scr - restorative & professionalism Flashcards
(35 cards)
caries on radiograph
if 2/3s way through enamel dentine affected
* caries always deeper than what it looks on radiograph
if caries subgingival
difficulty achieving moisture control & if reaching pulp = RCT / XLA
what to check when considering to restore or not to restore
TAP
t - tooth
a - apical tissues
p - periodontal tissues
principles of caries removal
- identify carious lesion
- remove enamel to extent of lesion at ADJ
- remove caries at outer extent moving circumferentially deeper
- remove deep caries over the pulp
- smooth cavosurface margins & check occlusion
- internal design modification = line angle, point angle
when would you select a crown
as a last resort:
- failed previous restoration
- insufficient tooth tissue present to retain comp / AM / veneer
- RCT of molar as gives cuspal coverage
- RCT of anterior
note - pt requires stabilised gingival margins
risks of crowns
- risk of pulp exposure
- crown margins = caries risk & perio
- crown #
- metal showing at margins due to recession of gingiva
- wear to opposing teeth
- only expected to last approx 10 yrs
benefits of placing crowns
- aesthetics
- function
- reduced risk of # of extensively restored teeth
- retentive & strong
- only restorative option left other than XLA & space fill
principles of crown prep
- preserve tooth structure
- retention (6 degree taper) & resistance (longer walls)
- structural durability - occlusal reduction, axial reduction, functional cusp bevel
- marginal integrity;
chamfer - for metal / veneer & shoulder - for MCC (wider margin required for thickness of metal & ceramic) - preservation of periodontium; margins should not impinge on supra crestal attachment
- aesthetics - should be least destructive to tooth tissue / least destructive to opposing dentition
to check diameter of crown prep
BPE probe tip = 0.5mm
flat fissure bur = 1mm
shoulder bur = 1.3mm
chamfer = 1.1mm
+/- of MCC
increased strength
increased labial reduction (to fit ceramic & metal) so more destructive
possible metal shine through (anterior)
1.5-2mm occlusal reduction
0.5mm lingual chamfer
1.3mm buccal shoulder
metal = CoCr
ceramic = zirconia / lithium disilicate
+/- all ceramic crowns e.g. emax
LiDiSi
glass based & etchable, bonded with resin cement, better aesthetic, more expensive, low strength, won’t mask underlying dark colour
occlusal reduction 1.5-2mm
axial reduction 1.2-1.5mm
margins = 1-1.5mm chamfer (or shoulder depending on core used)
gold crown +/-
not aesthetic but less destructive so can be useful in posterior
zirconia / alumina crown +/-
high strength, opaque so masks underlying dark colours, not etchable, cemented with resin cement, wear of opposing teeth, increased cost
for aesthetics margins should be
sub gingival
if not for aesthetic zone prep should be supragingival
if GI used to cement crown what post op advice do you give pt
avoid sticky / chewy foods in first 24-48hrs until GI has fully set
3 different methods for taking imps for crown fit
- a 1 step putty wash; this is good if you can be accurate but issue arises when one side fits before the other as putty does not have good flow so material struggles to flow and capture other side leaving 1 side distorted
- a 2 step putty and wash; take putty imp (heavy bodied silicone) then go in with light body silicone i.e. extrude as the wash which you place in the impression and around crown prep. issue here is relocating the putty due to undercuts so cut out undercuts in putty imp with scalpel prior to wash imp - also syringe into tray before mouth as will set quicker in the mouth due to heat
- impregum; medium bodied polyether, excellent surface detail but very messy and very strong. need to be aware of what else is in the mouth as can pull out veneers / crowns & if it gets stuck under bridge it won’t come out
effect of abscess on LA
increase in acidic ions from infection lowers pH so the LA’s ionised form is dominant which can delay the onset of action
how does LA work
block voltage gated sodium channels which prevents sodium influx into cell and blocks impulse transmission
adhesive bridge prep
0.7mm thickness so 0.7mm chamfer supragingival
(can use small round bur to create prep)
then putty wash imp
when cementing with panavia
requires anaerobic setting so must use oxyguard
options for onlays
composite - aesthetic, increased strength when cured outside mouth under pressure; overcomes polymerisation shrinkage), easy to adjust, marginal leakage, wear
porcelain - aesthetics, difficult to place & adjust, more prone to #, wear on opposing teeth
gold - strength, aesthetics, expensive
amalgam - strength, cheap, aesthetics
posts
to increase intra radicular support for definitive restorations
- should leave 4-5mm GP apically
- post should be no more than 1/3 of root width (1mm circumferential dentine left over)
- alveolar bone should be half of post length into root
- 1:1 post length to clinical crown minimum
should only be used incisors / canines / premolars
indications for veneer
- improve aesthetics
- change teeth shape or colour i.e. trauma, AI, fluorosis, peg laterals
- reduce / close interproximal spaces & diastemas
- align labial surfaces of instanding teeth
4 types of veneer design
- bevel
- feather
- window
- incisal overlap
