Evaluation of ISO 4049: water sorption and water solubility of resin cements

Proposing new standards for testing solubility of pulp preservation materials

OBJECTIVES

Quality control testing of dental materials requires a standard to enable the generation of reproducible and comparable data. Currently there are no standards for testing materials used for vital pulp therapy. The aim of this study was to develop a new standard to evaluate solubility of pulp preservation materials.

METHODS

The solubility of three materials used for vital pulp therapy: Biodentine, TheraCal and Activa was evaluated using two international standards for dental materials ISO 4049:2019 (S1) and ISO 6876:2012 (S2). For both standards, a modified methodology was evaluated. This included changing the volume of the solution used (S1M, S2M), using Dulbecco's modified eagle medium (DMEM) as an alternative to water (S1D, S2D) and periodic solution change for the ISO 4049 method (S1P, S1MP). Materials were characterised before and after completion of solubility test using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.

RESULTS

The test materials exhibited different solubility values depending on the methodology used. Biodentine exhibited significantly lower solubility when lower volumes of solution were used when tested using both ISO methods (p ≤ 0.05). TheraCal and Activa showed negative solubility values after desiccation when tested using ISO 4049:2019. The Biodentine exhibited changes in its microstructure which was dependent on the method used to test solubility.

CONCLUSIONS

The solubility values obtained were dependent on the method used. It is thus important to use methods that replicate the clinical environment for meaningful evaluations.

Effects of Hexagonal Boron Nitride and Mesoporous Silica Nanoparticles on the Morphology, Mechanical Properties and Antimicrobial Activity of Dental Composites

Hexagonal boron nitride (HBN), an artificial material with unique properties, is used in many industries. This article focuses on the extent to which hexagonal boron nitride and silica nanoparticles (MSN) affect the physicochemical and mechanical properties and antimicrobial activity of prepared dental composites. In this study, HBN, and MSN were used as additives in dental composites. 5% and 10% by weight of HBN are added to the structure of the composite materials. FTIR analysis were performed to determine the components of the produced boron nitride powders, hexagonal boron nitride-containing composites, and filling material applications. The structural and microstructural properties of dental composites have been extensively characterized using X-ray diffractometry (XRD). Surface morphology and distributions of nano boron nitride were determined by scanning electron microscopy (SEM)-EDS. In addition, the solubility of dental composites in water and their stability in water and chemical solution (Fenton) were determined by three repetitive experiments. Finally, the antimicrobial activity of dental composites was detected by using Minimum Inhibitory Concentration (MIC) measurement, as well as Minimum Fungicidal Concentration (MFC) method against yeast strain Saccharomyces cerevisiae, and Minimum Bactericidal Concentration (MBC) method against bacteria strains, Staphylococcus aureus and Escherichia coli. Since the HMP series have better antimicrobial activity than the HP series, they are more suitable for preventing dental caries and for long-term use of dental composites. In addition, when HMP and HP series added to the composite are compared, HMP-containing dental composites have better physicochemical and mechanical properties and therefore have a high potential for commercialization.

The chemical and optical stability evaluation of injectable restorative materials under wet challenge

OBJECTIVES

To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer.

METHODS

Two injectable nano-filled composite resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE⁎, ΔL⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05.

RESULTS

GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DCIM and DC24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility.

CONCLUSIONS

The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. Wsp and Wsl are influenced by many common factors, and the values are highly positively related.

CLINICAL SIGNIFICANCE

A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.

Effect of curing mode of resin composite cements on water sorption, color stability, and biaxial flexural strength

OBJECTIVES

To determine whether water sorption and solubility of a recently introduced self-adhesive cement is comparable to two clinically tested resin composite cements after thermal aging, and if this is affected by the curing mode. Whether water sorption is correlated with color difference and biaxial flexural strength was also investigated.

METHODS

Water sorption and solubility of three resin composite cements {RelyX Universal (RUV), (Panavia V5 (PV5), Panavia SA plus (PSA)} were measured after thermal aging. Disk-shaped specimens were either light-cured or autopolymerized (n = 15 per group). Color difference ΔE00 and biaxial flexural strength were also obtained.

RESULTS

Sorption was highest for RUV (auto: 54.9 ± 9.0 µg/mm3, light: 49.7 ± 4.9 µg/mm3), followed by PSA (auto: 37.7 ± 1.4 µg/mm3, light: 34.5 ± 1.1 µg/mm3) and PV5 (auto: 21.7 ± 0.7 µg/mm3, light: 22.1 ± 0.4 µg/mm3). Light-curing reduced solubility values, particularly for RUV (from 60.7 ± 20.8 µg/mm3 to 6.4 ± 0.8 µg/mm3). Color differences of ΔE00 > 1.8 (considered clinically not acceptable) were noted after aging for RUV and PSA. Sorption and ΔE00 values after aging were correlated linearly (R2 = 0.970). Biaxial flexural strength values were highest for PV5 (light: 153.4 ± 15.9 MPa; auto: 133.2 ± 18.0 MPa) and lowest for RUV (light: 99.3 ± 12.8 MPa; auto: 35.1 ± 8.3 MPa).

SIGNIFICANCE

Light-curing has beneficial effects on sorption, color stability, and biaxial flexural strength of resin composite cements. Cements containing 2-hydroxymethacrylate such as RUV and PSA are more prone to water sorption and color changes.

Residual stresses in glass crowns generated by polymerization and water sorption of resin cements

This study investigated residual stresses in glass crowns cemented with resin cements. Glass caps were cemented to cylindrical cores using a conventional resin composite cement, a self-adhesive resin cement, or a methyl methacrylate (MMA)-based cement in dual-cure or self-cure mode. The cemented caps were stored in 37°C water for 28 days, and stresses on the cap surface were repeatedly measured. The water sorption, water solubility, and elastic modulus of the cements were also measured. Polymerization of the cements initially generated compressive stresses on the surfaces. Dual-curing or a greater modulus yielded greater initial stress. The stresses gradually decreased over time and lingered on the surfaces at 28 days with all the cements. Greater sorption tended to lead to greater stress reduction; however, the MMA-based cement exhibited less stress reduction despite exhibiting the greatest sorption. The use of a resin composite cement or dual-curing is recommended to reinforce crown restorations.

