Effect of surface treatments on the resin bond to zirconium-based ceramic

Purpose: This study tested the hypothesis that the tribochemical silica coating on ceramic surfaces increases the bond strength of resin cement to a glass-infiltrated zirconium-based ceramic. Materials and Methods: Fifteen blocks of In-Ceram Zirconia from CEREC InLab (5 per group) and 15 composite blocks (Z-250) 5 mm x 5 mm x 4 mm were made. The ceramic surfaces were polished, and the blocks were divided into three groups: (1) airborne abrasion with 110-μm aluminum oxide particles; (2) Rocatec system, tribochemical silica coating; and (3) CoJet system, tribochemical silica coating. The ceramic blocks were cemented to the composite blocks using Panavia F according to the manufacturer's specifications. All samples were stored in 37°C distilled water for 7 days and later sectioned in two axes using a diamond disk under cooling to obtain specimens with a cross-sectional area of approximately 1 mm2 (n = 45). Each specimen was then attached with cyanoacrylate glue to an adapted device for the microtensile test, which was carried out on a universal testing machine. Results: The results were subjected to ANOVA and Tukey's test. Group 2 (23.0 ± 6.7 MPa) and group 3 (26.8 ± 7.4 MPa) showed greater bond strength than group 1 (15.1 ± 5.3 MPa). There was no significant difference between groups 2 and 3. All failures were in the adhesive zone. Conclusion: The hypothesis was confirmed - the tribochemical systems increased the bond strength between Panavia F and In-Ceram Zirconia.

Evaluation of the flexural strength of carbon fiber-, quartz fiber-, and glass fiber-based posts

This study investigated the flexural strength of eight fiber posts (one carbon 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: REFORPOST (Angelus). All of the samples were tested using the three-point bending test. The averages obtained were submitted 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 fiber post (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). Copyright © 2005 by the American Association of Endodontists.

Influence of voids in the hybrid layer based on self-etching adhesive systems: a 3-D FE analysis

The presence of porosities at the dentin/adhesive interface has been observed with the use of new generation dentin bonding systems. These porosities tend to contradict the concept that etching and hybridization processes occur equally and simultaneously. Therefore, the aim of this study was to evaluate the micromechanical behavior of the hybrid layer (HL) with voids based on a self-etching adhesive system using 3-D finite element (FE) analysis. Three FE models (Mr) were built: Mr, dentin specimen (41x41x82 μm) with a regular and perfect (i.e. pore-free) HL based on a self-etching adhesive system, restored with composite resin; Mp, similar to M, but containing 25% (v/v) voids in the HL; Mpp, similar to Mr, but containing 50% (v/v) voids in the HL. A tensile load (0.03N) was applied on top of the composite resin. The stress field was obtained by using Ansys Workbench 10.0. The nodes of the base of the specimen were constrained in the x, y and z axes. The maximum principal stress (σmax) was obtained for all structures at the dentin/adhesive interface. The Mpp showed the highest peak of σmax in the HL (32.2 MPa), followed by Mp (30 MPa) and Mr (28.4 MPa). The stress concentration in the peritubular dentin was high in all models (120 MPa). All other structures positioned far from voids showed similar increase of stress. Voids incorporated into the HL raised the σmax in this region by 13.5%. This behavior might be responsible for lower bond strengths of self-etching and single-bottle adhesives, as reported in the literature.

Analysis of polymerization time on abrasive wear of dental resins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Clinical evaluation of two packable resin-based composite restorations: A three-year report

This randomized clinical trial sought to evaluate the performance of two packable composites over a period of 36 months. A total of 39 Class I and II restorations were placed in the permanent teeth of 20 patients. Using United States Public Health Services criteria, two investigators evaluated the restorations immediately after placement and again after 12 and 36 months, examining color match, marginal discoloration, marginal integrity, recurrent caries, proximal contact, anatomical shape, surface texture, and postoperative sensitivity. It was concluded that the packable composites evaluated showed satisfactory clinical performance after three years.

