Maturation of restorative glass ionomers with simplified application procedure

Microtensile bond strength of glass ionomer cements to a resin composite using universal bonding agents with and without acid etching

OBJECTIVES

To assess the effect of two universal bonding agents on the microtensile bond strength (μTBS) of encapsulated conventional glass ionomers (CGICs) and resin-modified glass ionomers (RMGICs) to a resin composite, with or without the use of 35% phosphoric acid.

METHODS

Four materials were used in this study: Riva Self-cure and Riva Light-cure; SDI and Equia Forte Fil and Fuji II LC; GC. The specimens were prepared in Teflon moulds with half the specimens for each GIC etched using 35% phosphoric acid (Ultra-Etch) and the remainder not etched. Each group was randomly subdivided into three groups, where the first two groups received an air-thin layer of bonding agent (G-Premio Bond = GPB or Clearfil Universal Bond = CUB) then light cured; and the third group had no bonding agent. For all groups, a nanohybrid composite (GC Kalore; GC) was placed incrementally on the GIC. Following 24 h immersion in distilled water, each block was embedded in epoxy resin in a cubic mould and sectioned by a cutting device. The stick specimens were then subjected to μTBS testing.

RESULTS

The application of both universal bonding agents significantly enhanced the μTBS of all GICs (p < 0.001). Both RMGICs exhibited higher μTBS compared to that of CGICs (p < 0.001). The application of universal bonding agents with acid etching significantly increased the μTBS of both CGICs and RMGICs to resin composite in contrast to without acid etching.

CONCLUSION

Using 35% phosphoric acid for 15 s prior to the application of universal bonding agents improved the μTBS of GIC to resin composite.

CLINICAL SIGNIFICANCE

Using Universal bonding agents with 15 s acid etching may increase the bond strength of both CGICs and RMGICs to resin composite when utilising the sandwich technique.

Quality of approximal surfaces of posterior restorations in primary molars

PURPOSE

To evaluate the influence of the restorative material and matrix system on proximal contact tightness and morphological characteristics of class II restorations in primary molars.

METHODS

Occluso-mesial cavities in second primary artificial molars were randomly restored using different materials (Filtek Z500 or Filtek Bulk Fill composites or high-viscosity glass ionomer cement Ketac Universal) and different matrix system (Tofflemire, AutoMatrix, matrix band with ring, contoured sectional matrix) (n = 12). Proximal contact tightness was measured using a custom-made device in an Instron 3345, and proximal surface morphology and marginal adaptation were scored after digital scanning. Two-way ANOVA, Tukey and Fischer's exact tests were performed (P < 0.05).

RESULTS

Proximal contact tightness values were significantly influenced by the restorative material (P < 0.05), the matrix system (P < 0.001), and their interaction (P < 0.01). Both resin composites showed statistically differences in proximal shape according to the matrix used to restore and exhibited overhanging margins. Ketac Universal restorations showed similar morphology and gaps on the margins regardless of the matrix system.

CONCLUSIONS

Overall, both composite restorations achieved tighter proximal contact than those restored with the high-viscosity glass ionomer cement. None of the matrix systems tested provided a convex seamless proximal morphology.

Evaluation of F, Ca, and P release and microhardness of eleven ion-leaching restorative materials and the recharge efficacy using a new Ca/P containing fluoride varnish

OBJECTIVES

The objectives of this study were to evaluate fluoride (F), calcium (Ca), and phosphate (P) release of ion-leaching restorative materials (ILMs), their recharge efficacy with a Ca/P-containing F varnish, and relative microhardness.

METHODS

Thirteen groups of materials were investigated. Cylindrical-shaped specimens were fabricated. Deionised water or lactic-acid solution were used as the storage media. Solutions were changed after 1d, 4d, 7d, and 14d of ion release and at the same periods after recharge with MI Varnish (7 -h storage). F, Ca, and P measurements were accomplished using a fluoride-ion selective electrode, atomic absorption spectrometry, and colourimetric method by spectrophotometer, respectively. Relative Vickers hardness was proceeded with similar specimens used in the F assay (4 periods). SEM/EDS was additionally performed. Statistical analyses were calculated in each parameter (p < 0.05).

