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intermediary liners and bases Flashcards

1
Q

What are cavity liners and insulating bases?

A

materials placed between dentin (sometimes pulp) and restorative material to provide pulpal protection or pulpal response

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1
Q

What forms the restorative system?

A

intermediate materials + restorative material + tooth structure

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2
Q

What is the best barrier between the restorative
material and the pulp?

A

sound dentin

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3
Q

What do restorative materials always suffer from?

A

micro-gap at the tooth/restoration interface –> microleakage

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4
Q

What will microleakage cause?

A
  • hypersensitivity through dentinal fluid flow after applying restoration
  • marginal discoloration
  • recurrent caries
  • adverse pulp reaction
  • failure of restoration
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5
Q

What is dentin bridge?

A

the amount of remaining dentin thickness between the pulp and the restoration (ideal barrier)

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6
Q

What are the types of pulpal protection?

A
  • chemical
  • mechanical
  • electrical
  • thermal
  • biological
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7
Q

What is chemical protection?

A
  • sealing of dentinal tubules is essential against the penetration of
  • metallic ions, corrosion products, acids and chemicals from the restorative material
  • bacterial toxins, salivary ions and various irritants
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8
Q

What is thermal protection?

A

protection from thermally conductive metallic restorations such as amalgam and cast gold

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9
Q

What is electrical protection?

A

against galvanism due to use of dissimilar metals e.g., amalgam and cast gold restorations

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10
Q

What is mechanical protection?

A

against condensation of amalgam and cementation of inlays as well as the stresses during masticatory function

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11
Q

What is biological protection (pulpal medication)

A

through the use of calcium hydroxide that facilitates reparative dentin formation

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12
Q

What are the ideal requirements for intermediary materials?

A
  • should provide a sedative action to the pulp
  • should be compatible with pulp-dentin organ and stimulate
    reparative dentin formation
  • should improve the marginal sealing and the adaptation to the
    cavity walls (bonded to tooth structure)
  • should possess thermal and electrical insulating capacity at minimal film thickness
  • should have sufficient strength to resist fracture during condensation of the permanent restoration
  • should have minimal effective film thickness without affecting the bulk of the restoration
  • should be compatible with overlying restorative material
  • should resist degradation in the oral fluids
  • should have adequate workability and be easy to apply
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13
Q

What are liners?

A

thin film materials that are used mainly for sealing of dentinal tubules to provide chemical protectio

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14
Q

What are the functions of varnish?

A
  • forms a barrier against chemical irritations
  • seals dentinal tubules –> decreases hypersensitivity
  • decrease microleakage
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15
Q

What are the indications of varnish?

A
  • under amalgam restoration: it prevents penetration of metallic ions and corrosion products into dentinal tubules, tooth discoloration (amalgam blues)
  • inder zinc phosphate cement: it was irritant cement that used to
    cement metallic crowns and cast gold restorations
16
Q

What are the contraindications of varnish?

A
  • under resin composite restorations (will not be retained)
  • under glass ionomer, resin modified glass ionomer and Zn polycarboxylate cement (varnish will not allow formation of chemical bond)
17
Q

How can calcium hydroxide be supplied?

A
  • two pastes (chemical-cured)
  • one paste (light-cured)
18
Q

What are the proprties and indications of calcium hydroxide?

A
  • applied for pulpal medication (when the remaining dentin bridge is < 0.5mm or in direct contact with exposed pulpal tissue) –> indirect capping
  • t will stimulate odontoblasts –> form reparative dentin at the exposure site
  • relieves pulpal inflammation
  • used in direct pulp capping (calcium hydroxide is added directly on pulp)
  • porous and soluble; it is not used as electric or chemical insulators (disadvantage)
19
Q

What is flowable composite?

A
  • low-filled composite with low viscosity
  • used as a liner/base under composites to absorb stresses and increase the adaptability
  • applied in 0.5-1mm thickness
20
Q

What are base materials?

