A Review of Glass-Ionomer Cements for Clinical Dentistry

Flexural Strength of Glass Carbomer Cement and Conventional Glass Ionomer Cement Stored in Different Storage Media over Time

OBJECTIVES

Glass ionomer cement (GIC) is routinely placed as a restorative material in dentistry. However, due to its poor physical properties, its use is limited to cases where the level of stress on restoration is minimal. Improved formulations of GIC have been developed to overcome these drawbacks. The purpose of this study was to evaluate flexural strength of a conventional GIC (Fuji IX) against a newly developed glass carbomer cement (GCP).

MATERIALS AND METHODS

For Fuji IX and GCP, a total of 80 blocks were prepared and divided into 16 groups (n = 5). These groups were further categorized according to the storage medium (artificial saliva and Vaseline) and time intervals (24 h and 1, 2, and 4 weeks). A 3-point bending test was carried out, and statistical analysis was done using ANOVA and Tukey post hoc tests.

RESULTS

Fuji IX showed a mean flexural strength of 25.14 ± 13.02 versus 24.27 ± 12.57 MPa for GCP. There was no significant statistical difference between both materials when compared under storage media. Both materials showed the highest value for flexural strength at 2 weeks of storage and lowest at 4 weeks.

CONCLUSION

The storage media do not affect the flexural strength of the specimens with reference to time. Time is the unique factor with relative influence on mean resistance to fracture. Further testing is required to evaluate the true potential of the newly developed GCP.

Evaluation of retentive strength of four luting cements with stainless steel crowns in primary molars: An in vitro study

BACKGROUND

Stainless steel crown (SSC) is the most reliable restoration for primary teeth with extensive caries. Retention is of great importance for a successful restoration and is provided by various factors such as luting cements. The aim of this study was to evaluate the retentive strength of SSC cemented with four different luting cements.

MATERIALS AND METHODS

In this in vitro study, A total of 55 extracted primary first molars were selected. Following crown selection and cementation (one with no cement and four groups cemented with resin, glass ionomer, zinc phosphate, and polycarboxylate), all the specimens were incubated and thermocycled in 5°C-55°C. Retentive properties of SSCs were tested with a mechanical test machine. First dislodgement of each specimen and full crown removal were recorded. One-way ANOVA test followed by least significant difference test and Kruskal-Wallis test was used for retentive strength comparison at the level of significance of P < 0.05.

RESULTS

The results of the study showed that the specimens cemented with zinc phosphate exhibited higher retentive strength as compared to glass ionomer and polycarboxylate (P < 0.001 and P = 0.023, respectively).

CONCLUSION

Zinc phosphate cement showed the most promising results; thus, it can be preferably used for cementation of the teeth with no grossly broken down crowns.

Antibacterial properties and compressive strength of new one-step preparation silver nanoparticles in glass ionomer cements (NanoAg-GIC)

OBJECTIVES

This work aimed (1) to develop polyacid formulations by the one-step photoreduction of silver nanoparticles (AgNP) in a polyacrylate solution of conventional glass ionomer cement (GIC), imparting antibacterial activity; and (2) to evaluate handling and mechanical properties of experimental ionomers in comparison to a commercially available conventional GIC.

METHODS

Formulations with increasing sub-stoichiometric amounts of AgNO₃ were monitored during continuous UV light exposure by UV-vis spectroscopy and analyzed by transmission electron microscopy. The resulted synthesis of formulations containing small and disperse spherical nanoparticles (∼6 nm) were used to design the experimental nano-silver glass ionomer cements (NanoAg-GIC). The cements were characterized as to net setting time and compressive strength according to ISO 9917-1:2007 specifications. The antibacterial activity of these cements was assessed by Ag⁺ diffusion tests on nutritive agar plates (E. coli) and by MTT assay (S. mutans).

RESULTS

The higher concentration of silver (0.50% by mass) in the matrix of NanoAg-GIC allowed viable net setting time and increased in 32% compressive strength of the experimental cement. All groups containing AgNP induced statistically significant E. coli growth inhibition zones (p-value <.05), indicating diffusion of Ag⁺ ions on the material surroundings. Metabolic activity of S. mutans grown on NanoAg-GIG with higher concentration of silver was significantly affected compared to control (p-value <.01).

CONCLUSIONS

Silver nanoparticles one-step preparation in polyacrylate solution allowed the production of highly bioactive water-based cements within suitable parameters for clinical use and with large potential of dental and biomedical application.

The Use of Pit and Fissure Sealants-A Literature Review

This paper reviews the literature and discusses the latest updates on the use of pit and fissure sealants. It demonstrates the effectiveness of pit and fissure sealants in preventing caries and the management of early carious lesions. It compares the use of different sealant materials and their indications. It describes the application technique for sealants. It also reviews the cost-effectiveness of sealants as a preventive strategy. From this review and after the discussion of recently published studies on pit and fissure sealants, it is evident that sealants are effective in caries prevention and in preventing the progression of incipient lesions. It is therefore recommended that pit and fissure sealant be applied to high-caries-risk children for optimum cost-effectiveness. It is a highly sensitive technique that needs optimum isolation, cleaning of the tooth surface, etching, and the application of a thin bonding layer for maximum benefit. Recall and repair, when needed, are important to maximize the effectiveness of such sealant use.

