Effect of CPP-ACP addition on physical properties of zinc oxide non-eugenol temporary cements

Objectives

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is a milk derivative which holds nanoclusters of calcium and phosphate ions. The presence of CPP-ACP has been found to reduce demineralization and enhance remineralization in subsurface enamel and in dentin. Incorporation of CPP-ACP into luting cements has not been investigated. The aim of this study was to determine the effect on the physical properties of two commercially available zinc oxide non-eugenol temporary luting cements with incorporation of up to 8% (w/w) CPP-ACP.

Methods

Setting time, compressive strength, diametral tensile strength, film thickness and solubility tests were investigated for 0, 0.5, 1.0, 2.0, 3.0, 4.0 and 8.0% (w/w) CPP-ACP incorporated into Freegenol™ and Temp-Bond^® NE. Tests were carried out based on ISO 3107 requirements.

Results

Compressive and diametral tensile strengths progressively decreased with increasing concentrations of up to 8.0% (w/w) CPP-ACP incorporated into both Freegenol™ and Temp-Bond^® NE. Setting time was delayed beyond ISO requirements. Film thickness was not adversely affected. Increased solubility of Temp-Bond^® NE with 8.0% (w/w) CPP-ACP incorporation suggested an effect of the CPP-ACP on this property for this cement.

Significance

The incorporation of up to 8.0% (w/w) CPP-ACP into two zinc oxide non-eugenol luting cements has no adverse effects on the film thickness, compressive strength and diametral tensile strength of the cements investigated. Solubility investigations suggest that CPP-ACP leaches out of the zinc oxide non-eugenol luting cements into an aqueous environment.     

Titanium dioxide nanoparticles addition to a conventional glass-ionomer restorative: influence on physical and antibacterial properties

Objectives

The aim of this study was to evaluate the addition of titanium dioxide (TiO₂) nanoparticles to a conventional glass-ionomer (GI) on physical and antibacterial properties.

Methods

TiO₂ nanoparticles were incorporated into the powder component of Kavitan^® Plus (SpofaDental, Czech Republic) at 3%, 5% and 7% (w/w). Unblended powder was used as control. Fracture toughness, compressive strength, flexural strength and microtensile bond strength were evaluated using a universal testing machine. Surface microhardness was measured using Vickers microhardness tester. Setting time was determined as specified in the ISO standard. The antibacterial activity was evaluated using direct contact test against Streptococcus mutans. Fluoride release and SEM analysis were carried out. Data were analysed using ANOVA and Tukey's test.

Results

GI-containing 3% and 5% (w/w) TiO₂ nanoparticles improved the fracture toughness, flexural strength and compressive strength compared to the unmodified GI. However, a decrease in the mechanical properties was found for GI-containing 7% (w/w) TiO₂ nanoparticles. GI-containing 5% and 7% (w/w) TiO₂ nanoparticles compromised the surface microhardness. Setting time of GI-containing TiO₂ nanoparticles decreased but the values remained within ISO limits. The addition of TiO₂ nanoparticles to the conventional GI did not compromise its bond strength with dentine or fluoride release of the GI. GI-containing TiO₂ nanoparticles possessed a potent antibacterial effect.

Conclusions

GI-containing 3% (w/w) TiO₂ nanoparticles is a promising restorative material with improved mechanical and antibacterial properties. This novel experimental GI may be potentially used for higher stress-bearing site restorations such as Class I and II.     

Resin-modified glass ionomer cements: fluoride release and influence on Streptococcus mutans growth

The aims of the present study were to measure the fluoride release of 1 glass ionomer cement, 1 cermet cement, 3 resin-modified glass ionomer cements and 1 compomer, and to determine the influence of each material on bacterial growth. Test specimens were eluted in saline for 180 days. Every 2 days, the specimens were transferred into fresh saline and the fluoride content of the solution was measured. Furthermore, 48-h, 14-d, 90-d, and 180-d eluates were inoculated with Streptococcus mutans and bacterial growth was recorded nephelometrically. Fluoride release dropped significantly over time for each material with values between 6.2 (Ketac-Silver) and 29.3 (Photac-Fil) ppm after 48 h to values between 0.6 (Ketac-Silver) and 1.7 (Ketac-Fil, Vitremer) ppm after 180 days. Each material reduced bacterial growth at each time of examination, but the effect decreased significantly over time with a maximum growth of 71.7% (Ketac-Fil) to 85.6% (Ketac-Silver) after 48 h and 94.7 (Vitremer) to 99.0% (Ketac-Silver) after 180 days (growth control = 100%). Both Ketac-Silver and Dyract showed a significantly lower inhibiting effect on bacterial growth than the other materials. The tested materials showed a good correlation between fluoride release and influence on bacterial growth. However, both effects dropped dramatically over the 180-days period.     

