Effect of heat application on the mechanical behaviour of glass ionomer cements

Randomized Clinical Trial of Heated High Viscosity Glass Ionomer Class II Restorations in Deciduous Molars: 12 Months Follow Up

Objective: New generation High Viscosity Glass Ionomer Cements (HVGICs) have enhanced physical and mechanical properties. By effectively closing the restoration margin, it ensures that the restorations will last longer. The aim of this study was to investigate the clinical performances of heat-cured versus non heated HVGIC in class II restorations of deciduous molars. Methods: This randomized, split mouth, multicentre study was performed in four different centres. A total of 250 deciduous molars from 88 individuals were randomly allocated to one of the following groups: 1) non-heated (n = 125) 2) heated (n = 125) and restored with a HVGIC using LED light for heat application. Restorations were clinically evaluated according to the modified USPHS at the baseline, 6 months and 12 months. The survival analysis was performed by Kaplan Meier and Life Tables. This study was retrospectively registered to the ClinicalTrials.gov with the ID number of NCT04291872 at 2nd March 2020. Results: No statistically significant differences were found between the groups regarding to modified USPHS criteria (p>0.05). Success rate in retention criteria was 94.1% of the heat-cured and 92.6% of the non-heated restorations after 12 months. The mean survival time was 11.8 ±0.1 months in the heated group, while 11.9±0.1 months in the non-heated group. Conclusion: The heat treated HVGIC for Class II restorations did not show any significant differences in 12 months’ follow-up compared with the conventional technique.

In Vitro Evaluation of the Stabilization Time of Chemical Bonds During Setting Reaction and Microhardness of Preheated Glass-Ionomer Cements

OBJECTIVES

To evaluate the effect of preheating glass-ionomer cement (GIC) restorative materials on stabilization time (ST) of their metal carboxylate bonds and on microhardness.

METHODS AND MATERIALS

Two conventional highviscosity GICs, Ketac Universal (3M ESPE) and Equia Forte (GC), were evaluated. The thermographic camera was used to measure the temperature inside the glass-ionomer cement capsules before and after heating. The preheating of capsules was performed at 54°C for 30 seconds in a commercial device. Characterization of ST in the GICs was determined by Fourier Transform Infrared (FTIR) spectroscopy. For this, 10 samples of each material were prepared, five in the non-preheated group (control) and five with preheating. FTIR spectra were obtained 10 minutes after mixing (control group) or after heating and then every 10 minutes for 120 minutes. For the microhardness test, 20 cylindrical specimens (3 mm height × 6 mm diameter) were prepared for each material (10 preheated, 10 control). The microhardness was determined at three time intervals: 10 minutes after mixing, after the ST as detected through the FTIR part of the study, and after one week. Knoop microhardness was assessed using a diamond indenter with a 25 g load and 15 seconds dwell time.

RESULTS

Ketac Universal showed an increase in temperatures of 15.7°C for powder and 3.6°C for liquid, while Equia Forte showed 16.4°C for powder and 8.5°C for liquid. FTIR spectra indicated that preheating reduced the ST for Equia Forte but increased it for Ketac Universal. Preheating increased the initial microhardness (T1) of Equia Forte. With maturation over one week, it was observed that preheating significantly improved the microhardness of both materials compared with the control specimens.

CONCLUSION

Preheating influenced the ST and the microhardness of Ketac Universal and Equia Forte. The ST and microhardness of Ketac Universal increased after seven days, whereas Equia Forte showed a reduced ST and increased microhardness from the outset.

Tooth-coloured materials for class II restorations in primary molars: systematic review and meta-analysis

PURPOSE

The aim of this systematic review was to compare the success rate of five tooth-coloured materials, namely Glass Ionomer (GI), Resin-Modified Glass Ionomer (RMGI), Composite Resin (CR), Polyacid-Modified Composite Resin or Compomer (CO) and High-Viscosity Glass Ionomer (HVGI) in primary molar Class II restorations.

METHODS

Five databases were searched from inception to April 23, 2020 for randomized clinical trials comparing the failure rate of these materials. After duplicate study removal, data extraction and risk of bias assessment with the Cochrane tool, data synthesis was conducted, comparing all five tooth-coloured materials in pairs and computing the overall success rate for each one, respectively.

