Effect of ceramic shade on the degree of conversion of a dual-cure resin cement analyzed by FTIR

Objectives: The aim of this research was to evaluate the degree of monomer conversion of different resin cement shades when photocured under different feldspathic ceramic shades. The photocuring time was also evaluated as well as the translucency of each ceramic shade. Methods: Three VITA VM7 ceramic shades (Base Dentin 0M1, Base Dentin 2M2 and Base Dentin 5M3) were used to determine the translucency percentage. A spectrophotometer MiniScan was used to measure the opacity percentage of each specimen (2-mm-thick) and then the translucency was calculated. To measure the degree of conversion (DC), the resin cement (Variolink II; A3 Yellow and transparent) specimens (thickness: 100 μm) were photocured under a ceramic block (2-mm-thick) for 20 or 40 s. Specimens photocured without the ceramic block were used as control. Sixteen groups (n = 3) were evaluated. Micro-ATR/FTIR spectrometry was used to evaluate the extent of polymerization of all specimens after 24 h. The %DC was calculated of experimentally polymerized versus maximally polymerized composite. Results: The translucency percentages of 0M1, 2M2 and 5M3 ceramics were 12.41 (1.02)%, 5.75 (1.91)% and 1.07 (0.03)%, respectively. The %DC of both resin cement shades cured under ceramic 5M3 was significantly lower than the other groups (p < 0.05). The %DC of 0M1 groups exhibited no significant difference from 2M2 groups (p > 0.05), with the exception of the transparent cement photocured for 40 s. Conclusion: Photocuring under 2 mm ceramic showed that the increase in chroma saturation significantly decreased Variolink II resin cement %DC (100-μm-thick). © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of Cement Shade and Light-curing Unit on Bond Strength of a Ceramic Cemented to Dentin

Purpose: To evaluate the effect of cement shade, light-curing unit, and water storage on tensile bond strength (a) of a feldspathic ceramic resin bonded to dentin.Materials and Methods: The dentin surface of 40 molars was exposed and etched with 37% phosphoric acid, then an adhesive system was applied. Forty blocks of feldspathic ceramic (Vita VM7) were produced. The ceramic surface was etched with 10% hydrofluoric acid for 60 s, followed by the application of a silane agent and a dual-curing resin cement (Variolink II). Ceramic blocks were cemented to the treated dentin using either A3 or transparent (Tr) shade cement that was activated using either halogen or LED light for 40 s. All blocks were stored in 37 degrees C distilled water for 24 h before cutting to obtain non-trimmed bar-shaped specimens (adhesive area = 1 mm(2) +/- 0.1) for the microtensile bond strength test. The specimens were randomly grouped according to the storage time: no storage or stored for 150 days in 37 degrees C distilled water. Eight experimental groups were obtained (n = 30). The specimens were submitted to the tensile bond strength test using a universal testing machine at a crosshead speed of 1 mm/min. The data were statistically analyzed using ANOVA and Tukey's post-hoc tests (alpha = 0.05).Results: The mean bond strength values were significantly lower for the corresponding water stored groups, except for the specimens using A3 resin cement activated by halogen light. There was no significance difference in mean bond strength values among all groups after water storage.Conclusion: Water storage had a detrimental effect under most experimental conditions. For both cement shades investigated (Tr and A3) under the same storage condition, the light-curing units (QTH and LED) did not affect the mean microtensile bond strengths of resin-cemented ceramic to dentin.

