M uch confusion exists in the dental com m unity regarding the restoration o f endodontically treated teeth; few review articles present succinct guidelines fo r the restoration o f these teeth. This article reviews the literature and presents guidelines fo r restoration of endodontically treated teeth.
Guidelines for the restoration of endodontically treated teeth James W. Robbins, DDS, MS
he restoration of an en dodon tically treated to o th can be difficult, both diagnostically and technically. Much has been w ritten on the subject in recent years, yet consid erable confusion still exists am ong dental practitioners. A lthough the subject has no t been made clear by the p ublished research , the lite ra tu re is h e lp fu l in developing guidelines. T his article makes recom m endations for the restoration of endodontically treated teeth and based on a review of the literature.
Guidelines The endodontic treatment must be successful. A greater num ber of endodontically treated teeth are lost because of fracture caused by im p ro p e r resto ratio n s th an because of p o o r en d o d o n tic r e s u lts .1 However, every effort should be made to en su re en d o d o n tic success before placement of the definitive restoration.
The practitioner should minimize the 558 ■ JADA, Vol. 120, May 1990
loss of tooth structure both in endodontic preparation and post preparation. As the channel diameter increases, the dentin is weakened. Therefore, the dowel diam eter should be as small as possible while retaining the necessary rigidity. It is com m only stated that endodon tically treated teeth are more susceptible to fra c tu re as the re su lt of increased brittlen ess. A lth o u g h p ro b ab ly valid, there is m inim al support for this assertion in the literature.2 T he fracture resistance of a restored endodontically treated tooth decreases as the am ount of dentin removed increases.84 Similarly, the internal stress increases as the post diameter increases.5-6
Increased post length results in increased retention and resistance to fracture.7' 12
It has been advocated for many years that a m inim um of 4 mm of gutta-percha should be left in the apical portion of the canal space to minimize the risk of ap ical leakage.13 A post sh o u ld be as long as possible w ithout encroaching
on the rem aining gutta-percha or causing perforation in a curved canal. In terms of p o st re te n tio n , the th read ed post (active) has the m ost, followed by the parallel post, and the tapered post has the least retention. One post system is not adequate to meet all restorative needs. A tooth w ith a short canal space may require a threaded post for additional retention, and a tooth with a canal space of greater length m ight only need a more conservative passive post. T h e m ost conservative post should be chosen to give adequate reten tio n w ith o u t com prom ising the fracture resistance of the root.
An intact anterior tooth with conservative endodontic access and intact marginal ridges does not require a post or coronal coverage.3«14-16 It has been shown repeatedly that the fractu re resistance of an in ta c t e n d o d o n tic a lly treated a n te rio r to o th approaches that of an untreated tooth.
An anterior endodontically treated tooth,
which is to receive a crown, commonly requires a post or a post and core.17
The preparation of an anterior tooth for a full coverage esthetic restoration requires significant removal of tooth structure. This, coupled with the tooth structure lost during endodontic access preparation, commonly results in a crown preparation which lacks the strength to resist shear forces. The purpose of the post or post and core is to increase the fracture resistance of the coronal portion of the tooth. Posterior endodontically treated teeth require cuspal coverage, except possibly mandibular first premolars.
