2014 #4 Use of composite restoration materials Flashcards
Why regular polishing paste can’t be used for teeth cleaning prior to a restoration?
Fluoride and glycerin in the paste may counter-act the effect of the etchant and decrease bonding strength of the sealant.
Flour pumice is a good choice for polishing material prior to restoration.
Name the sequences outlined by Black for Tooth cavity preparation (7 forms)
- Outline Form: Determine external and internal boundaries of preparation (considered disease area, undermined enamel, adjacent patho, tooth contour, anomalous anatomy) - hand curette, round-taper fine diamond bur
- Resistance Form: Determine shape fo preparation to resist fracture of tooth and restoration (all internal line angles should be rounded and flood rounded) - hand curette, round-taper fine diamond bur
- Retention Form: Determine shape to prevent displacement of restoration (undercuts, groove cuts, internal wall angle form) - hand curette, round-taper fine diamond bur
- Convenience Form: Determine shape to provide adequate visualization, accessibility, ease for restoration and finishing - hand curette, round-taper fine diamond bur
- Pathology Removal Form: Determine shape to assure removal or compensate for disease/injured or unestetical dental tissue - hand curette, round-taper fine diamond bur
- Wall Form: Refinement of shaping (remove unsupported enamel rods, smoothing of irrugular outline - hand curette, conical Arkansas whitestone bur or shaping discs
- Preparation cleansing forms: Removal of debris from preparation - water spray, cotton pellets, agents
- Margin placement: respect biologic width (2 mm) and not subgingival to avoid peridontal inflammation.
- Pulpal protection: pulp capping with MTA or calcium hydroxide if prep gets within 0.5mm of the pulp; if deep restoration but >0,5mm from pulp, liner or base prior to restoration
Not to agressive, stay conservative!
What are the steps for restoration?
- Preparation form (as Black classification) +/- beveling of margins depending on class restoration
- Depending on bonding agents:
- acids etching +/- rinsing, primer, unfilled or lightly filled resin. gently dry air 5 sec, light-cured 10 sec.
- Composite resin (flowable or packable), light-cured 20 sec./2mm increments, then 60 sec. (Philipps recommand 40 sec/2mm increment; =16000mJ/cm2 every 2mm increment)
- Finishing - fine diamond bur, Arkansas whitestone, finishing discs
- Polishing - composite paste
- Tactile examination of restoration - hand curette and explorer
In which classes of cavity preparation is beveling of the cavosurfaces contraindicated ?
Class I or II because it enlarges the surface area of the restorative in occlusion and
- composite restoration are not as strong as enamel, so wear faster and
- thinner areas of composite along the margin are more prone to fracture from occlusal stress, predisposing to marginal leakage
In which classes of cavity preparation is beveling of the cavosurfaces advised ?
Class III - VI because provides greater retention strength due to greater enamel surface area and improves esthetics
What do acid etchants do?
Dentin is demineralised, exposing the connective tissue for bonding
Collagen fibres within the dentinal tubules are opened exposing more micropores for infiltration by the resin
Removes the smear layer
What product is mostly used for etching?
How long should it stay on dentin and enamel?
How long should it be rinse?
How should the tooth be dry after rinsing?
- Phosphoric acid 10-38% for dentin for 15 seconds
- Phosphoric acid 35-38% for enamel for 30 seconds
- Should be rinse for 10-20 seconds
- Should be dry with moist cotton pellets to remove excess moisture without desiccating the dentin
What happen if the tooth is etch to long or thoroughly dried after etching?
- Both would over-dry the collagen fibers and the fibrils would collapse upon themselves, decreasing the size of interfibrillar spaces that are necessary for resin uptake, decreasing bonding surface and bonding strength
What do applied bonding agents do?
- Improve retention of the restorative
- Prevent leakage at the margins
- Decrease discolouration and pulp sensitivity
How deep do bonding agents penetrate to?
200 - 400 microns
How long a bonding agent will protect a fractured tooth, allowing the tooth time to repair?
3 to 12 months, so tooth treated with sealant should be radiograph 6 - 12 month following treatment to ensure no devitalization or infection.
What are the different types of bonding agents?
- 1st generation – 3 steps - Did not used acid etchants; bond to smear layer
- 2nd generation – 3 steps - Did not used acid etchants; ionic bond in dentin
- 3rd generation – 3 steps - Used acid etchants to partly remove smear layer; bond by infiltrating smear layer
- 4th generation – 3 steps (etch/rinse, primer, adhesive) - Used total etch techn to removed completely smear layer; create hybrid layer. Techn. sensitive
- 5th generation - 2 steps (etch/rinse, primer/adhesive) - Used total etch techn to removed completely smear layer; create hybrid layer, resin tags and adhesive lateral branches which form a micromechanical interlock; Better seal than self-etching adhesives
Available in multi and uni dose
-
6th generation - 2 steps (self-etch primer, adhesive) NO RINSING
- type 1: self-etch primer place on tooth then adhesive application
- type 2: self-etch primer mixed with adhesive prior to place on tooth
Must constantly reapply, poor enamel etching, bond and marginal seal not as good as 5th generation
-
7th generation - 1 step (all-in-one sln) NO RINSING
- 2 components: self etching primer/adhesive (uni dose that get to mixe on application)
- 1 component: self-etching adhesive
Idem as 6th generation
- 8th generation - 1 step (all-in-one sln) NO RINSING - as 7th generation but contain nonofiller (used for direct and indirect restoration)
Which type of bonding agents are light-cured or self-cured?
- All 4th to 7th generations bonding agents are light-cure
- 5th and 6th generations can also be dual-dure
For a light curing resin what strength of visible light is required to set it?
Blue light between 460 - 480nm
What are the 2 different forms of resins composite available?
- Flowable composite: less fillers, less viscous, better handling, bond well, more shrinkage and wear more than paste
- Packable (paste) composite: more fillers, less shrinkage, stiffer, resist more to wear
What are the different size of fillers and their impacts on the restoration?
- Macro and intermediate : best durability and strength but least esthetic
- Microfills: good esthetic but less resistant to fracture
- Hybrids: combine micro and intermediate, good strength, durability and esthetic
- Microhybrid: universal composite with tood esthetic and wear resistance
- Nanofill: good wear resistance and better esthetic
