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207 Cards in this Set
- Front
- Back
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What principles does a PRR combine?
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The preventive approach of sealing susceptible pits and fissures with conservative cavity preparation of caries occurring on the same occlusal surface
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What is the benefit of PRR?
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Preserve non-carious enamel. Instead of traditional amalgam extension for prevention only the decayed areas are prepped
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What material is usually used for a PRR?
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Adhesive material usually composite then seal the entire occlusal surface
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What are the classification systems for PRR?
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Autopolymerizing PRR are types A, B, and C. Visible- light polymerized composite resin PRRs are Types 1, 2, and 3. In both systems A or 1 is the most conservative tooth preparation and C or 3 is more involved
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What is Type 1?
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Minimal preparation or widening of the pits and fissures sealant Incipient decay confined to enamel. This is considered a sealant application not a restorative technique
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What is Type 2?
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Prep extends to dentin. Resin used to fill prep and seal the tooth
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What is type 3?
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Prep similar to type 2: prep extends to dentin resin is used to fill the prep then a pit and fissure sealant is used to seal the tooth
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What does CAR stand for?
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Conservative adhesive restoration, its just a different way of saying PRR
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What is CAR ideally suited for?
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Minimal carious lesions in teeth that would otherwise lose a considerable amount of tooth structure if the extension for prevention treatment were followed
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For which types of PRR is bonding agent necessary?
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Types 2 and 3.
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What are the steps for a CAR?
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Excavate decay, Place composite, and place sealant
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What is the code for a PRR?
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D1352, in a moderate to high caries risk pt – permanent tooth
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What are the types of SSCs?
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Pretrimmed (Unitek), Precontoured and trimmed (3M), Preveneered (NuSmile)
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Why use SSC?
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Superior to large multi-surface amalgams. Longer clinical lifespan than 2 or 3 surface restorations. SSC longevity does not appear to be affected by moisture or technique sensitivity
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What is the failure rate of class II restiorations compared to SSCs?
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Failure rate of CL II is 2-7 times that of SSC. SSCs fail much less frequently than amalgams in spite of being used to restore signigicantly larger carious lesions
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What is the main reason for SSC failure?
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SSC need for re-cementation
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What is the main reason for failure of amalgam?
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Fracture of recurrent decay
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What is the survival of SSCs Cl I amalgams and CL II amalgams at 5 yrs?
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SSC – 98%, CL I – 93%, CL II – 70%
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What % of CL II amalgams failure in children less than 4yr?
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46%
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How many amalgams fail for each failed SSC?
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1.5-9 failed amalgams for each failed SSC
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What are the indications for SSCs?
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Primary or permanent teeth with extensive carious lesions, Hypoplastic teeth, teeth after pulpal procedures, teeth with hereditary anomalies such as DI or AI, restorations in disabled individuals with poor OH, Abutments for space maintainers or prosthetic appliances, and children undergoing treatment under GA with multi-surface lesions
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What does the SSC prep look like?
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Occlusal reduction 1.5mm (may need more especially with opposing SSC’s), Maintain the cuspal inclines, Proximal reduction – break contact, not too much taper, feather edge gingival margin. May need to reduce cervical bulge on the buccal but only if necessary to seat SSC. Round the line angles, especially MB
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What burs are recommended to reduce the occlusal?
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Football diamond, 169L, and 557
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What kind of margin should a SSC prep have?
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A feather margin
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What is the goal of selecting and seating a SSC?
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Goal is to place the smallest crown that will fit and restore pre-existing proximal contacts
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What are the most common crown sizes for SSC’s?
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size #4 on 1st molars and size #3 on 2nd molars
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How should a properly selected SSC fit?
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Tightly, perhaps with a snap. If the crown is to big crimp and contour it its too small trim 1.5mm from the proximal /lingual
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How is occlusal relationship evaluated on an SSC?
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After seating compare to adjacent teeth. If its too high you may have a ledge or need more occlusal reduction or need to break contact with adjacent tooth
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What does it mean if there is excessive gingival blanching when the crown is tried on?
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The crown is too long of too bulky
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How far into the sulcus should a properly trimmed SSC extend?
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1mm
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What is used to trim an SSC?
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C&B scissors or a heatless stone
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That instruments are used to contour and crimp the crown?
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Contour with either a 114 ball and socket or 137 Gordon pliers. Crimp with Unitek 800-147 pliers
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What does a tight fitting margin for an SSC aid in?
