Hypermineralization of dentinal lesions adjacent to glass-ionomer cement restorations

Clinical Effectiveness of Biomaterials in Indirect Pulp Therapy Treatment of Young Permanent Molars with Deep Carious Lesions: A Case-Control Study

Aim

The present case-control study was planned to assess the comparative efficacy of resin-modified calcium silicate, resin-modified glass ionomer, and Dycal as pulp capping agents in indirect pulp therapy for deeply carious young permanent molars.

Materials and methods

Thirty deeply carious young posterior teeth were treated by indirect pulp therapy. During the treatment, the cavity floor was lined with TheraCal or resin-modified glass ionomer cement (RMGIC) in the study group and with Dycal (control group) followed by GC IX and composite restoration. The teeth were reviewed and evaluated clinically and radiographically after 6 and 12 months.

Results

None of the study subjects experienced pain in any of the three study groups up to 12 months. Maturogenesis was seen in all 30 study teeth. Maximum% gain in dentin formation was seen in group I (TheraCal), that is, 16.100 ± 2.42, followed by group II (RMGIC), that is, 11.6000 ± 1.42, and group III (Dycal), that is, 9.6000 ± 0.96, and the difference between group I and group II and group I and group III was highly significant (p < 0.0001). Dentin formation was observed earlier at 6 months in 82.5% of cases with mesio-occlusal (MO) cavities as compared to 62.5% of cases with disto-occlusal (DO) extension.

Conclusion

TheraCal LC may be preferred as a pulp capping agent in the management of deeply carious young permanent molars for better healing in less time.

How to cite this article

Altaf G, Garg S, Saraf BG, et al. Clinical Effectiveness of Biomaterials in Indirect Pulp Therapy Treatment of Young Permanent Molars with Deep Carious Lesions: A Case-Control Study. Int J Clin Pediatr Dent 2024;17(11):1199-1205.

Material of choice for non-invasive treatment of dentin caries: An in vitro study using natural carious lesions

INTRODUCTION

In community settings with limited dental personnel and equipment, and in an era when the aerosol transmission of infectious agents is on the rise, a non-invasive approach to caries management is critical. To provide information on non-invasive material selection, the aim of this study was to compare the remineralization effect of commonly used fluoride-containing materials, adjunctive to the everyday use of fluoride toothpaste (F-toothpaste), on primary tooth natural dentin caries.

METHODS

Fifty-five specimens were randomly divided into five groups: 38% silver diamine fluoride (SDF), 5% fluoride varnish (F-varnish), glass-ionomer cement (GIC), deionized water (DW) with F-toothpaste slurry, and DW as a control group (n = 11). The lesion depth and mineral density were measured before and after bacterial pH-cycling using micro-computed tomography. The percentage of mineral density change (%MDchange) was quantified. The dependent t-test, Wilcoxon-Signed-Rank Test, and one way ANOVA with Bonferroni correction were used to analyse the data.

RESULTS

SDF application reduced lesion depth from 844.6 to 759.1 μm (p < 0.045) while increasing mineral density from 551.4 to 763.0 mgHA/cm3 (p < 0.003). Only mineral density rose from 600.2 to 678.4 mgHA/cm3 (p < 0.013) when GIC was used. The other groups showed no difference. The highest %MDchange was also found after SDF treatment (49.7%, p < 0.05), whereas GIC (17.2%, p < 0.05) presented a higher percentage than the F-varnish (2.0%), F-toothpaste (-1.1%) and no-treatment groups (-1.4%).

CONCLUSION

In this in vitro study, where the pH of cycling was almost neutral, using SDF as an adjunct to F-toothpaste resulted in the highest remineralization compared with other remineralizing materials.

Evaluation of Surface Topography and Biomimetic Remineralization Capacity of Dendrimers in Comparison With Calcium Silicate Cement: An In Vitro Study

INTRODUCTION

Biodentine, a calcium silicate-based material, is known for its biocompatibility and ability to promote dentin regeneration. With their unique branching structure, polyamidoamine (PAMAM) dendrimers have shown promise in facilitating biomimetic remineralization processes.

AIM

This study investigates the synergistic effects of combining PAMAM with Biodentine on root dentin remineralization, aiming to develop a novel bioactive compound that offers superior protective and regenerative properties.

METHODS

The following predictions were made: (1) In a cyclic artificial saliva/acid regimen, among the test groups, the combination of Biodentine and PAMAM would cause the most root dentin remineralization (2). Biodentine alone would increase Ca and P concentrations, neutralize acid, and promote root dentin remineralization (3). PAMAM, on the other hand, can remineralize the demineralized root dentin.

RESULTS

Minimal mineral regeneration was accomplished in demineralized root dentin when treated with Biodentine or PAMAM alone. Root dentin remineralization was most pronounced when Biodentine and PAMAM were used together, and the hardness of demineralized root dentin was raised to an equivalent level to that of healthy root dentin.

DISCUSSION

The study demonstrated the exceptional ability of PAMAM + Biodentine to promote root dentin remineralization. In an acid-challenging environment, PAMAM + Biodentine promoted full and efficient root dentin remineralization. Restorations made using innovative PAMAM + Biodentine technology show promise in remineralizing and protecting tooth structures.

Changes in enamel hardness, wear resistance, surface texture, and surface crystal structure with glass ionomer cement containing BioUnion fillers

This study investigated the potential of BioUnion filler containing glass ionomer cement (GIC) to enhance the properties of enamel surrounding restorations, with a specific focus on the effect on hardness. The hardness of the bovine enamel immersed in the cement was measured using Vickers hardness numbers. Following sliding and impact wear simulations, the enamel facets were examined using confocal-laser-scanning microscopy and scanning-electron microscopy. Surface properties were further analyzed using energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). A significant increase in Vickers hardness numbers was observed in the BioUnion filler GIC after 2 days. Furthermore, the mean depth of enamel facets treated with BioUnion filler GIC was significantly less than that of untreated facets. Characteristic XRD peaks indicating the presence of hydroxyapatite were also observed. Our findings imply that GIC with BioUnion fillers enhances the mechanical properties of the tooth surface adjacent to the cement.

Chlorhexidine gluconate enhances the remineralization effect of high viscosity glass ionomer cement on dentin carious lesions in vitro

Background

To compare the mean mineral density (MMD) and examine the remineralization of carious dentin after cavity disinfection with chlorhexidine gluconate (CHX) and restoration with high viscosity glass ionomer cement (H-GIC) in vitro.

