Lesson 11 Flashcards
True or false
Inadequate root fillings should be re-treated before fixed prosthodontic treatment is begun
True
True or false
Additional retention from posts is rarely need ed in molars
True
True or false
FDPs (the bridge) was significantly lower than that of restorations under single crown
True
True or false
four to five years after cementation, reported failure rates were significantly higher in male patients than in female patients and failure rates were three times higher in patients older than 60 than for younger patients
True
True or false
maxillary failure rates (15%) were three times as high as mandibular failure rates (55%) and more prevalent in lateral incisors, canines, and premolars than in central incisors and molars
True
True or false
custom cast post and core restorations exhibited slightly higher failure rates than did amalgam foundations
True
True or false
CONSIDERATIONS FOR ANTERIOR TEETH
→ do not always need a complete crown after endodontics except when the size of plastic restorative materials limit their prognosis
True
True or false
CONSIDERATIONS FOR ANTERIOR TEETH endodontically treated teeth are weaker or more brittle than
vital teeth
True
True or false
CONSIDERATIONS FOR ANTERIOR TEETH endodontically treated teeth may reduce moisture content
True
True or false
CONSIDERATIONS FOR ANTERIOR TEETH
cementing a post in an endodontically treated tooth enhances
prognosis but limits endodontic treatment
True
True or false
CONSIDERATIONS FOR POSTERIOR TEETH
complete coverage is recommended on teeth with high risk of fracture like maxillary premolar
True
True or false
CONSIDERATIONS FOR POSTERIOR TEETH
→ if significant coronal tooth loss has occurred, a cast post and core restoration or amalgam foundation restoration is needed
→ complete coverage gives the best protection against fracture because the tooth is completely encircled by the restoration
True
→ minimal tooth structure removal for post space
→ remaining dentin thickness gives fracture resistance of the root
→ thinner dentin walls with thicker post fractures more easily
→ root canal should be enlarged, enough for the post to fit with
strength and retention
PREPARATION OF THE CANAL
→ adequate apical seat
→ minimum canal enlargement (no undercuts remaining)
→ adequate post length
→ positive horizontal stop (to minimize wedging)
→ vertical wall to prevent rotation (like a box)
→ extension of the final restoration margin onto sound tooth
structure
FEATURES OF SUCCESSFUL DESIGN
→ save as much coronal tooth structure to reduce stress concentration at the gingival margin
→ if more than 2 mm of coronal tooth structure is remaining, the post design has limited role in the fracture resistance of the restored tooth
→ coronal reduction to the gingival level before fabrication of a post and core should be avoided
→ preserving as much coronal structure as possible enhances prognosis
PREPARATION OF CORONAL TISSUE
→ extension of the axial wall of the crown apical to the wing tooth structure
→ help bind the remaining tooth structure together, while simultaneously preventing root fracture during function
FERRULE
True or false
Anterior crown and the post and core restoration are frequently dislodged simultaneously.