Persistence of epoxy-based sealer residues in dentin treated with different chemical removal protocols

The presence of residual endodontic sealer in the pulp chamber may cause discoloration of the dental crown and interfere with the adhesion of restorative materials. The aim of this study was to compare the efficacy of different solvents in removing residues of an epoxy resin-based sealer (AH Plus) from the dentin walls of the pulp chamber, by scanning electron microscopy (SEM). Forty-four bovine incisor dental crown fragments were treated with 17% EDTA and 2.5% NaOCl. Specimens received a coating of AH Plus and were left undisturbed for 5 min. Then, specimens were divided in four groups (n = 10) and cleaned with one of the following solutions: isopropyl alcohol, 95% ethanol, acetone solution, or amyl acetate solution. Negative controls (n = 2) did not receive AH Plus, while in positive controls (n = 2) the sealer was not removed. AH Plus removal was evaluated by SEM, and a score system was applied. Data were analyzed by Kruskal-Wallis and Dunn tests. None of the solutions tested was able to completely remove AH Plus from the dentin of the pulp chamber. Amyl acetate performed better than 95% ethanol and isopropyl alcohol (p < 0.05), but not better than acetone (p > 0.05) in removing the sealer from dentin. No significant differences were observed between acetone, 95% ethanol, and isopropyl alcohol (p > 0.05). It was concluded that amyl acetate and acetone may be good options for cleaning the pulp chamber after obturation with AH Plus. SCANNING 35:17-21, 2013. © 2012 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Effects of dentin dry/moist condition on the immediate adhesive performance of different solvent-based etch-and-rinse adhesivesystems

Purpose: The purpose of this research was to analyze and measure, under optical microscopy, the hybrid layer thickness and resin tags length, as well as the microtensile bond strength of two conventional adhesive systems when applied to dry and moist dentinal substrate. Methods: Thirty-two extracted human molars were randomly distributed into four groups according to the adhesive systems (XP Bond and Prime&Bond 2.1) and moisture condition (dry and moist). In Groups I and II, XP adhesive system was applied on dry and moist dentin, respectively; while Groups III and IV received PB adhesive system, in the same way as was done in Groups I and II, respectively. After adhesive and restorative procedures, all specimens were sectioned along their long axes; one hemi-tooth sample was subjected to the microtensile bond strength test while the other was decalcified and serially sectioned into six micron thick slices and sequentially mounted on glass slides. These sections were stained by the Brown and Brenn method for posterior analysis and measurement of the hybrid layer and resin tags under a light microscope with a micrometric ocular 40/075. Results: Data were analyzed using two-way ANOVA and Tukey's test (α=0.05). For the variable hybrid layer thickness, XP showed no significant differences between dry and moist dentin (5.2 μm and 5.5 μm, respectively), but for PB, hybrid layer was significantly thicker for moist (4.0 μm) than for dry dentin (3.0 μm). For the variable resin tags length XP showed 17.9 μm length for dry dentin and 20.8 μm for moist dentin; PB 11.7 μm for dry and 12.69 μm for moist dentin;there was no significant differences between them, independent of the moisture condition. For the variable microtensile bond strength, XP showed 38.0 MPa for dry dentin and 44.5 MPa for moist dentin; and PB showed 22.7 MPa for dry dentin and 20.8 MPa for dry dentin no significant difference was observed between moist and dry dentin for XP (p=0.2) and PB (p=0.7), but XP was presented significantly higher bond strength values than PB in both moisture conditions (p=0.003 for dry and p=0.002 for moist). Conclusion: The two-step butanol-based etch-and-rinse adhesive XP Bond presented a superior behavior with regard to the hybrid layer thickness, length of resin tags and bond strength to dry and moist dentin substrates when compared with two-step acetone-based adhesive system Prime&Bond2.1. © 2013 Elsevier Ltd.

Influence of convergence angle of tooth preparation on the fracture resistance of Y-TZP-based all-ceramic restorations

Objective: To investigate the influence of the convergence angle of tooth preparation on the fracture load of Y-TZP-based ceramic (YZ-Vita YZ) substructure (SB) veneered with a feldspathic porcelain (VM9-Vita VM9). Methods: Finite element stress analysis (FEA) was performed to examine the stress distribution of the system. Eighty YZ SB were fabricated using a CAD-CAM system and divided into four groups (n = 20), according to the total occlusal convergence (TOC) angle: G6-6° TOC; G12-12° TOC; G20-20° TOC; and G20MOD-20° TOC with modified SB. All SB were veneered with VM9, cemented in a fiber reinforced epoxy resin die, and loaded to failure. Half of the specimens from each group (n = 10) were cyclic fatigued (106 cycles) before testing. Failure analysis was performed to determine the fracture origin. Data were statistically analyzed using Anova and Tukey's tests (α = 0.05). Results: The greatest mean load to fracture value was found for the G20MOD, which was predicted by the FEA. Cyclic fatigue did not significantly affect the load of fracture. Catastrophic failure originating from the internal occlusal surface of the SB was the predominant failure mode, except for G20MOD. Significance: The YZ-VM9 restorations resisted greater compression load than the usual physiological occlusal load, regardless of the TOC angle of preparations. Yet, the G20MOD design produced the best performance among the experimental conditions evaluated. © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of the root canal final rinse protocols on the debris and smear layer removal and on the push-out strength of an epoxy-based sealer

