Contemporary restorative ion-releasing materials: current status, interfacial properties and operative approaches

Orifice barrier preferences for coronal restoration of root filled teeth by endodontists and other dental practitioners in Australia: A questionnaire survey

OBJECTIVES

To compare the use of orifice barriers (OB) in root-filled teeth (RFT) between specialist endodontic practitioners (SEP) and general and other specialist practitioners (GDP+), and identify common materials, reasons for selection, and techniques.

METHODS

An online survey was distributed to SEP and GDP+ practising in Australia. Demographic and multiple-choice questions relating to material selection and technique choices were asked to evaluate and relate usage patterns to practising and training backgrounds. Fisher's exact tests were undertaken to compare categorical variables across practitioner groups. Significance level was set at p<.05.

RESULTS

There were 457 eligible responses: 393(86%) GDP+ and 64(14%) SEP. Of 429 reporting endodontically treating or restoring teeth, 317(73.9%) placed OB; preferred depth of root filling removal by most (91.8%) was ≤ 2 mm, with more SEP preferring 2 mm than GDP+(p=.02). Preferred materials for OB were conventional and resin-modified GIC (GIC), resin composite materials (RC), Cavit™ and zinc polycarboxylate cement (ZPC). 'Ease of use' was a common reason among all practitioners for GIC and RC. Significantly more SEP(p<.001) chose ZPC in all teeth and more commonly because of 'Ease of use' for both posterior (p<.001) and anterior (p=.002) teeth. All ZPC-using SEP preferred using a paste-filler/lentulo spiral, significantly more than GDP+ for posterior (p<.001) and anterior (p=.002) teeth. Cavit™ was often chosen for 'Sealing ability'.

CONCLUSIONS

OB were widely placed by dental practitioners in Australia, with a small group of materials selected, most commonly for ease of use or sealing ability. The findings of this study suggest that further research should be undertaken to investigate the relative performance of these materials as OB and to inform the clinician's choices when restoring RFT.

Comparative measurement of short-term fluoride release and inhibition of caries around restoration by ion releasing restorative materials: an in vitro study

The main objective of the current study is to compare short-term fluoride release of three ion releasing restorative materials and assess their inhibitory effect on secondary caries. Materials used in this study included, Self-adhesive hybrid composite (group A), Ion releasing flowable composite liner (group B), and alkasite restorative material (group C). Twenty-two discs were fabricated from each material for short-term fluoride release test, conducted on days 1, 7, and 14. For assessing secondary caries inhibition, sixty-six sound molar teeth were used and standardized class V cavities were prepared. Teeth were divided into three groups according to each material, followed by 800 cycles of thermocycling. Subsequently, teeth were immersed in a solution containing cariogenic bacteria for 30 days. After that, teeth were sectioned bucco-lingually and analyzed using a polarized light microscope to measure inhibition area, outer lesion depth, and extension. Data was statistically analyzed using different tests. The study results revealed a statistically significant differences in fluoride release existed among materials. Self-adhesive hybrid composite exhibited the highest fluoride release. Lesion extension and depth were statistically significantly greater next to Ion-releasing flowable composite liner. The inhibition areas next to the Self-adhesive hybrid composite were statistically significantly larger than the other two materials. In conclusion, all tested ion-releasing restorative materials displayed fluoride release and the potential to inhibit secondary caries formation. Self-adhesive hybrid composite demonstrated the highest fluoride-releasing potential and the greatest ability to inhibit secondary caries. Conversely, Ion-releasing flowable composite liner exhibited the least fluoride release with minimal secondary caries inhibition. Increasing fluoride release correlated with larger inhibition areas and reduced outer lesion depth and extension.

Effect of customized bioactive glass in experimental composites on dentin bond strength after 12 months of aging

OBJECTIVES

This study aimed to investigate the effect of a customized low-sodium bioactive glass (BG) fillers in experimental resin composites on their bond strength to dentin after 12 months of artificial aging. Specifically, it evaluated whether the bond strength was affected by different BG concentrations (0, 10, 20, 40 wt%) and artificial aging durations (1, 6, and 12 months).

MATERIALS AND METHODS

Experimental composites were prepared with 10, 20, and 40 wt% of a customized low-sodium fluoride-containing BG. The experimental composite with 0 wt% BG was used as a control, while Beautifil II (Shofu) was used as an external reference material. A universal adhesive system was applied to dentin substrates and composite build-ups were made. Bond strength was measured using a macro-shear bond strength test, and Weibull statistics were used to assess the reliability of the materials. Failure modes were analyzed to evaluate the type of the fracture.

RESULTS

After 12 months, the bond strength of all experimental composites remained stable and comparable to the control material, with statistically significant improvements between 6 and 12 months for all experimental materials. The bond strength was statistically similar across materials, except at the 12-month point, where the 20 wt% BG-composite showed significantly higher bond strength than the 40 wt% BG-composite. The frequency of mixed failures in composite increased after 12 months, particularly in experimental composites containing higher BG content.

CONCLUSIONS

The incorporation of a customized low- sodium BG into resin composites did not negatively impact their bond strength to dentin over 12 months. Instead, bond strength improved over time, and the composites remained mechanically stable, although a higher incidence of mixed failures was observed with increased BG content.

CLINICAL RELEVANCE

The customized low-sodium BG demonstrated stable bond strength over the 12-month period, offering a promising option for functional fillers in restorative composites without compromising the longevity of the adhesive-dentin interface.

