Cavity Lining Materials Flashcards

Question

what is the setting reaction in calcium hydroxide liner?

Answer 1

chelation reaction between the ZnO and the butylene glycol disalicylate. - Acid base reaction between calcium hydroxide and acid catalyst This results in a cement with an initial pH of around 12.

Answer 2

Bactericidal to cariogenic bacteria Irritation leads to reparative dentine formation

Answer 3

Cariogenic bacterial survive in an acidic environment. The highly alkaline liner kills the bugs. pH12 good as bugs that cause caries like acid environment - die

Answer 4

The cement causes irritation to the odontoblast layer. Necrosis follows which in turn results in a layer of tertiary dentine being produced. This eventually forms a calcified bridge walling the base of the cavity off from the pulp. (The calcium comes from the pulp not the cement). - Cause a degree of irritation in pulp which initiates tertiary dentine being laid down, increasing the distance between cavity base and pulp

Answer 5

- Quick setting time - Radiopaque - Easy to use

Answer 6

- Low compressive strength (can’t put amalgam on top, will crack) - Unstable and soluble - If the cavity leaks then the lining will disappear – break restoration - It may even disappear just because it is in contact with moist dentine

Answer 7

- Zinc Phosphate - Zinc Polycarboxylate - Zinc Oxide Eugenol (ZOE) - Resin Modified ZOE - Ethoxybenzoic acid (EBA) ZOE

Answer 8

In use for 100+ years, under silver amalgams Acid base reaction Powder and liquid Excellent clinical service - Over time hardens - Decent base - Insulating Under many restorations may need to remove Need to understand that extremely strong and hard-wearing material Easy to use Cheap

Answer 9

Zinc Oxide >90% - Main reactive ingredient) Magnesium Dioxide <10% - Gives white colour; - Increases compressive strength Other Oxides (Alumina and Silica) - Improve physical properties, - Alter shade of set material

Answer 10

Aqueous solution of phosphoric acid (approx. 50%) Oxides which buffer the solution - Aluminium oxide (Ensures even consistency of set material ) - Zinc Oxide (Slows the reaction giving better working time)

Answer 11

The initial reaction is acid base ZnO + 2 H3PO4 --> Zn(H2PO4)2 + H2O This is followed by a hydration reaction resulting in the formation of a crystalised phosphate matrix – makes stronger ZnO + Zn(H2PO4)2 + 2H2O --> Zn3(H2PO4)2.4H2O The aluminium oxide prevents crystalisation leading to an amorphous glassy matrix of the acid salt surrounding unreacted ZnO powder. (ZnO powder surrounds zinc phosphate) matrix is almost insoluble, but it is porous (with time) and contains free water from the setting reaction. But still strong The cement subsequently matures binding this water leading to a stronger, less porous material

Answer 12

matrix is almost insoluble, but it is porous (with time) and contains free water from the setting reaction. But still strong The cement subsequently matures binding this water leading to a stronger, less porous material

Answer 13

Low initial pH approx. 2 - Can cause pulpal irritation as pH can take 24hrs to return to neutral Exothermic setting reaction – gives off heat Not adhesive to tooth or restoration - Retention may be slightly micromechanical due to surface irregularities of cavity - No chemical bond to tooth Not cariostatic Final set takes 24hrs (reasonably hard within 5 minutes, could probably pack on top of then) Brittle Opaque

Answer 14

good as temporary dressing which will remove and replace with resin based restorative e.g. inlay - No need to drill as doesn’t stick to tooth Glue for sticking on crowns - temporary crown worried about cementation can use this to stick on better, since wont bond to tooth can remove all cement before placing final crown

Answer 15

material had the advantage of bonding to tooth surfaces in a similar way to glass ionomer cements. - Main advantage – sticks to dentine, not as well as glass ionomer though There is less heat of reaction. The pH is low to begin with but returns to neutral more quickly and longer chain acids do not penetrate dentine as easily. - Higher pH so less toxic to pulp - Polyacrylic acid is bigger so less penetrable Cheap.

