RESUMO
Objective To investigate the stress in the periodontal tissues using three-dimansional finite element method when Richtts Arch was used.Methods Three-dimensional finite element models of the lower left central incisor and first molar were set up by means of CT.Stress distribution in root,PDL and alveolar bone,and the tendency of the tooth movement were obtained by calculation under Richtts Arch.Results The value of the force at the left lower incisor was -0.34 Newton and the value of the force at the left lower molar was 0.65 Newton.The molar model revealed that the tensile stress concentration was at the mesial root cervix and the compressive stress was at the distal root cervix.The incisor model showed that the tensile stress was concentrated at the lingual cervix and the compressive stress was concentrated at the apical tip.The arch wire exerted intruding force,lingual force and the incisor tended to lingual movement and intruding movement.The molar had the tendency of lingual movement and distal tipping movement.Conclusion The anchorage molar will incline mesially when Richtts Arch is used in treatment of deep overbite,the additional torque must be used in the anchorage molar.