Mastering molar mesialization: the role of attachment designs and tipping compensation in clear aligner therapy—a finite element analysis

INTRODUCTION: To investigate the effects of attachment design and compensation angulation on long-distance molar mesialization in clear aligner therapy (CAT). METHODS: The study used a dental model from an adult volunteer with missing first molar (M1), wherein the second and third molars (M2 and M3) required mesialization. Three attachment designs-horizontal rectangular (HA), single 45°(SA), and double 45°(DA)-were applied to the buccal surface of M2 to assess their influence on movement efficiency. Subsequently, distal tipping overcorrection angles of 0°, 0.5°, 1° and 1.5°were applied to M2 to assess their effect on tipping control. Finite element analysis (FEA) was performed to analyze displacement patterns and stress distribution. RESULTS: Mesial tipping and transverse crown rotation of the M2 constituted the primary adverse outcomes during molar mesialization. The attachments effectively mitigated these undesirable movements, with the DA design demonstrating the highest efficacy, followed by the SA. For the SA design, a 1.5° distal compensation angle was required to may facilitate near-bodily movement. In contrast, the DA design may facilitate, near-bodily movement with only a 1° compensation angle. CONCLUSION: Long-distance molar mesialization primarily results in the adverse effects of mesial tipping and transverse crown rotation in CAT. While attachments can mitigate these adverse effects, applying appropriate angular compensation is more effective in promoting bodily movement of the molars.