Antibacterial activity of resin composites containing surface pre-reacted glass-ionomer (S-PRG) filler

Bioactive Self-Polymerizing Resin with Surface Pre-Reacted Glass Ionomer Fillers for Suppressed Enamel Demineralization

The treatment of damaged enamel surfaces involves modification of the enamel surface with artificial materials or the development of a pseudo-enamel, with research focusing on bioactive and biomimetic materials. In this study, a bioactive auto-polymerizing resin (APR) was developed by adding surface-pre-reacted glass ionomer (S-PRG) fillers of different quantities to APR. Its bioactive effects were evaluated via pH neutralization, ion release, and inhibition of enamel demineralization studies. The pH and fluoride ion release were measured using ion-specific electrodes, revealing that the APR disk with the S-PRG filler immediately neutralized the lactic acid solution (pH 4.0) through ion release. Inductively coupled plasma atomic emission spectrometry revealed that the Sr ion release peaked on the first day, with the other ions following the order F > B > Si > Al > Na, exhibiting a weekly decrease in the same order. Scanning electron microscopy was used to examine the enamel block morphology of the disks after 7 d of incubation, revealing enamel demineralization in disks without the S-PRG filler, whereas no demineralization occurred in disks with the S-PRG filler. APR containing the S-PRG filler demonstrated acid buffering suppressed enamel demineralization and bioactive properties.

The formation of cariogenic plaque to contemporary adhesive restorative materials: an in vitro study

The research exploiting the ability of dental materials to induce or prevent secondary caries (SC) development still seems inconclusive. Controlling bacterial adhesion by releasing bacteriostatic ions and improving the surface structure has been suggested to reduce the occurrence of SC. This paper analyses the impact of five distinctively composed dental materials on cariogenic biofilm formation. Forty-five specimens of three composites (CeramX Spectra ST, Admira Fusion, Beautifil II) and two glass-ionomers (Fuji II LC, Caredyne Restore), respectively, were incubated in bacterial suspension composed of Streptococcus mutans, Lactobacillus acidophilus, Streptococcus mitis, Streptococcus sanguinis, and Streptococcus salivarius at pH 7.0 and 5.5. Coverslips were used as a control. Adhered bacteria were collected after 2, 4, 6, 12, 24, and 48 h and analyzed using quantitative polymerase chain reaction (qPCR). Fluoride leakage was measured at each collection. The specimens' surface topography was assessed using interferometry. In the present study, surface roughness seemed to have a partial role in bacterial adhesion and biofilm formation, together with chemical composition of the materials tested. Despite differences in fluoride leakage, biofilm accumulation was similar across materials, but the number of adhered bacteria differed significantly. A release of other ions may also affect adhesion. These variations suggest that certain materials may be more prone to initiating secondary caries.

Inhibitory Effects of Surface Pre-Reacted Glass Ionomer Filler Eluate on Streptococcus mutans in the Presence of Sucrose

The surface pre-reacted glass ionomer (S-PRG) filler is a type of bioactive functional glass that releases six different ions. This study examined the effects of the S-PRG filler eluate on Streptococcus mutans in the presence of sucrose. In a solution containing S. mutans, the concentrations of BO33-, Al3+, Sr2+, and F- were significantly higher in the presence of the S-PRG filler eluate than in its absence (p < 0.001). The concentrations of these ions further increased in the presence of sucrose. Additionally, the S-PRG filler eluate significantly reduced glucan formation by S. mutans (p < 0.001) and significantly increased the pH of the bacterial suspension (p < 0.001). Bioinformatic analyses revealed that the S-PRG filler eluate downregulated genes involved in purine biosynthesis (purC, purF, purL, purM, and purN) and upregulated genes involved in osmotic pressure (opuAa and opuAb). At a low pH (5.0), the S-PRG filler eluate completely inhibited the growth of S. mutans in the presence of sucrose and significantly increased the osmotic pressure of the bacterial suspension compared with the control (p < 0.001). These findings suggest that ions released from the S-PRG filler induce gene expression changes and exert an inhibitory effect on S. mutans in the presence of sucrose.

Antimicrobial effects of surface pre-reacted glass-ionomer (S-PRG) eluate against oral microcosm biofilm

This study investigated the antimicrobial activity of surface pre-reacted glass ionomer eluate (S-PRG) against oral microcosm biofilms collected from the oral cavity of patients. Dental biofilm samples were collected from three volunteers to form microcosm biofilms in vitro. Initially, screening tests were carried out to determine the biofilm treatment conditions with S-PRG eluate. The effects of a daily treatment for 5 min using three microcosm biofilms from different patients was then evaluated. For this, biofilms were formed on tooth enamel specimens for 120 h. Biofilms treated with 100% S-PRG for 5 min per day for 5 days showed a reduction in the number of total microorganisms, streptococci and mutans streptococci. SEM images confirmed a reduction in the biofilm after treatment. Furthermore, S-PRG also reduced lactic acid production. It was concluded that S-PRG eluate reduced the microbial load and lactic acid production in oral microcosm biofilms, reinforcing its promising use as a mouthwash agent.

The Effect of Mechanical Alteration on Repair Bond Strength of S-PRG-Filler-Based Resin Composite Materials

This study investigates the impact of mechanical alteration on resin composite surfaces and its subsequent effect on repair bond strength. A total of 100 resin composite disks were prepared and were allocated for 24 h or 1 year of artificial aging. Specimens were embedded in epoxy resin, and the composite surfaces were mechanically altered using either diamond burs or air abrasion with aluminum oxide or glass beads. A universal bonding material was applied and a 2 mm circular and 3 mm high repair composite cylinder were prepared using a Teflon mold. Then, the specimens were tested for their shear bond strength, and the de-bonded specimens were observed under a scanning electron microscope to determine the failure pattern. SPSS 26.0 statistical software was used to analyze the data. Two-way ANOVA showed a statistically significant effect of mechanical alteration and aging on the shear bond strength of S-PRG-filler-based resin composite (p < 0.05). Surface modification with a fine diamond bur showed a significantly higher bond strength in both 24-h- and 1-year-aged specimens. Surface modification with alumina significantly increased the bond strength of 1-year-aged specimens; however, it was statistically insignificant for 24 h-aged specimens. Mechanical alteration with a fine diamond bur and 50-micron alumina can improve the repair bond strength of the composite.

Single-session associative protocol for dentin hypersensitivity management: a 1-year randomized, blinded clinical study

Objectives

This study aimed to establish a single-session associative protocol for non-restorative management of dentin hypersensitivity (DH).

Materials and Methods

Twenty-four individuals with DH and a minimum sensitivity level of 4 on the visual analog scale (VAS) were selected. The study was conducted in a split-mouth design, with each participant (n = 20) having at least 1 affected tooth in all quadrants. The management protocols consisted of control group: universal adhesive, Neural Desensitizing Protocol group: 5% potassium nitrate, Mixed Desensitizing Protocol (PAM) group: 5% sodium fluoride and 5% potassium nitrate, Remineralizing Desensitizing Protocol (PDR) group: surface-partially reacted glass technology photopolymerizable varnish. Evaluations were performed immediately after application, at 1 week, 1 month, 2 months, and 12 months using the VAS sensitivity test.

Results

The scores were subjected to statistical analysis using the Friedman test (p < 0.05), Durbin-Conover test (p < 0.05), and Wilcoxon test (p < 0.05). At the 12-month evaluation, all groups showed statistically significant differences compared to the initial assessment. For the evaluation after 12 months, there was a statistically significant difference between the PAM group, the control group, and the PDR group.

Conclusions

It can be concluded that all groups were effective in controlling DH, but there were significant results in the control group and PDR group. The clinical relevance of this study is to demonstrate that the application of single-session desensitizing protocols can be effective in controlling DH for up to 12 months.

Trial Registration

Brazilian Clinical Trials Registry Identifier: RBR-4r63d7s.

Bioactivity of human dental pulp-derived stem cells with boron-controlled S-PRG filler eluate by anion exchange

Surface pre-reacted glass-ionomer (S-PRG) filler is a bioactive glass filler capable of releasing various ions. A culture medium to which was added an S-PRG filler eluate rich in boron was reported to enhance alkaline phosphatase (ALP) activity in human dental pulp-derived stem cells (hDPSC). To clarify the role of boron eluted from S-PRG fillers, the modified S-PRG filler eluate with different boron concentrations was prepared by using an anion exchange material. Therefore, elemental mapping analysis of anion exchange material, adsorption ratio, hDPSCs proliferation and ALP activity were evaluated. For statistical analysis, Kruskal-Wallis test was used, with statistical significance determined at p<0.05. ALP activity enhancement was not observed in hDPSC cultured in the medium that contained the S-PRG filler eluate from which boron had been removed. The result suggested the possibility that an S-PRG filler eluate with controlled boron release could be useful for the development of novel dental materials.

