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

Effect of different topical fluoride applications on the surface roughness of a colored compomer

Objective

The aim of this study was to evaluate the effect of neutral sodium fluoride (NNaF) gel and acidulated phosphate fluoride (APF) gel on the surface roughness of colored compomer (Twinky Star), conventional compomer (Compoglass F) and resin-modified glassionomer cement (RMGIC) (Photac-Fil).

Material and Methods

A total of 45 standardized disc-shaped specimens were prepared for each material. After 24 h, finishing and polishing of specimens were done with aluminum oxide disc. Surface treatments with topical fluoride agents or distilled water (control) were performed four times, and interspersed with 8 pH cycles, simulating high cariogenic challenges. After the treatment, the surface roughness (Ra) was determined using a profilometer. In each group, specimens with Ra closest to the mean were examined with a scanning electron microscope (SEM) at ×1,000 and ×3,500 magnifications. Two-way ANOVA was used to evaluate Ra measurements, and the differences in Ra values between subgroups for each material and each topical applications were compared by Tukey’s highly significant difference pairwise comparisons.

Results

No statistically significant difference in Ra between the Twinky Star and Compoglass F was found. However, Photac Fil showed significantly higher Ra than these materials after all surface treatments. There was a general trend of Ra increase from controls to NNaF and APF gels for all materials. SEM observations revealed that the surface micromorphology of Twinky-Star did not differ significantly from that of Compoglass F.

Conclusion

Both the compomers and the RMGIC showed significantly higher surface roughness when subjected to APF gel application.

Biofilm Formation on Dental Restorative and Implant Materials

Biomaterials for the restoration of oral function are prone to biofilm formation, affecting oral health. Oral bacteria adhere to hydrophobic and hydrophilic surfaces, but due to fluctuating shear, little biofilm accumulates on hydrophobic surfaces in vivo. More biofilm accumulates on rough than on smooth surfaces. Oral biofilms mostly consist of multiple bacterial strains, but Candida species are found on acrylic dentures. Biofilms on gold and amalgam in vivo are thick and fully covering, but barely viable. Biofilms on ceramics are thin and highly viable. Biofilms on composites and glass-ionomer cements cause surface deterioration, which enhances biofilm formation again. Residual monomer release from composites influences biofilm growth in vitro, but effects in vivo are less pronounced, probably due to the large volume of saliva into which compounds are released and its continuous refreshment. Similarly, conflicting results have been reported on effects of fluoride release from glass-ionomer cements. Finally, biomaterial-associated infection of implants and devices elsewhere in the body is compared with oral biofilm formation. Biomaterial modifications to discourage biofilm formation on implants and devices are critically discussed for possible applications in dentistry. It is concluded that, for dental applications, antimicrobial coatings killing bacteria upon contact are more promising than antimicrobial-releasing coatings.

Novel CaF(2) nanocomposite with high strength and fluoride ion release

Secondary caries and restoration fracture remain common problems in dentistry. This study tested the hypothesis that combining nano-CaF(2) and glass fillers would yield nanocomposites with high mechanical properties and F release. Novel CaF(2) nanoparticles (56-nm) were synthesized via spray-drying and incorporated into resin. F release increased with increasing the nano-CaF(2) content, or with decreasing pH (p < 0.05). F-release rates at 70-84 days were 1.13 microg/(cm(2) x day) and 0.50 microg/(cm(2) x day) for nanocomposites containing 30% and 20% nano-CaF(2), respectively. They matched the 0.65 microg/(cm(2) x day) of resin-modified glass ionomer (p > 0.1). The nanocomposites had flexural strengths of 70-120 MPa, after 84-day immersion at pH 4, pH 5.5, and pH 7. These strengths were nearly three-fold that of resin-modified glass ionomer, and matched/exceeded a composite with little F release. In summary, novel CaF(2) nanoparticles produced high F release at low filler levels, thereby making room in resin for reinforcement glass. This yielded nanocomposites with high F-release and stress-bearing properties, which may help reduce secondary caries and restoration fracture.

