Sensory nerves, but not sympathetic nerves, promote reparative dentine formation after dentine injury via CGRP-mediated angiogenesis: An in vivo study.

AIM: Dental pulp is richly innervated by nerve fibres, which are mainly involved in the sensation of pain. Aside from pain sensation, little is known regarding the role of dental innervation in reparative dentine formation. We herein generated a mouse model of experimental dentine injury to examine nerve sprouting within the odontoblast and subodontoblastic layers and investigated the potential effects of this innervation in reparative dentinogenesis. METHODOLOGY: Mouse tooth cavity model (bur preparation + etching) was established, and then nerve sprouting, angiogenesis and reparative dentinogenesis were determined by histological and immunofluorescent staining at 1, 3, 7, 14 and 28 days postoperatively. We also established the mouse-denervated molar models to determine the role of sensory and sympathetic nerves in reparative dentinogenesis, respectively. Finally, we applied calcitonin gene-related peptide (CGRP) receptor antagonist to analyse the changes in angiogenesis and reparative dentinogenesis. RESULTS: Sequential histological results from dentine-exposed teeth revealed a significant increase in innervation directly beneath the injured area on the first day after dentine exposure, followed by vascularisation and reparative dentine production at 3 and 7 days, respectively. Intriguingly, abundant type H vessels (CD31+ Endomucin+ ) were present in the innervated area, and their formation precedes the onset of reparative dentine formation. Additionally, we found that sensory denervation led to blunted angiogenesis and impaired dentinogenesis, while sympathetic denervation did not affect dentinogenesis. Moreover, a marked increase in the density of CGRP+ nerve fibres was seen on day 3, which was reduced but remained elevated over the baseline level on day 14, whereas the density of substance P-positive nerve fibres did not change significantly. CGRP receptor antagonist-treated mice showed similar results as those with sensory denervation, including impairments in type H angiogenesis, which confirms the importance of CGRP in the formation of type H vessels. CONCLUSIONS: Dental pulp sensory nerves act as an essential upstream mediator to promote angiogenesis, including the formation of type H vessels, and reparative dentinogenesis. CGRP signalling governs the nerve-vessel-reparative dentine network, which is mostly produced by newly dense sensory nerve fibres within the dental pulp.

Irritation of Dental Sensory Nerves Promotes the Occurrence of Pulp Calcification.

INTRODUCTION: Pulp calcification (PC) often appears in strong association with nerve fiber bundles, which indicates the important role of dental nerves in the formation of PC. Additionally, given that sensory nerves and calcitonin gene-related peptide (CGRP) secreted from sensory nerve fibers are involved in physiological and pathological bone formation, we aimed to determine whether chronic irritation of sensory nerves can promote the occurrence of PC. METHODS: A sensory nerve irritation rat model was established via ligation of the inferior alveolar nerve (IAN), and face grooming behavior was analyzed as a measure of pain sensation. Two months post-surgery, PC was determined by imaging and histologic analyses. RESULTS: Rats in the IAN-chronic constriction injury (IAN-CCI) group showed spontaneous pain-associated behavior after the operations and pain tolerance on the 60th postoperative day. The imaging and histological analysis showed more calcified particles in the IAN-innervated first and second molars after day 60 of the dental sensory nerve irritation. These calcified masses had a dentin-like structure that contained sparse, irregularly oriented tubules. Compared to the control and sham groups, the odontoblasts located in the periphery of radicular pulp aligned along a thicker layer of predentin; which expressed more nestin with longer and stouter processes in the IAN-CCI group. Additionally, more CGRP-positive nerves were observed in the IAN-CCI group. CONCLUSIONS: Irritation of sensory nerves promotes PC formation, and the increased density of CGRP-immunolabeled fibers probably contributes to this process. This highlights the significance of dental sensory nerves in the formation of PC.

SHED promote angiogenesis in stem cell-mediated dental pulp regeneration.

