Comparison of effects of two distalization appliances on maxillary permanent first molar: A finite element study

Background: In clinical contemporary orthodontics, various treatment options are available for correction of Angle’s Class II molar relation. Distalization of the maxillary molar is one of the common approaches for nonextraction treatments of the same. Aim: The aim of this study was to test the effects of two different pendulum springs on the permanent maxillary first molars with the help of a finite element analysis. Materials and Methods: A three-dimensional analytical model of the permanent maxillary first molar was developed from a sequential computed tomography scan based on Wheeler’s dimensions. Forces and moments generated during the distalization of the maxillary first molar with the conventional pendulum spring and the modified pendulum spring were analyzed with the help of finite element analysis. Results: The conventional pendulum (Hilger’s) spring produced a distalizing force of 274 g, and the modified pendulum spring (Scuzzo’s) produced a force of 271 g. A high-stress concentration was seen on the cervical level of the distal surface of the palatal root, Hilgers’ pendulum spring (0.0824 kg/mm²), and M-pendulum spring (0.0823 kg/mm 2 ). High stress was seen on the palatal root (0.0541/0.0539 kg/mm²), followed by the mesiobuccal root (0.0212/0.0208 kg/mm²) and distobuccal root (0.0293/0.0288 kg/mm²). Conclusion: M-pendulum spring effects a lesser force and moment, and a relatively more translatory distalization of the molar as compared to Hilgers’ conventional spring.