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Prosthodontic/Crowns
Vet Dentistry
| Question | Answer |
|---|---|
| What is the first rule of operative dentistry? | Conservation of tooth structure |
| What is meant by extension for prevention? | a restoration preparation outline should be designed to allow for proper oral hygiene to prevent additional disease Hygienic conditions of the mouth must be taken into consideration and prep outline must be designed accordingly |
| What are benefits of placing the restoration outline coronal to the gingival margin? | tooth structure is conserved improved visualization of work easier marginal finishing=less chance of overhangs and less gingival irritation |
| What are benefits of placing the restoration outline apical to the gingival margin? | enhanced esthetics and retention b/c greater surface area for cementation protected restorative margin |
| What is the common result of placing a cavity outline level with the gingival margin? | gingival irritation |
| What are 5 factors that should be taken into account when planning restoration treatment? | 1. underlying cause for needed tx 2. periodontal health 3. occlusion 4. the tooth's retentive qualities and ability to sustain a load 5. esthetics |
| What is a contraindication for crown placement? | tooth mobility |
| What is another name for the cavosurface angle? | preparation margin |
| What is the restorative margin? | The restorative surface that abuts the cavosurface angle |
| What are 5 things that are affected by the preparation margin design? | 1. retentive quality 2. resistance to marginal leakage 3. physiologic contour reactions 4. gingival health 5. resistance to attrition, abrasion, fx of the restoration and/or restored tooth |
| What 4 factors should be considered when choosing which design to use for preparation margin? | 1. type of restoration selected 2. restoratie materials to be used 3. degree of anticipated stres demand on the restoration 4. length and direction of enamel prisms |
| With what type of material and what type of restorations are knife-edge and occult finish lines more typically used? | metal onlays |
| What are benefits of using knife edge or occult finish lines? | less tooth structure removed=stronger tooth |
| What is the drawback of using knife edge or occult finish lines? | creates an over-sized crown so can only be used where occlusal space allows and esthetics are not of concern |
| What factors must be considered in choosing the design of a preparation outline? | 1. location (GV Black classification) 2. Extent (depth of prep, pulp capping, etc) 3. Stresses (occlusal, leverage, etc) 4. Tooth condition (vitality, perio status) 5. esthetics |
| What technique is employed in the fabrication of most dental metal restoratives? | The lost wax technique |
| How are metals categorized in dentistry? | 1. Nobility 2. Fusing characteristics |
| What are the 3 different classes of metal regarding nobility? | 1. Noble 2. precious or semi-precious 3. non-precious or base |
| How many noble metals are there? What are the 2 groups? | seven: 1. Gold 2. Platinum (6 kinds) |
| What are the 6 noble metals in the platinum group? | 1. platinum 2. palladium 3. irridium 4. osmium 5. ruthenium 6. rhodium |
| What characteristics to noble metals have? | Stable in the oral cavity and fluids resistant to corrosion reduced risk of contact irritation and allergic reactions |
| What attributes does gold have as a dental restorative material? What is the drawback? | easily cast strong high ductility and burnishability low allergic-reaction rate Downside: cost |
| What metals comprise the semi-precious group? | seven nobles plus silver |
| Why isn't silver a noble metal? | tarnishing and corrosion characteristics |
| What are the non-precious metals? | Base metals: nickel-based alloys chrome-based alloys technic metals (copper added for color) |
| What are adverse effects often seen with base metals? | contact stomatitis and dermatitis allergic reactions periodontitis w/bone loss |
| What are the 2 metal classes based on fusion characteristics? | 1. normal fusing alloys 2. high fusing alloys |
| What fusion class of alloy must be used with porcelain fused to metal restorations? | high fusing metals b/c they don't melt or creep during repeated heating required to bake on porcelain layers |
| What are the 4 types of normal fusing alloys? | type I (soft) type II (medium) type III (hard) type IV (extra hard) |
| What are 7 groups of high-fusing metals? | 1. noble gold 2. white noble 3. palladium-silver alloys 4. gold-palladium alloys 5. nickel/chromium-base metal alloys 6. cobalt-base metal alloys 7. high-palladium alloys |
| What is a potential disadvantage of the hardness of porcelain? | May increase the rate of attrition of occluding teeth |
| What is an esthetic disadvantage of porcelain? | difficult to polish to original luster after adjustments are made |
| What are 2 advantages of indirect composite resin restorations over porcelain? | less hard, won't accelerate wear of occluding teeth easily re-polished |
| What depth of facial reduction can be used with feather margin prep for composite veneers? | 0.25-0.5 mm |
| What depth of reduction should be used for composite restorations over incisal, cusp, and occlusal surfaces? | 1-1.5 mm |
| With indirect composite restorations, where can shoulders and chamfer margin design be used? What depth should this be? | gingival cavosurface. at least 0.5 mm |