Comparative bonding performance of coronal dentin disks and CAD/CAM resin composite disks for biological restoration: The impact of resin-coating technique

This study evaluated the bonding performance of coronal dentin disks, designed for biological restoration, and CAD/CAM resin composite disks when bonded to flat dentin surfaces using dual-cure resin cements, with and without a resin-coating (RC) technique. Three distinct groups were established within the non-RC group, each using one of the two types of resin cements in a self-adhesive mode: one-step self-etch adhesive (1-SEA) without light-cure, 1-SEA with light-cure, and a separate group using an alternate cement. Within the RC group, a subgroup was established for each cement. The microtensile bond strength (μTBS) of the disk-dentin beam was tested after 0 and 10,000 thermocycles in a 5°C/55°C. No significant μTBS difference was observed among the non-RC groups. However, when using RC, the μTBSs of coronal dentin disks significantly exceeded those of CAD/CAM resin composite disks. Thermocycle aging did not affect μTBS in any of the bonding methods, except in self-adhesive mode.

Effect of post-curing conditions on surface characteristics, physico-mechanical properties, and cytotoxicity of a 3D-printed denture base polymer

OBJECTIVE

This study aims to investigate the influence of post-polymerization (post-curing) conditions on surface characteristics, flexural properties, water sorption and solubility, and cytotoxicity of additively manufactured denture base materials.

METHODS

The tested specimens were additively manufactured using digital light processing and classified into different post-curing condition groups: submerged in water (WAT), submerged in glycerin (GLY), and air exposure (AIR). An uncured specimen (UNC) was used as a control. The surface topography and roughness were observed. The flexural strength and modulus were determined via a three-point bending test. The water sorption and solubility were subsequently tested. Finally, an extract test was performed to assess cytotoxicity.

RESULTS

Different post-curing conditions had no significant effects on the surface topography and roughness (Sa value). Various post-curing conditions also had no significant effects on the flexural strength. Notably, the flexural modulus of the WAT group (2671.80 ± 139.42 MPa) was significantly higher than the AIR group (2197.47 ± 197.93 MPa, p = 0.0103). After different post-curing conditions, the water sorption and solubility of the specimens met the ISO standards. Finally, all post-curing conditions effectively reduced cytotoxic effects.

SIGNIFICANCES

Post-curing with different oxygen levels improved flexural properties, and flexural modulus significantly increased after the specimens were submerged in water. In addition, water sorption and solubility, and cytocompatibility were optimized by post-curing, irrespective of the post-curing conditions. Therefore, the water-submerged conditions optimized the flexural modulus of the 3D-printed denture base materials.

A 3D-simulation study of the deformation, tension, and stress of 3D-printed and conventional denture base materials after immersion in artificial saliva

INTRODUCTION

The worldwide application of digital technology has presented dentistry with transformative opportunities. The concept of digital dentures, incorporating computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques, holds the promise of improved precision, customization, and overall patient satisfaction. However, the shift from traditional dentures to their digital counterparts should not be taken lightly, as the intricate interplay between oral physiology, patient comfort, and long-term durability requires thorough examination.

Influence of Specimen Dimension, Water Immersion Protocol, and Surface Roughness on Water Sorption and Solubility of Resin-Based Restorative Materials

The evaluation of water sorption and solubility is pivotal for the development of new resin-based restorative materials with the potential for clinical application. The purpose of the present study was to evaluate the influence of the specimen dimension, water immersion protocol, and surface roughness on the water sorption and solubility of three resin-based restorative materials. Disk-shaped specimens of 15 mm × 1 mm, 10 mm × 1 mm, and 6 mm × 1 mm were produced with a composite resin (Z100), a resin cement (RelyX ARC), and an adhesive system (Single Bond 2-SB2). The specimens were immersed in distilled water according to four protocols: ISO (all the specimens for each group were vertically immersed in 50 mL); IV-10 (the specimens were individually and vertically immersed in 10 mL); IH-10 (the specimens were individually and horizontally immersed in 10 mL); and IH-2 (the specimens were individually and horizontally immersed in 2 mL). The surface roughness (Sa and Sp) was evaluated using an atomic force microscope, and the degree of conversion was determined using FT-IR spectrometry. The specimen dimension and water immersion protocol had no effect on water sorption and solubility. For the three resin-based restorative materials, Sp was higher than Sa. The degree of conversion was not influenced by the specimen dimension. The variations in the specimen dimension and water immersion protocol compared to those determined by ISO 4049 did not prevent the comparison between the values of water sorption and solubility obtained for a given resin-based restorative material.

In vitro characterization of a novel resin-based restorative material containing alkaline fillers

OBJECTIVE

In this study, a comparative evaluation of the physicochemical properties of Cention N and other direct restorative materials was performed. Three restorative materials-a resin-modified glass ionomer (Fuji II LC), an alkasite-based resinous material (Cention N), and a resin composite (Tetric N Ceram)-were characterized in terms of degree of conversion, Knoop hardness number (KHN) ratio, flexural strength, elastic modulus, water sorption, water solubility, microshear bond strength to dentin, immediate microleakage, and radiopacity.

METHODOLOGY

The microshear bond strength to dentin and microleakage of Cention N were evaluated with and without the application of an adhesive system (Tetric N Bond Universal). A one-way ANOVA test was used to analyze the data in terms of degree of conversion, KHN ratio, water sorption, water solubility, microshear bond strength to dentin, and radiopacity. A two-way ANOVA test (carried out considering the material type and ethanol aging as factors) was used to analyze the data in terms of flexural strength and elastic modulus. The Kruskal-Wallis test was used to statistically analyze the data on microleakage. A significance level of α=0.05 was used for all tests.

