Differential expression of matrix metalloproteinase-2 in human coronal and radicular sound and carious dentine

Role of Metalloproteinases in Adhesion to Radicular Dentin: A Literature Review

INTRODUCTION

Root dentin is a porous and complex dental surface that may have irregularities and deposits of organic material. To achieve an effective bond between restorative materials and root dentin, it is necessary that the restorative materials adhere intimately to the dentin surface. Metalloproteinases (MMPs) are a group of proteolytic enzymes that perform an important role in degrading the extracellular matrix and remodeling connective tissue. The aim of this research was to determine the scientific evidence available on the role played by MMPs in adhesion to root dentin and their putative inhibitors.

MATERIALS AND METHODS

Several techniques have been used to evaluate the presence of MMPs in the root dentin of human and bovine teeth, such as Western blot, immunohistochemistry, immunofluorescence, and zymography, the latter also being used together with the EnzCheck assay to evaluate the inhibitory effect of adhesion protocols on the activity of root MMPs in vitro.

RESULTS

When analyzing the databases, 236 articles were found, 12 of which met the selection criteria. The variables analyzed were articles that evaluated different MMP inhibitors in root dentin.

CONCLUSIONS

In the adhesion to radicular dentin, MMPs have a crucial role in the degradation of the extracellular matrix of dentin and the remodeling of the dentin surface because excessive MMP activity can be harmful to dental health, since excessive degradation of the extracellular matrix of dentin can weaken the tooth structure and decrease fracture resistance. Therefore, it is important to monitor MMP activity during root dentin bonding procedures.

Correlation between Matrix Metalloproteinase Presence and Caries Surface Appearance

INTRODUCTION

Cariogenic bacterial acids dissolve the inorganic elements in dentine, leaving the dentine matrix exposed. Host-derived matrix metalloproteinases (MMPs) play an essential role in caries progression as they are significant regulators of extracellular matrix turnover and can degrade exposed collagen. This paper investigates the expression of MMP2 and MMP9 across various stages of caries in primary human teeth and relate this with a diagnosis recorded by the International Caries Detection and Assessment System (ICDAS).

METHODS

Twenty-four sections (150 μm in thickness) from extracted teeth, clinically diagnosed using ICDAS, were immunohistochemically treated with monoclonal anti-MMP2 and anti-MMP9 antibodies. Positive staining was visualised by immunofluorescence using a VectorFluor Duet Double Labeling Kit. Images from triplicate samples for each ICDAS score were analysed using ImageJ software. Collagen degradation in caries lesions was detected using a hydroxyproline assay.

RESULTS

MMPs were weakly detected in caries with ICDAS 1-2 scores, and an insignificant increase was detected in ICDAS 3. However, a significant increase in MMP expression was seen in caries with an ICDAS score of 4-6. There was a strong positive correlation between the ICDAS score and MMP2 (r [6] = 0.86, p = 0.002) and between ICDAS and MMP9 (r [6] = 0.82, p = 0.004). Data were analysed using two-way ANOVA followed by Tukey multiple comparison test (*p < 0.05).

CONCLUSION

The use of ICDAS to assess the severity of caries lesions and how this correlates with the presence of MMP in these lesions validates the modern approach to caries management with a minimally invasive concept.

Dentine biomodification by sulphonamides pre-treatment: bond strength, proteolytic inhibition, and antimicrobial activity

We evaluated the effects of dentine biomodification after pre-treatment with two sulphonamide carbonic anhydrase inhibitors (CAIs) of the N-[4-sulphamoylphenethylcarbamoyl]benzenesulphonamide type, investigating matrix metalloproteases activity, resin-dentine micro tensile bond strength, dentine surface wettability, and antimicrobial activities. Ninety-five sound-extracted human molars were selected for the study. Inhibitory effects were evaluated by gelatinase and collagenase activity tests and collagen degradation FT-IR spectroscopic analysis. Pre-treatment with the two CAIs kept the micro tensile values after 12 months of storage (32.23 ± 5.95) and cariogenic challenge (34.13 ± 2.71) similar to the initial, pre-treatment values (33.56 ± 4.34). A decreased Streptococcus mutans biofilm formation on dentine surfaces and antibacterial activity against planktonic bacteria were observed after CAI treatment. Dentine pre-treatment with sulphonamide CAIs maintained adhesion strength stability, allowed better dentine wettability, maintained matrix collagen, and showed anti-S. mutans activity.

Presence of host and bacterial-derived collagenolytic proteases in carious dentin: a systematic review of ex vivo studies

Introduction and aim

The presence of host collagenases in the degradation of the protein matrix at later stages of carious dentin lesions development, as well as the potential involvement of bacterial collagenases, have been suggested but lack conclusive evidence. This study aims to conduct a systematic review to comprehensively assess the profile of host and bacterial-derived collagenolytic proteases in both root and coronal dentin carious lesions.

Methods

The search was performed in eight databases and the grey literature. Studies evaluating ex vivo dentin, extracted teeth, or biofilms from natural caries lesions were included. The methodological quality of studies was assessed using the Joanna Briggs Institute tool. Synthesis of the results and the certainty of evidence were performed following the Synthesis without Meta-analysis (SWiM) checklist and GRADE approach for narrative synthesis, respectively.

Results

From 935 recovered articles, 18 were included. Although the evidence was very uncertain, it was possible to suggest that 1) MMP-2, MMP-9, MMP-13, and CT-B may be increased in carious dentin when compared to sound dentin; 2) there is no difference in MMP-2 presence, while MMP-13 may be increased in root when compared to coronal carious dentin; 3) there is no difference of MMP-2 and MMP-9 expression/activity before and after cavity sealing; 4) MMP-8 may be increased in the dentin before cavity sealing compared to dentin after cavity sealing; 5) there is no difference of MMP-20 in irradiated vs. non-irradiated carious dentin. MMP-20 probably reduces in carious outer dentin when compared to carious inner dentin (moderate certainty). Genes encoding bacterial collagenolytic proteases and protein-degrading bacteria were detected in coronal and root carious lesions.

