A first study on the usefulness of matrix metalloproteinase 9 from dentinal fluid to indicate pulp inflammation

Design and evaluation of an MMP-9-responsive hydrogel for vital pulp therapy

OBJECTIVE

To design and evaluate a matrix metalloproteinase 9 (MMP-9)-responsive hydrogel for vital pulp therapy.

METHODS

A peptide linker with optimized sensitivity toward MMP-9 was crosslinked with 4-arm poly (ethylene glycol)-norbornene (PEG-NB) by thiol-norbornene photo-polymerization. This resulted in the formation of a hydrogel network in which the peptide IDR-1002 was incorporated. Hydrogel characterization and gelation kinetics were examined with Fourier-transform infrared spectroscopy, scanning electron microscopy, rheological testing, and swelling evaluation. Hydrogel degradation was examined through multiple exposure to pre-activated MMP-9, to simulate flare-ups of dental pulp inflammation. The IDR-1002 released from degraded hydrogels was measured with high-performance liquid chromatography. Effect of IDR-1002 released from hydrogels on one-week-old multispecies oral biofilms was evaluated using confocal laser scanning microscopy.

RESULTS

MMP-9-responsive, injectable, and photo-crosslinkable hydrogels were successfully synthesized. When hydrogel degradation and release of IDR-1002 were examined with exposure to pre-activated MMP-9, IDR-1002 release was significantly correlated with elevated levels of MMP-9 (p < 0.05). The effectiveness of IDR-1002 in killing bacteria in multispecies oral biofilms was significantly enhanced when the hydrogels were immersed in 10 nM or 20 nM pre-activated MMP-9, compared to immersion in phosphate-buffered saline (p < 0.05).

CONCLUSIONS

The MMP-9-responsive hydrogel is a promising candidate for on-demand delivery of bioactive agent in vital pulp therapy.

CLINICAL SIGNIFICANCE

MMP-9 is one of the most important diagnostic and prognostic biomarkers for pulpitis. An MMP-9-responsive hydrogel has potential to be used as an in-situ on-demand release system for the diagnosis and treatment of dental pulp inflammation.

Revolutionizing the diagnosis of irreversible pulpitis - Current strategies and future directions

BACKGROUND

Pulpitis primarily arises from the pulp space infection by oral microbiota. Vital pulp therapy is a minimally invasive approach that relies on assessing the severity of pulpal inflammation to facilitate repair. However, the current evaluation methods prescribed by the American Association of Endodontics are subjective, leading to ambiguity in assessment. Therefore, this review aims to explore molecular strategies for evaluating the severity of pulpal inflammation to accurately predict the success of pulp vitality preservation in clinical settings.

METHODOLOGY

This review was conducted by searching relevant keywords, such as irreversible pulpitis, pulpitis biomarkers, molecular diagnosis, inflammation, and genomic strategies, in databases such as PubMed, Web of Science, and Scopus to address the subjective nature of diagnosis. The data included in this review were collected up to April 2023. The literature search revealed well-documented limitations in clinically assessing the pulp inflammatory. Molecular approaches that aid in clinical differentiation between irreversible and reversible pulpitis may potentially enhance favorable outcomes in vital pulp therapy. Non-invasive diagnostic methods for pulpal assessment would also be valuable for determining whether the inflamed pulp is reversible, irreversible, or necrotic.

CONCLUSION

The present review examines the various molecular diagnostic approaches that have revolutionized the medical field and are considered the most promising empirical methodologies for the proactive detection of pulpal diseases. It also provides comprehensive insights into the current diagnostic methods, associated challenges, next-generation strategies, and future directions for diagnosing the severity of pulp inflammation.

Data-driven dentistry: Computational revelations redefining pulp capping

Introduction

Pulpal and periradicular diseases stem from immune reactions to microbiota, causing inflammation. Limited blood supply hampers dental pulp self-healing. Managing inflammation involves eliminating bacteria and reducing pro-inflammatory mediators especially MMP-9, which has a significant correlation with pulpitis. s. Flavonoids like Hesperidin, Baicalein, Epigallocatechin gallate, Genistein, Icariin, and Quercetin show potential for pulp capping.

Aim

This in-silico study compares various Flavonoids for their anti-inflammatory effects on MMP-9, with Chlorhexidine as a control, a known MMP-9 inhibitor.

Materials and Methods

Protein and Ligand Preparation: The human MMP-9 catalytic domain (PDB ID: 4XCT) structure was retrieved, and necessary modifications were made. Flavonoids from PubChem database were prepared for docking using AutoDock Vina. A grid for docking was created, and molecular dynamics simulations were conducted using Gromacs-2019.4 with GROMOS96 force field. Trajectory analysis was performed, and MM-PBSA calculation determined binding free energies.

Results

Analysis of MMP-9 and ligand interactions revealed Hesperidin's high binding affinity, forming numerous hydrogen bonds with specific amino acids. Molecular dynamics simulations confirmed stability, with RMSD, RMSF, Rg, and SASA indicating consistent complex behaviour over 100 ns. MM-PBSA calculation affirmed favourable energy contributions in MMP-9-Hesperidin interactions.

Conclusion

MMP-9 plays a crucial role in prognosis of pulpitis. Incorporating MMP-9 inhibitors into pulp capping agents may enhance therapeutic efficacy. Hesperidin emerges as a potent MMP-9 inhibitor, warranting further in vivo validation against other agents.

Molecular biomarkers for objective assessment of symptomatic pulpitis: A systematic review and meta-analysis

BACKGROUND

Inflammatory biomarkers are potentially useful targets for pulpal diagnostic tests that can identify pulp status and predict vital pulp treatment (VPT) outcome, however, their accuracy is unknown.

OBJECTIVES

(1) Calculate sensitivity, specificity and diagnostic odds ratio (DOR) of previously investigated pulpitic biomarkers; (2) Determine if biomarker levels discriminate between clinical diagnoses of pulpitis based on the presence or absence of spontaneous pain (3) Evaluate if biomarker level can predict VPT outcome.

METHODS

Searches: PubMed/MEDLINE, Ovid SP, Cochrane Central Register of Controlled Trials (CENTRAL), International Clinical Trials Registry Platform (ICTRP), ClinicalTrials.gov, Embase, Web of Science and Scopus in May 2023.

INCLUSION

prospective and retrospective observational studies and randomized trials. Participants were humans with vital permanent teeth and a well-defined pulpal diagnosis.

EXCLUSION

deciduous teeth, in vitro and animal studies. Risk of bias was assessed with modified-Downs and Black quality assessment checklist. Meta-analysis was performed using bivariate random effect model in Meta-DiSc 2.0 and RevMan and the quality of the evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation.

RESULTS

Fifty-six studies were selected, reporting >70 individual biomolecules investigating pulpal health and disease at the gene and protein level. Most studies were of low and fair quality. Among the biomolecules investigated, IL-8 and IL-6 demonstrated a level of diagnostic accuracy with high sensitivity, specificity and DOR to discriminate between healthy pulps and those exhibiting spontaneous pain suggestive of IRP (low-certainty evidence). However, none was shown to have high DOR and the ability to discriminate between pulpitic states (very low certainty evidence). Limited data suggests high levels of matrix metalloproteinase 9 correlate with poorer outcomes of full pulpotomy.

DISCUSSION

The inability of identified molecular inflammatory markers to discriminate between dental pulps with spontaneous and non-spontaneous pain should shift the focus to improved study quality or the pursuit of other molecules potentially associated with healing and repair.

CONCLUSIONS

Low-quality evidence suggests IL-8 and IL-6 demonstrated level of diagnostic accuracy to discriminate between healthy pulps and those exhibiting spontaneous pain. There is a need for standardized biomarker diagnostic and prognostic studies focusing on solutions that can accurately determine the degree of pulp inflammation.

REGISTRATION

PROSPERO CRD42021259305.

