Dentinal Fluid Research Articles

Calcium Silicate Cements Application in Lateral Root Perforation Repair: A Case Report with 16-Month Follow-Up

Lateral root perforations are unfortunate procedures during endodontic treatment and often lead to tooth extraction. Conditioning factors such as time, size, location, inappropriate disinfection and sealing, are indispensable to achieve acceptable long-term outcomes. Calcium silicate cements are bioactive materials used for perforation repair. They can be set in moist environments such as blood, saliva and dentinal fluid making them a reliable material for clinical applications. This case report describes the treatment and repair after a 16-month follow-up of a lateral root perforation of the maxillary lateral incisor.

Individual prediction of development of cervical dental tissue pathology based on the parameters of oral fluid

Annotation. Significant prevalence of cervical lesions of hard dental tissues is the reason for the search for the ways to predict their development that is possible only with an individual approach to solving this problem. The aim of the study is to determine the chemical composition of the patients’ oral fluid with clinically intact hard tissues, cervical caries and wedge-shaped defect, identify its critical values and the subsequent development of the method for individual prediction of the onset of pathology in young people. To accomplish it we used JSM-6490 LV focused beam electron microscope (scanning) to determine the chemical composition of the enamel and dentin of 29 teeth and their longitudinal sections, the chemical composition of the oral fluid of 33 patients who were divided into three groups depending on the state of their hard dental tissues. The approbation of the proposed method was carried out in 45 young people, the results were compared with the data of the clinical examination of 42 patients a year later. To verify the relationship between the variables, the Pearson parametric correlation method was used based on the determination of the Brave-Pearson parametric coefficient (r) with a 95% confidence level. The reliability of the obtained results was evaluated by Student's t-test, the correlation between indicators – by Student’s test using the Z-test (Fisher’s z-test). The level of significance of differences at p≤0.05 was considered statistically significant. It was determined that the values of the Ca+Na+Mg/P coefficient in enamel, dentin and oral fluid significantly differed depending on the state of hard dental tissues (p≤0.05). Moderate and high inverse correlation was revealed between Ca/P and Ca+Na+Mg/P coefficients in cervical enamel and oral fluid (p≤0.05). Obtained results became the basis for the development of the method for individual prediction of the onset of cervical pathology in young people: with the values of the Ca+Na+Mg/P coefficient higher than 22 – a low level, from 11 to 22 – an average level, lower than 11 – a high risk level. Thus, we have proved that the proposed method is informative (the predictive accuracy reaches 85%), its non-invasiveness is the basis for its widespread use. We consider the search for the ways of individual prediction of the development of cervical caries and wedge-shaped defect in young people based on the parameters of the oral fluid to be promising.

Fluoride bioactive glass paste improves bond durability and remineralizes tooth structure prior to adhesive restoration

ObjectiveThe current study aimed at examining a fluoride containing bioactive glass (BiominF®) paste as a temporary filling material capable of remineralizing the demineralized enamel or dentin, and its ability to decrease a simulated dentinal fluids pressure on the resin/dentin interface, without affecting the shear bond strength of a universal bonding agent to enamel and dentin. Methods60 premolars were utilized for the acid resistance, trans-microradiography (TMR) and shear bond strength (SBS) experiments. Enamel and dentin discs were demineralized for 4 days to create a subsurface demineralized zone followed by applying BiominF® paste, 1.23% acidulated phosphate fluoride, or a temporary filling material for 24 h.30 extracted human non-carious third molars were utilized for the pulpal pressure experiment in which direct communication to the pulp chamber was created by cutting at a level approximately 1 mm below the cemento-enamel junction while the coronal enamel was ground to expose mid coronal dentin. The dentin surface was exposed to a simulated pulpal pressure. The dentin surfaces had BiominF® paste, an oxalate desensitizing agent, or temporary filling material followed by application of a universal adhesive system. ResultsOne way ANOVA showed that BiominF® paste remineralized effectively the demineralized enamel or dentin, did not affect the bond strength of the enamel and dentin surfaces to the tested adhesive system p < 0.05, and improved the acid resistance of the demineralized enamel and dentin against a secondary erosive challenge. Moreover, BiominF® paste decreased the nanoleakage expression in the dentin/adhesive interface exposed to a simulated pulpal pressure. SignificanceBiominF® paste may serve as a temporary filling material that may improve the longevity of adhesive restorations and help to conserve tooth structures by preserving the demineralized enamel and dentin form cutting during cavity preparation.