Conclusion

Trends in the direction of the effect were observed for some collagenolytic proteases in carious dentin, which may represent a potential target for the development of new treatments. (Protocol register-PROSPERO: CRD42020213141).

The Role of Bacterial, Dentinal, Salivary, and Neutrophil Degradative Activity in Caries Pathogenesis

Until recently, it was widely accepted that bacteria participate in caries pathogenesis mainly through carbohydrate fermentation and acid production, which promote the dissolution of tooth components. Neutrophils, on the other hand, were considered white blood cells with no role in caries pathogenesis. Nevertheless, current literature suggests that both bacteria and neutrophils, among other factors, possess direct degradative activity towards both dentinal collagen type-1 and/or methacrylate resin-based restoratives and adhesives, the most common dental restoratives. Neutrophils are abundant leukocytes in the gingival sulcus, where they can readily reach adjacent tooth roots or gingival and cervical restorations and execute their degradative activity. In this review, we present the latest literature evidence for bacterial, dentinal, salivary, and neutrophil degradative action that may induce primary caries, secondary caries, and restoration failure.

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.

Impact of tooth mineral tissues genes on dental caries: a birth-cohort study

OBJECTIVE

We aimed to investigate whether Single Nucleotide Polymorphisms present in the genes of tooth mineral tissues influence dental caries trajectory across the life course, and if there is an epistatic (gene-gene) interaction between these SNPs.

METHODS

A representative sample of all 5,914 births from the 1982 Pelotas birth cohort study was prospectively investigated. Dental caries trajectory across the life course was assessed at 15(n=888), 24(n=720), and 31 years old(n=539). Group-based trajectory modelling was used to identify distinct subgroups of individuals whose caries measurements followed a similar pattern over time. Genetic material was collected, and individuals were genotyped [rs4970957(TUFT1), rs1711437(MMP20), rs1784418(MMP20), rs2252070(MMP13), rs243847(MMP2), rs2303466(DLX3), rs11656951(DLX3), rs7501477(TIMP2), rs388286(BMP7), and rs5997096(TFIP11)]. Analyzes were performed for allele and genotype using logistic regression and generalized multifactor dimensionality reduction for epistatic interactions.

RESULTS

The analyses included 678 individuals, those with allele C (OR=0.74, CI95%[0.59-0.92]), genotype CC in the additive effect (OR=0.52, CI95%[0.31-0.89]), and the genotype TC/CC in dominant effect (OR=0.72, CI95%[0.53-0.98]) on the rs243847(MMP2) were associated with low caries trajectory. Individuals with the allele T (OR=0.79, CI95%[0.64-0.98]) and the genotype TC/CC in dominant effect (OR=0.66, CI95%[0.47-0.95]) on the rs5997096(TFIP11) were associated with low caries trajectory. Positive epistatic interactions were observed involving two (MMP2 and BMP7; p=0.006) and three (TUFT1, MMP2, and TFIP11; p<0.001) loci and high caries trajectory.

CONCLUSIONS

Some SNPs present in the genes of tooth mineral tissues were associated with caries trajectory and epistatic interactions increasing the network of SNPs involved in individual caries experience.

CLINICAL SIGNIFICANCE

Single nucleotide polymorphisms in the pathway of tooth mineral tissues genes may contribute significantly to the individual caries experience across the life course.

Determination and correlation of matrix metalloproteases profile and total antioxidant capacity in severe early childhood caries children - A randomized clinical trial

Background and Objective

Matrix metalloproteinases (MMPs) are a multigene family that belongs to the metalloproteinase class of endopeptides, responsible for the remodeling and degeneration of extracellular matrix molecules. MMPs are collectively called Matrixins are known to participate in tooth development and dentin-caries progression. Total antioxidant capacity (TAC) is the measure of the amount of free radicals scavenged by a test solution, being used to evaluate the antioxidant capacity of biological samples. Oxidative stress can affect the initiation and progression of many inflammatory and infectious diseases such as dental caries. Early childhood caries (ECC) is a serious public health problem that adversely affects children's physical and mental health.

Aim

The study aims to investigate and correlate the presence of MMPs and TAC in saliva of children with ECC.

Materials and Methods

The present study was done on 50 children aged 3-6 years with severe ECC. Unstimulated, whole saliva samples were collected and stored and all 50 samples were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis to determine MMPs and were subjected to spectrometry to assess the TAC of saliva. The samples with the presence of MMPs and increased TAC values were subjected to liquid chromatography-mass spectrometry to check the correlation of MMPs and TAC in ECC.

Results

TAC was 0.81 ± 0.14 mmol/l in the caries-active group and 0.15 ± 0.05 mmol/l in the caries-free group and was statistically significant at P < 0.001. MMP level in the caries-active group was 715.75 ± 102.42 μg/ml, whereas, in the caries-free group, it was 250.89 ± 86.51 μg/ml and was statistically significant at P < 0.001. The salivary MMP and TAC levels showed a significant positive moderate correlation with caries scores in the caries-active group and the finding was statistically significant at P < 0.001.

Conclusion

From our results, it can be concluded that the both MMPs and TAC levels were high in caries active group than in the caries-free group. The salivary MMPs showed a moderate positive correlation with TAC in the ECC group. In age-wise comparison, the mean MMP levels in the caries active group were higher in children between 3 and 4 years than in 5-6 years. In the caries-free group, the mean MMP level was similar in both the age groups.

Synergistic effect of collagen cross-linking and remineralization for improving resin-dentin bond durability

In this study, the synergistic effect of glutaraldehyde-cross-linking and remineralization on the strength and durability of resin-dentin bonds was investigated. Dentin surfaces were etched with 35% phosphoric acid. The control specimens were bonded with Adper Single Bond 2 using wet bonding without pretreatment. The experimental specimens were pretreated with 5% (v/v) glutaraldehyde solution for 3 min and placed in a remineralizing solution for 0, 12, and 24 h, followed by dry bonding. After performing composite build-ups on the specimens, they were longitudinally sectioned, immediately, and after aging for 3 h with sodium hypochlorite (NaOCl), to evaluate microtensile bond strength (µTBS). The cross-linked specimens exhibited µTBS values comparable with those of the control group, but the µTBS decreased significantly after NaOCl aging. The cross-linked dentin remineralized for 24 h exhibited an increase in µTBS. After aging in NaOCl, the µTBS of the specimens remineralized for 24 h did not decrease and was significantly higher than for the other experimental groups. Cross-linking with dry bonding maintained µTBS in specimens before aging in NaOCl, but the bonding durability was compromised. Remineralization of cross-linked dentin for 24 h followed by dry bonding increased the immediate µTBS and improved bond durability. Therefore, combining cross-linking with remineralization of collagen fibrils progressively increased resistance to degradation, improving bond durability.

