Bond strength of adhesive systems to sound and demineralized dentin treated with bioactive glass ceramic suspension

Limitations, challenges and prospective solutions for bioactive glasses-based nanocomposites for dental applications: A critical review

Several nanomaterials have been recently used to overcome various challenges in the dental domain. Bioactive glasses, a class of bioceramics, with their outstanding properties including but not limited to their strong biocompatibility, antibacterial characteristics, and bioactivity inside the body's internal milieu have made them valuable biomaterials in a variety of dental domains. The utilization of nanomaterials has improved the performance of teeth, and the incorporation of bioactive glasses has the field of dentistry at an unsurpassed level in different categories such as esthetic and restorative dentistry, periodontics and dental implants, orthodontics, and endodontics. The current study discusses the most recent developments of the bioactive glasses' creation and implementation for dental applications, as well as the challenges and opportunities still facing the field. This work provides an overview of the current obstacles and potential future prospects for bioactive glasses-based nanocomposites to improve their dental uses. It also emphasizes the great potential synergistic effects of bioactive glasses used with other nanomaterials for dental applications.

Dentin surface modification by MDP to improve dentin bonding stability: Topological enhancement and mineralization of collagen structure in hybrid layers

Decades of research have been conducted on 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) through numerous studies. The mechanisms by which its residual calcium salts benefit dentin bonding remain undetermined. The objective of the research was to investigate the role and process of remaining calcium salts in the priming procedure and their capacity for remineralization. The investigation focused on the variations in topological structure, mechanical properties, and chemical interactions between the main agent and the dentin surface. Two adhesive modes including prime-and-rinse(P&R) and prime-and-nonrinse (P&NR) utilized to evaluate the bonding performance and remineralization ability. The findings indicated that both P&R and P&NR methods could eliminate the smear-layer, uncover dentinal-tubules, and generate a textured/rough surface on the dentin. Collagen fibrils exhibited a greater presence of inorganic minerals in the P&NR mode. Compared to control group, both P&R and P&NR groups improved immediate and aging bond strength significantly (P < 0.05). AFM and 3D-STORM revealed MDP and its residual calcium salts distributed in collagen fibrils and expanded collagen matrix. In the P&NR group, TEM revealed that the dentin collagen matrix experienced some remineralization, and there was also mineralization within the collagen fibrils embedded in the bonding interface. Thus, MDP priming improved dentin bonding stability. Residual calcium salts of P&NR process can enhance topological structure of the collagen matrix and induce intrafibrillar mineralization.

Effect of the use of bromelain associated with bioactive glass-ceramic on dentin/adhesive interface

OBJECTIVES

To evaluate the effect of bromelain associated with Biosilicate on the bond strength (BS) of a universal adhesive system to sound (SD) and caries-affected dentin (CAD), and on the proteolytic activity.

MATERIALS AND METHODS

Cavities were prepared in 360 molars, half submitted to cariogenic challenge. Teeth were separated into groups (n=20): Control-No treatment; CHX-0.12% chlorhexidine; NaOCl-5% sodium hypochlorite; Br5%-5% bromelain; Br10%-10% bromelain; Bio-10% Biosilicate; NaOClBio-NaOCl+Bio; Br5%Bio-Br5%+Bio; Br10%Bio-Br10%+Bio. Following treatments, the adhesive system was applied, and cavities were restored. Samples were sectioned into sticks and stored at 37 °C for 24 h, 6 months, and 1 year. Microtensile BS (2-way ANOVA, Bonferroni's test, α=0.05), fracture patterns (SEM), and adhesive interfaces (TEM) were evaluated. Bacterial collagenase assay and in situ zymography were performed.

RESULTS

In CAD, Br10% presented higher BS (p=0.0208) than Br5%Bio. Br5% presented higher BS (p=0.0033) after 6 months than after 24 h; and association of treatments, higher BS (p<0.05) after aging than after 24 h. Mixed fractures were the most prevalent. Association of treatments promoted a more uniform hybrid layer with embedded Bio particles. Experimental groups presented lower (p<0.0001) relative fluorescence units than Control. Bromelain, associated or not with Bio, showed collagenolytic degradation.

CONCLUSIONS

Bromelain associated with Biosilicate did not affect the BS to SD. In CAD, Br5%Bio decreased immediate BS but had no long-term influence. This association decreased the proteolytic activity.

CLINICAL RELEVANCE

Bromelain and Biosilicate may enhance the longevity of adhesive restorations by inhibiting endogenous proteases.

