Lining Materials Flashcards

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1
Q

what is the purpose of a liner

A

thermal - protect pulp from temperature damage
chemical - protect pulp from chemicals released from restoration
bacteria - protect pulp from bacteria due to microleakage from restoration

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2
Q

what is the difference between a therapeutic liner and a palliative liner

A

therapeutic - put down to reduce inflammation of pulp, stops thermal conduction of restorative material, definitive restoration can be placed on top
palliative - put down in reversible pulpitis, causes pulp to regress and tertiary dentine is formed, temp restoration placed over, can then go back and do definitive restoration

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3
Q

give some examples of ideal properties of a liner material

A

low thermal conduction - reduce heat transferred to pulp to prevent pulpal injury
thermal expansion - should be similar to that of dentine and enamel, prevent micro leakage, 8 or 11
mechanical strength - needs to be high to withstand pressure of placing restorative material on top
low solubility - if soluble, dentinal fluid will cause it to wash away

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4
Q

why is a calcium hydroxide liner useful

A

creates an environment with a pH of 12, bacteria requires an acidic environment, therefore, kills any bacteria remaining. also irritates the dentine, causing odontoblasts to produce tertiary dentine, results mineralised layer between pulp and restoration

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5
Q

what is a disadvantage of calcium hydroxide

A

low mechanical strength, and highly soluble, any microleakage can result in the lining disappearing

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6
Q

what are the constituents of zinc phosphate liner and what is the reaction

A

zinc oxide and phosphoric acid, acid base reaction followed by a hydration reaction

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7
Q

what is a problem associated with zinc phosphate

A

has an initial low pH, can cause pulpal irritation, also an exothermic reaction and heat damages the pulp, doesnt bind to the tooth tissue, micro leakage is possible

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8
Q

what is the difference between zinc phosphate and zinc polycarboxylate

A

both use zinc oxide but different acids

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9
Q

what benefits does zinc polycarboxylate acid have

A

bonds to tooth in similar way to GIC, less heat released, has a low initial pH but returns to normal much faster

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10
Q

what are some disadvantages of zinc polycarboxylate

A

lower mechanical strength than zinc phosphate, high solubility, opaque

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11
Q

what is the reaction in zinc oxide eugenol

A

chelation reaction between zinc oxide and eugenol, produces zinc eugenolate mix, integrates unreacted zinc oxide into material

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12
Q

what are some properties of ZOE

A

low thermal conduction, soluble - bad as break down material but good as eugenol is released which calms down the pulp, low mechanical strength - cant be used under amalgam as wouldnt withstand packing

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13
Q

why can ZOE not be used under composite restorations

A

prevents the resin from setting

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14
Q

how is ZOE resin modified

A

addition of resin, doesnt interact with setting reaction just increases mechanical strength

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15
Q

what is added in EBA ZOE

A

ethoxybenzoic acid, quartz and alumina

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16
Q

how the properties change in EBA ZOE

A

increases mechanical strength by encorporating crystalline structure, reduces solubility

17
Q

what benefits does GIC have over other lining materials

A

command set, thermal expansion similar to tooth, low thermal conductivity, binds well to tooth tissue and can then bond to composite resin, good marginal seal, has very high mechanical strength, much higher than any other liner, can be cariostatic and release fluoride

18
Q

when should calcium hydroxide be used

A

when the cavity approaches the pulp or a pulpotomy, direct or indirect pulp cap

19
Q

when should GIC be used

A

all amalgam fillings and a large composite filling, also for crown prep or placing indirect restorations