RESULTS

A total of 5615 articles were obtained by electronic and hand literature search. After the application of the eligibility criteria, ten RCTs were included in this systematic review and six RCTs for meta-analysis. Their risk of bias was assessed to be high to moderate. Due to the small number of RCTs comparing the five restorative materials in pairs investigated in the same study, only three MAs were available for heterogeneity assessment. These were: (1) between CO-RMGI (RR 1.04 [0.59, 1.84]; p = 0.88; I² = 1%), (2) CR-CO (RR 1.12 [0.41, 3.02]; p = 0.83; I² = 57%), and (3) between CR-RMGI (RR 1.10 [0.74, 1.63]; p = 0.65; I² = 0%). No statistically significant differences were found between the two materials in all three comparisons.

CONCLUSION

CR, RMGI and CO presented no statistical differences. In comparison to other tooth-coloured materials, studies on GI were too few to allow recommendations about its use. More studies on HGVI are needed for evidence-based recommendations to be made. The evidence extracted from this meta-analysis was not strong enough (moderate), due to the small number of RCTs and the risk of bias ranging from high to moderate. More, well-designed RCTs comparing tooth-coloured materials for primary molar Class II restorations are necessary.

Ion release of chitosan and nanodiamond modified glass ionomer restorative cements

Purpose

Ion release from glass ionomer restorative cements (GICs) plays an important role in GICs. The ion release from chitosan and nanodiamond-modified glass ionomers was assessed.

Materials and methods

Three GICs (Fuji IX, Ketac Universal and Riva Self Cure) were modified in the powder phase per weight by adding 5% or 10% of a commercially available chitosan powder (CH) or nanodiamond (ND) powder to the GICs. The specimens with dimensions 4 mm diameter and 6 mm height manufactured from the 15 GIC formulations were allowed to set for 1 hr and subsequently placed in neutral de-ionised water. The released ions were assessed using inductively coupled plasma-mass spectrometer (ICP-MS) to determine the elemental release. Additionally, three different disc-shaped specimens (3 mm in diameter and 1 mm thick) were constructed from each material for scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (SEM-EDS) microanalysis to establish an ion weight percentage.

Results

There were no significant differences in the ion release between the control materials for aluminium, silicon and strontium. The ion release from CH and most ND-modified GICs were significantly (p<0.00001) increased compared to the control materials. CH modifications significantly increased the ion release of aluminium, sodium, silicon and strontium for all three control materials (with the exception of the strontium release from Ketac Universal that was modified with 5% chitosan).

Conclusion

Ion release can be advantageous to tooth structure due to the interaction of chitosan with the GIC chemistry and moisture during maturation. Ion release up to five times greater than the control was noted for some ions.

Mechanical properties and water sorption of two experimental glass ionomer cements with hydroxyapatite or calcium fluorapatite formulation

In this study the mechanical behavior and water sorption (Ws) of experimental glass-ionomer-cements (GICs) with hydroxyapatite (HA) or calcium fluorapatite (CFA) prototype formulations were examined. Specimens from two experimental and one commercially available GIC were prepared in three protocols; (1) according to the manufacturer's instructions, (2) with coating and (3) with heat application. The specimens were stored in distilled water or artificial saliva at 37°C for 7- and 30-days. Flexural strength (FS), Vickers hardness (VHN) and Ws of GICs were evaluated. Experimental GICs showed higher FS values than commercial GIC (p<0.001). Higher FS and VHN values were observed when GICs were prepared according to manufacturer's recommendation. FS was affected only by GIC-type (η²=0.027), whereas VHN was affected by GIC-type (η²=0.331), treatment-protocols (η²=0.067), storage-medium (η²=0.100) and increased storage-duration (η²=0.317). The tested parameters did not significantly influence the Ws of all tested GICs (p>0.05). The GICs with HA or CFA formulations might represent a promising approach due to their FS, VHN and Ws characteristics.

