Response characteristics of the cat somatosensory cortex following the mechanical stimulation to non-vital and vital canine.

Patients sometimes complain that non-vital teeth after root canal treatment (RCT) are paresthesia compared with vital teeth, and previous psychological studies on the tactile sensibility of non-vital teeth remained controversial. In the present study, intrinsic signal optical imaging, which served as an objective tool, was employed to compare the cortex response characteristics following forces applied to the cat non-vital and vital canines. Based on the evoked cortical responses, the response threshold, signal strength, spatial pattern, temporal dynamics and the preference of force direction, they were not significantly different between vital and non-vital canines. It seemed that the tactile sensibility of vital and non-vital teeth was comparable at the cortical response level, and pulpal receptors were not concerned in tactile function.

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.

Tracking local anesthetic effects using a novel perceptual reference approach.

Drug effects of loco-regional anesthetics are commonly measured by unidimensional pain rating scales. These scales require subjects to transform their perceptual correlates of stimulus intensities onto a visual, verbal, or numerical construct that uses a unitless cognitive reference frame. The conceptual understanding and execution of this magnitude estimation task may vary among individuals and populations. To circumvent inherent shortcomings of conventional experimental pain scales, this study used a novel perceptual reference approach to track subjective sensory perceptions during onset of an analgesic nerve block. In 34 male subjects, nociceptive electric stimuli of 1-ms duration were repetitively applied to left (target) and right (reference) mandibular canines every 5 s for 600 s, with a side latency of 1 ms. Stimulus strength to the target canine was programmed to evoke a tolerable pain intensity perception and remained constant at this level throughout the experiment. A dose of 0.6 ml of articaine 4% was submucosally injected at the left mental foramen. Subjects then reported drug effects by adjusting the stimulus strength (in milliamperes) to the reference tooth, so that the perceived intensity in the reference tooth was equi-intense to the target tooth. Pain and stimulus perception offsets were indicated by subjects. Thus, the current approach for matching the sensory experience in one anatomic location after regional anesthesia allows detailed tracking of evolving perceptual changes in another location. This novel perceptual reference approach facilitates direct and accurate quantification of analgesic effects with high temporal resolution. We propose using this method for future experimental investigations of analgesic/anesthetic drug efficacy.

Multivariate assessment of site of lingual nerve.

Injury to the lingual nerve can cause debilitating symptoms. The nerve lies in the retromolar region and its anatomical site can vary within patients and according to sex, age, and dentate status. To our knowledge, no previous studies have recorded its course from multiple bony landmarks and examined the association between age, dentate status, and sex, in the same sample. We dissected 30 white cadavers and took primary and secondary reference points from the internal oblique ridge. We measured the distance to the lingual nerve in sagittal, vertical, and horizontal planes, and recorded the position where the nerve was closest to the lingual plate. We dissected 46 hemimandibles (23 male, mean age 79 years, range 52-100) of which 26 were from the left side. Mean (SD) sagittal, vertical, and horizontal distances from the primary reference point were 9.29 (3.41)mm, 9.15 (3.87)mm, and 0.57 (0.56)mm, respectively. Mean (SD) vertical and horizontal distances from the secondary point were 7.79 (5.45) mm and 0.59 (0.64)mm, respectively. The proximity of the nerve to the lingual plate varied widely (range -13.00 to 15.17mm from the primary reference point). Dentate status was significant for the sagittal measurement from the primary point, and the vertical measurement from the secondary point. Differences in age, sex, or site of the contralateral nerve were not significant (n=16 pairs). Our findings suggest that the site of the nerve is consistent between and within subjects for sex and age, but not for dentate status. The association between the nerve and the lingual plate varied, which suggests that care must be taken when operating in the area.

The human brain response to dental pain relief.

Local anesthesia has made dental treatment more comfortable since 1884, but little is known about associated brain mechanisms. Functional magnetic resonance imaging is a modern neuroimaging tool widely used for investigating human brain activity related to sensory perceptions, including pain. Most brain regions that respond to experimental noxious stimuli have recently been found to react not only to nociception alone, but also to visual, auditory, and other stimuli. Thus, presumed functional attributions have come under scrutiny regarding selective pain processing in the brain. Evidently, innovative approaches are warranted to identify cerebral regions that are nociceptive specific. In this study, we aimed at circumventing known methodological confounders by applying a novel paradigm in 14 volunteers: rather than varying the intensity and thus the salience of painful stimuli, we applied repetitive noxious dental stimuli at constant intensity to the left mandibular canine. During the functional magnetic resonance imaging paradigm, we suppressed the nociceptive barrage by a mental nerve block. Brain activity before and after injection of 4% articaine was compared intraindividually on a group level. Dental pain extinction was observed to correspond to activity reduction in a discrete region of the left posterior insular cortex. These results confirm previous reports demonstrating that direct electrical stimulation of this brain region-but not of others-evokes bodily pain sensations. Hence, our investigation adds further evidence to the notion that the posterior insula plays a unique role in nociceptive processing.

