Interaction of glass-ionomer cements with moist dentin

Current Trends for Cementation in Prosthodontics: Part 1-The Substrate

With the vast possibilities of restorative dentistry nowadays and the constant development and release of restorative materials with improved mechanical and esthetical properties, there is a growing body of research on adhesive systems and cementation materials, as well as the adequate choices thereof in everyday clinical practice. There are high demands from the dental cements with regard to their adhesion to various substrates and restorative materials, their mechanical properties, resistance to dissolution in the oral environment, esthetic considerations, etc. A material that meets all these requirements is not yet available, and each available material presents certain shortcomings. However, thanks to the advancements in dental material research, polymers-based cements have gained admirable mechanical and esthetic properties, as well as versatility. With the plethora of products available on the market, clinicians are often faced with difficulties in the choice of a material adequate for certain clinical situations. Indeed, important factors to consider are the substrate for cementation and the restoration material. The aim of this review was to provide clear and literature-based clinical recommendations for the adequate cementation of prosthodontic restorations with regard to the cementation substrate. Considering that there is no gold standard protocol applicable in all clinical cases, since the properties of the cementation abutment could substantially differ, important individual considerations must be made for each situation.

Bioactivity and remineralization potential of modified glass ionomer cement: A systematic review of the impact of calcium and phosphate ion release

This systematic review investigates the effectiveness of calcium and phosphate ions release on the bioactivity and remineralization potential of glass ionomer cement (GIC). Electronic databases, including PubMed-MEDLINE, Scopus, and Web of Science, were systematically searched according to PRISMA guidelines. This review was registered in the PROSPERO database. Five eligible studies on modifying GIC with calcium and phosphate ions were included. The risk of bias was assessed using the RoBDEMAT tool. The incorporation of these ions into GIC enhanced its bioactivity and remineralization properties. It promoted hydroxyapatite formation, which is crucial for remineralization, increased pH and inhibited cariogenic bacteria growth. This finding has implications for the development of more effective dental materials. This can contribute to improved oral health outcomes and the management of dental caries, addressing a prevalent and costly oral health issue. Nevertheless, comprehensive longitudinal investigations are needed to evaluate the clinical efficacy of this GIC's modification.

Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO₂ nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

In-air micro-proton-induced X-ray/gamma-ray emission analysis of the acid resistance of root dentin after applying fluoride-containing materials incorporating calcium

This study employed an in-air micro-proton-induced X-ray/gamma-ray emission system to assess the effectiveness of fluoride-containing materials (FCMs) incorporating calcium in preventing root caries. Dentin surfaces of human third molars were coated with one of three FCMs: fluoride-releasing glass-ionomer cement (F7) and experimental materials in which half (P1) or all (P2) of the strontium in F7 was replaced with calcium. Dentin without FCM coating served as the control. Specimens were immersed in saline at 37°C for 1 month, sectioned, and then demineralized. Calcium loss after demineralization was lower in the Ca-substituted groups than in the Ca-unsubstituted groups (p<0.05). Calcium loss was negatively correlated with fluoride uptake (p<0.01). In the F7, P1, and P2 groups, the retraction of the dentin surface was significantly suppressed as compared with the control group. FCMs incorporating calcium improved the acid resistance of root dentin and could help prevent root caries.

The forgotten merits of GIC restorations: a systematic review

Objective

To reevaluate proven strengths and weakness of glass ionomer cements (GICs) and to identify agreement versus conflicting evidence in previous reports regarding the transition between GIC and the tooth, and the existence of an “interphase”.

Materials and methods

Relevant electronic databases (PubMed, Embase via Ovid and Medline via Web of science) were searched for publications of evidence relating to the transition zone at the GIC-tooth interphase. Studies were examined and grouped according to characteristics of GIC-tooth attachment area quantified by X-ray and optical microscopy techniques in 2D and 3D.

Results

Inclusion criteria comprised of in vitro studies that showed images of the conventional GIC-tooth substrate attachments using at least one of the following techniques: SEM, CLSM, or μCT. The search identified 419 studies, from which 33 were included. Ten studies demonstrated the existence of an interphase layer and five studies quantified the layer thickness (1–15 μ). Twenty-nine publications studied different failure modes of the GIC-tooth interphase. Eleven studies described discontinuities inside the GIC bulk.

Conclusion

The GIC-tooth interphase attributes evolve with time. Good attachment is evident even under compromised surface preparation. The GIC-tooth attachment area is resistant to acidic dissolution as compared to both tooth and GIC bulk. In general, studies revealed mostly intact GIC-tooth interphases with only some cracked interphases.

Clinical significance

GIC bonds to the tooth structure and forms an acid resistant attachment zone that might enhance caries inhibition. Due to fluoride release and ease of use, GIC provides a cost effective treatment, ideal for low income or high caries populations.

Influence of external energy sources on the dynamic setting process of glass-ionomer cements

OBJECTIVE

To evaluate the influence of external energy sources on the dynamic setting process of glass-ionomer restorative materials.

