RelyXTM U200 Research Articles

Effect of Ceramic Thickness on the Bond Strength to Resin-Luting Agents before and after Thermal Cycling.

This study investigated microshear bond strength (µSBS) of two (2) dual-cured resin-luting agents (RelyX™ Ultimate and RelyX™ U200) when photoactivated through varying thicknesses of lithium disilicate, with or without thermal cycling. Discs of IPS e.max Press of 0.5, 1.5, and 2 mm in thickness were obtained. Elastomer molds (3.0 mm in thickness) with four cylinder-shaped orifices 1.0 mm in diameter, were placed onto the ceramic surfaces and filled with resin-luting agents. A Mylar strip, glass plate, and load of 250 grams were placed over the filled mold. The load was removed and the resin-luting agents were photoactivated through the ceramics using a single-peak LED (Radii Plus.) All samples were stored in distilled water at 37oC for 24 h. Half of the samples were subjected to thermal cycling (3,000 cycles; 5ºC and 55ºC). All samples were then submitted to µSBS test using a universal testing machine (Instron 4411) at a crosshead speed of 0.5 mm/min. Data were submitted to three-way ANOVA and Tukey post-hoc test (α=0.05). The mean µSBS at 24 h was significantly higher than after thermal cycling (p<0.05). No statistical difference was found between resin-luting agents (p > 0.05). The mean µSBS for groups photoactivated through 0.5 mm ceramic were significantly higher than 1.5 mm and 2.0 mm (p < 0.05). In conclusion, increased ceramic thicknesses reduced the bond strength of tested resin-luting agents to lithium disilicate. No differences were found between resin-luting agents. Thermal cycling reduced the bond strength of both resin-luting agents.

Exploring Zirconia Adhesion: Pre and Postsintering Physical Surface Treatment, Chemical Treatment, and Cement Interactions.

Background: Adhesion to zirconia remains a significant dental challenge. This study is aimed at assessing the bond strength of zirconia based on surface treatment with pre or postsintering sandblasting associated with different chemical treatments and resin cements. Methods: Zirconia blocks were divided into 12 experimental groups based on the surface treatment (presintering sandblasting or postsintering sandblasting/tribochemical abrasion treatment), chemical treatment (none, Single Bond Universal, or Signum Zirconia Bond), and choice of cement (Panavia F or RelyX™ U200). The bond strength was measured by shear tests using a universal testing machine. The fracture analysis was performed using stereomicroscopy. Data were analyzed using three-way ANOVA and Tukey's test (α = 5%). Results: Triple and double factor's interactions were not significant (p > 0.05). Regarding the surface treatment factor, the bond strength following postsintering sandblasting treatment associated with tribochemical abrasion (9.15 ± 3.62 MPa) was significantly higher than presintering sandblasting treatment (5.24 ± 3.53 MPa). Concerning the chemical treatment factor, bond strengths were ranked as follows: Signum Zirconia Bond > Single Bond Universal > no treatment. The bond strength of the resin cements did not differ among them. Most fractures (67%) were classified as adhesive, and 32% were categorized as mixed fractures. Conclusion: Surface treatment via postsintering sandblasting combined with tribochemical abrasion demonstrated superior efficacy than in presintering sandblasting. Additionally, chemical treatment with zirconia primer increased the bond strength of zirconia irrespective of the surface physical treatment.

Effect of Self-Adhesive Resin Cement Film Thickness on the Shear Bond Strength of Lithium Disilicate Ceramic–Cement–Tooth Triplex

Cement film thickness may have an impact on the shear bond strength (SBS) of lithium disilicate dental ceramics luted to human enamel with resin cement. The objective of this study was to evaluate SBS of lithium disilicate ceramics adhered to enamel using resin cement at different thicknesses. In total, 50 ceramic specimens (3 × 3 × 3 mm) and 50 premolar teeth were prepared and randomly assigned to 5 groups (n = 10 each). Ceramic specimens were designed with five cement film thicknesses (50 μm; 100 μm; 150 μm; 200 μm; and 300 μm). Teeth surfaces (4 × 4 mm) were prepared with a high-speed handpiece mounted on a dental surveyor. Ceramic specimens were cemented to teeth with resin cement (3MTM RelyXTM U200, Resin-Self-Adhesive-Cement). The specimens were then thermocycled for 6000 cycles with a 30 s dwell time and a 5 s transfer time in water (5 °C and 55 °C). A Universal-Testing-Machine was used to measure SBS (MPa). Statistical analysis in SPSS included Anova and Tukey’s tests. The SBSs of ceramics adhered to teeth revealed significantly different values across all test groups (p = 0.000). The findings showed that as cement layer thickness increased, so did the SBS. The cement spaces at 50 and 300 μm had the lowest SBS (9.40 + 1.15 MPa) and maximum SBS (21.98 + 1.27 MPa), respectively. The SBS of the lithium disilicate ceramic luted to natural human enamel increased along with the cement layer thickness.