The effect of sonophoresis on topical anesthesia: a pilot project.

The dental anesthesia sonophoresis device (DASD) is a novel device that is intended to reduce the discomfort associated with intraoral mucosa needle puncture. The DASD produces ultrasonic energy that provides a sonophoretic effect on the oral mucosa, generating microchannels through the lipids between the keratinized cells that make up the stratum corneum. Once the topical anesthetic has permeated the stratum corneum, it quickly diffuses through the soft tissue, desensitizing the nerve endings and reducing the perception of pain caused by needle penetration. The aim of this study is to evaluate whether topical anesthesia applied using the DASD will reduce the discomfort of the needle puncture when compared to the control device. A split-mouth model, using 50 healthy subjects with puncture site at the maxillary canine vestibule, was used for this study. Subjects received a needle puncture on both sides of the mouth. Prior to the needle puncture, there was randomized application of 5% lidocaine with the DASD and a control device. Subjects rated their discomfort after needle punctures utilizing the visual analog scale pain scoring system. There was no statistically significant difference in the pain perception using the DASD versus the control device.

Vitality of intact teeth anterior to the mental foramen after inferior alveolar nerve repositioning: nerve transpositioning versus nerve lateralization.

The aim of the present study was to compare two methods used in inferior alveolar nerve (IAN) repositioning to evaluate their effect on the vitality of intact teeth anterior to the mental foramen. Nerve lateralization (NL) is defined as the lateral reflection of the IAN without incisive nerve transection; nerve transposition (NT) involves sacrifice of the incisive nerve. Twenty-one patients were included in this study. Vitality tests for the teeth anterior to the mental foramen, including pulse oximetry and electric pulp testing, were evaluated at 1 week prior to surgery and at 1 week, 1, 3, 6, and 12 months after surgery. Lower lip and chin neurosensory changes were also recorded at the same time intervals by static light touch test with a cotton-tipped applicator and two-point discrimination test with sharp callipers. Vitality tests were negative after the operation in the NT group, while all had normal values at 1 week prior to the operation. In the NL group, only two patients (20%) had negative test results at 1 week after surgery. Lip and chin neurosensory changes in the total transpositions (28 operations) were seen in 7.1% at 1 year after the operation. It appears that NL is a more physiological procedure than NT.

Accessory neurovascular foramina on the lingual surface of mandible: incidence, topography, and clinical implications.

CONTEXT: It was suggested that the accessory neurovascular foramina of the mandible might be of significance in relation to the effectiveness of local anesthesia following the routine inferior alveolar nerve block. AIMS: To investigate the incidence of neurovascular foramina over the lingual surface of the mandible in South Indian population. SETTINGS AND DESIGN: The study was conducted at the department of anatomy. MATERIALS AND METHODS: The study included 67 human adult dry mandibles, the exact ages and sexes of which were not known. The location and number of neurovascular foramina were topographically analyzed. STATISTICAL ANALYSIS USED: Descriptive statistics. RESULTS: The foramina were observed in 64 mandibles (95.5%) and were often multiple in most of the cases. They were located between the two medial incisors in 8 mandibles (1.9%), between the medial and lateral incisor in 34 mandibles (50.7%; 25-bilateral; 7-right; 2-left), between the lateral incisor and canine in 7 mandibles (10.4%; 2-bilateral; 3-right; 2-left), between the canine and first premolar in 6 cases (8.9%; 3 on each side). Foramina were also present around the genial tubercle in 56 mandibles (83.6%). Among them, 52 mandibles showed a single foramen just above the genial tubercle, 34 mandibles had foramina below the tubercles, 13 mandibles had foramina on the right side of genial tubercle and 17 were having on the left side. CONCLUSION: Since the anatomical details of these foramina are important to various fields of dentistry and oncology, the present investigation was undertaken. The clinical significance and implications are emphasized.