Incorporation of bioactive glass-ceramic into coconut oil for remineralization of incipient carious lesions

This study evaluated the efficacy of incorporating different concentrations of bioactive glass-ceramic (Biosilicate) into coconut oil on the remineralizing potential and surface roughness of white spot lesions. Fragments (6 x 6 x 2mm) of bovine teeth were sectioned and initial microhardness (KHN) and surface roughness (Ra) readings were obtained. The samples were submitted to cariogenic challenge to form white spot lesions and were separated into six groups (n=13): 1) Artificial Saliva (AS); 2) Coconut Oil (CO); 3) CO+2% Biosilicate (CO+2%Bio); 4) CO+5% Biosilicate (CO+5%Bio); 5) 2% Biosilicate Suspension (2% Bio) and 6) 5% Biosilicate Suspension (5% Bio). The treatments for 1 cycle/day were: immersion into the treatments for 5 minutes, rinsing in distilled water, and storage in artificial saliva at 37ºC. After 14 days, KHN and Ra readings were taken. The surface roughness alteration ((Ra) was analyzed (Kruskal-Wallis, Dunn's post-test, p<0.05). CO+2%Bio had higher (p = 0.0013) (Ra followed by CO+5%Bio (p = 0.0244) than AS. The relative KHN and remineralization potential were analyzed (ANOVA, Tukey, p<0.05), and 5% Bio treatment presented a higher relative microhardness than all other groups (p>0.05). The remineralizing potential of all the treatments was similar (p > .05). When Biosilicate was added, the pH of the suspensions increased and the alkaline pH remained during the analysis. Biosilicate suspension is more efficient than the incorporation of particles into coconut oil at white spot lesion treatment. In addition to the benefits that coconut oil and Biosilicate present separately, their association can enhance the remineralizing potential of Biosilicate.

Effect of limonene associated with bioactive glass-ceramic on dentin/adhesive interface

This study evaluated the effect of pretreatment with limonene and/or biosilicate on the bond strength of a universal adhesive system in self-etch mode to dentin. Occlusal cavities were prepared in 80 human molars and the teeth were randomly allocated to one of four groups (n = 20), according to the pretreatment regimens applied before the adhesive. The pretreatments were (i) Control, no pretreatment, (ii) LIM, 0.5% limonene; (iii) Bio, 10% biosilicate; and (iv) LIMBio, LIM + Bio. After adhesive application and restoration, the specimens were sectioned into sticks, separated, and stored in distilled water at 37°C for 24 h or 6 months. Microtensile bond strength test was carried out and measurements were compared across pretreatment groups and storage times. Fracture patterns and adhesive interfaces were observed. Loss of dry mass was calculated (n = 10). There was no statistically significant difference in the bond strength between the groups and the most prevalent fracture pattern was the non-adhesive. LIM and LIMBio resulted in more open dentinal tubules. LIM and Bio, whether separate or combined, showed particles of those substances, which decreased in size and number after 6 months. All groups lost mass weight after treatment, with no statistically significant differences between them. Limonene and biosilicate pretreatment did not affect the bond strength to dentin of the universal adhesive system, but resulted in more non-adhesive fractures, even after 6 months.

Anti-inflammatory properties of S53P4 bioactive glass implant material

OBJECTIVES

To assess whether the dissolution products of S53P4 bioactive glass (BG) affect cellular response of macrophages and clinically relevant peri‑implant cell populations to dental implant particles in vitro. Cells chosen were human gingival fibroblasts (HGFs), osteoblasts and bone marrow derived stromal cells (HBMSCs).

METHODS

Melt-derived S53P4 bioactive glass were prepared. HGFs, Saos-2 human osteoblastic cell line, HBMSCs and macrophages, derived from THP-1 human monocytic cell line, were cultured in the presence of particles from commercially pure titanium (Ti-CP4), grade 5 titanium alloy (Ti-6Al-4V), titanium-zirconium alloy (Ti-15Zr) or zirconia (Zr) (with respective diameters of 34.1 ± 3.8, 33.3 ± 4.4, 97.8 ± 8.2 and 71.3 ± 6.1 µm) with or without S53P4 dissolution products (conditioned media contained 327.30 ± 2.01 ppm Ca, 51.34 ± 0.41 ppm P and 61.48 ± 1.17 ppm Si, pH 8.01 ± 0.21). Inflammatory and macrophage polarisation markers including TNF-ɑ, IL-1, IL-6 and CD206 were quantified using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The presence of Ti-6Al-4V implant particles significantly induced the expression of pro-inflammatory markers in all tested cell types. S53P4 BG dissolution products regressed the particle induced up-regulation of pro-inflammatory markers and, appeared to suppress M1 macrophage polarisation.