RESULTS

Fuji II LC was found to have the highest degree of conversion, water sorption, and microleakage, as well as the lowest flexural strength. Cention N had the highest solubility; when used with an adhesive system, it achieved bond strength and microleakage similar to those of the Tetric N Ceram composite. Tetric N Ceram had the highest degree of conversion, KHN ratio, and radiopacity. Conclusion: The properties of Cention N validate its efficacy as an alternative direct restorative material when used in conjunction with an adhesive system.

Effect of denture cleansers on the physical and mechanical properties of CAD-CAM milled and 3D printed denture base materials: An in vitro study

STATEMENT OF PROBLEM

Studies on the impact of denture cleansers on the physical and mechanical properties of denture bases designed and constructed by using computer software programs are lacking.

PURPOSE

The purpose of this in vitro study was to test the effect of a peroxide denture cleanser on the hardness, fracture toughness, water sorption, and solubility of denture base materials manufactured by 3D printing and computer-aided design and computer-aided manufacturing (CAD-CAM) milling.

MATERIAL AND METHODS

The hardness, fracture toughness, water solubility, and sorption of CAD-CAM milled and 3D printed groups (n=40) were evaluated before and after exposure to a denture cleanser. Hardness (n=10) was analyzed with a Vickers hardness testing machine, and fracture toughness (n=20) with the 3-point bend test. After the fracture of specimens, a scanning electron microscope at ×300 was used for fractographic analysis. Water sorption and solubility (n=10) were evaluated before and after immersion in denture cleanser for 6 days to simulate 180 days of immersion. Two-way repeated ANOVA and 2-way ANOVA were used to test normally distributed data, whereas the Mann Whitney U test and Wilcoxon signed ranks test were used for data that were not normally distributed (α<.05).

RESULTS

The Vickers hardness and fracture toughness of both materials decreased after immersion in denture cleansers, with a higher decrease in values for the 3D printed group (P<.001). The denture cleanser had no effect on the water sorption and solubility of either group.

CONCLUSIONS

Milled specimens had higher hardness values and fracture toughness before and after immersion in the denture cleanser. Denture cleansers resulted in the reduced hardness and fracture toughness of both groups, but the percentage change in the milled group was lower. Denture cleansers had no effect on water sorption or solubility.

The Depth of Cure, Sorption and Solubility of Dual-Cured Bulk-Fill Restorative Materials

This study aimed to examine depth of cure (DoC), mass change, water sorption and solubility of dual-cured bulk-fill restorative materials (Surfil One and Activa) in comparison with a light-cured bulk-fill composite (Filtek One Bulk-Fill) and a resin-modified glass ionomer (Fuji II LC). Twenty specimens were prepared of each material using stainless steel molds designed with a slot (8 × 4 × 2 mm) and irradiated for either 20 or 40 s. The Vickers hardness (VHN) was measured at every 0.5 mm to assess the DoC after 24 h of storage at 37 °C. The depth of cure was reported as the depth corresponding to 80% of the maximum Vickers hardness. Disc-shaped specimens were prepared of each material (n = 5) to investigate mass change, sorption and solubility after 4 months of water storage. The data were analyzed using a two-way and one-way analysis of variance (ANOVA) followed by the Tukey post hoc test (p ≤ 0.05). Fuji II LC had the greatest DoC while Activa had the lowest. The two different irradiation times did not demonstrate a significant difference in DoC for all dual-cured materials (p > 0.05). Fuji II LC had the highest sorption while Filtek One showed the lowest. Surefil One and Fuji II LC had a negative solubility. This study concluded that dual-cured materials showed different depth of cure values despite having the same setting reaction. Both materials exhibited a high water sorption, which might jeopardize their dimensional stability and effect their clinical performance.

Comparison of the translucency parameters and bond strength of 5Y-ZP zirconia, 3-YTZP zirconia, and lithium disilicate

Background

E-max is a more aesthetic material than traditional zirconia. In addition, the bond strength of traditional zirconia with adhesive cements is lower. There are not enough studies on how the aesthetic values and bond strength of 5-YZP, the new generation zirconia, compare to e-max and traditional zirconia. Can 5-YZP be an alternative to e-max in terms of aesthetics and bond strength?

Aim

The aim of the study is to compare the translucency property and bonding ability of 5y-zp zirconias with previous generation zirconias and lithium disilicate.

Materials and Methods

Two types of zirconia Katana UT and Katana HT for measuring translucency values; and using a type of lithium disilicate IPS e.max CAD LT, three groups were formed (n = 10). Translucency specimens were fabricated (n = 10). Their L*a*b* values were measured against a black-and-white background with a spectrophotometer, and DE00 was calculated. To perform micro-shear tests, a cylinder design was made from zirconia and IPS e.max CAD blocks (n = 20). After the samples were aged by thermal cycle, the micro-shear test was applied to specimens cemented to teeth extracted with two different adhesive cement systems.

Results

According to the results of one-way analysis of variance, a statistically significant difference was found between the translucency parameter (TP) values of the groups. According to Tukey's honestly significant difference (HSD) multiple comparisons, the values of the three groups are statistically different from each other. Although IPS e.max CAD group has the highest TP values, the Katana HT group has the lowest values.

Conclusion

5Y-PZ has a TP intermediate to those of 3Y-TZP and lithium disilicate. Long-term bond strength of 3Y-TZP and 5Y-ZP were similar to those of lithium disilicate. To be an alternative to glass ceramics in the anterior region, translucency and bond strength values need to be improved.

The effect of varying monocalcium phosphate and polylysine levels on dental composite properties

OBJECTIVES

The aim was to quantify effects of polylysine (PLS, 2 or 5 wt%) and monocalcium phosphate (MCP, 4 or 8 wt%) on properties of dental composites.

