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Biocompatibility and Classification of Dental Materials Dr. Amr Saad References Phillips’ Science of Dental Materials - Saunders; 12th edition. Chapter 1 & 7 Goal of Studying Dental Materials To be familiar with all materials used in dentistry K...

Biocompatibility and Classification of Dental Materials Dr. Amr Saad References Phillips’ Science of Dental Materials - Saunders; 12th edition. Chapter 1 & 7 Goal of Studying Dental Materials To be familiar with all materials used in dentistry Know all the properties of dental materials Know how to manipulate dental materials Know and understand causes of failure of restorations Improve dental materials An understanding of the physical, chemical and mechanical properties of materials used in dentistry is of tremendous importance. This is because these materials are exposed to the oral environment and subjected to biting forces. Oral environment is characterized by: ✓ Wet (saliva, food and drinks). This may have an effect on solubility, water sorption and staining of the restorations. ✓ Temperature Fluctuation ✓ The pH of saliva, food and drinks ✓ Masticatory forces (biting, chewing and grinding). Ideal Dental Materials Biocompatibility (nontoxic, non-irritating, non allergic). Mechanically stable and durable (strong and fracture resistant). Dimensionally stable (minimally affected by temperature or solvents). Esthetics (oral tissue-like appearance) Easy manipulation Tasteless and odorless Cost effective Resistance to corrosion or chemicals (does not deteriorate over time) Classification of Materials Used in Dentistry Based on the chemical composition: Metals (Gold, Ni-Cr, Co-Cr, Ti, Dental Amalgam) Ceramics (Zirconia, Li disilicate) Polymers (Acrylic resin) Composites  Pure metals are rarely used for dental applications, although commercially pure titanium can be used to make dental implants, inlays, onlays, crowns, and bridges. Pure gold in a foil form can be used to make dental restorations (“fillings”) directly on teeth, but this technique is rarely today. Cast gold is more common as gold restoration. Co-Cr and Ni-Cr used for metallic denture base and indirect restorations. Metals and alloys can also be used to construct orthodontic appliances, partial denture frameworks and clasp arms  Ceramics can be used to produce inlays, onlays, crowns, and multiple-unit fixed dental prostheses. It is also possible to use yttria-stabilized zirconia for implant bodies and endodontic posts and cores. Polymers such as cements, impression materials, impression trays, mouth guards, orthodontic appliances, and interocclusal records. When a monomer resin contains inorganic or polymeric filler particles that are bonded to the matrix resin by means of an organosilane coupling agent, the material is classified as a dental composite or resin-based composite. Classification of Materials Used in Dentistry Based on the use Preventive materials of materials: Restorative materials Auxiliary materials Preventive Dental Material Cement, coating, or restorative material that either seals pits and fissures or releases a therapeutic agent such as fluoride and/or mineralizing ions to prevent or arrest the demineralization of tooth structure. Restorative Dental Material Substances that are used to repair, replace, or enhance a patient's teeth, these materials include metals, porcelains, and composite resins Restorative materials may be used for temporary, short-term purposes (such as temporary cements and temporary crown and bridge resins) or for longer-term applications (dentin bonding, and indirect inlays, onlays, crowns, removable dentures, fixed multiple-unit, and orthodontic appliances). Restorative materials may further be classified as direct restorative materials fabricated intraorally (Glass ionomers, Amalgam, Composite) or indirect restorative materials, fabricated extraorally (cast gold, ceramics, polymethylmethacrylate) Auxiliary Dental Materials Substance that is used in the construction of a dental prosthesis but that does not become a part of the structure These include acid-etching solutions, impression materials, casting investments, gypsum cast and model materials, dental waxes, acrylic resins for impression and bleaching trays, acrylic resins for mouth guards and occlusion aids, and finishing and polishing abrasives. Biocompatibility The ability of a biomaterial to perform its desired function with respect to a medical (or dental) therapy, without eliciting any undesirable local or systemic effects in the recipient or beneficiary of that therapy, but generating the most appropriate beneficial cellular or tissue response in that specific situation, and optimizing the clinically relevant performance of that therapy. Biocompatibility Is there a difference between material biocompatibility requirements between a metal hip replacement, and a metal crown? Biocompatibility What about a restorative material which will be placed in proximity to the pulpal tissue, compared to another simple filling material? Biocompatibility on a spectrum Depending on the tissue in contact, the required level of biocompatibility could vary. The biocompatibility requirements of a dental implant that will be in contact with living bone structure, is not necessarily the same as those if a dental filling that will be placed far from pulpal living tissues. If a device does not have any direct or indirect tissue contact, then the FDA does not need biocompatibility information in the submission. 