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Op Dent 1 > Materials Science 3 > Flashcards

Materials Science 3 Flashcards

1
Q

SEALANTS

A

¢ Polymeric Coating to Protect Teeth
¢ Flowable Resin That is Light Cured
¢ Designed to Flow into Pits
¢ Seal Tooth Surface to Prevent Further Decay ¢ Etching is Recommended to Prepare Enamel ¢ Balance between Flow and Sealing Capability

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2
Q

SEALANT CHEMISTRY

A

Considered a Preventive Material
¢ Usually a BisGMA-TEGDMA system but no Filler
¢ Low Viscosity – Easy to Flow and Coat a Surface

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3
Q

BONDING

A

¢ Bonding is Mostly Mechanical
¢ Not Designed for Longevity
¢ Etching Creates a Clean, Rough Surface

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4
Q

BOND TO ENAMEL

A 
Macrotags
—  Interprism resin penetration
¢  Microtags
—  Intraprism resin
penetration
¢ Microtags provide the major retention
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5
Q

OXYGEN INHIBITION LAYER

A

¢ Oxygen Interferes with Radical Polymerizations
¢ Surface of VLC Materials are often Uncured
¢ For thin Layers such a Sealants more of a Problem

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6
Q

ADHESIVES

A

¢ Based on Composite Resin Chemistry
¢ Contains Acidic Groups to Promote Bonding ¢ Dimethacrylates that Are Visibly Light Cured ¢ Unfilled or Lightly Filled

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7
Q

REQUIREMENTS FOR GOOD BONDING

A

¢ Flowable
¢ Compatible With Both Surfaces — Surface Energy
— Forming Bonds or Interactions
¢ Mechanical Properties ¢ Long-Term Stability

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8
Q

Resin

A

Increase in Mechanical Properties = Increase in

Viscosity

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9
Q

Increased Filler Loading

A

— Decreases Flowability (Increases Viscosity) — Improves Mechanical Properties

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10
Q

BONDING TO TUBULAR DENTIN

A 
Smear layer created
from preparation
—  Ground collagen and HA
—  Adhered to surface
¢ Interferes with bonding
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11
Q

TRADITIONAL STEPS FOR DENTIN BONDING

A

¢ Etch
¢ Prime
¢ Adhesive
¢ Restoration

¢ 30 sec etch with 37% H3PO4
¢ Rinse

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12
Q

PRIMER

A

Hydrophilic Monomer
To Stabilize Dentin
Followed by Adhesive and Composite

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13
Q

TWO OR ONE STEPS

A

Most Current Adhesive Systems Require Only
One or Two Steps
¢ Combine Etchant and Primer
¢ Combine Etchant, Primer and Adhesive
¢ All These Components are Based on Methacrylate Monomers

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14
Q

CEMENTS, LINERS AND BASES

A

¢ In Dentistry Cements, Liners and Bases describe more of a Function than a Specific Class of Materials.
¢ Often There is Overlap Between the Function and Chemical Classification
¢ Cements also refer to a Type of Materials such as a Glass-Ionomer Cement
¢ Confusing because a Glass-Ionomer Cement can be used as a Base.
¢ Glass-Ionomers can be Cements and a Base
¢ Zinc Oxide Eugenol (ZOE) can be a cement, liner
and a Base
¢ Calcium Hydroxide can be a liner and a Base

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15
Q

Water-Based Cements

A

— Glass-Ionomers
— Resin Modified Glass-Ionomers — Zinc Phosphate
— Zinc Polyacrylate

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16
Q

Resin Based Cements

A

— Composites

— Compomers

17
Q

Oil Based Cements

A

— Zinc Oxide Eugenol

18
Q

Curing mechs.

A

CURING MECHANISMS
¢ Sometimes Light Cure Not Possible ¢ Cold-Cure for Methacrylate
¢ Water Cure for Cements

19
Q

REQUIREMENT FOR CEMENTS

A

¢ Low Viscosity but Good Mechanical Properties

¢ 25 μm Thickness

20
Q

HOW TO BALANCE MECHANICAL PROPERTIES AND VISCOSITY?