Effects of protease inhibitors on dentin erosion: an in situ study

OBJECTIVE

This in situ study aimed to evaluate the effects of the inhibitors of matrix metalloproteinases (MMPs) and cysteine cathepsins on dentin erosion.

MATERIALS AND METHODS

Ten volunteers participated in this study. Each volunteer wore an intraoral appliance containing 4 dentin specimens subjected to different treatments: deionized water as a control, 1 mM 1,10-phenanthroline (an MMP inhibitor), 50 µM E-64 (a cysteine cathepsin inhibitor), and 1 mM 1,10-phenanthroline + 50 µM E-64. The specimens were dipped in 5 ml of the respective solutions for 30 min at room temperature and then exposed to in vivo erosive challenges by rinsing with 150 ml of a cola drink (4 × 5 min/day) for 7 days. The substance loss of the specimens was measured by profilometry. The transverse sections of the specimens were examined using scanning electron microscopy. Thereafter, the demineralized organic matrix (DOM) of the specimens was removed using type I collagen enzyme and assessed by performing profilometry. The differences in substance loss and DOM thickness among the groups were analyzed by one-way repeated-measures analysis of variance (ANOVA) and Bonferroni's test at a level of P < 0.05.

RESULTS

Protease inhibitors significantly reduced substance loss in comparison to that of the control group (all P < 0.05). A significantly thicker DOM was observed for the specimens treated with protease inhibitors than for the control specimens (all P < 0.05). No significant differences in substance loss or DOM thickness were found among the MMP inhibitor, cysteine cathepsin inhibitor, and MMP + cysteine cathepsin inhibitor groups.

CONCLUSIONS

The use of MMP and cysteine cathepsin inhibitors was shown to increase the acid resistance of human dentin, which may be due to the preservation of the DOM.

CLINICAL RELEVANCE

The application of protease inhibitors could be considered an appropriate preventive strategy for dentin erosion.

Dexamethasone and zinc loaded polymeric nanoparticles reinforce and remineralize coronal dentin. A morpho-histological and dynamic-biomechanical study

OBJECTIVE

To investigate the effect of novel polymeric nanoparticles (NPs) doped with dexamethasone (Dex) on viscoelasticity, crystallinity and ultra-nanostructure of the formed hydroxyapatite after NPs dentin infiltration.

METHODS

Undoped-NPs, Dex-doped NPs (Dex-NPs) and zinc-doped-Dex-NPs (Zn-Dex-NPs) were tested at dentin, after 24 h and 21 d. A control group without NPs was included. Coronal dentin surfaces were studied by nano-dynamic mechanical analysis measurements, atomic force microscopy, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05).

RESULTS

At 21 d of storage time, both groups doped with Dex exhibited the highest complex, storage and loss moduli among groups. Zn-Dex-NPs and Dex-NPs promoted the highest and lowest tan delta values, respectively. Dex-NPs contributed to increase the fibril diameters of dentin collagen over time. Dentin surfaces treated with Zn-Dex-NPs attained the lowest nano-roughness values, provoked the highest crystallinity, and produced the longest and shortest crystallite and grain size. These new crystals organized with randomly oriented lattices. Dex-NPs induced the highest microstrain. Crystalline and amorphous matter was present in the mineral precipitates of all groups, but Zn and Dex loaded NPs helped to increase crystallinity.

SIGNIFICANCE

Dentin treated with Zn-Dex-NPs improved crystallographic and atomic order, providing structural stability, high mechanical performance and tissue maturation. Amorphous content was also present, so high hydroxyapatite solubility, bioactivity and remineralizing activity due to the high ion-rich environment took place in the infiltrated dentin.

Effect of Endodontic Irrigating Solutions on Radicular Dentine Structure and Matrix Metalloproteinases-A Comprehensive Review

Irrigating solutions play an important role in the eradication of intracanal microbes and debris dissolution during endodontic treatment. Different combinations of solutions and protocols have been advocated, with sodium hypochlorite (NaOCl), ethylenediamine tetra acetic acid (EDTA), and chlorhexidine (CHX) remaining the most widely used ones by many clinicians. Although these solutions provide efficient inorganic dissolution and antimicrobial capacity, their use has also been reported to cause undesired effects on root dentin composition and mechanical and biomechanical properties, such as microhardness, surface roughness, bond strength, and matrix metalloproteinase (MMP) activity. Several corroborating studies attribute these changes in mechanical properties of dentine to the use of irrigating solutions, and there are limited reports on how the solutions affect the expression of MMPs, which may be a correlating link to understanding the role of these enzymes in dentin collagen and changes in the mechanical properties of dentin. Hence, using the basis of several studies from the literature, the objective is to comprehensively review the influence of individual and combined irrigating solutions on root dentine structure and the activity of the MMPs.

