Determination of plasma proteins in dentinal fluid from cavities prepared in healthy young human teeth

Evaluation of the Impact of Irradiance Lamps and Storage Media on Elution of TEGDMA from Dental Composites

OBJECTIVES

 The aim of this study was to evaluate and compare the effect of irradiance light and storage media on the elution of triethylene glycol dimethacrylate (TEGDMA) from conventional Filtek Z350XT 3M ESPE and two bulk-fill composites Shofu Beautifil-Bulk and Filtek Bulk fill flowable 3M ESPE using high-performance liquid chromatography (HPLC).

MATERIALS AND METHODS

 Shofu Beautifil-Bulk, Filtek Bulk fill flowable 3M ESPE, and Filtek Z350XT 3M ESPE were the three types of composites used in this study. Disk shaped samples of 4-mm thickness and 10-mm diameter were fabricated using a stainless steel mold and were polymerized using light emitting diode (LED) and quartz tungsten halogen (QTH) lamps. After polymerization, the samples were immersed in ethanol, artificial saliva with betel quid extract, and distilled water for 1, 7, and 30 days, respectively. The elution of monomer TEGDMA was evaluated using HPLC.

STATISTICAL ANALYSIS

 To evaluate the mean concentration difference, mixed way analysis of variance (ANOVA) was applied. Between different light, materials, and within the time duration, Tukey's post hoc test was used. A p value of 0.05 was considered significant.

RESULTS

 During the first day of storage, a significant amount of monomer TEGDMA elution was seen in all the materials. The highest values observed to be in the disks cured with QTH lamp. However, the highest elution was seen when the disks were immersed in ethanol/water solution. While the most stable medium was distilled water, artificial saliva with betel nut extract also had a significant effect on the elution of TEGDMA. The highest value obtained was of Filtek Bulk fill flowable 3M ESPE after 30 days of immersion in both LED and QTH cured disks.

CONCLUSION

 Filtek Bulk fill flowable 3M ESPE shows better properties in relation to the release of monomer TEGDMA as it releases less amount of monomer in the storage media. The release of monomer was highest in ethanol as compared to artificial saliva and distilled water with the passage of time.

Efficacy of diode laser application versus silver diamine fluoride (SDF) as a modification of Hall technique in primary teeth

Background

The Hall technique is a new technique aimed at depriving bacteria of any substrate, thereby limiting the progression of caries. Silver diamine fluoride (SDF) and diode laser are documented to have an antibacterial effect on carious enamel and dentin by eradicating bacteria such as Streptococcus mutans.

Aim

The current study aimed to increase the success rate of the Hall technique in carious primary molars by eradicating bacteria present in carious lesions using SDF or diode laser in combination with the Hall technique.

Materials and methods

A total of 159 children aged 4-8 years were randomly divided into three equal groups: Group I, application of the Hall technique; Group II, SDF with Hall technique; Group III, diode laser with Hall technique. Children were recalled at regular intervals over a year. Results: At the end of the follow-up period, Group III showed the highest clinical success rate (94.3 %), followed by Group II (96.2 %), while Group I showed the lowest clinical and radiographic success rates (88.7 % and 86.8 %, respectively); however, these differences were statistically non-significant.

Conclusion

Treatment of carious lesions using SDF or Diode Laser increased the success rate of the Hall technique in primary teeth.

Evaluation of the Level of Salivary sHLA-G in Children Aged 3-5 Years with or without Dental Caries

Methods and Materials

This analytic cross-sectional study was carried out on 83 healthy children aged 3 to 5 years of both genders, who were divided into three groups based on decayed dental surfaces (ds): group 1, caries-free children (CF, n = 29); group 2, children with 1 ≤ ds ≤ 3, 1 ≤ ds ≤ 4, and 1 ≤ ds ≤ 5 for age 3, 4, and 5 years, respectively (ECC, n = 20); and group 3, children with ds ≥ 4, ds ≥ 5, and ds ≥ 6 for age 3, 4, and 5 years, respectively (S-ECC, n = 34). The unstimulated saliva samples were collected, and the salivary sHLA-G concentration was measured by the ELISA kit. The SPSS Statistics v17.0 software and Mann–Whitney, Kruskal–Wallis, chi-square, and Spearman's rank correlation tests were used for statistical analysis. The level of significance was considered at p < 0.05.

Results

The mean concentrations of salivary sHLA-G in CF, ECC, and S-ECC groups were 3.18 ± 2.28, 5.64 ± 5.51, and 6.21 ± 6.03 ng/l, respectively (p = 0.047), and the mean salivary sHLA-G level was comparatively higher in children with dental caries than that of the CF group (p = 0.02), but there is no significant difference between ECC and S-ECC groups (p > 0.05). Spearman's rank correlation test showed a weak positive correlation (p = 0.039, r = 0.22), between the level of salivary sHLA-G and dental caries.

