Direct winter 2013

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Direct winter 2013
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2013-03-14 01:44:03
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  1. Discuss the etiology of root caries and describe treatment alternatives based on etiology including, but not limited to, dietary factors, xerostomia, remineralization, root
    planing, and restorative techniques.
    • Etiology of root caries
    • o    Xerostomia
    • o    Dietary Factors
    • o    Hypoplasia / fluorosis - defects
    • o    Plaque and bacteria - caries
    • o    Gingival recession  - cervical sensitivity and root caries
    • o    Abrasion - improper brushing
    • o    Abfraction  - occlusal disharmony 
    • o    Erosion - acid dissolution
    • o    Ablation – soft tissue pressure leading to tooth wear (ex sand rubbing stone)
    • ·         
    • Treatment alternatives
    • o    Eliminate etiology
    • o    Remineralization
    • §  Fluoride
    • §  Potassium oxalate
    • o    Oral hygiene instruction
    • o    OTC desensitizing toothpastes
    • o    Root plane + fluoride or DBA (dentinal bonding agent)
    • o    Surgical restorative procedure
    • §   Amalgam (abrasion reistant, wet field)
    • §   Composite (less bonding to dentin, bond breaks down, esthetic)
    • §   GI  (Good bonding, Good Co-E Thermal expansion, Fluoride release)
  2. Contrast the basic chemistry and characteristics of tooth structure bonding to (a) composite resin versus to (b) glass ionomer.  Do not include clinical placement
    technique.
    • Composite bonding:
    • • Conditioner/Etch: 
    • o Acid removes or some or all of smear layer, exposing and opening dentinal tubules and increasing micromechanical attachment on enamel and dentin.
    • • Primer: 
    • o Contains monomer in a solvent (ethanol) that flows into dentinal tubules well.
    • • Bond (Adhesive):
    • o  Contains unfilled resin [Methacrylate monomer and TGMA (a crosslinking monomer)] and photoinitiators that lock into micromechanical undercuts when light cured creating a hybrid layer.
    • • Composite:  
    • o Filled resin that chemically bonds to adhesive and micromechanically adheres to enamel.
    • • Characteristics:
    • o More setting shrinkage
    • o More expansion (after water immersion)
    • o Less fluoride release
    • o Increased thermal expansion
    • Glass Ionomer:
    • • Acid etch eliminates smear layer exposes micromechanical undercuts in dentin and enamel.
    • • Powder - Ground calcium aluminosilicate  glass (containing fluoride)
    • • Liquid - 50% aqueous solution of polyacrylic acid, itaconic acid, tataric acid (accelerator)
    • • Setting Reaction – 
    • o Acid-base reactions release protons from acid that attack the calcium aluminosilicate glass, partially liberating calcium.  
    • o The aluminum and calcium molecules are chemically attracted to both the silicate glass and the decalcified hydroxyapatite (phosphate groups) creating an ionic bond.   
    • o The polyacid monomers of the GI bond to the Ca2+ in the dentin via an Ionic interaction; 
    • o polyacrylate also displaces PO4 and Ca2+ ions from the tooth structure so that only those Ca2+ ions that are attached to the tooth structure are bound by the GI monomer. 
    • o  
    • • Characteristics:
    • o Less setting shrinkage
    • o High fluoride release
    • o Stiffer
    • o Low thermal expansion
  3. Describe the principal features covered under (1) external form and (2) internal form
    with specific ideal measurements for a competency examination on a class 2
    cavity preparation for amalgam restoration.
