Restoration of endodontically treated teeth

Restoration of endodontically treated teeth

1. V.NIVEDHA RESTORATION OF ENDODONTICALLY TREATED TEETH

2. HISTORY INTRODUCTION STATUS OF ROOT FILLED TEETH VULNERABLE TO TOOTH LOSS SPECIFIC TISSUE MODIFICATIONS AND CLINICAL IMPLICATIONS FACTORS IN SELECTING RESTORATVE APPROACH RESIDUAL ROOT STRUCTURE FUNCTION AND TOOTH POSITION IN ARCH CLASSIFICATIONS RESTORATIVE MATERIALS DIRECT COMPOSITE INDIRECT RESTORATIONS CONTENTS:

3. ENDOCROWNS FULL CROWNS WHY TOOTH FRACTURE POST AND CORE FIBER POST CAST POST CORE MATERIALS COMPOSITE AMALGAM GIC INTERIM PESTORATIONS TEMPORARY RESTORATIONS DEFINITIVE RESTORATIONS ENDODONTICS VS IMPLANTS RESTORATIVE ASPECTS CONCLUSION CONTENTS:

4. Various methods of restoring pulpless teeth have been reported for more than 200 years. In 1747, Pierre Fauchard described the process by which roots of maxillary anterior teeth were used for the restoration of single teeth and the replacement of multiple teeth Posts were fabricated of gold or silver and held in the root canal space with a heat-softened adhesive called ‘‘mastic.’’ The replacement crowns were made from bone, ivory, animal teeth, and sound natural tooth crowns. Gradually the use of these natural substances declined, to be slowly replaced by porcelain A pivot (what is today termed a post) was used to retain the artificial porcelain crown into a root canal and the crown–post combination was termed a ‘‘pivot crown.’’ HISTORY:

5. Early pivot crowns in the United States used seasoned wood (white hickory) pivots. The pivot was adapted to the inside of an all-ceramic crown and also into the root canal space. Moisture would swell the wood and retain the pivot in place. Subsequently, pivot crowns were fabricated using wood/metal combinations and then more durable all-metal pivots were used. Metal pivot retention was achieved by various means such as threads, pins, surface roughening, and split designs that provided mechanical spring retention

6. Today, both endodontic and prosthodontic aspects of treatment have advanced significantly, new materials and techniques have been developed, and a substantial body of scientific knowledge is available upon which to base clinical treatment decisions.

7. Root-filled teeth are generally weakened by caries and subsequent restorative procedures. Loss of dental tissue, due to either caries or cavity preparation, reduces tooth stiffness and fracture strength of the remaining tooth structure in proportion to the increase in cavity width and depth. Marginal ridges are strategic for tooth strength, and their loss considerably reduces tooth stiffness, while endodontic access appears to exert only a modest influence on tooth strength. Excessive coronal flaring during root canal therapy further weakens the tooth and predisposes the tooth to subcrestal Fractures. INTRODUCTION:

8. The restoration must be planned carefully to ensure that weakened cusps are adequately protected, but at the same time the tooth is not further weakened by excessive restorative procedures.

9. Root filled teeth are structurally and aesthetically compromised .The loss of tissue at root and crown levels leads to significant biomechanical changes resulting in a high incidence of fractures . Evidence suggests that fracture of root filled teeth and, in consequence, the risk of tooth loss are consid erably higher than that of teeth with vital pulps. Loss of internal tooth structure leads to increased cusp deflection during occlusal function. Deflection is more pronounced in root filled premolars with mesial , occlusal and distal (MOD) cavities, and by doubling the depth of the MOD cavity, the cuspal deflection has been reported to increase. The discoloration of tooth can also result because of incomplete cleaning and shaping of the root canal system, the accumulation of sealer, debris or filling materials left in the chamber. STATUS OF ROOT FILLED TEETH

10. Root filled teeth are more vulnerable to tooth loss than teeth with vital pulps due to the following risk factors: Post-treatment disease following root canal treatment Loss of substantial tooth structure through caries, previous restorative treatment and endodontic procedures Weakening of tooth structure through use of endodontic chemicals (calcium hydroxide, sodium hypochlorite, EDTA, chlorhexidine , alcohol. Dehydration of dentine and transformation of collagen fibre structure (age factor, loss of unbound water from the root canal space and the dentinal tubules in pulpless teeth. Reduction in the level of proprioception , which can lead to uncontrolled occlusal forces. VULNERABLE TO TOOTH LOSS??