Conclusion

The present study provides some preliminary evidences on relationship between sHLA-G and dental caries in children.

Biochemical analysis of oral fluids for disease detection

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

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

Background

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

Methods

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

Results

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

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

Conclusions

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

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION AND CLINICAL SIGNIFICANCE

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

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

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

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

Sealing can arrest caries lesions. We aimed to evaluate if sealing effects and kinetics are bacterial-strain and sealing-material specific. Human dentin discs were mounted in a dual-chamber device. Caries lesions were induced chemically and contaminated with either Lactobacillus rhamnosus (LR) or Streptococcus sobrinus (SS). For (1) kinetics assessment, the initial bacterial load and the sealing period were varied, and lesions sealed using a self-etch adhesive and composite. For (2) comparing materials, six sealing protocols (#1-#6) were evaluated: 1# Self-etch adhesive plus composite placed without a liner, or #2 calcium hydroxide, or #3 mineral trioxide aggregate, or #4 Biodentine liners; #5 antibacterial adhesive plus composite; #6 glass ionomer cement. Pulpal fluid flow was simulated during sealing. The outcome was the number of surviving bacteria (CFU) per g dentin. For LR, bacterial survival increased significantly with increasing initial bacterial load and decreased with longer sealing periods. The relative reduction followed a first-order kinetics. More LR survived under calcium hydroxide or MTA than other materials (p < 0.001). For SS, nearly no bacteria survived sealing regardless of sealing period, initial bacterial load or sealing material. In conclusion, sealing effects and kinetics were strain- and material-specific.

MMP-9 in Dentinal Fluid Correlates with Caries Lesion Depth

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluation of monomer leaching from a resin cement through dentin by a novel model

OBJECTIVE

To evaluate the elution of HEMA, BPA, UDMA and BisGMA from a conventional resin cement (Multilink Automix^®, Ivoclar Vivadent) through human dentin, under constant positive pulpal pressure.

METHODS

Ten human dentin disks (n=10) were adjusted in a new testing device and transparent glass slabs were luted with Multilink Automix^® resin cement, following manufacturer's instructions, under a steady pressure of 25N. The device was filled with Ringer's solution. At 5min, 20min, 1h, 2h, 21h, 3 days, 7 days, 10days and 21days time intervals, the whole eluate was retrieved from each one of the ten specimens and then, the specimens were refilled with fresh Ringer's solution. The eluates were analyzed by High Performance Liquid Chromatography (HPLC).

RESULTS

HEMA was detected in the eluate of all of the specimens, from 5min until 10 days. At four of the specimens, HEMA was also detected in the 21days eluate at very low concentrations. BPA, UDMA and BisGMA were not detected at any eluate. An unknown compound was also detected at 4.4min.

SIGNIFICANCE

The concentrations of HEMA that enabled to diffuse from Multilink Automix^® cement in an aqueous solution, through a dentin barrier, did not reach toxic levels and BPA, UDMA and BisGMA were not detected at all.

Pulpal Remineralisation of Artificial Residual Caries Lesions in vitro

We assessed pulpal remineralisation of caries lesions in vitro. On the coronal aspect of human dentin discs (n = 70), artificial lesions [mineral loss x0394;Z (mean ± SD) = 3,060 ± 604 vol% × µm] were induced, covered and pulpal surfaces exposed to pulpal fluid, remineralisation medium or water at pressures of 0, 1.47 or 2.94 kPa for 3 months. Mineral loss differences were assessed using transversal microradiography. No significant mineral gain occurred at 0 kPa and in samples exposed to water. At 1.47 and 2.94 kPa, pulpal and remineralisation fluid induced significant mineral gain [x0394;x0394;Z = 1,317 (25th/75th percentiles: 735/1,541) vol% × µm; p < 0.001]. Pressure and fluid composition determined pulpal remineralisation in vitro.

Physiological adaptations of key oral bacteria

Oral colonising bacteria are highly adapted to the various environmental niches harboured within the mouth, whether that means while contributing to one of the major oral diseases of caries, pulp infections, or gingival/periodontal disease or as part of a commensal lifestyle. Key to these infections is the ability to adhere to surfaces via a range of specialised adhesins targeted at both salivary and epithelial proteins, their glycans and to form biofilm. They must also resist the various physical stressors they are subjected to, including pH and oxidative stress. Possibly most strikingly, they have developed the ability to harvest both nutrient sources provided by the diet and those derived from the host, such as protein and surface glycans. We have attempted to review recent developments that have revealed much about the molecular mechanisms at work in shaping the physiology of oral bacteria and how we might use this information to design and implement new treatment strategies.

In vitro activity of photoactivated disinfection using a diode laser in infected root canals

OBJECTIVE

To investigate the lethal activity of photoactivated disinfection (PAD) on Enterococcus faecalis (ATCC 29212) and mixed populations of aerobic or anaerobic bacteria in infected root canals using a diode laser after the application of a photosensitizer (PS).

