Pulp inflammation induces Kv1.1 K+ channel down-regulation in rat thalamus.

OBJECTIVES: Signals from inflamed tooth pulp activate thalamic neurons to evoke central sensitization. We aimed to gain insights into the mechanisms mediating the early phase of pulpal inflammation-induced thalamic neural and glial activation. MATERIALS AND METHODS: Pulpal inflammation was induced via the application of mustard oil (MO) to the upper first molar of Wistar rats with local anesthesia (LA) or saline injection. After 0.5, 1, 2, and 24 hr, contralateral thalami were subjected to microarrays, a real-time polymerase chain reaction and immunohistochemistry to identify differentially expressed genes and assess potassium voltage-gated channel subfamily A member 1 (Kv1.1)-expressing axons and glial fibrillary acidic protein (GFAP)-expressing astrocytes. RESULTS: The Kv1.1 gene (Kcna1) was down-regulated and the density of Kv1.1-expressing axons decreased in non-anesthetized rats, but not in anesthetized rats 1 hr after the MO treatment. The density of GFAP-expressing astrocytes increased in both groups until 24 hr after the MO treatment, with a greater increase being observed in the saline-injection group than in the LA group. CONCLUSIONS: MO induced the transient down-regulation of Kcna1, transiently reduced the density of Kv1.1-expressing axons, and increased astrocytes in thalami within 1 hr of pulpal application. These results suggest central sensitization represented by neuronal hyperexcitability and astrocyte activation.

[Outcomes of Infection Control Team Inspections at the Dental Hospital, Tokyo Medical and Dental University].

In the Dental Hospital, Tokyo Medical and Dental University, an infection control team (ICT) has been formed to inspect each diagnosis department of clinics and wards in order to identify problems regarding nosocomial infection control. In this study, we analyzed the inspection reports and highlighted the following serious problems: 1) inadequate hygienic hand-washing for out- and in-patient treatment, 2) incomplete wearing of personal protective equipment (PPE) by dental health care workers, 3) necessity of environmental improvement in the clinics, and 4) cross-infection risk induced by. the continuous use of treatment devices without appropriate disinfection. The ICT provided feedback to the inspected departments, suggesting solutions to problems regarding nosocomial infection control. In order to enhance infection control in our hospital, dental healthcare practitioners must make further efforts on nosocomial infection control and prevention, and act according to their position by continuously educating students and enlightening hospital staff about the importance of infection control.

[Economic effects of single-pack dental hygienic materials introduced into daily clinical practice].

To improve and maintain medical safety and quality, it is necessary to construct and manage a safe and economical medical system. Almost five years have passed since single-pack dental hygienic materials were introduced into daily clinical practice in the University Hospital, Faculty of Dentistry, Tokyo Medical and Dental University. The costs of purchasing hygienic materials themselves are higher when using outsourced sterilized single packed ones, compared with when using intra-murally sterilized ones in the past. Proper usage of single-pack hygienic materials sterilized with Ethylene Oxide Gas (EOG) would reduce waste of unused materials and save labor for staff in the Section of Central Supplies. Financially, the use of hygienic materials could be reduced if single-pack dental hygienic materials by outsourcing were introduced into the hospital, because all costs for sterilizing hygienic materials in the hospital could be eliminated.

[Effectiveness and difficulty of education on nosocomial infection control for pre-clinical practice in the clinic, so-called inclusive clinical practice phase I, for students in the Faculty of Dentistry, Tokyo Medical and Dental University].