Functional properties of tooth pulp neurons responding to thermal stimulation.

The response properties of tooth pulp neurons that respond to noxious thermal stimulation of the dental pulp have been not well-studied. The present study was designed to characterize the response properties of tooth pulp neurons to noxious thermal stimulation of the dental pulp. Experiments were conducted on 25 male ferrets, and heat stimulation was applied by a computer-controlled thermode. Only 15% of tooth pulp neurons (n = 39) responded to noxious thermal stimulation of the teeth. Tooth pulp neurons were found in both the superficial and deep nuclear regions of the subnucleus caudalis (Vc) and in the interface between the nucleus caudalis and interpolaris (Vc/Vi). Thirty-seven neurons had cutaneous receptive fields and were classified as either NS (16) or WDR (21) neurons. Repeated heat stimulation of the dental pulp sensitized and increased the number of electrically evoked potentials of tooth pulp neurons. These results provide evidence that both the Vc and Vc/Vi regions contain neurons that respond to noxious thermal stimulation of the dental pulp, and that these cells may contribute to the sensitization process associated with symptomatic pulpitis.

Tracing toothache intensity in the brain.

Identification of brain regions that differentially respond to pain intensity may improve our understanding of trigeminally mediated nociception. This report analyzed cortical responses to painless and painful electrical stimulation of a right human maxillary canine tooth. Functional magnetic resonance images were obtained during the application of five graded stimulus strengths, from below, at, and above the individually determined pain thresholds. Study participants reported each stimulus on a visual rating scale with respect to evoked sensation. Based on hemodynamic responses of all pooled stimuli, a cerebral network was identified that largely corresponds to the known lateral and medial nociceptive system. Further analysis of the five graded stimulus strengths revealed positive linear correlations for the anterior insula bilaterally, the contralateral (left) anterior mid-cingulate, as well as contralateral (left) pregenual cingulate cortices. Cerebral toothache intensity coding on a group level can thus be attributed to specific subregions within the cortical pain network.

Area extent anaesthesia from buccal nerve block.

This study investigated the extent of complete anaesthesia from buccal nerve block. 40 healthy Thai patients (20 males; 20 females) requiring buccal nerve block for surgery were studied. After the buccal nerve was blocked, the buccal mucosa was explored using a sharp probe to map out the extent of anaesthesia. The operation was carried out after inferior alveolar and lingual nerve block. The extent of the anaesthesia was mainly from the retromolar area to the second molar, followed by the first molar to the second premolar, whilst the first premolar to the central incisor was the area least affected. An important finding of this study was that the anaesthetized extent of some patients extended to the anterior region on the same quadrant. This study showed the affected areas of buccal nerve anaesthesia extended through the buccal mucosa from the first premolar to the central incisor in some patients. It can serve as another informative indication for lower anterior surgery.

Histomorphological study of myelinated nerve fibres in the periodontal ligament of human canine.

OBJECTIVE: This study aims to describe the human periodontal ligament (PDL) using serial sections, with a focus on mechanoreceptor distribution and morphology. MATERIALS AND METHODS: One permanent lower canine with surrounding PDL and alveolar bone tissues was retrieved from a human cadaver. After being embedded into paraffin block, the canine was horizontally cut in 6 µm thick serial sections. At root levels of 0.3, 1.5, 3, 4.5 and 6 mm from the apex, five slices each level were evaluated. Immunocytochemisty was performed on the same serial sections, enabling a more reliable description of neural structures. RESULTS: The distribution of myelinated fibres varied from apical to coronal level, with a total number of 38 at 0.3 mm from the apex, 25 at 1.5 mm, 25 at 3 mm, 31 at 4.5 mm and 32 at 6 mm. At all times, mesial and buccal regions were typically more densely innervated (p < 0.01) except at the 3 mm level. The average density of myelinated nerve fibres increased by arriving closer to the apex. However, the average diameter did not show any significant differences amongst quadrants or root levels (p > 0.05). The average diameter of myelinated fibres varied between 5.3-7.8 µm. Grouped myelinated axons were twice as common as isolated ones, with the innervation being rather close to the alveolar bone. Isolated myelinated axons showed a tendency to group around large blood vessels. CONCLUSION: The present results add to the understanding of human PDL innervation, indicating dense innervations by myelinated nerve fibres in close proximity to collagen fibres and alveolar bone. It also reveals that apical as well as mesial and buccal sites of the human canine are more densely innervated.

