Human Dentin Research Articles

Demineralized human dentin matrix for alveolar ridge preservation using a volumetric and histologic analyses in rats.

The aim of this study was to evaluate a Demineralized Human Dentine Matrix (DHDM) as viable biomaterial for alveolar ridge preservation in a rat model. Wistar rats were submitted to the extraction of maxillary first molars bilaterally. Sockets were filled with biomaterials and divided into 4 experimental groups (n=5): blood clot, autogenous bone, bovine-derived xenograft (BDX) and DHDM. Animals were sacrificed at 7, 14 e 28 days. Microtomography (uCT) volumetric evaluation and qualitative histological analyses were performed. Results obtained through the uCT showed similar values between the DHDM and the other experimental groups. The histological evaluation demonstrated DHDM with an unspecific inflammatory process and bone neoformation with slow reabsorption of the material. This result indicates that DHDM implanted in rat sockets is biocompatible and reduces the alveolar ridge volume loss after tooth extraction.

Thermal Conductivity and Diffusivity of Human Enamel and Dentin Measured by the Laser Flash Method

Thermal Conductivity and Diffusivity of Human Enamel and Dentin Measured by the Laser Flash Method

Impact of deproteinization methods on the physical and mechanical properties of dentin

This study was performed to evaluate the effects of thermal and chemical deproteinization methods on the microhardness and mineral phases of human dentin. Forty extracted non-carious human premolars were cut from below the cementoenamel junction to prepare 5 mm-thick dentin slices, and then randomly divided into four groups of 10 in each according to the treatments. Group A: thermal treatment (300 °C, rate of 30 °C /min for 10 min); Group B: 50 ml of 1N NaOH; Group C: 50 ml of 30% H2O2, at 37 °C for 7 days; Group D: control. Dry ash was obtained to measure the mass loss of organic content. The microhardness value (MHV) of the exposed root dentin was tested with a Vickers microhardness tester. The structure of the residual dentin mineral was examined using a SEM. Crystallinity was assessed by X-ray diffraction spectroscopy. Data were analyzed with one-way ANOVA and Post Hoc Tukey tests. In the comparison of microhardness values between heat, NaOH, H2O2, and control groups, significant differences were noticed between groups (P < 0.05). Since the organic component was largely removed, it can be seen that the main influence on the hardness of dentin could be the inorganic component rather than the protein content. Thermal treatment was able to completely deproteinize human dentin without significant effects on its physical and mechanical properties, while chemical deproteinization significantly changed the mechanical properties and crystallography of human dentin (P < 0.05).

Dentin Particulate for Bone Regeneration: An In Vitro Study.

The aim of this in vitro study was to investigate the commitment and behavior of dental pulp stem cells (DPSCs) seeded onto two different grafting materials, human dentin particulate (DP) and deproteinized bovine bone matrix (BG), with those cultured in the absence of supplements. Gene expression analyses along with epigenetic and morphological tests were carried out to examine odontogenic and osteogenic differentiation and cell proliferation. Compressive testing of the grafting materials seeded with DPSCs was performed as well. DPSC differentiation into odontoblast-like cells was identified from the upregulation of odontogenic markers (DSPP and MSX) and osteogenic markers (RUNX2, alkaline phosphatase, osteonectin, osteocalcin, collagen type I, bmp2, smad5/8). Epigenetic tests confirmed the presence of miRNAs involved in odontogenic or osteogenic commitment of DPSCs cultured for up to 21 days on DP. Compressive strength values obtained from extracellular matrix (ECM) synthesized by DPSCs showed a trend of being higher when seeded onto DP than onto BG. High expression of VEGF factor, which is related to angiogenesis, and of dentin sialoprotein was observed only in the presence of DP. Morphological analyses confirmed the typical phenotype of adult odontoblasts. In conclusion, the odontogenic and osteogenic commitment of DPSCs and their respective functions can be achieved on DP, which enables exceptional dentin and bone regeneration.