True
canals with elliptical cross section must be prepared with usually
6-8 degrees
POST GEOMETRY
→ parallel-sides posts are more retentive than tapered posts
→ threaded posts are the most retentive but should ensure
passivity
POST GEOMETRY
→ retention increases as post length increases
→ short post will fail while long post will damage apical seal or
increase root perforation
POST LENGTH
→ maintain 5 mm apical seal; 1 mm is considered acceptable
→ post should be as long as possible without jeopardizing apical
seal of strength of remaining tooth structure
POST LENGTH
→ increasing post diameter to increase retention is not recommended because it weakened the remaining root structure
→ should not exceed one-third of the cross-sectional root diameter
POST DIAMETER
→ serrated or roughened post is more retentive than smooth one
→ controlled grooving of the post and root canal increases the
retention of the tapered post
POST SURFACE TEXTURE
True or false
adhesive resin luting agent have no potential to improve the performance of post and core restorations
False
adhesive resin luting agent have the potential to improve the performance of post and core restorations
→ resin cement is affected by eugenol containing root canal sealer
→ zinc phosphate and glass ionomer have comparable retentive
properties
LUTING AGENT
the choice of luting agent may become more important if the
post has poor fit within canal
LUTING AGENT
→ long post should be avoided
→ two or more relatively short post in divergent canals, for better retention
RETENTION FORM in POSTERIOR TEETH
→ when amalgam is used as the core material, it can be condensed around cemented post or directly into short prepared post space
→ single metal post will be used if there is reasonable amount of coronal tooth structure cemented into the largest canal
→ if there is remaining 3-4 mm thickness of coronal tooth structure, post is not necessary
RETENTION FORM in POSTERIOR TEETH
→ greatest stress concentrated at the shoulder margin
→ stresses are reduced as post length increases
→ parallel-sided posts may distribute stress more than tapered
post
In Vitro Studies Conclusions:
→ sharp angles should be avoided
→ high stress can be generated during insertion with smooth
parallel-sided post; threaded post shown to distribute stress
evenly if post are backed off a half turn
→ fracture may occur in glass fiber post rather than in the
remaining tooth structure
In Vitro Studies Conclusions
→ preparation geometry is important to prevent a post with circular cross section from rotating during function
→ sufficient vertical coronal walls prevent rotation
→ small groove placed in the canal wall if coronal dentin has been
completely lost
ROTATIONAL RESISTANCE
→ grooves should be placed where the root is bulkiest
→ auxiliary pin and threaded post can prevent rotation
ROTATIONAL RESISTANCE
TOOTH PREPARATION (3) stages:
Removal of the Root Canal
Filling Material Enlargement of the Canal
Preparation of the Coronal Tooth Structure
o using a warmed endodontic plugger
o using a rotary instrument with chemical agents (ex.:
eucalyptus oil)
REMOVAL OF THE ROOT CANAL FILLING MATERIAL
→ (2) methods commonly used to remove gutta-percha
range widely in shape and size with varying radiopacity
Prefabricated Posts
recommended for roots with circular cross section
Parallel-Sided Prefabricated Posts
used for excessively flared canals
Custom Posts
→ prepare post space
→ reduce coronal tooth structure for the extracoronal restoration
→ reduction depends on type of restoration
PREPARATION OF THE CORONAL TOOTH STRUCTURE
readily available
Prefabricated Post
wax or resin pattern
Custom Made Post
radiographs are not normally necessary to verify post space
PREFABRICATED POSTS
(1) Use in canals that have a non-circular cross section or extreme tapered canal
(2) Be extra careful on molars to avoid root perforations
CUSTOM MADE POST
post is selected to match the dimensions of the canal and only minimum adjustments needed to seat it to the full depth of the post space
PREFABRICATED POSTS
→ platinum-gold-palladium
→ cobalt-chromium
→ stainless steel
Parallel-Sided Posts
→ stainless steel
→ titanium
→ non-oxidizing noble alloys
Serrated Posts
→ platinum-gold-palladium
→ titanium alloys
Tapered Metal Posts
→ consists of glass or carbon fibers embedded in a resin matrix
→ less stiffness and strength than ceramic and metal post
→ improve esthetics but shorter longevity than metal posts
→ ease of removal if endodontic retreatment is necessary
Composite Posts
→ embedded in an epoxy matrix
→ comparable to carbon fiber post
→ translucent post is available
Glass Fiber Post
→ excellent esthetic properties
→ high strength, rigid
Ceramic & Zirconia Posts
→ made of cast metal or zirconia fabricated with CAD/CAM technology
→ cast metal post and core made from direct pattern fabricated in the patient’s mouth or indirect patterns fabricated in the lab
o direct pattern technique with light polymerizing resin &
auto-polymerizing resin is recommended for single canals
with good clinical access
o an indirect procedure is more appropriate when access is
more problematic or for multiple canals
CUSTOM MADE POSTS
