In Vitro Study of Dentinal Tubule Occlusion with Sol-gel DP-bioglass for Treatment of Dentin Hypersensitivity

Nanofluorapatite Hydrogels in the Treatment of Dentin Hypersensitivity: A Study of Physiochemical Properties and Fluoride Release

The aim of this work was to prepare a new hydrogel based on nanohydroxyapatite (nFAP, 10% w/w) and fluorides (4% w/w), both of which are used as sources of fluoride ions in the treatment of dentin hypersensitivity, and to characterize its physicochemical properties. The release of fluoride ions from 3 gels (G-F, G-F-nFAP, and G-nFAP gel) was controlled in Fusayama–Meyer artificial saliva at pH 4.5, 6.6, and 8.0. The properties of the formulations were determined by an analysis of viscosity, a shear rate test, a swelling study, and gel aging. Various methods, i.e., FT-IR spectroscopy, UV-VIS spectroscopy, and thermogravimetric, electrochemical, and rheological analysis, were used for the experiment. The profiles of fluoride release indicate that the amount of fluoride ions released increases with a decrease in the pH value. The low pH value facilitated water absorption by the hydrogel, which was also confirmed by the swelling test, and it promoted the exchange of ions with the surrounding environment. Under conditions similar to physiological conditions (at pH 6.6), the amounts of fluorides released into artificial saliva were approximately 250 µg/cm2 and 300 µg/cm2 for the G-F-nFAP hydrogel and G-F hydrogel, respectively. The aging study and properties of the gels showed a loosening of the gel network structure. The Casson rheological model was used to assess the rheological properties of the non-Newtonian fluids. Hydrogels consisting of nanohydroxyapatite and sodium fluoride are promising biomaterials in the prevention and management of the dentin hypersensitivity.

Impact of silanization of different bioactive glasses in simplified adhesives on degree of conversion, dentin bonding and collagen remineralization

OBJECTIVE

To analyze simplified adhesive containing pure or silanized bioglass 45S5 (with calcium) or Sr-45S5 (strontium-substituted) fillers applied on dentin and to evaluate the microtensile bond strength (µTBS), interface nanoleakage, degree of conversion of adhesive, collagen degradation and remineralization.

METHODS

Ambar Universal adhesive (FGM) was doped with 10 wt% bioactive glasses to form following groups: Control (no bioglass), 45S5 (conventional bioglass 45S5), Sr-45S5 (Sr-substituted bioglass 45S5), Sil-45S5 (silanized bioglass 45S5) and Sil-Sr-45S5 (silanized bioglass Sr-45S5). Adhesives were applied after dentin acid-etching using phosphoric acid at extracted human molars. Resin-dentin sticks were obtained and tested for µTBS, nanoleakage at 24 h or 6 months. Degree of conversion was measured using micro-Raman spectroscopy. Dentin remineralization was assessed by FTIR after 6-month storage in PBS. Hydroxyproline (HYP) release was surveyed by UV-Vis spectroscopy. Statistical analysis was performed using ANOVA and Tukey's test (p < 0.05).

RESULTS

Regarding µTBS, Sr-45S5 and 45S5 presented higher and stable results (p > 0.05). Control (p = 0.018) and Sil-Sr-45S5 (p < 0.001) showed µTBS reduction after 6-month aging. Sil-Sr-45S5 showed higher HYP release than that obtained in the 45S5 group. Sil-45S5 showed mineral deposition and increase in µTBS (p = 0.028) after 6-months. All experimental adhesives exhibited higher degree of conversion compared to Control group, except for 45S5. All adhesives created gap-free interfaces, with very low silver impregnation, except for Sil-Sr-45S5.

SIGNIFICANCE

The incorporation of silanized 45S5 bioglass into the universal adhesive was advantageous in terms of dentin remineralization, bonding performance and adhesive polymerization. Conversely, Sil-Sr-45S5 compromised the µTBS, interface nanoleakage and had a negative impact on HYP outcomes.

