Comparative mechanical behavior of dentin enamel and dentin ceramic junctions assessed by speckle interferometry (SI).
OBJECTIVE
The dentin-enamel junction (DEJ) plays a crucial role in dental biomechanics; however, little is known about its structure and mechanical behavior. Nevertheless, natural teeth are a necessary model for prosthetic crowns. The mechanical behavior of the natural DEJ and the dentin ceramic junction (DCJ) manufactured with a CAD-CAM system are compared.


METHODS
The reference samples undergo no modification, while the experimental samples were drilled to receive a cemented feldspathic ceramic crown. Longitudinally cut samples were used to achieve a planar object observation and to look "inside" the tooth. A complete apparatus enabling the study of the compressive mechanical behavior of the involved tooth by a non-contact laser speckle interferometry (SI) was developed to allow nanometric displacements to be tracked during the compression test.


RESULTS
It is observed that the DEJ acted as a critical zone accommodating the movement between dentin and enamel. A smooth transition occurs between dentin and enamel. In the modeled prosthetic, the same kind of accommodation effects also occurs, but with a steeper transition slope between dentin and ceramic.


CONCLUSIONS
On the natural tooth, the stress accommodation arises from a differential behavior between enamel and dentin from the DEJ. In the ceramic crown, the cemented dentin-ceramic junction should play this role. This study demonstrates the possible realization of prosthetic crown reconstructions approaching biomechanical behaviors.
Department of Biologic Sciences, University of Montpellier I, Montpellier, France. mifages@wanadoo.fr
Michel
M
Fages
Pierre
P
Slangen
Jacques
J
Raynal
Stephane
S
Corn
Kinga
K
Turzo
Jacques
J
Margerit
Frédéric J
FJ
Cuisinier
D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003743:Dental Enamel / Q000737:chemistry*; D017267:Dental Prosthesis Design / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007368:Interferometry / Q000295:instrumentation / Q000379:methods; D019228:Tooth Crown / Q000737:chemistry*