Effects of Auxiliary Fiber Posts on Endodontically Treated Teeth With Flared Canals

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1 Ó Opertive Dentistry, 2011, 36-4, Effects of Auxiliry Fiber Posts on Endodonticlly Treted Teeth With Flred Cnls QLi BXu Y Wng Y Ci Clinicl Relevnce Mcro-Lock post combined with uxiliry fiber posts could increse the frcture resistnce of endodonticlly treted roots with over-flred cnls. However, n effect of the uxiliry fibers on retention strength ws not observed. Qing Li, resident, Key Lbortory for Orl Biomedicl Engineering of Ministry of Eduction, School nd Hospitl of Stomtology, Wuhn University, Wuhn, Chin Binting Xu, postgrdute student, School nd Hospitl of Stomtology, Wuhn University, Wuhn, Chin *Yining Wng, professor, Director of Deprtment of Prosthodontics, Key Lbortory for Orl Biomedicl Engineering of Ministry of Eduction, School nd Hospitl of Stomtology, Wuhn University, Wuhn, Chin *Yunqui Ci, professor, School of Civil nd Architecturl Engineering, Wuhn University, Wuhn, Chin *Corresponding uthors: 237# Luo Yu Rod, Wuhn, Chin; e-mil: wng.yn@whu.edu.cn, nd ciyunqi@yeh.net DOI: / L SUMMARY This study investigted the frcture resistnce nd retention of endodonticlly treted roots with over-flred cnls restored with different post systems, including one cst metl post nd four fiber posts with/without uxiliry fiber posts. One hundred endodonticlly treted incisor roots were experimentlly flred using tpered dimond bur. The roots were restored using one of the five post systems: Ni-Cr cst metl post (CM), D.T. Light glss fiber post (DT), Mcro-Lock glss fiber post (ML), ML+2 Fibercone uxiliry fiber posts (2FC), nd ML+5 Fibercone uxiliry fiber posts (5FC). After fbriction of the crowns, hlf of the specimens (n¼50) were subjected to frcture filure test loding with n incrementl sttic force t n ngle of 45 degrees to the long xis of the root. The other 50 smples underwent pull-out test. Frcture filure strength nd pull-out strength were mesured nd nlyzed using one-wy nlysis of vrince (ANOVA) followed by Tukey s post hoc test (¼0.05). After the tests were completed, ll specimens displyed oblique root frctures or crcks, inititing from the pltl cervicl mrgin nd propgting in lbil-picl direction. The order of the frcture filure strength ws s follows: 5FC¼CM¼2FC. ML.DT. Cst metl posts demonstrted the highest pull-out strength (p,0.05). No significnt differences in pull-out strength were found in the ML, 2FC, nd 5FC groups. Within the limittions of this study, it ws concluded

2 Li & Others: Effects of Auxiliry Fiber Posts on Flred Cnls 381 tht the ppliction of n uxiliry fiber post could significntly increse the frcture resistnce of over-flred roots; however, no beneficil effects in enhncing retention were observed. INTRODUCTION The restortions of endodonticlly treted teeth commonly present chllenge to dentists, especilly in cses of extensive crown-root destruction. 1,2 This sitution occurs with significnt loss of coronl tooth structure, frctures, or over-prepred root cnls for previous post-retined restortions. 3 Excessive root cnl flring cn result in wek root cnl wll nd n insufficiently retentive morphology for post. 4 Cst metl posts hve been used trditionlly in these situtions to provide necessry retention for the subsequent restortion. 3,5,6 However, these metllic posts hve been considered to hve biomechnicl disdvntges, such s high modulus of elsticity nd root frcture potentility. 7-9 Recently, ppliction of fiber-reinforced composite (FRC) posts in endodonticlly treted teeth hs incresed in populrity becuse of their purported fvorble biomechnicl properties, 10,11 esthetic ppel, esier removl for endodontic retretment, nd single visit plcement. 12 Bsed on theoreticl considertions nd finite element nlyses, FRC posts re more flexible thn cst metl posts nd llow better distribution of forces, resulting in fewer root frctures. 10,13 Clinicl studies hve reported success rte of 95% to 99% for teeth restored with FRC posts, with no occurrence of root frcture during the study periods. 14,15 However, controversil conclusions were reported by some in vivo nd in vitro studies. Some uthors hve indicted tht the frcture resistnce of teeth restored with FRC posts is equl to or greter thn tht of teeth restored with metl posts. 