In Situ Zymography Analysis of Matrix Metalloproteinases Activity Following Endodontic Irrigation Protocols and Correlation to Root Dentine Bond Strength

The objective was to evaluate the effect of different root canal irrigating solutions on the activity of matrix metalloproteinases (MMPs), and correlation to the push-out bond strength (PBS) and nanoleakage expression (NL) in the root dentin. Seventy-two single-rooted teeth were treated endodontically and distributed into four groups (n = 6 for in-situ zymography, n = 10 for PBS, and n = 2 for NL per group) according to the irrigating solutions used: (I) saline (S); (II) 5.25% sodium hypochlorite (SH); (III) 5.25% SH + 10% citric acid (CA); and (IV) 5.25% SH + 10% CA + 0.2% chlorhexidine (CHX). After root canal obturation, post space was prepared to receive the glass fiber post. Dual-cure resin was used for luting and light polymerization was performed. The root/fiber post assemblies were sectioned and subjected to in situ zymography, and PBS and NL expression analysis tests. The enzymatic activity was quantified and expressed as a percentage of the green fluorescence, while fractographic evaluation was performed after PBS with a stereomicroscope, and data were statistically analyzed at p < 0.05. The zymography analysis shows high expression of MMPs in the middle third of the root in all groups, while the most abundant activity of MMPs following the irrigating solutions is observed in groups I and III, where saline and citric acid are used, respectively. Inversely, group IV, where chlorhexidine is the final rinse, records the lowest MMP activity with the highest PBS, and the statistical analysis of the groups are ranked as: IV > II > III > I (p < 0.05). The combination of SH, CA, and CHX results in lower expression of MMPs and higher push-out bond strength of fiber posts to root dentin, with no difference seen in the nanoleakage expression (p > 0.05); hence, this irrigation regime with chlorhexidine as a final rinse is more favorable than other combinations in ensuring optimal adhesion to root dentine.

Fluoride and trimetaphosphate association as a novel approach for remineralization and antiproteolytic activity in dentin tissue

OBJECTIVE

The study evaluated the effect of solutions containing fluoride (F) and/or sodium trimetaphosphate (TMP) and F/TMP on the inhibition of MMP-2 and MMP-9, and on dentin remineralization in vitro.

DESIGN

Bovine root dentin blocks were prepared, and caries-like lesions were induced in two thirds of the surface. Blocks were then randomly divided into 13 groups/solutions (n = 10): Placebo; 0.3 %, 1 % and 3 % NaOH-hydrolyzed TMP; 0.3 %, 1 % and 3 % TMP; 250, 500 and 1100 ppm F; 250 ppm F + 0.3 % TMP; 500 ppm F + 1 % TMP and 1100 ppm F + 3 % TMP. One third of each specimen was treated with the respective solutions in pH-cycling. The mineral concentration (g_HAp × cm^-3 × µm) was determined by computed X-ray microtomography, and data submitted to ANOVA and Student-Newman-Keuls' test (p < 0.05). The ability of the solutions to inhibit MMP-2 and MMP-9 activity was assessed by zymography.

RESULTS

F/TMP association led to less mineral loss in the deeper region of the lesion and reduced the depth of lesions when compared to its counterpart without TMP (p < 0.001). 3 % TMP (hydrolyzed or not), 500 ppm F and 1100 ppm F completely inhibited MMP-2 activity, while for MMP-9 such effects were only achieved by treatment with 1100 ppm F + 3 % TMP.

CONCLUSION

Treatment with 1100 ppm F + 3 % TMP fully inhibits the gelatinolytic activity of MMPs-2 and - 9 and shows greater remineralizing capacity in artificial caries lesions in dentin. However, hydrolyzing TMP does not improve its anti-proteolytic activity and its remineralizing capacity.

Zn-containing Adhesives Facilitate Collagen Protection and Remineralization at the Resin-Dentin Interface: A Narrative Review

This is a narrative review of the literature assessing the potential effectiveness of doping dentin polymeric adhesives with zinc compounds in order to improve bonding efficacy, remineralization and protection against degradation. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI and Web of Science. Through our search, we found literature demonstrating that Zn-doped dentin adhesives promote protection and remineralization of the resin-dentin interfaces. The increased bioactivity has also facilitated dentinal tubules' occlusion by crystals' precipitation contributing to improved sealing efficacy of restorations. Loading dentin adhesives with zinc gives rise to an increase of both crystallinity of mineral and crosslinking of collagen. The main role of zinc, in dentin adhesives, is to inhibit collagen proteolysis. We concluded that zinc exerts a protective effect through binding at the collagen-sensitive cleavage sites of matrix-metalloproteinases (MMPs), contributing to dentin matrix stabilization. Zinc may not only act as a MMPs inhibitor, but also influence signaling pathways and stimulate metabolic effects in dentin mineralization and remineralization processes. Zn-doped adhesives increase the longevity of dentin bonding through MMPs inhibition. Zn poses a remineralization strategy in demineralized dentin.

Clinical Evaluation of Pathognomonic Salivary Protease Fingerprinting for Oral Disease Diagnosis

Dental decay (Caries) and periodontal disease are globally prevalent diseases with significant clinical need for improved diagnosis. As mediators of dental disease-specific extracellular matrix degradation, proteases are promising analytes. We hypothesized that dysregulation of active proteases can be functionally linked to oral disease status and may be used for diagnosis. To address this, we examined a total of 52 patients with varying oral disease states, including healthy controls. Whole mouth saliva samples and caries biopsies were collected and subjected to analysis. Overall proteolytic and substrate specific activities were assessed using five multiplexed, fluorogenic peptides. Peptide cleavage was further described by inhibitors targeting matrix metalloproteases (MMPs) and cysteine, serine, calpain proteases (CSC). Proteolytic fingerprints, supported by supervised machine-learning analysis, were delineated by total proteolytic activity (PepE) and substrate preference combined with inhibition profiles. Caries and peridontitis showed increased enzymatic activities of MMPs with common (PepA) and divergent substrate cleavage patterns (PepE), suggesting different MMP contribution in particular disease states. Overall, sensitivity and specificity values of 84.6% and 90.0%, respectively, were attained. Thus, a combined analysis of protease derived individual and arrayed substrate cleavage rates in conjunction with inhibitor profiles may represent a sensitive and specific tool for oral disease detection.

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.

