post and core.pptx

Prosthodontics

1. RESTORATION OF ENDODONTICALLY TREATED TEETH DR SHRIMANT RAMAN DEPARTMENT OF PROSTHODONTICS

2. INTRODUCTION During the past 20 -30 years there has been an increased interest in restoring endodontically treated teeth This mode of treatment is complicated by the fact that much or all of the coronal tooth structure which normally would be used in the retention of the restoration has been destroyed by : Caries Previous restoration Trauma Endodontic access itself

3. The complete coverage crown is the most ideal restoration to protect the remaining natural teeth in endodontically treated teeth. As coronal tooth structure is mostly damaged, the crown requires a core or a post and core for retention, depending on the extent of damage and location of the tooth

4. DEFINITIONS According to GPT 2005 Post (Dowel): A structure usually made of metal that is fitted into a prepared root canal of a natural tooth. When combined with an artificial crown or core, it provides retention and resistance for the restoration. Core: The center or base of a structure

5. Principles of restoration of endodontically treated teeth : • Provide good coronal seal • Protect/conserve remaining tooth structure. • Satisfy functional and aesthetic needs. • Reduction of stresses with favorable distribution within remaining tooth structure.

6. DIAGNOSIS & TREATMENT PLANNING

7. ENDODONTIC CONSIDERATIONS Attention must be given to the quality of the endodontic therapy. Predictable success in endodontic therapy requires a dense, uniform, three dimensional obturation of the root canal system, 0.5 to 1.0 mm from the radiographic apex of the root or roots.

8. PROSTHETIC CONSIDERTIONS The extent of coronal destruction is an important determinant in deciding on the restorative technique and materials to be used in returning the tooth to normal form and function. Contrary to popular belief, posts do not strengthen the tooth. The primary function of a post is to provide retention for the core .

9. Posts are indicated when there is inadequate tooth structure to retain a core for a coronal structure. It is evident now that care should be taken to preserve as much sound dentin during endodontic therapy and subsequent restorative procedures.

10. PERIODONTAL CONSIDERATIONS Periodontal disease should be treated prior to placement of definitive restorations. A healthy periodontium provides the best prognosis for the tooth and will make procedures such as placement of margins and making of an impression easier and more accurate.

11. TREATMENT OPTIONS Anterior teeth Intact coronal tooth structure except for prepared access opening – access opening is restored with composite resin if no discoloration is present. Less than 25% coronal tooth structure is damaged – a complete coverage crown is required. More than 25% coronal tooth structure is damaged – a post and core with crown is required.

12. Posterior teeth Less than 50% coronal tooth structure is damaged – core and crown are required. More than 50% coronal tooth structure is damaged – post, core and crown are required.

13. CLASSIFICATION All posts can be classified as rigid and non-rigid, which can be sub-classified according to the post material, shape and surface configuration. Posts can be classified according to the following features: Shape – parallel, tapered Stiffness – rigid, non-rigid Surface – smooth, serrated, threaded Colour – aesthetic, non-aesthetic Pressure on root – active, passive Fabrication – prefabricated, custom-made (cast posts).

14. Parallel sided, threaded post Parallel sided post with tapered end Parallel sided, vented post Parallel sided, passive posts

15. Parallel and tapered post : Parallel-sided posts direct the occlusal forces apically while tapered posts direct the forces laterally by producing a wedging effect. Hence, occlusal forces are better directed by parallel posts. They are also more retentive than tapered posts. Tapered posts are more conservative of tooth structure.

16. Rigid and Non-rigid : The post should be resilient enough to cushion an impact and strong enough to resist permanent deformation . Rigid Post Can be made of crown and bridge alloys (cast posts), stainless steel, titanium, zirconia (prefabricated posts). Zirconia has greatest stiffness followed by steel and titanium alloy. More chance of root fracture than non-rigid . Indicated for teeth with less than 3–4 mm vertical height or less than 25% tooth remains

17. Non- Rigid Post Made of glass, quartz or carbon fibres embedded in a resin matrix, also called ‘ fibre -reinforced composite’ posts (FRC). They have to be adhesively bonded to the root canal space. Can reinforce weak teeth with flared canals. Require less preparation – preserve integrity and strength of dentine. Less root fracture. Indicated in teeth with more than 25% remaining tooth structure.

18. Custom-made and prefabricated posts : The only custom-made post is the ‘cast post ’. It is also called ‘ one-piece ’ post, as the post and core are not separable. The use of this post is declining.

19. Cast post and core A one-piece foundation restoration for an endodontically treated tooth that comprises a post within the root canal and a core replacing missing coronal structure to form the tooth preparation (GPT8 ). Advantages of cast post : Conservative of tooth structure. High strength.

20. Disadvantages of cast post : Time – requires two appointments. Wedging effect – because they can only be made tapering and high rigidity. Porosity – problem and casting procedure. Fit – may not be very accurate because of indirect method. Unaesthetic – as it can be made only of crown and bridge alloys. Hence, it cannot be used with all-ceramic restorations . Cost – lab costs will be incurred.

21. Prefabricated posts: They are versatile. They are available in different configurations and can be selected as per the given clinical situation. They are also available in different diameters corresponding to the size of the drill. Hence, the fit is accurate. Though post and core is inserted in two separate procedures, it requires only one appointment with no laboratory costs.

