The use of acetone to enhance the infiltration of HA nanoparticles into a demineralized dentin collagen matrix

Physical-Mechanical Properties and Mineral Deposition of a Pit-and-Fissure Sealant Containing Niobium-Fluoride Nanoparticles-An In Vitro Study

This study investigated the combined effects of adding niobium-fluoride (NbF5) nanoparticles to a pit-and-fissure sealant. One resin sealant was reinforced with varying amounts of nanoparticles (0.3, 0.6, and 0.9 wt%). The surface hardness (SH), energy-dispersive X-ray spectroscopy (EDX), surface roughness (Ra), color change (ΔE), and mineral deposition were assessed. Bovine enamel blocks were subjected to demineralization and pH-cycling for SH. The elemental composition and Ca/P ratio were evaluated using EDX, while the mineral deposition was measured using Fourier transform infrared spectroscopy (FTIR). Data were analyzed using ANOVA and Tukey's test for the SH and EDX, ΔE, and Kruskal-Wallis for the Ra. The NbF5 modification increased the SH, with the 0.9 wt% sealant exhibiting higher SH values, and the 0.3 wt% one exhibiting significant differences compared to the control and the 0.9 wt% (p = 0.00) samples, even after pH-cycling. For the EDX analysis, the 0.3 and 0.6 wt% samples exhibited higher Ca/P ratios, with the 0.3% one showing evidence of P-O crystal formation. There was no significant difference in the Ra (p = 0.458), and the 0.6 and 0.9 wt% ones showed lower ΔE values compared to the control. The 0.3 wt% NbF5 demonstrated improved overall properties, making these results particularly promising for preventing tooth decay, reducing demineralization through increased ions release and promoting remineralization in posterior teeth.

Enhancing dentin bonding quality through Acetone wet-bonding technique: a promising approach

Objective: This paper aimed to assess the impact of the acetone wet-bonding (AWB) technique on dentin bonding and to investigate its potential underlying mechanisms. Materials and Methods: Caries-free third molars were sliced, ground, etched, water-rinsed. Then the specimens were randomly allocated to four groups according to the following pretreatments: 1. water wet-bonding (WWB); 2. ethanol wet-bonding (EWB); 3. 50% (v/v) acetone aqueous solution (50%AWB); 4. 100% acetone solution (AWB). Singlebond universal adhesive was then applied and composite buildups were constructed. The microtensile bond strength (MTBS), failure modes and interface nanoleakage were respectively evaluated after 24 h of water storage, 10,000 times of thermocycling or 1-month collagenase ageing. In situ zymography and contact angle were also investigated. Results: Acetone pretreatment preserved MTBS after thermocycling or collagenase ageing (p < 0.05) without affecting the immediate MTBS (p > 0.05). Furthermore, AWB group manifested fewer nanoleakage than WWB group. More importantly, the contact angle of the dentin surfaces decreased significantly and collagenolytic activities within the hybrid layer were suppressed in AWB group. Conclusion: This study suggested that the AWB technique was effective in enhancing the dentin bond durability by increasing the wettability of dentin surface to dental adhesives, removing residual water in the hybrid layer, improving the penetration of adhesive monomer, and inhibiting the collagenolytic activities. Clinical significance: The lifespan of adhesive restorations would be increased by utilization of acetone wet-bonding technique.

Effect of a bioactive pit and fissure sealant on demineralized human enamel: in vitro study

BACKGROUND

Incorporation of bioactive agent into pit and fissure sealant would halt demineralization and promote further remineralization. The aim was to assess the effect of bioactive and fluoride fissure sealants on calcium and phosphate content and surface topography of artificially demineralized enamel in young permanent teeth.

METHODS

30 sound extracted premolars free from cracks or any developmental anomalies were used. They were divided into group I bioactive fissure sealant, group II fluoride fissure sealant and group III no material applied. Each tooth was divided into halves in a buccolingual direction and evaluated by energy dispersive X-ray spectrometer (EDX) at baseline, demineralization and after applying the material. Another set of 7 sound extracted premolars was evaluated by scanning electron microscopy (SEM) at the same phases.

RESULTS

EDX showed that regaining calcium to demineralized enamel was significantly higher with bioactive sealant than either fluoride or the control group. SEM revealed minerals deposits with formation of distinct white zone at tooth/sealant interface for both pit and fissure sealant groups. Whereas no white zone formation was detected in control group.

