Resin-based Cements Research Articles

Novel Femto Laser Patterning of High Translucent Zirconia as an Alternative to Conventional Particle Abrasion.

Background: currently applied surface treatments for zirconia bonding may create undesired microcracks and surface flaws. The aim of the present study was to evaluate the efficacy of alternative surface treatments on the shear bond strength of high translucency zirconia to 10-Methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin-based cement. Methods: fifty disk-shaped specimens (10 mm × 5 mm) were fabricated from a commercial yttria-stabilized zirconia with 5 mole% yttrium oxide tetragonal zirconia polycrystal (5Y-TZP), and underwent air-abrasion with alumina particles (50 μm-AL50 and 90 μm-AL90), glass beads (GB 10–60 μm), and ablation with femtosecond laser (FEMTO). Shear bond strength was evaluated with a universal testing machine under a crosshead speed of 0.5 mm/min until fracture. Fracture type was evaluated with an optical stereomicroscope. Differences among groups were evaluated by one-way ANOVA and Bonferroni pairwise comparison tests (p < 0.05). Results: the highest shear bond strength values were presented by the laser treated group (23.97 ± 3.7 MPa). No statistically significant differences were found among the Cl, Al50, Al90 and FEMTO groups. The lowest mean value was presented by the glass-beads treated group (11.93 ± 2.88 MPa) which was significantly lower compared to all other groups (p < 0.001). Conclusions: under the limitations of this in vitro study, femtosecond laser treatment of High-translucent monolithic zirconia (HTZ) ceramics is a promising alternative method for the mechanical retention of resin cements.

Calcium Silicate Cements vs. Epoxy Resin Based Cements: Narrative Review

In recent years, calcium silicate cements have been introduced. The purpose of this study is to analyze the main differences between calcium silicate-based cements and epoxy resin-based cements, analyzing the scientific literature of the last year to highlight the main advantages for predictable clinical use. Data collected from the included studies were used in order to analyze different features: chemical-physical properties, cytotoxicity and cell migration, inflammatory response, mineralizing and osteogenic activity, ion release and the filling efficiency of root canals. The calcium silicate cements analyzed in these studies showed good biological and mechanical properties compared to conventional resin-based cements, resulting in better biocompatibility and less cytotoxicity; long-term studies are needed, but these cements have ideal characteristics to allow efficient filling of root canals.

Comparison of Volumetric Dimensional Changes of Calcium Aluminate, Resin Modified Glass Ionomers and Resin Luting Cements Among Different Storage Conditions

Objective: The aim was to evaluate the volumetric dimensional changes of calcium aluminate glass-ionomer luting agent to resin modified-Glass ionomer cement (RM-GIC), self-etch and conventional resin based cement (RBC) among different storage conditions. Methods: Twenty cylindrical specimens (7 mm × 2 mm) for four cements [Calcium aluminate (Ceramir-CM), RM-GIC (Fuji Plus-FP), RBC (Rely X Ultimate-RA) and RBC-self-etch (Rely X Unicem-RU)] were fabricated and polished. Five specimens from each material were randomly assigned to the four test conditions. These conditions were silicone oil at 22 °C and 37 °C and distilled water at 22 °C and 37 °C respectively. A resolution balance was used to measure the weight of each specimen at 1, 2, 3 and 4 weeks. Archimedes’ principle equations were used to measure volumetric dimensional changes. Ion release analysis for Ca+ and OH- of the storage medium solution of calcium aluminate cement was performed using atomic absorption spectroscopy and pH measurement respectively at 1, 2, 3 and 7 weeks. Data was analyzed using ANOVA and Tukey post hoc test. Results: A significant difference in volumetric changes (ρ &lt; 0.05) was observed for different cements. Calcium aluminate (CM) showed maximum volumetric changes followed by FP. However, resin cements (RA and RU) showed significantly lower volumetric changes. Oil immersion exhibited shrinkage and water immersion showed volumetric expansion in all materials. Increase in duration of immersion, increased the dimensional changes (shrinkage or expansion) among all cement groups (ρ &lt; 0.05). Both temperature and duration showed significant influence on Ca+ ion release. Conclusions: Calcium aluminate cement had the highest level of dimensional changes (17.28% and 20.52%) while both resin luting agents show least expansion without a significant difference between them. Ceramir luting agent expands significantly in water and continues to release Ca2+ ions with time and higher temperature. The clinical use of calcium aluminate cements based on the high dimensional changes observed in the study is debatable.

