Bonding systems Flashcards

Question

What does a DBA primer do

Answer 1

The primer is really the adhesive element in the process. A coupling agent. It has a bifunctional molecue with a hydrophilic end to bond to the hydrophilic dentine surface and a hyrdophobic, methacrylate end to bond to the resin

Answer 2

Lack of flexibility reduces bonding sites and bond strength

Answer 3

Ethanel Acetone Water

Answer 4

Hydroxy ethyl methacrylate

Answer 5

C=C bond forms a strong covalent bond with the next resin layer The hydroxyl group can form ionic bonds with polar groups on the hydroxyapatite and react with amine groups on the collagen protein

Answer 6

This is a mixture of resins. Usually Bis-GMA and HEMA. It is predominantly hydrophobic. It may contain some filler particles to make it stronger. It will contain Camphorquinone to allow it to light cure.

Answer 7

Penetrates the primed dentine which now has a hydrophobic surface. Forms a micromechanical bond within the tubules and exposed dentinal collagen fibres. -MOLECULAR ENTANGLEMENT Forms the HYBRID LAYER of collagen plus resin.

Answer 8

Etching Dentine --> demineralisation of the outer layer. The remaining collagen is hydrophilic and has low surface energy. Normal resin will not bond to it. Primer can penetrate the demineralised dentine due to its bifunctional molecules. This gives the surface high energy, making it hydrophobic Adhesive can now penetrate --> micro mechanical retention

Answer 9

Over etching - to collapse of the collagen fibres so no resin can penetrate Over etching - too deep an etch and the primer cannot penetrate to the full depth of the etch. Moisture dependent: -Too dry and the dentine surface collapses -Too wet and the primer is diluted --> reduced strength

Answer 10

Collapsed dentine-decrease in porosity Decrease in porosity - poor penetration of dentine by primer - poor bond

Answer 11

Scotchbond One Prime and Bond Optibond Solo i-Bond TE XP Bond

Answer 12

They do not attempt to remove the smear layer. They infiltrate it and incorporated themselves into it. They are not washed off. This removes the problem of how dry to make the dentine.

Answer 13

Acidic methacrylate monomers such as Methacryloyloxyalkyl acid phosphatase

Answer 14

These very complex Bifunctional monomers etch and infiltrate the dentine surface with their hydrophilic end while polymerising like a simpler bis-GMA material at the hydrophobic end

Answer 15

The smear layer is dissolved but then incorporated into the hybrid layer

Answer 16

Strong self etch bonds well to enamel but less well to dentine Etching by-products are not washed away as in total etch These are soluble and weaken the integrity of the bond If too much hydroxyapatite is dissolved away the exposed collagen is vulnerable to breakdown and the bond will fail

Answer 17

The challenge in these materials is to penetrate the smear layer without decalcifying the tooth surface too much and removing the HA -The HA is required for strong durable bonding -The HA protects the dentine from hydrolytic breakdown

Answer 18

Less technique sensitive -No rinsing -No excessive drying -No dentine collapse leading to low bond strength Simultaneous demineralisation and resin infiltration -Less chance of post-op sensitivity

Answer 19

There is great variability between products with regard to initial pH of the solution. The difference in pH results in different etch and different penetration of resin. Those materials with a lower initial pH may not etch enamel efficiently. There is little evidence of stronger bond to dentine than with total etch.