Week 5 Carving, Polishing, etc Flashcards
Polishing
involves the abrasion of a surface by an abrasive agent that is harder than the surface being abraded, or polished. The process of abrading the surface to reduce size of scratches and irregularities.
Cutting
removing material by a shearing off process
Abrasion
wearing away of a surface.
Finishing
producing the final shape and contour of a
restoration.
Abrasive
material used to wearing way a surface.
Tribology
science of interacting surfaces in motion. Principles of friction, lubrication, and wear.
Types of abrasives
▪Chalk
▪Pumice
▪Sand
▪Cuttle
▪Garnet
▪Emery
▪Silex
▪Tin oxide ▪Aluminum oxide
Bonded and Coated Abrasives
▪Diamond burs
▪Stones
▪Rubber wheels or points ▪Rubber cups
▪Disks or strips ▪Powders
Factors Affecting the Rate of Abrasion
▪Hardness ▪Size ▪Shape ▪Pressure ▪Speed ▪Lubrication
▪Care needs to be taken with softer materials and abrasive agents.
Why polish
▪To reduce adhesion
▪To make the surface feel smooth ▪To increase esthetics
▪To reduce corrosion
Abrasives used in dentifrices(toothpaste)
▪Phosphates ▪Carbonates
▪ Sodium bicarbonate ▪ Calcium carbonate
▪Silicas
Micromechanical bonding
bonding using surface irregularities smaller than can be seen with the naked eye or felt with a explorer. Interlocking of surfaces. ACID ETCHING is this!
Macromechanical bonding
the locking of two surfaces together using surface “roughness” and can be seen and/or felt.
Chemical adhesion in dentistry
▪Polycarboxylate cements
▪Glass ionomer cements
Adhesive failure
material breaks free from tooth, literally the adhesive material failed
Cohesive failure
breakage with in the material. Material broke, not the bond.
T or F Acid etching is used to bond material to the enamel not dentin.
true
Etch acid typically used
Orthophosphoric acids at 37% is the most common used.
How long to etch
15-30 seconds
Three-step dentinal bonding systems
- Etch dentin and enamel
- Apply primer
- Apply adhesive
- Composite placement
- Dentinal bonding adhesive mechanisms
- Clinical research
Hybrid layer composed of
resin and decalcified dentin
Dental Cements uses
luting agents (crowns), pulp protection 2mm thick as a base, temp restoration, endo sealers or perio packs, cavity sealers
Formulation of dental cements liquid/powder system
Liquid is an acid, powder is the base.
Powders used in cements
zinc oxide, powdered glass (silicon oxide)
Liquids Used in Dental Cements
▪Eugenol ▪Phosphoric acid ▪Polyacrylic acid
Eugenol
Organic liquid – oil of cloves (distinct smell) Inhibits free-radical polymerization
Phosphoric acid
▪Aqueous solution of approximately 2/3 phosphoric acid and 1/3 water
Polyacrylic acid
▪Dispensing – does not form independent drops. Drops can run together.
▪Bonding – stable in a wet environment
▪Water-hardening cements – liquid is predominately water ▪Viscous liquids.
How long does it take to mix temporary cement?
about 30 seconds, should be uniform in color, string between slab and spatula for correct consistency
Zinc Phosphate cement precautions and tips
-do not cool the slab beyond the dew out, condensation will adversely affect the mix and setting time.
-mix slowly in increments to dissipate heat
-close the bottles to prevent absorption of moisture
-Mix using a large area of slab to dissipate the heat.
-clean the slab and spatula immediately
Calcium hydroxide liner/base precautions and tips
humidity will accelerate the setting reaction. Mix until a homogeneous color, wipe mixing instrument clean with a gauze before applying material to cavity preparation.
Glass Ionomer Cement precautions and tips
-should be used when the mix is glossy
-when dispensing take the necessary time to make precise uniform drops
-mixing time is short usually 45 seconds or less.
ZOE precautions and tips
-If it’s sticky and difficult to place, there is not enough powder incorporated.
-Use firm pressure with the flat face of spatula when incorporating powder.
-Enough powder has been incorporated for a base consistency when the mix “flakes” from the spatula pressing on the cement.
Temporary Cement precautions
humidity will accelerate the setting of ZOE based materials, mix until homogenous color is obtained.
If a tooth becomes contaminated after etching, you must re-etch for ____ seconds
5 seconds
Dentinal bonding systems function by way of
micro mechanical bonding and secondary atomic bonds
