Developing a novel glass ionomer cement with enhanced mechanical and chemical properties.

OBJECTIVE: To develop a novel glass ionomer cement (NGIC) with enhanced mechanical and chemical properties and assess its biocompatibility, mechanical strength, and ion release. METHODS: Nanosilver doped bioactive glass (NanoAg BAG) was synthesized by sol-gel method and characterized by scanning electron microscopy with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The NanoAg BAG, together with poly(vinylphosphonic acid) (PVPA), alumino-fluorosilicate glass and poly-acrylic acid were used to synthesize NGIC. The optimal PVPA concentration for NGIC was determined by PVPA modified GIC's biocompatibility and mechanical properties and used to prepare NGIC specimens. NGIC specimens with NanoAg BAG at 0%, 1%, 2%, and 5% were allocated into Groups NGIC0, NGIC1, NGIC2, and NGIC5, respectively. The biocompatibility, surface morphology, elemental composition, surface topography, chemical properties, compressive strength, diametral tensile strength, and ion release of the NGIC were assessed. A conventional glass ionomer cement (GIC) was used as a control. RESULTS: A granular BAG with nano silver particles attached on its surface were found, indicating the successful synthesis of NanoAg BAG. PVPA at 10% presented the best effect in enhancing the biocompatibility and mechanical properties of PVPA modified GIC and was used to prepare NGIC specimens. NGIC1 showed similar biocompatibility, surface morphology and topography to GIC. Chemical properties results showed that NGICs showed the same adsorption peaks to GIC. The compressive strength (mean±SD in MPa) was 168.1 ± 29.7, 205.5 ± 29.5, 221.8 ± 46.8, 216.6 ± 59.3 and 167.7 ± 36.4, and the diametral tensile strength (mean±SD in MPa) was 14.1 ± 1.7, 18.3 ± 4.9, 21.2 ± 2.2, 17.2 ± 3.8 and 13.3 ± 3.3 for GIC, NGIC0, NGIC1, NGIC2 and NGIC5 respectively. NIGC0, NGIC1 and NGIC2 showed higher compressive and diametral tensile strength than GIC (p < 0.01). NGIC2 and NGIC5 showed higher release of fluoride, calcium, phosphate and silver ion than GIC and NGIC0 (p < 0.05). CONCLUSION: A biocompatible NGIC with enhanced mechanical properties were developed. It presented enhanced fluoride, calcium, phosphate and silver ion release compared to conventional GIC.

A novel glass ionomer cement with silver zeolite for restorative dentistry.

OBJECTIVE: To develop an antimicrobial silver zeolite glass ionomer cement (SZ-GIC) and determine its biocompatibility, physical, adhesive and antibacterial properties. METHODS: Silver nitrate and sodium zeolite were used to synthesize silver zeolite (SZ). SZ-GICs were prepared by incorporating SZ into GIC at 5% (SZ-GIC5), 2% (SZ-GIC2), or 1% (SZ-GIC1) by weight, respectively. The SZ-GICs were characterized by evaluating surface morphology, topography and elemental composition. SZ-GICs' biocompatibility was assessed by evaluating cell cytotoxicity. Their physical properties were determined by testing setting time, compressive strength, flexural strength, water sorption and solubility. Their adhesive property was assessed by evaluating micro-tensile bond strength. Their antibacterial properties were assessed by evaluating biofilm growth kinetic, metabolic activity, viability and morphology. GIC was used as a control. RESULTS: SZ was a three-dimensional crystalline mineral. SZ-GICs (including SZ-GIC 5, 2 and 1) showed similar surface morphology and topography to GIC. SZ-GIC1 and GIC had no difference in cell cytotoxicity (p>0.05). SZ-GICs and GIC showed no difference in setting time (p>0.05). SZ-GICs had higher compressive and flexural strength than GIC (p<0.05). SZ-GIC2 and SZ-GIC1 showed lower water sorption and solubility than GIC (p<0.05). SZ-GICs had higher micro-tensile bond strength than GIC (p<0.05). Biofilms on SZ-GICs' surfaces showed lower colony-forming units, decreased metabolic activities, higher percentages of dead cells and more ruptured bacterial cells compared with those on GIC. CONCLUSION: SZ-GIC with silver zeolite at 1% by weight are as biocompatible as conventional GIC. The SZ-GICs have enhanced physical, adhesive and antibacterial properties than GIC. CLINICAL SIGNIFICANCE: A silver zeolite glass ionomer cement was developed. The SZ-GICs have great potential for caries prevention and management.

