Tooth Coloured Filling Materials 1 Flashcards

Question

What is the advantage of using coupling agents

Answer 1

Coupling agents chemically coat filler surfaces and increase strength

Answer 2

They age quickly in a bottle and become ineffective Silanes are sensitive to water so the silane filler bond breaks down with moisture Water absorbed into composite results in hydrolysis of the silane bond and eventual filler loss

Answer 3

Compressible strength - 170-260MPa (Enamel 100-380, Dentine 250-350) Tensile strength - 30-55MPa (Enamel 10, Dentine 20-50) Coefficient of Thermal Expansion 20-77 (Enamel 11.4, Dentine 8.3) Polymer shrinkage 3%

Answer 4

Their percentage filler content by weight (50% to 70%) is less than that of traditional hybrid composite resins which givesthem a lower viscosity. Indications: – Class V restorations – Micropreparations – Extended fissure sealings – Adhesive cementation of ceramic restorations – Blocking out cavity undercuts – Initial (base) layer in any classification

Answer 5

The flowable composite resins have lower filler volumes and thus they exhibit increased shrinkage and wear with decreased strength

Answer 6

Bulk placed composites Stiffer materials

Answer 7

- BIS GMA resin + methacrylates - Polymerise through photo initiated mechanisms - Available in various shades and opacities - Does not adhere to tooth tissue unless are specifically self etching

Answer 8

- 95% HAP - 4% water - 1% non collagenous protein

Answer 9

- An acid (mostly 30-40% phosphoric acid) is appliedand rinsed off. - pH is 0.2 (very strong acid) and decalcification occursin 5-8 seconds - Etching decalcifies portions of enamel rods

Answer 10

- Calcium salts are dissolved which exposes interprismatic and prism areas for interlocking tagformation with the bonding resin. - This is purely mechanical bonding, not trueadhesion. - Bond strength ~20 MPa

Answer 11

Dentine contains: – 33% by volume of organic component (mainly Type I collagen). – 45% by volume of inorganic component(mainly hydroxyapatite). – 23% by volume of water. It is a moist, living tissue (hydrophobic) = issue

Answer 12

- Ultimate aim is to bond a hydrophobic, highly viscous composite to a hydrophilic adherent. - We therefore need something to change the properties of the dentine surface or smear layer from hydrophilic to hydrophobic

Answer 13

- Created by any mechanical cutting of dentine. - Essentially dentine debris of variable thickness. - In addition smear plugs are formed which block dentinal tubules

Answer 14

Can protect dentine and ultimately the pulp from penetrationof bacteria Eliminates diffusion of dentinal fluid

Answer 15

Impairs bond of composite to dentine. It’s self is only relatively loosely bound. Can harbour bacteria.

Answer 16

The smear layer is left alone The smear layer is removed The smear layer is modified The smear layer is practically removed and partially modified

Answer 17

The basic mechanism of bonding to enamel and dentin is essentially an exchange process involving replacement of minerals (removed from either of the hard dental tissues) by resin monomers, which, uponsetting, become micro-mechanically interlocked inthe created porosities Superficial surface demineralisation of HAP enamel Or Removing HAP filler from the dentine and the resin then locking into the dentine

Answer 18

It is a process that creates a molecular-level mixture of adhesive polymers and dental hardtissues – the hybrid layer

Answer 19

Hybridisation ~ the infiltration of resin monomers into the collagen fibrillar matrix of demineralised dentin, followed by polymerisation.

Answer 20

Etched dentine has removed some HAP and so end up with exposed collagen fibres

Answer 21

Then infiltrate with primer which acts as a deterent to wet collagen and provide a hydrophobic surface for the resin - dual functionality Resin is applied on top and then bond

Answer 22

- Improves the retention of the restoration - Increases the surface area of the dentine - Removes “smear layer” from prep - Allows for penetration of bonding agent into dentine - Protect pulp exposures before using! - Phosphoric acid (35-37%) gel or liquid - Isolate teeth, apply etchant, wait (5-15 seconds) - Rinse – don’t desiccate! – blot prep to remove wate

Answer 23

- Resin - monomer - Improves wettability of prep - Penetrates etched dentin tubules - Applied in a thin layer; thinned with air; blot - May require light-curing

Answer 24

- Un-filled or lightly filled resin - Adhesive bonds to collagen fibers in dentin - mechanically “locks-in” therefore a “Hybrid Layer” - Applied in a thin, uniform layer - Light-cured 10-20 seconds - New “generations” being developed Dental composite then applied

Answer 25

Yes Gives good bonding area It removes / modifies smear layer and exposes dentinal tubules

Answer 26

This etching step is followed by a priming step. - Primer is ampiphillic and low viscosity - Solvents are added to adjust primer viscosityand improve its wetting - Usually optimised for dentine surface characteristics rather than enamel

Answer 27

1. Acetone based e.g. All-bond 2, One Step 2. Ethanol based e.g. Optibond solo 3. Water based eg scotch bond MP

Answer 28

Final stage, application of the hydrophobic resin and cure, resulting in a three step process Simplified two-step etch-and-rinse adhesives combine the primer and adhesive resin into one application

Answer 29

Make use of acidic monomers that simultaneously etch and prime dentin. The application of the self-etch primer is followed by the application of a hydrophobic bonding resin. Without the need for rinsing, application time of self-etch adhesives is shorter and the technique-sensitivity lower

Answer 30

As one moves away from phosphoric acid towardsacidic organic monomers, the challenges increase! No option has yet been tested that is as effective asphosphoric acid for etching tooth structure - No typical microetching patterns on enamel pH initially only in the range 1-3 and this increases asthe etching proceeds

Answer 31

Upon application the SE primer must: – Dissolve the smear layer – Decalcify intertubular dentine whilst– - Penetrating to embed superficial collagen andproduce an effective hybrid layer Many complicated competitive events! Consequently, systems relatively unstable

Answer 32

Just as was the case with etch-and-rinse adhesives,simplified adhesives that combine the (self-etch) primer with the adhesive resin were developed tocreate what is known as the one-step self-etch adhesives or so-called 'all-in-one' adhesives.

Answer 33

- Some challenges as discussed above and inaddition it must create a surface compatible to hydrophobic restorative materials - May need to acid etch in advance in complexclinical situations. - The acidity of the bonding agent can interferewith the setting of self–cure composite andare CI

Answer 34

A pathway for successful bonding to dentine: – wetting – infiltration to produce a ‘hybrid zone’ – mechanical interlocking – stress resistance Ultimate goal is marginal integrity and sealing tubules to prevent ingress of bacteria