Clinical Use of Bases and Liners

What are the 5 main reasons to use dentin sealers, liners and bases?

* Seal the dentinal tubules to limit fluid movement and decrease sensitivity.

* Seal the dentinal tubules to limit external insult from restorative materials (acids) and bacteria.

* Pulpal medication CaOH and eugenol

* Replace missing dentin for indirect restorations (bases) "Blocking out"

* Concept of thermal protection for metallic restorations

What is a unique beneficial effect of eugenol?

eugenol is palliative ( sedative) to the pulp

What is a unique benefit of Calcium hydroxide ( Dycal) ?

dycal accelerates reparative dentin formation ( MTA)

What is a unique beneficial effect of glass ionomer?

glass ionomer can provide bonding, fluoride release, and protease inhibition.

Clinical need for base placement is determined by_______

this thickness of the remaining dentin

What level of remaining dentin qualifies as shallow?

>2mm remaining dentin

What level of remaining dentin qualifies as moderate?

>1 mm but less than 2mm remaining dentin

What level of remaining dentin qualifies as deep?

< 1mm remaining dentin

A cavity sealer is a ______ which provides _______

a cavity sealer is a thin film which provides a protective coating for fresh cut tooth structure in a prepared cavity ( seals the dentin tubules).

What is varnish? How effective is it?

With what do we use it?

copal resins. i.e: a natural gum dissolved in an organic solvent.

2 coats 75% effective

Rarely used as it has been replaced by adhesive materials

used only with metallic restorations/amalgam

Dentin bonding agent function

creates a chemical and mechanical bond between the tooth structure and the restorative material

Dentin bonding agent mechanism

involves infiltrating monomers into the dentin matrix, forming a hybrid layer, and then copolymerizing with the resin matrix of the composite restoration.

Dentin bonding purpose

ensures longevity and effectiveness of dental restorations by providing a secure and duravle bond.

Dentin Sealer function

covers and seals dentinal tubules, protecting them from irritation caused by restorative materials

Dentin sealer mechanism

a self curing ( or light cured), high molecular weight resin that covers the tubules

Dentin sealer purpose

Reduces dentin sensitivity and healps preven leakage under restorations ( under amalgams and crowns)

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What is one example of a low strength base

Calcium hydroxide ( Dycal)

properties and manipulation of Dycal

low strength ( must be covered with a stronger base

extremely soluble: can disappear over time simulating decay

What is the pH of dycal?

9.2 - 11.7

What are some of the beneficial effects of dycal?

stimulates reparative dentin formation if applied directly to the exposed pulp.

shows antibacterial activity ( chemical cure)

aids in producing a sterile environment

t/f dycal weakens the final restoration

true

Dycal should only be used for ______ or __________

Dycal, should only be used for direct pulp caping or lining deep cavities if a micro-exposure is suspected

(T/F) Dycal has no bonding capability

true

Dycal ________the final restoration

weakens

Dycal is not used in _____

shallow and moderate preps

What is a better choice over Dycal for a moderate prep?

Glass ionomer is a better choice for moderate preps over dycal

Where is it acceptable to place dycal without a stronger base?

it is acceptable to place dycal on the axial wall without using a stronger base

Where is it unnacceptable to place dycal without a stronger base?

it is unacceptable to place dycal on the gingival wall without a stronger base

All base and liner applications ( except ______) must be at least _____ mm from _______. Why?

All base and liner applications ( except for open sandwich with GI) must be at least 1mm from the cavosurface margin.

Why? because these materials are soluble in oral fluids.

What is MTA? What is it used for? Why?

MTA is a biocompatible, alkaline dental material

it is used for root repair, pulp capping, apexification, and other endodontic procedures due to its sealing ability and tissue regenerative properties

How is MTA able to perform its function?

MTA creates an alkaline nevironment that promotes tissue regeneration, mineralization, and antibacterial effects. Its hydrophilic nature allows it to form a tight seal, minimizing bacterial infiltration and leakage.

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Cavity liners are used in:

moderate and deep preps

How are cavity liners used? What do they do?

they are used like a varnish. they leave a thicker film of material to protect freshly cut dentin.

They serve to protect pulp from external stimuli like cements, restorative materials and bacterial products

What is the thickness of cavity liners?

they have variable thickness based on application technique

What are the two cavity liners of choice? How are they cured? Do they have bonding capability?