MATERIALS AND METHODS

First, the bactericidal activity of a low power diode laser (200 mW) against E. faecalis ATCC 29212 pre-treated with a PS (toluidine blue) for 2 min were examined after different irradiation times (30 s, 60 s and 90 s). The bactericidal activity in the presence of human serum or human serum albumin (HSA) was also examined. Second, root canals were infected with E. faecalis or with mixed aerobic or anaerobic microbial populations for 3 days and then irrigated with 1.5% sodium hypochlorite and exposed to PAD for 60 s.

RESULTS

Photosensitization followed by laser irradiation for 60 s was sufficient to kill E. faecalis. Bacteria suspended in human serum (25% v/v) were totally eradicated after 30 s of irradiation. The addition of HSA (25 mg/ml or 50 mg/ml) to bacterial suspensions increased the antimicrobial efficacy of PAD after an irradiation time of 30 s, but no longer. The bactericidal effect of sodium hypochlorite was only enhanced by PAD during the early stages of treatment. PAD did not enhance the activity of sodium hypochlorite against a mixture of anaerobic bacteria.

CONCLUSIONS

The bactericidal activity of PAD appears to be enhanced by serum proteins in vitro, but is limited to bacteria present within the root canal.

Comparison of vehicles to collect dentinal fluid for molecular analysis

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL SIGNIFICANCE

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

Development and validation of an in vitro model for measurements of cervical root dentine permeability

Objectives

The aim of this series of studies was the development and validation of a new model for evaluation of dentinal hypersensitivity (DH) therapies.

Materials and methods

Roots from extracted human teeth were sealed with a flowable composite. In the cervical area, a 3-mm-wide circular window was ground through the seal 1 mm deep into dentine. The pulp lumen was connected to a reservoir of artificial dentinal fluid (ADF) containing protein, mineral salts and methylene blue. At increased pulpal pressure, the ADF released through the said window was collected in containers each with 20 ml of physiologic saline for a consecutive series of 30-min intervals and ADF concentration (absorption) was determined photometrically. The model was verified by three experiments. In experiment 1, the lower limit of quantification (LLoQ, coefficient of variation = 20 % and difference of 5 standard deviations (SD) from blank) of ADF in physiologic saline was determined by measuring the absorption of 15 dilutions of ADF in physiologic saline (containing 0.625 ng to 12.5 μg methylene blue/ml) photometrically for ten times. In experiment 2, long-term linearity of ADF perfusion/outflow was investigated using 11 specimens. The ADF released through the window was collected in the said containers separately for each consecutive interval of 30 min for up to 240 min. Absorption was determined and analysed by linear regression over time. In experiment 3, perfusion before (2×) and after single treatment according to the following three groups was measured: BisGMA-based sealant (Seal&Protect®), an acidic fluoride solution (elmex fluid®) and control (no treatment).

Results

In experiment 1, the LLoQ was 0.005 μg methylene blue/ml. In experiment 2, permeability was different within the specimens and decreased highly linearly with time, allowing the prediction of future values. In experiment 3, Seal&Protect® completely occluded dentinal tubules. elmex fluid® increased tubular permeability by about 30 % compared to control.

Conclusions

A model comprising the use of artificial dentinal fluid was developed and validated allowing screening of therapeutic agents for the treatment of DH through reliable measurement of permeability of cervical root dentine.

Clinical relevance

The described in vitro model allows evaluation of potential agents for the treatment of DH at the clinically relevant cervical region of human teeth.

FLUID DYNAMICS ANALYSIS OF SHEAR STRESS ON NERVE ENDINGS IN DENTINAL MICROTUBULE: A QUANTITATIVE INTERPRETATION OF HYDRODYNAMIC THEORY FOR DENTAL PAIN

Noxious thermal and/or mechanical stimuli applied to dentine can cause fluid flow in dentinal microtubules (DMTs). The fluid flow induces shear stress (SS) on intradental nerve endings and may excite pulpal mechanoreceptors to generate dental pain sensation. There exist numerous studies on dental thermal pain, but few are mathematical. For this, we developed a computational fluid dynamics (CFD) model of dentinal fluid flow (DFF) in innervated DMTs. Based on this model, we systematically investigated the effects of various parameters (e.g., biological structure, DFF velocity, and fluid properties) on the SS experienced by intradental nerve endings and thus provide a quantitative interpretation to the hydrodynamic theory. The dimensions of biological structures, odontoblastic process (OP) movement, dentinal fluid velocity, and viscosity were found to have significant influences on the SS while dentinal fluid density showed negligible influence under conditions studied. The results indicate that: (i) dental pain study of animal models may not be directly applied to human being and the results may even vary from one person to another and (ii) OP movement caused by DFF changes the dimension of the space for the fluid flow, affecting thus the SS on nerve endings. The present work enables better understanding of the mechanisms underlying dental pain sensation and quantification of dental pain intensity resulted from clinical procedures such as dentine sensitivity testing and dental restorative processes.