METHODS

Eighteen brands of GIC were studied: Bioglass R (Biodinâmica; G1), Chemfil Rock (Dentsply; G2), Equia Forte (GC; G3), Gold Label 2 (GC; G4), Gold Label 9 (GC; G5), Glass Ionomer Cement Type II - (Shofu; G6), Ionglass R (Maquira; G7), Ion Z (FGM; G8), Ionomaster (Wilcos; G9), Ionofil Plus (Voco; G10), Ionostar Plus (Voco; G11), Ketac Molar easymix (3M ESPE; G12), Magic Glass R (Vigodent; G13), Maxxion R (FGM; G14), Riva Self Cure (SDI; G15), Vidrion R (SS White; G16), Vitro Fil R (Nova DFL; G17) and Vitro Molar (Nova DFL; G18). LED, halogen light or ultrasound (n=20 for each set) applied for 30s was used to activate setting, and a control group of each material was allowed to set without activation. Samples were analyzed by FTIR spectroscopy using the ratio of intensities of bands at 1637cm^-1 (carboxylate) and 1720cm^-1 (carbonyl) as a function of time. Means and standard deviations were subjected to ANOVA and Tukey tests (p<0.05).

RESULTS

All three activation modes significantly reduced the time at which the carboxylate content became stable in G2, G4, G5, G6, G8, G10, G14, G16, G17 and G18. By contrast, in G1, G7, G12 and G15 no activation source had any significant effect (p>0.05).

SIGNIFICANCE

External activation sources, namely LED, halogen light and ultrasound, typically but not always increase the setting rate of restorative GICs.

Study of the chemical interaction between a high-viscosity glass ionomer cement and dentin

Objective

To investigate the chemical interactions between a high-viscosity glass ionomer cement (GIC) (KetacTM Molar Easymix, 3M ESPE, Seefeld, Bavaria, Germany) and human dentin. It was also analyzed the dynamics of GIC setting mechanism based on the time intervals required for the GIC and the GIC mixed with dentin to achieve stability.

Material and Methods

Each constituent of GIC – powder (P) and liquid (L) – and powdered dentin (D), as well as the associations P+L, D+L, and P+L+D in the concentrations of 29%, 50%, 65%, 78%, 82%, and 92% of GIC were analyzed with Fourier transform infrared (FTIR) and Raman spectroscopy.

Results

New optical absorption bands and/or Raman bands, which were not present in P, L, or D, were observed in the associations. The concentrations of 29% and 50% of GIC showed higher interaction, revealing that the amount of dentin influences the formation of new optical absorption or scattering bands. FTIR bands showed that the setting time to achieve bond stability was longer for the high-viscosity GIC (38±7 min) than for the sample with 29% of GIC (28±4 min).

Conclusions

The analysis revealed the formation of new compounds or molecular rearrangements resulting from the chemical interactions between GIC and dentin. Moreover, this study provides an effective method to evaluate the dynamics of the setting mechanism of GICs.

Physical property investigation of contemporary glass ionomer and resin-modified glass ionomer restorative materials

OBJECTIVES

The objective of this study was to investigate selected physical properties of nine contemporary and recently marketed glass ionomer cement (GIC) and four resin-modified glass ionomer cement (RMGI) dental restorative materials.

MATERIALS AND METHODS

Specimens (n = 12) were fabricated for fracture toughness and flexure strength using standardized, stainless steel molds. Testing was completed on a universal testing machine until failure. Knoop hardness was obtained using failed fracture toughness specimens on a microhardness tester, while both flexural modulus and flexural toughness was obtained by analysis of the flexure strength results data. Testing was completed at 1 h, 24 h, 1 week, and then at 1, 3, 6, and 12 months. Mean data was analyzed with Kruskal-Wallis and Mann-Whitney (p = 0.05).

RESULTS

Physical properties results were material dependent. Physical properties of the GIC and RMGI products were inferior at 1 h compared to that at 24 h. Some improvement in selected physical properties were noted over time, but development processes were basically concluded by 24 h. A few materials demonstrated improved physical properties over the course of the evaluation.

CONCLUSIONS

Under the conditions of this study: 1. GIC and RMGI physical property performance over time was material dependent; 2. Polyalkenoate maturation processes are essentially complete by 24 h; 3. Although differences in GIC physical properties were noted, the small magnitude of the divergences may render such to be unlikely of clinical significance; 4. Modest increases in some GIC physical properties were noted especially flexural modulus and hardness, which lends support to reports of a maturing hydrogel matrix; 5. Overall, GIC product physical properties were more stable than RMGI; 6. A similar modulus reduction at 6 months for both RMGI and GIC produced may suggest a polyalkenoate matrix change; and 7. Globally, RMGI products demonstrated higher values of flexure strength, flexural toughness, and fracture toughness than GIC materials.

CLINICAL RELEVANCE

As compared to RMGI materials, conventional glass ionomer restorative materials demonstrate more stability in physical properties.