Traditional GI and resin modified GI

which can be chemical and light cured

they both have bonding capability to tooth structure unlike dycal

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Traditional glass ionomer is more tolerant of ______

moisture during placement

What should be done to GI during setting?

GI should be covered with sealer during setting

Slide discussing differences between Fuji II LC ( light cure) Vs Fuji IX GP ( traditional glass ionomer)

Slide discussing EQUIA Forte - a newer, bulk-fill glass hybrid restorative material

basically uses fluoro-aluminosilicate glasses reinforced with a second, smaller and more reactive silicate particle so has higher molecular weight and improves mechanical properties and handling.

What is the adhesion mechanism of GI ?

Weak polyacrylic acid attackes the glass to release Al+ and Ca+ cations. cross linking then occurs between acid chains

additional crosslinks are made between acid chains and tooth structure

( strong acids demineralize dentin removing too much Ca+)

How does the application technique of GC Fuji LC differ between Class3,4,5 , primary teeth vs Class 1 and 2 cavities

Describe the difference between the closed and open sandwich technique

Closed: the underlying material does not come into contact with the oral cavity

Open: usually used for class 2 restorations where the underlying material forms part of the axial wall and is exposed to the oral environment

Benefits of resin modified glass ionomer cement as a liner

bonds both to tooth structure and the composite

increased retention form

provides better seal when used at non-enamel margins

fluoride in GI material reduces recurrent caries

(*some conflicting research)

Benefits of flowable composite as a liner

acts as a shock absorber

distributes stresses applied to the more rigid composite

may reduce some of the negative effects of polymerization shrinkage

( * some conflicting research)

Main indications for use of RMGIC ( ** double check on lecture this is what he is talking about ***)

Main advantages of RMGIC (**** double check on lecture that this is what he is talking about)

What is the function of conditioner? What are two commonly used conditioners?

creates stronger bond between tooth and GIC by removing smear layer and debris from tooth surface

commonly used conditioners: citric acid and polyacrylic acid

What is indication for sandwich technique?

gingival margin below the CEJ

Next few slides are review of clinical steps for RMGI usage

This card: steps 1 and 2

this card: step 3 of RMGI usage

also: describe the difference between open and closed sandwich

this card: step 4 of RMGI usage

this slide: step 5,6, 7 of RMGI usage

What are the three main benefits of GI over flowable composite

GI is:

more moisture tolerant

bonds to tooth structure

releases fluoride

No cards this slide as I am not sure exactly what he means. Need to rewatch lecture and review

What is the snowplow technique ?

The "snowplow technique" is placing flowable composite in a layer, on the gingival margin of the proximal box as well as on the pulpal floor of a composite resin restoration. This layer of the composite is uncured before the placement of a composite restorative material that is denser filled

How is a cement base placed and why?

cement bases are placed under permanent restorations in order to protect injured pulp and encourage pulp recovery. They also provide thermal protection ( when beneath metallic restorations) and protection from chemical injury.

What thickness is require for cement composite to provide thermal protection?

0.75-1mm thickness of cement base is needed for thermal protection

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What are the two types of Zinc oxide eugenol (ZOE) / IRM

type 1: unmodified

type 2: polymer reinforced ( IRM)

What are the two powder bases used in ZOE / IRM?

zinc oxide

poly methyl methacrylate

what are the two liquid bases used in ZOE / IRM?

eugenol

olive oil

Mixing ZOE / IRM

final base consists of:

undissolved powder particles surrounded by a matrix

increasing powder content in liquid results in:

increased strength ( until powder becomes excessive)

excessive powder results in

crumbling matrix

Mixing ZOE / IRM

water is necessary for _____ but continued exposure to water can cause:

Water is necessary for the reaction to occur but continued exposure to ware can cause a destabilizing effect, releasing free eugenol

What is the chemical reaction of ZOE / IRM?

What happens to the chemical reaction of ZOE / IRM formation if there is excess water?

the reaction can reverse resulting in a release of free eugenol

Explanatory slide on ZOE / IRM and releasing mechanisms

4 main properties of ZOE / IRM

1) bacteriocidal / bacteriostatic

2) obtundant in low concentrations ( dentin barrier) * can be toxic in high concentrations

3) pH 4-8; neutral and non irritating

4) Low thermal conductivity

5 ZOE / IRM applications

1) as a high strength base providing obtundant effects

2) use of modified type under temporary restorations

3) crown cementation

4) endodontic sealers

5) tissue management in periodontic treatment

(T/F)

ZOE / IRM is compatible with composite resin

false