post and core implications in prosthodontics

post and core

1. Presented by: Dr. Pratibha Katiyar 06-05-2009 POST AND CORE IN PROSTHODONTICS 1

2. Table of contents Definitions Introduction History Purpose When to use a post? Indications & contraindications Classification of post systems Materials used Biomechanical principles for post selection Impression for post and core 2

3. Pattern construction for custom cast post Direct Indirect Temporization Cementation Core materials Properties of core materials Review / evidence based solutions. Summary and conclusion References 3

4. Definitions: Post : A dowel usually made of metal is fitted in to a prepared canal of a natural tooth. When combined with an artificial crown or core, it provides retention and resistance for the restoration. (Glossary of Prosthodontics 8) Post : A Post is defined as the segment of the restoration inserted into the tooth canal to aid in retention of a core component. (JPD 1985 Apr) Core : A centre or a base of a structure. The core is designed to resemble or become the crown preparation or crown itself. (Glossary of Prosthodontics 8) 4

5. Cast Metal Core : The foundation restoration made for a fixed dental prosthesis formed indirectly by lost-wax casting. 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. Dowel : A post 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. 5

6. Introduction: The extraction of grossly decayed teeth with minimal tooth structure has now become an absolute outdated treatment modality. With advancement in the field of dentistry, teeth formerly considered fit for extraction are now being effectively saved. The restoration of Endodontically treated teeth with post and core is an extensively studied topic in dentistry as such teeth usually have a reasonably good prognosis and can assume full function after the treatment. 6

7. The successful treatment of badly broken tooth with pulpal disease depends not only on good endodontic treatment but also on a good subsequent prosthodontic reconstruction. After Endo therapy a tooth must be restored to fulfill functional and esthetic demands. 7

8. Teeth serving as abutments in prosthodontic reconstructions must be judged carefully regarding their ability to carry the load more higher than the physiological one. There is evidence for changes in receptor properties in teeth with non-vital pulp leading to higher bite forces than in vital teeth. This must be considered by estimating the fracture susceptibility of a root filled tooth, specially within a prosthodontic reconstruction substituting some more teeth. 8

9. Brief history: Started in 737 A.D. by Frank who described the use of wooden dowel post ,placed in the root to act as an anchor and metal posts were fixed into place with wooden wedge, as cements had not yet been developed. In 1725 , Pierre Fouchard described the use of TENONS which were metal posts screwed into the root of teeth to retain the prosthesis. He also described the technique of pivoting teeth to allow a post fabricated from a precious metal and to be fitted and secured into a canal prepared with watch makers reamers. 9

10. Posts were made up of gold, silver and held in root canal with a heat softened adhesive called “mastic’’ 10

11. Purpose: The roof of the pulp chamber has the configuration of an arch which is a shape that is extremely resistant to pressure and stress. When this roof is removed the inherent resistance of the treated tooth is reduced. This weakening leads to the need for strong exterior and interior support. Canal enlargement removes a portion of inner substances and decrease in the dentine in the root. 11

12. In the past it was thought that post reinforced endo treated teeth and the tooth and subsequent restoration become stronger. The research has shown that posts don’t reinforce teeth, in fact they may weaken the tooth structure. The main reason for using the post is now recognized as to aid in retaining a CORE ,to restore the lost tooth structure for retention of the restoration, and not to provide the strength or resistance to fracture. 12

13. When to use a post: Since a post does not strengthen an ET tooth and the preparation of a post space may increase the risk of root fracture and risk of treatment failure. The decision weather to use a post in any clinical condition must be made judiciously. 13

14. Most teeth require ET as a result of trauma, extensive caries or restoration. ET follows the concept of crown down i.e. more sound coronal and radicular dentine must be removed for efficient cleaning and shaping of root canal system. 14

15. Therefore the evaluation of weather a post is needed is based on how much natural tooth substance remains to retain the core buildup and support the final restoration after caries removal and ET are completed. Many ET molars do not require a post bcz they have more tooth substance and a larger pulp chamber to retain a core buildup. 15

16. When a post is required as a result of extensive loss of natural tooth substance, it should be placed in the largest and straightest canal to avoid weakening the root too much during post space preparation and root perforation in curved canals. 16

17. The distal canal of mandibular molars and the palatal canal of maxillary molars usually are the best canals for post placement. 17

18. When core retention still is insufficient after a single post is inserted, placement of pins can be considered for additional retention 18

