Arm design of band and loop space maintainer affects its longevity: a patient-specific finite element study

Fixed space maintainers (FSMs) are commonly utilized in pediatric dentistry to prevent space loss following premature tooth extraction. Although previous studies have examined the survival rates and causes of FSM failure, the impact of arm design on failure has not been investigated. This study aimed to investigate the tensile and compressive stresses related to FSMs with different arm designs and evaluate the effect of arm designs on FSM failure. Cone beam computed tomography images of a child who experienced premature loss of a primary mandibular left second molar tooth were retrieved from our database, then processed and simulated using the Rhinoceros software. Finite element analysis was performed to evaluate the stresses on four distinct FSM arm designs under simulated chewing forces. The results showed that the straight-arm FSM design exhibited the highest von Mises principal stress, while FSMs with curved arms and surrounding primary mandibular left first molar in the mesial area demonstrated the lowest von Mises stress accumulation. Intense stress accumulation on the distal surface of tooth 74 was observed in the test models due to the transmitted forces by the FSM. The maximum principal stresses accumulated at the base of the alveolar socket of the mesial root of tooth 36, while the minimum principal stresses were identified at the mesio-marginal area of the alveolar crest. The arm design played a crucial role in enabling the appliance to effectively withstand the stresses accumulating on the Space maintainer (SM) and orthodontic band. Bending the SM arms to match the surrounding profile with curvature increased the stress absorption capacity by increasing the arm length.