FIXED PROS - Impressions and Soft Tissue Management Flashcards
when planning extra coronal restorations, how should the tissues be considered?
- good health for clinical success
- restorations designed to allow plaque control
- avoid iatrogenic damage
why must the gingiva be healthy before placing an extra coronal restoration?
- stable gingival margin
- easy to prepare and impression taking
- patient will have good motivation for good oral hygiene
how is good periodontal care established?
- OHI
- patient motivation
- remove PRF - calculus, overhangs, temp crowns
- no BOP
what 4 things must be considered with restoration designs?
- margins
- material
- embrasure spaces - like my front teeth
- contour
what are the 3 margins to consider?
- subgingival
- supragingival
- equigingival - remaining even with the tissue to place the margin
6 reasons why you may want to place a subgingival margin?
- to not interfere or damage the natural gingival tissue
- to discourage plaque accumulation by not leaving an edge by the gingival crevice
- increase retention
- improves aesthetics
- to protect against dentinal hypersensitivity
- if there is a subgingival fracture
how can you minimise the effect of subgingival margin placement?
- use of retraction cord
- take a sulculus impression
- restorations must be well-fitted and contoured
- good hygiene observation
what is a gingival retraction cord?
a absorbent string inserted into the gingival crevice to provide mechanical tissue displacement
why must the contour be considered? (2)
- plaque control
- excessive bulk in gingival third = plaque accumulation
what is the purpose of taking an impression?
to obtain:
- accurate
- dimensionally stable
- fully supported impression
of prepared teeth and associated soft tissues
what has to be considered for a good impression?
- choice of tray
- choice of material
- moisture control
- handling of material and completed impression - label, disinfect, transport, storage
- managing the patient
- accurate assessment of impression
- casting
3 ways the soft tissue is managed.
- retract the tissue
- remove the tissue
- control bleeding
two ways in which you can retract the gingival tissue.
retraction cord
astringent retraction paste
how is gingival tissue removed?
- rotary curette - not recommend, uncomfortable and bleeding
- electrosurgery
- laser
state 4 advantages to using a retraction cord and 4 disadvantages.
advantages
- universal technique
- various degrees of retraction are possible
- cheap
- double or single cord available
disadvantages
- bleeding
- painful
- time consuming
- can damage the epithelial attachment, lead to recession
describe the double cord/twin cord technique
one chord placed deep
another chord placed on top and removed just before impression taken
- usually with triple 0 chord
is there a relationship for a retraction cord and potential for adverse reactions?
yes, direct link
esp more if it is dry
what must you note down regarding the retraction cord?
that is has been used
that is has been removed
how may bleeding be controlled?
- electrocautery
- pressure effect from cord/putty
- haemostatic agent (astringents)
give 4 haemostatic agents (astringents) which can be used to control bleeding. describe: the pH they work at and how they work
- ferric sulfate
pH 1.2
cauterizes tissues - aluminium chloride
pH 3
constricts tubules - aluminium sulfate
pH 3
constricts tubules - adrenaline
pH 7
vasoconstrictor
how is ferric sulfate astringent used?
rub on gingival margin using microbrush
wash away black bits before placing cord
which astringent:
1. is the least reactive with silicone impression materials?
2. turns tissues black?
3. bleeds on cord removal?
4. can inhibit the setting of impression?
5. has an offensive taste?
6. is difficult to control the dose and can increase heart rate?
1) aluminium chloride
2) ferric sulfate
3) ferric sulfae
4) ferric sulfate
5) aluminium sulfate
6) adrenaline
give an advantage to using electrosurgery and 3 disadvantages.
advantage
- post surgical haemorrhage is well control if the tissue is not inflamed
disadvantages
- recession potential
- pacemakers - electrocautery can mimic programming signal and cause device to be reprogrammed
- plastic instruments to be used to not conduct electricity
what needs to be considered when assessing the impression?
- assess when it is dry
- all teeth present?
- areas where tray is showing?
- any air blows?
- prep - visible margins? detail of each tooth? shapes of each tooth?
why can provisional restorations affect the gingival health?
- always a gap present - PRF
- needs to be finished, surface roughness - PRF
is there a relationship between fit of the crown and periodontal disease?
yes, direct correlation
- defective crown margins and reduction interdental alveolar bone
what is the ideal finished margin?
- closest possible fit
- thinnest layer of cement visible
- taper with no irregularities, irregularities prevent proper seating
what is the least marginal gap most operators miss by?
120μm
