Kohji Ishihama

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.

Differential discharge patterns of rhythmical activity in trigeminal motoneurons during fictive mastication and respiration in vitro

Rhythmical activity in trigeminal motoneurons (TMNs) was studied in an in vitro neonatal rat brainstem preparation that retains functionally active circuits for oral-motor behaviors. Whole-cell current-clamp recording from TMNs demonstrated rhythmical activities during both spontaneously generated respiratory activity and neurochemically induced rhythmical oral-motor activity. TMNs showed spontaneous rhythmical (0.08 +/- 0.04 Hz) activities of burst-firing pattern during inspiration synchronized with inspiratory activities recorded in hypoglossal nerves. During rhythmical oral-motor activity induced by bath application of N-methyl-d,l-aspartic acid and the GABA(A) receptor antagonist bicuculline methiodide, TMNs showed only a rhythmical (5.6 +/- 0.8 Hz) pattern of single-spike discharge. TMNs never showed a burst-firing pattern during rhythmical oral-motor activity even when membrane potentials were shifted either to depolarized or hyperpolarized levels. Rhythmical activity in TMNs exhibited different discharge patterns between rhythmical oral-motor activity and respiratory activity generated in vitro.

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.

Comparison of Surgical and Nonsurgical Treatment of Bilateral Condylar Fractures Based on Maximal Mouth Opening

Abstract 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.

Temporal patterns of trigeminal respiratory activity in rat brainstem-spinal cord in vitro

Respiratory activity in trigeminal (V) motoneurons was studied in rhythmically active en bloc brainstem-spinal cord preparations isolated from neonatal rats (P0-P3). In the majority of preparations (83%), the temporal pattern of V activity consisted of spontaneous inspiratory phasic discharge with onset delayed or coincident with onset of phrenic motoneuron discharge. Blockade of alpha-2 noradrenergic receptor activation shifted onset of V respiratory discharges earlier than phrenic discharges, while elevation of extracellular potassium concentration or blockade of GABAergic and glycinergic inhibitory synaptic transmission had little effect on temporary pattern of V respiratory discharges. We conclude V motoneurons in the in vitro preparation generate respiratory activity during inspiratory phase, and their temporal patterns are modulated by inhibitory noradrenergic synaptic transmission.

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.

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.

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.

Regulation of Trigeminal Respiratory Motor Activity in the Brainstem

The trigeminal motor system participates in the control of respiration as well as suckling and mastication. However, the central mechanism underlying respiratory activity in trigeminal motoneurons is not well-understood. In this study, we aimed to elucidate brainstem circuitry for rhythm generation and signal transmission of trigeminal respiratory activity in in vitro neonatal rat brainstem-spinal cord preparations. We further examined the role of midline-crossing trigeminal interneurons in the bilateral synchronization of respiratory and suckling activity in trigeminal motor nerves. The results of brainstem-sectioning experiments indicated that respiratory rhythms were generated in the medulla and ipsilaterally transmitted to trigeminal motoneurons in the pons. We conclude that the trigeminal motor system, as well as the hypoglossal and phrenic motor system, is regulated by medullary respiratory networks, and that pontine interactions between bilateral trigeminal interneurons are not critical for the generation or synchronization of trigeminal respiratory activity, but are crucial for trigeminal suckling activity.

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.