Microcirculation of the dental pulp in health and disease

Implementing microfluidic flow device model in utilizing dural substitutes as pulp capping materials for vital pulp therapy

Vital pulp therapy (VPT) has gained prominence with the increasing trends towards conservative dental treatment with specific indications for preserving tooth vitality by selectively removing the inflamed tissue instead of the entire dental pulp. Although VPT has shown high success rates in long-term follow-up, adverse effects have been reported due to the calcification of tooth canals by mineral trioxide aggregates (MTAs), which are commonly used in VPT. Canal calcification poses challenges for accessing instruments during retreatment procedures. To address this issue, this study evaluated the mechanical properties of dural substitute intended to alleviate intra-pulp pressure caused by inflammation, along with assessing the biological responses of human dental pulp stem cells (hDPSCs) and human umbilical vein endothelial cells (HUVECs), both of which play crucial roles in dental pulp. The study examined the application of dural substitutes as pulp capping materials, replacing MTA. This assessment was conducted using a microfluidic flow device model that replicated the blood flow environment within the dental pulp. Computational fluid dynamics simulations were employed to ensure that the fluid flow velocity within the microfluidic flow device matched the actual blood flow velocity within the dental pulp. Furthermore, the dural substitutes (Biodesign; BD and Neuro-Patch; NP) exhibited resistance to penetration by 2-hydroxypropyl methacrylate (HEMA) released from the upper restorative materials and bonding agents. Finally, while MTA increased the expression of angiogenesis-related and hard tissue-related genes in HUVEC and hDPSCS, respectively, BD and NP did not alter gene expression and preserved the original characteristics of both cell types. Hence, dural substitutes have emerged as promising alternatives for VPT owing to their resistance to HEMA penetration and the maintenance of stemness. Moreover, the microfluidic flow device model closely replicated the cellular responses observed in live pulp chambers, thereby indicating its potential use as anin vivotesting platform.

A Correlation between Clinical Classification of Dental Pulp and Periapical Diseases with its Patho Physiology and Pain Pathway

Background

Dental pain due to pulpal involvement is difficult to diagnose due to the apparent inaccessibility of pulp to the clinical tests, indistinct symptoms, and referred toothache originating from the periodontal tissues. Though we have various clinical classification systems to categorize pulpal diseases, we are yet biased about the exact pathophysiology and pain pathway associated with it. Dental pulp has a complex physiology, and so is its pathophysiology.

Aims & objectives

To concisely reviews the basic understanding of the pathophysiology of pulp, pain pathway, and its correlation with the classification of various clinical conditions of pulpal inflammation and periapical diseases.

Methodology

Literature search on pulpal diseases and pathophysiology from the sources: MEDLINE, PubMed, Web of Science and Cochrane Databases dated from 1965 till December 2020 was carried on to collect 163 articles.

Results

Filtered search on the pathophysiology of pulp, pain pathway, and classification of various clinical conditions of pulpal inflammation resulted us to precise 36 articles required for our understanding and demystifying the correlation.

Conclusion

The emphasis should be laid on understanding the minute changes occurring inside the pulp in due course of inflammation to aid its diagnosis and a treatment plan accordingly.

How to cite this article

Samir PV, Mahapatra N, Dutta B, et al. A Correlation between Clinical Classification of Dental Pulp and Periapical Diseases with its Patho Physiology and Pain Pathway. Int J Clin Pediatr Dent 2023;16(4):639-644.

Inflammation of the Human Dental Pulp Induces Phosphorylation of eNOS at Thr495 in Blood Vessels

The activity of endothelial nitric oxide synthase (eNOS) in endothelial cells increased with the phosphorylation of the enzyme at Ser1177 and decreased at Thr495. The regulation of the phosphorylation sites of eNOS at Ser1177 and Thr495 in blood vessels of the healthy and inflamed human dental pulp is unknown. To investigate this, healthy and carious human third molars were immersion-fixed and decalcified. The localization of eNOS, Ser1177, and Thr495 in healthy and inflamed blood vessels was examined in consecutive cryo-sections using quantitative immunohistochemical methods. We found that the staining intensity of Ser1177 in healthy blood vessels decreased in inflamed blood vessels, whereas the weak staining intensity of Thr495 in healthy blood vessels strongly increased in inflamed blood vessels. In blood vessels of the healthy pulp, eNOS is active with phosphorylation of the enzyme at Ser1177. The phosphorylation of eNOS at Thr495 in inflamed blood vessels leads to a decrease in eNOS activity, contributing to eNOS uncoupling and giving evidence for a decrease in NO and an increase in O2− production. Since the formation of the tertiary dentin matrix depends on intact pulp circulation, eNOS uncoupling and phosphorylation of eNOS at Thr495 in the inflamed pulp blood vessels should be considered during caries therapy.

Bacterial Invasion of Pulp Blood Vessels in Teeth with Symptomatic Irreversible Pulpitis

INTRODUCTION

This study described the degenerative changes and infection patterns of the pulp tissue associated with symptomatic irreversible pulpitis.

METHODS

The material consisted of 32 extracted teeth with untreated deep caries that were clinically and histologically diagnosed with irreversible pulpitis and were part of the histopathologic collection of 1 of the authors. The controls consisted of intact teeth with normal uninflamed pulps and teeth with reversible pulpitis. Teeth were processed for histopathologic and histobacteriologic analyses.

RESULTS

All teeth with irreversible pulpitis showed areas of severe acute inflammation, necrosis, microabscesses, and bacterial infection in the pulp chamber. These areas were surrounded by a chronic inflammatory infiltrate, and, at the distance, the pulp tissue was often uninflamed. Bacteria were also observed in the areas surrounding the necrotic foci, both as scattered cells through the extravascular space and at varying numbers within the blood vessel lumen. The number of bacteria and the density of the intravascular bacterial aggregations varied considerably. In one third of the cases, bacteria occurred in the lumen of venules in areas at a considerable distance from the necrotic focus in the coronal third of the root. No intravascular bacteria were noted in the middle and apical segments of the canal. No bacteria were found in the pulps of any of the control specimens.

CONCLUSIONS

Bacterial invasion and colonization of necrotic areas were observed in the pulp of all teeth with caries exposure and symptomatic irreversible pulpitis. Bacterial penetration of blood vessels occurred in all cases, suggesting that this may be an important mechanism of spread of bacterial infection through the pulp tissue in an endodontic infection.

