3D-microleakage assessment of adhesive interfaces: exploratory findings by µCT.

OBJECTIVES: To explore the feasibility of a 3D-microleakage protocol for the evaluation of various configurations of adhesive-tooth interfaces. METHODS: Three different kinds of specimens were prepared: (1) a Class-I composite restoration placed without any bonding to maximize gap formation at the interface; (2) a glass-fiber post cemented with a self-adhesive composite cement into a prepared root canal; and (3) inlay MOD composite restorations placed with either a 1-step self-adhesive or a 2-step etch-and-rinse composite cement. After silver-nitrate (AgNO3) infiltration, the specimens were scanned using a Skyscan 1172 X-ray microtomograph (µCT; Skyscan Bruker) at 100kV, 100µA and 7.8-9.5µm resolution. Projection images were reconstructed, after which maximum-intensity projections (MIPs) and 3D-volumetric renderings were produced. For the inlays, an additional conventional stereomicroscopic (SM) microleakage evaluation was accomplished after specimen sectioning. RESULTS: MIPs and 3D-renderings from specimens (1) and (2) revealed strongly varying microleakage patterns along the marginal gap/interface. For the specimens of setup (3), the high radiopacity of the 2-step composite cement hindered evaluation of the MIPs. MIP-microleakage patterns along the enamel margin of the restoration cemented with the 1-step composite cement corresponded well to the stereomicroscopic images. SIGNIFICANCE: The reported µCT-protocol revealed good sensitivity to detect AgNO3 infiltration at the adhesive-tooth interface when considerable microleakage was present. When microleakage was less apparent and spread in a more diffuse pattern, evaluation with µCT was less sensitive compared to stereomicroscopic evaluation.

Effect of fiber posts with different emerging diameters on the fracture strength of restored crownless teeth.

The relatively low elastic modulus of fiber posts reduces the risk of root fracture, but it also decreases composite core stabilization. To compensate for the lack of rigidity, larger post sizes can be necessary when restoring crownless teeth that have significant internal destruction of the root canal. This study evaluated the effectiveness of fiber posts with different emerging diameters and shapes on composite core stabilization as measured by fracture strength testing. Fracture strengths ranged from 262.6 ± 81 N to 422.8 ± 56 N. A one-way ANOVA test showed that fracture strength was affected by type of post (p<0.0001); single-tapered posts were weaker than double-tapered posts. Pearson's linear correlation test showed that the fracture strength results appear to have a direct correlation to the emerging diameter of the post (p<0.0001; r(2)=0.6191). The emerging diameter of fiber posts is important to stabilize the core. When restoring crownless teeth, it is advisable to use fiber posts with large emerging diameters; no additional preparation of the internal root dentin is necessary to enlarge the post diameter.

An up to 3-Year Controlled Clinical Trial Comparing the Outcome of Glass Fiber Posts and Composite Cores with Gold Alloy-Based Posts and Cores for the Restoration of Endodontically Treated Teeth.

PURPOSE: This controlled clinical trial aimed to compare the 3-year outcomes of glass fiber posts and composite cores with gold alloy-based posts and cores for the restoration of endodontically treated teeth. MATERIALS AND METHODS: One hundred forty-four patients in need of 205 restorations on endodontically treated teeth were selected and followed for 7 to 37 months (mean: 21 ± 9 months). The teeth were primarily stratified based on the remaining tissue available to restore the tooth core with or without a post. Then, randomization allocated the teeth to either test group 1 (prefabricated glass fiber posts), test group 2 (custom-made glass fiber posts), or test group 3 (composite cores without posts). The control group consisted of gold alloy-based posts and cores. All posts/cores were covered with all-ceramic single crowns. Failures were either absolute, such as root fractures or irreparable fractures of the post/core, or relative, such as loss of post retention or reparable fractures of the core. Success and survival probability lifetime curves, corrected for clustering, were drawn for the entire data set. RESULTS: The recall rate at 3 years was 97.1%. Absolute failures consisted of two root fractures and one endodontic failure, while relative failures included three instances of retention loss of the post/core and one post fracture. Because of the low number of events, no statistical tests were performed. The success and survival probabilities over all groups together at 3 years amounted to 91.7% and 97.2%, respectively. CONCLUSIONS: After being followed for up to 3 years, both cast gold and composite post and core systems performed well clinically. Longer follow-up times are needed to detect possible significant differences. Int J Prosthodont 2011;24:363-372.

Bonding effectiveness and sealing ability of fiber-post bonding.

OBJECTIVES: To evaluate the push-out bond strength and the sealing ability of five adhesive cements routinely used for fiber-post bonding. METHODS: Fifty extracted single-rooted teeth were randomly divided in five groups and restored using Parapost FiberLux and the following luting agents: Panavia 21 (PAN), Clearfil Esthetic Cement (CLF), Variolink II (VAR), RelyX Unicem (UNI) and experimental GC self-adhesive cement (EGC). After 1 week of water storage at 37 degrees C, three sections (coronal, middle and apical) of 2mm thickness were prepared from each specimen. Sealing ability was quantified with a fluid-filtration system (Flodec) during 10 min, after which the push-out bond strength was immediately measured. Data were analyzed with ANOVA (push-out) and Kruskal-Wallis (sealing ability). RESULTS: The push-out bond strength and sealing ability were not significantly different among the coronal, middle and apical sections for each luting agent. The highest push-out bond strength was measured for CLF (14.60+/-3.63 MPa), which was not significantly different from PAN (12.57+/-2.45 MPa), but significantly higher than VAR (11.09+/-4.09 MPa), UNI (11.29+/-4.31 MPa) and EGC (7.65+/-4.79 MPa). When evaluating the sealing ability, significant differences were not found among PAN, CLF and VAR, and between UNI and EGC. The latter luting agents scored significantly lower than the former ones. The push-out bond strength was correlated to the sealing ability (p<0.001). SIGNIFICANCE: The self-etching MDP-based cements presented the highest push-out bond strength. Although the bonding effectiveness of self-adhesive cements appears promising, their interaction with root dentin might be too weak to minimize microleakage at the post-cement-dentin interface.

Effect of root canal treatments on quartz fiber posts bonding to root dentin.

The aim of this study was to evaluate the effect of irrigants and endodontic sealers on fiber post push-out strength in both fatigue cycling and no-cycling conditions. Fifty single-rooted human teeth received five endodontic treatments. The posts were cemented using a flowable composite and a three-steps adhesive. Five specimens from each group were subjected to 2 x 10(6) cycles of 37.5 N. There were 200 sections obtained for the push-out test. Fatigue cycled groups treated with an eugenol-containing sealer showed the lowest push-out strength (p < 0.001). No significant differences were found among no-cycled groups (p = 0.665). The post-cement interface was found to be weaker than the cement-dentin one. However, fatigue cycles increased the occurrence of cement-dentin failures (p = 0.001). The eugenol-containing sealer reduced the bonding of fiber posts when mechanically cycled, thus the use of a resin-based sealer is advisable.