Dental Materials for Dental Assisting Exam Study Guide
Practice problems for this study guide can be found at:
Knowing how to manipulate, store, and handle dental materials is critical for chairside assisting. A well-rounded understanding of the choice of material and its use is beneficial for the patient and the operator. The dentist will determine the type of material needed based on the extent of the decay, the condition of the patient’s oral cavity, the location of the dental defect, and the cost factor for the patient. Additionally, each area of dentistry will have its own unique materials that may be used only in that specialty.
Concepts and Skills
This article will include questions that focus on dental materials, covering seven main concepts:
- Bases and Liners
- Bonding Procedures
- Restorative Dental Materials
- Dental Cements
- Impression Materials
- Laboratory Materials
- Laboratory Equipment
- Accessory Materials
Bases and Liners
Bases and liners are used just prior to the filling of a prepped tooth to protect the pulp (base) or to stimulate secondary dentin growth (liner).
Dental bases are layers placed under the restoration to protect, insulate, and sedate the pulp. Two of the most popular bases are glass ionomer, and zinc oxide eugenol (ZOE).
- Glass ionomer is probably the most popular base because of its specialized functions:
- It releases fluoride ions.
- It bonds to enamel and dentin.
- It is radiopaque (blocking radiation, such as from X-rays).
- It is compatible with all dental restorative materials.
Zinc Oxide Eugenol (ZOE)
Zinc oxide eugenol is one of the most popular dental bases for the following reasons:
- It is sedative (soothing) to the pulp.
- It insulates the pulp from thermal forces.
- It protects the pulp.
- Oil of cloves in the eugenol produces a calming effect on the pulp.
- It is not compatible under resin-based restorations because the oil of cloves interferes with the bonding of the resin.
Dental liners are thin layers that protect the pulp from irritation. One of the most popular liners is calcium hydroxide.
Calcium hydroxide is one of the most popular dental liners for the following reasons:
- It promotes secondary dentin as a measure to protect the pulp.
- It is placed only on dentin (on the walls and floor of the preparation area).
- It is compatible with all types of restorative materials.
- Some brand names include Dycal, Life, and Vitrebond.
Dental varnish is a type of sealer that seals the dentinal tubules and flows easily but evaporates quickly. It should not be used under glass ionomer or resin restorations. Varnish is always applied after the liner.
Restorations can be bonded to both enamel and dentin. Bonding materials prepare the tooth structure to accept a new restoration, sealant, or to bond for various orthodontic procedures. When a tooth is being prepared with the hand piece and bur, the oily layer that the tooth secretes is known as the smear layer. There are numerous techniques and manufacturers of these bonding systems, which are discussed below.
Acid Etchant (“Conditioner”)
An acid etchant, or “conditioner,” uses phosphoric or maleic acid (liquid or gel) to help form a bond between the restoration and the tooth. It can be used on enamel or dentin. Acid etching removes the smear layer just prior to bonding of new restorative material. Phosphoric acid is placed on the tooth structure for 15–20 seconds, then rinsed thoroughly and dried. The tooth structure should appear chalky. This process creates enamel tags that allow the resin-based materials to bond.
Application of Various Bonding Agents
Bonding agents have evolved over the past decade and have revolutionized the application and retention of composite and porcelain materials. The use of bonding creates a micromechanical retention between the restoration and tooth structure. A primer prepares the tooth for the resin materials and can also be a desensitizing agent. An adhesive creates a layer on which to place the resin material. The primer and adhesive can also be applied in one step. However, bonding systems by different manufacturers should not be used interchangeably. Dry field must be maintained via isolation techniques like rubber dam, cotton roll, or dry angle. Self-cure, light-cure, and dual-cure are types of adhesives.
Dental sealants protect teeth, particularly posterior teeth, from decay by coating the pits and fissures with resin sealant. Sealants are placed on the occlusal surfaces of posterior teeth. There is a specific order to apply the sealant: coronal polish, cotton roll isolation, acid etch-rinse-dry, primadry—then, sealant material is placed and cured. A properly placed sealant should last ten years. Pit and fissure sealants are flowable composite dental materials.