OPTEC- Composite Flashcards
Includes: DMS- composite resin OPTEC- clinical composite lecture
What is shown in this image?
This is an Enamel fracture and is characterised by the white line around the edge of the restoration. This shows that the restoration is doomed for failure.
What dentine is used in the creation of the hybrid layer and why?
Primary dentine is used as it has open tubules.
Tertiary dentine is unfavourable due to its irregular structure.
What is the configuration factor?
This is the ratio of surfaces bonded to the tooth and surfaces not bonded to the tooth.
High configuration factor= more surfaces bonded = increased polymerisation contraction stress.
Low configuration factor= less surfaces bonded = lower polymerisation contraction stress.
What is polymerisation contraction shrinkage?
when the material shrinks and tries to pull away from the tooth surface as the restoration polymerises (hardens)
How do we compensate for the composite shrinking?
By putting in more composite than is needed in order to keep the contacts.
Describe the procedure of placing a composite restoration:
- Check the dentine quality
- Etch the tooth- 10s enamel and 10s enamel + Dentine
- Prime the dentine surfaces
- Add composite (first to the floor and then in increments)
- Cure the composite
- Polish the tooth
- Surface seal.
Discuss the placement theory for composite restorations
Use a lower viscosity composite (flowable) to the floor of the cavity to act as a stress reducer.
The composite is added in increments touching as few walls as possible.
Do not join the enamel margins for the final increments.
What is composite made of?
- Filler particles
- Resin
- Camphorquinone
- Low weight dimethacrylates
- Silane coupling agent
What is the function of filler particles in composite?
These make the material harder.
What is the function of Camphorquinone in composite?
This is the photo initiator that is activated by blue light.
This causes free radical production for polymerisation to make the material stronger.
What is the function of the silane coupling agent?
The silane coupling agent is used to create a good bond between filler and resin by bonding to them.
How does the filler type affect composite?
The more filler particles the harder, stronger and more rigid the restoration. It also lowers polymeristion shrinkage.
The filler is commonly a hybrid- a mixture of large conventional particles and small microfine particles. This is to try and pack the full area.
Compare the light cure mechanism to the self cure mechanism
Light cure is made out of 1 paste (Camphorquinone) and blue light.
Self cure is made of 2 pastes (Benzoyl peroxide and aromatic tertiary amine).
These react to give free radicals.
What is the depth of cure?
Where the hardness of the material is half of that at the surface.
This is 2mm.
Why is the depth of cure important?
If we use greater than 2mm incremments of composite, they will not adequately polymerise. This results in a soggy bottom.