METHODS

Light-activated, lower surface polymerisation kinetics versus sample depth (1-4 mm) of 4 formulations were quantified using ATR-FTIR. Water sorption and solubility (at 1 week) were assessed following ISO/4049. PLS release (over 1 month) and biaxial flexural strength (over 6 months) of fully-cured, water-immersed, 1 mm thick discs were determined. Surface mineral precipitation, following immersion in simulated body fluid (SBF), was assessed by SEM. Z250 was used as a conventional composite comparator.

RESULTS

With 40s light exposure, increasing depth (from 1 to 4 mm) led to enhanced delay before polymerisation (from 3 to 17s) and decreased final conversion (72-66%) irrespective of PLS and MCP level. Increasing PLS and MCP raised solubility (4-13 μg/mm3). Water sorption (between 32 and 55 μg/mm3) and final PLS release (8-13% of disc content) were raised primarily by increasing PLS. Higher PLS also reduced strength. Strength reached minimum values (69-94 MPa) at 3 months. Surface mineral deposition was enhanced by increased MCP. For Z250, polymerisation delays (3-6s) and final conversions (55-54%) at 1-4 mm depth, solubility (0 μg/mm3), water sorption (16 μg/mm3) and strength (180 MPa) were all significantly different.

CONCLUSION

Delay time increased whilst final conversion decreased with thicker samples. Higher PLS enhances its percentage release, but lower level is required to keep water sorption, solubility and mechanical properties within ISO 4049 recommendations. Doubling MCP raises solubility and enhances minerals reprecipitation with minimal mechanical property compromise.

Can Modification with Urethane Derivatives or the Addition of an Anti-Hydrolysis Agent Influence the Hydrolytic Stability of Resin Dental Composite?

Due to the questionable durability of dental restorations, there is a need to increase the lifetime of composite restoration. The present study used diethylene glycol monomethacrylate/4,4'-methylenebis(cyclohexyl isocyanate) (DEGMMA/CHMDI), diethylene glycol monomethacrylate/isophorone diisocyanate (DEGMMA/IPDI) monomers, and bis(2,6-diisopropylphenyl)carbodiimide (CHINOX SA-1) as modifiers of a polymer matrix (40 wt% urethane dimethacrylate (UDMA), 40 wt% bisphenol A ethoxylateddimethacrylate (bis-EMA), and 20 wt% triethyleneglycol dimethacrylate (TEGDMA)). Flexural strength (FS), diametral tensile strength (DTS), hardness (HV), sorption, and solubility were determined. To assess hydrolytic stability, the materials were tested before and after two aging methods (I-7500 cycles, 5 °C and 55 °C, water and 7 days, 60 °C, 0.1 M NaOH; II-5 days, 55 °C, water and 7 days, 60 °C, 0.1 M NaOH). The aging protocol resulted in no noticeable change (median values were the same as or higher than the control value) or a decrease in the DTS value from 4 to 28%, and a decrease in the FS value by 2 to 14%. The hardness values after aging were more than 60% lower than those of the controls. The used additives did not improve the initial (control) properties of the composite material. The addition of CHINOX SA-1 improved the hydrolytic stability of composites based on UDMA/bis-EMA/TEGDMA monomers, which could potentially extend the service life of the modified material. Extended studies are needed to confirm the possible use of CHINOX SA-1 as an antihydrolysis agent in dental composites.

Effect of Temporary Cement, Surface Pretreatment and Tooth Area on the Bond Strength of Adhesively Cemented Ceramic Overlays-An In Vitro Study

Several viewpoints have been reported regarding the effect of temporary cements, different surface pretreatment protocols before adhesive cementation, and predictive factors. This in vitro study tested if temporary cement, pretreatment of the tooth surface, the size of enamel or dentine influence adhesive cementation to zirconia ceramics. Twenty premolars were prepared for determination of enamel and dentin area, bond strength test and failure analysis. The samples were divided into two groups: untreated prior adhesive cementation (n = 10) and with temporary cementation done, pretreated prior adhesive cementation (n = 10). Zirconia overlays (Katana Zirconia STML) were cemented on the grounded flat teeth surfaces using Panavia V5. An additional six premolars underwent dentine tubule analysis with SEM to detect temporary cement residues after temporary cementation on an untreated tooth surface (n = 3) and on a pretreated surface (n = 3). The independent sample t-test was used to compare the two groups and the means of the total tooth, dentin or enamel areas did not differ significantly between the untreated and pretreated specimens. The mean tensile bond strength was significantly (p = 0.005) higher in the pretreated specimens (337N) than in the untreated ones (204N). The overall multivariable linear regression model with three predictors (surface pre-treatment, enamel area and dentine area) was significant (p = 0.003), among which the size of enamel was the strongest predictor (β = 0.506; p = 0.049), followed by the pretreatment effect (β = 0.478; p = 0.001) and the size of dentin area (β = -0.105; p = 0.022).

Influence of Novel Experimental Light-Cured Resin Cement on Microtensile Bond Strength

The purpose of this study was to evaluate the microtensile bond strength (µTBS) and Knoop hardness number (KHN) of a novel experimental light-cured resin cement (HL). Eighteen flat dentin surfaces of human molars were polished using #600 SiC paper and bonded to CAD/CAM resin blocks with the respective resin cements and composites: HL, Panavia V5 (PV), and Clearfil AP-X (AP). All specimens were stored in distilled water at 37 °C for 24 h and 7 days. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) observations were performed to evaluate filler morphology and to detect the elements. The resin cements had a significant effect on the immediate µTBS (F = 22.59, p < 0.05) and after water storage µTBS (F = 22.83, p < 0.05). Significant differences (p < 0.05) in the KHN between the tested materials were observed, and HL indicated the highest KHN when compared with PV. HL showed a combination of the regular-shaped filler and spherical-shaped filler within the matrix. Silicon was detected in HL from the EDX evaluation. HL exhibited better bonding performance and polymerization, which may have contributed to the improvement of the adhesive strength.

Intrapulpal temperature changes during the cementation of ceramic veneers

Adhesive cementation of ceramic veneers may increase pulpal temperature (PT) due to the combined effect of heat generated by the curing unit and the exothermic reaction of the luting agent (LA). PT increase may induce pulpal damage. The aim was to determine the PT rise during the luting of ceramic veneers (CV) of different thicknesses with light- or dual-curing (LC, DC) adhesive cements as well as pre-heated restorative resin-based composites (PH-RBC). For this a thermocouple sensor was positioned in the pulp chamber of a prepared maxillary central incisor. LC, DC adhesive cements and PH-RBCs heated to 55 °C were used for the luting of CVs of 0.3, 0.5, 0.7, and 1.0 mm thicknesses. The exothermic reaction of LAs added significantly to the thermal effect of the curing unit. PT change ranged between 8.12 and 14.4 °C with the investigated combinations of LAs and ceramic thicknesses (p ≤ 0.01). The increase was inversely proportional to the increasing CV thicknesses. The highest rise (p ≤ 0.01) was seen with the polymerization of PH-RBCs. Temperature changes were predominantly influenced by the composition of the LA, which was followed by CV thickness.

Investigation of antimicrobial and mechanical effects of functional nanoparticles in novel dental resin composites

OBJECTIVES

Imidazole and benzimidazole derivatives have recently attracted attention as remarkable materials due to their advantages in chemistry, pharmacology, and biomaterials. This article focuses on dental composites with azole functional groups incorporated to affect their physicochemical and mechanical properties and antibacterial activity.

METHODS

Dental composites were fabricated by embedding the functionalized imidazole and benzimidazole nanoparticles into a Bis-GMA/TEGDMA matrix to form the imidazole and benzimidazole dental composites series (I and B). The material was produced through hand blending of the monomer (50:50, wt%), filler (0-30, wt%), and initiator combination (CQ/EDMAB:0.8:1.6, wt%), and LED light-curing unit for 60 s.

RESULTS

Using various characterization techniques, I and B series were validated. The dental composites' approximate solubility and sorption significances were evaluated by conducting experiments on specific dental composite formulations. Fenton reaction test was performed to determine the chemical stability of the dental composites. The mechanical properties of the dental composites were investigated. Finally, by testing cell growth in the presence of composites, their antibacterial activities were determined.

CONCLUSIONS

In this study, it was observed that the mechanical, physiochemical, and antibacterial properties of the functional azole-containing nanoparticles were positively improved by adding them to the structure of dental composites. These experimental results paved the way for the synthesized materials to be used in industrial applications.

CLINICAL SIGNIFICANCE

Since the chemical, mechanical, and antimicrobial properties of dental composites containing 10% imidazole and benzimidazole functional nanoparticles are far superior, they constitute an excellent alternative for preventing dental caries and long-term use of dental composites.

Long-Term Assessment of Contemporary Ion-Releasing Restorative Dental Materials

The objective was to evaluate new commercially available ion-releasing restorative materials and compare them to established anti-cariogenic materials. Four materials were tested: alkasite Cention (Ivoclar Vivadent) in self-cure or light-cure mode, giomer Beautifil II (Shofu), conventional glass-ionomer Fuji IX (GC), and resin composite Tetric EvoCeram (Ivoclar Vivadent) as a control. Flexural strength, flexural modulus, and Weibull modulus were measured one day, three months, and after three months with accelerated aging in ethanol. Water sorption and solubility were evaluated for up to one year. Degree of conversion was measured during 120 min for self-cured and light-cured Cention. In this study, Beautifil II was the ion-releasing material with the highest flexural strength and modulus and with the best resistance to aging. Alkasite Cention showed superior mechanical properties to Fuji IX. Weibull analysis showed that the glass-ionomer had the least reliable distribution of mechanical properties with the highest water sorption. The solubility of self-cured alkasite exceeded the permissible values according to ISO 4049. Degree of conversion of light-cured Cention was higher than in self-cure mode. The use of alkasite Cention is recommended only in the light-cure mode.

The First Step in Standardizing an Artificial Aging Protocol for Dental Composites—Evaluation of Basic Protocols

The clinical performance of a dental restoration is strongly influenced by the complex and dynamically-changing oral environment; however, no standard procedure exists to evaluate this lifetime. This research provides an in-depth analysis of the effect of different aging procedures on the flexural strength (FS), diametral tensile strength (DTS) and hardness (HV) of selected dental materials (Resin F, Flow-Art and Arkon). Material structure was evaluated by scanning electron microscopy. It was found that each aging protocol had some influence on the tested properties, with continual erosion and degradation being observed. Greater mechanical degradation was observed for Resin F (neat resin) after the applied aging protocols, suggesting that a resin matrix is more susceptible for degradation. The most aggressive aging protocol was Protocol 5: 0.1 M NaOH, seven days, 60 °C. Further studies on the effect of artificial aging on dental materials should include a study of the thermal and chemical factors. A standardized aging procedure is crucial for improving the resistance of dental resin composite to oral conditions and their clinical performance.

Surface Characteristics and Color Stability of Dental PEEK Related to Water Saturation and Thermal Cycling

(1) Background: The study was undertaken to evaluate the surface characteristics, microhardness, and color stability of PEEK materials related to water saturation and in vitro aging. (2) Methods: Custom specimens of unmodified and modified PEEK CAD/CAM materials were investigated: BioHPP, a ceramic reinforced PEEK, and Finoframe PEEK and Juvora medical PEEK, 100% PEEK materials. Forty-eight plates were sectioned in rectangular slices. The specimens were immersed in distilled water at 37 °C for a period of 28 days, and then subjected to aging by thermal cycling (10,000 cycles). Surface roughness was measured with a contact profilometer; nanosurface topographic characterization was made by Atomic Force Microscopy; Vickers hardness measurements were performed with a micro-hardness tester; color changes were calculated. All registrations were made before immersion in water and then subsequently once a week for 4 weeks, and after thermocycling. (3) Results: The studied reinforced and unfilled PEEK materials reached water saturation after the first week of immersion, without significant differences between them. The most affected from this point of view was the reinforced PEEK material. Thermocycling induces a significant increase inmicroroughness, without significant differences between the studied materials. In relation to the nanosurface topography and roughness, the reinforced PEEK material was the least modified by aging. The color changes after 4 weeks of water immersion and one year of simulated in vitro aging ranged from extremely slight to slight, for all materials. (4) Conclusions: Water absorption was associated with a decrease in microhardness. Surface characteristics are affected by water immersion and thermocycling. Perceivable or marked color changes of the materials were not detected during the study.

