Development of resurgent and persistent sodium currents in mesencephalic trigeminal neurons.

Sodium channels play multiple roles in the formation of neural membrane properties in mesencephalic trigeminal (Mes V) neurons and in other neural systems. Mes V neurons exhibit conditional robust high-frequency spike discharges. As previously reported, resurgent and persistent sodium currents (INaR and INaP , respectively) may carry small currents at subthreshold voltages that contribute to generation of spike firing. These currents play an important role in maintaining and allowing high-frequency spike discharge during a burst. In the present study, we investigated the developmental changes in tetrodotoxin-sensitive INaR and INaP underlying high-frequency spike discharges in Mes V neurons. Whole-cell patch-clamp recordings showed that both current densities increased one and a half times from postnatal day (P) 0-6 neurons to P7-14 neurons. Although these neurons do not exhibit subthreshold oscillations or burst discharges with high-frequency firing, INaR and INaP do exist in Mes V neurons at P0-6. When the spike frequency at rheobase was examined in firing Mes V neurons, the developmental change in firing frequency among P7-14 neurons was significant. INaR and INaP density at -40 mV also increased significantly among P7-14 neurons. The change to an increase in excitability in the P7-14 group could result from this quantitative change in INaP. In neurons older than P7 that exhibit repetitive firing, quantitative increases in INaR and INaP density may be major factors that facilitate and promote high-frequency firing as a function of age in Mes V neurons.

Asymmetric Anterior Distraction for Transversely Distorted Maxilla and Midfacial Anteroposterior Deficiency in a Patient With Cleft Lip/Palate: Two-Stage Surgical Approach.

The present report describes a male patient with a unilateral cleft lip and palate who presented with midfacial anteroposterior and transverse deficiency. Correction involved a two-stage surgical-orthodontic approach: asymmetric anterior distraction of the segmented maxilla followed by two-jaw surgery (LeFort I and bilateral sagittal splitting ramus osteotomies). The present case demonstrates that the asymmetric elongation of the maxilla with anterior distraction is an effective way to correct a transversely distorted alveolar form and midfacial anteroposterior deficiency. Furthermore, successful tooth movement was demonstrated in the new bone created by distraction.

Protein kinase A regulates the long-term potentiation of intrinsic excitability in neonatal trigeminal motoneurons.

Although much is known about neuronal plasticity in the mammalian hippocampus and other cortical neurons, the subcellular mechanisms underlying plasticity at the level of motor pools are less well characterized. Protein kinase A (PKA) activation plays an essential role in long-term potentiation of intrinsic excitability (LTP-IE) in layer V (LV) visual cortical neurons and may be involved in other systems as well. Trigeminal motoneurons (TMNs) participate in rhythmical motor behaviors, such as suckling, chewing, and swallowing. Using the whole-cell patch clamp method and various kinase inhibitors and activators, we investigated the mechanism of LTP-IE in neonatal rat TMNs. Ca(2+) depletion using ACSF with 0mM Ca(2+) or the Ca(2+) chelator bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) blocked the long-lasting increase in intrinsic excitability in TMNs, showing that intracellular Ca(2+) during the induction protocol is necessary for the induction of LTP-IE. We next used specific inhibitors of PKA, protein kinase C, and calcium/calmodulin-dependent protein kinase II during the induction protocol. Only the PKA inhibitor H-89 blocked the increase in the firing rate induced by the induction protocol. In addition, forskolin, which activates PKA, induced a long-lasting increase in excitability that resembled the excitability produced by the induction protocol. Thus, we conclude that LTP-IE in TMNs is calcium-dependent, and PKA is the primary regulator of this process.

Role of endothelin receptor signalling in squamous cell carcinoma.

Endothelin plays important roles in various physiological functions including vascular constriction. Recent studies reported that the endothelin receptors ETA and ETB are highly expressed in lung and skin tumor tissues. In contrast, there are few reports on endothelin signalling in the proliferation of head and neck cancer. We found that both ETA and ETB endothelin receptors were overexpressed in tumor cells of tongue cancer samples by immunohistochemistry. ETA and ETB were expressed in cultured lingual and esophageal squamous cell carcinoma (SCCs) cell lines. When both cultured cell lines were treated with an ETA selective antagonist (BQ123) or an ETB selective antagonist (BQ788), inhibition of cell growth was observed. Similar results were observed when SCCs were treated with specific siRNA for the suppression of ETA or ETB. Furthermore, inhibition of the mitogen-activated protein (MAP) kinase pathway by the treatments with ET receptor antagonists and siRNA was also observed. These results indicate that endothelin signalling may, in part, play important roles in cell growth in SCCs through the MAP kinase pathway.