Answer 16

- Difficult to mix - Difficult to manipulate - Soluble in oral environment at lower pH - Opaque - Lower modulus and compressive strength than Zinc Phosphate

Answer 17

Linings/base in deep cavities - under amalgam restorations Temporary restorations - Resin modified or EBA ZOE Root canal sealer - Slow setting 24hrs Periodontal dressings - Fast setting , 5 minutes

Answer 18

base acid reaction - base is ZnO - acid is Eugenol Base + Acid --> Salt + Water Chelation reaction of zinc oxide with the eugenol to form zinc eugenolate matrix. This matrix bonds the unreacted ZnO particles same idea as zinc phosphate

Answer 19

Adequate working time Relatively rapid setting time - Sets quicker in the mouth due to moisture and heat - Can be modified by addition of accelerators - Expands on setting Low thermal conductivity Low strength around 20MPa - Weak hydrogen bonds between the eugenolate molecules - Not strong enough to use as a base beneath an amalgam filling. The packing pressure would damage it. But can be used as a long term filling Radiopaque High solubility - Eugenol is constantly released - This is good and bad Eugenol is replaced by water which leads to disintegration of the material (more brittle and break up) BUT Eugenol when liberated has an obtundant effect on the pulp and can reduce pain

Answer 20

no softens them and can cause discoloration. - Acts as a plasticizer ZOE materials should NOT be used under composite resin materials – as they will not set

Answer 21

Eugenol is constantly released - This is good and bad Eugenol is replaced by water which leads to disintegration of the material (more brittle and break up) BUT Eugenol when liberated has an obtundant effect on the pulp and can reduce pain

Answer 22

- Polymethylmethacrylate in IRM - Polystyrene in Kalzinol added to the powder and liquid

Answer 23

These do not take part in the reaction but give a stronger backbone to the set material (act as a filler) - increases the compressive strength to >40MPa making it suitable as a cavity lining. – resin chains make whole material stronger Greatly decreases solubility

Answer 24

modified ZOE Same acid base reaction - Quarts and alumina in matrix – stronger, reinforcing - EBA longer chain eugenol – stronger, reactive Powder - ZnO 65%; Quartz or Alumina 35%; Hydrogenated rosin Around 6% Liquid - Eugenol 37%; Ethoxybenzoic acid EBA 63%

Answer 25

Stronger than ZOE or resin modified ZOE, around 60MPa - Suitable for amalgam filling, medium-long term temporary dressing Less soluble encourages crystalline structure which imparts greater strength to the set material

Answer 26

glass ionomers

Answer 27

can bond to and seal the dentine It then in turn can bond to the composite resin filling placed over it

Answer 28

cariostatic - releases fluoride easy to use (clicker system) command set Thermal conductivity and diffusivity are lower than dentine for both GIC and RMGIC Thermal expansion is similar to dentine for GIC, RMGI is less but still better than filling material Compressive strength is > 170MPa, higher than any of the ZnO based materials Most materials are radiopaque, the radiopacity varies between materials. - Good as can tell difference between them and caries Marginal seal is better than any of the other materials as there is a chemical bond to enamel and dentine. - Good as prevents secondary preventative barrier from microleakage of pulp They are the only material to predictably seal dentinal tubules. - This decreases microleakage and helps prevent post treatment sensitivity Solubility is greater for GIC than RMGIC and is greatest initially. - However, GIC materials are less soluble than any of the other liners apart from Zinc Phosphate cement. - RMGIC is less soluble than any other cement.

Answer 29

- This gives a long working time and a conveniently short setting time (30 seconds) - Unlike all previous material which where own rate set, glass ionomer is command set

Answer 30

Benzoyl iodides and benzoyl bromides are released during the polymerisation reaction of RMGICs. - These are cytotoxic and can be effective against residual cavity bacteria. complete cure of RMGICs is required as any unreacted HEMA may damage the pulp too - As cytotoxic to both bacteria and pulp so need fully cured to prevent damage to pulp but provide protection from bacteria

Answer 31

only lining able to bond to restorative materials. Some conventional glass ionomer materials may require to be etched prior to bonding. - RMGICs require no surface treatment

Answer 32

Consider use of a lining of RMGIC (such as vitrabond) for amalgam and for larger cavities to be filled with composite

Answer 33

calcium hydroxide - Either as a direct or indirect pulp cap over the deepest part of the cavity because: - Protect from hot and cold e.g. heat of composite setting) - place as dentine isn't good for bonding point of view (Glass ionomer bonds to Ca ions instead of mesh way of composite)

Answer 34

RMGIC prior to a final restoration being placed. | - to protect it and stop CaOH being dissolved away

Cavity Lining Materials Flashcards

(58 cards)