Physical-mechanical properties of glass ionomer cements indicated for atraumatic restorative treatment

Coating glass-ionomer cements with a nanofilled resin

OBJECTIVES

The objective of this study was to investigate the effect of a nanofilled resin coat on the flexural strength (FS) and the early wear (after 50,000 and 200,000 cycles) of the glass-ionomer cements Fuji IX GP Extra (FIXE) and Ketac Molar Aplicap (KM).

MATERIALS AND METHODS

Specimens were prepared and half of them were coated with G-Coat plus. The uncoated specimens were used as controls. Flexural strength (n = 10) was evaluated after 24 h using a 3-point bending test on a universal testing machine (ISO 9917-2). Wear (n = 20) was evaluated after 50,000 and 200,000 cycles using the ACTA wear machine. One-way, two-way ANOVA and Tukey post-hoc tests were used to analyze differences in FS and wear.

RESULTS

For FIXE the coat significantly increased the FS and the wear along the two time spans. KM did not show a significant difference in FS with the coat. Improvements in wear were observed only after 50,000 cycles.

CONCLUSION

Based on these laboratory results, it is concluded that G-coat Plus is indicated in association with GP IX Extra with the aim to improve the mechanical properties of the former. However, this study is limited to a short-term observation.

Restoration of endodontically treated teeth with major hard tissue loss--bond strength of conventionally and adhesively luted fiber-reinforced composite posts

AIM

To evaluate the influence of the luting system on the pull-out bond strength of conventionally and adhesively luted fiber-reinforced composite posts (FRCPs).

MATERIAL AND METHODS

One hundred extracted bovine teeth (Di 3) were endodontically treated and randomly assigned to nine test groups and one control group (n = 10) according to luting system. After preparing the post cavities (8 mm), the custom-made FRCPs were inserted using conventional glass-ionomer cement (Ketac Cem), resin-reinforced glass-ionomer cement (Meron Plus and Fuji Plus), self-adhesive resin cement (RelyX Unicem and BisCem), self-conditioning adhesive and resin cement [Multilink Primer + Multilink and AdheSE + DC Activator + MultiCore Flow, or etch-and-rinse adhesive and resin cement (SealBond Ultima + CoreCem, and LuxaBond + LuxaCore Z). As a control, custom-made titanium posts were inserted with Ketac Cem. After water storage (37°C, 24 h, dark), the pull-out test was performed, followed by failure mode evaluation. The data were statistically analyzed (α = 0.05) using analysis of variance and the Dunnett T3 post hoc test.

RESULTS

Luting system type and identity significantly influenced bond strength (P < 0.001); the bond strengths of all luting systems except Ketac Cem, MeronPlus, and BisCem were significantly higher than the control (4.4 ± 1.1 MPa). RelyX Unicem (12.0 ± 3.0 MPa) and LB + LCZ (14.8 ± 2.3 MPa) generated the highest bond strengths. The clinical application was demonstrated by restoring a traumatized tooth with extensive coronal destruction and thin root canal walls, using a FRCP combined with direct composite build-up.

CONCLUSION

Luting system selection significantly influenced the bond strength of conventionally and adhesively luted FRCPs to bovine root canal dentin.

Survival rate of approximal-ART restorations using a two-layer technique for glass ionomer insertion

OBJECTIVE

Good survival rates (SR) have been reported for occlusal-atraumatic restorative treatment (ART) restorations but not for approximal-ART restorations. The high-viscosity consistency of the glass ionomer cement (GIC) may lead to its incorrect adaptation into the cavity and thus to failure of the restoration. Because the use of a flowable GIC layer seemed to improve its adaptation in approximal restorations in vitro, we evaluated whether the use of an intermediate flowable GIC layer would improve the SR of approximal-ART restorations.