Preoperative Factors Associated with Anesthesia Failure for Patients Undergoing Nonsurgical Root Canal Therapy: A National Dental Practice-Based Research Network Study

INTRODUCTION

The aim of this study was to identify preoperative factors associated with local anesthesia failure.

METHODS

The National Dental Practice-Based Research Network (www.NationalDentalPBRN.org) data from 534 patients who received a nonsurgical root canal treatment completed in a single appointment were included in this analysis. Three methods for defining anesthesia failure were used: definition 1, patient-reported level of numbness; definition 2, provider-reported quality of anesthesia; and definition 3, provider-reported use of supplemental anesthesia. Fifty-one preoperative factors were investigated and analyzed individually against the overall failure rate for each method, and multivariate generalized estimating equation logistic models were fit with predictors chosen using stepwise model selection to evaluate factors that may interact with each other.

RESULTS

The overall anesthesia failure rates were 5%, 15%, and 30% for definitions 1, 2, and 3, respectively. Provider experience, diabetes, absence of sharp or aching pain, absence of smoking, and a fair expected outcome were associated with anesthesia failure (definition 1). Provider level of training, absence of a sinus tract, bite sensitivity, and stress making the pain worse were associated with anesthesia failure (definition 2). Provider level of training, pain provoked by stimulus, mandibular teeth, teeth with vital pulps, and pain interfering with daily activities were associated with the use of supplemental anesthesia (definition 3).

CONCLUSIONS

With the range of 5%-30% of anesthesia failures, a few common factors across the models assessed were elucidated. Providers with higher levels of training had significantly fewer anesthesia failures. Patient self-reported history of diabetes and preoperative pain-related interference with daily activities were associated with more anesthesia failures. Greater severity of various tooth-related pain characteristics, as a group but not individually, accounted for more anesthesia failures.

Nanomaterials Application in Endodontics

In recent years, nanomaterials have become increasingly present in medicine, especially in dentistry. Their characteristics are proving to be very useful in clinical cases. Due to the intense research in the field of biomaterials and nanotechnology, the efficacy and possibilities of dental procedures have immensely expanded over the years. The nano size of materials allows them to exhibit properties not present in their larger-in-scale counterparts. The medical procedures in endodontics are time-consuming and mostly require several visits to be able to achieve the proper result. In this field of dentistry, there are still major issues about the removal of the mostly bacterial infection from the dental root canals. It has been confirmed that nanoparticles are much more efficient than traditional materials and appear to have superior properties when it comes to surface chemistry and bonding. Their unique antibacterial properties are also promising features in every medical procedure, especially in endodontics. High versatility of use of nanomaterials makes them a powerful tool in dental clinics, in a plethora of endodontic procedures, including pulp regeneration, drug delivery, root repair, disinfection, obturation and canal filling. This study focuses on summing up the current knowledge about the utility of nanomaterials in endodontics, their characteristics, advantages, disadvantages, and provides a number of reasons why research in this field should be continued.

A Clinical Study Determining Pulp Vitality in Oropharyngeal Cancer Patients Undergoing Radiotherapy Using Diagnostic Tool-Pulse Oximetry

Pulse oximetry is an equipment that evaluates pulp vitality for concrete endodontic diagnosis and treatment plan. One of the treatment methods of oropharyngeal cancer is radiotherapy. Radiotherapy has some harmful effects on dental pulp that affects pulp vitality. The objective of study was to assess pulp vitality before, at the end of radiotherapy and six months after radiotherapy (RT) in oropharyngeal cancer patients undergoing radiotherapy. 25 patients who were diagnosed with oropharyngeal cancer having asymptomatic intact crowns were selected for the study. Pulp vitality was checked before the commencement of radiotherapy (PV1), immediately after radiotherapy (PV 2) and six months post radiotherapy (PV 3). Pulp vitality of first posterior tooth was selected of each patient and was checked with pulse oximetry. Paired t-test was used as statistical analysis. Statistically significant difference was observed when PV 1 and PV 2, PV 1 and PV 3 and PV 2 and PV 3 were compared amongst each other. There was reduction noted in mean SpO2 value when groups PV 2 and PV1 were compared. This was statistically significant. Statistically significant increase in mean SpO2 value was observed six months post radiotherapy (PV 3). Thus, it can be concluded that statistically significant reduction in mean SpO2 level post radiotherapy recovers after six months.

Deciphering Reparative Processes in the Inflamed Dental Pulp

Research over several decades has increased our understanding of the nature of reparative and regenerative processes in the dental pulp, at both the cellular and molecular level. However, advances in scientific knowledge have not translated into novel clinical treatment strategies for caries-induced pulpitis. This narrative review explores the evidence regarding the ability of inflamed pulp tissue to heal and how this knowledge may be used therapeutically. A literature search and evidence analysis covering basic, translational and clinical pulp biology research was performed. The review focuses on (1) the regenerative and defense capabilities of the pulp during caries-induced inflammation; (2) the potential of novel biomaterials to harness the reparative and regenerative functions of the inflamed pulp; and (3) future perspectives and opportunities for conservative management of the inflamed pulp. Current conservative management strategies for pulpitis are limited by a combination of unreliable diagnostic tools and an outdated understanding of pulpal pathophysiological responses. This approach leads to the often unnecessary removal of the entire pulp. Consequently, there is a need for better diagnostic approaches and a focus on minimally-invasive treatments utilizing biologically-based regenerative materials and technologies.

Effect of high-irradiance light curing on exposure times and pulpal temperature of adequately polymerized composite

This study investigated the effect of high-irradiance light-curing on exposure time and pulpal temperature of adequately-cured composite. Composite placed in a molar preparation was cured using high-irradiance light-curing units (Flashmax P3, Valo, S.P.E.C. 3 LED, Cybird XD) and tested for hardness occlusal-gingivally. The first group had exposure times set according to manufacturer settings (recommended), second group to yield 80% of maximum hardness at the 2 mm depth (experimental), and third group was set at 20 s (extended). Exposure time necessary to adequately polymerize the composite at 2 mm depth was 9 s for the Cybird XD and Valo and 12 s for S.P.E.C. 3 LED and Flashmax P3. None of the high-irradiance light-curing units adequately polymerized the composite at the manufacturer-recommended minimum-exposure times of 1-3 s. Exposure times necessary to adequately polymerize composite at 2 mm resulted in a maximum pulpal-temperature increase well below the temperature associated with possible pulpal necrosis.

