Crown And Bridge Flashcards
What are the advantages of a 3/4?
More conservative than full gold crown or PFM
Assess the accuracy of marginal fit easily
Allows pulp testing from buccal cusp
Allows natural Appearnce of tooth to she
When is a 3/4 gold crown indicated?
On a tooth where the lingual cusp has been lost and would compromised the remaining core if thr buccal cusp has to be prepared for a PFM
What are the disadvantages of 3/4?
Sides of crown can splay if heavy loads applied and stengh thing features not incorporated
Greater marginal area can lead to Increaed microleakage
What are the uses of 3/4 gold crown?
Heavily restored tooth with intact buccal cusp
Conventional bridge retainer
Tooth wear
Part of treatment plan for denture
What assessment would you do on the tooth before placing 3/4?
PROVE
How can the resistance and retention form of the 3/4 crown be improved?
Incorporate slots and grooves
What is the disadvantage of the slots and grooves?
Increase the complexity of cavity since must all be parallel
What is the stage of 3/4 gold crown prep?
- Occlusal reduction and Bevel
- Axial reduction
- Proximal surface groove and slot
- Occlusal grove
5 finish
How do you do the occlusal reduction 3/4?
Functional cusp: 1.5mm
Non : 1mm
What is the purpose of the reverse bevel 3/4?
Aka Functional cusp bevel
Brings cusp back in line, offers resistance to oblique forces
Which two bevels are placed on the 3/4 crown?
Functional and no function
What type of finish is at the gingival margin of a 3/4?
Chamfer
How much is the axial reduction ?
0.7-1.0mm
What taper should the 3/4 hVe?
3-4 degrees
Where do you place the slot on the 3/4 prep?
In the filling
Where do you place the groove in the 3/4 ?
Not commonly
Placed in teeth that are heavily restored and subjected to tooth wear and placed into natures tooth
What does the occlusal grove help with in 3/4?
Resistance and strengthened the casting to cannot splay
Aids retention and resist crown dislodgement
Should be placed as far buccal as possible in Area of fissure
When would you do the contemporary design for 3/4?
When cementing with super bond and panavia bit need to sand blast or oxidised fit surface of gold
What does super bond have?
4 META
What are the indication for veneers?
Alter the shaoe and size of tooth Close diastema Align mal aligned teeth Mask areas of Hypoplasia and hypo calcification Mask dis coloured teeth
What are the advantages of veneer over crown?
Less destruction
No LA
Easier to record impressions
No need to provisional restoration
What are the disadvantages if a veneer over a crown!
More challenging to place a veneer on only one tooth and get good shade match
Try in is difficult
Luting is multistage and takes time to finish well
Poor prep can lead to porcelain fracture
How much should you reduce the labial surface by on a veneer?
0.5mm
What is the purpose of labial reduction on a veneer?
To avoid over contoured prep
How many planes should you prepare the labial surface for a veneer in?
3
Gingival plane
Mid labial plane
Incisal plane
Where can you place the gingival margin of the veneer?
Subginginval
Equigingival
Supra
Where should the proximal margins be placed for a veneer?
Just Labial to contact point but can consider extending round the contact when veneer is used to close a diastema
When would you bring the promxila preparation of a veneer interpromximal?
When recession present
Closing a diastema
What are the options for the incisal edge of a veneer?
Over lapped
Overlap
But joint
What are the advantages of restoring an edentulous ridge?
Appearnce Occlusal stability Masticatory effeciency Speech Psychological
What are the disadvantages of restoring an edentulous ridge?
Damage to toot and pulp Risk of Sedondary caries Failures Cost Periodontal effect
What general factors about the patent do you need to consider before placing a bridge?
Attitude:
Age: young teeth have large pulps
Confidence: some patient lack confidence with dentre
Occupation: contact sport players do not give bridge, public speakers and singers give bridge and wind instruments too
Medical: epilipetics: consider fixed
appearance: high lip line, loss of tooth and bone an denture maybe better
OH: perio must be stabilised, bridge maybe better for perio
Disturbuton of missing teeth: multiple missing teeth consider denture
Occlusion: diffucult for denture in class 2/1
What local factors do you need to consider before placing a bridge?
