Which teeth need post crown and what does it depend an?
Usually a considerable amount of tooth structure has been lost because of caries, the placement of previous restorations, and the endodontic treatment.
- extent of coronal destruction and by the type of tooth.
How do you manage crown for anterir teeth?
- Endodontically treated anterior teeth do not automatically require crowns.
• If a moderate-sized anterior tooth is intact except for the endodontic access and one or two small proximal lesions, composite resin restorations will suffice. Hi
Managment of discolored devitalized tooth?
For a tooth that has become discolored following devitalization, bleaching is preferable to crown placement if the tooth is relatively intact.
When do we use vaneers?
A laminate veneer offers a less destructive alternative if the facial surface of a reasonably intact tooth must be masked by a restoration.
Managment of endodontically treated molar?
When is post not necessory and when is it necessory?
- The minimum treatment indicated for an endodontically treated molar or premolar is the placement of a cast restoration with occlusal coverage, such as an MOD onlay.
- So endodontically treated posterior teeth with sufficient sound tooth structure are restored with an MOD onlay,
• A pulpless molar with a moderately damaged clinical crown can be built up with an amalgam or composite resin core prior to placement of an artificial crown.
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When more than 3 to 4 mm of coronal tooth structure with reasonable wall thickness remains, use of a post in the root canals for retention is not necessary, and not having to prepare post space reduces the risk of perforation.
When a post is not used, the chamber must provide adequate retention for the core material. While those with limited coronal tooth structure remains to be used for retaining the definitive restoration are restored with post crown
Enumerate components of post crown.
Post (Dowel): is the part which extend into the root canal and connect with a core coronally and is used to provide the necessary retention for the core.
Core replaces any lost coronal tooth structure, allowing optimal tooth preparation geometry
Artificial crown
What are Function of a dowel?
- A dowel is placed to provide the crown retention that ordinarily would have been gained from coronal tooth structure.
- A dowel increases resistance to lateral forces applied to the crown
- Cementing the dowel with bonded resin cement strengthens the weakened dentin around the dowel.
What are the systems of post crown?
What type of post was used in the past and present and why?
Whats the difference bewteen glass ionomer and metal post?
- one-piece post crown system (post+core+crown) custom cast
- two-unit system:- (post+core) + (crown) —– custom cast or Prefabricated systems
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Typically, dentists use the two unit system with two-step technique which consist of initial placement of a post and core foundation restoration, followed by placement of a separately fabricated crown.
In the past, a metal post was used most often, although esthetic concerns have increased the use of tooth-colored glass fiber and zirconia ceramic posts, which provide the necessary retention for the core.
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The choice of post material will influence the clinical failure rates: Glass fiber posts have somewhat higher failure rates than do metal posts.
two-unit system offers several advantages over a one-piece postcrown? 4 points
- The marginal adaptation and fit of the restoration are independent of any dowel that must be used.
- The restoration can be replaced at some future time, if necessary,
- the choice is not limited to a custom cast device. Prefabricated systems can be used
- If the endodontically treated tooth must serve as a fixed partial denture abutment, it is not necessary to make the root canal preparation parallel with the path of insertion of other preparations.
What are Specific consideration for post crown preparation?
Minimum sound tooth structure coronally 2.0 mm this creates a ferrule effect around the tooth to protect it from fracture
What are general consideration?
Apical seal
- The use of a dowel requires that the canal be obturated with gutta-percha .
- Most endodontic texts advocate maintaining a 5-mm apical seal , a shortened apical seal of a minimum of 3 mm is considered acceptable, this is to prevent dislodgment and subsequent leakage
Minimal enlargement
- Enlarge the canal one size larger than last largest file was used.
- The post diameter should be no more than one third the root diameter at CEJ, with the root and walls at least 1 mm thick circumferentially.
Length
Dowel extension into the root must at least equal the length of the crown for optimum stress distribution and maximum retention, or the dowel should be two-thirds the length of the root
Optimum length =2/3 of root length
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Stop - Antirotation -Margjnal Extention
Extending a preparation apically creates a ferrule and helps prevents fracture of an endodontically treated tooth during function.
Types of Dowel core:-
1- Prefabricated systems
2- Custom cast dowel cores
Explain both
Prefabricated systems Typically, prefabricated posts are used in a two-step procedure in conjunction with a plastic material such as composite resin, glass ionomer, or amalgam:
First the post is cemented; then the selected core material is applied.
After shaping of the core and remaining tooth structure to optimal crown preparation form, an impression is made and a crown fabricated.
- Prefabricated dowels with amalgam or composite resin cores are the most commonly used dowel cores today
- Kits for prefabricated dowels use special reamers or drills for canal preparations that are the same size and configuration as the dowels.
- it is possible to complete the entire procedure in a single appointment.
- Threaded posts can heighten stress concentrations during insertion and loading, but they have been shown to distribute stress evenly if the posts are backed off a half-turn
Which root or canal is more preferable to prepare it?
Palatal for upper
Distal for lower