Retention strength of monolithic zirconia crowns cemented with different primer-cement systems

BACKGROUND

The purpose of this in vitro study was to assess the influence of different cement systems with different ceramic primers on the retention strength of zirconia crowns.

METHODS

Thirty extracted molars were prepared with flat occlusal surfaces, 20 degrees taper, and 3 mm axial wall height. A zirconia crown with an occlusal bar was fabricated for each tooth. All specimens were divided (n = 10) into; Group M: Multilink Speed/Monobond N, Group P: Panavia V5/Clearfil Ceramic Primer Plus, Group D: Duo-Link universal/Z-Prime Plus. The intaglio surfaces of crowns were air-abraded using 50 µm alumina at 2.5 bar for 10 s. Then each crown was cemented onto its corresponding tooth. All specimens were thermocycled for 10,000 cycles between 5 and 55 °C. Each crown was subjected to gradually increasing vertical load along the path of insertion through hooks engaging the occlusal bar using a universal testing machine until failure. The force at dislodgment was recorded and retention strength was calculated for each specimen. The failure modes were recorded for each specimen. The data were statistically analyzed using one way ANOVA test followed by Tukey HSD test (α = .05).

RESULTS

Group D showed lowest strength (1.42 ± 0.23 MPa) and differed significantly (P < .001) from Group M (2.71 ± 0.45 MPa) and Group P (2.47 ± 0.41 MPa). There was no significant difference (P = .34) between Group M and Group P. The failure modes for Groups M and Group P were mainly cohesive, while Group D showed adhesive failure.

CONCLUSIONS

The retention strength of zirconia crowns was improved with Multilink Speed and Panavia V5 cement systems, while the use of the Duo-Link Universal cement system only showed half of those retention strength values.

Evaluation of the Water Sorption and Solubility Behavior of Different Polymeric Luting Materials

Objective: The study evaluated the water sorption (WSP) and water solubility (WSL) characteristics of different luting agents over a 180-day water storage period. Materials and Methods: Nine luting materials, i.e., conventional resin cement: Panavia F (PF), Rely X ARC (RA), self-adhesive resin cement: Rely X Unicem (RU), Breez (BZ), Maxcem Elite (MX), BisCem (BC) and resin-modified glass ionomer cement: FujiCem (FC), FujiPlus (FP) Rely X luting plus (RL) were assessed and fifty-two-disc specimens of each material were fabricated. All specimens were desiccated until a constant weight (W0) was reached. Thirteen specimens for each luting material were then randomly assigned to one of the four water immersion periods (7, 30, 90, and 180 days). After each period, the specimens were removed from the water and weighed to get W1. The samples were again desiccated for a second time and W₂ was measured. Both WSP and WSL were determined by the following equations: WSP (%) = (W₁ − W₂) × 100/W₀ and WSL (%) = (W₀ − W₂) × 100/W₀. Assessments were performed following ISO standards. ANOVA was used to assess the effect of luting agent and time period on water sorption and solubility. Pair-wise comparisons were adjusted using Tukey’s multiple comparison procedure. A significance level of 0.05 was used for all statistical tests. Results: The highest mean WSP and WSL (WSP/WSL) were demonstrated by resin-modified glass-ionomers (RL 18.32/3.25, FC 17.08/4.83, and FP 14.14/1.99), while resin luting agents showed lower WSP and WSL results (PF 1.6/0.67 and RA 1.76/0.46), respectively. The self-adhesive agents exhibited a wide range of WSP and WSL values (RU 1.86/0.13, BZ 4.66/0.93, and MX 3.68/1.11). Self-adhesive cement showed lower WSP and WSL compared with the resin-modified glass-ionomers (p < 0.05). All the materials reached equilibrium after 90-days. Conclusions: Resin-based luting materials have the lowest sorption and solubility. Rely X Unicem self-adhesive luting materials were comparable to resin luting materials for WSL and WSP. Resin-modified glass-ionomer showed the highest water sorption and solubility compared with both resin and self-adhesive materials.

Changes of residual stresses on the surface of leucite-reinforced ceramic restoration luted with resin composite cements during aging in water

The objective of this study was to compare the changes in the residual stresses present on the surface of leucite-reinforced dental ceramic restorations luted with a self-adhesive and a conventional resin composite cement during aging in water. Ring specimens made of a leucite-reinforced ceramics were luted to ceramic cylinders using a self-adhesive (Panavia SA Luting Plus) or a conventional resin composite cement (Panavia V5) in dual-cure or self-cure mode. Residual stresses on the ring surface were measured using indentation fracture method at 1 h, 1, 3, 7, 14 and 28 days of the 37 °C water immersion. Water sorption, water solubility and elastic modulus of the cements were also measured. Compressive stress was generated on the surface of the ceramic rings by the polymerization of the resin composite cements, and the stresses appeared to decrease over time by water sorption of the cements. The dual-cured conventional resin composite cement remained compressive stresses on the ceramic surface, while only the self-cured self-adhesive cement, which demonstrated the greatest water sorption, generated tensile stresses during the four weeks of aging in water. The elastic moduli of cements did not significantly change through the immersion, suggesting that the stresses were less affected by the modulus. To prevent the generation of tensile stresses on the leucite-reinforced ceramic restoration, self-adhesive cements exhibiting small water sorption should be clinically selected.

