Crown And Bridge 2 Flashcards
What are the advantages of a fixed fixed bridge?
Robust design for maximum strength
Splinting of abutment teeth
More practical for large spans
Lab construction easier than othe designs
What is the issue with having a narrow occlusal table on a posterior bridge?
It may help with cleaning but may not help stabilise occlusion
WHat are the diasadvantes of a fixed fixed deisign?
Paralleling of teeth can be diffucult
Both preps need to be major retainers
Cementation proem may arise since needs to be cemented on one go
Design not suitable for very tilted teeth
What happens to the surrounding teeth when the lower first molar is lost?
Lower second molar tilts mesial rotates and tilt lingual
Over eruption of oppsing tooth
Opening of the contact on upper arch acting as food trap
Increased susceptibility to caries and perio
What effect does losing the lower first molar have on prep?
Danger of exposing pulp on mesial of 7 when parallel with premolar
Creation of undercut on lingual or molar and buccal of premolar
No need to reduce the mesial occlusal of 7 since has tilted
What are the stages of full gold crown prep?
- Occlusal reduction functional 1.5mm, non functional 1.00mm
- Bevel: largely functional cusp and smaller non functional
- Axial: buccal and Palatal/lingual
- Interproximal
- Consider retention grove: more for preps with low height
- Assess retention: clinical height and parallelism need 3-5 degree taper
- Finnish the prep
When prepping for a bridge what do you need to consider?
Parpired prep of axial walls
Distal of 5 with mesial of 7 etc
Buccal of 5 with lingual of 7
What should the functional cusp bevel be parallel with?
Palatal surface of the maxillary buccal cusps of opposing tooth
How thick is the red coping used for the wax up?
0.1mm
How thick is the clear coping used in the wax up?
0.6mm
What colours waxes and instruments are used for waxing up a crown?
Yellow cusp cone Blue marginal ridge Red axial rides Green axial contout PKT4 Red triangular ridge
Grooves and fossa with PKT5
All others are PKT1/2
Finish with a smooth cloth
What is an inlay?
Intra coronal restoration which are constructed completely or partial out of the mouth
What is an onlay?
Inlays with cuspal coverage
What material can inlayes and onlays be made from?
Metal: gold alloys
Tooth coloured eg composite, ceramic zirconia
What is the minimum percentage of gold needed by law to be gold onlay?
60%
What are the advantage of using gold for inlay or onlay?
High compressive , tensile stengh
Allows thin bevels of metal to be placed over margin
They do not discolour a tooth or tarnish
Wear resistant
Malleable material
What are the indications for an inlay/onlay?
Good OHI
Regular attendee
Good compliance
Suffedient enamel to bond
Strengthen of tooth following RCT needed
Where the height of the cusp from the pulpal floor is greater than its bucco Palatal dimensions
When the width of the MOD cavity exceeds half the width of the occlusal surface
Maintain or restore vertical dimensions
Horizontal crack in tooth
Lack of dentine under cusp
Heavy occlusion
Heavily discoloured cusp (composte)
What taper is needed for a gold onlay?
3-5 degrees ideal
What are the stages of onlay prep?
- Prepare MOD
- Reduce non functional cusp and reverse bevel
- Reduce functional cusp and half enamel prep which is 0.5mm deep to increase support for the cusp
- Bevel all margins
- Proximal flare
What are the options for tooth coloured inlays?
Resin bases composition
Ceramics
Zirconia oxide
What are the advantages of tooth coloured inlays and onlays?
Aesthetics More wear resistant that tooth coloured plastic restorations Strengthen the tooth by 75% Less susceptible to decay Elimate concersn re mercury
What are the contra indications for tooth coloured onlays/inlays?
Evidence of excessive tooth wear
Bruxism
Insufficient tooth substance for adequate bondig
How can composite inlays and onlays be made?
Indirect and smi- direct
What is the indirect composite onlay inlay techqnie?
Two visits needed with temporisation
Completly made outside the mouth
What is the semi direct composite onlay inlay techqnie?
Performed chair side with intrs and extra oral steps in one visit
How can composte resin inlays be classified?
Type of composte: microfilmed or hybrid
Method of construction: semi direct or indirect
Method of curing: light cured, light and heat cured, light heat and pressure cured
What are the advantages of indirect composites over direct composites?
Polymerisation of fit surface possible More effect overall polymerisation Polymerisation occurs outside mouth Reduced clinical time shaping the filling Better contours and contacts
What are the diasadvantes to indirect composites?
Wear
Economic
Needs good bond
How does the semi direct composte inlay onlay work?
Pace composite in cavity and initial cure
Remove the inlays and then place in a heat and light oven for 110 degrees for post curing polymerisation
How can ceramic inlays and onlays be classified?
Method of processing: firing pressing, casting maching
Method of construction: semi direct or indirect
What is the main difference between composite and ceramic inlays onlays ?
Ceramics wear oppsing teeth
And they are no reparable
Other than that ceramic generally better than composites
What are the features of a composite inlay compared to porcelain inlay?
Occlusal key 2mm wide
10-20 degree flare
2mm depth minimum rounded box and deoth OD box more than 1mm
But joint margins
What are the features if a porcelain inlay?
Occlusal key 3mm wide 10-20 degree flare 1.5mm depth U shaped box Box depth 1mm Butt joint cabo surface angle
What is the aim of temporisation ?
Protect the pulp from mechanical thermal and bacterial irrigation
Maintenon of proximal and occlusal contacts
Maintainence of function
What should you apply to the fit surface of the composte and ceramic inlays before cementing?
Composite: sandblast and then silane
Ceramic: HF acid and then silane
What are the advantages of CAD/CAM?
Eliminates traditional impression technique Incresed profits for dentist Improves restoration fit Standardises the construson No lab needed
How much composite must cover the cusp in an overlays?
Min 2mm