A laboratory study to detect simulated pulpal blood flow in extracted human teeth using ultrasound Doppler flowmetry

AIM

To develop a laboratory-based tooth model of simulated blood flow in teeth and evaluate it using ultrasound Doppler flowmetry (UDF).

METHODOLOGY

A laboratory-based tooth model for UDF was created based on a microfluidic experimental model proposed by Kim & Park (2016 a,b). Twenty-one maxillary or mandibular anterior human teeth within 1 month of extraction were used. Four holes were made in each tooth to fit 1.6-mm diameter polytetrafluoroethylene (PTFE) tubes: at the apical foramen, palatal surface in the centre of the crown, palatal surface apical to the cementoenamel junction (CEJ) and the root centre. Fluid mimicking pulsating blood was pumped (pressure range: 0-200 mbar, flow rate range: 0-80 μL min^-1 ) into the apical foramen via the PTFE tubes, which exited the tooth through the palatal surface in the centre of the crown (control group), palatal surface below the CEJ (group 1) and the palatal surface at the mid-root level (group 2). An UDF transducer of 20 MHz was placed at a 60° angle to the labial surface of tooth and was used to measure the fluid flow velocity (Vs, Vas, Vm, Vam, Vd, Vad and Vakd). The flow velocity of the different groups was compared using the Wilcoxon signed-rank test, with a 95% confidence level.

RESULTS

UDF facilitated the detection of the simulated pulpal blood flow in the control group and group 1, but not in group 2. The mean and standard deviations of Vas, Vam and Vakd were 0.921 ± 0.394, 0.479 ± 0.208 and 0.396 ± 0.220 cm s^-1 , respectively, in the control group, and 0.865 ± 0.368, 0.424 ± 0.215 and 0.487 ± 0.279 cm s^-1 , respectively, in group 1. The pulpal blood flow values of the control group and group 1 were not significantly different (p > 0.05).

CONCLUSIONS

This laboratory study revealed that ultrasound Doppler flowmetry enabled the detection of simulated blood flow below the level of the CEJ but not at the mid-root level.

Ancient dental pulp: Masterpiece tissue for paleomicrobiology

Introduction

Dental pulp with special structure has become a good reference sample in paleomicrobiology‐related blood‐borne diseases, many pathogens were detected by different methods based on the diagnosis of nucleic acids and proteins.

Objectives

This review aims to propose the preparation process from ancient teeth collection to organic molecule extraction of dental pulp and summary, analyze the methods that have been applied to detect septicemic pathogens through ancient dental pulps during the past 20 years following the first detection of an ancient microbe.

Methods

The papers used in this review with two main objectives were obtained from PubMed and Google scholar with combining keywords: “ancient,” “dental pulp,” “teeth,” “anatomy,” “structure,” “collection,” “preservation,” “selection,” “photography,” “radiography,” “contamination,” “decontamination,” “DNA,” “protein,” “extraction,” “bone,” “paleomicrobiology,” “bacteria,” “virus,” “pathogen,” “molecular biology,” “proteomics,” “PCR,” “MALDI‐TOF,” “LC/MS,” “ELISA,” “immunology,” “immunochromatography,” “genome,” “microbiome,” “metagenomics.”

Results

The analysis of ancient dental pulp should have a careful preparation process with many different steps to give highly accurate results, each step complies with the rules in archaeology and paleomicrobiology. After the collection of organic molecules from dental pulp, they were investigated for pathogen identification based on the analysis of DNA and protein. Actually, DNA approach takes a principal role in diagnosis while the protein approach is more and more used. A total of seven techniques was used and ten bacteria (Yersinia pestis, Bartonella quintana, Salmonella enterica serovar Typhi, Salmonella enterica serovar Paratyphi C, Mycobacterium leprae, Mycobacterium tuberculosis, Rickettsia prowazeki, Staphylococcus aureus, Borrelia recurrentis, Bartonella henselae) and one virus (Anelloviridae) were identified. Y. pestis had the most published in quantity and all methods were investigated for this pathogen, S. aureus and B. recurrentis were identified by three different methods and others only by one. The combining methods interestingly increase the positive rate with ELISA, PCR and iPCR in Yersinia pestis diagnosis. Twenty‐seven ancient genomes of Y. pestis and one ancient genome of B. recurrentis were reconstructed. Comparing to the ancient bone, ancient teeth showed more advantage in septicemic diagnosis. Beside pathogen identification, ancient pulp help to distinguish species.

Conclusions

Dental pulp with specific tissue is a suitable sample for detection of the blood infection in the past through DNA and protein identification with the correct preparation process, furthermore, it helps to more understand the pathogens of historic diseases and epidemics.

Vascularity and VEGF/VEGFR2 Signaling in the Dentine-Pulp Complex of Immature and Mature Permanent Teeth

Objective

To examine the microvessel density (MVD) and spatial distribution of endothelial cells and angiogenic activity in immature and mature permanent teeth using immunohistochemistry.

Methods

Healthy third molars with immature and mature root development were formalin-fixed, decalcified in 10% ethylenediaminetetraacetic acid, and processed for routine immunohistochemistry with endothelial cell markers anti-CD34 and anti-CD146 and angiogenic markers anti-vascular endothelial growth factor (VEGF) and anti-VEGF receptor-2 (VEGFR2). Staining was visualized with diaminobenzidine and examined using light microscopy. The distribution of markers was analyzed qualitatively and quantitatively in the coronal, middle, and apical regions of the dentine-pulp complex.

Results

There were spatial differences in protein expression for immature and mature teeth. The pulps of immature teeth were more vascular, had a greater number of CD34+ and CD146+ cells, and a significantly higher MVD in the coronal region than those of mature teeth (P=0.03). The apical papilla contained few blood vessels. VEGF/VEGFR2 activity was significantly greater for immature teeth (P=0.001). VEGF was expressed throughout the pulp-dentine complex, but there was significantly more growth factor coronally (immature P=0.04 and mature P=0.02). VEGFR2 was expressed less than VEGF but was seen on the endothelial cells and single cells unrelated to a vessel lumen.

