In vitro biocompatibility of hydroxyapatite-added GIC: An SEM study using human periodontal ligament fibroblasts

Incorporation of Nanomaterials in Glass Ionomer Cements-Recent Developments and Future Perspectives: A Narrative Review

Glass ionomer cements (GICs), restorative materials with commercial availability spanning over five decades, are widely applied due to their advantages (including bio-compatibility, fluoride release, or excellent bonding properties). However, GICs have shortcomings. Among the disadvantages limiting the application of GICs, the poor mechanical properties are the most significant. In order to enhance the mechanical or antimicrobial properties of these materials, the addition of nanomaterials represents a viable approach. The present paper aims to review the literature on the application of different types of nanomaterials for the enhancement of GICs' mechanical and antimicrobial properties, which could lead to several clinical benefits, including better physical properties and the prevention of tooth decay. After applying the described methodology, representative articles published in the time period 2011-present were selected and included in the final review, covering the modification of GICs with metallic nanoparticles (Cu, Ag), metallic and metalloid oxide nanoparticles (TiO₂, ZnO, MgO, Al₂O₃, ZrO₂, SiO₂), apatitic nanomaterials, and other nanomaterials or multi-component nanocomposites.

A Novel Self-Mineralizing Antibacterial Tissue Repair Varnish to Condition Root-end Dentin in Endodontic Microsurgery

INTRODUCTION

A novel 2-part varnish system containing chitosan nanoparticles (part 1) and chitosan-grafted hydroxyapatite precursor nanocomplex (part 2) was developed to condition the root-end dentin using the principle of biomineralization while rendering both antimicrobial efficacy and bioactivity. This in vitro study aimed to characterize and assess the effectiveness of the chitosan nanoparticles and chitosan-grafted hydroxyapatite precursor nanocomplex containing self-mineralizing antibacterial tissue repair varnish to condition as well as seal root-end dentin during endodontic microsurgery.

METHODS

In phase 1, the antibacterial properties and cellular response of the varnish were characterized. The antibacterial activity and cellular responses were evaluated using Enterococcus faecalis and periodontal ligament (PDL) fibroblasts, respectively. In phase 2, a resected root-end model was used to apply the 2-part varnish and examine the dentin-varnish interface using transmission electron microscopy. The percentage of root end sealed with time was determined using scanning electron microscopy (n = 6/time point). Statistical analysis was performed using 1-way analysis of variance where applicable.

RESULTS

The part 1 and 2 of the varnish displayed significant antibacterial activity and reduced bacterial adherence/survival (P < .01). The attachment and spreading of PDL fibroblasts on the varnish-conditioned dentin was enhanced compared with unconditioned dentin (P < .01). In the resected root-end model, the 2-part varnish displayed a biomineralized varnish layer with close interaction with the subsurface dentin. Root-end coverage with the biomineralized layer increased with incubation time (P < .01), reaching approximately 95% coverage after 24 hours.

CONCLUSIONS

The 2-part varnish system effectively conditioned/sealed the root end with a biomineralized layer while reducing bacterial load and promoting PDL fibroblast attachment. This therapeutic modification of root-end dentin could provide optimal conditions to enhance healing and improve prognosis in teeth with root-end cracks after endodontic microsurgery.

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.

Tissue Response after Subcutaneous Implantation of Different Glass Ionomer-Based Cements

The aim of this study was to evaluate the subcutaneous connective tissue response of isogenic mice after implantation of different glass ionomer-based cements (EQUIA® Forte Fil, EQUIA® Fil and Ketac™ Universal Aplicap™). Eighty-seven isogenic BALB/c mice were allocated in 12 groups, 9 were considered as experimental groups (Ketac, E. Fil and E. Forte at 7, 21 and 63 days) and 3 controls (empty polyethylene tubes at 7, 21 and 63 days). After the experimental periods, the subcutaneous connective tissue surrounding the implanted material was removed and subjected to histotechnical processing and staining with hematoxylin and eosin. A histopathological description of the tissue reaction surrounding each material and a semi-quantitative analysis of collagen fiber formation and inflammatory infiltrate were performed. Additionally, the thickness of the granulomatous tissue in contact with each material was measured. Data were analyzed statistically (α=0.05) by the Kruskal-Wallis test, followed by Dunn post-test. Initially, the collagen fiber formation was not different among all the tested materials (p>0.05) but was different at 21 days with the control group presenting the most advanced stage of collagen fiber formation. At 63 days, EQUIA® Forte Fil group showed the most advanced stage of collagen fiber formation, compared to EQUIA® Fil group (p<0.05). The inflammatory infiltrate was not different among the tested materials in any experimental period (p>0.05). The thickness of the granulomatous tissue was greater in the E. Forte group, compared to control in all periods. All glass ionomer-based cements showed tissue compatibility, according to the evaluated parameters.