Antibacterial activity of composite resin with glass-ionomer filler particles

The purpose of this study was to examine the antibacterial activity of composite resin with glass-ionomer filler particles versus that of contemporary commercial composite resins. Three composite resins were used: Beautifil II (containing S-PRG filler), Clearfil AP-X, and Filtek Z250. Resin blocks were bonded to maxillary first molars, and plaque accumulation on the resin block surface was examined after 8 hours. For the antibacterial test, the number of Streptococcus mutans in contact with the composite resin blocks after incubation for 12 hours was determined, and adherence of radiolabeled bacteria was evaluated. Less dental plaque was formed on Beautifil II resin block as compared to the other two materials. Antibacterial test revealed that there were no significant differences in the number of Streptococcus mutans among the three composite resins. However, the adherence of radiolabeled bacteria to the saliva-treated resin surface was significantly (p<0.01) lower in Beautifil II than in the other two materials. These results suggested that Beautifil II could reduce dental plaque formation and bacterial adherence, leading to prevention of secondary caries.

Clinical Performance of Viscous Glass Ionomer Cement in Posterior Cavities over Two Years

In this controlled prospective clinical study the highly viscous glass ionomer cement Ketac Molar was clinically assessed in Class I and Class II cavities. Forty-nine subjects (mean age 32.3 years) received 108 restorations placed by six operators in conventional Black I and II type cavities with undercuts after excavating primary lesions or after removing insufficient restorations. At baseline, and after 6, 12, and 24 months, restorations were assessed by two independent investigators according to modified USPHS codes and criteria. Impressions of the restorations were taken and epoxy replicas were made. Between the baseline and the 24-month recall, 51 representative samples were analyzed at 130 × magnification by use of a stereo light microscope (SLM). Recall rates were 83% after 6 months, 50% after 12 months, and 24% after 24 months. Failure rates after 24 months were 8% for Class I and 40% for Class II fillings, mainly due to bulk fracture at occlusally loaded areas (Kaplan Meier survival analysis). Significant changes over time were found for the criteria “surface roughness”, “marginal integrity”, “restoration integrity”, and “overall judgement” (P < .05; Friedman test). SLM analysis revealed statistically significant differences for the following criteria over time (baseline/6 months/12 months (in % of entire evaluable margin length); P < .05; Friedman 2-way ANOVA): perfect margin 37/19/11, negative step formation 26/49/57, gap formation 2/7/9, and overhang 24/11/8. Replicas exhibited mainly negative step formation as main finding due to apparently inferior wear resistance (P < .05). Gap formations were more frequently observed in Class II restorations than in Class I (12% versus 3% after 12 months; P < .05, Mann-Whitney-U test). The evaluated margin lengths were not statistically different (P > .05, Friedman 2-way ANOVA).

Strong nanocomposites with Ca, PO(4), and F release for caries inhibition

This article reviews recent studies on: (1) the synthesis of novel calcium phosphate and calcium fluoride nanoparticles and their incorporation into dental resins to develop nanocomposites; (2) the effects of key microstructural parameters on Ca, PO(4), and F ion release from nanocomposites, including the effects of nanofiller volume fraction, particle size, and silanization; and (3) mechanical properties of nanocomposites, including water-aging effects, flexural strength, fracture toughness, and three-body wear. This article demonstrates that a major advantage of using the new nanoparticles is that high levels of Ca, PO(4), and F release can be achieved at low filler levels in the resin, because of the high surface areas of the nanoparticles. This leaves room in the resin for substantial reinforcement fillers. The combination of releasing nanofillers with stable and strong reinforcing fillers is promising to yield a nanocomposite with both stress-bearing and caries-inhibiting capabilities, a combination not yet available in current materials.

Dental Glass Ionomer Cements as Permanent Filling Materials? – Properties, Limitations and Future Trends

Glass ionomer cements (GICs) are clinically attractive dental materials that have certain unique properties that make them useful as restorative and luting materials. This includes adhesion to moist tooth structures and base metals, anticariogenic properties due to release of fluoride, thermal compatibility with tooth enamel, biocompatibility and low toxicity. The use of GICs in a mechanically loaded situation, however, has been hampered by their low mechanical performance. Poor mechanical properties, such as low fracture strength, toughness and wear, limit their extensive use in dentistry as a filling material in stress-bearing applications. In the posterior dental region, glass ionomer cements are mostly used as a temporary filling material. The requirement to strengthen those cements has lead to an ever increasing research effort into reinforcement or strengthening concepts.