Improving retention of dental veneers fabricated from an experimental enamel-based biopolymer compared with CAD/CAM hybrid materials

ObjectivesCAD/CAM hybrid materials have become increasingly utilized in restorative dentistry. However, their low tensile bond strength (TBS) may lead to the detachment of minimally invasive restorations. When prepared, an experimental enamel-based biopolymer prosthesis provided a honeycomb-like interfacial layer with luting adhesives leading to a higher TBS than Ni–Cr–Be based alloy, lithium disilicate-based ceramic, and cured-resin-composite. This study aimed to compare TBSs of dental veneers fabricated from experimental biopolymer and commercial hybrid materials bonded to enamel using two different luting adhesives. MethodsLaminate veneers (4 × 4 mm) 1 mm thick were prepared from commercial CAD/CAM blocks: VITA ENAMIC, SHOFU Block HC, KATANA AVENCIA, and an experimental biopolymer. The flat bonding surface of the veneers was ground to 600-grit, followed by 50-μm alumina air-abrading for standardization. Each veneer was fixed on flat ground bovine enamel using either Super-Bond C&B or RelyX™ U200 resin (n = 10). The surface treatment and bonding procedures were treated as recommended by the manufacturers. All bonded specimens were stored in water at 37 °C for 24 h before tensile testing with a universal testing machine at a cross-headed speed of 1.0 mm/min. The fractured surface was examined with a stereomicroscope and scanning electron microscope. TBS data were statistically analyzed using two-way ANOVA and Tukey's HSD test (α = 0.05). ResultsExperimental biopolymer veneers demonstrated the highest mean TBS with cohesive failure in the luting agents. Adhesive failure at the veneer side interface was found in other groups. There was no significant difference between the two luting agents. ConclusionThe results indicate that the experimental biopolymer veneer bonded to enamel provided the best retention. The TBS at the enamel-resin interface is higher than at the veneer-resin interface for all commercial CAD/CAM hybrid materials. Clinical significanceAn experimental enamel-based biopolymer veneer can provide better retention than CAD/CAM hybrid materials in clinical treatment.

Effect of Different Desensitizers on Shear Bond Strength of Self-Adhesive Resin Cements to Dentin.

The sealing and bonding characteristics of luting cements may be affected by the application of desensitizers containing ingredients that induce chemical interaction with dentin organic matrix. This study evaluated the effect of different desensitizers on the immediate and long-term shear bond strength (SBS) of a self-adhesive resin cement (SARC) to dentin. Healthy bovine dentin specimens were used for the study. Gluma® Desensitizer, Desensibilize Nano P®, and Soothe® desensitizer were used in study groups, while the control group did not receive any treatment. Next, SARC (RelyXTM U200) in cylindrical mold was applied to the sample surface. All specimens were stored at 37 °C for 24 h or six months and tested for SBS. Additionally, water contact angle was measured using an optical tensiometer. Results were analyzed by analysis of variance and Student-t tests (p ˂ 0.05). Application of the different types of desensitizers had no significant influence on immediate or long-term SBS of SARC to dentin (p > 0.05). Differences for water contact angle were not statistically significant among the tested groups (p = 0.450). Within the limitations of the present study, it can be concluded that the application of the different types of desensitizers had no significant influence on the SBS of a SARC to dentin.