Methods

Selective caries removal to leathery dentin was performed in 40 extracted primary molars. The samples were scanned using micro-computed tomography (micro-CT) to determine the MMD baseline and randomly divided into 4 groups (n = 10): Equia™ group, applied dentin conditioner and restored with H-GIC (Equia Forte™), CHX-Equia™ group, disinfected the cavity with 2% CHX before applying dentin conditioner and restored with H-GIC (Equia Forte™), Ketac™ group, restored with H-GIC (Ketac Universal™) and CHX-Ketac™ group, disinfected the cavity with 2% CHX before restored with H-GIC (Ketac Universal™). The samples underwent micro-CT scanning post-restoration and post-pH-cycling to determine their respective MMDs. One sample from each group was randomly selected to analyze by scanning electron microscopy (SEM).

Results

The MMD gain in the 4 groups post-restoration was significantly different between the Equia™ and CHX-Ketac™ groups (oneway ANOVA with Post hoc (Tukey) test, P = 0.045). There was a significant difference in MMD gain post-restoration between the Equia™ and CHX-Equia™ groups (Independent t-test, P = 0.046). However, the Ketac™ and CHX-Ketac™ group’s MMD were similar. The SEM images revealed that the CHX-Ketac™ group had the smallest dentinal tubule orifices and the thickest intertubular dentin among the groups. However, the CHX-Equia™ group had thicker intertubular dentin than the Equia™ group.

Conclusion

Applying 2% CHX on demineralized dentin enhances the remineralization of the dentin beneath the restoration.

Establishment of novel in vitro culture system with the ability to reproduce oral biofilm formation on dental materials

Intensive research has been conducted with the aim of developing dental restorative/prosthetic materials with antibacterial and anti-biofilm effects that contribute to controlling bacterial infection in the oral cavity. In situ evaluations were performed to assess the clinical efficacy of these materials by exposing them to oral environments. However, it is difficult to recruit many participants to collect sufficient amount of data for scientific analysis. This study aimed to assemble an original flow-cell type bioreactor equipped with two flow routes and assess its usefulness by evaluating the ability to reproduce in situ oral biofilms formed on restorative materials. A drop of bacterial suspension collected from human saliva and 0.2% sucrose solution was introduced into the assembled bioreactor while maintaining the incubation conditions. The bioreactor was able to mimic the number of bacterial cells, live/dead bacterial volume, and volume fraction of live bacteria in the in situ oral biofilm formed on the surface of restorative materials. The usefulness of the established culture system was further validated by a clear demonstration of the anti-biofilm effects of a glass-ionomer cement incorporating zinc-releasing glasses when evaluated by this system.

A Repeated State of Acidification Enhances the Anticariogenic Biofilm Activity of Glass Ionomer Cement Containing Fluoro-Zinc-Silicate Fillers

This study aimed to evaluate the anticariogenic biofilm activity of a novel zinc-containing glass ionomer cement, Caredyne Restore (CR), using a flow-cell system that reproduces Stephan responses. Streptococcus mutans biofilms were cultured on either CR or hydroxyapatite (HA) discs mounted on a modified Robbins device. The media were allowed to flow at a speed of 2 mL/min for 24 h while exposed to an acidic buffer twice for 30 min to mimic dietary uptake. Acid exposure enhanced biofilm inhibition in the CR group, which showed 2.6 log CFU/mm² in viable cells and a 2 log copies/mL reduction in total cells compared to the untreated group after 24 h of incubation, suggesting enhanced anticariogenic activity due to the release of fluoride and zinc ions. However, there was no difference in the number of viable and total cells between the two experimental groups after 24 h of incubation in the absence of an acidic environment. The anticariogenic biofilm activity of CR occurs in acidic oral environments, for example in the transient pH drop following dietary uptake. CR restorations are recommended in patients at high risk of caries due to hyposalivation, difficulty brushing, and frequent sugar intake.

Effects of bioactive glass incorporation into glass ionomer cement on demineralized dentin

The effects of the incorporation of sodium-free bioactive glass into glass ionomer cement (GIC) on the demineralized dentin are studied. Four experimental groups with various amounts of BAG in GIC were considered: BG0 group: 0 wt% (control); BG5 group: 5 wt%; BG10 group: 10 wt%; BG20 group: 20 wt%. The GIC surface and GIC-approximated demineralized dentin surfaces were evaluated using field emission scanning electron microscopy (FE–SEM). X-ray diffraction (XRD) analysis was performed to evaluate the chemical changes in the GIC-approximated dentin surface. In addition, a shear bond strength test was performed to evaluate the effects of BAG incorporation on the bond strength of GIC. FE–SEM analysis indicated that BAG-incorporated GICs formed distinct precipitates on their surface. Precipitates were also formed on the GIC-approximated demineralized dentin surface. It was more obvious when the amount of BAG increased. In the XRD analysis, fluorapatitie (FAP) peaks were detected in the BG5, BG10, and BG20 groups. There was no significant difference in the shear bond strength among all experimental groups. BAG-incorporated GIC precipitated FAP crystals underlying demineralized dentin surface without affecting bond strength. This study suggests the possibility of BAG as a beneficial additive in GIC.

Evaluation of ion release and the recharge ability of glass-ionomer cement containing BioUnion filler using an in vitro saliva-drop setting assembly

OBJECTIVE

A glass-ionomer cement (GIC) containing BioUnion filler has been reported to release Zn²⁺ under acidic conditions and to inhibit oral bacteria on its surface. However, previous results are based on in vitro experiments under static conditions. This study aimed to assemble an in vitro saliva-drop setting to simulate in vivo conditions of the oral cavity and to investigate the ion releasing and recharging properties of the GIC containing BioUnion filler.

METHODS

The effective concentrations of Zn²⁺ and F^- against Streptococcus mutans and saliva-derived multi-species biofilms were determined. Artificial saliva was dropped on the GIC containing BioUnion filler using the in vitro saliva-drop setting assembly and was periodically replaced with acetic acid. Ion release/recharge properties were investigated by measuring the release concentrations of Zn²⁺ and F^-.

RESULTS

The concentration of Zn²⁺ released from the BioUnion filler-containing GIC during seven days with repeated exposure to acid could be maintained at the level to inhibit S. mutans and saliva-derived multi-species biofilm formation. Moreover, the BioUnion filler-containing GIC could be recharged with Zn²⁺ and F^- by the application of a tooth gel containing Zn²⁺ and F^-. The release concentration of Zn²⁺ after recharging was significantly higher than the effective concentration of Zn²⁺ to hinder S. mutans and saliva-derived multi-species biofilm formation on material surfaces.

SIGNIFICANCE

The GIC containing BioUnion filler was shown to have the potential to inhibit biofilm formation in the oral cavity. In addition, recharging Zn²⁺ and F^- would further enhance the effect of the GIC containing BioUnion filler.

Fluoride Release of Fresh and Aged Glass Ionomer Cements after Recharging with High-Fluoride Dentifrice

Objective

This study aimed to evaluate F release from GICs before and after recharging with F-dentifrices and after aging process.