Ceramic Nanomaterials in Caries Prevention: A Narrative Review

Ceramic nanomaterials are nanoscale inorganic metalloid solids that can be synthesised by heating at high temperatures followed by rapid cooling. Since the first nanoceramics were developed in the 1980s, ceramic nanomaterials have rapidly become one of the core nanomaterials for research because of their versatility in application and use in technology. Researchers are developing ceramic nanomaterials for dental use because ceramic nanoparticles are more stable and cheaper in production than metallic nanoparticles. Ceramic nanomaterials can be used to prevent dental caries because some of them have mineralising properties to promote the remineralisation of tooth tissue. Ceramic minerals facilitate the remineralisation process and maintain an equilibrium in pH levels to maintain tooth integrity. In addition, ceramic nanomaterials have antibacterial properties to inhibit the growth of cariogenic biofilm. Researchers have developed antimicrobial nanoparticles, conjugated ceramic minerals with antibacterial and mineralising properties, to prevent the formation and progression of caries. Common ceramic nanomaterials developed for caries prevention include calcium-based (including hydroxyapatite-based), bioactive glass-based, and silica-based nanoparticles. Calcium-based ceramic nanomaterials can substitute for the lost hydroxyapatite by depositing calcium ions. Bioactive glass-based nanoparticles contain surface-reactive glass that can form apatite crystals resembling bone and tooth tissue and exhibit chemical bonding to the bone and tooth tissue. Silica-based nanoparticles contain silica for collagen infiltration and enhancing heterogeneous mineralisation of the dentin collagen matrix. In summary, ceramic nanomaterials can be used for caries prevention because of their antibacterial and mineralising properties. This study gives an overview of ceramic nanomaterials for the prevention of dental caries.

Effect of bioactive glasses used as dentin desensitizers on the dentin-pulp complex in rats

Bioactive glasses have been recommended for the occlusion of dentinal tubules in treating cervical dentin hypersensitivity. This study evaluates an in vivo model of dentin exposure, and tests the efficacy of bioglass treatments. Thirty male Wistar rats received gingival recession surgery on the upper left first molar. The treatments were applied over the surface of the exposed dentin every 4 days for 28 days. The groups were as follows: Naive; Gingival recession; Cavity varnish; Biosilicate^®; Strontium bioglass; and Potassium bioglass. Changes in the dentin-pulp complex, and the presence of substance P, were evaluated through hematoxylin-eosin and immunohistochemical staining. The groups had similar results. Teeth with exposed dentinal tubules in rats showed a typical pattern in the dentin-pulp complex and immunotracing for substance P. The materials did not cause pulp damage. The effects of gingival recession and open dentinal tubules on pulp tissue require further clarification.

Sol-gel bioactive glass containing biomaterials for restorative dentistry: A review

OBJECTIVE

Bioactive glasses (BAGs) have been researched extensively for dentistry due to their favourable biocompatibility and hard tissue bonding ability. However, the specific application of BAGs produced through sol-gel synthesis in restorative dentistry has not been reviewed previously. This review provides a comprehensive account of the principles behind sol-gel derived BAGs and their investigation for dental tissue restoration materials.

METHODS

A search for in vitro and in vivo studies was performed using the databases Web of Science®, Medline®, Scopus® and Google Scholar®. Articles published over the past 20 years were selected and data on the BAG composition and morphology was extracted. Analysis of the effect of specific BAG additives on the properties of experimental dental materials was also performed.

RESULTS

A majority of BAG particles investigated were spheres ranging in size from 5 nm to ~650 µm. Sol-gel BAGs are mainly applied in the treatment of hypersensitive dentine and for pulp-dentine tissue engineering, while a handful have been used in target drug delivery. BAG fillers are promising additives that result in improved biological properties, antibacterial effects, hardness, acid buffering and remineralization. Unfortunately, some detrimental effects on optical properties have been observed with BAG addition. Additionally, in vivo data, investigations into radiopacity and standardization of test protocols are identified as areas for improvement and further studies.

SIGNIFICANCE

Future work should consider the pertinent issues raised in order to improve the quality of available data and expand knowledge in this area of dental biomaterials research and development.