Conclusion

The spatial distribution of vascular and angiogenic (VEGF/VEGFR2) markers indicates the potential for altered healing responses in the pulps of immature and mature teeth. Immature teeth have a greater MVD and VEGF/VEGFR2 expression than mature teeth, and the increased expression of these markers in the coronal region of both tooth types is important for pulp healing.

Late Effects of Head and Neck Radiotherapy on Pulp Vitality Assessed by Pulse Oximetry

INTRODUCTION

Radiation therapy (RT) of malignant tumors in the head and neck area may have damaging effects on surrounding tissues. The aim of this investigation was to evaluate the long-term effects of ionizing radiation on pulp vitality by measuring pulp oxygenation levels (%SpO2) in patients with history of RT of intraoral and oropharyngeal tumors 4-6 years after treatment.

METHODS

In an experimental group RT (n = 90, history of RT) and a control group CON (n = 90, no history of RT), pulp vitality was assessed by measuring %SpO2 by using pulse oximetry and pulp sensitivity by cold thermal testing. All anterior teeth without history of endodontic therapy of the participants in group RT were measured (n = 693), regardless of the quadrant and the irradiated area. An equal number of anterior teeth were tested in group CON.

RESULTS

There was no significant difference between the %SpO2 levels in group RT (92.7%; standard deviation, ± 1.83) and group CON (92.6%; standard deviation, ± 1.80). All teeth in RT and CON groups showed a positive response to the thermal test. All tested teeth were considered vital.

CONCLUSIONS

Pulp %SpO2 was found to be within normal limits 4-6 years after RT. This suggests that RT may not have a long-term influence on pulp vitality, and reported short-term changes in pulpal microcirculation because of RT may be temporary.

Sympathetic Regulation of Tertiary Dentinogenesis via Beta-2 Adrenergic Receptor on Rat Odontoblasts

INTRODUCTION

Beta-2 adrenergic receptor has been found within the osteoblast membrane meditating bone remodeling. Propranolol is a sympatholytic beta antagonist commonly used as long-term medication for the management of many common diseases such as hypertension. This study was performed to verify the presence of this receptor on odontoblasts in rats and, if present, to investigate its possible association with tertiary dentinogenesis.

METHODS

Twenty male Sprague-Dawley rats (9 weeks old) were randomly assigned to 4 groups: CP0.8 group, cavity preparation + propranolol treatment (0.8 mg/day, n = 5); CP4 group, cavity preparation + propranolol treatment (4.0 mg/day, n = 7); CON group, cavity preparation + saline treatment (0.2 mL/day, n = 5); and NT group, no treatment (n = 3). Cavity preparation was performed on the mesial aspect of the maxillary first molars bilaterally. After 2 weeks, the tertiary dentinogenesis (CP0.8, CP4, and CON) was examined by hematoxylin-eosin staining, and the localization of beta-2 adrenergic receptor (NT) was examined by immunohistochemistry.

RESULTS

The beta-2 adrenergic receptor immunoreactivity was observed in the odontoblastic layer in normal rat molar dental pulp. The tertiary dentinogenesis beneath the prepared cavity was significantly higher in the rats receiving 2-week systemic administration of propranolol than in those without the propranolol treatment. The higher-dose treatment of propranolol (P < .001) presented more effective up-regulation of tertiary dentinogenesis than the lower-dose treatment (P < .01).

CONCLUSIONS

These results indicate that the sympathetic nervous system decreases tertiary dentin formation via beta-2 adrenergic receptors located on rat odontoblasts. It suggests that adrenergic beta antagonist is expected to use in the treatment of inducing tertiary dentin formation to protect dental pulp.

Assessment of oxygen saturation in dental pulp of permanent teeth with periodontal disease

INTRODUCTION

In individuals with periodontal disease, dental pulp status should be determined before a treatment plan is made. Pulse oximeters are promising diagnostic tools to evaluate pulp vascularization. This study used pulse oximetry to determine the level of oxygen saturation in dental pulp of intact permanent teeth with periodontal attachment loss (PAL) and gingival recession (GR) and to evaluate the correlation between periodontal disease and level of oxygen saturation in the pulp.

METHODS

This study included 67 anterior teeth of 35 patients; all teeth showed intact crowns, PAL, a periodontal pocket (PP), and GR. The teeth underwent periodontal examination, cold and electric pulp testing, and pulse oximetry measurements. The Pearson correlation coefficient and a linear regression coefficient were calculated to evaluate the degree of correlation between periodontal disease markers (PAL, PP, and GR) and the level of oxygen saturation in dental pulp. These tests also evaluated possible associations between oxygen saturation and cold and electric pulp testing.

RESULTS

PAL, PP, and GR had negative correlations with oxygen saturation in dental pulp. Conversely, no statistically significant association was found between oxygen saturation in dental pulp and the response to electric sensibility testing.

CONCLUSIONS

Oxygen saturation was lower in the pulp of permanent teeth with PAL, PP, and GR, indicating that periodontal disease correlates with the level of oxygen saturation in the pulp.

Activation of p38, p21, and NRF-2 mediates decreased proliferation of human dental pulp stem cells cultured under 21% O2

High rates of stem cell proliferation are important in regenerative medicine and in stem cell banking for clinical use. Ambient oxygen tensions (21% O₂) are normally used for in vitro culture, but physiological levels in vivo range between 3% and 6% O₂. We compared proliferation of human dental pulp stem cells (hDPSCs) cultured under 21% versus 3% O₂. The rate of hDPSC proliferation is significantly lower at 21% O₂ compared to physiological oxygen levels due to enhanced oxidative stress. Under 21% O_2, increased p38 phosphorylation led to activation of p21. Increased generation of reactive oxygen species and p21 led to activation of the NRF-2 signaling pathway. The upregulation of NRF-2 antioxidant defense genes under 21% O₂ may interact with cell-cycle-related proteins involved in regulating cell proliferation. Activation of p38/p21/NRF-2 in hDPSCs cultured under ambient oxygen tension inhibits stem cell proliferation and upregulates NRF-2 antioxidant defenses.