Comparison between Different Shades of Monolithic Zirconia over Microhardness and Water Solubility and Sorption of Dual-cure Resin Cement

To compare the different shades of monolithic zirconia over microhardness and water solubility and water sorption of dual-cure resin cement. Eighty specimens were included in the study. They were categorized into four categories having 20 samples each. Category one: No ceramic disks were present in the control group; the cement was directly activated. Category two: Curing of the resin cement with one shade of monolithic zirconia topping. Category three: Curing of the resin cement with an overlaying layer A monolithic zirconia version with two shades. Category four: Curing of the resin cement with an overlaying layer A three-tone monolithic zirconia version. In each category, two subgroups were further created (n = 10). One subgroup consisted of conventional dual-cure resin-based cement, while the other subgroup consisted of self-adhesive dual-cure resin-based cement. Vickers microhardness, water solubility, and water sorption of resin cement sorption were precisely measured after 24 hours of storage in an incubator at 37°C. The statistical analysis was undertaken with the help of statistical tests like two-way analysis of variations (ANOVA), one-way ANOVA, independent t-tests, Tukey's test, and Tamhane's T2 test. The p ≤0.05 was considered statistically significant. Microhardness was more excellent in conventional dual-cure resin-based cement in comparison with self-adhesive dual-cure cement. At the same time, the water solubility and water sorption were lower in conventional dual-cure resin-based cement than self-adhesive dual-cure resin cement. The effect of shade of monolithic variant of zirconia was significant over the microhardness of both dual-cure resin-based cement; however, the impact was nonsignificant over the water solubility and water sorption of the resin-based resin cement. Further, it was also observed that the use of a monolithic variant of zirconia led to a decrease in microhardness of both dual resin-based cement in comparison to the condition when no ceramics were used. The effect of shade of monolithic variant of zirconia was statistically significant over the microhardness of both dual-cure resin-based cement; however, the result was not significant over the water solubility and water sorption of the resin-based cement. The use of a monolithic variant of zirconia led to a decrease in the microhardness of both dual resin-based cement compared to the condition when no ceramics were used. The quantity of polymerization in resin-based cement affects their clinical effectiveness for a more extended period. It is believed that the measurement of microhardness is a reliable and straightforward process for evaluating the amount of polymerization of resin-based cement. Very few studies have been conducted in the past to compare the shades of monolithic zirconia over the microhardness, water solubility, and water sorption of the dual-cure resin-based cement.

Immediate and long-term microshear bond strength of resin-based cements to core build-up materials.

BackgroundTo evaluate the microshear bond strength (μ-SBS) between resin-based cements and core build-up materials after water storage. Material and MethodsCylinders (1x1 mm) of conventional dual-cure resin cement (RelyX ARC, 3M ESPE), universal dual-cure resin cement (RelyX Ultimate, 3M ESPE) or self-adhesive resin cement (RelyX U200, 3M ESPE) were adhered to disks (6x2 mm) made with commercial core build-up materials (Bis-Core, Bisco or LuxaCore Z, DMG) or conventional nanocomposite resin (Filtek Z350 XT, 3M ESPE). The specimens (n=10) were submitted to μ-SBS test using a universal testing machine and fracture pattern analysis at 48 hours or after 9 months of water storage. The data were evaluated by three-way ANOVA for repeated measures and Tukey’s test (α=0.05). ResultsAfter 48 hours, regardless of the resin-based cement used, the μ-SBS to the conventional resin composite (Filtek Z350 XT) was greater compared to other materials. However, after 9 months, there was a statistically significant decrease in μ-SBS values between the conventional resin composite and evaluated luting agents. The μ-SBS values of core build-up commercial materials (Bis-Core and LuxaCore Z) did not change over time. Regardless of the composite used and storage time, there was no statistically significant difference between the resin-based cements. After 48 h, the most prevalent failure was mixed for all groups. However, after 9 months, the core build-up materials showed a predominantly mixed fracture pattern whereas the resin composite presented an adhesive pattern. ConclusionsCommercial core build-up materials achieved stable bonding performance with resin-based cements over time. Key words:Composite resins, resin cement, dental restoration failure.