Caries Management with Non-Metallic Nanomaterials: A Systematic Review.

Background: Non-metallic nanomaterials do not stain enamel or dentin. Most have better biocompatibility than metallic nanomaterials do for management of dental caries. Objective: The objective of this study is to review the types, properties and potential uses of non-metallic nanomaterials systematically for managing dental caries. Methods: Two researchers independently performed a literature search of publications in English using PubMed, Scopus and Web of Science. The keywords used were (nanoparticles OR nanocomposites OR nanomaterials) AND (caries OR tooth decay). They screened the titles and abstracts to identify potentially eligible publications of original research reporting non-metallic nanomaterials for caries management. Then, they retrieved and studied the full text of the identified publications for inclusion in this study. Results: Out of 2497 resulting publications, this study included 75 of those. The non-metallic nanomaterials used in these publications were categorized as biological organic nanomaterials (n=45), synthetic organic nanomaterials (n=15), carbon-based nanomaterials (n=13) and selenium nanomaterials (n=2). They inhibited bacteria growth and/or promoted remineralization. They could be incorporated in topical agents (29/75, 39%), dental adhesives (11/75, 15%), restorative fillers (4/75, 5%), dental sealant (3/75, 4%), oral drugs (3/75, 4%), toothpastes (2/75, 3%) and functional candies (1/75, 1%). Other publications (22/75, 29%) do not mention specific applications. However, most publications (67/75, 89%) were in vitro studies. Six publications (6/75, 8%) were animal studies, and only two publications (2/75, 3%) were clinical studies. Conclusion: The literature showed non-metallic nanomaterials have antibacterial and/or remineralising properties. The most common type of non-metallic nanomaterials for caries management is organic nanomaterials. Non-metallic nanomaterials can be incorporated into dental sealants, toothpaste, dental adhesives, topical agents and even candies and drugs. However, the majority of the publications are in vitro studies, and only two publications are clinical studies.

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.

In Vitro Studies of Graphene for Management of Dental Caries and Periodontal Disease: A Concise Review.

Graphene is a single-layer two-dimensional carbon-based nanomaterial. It presents as a thin and strong material that has attracted many researchers' attention. This study provides a concise review of the potential application of graphene materials in caries and periodontal disease management. Pristine or functionalized graphene and its derivatives exhibit favorable physicochemical, mechanical, and morphological properties applicable to biomedical applications. They can be activated and functionalized with metal and metal nanoparticles, polymers, and other small molecules to exhibit multi-differentiation activities, antimicrobial activities, and biocompatibility. They were investigated in preventive dentistry and regenerative dentistry. Graphene materials such as graphene oxide inhibit cariogenic microbes such as Streptococcus mutans. They also inhibit periodontal pathogens that are responsible for periodontitis and root canal infection. Graphene-fluorine promotes enamel and dentin mineralization. These materials were also broadly studied in regenerative dental research, such as dental hard and soft tissue regeneration, as well as periodontal tissue and bone regeneration. Graphene oxide-based materials, such as graphene oxide-fibroin, were reported as promising in tissue engineering for their biocompatibility, bioactivity, and ability to enhance cell proliferation properties in periodontal ligament stem cells. Laboratory research showed that graphene can be used exclusively or by incorporating it into existing dental materials. The success of laboratory studies can translate the application of graphene into clinical use.

Application of Copper Nanoparticles in Dentistry.

Nanoparticles based on metal and metallic oxides have become a novel trend for dental applications. Metal nanoparticles are commonly used in dentistry for their exclusive shape-dependent properties, including their variable nano-sizes and forms, unique distribution, and large surface-area-to-volume ratio. These properties enhance the bio-physio-chemical functionalization, antimicrobial activity, and biocompatibility of the nanoparticles. Copper is an earth-abundant inexpensive metal, and its nanoparticle synthesis is cost effective. Copper nanoparticles readily intermix and bind with other metals, ceramics, and polymers, and they exhibit physiochemical stability in the compounds. Hence, copper nanoparticles are among the commonly used metal nanoparticles in dentistry. Copper nanoparticles have been used to enhance the physical and chemical properties of various dental materials, such as dental amalgam, restorative cements, adhesives, resins, endodontic-irrigation solutions, obturation materials, dental implants, and orthodontic archwires and brackets. The objective of this review is to provide an overview of copper nanoparticles and their applications in dentistry.

A novel, doped calcium silicate bioceramic synthesized by sol-gel method: Investigation of setting time and biological properties.