Inflammatory mediators in fluid extracted from the coronal occlusal dentine of trimmed teeth

BACKGROUND

Chemokines and cytokines may occur in dentinal fluids in response to local infection and inflammation. To test this hypothesis, we assessed the presence and concentration of inflammatory mediators in fluid extracted from the coronal occlusal dentine of trimmed teeth.

DESIGN

Freshly extracted sound, carious, and restored molars were trimmed through the enamel to expose the underlying dentine, etched with 35% phosphoric acid, and rinsed. Fluid was extracted from the coronal occlusal dentine of these trimmed teeth by centrifugation at 2750 × g for 30 min.

RESULTS

When assessed by MALDI-TOF, fluid extracted from the coronal occlusal dentine from 16 molars contained at least 117 peaks with different masses suggesting that this fluid was rich with molecules within the appropriate mass range of potential mediators. Indeed, when assessed for chemokines and cytokines, fluid extracted from the coronal occlusal dentine from 25 extracted molars with caries lesions, 10 extracted restored molars with occlusal amalgam, and 77 extracted sound molars contained IL-1β, TNF-α, IL-6, IL-8, IL-12(p70), and IL-10. A significant elevation was found for TNF-α (p=0.041) in extracted fluid from teeth restored with amalgam fillings.

CONCLUSIONS

Overall, fluid extracted from the coronal occlusal dentine of trimmed teeth may be useful in identifying proteins and other molecules in dentine and pulpal fluids and determining their role as mediators in the pathogenesis of oral infection and inflammation.

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

INTRODUCTION

Pulpal diagnostics might be improved by using molecular markers found in dentinal fluid. In the current pilot study, we tested whether matrix metallopeptidase 9 (MMP-9) levels in dentinal fluid were detectable and differed between pulps from symptomatic teeth diagnosed with irreversible pulpitis and healthy counterparts.

METHODS

Thirty-one patients participated; 19 were diagnosed with irreversible pulpitis, and 12 were in need of replacement of a filling close to the pulp space in a clinically healthy tooth. Dentinal fluid was collected during a period of 2 minutes from dentin cavities by using folded polyvinylidene difluoride (PVDF) membranes, which were then transferred to microcentrifugation tubes containing physiologic saline solution. Total MMP-9 levels in these solutions were assessed by using a human MMP-9 fluorescent assay, detection limit 0.25 ng/mL. MMP-9 levels between groups were compared by using Mann-Whitney U test (alpha <0.05).

RESULTS

Three specimens from the symptomatic teeth were not included because coronal pulps proved to be necrotic on access. Dentinal fluid samples from symptomatic teeth had significantly higher MMP-9 levels than those from clinically healthy counterparts (P < .05). However, merely 7 of the 16 pulpitis samples contained detectable levels of MMP-9. None of the clinically healthy control specimens contained any detectable amounts of MMP-9.

CONCLUSIONS

With a sensitive assay, it was possible to detect an enzyme linked with pulp tissue destruction (MMP-9) in dentinal fluid. However, the collection method needs to be improved to provide predictable fluid yields. Longitudinal studies should be performed to assess the predictive value of molecular markers in dentinal fluid on pulpal pathosis.

Innate Immune Responses of the Dental Pulp to Caries

Various cells and inflammatory mediators are involved in the initial pulpal responses to caries. This review focuses on the cellular, neuronal, and vascular components of pulpal innate responses to caries. Discussion will include dentinal fluid, odontoblasts, neuropeptides, and neurogenic inflammation, which are not classic immune components but actively participate in the inflammatory response as the caries progress pulpally. Summaries of innate immune cells as well as their cytokines and chemokines in healthy and reversible pulpitis tissues are presented.

Spectroscopic investigation of the function of aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution as a dentin desensitizer

Fourier-transform (FT)-Raman and -infrared (IR) spectroscopy were employed to investigate the function of the aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution (Gluma) as a desensitizer. 2-Hydroxyethylmethacrylate (HEMA), glutaraldehyde (GA), and the mixture of HEMA/GA (i.e. Gluma) were used to interact with dentin, collagen, hydroxyapatite (HAP), and bovine serum albumin (BSA) individually. All the interactions were monitored by an FT-Raman spectrometer. FT-IR spectroscopy was also used in this study. The results show that HEMA could be absorbed by dentin and collagen; GA could cross-link collagen and BSA; and when BSA was added to Gluma, polymerization of HEMA occurred. The results suggest that Gluma acts as a desensitizer whereby, first, GA reacts with part of the serum albumin in dentinal fluid, which induces a precipitation of serum albumin, then, second, a reaction of GA with serum albumin induces polymerization of HEMA. The function of Gluma as a desensitizer to block dentinal tubules occurs via these two reactions.