Effect of cementation techniques on fracture load of monolithic zirconia crowns

Aim The aim of this study was to evaluate the effect of cement on the fracture load of monolithic zirconia crowns with different yttria content (3 and 5 mol%). Methods A total of 62 monolithic zirconia crowns, 40 3Y-zirconia crowns (Prettau® Zirconia, Zirkonzahn) and 22 5Y-zirconia crowns (Prettau® 4 Anterior®, Zirkonzahn) were produced to a shallow chamfer molar preparation. The 3Y-crowns were divided into four groups and attached to composite abutment duplicates (SDR® flow+, Dentsply DeTrey GmbH) using the following four cementation techniques; (1) Self-adhesive resin-based cement, (2) Pre-treatment with air-abrasion and self-adhesive resin-based cement, (3) Zinc phosphate cement, (4) Glass-ionomer cement. The 5Y-crowns were divided into two groups and attached to the duplicates with; (1) Self-adhesive resin-based cement, or (2) Air-abrasion pre-treatment and self-adhesive resin-based cement. All crowns were loaded axially (0.5 mm/min) on the occlusal surface until fracture occurred. Results Among the 3Y-zirconia groups, the zinc phosphate cement group fractured at lower loads compared to the resin-based cement groups, with and without air-abrasion, (p < .012). Among the 5Y-groups the air-abraded crowns fractured at statistically significant lower loads compared to the untreated crowns (p < .028). Load at fracture values were significantly different between the two zirconia materials (p < .001), with fracture loads ranging from 3873 to 7500 N in the 3Y-groups, and 2100 to 4948 N in the 5Y-groups. Conclusions Resin-based cementation increased the fracture load compared to non-adhesive cementation. The 3Y-crowns fractured at almost twice the loads of the 5Y-crowns. Pre-treatment with air abrasion reduced the strength of the 5Y-crowns only, showing the importance of differentiating the treatment of the two materials.

The Influence of Surface Treatments on Resin Bond Strength to Zirconia

Background: It’s shown that the clinical success of ceramic restorations much depends on the quality and durability of the bond to ceramic. For zirconia-based ceramics (Y-TZP), the surface treatment has a substantial impact on bond strength. Therefore, the bond strength evaluation of Y-TZP surface treatments is a requirement for predicting the clinical performance of such restorations. Objective: Evaluating the resin bond strength to Y-TZP after different surface treatments. Methods: Monolithic Y-TZP (Zenostar Zr Translucent, Wieland Dental, Rosbach vor der Höhe, Germany) blocks were bonded to resin composite blocks using a resin-based cement system after two Y-TZP surface treatments: APA- airborne particle abrasion with alumina particles; and CJ- silicatization (Cojet sand, 3M ESPE, St. Paul, MN, USA). A silane coupling agent and an adhesive system were applied to the treated Y-TZP surfaces and resin composite blocks were cemented (RelyX Ultimate, 3M ESPE, St. Paul, MN, USA) and light activated from all sides. These structures were cut to obtain bar-shaped specimens (n=30), which were stored in 37ºC distilled water for 7 days before microtensile testing. Specimens were loaded to failure under tension using a universal testing machine. Data was statistically analyzed using Students t test (α=0.05) and Weibull distribution. Failure modes were evaluated using optical (OM) and scanning electron microscopy (SEM). Results: Mean bond strength values (CJ= 25.7±8.2 MPa; APA= 22.0±6.3 MPa) were statistically similar (p&gt;0.05). No difference was found for the characteristic strengths (σ0) and for Weibull moduli (m) since the confidence intervals (95% CI) overlapped. The bond strength values for a 5% failure probability (σ5%) were 12.4 (CJ) and 11.5 (APA). All fractures were due to cohesive failure within the adhesive cement system. Conclusion: Both Y-TZP surface treatments (CJ and APA) produced similar structural reliability and short-term bond strength to a resin cement system.