Effect of bioactive glasses containing strontium and potassium on dentin permeability

Dentin hypersensitivity (DH) is characterized by pain caused by an external stimulus on exposed dentin. Different therapeutic approaches have been proposed to mitigate this problem; however, none of them provide permanent pain relief. In this study, we synthesized and characterized experimental bioactive glasses containing 3.07 mol% SrO or 3.36 mol% K₂ O (both equivalent to 5 wt% in the glass), and evaluated their effect on dentin permeability to verify their potential to treat DH. The experimental materials were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction to confirm the respective structures and chemical compositions. The reduction in the hydraulic conductance of dentin was evaluated at the three stages: minimum permeability; maximum permeability (24% ethylenediaminetetraacetic acid [EDTA] treatment); and final dentin permeability after treatment with the bioactive glasses. They all promoted a reduction in dentin permeability, with a significant difference for each sample and posttreatment group. Also, a significant reduction in dentin permeability was observed even after a simulated toothbrushing test, demonstrating effective action of these materials against DH. Besides, incorporating 3.07 mol% SrO was a positive factor. Therefore, strontium's desensitizing and re-mineralizing properties can be further exploited in bioactive glasses to promote a synergistic effect to treat DH.

Bioactivity assessment of bioactive glasses for dental applications: A critical review

OBJECTIVE

In the context of minimally invasive dentistry and tissue conservation, bioactive products are valuable. The aim of this review was to identify, clarify, and classify the methodologies used to quantify the bioactive glasses bioactivity.

METHODS

Specific search strategies were performed in electronic databases: PubMed, Embase, Cochrane Library, and Scopus. Papers were selected after a review of their title, abstract, and full text. The following data were then examined for final selection: BAG investigated, objectives, criteria, methods, and outcomes.

RESULTS

Sixty-one studies published from 2001 to 2019, were included. The bioactivity of BAG can be evaluated in vitro in contact with solutions, enamel, dentin, or cells. Other studies have conducted in vivo evaluation by BAG contact with dentin and dental pulp. Studies have used various analysis techniques: evaluation of apatite with or without characterization or assessment of mechanical properties. Reprecipitation mechanisms and pulp cell stimulation are treated together through the term 'bioactivity'.

SIGNIFICANCE

Based on these results, we suggested a classification of methodologies for a better understanding of the bioactive properties of BAG. According to all in vitro studies, BAG appear to be bioactive materials. No consensus has been reached on the results of in vivo studies, and no comparison has been conducted between protocols to assess the bioactivity of other bioactive competitor products.

Efficacy of Ca2+- or PO4 3--conjugated mesoporous silica nanoparticles on dentinal tubule occlusion: an in-vitro assessment

Background

Maintaining a long-term biological effect of dental materials on dentinal tubule occlusion is one of the great technical challenges in dental clinics. In addition to physical treatment, chemical treatment to produce insoluble precipitates to seal dentinal tubules has been used. As dentin is mostly composed of calcium and phosphate complexes, in this study, we have developed a novel tubule-occluding material [Ca²⁺/PO₄³⁻@mesoporous silica nanoparticles (MSNs)] by separately conjugating either Ca²⁺ or PO₄³⁻ with MSNs.

Methods

The shape and structure of the MSNs were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The surface morphology and chemical compositions of Ca²⁺@MSNs/PO₄³⁻@MSNs and Ca²⁺/PO₄³⁻@MSNs were examined using SEM and X-ray fluorescence (XRF). The element distribution of Ca²⁺/PO₄³⁻@MSNs was detected using energy dispersive spectrometer (EDS). The sustained release ability of Ca²⁺@MSNs/PO₄³⁻@MSNs was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficacy of Ca²⁺/PO₄³⁻@MSNs on dentinal tubule sealing was evaluated using SEM, and the results were analyzed by Image-Pro software to determine the best water-powder ratio. We also compared the sealing efficacy between Ca²⁺/PO₄³⁻@MSNs and NovaMin, which is currently used in clinics, under the simulated conditions of oral acidic corrosion and mechanical friction.