Zinc oxide and copper nanoparticles addition in universal adhesive systems improve interface stability on caries-affected dentin

This study evaluated the MMP inhibition of the zinc oxide and copper nanoparticles (ZnO/CuNp), and the effects of their addition into adhesives on antimicrobial activity (AMA), ultimate tensile strength (UTS), in vitro degree of conversion (in vitro-DC), as well as, resin-dentin bond strength (μTBS), nanoleakage (NL) and in situ-DC on caries-affected dentin. Anti-MMP activity was evaluated for several MMPs. ZnO/CuNp (0% [control]; 5/0.1 and 5/0.2 wt%) were added into Prime&Bond Active (PBA) and Ambar Universal (AMB). The AMA was evaluated against Streptococcus mutans. UTS were tested after 24 h and 28d. After induced caries, adhesives and composite were applied to flat dentin surfaces, and specimens were sectioned to obtain resin-dentin sticks. μTBS, NL, in vitro-DC and in situ-DC were evaluated after 24 h. ANOVA and Tukey's test were applied (α = 0.05). ZnO/CuNp demonstrated anti-MMP activity (p < 0.05). The addition of ZnO/CuNp increased AMA and UTS (AMB; p < 0.05). UTS for PBA, in vitro-DC, in situ-DC and μTBS for both adhesives were maintained with ZnO/CuNp (p > 0.05). However, lower NL was observed for ZnO/CuNp groups (p < 0.05). The addition of ZnO/CuNp in adhesives may be an alternative to provide antimicrobial, anti-MMP activities and improves the integrity of the hybrid layer on caries-affected dentin.

Modified Polymeric Nanoparticles Exert In Vitro Antimicrobial Activity Against Oral Bacteria

Polymeric nanoparticles were modified to exert antimicrobial activity against oral bacteria. Nanoparticles were loaded with calcium, zinc and doxycycline. Ions and doxycycline release were measured by inductively coupled plasma optical emission spectrometer and high performance liquid chromatography. Porphyromonas gingivalis, Lactobacillus lactis, Streptoccocus mutans, gordonii and sobrinus were grown and the number of bacteria was determined by optical density. Nanoparticles were suspended in phosphate-buffered saline (PBS) at 10, 1 and 0.1 mg/mL and incubated with 1.0 mL of each bacterial suspension for 3, 12, and 24 h. The bacterial viability was assessed by determining their ability to cleave the tetrazolium salt to a formazan dye. Data were analyzed by ANOVA and Scheffe’s F (p < 0.05). Doxycycline doping efficacy was 70%. A burst liberation effect was produced during the first 7 days. After 21 days, a sustained release above 6 µg/mL, was observed. Calcium and zinc liberation were about 1 and 0.02 µg/mL respectively. The most effective antibacterial material was found to be the Dox-Nanoparticles (60% to 99% reduction) followed by Ca-Nanoparticles or Zn-Nanoparticles (30% to 70% reduction) and finally the non-doped nanoparticles (7% to 35% reduction). P. gingivalis, S. mutans and L. lactis were the most susceptible bacteria, being S. gordonii and S. sobrinus the most resistant to the tested nanoparticles.

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.

Gene expression of bacterial collagenolytic proteases in root caries

Objective: It is unknown whether bacteria play a role in the collagen matrix degradation that occurs during caries progression. Our aim was to characterize the expression level of genes involved in bacterial collagenolytic proteases in root biofilms with and without caries. Method: we collected samples from active cavitated root caries lesions (RC, n = 30) and from sound root surfaces (SRS, n = 10). Total microbial RNA was isolated and cDNA sequenced on the Illumina Hi-Seq2500. Reads were mapped to 162 oral bacterial reference genomes. Genes encoding putative bacterial collagenolytic proteases were identified. Normalization and differential expression analysis was performed on all metatranscriptomes (FDR<10-3).

Result: Genes encoding collagenases were identified in 113 bacterial species the majority were peptidase U32. In RC, Streptococcus mutans and Veillonella parvula expressed the most collagenases. Organisms that overexpressed collagenolytic protease genes in RC (Log2FoldChange>8) but none in SRS were Pseudoramibacter alactolyticus [HMPREF0721_RS02020; HMPREF0721_RS04640], Scardovia inopinata [SCIP_RS02440] and Olsenella uli DSM7084 [OLSU_RS02990].

Conclusion: Our findings suggest that the U32 proteases may be related to carious dentine. The contribution of a small number of species to dentine degradation should be further investigated. These proteases may have potential in future biotechnological and medical applications, serving as targets for the development of therapeutic agents.

The effects of 2-hydroxyethyl methacrylate on matrix metalloproteinases 2 and 9 in human pulp cells and odontoblast-like cells in vitro

AIM

To assess the effects of 2-hydroxyethyl methacrylate (HEMA) on proliferation and migration of human pulp cells, as well as on matrix metalloproteinase (MMP-2 and MMP-9) expression in human odontoblast-like cells, contributing to the goal of determining the relationship between resin materials and MMP activity in pulp-dentine complexes.

METHODOLOGY

Dental pulp cell cultures were established from pulp tissue of human teeth extracted for orthodontic purposes. Pulp cell differentiation was characterized in the presence of dentine sialophosphoprotein, bone sialoprotein and alkaline phosphatase by reverse transcription polymerase chain reaction. MMP activity was assessed by gelatine zymography with media containing HEMA. Cell viability was evaluated using methyl thiazolyl tetrazolium assay for 24-72 h. Cell migration was tested using Transwell migration assay. Western blotting was used to visualize MMP expression with the nontoxic HEMA concentrations (0-400 μg mL^-1 ) for 48 h.

RESULTS

Pulp cell proliferation decreased with HEMA exposure in a time- and concentration-dependent manner. HEMA concentrations ≤400 μg mL^-1 did not induce changes in cell viability at 48 h (P < 0.05). Pulp cells were induced to differentiate into odontoblast-like cells in media containing 5 mg mL^-1 ascorbic acid and 10 mmol L^-1 β-sodium glycerophosphate for 3-4 weeks. After incubation with HEMA, dose-dependent inhibition was observed; HEMA had a strong inhibitory effect on MMP activity. Compared with the control group, cell migration and MMP expression were inhibited significantly with increasing HEMA concentration at noncytotoxic doses (P < 0.05).

CONCLUSIONS

Cell viability was not affected at HEMA concentrations ≤400 μg mL^-1 . Within this range, HEMA inhibited MMP-2 and MMP-9 expression and activity, which may protect against type I collagen degradation effectively during dentine adhesive procedures.

Degradation of resin-dentine bond of different adhesive systems to primary and permanent dentine

AIM

To evaluate the water storage degradation of resin-dentine bonds of different adhesive systems to primary and permanent human dentine.