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1. Mechanical retention 2. Maintenance of gingival health 3. Less marginal leakage
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Should you be able to remove the crown with just finger pressure?
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No the crown should fit with resistance use spoon or carver to remove
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Why does Morbidity and mortality increase with children with Foreign body aspiration?
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Narrow airways, and immature protective mechanisms
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What factors need to be considered for the pediatric pt?
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1. Pts age and behavior 2. Presence and extent of disability 3. Local anesthesia 4. Body positioning 5. Loose teeth
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What does FBA require?
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Prompt recognition and early treatment to minimize potentially serious and sometimes fatal consequences
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Should you do a build up on a tooth that is being prepped for a SSC?
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NO, cement will fill in the area
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What type of cement should be used with SSC?
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GI cement
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Do you adjust the occlusal surface of the SSC if its high after cementation?
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No do not adjust the occlusal surface of the SSC
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When doing adjacent SSC what adjustments need to be made?
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Reduce the occlusal of one tooth completely before beginning the nest, more proximal reduction (about 1.5mm between preps at gingival level). Cement multiple crown in the same sequence that you tried them on (usually start with distal tooth)
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What shouldn’t the final product look like after placing a SSC?
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A rooster with socks on
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How is a direct restoration usually done?
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In one in-office visit utilizing materials such as amalgam, composite, and GI
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How is an indirect restoration usually done?
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In multiple visits, fabricated by a dental lab through the use of impressions and models. They require cementation for the finished restoration. Es – crowns, bridges, inlays, onlays, veneers
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When is an inlay indicated?
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When less than 1/3 to ½ of the intercuspal width of the tooth and no cuspal coverage required. CL I or II MO, DO, or MOD ( proper isolation and moisture control is required. Keep marins supragingival where possible)
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What advantage do inlays have over direct composite?
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No polymerization shrinkage
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What are alternatives to inlays?
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Amalgam and direct composite
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When are onlays indicated?
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More than ½ the width of occlusal surface is involved requiring cuspal coverage, when one or more cusps needs replacing
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What is a conservative alternative to a full coverage crown?
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Onlays. They require proper isolation and moisture control. Margins should be kept supragingival where possible
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What type of gold is used for direct gold restorations?
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Pure gold 99.9% in either cohesive or non-cohesive form used to restore small cavities directly inside the pt mouth (gold foil)
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What is used for indirect gold restorations?
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Cast gold alloys made in the lab then cemented and finished in the mouth
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What forms does gold for direct restorations come in?
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Foil – cohesive, sheets are manufactured by gold beating or rolling process also as pellets, ropes, or laminated. Sponge or Mat gold – cohesive, used in combo with foil for ease of handling. Powdered gold – non-cohesive, very difficult to use
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What is the purpose of annealing/degassing gold?
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Remove surface contaminants to produce clean surface and render the material cohesive. Use Alcohol flame or electric annealer carefully to prevent under or over heating
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What is used to compact gold?
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A hand instrument or an automatic mallet can be used to compact gold inside the cavity prep
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What are properties of direct/ cohesive gold?
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Pure 23 karat gold, used in small occlusal cavities, CL III, and repairs, its most important property is the ability to be cold welded by application of force. When two clean pieces are pressed together they are cold worked w/o application of heat
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What are the types of Gold casting alloys?
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Type I – soft used for casting inlays subject to slight stress during mastication. Type II – Medium alloy can be used for practically all types of cast inlays, and onlays and possibly posterior bridge abutments. Type III – Hard alloy acceptable for inlays, onlays, full crowns, ¾ crowns and anterior/posterior bridge abutments. Type IV – Extra-hard alloy designed for long-span fixed partial dentures and cast-removable partial dentures
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What is karat and what is fineness?
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Karat – indicate the number of parts by weight of gold in 24 parts of alloy 24K =99.9% pure, 18K=75% pure. Fineness – indicate the number of parts by weight of gold in 1000 parts of alloy. 24K = 999, 18K = 750, 14K = 585
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What is meant by precious metal?
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Alloy containing metals of high economic value such as gold, platinum, palladium, silver, rhodium, iridium, rhuthenium and osmium.
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What are noble metals?
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A precious metal that is resistant to tarnish. Silver is not a noble metal because it tarnishes
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What are low gold alloys?
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Alloys that contain <75% gold (less than 50 % gold) which means that gold atoms represent less than every other atom
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What are gold-substitute alloys?
