Morphometric nerve fiber analysis of the human inferior alveolar nerve: lateral asymmetry.
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We studied morphometric nerve fiber analysis and the lateral asymmetry of the inferior alveolar nerve (IAN). Human IANs were resected at the mandibular foramen. The preparation of sections involved fixation, washing, dehydration, embedding, sectioning and staining as described in our previous reports. We estimated the average total number of myelinated axons in the right IAN to be 22,808, with an average transverse area of 37.6 microm2, an average perimeter of 23.0 microm, and average circularity ratio of 0.85, with the same measurements in the left IAN being 24,289, 33.9 microm2, 21.6 microm, and 0.86, respectively. Morphological differences between the right and left side were analyzed by applying parametric tests (unpaired t-test) to all measured items. According to these results, the IAN did not demonstrate notable lateral asymmetry in any measured item. We considered that these results were caused by using subjects with the same dentulous condition in both sides. (+info)
Differences in the axonal compositions of the human mandibular nerve between dentulous and edentulous jaws.
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We examined the human mandibular nerve to find differences in the composition of nerve fiber axons between dentulous and edentulous jaws Using Goto's modification of Masson-Goldner's method. We discovered that the edentulous jaw did not contain any large size axons, compared with the dentulous jaw. This can be considered as evidence that the larger fibers innervating the periodontal ligament decreased degenerated after tooth loss. (+info)
The involvement of brain-derived neurotrophic factor (BDNF) in the regeneration of periodontal Ruffini endings following transection of the inferior alveolar nerve.
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The present study employed immunohistochemistry for protein gene product 9.5 (PGP 9.5) to examine the regeneration process of Ruffini endings, the primary mechanoreceptor in the periodontal ligament, in heterozygous mice with targeted disruption of the brain-derived neurotrophic factor (BDNF) gene and their littermates, following transection of the inferior alveolar nerve. When immunostained for PGP 9.5, periodontal Ruffini endings appeared densely distributed in the periodontal ligament of the heterozygous mice, but the density of the positively stained nerve fibers in the ligament was 20% lower than that in the control littermates. At 3 days after surgery, the PGP 9.5-positive neural elements had disappeared; they began to appear in the periodontal ligament of both animals at 7 days. However, the recovery pattern of the PGP 9.5-positive nerves differed between heterozygous and wild type mice, typical periodontal Ruffini endings morphologically identical to those in the control group appeared in the wild-type mice at 7 days, whereas such Ruffini endings were detectable in the heterozygous mice at 28 days, though much smaller in number. On day 28, when PGP 9.5-positive nerves were largely regenerated in wild type mice, their distribution was much less dense in the ligament of the heterozygous mice than in the non-treated heterozygous mice. The density of PGP 9.5-positive nerve fibers was significantly lower in the heterozygous mice than in wild type mice at any stage examined. These data showing that a reduced expression of BDNF causes delayed regeneration of the periodontal Ruffini endings suggest the involvement of BDNF in the regeneration process of these mechanoreceptors. (+info)
Mandibular nerve paresthesia caused by endodontic treatment.
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The paresthesias of the inferior dental nerve consists of a complication that can occur after performing various dental procedures such as cystectomies, extraction of impacted teeth, apicoectomies, endodontic treatments, local anesthetic deposition, preprosthetic or implantologic surgery. The possible mechanisms of nervous lesions are mechanical, chemical and thermal. Mechanical injury includes compression, stretching, partial or total resection and laceration. The lesion can cause a discontinuity to the nerve with Wallerian degeneration of the distal and integrated fibers of the covering (axonotmesis) or can cause the total sectioning of the nerve (neurotmesis). Chemical trauma can be due to certain toxic components of the endodontic filling materials (paraformaldehyde, corticoids or eugenol) and irrigating solutions (sodium hypochlorite) or local anesthetics. Thermal injury is a consequence of bone overheating during the execution of surgical techniques. We present a clinical case of paresthesia of the inferior dental nerve after the introduction of a gutta-percha point in the mandibular canal during the performance of a root canal therapy of the inferior first molar. The etiology and the treatment of this endodontic complication are described. (+info)
Reconstruction of the inferior alveolar nerve by autologous graft: a retrospective study of 20 cases examining donor nerve length.