Aerial dispersal of blood-contaminated aerosols during dental procedures.

OBJECTIVES: Dental procedures with high-speed instruments produce large amounts of aerosols. The present study aimed to clarify whether blood-contaminated aerosols were existent and floating in air during dental procedures and to evaluate the effect of an extraoral evacuator system. METHOD AND MATERIALS: An extraoral evacuator system with a test filter was used for sample collection at distances from 50 cm (n = 102) and 100 cm (n =124) behind the patient. A leucomalachite green presumptive test was performed on the test filter. One or more positive reactions on the test filter was considered a positive result, and the positive ratio in each procedure was compared. To assess the effect of the extraoral evacuator, an additional extraoral evacuator was introduced, and the positive ratio during third molar extractions at 100 cm behind the patient was compared (n = 55). RESULTS: At 50 cm from the mouth of the patient during third molar surgery, full-crown preparation, inlay cavity (Black Class II) preparation, and scaling with an ultrasonic scaler, positive results were obtained in 92% (12/13), 70% (21/30), 35% (9/26), and 33% (11/33) of cases, respectively. At a distance of 100 cm, positive ratios sustained 90% (35/39), 48% (15/31), 29% (6/21), and 12% (4/33), respectively. When the second extraoral evacuator was utilized, the positive ratio, at a distance of 100 cm, decreased significantly from 90% (35/39) to 60% (33/55) (P = .0015, chi-square test). CONCLUSION: This study showed that blood-contaminated aerosols can be suspended in air, even in general dental settings, and that extraoral evacuators are useful for reducing contaminated aerosols.

Inferior alveolar nerve canal and branches detected with dental cone beam computed tomography in lower third molar region.

PURPOSE: To evaluate the course of the inferior alveolar nerve and its branches, the detectable branches were investigated with dental cone beam computed tomography (CBCT). MATERIALS AND METHODS: Patients in whom the lower third molar (M3) and inferior alveolar nerve canal showed overlapping in the initial panoramic image were included. One hundred twelve impacted lower M3s were extracted after examination with dental CBCT. The detection ratio, the course of the branches, and their relation with the M3 were retrospectively investigated. RESULTS: One hundred fifty-five branches were observed in 106 cases (94.6%, 106/112) around the M3. Most branches coursed under the M3 (55.5%, 86/155), and 85 branches (54.8%, 85/155) were in contact with the M3. The inferior alveolar nerve canal and branch(es) were mostly in contact with the M3 (57.5%, 61/106). CONCLUSIONS: Dental CBCT can detect most tubular structures representing branches in the impacted lower M3 region.

Floating aerial blood mists in the operating room.

High-speed surgical instruments and electric coagulator devices produce contaminated particles and aerosols. This study aimed to investigate the presence of blood-contaminated aerosol in a class 6 and 7 (ISO14644-1) operating room environment. Test filters were fitted to the extract ducts of a standard central air conditioning system, and were left in place for 1, 2, or 4 weeks. In a separate experiment to analyze contributing factors, the test filters were changed following every operation. Green dots showing a reaction with leucomalachite green method were counted. In the accumulation experiment, the number of positive dots tended to increase over time (26, 60, and 143 dots after 1, 2, and 4 weeks, respectively). The distance between the test filters and surgical field ranged from 3.8 to 4.6m. In our analysis of contributing factors, positive filters were present in 9 of 10 surgeries that used high-speed instruments and in 16 of 17 using electric coagulator devices. Surgical procedures performed with these devices produce aerosolized blood, which can float in the operating room. Thus, caution must be taken by perioperative staff, such as anaesthetists and surgical assistants, as well as by surgeons.

Bone formation without lamina dura in the middle-aged and elderly: possible dependence on enamel.

Bone formation below the crown of mandibular horizontal incompletely impacted third molar is frequently seen in the middle-aged and elderly. The phenomenon shows lamina dura loss without radiolucency and we hypothesized the participation of mature enamel without any influence on the environmental oral status. In order to investigate the characteristics of the phenomenon based on the presence/absence of the lamina dura and radiolucency below the crown, we studied the relationship between 58 men and 43 women with a lamina dura without radiolucency, 12 men and 8 women without a lamina dura with radiolucency, 34 men and 16 women without a lamina dura without radiolucency, and the status of teeth in the ipsilateral mandible. Subjects without a lamina dura without radiolucency were significantly older than those with a lamina dura without radiolucency in both men (P < 0.0001) and women (P <0.01), indicating different chronological causes. Men without lamina dura with radiolucency showed significantly more tooth loss than those with a lamina dura without radiolucency (P < 0.00001) and those without a lamina dura without radiolucency (P < 0.0001), indicating the influence of poor oral health. Thus, the phenomenon without a lamina dura without radiolucency may show the clinical importance of bone formation in the elderly.

