Dental Materials Lecture Notes PDF

Dental Material 1 Introduction of dental materials DR NOUR ALFAKS  The science of dental materials involves a study of the composition and properties of materials and the way in which they interact with the environment in which they are placed. The dentist spends much of his professional...

Dental Material 1 Introduction of dental materials DR NOUR ALFAKS  The science of dental materials involves a study of the composition and properties of materials and the way in which they interact with the environment in which they are placed. The dentist spends much of his professional career handling materials and the success or failure of many forms of treatment depends upon the correct selection of materials possessing adequate properties, combined with careful manipulation. The dentist and dental technician have a wider variety of materials at their disposal than any other profession.  Oral Environment It is very important to know the variables that occur in oral cavity to understanding the oral environment : 1-Temperature variations 2- PH Variations. 3-Variations in Masticatory forces  Temperature variations Normal temperature of oral cavity 36-37 C. On intake of a cold, hot food , or drink The temperature range increases ( 0 to 75 c)  pH Variations The acidity or alkalinity of fluids in the oral cavity as measured by pH varies from around pH 4 to pH 8.5 On intake of acidic fruit juice or alkaline medicament; PH may vary from 2.0 to 11.0  Variations in Masticatory Forces In the oral environment, restorations are subjected to heavy masticatory forces. These forces act on teeth and/ or material producing different reactions that lead to deformation, which can ultimately compromise their durability over time. It is important to introduce some concepts that are extremely relevant to understand the performance presented by such materials under specific test conditions.  Variations in Masticatory Forces Muscles of Mastication apply forces to the dentition. Masticatory forces vary from tooth to tooth. Average force applied by the tooth increases from anterior to posteriors.  Selection of dental materials The process of materials selection should ideally follow a logical sequence involving (1) analysis of the problem, (2) consideration of requirements, (3) consideration of available materials and their properties, leading to (4) choice of material Evaluation of the success or failure of a material may be used to influence future decisions on materials’ selection.  Analysis: An incorrect decision may cause failure of the restoration or appliance. For example, when considering the selection of a filling material it is important to decide whether the restoration is to be placed in an area of high stress. Will it be visible when the patient smiles? Is the cavity deep or shallow? These factors and many more must be evaluated before attempting materials’ selection.  Requirements: it is possible to develop a list of requirements for a material to meet the needs of that situation. For the example, it may be decided that a filling material which matches tooth colour and is able to withstand moderately high stresses without fracture is required. Some tooth cavities are caused by toothbrush/toothpaste abrasion. In this special case the restorative material used should naturally possess adequate resistance to dentifrice abrasion.  Available materials The consideration of available materials, their properties and how these compare with the requirements is carried out at two levels. It is of paramount importance that the practitioner keeps up to date with developments in materials whilst taking a conservative approach towards adopting new products for regular use until they are properly tested.  Choice of material Having compared the properties of the available materials with the requirement, it is possible to narrow the choice to a given generic group of products. The final choice of material brand is often a matter of personal preference on the part of the dentist. Factors such as ease of handling, availability and cost may play a part at this stage of the selection process.  WHAT ARE DENTAL MATERIALS? The goal of dentistry is to maintain or improve the quality of life of the dental patient. This goal can be accomplished by preventing disease, relieving pain, improving mastication efficiency, enhancing speech, and improving appearance. The primary objective of restorative dentistry is to replace diseased or lost tooth structure with materials that restore function and appearance.  Characteristics of Ideal Materials It should be: Biocompatible Non-toxic, non-irritating, non-allergenic Mechanically stable & durable Strong, resistant to fracture Resistant to Corrosion Does not deteriorate over time Dimensionally Stable Little change by temperature & solvents Minimal conduction Insulates against thermal/electrical change Esthetic Looks like oral tissue Easy to manipulate Minimal/reasonable effort & time needed Adheres to tissues Retains onto, and seals, tooth structure Tasteless and Odorless Not unpleasant to patient Cleanable/Repairable Easily maintained or fixed Cost-effective General classification of all materials All dental materials fall under 4 main groups: Polymers. Metals. Ceramics. Composites. Diagram indicating the wide variety of materials used in dentistry and some of their applications.  