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ePaper created 2016-03-31, 16:35:38 | version 1.38.0
| literature review fibre post restorations 26 roots1 2016 brideacanal,microleakage/bacterialcontamination/ exposuretoendotoxinsafterendodontictherapyis performed, but before a final restoration is placed (all endodontic procedures should be followed by immediate restoration),39, 40 or due to failure and microleakageofthecoronalrestoration.Ithasbeen estimated that 25 % of re-treatments involve the presence of a post. Fibre posts are atraumatically removedinamatterofafewminuteswithavailable proprietary removal drill systems.41–43 No discussion of the restoration of a badly broken down endodontically treated tooth would be com- plete without discussing the concept of the circum- ferential ferrule, which is defined as ‘a metal band or ring that encircles the tooth in order to provide re- tention and resistance form, as well as protect the tooth from fracture’.44 Most of the published articles, based on in vivo and in vitro data, suggest that a 2 mmferruleisbestforimprovingresistancetofrac- ture with significant decreases when the ferrule is 1 mmornon-existent.45–47 However,itisnotonlythe height of the remaining dentine that is critical for creating the ferrule, but just as important is the width of the remaining dentine and the number of walls. As shown in Figures 7 and 8, there is a drastic differenceinoutcomeswhenpreparingaferruleina modestly flared canal versus a wide flare. As can be seen, when a wide flare exists, the preparation of a ferrule actually removes the dentinal lateral walls, creating a standalone core that essentially has no ferrule at all. It is important to note here that glass ionomercementsandresinmodifiedglassionomers lackthephysicalpropertiestofunctionasacorema- terial.48, 49 Jotkowitz et al. in their article on ‘Rethink- ing the Ferrule’, provides one of the best regression analyses and clinical guidelines in the literature, evaluatingtheeffectsoftheheight,numberofwalls remaining,thicknessofthewalls,andwhetherame- sial/distalorbuccal/lingualwallisremaininginrela- tionshiptothefunctionalstressesinvolved.50 Asim- ple example would be the difference of losing a lingual wall on an upper central—even if three walls remain—whichcanbecatastrophicduetothetorque placed on the lingual in function, as opposed to los- ing an interproximal wall that has little weakening effect when lingual stress is applied. Their conclu- sion is that no ferrule equals unrestorable. ‘Clinical protocols should feature well-defined inclusion cri- teria,includingdelineationofthenumberofresidual coronal walls, for a clearer assessment of the influ- ence of the remaining tooth structure on treatment outcomes.’51 As the number of remaining walls de- crease, the fracture resistance decreases when no post is used, but the fracture resistance is increased significantly when fibre posts are placed—except when there is no wall left.52 ‘ The success rate for all posts decreases drastically in the absence a residual coronal wall.’51 The literal definitions of reinforcement from vari- ous sources includes: ·· A device designed to provide additional strength. ·· To strengthen by adding extra support. ·· To make stronger. ·· To strengthen with some added piece, support or material. ·· To make a structure stronger. Much of the dental literature and texts from the 1970stotheearly1990sindicatethatapostisplaced when there is insufficient structure left to retain a core/crown,andthatmetalpostsdonotreinforcethe root.53–56 Retrospectively looking at research on end- odontically treated teeth utilising metal posts cer- tainly support this finding.57, 58 However, more recent researcharticlesandpublicationsarecreatingabody ofworkthatfibrepostsdoindeedmaketherootmore resistant to fracture and may strengthen the root. What follows is only a partial list, with short summa- Fig.4: In irregular or ovoid canals,the use of Fibercones lateral to the Macro-Lock X-RO has many clinical advantages,increasing longevity. Fig.5: A clinical photograph showing the placement of Fibercones laterally to the main Macro-Lock Post,which decreases composite volume,adds anti-rotational elements,and decreases microleakage. Fig.4 Fig.5