Dentin Degradation: From Tissue Breakdown to Possibilities for Therapeutic Intervention

Purpose of the Review

Presently, dental materials science is driven by the search for new and improved materials that can trigger specific reactions from the affected tissue to stimulate repair or regeneration while interacting with the oral environment to promote or maintain oral health. In parallel, evidence from the past decades has challenged the exclusive role of bacteria in dentin tissue degradation in caries, questioning our understanding of caries etiopathogenesis. The goal of this review is to recapitulate the current evidence on the host and bacterial contributions to degradation, inflammation, and repair of the dentin-pulp complex in caries.

Recent Findings

Contrasting findings attribute dentin breakdown to the activity of endogenous enzymes, such as matrix metalloproteinases (MMPs) and cathepsins, while the role of bacteria and their by-products in the destruction of dentin organic matrix and pulp inflammation has been for decades supported as an incontestable paradigm. Aiming to better understand the mechanisms involved in collagen degradation by host enzymes in caries, studies have showed that these proteinases are expressed in the mature dentin (i.e., after dentin formation) and become activated by the low pH in the acidic environment resulted by bacterial metabolism in caries. However, different host sources other than dentin-bound proteinases seem to also contribute to caries progression, such as saliva and pulp. Interestingly, studies evaluating pulp responses to bacteria invasion and inflammation in caries report higher levels of MMPs and cathepsins in inflamed tissue, but also showed MMP potential to resolve inflammation and stimulate wound healing. Notably, as reported for other tissues, MMPs exert dual roles in the dentin-pulp complex in caries, participating or regulating both degradative and reparative mechanisms.

Summary

The specific roles of host and bacteria and their by-products in caries progression have yet to be clarified. The complex interactions between inflammation and repair in caries pose challenges to a clear understanding of the dentin-pulp complex responses and changes to bacteria invasion. However, it opens new venues for the development of novel therapies and dental biomaterials based on the modulation of specific mechanisms to favor tissue repair and healing.

Factors that influence the outcome of pulpotomy in permanent teeth

The promotion of minimally invasive treatments focussed on the maintenance of pulp vitality has become a priority area in Endodontics. These vital pulp treatments (VPT) include partial and full pulpotomy, during which diseased coronal pulp tissue is removed prior to placement of a capping biomaterial and restoration. Traditionally, pulpotomies were confined to the treatment of carious primary and traumatized permanent teeth. However, these treatments have now been proposed as definitive solutions for cariously exposed permanent teeth with mild symptoms or even symptoms indicative of irreversible disease. Until recently, it was recommended that carious exposure of mature permanent teeth be managed by root canal treatment. The promotion of pulpotomy as an alternative treatment has opened up a wave of laboratory and clinical research aimed at improving therapies or evaluating clinical outcomes. In modern evidence-based endodontics, it is imperative that the outcomes of both partial and full pulpotomy are considered and important prognostic factors identified, so that improvements can be made to aid clinical decision-making and to direct new research. In this narrative review, the outcomes of partial and full pulpotomy are discussed, before analysis of patient, intraoperative and postoperative factors that influence the outcome of the pulpotomy procedure. The review highlights that although partial and full pulpotomy for the treatment of even pulpal disease are highly successful procedures, this is based on low-quality evidence with a lack of prospective, comparative trials investigating potential prognostic factors. Based on current evidence, it appears that age, gender, tooth type, root development and intraoperative pulpal haemorrhage do not impact significantly on pulpotomy outcome, whilst others such as caries depth, inflammatory status of the pulp, capping material, level of inflammatory pulpal-biomarkers and the final restoration integrity do. Other factors, including the influence of exposure type, periodontal condition, pulpal lavage, magnification, operator experience, isolation of the operating field and type of pulpotomy, require further experimental investigation before definitive conclusions can be made relating to the success of the pulpotomy procedure. Finally, there is not only a need for future well-designed prospective research addressing these issues but also a widening of our understanding of outcome to include patient-reported as well as clinician-reported outcomes.

Salivary Enzymatic Activity and Carious Experience in Children: A Cross-Sectional Study

Salivary biomolecules are considered important modulators of the oral microflora, with a potential subsequent impact on dental health. The present study aimed to investigate the relationship between salivary enzymatic activity and carious experience in children. The carious experience of a sample of 22 school children was evaluated by calculating dmf/DMF indices, following WHO recommendations. Unstimulated whole saliva was collected, and salivary alpha-amylase levels, total protease activity, and matrix metalloproteinase levels (MMP-8 and MMP-9) were measured. The data were analyzed using parametric and nonparametric tests. Our findings revealed no significant relationship between the investigated salivary parameters and the carious experience in permanent teeth (DMFT/DMFS scores). Carious indices scores for primary teeth (dmft and dmfs) were positively associated with MMP-8 levels (r = 0.62, p = 0.004 and r_s = 0.61, p = 0.006, respectively) and MMP-9 levels (r = 0.45, p = 0.05 and r_s = 0.48, p = 0.039, respectively) and negatively associated with alpha-amylase levels (r_s = −0.54, p = 0.017 and r_s = −0.59, p = 0.006, respectively). Although with a marginal significance, PEK−054 levels positively correlated with dental caries, while for PFU−089, a negative correlation was observed. These results suggest that salivary alpha-amylase and MMP-8 and MMP-9 levels may be considered potential indicators of carious experience in children. Further studies with a prospective design are needed in order to elucidate the role of these biomolecules in caries development.

Present status and future directions - Vital pulp treatment and pulp preservation strategies

Therapeutic strategies focussed on the pulp preservation, are important when managing vital teeth with deep caries and an exposed pulp. These vital pulp treatments (VPTs); however, are not new, with indirect and direct pulp capping procedures being described as a therapy for carious teeth for over a century. As a result of unpredictable outcomes, the traditional indications for VPT particularly when the pulp was exposed were limited to the treatment of immature teeth with incomplete root formation. Over the last 20 years, the advent of regenerative endodontics and the promotion of biologically based therapies aimed at reducing intervention have reinvigorated VPT with new waves of basic science and clinical research indicating a role for VPT not only in mature cariously affected teeth, but also in teeth with signs and symptoms indicative of irreversible pulpitis. Driven by new materials such as hydraulic calcium silicate cements, a better understanding of pulpal immunity and biology as well and improved tissue handling, VPT has been at the forefront of treatment recommendations made by global Cariology and Endodontic organizations. Care must be exercised, however, as key gaps in scientific knowledge remain alongside severe limitations in educational dissemination amongst dentists. Although research has highlighted that carious injury to the dentine–pulp complex stimulates a wide range of responses and that the interaction between infection, inflammation and repair will eventually impact on the outcome of pulpitis, our ability to accurately and objectively diagnose the true inflammatory state of the pulp remains poor. An overreliance on symptoms leaves clinicians with subjective, crude diagnostic tools by which to inform treatment planning and decision‐making, which results in large variations in the treatments offered to patients. Not only is there an urgent need to develop preoperative and intraoperative diagnostic tools, but there is also a paucity of the high‐quality comparative evidence required to answer the most important questions and justify treatment options. The aim of this review was to consider the current status of VPT and to discuss the principle problems that are hindering clinical acceptance of these techniques. Potential solutions and opportunities are offered to suggest ways that VPT may become a more consistently prescribed evidenced‐based treatment in dental practice.

A Mini Review: The Potential Biomarkers for Non-invasive Diagnosis of Pulpal Inflammation

For assessing the adequacy of vital pulp therapy for an inflamed pulp, the use of non-invasive diagnostic tools is necessary to avoid further damage to the teeth. Detection of biomarkers that are indicative of the inflammatory status in pulp can be a promising tool for this purpose. These biomarkers need to be reliably correlated with pulpal inflammation and to be easily detected without pulp exposure. This mini-review article aims to review biomarkers that are present in gingival crevicular fluid (GCF) in inflamed pulp conditions. Several studies have reported the availability of various biomarkers including cytokines, proteases, elastase, neuropeptides, and growth factors. Non-invasive pulpal diagnostic methods will be useful as well to determine reversibility, irreversibility, or necrosis of inflamed pulp. These types of molecular diagnoses via analyzing the proteome have revolutionized the medical field, and are one of the most promising empirical methodologies that a clinician can utilize for the proactive identification of pulpal disease.