Antibiofilm Properties and Demineralization Suppression in Early Enamel Lesions Using Dental Coating Materials

This study aimed to investigate the effects of dental coating materials on Streptococcus mutans biofilm formation. The test materials were PRG Barrier Coat (PRG), BioCoat Ca (BioC), and FluorDental Jelly (FluorJ). Bovine enamel specimens were demineralized to mimic early enamel lesions. The biofilm was developed on a specimen treated with one of the materials by using a modified Robbins device flow-cell system. Scanning electron and fluorescence confocal laser scanning microscopy, viable and total cell counts, and gene expression assessments of the antibiofilm were performed. Ion incorporation was analyzed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyzer. All materials allowed biofilm formation but reduced its volume. FluorJ was the only material that inhibited biofilm accumulation and had a bactericidal effect, revealing 0.66 log CFU in viable cells and 1.23 log copy reduction in total cells compared with the untreated group after 24 h of incubation. The ions released from PRG varied depending on the element. BioC contributed to enamel remineralization by supplying calcium ions while blocking the acid produced from the biofilm. In summary, the dental coating materials physically prevented acid attacks from the biofilm while providing ions to the enamel to improve its mechanical properties.

Effects of Sr2+, BO33-, and SiO32- on Differentiation of Human Dental Pulp Stem Cells into Odontoblast-Like Cells

This study aimed to clarify the effects of strontium (Sr2+), borate (BO33-), and silicate (SiO32-) on cell proliferative capacity, the induction of differentiation into odontoblast-like cells (OLCs), and substrate formation of human dental pulp stem cells (hDPSCs). Sr2+, BO33-, and SiO32- solutions were added to the hDPSC culture medium at three different concentrations, totaling nine experimental groups. The effects of these ions on hDPSC proliferation, calcification, and collagen formation after 14, 21, and 28 days of culture were evaluated using a cell proliferation assay, a quantitative alkaline phosphatase (ALP) activity assay, and Alizarin Red S and Sirius Red staining, respectively. Furthermore, the effects of these ions on hDPSC differentiation into OLCs were assessed via quantitative polymerase chain reaction and immunocytochemistry. Sr2+ and SiO32- increased the expression of odontoblast markers; i.e., nestin, dentin matrix protein-1, dentin sialophosphoprotein, and ALP genes, compared with the control group. BO33- increased the ALP gene expression and activity. The results of this study suggested that Sr2+, BO33-, and SiO32- may induce hDPSC differentiation into OLCs.

In vitro analysis of durability of S-PRG filler-containing composite crowns for primary molar restoration

OBJECTIVE

To evaluate the reliability, maximum principal stress, shear stress, and crack initiation of a computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite (RC) incorporating surface pre-reacted glass (S-PRG) filler for primary molar teeth.

METHODS

Mandibular primary molar crowns fabricated by experimental (EB) or commercially available CAD/CAM RCs (HC) were prepared and cemented to a resinous abutment tooth using an adhesive resin cement (Cem) or a conventional glass-ionomer cement (CX). These specimens were subjected to a single compressive test (n = 5/each) and the step-stress accelerated life testing (SSALT) (n = 12/each). Data was evaluated using Weibull analyses and reliability was calculated. Afterwards, the maximum principal stress and crack initiation point of each crown was analyzed by finite element analysis. To evaluate bonding of EB and HC to dentin, microtensile bond strength (μTBS) testing was conducted using primary molar teeth (n = 10/each).

RESULTS

There was no significant difference between the fracture loads of EB and HC for either cement (p > 0.05). The fracture loads of EB-CX and HC-CX were significantly lower than EB-Cem and HC-Cem (p < 0.05). The reliability at 600 N for EB-Cem was greater than that for EB-CX, HC-Cem, and HC-CX. The maximum principal stress concentrated on EB was lower than that on HC. The shear stress concentrated in the cement layer for EB-CX was higher than that for HC-CX. There was no significant difference among the μTBSs of EB-Cem, EB-CX, HC-Cem, and HC-CX (p > 0.05).

SIGNIFICANCE

The crowns fabricated with the experimental CAD/CAM RC incorporating S-PRG filler yielded greater fracture loads and reliability than the crowns manufactured with commercially available CAD/CAM RC regardless of the luting materials. These findings suggest that the experimental CAD/CAM RC crown may be clinically useful for the restoration of primary molars.

Antibacterial Activity of a Bioactive Tooth-Coating Material Containing Surface Pre-Reacted Glass in a Complex Multispecies Subgingival Biofilm

Bioactive materials were developed with the ability to release fluoride and provide some antimicrobial potential, to be widely used in dentistry today. However, few scientific studies have evaluated the antimicrobial activity of bioactive surface pre-reacted glass (S-PRG) coatings (PRG Barrier Coat, Shofu, Kyoto, Japan) on periodontopathogenic biofilms. This study evaluated the antibacterial activity of S-PRG fillers on the microbial profile of multispecies subgingival biofilms. A Calgary Biofilm Device (CBD) was used to grow a 33-species biofilm related to periodontitis for 7 days. The S-PRG coating was applied on CBD pins from the test group and photo-activated (PRG Barrier Coat, Shofu), while the control group received no coating. Seven days after treatment, the total bacterial counts, metabolic activity, and microbial profile of the biofilms were observed using a colorimetric assay and DNA-DNA hybridization. Statistical analyses were applied; namely, the Mann-Whitney, Kruskal-Wallis, and Dunn's post hoc tests. The bacterial activity of the test group was reduced by 25.7% compared with that of the control group. A statistically significant reduction was observed for the counts of 15 species: A. naeslundii, A. odontolyticus, V. parvula, C. ochracea, C. sputigena, E. corrodens, C. gracilis, F. nucleatum polymorphum, F. nucleatum vincentii, F. periodonticum, P. intermedia, P. gingivalis, G. morbillorum, S. anginosus, and S. noxia (p ≤ 0.05). The bioactive coating containing S-PRG modified the composition of the subgingival biofilm in vitro, thereby decreasing colonization by pathogens.

Effect of Biosilicate® Addition on Physical-Mechanical and Biological Properties of Dental Glass Ionomer Cements

This study investigated the influence of incorporating Biosilicate^® on the physico-mechanical and biological properties of glass ionomer cement (GIC). This bioactive glass ceramic (23.75% Na₂O, 23.75% CaO, 48.5% SiO₂, and 4% P₂O₅) was incorporated by weight (5%, 10%, or 15%) into commercially available GICs (Maxxion R and Fuji IX GP). Surface characterization was made by SEM (n = 3), EDS (n = 3), and FTIR (n = 1). The setting and working (S/W time) times (n = 3) and compressive strength (CS) were analyzed (n = 10) according to ISO 9917-1:2007. The ion release (n = 6) was determined and quantified by ICP OES and by UV-Vis for Ca, Na, Al, Si, P, and F. To verify cell cytotoxicity, stem cells from the apical papilla (SCAP) were exposed to eluates (n = 3, at a ratio of 1.8 cm²/mL) and analyzed 24 h post-exposure. Antimicrobial activity against Streptococcus mutans (ATCC 25175, NCTC 10449) was analyzed by direct contact for 2 h (n = 5). The data were submitted for normality and lognormality testing. One-way ANOVA and Tukey's test were applied for the working and setting time, compressive strength, and ion release data. Data from cytotoxicity and antimicrobial activity were submitted for Kruskal-Wallis' testing and Dunn's post hoc test (α = 0.05). Among all experimental groups, only those with 5% (wt) of Biosilicate^® showed better surface quality. Only M5% showed a comparable W/S time to the original material (p = 0.7254 and p = 0.5912). CS was maintained for all Maxxion R groups (p > 0.0001) and declined for Fuji IX experimental groups (p < 0.0001). The Na, Si, P, and F ions released were significantly increased for all Maxxion R and Fuji IX groups (p < 0.0001). Cytotoxicity was increased only for Maxxion R with 5% and 10% of Biosilicate^®. A higher inhibition of S. mutans growth was observed for Maxxion R with 5% of Biosilicate^® (less than 100 CFU/mL), followed by Maxxion R with 10% of Biosilicate^® (p = 0.0053) and Maxxion R without the glass ceramic (p = 0.0093). Maxxion R and Fuji IX presented different behaviors regarding Biosilicate^® incorporation. The impacts on physico-mechanical and biological properties were different depending on the GIC, but therapeutic ion release was increased for both materials.