| What is Inceram? | glass ceramic that incorporates zirconium oxide to enhance color and strength |
| What type of fabrication requirements do cast glass ceramics have? | similar to cast metals |
| What is CERAMMING? | A process used to treat the formed glass cast to obtain full strength by converting it into a crystalline glass ceramic |
| What restorative marginal characteristics support bacterial colonization and resultant gingivitis? | poor marginal adaptation rough, porous surfaces |
| What benefits does cast glass offer regarding risk of gingivitis associated with the margin? | Cast glass is less prone to plaque accumulation than any other restorative and even enamel b/c it is 1. smooth 2. has low surface tension 3. generates a form of electrostatic repulsion |
| Which restorative material is better for anterior teeth b/c of esthetic properties, but poor choice for posterior teeth due to weakness and risk of cracking? | porcelain |
| What is a GRIFFITH FLAW? | microscopic defect created during fabrication of porcelain |
| Which has greater compressive strength: cast glass or porcelain? | cast glass |
| Which is less abrasive, with lower risk of accelerated wear to occluding teeth: cast glass or porcelain? | cast glass |
| Which dog teeth are best suited to receive cast glass restorations? | canine teeth |
| What is the purpose of Porcelain fused to Glass restorations? | Strength of cast glass combined with esthetic qualities of procelain |
| What material is well suited for restorations of posterior teeth in humans, but not dogs? | cast glass: complex shearing forces in dogs pose risk to this material |
| Which has better esthetic qualities: PFM OR PFG? | PFG |
| Which is most resistant to fracture: PFM OR PFG? | PFM |
| What are benefits of polymer glass? | esthetics improved over regular composite resin strength improved over porcelain w/o increased abrasiveness and risk of wear to occluding teeth |
| What is the downside of polymer glass? | Requires full polymerization , special curing procedures |
| What is SINTERING? | the actual fusing of porcelain powders into a single solid structure |
| What are 3 different fusion types of porcelain? | low, medium and high-fusing |
| What is the advantage of low and medium fusing porcelain? | less tress on the metals used in PFM restorations during fusing of the porcelain to the unit |
| What are advantages of an all-porcelain restoration over a PFM? | 1. improved esthetics 2. better biocompatibility (metal allergies, toxicities) 3. no darkening of adjacent tooth structure resultant from metal leaching |
| What are disadvantages of an all-porcelain restoration over a PFM? | low compressive strength requires substantial remaining tooth structure increase wear to opposing tooth structures |
| What is the main advantage of PFM? | Increased compressive strength |
| How does porcelain fuse to metal? | chemically and mechanically |
| What is SLUMPING? | slow deformation of porcelain from repeated heating |
| What is DEVITRIFICATION? | Crystallization that occurs from repeated firings, resulting in clouding of porcelain which gives a non-vital appearance to the restoration |
| What axial reduction is generally required for PFM? | 1.5 mm: 0.5 mm for metal, 1 m for porcelain |
| How much redcution of incisal and occlusal surfaces is recommended for PFM? | incisal 2 mm occlussal 1.5 mm |
| What results are seen with failure to perform sufficient reduction? | poor esthetics weak restoration or oversized restoration |
| What is a PARTIAL ONLAY OR OVERLAY CROWN? | restoration that covers a cusp and only a portion of the clinical crown |
| What is a PARTIAL INLAY CROWN? | restoration that covers only a portion of the clinical crown, but NOT the cusp |
| What are partial crowns used for most commonly | cage biter syndrome |
| What class of preparation is an inlay for cage biter syndrome? | class II |
| What class of preparation is an onlay? | Class VI |
| What margin design should be used for inlays and onlays? | beveled or chamfered |
| What is an ABUTMENT? | A tooth, crown, or portion of an implant used to support, stabliize, or anchor a fixed or removable dental prosthesis |
| What is a PIER? What is another name for it? | any abutment other than the terminal abutments aka INTERMEDIATE ABUTMENTS |
| What is a PONTIC? | the portion of a bridge that replaces a missing tooth |
| What is a bridge RETAINER? | the portion that rebuilds the prepared abutment and pier teeth |
| What is a bridge JOINT or CONNECTOR? | THE part of the bridge that unites the retainer with the pontic |
| What is a DOVETAIL? | A type of connector used as the movable jiont for a minor retainer |
| What is a bridge SPAN? | The portion of the bridge suspended between the abutments |
| What is a FIXED-FIXED bridge? | one-piece bridge with pontic(s) attached to the span between retainers at both ends |
| What is a FIXED-MOVABLE bridge? | 2 piece bridge with the pontic(s) integrally attached to the retainer only at one end |
| What is a CANTILEVER bridge? | a one-piece bridge with the pontic supported only from one end by a retainer |
| What is a SPRING CANTILEVER bridge? What is the advantage? | one piece bridge in which the pontic is remotely attached to the retainer by a spring or bar. allows for naturally appearing open contacts mesially and distally |
| What is a MARYLAND bridge? | retainers are simply acid etched at the areas that make contact with the tooth to enhance cementation |