In a large retrospective study of endodontically treated teeth, Sorensen and Martinoff18 found that the clinical success of posterior endodontically treated teeth was enhanced when restored with cuspal coverage restorations. This same finding has been reported in a laboratory study.19 Recently, there has been significant .interest in the strengthening capability of bonded restorations, both composite resin and porcelain. Many investigations have suggested that a bonded restoration increases fracture resistance of the restored tooth.20-26 In an in vitro study, Wendt and others27 found that the restoration of mesio-occlusodistal (MOD) prepa rations in endodontically treated pre molars with composite resin/glass ionomer restorations returned the fracture resistance to that of untreated controls. Kanca28 reported a high clinical success rate in restoring endodontically treated posterior teeth with composite resin restorations. Although bonded restora tions show promise, their strengthening ability has not been demonstrated con clusively. In several laboratory studies,2932 no strengthening effect of composite resin over amalgam was shown. There is also concern that the rein forcing effect may decrease with time. In an in vitro study, Eakle33 reported a significant reduction in fracture resis tance of maxillary premolars restored with composite resin after thermocycling. In a retrospective in vivo study, Hansen84 compared the success of endodontically treated premolars restored with composite resin or amalgam. During the first 3 years, the teeth restored with composite resin were significantly more resistant to fracture than the teeth restored with amalgam. However, in subsequent years, 560 ■ JADA, Vol. 120, May 1990
the fractures occurred with approximately the same frequency in both groups. Although the restorations were etched and low viscosity enamel bonding resin was used, the composite resin was bulk placed. On the basis of current research, it appears prudent to restore posterior endodontically treated teeth with cuspal coverage restorations. Posts in molars are required only for retention of the buildup material and are rarely needed as many other retention and resistance features are available.
The significant morbidity associated with the placement of posts in posterior teeth includes perforation and inability to retreat once the post is cemented. Many alternative retention and resistance fea tures for crown buildups are currently available.85 In their retrospective study, Sorensen and Martinoff18 reported no significant increase in resistance to fracture or dislodgement gained with the placement of posts in posterior teeth. Plasmans and others86 found no difference between an amalcore, an amalcore with a post, and a buildup with four amalgapins when stressed at 45°. Gordon and Metzger87 found no statistical difference between a four-pin amalgam and a post reinforced amalgam restoration when stressed at 90°. In contrast, Kern and others88 (stressed at 60°) and Christian and others39 (stressed at 90°) reported that the post-reinforced amalgam res toration was more resistant to fracture than the amalcore. In the latter study, no statistical analysis was performed; therefore, the statistical significance of the difference is not known. Rarely is a posterior tooth stressed by shear forces approaching 90° to its long axis; there fore, the clinical significance of these findings is questionable. In the restoration of endodontically treated premolars, judgment is required. Tooth morphologic structure and func tion must be considered when determin ing the need for a post and core.
If a premolar serves as an abutment,40 receives significant lateral stress, or the height of the crown is tall in relation to the diameter of the root at the alveolar crest, then a post is indicated. The delicate morphologic structure of the maxillary premolar root must be considered during post space preparation.41-42 Posts that necessitate minimal canal enlargement should be chosen for maxillary premolars.
Ideally, after com pletion of the end odontic filling, the canal(s) should not be further enlarged. Rather, the post(s) should be modified to fit the canal(s). Surface roughness, such as sandblasting or notching, of the post enhances the retention.4*-47
Surface roughness is usually incor porated into prefabricated post systems. However, this feature must be added to the custom cast post and core. An antirotation device is required in all posts, such as keyway(s), or pin(s ).45-48
In a ribbon-shaped or oblong canal, antirotation is easily obtained in the core. However, as the canal becomes more round, the need for accessory antirotation increases. Peripheral distribution of retention and resistance features of the core w ill enhance fracture resistance of the final restoration.
This principle, in part, explains the consistent success of pin-retained cores in relation to custom cast posts and cores in laboratory studies of anterior teeth.16-48-49 In contrast, Brandal and others50 found a parallel post and composite core to have greater fracture resistance than a three-pin amalgam restoration. It should be noted that no amalgam was placed into the canal space. Peripheral distribution of retention and resistance features has been equally successful in posterior teeth.86-37 Pins and amalgapins are much smaller in diameter than custom or prefabricated posts. However, by necessity, the post must be centrally located as it is within the canal. In contrast, the alternative devices, such as pins, can be placed peripherally. The mechanical advantage gained with peripheral placement appears to outweigh the decreased inherent strength of a pin compared with a post. To increase resistance form, irregularities and vertical height should be left in the coronal preparation for the core.51
The clinical crown should not be removed to provide a flat surface for the core. When an endodontically treated tooth is prepared for a crown, a ferrule should be placed on natural tooth structure below the post and core finish line. However, it is not clear whether a ferrule in the core itself is beneficial. In a laboratory
study, Barkhordar and others52 reported increased fracture resistance when a ferrule was incorporated in the core. However, in the control cores that did not have a ferrule, no castings with ferrules were placed over the cores, as is advocated. Therefore, the clinical significance is questionable. In a similar study, Tjan and Whang53 reported no benefit from incorporating a ferrule in the core. T he concentration of stress should be minimized during post insertion.