METHODS

A total of 208 children (6-7 years old) with at least one occluso-proximal carious lesion in a primary molar were selected and randomly allocated to two groups: G1, conventional technique, one-layer GIC (powder/liquid ratio 1:1); and G2, two-layer technique, consisting of a first layer of GIC with a flowable consistency (powder/liquid ratio 1:2) and a second layer of a regular consistency. Restorations were made by final-year students and evaluated after 1, 6, 12 and 18 months. Restoration survival was evaluated using Kaplan-Meier survival and logrank test. Poisson regression analyses (α = 5) were used to verify the influence of factors such as insertion technique, restoration surface and operators.

RESULTS

The overall SR of the restorations after 18 months was 68 %. There was no difference in SR between the techniques, neither did the other factors influence the SR.

CONCLUSIONS

Over 18 months, the use of an intermediate flowable GIC layer in approximal-ART restorations does not improve the restoration survival.

CLINICAL RELEVANCE

This study suggests that the two-layer technique is not the answer for increasing approximal-ART restoration longevity.

Twenty-five-year atraumatic restorative treatment (ART) approach: a comprehensive overview

Background

The atraumatic restorative treatment (ART) approach was born 25 years ago in Tanzania. It has evolved into an essential caries management concept for improving quality and access to oral care globally.

Results

Meta-analyses and systematic reviews have indicated that the high effectiveness of ART sealants using high-viscosity glass ionomers in carious lesion development prevention is not different from that of resin fissure sealants. ART using high-viscosity glass ionomer can safely be used to restore single-surface cavities both in primary and in permanent posterior teeth, but its quality in restoring multiple surfaces in primary posterior teeth cavities needs to be improved. Insufficient information is available regarding the quality of ART restorations in multiple surfaces in permanent anterior and posterior teeth. There appears to be no difference in the survival of single-surface high-viscosity glass-ionomer ART restorations and amalgam restorations.

Discussion

The use of ART results in smaller cavities and in high acceptance of preventive and restorative care by children. Because local anaesthesia is seldom needed and only hand instruments are used, ART is considered to be a promising approach for treating children suffering from early childhood caries. ART has been implemented in the public oral health services of a number of countries, and clearly, proper implementation requires the availability of sufficient stocks of good high-viscosity glass ionomers and sets of ART instruments right from the start. Textbooks including chapters on ART are available, and the concept is being included in graduate courses at dental schools in a number of countries. Recent development and testing of e-learning modules for distance learning has increasingly facilitated the distribution of ART information amongst professionals, thus enabling more people to benefit from ART. However, this development and further research require adequate funding, which is not always easily obtainable. The next major challenge is the continuation of care to the frail elderly, in which ART may play a part.

Conclusion

ART, as part of the Basic Package of Oral Care, is an important cornerstone for the development of global oral health and alleviating inequality in oral care.

Influence of ultrasound or halogen light on microleakage and hardness of enamel adjacent to glass ionomer cement

BACKGROUND

The use of external sources of energy may accelerate the setting rate of glass ionomer cements (GICs) allowing better initial mechanical properties.

AIM

To investigate the influence of ultrasound and halogen light on the microleakage and hardness of enamel adjacent to GIC restorations, after artificial caries challenge.

DESIGN

Cavities were prepared in 60 primary canines, restored with GIC, and randomly distributed into three groups: control group (CG), light group (LG) - irradiation with a halogen light-curing unit for 60s, and ultrasonic group (UG) - application of ultrasonic scaler device for 15s. All specimens were then submitted to a cariogenic challenge in a pH cycling model. Half of sample in each group were immersed in methylene blue for 4h and sectioned for dye penetration analysis. The remaining specimens were submitted to Knoop cross-sectional microhardness assessments, and mineral changes were calculated for adjacent enamel.

RESULTS

Data were compared using Kruskal-Wallis test and two-way ANOVA with 5% significance. Higher dye penetration was observed for the UG (P<0.01). No significant mineral changes were observed between groups (P=0.844).

CONCLUSION

The use of halogen light-curing unit does not seem to interfere with the properties of GICs, whereas the use of ultrasound can affect its marginal sealing.