Current strategies for biomimetic remineralization of human dentin: a scoping review

The purpose of this scoping review was to present the published successful techniques and strategies for biomimetic remineralization of human dentin. Studies whose primary objective was to present the strategy of successful dentin biomimetic remineralization were included. No language, participant age, or time restrictions were set. Stud-ies were retrieved via CENTRAL, LILACS, PubMed/MEDLINE, SciELO, SCOPUS and Web of Science. Gray literature searches on Google Scholar and OpenGrey were also conducted to find additional references. Based on the main research objectives, articles were classified by technique according to the methodology used for the research. One hundred forty-five articles, published be-tween 2003 and 2019, were included in the final scoping review. Protocols that imitate dentin's natural mineralization seek to restore lost minerals in dental tissues. Biomimetic remineralization proposes different ways to replace demineralized collagen in dentin by using inorganic materials like natural minerals, with the primary purpose of optimizing the clinical longevity of restorations and improving dental treatment.

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

This in situ study aimed to evaluate the effects of the inhibitors of matrix metalloproteinases (MMPs) and cysteine cathepsins on dentin erosion. 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, 1mM 1,10-phenanthroline (an MMP inhibitor), 50µM E-64 (a cysteine cathepsin inhibitor), and 1mM 1,10-phenanthroline + 50µM E-64. The specimens were dipped in 5ml of the respective solutions for 30min at room temperature and then exposed to in vivo erosive challenges by rinsing with 150ml of a cola drink (4 × 5min/day) for 7days. 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. 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. 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. The application of protease inhibitors could be considered an appropriate preventive strategy for dentin erosion.

Dental Age Estimation Using Multiphoton Microscopy: A Potential Tool for Forensic Science.

Normal aging affects the different structures of teeth, in particular, the dentine. These changes are useful in forensic disciplines as a tool for age estimation. Although multiphoton (MP) microscopy has been used to explore dental pieces, a relationship between age and MP response of the human dentine has not been proposed yet. The relationship between MP signals and natural dentine aging is investigated herein. An index of age (INAG) combining two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) images has been used to quantify these changes. The results show that the INAG significantly decreases with age. Moreover, peritubular dentine size and collagen internal properties are also modified with age. This information confirms the usefulness of this technique in forensic age estimation after disasters (natural or manmade) with a lack of comprehensive fingerprint database. Courts and other government authorities might also benefit from this tool when the official age of individuals under special circumstances is required for legal or medical reasons.

Collagen-depletion strategies in dentin as alternatives to the hybrid layer concept and their effect on bond strength: a systematic review

Strategies aiming to improve the longevity of resin–dentin adhesive interface developed so far have only been able to retard the problem. Different approaches are thus needed. The objective of this review was to determine whether the use of collagen-depletion strategies after acid-etching procedures may improve the bond strength of resin-based materials to dentin. A systematic review was planned following 2021 PRISMA statement guidelines, with a search strategy performed in five electronic databases: PubMed/Medline, Scopus, EMBASE, SciELO and IADR Archive (last search: 17/01/2022). Inclusion criteria encompassed studies which evaluated a collagen-depletion strategy in acid-etched human dentin and tensile/shear bond strength tests. Risk of bias assessment was carried out by two reviewers, working independently on an adapted five-domain risk of bias (RoB) checklist for laboratory studies. Results were synthesized qualitatively, as a meta-analysis was not possible due to limited number of studies and their RoB. A total of eight studies were eligible for inclusion in the systematic review after inclusion/exclusion criteria application. Out of these, two evaluated the effect of using NaOCl followed by an antioxidant, and the remaining six evaluated different enzymatic treatments (bromelain, chondroitinase ABC, papain, and trypsin). None of the studies reported a decrease of bond strength when a collagen-depletion strategy was used, in comparison to traditional hybrid layers (control). All enzymatic treatment studies which respected the inclusion criteria improved the bond strength to dentin. Some specific collagen-depletion strategies seem to play a favorable role in improving immediate bond strengths to dentin. Further research with sound methodology is required to consolidate these findings, since limitations in RoB and a low number of studies were found. The assessment of further proteolytic agents and long-term outcomes is also required.

