Effect of Three Different Injection Sites on the Success of Anterior Middle Superior Alveolar Nerve Block with 3% Mepivacaine: A Randomized Controlled Trial.

AIM: Anterior middle superior alveolar (AMSA) nerve block injection targets the anterior superior alveolar nerve and the middle superior alveolar nerve branches of the infraorbital nerve through nutrient canals. Therefore, the central incisor to the second premolar teeth of one quadrant can be anesthetized. The aim of the present study was to evaluate the efficacy of AMSA nerve block injection with 3% mepivacaine solution at three different injection sites. MATERIALS AND METHODS: In a double-blind crossover study, 47 volunteers participated and three AMSA nerve block injections of 3% mepivacaine solution without epinephrine were administered at the anterior, posterior, and the most common injection sites with a 1-week interval between injections. Anesthesia of the central incisor to the second premolar of the injected side was evaluated by using an electric pulp tester. The success of the injection was considered as lack of response to two consecutive 80 readings. The generalized estimating equation analytic tests were administered (α = 0.05). RESULTS: The success rate of the AMSA nerve block injection ranged from 27.5-47.5% for the most common injection site and 22.5-42.5% for both the anterior and posterior injection sites. CONCLUSION: Changing the injection site did not result in statistically significant improvements (p > 0.05). CLINICAL SIGNIFICANCE: Changing the injection site anteropos-teriorly did not influence the success rate of the AMSA nerve block injection.

Sema3A chemorepellant regulates the timing and patterning of dental nerves during development of incisor tooth germ.

Semaphorin 3A (Sema3A) axon repellant serves multiple developmental functions. Sema3A mRNAs are expressed in epithelial and mesenchymal components of the developing incisor in a dynamic manner. Here, we investigate the functions of Sema3A during development of incisors using Sema3A-deficient mice. We analyze histomorphogenesis and innervation of mandibular incisors using immunohistochemistry as well as computed tomography and thick tissue confocal imaging. Whereas no apparent disturbances in histomorphogenesis or hard tissue formation of Sema3A (-/-) incisors were observed, nerve fibers were prematurely seen in the presumptive dental mesenchyme of the bud stage Sema3A (-/-) tooth germ. Later, nerves were ectopically present in the Sema3A (-/-) dental papilla mesenchyme during the cap and bell stages, whereas in the Sema3A (+/+) mice the first nerve fibers were seen in the pulp after the onset of dental hard tissue formation. However, no apparent topographic differences in innervation pattern or nerve fasciculation were seen inside the pulp between postnatal and adult Sema3A (+/+) or Sema3A (-/-) incisors. In contrast, an abnormally large number of nerves and arborizations were observed in the Sema3A (-/-) developing dental follicle target field and periodontium and, unlike in the wild-type mice, nerve fibers were abundant in the labial periodontium. Of note, the observed defects appeared to be mostly corrected in the adult incisors. The expressions of Ngf and Gdnf neurotrophins and their receptors were not altered in the Sema3A (-/-) postnatal incisor or trigeminal ganglion, respectively. Thus, Sema3A is an essential, locally produced chemorepellant, which by creating mesenchymal exclusion areas, regulates the timing and patterning of the dental nerves during the development of incisor tooth germ.

Nerve damage assessment following implant placement in human cadaver jaws: an ex vivo comparative study.

The present study compared the use of cone beam computerized tomography (CBCT) images and intra-oral radiographs in the placement of final implant drills in terms of nerve damage to cadaver mandibles. Twelve cadaver hemimandibles obtained from 6 cadavers were used. Right hemimandibles were imaged using peri-apical radiography and left hemimandibles using CBCT, and the images obtained were used in treatment planning for the placement of implant drills (22 for each modality, for a total of 44 final drills). Specimens were dissected, and the distances between the apex of the final implant drill and the inferior alveolar neurovascular bundle and incisive nerve were measured using a digital calliper. Nerves were assessed as damaged or not damaged, and the Chi-square test was used to compare nerve damage between modalities (P < 0.05). Nerve damage occurred with 7 final drills placed based on peri-apical radiography (31.8%) and 1 final drill placed using CBCT images (4.5%). The difference in nerve damage between imaging modalities was statistically significant (P = 0.023), with CBCT outperforming intraoral film in the placement of final implant drills ex vivo. In order to prevent nerve damage, CBCT is recommended as the principal imaging modality for pre-implant assessment.

