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Dentistry in a Nutshell > Crowns & Onlays > Flashcards

Crowns & Onlays Flashcards

1
Q

what to warn pt of when crown / onlay on tooth

A

20-30% risk of devitalisation which would require RCT in future.
it tooth non vital & previously RCT risk of failure and need for new crown/onlay

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2
Q

what is an inlay & indications

A

indirect intracoronal restoration that does not provide cuspal coverage
proximal & occlusal surface replaced
used for occlusal and/or proximal cavities or when failure of direct restoration

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3
Q

prep principles of inlay

A

isthmus 1.5-2mm
flat pulpal floor
4-6 degree tapered walls
no undercuts
if ceramic - butt joint 90 degree cavosurface margins
if metal 20-30 degree bevel on cavosurface margins
contact points clear
rounded internal line angles

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4
Q

what is an onlay & indications

A

indirect intra & extra coronal restoration that incorporates cusps & provides cuspal coverage
used if: cusp #, tooth wear, caries, preexisting failed rest with large isthmus, rest of RCT treated tooth

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5
Q

prep principles for onlay

A

isthmus to follow restoration pattern
flat pulpal floor
4-6 degree tapered walls
no undercuts
butt joint 90 degree CVSM
contact points clear (proximal only)
rounded internal line angles
axial shoulder or chamfer = 1mm reduction
ceramic -> functional cusp 2mm reduction, non functional cusp 1.5mm reduction
gold type III -> functional cusp 1mm reduction, non functional cusp 0.5mm reduction

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6
Q

what is a crown & indications

A

indirect restoration that fully covers coronal aspect of tooth
used if: cusp #, toothwear, caries, preexisting restoration had large isthmus, restoration of RCT treated tooth, high aesthetic demand, onlay not possible

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7
Q

if 2 stage impression technique chosen

A

must take silicone impression with a separator prior to starting prep

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8
Q

ceramic crown prep

A
  • take sectional silicone imp for temp crown/onlay production (ensure it is taken in sectional tray)
  • remove prev rest & caries removal
  • immediate dentine sealing
  • begin with occlusal reduction, then axial & interproximal (use depth cutting burs to prevent over prep)
  • non functional cusp reduction = 1.5-2mm, functional cusp reduction = 2mm, aim for 6 degree tapered axial walls & 1-1.5mm marginal reduction
  • bevel functional cusp; this should be the same angle as the non functional cusp incline
  • finishing inc: polishing proximal boxes & flare edges, pep a rounded shoulder/chamfer margin, round off internal sharp angles, remove enamel lips, no undercuts
  • continue at temp crown construction
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9
Q

metal crown prep

A
  • take sectional silicone imp for temp crown / onlay construction
  • remove prev rest, caries removal
  • immediate dentine sealing
  • place composite core
  • occlusal reduction followed by axial & interproximal (use depth cutting burs & mark depth cuts in pencil to ensure even reduction)
  • non functional cusp reduction = 1.5-2mm, functional cusp reduction = 2mm, aim for 6 degree tapered axial walls & 1-1.5mm marginal reduction
  • bevel functional cusp; should be same angle as non functional cusp incline
  • continue at temp crown construction
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10
Q

anterior crown preparation

A
  • take sectional silicone matrix (using diagnostic wax up if available)
  • prep tooth in 3 planes; cervical 1/3, middle 1/3, incisal 1/3 to prevent encroaching on pulp (the darker the underlying tooth the the deeper the reduction buccally to allow for masking)
  • place composite core
  • special attention to gingival contour (related to smile line & how much tooth exposed when smiling & talking)
  • perform incisal edge reduction & ensure 2mm interocclusal space
  • labial, lingual / palatal & interproximal reduction 1.2-1.4mm depth cuts will improve accuracy
  • porcelain fused to metal; 0.7mm palatal chamfer, 0.7mm cingulum reduction & 1.5mm labial shoulder margin
  • all ceramic; 1-1.5mm palatal shoulder/chamfer margin, 1mm cingulum reduction, 1-1.5mm labial shoulder/chamfer margin
  • assess prep from occlusal & axial views; use reduction stent to confirm adequate prep dimensions
  • smooth & polish
  • continue to temp crown construction
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11
Q

temp crown construction

A
  • check for easy placement & removal of sectional silicone imp over pre (remove excess with scalpel if interfering with proper index placement)
  • dry prep site with 3in1
  • fill prepared tooth in putty matrix with temp crown/onlay material & place over prep
  • bisacryl composite / poly n butyl methacrylate
  • after initial set remove imp and allow it to cure fully out of the mouth
  • use thickness of temp crown/onlay as an indicator of adequate tooth reduction; if temp has voids / too thin / slightly translucent assess cause
  • use burs & discs to remove excess temp material, smooth & polish with soflex
  • bis acryl comp affects setting of silicone so make sure prep has been cleaned with alcohol prior to taking imps
  • temp crown is cemented after final imp of prep is taken
  • continue to imp taking stage
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12
Q

