Composite Resin Blocks Research Articles

Impact of Immediate Dentin Sealing Using Universal Adhesive under Simulated Pulp Pressure on Microtensile Bond Strength of Indirect Resin Composite Restorations and Dentin Permeability.

Objective The aim of this study was to investigate the effect of immediate dentin sealing (IDS) technique using universal adhesive under simulated pulp pressure on microtensile bond strength (μTBS) of indirect resin composite restorations and dentin permeability. Materials and Methods Fifty extracted caries-free human third molars were used for specimens' preparation. Each molar's occlusal table was abraded flat and their roots were separated under continuous water cooling. Forty specimens were used for microtensile bond strength test (μTBST) evaluation. The μTBST specimens were randomly assigned to two groups according to the dentin sealing time; Immediate dentin sealing (IDS) and delayed dentin sealing (DDS). Each group was further subdivided into two subgroups according to the adhesive system used for dentin sealing: iBOND self-etch adhesive and GLUMA Bond Universal. All specimens were exposed to simulated pulp pressure for 1 week then restored using computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks. The μTBS was evaluated for all tested subgroups after 24 hours and 6 months of water storage. The remaining 10 teeth were used for the preparation of dentin discs for dentin permeability evaluation. They were divided into two groups according to type of self-etch adhesive used. Fluid filtration rate was evaluated after etching, with smear layer and after adhesive application. Results obtained were statistically analyzed using Shapiro–Wilk test and Weibull analysis. Results Statistically significant difference was recorded between µTBS mean values of both IDS and DDS techniques at 24 hours and after 6 months of water storage. GLUMA Bond Universal adhesive had significantly higher bond strength compared with iBond at both IDS and DDS techniques, but both adhesives showed a significant reduction in the Weibull characteristic strength after 6 months of water storage. Significant reduction in dentin permeability was recorded by both adhesives without any significant difference between them. Conclusions The IDS technique using universal adhesive in self-etch mode is an effective strategy for improving the final bond strength of CAD/CAM resin composite restorations and reducing dentin permeability.

Effect of Dimethyl Sulfoxide wet bonding technique on the durability of resin-dentin bond of an etch-and rinse adhesive system under in-vivo simulating conditions

Purpose: This study assessed the influence of new dimethyl sulfoxide (DMSO) containing pretreatments on the aged resin-dentin micro-tensile bond strength (μTBS) of a two-step etch-and rinse adhesive system. Methods: Occlusal enamel of forty-eight sound molar teeth were ground to expose mid-coronal dentin. Prepared specimens were restored with AdperTM Single Bond2 (SB2) adhesive systems. Prior to the adhesive system application, specimens were randomly assigned into three groups according to dentin pretreatment [no treatment (control group), ethanol wet-bonding (EtOH), or 50 vol% DMSO dissolved in ethanol (DMSO/EtOH)]. Resin composite block was build-up for each specimen. Specimens were stored under simulated IPP 20 mmHg, immersed in artificial saliva at 37 oC for either 24h or 6m. Specimens were sectioned into sticks of 1mm2 for μTBS testing using a universal testing machine. Mode of failure was analyzed using a scanning electron microscope. Three extra sticks from each subgroup were prepared and assessed for the amount of silver nitrate penetration (wt%) using energy dispersive analytical x-ray (EDAX). Data were statistically analyzed by Two-way ANOVA of Variance. Results: (DMSO/EtOH) group revealed the highest statistically significant mean bond strength and the least silver nitrate penetration compared to the (control) and (EtOH) groups at 24h and 6m. Adhesive failures was most predominant for control group at 24h, with increased percentage of mixed failure for EtOH and DMSO/EtOH groups at 24h and 6m. Conclusions: DMSO/EtOH dentin pretreatment improved the immediate and delayed resin-dentin bond.

