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.

Expression pattern of sonic hedgehog signaling and calcitonin gene-related peptide in the socket healing process after tooth extraction.

Sonic Hedgehog (SHH), a neural development inducer, plays a significant role in the bone healing process. Calcitonin gene-related peptide (CGRP), a neuropeptide marker of sensory nerves, has been demonstrated to affect bone formation. The roles of SHH signaling and CGRP-positive sensory nerves in the alveolar bone formation process have been unknown. Here we examined the expression patterns of SHH signaling and CGRP in mouse socket by immunohistochemistry and immunofluorescence analysis. We found that the expression level of SHH peaked at day 3 and was then decreased at 5 days after tooth extraction. CGRP, PTCH1 and GLI2 were each expressed in a similar pattern with their highest expression levels at day 5 and day 7 after tooth extraction. CGRP and GLI2 were co-expressed in some inflammatory cells and bone forming cells. In some areas, CGRP-positive neurons expressed GLI2. In conclusion, SHH may affect alveolar bone healing by interacting with CGRP-positive sensory neurons and thus regulate the socket's healing process after tooth extraction.

Risk assessment of inferior alveolar nerve injury for immediate implant placement in the posterior mandible: a virtual implant placement study.

OBJECTIVES: To investigate the prevalence and morphological parameters of lingual concavity, and whether these factors are related to a higher risk of inferior alveolar nerve (IAN) injury when performing an immediate implant surgery in posterior mandible region. METHODS: The CBCT images from 237 subjects (1008 teeth) were analysed the shape of the mandibles (C, P, U type), dimensional parameters of lingual concavity (angle, height, depth), and its relation to inferior alveolar canal (IAC) (A, B, C zone), RAC (distance from root apex to IAC) and probability of IAN injury. Multiple logistic regression modelling to determine the odds ratio of variables that made an important contribution to the probability of IAN injury and to adjust for confounding variables. RESULTS: The U type ridge (46.7%) and the most concave point located at C zone (48.8%) are most prevalent in this region. The mandibular second molar presents highest risk for IAN injury than other tooth type (p<0.001), which were 3.82 times to occur IAN injury than the mandibular second premolar. The concave point located at A zone and B zone were 7.82 and 3.52 times than C zone to have IAN damage, respectively. The probability of IAN injury will reduce 26% for every 1mm increase in RAC (p<0.001). CONCLUSIONS: The tooth type, morphological features of lingual concavities, and RAC are associated with risks of IAN injury during immediate implant placement. CLINICAL SIGNIFICANCE: Pre-surgical mapping of the IAC and identification of its proximity relative to the lingual concavity in the posterior mandible regions may avoid unpleasant complications, specifically when performing immediate implant procedures.

Healing of periodontal defects and calcitonin gene related peptide expression following inferior alveolar nerve transection in rats.

The roles of nerve and neuropeptides in the process of bone formation and remolding have been studied previously. However, the effects of nervous system and neuropeptide on periodontal alveolar bone formation remained unknown. The aim of this study was to assess the effect of innervation on regeneration of alveolar bone and expression levels of calcitonin gene related peptide (CGRP) in periodontal tissues of rats, so as to have a better understanding of the effect of nerve and its related neuropeptide on periodontal tissue regeneration. Rats received transection of the left inferior alveolar nerve and a surgery to produce bilateral periodontal defect, then the alveolar tissue was obtained from animals of each group at week 1, 2, 4, 6 and 8 weeks after operation, respectively. Hematoxylin and eosin staining, and Masson staining were performed to evaluate the ability to restore and repair periodontal tissues at 4, 6 and 8 after surgery. Then new bone formation area and mineralized area were quantified using imagepro-plus6.0 software after pictures were taken under the microscope and SPSS17.0 was used for statistical analysis. Immunohistochemical staining was applied to investigate the expression of CGRP at 1, 2, 4, 6 and 8 weeks. Rats received transection of the left inferior alveolar nerve surgery and were then sacrificed at day 1, 3, 7, 14, 21, 28 after the operation. The change of CGRP expression in periodontal tissue was detected using immunohistochemical methods. The results showed that the volume of new bone formation was not significantly difference between the experimental and control groups, but the mineralized new bone area between the two groups was statistically significant. The level of CGRP expression was lower than normal at week 1, and then it began to rise in the next stage. The plateau, at higher than normal level, was reached at 6 weeks post-surgery. Results of transection of the left inferior alveolar nerve demonstrated the expression of CGRP was decreased in early stage; it reached the lowest level at day 7. Then the expression level began to increase until it returned to normal level at day 28. The results of this study suggest that nerve and its related neuropeptide CGRP are the important factors that can affect the quality of regenerated alveolar bone by reducing bone density during the mineralization process.

