Restoration of endodontically treated teeth: criteria and technique considerations

Q U I N T E S S E N C E I N T E R N AT I O N A L ENDODONTICS Richard D. Trushkowsky Restoration of endodontically treated teeth: Criteria and technique considerations Richard D. Trushkowsky, DDS1 The restoration of endodontically treated teeth is often required and may represent a challenge as there is no consensus on ideal treatment. The failure of endodontically treated teeth is usually not a consequence of endodontic treatment, but inadequate restorative therapy or periodontal reasons. Prior to the initiation of endodontic treatment the restorability, occlusal function, periodontal health, biologic width, and crown-to-root ratio need to be assessed. If acceptable, the appropriate technique, material, and type of restoration to re- store function need to be considered. Posts are used to provide retention for the core material and to replace missing tooth structure. The residual amount of tooth structure will determine its stability for restoration. The creation of adequate ferrule (approaching 2 mm circumferentially is ideal) minimizes the damaging effects of lateral and rotational forces on the restoration and post. (Quintessence Int 2014;45:557–567; doi: 10.3290/j.qi.a31964) Key words: core, endodontically treated tooth, post Caries and trauma are the most frequent causes of irreversible pulp damage resulting in root canal therapy. The restoration of these endodontically treated teeth is often required and may represent a challenge as there is no consensus on ideal treatment. However, endodontically treated teeth have been reported to have a reduced survival rate compared to vital teeth.1 The failure of endodontically treated teeth is usually not a consequence of endodontic treatment, but inadequate restorative therapy or periodontal reasons.2 Excessive removal of tooth structure during mechanical instrumentation of the root canal system, mechanical pressures during obturation, lack of cuspal protection, and large restorations can 1 Clinical Associate Professor, Associate Director, The Advanced Program for International Dentists in Esthetic Dentistry, New York University College of Dentistry, New York, USA. Correspondence: Dr Richard D. Trushkowsky, The Advanced Program for International Dentists in Esthetic Dentistry, New York University College of Dentistry, 345 E 24th St, New York, NY 10010, USA. Email: rt587@ nyu.edu VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 weaken the tooth. The prognosis of endodontically treated teeth is contingent not only on apical seal but also on the coronal sealing of the canal thereby reducing leakage of oral fluids and bacteria into the periradicular areas (Fig 1).3 The neurosensory response apparatus is impaired with the removal of the pulpal tissue, which may result in decreased protection of the endodontically bacteria Fig 1 The coronal seal is important to prevent microleakage. Decementation and micromovement produce microleakage. Where there is presumed shrinkage, the bacteria can infiltrate, causing secondary decay. 557 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky treated tooth during mastication.4 Prior to the initiation of endodontic treatment the restorability, occlusal function, periodontal health, biologic width, and crown-toroot ratio need to be assessed. If acceptable, the appropriate technique, material, and type of restoration to restore function need to be considered.5 An ideal permanent restoration should restore esthetics and function, and protect the endodontically weakened tooth.6 • Class V teeth have no remaining walls, and a post will be required to provide retention for core material. A ferrule, which is characterized by a 360-degree metal crown collar surrounding parallel walls of dentin and extending coronal to the shoulder of the preparation, would greatly increase the fracture resistance of the tooth.14 If a ferrule cannot be obtained, surgical crown lengthening or forced eruption may be required. INDICATIONS FOR A POST The indications for a post have been modified in recent years based on the advantages of adhesive restorations, which may obviate the need for posts.7 Posts are used to provide retention for the core material and to replace missing tooth structure. The residual amount of tooth structure will determine its stability for restoration. Preparation for pulpal access diminishes mechanical strength by about 5%, but a mesio-occlusal-distal (MOD) cavity will result in a 63% reduction in strength.7 The importance of the marginal ridge was specified by Strand et al.8 The loss of tooth vitality does not result in a substantial change in moisture content compared to vital teeth.9 Unfortunately, the degree of remaining tooth structure left to require a post has not been delineated. Preoz et al7 established