Cytokine signalling in rat pulp interstitial fluid and transcapillary fluid exchange during lipopolysaccharide-induced acute inflammation

The dental pulp consists of loose connective tissue encased in rigid dentinal walls. Because of its topography the tissue has low interstitial compliance and limited capacity to expand during fluid volume changes. Due to limitations regarding access to interstitial fluid, basic knowledge on transcapillary fluid transport parameters is lacking for this organ. The scope of this project was dual: first we aimed at establishing a method for isolation of pulp interstitial fluid (IF), and second we applied the method in rats subjected to lipopolysaccharide (LPS)-induced endotoxaemia. The aim was to measure colloid osmotic pressure (COP) and pro-inflammatory cytokines in the pulp IF during acute inflammation. Fluid volumes and pulpal blood flow (PBF) were measured to obtain more information about microcirculatory changes that take place in this pulpitis model. By centrifugation of incisor pulp at 239 g we were able to extract fluid representative for IF. Pulp IF had a relative high control COP (approximately 83% of plasma COP) and was similar to plasma COP 3 h after LPS challenge. The pulp exhibited a high content of IF (0.60 +/- 0.03 ml (g wet weight)(-1)) and a vascular volume of 0.03 +/- 0.01 ml (g w.w.)(-1) No differences were observed in the distribution of fluid volumes after 1.5 and 3 h LPS exposure. PBF and systemic blood pressure dropped significantly after LPS administration. PBF remained low whereas systemic blood pressure was re-established during the 3-h period, implying organ dysfunction. There was a differential pattern of cytokine expression in pulp IF and serum with cytokines such as IL-1alpha, IL-1beta and TNF-alpha locally produced, whereas others such as IFN-gamma and IL-6 were produced systemically and probably spilled over to the pulp IF after LPS exposure. Our findings show that pulp IF can be isolated by centrifugation and that this method is useful when studying fluid balance and extracellular signalling mechanisms in the dental pulp in normal and pathological conditions.

Phenotypic and genotypic selection of microbiota surviving under dental restorations

The effects of sealing infected carious dentine below dental restorations on the phenotypic and genotypic diversity of the surviving microbiota was investigated. It was hypothesized that the microbiota would be subject to nutrient limitation or nutrient simplification, as it would no longer have access to dietary components or salivary secretion for growth. The available nutrients would be limited primarily to serum proteins passing from the pulp through the patent dentinal tubules to the infected dentine. Ten lesions were treated, and infected dentine was sealed below dental restorations for approximately 5 months. Duplicate standardized samples of infected dentine were taken at baseline and after the removal of the restorations. The baseline microbiota were composed primarily of Lactobacillus spp., Streptococcus mutans, Streptococcus parasanguinis, Actinomyces israelii, and Actinomyces gerencseriae. None of these taxa were isolated among the microbiota of the dentine samples taken after 5 months, which consisted of only Actinomyces naeslundii, Streptococcus oralis, Streptococcus intermedius, and Streptococcus mitis. The microbiota of the final sample exhibited a significantly (P < 0.001) increased ability to produce glycosidic enzymes (sialidase, beta-N-acetylglucosaminidase, and beta-galactosidase), which liberate sugars from glycoproteins. The genotypic diversity of S. oralis and A. naeslundii was significantly (P = 0.002 and P = 0.001, respectively) reduced in the final samples. There was significantly (P < 0.001) greater genotypic diversity within these taxa between the pairs of dentine samples taken at baseline than was found in the 5-month samples, indicating that the dentine was more homogenous than it was at baseline. We propose that during the interval between placement of the restorations and their removal, the available nutrient, primarily serum proteins, or the relative simplicity and homogeneity of the nutrient supply significantly affected the surviving microbiota. The surviving microbiota was less complex, based on compositional, phenotypic, and genotypic analyses, than that isolated from carious lesions which were also exposed to salivary secretions and pH perturbations.

Effect of dentinal fluid composition on dentin demineralization in vitro

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.

Effect of dentin perfusion on the sealing ability and microtensile bond strengths of a total-etch versus an all-in-one adhesive

OBJECTIVES

To test the null hypothesis that perfusion of dentin has no effect on the sealing or bond strength in Class V resin composite restorations using a two-step total-etch (Scotchbond 1), or a one-step self-etch (all-in-one) (Prompt L-Pop) adhesive.

METHODS

Dentin permeability in Class V cavity preparations cut into extracted human third molars was measured in a fluid transport setup. Resin composites were placed using either Scotchbond 1, or Prompt L-Pop with or without dentin perfusion at 1.47 kPa. Permeability was re-measured, and the reduction in permeability was calculated as a percentage of the initial value. Additionally, microtensile bond strength (microTBS) to dentin was measured.