CONCLUSIONS

Implant particles, Ti-6Al-4V in particular, resulted in significant inflammatory responses from cells. S53P4 BG may possess anti-inflammatory properties and potentially mediate macrophage polarisation behaviour.

CLINICAL SIGNIFICANCE

The findings highlight that the use and benefits of BG is a promising field of study. Authors believe more collective efforts are required to fully understand the reliability, efficiency and exact mechanisms of action of BG in the search for new generation of treatment modalities in dentistry.

Remineralization of caries-affected dentin and color stability of teeth restored after treatment with silver diamine fluoride and bioactive glass-ceramic

OBJECTIVES

The aim of this study was to evaluate the microhardness of caries-affected dentin and color stability of teeth restored after treatments with silver diamine fluoride (SDF) associated to potassium iodide (KI) and Biosilicate.

MATERIAL AND METHODS

Different samples from bovine teeth were obtained. For color readings, 80 cavities (6 mm × 6 mm × 2 mm) were prepared, and for microhardness, teeth were flattened into dentine to obtain 40 samples. All samples were submitted to cariogenic challenge and separated in 4 groups, according to the treatment used: 12% SDF + KI; 38% SDF; Biosilicate and control (no treatment). Cavities were restored with resin-modified glass-ionomer cement (RMGIC, Vitremer, 3 M ESPE) or composite resin (CR, Z350, 3 M ESPE). After restoration, the samples were submitted to thermo-mechanical cycling (TMC) for 1,200,000 cycles. Color readings (EasyShade, Vita) were performed after restorations, after TMC, and 30 days after TMC. Knoop microhardness was evaluated on the planned samples before and after cariogenic challenge, after treatments, and after 30 days. Scanning electron microscopy (SEM) evaluated the dentine surface after treatments. Data were analyzed (ANOVA, Bonferroni, p < .05).

RESULTS

The results showed a higher color alteration for RMGIC than CR. The time of analysis was significant (p < .05) for the 12% SDF + KI and control group. There was no difference (p < .05) in microhardness between groups. However, there was evidence of dentin remineralization after treatments.

CONCLUSIONS

It was concluded that the samples treated with Biosilicate resulted in a color alteration similar to control. The treatments presented dentin remineralizing potential for microhardness, below the demineralization level, caused by the cariogenic challenge.

CLINICAL RELEVANCE

Considering the remineralizing potential presented by Biosilicate, this agent is a promising alternative that overcomes the SDF adverse effects such as tooth staining.

Effect of 45S5 bioactive glass on the microshear bond strength of dental fluorosis

The aim of this in vitro study was to estimate the effect of the species concentration of 45S5 bioactive glass (BAG) used as pretreatment on the microshear bond strength (MSBS) of dental fluorosis (DF). Based on the Thylstrup and Fejerskov index, 80 teeth were randomly divided equally into four groups: TFI 0, sound dentin; TFI 1-3, mild fluorosis; TFI 4-5, moderate fluorosis; and TFI 6-9, severe fluorosis. Each group was randomized into five subgroups. After preparing the dentin hypersensitivity model of DF, the dentin was pretreated as follows, Subgroup 1: deionized water (Control group); Subgroup 2: 1% BAG; Subgroup 3: 5% BAG; Subgroup 4: 10% BAG, and Subgroup 5: 20% BAG. Stochastically one specimen was selected from each subgroup for scanning electron microscope and energy dispersive spectrometer analysis. After being made of resin-tooth bonding samples, the remains were in water bath at 37 °C for 24 hr. Subsequently, samples from each subgroup were randomly selected to test MSBS without aging, or after a thermocycle of 5,000 and 10,000 times, respectively. The fracture modes were analyzed. Compared with the group of 1% BAG and Control, the exposure area of tubules in 5%, 10%, and 20% BAG group had significant difference (p < .05). MSBS results indicated that there were significant differences between 10% BAG with other groups. The 20% BAG group showed the lowest MSBS among all groups. Pretreatment of 10% BAG solution may be conductive to enhance the bond strength of DF, while 20% BAG solution adversely.

