Dental Materials - Final Exam (PT.2)

materials composed of particles that are hard and sharp enough to cut or scratch the surface

abrasive

The process of abrading a surface to eventually reduce the size of the scratches until the surface appears shiny

polishing

describes the size of an abrasive particle; classified as coarse, medium, fine and superfine

grit

reducing excess restorative material to develop contours/occlusion of a restoration + smooth surface; uses rotary instruments

finishing

What factors affect abrasion?

1) size, irregularity, and hardness of particles

2) number of particles contacting surface

3) speed and pressure

What are the steps of amalgam polishing and the materials used at each step?

1) define anatomy

- rounded finishing burs, football shaped

2) intermediate finishing

- stone burs > flame shape on low speed

- begin with green, end with white

3) initial polishing

- shofu rubber points

- brownie > greenie > super greenie

4) final polishing

- tin oxide powder, mix with water and use cup to apply

What are the steps of composite polishing and the materials used at each step?

1) remove excess composite material

- multifluted carbide bur

2) intermediate finishing

- flexible discs, cups and strips

- begins with coarse, finish with superfine

3) final polishing

- aluminum oxide polishing paste (soft cup/pads)

What are the benefits of polishing restorations?

1) decreased plaque retention

2) tarnish/corrosion resistance

3) increased longevity of restoration

4) improved esthetics

5) improved health of surrounding tissues

material that adheres, seals, lutes or bonds two objects by adhesion

cement

- ex: base, liner, luting agents etc

any material placed in a thin layer between the cavity floor and restoration

liner

material used to provide foundational support for direct restorative materials; provides protection from thermal conduction of metal restorations

base

a material that reduces irritation or has a soothing effect on the pulp; contains eugenol

sedative

any material placed on top of pulp to stimulate formation of secondary (reparative) dentin

pulp stimulator

Compare the different types of cement and uses of each

1) luting agents: permanent restorations

2) temp restorations: deep cavities

3) bases/liners: <.5mm remaining dentin

4) pulp capping: little or no dentin

5) root canal sealer: paste system for canal

6) cementation of orthodontic bands

reaction that releases heat

exothermic reaction

What is the criteria for max/mand impressions?

basically just all teeth and anatomy are visible without voids or air bubbles

What are the uses for alginate impressions

alginate:

- Preliminary Impressions

- study models

- working casts

What are the properties of alginate

low dimensional stability

- low tear strength

- should not be used for final impressions

the loss of water, occurs within alginate if exposed to air

syneresis

the uptake of water, occurs to alginate if left in water

Imbibition

time to mix, load and set the impression

gelation time

How does the change of water temp affect gelation time?

warm water > speeds up

cold water > slows down

Compare the two types of customized crowns

1) acrylic materials:

- exothermic, ^shrinkage during polymerization

- difficult to repair

- inexpensive

2) Bis-acrylic composite materials

- low heat, decreased shrinkage

- easy to repair

- expensive

What are the properties and uses of acrylic resins?

1) shrinkage during polymerization

2) good biocompatibility

3) low thermal conductivity

4) good fatigue resistance

5) fairly low strength

6) coefficient of thermal expansion is high

What monomer is used in acrylic resins

methyl methacrylate (MMA)

What are the retarders of gypsum

- cold water

- shorter mixing time

What are the different types of gypsum?

I: impression plaster

II: model plaster

III: dental stone

IV: die stone

V: high strength

I is lowest strength, V is strongest

- cheapest/weakest gypsum material

plaster

RCT is ____% successful

95%

If RCT fails, what are the tx options?

1) retreatment

2) apicoectomy + retrofill

3) extraction

metal or fiber robs placed in canal after RCT to retain the core build up (under crown)

endodontic post

What restorative material weakens the tooth?

retention pins

Dental implants must ______

osseointegrate