Resin bond strength to translucent zirconia: A 2-year follow-up

The aim of this study is to evaluate the effect of aging on resin bond strength to translucent zirconia treated with the most clinically used bonding procedures. Monolithic translucent zirconia-based ceramic (3Y-TZP) blocks were surface treated using airborne-particle abrasion with alumina particles (AP) or silica-coated alumina particles (SC) then bonded to resin composite blocks using a resin cement system containing a silane coupling agent and an adhesive with a phosphate (MDP) monomer. Bar-shaped specimens (bonding area: 1 mm 2 ) were fabricated (n = 30) and stored in 37 °C distilled water for the following time before testing: 7 days (SCI and API); 1 year (SC1 and AP1); and 2 years (SC2 and AP2). Specimens were loaded to failure under tension using an Instron testing machine. Microtensile bond strength (σ f ) data was statistically analyzed using Weibull distribution, analysis of variance (ANOVA) and Tukey tests (α = 0.05). Failures were evaluated using fractographic principles. Mean σ f values significantly decreased after 2 years of water storage (SC2 and AP2) (p < 0.05), although there was no difference in the Weibull modulus. All specimens failed cohesively within the adhesion zone at the zirconia-cement adhesive interface.

Effect of sandblasting and/or priming treatment on the shear bond strength of self-adhesive resin cement to CAD/CAM blocks.

The aim of this study was to investigate the effect of two different priming agents and/or sandblasting on the shear bond strength of self-adhesive resin cement to the resin composite for core build-up to CAD/CAM blocks. A CAD/CAM ceramic block (GN I CERAMIC BLOCK, GC) and a CAD/CAM resin composite block (CERASMART 270, GC), a self-adhesive resin cement (G-CEM ONE, GC) and two different primers, i.e., a multipurpose primer (MP; G-Multi Primer, GC) and a ceramic primer (CP; Ceramic Primer II, GC), were examined. Five different surface treatments with priming and/or sandblasting and no surface treatment (control) were performed on the block. Disk specimens (6mm in diameter and 4mm in thickness) made from core composites were cemented to the blocks after the surface treatments. Then, the 24-h shear bond strength of the resin cement between the block and the resin composite core was determined (n = 15). Sandblasted specimens had greater bond strength than controls for both blocks (p < 0.05). Priming to both blocks significantly increased the bond strength of resin cement compared to that of controls (p < 0.05). Although Weibull moduli were not significantly changed among all surface treatments for both blocks, the strengths with 5% and 95% failure probability of sandblasted and/or primed blocks were estimated to be greater than those of controls. The combination of priming and sandblasting to the CAD/CAM composite and ceramic surface was effective in increasing the bond strength of the resin cement.

Reparo em resina composta usando adesivo universal melhora a estabilidade da união

Repair in resin-based composite is a procedure that has shown good results, when properly indicated. In cases of fracture or stainning, the total removal of the restoration can cause unnecessary wear on the dental element. This study evaluated the aging effect on the bond strength of a universal adhesive containing silane, and/or application of silane separately for composite repairs. Resin composite blocks were thermocycled and divided according to adhesion protocol (n=10): silane(Sil), conventional adhesive(CA), universal adhesive(UA), Sil+CA(SilCA), and Sil+UA(SilUA). Layers of resin composite were added and blocks were sectioned and divided into 2 subgroups: 24h and 4 months of water storage. Microtensile bond strength test was performed and data were statistically analyzed (a = 0.05). After 4months of aging SilCA and SilUA showed a significant bond strength reduction, while for UA the bonding remained stable.

Evaluation of self-etching primer on bond strength in feldspathic ceramic

The aim of the study was to evaluate the effect of self-etching silane primer on long-term bonding strength on feldspathic ceramic. Ceramic blocks (IPS Empress CAD, Ivoclar Vivadent) were cut with a low-speed diamond disk (Isomet 1000, Buehler) into 40 blocks of 12x7x6mm, under water cooling, and randomly divided into two groups (n=20), according to the surface conditioning: hydrofluoric acid (HF) (Condac, FGM) or self-etching silane primer (MEP) (Monobond Etch and Prime, Ivoclar Vivadent). After the blocks were bonded to composite resin blocks (12 x 7 x 3mm) (Liss, FGM) with a light cured cement (Variolink Esthetic LC, Ivoclar Vivadent) and LED photoactivation (Radii Cal, SDI) for 40 s on each luting interface line. The sets were cut in sticks with 1-mm2 cross-section composed of ceramic/cement/composite and tested after 24h (baseline) and 90 days aging by stored in distilled water at 37ºC. Microtensile bond strength testing (mTBS) was performed using a universal machine (DL-1000, EMIC) submitted to traction with speed of 0.5mm/ min until rupture of adhesion. Fracture of specimens were examined under stereomicroscopy to determine the failure pattern. Bond strength (MPa) was calculated, and the failure pattern and interface topography were assessed using scanning electron microscopy (SEM). No significant different mTBS was observed between groups HF and MEP (p&gt;0.05). Storage time of the samples did not affect the mTBS from the groups. Surface etching pattern with HF produced higher surface alterations than a self-etching primer. Application of MEP may be considered an alternative for silanization for feldspathic ceramic.

