Fernanda B. Leal

Lack of correlation between sealer penetration into dentinal tubules and sealability in nonbonded root fillings

AIM To determine the correlation between leakage and sealer penetration into dentinal tubule. METHODOLOGY The root canal of 60 mandibular central incisor teeth were prepared and filled under standardized conditions. Teeth were placed into a device to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured using an enzymatic reaction. Each specimen was then sectioned horizontally at 3, 6 and 8 mm from the apex, and a standard metallographic preparation was performed. The coronally facing surface of each slice was examined in a high-resolution stereomicroscope and under Confocal Laser Scanning Microscope. For each slice, the external outline of the root canal, the internal circumference of the root canal walls and the areas along the canal walls where the sealer had penetrated into the dentinal tubules (sealer tags) were outlined and measured. Afterwards, the percentage of the sealer penetration in each section was calculated. The Spearman correlation test was used to verify the correlation between the variables studied (glucose leakage and sealer penetration into dentinal tubules). RESULTS The means and standard deviations of glucose leakage were 0.744 g L(-1) (±0.5), and the percentage of the dentinal tubule sealer penetration varied between teeth from 5.6% to 42.21%, with an average of 13.7 ± 17.2%. The Spearman correlation test revealed no significant correlation between the two factors analysed (P = 0.082). The r(2) value was equal to 0.12. CONCLUSIONS There was no significant correlation between sealability sealer penetration into dentinal tubules. The lack of correlation reported is of relevance as sealer penetration into dentinal tubules has been used as an advantageous property during the launch of new root filling materials and techniques.

Comparison of the root-end seal provided by bioceramic repair cements and White MTA

AIM To compare the ability of Ceramicrete, BioAggregate and white ProRoot MTA (mineral trioxide aggregate) to prevent glucose leakage through root-end fillings. METHODOLOGY After root canal instrumentation, the apical 3 mm of maxillary incisors were resected and retropreparations, 3 mm in depth, were created with ultrasound. Root-end cavities were filled with the tested materials (15 roots per group). All roots were mounted in a double-chamber system to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured following an enzymatic reaction. Four roots were used as controls. One-way anova verified differences in glucose leakage between groups and Tukey test performed multiple comparisons. Significance was set at α = 5%. RESULTS There was a significant difference between the three materials (anova, P < 0.05). Ceramicrete had significantly lower glucose penetration than BioAggregate (Tukey, P < 0.05). There was no difference between the two bioceramic cements and white MTA (P > 0.05). CONCLUSIONS Both endodontic bioceramic repair cements displayed similar leakage results to white MTA when used as root-end fillings materials. Ceramicrete had significantly lower glucose penetration.

Strong effect on dentin after the use of high concentrations of citric acid: An assessment with co-site optical microscopy and ESEM

OBJECTIVES To perform a longitudinal analysis of the effect of four substances (citric acid at 1%, 5% and 10% concentrations and 17% EDTA) on dentin. METHODS Sixteen human molars had their crowns removed exposing cervical root dentin. A grinding procedure was used to produce a standardized smear layer and to create a smooth surface for analysis. Environmental scanning electron microscopy (ESEM) was used for qualitative observations while co-site optical microscopy (CSOM) and image analysis (IA) provided a quantitative comparison of the effect of the substances for several experimental times from 15 to 300s. The methods allowed the observation of the same areas after each experimental time. The open tubule area fraction was measured for several CSOM image fields, at each experimental time, for the four substances. Thus, it was possible to follow the phenomenon and quantitatively analyze the effect of the substances. Kolmogorov-Smirnov, Kruskal-Wallis H and Wilcoxon signed-ranks (with Bonferroni correction) tests were used to analyze the data. The level of significance was set at p<0.05. RESULTS The CA solutions showed the greatest chelating effect, which was proportional to concentration (EDTA: 9.4-32.8% (15-300s); 1% CA: 21.1-32.2% (15-300s); 5% CA: 32.4-43.1% (15-300s); 10% CA: 35.1-39.5% (15-30s). Erosive effects were observed on inter and peritubular dentin for 5% CA and 10% CA after 60s. SIGNIFICANCE ESEM allowed a detailed qualitative comparison of the effect of the four substances. CSOM and IA provided a quantitative comparison method with good statistical significance. Future studies should focus on the consequences of dentin erosion caused by citric acid.