Dental pulp, plays an indispensable role in maintaining homeostasis of the tooth. Pulp necrosis always causes tooth nutrition deficiency and abnormal root development, which leads to tooth discoloration, fracture or even loss. Our previous study showed implantation of autologous SHED could regenerate functional dental pulp. However, the detailed mechanism of the implanted SHED participating in dental pulp regeneration remains unknown. In this study, we implanted SHED in a porcine dental pulp regeneration model to evaluate the regenerative effect and identify whether SHED promoted angiogenesis in regenerated dental pulp. Firstly we verified that xenogenous SHED had the ability to regenerated pulp tissue of host in vivo. Then we found the vasculature in regenerated pulp originated from implanted SHED. In addition, stem cells were isolated from regenerated dental pulp, which exhibited good multi-differentiation properties and promoted angiogenesis in pulp regeneration process and these results demonstrated that SHED promoted angiogenesis in stem cell-mediated dental pulp regeneration.

Mode of delivery alters dental pulp nociception and pain-induced changes in cognitive performance in adults male rats.

This study examined the effects of delivery mode on the response to inflammatory pulpal pain and pain-induced changes in cognitive performance in adult rats. Experiments were done on rats born by vaginal or caesarean section (C-section) delivery. Dental pulp was irritated by intradental capsaicin (100 µg) application and then nociceptive scores were recorded for 40 min. Spatial and passive avoidance learning and memory were assessed using the Morris water maze (MWM) and shuttle box tools, respectively. Additionally, in vivo recording of field excitatory postsynaptic potential (fEPSP) in the CA1 of the hippocampus was used to verify synaptic plasticity. Capsaicin produced more significant nociceptive behavior in vaginally delivered rats compared to C-section rats (P < 0.01). C-section-delivered rats show better performance in both MWM and shuttle box tests. Likewise, C-section rats had greater fEPSP slopes compared to the vaginally delivered group (P < 0.05). Capsaicin impairs cognitive performance in rats born by each delivery route. However, capsaicin effects were more significant in rats delivered vaginally than by C-section. Overall, C-section-delivered rats show lower sensitivity to capsaicin-evoked pulpal nociception and better cognitive performance than vaginally delivered rats. These effects are in part mediated by reduced neuroinflammation and enhanced neuronal synaptic plasticity following C-section delivery.

Evoked and spontaneous pain assessment during tooth pulp injury.

Injury of the tooth pulp is excruciatingly painful and yet the receptors and neural circuit mechanisms that transmit this form of pain remain poorly defined in both the clinic and preclinical rodent models. Easily quantifiable behavioral assessment in the mouse orofacial area remains a major bottleneck in uncovering molecular mechanisms that govern inflammatory pain in the tooth. In this study we sought to address this problem using the Mouse Grimace Scale and a novel approach to the application of mechanical Von Frey hair stimuli. We use a dental pulp injury model that exposes the pulp to the outside environment, a procedure we have previously shown produces inflammation. Using RNAscope technology, we demonstrate an upregulation of genes that contribute to the pain state in the trigeminal ganglia of injured mice. We found that mice with dental pulp injury have greater Mouse Grimace Scores than sham within 24 hours of injury, suggestive of spontaneous pain. We developed a scoring system of mouse refusal to determine thresholds for mechanical stimulation of the face with Von Frey filaments. This method revealed that mice with a unilateral dental injury develop bilateral mechanical allodynia that is delayed relative to the onset of spontaneous pain. This work demonstrates that tooth pain can be quantified in freely behaving mice using approaches common for other types of pain assessment. Harnessing these assays in the orofacial area during gene manipulation should assist in uncovering mechanisms for tooth pulp inflammatory pain and other forms of trigeminal pain.

Nell-1 promotes the neural-like differentiation of dental pulp cells.

Previous studies showed that Nel-like molecule-1 (Nell-1) can positively regulate odontoblastic differentiation and dentin formation. Intriguingly, our group found that Nell-1 is co-expressed with neural markers. The purpose of this study was to investigate whether Nell-1 protein plays a regulatory role in the differentiation of dental pulp cells into neural-like cells by in vivo and in vitro studies. The expression patterns of Nell-1 and dental pulp neural markers were observed by double immunofluorescence staining in normal dental pulp tissue sections of Wistar rat. Collagen sponge containing Nell-1 protein was added into the pulp cavity of rat molars in order to observe the expression patterns of neural markers in rat dental pulp repair and regeneration model by immunohistochemical staining. Moreover, human dental pulp stem cells (hDPSCs) were cultured, and different concentrations of Nell-1 protein were added for 12 h, 24 h, and 72h. The expression of neural markers was detected by using quantitative real-time polymerase chain reaction and Western blot. Nell-1 was co-expressed with neural markers including substance P (SP) and Nestin in rat dental pulp tissue. The expression of neural markers including SP, neuron-specific enolase (NSE), and Nestin was increased obviously in rat dental pulp tissues stimulated with Nell-1 protein. In cultured hDPSCs induced by Nell-1 protein, the expression of neural markers including glial fibrillary acidic protein (GFAP), Nestin, and ß-III tubulin was increased. Nell-1 plays a positive role in inducing the differentiation of DPSCs into neural-like cells.