Methods

Fifteen specimens of GICs (conventional, resin modified, and high viscosity) and composite resin were stored individually in a polystyrene tube containing 2 ml of deionized water (DW), with water replacement every 24 hours. After 15 days, the specimens were treated with a dentifrice suspension (1 : 3 by volume) containing 0 μg F/g (n = 5), 1,100 μg F/g (n = 5), or 5,000 μg F/g (n = 5). After 3 min, the specimens were rinsed and replaced in new tubes with 2 ml of DW. This procedure was performed 2x/day for 2 days. The readings were taken on days 1, 5, 10, and 15 before and after the treatments. A second experiment was performed, using the same specimens of the previous study that were submitted to an aging process (specimens were kept in 2 ml of DW, remaining at 37°C for 36 weeks). Readings using specific electrode for F detection were taken on days 1, 5, 10, and 15 after treatment of the samples as described above. Data were analyzed by ANOVA and Tukey's test with α fixed at 5%.

Results

It was observed that the highest release of F for all the GICs occurred on the first day after the treatments, especially when using a high-fluoride dentifrice, with decreasing release over time. Also, although aged GICs still recharge with F treatments, the amount of F released was lower than fresh materials.

Conclusion

GICs present a high F recharge and release capacity, especially in the first 24 hours and after the treatment with a high-fluoride dentifrice, even after material aging.

Tissue Response after Subcutaneous Implantation of Different Glass Ionomer-Based Cements

The aim of this study was to evaluate the subcutaneous connective tissue response of isogenic mice after implantation of different glass ionomer-based cements (EQUIA® Forte Fil, EQUIA® Fil and Ketac™ Universal Aplicap™). Eighty-seven isogenic BALB/c mice were allocated in 12 groups, 9 were considered as experimental groups (Ketac, E. Fil and E. Forte at 7, 21 and 63 days) and 3 controls (empty polyethylene tubes at 7, 21 and 63 days). After the experimental periods, the subcutaneous connective tissue surrounding the implanted material was removed and subjected to histotechnical processing and staining with hematoxylin and eosin. A histopathological description of the tissue reaction surrounding each material and a semi-quantitative analysis of collagen fiber formation and inflammatory infiltrate were performed. Additionally, the thickness of the granulomatous tissue in contact with each material was measured. Data were analyzed statistically (α=0.05) by the Kruskal-Wallis test, followed by Dunn post-test. Initially, the collagen fiber formation was not different among all the tested materials (p>0.05) but was different at 21 days with the control group presenting the most advanced stage of collagen fiber formation. At 63 days, EQUIA® Forte Fil group showed the most advanced stage of collagen fiber formation, compared to EQUIA® Fil group (p<0.05). The inflammatory infiltrate was not different among the tested materials in any experimental period (p>0.05). The thickness of the granulomatous tissue was greater in the E. Forte group, compared to control in all periods. All glass ionomer-based cements showed tissue compatibility, according to the evaluated parameters.

Gastrointestinal Absorption and Renal Excretion of Fluoride After Ingestion of a High-Fluoride Dentifrice

This study aimed to evaluate the gastrointestinal absorption and renal excretion of fluoride after the ingestion of high-fluoride dentifrice. Twelve volunteers participated in this in vivo, crossover, and blinded study. In three experimental phases, the volunteers were randomly assigned to one of three treatment groups, who ingested either the following: distilled and deionized water (control), conventional dentifrice (1100 μg/g), or high-fluoride dentifrice (5000 μg/g). Both dentifrices contained fluoride in the form of NaF/SiO₂. To determine the rate of fluoride absorption, non-stimulated saliva was collected for up to 120 min after ingestion and the area under the curve of the salivary fluoride concentration was plotted as a function of time and the maximum concentration determined. All urine produced during the 24 h before and after ingestion was collected, and urinary excretion was calculated from the difference between the urinary fluoride concentrations in the two periods. A specific ion electrode coupled to an ion analyzer was used to measure fluoride concentrations. Statistical analysis was performed by ANOVA followed by Tukey's test with p set at 5%. All measured parameters were highest after the ingestion of the dentifrice with 5000 μg/g (p < 0.001), confirming that this has an increased level of bioavailable fluoride compared with the conventional dentifrice. The high-fluoride dentifrice increases the concentration of salivary fluoride, which may explain its greater anticaries effect. However, it poses a potential risk of causing dental fluorosis and so should not be used by children.

Evaluation of Microleakage in Zirconomer®: A Zirconia Reinforced Glass Ionomer Cement

Objective

To evaluate the microleakage of four direct restorative materials.

Materials and Methods

Sixteen sound bovine incisors were chosen and randomly divided into four groups; Group I-Zirconomer, Group II-Ketac^TM Silver, Group III-Filtek^TM Z500 (composite) and Group IV-Dispersalloy^® (amalgam). Seven proximal (mesial & distal) cavities, for each material were prepared and restored. All restored samples were stored in 37^oC distilled water for 24 hr and then subjected to thermo-cycling process at temperatures between 5-55^oC. The samples were immersed in dye solution of 0.5% methylene blue for 24 hr. Each filled cavity was sectioned through the centre of restoration and then studied under a stereomicroscope to assess the marginal leakage. The obtained microleakage scores were statistically analysed.

Results

The highest mean score of leakage was recorded in Group II-Ketac^TM Silver followed by Group I-Zirconomer and Group III-Filtek^TM Z500 (composite). The lowest mean score of dye penetration was verified in Group IV-Dispersalloy^® (amalgam). Statistically, there were significant differences between Zirconomer and other groups of Ketac^TM Silver and amalgam, whereas the Zirconomer groups had no significant differences with composites. All tested groups showed significant differences with amalgam restorations.

Conclusions

The marginal leakage was evident in all restorative materials. Further studies with clinical trial have to be done.

Thermo-cured glass ionomer cements in restorative dentistry

Numerous positive properties of glass ionomer cements including biocompatibility, bioactivity, releasing of fluoride and good adhesion to hard dental tissue even under wet conditions and easy of handling are reasons for their wide use in paediatric and restorative dentistry. Their biggest drawbacks are the weaker mechanical properties. An important step forward in improving GIC’s features is thermo-curing with the dental polymerization unit during setting of the material. Due to their slow setting characteristics the GIC is vulnerable to early exposure to moisture. After thermo curing, cements retain all the benefits of GIC with developed better mechanical properties, improved marginal adaptation, increased microhardness and shear bond strength. Adding external energy through thermocuring or ultrasound during the setting of conventional GIC is crucial to achieve faster and better initial mechanical properties. Further clinical studies are needed to confirm these findings.