In vitro mechanical stimulation facilitates stress dissipation and sealing ability at the conventional glass ionomer cement-dentin interface

OBJECTIVE

The aim of this study was to evaluate the induced changes in the chemical and mechanical performance at the glass-ionomer cement-dentin interface after mechanical load application.

METHODS

A conventional glass-ionomer cement (GIC) (Ketac Bond), and a resin-modified glass-ionomer cement (RMGIC) (Vitrebond Plus) were used. Bonded interfaces were stored in simulated body fluid, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling, 24 h cycled in sine or loaded in sustained hold waveforms. The cement-dentin interface was evaluated using a nano-dynamic mechanical analysis, estimating the complex modulus and tan δ. Atomic Force Microscopy (AFM) imaging, Raman analysis and dye assisted confocal microscopy evaluation (CLSM) were also performed.

RESULTS

The complex modulus was lower and tan delta was higher at interfaces promoted with the GIC if compared to the RMGIC unloaded. The conventional GIC attained evident reduction of nanoleakage. Mechanical loading favored remineralization and promoted higher complex modulus and lower tan delta values at interfaces with RMGIC, where porosity, micropermeability and nanoleakage were more abundant.

CONCLUSIONS

Mechanical stimuli diminished the resistance to deformation and increased the stored energy at the GIC-dentin interface. The conventional GIC induced less porosity and nanoleakage than RMGIC. The RMGIC increased nanoleakage at the porous interface, and dye sorption appeared within the cement. Both cements created amorphous and crystalline apatites at the interface depending on the type of mechanical loading.

CLINICAL SIGNIFICANCE

Remineralization, lower stress concentration and resistance to deformation after mechanical loading improved the sealing of the GIC-dentin interface. In vitro oral function will favor high levels of accumulated energy and permits micropermeability at the RMGIC-dentin interface which will become remineralized.

Clinical performance of laminate and non-laminate resin composite restorations: a systematic review

BACKGROUND

A systematic review was undertaken to determine the clinical outcomes of resin modified glass-ionomer cement or glass-ionomer cement-resin composite (RMGIC/GIC-RC) laminate restorations and flowable resin composite (FRC)-lined RC restorations compared to that of non-laminate RC restorations.

METHODS

Electronic databases were searched and filtered for relevant papers by assessing titles, abstracts and full-text articles. Randomized controlled clinical trials (RCTs) were included, comparing the clinical performance of RMGIC/GIC-RC laminate restorations and FRC-lined restorations with RC restorations as the control. The articles were categorized and critically appraised. Raw data were used for a fixed effects meta-analysis.

RESULTS

Thirteen articles were included in the review. Five evaluated FRC-lined restorations, and eight studies evaluated RMGIC/GIC-RC laminate restorations, comparing with non-laminate RC restorations. Three of eight RMGIC/GIC-RC laminate restorations assessed only postoperative sensitivity. A meta-analysis could only be conducted in three studies with the FRC-lined restorations as the intervention. The meta-analysis found no significant difference in clinical failures between FRC-lined RC restorations and RC restorations with no lining (p > 0.05).

CONCLUSIONS

Based on current clinical evidence, a FRC lining is no more advantageous than RC restorations with no FRC lining. More long-term RCTs are required, particularly for evaluating RMGIC/GIC-RC laminate restorations.

In vitro fracture strength and patterns in root-filled teeth restored with different base materials

BACKGROUND

There is little research on the effects of an intermediate base on the fracture strength of root-filled teeth. This study compared the fracture strengths and patterns of root-filled teeth restored with intermediate bases of glass-ionomer cement (GIC), zinc polycarboxylate cement (ZPC), dual-cured resin composite (DCRC) and Biodentine^® under resin composite.

METHODS

Standardized cavities were prepared in 100 extracted human maxillary and mandibular premolars, and root canal treatment was performed. The teeth were stratified and randomly allocated to five groups (n = 20): (i) GIC; (ii) ZPC; (iii) DCRC; (iv) Biodentine; and (v) prepared but unrestored (control). The teeth were subjected to an oblique, ramped load until fracture. The fracture loads, level, mode and location were recorded.

RESULTS

Mean fracture strengths of all restored groups were not significantly different amongst the groups. There were significant overall effects on mean fracture strength for tooth type (P = 0.002) and buccolingual width of the crown (P = 0.001).

CONCLUSIONS

The four materials were appropriate intermediate bases. The laminate restorative technique promoted fracture strengths that are likely to withstand normal and maximum masticatory function. The base material can influence failure mode, which may have implications for the clinical presentation of fractures of root-filled teeth.