Evaluation of Pulp Repair after BiodentineTM Full Pulpotomy in a Rat Molar Model of Pulpitis

Dental pulp is a dynamic tissue able to heal after injury under moderate inflammatory conditions. Our study aimed to evaluate pulp repair under inflammatory conditions in rats. For this purpose, we developed a rat model of controlled pulpitis followed by pulpotomy with a tricalcium silicate-based cement. Fifty-four cavities were prepared on the occlusal face of the maxillary upper first molar of 27 eight-week-old male rats. E. coli lipopolysaccharides at 10 mg/mL or phosphate-buffered saline PBS was injected after pulp injury. Non-inflamed molars were used as controls. Levels of inflammation-related molecules were measured 6 and 24 h after induction by enzyme-linked immunosorbent assay of coronal pulp samples. Pulp capping and coronal obturation after pulpotomy were performed with tricalcium silicate-based cement. Four and fifteen days after pulpotomy, histological and immunohistochemical analysis was performed to assess pulp inflammation and repair processes. Our results showed significantly higher levels of innate inflammatory proteins (IL-1β, IL-6, TNF-α and CXCL-1) compared with those in controls. Moderate residual inflammation near the capping material was demonstrated by histology and immunohistochemistry, with the presence of few CD68-positive cells. We showed that, in this model of controlled pulpitis, pulpotomy with Biodentine^TM allowed the synthesis at the injury site of a mineralized bridge formed from mineralized tissue secreted by cells displaying odontoblastic characteristics. Analysis of these data suggests overall that, with the limitations inherent to findings in animal models, pulpotomy with a silicate-based cement is a good treatment for controlling inflammation and enhancing repair in cases of controlled pulpitis.

Identification and validation of novel biomarkers and therapeutics for pulpitis using connectivity mapping

AIM

To create an irreversible pulpitis gene signature from microarray data of healthy and inflamed dental pulps, followed by a bioinformatics approach using connectivity mapping to identify therapeutic compounds that could potentially treat pulpitis.

METHODOLOGY

The Gene Expression Omnibus (GEO) database, an international public repository of genomics data sets, was searched for human microarray datasets assessing pulpitis. An irreversible pulpitis gene expression signature was generated by differential expression analysis. The statistically significant connectivity map (ssCMap) method was used to identify compounds with a highly correlating gene expression pattern. qPCR was used to validate novel pulpitis genes. An ex vivo pulpitis model was used to test the effects of the compounds identified, and the level of inflammatory cytokines was measured with qPCR, ELISA and multiplex array. Means were compared using the t-test or ANOVA with the level of significance set at p ≤ .05.

RESULTS

Pulpitis gene signatures were created using differential gene expression analysis at cutoff points p = .0001 and .000018. Top upregulated genes were selected as potential pulpitis biomarkers. Among these, IL8, IL6 and MMP9 were previously identified as pulpitis biomarkers. Novel upregulated genes, chemokine (C-C motif) ligand 21 (CCL21), metallothionein 1H (MT1H) and aquaporin 9 (AQP9) were validated in the pulp tissue of teeth clinically diagnosed with irreversible pulpitis using qPCR. ssCMap analysis identified fluvastatin (Statin) and dequalinium chloride (Quaternary ammonium) as compounds with the strongest correlation to the gene signatures (p = .0001). Fluvastatin reduced IL8, IL6, CCL21, AQP9 (p < .001) and MMP9 (p < .05) in the ex vivo pulpitis model, while dequalinium chloride reduced AQP9 (p < .001) but had no significant effect on the other biomarkers.

CONCLUSIONS

AQP9, MT1H and CCL21 were identified and validated as novel biomarkers for pulpitis. Fluvastatin and dequalinium chloride identified by the ssCMap as potential therapeutics for pulpitis reduced selected pulpitis biomarkers in an ex vivo pulpitis model. In vivo testing of these licenced drugs is warranted.

Detection of Inflammatory and Homeostasis Biomarkers after Selective Removal of Carious Dentin-An In Vivo Feasibility Study

Deep carious dentin lesions induce an immune reaction within the pulp-dentin complex, leading to the release of cytokines, which might be suitable biomarkers in pulp diagnostics. This in vivo feasibility study determines the concentration of different cytokines after selective removal of carious infected dentin (SCR). In our methodology, paired samples are obtained from 21 patients—each of them with two deep carious lesions at posterior teeth without clinical symptoms. After SCR, lesions are randomly assigned to treatment strategy: Group 1 (11 patients): Carious dentin is covered either with Biodentine^TM (n = 11) or gutta-percha (n = 11) before using the adhesive Optibond^TM FL. Group 2 (10 patients): The adhesives Clearfil^TM SE Protect Bond (n = 10) or Clearfil^TM SE Bond 2 (n = 10) are directly applied. Prepared cavities are rinsed with phosphate buffered saline containing 0.05% Tween 20 (10X) for five minutes immediately after SCR (visit 1) and eight weeks later (visit 2). Rinsing liquid is regained. Concentrations of IL-1β, IL-6, IL-10, C-reactive protein (CRP), TNF-α, IFN-γ, TIMP-1, -2, and MMP-7, -8, -9 are assessed by customized multiplex assays, evaluated with fluorescence analyzer. Non-parametric statistical analysis (Wilcoxon, Mann–Whitney U Test, p < 0.05) is performed (SPSS 25). Our results show that concentrations of CRP, IL-1β, IL-6, TIMP-1, -2, and MMPs were detectable. Median concentrations of CRP, IL-1β und IL-6 were significantly higher in visit 1 (304.9, 107.4, 3.8 pg/mL), compared to visit 2 (67.8, 2.3, 0.0 pg/mL; p_i < 0.001). The study revealed that the non-invasive determination of cytokines from prepared dental cavities is possible.

Extracellular matrix degradation by host matrix metalloproteinases in restorative dentistry and endodontics: An overview

Matrix metalloproteinases (MMPs) are a group of over 25 secreted and membrane-bound enzymes responsible for pericellular substrate degeneration. In response to injury, they play key roles in morphogenesis, wound healing, tissue repair and remodeling. They have been isolated from dentin, odontoblasts, pulp and periapical tissue. They play a major role in the formation of dentin matrix and secondary and tertiary dentin. These are also responsible for releasing dentinal growth factors. MMP family proteins elicit a dual role in the pathogenesis of inflammation, stimulating protective innate and/or adaptive immune functions, as well as tissue destruction. The main organic component of tooth structure is collagen, and MMPs that degrade collagen and the extracellular matrix have been implicated in the progression of dental caries, dental erosion as well as degradation of the hybrid layer. MMPs have also been shown to be active in pulpitis, and studies have shown that they can be used as diagnostic markers of pulpal and periapical inflammation. This review describes the role of MMPs in dental caries, dental erosion, bond stability as well as in pulpal and periapical inflammation.

[Comparative analysis of methods to stimulate and collect dentinal fluid: a clinical and experimental study]

OBJECTIVE

The aim - to determine the most effective method of dentinal fluid collection and dentinal fluid flow rate stimulation.

MATERIAL AND METHODS

In a series of dentinal fluid collection tests, 3 types of filter membranes «Technofilter» were compared to a blotting nitrocellulose membrane Sartorius 1288. An ability of the studied membranes to adsorb dentinal fluid was assessed based on the data of proton magnetic resonance using signal magnitudes of the organic molecules accumulation in dentine fluid samples. In the study 30 permanent teeth with a diagnosis of K04.00 «Initial pulpitis» were included. Teeth were randomly divided into 5 groups in accordance with the method used to stimulate the dentinal fluid flow rate. Dentinal fluid volume before and after stimulation within and between the groups was compared.

RESULTS

The nitrocellulose membrane Sartorius 1288 has the highest ability to adsorb dentinal fluid; predominant dentinal fluid volume was obtained using a 10% dextran solution with low molecular weight. Based on the results of the study, the author proposed the method of dentinal fluid collection.

CONCLUSION

The proposed stimulation method increases the dentinal fluid yields by 2 times in comparison with sampling under natural conditions.