Results

Ca²⁺/PO₄³⁻@MSNs are a new type of tubule-occluding material with sustained release properties. The ratio of Ca²⁺@MSNs: PO₄³⁻@MSNs: H₂O =0.015 g: 0.015 g: 150 µL exhibited an excellent sealing effect on dentinal tubules as well as resistance to oral acid corrosion and daily oral friction.

Conclusions

The novel dental material Ca²⁺/PO₄³⁻@MSNs demonstrates potential long-term effectiveness in sealing dentinal tubules and reducing dentin sensitivity, which is one of the most important problems in dental clinics.

Novel calcium encapsulated mesocellular siliceous foams for crystal growth in dentinal tubules

OBJECTIVES

The aim of this study was to investigate the novel mesocellular siliceous foams (MCF) containing CaCO₃ nanoparticles (denoted as CMCF) combined with phosphoric acid could occlude dentinal tubules through the formation of biomimetic crystal barrier.

METHODS

Ultrastructures of MCF and CMCF were examined by transmission electron microscopy (TEM). Elemental components were analyzed with energy dispersive X-ray spectrometry (EDX). CMCF was mixed with distilled water, 10%, 20% and 30% phosphoric acid then applied on dentine discs. Crystals were characterized by X-ray powder diffractometry (XRD). The sealing efficacy of the dentinal tubules was examined by scanning electron microscopy.

RESULTS

TEM images showed MCF presented a pore size of approximately 30.0 nm and CMCF contained abundant nano-CaCO₃. Sealing efficacy showed that CMCF, when reacted with 30% phosphoric acid, would form crystals in the dentinal tubules to a depth of 83.2 ± 17.6 μm at an occlusion percentage of 75.6 ± 12.8% on average; both occlusion percentage and depth were higher than those obtained with 10% or 20% phosphoric acid (p < 0.05). The results of XRD and EDS indicated that the crystal growth in the dentinal tubules could be transformed into the biomimetic crystals.

CONCLUSION

This study showed that the CMCF with 30% phosphoric acid could effectively occlude the dentinal tubules through the formation of biomimetic crystal barrier.

CLINICAL SIGNIFICANCE

The novel CMCF combined with phosphoric acid may have potential for the treatment of dentine hypersensitivity.

Effects of fluoride and epigallocatechin gallate on soft-drink-induced dental erosion of enamel and root dentin

BACKGROUND/PURPOSE

Fluoride and epigallocatechin gallate (EGCG) have been proven to prevent dental caries. The purpose of this study was to evaluate the effects of fluoride and EGCG on soft-drink-induced dental erosion in vitro.

METHODS

Forty enamel and dentin specimens were prepared from extracted human teeth. The specimens were divided into 4 groups and treated separately with distilled water (as control), 0.5 M sodium fluoride (NF), 400 μM EGCG (EG), and a solution containing 0.5 M NaF and 400 μM EGCG (FG). Cyclic erosive treatment was performed according to the experimental procedures. The specimens were analyzed using laser scanning confocal microscopy, scanning electron microscopy, and a microhardness tester. The data were analyzed using ANOVA and Bonferroni's post hoc test. The significance level was set at 5%.

RESULTS

The amount of substance loss was lower in the NF and EG groups than in the control group (p < 0.05). The erosion-caused substance loss was more pronounced in the dentin than in the enamel specimens. Surface microhardness loss was lower in the NF and EG groups than in the control group (p < 0.05). The diameter of the dentinal tubule was wider in the control group than in the NF and EG groups (p < 0.05). No combined effects were observed in the FG group.

CONCLUSION

Both fluoride and EGCG are effective in preventing soft-drink-induced erosion compared with the control group. Fluoride and EGCG may interfere with each other. The mechanisms of the anti-erosive effect need to be explored in the future.

Application of electrophoretic deposition to occlude dentinal tubules in vitro

OBJECTIVES

This study aims to apply electrophoretic deposition (EPD) for occlusion of dentinal tubules in vitro and investigate its effect on tubule occlusion and shear bond strength (SBS).

