Dental Auxiliary Materials
In the field of dentistry, auxiliary materials are substances used in the fabrication of dental prostheses and appliances but that do not become part of these devices. They include acid-etching solutions, impression materials, casting investments, gypsum products, waxes, acrylic resins for trays, mouth guards and occlusion aids, and finishing and polishing abrasives.
Auxiliary Dental Materials
Dental materials, as the name implies, are used in dentistry for the prevention and treatment of oral diseases (preventive dental materials) and for the rehabilitation of missing or damaged hard or soft tissues in teeth and gums (restorative dental materials). Preventive dental materials include sealants that prevent leakage, liners, bases, cements, compomers, and hybrid ionomer cement that release fluoride or other therapeutic agents to prevent or arrest caries development.
Restorative dental materials are used to replace or repair damaged, missing, or destroyed tooth hard and soft tissue, such as the tooth enamel, dentin, and bone. The main types of restorative dental materials include dental amalgam, resin-based composites, compomers, ceramics, and metal ceramics.
There are many different types of dental materials and their use in dentistry depends on the specific needs of each individual patient. These include direct restorations such as inlays, onlays, crowns, bridges, and dentures; indirect restorations such as veneers, bondings, and inlays/onlays; and removable and fixed partial dentures and appliances.
The use of these dental materials is a crucial component in achieving the goal of providing optimum oral health. The selection of these materials must be based on sound knowledge of their properties, including the strength and other mechanical and physical characteristics. This knowledge will help dentists to select the most appropriate material for each patient, which is important in minimizing clinical risks and increasing long-term success.
Manufacturers of dental materials often provide information Auxiliary Materials regarding the strength and other properties of their products. However, the reliability of this information can vary from product to product and from application to application. In addition, it is difficult to predict the clinical performance of a material based on strength and other mechanical properties alone.
The dental profession has a strong interest in the use of alternative materials to amalgam and is actively engaged in research to develop new appropriate materials. This includes basic, clinical, and public health research to improve the quality of existing dental materials alternative to amalgam and develop new appropriate materials for dental care.
Impression materials are categorized into reversible and irreversible impression materials (Figure 2-33). Reversible impression materials are those that can be removed from the patient’s mouth without compromising the fidelity of the impression, such as plaster, zinc-oxide-eugenol, and the compounds that form gypsum or epoxy casts.
Reversible impression materials can be made from either aqueous or nonaqueous elastomers. Aqueous impression materials include alginates or irreversible hydrocolloids, which are the most commonly used impression materials.
Condensation impression materials are made from bifunctional or multifunctional monomers that react to form first dimers, then trimers, and eventually long-chain polymers. The reactions yield by-products, which affect the dimensional stability of the impression material.
The chemistry of condensation impression materials is complex, but their stability can be significantly improved by adding a catalyst to the compound. Typically, the catalyst is a solid substance such as sodium silicate or potassium aluminosilicate. The catalyst is then mixed with the base compound and the two mixtures are poured together to form a liquid or paste.
Aqueous elastomeric impression materials are manufactured from either a polysulfide or a silicone rubber and may be supplied in collapsible tubes, much like toothpaste. The reactants can be dispensed by counting drops or by using a ‘paste-paste’ system, in which one part is dissolved in a liquid and the other is poured into it.
Depending on the polymer, fusion temperature is achieved at different temperatures. For example, the fusion temperature of polysulfide is 39 degrees Celsius, while the fusion temperature of silicone rubber is 43.5 degrees Celsius.
In addition, all elastomeric impression materials exhibit viscoelastic characteristics. They are able to deform in response to external pressure, but they must return to their preremoval shape as soon as the pressure is released.
This is important for a number of reasons. It is necessary to capture occlusal pins and subgingival margins in an impression, but it also helps to prevent tearing when the impression is withdrawn from the mouth.
The tear resistance of elastomeric impression materials depends on their strain rate. The higher the strain, the less likely it is that an impression will tear. However, if the impression is strained for too long, it can permanently distort and become difficult to handle. This is particularly true of polysulfide impression materials that are too thin to resist tearing.
Gypsum products have a wide range of uses in the construction industry. It is an economical and easy-to-work material that provides a variety of aesthetic design options. It is also an environmentally friendly product that is free of odors and has the ability to balance indoor climate and humidity.
Gypsum can be a natural or synthetic mineral, or a mixture of both. It is a white cementing material that is formed by partial or complete dehydration of the gypsum mineral, commonly with special retarders or hardeners added. It sets and hardens by chemical recombination with water.
It is a common raw material for plaster and building materials, including gypsum wallboard, drywall, and gypsum plaster. It is also a natural food additive, as a calcium source and a dietary supplement, and used as a colorant in medicine and cosmetics.
The major raw material for gypsum is natural dihydrate gypsum (CaSO4 * 2H2O) and natural anhydrite (CaSO4), which are calcined to produce hemi-hydrate gypsum (CaSO4 + CaSO4 2H2O). Hemi-hydrate gypsum is produced when dihydrate and anhydrite are heated at 1500-1700 oC.
Hemi-hydrate gypsum has a high compressive strength and is resistant to heat. It is the primary component of gypsum plaster and other hard gypsum products.
A gypsum plaster is made by mixing a slurry of gypsum, water, a foaming agent, an accelerator, a dispersant, and an anti-deformation additive. The slurry is then disposed between two liners to form sandwich structures.
It is then cut into first boards and second boards with desired lengths after a hardening process. The second boards are then dried to evaporate excess water.
The sagging resistance of a gypsum board containing anti-deformation additive comprising at least one selected from a group consisting of dehydroascorbic acid, dehydroascorbate and MDHA is significantly improved compared to existing gypsum products. The mass ratio of the gypsum product with the anti-deformation additive can be from 0.01% to 5.0%.
In addition to its high sagging resistance, this gypsum product has good thermal insulation properties and acoustic insulation qualities. It also has a low energy footprint and is recyclable.
Wax is a class of organic compounds that have a wide range of melting points and physical properties. It is a common ingredient in wax paper and can be used to impregnate paper or card to waterproof it or make it resistant Auxiliary Materials to staining. It is also used as a mold release agent in the manufacture of many types of molding and casting, to coat cheeses and to waterproof leather or fabric.
It is also a natural material that is produced by plants and animals. The waxes of different plants are mixtures of substituted long-chain aliphatic hydrocarbons that include alkanes, alkyl esters, fatty acids, primary and secondary alcohols, diols, ketones and aldehydes. The most important plant wax is carnauba wax, a hard wax that comes from the Brazilian palm Copernicia prunifera and contains the ester myricyl cerotate. Other more specialized vegetable waxes are candelilla wax and ouricury wax.
Waxes can be either natural or petroleum-based, and they have a variety of uses in the dental laboratory. They can be used for impression, modeling, investment, abrasion and polishing and as an insulating material.
There are a number of types of wax, but paraffin wax is the most commonly used type of wax. It is light in color, odorless and comes in different melt points.
It is often referred to as the “king of waxes.” Millions of tons are produced each year.
Some of the most common products made with wax are crayons, china markers and colored pencils. They are made of a combination of fats and waxes that have been colored with pigments. A black coloring agent is usually lamp black (carbon soot), while a brown one might be iron oxide or rust.
Other cosmetic products use wax, such as mascara and lipstick. These are blends of waxes and other fats and oils, as well as other coloring agents like chromic oxide or ultramarine.
Other waxes are derived from animal sources, including beeswax and spermacetic wax from the head oil of sperm whales. Beeswax is a mixture of sterols and esters, and spermacetic wax is a combination of beeswax, lanolin and glycerin.