Development of resin-based bioactive endodontic cements with glycerol salicylate and calcium silicate

Introduction: The combination of sol-gel derived calcium silicate particles and glycerol salicylate resins may enhance the pyhisico-chemical properties contribute to the understanding of the interaction between these materials. This study aims to evaluate the physical-chemical properties of resin-based bioactive endodontic cements with glycerol salicylate resins and calcium silicate particles. Materials and methods: Calcium silicate was produced by the sol-gel route, while the resin was produced by mixing 60wt% glycerol salicylate, 30wt% methyl salicylate and 10wt% distilled water. Calcium silicate was added in three different concentrations, 50, 40 and 25% by weight. The cement was tested for setting time, flow, radiopacity and pH. Results: The 50:50 group shows the time of 15min8s while the 75:25 shows the time of 256min13s (p

INFLUENCE OF LUTING RESIN CEMENT POLYMERIZATION MODE AND VENEER THICKNESS ON THE COLOR STABILITY OF FELDSPATHIC CAD/CAM VENEERS

Introduction: The color stability of the resin-based cement employed for the cementation procedure may be as important for the long-term clinical success of the restoration as the mechanical properties of the veneer. Objectives: The aim of this study was to evaluate the effect of different polymerization modes of resin cements and ceramic thicknesses on the color stability of feldspathic CAD/CAM veneers. Materials and Methods: Sixty-four sound human maxillary central incisor teeth were divided according to ceramic veneer thickness used into two main groups (n = 32); Group I; 0. 5 mm ceramic thickness and Group II; 1 mm ceramic thickness, each group was then subdivided according to the type of resin cement received (Light cure LC or Dual cure DC) into four sub groups of 16 specimens each: Group I A:(0.5 + LC); Group I B:(0.5 + DC); Group II A:(1 + LC); Group II B (1 +DC) . Sixty four Ceramic discs were prepared; for group I, 32 discs of diameter 7 mm and height 0.5mm while for group II, 32 discs of diameter 7mm and height 1mm. The shade was measured using digital spectrophotometer at 3 different time intervals. Results: Ceramic thickness alone revealed statistically significant effect on the ∆E values of all groups (p ≤ 0.05), irrespective of the type of the resin cement. The highest mean ∆E values were recorded in group I A and the lowest ∆E values were recorded in group II B .There was statistically significant difference in ∆E 2 between groups IA and IB. Conclusions: All studied cements showed ∆E within clinically acceptable range in both dual cure and light cure resin cements. Increasing ceramic thickness can serve to mask the underlying color change.

Does ceramic translucency affect the degree of conversion of luting agents?