Inferior alveolar nerve sensory disturbance after impacted mandibular third molar evaluation using cone beam computed tomography and panoramic radiography: a pilot study.

PURPOSE: To measure sensory disturbances of the inferior alveolar nerve (IAN) after removal of impacted mandibular third molars using cone beam computed tomography (CBCT) and dental panoramic radiography (PAN) for preoperative assessment in a randomized controlled trial and to measure the efficacy of the observers' prediction of IAN exposure at surgery based on CBCT compared with PAN. MATERIALS AND METHODS: The sample consisted of 86 impacted third molars (from 79 consecutive patients) in close relation to the IAN as determined by PAN and judged as showing a "moderate" risk of IAN damage. Cases presenting with no close relation between the IAN and roots and extremely risky cases with an obvious interrelation were excluded. Potential neurosensory disturbances of the lip and chin were assessed before surgery and during the postoperative recall by measuring the function of the IAN with the light-touch sensation method. RESULTS: Postoperative sensory disturbances occurred in 1 patient in the CBCT group and 1 patient in the PAN group. The light-touch sensation test showed no significant differences at the lip (P = .10) and chin (P = .17) levels for CBCT- versus PAN-based surgery. Significant differences in making a correct diagnosis of neurovascular bundle exposure at the extraction of impacted teeth were found between the 2 modalities (P = .029). CONCLUSIONS: Within the limits of the present pilot study, CBCT was not superior to PAN in predicting postoperative sensory disturbances but was superior in predicting IAN exposure during third molar removal in cases judged as having "moderate" risk.

Correlation of radiographic signs, inferior dental nerve exposure, and deficit in third molar surgery.

PURPOSE: To identify the specific radiographic signs on orthopantomograms that are positive predictors of intraoperative inferior dental nerve (IDN) exposure and postoperative IDN deficit in lower third molar surgery. MATERIALS AND METHODS: A prospective clinical cohort of patients with lower third molars with specific radiographic signs showing a close proximity of the roots to the IDN who underwent total excision at our center from June 2006 to June 2008 were recruited as the study group. The prevalence of intraoperative IDN exposure and postoperative IDN deficit were recorded. The correlations between the various radiographic signs and the prevalence of IDN exposure and deficit were analyzed. The prevalence of IDN deficit in the sample was compared with an age-, gender-, and operator experience-matched control group of patients who had undergone lower third molar surgery without any of the radiographic signs present. RESULTS: Patients with a total of 178 lower third molars with 1 or more of the specific radiographic signs present were recruited as the study group. The prevalence of IDN deficit in the study group (5.1%) was significantly greater than that in the control group (0.56%; P = .01). In the study group, darkening of root and displacement of the inferior dental canal by the root were radiographic signs significantly related to IDN exposure (P = .001 and P = .019, respectively). Darkening of the root was the only sign significantly related to a postoperative IDN deficit (P = .016). When 2 or more radiographic signs were present, the risk of a postoperative IDN deficit was significantly increased (P = .001). CONCLUSIONS: Darkening of the root and displacement of the inferior dental canal by the root were positive predictors of intraoperative IDN exposure. Darkening of the root or the presence of 2 or more radiographic signs were positive predictors of a postoperative IDN deficit.

Surgical extraction of impacted inferior third molars at risk for inferior alveolar nerve injury.