11. Additionally, other individual factors, such as gender, occlusion, parafunctions , the material of the antagonist occlusal surface (e.g. implant supported crown), oral hygiene or saliva flow, can influence the prognosis of restored teeth

12. Residual crown structure One of the most important factors influencing the success of a restoration is the amount of remaining supragingival tooth structure. The ferrule effect, described as a band that encircles the perimeter of the residual tooth, has a crucial influence on fracture resistance, especially in decoronated teeth . A properly executed ferrule reduces the incidence of fractures in root filled teeth by reinforcing the external surface of the tooth and dissipating the forces that concentrate at the narrowest circumference of the tooth IMPORTANT FACTORS IN SELECTING RESTORATIVE APPROACH

13. Increasing the ferrule height, particularly on the palatal side, enhances tooth resistance .As little as 1 mm of coronal dentine above the gingival margin during crown preparation will double the fracture resistance of preparations in which the core terminates on a flat surface directly above the margin However, for a more predictable restoration, a properly executed ferrule must be 1.5–2 mm high, especially on the palatal and buccal If destruction of the tooth structure renders a sufficient ferrule unachievable, crown lengthening or orthodontic extrusion should be performed

14. In addition to the amount of remaining coronal tooth structure, the amount of residual root is also significant. A 1 : 1 ratio has been recommended as the minimally acceptable necessary for resisting lateral forces when the periodontium is healthy and the occlusion is controlled. Long-term maintenance of a tooth with an unfavourable crown-to-root ratio, due to the presence of reduced alveolar bone support, might lead to increased mobility and possible periodontal issues RESIDUAL ROOT STRUCTURE:

15. Occlusal load is key to treatment planning for root filled teeth. It is important for the clinician to understand whether the patient has acceptable function or can be classified as belonging to one of three groups of abnormal occlusal attrition: constricted path of closure, occlusal dysfunction or parafunction . In the case of excessive occlusal wear, more destructive loadings are expected, which can predispose compromised root filled teeth to fracture or other types of failure such as post fracture , debonding or composite core fracture. Occlusal forces on one tooth have been reported to be up to 10 times greater than the maximum biting forces distributed in a balanced occlusion.Research has demonstrated that due to progressive cuspal displacement, both time- and load dependent, continuous loading as a result of clenching is more destructive than chewing. FUNCTION AND TOOTH POSITION IN THE ARCH

16. Understanding occlusal problems and planning an appropriate reinforcement of the tooth to be treated may help to reduce future failure risk

17. In order to decrease the magnitude of stresses, it is important to maintain occlusal points of contact with opposing teeth rather than wider areas of occlusal contacts In posterior teeth, fibre posts should be used only for adhesive purposes . A fibre post should be inserted only in the presence of limited coronal dentine with the aim of increasing the amount of bonded dentine .In such cases, the fibre post is luted to increase the adhesive surface area. When full crowns are planned, root filled molars and premolars with limited tissue loss can be restored without posts. Posts could be helpful in those teeth, particularly in premolars, if cusp protection is not provided. In the case of a premolar with severe periodontal loss, a large diameter post seems essential .Severe periodontal bone loss increases the length of the tooth above the bone which significantly increases the risk of tooth fracture.

18. For anterior teeth, the situation is entirely different. Whilst posterior teeth have to support compressive loads, where elasticity is the most important characteristic ,maxillary anterior teeth have to support flexural stresses, where rigidity is the most important characteristic. In anterior teeth, fibre posts are often luted for functional rather than adhesive reasons in order to increase rigidity

19. Improved physical properties of composite resins and the introduction of adhesive systems offer increased potential for the restoration of root filled teeth Mechanical interlocking of resin with peritubular / intertubular dentine and hybrid layer formation is important for the performance of composite resin restorations. Adhesive restorations promote sufficient retention and create an adhesive bridge between the buccal and lingual cusps of the tooth. Composite resins may have the potential to decrease deflection and fracture of cusps under occlusal load . In cases with sufficient remaining tooth structure, especially if intact enamel is present, the use of indirect adhesive restorations without posts provides alternatives to conventional treatment concepts RESTORATION CONCEPTS:

20. Immediate dentine bond strength values do not always correlate with long-term bond stability as degradation throughout the dentine-bonded interface occurs in months Alternatives to cast posts and cores have been developed as fibre posts have an elasticity modulus (E) closer to that of dentine (post = 20 GPa , dentine = 18 GPa ) when compared with prefabricated and cast metal posts (E = 200 GPa ) and ceramic posts (E = 150 GPa ) allowing the absorption and uniform distribution of stresses to the remaining root structure instead of concentrating them . Although prefabricated metal posts have an elastic modulus greater than that of dentine, their behaviour in the root canal is similar to fibre posts contrary to cast posts, which concentrate the stress apically.

21. The use of prefabricated posts and custom-made cores with composite simplifies the restorative procedure, because all steps can be completed chairside , and clinical success can be expected Dual-cure materials provide the most reliable option for achieving good cement polymerization along the post length .Although it is able to polymerize even in the complete absence of light, dual-curing resins develop better mechanical properties when light irradiated

22. Class I: 4 remaining cavity walls (access cavity) If all the axial walls of the cavity remain and have a thickness greater than 1 mm, it is not necessary to insert posts ,provided the tooth is not subjected to undue occlusal forces Classes II and III: 2 or 3 remaining cavity walls Treatment in cases involving the loss of 1 or 2 cavity walls does not necessarily require the insertion of a post, a core followed by a crown is indicated Class IV: 1 remaining cavity wall In cases where only 1 cavity wall remains, the core material has little or no effect on the fracture resistance.Thus post is indicated