Effect of massage on the efficacy of the mental and incisive nerve block.

The purpose of this trial was to assess the effect of soft tissue massage on the efficacy of the mental and incisive nerve block (MINB). Thirty-eight volunteers received MINB of 2.2 mL of 2% lidocaine with 1 : 80,000 epinephrine on 2 occasions. At one visit the soft tissue overlying the injection site was massaged for 60 seconds (active treatment). At the other visit the crowns of the mandibular premolar teeth were massaged (control treatment). Order of treatments was randomized. An electronic pulp tester was used to measure pulpal anesthesia in the ipsilateral mandibular first molar, a premolar, and lateral incisor teeth up to 45 minutes following the injection. The efficacy of pulp anesthesia was determined by 2 methods: (a) by quantifying the number of episodes with no response to maximal electronic pulp stimulation after each treatment, and (b) by quantifying the number of volunteers with no response to maximal pulp stimulation (80 reading) on 2 or more consecutive tests, termed anesthetic success. Data were analyzed by McNemar, Mann-Whitney, and paired-samples t tests. Anesthetic success was 52.6% for active and 42.1% for control treatment for lateral incisors, 89.5 and 86.8% respectively for premolars, and 50.0 and 42.1% respectively for first molars (P = .344, 1.0, and .508 respectively). There were no significant differences in the number of episodes of negative response to maximum pulp tester stimulation between active and control massage. A total of 131 episodes were recorded after both active and control massage in lateral incisors (McNemar test, P = 1.0), 329 (active) versus 316 (control) episodes in the premolars (McNemar test, P = .344), and 119 (active) versus 109 (control) episodes respectively for first molars (McNemar test, P = .444). Speed of anesthetic onset and discomfort did not differ between treatments. We concluded that soft tissue massage after MINB does not influence anesthetic efficacy.

[Anatomical and radiological studies on additional mandible teeth anesthesia considering innervation variability].

The paper presents studies on nutritional foramina of the mandible. Some nutritional foramina located in the frontal mandibular region on the lingual surface and containing significant blood vessels and nerves are found to be more typical for teeth-bearing mandible. In retromolar area in case of third molars presence intraosseous canals were revealed leading to inferior alveolar nerve canal. One should consider intraligamental and lingual anesthesia by lower incisors extraction. Intraosseous anesthesia and retromolar area infiltration significantly increase anesthesia efficiency by third molar extraction.

Histology and intramandibular course of the inferior alveolar nerve.

The morphology of the inferior alveolar nerve is a very important factor for all surgical procedures in the mandibular region. The aim of this anatomical and histological study was to describe the intramandibular course and the microscopic histology of the inferior alveolar nerve in the dissected human cadaver. Twenty partially dentulous hemimandible specimens from human cadavers were dissected and embalmed, and the findings were interpreted by standard and histological imaging. The result of this study showed that the inferior alveolar nerve comprises two larger nerves that are separately wrapped in perineural sheaths and spirally twisted around each other. The mental nerve exits through the mental foramen in the premolar region and the dental nerve continues from the premolar region as the incisive nerve in the incisive canal. These findings provide relevant data for clinical dentistry, especially when planning oral and dental operative treatment procedures in the mandibular region.

A manually controlled new device for punctuate mechanical stimulation of teeth during functional magnetic resonance imaging studies.