The effect of different storage media on the monomer elution and hardness of CAD/CAM composite blocks

ObjectiveThis study aimed to assess the effect of different storage media on the hardness and monomer elution of CAD/CAM composite blocks. MethodsFive resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block (Enamic (EN)), one ceramic-filled poly ether ether ketone (PEEK) block (Dentokeep (DK)), and one feldspathic ceramic block. Microhardness was measured using a Vickers indenter tester (FM-700, Future Tech Corp., Japan). In addition 4 conventional resin-composites were investigated for monomer elution using high performance liquid chromatography (HPLC) after storage in different media for 3 months. The data were analysed by three-way ANOVA, two-way ANOVA, one-way ANOVA, Tukey’s post hoc test and the independent t-test (α=0.05 for all tests). ResultsThe specimens stored in the water had a hardness reduction ranging from 0.9% to 24.4%. In artificial saliva, the specimens had a hardness reduction ranging from 2.8% to 23.2%. The hardness reduction percentage in 75% Ethanol/Water (E/W) ranged between 3.8% and 35.3%. All materials, except GR (resin-composite block) and DK (Polyetheretherketone (PEEK)), showed a variable extent of monomer elution into 75% E/W with significantly higher amounts eluted from conventional composites. GRA and GND (conventional resin-composites) eluted TEGDMA in artificial saliva and GRA eluted TEGDMA in water. SignificanceThe hardness of CAD/CAM composite blocks was affected by different storage media, and they were not as stable as ceramic, with PICN exhibited superior hardness stability to all of the resin-composite blocks in all the storage media and was comparable to ceramic block. The hardness reduction percentage of the CAD/CAM composite blocks was influenced by the filler loading and resin-matrix composition.Minimal or no monomer elution from CAD/CAM blocks was detected.

Detection of the hybrid layer biodegradation initiation factor with a scanning electron microscope.

The purpose of this study was to elucidate the origin of initiation of hybrid layer biodegradation. Ninety caries-free human third molars were divided into three surface groups: enamel, dentin, and NaOCl-treated dentin. (n=30/group) Each group was divided into three subgroups (n=10/group) of luting resin materials with etch-and-rinse; self-etch and self-adhesive systems. Resin composite blocks and sticks were fabricated and adhered onto dentin and enamel surfaces. The bond strength values were evaluated with micro shear test and statistical analysis were made. On the other hand, teeth were sectioned with a slow-speed saw into multiple beams. After thermocycling, samples were kept in 50% silver nitrate solution. Samples were analyzed with SEM in back-scattered mode. According to the micro-shear bond tests, higher bond strength values were observed in etch-and-rinse system. Bond strength values in self-adhesive and etch-and-rinse groups were significantly higher than self-etch groups in dentin surface and dentin surface treatment with NaOCl. Back-scattered scanning electron microscope results showed that, different degradation mechanism was observed. The present study indicates that, due to the acid etching in dentin, collagen biodegradation was observed within the hybrid layer. On the enamel surfaces, resin degradation was related with resin monomers in adhesive systems.

Resin Composite Materials for Chairside CAD/CAM Restorations: A Comparison of Selected Mechanical Properties.

Objective The aim was to evaluate the flexural strength, flexural modulus, microhardness, Weibull modulus, and characteristic strength of six resin composite blocks (Grandio Blocs-GR, Tetric CAD-TE, Brilliant Crios-CR, Katana Avencia-AV, Cerasmart-CS, and Shofu Block HC-HC). Methods Flexural strength and flexural modulus were measured using a three-point bending test and microhardness using the Vickers method. Weibull analysis was also performed. Results The materials showed flexural strength ranging from 120.38 (HC) to 186.02 MPa (GR), flexural modulus from 8.26 (HC) to 16.95 GPa (GR), and microhardness from 70.85 (AV) to 140.43 (GR). Weibull modulus and characteristic strength ranged from 16.35 (CS) to 34.98 (TE) and from 123.45 MPa (HC) to 190.3 MPa (GR), respectively. Conclusions GR, TE, and CR presented significantly higher flexural strength, modulus, Weibull modulus, and characteristic strength than the others.

