Bacterial reduction in sealed caries lesions is strain- and material-specific

Detection, Diagnosis, and Monitoring of Early Caries: The Future of Individualized Dental Care

Dental caries remains a significant global health issue. It was highlighted by the World Health Organization's 2022 reports that despite the efforts and scientific advancements in caries detection and management, the situation has only marginally improved over the past three decades. The persistence of this problem may be linked to outdated concepts developed almost a century ago but are still guiding dentists' approach to caries management today. There is a need to reconsider professional strategies for preventing and managing the disease. Contemporary dentistry could benefit from embracing new concepts and technologies for caries detection and management. Dentists should explore, among others, alternative methods for caries detection such as optical-based caries detection. These tools have been established for over a decade and they align with current disease understanding and international recommendations, emphasizing early detection and minimally invasive management. This narrative review presents the current state of knowledge and recent trends in caries detection, diagnosis, monitoring, and management, offering insights into future perspectives for clinical applications and research topics.

Antibacterial Activity of Root Repair Cements in Contact with Dentin-An Ex Vivo Study

This study assessed the antibacterial characteristics of the dentin/material interface and dentin surfaces exposed to experimental hydraulic calcium silicate cement (HCSC) with or without bioactive glass (BG) replacement (20% or 40%) or mixed with a silver nanoparticle (SNP) solution (1 or 2 mg/mL), and Biodentine, TotalFill BC RRM putty and Intermediate Restorative Material (IRM). Human root dentin segments with test materials were assessed at 1 or 28 days. In one series, the specimens were split to expose the dentin and material surfaces. A 24 h direct contact test was conducted against three-day established Enterococcus faecalis and Pseudomonas aeruginosa monospecies biofilms. In another series, the dentin/material interface of intact specimens was exposed to biofilm membranes for 3 days and the antibacterial activity was assessed via confocal microscopy. The interface was additionally characterised. All one-day material and dentin surfaces were antibacterial. Dentin surfaces exposed to HCSC with 40% BG-replacement, Biodentine and IRM had decreased antibacterial properties compared to those of the other cements. The HCSC mixed with a 2 mg/mL SNP solution had the highest antimicrobial effect in the confocal assay. The interfacial characteristics of HCSCs were similar. The test materials conferred antibacterial activity onto the adjacent dentin. The BG reduced the antibacterial effect of dentin exposed to HCSC; a 2 mg/mL SNP solution increased the antibacterial potential for longer interaction periods (three-day exposure).

Fast-Setting Calcium Silicate-Based Pulp Capping Cements-Integrated Antibacterial, Irritation and Cytocompatibility Assessment

Calcium silicate-based cements (CSCs) are endodontic materials widely used in vital pulp-capping approaches. Concerning the clinical application, the reduced set time and pre-mixed formulations are relevant characteristics during the operative management of pulpal exposure, aiming to optimise the work time and improve cross-infection/asepsis control. Additionally, clinical success seems to be greatly dependent on the biological performance of the materials that directly contact the living pulp. As such, this work approaches an integrative biological characterisation (i.e., antibacterial, irritation, and cytocompatibility assays) of three fast-setting CSCs-Biodentine^TM, TotalFill^® BC RRM™ Fast Putty, and Theracal LC^®. These cements, after setting for 24 h, presented the expected topography and elemental composition (assessed by scanning electron microscopy, coupled with EDS analysis), in accordance with the information of the manufacturer. The set cements displayed a significant and similar antibiofilm activity against S. mutans, in a direct contact assay. Twenty-four-hour eluates were not irritant in the standardised CAM assay, but elicited distinct dose- and time-dependent cytotoxicity profiles on fibroblastic cells-i.e., Biodentine was devoid of toxicity, TotalFill presented a slight dose-dependent initial toxicity that was easily overcome, and Theracal LC was deleterious at high concentrations. When compared to long-setting ProRoot MTA cement, which highlighted the pursued integrative approach, Biodentine presented a similar profile, but TotalFill and Theracal LC displayed a poorer performance regarding antibiofilm activity/cytocompatibility features, and Theracal LC suggested eventual safety concerns.

A multi-functional dentine bonding system combining a phosphate monomer with eugenyl methacrylate

OBJECTIVE

The tooth-resin composite interface is frequently associated with failure because of microbial contamination, hydrolytic and collagenolytic degradation. Thus, designing a dentine bonding system (DBS) with an intrinsically antimicrobial polymerisable monomer is of significance especially if it can be used with self-etching primers enabling resistance to degradation of the interface.

