Dental Ceramics and Restoration Techniques

The lost wax technique was replaced with metal due to recurring errors in casting. While metal provided strength, it lacked aesthetics. The addition of porcelain to metal (PFM) crowns improved aesthetics. However, nickel alloys in PFM crowns caused sensitivities. Nickel-free alloys were developed. Metal is prone to corrosion which led to the development of improved ceramics and porcelains.

Inorganic compounds composed of metallic and non-metallic elements (mainly oxides). Formed by firing at high temperatures to achieve desired properties.

Ceramics are mainly composed of silica (SiO2) and feldspar, with small additions of crystalline oxides like alumina (Al2O3), magnesia (MgO), and zirconia (ZrO2). Composite materials like ceramics have fillers within a matrix.

Porcelain is a family of ceramic materials composed of kaolin, quartz, and feldspar. Feldspathic porcelain omits kaolin and primarily consists of feldspar with a smaller amount of quartz. It includes silica for strength and feldspar for translucency.

Ceramics are essentially feldspathic porcelain, with a minimal amount of kaolin. They are chemically inert, resistant to staining, and possess excellent aesthetics.

Ceramics are strong but brittle. They have high compressive strength, but are weak in tension and shear. They also have low thermal diffusivity and a coefficient of thermal expansion close to natural teeth. However, they are expensive and abrasive to natural teeth.

Used for crowns, bridges, veneers, inlays, onlays, denture teeth, posts, implant fixtures, orthodontic brackets, and ceramic burs.

Feldspar, naturally occurring mineral, constitutes 60-80% of ceramic composition. Added to increase translucency and lower the fusing temperature. Comes in two forms: Potassium feldspar (K2O-Al2O3-6SiO2) for translucency and Sodium feldspar (Na2O-Al2O3-6SiO2) for lower fusion temperature.

Pure crystals of SiO2 (Silica) that make up 15-25% of ceramic composition. Added to increase strength and provide a framework for other components to adhere to. Has the highest melting point, ensuring its solidification while other components melt.

A type of clay comprising 4% of ceramic composition. Acts as a binder, increasing mouldability and providing plasticity to unfired porcelain. However, it contributes to opacity, limiting light transmission.

Added to achieve desired shades. Opacifiers (Zr, Ti, Sn, Ce oxides) are important for opacity, and pigments provide color. Glass modifiers (Borax, Boric acid) lower the softening temperature, while fluxers disrupt silica networks, making them more fluid.

Ceramics are supplied in powder form. Manufacturing involves mixing raw materials, forming a frit, firing at high temperatures, quenching, and grinding to create fine powder. This powder is then mixed with water to form a slurry, which is used to build up the restoration.

The ceramic frit has amorphous (glassy/vitreous) and crystalline phases. Feldspar, a part of the amorphous phase, increases translucency, but reduces strength. Quartz, part of the crystalline phase, reinforces the structure, but reduces translucency.

A process where closely packed porcelain particles are heated to a specific temperature below their melting point. This helps to densify the structure by removing voids, increasing strength and translucency, while also causing the particles to fuse together.

Ceramics that require temperatures between 1315-1370°C for firing and are typically used for denture teeth.

Ceramics that require temperatures between 1090-1260°C for firing and are used for denture teeth and some dental ceramics.

Ceramics that require temperatures between 870-1065°C for firing and are primarily used for dental ceramics.

Ceramics that require very low firing temperatures, making them ideal for dental ceramics.

A type of glass ceramic that contains a high percentage of leucite (around 50%). This high content improves mechanical and physical properties such as fracture resistance, thermal shock resistance, and erosion resistance.

A glass ceramic that features a high percentage of lithium disilicate crystals. This type offers enhanced translucency and strength, making it suitable for various applications.

A ceramic system where a full crystal base is infused with glass particles. This creates a strong and durable material.

A ceramic consisting of a dense polycrystalline structure with no glass matrix. This type is known for its high strength but can be prone to fracture.

A ceramic material notable for its high strength and toughness, making it suitable for various dental applications.

A strengthening mechanism in zirconia where the volume of a tetragonal crystal increases upon crack formation, creating compressive stress that prevents the crack from propagating.

A process used to create a thin surface layer of high compressive stress on ceramic objects. It involves exchanging smaller ions with larger ones, increasing the surface's strength.

A strengthening method that involves rapid cooling of a ceramic surface from a molten state. This creates a compressive stress layer that inhibits crack initiation.

A technique used to improve the bonding strength of glass-based ceramics. This involves etching the surface with acid to expose crystal particles.

A common type of cement used for glass-based ceramics, but it's not recommended for zirconia because zirconia cannot be acid-etched.