Electric current effects on bond strength, nanoleakage, degree of conversion and dentinal infiltration of adhesive systems

To evaluate the effect of three adhesive systems applied under electric current on microtensile bond strength (μTBS) and degree of conversion (DC). Molar teeth were restored with the aid of three adhesive systems (Adper Single Bond 2—SB2; Clearfil SE Bond—CSE; and Single Bond Universal—SBU) under different electric current intensities (0 μA; 25 μA; and 50 μA). Composite resin blocks were built up in increments (2 mm) and sectioned into 1 × 1 mm beams. The μTBS was tested after 24 h and 1 y distilled water storages. Samples (n = 10) from 24 h to 1 y storages were immersed in a 50% ammoniacal silver nitrate solution and submitted to scanning electron microscopy. The silver nitrate in the hybrid layer was quantified (ImageJ software). The adhesive systems' dentinal infiltration was analyzed using confocal laser scanning microscopy. Fourier transform near infrared spectroscopy was used to measure the DC. The μTBS data were submitted to two-way ANOVA (time vs. electric current) and Bonferroni's test (α = 0.05). Quantitative nanoleakage data were submitted to two-way ANOVA (electric current vs. adhesive) and Bonferroni's test (α = 0.05). DC data were submitted to one-way ANOVA and Tukey's test (α = 0.05) for each adhesive system. The electric current statistically increased the μTBS for SB2 and CSE in 24 h storage, as well as for SB2, CSE and SBU in 1 y storage. No significant difference was observed between storage time for CSE and SBU. When compared to the control, electric currents (25 μA and 50 μA) showed significantly higher DC mean values for SB2 and SBU, and had no effect on CSE. The electric currents (25 μA and 50 μA) reduced the adhesive system's nanoleakage after 1-year storage, and improved the infiltration of SB2 and CSE. Both electric current intensities improved dentinal interface stability.

A novel CAD/CAM resin composite block with high mechanical properties

ObjectiveTo determine the mechanical properties of a newly-developed CAD/CAM resin composite block and compare with other resin composite blocks and a polymer-infiltrated ceramic block. MethodsExperimental composite block was formulated by our proprietary resin and filler technologies and cured via Hot Isostatic Pressing (HIP). Bar-shaped specimens (1 × 4×12 − 13 mm, n = 10) for flexural strength, flexural modulus and modulus of resilience were sectioned from block materials and measured in accordance to modified ISO-6872. Cylinder specimens for compressive strength (2 × 4 mm, n = 8) and for diametral tensile strength (6 × 3 mm, n = 8) were milled from the block materials and tested according to ASTM-D695 and ANSI/ADA-Specification #27, respectively. Block specimens (5 mm, n = 3) for Vickers hardness were polished and measured for five indentations on each specimen. The data was analyzed by one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). ResultsExperimental composite block showed higher or significantly higher flexural strength, flexural modulus, modulus of resilience, compressive strength, diametral tensile strength and Vickers hardness than the other commercially available block materials except Vita Enamic for flexural modulus and hardness and Cerasmart for modulus of resilience. Some positive correlations were observed among the different mechanical properties. SignificanceNew composite block exhibited higher mechanical properties as compared to commercially available composite block materials. Superior mechanical properties for resin composite block materials were obtained by composite and curing processing technologies. Resin composite blocks with higher mechanical properties are good options for the fabrication of CAD/CAM indirect restorations.

The Effect of Arabian Coffee, Black Tea and Orange-juice on Microhardness and Color Stability of Hybrid Composite Resins. An in vitro Study

The main aim of the present in-vitro study is to assess the effect of daily consumable drinks on the aesthetics of the dental composite resin materials. Sixty-four microhybrid and nanohybrid direct composite resin (3M™ Filtek™ Z350 XT Universal Restorative, Filtek™ Bulk Fill Flowable Restorative, USA) block samples were made with a dimension of 15mm X 2mm and are allocated into four groups. Each sample was immersed in test media such as Arabic coffee, black tea, orange-juice and distilled water as control group at room temperature for 15 days (n = 16). The color stability and microhardness measurements were taken at pre-immersion and after two weeks of immersion in test media. These parameters were assessed by electro spectrophotometerusing the CIE (Commission Internationale de l'Eclairage) system and Vickers microhardness indenter respectively. Each group was immersed in its test media for the complete duration of the study. On completion of 15 days, the samples were blot dried out with absorbent paper and microhardness dimensions and color stability measures were performed. The collected data was subjected to statistical analysis to formulate the results. Significant discoloration was observed with the Arabic coffee, black tea and orange-juice compared with control group. The Arabic coffee caused most significant discoloration followed by black tea and orange-juice. Although the highest values of microhardness was noted in the Arabic coffee followed by black tea and orange juice, whereas the lowest values were noted in the control. The color stability and microhardness of the composite resin restorations is affected by the everyday drinks that are consumed, from some more than others. Some of the everyday drinks affect the color stability and microhardness of the composite resin restorations more than the others.

