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INDIAN DENTAL ACADEMY Leader in continuing dental education

contents  Introduction  Effects of endodontic treatment on teeth  Considerations for anteriro and posterior teeth  Requirements of posts  Key features of post and core design  Factors affecting selection of posts

       

Factors affecting retention of posts Classification of esthetic post systems Properties of fiber post systems Clinical techniques Cementation Summary Conclusion references


Effect of endodontic treatment on teeth  Tooth structure after endodontic treatment weakened by previous episodes of    

Fracture Tooth preparation Restoration Endodontic manipulation

 Loss of tooth structure  Altered physical characteristics  Altered esthetic characteristics

considerations  Anterior teeth  Intact , non-vital , has not lost tooth structurebeyond access cavity preperation Less risk of fracture Sealing the access cavity

considerations  Anterior teeth  Intact , non-vital , has lost significant tooth structure More risk of fracture crown retained by dowel and core

 Posterior teeth  Depends on remaining tooth structure  If adeqaute tooth structure present , core and crown is sufficient  If inadeqaute, post and core with crown necessary

Requirements of post and core    

Physical properties similar to dentine Maximum Retention with little removal of dentin Distribution of functional stresses evenly along the root surface,  Esthetic compatibility with the definitive restoration and surrounding tissue,  Minimal stress during placement and cementation,

     

Resistance to displacement, Good core retention, Easy retrievability, Material compatibility with core, Ease of use, safety and reliability, Reasonable cost.

Key features for a succesful post and core design

Factors determining selection of posts  Root length  Greater the post length, the better the retention and stress distribution  Reserve 3 to 5mm of apical gutta-percha to maintain the apical seal

 Tooth anatomy  A consideration of the root size and length is important, because improper post space preparation and use of large-diameter posts present the risk of apical or lateral perforation.  An active post can initiate cracks in the thin dentinal wall

 Post width  Preserving tooth structure, reducing the chances of perforation, and permitting the restored tooth to resist fractures are criteria in selection of the post width

Lloyd PM, Palik JF. The philosophies of dowel diameter preparation: a literature review. J Prosthet Dent 1993;69:32-6.

 Selection of post width sumarised by Lloyd and palik into 3 categories  Conservationist  Preservationist  Proportionist

 Canal configuration and post adaptability  Canal configuration aids in making a choice between a custom-designed post and a prefabricated post  If post confirms to the shape of the canal closly  more conservative procedure  more resistance to fracture

 Coronal structure  The bulk of the tooth above the restorative margin should be at least 1.5 to 2 mm to achieve resistance form.  Teeth restored with carbon fiber posts had inferior strength compared with those restored with metal posts when subjected to forces simulating those in a clinical setting  (Sidoli GE, King PA, Setchell DJ. An in vitro evaluation of a carbon fiber based post and core system. J Prosthet Dent 1997;78:5-9.)

 Carbon fiber post system, can be used when ample coronal dentin remains and the crown is well supported by remaining tooth structure; otherwise, cast post and core may be used when there is moderate to severe tooth loss.

 Stress  Post and core–restored endodontically treated teeth are subjected to various types of stresses:  compression,  tensile, and shear  An increase in the post length with diameter kept to a minimum will help to reduce shear stresses and preserve tooth structure

 Torsional forces  Intraorally, post and core–restored teeth are subjected to various types of forces. Torsional forces on the post-core-crown unit may lead to loosening and displacement of the post from the canal, causing failure of the system

 Role of hydrostatic pressure  Cementation plays a significant role in enhancing retention, stress distribution, and sealing irregularities between the tooth and the post

 Post design  Classified according to shape design and surface characteristics.  According to shape design   

Parallel sided Tapered Parallel tapered combination According to surface characteristics Active and passive

 Post material   

Metal post systems Carbon fiber posts Zirconia posts

(Mannocci E, Ferrari M, Watson TF. Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber and zirconium dioxide ceramic root canal posts. J Adhes Dent 1999;1:153-8.)

 Bonding ability  Resin luting agents showed good adhesion to carbon  Fiber posts and glass fiber posts.69 The adhesion to zirconia posts was found to be unsatisfactory.69 It was also observed that to improve retention, the carbon fiber post did not require any surface treatment as compared with the zirconia post.

 Core material  Retrievebility  Esthetics

Factors affecting the retention of posts  Post length  The post should equal the incisocervical or occlusocervical dimension of the crown.  The post should be as long as possible without disturbing the apical seal  Short posts are especially dangerous and have a much higher failure rate

 Post diameter  Increasing the diameter of the post does not provide a significant increase in the retention of the post; however, it can increase the stiffness of the post at the expense of the remaining dentin and the fracture resistance of the root.  post diameter must be controlled to preserve radicular dentin, reduce the potential for perforations, and permit the tooth to resist fracture

 Luting cements  Resistance form  Stress distribution  Rotational resistance

Ferrule effect

Classification of esthetic posts  Polyethylene fiber posts  Ribond

 Glass fiber posts  Fibrekor posts (Generic Pentron)

 Carbon fiber posts  Composipost  C – Post systems

 Quartz fibers bound in an epoxy matrix   

D T Light post (Bisco Usa) Astheti Plus posts Light posts

 Ceramic posts  Direct method  Cerapost (Lemgo, Germany)

 Indirect method  Split casting technique (Inceram posts)  Copy milling technique (In ceram Celay posts)  Two Piece technique (ER – Post systems, Brassler Germany)  Heat preassure technique  Cosmopost (Ivoclar)

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