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.

Evaluation of sensitivity of teeth after mandibular fractures.

The sensitivity of teeth anterior to a fracture between the mental and mandibular foramina has been tested and followed up until reinnervation or 3 years has passed. This study assessed the reinnervation period, the number of denervated teeth, and their clinical importance. Fifty patients and 459 teeth were examined. Two hundred and seventy-three teeth were affected and had potentially impaired innervation. Tests after injury showed non-responsive teeth in 81% of affected teeth. Six weeks after injury, 19% of teeth were reinnervated; by 1 year after injury, 92% of initially non-responsive teeth were reinnervated. Most teeth (34%) were reinnervated from 6 weeks to 3 months. All 23/186 initially non-responsive, unaffected, contralateral corresponding teeth were reinnervated within 6 weeks. A year after injury, 95% of incisors, 91% of canines, 94% of premolars, and 82% of molars were reinnervated. Three years after injury, 8% of teeth remain denervated. During the second and third years, no reinnervation occurred, but clinical signs of pulp devitalisation of denervated teeth occurred in 18% or 1% of the initially non-responsive affected teeth. The results revealed the stability of pulp 1 year after injury. Denervated teeth should not be treated if no clinical or radiological signs of devitalisation exist.

A comparison of the anterior middle superior alveolar nerve block and infraorbital nerve block for anesthesia of maxillary anterior teeth.

BACKGROUND: The authors conducted a study to compare the efficacy of the anterior middle superior alveolar (AMSA) nerve block with that of the infra-orbital nerve block (IONB) in achieving pulpal anesthesia in the anterior maxilla. METHODS: Twenty-eight healthy adult volunteers received 1.0 milliliter of 2 percent lidocaine with 1:80,000 epinephrine as an AMSA nerve block or IONB via computer-controlled local anesthetic delivery (CCLAD) across two visits. The authors used electronic pulp testing to measure pulpal anesthesia. Participants provided subjective reports of lip numbness and injection discomfort. The authors analyzed the data by using the McNemar, Mann-Whitney and t tests. RESULTS: Anesthetic success, defined as two or more consecutive episodes of no sensation in response to maximal stimulation, was significantly greater with the AMSA nerve block than with the IONB in central (P = .012) and lateral (P < .001) incisors; however, anesthesia was achieved in only 42.9 percent of central incisors with the AMSA nerve block. The authors observed a significantly greater number of episodes of no response in the premolar and canine teeth after IONB. Onset of anesthesia was shorter after IONB in canines (P = .002) and central incisors (P = .022). The incidence of subjective lip numbness was 100 percent after IONB and 14.3 percent after AMSA nerve block (P < .001), with numbness lasting twice as long after IONB (P = .019). The authors noted no significant difference in injection discomfort between the two techniques (P = .768). CONCLUSIONS: The IONB produced anesthetic success in canine and premolar teeth, with a more rapid onset than that for the AMSA nerve block. Although the AMSA technique was significantly more successful than IONB in attaining incisor anesthesia, it was ineffective for central incisors, as assessed according to rigorous electronic pulp testing. The IONB and AMSA nerve block produced similar levels of injection discomfort.

A prospective, randomized, double-blind comparison of the anesthetic efficacy of two percent lidocaine with 1:100,000 epinephrine and three percent mepivacaine in the maxillary high tuberosity second division nerve block.

INTRODUCTION: The purpose of this prospective, randomized, double-blind study was to compare the anesthetic efficacy of 2% lidocaine with 1:100,000 epinephrine and 3% mepivacaine in the maxillary high tuberosity second division nerve block. METHODS: Fifty subjects randomly received maxillary high tuberosity second division nerve blocks by using 3.6 mL of 2% lidocaine with 1:100,000 epinephrine and 3.6 mL of 3% mepivacaine at 2 separate appointments spaced at least 1 week apart. The anterior, premolar, and molar teeth were pulp tested in 4-minute cycles for a total of 60 minutes. Success was defined as no subject response to 2 consecutive 80 readings with the electric pulp tester. RESULTS AND CONCLUSIONS: The high tuberosity approach to the maxillary second division nerve block with both anesthetic formulations resulted in a high success rate (92%-98%) for the first and second molars. Approximately 76%-78% of the second premolars were anesthetized with both anesthetic formulations. Both anesthetic formulations were ineffective for the anterior teeth and first premolars. The use of 3% mepivacaine provided a significantly shorter duration of pulpal anesthesia than 2% lidocaine with 1:100,000 epinephrine in the molars and premolars.