AIM: To design a simple and affordable device that could apply standardized mechanical punctuate stimuli to trigger the periodontal mechanoreceptors during functional magnetic resonance imaging (fMRI). MATERIAL AND METHODS: A new manually controlled device using von Frey monofilaments was tested on a phantom and on eight volunteers. Four block design paradigms with different timing were compared. Teeth 11, 12, 13, 21, 22, 23 and the thumb were stimulated. RESULTS: The device did not induce any artefacts in MR images. The most efficient protocol included an epoch duration of 24 s and stimuli delivered at 1 Hz. When stimulating the teeth, activations of the primary (S1) and secondary (S2) somatosensory areas were consistently obtained, either on the ipsilateral, contra-lateral or both sides. Stimulation of the thumb led to activations of the contra-lateral S1 area and either ipsilateral or contra-lateral S2 area. CONCLUSION: The use of this innovative tool should allow to perform fMRI studies aimed to unveil the neural correlates of periodontal neural receptors, and to understand their plasticity induced by tooth loss and their eventual replacement by endosseous oral implants.

Effects of periodontal afferent inputs on corticomotor excitability in humans.

The aim of the present study was to determine in humans whether local anaesthesia (LA) or nociceptive stimulation of the periodontal ligaments affects the excitability of the face primary motor cortex (MI) related to the tongue and jaw muscles, as measured by transcranial magnetic stimulation (TMS). Twelve healthy volunteers (11 men, 1 woman, 25.3 +/- 4.2 years) participated in two 3-h sessions separated by 7 days. The LA carbocain or the nociceptive irritant capsaicin was randomly injected into the periodontal ligament of the lower right central incisor. In both sessions, TMS-motor evoked potential (MEP) stimulus-response curves and corticomotor maps were acquired for the tongue and masseter muscles before (baseline) and at 5, 30 and 60 min post-application of carbocain or capsaicin. Transcranial magnetic stimulation-MEP stimulus-response curves were also acquired at these time points for the first dorsal interosseous (FDI) as an internal control. Burning pain intensity and mechanical sensitivity ratings to a von Frey filament applied to the application site were recorded on an electronic visual analogue scale (VAS). All subjects reported a decreased mechanical sensitivity (anova: P = 0.004) in the LA session and a burning pain sensation (VAS peak pain: 6.4 +/- 1.0) in the capsaicin session. No significant changes in cortical excitability of the MI, as reflected by TMS-MEP stimulus-response curves or corticomotor maps for the tongue, masseter or FDI were found between baseline and post-injection for the LA (anovas: P > 0.22) or capsaicin (anovas: P > 0.16) sessions. These findings suggest that a transient loss or perturbation in periodontal afferent input to the brain from a single incisor is insufficient to cause changes in corticomotor excitability of the face MI, as measured by TMS in humans.

Pivotal Role of Tenascin-W (-N) in Postnatal Incisor Growth and Periodontal Ligament Remodeling.

The continuously growing mouse incisor provides a fascinating model for studying stem cell regulation and organ renewal. In the incisor, epithelial and mesenchymal stem cells assure lifelong tooth growth. The epithelial stem cells reside in a niche known as the cervical loop. Mesenchymal stem cells are located in the nearby apical neurovascular bundle and in the neural plexus. So far, little is known about extracellular cues that are controlling incisor stem cell renewal and guidance. The extracellular matrix protein tenascin-W, also known as tenascin-N (TNN), is expressed in the mesenchyme of the pulp and of the periodontal ligament of the incisor, and is closely associated with collagen 3 fibers. Here, we report for the first time the phenotype of tenascin-W/TNN deficient mice, which in a C57BL/6N background exhibit a reduced body weight and lifespan. We found major defects in the alveolar bone and periodontal ligament of the growing rodent incisors, whereas molars were not affected. The alveolar bone around the incisor was replaced by a dense scar-like connective tissue, enriched with newly formed nerve fibers likely leading to periodontal pain, less food intake and reduced body weight. Using soft food to reduce mechanical load on the incisor partially rescued the phenotype. In situ hybridization and Gli1 reporter mouse experiments revealed decreased hedgehog signaling in the incisor mesenchymal stem cell compartment, which coordinates the development of mesenchymal stem cell niche. These results indicate that TNN deficiency in mice affects periodontal remodeling and increases nerve fiber branching. Through periodontal pain the food intake is reduced and the incisor renewal and the neurovascular sonic hedgehog secretion rate are reduced. In conclusion, tenascin-W/TNN seems to have a primary function in rapid periodontal tissue remodeling and a secondary function in mechanosensation.