Combining Bioactive Multifunctional Dental Composite with PAMAM for Root Dentin Remineralization

Objectives. The objectives of this study were to: (1) develop a bioactive multifunctional composite (BMC) via nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); and (2) investigate the effects of combined BMC + poly (amido amine) (PAMAM) on remineralization of demineralized root dentin in a cyclic artificial saliva/lactic acid environment for the first time. Methods. Root dentin specimens were prepared and demineralized with 37% phosphoric acid for 15 s. Four groups were prepared: (1) root dentin control; (2) root dentin with BMC; (3) root dentin with PAMAM; (4) root dentin with BMC + PAMAM. Specimens were treated with a cyclic artificial saliva/lactic acid regimen for 21 days. Calcium (Ca) and phosphate (P) ion concentrations and acid neutralization were determined. The remineralized root dentin specimens were examined via hardness testing and scanning electron microscopy (SEM). Results. Mechanical properties of BMC were similar to commercial control composites (p = 0.913). BMC had excellent Ca and P ion release and acid-neutralization capability. BMC or PAMAM alone each achieved slight mineral regeneration in demineralized root dentin. The combined BMC + PAMAM induced the greatest root dentin remineralization, and increased the hardness of pre-demineralized root dentin to match that of healthy root dentin (p = 0.521). Significance. The excellent root dentin remineralization effects of BMC + PAMAM were demonstrated for the first time. BMC + PAMAM induced effective and complete root dentin remineralization in an acid challenge environment. The novel BMC + PAMAM method is promising for Class V and other restorations to remineralize and protect tooth structures.

The Effects of Gic Restorations on Enamel and Dentin Demineralization and Remineralization

Glass-ionomer cement (GIC) restorations release fluoride after placement in the oral environment. This is assumed to be one of the reasons for the decreased prevalence of secondary caries. In the current studies, the effects of GIC restorations on demineralization and remineralization of enamel and dentin lesions were studied, in an in vitro and an intra-oral model, respectively. The in vitro pH-cycling study revealed that the excessive fluoride release of the freshly placed restorations upset the (commonly observed) mineral balance between the specimens and the de/remineralizing solutions. Anomalous patterns of calcium uptake by the specimens (with GIC) during the demineralization phase and calcium loss during the remineralization phase were observed. This was hypothetically explained from the behavior of a surface coating on the GIC restorations, which was observed with SEM. The intra-oral studies showed, after three months in situ, hypermineralization of dentin close to or in contact with the restoration. It is concluded that the fluoride released from GIC or the decreased permeability as a result of hypermineralization causes lower susceptibility of the dentin of the cavity walls.

Casein Phosphopeptide-Amorphous Calcium Phosphate Reduces Streptococcus mutans Biofilm Development on Glass Ionomer Cement and Disrupts Established Biofilms

Glass ionomer cements (GIC) are dental restorative materials that are suitable for modification to help prevent dental plaque (biofilm) formation. The aim of this study was to determine the effects of incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into a GIC on the colonisation and establishment of Streptococcus mutans biofilms and the effects of aqueous CPP-ACP on established S mutans biofilms. S. mutans biofilms were either established in flow cells before a single ten min exposure to 1% w/v CPP-ACP treatment or cultured in static wells or flow cells with either GIC or GIC containing 3% w/w CPP-ACP as the substratum. The biofilms were then visualised using confocal laser scanning microscopy after BacLight LIVE/DEAD staining. A significant decrease in biovolume and average thickness of S. mutans biofilms was observed in both static and flow cell assays when 3% CPP-ACP was incorporated into the GIC substratum. A single ten min treatment with aqueous 1% CPP-ACP resulted in a 58% decrease in biofilm biomass and thickness of established S. mutans biofilms grown in a flow cell. The treatment also significantly altered the structure of these biofilms compared with controls. The incorporation of 3% CPP-ACP into GIC significantly reduced S. mutans biofilm development indicating another potential anticariogenic mechanism of this material. Additionally aqueous CPP-ACP disrupted established S. mutans biofilms. The use of CPP-ACP containing GIC combined with regular CPP-ACP treatment may lower S. mutans challenge.

Comparative Evaluation of the Antibacterial Efficacy of Type II Glass lonomer Cement, Type IX Glass lonomer Cement, and AMALGOMER™ Ceramic Reinforcement by Modified "Direct Contact Test": An in vitro Study

Background:Streptococcus mutans (ATCC25175) has a profound effect on the incidence of dental decay in the human population. Many studies have been performed to assess the antimicrobial activity of different cements. However, little or no information is available about the antibacterial properties of Type II glass ionomer cement (GIC), Type IX GIC, and AMALGOMER™ ceramic reinforcement (CR).

Aim: To comparatively evaluate the antibacterial activity of Type II GIC, Type IX GIC, and AMALGOMER™ CR by modified direct contact test.

Materials and methods: The total sample size was 72 which was divided into four study groups. Six wells were coated by each: Type II GIC, Type IX GIC, AMALGOMER™ CR, and control group (only S. mutans). Statistical analysis was done using analysis of variance and the intergroup comparison was done using post hoc Tukey test.

Results: AMALGOMER™ CR was found to have a better antibacterial effect as compared with Type II and IX GIC.

Conclusion: AMALGOMER™ CR can serve as a valuable cement in pediatric dentistry due to its anticariogenic property.

How to cite this article: Hugar SM, Assudani HG, Patil V, Kukreja P, Uppin C, Thakkar P. Comparative Evaluation of the Antibacterial Efficacy of Type II Glass lonomer Cement, Type IX Glass Ionomer Cement, and AMALGOMER™ Ceramic Reinforcement by Modified “Direct Contact Test”: An in vitro Study. Int J Clin Pediatr Dent 2016;9(2):114-117.

Glass hybrid, but not calcium hydroxide, remineralized artificial residual caries lesions in vitro

OBJECTIVES

For deep carious lesions, less invasive carious tissue removal is recommended. The resulting residual carious lesions might benefit from remineralization by lining or restoration materials. We aimed to compare mineral gains in artificial residual lesions provided by calcium hydroxide and glass hybrid materials in combination with pulpal fluid simulation.

METHODS

On the coronal aspect of human dentin discs (n = 20), artificial carious lesions were induced using acetic acid. Median mineral loss ΔZ [25th/75th percentiles] of resulting lesions was 1643 [1301/1858] vol% μm. One third of each disc served as baseline sample. The remaining disc was divided into four groups, each being covered with one experimental material (n = 20/group): flowable composite (control (CO)), setting or non-setting calcium hydroxide liner plus flowable composite (CH-S, CH-NS), and glass hybrid (GH). Samples were mounted in a dual-chamber device. Pulpal surfaces were exposed to simulated pulpal fluid at 2.94 kPa. Coronal surfaces were exposed to artificial saliva and rinsed with 200 ppm NaF every 2 weeks. After 12 weeks, mineral loss differences (ΔΔZ) were assessed using transverse microradiography. Electron probe microscopic analysis was used to measure fluoride and strontium concentrations.