Investigation of water sorption and aluminum releases from high viscosity and resin modified glass ionomer

Background

High viscosity glass ionomer cement (HVGIC) and resin-modified glass ionomer cement (RMGIC) have recently been clinically preferred thanks to their numerous advantages. However, initial moisture contamination has a negative effect on the mechanical and physical properties of these cements. The aim of this study was in vitro of HVGICs and RMGICs, with and without surface protection, on water sorption, solubility and release of aluminum.

Material and Methods

In this study, as HVGICs; Equia Forte, IonoStar Plus, Riva Self Cure; as RMCIS, Ionolux and Riva Light Cure; and as control, Z250 universal composite was used. Equia coat, Voco varnish and Riva coat were chosen as surface protective. Water sorption and solubility levels of the samples were measured according to ISO 4049:2009. Al levels released from samples were determined by graphite furnace atomic absorption spectroscopy (GFAAS) for 7, 14 and 21 days. Statistical evaluation of the results was made using one-way variance analysis (ANOVA) and Tukey post-hoc test (p<0.05).

Results

RMGICs from restorative materials showed more water absorption than HVGICs, but no differences in solubility. Among the materials tested, the water absorption values of the HVGIC and RMGIC materials without surface protection were higher than those with the surface protection (p<0.001).

Conclusions

It was determined that the Al release of HVGIC and RMGIC groups with the surface protection were lower in all time periods than the groups without surface protection (p<0.001). The application of surface protection effectively reduced water sorption and Al release from HVGICs and RMGICs.

Key words:Highly viscous glass ionomer cement, resin coating, aluminum release, water sorption, solubility.

CAD/CAM-fabricated inlay restorations: Can the resin-coating technique improve bond strength and internal adaptation?

This study assessed the effect of the resin-coating technique on the bond strength and internal adaptation of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated inlays. Seventy-two mesio-occlusal-distal (MOD) cavities were prepared and distributed into 3 groups according to the resin-coating technique utilized: uncoated group, G-Premio Bond (1-step) group, and Clearfil SE Bond 2+Clearfil Majesty ES Flow (2-step+Flow) group. The MOD inlays were fabricated and cemented with RelyX Ultimate (RXU), G-CEM LinkForce (LinkForce), or Panavia V5 (PV5). After 5,000 thermal cycles, each specimen was sectioned and subjected to microtensile bond strength (MTBS) testing and an internal adaptation evaluation. For the uncoated group, RXU exhibited higher MTBS than LinkForce and PV5 (p<0.05). The MTBS of all 1-step and 2-step+Flow groups was greater than 30 MPa. Resin coating did not influence the MTBS of RXU, whereas resin coating increased the MTBS of LinkForce and PV5. More than 95% gap-free margins were found in all groups.

Comparison of the Effect of Proanthocyanidin Surface Treatments on Shear Bond Strength of Different Cements

This study aimed to compare the effect of proanthocyanidin-rich grape seed extract (Pa-rich GSE) in two different concentrations on the bond strength to dentin tissue for four different cement groups (resin cement (P), resin modified glass ionomer cement (K), calcium aluminate glass ionomer cement (C), glass ionomer cement (G)). One hundred and eighty dentin surfaces of the extracted molar teeth placed on acrylic cylinders were divided into 12 groups randomly (n = 15). Each cement group was further divided into control (CP, CC, CK, CG), 6.5% Pa-rich GSE (P6.5, C6.5, K6.5, G6.5) and 12.5% Pa-rich GSE (P12.5, C12.5, K12.5, G12.5) subgroups. In accordance with the manufacturer’s recommendations the cements were applied. After shear bond tests, surfaces were examined under a stereomicroscope. Median shear bond strength (in MPa) of CP, CK, CC, CG groups were 14.13, 7.05, 4.87, 3.86; for the P6.5, G6.5, C6.5, K6.5 groups they were 13.98, 13.42, 6.21, 3.27; and for the P12.5, C12.5, K12.5, G12.5 groups they were 15.08, 5.40, 3.10, 0.00, respectively. CK and K6.5 groups showed a significant difference from the K12.5 group (p < 0.05). Also, CG, G6.5 and G12.5 groups were found statistically different from each other (p < 0.05). Applied to the dentin surface, 6.5% Pa-rich GSE enhanced the bond strength of glass ionomer cements.

Evaluation of Fracture Resistance and Microleakage of Endocrowns with Different Intracoronal Depths and Restorative Materials Luted with Various Resin Cements

The aim of this study was to determine the effect of restoration design on the fracture resistance of different computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics and investigate the marginal leakage of endocrowns according to different types of cement. In total, 96 extracted mandibular first premolars were used for fabrication of endocrowns; 48 of the endocrowns were divided into 6 groups (n = 8) according to intracoronal cavity depth (2 and 3 mm) and CAD/CAM ceramics (lithium disilicate IPS e.max-CAD, zirconia-reinforced glass-ceramic Vita Suprinity, and poly-ether-ether-ketone (PEEK)). Teeth were subjected to a fracture resistance test with a universal test machine following thermo-cycling. Failure modes were determined by stereomicroscope after the load test. The rest of the endocrowns (n = 48) were produced by Vita Suprinity ceramic and divided into 6 groups (n = 8) according to the cement used (Panavia V5, Relyx Ultimate, and GC cement) with intracoronal cavity depths of 2 and 3 mm. Microleakage tests were performed using methylene blue with stereomicroscope after thermo-cycling. Numerical data for both fracture resistance and microleakage tests were obtained and evaluated by three-way ANOVA. PEEK endocrowns had higher fracture resistance compared to lithium disilicate and Vita Suprinity. Panavia V5 cement had the lowest degree of microleakage, while GC cement had the highest. Different intracoronal cavity depths had no correlation with fracture resistance and microleakage.