Association between concentration of active MMP-9 in pulpal blood and pulpotomy outcome in permanent mature teeth with irreversible pulpitis - a preliminary study

AIM

To investigate the correlation between the concentration of active-matrix metalloproteinases-9 (aMMP-9) in pulpal blood and the outcome of pulpotomy in mature permanent teeth with symptomatic irreversible pulpitis (SIP).

METHODOLOGY

Forty permanent molar teeth with a clinical diagnosis of SIP and normal apical tissues with periapical index (PAI) score ≤ 2 and ten permanent teeth (8 molars and two premolars) with a diagnosis of normal pulp that required root canal treatment for prosthetic reasons from patients between the ages of 15-35 years were recruited. All clinical procedures were performed under local anaesthesia and rubber dam isolation. After access opening, the coronal pulp tissue was amputated up to the canal orifice. A 100 μL volume of the pulpal blood was collected using a micropipette and transported to the laboratory. Sodium hypochlorite (2.5 %) was used as a haemostatic agent, and mineral trioxide aggregate (MTA) was used as the pulp capping material. The tooth was restored with composite at the same visit. Teeth with normal pulps were treated with single-visit root canal treatment. Patients with pulpotomy were recalled at 6 and 12 months. Outcome assessment of teeth with pulpotomy was carried out at 12 months and was categorized as success (asymptomatic patients with PAI score ≤ 2) or failure (symptomatic patients or PAI score ≥ 3). Quantification of aMMP-9 in pulpal blood was achieved using a fluorometric assay. The following statistical analyses were performed to assess the data: t-test, Fisher's exact test, kappa coefficient, non-parametric test, Wilcoxon rank-sum test, Spearman rank correlation test and receiver operating characteristic curve (ROC).

RESULT

The success rate of pulpotomy was 88 % at 12-months. There was a significant difference between the median concentrations of aMMP-9 in pulpal blood of teeth with normal pulps (52 (12-96) ng mL^-1 :) and SIP (193.3 (25.8-607.7) ng mL^-1 :) (P = 0.0003) and successful (132.3 (25.8-548.3) ng mL^-1 :) and failed cases (512.4 (334.8-607.7 ng mL^-1 :) (P = 0.0015) of MTA pulpotomy. A significant association was established between aMMP-9 concentration and outcome of pulpotomy. The area under the receiver operating characteristics curve (0.9484, 95%CI) suggested excellent discriminatory power of aMMP-9 concentration in pulpal blood to predict the pulpotomy outcome.

CONCLUSION

The pulpal blood concentration of aMMP-9 was significantly associated with the outcome of pulpotomy in teeth with symptomatic irreversible pulpitis, where it may be used as a potential prognostic biomarker.

Diagnostic biomarker candidates for pulpitis revealed by bioinformatics analysis of merged microarray gene expression datasets

Background

Pulpitis is an inflammatory disease, the grade of which is classified according to the level of inflammation. Traditional methods of evaluating the status of dental pulp tissue in clinical practice have limitations. The rapid and accurate diagnosis of pulpitis is essential for determining the appropriate treatment. By integrating different datasets from the Gene Expression Omnibus (GEO) database, we analysed a merged expression matrix of pulpitis, aiming to identify biological pathways and diagnostic biomarkers of pulpitis.

Methods

By integrating two datasets (GSE77459 and GSE92681) in the GEO database using the sva and limma packages of R, differentially expressed genes (DEGs) of pulpitis were identified. Then, the DEGs were analysed to identify biological pathways of dental pulp inflammation with Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and Gene Set Enrichment Analysis (GSEA). Protein–protein interaction (PPI) networks and modules were constructed to identify hub genes with the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and Cytoscape.

Results

A total of 470 DEGs comprising 394 upregulated and 76 downregulated genes were found in pulpitis tissue. GO analysis revealed that the DEGs were enriched in biological processes related to inflammation, and the enriched pathways in the KEGG pathway analysis were cytokine-cytokine receptor interaction, chemokine signalling pathway and NF-κB signalling pathway. The GSEA results provided further functional annotations, including complement system, IL6/JAK/STAT3 signalling pathway and inflammatory response pathways. According to the degrees of nodes in the PPI network, 10 hub genes were identified, and 8 diagnostic biomarker candidates were screened: PTPRC, CD86, CCL2, IL6, TLR8, MMP9, CXCL8 and ICAM1.

Conclusions

With bioinformatics analysis of merged datasets, biomarker candidates of pulpitis were screened and the findings may be as reference to develop a new method of pulpitis diagnosis.

Biochemical analysis of oral fluids for disease detection

The field of diagnostics using invasive blood testing represents the majority of diagnostic tests used as part of routine health monitoring. The relatively recent introduction of salivary diagnostics has lead to a major paradigm shift in diagnostic analyses. Additionally, in this era of big data, oral fluid testing has shown promising outcomes in a number of fields, particularly the areas of genomics, microbiomics, proteomics, metabolomics, and transcriptomics. Despite the analytical challenges involved in the interpretation of large datasets generated from biochemical studies involving bodily fluids, including saliva, many studies have identified novel oral biomarkers for diagnosing oral and systemic diseases. In this regard, oral biofluids, including saliva, gingival crevicular fluid (GCF), peri-implant crevicular fluid (PICF), dentinal tubular fluid (DTF), are now attracting increasing attention due to their important attributes, such as noninvasive sampling, easy handling, low cost, and more accurate diagnosis of oral diseases. Recently, the utilization of salivary diagnostics to evaluate systemic diseases and monitor general health has increased in popularity among clinicians. Saliva contains a wide range of protein, DNA and RNA biomarkers, which assist in the diagnosis of multiple diseases and conditions, including cancer, cardiovascular diseases (CVD), auto-immune and degenerative diseases, respiratory infections, oral diseases, and microbial (viral, bacterial and fungal) diseases. Moreover, due to its noninvasive nature and ease-of-adoption by children, it is now being used in mass screening programs, oral health-related studies and clinical trials in support of the development of therapeutic agents. The recent advent of highly sensitive technologies, such as next-generation sequencing, mass spectrometry, highly sensitives ELISAs, and homogeneous immunoassays, suggests that even small quantities of salivary biomarkers are able to be assayed accurately, providing opportunities for the development of many future diagnostic applications (including emerging technologies, such as point-of-care and rapid molecular technologies). The present article explores the omics and biochemical compositions of various oral biofluids with important value in diagnostics and monitoring.

Metalloproteinase 14 (MMP-14) and hsa-miR-410-3p expression in human inflamed dental pulp and odontoblasts

The objective of this study is to evaluate MMP-14 expression in odontoblasts and in the bulk of dental pulp of teeth with pulpitis; to determine the expression of microRNA-410 (miR-410) in pulp tissue, since sequence analysis suggests that miR-410 has potential binding site on MMP-14’s 3′UTR, and hence, can regulate expression of the latter one. Tissue samples of dental pulp from teeth with pulpitis and healthy (control) were formalin fixed and paraffin embedded (FFPE). Samples were examined using immunohistochemical staining for MMP-14 and the expression of miR-410 was evaluated using qRT-PCR. In both, healthy and inflamed pulp odontoblasts stained more intensively than remaining pulp tissue, but this difference was not statistically significant. More positive staining was observed in inflamed pulps compared to healthy pulps. Expression of miR-410 was found significantly lower in inflamed pulps than in healthy ones. In the two examined zones, odontoblasts and remaining pulp, miR-410 was expressed on a similar level. No statistically significant correlation of miR-410 and MMP-14 expression was found. We showed that inflammation changes the MMP-14 expression in pulp tissue and odontoblasts. This study demonstrates for the first time miR-410 expression in human dental pulp and that expression of this microRNA was downregulated in inflamed dental pulp and odontoblasts.