RESULTS

Whereas the ability of Scotchbond 1 to seal dentin was significantly decreased due to dentin perfusion (p = 0.00025), that of Prompt L-Pop was not affected (p = 0.099). Scotchbond 1 produced significantly less dentinal seal than Prompt L-Pop only in the restorations carried out with perfusion (p = 0.0003), in the absence of perfusion, however, the difference was not significant (p = 0.343). Dentin perfusion significantly decreased the microTBS of Scotchbond 1 to dentin (p = 0.001). Due to excessive premature failure during sectioning, microTBS test could not be performed with Prompt L-Pop.

SIGNIFICANCE

Dentinal fluid flow may have detrimental effects on the sealing ability of dental adhesives depending on the type of adhesive used. Studies aiming to rank adhesives in relation to their sealing ability in vitro should not disregard dentin perfusion.

Invasion of dentinal tubules by oral bacteria

Bacterial invasion of dentinal tubules commonly occurs when dentin is exposed following a breach in the integrity of the overlying enamel or cementum. Bacterial products diffuse through the dentinal tubule toward the pulp and evoke inflammatory changes in the pulpo-dentin complex. These may eliminate the bacterial insult and block the route of infection. Unchecked, invasion results in pulpitis and pulp necrosis, infection of the root canal system, and periapical disease. While several hundred bacterial species are known to inhabit the oral cavity, a relatively small and select group of bacteria is involved in the invasion of dentinal tubules and subsequent infection of the root canal space. Gram-positive organisms dominate the tubule microflora in both carious and non-carious dentin. The relatively high numbers of obligate anaerobes present-such as Eubacterium spp., Propionibacterium spp., Bifidobacterium spp., Peptostreptococcus micros, and Veillonella spp.-suggest that the environment favors growth of these bacteria. Gram-negative obligate anaerobic rods, e.g., Porphyromonas spp., are less frequently recovered. Streptococci are among the most commonly identified bacteria that invade dentin. Recent evidence suggests that streptococci may recognize components present within dentinal tubules, such as collagen type I, which stimulate bacterial adhesion and intra-tubular growth. Specific interactions of other oral bacteria with invading streptococci may then facilitate the invasion of dentin by select bacterial groupings. An understanding the mechanisms involved in dentinal tubule invasion by bacteria should allow for the development of new control strategies, such as inhibitory compounds incorporated into oral health care products or dental materials, which would assist in the practice of endodontics.

Inverse relationship between tensile bond strength and dimensions of bonded area

It is a known fact that there is a relationship between magnitude of bonded area and laboratory tensile test results. This relationship has been described for a range of areas between 1 and 10 mm(2), in extracted, nonperfused teeth. The aim of this study is to test this relationship in perfused teeth, with bonded areas ranging from 0.7 to 110.9 mm(2). Dentin of 92 sound third human molars was exposed and perfused, and three groups of bonded areas (BA) were delimited: small (0.69-1.89 mm(2)), medium (8.66-19.54 mm(2)), and large (58.91-110.86 mm(2)). Tensile bond strength (TBS) of three adhesive restorative systems was found. The best nonlinear curve estimation was searched (SPSS 9.0) between TBS and BA, for each and all materials. The best estimation was, for all materials, TBS = 4.17 + 10.35/BA (p < 0.0001).

Effect of perfusion with water on demineralization of human dentin in vitro

Dentinal fluid rarely features in caries studies of dentin. The mutual effects of in vitro perfusion and dentin demineralization were investigated. The correlation between the remaining dentin thickness and demineralization was also analyzed. Buccal cervical dentin windows in human tooth segments were demineralized either with or without perfusion with water at 3.14 kPa. Transverse microradiography revealed that dentin perfusion reduced the amount of mineral loss from the lesions by 22 vol%; the reduction in lesion depth was 8%. Perfusion rate, which was measured throughout the demineralization process by means of a fluid transport model, did not change significantly. Lesions formed closer to the pulp exhibited increased mineral loss and lesion depth. In conclusion, dentinal fluid flow offers some protection against demineralization. For a better approximation of clinical reality, therefore, in vitro studies on dentinal caries should consider the effect of dentinal fluid flow.

The localization of matrix metalloproteinase-20 (MMP-20, enamelysin) in mature human teeth

MMP-20 (enamelysin), the matrix metalloproteinase family member discovered in the enamel organ, has also been detected in odontoblasts during dentin formation. We studied the presence and localization of MMP-20 in mature human teeth in health and disease. In immunohistochemistry, MMP-20-positive staining was observed most intensively in the radicular odontoblastic layer and also in dilated dentinal tubuli of caries lesions. By Western blotting, MMP-20 was detected in odontoblasts and pulp tissue of both sound and carious teeth, in dentinal fluid and dentin of sound teeth, but not in soft carious dentin. We conclude that MMP-20 produced during primary dentinogenesis is incorporated into dentin and may be released during caries progression. The main cellular source of MMP-20 in the dentin-pulp complex is the odontoblasts, which secrete MMP-20 into the dentinal fluid.