five classes depending on the number of axial cavity walls remaining: • Class 1 teeth have four remaining cavity walls, with a thickness greater than 1 mm. In this case, it was felt a post is not necessary and any final restoration can be utilized.10 • Class II and Class III have two or three remaining cavity walls. These teeth can possibly be restored without a post. The use of an adhesive core can provide adequate fracture resistance without the need for a post.11 • Class IV teeth have one remaining wall, and the core material will provide minimal or no effect on the fracture resistance of the endodontically treated tooth.12 The use of the tooth as an abutment for a fixed or removable partial denture will result in reduced fracture resistance as a consequence of crown preparation.13 558 INDICATIONS FOR A CROWN Baba and Goodacre15 suggest that most endodontically treated posterior teeth require a crown for longevity. However, although crowns improve the success of posterior teeth, this was not demonstrated for anterior teeth.16 Anterior teeth with minimal loss of tooth structure can be conservatively restored with composite in the lingual access opening and no post.17 A post provides minimal or no benefit for a structurally sound tooth.18 Many classical indications for the use of a crown have also been questioned.19 Unfortunately, the literature is equivocal as to the requirement for full coverage, although cuspal coverage is often recommended. Rocca and Krejci20 report that currently available adhesive techniques permit the use of direct composites and an endocrown (a circular butt-joint margin and a central retention cavity inside the pulp chamber, lacking intraradicular anchorage). The basis of this technique is to use the surface available in the pulpal chamber to assume the stability and retention of the restoration through adhesive procedures. The endocrowns provide full occlusal coverage and the use of the pulp chamber increases the available surfaces for adhesion. A variety of materials can be used including feldspathic porcelain, glass ceramic (eg, IPS e.max, Ivoclar Vivadent), or CAD/CAM blocks of either ceramic or composite or combinations of the two (Lava Ultimate Restorative, 3M ESPE). Molars can more readily be utilized in this fashion. Premolars are more in danger if canine guidance is absent as group function may permit a combination of both axial and shear forces on the premolar cusps. VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky Fig 2 Fig 3 A wide variety of post shapes and materials is available. An anatomic glass fiber post conforms to the root shape. DESIGN AND TYPE OF POSTS Posts can be active (most retentive, eg, ParaPost XT, Coltène Whaledent; Flexipost, Essential Dental Systems), passive parallel or passive tapered (least retentive, eg, ParaPost Taper Lux, Coltène Whaledent), double tapered (DT Light-Post Illusion X-RO, Bisco), or parallel tapered (TENAX® Fiber White, Coltène Whaledent; ParaPostXP No-Ox, Coltène Whaledent). Regarding post shape, parallel-sided posts provide better retention, less stress formation, and increased fracture resistance than tapered posts.21 Regarding surface design, serrated posts provide better retention than smooth-sided posts, and threaded posts provide even better retention (Fig 2).22 An increase in post length has also been shown to be beneficial, but an apical seal of approximately 5 mm of gutta-percha is required.23 Excessive length can also become detrimental as the dentin in the apical third is very thin and perforation or increasing root fracture can become a possibility. The length of custom metal posts is usually recommended as two-thirds to three-quarters VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Fig 4 A glass fiber post provides a degree of light conduction into the canal and allows more complete polymerization. (Courtesy of Coltène Whaledent.) of root length, and equal to or more than the length of the crown to be fabricated.24 Posts can be metallic (either custom cast posts or prefabricated) or fiber (custom [Fig 3] or prefabricated). Since their introduction in 1990,25 fiber posts have changed in shape and mechanical physical properties. Initially the posts were quartz or carbon fiber but now most are glass fibers, possessing a translucency that makes an esthetic restoration more easily obtainable. They also allow some degree of light transmission so that dual-cure cement can be used (Fig 4),26 as the translucency helps to provide adequate polymerization of dual-cure cements. However, the light intensity at the apical portion may be inadequate because of the distance from the light source and the light-scattering nature of the resin cement and the post. The quantity of light that is absorbed, reflected, and transmitted seems to be related to the resin matrix, the fiber