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Precious metal alloys not containing gold
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What are base-metal alloys?
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Alloy not containing precious metals to impart their corrosion resistance. Allergies to base metals is much more common. Noble metal content less than 25% most complex and diverse
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What is high noble?
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Alloys that are 60% noble metal by weight with 40% gold
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What are noble alloys?
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25% noble metal. No limit on gold content
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What are the coefficients of thermal expansion for the tooth, PFM alloys, Gold alloys, Amalgam and Composite?
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Tooth – 9-11 ppm/C. PFM alloys – 14, Gold alloys – 18, Amalgam – 25, Composite – 35-45.
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What are the physical property general requirements for alloys?
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Reasonably low temp for flow, Moderately high density (castability), Low coefficient of thermal expansion
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What are the general requirements for chemical properties?
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Chemical corrosion (tarnish) resistance, Electrochemical corrosion resistance, Solubility (solderability)
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What are the Mechanical property general requirements?
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High modulus or resistance to strain, Moderately high resistance to plastic deformation, Hardenable by heat treatment (retention of polish)
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What are the Biological property general requirements?
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Biocompatible (no toxic soluble phases), Non-reactive in the oral environment
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What must be done on a gold inlay or onlay prep?
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Must have a marginal finish line of a chamfer or a bevel. Gold cannot be finished to a shoulder without incorporating the possibility of voids. Must have ample protection for functional cusps. Must have adequate reduction for the thickness of the cast metal
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What are the specs for the Gold inlay/ onlay prep?
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Occlusal clearance (1-1.5mm on functional cusps .5-1mm on non-functional cusps), remove occlusal decay, open proximal boxes, all occlusal walls must be divergent, all axial walls must be convergent, occlusal bevels cannot end in areas of excursive contact, all cavo surface bevels are continuous with the proximal wall flares
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What is shoeing?
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Veneer coverage of the cusp of a tooth with only a slight finishing bevel on the crest of the cusp. Use on the non-functional cusp
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What is capping?
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Complete coverage of the cusp or cusps of a tooth with sufficient extension for the bevel onto the buccal or lingual surfaces of the tooth to carry the margin of the restoration into areas where stresses cannot be brought to bear directly into them. Use on the functional cusp
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After taking impressions of your inlay/onlay prep what type of stone should be used to pour up the model?
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Type 3 or 4 die stone
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Following preparation what is done for indirect restorations?
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Tooth isolation with retraction cord, final impression of the prepared teeth with PVS impression material, Opposing impression with alginate or an alginate substitute, bite registration, and lab instructions
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What kind of impression materials are plaster, compound, wax, and ZOE?
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Non-elastic
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What materials are aqueous hydrocolloids?
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Agar (reversible) and alginate (irreversible)
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What are types of non-aqueous elastomers?
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Polysulfide, silicones (condensation or addition), and polyether
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What kind of impression material is PVS?
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Addition reaction silicone elastomers.
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What are the base and accelerator used in PVS?
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Base contains polymethyl hydrogen siloxane (silane terminal groups) and the accelerator contains polydimethyl siloxane (vinyl terminal groups)
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Are there any by-products of the PVS reaction?
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No. early material formed hydrogen gas bubbles on the surface of gypsum dies but palladium has been added to absorb hydrogen
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Is it necessary to wait 1 hour before pouring up PVS impressions?
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No
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What is another name for addition silicones and what are they used for?
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Vinyl polysiloxane used for crown and bridge, denture/ partial denture and bite registration
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How does shear force affect PVS?
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Viscosity is affected material will thin out under shear. Ex a medium bodied material can resist flow when placed in a tray, yet it demonstrates lowered viscosity when expressed through a syringe tip. Occurs due to the very small filler particles
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What changes the viscosity of PVS (LB, Med, Heavy, or putty)?
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Increasing proportion of added filler which is amorphous silica or fluorocarbons
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How can the working and setting times of PVS be altered?
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Refrigerate the material before mixing to increase working time. Never attempt to alter the base/ accelerator proportion to change working time
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What is the reproduction standard for PVS?
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20 microns. Heavy body and medium body meet this light bodied can reproduce down to 1-2 microns
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Can you use putty and wash for impression?
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No there are many problems with this technique including not having the accuracy needed. A monophasic heavy body and wash impression is significantly more accurate
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Does PVS shrink?
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Yes, however shrinkage is well matched to the setting expansion of type IV and type V die stones which results in a slightly larger replication of the prep.
