Abstract: BACKGROUND: The factors that affect the effect of fractured crown reattachment include the preservation of fractured crown, adhesive resin and retention form, etc. There is no comprehensive study on the effect of retention form and elastic modulus of resin on fractured crown reattachment stress. 
OBJECTIVE: To study the effect of different retention forms and resins on the central incisor reattachment by three-dimensional finite element analysis.
METHODS: Based on CT scan data, Mimics software and Geomagic software were used to generate 3D digital model of anterior teeth. SolidWorks software was used to establish four types of retention forms, including direct reattachment, internal dentin groove, overcontour and internal groove. Five types of resins were used to generate 20 ANSYS finite element models. The adhesive shear force, shear stress and resin equivalent stress, and the first principal stress were selected as evaluation indicators through material mechanics analysis.  
RESULTS AND CONCLUSION: (1) The shear stress distributions of the direct reconnection and the lip-covering retention were similar, and the shear stress peaks were distributed at the junction of dentin and enamel, and concentrated on the left and right sides. The shear stress peak distribution of the dentin internal groove retention was on the left and right sides of the junction between the dentin groove and the section. The shear stress peaks of the internal groove retention form were distributed on the left and right sides of the junction between the groove and the section. (2) The equivalent stress peaks of resin Von Mises of various retention forms were distributed equally in the middle part of the lingual side. The lip surface covering the retention form was filled with resin with less stress, and the farther away from the cross-section, the less stress. (3) The first principal stress peaks of various retention forms were at the boundary of the dentin and enamel where the resin bore greater tensile stress here, and the resin bore greater compressive stress on the lingual side. (4) The retention form had a great influence on the shear force and shear stress of the adhesive, and the elastic modulus only affected the shear stress of adhesive. The retention form had a great influence on the Von Mises stress peak and the first principal stress peak of the resin, and the elastic modulus only affects the first principal stress of the resin. (5) The evaluation indexes of the dentin internal groove retention form are the best, so it is recommended to use the dentin internal groove retention form in clinical practice.

Key words: incisor reattachment, finite element, shear force, stress, retention form, resin, adhesive, oral biomaterial