Development of a Self-etch Adhesive for Resin-modified Glass Ionomers

The favorable self-adhesiveness of resin-modified glass ionomers (RMGIs) might be even further improved if the time-consuming and technically sensitive etch-and-rinse pre-treatment step with polyalkenoic acids could be avoided. We undertook this study to assess the effectiveness of an experimental self-etch adhesive for RMGIs that does not need to be rinsed off. Ultrastructural analysis and micro-tensile bond strength testing to enamel and dentin of a RMGI restorative material and a RMGI adhesive were performed after 4 different surface pre-treatments: no conditioning; 25% polyalkenoic acid; an experimental self-etch adhesive; and 37.5% phosphoric acid followed by the experimental self-etch adhesive. The use of an experimental self-etch adhesive increased the bond strength of RMGIs, especially after an additional conditioning step. Interfacial analysis showed the formation of a thin hydroxyapatite-containing hybrid layer. The self-etch technique enhances the user-friendliness of RMGIs and lowers their technique-sensitivity, while maintaining desirable characteristics of the conventional etch-and-rinse approach with polyalkenoic acids.

Minimizing Dentinal Fluid Flow Associated with Gap Formation

The relationship between gap formation and outward fluid flow and procedures to minimize both phenomena were investigated in extracted human premolars restored in vitro with MOD composite restorations. We hypothesized that either glass-ionomer cement (GIC) liners or low-shrinkage composite could reduce fluid flow related to gap formation. Two groups restored with bonding agents with either high- or low-shrinkage resin composites, and 2 groups restored by either conventional or light-cured GIC liner plus resin composite were compared (8 teeth/group). Fluid flow was measured with an automated apparatus. Baseline fluid flow was low and unchanged after bonding, but increased sharply (though transiently) after teeth were lined with GIC. Outward flow was significantly greater with conventional than with light-cured GIC. Inward fluid flow occurred during light-curing, followed by extensive, prolonged outward flow after curing. Low-shrinkage composite or GIC liners reduced gap formation and limited outward fluid flow. GIC liners promoted outward fluid flow during their setting reactions. Abbreviations: GIC, glass-ionomer cement; CEJ, cemento-enamel junction; MOD, mesio-occluso-distal; SEM, scanning electron microscopy.

Influence of acceleration setting reaction by halogen light-curing on GIC-dentin interface: Qualitative analysis by SEM

The aim of this study was to evaluate by scanning electron microscope (SEM) photomicrographs the influence of application of halogen light-curing for fastening the set reaction of high-viscosity glass ionomer cements (GIC) by assessing the material/dentin interface. Twelve human primary canines were assigned in four groups (n = 3) according to the GIC (Fuji IX, GC or Maxxion R, FGM) and application of halogen light-curing (60 sec or control-no external energy). Blocks with approximately 6 mm of height were buildup on previously pre-treated dentin surface in according to the experimental group. After storage at 37 °C, 100% humidity for 48 h, the specimens were then sectioned in slices with 1-mm thick. The slices were qualitative analyzed using SEM to evaluate possible structural changes. Two examiners independently evaluated the images in order to observe the spherical hollow spaces of each tooth. The photomicrographs revealed the presence of spherical hollow spaces in all experimental groups. However, in both groups that received halogen light-curing application, it was possible to observe that the presence of these hollow spaces decreased in size and quantity. It can be concluded that the halogen light-curing application positively decreases in size and quantity in the presence of spherical hollow spaces in GIC.

Comparative Evaluation of Microleakage Between Nano-Ionomer, Giomer and Resin Modified Glass Ionomer Cement in Class V Cavities- CLSM Study

INTRODUCTION

Marginal integrity of adhesive restorative materials provides better sealing ability for enamel and dentin and plays an important role in success of restoration in Class V cavities. Restorative material with good marginal adaptation improves the longevity of restorations.

AIM

Aim of this study was to evaluate microleakage in Class V cavities which were restored with Resin Modified Glass Ionomer Cement (RMGIC), Giomer and Nano-Ionomer.

MATERIALS AND METHODS

This in-vitro study was performed on 60 human maxillary and mandibular premolars which were extracted for orthodontic reasons. A standard wedge shaped defect was prepared on the buccal surfaces of teeth with the gingival margin placed near Cemento Enamel Junction (CEJ). Teeth were divided into three groups of 20 each and restored with RMGIC, Giomer and Nano-Ionomer and were subjected to thermocycling. Teeth were then immersed in 0.5% Rhodamine B dye for 48 hours. They were sectioned longitudinally from the middle of cavity into mesial and distal parts. The sections were observed under Confocal Laser Scanning Microscope (CLSM) to evaluate microleakage. Depth of dye penetration was measured in millimeters.

STATISTICAL ANALYSIS

The data was analysed using the Kruskal Wallis test. Pair wise comparison was done with Mann Whitney U Test. A p-value<0.05 is taken as statistically significant.

RESULTS

Nano-Ionomer showed less microleakage which was statistically significant when compared to Giomer (p=0.0050). Statistically no significant difference was found between Nano Ionomer and RMGIC (p=0.3550). There was statistically significant difference between RMGIC and Giomer (p=0.0450).

CONCLUSION

Nano-Ionomer and RMGIC showed significantly less leakage and better adaptation than Giomer and there was no statistically significant difference between Nano-Ionomer and RMGIC.

