Inhibitory effect of zinc-containing desensitizer on bacterial biofilm formation and root dentin demineralization

MMP inhibition, marginal integrity and cytotoxicity of zinc-releasing GIC

OBJECTIVES

The degradation of the restorative-dentin interface due to endogenous dentin enzymes, such as matrix metalloproteinases (MMPs), is a significant issue that accelerates the deterioration of the dentin matrix and leads to the failure of restorative treatments. Caredyne Restore (CR), a novel glass ionomer cement (GIC) with zinc ions in its formulation, represents the latest effort to mitigate this issue. This investigation aimed to evaluate the MMPs inhibitory effect, marginal integrity, and cytotoxicity of CR compared to a conventional GIC, Fuji IX (FIX).

METHODS

The inhibitory effect of CR on MMPs activity was evaluated using in-situ zymography to visualize the endogenous gelatinolytic activity in the GIC-dentin interface. Additionally, CR's sealing properties were investigated using dye-assisted confocal laser microscopy (CLSM) to assess marginal leakage across the GIC-dentin interface. Both in-situ zymography and CLSM observations were conducted 1 day and seven days after pH cycling. Finally, the cytotoxicity of the GIC eluates was examined on rat dental pulp cells (RPCC2A). Assay measurements were performed after 24 and 48 h of incubation with test solutions prepared using various GIC eluate concentrations.

RESULTS

The MMPs activity of the CR specimens was significantly lower than that of FIX specimens after seven days of pH cycling. Signs of marginal leakage were also lower in the CR specimens. Comparison of CR and FIX eluates at the same concentration showed no significant difference in terms of biocompatibility.

CONCLUSIONS

Caredyne restore is capable of inhibiting endogenous enzyme activity and improving sealing properties, while maintaining sufficient biocompatibility.

CLINICAL SIGNIFICANCE

Zinc ions released from Caredyne Restore offer a safe way to improve the quality of dental restorations and promote minimally invasive treatment, especially in lesions where the dentin matrix is susceptible to enzymatic degradation and recurrent caries.

Changes in enamel hardness, wear resistance, surface texture, and surface crystal structure with glass ionomer cement containing BioUnion fillers

This study investigated the potential of BioUnion filler containing glass ionomer cement (GIC) to enhance the properties of enamel surrounding restorations, with a specific focus on the effect on hardness. The hardness of the bovine enamel immersed in the cement was measured using Vickers hardness numbers. Following sliding and impact wear simulations, the enamel facets were examined using confocal-laser-scanning microscopy and scanning-electron microscopy. Surface properties were further analyzed using energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). A significant increase in Vickers hardness numbers was observed in the BioUnion filler GIC after 2 days. Furthermore, the mean depth of enamel facets treated with BioUnion filler GIC was significantly less than that of untreated facets. Characteristic XRD peaks indicating the presence of hydroxyapatite were also observed. Our findings imply that GIC with BioUnion fillers enhances the mechanical properties of the tooth surface adjacent to the cement.

Systematic Review of Zinc's Benefits and Biological Effects on Oral Health

BACKGROUND

This review was based on the following question: "What is the state-of-the-art regarding the effect of zinc exposure in the oral cavity on a population of adults and children, compared to dental products containing materials other than zinc, considering in vivo (clinical trials and observational studies) and in vitro studies?" according to a PICOS strategy format. This study aims to analyze zinc application in dental materials, with different compositions and chemical formulations, considering how mechanical and biological properties may influence its clinical applicability.

METHODS

In vivo (clinical trials: controlled clinical trials (CCTs) and randomized controlled trials (RCTs); and observational studies: case control and cohort studies) trials or in vitro studies published in English or Italian during the last 10 years on children and adult patients with zinc exposure were included by three different reviewers using the MEDLINE (via PubMed), Scopus, and Web of Science electronic databases.

RESULTS

Titles and abstracts were evaluated following the eligibility criteria. The full texts of eligible studies were then reviewed against the inclusion/exclusion criteria. Scientific and technical information of the 33 included studies were collected into evidence tables, reporting data on in vivo and in vitro studies. A narrative approach was adopted.

CONCLUSIONS

Antibacterial activity was found to be the most studied property of zinc, but further investigations are needed to establish adjuvant zinc therapies in patients with oral disease.

