Objectives: The relatively low elastic modulus of fiber posts reduce the risk of root fracture, but also decrease the composite core stabilization. To compensate for the lack of rigidity, larger post sizes are needed when restoring crownless teeth. The aim of this study was to evaluate the effect of the post emerging diameter on the composite core stabilization of restored flat root human teeth.
Methods: Forty single rooted, crownless human teeth were divided in 8 groups and randomly restored with quartz (Endolightpost and DT Light - Post, RTD, France) and glass (Premier Anatomic and Compaq, Innotech, Italy) fiber posts, each type represented with #1 and #2 sizes. Single tapered and double tapered post shapes were used. The posts were inserted 10mm deep in the root canal and cemented using Duo-Link and One-Step adhesive (Bisco, USA)The emerging diameter ranged from 1.00 to 1.50mm. The core was realized using Light-Core (Bisco) placed in transparent standardized shells. The specimens were stored in 100% humidity until the Instron loading tests, carried out at a 45° angle. The force required to detach the core from the dentin flat surface was considered as the fracture strength (FS). Data obtained were statistically analyzed with ANOVA and linear regression.
Results: FSs ranged from 264±95N (Endolightpost #1) to 425.1 +/- 55N (DT Light-Post #2) (P<0.05). Single tapered posts were weaker than double tapered ones. FS was directly correlated to post emerging diameter (P=0.017). Notwithstanding the loss of dentin required to place larger posts, the root fracture rate was not significantly correlated to the post diameter (P=0.8).
Conclusion: The emerging diameter of fiber post is extremely important to stabilize the core. When restoring crownless teeth, it is advisable to use fiber posts having large emerging diameters. Data obtained suggest that diameters of 1.5mm do not jeopardize the root dependability.

Objectives: When restoring endodontically treated teeth with fiber post, the coronal third of the root canal is often much more larger than both medium and apical portion. Fiber posts are frequently too small in diameter at this level, particularly in teeth previously treated, and a large amount of cement is required to fill the post/dentin gap. The aim of this study was to determine the root canal shape immediately prior the post space preparation, to obtain data for an improved post design.
Methods: After gutta-percha removal, 40 poly-vinyl polysiloxane impressions of the root canal of endodontically treated teeth scheduled for fiber post restorations were taken by a single operator. Molars and lower incisors were excluded. Stone casts were obtained from the impressions. The casts were progressively grinded, taking a standardized microphotograph every 1mm. The canal length and both bucco-lingual and mesio-distal diameters were measured, obtaining a mean computer-designed 3-D canal profile. The canal shapes were compared to different fiber posts using graphics software.
Results: the coronal and central thirds of the incisors, canines and 2nd bicuspids were found significantly larger than standard fiber posts. In these teeth, DT Light-Post (RTD, France) showed the best fit (although not ideal) when compared to single tapered or parallel sided posts. The mean canal length was 8.9„b1.4mm. When graphically superimposed on the 3-D images, extremely good adaptation was found with a post having a tapered root portion of 6¢X, 12mm in length, and parallel-sided coronal head 5mm in length. The head diameters should vary from 1.8 to 2.4mm to match the different tooth sizes.
Conclusions: The canals of endodontically treated teeth are larger than available fiber posts, particularly at the coronal segment. An increased tapering and a larger coronal diameter have been introduced in a new post design obtaining a better post/dentin adaptation.

Abstract/conclusions: A wide variety of prefabricated posts systems are manufactured with different materials and offered with different shapes. Post and core adaptation presents an important element in the biomechanical performance of the prosthetic restoration. The double taper post system was designed with the purpose of providing close canal adaptation with minimal tooth structure removal. The association of a quartz fiber/epoxy material with a more anatomical double taper shape provides a conservative and esthetic approach for the restoration of endodontically-treated teeth. The double taper post (D.T. LIGHT-POST; RTD/Bisco Dental) allows one to rebuild the missing tooth structure using adhesive technology without obstructing the esthetics of the all-ceramic restorative systems. The double taper post closely imitates the post-endodontic shape of a radicular canal, and leaves a thin and uniform thickness of cement at the post/canal interface. This improved adaptation of the post promotes the mechanical properties of the quartz fiber/epoxy material, instead of the weaker composite resin cement. In as much as in vitro and early clinical follow-up are encouraging, long-term clinical study is needed to evaluate the behavior of this post system and the prosthetic prognosis of teeth with extensive coronal destruction.

Abstract/conclusions: Endodontically treated teeth frequently require a post and core to serve as a foundation for the coronal restoration. Remaining tooth structure, physical properties of the post material, post shape, and cement type all contribute to the success of the restoration. Post adaptation to the canal walls also represents an important element in the biomechanical performance of the prosthetic restoration. A double taper post system made of quartz fiber and epoxy was developed to conform more precisely to the shape of endodontically treated canals. Immediate benefits of this post system include minimal tooth structure removal during canal reshaping, greater post-to-canal adaptation in the apical and coronal half of the canal, and good post retention. The use of a quartz fiber/epoxy material with a lower modulus of elasticity also reduces the incidence of root fracture. Furthermore, the esthetic nature of the colors offered with this post system (translucent and off-white) provide a favorable foundation for eliminating discoloration caused by a metallic post placed under all-ceramic crown systems.

Abstract/conclusions: An in vitro nondestructive fatigue test was applied to adhesive posts and cores made on endodontically treated human teeth. Five post-and-core systems were evaluated: one Zirconia oxide post, two Titanium posts (with resinous or ceramic coating), and two resin-fiber posts. Each test specimen was intermittenly loaded and thermocycled. The scanning electron microscope observation of sample sections showed that only the interfaces between restorative materials and dentin exhibited substantial deficiencies. The Komet ER (Brasseler) exhibited the greatest percentages of continuity at the coronal (83.88%) or the radicular (78.12%) dentin levels, while the Zircon experimental post presented insufficient adaptation to the radicular 21.25% continuity) and to the coronal (53.25% continuity) dentin. Seven of eight samples in the Komet group showed root fractures. The carbon-fiber post (Composipost) behaved satisfactorily (67.38% radicular continuity), in spite of the use of an older bonding agent formulation.