The objective of the study was to prospectively assess the intraoperative findings and the radiographic signs of a study population of patients with impacted third molars at risk of inferior alveolar nerve injury. One hundred thirty-four patients with impacted mandibular third molars at risk for nerve injury were included in the study. Radiographic signs of possible close relationship between the 2 structures and intraoperative exposition or damage of the inferior alveolar nerve were recorded. The follow-up controls comprised clinical examinations and assessment for the sensation of the lower lip and chin. In 24 patients, a real contiguity was encountered between the third molars and nerve. Among these, intraoperative neural exposition was observed in 19 patients. Four patients complained of postoperative temporary hypoesthesia. No deficit of sensibility was found in cases with no exposition of the nerve. The accidental exposition of the inferior alveolar nerve is associated with an increased risk for neural injuries. At panoramic radiograph, the presence of signs of bifid and radiolucent apex, superimposition, and radiolucent root band should be considered at high risk for neural damage.

Osseoperception: active tactile sensibility of osseointegrated dental implants.

PURPOSE: The phenomenon of developing a certain tactile sensibility through osseointegrated dental implants is called osseoperception. Active tactile sensibility can be tested by having the subject bite on test bodies. The aim of the study was to describe the active tactile sensibility of single-tooth implants based on the 50% value and the slope of the sensibility curve at the 50% value. MATERIALS AND METHODS: Sixty-two subjects with single-tooth implants with natural opposing teeth were included in the study. In a computer-assisted and randomized way, copper foils of varying thickness (0 to 200 Μm) were placed inter?occlusally between the single-tooth implant and the natural opposing tooth, and the active tactile perception was studied according to the psychophysical method of constant stimuli and statistically evaluated by logistic regression. RESULTS: Tactile perception of the implants at the 50% value estimated by logistic regression was 20.2 ± 10.9 Μm on average, and the slope was 29 ± 15. Regarding implant surface structure, significant differences were observed. The sandblasted and acid-etched surface was significantly more sensitive than the titanium plasma-sprayed surface, and the machined surface was similar to the titanium plasma-sprayed surface. CONCLUSIONS: Active tactile sensibility of implants with natural antagonistic teeth is very similar to that of teeth, but the slope of the tactile sensibility curve is flatter. Significant differences in tactile sensibility as a function of different implant surfaces may indicate that receptors near the implant form the basis of osseoperception.

Progressive recovery of osseoperception as a function of the combination of implant-supported prostheses.

UNLABELLED: The extraction of teeth involves the elimination of extremely sensitive periodontal mechanoreceptors, which play an important role in oral sensory perception. OBJECTIVES: The aim of this study was to evaluate the recovery of interocclusal sensory perception for micro-thickness in individuals with different types of implant-supported prostheses. MATERIALS AND METHODS: Wearers of complete dentures (CDs) comprised the negative control group (group A, n=17). The experimental group consisted of wearers of prostheses supported by osseointegrated implants (Group B, n=29), which was subsequently divided into 4 subgroups: B(1) (n=5)--implant supported overdentures (ISO) occluding with CD; B(2) (n=6)--implant-supported fixed prostheses (ISFP) occluding with CD; B(3) (n=8)--wearers of maxillary and mandibular ISFP, and B(4) (n=10)--ISFP occluding with natural dentition (ND). Individuals with ND represented the positive control group (Group C, n=24). Aluminum foils measuring 10 microm, 24 microm, 30 microm, 50 microm, 80 microm, and 104 microm thickness were placed within the premolar area, adding up to 120 tests for each individual. RESULTS: The mean tactile thresholds of groups A, B1, B2, B3, B4, and C were 92 microm, 27 microm, 27 microm, 14 microm, 10 microm, and 10 microm, respectively. [Correction added after publication online 18 April 2008: in the preceding sentence 92 microm, 27 microm, 14 microm, 10 microm and 10 microm, was corrected to 92 microm, 27 microm, 27 microm, 14 microm, 10 microm and 10 microm]. The Kruskal-Wallis test revealed significant difference among groups (P<0.05). The Dunn test revealed that group A was statistically different from groups C, B(3), and B(4), and that B(1) and B(2) were statistically different from group C. CONCLUSION: Progressive recovery of osseoperception as a function of the combination of implant-supported prostheses could be observed. Moreover, ISO and/or ISFP combinations may similarly maximize the recovery of osseoperception.

