Altering the Angle of Attachment for Fixed Functional Appliances to Control Lower Incisor Proclination - An...

The management of Class II malocclusion is challenging in growing patients, where the objective is to modulate skeletal growth rather than dentoalveolar correction only. Fixed functional appliances (FFA) have become a cornerstone in treating Class II malocclusions, offering an efficient alternative for mandibular advancement in non-compliant patients. However, one side effect of FFA is the proclination of lower incisors, which may require careful management through biomechanical control.

The present study analysed the impact of altering the angle of FFA attachment on proclination of lower incisors, using mathematical modelling and clinical outcomes from two orthodontically treated cases. The FFA was placed from the maxillary first molar tube to the lower archwire, distal to the mandibular first premolar in a short attachment and distal to the mandibular canine in a long attachment case.

The mathematical evaluation of the force vectors with long and short attachments of FFA revealed that the short attachment delivered 6 g less horizontal force and 20 g more intrusive force, along with six times more moment, in comparison to the long attachment. The clinical outcomes of the orthodontically treated cases indicated proclination of the lower incisors in both cases.

Altering the angle of attachment altered the vector of forces applied to the lower incisors, leading to a more intrusive force in the case of short-attachment FFA. However, future research with a larger, controlled sample is required to establish the extent and nature of the impact.