impression stage

A
  • assess gingival condition (if inflamed / oedematous / traumatised consider deferring)
  • tray selection (rigid tray preferred)
  • apply appropriate adhesive material (for 10mins) based in imp material
  • place gingival retraction cord; use angulated cord packer to ‘walk’ cord into crevice & leave for minimum of 2mins
  • gently remove retraction cord in accordance with technique used ( double cord preferred for thick gingival biotypes and single cord preferred for thin gingival biotype due to high recession risk)
  • assess gingivae to ensure adequate retraction achieved
  • wash and dry prep
  • use 1or 2 stage imp technique
  • remove impression & check for bubbles, air blows, defects. ensure occlusal surface & margins or prep are captured adequately (if not repeat)
  • take opposing arch alginate / silicone / polyether imp
  • take bite reg. use silicone bite paste & ensure pt is occluding in ICP
  • cement temp crown / onlay with temp cement
  • remove excess cement with probe & floss. check occlusion, guidances & excursions adjusting as necessary
  • fill lab card & send disinfected samples
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13
Q

1 stage impression technique

A
  • for upper preps the hard palate does not need to be captured
  • syringe light body silicone or medium body polyether around the prep into gingival crevice & across all occlusal surfaces on same arch
  • take imp with medium / heavy body silicone or medium body polyether & await final set
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14
Q

2 stage imp technique

A
  • prior to starting prep use heavy body silicone with plastic separator to take an imp of the arch ( this will act as special tray)
  • proceed with the prep & gingival retraction
  • syringe light body silicone around the prep & into the gingival crevice & into heavy body silicone imp taken earlier
  • seat tray & await final set
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15
Q

information to include on lab card

A
  1. shade; for LiDiSi inc core shade & photos
  2. for LiDiSi request HF acid tx on fit surfaces
  3. for zirconia & metal request sandblasting of fit surfaces
  4. request for casts to be articulated according to jaw reg +/- facebow for multiple crowns
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16
Q

crown cementation

A
  • check fit of crown on working model
  • remove temp crown/onlay
  • after try in use cleaning agent e.g. ivoclean or silane to remove any contaminants
  • recheck reference contact points on L & R using 8 micron shimstock foil (it should just pull through)
  • try in crown / onlay with or without try in paste, check occlusion, lateral excursive movements & aesthetics
  • for ceramic crowns sandblast crown & use all in 1 etch & primer e.g. monobond etch and prime or 5% HF etch (if not done in lab) followed by conventional etch & primer
  • prepare crown / onlay for bonding
  • prep tooth for bonding isolating using rubber dam (split dam technique preferred) PTFE tape placement will protect adjacent teeth
  • sandblast or pumice +/- etching & bonding depending on cement choice; this activates the dentine & composite core for bonding
  • load crown / onlay with cement filling it 1/2 way then seat fully to prep margins
  • floss & remove excess cement
  • add glycerine & cure fully
  • check occlusion, adjust & polish
17
Q

immediate dentine sealing

A
  • if not already placed then place rubber dam
  • reconfirm tooth is caries free & that there are no remnants of any previous restoration
  • using 37% phosphoric acid etch exposed dentine and 1-2mm enamel for 5-15secs
  • thoroughly rinse & dry but not over dry
  • bond; primer & adhesive apply using ball end probe & light cure for 20 secs
  • if there are deep dentine areas or undercuts apply heated composite or flowable to keep even bonding surface keeping prep conservative
  • cure through glycerine to remove oxygen inhibition layer
  • reprepare enamel margins to remove excess resin
  • continue with imp taking & temporisation
18
Q

adv of dentine sealing

A
  1. less bacterial leakage / contamination of dentine during temporisation
  2. reduced post op sensitivity due to less polymerisation shrinkage
  3. increased bond strengths as bonding to fresh cut dentine
  4. better fitting restorations as uniform bonding surface
19
Q

alginate imp material +/-

A

irreversible hydrocolloid that is mucodisplasive
+ easy to use, low cost, comfortable for pt, hydrophilic so less sensitive to moisture, powder : water can be adjusted to whatever viscosity
- poor dimensional stability due to syneresis & imbibition of water, low tear resistance