A

¢ For Glass-Ionomers it is the Powder to Liquid Ratio
¢ Powder = Filler
¢ More Filler = More Viscosity More Filler = More Modulus

¢ This concept is true for most Materials that Are
Set by Mixing a Powder and Liquid
¢ ZOE, Calcium Hydroxide
¢ Low Powder to Liquid also Increasing Working and Setting Time

21
Q

4-META MODIFIER

A

¢ Additive to Promote Bonding
¢ Very Common in Resin Adhesives
¢ Manufactures will Tailor Cements to Products

22
Q

ZINC PHOSPHATE

A

¢ ZnO + H3PO4 = Zn3(PO4)2
¢ Used for Crowns
¢ More of Legacy Material?
¢ Handling Can be Controlled by Powder to Liquid Ratio

23
Q

ZINC POLYACRYLATE (POLYCARBOXYLATE)

A

¢ Polyacid + ZnO = Cement
¢ Zn is only Divalent
¢ More of a Legacy Material
¢ Controlled by Powder to Liquid Ratio

24
Q

LINER

A

¢ A relatively thin layer of material used to protect the dentin from residual reactants that diffuse out of the restoration or oral fluids that may penetrate leaky restoration interface
¢ Thin Layer so Materials are Lower Viscosity

¢ Solution liners (2-5μm)
— Copal varnish-under Amalgam — Adhesives- under composites
¢ Suspension Liners (20-25μm)
— CaOH2 (Dycal)-under Ag or Comp
¢ Cement Liners (200-1000μm)
— GI (KetacCem), RMGI (vitrebond) — Under amalgam (Ag) or Composite

25
Q

Pulp capping

A 
¢  Near exposure
—  RDT <0.5 mm
—  Indirect pulp cap
¢  Pulp exposure
—  Direct pulp cap
Apply Calcium Hydroxide (CaOH2) liner
26
Q

Defensive reparative dentin

A

15 days -cells differentiate

30 days-microscopic reparative dentin 100 days -radiographic reparative dentin

27
Q

CAOH2 LINERS

A

¢ Paste(CaOH2)/Paste (polyphenolics)
¢ Acid - base reaction
¢ Ca+ ions act to crosslink polyphenol groups ¢ Insulator
¢ High solubility (10-30% vol loss in 10yrs) ¢ Stimulates reparative dentin

Works by: ¢ Release hydroxide ions (pH>11)
¢ When ionized in low concentration — Stimulateodontoblastformation
¢ Dycal-brand name

28
Q

REINFORCED ZOE

A

¢ IRM (intermediate Restorative Material)
¢ B&T (base and temporary)
— Reinforced fillers (PMMA beads-powder)
— ZnO (powder)
— Eugenol (liquid) oil of clove
¢ Oil of clove acts as obtundent (dulls pain) ¢ Expands when set –seals
¢ *cannot use under composite ¢ *Inhibits polymerization

29
Q

BASES

A

¢ Are used to provide thermal protection for the pulp and to supplement mechanical support for the restoration by distributing local stresses from the restoration across the underlying dentin surface during amalgam condensation (or cementation of indirect restorations)
¢ Require Greater Mechanical Properties

All water based and acid-base reactions

30
Q

ADVANTAGES OF GLASS IONOMER

A 
¢  Adheres to tooth structure —  Mineralportion
—  Dynamicionicprocess
¢  Fluoriderelease
¢  Proven clinical record of retention
—  Better than composite
¢  Dimensionally stable
¢  Biocompatible
31
Q

DISADVANTAGES OF GLASS IONOMER

A 
¢  slow setting
¢  early dissolution
¢  optical properties
¢  stain resistance
¢  poor physical properties
32
Q

WAXES

A

¢ Temporary Materials
¢ Should Melt at Lower Temperatures ¢ Be Carveable
¢ Burn off
¢ Dimensionally stable

33
Q

DIMENSIONAL STABILITY

A

¢ Desirable So That Restoration is Accurate
¢ Wax is Normally Used Above Tm Then Cooled
¢ Above Tm Thermal Expansion Coefficient is Large

Op Dent 1 (17 decks)

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