Shockwave application enhances the effect of dentin desensitizer

ObjectivesThe purpose of this study was to develop a new device that can improve the effect of desensitizer using shockwaves and to verify its efficacy. MethodsA micro-shockwave generator was developed using a piezoelectric actuator (PIA-1000, piezosystem jena GmbH, Jena, Germany), an Arduino Uno microcontroller (Arduino, Torino, Italy), and a high voltage pulser (HVP-1000, piezosystem jena GmbH) at 700 V (400 A) and 100 μs. The occlusal surfaces of 20 extracted human upper and lower third molars without caries or restoration were reduced to expose the occlusal dentin, and the prepared occlusal surfaces were acid-etched with 32% phosphoric acid to remove the smear layer. The tooth specimens were connected to a fluid flow measurement instrument (nanoFlow, IB SYSTEMS, Seoul, Korea), permeability through dentin via dentinal fluid flow (DFF) was measured for 300 s, and the average DFF rate (Baseline DFF rate) was calculated. A desensitizer (SuperSeal, Phoenix Dental, Fenton, MI, USA) was applied to the acid-etched occlusal dentin surface of 10 randomly selected tooth specimens, left for 10 s, and rubbed with a microbrush for 30 s (Group 1). For the remaining teeth, the desensitizer was applied, and a shockwave (100 μm stroke, 10,000 G) was applied for 10 s (2 shots/s) and rubbed with a microbrush for 30 s (Group 2). After desensitizer application, subsequent DFF was measured for 600 s, and the average DFF rate was calculated (post-application DFF rate). DFF was continuously measured in real-time at 25 ± 0.5 ℃ under a hydrostatic pressure of 25 cm. The percentage reduction in DFF rate after desensitizer application (with or without shockwave) was calculated with respect to baseline DFF rate. Data were analyzed with independent t-test (α = 0.05). ResultsFor all tooth specimens, DFF rate decreased after desensitizer application irrespective of the presence of shockwaves. The percentage reduction in DFF rate of SuperSeal with shockwave (Group 2) was 42.8 ± 19.0%, which was significantly higher than the 26.2 ± 13.6% of the SuperSeal only group (Group 1) (p < 0.05). SignificanceMeasurement of DFF change in real-time shows that shockwaves can help reduce dentin permeability beyond that SuperSeal dentin desensitizer produced alone.

A method for determining the natural moisture content of dentin in a clinical setting

The purpose of the study is a quantitative assessment of the yield of dentinal fluid on the surface of the treated dentin of the tooth when restoring its structure with a composite filling material. To achieve this goal, digital images of the coronal parts of the teeth having formed carious cavities were used; virtual models of hard tissues of teeth recreated using specialized computer programs; A computer program that provides the ability to accurately determine the area of the treated dentin tooth. The results made it possible to draw the following conclusions: with an increase in the depth of the carious cavity, the amount of dentin fluid that can stand out on its surface (1–2 mm from the tooth cavity) sharply increases; with an increase in the area of the formed carious cavity (more than 30 mm2), the risk of release of a critical mass of dentinal fluid (more than 0.4 mg), which can adversely affect the strength of the adhesive interaction between the composite material and the hard tissues of the tooth, increases significantly; the same dynamics is observed with increasing time, at which there is the possibility of free exit of dentinal fluid to the surface of the cavity prepared for filling (more than 45 seconds).