It has been planned to give pre-clinical practice in the clinic, so-called inclusive clinical practice phase I, for fifth-grade students in the School of Dentistry, Faculty of Dentistry, Tokyo Medical and Dental University, to give them the clinical training needed to perform dental practice and clinical practicum for comprehensive patient care, namely inclusive clinical practice phase II. This study analyzed the educative efficiency of the class on nosocomial infection control (NIC) by comparing achievements pre- and post-test, and discussed appropriate education planning on the NIC for dental students. Sixty-two fifth-grade students in the 2007 academic year sat the pre- and post-tests; the mean score and standard deviation of these tests were 5.30 +/- 1.26 (n = 56) and 8.59 +/- 1.18 (n = 59), respectively. There was a statistically significant difference between them (paired t-test, p < 0.01). Another finding was that students with high scores in the post-test did not necessarily achieve high ratings in the pre-test. It is suggested that the introduction of pre- and post-tests and the clarification of main points in the class as a theme of NIC could be a useful tool for increasing the comprehension of students on the theme. Since students at lower grades will attend clinical practice in the university hospital, it is thought that students should be given NIC training early in the clinical course, and the current curriculum should be improved to increase the opportunity for students to study this important issue.

Analysis of factors related to needle-stick and sharps injuries at a dental specialty university hospital and possible prevention methods.

Needle-stick and sharps injuries (NSIs) can happen even when dental health care workers (DHCWs) act in compliance with standard precautions to prevent transmitting blood-borne infections. The objective of this study was to investigate causes of NSIs that had occurred at a dental specialty university hospital during the past 12 academic years. A total of 215 NSIs were reported during the investigation period, and NSIs ascribed to female DHCWs (n = 148; 68.8%) were significantly (P < 0.05) more common than those ascribed to male DHCWs (n = 67; 31.2%). One hundred twenty-six NSIs (58.6%) were caused by DHCWs with little experience (P < 0.05), and 37 of those (17.2% of the total) were ascribed to undergraduate students during clinical training (P < 0.05). The NSIs occurred both during treatment (n = 119; 55.3%) and during cleaning up used devices (n = 89; 41.4%). The NSIs at the dental hospital occurred with a probability of 0.004% of total therapeutic opportunities. Prevention of NSIs should be the responsibility of dental students and DHCWs, and should be a part of education about infection control to prevent the nosocomial transmission of blood-borne pathogens.

Evaluation of Root Canal Anatomy of Maxillary Premolars Using Swept-Source Optical Coherence Tomography in Comparison with Dental Operating Microscope and Cone Beam Computed Tomography.

OBJECTIVE: This study aimed to evaluate the ability of swept-source optical coherence tomography (OCT) to detect internal anatomy of maxillary premolars in comparison with dental operating microscope (DOM) and cone beam computed tomography (CBCT). BACKGROUND DATA: The ability of OCT to observe the pulp horn during cavity preparation and assess the remaining dentin thickness (RDT) has been demonstrated, whereas validation of OCT in comparison with other imaging techniques seems required. METHODS: Ten extracted human maxillary premolars were sectioned perpendicular to the tooth axis from the occlusal surface at approximately 2 mm increments. OCT and DOM were performed after each cut, and microfocus X-ray computed tomography (micro-CT; reference standard) and CBCT were conducted before sectioning and after the first and second cuts. Three examiners evaluated all images for presence of the pulp horn/pulp chamber, isthmus, lateral canals, and the number of root canals. RDT was determined from OCT, micro-CT, and CBCT images. Correlations were analyzed with Pearson's correlation coefficient. RESULTS: OCT had a sensitivity and specificity of 0.90 and 0.80 in detecting the pulp horn/pulp chamber and 0.84 and 0.71 in detecting the isthmus, respectively. The three techniques showed strong correlations in detecting the number of root canals compared with micro-CT. OCT and DOM did not detect lateral canals. For RDT values, strong correlations were observed between micro-CT and CBCT, micro-CT and OCT, and CBCT and OCT (p < 0.01 for all). CONCLUSIONS: Under the present experimental condition, OCT accurately measured RDT and detected internal tooth anatomy such as the pulp horn, isthmus, and root canals.

Spreading of root canal irrigants on root dentine.