19. Post are required in pre molars bcz they have less tooth substance and smaller pulp chambers. However root taper, curvature, proximal root invagination ,clinical crown of mandibular 1 st molar all these anatomical characteristics must be considered carefully during post space preparation to avoid perforating the root. 19

20. Few studies have concluded that the post is not necessary in an ET anterior tooth with minimal loss of tooth structure and can be restored with a bonded restoration in the access cavity. A post is needed when good amount of tooth structure is lost and tooth must be prepared to receive a crown. 20

21. A post may be necessary to retain the core so that these teeth can resist functional forces . Care must be taken to place post in mandibular incisors as the root of these are thin M-D. 21

22. How they work They reinforces the remaining tooth structure by transferring the load away from area susceptible to stress concentration and by increasing the stiffness and resistance to bending. However it is mainly the structure and the amount of remaining dentine that provide strength and resistance to fracture rather than the post itself. 22

23. INDICATIONS OF POSTS 23

24. Indications of posts depends:- According to Remaining Tooth structure Type of tooth Remaining axial cavity walls 24

25. Remaining Tooth structure: Minimal coronal tooth structure missing: Do not require post and core as its inherent strength is still present and can be treated adequately by placing restorative material in the root canal ,approx to the level of bone including access opening. Material of choice are conventional / resin modified GIC, bonded composite, and bonded spherical amalgam. 25

26. Up to one half of coronal tooth structure is missing: Also do not require post and core except tooth that provide canine or incisal guidance or is in significant group function occlusion. In such situation the lateral stresses of the tooth require more lateral resistance to fracture of the coronal portion from the root portion and therefore may need a post. 26

27. More than half of the tooth structure is missing: It is logical to place a post attaching the root structure to the core material that is being bonded to the coronal tooth structure. The remaining coronal tooth structure will provide the anti rotational characteristics to the post. 27

28. All the coronal tooth structure is missing: It require post with anti rotational feature by placing channel 1-1.5mm deep into the lateral and occlusal portion of the root, the anti rotational pins on the mesial, distal, and lingual surfaces of the remaining root or by placing small box into the root. The coronal portion must extend 1.5- 2mm apically to prevent crown rotation. 28

29. Type of tooth: In anterior tooth: They need posts more often than posterior tooth due to shearing forces on them. They are placed at an angle to the occlusal plane and forces are therefore not directed along their long axis. Post are indicated when there is a inadequate tooth structure to retain a core . If it is to be restored with a crown, and must serve as an abutment to a prosthesis, a post is needed irrespective of amount of remaining coronal tooth structure. It is advised to drive resistance to RCT tooth by preserving as much coronal dentine as possible and providing a ferrule as a part of the crown. 29

30. Tooth colored dowel, composite resin, or ceramic posts , esthetic cements, and ceramic crowns can be given. In posteriors: Premolars : indicated in moderate – severe crown destruction. Molars : If sufficient tooth structure is remaining – onlay / crown, if extensive- post and core The posts are placed in longest, straightest root with greatest circumferential diameter for better distribution of stresses during function and lesser chances of lateral and apical perforation. 30

31. Remaining Axial cavity walls Class 1: All axial wall are remaining: If the thickness is > 1mm post is not indicated. Any type of definitive restoration can be given. Class 2: Loss of one axial wall( MO/DO)- not indicated Class 3: MOD cavity with 2 remaining wall- onlay / crown indicated 31

32. Class 4: One remaining cavity wall- Core material has little / no effect on fracture resistance of RCT treated tooth. If the tooth has to be used as an abutment, crown prep further reduces the fracture resistance. So the present concept suggest using posts in such cases. Either metal or non metal can be used. 32

33. Class 5: No remaining cavity walls. Insertion of post is mandatory for core material retention. Ferrule given to increase fracture resistance and should have 1.5 – 2mm height. The post length design (parallel/ tapered) are of secondary importance. 33

34. Contra indications: Persistent periapical pathosis , poor root filling ( short , gross, excess, inadequately condensed). Poor oral hygiene, poor motivation. Very thin translucent crown difficult to match to adjacent teeth. Natural crown still has reasonable aesthetics with little discoloration or loss of tooth substance. 34

35. Post not needed: post concepts are changing No tooth structure missing other than access hole. No horizontal cracks in the coronal portion of the tooth. No excess occlusal stress. 35