The aim of the current study was to synthesize a fast-setting ion-doped calcium silicate bioceramic by the sol-gel method and to characterize its in vitro apatite-forming ability and cell viability. Calcium silicate (CS), doped calcium silicate with zinc and magnesium, with Ca/Zn molar ratios of 6.7:1 (DCS1), and 4.5:1 (DCS2), were synthesized by the sol-gel method. Matreva white MTA (WMTA, Matreva, CA, Egypt) was used as a control. The synthesized powders were characterized by x-ray diffraction. Setting time was measured using the Gilmore needle indentation technique. The in vitro apatite-forming ability of the materials was evaluated by scanning electron microscope and energy dispersive X-ray. NIH3T3-E1 cells viability was tested using MTT assay. The ion release of Ca, Si, Zn, and Mg was measured using inductive coupled plasma-optical emission spectroscopy (ICP-OES). One-way ANOVA was used to analyze setting time results. The Tukey's HSD post hoc test was used to establish significance (p < 0.001). For nonparametric data, the Kruskal-Wallis H test with Dunn's correction for post hoc comparison was used (p < 0.05). CS, DCS1, and DCS2 showed a significant decrease in setting time 33 ± 1.63 min, 28 ± 1.63 min, and 41.75 ± 2.87 min, respectively, compared to WMTA 91 ± 3.16 min (p < 0.001). DCS1 showed the highest apatite-forming ability and cell viability compared to the other groups. Ca and Si ions release decreased in both DCS1 and DCS2. The physical and biological properties of CS can be successfully improved by the sol-gel synthesis and ions doping. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:56-66, 2020.

Silane adhesion mechanism in dental applications and surface treatments: A review.

OBJECTIVE: To give a current review of silane adhesion chemistry, applications of silane coupling agents and related surface pretreatment methods in contemporary dentistry. METHODS: Silane coupling agents are adhesion promoters to chemically unify dissimilar materials used in dentistry. Silanes are very effective in adhesion promotion between resin composites and silica-based or silica-coated indirect restorative materials. It is generally accepted that for non-silica-based restorations, surface pretreatment is a mandatory preliminary step to increase the silica content and then, with help of silane, improve resin bonding. This review discusses the silane-based adhesion chemistry, silane applications in dentistry, surface pretreatment methods, and presents the recent development of silane coupling agents. RESULTS: A silane coupling agent is considered a reliable, good adhesion promoter to silica-based (or silica-coated) indirect restorations. Surface pre-treatment steps, e.g., acid etching for porcelain and tribo-chemical silica-coating for metal alloys, is used before silanization to attain strong, durable bonding of the substrate to resin composite. In clinical practice, however, the main problem of resin bonding using silanes and other coupling agents is the weakening of the bond (degradation) in the wet oral environment over time. SIGNIFICANCE: A silane coupling agent is a justified and popular adhesion promoter (adhesive primer) used in dentistry. The commercial available silane coupling agents can fulfil the requirements in clinical practice for durable bonding. Development of new silane coupling agents, their optimization, and surface treatment methods are in progress to address the long term resin bond durability and are highly important.

Effect of silanization of hydroxyapatite fillers on physical and mechanical properties of a bis-GMA based resin composite.

To evaluate the physical and mechanical properties of an experimental bis-GMA-based resin composite incorporated with non-silanized and silanized nano-hydroxyapatite (nHAP) fillers. Experimental bis-GMA based resin composites samples which were reinforced with nHAP fillers were prepared. Filler particles were surface treated with a silane coupling agent. Five test groups were prepared: 1. Unfilled, 2. Reinforced with 10wt% and 30wt% non-silanized nHAP fillers, and 3. Reinforced with 10wt% and 30wt% silanized nHAP fillers. The samples were subjected to tests in dry condition and in deionized water, aged at 37°C for 30 days. Prepared silanized and non-silanized nHAP were analyzed with Fourier Transform Infrared (FTIR) Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The micro-hardness and water sorption were evaluated. Data were analyzed by one-way ANOVA (p<0.05). The samples were characterized by FTIR Spectroscopy, Thermogravimetric Analysis and Differential Scanning Calorimetry. The surface morphology of sample surfaces was examined by Scanning Electron Microscope (SEM). The results showed that the water sorption for nHAP fillers reinforced resins was significantly lower than unfilled resins. Surface hardness for resins reinforced with silane treated fillers was superior to unfilled and untreated fillers resins. The resin matrix loaded with 30wt% silanized-nHAP fillers would improve the physical and mechanical properties of a bis-GMA based resin.