A

materials with thick consistency to substitute lost dentin and provide thermal, electrical and mechanical pulpal protection

21
Q

What are the types ofbases?

A
  • reinforced zinc oxide and eugenol (RZOE)
  • zinc phosphate cement (ZPC)
  • zinc polycarboxylate cement (PCC)
  • resin modified glass ionomer (RMGI)
22
Q

What are the characteristics of RZOE?

A
  • eugenol produces palliative, sedative and obtundent action on the pulp when used in very low concentrations
  • ZOE has an antiseptic and anti-inflammatory effect.
  • an excellent thermal insulator in a film thickness as low as 0.25mm
  • an excellent electrical insulator and has a good sealing ability
  • used as a temporary filling material and temporary cement or base material
23
Q

What are the characteristics of ZPC?

A
  • has high compressive strength –> most rigid, tough and durable base material (highest mecanical protection) –> advantage
  • excellent thermal and electrical insulator in thickness of 1mm or more
  • the most irritating base material (its acidic pH is 2 after mixing and reach neutrality after 48 hours) –> disadvantage
  • has an exothermic setting reaction –> thermal irritation
  • mixing is done on a glass slab to distribute heat (exothermic reaction) –> powder is separated to quadrants (total is 6 portions) –> this decreases mixing which decreases heat generation
24
Q

What are thecharacteristics of PCC?

A
  • it bonds chemically to tooth structure –> decreased microleakage
  • it produces minimal irritation to pulp-dentin organ
  • good thermal insulator in thickness not less than 1.5 mm (high thickness)
  • an electrical insulator
  • compatible with all restorative materials except ZOE and
    varnish
25
Q

What are the characteristics of RMGI?

A
  • it has an excellent sealing ability due to chemical adhesion to tooth structure
  • it has an anti-cariogenic property due to fluoride release
  • biocompatible with dentin pulp organ and all permanent restorative materials
  • provides adequate thermal, chemical and mechanical protection
  • an excellent material to be used as dentin substitute.
26
Q

What are the indications of RMGI?

A

they can be used as liners, bases, luting cements as well as restorations

27
Q

What are the factors affecting selection of intermediary materials?

A
  • remaining dentin thickness (RDT); increased depth of the cavity –> RDT decreases –> need for intermediary materials
  • adhesive properties of liner or base
  • type of restorative material (metallic or esthetic restoration, a direct or indirect one)
28
Q

What should be done in shallow cavities (RDT > 2mm)?

A
  • there is no need for pulpal protection, only chemical protection (sealing) is needed
  • amalgam restoration –> only a solution liner (varnish)
  • resin composite –> only its bonding system is needed
  • GIC restoration –> does not need any pulpal protection in this case
  • Indirect restoration –> only its bonding system and resin cement is needed
29
Q

What should be done in moderately-deep cavities (RDT=0.5-2mm)?

A
  • amalgam –> varnish + base (chemical protection of pulp)
  • resin composite –> bonding system + flowable composite
  • GIC restoration –> does not need placement of any intermediary material
  • indirect restorations –> only its bonding system & resin cement is needed
30
Q

What should be done in very deep cavities (RDT < 0.5mm)?

A
  • there is strong need for pulpal protection
  • in this case, pulpal medication with Ca(OH)2 is essential in case of frank pulp exposure to induce secondary dentin formation and relief pulpal inflammation
  • sealing is also essential by (varnish + strong base) with amalgam or by (adhesive + flowable composite) with composite
31
Q

What do intermediary materials do at micro-gaps?

A

act as sealant

32
Q

Why is intermediary material added beforerstoration?

A

to protect pulp or stimulate pulp to produce reparatuive dentin

33
Q

What happens if there are micro-gaps present?

A

leakage of oral fluids

34
Q

What type of sensation do irritants cause?

A

pain

35
Q

Do liners provide mechanical protection?

A

no as they are placed as thin film

36
Q

Where is varnishing done in the tooth?

A

floor and walls

37
Q

On which restoration is varnish used?

A

amalgam

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