Synthesis and performance of experimental resin-based dental adhesives reinforced with functionalized graphene and hydroxyapatite fillers

Functionalized graphene and hydroxyapatite fillers are proposed as reinforcing particles in light-cured adhesives for dental applications. Silica-silver-graphene (SiO2-Ag-Gr), silver-doped hydroxyapatite (HA-Ag), graphene and silver doped hydroxyapatite (HA-Ag-Gr), and regular silica (SiO2) as inorganic powders, together with bis-GMA (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) oligomers, as main components of the organic matrix, were synthesized. Light field transmission electron microscopy and electron diffraction proved the successful synthesis of the powders. The experimental adhesives showed a positive influence on local biocompatibility up to 6 months in an in-vitro simulation of clinically relevant environmental conditions and aging. Bonding to human dentin reveal a particular fracture pattern with preferential adhesion to the restorative material in contrast to the gold standard adhesive used as reference, which adheres preferentially to the tooth structure. Bond strength was slightly lower, initial bond reliability slightly improved, and the morphology of interaction with tooth structure similar to the reference. Functionalized graphene and hydroxyapatite fillers in dental adhesives have demonstrated their potential for use in dental applications.

Induction of Cartilage Regeneration by Nanoparticles Loaded with Dentin Matrix Extracted Proteins.

Due to the limited self-repair capacity of articular cartilage, tissue engineering has good application prospects for cartilage regeneration. Dentin contains several key growth factors involved in cartilage regeneration. However, it remains unknown whether dentin matrix extracted proteins (DMEP) can be utilized as a complex growth factor mixture to induce cartilage regeneration. In this work, we extracted DMEP from human dentin and improved the content and activity of chondrogenic-related growth factors in DMEP by alkaline conditioning. Afterward, mesoporous silica nanoparticles (MSNs) with particular physical and chemical properties were composed to selectively load and sustain the release of proteins in DMEP. MSN-DMEP promoted chondrogenic differentiation of rat bone marrow-derived mesenchymal stem cells with fewer growth factors than exogenously added transforming growth factor-β1 (TGF-β1). Therefore, MSN-DMEP may serve as a promising candidate for cartilage regeneration as an alternative to expensive synthetic growth factors. Impact statement Several growth factors embedded in dentin matrix could be involved in cartilage regeneration. This article reports that alkaline conditioning could improve the content and activity of chondrogenic-related growth factors in dentin matrix extracted proteins (DMEP). Mesoporous silica nanoparticles (MSNs) with particular physical and chemical properties performed well in loading and sustained releasing of proteins in DMEP. In vitro and in vivo studies suggest that MSN-DMEP could be a promising candidate for cartilage regeneration as an alternative to expensive synthetic growth factors.

Experimental pastes containing niobophosphate and 45S5 bioactive glasses for treatment of dentin hypersensitivity: dentin permeability and tubule obliteration.

This study tested the ability of bioactive pastes containing niobophosphate and 45S5 glasses to reduce dentin permeability and to obliterate dentinal tubules, as a mean of reducing human dentin hypersensitivity. Experimental pastes with concentrations of 10, 20, and 30 wt% of two bioactive glasses (45S5 or niobophosphate [NbG]) were formulated. A paste without bioactive glass (placebo) and a commercial paste (Nano P, FGM) were used as controls. Forty dentin disc specimens were obtained from caries-free extracted third human molars and divided in 8 groups (n = 5). Percentage of permeability (%Lp) was assessed in a dental permeability machine considering hydraulic conductance, immediately after pastes application and at day 7, day 14, and day 21. The precipitates formed on the surface of the dentin discs (and dentinal tubules) were analyzed by SEM/EDS and micro-Raman spectra. Data of dentin permeability (%) 2-way repeated-measures (ANOVA) and Holm-Sidak post-tests (α = 0.05). Dentinal tubule obliteration was visually (and elemental) evaluated and descriptively reported. The experimental bioactive glass pastes containing NbG and 45S5, regardless of the concentration, reduced dentin permeability in comparison with pastes without bioactive glasses (P < 0.05). The formulated placebo and commercial paste did not reduce permeability over time (P < 0.05). SEM/EDS and micro-Raman analyses showed that both type of bioactive pastes (NbG or 45S5-based) presented mineral precipitates obliterating the dentinal tubules at day 21. NbG seems to offer a better initial effect than 45S5, while at 21 days there is no difference between both glasses. Experimental bioactive pastes containing NbG and 45S5 (at concentrations of 10%, 20%, or 30%) have potential to reduce dentin permeability (over time) in comparison with pastes without bioactive glasses; and this occurs on behalf of obliteration of dentinal tubules by microparticle and precipitate formation. Bioactive pastes containing NbG and 45S5 may benefit patients presenting dentin hypersensitivity, because these pastes can start acting fast after application and maintain their action up to 21 days.