Effect of laser bleaching, ultrasonic scaling and powered tooth brushing on surface roughness and bacterial adherence of class V composite restorations

Objective

To evaluate and compare the effect of diode laser assisted bleaching, ultrasonic scaling and powered tooth brushing on surface roughness and bacterial adherence on class V cavities restored with composites.

Materials and methods

A total of one hundred and twenty samples (40 samples each of Brilliant Everglow, Beautifil II and Heytec-N) were prepared in standardized stainless steel molds. The samples were further subdivided into four subgroups i.e. one control group (without any intervention) and three experimental groups - diode laser assisted bleaching, ultrasonic scaling and powered tooth brushing consisting of 10 sample each. Surface roughness was measured quantitatively with the help of 3D Optical Profilometer. For bacterial adherence analysis S. mutans strain (ATCC 25175) was cultured in BHI medium and samples were evaluated for the presence of viable bacteria using the Colony Forming Unit (CFU) count. Results obtained were then tabulated and subjected to statistical analysis.

Results

Diode laser bleaching caused a significant increase in surface roughness and bacterial adherence with lowest mean change exhibited by Heytec-N followed by Beautifil II and highest by Brilliant Everglow group. Similarly, Ultrasonic scaling increased the surface roughness of all the three tested samples with significant difference between the groups. Powered tooth brushing had no effect on the surface roughness and bacterial adherence of the tested composites.

Conclusion

Diode assisted laser bleaching and ultrasonic caused significantly higher surface roughness and bacterial adherence values for all the tested composites. It may therefore be recommended to do finishing and polishing of restorations after such procedures.

Multiple-Ion Releasing Bioactive Surface Pre-Reacted Glass-Ionomer (S-PRG) Filler: Innovative Technology for Dental Treatment and Care

Surface Pre-Reacted Glass-ionomer (S-PRG) filler, which releases strontium (Sr²⁺), borate (BO₃^3-), fluoride (F^-), sodium (Na⁺), silicate (SiO₃^2-), and aluminum (Al³⁺) ions at high concentrations, is a unique glass filler that are utilized in dentistry. Because of its multiple-ion releasing characteristics, S-PRG filler exhibits several bioactivities such as tooth strengthening, acid neutralization, promotion of mineralization, inhibition of bacteria and fungi, inhibition of matrix metalloproteinases, and enhancement of cell activity. Therefore, S-PRG filler per se and S-PRG filler-containing materials have the potential to be beneficial for various dental treatments and care. Those include restorative treatment, caries prevention/management, vital pulp therapy, endodontic treatment, prevention/treatment of periodontal disease, prevention of denture stomatitis, and perforation repair/root end filling. This review summarizes bioactive functions exhibited by S-PRG filler and its possible contribution to oral health.

Effect of Particle Sizes and Contents of Surface Pre-Reacted Glass Ionomer Filler on Mechanical Properties of Auto-Polymerizing Resin

Herein, the mechanical properties of an auto-polymerizing resin incorporated with a surface pre-reacted glass ionomer (S-PRG) filler were evaluated. For this, S-PRG fillers with particle sizes of 1 μm (S-PRG-1) and 3 μm (S-PRG-3) were mixed at 10, 20, 30, and 40 wt% to prepare experimental resin powders. The powders and a liquid (powder/liquid ratio = 1.0 g/0.5 mL) were kneaded and filled into a silicone mold to obtain rectangular specimens. The flexural strength and modulus (n = 12) were recorded via a three-point bending test. The flexural strengths of S-PRG-1 at 10 wt% (62.14 MPa) and S-PRG-3 at 10 and 20 wt% (68.68 and 62.70 MPa, respectively) were adequate (>60 MPa). The flexural modulus of the S-PRG-3-containing specimen was significantly higher than that of the S-PRG-1-containing specimen. Scanning electron microscopy observations of the specimen fracture surfaces after bending revealed that the S-PRG fillers were tightly embedded and scattered in the resin matrix. The Vickers hardness increased with an increasing filler content and size. The Vickers hardness of S-PRG-3 (14.86–15.48 HV) was higher than that of S-PRG-1 (13.48–14.97 HV). Thus, the particle size and content of the S-PRG filler affect the mechanical properties of the experimental auto-polymerizing resin.

The inhibitory effects of various ions released from S-PRG fillers on dentin protease activity

This study investigates the effect of ions released from S-PRG fillers on host-derived enzymatic degradation of dentin collagen matrices. Dentin beams (n=80) were demineralized and distributed to eight groups following baseline dry mass and total MMP activity assessments. Each group treated with boron, fluoride, sodium, silicone, strontium, aluminium, or S-PRG eluate solutions for 5 min. Untreated beams served as control. After pre-treatment, MMP activity was reassessed, beams were incubated in complete medium for 1 week, dry mass was reassessed. Incubation media were analyzed for MMP and cathepsin-K-mediated degradation fragments. Data were analyzed with ANOVA and Tukey's test. All pretreatment groups showed significant reduction in total MMP activity (p<0.05) that was sustainable after incubation in all groups except for boron and silicone groups (p<0.05). Cathepsin-K activity did not differ between control or treatment groups. The results indicated that ions released from S-PRG fillers have the potential to partly inhibit MMP-mediated endogenous enzymatic activity.

Bacterial adhesion and antibacterial property of coating materials containing theobromine and S-PRG filler

Theobromine (TB) has been reported to promote tooth remineralization, strengthen tooth substance, and relieve dentin hypersensitivity. This study aimed to evaluate experimental tooth coating materials containing TB and surface pre-reacted glass-ionomer (S-PRG) fillers by examining the effects on bacterial adhesion and antibacterial properties. In addition, the amount of TB eluted from the coating material was measured. There was no significant difference in bacterial adhesion depending on the presence or absence of TB in the coating material, however, a significant decrease in the amount of bacterial adhesion was observed when S-PRG fillers were added to the coating material. The amount of eluted TB did not differ depending on the type of the filler in the coating material. It was suggested that TB could be used to develop a new dental material with the potential ability to inhibit the initiation and progression of dental caries.

Impact of surface pre-reacted glass ionomer filler eluate on lipase gene expression in Candida albicans: An in vitro study

Although a surface pre-reacted glass ionomer (S-PRG) exerts a suppressive effect on Candida albicans (C. albicans) activity and growth, its influence on the expression of the lipase gene (LIP) family including LIP1-LIP10, an indicator of clinical infection, has not yet been investigated. Therefore, in this study, we evaluated the effect of S-PRG filler eluates on LIP expression in C. albicans using real-time reverse-transcription polymerase chain reaction. Candida albicans was treated with an S-PRG filler diluted at ratios of 1:32 and 1:64 for 24 h at 37°C. The diluted S-PRG filler eluates (1:32) suppressed lipase activity in C. albicans by downregulating LIP5 (0.54±0.25 relative to that of the control) and LIP8 (0.35±0.074) expression after 24 h, which corresponded with decreased lipase activity. At a dilution factor of 1:64, there was no significant difference in LIP expression. Thus, the S-PRG filler eluate has potential to suppress fungal activity by downregulating LIP expression.

Optimal Surface Pre-Reacted Glass Filler Ratio in a Dental Varnish Effective for Inhibition of Biofilm-Induced Root Dentin Demineralization

A unique type of dental varnish (DV) containing surface pre-reacted glass (S-PRG) fillers of different concentrations was evaluated to determine the unpresented optimal ratio for inhibiting root dentin bio-demineralization. S-PRG DVs (10% to 40%)—10%-S, 20%-S, 30%-S, and 40%-S—were applied to bovine root dentin blocks and compared with controls—0%-f (no S-PRG) and 5%-NaF (5%-NaF). The Streptococcus mutans biofilm challenge was executed inside and outside an oral biofilm reactor for 7 days. The specimens were examined using a confocal laser scanning microscope and swept-source optical coherence tomography. Furthermore, they were observed using a scanning electron microscope and analyzed using energy-dispersive X-ray spectroscopy. The roughness (SzJIS) due to leaching of DV materials and demineralization depth were significantly less in the S-PRG groups than the control groups (p < 0.05). Complete or partially plugged dentinal tubules (DTs) were observed in 20%-S, 30%-S, and 40%-S, while wide-open DTs were observed more in controls. Cylindrical tags were present in groups containing more than 20% S-PRG. F, Na, Al, and Sr were detected in a higher percentile ratio in the 20%-S, 30%-S, and 40%-S groups compared to 0%-f and 10%-S. Nonetheless, it is suggested that incorporating 20% to 30% S-PRG fillers in DVs would be effective enough as an anti-demineralization coating, together with supplementing minerals; further evaluation is required to validate these findings.

