THE BIOMECHANICAL COMPARISONS OF DIFFERENT PERIODONTAL CONDITIONS UNDER THE DIFFERENT EXTRACORONAL PRECISION ATTACHMENT RESTORATIONS FOR THE MANDIBULAR KENNEDY I DENTITION DEFECT

Abstract

Extracoronal precision attachment provides an available solution for complicated periodontal conditions in patients with dentistry defect. The mandibular Kennedy I dentition defect refers to the dentition defect at bilateral free-end molars. The bilateral nearby teeth are used as the abutment of extracoronal precision attachment to offer supporting forces. However, it is difficult to choose the quantities of abutments for patients with various periodontal conditions. The aim of this study is to suggest quantities of abutments based on stress distributions under various periodontal conditions for patients with mandibular Kennedy I dentition defect. Models were constructed from computed tomography, and they were assembled and analyzed in ANSYS. Seven models were used in our study based on different periodontal conditions and quantities of abutments (three models in healthy periodontal condition using single, double and triple abutment(s) restorations, two models with one absorbed abutment using double and triple abutments restorations and two models with two absorbed abutments using double and triple abutments restorations). The degree of absorbed abutments was 1/3. The mandible and other structures were considered as an orthotropic material and isotropic materials, respectively. Loads and boundary conditions corresponded to the realistic occlusion. Poor periodontal conditions enlarge the stress on abutments and surrounding structures. In addition, the increase in quantity of abutments causes the decrease and distribution of stress to differ. Different periodontal conditions require different quantities of abutments for recommendation in rehabilitation. The double abutments restoration is suitable for patients without absorbed abutment. The triple abutments restoration should be considered for patients with only one absorbed abutment. If more than two absorbed abutments exist, the extracoronal attachment denture restoration is not recommended for patients.