Fra¨nkel appliance therapy: Orthopedic or orthodontic?

Abstract

The purpose of this article is to evaluate (1) the difference in mandibular growth response of Class II corrected malocclusions compared to Class I corrected malocclusions treated with Fra¨nkel therapy; (2) the influence of a functional orthopedic appliance (Fra¨nkel) on the growing facial complex compared to an untreated sample; (3) difference in Fra¨nkel therapy and edgewise therapy with extraoral traction; (4) individual variations in growth and response to orthodontic therapy; (5) currently proposed diagnostic criteria in the treatment of Class II malocclusions; (6) the capability of Fra¨nkel therapy to elicit differential growth response according to the skeletal deficiencies of the beginning malocclusion. Nine Class I and eleven Class II patients were treated with the Fra¨nkel appliance. Orthopedic and orthodontic changes were evaluated cephalometrically. Orthopedic and orthodontic changes of the Fra¨nkel samples were then compared to an untreated control sample (30 females and 32 males; mean age, 10 years 2 months; mean time lapse, 2 years 5 months; 50 Class I, 12 Class II) and an edgewise-treated sample (32 females and 18 males; mean age, 12 years 1 month; mean time lapse, 2 years 5 months; 25 Class I, 25 Class II). No subjects in any of the groups had teeth removed. Cephalometric measurements were made on a “diagnostic control patient” (dcp) in which the mandible was postured forward approximately 5 mm. to determine whether this total mandibular orthopedic correction of the Class II malocclusion was achieved with Fra¨nkel therapy. Frequency tables depicting individual variations in growth and response to orthodontic therapy were compared to each other and to their averaged values. Individual growth responses were not predictable. On the average, there was a statistically significant difference in response of the Class I and Class II malocclusions in the Fra¨nkel groups to the therapy. The Class II occlusion was corrected to a Class I occlusion, resulting in comparable Class I occlusions after Fra¨nkel therapy. There were no significant differences in orthopedic changes between the Class II group treated with 3 to 4 mm. hyperpropulsion of the mandible compared to the Class I group treated with minimal hyperpropulsion of the mandible. The significant differences were orthodontic. Compared to the untreated control sample, the combined Fra¨nkel groups had a significant (1) increase in mandibular length of 1.1 mm. as a result of an increased backward direction of condylar growth; (2) increase in lower face height; (3) decrease in forward growth of the maxilla; (4) retraction and elongation of maxillary incisors; (5) retraction of maxillary molars; (6) protraction of mandibular incisors; and (7) increased vertical height of mandibular molars. Significant differences of edgewise therapy compared to Fra¨nkel therapy were (1) edgewise therapy had a greater retractive influence on the maxilla; (2) edgewise therapy also produced a similar backward direction of condylar growth but 1.2 mm. less than the Class II Fra¨nkel group; (3) maxillary incisors were retracted more with no elongation; (4) mandibular incisors were retracted rather than protracted; (5) pogonion came forward 1 mm. less than in the Fra¨nkel group. The Class II Fra¨nkel sample did not approach the diagnostic control goal, and averages do not begin to describe the majority of individual changes. Pretreatment measurements of point A and pogonion to the nasion perpendicular plane were not effective diagnostic criteria for differentiating between the Class I and Class II malocclusions in this sample. Pretreatment anteroposterior position of the maxilla or mandible did not appear to have a bearing on the response to Fra¨nkel therapy. In this sample, the additional hyperpropulsion of the mandible in the Class II cases did not elicit more of a mandibular growth response than the Class I sample. However, on the average, both Fra¨nkel samples had approximately 1 mm. more mandibular growth than the untreated sample. This increase in mandibular growth resulted in a longer face, not a more prognathic mandible.