Bismuth Quantum Dot (Bi QD)/Polydimethylsiloxane (PDMS) Nanocomposites with Self-Cleaning and Antibacterial Activity for Dental Applications

In the oral microenvironment, bacteria colonies are easily aggregated on the tooth-restoration surface, in the manner of a biofilm, which usually consists of heterogeneous structures containing clusters of a variety of bacteria embedded in an extracellular matrix, leading to serious recurrent caries. In this contribution, zero-dimensional (0D) bismuth (Bi) quantum dots (QDs) synthesized by a facile solvothermal method were directly employed to fabricate a Bi QD/polydimethylsiloxane (PDMS)-modified tooth by simple curing treatment. The result demonstrates that the as-fabricated Bi QD/PDMS-modified tooth at 37 °C for 120 min not only showed significantly improved hydrophobic performance with a water contact angle of 103° and 115° on the tooth root and tooth crown, respectively, compared to that (~20° on the tooth root, and ~5° on the tooth crown) of the pristine tooth, but also exhibited excellent antibacterial activity against S. mutans, superior biocompatibility, and biosafety. In addition, due to the highly photothermal effect of Bi QDs, the antibacterial activity of the as-fabricated Bi QD/PDMS-modified tooth could be further enhanced under illumination, even at a very low power density (12 mW cm^-2). Due to the facile fabrication, excellent hydrophobicity, superior antibacterial activity, and biocompatibility and biosafety of the Bi QD/PDMS-modified tooth, it is envisioned that the Bi QD/PDMS-modified tooth with a fascinating self-cleaning and antibacterial performance can pave the way to new designs of versatile multifunctional nanocomposites to prevent secondary caries in the application of dental restoration.

Effect of surface prereacted glass ionomer nanofillers on fluoride release, flexural strength, and surface characteristics of polymethylmethacrylate resin

OBJECTIVE

Dentures should have proper fluoride release and physical properties. We evaluated how surface prereacted glass ionomer (S-PRG) nanofillers influenced fluoride release, flexural strength, and surface characteristics of polymethylmethacrylate (PMMA) resin.

MATERIALS AND METHODS

PMMA resin disc (n = 14) and rectangular (n = 5) specimens containing 0, 20 wt% microparticles, and 20 wt% nanoparticles of S-PRG were prepared. Six-disc specimens were examined for surface roughness; eight-disc specimens were immersed in 5 ml of deionized water for 24 h before analyzing the fluoride levels on days 1-3, 12, and 15. They were recharged with 1000 ppm fluoride solution for 24 h and stored in deionized water for five cycles. Fluoride release was examined. The flexural strength of the rectangular specimens was determined using a three-point bending test. Data were analyzed by two-way repeated-measures ANOVA.

RESULTS

S-PRG nanofiller had the highest fluoride exchange rate and did not significantly change the surface roughness compared with the microparticle and control groups; however, the nanofillers agglomerated and reduced the flexural strength to below 65 MPa.

CONCLUSIONS

Incorporating 20 wt% nanofillers into resin enhanced the fluoride exchange property greater than microfillers at the same content, but diminished the mechanical properties of the resin.

CLINICAL SIGNIFICANCE

Incorporating 20 wt% S-PRG nanofillers in resin denture base can improve the fluoride releasing property without affecting the surface roughness.

Antibacterial Performance of Composite Containing Quaternary Ammonium Silica (QASi) Filler - a Preliminary Study

BACKGROUND

Antibacterial composite will have a significant clinical advantage in controlling caries. This study tests the antibacterial properties of a novel bulk-fill flowable composite (Infinx™, Nobio™ Ltd.) containing quaternary ammonium silica (QASi) filler particles.

METHODS

Infinix™ was tested in-vitro by the direct contact test (DCT), using E. faecalis or whole saliva as inoculum. A similar formula composite without QASi served as a control. In addition, composite test samples were polymerized on three volunteers' intact buccal enamel surfaces of mandibular first premolars in a split-mouth design experiment. Traditional composite served as control (Filtekt Bulk Fill™ 3M). Bacterial viability on the composite surfaces weres assessed ex-vivo microscopically six months later, using a fluorescent dead/live stain. Images of each bacterial sample were taken using a fluorescent microscope (Nikon Eclipse 80i), and further live/total cell analysis was performed using ImageJ software.

RESULTS

Following direct contact with one week of aged Infinix, more than 1 million E. faecalis bacteria were killed. Similarly, when using the saliva as inoculum, no single microorganism survived. Six-month in-vivo experiments supported these results by showing a reduction of 54%, 30% and 28% in live/total number of bacteria ratio retrieved from antibacterial composite vs. the control in volunteers #1, #2, #3 respectively.

CONCLUSION

Within the limitations of the experimental design, the present study suggest that antibacterial activity of quaternary ammonium silica particles (QASi) is comparable to that of previously described quaternary ammonium polyethyleneimine particles (QPEI). In addition, whole saliva bacteria are effectively killed by QASi-containing composite in-vitro and in-vivo, for a period of six month at least. Long-term full-scale clinical study is needed to confirm the findings of the present study and their implication on maintaining health balance.

CLINICAL SIGNIFICANCE

Antibacterial composites containing QASi filler is a novel class of restoratives that may contributes to caries lesion control.

Biological properties of lithium-containing surface pre-reacted glass fillers as direct pulp-capping cements

OBJECTIVE

Surface pre-reacted glass fillers (S-PRG) can release different types of ions and in our previous study, we modified these fillers with lithium chloride (S-PRG/Li-100 mM) to induce reparative dentin formation by activating the Wnt/β-catenin signaling pathway. Here, we assessed the biological performance of S-PRG/Li-100 mM and compared it with that of mineral trioxide aggregate (MTA) and S-PRG without additives.

METHODS

In vivo studies were conducted on male Wistar rats using Masson's trichrome staining in pulp-capped molars. The test materials were implanted subcutaneously to evaluate their capacity for vascularization and biocompatibility. The ability of the test materials to form apatite was tested by immersing them in simulated body fluid. Rhodamine-B staining was conducted to assess their sealing ability in bovine teeth, while their antibacterial activity was evaluated against Streptococcus mutans and Lactobacillus casei in terms of colony-forming units and by live/dead staining.

RESULTS

Masson's trichrome staining and tissue-implantation tests confirmed the biocompatibility of S-PRG/Li-100 mM and it was similar to that of MTA and S-PRG; inflammation regression was observed 14 days after operation in the subcutaneous tissues. S-PRG/Li-100 mM promoted the formation of apatite on its surface. Both the S-PRG groups showed higher sealing capability and bactericidal/bacteriostatic activity against oral bacterial biofilms than MTA.

SIGNIFICANCE

Lithium-containing surface pre-reacted glass cements exhibit better antibacterial and sealing capabilities than MTA, suggesting their potential as high-performance direct pulp-capping materials.

Giomer composite compared to glass ionomer in occlusoproximal ART restorations of primary molars: 24-month RCT

BACKGROUND

Occlusoproximal restorations of primary molars usually fail, so it is necessary to investigate new materials that may overcome this challenge. Thus, this trial aimed to evaluate the longevity of occlusoproximal ART restorations in primary molars using a glass ionomer cement - GIC (Equia Forte^® - GC Corp) and a Giomer resin composite - GCR (Beautifil Bulk Restorative^® - Shofu Inc) after 24 months.

METHODS

One hundred and eighty-two (182) children aged from 4 to 8 years were selected and randomly assigned to GIC or GCR. A paediatric dentist treated them in the school setting in Cerquilho, Brazil, and the restorations were assessed after 3, 6, 12, 18 and 24 months. The primary outcome was the restoration survival, evaluated using the Kaplan-Meier and superiority Cox regression analyses. Intention to treat (ITT) was performed as a sensitivity analysis using superiority test P value and confidence interval (CI = 95%). Independent variables included gender, age, molar, jaw, cavity volume and caries experience.

RESULTS

The restoration survival after 24 months was GIC = 58.1% and GCR = 49.1% (HR = 1.24; CI = 0.97-1.59). ITT analysis showed a success of GIC = 61.1% and GCR = 52.2% (RR = 1.17; CI = 0.91-1.52). The superiority hypothesis was not proved in both analyses (P > 0.05).

CONCLUSION

GCR does not have superior longevity than GIC in occlusoproximal ART restorations of primary molars.