36. Post recommended: Good prognosis Questionable prognosis Significant amount of coronal tooth structure missing but not more than half. Factors to consider: Heavy occlusion canine rise Incisal guidance Use as an abutment Visible horizontal cracks All coronal tooth structure missing up to the level of gingiva. Can improve prognosis in long root tooth by increasing clinical crown. Crown Lengthening Orthodontic extrusion “Best treatment in this case is implant placement” 36

37. CLASSIFICATIONS 37

38. Mainly classified as Pre fabricated and custom made/ cast 38

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40. According to type of attachment Active Passive Passive posts Active posts Retained with the Luting agent. Prefabricated: SS, Zr , C, Ti, FRC Parallel. Tapered. Custom fabricated: Cast post and core. Indication: In tooth with thin root and delicate morphology Mechanical engagement of dentine. Indication: This is restricted only to the tooth with short root requiring maximum retention. 40

41. According to design Smooth Serrated Parallel sided Tapered Combination of above. 41

42. Parallel posts Tapered posts More retentive Greatest stress at apex of preparation Resistance to shear, tensile and torque forces is better than tapered. Cement adhere to post when dislodged. less retentive ,(angle of convergence>3.5) Stress at coronal shoulder Less resistant Failure occurs at post cement interface. 42

43. Prefabricated posts: Currently there are more than 150 different prefabricated post systems are available. There is no perfect post system that will cover each and every type of clinical situation. Even with this huge number to select from, there are really only five basic systems of prefabricated posts that are commercially available. Other prefabricated systems are variations of these five basic designs. The basic post designs are the following. 43

44. 1. Tapered, smooth-sided post systems are cemented into a channel prepared with endodontic files or reamers of matching sizes. An example is the Kerr Endopost . 2. Parallel-sided , serrated, and vented post systems are cemented into a matched channel prepared with a twist drill of matching size. An example is the Whaledent Parapost . 44

45. 3. Tapered, self-threading post systems are screwed into a channel prepared with matched reamers. An example is the Dentatus screw. 4. Parallel-sided, threaded post systems engage the dentin wall by self-threading or with use of matched taps. Examples are the Radix anchor / which is self-tapped, and the Kurer anchor , which is first tapped and then threaded into dentin. 45

46. 5. Parallel-sided, threaded, split-shank post systems engage the dentin wall in a channel prepared with matched reamers. An example is the Flexipost . 46

47. Pre fabricated- materials Materials Advantages Disadvantages Stainless steel Strong Nickel allergy Rigid metal color transfer Titanium Radio opaque Easy to use None Zirconia Radio opaque Tooth colored Strong Difficult to use Expensive Lack retention Carbon Easy to remove and use Flexible Radiolucent Black color Fibre reinforced resin based composite Easy to use and remove Strong Radio opaque , tooth coloreds None 47

48. Fibre posts system: Recently 6 type of posts has been introduced. A Fibre post that is coupled with the frictionless bonded technique, was developed to reduce the occurrence of root fracture due to wedging effect of metal posts. Advantages: Mod of elasticity- similar to dentine High fatigue and tensile strength Ability to be cemented using an adhesive Compatible with BIG-GMA resin Micro mechanical retention with resin tags Low failures rates 48

49. Made of up of carbon or silicon fibers surrounded by a matrix of polymer resins mainly epoxy resins. Fiber are 7 to 10 micron in diameter and available in different configuration. Configuration including braided, woven, and longitudinal. Less chances of fracture of root as compared to the metal bcz the flexural modulus of these posts are closer to that of dentine. 49

50. They are fabricated to bond with most resin cement and resin based composite core material. And the successful bonding minimizing the wedging effect of the post within root canal . Require less dentine removal to accommodate a short and thin post and leads to lower susceptibility to tooth fracture. 50

51. Do not cause metal allergy / corrode Offer good esthetics specially under all ceramic crown, can be removed easily. 51

52. + / - Advantages Disadvantages Less expensive Faster to fabricate More conservation of tooth structure variety of width and length and taper of materials Lack of strength Lack esthetics in anterior region Less adaptation to the canal Technique sensitive. 52

53. Recommendations: Posterior teeth Room for bulk build up Canal angulations is of less problem Moderate amount of tooth structure is remaining Crown margin can be prepared up to >_ 2mm past core. Undercuts in canal or chamber. 53