Clinical application of autogenous tooth as bone graft material in extraction socket- A prospective study

IntroductionAmong the different graft materials used in dental clinics, autogenous bone is the most ideal. However, its biggest short coming is that the amount invested is limited, resorption is unavoidable and a secondary defect is generated at the donor site. Extracted tooth has been discarded as infective medical dust. So, the present study was aimed to evaluate the efficacy of autogenous tooth as graft material in the extraction socket of third molar region. Materials and methodA split mouth study design was undertaken. 20 patients requiring extraction of bilateral mandibular third molars were included in the study. This study was carried out in third molar region. Group A: PRF membrane was placed in the third molar extraction socket. Group B: Autogenous tooth processed into bone graft was used in the third molar extraction socket, over which PRF membrane was placed. Postoperative pain and bone healing were assessed in the post-operative follow-up visits. ResultsWe observed that Group B showed significantly faster bone healing as compared to Group A, in terms of overall density and trabecular pattern of bone at the end of 3 months and 6 months following extraction. ConclusionThis study clearly indicates that autogenous tooth used as bone graft material showed improved bone healing at the third molar extraction sockets. This study emphasis on use of human dentin as graft material as it was simple, cost effective, required no special armamentarium and infrastructure for preparation and even did not require additional donor site.

Antimicrobial effects of agitational irrigation on single- and multispecies biofilms in dentin canals.

This study aimed to compare the antibacterial effects of different agitation devices on single- and multispecies biofilms in dentin canals using confocal laser scanning microscopy (CLSM). Dentin blocks were prepared from human root dentin. Enterococcus faecalis and multiple species were introduced into the dentinal tubules via centrifugation and incubation. Two infected dentin samples were placed at 8 and 16mm in a customized model. Samples were randomly divided into eight groups according to the agitation device used: syringe needle irrigation, EndoActivator, passive ultrasonic irrigation (PUI), and EDDY, at 2.5% or 6% NaOCl concentrations. The samples were stained and observed using CLSM. Statistical analysis was performed using an independent sample t test and analysis of variance. Linear models were used to assess the joint impact of the experimental groups on the proportion of biofilms killed. No significant differences were observed between the killing rates of the single- and multispecies biofilms. Both concentrations of NaOCl significantly increased the percentage of dead bacteria compared with the control. Biofilms in dentin tubules was more effectively killed when NaOCl was agitated; however, the difference between PUI and EDDY was not significant. Significantly more bacteria were killed in dentin blocks placed at 8mm than at 16mm (p < 0.05). In conclusion, EDDY was as effective as PUI when combined with NaOCl. However, the apical portion, which had a low antimicrobial efficiency, remains a concern. Mechanical instrumentation is incapable of completely eradicating bacteria, and additional research is required to improve the efficacy of root canal disinfection.

Growth factor release and dental pulp stem cell attachment following dentine conditioning: An in vitro study.