METHODS

Flat occlusal human dentine surfaces of 15 primary molars and 15 permanent molars were randomly assigned according to adhesive systems: Adper Single Bond 2; Clearfil SE Bond and One Up Bond F Plus. After bonding procedures, the adhesives were applied according to the manufacturers' instructions and composite resin blocks were built. Restored teeth were sectioned rendering rectangular sticks (RS) (0.4 mm²). The RS were submitted to microtensile bond strength (µTBS) test according to the water storage time: 24 h, 1-year, and 2-years. Mean µTBS values were analysed by three-way analysis of variance (mixed design) and Tukey post hoc test (α = 0.05). The failure mode was analysed at 400× magnification.

RESULTS

All three factors isolated showed significant influences on µTBS, as did the cross-product interactions between material vs. storage time (p = 0.01) and substrate vs. storage time (p = 0.002). Bond strength means to primary dentine were lower than to permanent dentine (34.7 ± 10.1 and 45.8 ± 12.9 mPa, respectively) after 2-years of water storage. The one-step self-etch adhesive (One Up Bond F Plus) showed less stable bond strength after 2-years of water storage.

CONCLUSION

The resin-dentine bond of primary teeth was more prone to degradation over time compared to permanent dentine.

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.

Effect of sealing infected dentin with glass ionomer cement on the abundance and localization of MMP-2, MMP-8, and MMP-9 in young permanent molars in vivo

BACKGROUND

The study of MMPs' behavior in carious lesions contributes to the understanding of the mechanisms involved in dentin reorganization after restoration.

AIM

To compare the abundance and localization of MMPs 2, 8, and 9 in infected dentin before and after restoration.

DESIGN

The sample consisted of 23 young permanent molars with active deep carious lesions. Infected carious dentin samples were collected from the same tooth at baseline and 60 days after cavity lining with GIC and composite resin restoration and processed for immunohistochemistry assays. After digital images were obtained, two calibrated operators analyzed the samples according to the immunostaining intensity and the MMPs' localization. Chi-square test was used for statistical analysis.

RESULTS

The intensity of immunostaining for MMP-8 was reduced after 60 days (P = 0.02), and no difference was observed for MMP-2 (P = 0.32) and MMP-9 (P = 0.14). The MMPs' distribution was generalized in the intertubular dentin and absent or located in the intratubular dentin, regardless of the period.

CONCLUSION

The sealing of infected carious dentin in young permanent molars reduced the expression of MMP-8, which is consistent with the initial remodeling process of the dentin matrix.

Role of matrix metalloproteinases in dental caries, pulp and periapical inflammation: An overview

Matrix metalloproteinases (MMPs) are a group of more than 25 secreted and membrane bound enzymes that represent class of enzymes responsible for degradation of pericellular substrates. They have been isolated from dentine, odontoblasts, pulp and periapical tissue. They play an important role in dentine matrix formation, modulating caries progression and secondary dentine formation. Earlier microbial proteolytic enzymes were believed to be responsible for degradation of dentine organic matrix, but lately the accumulated body of evidence suggests that MMPs have an important role in the process. During normal tissue modelling, differentiation during development, in modulating the cell behaviour, maintaining homeostasis and in numerous extracellular pathologic conditions, MMPs tends to be an equally important participant. Odontoblasts secrete some of the essential MMPs for both physiologic and pathologic conditions. MMPs also appear to be a participant in the process of reversible and irreversible pulpitis. Although they tend to have low expression and activity in adult tissues but at the onset of any destructive pathologic process, their production shoots up. They appear to have a significant presence during times of inflammation in the periapical region as well. We take a look at the various factors and evidence pointing towards the role of MMPs in the progression of caries, pulpal and periapical inflammation.

Effect of ultraviolet A-induced crosslinking on dentin collagen matrix

OBJECTIVES

The aim of this study was to evaluate the effect of using UVA-induced crosslinking with or without riboflavin as photosensitizers on degradation of dentin matrix by dentin proteases.

METHODS

Demineralized dentin specimens (0.4×3×6 mm(3), n=10/group) were subjected to: (RP1), 0.1% riboflavin-5 phosphate/UVA for 1 min; (RP5), 0.1% riboflavin-5 phosphate/UVA for 5 min; (R1), 0.1% riboflavin/UVA for 1 min; (R5), 0.1% riboflavin-UVA for 5 min; (UV1), UVA for 1 min; (UV5), UVA for 5 min. Specimens were incubated in 1 mL zinc and calcium containing media for 1 day and 1 week. An untreated group served as control (CM). After incubation, the loss of dry mass of samples was measured and aliquots of media were analyzed for the release of C-terminal fragment telopeptide (ICTP vs. CTX) of collagen to evaluate for cathepsin K (CA-K) and total matrix metalloproteinase (MMP)-mediated degradation. Data were analyzed using repeated measures ANOVA at α=0.05.

RESULTS

Although UVA radiation alone reduced dentin degradation, UVA-activated riboflavin or riboflavin-5 phosphate inhibited MMP and CA-K activities more than UVA alone. The effects of crosslinking were more pronounced in 7-day samples; only with CA-K were the effects of crosslinking with or without photosensitizer significantly different from controls in 1-day samples.

SIGNIFICANCE

The use of bioactive forms (RP) or longer treatment time did not result with better effect. The use of UVA crosslinking reduces dentin matrix degradation, especially with photosensitizers.

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.

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.

Influence of metalloproteinases on dentin hybridization of one-bottle or self-etch dental bonding systems

AIM

To assess the influence of dentin substrate and chlorhexidine on the marginal seal of composite resin restorations.

MATERIALS AND METHODS

The sample comprised 20 third molars. Four cavities were drilled in the dentin sur face, followed by sealing and restoration of sound dentin (n = 10) or carious dentin (n = 10). In the control group, cavities were immediately restored as follows: G1: one-bottle bonding agent (OB) + composite resin (CR); G2: chlorhexidine 2.0% (CLX) + OB + CR; G3: self-etch bonding agent (SE) + CR; G4: CLX + SE + CR. In the experimental group (carious dentin), carious lesions were induced with S. mutans and cavities were restored as in the control group. Five specimens from each group (sound and carious) were stored in brain-heart infusion (BHI) medium for 6 months. All specimens were submerged in methylene blue 0.5% to test for microleakage. The Kruskal-Wallis and Student-Newman-Keuls tests were used to assess results.