composition of each post, and the intensity of the light source.27 Post shapes have been modified from a retentive shape to cylindrical or oval, which is more anatomical. Posts of this type provide better adaptation and remove less remaining root dentin.28 559 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky Fractured Post and Crown Fractured root Fractured Post and Crown Vector of Force Fractured root Vector of Force Vector of Force a Vector of Force b Figs 5a and 5b Failure can be more catastrophic with a metal post than a glass fiber post. (a) Potential fracture location with glass fiber–reinforced composite posts. (b) Potential fracture location with metal posts. parallel post space 1+ mm 1+ mm Teeth restored with metal posts many times fail catastrophically with root fracture (Fig 5). The most frequent cause of failure in teeth reconstructed with fiber posts is not root fracture but debonding of the post, which can occur at the post-cement interface and/or between cement and root dentin.29 Boschian et al30 underscored the effect of elastic modulus of the post material on stresses transferred to tooth structures as an important factor. They reported that post materials that have a higher elastic modulus than dentin are capable of causing dangerous and nonhomogenous stresses in root dentin. The authors concluded that the arrangement that best preserves the integrity of the root, post, and core unit is when fiber posts are used for restoration. Unlike cast posts, post 560 narrow walls <1 mm Fig 6 An ideal post should fit the morphology of the canal and not remove unnecessary tooth structure. length, post diameter, or taper of the post do not meaningfully affect the adhesion and the long-term behavior of glass fiber posts. However, the low modulus of elasticity of fiber posts (which is similar to dentin) creates a root strain similar to that of an intact tooth at 8 to 10 mm, and a shorter length (5 mm) causes reduction of the absorptive forces of the post system. This creates a transfer of forces to the less rigid dentin in the cervical area and possible fracture.31 In addition, glass fiber posts are biocompatible and their esthetic appearance does not cause discoloration at the gingival margin.32 Endodontically treated teeth that are used as abutments for fixed partial dentures (FPDs) have a higher failure rate than vital abutment teeth.33 The FPD can consist of a short span, long span, or be cantilevered. VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky These abutment teeth undergo both horizontal and torqueing forces when used for FPDs or removable partial dentures (RPDs).33,34 CEMENTS AND CEMENTATION The main reason for failure of glass fiber posts is debonding, which occurs mainly because of the difficulties in achieving proper adhesion to intraradicular dentin and to the post.35 Posts cemented with composite cements exhibit enhanced retention, and the roots are more fracture-resistant because of more uniform stress distribution.36 Dual-cured resin cements and adhesive systems are usually suggested as merging self-curing and lightcuring. Despite the use of two initiation systems by some products, adequate light transmission is required to get light activation and the best results.37 Self-adhesive cements have been promoted as being simpler and less technique-sensitive, but some of them demineralize the dentin, and the depth of resin penetration is not equivalent. In addition, residual acidic monomers may be present, reducing adhesion capabilities.38 However, some studies favor the use of self-adhesive cements.39 The retention of glass fiber posts that had been pretreated with silane has been reported to be higher compared with posts that were not pretreated or that were pretreated with other products.40 However, fiber-reinforced posts that have highly cross-linked polymers in the matrix do not have functional groups that can chemically interact with silane. Microabrasion with 50-mm aluminum oxide at 2.8 bar (0.28 MPa) pressure for 5 seconds has also been shown to increase surface area and minimize damage.41 Another problem is the bond to intraradicular dentin, as it is variable. The number of tubules declines toward the apical region, and the ratio between the peritubular and intertubular dentin changes significantly from the apical to the coronal third.42 An ideal adaptation of the post is a crucial factor for an adequate cement thickness, as the clinical success of a tooth rebuilt with a glass fiber post is given mainly by its ability to limit root dentin removal and to fit to it. VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Fig 7 Fiber post with surrounding Quartz Splint Unidirectional. (Courtesy of RTD Dental.) Fig 8 Fiber post with accessory Fibercones. (Courtesy of RTD Dental.) The availability of fiber posts with different shapes reflects