Inhibitory effect of a gel paste containing surface pre-reacted glass-ionomer (S-PRG) filler on the cariogenicity of Streptococcus mutans

Surface pre-reacted glass-ionomer (S-PRG) filler is a bioactive functional glass that releases six different ions. Although several dental materials containing S-PRG filler have been developed, few self-care products containing S-PRG filler have been reported. We investigated the inhibitory effects of PRG gel paste containing S-PRG filler on Streptococcus mutans, a major pathogen of dental caries. PRG gel paste inhibited bacterial growth of S. mutans in a concentration-dependent manner, and all S. mutans were killed in the presence of ≥ 1% PRG gel paste. Additionally, it was difficult for S. mutans to synthesize insoluble glucan from sucrose in the presence of 0.1% PRG gel paste. A biofilm formation model was prepared in which slices of bovine enamel were infected with S. mutans after treatment with or without PRG gel paste. Biofilm formation was inhibited significantly more on the enamel treated with PRG gel paste than on enamel without PRG gel paste (P < 0.001). The inhibitory effects on bacterial growth and biofilm formation were more prominent with PRG gel paste than with S-PRG-free gel paste, suggesting that PRG gel paste may be effective as a self-care product to prevent dental caries induced by S. mutans.

Physical properties and wear behavior of CAD/CAM resin composite blocks containing S-PRG filler for restoring primary molar teeth

OBJECTIVES

This study aimed to develop computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks (RCBs) containing surface pre-reacted glass-ionomer (S-PRG) filler for primary molar teeth and evaluate their physical properties and wear resistance.

METHODS

Experimental CAD/CAM RCBs containing S-PRG filler for primary molar teeth (EB), a commercial CAD/CAM RCB (HC), two resin composites for primary teeth (BKP and BKZ) and one for permanent teeth (BⅡ) were used. Hardness tests, three-point bending tests, fracture toughness tests, and water absorption tests were conducted. Wear tests were conducted for these materials and stainless steel crowns (SSCs).

RESULTS

The Vickers hardness of EB was lower than that of HC (p < 0.05), and there was no significant difference among BKZ, BKP, and BⅡ (p > 0.05). After 1 week of water immersion, EB and HC showed greater flexural strength than the other materials (p < 0.05). EB showed greater fracture toughness than the other materials (p < 0.05). The water absorption of EB was lower than that of HC, BKZ, and BKP (p < 0.05), and greater than that of BⅡ (p < 0.05). Antagonist wear was significantly smaller in EB than in HC and BⅡ (p < 0.05), and significantly greater than in BKZ (p < 0.05). Antagonist wear could not be measured in SSC because of excessive wear that was out of range of the surface roughness tester.

SIGNIFICANCE

The CAD/CAM RCBs containing S-PRG filler for primary molar teeth developed in this study demonstrated adequate physical properties and wear performance, suggesting that they are suitable for restoration of primary molar teeth and could function in place of SSCs.

Tissue Conditioner Incorporating a Nano-Sized Surface Pre-Reacted Glass-Ionomer (S-PRG) Filler

We aimed to evaluate the properties of a novel tissue conditioner containing a surface pre-reacted glass-ionomer (S-PRG) nanofiller. Tissue conditioners containing 0 (control), 2.5, 5, 10, 20, or 30 wt% S-PRG nanofiller or 10 or 20 wt% S-PRG microfiller were prepared. The S-PRG nanofillers and microfillers were observed using scanning electron microscopy. The ion release, acid buffering capacity, detail reproduction, consistency, Shore A0 hardness, surface roughness, and Candida albicans adhesion of the tissue conditioners were examined. The results indicated that the nanofiller particles were smaller and more homogeneous in size than the microfiller particles. In addition, Al, B, F, and Sr ions eluted from S-PRG were generally found to decrease after 1 day. Acid neutralization was confirmed in a concentration-dependent manner. The mechanical properties of tissue conditioners containing S-PRG nanofiller were clinically acceptable according to ISO standard 10139-1:2018, although the surface roughness increased with increasing filler content. Conditioners with 5-30 wt% nanofiller had a sublethal effect on C. albicans and reduced fungal adhesion in vitro. In summary, tissue conditioner containing at least 5 wt% S-PRG nanofiller can reduce C. albicans adhesion and has potential as an alternative soft lining material.

Anti-Demineralization Effects of Dental Adhesive-Composites on Enamel-Root Dentin Junction

Oral biofilm reactor (OBR) and pH cycling (pHC) artificial caries model were employed to evaluate the anti-demineralization effects of four composite filling systems on enamel-root dentin junction. Sixty-four enamel-root dentin blocks (6 mm × 6 mm × 2 mm) each with a cylindrical cavity were randomly assigned to the pHC and OBR group, then four subgroups (n = 8) and filled with either the Beautifil II (BEF, SPRG-filler-containing) or Estelite (EST) composite after the adhesive (either Single Bond Universal (SBU) or FL Bond II (FL, SPRG-filler-containing)). The demineralization lesions of filling interface were examined by micro-computerized tomography (μCT) and swept-source-optical coherence tomography (SS-OCT). According to the degree of interface damage, the caries lesions were sorted into four types: Type A and B (no attachment loss); Type C and D (attachment loss). EST/SBU showed the worst demineralization lesion and attachment loss (100% Type D), while BEF/FL exhibited the shallowest lesion depth (p < 0.05, 145 ± 45 μm on enamel, 275 ± 35 μm on root dentin) and no attachment loss (75% Type A and 25% Type B). Using FL adhesive alone does not effectively reduce enamel demineralization. BEF plays a leading role in acid resistance. The combination of BEF and FL showed a cumulative synergistic effect on anti-demineralization.

Thermochromic Polyvinyl Alcohol-Iodine Hydrogels with Safe Threshold Temperature for Infectious Wound Healing

Iodophor (povidone-iodine) has been widely used for antibacterial applications in the clinic. Yet, limited progress in the field of iodine-based bactericides has been achieved since the invention of iodophor. Herein, a blue polyvinyl alcohol-iodine (PAI) complex-based antibacterial hydrogel is explored as a new generation of biocompatible iodine-based bactericides. The obtained PAI hydrogel maintains laser triggered liquefaction, thermochromic, and photothermal features for highly efficient elimination of bacteria. In vitro antibacterial test reveals that the relative bacteria viabilities of Escherichia coli (E.coli) and methicillin-resistant Staphylococcus aureus (MRSA) incubated with PAI hydrogel are only 8% and 3.8%, respectively. Upon single injection of the PAI hydrogel, MRSA-infected open wounds can be efficiently healed in only 5 days, and the healing speed is further accelerated by laser irradiation due to the dynamic interaction between iodine and polyvinyl alcohol, causing up to ∼29% of wound area being closed on day 1. In addition, a safe threshold temperature of skin scald (∼45 °C) emerges for PAI hydrogels because of thermochromic properties, avoiding thermal injuries during irradiation. In addition, no observed toxicity or skin irritation is observed for the PAI hydrogel. This work expands the category of iodine-based bactericides for safe and controllable management of infected wounds.

The biocompatibility of glass-fibre reinforced composites (GFRCs) - a systematic review

Purpose Fiber-reinforced composites (FRCs) have received considerable attention, owing to their potential use in dental prostheses or bone fracture fixation applications. The aim of this systematic review was to analyze and report the biological properties of FRCs reported in the existing literature.Study selections A systematic search of four databases (PubMed/MEDLINE, Scopus, Web of Science, and Cochrane library) was performed to identify all relevant studies published between 1962 and 2019. The search was limited to laboratory-based studies published in English. Citation mining was also performed through cross-referencing of included studies and hand searching of relevant journals.Results A total of 1283 potentially relevant articles were initially identified, and thirty-three articles were full-text screened. In the final ten studies included for review, four investigated bacterial adhesion and growth abilities on FRCs, four investigated the fibroblastic cytotoxicity of different surface-treated FRCs, and two investigated the osseointegration between bone and FRCs. Owing to the heterogeneity of fiber types, FRC-coating, and lack of standardized testing protocols, a meta-analysis was not feasible. The included studies indicated that glass fibers, and in particular E-glass fibers, are superior to ceramics and other FRCs in terms of bacterial adherence, fibroblast cytotoxicity, and cell viability.Conclusions Glass-fiber-reinforced composites are cytocompatible materials that possess satisfactory biological properties and can be used in dental prosthesis and craniofacial implants. Further research is necessary to regulate the matrix ion release/degradation of FRCs to prolong the initially demonstrated properties.

