Cumhuriyet Dental Journal

Abstract

Objectives: The aim of the study was to evaluate and
compared the effects of 2 different tooth preparation designs on the stress
distribution in tooth, cement, core and two ceramic layers of all ceramic
anterior crown using the 3 Dimensional (3D) Finite-Element-Analysis (FEA) method.
Anterior tooth-crown configuration composed of both layers of restoration is
lacking.

Materials and Methods: 1
mm circumferential shoulder and chamfer finish line
preparations were performed with rounded shoulder and chamfer diamond
cylindrical burs with rounded angles on 2 maxillary central teeth. 1 mm
thickness of the frameworks were (IPS e.max Press, Ivoclar-Vivadent, Schaan,
Liechtenstein) prepared by pressing technique. After scanning the frameworks
for FEA, dentin and enamel ceramics (IPS e.max Ceram, Ivoclar-Vivadent) were
applied. Each ceramic layer was scanned for finite-element models. The
Variolink II (Ivoclar-Vivadent) was used as a luting material and modeled. A
200 N static load was applied at 45° to the palatal surface. 3D-FEA was performed
with I-DEAS software.

Results: Rounded-shoulder
model showed higher Von Mises stress values in prepared tooth, core, resin
cement, and both two layers of the ceramic than chamfer model. Rounded-shoulder
preparation type within all evaluated models had more dispersed stress
distribution localization areas than chamfer preparation type’s models. The
highest Von-Mises stress values were found within the first ceramic layer of
the shoulder model (26.5 MPa) on 1/3 of the buccal surface. Low stress values
were found at dentin tooth structures for both chamfer and rounded-shoulder
models.

Conclusions: Rounded-shoulder
preparation type showed higher Von-Mises stress values at both layers of crown.
Minimum Von-Mises stress values were found at dentin regardless of the
preparation type.