the different morphologies of human root canals that they need to fit (Fig 6). Root canal crosssectional shapes can be classified as round, oval, long oval, flattened, or irregular. Among these, the oval and long oval shapes are the most common. Recently, a new type of fiber post and fiber mesh (Fibercone, a small, slender fiber post, and pre-cut sections of Quartz Splint Unidirectional; RTD) that address the problem of restoring wide, oval, flared, or otherwise large or irregularly shaped root treatment spaces in combination with a master fiber post and any resin cement and core composite, has been introduced to avoid excessive removal of residual dentin and to obtain a more uniform cement layer (Figs 7 and 8).43 If the post does not fit well, there will be an excessively thick layer of cement, especially at the coronal level, where air bubbles or voids could be incorporated, predisposing to debonding. Many authors have investigated the influence of cement thickness on the bond strength of fiber posts. As yet, there is no agreement in the literature on the ideal cement thickness or on the influence of voids (gaps, air bubbles, emptiness within the cement layer, or at the post-cement and cavity-wall–cement interface) on the bond strength of fiber posts and their clinical consequence. 561 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky The application of NaOCl could act as a polymerization inhibitor of resin materials due to the formation of an oxygen-enriched dentin surface.44 However, NaOCl is the most commonly used irrigant because it has the ability to remove the smear layer, which is created on the dentin surface during the post space preparation. The removal of the smear layer, which contains organic and inorganic components, sealer and gutta-percha remnants, microorganisms, and infectious deteriorated dentin is necessary for the penetration of the adhesive system and resin cement into the dentin tubules.45 Ideally the root canal should be irrigated with chlorhexidine (eg, Endo-CHX, Essential Dental Systems) or sterile saline solution before post cementation in order to eliminate the negative effect of NaOCl on the adhesive bond to dentin. The smear layer, consisting of sealer and gutta-percha remnants, is plasticized by the heat of the drill bur during the post space preparation, and can act as insulation against any kind of adhesive material intended to bond to the root canal dentin.46 In addition, this smear layer can also reduce the chemical action of orthophosphoric acid to provide an ideal bonding substrate. GuttaFlow (Coltène Whaledent) can be used to fill the canal, and this contains a silicone that can also make the smear layer more resistant to acid etching.47 FERRULE A dental ferrule is an encompassing band of cast metal around the coronal surface of the tooth. The ferrule may resist stresses such as functional lever forces, the wedging effect of tapered posts, and the lateral forces exerted during the post insertion.48 Some clinicians interpret the ferrule as the amount of dentin above the finish line but it is the definite bracing of the crown encompassing the tooth structure that establishes the ferrule. Eissmann and Radke49 discussed the importance of the ferrule effect for preventing tooth fracture and recommended a ferrule height of at least 2 mm. Libman and Nicholls50 compared the effect of different ferrule heights (0.5, 1.0, 1.5, and 2.0 mm) of a maxillary incisor under fatigue loading. They found the minimum 1.5-mm ferrule height meaningfully improved crown 562 resistance. This in vitro study tested the breakage of cement seal (which can lead to secondary caries, crown dislodgement, or tooth fracture) in a clinically pertinent manner using dynamic repetitive loading.50 In addition, ferrule effect increases the post/core ratio and prevents the luting cement from being washed away, in turn improving post retention. Hsu et al51 demonstrated that the total bonding area between dowel-core and tooth structure meaningfully influenced crown resistance. It was demonstrated that the type of cement used for both the dowel-core and crown can significantly affect the durability of the restoration and the tooth.51 Unfortunately, many of these studies were done on maxillary central incisors and may not pertain to posterior teeth. There are many factors that have to be considered in the effectiveness of the ferrule: ferrule height, ferrule width, number of walls, ferrule location, type of tooth, lateral loads, type of post, and type of core material.52 Ferrule height Most studies have indicated that a ferrule height of 1.5 to 2 mm of vertical tooth structure would be the most beneficial.53 The crown should encompass at least 2 mm past the tooth core connection to achieve the most protective ferrule effect.54 Ferrule width Esthetic restorations often