The rate of abrasion is determined primarily by which three factors?
- *size of the abrasive particle.
- *pressure of the abrasive against the material being abraded.
- *speed at which the abrasive particle moves across the surface being abraded.
During polishing larger particles cause?
deeper scratches in the material.
During polishing heavy pressure causes?
deeper scratches and more rapid removal of material
Types of Abrasives
Hard, coarse, abrasives for development of desired contours of a restoration or tooth preparation
Types of Abrasives
- Finer particle sizes, generally less hard than abrasives used for finishing
- Used to smooth surfaces roughened typically by finishing abrasives or wear particles
Types of Abrasives
Generally soft with small particle sizes to remove soft adherent material
The more concentrated [packed] the particles in abrasives the more?
quickly the surface will be abraded.
If a lubricant is used to dilute the concentration of the abrasive particles, the abrasiveness is?
What are common lubricants used to dilute the effects of abrasion?
water and saliva
Abrasives mixed with water, glycerin, or some other medium produce?
- slurries or pastes.
- The slurry or paste is rubbed over the surface with a cloth or felt wheel, brush, or rubber cup.
Dental Materials Used in Abrasion?
- Aluminum oxide
- Carbide finishing bur
- Calcite-Calcium carbonate
- Tin oxide
- Silicone dioxide
- Silicone carbide
The smaller the abrasive particles?
the smoother the surface of the composite will be after finishing and polishing and the longer it will be able to retain its luster.
Composite restorations require?
polishing as part of the restorative procedure
Marginal and occlusal excesses are removed in initial finishing with?
diamonds or multi-fluted carbide burs.
Intermediate finishing is accomplished with?
flexible disks, cups, and strips.
Final polishing is accomplished with a?
submicron aluminum oxide–based polishing paste applied with soft cups or felt pads.
Finished and polished of composite restorations in three steps as part of the restorative procedure:
1.Marginal and occlusal excesses removed in initial finishing with diamonds or multifluted carbide burs
2.Intermediate finishing accomplished with flexible disks, cups, and strips, beginning with coarse and sequentially proceeding to superfine
3.Final polishing accomplished with a submicron aluminum oxide–based polishing paste applied with soft cups or felt pads
Initial contouring and smoothing are done with?
a coarse abrasive or bur.
The abrasive tool or slurry must not be used in a ?
what are the forms supplied for Dental abrasives?
- Loose abrasive paste and powder abrasives classified by grit
- Coated abrasives attached to disks or strips
- Bonded abrasives attached to a rotary instrument
Why should a non-stick autoclavable placement instrument be used for composite restorations?
some metal instruments can stain the composite material
What type of mylar strip should be used for composite restorations?
When should you ‘Take a shade’ to match tooth color?
before tooth is prepped, while tooth is still wet with patients saliva
Basic Steps in Composite Restorative Procedure:
- After cavity is prepared and tooth isolated.
- Acid Etch
- Bonding Agent
- Composite applied and cured
- Carve restoration and check bite
Acid etching – phosphoric acid provides?
- mechanical retention with interlocking mechanical ‘tags’
- More surface area
- Cleans the surface
A properly etched tooth appearance is ________?
frosty, dull, chalky
If not etched enough, what is done? __________
Some light-cured composites are slightly darker right after polymerization and will lighten within _____
hours as the composite absorbs saliva
Always acid etch composites because they?
will not stay bonded to tooth structure very long without it
- Same as composites.
- Materials that bond and set like dentinal bonding/ composites, but release fluoride like glass Ionomers.
- (hybrid of two dental materials: dental composites and glass ionomer cement and Fl2)
Advantages for using compomers?
- Good handling characteristics
- Release fluoride
- most are light-cured
- Some are flowable
- Supplied in compules or syringes
steps for Manipulation of Powder and Liquid:
- 1. Powder placed on paper pad
- 2. Liquid placed on paper pad
- 3. Add HALF of powder to liquid – mix until homogenous (milky even consistency)
- 4. Add remaining powder
- 5. Total mixing time = 30 – 40 seconds
- 6. Apply to cavity prep or cervical area
- 7. Light-cure
- 8. Contour or carve and check bite depending on class of restoration
- 9. Can apply varnish or bonding agent to protect restoration
- 10. Trim and polish after 24 hours
steps for Manipulation of Single Paste Systems:
- After acid etching and bonding:
- 1. Syringe or compule dispenses material
- 2. Material is placed in cavity preparation by syringe or carriers
- 3. Material is condensed, packed, pressed into prep and contoured. Some restorations may need a Mylar strip or crown former.
- 4. Exposure to visible blue light for curing, polymerization. Some darker shades may require longer curing time
- 5. Finishing and polishing of composite
Manipulation of a 2 Paste System?
Base is a universal shade paste to be mixed with the catalyst paste. Use a disposable plastic or wooden mixing stick; one end used to dispense base and the other to dispense catalyst, mix with either end.
Steps for Manipulation of a 2 Paste System?
- 1. Place an amount of base paste = to ½ the size of the restoration (using one end of the mixing stick) onto mixing pad.
- 2. Place = amount of catalyst on to mixing pad
- 3. Mix when D.D.S. indicates
- 4. Mix 20 – 30 seconds
- 5. Use plastic, wooden, or Agate spatula, metal abrades and discolors the material
- 6. Pass composite to Doctor – remaining working time of 1 – 1½ minutes
- 7. Allow material to set (cure) for 3 – 6 minutes
- 8. Finish and polish in a wet field as little as possible
- 9. Place a glazing compound as per manufactures recommendations.