Clinical Composites Flashcards
There are lots of things that can go wrong for a composite restoration to fail, can you name some of these? (20 points)
- The wrong patient
- The wrong tooth
- Isolation
- Removing the (restoration) caries
- Designing the cavity
- Managing the dentine/pulp complex
- Matrix application
- Contact point
- Etching
- Washing
- Drying
- Lining
- Primar application
- Wet & dry surfaces
- Bonding
- Placing & handling materials
- Curing
- Finishing and polishing
- Occlusal considerations
- Post operative advice
What are some factors that we need to consider that are all interlinked intimately when placing a restoration? (6 points)
- Tooth biology
- Materials science
- Interfaces
- Marginal seal
- Manipulation
- Polymerisation
What is a cavosurface angle?
- The angle of tooth structure formed by the junction of a prepared cavity wall and the external surface of a tooth. The actual junction is referred to as the cavosurface margin
What is the problem with leaving caries at the ADJ?
- This will result in unsupported enamel and early breakdown of the restoration margin if microleakage occurs
What is a centric stop?
- The stable points of contact between occluded maxillary and mandibular teeth, located in the central pits, marginal ridges, and buccal and lingual cusps of posterior teeth and the incisal and lingual aspect of anterior teeth
- Areas of occlusal contact that a supporting cusp makes with the opposing teeth in centric occlusion
What is a good design for interproximal caries cavity prep? (3 points)
- No unsupported enamel
- Proximal axial bevel
- Gingival bevel
What is a bevel?
- The angulation which is made by 2 surfaces of a prepared tooth which is other than 90 degrees. Bevels are given at various angles depending on the type of material used for restoration and the purpose the material serves
What can you do to prevent enamel fracture from a restoration and how can you see that this has happened? (5 points)
- Resolved by: cavity design, etch times, washing, curing protocol
- When you put in a restoration and cure it - if there is a white line round the edges then the restoration will fail
Which type if dentine is not good to bond a restoration to as it is likely the restoration will fail?
- Tertiary dentine
What are the tubules like in primary dentine?
- Open tubules
What type of dentine is favourable for hybri d layer creation and what makes a good hybrid layer?
- Primary dentine - open tubules
- Dentine bonding creates a hybrid layer of resin, collagen fibres, dentine surface structure and intertubular structures
- Formation of hybrid layer is an integral part of denrtine bonding. The quality of hybrid layer formed decides the strenght of resin-dentine interface. The thicker and more uniform the hybrid layer, the better the bond strength is. Along with the thickness of hybrid layer, the uniformity in the formation of hybrid layer is also important. A uniform hybrid layer is seen with total etch technique whereas the hybrid layer formed with self etch technique is less uniform and discontinuous with lots of debris
What are the tubules like in tertiary dentine?
- Irregular structure
What is meant by tubular patency?
- When the dentinal tubules are open and unobstructed
What are 3 characteristics of deeper dentine compared to surface dentine?
- Wetter
- More mineralised
- More tubules
What do you need to consider about the dentinal tubules when placing a composite restoration? (8 points)
- Removal of smear layer
- Creation of hybrid layer
- Dentine physiology
- Peri/inter tubular
- Tubule size
- Tubule densit y
- Water content
- Water transport
What are 3 properties of older dentine?
- Fewer tubules
- More minerlalised
- Occluded tubules
What are 3 properties of reactive dentine?
- Occluded tubules
- More mineralised/contaminated
- Irregular tubules
What are dead tracks?
- Dentine areas characterised by degenerated odontoblastic processes; may result from injury caused by caries, attrition, erosion or cavity preparation
What is sclerotic dentine?
- Dentin characterized by calcification of the dentinal tubules as a result of injury or normal aging
How does RMGI allow adhesion to dentine?
- Through ion exchange
What is the reason for placing linings in a composite restoration?
- To create a barrier between poor quality dentine that will result in the restoration failing
- Prevents enamel contamination
- Protection of pulpal therapeutic agents
In terms of cavity preparation what is a common issue when placing a composite restoration?