Bond Strength of Different Resin Cement and Ceramic Shades Bonded to Dentin

Purpose: To evaluate the microtensile bond strength (MTBS) of ceramic cemented to dentin varying the resin cement and ceramic shades.Materials and Methods: Two VITA VM7 ceramic shades (Base Dentine 0M1 and Base Dentine 5M3) were used. A spectrophotometer was used to determine the percentage translucency of ceramic (thickness: 2.5 mm). For the MTBS test, 80 molar dentin surfaces were etched and an adhesive was applied. Forty blocks (7.2 x 7.2 x 2.5 mm) of each ceramic shade were produced and the ceramic surface was etched (10% hydrofluoric acid) for 60 s, followed by the application of silane and resin cement (A3 yellow and transparent). The blocks were cemented to dentin using either A3 or transparent cement. Specimens were photoactivated for 20 s or 40 s, stored in distilled water (37 degrees C/24 h), and sectioned. Eight experimental groups were obtained (n = 10). Specimens were tested for MTSB using a universal testing machine. Data were statistically analyzed using ANOVA and Tukey's post-hoc tests (alpha <= 0.05).Results: The percentage translucency of 0M1 and 5M3 ceramics were 10.06 (+/- 0.25)% and 1.34 (+/- 0.02)%, respectively. The lowest MTBS was observed for the ceramic shade 5M3. For the 0M1 ceramic, the A3 yellow cement that was photocured for 20 s exhibited the lowest MTBS, while the transparent cement that was photocured for 40 s presented the highest MTBS.Conclusions: For the 2.5-mm-thick 5M3 ceramic restorations, the MTBS of ceramic cemented to dentin significantly increased. The dual-curing cement Variolink II photocured for 40 s is not recommended for cementing the Base Dentine 5M3 feldspathic ceramic to dentin.

Resin cement thickness in oval-shaped canals: Oval vs. circular fiber posts in combination with different tips/drills for post space preparation

Purpose: To evaluate the cement thickness around oval and circular posts luted in oval post spaces prepared with different drills/tips. Methods: Extracted premolars were endodontically treated and obturated, then randomly divided into three groups (n = 5) according to the tips/drills used for post-space preparation and to the type of fiber post luted: medium grit oval tip + oval posts, fine grit oval tip + oval posts, Mtwo Post File drill + circular posts. The specimens were sectioned in horizontal slices; one slice per canal third was chosen for each post-space, resulting in three slices for each specimen. The distances between the canal wall and the post perimeter were measured on SEM images of each slice. Results: The fine grit tip + oval post group obtained statistically significant lower cement thicknesses than the other groups (P < 0.05), in particular in the apical third. The MtwoPF + circular post group showed the highest cement thickness, comparable to that of the medium tip + oval post group. A good post fitting in oval-shaped canals can be obtained using a fine grit oval tip combined with oval posts. (Am J Dent 2009;22:290-294).

Push-out Bond Strength of Fiber Posts Luted with Unfilled Resin Cement

Purpose: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. Materials and Methods: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. Results: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. Conclusion: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin.

Influence of Post and Resin Cement on Stress Distribution of Maxillary Central Incisors Restored with Direct Resin Composite

The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm(2) was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 mu m). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.

Bond Strength of Fiber Posts in Different Root Thirds Using Resin Cement

Purpose: The aim of the study was to assess the in vitro bond strength (BS) of glass fiber posts (GF) and carbon fiber posts (CF) in the cervical, middle, and apical thirds of root canals cemented with RelyX-Unicem (RX) and Cement-Post (CP). Materials and Methods: Forty maxillary canines were divided into 4 groups (n = 10) according to the cement and post used: group 1: GF and RX; group 2: CF and RX; group 3: GF and CP; group 4: CF and CP. The push-out test was applied in the cervical, middle and apical thirds of each specimen to assess bond strength of the cement/post complex to the root canal wall. The data obtained were submitted to ANOVA (Bonferroni test, p < 0.05), and fracture analysis was done with SEM. Results: The GF posts presented the best results when cemented with RX and with CF (p < 0.05). RX presented the highest BS values for both GF and CF (p < 0.05). For all the groups, BS was higher in the cervical third, followed by the middle and apical thirds. Fracture analysis showed a predominance of cohesive fracture of posts for RX, and a predominance of adhesive fracture between dentin/cement, and mixed failure mode for CP. Conclusion: GF posts cemented with RX presented the highest BS values in all root thirds.