Effect of gamma irradiation on fluoride release and antibacterial activity of resin dental materials

This study evaluated the effect of gamma irradiation on fluoride release and antibacterial activity of FluroShield (FS) and Clearfil Protect Bond (CPB). Four groups were formed: G1-FS + gamma; G2-FS without gamma; G3-CPB + gamma; G4-CPB without gamma. For fluoride release analysis, 12 disks of each material were prepared and covered with nail polish, except for one side (50.4 mm(2) area). G1 and G3 were sterilized with a 14.5 KGy dose at 27 degrees C for 24 h, while G2 and G4 (controls) were not sterilized and were maintained under the same time and temperature conditions. Fluoride release measurements were made in duplicate (n=6) by an ion specific electrode. The antibacterial activity of the CPB and FS against Streptococcus mutans after gamma sterilization was evaluated by the agar-disc diffusion method. The diameter of the zones of microbial growth inhibition was recorded after 48 h. Data were analyzed statistically by ANOVA and Tukey's test (alpha=5%). Gamma sterilization decreased the fluoride release of FS by approximately 50%, while CPB was not affected. There was no statistically significant difference (p>0.05) in the antibacterial effect of CPB between gamma and non-gamma sterilization groups. FS presented no antibacterial activity. Gamma irradiation decreased the fluoride release of FS, but did not affect the antibacterial activity of the studied materials.

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90microm) and beta-tricalcium phosphate (beta-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.

Preparation and evaluation of an experimental luting glass ionomer cement to be used in dentistry

The aim of this paper is to compare the fluoride-releasing and mechanical properties of an experimental luting glass ionomer cement, which has a modified composition and a commercial luting cement. The experimental powder was obtained by sol-gel process and then, it was used to prepare the experimental cements. The properties of cement pastes, such as setting time and working time, microhardness and diametral tensile strength were determined. Fluoride release from GICs was evaluated at time intervals of 1, 7, 14, 21 and 28 days in deionized water. Atomic force microscopy (AFM) analyses showed that the surface of the experimental cements is more homogeneous than commercial GICs. The mechanical properties and the measure of liberation of fluoride of the two cements were influenced by ratio powder:liquid and chemical composition of the precursor powders. Experimental cements released less fluoride than commercial cements. However, this liberation was more constant during the analyzed period. Thus, the results obtained in this study indicated that the composition of the experimental powder modified by the niobium can lead the formation of the polysalt matrix with good mechanical properties. In other words, we can say that experimental powder offered considerable promise for exploitation in dental field.

Antibacterial agents in composite restorations for the prevention of dental caries

BACKGROUND

Dental caries is a multifactorial disease in which the fermentation of food sugars by bacteria from the biofilm (dental plaque) leads to localised demineralisation of tooth surfaces, which may ultimately result in cavity formation. Resin composites are widely used in dentistry to restore teeth. These restorations can fail for a number of reasons, such as secondary caries, excessive wear, marginal degradation, tooth sensitivity, pulpal death, and restorative material fracture. Caries adjacent to restorations is one of the main causes for restoration replacement. The presence of antibacterials in both the filling material and the bonding systems would theoretically be able to affect the initiation and progression of caries adjacent to restorations.

OBJECTIVES

To assess the effects of antibacterial agents incorporated into composite restorations for the prevention of dental caries.

SEARCH STRATEGY

We searched the following databases in February 2009: the Cochrane Oral Health Group's Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 1); MEDLINE via OVID (1950 to February 2009) without filter; and EMBASE via OVID (1980 to February 2009) without filter.

SELECTION CRITERIA

Randomised controlled clinical trials (RCTs) comparing resin composite restorations containing antibacterial agents with non-antibacterial containing composite restorations.

DATA COLLECTION AND ANALYSIS

Two review authors conducted screening of studies in duplicate and independently, and although no eligible trials were identified, the two authors had planned to extract data independently and assess trial quality using standard Cochrane Collaboration methodologies.

MAIN RESULTS

We retrieved 128 references to studies, none of which matched the inclusion criteria for this review and all of which were excluded.

AUTHORS' CONCLUSIONS

We were unable to identify any randomised controlled trials on the effects of antibacterial agents incorporated into composite restorations for the prevention of dental caries. The absence of high level evidence for the effectiveness of this intervention emphasises the need for well designed, adequately powered, randomised controlled clinical trials.