RESULTS

Mineral gains were not significantly different between CO (ΔΔZ = 372 [115/501] vol% μm), CH-S (ΔΔZ = 317 [229/919] vol% μm), or CH-NS (ΔΔZ = 292 [130/579] vol% μm; p > 0.05/Wilcoxon test) but significantly increased in GH (ΔΔZ = 1044 [751/1264] vol% μm, p < 0.001). Samples in GH showed fluoride and strontium enrichment deep into the dentin. Such enrichment was not found in CO.

CONCLUSIONS

Within the limitations of this study, GH, but not calcium hydroxide, provided coronal remineralization of residual carious lesions.

CLINICAL RELEVANCE

Glass hybrids might provide additional remineralization of residual carious lesions. The functional implications of this mineral gain need to be evaluated.

Atomic and vibrational origins of mechanical toughness in bioactive cement during setting

Bioactive glass ionomer cements (GICs) have been in widespread use for ∼40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of calorimetry, terahertz (THz) spectroscopy and neutron scattering, how GIC's developing fracture toughness during setting is related to interfacial THz dynamics, changing atomic cohesion and fluctuating interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass-polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces. Subsequently, toughness declines asymptotically to long-term fracture test values. We expect the insight afforded by these in situ non-destructive techniques will assist in raising understanding of the setting mechanisms and associated dynamics of cementitious materials.

Do Laboratory Results Concerning High-Viscosity Glass-Ionomers versus Amalgam for Tooth Restorations Indicate Similar Effect Direction and Magnitude than that of Controlled Clinical Trials? - A Meta-Epidemiological Study

BACKGROUND

A large percentage of evidence concerning dental interventions is based on laboratory research. The apparent wealth of laboratory evidence is sometimes used as basis for clinical inference and recommendations for daily dental practice. In this study two null-hypotheses are tested: whether trial results from laboratory and controlled clinical trials concerning the comparison of high-viscosity glass-ionomer cements (HVGIC) to amalgam for restorations placed in permanent posterior teeth have: (i) similar effect direction and (ii) similar effect magnitude.

METHODS

7 electronic databases were searched, as well as reference lists. Odds ratios (OR) and Standardised Mean Differences (SMD) with 95% Confidence intervals were computed for extracted dichotomous and continuous data, respectively. Pooled effect estimates for laboratory and clinical data were computed to test for effect direction. Odds ratios were converted into SMDs. SMDs from laboratory and clinical data were statistically compared to test for differences in effect magnitude. The analysed results were further investigated within the context of potential influencing or confounding factors using a Directed acyclic graph.

RESULTS

Of the accepted eight laboratory and nine clinical trials, 13 and 21 datasets could be extracted, respectively. The pooled results of the laboratory datasets were highly statistically significant in favor of amalgam. No statistically significant differences, between HVGICs and amalgam, were identified for clinical data. For effect magnitude, statistically significant differences between clinical and laboratory trial results were found. Both null-hypotheses were rejected.

CONCLUSION

Laboratory results concerning high-viscosity glass-ionomers versus amalgam for tooth restorations do not indicate similar effect direction and magnitude than that of controlled clinical trials.

Shear bond strength of Biodentine, ProRoot MTA, glass ionomer cement and composite resin on human dentine ex vivo

Introduction

The aim of this study was to compare the shear bond strength of Biodentine, ProRoot MTA (MTA), glass ionomer cement (GIC) and composite resin (CR) on dentine.

Methods

120 extracted human third molars were embedded in cold-cured-resin and grinned down to the dentine. For each material 30 specimens were produced in standardised height and width and the materials were applied according to manufacturers´ instructions on the dentine samples. Only in the CR group a self-etching dentine-adhesive was used. In all other groups the dentine was not pre-treated. All specimens were stored at 37.5 °C and 100% humidity for 2d, 7d and 14d. With a testing device the shear bond strength was determined (separation of the specimens from the dentine surface). The statistical evaluation was performed using ANOVA and Tukey-test (p < 0.05).

Results

At all observation periods the CR showed the significant highest shear bond strength (p < 0.05). After 2d significant differences in the shear bond strength were detectable between all tested materials, whereby CR had the highest and MTA the lowest values (p < 0.05). After 7d and 14d the shear bond strengths of MTA and Biodentine increased significantly compared to the 2d investigation period (p < 0.05). Biodentine showed a significantly higher shear bond strength than MTA (p < 0.05), while the difference between Biodentine and GIC was not significant (p > 0.05).

Conclusions

After 7d Biodentine showed comparable shear bond values than GIC, whereas the shear bond values for MTA were significantly lower even after 14d. The adhesion of Biodentine to dentine surface seams to be superior compared to that of MTA.

The incorporation of nanoparticles into conventional glass-ionomer dental restorative cements

Conventional glass-ionomer cements (GICs) are popular restorative materials, but their use is limited by their relatively low mechanical strength. This paper reports an attempt to improve these materials by incorporation of 10 wt% of three different types of nanoparticles, aluminum oxide, zirconium oxide, and titanium dioxide, into two commercial GICs (ChemFil® Rock and EQUIA™ Fil). The results indicate that the nanoparticles readily dispersed into the cement matrix by hand mixing and reduced the porosity of set cements by filling the empty spaces between the glass particles. Both cements showed no significant difference in compressive strength with added alumina, and ChemFil® Rock also showed no significant difference with zirconia. By contrast, ChemFil® Rock showed significantly higher compressive strength with added titania, and EQUIA™ Fil showed significantly higher compressive strength with both zirconia and titania. Fewer air voids were observed in all nanoparticle-containing cements and this, in turn, reduced the development of cracks within the matrix of the cements. These changes in microstructure provide a likely reason for the observed increases in compressive strength, and overall the addition of nanoparticles appears to be a promising strategy for improving the physical properties of GICs.

Influence of the addition of chlorhexidine diacetate on bond strength of a high-viscosity glass ionomer cement to sound and artificial caries-affected dentin

INTRODUCTION: The aim of adding chlorhexidine (CHX) to glass ionomer cements (GIC) is to improve their antibacterial property, but it may interfere with their bond to dentin. OBJECTIVE: To evaluate the influence of adding chlorhexidine diacetate at different concentrations to a high-viscosity GIC on its bond to sound and artificial caries-affected dentin. MATERIAL AND METHOD: Eighty human third molars were used, on which an area of dentin was exposed on the occlusal surface. Half of the specimens were kept sound and the other half were subjected to artificially induced caries. CHX was mixed with GIC powder at 0.5%, 1% and 2% (w/w). GIC without CHX was used as control. On each dentin surface a specimen measuring 1 mm in diameter and 1 mm high was made. The samples were kept at 37 °C and 100% humidity for 24 hours and subject to microshear testing. The results were analyzed using Kruskal-Wallis and Mann Whitney tests (α=0.05). RESULT: There was no significant difference between bond strength of sound and caries-affected dentin (p>0.05). For both substrate conditions, groups GIC, GIC+0.5% CHX and GIC+1% CHX showed statistically similar bond strength (p>0.05), and higher than that of GIC+2% CHX (p<0.025). Cohesive and mixed failures were predominant in all groups. CONCLUSION: The addition of 0.5% and 1% chlorhexidine did not result in negative changes in the bond strength of GIC to caries-affected and sound dentin.

