Influence of occlusal contact and cusp inclination on the biomechanical character of a maxillary premolar: a finite element analysis.
BACKGROUND
Restoring teeth with large amounts of dentin loss is challenging, especially for posterior teeth with high cusps. However, strategies for reducing the lateral forces are based on clinical experience instead of than scientific evidence.


OBJECTIVE
The purpose of this study was to analyze the biomechanical characteristics of maxillary premolars with different ferrule configurations and to investigate the influence of occlusal contact and cusp inclination on stress distribution with the finite element method.


METHODS
Five numerical casts of a maxillary premolar were generated; each adopted 1 of the 5 coronal dentin configurations: i (access cavity with 4-mm dentin height) and ii to v (2-mm complete ferrule, 2-mm facial ferrule, 2-mm palatal ferrule, 2-mm proximal ferrule, and restored with a post and core, respectively). Both gold-alloy and glass-fiber posts were modeled. An oblique load of 200 N was applied to the top, middle, and bottom of the 45-degree facial cusps. The cusp inclination was remodeled to 60 degrees, followed by the application of a 200-N load to the top. The values of the maximum principal stress and von Mises stress were calculated to assess overload risk.


RESULTS
When the top of 45-degree facial cusps was loaded, the maximum local stress concentration on dentin was found in teeth with a facial ferrule and restored with a gold-alloy post. When the middle of 45-degree facial cusps were loaded, the principal stresses of teeth with a complete ferrule, palatal ferrule, and proximal ferrule were similar to those of the access cavity teeth. In contrast, the principal stress of a tooth with a facial ferrule was close to that of the access cavity tooth after remodeling the facial inclination to 60 degrees.


CONCLUSIONS
Maxillary premolars with only facial dentin remaining show higher local stress on root dentin. Altering the loading position and reducing the facial cusp inclination can reduce local stresses.
Doctoral student, Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Shiming
S
Liu
Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China. Electronic address: lyhdentist@163.com.
Yuhua
Y
Liu
Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Jun
J
Xu
Professor, Department of Mechanical Engineering, Peking University, Beijing, China.
Qiguo
Q
Rong
Associate Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Shaoxia
S
Pan
D001641:Bicuspid / Q000033:anatomy & histology* / Q000502:physiology; D001696:Biomechanical Phenomena; D001732:Bite Force; D003198:Computer Simulation; D017267:Dental Prosthesis Design; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000502:physiology; D003804:Dentin / Q000033:anatomy & histology* / Q000502:physiology; D020342:Finite Element Analysis; D005898:Glass / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008422:Materials Testing; D008437:Maxilla; D008954:Models, Biological; D011176:Post and Core Technique / Q000295:instrumentation; D013314:Stress, Mechanical; D019228:Tooth Crown / Q000033:anatomy & histology; D019231:Tooth Preparation, Prosthodontic / Q000295:instrumentation / Q000379:methods*; D019553:Tooth, Nonvital / Q000473:pathology* / Q000503:physiopathology
D006047:Gold Alloys; C009753:fiberglass