Influence of Different Ceramics on Resin Cement Knoop Hardness Number

This study evaluated: 1) the effect of different ceramics on light attenuation that could affect microhardness, measured as the Knoop Hardness Number (KHN), of a resin cement immediately and 24 hours after polymerization and 2) the effect of different activation modes (direct light-activation, light activation through ceramics and chemical activation) on the KHN of a resin cement.Resin cement Rely X ARC (3M ESPE) specimens 5.0 mm in diameter and 1.0 nun thick were made in a Teflon mold covered with a polyester film. The cement was directly light activated for 40 seconds with an XL 2500 curing unit (3M ESPE) with 650 mW/cm(2), light activated through ceramic discs of Duceram Plus (DeguDent), Cergogold (DeguDent), IPS Empress (Ivoclar), IPS Empress 2 (Ivoclar), Procera. (NobelBiocare), In Ceram Alumina (Vita) and Cercon (DeguDent), having a 1.2 mm thickness or chemically activated without light application. The resin cement specimens were flattened, and KHN was obtained using an HMV 2 microhardness tester (Shimadzu) with a load of 50 g applied for 15 seconds 100 pin from the irradiated surface immediately and after storage at 37 degrees C for 24 hours. Ten measurements were made for each specimen, with three specimens for each group at each time. The data were submitted to ANOVA and Tukey's test (p=0.05). The KHN of the resin cement was not only affected by the mode of activation, but also by the post-activation testing time. The mean KHN of the resin cement for chemical activation and through all ceramics showed statistically significant lower values compared to direct activation immediately and at 24 hours. The KHN for 24 hours post-activation was always superior to the immediate post-activation test except with direct activation. The most opaque ceramics resulted in the lowest KHN values.

EFFECT of DIFFERENT AIRBORNE-PARTICLE ABRASION/BONDING AGENT COMBINATIONS on THE BOND STRENGTH of A RESIN CEMENT TO A BASE METAL ALLOY

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

Efficacy of Air-abrasion Technique and Additional Surface Treatment at Titanium/Resin Cement Interface

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

Influence of Er,Cr: YSGG laser on bond strength of self-adhesive resin cement

The purpose of this study was to investigate the bond strength of fiber post previously laser treated root canals. Forty single-rooted bovine teeth were endodontically treated, randomly and equally divided into two main groups according to the type of pretreatment: G1: 2.5% NaOCl (control group); and G2: Er,Cr:YSGG laser. Each group was further subdivided into 2 groups based on the category of adhesive systems/ luting materials used: a: an etch-and-rinse resin cement (Single Bond/RelyX ARC; 3M ESPE), and b: a self-adhesive resin cement (Rely X Unicem; 3M ESPE). Three 1.5 mm thick slabs were obtained per root and the push-out test was performed at a crosshead speed of 0.5 mm/min until post dislodgement occurred. Data were analyzed by ANOVA and post-hoc Tukey's test at a pre-set alpha of 0.05. Analysis of variance showed no statistically significant difference (p > 0.05) among the groups G1a (25.44 ± 2.35) and G1b (23.62 ± 3.48), G2a (11.77 ± 2.67) and G2b (9.93 ± 3.37). Fractures were observed at the interface between the dentin and the resin in all groups. The Er,Cr:YSGG laser irradiation did not influence on the bond strength of the resin cements and the etch-and-rinse resin cement had better results on bond strength than self-adhesive resin cement.