54. Custom fabricated: Cast gold post and core has been used for decades as a foundation restoration to support an ET tooth. For many years the posts were cast in gold, separately or along with the core, then gradually cast post use decreased with the introduction of pre fabricated post systems. 54

55. + / - Advantages: Disadvantages: Resistance to leakage Biocompatibility High corrosion resistance Low rigidity High strength High cost Indirect fabrication Provisional restoration Amount of tooth structure to be removed Root fracture Esthetics 55

56. Recommendations: The cast post and core is indicated where the inclination of the canal is significantly different from the alignment of the crown. Decreased amount of tooth structure in anterior teeth makes its difficult to adequately build a core around a post. 56

57. Bio mechanical principles for post selection The retention and the stress distribution to the surrounding tooth depends on Type Length Diameter Design Surface texture of the post 57

58. Type: Pre fabricated and Custom made Pre fabricated posts Threaded Non threaded Active or Passive Tapered or Parallel 58

59. Length of the post: It has a direct effect on retention regardless of post system used. Longer the post greater is the retention and support and better is the stress distribution with reduction of shear and compression concentration. Post should be as long as possible with out jeopardizing the apical seal or risking the perforation of a narrowing or fluted root. 59

60. It should equal the length of clinical crown. It should be equal to ½ to 2/3 of the length of remaining root. It should end ½ way between crestal bone and root apex. 60

61. Short posts are dangerous and often lead to root fracture bcz of failure to be surrounded by peri radicular bone completely. Craze Lines: in dentin are areas of weakness where further crack propagation may result in root fracture and tooth loss. The patient should be informed of their presence. If possible, avoid post placement in favor of a restorative material core. If a post is required, it should passively fit the canal, and the definitive restoration should entirely encompass the cracked area, whenever possible, by forming a ferrule 61

62. Diameter of post: The post should be as long as possible, conformed to the shape of the root canal, lie within the log axis of the tooth and be of a minimum diameter to maximize the preservation of remaining dentine. Increase in post diameter will increase the stress level in the apical portion of the root, and decrease the fracture resistance of the root. 62

63. Optimal post diameter Have been determined to be: Mandibular incisors  0.6 – 0.7 mm. Maxillary central incisors, canines, and the palatal root of the maxillary 1 st molar  1.0 – 1.2 mm & may upto1.7 mm. The rest of teeth  0.8 mm- 0.9 mm 63

64. Mesial roots of mandibular molars and the buccal roots of maxillary molars shouldn’t be used for posts . Mandibular premolars with oval or ribbon shaped canals shouldn’t be prepared further for a post  the gap is filled with luting cement which add elasticity to it. Roots with remaining dentine thickness less than 1mm are indicated For custom made posts . . 64

65. Design and surface texture: The parallel sided threaded post have the greatest retention. where as the parallel sided serrated cemented posts have intermediate retention. Tapered smooth surface posts are least retentive. 65

66. Post preparation: Features include: 4-5mm of Gutta purcha at the apices. 2/3 rd length of the root. ½ the length of the root in the bone. Apical tip of the post 7mm below the crest of the bone. Length of the post is equal to the length of the crown. Post space not greater than the 1/3 rd of the width of the root There must be Ferrule effect on at least 2 sides of the preparation 66

67. Und he 2/3 7 mm Bone crest 67

68. Impression for post and core: A lubricant is painted on the portion of the post that will be with in the canal. Then in is firmly placed . If rubber base impression materials is to be used ,adhesive may be placed on the exposed portion of the post. Gingival retraction is gained by method of choice. A syringe is used to place the impression material into the orifice with a gentle stream of air to blow the impression material into the orifice and around the post to reduce air bubbles. 68

69. Additional materials is then placed around the preparation. This is very important step bcz the picking up of the orifice portion of the preparation is necessary for increased retention of the core. The post should pick up cleanly with the impression. 69

70. Pattern construction of custom-cast post Direct method Material: Wax. Self cure A.R. Plastic ready-made burn out post Steps involves: Lubrication of root canal (die lubricant). 70

71. 2. IF DIRECT WAX PATTERN: Select a metallic sprue former: - Fits loosely inside R.C. - Length > than that of core. - Serrated using diamond stone or disc (to ensure good retention bet. wax & sprue). Softening of blue casting wax and insertion into the R.C. Heating of sprue. Wait till hardening of wax. Add for any deficiencies until it’s removed with slight resistance “snugly fit”. Core can be made of wax, followed by investing and casting. 71