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What is one thing that can be done to counter act PVS shrinkage?
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After removing the impression from the mouth reheat the impression to 37 degree centigrade
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Does humidity change the PVS impression?
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NO. impression will remain stable for 7 days
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How much more energy can PVS absorb before deformation than other elastomers?
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3x’s PVS deforms less and exhibits better recovery than other elastomeric materials
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What happens when impressions are removed slowly?
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The possibility of permanent distortion is greater when removal is slow. PVS impression should be removed with a rapid continuous movement during removal.
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What is wetting?
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The degree to which a drop of liquid will spread on a solid surface and can be quantified by its contact angle. Poor wetting = angle greater than 90 degrees. Zero angle indicates perfect wetting
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What helps make impression material hydrophilic?
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Surfactants. Materials with surfactants offer better wetting with moistened dentin and improved accuracy with poured dies
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Can the newest hydrophilic PVS materials be syringed into a wet sulcus?
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No evidence does not support the claims accuracy will be affected
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What is good wetting?
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The ability of a liquid to cover the surface of the substrate completely
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How long should you wait after applying tray adhesive before taking the impression?
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10-15min
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What type of trays should be avoided?
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Poor fitting or non-rigid trays lacking adhesive. Stock trays are OK to use
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When using putty why is mechanical retention necessary?
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Putty does not demonstrate chemical adhesion to the adhesive
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Can PVS be disinfected?
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Yes, PVS is unaffected by immersion in disinfectants like sodium hypochlorite, 2% glutaraldehyde, halogenated phenols, or .5% povidone-iodine
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To what detail can gypsum stones reproduce?
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20 microns crystal sixe ranges from 15-20 microns limiting reproducibility
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How much detail can Epoxy and polyurethane resin die materials reproduce?
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Dow to 1-2 microns which is comparable with detail capability of light bodied PVS
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What do natural latex gloves do to PVS?
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Cause an inhibiting of the clinical setting reaction of PVS materials. This occurs form direct contact with the gloves or form contact with mucosa previously contacted by latex gloves
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What 11 things do good impressions have?
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1. Uniform, homogeneous mix of material 2. Tray is sufficiently filled with impression material 3. Thoroughly applied tray adhesive 4. Rigid, sturdy impression tray 5. No voids or pulls on margin detail 6. Detailed margins with no tears or rough surfaces 7. No tray show-through of the impression material 8. Good blend between heavy body and light body materials 9. Strong bond between impression material and tray 10. No tooth contact with the tray 11. Complete information about the impression material used provided to the dental laboratory
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What can be done prevent margin tears of the impression?
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Displace tissue to allow the impression material access to area. Consider two-cord retraction. Leave pilot cord in the sulcus when taking the impression. Use impression material with sufficient tear resistance
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How can pulls and voids be minimized?
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Follow manufacturers working time specifications, do not move tray after seating, use more material to create back flow effect, use a tray that supports the flow of the material with a lingual stop.
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How can trapped air or moisture problems be solved?
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Use good moisture control technique. Rinse and dry prep area before taking impression. Stop bleeding by using appropriate retraction technique and hemostatic agent consider two-cord retraction
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What happens when PVS material contacts methacrylate residue?
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Will result in a poor bond between heavy body and light body material
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what is the benefit of doing an indirect ceramic or composite restoration over a direct composite restoration?
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Indirect methods do not have t he problem of polymerization shrinkage like direct composites do
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why is it important to bond the restoration with a rubber dam in place?
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The bond is with a resin cement and with out the isolation of a rubber dam you are seriously compromising the success of the procedure
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what do most indirect composite systems use?
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Highly filled microhybrid composites
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Where are the differences in indirect composite systems?
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With ceramic filler content, particle size and the processing method to achieve polymerization.
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How do newer indirect composite systems achieve a substantially high reaction completion?
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Cure composite under light, heat and pressure in an oxygen free environment this leads to ~90-95% reaction completion
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What are common prep design and bonding procedures of the different indirect systems?
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Prep with a deep chamfer or shoulder and bond with a resin cement, make sure all internal angles are rounded not sharp
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What are the disadvantages of indirect composites?
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The same inherent disadvantages of all composites such as a high coefficient of thermal expansion
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How are all ceramic restorative materials classified?
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by three things 1. Fusing temperature 2. Processing technique 3. Material make up
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What are the different categories for fusing temp?
