Lesson 12 Flashcards
strong, esthetic post and core restoration can be fabricated from strong zirconia with CAD/CAM technology
CAD/CAM ZIRCONIA POST AND CORE RESTORATION
replaces the missing coronal tooth structure, in combination with the remaining coronal tissue
CORE FABRICATION
→ shaped in resin or wax
→ cast directly onto prefabricated post
CORE FABRICATION
make a core from plastic restorative material (amalgam,
composite resin, or glass ionomer)
CORE FABRICATION
→ maximum tooth structure can be conserved because undercuts do not need to be removed
→ treatment requires one fewer patient visit
ADVANTAGES of PLASTIC FILLING MATERIALS
→ there are fewer laboratory procedures
→ testing has generally revealed good resistance to fatigue
testing and good strength characteristics, possibly because of the good adaptation to tooth structure
ADVANTAGES of PLASTIC FILLING MATERIALS
long-term success may be affected by corrosion of amalgam cores, the low strength of glass ionomer or the continued polymerization and high thermal expansion coefficients of composite resin cores
DISADVANTAGES of PLASTIC FILLING MATERIALS
microleakage with temperature fluctuations (thermocycling) is greater under composite resin and amalgam cores than under conventional crown preparations (however, the extent of leakage under cast cores has yet to be determined)
DISADVANTAGES of PLASTIC FILLING MATERIALS
difficulty may be encountered with certain operative procedures such as rubber dam or matrix application particularly on badly damaged teeth
DISADVANTAGES of PLASTIC FILLING MATERIALS
can be performed by combining a prefabricated post with auto polymerizing resin
DIRECT PROCEDURE FOR SINGLE-ROOT TEETH for CAST METAL
cast post and core restoration should be slightly undersized in relation to the prepared post space in order to ensure full seating
INVESTING AND CASTING
post fit should not be loose that light finger pressure causes rocking, rotation, or wobbling
INVESTING AND CASTING
→ tight fit can cause root fracture
→ casting alloy should have suitable physical properties
→ Ni-Cr alloys have high moduli of elasticity and are
recommended for cast posts
INVESTING AND CASTING
→ casting defects (small nodules)
→ post insertion resistance
→ the shape of the foundation is evaluated and adjusted as
necessary until tooth preparation geometry is optimal
EVALUATION
→ the luting agent must fill all space within the root canal system → voids may be a cause of periodontal inflammation via lateral
canals
CEMENTATION
→ a rotary (Lentulo) spiral filler or cement tube is used to fill the
canal with cement
CEMENTATION
→ the post and core restoration is inserted gently to reduce
hydrostatic pressure, which could cause root fracture
CEMENTATION
use of such venting procedures has also been shown to reduce the necessary seating force, although the latter is probably
cement specific
CEMENTATION
- an existing post and core restoration must be removed (ex.: for re-treatment of a failed root canal filling)
- patients must understand in advance that post removal is a risky process and occasionally results in radicular fracture and tooth loss
REMOVAL OF EXISTING POSTS
→ thin-beaked forceps will be used if post exposed coronally
→ ultrasonic scaler weakens water-based cement
→ a thin scaler tip or special post removal tip is recommended
REMOVAL OF EXISTING POSTS
a post that has fractured within the root canal cannot be removed with a post puller or forceps
REMOVAL OF EXISTING POSTS
→ the post may be possible drilled out, but great care is needed to avoid perforation
→ drill out if post has been fractured within the root canal
REMOVAL OF EXISTING POSTS
another means of handling an embedded fractured post (described by Masserann in 1966) is to use a special hollow end-cutting tube (or tephrines) to prepare a thin trench around the post
MASSERANN TECHNIQUE
retrieval can be facilitated by using an adhesive to attach a hollow tube extractor or by using a threaded extractor
MASSERANN TECHNIQUE