Antimicrobial properties,mechanics, and fluoride release of ionomeric cements modified by red propolis

ObjectivesTo evaluate the antimicrobial activity, mechanical properties, and fluoride release capacity of glass ionomer cement (GIC) used for cementing orthodontic bands and modified by ethanolic extract of red propolis (EERP) in different concentrations.Materials and MethodsTwo orthodontic GICs containing EERP at 10%, 25%, and 50%, were used. The following assays were carried out: cell viability tests against Streptococcus mutans and Candida albicans, diametral tensile strength, compressive strength, shear bond strength, microhardness, and fluoride release capacity. The statistical analyses of the antimicrobial tests, fluoride release, diametral tensile strength, compressive strength, and microhardness were performed using two-way analysis of variance and Tukey test (P < .05). Shear bond strength data were analyzed using one-way analysis of variance followed by Tukey test (P < .05).ResultsAt the concentrations of 25% and 50%, EERP was shown to be a promising antimicrobial agent incorporated into GICs against C albicans (P < .001) and S mutans (P < .001). The fluoride release capacity of the GICs was not affected, and the EERP concentration of 25% was the one that least affected the mechanical properties of the cements (P > .05).ConclusionsThe GICs containing EERP at 25% showed a significant increase in their antimicrobial activity against S mutans and C albicans, while mechanical properties and fluoride release remained without significant changes.     

Effect of green propolis addition to physical mechanical properties of glass ionomer cements

Objective

This study investigated the mechanical properties of glass ionomer cements (GICs) combined with propolis as a natural antimicrobial substance

Material and Methods

Typified green propolis, as an ethanolic extract (EEP) or in the lyophilized form (powder), was incorporated to specimens of Ketac Fil Plus, ChemFlex and Ketac Molar Easymix GICs. For each test, 8 specimens of each material were prepared. For water sorption and solubility tests, specimens were subjected to dehydration, hydration and re-dehydration cycles until a constant mass was obtained for each step. Measurements were recorded using a digital balance of 10^-4 g precision. For the diametral tensile strength test, specimens were tested in a universal test machine at 0.5 mm/min crosshead speed after 24 h storage in deionized water. Data were evaluated by one-way ANOVA and Tukey’s tests (p<0.05).

Results

The addition of propolis to GIC clearly increased water sorption compared to pure material. Solubility was material-dependent and was not clearly evident. For the diametral tensile strength test, association with propolis altered negatively only Chemflex.

Conclusion

It may be concluded that incorporation of propolis to GICs alters some properties in a material-dependent condition.     

Glass ionomer cements: Effect of strontium substitution on esthetics,radiopacity and fluoride release

Objective

SrO and SrF₂ are widely used to replace CaO and CaF₂ in ionomer glasses to produce radiopaque glass ionomer cements (GIC). The purpose of this study was to evaluate the effects of this substitution on release of ions from GIC as well as its effect on esthetics (translucency) and radiopacity.

Materials and methods

Cements were produced from ionomer glasses with varying content of Sr, Ca and F. The cements were stored in dilute acetic acid (pH 4.0) for up to 7 days at 37 °C. Thereafter, the cements were removed and the solution was tested for F⁻, Sr²⁺, Ca²⁺, and Al³⁺ release. Radiopacity and translucency were measured according to BS EN ISO 9917-1:2003.

Results

Ion release was linear to t^1/2 suggesting that this is a diffusion controlled mechanism rather than dissolution. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium. Radiopacity shows a strong linear correlation with Sr content. All cements were more opaque than the C_0.70 0.55 standard but less opaque than the C_0.70 0.90 standard which is the limit for the ISO requirement for acceptance.

Significance

This study shows that the replacement of calcium by strontium in a glass ionomer glass produces the expected increase in radiopacity of the cement without adverse effects on visual properties of the cement. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium.     