RESULTS

On immediate assessment, there were no significant between-group differences in the sound dentin group, whereas in carious dentin, there was less leakage when OB and CLX were used. At 6 months, there was less leakage in the sound dentin group when OB and CLX were used; there were no between-group differences in carious dentin. Comparison of immediate and 6-month assessments showed a significant increase in leakage at 6 months when sound dentin was treated with SE and CLX and when carious dentin was treated with OB and CLX.

CONCLUSION

To ensure better dentin hybridization and preservation of the organic constituents of the dentin matrix, the properties of chlorhexidine digluconate and the components of the resin matrix must be taken into account.

CLINICAL SIGNIFICANCE

Metalloproteinases influence degradation of the hybrid layer in composite resin restorations, regardless of whether the bonding system used is one-bottle or self-etching.

Masticatory function induced changes, at subnanostructural level, in proteins and mineral at the resin-dentine interface

OBJECTIVE

This study evaluated the ability of different in vitro mechanical loading tests to promote new mineral formation at the bonded dentine interfaces created with a two-step self-etching resin adhesive.

METHODOLOGY

Restored teeth were divided in the following groups: (1) unloaded, load cycling with (2) sine waveform, (3) square waveform, and hold waveform for (4) 24h, and (5) 72 h. Raman spectroscopy and cluster analysis were used to assess the resin-dentine interface.

RESULTS

Mechanical loading in CSEB-treated samples promoted a generalized increase of relative presence of minerals and ratio of phosphate peaks, except in square waveform, where the nature of collagen resulted damaged. Crystallinity of carbonate was higher than phosphate. The organic component showed, in general terms, an increase in crosslinking. Molecular orientation (α-helices) peaks augmented in all tests. Pentosidine vibration increases in all tests, except in hold 72 h. Ratios amide I and II/CH2 incremented, in general. Non uniform parameters of Bis-GMA and adhesive penetration were encountered, as both increased at the bottom of the hybrid layer when loading square and hold 72 h were applied.

SIGNIFICANCE

Functional remineralisation at the resin-dentine interface was attained after in vitro mechanical stimuli application. When loading in square waveform, the lowest vibrations to favor remineralisation were attained.

Transdentinal cytotoxicity of carbodiimide (EDC) and glutaraldehyde on odontoblast-like cells

OBJECTIVE

To evaluate the transdentinal cytotoxicity of three different concentrations of carbodiimide (EDC) or 5% glutaraldehyde (GA) on MDPC-23 cells.

METHODS

Seventy 0.4-mm-thick dentin disks obtained from human molars were adapted to artificial pulp chambers. MDPC-23 cells were seeded on the pulpal surface of the disks. After 48 hours, the occlusal dentin was acid-etched and treated for 60 seconds with one of the following solutions (n=10): no treatment (negative control); 0.1 M, 0.3 M, or 0.5 M EDC; 5% GA; Sorensen buffer; or 29% hydrogen peroxide (positive control). Cell viability and morphology were assessed by methyltetrazolium assay and scanning electron microscopy (SEM), respectively. The eluates were collected after the treatments and applied on MDPC-23 seeded in a 24-well plate to analyze cell death, total protein (TP), and collagen production. The last two tests were performed 24 hours and seven days after the challenge. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (p<0.05).

RESULTS

EDC at all test concentrations did not reduce cell viability, while 5% GA did increase cell metabolism. Cell death by necrosis was not elicited by EDC or 5% GA. At the 24-hour period, 0.3 M and 0.5 M EDC reduced TP production by 18% and 36.8%, respectively. At seven days, increased TP production was observed in all groups. Collagen production at the 24-hour period was reduced when 0.5 M EDC was used. After seven days, no difference was observed among the groups. SEM showed no alteration in cell morphology or number, except in the hydrogen peroxide group.

CONCLUSIONS

Treatment of acid-etched dentin with EDC or GA did not cause transdentinal cytotoxic effects on odontoblast-like cells.

Caries: review of human genetics research

The NIH Consensus Development Program released a statement in 2001 (http://consensus.nih.gov/2001/2001DentalCaries115html.htm) and listed six major clinical caries research directions. One of these directions was the need for genetic studies to identify genes and genetic markers of diagnostic, prognostic and therapeutic value. This last decade has seen a steep increase in studies investigating the presence of genetic factors influencing individual susceptibility to caries. This review revisits recent caries human genetic studies and provides a perspective for future studies in order to fulfil their promise of revolutionizing our understanding of and the standard of care for the most prevalent bacteria-mediated non-contagious disease in the world.

Immunohistochemical analysis of matrix metalloproteinase-13 in human caries dentin

The immunoexpression profile of matrix metalloproteinase-13 was investigated for the first time in dentin of human caries and healthy teeth. Twelve permanent premolars (10 caries and 2 sound) were decalcified in ethylenediaminetetraacetic acid and processed for embedding in paraffin wax. Sections 3-4 µm in thickness were cut and processed for immunohistochemistry. A mouse monoclonal anti-metalloproteinase-13 antibody was used for localisation using an immunoperoxidase technique. Dentinal immunoreactivity was detected in all teeth; it was weak in sound teeth and strong close to the caries area. These in vivo findings suggest a role for metalloproteinase-13 in the development and progression of adult human dental tissue disorders.

Pre-treatment of radicular dentin by self-etch primer containing chlorhexidine can improve fiber post bond durability

We evaluated whether the pre-treatment of radicular dentin by ED Primer containing different concentrations of chlorhexidine can improve the bond durability of fiber post to radicular dentin. Experimental ED primers containing different concentrations of chlorhexidine (0%, 0.5% and 1.0%) were prepared. Thirty extracted maxillary anterior teeth were divided into 3 groups, each group corresponding to different chlorhexidine concentrations. Fiber posts were cemented in endodontically treated teeth with experimental ED primers and Panavia F. The bonded teeth were transversally sectioned into six slices and then were processed for thin slice push-out test 24 h later or after 18-months water storage. Eighteen-month storage resulted in significant bond strength reduction of all groups (p<0.05). The bond strength reduction of 1.0% group was significantly lower than that of control group and 0.5% group (p<0.05). In conclusion, the incorporation of 1.0% chlorhexidine into ED primer can extend the bond longevity of fiber post to radicular dentin.