Synergistic Effect of Bioactive Inorganic Fillers in Enhancing Properties of Dentin Adhesives-A Review

Dentin adhesives (DAs) play a critical role in the clinical success of dental resin composite (DRC) restorations. A strong bond between the adhesive and dentin improves the longevity of the restoration, but it is strongly dependent on the various properties of DAs. The current review was aimed at summarizing the information present in the literature regarding the improvement of the properties of DAs noticed after the addition of bioactive inorganic fillers. From our search, we were able to find evidence of multiple bioactive inorganic fillers (bioactive glass, hydroxyapatite, amorphous calcium phosphate, graphene oxide, calcium chloride, zinc chloride, silica, and niobium pentoxide) in the literature that have been used to improve the different properties of DAs. These improvements can be seen in the form of improved hardness, higher modulus of elasticity, enhanced bond, flexural, and ultimate tensile strength, improved fracture toughness, reduced nanoleakage, remineralization of the adhesive-dentin interface, improved resin tag formation, greater radiopacity, antibacterial effect, and improved DC (observed for some fillers). Most of the studies dealing with the subject area are in vitro. Future in situ and in vivo studies are recommended to positively attest to the results of laboratory findings.

Effects of Bioactive Agents on Dentin Mineralization Kinetics After Dentin Bleaching

Objectives:

This study evaluated effects of Bioglass 45S5 (BG) and Biosilicate (BS) remineralization on the chemical composition and bond strength of control dentin (CD) and bleached dentin (BD) surfaces.

Methods and Materials:

Dentin bleaching treatment was performed using the walking bleaching technique with 0.01 g of sodium perborate and 0.5 mL of 3% hydrogen peroxide for 14 days. Remineralization treatment was carried out by rubbing a remineralization solution (0.015 g of BG or BS diluted in 1.35 mL of distilled water) on the etched dentin surface for 30 seconds. Micro-Raman spectroscopy (MRS) was used to quantitatively analyze the mineral matrix ratios of CD and BD (n=5) after remineralization treatment with BG and BS over 15 days of incubation in artificial saliva. The CD and BD discs (n=10) with and without remineralization treatment with BG and BS were restored using a two-step etch-and-rinse adhesive system (Optibond S, Kerr) and five layers of 1-mm-thick composite resin (Filtek Z250, 3M ESPE). The restored dentin discs were sectioned into nine bonded beams with cross-sectional areas of approximately 0.9 mm2 and tested for microtensile bond strength (μTBS). The dentin surface of one fractured beam per tooth was submitted to MRS to characterize the physicochemical composition (n=10) at the interface. The data were analyzed using one-way analysis of variance and the Tukey-Kramer post hoc test (p&lt;0.005).

Results:

MRS bioactive analyses revealed that both BG and BS promoted increased mineral matrix ratios in the CD and BD. Significantly higher μTBS values were found after CD treatment with BG (CD: 57 MPa±11; CD-BG: 78 MPa±15) and when BG and BS were applied to the BD (BD: 42 MPa±5; BD-BG: 71 MPa±14; BD-BS: 64 MPa±11) (p&lt;0.005). The MRS analysis of the fractured dentin beam showed that the remineralization treatment significantly increased the dentin relative mineral concentration and promoted the appearance of new interface peaks, indicating a chemical interaction (p&lt;0.005).

Conclusion:

Remineralization of BD is an effective therapy to restore damage caused by dentin bleaching and acid conditioning. This approach not only increases dentin mineral compounds but also improves dentin's ability to interact chemically with the adhesive system.

Effect of the photoinitiator system on the polymerization of secondary methacrylamides of systematically varied structure for dental adhesive applications

OBJECTIVE

The aim of this study was to investigate the influence of the photoinitiator system on the polymerization kinetics of methacrylamide-based monomers as alternatives to methacrylates in adhesives dental-based materials.

METHODS

In total, 16 groups were tested. Monofunctional monomers (2-hydroxyethyl methacrylate) - HEMA; (2-hydroxy-1-ethyl methacrylate) -2EMATE, (2-hydroxyethyl methacrylamide) - HEMAM; and (N-(1-hydroxybutan-2-yl) methacrylamide) -2EM; were combined with bifunctional monomers containing the same polymerizing moieties as the monofunctional counterparts (HEMA-BDI; 2EMATE-BDI; HEMAM-BDI; and 2EM-BDI) at 50/50 M ratios. BHT was used as inhibitor (0.1 wt%) and the photoinitiators used were: CQ + EDMAB (0.2/0.8), BAPO (0.2), IVOCERIN (0.2), and DMPA (0.2), in wt%. The polymerization kinetics were monitored using Near-IR spectroscopy (∼6165 cm-1) in real-time while the specimens were photoactivated with a mercury arc lamp (Acticure 2; 320-500 nm, 300 mW/cm2) for 5 min, and maximum rate of polymerization (Rpmax, in %.s-̄1), degree of conversion at Rpmax (DC@Rpmax, in %), and the final degree of conversion (Final DC, in %) were calculated (n = 3). Initial viscosity was measured with an oscillating rheometer (n = 3). Data were analyzed using Two-way ANOVA for the polymerization kinetics and one-way ANOVA for the viscosity. Multiple comparisons were made using the Tukey's test (∝ = 0.05).