Impact of biomineralization on resin/biomineralized dentin bond longevity in a minimally invasive approach: An “in vitro” 18-month follow-up

ObjectivesTo determine the impact of treating caries-affected dentin (CAD) with: 0.2% sodium fluoride (NaF), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP/MI Paste™) or peptide P11-4 (Curodont™ Repair) on the longevity of resin/CAD interface at storage times of 24 -h, 6- and 18-month. Methods255 caries-free third molars were used, and CAD was produced by a biological method. The teeth were randomly distributed into: G1- Sound dentin (SD); G2- CAD; G3- CAD + 0.2% NaF (CAD/NaF); G4- CAD + CPP-ACP (CAD/ACP); G5- CAD + Curodont™ Repair (CAD/P11-4). The Filtek Z350 composite resin block was bonded to dentin using Adper™ Single 2 (4 mm/height). Resin/dentin blocks were stored in a solution of Simulated Body Fluid at 37 °C, pressures were modified to simulate natural pulpal pressures. Specimens were investigated by microtensile bond strength (μTBS) (n = 8), Scanning Electron Microscopy (to assess the failure mode) (n = 8), nanoinfiltration (to assess the interface sealing) (n = 3), in situ zymography (to assess the gelatinolytic activity) (n = 3) and micro-computed microtomography (μ-CT) (to assess the mineralization) (n = 3). Data from μTBS, μ-CT and, nanoinfiltration and hybrid layer formation/degradation were submitted to two-way ANOVA and Tukey tests, and failure patterns and in situ zymography to Kruskal–Wallis and Dunn tests (α = 5%). ResultsThe highest mineral density change by μ-CT, smallest silver nitrate infiltration and proteolytic activity in the adhesive layer were obtained significantly for the groups SD, CAD/ACP and CAD/P11-4, with most mixed fractures at 18-month (p < 0.001). CAD/NaF showed significantly similar values to CAD, CAD and CAD/NaF which presented a high percentage of adhesive fracture (p < 0.001) at all time periods. SignificanceTreating caries-affected dentin with remineralizing agents CPP-ACP and Curodont™ Repair, has the potential to be a clinically relevant treatment protocol to increase the longevity of adhesive restorations.

Resin composite adhesion to dentin using different curing lights and adhesive systems applied under electric current.

To evaluate the effect of electric current application on the resin composite-tooth bond strength and hybrid layer of three adhesive systems light-cured by two light-curing units (LCUs). Human molar teeth were distributed into 12 groups (n=6). Three adhesive systems were used: two-step etch-and-rinse (SB2; Adper Single Bond 2, 3M ESPE); two-step self-etch (CSE; Clearfil SE Bond, Kuraray); and one-step self-etch (SBU; Single Bond Universal, 3M ESPE) applied with (50μA) and without (control; conventional application) electric current, and light-cured with different LCUs. Resin composite blocks (Filtek Z350XT, 3M ESPE) were produced and cut into sticks (~1mm2) for microtensile bond strength (μTBS). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive, or mixed. Specimens were prepared for scanning electron microscope observation. The hybrid layer analysis was carried out using a confocal laser scanning microscopy (n=2). Data were submitted to three-way ANOVA followed by Tukey's post hoc test (α=0.05). The electric current increased the μTBS for all adhesive systems light-cured with single-emission peak and multiple-emission peak LCUs. Both LCUs presented similar μTBS values. CSE applied under electric current showed the highest μTBS mean values. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems. The adhesive systems applied under electric current increased the bond strength using single-emission peak and multiple-emission peak LCUs. Electric current at 50μA applied throughout the dentin is a safe mode and results in better impregnation of the adhesive systems.

The effect of different surface preparation methods and various aging periods on microtensile bond strength for composite resin repair.