Shear Bond Strength of Brackets Rebonded with a Fluoride-Releasing and -Recharging Adhesive System

Objective: To ascertain the effects of repeated bonding on the shear bond strength of orthodontic brackets bonded with a fluoride-releasing and -recharging adhesive system with a self-etching primer in comparison with two other types of adhesive system.

Materials and Methods: A total of 48 premolars were collected and divided equally into three groups of 16. Each group was assigned one of three adhesive systems: Transbond XT, Transbond Plus, or a fluoride-releasing and -recharging adhesive system, Beauty Ortho Bond. Shear bond strength was measured 24 hours after bracket bonding, with the bonding/debonding procedures repeated twice after the first debonding. A universal testing machine was used to determine shear bond strengths, and bracket/adhesive failure modes were evaluated with the adhesive remnant index after each debonding.

Results: At every debonding sequence, all of these three adhesive systems had a shear bond strength of 6 MPa, which is a minimum requirement for clinical use. Transbond XT and Transbond Plus had significantly higher mean shear bond strengths than did Beauty Ortho Bond at each debonding. No significant differences in mean bond strength were observed between the three debondings in each adhesive system. Bond failure at the enamel/adhesive interface occurred more frequently in Beauty Ortho Bond than in Transbond XT or Transbond Plus.

Conclusions: The fluoride-releasing and -recharging adhesive system with the self-etching primer (Beauty Ortho Bond) had clinically sufficient shear bond strength in repeated bracket bonding; this finding can help orthodontists to decrease the risk of damage to enamel at debonding.

Biocompatibility of Resin-based Dental Materials

Oral and mucosal adverse reactions to resin-based dental materials have been reported. Numerous studies have examined the biocompatibility of restorative dental materials and their components, and a wide range of test systems for the evaluation of the biological effects of these materials have been developed. This article reviews the biological aspects of resin-based dental materials and discusses the conventional as well as the new techniques used for biocompatibility assessment of dental materials.

Does fluoride in compomers prevent future caries in children?

Compomer restorations release fluoride to help prevent future caries. We tested the hypothesis that compomer is associated with fewer future caries compared with amalgam. The five-year New England Children's Amalgam Trial recruited 534 children aged 6-10 yrs with >or= 2 carious posterior teeth. Children were randomized to receive compomer or amalgam restorations in primary posterior teeth, placed with a fluoride-releasing bonding agent. The association between restorative material and future caries was assessed by survival analysis. Average follow-up of restorations (N = 1085 compomer, 954 amalgams) was 2.8 + 1.4 yrs in 441 children. No significant difference between materials was found in the rate of new caries on different surfaces of the same tooth. Incident caries on other teeth appeared slightly more quickly after placement of compomer restorations (p = 0.007), but the difference was negligible after 5 yrs. Under the conditions of this trial, we found no preventive benefit to fluoride-releasing compomer compared with amalgam.

Indirect pulp treatment in a permanent molar: case reort of 4-year follow-up

This case report describes the Indirect Pulp Treatment (IPT) of deep caries lesion in a permanent molar. A 16-year-old male patient reported discomfort associated with thermal stimulation on the permanent mandibular left first molar. The radiographs revealed a deep distal caries lesion, very close to the pulp, absence of radiolucencies in the periapical region, and absence of periodontal space thickening. Pulp sensitivity was confirmed by thermal pulp vitality tests. Based on the main complaint and the clinical and radiographic examinations, the treatment plan was established to preserve pulp vitality. Clinical procedures consisted of removing the infected dentin and lining the caries-affected dentin with calcium hydroxide paste. The tooth was provisionally sealed for approximately 60 days. After this period, tooth vitality was confirmed, the remaining carious dentin was removed, and the tooth was restored. At 4-year follow-up, no clinical or radiographic pathological findings were found.

Surface Characteristics of Orthodontic Materials and Their Effects on Adhesion of Mutans streptococci

Objective: To test the hypothesis that there are no significant differences in the adhesion of mutans streptococci (MS) to various orthodontic materials based on their surface characteristics.

Materials and Methods: Surface roughness (SR) and surface free energy (SFE) characteristics were investigated for nine different orthodontic materials (four orthodontic adhesives, three bracket raw materials, hydroxyapatite blocks, and bovine incisors) using confocal laser scanning microscopy and sessile drop method. Each material, except the bovine incisors, was incubated with whole saliva or phosphate-buffered saline for 2 hours. Adhesion assays were performed by incubating tritium-labeled MS with each material for 3 or 6 hours.