16,17 Other uthors hve reported tht endodonticlly treted teeth restored with fiber posts showed decresed frcture resistnce compred with teeth restored with metl posts. 18,19 It hs been suggested tht the inconsistency in these outcomes might be relted to fctors relted to the mount of remining helthy tooth structure, 20,21 s well s to chrcteristics of the post, such s mteril composition, 22 modulus of elsticity, 23 dimeter, 24 nd length. 25 Therefore, for roots with extreme crownroot destruction, the frcture susceptibility of different post systems needs to be further investigted. Despite these somewht conflicting findings, in vitro 26,27 nd in vivo studies showed tht the most common cuse of post-core restortion filure ws not the frcture, but rther the pull-out of the cement-post-restortion ssembly. Debonding occurred between post-cement nd/or cement-root cnl dentin interfces s result of indequte bonding strength. Specilized drills ccompnying the FRC post systems re developed to improve the dpttion of the posts to the root cnls. Nevertheless, the prefbricted FRC posts could not idelly mtch the root cnl in full work length, especilly in cses of excessive root cnl flring, thus resulting in lrge, conicl, nd insufficiently retentive post. 4,31,32 In these cses, high bonding strength nd dequte retention re indispensble when FRC posts re pplied. 33 Recently, new product, Fibercone (RTD Inc, St Egreve, Frnce), ws introduced in dentistry. It ws developed s n uxiliry post simultneously pplied with mster post. Generlly speking, the uxiliry posts could increse the dpttion of FRC posts in cses of flred or ovl cnls, thus minimizing polymeriztion shrinkge nd preventing decementtion. However, no consensus is evident in the literture bout the fesibility of using fiber posts to restore over-flred root cnls. And no scientific dt re vilble relted to the clinicl ppliction of uxiliry fiber posts. Therefore, the purpose of this study ws to evlute the effects of different post systems, including the ppliction of ccessory fiber posts, on restoring over-flred roots. The null hypothesis ws tht frcture resistnce nd retention do not vry s function of the post system. MATERIALS AND METHODS The study protocol ws reviewed nd pproved by the Ethics Committee of the School nd Hospitl of Stomtology, Wuhn University. One hundred sound humn mxillry centrl incisors, extrcted for periodontl resons, were involved in this study. Ptients who donted their teeth were informed of the purposes of the reserch, nd written informed consents were obtined prior to teeth extrction. Dentl plque, clculus, nd periodontl tissues were removed, nd teeth were stored in 0.9% sline solution t 378C. The teeth were exmined using microstereomicroscope (Stemi SV11 Apo, Crl Zeiss Micro Imging Inc, Thornwood, NY, USA) t 63 mgnifiction to verify the bsence of cries nd crcks. And cnl morphology ws verified from stndrdized peripicl rdiogrphs. Teeth with lrge root cnls or roots with pex dilcertions, fissures, or surfce defects were excluded. To verify the men dimensions of the teeth, root lengths (from

3 382 Opertive Dentistry Figure 1. Schemtic digrm of the preprtion of specimen. (A): Criterion for specimen fbriction. (B1, B2): Group CM nd x-ry photogrph. (C1, C2): Group DT nd x-ry photogrph. (D1, D2): Group ML nd x-ry photogrph. (E1, E2): Group 2FC nd x-ry photogrph. (F1, F2): Group 5FC nd x-ry photogrph. (G): Specimen with full metl crown. the root pex to the buccl midpoint of the cementoenmel junction [CEJ]) nd buccolingul nd mesiodistl dimensions (t the level of the cervicl mrgin) were mesured using cliper (LA-6, Dentsply, York, PA, USA). Overll, the men of root length ws mm, while the mens of buccolingul nd mesiodistl dimensions were mm nd mm. Preprtion of Over-flred Root Cnls Antomicl crowns were trnsversely sectioned t 1.0 mm coronl to the CEJ of the buccl spect using dimond low-speed rotry cutting instrument (SP1600, Leic Microsystems GmbH, Wetzlr, Germny). The section surfce ws flttened to be perpendiculr to the longitudinl xis of the tooth using SiC snd pper (600-grit). Afterwrd, the root cnls were endodonticlly