require fairly aggressive preparations at the gingival margin and sometimes buccal defects such as abfraction may compromise the buccal dentin wall. Generally it has been accepted that the walls are considered too thin if they are less than 1 mm in thickness, and would negate the ferrule effect. Therefore crown lengthening on teeth with conical roots may add dentin height but the dentin width at the margin may not be adequate. Number of walls and ferrule location A circumferential ferrule would be optimal but caries may affect the interproximal areas and abrasion or erosion the buccal walls. A crown preparation will further reduce the wall thickness and only a partial ferrule will remain. Al-Wahadni and Gutteridge55 found having a VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky 3-mm ferrule on the buccal aspect was better than having no ferrule at all. It created a significantly higher resistance to fracture.55 Ng et al56 proposed that the location of the sound tooth structure to resist occlusal forces is more significant than having a circumferential dentin wall. The authors demonstrated that the presence of a palatal wall allowed resistance of forces applied in function to a maxillary incisor. A maxillary incisor with three walls present but no palatal wall demonstrated poor fracture resistance.56 This may indicate that a partial ferrule provides a degree of fracture resistance, although it is not as ideal as a 360-degree, 2-mm ferrule. TYPE OF TOOTH AND DIRECTION OF LOAD Anterior teeth are loaded non-axially while posterior teeth usually are loaded in an occluso-gingival direction. Lateral forces usually are more detrimental to the tooth restoration interface. The restoration of anterior or posterior teeth may require an altered approach. Anterior teeth with a deep overbite and parafunction are at a higher risk of failure. Posterior teeth with different occlusal arrangements and cuspal heights affect the direction and nature of the load applied to each tooth. Teeth that are in group function with long maxillary buccal cusps produce higher lateral forces than if there was canine guidance. As the cusps wear, lateral forces may be converted to vertical trajectories.57 TYPE OF POST Clear guidelines for the selection of the type of post are lacking.7 However, the existence of a 1.5- to 2-mm ferrule of sound coronal tooth structure is more important than the post itself.58 Cast posts have been used for many years for the support of the final restoration. However, in recent years this type of restoration has been progressively replaced by composite cores with a glass fiber post or metal post.59 Fiber-reinforced posts have found favorable use, notwithstanding their significantly lower bearing values. Their performance is VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 favorable because this type of post is shielding the remaining tooth structure by failing in a more noncatastrophic form (Fig 5). FIBER POST CEMENTATION AND CORE BUILDUP The literature on when to prepare the post space is inconclusive. Gutta-percha or Resilon (eg, Epiphany, Pentron Clinical Technologies) are removed with heat (eg, System B, Sybron Endo) or with rotary instruments.60 Ideally there should be minimal enlargement of the canal past that incurred during endodontic instrumentation. 1. Select prefabricated post suitable for both the tooth and the restoration being utilized. 2. Prepare the coronal residual tooth structure to accommodate the crown with a minimal wall thickness ≥ 1.5 mm and determine if the post is going to be fabricated by direct or indirect means depending on residual tooth structure. 3. Determine the prerequisite preparation depth and mark this length on the corresponding instruments with silicone stoppers. a. The remaining root canal filling from the post terminus to the apex should be no shorter than 4 mm. b. The length of the post within the canal should be at least equal to coronal length of the final restoration. 4. Remove the root canal filling with a Gates-Glidden or Peeso reamer to the desired length. 5. Prepare the post space to the same depth with the appropriate size drill that corresponds to the size post selected. 6. If necessary apply antirotation protection. 7. Rinse the canal and flush with alcohol. 8. Clean the canal with a CanalBrush (Coltène Whaledent) or similar. 9. Check proper fit of the post 10. Shorten the post as necessary with rotary diamonds. 