A comparison of the postnatal development of muscle-spindle and periodontal-ligament neurons in the mesencephalic trigeminal nucleus of the rat.

The trigeminal mesencephalic nucleus (Vmes) is known to include primary afferent neurons of jaw muscle spindles (MS neurons) and periodontal ligament receptors (PL neurons). The aim of this study was to clarify the postnatal development of Vmes neurons by comparing MS neurons with PL neurons using horseradish peroxidase labeling. We measured somal diameter and somal shape of MS and PL neurons in rats from postnatal day (P)7 to P70. No significant changes were seen between postnatal day P7 and P70 in somal diameter or somal shape of MS neurons. Conversely, PL neurons showed a larger somal diameter at P7 than at P14, and in terms of somal profile, multipolar neurons comprised 0% at P7, but 4.8% at P14 and 16.9% at P70. These findings suggest that PL neurons develop with the eruption of teeth, taking into account the fact that tooth eruption occurs from around P14 in rats. Conversely, the lack of postnatal changes in MS neurons is due to the fact that these neurons have been active since the embryonic period, as swallowing starts in utero.

Long-term potentiation of intrinsic excitability in trigeminal motoneurons.

Trigeminal motoneurons (TMNs) relay the final output signals generated within the oral-motor pattern-generating circuits to the jaw muscles for execution of various patterns of motor activity. Activity-dependent plasticity, referred to as long-term potentiation (LTP), in the central nervous system has been the subject of many studies. The mechanisms of plasticity in the trigeminal system, an important component of the oral-motor system underlying mastication, swallowing, and other behaviors, remain to be fully elucidated. In the present study, we investigated long-term potentiation of intrinsic excitability (LTP-IE) in TMNs. Experiments were performed using extracellular recording and whole-cell patch-clamp recording to assess the intrinsic excitability of TMNs. Intrinsic response properties were examined using an induction pulse with ionotropic transmission blocked. The output of the trigeminal motor branch exhibited long-lasting potentiation of intrinsic neuronal excitability following induction. Applying brainstem transection techniques to the neonatal rat brainstem in vitro, we found that the activity of the motoneuron population recorded from the motor branch of the trigeminal nerve exhibited LTP-IE. We thus demonstrated the usefulness of this type of preparation for the study of rudimentary oral-motor activity and observed changes in TMN excitability. In addition, on testing with the whole-cell patch-clamp method, TMNs exhibited a significant increase in excitability with a leftward shift in F-I curves generated with depolarizing current injections, whereas resting membrane potential and input resistance exhibited no remarkable changes. These findings indicate that TMNs exhibit LTP of intrinsic excitability.

Occupational safety among dental health-care workers.

Compared to other health-care workers, dental health-care workers come in close contact with patients and use a variety of sharp and high-speed rotating instruments. It is important to understand the characteristics of the occupational accidents that occur. We reviewed incident reports from April 1, 2005, to March 31, 2010, at Matsumoto Dental University Hospital. In addition, questionnaires dealing with identification of occupational safety issues, especially splash exposures, were conducted for dentists, dental hygienists, and nurses. Thirty-two occupational injuries were reported during the study period, including 23 sharp instrument injuries (71.9%), 6 splash exposures (18.8%), and 3 others. Of the six splash exposures, only two cases involved potential contamination with blood or other potentially infectious patient material. Of the 66 workers who experienced sharps injuries, 20 workers (30.3%, 20/66) reported them to the hospital work safety team. The questionnaire revealed high incident of splash exposures and conjunctiva exposures: 87.9% (51/58) and 60.3% (35/58) in dentists and 88.6% (39/44) and 61.4% (27/44) in dental hygienists. The compliance rate for routine use of protective eyewear was 60.3% (35/58) for dentists and 34.1% (15/44) for hygienists. Of the presented informational items included in the questionnaire, those that strongly persuaded respondents to use protective eyewear were 'splatters from the patient's mouth contain blood' (90%, 99/110) and 'dental operations at our clinic are performed based only on a questionnaire without serious examinations for HBV, HCV, and HIV' (71.8%, 79/110). The reason of low compliance of protective eyewear among dentists might relate to fine dental procedures. Appropriate information is important for the motive of wearing personal protective equipment, and an early educational program may have a potential to increase compliance with the use of that equipment.

Age-related disruption of the lamina dura: evidence in the mandibular horizontal incompletely impacted third molar.