treted nd obturted with gutt-perch (Lexicon Gutt Perch Points, Dentsply, Tuls, OK, USA). After storge in 0.9% sline solution t 378C for 72 hours, the entrnce of the root cnl ws enlrged using tped dimond bur (with tper of 0.5) with length of 6 mm. Restortive Procedures: Fbricting the Postcores nd Crowns The prepred roots were restored with one of five post systems s follows (n¼10): Ni-Cr lloy cst metl post (Bego, Bremen, Germny) (group CM), D.T. Light FRC post (Bisco Inc, Schumburg, IL, USA) (group DT), Mcro-Lock FRC post (RTD Inc) (group ML), Mcro-Lock plus 2 Fibercone FRC posts (group 2FC), nd Mcro-Lock plus 5 Fibercone FRC posts (group 5FC). The post spce of the root cnls ws prepred using respective drills recommended by ech post system. A schemtic digrm of the root cnl preprtion is shown in Figure 1 nd Tble 1. To simulte the periodontl ligment (only for the frcture filure test), the root surfce of 50 specimens ws coted with thin lyer of polyvinyl-siloxne impression mteril (Exmixfine, GC Inc, Tokyo, Jpn). Finlly, the roots were embedded in crylic resin blocks (Uni-Fst II, GC Inc) prllel to the long xis of the teeth t level 2 mm below the CEJ of the buccl spect. Prllelism mong the post, the cnl, nd the crylic resin block ws obtined by using prllel grinding instrument (CL-MF2002S, Hereus- Kulzer Inc, Hnu, Germny). For group CM, Ni-Cr lloy metl post cores were csted nd cemented using conventionl glss ionomer cement (Fuji, GC Inc). The coronl portion ws 6 mm in height with 1-mm height, 0.5-mm width ferrule end (Figure 1). For FRC post groups, the cnls were etched with 37% phosphoric cid (Ultr-Etch, Ultrdent, South Jordn, UT, USA) for 15 seconds, rinsed with

4 Li & Others: Effects of Auxiliry Fiber Posts on Flred Cnls 383 Tble 1: Post Systems nd Mterils Tested in This Study Group Post System Cnl Preprtion Core Mnufcturer Btch Apex Entrnce CM Cst metl post-core GG drill #1-4 Cst Ni-Cr Bego, Bremen, Germny DT D.T. Light (3#) #1-3 PermCem Bisco Inc, Schumburg, L, USA ML Mcro-Lock (4#) #1-4 Dimond bur with tper of 0.5 RTD Inc, St Egreve, Frnce FC Mcro-Lock (4#)þ2 # Fibercone 5FC Mcro-Lock (4#)þ5 Fibercone #1-4 distilled wter for 30 seconds, nd dried with bsorbent pper points. Adhesive resin ws pplied (Adper Single Bond 2, 3M ESPE, St Pul, MN, USA) nd light polymerized for 20 seconds using hlogen light-polymerizing unit (ESPE Elipr Trilight, 3M ESPE). All FRC posts nd uxiliry FRC posts were cemented with resin cement (PermCem, DMG Inc, Hmburg, Germny) nd were light-cured for 40 seconds. The FRC posts were cut, leving 6 mm out of the root cnl entrnce to retin composite cores. Ten polyester trys, replicted from the specimens in group CM, were fbricted using het/vcuum try-forming mchine (Ultr-form, Ultrdent). Core build-up composite resin (Lux- Core, DMG Inc, Hmburg, Germny) ws filled into these trys nd ws used to build the cores for the FRC post groups. Finlly, ll cores nd roots were prepred in keeping with the criteri mentioned previously. For the stndrdiztion of pplying loding during the mechnicl tests, full metl crowns were mde for ll specimens. The crowns were irborne prticle brded with 50 lm luminum-oxide powder, nd were cemented using conventionl glss ionomer cement. The specimens were then stored in 100% reltive humidity, t 378C, for period of 72 hours. Thermomechnicl Aging Specimens were subjected to thermomechnicl ging before the frcture nd pull-out tests were performed. 34 Mechnicl ging ws pplied with universl testing mchine using stinless steel sphericl ntgonist (with tip 3 mm in dimeter) contcting on the lingul surfce, 2 mm below the incisl edge of the crowns. A 45-degree oblique lod of N ws pplied in 60,000 cycles with crosshed speed of 10 mm/s downwrd nd 70 mm/s upwrd. Lod frequency ws 1.7 Hz, nd lod cycle durtion ws 0.6 second. Thermocycling ging ws performed with 12,000 cycles t 58C to 508C with dwell time of 70 seconds. Finlly, the specimens were rndomly divided into two hlves, nd ech hlf ws subjected to frcture filure test or pull-out test (n¼50). Frcture Filure Tests A totl of 50 specimens were subjected to frcture filure tests using the universl testing mchine (Model 8841, Instron, Norwood, MA, USA). A custom-fbricted jig