Biocompatibility and osteogenic assessment of experimental fluoride-doped calcium-phosphate cements on human dental pulp stem cells

OBJECTIVES

This study investigated the impact of some specific experimental calcium phosphate cements doped with different fluoride salts (FDCPCs) concentrations on the basal functions of human Dental Pulp Stem Cells (hDPSCs). Furthermore, this study also examined the migration, as well as the mineralisation through osteogenic differentiation.

METHODS

Experimental FDCPCs were formulated using different concentrations of calcium/sodium fluoride salts [(5 wt%: VS5F), (10 wt%: VS10F), (20 wt%: VS20F)]. A fluoride-free calcium phosphate (VS0F) was used as a control. The hDPSCs were assessed to evaluate their self-renewal and migration activity in the presence of eluates of the different FDCPCs. A viability assay in osteogenic conditions was carried out, along with the differentiation potential through Alkaline Phosphatase Activity (ALP), and Alizarin Red Staining (ARS). Moreover, the gene expression of specific markers (RUNX2, ALP, COL1α1, OCN, OPN, DSPP, MEPE, and DMP-1) was also evaluated.

RESULTS

All the tested FDCPD had no influence on cell migrations, but they caused a decrease in cell viability in osteogenic conditions when not diluted. Conversely, the eluants of VS20F showed a positive effect on stem cell differentiation. This result was corroborated through ALP activity, ARS assay. Moreover, upregulation of specific gene markers such as RUNX2, DMP-1, and DSPP was observed in hDPSCs, especially when treated with VS20F.

SIGNIFICANCE

The experimental FDCPC tested in this study exhibits a dose-dependent capacity to promote mineralisation in osteogenic environment. The FDCPC-VS20F seems to be the most promising experimental material suitable for developing of pulp-capping materials with osteogenic and bioactive properties.

A Critical Review on the Factors Affecting the Bond Strength of Direct Restorative Material Alternatives to Amalgam

This article comprehensively reviews the performance of simplified direct restorative materials that have the potential to be an alternative to amalgam. Following an understanding of the material structures and clinical performances, this review provides an analysis of the bonding mechanisms and influential factors on the bond strength. These factors include substrate-related variations, involving primary vs. permanent dentin, sound- vs. caries-affected/demineralized dentin comparisons and surface-related factors and pretreatments. Special attention is given to the factors changing the substrate surface, such as different contaminants, remedy methods after contamination and different conditioning methods related to the materials. Variations in sample preparation and bond strength test parameters are also evaluated for the analysis of the outcomes. This review aims to provide an overview of the factors involved in the application procedure of direct restorations together with in vitro testing variations to guide the selection of suitable materials by understanding strengths and shortcomings.

Retention of strength and ion release of some restorative materials

This study aimed to investigate the retention of strength in accelerated aging condition and ion release from an experimental fiber-reinforced bioactive flowable composite resin (Bio-SFRC), comparing it with various commercially available ion-releasing materials. The flexural strength of Bio-SFRC and other materials (Biodentine, TheraCal LC, Fuji II LC and Surefil one) was evaluated (n = 8) before and after hydrothermal accelerated aging. Ion concentrations of silica and phosphorus were measured after 1, 2, 3, 4, 7, 10, 14, and 21 days of specimen immersion in simulated body fluids (SBF) using UV-Vis spectrometry. In addition, ion release and pH change were studied in a continuous dynamic system in SBF over a period of 72 h. SEM and EDS were used to evaluate the microstructure on the top surface of the materials after SBF immersion. Data were statistically analyzed using variance ANOVA analysis (p = 0.05). Bio-SFRC showed higher flexural strength before (134.9 MPa) and after (63.1 MPa) hydrothermal aging compared to other tested materials (p < 0.05). Flexural strength significantly decreased after aging (p < 0.05) except for Fuji II LC which showed no significant differences. Ion release data showed that experimental Bio-SFRC slowly released phosphate ions. Biodentine and TheraCal LC had the strongest ability to form calcium phosphate precipitation on the material surface. Phosphate ion release cannot be detected clearly from these materials. Surefil one and Fuji II LC were more stable materials without any observable ion release. The advantages of fiber containing structure and slow release of ions suggest that experimental Bio-SFRC is a promising bioactive material to provide ions for mineralization of surrounding tissues, and keeping the durability of the materials at higher level than that of other tested materials.

Transdentinal effects of S-PRG fillers on odontoblast-like cells

OBJECTIVES

To investigate the transdentinal effects of surface reaction-type pre-reacted glass-ionomer (S-PRG) fillers on odontoblast-like cells.

METHODS

An eluate of S-PRG fillers was obtained by dissolving the particles in distilled water (1:1 m/v). Dentin discs with similar permeability were mounted into artificial pulp chambers and MDPC-23 cells were seeded on their pulpal surface. The occlusal surface was treated with (n = 10): ultrapure water (negative control - NC), hydrogen peroxide (positive control - PC), S-PRG eluate exposure for 1 min (S-PRG 1 min), or S-PRG filler eluate exposure for 30 min (S-PRG 30 min). After 24 h, cell viability (alamarBlue) and morphology (SEM) were evaluated. The extract obtained from transdentinal diffusion was applied to MDPC-23 pre-cultured in plates for another 24 h to evaluate viability (alamarBlue, 1, 3, and 7 days), gene expression of Col1a1, Alpl, Dspp, and Dmp1 (RT-qPCR, 1 and 7 days), and mineralization (Alizarin Red, 7 days). Data were analyzed with ANOVA (α = 5 %).