Changes in the lamina dura are associated with dental diseases around the root of the tooth and with systemic diseases; however, the lamina dura below the crown of horizontal, incompletely impacted third molars has not been studied. Using orthopantomography, we studied the age of subjects with and without the lamina dura in 419 subjects. The participants were between the ages of 21 and 89 years. Mean age in men with the lamina dura was 30.29 +/- 9.92 and without the lamina dura was 47.64 +/- 16.32 (P < 0.0001), and in women with a lamina dura it was 29.65 +/- 8.19 and without a lamina dura 41.97 +/- 11.07 (P < 0.0001). To study the effect of aging, the relationship between the lamina dura and dental status was assessed in subjects over the age of 31 years. Alveolar bone resorption in the canine and the first molar of the ipsilateral mandible in subjects without the lamina dura was not significantly higher than in those with the lamina dura. There were no significant differences in the number of teeth lost, except in men, the number of treated teeth and the number of decayed teeth differed between groups. Disruption of the lamina dura was related to age, but with no alveolar bone resorption in the mandible.

High incidence of blood exposure due to imperceptible contaminated splatters during oral surgery.

PURPOSE: To evaluate the incidence of blood exposure during outpatient oral surgery from splattering caused by use of high-speed rotary instruments at the Referral and Teaching Center, University Dental Hospital. MATERIALS AND METHODS: Twenty-five consecutive patients who had impacted mandibular third molars were selected. The attending surgeon wore an operation gown and visor mask, and carried out the tooth extraction with the regular procedure. We counted the number of bloodstains found on the operation gown and visor mask, and confirmed the presence of diluted and invisible bloodstains using a leucomalachite green presumptive test, which was able to detect dilutions up to 1:4,000. RESULTS: There were 469 separate bloodstains on the gown and visor mask of oral surgeons, which came from 19 (76%) of 25 patients during impacted mandibular third molar surgery. Presumptive tests for invisible bloodstains resulted in 1,206 positive reactions, 2.57-fold greater than the visible stains, from 88% of the cases. All of the surgeons were right-handed and the common areas of staining were the right forearm, face, and thorax regions. CONCLUSIONS: Dental procedures with high-speed instruments exposed surgeons to possible blood-borne infections by splashing in nearly 90% of the cases. Greater than 50% of the stains were invisible to the naked eye. Based on our results, strict compliance with barrier precautions, including routine use of an operation gown and visor mask, is recommended whenever oral surgery is carried out with high-speed rotary instruments.

Possible involvement of neurons in locus coeruleus in inhibitory effect on glossopharyngeal expiratory activity in a neonatal rat brainstem-spinal cord preparation in vitro.

In this study, we found that a certain motor branch of glossopharyngeal (IX) motor nerves stably exhibits not only inspiratory activity but also expiratory activity with pons removal in neonatal rat brainstem-spinal cord preparations in vitro. Because this finding indicates that IX expiratory activity is masked by an inhibitory mechanism operating in the pons, we sought to determine the candidate neurons that exert an inhibitory effect on IX expiratory activity. IX expiratory activity was observed when only the pons was perfused with noradrenaline (NA) or clonidine (alpha2 adrenergic receptor agonist), but not when NA and yohimbine (alpha2 adrenergic receptor antagonist) were perfused together. IX expiratory activity was also observed following the removal of the dorsal pons but not the ventral pons. The local administration of clonidine into the bilateral locus coeruleus (LC) evoked burst discharges during the expiratory phase in the IX motor rootlet. These results suggest that neurons in the LC that possess an alpha2 adrenergic receptor on the membrane surface exert a tonic inhibitory effect on IX expiratory activity in neonatal rat brainstem-spinal cord preparations.

Comparison of surgical and nonsurgical treatment of bilateral condylar fractures based on maximal mouth opening.

This study presents a comparative analysis of the open surgical and nonsurgical treatment of patients with bilateral condylar fractures. Sixty-seven (67) patients were treated, and the completed data on 55 patients were reviewed to compare both therapeutic modalities, which consisted of nonsurgical and surgical treatment in 37 and 18 patients, respectively. In the nonsurgical group, 23 patients (23/37, 62%) had normal mouth opening. Functional success rate was 79% (15/19) and 44% (8/18) in young adult patients (-29yrs) and older patients (30+yrs), respectively, and there was a significant difference of outcome between the two groups. In nonsurgically treated young patients with disorders, bilateral dislocation and existence of concomitant mandibular fractures were commonly observed. In the open surgical group, seven (7/11, 64%) young adult and three (3/7, 43%) older patients gained normal mouth opening, and no significant difference was observed. Additionally, there was no difference between non-surgical and surgical treatment in any category. Patients undergoing rigid fixation benefited from restoring maximum mouth opening, although there was no significant difference between the rigid and non-rigid fixation groups. Based on these findings, nonrigid fixation should be avoided, and rigid fixation might improve outcome in young adult patients with severe fracture pattern, such as bilateral dislocation and concomitant mandibular fracture.