Adjacent teeth: sound or heavily restored, vital, tilted or rotated, bone support and perio
Oppsing dentitions: presence of over eruption,mapping of tooth wear, occlusal stops and crowding
Edentate ridge: degrees of resorption, condition of ridge, correct space for lost teeth
What do you need for treatment planning?
History Mounted study models Periaplcals Bite wings Pocket depth Vitality Crown and root ratio
What are the options for provisional restorations?
Lab made
Chair side
How are the chair side provisional restorations made?
Using higher acrylic (trim)
Mould of mouth or from study models and then make vacum formed PVC stent
What are the three requirements for provisional restorations?
BAM
Biological
Aesthetic
Mechanical
What should you use to cement the provisional?
ZnO eugenol
What can you consider getting made before the final bridge?
Metal try in
Can try this and assess
- seating
- margin quality
- occlusal stop
- interference in occlusion
What are the clinical problems if the bridge fails to seat?
Preparation errors: undercuts on teeth or not paralle
Impression error: incorrect tray
Temp errors: allowed over eruption, some Luting cement stillln prep
What are the lab errors related to filling to seat?
Cast and die: porous or damage
Wax pattern : distorted, no separator, no reservoir
Investment: needs to compensate for setting expansion, hygroscopic expansion and thermal expansion
Casting: insufficient temp of investment and porosity of sprue, alloy too high temp
Finishing and polishing: trim margins, distorted since thing nodules on fit surface
What can cause a rough fit surface of a lab made commonest?
Breakdown of investment or weak
Cracking of investment
What do you do if bridge fails to seat?
Check fit surface for imperfections
Check contacts for over contoured
Section metal frames work through Pontic
Re unite with duraly and recheck in mouth
What can you consider doing once you happy with with final bridge and before cementation?
Can consider temp cementing it using ZOE with 50% modifier paste
This enables minor tooth movements
Patient can inspect the crown
Adjust any occlusal interferences
Why are bridges sometimes difficult to seat?
Hinge hydrostatic pressure due to large surface area and paralle
What should you check on the bridge?
Margins
Occlusion
Gingival health
Mechanical integrity
How many bridges failed after 15 years?
33%
How many bridges failed after 10 years?
<5% abutment extracted
Wheh should a provisional bridge be made?
Before the impression of the bridge prep to enable checking that you have reduced the teeth enough
Why may provisional bridges be placed long term?
Ppfollwing pre prosthetic surgery
Assess healing of endo or perio
What are the biological requirements of a provisional restorations?
Biocompatible
Non exothermic
Stabilise tooth position eg prevention of over eruption or tilting
What are the mechanical requirement of a provisional restoration?
Attain rubbery stage quick
Rapid hardening
Suffering strength to resist wear and fracture
Strong in thin sections
What are the aesthetic requirements of a provisional restoration?
Tooth coured
Range of shades
Surface texture and staining possible.
What are the resins available for provisional restorations?
Acrylic: powder and liquid. Powder PMMA beads + peri oxide. Liquid is MM monomer +activator
Higher meathcrykate trim: powder and liqueurs. Powder: PMM beads + peri oxide, liquid: isobutylmethacrylate + activator
Epimine eg Scutan: paste and liquid p. Paste: imine pre polymer + poly amide filler and liquid : soul phonic acid ester
Composte eg protemp: 2 pastes methacrylic acid ester + filler
How does the lab made the provisional restoration ?
Minimal deoth th prep and the heat cured acrylic resin by lost wax technique an then relines at chair side using trim
Ad: custom shape of retainer and Pontic, good strength, can be used for long term
Dis: cost and must be made in advance if tooth prep
How can you make provisional restorations chair side?
Using Higher acrylic and take a mould from the mouth using ROD of waxed study model then fill PVC stent with matersl
Ad: cheaper, made on same day as abutment prep, strong enough to last until final bridge,clinician can check if sufficiently reduces the prep
Dis: limited customising of Pontic and retainer