RESULTS

While S-PRG 1 min did not differ from NC, S-PRG 30 min reduced 17.9 % viability of cells from discs. S-PRG treatments resulted in low cell detaching from dentin, and the remaining cells exhibited typical morphology or minor cytoplasmic contraction. S-PRG 30 min slightly increased cell viability (6 %) 1 day after contact with the extract. S-PRG treatments upregulated the expression of the investigated genes, especially after 1 day. S-PRG 30 min stimulated mineralization activity by 39.7 %.

CONCLUSIONS

S-PRG filler eluate does not cause transdentinal cytotoxicity on odontoblast-like cells, and long-term exposure can stimulate their dentinogenic-related mineralization activity.

SIGNIFICANCE

The transdentinal elution of ions from S-PRG fillers is not expected to be harmful to the dental pulp and may exert bioactive effects by inducing dentin matrix deposition through the metabolism of underlying odontoblasts.

A Comparative In Vitro Physicochemical Analysis of Resin Infiltrants Doped With Bioactive Glasses

Objective This study aimed to investigate the longevity and effectiveness of bioactive glass (BAG)-based dental resin infiltrants. Materials and methods The three types of BAG - 45S5 bioglass (RIS), boron-substituted (RIB), and fluoride-substituted (RIF) - were incorporated with photoinitiated dimethacrylate monomers to create experimental resin infiltrants. ICON® (CN; DMG-America, Ridgefield Park, NJ) and pure resin (PR) were used as control groups in this study. Disc-shaped samples were prepared for the experimental and control groups. The samples were challenged with the pH cycle and immersed in the artificial saliva for 30 days. On Day 0 and Day 30, the pH cycle and artificial saliva immersion, Vicker's microhardness, surface roughness, and surface morphology were investigated. Results The RIF group's disc samples showed the highest Vicker's microhardness values (78.20 ±0.06) on Day 30 of artificial saliva immersion, whereas the CN group's values were the lowest (55.99 ±0.24). Following the pH cycling, the RIF displayed the highest hardness (64.15 ±1.89) whereas the CN group's values were the lowest (33.47 ±1.28). Regarding surface roughness, on Day 30, the RIB resin group exhibited the highest (1.14 ±0.001 µm). In contrast, the CN resin showed the lowest (1.07 ±0.06 µm) values, while immersed in the artificial saliva solution. In the same duration of time, in the pH cycling solution, PR showed the least (0.85 ±0.89 µm), while RIF showed the highest roughness value (0.94 ±0.54 µm). Morphological analysis revealed that following the artificial saliva immersion, the RIB, CN, and PR exhibited smoother surfaces compared to the RIS and RIF groups. However, when immersed in the pH cycling solution, RIB and RIF showed more resistance against acid attack. Conclusions Our results revealed that the experimental resin groups performed much better than the commercial resin infiltrants following artificial saliva and pH cycling challenges.

Comparisons of ammonia- and water-based silver-containing solutions on dentin bonding and enzymatic activity: 1-yr evaluation

OBJECTIVE

To evaluate the effects of an ammonia-based and a water-based silver-containing solutions on bonding performance and matrix-metalloproteinases (MMPs) activity of a universal adhesive to dentin after 1 year of artificial aging.

METHODS

Mid-coronal dentin surfaces of 60 sound human molars were exposed and the following groups were formed according to the surface pre-treatment and etching mode of the universal adhesive (Zipbond Universal, SDI) (n = 10): G1) Zipbond in the self-etch mode (ZSE); G2) Riva Star (SDI) applied before ZSE; G3) Riva Star Aqua (SDI) applied before ZSE; G4) Zipbond in the etch-and-rinse mode (ZER); G5) Riva Star applied before ZER; G6) Riva Star Aqua applied before ZER. The specimens were sectioned and subjected to microtensile bond strength (µTBS) test at baseline (T0) and after 12 months (T12) of artificial storage. Scanning electron microscope (SEM) and energy dispersive spectroscopy analysis (EDS) were also conducted. Three additional molars per group were processed for the in situ zymography analysis at T0 and T12. Data were statistically analyzed (p < 0.05).

RESULTS

Dentin pre-treatments and aging decreased bonding values, regardless of the etching mode (p < 0.05). No differences in µTBS were observed between the two silver-containing solutions, both at T0 and T12. Riva Star Aqua and etching significantly increased the MMPs activity, independent of the storage period (p < 0.05).

SIGNIFICANCE

Dentin surface pre-treatment with silver-containing solutions negatively affects the bonding performances of resin composite restorations placed with a universal adhesive. However, the ammonia-based product Riva Star might show better stability in the long term, due to lower activation of MMPs.

Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study

AIM

This study aimed to assess the color stability of bioactive restorative materials vs nanohybrid resin composites after 3 months of immersion in three frequently consumed beverages.