23. Class V: No remaining cavity wall In cases of teeth with a high degree of destruction where no cavity wall remains, the insertion of posts appears necessary to provide for core material retention

24. Teeth with minimal tooth loss – coronal restorations Teeth more than 50% of remaining coronal structure - restored with crowns Teeth with 25 to 50 % of remaining tooth structure – restored with non – rigid posts Teeth with less than 25% of remaining tooth structure - to be restored with rigid posts COHEN CLASSIFICATION:

25. Class 0 (no post – composite core build-up) It is possible to take advantage of the anatomy of the pulp chamber, particularly in posterior teeth, to increase adhesive surface area and thus mechanical retention . Unless the destruction of coronal tooth structure is extensive, the pulp chamber and canals provide adequate retention for a core build-up .Given these anatomical features, root filled molars and some anterior teeth may not require posts. However, occlusal relationships should be carefully evaluated in anterior teeth. The possibility of restoring anterior and posterior teeth without the use of a post is an advantage because more tooth substance is preserved and the clinical procedure is easier to achieve .According to Magne et al. (2017), fibre posts are always detrimental to the failure mode, and should be avoided in incisors when a ferrule is present. CLASSIFICATION - Zarrow

26. (a) Temporary restoration in tooth 26 prior to root canal treatment. (b) Tooth 26 following removal of the temporary restoration. (c) Direct reconstruction of tooth 26 without using a post. (d) Final restoration of tooth 26. (e) Final periapical radiograph of tooth 26.

27. Preoperative image of anterior teeth. (b) Tooth 11 and 21. Class 0: >50% of coronal structure remaining without the necessity of fibre post placement. (c) Rubber dam isolation on teeth 11 and 21. (d) Direct restorations on teeth 11 and 21 (e) Final radiographs of teeth 11 and 21.

28. Post placement is recommended in anterior teeth and premolars with compromised tooth structure (<50% structure; Meyenberg 2013, Guldener et al. 2017). Structurally compromised teeth have less than 50% of remaining coronal structure. The placement of a post is indicated when two or fewer walls are present in anterior teeth and premolars . Premolars, unlike molars, often have less tooth substance and smaller pulp chambers to retain a core build-up after root canal treatment .Premolars are also more likely to be subjected to lateral forces during mastication . It has been well documented that the fracture resistance of a tooth depends on the angle of the applied load, with oblique forces being more detrimental .In retrospective clinical reports , premolars were found to be the most frequently fractured teeth. For these reasons, they may require posts more often than molars. CLASS 1 –FIBRE POST

29. Fibre post placement significantly reduced failure risk for root filled premolars. In particular, fibre posts appeared to play a protective role against root fracture . In the case of molars, there is no need for a post, except in cases of totally missing coronal tooth tissue and insufficient pulp chamber surface . Anterior maxillary teeth have to support flexural stresses, and fibre posts are often luted for functional reasons to increase biomechanical properties. Additionally, applying fibre posts with highly fluorescent characteristics is purported to improve the final aesthetic outcome of the restoration.

30. Post placement cannot compensate for total or partial ferrule loss. A fibre post might be placed only after orthodontic or surgical crown lengthening. This decision should be based on the position of the tooth in the arch: for molars, surgical crown lengthening, and for premolars and anteriors , orthodontic extrusion is reported to be preferable . In general, crown lengthening involves a number of significant disadvantages. From the patient’s perspective, these include treatment delay (especially for wound healing or orthodontic extrusion), discomfort and the considerable added cost to an already expensive sequence of procedures. Initiation of final prosthetic treatment should wait at least 3 months and possibly up to 6 months for aesthetically important areas, as the free gingival margin requires a minimum of 3 months to establish its final vertical position CLASS 2 – pre restorative procedures are required, such as crown lengthening or orthodonic extrusion

31. In the anterior zone, surgical crown lengthening of a single tooth has a negative aesthetic impact, particularly in medium and high smiles, making forced tooth eruption via orthodontic extrusion the technique of choice when clinical crown lengthening is needed in isolated teeth in the anterior zone. Biomechanically, the disadvantages include an increased crown-to-root ratio, especially in surgical crown lengthening, and loss of tooth structure resulting from apical relocation of the preparation finish line Surgical crown lengthening inevitably increases the tooth length above the bone level, and the more height of tooth structure above the bone level the greater is the risk of failure of root filled teeth. Orthodontic extrusion is a predictable procedure and combined with a fiberotomy and gingival recontouring allows an optimal relation between the gingiva and the margin of the restoration to be created

32. (a) Tooth 11 Class 2: <50% of structure remaining without ferrule effect. (b) Rapid orthodontic extrusion on tooth 11 with fiberotomy . (c) Image of tooth 11 after orthodontic extrusion. (d) Image of tooth 11 after orthodontic extrusion.