Clinical Investigation of the Inhibitory Effects of Tooth-Coating Materials on Initial Active Root Caries: A Pilot Randomized Controlled Trial

Background and Objectives: Caredyne ZIF-C is a novel, capsule-mixed zinc-containing prototype glass ionomer cement (GIC). Zinc ions are reported to inhibit root dentin demineralization, dentin collagen degradation, bacterial growth, acid production, and in vitro bacterial biofilm formation. However, the effectiveness of GICs against initial root caries lesions is unclear. Therefore, this study aimed to evaluate the efficacy of GICs, especially the new zinc-containing Caredyne ZIF-C GIC, as tooth-coating materials in patients with initial active root caries. Materials and Methods: A total of 58 lesions in 47 older adults (age > 65 years) were randomly allocated to one of the following three groups: Caredyne ZIF-C, Fuji VII (a conventional GIC), and sodium fluoride (NaF). All the lesions were treated with the assigned materials without removing the infected dentin, and the rates of dental plaque attachment and coating material fall-out were evaluated after 3, 6, and 12 months. The failure rate was defined as the number of teeth that needed restoration due to caries progression. Results: The plaque attachment rates tended to be lower in the material-coated root surfaces than in the healthy exposed root surfaces after 3, 6, and 12 months, although the differences among the three groups were not significant. Moreover, the coating material fall-out rate tended to be lower in the Caredyne ZIF-C group than in the Fuji VII group. There was no significant difference in the failure rate among the three groups at the 12 months mark. Conclusions: Though this pilot study offers a new direction for suppressing the progression of initial active root caries by controlling plaque attachment using GICs including Caredyne ZIF-C, clinical studies with a larger sample size are needed.

Quantitative analysis of the degree of demineralization for bleached enamel by optical coherence tomography

BACKGROUND

Tooth bleaching imparts whitening effects along with adverse effects such as increased tooth sensitivity and enamel surface changes. Herein, we employed optical coherence tomography (OCT), a nondestructive optical detection technique, for evaluation of tooth enamel after treatment with peroxide-based bleaching agents.

METHODS

Fifteen enamel samples were bleached using 38% acidic hydrogen peroxide-based bleach, subjected to OCT scanning, and then cross-sectioned and imaged under polarized light microscopy (PLM) and transverse microradiography (TMR). OCT cross-sectional images were compared with PLM and TMR. The depth and severity of demineralization produced in the bleached enamel were measured by OCT, PLM, and TMR. Comparison between the three techniques was performed using Kruskal-Wallis H non-parametric test and Pearson correlation.

RESULTS

In comparison with PLM and TMR, OCT clearly detected the changes in the enamel surface after hydrogen peroxide bleaching. Significant correlations (p<0.05) were observed in lesion depth between OCT and PLM (r=0.820), OCT and TMR (r=0.822), and TMR and PLM (r=0.861). There was no statistically significant difference in demineralization depth values measured by OCT, PLM, and TMR (p>0.05).

CONCLUSION

OCT can allow real-time, non-invasive imaging of artificially bleached tooth models and automatically measure the early changes in the enamel lesion structure upon exposure to hydrogen peroxide-based bleaching agents.

Biological considerations of dental materials as orifice barriers for restoring root-filled teeth

There is ample published literature regarding the technical aspects of restoring root-filled teeth, but little concerning the biological impacts, consequences, and criteria for the selection of direct restorative materials following endodontic treatment. The provision of an effective coronal seal in addition to a sound root filling is known to be important in the prevention of root canal infection. This review seeks to explore the evidence concerning the selection of dental materials in the restoration of root-filled teeth, specifically with a close examination of the properties of commonly used materials as orifice barriers. © 2023 Australian Dental Association.

Bacterial adhesion and antibacterial property of coating materials containing theobromine and S-PRG filler

Theobromine (TB) has been reported to promote tooth remineralization, strengthen tooth substance, and relieve dentin hypersensitivity. This study aimed to evaluate experimental tooth coating materials containing TB and surface pre-reacted glass-ionomer (S-PRG) fillers by examining the effects on bacterial adhesion and antibacterial properties. In addition, the amount of TB eluted from the coating material was measured. There was no significant difference in bacterial adhesion depending on the presence or absence of TB in the coating material, however, a significant decrease in the amount of bacterial adhesion was observed when S-PRG fillers were added to the coating material. The amount of eluted TB did not differ depending on the type of the filler in the coating material. It was suggested that TB could be used to develop a new dental material with the potential ability to inhibit the initiation and progression of dental caries.