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The purpose of this study was to confirm the length and kind of donor nerves used in nerve grafts for reconstruction of inferior alveolar nerve defects. The authors conducted a retrospective study of surgeries that were performed between 1977 and 1996. A total of 20 patients underwent nerve grafting procedures during this period. The greater auricular nerve was selected as the donor nerve in 16 cases, while the sural nerve was selected in 4. Mean lengths of donor nerves were 7.28 +/- 1.6 cm and 11.5 +/- 3.4 cm for the greater auricular and sural nerves, respectively. As indicated, the sural nerves were significantly longer (p < 0.01). Mean lengths of donor nerves grafted for partial resection and hemi-mandibulectomy were 7.23 +/- 1.6 cm and 10.8 +/- 3.4 cm, respectively. Statistical analysis indicated that grafts used in the hemi-mandibulectomy group were significantly longer (p < 0.05). In terms of types of donor nerve used in mandibulectomies, the greater auricular nerve was used in the majority of partial resections, and the sural nerve was employed for hemi-mandibulectomy. (+info)
MR imaging of traumatic lesions of the inferior alveolar nerve in patients with fractures of the mandible.
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BACKGROUND AND PURPOSE: The objective of this study was to assess whether MR imaging can image the neurovascular bundle in patients with fractures of the mandible. In addition, an attempt was made to evaluate whether MR images provide information regarding the continuity of the inferior alveolar nerve before surgery and regarding signal intensity changes after trauma. METHODS: We analyzed preoperative MR images of 23 patients with mandibular fractures. Object-oriented sagittal view proton density- and T1-weighted sequences (before and after the administration of contrast agent) were used not only in an attempt to obtain purely qualitative information regarding nerve continuity in the neurovascular bundle (inferior alveolar nerve, artery, vein) but also to perform quantitative region-of-interest measurements of signal intensities at four defined measurement sites. The measurements were compared with those obtained for a patient population with healthy mandibles. RESULTS: It was possible to interpret MR images in 21 cases. MR imaging findings showed that the neurovascular bundle had been cut in two patients and was intact in the remaining 19 patients. These MR imaging findings were confirmed intraoperatively in all cases. Although we found no significant signal intensity differences between patients with intact nerves and patients with cut nerves, we found significant differences between patients with mandibular fractures and patients with unremarkable mandibles. CONCLUSION: It is possible to diagnose the interruption of nerve continuity by using MR imaging. Signal intensity measurements in the neurovascular bundle provide no information regarding nerve continuity. (+info)
Effectiveness of 20% benzocaine as a topical anesthetic for intraoral injections.
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The use of topical anesthetics has been advocated prior to the administration of various types of anesthetic injections. Reported results have varied between studies. The purpose of this study was to compare the effectiveness of 20% benzocaine in reducing the pain of needle insertion during maxillary posterior and anterior infiltration and inferior alveolar nerve block injections. In this retrospective study, 1080 patients received 2336 injections using a 27-gauge needle. Topical anesthetic was applied prior to 720 of the injections. Patients rated pain of needle insertion using a 0-4 pain scale. Logistic regression analysis showed no differences in pain ratings between topical and no topical groups for the inferior alveolar nerve block and posterior maxillary infiltration injections. The use of topical anesthetic did reduce the pain of needle insertion with the maxillary anterior injections (P = .0041). (+info)
Comparison of effectiveness of 4% articaine associated with 1: 100,000 or 1: 200,000 epinephrine in inferior alveolar nerve block.
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This comparative study using 20 healthy volunteers evaluated the anesthetic efficacy of 4% articaine in association with 2 different concentrations of epinephrine, 1:200,000 (G1) and 1:100,000 (G2). The first premolars were tested with a pulp tester to verify the anesthesia induced by the inferior alveolar nerve block. The following parameters were measured: period of latency (PL; interval between the end of anesthetic injection and absence of response to the maximum output--80 reading--of the pulp tester); complete pulpal anesthesia (CPA; period in which the subject had no response to maximal output of the pulp tester 80 reading); partial anesthesia (PA; interval between the first reading below 80 and the return to basal levels); and the anesthesia of the soft tissues (AST; period of time from onset of anesthesia until the return to normal sensation of the lip). The Wilcoxon test (alpha = 0.05) was used to analyze the data. No significant difference was found regarding PL (P = .47), CPA (P = .88), PA (P = .46), and AST (P = .85). The results indicated that both solutions presented the same clinical effectiveness in blocking the inferior alveolar nerve. (+info)