RESULTS

There was statistically significant interaction between monomer and photoinitiator (p < 0.001). For the methacrylates groups, the highest Rpmax was observed for HEMA + DMPA and 2EMATE + BAPO. For methacrylamides groups, the highest Rpmax were observed for HEMAM and 2EM, both with DMPA. Final DC was higher for the methacrylate groups, in comparison with methacrylamide groups, independent of the photoinitiators. However, for the methacrylamide groups, the association with BAPO led to the lowest values of DC. In terms of DC@Rpmax, methacrylate-based systems showed significantly higher values than methacrylamide formulations. DMPA and Ivocerin led to higher values than CQ/EDMAB and BAPO in methacrylamide-based compounds. BAPO systems showed de lowest values for both HEMA and HEMAM formulations. For the viscosity (Pa.s), only 2EM had higher values (1.60 ± 0.15) in comparison with all monomers. In conclusion, polymerization kinetics was affected by the photoinitiators for both monomers. Viscosity was significantly increased with the use of secondary methacrylamide.

SIGNIFICANCE

this work demonstrated the feasibility of using newly-synthesized methacrylamide monomers in conjunction with a series of initiator systems already used in commercial materials.

Mechanisms of Bioactive Glass on Caries Management: A Review

This review investigates the mechanisms of bioactive glass on the management of dental caries. Four databases (PubMed, Web of Science, EMBASE (via Ovid), Medline (via Ovid)) were systematically searched using broad keywords and terms to identify the literature pertaining to the management of dental caries using "bioactive glass". Titles and abstracts were scrutinized to determine the need for full-text screening. Data were extracted from the included articles regarding the mechanisms of bioactive glass on dental caries management, including the aspect of remineralizing effect on enamel and dentine caries, and antimicrobial effect on cariogenic bacteria. After removal of duplicates, 1992 articles were identified for screening of the titles and abstracts. The full texts of 49 publications were scrutinized and 23 were finally included in this review. Four articles focused on the antimicrobial effect of bioactive glass. Twelve papers discussed the effect of bioactive glass on demineralized enamel, while 9 articles investigated the effect of bioactive glass on demineralized dentine. In conclusion, bioactive glass can remineralize caries and form apatite on the surface of enamel and dentine. In addition, bioactive glass has an antibacterial effect on cariogenic bacteria of which may help to prevent and arrest dental caries.

Bioactive Glass Applications in Dentistry

At present, researchers in the field of biomaterials are focusing on the oral hard and soft tissue engineering with bioactive ingredients by activating body immune cells or different proteins of the body. By doing this natural ground substance, tissue component and long-lasting tissues grow. One of the current biomaterials is known as bioactive glass (BAG). The bioactive properties make BAG applicable to several clinical applications involving the regeneration of hard tissues in medicine and dentistry. In dentistry, its uses include dental restorative materials, mineralizing agents, as a coating material for dental implants, pulp capping, root canal treatment, and air-abrasion, and in medicine it has its applications from orthopedics to soft-tissue restoration. This review aims to provide an overview of promising and current uses of bioactive glasses in dentistry.

