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133 Cards in this Set
- Front
- Back
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What are the 4 uses of dental bonding?
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1. All cavity prep classes
2. Addition to tooth anatomy 3. Masking stains and imperfections 4. Indirect Veneering |
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What are 3 qualities of unfilled resin that is used as adhesive?
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1. Flows Better
2. Less hard and strong 3. Greater polymerization shrinkage |
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How does resin penetrate into the micro irregularities?
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It is aided by capillary action.
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What may happen with increases or decreases in the time or concentration of the acid etch?
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Formation of precipitates, like Mono-calcium phosphate mono-hydrate which could interfere with adhesion because it does not dissolve with water.
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What are the 2 types of Mechanical bonding?
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1. Interlocking: Undercuts, retention grooves
2. Penetration: formation of resin tags |
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What is the purpose of acid etching?
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To transform smooth enamel into a very irregular surface.
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In the veneer example, why didn't Hadavi use a rubber dam?
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1. The gums were healthy
2. He needed to be able to see the gingival contour |
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What should you do if the 'frosty' dried surface is contaminated?
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Repeat the process, starting from the etch.
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What are the 5 Enamel Bonding steps?
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1. Acid etch enamel for 20-30 seconds
2. Wash throughly for at least 20 seconds 3. Dry - bone dry, chalky 4. Apply adhesive bonding agents 5. Apply composite resin |
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What are the 2 components of the enamel bonding system?
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1. Etchant: 37% phosphoric Acid
2. Unfilled Resin: Bis-GMA + HEMA |
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When do you have complete wetting?
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When the contact angle between the adhesive and adherend is zero.
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What are the 3 objectives of enamel etching?
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1. Remove all debris and pellicle
2. Increase enamel surface free energy 3. Formation of Irregularities |
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What are the 3 Classifications of Adhesion?
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1. Mechanical
2. Chemical 3. Physical - weakest |
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What are the 2 types of physical bonding?
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1. Van der Waals
2. Electrostatic interaction |
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What are the 2 effects of adhesion?
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1. Increases Retention
2. Decreases Microleakage |
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How does the bonding agent attach to the tooth and to the composite?
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Tooth: Polymerization of monomers become interlocked into the enamel surface
Composite: OIL |
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Which irregularities are most important for bonding?
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Micro irregularities because there are millions of them and macros usually break because they are too thin and long.
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What are 2 properties of clean surfaces?
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1. Has the highest surface energy
2. Capable of rapidly absorbing contaminants from the air like moisture and dust |
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What material does chemical bonding?
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Glass Ionomer (IRM) - only one that adheres chemically to the tooth structure
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What is a non-wetting liquid?
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One whose surface energy is higher than the tooth.
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Why must the acid etched enamel surface be thoroughly washed?
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To remove all the acid and precipitates like calcium phosphate salts and silicate particles.
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What is the difference between micro and macro irregularities?
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Micro: formed when hydroxyapatite crystals are dissolved
Macro: Formed between peripheries of enamel rods |
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How does acid etch effect tooth wetting?
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Acid etch cleans the surface and brings it to a high surface energy so adhesive can spread well.
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What happens if too much bonding agent is applied?
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Will cause microleakage and stain around the composite because it will wear out faster than composite and leave a void.
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What are the 2 requirements for adhesion?
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1. Good wetting
2. Clean Surface |
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What is the proper direction of pull of the mylar strip after composite placement?
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Away from the opening of the prepared cavity. Stabilize the strip with index finger over the opening and pull and wrap the strip over the other side of the tooth.
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How should the Sof-lax discs be used?
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1. Low-speed handpiece
2. Final surface finishing 3. Very light touch - on/off 4. Constant cow-horn checking |
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Why should you wait 15 minutes to finish a composite?
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Significantly improves the wear rate than if done immediately, even better after 24 hours.
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What 2 things should composite wedges not do?