Regulation of bite force increase during splitting of food.

The purpose of the study was to analyze how increases in the bite force, during the splitting of food morsels of different hardness, are modulated, and to evaluate the role of periodontal mechanoreceptors in this control. Fifteen subjects were instructed to hold and split food morsels of different hardness (peanuts and biscuits) between a pair of opposing central incisors before and during anesthesia of the teeth. The split occurred at an average bite force of 9 N for biscuits and at an average bite force of 18 N for peanuts. The duration of the split phase was longer, and the split force rate higher, for peanuts compared with biscuits. Furthermore, a steeper force trajectory was observed for the peanut. During anesthesia of the teeth, the duration of the split phase increased and the mean split force rate decreased for peanuts. Force trajectories for peanuts and biscuits were indistinguishable during anesthesia. The present results show that when higher bite forces are needed to split a morsel, both the duration and the rate of the bite force produced is increased. Furthermore, adaptation of the bite force rate to the hardness of the food is dependent on information from periodontal mechanoreceptors.

Articaine buccal infiltration enhances the effectiveness of lidocaine inferior alveolar nerve block.

AIM: To compare mandibular tooth pulpal anaesthesia and reported discomfort following lidocaine inferior alveolar nerve block (IANB) with and without supplementary articaine buccal infiltration. METHODOLOGY: In this prospective randomized double-blind cross-over study, thirty-six healthy adult volunteers received two IANB injections of 2 mL lidocaine 2% with epinephrine 1 : 80,000 over two visits. At one visit, an infiltration of 2 mL of articaine 4% with epinephrine 1 : 100,000 was administered in the mucobuccal fold opposite a mandibular first molar. At the other visit, a dummy injection was performed. Injection discomfort was recorded on 100 mm visual analogue scales. Pulpal anaesthesia of first molar, premolar, and lateral incisor teeth was assessed with an electronic pulp tester until 45 min post-injection. A successful outcome was recorded in the absence of sensation on two or more consecutive maximal pulp tester stimulations. Data were analysed using McNemar and Student's t-tests. RESULTS: The IANB with supplementary articaine infiltration produced more success than IANB alone in first molars (33 volunteers vs. 20 volunteers respectively, P < 0.001), premolars (32 volunteers vs. 24 volunteers respectively, P = 0.021) and lateral incisors (28 volunteers vs. 7 volunteers respectively, P < 0.001). Buccal infiltration with articaine or dummy injection produced less discomfort than IANB injection (t = 4.1, P < 0.001; t = 3.0, P = 0.005 respectively). CONCLUSIONS: The IANB injection supplemented with articaine buccal infiltration was more successful than IANB alone for pulpal anaesthesia in mandibular teeth. Articaine buccal infiltration or dummy buccal infiltration was more comfortable than IANB.

Assessment of the outcomes of cerebral blood flow measurements after electrical stimulation of upper right incisor tooth in rabbits.