Premixed calcium phosphate cements: synthesis, physical properties, and cell cytotoxicity.

OBJECTIVES: Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder-liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. METHODS: PCPCs were formulated from CPC powder+non-aqueous liquid+gelling agent+hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. RESULTS: Setting time (mean+/-S.D.; n=4) for PCPC-Tartaric was 8.2+/-0.8 min, significantly less than the 61.7+/-1.5 min for the Premixed Control developed previously (p<0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5+/-0.8 MPa, higher than 4.5+/-0.8 MPa of Premixed Control (p=0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p=0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p>0.1) from that of the non-premixed CPC control. SIGNIFICANCE: PCPCs will eliminate the powder-liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs.     

Surface antibacterial properties of resin and resin-modified dental cements.

OBJECTIVE: Cements possessing antibacterial properties may reduce bacteria-induced fixed partial denture complications. The purpose of this study was to evaluate the antibacterial properties of 4 dental cements using the direct contact test (DCT) and the agar diffusion test (ADT). METHOD AND MATERIALS: The ADT was performed using mitis salivarius agar plates. Each plate was evenly inoculated with freshly grown mutans streptococci. Two samples of each test material-RelyX ARC, Variolink II, GC FujiCEM, and Principle-were placed, and the inhibition halo obtained was measured after 48 hours. For the DCT, 8 samples were placed on the sidewalls of wells in a 96-well microtiter plate. After polymerization, freshly grown Streptococcus mutans cells (1 X 10(6)) were placed on the surface of each sample for 1 hour at 37 degrees C. Fresh medium was then added to each well, and bacterial growth was followed for 16 hours in a temperature-controlled spectrophotometer. Similarly prepared samples were aged in phosphate-buffered saline for 1 or 7 days and the DCT was repeated. Analysis of variance (ANOVA) and Tukey multiple comparisons were applied to the data. RESULTS: In the ADT, GC FujiCEM showed an inhibition zone of 2.0 +/- 0.3 mm, and Principle showed an inhibition zone of 1.2 +/- 0.2 mm. In the DCT, freshly polymerized samples of GC FujiCEM and Principle exhibited potent antibacterial properties, while samples of Variolink II and RelyX ARC showed moderate antibacterial properties. Principle showed some antibacterial properties even after 1 day (P < .001). CONCLUSION: None of the tested cements in this study possesses long-term antibacterial properties.     

Effect of acetic acid on the fluoride release profiles of restorative glass ionomer cements.

OBJECTIVES: This study investigates the fluoride release of glass ionomers in an acetic acid solution in order to substantiate a model according to which the short-term release results from an elution of loosely bound fluoride and the long-term release from an erosive leaching of the glass particles in the bulk of the cement. METHODS: Individual fluoride release profiles of five specimens of 10 acid-base setting restorative glass ionomers were obtained by determining the amounts of fluoride released by each sample at 37 degrees C in consecutive elutions for up to 140 days with 25 ml of a 0.01 mol/l acetic acid solution with pH = 4. Differences in the fluoride release profiles were determined with a Multivariate Data Analysis on the basis of a Principal Component Analysis. RESULTS: The fluoride release profiles of the 10 glass ionomers can be classified into five distinct groups which are characterized by a cumulative fluoride release described by the equation [F]c = [F]l t/(t + t1/2) + beta square root of t. The parameters ([F]l, t1/2) and beta are characteristic for the materials in the groups, and refer to the short-term and long-term fluoride release, respectively. The acidic solution enhances both processes compared to an elution in water, the effect being more pronounced for the long-term release. SIGNIFICANCE: The fluoride release mechanism is intrinsically the same as determined for elutions in water. The increased amount of fluoride released under acidic conditions, especially in the long term, corroborates that an erosive leaching of the glass particles in the bulk of the cement accounts for the long-term fluoride release.     

Characterization of glass-ionomer cements. 4. Effect of molecular weight on physical properties.

The properties of glass-ionomer cements are affected by the molecular weight of the polyacid used in their preparation. At equivalent acid concentrations and powder : liquid ratios, polyacids of high molecular weight yield cements of enhanced strength, but the high viscosity of their aqueous solutions imposes a limitation on their use and the working time of the cement pastes is reduced. Moreover, powder : liquid ratios have to be lowered and the polyacids themselves can be used only at relatively low concentrations (about 25 per cent m/m); these are factors which adversely affect cement strength.     