ObjectivesSolely light-activated luting agents have been suggested for cementing procedures with aesthetic rehabilitations, but questions remain regarding their curing potential under more opaque prosthesis. To determine the degree of carbon double bond (C=C) conversion (DC) of four categories of luting strategies when considering the interposition of lithium-disilicate ceramic laminates with different translucencies during the photo-activation procedures.Materials and methodsFour different luting strategies were considered: a dual-activated resin-based cement (control, RelyX ARC, 3M ESPE), a solely light-activated resin-based cement (RelyX Veneer, 3M ESPE), a flowable resin-based composite (Filtek Z350 XT Flow, 3M ESPE), and a pre-heated (68 °C for 30 min) regular resin-based composite (Filtek Z350 XT, 3M ESPE). The DC was determined by Fourier-transformed infrared spectroscopy (n = 6), 1 min after light-activation in two conditions: (a) with direct light exposure and (b) with light exposure with the interposition of lithium-disilicate disks (e.max Press, Ivoclar Vivadent) with 1.5 mm thickness with three translucent degrees: high translucency (HT), low translucency (LT), and medium opacity (MO). The translucency parameter (TP) formula was performed to quantitatively evaluate the ceramics’ translucencies using white (L* = 93.7, a* = 1.2, and b* = 0.8) and black (L* = 8.6, a* = − 0.7, and b* = − 1.5) backgrounds. The irradiance from the light curing unit (Bluephase G2, Ivoclar Vivadent) was calculated with a power meter (Ophir Optronics) with direct light exposure to the sensor and also with the interposition of the light ceramic discs. Degree of conversion data was submitted to two-way ANOVA and Tukey’s test (α = 0.05).ResultsTranslucency parameters values were 16.4, 13.4 and 12.6 for HT, LT and MO ceramics—respectively—and affected the percentage of light transmission. For all ceramic translucencies the highest DC values were observed for the dual-activated resin-based cement followed by the solely light-activated resin-based cement, the flowable composite and then by pre-heated regular composite. The ceramic’s translucency influenced the DC only for the pre-heated composite.ConclusionsThe effect of the ceramic translucency on the curing behavior was dependent on the luting strategy. The DC was only affected for the pre-heated composite, which demonstrates lower conversion with the increased ceramic opacity.

The bulk compressive creep and recovery behavior of human dentine and resin-based dental materials

ObjectiveTo evaluate and compare the viscoelastic properties of dentine and resin-based dental materials by bulk compressive test and the Burgers model. Materials and methodsSound dentine, three resin composites as well as a resin-based cement were prepared into cylindrical specimens (n = 8). A bulk compressive creep test was applied with a constant load of 300 N (23.9 MPa) for 2 h, followed by another 2 h recovery. The maximum strain, creep stain, percentage of recovery and permanent set was measured using a linear variable displacement transducer. The viscoelastic properties were characterized via the Burgers model, and the instantaneous elastic, viscous as well as elastic delayed deformation were separated from the total strain. Data were analysed via ANOVA (or Welch's Test) and Tukey (or Games–Howell Test) with a significance level of 0.05. ResultsSound dentine presented the lowest maximum strain, creep strain, permanent set and the highest percentage of recovery, followed by 3 resin composites with comparable parameters, while the cement showed a significantly higher maximum strain, permanent set and lower percentage of recovery (p < 0.001). The Burgers model presented acceptable fits for characterization viscoelastic processes of both dentine and resin-based dental materials. Viscous and elastic delayed strain of dentine was significantly lower than those for tested materials (p < 0.001) with the highest instantaneous elastic strain percentage. Similar viscous and delayed strain was found among the 4 resin-based materials (p > 0.05). SignificanceSound dentine exhibited superior creep stability compared to resin-based dental materials. The viscous deformation in sound dentine could be ignored when loading parallel to dentine tubules.

Effects of 10-MDP Based Primer on Shear Bond Strength between Zirconia and New Experimental Resin Cement.

To date, numerous materials in the dental field are marketed to ensure stable adhesive cementation of zirconia ceramics (Y-TZP). The aims of this study were to assess the shear bond strength of the new experimental cement Surgi Dual Flo’ Zr to Y-TZP compared to Panavia V5 cement, and to evaluate the effect of 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate) containing primer on their bond strength. Twenty composite cylinders and Y-TZP disks were adhesively luted and divided into four groups based on cement type used and application or not of 10-MDP. The groups (n = 5 each) were S 10MDP (Surgi Dual Flo’ Zr with 10-MDP); S no 10MDP (Surgi Dual Flo’ Zr without 10-MDP); P 10MDP (Panavia V5 with 10-MDP); P no 10MDP (Panavia V5 without 10-MDP). Maximum load resistance (ML) and shear bond strength (SBS) were tested and mode of failure qualitative documented via scanning electron microscopy. The data were analyzed with one-way ANOVA, Holm-Sidak method, and Bayesian analysis. ML and SBS were significantly higher in S 10MDP than in S no 10MDP; and in P 10MDP than in P no 10MDP (p < 0.05). No significant differences were found between S 10MDP and P 10MDP; S no 10MDP and P no 10MDP (p > 0.05). Cohesive, adhesive, and mixed failure occurred among the groups. Bond strength between the experimental resin-based cement and Y-TZP was adequate for clinical application when 10-MDP was added. 10-MDP containing primer was effective improving the bond strength to Y-TZP more than the different type of resinous cement.