BAPO as an alternative photoinitiator for the radical polymerization of dental resins

OBJECTIVES This study evaluated the performance of phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) as an alternative photoinitiator in the polymerization kinetics (PK), flexural strength (σ) and elastic modulus (E) of a model dental resin. METHODS A monomer mixture based on Bis-GMA and TEGDMA was used as model dental resin. Initially a screening was performed to evaluate BAPO concentrations (0.125, 0.25, 0.50, 1, 2, and 4 mol%). Photoinitiator systems were formed with the combination of camphorquinone (CQ), ethyl-dimethylamino benzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), and BAPO. Groups with unitary photoinitiator systems (BAPO and CQ), binary (BAPO+EDAB, BAPO+DPIHFP and CQ+EDAB), ternary (BAPO+CQ+EDAB, BAPO+CQ+DPIHFP, BAPO+EDAB+DPIHFP and CQ+EDAB+DPIHFP) and quaternary (BAPO+CQ+EDAB+DPIHFP) were formulated for evaluation. Real-time Fourier transform infrared spectroscopy was used to investigate the PK and test mini-bending to evaluate σ and E. RESULTS When only CQ was used, a slow polymerization reaction was observed and a lower monomer conversion. When only BAPO was used as photoinitiator an increase in the polymerization rate was observed and conversion was higher than CQ+EDAB. The ternary system (BAPO+EDAB+DPIHFP) showed the highest polymerization and conversion rate, in short photo-activation time. SIGNIFICANCE BAPO it is a potential photoinitiator for the photopolymerization of dental materials.

Strengthening of Porcelain Provided by Resin Cements and Flowable Composites

This study evaluated the effect of mechanical properties of resin-based luting agents on the strength of resin-coated porcelain. The luting agents tested were two flowable resin composites (Filtek Z350 Flow and Tetric-N Flow), a light-cured resin cement (Variolink Veneer [VV]), and a dual-cured resin cement (Variolink II) in either light-cured (base paste) or dual-cured (base + catalyst pastes [VD]) mode. Flexural strength (σf) and modulus of elasticity (Ef) of the luting agents were measured in three-point bending mode (n=5). Porcelain discs (Vita VM7) were tested either untreated (control) or acid etched, silanized, and coated with the luting agents. Biaxial flexural strength (σbf) of the porcelain discs was tested using a ball-on-ring setup (n=30). The σbf of the resin-coated specimens was calculated at z-axial positions for multilayer specimens in the ball-on-ring test: position z = 0 (ceramic surface at the bonded interface) and position z = -t2 (luting agent surface above ring). The σf and Ef data were subjected to analysis of variance and the Student-Newman-Keuls test (α=0.05). A Weibull analysis was performed for σbf data. Weibull modulus (m) and characteristic strength (σ0) were calculated. Linear regression analyses investigated the relationship between mechanical properties of the luting agents and the strengthening of porcelain. VD had higher and VV had lower mechanical strength than the other materials. At z = 0, all resin-coated groups had higher σbf than the control group. No significant differences between the luting agents were observed for σbf and σ0. At z = -t2, VD had the highest σbf and σ0, whereas VV had the poorest results. No significant differences in m were observed across groups. A linear increase in flexural strength of the porcelain was associated with increased σf and Ef of the luting agents at position z = -t2. In conclusion, resin coating and use of luting agents with better physical properties generally improved the mechanical performance of porcelain.

Similar glucose leakage pattern on smear-covered, EDTA-treated and BioPure MTAD-treated dentin.

This study assessed the effect of BioPure MTAD on the sealing ability on the basis of the filtration rate of glucose along the root fillings. Both 17% ethylenediaminetetraacetic acid (EDTA) and smear-covered dentin were used as reference patterns to compare the results. Sixty-four human upper incisors were prepared with different irrigation protocols (n = 18): G1, NaOCl; G2, NaOCl + EDTA; and G3, NaOCl + BioPure MTAD. The teeth were obturated and then prepared in a double-chamber apparatus to evaluate the glucose leakage along the root fillings. The amount of glucose leakage was quantified with spectrophotometry at 7, 14, 21, 28, 35, 42, 49, and 56 days. Leakage existed in every sample and was variable in all of the experimental groups, and Kruskal-Wallis H test results showed that there were no significant differences among the experimental groups (P > .05). The smear-covered dentin did not allow more glucose leakage than EDTA-treated and BioPure MTAD-treated dentin.

Effect of antioxidants on the dentin interface bond stability of adhesives exposed to hydrolytic degradation.