METHODS

Charged mesoporous silica nanoparticles (MSNs) were synthesized and characterized through field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared (FT-IR) spectroscopy analyses. Thirty-nine sensitive dentin specimens were modeled and assigned randomly to three groups with different treatments (n = 13 each): group 1, immersion in the MSN suspension; and groups 2 and 3, anodic EPD with the specimen on the negative and positive electrode respectively. The effect of dentinal tubule occlusion was evaluated by dentin permeability test (n = 10 each) and FESEM examination (n = 3 each). Moreover, 18 specimens were grouped (n = 6 each) and treated in the same method. A resin stick was bonded onto each of the specimen using a self-etch adhesive (single bond universal) for SBS testing.

RESULTS

Negatively-charged MSNs were synthesized and characterized as small and well-dispersed particles. After the EPD treatment (group 3), the dentinal tubules were effectively occluded by MSNs, which infiltrated into the tubules at a depth of approximately 7-8 μm and tightly associated with the tubular inwalls. SBS was not significantly different among the three groups (P > 0.05).

CONCLUSIONS

Synthesized MSNs were deposited into dentinal tubules by EPD treatment without compromising dentin bond strength.

CLINICAL SIGNIFICANCE

Application of EPD is a new approach for occlusion of dentinal tubules and exhibits potential in the study of dentin hypersensitivity.

Ability of three desensitizing agents in dentinal tubule obliteration and durability: An in vitro study

Aim:

The purpose of this study was to evaluate the effectiveness of three desensitizing agents on dentinal tubule obliteration and their durability in use on the dentinal tubules.

Materials and Methods:

Sixty specimens were obtained from 30 extracted sound human maxillary first premolars. Each tooth was mesiodistally sectioned to obtain 30 buccal and 30 lingual surfaces, and enamel was removed in order to simulate hypersensitive dentin. Specimens were divided into four groups with 15 specimens each. Group 1 samples were immersed in artificial saliva, Group 2 samples were coated with Vivasens, Group 3 samples were coated with VOCO Admira Protect, and Group 4 samples were coated with Neo Active Apatite suspension. These specimens were examined under scanning electron microscope (SEM) to find out the occluding ability of the respective products. The specimens were brushed to find out their durability for 1 week and 1 month and were examined under SEM.

Statistical Analysis:

The results were statistically analyzed by analysis of variance (ANOVA) and Tukey's test.

Results:

Group 1 differed significantly from the Vivasens, Admira, and Neo Active Apatite groups at 5% level of significance (P < 0.05). The Vivasens group differed significantly from the Admira and Neo Active Apatite groups at 5% level of significance (P < 0.05).

Conclusion:

The Ormocer-based Admira Protect showed the best results.

After bleaching enamel remineralization using a bioactive glass-ceramic (BioSilicate®)

Tooth bleaching agents may weaken the tooth structure, therefore, it is important to minimize any risks of enamel and dentine damage caused by them. In this way, different materials have been used to avoid or minimize the tooth damage during bleaching. Recently, bioactive glasses have been demonstrated to be effective in mineralization of dental structures. Therefore, this study evaluated the effect of BioSilicate® (a polycrystalline bioactive glass-ceramic) after bleaching by Laser-induced breakdown spectroscopy (LIBS) technique. Bovine dental blocks with 4 × 4 × 3 mm were obtained (n = 20), sequentially embedded in epoxy resin and then polished. Bleaching was performed using 35% hydrogen peroxide (Whiteness HP). Calcium (Ca) and phosphate (P) intensity values by LIBSwere obtained before the treatment (T0, baseline – control Group), after bleaching (T1), and after BioSilicate® application (T2). The use of BioSilicate® after bleaching showed to be an optimal way to remineralize enamel surface making BioSilicate® application a promising adjunct step to avoid or minimize the mineral loss on enamel surface after bleaching.