27 Category In vivo method In vitro model Expensive because it involves This model uses cells derived experimental animals or human from animals or cell lines. Cost and preparation volunteers Therefore: relatively cheap, Ethical dilemmas while simple to procure, and efficient recruiting humans and animals Takes longer to arrive at the Time Results are rapid result Findings need to be confirmed Result More specific and detailed on live volunteers by in vivo methods Cell cultures are studied in the Strict because it involves live Testing regulations lab. Resting regulation is more subjects relaxed than that in vivo https://www.medicinenet.com/why_is_in_vivo_better_than_in_vitro/article.htm Biocompatibility factors 1. Nature of contact: With which tissues does the device or part of the device come into contact? 2. Type of contact: Is there direct or indirect contact? 3. Frequency and duration of contact: How long is the device in contact with tissues? 4. Materials: What is the device made from, its chemical and physical properties 5. Surface properties of the material: Rough Vs. Smooth surface 6. Material Byproducts : Does the material release byproducts or is it inert and stable? Dr Ahmed Abyad-BDS 220 30 Adverse effect severity An adverse effect may be mild or sever, it may also be local or systemic. What are the systemic routes? 1. Ingestion: parts of the material entering the digestive system 2. Inhalation: Through vapors (e.g Amalgam and hydrofluoric acid) 3. Apical foramen: Mostly through root canal filling materials 4. Oral mucosa: Materials in contact with the gingival tissues (e.g. Implants) Dr Ahmed Abyad-BDS 220 31 Adverse reactions Types of Adverse Reactions 1. Inflammatory reaction 2. Allergic reaction 3. Toxic reaction 4. Mutagenic reaction 1. Inflammatory reaction The inflammatory response involves the activation of the host’s immune system toward a threat. Inflammation could be caused by: 1. Rough restoration 2. Restorations with overextended margins 3. High biting occlusion causing inflammation of the periodontal tissues.(Trauma from occlusion 2. Allergic reaction The body recognizing a material as a foreign object causing an overreaction of the immune system Could be cause by 1. Metals: Nickle, cobalt, chromium, amalgam, titanium. 2. Acrylic denture base materials 3. BisGMA resins 4. Latex gloves 5. Impression materials 6. Anesethia In severe cases, an allergic reaction may elicit an anaphylactic shock and could cause obstruction of he airways due to edema around the neck area which is a life-threatening condition. Case of latex allergy after dental treatment  Allergic contact stomatitis Source: Contact allergy in the mouth: Diversity of clinical presentations and diagnosis of common allergens relevant to dental practice Allergic reactions to nickel-containing metals watchband buckle fixed metal- ceramic prostheses 3. Toxic Reaction Fluoride is a proven toxic material and its ingestion in high doses can cause systemic toxicity. Can cause a condition called fluorosis which is characterized by enamel pitting and discoloration if ingested in high doses during tooth development period. 4. Mutagenic reaction Occurs when the components of the material alter the base-pair sequences of the DNA cells 4. Mutagenic reaction Mutagenicity does not have the same consequences as carcinogenicity, “the ability to form malignant tumors” Mercury and Amalgam Metallic mercury gains access to the body via the skin or as a vapor through the lungs. Ingested metallic mercury is poorly absorbed from the gut (0.01%), so the primary portal into the body is through inhalation of mercury vapor. Mercury and Amalgam Exposure to high levels of mercury can injure the brain, kidneys, and the developing fetus. Chronic mercury toxicity may be manifested as tremors; memory loss; and changes in personality, vision, and hearing. The lowest known level for any observable toxic effect is 3 μg/kg. In summary, there are simply no data to show that mercury released from dental amalgam is harmful to the general population. Hydrofluoric Acid HF is an extremely corrosive acid, it is significantly more hazardous than many of the other acids used in dental labs and offices. Exposure of the eyes to HF may result in blindness or permanent eye damage Thank You !!!