Results: Orthodontic adhesives had higher SFE characteristics and lower SR than bracket materials. Orthodontic adhesives showed a higher MS retaining capacity than bracket materials, and MS adhesion to resin-modified glass ionomer and hydroxyapatite was highest. Extended incubation time increased MS adhesion, while saliva coating did not significantly influence MS adhesion. SFE, specifically its dispersive and polar components, was positively correlated with MS adhesion, irrespective of saliva coating.

Conclusions: The hypothesis is rejected. This study suggests that SFE characteristics play an important role in the initial MS adhesion to orthodontic materials.

Microbiological or chemical models of enamel secondary caries compared by polarized-light microscopy and energy dispersive X-ray spectroscopy

Different secondary caries models may present different results. The purpose of this study was to compare different in vitro secondary caries models, evaluating the obtained results by polarized-light microscopy (PLM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Standardized human enamel specimens (n = 12) restored with different materials (Z250 conventional composite resin-CRZ, Freedom polyacid-modified composite resin-CRF, Vitremer resin-modified glass-ionomer-GIV, and Fuji IX conventional glass-ionomer cement-GIF) were submitted to microbiological (MM) or chemical caries models (CM). The control group was not submitted to any caries model. For MM, specimens were immersed firstly in sucrose broth inoculated with Streptococcus mutans ATCC 35688, incubated at 37 degrees C/5% CO(2) for 14 days and then in remineralizing solution for 14 days. For CM, specimens were submitted to chemical pH-cycling. Specimens were ground, submitted to PLM and then were dehydrated, gold-sputtered and submitted to SEM and EDS. Results were statistically analyzed by Kruskall-Wallis and Student-Newman-Keuls tests (alpha = 0.05). No differences between in vitro caries models were found. Morphological differences in enamel demineralization were found between composite resin and polyacid-modified composite resin (CRZ and CRF) and between the resin-modified glass-ionomer and the glass-ionomer cement (GIF and GIV). GIF showed higher calcium concentration and less demineralization, differing from the other materials. In conclusion, the glass-ionomer cement showed less caries formation under both in vitro caries models evaluated.

Novel F-releasing composite with improved mechanical properties

In recent years, the authors have been developing novel fluoride-releasing dental composites containing ternary zirconium fluoride chelates. The aim of this study was to improve the physical and mechanical properties of these composites by improving the formulation of the monomers and photoinitiators. The hypothesis was that reduction of hydrophilic monomers and improvement of the photoinitiators could reduce water sorption and significantly increase the mechanical properties of the composite. The degree of conversion of the composites containing different compositions of photoinitiators was studied by Fourier transform near-infrared spectroscopy (FT-NIR). Ten experimental composites containing different compositions of ethoxylated bisphenol-A dimethacrylate (EBPADMA), 1,6-hexanediol dimethacrylate (HDDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-propane (BisGMA) were tested for flexural strength, viscosity, and water sorption. The experimental composite containing 20% synthesized fluoride-releasing monomer, 30% BisGMA, 30% EBPADMA, and 20% HDDMA showed significantly higher fluoride release and recharge, but physical and mechanical properties similar to those of the control composite containing 40% BisGMA, 40% EBPADMA, and 20% HDDMA.

The ART approach: clinical aspects reviewed

The success of ART as a caries management approach is supported by more than 20 years of scientific evidence. ART follows the contemporary concepts of modern cariology and restorative dentistry. It challenges treatment concepts such as step-wise excavation and the need for complete removal of affected dentine. The ART approach so far has mainly used high-viscosity glass-ionomer as the sealant and restorative material. Cariostatic and remineralization properties have been ascribed to this material which requires further research to establish its clinical relevance. The adhesion of high-viscosity glass-ionomer to enamel in pits and fissures is apparently strong, as its remnants, blocking the pits and fissures, have been considered a possible reason for the low prevalence of carious lesion development after the glass-ionomer has clinically disappeared from it. Encapsulated high-viscosity glass-ionomers may lead to higher restoration survival results than those of the hand-mixed version and should, therefore, not be neglected when using ART. Similarly, the use of resin-modified glass-ionomer with ART should be researched. The effectiveness of ART when compared to conventional caries management approaches has been shown in numerous studies. Proper case selection is an important factor for long-lasting ART restoration survival. This is based on the caries risk situation of the individual, the size of the cavity opening, the strategic position of the cavitated tooth and the presence of adequate caries control measures. As the operator is one of the main causes for failure of ART restorations, attending a well-conducted ART training course is mandatory for successful implementation of ART.