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High (1315-1370 Centigrade) Medium (1090-1260 C) low (879-1065 C)
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What are the different categories for processing techniques?
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1. Slip casting 2. Sintered 3. Meat pressed and 4. Milled
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What era the different ceramic material make ups?
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Feldspathic – (silica in high conc.) Leucite-reinforced feldspathic (PFM) Lithium-reinforced feldspathic (Flexure). Glass-infiltrated alumina core (silica) Pure Alumina cores (no silica) Stabilized Zirconia cores (no silica) and Milled (variety of substrates)
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What is slip casting?
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Condensation of a aqueous porcelain slip on a refractory die. The porcelain is condensed by the capillary action of the water being absorbed ito the die. The slip is fired at high temp on the die result is less porous high strength porcelain. Ex. InCeram and Spinell
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What is sintering?
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Heating a slip casting for 10 hrs at 1120 C (until molten) multiple layers can then be added to develop characterization
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What is the heat pressed technique?
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Utilizes the lost was technique resulting mold is then pressed in a vacuum with a molten ingot of ceramic Ex. Empress which is what we use here at school.
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How are feldspathic porcelains made?
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They are built up and sintered
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What is IPS Empress?
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Leucite reinforced castable ceramic based on the lost was technique they demonstrate excellent wear and are cemented using a total-etch resin cement
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Which ceramic material comes closest to the 900MPa strength that gold has?
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Inceram Zirconia which is about 700 MPa, Inceram alumina is around 400-500MPa
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Which indirect esthetic material shows more wear?
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Composite shows more wear, pitting, discoloration and loss of gloss. Solution is vacuum compression to reduce porosity, and smaller particle composite to enhance wear characteristics
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Does composite or ceramic have a higher rate of bond failure?
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Debonding of composites is higher than ceramics. Usually preceded by discoloration which is indicative of micro leakage
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Is composite or ceramic better for indirect restorations in bruxers?
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Composite is better – less wear on the opposing teeth. Feel softer
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Is ceramic or composite better for inlays and onlays?
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Both work ceramic is better but composite is a less expensive alternative
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What are the dimensions for ceramic inlays/ onlays?
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1-1.5mm wide gingival floor, 1.5-2mm isthmus width, 1.5-2mm deep
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What is included in the ceramic inlay preparation design?
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Diverging walls, no undercuts, rounded internal angles, NO bevels, rounded transition of external outlining surfaces, flat pulpal and gingival floors, GI bases needed to idealize internal form
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What is included in the ceramic onlay preparation design?
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Diverging walls, flat floors, no undercuts, rounded internal angles, NO bevels, smooth rounded trasition of the external outline form, GI base required to block-out undercuts and idealize the pulpal and axial walls, No undulating floor, open gingival contact
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What is the current break down for lab processed restorations?
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15% all ceramic, 85% PFM
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What are the rules for Margin design using CAD-CAM?
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Avoid bevels and knife edge (margin too thin), Shoulder/ butt joint (no sharp internal angles), Chamfer (need thickness for success), Avoid occlusal contacts on margins
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What must a cerec prep account for?
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Optical impression technique, Computergraphic design program, restorative material, adhesive cementation vs mechanical retention
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What is required to optain an accurate optical impression?
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A uniformly reflective surface to accurately determine height values. Need – imaging liquid, Powder, Camera, and a steady hand
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what are some things to remember when using the camera?
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Avoid scratching the lens, No need to touch teeth with lens surface, 10mm depth of focus starting 4mm from lens
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what is the proximal contact line?
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the design parameter that represents the height of contour entirely around the tooth.
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What does the marginal ridge line include?
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The marginal ridge height as well as the cusp tips
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When evaluating the optical impression what are you looking for?
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Sharp focus, centered in the screen, margins are visible, line of draw is appropriate
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What does the bottom line represent when designing a crown on the computer?
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The cavity floor. Always start with cervical segment careful cursor position is important
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What does the fissure line include?
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The central fossa/groove No secondary grooves
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What seems to be the problem with zirconium crowns?
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The veneering porcelain separating from the zirconia core
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What are the two milling diamonds on the cerec 3?
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A cylinder - rest bottom and a tapered – occlusal surface
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How does margin fit compare for in office milling?
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Not comparable to lab restorations. A margin less than 100 microns is needed to achieve complete seating with adhesive cement. The smaller the margin the better (prevents cement wear)
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When curing the cement under a ceramic restoration how much light energy is absorbed by the ceramic?