The synthesis and characterization of a novel potassium chloride-fluoridated hydroxyapatite varnish for treating dentin hypersensitivity

Dentin hypersensitivity is treated using materials that occlude the dentinal tubules or release potassium ions that induce nerve desensitization. In this study we formulated a novel varnish containing potassium chloride and fluoridated hydroxyapatite and evaluated its physical properties and cytotoxicity. Potassium ion release from the varnish was measured. Dentin permeability was evaluated by measuring the hydraulic conductance of etched dentin discs treated with the varnish. The direct contact test and MTT assay were performed to evaluate the varnish's cytotoxicity. We found that the varnish released potassium ions over 6 h, and demonstrated a statistically higher reduction in dentin permeability compared to commercial fluoride varnish or control. Dentin disc scanning electron microscopy images demonstrated occluded dentinal tubules in the novel varnish group after brushing. The cytotoxicity tests indicated the varnish was biocompatible with gingival and pulpal fibroblasts. We propose the novel varnish is a potential material for use in hypersensitivity management.

A mesoporous silica biomaterial for dental biomimetic crystallization

The loss of overlying enamel or cementum exposes dentinal tubules and increases the risk of several dental diseases, such as dentin hypersensitivity (causing sharp pain and anxiety), caries, and pulp inflammation. This paper presents a fast-reacting, more reliable and biocompatible biomaterial that effectively occludes exposed dentinal tubules by forming a biomimetic crystalline dentin barrier. To generate this biomaterial, a gelatin-templated mesoporous silica biomaterial (CaCO3@mesoporous silica, CCMS) containing nanosized calcium carbonate particles is mixed with 30% H3PO4 at a 1/1 molar ratio of Ca/P (denoted as CCMS-HP), which enables Ca2+ and PO4(3-)/HPO4(2-) ions to permeate the dentinal tubules and form dicalcium phosphate dihydrate (DCPD), tricalcium phosphate (TCP) or hydroxyapatite (HAp) crystals at a depth of approximately 40 μm (sub-μ-CT and nano-SEM/EDS examinations). In vitro biocompatibility tests (WST-1 and lactate dehydrogenase) and ALP assays show high cell viability and mineralization ability in a transwell dentin disc model treated with CCMS-HP (p<0.05). The in vivo efficacy and biocompatibility analyses of the biomaterial in an animal model reveal significant crystal growth (DCPD, TCP or HAp-like) and no pulp irritation after 70 days (p<0.05). The developed CCMS-HP holds great promise for treating exposed dentin by growing biomimetic crystals within dentinal tubules. These findings demonstrate that the mesoporous silica biomaterials presented here have great potential for serving as both a catalyst and carrier in the repair or regeneration of dental hard tissue.

Enhancement of nano-hydroxyapatite bonding to dentin through a collagen/calcium dual-affinitive peptide for dentinal tubule occlusion

Calcium phosphate crystals, as the main component of dentin and enamel, have been widely used for the occlusion of dentinal tubules. However, the low bond strength and poor sealing effect limit their clinical practicality. In this study, a collagen/calcium dual-affinitive peptide E8DS (EEEEEEEEDSpESpSpEEDR) and nano-hydroxyapatite (nano-HAp) flocculi were developed to seal dentin tubules for reducing dentin hypersensitivity, whereas the E8DS peptides were pre-applied to improve the adhesion of occlusive hydroxyapatite coating on dentin collagen matrix for the long-lasting sealing effect and relief from hypersensitivity. Our study showed that E8DS peptides had a strong affinity with dentin collageneous matrix that almost 43.7% of initial E8DS peptides immobilized on exposed dentin samples remained detained after continuous washing by distilled water for four weeks at a rate of 1 mL/min. Nano-HAp flocculi were obtained by re-neutralization of HAp-HCl solution and then brushed onto the surfaces of pre-treated human dentin disks with E8DS peptides, which showed a perfect occlusion of exposed dentinal tubules, as compared with Nano-HAp only and a commercial desensitizer, Green Or. With only around 10-min E8DS peptide pre-treatment, the occlusive mineral layers remained intact against consecutively stirred washing in phosphate-buffered saline or coke for 15 min, and 6 min of tooth-brushing, which implied that our E8DS peptide could comparatively improve the durability of sealant-dentin interface bonds for long-lasting dentine desensitization.