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.

A comparison of the local anesthetic efficacy of the extraoral versus the intraoral infraorbital nerve block.

BACKGROUND: The efficacy of the extraoral infraorbital nerve block has not been studied sufficiently to ensure its appropriate clinical use. To compare the local anesthetic efficacy of the extraoral versus the intraoral infraorbital nerve block, the authors conducted a prospective, randomized crossover study. METHODS: Forty adult participants randomly received extraoral infraorbital nerve blocks of 1.8 milliliters of 2 percent lidocaine with 1:100,000 epinephrine at one appointment and intraoral infraorbital nerve blocks of 1.8 mL of 2 percent lidocaine with 1:100,000 epinephrine at another appointment in a crossover design. After administering the injections, the authors used an electric pulp tester to assess the maxillary central and lateral incisors, canine, premolars and first molar for pulpal anesthesia in four-minute cycles for 60 minutes. They considered anesthesia to be successful when the participant had no response to two consecutive 80 readings (the maximum output) with the electric pulp tester. CONCLUSIONS: The authors found that the extraoral and intraoral infraorbital nerve blocks were ineffective in providing profound pulpal anesthesia of the maxillary central incisor (15 percent success rate) and lateral incisor (22 percent success rate). The pulpal anesthesia success rate was 92 percent for the canine for both types of nerve blocks, 80 to 90 percent for first and second premolars and 65 to 70 percent for the first molar, with no significant differences (P < .05) between the two nerve blocks. Pulpal anesthesia did not last for an hour in any of the teeth. Needle insertion pain and postoperative sequelae were more common after the extraoral infraorbital nerve block was administered. CLINICAL IMPLICATIONS: Both nerve blocks would be ineffective in the central and lateral incisors. Both nerve blocks would be somewhat successful in the canine and premolars but not in the first molar.

A prospective, randomized, double-blind comparison of the anesthetic efficacy of two percent lidocaine with 1:100,000 and 1:50,000 epinephrine and three percent mepivacaine in the intraoral, infraorbital nerve block.

INTRODUCTION: The purpose of this prospective, randomized, double-blind study was to compare the anesthetic efficacy of 2% lidocaine with 1:100,000 epinephrine, 2% lidocaine with 1:50,000 epinephrine, and 3% mepivacaine in the intraoral, infraorbital nerve block. METHODS: Forty subjects randomly received intraoral, infraorbital nerve blocks by using a cartridge of 2% lidocaine with 1:100,000 or 1:50,000 epinephrine and a cartridge of 3% mepivacaine at 3 separate appointments spaced at least 1 week apart. The anteriors, premolars, and first molar were pulp tested in 4-minute cycles for a total of 60 minutes. RESULTS AND CONCLUSIONS: The intraoral, infraorbital nerve block was ineffective in providing profound pulpal anesthesia of the maxillary central incisor, lateral incisor, and first molar. Successful pulpal anesthesia of the canine and first and second premolars ranged from 75%-92% by using 2% lidocaine with 1:100,000 and 1:50,000 epinephrine. However, pulpal anesthesia did not last for 60 minutes. The use of 3% mepivacaine provided a shorter duration of anesthesia than the lidocaine formulations with epinephrine in the canines and premolars.

A prospective, randomized comparison of the anesthetic efficacy of the greater palatine and high tuberosity second division nerve blocks.

INTRODUCTION: Few clinical studies have evaluated the efficacy of the maxillary second division nerve block. The purpose of this prospective, randomized study was to compare the anesthetic efficacy of the greater palatine second division nerve block and the high tuberosity second division nerve block technique by using 3.6 mL of 2% lidocaine with 1:100,000 epinephrine. METHODS: Forty subjects randomly received greater palatine nerve blocks and high tuberosity nerve blocks of 3.6 mL of 2% lidocaine with 1:100,000 epinephrine at 2 separate appointments spaced at least 1 week apart. The anterior, premolar, and molar teeth were pulp tested in 4-minute cycles for a total of 60 minutes. RESULTS AND CONCLUSIONS: Both techniques resulted in a high success rate of pulpal anesthesia (95%-100%) for first and second molars. Around 70%-80% of the second premolars were anesthetized with both techniques. Both techniques were ineffective for profound pulpal anesthesia of the anterior teeth and first premolars.