Ret Signaling Is Required for Tooth Pulp Innervation during Organogenesis.

During organogenesis, the timing and patterning of dental pulp innervation require both chemoattractive and chemorepellent cues for precise spatiotemporal regulation. Our understanding of the signaling mechanisms that regulate tooth innervation during development, as well as the basic biology of these sensory neurons, remains rudimentary. In this study, we analyzed the expression and function of glial cell line-derived neurotrophic factor (GDNF) and its receptor tyrosine kinase, Ret, in the regulation of innervation of the mouse tooth pulp by dental pulpal afferent (DPA) neurons of the trigeminal ganglion (TG). Using reporter mouse models, we demonstrate that Ret is highly expressed by a subpopulation of DPA neurons projecting to the tooth pulp at both postnatal day 7 (P7) and in the adult. In the adult tooth, GDNF is highly expressed by many cell types throughout the dental pulp. Using a ubiquitous tamoxifen (TMX)-inducible Cre ( UBC-Cre/ERT2) line crossed to Ret conditional knockout mice ( Retfx/fx), Ret was deleted immediately prior to tooth innervation, and the neural projections into P7 molars were analyzed. TMX treatment was efficient in ablating >95% of Ret protein. We observed that UBC-Cre/ERT2; Retfx/fx mice had a significant reduction in the total number of neurites present within the pulp at P7, with a significant accumulation of aberrant fibers in the dental follicle and periodontium. In agreement with these findings, inhibition of Ret signaling through in vivo administration of a highly specific pharmacologic inhibitor (1NM-PP1) of Ret also caused a substantial reduction in pulpal innervation. Taken together, these findings indicate that Ret signaling regulates the timing and patterning of tooth innervation by dental primary afferent neurons of the TG during organogenesis and provide a rationale to explore whether alterations in the GDNF-Ret pathway contribute to pathophysiological conditions in the adult dentition.

Trigeminal Nerve Transection-Induced Neuroplastic Changes in the Somatosensory and Insular Cortices in a Rat Ectopic Pain Model.

The primary sensory cortex processes competitive sensory inputs. Ablation of these competitive inputs induces neuroplastic changes in local cortical circuits. However, information concerning cortical plasticity induced by a disturbance of competitive nociceptive inputs is limited. Nociceptive information from the maxillary and mandibular molar pulps converges at the border between the ventral secondary somatosensory cortex (S2) and insular oral region (IOR); therefore, S2/IOR is a suitable target for examining the cortical changes induced by a disturbance of noxious inputs, which often causes neuropathic pain and allodynia. We focused on the plastic changes in S2/IOR excitation in a model of rats subjected to inferior alveolar nerve transection (IANX). Our optical imaging using a voltage-sensitive dye (VSD) revealed that the maxillary molar pulp stimulation-induced excitatory propagation was expanded one to two weeks after IANX at the macroscopic level. At the cellular level, based on Ca2+ imaging using two-photon microscopy, the amplitude of the Ca2+ responses and the number of responding neurons in S2/IOR increased in both excitatory and inhibitory neurons. The in vitro laser scanning photostimulation (LSPS) revealed that Layer II/III pyramidal and GABAergic fast-spiking neurons in S2/IOR received larger excitatory inputs from Layer IV in the IANX models, which supports the findings obtained by the macroscopic and microscopic optical imaging. Furthermore, the inhibitory postsynaptic inputs to the pyramidal neurons were decreased in the IANX models, suggesting suppression of inhibitory synaptic transmission onto excitatory neurons. These results suggest that IANX induces plastic changes in S2/IOR by changing the local excitatory and inhibitory circuits.

Evidence for changing nerve growth factor signalling mechanisms during development, maturation and ageing in the rat molar pulp.