Novel antimicrobial denture adhesive containing S-PRG filler

The antimicrobial effects of denture adhesives containing novel surface pre-reacted glass-ionomer (S-PRG) fillers were assessed. We prepared denture adhesives containing S-PRG (particle sizes: 1 and 3 µm; quantities: 5, 7.5, and 10 wt%). We evaluated acid buffering capacity, ion release, and antimicrobial effects of denture adhesives with and without S-PRG. Significantly higher pH changes were observed in 1 µm S-PRG adhesives than in 3 µm S-PRG adhesives. Adhesives containing 7.5 and 10 wt% S-PRG exhibited significantly higher ion release than adhesives with 5 wt% S-PRG. The 1µm-10wt% S-PRG denture adhesive exhibited significantly lower colony-forming units on the denture adhesive contact surface than in the control group; additionally, it exhibited excellent acid buffering capacity, ion release properties, and antimicrobial effect against C. albicans, C. glabrata, S. mutans, and A. naeslundii. Longer contact periods resulted in significantly lower adhesion of Candida albicans to the denture base resin treated with denture adhesive.

Effects of multi-components released from S-PRG filler on the activities of human dental pulp-derived stem cells

Numerous studies have shown that the sustained release of ions from dental restorative materials have acid buffering capacity, prevents tooth enamel demineralization, and inhibits bacterial adhesion. Herein, the release behavior and bioresponsiveness of ions released from surface pre-reacted glass-ionomer (S-PRG) fillers were investigated in different types of media based on human dental pulp-derived stem cell (hDPSC) responses. The hDPSCs were cultured for 1-7 days in S-PRG eluates diluted with varying amounts of cell culture media. S-PRG released several types of ions, such as F^-, Sr²⁺, Na⁺, Al³⁺, BO₃^3-, and SiO₃^2-. The balance of eluted ions differed depending on the dilution and solvent, which in turn affected the cytotoxicity, cell morphology, cell proliferation, and alkane phosphatase activity of hDPSCs, among other properties. The results suggest that tailored S-PRG filler eluates could be designed and prepared for application in dental practice.

S-PRG Filler Eluate Induces Oxidative Stress in Oral Microorganism: Suppression of Growth and Pathogenicity, and Possible Clinical Application

Controlling the oral microbial flora is putatively thought to prevent not only oral diseases, but also systemic diseases caused by oral diseases. This study establishes the antibacterial effect of the novel bioactive substance “S-PRG filler” on oral bacteria. We examined the state of oxidative stress caused by the six types of ions released in eluate from the S-PRG filler in oral bacterial cells. Moreover, we investigated the effects of these ions on the growth and pathogenicity of Gram-positive and Gram-negative bacteria. We found that the released ions affected SOD amount and hydrogen peroxide in bacterial cells insinuating oxidative stress occurrence. In bacterial culture, growth inhibition was observed depending on the ion concentration in the medium. Additionally, released ions suppressed Streptococcus mutans adhesion to hydroxyapatite, S. oralis neuraminidase activity, and Porphyromonas gingivalis hemagglutination and gingipain activity in a concentration-dependent manner. From these results, it was suggested that the ions released from the S-PRG filler may suppress the growth and pathogenicity of the oral bacterial flora. This bioactive material is potentially useful to prevent the onset of diseases inside and outside of the oral cavity, which in turn may have possible applications for oral care and QOL improvement.

Effect of the S-PRG filler content in the multi-ion releasing paste on the acid resistance of the enamel surface after polishing with the paste

This study aimed to investigate the effect of the multi-ion releasing paste (MP) on the acid resistance of the enamel surface of an extracted human tooth. Five kinds of MP were prepared according to the content (wt%) of S-PRG fillers: 0 wt% (MP0, control), 1 wt% (MP1), 5 wt% (MP5), 20 wt% (MP20), and 30 wt% (MP30). The buccal coronal surfaces of the extracted anterior teeth were polished with each kind of MP for 1 min. After removing radicular parts, the coronal parts underwent a pH cycling, and then sliced to make thin sections. The lesion depth of each section was measured using a polarization microscope. Each lesion's depth of enamel polished with MP5, MP20, and MP30 was significantly shallower than that polished with MP0.

Recent Progress in Antimicrobial Strategies for Resin-Based Restoratives

Repairing tooth defects with dental resin composites is currently the most commonly used method due to their tooth-colored esthetics and photocuring properties. However, the higher than desirable failure rate and moderate service life are the biggest challenges the composites currently face. Secondary caries is one of the most common reasons leading to repair failure. Therefore, many attempts have been carried out on the development of a new generation of antimicrobial and therapeutic dental polymer composite materials to inhibit dental caries and prolong the lifespan of restorations. These new antimicrobial materials can inhibit the formation of biofilms, reduce acid production from bacteria and the occurrence of secondary caries. These results are encouraging and open the doors to future clinical studies on the therapeutic value of antimicrobial dental resin-based restoratives. However, antimicrobial resins still face challenges such as biocompatibility, drug resistance and uncontrolled release of antimicrobial agents. In the future, we should focus on the development of more efficient, durable and smart antimicrobial dental resins. This article focuses on the most recent 5 years of research, reviews the current antimicrobial strategies of composite resins, and introduces representative antimicrobial agents and their antimicrobial mechanisms.

Fabrication and characterization of remineralizing dental composites containing calcium type pre-reacted glass-ionomer (PRG-Ca) fillers

OBJECTIVE

To fabricate and characterize dental composites with calcium type pre-reacted glass-ionomer (PRG-Ca) fillers.

METHODS

PRG-Ca fillers were prepared by the reaction of calcium fluoroaluminosilicate glass with polyacrylic acid. Seven dental composites were produced from the same organic matrix (70/30wt% Bis-GMA/TEGDMA), with partial replacement of barium borosilicate (BaBSi) fillers (60wt%) by PRG-Ca fillers (wt%): E0 (0) - control, E1 (10), E2 (20), E3 (30), E4 (40), E5 (50) and E6 (60). Enamel remineralization was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), roughness (Ra), Knoop hardness (KHN), flexural strength (FS), flexural modulus (FM), water sorption (W_sp), water solubility (W_sl), and translucency (TP). Data were analyzed to one-way ANOVA and Tukey's HSD test (α=0.05).

RESULTS

All composites with PRG-Ca induced enamel remineralization. E0 and E1 presented similar and highest DC% than E2=E3=E4=E5=E6. Ra and KHN were not influenced by PRG-Ca fillers (p<0.05). The higher the content of PRG-Ca, the lower FS, FM and TP (p<0.05). W_sp increased linearly with the content of PRG-Ca fillers (p<0.05). E6 presented the highest W_sl (p<0.05), while the W_sl of the other composites were not different from each other (p>0.05).

SIGNIFICANCE

Incorporation of 10-40wt.% of PRG-Ca fillers endowed remineralizing potential to dental composites without jeopardizing the overall behavior of their physicochemical properties. Dental composites with PRG-Ca fillers seems to be a good alternative for reinforcing the enamel against caries development.

Micro-computed tomographic evaluation of single-cone obturation with three sealers

Objectives

This study used micro-computed tomography (µCT) to compare voids and interfaces in single-cone obturation among AH Plus, EndoSequence BC, and prototype surface pre-reacted glass ionomer (S-PRG) sealers and to determine the percentage of sealer contact at the dentin and gutta-percha (GP) interfaces.

Materials and Methods

Fifteen single-rooted human teeth were shaped using ProTaper NEXT size X5 rotary files using 2.5% NaOCl irrigation. Roots were obturated with a single-cone ProTaper NEXT GP point X5 with AH Plus, EndoSequence BC, or prototype S-PRG sealer (n = 5/group).

Results

The volumes of GP, sealer, and voids were measured in the region of 0–2, 2–4, 4–6, and 6–8 mm from the apex, using image analysis of sagittal µCT scans. GP volume percentages were: AH Plus (75.5%), EndoSequence BC (87.3%), and prototype S-PRG (94.4%). Sealer volume percentages were less: AH Plus (14.3%), EndoSequence BC (6.8%), and prototype S-PRG (4.6%). Void percentages were AH Plus (10.1%), EndoSequence BC (5.9%), and prototype S-PRG (1.0%). Dentin-sealer contact ratios of AH Plus, EndoSequence BC, and prototype S-PRG groups were 82.4% ± 6.8%, 71.6% ± 25.3%, and 70.2% ± 9.4%, respectively. GP-sealer contact ratios of AH Plus, EndoSequence BC, and prototype S-PRG groups were 65.6% ± 29.1%, 80.7% ± 25.8%, and 87.0% ± 8.6%, respectively.

Conclusions

Prototype S-PRG sealer created a low-void obturation, similar to EndoSequence BC sealer with similar dentin-sealer contact (> 70%) and GP-sealer contact (> 80%). Prototype S-PRG sealer presented comparable filling quality to EndoSequence BC sealer.

