Clinical relevance of step-by-step mandibular advancement in the treatment of mandibular retrusion using the Fränkel appliance.

The effect of the Fränkel appliance was evaluated in patients with mandibular retrusion who were monitored during an active treatment phase of approximately 14 months in the early mixed dentition. The sample treated with the Fränkel appliance consisted of 120 subjects. In 60, the initial construction bite was taken with the incisors in an end-to-end relationship (Fränkel group A). In 60 patients (Fränkel group B), mandibular position was advanced sequentially in small steps. Fifty untreated subjects of approximately the same age and with almost identical characteristics of skeletal Class II malocclusion served as a comparison group. Permanent teeth were not extracted during the period studied in any of the subjects. For statistical analysis of the difference between the variables used in this study, analysis of variance and the t test were used. The results of this study indicate that the distances between pogonion and condylion or articulare increased in both Fränkel groups A and B significantly more than in the untreated sample. However, the anteroposterior position of pogonion relative to the maxillary landmarks remained unchanged in Fränkel group A. The increase in the distance between pogonion and articulare or condylion primarily resulted from a positional change of pogonion inferiorly, which was accompanied by a significant increase of the mandibular plane angle and the gonial angle. In contrast, pogonion moved anteriorly in Fränkel group B significantly more than in the untreated group, that is, the sagittal discrepancy between maxilla and mandible significantly improved in Fränkel group B, whereas it remained unchanged in Fränkel group A.(ABSTRACT TRUNCATED AT 250 WORDS)