22. SELECTION OF POST The following parameters govern post selection : Length Diameter Shape Surface configuration Location

23. Guidelines for determining post length are : Equal to half the remaining length of the tooth . Equal to two-thirds the root length of the root . Equal to the length of the remaining crown. Half the length of root contained in bone. Have minimum of 4 mm of gutta-percha apically to provide adequate seal. LENGTH

24. DIAMETER Post diameter should not exceed one-third mesio-distal root diameter. 1 mm dentine should surround the post preparation.

25. SHAPE Parallel-sided posts are preferred as they have better retention and more favourable stress distribution. Tapered posts are indicated for the significantly tapered canal system, where use of a parallel-sided dowel would involve vigorous preparation of the radicular dentine walls. To minimize the splitting potential of a tapered dowel, there should be flat seat at the occlusal end of the preparation to resist apically directed forces and prevent wedging.

26. SURFACE CONFIGURATION Parallel-sided serrated posts are generally indicated. If root length is less, threaded posts offer better retention.

27. LOCATION Posts should be placed in roots that are round straight and long In the anterior teeth, roots are seen mostly with circular cross-section . Root anatomy of multi-rooted teeth is most suitable in the palatal roots of maxillary molars, palatal roots of maxillary premolars and distal roots of mandibular molars.

28. TOOTH PREPARATION FOR POST Coronal tooth structure is prepared according to the type of extra coronal restoration planned. All existing caries, restorations, cements, bases and unsupported tooth structures are removed. Preserve as much of intact coronal tooth structure as possible to externally brace the tooth.

29. Ferrule: Minimum of 1.5 mm of sound tooth structure 360° around the tooth should be present, apical to the core. It improves structural integrity of the tooth and prevents fracture

30. PREPARATION OF POST SPACE Peso reamers Gates G lidden Drill (GG Drill)

31. The procedure is begun with the largest Peso or Gates that will fit into the canal. Once the root filling is removed, successively larger Peso or Gates is used to enlarge the canal to desired dimensions. Radiograph with reamer in position is used as a guide to determine length and diameter. Peso reamer in use is placed and radiograph taken

32. Appropriate length and diameter of the post are determined using a radiograph as a guide and following the guidelines The dimensions of the previous endodontic filling, if available, can also be a good guide to determine length and diameter. An endodontic stopper is placed in the shank of reamer or drill to ensure appropriate length.

33. Some prefabricated post systems are provided with specific drills corresponding to the diameter of the posts. These drills are used to enlarge the canals to the required diameter, when available. Prefabricated posts of varying widths with their corresponding drills.

34. Custom-Made Posts (Cast Posts ) Custom-made posts are categorized as rigid, metal, tapered, smooth, in the classification for posts. They can be fabricated: 1 . Direct method 2 . Indirect method

35. Direct Method A pattern of the post and core is fabricated directly in the patient’s mouth and then cast in the laboratory. Disadvantages : Consumes a lot of clinical time. Any problem in casting, procedure has to be repeated intra-orally .

36. Procedure: A 14-gauge plastic sprue (a plastic toothpick or stainless steel wire can also be used) is trimmed to check the fit in canal. Grooves are cut on the surface for retention of the pattern material. A mark or notch is made facially to allow re-orientation subsequently.

37. Canal and surrounding areas are lubricated with petroleum jelly . Autopolymerizing acrylic resin is mixed to a running consistency, coated on sprue and inserted in the canal. As the resin becomes doughy, move the pattern up and down to ensure it is relieved from any undercuts . Any voids can also be filled with new resin, pattern reseated and finally allowed to set outside the mouth.

38. After the resin in the post portion sets, the core is built up with the same material and moulded with fingers (Fig.1) After setting, it is prepared to the appropriate shape of core (Fig.2) Fig.1 Fig.2

39. Indirect method In this technique, an impression is made of the canal space using a putty and light body wash, and the pattern is fabricated indirectly on a model and cast. This is indicated for multiple posts and posts in multi-rooted teeth. Putty impression is made of prepared tooth along with the entire arch Light body material injected into post space and placed on the putty impression

40. Advantages :- There is less usage of chair-side time and as a cast is available, any problems in casting can be easily repeated. A second impression is made. Following removal of final impression – cast can be poured where the post can be fabricated

41. Fabrication of Cast Post in Molar Post can be made in one-piece if the canals are convergent or parallel. Upper molar palatal and disto-buccal canal prepared for cast post One piece cast post fabricated Cemented cast post and core

42. Post for posterior teeth may need to be made in two parts if canals are divergent. Post space in mesio-buccal , disto-buccal and distal canals in mandibular molar with divergent canals Post space impression made with putty and light body wash

43. Cast is poured and cast post to fit distal canal (overextended occlusally ) is fabricated first Wax pattern with distal post Wax pattern minus the distal post Wax pattern fabricated for the remaining posts along with the core is fabricated around the distal post

44. The pattern is cast and distal post is fitted Larger casting (buccal posts with core) Distal post is cemented

45. After the cement sets overextension in distal post is trimmed Cemented two piece cast post

46. Core Materials : Cast core Amalgam Glass ionomers Composite resin Cements: Zinc Phosphate GIC Resin Cement

47. POST CROWN This is a one-piece post crown. It is also called ‘Richmond crown ’. Indicated in patients with deep incisal overbite where it is difficult to provide space for a core and crown separately Fracture maxillary central incisor (tooth no: 11) with lack of occlusal clearance Coronal tooth preparation

48. Preparation of canal space Post crown fabricated by indirect method Cemented post crown

49. THANK YOU