11. Fiber posts should be cleaned with phosphoric acid for 60 seconds then washed and dried. Metal posts 563 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky Fig 9 After etching with phosphoric acid, the canal should be rinsed and dried with high volume suction. (Courtesy of Premier Dental.) Fig 10 A dual-cured bonding agent should be mixed and placed in the canal. (Courtesy of Premier Dental.) Fig 11 The bonding agent is placed in the canal with a cylindrical microbrush. (Courtesy of Premier Dental.) Fig 12 An endo-tip allows the dual cure cement to be placed in the canal without bubble formation if it is kept immersed. The post is placed immediately. (Courtesy of 3M ESPE.) Fig 13 An automix syringe with two different diameter tips expedites both placement of cement into the canal and the core build-up. The cement is then allowed to self-cure or it can be light-cured for 20 seconds. (Courtesy of Premier Dental.) Fig 14 The final core build is cured for 40 seconds. (Courtesy of Premier Dental.) can be micro-etched and a metal primer applied (eg, Alloy Primer, Kuraray). 12. Some fiber posts benefit from silane application (eg, Monobond-S, Ivoclar Vivadent) for 60 seconds. 13. Air dry and do not touch with fingers. 14. Adhesive cementation of the post can be with either a dual- or self-curing luting composite (eg, Multilink Automix or Variolink II, Ivoclar Vivadent). A total etch, self-etch, or an adhesive cement can be used (eg, RelyX Ultimate Adhesive Resin Cement, 3M ESPE). If a total etch is used, place 37% phosphoric acid in the canal for 10 to 15 seconds. Irrigate with water in an irrigating syringe, then use the high volume vacuum and a paper point to dry the canal (Fig 9). 15. Use the specific instructions of the cementation system. If an adhesive is used (Fig 10), a paper point 564 or preferably an endo brush is used to place the dual-cured adhesive in the canal and remove excess (longer cylindrical shape) (Fig 11). 16. If available, use an endo-tip to place the cement into the canal (Fig 12). Immediately place the fitted post. 17. If a dual-cure luting cement is used, polymerize for 20 seconds from the occlusal aspect of the post and as near to the post as possible, or wait 5 minutes to allow self-curing initially and then light cure (Fig 13). 18. Ideally the core can be built up using the same luting material. After proper contour is achieved of the dual-cure material, light cure for a final 40 seconds (Fig 14). A highly filled core such as MultiCore Flow or MultiCore HB (Ivoclar Vivadent) can be sculpted as it is placed. 19. The tooth is then prepared for the final restoration located on 2 to 3 mm of natural tooth structure. VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky 11 mm 9 mm 7 mm 1.5 mm (min.) a 5 mm b Fig 16 A plastic post with GC Pattern Resin is used to shape the post and core. 11 mm 9 mm 7 mm c d Fig 17 The pattern is removed from the mouth to be cast. e Fig 18 The cast post duplicates the pattern previously formed. 1.5 mm (min.) a 5 mm b VOLUME 45 • NUMBER 7 • JULY / AUGUST 2014 c d e Figs 15a to 15e The ParaPost direct technique for a cast post. (a) Post space preparation. (b) Keyway. (c) Direct waxup on burnout post. (d) Provisional crown with temporary post. (e) Final cast post and core. (Courtesy of Coltène Whaledent.) Fig 19 The cast post is then cemented and the preparation refined. Figs 20a to 20e The ParaPost indirect casting system will allow the laboratory to create the post pattern. This is especially useful if multiple teeth are involved. (a) Post space preparation. (b) Impression with impression post. (c) Provisional crown with temporary post. (d) Wax-up with burnout post. (e) Final cast post and core. (Courtesy of Coltène Whaledent.) 565 Q U I N T E S S E N C E I N T E R N AT I O N A L Trushkowsky Alternatively a cast post can be fabricated directly (Figs 15 to 19) using Pattern Resin LS (GC America) and ParaPost Burnout Posts - Serrated and Vented (ParaPost XP Casting System-Plastic Burnout, Coltène Whaledent), or an indirect casting technique with an impression post (ParaPost XP Casting System) (Fig 20). CONCLUSION The restoration of endodontically treated teeth encompasses many different materials and techniques. There is no consensus of opinion on the need for a crown, and in the anterior with only a lingual access a composite restoration will suffice. Posts are only indicated where inadequate tooth exists to retain a core if a crown is required. Preparation for a post should wherever possible maintain coronal and radicular tooth structure. No post is ideal for all clinical situations and the selection of a post should depend on the tooth position in the arch, possible abutment, and occlusion. The post should provide all the mechanical requirements to restore the tooth. The creation of adequate ferrule approaching 2 mm circumferentially would be ideal and minimize the damaging effects of lateral and rotational forces on the restoration and post. REFERENCES 1. Hämmerle CHF, Ungerer MC, Fantoni PC, Bragger U, Burgin W, Lang NP. Long-term analysis of biologic and technical aspects of fixed partial dentures with cantilevers. Int J Prosthodont 2000;13:409–415. 2. Vire DE. 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