Clinical Evidence of Biomimetic Hydroxyapatite in Oral Care Products for Reducing Dentin Hypersensitivity: An Updated Systematic Review and Meta-Analysis

Dentin hypersensitivity (DH) is a very common dental problem that can have a negative impact on the quality of life and can lead to invasive dental procedures. Prevention of DH and control of symptoms are highly desirable. Hydroxyapatite (HAP) has been shown in vitro to block dentinal tubules and in vivo to be a safe and effective additive in oral care products that reduce DH clinically. This study's aim was to conduct a systematic review and meta-analysis of the current evidence that HAP-containing oral care products reduce DH. Databases were searched, and only clinical trials in humans were included; studies conducted in vitro or on animals were not included. Publications in a foreign language were translated and included. We found 44 published clinical trials appropriate for systematic analysis. More than half of the trials had high-quality GRADE scores. HAP significantly reduced dentin hypersensitivity compared to placebo (39.5%; CI 95% [48.93; 30.06]), compared to fluoride (23%; CI 95% [34.18; 11.82]), and with a non-significant tendency compared to other desensitizing agents (10.2%; CI 95% [21.76; -19.26]). In conclusion, the meta-analysis showed that HAP added to oral care products is a more effective agent than fluoride in controlling dentin hypersensitivity and may be superior to other desensitizers.

The efficacy of a novel zinc-containing desensitizer CAREDYNE Shield for cervical dentin hypersensitivity: a pilot randomized controlled trial

Background

Recently, a novel zinc-containing desensitizer, CAREDYNE Shield, was developed. This new type of desensitizer induces chemical occlusion of dentinal tubules for desensitization and releases zinc ion for root caries prevention. Despite these features, its clinical effectiveness in the improvement of cervical dentine hypersensitivity remains to be elucidated. Thus, we aimed to evaluate the effectiveness of CAREDYNE Shield in patients with CDH.

Methods

Forty CDH teeth which matched the eligibility criteria were randomly allocated to two groups in a 1:1 ratio: the CAREDYNE Shield group (intervention group) and the Nanoseal group (control group). The pain intensity in response to air stimuli, gingival condition, and oral hygiene status of CDH teeth were assessed before and at 4 weeks after treatment. The primary outcome was the reduction of pain intensity in response to air stimuli from baseline to 4 weeks after intervention.

Results

From November 2019 to April 2021, 24 participants with 40 teeth were enrolled in this study and 33 teeth in 20 participants were assessed at 4 weeks after treatment. A significant reduction of pain in response to air stimuli was observed in both groups; however, no significant difference was observed between the groups.

Conclusions

This study showed that CAREDYNE Shield is effective for CDH and its effectiveness is similar to Nanoseal.

Trial registration

UMIN Clinical Trials Registry (UMIN-CTR), UMIN000038072. Registered on 21st September 2019, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043331

Systematic review and meta-analysis on physical barriers to prevent root dentin demineralization

The present review systematically analyzed in vitro and in situ studies investigating physical diffusion barriers (sealants, desensitizer or adhesives) to prevent the development or the progression of root (dentin) demineralization. Three electronic databases (PubMed-Medline, CENTRAL, Ovid-EMBASE) were screened for studies from 1946 to 2022. Cross-referencing was used to identify further articles. Article selection and data abstraction were done in duplicate. Languages were not restricted. The type of outcome was not restricted, and their mean differences (MD) were calculated using fixed- or random-effects models. Risk of Bias was graded using Risk of Bias 2.0 tool. From 171 eligible studies, 34 were selected for full-text analysis evaluating 69 different materials, and 17 studies-still evaluating 36 different materials-were included (3 in situ and 14 in vitro). Ten studies evaluated desensitizers; 8 adhesives; and 1 infiltration. Meta-analyses were possible for all 17 studies. Meta-analyses revealed that lesion depth after no treatment was significantly higher than after the application of single-step adhesives (MD[_95%CI] = - 49.82[- 69.34; - 30.30]) and multi-step adhesives (MD[_95%CI]=-60.09 [-92.65, -27.54]). No significant differences in the lesion depth increase between single- and multi-step adhesives could be observed (MD[_95%CI]=30.13 [-21.14, 81.39]). Furthermore, compared to no treatment the increase of the lesion depth was significantly hampered using desensitizers (MD[_95%CI] = - 38.02[- 51.74; - 24.31]). Furthermore, the included studies presented unclear or high risk. A physical diffusion barrier can significantly hamper the increase of lesion depth under cariogenic conditions. Furthermore, multi-step adhesives seem not to be more effective than single-step adhesives. However, this conclusion is based on only few in vitro and in situ studies.