MATERIALS AND METHODS

Thirty disk-shaped specimens of Giomer dental restorative material (Shofu, Japan) and nanohybrid resin composite (Tokuyama, Japan) were performed using a Teflon mold. Super-Snap system (Shofu, Japan) was utilized to finish and polish the specimens to be preserved for 24 hours in distilled water at 37°C. The samples had been divided into three subgroups (Coffee, tea, Pepsi) (n = 5). The initially displayed color measurements of the samples were performed using a spectrophotometer (VITA Easyshade® V). After 7 days, 30 days, and 90 days, color measurements were repeated, and the E of each sample was estimated. E of each sample was calculated.

RESULTS

The Giomer group showed statistically significant higher E values than the nanohybrid resin composite where the p-value was ≤0.0001. Tea subgroup showed the highest statistically significant E values in both groups where the p-value was ≤ 0.0001. The highest statistically significant color change was recorded at 3 months.

CONCLUSION

The color of bioactive restorative material is less stable if compared with nanohybrid resin composite.

CLINICAL SIGNIFICANCE

As tea and coffee are popular beverages, particularly in Middle Eastern nations, dentists must advise patients about the color change of resin restorations. Patients are advised to brush their teeth immediately after consuming these beverages. How to cite this article: Saber EH, Abielhassan MH, Abed YA, et al. Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study. J Contemp Dent Pract 2024;25(3):221-225.

Bonding performance and interfacial adaptation of modern bulk-fill restorative composites after aging in artificial saliva: an in vitro study

OBJECTIVES

This study aimed at comparing the microtensile bond strength (MTBS) and interfacial adaptation of a modern self-curing and a light-curing restorative bulk-fill composite to a conventional composite applied with the layering technique.

METHODS

Forty-eight occlusal cavities were divided in three main groups (16/group) based on tested materials: (i) STELA, bulk-fill self-curing restorative (STELA, SDI Ltd.); (ii) 3 M-BULK, bulk-fill composite (Filtek One Bulk-Fill, 3 M Oral Care); and (iii) 3 M-CTR, a conventional composite (Filtek Supreme XTE, 3 M Oral Care). These were used in combination with their adhesives in self-etch (SE) or etch-and-rinse (ER) mode. Specimens stored in artificial saliva (24 h or 12 months) were evaluated for MTBS and fractography. The interfacial analysis was performed through confocal microscopy. ANOVA and Fisher's LSD post hoc tests were performed with a level of significance of 5%.

RESULTS

All the tested materials applied in ER mode presented (24 h) greater bond strength than in SE mode. Although all materials showed a significant drop in the bond strength after prolonged storage, STELA showed the highest bonding performance and interfaces with few gaps. 3 M-BULK had the lowest bond strength and an interface with several voids and gaps.

CONCLUSIONS

All materials were affected by interface degradation and bonding reduction over prolonged aging. However, their use in combination with adhesives applied in ER mode may offer greater immediate bonding performance.

CLINICAL RELEVANCE

The use of restorative light-curing bulk-fill composites may generate gaps at the bonding interface and voids. STELA may represent a suitable alternative to avoid such issues.

Effect of different storage media on elemental analysis and microhardness of cervical cavity margins restored with a bioactive material

Objectives

This study aimed to investigate the elemental analysis and microhardness of a bioactive material (Activa) and marginal tooth structure after storage in different media.

Materials and Methods

Fifteen teeth received cervical restorations with occlusal enamel and gingival dentin margins using the tested material bonded with a universal adhesive, 5 of them on the 4 axial surfaces and the other 10 on only the 2 proximal surfaces. The first 5 teeth were sectioned into 4 restorations each, then stored in 4 different media; deionized water, Dulbecco's phosphate buffered saline (DPBS), Tris buffer, and saliva. The storage period for deionized water was 24 hours while it was 3 months for the other media. Each part was analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis for different substrates/distances and the wt% of calcium, phosphorus, silica, and fluoride were calculated. The other 10 teeth were sectioned across the restoration, stored in either Tris buffer or saliva for 24 hours or 3 months, and were evaluated for microhardness of different substrates/areas. Data were analyzed using analysis of variance and Tukey's post hoc test.

Results

Enamel and dentin interfaces in the DPBS group exhibited a significant increase in calcium and phosphorus wt%. Both silica and fluoride significantly increased in tooth structure up to a distance of 75 μm in the 3-month-media groups than the immediate group. Storage media did not affect the microhardness values.

Conclusions

SEM-EDS analysis suggests an ion movement between Activa and tooth structure through a universal adhesive while stored in DPBS.

Release Kinetics of Monomers from Dental Composites Containing Fluoride-Doped Calcium Phosphates

This study analyse the type of release kinetic of specific monomers from dental resin composites containing various fluoride-doped calcium phosphates. The release behavior of urethane dimethacrylate (UDMA), ethoxylated bisphenol-A dimethacrylate (bis-EMA) and 1.6-hexanediol ethoxylate diacrylate (HEDA) was evaluated over a period of 35 days. Two tailored calcium phosphates doped with different concentrations of fluoride salts (VS10% and VS20%) were prepared and incorporated in the dimethacrylate matrix at various concentrations to generate a range of experimental composites. The release kinetics were characterized using mathematical models such as zero-order, first-order, Peppas and Higuchi models. The results showed that the first-order model best described the release kinetics. UDMA and HEDA exhibited significant differences in release compared to bis-EMA from day 1, while no significant differences were observed between UDMA and HEDA, except on day 35, when UDMA exhibited a higher release rate than HEDA. When comparing the release of each monomer, VS20-R20% had the highest total release percentage, with 3.10 ± 0.25%, whereas the composite VS10-R5% showed the lowest release percentage, with a total of 1.66 ± 0.08%. The release kinetics were influenced by the composition of the resin composites and the presence of calcium fluoride and sodium fluoride in the calcium phosphate played a role in the maximum amounts of monomer released. In conclusion, the release of monomers from the tested resin composites followed a first-order kinetic behaviour, with an initial rapid release that decreased over time. The composition of the resin monomers and the presence of fluoride salts influenced the release kinetics. The VS10-R5% and VS10-R10% resin composites exhibited the lowest total monomer release, suggesting its potential favourable composition with reduced monomer elution. These findings contribute to understanding the release behavior of dental resin composites and provide insights for the development of resin-based bioactive dental materials.

