Dental Ceramics for Restoration and Metal Veneering

Abstract

A survey of the development of dental ceramics is presented to provide a better understanding of the rationale behind the development and clinical indications of each class of ceramic material. Knowledge of the composition, microstructure, and properties of a material is critical for selecting the right material for specific applications. The key to successful ceramic restorations rests on material selection, manufacturing technique, and restoration design, including the balancing of several factors such as residual stresses, tooth contact conditions, tooth size and shape, elastic modulus of the adhesives and tooth structure, and surface state.

Keywords: All-ceramic restorations; Ceramic-polymer interpenetrating network; Dental ceramics; Glass-ceramics; Metal-ceramic restorations; Porcelain; Zirconia.

Figure 1

The timeline of the development of dental ceramics and their processing technologies.

Figure 2

Microstructures of leucite-containing feldspathic ceramics. Images were taken using secondary electrons in a SEM. Feldspathic overlay porcelains for zirconia (A) LAVA Ceram and (B) Vita VM9. Porcelain overlay for metal (C) d.SIGN. A dispersion strengthened glass-ceramic (D) Empress CAD. Acid-etched surface revealing craters once occupied by leucite crystals and microcracks in the glassy matrix. Note: the leucite content increases from porcelain veneers for ceramic to metal to dispersion strengthened glass-ceramic.

Figure 3

Microstructures of lithium disilicate glass-ceramics (A) CAD and (B) Press. Images were taken on an acid-etched surface using secondary electrons in a SEM, revealing elongated lithium disilicate crystallites. Note in the Press material (B), the preferential orientation of the ‘coarse’ elongated lithium disilicate crystallites.

Figure 4

Scanning electron micrograph, showing a typical fine-grained microstructure of high-strength dental zirconias (Y-TZP). Specimen surface was polished and thermally etched.

Figure 5

Microstructure of Vita Enamic observed using secondary electrons in a SEM. (A) A polished and then thermally etched surface, revealing a ceramic network structure consisting of ~25 vol% porosity following selective removal of the polymer phase. (B) A polished and then acid etched surface, showing the polymer network after selective removal of the surface ceramic material.

Figure 6

Scanning electron micrograph of a resin-based composite, Lava Ultimate. The material surface was polished down to 1 μm prior to imaging.

Figure 7

Schematic diagram illustrating various fracture modes in all-ceramic (A) crown and (B) FDP structures: axisymmetric cone (C) and median (M) cracks; partial cone (P) cracks; edge chipping (E) cracks; radial (R) cracks at cementation surfaces; flexure (F) cracks at connectors. Linear-trace cracks (C, P, E, F) extend out of the plane of diagram, shaded (R, M) cracks extend within the plane of diagram. Modified from Zhang Y, Sailer I, Lawn BR. Fatigue of dental ceramics. Journal of Dentistry 2013; 41(12): 1136; with permission.