ws used to stndrdize the position of specimens t the bse of the pprtus, so tht loding ws pplied t n ngle of 45 degrees in reltion to the long xis of the roots (Figure 2). A compressive force ws pplied on the lingul surfce (2 mm below the incisl edge) t crosshed speed of 0.5 mm/min until frcture occurred. Modes of frcture were observed using x-ry photogrphs. Frcture modes were clssified into three ctegories s follows: root frcture, post frcture, invisible frcture. With respect to frcture loction, the frcture modes were clssified s follows: -cervicl, b-middle, nd c-picl. Pull-out Tests The remining 50 specimens were subjected to pull-out test using the universl testing mchine mentioned previously. The crylic resin block nd the crown were fitted to dynmometer clmps

5 384 Opertive Dentistry Figure 2. Schemtic drwing of the setup for frcture filure testing nd pull-out testing of the post. (A): Frcture filure testing. (B): Pull-out testing. (Figure 2). A 0.5 N prelod ws pplied to mintin the specimens in tension nd to llow for selflignment before testing. A force ws pplied on the full metl crowns t crosshed speed of 0.5 mm/ min until detchment occurred. Pull-out strength vlues were recorded. The pulled out post frgments were collected nd observed with the microstereomicroscope t 13 nd 43 mgnifictions. Sttisticl Anlysis The mens of frcture filure strength nd pull-out strength were clculted. The dt were nlyzed using one-wy nlysis of vrince (ANOVA) with the post system setting s the vrible. Tukey s post hoc test ws performed to evlute differences mong the post systems. All nlyses were performed using the Sttisticl Pckge for the Socil Sciences (SPSS) sttisticl pckge (SPSS 13.0 for Windows, SPSS Inc, Chicgo, IL, USA). The level of significnce ws set t RESULTS All specimens remined intct fter 60,000 cycles of dynmic loding nd 12,000 therml cycles. Evlution of the Frcture Filure Tests The mens of frcture filure strengths (N) nd stndrd devitions re presented in Tble 2. The frcture filure strength of group DT ws the lowest. No sttisticl difference in frcture strength ws noted mong the groups CM, 2FC, nd 5FC. The results of the frcture modes re presented in Tble 3. Almost ll smples encountered root frcture, except for four specimens with invisible frcture. All root frctures occurred opposite the re where the force ws pplied. No post frcture occurred in the groups CM nd 5FC. The percentges of post frcture were 50%, 30%, nd 30% in the groups of DT, ML, nd 2FC, respectively. With respect to root frcture loction, most frctures hppened in the cervicl region of the roots in which the fiber post systems were used, wheres 50% of root frctures were locted in the middle of the roots in group CM. Representtive x-ry photogrphs of frctures re shown in Figure 3. Anlysis of Pull-out Tests Tble 4 shows the mens of pull-out strengths (N) nd Tukey s post hoc nlysis results. In group CM, debonding filure strength ws significntly greter thn tht of the fiber post groups (p,0.05). No sttisticl differences in pull-out strength were noted mong groups ML, 2FC, nd 5FC (p.0.05). The lowest vlue of pull-out strength ppered in group DT (p,0.05). Figure 4 presents the representtive pulled out post frgments. A rough surfce

6 Li & Others: Effects of Auxiliry Fiber Posts on Flred Cnls 385 Tble 2: Mens nd Tukey s Post Hoc Comprisons of Frcture Filure Strength, N Group n Men, N SD Minimum, N Mximum, N Tukey s Intervl CM DT b ML c 2FC FC For Tukey s intervls, the sme letter mens no significnt difference within groups. with thin lyer of glss ionomer ws detected in group CM. In group DT, the seprtion presented t the interfce of the post-cement lyer, nd no cement remined on the post surfce. A residul cement lyer ws obvious on post-frgment surfces in most of the specimens of groups ML, 2FC, nd 5FC. A thin lyer of residul cement ws observed in the serrtions nd the pssive threding cut in the Mcro-Lock post surfce. DISCUSSION Bsed on these findings, the null hypothesis tht frcture resistnce nd retention do not vry s function of the post system ws rejected. It is difficult to stndrdize the extensively destroyed root cnls in lbortory study. In the present study, the over-flred root ws chieved