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73. 3. If direct Acrylic Resin pattern: 1) Select a plastic dowel: - Fits loosely inside R.C - Long. - Serrated (notched). 2) Mixing of Acrylic resin and insertion into the R.C. before the dough stage. 3) Before complete curing, moisten the dowel with monomer and insert into R.C. 4) Also before complete curing, move the plastic dowel inward and outwards to prevent interlocking in any undercuts or roughness. 5) Add any modifications until it’s removed with slight resistance “snugly fit”. 6) Investing and casting. 73

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75. 4. Plastic ready made burnout post: 1) Plastic posts supplied with its special drills (same size & shape). 2) Prepare root canal. 3) Build up core with wax or acrylic resin. 4) Investing and casting. 75

76. INDIRECT METHOD: STEPS: 1. Impression: By light body Elastomer applied by a syringe, starting from apex. Insert an SS wire to: - support impression Material. - prevent imp. tearing during removal. - Use a (Cu band) or (tray) to complete impression procedures. - Remove the impression and evaluate it, then pour a stone cast. 76

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80. Temporization: The objective is to keep tooth to tooth relationship from being altered while the lab procedures are performed and to prevent gingival tissues from creeping over the margins. Polycarbonates crow, acrylic resins 80

81. Cementation: It is more dependent on operator techniques than the material used. The objective is to lute a post in place with minimum film thickness bw the dentine and the post. The vertical vent in the post design reduce the hydrostatic pressure that builds up during the cementation and minimum film thickness is attained when parallel sided vented posts are used. Post cementation using unfilled BIS GMA offers promise by eliminating the smear layer prior to cementation bcz the adhesion of cementing agent is more important than their resistance to shearing forces. 81

82. method: Temporary restoration is removed and the canal is cleaned thoroughly with the file , the area is isolated with air and paper points. The post and core is tried in and adjustments are made for adequate clearance of opposing teeth. A creamy mix of crown and bridge cement is prepared and inserted into the canal with lentulo spiral filling instrument. 82

83. Cementing medias: Zinc phosphate Zinc polycarboxylate GIC Resin based composite 83

84. Post and core is also painted with the same cement and gently placed by hand pressure. Hammering and tapping the post and core to place are absolutely unacceptable bcz the hydraulic pressure built up within the canal could lead to root fracture. From this point, the tooth is handled as a routine abutment. 84

85. Evidence based solution: Cast post and core accumulate stresses within post and core. Fibre post distribute stresses to the cervical third and supporting structure. Results from this study showed that cast post and core showed 100% post displacement and 70% root fracture. Fibre post showed 70 % core fracture, 20 % root fracture and 10 % post displacement. Eskitascoglu et al 2002. 85

86. Core materials: Direct placement Dental amalgam Resin composite Glass ionomer Resin modified GIC or compomer Indirect placement( post and core) casting 86

87. Properties of core materials: Compressive strength Flexural strength Bio compatibility Ease of manipulation Ability to bond to tooth structure Coefficient of thermal expansion Dimensional stability Minimum water absorption Short setting time Compatible with other materials cariostatic potential Low cost Contracting color to tooth tissues 87

88. Amalgam: Advantages Disadvantages Not technique sensitive Strong in bulk section Sealed by corrosion products Can be gluted into place with cement and resin. Best left to set for 24 hrs before tooth preparation. Weak in thin section. Mercury content may be of concern to some patient. Potential electrolytic action bw core and metal crown. Not intrinsically adhesive. Recommendation: Excellent core build up material for posterior tooth. Excellent interim restoration for posterior teeth. Adhesives and preparation features can often substitute for pin retention. 88

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90. Evidence based solution: The MOE of amalgam is significantly higher than all other material tested and is closer to that of the dentine. Combe et al 1999 , martinez - Insua et al 2002, 90

91. Resin composite: Advantages Disadvantages Strong Can be used in thinner sections than amalgam. Fast setting ( light/ chemical cured) Does not always need a matrix during placement. Highly technique sensitive. Relies on multistage dentine bonding. Requires effective isolation. Material shrinkage. Dimensional changes. Difficult to distinguish bw tooth and core during preparation. Recommendation: Excellent build up material for anterior and posterior teeth, if isolation is assured. Esthetic interim restoration but takes far longer to place than amalgam. Pin retention is rarely necessary. 91