Silica coating of zirconia by silicon nitride hydrolysis on adhesion promotion of resin to zirconia.

In this study, the effect of silica coating on zirconia by silicon nitride hydrolysis in resin zirconia bonding was investigated. The silica coated zirconia samples were prepared in silicon nitride dispersion at 90 °C under different immersion times followed by a thermal treatment at 1400 °C. Four test groups were prepared: 1) zirconia samples treated by sandblasting, 2) zirconia samples treated by immersion in silicon nitride dispersion for 6 h, 3) zirconia samples treated by immersion in silicon nitride dispersion for 24 h and 4) zirconia samples treated by immersion in silicon nitride dispersion for 48 h. The coatings were characterized by SEM, EDX, XRD and Raman. The resin zirconia bond strengths of the four test groups were evaluated under three storage conditions: dry storage, water storage in deionized water at 37 °C for 30 days and thermo-cycling for 6000 cycles between 5.0 and 55.0 °C. Surface morphology and composition of zirconia were changed after surface treatments. Phase transformation was observed for zirconia surface by sandblasting treatment but was not observed for zirconia surface treated with silicon nitride hydrolysis. Significant differences in bond strengths were found under different surface treatments (p<0.001) and under three storage conditions (p<0.005). The highest bond strength values were obtained by sandblasting treatment.

Surface treatment of titanium by a polydimethylsiloxane coating on bond strength of resin to titanium.

PURPOSE: To evaluate the in vitro effect of titanium surface treatment by a polydimethylsiloxane coating on the shear bond strength of a resin composite cement to titanium. MATERIALS AND METHODS: The titanium samples (40×30mm) were divided into 4 groups (n=12). A control group was surface treated by sandblasting using 110µm silica-coated alumina powder at a constant pressure of 300kPa for 15s/1cm(2). For other three test groups, a polydimethylsiloxane silicone grease was applied onto the surface. The samples were subjected to thermal treatment in air at temperatures of 800°C, 1000°C, and 1100°C for 2h. A silane coupling agent was then applied and a resin composite stub was bonded using a polyethylene mold. The samples were submitted to three different storage conditions: dry storage, water storage in deionized water at 37°C for 30 days and thermo-cycled for 6000 cycles between 5.0 and 55.0°C. The shear bond strengths of all test groups were determined using a universal testing machine. Data were analyzed by two-way ANOVA and Tukey HSD (p<0.05). The surface morphology of titanium and elemental composition were examined with SEM and EDAX. RESULTS: The results showed that there was a significant difference for different surface treatments (p<0.001) and different storage conditions (p<0.01) on the mean shear bond strengths. EDAX analysis showed there was a change of elemental composition of titanium surface after thermal treatment of the coating. CONCLUSION: Surface treatment of titanium with a polydimethylsiloxane coating at 1000°C and 1100°C curing provides sufficient resin bonding for clinical services.

The effect of silica-coating by sol-gel process on resin-zirconia bonding.

The effect of silica-coating by sol-gel process on the bond strength of resin composite to zirconia was evaluated and compared against the sandblasting method. Four groups of zirconia samples were silica-coated by sol-gel process under varied reagent ratios of ethanol, water, ammonia and tetraethyl orthosilicate and for different deposition times. One control group of zirconia samples were treated with sandblasting. Within each of these five groups, one subgroup of samples was kept in dry storage while another subgroup was aged by thermocycling for 6,000 times. Besides shear bond testing, the surface topography and surface elemental composition of silica-coated zirconia samples were also examined using scanning electron microscopy and X-ray photoelectron spectroscopy. Comparison of silica coating methods revealed significant differences in bond strength among the Dry groups (p<0.001) and Thermocycled groups (p<0.001). Comparison of sol-gel deposition times also revealed significant differences in bond strength among the Dry groups (p<0.01) and Thermocycled groups (p<0.001). Highest bond strengths were obtained after 141-h deposition: Dry (7.97±3.72 MPa); Thermocycled (2.33±0.79 MPa). It was concluded that silica-coating of zirconia by sol-gel process resulted in weaker resin bonding than by sandblasting.

Resin zirconia bonding promotion with some novel coupling agents.