Micro-computerized tomography assessment of fluorescence aided caries excavation (FACE) technology: comparison with three other caries removal techniques

BACKGROUND

The aim of this study was to determine the caries removal effectiveness (CRE) and minimal invasiveness potential (MIP) of four dentine caries removal methods.

METHODS

After carious molars were scanned using micro-computerized tomography (micro-CT), dentine caries were removed by fluorescence aided caries excavation (FACE) technology, laser induced fluorescence (LIF), chemomechanical excavation (CME), and conventional excavation (CE). Micro-CT was then repeated. CRE was determined based on the volume of residual caries/initial caries (RC/IC) and the mean mineral density (MD) at the cavity floor. MIP was determined by measuring the volume of the prepared cavity/initial cavity (PC/IC).

RESULTS

Among the four groups, the LIF group had the smallest RC/IC (0.08), the highest mean MD at the cavity floor (1.32 g/cm(3) ) and the highest MIP (4.47). The CME group had the highest RC/IC (0.24), the lowest mean MD (1.01 g/cm(3) ) and the lowest MIP (2.23). The CE group exhibited a more acceptable CRE (RC/IC = 0.13, mean MD = 1.21 g/cm(3) ) but had a higher MIP (3.95). Both the CRE and MIP parameters of FACE technology were the second most acceptable (RC/IC = 0.12, mean MD = 1.13 g/cm(3) , MIP = 3.20) and did not differ significantly from the most acceptable.

CONCLUSIONS

FACE is an effective caries removal technology for removing infected dentine without significantly increasing cavity size.

Interfacial properties of three different bioactive dentine substitutes

Three different bioactive materials suitable as dentine substitutes in tooth repair have been studied: glass-ionomer cement, particulate bioglass, and calcium-silicate cement. On 15 permanent human molars, Class V cavities were prepared and the bottom of each cavity was de-mineralized by an artificial caries gel. After the de-mineralization, the teeth were restored with: (1) Bioglass®45S5 and ChemFil® Superior; (2) Biodentine™ and ChemFil® Superior; and (3) ChemFil® Superior for a complete repair. The teeth were stored for 6 weeks in artificial saliva, then cut in half along the longitudinal axis: the first half was imaged in a scanning electron microscope (SEM) and the other half was embedded in resin and analyzed by SEM using energy-dispersive X-ray analysis. The glass-ionomer and the bioglass underwent ion exchange with the surrounding tooth tissue, confirming their bioactivity. However, the particle size of the bioglass meant that cavity adaptation was poor. It is concluded that smaller particle size bioglasses may give more acceptable results. In contrast, both the glass-ionomer and the calcium-silicate cements performed well as dentine substitutes. The glass-ionomer showed ion exchange properties, whereas the calcium silicate gave an excellent seal resulting from its micromechanical attachment.

Effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria-material interface: an in vitro model study

OBJECTIVES

Inhibition of bacterial acid production by dental restorative materials is one of the strategies for secondary caries prevention. This study aimed to evaluate the effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria-material interface.

METHODS

Four fluoride-releasing restorative materials, glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RMGIC), resin composite (RC) and flowable resin composite (FRC) were used. Each specimen was immersed in potassium phosphate buffer at pH 7.0 for 10min and 4 weeks, and in potassium acetate buffer at pH 5.5 for 4 weeks. An experimental apparatus was made of polymethyl methacrylate and had a well with restorative materials or polymethyl methacrylate (control) at the bottom. The well was packed with cells of Streptococcus mutans, and the pH at the interface between cells and materials was monitored using a miniature pH electrode after the addition of 1% glucose for 90min, and the fluoride released into the well was quantified using a fluoride ion electrode.

RESULTS

The pH of GIC (4.98-5.18), RMGIC (4.77-4.99), RC (4.62-4.75) and FRC (4.54-4.84) at 90min were higher than that of control (4.31-4.49). The fluoride amounts released from GIC were the highest, followed by RMGIC, RC and FRC, irrespective of immersion conditions. Saliva coating on materials had no significant effect.

CONCLUSIONS

The fluoride-releasing restorative materials inhibited pH fall at the bacteria-material interface. The degree of inhibition of pH fall seemed to correspond to the amount of fluoride detected, suggesting that the inhibition was due to the fluoride released from these materials.

CLINICAL SIGNIFICANCE

A little amount of fluoride actually released from the fluoride-releasing materials may have caries preventive potential for oral bacteria.

Biomimetic remineralization of dentin

OBJECTIVES

Remineralization of demineralized dentin is important for improving dentin bonding stability and controlling primary and secondary caries. Nevertheless, conventional dentin remineralization strategy is not suitable for remineralizing completely demineralized dentin within hybrid layers created by etch-and-rinse and moderately aggressive self-etch adhesive systems, or the superficial part of a caries-affected dentin lesion left behind after minimally invasive caries removal. Biomimetic remineralization represents a different approach to this problem by attempting to backfill the demineralized dentin collagen with liquid-like amorphous calcium phosphate nanoprecursor particles that are stabilized by biomimetic analogs of noncollagenous proteins.

METHODS

This paper reviewed the changing concepts in calcium phosphate mineralization of fibrillar collagen, including the recently discovered, non-classical particle-based crystallization concept, formation of polymer-induced liquid-precursors (PILP), experimental collagen models for mineralization, and the need for using phosphate-containing biomimetic analogs for biomimetic mineralization of collagen. Published work on the remineralization of resin-dentin bonds and artificial caries-like lesions by various research groups was then reviewed. Finally, the problems and progress associated with the translation of a scientifically sound concept into a clinically applicable approach are discussed.

RESULTS AND SIGNIFICANCE

The particle-based biomimetic remineralization strategy based on the PILP process demonstrates great potential in remineralizing faulty hybrid layers or caries-like dentin. Based on this concept, research in the development of more clinically feasible dentin remineralization strategy, such as incorporating poly(anionic) acid-stabilized amorphous calcium phosphate nanoprecursor-containing mesoporous silica nanofillers in dentin adhesives, may provide a promising strategy for increasing of the durability of resin-dentin bonding and remineralizing caries-affected dentin.