92. Encore® Self-Cure Composite Core Buildup Material Encore® D/C Automix Dual-Cure Core Buildup Material 92

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94. Evidence based solution: Composite was significantly stronger than amalgam after the preparation of the build up, having significantly higher tensile strength. Coombe et al 1999 Tensile and flexural strength of composite are significantly higher than that of amalgam and GIC. Kovarik et al 1992 94

95. Glass ionomer cement: Advantages Disadvantages Intrinsically adhesive. Fl release. Similar co eff of thermal expansion as tooth. Weaker than amalgam and composite. Tendency to crack. Some are radiolucent. Recommendation: Excellent filler but relies on having sufficient dentine to support crown. When used as a build up, best to leave the preparation till next appointment. Good material to bond restoration with the resin cement. 95

96. Evidence based solution: Its tensile strength and MOE are significantly lower than dentine and amalgam. Combe et al 1999 Evidence based solution: Relatively slow setting and their resistance to moisture is poor. Walmsley et al 2002 GIC should reserved for use as fillers and bases. Wassell et al 2002 96

97. Resin modified GIC Advantages Disadvantage Stronger than regular GIC. Either intrinsically adhesive or with simplified bonding system. Fl release. Weaker than amalgam and composite. Can crack overlying porcelain. Some materials can inhibit surface setting of addition silicones. Not reliable as an interim restoration. Recommendation: Useful filler but confers few advantages over regular GIC. 97

98. Evidence based solution: Have a better flexural sterngth compared to conventional GIC whilethe high co efff of thermal expansion of composite has been reduced. Walmsley et al 2002 These materials are significantly waeker than natural tooth and should be limited to use as fillers. Christensen et al 2000 98

99. Final restoration: Option available: Gold onlay and crown Metal ceramic crown All ceramic with cuspal coverage Studies shows that routine use of crown on ET teeth may not be necessary if the marginal ridges are intact and most of natural tooth substance is preserved. If MR is lost, cuspal protection may be necessary for long term preservation of tooth and onlay / crown can accomplish this. 99

100. Post removal: Use of Rotatory instruments and solvents. Use of Ultrasonics Using special kits like Masseran kit post remover and endodontic extractor. 100

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103. Summary: The post do not strengthen ET tooth and should not be used routinely. The main function of post is the retention of the core, if there is an insufficient tooth substance is left to support the final coronal restoration. Selection criteria should include adequate strength, MOE, retention, biocompatibility, esthetics and retrievability . 103

104. Post space preparation requires good understanding and knowledge of tooth anatomy to avoid unnecessary mishaps. Cementation of posts with the resin cements, seems to offer better retention, less microleakage and high resistance to tooth fracture. Gold amalgam and resin bonded composites are acceptable core materials and each has its advantages and disadvantages. 104

105. The use of GIC as a core material should be avoided bcz of its low strength, stiffness, poor bonding and high solubility. 105

106. Conclusion: There has been a tremendous evolution in the post and core concept over the past 50 yrs ,dogmatic support of custom cast post and core has dissipated and support of pre fabricated post and cores has dominated. currently, numerous techniques advocate eliminating posts in many situations or using flexible posts that are resilient. With the increased use of crown and fixed prosthesis, it is anticipated that post and core procedures are not only important, but also will be improved and changed significantly. 106

107. References: The Prosthodontic Management of Endodontically Treated Teeth: A Literature Review. Part I. Success and Failure Data, Treatment Concepts. JProsthod 1994;3:243-250. The Prosthodontic Management of Endodontically Treated Teeth: A Literature Review. Part 11. Maintaining the Apical Seal. J Prosthod 1995;4:57-53. The Prosthodontic Management of Endodontically Treated Teeth: A Literature Review. Part 111. Tooth Preparation Considerations. J Prosthod 1995;4: 122- 128. 107

108. A review of the management of Endodontically treated teeth. J Am Dent Assoc, Vol : 136, No 5, 611-619 Text book of Endodontic’s : Restoration of the Endodontically Treated Tooth. By Steven R. Potashnick, Franklin S. Weine, Sherwin Strauss. Text book of endodontics. Mehta and T.D. Text book of endodontic therapy .By Franklin s. Weine Fundamentals of fixed prosthodontics. By Herbert shillenberg 108

109. http://synovio.com/_wsn/page4.html www.centrixdental.com/core-buildup_details.asp www.dentalproductshopper.com/eds-ti-core-with-fiber-reinforcement 109