When a custom cast post is fabricated, the sharp angles should be smooth in the post preparation and in the post.12 Unless the post is designed to actively engage the dentin, it should fit passively in the canal. In addition, there is a significant rise in hydrostatic pressure during cementation.54 Therefore, a vent should be used in parallel, active, and custom cast posts to minimize this stress. A core material that is dim ensionally stable with adequate strength to resist displacement should be used.
Several core materials are available to the clinician. Amalgam has a long history of successful use. After the prefabricated post is cemented, all excess cement should be removed to ensure that amalgam can be condensed into the canal space around the post as it exits the canal.39 Lindhe55 has reported long-term suc cessful clinical use of composite resin as a core material. However, Oliva and Lowe56'57 investigated the dimensional stability of composite resin and amalgam as core materials in a wet environment, in vitro. They found amalgam to be stable and composite resin, dimensionally unstable. This instability of composite resin significantly affected the marginal seating of crowns. In a similar study, Vermilyea and others58 found composite resin to be dimensionally stable compared with dentin in a wet environment. It is well established that composite resin absorbs water.59-60 However, the clinical significance of this fact is still unknown. Reinforced glass ionomer has been advocated as a buildup material61-62; the dimensional stability of this material in a wet environment has been demon strated.63 Regarding fracture resistance, Taleghani and Leinfelder62 found no difference between a cast gold post and core and a parallel post with a silver562 ■ JADA, Vol. 120, May 1990
reinforced glass ionomer core. In molars, Robbins and others63 found no difference in the fracture resistance of four-pin buildups done with amalgam or silver-reinforced glass ionomer. How ever, Lloyd and Adamson64 studied the fracture toughness (K]C) of reinforced glass ionomer (Ketac-Silver, ESPE), composite resin, and amalgam. This parameter helps to predict the function of a material under tensile and flexural stress; the higher the Kic, the more resistant is the material to stress failure. They found the K|c of Ketac-Silver to be no greater than that of conventional glass ionomer and low in comparison to composite and amalgam. Although glass ionomer appears to be a potentially useful material, its success must first be confirmed with controlled clinical studies. Presently, amalgam continues to be the most predictable choice as a buildup material. N either the method of gutta-percha removal nor the time (early versus delayed) appears to significantly influence apical leakage.
The most common methods of gutta percha removal include a heated instru ment, a rotary instrument, and chlo roform. One study65 found a rotary instrument to be superior for early gutta percha removal and another study66found the rotary instrument to be superior for delayed removal. However, in other studies67"69 no differences were found when comparing two or all three of the techniques. Although one study found immediate removal of gutta-percha from the post space to be superior,70 and another study69 found delayed removal to be the best method, other studies67-71-72 reported no difference. The type of cement used appears to be of minimal importance when retention and resistance of the post are adequate.
Many studies have investigated the retention of posts cemented with various cements.10-73'89 Each cement, composite, resin glass ionomer, polycarboxylate, and zinc phosphate has its distinct advantages. A cement should be chosen for its advantages in a given situation. However, none of the cements overcomes the inadequacies of a poorly designed post. The canal should be cleaned with a cavity
cleaner before post cementation.
It is imperative that the canal be cleaned after lubricant has been used in the canal to fabricate a direct post and core pattern.90 However, its use, even without lubricant in the canal, has enhanced retention with zinc phosphate cement90 and composite resin.85-91 A lentulo spiral should be used to carry cement to the canal before cementation of the post.