Antibacterial effects and physical properties of a glass ionomer cement containing BioUnion filler with acidity-induced ability to release zinc ion

BioUnion filler is a bioactive glass particle that releases Zn²⁺ in an acidic environment. In this study, the ion release, antibacterial, and physical properties of a glass ionomer cement (GIC) incorporating BioUnion filler (CA) were assessed in vitro. The concentration of Zn²⁺ released from CA into acetic acid was higher than that released into water and its minimum inhibitory concentrations against six oral bacterial species. Moreover, the concentration of Zn²⁺-release was maintained during all the seven times it was exposed to acetic acid. Compared to a conventional cement and resin composite, CA significantly inhibited the growth of oral bacteria and hindered their adhesion on the material surface. Thus, our study outcomes show that the release of Zn²⁺ from CA in the acidic environment does not affect its compressive strength.

Assessment of Demineralization Inhibition Effects of Dentin Desensitizers Using Swept-Source Optical Coherence Tomography

The purpose of this study was to evaluate the mechanism of action and the inhibiting effects of two types of desensitizers against dentin demineralization using pre-demineralized hypersensitivity tooth model in vitro. In this study, we confirmed that a hypersensitivity tooth model from our preliminary experiment could be prepared by immersing dentin discs in an acetic acid-based solution with pH 5.0 for three days. Dentin discs with three days of demineralization were prepared and applied by one of the desensitizers containing calcium fluoro-alumino-silicate glass (Nanoseal, NS) or fluoro-zinc-silicate glass (Caredyne Shield, CS), followed by an additional three days of demineralization. Dentin discs for three days of demineralization (de3) and six days of demineralization (de6) without the desensitizers were also prepared. The dentin discs after the experimental protocol were scanned using swept-source optical coherence tomography (SS-OCT) to image the cross-sectional (2D) view of the samples and evaluate the SS-OCT signal. The signal intensity profiles of SS-OCT from the region of interest of 300, 500, and 700 µm in depth were obtained to calculate the integrated signal intensity and signal attenuation coefficient. The morphological differences and remaining chemical elements of the dentin discs were also analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. SS-OCT images of CS and NS groups showed no obvious differences between the groups. However, SS-OCT signal profiles for both the CS and NS groups showed smaller attenuation coefficients and larger integrated signal intensities than those of the de6 group. Reactional deposits of the desensitizers even after the additional three days of demineralization were observed on the dentin surface in NS group, whereas remnants containing Zn were detected within the dentinal tubules in CS group. Consequently, both CS and NS groups showed inhibition effects against the additional three days of demineralization in this study. Our findings demonstrate that SS-OCT signal analysis can be used to monitor the dentin demineralization and inhibition effects of desensitizers against dentin demineralization in vitro.

Effects of desensitizer containing fluoroaluminocalciumsilicate glass nanoparticles on remineralization of root dentin subsurface lesions in vitro

We investigated the remineralization effects of Nanoseal (NS) dentin desensitizer on demineralized root dentin. Baseline lesion specimens prepared from bovine root dentin were immersed in artificial saliva (AS) or deionized water (DW) after treatment with NS or fluoride-free Nanoseal (NS(-)). Treatment and control groups comprised: 1, AS; 2, NS/AS; 3, NS(-)/AS; 4,NS/DW; 5, NS(-)/DW; and 6, baseline demineralization. Integrated mineral loss (IML) and lesion depth (LD) were determined by transverse microradiography. Fluoride concentrations in the immersion solutions were measured. AS, NS/AS and NS(-)/AS showed higher mineral volume % at the surface and lesion body than did other groups. NS/AS showed significantly lower IML than did AS. There was no significant difference in IML between NS/AS and NS(-)/AS. The highest concentration of fluoride was in the NS/AS immersion solution. The findings suggest Nanoseal facilitated remineralization of demineralized root dentin, and fluoride and other ions included may have contributed to this effect.