Biological, thermal and mechanical characterization of modified glass ionomer cements: The role of nanohydroxyapatite, ciprofloxacin and zinc l-carnosine

The study evaluated the effects of 4 wt% nanohydroxyapatite (HA), 6 wt% zinc l-carnosine (MDA) and 1.5 wt% Ciprofloxacin (AB) on the mechanical, thermal and biological properties of glass ionomer cements (GIC). Filler and additive concentrations were selected after a previous study had tested single components and different percentages. Specimens included five silicon molds of each GIC cement for all tests. They were stored at room temperature for 24 h from specimen collection to analysis. Mechanical tests, calorimetric analysis, morphological investigation, antibacterial and cell viability assays were conducted. One-way analysis of variance (ANOVA) was used for data analysis with significance set at p < 0.05. Adding HA, MDA and AB to GICs modified their thermal, mechanical and microbiological properties. Polymerization increased. A slight decrease in the compressive strength of modified GICs was observed in dry condition (p < 0.05). Cement extracts affected cell viability in relation to extract dilution. Mechanical behavior improved in modified glass ionomer cements, especially with the powder formulated antibiotic. Overall cytotoxicity was reduced. Therefore adding nanohydroxyapatite, antibiotic and a mucosal defensive agent to conventional glass ionomer cement in special need patients could improve the clinical, preventive and therapeutic performance of the cements, without altering their mechanical properties.

Effect of a calcium chloride solution treatment on physical and mechanical properties of glass ionomer cements

This paper details a novel method to improve wear resistance of dental glass ionomer cement (GIC) restorations. The purpose of this in vitro study was to evaluate the effect of a calcium chloride (CaCl₂) solution treatment on surface hardness, surface roughness, compressive strength, water sorption and solubility of three conventional glass ionomer cements (GICs). Additionally, the changes of the Ca composition and morphology of the surface of the tested GICs were also investigated. The experimental groups of the study were: Group 1 (control) specimens after mixing were left in the mold to set without any treatment for 5 min; Group 2 specimens were left in the mold to set for 5 min and then each specimen was immersed in 10 ml of 42.7 wt% CaCl₂ solution for 60 s. Statistical analysis was performed using one-way ANOVA and Tukey post hoc tests (a = 0.05). Calcium chloride solution treatment increased surface hardness of the GICs compared to control groups (P < 0.05), while surface roughness and compressive strength did not change after the treatment (P > 0.05). Reduction in water sorption and solubility was detected but not in all CaCl₂ solution-treatment groups. No alterations were observed in surface morphology of the GICs, while surface calcium composition was increased after the treatment (P < 0.05). The use of a CaCl₂ solution immediately after initial setting of GICs may be advantageous for some properties of the materials and possibly leads to improved prognosis and wear resistance of their restorations.

Clinical Performance of Heat-Cured High-Viscosity Glass Ionomer Class II Restorations in Primary Molars: A Preliminary Study

OBJECTIVES

The present preliminary study evaluated the clinical and radiographic performances of heat-cured high viscosity glass ionomer (HCHVGI) in class II restorations of primary molars.

STUDY DESIGN

A retrospective study on a cohort of patients who had dental caries restored at a private practice was conducted. Restorations were evaluated radiographically and photographically by two separate examiners.

RESULTS

Ninety-three Class II restorations in 44 patients (average age: 108 months ± 25.3, 24 males, 20 females) were examined. Average recall time was 22.2 months ± 4.2. All but three restorations (96.8%) were present and intact, with no incidents of secondary caries. Three additional restorations had occlusal defects that required retreatment, resulting in an overall success rate of 93.5%. Ninety-seven percent of the restorations were rated optimal for marginal integrity with no staining of the restoration surfaces. No patients complained of post-operative sensitivity. The most common flaw found was a concavity on the proximal wall of the cavity box (27%, mean age 16 months ± 3.9).

CONCLUSION

The findings in this preliminary study suggest that heat cured high viscosity glass ionomer cement may be an effective restorative material for Class II restorations in primary molars that are a year or two from shedding.