The effect of heat treatment and surface neutralization on bond strength of orthodontic brackets to lithium disilicate glass-ceramic

PurposeThe study evaluated and compared the effect of pre-etching heat treatment and post-etching surface neutralization on the surface texture parameters and initial adhesion strength of orthodontic brackets bonded to lithium disilicate glass-ceramic using water-based and resin-based cement. Materials and methodsA total of 120 samples were fabricated by duplicating the buccal surface of the maxillary premolar. The samples were randomly assigned to two groups: the cementing surface of group 1 samples was heat-treated, and that of group 2 samples was left untreated. The samples of each group were further divided into 4 subgroups (n = 15) according to the use of neutralization and the type of cement used for bonding. The surface texture parameters after etching were determined using a non-contact surface profilometer, and the bond strength was determined by a universal material tester. The results were analyzed by analysis of variance and the Scheffe post hoc test. ResultsThe samples that were heat-treated showed statistically significant higher bond strength in all the subgroups, and the acid-neutralized samples showed higher bond strength using both types of cement; however, the increase was statistically significant only in resin-based cement-bonded samples. Resin-based cement-bonded samples showed higher bond strength than water-based cement-bonded samples. ConclusionPre-etching heat treatment and post-etching acid neutralization of the cementing surface of lithium disilicate glass-ceramic significantly improve the surface texture and initial bond strength to orthodontic brackets.

In vitro fracture strength and modes of cast post and cores luted with self-adhesive resin-based cement

Aim: Cast post and core (CPC) is the main used post type; however, the biomechanical behavior of CPCs adhesively luted to the dentin is still unclear. Therefore, we aimed to evaluate the fracture resistance (FR) and fracture modes of teeth restored with CPCs luted with zinc-phosphate (ZP) or resin-based self-adhesive (SA) cements, as well as the influence of the coronal remnant. Methods: For that, 24 human premolars were divided into four groups according to the cement (ZP or SA) and coronal remnant (with or without 2mm). FR was tested in a universal machine and data analyzed by two-way ANOVA and Tukey HSD (α=.05). Fracture modes were classified according to the degree of dental destruction. Results: The results showed that there was no difference in FR (p=.352); however, teeth without ferrule presented more irreparable fractures, specially in the ZP group. Conclusion: All in all, self-adhesion of CPCs does not enhance fracture resistance, however it reduces the number of irreparable fractures, compared to ZP cement.

3D Digital Image Correlation Analysis of the Shrinkage Strain in Four Dual Cure Composite Cements.

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.

The effect of crown fabrication process on the fatigue life of the tooth-crown structure.

To compare the fatigue strength of lithium disilicate ceramic crowns when cemented as a compound structure, as a function of the manufacturing process and the type of ceramic variation. A typodont maxillary first premolar was prepared for an all-ceramic crown in accordance with the manufacturer's guidelines for monolithic ceramic crowns (IPS e. max®; Ivoclar-Vivadent, Liechtenstein). 60 dies were duplicated in a polymer with a Young's Modulus closely matched to dentine (Alpha die, Schütz GmbH). Three different crown fabrication techniques were used (n = 20): (i) Manually applied wax spacer and pressed-crown; (ii) digitally scanned preparation, CAD-printed wax-pattern (D76PLUS, Solidscape Inc.) and pressed-crown; (iii) digitally scanned preparation and machined-crown (CEREC-inLab® v3.6 Sirona GmbH). Resin-based cement (Variolink-II®, Ivoclar-Vivadent, Liechtenstein) was employed with a standardised mechanised cementation technique to apply a controlled axial cementation pressure [Universal testing machine (Lloyd LRX®, Lloyd Materials Testing Inc)]. The samples were subjected to fatigue life testing with a cyclic impact load of 453 N for 1.25 × 106cycles at 37C⁰ and 1 Hz frequency until the point of fracture. There was a significant difference in the resistance to fatigue loading between the three groups. Weibull probability analysis and the α and β Weibull parameters indicate that the teeth restored with a 'Manually-applied wax spacer and pressed-crown' are best able to resist cyclic fatigue loading. They also have the most uniform interface geometry. Teeth restored with IPS e. max® crowns constructed by manually applied wax spacer and pressing, have a more uniform interface and a greater structural integrity than wax CAD-printed patterns or CAD-CAM crowns.