The purpose of this study was to evaluate the spreading of root canal irrigants on human root dentine. The spreading of various solutions on dentine surfaces was measured after pre-treatment with various conditional solutions. Seven experimental groups were set based on the combination of conditioning solution-test solution: none-distilled water; none-6% sodium hypochlorite (NaOCl); none-14.3% ethylenediaminetetraacetic acid containing surfactant 0.084% cetrimide (Morhonine); NaOCl-NaOCl; NaOCl-Morhonine; Morhonine-Morhonine and Morhonine-NaOCl. After application of 0.1 mL of conditioning solution for 60 s, 0.5 microL of test solution was placed on dentine surfaces. Spreading of test solution was measured for 480 s to examine the size of the contact area ratio. Those at 300 s were compared among groups using Fisher's Protected Least Significant Difference (P < 0.05). It was concluded that the contact area ratio of Morhonine-NaOCl increased the most significantly among all the experimental groups.

[Inspection by infection control team of the University Hospital, Faculty of Dentistry, Tokyo Medical and Dental University].

Factors affecting infection are the existence of infectious microorganisms, sensitivity of hosts, number of microorganisms, and infectious routes. Efforts to prevent infection focus on not allowing these factors to reach the threshold level. Inspection by an infection control team (ICT) of a hospital is one countermeasure for preventing nosocomial infection. We summarize here the problems for complete prevention of nosocomial infection based on the results of inspection by our ICT, so that staff working in the hospital can recognize the importance of preventing nosocomial infection. The following were commonly observed problems in our clinics found by the ICT : (1) incomplete practice of standard precautions and/or isolation precautions, (2) noncompliance with guidelines for the prevention of cross-infection, and (3) inappropriate management of medical rejectamenta. Infection control can be accomplished by strictly observing the standard precautions and isolation precautions. The ICT inspection round in the hospital could be an effective metaff working in the hod to clarify and overcome the problems involved in infection.

Removal of two types of root canal filling material using pulsed Nd:YAG laser irradiation.

OBJECTIVE: The aim of this study was to examine the usefulness of a pulsed Nd:YAG laser in removing two types of endodontic obturation material from the root canal in vitro. BACKGROUND DATA: Recently, a fine flexible glass fiber made of quartz has been developed to transmit the laser beam more effectively and permit its concentration in a specific area. This has increased the potential usefulness of the Nd:YAG laser in root canal treatment. METHODS: The time required for removing the root canal obturation material (Gutta-percha cones and, Sealapex or AH26) by means of either Nd:YAG laser irradiation or a conventional method (Gates Glidden drills and K files) was measured. Contact microradiography was used to assess the radiopacity of the root canals before and after the removal of obturation material. The surfaces of the root canal after removal of the obturation materials were also observed by scanning electron microscopy. RESULTS: Although none of the methods used in this study resulted in complete removal of debris from the root canal wall, the time required for the removal of any of the root canal obturation materials using laser ablation was significantly shorter than that required using the conventional method (p < 0.05). It appeared that some orifices of the dentinal tubules were blocked with melted dentin following laser irradiation. CONCLUSIONS: Nd:YAG laser irradiation is an effective tool for the removal of root canal obturation materials, and may offer advantages over the conventional method.

Up-regulation of p38 mitogen-activated protein kinase during pulp injury-induced glial cell/neuronal interaction in the rat thalamus.