The ability of a potassium oxalate gel strip to occlude human dentine tubules; a Novel in vitro: In situ Study

ObjectivesTo determine if an oxalate strip reduced fluid flow in dentine samples and whether this reduction was maintained following a 14 day intra-oral period. MethodsDentine tubule fluid flow was measured by a modified Pashley cell in 40 acid-etched dentine discs 1 mm thick, diameter >10 mm, with an acquired pellicle, pre-equilibrated with Hartmann’s solution and conditioned by toothbrushing, pre and post treatment (10 min) with an oxalate (3.14 %) gel strip or no treatment. One control and one test sample were exposed in-situ for 14 days to the oral environment in 20 healthy adult volunteers, and fluid flow re-measured. The appliance containing the two samples was removed for brushing with water after mealtimes when the participant brushed their teeth and for a 2 min daily soak in chlorhexidine. ResultsFluid flow rate was reduced significantly immediately following treatment with the oxalate strip compared to baseline flow rate by 58 %. Following 14 days in-situ oral environment phase, a significant further reduction in fluid flow compared to baseline was identified in both control and oxalate strip treated samples, both (p < 0.0001), but the reduction was greater in the test samples, 94 % vs 87 %, p < 0.01. ConclusionsThis novel investigation is the first to show fluid flow measurement using the Pashley model in dentine samples that have been housed in the mouth for 14 days. Treatment with an oxalate strip designed for dentine hypersensitivity alleviation reduced dentine fluid flow more than control providing evidence that the oxalate treatment withstood the oral environment over a prolonged time. Clinical SignificanceThis study demonstrated the efficacy and durability of the oxalate precipitate over a 14 day period in achieving and maintaining dentine tubule occlusion when participants had no dietary restrictions. This demonstrates the suitability of the oxalate strip for the treatment of patients suffering from dentine hypersensitivity pain.

Inflammatory biomarkers in dentinal fluid as an approach to molecular diagnostics in pulpitis.

To explore a set of inflammatory biomarkers obtained from dentinal fluid (DF) from patients with symptomatic irreversible pulpitis (IP), reversible pulpitis (RP) and normal pulp (NP). A cross-sectional exploratory study was performed, recruiting 64 patients on the basis of their respective pulp condition. DF samples were obtained from all patients (23, from IP patients; 20, from RP patients; and 21, from NP patients). Quantification of biomarkers was performed using a Luminex® MAGPIX platform system and multiplex assay kits. The Kruskal-Wallis test was used for comparisons with regard to pulp state. A simple logistic regression model and the odds ratio (OR) with a 95% level of confidence (P=0.05) were used to evaluate associations between biomarker levels and pulpal diagnosis. The performance discrimination of the biomarkers was evaluated through the construction of a receiver operating characteristic (ROC) curve by calculating the area under the curve (AUC) for IP versus RP after logistic regression modelling. Youden criteria were used to establish cut-off points for biomarkers alone with AUC>70 and P-value<0.05, or estimated probabilities from the multivariable logistic model. The biomarkers that had significantly higher values in participants with IP versus RP were IL-1α, VEGF-α and FGF acid (P<0.05). FGF acid (OR: 12.62; P=0.0085; CI 95% 1.91-83.29) and VEGF-α (OR: 2.61; P=0.0252; CI 95% 1.13-6.03) were associated with pulp diagnoses of IP versus RP. The AUC-ROC curve for FGF acid was 0.79. The model containing FGF acid, IL-1α, IL-6 and TIMP-1 had an AUC-ROC of 0.92 for IP versus RP with a significant difference from the FGF acid ROC curve (P=0.0231). Dentinal fluid could be used to assay pulpal mediators in the molecular diagnosis of pulpitis. Despite the limitation of the clinical diagnostics used in the present study, it was possible to detect a difference between irreversible symptomatic pulpitis and reversible pulpitis associated with the following combined biomarkers: FGF acid+IL-6+IL-1α, +TIMP-1.

