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Dental prostheses mimic the natural enamel behavior under functional loading: A review article

View Article: PubMed Central - PubMed

ABSTRACT

Alumina- and zirconia-based ceramic dental restorations are designed to repair functionality as well as esthetics of the failed teeth. However, these materials exhibited several performance deficiencies such as fracture, poor esthetic properties of ceramic cores (particularly zirconia cores), and difficulty in accomplishing a strong ceramic–resin-based cement bond. Therefore, improving the mechanical properties of these ceramic materials is of great interest in a wide range of disciplines. Consequently, spatial gradients in surface composition and structure can improve the mechanical integrity of ceramic dental restorations. Thus, this article reviews the current status of the functionally graded dental prostheses inspired by the dentino-enamel junction (DEJ) structures and the linear gradation in Young's modulus of the DEJ, as a new material design approach, to improve the performance compared to traditional dental prostheses. This is a remarkable example of nature's ability to engineer functionally graded dental prostheses. The current article opens a new avenue for recent researches aimed at the further development of new ceramic dental restorations for improving their clinical durability.

No MeSH data available.


Elastic modulus distribution in natural dentino-enamel junction.
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fig0010: Elastic modulus distribution in natural dentino-enamel junction.

Mentions: Natural teeth are composed by layered structures, dentin and enamel, that are bonded by a functionally graded dentino-enamel junction (DEJ) layer [97], [98], [99]. Marshall et al. [92] stated the DEJ acts as a bridge between the hard brittle enamel (E ∼ 70 GPa) and the softer durable dentin layer (E ∼ 20 GPa), allowing a smooth Young's modulus transition between the two structures (Fig. 2). Huang et al. [51] studied the microstructure of the DEJ and they reported that collagen fibrils from the dentin gather into coarse bundles and penetrate across the junction, anchoring into the enamel. The hydroxyapatite is continuous across the junction. The interface is not smooth, but instead is a series of linked semi-circles, or scallops, that increase contact area, and thus the adhesion when DEJ serves as the bonding between dentin and enamel. It also resists cracks that originate in enamel from penetrating into the dentin. Lin and Douglas [99] noticed that there was an extensive plastic deformation, 8%, collateral to the fracture process in the DEJ. Correspondingly, microscopic analysis revealed clear evidence of crack-tip blunting and crack deflection. The parallel-oriented coarse collagen bundles at the DEJ may play a significant role in resisting the crack. Likewise, White et al. [100] investigated the DEJ failure mechanisms by performing micro-indentation tests across the DEJ. Their results exhibited that DEJ does not undergo catastrophic interfacial delamination and the damage was distributed over a broad zone instead.


Dental prostheses mimic the natural enamel behavior under functional loading: A review article
Elastic modulus distribution in natural dentino-enamel junction.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382785&req=5

fig0010: Elastic modulus distribution in natural dentino-enamel junction.
Mentions: Natural teeth are composed by layered structures, dentin and enamel, that are bonded by a functionally graded dentino-enamel junction (DEJ) layer [97], [98], [99]. Marshall et al. [92] stated the DEJ acts as a bridge between the hard brittle enamel (E ∼ 70 GPa) and the softer durable dentin layer (E ∼ 20 GPa), allowing a smooth Young's modulus transition between the two structures (Fig. 2). Huang et al. [51] studied the microstructure of the DEJ and they reported that collagen fibrils from the dentin gather into coarse bundles and penetrate across the junction, anchoring into the enamel. The hydroxyapatite is continuous across the junction. The interface is not smooth, but instead is a series of linked semi-circles, or scallops, that increase contact area, and thus the adhesion when DEJ serves as the bonding between dentin and enamel. It also resists cracks that originate in enamel from penetrating into the dentin. Lin and Douglas [99] noticed that there was an extensive plastic deformation, 8%, collateral to the fracture process in the DEJ. Correspondingly, microscopic analysis revealed clear evidence of crack-tip blunting and crack deflection. The parallel-oriented coarse collagen bundles at the DEJ may play a significant role in resisting the crack. Likewise, White et al. [100] investigated the DEJ failure mechanisms by performing micro-indentation tests across the DEJ. Their results exhibited that DEJ does not undergo catastrophic interfacial delamination and the damage was distributed over a broad zone instead.

View Article: PubMed Central - PubMed

ABSTRACT

Alumina- and zirconia-based ceramic dental restorations are designed to repair functionality as well as esthetics of the failed teeth. However, these materials exhibited several performance deficiencies such as fracture, poor esthetic properties of ceramic cores (particularly zirconia cores), and difficulty in accomplishing a strong ceramic–resin-based cement bond. Therefore, improving the mechanical properties of these ceramic materials is of great interest in a wide range of disciplines. Consequently, spatial gradients in surface composition and structure can improve the mechanical integrity of ceramic dental restorations. Thus, this article reviews the current status of the functionally graded dental prostheses inspired by the dentino-enamel junction (DEJ) structures and the linear gradation in Young's modulus of the DEJ, as a new material design approach, to improve the performance compared to traditional dental prostheses. This is a remarkable example of nature's ability to engineer functionally graded dental prostheses. The current article opens a new avenue for recent researches aimed at the further development of new ceramic dental restorations for improving their clinical durability.

No MeSH data available.