Placement of the cement with a lentulo spiral demonstrated the best cement distribution and post retention when compared with placing the cement with a paper point, an endodontic explorer, or directly onto the post.91-92 Ideally, dissim ilar m etals should not be used in the post, core, and crown.9*-94
Corrosion occurs in the canal space when dissimilar metals are used for the post, core, and crown. It has been postulated that these corrosion products could be a causative factor in the fracture of endodontically treated teeth that have been restored with dissimilar metals. However, it is not clear presently that corrosion is a clinically significant issue. Conclusion
There are many ways to restore end odontically treated teeth effectively. It has not been the purpose of this article to develop a consensus on the restoration of these teeth. Rather, a review of the salient literature has been presented from which a group of guidelines has been developed. It is hoped that these guide lines will serve as a framework on which practitioners may develop their own treatment philosophy. ---------------------------------------------------------------------Dr. Robbins is assistant professor, department of general practice, University of Texas Health Science Center at San Antonio, TX. Address requests for reprints to Dr. Robbins at the University of Texas Dental School, Department of General Practice, 7703 Floyd Curl Dr., San Antonio 78284-7914. 1. W eine FS. Endodontic therapy. St. Louis: Mosby; 1989:4. 2. Heifer AR, Melnick S, Schilder H. Determi nation o f moisture content of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol 1972;34:66170. 3. Trabert KC, Caputo AA, Abou-Rass M. Tooth fracture—a comparison of endodontic and restorative treatments. J Endod 1978;4:341-5.
4. Deutsch AS, Musikant BL, Cavallari J, Silverstein L, Lepley J, Ohlen K, Lesser M. Root fracture during insertion of prefabricated posts related to root size. J Prosthet Dent 1985;53:786-9. 5. Mattison GD, von Fraunhofer JA. Angulation loading effects on cast-gold, endodontic posts: a p h o to ela stic stress analysis. J Prosthet Dent 1983;49:636-8. 6. Mattison GD. Photoelastic stress analysis of cast-gold endodontic posts. J Prosthet Dent 1982;48:407-11. 7. Leary JM , Aquilino SA, Svare CW. An eval uation of post length w ithin the elastic lim its of dentin. J Prosthet Dent 1987;57:277-81. 8. Sorensen JA, Martinoff JT. Clinically significant factors in dowel design. J Prosthet Dent 1984;52:2835. 9. Cooney JP, Caputo AA, Trabert KC. Retention and stress distribution of tapered-end endodontic posts. J Prosthet Dent 1986;55:540-6. 10. Standlee JP, Caputo AA, Hanson EC. Reten tion of endodontic dowels: effects of cement, dowel len gth , diameter, and design. J Prosthet Dent 1978;39:400-5. 11. Johnson JK, Sakamura JS. Dowel form and tensile force. J Prosthet Dent 1978;40:645-9. 12. Standlee JP, Caputo AA, Collard EW, Pollack MH. Analysis of stress distribution by endodontic posts. Oral Surg Oral Med Oral Pathol 1972;33:95260. 13. Neagley RL. The effect of dowel preparation on the apical seal of endodontically treated teeth. Oral Surg Oral Med Oral Pathol 1969;28:739-45. 14. Trope M, Maltz DO, Tronstad L. Resistance to fracture of restored endodontically treated teeth. Endod Dent Traumatol 1985;1:108-11. 15. Guzy GE, N icholls JI. In vitro comparison o f intact end od on tically treated teeth w ith and without endo-post reinforcement. J Prosthet Dent 1979;42:39-44. 16. Lovdahl PE, Nicholls JI. Pin-retained amalgam cores vs cast-gold dowel-cores. J Prosthet Dent 1977;38:507-14. 17. Zakhary SY, Nasr HH. In vitro assessment of intact endodontically treated anterior teeth with different restorative procedures. Egypt Dent J 1986;32:221-39. 18. Sorensen JA, M artinoff MD. Intracoronal reinforcem ent and coronal coverage: a study of end od on tically treated teeth. J Prosthet Dent 1984;51:780-4. 19. Hoag EP, Dwyer TG. A comparative evaluation of three post and core techniques. J Prosthet Dent 1982;47:177-81. 