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hDPSC proliferation rate is significantly lower at 21% O₂ than at 3% O₂

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This is due to increased levels oxidative stress at 21% O₂

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Oxidative stress activates the cell signaling pathway p38 →p21 → NRF-2

The role of hypoxia in orthodontic tooth movement

Orthodontic forces are known to have various effects on the alveolar process, such as cell deformation, inflammation, and circulatory disturbances. Each of these conditions affecting cell differentiation, cell repair, and cell migration, is driven by numerous molecular and inflammatory mediators. As a result, bone remodeling is induced, facilitating orthodontic tooth movement. However, orthodontic forces not only have cellular effects but also induce vascular changes. Orthodontic forces are known to occlude periodontal ligament vessels on the pressure side of the dental root, decreasing the blood perfusion of the tissue. This condition is accompanied by hypoxia, which is known to either affect cell proliferation or induce apoptosis, depending on the oxygen gradient. Because upregulated tissue proliferation rates are often accompanied by angiogenesis, hypoxia may be assumed to fundamentally contribute to bone remodeling processes during orthodontic treatment.

Pulp vitality in patients with intraoral and oropharyngeal malignant tumors undergoing radiation therapy assessed by pulse oximetry

INTRODUCTION

The aim of this study was to evaluate pulp oxygenation levels (%SpO(2)) in patients with malignant intraoral and oropharyngeal tumors treated by radiotherapy (RT).

METHODS

Pulp oxygenation levels were measured by pulse oximetry. Twenty patients were selected, and two teeth of each participant (n = 40) were analyzed, regardless of the quadrant and the area irradiated, at four different time points: TP1, before RT; TP2, at the beginning of RT with radiation doses between 30 and 35 Gy; TP3, at the end of RT with radiation doses between 60 and 70 Gy; and TP4, 4 to 5 months after the beginning of cancer treatment.

RESULTS

Mean %SpO(2) at the different time points were 93% (TP1), 83% (TP2), 77% (TP3), and 85% (TP4). The Student's t test showed statistically significant differences between TP1 and TP2 (P < .01), TP3 (P < .01), and TP4 (P < .01). TP3 was also statistically significantly different when compared with TP2 (P < .01) and TP4 (P < .01). No statistically significant difference could be observed between TP2 and TP4.

CONCLUSIONS

Because the mean %SpO(2) before RT was greater than during and after therapy and values obtained 4 to 5 months after the beginning of RT were close to the initiation of RT, pulp tissue may be able to regain normal blood flow after RT. If the changes in the microcirculation of the dental pulp were indeed transitory, preventive endodontic treatment or extraction in patients who are currently undergoing or recently received RT and who show negative signs of pulp sensitivity may not be necessary for pulpal reasons.

The effect of dentine-bonding agents on substance P release in human dental pulp

AIM

To quantify the effect of dentine-bonding agents on Substance P (SP) release in healthy human dental pulp tissue.

METHODOLOGY

Forty pulp samples were obtained from healthy pre-molars where extraction was indicated for orthodontic reasons. In thirty of these pre-molars, a standardized Class V cavity preparation was performed, and teeth were divided equally into three groups: (i) Unetched-cavity control group: Class V cavities only; (ii) Experimental Group I: 'One-step' self-etch bonding agent was placed in the cavity; and (iii) Experimental Group II: 'Two-step' total-etch bonding agent was placed in the cavity. The remaining ten healthy pre-molars where extracted without treatment and served as an intact-teeth control group. SP was measured by radioimmunoassay.

RESULTS

Greater SP release was found in the 'one-step' bonding agent group, followed by the 'two-step' bonding agent group and the unetched-cavity control group. The lower SP values were for the intact-teeth control group. anova showed statistically significant differences between groups (P = 0.0001). Tukey HSD post hoc tests showed statistically significant differences in SP release between the intact-teeth control group and the three other groups (P < 0.01) and between the unetched-cavity control group and the 'one-step' bonding agent group (P < 0.05). No significant difference was found between the 'two-step' bonding agent and the unetched-cavity control group.

CONCLUSION

Dentine-bonding agents placed over Class V cavity preparations increased SP release. One-step dentine-bonding agents increased SP release most.

The effect of different vasoconstrictors and local anesthetic solutions on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of the infiltration injection of different vasoconstrictor and anesthetic solutions on substance P (SP) expression in healthy human dental pulp. Thirty pulp samples were obtained from healthy upper premolars in which extraction was indicated for orthodontic reasons and were randomly assigned into three groups of 10 samples each: 2% lidocaine with 1:80,000 epinephrine (Lido group), 3% Prilocaine with 1:200000 felypressin (Prilo group); and 4% Prilocaine without vasoconstrictor (Prilo-no-VC group). All teeth were extracted 10 minutes after anesthetic application. Pulp samples were processed and SP was measured by radioimmunoassay. SP expression for the Lido, Prilo, and Prilo-no-VC groups were 616.49, 663.76, and 760.79 pmol/mg pulp tissue, respectively. Analysis of variance showed statistically significant differences between groups (p = 0.001). Tukey Honestly Significant Difference (HSD) post hoc tests showed significant statistical differences between the Prilo-no-VC group and the Lido group (p < 0.01) and between the Prilo-no-VC group and the Prilo group (p < 0.05). It can be concluded that infiltration injection of local anesthetics with vasoconstrictor attenuate SP expression in human dental pulp.

The effect of tooth bleaching on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of tooth bleaching on substance P (SP) expression in healthy human dental pulp. Forty pulp samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Thirty of these premolars were assigned into three different tooth-bleaching protocols: group 1 (n = 10): Opalescence Xtra Boost (Ultradent Products, South Jordan, UT) (38% H(2)O(2)) for 15 minutes; group 2 (n = 10): Lase Peroxide (DMC, Brazil) (35% H(2)O(2)) activated with infrared laser diode (Biolux; BioArt, Brazil) for 3 minutes, and group 3 (n = 10): Zoom! Whitening System (Discuss Dental, Culver City, CA) (25% H(2)O(2)) light activated for 20 minutes. The remaining 10 healthy premolars serve as a control group. Teeth were anesthetized immediately after bleaching and were extracted 10 minutes later. All pulp samples were processed and SP was measured by radioimmunoassay. Greater SP expression was found in the Zoom! Whitening System, followed by the Lase Peroxide group, Opalescence Xtra Boost, and the lower SP values were for the control group. Analysis of variance showed statistically significant differences between groups (p = 0.0001). Tukey HSD post hoc tests showed significant differences in the light (p < 0.01) and laser (p < 0.05) activated bleaching systems when compared with control values. It can be concluded that light- and laser-activated tooth-bleaching systems increase SP expression in human dental pulp significantly higher than normal values.