Results of electrometric assessment of quality of marginal fit of composite material to hard tissues of teeth in various clinical conditions

The purpose of the study was a clinical electrometric assessment of the quality of the marginal fit of the composite material to the hard tissues of the tooth, depending on the type and amount of adhesive used the influence of the adhesive, namely: the mechanism of its action and quantity, on the quality of restoration of the hard tissues of the tooth lost by the carious process in the composite material over time.Material and methods. In clinical conditions, 140 fillings were examined, the placement of which was carried out only in cavities of classes 1 and 2, with the area affected by the carious process of hard tooth tissues from 30 to 50 mm2. For this, composite material ESTET X and adhesive systems were used: one-component XP BOND and self-etching XENO V in different volumes (6.6 and 17.7 mg). To assess the marginal fit of the filling material to the hard tissues of the tooth, the multifunctional electro-diagnostic device EST-DENT (Geosoft, Russia) was used. The principle of operation of the device is based on measuring the strength of the current flowing through the hard tissues of the tooth under the influence of a low-voltage source of electrical power. Results. The quality of the marginal fit of composite fillings to the hard tissues of the tooth, which is the main factor determining the durability of their functioning, largely depends on the amount of adhesive used, its mechanism of action, the area and depth of the carious lesion of dentin. Over time, there is a change in the structure obtained as a result of the mechanical and chemical interaction of the adhesive system and hard tissues of the tooth (primarily the hybrid layer), in the direction of decreasing its density and breaking integrity. This in turn increases the amount of electric current passing through it.Conclusions. An analysis of the obtained clinical data shows that when restoring hard tissues of teeth lost over large areas and located close to the pulp cavity of the coronal part of the tooth, it is necessary to take into account the effect of dentinal fluid on the quality and durability of the restoration. The use in these cases of adhesive systems in an amount of not less than 17.7 mg (a drop from dispenser), careful preparation of the affected tooth tissues, rational design of the formed cavity, strict adherence to the manufacturer’s recommendations on the time of use of the adhesive. can significantly reduce the risk of unsatisfactory treatment results.

Effect of tooth-brushing with a microcurrent on dentinal tubule occlusion.

The purpose of this study was to investigate whether tooth-brushing with a microcurrent was effective in inducing dentinal tubule occlusion. The specific aims of the study were (1) to evaluate the effectiveness of tooth-brushing with a microcurrent on dentinal tubule occlusion by using scanning electron microscopy (SEM); and (2) to compare the dentinal fluid flow rate after tooth-brushing with a microcurrent by using a sub-nanoliter-scaled fluid flow measuring device (NFMD). All experimental groups showed partially occluded dentinal tubules and crystal-like structures at a specific microcurrent intensity indicated that tooth-brushing with a microcurrent could efficiently occlude dentinal tubules. The decrease in dentinal fluid flow rate in the tooth-brushing with microcurrents group indicated that dentinal tubules were occluded and the flow of dentinal fluid had decreased.

Comparative analysis of dentine and gingival fluid molecular composition and protein conformations during development of dentine caries: A pilot study

BackgroundOne of the most important yet unresolved tasks facing therapeutic dentistry is the problem of efficient personalised diagnostics of pathological processes in the dentine tissues of human teeth. In this regard, dentine fluid is an ideal screening candidate, which acts as an important factor in the development of dentine caries. However, the serious difficulty and practical impossibility of dentine fluid sampling in vivo is the main obstacle to its use in advancing a new line of diagnostics. Extracting gingival crevicular fluid for diagnosing is a much simpler approach. Therefore, we sought to establish the molecular composition and protein conformation of blood, dentine fluid, and gingival fluid during the development of dentine caries using synchrotron FTIR investigations. MethodsTen participants aged 22–28 participated in the study. Each participant had teeth with lesion foci related to primary and secondary enamel surface caries (tooth decay). Three biological fluid samples were obtained for each participant: dentine fluid, gingival crevicular fluid, and blood. The molecular composition of the samples was investigated using FTIR synchrotron spectroscopy technique. FindingsBased on the mathematical simulation of absorption band Amide I in the FTIR spectra of the samples, it was found that the development of pathological processes of the carious type in dentine tissue affects the molecular composition of the biological fluids coming in contact with hard dental tissue. In addition, for the first time, we observed an increased content of thiocyanates and complex esters as well as the presence of anti-inflammatory cytokines, and their interaction with the secondary protein structure in the dentine fluid and gingival crevicular fluid for people with pathological carious processes in the dental tissues. ConclusionThe detected features in the FTIR spectra of biological fluids within the oral cavity in combination with the well-known in literature spectral markers of the development of carious process in dentine prove to be significant, reliable signatures of pathology that can relatively easily detected in the analysis of gingival fluid.