Subclinical concentrations of chlorhexidine inhibit gelatinase activity of carious dentine in vitro

BACKGROUND

There is evidence that dentine matrix gelatinases are involved in the destruction of carious dentine after demineralization by bacterial acids. It has also been observed that chlorhexidine, in very low concentrations, inhibits the activity of these enzymes in mammalian cells. The goal of this study was to determine if the gelatinase activity of carious dentine may be inhibited by chlorhexidine in clinical use concentrations.

METHODS

Gelatinolytic activity was evaluated through zymography and identified by Western blot. The inhibitory effects of chlorhexidine at concentrations of 0.01%, 0.04%, 0.08% and 1% on the enzymatic activity of softened carious dentine samples were determined.

RESULTS

In carious dentine, five bands of gelatinolytic activity were detected, with molecular sizes of 86, 75, 38, 33 and 32 kDa. The two bands of the greatest molecular size corresponded to latent and active metalloproteinase-9, respectively. Concentrations of chlorhexidine that were greater than or equal to 0.04% were sufficient to inhibit gelatinolytic activity in the observed bands of carious dentine.

CONCLUSIONS

These results support the use of chlorhexidine in clinical use concentrations for the treatment and control of dentine caries. Our study demonstrates for the first time the inhibitory effect of chlorhexidine on gelatinases from carious human dentine.

Dentin matrix degradation by host matrix metalloproteinases: inhibition and clinical perspectives toward regeneration

Bacterial enzymes have long been considered solely accountable for the degradation of the dentin matrix during the carious process. However, the emerging literature suggests that host-derived enzymes, and in particular the matrix metalloproteinases (MMPs) contained in dentin and saliva can play a major role in this process by their ability to degrade the dentin matrix from within. These findings are important since they open new therapeutic options for caries prevention and treatment. The possibility of using MMP inhibitors to interfere with dentin caries progression is discussed. Furthermore, the potential release of bioactive peptides by the enzymatic cleavage of dentin matrix proteins by MMPs during the carious process is discussed. These peptides, once identified, may constitute promising therapeutical tools for tooth and bone regeneration.

Multi-dimensional prioritization of dental caries candidate genes and its enriched dense network modules

A number of genetic studies have suggested numerous susceptibility genes for dental caries over the past decade with few definite conclusions. The rapid accumulation of relevant information, along with the complex architecture of the disease, provides a challenging but also unique opportunity to review and integrate the heterogeneous data for follow-up validation and exploration. In this study, we collected and curated candidate genes from four major categories: association studies, linkage scans, gene expression analyses, and literature mining. Candidate genes were prioritized according to the magnitude of evidence related to dental caries. We then searched for dense modules enriched with the prioritized candidate genes through their protein-protein interactions (PPIs). We identified 23 modules comprising of 53 genes. Functional analyses of these 53 genes revealed three major clusters: cytokine network relevant genes, matrix metalloproteinases (MMPs) family, and transforming growth factor-beta (TGF-β) family, all of which have been previously implicated to play important roles in tooth development and carious lesions. Through our extensive data collection and an integrative application of gene prioritization and PPI network analyses, we built a dental caries-specific sub-network for the first time. Our study provided insights into the molecular mechanisms underlying dental caries. The framework we proposed in this work can be applied to other complex diseases.

Optimizing dentin bond durability: control of collagen degradation by matrix metalloproteinases and cysteine cathepsins

OBJECTIVES

Contemporary adhesives lose their bond strength to dentin regardless of the bonding system used. This loss relates to the hydrolysis of collagen matrix of the hybrid layers. The preservation of the collagen matrix integrity is a key issue in the attempts to improve the dentin bonding durability.

METHODS

Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface.

RESULTS

The identities, roles and function of collagenolytic enzymes in mineralized dentin has been gathered only within last 15 years, but they have already been demonstrated to have an important role in dental hard tissue pathologies, including the degradation of the hybrid layer. Identifying responsible enzymes facilitates the development of new, more efficient methods to improve the stability of dentin-adhesive bond and durability of bond strength.

SIGNIFICANCE

Understanding the nature and role of proteolytic degradation of dentin-adhesive interfaces has improved immensely and has practically grown to a scientific field of its own within only 10 years, holding excellent promise that stable resin-dentin bonds will be routinely available in a daily clinical setting already in a near future.

MMP13 polymorphism decreases risk for dental caries

Recent evidence suggests that genetic studies may contribute to a better understanding of individual susceptibility to caries. Matrix metalloproteinases (MMPs) and their tissue inhibitors have been suggested to be involved in the caries process. The purpose of this study was to determine if polymorphisms in MMP2 (rs243865), MMP9 (rs17576), MMP13 (rs2252070), and TIMP2 (rs7501477) were associated with caries. Eligible unrelated children and adolescents were evaluated using a cross-sectional design. Data on oral health habits was obtained through a questionnaire and caries data was collected by clinical examination. Genotyping of the selected polymorphisms was carried out by real-time PCR. Allele and genotype frequencies were compared between individuals with and without caries experience. Of 505 subjects, 212 were caries-free and most subjects (61.2%) had mixed dentition. Allele frequency of MMP2, MMP13 and TIMP2 was different between caries-affected and caries-free individuals, with significant association for MMP13 (p = 0.004). Mutant allele carriers for MMP13 demonstrated a significantly decreased risk for caries (OR = 0.538, 95% CI 0.313-0.926); this result remained significant after adjustment for candidate genes, type of dentition and dietary factors. Allelic and genotype frequencies of the polymorphism in MMP9 were similar in caries-affected and caries-free individuals. Genetic variations in MMP13 may contribute to individual differences in caries susceptibility. Our findings reinforce that susceptibility to caries results from gene-environment interactions.