Dissecting dentine-pulp injury and wound healing responses: consequences for regenerative endodontics

A thorough understanding of the biology of the dentine-pulp complex is essential to underpin new treatment approaches and maximize clinical impact for regenerative endodontics and minimally invasive vital pulp treatment (VPT) strategies. Following traumatic and carious injury to dentine-pulp, a complex interplay between infection, inflammation and the host defence responses will occur, which is critical to tissue outcomes. Diagnostic procedures aim to inform treatment planning; however, these remain clinically subjective and have considerable limitations. As a consequence, significant effort has focussed on identification of diagnostic biomarkers, although these are also problematic due to difficulties in identifying appropriate diagnostic fluid sources and selecting reproducible biomarkers. This is further compounded by the link between inflammation and repair as many of the molecules involved exhibit significant multifunctionality. The tertiary dentine formed in response to dental injury has been purposefully termed reactionary and reparative dentine to enable focus on associated biological processes. Whilst reactionary dentine produced in response to milder injury is generated from surviving primary odontoblasts, reparative dentine, in response to more intense injury, requires the differentiation of new odontoblast-like cells derived from progenitor/stem cells recruited to the injury site. These two diverse processes result in very different outcomes in terms of the tertiary dentine produced and reflect the intensity rather than specific nature (nonexposure versus exposure) of the injury. The subsequent identification of the odontoblast-like cell phenotype remains challenging due to lack of unique molecular or morphological markers. Furthermore, the cells ultimately lining the newly deposited dentine provide only a snapshot of events. The specific source and plasticity of the progenitor cells giving rise to the odontoblast-like cell phenotype are also of significant debate. It is likely that improved characterization of tertiary dentine may better clarify the influence of cell derivation for odontoblast-like cells and their diversity. The field of regenerative endodontics offers exciting new treatment opportunities, and to maximize outcomes, we propose that the term regenerative endodontics should embrace the repair, replacement and regeneration of dentine-pulp.

Management of deep caries and the exposed pulp

Caries prevalence remains high throughout the world, with the burden of disease increasingly affecting older and socially disadvantaged groups in Western cultures. If left untreated, caries will advance through dentine stimulating pulpitis and eventually pulp infection and necrosis; however, if conservatively managed, pulpal recovery occurs even in deep carious lesions. Traditionally, deep caries management was destructive with nonselective (complete) removal of all carious dentine; however, the promotion of minimally invasive biologically based treatment strategies has been advocated for selective (partial) caries removal and a reduced risk of pulp exposure. Selective caries removal strategies can be one-visit as indirect pulp treatment or two-visit using a stepwise approach. Management strategies for the treatment of the cariously exposed pulp are also shifting with avoidance of pulpectomy and the re-emergence of vital pulp treatment (VPT) techniques such as partial and complete pulpotomy. These changes stem from an improved understanding of the pulp-dentine complex's defensive and reparative response to irritation, with harnessing the release of bioactive dentine matrix components and careful handling of the damaged tissue considered critical. Notably, the development of new pulp capping materials such as mineral trioxide aggregate, which although not an ideal material, has resulted in more predictable treatments from both a histological and a clinical perspective. Unfortunately, the changes in management are only supported by relatively weak evidence with case series, cohort studies and preliminary studies containing low patient numbers forming the bulk of the evidence. As a result, critical questions related to the superiority of one caries removal technique over another, the best pulp capping biomaterial or whether pulp exposure is a negative prognostic factor remain unanswered. There is an urgent need to promote minimally invasive treatment strategies in Operative Dentistry and Endodontology; however, the development of accurate diagnostic tools, evidence-based management strategies and education in management of the exposed pulp are critical in the future.

Epigenetic Approaches to the Treatment of Dental Pulp Inflammation and Repair: Opportunities and Obstacles

Concerns over the cost and destructive nature of dental treatment have led to the call for novel minimally invasive, biologically based restorative solutions. For patients with toothache, this has resulted in a shift from invasive root-canal-treatment (RCT) toward more conservative vital-pulp-treatment (VPT) procedures, aimed to protect the pulp and harness its natural regenerative capacity. If the dental pulp is exposed, as long as the infection and inflammation can be controlled, conservative therapies can promote the formation of new tertiary dentine in a stem cell-led reparative process. Crucially, the volume and quality of new dentine is dependent on the material applied; however, currently available dental-materials are limited by non-specific action, cytotoxicity and poor clinical handling. Looking to the future, an improved understanding of the cellular regulators of pulpal inflammation and associated repair mechanisms is critical to predict pulpal responses and devise novel treatment strategies. Epigenetic modifications of DNA-associated proteins and the influences of non-coding RNAs have been demonstrated to control the self-renewal of stem cell populations as well as regulate mineralised tissue development and repair. Notably, the stability of microRNAs and their relative ease of sampling from pulpal blood highlight their potential for application as diagnostic inflammatory biomarkers, while increased understanding of their actions will not only enhance our knowledge of pulpal disease and repair, but also identify novel molecular targets. The potential therapeutic application of epigenetic modifying agents, DNA-methyltransferase-inhibitors (DNMTi) and histone-deacetylase-inhibitors (HDACi), have been shown to promote mineralisation and repair processes in dental-pulp-cell (DPC) populations as well as induce the release of bioactive dentine-matrix-components. Consequently, HDACis and DNMTis have the potential to enhance tertiary dentinogenesis by influencing the cellular and tissue processes at low concentrations with minimal side effects, providing an opportunity to develop a topically placed, inexpensive bio-inductive restorative material. The aim of this review is to highlight the potential role of epigenetic approaches in the treatment of the damaged dental pulp, considering the opportunities and obstacles, such as off-target effects, delivery mechanisms, for the therapeutic use of miRNA as an inflammatory biomarker or molecular target, before discussing the application of HDACi and DNMTi to the damaged pulp to stimulate repair.

The Effect of Chemically Modified Tetracycline-3 on the Progression of Dental Caries in Rats

OBJECTIVE

Matrix metalloproteinases (MMPs) exist in human saliva and dentin and play an important role in the degradation of organic matrix in teeth. Chemically modified tetracycline-3 (CMT-3) is an inhibitor of MMPs. CMT-3 has been used experimentally to treat caries since 1999, but no distinction between dental caries prevalence and dentin caries prevalence has been described.

METHODS

A total of 65 Sprague-Dawley rats were randomly divided into three groups. The positive control group (25 rats) was inoculated with Streptococcus mutans (ATCC700610) and fed the cariogenic feed of improved Keyes Diet 2000. The CMT-3 group (25 rats) was also inoculated with S. mutans and fed the cariogenic feed of improved Keyes Diet 2000; the surfaces of rats' molars were daily treated with 0.02% CMT-3. The negative control group (15 rats) was only fed the standard rodent chow. At the end of the 10th week, the dental caries prevalence and dentin caries prevalence of each group were calculated, and the regions of caries were assessed.

RESULTS

No caries was found in the negative control group. The dental caries prevalence of the CMT-3 and the positive control group was 75.0 and 83.3%, respectively (p > 0.05, Table 2). The dentin caries prevalence of the CMT-3 and the positive control group was 33.3 and 70.8%, respectively (p < 0.05, Table 2). The Keyes scoring of dentin caries in the CMT-3 group was significantly lower than that in the positive control group (p < 0.05, Table 3).

CONCLUSIONS

CMT-3 had no effect on the prevalence of dental caries, but could lower the prevalence and slow down the progression of dentin caries.

Salivary Protein Roles in Oral Health and as Predictors of Caries Risk

This work describes the current state of research on the potential relationship between protein content in human saliva and dental caries, which remains among the most common oral diseases and causes irreversible damage in the oral cavity. An understanding the whole saliva proteome in the oral cavity could serve as a prerequisite to obtaining insight into the etiology of tooth decay at early stages. To date, however, there is no comprehensive evidence showing that salivary proteins could serve as potential indicators for the early diagnosis of the risk factors causing dental caries. Therefore, proteomics indicates the promising direction of future investigations of such factors, including diagnosis and thus prevention in dental therapy.

