Restorative and Esthetic Dental Materials - Selection and Uses

CHAPTER 43 Restorative and esthetic materials ▪ ▪ Section of the most appropriate dental material depends on: - The extent of decay - How much tooth structure remains intact - Condition of entire mouth - Location of restoration - Cost factors Most common dental materials: - Silver amalgam (Am) - Composite resin (CR) - Glass ionomer (GI) - Temporary materials - Tooth Whitening products - Gold Alloys - Ceramic castings Restorative: the ability to remove decay & restore proper function of tooth Esthetic(aesthetic): restoring to an artistically pleasing appearance ▪ Standardization of dental materials ▪ ▪ ▪ When a new dental material is developed, the product undergoes a strict evaluation and assessment before it is marketed to the profession. Criteria for new dental material - Not be poisonous or harmful or irritation to the tissues of the oral cavity & the body - It must help protect tooth and tissues of the oral cavity - It must resemble the natural dentition as closely as possible to be esthetically pleasing - It must be easily formed and placed in the mouth to restore the mouth’s natural contour - It must conform and function despite limited access, wet conditions and poor visibility. ▪ ▪ ▪ Dental Assistant needs to know - General characteristic of materials - Selection criteria for each - Preparation of material for each procedure - Set up for each material Properties of dental materials - Mechanical properties - Thermal properties - Electrical properties - Corrosive properties - Application properties Mechanical Forces - Average biting and chewing force with natural dentition = 130 – 170lbs molars - A Force is any push or pull-on matter, which produces a stress and a strain - Stress is the internal resistance or force that can cause distortion - Strain Is the change or deformation of material as the result of stress - Stress and strain are applicable to both liquids and solid - Stress and strain go together; you cannot have one without the other Types of Stress and Strain • • • • Tensile Stress & Strain: Pulls and stretches the material, like a tug of war Compressive stress & strain: Pushes the material together. Example: Chewing Shear Stress & Strain: The breakdown of the material as a result of something sliding over the 2 areas. Example: cutting with scissors Shear Stress & Strain: The breakdown of the material as a result of something sliding over the 2 areas. Example: cutting with scissors Ductility and Malleability - A measure of a material’s ability to withstand permanent deformation by either tensile or compressive forces Ductility - Ability of material to have its shape changed by being stretched or by being stretched or by a pulling or tensile force without it losing strength or breaking This property allows a metal to be made into thin wire Malleability - Is the measure of a material’s ability to be extended in all directions by a compressive force, such as rolling or hammering This property allows a metal to be shaped into thin sheet or plate. Thermal Change - Going from hot coffee to cold ice cream within seconds Causes contraction and expansion, material pulls away from the tooth causes microleakage or a faulty restoration Need to protect the pulp from thermal shock Contraction and Expansion - When temperature changes occur, each type of dental material will contract or expand at its own rate It is essential that the tooth structure and the restorative material have, as nearly as possible, the same rate of contraction and expansion Significant changes cause a dental material to pull away from the tooth, which can result in microleakage. This microscopic separation of material and tooth can allow oral fluids, debris, and microorganisms to enter between the restoration and the wall of a cavity preparation. The term for this process is percolation. Electrical Properties - An electrical current or galvanic action, is created when two different or dissimilar metals are present in the oral cavity. Conditions for this to occur: ◦ Saliva (contains salt), good conductor ◦ Two metallic components of different composition Corrosive Properties - • • Corrosive is the reaction that occurs within a metal when it is exposed to corrosive factors such as temperature, humidity, and saline. Certain foods contain metallic forms that cause corrosion of a dental material The surface discoloration that we see in older amalgam restorations in the mouth is referred to as tarnish Most corrosion, however, involves surface discoloration and can be removed easily with use of polishing agents Hardness - Any restoration must have enough hardness to resist indentation, scratching & abrasion - Indication of strength & wearability Solubility - The degree to which a substance will dissolve in a given amount of another substance - A material that dissolves easily on the oral cavity is of limited use as it will wash away and leave the tooth structure exposed Application Properties - Flow: ability of the materials to move and fill in the preparation of the tooth Retention: the ability of 2 different materials to adhere to each other Characteristics of materials will affect adhesion: - - Wetting is the ability of a liquid to come over solid surface = Water has a high wetting ability Viscosity is the property of a liquid that causes it not to flow easily = syrup is liquid with high viscosity and does not flow easily, this is not effective in wetting a surface Surface characteristic: chemical nature of the tooth ◦ Film thickness: very thin layers should be added to make the junction strong.