Surface morphology and mechanical properties of conventional and self-adhesive resin cements after aqueous aging

The stable long-term performance of resin cement under oral environmental conditions is a crucial factor to obtain a satisfactory success of the allceramic dental restoration. Objective: This study aimed at evaluating and comparing the surface morphology and mechanical property of conventional and self-adhesive resin cement after aqueous aging. Materials and Methods: Disc-shaped specimens of 3 conventional (C1: Multilink N, C2: Duolink, C3: Nexus 3) and 3 self-adhesive (S1: Multilink Speed, S2: Biscem, S3: Maxcem) types of resin cements were subjected to irradiation. After 24 h, the Knoop microhardness of each resin cement was evaluated. The specimens were immersed separately in distilled water and maintained at 37°C. A total of 5 specimens of each resin cement were collected at the following time intervals of immersion: 1, 6, 12 and 18 months. The samples were used to evaluate the Knoop parameters of microhardness, sorption and solubility. The surface morphology of the specimens after 18 months of immersion was observed by scanning electron microscopy. The sorption and solubility data were analyzed by two-way ANOVA. The Knoop microhardness was tested by the ANOVA repeated measures (P<0.05). Results: The sorption and solubility parameters of C1 and S1 exhibited significant fluctuations during the aqueous aging. The hardness of the S1 and S2 specimens decreased significantly after an 18-month water immersion. The S1, S2 and S3 specimens indicated higher filler exposure and stripping and apparent pores and cracks compared to specimens C1, C2 and C3, respectively. Conclusion: The surface of selfadhesive resin cements is more susceptible to aqueous damage than that of the conventional resin cements.

Contraction and Hydroscopic Expansion Stress of Dental Ion-Releasing Polymeric Materials

Ion-releasing polymeric restorative materials seem to be promising solutions, due to their possible anticaries effect. However, acid functional groups (monomers) and glass filler increase hydrophilicity and, supposedly, water sorption. The purpose of the study was to evaluate the influence of water sorption of polymeric materials on the stress state at the restoration-tooth interface. Beautifil Bulk Fill Flow, Beautifil Flow Plus F00, Beautifil Flow F02, Dyract eXtra, Compoglass Flow, Ionosit, Glasiosite, TwinkiStar, Ionolux and Fuji II LC were used for the study. The stress state was measured using photoelastic analysis after: 0.5, 24, 72, 96, 168, 240, 336, 504, 672, 1344 and 2016 h. Moreover, water sorption, solubility and absorption dynamic were assessed. The water sorption, solubility and absorption dynamic of ion-releasing restorative materials are material dependent properties. The overall results indicated that the tested restorative materials showed significant stress decrease. The total reduction in contraction stress and water expansion stress was not observed for materials with low value of water sorption (Beautifil Bulk Fill, Dyract eXtra, Glasionosit and Twinky Star). The photoelastic method turned out to be inadequate to evaluate stress changes of resin modified glass-ionomer cement (RMGI, Fuji II LC and Ionolux).

Dental Resin Cements-The Influence of Water Sorption on Contraction Stress Changes and Hydroscopic Expansion

Resin matrix dental materials undergo contraction and expansion changes due to polymerization and water absorption. Both phenomena deform resin-dentin bonding and influence the stress state in restored tooth structure in two opposite directions. The study tested three composite resin cements (Cement-It, NX3, Variolink Esthetic DC), three adhesive resin cements (Estecem, Multilink Automix, Panavia 2.0), and seven self-adhesive resin cements (Breeze, Calibra Universal, MaxCem Elite Chroma, Panavia SA Cement Plus, RelyX U200, SmartCem 2, and SpeedCEM Plus). The stress generated at the restoration-tooth interface during water immersion was evaluated. The shrinkage stress was measured immediately after curing and after 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Water sorption and solubility were also studied. All tested materials during polymerization generated shrinkage stress ranging from 4.8 MPa up to 15.1 MPa. The decrease in shrinkage strain (not less than 57%) was observed after water storage (56 days). Self-adhesive cements, i.e., MaxCem Elite Chroma, SpeedCem Plus, Panavia SA Plus, and Breeze exhibited high values of water expansion stress (from 0 up to almost 7 MPa). Among other tested materials only composite resin cement Cement It and adhesive resin cement Panavia 2.0 showed water expansion stress (1.6 and 4.8, respectively). The changes in stress value (decrease in contraction stress or built up of hydroscopic expansion) in time were material-dependent.

Effect of aging and curing mode on the compressive and indirect tensile strength of resin composite cements

BACKGROUND

Resin composite cements are used in dentistry to bond ceramic restorations to the tooth structure. In the oral cavity these cements are subjected to aging induced by masticatory and thermal stresses. Thermal cycling between 5 and 55 °C simulates the effect of varying temperatures in vitro. Purpose of this study was to compare indirect tensile to compressive strength of different cements before and after thermal cycling. The effect of the curing mode was additionally assessed.

METHODS

Indirect tensile strength and compressive strength of 7 dual-curing resin composite cements (Multilink Automix, Multilink SpeedCem, RelyX Ultimate, RelyX Unicem 2 Automix, Panavia V5, Panavia SA Plus, Harvard Implant semi-permanent) was measured. The specimens were either autopolymerized or light-cured (n = 10). The mechanical properties were assessed after 24 h water storage at 37 °C and after aging (20,000 thermo cycles) with previous 24 h water storage at 37 °C.

RESULTS

Indirect tensile strength ranged from 5.2 ± 0.8 to 55.3 ± 4.2 MPa, compressive strength from 35.8 ± 1.8 MPa to 343.8 ± 19.6 MPa.

CONCLUSIONS

Thermocyclic aging of 20,000 cycles can be considered a suitable method to simulate the degradation of indirect tensile strength but not compressive strength of resin composite cements. The effect of thermocycling and the curing mode on the resin composite cements is material dependent and cannot be generalized.