Shear bond strength of resinous cements to Zirconia Katana™ UTML

The aim of this study is to assess the bond strength of three resinous cements to Zirconia Katana™ UTML (Kuraray Noritake Dental Inc, Miyoshi, Aichi, Japan). Thirty-six blocks of Zirconia were milled and included in polyvynil chloride (PVC) pipes with self-polymerizable acrylic resin. Each sample was polished in a polishing machine, blasted with aluminum particles, cleaned with ultrasound, and dried with compressed air. The cementation was done according to the protocol recommended by the manufacturer. The samples were divided in 3 groups (n=12) according to the resinous cement used: Group R - RelyX™ U200 Automix (3M ESPE, Sumaré, São Paulo, Brazil); Group M - Multilink® N (Ivoclar Vivadent, Schaan, Liechtenstein); and Group P - Panavia™ V5 Paste (Kuraray Noritake Dental Inc, Cotia, São Paulo, Brazil). The shear stress test was performed in EMIC DL2000 (EMIC, São Paulo, SP, Brazil), and failure type was analyzed. Average bond strengths were 5.4 kgf, 5.8 kgf, and 6.68 kgf for groups R1, M1 and P1, respectively. Variance analysis showed no significant difference between groups. None of the groups showed cohesive failure; there was no significant difference in the frequency of mixed and adhesive failure between groups. All three cements showed similar performance in the tests.

Retention Strength of Polyetheretherketone Crowns Vs. Zirconia Crowns Restoring Molar Teeth: An in Vitro Study

Aim: This study was designed to compare the retention strength of monolithic CAD/CAM PEEK crowns to that of CAD/CAM monolithic YTZP-zirconia crowns, both resin-cemented to epoxy resin dies resembling lower molar teeth; after thermomechanical aging simulating 3 months of in-vivo service. Materials and methods: 22 identical epoxy dies, resembling the preparation of a lower second molar (4mm height, 6° axial convergence and 1 mm-thick deep chamfer finish line), were produced by replicating one master stainless steel die via 22 polyvinyl siloxane impressions. The epoxy dies were randomly equally distributed into 2 groups (Zr and P groups); 11 dies each. The first (control) group (Zr) received CAD/CAM milled monolithic Y-TZP zirconia crowns (Katana™ ML), while the other group (intervention) received CAD/CAM milled monolithic PEEK crowns (breCAM.BioHPP™). Two opposing, laterally projecting (mesial and distal) arms were included in the design of all crowns for the retention test. The fitting surfaces of crowns of both groups were sandblasted with 110-µm alumina particles. All crowns were cemented over their corresponding epoxy dies using the (hand-mixed) dual-cured, self-adhesive resin cement (RelyX™ U200) (3-kg seating force). Samples were stored in water incubator for 24 hours (37 °C); then, subjected to mechanical aging (37,500 cycles, 49 N load) with simultaneous thermocycling (300 cycles, 5-55 °C, 12 s dwell time). Retention strength was evaluated by vertically pulling-up the crowns from their corresponding dies, through the pull-out test performed via a universal testing machine (UTM). Failure modes were then observed under digital microscope. The mean dislodgment force (retention strength) for each group was calculated, and statistically compared using Student t-test. Statistical analysis was performed with three-way ANOVA. Pair-wise comparison of groups was made with the Tukey test. Pearson’s Chi-Square test was used to analyze the failure modes. Results: PEEK crowns group (P) demonstrated statistically insignificant higher retention strength (171.28 N ± 26.30) than zirconia (Zr) crowns group (150.40 N ± 24.40). “Mixed” failure mode was predominant in both groups, followed by the adhesive “cement on crown” failure-mode.

Effect of femtosecond, Er: YAG and Nd: YAG Laser Systems on bond strength resin cement with esthetic post system

Purpose: The aim of this study was to investigate the results and contributions of surface treatments with different laser systems on bond strength of resin cement with aesthetic post system made of different materials. Material and Methods: 3 different aesthetic post systems (RelyXTM fiber post, C-Post® zirconium oxide post, Easy Post TM zirconia reinforced fiber post), including 40 from each, were used. On these posts, 3 different surface treatments (Er:YAG laser, Nd:YAG laser and Femtosecond (Fs) laser), including 10 pieces from each system, were applied. In the remaining 10 samples, no action was taken, and a control group was created. The obtained posts were cemented into the composite post slots of 12 mm length and 4 mm diameter using self-adhesive resin cement (RelyXTM U200). From the coronal, medial and apical regions of each prepared sample, 2 mm-thick sections were taken to make push-out tests. Afterward, the push-out resistance was measured using a universal testing machine with 0.5 mm/min head speed.Results: There were statistically significant differences between the glass fiber posts and the zirconium-reinforced glass fiber posts with zirconium posts (p

Acoustic properties of fracture of dental restorative materials and endocrown restorations under quasi-static loading