RESULT

Hardness of several ILMs immediately increased after recharge. After 28d, Ketac Universal [a high-viscosity glass-ionomer cement (HVGIC)] showed the highest hardness similar to the resin composite control. Although 2 HVGICs (Zirconomer and Equia Forte Fil) ranked as first and second for F release/re-release, some HVGICs had inferior or comparable F capacity to RMGICs (Fuji VIII and Fuji II LC) and a resin-based (RB) ILM (Cention N). Cention N, Activa-Restorative (RB-ILM), and Zirconomer were the top-3 ranking for Ca release/re-release. Activa-Restorative showed the highest P release, whereas Cention N displayed the greatest recharge ability for P.

CONCLUSIONS

Zirconomer showed a versatile performance for ion-release/re-release, especially for F. Cention N had excellent capacity in relation to Ca release and recharge ability of Ca/P.

CLINICAL SIGNIFICANCE

With the F varnish recharge protocol, Zirconomer, Equia Forte, and Fuji VIII seems to have an ability to inhibit initial caries initiation. Cention N is a promising resin-based material that could be an alternative for high caries risk patients due to the high Ca release/recharge with acceptable F release.

Physical Properties of Glass Ionomer Cement Containing Pre-Reacted Spherical Glass Fillers

The aim of this study was to assess the effect of different commercial liquid phases (Ketac, Riva, and Fuji IX) and the use of spherical pre-reacted glass (SPG) fillers on cement maturation, fluoride release, compressive (CS) and biaxial flexural strength (BFS) of experimental glass ionomer cements (GICs). The experimental GICs (Ketac_M, Riva_M, FujiIX_M) were prepared by mixing SPG fillers with commercial liquid phases using the powder to liquid mass ratio of 2.5:1. FTIR-ATR was used to assess the maturation of GICs. Diffusion coefficient of fluoride (DF) and cumulative fluoride release (CF) in deionized water was determined using the fluoride ion specific electrode (n=3). CS and BFS at 24 h were also tested (n=6). Commercial GICs were used as comparisons. Riva and Riva_M exhibited rapid polyacrylate salt formation. The highest DF and CF were observed with Riva_M (1.65x10-9 cm2/s) and Riva (77 ppm) respectively. Using SPG fillers enhanced DF of GICs on average from ~2.5x10-9 cm2/s to ~3.0x10-9 cm2/s but reduced CF of the materials on average from ~51 ppm to ~42 ppm. The CS and BFS of Ketac_M (144 and 22 MPa) and Fuji IX_M (123 and 30 MPa) were comparable to commercial materials. Using SPG with Riva significantly reduced CS and BFS from 123 MPa to 55 MPa and 42 MPa to 28 MPa respectively. The use of SPG fillers enhanced DF but reduced CF of GICs. Using SPG with Ketac or Fuji IX liquids provided comparable strength to the commercial materials.

Effects of surface coating on the flexural strength of fluoridereleasing restorative materials after water aging for one year

Purpose:

To evaluate the effects of surface coating and one-year water storage on the flexural strength of fluoride-releasing restorative materials.

Materials and methods:

Forty specimens were prepared from each material; GCP Glass Fill (GCP), Amalgomer CR (AHL), Zirconomer (Shofu), Fuji IX GP Capsule (GC), Beautifil II (Shofu), Estelite Σ Quick (Tokuyama) and reliaFIL LC (AHL). The specimens were randomly divided into two groups; surface coated with G-Coat Plus (GC) and uncoated. Each group was subdivided into two groups stored in distilled water at 37◦C for 24 h and 1 year before testing (n=10). The flexural strength was evaluated using three-point bending test according to the ISO 4049:2009 standard using a universal testing machine. After flexural strength test, a cross-section of the coated specimens was evaluated with scanning electron microscopy (SEM).

Results:

A significant increase was observed on the flexural strength of Amalgomer CR, Zirconomer and Fuji IX GP after 24 h when G-Coat Plus was applied (p<0.05). This significant increase was observed on the flexural strength of only Amalgomer CR and Zirconomer after 1 year (p<0.05). The highest flexural strength was obtained with Beautifil II, Estelite Σ Quick and reliaFIL LC after 24 h and 1 year (p<0.05). After 1 year, there was decrease on the flexural strength of the other materials except Beautifil II, Estelite Σ Quick and reliaFIL LC.

Conclusion:

The resin coating improved the flexural strength of some glass ionomer-based materials but the water aging decreased the same physical properties.

In vitro compressive strength and edge stability testing of directly repaired glass-ionomer cements

Objective

To study the repair potential of seven commercial glass-ionomer cements (GICs) using an in vitro edge compression test model.