AIM: To examine rat molar pulp innervation and identify complex cellular signalling systems involving nerve growth factor (NGF) and its p75 receptors (NGFR) at different stages of development, maturation and ageing. METHODOLOGY: Decalcified mandibular first molar mesial cusps from Wistar rats of ages 0 day; 1, 2, 3, 4, 6, 9, 12 and 24 weeks (n = 5 per group) were sectioned (10 µm) and incubated with antibodies for NGF, NGFR, calcitonin gene-related peptide (CGRP) and neurofilament. Nerve densities in worn and intact regions of 3- to 24-week-old rats were compared by anova, Bonferroni and t-tests. RESULTS: During odontogenesis, differences in NGF and NGFR expression were observed, with no evidence of nerve fibres, suggesting a signalling mechanism controlling cellular differentiation and dentine formation. Tooth wear in 4-week rats was associated with reduced NGF expression and significantly decreased CGRP axons within affected odontoblast regions. The underlying subodontoblasts started expressing NGF which continued until 9 weeks. This may promote a significant increase in CGRP nerve density in affected regions. Nerve density in intact odontoblast regions increased gradually and reached significant levels in 12-week rats. Reduction in nerve densities within worn and intact regions of cusps was observed at 24 weeks. CONCLUSIONS: Age-related changes and responses to tooth wear may be controlled by the NGF signalling mechanism, with roles in odontoblast/subodontoblast communication and control of sensory innervation at different stages of tooth development, maturation and ageing. Greater understanding of cellular and nerve regulation in the injured pulp may promote therapeutic strategies for pulp survival.

Comprehensive Characterization of 2 Immature Teeth Treated with Regenerative Endodontic Procedures.

INTRODUCTION: Regeneration of the pulp-dentin complex is the penultimate goal of regenerative endodontic procedures (REPs). Histological outcomes have demonstrated reparative tissue formation in human teeth extracted post-REPs. However, lack of accurate characterization has precluded identification of the true nature of tissues formed post-REP. METHODS: Here, we present 2 case reports of tooth #29 and #9 treated with REPs and demonstrate their clinical, radiographic, and histological outcomes. RESULTS: Clinical outcomes revealed healing of apical periodontitis in both teeth and re-establishment of vitality responses in tooth #29. Moreover, radiographic assessments using 2D and 3D-volumetric analyses demonstrate considerable increase in root development for both teeth. Further, histological outcomes evaluated using Hematoxylin and Eosin and immunohistochemical staining demonstrates presence of vascular and lymphatic structures as well as immune cell markers indicative of regeneration of an immunocompetent pulp. Lastly, examination of hard tissue deposition shows dentin-like tissue in parts of tooth #29 demonstrating for the first time, regeneration of a pulp-dentin complex post-REP. CONCLUSIONS: Collectively, this is the first study demonstrating recapitulation of several tissues commonly found as part of a pulp-dentin complex in teeth treated with REPs.

TRPM8 and TRPA1 do not contribute to dental pulp sensitivity to cold.

Sensory neurons innervating the dental pulp have unique morphological and functional characteristics compared to neurons innervating other tissues. Stimulation of dental pulp afferents whatever the modality or intensity of the stimulus, even light mechanical stimulation that would not activate nociceptors in other tissues, produces an intense pain. These specific sensory characteristics could involve receptors of the Transient Receptor Potential channels (TRP) family. In this study, we compared the expression of the cold sensitive receptors TRPM8 and TRPA1 in trigeminal ganglion neurons innervating the dental pulp, the skin of the cheek or the buccal mucosa and we evaluated the involvement of these receptors in dental pulp sensitivity to cold. We showed a similar expression of TRPM8, TRPA1 and CGRP in sensory neurons innervating the dental pulp, the skin or the mucosa. Moreover, we demonstrated that noxious cold stimulation of the tooth induced an overexpression of cFos in the trigeminal nucleus that was not prevented by the genetic deletion of TRPM8 or the administration of the TRPA1 antagonist HC030031. These data suggest that the unique sensory characteristics of the dental pulp are independent to TRPM8 and TRPA1 receptors expression and functionality.

Assessment of Regaining Pulp Sensibility in Mature Necrotic Teeth Using a Modified Revascularization Technique with Platelet-rich Fibrin: A Clinical Study.

