Residual thermal stress simulation in three-dimensional molar crown systems: a finite element analysis.
OBJECTIVE
To simulate coefficient of thermal expansion (CTE)-generated stress fields in monolithic metal and ceramic crowns, and CTE mismatch stresses between metal, alumina, or zirconia cores and veneer layered crowns when cooled from high temperature processing.


METHODS
A 3D computer-aided design model of a mandibular first molar crown was generated. Tooth preparation comprised reduction of proximal walls by 1.5 mm and of occlusal surfaces by 2.0 mm. Crown systems were monolithic (all-porcelain, alumina, metal, or zirconia) or subdivided into a core (metallic, zirconia, or alumina) and a porcelain veneer layer. The model was thermally loaded from 900°C to 25°C. A finite element mesh of three nodes per edge and a first/last node interval ratio of 1 was used, resulting in approximately 60,000 elements for both solids. Regions and values of maximum principal stress at the core and veneer layers were determined through 3D graphs and software output.


RESULTS
The metal-porcelain and zirconia-porcelain systems showed compressive fields within the veneer cusp bulk, whereas alumina-porcelain presented tensile fields. At the core/veneer interface, compressive fields were observed for the metal-porcelain system, slightly tensile for the zirconia-porcelain, and higher tensile stress magnitudes for the alumina-porcelain. Increasingly compressive stresses were observed for the metal, alumina, zirconia, and all-porcelain monolithic systems.


CONCLUSIONS
Variations in residual thermal stress levels were observed between bilayered and single-material systems due to the interaction between crown configuration and material properties.
Postgraduate Program in Dentistry, UNIGRANRIO University-School of Health Sciences, Duque de Caxias, Brazil. estevamab@gmail.com
Estevam A
EA
Bonfante
Brian T
BT
Rafferty
Nelson R F A
NR
Silva
Jay C
JC
Hanan
Elizabeth Dianne
ED
Rekow
Van P
VP
Thompson
Paulo G
PG
Coelho
D000537:Aluminum Oxide; D019245:Compressive Strength; D003198:Computer Simulation; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000379:methods; D003801:Dental Veneers; D020342:Finite Element Analysis; D006358:Hot Temperature; D006801:Humans; D021621:Imaging, Three-Dimensional; D008670:Metals; D008963:Molar; D013314:Stress, Mechanical; D013718:Tensile Strength; D015019:Yttrium; D015040:Zirconium
D008670:Metals; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide