The effect of desiccation on water sorption, solubility and hygroscopic volumetric expansion of dentine replacement materials

In vitro evaluation of the enhancement of glass ionomer cement features by using chitosan and nanodiamond

This study investigated the influence of chitosan and nanodiamond incorporation on the surface, optical, and mechanical properties of glass ionomer cement. Total 56 samples (5 mm diameter and 2 mm thickness) were prepared and divided into 4 groups according to the incorporation of chitosan and nanodiamond on Fuji II glass ionomer cement: Control group: no incorporation; 10%CH group: incorporation of 10% chitosan; 10%ND group: incorporation of 10% of nanodiamond; 5%CH-5%ND group: incorporation of 5% chitosan and 5% nanodiamond (n=14). Analyses of color stability, surface roughness, fluorescence intensity, microhardness, morphology, and chemical composition were investigated. Additionally, water sorption, hygroscopic expansion, contact angle, surface free energy, and total free energy of interaction were also assessed. After the initial readings, the samples were individually stored in red wine solution for 28 days. Data were subjected to ANOVA followed by Tukey´s test (α=.05). Aging in wine solution altered the optical, mechanical, and surface properties of glass ionomer cement regardless of the incorporation of the compound (P<.05). 10% chitosan-incorporated glass ionomer cement promoted higher color alteration, surface roughness, and water sorption after aging (P<.05). 10% nanodiamond-incorporated glass ionomer cement showed higher microhardness compared to the other groups before aging (P<.05), however there were no differences among them after aging (P>.05). In general, no differences between the 5% chitosan- and 5% nanodiamond-incorporated glass ionomer cement and control groups were noted on the evaluated analyses (P>.05). Thus, the incorporation of 5% chitosan and 5% nanodiamond is a satisfactory alternative for maintain the surface, optical, and mechanical properties of the glass ionomer cement.

Comparison of three dentine replacement materials in terms of different characteristics

This in vitro study evaluated three dentine replacement materials: Biodentine, Ketac Molar and TheraBaseCa. Specimens of each material (n = 19) were prepared for investigations of hardness, calcium release, pH and water sorption-solubility. SEM and EDX analysis were also used for these investigations. One-way ANOVA and robust ANOVA tests were used for normally and non-normally distributed data for statistical analysis, respectively. TheraBaseCa showed the lowest hardness (p < 0.001), while Biodentine had the highest pH and calcium release (p < 0.001). Significant differences in water sorption-solubility were observed as Biodentine>Ketac Molar>TheraBaseCa (p < 0.001). SEM and EDX revealed that Biodentine had a crystalline structure with O, Ca, C, Si and Bi; Ketac Molar had a particulate matrix with O, C, F, Ca, Si and Al; and TheraBaseCa had a matrix with C, O, Si, Yb, Al and Ca. In conclusion, Biodentine was more alkaline and released more calcium, while TheraBaseCa had the lowest water sorption-solubility over 28 days.

Improving the Mechanical Properties of Glass Ionomer Cement With Nanocrystalline Cellulose From Rice Husk

This study aimed to evaluate the effect of incorporating nanocrystalline cellulose (NCC) sourced from rice husk on the mechanical properties of a commercial glass ionomer cement (GIC). NCC was isolated through acid hydrolysis, and its crystallinity, chemical structure, and morphology were characterized through x-ray diffractometry, Fourier-transform infrared spectroscopy, and transmission electron microscopy, respectively. Various concentrations of NCC (0%, 0.5%, 1%, and 1.5%) were added to reinforce the GIC matrix. Mechanical tests including compressive strength, flexural strength, hardness, and shear bond strength were conducted on the modified GIC samples. The addition of NCC resulted in increased hardness and shear bond strength values, with 1% NCC showing the highest values compared to other concentrations. However, there was no significant improvement observed in the compressive and flexural strength of the modified GIC. Failure mode test revealed a reduction in adhesive failure with the addition of NCC. Incorporating small amounts of NCC (0.5%-1%) suggests a promising and affordable modification of GIC restorative material using biomass residue, resulting in improved mechanical properties.

The influence of hygroscopic expansion of resin supporting dies on the fracture resistance of ceramic restorations during thermal cycling

OBJECTIVES

To evaluate the hygroscopic expansion characterization of resin composite dies during thermal cycling, and their influence on the fracture resistance of dental ceramic materials as well as the effect of pre-immersion on these measurements.

METHODS

Disc-shaped specimens (φ = 15.0 mm, h = 1.2 mm) and anatomical crown dies of four resin composites (epoxy, Z350, P60, G10) were fabricated. Disc-shaped samples were continuously soaked in distilled water and the volume expansion was measured at different time point by Archimedes method. Disc-shaped samples were pre-immersed for 0, 7, or 30 days, elastic modulus and hardness were measured using Nanoindentation test; thermal cycling (TC) test was performed (5 °C-55 °C, 104 cycles), and volume expansion during TC was measured. Four kinds of resin die with pre-immersion for 0, 7, or 30 days were cemented to 5Y-Z crown, or epoxy dies without pre-immersion were cemented to 5Y-Z, 3Y-Z and lithium disilicate glass (LDG) crowns, and load-to-failure testing was performed before and after TC. Finite element analysis (FEA) and fractography analysis were also conducted.

RESULTS

The hygroscopic expansion was in the order: epoxy > Z350 > P60 > G10. Except for G10, the other three resin composites exhibited different degrees of hygroscopic expansion during TC. Only the elastic modulus and hardness of epoxy decreased after water storage. However, only the fracture loads of 5Y-Z and LDG crowns supported by epoxy dies were significantly decreased after TC. FEA showed a stress concentration at the cervical region of the crown after volume expansion of the die, leading to the increase of the peak stress at the crown during loading.

SIGNIFICANCE

Only the hygroscopic expansion of epoxy dies caused by TC led to the decrease in the fracture resistance of the 5Y-Z and LDG crown, which may be related to the decrease in the elastic modulus of the epoxy die and the tensile stress caused by it.

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.

Biaxial flexural strength of hydrothermally aged resin-based materials

PURPOSE

The strength of temporary restorations plays a vital role in full-mouth reconstruction, and it can be impacted by the aging process. The aim of this in vitro study was to evaluate the biaxial flexural strength and fractographic features of different resin-based materials submitted to thermal aging.

MATERIAL AND METHODS

One hundred and ninety-two resin disc-shaped specimens (6.5 mm in diameter and 0.5 mm in thickness) were fabricated and divided into six experimental groups according to the resin-based materials (Filtek Bulk-Fill flowable resin; J-Temp temporary resin; and Fuji Lining glass ionomer cement) and aging process (before and after thermal cycling). Biaxial flexural strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min before and after thermal cycling (5 °C and 55 °C, 5760 cycles, 30 s). The mechanical properties were assessed using Weibull parameters (characteristic strength and Weibull modulus) (n = 30). Fractured specimens were examined under a polarized light stereomicroscope to identify crack origin and propagation direction. The surface microstructure of the resin-based materials was assessed by scanning electron microscopy (n = 2). The Weibull modulus (m), characteristic strength, and reliability properties were calculated, and a contour plot was used to detect differences among groups (95% confidence interval).

RESULTS

The Weibull modulus (m), characteristic strength, and reliability of the resin-based compounds were influenced by material type and thermal aging (p < 0.05). Weibull modulus (m) revealed no differences when comparing the materials and aging process (p > 0.05), except for the preceding aging period where Filtek Bulk-Fill exhibited higher values compared to J-Temp (p < 0.05). Filtek Bulk-Fill demonstrated superior characteristic strength and reliability compared to J-Temp and Fuji Lining before and after thermal cycling (p < 0.05). Fractography of the resin-based materials showed fractures originating from surface defects exposed to tensile side and their propagation toward the compressive side. Generally, no differences in surface microstructure were observed on micrographs before and after thermal aging for Filtek Bulk-Fill and Fuji Lining. However, the aging process developed flaws in J-Temp.

CONCLUSION

Resin-based material composition resulted in different flexural strength performance, impacting the Weibull modulus (m), characteristic strength, and reliability of the resin-based restorations.

A critical review of the material properties guiding the clinician's choice of root canal sealers

OBJECTIVES

The introduction of hydraulic cement sealers has increased the popularity of single cone obturation where the chemistry and properties of hydraulic cement sealers are crucial. This article has investigated the materials present on the market by reviewing the chemistry aiming at understanding whether these materials are optimized or have been tested appropriately.

METHODOLOGY

A market search on materials called bioceramic and hydraulic sealers was undertaken. The safety data sheet and manufacturer details for every material were searched and the components were checked. The literature was searched for information about the properties of these materials based on their composition.

RESULTS

The safety data sheets and manufacturer details were imprecise with some manufacturers providing little detail on composition. From the publications reviewed, it is apparent that the materials used clinically are not optimized, and there is little evidence that the material chemistry and presentation aid the clinical technique in any way.

CONCLUSIONS

There has been a rapid increase in materials identifying as bioceramics on the market. These materials have diverse chemistries, and some of the constituents are not declared. This may affect the clinical performance of these materials.

CLINICAL SIGNIFICANCE

Smart materials developed on the clinical need which are appropriately tested are necessary for a paradigm shift in root canal obturation. It is important to use reputable materials that have been adequately researched in clinical practice.

Resin-modified glass ionomer enriched with BIOGLASS: Ion-release, bioactivity and antibacterial effect

Developing dental materials for the prevention of remineralization or demineralization is important for high-risk caries patients. This study aimed to evaluate the physicochemical and microbiological effects of adding 45S5 bioglass to resin-modified glass ionomer cement (RMGIC). Samples belonged to the following groups: GIC: conventional glass ionomer cement (Vitro Fil), RMGIC: resin-modified GIC (Vitro Fil LC), and RMGIC/45S5: RMGIC with 10% (wt %) of 45S5. Changes in pH and release of fluoride, calcium, and phosphorus ions under acidic (pH 4) and neutral (pH 7) pH conditions were evaluated. Antibacterial activity was verified based on colony-forming units. Material sorption and solubility were analyzed after bacterial exposure. After 28 days, the bioactivity of the materials was evaluated using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis of variance, post hoc Scheffe, and Tukey (α = 0.05) tests were employed for statistical analysis. RMGIC/45S5 showed higher alkalization activity, calcium release at pH 4 and 7, and sorption than GIC and RMGIC (p < .05). Release of phosphorus and fluoride at pH 4 and 7 was higher for GIC than that for RMGIC and RMGIC/45S5 (p < .05). RMGIC/45S5 showed higher values than RMGIC (p < .05). However, antibacterial activity did not differ among the groups. Precipitates of calcium and phosphorus were visualized in RMGIC/45S5 samples via SEM/EDS. These results indicate that the RMGIC/45S5 promotes alkalization and increases the release of calcium, phosphorus, and fluoride ions, resulting in precipitate deposition rich in calcium and phosphorus, thereby being a promising option to improve the bioactivity of RMGIC.

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.

Methods for testing solubility of hydraulic calcium silicate cements for root-end filling

Regulatory testing of hydraulic cements used in dentistry and standard test methods for root-end filling materials do not exist. The aim of this study was to identify a simple, reproducible method for testing the solubility of materials that set with water (hydraulic) used as root-end filling materials in dentistry. Commercial and prototype hydraulic cements were characterized by scanning electron microscopy and X-ray diffraction analyses and their solubilities were determined using ISO 6876; 2012 standard, a modified ISO 6876 method with media alternative to water and a new method measuring the percentage mass loss and volume change of materials (micro-CT method) from a single surface exposed to three solutions. The solubility testing was performed by three operators to enable an intra-laboratory comparison. The solubility data obtained from the two commercial and two prototype materials varied depending on the method used, with the ISO 6876 method identifying differences in solubility of the materials (p < 0.05) but when modified with alternative solutions, no differences were found (p > 0.05). The changes in solution thus effected the solubility of the tested materials. Inter-operator differences were observed with the weight changes determined from the new method indicating this method was not robust. The weight and volume assessments using the new method were not solution-dependent. The advantage of the proposed method compared with the ISO standard is its simplicity, enabling a number of tests to be performed on the same set of samples that also more closely mimics the clinical environment.