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1. Interfere with the gingival csm
2. Impinge on the development of a harmonious interproximal contour |
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What are the chances of bonding after the OIL has been removed?
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NIL so check it carefully for under-contour and marginal discrepancy before starting to polish.
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Why should the facial end of the matrix strip be pulled labially first?
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Insures flow of the material from the proximal surface where there is excess, along the facial surface and CSM.
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Why should the matrix strip be pulled incisally second?
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Tightens the gingival aspect of the strip ahead of the the incisal portion which eliminates excess material in the gingival area.
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How does the shade of resin affect the curing?
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Darker shades cure more slowly and less deeply than lighter shades.
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When should the mylar matrix be placed and why?
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Before application of etch, primer, and adhesive to avoid contamination of soft tissue and bonding of adjacent teeth.
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Why is the heat generated from finishing composites a problem?
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1. results in surface cracking or crazing
2. may lead to early wear and staining |
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Why are microfilled composites more difficult to cure?
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The smaller particles absorb more light than the larger ones.
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What are the 3 steps to composite wedge placement?
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1. Fold and hold the matrix band around the tooth
2. Stretch the dam gingivally on the side where the wedge is inserted 3. Place the wedge from the buccal for lingual approach, from lingual for buccal approach |
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To what length should Mylar Strips be cut?
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1.25 inches
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What are the 2 reasons the incremental technique is better than bulk?
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1. Less total polymerization shrinkage
2. Less stress is placed on the interfacial bond to the tooth structure |
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How are diamond finishing burs used in the clinic?
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1. High speed with medium rotation
2. Light sweeping motion to avoid gouging the surface 3. Copious amounts of water to prevent heat build-up |
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What needs to be done before disc use to avoid cutting ridges into the restoration?
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Flex the discs by running them over an instrument handle.
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What are 5 tips for finishing composites?
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1. Clean restoration surface with cotton to remove debris between polishing steps
2. Discs can snap in either way 3. Small diameter discs can be used like the composite knife 4. Don't touch the mandrel metal to tooth or restoration 5. Use the adjacent tooth for guidance for contours |
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What are the 3 reasons for using the mylar matrix?
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1. Control the basic form and contour
2. Reduce the amount of excess materials 3. Isolate the cavity prep |
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How should the composite knife be used?
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1. Shaving action
2. Continuous checking of the margins with the cow horn explorer 3. Keep part of the edge on enamel 4. Do not lift or fracture excess composite |
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What are the 5 criteria of composite restorations?
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1. Resin Material completely fills cavity, no voids or defects
2. Restores surface contour, conforms to tooth morphology 3. Smooth surface because of proper instrumentation 4. Margins do not have any crevices, voids, or over-extensions 5. Finished cervical area without damage to tooth tissue |
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What are the 3 reasons for placing the wedge in composites?
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1. Holds the strip in position
2. Provides slight separation of the teeth 3. Prevents gingival overhang |
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What is the extent of the OIL? (how thick)
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Can vary from 15-50 microns.
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What will happen if too much pressure is applied to the matrix?
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1. May cause a negative contour
2. Develop excessive flash 3. Prevent establishment of contact |
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What are the 4 reasons to slightly overfill(2%) the cavity?
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1. Good contour after finishing and polishing
2. Coverage of all CSM 3. Removal of the OIL during polishing 4. Compensation for polymerization shrinkage |
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Composites are rather _____ and sometimes _____. Therefore they cannot be condensed and must be _____ into the prep and _____ into place with the plugger.
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Viscous
Sticky Wiped Jiggled |
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What is the proper angle of pull of the mylar strip after composite placement?
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From cervical to incisal to provide the best proximal contour and gingival adaptation.
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Where should excess composite be scored and with which instruments?
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1mm outside the CSM, to prevent marginal fracture, with the #12 scalpel blade or composite knife.
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What is the PFI 8A & the PFI W3?
