Clarifying the mechanism of effect of the Bionator for treatment of maxillary protrusion: A percentile growth study

Authors:

ABSTRACT

Aim

The reported effects of Bionator treatment in patients with mandibular retrognathism are conflicting. This study
evaluated the changes in craniofacial morphology resulting from treatment with a Bionator, based on measurement percentiles
previously reported, to clarify the mechanism of the effect of this commonly used functional device.

Methods

Study Design: Retrospective. Setting: A private orthodontic clinic. Participants: Forty-two children (mean age, 10.13 years) requiring
treatment with a Bionator for Class II malocclusion (mandibular retrognathism). Children were randomly assigned to a Bionator group
with or without an expansion screw. Measurements on lateral cephalometric radiographs were taken before and upon completion of
Bionator treatment. All parameters measured were characterised according to the measurement percentiles previously reported. Each
parameter was compared before and after treatment for all patients and for each treatment group using Wilcoxon's test.

Results

No
significant differences in cranial length or mandibular body length were seen in any of the 3 groups, but anterior cranial base length and
maxillary length were significantly decreased while mandibular ramus height and mandibular length were significantly increased after
treatment in the Bionator with expansion screw group and in the all-patient group. CONCLUSIONS: The findings suggest that treatment
with a Bionator with expansion screw during the growth and development stage results in increased mandible length and ramus height
and inhibits the growth of the maxilla and anterior cranial base bone.

PLUMX METRICS