MMP-9 in Dentinal Fluid Correlates with Caries Lesion Depth

The analysis of molecular cues in dentinal fluid from an excavated cavity could improve diagnostics in the context of minimally invasive caries treatment. In the current clinical trial we assessed whether the dentinal fluid levels of MMP-9 (matrix metalloproteinase-9; neutrophil gelatinase) would increase with the progression of carious lesions. MMP-9 is associated with neutrophil-related tissue breakdown in the pulp. Absolute MMP-9 levels were contrasted against the levels of MMP-2, an enzyme related to normal tissue turnover. Dentinal fluid was collected below deep and shallow caries from molars and premolars within the same patients aged 18 years and older (n = 30, 1 tooth per group/patient). Experimental teeth were isolated under a rubber dam prior to excavation. Dentinal fluid was collected from the bottom of the cavity using a size 25 paper point. MMP levels were assessed using an enzyme-linked immunosorbent assay. Nonparametric methods were applied to test for differences between groups. Significantly more (p < 0.05, Wilcoxon test) MMP-9 was collected from the deep carious lesions than from the shallow counterparts. Pairwise comparison of MMP-9 values within patients revealed that there was more MMP-9 collected from deep lesions than from shallow counterparts in 27 of the 30 individuals under investigation (pairwise Wilcoxon test, p < 0.001). In contrast, no such difference existed for MMP-2. There was a high correlation between MMP-9 from deep and shallow lesions (Spearman's ρ = 0.72, p < 0.001), indicating that patients with more MMP-9 in the deep carious lesion also tended to have more MMP-9 in the shallow lesion.

Immunohistochemical expression of TGF-β1 and MMP-9 in periapical lesions

The objective of this study was to evaluate the expression of matrix metalloproteinase 9 (MMP-9) and transforming growth factor beta (TGF-β1) in periapical lesion samples correlated with the intensity of the inflammatory infiltrate and thickness of the epithelial lining. Forty-five cases of periapical lesions (23 periapical granulomas and 22 radicular cysts) were subjected to morphological and immunohistochemical analyses using anti-MMP-9 and anti-TGF-β1 antibodies. The data were analyzed using the following tests: non-parametric Mann-Whitney, chi-square, Fisher's exact test and Spearman's correlation test (P<0.05). Analysis of inflammatory infiltrate revealed that 78% of periapical granulomas presented infiltrate grade III, in contrast with 32% of radicular cysts (P<0.001). Morphological evaluation of the epithelial thickness in radicular cysts revealed the presence of atrophic epithelium in 86% of the cysts. The immunostaining of MMP-9 was score 2 in 67% of the granulomas and 77% of the cysts. Both lesions were predominantly score 1 for TGF-β1. Significant differences were confirmed between the expression scores of TGF-β1 and MMP-9 in periapical granulomas (p = 0.004) and in radicular cysts (p < 0.001). Expression of TGF-β1 was different for periapical granulomas and radicular cysts. This immunoregulatory cytokine seems more representative in asymptomatic lesions. The extracellular matrix remodeling process dependent on MMP-9 seems to be similar for both periapical granulomas and radicular cysts. TGF-β1 and MMP-9 may play an important role in the maintenance of periapical lesions.

Insight into Oral Biofilm: Primary, Secondary and Residual Caries and Phyto-Challenged Solutions

INTRODUCTION

Dental caries is known to be one of the most widespread, chronic infections affecting all ages and populations worldwide. The plethora of oral microbial population paves way for various endogenous infections and plays a crucial role in polymicrobial interactions contributing to biofilm-mediated diseases like caries and periodontal diseases.

METHODS

Extensive literature survey was conducted using the scientific databases like PubMed, Google scholar, Science Direct, etc. using the key words like dental caries, orodental infections, dental microbes, dental biofilm, secondary caries, phytotherapy, etc. The literature was analyzed thoroughly and critical review was performed.

RESULTS

The risk of development of secondary caries and residual caries further results in treatment failure. Drug resistance developed by oral microbes and further side effects pose serious hurdles in the current therapeutic strategies. The hyperactivities of various MMPs and the resulting massive ECM degradation are the challenging part in the design of effective therapeutic approaches. Anticariogenic phytotherapy is well appreciated owing to lesser side effects and versatility of their action. But appreciable outcomes regarding the phytochemical bioavailability and bioretention are still challenging. Site-specific delivery of phytoagents at the infected site may enhance the efficiency of these drugs. Accordingly emerging phytodentistry can be promising for the management of secondary and residual caries.

CONCLUSION

This article presents major cariogens and their mechanisms in initiating and aggravating dental caries. Effectiveness of phytotherapy and different mode of action of phytochemicals against cariogens are outlined. The article also raises major concerns and possibilities of phytochemical based therapeutics to be applied in the clinical arena of caries management.

Inflammatory cytokines in normal and irreversibly inflamed pulps: A systematic review

OBJECTIVE

To review the available literature in regard to the inflammatory process and pulpitis. Setting forth to evaluate if differences in the levels of various cytokines (TNF-α, IL-1β, IL-2, IL-6 and IL-8) can be observed in clinically diagnosed normal and irreversibly inflamed pulps that could serve as possible markers and/or diagnostic tools to predict and differentiate between certain states of inflammation. Methods used to measure and assess levels of cytokines have been limited to two protein quantification methods ELISA and/or Multiplex Array.

DESIGN

The databases PubMed, EMBASE/Ovid, The Cochrane Central Register of Controlled Trials, Cochrane Reviews and Scopus were consulted for the electronic literature search. Screening of titles and abstracts followed the PRISMA guidelines while data extraction and the assessment of the full texts were carried out in accordance to the GRADES assessment.

RESULTS

The review showed that significant increases in levels of IL-1β, IL-2, IL-6, IL-8 and TNF-α in irreversible pulpitis samples exist, in comparison to normal pulp samples which serve as a good basis for potential markers. Due to larger discrepancies in available literature, IL-2 seems rather unsuitable at the moment, while IL-6 and TNF alpha seem to be more promising.

CONCLUSION

It may be concluded that even by combining two protein quantification methods inconsistencies between studies exist. At the moment it is difficult to select just one specific cytokine suitable for testing, rather it supports the rationale that further high-quality clinical studies are needed.

Pulp Inflammation Diagnosis from Clinical to Inflammatory Mediators: A Systematic Review

INTRODUCTION

Similar to other tissues, the dental pulp mounts an inflammatory reaction as a way to eliminate pathogens and stimulate repair. Pulp inflammation is prerequisite for dentin pulp complex repair and regeneration; otherwise, chronic disease or pulp necrosis occurs. Evaluation of pulp inflammation severity is necessary to predict the clinical success of maintaining pulp vitality. Clinical limitations to evaluating in situ inflammatory status are well-described. A molecular approach that aids clinical distinction between reversible and irreversible pulpitis could improve the success rate of vital pulp therapy. The aim of this article is to review inflammatory mediator expression in the context of clinical diagnosis.

METHODS

We searched PubMed and Cochrane databases for articles published between 1970 and December 2016. Only published studies of inflammatory mediator expression related to clinical diagnosis were eligible for inclusion and analysis.

RESULTS

Thirty-two articles were analyzed. Two molecular approaches were described by study methods, protein expression analysis and gene expression analysis. Our review indicates that interleukin-8, matrix metalloproteinase 9, tumor necrosis factor-α, and receptor for advanced glycation end products expression increase at both the gene and protein levels during inflammation.

CONCLUSIONS

Clinical irreversible pulpitis is related to specific levels of inflammatory mediator expression. The difference in expression between reversible and irreversible disease is both quantitative and qualitative. On the basis of our analysis, in situ quantification of inflammatory mediators may aid in the clinical distinction between reversible and irreversible pulpitis.

Biological Markers for Pulpal Inflammation: A Systematic Review

Background and Objective

Pulpitis is mainly caused by an opportunistic infection of the pulp space with commensal oral microorganisms. Depending on the state of inflammation, different treatment regimes are currently advocated. Predictable vital pulp therapy depends on accurate determination of the pulpal status that will allow repair to occur. The role of several players of the host response in pulpitis is well documented: cytokines, proteases, inflammatory mediators, growth factors, antimicrobial peptides and others contribute to pulpal defense mechanisms; these factors may serve as biomarkers that indicate the status of the pulp. Therefore, the aim of this systematic review was to evaluate the presence of biomarkers in pulpitis.