- Failure to remove all caries
In terms of bonding, what is a common issue when placing a composite restoration?
- Failure to follow the manufacturers instructions for the right bond
In terms of placement and curing, what is a common issue when placing a composite restoration?
- How do you know that you have adequately cured all of the material
In terms of countering contraction stresses, what is a common issue when placing a composite restoration?
- If material is successfully bonded to the tooth and then shrinks, it will then put pressure onto the tooth
In terms of optimising interfaces, what do you need to consider when placing a composite restoration? (4 points)
- Marginal - need margins that are going to get the best seal
- Enamel bonding - no unsupported enamel
- Dentine bonding - quality of the dentine you are bonding to
- Bonding to other materials
The materials properties, cavity design, matrices and manipulation of material are all important factors when placing a composite restoration, but what are the 2 more important factors?
- Configuration factor
- Polymerisation contraction stress
What is configuration factor?
- The ratio of the surfaces that are bonded to the tooth and the surfaces that are not bonded to the tooth
- High configuration factor - there are lots of surfaces of the tooth that are bonded to the restoration
What happens to the polymerisation contraction stress with high configuration factor and is this advantageous?
- Increases
- This is not what we want
What happens to the polymerisation contraction stress with low configuration factor and is this advantageous?
- Reduced
- Yes, this is what we want
The greatest limitation in the field of resin composite seems to be polymerisation shrinkage. This results in the development of internal contraction stress which can damage the marginal seal of the bonded restorations. This results in interfacial gap formation. What does this lead to? (3 points)
- Postoperative sensitivity
- Marginal staining
- Recurrent caries
What is plasticity?
- A property of a material to undergo a non-reversible change of shape in response to an applied force (polymerisation)
What is deformation?
- A change in shape due to an applied force (contraction)
What is plastic deformation equal to?
- Polymerisation contraction
What happens due to polymerisation contraction shrinkage when placing a single increment of composite into a cavity? (5 points)
- Composite is placed in single increment
- Imperfect dentine bond on base of cavity so have a poor bond
- Enamel bond is ideal
- So, nice bonded surface up the top but on the floor of the cavity the composite lifts
- Now have a gap on the bottom - this fills with dentinal tubule fluid which bounces up and down in the dentinal tubules
- So, tooth is sore to bite on but does not physically appear wrong
What factors do you need to consider when looking at different types of dentine? (5 points)
- Type: 1,2,3
- Intra/inter/peri tubular
- Diameter
- Density
- Contents/mineralisation
What is better, contoured or flat matrix bands?
- Contoured, this allows better positioning of the contact
What are the clinical procedures when placing a composite restoration? (6 points)
- Etch (enamel and dentine)
- Prime (dentine surface)
- Bond (dentine surface)
- Placement of composite (will shrink a bit)
- Characterisation
- Finish
What should you consider the need for on areas where bonding of composite may be problematic?
- RMGI
Why do you need to consider the placement of flowable composite onto the cavity floor?
- To mediate contraction stresses on interface and to achieve optimal adaption to non load bearing margins
What is the minimum intensity required to adequately cure 1.5-2mm of composite resin?
- Between 280/300 mW/cm2
What is ‘soft start’ curing regime?
- It propses a slower rate of conversion will allow better flow of resin with a decrease in contraction stress
- It may be divided into three separate techniques; stepped, ramped and pulse delay.
What is ‘soft start’ stepped curing?
A stepped programme emits a low irradiance for 10 seconds and then increases immediately to a max value for the duration of the exposure.
What is a ‘soft start’ ramped curing regime?
- The irradiance gradually increases from a low value to a max intensity over a 10 sec period, after which it remains constant for the duration of the exposure.
what is the ‘soft start’ pulse curing regime?
- Uses a short low-level burst, a delay for polishing and finally a long exposure at full intensity
When would you use the curing light at a low power?
- When you are curing close to the pulp