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PFI 8A: 2 Blades (Chisel and Hatchet)
PFI W3: Plugger and Large Blade |
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What can be use to remove excess material from the cervical margin prior to matrix folding?
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An explorer
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What is the purpose of finishing & polishing?
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To get the best possible surface with the least restorative surface damage and marginal fracture.
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What are the 2 keys for function of the OIL?
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1. Cover as quickly as possible
2. Protect it from contamination of moisture and debris |
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Once the matrix has been pulled, what are the next 4 steps?
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1. Do not readjust the strip after the initial pull
2. Cure the composite 20 seconds facially 3. Then 20 seconds lingually 4. Do not touch the strip with the tip of the light rod |
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Where should the first increment of composite be placed?
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On the facial wall, facial csm and facial line angles.Keep the lingual entrance free of composite.
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Which cavity classes use the mylar matrix?
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Only Class 3 & 4
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What is the minimum curing intensity?
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468 +/- 20 nm
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What does the Oxygen Inhibition Layer do betwee increments?
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Functions as the bonding agent that later cures and unites the two composite increments together.
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What 3 important things does jiggling the composite do?
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1. Brings the resin to the composite surface
2. Wets the instrument and prevents sticking to it 3. Eliminates air bubbles and porosity |
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What are the 3 components of the double-abrasive finishing strip?
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1. Rougher: aluminium oxide, heavier finishing
2. Center, abrasiveless portion for placement 3. Smoother: zirconium silicate, finer finishing |
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What is the proper thickness of composite to be cured?
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Between 0.5-1.5mm
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What are the 6 steps of Finishing & Polishing composites?
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1. Use a scalpel to remove gross flash
2. Begin finishing with the contouring knife 3. Use abrasive finishing strip for interproximal areas 4. Use the Sof-lax disks for final surface finishing 5. Remove the rubber dam and evaluate the restoration and occlusion 6. Use diamond-finishing bur where access is difficult |
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What does dry finishing do to a composite?
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1. Increase the surface temperature which
2. Increases surface hardness 3. Decreases surface porosity 4. Produces an artificial smear layer over the resin |
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Where should the mylar strip be placed?
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At least 1 mm below the gingival floor of the prep, between the tooth and gum.
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What is the minimum curing time?
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40 seconds to allow 'dark' curing to continue until completion
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Where should the convex and concave edges of the composite knife be used?
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Convex: lingual surface
Concave: Interproximal area |
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What effect does enamel and matrix have on curing?
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through enamel: only 1/3 to 2/3 as effective
through matrix: increase surface polymerization because air inhibition is reduced |
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What is the ideal distance between the light source and the composite?
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1 mm
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What does wet finishing do to a composite?
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1. Reduces heat and friction
2. Reduces surface damage to the body of the restoration 3. and the margins of the restoration |
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What are the 3 pre-requisites to choosing the composite shade?
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1. Use pumice (without fluoride) to remove stain
2. Wet the tooth 3. Be in natural light |
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What are the 3 types of stress due to polymerization shrinkage?
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1. Adhesion Force
2. Shrinkage Force 3. The fight for remaining monomer |
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When placing the first layer of composite, should it be more apical or incisal?
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Apical
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What are 4 problems to overcome when composite polymerizes?
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1. Inadequate proximal contact
2. Inadequate polymerization at the deepest part of the cavity 3. Formation of gap due to shrinkage towards the light 4. Stress build-up on tooth and composite due to shrinkage |
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What is the best way to check the shade of composite you have chosen?
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Put it on the tooth, before etching, and cure it because curing changes the color.
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In what direction does the composite shrink in chemical and light curing?
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Chemical: towards the center
Light: towards the light |
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Why does composite separate from the walls in large restorations using the bulk technique?
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Polymerization shrinkage forces are greater than adhesive forces.
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Why does the wear rate improve after waiting 24 hours?
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The stresses are relieved.
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Where in a class 3 composite is the bonding the strongest?
