Clinical application effects of cast post and cores with traction design in coronal extrusion of upper anterior teeth with subgingival fracture

Objective To evaluate the clinical effects of cast post and cores with traction design in coronal extrusion of upper anterior teeth with subgingival fracture. Methods Twenty-five upper anterior teeth with subgingival fracture were treated by root canal therapy, then cast post and cores with traction design and composite resin crown restorations were made for orthodontic extrusion. Position retention and gingival margin modification were performed before crown restoration of these teeth. The correlation between extrusion length and extrusion time was evaluated, as well as the correlation between extrusion length and migration distance in coronal direction about the gingival margin. Crown-root ratio and post-root ratio below the alveolar crest was evaluated after the crown restorations were finished. Evaluation of restoration effects was carried out in 3, 6, 12 months follow-up period. Results Root resorption began to appear on one tooth at six weeks; the remaining 24 teeth were migrated to target position and prosthesis were finished. There was a positive correlation between the extrusion length (x) and extrusion time (y1), also between the extrusion length (x) and migration distance in coronal direction about the gingival margin (y2) by statistical analysis. There was no significant difference (P>0.05) between the extrusion teeth and compared teeth on crown-root ratio. More than 1/2 of the ratio between the length of post to the length of root below the alveolar crest. The prognostic stability was satisfied in 3, 6, 12 months follow-up period. Conclusion There are satisfactory clinical application effects of cast post and cores with traction design in coronal extrusion of upper anterior teeth with subgingival fracture.