Nanoclay-Reinforced Glass-Ionomer Cements: In Vitro Wear Evaluation and Comparison by Two Wear-Test Methods

Glass ionomer cement (GIC) represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task. The aim of this paper was to evaluate the wear resistance of novel glass ionomer cement by two wear-test methods and to compare the two wear methods.The wear resistance of a conventional glass ionomer cement (HiFi Advanced Health Care Kent, UK) and cements modified by including various percentages of nanoclays (1, 2 and 4 wt %) was measured by a reciprocating wear test (ball-on-flat) and Oregon Health and Sciences University's (OHSU) wear simulator. The OHSU wear simulation subjected the cement specimens to three wear mechanisms, namely abrasion, three-body abrasion and attrition using a steatite antagonist. The abrasion wear resulted in material loss from GIC specimen as the steatite antagonist forced through the exposed glass particles when it travelled along the sliding path.The hardness of specimens was measured by the Vickers hardness test. The results of reciprocation wear test showed that HiFi-1 resulted in the lowest wear volume 4.90 (0.60) mm³ (p < 0.05), but there was no significant difference (p > 0.05) in the wear volume in comparison to HiFi, HiFi-2 and HiFi-4. Similarly, the results of OHSU wear simulator showed that the total wear volume of HiFi-4 1.49 (0.24) was higher than HiFi-1 and HiFi-2. However, no significant difference (p > 0.05) was found in the OHSU total wear volume in GICs after nanoclay incorporation. The Vickers hardness (HV) of the nanoclay-reinforced cements was measured between 62 and 89 HV. Nanoclay addition at a higher concentration (4%) resulted in higher wear volume and wear depth. The total wear volumes were less dependent upon abrasion volume and attrition volume. The total wear depths were strongly influenced by attrition depth and to some extent by abrasion depth. The addition of nanoclay in higher wt % to HiFi did not result in significant improvement in wear resistance and hardness. Nonetheless, wear is a very complex phenomenon because it is sensitive to a wide number of factors that do not necessarily act in the same way when compared using different parameters.

Evaluation of alternative monomers to HEMA for dental applications

OBJECTIVE

The objective of this work is to find potential alternative monomers to 2-hydroxyethyl methacrylate (HEMA) for dental materials (self-etch adhesives and luting composites).

METHODS

Monomers 1-9 were tested as potential HEMA substitutes. Methacrylates 4, 5 and 6 and (N-methyl)acrylamides 7-9 were synthesized and characterized by ¹H NMR spectroscopy. The reactivity of each monomer was studied using photo-DSC. Mixtures of monomers 1-9 with the urethane dimethacrylate UDMA (1/1: wt/wt) were formulated and cured. The water sorption and solubility of these materials were determined according to ISO 4049. Luting composites based on monomers 1-9 or on HEMA were formulated. The flexural strength and modulus of elasticity were measured using a three-point bending setup, according to ISO 4049. Self-etch adhesives containing monomers 1-9 or HEMA were prepared and used to mediate a bond between the dental composite Tetric EvoCeram^® and both dentin and enamel. The shear bond strength (SBS) was measured using a Zwick universal testing machine.

RESULTS

Polymerizable diols 3 and 4 as well as (N-methyl)acrylamides 7-9 were found to be significantly more reactive than HEMA. Resins based on the hydrophilic monomers 3, 7 and 8 exhibited a significantly higher water sorption than the corresponding HEMA-containing material. Luting composites containing monomers 2, 3, 6 and 7 showed similar or even improved mechanical properties compared to the reference material containing HEMA. Self-etch adhesives containing monomers 4 and 9 provided significantly higher dentin SBS than the reference material.

SIGNIFICANCE

Some of the evaluated monomers are promising candidates for the development of HEMA-free dental materials.

The influence of the lining material on the repair of the infected dentin in young permanent molars after restoration: A randomized clinical trial

Aim:

This study evaluated the impact of liner material on the fluorescence, morphological and mineral characteristics of permanent carious dentin after cavity sealing.

Methods:

Thirty children (11.0 ± 2.7 years old) presenting at least one active deep carious lesion in permanent molars were selected. Fragments of carious dentin were removed from teeth before lining the cavity (baseline samples) with high-viscosity glass ionomer cement (G1) or an inert material (wax - G2). Cavities were restored with composite resin and reopened 60 days later, and other fragments were removed (60-day sample). The laser fluorescence (LF) readings and morphological and mineral changes of both groups were compared.

Results:

After 60 days, forty teeth were available for evaluation. Lower LF means were obtained (Wilcoxon signed-rank test; P < 0.05), and enhanced calcium and phosphorus levels were detected for both groups (t-test, P < 0.05). An uptake of fluorine was observed only in G1 (t-test; P < 0.05). Regardless of the group, baseline samples exhibited clear signs of bacterial invasion, and the collagen fibers were exposed; the 60-day samples showed a better-organized tissue with a more compact intertubular dentin.

Conclusion:

Caries arrestment with dentin reorganization occurs regardless of the lining material placed in contact with the infected dentin.