INTRODUCTION: We have recently reported that the signal of pulp injury induces both neuronal and glial cell activation in the contralateral thalamus in rats, although the mechanisms of the glial cell/neuronal interaction remain unclear. This study was undertaken to test our hypothesis that p38 mitogen-activated protein kinase (MAPK) signaling pathways are involved in the pulp injury-induced glial cell/neuronal interaction in the thalamus. METHODS: A local anesthetic (lidocaine with epinephrine) or saline (control) was injected into the tissue surrounding the left mandibular first molar of Wistar rats. The tooth was then pulp-exposed, and the cavity was sealed with flowable composite. After 0 (normal pulp with local anesthetic or saline pretreatment), 24, and 72 hours, the contralateral side of thalamus was retrieved and subjected to immunohistochemistry for phospho-p38 MAPK and glial fibrillary acidic protein and real-time polymerase chain reaction analysis of p38-MAPK family (MAPK 13 and MAPK 14) mRNAs. RESULTS: The area immunopositive to phospho-p38 MAPK increased until 72 hours after pulp exposure in both local anesthetic-pretreated and saline-pretreated animals, but the rate of increase was lower in the local anesthetic-pretreated animals. The density of glial fibrillary acidic protein-expressing astrocytes showed a significant increase only in the saline-pretreated animals. Expression levels of MAPK 13 and MAPK 14 mRNAs increased at 24 hours and still higher at 72 hours in the saline-pretreated animals. Notably, MAPK 13 and MAPK 14 mRNA levels at 24 and 72 hours in the local anesthetic-pretreated animals showed significantly lower levels than those in the saline-pretreated animals. CONCLUSIONS: It was concluded that pulp injury-induced up-regulation of MAPK 13, MAPK 14, and phospho-p38 MAPK in the thalamus was suppressed by the local anesthetic pretreatment, suggesting the involvement of p38 MAPK signaling pathways in the glial cell-neuronal interaction induced by pulpal nociception.

The role of N-methyl-D-aspartate receptor subunits in the rat thalamic mediodorsal nucleus during central sensitization.

We have identified tooth pulp-driven neurons (TPDNs) in the thalamic mediodorsal nucleus (MD) in rats and showed that the TPDNs' responsiveness in the MD is increased by chemical conditioning stimulation of allyl-isothiocyanate (mustard oil) to the molar tooth pulp. The aim of the present study was to address the role of N-methyl-d-aspartate receptors (NMDA receptors) in the sensitized central nervous system following the mustard oil application to the rat tooth pulp. Microinjection of MK-801, a noncompetitive NMDA receptor antagonist, to the thalamic MD nucleus reduced the TPDNs' responsiveness in the thalamic MD nucleus. Gene expression analysis showed that expression levels of NMDA receptor subunits NR2A and NR2D mRNAs in the thalamus were increased by the mustard oil application and that the increases were reduced by MK-801. When naloxone, an opioid receptor antagonist, was given systemically following the MK801 microinjection, the TPDNs' responsiveness was rekindled and expression levels of NR2D and NR2A mRNAs were increased. Moreover, lidocaine pretreatment abolished the mustard oil-induced upregulation of NR2D and NR2A mRNAs. These results suggest that, during central sensitization, interaction of NMDA receptors and endogeneous opioid-related inhibitory mechanisms plays critical role in the alteration of the TPDNs' responsiveness in the thalamic MD nucleus.

Gene expression analysis of acutely traumatized pulps.

INTRODUCTION: Vertical root fracture of vital teeth is a relatively rare occurrence. To address early molecular biologic events that take place in the pulp of such cases, we measured mRNA expression levels of selected molecules related to nociception, bacterial pattern recognition, and hard tissue repair/mineralization. METHODS: Three extracted roots obtained from vital molars diagnosed as vertical root fracture were used. The samples were first analyzed with light and transmission electron microscopy. Then mRNA expression in the apical (root fractured) and coronal portions of the pulp was analyzed by using reverse transcription-polymerase chain reaction (PCR) or real-time PCR after laser capture microdissection. RESULTS: In all the samples, cracks and vital pulp tissue, but not signs of infection and inflammation, were recognized in the apical portion of the fractured root. The gene expression analysis showed that mRNAs of pattern recognition receptors (CD14, Toll-like receptor 2, and Toll-like receptor 4) and neurokinin-1 receptor were equally expressed in both regions of the pulp. On the other hand, mRNA expression levels of hard tissue-associated proteins (osteopontin, osteonectin, and osteocalcin) and calcium channel voltage-dependent alpha 2 delta subunit 1 (CACNA2D1) in the apical portion of the pulp tissue and periodontal ligaments were significantly up-regulated, as compared with those in the coronal portion of the pulp. CONCLUSIONS: In the traumatized apical pulp of vertically root-fractured vital teeth, elevated mRNA expression of CACNA2D1, a nociception-related molecule, and proteins related to hard tissue repair/mineralization occurs under noninfectious condition.

