The influence of Fränkel-2 Function Regulator in the lower anterior teeth crown length

Functional orthopedic appliances used for Class II malocclusion treatment, usually work by guiding jaws growth and modifying dental positions. Among these dentoalveolar effects, it is the lower incisors buccal tipping, that helps to improve the overjet, but may cause gingival recessions, especially when associated with other etiological factors. The objective of this study was to evaluate the clinical crown length of the lower anterior teeth in individuals with Angle's Class II malocclusion, after treatment with Fränkel-2 function regulator appliance (RF-2). Fifty Class II-malocclusion individuals were divided into 2 groups: G1 - 14 male, and 11 female, treated with the Fränkel-2 function regulator appliance for 18 months, with average pre-treatment age (T1) of 11 years (sd=7 months) and average post-treatment age (T2) of 12 years and 7 months (sd=7 months); and G2 - a control group with 25 individuals (12 male and 13 female) with average age at T1 of 10 years and 3 months (sd=11 months) and at T2 of 12 years and 1 month (sd=11 months), which was part of a normal occlusion sample. The 100 dental cast models were analyzed at T1 and T2, with a digital caliper, measuring the distance from the incisal edge to the most concave portion of the gingival margin of lower incisors and canines. Data were checked by a Student's t-test and a paired t-test. Considering T2, the group 1 presented a significant increase in the crown length of all lower anterior teeth. On the other hand, in the group 2, this was observed only for the teeth 33, 42 and 43, suggesting that patients treated with RF-2 had more gingival recession than the control group.