CONCLUSIONS

Incorporating bioactive material into pit and fissure sealant through microcapsules provided better results than incorporating fluoride by enhancing the biological process of remineralization.

CLINICAL RELEVANCE

The more use of bioactive pit and fissure sealant would maintain the occlusal surfaces as sound structures and decrease the need for operative procedures to restore teeth cavitation.

Calcium phosphate nanoparticles for potential application as enamel remineralising agent tested on hydroxyapatite discs

Calcium phosphate exhibits excellent biocompatibility, and with particle size in the nanoscale, calcium phosphate nanoparticles (CPNPs) were explored to replace the hydroxyapatite lost in the nanoporous teeth due to dental erosion. CPNPs (2% w/v) colloidally stabilised by sodium citrate were synthesised via co-precipitation. They were characterised in terms of particle size, morphology, crystallinity, Ca/P ratio and calcium ion release. To ensure uniformity of the substrate, hydroxyapatite (HA) discs were examined as an alternative substrate model to enamel. They were eroded in acetate buffer (0.5 M; pH 4.0) at various timepoints (1, 5, 10, 30 min, and 2, 4 h), and their physical differences compared to enamel were assessed in terms of surface microhardness, surface roughness and step height. The remineralisation properties of the synthesised CPNPs on eroded HA discs at different pH levels were investigated. It was established that CPNPs were heterogeneously deposited on the HA discs at pH 9.2, whereas newly precipitated minerals from CPNPs were potentially formed at pH 6.2.

Bond strength of demineralized dentin after synthesized collagen/hydroxyapatite nanocomposite application

Treatment the deeper and remineralizable carious zone (DRCZ) in dentin with various remineralizing methods, either with classic top-down or biomimetic bottom-up remineralization approaches, has remained a constant main issue to enhance dentin substrate bonding quality. The concern of remineralizing the remaining, partially demineralized and physiologically re-mineralizable collagen fibrils was the optimum target. However, applying already mineralized type I collage fibrils which have the ability to chemically cross-link with remaining collagen and minerals did not gain much interest. Synthesis of collagen/hydroxyapatite (Col/Hap) nanocomposite was done with self-assembling Hap in situ onto Col fibrils with different % (70/30, 50/50, 30/70% of Col/Hap, respectively). Micro-tensile bond strength (μTBS) was evaluated after pre-treatment of artificially demineralized dentin with these suggested protocols [nanocomposite together with grape seed extract (GSE; 6.5%) cross-linker for two periods, 10min and 1 h] then applying self-adhesive bonding system. Applied Col/Hap (30/70%) together with GSE (6.5%) gave the significantly highest μTBS (25.04 ± 5.47 and 25.53 ± 7.64 MPa, for 10min and 1 h application times, respectively). After thermocycling for 10,000 cycles at 5 and 55 °C, μTBS for all protocols and both application times substantially decreased especially for the two control groups. Using the suggested dentin pre-treatment protocols, in chair-side, may possibly enhance the bond strength to DRCZ and its durability.

Polymeric zinc-doped nanoparticles for high performance in restorative dentistry

OBJECTIVES

The aim was to state the different applications and the effectiveness of polymeric zinc-doped nanoparticles to achieve dentin remineralization.

DATA, SOURCES AND STUDY SELECTION

Literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken.

CONCLUSIONS

Polymeric nanospheres (NPs) were efficiently loaded with zinc. NPs sequestered calcium and phosphate in the presence of silicon, and remained effectively embedded at the hybrid layer. NPs incorporation did not alter bond strength and inhibited MMP-mediated dentin collagen degradation. Zn-loaded NPs remineralized the hybrid layer inducing a generalized low-carbonate substitute apatite precipitation, chemically crystalline with some amorphous components, and an increase in mechanical properties was also promoted. Viscoelastic analysis determined that dentin infiltrated with Zn-NPs released the stress by breaking the resin-dentin interface and creating specific mineral formations in response to the energy dissipation. Bacteria were scarcely encountered at the resin-dentin interface. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Zn-NPs application at both cervical and radicular dentin attained the lowest microleakage and also promoted durable sealing ability. The new zinc-based salt minerals generated covered the dentin surface totally occluding cracks, porosities and dentinal tubules.

CLINICAL SIGNIFICANCE

Zinc-doped NPs are proposed for effective dentin remineralization and tubular occlusion. This offers new strategies for regeneration of eroded cervical dentin, effective treatment of dentin hypersensitivity and in endodontically treated teeth previous to the canal filling. Zn-NPs also do reduce biofilm formation due to antibacterial properties.