20. Reeh ES, Douglas WH, Messer HH. Stiffness of endodontically treated teeth related to restoration technique. J Dent Res (Special Issue n o. 1510) 1988;67:301. 21. Landy NA, Sim onsen RJ. Cusp fracture strength in class 2 com posite resin restorations. J Dent Res (Special Issue no. 39) 1984;63:175. 22. Share J, Mishell Y, Nathanson S. Effect of restorative material on resistance to fracture of tooth structure in vitro. J Dent Res (Special Issue no. 622) 1982;61:247. 23. Sim onsen RJ, Barouch E, Gelb M. Cusp fracture resistance from com posite resin in class 2 restorations. J Dent Res (Special Issue no. 761) 1983;62:254. 24. Mishell Y, Share J, Nathanson D. Fracture resistance of Class II amalgam vs. light activated composite restorations in vitro. J Dent Res (Special Issue no. 1099) 1984;63:293. 25. Morin D, D eL ong R, D ou glas WH. Cusp reinforcement by the acid-etch technique. J Dent Res 1984;63:1075-8. 26. Jensen ME, Redford DA, Williams BT, Gardner
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F. Posterior etched-porcelain restorations: an in vitro study. Compend Contin Educ Dent 1987;8:61522. 27. Wendt SL Jr, Harris BM, Hunt TE. Resistance to cusp fracture in endodontically treated teeth. Dent Mater 1987;3:232-5. 28. Kanca J. Conservative resin restoration of endodontically treated teeth. Quintessence 1988;19:258. 29. Reeh ES, Messer HH, Douglas WH. Fracture patterns in occlusally loaded endodontically treated and restored teeth. J Dent Res (Special Issue no. 1645) 1989;68:387. 30. Stam palia LL, N ich o lls JI, Brudvik JS. Fracture resistance of teeth w ith resin-bonded restorations. J Prosthet Dent 1986;55:694-8. 31. Joynt RB, W ieczkowski G Jr, Klockowski R, Davis EL. Effects of composite restorations on resistance to cuspal fracture in posterior teeth. J Prosthet Dent 1987;57:431-5. 32. Joynt RB, D avis EL, W ieczkowski GJ Jr, Williams DA. Fracture resistance of posterior teeth restored with glass ionomer-composite resin systems. J Prosthet Dent 1989;62:28-31. 33. Eakle WS. Effect of thermal cycling on fracture strength and microleakage in teeth restored with a bonded composite resin. Dent Mater 1986;2:1147. 34. Hansen EK. In vivo cusp fracture of endo dontically treated premolars restored w ith MOD am algam or MOD resin fillin g s. Dent Mater 1988;4:169-73. 35. Robbins JW, Burgess JO, Sum m itt JB. R etention and resistance features for com plex amalgam restorations. JADA 1989;118:437-41. 36. Plasmans PJ, Visseren LGH, Vrijhoef MMA, Kayser AF. In vitro comparison of dowel and core techniques for en dodontically treated m olars. J Endod 1986;12:382-7. 37. Gordon M, Metzger Z. Resistance to horizontal forces of dowel and am algam -core restorations: a comparative study. J Oral Rehabil 1987;14:33744. 38. Kern SB, von Fraunhofer JA, M ueninghoff LA. An in vitro comparison of two dowel and core techniques for endodontically treated m olars. J Prosthet Dent 1984;51:509-14. 39. Christian GW, Button GL, Moon PC, England MC, D ouglas HB. Post core restoration in end od on tically treated posterior teeth. J Endod 1981;7:182-5. 40. Sorensen JA, Martinoff JT. Endodontically treated teeth as abutm ents. J Prosthet Dent 1985;53:631-6. 41. Yaman P, Zillich R. Restoring the endodon tically treated bi-rooted prem olar—the effect of endodontic and post preparation on width of root dentin. J Mich Dental Assoc 1986;68:79-81. 42. Zillich R, Yaman P. Effect of root curvature on post length in restoration of endodontically treated premolars. Endod Dent Traumatol 1985;1:1357. 43. Tjan AHL, Whang SB. Retentive properties of some simplified dowel-core systems to cast gold dowel and core. J Prosthet Dent 1983;50:203-6. 44. C olley IT , H am pson EL, Lehm an ML. Retention of post crowns. Br Dent J 1968; 124:639. 45. R uem p in g DR, Lund MR, S ch n ell RJ. Retention of dowels subjected to tensile and torsional forces. J Prosthet Dent 1979;41:159-62. 46. Ricker JB, Lautenschlager EP, Greener EH. Mechanical properties of post and core systems. Dent Mater 1986;2:63-6. 47. M aniatopoulos C, P illiar RM, Sm ith DC. Evaluation of shear strength at the cement endodontic post interface. J Prosthet Dent 1988;59:662-9.