Evaluation of ion release and the recharge ability of glass-ionomer cement containing BioUnion filler using an in vitro saliva-drop setting assembly

OBJECTIVE

A glass-ionomer cement (GIC) containing BioUnion filler has been reported to release Zn²⁺ under acidic conditions and to inhibit oral bacteria on its surface. However, previous results are based on in vitro experiments under static conditions. This study aimed to assemble an in vitro saliva-drop setting to simulate in vivo conditions of the oral cavity and to investigate the ion releasing and recharging properties of the GIC containing BioUnion filler.

METHODS

The effective concentrations of Zn²⁺ and F^- against Streptococcus mutans and saliva-derived multi-species biofilms were determined. Artificial saliva was dropped on the GIC containing BioUnion filler using the in vitro saliva-drop setting assembly and was periodically replaced with acetic acid. Ion release/recharge properties were investigated by measuring the release concentrations of Zn²⁺ and F^-.

RESULTS

The concentration of Zn²⁺ released from the BioUnion filler-containing GIC during seven days with repeated exposure to acid could be maintained at the level to inhibit S. mutans and saliva-derived multi-species biofilm formation. Moreover, the BioUnion filler-containing GIC could be recharged with Zn²⁺ and F^- by the application of a tooth gel containing Zn²⁺ and F^-. The release concentration of Zn²⁺ after recharging was significantly higher than the effective concentration of Zn²⁺ to hinder S. mutans and saliva-derived multi-species biofilm formation on material surfaces.

SIGNIFICANCE

The GIC containing BioUnion filler was shown to have the potential to inhibit biofilm formation in the oral cavity. In addition, recharging Zn²⁺ and F^- would further enhance the effect of the GIC containing BioUnion filler.

The efficacy of the novel zinc-containing desensitizer CAREDYNE Shield on dentin hypersensitivity: a study protocol for a pilot randomized controlled trial

Background

Dentin hypersensitivity (DH) is a condition characterized by short and sharp episodes of pain which will arise in response to tactile, chemical, thermal, evaporative or osmotic stimuli. The painful symptoms cause discomfort in patients and reduce their quality of life. Recently, the novel zinc-containing desensitizer CAREDYNE Shield has been developed as a new type of desensitizer that acts by inducing chemical occlusion of dentinal tubules, and releasing zinc ion for root caries prevention. However, the clinical effectiveness of CAREDYNE Shield on DH remains unclear. Therefore, the aim of this study is to evaluate the effectiveness of CAREDYNE Shield on DH by comparing with that of another desensitizer, Nanoseal, commonly used in Japan.

Methods/design

This study protocol is a two-arm, parallel, pilot randomized controlled trial. Forty DH patients will be randomly allocated to two groups. Participants in the intervention group will be treated with CAREDYNE Shield, while those in the control group will be treated with Nanoseal. The primary outcome is the reduction of pain intensity in response to air stimuli measured with a 5-point verbal response scale from baseline to 4 weeks after the intervention, and Fisher’s exact test will be used for analyses.

Discussion

CAREDYNE Shield can be casually applied to subgingival areas and proximal surfaces because it reacts with only tooth substance. Furthermore, zinc has been reported to reduce the demineralization of enamel and dentin and inhibit biofilm formation, plaque growth and dentin-collagen degradation. Therefore, CAREDYNE Shield may be expected to be a useful novel desensitizer that acts not only as a desensitizer but also as a root caries inhibitor.

Trial registration

UMIN Clinical Trials Registry (UMIN-CTR), ID: UMIN000038072. Registered on 21 September 2019.

Trial status

This study (protocol version number: version 1.4.0; approved on 22 October 2019) is ongoing. The recruitment of participants began in December 2019 and will be continued until November 2020 (Hanke, Am Dent Assoc 27:1379–1393, 1940).