Tooth wear and indirect restorations - Mods to standard preps Flashcards
What percentage of tooth structure remaining above the gingival margin does there need to be for a fixed restoration to be completed?
- 50 %
Why is tooth preparation in tooth wear cases really difficult?
- Lack of occluso-gingival height
- Lack of occlusal space
- Severely compromised tooth
What is meant by occluso-gingival height?
What techniques can you do to create retention and resistance in small tooth wear teeth?
- Diff materials diff prop
- Grooves
- Inlays
- Ferrule
- Parallel preps
- Margins and occluding surfaces
- Cores
- Electrosurgery
- Surgical crown lengthening
Compare metal and porcelain as an indirect restoration
- Metal is more ductile than porcelain which is brittle
- Metal not as aesthetic
- Metal higher flexural strength so good for biting surfaces (less likely to fracture)
How can grooves help with small teeth tooth wear retention?
- Helps Maximise retention and resistance
- Need to parallel them with POI and removal
- Tell technician want metal and fitting surface of crown to fit into the grooves
- Can also create grooves into inlay prep
Logically how do grooves create retention and resistance? Where should they placed
- Enhance resistance form by reduction in radius of rotation
- Place inlays and grooves in the long axis of tooth
What is a ferrule?
- A circular band of tooth structures, left after crown preparation, in order to support and stabilize the overlying dental crown
How is this tooth 33 a ferrule? What else does it have placed? What does this help with?
- Metal post placed
- Allows coronal ferule of dentine at gingival margin
- Enhances resistance form of prep
What does the dental practicality index do?
- Assesses the restorability of teeth
- Useful when deciding on restoration or XLA
What is meant by parallel prep?
Give and advantage and disadvantage
- Prep the tooth for a crown more parallel to original prep
- Gives less coronal dentine for lab technician to work
- May give more opaque crowns
- But may give better retention of the crown in tooth wear cases
Compromise of aesthetic v function
This 12 has been root treated and requires a crown. The pt has severe tooth wear. What 3 things has been done to this teeth that improves the chances of this tooth maintain the crown.
- Minimally destructive post core placed ontop of a ferulle
- Coronal dentine has been kept and a parallel prep taken
- Retention grooves have been added to the post core
This is an already restored canine in a tooth wear case. Describe the things that have been done to help with retention of the tooth
- Placed a core in a deep subgingival cavity
- Used Electrosurgery to remove gingiva to ensure accuracy of impression
- This creates a ferrule
- Placed a palatal groove instead of buccal (specific to this circumstance so it wouldn’t compromise pulp)
In tooth wear cases we are dealing with high loads. You decide to use a Metal ceramic crown for the maxillary anterior teeth.
How should you prep the metal margin and where should it be? How should you prep the porcelain margin and where should it be?
Metal margin prepped as a chamfer and is on the palatal aspect so that when the pt bites together the load is on the metal not the porcelain
Porcelain margin prepped as as shoulder and on the buccal aspect for aesthetic .
The porcelain buccal prep should also be curved to reduce the chance of crack propagation resulting from the high loads of tooth wear cases
You have a pt with heavily restored posterior teeth that require crowns. What can you use a core material and what can be used a crown material?
- Reinforced composite
- If tooth has been root treated then can use amalgam posts or Nayyar core
- Can use Metal ceramic crown - gives metal margin but not concerned with this as posterior teeth