Restorative dental materials Direct restorative materials: Used intra orally. fabricate restorations / prosthetic devices directly on the teeth or tissues. Indirect restorative materials: Used extra orally. Formed indirectly over a cast or models or Digital impression ,CAD-CAM….  Direct Restorative These include: Amalgam. Bonding agents. Resin based composites. Compomers. Liners. Cement bases. Dental polymers.  Resin Composite Materials First , the loss of tooth structure, which requires restoration of a portion of an anterior tooth, may be caused either by injury or by caries. Resin composite materials usually are chosen for these restorations. These materials are shaded to match the teeth in appearance. Their strength is a secondary factor because the anterior teeth are usually not subject to high biting forces. Although resin composite materials are weaker than metals, their excellent appearance and acceptable durability are the main reasons for their choice.  Metallic Restorations A metallic restoration may be preferable to a resin composite material for the restoration of the portion of a posterior tooth subject to greater biting forces because of strength and wear resistance considerations. Dental silver amalgam restorations and gold inlays are used most often for this type of posterior restoration. An amalgam paste is placed directly into the prepared tooth cavity and carved to the correct anatomy.  Amalgam The cavity preparation for the amalgam restoration is tapered so that it is larger at the base than at the occlusal surface. This design is necessary because amalgam cannot be bonded adequately to tooth structures and the restoration must be retained mechanically.  GOLD In dentistry gold is found in the form of gold alloys. It is an ideal material because of its harmlessness, precision, and rigidity, which is essential for important prosthetic realisations. It is mainly used for posterior reconstructions.  Indirect Restoration A restoration that created OUTSIDE of the mouth on a model of the prepared tooth and later FIXED into the mouth. Crown, bridges, inlay, onlay, veneers, complete ,partial, dentures.  INLAYS An inlay is a restoration prepared outside the mouth and cemented to the prepared tooth. The cavity preparation for the gold alloy inlay is tapered so that the base is slightly smaller than the occlusal surface. This design is required because the solid cast gold alloy or ceramic restoration must be able to be inserted and cemented to the cavity preparation.  onlays The inlay involves the occlusal and proximal surface or surfaces of the tooth but also may cover one of the cusps of the posterior tooth. When the inlay involves the occlusal and proximal surface or surfaces and covers all the cusps it is called an onlay.  GOLD CROWN A crown is a restoration of part or the entire coronal portion of a tooth. The cast metallic crown is suitable for the posterior portion in the mouth, where strength is needed and appearance is secondary.  CERAMIC CROWN A crown made from a ceramic can be used because this material combines strength with excellent esthetic properties. Different types of ceramics are available. A ceramic-fused-to- metal crown, which combines the esthetics of a ceramic veneer and the strength and fit of a cast metal crown may be used.  Veneers Esthetic veneers may be used to cover unsightly areas of anterior teeth that are severely discolored, malformed, or eroded. The veneer can be made from a resin composite that can be placed directly or indirectly (cemented) or can be a cemented ceramic veneer.  Bridge The fixed partial denture (bridge) is used to replace a missing tooth or teeth. The two teeth adjacent to the space must be prepared with abutment restorations to support the artificial tooth (pontic) or teeth. Gold or nickel-chromium alloys are used for fixed partial dentures Because of Their strength Tarnish resistance Ease of casting (fabrication). A fixed partial denture may be made with a facing of acrylic resin or veneered with porcelain. Cements are used to retain the fixed partial denture permanently in place on the abutment teeth.  Removable partial denture If a number of teeth are missing, a more complex prosthetic appliance known as a removable partial denture may be used. The artificial teeth are mounted on a metal framework. Clasps are used to attach the partial denture to the remaining abutment teeth. Silver-colored metals composed of mainly nickel, cobalt, and chromium are strong and highly resistant to corrosion. Acrylic resin materials that possess excellent esthetic qualities are used to fabricated artificial teeth on the removable partial denture The teeth are made from acrylic resin or porcelain. The porcelain teeth are more resistant to wear but more brittle than acrylic resins.  complete denture(Acrylic resin) If all the natural teeth in an arch are lost, a full denture or complete denture is required. The denture consists of a base with artificial teeth. Most denture bases are made from acrylic resins that are pigmented to match the pink shades of the oral tissues.  Implants Implant have been used to replace the root of extracted teeth, and after bone growth has stabilized the implant a full crown can be constructed that is supported by the implant. Manufactures use titanium or a titanium alloy to construct the implant, and ceramic implants have been used. The surface may be plasma-sprayed with Titanium or coated with hydroxyapatite (similar to the mineral portion of human enamel). THANK YOU FOR LISTINING