Spectroscopic studies of the molecular composition of the dentinal and gingival fluids and their diagnostic potential for preventive screening of dentin caries

The aim of the work is a spectroscopic investigation and comparison of the molecular composition of dentine and gingival fluids as well as of their diagnostic potential for the preventive screening of dentin caries. Applying infrared spectroscopy including synchrotron radiation the samples of biological fluids taken from the oral cavity (dentine fluid, fluid from the gingival sulcus and blood) were studied for the patients with the progressive dentine caries. The part of this research was undertaken with the infrared microspectroscopy beamline at the Australian Synchrotron. Dentine and gingival fluids were shown to have no less complicated composition than the blood serum. Having all this in mind, in spite that these two fluids are derivatives of the blood serum, and a majority of the molecular groups observed in all of the three fluids can be detected in their IR-spectra, it follows that there is a number of signature modes that are in fact present in the IR spectra of only dentine and gingival fluids. This fact indicates at the molecular exchange between them under certain conditions. It means the high diagnostic potential in the study of the pathologic processes occurring in the oral fluid of a human. We have observed and fixed an increase of thiocyanates and esters in the samples of both dentine and gingival fluids under the development of dentin caries. Utilization of the gingival fluid for screening taking into account that its sampling is not such a complicated challenge as dentine fluid sampling will promote a transition to the personalized medicine, the development of high-technology healthcare and technology of the health preservation as a whole.

The results of computer simulation of the dentinal fluid hydrodynamics in the open crown dentinal tubule

To study the hydrodynamics of the dentinal fluid along the dentinal tubule in the event of its opening as a result of mechanical and acid treatment of the dental crown dentin. Material and methods: A licensed version of the ANSYS / FLOTRAN computer program was used, which is a software tool for solving various problems of hydrodynamics, including laminar and turbulent flow of an incompressible or compressible fluid. The results of computer simulation showed that 1.5 ms after drying of the dentin tubule (length 6 mm) it is refilled with dentin fluid, which then begins to accumulate on the treated surface of the dental hard tissues. Reducing the length of the dentinal tubule as a result of the cavity preparation leads to an increase in the speed and mass of pulp fluid released through it.

Comparative assessment of the human blood plasma impact on the properties of various adhesive systems

To assess the degree of influence of human blood plasma simulating dentinal fluid on the composite resin adhesion to dental hard tissues. The strength of the adhesive bond between the composite material and dental hard tissues was studied using a shear test machine Zwick Roell Z 010 («Zwick», Germany) on extracted human teeth. XP Bond one-component adhesive system and XENOV self-etching adhesive system (DENTSPLY, Germany), high-definition micrometric restoration material Esthet X HD (DENTSPLY, Germany), as well as centrifuged blood plasma were used. Adhesion strength decreased by 26-78% when blood plasma weighing from 0.2 to 2.0 mg mixed up the self-etching system (weight 6.6 mg). A significant decrease in the adhesion force occurred when plasma with a mass of 0.7 mg or more mixed up with the monomer (a decrease in adhesion by 19.1%). A critical decrease in the adhesion force (43% or more) occurred with the mixture of blood plasma weighing 2.0 mg or more.

The results of evaluating the degree of influence of human blood plasma on the strength of adhesion of composite material to dentin (one-component adhesive system)

To study the dynamics of changes in the adhesion between the composite and dentin of the tooth when using different volumes of a single-component adhesive system in case of contamination of it with human blood plasma. To achieve this goal, the following were used: extracted human teeth, XP Bond one-component adhesive systems (DENTSPLY, Germany), Esthet X HD micrometric restoration material (DENTSPLY, Germany), and centrifuged blood plasma. The strength of the adhesive bond between the composite material and the hard tissues of the tooth was studied using a shear test machine Zwick Roell Z 010 («Zwick», Germany). The use of a single-component adhesive system in an amount of 17.7 mg (1 drop from a dispenser) for treating open dentin makes it more resistant to contamination compared to using the same adhesive, but in an amount of 6.6 mg (the amount of adhesive that adsorbs a medium-sized dental take). A decrease in the adhesion force between the composite material and tooth hard tissues from 1.5 to 17.7% occurs when a single-component adhesive system weighing 17.7 mg of blood plasma simulating a dentinal fluid weighing from 0.2 to 2.0 mg enters. The ingestion of the same amount of blood plasma in a single-component adhesive system weighing 6.6 mg leads to a decrease in its adhesion from 4.3 to 43%.