Influence of Application Time on Dentin Bond Performance in Different Etching Modes of Universal Adhesives

We attempted to determine the effect of universal adhesive application time on dentin bond performance in different etching modes based on shear bond strength (SBS) tests and surface free energy (SFE) measurements. The five universal adhesives used were Adhese Universal (AU), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Scotchbond Universal (SU), and Tokuyama Universal Bond (TU). Bovine dentin specimens were divided into four groups of 10 for each adhesive. SBS and SFE were determined after applying the following surface treatments: 1) self-etch (SE) mode with immediate air blowing after adhesive application (IA treatment), 2) SE mode with prolonged application time (PA treatment), 3) etch-and-rinse (ER) mode with IA treatment, and 4) ER mode with PA treatment. Bonded specimens were subjected to SBS testing. The SFE of adhesive-treated dentin surfaces was measured after rinsing with acetone and water. Three-way analysis of variance revealed that dentin SBS values (p<0.001) were significantly influenced by the factors of adhesive type and application duration, but the factor of pre-etching was not significant (p=0.985). The manufacturer's instructions require longer application times for AU and SU, which showed significantly lower SBS values in IA than in PA treatment in both etching modes. However, the difference in the other adhesives was not significant between the IA and PA treatments in either etching mode. The total SFE (γ_S) was dependent on the adhesive and etching mode. The γ_S value of the initial group (SiC paper ground group) at baseline was 69.5 (mN·m^-1) and that of the pre-etching group at baseline was 30.6 (mN·m^-1). For all the adhesives, γ_S in SE mode showed significantly higher values than in ER mode, regardless of the application time. In SE mode, almost all universal adhesives tested showed lower γ_S values in PA treatment than in IA treatment. For ER mode, all the adhesives showed significantly higher γ_S values than those of the pre-etching baseline, regardless of the application time. Most adhesives did not show any significant differences in γ_S values between IA and PA treatments, regardless of etching mode.

Effect of hydroxyapatite nanoparticles on enamel remineralization and estimation of fissure sealant bond strength to remineralized tooth surfaces: an in vitro study

Background

The management of noncavitated caries lesions before sealant therapy is a clinical challenge when the tooth needs sealant application. Sealing noncavitated carious lesions in pits and fissures may lead to failure of the fissure sealant (FS) due to incomplete sealing. Therefore the use of remineralizing agents such as nanoparticles has been suggested. This study investigated the ability of hydroxyapatite nanoparticles (nano-HA) to remineralize enamel, and their effect on sealant microleakage and shear bond strength (SBS).

Methods

A total of 192 third molars were demineralized and pretreated with two concentrations of nano-HA with and without sodium hexametaphosphate (SHMP), followed by phosphoric acid etching and resin FS application. The study groups were 1) etching + FS, 2) etching + nano-HA 0.15% + FS, 3) etching + nano-HA 0.03% + FS, 4) etching + mixture of nano-HA 0.15% and SHMP 0.05% + FS, 5) etching + mixture of nano-HA 0.03% + SHMP 0.01% + FS. The laboratory tests included microleakage in 50 teeth, scanning electron microscopy (SEM) evaluation in 10 samples, and SBS in 100 samples. Enamel remineralization changes were evaluated in 32 teeth with energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscope (FESEM).

Results

Nano-HA enhanced the SBS to remineralized enamel in a large percentage of nanoparticles. Mean SBS in group 2 was significantly greater than in groups 1, 3 and 4 (all P < 0.05). SBS was related to nano-HA concentration: nano-HA 0.15% yielded greater SBS (16.8 ± 2.7) than the 0.03% concentration (14.2 ± 2.1). However, its effect on microleakage was not significant. Nano-HA with or without SHMP led to enhanced enamel remineralization; however, the Calcium (Ca)/Phosphate (P) weight percent values did not differ significantly between the groups (P > 0.05). SEM images showed that SHMP did not affect sealant penetration into the deeper parts of fissures. FESEM images showed that adding SHMP led to increased nanoparticle dispersal on the tooth surface and less cluster formation.

Conclusions

The ultraconservative approach (combining nano-HA 0.15% and SHMP) and FS may be considered a minimal intervention in dentistry to seal demineralized enamel pits and fissures.

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.