METHODS

Experimental adhesives were developed incorporating eugenyl methacrylate (EgMA) at concentrations of 0,10 or 20 wt%, designated as EgMA0, EgMA10 and EgMA20, respectively, for use as a two-step self-etch DBS with the functional monomer bis[2-(methacryloyloxy) ethyl] phosphate (BMEP) in the primer. The curing, thermal and wettability properties of the adhesives were determined, and hybrid layer formation was characterised by confocal laser scanning microscopy, microtensile bond strengths (µTBS) and nanoleakage by back-scattered SEM. In situ zymography was used to assess MMP inhibitory activity of the BMEP-EgMA DBS.

RESULTS

EgMA in the adhesives lowered the polymerisation exotherm and resulted in higher Tg, without negatively affecting degree of conversion. Water sorption and solubility were significantly lower with higher concentrations of EgMA in the adhesive. The formation of a distinct hybrid layer was evident from confocal images with the different adhesives, whilst EgMA20 yielded the highest µTBS post water storage challenges and lowest nanoleakage after 6 months. The experimental DBS exhibited minimal to no MMP activity at 3 months.

SIGNIFICANCE

The hydrophobic nature of EgMA and high cross-link density exerts considerable benefits in lowering water uptake and polymerisation exotherm. The application of EgMA, adhesives in conjunction with BMEP in a multi-functional self-etching DBS can resist MMP activity, hence, enhance longevity of the dentine-resin composite interface.

Current status on antimicrobial activity of a tricalcium silicate cement

Biodentine (BD) is a bioactive material with many indications in endodontic therapy. The purpose of this study was to compile and review the outcomes of in vitro and in vivo studies of BD in terms of antimicrobial effectiveness. An electronic search was carried out in PubMed, from January 2009-April 2021 using the keywords: (Biodentine or dentine substitute or "Ca₃SiO₅" or tricalcium silicate cement or bioceramic cement) and (antimicrobial activity or antimicrobial effect or antimicrobial effectiveness or antibacterial activity or antibacterial effect or antibacterial effectiveness or antibiofilm activity or antibiofilm effectiveness). Two independent reviewers evaluated the studies for eligibility. All studies that did not include BD or its antimicrobial properties, as well as abstracts not written in English, were excluded. This review identified the need to develop standardized methods to evaluate antimicrobial activity in vitro. Most of the studies were against planktonic bacteria and gave conflicting results. Studies ex vivo and in vivo against biofilm are required to elucidate the antimicrobial activity of BD.

Antibiofilm potential over time of a tricalcium silicate material and its association with sodium diclofenac

OBJECTIVES

The objectives of this study are to investigate, over time, the antimicrobial activity against polymicrobial biofilms and ability to inhibit biofilm formation, of Biodentine (BD) alone and with 5% and 10% sodium diclofenac (DC).

MATERIAL AND METHODS

The antimicrobial activity of BD alone and modified with 5% and 10% DC against polymicrobial biofilm growth in dentin was determined by a modified direct contact test. The study groups were (1) BD; (2) BD + 5% DC; and (3) BD + 10% DC. The viability of microorganisms after 1 and 4 weeks was quantified by means of an ATP assay and flow cytometry. The antibiofilm efficacy of the materials, preventing polymicrobial biofilm formation over time, was assessed by confocal laser scanning microscopy (CLSM).

RESULTS

The results obtained with both the ATP test and flow cytometry showed that BD alone and with 5% and 10% DC exerted antibiofilm activity with respect to the control, in the two evaluated times (p < 0.001). Comparison between groups showed a tendency of increased antimicrobial effect, both over time and depending on the DC concentration. These results coincide with those obtained in CLSM analysis, where efficacy increased with time and DC concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Biodentine, over time, showed antimicrobial and antibiofilm efficacy on polymicrobial biofilms. The addition of 5% and 10% DC to BD enhanced this effect, in a concentration- and time-dependent manner.

Antibacterial effect of a brominated self-etch adhesive on carious dentin - An in vivo study

OBJECTIVES

This in vivo study compared the antibacterial effect of a self-etch adhesive with and without the brominated monomer 12-methacryloyloxydodecyl-pyridinium bromide (MDPB) on carious dentin after selective caries removal.