OBJECTIVES: To evaluate and compare three novel coupling agents: 2-hydroxyethyl methacrylate, itaconic acid and oleic acid to two silane coupling agents, one commercial silane product and 3-acryloxypropyltrimethoxysilane on the bond durability of resin composite to zirconia. METHODS: Zirconia samples were silica-coated by air abrasion and each of the five coupling agents was then applied to give five test groups. Resin composite stubs were bonded onto the conditioned zirconia surfaces. The samples were stored: dry storage, 30 days in water and thermocycled to give a total of fifteen test groups. The shear bond strengths were determined using a universal testing machine and data analyzed by two-way ANOVA and Tukey HSD (p<0.05) with shear bond strength as dependent variable and storage condition and primers as independent variables. The bond formation of the five coupling agents to zirconia was examined by X-ray photoelectron spectroscopy (XPS). RESULTS: Two-way ANOVA analysis showed that there was a significant difference for different primers (p<0.05) and different storage conditions (p<0.05) on the shear bond strength values measured. XPS analysis showed a shift in binding energy for O(1s) after priming with the five coupling agents which revealed different bond formations related to the functional groups of the coupling agents. SIGNIFICANCE: The shear bond strength values measured for all coupling agents after water storage and thermocycling exceed the minimum shear bond strength value of 5MPa set by ISO. The silane coupling agent, 3-acryloxypropyltrimethoxysilane, showed the highest bond strength of the three storage conditions.

Shear bond strength between resin and zirconia with two different silane blends.

OBJECTIVE: To study in vitro the effect of two cross-linking silanes, bis-1,2-(triethoxysilyl)ethane and bis[3-(trimethoxysilyl)propyl]amine, blended with an organofunctional silane coupling agent, (3-acryloxypropyl)trimethoxysilane, on the shear bond strength between resin-composite cement and silicatized zirconia after dry storage and thermocycling. MATERIALS AND METHODS: Six tested groups of 90 samples of yttria stabilized zirconia were used for sample preparation. The surfaces of the zirconia were silica-coated. 3M ESPE Sil silane was used as a control. Solutions of (3-acryloxypropyl)trimethoxysilane with cross-linking silanes bis-1,2-(triethoxysilyl)ethane and bis[3-(trimethoxysilyl)propyl]amine were applied onto the surface of silicatized zirconia. 3M ESPE RelyX resin-composite cement was bonded onto the silicatized and silanized zirconia surface and light-cured. Three groups were tested under dry condition and the other three groups were tested for thermocycling. The shear bond strength was measured using a materials testing instrument. Group mean shear bond strengths were analysed by ANOVA at a significant level of p < 0.05. The zirconia surface composition was analysed by X-ray Photoelectron Spectroscopy. RESULTS: The highest shear bond strength was 11.8 ± 3.5 MPa for (3-acryloxypropyl)trimethoxysilane blended with bis-1,2-(triethoxysilyl)ethane (dry storage). There was a significant difference between mean shear bond strength values for (3-acryloxypropyl)trimethoxysilane blended with two cross-linking silanes, bis-1,2-(triethoxysilyl)ethane and bis[3-(trimethoxysilyl)propyl]amine, after thermocycling (p < 3.9 × 10(-8)). Various surface treatments of zirconia influenced the surface roughness (p < 4.6 × 10(-6)). The chemical composition analysis showed there was an increase in silicon and oxygen content after sandblasting. CONCLUSIONS: The results suggest that the combination of functional (3-acryloxypropyl)trimethoxysilane with cross-linking bis[3-(trimethoxysilyl)propyl]amine showed superior hydrolytic stability than with bis-1,2-(triethoxysilyl)ethane.

Aspects of silane coupling agents and surface conditioning in dentistry: an overview.

OBJECTIVES: To give an overview of aspects of silane coupling agents and surface conditioning in dentistry. METHODS: Currently, silane coupling agents are used as adhesion promoters. Silanes are effective in enhancing adhesion between resin composite and silica-based ceramics. They do not bond effectively to non-silica based dental restorative materials. Surface conditioning of non-silica based ceramics with silica coating improves the bonding. This current overview will focus on the silane coupling agents: their properties, limitations in adhesion promotion and the clinical problems with the use of silanes. It will also focus on the current surface conditioning methods as well as new surface conditioning techniques to enhance the bonding through conventional silanization approaches. RESULTS: Several surface conditioning methods are being used clinically to enhance the adhesion of resin composites to non-silica based restorative materials. Other approaches are under investigation. The clinical problem of using silanes in adhesion promotion is the bond degradation over time in oral environment. SIGNIFICANCE: The current silane coupling agents are not ideal. The current silane coupling agents can fulfill the minimum requirements in clinical practice to enhance the bonding of resin composite to dental restorative materials. Developments of novel surface conditioning methods and silane coupling agents are required to address the bond durability problem.