Effect of water on the physical properties of resin-modified glass ionomer cements.

OBJECTIVES: Resin-modified glass ionomer cements (GIC) are available for clinical use as restorative materials or as liners and bases. This work was conducted to study the effect of water sorption on the physical properties of several resin-modified GIC, by changing the samples' storage conditions. METHODS: The water sorption, the flexural strength, the flexural elastic modulus, the Vickers hardness and the dimensional changes of five resin-modified GICs were measured using specimens aged for 24 h to 3 mon. The specimens were stored at 37 degrees C, either in a dry environment (A), immersed in water (B), stored in a humid environment (C), stored in a humid environment for 1 h and then immersed in water (D), or immersed in water and subsequently dried (B + A). An analysis of variance was used to compare the results. RESULTS: The resin-modified GIC absorb during the first 24 h large amounts of water (114-172 mg/cm3) compared to the conventional GIC (30-63 mg/cm3). Water alters the physical properties of resin-modified GICs: With regard to dry specimens, a decrease in the flexural strength of 20 to 80% was observed for samples immersed in water. Decreases in their flexural elastic modulus (50 to 80%) and in their hardness (approximately 50%) were also observed. Water sorption also provoked an expansion in volume of the immersed specimens, ranging from 3.4 to 11.3% after 24 h. SIGNIFICANCE: The flexural strength and Vickers hardness of the resin-modified GICs are sensitive to the water contained in the tested specimens. A correlation was established between the decrease in their physical properties and the water uptake. However, it should not be concluded that these materials are not adequate for use in applications in direct contact with oral fluids. Probably, resin-modified GIC placed in oral cavities would not be affected to the same extent as in in vitro tests. In an oral environment, the constituents of saliva will certainly decrease the rate of water sorption and will hence delay its effects.     

Effect of a neutral citrate solution on the fluoride release of conventional restorative glass ionomer cements.

OBJECTIVES: This study investigates the effect of a neutral citrate solution on the fluoride release of 10 acid-base setting glass ionomer cements during 140 days at 37 degrees C. METHODS: Five disks of 10 acid-base setting restorative glass ionomers were prepared according to the manufacturer's instructions. These specimens were immersed individually in 25 ml of a 0.01 mol/l citrate solution with pH = 7. Over 140 days, the solutions were regularly renewed and the fluoride concentration eluted during each period was determined with a combined fluoride ion selective electrode. RESULTS: The cumulative fluoride release was the result of an initial high release that ceased after some time and a long-term of low fluoride release. The long-term fluoride release was higher in neutral citrate solution than in water. For some formulations the short-term fluoride release also was higher in neutral citrate solution than in water suggesting that the polysalt matrix composition could be important in this respect. SIGNIFICANCE: The fluoride release process is due not only to a loss of relatively loosely bound fluoride in the cement matrix, but also to the release of strongly bounded fluoride inducing a long-term fluoride release. The effect of citrate on the fluoride release process may increase depending on the acid (polyacrylic acid versus copolymers of polyacrylic acid) used for the polysalt formation in the hardening cement. Depending on the competition between the polyacrylate anion and the citrate anion for the metal cation extraction the fluoride release process may be retarded.     

Review on fluoride-releasing restorative materials--fluoride release and uptake characteristics, antibacterial activity and influence on caries formation.

OBJECTIVES: The purpose of this article was to review the fluoride release and recharge capabilities, and antibacterial properties, of fluoride-releasing dental restoratives, and discuss the current status concerning the prevention or inhibition of caries development and progression. METHODS: Information from original scientific full papers or reviews listed in PubMed (search term: fluoride release AND (restorative OR glass-ionomer OR compomer OR polyacid-modified composite resin OR composite OR amalgam)), published from 1980 to 2004, was included in the review. Papers dealing with endodontic or orthodontic topics were not taken into consideration. Clinical studies concerning secondary caries development were only included when performed in split-mouth design with an observation period of at least three years. RESULTS: Fluoride-containing dental materials show clear differences in the fluoride release and uptake characteristics. Short- and long-term fluoride releases from restoratives are related to their matrices, setting mechanisms and fluoride content and depend on several environmental conditions. Fluoride-releasing materials may act as a fluoride reservoir and may increase the fluoride level in saliva, plaque and dental hard tissues. However, clinical studies exhibited conflicting data as to whether or not these materials significantly prevent or inhibit secondary caries and affect the growth of caries-associated bacteria compared to non-fluoridated restoratives. SIGNIFICANCE: Fluoride release and uptake characteristics depend on the matrices, fillers and fluoride content as well as on the setting mechanisms and environmental conditions of the restoratives. Fluoride-releasing materials, predominantly glass-ionomers and compomers, did show cariostatic properties and may affect bacterial metabolism under simulated cariogenic conditions in vitro. However, it is not proven by prospective clinical studies whether the incidence of secondary caries can be significantly reduced by the fluoride release of restorative materials.     