Increased gene expression of Toll-like receptors and antigen-presenting cell-related molecules in the onset of experimentally induced furcation lesions of endodontic origin in rat molars.

INTRODUCTION: Early immunopathogenic mechanisms behind pulp infection-induced furcal inflammation have not been well understood. To address the immunopathology of the pulp infection-induced furcal region of the periodontal ligament (PDL), we performed immunohistochemical and quantitative gene expression analyses for toll-like receptors (TLRs) in the furcal PDL of rat molars subjected to unsealed or sealed pulpotomy. METHODS: Furcal inflammation in rat molars was generated by making unsealed pulpotomies that were exposed to the oral environment for 24 hours. Pulpotomized teeth sealed with a temporary filling material and untreated normal teeth served as controls. Gene expression was analyzed with laser capture real-time polymerase chain reaction for TLR-2, TLR-4, and antigen presenting cell (APC)-related molecules (class II MHC, CD83, and CD86). Immunohistochemistry for TLR-2 and TLR-4 was also performed. RESULTS: Messenger RNA expression levels of TLRs and the APC-related molecules in the furcal periodontal ligament were significantly up-regulated in teeth with unsealed pulpotomy. Immunohistochemistry for unsealed pulpotomized teeth revealed that TLRs-expressing cells were predominantly distributed within the PDL beneath the furcal dentin. CONCLUSIONS: These results suggested the involvement of innate immune mechanisms involving TLRs and resulting activation of APCs in the early pathogenesis of pulp infection-induced furcal inflammation.

Artificial dental pulp exposure injury up-regulates antigen-presenting cell-related molecules in rat central nervous system.

INTRODUCTION: Bacterial infection and resulting inflammation of the dental pulp might not only trigger neuroimmune interactions in this tissue but also sensitize the central nervous system (CNS) such as the thalamus via nociceptive neurons. Thus, immunopathologic changes in the rat thalamus that take place after pulp inflammation were investigated. METHODS: Pulp exposure was made in mandibular right first molars of 5-week-old Wistar rats. After 24 hours, the thalamus was retrieved and subjected to either immunohistochemistry for class II major histocompatibility complex (MHC) molecules and glial fibrillary acidic protein (GFAP) or mRNA expression analysis of antigen-presenting cell-related molecules and N-methyl-D-aspartate receptor 2D subunit (NR2D) by means of reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. RESULTS: At 24 hours after pulp exposure, the density of class II MHC molecule-expressing and GFAP-expressing cells was increased in the contralateral thalamus. Gene expression analysis revealed the up-regulation of class II MHC molecules, CD80, CD83, CD86, and NR2D in the contralateral thalamus, as compared with the ipsilateral thalamus. CONCLUSIONS: These results suggest the signal of pulp inflammation induces neuronal activation in the CNS.

The possibility of dowel removal by pulsed Nd:YAG laser irradiation.

BACKGROUND AND OBJECTIVES: Nd:YAG laser is one of the popularly used laser, in dentistry for treatment and technologic processing. Removal of dowel from root canal is very troublesome at endodontic retreatment. This study aimed to examine the possibility and efficiency of dowel removal from the root canal using the Nd:YAG laser in vitro. STUDY DESIGN/MATERIALS AND METHODS: Irradiation time and energies required for complete removal of the dowel set in the root canal using the laser were measured. The dowel ablation was observed by contact microradiographs (CMRs). The surface of the root canal after lasing was observed by a scanning electron microscope (SEM). RESULTS: A significant difference existed in irradiation times and energies to remove dowels among various combinations of metal and cement (P < 0.05). The CMRs showed that both dowel and dentin were ablated, and the SEM observation demonstrated that root canal surface was melted. CONCLUSIONS: The Nd:YAG laser irradiation could remove set dowels from the root canal.