Objectives(1) To investigate the properties of acoustic emission (AE) signals from fracture of dental materials and endocrown restorations during quasi-static compression using the continuous wavelet transform analysis. (2) To determine by the parameters of AE signals in which structural element of tooth-endocrown system the fracture starts. MethodsFive restorative materials (zirconium dioxide (Prettau zirconia), ceramics (IPS e.max Press), metal ceramics (GC Initial MC+Nicrallium N2 BCS), composite resin (Nano Q), luting cement (Relyx™ U200)) were manufactured into discs, 13mm diameter, 5mm thick, which were divided into 5 groups (Group B, C, D, E, F, respectively) and included into Type 1. Twenty-five extracted human molars were divided into 5 groups and included into Type 2: Group A (control, no restoration); BE (tooth restored by zirconium dioxide endocrowns); CE (restored by ceramic endocrowns); DE (restored by metal ceramic endocrowns); EE (restored by composite resin endocrowns). An increasing load was applied to the center of the samples with a hard steel ball until a fracture occurred. The loading rate was 0.12mm/min. Two-channel AE detection system was used to record the AE activity during testing. The parameters including the peak frequency, bandwidth, duration time and energy of AE signals were analyzed. ResultsThe restorative materials (Type 1) differ from each other by acoustic properties such as the peak frequency main bands and energy of AE signals. The detected AE signals correspond to the different fracture types. The dominant fracture mechanism of Group C, E and F specimens was the macrocracking (brittle fracture), and of Group D specimens was the microcracking, which alternated with the plastic deformation and macrocracking. For the number of events corresponding to the brittle fracture, statistically significant differences (p<0.05) were found between all group pairs. AE signals were not released during compression test of the zirconium dioxide samples, thus the fracture was not detected.All the AE signals detected during compression test of the different endocrown systems (Type 2) had two peak frequency bands. The fracture of Groups A, BE, CE and DE samples characterized by alternating the micro- and macrocracking with plastic deformation, and the brittle fracture was the dominant fracture mechanism. The restorations of Group EE fractured without plastic deformation. For the number of events corresponding to the brittle fracture, statistically insignificant differences (p>0.05) were found between Groups A vs CE and A vs EE, and statistically significant differences (p<0.05) were found between Groups A vs BE and A vs DE. SignificanceThe initiation of fracture in the restorations with endocrowns made from different materials begins with the tooth damage. The metal ceramic endocrown restoration showed the highest fracture resistance, what is especially important for clinical use.

Effect of ethanol-wet bonding on porosity and retention of fiberglass post to root dentin.

This in vitro study aimed to assess the effects of different pretreatments used to adapt glass-fiber posts cemented to root canals with different resin cements, regarding porosity percentage and bond strength. Twelve bovine incisor roots were prepared with Largo drills. After post space preparation, the specimens were randomized into two types of pretreatment groups (n = 3): water-wet bonding and ethanol-wet bonding. After the post were cemented, the roots were stored in 100% humidity at room temperature for 7 days. The samples were scanned by microcomputed tomography (micro-CT). Images were reconstructed by NRecon software, and CTAn software was used to analyze the porosity percentage (%) at the luting interface. Evaluation of the push-out bond strength was performed by serially cutting the roots, and submitting the slices to testing. Additionally, the resin cement post-gel shrinkage values (%) were measured using the strain-gauge method (n = 10). Data were analyzed by two-way ANOVA, Tukey's test and Student's t test (a = 0.05). The roots prepared with ethanol-wet bonding using RelyX™ U200 had significantly lower porosity in the coronal and apical thirds (p < 0.05). The group prepared with ethanol-wet bonding using RelyX™ ARC presented better bond strength results in the coronal and apical thirds (p < 0.05). RelyX™ ARC (0.97%) produced a higher post-gel shrinkage value than RelyX™ U200 (0.77%). Canals pretreated with ethanol-wet bonding presented better outcomes in regard to porosity percentage and push-out bond strength.