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40-50%. The darker the shade the less the light penetrates over-cure rather than under-cure the cement
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What should be used to finish porcelain?
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Microfine diamonds <40 microns, use copious water spray and avoid preparation diamonds 60-100 microns and avoid carbides ( chatter across porcelain will result in fracture)
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Why is polishing porcelain so important?
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If porcelain is not polished it will have a sandpaper effect on the opposing teeth this is more of a problem than the hardness of porcelain.
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What are two typical fracture of milled porcelain?
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Isthmus fracture at cementation usually b/c relying on cement to fill too many voids and Fractured marginal ridge
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What are the wear considerations for porcelain?
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Conventionally thought of as a property of the restorative material but porcelain is generally considered to be abrasive on opposing tooth structure. Wear is more a function of surface smoothness and microstructure rather than hardness (sandpaper effect)
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For with teeth are inraoral composite inlays good for?
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Premolars and 1st molars
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When is an extra oral composite inlay or onlay recommended?
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Good alternative where access is not ideal a fast-setting silicone model material is required.
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How much taper is needed for a chairside inlay?
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Combined divergence of 15-20 degrees
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What is used to facilitate removal of the inlay after intraoral light curing?
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Glycerin
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Why bother with chairside inlays/onlays?
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Improved wear resistence (higher degree of monomer conversion) Better more anatomical contacts, adjustments are relatively easy, Polymerization shrinkage is outside the mouth and compensated for with resin cement.
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If you need to cement a temporary what shouldn’t you use?
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A eugenol temporary cement b/c the final restoration will use a resin cement
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What are luting cements?
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Cements that achieve retention by filling in the gaps between the tooth and the restoration. Adhesion is at best a surface phenomenon of wetting and micro-mechanical interlocking
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How do bonding cements work?
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Stronger than luting cements. Bonding to tooth structure through the smear layer or into dentinal tubules is more than just a surface phenomenon. Best to use primers which allow for the chemical adhesion to inorganic fillers or metal oxides
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What is a cohesive bond?
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A bond between two similar materials
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What is an adhesive bond?
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Bond between two dissimilar materials. Adherons are the dissimilar material and the adhesive fills in the irregularities on the surfaces of the adherons to join them together
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How do we create more surface energy for bonding?
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Roughen or acid etch surfaces before bonding.
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What is surface tension?
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Fluids take the shape of a sphere b/c it is the lowest energy form to distribute forces evenly
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What is wetting?
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Interaction of a fluid with a solid surface. A roughened surface increases the surface energy and facilitates the fluid spreading out on the surface of the solid. Wetting is a very desirable property for bonding anything in dentistry
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Why can resin bonding be difficult?
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“nothing in ceramics or metal will chemically bond to resin” Dr. Tozzi
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How then is resin bonding accomplished?
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A coupling agent which interfaces between the ceramic and the resin is necessary for a bond to take place
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What does silane allow for?
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It is the coupling agent that allows for covalent bonding between the glass in ceramics and resin
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How should silane be applied?
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As two thin layers to assure complete coverage and to act as a shock absorbing layer
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Why do ceramics need stiffness?
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Because they do not flex and all ceramics have minute cracks on their inner surface. A high strength core add toughness/stiffness
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What is the definition of ceramics?
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A glazed or unglazed body of crystalline or partially crystalline structure or of a glass. An inorganic non-metallic substance formed from a molten mass which solidifies upon cooling. Formed and simultaneously cured by the action of heat
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How is micromechanical bonding to ceramic achieved?
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Micro etch and acid etch. Acid etching with HF works well for silica based materials because it will etch glass. Acid etch won’t touch alumina oxide and zirconia cores and may cause cracking.
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Can phosphoric acid be used for ceramic?
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NO it only works on enamel and dentin
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How is a chemical bond to ceramic achieved?
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Only with silane and only if silica is present. Use HF to etch silica-based ceramics
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When is macromechanical retention used when bonding to lab composite?
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When repairing lab composite place undercuts or rounded divots on the surfaces to be bonded
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How is micromechanical bonding to lab composite achieved?
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Micro-etching removes resin-rich layer exposing filler particles. Do not acid-etch this will remove the filler particles exposed by the micro-etching
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How do you form a chemical bond to lab composite?
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Apply silane since most heat processed composite is highly filled
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Should macromechanical retention be used when bonding to existing composite?