AimThe aim of the study was to investigate the effect of dentine conditioning agents on growth factor liberation and settlement of dental pulp progenitor cells (DPSCs) on dentine surfaces.MethodologyThe agents used included ethylenediaminetetraacetic acid (EDTA; 10%, pH 7.2), phosphoric acid (37%, pH < 1), citric acid (10%, pH 1.5) and polyacrylic acid (25%, pH 3.9). Human dentine slices were conditioned for exaggerated conditioning times of 5 and 10 min, so that the growth factor liberation reached quantifiable levels above the limit of detection of the laboratory methods employed. Transforming growth factor beta‐1 (TGF‐β1) release and surface exposure were quantified by enzyme‐linked immunosorbent assay (ELISA) and immunogold labelling. Scanning electron microscopy (SEM) was used to assess the morphology of cells and coverage by DPSCs cultured on dentine surfaces for 8 days.ResultsAfter 5‐min conditioning of dentine slices, citric acid was the most effective agent for growth factor release into the aqueous environment as measured by ELISA (Mann–Whitney U with Bonferroni correction, p < .01 compared with phosphoric and polyacrylic acid). As well as this, dentine slices treated with phosphoric acid for the same period, displayed significantly less TGF‐β1 on the surface compared with the other agents used, as measured by immunogold labelling (MWU with Bonferroni correction, p < .05). After 8 days, widespread coverage by DPSCs on dentine surfaces conditioned with citric acid and EDTA were evident under SEM. On dentine surfaces conditioned with phosphoric and polyacrylic acid, respectively, less spread cells and inconsistent cell coverage were observed.ConclusionsBased on the findings of this in vitro study, a desirable biological growth factor‐mediated effect may be gained when conditioning dentine by milder acidic or chelating agents such as citric acid and EDTA. The results must be interpreted in the context that the potential of the applied materials inducing a desirable biological response in DPSCs is only one consideration amongst other important ones in a clinical setting. However, it is crucial to look beyond the mere physical effects of materials and move towards biologically based treatment approaches as far as the restorative management of teeth with viable dental pulps are concerned.

HUMAN DIET DURING THE STONE AGE AND EARLY METAL PERIOD (7000–1 CAL BC) IN LITHUANIA: AN UPDATE

ABSTRACTIn this study we present new carbon (δ13C) and nitrogen (δ15N) stable isotope data of human (n=13) and animal (n=40) bone and/or dentine collagen samples, alongside accelerator mass spectrometry radiocarbon (AMS 14C) dates of human remains (n=16). The studied material was sampled from Lithuanian sites dating from the Late Mesolithic to the pre-Roman Iron Age. For the first time, we present δ13C and δ15N data from Lithuanian freshwater fish as well as AMS 14C, δ13C, and δ15N measurements of human remains from six disturbed graves at the Donkalnis cemetery and from two pre-Roman Iron Age graves. According to the new results, human diet derived protein from the Late Mesolithic to Subneolithic (ca. 7000–2900 cal BC) was primarily based on freshwater fish. While previous macrobotanical and stable isotope studies has suggested that C4 plants, i.e., millet, became more widely used from the Late Bronze Age (1100–500 cal BC), our data suggests that millet consumption may have decreased during the pre-Roman Iron Age (500–1 cal BC) in the southeastern Baltic.

Breastfeeding and Weaning in Roman Thessaloniki. An Investigation of Infant Diet based on Incremental Analysis of Human Dentine

ABSTRACT In the present study, we report isotope (δ15N, δ13C) measurements on dentine increments from first permanent molars, to investigate breastfeeding practices in Thessaloniki, a provincial capital of the Roman Empire in northern Greece (168 BC–324 AD). For this purpose, we reconstructed diets from birth to seven yoa and estimated weaning ages for 20 individuals. We compared the individuals in relation to their biological sex and investigated diet during three distinct phases i.e. breastfeeding, weaning and fully weaned. The results of our study show a general trend in breastfeeding duration (mean weaning age: two yoa) for seventeen individuals and no breastfeeding for three male individuals. Moreover, males (n = 10) were fully weaned approximately six months earlier than females (n = 10). The weaning diet consisted mainly of terrestrial sources (C3 and C4 plants, animals/animal-byproducts) or small fish. Our observations are in accordance with ancient texts (e.g. Gynaecology of Soranus) and other isotopic studies on Roman period datasets highlighting the pivotal role of Thessaloniki as a cultural hub of the Empire.