Single blinded in-vitro study comparing microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramic, cemented with three resin cements

Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) crowns are abundant. However many of them are inconclusive, especially those using self adhesive cements.&#x0D; Aims: To compare the microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramics, cemented with three resin cements.&#x0D; Materials and Methods: Crown preparation was made on 54 extracted human premolars. Impressions were captured optically using CEREC 3D machine intraoral camera, and crowns were milled from feldspathic ceramic (CEREC® Blocs PC, VITA) and resin nano ceramic (Lava™ Ultimate CAD/CAM Restorative, 3M ESPE) blocks. The crowns were then cemented with three cements (n = 9); RelyX™ U200 Self-Adhesive Resin Cement (3M ESPE); NX3 Nexus ® cement with two-step etch-and-rinse adhesive (Kerr Corporation) or three/multistep etch-and-rinse resin cement, Variolink® II/Syntac Classic (Ivoclar Vivadent). The specimens were kept in water for 24 hours, thermocycled, and then soaked in methylene blue dye for 24 hours, before being sectioned mesiodistally. Microleakage was assessed using a fivepoint scale using stereomicroscope. Statistical analysis of the data was carried out using ONEWay ANOVA.&#x0D; Results: CEREC® Blocs PC crowns showed significantly less microleakage (p&lt; 0.001) compared to Lava™ Ultimate. RelyX™ U200 showed significantly lower microleakage (p&lt; 0.001) compared to other cements. Combination of Lava™ Ultimate crown cemented with RelyX™ U200 showed the least microleakage (p&lt; 0.001).&#x0D; Conclusions: The microleakage scores were affected by the types of crown and cements.&#x0D; Bangladesh Journal of Medical Science Vol.18(4) 2019 p.764-772

Effect of Plasma Treatment and Its Post Process Duration on Shear Bonding Strength and Antibacterial Effect of Dental Zirconia.

We have investigated the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment and the post process time on the bonding strength and surface sterilization of dental zirconia. Presintered zirconia specimens were manufactured as discs, and then subjected to a 30-min argon treatment (Ar, 99.999%; 10 L/min) using an NTAPP device. Five post-treatment durations were evaluated: control (no treatment), P0 (immediate), P1 (24 h), P2 (48 h), and P3 (72 h). The surface characteristics, shear bonding strength (SBS) with two resin cements, and Streptococcus mutans biofilm formation of these plasma-treated dental zirconia were tested. Plasma did not change the roughness, and caused surface element changes and surface energy increase. Due to this increase in surface energy, SBS increased significantly (p < 0.05) within 48 h when RelyXTM U200 was used. However, the increase of surface oxygen significantly decreased (p < 0.05) the SBS of Panavia F 2.0 when using plasma immediately (P0). S. mutans adhesion decreased significantly (p < 0.05) for the P0, P1, and P2 groups compared to the control. The P0 group exhibited lower biofilm thickness than the other experimental groups due to the increased hydrophilicity (p < 0.05). Our study suggests that there is a suitable time window for the post NTAPP treatment regarding bonding strength and antimicrobial growth persist.

Influence of monolithic lithium disilicate and zirconia thickness on polymerization efficiency of dual-cure resin cements.

To evaluate the influence of anterior monolithic zirconia and lithium disilicate thickness on polymerization efficiency of dual-cure resin cements. Twelve ceramic disks (4.0-mm diameter) with thicknesses of 0.5, 1, 1.5, 2, 2.5, and 3 mm were prepared from monolithic zirconia (Prettau® Anterior; n = 6) and lithium disilicate (IPS e.max® CAD HT; n = 6). Three dual-cure resin cements (Panavia F 2.0, DuoLink Universal™, and RelyX™ U200) were used for polymerization beneath ceramic disks. For each resin cement, 10 specimens were prepared by light curing under monolithic zirconia and lithium disilicate disks of each thickness. Vickers hardness measurements were conducted at four different measurement depths. Data were statistically analyzed using univariate four-, three-, two-, and one-way analysis of variance and independent samples t-tests. Microhardness of resin cements decreased significantly with increasing measurement depth and thickness of monolithic zirconia or lithium disilicate (P < .001). Cements polymerized under lithium disilicate showed higher microhardness values than did those polymerized under zirconia (P < .001). For both ceramics, Panavia F 2.0 exhibited the greatest microhardness, followed by DouLink Universal and RelyX™ U200 (P < .001). Different dual-cure resin cements may have different polymerization efficiencies, and the type and thickness of the overlying ceramic can influence polymerization. The findings of this study suggest that an increase in the thickness of monolithic lithium disilicate or anterior monolithic zirconia restorations can significantly decrease the microhardness of the dual-cure resin cement polymerized beneath the restoration. Dual-cure resin cements can be used for the cementation of anterior monolithic zirconia restorations up to 2 mm thickness and for monolithic lithium disilicate restorations up to 2.5 mm thickness. However, for lithium disilicate restorations with a ≥2.5 mm thickness and zirconia restorations with a ≥2-mm thickness, different cementation approaches must be further studied, such as: extended light curing; the use of dual-cure resin cement with a higher self-curing component than the ones used in this study; or a self-cure resin cement.