Effect of Resin Cement System and Root Region on the Push-out Bond Strength of a Translucent Fiber Post

Objectives: This study evaluated the bond strength of luting systems for bonding glass fiber posts to root canal dentin. The hypothesis tested was that there are no differences in bond strength of glass fiber posts luted with different cement systems.Methods: Forty bovine incisors were randomly assigned to five different resin cement groups (n=8). After endodontic treatment and crown removal, translucent glass fiber posts were bonded into the root canal using five different luting protocols (self-cured cement and etch-and-rinse adhesive system; dual-cured cement and etch-and-rinse adhesive system; self-cured cement and self-etch adhesive system; dual-cured cement and self-etch adhesive system; and dual-cured self-adhesive cement). Push-out bond strength was evaluated at three different radicular levels: cervical, middle, and apical. The interface between resinous cement and the post was observed using a stereoscopic microscope.Results: Analysis of variance showed a statistically significant difference among the cements (p<0.05) and the root canal thirds (p<0.05). The self-adhesive resinous cement had lower values of retention.Conclusions: The resin cements used with etch-and-rinse and self-etch adhesive systems seem to be adequate for glass fiber post cementation.

Does the Ultrasonic Cleaning Medium Affect the Adhesion of Resin Cement to Feldspathic Ceramic?

Purpose: To evaluate the effect of different cleaning media on the adhesion of resin cement to feldspathic ceramic after etching.Materials and Methods: The cementation surfaces of ceramic blocks (N = 20, n = 5 per group) were etched with 10% hydrofluoric acid (HF) gel for 20 s and rinsed for 60 s. They were then randomly assigned to 4 groups: G1: air-water spray+drying (control); G2: ultrasonic cleaning in distilled water for 4 min+drying; G3: ultrasonic cleaning in 99.5% acetone for 4 min+drying; G4: ultrasonic cleaning in 70% alcohol for 4 min+drying. The ceramic blocks were silanized and cemented (RelyX ARC) to the composite blocks. Subsequently, the microtensile bond strength test (mu TBS) was performed. In addition, EDS analysis was made to assess the elemental composition of the conditioned and cleaned ceramic surfaces.Results: A significantly higher mean mu TBS was obtained when specimens had been ultrasonically cleaned in distilled water (G2: 18.8 +/- 0.4 MPa) (p < 0.05) compared to other groups (G1: 16.6 +/- 0.5; G3: 16.1 +/- 0.9; G4: 15.8 +/- 1.4) (one-way ANOVA). EDS analysis indicated the presence of F- only in G1. Dissolved precipitates after HF etching were removed by ultrasonic cleaning.Conclusion: Cleaning the HF-etched ceramic surface ultrasonically in distilled water is recommended, instead of rinsing it with air-water spray only.

Hardening of a dual-cure resin cement using QTH and LED curing units

Objective: This study evaluated the surface hardness of a resin cement (RelyX ARC) photoactivated through indirect composite resin (Cristobal) disks of different thicknesses using either a light- emitting diode (LED) or quartz tungsten halogen (QTH) light source. Material and Methods: Eighteen resin cement specimens were prepared and divided into 6 groups according to the type of curing unit and the thickness of resin disks interposed between the cement surface and light source. Three indentations (50 g for 15 s) were performed on the top and bottom surface of each specimen and a mean Vickers hardness number (VHN) was calculated for each specimen. The data were analyzed using two-way ANOVA and Tukey-Kramer test was used for post-hoc pairwise comparisons. Results: Increased indirect resin disk thickness resulted in decreased mean VHN values. Mean VHN values for the top surfaces of the resin cement specimens ranged from 23.2 to 46.1 (QTH) and 32.3 to 41.7 (LED). The LED curing light source produced higher hardness values compared to the QTH light source for 2- and 3-mm-thick indirect resin disks. The differences were clinically, but not statistically significant. Increased indirect resin disk thickness also resulted in decreased mean VHN values for the bottom surfaces of the resin cement: 5.8 to 19.1 (QTH) and 7.5 to 32.0 (LED). For the bottom surfaces, a statistically significant interaction was also found between the type of curing light source and the indirect resin disk thickness. Conclusions: Mean surface hardness values of resin cement specimens decreased with the increase of indirect resin disk thickness. The LED curing light source generally produced higher surface hardness values.

The adhesive system and root canal region do not influence the degree of conversion of dual resin cement

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