Ion Release From Prototype Surface Pre-Reacted Glass Ionomer (S-PRG) Sealer and EndoSequence BC Sealer

OBJECTIVE

Bioactive ions, when incorporated in an endodontic sealer, can contribute to the long-term success of endodontic therapy by combating the re-infection of a tooth and promoting the healing of the periapical bone. The objective of this study was to measure the release of boron, strontium, and silicon ions from surface pre-reacted glass ionomer (S-PRG) filler containing prototype endodontic sealer over a sustained period in comparison to EndoSequence BC sealer in a simulated clinical model using extracted human teeth in vitro.

METHODS

Twelve extracted human anterior teeth were instrumented using ProTaper Next (Dentsply Sirona, Johnson City, TN, USA) files up to size X3 (#30/variable taper) with copious 2.5% NaOCl irrigation. Teeth were obturated using a single-cone technique with a matching size tapered gutta-percha point and one of two endodontic sealers: prototype S-PRG (Shofu Inc., Kyoto, Japan) or EndoSequence BC (Brasseler, Savannah, GA, USA). The teeth were soaked in phosphate-buffered saline (PBS) solution for 336 hours. Periodically, 1-mL samples of the PBS were analyzed via an inductively coupled plasma mass spectrometer to determine the concentrations of ions released by the sealers.

RESULTS

The average (S.D.) cumulative release (ng/ml) of boron, silicon, and strontium ions over 2 weeks for the prototype S-PRG sealer was 8614.9 (1264.3), 35758.9 (5986.5), and 3965.2 (145.6), and for EndoSequence BC sealer was 1860.5 (82.7), 164648.7 (16468.1), and 227.7 (4.7). Generalized linear mixed model analysis showed significant differences in ion concentration among boron, silicon, and strontium over time between the two sealer groups (Boron: P<0.0001, Silicon: P=0.010, Strontium: P=0.028). Of the three ions, strontium had the lowest amount of release for both sealers. The prototype S-PRG sealer showed a rapid initial burst followed by a slow, continuous release of strontium ions.

CONCLUSION

The prototype S-PRG sealer released boron and strontium ions in higher cumulative concentrations over 2 weeks compared to the EndoSequence BC sealer. Both the prototype S-PRG and EndoSequence BC sealers released silicon ions, although significantly more were eluted from the EndoSequence BC sealer. Antimicrobial and osteogenic ion release from sealers is expected to positively influence the post-treatment control of microbial infections to improve periapical healing.

Pulp tissue reaction to a self-adhesive, resin-based direct pulp capping material containing surface pre-reacted glass-ionomer filler

OBJECTIVE

This study aimed to evaluate the effect of direct pulp capping using an experimental self-adhesive resin for direct pulp capping (SRD) containing silica and surface pre-reacted glass-ionomer (S-PRG) filler on pulpal healing and to monitor the dentin bridge formation in rat pulp 2-4 weeks after operation.

METHODS

Five types of SRDs (SRD-0: S-PRG fillers 0 wt%; SRD-1: S-PRG fillers 9.1 wt%; SRD-2: S-PRG fillers 18.4 wt%; SRD-3: S-PRG fillers 27.8 wt%; and SRD-6: S-PRG fillers 57.4 wt%) were prepared, and mineral trioxide aggregate (MTA) was used as control (n = 8). Direct pulp capping was performed on rats that were sacrificed for further evaluation 2 or 4 weeks after the operation. The pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and reparative dentin formation were histopathologically evaluated; the data were statistically analyzed using the Kruskal-Wallis and the Mann-Whitney U tests.

RESULTS

The histopathological evaluation of SRD-1-treated test animals 2 weeks post-operation revealed inferior PTD and ICI when compared with that of MTA. Even 4 weeks after the operation in SRD-1- and SRD-2-treated rats, the PTD and ICI were inferior when compared with those of MTA. The dental specimens of SRD-0 and MTA showed orthodentin formation, whereas SRD-treated test animals showed osteodentin formation at a position slightly deeper than the site of the pulpal exposure.

SIGNIFICANCE

The reparative dentin formed by SRD-0 and MTA was genuine, whereas that formed by SRD-3 and SRD-6 was ossified and ectopic. SRD may have the potential to be utilized clinically as a direct pulp capping material.

The biocompatibility of glass-fibre reinforced composites (GFRCs) - a systematic review

PURPOSE

Fiber-reinforced composites (FRCs) have received considerable attention, owing to their potential use in dental prostheses or bone fracture fixation applications. The aim of this systematic review was to analyze and report the biological properties of FRCs reported in the existing literature.

STUDY SELECTIONS

A systematic search of four databases (PubMed/MEDLINE, Scopus, Web of Science, and Cochrane library) was performed to identify all relevant studies published between 1962 and 2019. The search was limited to laboratory-based studies published in English. Citation mining was also performed through cross-referencing of included studies and hand searching of relevant journals.

RESULTS

A total of 1283 potentially relevant articles were initially identified, and thirty-three articles were full-text screened. In the final ten studies included for review, four investigated bacterial adhesion and growth abilities on FRCs, four investigated the fibroblastic cytotoxicity of different surface-treated FRCs, and two investigated the osseointegration between bone and FRCs. Owing to the heterogeneity of fiber types, FRC-coating, and lack of standardized testing protocols, a meta-analysis was not feasible. The included studies indicated that glass fibers, and in particular E-glass fibers, are superior to ceramics and other FRCs in terms of bacterial adherence, fibroblast cytotoxicity, and cell viability.

CONCLUSIONS

Glass-fiber-reinforced composites are cytocompatible materials that possess satisfactory biological properties and can be used in dental prosthesis and craniofacial implants. Further research is necessary to regulate the matrix ion release/degradation of FRCs to prolong the initially demonstrated properties.

Evaluation of surface characteristic and bacterial adhesion of low-shrinkage resin composites

This study aimed to examine the surface characteristics of low shrinkage composites and adhesion of Streptococcus mutans and Streptococcus mitis to these materials. Control material (glass) and three low shrinkage composites (Charisma Diamond, Kalore GC, Beatiful II LS) were used. After polishing procedure was applied to composite specimens, surface roughness (SR), surface free energy (SFE), and contact angle measurements were performed. Surfaces of composite were analyzed using scanning electron microscope and energy-dispersive X-ray spectroscopy. After pellicle formation with artificial saliva, S. mutans and S. mitis biofilms were incubated in 5% CO₂ for 24 h at 37°C and were analyzed using confocal laser scanning microscopy. The lowest SR and highest SFE values were found in the control group. While the contact angle of control was statistically lower than composites, statistically difference was not found between composite groups. S. mutans adhesion of composites was significantly lower than control group, but there was no significant difference between composites. S. mitis adhesion of all groups was statistically similar. SR did not affect the S. mutans and S. mitis adhesion. Less adherence of S. mutans to low shrinkage composites was associated with low SFE and high contact angle values. Even though the highest SR was observed in the Charisma Diamond, no difference was found between the composites in terms of bacterial adhesion.

Antibacterial coating of tooth surface with ion-releasing pre-reacted glass-ionomer (S-PRG) nanofillers

OBJECTIVES

Surface pre-reacted glass-ionomer (S-PRG) fillers release antibacterial borate and fluoride ions. We fabricated nanoscale S-PRG fillers (S-PRG nanofillers) for antibacterial coating of tooth surfaces and assessed the antibacterial effects of this coating in vitro. In addition, we creating a canine model of periodontitis to evaluate the effectiveness of S-PRG nanofiller application on tooth roots and improvement of periodontal parameters.

METHODS

Human dentin blocks were coated with S-PRG nanofiller (average particle size: 0.48 μm) and then characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), and ion-releasing test. Antibacterial effects of dentin blocks coated with S-PRG nanofiller were examined using bacterial strains, Streptococcus mutans and Actinomyces naeslundii. Next, we created an experimental model of periodontitis in furcation of premolars of beagle dogs. Then, S-PRG nanofiller coating was applied onto exposed tooth root surfaces. Periodontal parameters, gingival index (GI), bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment level (CAL), were measured from baseline until 4 weeks. In addition, bone healing was radiographically and histologically examined.

RESULTS

SEM and EDX revealed that S-PRG nanofillers uniformly covered the dentin surface after coating. Dentin blocks coated with S-PRG nanofiller showed ion-releasing property, bacterial growth inhibition, and sterilization effects. In the experimental periodontitis model, S-PRG nanofiller coating significantly reduced clinical inflammatory parameters, such as GI (P < 0.01) and BOP (P < 0.05), compared to uncoated samples. In addition, PPD and CAL significantly decreased by S-PRG nanofiller coating (2 weeks: P < 0.05; 3 and 4 weeks: P < 0.01), suggesting the improvement of periodontitis. Micro-CT and histology revealed that bone healing of furcation defects was enhanced by S-PRG nanofiller coating.