Bioactive Restorative Materials Applied over Coronal Dentine-A Bibliometric and Critical Review

The objective of the research was to examine the scientific literature concerning restorative materials with bioactive properties for the purpose of covering dentin. Searches were performed in various databases including MEDLINE, Scopus, Web of Science, Cochrane Library, Lilacs/BBO, and Embase. Inclusion criteria involved studies that utilized the terms "dentin" and "bioactive", along with "ion-releasing", "smart materials", "biomimetic materials" and "smart replacement for dentin". The information extracted included the title, authors, publication year, journal and the country of affiliation of the corresponding author. The studies were categorized based on their study design, type of material, substrate, analytical method, and bioactivity. A total of 7161 records were recovered and 159 were included for data extraction. Most of the publications were in vitro studies (n = 149), testing different types of materials in sound dentine (n = 115). Most studies were published in Dental Materials (n = 29), and an increase in publications could be observed after the year 2000. Most of the articles were from the USA (n = 34), followed by Brazil (n = 28). Interfacial analysis was the most investigated (n = 105), followed by bond strength (n = 86). Bioactivity potential was demonstrated for most tested materials (n = 148). This review presents insights into the current trends of bioactive materials development, clearly showing a severe lack of clinical studies.

Biological considerations of dental materials as orifice barriers for restoring root-filled teeth

There is ample published literature regarding the technical aspects of restoring root-filled teeth, but little concerning the biological impacts, consequences, and criteria for the selection of direct restorative materials following endodontic treatment. The provision of an effective coronal seal in addition to a sound root filling is known to be important in the prevention of root canal infection. This review seeks to explore the evidence concerning the selection of dental materials in the restoration of root-filled teeth, specifically with a close examination of the properties of commonly used materials as orifice barriers. © 2023 Australian Dental Association.

Secondary caries and marginal adaptation of ion-releasing versus resin composite restorations: a systematic review and meta-analysis of randomized clinical trials

This systematic review was aimed to evaluate occurrence of secondary caries and marginal adaptation in ion-releasing materials versus resin composite. Electronic search of PubMed, Scopus, and Open Grey databases with no date or language restrictions until May 21st, 2021, was conducted. Randomized clinical trials that compared ion-releasing restorations versus resin composite were included. For quantitative analysis, a random-effects meta-analysis with risk difference as an effect measure and a 95% confidence interval was used. Quality of evidence was assessed using The Grading of Recommendations, Assessment, Development, and Evaluation criteria. The risk of bias was evaluated using the Cochran Collaboration Risk of Bias tool. The inclusion criteria were met by 22 studies, and 10 studies were included in the meta-analysis. Three follow-up periods (1 year, 18 months-2 years, and 3 years) were evaluated. The overall quality of evidence for secondary caries and marginal adaptation outcomes was low. The results of the meta-analysis showed no significant difference (p > 0.05) in both outcomes between ion-releasing materials and resin composite. The occurrence of secondary caries was not dependent on the nature of the restorative material. It is more likely a complex process that involves the same risk factors as primary carious lesions.

Improved Flexural Properties of Experimental Resin Composites Functionalized with a Customized Low-Sodium Bioactive Glass

This study evaluated the flexural properties of an experimental composite series functionalized with 5-40 wt% of a low-Na F-containing bioactive glass (F-series) and compared it to another experimental composite series containing the same amounts of the conventional bioactive glass 45S5 (C-series). Flexural strength and modulus were evaluated using a three-point bending test. Degree of conversion was measured using Fourier-transform infrared spectroscopy. Weibull analysis was performed to evaluate material reliability. The control material with 0 wt% of bioactive glass demonstrated flexural strength values of 105.1-126.8 MPa). In the C-series, flexural strength ranged between 17.1 and 121.5 MPa and was considerably more diminished by the increasing amounts of bioactive glass than flexural strength in the F-series (83.8-130.2 MPa). Analogously, flexural modulus in the C-series (0.56-6.66 GPa) was more reduced by the increase in bioactive glass amount than in the F-series (5.24-7.56 GPa). The ISO-recommended "minimum acceptable" flexural strength for restorative resin composites of 80 MPa was achieved for all materials in the F-series, while in the C-series, the materials with higher bioactive glass amounts (20 and 40 wt%) failed to meet the requirement of 80 MPa. The degree of conversion in the F-series was statistically similar or higher compared to that of the control composite with no bioactive glass, while the C-series showed a declining degree of conversion with increasing bioactive glass amounts. In summary, the negative effect of the addition of bioactive glass on mechanical properties was notably less pronounced for the customized bioactive glass than for the bioactive glass 45S5; additionally, mechanical properties of the composites functionalized with the customized bioactive glass were significantly less diminished by artificial aging. Hence, the customized bioactive glass investigated in the present study represents a promising candidate for functionalizing ion-releasing resin composites.