Methods

The electronic databases of MEDLINE, EMBASE, Scopus and other sources were searched for English and non-English articles published through February 2015. Two independent reviewers extracted information regarding study design, tissue or analyte used, outcome measures, results and conclusions for each article. The quality of the included studies was assessed using a modification of the Newcastle-Ottawa-Scale.

Results and Conclusions

From the initial 847 publications evaluated, a total of 57 articles were included in this review. In general, irreversible pulpitis was associated with different expression of various biomarkers compared to normal controls. These biomarkers were significantly expressed not only in pulp tissue, but also in gingival crevicular fluid that can be collected non-invasively, and in dentin fluid that can be analyzed without extirpating the entire pulpal tissue. Such data may then be used to accurately differentiate diseased from healthy pulp tissue. The interplay of pulpal biomarkers and their potential use for a more accurate and biologically based diagnostic tool in endodontics is envisaged.

Ecological Hypothesis of Dentin and Root Caries

Recent advances regarding the caries process indicate that ecological phenomena induced by bacterial acid production tilt the de- and remineralization balance of the dental hard tissues towards demineralization through bacterial acid-induced adaptation and selection within the microbiota - from the dynamic stability stage to the aciduric stage via the acidogenic stage [Takahashi and Nyvad, 2008]. Dentin and root caries can also be partly explained by this hypothesis; however, the fact that these tissues contain a considerable amount of organic material suggests that protein degradation is involved in caries formation. In this review, we compiled relevant histological, biochemical, and microbiological information about dentin/root caries and refined the hypothesis by adding degradation of the organic matrix (the proteolytic stage) to the abovementioned stages. Bacterial acidification not only induces demineralization and exposure of the organic matrix in dentin/root surfaces but also activation of dentin-embedded and salivary matrix metalloproteinases and cathepsins. These phenomena initiate degradation of the demineralized organic matrix in dentin/root surfaces. While a bacterial involvement has never been confirmed in the initial degradation of organic material, the detection of proteolytic/amino acid-degrading bacteria and bacterial metabolites in dentin and root caries suggests a bacterial digestion and metabolism of partly degraded matrix. Moreover, bacterial metabolites might induce pulpitis as an inflammatory/immunomodulatory factor. Root and dentin surfaces are always at risk of becoming demineralized in the oral cavity, and exposed organic materials can be degraded by host-derived proteases contained in saliva and dentin itself. New approaches to the prevention and treatment of root/dentin caries are required.

Translational opportunities in stem cell-based endodontic therapy: where are we and what are we missing?

Pulp regeneration is a biologic process occurring under specific circumstances. An endodontic treatment modality to accomplish pulp regeneration has emerged based on the response of undifferentiated cells that are often referred to as stem cells. The treatment itself is currently empirical based on clinicians' thoughts and observations. The demonstration of a variety of dental stem cells initiated basic research detailing the properties and behavior of these cells. Attempts are made to bridge gaps in knowledge regarding treatment strategies by translating basic stem cell research into practice. However, neither the patient population likely to benefit from pulp regeneration nor most clinical parameters are well described. Classic topics in endodontics (eg, indication/clinical diagnosis, disinfection/irrigation, and root canal preparation/pretreatment) have to be revisited under the premises of pulp regeneration. Furthermore, new topics like the development of new diagnostic tools or new clinical success criteria will emerge, and the translational research itself will generate new insight into pulp regeneration mechanisms.

Scaffolds to control inflammation and facilitate dental pulp regeneration

In dentistry, the maintenance of a vital dental pulp is of paramount importance because teeth devitalized by root canal treatment may become more brittle and prone to structural failure over time. Advanced carious lesions can irreversibly damage the dental pulp by propagating a sustained inflammatory response throughout the tissue. Although the inflammatory response initially drives tissue repair, sustained inflammation has an enormously destructive effect on the vital pulp, eventually leading to total necrosis of the tissue and necessitating its removal. The implications of tooth devitalization have driven significant interest in the development of bioactive materials that facilitate the regeneration of damaged pulp tissues by harnessing the capacity of the dental pulp for self-repair. In considering the process by which pulpitis drives tissue destruction, it is clear that an important step in supporting the regeneration of pulpal tissues is the attenuation of inflammation. Macrophages, key mediators of the immune response, may play a critical role in the resolution of pulpitis because of their ability to switch to a proresolution phenotype. This process can be driven by the resolvins, a family of molecules derived from fatty acids that show great promise as therapeutic agents. In this review, we outline the importance of preserving the capacity of the dental pulp to self-repair through the rapid attenuation of inflammation. Potential treatment modalities, such as shifting macrophages to a proresolving phenotype with resolvins are described, and a range of materials known to support the regeneration of dental pulp are presented.

A Prospective Clinical Pilot Study on the Level of Matrix Metalloproteinase-9 in Dental Pulpal Blood as a Marker for the State of Inflammation in the Pulp Tissue

INTRODUCTION

Differentiation between reversible pulpitis (savable pulp) and irreversible inflammation of the pulp tissue (nonsavable pulp) based only on clinical and radiographic diagnoses has proven to be difficult. Pulp exposure allows for the collection of pulpal blood to quantitatively determine the level of inflammation markers or proteolytic enzymes, even with small samples. Pulpitis is associated with the invasion of neutrophil granulocytes and their release of matrix metalloproteinase-9 (MMP-9).

METHODS

Forty-four patients (aged 18-74 years, mean = 35 years), each with 1 tooth with carious pulp exposure presenting with different stages of pulpitis, were included in this prospective, 2-center clinical study; 26 patients presented with irreversible pulpitis (groups 3 and 4), 10 with reversible pulpitis (group 2), and 8 with completely asymptomatic teeth with deep carious lesions (group 1). Six of the 26 patients with teeth diagnosed with irreversible pulpitis had not taken any nonsteroidal anti-inflammatory drugs and were evaluated as a separate group (group 4). Partial pulpotomy and blood sample collection from the pulp chamber were performed. The total levels of MMP-9 and tissue inhibitor of metalloproteinase-1 were assessed by fluorometric and colorimetric enzyme-linked immunosorbent assays, respectively. The Mann-Whitney U test and Spearman rank correlations were used to compare the MMP-9 levels with different stages of pulpal inflammation; significance was set at .05.

RESULTS

The MMP-9 levels in the asymptomatic teeth (group 1) were significantly different from those in the teeth with reversible pulpitis (group 2, P = .006) or irreversible pulpitis (group 4, P < .001). A statistically significant difference was also observed between the MMP-9 levels in group 1 and group 3 (P < .001) in which the patients had taken nonsteroidal anti-inflammatory drugs.

CONCLUSIONS

These findings indicate that the MMP-9 levels in pulpal blood samples could be a useful ancillary diagnostic tool for distinguishing different stages of pulp tissue inflammation.

Elevated Matrix Metalloproteinase Levels in Bronchi Infected with Periodontopathogenic Bacteria

Objectives

To determine whether bronchial colonisations/infections with periodontopathogenic bacteria are associated with elevated inflammatory markers such as MMPs, interleukins and Tumor necrosis factor alpha in the bronchial fluid.

Methods

Periodontal status was assessed in consecutive outpatients planned for elective bronchoscopies, and PCR for periodontopathogenic bacteria was performed from a protected specimen brush sample taken from the bronchial mucosa. Additionally, MMPs, interleukins and Tumor necrosis factor alpha were measured in the bronchial fluid.

Results

Out of the four species assessed, one species was found in 13 of 91 (14%) patients, and two in 12 (13%), three in 13 (14%) and all four in 1 (1%) patient, respectively. In multiple linear regression models the presence of Treponema denticola showed a consistent pattern of positive effects in bronchial fluid (Bonferroni adjusted p-values) on the levels of MMP9 (p adj.: 0.028) and MMP12 (p adj.: 0.029). Active smoking was independently associated with increased levels of aMMP8 (p adj.: 0.005) and MMP9 (p adj.: 0.009). Levels of IL-1 ß, IL-8 and Tumor necrosis factor alpha measured in the bronchial fluid were not affected by the presence of periodontopathogenic bacteria.