Effect of resin-modified glass ionomer containing bioactive glass on the flexural strength and morphology of demineralized dentin

INTRODUCTION

Recently, bioactive materials have been incorporated into glass ionomer cements to promote the precipitation of calcium phosphates in surrounding tooth structures. This in vitro study was undertaken to evaluate the effect of resin-modified glass ionomer (RMGI) containing bioactive glass (RMGI-BAG) on the flexural strength (FS) of demineralized dentin.

MATERIALS AND METHODS

A total of 120 dentin bars (2×2×6 mm) were prepared from sound human third molars. Of these, 60 bars were immersed in a demineralizing solution for 96 hours. This produced dentin in two demineralization conditions (DC): untreated and demineralized. Each dentin bar was immersed for 14 days in simulated body fluid (SBF) at 37°C. Three immersion conditions (IC) were investigated: IC1-SBF only; IC2-SBF + an RMGI bar; IC3-SBF + an RMGI-BAG bar. The combination of the DCs and ICs produced six groups (n=20). FS values of the specimens were measured using a three-point bending test. The microstructural changes and the elemental contents of dentin surfaces were evaluated by scanning electron microscopy. Data were analyzed using a two-way analysis of variance (ANOVA) for the effects of the two independent variables, ie, DC and IC, on mean flexural strength. Tukey multiple comparison tests and simple main effects models were used as needed. The significance level of all tests was set at α=0.05.

RESULTS

Both DC (p=0.001) and IC (p=0.049) significantly influenced FS (two-way ANOVA). The interaction between DC and IC did not significantly affect FS (p=0.36). For undemineralized dentin, IC did not affect the mean FS (simple main effects model; p=0.4). However, for demineralized dentin, IC significantly affected FS (small main effects model; p=0.008). The Tukey test showed that for demineralized dentin, the mean FS produced by immersion in SBF + RMGI-BAG was significantly stronger than that produced by either immersion in SBF only (p=0.011) or in SBF + RMGI (p=0.034). Scanning electron microscope/energy-dispersive x-ray spectroscopy analyses revealed more calcium and phosphate ions on the surface of dentin immersed in SBF + RMGI-BAG than on dentin immersed in SBF + RMGI.

CONCLUSION

Immersion in SBF + RMGI-BAG increased the FS of demineralized dentin more than immersion in SBF + RMGI.

Ion concentration adjacent to glass-ionomer restorations in primary molars

OBJECTIVES

The aim was to compare the levels of fluoride, calcium and phosphorus in enamel and dentin alongside glass-ionomer-based restorations over time.

METHODS

This CCT consisted of children with cavities in the occlusal surface of primary molars that were restored with either a high-viscosity (Fuji IX GP(®)) or a resin-modified glass-ionomer (Vitremer(®)), being the test groups. Sound teeth (controls) were harvested from the children belonging to the test groups. Sampled teeth were cut in half and the ion concentration measured using EPMA. ANOVAs, and Newman-Keuls tests were performed to analyze the data. The study sample consisted of 35 children having 29 teeth per group available for analyses.

RESULTS

Although statistically significantly higher, the mean ion-concentration of calcium in enamel and dentin, and that of phosphorous in dentin hardly differed between the tests and control groups. The mean fluoride concentration in enamel (0.20ppm×10(3) and 0.24ppm×10(3)) and dentin (0.71ppm×10(3) and 0.78ppm×10(3)) surrounding the Fuji IX GP(®) and Vitremer(®) restored teeth, respectively was statistically significantly higher than in enamel (0.12ppm×10(3)) and dentin (0.12ppm×10(3)) for the control teeth.

SIGNIFICANCE

The present in vivo investigation showed that fluoride ions are released from high-viscosity and resin-modified glass-ionomer primary restoration into the restorations' surrounding enamel and, and in particular, dentin.

Ion migration from fluoride-releasing dental restorative materials into dental hard tissues

This study was carried out in order to determine the extent to which ions released from fluoride-containing dental restoratives migrated through the enamel and dentine of extracted teeth. A total of 40 permanent human 3rd molars were used. They were extracted for orthodontic reasons, and employed within 1 month of extraction. A cervical (Class V) cavity was prepared in each tooth, then filled with one of: a conventional glass-ionomer, a resin-modified glass-ionomer, a polyacid-modified composite resin ("compomer") or a fluoride-releasing resin composite. Ten samples were prepared per material. After 1 month, five specimens per material were prepared and examined under SEM/EDX. Concentrations of sodium, aluminium, strontium, fluorine, magnesium, silicon, phosphorus and calcium were determined within the tooth. After 18 months, the remaining five specimens for each material were prepared and studied in the same way. The greatest extent of ion migration into the tooth was found with the conventional glass-ionomer and least migration was found for the fluoride-releasing composite, which showed no evidence of fluoride migration at all. Levels of migrating ions were generally higher in the 18 month specimens than in the 1 month specimens, and also higher in the dentine than in the enamel. Ions released by restorative dental materials have been shown conclusively for the first time to be capable of migrating into the enamel and dentine surrounding the restoration. The conventional glass-ionomer showed the highest level of ion migration whereas the fluoridated composite resin showed little if any ion migration. This suggests that the conventional glass-ionomer has the greatest caries inhibiting effects of all the materials tested, and the fluoridated composite the least.

Therapeutic effects of novel resin bonding systems containing bioactive glasses on mineral-depleted areas within the bonded-dentine interface

This study aimed in evaluating the effects of two experimental resin bonding systems containing conventional Bioglass 45S5 (BAG) or Zinc-polycarboxylated bioactive glass (BAG-Zn) micro-fillers on the resin-bonded dentine interface after storage in a simulated body fluid solution (SBFS). Three resin bonding systems were formulated: Resin-A: (BAG containing); Resin-B; (BAG-Zn containing); Resin-C (no filler). The ability of the experimental resins to evoke apatite formation was evaluated using confocal Raman spectroscopy. Acid-etched dentine specimens were bonded, and prepared for AFM/nano-indentation analysis in a fully-hydrated status to evaluate the modulus of elasticity (Ei) and hardness (Hi) across the interface at different SBFS storage periods. Further resin-dentine specimens were tested for microtensile bond strength after 24 h or 3 months of SBFS storage. SEM examination was performed after de-bonding and confocal laser microscopy was used to evaluate the ultramorphology of the interfaces and micropermeability. The resin A and B showed a consistent presence of apatite (967 cm(-1)), reduced micropermeability within the resin-dentine interface and a significant increase of the Ei and Hi along the bonded-dentine interface after prolonged SBFS storage. Bond strength values were affected by the resin system (P < 0.0001) and by storage time (P < 0.0001) both after 24 h and 3 months of SBFS storage. In conclusion, resin bonding systems containing bioactive fillers may a have therapeutic effect on the nano-mechanical properties and sealing ability of mineral-depleted resin-dentine interface.