The aim of the present study was to evaluate the efficacy of QMiX, SmearClear, and 17% EDTA for the debris and smear layer removal from the root canal and its effects on the push-out bond strength of an epoxy-based sealer by scanning electron microscopy (SEM). Forty extracted human canines (n=10) were assigned to the following final rinse protocols: G1-distilled water (control), G2-17% EDTA, G3-SmearClear, and G4-QMiX. The specimens were submitted to a SEM analysis to evaluate the presence of debris and smear layer, respectively, in the apical or cervical segments. In sequence, forty extracted human maxillary canines with the root canals instrumented were divided into four groups (n=10) similar to the SEM analysis study. After the filling with AH Plus, the roots were transversally sectioned to obtain dentinal slices. The specimens were submitted to a push-out bond strength test using an electromechanical testing machine. The statistical analysis for the SEM and push-out bond strength studies were performed using the Kruskal-Wallis and Dunn tests (α=5%). There was no difference among the G2, G3, and G4 efficacy in removing the debris and smear layer (P>0.05). The efficacy of these groups was superior to the control group. The push-out bond strength values of G2, G3, and G4 were superior to the control group. The ability to remove the debris and smear layer by SmearClear and QMiX was as effective as the 17% EDTA. The final rinse with these solutions promoted similar push-out bond strength values. © 2013 Wiley Periodicals, Inc.

Si-based thin film coating on Y-TZP: Influence of deposition parameters on adhesion of resin cement

This study evaluated the influence of deposition parameters for Si-based thin films using magnetron sputtering for coating zirconia and subsequent adhesion of resin cement. Zirconia ceramic blocks were randomly divided into 8 groups and specimens were either ground finished and polished or conditioned using air-abrasion with alumina particles coated with silica. In the remaining groups, the polished specimens were coated with Si-based film coating with argon/oxygen magnetron discharge at 8:1 or 20:1 flux. In one group, Si-based film coating was performed on air-abraded surfaces. After application of bonding agent, resin cement was bonded. Profilometry, goniometry, Energy Dispersive X-ray Spectroscopy and Rutherford Backscattering Spectroscopy analysis were performed on the conditioned zirconia surfaces. Adhesion of resin cement to zirconia was tested using shear bond test and debonded surfaces were examined using Scanning Electron Microscopy. Si-based film coating applied on air-abraded rough zirconia surfaces increased the adhesion of the resin cement (22.78 ± 5.2 MPa) compared to those of other methods (0-14.62 MPa) (p = 0.05). Mixed type of failures were more frequent in Si film coated groups on either polished or air-abraded groups. Si-based thin films increased wettability compared to the control group but did not change the roughness, considering the parameters evaluated. Deposition parameters of Si-based thin film and after application of air-abrasion influenced the initial adhesion of resin cement to zirconia. © 2013 Elsevier B.V. All rights reserved.

Esthetic and function improvement by direct composite resins and biomimetic concept

Aim: This case report describe a resin layering restorative technique based on biomimetic concept to improve esthetics in a patient with dental defects that affected both enamel and dentin in anterior teeth. Background: Severe structural defect in anterior teeth compromises esthetics and it is a high challenge to become the defect imperceptible after the restoration. Case description: A clinical sequence of applying different composite resin layers allowed the reproduction of the interaction between hard dental tissues and the restorative material. Conclusion: This technique achieved a satisfactory final esthetic outcome, preserving sound teeth structure and at same time, improved the quality of life of the young patient. Clinical significance: The utilization of the biomimetic concept to increase a disharmonic smile with dental defects is based in a conservative approach, which reached a satisfactory and esthetic outcome.

Effect of different solutions on color stability of acrylic resin-based dentures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of postpolymerization method on the color stability of composite resins submitted to ultraviolet aging

The aim of this research was to evaluate the effect of postpolymerization method on the color stability of resin-based composites. Samples of direct and indirect restorative materials were polymerized with two photo-curing units (Visio photo-curing oven system and LED Elipar Freelight 2). All samples were submitted to an initial chromatic analysis using a spectrometer and submitted to ultraviolet-accelerated artificial aging. The direct material showed less color change than the indirect material, independent of the photo-activation method used. Samples photo cured with the LED system showed less change than those photo cured with the Visio system. The postpolymerization oven did not improve the color stability of direct and indirect resin-based composites.