INTRODUCTION: The aim of the present study was to evaluate the possibility of regaining pulp sensibility in mature necrotic teeth using modified regenerative endodontic procedures by inducing bleeding in root canals and using platelet-rich fibrin (PRF). METHODS: Fifteen patients with necrotic pulp with symptomatic or asymptomatic apical periodontitis were included. At the first visit, the tooth was anesthetized, and an access cavity was performed. Mechanical preparation of root canals was performed using the standardized technique reaching apical canal preparation to K-file size #60-80. Double antibiotic paste was injected into the canal, and the cavity was temporarily sealed using glass ionomer cement. Three weeks from the first visit, regenerative endodontic procedures were performed by inducing bleeding, and a freshly prepared PRF membrane was placed in the canal. White mineral trioxide aggregate was placed directly over the PRF matrix, and the tooth was restored with a glass ionomer cement base and resin composite restoration. The electric pulp test was used to record if the teeth included in the study regained sensibility or not every 3 to 12 months follow-up. Readings at different times were compared as categoric qualitative data using the chi-square test and compared as means and standard deviations using the analysis of variance test. RESULTS: Readings of tooth sensibility revealed a highly significant difference (P < .0001) between baseline and the 12-month follow-up period. CONCLUSIONS: The presence of sensibility is indicative of the formation of vital pulplike tissue. Reestablishing real pulp tissue after regenerative endodontic treatment is debatable and still needs high level of evidence with large-scale investigations.

Computer-guided chin harvest: A novel approach for autogenous block harvest from the mandibular symphesis.

BACKGROUND: The introduction of CAD/CAM technology allowed clinicians to carry out complex procedures with a high level of precision and reproducibility and minimize the risk of injury during the procedure. PURPOSE: The aim of the present study is to evaluate the efficacy of the CAD/CAM surgical guide during chin harvesting procedures in reducing the risk of neurosensory damage and patient morbidity compared with the standard technique. MATERIALS AND METHODS: About 20 cases of autogenous block chin harvest were randomly into two groups. The first group received computer-guided chin block harvest while the second group received autogenous block chin harvest using the standard approach. RESULTS: In the guided group, out of the 10 subjects, 2 subjects presented with wound dehiscence which resolved within 1 month. No teeth showed any negative pulp sensitivity results. The pointed-Blunt test and 2 point discrimination tests showed a single case of neurodeficits at 1 week follow-up appointment which resolved within 1 month. In the nonguided group, out of the 10 subjects, 1 case presented with wound dehiscence that resolved completely within 1 month. Pulp vitality test showed negative results in 29.4% of the involved teeth at 1 week which decreased to 9.8% and 3.9% at 1 and 6 months follow-up, respectively. The pointed blunt test revealed 3 subjects with neurodeficits at 1 week, out of which 2 subjects showed persisting symptoms at 6 months follow-up. The 2 point discrimination test showed 3 subjects with neurodeficits, out of which two subjects showed persistent symptoms with no resolution at the 6 months follow-up. CONCLUSION: Within the limits of this study, computer-guided chin harvest shows promising results in the reduction of neurosensory complications following harvesting procedures and presents as a safe alternative to the standard technique.

Reduced Depth Technique with the Posterior Superior Alveolar Block.

Purpose: The posterior superior alveolar (PSA) block is one of many techniques used to provide profound anesthesia for invasive dental procedures. This technique has a long history, with a high success rate, but is not without complication risks. The purpose of this study was to determine if pulpal anesthesia of the maxillary second molar could be achieved using a posterior superior alveolar block with a reduced depth of penetration of 10 mm compared to the current suggested depth of 16 mm.Methods: Using a cold refrigerant, a thermal test was conducted using the buccal surface of a maxillary second molar of 43 participants. Positive neural responses were obtained from 100% of the participants (n=43) during the pretest. Each participant received a posterior superior alveolar block using a short (20mm), 27-gauge needle with the penetration depth reduced to 10mm. Post-test neural responses of these molars were evaluated using same cold thermal test technique.Results: Study results demonstrated that the reduced depth technique for the PSA block was successful in 88% (n=38) of the participants; pulpal anesthesia of the maxillary second molar had been achieved. Furthermore, there were zero positive aspirations and zero hematomas observed in the participants.Conclusion: The reduced needle depth technique showed promise in achieving desired results of pulpal anesthesia coupled with decreasing risk and complications associated with the PSA block. Additional blinded, randomized clinical studies are recommended to achieve evidence-based support for this reduced depth PSA block technique.

Semaphorin 3A receptor inhibitor as a novel therapeutic to promote innervation of bioengineered teeth.