Strength and fluoride release characteristics of a calcium fluoride based dental nanocomposite

Secondary caries and restoration fracture remain the two most common problems in restorative dentistry. Release of fluoride ions (F) could be a substantial benefit because F could enrich neighboring enamel or dentin to combat caries. The objective of this study was to incorporate novel CaF(2) nanoparticles into dental resin to develop stress-bearing, F-releasing nanocomposite. CaF(2) nanoparticles, prepared in our laboratories for the first time, were combined with reinforcing whisker fillers in a resin. Flexural strength (mean+/-sd; n=6) was 110+/-11 MPa for the composite containing 30% CaF(2) and 35% whiskers by mass. It matched the 108+/-19 MPa of a stress-bearing, non-releasing commercial composite (Tukey's at 0.05). The composite containing 20% CaF(2) had a cumulative F release of 2.34+/-0.26 mmol/L at 10 weeks. The initial F release rate was 2 microg/(hcm(2)), and the sustained release rate after 10 weeks was 0.29 microg/(hcm(2)). These values exceeded the reported releases of traditional and resin-modified glass ionomer materials. In summary, nanocomposites were developed with relatively high strength as well as sustained release of fluoride ions, a combination not available in current materials. These strong and F-releasing composites may yield restorations that can reduce the occurrence of both secondary caries and restoration fracture.

Fluoride content and recharge ability of five glassionomer dental materials

BACKGROUND

The relationship between fluoride content and fluoride release for glass-ionomer cements is not well understood. The aim of this laboratory study was: to determine the fluoride concentrations at the surfaces of glass-ionomer materials with respect to different storage media and different pH environments; to examine the recharge ability of the materials after NaF immersion; and to assess the morphological changes at the material surfaces using scanning electron microscope and energy dispersive spectroscopic techniques (SEM/EDS).

METHODS

Five glass-ionomer materials, Fuji Triage (FT), Fuji II LC (FII), Fuji VIII (FVIII), Fuji IX GP (FIX), and Ketac N100 (KN), were analyzed in this study. Resin-based fluoride releasing material Helioseal F (HSF) was used as a comparison material. The sample consisted of 120 cured cement disks (n = 20 disks of each tested material, 10 x 1.5 mm). Five disks of each material were stored in 4 different storage media (I- saline, II- acidic solution ph = 2.5, III- acid solution ph = 5.5, IV- NaF solution (c = 500/106). After 7 days, two disks of each material were transferred from media I, II and III to the NaF solution for 3 min. EDS analysis was conducted in 3 randomly selected spots of each experimental disk. SEM was used to determine morphological characteristics of the material surface. Differences between the experimental groups have been analyzed using Student's t-test with the level of significance set at p < 0.001.

RESULTS

FT showed the highest fluoride content at the surface of the material. The lowest amounts of fluoride ions were detected at the surfaces of the FT disks stored at low pH environments, and this difference was statistically significant (p < 0.001). Glass-ionomers showed significantly higher fluoride concentrations when compared to the HSF (p < 0.001). After immersion in the NaF solution, fluoride concentrations at the surfaces of the disks increased when compared with previous storage media (FT>FVIII>KN>FII>FIX). SEM analysis of the surface morphology revealed numerous voids, cracks and microporosities in all experimental groups, except for KN and HSF. More homogenous material structure with more discrete cracks was observed in samples stored at neutral pH environment, compared to disks stored in acidic solutions.

CONCLUSION

The tested materials could be considered as promising dental materials with potential prophylactic characteristics due to their relatively high fluoride content, but also the ability to extensively reabsorb fluoride ions, especially in acidic environments.

In vitro fluoride uptake by bovine enamel from aesthetic restorative materials

OBJECTIVES

The purposes of this in vitro study were to determine whether different types of fluoride-containing restoratives produce differing levels of fluoride uptake by bovine enamel, and to determine the effect of time on this uptake.