Bacterial adhesins--their role in tubule invasion and endodontic disease

Bacterial invasion of dentinal tubules is critical to the progression of dental caries and the development of pulp and periapical disease, and may also influence the progression of periodontal disease. However, little is known about the host or bacterial mechanisms involved in tubule invasion. Recent work has demonstrated that bacterial interactions with dentine, and salivary and tissue molecules influence invasion. Salivary molecules such as mucin and immunoglobulin G (IgG) co-aggregate with bacterial cells, which inhibits dentine invasion, while deposition of dentinal tubule fluid molecules e.g. albumin, IgG, or fibrinogen within dentinal tubules also inhibits invasion. Dentine invasion by streptococci has been shown to be associated with a bacterial growth response and adhesion to unmineralized collagen, which are mediated by streptococcal cell-surface antigen I/II polypeptides. These adhesins possess diverse binding properties including binding to salivary glycoprotein, other bacteria, and to collagen. Additionally, some antigen I/II polypeptides facilitate species-specific co-invasion between streptococci and obligate anaerobes that lack the ability to invade by themselves. An understanding of the mechanisms involved in bacterial invasion of dentine should allow development of new control strategies.

The effect of tissue molecules on bacterial invasion of dentine

Bacterial invasion of dentinal tubules is a critical step in the pathogenesis of dental caries and pulp and periapical disease. The purpose of this study was to determine the effect some molecules commonly found in saliva and dentinal tubule fluid may have on the bacterial invasion of dentine. The results showed that invasion of Streptococcus gordonii or Enterococcus faecalis cells was inhibited when the bacterial cells were in solution with mucin, immunoglobulin G (IgG) and serum, and this was related to bacterial cell aggregation, as a result of interaction with agglutinins, and/or inhibition of collagen binding. When dentine was soaked in growth media containing fibrinogen, IgG, albumin or serum prior to inoculation, bacterial invasion was inhibited. It is suggested that this may be due to reduced dentine permeability as a consequence of the deposition of the compounds within dentinal tubules.

Comparison of the in vitro permeability of human dentine according to the dentinal region and the composition of the simulated dentinal fluid

OBJECTIVE

To compare the permeability of the occlusal and the cervical dentinal regions within the same tooth, which represent the bottom of Class I and V cavities, respectively, with two different compositions of perfusion fluid, in vitro.

METHODS

An occlusal and a buccal disc were cut from each extracted third molar at a level close to the pulp chamber. The convective permeability of the discs was measured in a fluid transport model using de-ionised water or 1:3 diluted bovine serum and the hydraulic conductance was determined.

RESULTS

The mean hydraulic conductance values of the occlusal and the buccal cervical human dentine to water were 0.069 and 0.047 microl min(-1) cm(-2) cm H(2)O(-1), respectively. When diluted bovine serum was used, the corresponding values were 0.036 and 0.012 microl min(-1) cm(-2) cm H(2)O(-1), respectively. Statistical analysis revealed no significant difference between the permeability of these two regions. The composition of the perfusion fluid significantly influenced the permeability of dentine.

CONCLUSIONS

The occlusal and the buccal cervical regions of human dentine have similar permeability characteristics in vitro. There is a strong reverse correlation between the viscosity of the perfusion fluid and the perfusion through the dentine.

The effects of post-extraction time on the hydraulic conductance of human dentine in vitro

The permeability characteristics of dentine have been used in many in vitro studies to evaluate longitudinally the efficacy of various restorative and preventative procedures. However, the permeability of human dentine increases over time after tooth extraction. The aim here was to determine if there is a steady phase in dentine permeability in vitro over time. The convective permeability of dentine discs cut from extracted human third molars to 0.8% albumin solution was measured initially on day 7 after extraction using a fluid-transport model and the hydraulic conductance was calculated. The permeability of each disc was then re-measured de- and re-mounting the split-chamber 1h after the initial measurement as well as on days 8, 9, and 37 after extraction. No significant difference was found between the initial and 1h hydraulic conductances. A significant increase in hydraulic conductance was seen from day 7 to 9, but there was no significant difference between the hydraulic conductances on days 9 and 37. These results suggest that the measurements were reproducible and that a steady phase of dentine permeability is established 9 days after extraction under these study conditions in vitro.