Effect of Different Dimensions of Test Samples on the Volumetric Change Assessment Of Endodontic Materials

New methodologies using micro-CT to evaluate solubility besides dimensional and morphological changes of endodontic materials are proposed. However, there is no standardization in the methods. The aim of this study was to assess the effect of different dimensions of test samples on volumetric change evaluation of different endodontic materials. AH Plus, FillCanal and Sealapex root canal sealers, Biodentine, IRM and MTA root-end filling cements were used in the tests. Samples of each material with a thickness of 1.5 mm and different diameters were manufactured: 6.3, 7.75, and 9.0 mm. The samples were scanned in micro-computed tomography (micro-CT) after setting and after 7 days of immersion in distilled water. The volumetric change was evaluated by means of the difference in the total volume of the specimens before and after immersion. Data were submitted to ANOVA and Tukey tests (p<0.05). The size of the samples did not affect the percentage of volumetric change of the materials (p>0.05). All sample sizes had greater volume loss for Sealapex among the sealers and Biodentine for the cements (p<0.05). In conclusion, Biodentine and Sealapex had the highest volume loss after immersion. Samples with 1.5 mm thickness, and diameters ranging between 6.3 and 9.0 mm can be used to assess the stability of endodontic materials using micro-CT without affecting the percentage of volumetric change.

The effect of dentin age on the microshear bond strength and microleakage of glass-ionomer cements

OBJECTIVE

To compare the microshear bond strength (µSBS) and microleakage of glass-ionomer cements when bonded to aged and young dentin.

BACKGROUND

Glass-ionomer cement (GIC) is frequently used to restore root caries in elders. Many studies of GIC have been conducted using young dentin; however, few studies have assessed adhesion and microleakage of GICs to aged dentin.

MATERIALS AND METHODS

Seventy-eight non-carious human molars (patient age 16-30 = 39; patient age ≥ 65 = 39) were tested with three GICs (Fuji II LC, Equia Forte Fil and Fuji BULK). For µSBS, teeth were horizontally sectioned, embedded in resin and three tubes attached to the sectioned surface. Materials were mixed and injected into the tubes, allowed to set and the tubes removed leaving the GIC cylinders. Specimens were stored in deionised water for 24 hours and tested in a universal testing machine. For microleakage, a buccocervical cavity was prepared, restored with GIC and stored in deionised water. The specimens were polished, coated with varnish, placed in 0.5% basic fuchsin for 24 hours, sectioned at the midpoint and evaluated for microleakage under a stereomicroscope and scanning electron microscope.

RESULTS

For µSBS, Fuji II LC showed the highest bond strength among three products. There was no significant difference between age groups. (P = .93) For microleakage, Fuji II LC had more dye penetration (P < .01) and there was significant difference between age groups.

CONCLUSION

After bonding of GICs, aged dentin showed no difference in µSBS but less microleakage when compared to young dentin.

Commercially Available Fluoride-Releasing Restorative Materials: A Review and a Proposal for Classification

Resin composite and glass ionomer cement (GIC) are the most commonly used dental materials to perform direct restorations. Both have specific characteristics that explain their popularity and their limits. More than 20 years ago, the first attempt (followed by others) to combine the advantages of these two families was performed with compomers, but it was not very successful. Recently, new formulations (also called 'smart materials') with claimed ion release properties have been proposed under different family names, but there are few studies on them and explanations of their chemistries. This comprehensive review aims to gather the compositions; the setting reactions; the mechanical, self-adhesive, and potential bulk-fill properties; and the ion release abilities of the large existing families of fluoride-releasing restorative materials and the new restorative materials to precisely describe their characteristics, their eventual bioactivities, and classify them for an improved understanding of these materials. Based on this work, the whole GIC family, including resin-modified and highly viscous formulations, was found to be bioactive. Cention N (Ivoclar Vivadent, AG, Schaan, Lietschentein) is the first commercially available bioactive resin composite.

Comparison of the Water Sorption and Solubility of Four Reline Acrylic Resins after Immersion in Food-Simulating Agents

Objectives

Water sorption and water solubility adversely affect the mechanical properties and biocompatibility of the denture material. This study aimed to evaluate the water sorption and solubility of three direct hard reline acrylic resins and a heat-curing one after immersion in food-simulating agents.