METHODS

10 patients showing deep primary carious lesions at two posterior teeth without pulpal symptoms were included. At visit I, carious tissue was selectively removed and carious dentin was sampled with a sterile roundbur (Komet No. 18). One cavity was restored with composite (SDR, Ceram X; DENTSPLY DeTrey) using an MDPB-containing self-etch adhesive (Clearfil Protect Bond, Kuraray Noritake; PB). The other restoration served as a control (Clearfil SE Bond II, Kuraray Noritake; SE). At visit II after 8 weeks, carious dentin was sampled again. Bacterial growth in carious dentin was differentiated using microbial cultivation. Bacterial DNA from intact cells and cell-free DNA were quantified using 16S rRNA gene-based real-time PCR and the microbial community composition was analyzed by amplicon deep-sequencing. Wilcoxon test was applied for statistical analysis.

RESULTS

Both treatments showed a decrease of intact bacterial cells in carious dentin at visit II compared to visit I (PB: visit I: 1.1*10⁶, visit II: 1.7*10⁵ (p = 0.03); SE: visit I: 1.1*10⁷, visit II = 2.4*10⁵ (p = 0.002)). No statistically significant reduction of cell-free bacterial DNA was detected (PB: visit I: 6.1*10⁵, visit II: 1.6*10⁵ (p = 0.08); SE: visit I: 5.3*10⁵, visit II: 2.9*10⁵ (p = 0.10)). The decrease of intact cell-derived (p = 0.371) and cell-free DNA (p = 0.455) did not differ significantly between PB and SE. Lactobacillus was most abundant within the microbial community at both visits. Alpha-diversity was not affected by treatment and samples showed high intra- and interindividual diversity.

CONCLUSION AND CLINICAL SIGNIFICANCE

Both self-etch adhesives have an antibacterial effect due to a decrease of bacterial DNA after selective caries removal. However, the results do not reveal any additional antibacterial effect by MDPB. The study is registered with the German Clinical Trials Register (DRKS00011532).

Improving the Bond Strength of Radiographically Tagged Caries Lesions In Vitro

After selective carious tissue removal, residual carious lesions remain radiographically detectable. Radiopaque tagging resolves the resulting diagnostic uncertainty but impedes bond strengths of adhesives to tagged dentin. We developed a protocol mitigating these detrimental effects. A 30%/50%/70% SnCl₂ solution was dissolved in distilled water or a 30%/50%/90% ethanol solution (E30/60/90) and applied to artificially induced dentin lesions. Tagging effects were radiographically evaluated using transversal wavelength-independent microradiography (n = 6/group). Groups with sufficient tagging effects at the lowest SnCl₂ concentrations were used to evaluate how tagging affected the microtensile bond strength of a universal adhesive (Scotchbond Universal) to sound and carious dentin (n = 10/group). Two different protocols for removing tagging material were tested: 15 s phosphoric acid etching and 5 s rotating brush application. Scanning/backscattered electron microscopy (SEM/BSE) and energy-dispersive X-ray spectroscopy (EDS) were used to assess surfaces after tagging and removal. The most promising removal protocol was revalidated microradiographically. Tagging significantly increased the radiopacity, with consistent effects for 30% SnCl₂ dissolved in water or E30. Microscopically, tagged surfaces showed a thick carpet of SnCl₂, and tagging reduced bond strengths significantly on carious dentin but not on sound dentin (p < 0.01). On carious dentin, removal of tagging material using acid etching and rotating brush was microscopically confirmed. Acid etching also mitigated any bond strength reduction (median: 21.3 MPa; interquartile range: 10.8 MPa) compared with nontagged dentin (median: 17.4 MPa; interquartile range: 20.6 MPa). This was not the case for brushing (median: 13.2 MPa; interquartile range: 13.9 MPa). Acid etching minimally reduced the radiographic tagging effect (p = 0.055). Phosphoric acid etching reduces the detrimental bond-strength effects of tagging without significantly decreasing radiographic tagging effects when using a universal adhesive.

Clinical efficacy and the antimicrobial potential of silver formulations in arresting dental caries: a systematic review

Background

The use of silver-formulation as microbicide to arrest dentinal caries is gaining popularity. The primary objective of the present appraisal was to systematically review the clinical (in vivo) applications and antimicrobial potential of silver-containing formulations in arresting dentinal caries. Our secondary aim was to sum up the available in vitro applications of silver-containing formulations against cariogenic microbes isolated from dentine lesions.

Methods

Ovid MEDLINE, EBSCO host, Web of Science, and Cochrane Library databases was searched between January 2009–May 2019.

Results

In vivo: We observed conflicting evidence of antimicrobial efficacy of SDF on a diverse array of microbial taxa present in carious dentine of primary and permanent teeth. Moreover, there is insufficient evidence on the application of AgNP-fluoride as an effective microbicidal against cariogens of dentine lesions.

