Bioactive Restorative Dental Materials-The New Frontier

Biomechanics, Bioactive and Biomimetic Philosophy in Restorative Dentistry ̶ Quo vadis?

INTRODUCTION

In recent years, restorative dentistry has embraced various techniques, including direct, semi-direct, and indirect restorations, to address the replacement of lost tooth tissue. The focus has been on integrating the principles of Biomechanics, Bioactivity, and Biomimicry (3-Bio) as key drivers behind these innovations.

METHODS

Three enthusiastic researchers in dental materials have come together to collaborate on writing a concise opinion article addressing the three aspects of restorative dental materials: Biomechanics, Bioactivity, and Biomimetic principles. Their aim is to provide readers with relevant information on the 3-Bio concept, offering insights into the innovative approaches shaping modern restorative dentistry.

RESULTS

Developing restorative materials with interactive properties aligned with the 3-Bio concept poses a significant challenge. Currently, dentistry lacks a comprehensive system in this regard. Though, the development of dental materials based on the 3-Bio concept could potentially elicit positive mechanical and biological responses in targeted tooth tissues.

CONCLUSION

Assessing several parameters through a battery of in vitro and in silico assays could help in tailoring the different aspects of the 3-Bio concept, spanning from bioactivity to biomimetics via biomechanics. This approach could allow the prediction and translation of the clinical performance of the assessed restorative materials.

CLINICAL SIGNIFICANCE

The findings of this opinion article highlight that the development of restorative materials aligned with the 3-Bio concept could enhance the management of dental defects and extend the longevity of bonded restorations, thereby improving patient care through tissue preservation. The authors believe that more collective efforts between clinicians, researchers, and even industrial partners are required to fully understand the correlation between bioactive behaviour, biomechanical limitations, and biomimetics to provide suitable restorative materials for specific clinical applications.

The demineralization resistance and mechanical assessments of different bioactive restorative materials for primary and permanent teeth: an in vitro study

OBJECTIVES

This article examines the efficacy of two bioactive dental composites in preventing demineralization while preserving their mechanical and physical properties.

MATERIALS AND METHODS

The study compares Beautifil Kids and Predicta® Bioactive Bulk-Fill (Predicta) composites with conventional dental composite. Flexural strength and elastic modulus were evaluated using a universal testing machine. A pH-cycling model assessed the composites' ability to prevent dentin demineralization. Color stability and surface roughness were measured using a spectrophotometer and non-contact profilometer, respectively, before and after pH-cycling, brushing simulation, and thermocycling aging.

RESULTS

Beautifil Kids exhibited the highest flexural strength and elastic modulus among the materials (p < 0.05). Predicta demonstrated the highest increase in dentin surface microhardness following the pH-cycling model (p < 0.05). All groups showed clinically significant color changes after pH-cycling, with no significant differences between them (p > 0.05). Predicta exhibited greater color change after brushing and increased surface roughness after thermocycling aging (p < 0.05). While Beautifil Kids had higher surface roughness after pH-cycling (p < 0.05).

DISCUSSION/CONCLUSION

Bioactive restorative materials with ion-releasing properties demonstrate excellent resistance to demineralization while maintaining mechanical and physical properties comparable to the control group.

Comparative study of two bioactive dental materials

OBJECTIVES

New bioactive materials were introduced to not only restore the lost dental hard tissue but also to release fluoride that inhibits demineralization and occurrence of secondary caries. The current study thus aims to assess Fluoride release as well as the mechanical and physical properties of two new commercially available bioactive restorative materials.

METHODS

Two materials, Cention® Forte (CF) (Ivoclar Vivadent), Surefil one™ (SO) (Denstply Sirona), were evaluated in terms of fracture toughness (FT), flexural strength (FS), flexural modulus (FM) (ISO 4049), compressive strength (CS), and Vickers hardness (VH). In addition, thermogravimetric analysis (TGA) was performed, as well as pH measurements and quantification of Fluoride release after immersion in distilled water at times of 0, 7, 14 and 21 days. The sealing ability was evaluated using silver nitrate dye penetration on natural teeth. Finally, Energy-Dispersive X-Ray Spectroscopy (EDX) was used to investigate the surface composition of the two studied material surfaces. The data were statistically analyzed using Independent T-Tests; the chosen significance level was α = 0.05.