48. Newburg RE, Pameijer CH. Retentive prop erties of post and core systems. J Prosthet Dent 1976;36:636-43. 49. M oll JFP, Howe DF, Svare CW. Cast gold p ost and core and pin-retained com posite resin bases: A comparative study in strength. J Prosthet Dent 1978;40:642-4. 50. Brandal JL, N ich olls JI, H arrington GW. A comparison of three restorative techniques for end od on tically treated teeth. J Prosthet Dent 1987;58:161-5. 51. Sorensen JA, Engelman MJ, Mito WT. Effect of ferrule design on fracture resistance of pulpless teeth. J Dent Res (Special Issue no. 142) 1988;67:130. 52. Barkhordar RA, Radke R, Abbasi J. Effect of metal collars on resistance of endodontically treated teeth to root fracture. J Prosthet D ent 1989;61:676-8. 53. Tjan AHL, W hang SB. Resistance to root fracture of dowel channels with various thicknesses of buccal dentin walls. J Prosthet Dent 1985;53:496500. 54. Turner CH, Gross MJ. Investigation of hydrostatic pressure changes during cem entation of screw-retained posts, and post with integral cement release channels. J Oral Rehabil 1983;10:421-8. 55. Lindhe LA. The use of com posites as core material in root-filled teeth. Swed Dent J 1984;8:20916. 56. O liva RA, Lowe JA. Dim ensional stability of com posite used as a core material. J Prosthet Dent 1986;56:554-61. 57. Oliva RA, Lowe JA. Dim ensional stability of silver am algam and com posite used as core materials. J Prosthet Dent 1987;57:554-9. 58. Vermilyea SG, Gardner FM, Moergeli JR Jr. Com posite dowels and cores: effect o f m oisture on the fit of cast restorations. J Prosthet Dent 1987;58:429-31. 59. Pearson GJ. Long term water sorption and solubility of com posite fillin g materials. J Dent 1979;7:64-8. 60. Craig RG. Restorative dental materials. St. Louis: Mosby; 1989:264. 61. Taleghani M, Morgan RW. Reconstructive materials for endodontically treated teeth. J Prosthet Dent 1987;57:446-9. 62. Taleghani M, Leinfelder KF. Evaluation of a new glass ionomer cement with silver as a core b u ild u p under a cast restoration. Q uintessence 1988;19:19-24. 63. Robbins J, Cooley R, Barnwell S. Dimensional stability of reinforced glass ionomer core buildup. J Dent Res (Special Issue no. 559) 1989;68:251. 64. Lloyd CH, Adamson M. The developm ent of fracture toughness and fracture strength in posterior restorative materials. Dent Mater 1987;3:22531. 65. Kwan EH, H arrington GW. T h e effect of immediate post preparation on apical seiil. J Endod 1981;7:325-9. 66. M attison GD, D elivanis PD, Thacker RW Jr, and Hassell KJ. Effect of post preparation on the apical seal. J Prosthet Dent 1984;51:785-9. 67. M adison S, Zakariasen KL. Linear and volumetric analysis of apical leakage in teeth prepared for posts. J Endod 1984;10:422-7. 68. Suchina JA, Ludington JR Jr. Dowel space preparation and the apical seal. J Endod 1985;11:117. 69. Dickey DJ, Harris GZ, Lemon RR, Luebke RG. Effect of post space preparation on apical seal using solvent techniques and Peeso reamers. J Endod 1982;8:351-4. 70. Portell FR, Bernier WE, Lorton L, Peters DD. The effect of immediate versus delayed dowel space preparation on the integrity o f the apical
