fixed, split acrylic appliance (n= 50). The slow expansion appliance (n= 50) was activated by 0.2 mm per week and the result was retained for 3 to 6 months after expansion had been achieved. The RME device (n= 50) was activated twice a day (0.4 mm) and the treatment result was retained for a minimum of 3 months.<br>All measurements were made on plaster casts made at the following timepoints:<br>(a) T1 = before treatment, (b) T2 = after posterior crossbite correction, (c) T3 = at the end of active orthodontic treatment, (d) T4 = ca. 2 years after the end of orthodontic treatment.<br>All recordings were performed by one examiner to the nearest of 0.1 mm, using a Boley gauge. Overjet,<br>overbite, midline deviation and the following cephalometric parameters were also registered: angle ANB, SNA, SNB for evaluation of the skeletal classification of the malocclusion, and the SN- MeGo angle and the SGo:<br>NMe % (percentage ratio between the posterior and anterior facial height) for determination of the patient’s growth pattern.<br>The statistical analysis of the data revealed the following relevant results:<br>- The observation periods were approximately 8 years for the early-treatment groups and 6.5 years for the late-treatment groups.<br>- 79% of the treated patients showed long-term stability of the corrected unilateral posterior crossbite.<br>This finding was independent of the patient’s age at the start of treatment and of the applied orthodontic<br>expansion device.<br>- 72% of the patients were successfully treated for the mandibular midline deviation.<br>- At the end of active treatment 50% of our cases showed a skeletal Class III craniofacial morphology.<br>- The mean change was 1.1 ± 2.8 mm in the maxillary interpremolar arch width and 2.3 ± 2.1 mm in the<br>intermolar arch width in the slow expansion groups. The RME groups showed a mean change of 3.6 ±<br>2.7 mm in interpremolar arch width and of 3.8 ± 2.7 mm in intermolar arch width; this was significantly<br>greater than in the comparison groups.<br>In subjects where the wider lower arch is a co-factor for the crossbite, the treatment approach should be focused on both arches and not only on the constricted upper arch. The mean mandibular arch width values of the relapsed cases in the present study were initially greater than those of the non-relapsed cases.

Author dc:creator

• Bartzela, Theodosia

Contributors dc:contributor

• Jonas, Irmtrud

• Stability posterior crossbite

Repository record source_url

https://freidok.uni-freiburg.de/data/1241

OAI identifier oai:identifier

oai:freidok.uni-freiburg.de:1241