Calcitonin gene-related peptide receptor expression in alternatively activated monocytes/macrophages during irreversible pulpitis

The purpose of this study was to quantify the percentage and the mean fluorescence intensity of viable alternatively activated monocytes/macrophages (AAMø) CD163+ positive for calcitonin gene-related peptide receptor (CGRPr) within the total AAMø population in human dental pulp. Pulp tissue samples were collected from teeth with a clinical diagnosis of irreversible pulpitis (n = 13), pulps with induced inflammation (n = 13), and normal pulps (n = 13). All samples were labeled to identify positive cells for CGRPr and CD163 using a flow cytometry assay. Results demonstrated that a high percentage of total viable AAMø CD163+ expressed CGRPr on their membranes (72.12% in healthy pulp, 62.20% in irreversible pulpitis, and 58.01% in induced pulpitis). Significant differences were found between mean AAMø CD163+ fluorescence for CGRPr according to pulp condition, being greater in irreversible pulpitis. It can be concluded that AAMø CD163+ are expressed during normal and inflammatory processes, supporting the hypothesis that they could exercise an anti-inflammatory action that could be controlled by CGRP signaling after its binding.

Temperature excursions at the pulp-dentin junction during the curing of light-activated dental restorations

OBJECTIVES

Excessive heat produced during the curing of light-activated dental restorations may injure the dental pulp. The maximum temperature excursion at the pulp-dentin junction provides a means to assess the risk of thermal injury. In this investigation we develop and evaluate a model to simulate temperature increases during light-curing of dental restorations and use it to investigate the influence of several factors on the maximum temperature excursion along the pulp-dentin junction.

METHODS

Finite element method modeling, using COMSOL 3.3a, was employed to simulate temperature distributions in a 2D, axisymmetric model tooth. The necessary parameters were determined from a combination of literature reports and our measurements of enthalpy of polymerization, heat capacity, density, thermal conductivity and reflectance for several dental composites. Results of the model were validated using in vitro experiments.

RESULTS

Comparisons with in vitro experiments indicate that the model provides a good approximation of the actual temperature increases. The intensity of the curing light, the curing time and the enthalpy of polymerization of the resin composite were the most important factors. The composite is a good insulator and the greatest risk occurs when using the light to cure the thin layer of bonding resin or in deep restorations that do not have a liner to act as a thermal barrier.

SIGNIFICANCE

The results show the importance of considering temperature increases when developing curing protocols. Furthermore, we suggest methods to minimize the temperature increase and hence the risk of thermal injury. The physical properties measured for several commercial composites may be useful in other studies.

CD44 Presence in Inflamed Pulp Tissue

Inflammation of pulp tissue appears as a consequence of caries progression. Its main characteristic is inflamed infiltrate whose cells contain lymphocytes. CD44 is a widely expressed adhesion molecule present in several body cells such as leukocytes and parenchymatous cells, including endothelial cells, epithelial cells, and unstriated muscle cells. It interacts with hyaluronic acid, collagen, laminin, and fibronectin, and there are data that indicate an important role in the migration of leukocytes from the bloodstream toward inflammation areas. This project, which applied the immunologic assay method of agglutination inhibition of the CD44-hyaluronate system, evaluated the presence of CD44 in inflamed pulp tissue in both asymptomatic and symptomatic processes, as well as in healthy pulp tissue. The results demonstrated significant differences between both groups of pulp inflammatory processes with strong presence of the receptor. Moreover, healthy pulp had low to nondetectable levels of CD44. These results suggest that the expression of the CD44 molecule is higher during the initiation or maintenance of inflammatory processes.

An overview of the dental pulp: its functions and responses to injury

The dental pulp is a unique tissue and its importance in the long-term prognosis of the tooth is often ignored by clinicians. It is unique in that it resides in a rigid chamber which provides strong mechanical support and protection from the microbial rich oral environment. If this rigid shell loses its structural integrity, the pulp is under the threat of the adverse stimuli from the mouth, such as caries, cracks, fractures and open restoration margins, all of which provide pathways for micro-organisms and their toxins to enter the pulp. The pulp initially responds to irritation by becoming inflamed and, if left untreated, this will progress to pulp necrosis and infection. The inflammation will also spread to the surrounding alveolar bone and cause periapical pathosis. The magnitude of pulp-related problems should not be underestimated since their most serious consequence is oral sepsis, which can be life threatening, and hence correct diagnosis and management are essential. Clinicians must have a thorough understanding of the physiological and pathological features of the dental pulp as well as the biological consequences of treatment interventions.

Quantification of lactate-dehydrogenase and cell viability in postmortem human dental pulp

Understanding pulp repair and regeneration requires being familiar with this tissue's behavior under extreme conditions, such as postmortem state where an abrupt interruption of tissue blood supply occurs. The purpose of this study was to quantify cell viability and the amount of lactate-dehydrogenase (LDH) expressed in human pulp tissue 6, 12, and 24 hours postmortem to establish how long dental pulp remains viable after death. Pulp samples were obtained from 14 unidentified corpses of people who had received lethal injuries in car accidents or from gunshot wounds; they had at least three caries- and restoration-free incisors. Half of each sample was used for determining cell viability at three different time intervals. The rest of each sample was used for quantifying LDH expression at the same time intervals. Another 14 pulp samples were obtained from live patients' healthy premolars where extraction was indicated for orthodontic reasons to assess normal LDH value in pulp tissue. The results showed cell viability decreasing from 89 to 68 to 41% measured 6, 12, and 24 hours postmortem, respectively. LDH expression in healthy pulps was 246 U/mg pulp weight. Expression increased after death from 249 U/mg at 6 hours to 337 U/mg at 12 hours. LDH expression decreased to 131 U/mg 24 hours postmortem. These findings are valuable in understanding dental pulp survival capability under extreme conditions that may have important clinical significance in terms of repair and regeneration.