Evidence for bacterial causation of adverse pulpal responses in resin-based dental restorations

The widespread use of resin and resin-monomers for bonding of dental restorations to dentin has occurred because of a fundamental shift in the view that injury to the pulp is induced by restorative procedures. While, for many years, the toxic effects of restorative materials were thought to be of crucial importance in the development of adverse pulpal responses, the key role of bacterial leakage at the restoration-tooth interface is now well-recognized. Consequently, if optimal conditions for the preservation of pulpal health are to be ensured, dental restorations should provide an impervious seal against the surrounding tooth structure. However, polymerization shrinkage and contraction stresses induced during setting, as well as a variety of technical difficulties encountered during the clinical operation, often produce less than perfect results. Therefore, modern restorative procedures involving resin and resin-bonded restoratives must still rely on the ability of the pulp to cope with the injurious elements to which it may be exposed during and after the procedure. This review examines factors that may govern the pulp's response to restorative procedures that involve adhesive technologies. An assessment is made of the risks involved as far as the continued vital function of the pulp is concerned. It is concluded that an intact, although thin, wall of primary dentin often enables the pulp to overcome both toxic material effects and the influences of bacterial leakage. In contrast, the pulp may not do equally well following capping of open exposures with resin composites. A dearth of controlled clinical studies in this area of dentistry calls for confirmation that pulpal health prevails over the long term following the use of total-etch and resin-bonding techniques.

The effects of immunoglobulins on the convective permeability of human dentine in vitro

Immunoglobulin molecules are localized in the dentinal tubules of non-carious and carious teeth, but their possible role in caries invasion is not understood. This study sought to examine the effects of immunoglobulin molecules on dentine permeability using a fluid-filtration method. Crown segments cut from impacted human third molars were treated by filtration with 100 micrograms/ml IgG, 100 micrograms/ml IgA or 30 micrograms/ml IgM under a constant pressure. Flow rates were recorded and percent changes in flow rate analysed over time. Filtrates collected at various times were tested for changes in immunoglobulin concentrations by an enzyme-linked immunosorbent assay, and the percent retention of immunoglobulins to dentine was calculated. There was a decreasing non-linear exponential relation between the percent changes in flow rate and filtration time for all three immunoglobulins. The percentage of retained immunoglobulins was significantly related to the filtration time for all three classes of immunoglobulins. Immunoglobulin retention contributed to significant changes in flow rate with time. These in vitro results indicate the potential mechanism of immunoglobulins in decreasing tabular permeability.

A mathematical model of potassium ion diffusion in dentinal tubules

Desensitizing agents containing potassium ions (K+) are believed to inactivate intradental nerves by raising extracellular [K+]. A mathematical model was used to investigate factors affecting [K+] in dentinal tubules. The most important factors affecting the steady-state tubular [K+] were the tubular fluid-flow velocity, salivary [K+] and the permeability to potassium (k) of the barrier between the tubule and the pulp. Tubular [K+] decreased with increasing outward flow velocity and increasing k. whereas the dimensions of the tubule and odontoblast process had little effect. Following a 1 min simulated application of 500 mmol/1 K+ to the dentine surface, [K+] at the inner end of the tubule increased above steady-state levels for 20-30 min. The maximum [K+] attained at the inner end of the tubule was around 30 mmol/l for an impermeable barrier (k = 0) and flow velocity of 1.4 microns/s, but lower maximum tubular [K+] were achieved when either the outward flow velocity or k was increased. The model suggests that applying potassium-containing preparations to dentine may increase [K+] at the inner ends of dentinal tubules to levels sufficient to inactivate intradental nerves. However, the localized increase in [K+] is transient, and the concentration change will be lessened by conditions that increase the tubular fluid-flow velocity or the permeability of the barrier between the tubule and pulp.

Dynamics of the pulpo-dentin complex

Dentin has a relatively high water content due to its tubular structure. Once dentin is exposed, this intratubular water is free to move in response to thermal, osmotic, evaporative, or tactile stimuli. Fluid shifts across dentin are thought to cause sufficient shear forces on odontoblasts, nerve endings, nearby fibroblasts, and blood vessels to cause significant mechanical irritation, disruption, or damage, depending on the magnitude of the fluid shift. Even in the absence of fluid shifts, the water-filled tubules provide diffusion channels for noxious (i.e., bacterial products) substances which diffuse inward toward the pulp, where they can activate the immune system, provide chemotactic stimuli, cytokine production, and produce pain and pulpal inflammation. Viewed from this perspective, dentin is a poor barrier to external irritants. However, pulpal tissues react to these challenges by increasing the activity of nerves, blood vessels, the immune system, and interstitial fluid turnover, to make the exposed dentin less permeable either physiologically, via increased outward fluid flow, or microscopically, by lining tubules with proteins, mineral deposits, or tertiary dentin, thereby enhancing the barrier properties of dentin, and providing additional protection to pulpal tissues. These reactions involve dentin and pulp, both in the initiation of the processes and in their resolution. These responses of the dental pulp to irritation of dentin demonstrate the dynamic nature of the pulpo-dentin complex.