The effect of type of restoration on the stress field developed in terminal abutments with severely reduced periodontal support and coronal structure.
BACKGROUND
Periodontally compromised teeth (PCT) that serve as terminal abutments (TAs) are often challenging depending on the post-and-core treatment, the type of partial fixed dental prosthesis (PFDP), and the periodontal support.


OBJECTIVE
The purpose of this study was to investigate the biomechanical impact of 3 types of PFDP supported by cast post-and-cores on PCT serving as terminal abutments.


METHODS
A 3-dimensional (3D) model of a human mandible was fabricated by using computed tomography (CT) images and parameterized in a computer-aided design (CAD) environment as follows: Right premolar preparation geometries were designed. The second premolar was assembled with 7-mm or 10-mm cast post-and-core models. Both premolar-models were designed to support single, splinted, or 1-unit cantilever splinted crowns. In each situation, their periodontium geometries were designed to be reduced by 10%, 50%, and 70%. All models were imported into a 3D finite element analysis (FEA) environment and loaded; von Mises stress values and distribution patterns were evaluated.


RESULTS
Insertion of the post primarily affected the apical areas of both the root and post; the type of PFDP and periodontal support mainly affected stress distribution. In patients with a normal periodontium, splinting the teeth did not contribute to their stress relief. By extending the post length, a stressful area close to the apex of the post was developed. Splinting mitigated the stress field of the coronal part of the 50% PCT (up to 98.9%); the 30% PCT experienced a substantial decrease (up to 215.9%) in stress in the radical part as well. The increase in the length of the post produced negligible stress-related differences in the apical part of the 50% PCT (0.2% to 2.6%). The use of the 7-mm post effectively relieved the radical part of the splinted 30% PCT. The magnitude of the stress on the radical part of post-restored PCT was considerably increased in the presence of a cantilever.


CONCLUSIONS
Splinted crowns supported by a 7-mm cast post-and-core are a favorable biomechanical approach for the restoration of PCT with severe loss of coronal structure. The use of a cantilever greatly aggravates the biomechanical response, especially of post-restored PCT.
Graduate student, Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Ioanna
I
Stasinopoulou
Marianthi
M
Manda
Christos
C
Galanis
Petros
P
Koidis
D000539:Alveolar Process / Q000503:physiopathology; D001641:Bicuspid / Q000503:physiopathology; D001696:Biomechanical Phenomena; D001732:Bite Force; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003804:Dentin / Q000503:physiopathology; D003779:Denture Design; D003830:Denture, Partial, Fixed; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000033:anatomy & histology; D008422:Materials Testing; D008953:Models, Anatomic; D008954:Models, Biological; D010510:Periodontal Diseases / Q000503:physiopathology*; D011176:Post and Core Technique / Q000295:instrumentation; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods; D019227:Tooth Apex / Q000503:physiopathology; D014092:Tooth Root / Q000503:physiopathology