Effect of radiant heat on conventional glass ionomer cements during setting by using a blue light diode laser system (445 nm)

The aim of this in vitro study was to evaluate the effect of radiant heat on surface hardness of three conventional glass ionomer cements (GICs) by using a blue diode laser system (445 nm) and a light-emitting diode (LED) unit. Additionally, the safety of the laser treatment was evaluated. Thirty disk-shaped specimens were prepared of each tested GIC (Equia Fil, Ketac Universal Aplicap and Riva Self Cure). The experimental groups (n = 10) of the study were as follows: group 1 was the control group of the study; in group 2, the specimens were irradiated for 60 s at the top surface using a LED light-curing unit; and in group 3, the specimens were irradiated for 60 s at the top surface using a blue light diode laser system (445 nm). Statistical analysis was performed using one-way ANOVA and Tukey post-hoc tests at a level of significance of a = 0.05. Radiant heat treatments, with both laser and LED devices, increased surface hardness (p < 0.05) but in different extent. Blue diode laser treatment was seemed to be more effective compared to LED treatment. There were no alterations in surface morphology or chemical composition after laser treatment. The tested radiant heat treatment with a blue diode laser may be advantageous for the longevity of GIC restorations. The safety of the use of blue diode laser for this application was confirmed.

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.

Effect of radiant heat and ultrasound on fluoride release and surface hardness of glass ionomer cements

PURPOSE

The purpose of this investigation was to evaluate the influence of radiant heat and ultrasound on fluoride release and surface hardness of 3 glass ionomer cements (GICs).

METHODS

There were 3 experimental groups for each GIC; in group 1, the specimens were left to set without any treatment; in group 2, the specimens were irradiated for 2 minutes using a LED unit; and in group 3, ultrasound was applied using a scaler for 55 seconds on the specimen surface. Fluoride release measurements were performed daily for 7 days and at days 14 and 28. Surface hardness of the tested GICs was determined using Vickers method. The measurements were performed 24 hours and 7 days after mixing. Statistical analysis of the data was made using 1-way ANOVA and Tukey's and Bonferroni post hoc tests (α = 0.05).

RESULTS

Radiant heat during setting reduced the fluoride release and increased the surface hardness of GICs (p&lt;0.05). Ultrasonic treatment also reduced the fluoride release and increased the surface hardness (p&lt;0.05) of GICs but in lower extent. Among the GICs there were differences in fluoride release and surface hardness properties depending on their composition (p&lt;0.05).

CONCLUSIONS

Radiant heat and ultrasonic treatments may be useful methods for GIC restorations in order to achieve faster adequate initial mechanical properties.

Análise da dureza de um novo material restaurador para ART: Glass Carbomer

Resumo Objetivo Este estudo avaliou a microdureza de dois materiais ionoméricos – Glass Carbomer (GC-GCP Dental) e Riva Light Cure (RL-SDI) ‒ em combinação com quatro unidades fotopolimerizadoras (Carbo LED lamp, GCP-Dental; Demi LED curing light, Kerr; Poli Wireless, Kavo; Radii Plus, SDI). Material e método Foram confeccionados 80 corpos de prova seguindo a orientação dos fabricantes, sendo 40 para cada material ionomérico e, para cada 10 corpos de prova, uma das unidades fotopolimerizadoras foi utilizada. Após sete dias de armazenamento em água destilada e temperatura ambiente, os 80 corpos de prova foram submetidos ao teste de microdureza Vickers (microdurômetro HMV 2T). Cinco indentações foram realizadas em cada corpo de prova (centro, extremidades direita e esquerda, e superior e inferior). O ensaio foi realizado sob uma carga de 100 gramas, com tempo de penetração de dez segundos. Resultado Independentemente da unidade fotopolimerizadora, o Riva Light Cure (RL-SDI) apresentou menor microdureza que o material Glass Carbomer (GC-GCP-Dental). A microdureza do Glass Carbomer (GC-GCP-Dental) foi influenciada pelo tipo de unidade fotopolimerizadora utilizada como fonte de calor. A análise de variância e o Teste de Tuckey (p<0,05) mostraram que a interação dos fatores ‘material’ vs. ‘unidade fotopolimerizadora’ (p<0,001) e os fatores principais ‘material’ (p<0,001) e ‘unidade fotopolimerizadora’ (p=0,002) foram estatisticamente significantes. Conclusão O material ionomérico Glass Cabomer (GCP- Dental) apresentou valor de microdureza significativamente superior quando comparado com o cimento de ionômero de vidro modificado por resina Riva Light Cure (SDI), independentemente da unidade fotopolimerizadora utilizada.