| What is the difference between a MARYLAND bridge and ROCHETE bridge? | in rochette bridge, retainers are perforated at the areas that make contact with the tooth enhance cementation |
| What is unique about Maryland and Rochette bridges? What is the downside of these bridges? | Don't cover the incisal edge or cusps. Most conservative regarding tooth reduction, but downside is less retentive quality |
| What is the most important factor to consider when planning bridge construction for an animal? | Owners committment to maintaining oral hygiene |
| What factors affect the retentive qualities of a bridge? | abutment tooth selection and retainer type |
| What is the minimal acceptable clinical crown height for teeth to be used as abutments? | 4 mm |
| What are contraindications for using a tooth as an abutment? | 1. tooth mobility 2. periodontal dz 3. insufficient clinical crown height |
| What should the root surface area of abutment teeth be relative to that of teeth to be replaced by a bridge? | at least equal, ideally 2X |
| What characteristic must be equal among teeth reduced to be used as abutments? | must have identical line of draw to be able to seat the bridge |
| What page in Wiggs has a table with reduction requirements for restoratives of all types in every location? | p. 413 |
| To what height are dog canine teeth generally restored? | not more than 2/3 of original crown height |
| What are the four types of straight fissure burs? | 1. plain end-cutting (56, 57, 58) 2. plain round end (556, 557, 558) 3. crosscut end-cutting (1156, 1157, 1158) 4. crosscut round end (1556, 1557, 1558) |
| How long is the operative surface of a standard straight fissure bur? | 4 mm |
| How long is the operative surface of a long straight fissure bur? | 5.5 mm |
| What is the diameter of a '56 bur? '57? '58? | 56: 0.9 mm diameter 57: 1.0 mm diameter 58: 1.2 mm diameter |
| Why is a crosscut bur better than a plain bur for restoration prep? | crosscut creates a rougher surface=better retention b/c greater surface area for luting |
| Why might the rougher surface created by cross-cut burs be detrimental? | if surface is too rough, can result in drag and microscopic tearing of alginate impression materials |
| How does acceptable taper change with height of tooth to receive crown? | The taller the supporting tooth structure, the more allowable taper and still maintain good retention shorter tooth requires more wall parallelism for retention |
| Which direction does the high speed air turbine turn the bur? | clockwise |
| Which direction should the bur be worked around a tooth for restoration prep? why? | counter clockwise so that debris are thrown away from the path of cutting, to maintain good visiblity of working field creates an air vortex that helps repel the gingival margin, protecting it from trauma |
| What is the minimum depth of dentin that should remain intact covering vital pulp? | 0.5 mm |
| What are the fundamentals of retention? | 1. axial wall taper 5-7 degrees max 2. maximize enamel coverage 3. maximize tooth coverage 4. retentive grooves 5. pin holes, pins 6. core build up 7. metal post and core 8. cross pinning 9. adhesion system |
| What is the minimum necessary height of contour for adequate retention? | 3-4 mm of sound, exposed tooth |
| What is BIOLOGIC WIDTH? | the distance physiologically maintained by the body's defense mechanisms between the restorative and the base of the sulcus |
| What is the biologic width in dogs? | 2 mm |
| What happens if you place a restoration too close to the alveolar crest such that it interrupts the biologic width? | the body engages a response to re-establish normal biologic width: inflammatory response results in crestal bone resorption and apical migration of periodontal soft tissues |
| What is CROWN LENGTHENING? | exposure of more root structure for use as clinical crown for restorative coverage |
| What are the 3 types of crown lengthening? | Type I: gingivoplasty Type II: gingivoplasty and bone recontouring Type III: forced eruption |
| When performing type I crown lengthening, how much attached gingiva should be maintained? | 2-4 mm |
| What is the difference between a post/dowel and apin? | size and placement: posts are larger and are placed into the endodontic system rather than into dentin |
| What is a CORE? | Substructure for seating a crown |
| How far from the gingival margin should the preparation margin be placed for supragingival restorations? | 0.5-1.0 mm |
| What impressions/models are required by the laboratory to fabricate a crown? | 1. full mouth models 2. area-specific impression (VPS) 3. Bite registration impression 4. color registration/matching if using composite, glass ceramic, porcelain |
| What is OSSEOINTEGRATION? | FUNCTIONAL ANKYLOSIS: process involves the metal oxides on the surface of an implant bonding to bone |
| What are the 3 major parts of an implant? | 1. implant that integrates with the jaw bone 2. abutment 3. restoration |
| What metal is used because it has been shown to be biocompatible, & osseointegrate, long term | titaneum |
| What are the 2 stages for implantation? | 1. implant placement 2. implant loading after osseointegration |
| How long does osseointegration generally take? | 3-5 months |
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lamarron
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