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Occlusally because the enamel is thicker, bonding will pull away more apically.
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What are the 13 factors affecting Visible Light Curing?
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1. Time
2. Intensity 3. Distance 4. Thickness 5. Air Inhibition 6. Curing through tooth structure 7. Shade of resin 8. Type of Filler 9. Amount of Light Activated Accelerator 10. Room Light Polymerization 11. Diameter of the curing Light Rod 12. Line voltage 13. Heat generated from Light curing units |
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What are 3 ways to decrease composite wear?
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1. Increase waiting time
2. Dry finishing 3. Higher curing rate |
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What are 2 reasons to choose the composite shade before rubber dam placement?
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1. Color of the dam interferes
2. Teeth too dry |
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What are the 7 Restorative Material Requirements?
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1. Multi-shade selection
2. Single Paste Form 3. Visible Light Curing 4. Enamel-like smoothness and Luster 5. Color Stability 6. Opacifying capabilities 7. Translucency capabilities |
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What are the 5 advantages of Light curing?
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1. Cure on demand
2. Increased color stability 3. Single paste - minimal voids 4. Reduced Finishing Time 5. Less Waste |
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What does the ease of finishing composite depend on?
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1. Size of the filler particles
2. Hardness of the filler particles 3. Fracture resistance of the filler particles |
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What is a potent initiator used in chemically cured resin?
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Benzoyl peroxide
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How is a polymerization reaction initiated?
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By making a free radical.
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What are 5 materials that can initiate the termination phase of composite?
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1. Oxygen
2. Eugenol 3. Blood 4. Saliva 5. Monomer Exhaustion |
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Which polymerization reaction does not produce by products: Condensation or Addition Reaction?
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Addition Reaction
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Define Free Radical
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A compound with an unpaired electron which has been split from a larger molecule, very reactive, not a catalyst.
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What is a mer?
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The simplest repeating chemical structural unit from which the polymer is composed.
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Potent initiators can be easily decomposed by which 3 things?
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1. Chemical Reaction
2. Heat 3. Light |
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What is the mer we care about?
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Methyl Methacrylate
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What are the 3 phases of composite?
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1. Organic
2. Inorganic 3. Coupling Agent |
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What are the 2 biggest shortcomings of Acrylic resin?
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1. High thermoexpansion coefficient
2. High polymerization shrinkage |
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Why should one not mix liquid and powder vigorously?
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To prevent air bubbles.
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How is the free radical formed?
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From the reaction between an unpaired electron and benzoyl peroxide.
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Name the uncured layer on the most superficial surface of composite?
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Oxygen Inhibition Layer
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FR + C=C =
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FR-C-C*
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What are the 4 ways composites are classifed?
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1. Filler Content: Weight or Volume
2. Filler Particle Size: most popular 3. Matrix composition: Bis-GMA or UDMA 4. Polymerization Methods: self curing, ultraviolet, visible, dual |
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How does the light curing reaction of composite resin polymerization work?
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1. Paste + Acc + Photo-initiator
2. Light + PI +Acc = free radical production |
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How does the heat reaction of acrylic resin polymerization work?
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1. Liquid
2. Powder + Benzoyl Peroxide 3. Add Liquid to the Powder 4. Heat decomposes the Benzoyl Peroxide to form the free radical |
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What are the 4 Curing Equipment Factors of the Light Curing Requirements?
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1. Output Efficiency
2. Bulb Degradation 3. Tip Contamination 4. Light Reflector degradation |
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What is a dental definition of composite?
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A tooth colored restorative material which is in a paste form.
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What is the coupling agent?
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Silane
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What happens to the mers in a condensation reaction?
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Mers formed later in the reaction have fewer atoms than the original mers due to the formation of by-products.
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What are the 3 functions of Bis-GMA?
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1. Reinforces Filler Particles
2. Lower Polymerization Shrinkage 3. Hardens rapidly under oral conditions. |
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How is the acrylic resin powder formed?