The cerebral vessels are innervated by sympathetic, parasympathetic, and sensory nerves. A sensory innervation of the cerebral vessels originating in the trigeminal ganglion has been described in a number of species by several investigations. It has been shown that the electrical stimulation of the trigeminal ganglion causes an increase of cerebral cortical blood flow (CCoBF). The aim of the present study was to determine the effects of dental electrical stimulation the CCoBF in rabbits. A stimulating electrode was located in the upper right incisor tooth of rabbits and trigeminal ganglion was stimulated orthodromically via the infraorbital nerve. Variations in the cortical CCoBF were evaluated by laser-Doppler flowmetry. In experiment group, CCoBF increased together with the beginning of electrical stimulation (5 V, 0.5-ms impulse duration, square-shaped, 10-Hz frequency). The right and left hemisphere CCoBF values of stimulation period at 15s, 30s, 45s, 60s, 75s, and 90s were significantly higher than those of baseline and 105 and 120s (p < 0.05). The maximum increase in right and left CCoBF was 15.6% and 15.1% respectively. In post-stimulation period, the right CCoBF decreased gradually and returned to the baseline values at 120 s. In experiment groups, the CCoBF values of right hemisphere were comparable that of left hemisphereL (p > 0.05). This study demonstrated that the electrical stimulation of the trigeminal nerve's infraorbital branch via dental pulp increases the cortical right and left CCoBF under physiological conditions.

Contribution of capsaicin-sensitive innervation to the continuous eruption of the rat mandibular incisors.

A major component of tooth innervation is made of capsaicin-sensitive primary afferents (CSPA). These fibers play a key role in tooth pain and inflammation; little is known, however, about the role of CSPA in tooth eruption. The aim of this study was to examine the role of the capsaicin-sensitive afferents in the process of eruption of intact rat incisors. CSPA fibers in several rat groups, were subjected to one of the following experimental procedures: systemic chemical ablation, systemic ablation followed by chemical sympathectomy and localized activation. The observed effects on incisor eruption were compared to those made on controls. The total amount of eruption in control/naïve rats, measured over a total period of 144 h, was 3.18 ± 0.07 mm and decreased to 2.43 ± 0.08 mm (n = 7; p < 0.001) following systemic ablation of CSPA. Further decrease to 2.24 ± 0.08 mm (n = 7; p < 0.001) was noticed when chemical sympathectomy was added to CSPA ablation. The average rate of eruption was 1.7 ± 0.25 mm following CSPA activation, compared to an average of 0.8 ± 0.07 mm for controls (n = 7; p < 0.001). Capsaicin sensitive fibers play an important role in tooth homeostasis, and intact neural supply is required for tooth growth under normal conditions.

Nerve electrical stimulation enhances osseointegration of implants in the beagle.

Dental implantation has been the primary method for the treatment of tooth loss, but longer than 3 months healing times are generally required. Because immediate load implants are suitable only for certain categories of implant patients, it has value to develop a novel method to facilitate the implant-bone osseointegration process. Cylindrical titanium implants were implanted in the tooth sockets of beagles, and microelectrode stimulation of the sympathetic nerves in the infraorbital nerve was performed after implantation for 1 week. The authors found that one-sided nerve stimulation was shown to evoke consistent electric potential changes in both sides of the infraorbital nerves. Moreover, after 4 weeks of implantation, more new bone was clearly observed around the implants in the beagles that received electrical stimulation treatment than was observed in the control animals. Furthermore, a higher mineralization density was measured in the new peri-implant bone tissues of the stimulated beagles when compared to controls. These results demonstrate that the simple and safe physical method of microelectrode stimulation to sympathetic nerves can promote the formation of new bone and the osseointegration of implants. This technique is worth promoting and has the potential to reduce the healing time of dental implantation in future clinical cases.

Periodontal-masseteric reflexes decrease with tooth pre-load.

The responses of incisal periodontal mechanoreceptors to increasing mechanical stimulation are known to follow a hyperbolic-saturating course. The implications of these properties for the reflexive control of bite-force have not been examined directly. In line with the above mentioned receptor characteristics, we hypothesized that the periodontal-masseteric reflex will reduce as a function of increasing incisal pre-load. In 10 participants, a central incisor was repeatedly tapped (0.4 N). We measured the modulation by pre-load (0.2-2.0 N) of the reflex frequency-response at and between 3 and 20 Hz. The entrainment of the reflex increased with frequency up to 20 Hz and diminished with increasing pre-load. Importantly, the hyperbolic relationship shown here between the periodontal-masseteric reflex and tooth pre-load agreed with the load/response relationships predicted by single-receptor and tooth movement studies. This study demonstrated that periodontal mechano-receptors are able to contribute to the ongoing control of only small bite-forces.