Effect of Methods of Biosilicate Microparticle Application on Dentin Adhesion

Restorative procedures associated with bioglasses have shown to be a strategy to satisfy the contemporary concept of minimally invasive dentistry. Thus, the aim of this study was to evaluate bond strength to dentin treated by two different methods of biosilicate microparticle application. Dentin surfaces from 30 sound human molars were exposed and randomly assigned into three groups (n = 10) according to the surface treatment: (1) blasting with biosilicate microparticles (distance = 1 cm/pressure = 5 bar/time = 1 min); (2) 10% biosilicate microparticles paste; and (3) control (no treatment). After, dentin surfaces were restored with self-etch adhesive (Adper Easy Bond) and nanofilled composite (Filtek Z350). Specimens were sectioned perpendicularly to the adhesive interface to obtain sticks (cross-section area = 1 mm²), which were submitted to microtensile test (0.5 mm/min; 50 kgf). Data were analyzed by ANOVA and Tukey's test (α = 5%). Dentin/adhesive interfaces were morphologically analyzed by scanning electron microscopy (SEM). Data analysis showed that biosilicate-treated groups reached similar results (p > 0.05) and both of them demonstrated higher values (p < 0.05) than control group. SEM micrographs revealed hybridization with clear resin tags and no separation between resin-dentin adhesive interfaces. Within the limitations of this study, surface treatment with biosilicate positively influenced the adhesion to dentin and does not alter the morphology of the adhesive interface.

Bonding durability, antibacterial activity and biofilm pH of novel adhesive containing antibacterial monomer and nanoparticles of amorphous calcium phosphate

OBJECTIVES

The dentin bonding often fails over time, leading to secondary caries and restoration failure. The objectives of this study were to develop an adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of storage in artificial saliva for six months on the bonding durability, antibacterial activity, ion release and biofilm pH properties for the first time.

METHODS

DMAHDM was added at 5% (by mass) to Scotchbond Primer and Adhesive (SBMP). NACP was added at 10%, 20%, and 30% to SBMP adhesive. Dentin bonding durability, antibacterial activity against Streptococcus mutans biofilms, and calcium (Ca) and phosphate (P) ion liberation properties were investigated after 1 day and 6months of storage in artificial saliva.

RESULTS

Dentin bond strength (n = 50) had 25% loss after 6 months of aging for SBMP control. However, SBMP + DMAHDM+10NACP and SBMP + DMAHDM+20NACP showed no loss in bond strength after storage in artificial saliva for 6 months. The DMAHDM + NACP incorporation method dramatically reduced the biofilm metabolic activity and acid production, and decreased the biofilm CFU by four orders of magnitude, compared to SBMP control, even after 6 months of aging (p < 0.05). DMAHDM + NACP had long-lasting Ca and P ion releases, and raised the biofilm pH to 6.8, while the control group had a cariogenic biofilm pH of 4.5.

CONCLUSIONS

Incorporating DMAHDM + NACP in bonding agent yielded potent and long-lasting antibacterial activity and ions liberation ability, and much higher long-term dentin bond strength after 6-month of aging. The new bonding agent is promising to inhibit caries at the restoration margins and increase the resin-dentin bonding longevity.

CLINICAL SIGNIFICANCE

The novel bioactive adhesive is promising to protect tooth structures from biofilm acids and secondary caries. NACP and DMAHDM have great potential for applications to a wide range of dental materials to reduce plaque and achieve therapeutic effects.

Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities

OBJECTIVES

A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties.

METHODS

MNP, DMAHDM and NACP were mixed into Scotchbond SBMP at 2%, 5% and 20% by mass, respectively. Two types of magnetic nanoparticles were used: acrylate-functionalized iron nanoparticles (AINPs); and iron oxide nanoparticles (IONPs). Each type was added into the resin at 1% by mass. Dentin bonding was performed with a magnetic force application for 3min, provided by a commercial cube-shaped magnet. Dentin shear bond strengths were measured. Streptococcus mutans biofilms were grown on resins, and metabolic activity, lactic acid and colony-forming units (CFU) were determined. Ca and P ion concentrations in, and pH of biofilm culture medium were measured.

RESULTS

Magnetic nanoparticle-containing adhesive using magnetic force increased the dentin shear bond strength by 59% over SBMP Control (p<0.05). Adding DMAHDM and NACP did not adversely affect the dentin bond strength (p>0.05). The adhesive with MNP+DMAHDM+NACP reduced the S. mutans biofilm CFU by 4 logs. For the adhesive with NACP, the biofilm medium became a Ca and P ion reservoir. The biofilm culture medium of the magnetic nanoparticle-containing adhesive with NACP had a safe pH of 6.9, while the biofilm medium of commercial adhesive had a cariogenic pH of 4.5.

SIGNIFICANCE

Magnetic nanoparticle-containing adhesive with DMAHDM and NACP under a magnetic force yielded much greater dentin bond strength than commercial control. The novel adhesive reduced biofilm CFU by 4 logs and increased the biofilm pH from a cariogenic pH 4.5-6.9, and therefore is promising to enhance the resin-tooth bond, strengthen tooth structures, and suppress secondary caries at the restoration margins.