NR3 protein expression in trigeminal neurons during postnatal development.

The N-methyl-d-aspartate (NMDA) receptor plays an important role in the generation of rhythmical oral motor activities. To compliment our previous studies, we examined the developmental regulation of NR3A and NR3B expression in trigeminal motoneurons (Mo5) and mesencephalic trigeminal neurons (Me5). NR3A-immunoreactive neurons were observed at all ages in both nuclei, decreasing in Mo5 and caudal Me5 after P14, and increasing in rostral Me5. NR3B protein expression only emerged in Mo5 after P21-23. Results indicate that NR3A and NR3B expression is differentially regulated between Mo5 and Me5 coincident with the transition from suckling to chewing.

Azithromycin as prophylaxis for the prevention of postoperative infection in impacted mandibular third-molar surgery.

Rotational use of antimicrobials is one of the strategies that have been suggested to reduce the development of drug-resistant bacteria. Cycling of homogeneous antimicrobial exposure is, however, unlikely to control the emergence of antimicrobial resistance. Penicillins and cephalosporins have been extensively used for therapeutic and prophylactic management of oral infection. The aim of the study was to investigate the clinical effects of azithromycin as prophylaxis on the prevention of postoperative infection in impacted mandibular third-molar surgery. The study design was a retrospective, single-center review. One (2.2%) of all 45 patients exhibited dry socket infection. In several categories, there was significant effectiveness of azithromycin in comparison with other antimicrobials, although there was no significant difference in the occurrence rate of dry socket infection. Azithromycin might be of value for prophylactic use in impacted mandibular third-molar surgery in which penicillins and cephalosporins were mainly used. Therefore, it might be available for one of the rotational agents.

Prenatal development of NMDA receptor composition and function in trigeminal neurons.

The prenatal development of neural circuits for rhythmical oral-motor behaviors used for feeding is essential for the survival of the newborn mammal. The N-methyl-D-aspartate (NMDA) receptor plays a critical role in brainstem circuits underlying postnatal oral-motor behaviors. To understand a role for the NMDA receptor in the emergence of sucking behavior we conducted physiological and immunohistochemical experiments using fetal rats. Physiology experiments examined the development of the NMDA dose response of the brainstem circuit responsible for generating rhythmical trigeminal activity by recording trigeminal motor outputs using an in vitro preparation. The high dose of NMDA agonist bath application affected the mean cycle duration of rhythmical trigeminal activity (RTA) at both embryonic day (E) 18-19 and E20-21 in comparison with standard concentration of NMDA agonist. NMDA receptor immunohistochemistry studies, using antibodies directed against subunits NR1, NR2A, NR2B, NR3A and NR3B were performed to determine the prenatal regulation of NMDA subunits in trigeminal motoneurons (Mo5), and mesencephalic trigeminal neurons (Me5) between E17 to E20. In Mo5, NR1, NR2A, NR2B and NR3A immunoreactivity was observed throughout the time frame sampled. NR3B immunoreactivity was not observed in Mo5 or Me5. In Mo5, there was a significant decrease in the percentage of NR2B immunoreactive neurons between E17 and E20, and a concurrent increase in the NR2A/NR2B ratio between E17 and E20. In Me5, NR1, NR2A and NR3A immunoreactivity was observed throughout the time frame sampled; a significant decrease in the percentage of NR2A immunoreactive neurons between E17 and E20, and NR3A immunoreactive neurons between E17 and E18 occurred. The timing of subunit changes between E17 and E18 is coincident with the prenatal emergence of rhythmical jaw movements, and in vitro rhythmical trigeminal activity, shown in earlier studies. Our data suggest that NMDA receptor plays an important role in the development and function of prenatal oral-motor circuits.

Oral-motor patterns of rhythmic trigeminal activity generated in fetal rat brainstem in vitro.

Development of neural circuits generating fetal oral-motor activity was characterized in an in vitro isolated brainstem block preparation. Rhythmical trigeminal activity (RTA) at E20-E21 resembled either the pattern or rhythm of neonatal RTA. Conversely, at E18-E19, RTA displayed a different pattern of discharge from neonatal RTA, and output was not regular but intermittent with another slow rhythm.