Effect of Phosphorylated Chitosan on Dentin Erosion: An in vitro Study

The aim of this study was to evaluate the antierosive effect of phosphorylated chitosan in dentin. Bovine dentin specimens were randomly distributed into the following groups: (1) no treatment (NoTx/negative control), (2) phosphate-buffered saline solution (PBS), (3) AmF/NaF/SnCl2 (positive control), (4) 0.5% chitosan solution (Chi), (5) 0.5% neutral phosphorylated (NP)-Chi, and (6) 0.5% alkaline phosphorylated (AP)-Chi. The specimens were submitted to de-remineralization treatment cycles for 5 days: 0.5% citric acid (2 min), remineralizing solution (30 min), and surface treatment according to assigned groups (2 min, 6×/day). The loss of dentin surface was measured by profilometry. Hardness and modulus of elasticity were measured using a nanoindenter equipped with a Berkovich diamond tip. The dentin surface was analyzed by scanning electron microscopy (SEM). The largest loss of dentin was observed in the No Tx and PBS groups (approx. 25 µm). The group treated with AmF/NaF/SnCl2 showed less loss of dentin (67% reduction vs. NoTx and PBS), followed by the groups treated with NP-Chi and AP-Chi (33% reduction), and Chi (18% reduction). Nanohardness and modulus of elasticity were similar in the NoTx and PBS groups, with a small increase in stiffness in all other groups. SEM revealed that the experimental solution of AP-Chi had a favorable effect on maintaining the integrity of collagen fibrils. AmF/NaF/SnCl2 showed a preserved mineralized collagen surface. Further studies are warranted to explore this nontoxic phosphorylated chitosan polymer as an effective agent in the prevention and treatment of dental erosion.

Bioactivity and properties of an adhesive system functionalized with an experimental niobium-based glass

OBJECTIVE

This study evaluated the incorporation of niobophosphate bioactive glass (NbG) fillers into a commercial adhesive resin.

MATERIALS AND METHODS

The silanized (NbGs) or non-silanized (NbG) NbG was added to the commercial adhesive system One Step (OS) at 30% by weight; unfilled adhesive served as control. The bioactivity of adhesives was analyzed by SEM and FTIR/ATR after 28 days in PBS. The adhesives were evaluated as regards microtensile bond strength immediately and after six months (n = 6); degree of conversion (n = 3), microhardness (n = 5); and radiopacity (n = 3). Data from each test were submitted to ANOVA and Tukey tests (P <0.05).

RESULTS

FTIR/ATR analysis showed phosphate and carbonate precipitates on the NbG adhesive specimen surface. Statistical analysis of microtensile bond strength values showed that material x time interaction was not significant, but NbG group values were similar to those of unfilled adhesive (p <0.05). Addition of NbG did not alter the degree of conversion, but did increase microhardness and radiopacity values of the adhesive systems compared with those of the control group (OS). Incorporation of NbG into the adhesive system did not compromise the properties of the adhesive.

CONCLUSION

A smart adhesive system with bioactive properties, high radiopacity, microhardness, and similar bond strength and degree of conversion was obtained by incorporating 30% by weight of NbG.

Penetration of sub-micron particles into dentinal tubules using ultrasonic cavitation

OBJECTIVES

Functionalised silica sub-micron particles are being investigated as a method of delivering antimicrobials and remineralisation agents into dentinal tubules. However, their methods of application are not optimised, resulting in shallow penetration and aggregation. The aim of this study is to investigate the impact of cavitation occurring around ultrasonic scalers for enhancing particle penetration into dentinal tubules.

METHODS

Dentine slices were prepared from premolar teeth. Silica sub-micron particles were prepared in water or acetone. Cavitation from an ultrasonic scaler (Satelec P5 Newtron, Acteon, France) was applied to dentine slices immersed inside the sub-micron particle solutions. Samples were imaged with scanning electron microscopy (SEM) to assess tubule occlusion and particle penetration.

RESULTS

Qualitative observations of SEM images showed some tubule occlusion. The particles could penetrate inside the tubules up to 60μm when there was no cavitation and up to ∼180μm when there was cavitation.

CONCLUSIONS

The cavitation bubbles produced from an ultrasonic scaler may be used to deliver sub-micron particles into dentine. This method has the potential to deliver such particles deeper into the dentinal tubules.

CLINICAL SIGNIFICANCE

Cavitation from a clinical ultrasonic scaler may enhance penetration of sub-micron particles into dentinal tubules. This can aid in the development of novel methods for delivering therapeutic clinical materials for hypersensitivity relief and treatment of dentinal caries.