Effect of exposed inferior alveolar neurovascular bundle during surgical removal of impacted lower third molars.

PURPOSE: In this prospective study, we sought to determine the incidence of inferior alveolar nerve (IAN) paresthesia in patients with an exposed IAN bundle seen intraoperatively. PATIENTS AND METHODS: We included consecutive patients undergoing third molar surgery in whom an exposed IAN bundle was seen in the third molar socket intraoperatively. Data recorded from patients included radiographic findings, variations in surgical method, intraoperative findings, complications, and postoperative sequelae. Patients were reviewed 1 week after surgery and evaluated subjectively and objectively to determine the incidence of paresthesia when the IAN bundle was exposed. Patients with paresthesia were followed for 2 years or until it resolved. RESULTS: An exposed IAN bundle was seen in 192 operation sites in 170 patients over a 5-year period, of which 166 patients with 187 operation sites were included in this study. Thirty-eight operation sites (20.3%) showed paresthesia at 1 week after surgery (95% confidence interval, 14.5% to 26.1%); 20 sites (15.0%) showed abnormal objective assessment results. By 3 months from surgery, 57.9% of nerves had recovered to normal sensation, 65.8% of nerves recovered by 6 months, and 71.1% of nerves recovered by 1 year. Eight patients were lost to follow-up. Logistic regression showed that the operator, male gender, older age, and root curvature were significant risk factors for paresthesia. CONCLUSIONS: Sighting an exposed intact IAN bundle during third molar surgery indicates its intimate relationship with the third molar and carries a 20% risk of paresthesia, with a 70% chance of recovery by 1 year from surgery.

Use of dental panoramic tomographs to predict the relation between mandibular third molar teeth and the inferior alveolar nerve. Radiological and surgical findings, and clinical outcome.

OBJECTIVES: To compare preoperative radiological observations from dental panoramic tomographs (DPT), with surgical findings at removal of third molars with respect to the inferior alveolar nerve. STUDY DESIGN: One surgeon viewed the radiographs of 219 patients and recorded the radiological observations of the mandibular third molar tooth and the inferior alveolar nerve. The same surgeon removed the teeth and made detailed records of morphology of the root and its relation to the inferior alveolar nerve. Patients were reviewed postoperatively. RESULTS: A total of 300 teeth were removed and the neurovascular bundle was directly observed the root was grooved, or roots apices were deflected by the bundle in 35 (12%) cases. Postoperatively no patient had altered labial sensation. CONCLUSION: There was an intimate relation between the mandibular third molar tooth and the inferior alveolar nerve in 12 (51%) cases when darkening of the root was observed, and in only 11 (11%) cases when interruption of the radiopaque outline of the inferior alveolar neurovascular bundle was observed.

Changes in response properties of periodontal mechanoreceptors during tooth movement in rats.

Using an in vitro model, we investigated the chronological effects of orthodontic force on the response properties of periodontal mechanoreceptors (PMRs) in the rat mandibular first molar (M1). Experimental tooth movement was obtained by attaching a super-elastic titanium-nickel (Ti-Ni) alloy closed coil spring from the mandibular incisors to the right M1. On 1, 2, 3, 4, 7 and 14 days after the appliances were set, three right mandibular molars were extracted and direct stimulation with von Frey hairs was applied to the PMRs remaining in the tooth sockets of right M1. Single unit discharges were recorded from the inferior alveolar nerve. Following results were obtained; (1) in the 1-, 2- and 3-day groups, the mechanical thresholds were significantly lower than those in the control group. In the 4-day group, the mechanical threshold was significantly higher than that of the 3-day group. (2) In the 3-, 4-, 7- and 14-day groups, the conduction velocities of A(beta) units were lower than those in the control group. These results imply that orthodontic force applied to M1 induced functional changes in the PMRs within a few days, suggesting that the PMR seems to respond to orthodontic force at early stage of tooth movement.