RESULTS

CF had significantly higher FT values compared to SO (p = 0.001). Also the FS results showed that CF had significantly higher values (90.11 MPa), followed by SO (22.15 MPa). The CS values showed the same order with significantly higher values for CF (231.79 MPa). While the FM and VH showed the reverse order with SO having significantly higher values than CF. pH measurements showed that CF evolved towards significantly higher pH values after 3 weeks in distilled water, while thermal properties showed more stability and higher resistance to degradation for CF compared to SO. The silver nitrate penetration results showed significantly better sealing ability for CF compared to the self-adhesive SO. Finally, EDX surface analysis results were consistent with the release profiles and confirmed the composition of the two tested materials.

SIGNIFICANCE

Both materials, demonstrated enhanced Fluoride release ability, and hence good remineralisation potential in vitro that could prevent recurrent carious lesions in vivo. The composition based on acrylic polymerization showed better mechanical resistance to bending and fracture, and higher sealing ability than those based on acid base reaction.

In vitro biocompatibility of ammonia-free silver fluoride products on human dental pulp stem cells

OBJECTIVES

Silver fluoride (SF) is a preventive and therapeutic option for dental pathological processes involving structural alterations of the hard tissues, either during their formation or those caused by caries or other pathological reasons. This study aimed to compare the biological properties of two commercial SF products, one of them with ammonium (Riva Star; SDF) and the other ammonium-free (Riva Star Aqua; AgF), both with or without potassium iodide (KI), by the assessment of the cytotoxicity of the materials' eluates.

METHODS

Human dental pulp stem cells (hDPSCs) were obtained from healthy 18-23-year-old donors. Three dilutions were prepared for the tested materials (0.005%, 0.0005%, and 0.0001%). The following groups were assessed: (AgF, AgF+KI, SDF, SDF+KI, KI, negative control). A series of cytocompatibility assays were performed: MTT assay, IC50 assay, wound healing (migration) assay, cell cytoskeleton staining, analysis of cell apoptosis and necrosis, and reactive oxygen species production. The normality in the distribution of the data was previously confirmed via a Q-Q plot. Statistical significance was tested using one way ANOVA and Tukey's post hoc test.

RESULTS

The incorporation of KI improved the cytocompatibility of both SF products in terms of viability, migration, morphology, apoptosis, and reactive oxygen species production. This difference was higher in the AgF group. The lowest dilutions of SF+KI and AgF+KI showed a similar cytocompatibility to that of the control group (MTT assay (p > 0.05 after 24, 48, and 72 h of culture); migration assay (p > 0.05 after 24, 48, and 72 h of culture); reactive oxygen species production (p > 0.05 after 72 h of culture).

SIGNIFICANCE

Riva Star Aqua shows lower cytotoxicity than Riva Star on hDPSCs. It can be considered as a good alternative in the conservative treatment of dental caries and in the preservation and remineralisation of viable dentine tissue.

Developing Bioactive Dental Resins for Restorative Dentistry

Despite its reputation as the most widely used restorative dental material currently, resin-based materials have acknowledged shortcomings. As most systematic survival studies of resin composites and dental adhesives indicate, secondary caries is the foremost reason for resin-based restoration failure and life span reduction. In subjects with high caries risk, the microbial community dominated by acidogenic and acid-tolerant bacteria triggers acid-induced deterioration of the bonding interface and/or bulk material and mineral loss around the restorations. In addition, resin-based materials undergo biodegradation in the oral cavity. As a result, the past decades have seen exponential growth in developing restorative dental materials for antimicrobial applications addressing secondary caries prevention and progression. Currently, the main challenge of bioactive resin development is the identification of efficient and safe anticaries agents that are detrimental free to final material properties and show satisfactory long-term performance and favorable clinical translation. This review centers on the continuous efforts to formulate novel bioactive resins employing 1 or multiple agents to enhance the antibiofilm efficacy or achieve multiple functionalities, such as remineralization and antimicrobial activity antidegradation. We present a comprehensive synthesis of the constraints and challenges encountered in the formulation process, the clinical performance-related prerequisites, the materials' intended applicability, and the current advancements in clinical implementation. Moreover, we identify crucial vulnerabilities that arise during the development of dental materials, including particle aggregation, alterations in color, susceptibility to hydrolysis, and loss of physicomechanical core properties of the targeted materials.

Evaluation of Antibacterial Activity of a Bioactive Restorative Material Versus a Glass-Ionomer Cement on Streptococcus Mutans: In-Vitro Study

BACKGROUND

Dental caries management consists of both preventive and restorative approaches. Pediatric dentists can rely on many techniques and materials to restore decayed teeth, but a high failure rate is still observed, mainly due to secondary caries. New restorative bioactive materials combine the mechanical and aesthetic characteristics of resinous materials with the capability to remineralize and the antimicrobial properties of glass ionomers, thus counteracting the occurrence of secondary caries. The aim of this study was to assess the antimicrobial activity against Streptococcus mutans of a bioactive restorative material (ACTIVA™ BioActive-Restorative™-Pulpdent©) and a glass ionomer cement with silver particles added (Ketac™ Silver-3M©), using agar diffusion assay.