To evaluate the effect of various aging periods and different surface preparation methods on microtensile bond strength (μTBS) for composite repair. One hundred twelve composite resin blocks were formed using a nanohybrid composite resin. The samples were distributed into four groups according to surface preparation methods (n = 28): control (sound composite blocks); Er, Cr: YSGG laser; air abrasion; silicone carbide. All samples were then divided into four subgroups according to various aging periods: (i) No aging, (ii) 10,000 thermocycling, (iii) 30,000 thermocycling, and (iv) 50,000 thermocycling. Following surface preparation and aging procedures, surface topography of one sample from each group was evaluated under scanning electron microscope (SEM). The repair composites were bonded to the sample surfaces, using a three-step etch&rinse adhesive. Finally, thirty beams of size 1 × 1 × 8 mm from each group were subjected to μTBS test and failure modes were determined. The data were analyzed using two-way ANOVA, Post-hoc Bonferroni, and Chi-square tests (P = 0.05). When different surface preparation methods were evaluated together, no aging and 10,000 thermocycling groups displayed higher μTBS values (P < 0.05). When all aging periods were evaluated together, the surface preparation with air abrasion provided higher μTBS (P < 0.05). The interactions of various aging periods with different surface preparation methods revealed significant variations in repair μTBS (P < 0.05). There were statistically significant differences on failure mode distributions among surface preparation methods (P < 0.001). SEM evaluations provided valuable outcomes that help to comment on the μTBS findings. Different surface preparation methods, various aging periods, and the interaction of both affected the repair μTBS of the tested nanohybrid composite resin.

Incorporation of chitosan into a universal adhesive system: Physicochemical characteristics, gelatinolytic activity, bond strength and interface micromorphology analyses

This study evaluated the physicochemical characteristics (particle size, zeta potential and polydispersity index) of a universal adhesive system (Scotchbond Universal/3 M ESPE) containing 0.5% chitosan (Ch), used as a self-etching (SE) or a total-etching (TE) strategy, and the effects of this chitosan-incorporated adhesive on microtensile bond strength stability to dentin, dentin-restoration interface, and gelatinolytic activity by in situ zymography. Dentin surfaces received treatments applying adhesive systems with or without Ch, and were used with an SE or a TE strategy. Composite resin blocks were built, and sticks were obtained and separated for microtensile bond strength tests (n = 10). Assessments were made after 24-h and 6-month storage, and the dentin/resin interface was evaluated by scanning electron microscopy (SEM) and zymography analyses (n = 4). Particle size and polydispersity index increased significantly, whereas zeta potential increased and decreased significantly over time. Microtensile bond strength for the SE (without Ch) and TE (with Ch) strategies decreased significantly after 6 months (p < 0.0001). At 6 months, the TE strategy had significantly higher microtensile bond strength than SE. SE and TE strategies (both with Ch) provided higher collagenolytic activity than SE and TE (without Ch) (p = 0.0007). Addition of 0.5% chitosan promoted solution instability. Both the TE strategy and the Ch incorporation affected microtensile bond strength negatively. There was higher collagenolytic activity when Ch was incorporated into the adhesive, regardless of the application strategy.

Evaluation of Degree of Conversion, Resin-Dentin Bond Strength, and Durability of Polydopamine Incorporated Total Etch Adhesive System.

Objectives:This study aimed to evaluate the degree of conversion (DC%), shear bond strength (SBS), bond durability, and the resin-dentin interface of polydopamine (PDA) incorporated total-etch adhesive system.Materials and Methods:Five percentage by weight (wt%) concentration of PDA incorporated adhesive was prepared and its polymerization was evaluated using Fourier-transform infrared spectroscopy. The results were compared with the DC% of conventional total-etch adhesive (Adper Single Bond 2) using independent t-test. Occlusal surfaces of 80 freshly extracted human premolars were sectioned to expose the dentin, which was acid-etched. The samples were divided into two groups (n=40) of total-etch adhesive and total-etch adhesive+PDA. Composite resin blocks were built up over the bonded surface and cured. Each group was subdivided into two subgroups (n=20) of immediate and post-aging evaluation. Samples were immersed in 10% sodium hypochlorite for five hours, and then, the SBS was evaluated using a universal testing machine at a crosshead speed of 1 mm/minute. The resin-dentin interface was evaluated using confocal laser scanning microscopy. Data were analyzed using two-way analysis of variance and post-hoc Bonferroni test.Results:DC% was not affected by the addition of 5% PDA to the adhesive (group 2). The SBS of group 2A was significantly higher than that of group 1A. There was no significant reduction of SBS in group 2B. The hybrid layer was less degraded after aging in group 2B compared to group 2A.Conclusion:PDA incorporated adhesive increased the immediate bond strength and durability without changing the DC%.

