Early treatment of posterior crossbite--a randomised clinical trial

Abstract

Background: The aim of this randomised clinical trial was to assess the effect of early orthodontic treatment in contrast to normal growth effects for functional unilateral posterior crossbite in the late deciduous and early mixed dentition by means of three-dimensional digital model analysis.

Methods: This randomised clinical trial was assessed to analyse the orthodontic treatment effects for patients with functional unilateral posterior crossbite in the late deciduous and early mixed dentition using a two-step procedure: initial maxillary expansion followed by a U-bow activator therapy. In the treatment group 31 patients and in the control group 35 patients with a mean age of 7.3 years (SD 2.1) were monitored. The time between the initial assessment (T1) and the follow-up (T2) was one year. The orthodontic analysis was done by a three-dimensional digital model analysis. Using the 'Digimodel' software, the orthodontic measurements in the maxilla and mandible and for the midline deviation, the overjet and overbite were recorded.

Results: Significant differences between the control and the therapy group at T2 were detected for the anterior, median and posterior transversal dimensions of the maxilla, the palatal depth, the palatal base arch length, the maxillary arch length and inclination, the midline deviation, the overjet and the overbite.

Conclusions: Orthodontic treatment of a functional unilateral posterior crossbite with a bonded maxillary expansion device followed by U-bow activator therapy in the late deciduous and early mixed dentition is an effective therapeutic method, as evidenced by the results of this RCT. It leads to three-dimensional therapeutically induced maxillary growth effects. Dental occlusion is significantly improved, and the prognosis for normal craniofacial growth is enhanced.

Trial registration: Registration trial DRKS00003497 on DRKS.

Figure 1

Workflow.

Figure 2

Bonded maxillary expansion. Palatal expansion appliance used for slow expansion of the maxillary bones, bonded onto the posterior teeth.

Figure 3

U-bow activator. U-bow activator Type 1, as described by Karwetzky, used to achieve midline coordination and retain palatal expansion. (a) Outer view, (b) inner view.

Figure 4

Maxillary transversal measurements. For the analysis of the intercanine, anterior, middle and posterior transversal widths, all measurements were performed by projection on the occlusal plane. For the intercanine width, the canine cuspids, the first and second deciduous molars, and the six-year molars, the deepest points of the fossae were taken as reference points.

Figure 5

Maxillary arch length and inclination. The length of the perpendicular reference line between the tuber plane and the maxillary incisors was defined as the sagittal arch length. The angle that spans between the right and left connecting lines was defined as the arch inclination.

Figure 6

Transversal palatal base arch length. Based on the three-dimensional digital model mesh, the anterior, middle and posterior transversal palatal base arch lengths were measured. Reference points were the middle palatal dentogingival transitions of the right and left sides for both the first and second deciduous molars and, if present, for the first permanent molars.

Figure 7

Palatal depth. Palatal depth was measured for the first and second deciduous molars perpendicularly to the occlusal plane in the median raphe. Due to the reference point differences between T1 and T2 caused by possible vertical growth of the first permanent molars, no measurement was performed.

Figure 8

Mandibular transversal measurements. The mandibular intercanine distance was measured between the right and left canines. The mandibular anterior transversal width was defined as the distance between the approximal contact points of the mandibular first and second deciduous molars. For the middle and posterior transversal widths, the distance between the distobuccal cusps was registered.

Figure 9

Midline deviation. The midline deviation was measured in the frontal plane between the upper and lower midlines on the occlusal plane.

Figure 10

Overbite and overjet. The vertical overbite was measured between the edge of the uppermost vertically erupted middle incisor and the corresponding incisal edge of the opposite mandibular tooth perpendicular to the occlusal plane. The sagittal overjet was measured between the most anterior point of the maxillary central incisors and the corresponding reference point on the mandibular incisor.