The role of endothelial nitric oxide in the Substance P induced vasodilation in bovine dental pulp

Vasodilation, an important response in neurogenic inflammation, involves release of Substance P (SP) from the sensory nerve endings. It is now well known that SP causes edema formation and vascular relaxation in nondental tissues, however, the SP vasodilatory mechanism in the dental pulp is not completely understood. Endothelium-dependent relaxation is mediated by nitric oxide (NO) release with consecutive intracellular cyclic-GMP elevation in many vascular preparations. Recently, it has been shown in different vascular systems that SP-induced vasodilation is mediated by cyclic-GMP production through different pathways involving endothelial NO or direct endothelial-independent pathways. In the present study, the role of endothelial NO in SP induced vasodilation in the dental pulp was investigated to better understand the inflammatory mechanisms. Freshly extracted bovine dental pulp was used to measure NO production. Sodium nitroprusside (SNP), L-NAME and SP were utilized to induce and to inhibit NO production in endothelial cells. Released NO byproducts were measured with chemiluminescence assay technique. The present data demonstrate that SP induces NO production by activating NOsynthase (NOS) in endothelial cells. The NOS inhibitor L-NAME blocks NO production completely. In conclusion, in the bovine dental pulp, SP-induced vascular relaxation can be mediated by inducing NOS, and subsequently NO production in endothelial cells.

Effect of Iontophoretical Application of NK1 Receptor Antagonists on Pulpal Blood Flow in Cats

The influence of NK1 receptor antagonists applied iontophoretically on pulpal blood flow (PBF) was investigated. Along with substance P (SP, 0.8 approximately 20.0 ng/kg) administration to the canine pulp through the catheterized lingual artery, two NK1 receptor antagonists, [D-Pro2,D-Trp7,9]-SP and [D-Pro2,D-Phe7,D-Trp9]-SP (0.2 approximately 3.4 mM) were applied iontophoretically (cathodal current, 0.02 approximately 0.1 mA, 1 min) to the prepared class V dentinal cavity of ipsilateral teeth in 11 generally anesthetized cats. A paired t-test showed that SP administration caused significant increases of PBF (p < 0.05) without changing systemic blood pressure, and that SP and SP antagonist administration caused significantly less increase of PBF than in control of SP and 0.9% saline administration (p < 0.05). These data provide evidence that the iontophoretic application of NK1 receptor antagonists effectively attenuates SP-induced vasodilatation and show the possibility of their use in the control of neurogenic inflammation in the dental pulp.

beta 2-Adrenoceptor regulation of CGRP release from capsaicin-sensitive neurons

Previous studies have suggested that neurotransmitter substances from the sympatho-adrenomedullary system regulate pulpal blood flow (PBF), in part, by the inhibition of vasoactive neuropeptide release from pulpal sensory neurons. However, no study has evaluated the role of beta-adrenoceptors. We evaluated the hypothesis that activation of beta-adrenoceptors inhibits immunoreactive calcitonin gene-related peptide (iCGRP) release from capsaicin-sensitive nociceptive neurons via in vitro superfusion of bovine dental pulp. Either norepinephrine or epinephrine inhibited capsaicin-evoked iCGRP. The norepinephrine effect was blocked by the selective beta(2)-adrenoceptor antagonist, ICI 118,551, but not by pre-treatment with the selective beta(1)-adrenoceptor antagonist, atenolol. In addition, application of albuterol, a selective beta(2)-adrenoceptor agonist, significantly blocked capsaicin-evoked release of iCGRP. Collectively, these studies demonstrate that activation of beta(2)-adrenoceptors in dental pulp significantly reduces exocytosis of neuropeptides from capsaicin-sensitive nociceptors. This effect may have physiologic significance in regulating PBF. Moreover, since capsaicin selectively activates nociceptors, beta(2)-adrenoceptor agonists may have clinical utility as peripherally acting therapeutics for dental pain and inflammation.

Measurement of blood flow with radiolabeled microspheres in reflected mucogingival flaps in cats

To quantify and compare blood flow in maxillary mucogingival flaps, a total of 16 cats (32 mucogingival specimens) were divided into two groups. In group I the blood flow in attached or reflected maxillary tissues were measured. In Group II the effects on blood flow were measured in reflected tissues after the injection of the following solutions: (1) saline solution; (2) 2% lidocaine plain; (3) 2% lidocaine with 1:50,000 epinephrine; (4) no injection. After an injection of 153 Gadolinium microspheres into the left ventricle of the heart, the tissues were harvested and placed in a gamma counter. Group I had a mean blood flow value of 34.4 ml/min/100 gm of tissue for the unreflected samples and 152.3 ml/min/100 gm of reflected tissue. The levels of blood flow in tissue samples in group II results were: no injection (control), 41.2 ml/min/100 gm; saline solution, 46.8 ml/min/110 gm; 2% lidocaine with 1:50,000 epinephrine, 60.6 ml/min/100 gm; and 2% lidocaine plain, 90.2 ml/min/100 gm. On the basis of these results it appears that reflection of gingival tissue and injection of 2% lidocaine plain induces increased blood flow 90 minutes postoperatively.

Inflammation and dental pain in man

In the present article special interest has been focused on indicators of latent and manifest pulpal inflammation studied by psychophysical and electrophysiological techniques. Intradental A-delta nerve activity was recorded from two electrodes placed in the dentin on the labial tooth surface. The psychophysical measures were obtained by means of direct scaling methods in combination with sensory verbal descriptors. For stimulation cooling (ethyl chloride) and heating (hot guttapercha) of the tooth surface were employed. In addition, potentially algogenic substances, bradykinin and histamine, were administered on partly exposed pulps. Hot guttapercha induced a more complex neural response pattern than ethyl chloride. In all the recordings the responses evoked by heat showed a characteristic pattern consisting of three phases: an initial phase of short duration (i) followed by a depression in activity relative to the baseline (ii) and a slow spontaneously emerging activity in the absence of a physical stimulus (iii). The latter neutral event (iii) passed unnoticed by all the subjects. In the light of earlier experiments on feline pulp it was hypothesized that this third phase of the neural response was an indication of hyperexcitability in dental pulps and thus inflammation. Those subjects who experienced pulsating, dull, lingering pain (clinically diagnosed as pulpitis) showed a poor correlation between magnitude estimates of their mixed pain percepts and the total flux of A-delta nerve activity. Bradykinin and histamine evoked dull pain in the majority of cases probably caused by excitation of pulpal C fibers. In one experiment A-delta neural discharge of short duration could also be triggered by histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of systemic and topical nicotine on pulpal blood flow in dogs