Influence of roughening procedures and priming agents on shear bond strength of CAD/CAM materials to zirconia frameworks.

This study investigated the influence of roughening procedures and application of primers on shear bond strengths of CAD/CAM composite resin material or ceramic material to zirconia frameworks. A CAD/CAM composite resin block (Katana Avencia Block; AVE) and lithium disilicate glass-ceramic block (IPS e.max CAD; IEC) were used as veneer materials. The veneers were divided into three surface treatment groups; HF, hydrofluoric acid etching; AB, airborne-particle abrasion; and CON, no surface treatment. Each veneer was primed with four agents: Clearfil Porcelain Bond Activator (ACT), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Porcelain Bond Activator (CPB+ACT), and no priming (UP). The zirconia frameworks and AVE or IEC veneers were resin-bonded. In the AVE specimen, AB treatment showed significantly higher shear bond strength than the other treatments at 0 and 20,000 thermocycles, except for UP and CPB+ACT groups at 20,000 thermocycles. Airborne-particle abrasion is necessary for resin bonding to Avencia blocks.

Effect of degradation of filler elements on flexural strength for dental CAD/CAM resin composite materials in water.

Purpose This study aimed to evaluate the effects of degradation on the strength of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks (RCBs) by subjecting them to accelerated degradation in water and conducting biaxial flexural strength tests.Methods Six commercial RCBs were tested. The RCBs were cut into disks, after which the disks were immersed in purified water. For the aging experiment, the samples were subjected to heat treatment at 37, 60, 70, and 80 °C, in a constant temperature oven and stored statically for 30 d. After the aging experiment, the elements released from the RCB fillers were measured by inductively coupled plasma atomic emission spectroscopy. In addition, the biaxial flexural strength of the RCB fillers was measured after accelerated degradation at 70 °C.Results Si (the main component of the filler) was detected in all the RCB solutions after the aging experiment; however, the type and amount of other elements differed considerably among the RCBs. The flexural strength of some of the RCBs decreased by approximately 20-40% after the accelerated degradation. For most materials, the Weibull coefficient decreased or remained unchanged after the test, whereas it increased in some materials.Conclusions The strength of all the RCBs decreased after the accelerated degradation tests; however, this behavior differed among the materials. In addition, the release of elements from the filler of some of the materials into the water correlated with the decrease in the strength of these materials. These findings indicate that the evaluation of the degradation behavior of RCBs in water is essential for their long-term usage.

Restoration's thickness and bonding tooth substrate are determining factors in minimally invasive adhesive dentistry.

Purpose To explore fracture strength and failure behaviour of minimally invasive CAD-CAM composite resin overlay restorations.Methods Eighty bi- and tri-layer cylindrical overlay model including the restoration bonded over bovine tooth dentin (Groups D) and enamel-dentin (Groups E) were assembled (diameter 9 mm). Restorations were milled from CAD-CAM composite resin blocks (Brilliant Crios, Coltène/Whaledent AG) in different thicknesses (0.5mm, 1mm, 1.5mm, 2mm) and equally distributed in four Groups D and four Groups E (n=10). All specimens were submitted to an Hertzian load-to-failure contact test with spherical indenter. Critical loads were recorded in Newton and data were analysed using Kruskal-Wallis test for multiple and Mann-Whitney test for 2-samples comparisons (p < 0.05). Fragments were examined using SEM. The stress distribution for specimens with restorations of 0.5 mm and 2 mm was also investigated with FEA.Results For all specimens, the mean static loads in Newton increased with an increase in restoration thickness. On contrary, restorations with the same thickness displayed higher resistance values when bonded over enamel than dentin, except for the 2-mm thick restorations. A damage competition was detected between cone/median cracks originating at the loading contact area of the restorations and radial cracks beginning at their inner surface, with the former prevailing in restorations bonded on enamel and the latter being dominant for restorations bonded on dentin.Conclusions For bonded ultra-thin resin composite restorations (0.5 mm to 1.5 mm) enamel as bonding substrate assures higher critical loads to fracture than dentin. This influence gradually decreases as restoration thickened.