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The powder spheres are polymerized from monomer which has been heated in non-polymerizing liquid under agitation.
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What are the 4 functions of filler particles?
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1. Reduce the coefficient of thermal expansion
2. Higher Hardness 3. Higher Strength 4. Control the fluidity of composite |
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Why doesn't monomer exhaustion ever happen?
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Because no polymerization reaction ever goes to 100%.
~70% is considered success. |
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What are the 2 components of acrylic resin?
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1. Liquid
2. Powder Both are made of Methyl Methacrylate |
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What is the Photo-Initiator?
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1. Absorbs photons of light energy at 474 nm
2. Camphoro-Quinone |
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What are the coefficients of thermal expansion for resin, amalgam, composite, & teeth?
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resin: 80
amalgam: 22 composite: 14 teeth: 11.4 10^-6/cent |
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How does the chemical reaction of composite resin polymerization work?
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1. 2 pastes
2. One with BP, other with TA 3. Mix them to make the free radical and initiate polymerization |
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What is an unfortunate side effect of the BP-TA interaction?
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It discolors the composite yellow.
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What are the 7 shortcomings of unfilled resin?
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1. Low Hardness
2. Low Strength 3. High Wear 4. High Solubility 5. High Water Sorption 6. High polymerization shrinkage (6%) 7. High coefficient of thermal expansion |
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What are the 5 Procedural Factors of the Light Curing Requirements?
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1. Light tip direction
2. Light Access to restoration 3. Distance from surface 4. Size of the tip 5. Time of exposure |
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What are the 4 stages of polymerization?
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1. Activation: production of free radicals
2. Initiation: Free Radicals react with mers to form initial end of polymer 3. Propagation: rapid addition of more mers 4. Termination: by contamination |
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How does particle size effect polymerization?
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Smaller particles have more surface area so they will react further and cause more polymerization shrinkage. Need to fill composites with smaller increments.
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What are the 4 Restoration Factors of the Light Curing Requirements?
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1. Restorative Thickness
2. Filler Amount & Size 3. Restoration Shade 4. Cavity Design |
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Why does IRM smell like cloves?
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IRM = zinc oxide eugenol
Eugenol is a component of clove oil. |
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What are the 2 types of restorative resins?
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Type 1: Unfilled, Acrylic Resin
Type 2: Filled, Composite Resin |
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How does the chemical reaction of acrylic resin polymerization work?
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1. Liquid + Tertiary Amine
2. Powder + Benzoyl Peroxide 3. Add liquid to the powder 4. Tertiary Amine decomposes the Benzoyl Peroxide to make the free radical |
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What 5 qualities of the filler particles can effect the physical and handling properties of composite?
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1. Shape
2. Size 3. Hardness 4. Concentration 5. Distribution |
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What are 4 things can happen that will mess up how well the light curer works?
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1. Inefficient lamp
2. Broken fibers in light conducting tube 3. Low (fluctuating) voltage 4. Dirty Tip |
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What is the function of the TEGDMA?
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Used to dilute and make Bis-GMA and UMDA less viscous.
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What do monomer-to-monomer bonds do?
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Cause shrinkage, decreasing the net volume of the system.
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What are the most popular fillers used in composite and why?
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Silicate glasses because they bond easily to the coupling agent.
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What are the 3 ways acrylic resin can be polymerized?
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1. Chemical Reaction
2. Heat Reaction 3. Light Reaction |
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What are the 3 components of the composite organic matrix?
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1. Bis-GMA = Bisphenol A + Glycidal MethAcrylate
2. UDMA = Urethane Di-MethAcrylate 3. TEGDMA |
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What are the 5 functions of the coupling agent?
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1. Provides interfacial bonding between the phases
2. Provides a strong bond 3. Prevents dislodgment of filler particles 4. Prevents penetration of water between phases 5. Acts as a stress absorber |