Influence of pH and oxygen-inhibited layer on fluoride release properties of fluoride sealant

OBJECTIVES: This study tested the hypothesis that the oxygen-inhibited layer on a light-cured methacrylate based resin and the pH of the storage medium would increase significantly the initial fluoride release and long-term release rate from fluoride dental sealant. METHODS: Forty-eight discs (16-mm diameter x 1-mm thick) were made from FluroShield (<5 wt% NaF) and Helioseal F (<30 wt% fluorosilicate glass) sealants. For each sealant, 24 discs were cured through a Mylar strip that covered the surface and the remaining 24 discs were cured in air allowing formation of the oxygen-inhibited surface. Each specimen in the 24-disc groups was stored individually in 25-mL vials, and divided into four six-vial groups to receive 10 mL of pH4-pH7 (designation of pH 4-7) lactate buffer solutions. The buffer solutions were replaced periodically up to 121 days. The cumulative fluoride release over time was used to determine the coefficients for short-term and long-term release. RESULTS: Two-way ANOVA showed that the mean coefficient values for either sealant were significantly influenced by the curing condition (p<0.0001) and pH (p<0.0001), except for short-term release from NaF sealant. The duration of short-term release was much longer for the fluorosilicate glass sealant. CONCLUSIONS: Both pH and the source of fluoride source incorporated in the sealant play significant roles in fluoride release.     

The effect of temperature and ionic solutes on the fluoride release and recharge of glass-ionomer cements

ObjectiveTo determine the effect of storage temperature and the presence of sodium chloride in solution on the fluoride uptake and release of glass-ionomer cements.MethodsSeveral commercial brands were used, and stored at either room temperature (21–23 °C) or 37 °C, in KF solution at a concentration of 1000 ppm F⁻ with and without 0.9% NaCl present. Fluoride levels in the storage solutions after 24 h were measured using a fluoride-ion selective electrode. Specimens were then stored in water, and fluoride release after 24 h was determined. Studies were also carried out to determine chloride levels when specimens were stored in 0.9% NaCl, with or without 1000 ppm fluoride, again using an ion selective electrode.ResultsAll glass-ionomer specimens took up fluoride, and most of the fluoride was retained over the next 24 h when the specimens were stored in water. There was a slight variation in the amount of fluoride taken up with storage temperature and with the presence of sodium chloride. All specimens also took up chloride, with greater uptake at higher temperatures, but little or no effect when KF was also present in solution.SignificanceThe substantial retention of fluoride after 24 h in deionised water confirms previous findings and suggests that an insoluble species, possibly SrF₂, forms in situ. Chloride uptake has not been reported previously, and its significance requires further investigation. Fluoride and chloride uptake were apparently independent of each other, which suggests that the ions are taken up at different sites in the cement. This may relate to differences in the respective sizes and hydration states of F⁻ and Cl⁻ ions.     

Characterization of glass-ionomer cements. 3. Effect of polyacid concentration on the physical properties.

A study of the effect of the polyacid concentration of the liquid on the physical properties of one formulation of the glass-ionomer cement was made. All the cements were prepared at the same consistency. The required powder: liquid ratio and working time of the cement paste were constant between 28 and 38 per cent w/w polyacid concentration. At higher polyacid concentrations the powder: liquid ratio decreased and the working time increased. Setting time of the cement varied in a complex manner. Both the compressive and tensile strengths of the cement increased linearly over the range of polyacid concentrations studied and the solubility and disintegration fell non-linearly. The work suggests that it is desirable to use a high polyacid concentration.