using dimond drill to enlrge the root entrnce. Furthermore, reltively shorter nd nrrower ferrule with height of 1.0 mm nd width of 0.5 mm ws set s the criterion of the tooth preprtion. This ws done becuse of the extensive coronl structure loss of specimens used in the present study. Sttic compressive loding is usully used to ssess the frcture resistnce of pulpless teeth. However, most filures of post-retined restortions were not cused by sttic compress, but by ftigue frcture of ordinry chewing force. So thermomechnicl ging is vitlly importnt before the effects of post-retined pulpless teeth cn be evluted. In the present study, ll teeth suffered from 60,000 cycles of dynmic loding nd 12,000 therml cycles before initil testing. Reserch hs demonstrted tht ordinry chewing force in dults rnges from 7 kg to 15 kg. 35 In the present investigtion, the frcture filure strength of ll specimens ws beyond norml chewing forces. However, the clinicl significnce of these results should be questioned. In clinicl sitution, the filure of post-nd-core restortion is complex result of cyclic loding, mterils ftigue, nd microlekge. So the restortion cn be expected to fil with less loding thn ws pplied in this study. Moreover, continuous ferrule ws set in the present study, which could probbly increse the frcture resistnce of the roots. Thus, frcture filure strengths were given only for comprison mong groups. No significnt difference ws found mong the groups of CM, 2FC, nd 5FC, nd frcture filure strengths of groups 2FC nd 5FC were greter thn tht of group ML. These findings might be explined by the fct tht incresing dimeter of the FRC post using uxiliry fiber posts hs positive effect on stress distribution. 11 X-ry photogrphs showed tht the frcture mode of the FRC post groups ws cervicl frcture or crck, nevertheless 50% of the frctures in group CM were locted t the middle of the roots. It could be ssumed tht the fiber posts were ble to trnsmit prtil loding stresses to the prepred root cnls, thus distributing the lod over bigger surfce re of the tooth structure. 23,36 However, either of the middle or cervicl root frctures could be considered s n unfvorble frcture. Therefore, results indicte tht once frcture filure hd occurred in extensively flred roots, it ws nonrepirble whether cst metl posts or FRC posts were used. A push-out test ws performed nd ws recommended for evlution of the bonding strength of post-retined restortions. 37 However, in the pre-

7 386 Opertive Dentistry Tble 3: Modes of Frcture Observed by Visul Inspection Using X-ry Photogrphs,b Smple No. Lod, N CM DT ML 2FC 5FC Type Loction Lod, N Type Loction Lod, N Type Loction Lod, N Type Loction Lod, N Type Loction RF RF RF RF RF RF RF RF RF RF RF b RF RF RF RF RF RF invisible frcture invisible frcture RF RF b RF,b RF RF RF RF RF RF RF RF RF b invisible frcture RF c RF b b RF RF RF RF RF RF RF b RF b RF RF RF RF b RF RF RF c invisible frcture Frcture type ws clssified into three ctegories s follows: root frcture (RF), post frcture (), nd invisible frcture. b With respect to loction, frctures were clssified ccording to the root or post in which they occurred: -cervicl, b-middle, or c-picl liminry study, the wek dentin wll, especilly in the cervicl region, ws not strong enough to support the push-out force. Moreover, the section of cst post might potentilly destroy the bonding surfce. Therefore, the pull-out test ws performed in this study. Tukey s multiple comprisons showed tht the order of pull-out strength vlues ws CM.ML¼2FC¼5FC.DT. As expected, the cst post fit the cnl spce better thn the FRC posts. Therefore, the cement lyer ws thinner nd more uniform in group CM, which might contribute to the higher retention of cst posts compred with fiber posts. With respect to the FRC post groups, two interfces were used: the dentin-cement lyer nd the cement-lyer post. Investigtion with microstereoscopy showed tht most of the debonding occurred in the cement lyer-post interfce in group DT, nd in the dentin-cement lyer interfce in the ML, 2FC, nd 5FC groups. Residul cement mterils were found in series of serrtions long with pssive threding into the surfce of Mcro-Lock posts. It ws presumed tht the design of notches in the Mcro-Lock post surfce could significntly reinforce the retention of the post-cement interfce. Tukey s multiple nlysis reveled tht no significnt differences mong the ML, 2FC, nd 5FC groups. It indicted tht the ppliction of uxiliry posts could not positively increse the retention of flred pulpless roots. One limittion of the study is tht the bonding procedures were performed in vitro. The mnufc-

