Abstract: This study investigated the flex-

ural strength of eight fiber posts (one car-

bon fiber, one carbon/quartz fiber, one

opaque quartz fiber, two translucent quartz

fiber,and three glass fiber posts). Eighty

fiber posts were used and divided into eight

groups (n=10): G1:C-POST (Bisco); G2:

ÆSTHETI-POST (Bisco); G3: ÆSTHETI-PLUS

(Bisco); G4: LIGHT-POST (Bisco); G5: D.T.

LIGHT-POST (Bisco); G6: PARAPOST WHITE

(Coltene);G7: FIBERKOR (Pentron); G8: RE-

FORPOST (Angelus). All of the samples

were tested using the three-point bending

test. The averages obtained were submit-

ted to the ANOVA and to Tukey’s test

(p<0.05). The mean values (MPa) of the

groups ÆSTHETI-POST—carbon/quartz fiber

post (Bisco) and ÆSTHETI-PLUS—quartz

fiber post (Bisco) were statistically similar

and higher than the mean values of the other

groups. The mean values of the groups C-

POST—carbon fiberpost (Bisco), LIGHT-POST—

translucent quartz fiber post (Bisco), D.T.

LIGHT-POST—double tapered translucent

quartz fiber post (Bisco), PARAPOST WHITE—

glass fiber post (Coltene) and FIBREKOR—-

glass fiber post (Pentron) were similar and

higher than the group REFORPOST—glass

fiber post (Angelus).

Considering this evidence, the type of resinous

matrix and the fabrication process used to pro-

mote chemical bonding between fiber and resin

may possibly be the most important factors for the

fiber post strength. Much of this information is

kept under industrial secret unfortunately; how-

ever, it is reasonable to ask sales representatives.

Evaluation of the Flexural Strength of Carbon Fiber-, Quartz Fiber-, and Glass Fiber-Based Posts Graziela A´ vila Galhano, DDS, Luiz Felipe Valandro, DDS, MSc,Renata Marques de Melo, MD, DDS, Roberto Scotti, MD, DDS, and

Marco Antonio Bottino, DDS, PhD

Rigid versus Flexible Dentine-like Endodontic Posts—Clinical Testing of a Biomechanical Concept: Seven-year Results of a Randomized Controlled Clinical Pilot Trial on Endodontically Treated Abutment Teeth with Severe Hard Tissue Loss Guido Sterzenbach, Dr med dent, DDS, Alexandra Franke, DDS,and Michael Naumann, Prof, Dr med dent, DDS

Abstract Introduction: This is the first clinical long-term pilot study that tested the biomi-metic concept of using more flexible, dentine-like (low Young modulus) glass fiber–reinforced epoxy resin posts (GFREPs) com-pared with rather rigid, stiff (higher Young modulus) titanium posts (TPs) in order to im-prove the survival rate of severely damaged endodontically treated teeth. Methods: Ninety-one subjects in need of postendodon-tic restorations in teeth with 2 or less remain-

ing cavity walls were randomly assigned to receive either a tapered TP (n = 46) or a ta-pered GFREP(n = 45). The posts were adhe-sively luted using selfadhesive resin cement. The composite core build-ups were prepared ensuring a circumferential 2-mm ferrule. The primary endpoint was a loss of restoration for any reason. To study group differences, the log-rank test was calculated (P < .05). Hazard plots were constructed. Results: After 84 months of observation (mean = 71.2 months),

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F E B R U A R Y 2 0 1 3

V O L U M E 1 I S S U E 2

E N D O I N V I V O

S P E C I A L P O I N T S O F I N T E R E S T :

Flexural strength of various fibre post systems

Rigid versus Flexible Dentin-like Endodontic Posts

Vertical root fractures in upper premolars with endodontic posts

Self-etching adhesives increase colla-genolytic activity in radicular dentin

A simple etching tech-nique for improving the retention of fiber posts to resin compos-ites

Geometric factors affecting dentin bond-ing in root canals: A theoretical modeling approach

7 restorations failed (ie, 4 GFREPs and 3 TPs). The failure modes were as fol-lows: GFREP:- root fracture (n = 3), core fracture (n = 1) and TP:endodontic failure (n = 3). No statistical differ-ence was found between the survival rates (GFREPs = 90.2%, TPs = 93.5%, P = .642). The probability of no failure was comparable for both post materials (risk ratio; 95% confidence inter-val, 0.965–0.851/1.095).

Conclusions: When using self-adhesive luted prefab-ricated posts in severely destroyed abutment teeth with 2 or less cavity walls and a 2-mm ferrule, pos-tendodontic restorations achieved high long-term survival rates irrespective of the post material used (ie, glass fiber vs tita-nium).

Rigid Versus Flexible Dentine-like Endodontic Posts (cont’d)

Vertical Root Fracture in Upper Premolars with Endodontic Posts: Finite Element Analysis Andrea F.V. Santos, Carina B. Tanaka, Raul G. Lima, PhD, Camila O.M. Espósito, et al JOE — Volume 35, Number 1, January 2009

Page 2 E N D O I N V I V O

than for the bonded or intact models, therefore confirming the second hypothesis.