33. Teeth with no ferrule effect may fail and root fracture may result . If a ferrule is not possible (either periodontally or orthodontically ), but the patient still prefers to save the tooth, a gold cast could provide a possible alternative . There are several long-term clinical studies that report high success rates with cast gold posts .From the endodontist’s perspective, cast gold posts are easily removed for retreatment. Silver–palladium alloys can be used as an alternative to gold. These posts are easy to adjust at the chairside , demonstrate acceptable casting accuracies and have properties similar to those of gold casting alloys. With minimal residual tooth structure and absence of a ferrule effect, newer options such as fibre-reinforced posts and cores have a reduced longevity .Under mechanical stress and high temperatures, they undergo greater deformation. Absorption of liquid also has a negative effect on the three-dimensional stability of composite build-ups leading to a tendency towards the development of microleakage caries and post-treatment endodontic disease CLASS 3 – CAST GOLD POST

34. Laboratory studies report a higher frequency of core failure for composite cores than for metal cores. Mechanical qualities of the core material play a more important role, particularly in cases where less residual dentine is present Teeth restored with a cast post and core support a greater compressive load in comparison with fibre posts, but when they fail they fracture in a catastrophic manner . A stiff post, in the case of minimal residual coronal dentine, distributes the forces along the post into the root. Failures caused by fatigue would occur at higher stress levels and after a considerably longer time compared with fibre posts, but the risk of an irreparable root fracture would be increased

35. Other drawbacks to cast posts include the clinical time required, the need for an additional appointment, the need to place a temporary crown ,the higher cost and the risk of bacterial contamination during temporization. After post space preparation, the clinician’s main concern is the small amount of filling material that remains in the root canal. This most apical portion serves as the only barrier against penetration of microorganisms that may cause periapical inflammation . To reduce the risk of contamination of the canal and colonization of bacterial species on the walls of the apical portion of the root canal, it may be preferable to restore the tooth immediately

36. In some cases, treatment and restoration of the compromised root filled tooth can be too complex (no ferrule, retreatment, ortho - or perio -crown lengthening, post, crown) and time-consuming with no predictable outcome CLASS 4 - EXTRACTION

37. Tooth 25 (Class 4) Given the lack of ferrule and poor coronal structure, implant therapy was proposed.

38. Restorations of endodontically treated teeth are designed to (1) protect the remaining tooth from fracture, (2) prevent reinfection of the root canal system, and (3) replace the missing tooth structure. Although the use of a crown built on post and core is a traditional approach, others have advocated the use of direct composite resins for restoring small defects in endodontically treated teeth. More recently, indirect restorations such as overlays or endocrowns made of composite resins or ceramics have also been used. RESTORATIVE MATERIALS AND OPTIONS:

39. When a minimal amount of coronal tooth structure has been lost after endodontic therapy, a direct resin composite restoration may be indicated Unfortunately, the shrinkage that accompanies polymerization of contemporary composite resin remains a significant problem to the long-term success of these restorations. Direct composite restorations have been placed in anterior teeth that have not lost tooth structure beyond the endodontic access preparation. In such cases, the placement of a direct composite restoration offers an immediate sealing of the tooth, which prevents coronal leakage and recontamination of the root canal system with bacteria They are contraindicated when more than a third of coronal tissue has been lost. DIRECT COMPOSITE RESTORATIONS:

40. Ceramic or resin composite onlays and endocrowns can also be used to restore endodontically treated teeth. Whereas overlays incorporate a cusp or cusps by covering the missing tissue, endocrowns combine the post in the canal, the core, and the crown in one component. Both onlays and endocrowns allow for conservation of remaining tooth structure, whereas the alternative would be to completely eliminate cusps and perimeter walls for restoration with a full crown. Ceramics are a material of choice for long-term esthetic indirect restorations because their translucency and light transmission mimic enamel. INDIRECT RESTORATIONS:

41. Onlays , overlays, and endocrowns can also be fabricated from resin composites processed in the laboratory. Using various combinations of light, pressure, and vacuum, these fabrication techniques are claimed to increase the conversion rate of the polymer and consequently the mechanical properties of the restorative material.

42. Endocrown -type restorations are single prostheses fabricated from reinforced ceramics that can be acid etched, indicated for endodontically treated molar teeth that have significant loss of coronal structure. Endocrowns are formed from a monoblock containing the coronal por tion integrated into the apical projection that fills the pulp chamber space, and possibly the root canal entrances. The endocrown is a total porcelain crown fixed to a depulped posterior tooth, which is anchored to the internal portion of the pulp chamber and to the cavity margins, thus obtaining macromechanical retention (provided by the pulpal walls), and microretention (by using adhesive cementation). ENDOCROWNS:

43. Endocrowns are especially indicated in cases of molars with short, obliterated, dilacerated, or fragile roots. They may also be used in situations of excessive loss of coronal dental tissue and limited interocclusal space, in which it is not possible to attain adequate thickness of the ceramic covering on the metal or ceramic substructures.