    • 1) External form
    • a. Outline form
    • i. smooth-flowing form across occlusal outline
    • ii. centered isthmus/s-curve to proximal wall where required
    • iii. dovetail adjacent to marginal ridge/fishtail around distal cusp
    • b. Outline size
    • i. 0.9-1.3 mm isthmus width 
    • ii. 0.9-1.3 mm  occlusal groove extensions
    • iii. 0.25 – 0.5 mm dovetail extensions
    • iv. 0.8 -1.0 mm fishtail extension (distal cusp)
    • c. Buccoproximal and linguoproximal walls
    • i. 0.5 mm proximal clearance (0.25 – 0.75 mm)
    • ii. Proximal walls parallel to embrasures (func. cusp = acute; nonfunc. cusp = 90 degrees)
    • d. Gingival wall
    • i. Horizontal buccolingually
    • ii. 0.5 mm gingival wall clearance (0.5-1.0 mm)
    • e. Cavosurface margins are smooth-flowing; supported enamel margins
    • 2) Internal form
    • a. Pulpal wall
    • i. 1.5-1.9 mm pulpal wall depth, parallel to occlusal table
    • b. Occlusal walls
    • i. Buccal and lingual walls convergent occlusally
    • ii. Supported enamel at marginal ridge (slightly divergent)
    • c. Proximal walls
    • i. 90 degree exit angles at bucco- and linguo-proximal walls to cavosurface (occlusal view)
    • ii. Gingival bevel follows enamel rods
    • d. Axial wall
    • i. 1.0-1.5 mm axial wall depth
    • ii. Axial wall at obtuse angle to gingival wall; rounded axiopulpal line angle
    • e. Buccal and lingual retention grooves
    • i. 0.25 mm buccal and lingual retention grooves at axioproximal line angles
  4. Compare and contrast class 5 and root caries preparations designed to receive amalgam,
    composite resin, and glass ionomer restorative material.  Include in your response preparations that
    occur exclusively in enamel, exclusively in dentin, and half-enamel/half
    dentin.  Defend your preparation designs
    with rationale with specific correlation to tooth structure and dental material
    properties.
    • • Amalgam design
    • o Remove carious and affected dentin and enamel on locations where esthetics is not a factor, dry field cannot be obtained, and/or maximum abrasion resistance is required.  As with all amalgam preparations the external and internal walls should be smooth and flowing with a typical kidney bean shaped outline form.
    • o Margins in Enamel
    •  90o exit angles with incisogingival retention grooves at least .5mm into dentin
    • o Margins in Dentin
    •  90o exit angles with I/G retention grooves at least .5mm into dentin.
    • • Composite Resin
    • o Composite is preferred on enamel margins (bevel indicated) for improved esthetics and abrasion resistance
    • o Margins in Enamel
    •  45 deg beveled Enamel margins with optional retention grooves (always incisogingivally) at least 0.5mm into dentin if little enamel for bonding.
    • o Margins in Dentin
    •  90o exit angles with retention groves placed incisogingivally at least .5 mm into dentin.
    •  Never add a bevel to dentin
    • • Glass Ionomer
    • o GI indicated for:
    •  deep preparations (closest Coefficient of Thermal Expansion) that have dentin margins (greatest bonding to dentin). 
    •  Indications all include areas of high risk (b/c of fluoride release/recharge) and areas of limited esthetic demand (it is not translucent)  
    • o Preparation removes all carious enamel and dentin.  Fuji II LC for shallower preps, Fuji IX otherwise
    • o Margins in Enamel
    •  Smooth walls and Axial wall with no retention grooves 
    •  90o exit angle at cavosurface margin or beveled enamel margin with composite open sandwich.  
    •  GI on enamel margins not preferred
    • o Margins in Dentin
    •  Smooth axial walls and 90o exit angles.  
    •  Retention grooves optional due to ionic bonding for retention
  5. Describe
    the pulp therapy concepts for direct and indirect pulp capping including
    indications for each, citing (1) patient symptoms and clinical signs, (2)
    factors affecting prognosis, and (3) clinical technique for direct and indirect
    procedures with specific therapeutic products used
    • Pulp Therapy-Is part of the process of Caries Removal
    • • Direct Pulp Capping
    • • Indications:
    • 1. Patient symptoms and clinical signs
    •  In the process of acute or chronic caries removal, non carious dentin is removed over the pulp chamber, exposing less than 1mm diameter pulpal exposure.  
    •  The pulp is healthy and vital with possible bleeding.  
    •  Complete caries removal. Non carious dentin will have a hard texture.
    • 2. Factors Affecting Prognosis
    •  Positive Prognosis
    • • Bleeding and coagulation
    • • Mild or no symptoms
    • • little or no caries
    • • iatrogenic damage
    •  Negative (contraindications-go to RCT)
    • • Large Carious Exposure
    • • Necrotic Pulp
    • • History of Pain, sensitivity, toothache
    • 3. Clinical Techniques
    •  Product:  Dycal Cap, GI Base, Amalgam
    •  Technique:  
    • • Complete Caries Removal
    • • Mix equal Base and Catalyst of Dycal.  