Materials and Methods

This study was performed on four groups of samples (n = 10 per group). The samples were made of three direct hard reline acrylic resins (TDV Cold Liner Rebase, Tokuyama Rebase II Fast, GC Reline Hard) and a heat-curing one (Meliodent). Each group was divided into four subgroups (n = 10) to undergo 7-day immersion in distilled water, 75% ethanol/water, 0.02 N citric acid, and heptane. Water sorption and solubility were calculated according to Oysaed and Ruyter formula. The statistical analyses were done by using SPSS software (version 22). Kruskal-Wallis H Test and Dunn's test were used to detect any significant difference among the groups (P < 0.05).

Results

The median range of water solubility and water sorption values were -0.87-4.92 and 3.75-27.25 μg/mm³, respectively. The median solubility and sorption values of different resins differed significantly in the same solution (P < 0.05). Besides, immersion in different solutions caused significant differences in the median solubility and sorption values of each reline material (P < 0.05), except for Meliodent whose solubility was not significantly affected by different solutions (P = 0.16).

Conclusions

Water sorption and solubility values of the tested hard reline resins were within the range of International Standards Organization 1567:1999. Given the low sorption and solubility values, these hard reline materials can be safely used in clinical situations.

Avaliação da solubilidade e sorção em água de alguns materiais restauradores diretos

Resumo Introdução A solubilidade e sorção dos materiais restauradores são considerados fatores críticos, pois podem interferir na qualidade e durabilidade das restaurações. Objetivo Avaliar a solubilidade e sorção de água de alguns materiais restauradores. Material e método Foram confeccionados quatorze espécimes de cada um dos seguintes materiais: Equia® Forte, Z100, Fuji IX/ e Vidrion R, os quais foram levados a uma dessecadora e pesados diariamente até estabilização. Em seguida, foram inseridos em recipientes individuais contendo 40 mL de água destilada cada e divididos em dois grupos de acordo com o tempo de armazenagem: 7 ou 30 dias. Ao final de cada período, os espécimes foram retirados da água, pesados, levados à dessecadora e pesados novamente até estabilização. Os resultados foram analisados estatisticamente utilizando os testes ANOVA 2 critérios e Tukey. Resultado Com exceção do Equia® Forte e Z100, os demais materiais, apresentaram uma variação significativa da solubilidade ao longo do tempo. Quanto à sorção, observa-se que apenas o material Z100 não apresentou diferença significativa em relação ao tempo de armazenagem, mas, na comparação entre os materiais, todos apresentaram diferenças significativas em ambos os períodos. Conclusão Após os períodos de armazenagem de 7 e 30 dias em água, os materiais restauradores Equia® Forte e Z100 não apresentam variação significativa da solubilidade, sendo mais estáveis que os materiais Fuji IX e Vidrion R. Os materiais à base de ionômero de vidro, Equia® Forte, Fuji IX e Vidrion R, sofrem mais sorção em água quando comparados ao material Z100 em ambos os períodos.

The Chemical and Morphological Study of Calcium Silicate-Based Material (Biodentine®) and Glass Ionomer Cement (GIC®)

Background:

Attention was paid to the chemical properties of bioactive materials, and the reaction that could occur on their surface.

Objective:

The evaluation of the chemical properties includes the solubility, water sorption, pH changes and calcium release of two dental materials (BD and GIC). In addition, the morphological structure of each material was studied after its immersion in two different solutions,i.e.deionized water and phosphate solution.

Methods:

The chemical study was carried out for two sets of samples; 28 samples of each material. Samples were immersed in 10 mL of deionized water and stored at 37 °C for different times. The morphological structure and elemental analysis of BD and GIC samples were studied after immersion in the two solutions for 1, 7, 14 and 28 days.

Results:

Solubility of BD increased with time reaching a maximum value after 60 days (13.63 ± 2.08%). The solubility of GIC was negatively correlated with time, with a maximum value of 4.11 ± 0.47% for 3 h. The released Ca+2ions varied between 1.0 ± 0.3 mg (3 h) and 5.3 ± 0.8 mg (60 days) for BD. However, calcium was not detected in the GIC samples. The formation of calcium hydroxy-fluorapatites and strontium-fluoro-alumino-silicate, on the surface of BD and GIC, respectively, was clarified for the first time in this study.

Conclusion:

A comparative study was carried out revealing the difference in the chemical properties and the morphological structure between the two studied materials. The results confirmed the biointeractivity and the bioactivity of BD and GIC.