METHODS

Seven aesthetic restorative materials were evaluated. Forty bovine enamel slabs were prepared for each tested material, five of which were used to determine baseline fluoride concentrations. Each slab was attached to a disc of the tested material and suspended in synthetic saliva for up to 64 days. After removal, the specimens were acid etched with perchloric acid, and the dissolved enamel was analysed for fluoride and calcium. Fluoride was determined by direct potensiometric analysis, whereas the amount of calcium was evaluated by means of atomic absorption spectrophotometry.

RESULTS

Higher values of fluoride uptake, not significantly different, were recorded in the first two groups. A statistically significant difference was found in fluoride uptake between Fuji II LC and the three compomers in all test intervals. No significant differences were found in the amounts of fluoride uptake between the three compomers. The highest fluoride uptake from all compomers was recorded by F2000.

CONCLUSION

Enamel acquired significant amounts of fluoride from all materials with variations during the test intervals.

A study of the fracture resistance of nyyar cores of three restorative materials

Despite the successful use of dental amalgam for coronal-radicular dowel and core build-up in endodontically-treated posterior teeth, newer materials offer many potential advantages over amalgam and have better patient acceptance. This study compared the fracture resistance of coronal-radicular restorations made from three different direct restorative materials. Sixty human premolars were selected, 45 of which were root treated and decoronated. Fifteen of these premolars were restored using amalgam, 15 with composite and 15 using resin-modified glass ionomer. The 15 unrestored teeth were used as a control group. All the teeth were mounted in acrylic within steel containers and subjected to compressive loading to failure on a universal testing machine. The force required to fracture each core specimen was recorded as well as the proportion of core lost due to failure. The results showed dental amalgam as having the highest fracture resistance (mean 1.93kN, sd 0.22) followed by resin-modified glass ionomer (mean 1.05kN, sd 0.20), sound tooth (mean 0.79kN, sd 0.20) and composite (mean 0.75kN, sd 0.11). The differences among all groups were significant. These results demonstrate that, although resin-modified glass ionomer is significantly weaker than amalgam, these restorations were stronger than unrestored teeth and failed at forces in excess of those encountered in normal mastication. Amalgam cores, along with resin-modified glass ionomer, tended to fail less catastrophically than the other materials and, given their strength, would remain the material of choice in situations where abnormally high forces are expected.

Mechanical behavior of glass ionomer cements as a function of loading condition and mixing procedure

With a view to comparing conventional (CGIC) and resin-modified glass ionomer cements (RMGIC) in terms of mechanical properties, these materials were subjected to different loading conditions for evaluation. In addition, this study investigated the assumption that capsulated systems possess superior mechanical properties compared to the hand-mixed systems, owing to the former's better material homogeneity and a more precise adjustment of the powder-liquid ratio. In view of the aims of this study, the following mechanical properties were determined: strength and modulus of elasticity in flexural test, diametric tensile and compressive strengths, as well as variation of hardness and modulus of elasticity with depth. In all macroscopic strength tests, the RMGICs performed significantly better than the CGICs. In microhardness evaluation, the differences were levelled out. In particular, the mechanical properties of RMGICs were comparable to those of microfilled and packable composites. The effect of mixing was closely intertwined with material property. The tested CGICs performed better when they were hand-mixed, whereas RMGICs fared better in the capsulated form.

Three-year survival of single- and two-surface ART restorations in a high-caries child population

The aim of this study was to evaluate the survival of single- and two-surface atraumatic restorative treatment (ART) restorations in the primary and permanent dentitions of children from a high-caries population, in a field setting. The study was conducted in the rainforest of Suriname, South America. ART restorations, made by four Dutch dentists, were evaluated after 6 months, 1, 2, and 3 years. Four hundred seventy-five ART restorations were placed in the primary dentition and 54 in first permanent molars of 194 children (mean age 6.09 ± 0.48 years). Three-year cumulative survivals of single- and two-surface ART restorations in the primary dentition were 43.4 and 12.2%, respectively. Main failure characteristics were gross marginal defects and total or partial losses. Three-year cumulative survival for single-surface ART restorations in the permanent dentition was 29.6%. Main failure characteristics were secondary caries and gross marginal defects. An operator effect was found only for two-surface restorations. The results show extremely low survival rates for single- and two-surface ART restorations in the primary and permanent dentitions. The variable success for ART may initiate further discussion about alternative treatment strategies, especially in those situations where choices have to be made with respect to a well-balanced, cost-effective package of basic oral health care.