    • • Apply just over and beyond exposure with ball end of Birtle’s Applicator
    • • Base with GI cement
    • • Etch, Rinse, Prime, Bond (DBA) and restore with amalgam
    •  Permanent restoration if successful
    •  Solid restoration for RCT &casting if not successful
    • • Indirect Pulp Capping
    • • Indications:
    • 1. Patient symptoms and clinical signs
    •  Near pulp exposure
    •  (May have pink hue to dentin) 
    •  ~1-2mm pulpal blush
    • 2. Factors Affecting Prognosis 
    •  Large Carious Exposure 
    •  Necrotic Pulp
    •  History of pain, sensitivity, toothache
    • 3. Clinical Techniques
    •  Product:  Dycal, IRM 
    •  Technique:  
    • • Incomplete Caries removal to avoid carious bacterial inoculation
    • • Place Dycal over carious dentin to incite healing
    • • Temporize with IRM
    • • Next visit Re-entry to: 
    • o evaluate prognosis that depends on bacterial/nutrient seal and recuperative potential of tooth
    • o respond to patient symptoms
    • o remove unresponsive affected caries 
    • o place new temporary or permanent restoration
  6. Your
    patient requires a full gold crown on #30 due to extensive caries and fractured
    loss to the CEJ of the mesiolingual cusp. 
    He cannot afford a gold crown now. 
    Describe the proper use of retention pins and other retentive features
    in designing an amalgam restoration for this tooth that will serve as a
    foundation restoration for a future full gold or porcelain-fused-to-metal crown
    • • Pin retention is a technique of last resort when other methods are exhausted
    • • Retention pin features
    • o Rubber dam is essential!
    • o 2mm into sound dentin
    • o 2mm of pin length
    • o 2mm of amalgam over pin
    • o 1 mm of amalgam around pin 
    • • Pin placement sites
    • o Primary sites: line angles of posteriors
    • o Secondary sites: D cusp of mandibular molars
    • o Danger sites (near root concavity)
    •  Mandibular molars: mid-B, mid-L
    • • Retention pin technique
    • o Considerations
    •  Complete preparation and place DBA, liner, or base prior to preparing pin channel 
    •  Use one pin per missing cusp
    •  Use multiple pins at different levels and non-parallel to one another 
    •  Oppose pins with groove, box, undercut for added retention
    • o Prepare horizontal platform with 1 mm around pin channel
    • o Use #1 round bur to prepare countersink for precise placement of twist drill
    • o Use 0.017” twist drill to prepare 2 mm pilot hole
    • o Follow with 0.021” twist drill 
    • o Place pin
    •  Regular (0.031”):  back up for minum 
    •  Minum (0.023”):  most situations 
    •  Minikin (0.019”):  small anterior teeth
    •  Minuta (0.015”):  rarely used due to adhesive materials
    • o Restore with amalgam
    • • Additional retentive techniques
    • o Extending outline form: 
    •  occlusal dovetails, fishtails 
    •  crossing transverse/oblique ridges
    •  buccal, lingual boxes
    • o Extending internal shapes/forms 
    •  Grooves, potholes into gingival wall
    •  Horizontal undercuts away from pulp
    •  vertical grooves through enamel
  7. Describe the requirements for a successful matrix application using the Tofflemire retainer and bitine ring systems, and list the advantages and disadvantages of each system.
    • • Matrix requirements
    • a. > 1 mm occlusal to marginal ridge height
    • b. Band is below and sealed at gingival margin with wedge
    • c. Enough tooth separation to compensate for band thickness
    • d. Band should be in contact with adjacent tooth, or you should be able to condense so you have contact with the adjacent tooth
    • i. Burnish band to ensure proximal contact
    • ii. Recreate proper marginal ridge form with 4 embrasures and even with adjacent marginal ridge
    • e. Rubber dam and gingival must not be trapped in the proximal box
    • o If the matrix band is too narrow, or caries too deep, select #2  (winged) band
    •  If a 3-surface (MOD), leave both wings
    •  If a 2-surface, cut one of the wings
    •  Wider part of wing faces coronally
    •  Tofflemire matrix tines face down
    • Describe all the requirements for a successful matrix application using the Tofflemire retainer system.