In vitro: We found a good evidence of microbicidal efficacy of silver diamine fluoride (SDF) on selective cariogenic microbes in human dentine model. Additionally, a good evidence was noted of in vitro application of silver nanoparticles (AgNPs) as a useful microbicidal against S. mutans adhesion, growth and subsequent biofilm formation in human dentine models.

Conclusions

Taken together, in vitro evidence indicates the promising antimicrobial potential of silver-based formulations (SDF and nanosilver) against the predominant cariogenic flora, particularly from dentine lesions. Post-treatment clinical data of either the bactericidal and bacteriostatic effects of SDF or nanosilver are sparse. Furthermore, the current understanding of the specific size, concentration, antimicrobial mechanisms, and toxicological aspects of nano-silver compounds is inadequate to draw firm conclusions on their clinical utility.

Ex vivo investigation on internal tunnel approach/internal resin infiltration and external nanosilver-modified resin infiltration of proximal caries exceeding into dentin

This ex vivo proof-of-concept study aimed to investigate the effect of nanosilver particles (AgNP) added to a conventional infiltrant resin (Icon) on external penetration into natural proximal enamel caries exceeding into dentin after internal tunnel preparation and internal infiltration. Carious lesions (ICDAS codes 2/3) of extracted human (pre-)molars revealing proximal caries radiographically exceeding into dentin (E2/D1 lesions) were preselected. Then, 48 of those specimens showing demineralized areas transcending the enamel-dentin border as assessed by means of near-infrared light transillumination (DIAGNOcam) were deproteinized (NaOCl, 5%). Using an internal tunnel approach, occlusal cavities central to the marginal ridge were prepared. Excavation of carious dentin, total etch procedure (H3PO4, 40%), and internal resin infiltration (FITC-labeled) followed, along with final restorations (flowable composite resin). Outer lesion surfaces were etched (HCl, 15%) prior to external infiltration (RITC-labeled). Group 1 (control; n = 24) used non-modified infiltrant, while an infiltrant/AgNP mixture (20 nm; 5.5 wt%) was used with experimental Group 2 (n = 24). Non-infiltrated pores of cut lesions were stained (Berberine), and specimens were analyzed using confocal laser scanning microscopy. Compared to the non-filled infiltrant, incorporation of AgNP had no effect on the resin's external penetration. Between the groups, no significant differences regarding internal or external infiltration could be detected, and non-infiltrated lesion areas did not differ significantly (p>0.109; t-test). The internal tunnel preparation in combination with both an internal resin infiltration and an additional external infiltration approach using a nanosilver-modified infiltrant resin leads to increased infiltrated lesion areas, thus occluding and adhesively stabilizing the porous volume of the demineralized enamel. While exerting antimicrobial effects by the nanosilver particles, this approach should have the potential as a viable treatment alternative for proximal lesions extending into dentin, thus avoiding the sacrifice of sound enamel, postponing the frequently inevitable restoration/re-restoration cycle of conventional proximal caries treatment, and improving dental health.

Effect of a bioactive cement on the microbial community in carious dentin after selective caries removal - An in-vivo study

OBJECTIVES

Selective caries removal in deep lesions means that soft carious affected dentin is left in the center of the cavity. Thus, using a tricalcium silicate cement Biodentine™ (Septodont, Paris) to seal the remaining soft dentin could have an antibacterial effect. This in-vivo study aimed to do quantitative and qualitative analyses on the bacterial composition within carious dentin before and after selective caries removal when applying Biodentine.

METHODS

Eleven patients with deep primary carious lesions at two posterior teeth without pulpal symptoms were included. Carious dentin was selectively removed and sampled with a sterile round bur (Komet No. 18) at baseline visit and eight weeks later. On the first visit, one lesion per patient, the remaining carious dentin was covered with Biodentine before adhesive restoration. Caries samples were investigated by microbial cultivation, molecular analysis and amplicon deep-sequencing of 16S rRNA genes. Bacterial DNA from intact cells was differentiated from cell-free DNA by DNase degradation prior to DNA isolation.

RESULTS

Reduction of cell-derived as well as cell-free bacterial DNA eight weeks after selective caries removal was significantly higher when Biodentine was applied. Lactobacillus was most abundant within the microbial community of deep carious dentin lesions at the first visit. After intervention with Biodentine application, Lactobacillus was diminished to a high degree. In general, the diversity in samples, as well as bacterial composition differed interindividually as well as intraindividually.

CONCLUSION AND CLINICAL SIGNIFICANCE

Despite the heterogenous and diversity of microbial composition in patients, Biodentine can have beneficial antibacterial effects when applied to residual carious dentin, offering an alternative and safe treatment option. The study is officially registered with German Clinical Trials Register (DRKS00011067).