Tensile strength of Ni-Cr copings subjected to inner surface sandblasting using different cementing agents: An in vitro study

OBJECTIVES

To evaluate the effect of thermal cycling and inner surface treatment with aluminum oxide at different granulations on the tensile strength of Ni-Cr copings cemented with different cementing agents.

MATERIALS AND METHODS

Ninety-six metal copings were manufactured and divided into two groups: before and after thermal cycling (n = 48). The copings of both groups were internally treated by sandblasting with aluminum oxide particles of 100 (n = 24) and 320 (n = 24) mesh. The copings were cemented on previously manufactured metal cores using zinc phosphate (n = 8), conventional glass ionomer (CGIC) (n = 8) and resin-modified glass ionomer (RMGIC) (n = 8) cements. The tensile strength before and after thermal cycling was then determined (Newtons).

RESULTS

The tensile strength before and after thermal cycling was significantly higher in copings cemented with RMGIC compared to CGIC (p < 0.05) and was similar to that for zinc phosphate (p > 0.05). Thermal cycling and sandblasting of the inner surface of the metal copings with different granulations did not influence retention (p > 0.05).

CONCLUSIONS

Zinc phosphate cements and RMGIC showed similar retention. Additionally, the retention of the cements was not influenced by either thermal cycling or the particle size of the aluminum oxide.

Push-out bond strengths of different dental cements used to cement glass fiber posts

STATEMENT OF PROBLEM

Since the introduction of glass fiber posts, irreversible vertical root fractures have become a rare occurrence; however, adhesive failure has become the primary failure mode.

PURPOSE

The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents on 3 segments of the root.

MATERIAL AND METHODS

Eighty human maxillary canines with similar root lengths were randomly divided into 8 groups (n=10) according to the cement assessed (Rely X luting, Luting and Lining, Ketac Cem, Rely X ARC, Biscem, Duo-link, Rely X U100, and Variolink II). After standardized post space preparation, the root dentin was pretreated for dual-polymerizing resin cements and untreated for the other cements. The mixed luting cement paste was inserted into post spaces with a spiral file and applied to the post surface that was seated into the canal. After 7 days, the teeth were sectioned perpendicular to their long axis into 1-mm-thick sections. The push-out test was performed at a speed of 0.5 mm/min until extrusion of the post occurred. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05).

RESULTS

ANOVA showed that the type of interaction between cement and root location significantly influenced the push-out strength (P<.05). The highest push-out strength results with root location were obtained with Luting and Lining (S3) (19.5 ±4.9 MPa), Ketac Cem (S2) (18.6 ±5.5 MPa), and Luting and Lining (S1) (18.0 ±7.6 MPa). The lowest mean values were recorded with Variolink II (S1) (4.6 ±4.0 MPa), Variolink II (S2) (1.6 ±1.5 MPa), and Rely X ARC (S3) (0.9 ±1.1 MPa).

CONCLUSIONS

Self-adhesive cements and glass ionomer cements showed significantly higher values compared to dual-polymerizing resin cements. In all root segments, dual-polymerizing resin cements provided significantly lower bond strength. Significant differences among root segments were found only for Duo-link cement.

Effect of luting cement and thermomechanical loading on retention of glass fibre posts in root canals

OBJECTIVES

To evaluate the effect of luting cement and thermomechanical loading on the retention of glass fibre posts in root canals.

METHODS

One hundred and forty-four single-rooted human premolars were endodontically treated and restored with RelyX Fibre Posts. The teeth were divided into four groups according to the cements used (Fuji I, Fuji CEM, RelyX Unicem and RelyX ARC). Each group was further divided into two subgroups according to the method of ageing (immediately tested and after thermomechanical loading). Bond strength was evaluated using a pull-out test. Microleakage was examined quantitatively with dye penetration. The dentine-cement-post bonding interface was assessed using scanning electron microscopy. Data were analysed with two-way ANOVA (pull-out test) and Kruskal-Wallis analysis (microleakage).

RESULTS

The pull-out bond strength and microleakage were significantly affected by the type of cement and ageing. Although RelyX ARC showed the highest bond strength before thermomechanical loading (p<0.05), the sealing ability of this cement was worse than those exhibited in Fuji CEM and RelyX Unicem (p<0.05). After thermomechanical loading, pull-out strengths of Fuji I and Fuji CEM were significantly increased, whereas that of RelyX ARC group significantly decreased (p<0.05). The sealing ability of Fuji CEM was significantly better than the two resin cement groups (p<0.05) after ageing.

CONCLUSION

Fuji CEM demonstrates increased pull-out strength after thermomechanical loading and favourable sealing ability compared with the other cements.

CLINICAL SIGNIFICANCE

Resin-modified glass ionomer cements have the potential benefit of achieving long-term retention when used for luting glass fibre post to root canal dentine. So it may be recommended for the cementation of glass fibre post in clinics.

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: biophotonics-based interfacial analyses in health and disease

Objective

Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers.

Methods

This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin–restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement–dentin interface samples behavior over time.

Results

The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials.