METHODS

Each material was formed into disks of 4 mm in diameter, and four discs of each material were placed on nine agar plates. The analysis was repeated seven times.

RESULTS

Both materials showed statistically significant growth inhibition properties against S. mutans (p < 0.05). The difference in the effectiveness of the two materials was not statistically significant.

CONCLUSION

Both ACTIVA™ and Ketac™ Silver can be recommended since both are similarly effective against S. mutans. However ACTIVA™, given its bioactivity and better aesthetics and mechanical properties compared to GICs, may provide better clinical performance.

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.

Evaluation of the clinical impact and In Vitro antibacterial activities of two bioactive restoratives against S. mutans ATCC 25175 in class II carious restorations

Background

Streptococcus mutans is a Gram-positive opportunistic bacterial pathogen and that causes dental caries and then restorative treatment remains the best clinical practice approach to repair and prevent dental caries.

Aims

This study compared the antimicrobial performance of resin modified glass ionomer cement (RM-GIC) and ACTIVA restoratives by evaluating the S. mutans count, pH levels, and plaque index (PI) scores before and on the 7^th day of restoration, and then determined the antimicrobial activities against S. mutans ATCC 25175 in both restoratives in vitro.

Materials and Methods

Seventy-eight eligible Saudi female participants, with class II carious lesions, were randomly distributed into RM-GIC and ACTIVA restorative groups. We evaluated the S. mutans count by the serial dilution technique and salivary pH by using a portable pH meter. The PI scores were determined by Silness-Löe method and the antibacterial activity by the agar well diffusion method. Statistical analysis of normality distribution was performed with the Kolmogorov-Smirnov and the difference between groups was an analysis by paired t-test. In addition, the independent sample was compared with the independent samples t-test.

Results

Both groups reduced the S. mutans count, pH acidity, and PI scores, and this reduction was statistically significant on the 7^th day of restoration (P < 0.05), preference for ACTIVA. The in vitro antibacterial activity against S. mutans ATCC 25175 showed a non-significant difference between both bioactive restorative materials (P < 0.05).

Conclusion

The novel application of ACTIVA restorative material is a promising option for patients at risk of caries.

Failure Load and Fatigue Behavior of Monolithic and Bi-Layer Zirconia Fixed Dental Prostheses Bonded to One-Piece Zirconia Implants

No evidence-based prosthetic treatment concept for 3-unit fixed-dental-prostheses (FDPs) on ceramic implants is currently available. Therefore, the aim of this in vitro study was to investigate the failure load and fatigue behavior of monolithic and bi-layer zirconia FDPs supported by one-piece ceramic implants. Eighty 3-unit FDPs supported by 160 zirconia-implants (ceramic.implant; vitaclinical) were divided into 4 groups (n = 20 each): Group Z-HT: 3Y-TZP monolithic-zirconia (Vita-YZ-HT); Group Z-ST: 4Y-TZP monolithic-zirconia (Vita-YZ-ST); Group FL: 3Y-TZP zirconia (Vita-YZ-HT) with facial-veneer (Vita-VM9); Group RL (Rapid-layer): PICN “table-top” (Vita-Enamic), 3Y-TZP-framework (Vita-YZ-HT). Half of the test samples (n = 10/group) were fatigued in a mouth-motion chewing-simulator (F = 98 N, 1.2 million-cycles) with simultaneous thermocycling (5−55 °C). All specimens (fatigued and non-fatigued) were afterwards exposed to single-load-to-failure-testing (Z010, Zwick). Statistical analysis was performed using ANOVA, Tukey’s post-hoc tests and two-sample t-tests (p < 0.05, Bonferroni-corrected where appropriate). All specimens withstood fatigue application. While the effect of fatigue was not significant in any group (p = 0.714), the choice of material had a significant effect (p < 0.001). Material FL recorded the highest failure loads, followed by Z-ST, Z-HT and RL, both with and without fatigue application. Taken together, all tested FDP material combinations survived chewing forces that exceeded physiological levels. Bi-Layer FL and monolithic Z-ST showed the highest resilience and might serve as reliable prosthetic reconstruction concepts for 3-unit FDPs on ceramic implants.