PURPOSE This study assessed the effect of antioxidants vitamin C (Vit. C), vitamin E (Vit. E) and quercetin (Querc) on the dentin bonding performance, degree of conversion, and rate of polymerization of three commercial adhesive systems (Adper Single Bond 2 [SB], Clearfil SE Bond [CSE], Adper Easy Bond [EB]). MATERIALS AND METHODS Human premolars were restored using antioxidant-doped adhesives. The samples were stored for 24 h in distilled water or 6 months under simulated pulpal pressure. Teeth were cut into sticks and the microtensile bond strength (μTBS) to dentin was tested in a universal testing machine. Qualitative nanoleakage analysis was performed from a central stick of each restored tooth. Degree of conversion and rate of polymerization of adhesive systems were evaluated in triplicate using real-time FT-IR. RESULTS Although the inclusion of the antioxidants negatively affected the μTBS over 24 h, the antioxidant-doped adhesives maintained (SB-Vit. C, SB-Vit. E, CSE-Vit. C, EB-Querc) or increased (SB-Querc, CSE-Vit. E, CSE-Querc, EB-Vit. E, and EB-Vit. C) their μTBS during 6 months of storage. Only the μTBS of Adper Single Bond 2 dropped significantly after 6 months among the control groups. Slight changes in the nanoleakage pattern after aging were observed in all groups, except for the EB-control group, which showed a noteworthy increase in nanoleakage after 6 months, and for EB-Vit. C, which presented a remarkable decrease. A lower degree of conversion was obtained with all antioxidants in SB and EB, except for the EB-Vit. E group. Similar degrees of conversion were attained in control and experimental groups for CSE. The rate of polymerization was reduced in antioxidant-doped adhesives. CONCLUSION The performance of antioxidants changed according to the adhesive system to which they were added, and antioxidant-doped adhesives appear to have a positive effect on the adhesive interface durability, since their bond strength obtained after 24 h was maintained or increased over time.

Similar Sealability Between Bioceramic Putty Ready-To-Use Repair Cement and White MTA

This study was designed to assess the ability to prevent glucose penetration of a bioceramic putty ready-to-use repair cement comparing to white mineral trioxide aggregate (WMTA). After root canal instrumentation, the apical 3 mm of maxillary incisors were resected and root-end cavities with depth of 3 mm were prepared with ultrasound and filled with the tested materials (15 roots per group). All roots were mounted in a double chamber system to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured following an enzymatic reaction. Four roots were used as controls. The Mann-Whitney test verified differences in glucose leakage between groups and the Tukeys test was used for multiple comparisons. Significance level was set at 5%. There was no significant difference in glucose leakage between iRoot BP Plus and White MTA groups. iRoot BP Plus had a similar ability to that of white MTA in preventing glucose leakage as a root-end filling material.

Dye Extraction Results on Bacterial Leakproof Root Fillings

This study was designed to assess and compare the sensitivity and sealability results between bacterial leakage and dye extraction. Eighty mandibular incisors were prepared, and their roots were filled as follows (n = 20): G1, lateral condensation; G2, System B; and G3, Thermafil system. All teeth were mounted in a 2-chamber apparatus, and the coronal access was exposed to human saliva for 100 days. The remaining bacterial leakproof specimens were randomly assigned to create 3 new and equal groups (n = 10). These bacterial leakproof specimens were submitted to a dye extraction setup. Each specimen was placed into a plastic vial with 5 mL of 2% methylene blue for 48 hours. After storage, the specimens were rinsed with tap water and dissolved in nitric acid. A sample of 100 microL of the supernatant from each specimen was analyzed in a UV-Visible spectrophotometer to determine the amount of methylene blue leakage. The log-rank test showed no significant difference in the bacterial leakage pattern among the groups (P > .05). In the dye extraction analysis, Kruskal-Wallis H test was unable to detect significant differences among all experimental groups (P > .05). The 3 filling techniques displayed similar leakage for both leakage models. Moreover, the present study demonstrated that all bacterial leakproof specimens leaked when submitted to the blue methylene extraction model.

Effect of final irrigation protocols on push-out bond strength of an epoxy resin root canal sealer to dentin.

The purpose of the present study was to evaluate the effect of different final irrigation protocols on push-out bond strength of an epoxy resin root canal sealer to dentin. Eighty single-rooted anterior teeth were used. The root canals were partially prepared using a rotary system and the final diameter was standardised using a #5 Gates-Glidden drill prior to the push-out bond test. During chemomechanical preparation, 5.25% NaOCl or 2% CHX gel was used. For smear layer removal, 17% ethylenediaminetetraacetic acid (EDTA) or QMix 2 in 1 was applied for 3 min. As final irrigant, 1 mL of NaOCl, CHX solution or distilled water was used. On conclusion of preparation, canals were filled with gutta-percha/AH Plus sealer. Bond strength was measured by the push-out test. Data were statistically analysed by Kruskal-Wallis and Mann-Whitney U-tests. The group NaOCl/EDTA/NaOCl showed significantly higher bond strength values than other groups. In all groups, there were mainly mixed failure patterns. It can be concluded that 5.25% NaOCl proved to be the best solution for the final irrigation when combined with EDTA. The final irrigation protocols affect the push-out bond strength of AH Plus to dentin.