Effect of heterotopic noxious conditioning stimulation on electrical and pressure pain thresholds in two different anatomical regions.

OBJECTIVES: The aims of the study were to investigate the influence of heterotopic noxious conditioning stimulation (HNCS) on pain thresholds in the orofacial and spinal regions and to find out whether there are gender differences in this respect. MATERIAL AND METHODS: Thirty healthy subjects (15 of each sex) with a mean (SD) age of 25.1 (4.4) years participated. Pain thresholds to electrical (EPT) and pressure stimuli (PPT) were recorded in the masseter muscle and 1st upper incisor (tooth), as well as in the fingertip, before, during, and 5 and 15 min after a cold pressor task to the contralateral hand immersed in ice-cold water for a maximum of 5 min. RESULTS: With the exception of the EPT in the orofacial region, all pain thresholds increased during the HNCS and then returned to baseline during the 15 min follow-up. The significant changes in EPT were greater in the finger than in the tooth, while the changes in PPT were greater in the masseter muscle than in the finger. Electrical stimuli in the finger induced greater significant changes of pain thresholds than pressure. In the orofacial region, pressure induced greater significant changes in pain thresholds during HNCS than electrical stimuli did. The HNCS induced pain of high intensity and unpleasantness, i.e. varying between 5 and 10 on the numeric rating scale (NRS). There were no gender differences in the response to the HNCS. CONCLUSION: We conclude that, in general, HNCS induced by cold pressor stimulation increases pain thresholds, but the magnitude of the effect differs between the orofacial region and the finger and is influenced by the tissue and type of test stimuli.

Role of the Inferior Alveolar Nerve in Rodent Lower Incisor Stem Cells.

In developing teeth, the sequential and reciprocal interactions between epithelial and mesenchymal tissues promote stem/progenitor cell differentiation. However, the origin of the stem/progenitor cells has been the subject of considerable debate. According to recent studies, mesenchymal stem cells originate from periarterial cells and are regulated by neurons in various organs. The present study examined the role of innervation in tooth development and rodent incisor stem/progenitor cell homeostasis. Rodent incisors continuously grow throughout their lives, and the lower incisors are innervated by the inferior alveolar nerve (IAN). In this study, we resected the IAN in adult rats, and the intact contralateral side served as a nonsurgical control. Sham control rats received the same treatment as the resected rats, except for the resection process. The extent of incisor eruption was measured, and both mesenchymal and epithelial stem/progenitor cells were visualized and compared between the IAN-resected and sham-operated groups. One week after surgery, the IAN-resected incisors exhibited a chalky consistency, and the eruption rate was decreased. Micro-computed tomography and histological analyses performed 4 wk after surgery revealed osteodentin formation, disorganized ameloblast layers, and reduced enamel thickness in the IAN-resected incisors. Immunohistochemical analysis revealed a reduction in the CD90- and LRIG1-positive mesenchymal cell ratio in the IAN-resected incisors. However, the p40-positive epithelial stem/progenitor cell ratio was comparable between the 2 groups. Thus, mesenchymal stem/progenitor cell homeostasis is more related to IAN innervation than to epithelial stem/progenitor cells. Furthermore, sensory nerve innervation influences subsequent incisor growth and formation.

Modulation of incisor eruption in rats by sympathetic efferents.