Materials and methods

A total of 448 normal and 192 repaired cylindrical specimens (6 × 4 mm) were produced from 6 GICs and one resin-modified GIC. Repaired samples consisted of a base aged for 1 month before repaired by an overlying layer. All samples were matured for 1 day, 1 week, 1 month or 3 months before compression, and edge tests were performed respectively on the whole surface (compressive strength, CS) or on the edge (edge stability, ES) using a universal testing machine.

Results

For normal specimens, Ketac Universal (KU) illustrated a significantly higher CS than other groups at all time points (p < 0.001). ES of KU was weaker than EQUIA Forte (EQF), FIX (Fuji IX) and RSC (Riva Self Cure) after 1 day, increasing after 1 week. Repaired specimens showed CS comparable to normal specimens (p > 0.05). Repaired KU significantly improved CS compared to repaired EQF and Fuji II (FII) after 1 day. No statistical difference was found in ES among these groups (p > 0.05).

Conclusions

KU provided the fastest maturation and greatest CS and ES in both normal and repair models after short-term ageing. Repair of GICs could potentially be achieved directly onto the fractured substrate and the subsequent improved mechanical performance could be maintained for at least 3 months.

Clinical relevance

This study provides a potential alternative in-vitro method to assess GIC restoration failure as well as provide insight into the mechanisms of GIC restoration repair.

Compressive Strength of New Glass Ionomer Cement Technology based Restorative Materials after Thermocycling and Cyclic Loading

OBJECTIVE

The objective of the study was to compare compressive strengths of two glass ionomer-based materials, with and without a light-cured, nano-filled coating, after cyclic loading and thermocycling.

MATERIALS AND METHODS

To determine compressive strength of new restorative materials over a longer period of time, materials were analysed under simulated conditions where cyclic loading replicated masticatory loading and thermocycling simulated thermal oscillations in the oral cavity. Four groups of samples (n=7)-(1) Equia Fil (GC, Tokyo, Japan) uncoated; (2) Equia Fil coated with Equia Coat (GC, Tokyo, Japan); (3) Equia Forte Fil (GC, Tokyo, Japan) uncoated; and (4) Equia Forte Fil coated with Equia Forte coat (GC, Tokyo, Japan)-were subjected to cyclic loading (240,000 cycles) using a chewing simulator (MOD, Esetron Smart Robotechnologies, Ankara, Turkey).

RESULTS

Compressive strength measurements were performed according to ISO 9917-1:2007, using the universal mechanical testing machine (Instron, Lloyd, UK). Scanning electron microscope (SEM) analysis was performed after thermocycling. There were no statistically significant differences between Equia Fil and Equia Forte Fil irrespective of the coating (p<0.05), but a trend of increasing compressive strength in the coated samples was observed.

CONCLUSIONS

Coating increases the compressive strength of Equia Fil and Equia Forte Fil, but not significantly.

A randomized controlled 10 years follow up of a glass ionomer restorative material in class I and class II cavities

OBJECTIVE

To evaluate the durability of a glass ionomer restorative material in Class I and Class II cavities during 10 years compared with a micro filled composite resin.

METHODS

Fifty-nine participants (mean age 24 years) received 140 (80 Class I and 60 Class II) glass ionomer (GI) or composite resin (CR) restorations. Evaluation was performed with slightly modified USPHS criteria at baseline, and yearly during the 10 years. Data were analyzed with Cohran's Q and McNemar's tests.

RESULTS

Fifty-one patients and 124 restorations (61 GI / 38 Class I - 23 Class II, 63 CR / 38 Class I, 25 Class II) were evaluated after 10 years. The recall rate was 86.4%. The overall clinical recall rate of restorations was 88.6%. The success rate of Class I and II restorations were calculated as 100% for both materials. The cumulative failure rate (CRF) of all Cl I and Cl II GI restorations was 3.17% in total, but CFR was 8 % for Cl II GI restorations. A significant difference was observed between the marginal discoloration scores of restorations at 10 years (p = 0.022). No significant difference was seen between two restorative materials in terms of marginal adaptation (p > 0.05). A significant change was seen in color match of GI restorations at 10 years (p < 0.05). No significant change was found for the anatomical form, secondary caries, postoperative sensitivity, surface texture, and retention for either restorative material (p > 0.05).

CONCLUSIONS

Both tested restorative materials showed an acceptable success rate in the restoration of Class I and Class II cavities during the 10-year follow up.