44. When a significant amount of coronal tooth structure has been lost by caries, restorative procedures, and endodontics , a full crown may be the restoration of choice. To be successful, the crown and crown preparation together must meet five requirements: 1. The ferrule (dentin axial wall height) must be at least 2 to 3 mm. 2. The axial walls must be parallel. 3. The restoration must completely encircle the tooth. 4. The margin must be on solid tooth structure. 5. The crown and crown preparation must not invade the attachment apparatus. FULL CROWNS:

45. Structures subjected to low but repeated forces can appear to fracture suddenly for no apparent reason. This phenomenon, also known as fatigue failure, occurs when a material or a tissue is subjected to cyclic loading. Fatigue may be characterized as a progressive failure phenomenon that proceeds by the initiation and propagation of cracks Fatigue failure of nonvital teeth restored with a post is more catastrophic because it may result in a complete fracture of the root. A post placed into a dentin root will function physically like any structural rod anchored in another material. This means that the forces applied on the post are transmitted to the root dentin with characteristic patterns depending on the modulus of elasticity of both the post and the dentin. If the post has a higher modulus than the dentin, the stress concentration is adjacent to the bottom of the post WHY ROOTS FRACTURE?

46. When the stiffness of the endodontic post is similar to that of dentin, stresses are not concentrated in the dentin adjacent to the apex of the post but rather dissipated by both the coronal and the root dentin

47. Post It is relatively rigid restorative material placed in the root of a nonvital tooth. It extends coronally to anchor the core material which supports the crown. Core Core is the supragingival portion which replaces the missing coronal tooth structure and forms the center of a new restoration. In other words it acts as a miniature crown Post Mainly Serves Two Functions • Helps in retaining the core • Helps in favorable distribution of the stresses through the radicular dentin portion of the teeth to apex POST AND CORE:

48. Retention and the Resistance Form Post retention refers to the ability of post to resist vertical dislodging forces. Post resistance refers to the ability of the post and the tooth to withstand the lateral and rotational forces Factors affecting post retention • Post length • Post diameter • Post taper and design • Luting agent • Luting method • Canal shape • Post position in dental arch. Factors affecting post resistance • Post length • Rigidity • Presence of antirotational features • Presence of ferrule. FACTORS TO BE CONSIDERED WHILE PLANNING A POST

49. Accepted Guidelines for Determining Post Length These include: • Post should be equal to clinical crown length. • Post should be equal to one-half to two-thirds of the length of the remaining root. • Post should end halfway between the crestal bone and the root apex. • Post should be as long as possible without disturbing the apical seal. Since root anatomy varies from tooth to tooth, so post space should be evaluated and planned accordingly.

50. Presently there are three different theories/philosophies regarding the post diameter in literature. these are: The conservationist: It suggests the narrowest diameter that allows the fabrication of a post to the desired length. It allows minimal instrumentation of the canal for post space preparation According to this, teeth with smaller dowels exhibit greater resistance to fracture. The preservationist: It advocates that at least 1 mm of sound dentin should be maintained circumferentially to resist the fracture The proportionist : This advocates that post width should not exceed one-third of the root width at its narrowest dimensions to resist fracture The guideline for determining appropriate diameter of post involves mesiodistal width of the roots. POST DIAMETER

51. FIBER POST

52. CAST POST

53. Advantage of the cast post/core system is that the core is an integral extension of the post, and that the core does not depend on mechanical means for retention on the post. This construction prevents dislodgment of the core from the post and root when minimal tooth structure remains. However, the cast post/core system also has several disadvantages. Valuable tooth structure must be removed to create a path of insertion or withdrawal. Second, the procedure is expensive because two appointments are needed, and laboratory costs may be significant. The laboratory phase is technique sensitive. Metal casting of a pattern with a large core and a small-diameter post can result in porosity in the gold at the post/core interface. Fracture of the metal at this interface under function results in failure of the restoration. Most important, the cast post/core system has a higher clinical rate of root fracture than preformed posts.

54. Studies on cast post retention have shown that the post must fit the prepared root canal as closely as possible to be perfectly retained. When a ferrule is present, custom cast posts and cores exhibit a higher fracture resistance compared to composite cores built on prefabricated metallic posts or carbon posts. Cast posts are also known to exhibit the least amount of retention and are associated with a higher failure rate compared to prefabricated parallel-sided posts.

55. The core replaces carious, fractured, or missing coronal structure and helps to retain the final restoration. Desirable physical characteristics of a core include (1) high compressive and flexural strength, (2) dimensional stability, (3) ease of manipulation, (4) short setting time, and (5) the ability to bond to both tooth and post. Core materials include composite resin, cast metal or ceramic, amalgam, and sometimes glass ionomer materials. The core is anchored to the tooth by extension into the coronal aspect of the canal or through the endodontic post. The importance of retention between the post, the core, and the tooth increases as remaining tooth structure decreases. CORE MATERIALS

56. COMPOSITE RESIN: Composite core materials take a number of strategies to enhance their strength and resistance; metal may be added, filler levels may be greater, or faster setting ionomers may be used. Composite core materials have been shown to exhibit slightly better mechanical values than conventional materials, but improvements are negligible. However, they appear to be superior to silverglass - ionomer cement and amalgam. The advantages of composite core resins are adhesive bonding to tooth structure and many posts, ease of manipulation, rapid setting, and translucent or highly opaque formulations. Composite cores have been shown to protect the strength of all-ceramic crowns equally to amalgam cores.