Conclusions

Bronchial colonisation/infection with Treponema denticola and smoking are independently associated with elevated MMPs (MMP9/MMP12 and MMP8/MMP9, respectively) in the bronchial fluid.

Matrix metalloproteinases and other matrix proteinases in relation to cariology: the era of 'dentin degradomics'

Dentin organic matrix, with type I collagen as the main component, is exposed after demineralization in dentinal caries, erosion or acidic conditioning during adhesive composite restorative treatment. This exposed matrix is prone to slow hydrolytic degradation by host collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins. Here we review the recent findings demonstrating that inhibition of salivary or dentin endogenous collagenolytic enzymes may provide preventive means against progression of caries or erosion, just as they have been shown to retain the integrity and improve the longevity of resin composite filling bonding to dentin. This paper also presents the case that the organic matrix in caries-affected dentin may not be preserved as intact as previously considered. In partially demineralized dentin, MMPs and cysteine cathepsins with the ability to cleave off the terminal non-helical ends of collagen molecules (telopeptides) may lead to the gradual loss of intramolecular gap areas. This would seriously compromise the matrix ability for intrafibrillar remineralization, which is considered essential in restoring the dentin's mechanical properties. More detailed data of the enzymes responsible and their detailed function in dentin-destructive conditions may not only help to find new and better preventive means, but better preservation of demineralized dentin collagenous matrix may also facilitate true biological remineralization for the better restoration of tooth structural and mechanical integrity and mechanical properties.

Dentin bonding: can we make it last?

In dentin bonding, contemporary dental adhesive systems rely on formation of the hybrid layer, a biocomposite containing dentin collagen and polymerized resin adhesive. They are usually able to create at least reasonable integrity of the hybrid layer with high immediate bond strength. However, loss of dentin-bonded interface integrity and bond strength is commonly seen after aging both in vitro and in vivo. This is due to endogenous collagenolytic enzymes, matrix metalloproteinases, and cysteine cathepsins, responsible for the time-dependent loss of hybrid layer collagen. In addition, the hydrophilic nature of adhesive systems creates problems that lead to suboptimal hybrid layers. These problems include, for example, insufficient resin impregnation of dentin, phase separation, and a low rate of polymerization, all of which may reduce the longevity of the bonded interface. Preservation of the collagen matrix integrity by inhibition of endogenous dentin proteases is key to improving dentin bonding durability. Several approaches to retain the integrity of the hybrid layer and to improve the long-term dentin bond strength have been tested. These include the use of enzyme inhibitors, either separately or as incorporated into the adhesive resins; increase of collagen resistance to enzymatic degradation; and elimination of water from the interface to slow down or eliminate hydrolytic loss of the hybrid layer components. This review looks at the principles, current status, and future of the different techniques designed to prevent the loss of hybrid layer and bond strength.

Role of dentin MMPs in caries progression and bond stability

Dentin can be described as a biological composite with collagen matrix embedded with nanosized hydroxyapatite mineral crystallites. Matrix metalloproteinases (MMPs) and cysteine cathepsins are families of endopeptidases. Enzymes of both families are present in dentin and collectively capable of degrading virtually all extracellular matrix components. This review describes these enzymes and their presence in dentin, mainly focusing on their role in dentin caries pathogenesis and loss of collagen in the adhesive hybrid layer under composite restorations. MMPs and cysteine cathepsins present in saliva, mineralized dentin, and/or dentinal fluid may affect the dentin caries process at the early phases of demineralization. Changes in collagen and noncollagenous protein structure may participate in observed decreases in mechanical properties of caries-affected dentin and reduce the ability of caries-affected dentin to remineralize. These endogenous enzymes also remain entrapped within the hybrid layer during the resin infiltration process, and the acidic bonding agents themselves (irrespective of whether they are etch-and-rinse or self-etch) can activate these endogenous protease proforms. Since resin impregnation is frequently incomplete, denuded collagen matrices associated with free water (which serves as a collagen cleavage reagent for these endogenous hydrolase enzymes) can be enzymatically disrupted, finally contributing to the degradation of the hybrid layer. There are multiple in vitro and in vivo reports showing that the longevity of the adhesive interface is increased when nonspecific enzyme-inhibiting strategies are used. Different chemicals (i.e., chlorhexidine, galardin, and benzalkonium chloride) or collagen cross-linker agents have been successfully employed as therapeutic primers in the bonding procedure. In addition, the incorporation of enzyme inhibitors (i.e., quaternary ammonium methacrylates) into the resin blends has been recently promoted. This review will describe MMP functions in caries and hybrid layer degradation and explore the potential therapeutic role of MMP inhibitors for the development of improved intervention strategies for MMP-related oral diseases.

Adjunctive application of chlorhexidine and ethanol-wet bonding on durability of bonds to sound and caries-affected dentine

OBJECTIVES

To examine the effect of adjunctive application of chlorhexidine (CHX) and ethanol-wet bonding (EWB) on bond durability and nanoleakage of hydrophobic adhesive to sound (SD) and caries-affected dentine (CAD).

METHODS

Dentine surfaces of molars were etched after caries removal and randomly allocated to four groups (n=12). In Groups 1 and 2, dentine surfaces were saturated with either 2 ml of 100% ethanol or 2 ml of ethanol with 2% CHX for 60s. In Groups 3 and 4, dentine surfaces were saturated with either 15 μL of distilled water or 15 μL of distilled water with 2% CHX for 60s. Two coats of primer, followed by neat resin were applied and light-cured for 40s. Resin composite build-ups were placed and bonded specimens were sectioned for bond strength testing after 24 h and 12 months' storage in artificial saliva. Bond strength data were analyzed using 3-way ANOVA and SNK tests. Interfacial nanoleakage was evaluated after 24 h and 12 months using a field-emission scanning electron microscopy and data were analyzed using Kruskal-Wallis test.

RESULTS

Significant differences were observed for the three factors: "substrate" (p<0.001), "rewetting agents" (p<0.001) and "time" (p<0.001) on bond strength. Incorporation of 2% CHX to EWB preserved bond strength to SD and CAD and reduced interfacial nanoleakage after 12 months. Incorporation of 2% CHX to WWB also preserved bond strength to SD after ageing.

CONCLUSIONS

Incorporation of chlorhexidine to ethanol-wet bonding has an interaction effect on preservation of bond durability to sound and caries-affected dentine.

CLINICAL SIGNIFICANCE

Incorporation of chlorhexidine to ethanol-wet bonding with hydrophobic adhesive enhances the success rate of aesthetic bonded restorations.

Comparison of vehicles to collect dentinal fluid for molecular analysis

OBJECTIVES

To test the hypothesis that a material with higher water absorption than polyvinylidene fluoride (PVDF) could increase the yield of target molecules from exposed dentine.

METHODS

In a series of standard tests, different cellulose membranes were compared to a PVDF counterpart for their ability to absorb water and release protein. In a subsequent randomized clinical trial, the cellulose material with the most favourable values was compared to PVDF regarding the levels of MMP-2 that could be collected from exposed dentine of healthy human teeth during filling replacement. MMP-2 levels were determined by enzyme-linked immunosorbent assay (ELISA). Data from the laboratory experiments were compared between materials using the appropriate parametric tests. The frequency of cases yielding quantifiable levels of MMP-2 was compared between materials by Fisher's exact test. The level of significance was set at 5%.

RESULTS

The cellulose membrane with the largest pore size (12-15μm) absorbed significantly (P<0.05) more water than PVDF. It showed a protein release that was similar to that of PVDF, while the cellulose membranes with smaller pore size retained significantly more protein (P<0.05). Using the large-pore cellulose membrane, MMP-2 could be collected at a quantifiable level from the dentine of healthy teeth in 9 of 13 cases, compared to 1 of 13 with the PVDF membrane (P<0.05).

CONCLUSIONS

Under the current conditions, a large-pore cellulose membrane yielded more of a molecule of diagnostic value compared to a standard PVDF membrane.

CLINICAL SIGNIFICANCE

Molecular diagnostics of dentinal fluid are hampered by low yields. In the current study, it was shown that cellulose membranes are more useful to collect MMP-2 from dentinal fluid than PVDF membranes.