Dental Materials Final Exam Review 2010-11 PDF

Dental Materials Review Know the terminology relating to the science of dental materials? - Acidity- ph level above 7 acidic below 7 alkaline - adhesion or force of attraction hold unlike substances together. Plaque(physical) cements(chemical) - tensile force is pullin ex. Ortho band...

Dental Materials Review Know the terminology relating to the science of dental materials? - Acidity- ph level above 7 acidic below 7 alkaline - adhesion or force of attraction hold unlike substances together. Plaque(physical) cements(chemical) - tensile force is pullin ex. Ortho bands - compressive force is pushing - shearing stress is side to side back and forth ex bruxism - hue is dominant color red yellow blue - value is lightness of color scale 1-10 1 black 10 white. Normal teeth 5-8 - chroma is intensity of color scale 1-10 1 pale 10 rich. Natural teeth 1-3 - translucency or amount of light entering the tooth. Edges of teeth blueish hue - corrosion result of chemical or electrochemical influences of the oral environment on metals - tarnish is when metals in mouth become dull or discolored - dimensional change is change in length in volume of material by imbibition too much liquid which results in stiffness called turgor. - ductility ability of material to withstand permanent deformity under tensile stress w/o fracturing - malleability ability of material to withstand permanent deformity under compressive stress w/o fracturing - elasticity ability to be distorted or deformed by applied force of catalyst to metal. Has limits when material doesn’t return to original shape. Modulus stillness of material below elastic limit. - flow aka creep continuous deformation of solid when under constant force - galvanism when two diff metals Present in oral cavity there is a potential for minute shock. Gold and amalgam - Hardness ability to withstand or resist scratching or indentation - micro leakage tiny space b/w tooth and restoration where fluids and microorganisms penetrate and flow Down wall of prep. Leads to recurrent decay, sensitivity, tooth discoloration. - retention process where certain materials attach to hard and soft tissues in mouth. Mechanical dentist makes retention grooves. Chemical reaction b/w tooth surface and material - solubility is ability of substance to dissolve in fluid. - wettability is ability of material to flow over hard or solid surface. - viscosity ability of a liquid to flow. More viscous more sticky. Heated less viscous. Cooled more viscous. - toxicity degree at which a material is harmful. - Thermal conductivity rate at which heat flows through a metal. - Thermal expansion when dental material is subjected to heat it expands. Shrinks when heat is removed. What organizations are involved with determining safety and use of materials? -ADA and FDA regulate dental materials. American National Standards Institute, ADA, International Organization for Standardization establish more than 100 standards for dental materials. What are the cements used in dentistry? - Zinc Oxide Eugenol cement (ZOE) - Zinc Phosphate - Polycarboxylate - Glass Ionomer (Fluoride releasing) - Composite Resin Type I used as luting agent Type II used as restorative materials Type III used as bases or liners What are the major brand names of the cements used in dentistry? - ZOE: ZOE 2200, Zogenol, Tempbond, Fynal - Zinc Phosphate: Schein, Accubite, Patterson, Modern Teacin, Fleck’s Extraordinary, Smiths Zinc Cement, Lang-C B, Elite - Polycarboxylate: Durelon, Dura Set, LivCarbo,Tylok, Chemit, Carboxylon, Poly-F - Glass ionomer: Fuji, Ionolux & Ionostar, Ketac, RelyX - Composites: Filtek, Esther-X, Premise, Point 4 Flowable, Gradia Flowable, Tetric, Componeer, Ionolux What is each cement used for? - ZOE sedative base, temp cement for provisional coverage, temp filling, mix on pad, base/luting agent should be runny, mixing for restoration putty like, 1:1 powder to liquid. - Zinc Phosphate perm cement of crowns, bridges, ortho bands, insulating base, irritation to pulp b/c of phosphoric acid. Powder divided and mixed into increments. Luting agent 1 inch string, putty like, mix on glass slab 68 degrees exothermic reaction prolongs working time. - Polycarboxylate perm cement for cast restoration, ortho bands, stainless steel crowns, base under composites and amalgam, intermediate restoration. Limited shelf life, viscous liquid, mix on pad/slab, mix all powder at once into liquid similar to zinc phosphate, less irritating than ZP. - Glass Ionomer: Type I cement for metal restoration and ortho brackets. Type II restorative material class v. Type III liner and dentin bonding agent. Fluoride releasing 2 yrs. Thermo- insulation. Works w/ composite - Composite: used in restorations and core build ups. Requires liners. Not to be used w/ ZOE and varnishes. Compatible w/ primer, dycal or glass ionomer. What is glass ionomer used for? - composite  - Compomer - Hybrid ionomer - Glass ionomer - Used for direct restorations. They are tooth colored restorative materials used to fill cavity prep. What factors affect cement/alginate mixing and setting times? - CEMENT: humidity (powder) temperature (exothermic reactions, cool glass slab needed), powder to liquid ratio (too much or too little powder) - ALGINATE: warm water increase set time, cool water decreases set time What are your types of gypsum products? - Model plaster - Dental stone - High strength dental stone How is alginate and stone measured and mixed? - Dental stone: 30 mL of water for every 100 g of powder. - High-strength stone: 24 mL of water for every 100 g of powder. - Model plaster: 50 mL of water for every 100 g of powder. Add powder gradually mixing smooth bubble free consistency. - Mandibular impression: 2 scoops of powder + 2 measures of water. - Maxillary impression: 3 scoops of powder + 3 measures of water. Add water to powder until smooth and homogenous. Cool water slows, warm water speeds up set time. What types of impression materials are used for taking final impressions? - Polyvinylsiloxane (Addition Silicone) - High dimensional stability and accuracy make it ideal for final impressions in crown, bridge, and implant cases. - Preferred due to its ease of use and minimal shrinkage. - Polyether - Excellent for capturing fine details due to its rigidity and dimensional accuracy. - Commonly used for crowns, bridges, and partial dentures. - Polysulfide - Provides flexibility and good detail reproduction. - Suitable for removable partial and complete denture impressions but requires longer working and setting times. - Condensation Silicone - Can be used for final impressions but is less stable compared to addition silicone due to the evaporation of byproducts. What are the components of an amalgam alloy? - Silver - Main component (50-70%): Adds strength, durability, and luster. - Tin - Weakens amalgam but slows hardening and reduces expansion. - Copper  - Increases hardness and expansion; high-copper alloys (12-30%) resist corrosion better than low-copper alloys. - Zinc -Acts as a deoxidizer, preventing oxidation but can cause expansion and corrosion if moisture contaminates the mixture. - Mercury - Makes up 43-54% of the mixture; allows amalgamation by mixing with powdered metals. What factors affect a good or bad amalgam? Good Amalgam Factors Proper ratio of alloy to mercury (50:50). Adequate trituration (mixing): ○ Slight overtrituration increases strength. Minimal dimensional change during the hardening process. Correct handling to avoid excess moisture. Bad Amalgam Factors Undertrituration: ○ Creates a grainy mix that hardens quickly and weakens the amalgam. Overtrituration (beyond limits): ○ Reduces working time, leading to improper carving and placement. Excess Mercury: ○ Decreases the final strength. Moisture Contamination: ○ Causes expansion, corrosion, and recurrent caries. Faulty Manipulation: ○ Leads to overhangs, poor margins, post-op pain, or premature failure. Know the various types of waxes used in dentistry - Pattern Wax: inlay wax, casting wax, baseplate wax - Processing Wax: boxing wax, sticky wax, utility wax - Impression wax: bite registration Know how the dental casting process works - Wax pattern: detailed of final restoration w/ anatomical features on die model - Spruing: made of wax/metal the channel in which molten, alloy travels to form the restorations attached to cusp on restoration - Investing: captures all detail of wax pattern filling casting ring w/ gypsum bonded investment - Burnout: 500-600 C temp to burn out wax pattern and sprue - Casting/removal: changing wax pattern to metal restoration. Heated by blow torch or electrical current in ceramic crucible. Once melted molten alloy is added to casting ring  and placed in centrifugal casting machine. Force pushes metal through sprue and into burned out wax pattern, after its cooled it is devested/removed - Pickling: after casting its placed in acidic solution to remove oxides. - Finishing: after pickling the sprue is removed with a disc and stone on lab hand piece. To polished with rubber wheels or mild abrasive and cloth wheels. If porcelain needed its painted on cast in layers then fired in oven - How are gold alloys used in the dental lab? - to increase strength and stability by mixing with noble (platinum, palladium,Gold) and base (zinc, copper, silver, tin, Titanium, nickel) metal for casting inlays, crowns, bridges, partials How is a denture constructed? - A temporary form, usually shellac or acrylic, which will represent the denture base during the construction of the full or partial denture. Bite block Attaches baseplate and bite rim and Gives height to denture. Bite rim is a Mass of wax which is attached to the baseplate and shaped to conform to the edentulous portion of the ridge and which will represent the teeth during the construction. Denture base is the Permanent Portion of a denture to which contact the soft tissue of the alveolar ridge and artificial teeth are attached Made of acrylic May be reinforced with metal mesh. Flange is Part of the base that extends over the attached mucosa from the cervical margin to the border of the denture. Post dam or posterior palatal seal Determines the retention of the maxillary denture through suction – Forms from the posterior border and the junction of the tissue. Artificial teeth are Acrylic or porcelain Third molars not included in construction – Interfere with patient’s speech, chewing, swallowing, and closing. How are acrylics and acrylic resins used in dentistry? - Maxillo facial materials, temp crowns and bridges, custom trays What are custom trays used for and how are they constructed? - inadequate stock trays - Final impressions - Full/partial dentures, crowns, bridges - Constructed w/ resin called polymethylmethacrylate (two components liquid monomer and powder polymer). Line cast w/ baseplate wax then create stops. Line wax w/ Vaseline then mold sheet of tray material to conform to model. Trim excess w/ lab knife. Place in light curing unit according to manufacturers instructions then separate and trim model. Don’t forget your safety rules for the lab! - fire drill map front of lab - fire extinguisher far back wall of lab - oxygen levers at each lab station - panic button on west wall and rear of lab - ventilation switch light switch rear of lab - Fire blanket metal box on west wall of lab - eyewash station east wall of lab  - first aid kit east wall What are the indications and contraindications for whitening? Indications - Aging - Consumption of staining substances (e.g., coffee, tea, tobacco) - Trauma affecting tooth vitality - Tetracycline staining (causing grayish or brownish discoloration) - Teeth discolored - Old restoration - Excessive fluoride (fluorosis, leading to white spots or streaks) - Nerve degeneration (resulting in internal discoloration) Contraindications Active oral conditions: - Soft tissue lesions or open wounds - Untreated caries or periodontal disease Restorative considerations: - Will not bleach restorative materials (e.g., amalgam, gold, composite, porcelain) - Materials like hybrid ionomers or glass ionomers may roughen. Patient conditions: - Hypersensitivity (can be exacerbated due to the removal of the smear layer) - Pregnant or lactating patients (precautionary) - Poor oral hygiene or unrealistic expectations What methods of bleaching are available? - In-Office Whitening - At-Home Whitening (Prescribed by Dentist) - Over-the-Counter Whitening (e.g., strips, paint-on gels)