Comparison of shear bond strengths between a mica-based glass-ceramic and human dentin using three different resin cements

Three resin cements, RelyX™ Ultimate, Panavia F2.0 and RelyX™ U200, were evaluated for their bond strengths between a mica glass-ceramic and human dentin. This research shows that a self-etch dental cement resin system, Panavia F2.0 provided the best bond strength. The glass-ceramic was produced and phases analysed. Biaxial flexural strength and hardness were measured and found to be comparable to that of human enamel and dentin. Bond strength was measured before and after thermocycling. Thermocycling was found to reduce the bond strength. Thermocycling reduced the shear bond strengths of all adhesives by 50–60%. The two-way ANOVA test was used to analyse the data (p = 0.05). Failure modes were analysed, showing failure predominately at the cement/glass-ceramic and dentin/resin cement interfaces. Failure modes changed after thermocycling. The resin cement bond between the dentin and mica glass-ceramics interfaces was examined for failure by optical microscopy (OM) and scanning electron microscopy (SEM).

Features of fracture of prosthetic tooth-endocrown constructions by means of acoustic emission analysis

ObjectiveThe study aims at comparing the fracture resistance of different restorative materials used in dental endocrown restorations and respective endocrown restorations under a quasi-static compressive load using acoustic emission (AE) method. MethodsFive restorative materials were used in this study. The restorative materials were manufactured into discs 13mm in diameter and 5mm thick, which were then divided into 5 groups and included into Type 1: Group B: zirconium dioxide (Prettau zirconia); Group C: ceramics (IPS e.max Press); Group D: metal ceramics (GC Initial MC+Nicrallium N2 BCS); Group E: composite resin (Nano Q); Group F: luting cement (RelyX™ U200). Twenty-five extracted human molars were divided into 5 groups and included into Type 2: Group A: control, no restoration; Group BE: restored by zirconium dioxide endocrowns; Group CE: restored by ceramic endocrowns; Group DE: restored by metal ceramic endocrowns; Group EE: restored by composite resin endocrowns. An increasing load was applied to the center of the samples with a hard steel ball until a fracture occurred. The loading rate was 0.12mm/min. An AE system was used to monitor the fracture of the samples. The load corresponding to the first AE event and the final fracture load were used to evaluate the fracture resistance of the restored teeth. The data were analyzed using ANOVA and Tukey’s post hot test (α=0.05). ResultsA lower threshold of 220μV was selected to exclude spurious background signals. For the initial fracture load of Type 1 samples, Group F (0.029kN)<Group E (0.039kN)<Group D (0.056kN)<Group C (0.253kN)<Group B (intact). The same trend was found for the final fracture load, i.e., Group F (1.289kN)<Group E (1.735kN)<Group D (3.362kN)<Group C (6.449kN)<Group B (intact). For the initial and final fracture load, statistically significant differences (p<0.05) were found between group C and the others groups. For the initial fracture load of Type 2 samples, Group EE (0.069kN)<Group DE (0.072kN)<Group CE (0.148kN)<Group BE (2.511kN). For the final fracture load, Group EE (1.533kN)<Group CE (2.726kN)<Group BE (3.082 kN)<Group DE (3.320kN). The initial fracture load of the ceramic samples is somewhat higher than that for the endocrown restorations with the endocrowns made of this material (0.253 and 0.148kN, respectively). At the same time, for the metal ceramic and composite resin samples, the initial fracture loads are somewhat lower than in case of compression of the endocrown restorations with the endocrowns made of these materials (0.056 and 0.072kN; 0.039 and 0.069kN, respectively). The final fracture load of all the samples of the dental materials exceeds the strength of the respective endocrown restorations. The final fracture loads of the endocrown restorations with zirconium dioxide and ceramic endocrowns (3.082 and 2.726kN, respectively) are significantly lower than the final fracture load of the respective endocrown materials (intact and 6.449kN, respectively). SignificanceDental restorations should be made of high-strength materials. Zirconia displayed the highest fracture strength, while composite resin had the lowest fracture strength out of the materials used for the endocrowns. For teeth restored with endocrowns, the use of metal ceramics as endocrown material may lower the risk of failure during clinical use.

