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29 Cards in this Set
- Front
- Back
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When is a Class I extenstion cavity necessary?
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Only when there is caries extending along the fissure or a very pronounced deep fissure. This extension weakens the remaining tooth structure.
A step is only necessary if caries is present or it is needed to include all the fissure. Walls remain at 90 degrees to conserve tooth structure. |
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What are the 4 functions of a matrix?
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Provide proximal contour to the restoration
Create a proper contact area with the adjacent tooth. Provides a firm wall for a proximal box to allow adequate condensation of amalgam against. With assistance of the wedge, matrix minimises the fomation of an overhanding peice of restorastive material. |
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What are the 2 functions of the wedge?
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Ensure adaption of the matrix at the gingival margin therby minimizing overhangs.
Very slightly separating teeth to compensate for the thickness of the band - thus when matrix removed there is a tight contact. |
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What are the 4 stages of placing an amalgam?
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Trituration
Condensation (and pre-carve burnish) Carving (and accomodating the occlusion, and post-carve burnish) Finishing (subsequent appointment) |
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What is Trituration?
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Wetting alloy particles with mercury so the setting reaction can take place. Carried out in an amalgamator.
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How can you tell if amalgam has been over or under triturated?
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Too little is dry and grainy
Too much will set too rapidly for condensation and carving |
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What is Condensation?
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The incremental placement of the amalgam into the prepared cavity and compression of these layers into each other to form a continuous homogenous mass that is well adapted to all the margins, walls and line angles of the prepared cavity.
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What are the aims of Condensation?
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Adapt amalgam to the margins, walls and line angles of the cavity
Minimise voids within the amalgam Leave the amalgam in the strongest state Bring excess Hg rich amalgam to the surface for removal, therby decreasing the final Hg/Alloy ratio of the amalgam (strengthens the restoration). |
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What type of packer suits spherical amalgam and which suits lathe cut?
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Lathe cut offers more resistance so it needs greater condensation pressure. Thus a smaller condenser (third of cavity width) should be used.
Spherical doesn't need as much pressure so a larger condenser (half to three quarters the cavity width) can be used. |
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How many minutes from Trituration should amalgam be used in?
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3 minutes. After this a fresh mix should be obtained.
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Why is a pre-carve burnish necessary?
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Provide further condensation
Bring additional mercury-rich excess to the surface Adapt the amalgam optimally at the margin |
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What is the effect of contaminating amalgam with moisture during condensation?
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Increased tarnish, corrosion, and decresed strength.
For zinc-containing amalgains, moisture contamination will result in excessive delayed expansion. |
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What does Carving refer to?
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The shaping of the amalgam to restore contour and functional anatomy.
Carve when some resistance is felt. |
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Why is a Post-Carve burnish necessary?
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Maximise adaption of the amalgam to the margin.
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How is the Occlusion checked?
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Tell patient that in a few seconds time you will:
1. Place in some (articulating) paper (on Miller's forceps) and will ask them 2. VERY GENTLY 3. To lightly close the teeth until they first contact and then gently slide from side to side. This is carried out until contact on the new amalgam is slightly less than on the surround tooth and adjacent teeth. At this stage the patient can close more heavily on the paper. |
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What are the goals of Finishing at a microscopic level?
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Provide smooth surface thereby minimising plaque retention.
Provide a surface composed of principally unreacted original alloy particles (most corrosion resistant component of the amalgam) |
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What are the 2 stages of Finishing?
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Contouring
(Axial contours adjusted, Occlusal anatomy adjusted, Junction of tooth surface and restoration surface is optimised) Smoothing (attract less plact, resist tarnish and errosion) |
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What are 4 clinical concerns associated with finishing an amalgam?
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Generation of excess heat
(thus use water spray and intermittent applicaton of bur) Liberation of Mercury (Mercury vapour released with finishing procedures, thus use water spray and suction) Avoidable Loss of Tooth Structure (Careless use can result in unnecessary loss -at least minimal loss of tooth structure should be assumed, thus appy topical fluoride following completion) Reduction of Amalgam Margin Angle (Finishing leads to steepening of cuspal inclines. If less than 70 degrees there is an increased liklihood of marginal fracture and crevice formation. Thus take great care in recontouring old amalgams) |
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What is used for final Contouring?
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Dura Green, White Stone, 12-Bladed Tungsten (all in Medium)
Blunted Steel Finishing Bur (in Low Speed) |
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What is used for final Smoothing?
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Either Brownie or Pumice + Bristle brush
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Why should techniques that achieve a high shine in the Polishing phase (eg Greenies, ZnO + alcohol paste) be avoided?
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Excess heat generation
Unnecessary mercury liberation |
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What are the 12 Steps to Carving a Complex Amalgam?
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1. Release Amalgam from matrix to a depth of 0.5-1mm and from any areas where amalgam is packed into the retainer with a probe.
2. Reduce marginal ridges to approximate height of ridges on adjacent teeth with a probe. 3. Remove wedges and matrix. Hold retainer very firmly while releasing screw from band. Support matrix very well while removing retainer. Remove band, first movement Bucco-lingual. 4. Remove any excess from the Gingival Margin with an Interproximal Carver. 5. Adjust Buccal and Lingual contours/excess of proximal areas with Probe or Interproximal Carver 6. Adjust height of ridges to same as adjacent teeth with wall carver, round end. 7. Adjust height of Cusp tips by bringing occlusal plane down to proposed level of cusp tips with Hollenback carver. 8. Shape the Buccal/Lingual contours with Hollenback carver. 9. Establish marginal ridges with a Half Hollenback. 10. Define the buccal-lingual cusp seperating fissures with a half hollenback. 11. Occlusal Anatomy - develop approx correct depth of central M-D fissure by carving incline on cusps. Finalise cusp tip location. 12. Check Occlusion and finalize carving. |
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What is IRM?
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A resin enfored Zinc Oxide Eugenol INTERMEDIATE RESTORATIVE MATERIAL
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What is Eugenol?
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A local anaethetic and antiseptic. An oily liquid extracted from certain essential oils eg Clove Oil
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What action does Zinc Oxide have?
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Antibacterial
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What are the aims of temporization?
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Relieve symptoms of pulp inflammation
Restore tooth to function temporarily and stabilze its position Provide the opportunity for defensive reactions in dentine/pulp |
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What materials are used for temporary restorations?
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Glass Ionomers
IRM Cavit (small short term temp in endo access cavities) |
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What is in Cavit?
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contains zinc oxide, calcium sulfate, zinc sulfate, glycol acetate, polyvinyl acetate, polyvinylchloride-acetate triethanolamine, red pigment
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Why should IRM be used cautiously?
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It has a sedative action when placed on dentine, but is an irritant when applied directly to pulp.
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