Significance

The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal.

Shear bond strength evaluation of resin composite bonded to glass-ionomer cement using self-etching bonding agents with different pH: In vitro study

Aim:

To evaluate the bonding ability of composite to unset glass-ionomer cement (GIC) using different self-etching bonding systems.

Materials and Methods:

One hundred samples of composite bonded to unset GIC were prepared and were divided into four groups. In Group A, composite was bonded to unset GIC employing a strong (pH 1) self-etch primer was used. In Group B, intermediary strong (pH 1.4) self-etch primer was employed. In Group C and D, mild (pH 2) and (pH 2.2) self-etch primer was employed. Shear bond strength analysis was performed at a cross-head speed of 0.5 mm/min.

Results:

Statistical analysis performed with one way analysis of variance and Tukey's test showed that the bond strength of composite to unset GIC was significantly higher for the mild self-etch primer group. In addition, energy dispersive x-ray (EDX) analysis was used to determine the composition of various structural phases identified by FE-SEM along the GIC-bonding agent interfaces.

Conclusion:

Hence this present study concludes that clinically the use of mild self-etching bonding agent over unset GIC has improved bond strength compared to the use of strong and intermediate self-etching bonding agent.

Randomized clinical trial of two resin-modified glass ionomer materials: 1-year results

With institutional review board approval, 33 patients who needed restoration of noncarious cervical lesions (NCCL) were enrolled in this study. A total of 92 NCCL were selected and randomly assigned to three groups: (1) Ambar (FGM), a two-step etch-and-rinse adhesive (control), combined with the nanofilled composite resin Filtek Supreme Plus (FSP; 3M ESPE); (2) Fuji II LC (GC America), a traditional resin-modified glass ionomer (RMGIC) restorative material; (3) Ketac Nano (3M ESPE), a nanofilled RMGIC restorative material. Restorations were evaluated at six months and one year using modified United States Public Health Service parameters. At six months after initial placement, 84 restorations (a 91.3% recall rate) were evaluated. At one year, 78 restorations (a 84.8% recall rate) were available for evaluation. The six month and one year overall retention rates were 93.1% and 92.6%, respectively, for Ambar/FSP; 100% and 100%, respectively, for Fuji II LC; and 100% and 100%, respectively, for Ketac Nano with no statistical difference between any pair of groups at each recall. Sensitivity to air decreased for all three adhesive materials from the preoperative to the postoperative stage, but the difference was not statistically significant. For Ambar/FSP, there were no statistical differences for any of the parameters from baseline to six months and from baseline to one year. For Fuji II LC, surface texture worsened significantly from baseline to six months and from baseline to one year. For Ketac Nano, enamel marginal staining increased significantly from baseline to one year and from six months to one year. Marginal adaptation was statistically worse at one year compared with baseline only for Ketac Nano. When parameters were compared for materials at each recall, Ketac Nano resulted in significantly worse color match than any of the other two materials at any evaluation period. At one year, Ketac Nano resulted in significantly worse marginal adaptation than the other two materials and worse marginal staining than Fuji II LC. Surface texture was statistically worse for Fuji II LC compared with the other two materials at all evaluation periods. The one-year retention rate was statistically similar for the three adhesive materials. Nevertheless, enamel marginal deficiencies and color mismatch were more prevalent for Ketac Nano. Surface texture of Fuji II LC restorations deteriorated quickly.

Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers' instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage, decreasing thereafter.

Influence of air-abrasion executed with polyacrylic acid-Bioglass 45S5 on the bonding performance of a resin-modified glass ionomer cement

The aim of this study was to test the microtensile bond strength (μTBS), after 6 months of storage in PBS, of a resin-modified glass ionomer cement (RMGIC) bonded to dentine pretreated with Bioglass 45S5 (BAG) using various etching and air-abrasion techniques. The RMGIC (GC Fuji II LC) was applied onto differently treated dentine surfaces followed by light curing for 30 s. The specimens were cut into matchsticks with cross-sectional areas of 0.9 mm(2). The μTBS of the specimens was measured after 24 h or 6 months of storage in PBS and the results were statistically analysed using two-way anova and the Student-Newman-Keuls test (α = 0.05). Further RMCGIC-bonded dentine specimens were used for interfacial characterization, micropermeability, and nanoleakage analyses by confocal microscopy. The RMGIC-dentine interface layer showed no water absorption after 6 months of storage in PBS except for the interdiffusion layer of the silicon carbide (SiC)-abraded/polyacrylic acid (PAA)-etched bonded dentine. The RMGIC applied onto dentine air-abraded with BAG/H(2)O only or with BAG/PAA-fluid followed by etching procedures (10% PAA gel) showed no statistically significant reduction in μTBS after 6 months of storage in PBS. The abrasion procedures performed using BAG in combination with PAA might be a suitable strategy to enhance the bonding durability and the healing ability of RMGIC bonded to dentine.