Assessment of the remineralisation induced by contemporary ion-releasing materials in mineral-depleted dentine

OBJECTIVES

Evaluate the ability of current ion-releasing materials to remineralise bacteria-driven artificial caries lesions.

MATERIALS AND METHODS

Standardised class I cavities were obtained in 60 extracted human molars. Specimens underwent a microbiological cariogenic protocol (28 days) to generate artificial caries lesions and then were randomly divided into four restorative groups: adhesive + composite (negative control); glass ionomer cement (GIC); calcium silicate cement (MTA); and resin-modified calcium silicate cement (RMTA). Microhardness analysis (ΔKHN) was performed on 40 specimens (10/group, t = 30 days, 45 days, 60 days in artificial saliva, AS). Micro-CT scans were acquired (3/group, t = 0 days, 30 days, and 90 days in AS). Confocal microscopy was employed for interfacial ultra-morphology analysis (2/group, t = 0 days and 60 days in AS). Additional specimens were prepared and processed for scanning electron microscopy (SEM) and FTIR (n = 3/group + control) to analyse the ability of the tested materials to induce apatite formation on totally demineralised dentine discs (60 days in AS). Statistical analyses were performed with a significance level of 5%.

RESULTS

Adhesive + composite specimens showed the lowest ΔKHN values and the presence of gaps at the interface when assessed through micro-CT even after storage in AS. Conversely, all the tested ion-releasing materials presented an increase in ΔKHN after storage (p < 0.05), while MTA best reduced the demineralised artificial carious lesions gap at the interface. MTA and RMTA also showed apatite deposition on totally demineralised dentine surfaces (SEM and FTIR).

CONCLUSIONS

All tested ion-releasing materials expressed mineral precipitation in demineralised dentine. Additionally, calcium silicate-based materials induced apatite precipitation and hardness recovery of artificial carious dentine lesions over time.

CLINICAL RELEVANCE

Current ion-releasing materials can induce remineralisation of carious dentine. MTA shows enhanced ability of nucleation/precipitation of hydroxyapatite compared to RMTA and GIC, which may be more appropriate to recover severe mineral-depleted dentine.

Development and characterization of ion-releasing fiber-reinforced flowable composite

OBJECTIVE

This study aimed to develop and characterize an ion-releasing experimental fiber-reinforced flowable composite (Bio-SFRC) and dentin treatment solution made of poly(acrylic acid) (PAA) with a high molecular weight. In addition we also evaluated the interface structure and mineralization potential between the Bio-SFRC and dentin.

METHODS

Some mechanical properties (flexural properties and fracture toughness) of Bio-SFRC in comparison with commercial inert (G-aenial Flo X) and ion-releasing materials (ACTIVA-BioActive Base/Liner and Fuji II LC) were assessed (n = 8/group). Calcium-release at different time-points was measured during the first six weeks by using a calcium-ion selective electrode. Surface analysis of composites after being stored in simulated body fluid (SBF) was investigated by using SEM/EDS. Dentin disks (n = 50) were prepared from extracted sound teeth and demineralization was simulated by acid etching. SEM/EDS was used to evaluate the microstructure of dentin on the top surface and at interface with composites after being stored in SBF.

RESULTS

Bio-SFRC showed higher fracture toughness (1.6 MPa m^1/2) (p < 0.05) compared to Flo X (1.2 MPa m^1/2), ACTIVA (1 MPa m^1/2) and Fuji II LC (0.8 MPa m^1/2). Accumulative calcium release after six weeks from Bio-SFRC (15 mg/l) was higher than other tested ion-releasing materials (≈ 6 mg/l). Mineralization was clearly seen at the interface between treated dentin and Bio-SFRC. None of the commercial tested materials showed signs of mineralization at the interface and dentinal tubules remained open.

SIGNIFICANCE

Developing such reinforced ion-releasing flowable composite and PAA solution might offer the potential for mineralization at the interface and inside the organic matrix of demineralized dentin.

Interfacial Bond Strength and Morphology of Sound and Caries-affected Dentin Surfaces Bonded to Two Resin-modified Glass Ionomer Cements

OBJECTIVE

To evaluate the shear bond strength and interfacial morphology of sound and caries-affected dentin (CAD) bonded to two resin-modified glass ionomer cements (RMGICs) after 24 hours and two months of storage in simulated body fluid at 37°C.

METHODS AND MATERIALS

Sixty-four permanent human mandibular first molars (32 sound and 32 with occlusal caries, following the International Caries Detection and Assessment System) were selected. Each prepared substrate (sound and CAD) was conditioned (10% polyacrylic acid) and bonded to Activa BioACTIVE Restorative (Activa) and Fuji II LC (F2LC) as per the manufacturers' instructions. Shear bond strength (SBS) was performed after 24 hours and two months of storage. The interfacial surfaces were examined using a digital microscope and scanning electron microscope (SEM). Three-way ANOVA, Bonferroni post-hoc tests (α=0.05), and independent T-tests were used for multifactorial analysis.