Effect of Incisal Porcelain Veneering Thickness on the Fracture Resistance of CAD/CAM Zirconia All-Ceramic Anterior Crowns.

Statement of Problem In some clinical situations, the vertical length of either a prepared tooth or an implant abutment is short, while the occlusal clearance to be restored by a porcelain crown is large. Incisal thickness of the veneering porcelain should be considered to prevent mechanical failure of the crown. Purpose The aim of this study is to evaluate the effect of two different incisal veneering porcelain thickness on the fracture resistance of the anterior all-ceramic CAD/CAM zirconia crown system as compared with the conventionally used metal ceramic crown system. Method CAD/CAM zirconia all-ceramic and metal ceramic crowns were fabricated on the prepared dies with standardized dimensions and designs using standardized methods according to the manufacturer's instructions. All crowns were then adhesively luted with resin-based cement (Multilink cement system), subjected to thermal cycling and cyclic loading, and were loaded until fracture using the universal testing machine to indicate the fracture resistance for each crown material in each veneering thickness. Results Statistical analysis was carried out, and the results showed that the fracture resistance of the nickel-chromium metal ceramic group was significantly higher than that of the CAD/CAM zirconia all-ceramic group. Also, the fracture resistance of crowns with 1.5 mm incisal veneering thickness was significantly higher than those with 3 mm incisal veneering thickness in both groups. Furthermore, there was no significant difference in the fracture mode of the two groups where 50% of the total specimens demonstrated Mode II (veneer chipping), while 35% demonstrated Mode I (visible crack) and only 15% demonstrated Mode III (bulk fracture). Conclusion High failure load values were demonstrated by the specimens in this study, which suggest sufficient strength of both incisal veneering thickness in both crown systems to withstand clinical applications; however, the fracture patterns still underline the requirement of a core design that support a consistent thickness of the veneering ceramic, and it is recommended to conduct long-term prospective clinical studies to confirm findings reported in the present study.

Analysis of the strain and hardness in self-cured and light-cured self-adhesive resin based cement

The study showed an application of the 3 D Digital Image Correlation Method (3 D-DIC) for detection of von Mises strain in samples of the self-etch, self-adhesive resin based cement (RBC). The aim was to determine and compare strain in the self-cured and light-cured Maxcem Elite, furthermore to investigate the hardness of these two cement-types. The experiment was carried out using two groups of Maxcem Elite (Kerr, Orange, CA, USA) samples; each tested group includes five (ø5 × 2 mm sized) samples, for both self-curing and light-curing mode. All samples were prepared by filling teflon ring-type molds. In addition, Vickers micro-hardness was measured for all samples. Maxcem Elite showed similar maximum strain values from 10% to 12% for both groups. Besides the maximum strain value, the 3 D-DIC method also enabled monitoring the change of strain field even after the recommended polymerization time. This method has shown that the polymerization shrinkage continues even after 10 min which disagreed with manufacturer’s suggestion. Group II showed maximum strain values of 12% in the peripheral zone after 10 min, in the last Stage (Stage 60). Statistically significant difference was not found in the overall strain between self- and light-cured Maxcem Elite neither peripherally (p = 0.118) nor centrally (p = 0.879). However, statistical significance was found in strain regarding central and peripheral zone in both, self-cured (p = 0.020) and light-cured (p = 0.002) Maxcem Elite. The mean von Mises strain values in the periphery of the samples (Section 0) were significantly higher compared to strain values in the center of the samples (for Section 1 and 2). The last stage (Stage 60) of the light-cured Maxcem Elite polymerization showed significantly higher values of von Mises strain compared to initial stage (Stage 0). Higher values of micro-hardness were noticed on the surfaces directly exposed to LED lamp after performing measurements of micro-hardness on light-cured samples.