Cements and adhesives for all-ceramic restorations

Dental cements are designed to retain restorations, prefabricated or cast posts and cores, and appliances in a stable, and long-lasting position in the oral environment. Resin-based cements were developed to overcome drawbacks of nonresinous materials, including low strength, high solubility, and opacity. Successful cementation of esthetic restorations depends on appropriate treatment to the tooth substrate and intaglio surface of the restoration, which in turn, depends on the ceramic characteristics. A reliable resin cementation procedure can only be achieved if the operator is aware of the mechanisms involved to perform the cementation and material properties. This article addresses current knowledge of resin cementation concepts, exploring the bonding mechanisms that influence long-term clinical success of all-ceramic systems.

Comparative Evaluation of the Remineralizing Effects and Surface Micro hardness of Glass Ionomer Cements Containing Bioactive Glass (S53P4):An in vitro Study

Dental cements including the glass ionomer cement (GIC) have found widespread use in restoring tooth structures. In this study, modifications of glass ionomer cements (GICs) were made by adding bioactive glass (BAG) to GIC to obtain bioactive restorative materials. This study used polarized light microscopy (PLM) to examine the remineralization effects of the study materials on dentin. It also evaluated the Vickers microhardness of the experimental materials. Experimental glass ionomer cement (GIC)-BAG materials were made by mixing 10 wt% of BAG particles with conventional cure and resin-modified GIC powders. Class V restorations were made in 80 extracted mandibular teeth which included 4 groups of 20 teeth each. 100 |jm sections of the teeth were examined under polarized light microscope after undergoing pH cycling. Materials were also processed into 80 cylindrical specimens and immersed in water for 7 and 30 days before mechanical tests. Resin-modified GIC containing BAG showed a thick uniform layer of mineralization on the restoration-dentin interface. The conventional cure GIC-based materials had higher surface microhardness than the resin-modified materials.

SIGNIFICANCE

The addition of BAG to GIC compromises the mechanical properties of the materials to some extent. Thus, their clinical use ought to be restricted to applications where their bioactivity can be beneficial, such as root surface fillings and liners in dentistry.

Differential bonds degradation of two resin-modified glass-ionomer cements in primary and permanent teeth

OBJECTIVES

To evaluate the effect of chemical degradation on bond strength of resin-modified glass-ionomer cements bonded to primary and permanent dentin.

METHODS

Class I cavities of permanent and primary extracted human molars were restored with two resin-modified glass-ionomer cements: Fuji II LC and Vitremer, and stored in water for 24h. Half samples were immersed in 10% NaOCl aqueous solution for 5h. Teeth were sectioned into beams and tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Tukey's tests (p<0.05). Analysis of debonded surfaces was performed by SEM.

RESULTS

24h bond strengths for Vitremer and Fuji II LC were similar. For Fuji II, bond strength values were higher for primary than for permanent dentin. Vitremer bond strength was similar for both. Chemical degradation did not affect Fuji II LC bond strength to dentin. However, decreases in bond strength were found for Vitremer groups after NaOCl immersion. Signs of glass ionomer-dentin interaction were evident by SEM analysis for Fuji II LC specimens.

CONCLUSIONS

Vitremer and Fuji II presented similar bond strength at 24. Vitremer dentin bonds were prone to chemical degradation. Fuji II LC-dentin bonds showed typical features of glass-ionomer dentin interaction at the bonded interfaces, and were resistant to in vitro degradation.

Tensile bond strength of glass fiber posts luted with different cements

Proper selection of the luting agent is fundamental to avoid failure due to lack of retention in post-retained crowns. The objective of this study was to investigate the tensile bond strength and failure mode of glass fiber posts luted with different cements. Glass fiber posts were luted in 40 mandibular premolars, divided into 4 groups (n = 10): Group 1 - resin-modified glass ionomer RelyX Luting; Group 2 - resin-modified glass ionomer Fuji Plus; Group 3 - resin cement RelyX ARC; Group 4 - resin cement Enforce. Specimens were assessed by tensile strength testing and light microscopy analysis for observation of failure mode. The tensile bond strength values of each group were compared by ANOVA and Tukey test. The significance level was set at 5%. The failure modes were described as percentages. The following tensile strength values were obtained: Group 1 - 247.6 N; Group 2 - 256.7 N; Group 3 - 502.1 N; Group 4 - 477.3 N. There was no statistically significant difference between Groups 1 and 2 or between Groups 3 and 4, yet the resin cements presented significantly higher tensile bond strength values than those presented by the glass ionomer cements. Group 1 displayed 70% of cohesive failures, whereas Groups 2, 3 and 4 exhibited 70% to 80% of adhesive failures at the dentin-cement interface. We concluded that resin cements and glass ionomer cements are able to provide clinically sufficient retention of glass fiber posts, and that glass ionomer cements may be especially indicated when the application of adhesive techniques is difficult.

