DENTAL MATERIALS AND TECHNOLOGY Dental students 2nd year 2012/2013 Dr. Kinga Turzó 4th of September 2012
Lectures:Faculty of Dentistry, Lecture HallTuesday 13:00-15:00 (2 hours /week), Examination, 3 creditsSept. 4.: Introduction to dental materials science. Importance of dental material knowledge in dentistry. History of dental materials. International standards for materials used in dentistry (ISO, DIN, etc.). Classification of dental materials based on structure and utilization.Sept. 11.: Basic physical properties of materials. Test methods for materials in dental material science.Sept. 18.: Types, classifications and applications of impression materials. Presentation of elastic impression materials.Sept. 25.: Examining, treating and preventive methods used in dentistry from technological point of view. Die materials and methods of model preparation.Oct. 2.: Polymers used in dentistry (1st part). Practical aspects of polymers used in dentistry (2nd part).
Lectures:Oct. 9.: Waxes. Occlusion papers and foils. Artificial teeth (acrylic and ceramic)Oct. 16.: 1st WRITTEN TESTOct. 30.: Filling materials and adhesive technologies. Dental cements and endodontic materials.Nov. 6.: Structure and properties of metals and alloys used in dentistry. Electroforming. Corrosion of metals.Nov. 13.: Investment, investment materials, metal casting. Processing of surfaces of dental appliances, polishing. Burs and polishing instruments in dentistry.Nov. 20.: Amalgam. Allergic reactions to dental materials.Nov. 27.: 2nd WRITTEN TESTDec. 4.: Materials used for porcelain-fused-to-metal restorations. All-ceramic systems, composition, characteristics, processing
Conditions for accepting thesemester and the credits: Active participation on lectures and practices, based on the study and exam regulations of the University and of the Faculty of Dentistry. Requirements of participation on lectures and practices and replacement of absenteeism based on the study and exam regulations of the Faculty of Dentistry. Method of proof of the absence on practices and lectures based on the study and exam regulations of the University and of the Faculty of Dentistry. Accomplishment of the tasks in the practices. The safety rules of the laboratory should be kept. It is mandatory the fulfillment of the WRITTEN TESTS (1st and 2nd). The average mark of the tests should be at least 2.0. Unsatisfactory test should be corrected; there is only ONE possibility for the correction during the semester! The date of this correction Test is given by the responsible of the subject. Failed Written tests are also included in the average. The absence from the Written tests can be certified with a medical certificate. In absence of this certificate the students Written test will be considered failed.
Requirements of signing thePractice: Active participation on the practices based on the study and exam regulations of the Faculty of Dentistry and the average mark of the practice written tests and oral questions should be at least 2.0. The practice teachers are continuously checking the knowledge of the students with written tests and oral questions. These tests are performed during the practice hours and their number can be equal with the number of practice hours. The subject of these practice tests contain topic of the lectures and the practice itself. It is compulsory the knowledge of the theoretical subjects related to the practices, and the average mark of all the tests should be at least 2.0. The mark of small tests may be max. 3 times 1. Failed written tests and oral questions are also included in the average. If the student already has three failed marks during the semester, then he will have only ONE opportunity to correct these tests. If the student fails on this last correction the Practice will not be signed. The correction can be written or oral. The date of the correction will be given by the practice teachers.
Mark of the Examination (Lectures) isestablished in the following way: If the average of the Written test and the practice written tests and oral questions is between 4.0 and 5.0 then an offered mark can be given to the student. Calculation of the average: [1st Written test + 2nd Written Test + practice written tests and oral questions average]/3. If the average is between 4.0-4.50 then good (4) is given, if the average is between 4.51-5.0 then excellent (5) can be given. In case the average is below 4.0 the student will perform an oral exam (Examination). Recommended literature:Dental Materials and Their Selection: Edited by W.J. O’Brien. Quintessence Publishing Co, Inc.
Subject of the 1st lecture: Introduction to dental materials science. Importance of dental material knowledge in dentistry. Historical overview. International standards for materials used in dentistry. Classification of dental materials based on structure and utilization.
Introduction to dental materials science. Theimportance of dental material knowledge in dentistry. The goal of dentistry: to maintain and improve the health of the human teeth (oral cavity) in order to improve the quality of life of the dental patient. Activities: - preventing disease, - tooth replacements, - replacement of missing portions of tooth structure, - improving mastication efficiency, - enhancing speech, improving appearance and - relieving pain. All these activities require the replacement or alteration of existing tooth structure and also the development of auxiliary dental appliances.