8 Li & Others: Effects of Auxiliry Fiber Posts on Flred Cnls 387 Figure 3. Representtive x-ry photogrphs of frcture filure testing. (A): Root frcture t the middle region of the root. (B): Root nd post frcture t the cervicl region of the root. (C): Root frcture t the cervicl region of the root. turer s recommendtions were followed, nd the moisture control might not be s idel, especilly in terms of the ppliction of glss ionomer cement. The frcture filure strength nd the pull-out strength could not fully revel the clinicl sttus of endodonticlly treted roots under chewing forces. Other properties of the mterils nd the effects of mteril ging should be investigted in future studies. CONCLUSIONS Within the limittions of this in vitro study, the following conclusions were drwn: 1. The Mcro-Lock post showed superior retention nd frcture resistnce compred with the D.T. Light post. 2. The Mcro-Lock post combined with the uxiliry fiber posts incresed the frcture resistnce of the over-flred root. Tble 4: Mens nd Tukey s Post Hoc Comprisons of Pull-out Strength, N Group n Men, N SD Minimum, N Mximum, N Tukey s Intervl CM DT b ML c 2FC c 5FC c For Tukey s intervls, the sme letter mens no significnt difference within groups.

9 388 Opertive Dentistry Figure 4. Photogrphs of pulled out post frgments observed using microstereomicroscope t 13 nd 43 mgnifictions. (A): Group CM. (B): Group DT. (C): Group ML. (D): Group 2FC. (E): Group 5FC. 3. The ppliction of uxiliry fiber posts hs no effect on the retention strength of over-flred roots. Acknowledgements Supported by the Ntionl Key Technology R&D Progrm of Chin during the 11th Five-yer Pln (No. 2007BAI18B05), nd the Fundmentl Reserch Funds for the Centrl Universities, Wuhn University (No ). (Accepted 6 December 2010) REFERENCES 1. Schwrtz RS & Robbins JW (2004) Post plcement nd restortion of endodonticlly treted teeth: literture review Journl of Endodontics 30(5) Dietschi D, Duc O, Krejci I & Sdn A (2007) Biomechnicl considertions for the restortion of endodonticlly treted teeth: systemtic review of the literture. Prt 1. Composition nd micro- nd mcrostructure ltertions Quintessence Interntionl 38(9) Sdek FT, Monticelli F, Gorcci C, Ty FR, Crdoso PE & Ferrri M (2007) Bond strength performnce of different resin composites used s core mterils round fiber posts Dentl Mterils 23(1) Boschin-Pest L, Cvlli G, Bertni P & Gglini M (2002) Adhesive post-endodontic restortions with fiber posts: push-out tests nd SEM observtions Dentl Mterils 18(8) Blkenhol M, Wöstmnn B, Rein C & Ferger P (2007) Survivl time of cst post-nd-cores: 10-yer retrospective study Journl of Dentistry 35(1) Jung RE, Klkstein O, Siler I, Roos M & Hmmerle CHF (2007) A comprison of composite post build ups nd cst gold post nd core build ups for the restortion of nonvitl teeth fter 5 to 10 yers Interntionl Journl of Prosthodontics 20(1) d Silv LM, Andrde AM, Mchuc MF, d Silv PM, d Silv RV & Veronezi MC (2008) Influence of different dhesive systems on the pull-out bond strength of glss fiber posts Journl of Applied Orl Science 16(6) Tit CM, Ricketts DN & Higgins AJ (2005) Wekened nterior roots intrrdiculr rehbilittion British Dentistry Journl 198(10) Peroz I, Blnkenstein F, Lnge KP & Numnn M (2005) Restoring endodonticlly treted teeth with posts nd cores review Quintessence Interntionl 36(9) Plotino G, Grnde NM, Bedini R, Pmeijer CH & Somm F (2007) Flexurl properties of endodontic posts nd humn root dentin Dentl Mterils 23(9) Lssil LVJ, Tnner J, LeBell AM, Nrv K & Vllittu PK (2004) Flexurl properties of fiber reinforced root cnl posts Dentl Mterils 20(1) Cheung W (2005) A review of the mngement of endodonticlly treted teeth: Post, core nd the finl restortion Journl of Americn Dentl Assocition 136(5)

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