The sensory innervation of the dental pulp is essential for tooth function and protection. It is mediated by axons originating from the trigeminal ganglia and is spatio-temporally regulated. We have previously shown that the innervation of bioengineered teeth can be achieved only under immunosuppressive conditions. The aim of this study was to develop a model to determine the role of Semaphorin 3A (Sema3A) in the innervation of bioengineered teeth. We first analysed innervation of the dental pulp of mandibular first molars in newborn (postnatal day 0: PN0) mice deficient for Sema3A (Sema3A-/- ), a strong inhibitor of axon growth. While at PN0, axons detected by immunostaining for peripherin and NF200 were restricted to the peridental mesenchyme in Sema3A+/+ mice, they entered the dental pulp in Sema3A-/- mice. Then, we have implanted cultured teeth obtained from embryonic day-14 (E14) molar germs of Sema3A-/- mice together with trigeminal ganglia. The dental pulps of E14 cultured and implanted Sema3A-/- teeth were innervated, whereas the axons did not enter the pulp of E14 Sema3A+/+ cultured and implanted teeth. A "Membrane Targeting Peptide NRP1," suppressing the inhibitory effect of Sema3A, has been previously identified. The injection of this peptide at the site of implantation allowed the innervation of the dental pulp of bioengineered teeth obtained from E14 dental dissociated mesenchymal and epithelial cells reassociations of ICR mice. In conclusion, these data show that inhibition of only one axon repellent molecule, Sema3A, allows for pulp innervation of bioengineered teeth.

The Effect of Sensory Innervation on the Inorganic Component of Bones and Teeth; Experimental Denervation - Review.

The effect of the nervous system on bone remodelling has been described by many studies. Sensory and autonomic nerves are present in the bone. Immunohistochemical analysis of the bone have indicated the presence of neuropeptides and neurotransmitters that act on bone cells through receptors. Besides carrying sensory information, sensory neurons produce various neuropeptides playing an important role in maintaining bone and tooth pulp homeostasis, and dentin formation. Bone tissue and teeth contain organic and inorganic components. Bone cells enable bone mineralization and ensure its formation and resorption. Studies focused on the effects of the nervous system on the bone are proceeded using various ways. Sensory denervation itself can be achieved using capsaicin causing chemical lesion to the nerve. Surgical ways of causing only sensory lesion to nerves are substantially limited because many peripheral nerves are mixed and contain a motor component as well. From this point of view, the experimental model with transection of inferior alveolar nerve is appropriate. This nerve provides sensory innervation of the bone and teeth of the mandible. The purpose of our paper is to provide an overview of the effects exerted by the nervous system on the inorganic component of the bone and teeth, and also to present an overview of the used experimental models. As we assume, the transection of inferior alveolar nerve could be reflected in changed contents and distribution of chemical elements in the bone and teeth of rat mandible. This issue has not been studied so far.

Fluorescent Labeling and 2-Photon Imaging of Mouse Tooth Pulp Nociceptors.

Retrograde fluorescent labeling of dental primary afferent neurons (DPANs) has been described in rats through crystalline fluorescent DiI, while in the mouse, this technique was achieved with only Fluoro-Gold, a neurotoxic fluorescent dye with membrane penetration characteristics superior to the carbocyanine dyes. We reevaluated this technique in the rat with the aim to transfer it to the mouse because comprehensive physiologic studies require access to the mouse as a model organism. Using conventional immunohistochemistry, we assessed in rats and mice the speed of axonal dye transport from the application site to the trigeminal ganglion, the numbers of stained DPANs, and the fluorescence intensity via 1) conventional crystalline DiI and 2) a novel DiI formulation with improved penetration properties and staining efficiency. A 3-dimensional reconstruction of an entire trigeminal ganglion with 2-photon laser scanning fluorescence microscopy permitted visualization of DPANs in all 3 divisions of the trigeminal nerve. We quantified DPANs in mice expressing the farnesylated enhanced green fluorescent protein (EGFPf) from the transient receptor potential cation channel subfamily M member 8 (TRPM8EGFPf/+) locus in the 3 branches. We also evaluated the viability of the labeled DPANs in dissociated trigeminal ganglion cultures using calcium microfluorometry, and we assessed the sensitivity to capsaicin, an agonist of the TRPV1 receptor. Reproducible DiI labeling of DPANs in the mouse is an important tool 1) to investigate the molecular and functional specialization of DPANs within the trigeminal nociceptive system and 2) to recognize exclusive molecular characteristics that differentiate nociception in the trigeminal system from that in the somatic system. A versatile tool to enhance our understanding of the molecular composition and characteristics of DPANs will be essential for the development of mechanism-based therapeutic approaches for dentine hypersensitivity and inflammatory tooth pain.

