1 - Treatment planning for fixed prosthodontics Flashcards
Define fixed prosthodontics.
- attached or fixed dental prostheses
- also known as indirect restorations
List types of indirect restoration.
- veneers
- inlays and onlays
- crowns
- post and cores
- bridgework
What should be examined in the lips for an E/O exam?
- vermillion borders
- commissures
- smile line
When is a face bow required in fixed prosthodontics?
- when changing occlusion or restoring key teeth in guidance
- used to mount cast in correct maxillary relationship to TMJ
What is a diagnostic wax up?
- provisional wax up of restoration
- check aesthetics and occlusion
- allows patient to see provisional result
What stage of treatment planning does fixed prosthodontics fall under?
Reconstructive
When are veneers indicated?
- improve aesthetics
- change teeth shape/contour
- correct peg laterals
- reduce or close proximal spaces or diastemas
- align labial surfaces of instanding teeth
- enamel defects
What is the Gurel minimal preparation technique for veneers?
- wax up
- stent
- intra-oral mock up
- preparation into mock up
When are veneers contraindicated? (10)
- poor OH
- high caries rate
- interproximal caries or unsound restorations
- gingival recession or root exposure
- high smile line
- if extensive prep is required (>50% no loner enamel)
- labial positioned, severely rotated or overlapping teeth
- extensive TSL
- heavy occlusal contacts
- severe discolouration
When are inlays/onlays indicated?
- TSL to increase OVD
- fractured cusps
- restoration of root treated teeth
- replace failed direct restorations
When are inlays/onlays contraindicated?
- active caries
- periodontal disease
- time
- cost
When are crowns indicated?
- protect weakened tooth structure
- improve or restore aesthetics
- retainer for bridgework
- when RPD design indicates
- restore tooth function
When are crowns contraindicated?
- active caries
- periodontal disease
- more conservative options available
- lack of tooth tissue for prep
- unable to provide post and core
- unfavourable occlusion
What are the principles of crown preparation?
- preservation of tooth structure
- retention and resistance
- structural durability
- marginal integrity
- preservation of periodontium
- aesthetic considerations
Describe preservation of tooth structure.
- avoid weakening tooth structure and damage to the pulp
- balance criteria for retention and resistance with structural durability
What does under preparation of crowns result in?
- poor aesthetics
- periodontal and occlusal interference
- insufficient thickness of restoration
What does over preparation of crowns result in?
- damage to pulp
- tooth strength being compromised
Define retention in crown preparation.
Prevents removal of restoration along the path of insertion or long axis of tooth preparation
Define resistance in crown preparation.
Prevents dislodging of restoration by forces in apical or oblique direction, and movement of the restoration by occlusal forces
How do you achieve retention and resistance in crown preparation?
- taper of opposing walls (6-10 degrees)
- length of walls
- path of insertion
- grooves or slots (rarer)
How does the wall length hinder displacement of crowns?
Longer walls interfere with tipping forces, has to slide more before it dislodges
How does the path of insertion hinder displacement of crowns?
Having fewer/only one path of insertion improves retention, as there is less directions the restoration can become dislodged
How do you achieve structural stability in crown preparation?
- bulk of material must be adequate to withstand occlusal forces
- achieved by occlusal reduction, functional cusp bevel and axial reduction
What should the occlusal reduction be on posterior crown preparations?
At least 2mm
How do you achieve marginal integrity in crown preparation?
Achieved using different types of burs
What are the different marginal finish configurations in crown preparation?
- knife edge
- bevel
- chamfer *
- shoulder *
- bevelled shoulder
How do you achieve a chamfer finish line?
Rounded tapered bur
How do you achieve a shoulder finish line?
Fissure bur
What type of crown requires a chamfer finish line?
Metal based
What types of crown require a shoulder finish line?
Ceramic
How do you achieve preservation of the periodontium in crown preparation?
- margins are smooth and fully exposed to cleaning
- margin is supra gingival or at the gingval margin
How do you achieve aesthetics in crown preparation?
- be aware of high smile lines
- material choice
- aesthetic v function (ie bruxists)
When is bridgework indicated?
- missing teeth
- aesthetics
- improve occlusal stability
- improve function
- periodontal splinting
- restoring OVD
- patient preference
When is bridgework contraindicated?
- damage to tooth and pulp
- secondary caries
- effect on periodontium
- cost
- failures