Targeting Persistent Biofilm Infections: Reconsidering the Topography of the Infection Site during Model Selection

The physiology of an organism in the environment reflects its interactions with the diverse physical, chemical, and biological properties of the surface. These principles come into consideration during model selection to study biofilm–host interactions. Biofilms are communities formed by beneficial and pathogenic bacteria, where cells are held together by a structured extracellular matrix. When biofilms are associated with a host, chemical gradients and their origins become highly relevant. Conventional biofilm laboratory models such as multiwall biofilm models and agar plate models poorly mimic these gradients. In contrast, ex vivo models possess the partial capacity to mimic the conditions of tissue-associated biofilm and a biofilm associated with a mineralized surface enriched in inorganic components, such as the human dentin. This review will highlight the progress achieved using these settings for two models of persistent infections: the infection of the lung tissue by Pseudomonas aeruginosa and the infection of the root canal by Enterococcus faecalis. For both models, we conclude that the limitations of the conventional in vitro systems necessitate a complimentary experimentation with clinically relevant ex vivo models during therapeutics development.

Shear Bond Strength of Ah26 to Human Dentin Treated with Dimethyl Sulfoxide (Dmso).

The purpose of this study was to examine the bond strength of AH26 to human coronal dentin exposed to DMSO. A total of 70 dentin specimens were equally divided into two groups. Each dentin surface was pre-treated with 2 mL of 2.5% NaOCl, 3 mL of EDTA 17%, and distilled water. One group was finally rinsed with 50% DMSO. Following the AH26 application, the bond strength was tested by subjecting the samples to a shear load at a crosshead speed of 0.5 mm/min using universal testing equipment. The results according to paired samples t-test indicated that there was a statistically insignificant difference between the two groups. Therefore, DMSO had no effect on the bond strength of AH26 root sealer to dentin.

Effect of an enamel matrix derivative (Emdogain) on the microhardness and chemical composition of human root dentin: an in vitro study

The advantage of using an Enamel matrix derivative EMD Emdogain as an intracanal medication could be a manner to strength the tooth structure, improving the physical and chemical properties of dentin. We tested, in vitro, the effect of Emdogain on the surface microhardness and chemical composition of root dentin. Ten human teeth were used to produce dentin specimens originated from the canal walls (n = 30) that remained in contact to Emdogain gel for 90 days. Baseline and 90-days after Emdogain treatment measurements were performed using Fourier Transform Infrared Spectroscopy (ATR/FTIR), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Knoop indenters. The use of EMD (Emdogain) for 90 days in contact with human root canal dentin specimens did not alter the microhardness and morphology of dentin. The elemental structure of dentin was altered because there was a reduction in carbonate content.

Smear layer deproteinization with NaOCl and HOCl: Do application/wash-out times affect dentin bonding of one-step self-etch adhesives?

This study investigated the influence of application/wash-out times of sodium hypochlorite (NaOCl) and hypochlorous acid (HOCl) on dentin bond strength of one-step self-etch adhesives (1-SEAs). Human coronal dentin discs with a standardized smear layer were pretreated with 6% NaOCl or 100 ppm HOCl for 5 s, 15 s, or 30 s, and washed out with water for 5 s, 15 s or 30 s with or without the application of Clearfil DC Activator (CDA). No pretreatment was used as a control. The discs were bonded with a 1-SEA (Bond Force II or Clearfil Universal Bond Quick) and microtensile bond strength (µTBS) was measured after 24 h. Pretreatment with NaOCl for 15 s and 30 s significantly decreased µTBS (p<0.05), irrespective of wash-out time. The application of CDA recovered µTBS but did not outperform the control group. Conversely, pretreatment with HOCl for 15 s and 30 s followed by 30 s wash-out time significantly increased µTBS of 1-SEAs (p<0.05), regardless of CDA application.