RESULTS

Activa exhibited reduced bond strength values to sound and CAD in comparison to F2LC after two time periods (p=0.01). There is a pronounced enhancement in SBS of F2LC when bonded to CAD (p=0.01) after storage, with no statistically significant effect on sound dentin (p=0.309). Activa showed stable SBS to sound and CAD immediately and post-aging (p>0.05). However, the evidence of mineral-like deposits under an SEM attached to the aged, debonded dentin surfaces, thereby obliterating the exposed dentinal tubules, might support the tissue repair potential of Activa.

CONCLUSIONS

The SBS of Activa was lower than F2LC when bonded to sound and CAD, but the bonding stability and sealing ability is advantageous in minimally invasive therapy, suggesting use with a resin composite coverage when used in stress-bearing areas.

Dental adhesion with resin composites: a review and clinical tips for best practice

Modern restorative dentistry would not be possible without the ability to bond to tooth structure. The development of dental adhesives has a lengthy gestation, from the beginnings around 1950, to the latest generation: modern universal adhesives, which were introduced during the 2010s. The foundation for these developments was a deeper understanding of the mechanisms of adhesion to the tooth structure, and to restoration materials. Typically, the performance of an adhesive does not depend on the use of a single ingredient, but on an overall balanced and optimised formulation that contains various components with different roles, such as functional adhesive monomers.While a wealth of literature exists on adhesives that have a long and successful clinical history ('gold standards'), some universal adhesives have also accumulated a lot of scientific evidence while offering benefits like ease of use, low technique sensitivity and versatility.To achieve reliable results with a modern adhesive, several tips should be kept in mind regardless of the product, which result in a homogeneous adhesive layer, proper cure and ultimately high bond strength. Although high performance is already achieved with the adhesives currently available, this is still an exciting area of ongoing research.

Assessment of remineralisation potentials of bioactive dental composite using an in-vitro demineralised dentine model

Objective

Minimally invasive dentistry encourages conservative caries excavation and remineralisation of the remaining dental tissues. However, dentine remineralisation is more difficult than enamel remineralisation due to the differences in their composition. This study aims to assess the remineralisation potential of Activa BioActive-Restorative and Beautifil II restoration on demineralised dentine samples, and compares it with glass-ionomer (GIC) restoration using energy dispersive X-ray (EDX) and Knoop hardness number (KHN).

Methods

Non-carious extracted molar teeth were used, a total number of ten teeth were sectioned into halves and partially demineralised using 37.0% phosphoric acid for 60 s. All samples are assessed using EDX and KHN prior to restorations. The samples are then subdivided into four groups (n = 5). Group 1 was restored with Activa BioActive-Restorative, Group 2 received Beautifil II, Group 3 was restored with GIC, and the last group was used as a negative control. After storage, the samples were analysed using EDX and KHN.

Results

The demineralisation protocol with 37.0% phosphoric acid significantly decreased the calcium:phosphate (Ca:P) ratio and KHN. Remineralisation occurred in all groups, but the highest percentage change in Ca:P ratio and KHN was observed in the Activa BioActive-Restorative group (20.7%, 82.0%, respectively), followed by the Beautifil II group, glass ionomer group, and the control group, in that order.

Conclusion

Activa BioActive-Restorative restoration presents superior remineralisation compared to Beautifil II and glass-ionomer dental restorations.

Color stability of bioactive restorative materials after immersion in various media

Objectives:

The aim of this article is to assess the color stability of the bioactive restorative materials (Activa Bioactive, Beautifil II) compared with the conventional resin composite and resin-modified glass ionomer cement after immersion in different staining solutions overtime.

Materials and Methods:

This is an in-vitro study that investigated four different material groups: (1) bioactive composite (ACTIVA Bioactive-Restorative, Pulpdent, USA), (2) Giomer composite (Beautifil II, SHOFU Dental GmbH, Japan), (3) resin-modified glass ionomer cement (Fuji II, GC Corporation, Japan), and (4) resin composite (Filtek Z350XT, 3M ESPE, USA). One hundred samples (n=25 each group) were fabricated using a custom acrylic mold (1 mm thick × 10 mm diameter) and then immersed in five different staining solution groups: coffee, black tea, cola, mixed berry juice, and saline. Baseline (T0) shade of samples was recorded using two spectrophotometers: VITA Easyshade Digital Advance and a spectrophotometer. Then shade was recorded at the intervals of 7 (T1), 14 (T2), and 28 (T3) days of immersion. Measurements were obtained and then ΔE was calculated for each group at each time point. Three-way analysis of variance tests were used to test the interactions between different variables at the 0.05 significance level.

Results:

All specimens showed a significant color change (P<0.001), following 7, 14, and 28 days of storage. Activa Bioactive and Filtek Z350 showed the highest color stability overtime in different staining solutions, whereas Fuji II and Beautifil II showed the least color stability. The most significant color change was noticed in the coffee group and then in the mixed berry juice group.

Conclusion:

Resin-based restorative materials showed higher color stability than glass ionomer-based restorations. Both spectrophotometers gave comparable results for materials’ color stability.