seal. J Endod 1982;8:154-60. 71. Schnell FJ. Effect of immediate dowel space preparation on the apical seal of endodontically filled teeth. Oral Surg Oral Med Oral Pathol 1978;45:470-4. 72. Bourgeois RS, Lem on RR. Dowel space preparation and apical leakage. J Endod 1981;7:669. 73. Goldman M, DeVitre R, White R, Nathanson D. An SEM study of posts cemented with an unfilled resin. J Dent Res 1984;63:1003-5. 74. Chapman KW, Worley JL, von Fraunhofer JA. Retention of prefabricated posts by cements and resins. J Prosthet Dent 1985;54:649-52. 75. Young HM, Shen C, Maryniuk GA. Retention of cast posts relative to cement selection. Quintessence 1985;16:357-60. 76. Krupp JD, Caputo AA, Trabert KC, Standlee JP. Dowel retention with glass-ionom er cement. J Prosthet Dent 1979;41:163-6. 77. Ben-Amar A, Gontar G, Fitzig S, Urstein M, Liberman R. Retention of prefabricated posts with dental adhesive and com posite. J Prosthet Dent 1986;56:681-4. 78. Gontar G, Liberman R, Urstein M, Fitzig S, Ben-Amar A. Retention of dowels using Conclude composite resin as a luting medium. Dent Mater
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1986;2:118-20. 79. H ill GL, Zidan O, Duerst L. Retention of etched based metal dowels with resin cement and bonding agent. J Prosthet Dent 1986;55:691-3. 80. Nasr HH, Eskander MMZ, Zake AM. The luting efficacy of cements in bonding dowels of different metals. Egypt Dent J 1987;33:155-71. 81. Brown JD, Mitchem JC. Retentive properties of dowel post systems. Oper Dent 1987;12:15-9. 82. Tjan AHL, Tjan AH, Grieve JH. Effects of various cementation methods on the retention of prefabricated posts. J Prosthet Dent 1987;58:1758. 83. Assif D, Etzion J. Serrating the channel walls— its influence on dowel retention. Q uintessence 1985;2:123-8. 84. Chapman KW, Worley JL, von Fraunhofer JA. Effect of bonding agents on retention of posts. Gen Dent 1985;33:128-32. 85. Goldman M, DeVitre R, Pier M. Effect of the dentin smeared layer on tensile strength of cemented posts. J Prosthet Dent 1984;52:485-8. 86. Assif D, Ferber A. Retention of dowels using a composite resin as a cementing medium. J Prosthet Dent 1982;48:292-6. 87. Radke RA, Barkhordar RA, Podesta RE. Retention of cast endodontic posts: Comparison
of cementing agents. J Prosthet Dent 1988;59:31820. 88. Coleman RA, Corcoran JF, Powers JM, Sloan KM, Lorey RE, LaTumo SAL. Dentin-bonded post and cores: an in vitro failure analysis. J Dent Res (Special Issue no. 229) 1987;66:135. 89. Wolff MS, Breuer J, Shiu A, Osborne JW. A comparison of three cements in retaining posts in teeth. J Dent Res (Special Issue no. 231) 1987;66:135. 90. Maryniuk GA, Shen C, Young HM. Effects of canal lubrication on retention of cemented posts. JADA 1984;109:430-3. 91. Goldman M, DeVitre R, Tenca J. Cement distribution and bond strength in cemented posts. J Dent Res 1984;63:1392-5. 92. G oldstein GR, H udis SI, Weintraub DE. Comparison of four techniques for the cementation of posts. J Prosthet Dent 1986;55:209-11. 93. Silness J, Gustavsen F, Hunsbeth J. Distri bution of corrosion products in teeth restored with metal crowns retained by stainless steel posts. Acta Odontol Scand 1979;37:317-21. 94. Arvidson K, W roblewski R. M igration of m etallic ion s from screwposts in to dentin and surrounding tissues. Scand J Dent Res 1978;86:2005.