Application of a Novel Modification of the Microbond Test for Evaluation of Adhesive Bond Strength Between Fiber Posts and Dual-Cure Dental Resin Cement.

BackgroundWhile several tests can be used in the laboratory evaluation of composite resin-based cement materials, the push-out test remains the most prevalent. Due to difficulties in sample preparation, as well as a highly complex procedure, we attempted to develop an alternative method for testing the bond strength of dental resin cement materials.Material/MethodsNinety-six experimental samples of 2 dual-cure resin cements and 1 fiber post system were prepared for the 2 testing procedures: the push-out test and the modified Microbond test. The degree of monomer conversion was measured by Fourier-transform infrared spectroscopy.ResultsThe push-out test results indicated that the bond strength of dual-cure resin cement differs depending on the tooth root region to which it is applied (p<0.05), In addition, our findings show that Variolink II exhibits a much lower bond strength relative to RelyX ARC. These findings were confirmed by the modified Microbond test results. The monomer conversion rate results indicate average conversion rates of 85.81% and 61.35% for RelyX ARC and Variolnik II, respectively.ConclusionsOur study confirms the practical utility of the modified Microbond test in the assessment of bond strength of dental cement resin-based materials. The proposed test method is particularly useful given that, relative to the push-out test, it requires a much smaller number of preparation and execution steps, thus reducing the potential for introducing errors, while increasing the reliability of the obtained findings.

Mechanical stability of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns.

To evaluate the bending moments and failure modes of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns after aging, and to compare them to titanium abutments restored with all-ceramic crowns. Forty-eight internal conical connection implants (Conelog, Camlog 4.3 mm diameter) were restored with four different computer-aided design/computed-aided manufacturing (CAD/CAM) abutment-crown combinations (n = 12). Thirty-six customized zirconia meso-abutments were bonded to titanium bases (Conelog Titanium Base CAD/CAM crown, Camlog) and divided into three groups according to the different crown materials: (T1) monolithic lithium-disilicate (e-max CAD, Ivoclar), (T2) monolithic PICN (polymer-infiltrated ceramic network [Enamic, Vita]), and (T3) monolithic zirconia (Lava Plus, 3M ESPE). Twelve titanium customized abutments restored with monolithic lithium-disilicate (e-max CAD, Ivoclar) crowns served as the control group (C). The crowns were equal maxillary central incisors and were adhesively bonded with a resin-based cement (Panavia 21, Kuraray). All samples were embedded in acrylic holders. After aging (1,200,000 cycles, 49 N, 1.67 Hz, 5°C to 50°C, 120 seconds), static load was applied until failure. Bending moments were calculated for comparison of the groups. Data were statistically treated with one-way analysis of variance (ANOVA) followed by Tukey post hoc test (P < .05). Failure modes were analyzed descriptively. The means of the bending moments were 356.4 ± 20.8 Ncm (T1), 357.7 ± 26.3 Ncm (T2), 385.5 ± 21.2 Ncm (T3), and 358.8 ± 25.3 Ncm (C). Group T3 revealed significantly higher mean bending moments than the other groups (P < .05). No differences were found between zirconia meso-abutments supported by titanium bases and customized titanium abutments when lithium-disilicate crowns were used (P > .05). No failures were identified during and after aging. After static load, failures occurred due to fracture of the abutment in the internal connection in all the groups. Zirconia meso-abutments bonded to titanium bases showed similar mechanical stability compared with customized titanium abutments. Regarding the crown material, all three tested ceramics (lithium-disilicate, PICN, and zirconia) revealed very good stability when used in the monolithic state.