57. Bond strength of composite cores to dentin depends on a complete curing of the resin materials, so dentin bonding agents must be chemically compatible with composite core materials. Self-cure composite resins require self-cure adhesives and are mostly incompatible with lightactive cure adhesives. However, no adhesive has been shown to completely eliminate microleakage at the margins of the restoration. A degradation of the resin core or the marginal integrity of the crown can result in invasion of oral fluids. Therefore, as with all buildup materials for decimated teeth, more than 2 mm of sound tooth structure should remain at the margin for optimal composite resin core function.

58. Composite core materials can be used in association with metallic, fiber , or zirconia posts. This is frequently observed in the presence of structurally compromised teeth. They may provide some protection from root fracture in teeth restored with metal posts compared with amalgam or gold cores. Loosening of the post, core, and crown with composite core can occur, but composite cores have been shown to fail more favorably than amalgam or gold

59. Dental amalgam is a traditional core buildup material with a long history of clinical success. Although there are many variations in the alloy’s composition, more recent formulations have high compressive strength (400 MPa after 24 hours), high tensile strength, and a high modulus of elasticity. High-copper alloys tend to be stiffer (60 GPa ) than lowcopper alloys. Amalgam can be used with or without a post. With the amalcore technique, amalgam is compacted into the pulp chamber and 2 to 3 mm coronally of each canal. The following criteria were considered for the application of this technique: the remaining pulp chamber should be of sufficient width and depth to provide adequate bulk and retention of the amalgam restoration, and an adequate dentin thickness around the pulp chamber was required for the tooth-restoration continuum rigidity and strength. AMALGAM CORE:

60. The fracture resistance of the amalgam coronal- radicular restoration with four or more millimeters of chamber wall was shown to be adequate, although the extension into the root canal space had little influence. Amalgam can also be used in combination with a prefabricated metallic post when the retention offered by the remaining coronal tissue needs to be increased. Amalgam cores are highly retentive when used with a preformed metal post in posterior teeth; they require more force to dislodge than cast posts and cores. Significant disadvantages of amalgam cores are the “ nonadhesive nature” of the material, the potential for corrosion, and subsequent discoloration of the gingiva or dentin. Amalgam use is declining worldwide because of legislative, safety, and environmental issues.

61. Glass ionomer and resin-modified glass ionomer cements are adhesive materials useful for small buildups or to fill undercuts in prepared teeth. The rationale for using glass ionomer materials is based on their cariostatic effect resulting from fluoride release. However, their low strength and fracture toughness result in brittleness, which contraindicates the use of glass ionomer buildups in thin anterior teeth or to replace unsupported cusps. They may be indicated in posterior teeth in which (1) a bulk of core material is possible, (2) significant sound dentin remains, and (3) caries control is indicated. GLASS IONOMER AND MODIFIED GLASS IONOMER CORE:

62. Resin-modified glass ionomer materials are a combination of glass ionomer and composite resin technologies and have properties of both materials. Resin-modified glass ionomers have moderate strength, greater than glass ionomers but less than composite resins. As a core material, they are adequate for moderate-sized buildups , but hygroscopic expansion can cause fracture of ceramic crowns and fragilized roots. The bond to dentin is close to that of dentin-bonded composite resin and significantly higher than traditional glass ionomers . Today, resin composites have replaced glass ionomer materials for core fabrication.

63. Interim restorations are those that provide structural integrity to the tooth while the tooth is undergoing endodontic treatment. An interim restoration is expected to remain in situ providing a good seal until the endodontic treatment is completed and a definitive restoration can be provided. These interim restorations should help provide support for weakened cusps preventing fracture between appointments as well as a good coronal seal. Where the tooth’s coronal structure is severely compromised or a crack is suspected, copper rings or orthodontic bands may act as interim restorations .Some have advocated the use of stainless steel orthodontic bands as interim restorations citing reduced cusp flexure often in premolar teeth and recommended that if one or more cusps are missing a band should be placed. INTERIM RESTORATIONS:

64. When metal bands are used, it is prudent to use chemically curing cements as well as ensure that the margins allow optimum oral hygiene and that the restoration is in keeping with the occlusion. It is not always possible to use metal bands around teeth in smile line such as premolars due to aesthetic considerations, although using a tooth coloured material to mask the buccal surface of the metal band have been described Using copper bands Using orthodontic bands