CONCLUSION

S-PRG nanofiller coating provides antibacterial effects to tooth surfaces and improves clinical parameters of periodontitis.

Inhibitory effect of toothbrush monofilament containing surface pre-reacted glass-ionomer (S-PRG) filler on Streptococcus mutans

The oral environment affects not only oral health, but also general health, and the importance of oral self-care has recently been recognised. Although toothbrushes are the most important self-care product, there are few toothbrushes that have an inhibitory effect on oral bacteria. In the present study, monofilaments used for toothbrushes containing surface pre-reacted glass-ionomer (S-PRG) filler (a component recently applied to various dental materials) were developed. Among nylon and polyester monofilaments commonly used for toothbrushes, nylon monofilaments can accommodate more S-PRG filler than polyester monofilaments, resulting in greater release of ions from the S-PRG filler. These monofilaments containing S-PRG filler formed less biofilm containing Streptococcus mutans, a major pathogen of dental caries, than monofilaments without S-PRG filler. Moreover, S. mutans adhering to monofilaments containing S-PRG filler were more easily exfoliated and eliminated than those adhering to monofilaments without S-PRG filler. Such inhibitory effects on S. mutans were more marked in nylon monofilaments than in polyester monofilaments. These findings that monofilaments containing S-PRG filler can release ions and have an inhibitory effect on S. mutans suggest that they may be an effective material for toothbrushes.

Surgical Sealing of Laterally Localized Accessory Root Canal with Resin Containing S-PRG Filler in Combination with Non-Surgical Endodontic Treatment: A Case Report

The spread of root canal infection to surrounding periodontal tissue through accessory root canals reduces the success rate of endodontic treatment. In this case, cone-beam computed tomography revealed a lesion (4 mm from the apex) resulting from an accessory root canal of the maxillary left central incisor. First, non-surgical endodontic treatment was conducted but the sinus tract remained. Surgical preparation of the root cavity was then conducted to remove potentially infected dentin surrounding the accessory root canal. The cavity was filled and the foramen was sealed with resin containing bioactive surface pre-reacted glass (S-PRG) filler. The photopolymerized resin was then contoured and polished. In combination with subsequent supportive non-surgical endodontic treatment, a good clinical outcome with the disappearance of the sinus tract and clinical symptoms such as discomfort and pressure pain and the regeneration of the alveolar bone hanging over the cavity was obtained. In this case, the good clinical outcome may have been due to the dentin-adhesive property and durability of the pre-adhesive system and composite resin. The better biocompatibility of S-PRG fillers presumably facilitated periodontal tissue healing.

Bioadhesion in the oral cavity and approaches for biofilm management by surface modifications

BACKGROUND

All soft and solid surface structures in the oral cavity are covered by the acquired pellicle followed by bacterial colonization. This applies for natural structures as well as for restorative or prosthetic materials; the adherent bacterial biofilm is associated among others with the development of caries, periodontal diseases, peri-implantitis, or denture-associated stomatitis. Accordingly, there is a considerable demand for novel materials and coatings that limit and modulate bacterial attachment and/or propagation of microorganisms.

OBJECTIVES AND FINDINGS

The present paper depicts the current knowledge on the impact of different physicochemical surface characteristics on bioadsorption in the oral cavity. Furthermore, it was carved out which strategies were developed in dental research and general surface science to inhibit bacterial colonization and to delay biofilm formation by low-fouling or "easy-to-clean" surfaces. These include the modulation of physicochemical properties such as periodic topographies, roughness, surface free energy, or hardness. In recent years, a large emphasis was laid on micro- and nanostructured surfaces and on liquid repellent superhydrophic as well as superhydrophilic interfaces. Materials incorporating mobile or bound nanoparticles promoting bacteriostatic or bacteriotoxic properties were also used. Recently, chemically textured interfaces gained increasing interest and could represent promising solutions for innovative antibioadhesion interfaces. Due to the unique conditions in the oral cavity, mainly in vivo or in situ studies were considered in the review.

CONCLUSION

Despite many promising approaches for modulation of biofilm formation in the oral cavity, the ubiquitous phenomenon of bioadsorption and adhesion pellicle formation in the challenging oral milieu masks surface properties and therewith hampers low-fouling strategies.

CLINICAL RELEVANCE

Improved dental materials and surface coatings with easy-to-clean properties have the potential to improve oral health, but extensive and systematic research is required in this field to develop biocompatible and effective substances.

A Novel Bioactive Endodontic Sealer Containing Surface-Reaction-Type Prereacted Glass-Ionomer Filler Induces Osteoblast Differentiation

Surface‑reaction‑type prereacted glass-ionomer (S‑PRG) fillers exhibit bioactive properties by the release of multiple ions. This study examined whether a novel endodontic sealer containing S‑PRG fillers (PRG+) has the capacity to induce osteoblast differentiation. Kusa‑A1 osteoblastic cells were cultured with extracts of PRG+, PRG- (an experimental sealer containing S‑PRG‑free silica fillers), AH Plus (an epoxy-resin‑based sealer), and Canals N (a zinc-oxide noneugenol sealer). Cell viability and mineralized nodule formation were determined using WST‑8 assay and Alizarin red staining, respectively. Osteoblastic-marker expression was analyzed with RT‑qPCR and immunofluorescence. Phosphorylation of extracellular signal‑regulated kinase (ERK) and p38 mitogen‑activated protein kinase (MAPK) was determined with Western blotting. Extracts of freshly mixed PRG+, PRG-, and AH Plus significantly decreased cell growth, but extracts of the set samples were not significantly cytotoxic. Set PRG+ significantly upregulated mRNAs for alkaline phosphatase and bone sialoprotein (IBSP) compared to set PRG-, and upregulation was blocked by NPS2143, a calcium‑sensing receptor antagonist. Set PRG+ significantly accelerated IBSP expression, mineralized nodule formation, and enhanced the phosphorylation of ERK and p38 compared with set PRG-. In conclusion, PRG+ induced the differentiation and mineralization of Kusa‑A1 cells via the calcium-sensing receptor-induced activation of ERK and p38 MAPK.

Opportunities for caries prevention using an ion-releasing coating material: a randomised clinical study

Ion-releasing materials (containing fluoride and boron, for example) have shown caries-preventive effects in vitro. The purpose of the present study was to investigate the impact of multi-ion-releasing coating material on pH stabilisation, plaque accumulation and the bacterial composition of dental plaque during a time period of 90 days. The null hypothesis tested here was that the evaluated material would not show any differences in pH stabilisation, plaque accumulation or bacterial composition compared with control material.

The study was carried out as a double-blind, split-mouth, randomised, controlled clinical trial in 28 volunteers. Over the evaluation period (days 4, 30, 60 and 90), pH measurements, plaque index and plaque sampling for bacterial analyses were conducted in a calibrated, standardized manner. The study received ethical permission and was carried out in accordance with the Helsinki Declaration.

A significant difference was observed, with less plaque accumulation over time in the subjects in whom the ion-releasing material was applied in comparison to the non-active group. No significant difference was evident in terms of either pH stabilisation or plaque levels of mutans streptococci.

The null hypothesis relating to plaque accumulation was rejected, with a lower plaque index shown for the test group up to 60–90 days. No adverse effects during the observation period were observed. Since the studied cohort was healthy from a caries perspective, more clinical studies are needed to further evaluate the caries-prevention potential of the ion-releasing material in other patient groups.

Effects of short-time exposure of surface pre-reacted glass-ionomer eluate on dental microcosm biofilm

This study evaluated the antibacterial effects of short-time exposure of surface pre-reacted glass-ionomer (S-PRG) eluate on oral microcosm biofilm. Biofilms were treated with an S-PRG eluate at different concentrations (25%, 50%, and 100%), distilled water (DW), and 0.1% chlorhexidine (CHX) twice a day for 5 min repeatedly. After 7 days, the total and aciduric bacterial counts and biofilm dry weights were measured. An image analysis program calculated the red/green (R/G) ratios in the biofilm autofluorescence images. Microscopic analyses quantified the biofilm thickness and live/dead cell ratio and determined morphological changes in the biofilm. Bacterial counts and dry weights were not significantly different in the DW group for all S-PRG eluate concentrations. An increasing trend in the R/G ratio for 7 days biofilm treatment was observed for the S-PRG eluate and the DW groups. Furthermore, the live/dead cell ratios in the biofilm and the biofilm thickness of the S-PRG eluate groups were similar to those of the DW group. The bacteria morphology inside the biofilm changed only in the CHX group. Short-time S-PRG eluate treatment showed no significant antibacterial and antibiofilm effects. These results indicated that limited biofilm formation inhibition can be obtained by using only the S-PRG eluate.