20
Q

polyvinyl siloxane +/-

A

addition reaction silicone polyether with mucodisplasive & mucostatic imps possible
+ range of viscosities available, long shelf life, good surface detail reproduction, good tear strength, low setting shrinkage, good dimensional stability, good elasticity (minimal permanent deformation upon removal from undercut regions), automated mixing machines available to minimise air bubbles
- hydrophobic so poor moisture control will reduce accuracy of the imp, may cause breakage of cast when pouring up, costly

21
Q

polyether +/-

A

non aqueous elastomer for mucostatic imps
+ hydrophilic (less sensitive to moisture), 5min setting time, long shelf life, accurate, low setting shrinkage, good surface detail reproduction, good dimensional stability, good elasticity (minimal permanent deformation upon removal from undercut regions), automated mixing machines available (avoids air bubbles)
- single viscosity available, may cause breakage of cast when pouring up, occasional allergies, difficult to remove from facial hair & adheres to clothing, bad taste, costly

22
Q

impression compound +/-

A

non elastic low viscosity so only mucodisplasive imps taken
+ easy to use, same material can be reused & manipulated
- poor surface detail, poor dimensional stability, may distort upon removal

23
Q

zinc oxide eugenol +/-

A

non elastic for mucostatic imps
+ additions can be made, good dimensional stability
- cannot be used in deep undercuts, may distort upon removal, long setting time in thick sections, possible eugenol allergies

24
Q

consequences of poor marginal fit of crown / fixed bridge retainer

A
  1. plaque retention
  2. 2ndary caries
  3. localised periodontitis
  4. cement dissolution
  5. poor aesthetics
25
Q

causes of poor marginal fit of crown / fixed bridge retainer

A
  1. inaccurate imp
  2. poor gingival retraction
  3. inadequate marginal prep
  4. lab related
26
Q

management of poor marginal fit of crown / fixed bridge retainer

A
  1. retake imp
  2. redefine margins ensuring sufficient proximal / axial reduction
27
Q

consequences of crown / fixed bridge retainer not seating

A
  1. pt discomfort
  2. plaque retention
  3. 2ndary caries
  4. localised periodontitis
  5. if not identified can lead to unnecessary occlusal adjustments
28
Q

causes of crown / fixed bridge retainer not seating

A
  • inaccurate imp
  • undercuts in final prep
  • insufficient taper of axial walls
  • drifting / tilting of adjacent teeth due to loss of temp crown & pt not seeking retemporisation
  • poor/open contact point on long term temp crown can result in minimal drifting of adjacent teeth reducing the interproximal space available
  • lab causes
29
Q

management of crown / fixed bridge retainer not seating

A
  • retake imp
  • check for undercuts in final prep
  • ensure 4-6 degree tapered axial walls
  • ensure good contact points on temp crown
  • minimal IP reduction with high speed handpiece
  • if dye is worn consider using occlude spray to identify undercut area on prep
30
Q

consequences of occlusal interferences of the crown onlay / bridge retainer / bridge pontic

A
  1. post op pain on biting
  2. occlusal trauma
  3. crown / onlay / bridge retainer / bridge pontic #
  4. opposing tooth cuspal #
  5. decementation
  6. bruxism
31
Q

causes of occlusal interferences of crown onlay / bridge retainer / bridge pontic

A
  • inaccurate imp
  • insufficient occlusal reduction
  • inaccurate bite reg
  • poor planning & clinical assessment
  • lab causes
32
Q

management of occlusal interferences of crown onlay / bridge retainer / bridge pontic

A
  • retake imp
  • ensure appropriate occlusal reduction has been carried out
  • if casts cannot be articulated take a facebow (ensure translucency of cusp tip areas in the set bite reg paste)
  • take a comprehensive occlusal assessment
  • minor interferences can be adjusted chairside to prior to cementation
33
Q

when to use GI cement e.g. Ketac-Cem / Fuji-ionomer type 1

A

porcelain fused to metal
metal crown
fixed pros

34
Q

when to use RMGI e.g. FujiCEM, riva luting plus or relyX plus luting cement

A

PFM
metal crown
fixed pros

35
Q

when to use light cure resin e.g. relyX veneer cement, variolink veneer

A

porcelain veneer
porcelain inlay / onlay

36
Q

when to use dual cure resin e.g. NX3 nexus 3rd gen, relyX UNICEM, panavia V5

A

PFM
metal crown
fixed pros
porcelain inlay / onlay
all ceramic crown

37
Q

when to use auto cure resin e.g. nobleprocera alumina, VITA in ceram alumina

A

PFM
metal crown
fixed pros
porcelain inlay / onlay
all ceramic crown

38
Q

when to use zinc phosphate cement e.g. detrey zinc improved, hy-bond

A

PFM
metal crown
fixed pros

39
Q

when to use zinc polycarboxylate cement e.g. durelon, tylok plus

A

PFM
metal crown
fixed pros

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