Evaluation of the fracture resistance of computer-aided design/computer-aided manufacturing monolithic crowns prepared in different cement thicknesses.

The purpose of this study was to evaluate the fracture resistance of monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) crowns that are prepared with different cement thickness. For this investigation, a human maxillary premolar tooth was selected. Master model preparation was performed with a demand bur under water spray. Master die was taken to fabricate 105 epoxy resin replicas. The crowns were milled using a CEREC 4 CAD/CAM system (Software Version, 4.2.0.57192). CAD/CAM crowns were made using resin nanoceramic, feldspathic glass ceramic, lithium disilicate, and leucite-reinforced ceramics. Each group was subdivided into three groups in accordance with three different cement thicknesses (30, 90, and 150 μm). Crowns milled out. Then RelyX™ U200 was used as a luting agent to bond the crowns to the prepared samples. After one hour cementations, the specimens were stored in water bath at 37°C for 1 week before testing. Seven unprepared and unrestored teeth were kept and tested as a control group. A universal test machine was used to assume the fracture resistance of all specimens. The compressive load (N) that caused fracture was recorded for each specimen. Fracture resistance data were statistically analyzed by one-way ANOVA and two-factor interaction modeling test (α = 0.001). There are statistically significant differences between fracture resistances of CAD/CAM monolithic crown materials (P < 0.001). It is seen that cement thickness is not statistically significant for fracture resistance of CAD/CAM monolithic crowns (P > 0.001). CAD/CAM monolithic crown materials affected fracture resistance. Cement thickness (30, 90, and 150 μm) was not effective on fracture resistance of CAD/CAM monolithic crowns.

Influence of Infected Root Dentin on the Bond Strength of a Self-adhesive Resin Cement.

Aim:The aim of this study was to determine the bond strength (BS) of a self-adhesive resin cement to the contaminated root dentin.Materials and Methods:The crown and apical third of twenty single-rooted teeth were removed. The root canals were flared and 1-mm-thick root sections were obtained. The sections were rinsed, dried, and sterilized. The control group (n=20) was composed of one section of each third, which remained immersed in sterile trypticase soy broth (TSB) for 2 months. The other sections comprised the experimental group (n = 40) and were immersed in a suspension of Enterococcus faecalis. The culture medium was changed at every 4 days for 2 months. The sections were rinsed with distilled water, dried, and the root canal space was filled with the self-adhesive resin cement RelyX™ U200. After 24 h, the push-out test was performed and the types of interface failure were observed on a stereo microscope.Statistical Analysis:Data were statistically analyzed by the nonparametric Mann–Whitney test (α=5%).Results:A significant reduction was observed in the BS of resin cement to the contaminated dentin compared to the healthy dentin, for both thirds analyzed (P < 0.05). The BS was significantly greater at the cervical third compared to the middle third for specimens in the experimental group (P < 0.05). Adhesive and mixed failures were observed more frequently in specimens contaminated with E. faecalis.Conclusion:Bacterial contamination negatively infl uenced the BS of the self-adhesive resin cement to the root dentin, and there was a predominance of adhesive and mixed failures.

Microtensile bond strength and scanning electron microscopic evaluation of zirconia bonded to dentin using two self-adhesive resin cements; effect of airborne abrasion and aging