It has been suggested that nicotine exerts cardiovascular effects which are similar to stimulation of the sympathoadrenal system. If this observation is true, nicotine administration would decrease pulpal blood flow and possible alter the pulpal response to injury. The purpose of this study was to measure pulpal blood flow in dogs using the radiolabelled microsphere method following topical or systemic administration of nicotine for 28 days. Thirteen dogs were divided into three groups. Group one received topical nicotine (8 mg nicotine/kg/day) combined with orabase which was applied in two equal doses to the mandibular anterior gingiva. Group two received systemic nicotine (2.5 mg/kg/day) delivered by osmotic pumps implanted subcutaneously in the back of each animals' neck. Group three were controls, and these animals received either topical orabase twice daily applied to the mandibular anterior gingiva or saline via osmotic pumps. Results indicated pulpal blood flow increased from Day 0 to Day 28 in both nicotine treated groups. Group one (topical nicotine) exhibited a mean increase in blood flow of 21.8 ml/min/100 g, while group two exhibited a mean increase of 50.1 ml/min/100 g. Group three, the control animals, exhibited a mean decrease in pulpal blood flow of 22.1 ml/min/100 g over the 28-day interval. These changes were not statistically significant (p > 0.05).

Systemic release of corticosteroids following intra-dental use

Concern has been expressed in the past that the use of corticosteroids within root canal medicaments or pulp capping agents may lead to deleterious systemic effects. Calculations of the highest possible amounts that could be used, plus an analysis of the release and diffusion characteristics, and comparisons with known endogenous levels of corticosteroids, reveal that the intradental use of Ledermix paste and Ledermix cement is unlikely to result in any systemic side-effects.

Response of pulpal blood flow to intra-arterial infusion of endothelin

Laser Doppler flowmetry was used to determine the effect of the vasoconstrictor endothelin 1 (ET-1) on the pulpal blood flow of intact dogs' teeth during mandibular arterial infusion. ET-1 produced a profound decrease in pulpal blood flow of a relatively long duration at lower doses than similar infusions of norepinephrine. The decrease in pulpal blood flow in response to ET-1 was partially attenuated by the calcium channel blocker nifedipine. These findings demonstrate the presence of receptors for ET-1 in the microvasculature of the dental pulp and suggests that ET-1 may function in the local control of the pulpal microcirculation.

Medication of the dental pulp: a review and proposals

For years, dentists have desired to treat the intact dental pulp. Since it is well-known that many substances, including some drugs, are capable of permeating dentin, we believe it is possible to treat certain types of pulpitis by applying drugs at the base of cavity preparations. Useful drugs include local anesthetics to block pain transmission, glucocorticoids or non-steroidal anti-inflammatory agents (NSAIA) to treat inflammation, NSAIA or narcotic analgesics for pain control, and antibiotics to treat infection. The literature is reviewed and proposals are presented to study medication of the dental pulp.

Epinephrine permeation across dentin in vitro

The permeation of epinephrine across human dentin discs was studied in vitro. Permeation was measured across dentin of two different thicknesses, with and without the presence of smear layers. Epinephrine was readily detected at the earliest measured time (10 min) and reached peak concentrations between 30 and 50 min. Epinephrine flux (concentration multiplied by the volume of the effluent per min) increased with decreasing thickness of the discs and increased significantly with the removal of the smear layer. The T 1/2 (half-time in min necessary to reach steady-state diffusion of epinephrine) decreased as dentin thickness was reduced and fell further in the absence of the smear layer. This study suggests that the permeation of epinephrine across dentin is inversely related to dentin thickness and retarded by the presence of a smear layer. Also, the topical use of 1 mg/ml epinephrine produced therapeutically useful drug concentrations, but the rate of permeation was relatively slow.

Neurovascular interactions in the dental pulp in health and inflammation

The two key components in pulpal inflammation are microcirculation and sensory nerve activity. With advancement of techniques they can be measured simultaneously in the same tooth. Excitation of A-delta fibers seems to have an insignificant effect on pulpal blood flow (PBF), whereas C fiber activation causes an increase in PBF. This C fiber-induced PBF increase is caused by neurokinins, especially substance P, which is released from the C fiber nerve terminals. Manipulation of PBF has varying effects on sensory nerve activity. An increase in PBF causes excitation of both A-delta and C fibers via an increase in tissue pressure, whereas flow reduction has an inhibitory effect on A-delta fibers, but no discernible effect on C fiber activity. Understanding of this complex neurovascular relationship in the pulp, especially given the fact that the pulp is in a low compliance system, is prerequisite to more comprehensive characterization of pulpal inflammation.

Pulpal healing after luxation injuries and root fracture in the permanent dentition

Pulpal healing patterns were studied in a clinical material of 637 luxated and 95 root-fractured permanent incisors followed routinely for up to 11 years. It was found that pulpal healing patterns could generally be divided into 3 groups according to the degree of injury sustained by the pulp: little, moderate or severe. Thus after luxation injuries, pulp survival could be without radiographic change (PS), with pulp canal obliteration (PCO) or nonhealing (pulp necrosis (PN]. After root fracture, similar healing patterns could be observed: healing by hard tissue union of fragments (HT), by connective tissue union of fragments (CT) or by nonunion due to interposition of granulation tissue between fragments (GT) resulting from PN of the coronal fragment. In both trauma situations, healing or nonhealing could be determined by type of luxation injury, stage of root development and type of fixation used (forceful application of orthodontic bands vs. passively applied acid-etch fixation). Pulpal healing complications (PN or GT) were based on clinical findings (coronal discoloration, loss of pulpal sensibility) and radiographic findings (resorption processes of the lamina dura at the root apex or at the level of the root fracture). However, in both injury groups the same changes could also be seen to be intermediate steps in the pulpal healing process. Based on findings from these studies, hypotheses for the mechanics of pulpal healing are proposed as well as guidelines for acute and later treatment of dental luxations, root fractures and the diagnosis of healing complications.