Phosphorus Effects of Mesoporous Bioactive Glass on Occlude Exposed Dentin

In recent studies, sealing of exposed dentinal tubules is generally considered as one of the most effective strategies to treat dentin hypersensitivity. Mesoporous bioactive glass (MBG) is a potential material for treating dentin hypersensitivity due to its highly specific areas for dissolution and re-precipitated reaction for reduction in dentin permeability. The groups of commercial products of PerioGlas®, synthetic MBG and MBG without phosphorus (MBGNP) were compared. The MBG and MBGNP powders were prepared by the sol-gel method and mixed with different calculated ratios of phosphoric acid (PA) and then was brushed onto dentin surfaces. We used X-ray diffractometer (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) to investigate the physiochemistry and the occlusion ability of dentinal tubules. The results showed that MBG paste mixed with PA solution has a better ability for occluding dentinal tubules than MBGNP; it has a short reaction time and good operability. The major crystallite phase of MBG agents was monocalcium phosphate monohydrate [Ca(H₂PO₄)₂·H₂O] in the early stages of the reactions. MBG pastes that were mixed with 30% and 40% PA had the ability to create excellent penetration depth greater than 80 μm. These agents have the potential to treat dentin hypersensitivity.

Bioengineering of the silica-polymerizing enzyme silicatein-alpha for a targeted application to hydroxyapatite

Since its discovery, numerous biotechnological approaches have aimed to explore the silica-polymerizing catalytic activity of the enzyme silicatein. In vivo, silicatein catalyzes polymerization of amorphous silica nanospheres from soluble precursors. In vitro, it directs the formation of nanostructured biosilica. This is of interest for various applications that strive to benefit from both the advantages of the biological system (i.e., silica synthesis under physiological conditions) and the cell mineralization-stimulating effect of biosilica. However, so far immobilization of silicatein has been hampered by the complex multistep procedure required. In addition, the chemical surface modifications involved not only restrict the choice of carrier materials but also render application of silicatein to hydroxyapatite (HA) of mineralized tissue impossible. Here we describe the bioengineering of silicatein, adapted for application in the fields of bone regeneration, tissue engineering, and dental care. Inspired by Glu-rich sequences of mammalian proteins that confer binding affinity to HA, a novel protein-tag was developed, the Glu-tag. Following expression of Glu-tagged silicatein, the HA-binding capacity of the enzyme is demonstrated in combination with synthetic and dental HA. Furthermore, immobilized Glu-tagged silicatein catalyzes synthesis of biosilica coatings on both synthetic HA nanofibrils and dental HA. Hence, Glu-tagged silicatein reveals a considerable biomedical potential with regenerative and prophylactic implementations.

Effect of monomer composition on crystal growth by resin containing bioglass

This study evaluated the effect of resin monomer composition on crystal growth at the interface between the resin/bioglass composites and water. Light-cured resin that contained 2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl], 2-hydroxyethyl methacrylate, and triethylene glycol dimethacrylate with different compositions were used. Resin/bioglass composites were prepared with 40 mass% bioglass and 60 mass% resin. The resin/bioglass composites were stored in deionized distilled water for 24 h (control group) or 3-12 months (experimental groups). After water storage, the disk surfaces were examined by light- and scanning electron microscopy. Chemical states of the crystals were analyzed by laser-Raman spectroscopy and micro-X-ray diffractometry. The microscopic analysis showed crystal on the resin disks surface after six months of water storage for hydrophilic resins. However, there was no crystal formation in the control and the experimental groups of specimens of hydrophobic resins. Raman analysis showed the chemical states of the crystals formed on the resin matrix and bioglass to be different. The micro-X-ray analysis of crystals on resin disks identified them to be calcium carbonate. This crystal formation occurred in water instead of simulated body fluid. In conclusion, the resin monomer compositions affected the ability to induce crystal growth on the surfaces of disks containing bioglass.