A Spectroscopic Study of Changes in the Secondary Structure of Proteins of Biological Fluids of the Oral Cavity by Synchrotron Infrared Microscopy

On the basis of the data of infrared spectroscopy with synchrotron radiation, the secondary structure of proteins of the dentinal and gingival fluids during the development of cariosity in deep dentin tissues is studied. It is shown that the change in the shape of the profile of the amide I band in the region of 1700‒1605 cm–1 is associated both with a change in the ratio of the integrated absorption intensities of the α‑helix and β-sheet secondary structures and with the position of the β-coil and β-sheet components in the spectrum. It is established that the α-helix/β-sheet ratio for both dentinal and gingival fluids is below the threshold level, at which significant changes in the secondary structure of proteins of biological fluids are observed, unequivocally indicating the development of pathology in hard dental tissues. The features that we discovered in the profile of the amide I band of biological fluids of the oral cavity, together with the spectral markers of the development of cariosity in dentin, are reliable spectroscopic signatures of the pathology and can be detected using the gingival fluid.

Update on dentin hypersensitivity: with the focus on hydrodynamic theory and mechanosensitive ion channels

Dentin hypersensitivity is an abrupt intense pain caused by innocuous stimuli to exposed dentinal tubules. Mechanosensitive ion channels have been assessed in dental primary afferent neurons and odontoblasts to explain dentin hypersensitivity. Dentinal fluid dynamics evoked by various stimuli to exposed dentin cause mechanical stress to the structures underlying dentin. This review briefly discusses three hypotheses regarding dentin hypersensitivity and introduces recent findings on mechanosensitive ion channels expressed in the dental sensory system and discusses how the activation of these ion channels is involved in dentin hypersensitivity.

CPNE7 Induces Biological Dentin Sealing in a Dentin Hypersensitivity Model

Dentin hypersensitivity commonly occurs due to opened dentinal tubules for many reasons. In our previous study, copine 7 (CPNE7) could induce dentin formation for an indirect pulp-capping model in vivo. This study aims to investigate the formation of tertiary dentin when CPNE7 is applied to intentionally exposed dentin with nothing over it in vivo, whether it affects microleakage of the teeth, and the penetration ability of CPNE7 molecules through dentinal tubules in vitro. Cervical dentin areas of 6 maxillary incisors of 5 beagles were exposed to a class V–like lesion, and 1 side of 3 maxillary incisors was adapted with recombinant CPNE7 protein for 5 min as the experimental group. The other side was the control group, and there was no treatment of ethylenediaminetetraacetic acid (EDTA) and CPNE7 after preparation. The defects were exposed without any restorations, and all beagles were sacrificed after 4 wk. The fluid penetration of exposed dentin areas was investigated by a microleakage-testing device and confocal laser scanning microscope. Tertiary dentin formation was confirmed with histological scanning electronic microscopic analysis. Tertiary dentin formation reduces dentinal fluid flow due to occluded tubules or discontinuity with primary or secondary dentin. The in vivo hypersensitivity model with the anterior teeth of beagle dogs showed newly formed tertiary dentin at the dentin-pulp boundary in recombinant CPNE7–treated teeth when compared with the untreated control group in histologic analysis. Scanning electronic microscopic analysis revealed occluded sites with mineral deposition of intratubular dentin. In the permeability test, the mean microleakage value of the CPNE7-treated group was significantly lower than that of the control group (P < 0.05). The tubular penetration of rhodamine B–combined CPNE7 was confirmed under confocal laser scanning microscope. CPNE7 induces formation of tertiary dentin through shallowly exposed dentinal tubules, which decreases dentin permeability.