    • - The matrix band should first be determined. Either a #1 or #2 (winged) matrix band should be chosen depending on the size of the cavity preparation. The band should be formed in a circle with the wide end of the band plaed towards the occlusal.
    • - Next either a contra-angled or universal tofflemire is chosen.  A universal tofflemire will be chosen unless there is a buccal preparation which requires the tofflemire to be placed on the lingual of the teeth.
    • - The band is inserted into the tofflemire in the guide slots. The guide slots of the tofflemire will always face towards the gingiva. This necessitates that the wide end of the folded matrix band faces away from the guide slots. Tighten the rotating spindle in order to hold the band in place.
    • - Position the matrix band and tofflemire on the tooth such that tofflemire is coming out of the mouth anteriorly.
    • - The matrix band should be positioned so that the band sits 1 mm above the adjacent marginal ridge. In addition, it should sit below the gingival margin.Twist the set screw to tighten the band slightly around the tooth.
    • - Insert the wedge to move the tooth over at least the thickness of the matrix band. The wedge should be placed so that it is sealing the gingival margin.
    • - Loosen the band using the set screw so that it is in contact with the adjacent tooth. Burnish the band intot the adjacent tooth.
    • Tofflemire retainer vs. Bitine ring
    • • Tofflemire
    • o Flat proximal contour
    • o Thin contact at marginal ridge
    • o Food trap below contact 
    • o Weaker resistance form
    • • Bitine Ring
    • o Contoured bands
    • o Anatomically correct contacts
    • o Contacts at height of contour
    • o More separation provides tight contacts
  8. For an amalgam restoration, retention form includes:
    • - Buccal and lingual walls which converge occlusally
    • - Retention grooves in axiobuccal and axiolingual walls of Class II preparations
    • - Convergence of proximal wall of functional cusp in Class II preparation
    • - Dovetail in class II preparation
    • - Groove extensions in class II preparation
    • - Retention grooves in class V preparation
    • For a composite resin, retention form includes:
    • - Buccal and lingual walls which converge occlusally
    • - Bevels  on cavosurface margins which will increase surface area of ends of enamel rods for bonding
    • - macromechanical undercuts such as retention grooves in class II, III, IV, V
    • - incisal cove in class III
    • - acid etching which removes smear layer. Creates microscopic (macromechanical undercuts esp enamel rod ends and enlarges dentinal opening)
  9. Describe one acceptable sequence of finishing and polishing a previously-placed large amalgam restoration that has expanded beyond the cavosurface margins.  List in proper sequence the  specific instruments, burs, discs, powders, points, cups, etc., by brand, generic, or
    descriptive name.
    • • Finishing proximal & gingival
    • o Hand instrument: Gold knife
    • o Moore’s Discs
    •  Garnett  sandpaper  cuttle
    •  From coarse to medium to fine
    • o Interproximal strips
    •  Coarse  medium  fine  super-fine
    • • Finishing and polishing cavosurface margins
    • o Burs (slow speed)
    •  H274-016
    •  H274UF-016
    •  7404
    •  7404F
    • o Finishing/polishing points
    •  Mounted green (coarse) stone  Mounted white (medium) stone brownie (medium-fine) point  greenie (fine) point  super-greenie (super-fine) point
    •  Can use cups in this order also
    • o Abrasives
    •  Rubber cup with moist pumice (medium), then moist tin oxide (fine)
    • • Sequence:
    • o Start off by using a Gold knife to remove the flash from the proximal and gingival areas.
    • o Then use Moore’s discs to remove flash from the proximal areas
    •  Garnet > Sandpaper > cuttle [course > medium > fine]
    • o Use interproximal strips going from coarse, medium, fine, and then super-fine to remove flash and smooth the restoration BELOW THE CONTACT AREA
    • o Then use rotary burs [7404, 7404F, 7901] to remove flash from the occlusal cavosurface margins
    •  Use the rotary burs perpendicular to margins
    •  Rotate from restoration towards the margins
    • o Polishing
    •  Then, use Brownies, greenies, and super greenies in a slow speed handpiece to properly polish the restoration.
    •  Also can use Pumice [medium] and tin oxide [fine] for the final polish.
    • • Final Sequence
    • o Green stone
    • o White stone
    • o Brownie
    • o Greenie
    • o Super Greenie

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