INTRODUCTION: Intact neural supply is necessary for tooth eruption. Sympathetic denervation accelerates or decelerates the eruption rate depending on the tooth condition (intact or injured). The aim of this study is to reexamine the role of the sympathetic innervation, through the observation of the effects of pre or post ganglionic chemical sympathectomy on the eruption of intact rat incisors. MATERIALS AND METHODS: Different groups of rats were subjected to either ganglionic or peripheral chemical sympathectomy and the observed effects on incisor eruption were compared to those made on intact/sham groups or on rats subjected to inferior alveolar nerve (IAN) lesion. RESULTS: The total amount of eruption in control/naïve rats, measured over a total period of 144 h, was 3 ±â€¯0.15 mm and decreased to 2.57 ±â€¯0.06 mm (n = 8; p < 0.01) or 2.8 ±â€¯0.10 mm (n = 8; p < 0.05) following treatment with guanethidine and hexamethonium, respectively. This amount decreased to 1.8 ±â€¯0.14 mm (p < 0.001 vs. control, n = 7; or p < 0.01 vs. sham, n = 5) in rats subjected to IAN lesion. CONCLUSION: Sympathectomy delayed tooth eruption. Blocking the sympathetic effectors with guanethidine exerted more potent effects than ganglionic block with hexamethonium. Intact sympathetic supply is required for tooth growth under normal conditions.

Immunolocalization of aquaporin-1 in the mechanoreceptive Ruffini endings in the periodontal ligament.

Previous ultrastructural studies have suggested an axon-Schwann cell interaction in the periodontal Ruffini ending, a primary mechanoreceptor. However, no information is available on the transport mechanism between them. The present study examined the immunolocalization of aquaporin-1 (AQP1) and -4 (AQP4), a member of the water-selective channel, in the periodontal Ruffini endings of the rat incisors and trigeminal ganglion. In addition, the expression of mRNA for AQP1 and 4 was detected in the trigeminal ganglion by a RT-PCR technique. A single PCR product of the sizes anticipated for AQP1 and 4 was detectable in a reverse transcripted cDNA sample from the trigeminal ganglion, whose neurons innervate the periodontal Ruffini endings. An AQP1 immunoreaction was recognizable in the axon terminals of the periodontal Ruffini endings as well as their associated terminal Schwann cells, as confirmed with a double staining with AQP1 and either PGP9.5 or S-100 protein. However, no immunoreaction for AQP4 was found in periodontal Ruffini endings. Although the AQP4 immunoreaction was localized in some satellite cells - but never in neurons - of the trigeminal ganglion, 16.1% trigeminal neurons showed the AQP1 immunoreaction. Furthermore, the AQP1 immunoreaction was found in certain satellite cells which surrounded AQP1-positive or -negative neurons. An analysis of a cross-sectional area of these positive neurons demonstrated that approximately 66.9% of the positive neurons were 400-1000 microm2 (671.4+/-172.4 microm2), indicating that they could be categorized as medium-sized neurons which mediate mechanotransduction. These findings suggest that AQP1 controls water transport in the periodontal Ruffini endings.

Developmental changes in pulpal sensory innervation of rat incisors and molars shown on a single injection of the fluorescent dye AM1-43.

Developmental changes in pulpal innervation of rat incisors and molars were examined using the fluorescent styryl dye AM1-43, which labels sensory cells and nerves in vivo. From 2 to 40 days after birth, the animals were injected once with a small amount of AM1-43 solution (2 microg/g bodyweight). One day after the injection, the animals were killed and examined. In 3-day-old rats, neither incisors nor molars were innervated. In 7-day-old rats, the pulp of incisors and molars was innervated as indicated by fine intensely stained varicose sensory fibers and thicker intensely stained fibers running mostly along the blood vessels. In 15-, 27-, and 41-day-old rats, sensory nerve fibers neither passed through the odontoblast layer nor penetrated into the dentin in incisors, whereas the sensory nerve fibers penetrated into the coronal dentin through the odontoblast layers in molars. These results suggest that innervation of dental pulp is composed of two phases: (i) linear penetration of nerve fibers along blood vessels into the pulp space; and (ii) sprouting and extension of nerve fibers into coronal dentin. Innervation of the incisor pulp may stop at the first phase.