Dental Pain: Dentine Sensitivity, Hypersensitivity and Cracked Tooth Syndrome.

Dentine hypersensitivity is a frequently encountered patient complaint that can present with a number of associated factors including erosion and abrasion. the hydrodynamic mechanism responsible for dentine hypersensitivity is intimately related to the anatomical and physiological composition of teeth. Alterations to the integrity of the enamel and dentine through processes of trauma, decay and toothwear can increase dentine permeability. This gives rise to symptoms of sensitivity as dentinal fluid movement in response to thermal, chemical and mechanical cues stimulate the pulpal Aδ fibres. Restorative procedures can also rapidly change the architecture of the protective enamel and dentine layers leading to pulpal inflammation and increased thermal sensitivity of the tooth.<br/> Patient-reported symptoms of dentine hypersensitivity can be attributed to a number of possible causes and a definitive diagnosis can therefore be difficult. A full history including social and medical factors such as occupation, diet and/or medication is likely to provide significant information to aid a diagnosis. Consideration of occlusal factors should not be overlooked as these may contribute to symptoms arising from a cracked tooth.<br/> Management strategies are linked to the diagnosis - from topically applied desensitising pastes and resin bonding agents to direct restorations and possibly more advanced restorative procedures such as root canal treatment. Management should, however, be staged to enable more conservative strategies to prevail prior to considering irreversible dental interventions.

Natural enamel caries, dentine reactions, dentinal fluid and biofilm

It is believed that penetration of dentinal fluid into natural enamel caries (NEC) is negligible because of the barrier created by underlying sclerotic dentine, but there are conflicting evidences on whether dentine subjacent to NEC is sclerotic or demineralized. This study aimed at investigating the relationship between NEC, subjacent dentine reactions, modification of dentinal fluid, and composition of cariogenic biofilm formed on the NEC surface. Proximal NEC (PNEC) lesions of human permanent posterior teeth were included in five experiments. Histologically, microradiographic analysis with contrast solution (MRC) in dentine revealed a decreased proportion of sclerotic dentine and an increased proportion of deep dentine demineralization compared to the classical stereomicroscopic histological analysis based on dentin color and translucency. Real-time MRC and 3D optical profilometry, and 3D microtomographic analysis evidenced a facilitated transport of modified dentinal fluid towards PNEC lesions. Cariogenic biofilm formed in vitro on the PNEC surface presented lower amounts of insoluble and soluble matrix polysaccharides when 2% chlorexidine was inserted in the pulp chamber. In conclusion, this study evidenced that dentine subjacent to PNEC is mostly demineralized, providing facilitated pathway for dentinal fluid to penetrate into PNEC and alter the composition of the biofilm formed on the PNEC surface.

The Role of Transient Receptor Potential (TRP) Channels in the Transduction of Dental Pain.

Dental pain is a common health problem that negatively impacts the activities of daily living. Dentine hypersensitivity and pulpitis-associated pain are among the most common types of dental pain. Patients with these conditions feel pain upon exposure of the affected tooth to various external stimuli. However, the molecular mechanisms underlying dental pain, especially the transduction of external stimuli to electrical signals in the nerve, remain unclear. Numerous ion channels and receptors localized in the dental primary afferent neurons (DPAs) and odontoblasts have been implicated in the transduction of dental pain, and functional expression of various polymodal transient receptor potential (TRP) channels has been detected in DPAs and odontoblasts. External stimuli-induced dentinal tubular fluid movement can activate TRP channels on DPAs and odontoblasts. The odontoblasts can in turn activate the DPAs by paracrine signaling through ATP and glutamate release. In pulpitis, inflammatory mediators may sensitize the DPAs. They could also induce post-translational modifications of TRP channels, increase trafficking of these channels to nerve terminals, and increase the sensitivity of these channels to stimuli. Additionally, in caries-induced pulpitis, bacterial products can directly activate TRP channels on DPAs. In this review, we provide an overview of the TRP channels expressed in the various tooth structures, and we discuss their involvement in the development of dental pain.