Abstract:

Objective To investigate the effect of different conditions of the second molar on maxillary molardistalization through Modified C Palatal Plate(MCPP)and its biomechanical mechanism using three-dimensional finite element analysis. Methods Three groups of three-dimensional FE models of maxillary molardistalization with MCPP were established. Model 1(M1): The second molar erupted, with the archwire inserted into the buccal tube;Model 2(M2): The second molar erupted without buccal tube;Model 3(M3): The second molar did not erupt. In M1, 1.5 N traction forces were applied between the MCPP notches which were 1 mm(F1), 4 mm(F4), and 7 mm(F7)above the alveolar crest ridge and the palatal arch hooks respectively to find out the force direction that could distally move the first molar bodily. Then the same force was applied on M2 and M3 to observe the movement of tooth. Results The first molar moved distally in M1 and had a bodily movement in the M1-F4. Compared with M1, the distal displacement of the first molar slightly increased in M2, but there was more significant buccal displacement and mesial-in rotation. The second molar had more distal inclination, less buccal movement and mesial-out rotation of the crown. The first molar movement in M2 was similar with M3. Conclusion Bringing the second molar into archwire will decrease the buccal displacement and rotation of the first molar. The eruption of the second molar has no significant effect on the lateral movement of the first molar.

Key words: three dimensional finite element analysis, modified C-palatal plate, second molar, biomechanical mechanism