Microhardness and chemical analysis of high-viscous glass-ionomer cement after 10 years of clinical service as ART restorations

OBJECTIVES

The aim of this study was to evaluate the Knoop microhardness (KHN) and chemical composition of high-viscous glass-ionomer cement (HVGIC) after 10 years of clinical service.

METHODS

Six HVGIC samples were cut from 10-year ART restorations. The sections were embedded in acrylic moulds with their longitudinal profile exposed. KHN was determined by performing three sequences of five indentations at 10, 30, 50, 70 and 90 μm of HVGIC outer surface. For the control group (n=6), HVGIC specimens were stored in distilled water for 24 months. Hardness measurements were taken at days 7, 30, 60, 120, 180, 360, and 720. For chemical analysis using SEM-EDX, 10-year and control specimens were dehydrated and coated with carbon. Data were analysed using T-test and ANOVA/Tukey's test (p<0.05).

RESULTS

A significant KHN increase was observed in the control group up to the 180-day period. From this point the values stabilized and no more significant differences were found between the 10-year and the control KHN values. No statistical differences were observed amongst the KHN from inner distances compared to the outer surface of the 10-year HVGIC specimens. In one 10-year specimen, SEM-images identified the transformation of HVGIC in an altered layer with no glass filler particles detectable, and raised Ca, K and P contents.

CONCLUSIONS

KHN values of ten-year HVGIC specimens were similar to the control group values at 180-day storage period. Except for one 10-year specimen in that an altered layer could be seen, chemical composition was similar amongst the depths evaluated.

Efficiency of different polyacrylic acid concentrations on the smear layer, after ART technique, by Scanning Electron Microscopy (SEM)

AIM

To assess the efficiency of different polyacrylic acid concentrations on the removal of the smear layer after caries removal with hand and rotary instruments in affected dentine of primary teeth.

STUDY DESIGN

In vitro study.

METHODS

Six exfoliated primary molars with carious lesions were divided into two groups for caries removal: (1) hand instrument or (2) low speed bur. Each tooth was cut into four pieces. One piece assigned as control surface and the other three surfaces were actively treated with either 40% Fuji IXGP Liquid (GC America), or 40% Fuji IXGP Liquid diluted with water, and 25% Ketac Molar(TM) Conditioner (3M-ESPE). Surfaces were prepared for scanning electron microscopy (SEM). All images were submitted to an analysis by an experienced SEM professional, regarding presence or absence of smear layer and dentinal demineralization pattern. Chi-squared test was carried out (5% significance).

RESULTS

There was no difference concerning the presence of a smear layer in relation to the method of caries removal, and 40% Fuji IXGP diluted with water causes a higher demineralization when compared with the control group of teeth (p=0.01).

CONCLUSION

Treatments with polyacrylic acid are indicated prior to glass ionomer cement application in primary teeth.

Effect of insertion method on knoop hardness of high viscous glass ionomer cements

The aim of this study was to assess the Knoop hardness of three high viscous glass ionomer cements: G1 - Ketac Molar; G2 - Ketac Molar Easymix (3M ESPE) and G3 - Magic Glass ART (Vigodent). As a parallel goal, three different methods for insertion of Ketac Molar Easymix were tested: G4 - conventional spatula; G5 - commercial syringe (Centrix) and G6 - low-cost syringe. Ten specimens of each group were prepared and the Knoop hardness was determined 5 times on each specimen with a HM-124 hardness machine (25 g/30 s dwell time) after 24 h, 1 and 2 weeks. During the entire test period, the specimens were stored in liquid paraffin at 37ºC. Significant differences were found between G3 and G1/G2 (two-way ANOVA and Tukey's post hoc test; p<0.01). There was no significant difference in the results among the multiple ways of insertion. The glass ionomer cement Magic Glass ART showed the lowest hardness, while the insertion technique had no significant influence on hardness.

The ART approach: clinical aspects reviewed

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