Paradigm shift in the effective treatment of caries in schoolchildren at risk

BACKGROUND

 Silver diamine fluoride (SDF) is an effective agent for the arrest of caries in children, is easy to apply and can be used outside the clinical environment. Interim restorative treatment (IRT) using glass ionomer cement has also been claimed to be a simple and effective method to arrest caries in deciduous teeth.

OBJECTIVE

 To examine whether, for underprivileged schoolchildren with cavities, treatment with 30% SDF gives better results than IRT for carries arrest.

METHOD

 This randomised controlled study compares the effect of IRT (FUJI IX) with 30% SDF in 91 children aged 5-6 years.

RESULTS

 After 1 year, treatment with SDF was more effective [relative risk (RR) = 66.9%] than IRT (RR = 38.6%) for the arrest of caries; this was statistically significant (P < 0.05).

CONCLUSION

 The SDF technique showed better results than IRT for the arrest of cavities in deciduous teeth, indicating that its use for underprivileged communities may justify a paradigm shift in paediatric dentistry.

Fluoride and aluminum release from restorative materials using ion chromatography

Objective

The aim of this study was to determine the amounts of fluoride and aluminum released from different restorative materials stored in artificial saliva and double-distilled water.

Material and Methods

Cylindrical specimens (10 x 1 mm) were prepared from 4 different restorative materials (Kavitan Plus, Vitremer, Dyract Extra, and Surefil). For each material, 20 specimens were prepared, 10 of which were stored in 5 mL artificial saliva and 10 of which were stored in 5 mL of double-distilled water. Concentrations of fluoride and aluminum in the solutions were measured using ion chromatography. Measurements were taken daily for one week and then weekly for two additional weeks. Data were analyzed using two-way ANOVA and Duncan's multiple range tests (p<0.05).

Results

The highest amounts of both fluoride and aluminum were released by the resin-modified glass ionomer cement Vitremer in double-distilled water (p<0.05). All materials released significantly more fluoride in double-distilled water than in artificial saliva (p<0.05). In artificial saliva, none of the materials were observed to release aluminum.

Conclusion

It was concluded that storage media and method of analysis should be taken into account when the fluoride and aluminum release from dental materials is assessed.

Qualitative assessment of microstructure and Hertzian indentation failure in biocompatible glass ionomer cements

Discs of biocompatible glass ionomer cements were prepared for Hertzian indentation and subsequent fracture analyses. Specifically, 2 × 10 mm samples for reproducing bottom-initiated radial fracture, complemented by 0.2 × 1 mm samples for optimal resolution with X-ray micro tomography (μCT), maintaining dimensional ratio. The latter allowed for accurate determination of volumetric-porosity of the fully cured material, fracture-branching through three Cartesian axes and incomplete bottom-initiated cracking. Nanocomputed tomography analyses supported the reliability of the μCT results. Complementary 2-dimensional fractographic investigation was carried out by optical and scanning electron microscopies on the larger samples, identifying fracture characteristics. The combined 3-D qualitative assessment of microstructure and fractures, complemented by 2-D methods, provided an increased understanding of the mechanism of mechanical failure in these cements. Specifically, cracks grew to link pores while propagating along glass-matrix interfaces. The methodological development herein is exploitable on related biomaterials and represents a new tool for the rational characterisation, optimisation and design of novel materials for clinical service.

The caries-reducing benefit of fluoride-release from dental restorative materials continues after fluoride-release has ended

OBJECTIVE

This study tested the hypothesis that the benefit of fluoride-releasing restorative materials continues even after their reserve of fluoride has been depleted.

MATERIALS AND METHODS

Pits in perspex blocks simulating cavities were filled with either a fluoride-releasing or a non-fluoride-releasing restorative material and a dentin single-section was placed 1 mm from the edge of the filled pit. These combinations were exposed to an acid gel system. Each demineralized dentin section was separated from the adjacent material and immersed in fresh demineralizing solutions. Transversal microradiographs were taken following the two experimental periods. This study defined ΔΔZ as the increase of integrated mineral loss (ΔZ) during the second acid attack.

RESULTS

The first acid attack substantially demineralized the near-surface region (depth < 40 μm) in all samples. The second acid attack, however, did not cause further demineralization in this near-surface region. Instead, it demineralized dentin deeper than 40-60 μm. The ΔΔZ of the material that did not release fluoride was significantly greater than that of fluoride-releasing materials. Negative correlations were found between ΔΔZ and the mineral volume% of the near-surface region and lesion body of the initial lesions. These results indicate that the dentin mineral in the near-surface region is chemically altered to become acid-resistant fluorapatite. In addition, lesion progression during the second period of demineralization, which was fluoride-free, may have been affected for the materials that have high mineral content of the surface layer and lesion body.

CONCLUSIONS

It is concluded that dentin surrounding fluoride-releasing materials is protected against demineralization even after the fluoride release has diminished.

An in-vitro assessment of weekly cumulative fluoride release from three glass ionomer cements used for orthodontic banding

OBJECTIVES

To compare the in-vitro Weekly Cumulative Fluoride Release (WCFR) of three Glass Ionomer Cements (GICs) used for orthodontic banding.

MATERIALS AND METHODS

The GICs tested were Granitec (Confi-Dental, Louisville, CO, USA), Bandtite (American Orthodontics, Sheboygan, WI, USA) and Ariadent (Apadana Tak Co, Tehran, Iran). Fifteen discs of each GIC were constructed (6mm diameter and 1.5mm depth). Specimens were immersed in 5 ml of deionised water and the WCFR was measured at weekly intervals, on days 1, 8, 15, 22 and 29 after immersion in deonised water, using the potentiometery device and single junction saturated calomel electrode technique (Jenway, England, UK). To compare the WCFR profile of 3 GICS, data were subjected to the one-way analysis of variance (ANOVA), and were appropriate, the Scheffe or Tamhane multiple comparison tests (post-hoc). For assessing the longitudinal changes of average WCFRs in 3 GICs, the repeated measures ANOVA were used. Post hoc tests using the Bonferroni correction was also used to compare the average WCFRs at different time-points.

RESULTS

One-way ANOVA and post-hoc multiple comparison tests revealed significant differences in WCFR among 3 GICs at five time-points (p<0.05). The post-hoc multiple comparison test revealed Bandtite cement had consistently higher WCFR at all time-points, compared to Granitec and Ariadent cements (p<0.05). The one-way ANOVA test revealed significant differences in WCFR at different time-points for all GIC groups (p<0.05). The day 8 exhibited the highest WCFR for all GICs. The repeated measures ANOVA test revealed significant differences in WCFR at different time-points for all GIC groups (p<0.0005). Reviewing average WCFR on days 22 and 29, these values for Granitec, Bandtite and Ariadent GICs, were higher (p<0.05), not different (p>0.05), and significantly lower (p<0.05) than the day 1 values, respectively.

CONCLUSIONS

Bandtite followed by Granitec showed higher WCFR compared to Ariadent.