Introduction to dental materials science. Theimportance of dental material knowledge in dentistry. Dentistry includes: - curing the diseases of teeth and oral cavity, - selection of the needed materials and instrumentation, - the knowledge of medicaments used in dentistry, - dental technology. The science of dental materials is critically important. A great deal of the daily practice of dentistry involves the selection and use of dental materials, either for the treatment procedure or in the instrumentation required. The dentist has to possess the knowledge from various disciplines, to know the properties of these materials: - chemical and physical-chemical structure, - mechanical properties, - technological, processing features, - biological properties, the interaction of the material with the surrounding medium and the host reactions of the biological system.
Hierarchy of evidences for dentalmaterials Scientific/published - Long-term clinical trials - Other clinical studies - Animal studies importance - In vitro studies amount - Physical properties data Speculative/unpublished – Deductions from clinical literature – Deductions from scientific theories – Product manufacturer literature – Popular media – Rumors and myths
EBD - Evidence Based Dentistry Definition: Scientific An approach to oral health care evidence that requires the judicious integration of systematicExperience assessments of clinically relevant Patient and needs scientific evidence, relating toJudgment patient’s oral and medical condition and history, with the dentists’ clinical expertise and Clinical/Patient the patient’s treatment needs Circumstances and preferences. American Dental Association
Example: replacement of missingportions of tooth structure In case of tooth filling only materials having no harmful biological effect on their environment can be used.Questions arising : Does it dissolve in the mouth? Does it produce electrochemical effects? Does it disturb or even damage compounds of normal biochemical processes (e.g. enzymes)? Does it have any irritating effect? Does it have any poisonous effect when absorbed (e.g. fluoride)? At the same time it is useful to know:- Abrasion resistance, hardness and corrosion resistance of the material concerning its durability and function.- The technological suitability (easy processing) of the material.
Biocompatibility The main challenges for centuries have been the development and selection of biocompatible prosthetic materials that can withstand the adverse conditions of the oral environment: extreme temperatures (5-55oC), acidic pH, abrasion, high magnitude forces, bacteria. Biocompatibility: Acceptance of a synthetic material or an artificial implant by the surrounding tissues and by the body as a whole. Does not irritate the surrounding structures. Does not provoke an abnormal inflammatory response. Does not incite allergic or immunologic reactions. Does not cause cancer. „Biocompatibility is a dynamic, always changing phenomenon.” J.E. Lemons, Journal of Prosthetic Dentistry, 2001
Utility of dental researchC. Bedos, P. Allison: Do Canadian Dentists find Dental Research useful?Journal of Canadian Dental Association, 68(9): 540, 2002. 450 dentists
Historical overview• 3000 B.C. : dentistry begun • 1756: Pfaff, described a method for making impressions of the mouth in wax• 2500 B.C.: gold bands and wireswere used by the Phoenicians for the • 1792: de Chamant patented a process forconstruction of partial dentures the construction of porcelain teeth• 700 B.C.: Etruscans used tooth • 1850 years: first studies on amalgamimplant material (ivory) • 1915: areas of Colorado, observations on• 600 A.D.: the Mayans used implants the effect of fluoride to prevent toothconsisting of seashell segments (1931, demineralizationHonduras, Dr. Wilson Popenoe) • 1935: introduction of polymerized acrylic• 1728: modern dentistry began, resin as a denture base material to supportFauchard „father of dentistry” artificial teethpublished a treatise describing manytypes of dental restoration • 1944: controlled water fluoridation (1 ppm) to reduce tooth decay
International standards for materialsused in dentistry The standard of a product contains:1. General properties, classification, field of application.2. Requirements (appearance, color, etc.).3. Usage, processing, packaging and storage instructions.4. Specific testing requirements.5. Scientific, published data.• Describes: composition, purity, physical, chemical features, for e.g.: - binding time, stress strength, solubility, the correct processing form, usage instructions, instructions regarding package and storage.Data’s provided by the manufacturer: name, date of production and expiration,weight, appearance, color.
International standards for materialsused in dentistry A performance standard is mandatory, any deviation from it has to be approved by the National Standard Organization. The task of these Organizations is to develop standards and to certify products. Hungary: M.Sz. (Magyar Szabványügyi Hivatal) Germany: DIN (Deutsches Institute für Normung) France: FDI (Fédération Dentaire International) International (agreement between ~ 60 countries, harmonization): ISO (International Organization for Standardization) USA: ADA (American Dental Association Specifications) British Standards, Australian Standards
International standards for materialsused in dentistry Dental materials – beside the quality and physical/chemicalrequirements – have to fit the needs of applicability in practice. Thishas to be supported by a comprehensive scientific study. Norms givethe required features of a material and the methods of testing them.Goals of the performance standards are:1. To protect the public from hazardous or ineffective dental devices.2. Proper information of the dentist/dental technician -> selection of the product3. Information of the merchant -> indications for the consumer4. Information of the producer -> production of a quality material, method ofquality controlEvery standard has a number, which has to appear on the product.