Cements for use in esthetic dentistry

Dental cements are designed to retain restorations, appliances, and post and cores in a stable and, presumably, long-lasting position in the oral environment. Conventional glass ionomer and zinc phosphate cements are among the most popular materials for luting metallic restorations and posts, whereas resin-based cements are preferred for esthetic applications. Successful cementation of esthetic restorations is largely dependent on the appropriate treatment and silane application to the internal surface of the restoration. Clinicians are frequently advised to use three-step total-etch or two-step self-etch adhesive for luting purposes to avoid problems of incompatibility between adhesives and chemical- or dual-cure cements. A reliable cementation procedure can only be achieved if the operator is aware of the mechanisms involved and the material limitations.

Durability of resin-dentin bonds: effects of direct/indirect exposure and storage media

OBJECTIVES

To evaluate the longevity of resin-dentin bonds of three adhesives using different storage media and specimen size.

METHODS

Flat dentin surfaces from extracted human third molars were bonded with: a two-step etch-and-rinse self-priming adhesive (Single Bond), a two-step self-etching adhesive (Clearfil SE Bond), and a one-step self-etching adhesive (One-Up Bond F). Composite build-ups were constructed. The bonded teeth were stored under three conditions: dry, distilled water, or mineral oil. Half of the specimens were stored as intact bonded teeth (Indirect Exposure/IE). The other half were first sectioned into beams and stored under same conditions (Direct Exposure/DE). After storage periods of 24h, 3 months or 1 year, the intact teeth (IE) were sectioned into beams and both subgroups (DE and IE) were tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Student-Newman-Keuls tests. Fractographic analysis was performed by SEM.

RESULTS

After 24h, Single Bond and Clearfil SE Bond performed equally and were superior to One-Up Bond F. After 3 months of DE to water storage, decreases in bond strengths were observed for Single Bond and One-Up Bond F, this decrease occurred for Clearfil SE Bond after 12 months of water storage. Bonded specimens aged in dry did not alter bond strengths over time. Bond strength increased when Single Bond was stored in mineral oil after 3 and 12 months. Micromorphological alterations were evident after water storage.

SIGNIFICANCE

Although dentin bond strength of all the adhesives fell over time in DE, SE Bond fells the least.

Effect of Hygroscopic Expansion on the Push-Out Resistance of Glass Ionomer-Based Cements Used for the Luting of Glass Fiber Posts

This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice push-out tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention.

Compound changes and tooth mineralization effects of glass ionomer cements containing bioactive glass (S53P4), an in vivo study

In this study, modifications of glass ionomer cements (GICs) were made by adding bioactive glass (BAG) to GIC to obtain bioactive restorative materials. This study used SEM, EDS and visual analysis to examine the bioactivity and the ability of the study materials to mineralize dentin. Conventional cure and resin-modified light-curing GIC were used. The materials consisted of powder and liquid. Three experimental materials were made by mixing 10-30 wt% of BAG powder with GIC powders. Commercially available GIC without BAG were used as controls. Class III restorations were made in altogether 62 intact beagle dog teeth, and the operation was performed under general anesthesia. The restorations were followed clinically for 1, 3 or 6 weeks. Resin-modified GIC containing BAG showed uniform CaP surface formation on the restorations. Mineral depositions in the close vicinity of the restoration-dentin interface and in deeper parts of dentin tubules were also noticed in resin-modified GIC containing BAG particles. It can be concluded that resin-modified GIC containing BAG have good potential in clinical applications where enhanced mineralization is expected.

Interaction of resin-modified glass-ionomer cements with moist dentine

OBJECTIVES

The objective of this study was to report on a novel phenomenon that occurs when resin-modified glass-ionomer cements (RMGICs) are bonded to moist human dentine.

METHODS

Dentine surfaces from extracted third molars were abraded with 180-grit SiC paper. Ten teeth were prepared for each of the two RMGICs tested (Fuji II LC, GC Corp. and Photac-Fil Quick, 3M ESPE). RMGIC buildups were made according to the manufacturers' instructions. After storage at 37 degrees C, 100% humidity for 24 h, the bonded specimens were cut occlusogingivally into 0.9 x 0.9 mm beams. Dentine surfaces bonded with the two RMGICs were examined along the fractured RMGIC/dentine interfaces. Additional beams fractured within the RMGICS and at 3 mm away from the interfaces were used as controls. The fractured beams were examined using scanning electron microscopy (SEM), field emission-environmental SEM (FE-ESEM) and transmission electron microscopy (TEM).

RESULTS

SEM and FE-ESEM revealed numerous solid spherical bodies along the RMGIC/dentine interfaces. By contrast, no spherical bodies could be identified within the RMGIC fractured 3 mm distant from the bonded interface. TEM and energy dispersive X-ray analyses performed on carbon-coated ultrathin sections showed that these solid spherical bodies consisted of a thin aluminum and silicon-rich periphery and an amorphous hydrocarbon core within the air voids of the original resin matrix.

CONCLUSION

The spherical bodies probably represent a continuation of GI reaction and poly(HEMA) hydrogel formation that results from water diffusion from the underlying moist dentine. Their existence provides evidence for the permeation of water through RMGIC/dentine interfaces.