Sustained-Release Fillers for Dentin Disinfection: An Ex Vivo Study

Enterococcus faecalis is the most commonly recovered species from failed root canal treatments. In this study, we tested the capability of a novel intracanal sustained-release filler (SRF) containing cetylpyridinium chloride (CPC) to disinfect dentinal tubules of segmented human tooth specimens. Human dental root specimens were infected with E. faecalis V583 for 3 weeks in a static environment. The tested intracanal medicaments were SRF-CPC and calcium hydroxide (CH). Each medicament was introduced into the canal of the dental specimen and incubated for 7 days. The bacteriological samples were taken by shaving the dentine surrounding the root canal with dental burs ranging in size from ISO 014-020. The obtained dentine powder was collected in test tubes containing phosphate-buffered saline, sonicated, and plated on agar plates. Colony-forming units were counted after 48 h of incubation. Random specimens were also examined under confocal laser scanning microscopy and scanning electron microscopy. A statistical difference was found in the bacterial counts obtained from all layers of infected dentin between the control and the SRF-CPC groups. CH reduced bacterial viability significantly only in the first layer of the infected dentin, up to 150 μm into the dentinal tubules. CLSM images showed that SRF-CPC killed most bacteria throughout the infected dentin up to 700 μm of penetration. SEM images demonstrated the adhesion ability of SRF-CPC to the dentinal wall. In conclusion, SRF-CPC is a potential intracanal medicament for disinfecting dentinal tubules.

Effect of reduced nutritional supply on the metabolic activity and survival of cariogenic bacteria in vitro

Sealed cariogenic bacteria are deprived from dietary carbohydrate, but could be provided with nutrients by pulpal fluids, with adaptive strain-specific activities being possible. We investigated survival and metabolic activity of the cariogenic bacteria Streptococcus sobrinus, Actinomyces naeslundii and Lactobacillus rhamnosus in different carbohydrate-limited media without carbon source (CLM), or containing glucose (CLM-G), albumin (CLM-A), or α1-acid glycoprotein (CLM-AGP) in vitro. Bacterial metabolite concentrations (lactate, pyruvate, oxaloacetate, citrate, acetate, formate, ethanol, acetoin) after 20 and 4 hours incubation, and bacterial numbers (CFU) after 24 hours incubation were analyzed using multivariate-analysis-of-variance (MANOVA). The medium (p = 0.02/MANOVA), strain and incubation-time (both p < 0.001) had significant impact on metabolite concentrations. Bacteria secreted mainly lactate (80.3 µg/10⁶ bacteria S. sobrinus) and acetate (54.5 µg/10⁶ bacteria A. naeslundii). Nearly all metabolites were produced in higher concentrations in S. sobrinus than in A. naeslundii or L. rhamnosus (p < 0.05/HSD). Metabolite concentration was significantly higher in CLM-G than in other media for most metabolites (p < 0.05). L. rhamnosus showed significantly lower survival than S. sobrinus and A. naeslundii (p < 0.05/HSD) regardless of the media, while S. sobrinus and A. naeslundii showed medium-specific survival. Survival of carbon starvation was strain- and medium-specific. Sustained organic acid production was found for all strains and media.

Tailored Dentistry: From "One Size Fits All" to Precision Dental Medicine?

Over the past 30 years and fueled by both a rapidly evolving understanding of dental diseases and technological advances in diagnostics and therapy, dentistry has been changing dramatically. Managing dental caries and carious lesions had, for nearly a century, encompassed only a small number of basic concepts that were applied to virtually all patients and lesions, namely, invasive removal of any carious tissue regardless of its activity or depth and its replacement with restorative materials (amalgams or crowns for most of the past) or tooth removal and prosthetic replacement. Grounded in a deeper understanding of the disease "caries," its management-aiming to control the causes of the disease, to slow down or alleviate existing disease, and, only as a last resort, to remove its symptoms using a bur or forceps-has become more complex and diverse. In parallel and at nearly unprecedented speed, our patients are changing, as mirrored by ongoing debates as to the demographic and, with it, the social future of most high-income countries. This article describes how these changes will have a profound future impact on how we practice dental medicine in the future. It will deduce, from both demographic and epidemiologic trends, why there is the need to apply not one but rather the whole range of existing evidence-based concepts in an individualized (personalized) manner, hence increasing the effectiveness and efficiency of dental management strategies, and also describe how these strategies should be tailored according not only to our patients (their age and risk profiles) but also to the specific tooth (or site or lesion).