Abstract: Upper premolars re-stored with endodontic posts present a high incidence of verti-cal root fracture (VRF). Two hy-potheses were tested: (1) the smaller mesiodistal diameter favors stress concentration in the root and (2) the lack of an effective bonding between root and post increases the risk of VRF. Using finite element analy-sis, maximum principal stress was analyzed in 3-dimensional intact upper second premolar models. From the intact models, new models were built including endodontic posts of different elastic modulus (E =37 or E =200 GPa) with circular or oval cross-section,either bonded or nonbonded to circular or oval cross section root canals. root canals. The first hypothesis was partially confirmed because the conditions involving nonbonded, low-modulus posts showed lower tensile stress for oval ca-nals compared to circular ca-nals. Tensile stress peaks for the nonbonded models were approximately three time higher

(A) A three-dimensional model of the intact tooth and

(B) a three-dimensional model with endodontic post.

Dimensions are in millimeters. E, elastic modulus; v,

Poisson’s ratio.

Abstract: Coupling of fiber posts to composites is hampered byabsence of chemi-

cal union between epoxy resins and methacrylate-based resins. This study exam-

ined a clinically feasible protocol for creating micromechanical retention on the

surface of fiber posts, using hydrogen peroxide etching to remove the surface

layer of epoxyresin. This was followed by silanization of the exposed quartz fibers

to enhance their chemical bonding to composites. Etching with 24% H2O2 for 10

min or 10% H2O2 for 20 min produced a 50 µm thick surface zone that is de-

pleted of epoxy resin, leaving intact, undamagedquartz fibers for silanization.

Low viscosity flowable composites were employed to infiltrate this zone, to simu-

late the creation of hybrid layers in acid-etched dentin by dentin adhesives. Inter-

facial strengths were enhanced with the adjunctive use of H2O2 etching and si-

lanization, and were probably dependent on the ability of the flowable compos-

ites to completely infiltrate this interdiffusion zone.

Self-Etching Adhesives Increase Collagenolytic Activity in Radicular Dentin Franklin R. Tay, David H. Pashley, Robert J. Loushine, R. Norman Weller, et al JOE—Volume 32, Number 9, September 2006

A Simple Etching Technique for Improving the Retention of Fiber Posts to Resin Composites Francesca Monticelli, DDS, MSc, Manuel Toledano, MD, DDS, PhD, Franklin R. Tay, DDS, MSc, PhD,

Fernanda T. Sadek, BDSc (Hons), PhD, et al JOE—Volume 32, Number 1, January 2006

Much of the fracture

susceptibility, however, is

intrinsic to the root and

canal morphology (dentin

thickness, canal shape and

size, external root shape)

and is beyond the

influence of the clinician.

Page 3 V O L U M E 1 I S S U E 2

Abstract: Endogenous matrix metalloproteinases (MMPs) release from crown dentin and

their activation results in degradation of hybrid layers created by dentin adhesives. This

study tested the hypothesis that instrumented intraradicular dentin possesses latent colla-

genolytic activity that is activated by mild self-etching adhesives. Root dentin shavings chlor-

hexidine for 10 minutes before or after adhesive application. Collagenolytic activities of the

nine groups were assayed with a fluorometer in 96-well plates, by recording the changes in

fluorescence before and after addition of fluorescein-labeled type I collagen. Epoxy resin-

embedded powders were examined with TEM for the extent of demineralization. Instru-

mented, mineralized intraradicular dentin possessed low but detectable collagenolytic activ-

ity that was inhibited by chlorhexidine (p <0.001) and EDTA (p<0.001). Both adhesives par-

tially demineralized the dentin powder and activated latent MMPs, with 14- to 15-fold in-

creases in collagenolytic activities (p<0.001) that were significantly (p<0.001)but incom-

pletely inactivated after 10 min application of chlorhexidine. Mild self-etching adhesives

activate latent MMPs without denaturing these enzymes, and may adversely affect the lon-

gevity of bonded root canal fillings and posts.

Sealer penetration demonstrated

by confocal photography

4310 Sherwoodtowne Blvd.,

Suite 300

Mississauga, ON

L4Z4C4

Phone - 905.270.3357

Fax - 905.270.4172

Email - kendo@endosolns.com

E N D O D O N T I C S O L U T I O N S

G E O M E T R I C F A C T O R S A F F E C T I N G D E N T I N B O N D I N G I N R O O T C A N A L S :

A T H E O R E T I C A L M O D E L I N G A P P R O A C H Franklin R. Tay, BDSc (Hons), PhD, Robert J. Loushine, DDS, Paul Lambrechts, DDS, PhD,

R. Norman Weller, DMD, MS, David H. Pashley, DMD, PhD JOE—Volume 31, Number 8, August 2005

P A T I E N C E , P E R S I S T E N C E , P E R S E V E R A N C E

www.endosolns.com

Abstract: Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded

surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded sur-

face area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses

to debond the material from dentin, thereby decreasing retention and increasing leakage. The important variables

influencing bonding adhesive root-filling materials to canals was examined using a truncated inverted cone model.

C-factors in bonded root canals exhibit a negative correlation with sealer thickness. For a 20 mm-long canal pre-

pared with a size 25 file, calculated C-factors ranged from 46 to 23,461 with decreasing sealer thickness (500–1

µm), comparedto a C-factor of 32 when the canal was filled only with sealer. As the thickness of the adhesive is

reduced, the volumetric shrinkage is reduced, which results in a reduction in shrinkage stress (S-factor). C-factors

above 954 calculated with sealer thickness smaller than 25 µm are partially compensated by increases in bonding

area and decreases in shrinkage volume. However, the interaction of these two geometrically related factors (C-

and S-factors) predicts that bonding of adhesive root-filling materials to root canals is highly unfavorable when

compared with indirect intracoronal restorations with a similar resin film thickness.