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Yes always place mechanical undercuts. Surface roughen or micro-etch to remove hydrated composite
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What ways can micromechanical bonding be achieved when adding to an existing composite?
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Micro-etching removes soft polymer matrix. Acid-etching (HF) removes glass filler
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When should you micro-etch vs acid-etch when adding to composite?
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If you have large filler particles then etch this increases surface area for an adhesive to bond with unreacted C=C bonds
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Chemical bonding to existing composite utilizes silane when should/ shouldn’t you silanate?
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If you remove glass with HF do not silanate. If you have large filler particles silanate
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What macromechanical retention should be used when repairing denture base resins?
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Roughen the surface and add keystone locks into the fractured pieces of denture base
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What forms the micromechanical retention in repairing denture base resins?
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You can swell the linear denture polymer by adding monomer prior to placing the repair acrylic resin. This allow the repair resin to flow between and inter-lock into the swollen polymer strands
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Is there a chemical bond in repairing denture base resins?
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No b/c there is no unreacted polymer network in denture base materials like there is in composite
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What type of element is calcium?
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A metal – so teeth are actually metallic
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How can macromechanical bonding be achieved for veneering resin to metals?
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Add beads to the wax-up for retention ex. Meshwork on the back of ortho. Brackets, and diamond pattern on pre-fab posts
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How can micromechanical bonding to metals be improved?
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Sand blasting surface to remove layer of contamination and expose the crystalline matrix. This also increases the surface area for better wetting
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Why can’t metals normally be silanated?
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Metals lack silica
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What can be done to make silanating a metal possible?
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3M ESPE CoJet embeds a silicon layer on the surface of metal enabling silane coupling with resin
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What do metal primers do?
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They form a tenacious chelation bond with metal oxides as a coupling agent between metal and resin work better with base metals
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What does tin plating do?
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Forms a great metal to metal cohesive bond and a very retentive surface area of tin. Excellent for noble metals also works well with base metals. Can increase retention of restoration by up to 250%
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Which restorations can luting cements be used for?
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Metal, metal-based or core strengthened glass-free ceramic restorations with retentive preparations
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What are the 4 classes of luting cements and which are used today?
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Zinc phosphate, polycarboxylate, conventional flass ionomer, resin-modified glass ionomer. Only GI and RMGI are used
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Should a dentin conditioner be used with GI cements?
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NO
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What are the characteristics of composite resin cements?
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High adhesion, low solubility, and good esthetics. Must use a bonding system
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What are the three subtypes of bonding systems?
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Total-etch system, self-etching system, and self-adhesive systems. These systems are in general moisture intolerant
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What is characteristic of self-etching systems?
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Typically dual cured, self-etching primer mixed and activated with a bonding agent. Specific primers for bonding to metal, composite and ceramic ex. Panavia F
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Which system is most used today?
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The self-adhesive cements with 3M – RelyX UniCem being the #1 selling cement in the US. It is dual-cured and eliminates separate etching and bonding steps. Uniquely moisture tolerant and low risk of post-proerative sensitivity. Another ex is Kerr MaxCem Elite
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What must not be used prior to cementation with UniCem or MaxCem?
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Do not use desensitizers, disinfectants, denting sealants or astringents following cleaning with pumice and water
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Why are self-etching cements questionable for composite/ceramic crown?
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Because of their weak etching
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What are the key factors that determine restoration and cement type?
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Esthetic demands, ability to maintain a dry field, occlusal forces, remaining tooth structure, prep design (retentive or non-retentive), and margin location
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Which restorations must be adhesively bonded with strong cements?
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Weak restorations
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What must be done to achieve bonding between ceramic restorations and resin cements?
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The undersurface of restoration must either be micro etched or acid etched then silane coated
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What do most self/dual cure resin cements used to initiate polymerization and curing?
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Benzoyl peroxide (BPO) and tertiary amine. This can result in discoloration over time due to oxidation of amine. Choose a cement that is color stable such as MaxCem Elite
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What are the standards for cements?
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Set by Am. National Standards ASA Specification #27. The maximum film thickness is 50 microns for resin based cenents and 25 microns for water-based cements at 2 min after mixing
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what is the fracture resistance from greatest to least for gold, amalgam composite and GI?
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That is the order. Gold, amalgam, composite, and GI
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what is a benefit of using dual-cured core build up material?
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Polymerization shrinkage is less
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what type of cement can be used to bond all types of restorations?
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Composite resin cement
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