Dental implants – Guidelines for fabricating dental implants(ISO/TR 11175:2003) Forces acting on transmucosal dental implants gingiva Forces acting on totally embedded dental implants
Dentistry. Fatigue testing of dental implants (ISO 14801:2003) F force The patent beside determining the general definitions, the Supporting system requirements for writing Implant the records defines alsoImplant the exact geometry andholding elements used in theelement testing device. 2b: nominal bone level
Classification of dental materialsbased on utilization Tooth replacements: Replacement of missing portions of Animal teeth tooth structure: Human teeth Seashells Metals Ivory Ceramics Bone Polymers Hydroxyapatite Composites Co-Cr alloy Titanium
Classification of dental materials basedon structure Metals Ceramics Polymers CompositesOther classifications for e.g.: - non-metallic and - metallic materials
Metals Classification: • precious metals (e.g.: gold, silver, Platinum) • non-precious metals (e.g.: Co, Cr, Ni, Ti) • alloys (e.g.: amalgam, Co-Cr, stainless steel) Advantages: strength, hardness, easy to shape, ductile Disadvantages: susceptible to corrosion, high density, expensive production Fields of application: denture base material, orthodontic arch wires, dental implant (total hip and knee joints, fracture healing aids as bone plates and screws, etc.) O’Brien classification: alloys (e.g.: gold-copper) and intermetallic compounds (e.g.: amalgam phases)
Ceramics Definition: refractory, polycrystalline compounds, usually inorganic materials (silicates, metallic oxides, and various refractory hydrides, sulfides and selenides)Advantages: high melting temperature, very biocompatible, inert, strong in compression, aesthetic appearanceDisadvantages: brittle, not resilient, difficult to makeFields of application: coating of dental and orthopedic implants (femoral head of hip replacement, etc.)O’Brien classification: inorganic salts (e.g.: gypsum, zinc phosphate), crystalline ceramics (e.g.: SiO2, Al2O3), glasses (e.g.: dental porcelain)
Classification of ceramics used infabricating implants Nonabsorbable, bioinert (dense and porous aluminum oxides Al2O3, zirconium ceramics ZrO2, single phase calcium aluminates) Bioactive or surface reactive, sem-inert (dense nonporous glasses, Bioglass, Ceravital and dense hydroxyapatites HAP) Biodegradable or resorbable, non-inert (calcium- phosphates Ca-P, calcium sulfate (CaSO4, plaster of paris), calcium aluminates Al-Ca-P, corals, tricalcium phosphate TCP, etc.)
PolymersDefinition: very long chain molecules which are formed by covalent bonding along the backbone chains. The long chains are held together either by secondary bonding forces (van der Waals and hydrogen bonds) or primary bonding forces through crosslink between chains.Classification: natural (cellulose, yeast, natural rubbers, DNA) synthetic (polyesters, polyamides (nylons), silicon, polyvinylchloride PVC, polyethylene PE, polypropylene PP, polymethylmethacrylate PMMA)O’Brien classification: rigid polymers (e.g.: PMMA), waxes, elastomers, (rubbers, e.g.: impression materials)Advantages: resilient, easy to fabricate (polymerization)Disadvantages: not strong, deforms with time, may degrade
Polymers and applications - prosthetic materials, - dental materials, - implants (sutures, blood vessels, hip socket, ear nose, other soft tissues, sutures, encapsulants, polymeric drug delivery systems, etc.)
CompositesDefinition: contain two or more distinct constituent materials or phases, on a scale larger than the atomic.Advantages: strong, stiff, tailor-made, lightweightDisadvantages: difficult to make, the interface between the constituents can be degraded by the body environmentTwo big classes: fibrous and particulate composites Natural composites: bone, dentin, cartilage, skin, lung
Composites Field of application: dental filling composites, orthopedic implants with porous surfaces, reinforced methyl methacrylate bone cement and ultrahigh molecular weight polyethylene, joint implants, heart valves, etc. Scanning electron micrograph of a fracture fixation plate. Laminae buckling and delamination (D) between lamina in a carbon fiber-reinforced PLA fracture fixation plate