Aim of the studyThis in vitro study was conducted to evaluate the microtensile bond strength (μTBS) of surface treated zirconia bonded to dentin specimens using two aged contemporary dual cured self-adhesive resin cements. Materials and methodsSixty cuboidal-shaped zirconia ceramic specimens were obtained using CAD/CAM system. Specimens were divided into two equal main groups; 30 specimens each, gp A in which specimens did not receive any further surface treatment & gp B in which only one surface of each specimen was airborne abraded. Each group was then divided into two equal groups; 15 each, according to the type of adhesive resin cement used for bonding zirconia specimens to ground flat dentine surfaces; RelyX™ U200 (cement I) and Multilink® Speed (cement II). The assemblies were further subdivided into 3 equal subgroups; 5 assemblies each, according to aging protocol. The aging protocols were storage in distilled water for 1 day, for 7 days without thermocycling and for 7dayes followed by thermocycling; subgroups 1, 2 and 3 respectively. After aging, the assemblies were sectioned into beams approximately 1 mm2 in cross section resulting in 25 beams for each subgroup; 20 of them were selected for μTBS (n = 20) and 5 were kept for SEM examination. ResultsGroup B showed statistically significantly higher mean micro tensile bond strength value than group A. The type of cement had statistically insignificant effect on mean micro tensile bond strength. Thermocycling significantly reduced μTBS of both cements bonded to untreated zirconia ceramic; IA3 and IIA3 subgroups.For SEM, cement I showed gaps at its interface with zirconia groups A and B regardless of aging protocol. Cement II showed only gaps at its interface with zirconia ceramic group A only but good adaptation appeared at its interface with zirconia ceramic group B for aged for 1 day (subgroup IIB1) and 7 days without thermocycling (subgroup IIB2). However, cement II bonding air abraded zirconia ceramic followed by thermocycling (subgroup IIB3) showed both gap free as well as gap containing areas at high magnification only. ConclusionsAirborne abrasion-surface treatment of zirconia significantly enhanced the μTBS of both cements adhered to dentin while aging had an adverse effect. MS showed higher insignificant μTBS.

Influência do hipoclorito de sódio a 1% na resistência adesiva entre dentina radicular e o pino de fibra de vidro utilizando três agentes cimentantes

Objective: To verify, in vitro, the influence of 1% NaOCl on the bond strength between intrarradicular dentin and fiberglass post using three luting systems. Methods: Sixty upper anterior teeth, endodontically treated, received a fiberglass post (White Post DC) and different luting systems: Relyx™ U200 (RU), Relyx ARC (RARC) and RelyX™ Luting 2 (RL). Before luting, samples were randomly divided into six groups: according to the irrigant, distilled water (DW) or 1% Sodium hypochlorite (NaOCl), and luting system: RU+DW, RU+NaOCl, RARC +DW, RARC+NaOCl, RL+DW, RL+NaOCl. After luting, roots were sectioned in three portions and subjected to “push out” test 0.5 mm/min in EMIC DL machine. Under stereoscopic microscope (25x), the type of fracture was evaluated. Results: According to the ANOVA and Tukey post hoc test (p<0.05), there was statistical significant difference in the interaction NaOCl/RARC. The RL had the lowest values of bond strength. The Relyx ARC showed greater bond strength in the cervical third. Most of fractures were in the interface adhesive bonding root/cement, followed by cement adhesive fractures in the interface and post. Conclusion: 1% NaOCl reduced bond strength into the cervical third to RARC. The glass ionomer cement showed the lowest values of bond strength in the different dentin regions.

Effect of Endodontic Retreatment on Push-out Bond Strength and Quality of Fiber Postbonding Interface of Resin Cements.

The aim of this study is to evaluate the impact of endodontic retreatment on push-out bond strength and dentin interface of two resin cements used for fiber postcementation during endodontic retreatment. The root canals of 40 extracted human canines were prepared, obturated and divided into four groups (n = 10). Gutta-percha was partially removed and fiber posts were immediately cemented in groups 1 and 2 using Panavia F with ED Primer and RelyX™ U200, respectively. In groups 3 and 4, the root canal access was sealed with temporary restorative cement, specimens were stored for 30 days, endodontically retreated, and fiber posts were cemented using the resin cements applied to groups 1 and 2, respectively. Push-out tests and scanning electron microscopy analyses of different areas were performed. Data from push-out bond strengths were analyzed by one-way analysis of variance and Tukey's tests. Higher bond strength values were detected in the apical third for group 1 than group 3 (p < 0.05). No differences were observed in other comparisons between the same third of different groups (p > 0.05). Comparisons between different thirds in the same group revealed a higher bond strength in the apical third for group 1. Scanning electron microscopy showed formation of hybrid layer and extensive resin tags in group 1. No hybrid layer was observed in groups 2 and 4. Endodontic retreatment had adverse effects on the push-out bond strength and dentinal interface of Panavia F with ED Primer when used for fiber postcementation specifically in the apical third, but not on RelyX™ U200. A significant interaction was detected between endodontic retreatment and resin cement, which indicated that endodontic retreatment might adversely affect the push-out bond strength and dentinal interface of Panavia F with ED Primer when used for fiber postcementation specifically in the apical third.