Secretoneurin and PE-11 immunoreactivity in the human dental pulp.

OBJECTIVE: To explore whether there are differences in the concentration of the secretogranin II-derived peptide secretoneurin and the chromogranin B-derived peptide PE-11 between the healthy and inflamed human dental pulps. Furthermore, colocalization studies with calcitonin gene-related peptide were performed to confirm the sensory origin of the peptidergic nerves in the dental pulp. DESIGN: The concentrations of secretoneurin and PE-11 were determined by highly sensitive radioimmunoassays in extracts of dental pulps, the molecular form of secretoneurin immunoreactivities by RP-HPLC with subsequent radioimmunoassay and colocalization studies with calcitonin gene-related peptide were performed by double immunofluorescence. RESULTS: Only secretoneurin but not PE-11 was detectable by radioimmunoassays whereas nerve fibers could be made visible for both secretoneurin and PE-11. Furthermore, there was a full colocalization of secretoneurin and PE-11 with calcitonin gene-related peptide in immunohistochemical experiments. There were no differences in the concentration of secretoneurin between the healthy and inflamed human dental pulp and moreover, the characterization of the secretoneurin immunoreactivities revealed that only authentic secretoneurin was detected with the secretoneurin antibody. CONCLUSIONS: There is unequivocal evidence that secretoneurin and PE-11 are constituents of the sensory innervation of the human dental pulp and although not exclusively but are yet present in unmyelinated C-fibers which transmit predominantly nociceptive impulses. Secretoneurin might be involved in local effector functions as well, particularly in neurogenic inflammation, given that this is the case despite of unaltered levels in inflamed tissue.

Molecular basis of dental sensitivity: The odontoblasts are multisensory cells and express multifunctional ion channels.

Odontoblasts are the dental pulp cells responsible for the formation of dentin. In addition, accumulating data strongly suggest that they can also function as sensory cells that mediate the early steps of mechanical, thermic, and chemical dental sensitivity. This assumption is based on the expression of different families of ion channels involved in various modalities of sensitivity and the release of putative neurotransmitters in response to odontoblast stimulation which are able to act on pulp sensory nerve fibers. This review updates the current knowledge on the expression of transient-potential receptor ion channels and acid-sensing ion channels in odontoblasts, nerve fibers innervating them and trigeminal sensory neurons, as well as in pulp cells. Moreover, the innervation of the odontoblasts and the interrelationship been odontoblasts and nerve fibers mediated by neurotransmitters was also revisited. These data might provide the basis for novel therapeutic approaches for the treatment of dentin sensibility and/or dental pain.

Determination of the Influence of Chronic Periodontitis on Pulp Sensibility by Means of Electric and Thermal Cold Testing.

INTRODUCTION: Communication between pulp and periodontal tissue has been well established. However, it is unknown when periodontal disease begins to affect the clinical response of pulp tissue. The aim of this study was to assess the influence of periodontal severity on pulp sensibility by means of electric and thermal cold testing. METHODS: The teeth assessed in this study were allocated into 3 groups considering radiographic alveolar bone loss (ABL) as follows: slight periodontitis (SP, ABL ≤7 mm without reaching the apex, n = 25), moderate periodontitis (ABL >7 mm without reaching the apex, n = 23), and severe periodontitis (SvP, ABL >7 reaching the apex, n = 8). Gingival recession (GR), probing depth (PD), and clinical attachment level (CAL) were also measured. RESULTS: The results showed higher levels of PD and CAL in the SvP group compared with the SP group (P < .05), with no significant difference in GR (P > .05). The SvP group showed significant ABL compared with the other groups (P > .05). The SP group showed a significant number of teeth with a positive pulp response, whereas the SvP group showed a significant number of teeth with a negative pulp response (P < .05); no significant differences were observed between the thermal cold and electric tests (P > .05). CONCLUSIONS: Within the limits of this study, it can be concluded that pulp clinical involvement with a negative response to thermal cold and electric testing occurs only in the most advanced stage of chronic periodontitis with apical involvement.