65. Temporary restorations are those that occupy the access cavity and provide a good coronal seal between appointments. The overriding requirement is that they should provide an effective and durable seal between appointments. Other desirable properties include ease of removal at the next appointment, inexpensive and having inferior aesthetic properties, thus making it more obvious at the time of removal so that additional tooth structure is not removed at the subsequent re-entry appointment. An array of potential materials are available, including zinc-oxide/ calcium-sulphate-based materials ( Cavit , Coltosol – Coltene Whaldent , Mahwah, NJ, USA), zinc-oxide-based reinforced intermediate restorative materials (IRM – Dentsply Caulk, Milford, USA), GIC, resin modified GIC (RMGIC), reinforced GIC ( Ketac Fil and Ketac Silver – 3M ESPE, Seefeld , Germany), composite (TERM – Dentsply Maillefer Switzerland), amalgam TEMPORARY RESTORATIONS:

66. The combination of Cavit and IRM have been recommended for various reasons including cost, ease of use and the fact that used together better dentine adaptation was seen when compared with IRM alone Cavit and IRM provided as good a seal as the original restoration when placed in access cavities through interim IRM restorations, amalgam fillings and gold or metal ceramic crowns

67. The definitive restoration should be placed as soon as possible after completion of root canal treatment Chugal (2007) found that 40% of teeth with temporary restorations failed when compared with 21% failure of those with definitive restorations Chugal found no difference in endodontic failure rates between crowns, amalgams or composites Residual endodontic sealers can also adversely affect bonding and a total etch procedure is recommended. GIC must be sticky to form a bond with tooth structure, yet also be packed down into the canal orifices. Composite can also be used, although air blows easily occur and adequate drying and curing to the depth of the canal orifice may be difficult to achieve DEFINITIVE RESTORATIONS:

68. Anterior teeth are loaded non-axially. Posterior teeth are loaded occlusally and therefore axially. The options for anterior teeth are direct composite restorations or replacement crowns with or without a post. The options for premolars is similar although these teeth are often loaded axially and may be loaded horizontally if they are involved in lateral guidance and cuspal coverage should be considered where marginal ridges are compromised. Molars can be restored with simple composite or amalgam restorations in the access cavity if the marginal ridges are intact or complex amalgams/composite providing cuspal coverage, onlays /overlays in gold (Fig. 5), indirect composite or porcelain, or full coverage crowns in metal, metal ceramic or all ceramic if marginal ridges are compromised.

69. When crowns are considered, the need for a ferrule is mandatory for a more predictable restoration Ferrules must be on sound tooth structure (not the core) and axial walls must be parallel and minimum thickness of 1 mm. The longer the ferrule the better with minimum of 1 mm height suggested by some. Ferrules should not invade periodontal attachment and therefore must be more than 0.4 mm from the base of the gingival crevice, although the depth of the gingival crevice may vary from patient to patient with the average biological width being approximately 2 mm

70. Nayyar cores are useful in posterior teeth as amalgam can be packed 2-3 mm into the canal orifice avoiding the need for a post and providing an orifice seal. It is also possible to place 3 mm of IRM or Cavit in the canal before the placement of an amalgam restoration. Bonded amalgam restorations have been shown to have strength almost comparative to unrestored teeth, and strengths higher than bonded composite restorations although no statistical significance was found between the two groups. Composite used for cuspal coverage in endodontically treated premolars has been shown to give fracture resistance similar to untreated teeth and higher fracture resistance compared to intracoronal composite restorations.

71. More recent studies on root filled teeth have also shown direct restorations to have lower ten-year survival rates than crowns (81% for crowns vs. 63% for amalgam, composite, cements). it was concluded that endodontically treated teeth were six times more likely to be lost if a crown was not provided and the outcomes were better if two proximal contacts existed Where a crown was not provided, tooth extractions were 4.8 times higher in anteriors , 5.8 times higher in premolars and 6.2 times higher in molars compared to teeth with crowns. A statistically significant difference (p <0.001) was found between teeth with a crown and those without. It must be remembered that endodontically treated teeth have an endodontic access cavity and any further preparation for an extracoronal restoration may leave a very thin band of dentine, prone to fracture. Minimal preparation restorations are ideal to preserve tooth structure .

72. Gold onlays with a 1-2 mm chamfer margin on worn teeth have shown a survival of 89% at five years when 50 micron alumina abraded copper containing type III cast gold alloy was used and cemented with Panavia (Kuraray Noritake Dental Inc. Okayama, Japan) Not enough evidence exists yet for the use of these restorations in the outcome of endodontically treated teeth.

73. Fracture resistance studies have shown that while gold onlays had improved fracture resistance when compared to glass ceramic and resin composite onlays , all onlay systems improve the fracture resistance when compared to unrestored teeth. Indirect composite onlays have been shown to have good medium term survival (96% at 2-4years) in posterior teeth

74. Dentists appear to make the decision for extracting a tooth on the basis of multiple risk factors including endodontic and periodontal criteria, remaining tooth structure, restorability with core build-ups and post and core, extent of previous restorations as well as the perceived strategic value of a tooth within the dentition ENDODONTICS OR IMPLANTS:

75. A review conducted by Doyle et al. in 2006 highlighted that the success rates between a RCT tooth and an implant-supported single crown (ISC) is quite similar . The success rates were 94% (RCT) and 96% ( ISC) at five years, while 97% (RCT) and 94% (ISC) at six years .The failure rates for each treatment were consistent at 6%. Complications were found to be 18% for implants with peri-implantitis as the common failure and 4% for endodontically treated teeth with persistent apical periodontitis or re-treatment. Because of similar outcomes, deciding whether to restore a tooth with root canal therapy or extraction and replacing it with an implant or another type of prosthesis must be based on multiple factors as opposed to treatment success alone. Root canal–treated (RCT) teeth and implant success rates

76. In RCT teeth, complications were mainly related to endodontic retreatment, or persistent apical periodontitis (AP) as assessed from radiographs, whilst in implants, several technical problems occurred or surgical interventions were required to treat peri-implantitis

77. In teeth without a periapical radiolucency , initial RCT secured a success rate of 96% after 8–10 years, whilst healing was reduced to 86% in cases with pulp necrosis and periapical radiolucency In a study evaluating the reasons for failure of RCT teeth, prosthetic reasons (crown fracture, root fracture at the level of a post, traumatic fracture) dominated and explained almost 60% of the failures; 32% failed due to periodontal reasons, whilst pure endodontic failures (vertical root fracture, instrumentation failure, root resorption ) were rare and accounted for less than 10% Eight years after initial nonsurgical root canal treatment, 96% of all teeth (almost 1.5 million) were retained without any untoward event; 0.4% required nonsurgical retreatment, in 0.6% apical surgery was performed, and 2.9% were extracted. Extractions occurred mainly within 3 years from completion of the RCT, and affectedprimarily those teeth without full coronal coverage

78. Complications and failures, however, occur either prior to implant osseointegration (early implant loss) or after initially successful osseointegration (late implant loss) and disease manifestation may necessitate several years or even decades of function According to a review analyzing longterm results of fixed implant restorations, 39% of all patients were affected by complications or failures during a 5-year observation period ( Pjetursson et al. 2004a). The 10-year survival rates reached 93% (implant-FDP) and 94% (single tooth implants, STI) on an implant level, whilst survival of the implant restorations varied between 87% (implant-FDP) and 90% for the ISC SUCCESS AND SURVIVAL OF IMPLANTS

79. CONTAINDICATIONS AND RISK FACTORS FOR IMPLANT FAILURES

80. According to the view of the specialists, good long-term prognosis and greater flexibility in clinical management indicate that RCT and even retreatment should be performed first in most instances unless the tooth is judged to be untreatable when implants are considered. As soon as other compromising factors or risks exist, such as insufficient coronal tooth structure and/ or moderate to severe periodontal involvement, the time and cost efforts engaged with the RCT may be questionable. When deciding if an impaired tooth with a questionable prognosis is maintained or extracted and possibly replaced by an implant, several different aspects have to be taken into account. These aspects comprise site-specific factors, the entire oral situation and patient-related factors RESTORATIVE ASPECTS:

81. Multiple factors need to be evaluated such as site-specific and patient-related factors in making an overall decision. Each case should be evaluated individually with thorough treatment planning. The evidence presented clearly indicates that the extraction of a natural tooth without any consideration of its health will result in a failure to recognize risks and complications that may possibly arise with implant treatment. Multiple risk factors tend to indicate tooth extraction and possible replacement by an implant, particularly in the posterior region when aesthetics are not crucial. Priority should always be given to preserving natural dentition to the highest possible function, as this is in the primary goal in periodontal therapy.

82. Restoration of the root-filled tooth Nessrin A Taha , Harold H Messer Prim Dent J . 2016; 5(2): 29-35 A new classification system for the restoration of root filled teeth M. Zarow1, A. Ramırez-Sebastia2 , G. Paolone3 , J. de Ribot Porta2, J. Mora2, J. Espona2, F. Duran-Sindreu2 & M. Roig2 International Endodontic Journal Restoration of the root canal treated tooth S. Eliyas ,*1 J. Jalili2 and N. Martin3 BRITISH DENTAL JOURNAL VOLUME 218 NO. 2 JAN 23 2015 Endodontics or implants? A review of decisive criteria and guidelines for single tooth restorations and full arch reconstructions N. U. Zitzmann, G. Krastl, H. Hecker, C. Walter & R. Weiger International Endodontic Journal , 42, 757–774, 2009 REFERRENCES:

83. Should retention of a tooth be an important goal of dentistry? How do you decide whether to retain and restore a tooth requiring endodontic treatment or to extract and if possible replace the tooth? Jessica J. Zachar , BDSc , fifth-year student, Aust Endod J 2015; 41: 2–6 Restoring endodontically treated teeth with posts and cores—A review Ingrid Peroz , Dr Med Dent1/Felix Blankenstein , Dr Med Dent1/ Klaus-Peter Lange, Prof Dr Med Dent2/Michael Naumann , Dr Med Dent3 VOLUME 36 • NUMBER 9 • OCTOBER 2005 Ingle 6 th edition Cohen south asian first edition

84. THANK YOU