Commercially Available Ion-Releasing Dental Materials and Cavitated Carious Lesions: Clinical Treatment Options

The contemporary approach for operative caries management emphasizes personalized interventions for each patient, dependent upon the individual's caries susceptibility/risk, the stage of the carious lesion and its activity. The clinician's challenge is to optimize the extent of cavity preparation and the choice of dental restorative biomaterials, appreciating the benefits offered by ion-releasing restorative materials. There is a growing application of bioactive/bio-interactive materials in minimally invasive operative dentistry, as they may help with tissue recovery by ion release. In case of moderate or extensive occlusal cavitation, the clinical criteria include the individual caries susceptibility and carious lesion activity. In high caries risk cases, ion-releasing biomaterials (IRB) can be used, as well as for active carious lesions. In proximal lesions, the clinical criteria include the individual caries susceptibility, the lesion activity and presence of cavities with little or no enamel at the gingival margin. This article aims to discuss the restorative ion-releasing options, according to different clinical situations, and the caries susceptibility to manage cavitated carious lesions in permanent adult teeth.

A Contemporary Evaluation on Posterior Direct Restoration Teaching among Undergraduates in Dental Schools in Malaysia

There is a current trend to restore posterior teeth with composite resin due to increasing demands on natural tooth colour restoration and increased concern about the safety of amalgam restorations. The objective was to evaluate the current teaching of posterior direct restoration among restorative dental lecturers in Malaysia compared to available international literature. An online questionnaire, which sought information on the teaching of posterior restoration was developed and distributed to 13 dental schools in Malaysia. The response rate for the questionnaire was 53.8%. The most popular posterior restoration teaching methods among the respondents were lecture (95.7%), demonstration (87.0%) and problem-based learning (PBL) (73.9%), while continuous assessment and a practical competency test (82.6%) were the most popular assessment methods. Placing a hard setting calcium hydroxide and GIC base for deep cavity restored by composite restoration was taught in 79.2% of cases. The standard protocols for posterior composite restoration were incremental filling in deep cavity (87.5%), using circumferential metal bands with wooden wedge (91.7%), with a total etch system (95.8%), using a light emitting diode (LED) light curing unit (91.7%), finishing using water cooling (80%) and finishing with a disc (87.5%). Graduates from dental schools in Malaysia received similar theoretical, preclinical and clinical teaching on posterior restoration techniques, although there were variations in the delivery methods, techniques and assessments, pointing to a need for uniformity and consensus.

An in-vitro study investigating the effect of air-abrasion bioactive glasses on dental adhesion, cytotoxicity and odontogenic gene expression

OBJECTIVE

To assess the microtensile bond strength (MTBS) and interfacial characteristics of universal adhesives applied on dentine air-abraded using different powders. The analysis includes the cytotoxicity of the powders and their effect on odontogenic gene expression.

METHODS

Sound human dentine specimens were air-abraded using bioglass 45S5 (BAG), polycarboxylated zinc-doped bioglass (SEL), alumina (AL) and submitted to SEM analysis. Resin composite was bonded to air-abraded or smear layer-covered dentine (SML) using an experimental (EXP) or a commercial adhesive (ABU) in etch&rinse (ER) or self-etch (SE) modes. Specimens were stored in artificial saliva (AS) and subjected to MTBS testing after 24 h and 10 months. Interfacial nanoleakage assessment was accomplished using confocal microscopy. The cytotoxicity of the powders was assessed, also the total RNA was extracted and the expression of odontogenic genes was evaluated through RT-PCR.

RESULTS

After prolonged AS storage, specimens in the control (SML) and AL groups showed a significant drop in MTBS (p > 0.05), with degradation evident within the bonding interface. Specimens in BAG or SEL air-abraded dentine groups showed no significant difference, with resin-dentine interfaces devoid of important degradation. The metabolic activity of pulp stem cells was not affected by the tested powders. SEL and BAG had no effect on the expression of odontoblast differentiation markers. However, AL particles interfered with the expression of the odontogenic markers.

SIGNIFICANCE

The use of bioactive glass air-abrasion may prevent severe degradation at the resin-dentine interface. Unlike alumina, bioactive glasses do not interfere with the normal metabolic activity of pulp stem cells and their differentiation to odontoblasts.

Monomer Conversion, Dimensional Stability, Biaxial Flexural Strength, Ion Release, and Cytotoxicity of Resin-Modified Glass Ionomer Cements Containing Methacrylate-Functionalized Polyacids and Spherical Pre-Reacted Glass Fillers

The aim of this study was to prepare RMGICs for pulp protection that contain polyacids functionalized with methacrylate groups (CMs) to enable light-activated polymerization without the need for toxic 2-hydroxyethyl methacrylate (HEMA) monomers. The effects of using CM liquids with 0 or 5 wt% HEMA on the physical/mechanical properties and cytotoxicity of the experimental RMGICs were assessed. Spherical pre-reacted glass fillers (SPG) were used as the powder phase. The experimental RMGICs were prepared by mixing SPG with CM liquid (0 wt% HEMA, F1) or CMH liquid (5 wt% HEMA, F2). Commercial materials (Vitrebond, VB; TheraCal LC, TC) were used for the comparisons. The degree of monomer conversion and fluoride release of both F1 and F2 were significantly lower than those of VB. F1 showed comparable biaxial flexural strength with VB but higher strength than TC. The dimensional stability (mass/volume changes) of the experimental materials was comparable with that of the commercial materials. F1 and F2 exhibited higher Sr/Ca ion release and relative cell viability than VB. The use of CMH liquid reduced the strength but enhanced the fluoride release of the experimental RMGICs. In conclusion, the experimental RMGICs showed comparable strength but lower cytotoxicity compared to the commercial RMGICs. These novel materials could be used as alternative materials for pulp protection.