Journal of Oral Science
Online ISSN : 1880-4926
Print ISSN : 1343-4934
ISSN-L : 1343-4934
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Showing 1-27 articles out of 27 articles from the selected issue
Review
  • Masayuki Kobayashi
    Type: review-article
    2020 Volume 62 Issue 2 Pages 125
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS
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  • Yong-Chul Bae, Atsushi Yoshida
    Type: review-article
    2020 Volume 62 Issue 2 Pages 126-130
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Dental pulp is densely innervated by sensory afferents that are primarily involved in nociception. Elucidating the type and properties of these afferents and their distribution patterns within the dental pulp is crucial for understanding the mechanisms of acute dental pain and dental hypersensitivity. Recent studies on the release of the transmitter glutamate and the expression of glutamate receptors and vesicular glutamate transporters (VGLUT) in the pulpal axons and trigeminal ganglion (TG) have suggested the possibility of a distinct glutamate signaling mechanism underlying the peripheral processing of dental pain. This review discusses recent findings on the innervation of dental pulp and glutamate signaling by pulpal axons. First, recent findings on the morphological features and types of axons innervating the dental pulp are summarized. Then, glutamate signaling in the dental pulp and changes in the expression of VGLUT1 and VGLUT2 in the pulpal axons and TG neurons following pulpal inflammation are explained. Finally, findings on glutamate release from odontoblasts are briefly described.

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  • Masamichi Shinoda, Yoshinori Hayashi, Asako Kubo, Koichi Iwata
    Type: review-article
    2020 Volume 62 Issue 2 Pages 131-135
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS

    Nociceptive stimuli to the orofacial region are typically received by the peripheral terminal of trigeminal ganglion (TG) neurons, and noxious orofacial information is subsequently conveyed to the trigeminal spinal subnucleus caudalis and the upper cervical spinal cord (C1-C2). This information is further transmitted to the cortical somatosensory regions and limbic system via the thalamus, which then leads to the perception of pain. It is a well-established fact that the presence of abnormal pain in the orofacial region is etiologically associated with neuroplastic changes that may occur at any point in the pain transmission pathway from the peripheral to the central nervous system (CNS). Recently, several studies have reported that functional plastic changes in a large number of cells, including TG neurons, glial cells (satellite cells, microglia, and astrocytes), and immune cells (macrophages and neutrophils), contribute to the sensitization and disinhibition of neurons in the peripheral and CNS, which results in orofacial pain hypersensitivity.

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  • Hossain M. Zakir, Yuji Masuda, Junichi Kitagawa
    Type: review-article
    2020 Volume 62 Issue 2 Pages 136-139
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: February 19, 2020
    JOURNALS FREE ACCESS

    Transient receptor potential vanilloid 1 (TRPV1) is a polymodal receptor channel, which plays an important role in pain transduction. It is important to understand the functional expression of this channel under neuropathic pain (NP) conditions. A novel method was used to investigate the dynamics of functional expression of this channel on regenerated neurons under NP conditions following trigeminal nerve injury using a combination of a permanently charged sodium channel blocker (QX-314) and a TRPV1 agonist (capsaicin; QX-CAP). The combination was originally introduced as a local anesthetic. Synchronization between the local anesthetic effect of QX-CAP and TRPV1 expression on regenerated neurons was observed following the nerve injury. QX-CAP had no local anesthetic effect under NP conditions 2 weeks after the injury when TRPV1 expression on regenerated neurons was low. However, this combination was effective under NP conditions 3 and 4 weeks following injury when TRPV1 expression in regenerated neurons was moderate to high. The current review, discusses the potential of QX-314 as a local anesthetic and a novel approach of using QX-CAP to reveal the dynamics of functional expression of TRPV1 on regenerated neurons following trigeminal nerve injury.

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  • Mamoru Takeda, Yoshihito Shimazu
    Type: review-article
    2020 Volume 62 Issue 2 Pages 140-143
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS

    Physiological pain protects the body and its systems from damage, but pathological pain has no obvious biological role. Complementary alternative medicine (CAM) agents are being increasingly studied in the treatment of clinical pain, and some dietary constituents (polyphenol, carotenoids, and fatty acids) and supplements may modify pain pathways. Because these substances modulate neuronal excitability—including the trigeminal pain pathway via various voltage-gated ionic channels and transient receptor potential and ligand-gated channels, dietary constituents could contribute to CAM as therapeutic agents for attenuating orofacial noxious sensory information. This review summarizes the current understanding of the mechanisms by which dietary constituents might attenuate excitability of trigeminal nociceptive neurons implicated in blocking pain, particularly in relation to the authors’ recent experimental data, and discusses the development of functional foods and the contribution of dietary constituents in the relief of clinical dental pain without the side effects of nonsteroidal anti-inflammatory drugs.

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  • Masayuki Kobayashi, Yuka Nakaya
    Type: review-article
    2020 Volume 62 Issue 2 Pages 144-146
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: February 27, 2020
    JOURNALS FREE ACCESS

    Corticofugal projections to neurons in the medullary dorsal horn, i.e., the trigeminal spinal subnucleus caudalis (Sp5C), are thought to play a critical role in regulating nociceptive information processing in the trigeminal nervous system. The Sp5C consists of 5 layers, each of which exhibits its own characteristic features of cellular organization. Therefore, the layers receiving corticofugal projections must be identified when discussing the role of the cerebral cortex in nociception arising from the trigeminal nerve. It is also necessary to discriminate between layers of the Sp5C where corticofugal projections terminate, because the Sp5C involves glutamatergic neurons and GABAergic/glycinergic neurons, which correspond to excitatory and inhibitory neurons, respectively. This review summarizes descending projections from the cerebral cortex, including the primary and secondary somatosensory and insular cortices, to the Sp5C.

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  • Masahiro Kondo, Ikuko Shibuta
    Type: review-article
    2020 Volume 62 Issue 2 Pages 147-149
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Pain can be divided into nociceptive, inflammatory, and neuropathic pain. It is important to understanding the molecular mechanism of pain signaling in the development of pain relief therapies. Twenty years ago, extracellular signal-regulated kinases (ERK) 1 and 2, which are members of the mitogen-activated protein kinase superfamily, were identified as molecules activated in neurons by the exposure of peripheral tissues to noxious stimuli. Further studies have revealed that peripheral nerve injury induces ERK activation in glial cells, sensory neurons, and second-order neurons, albeit at different time points. Moreover, inhibition of ERK suppresses pathological pain in animals with peripheral nerve injury. Therefore, ERK is currently recognized as an important molecule in pain signaling and a potential novel target for pain treatment. This review introduces recent advances in revealing the regulation of ERK in pain research.

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  • Akimasa Tashiro, David A. Bereiter
    Type: review-article
    2020 Volume 62 Issue 2 Pages 150-155
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS

    The signs and symptoms of persistent temporomandibular joint (TMJ)/muscle disorder (TMJD) pain suggest the existence of a central neural dysfunction or a problem of pain amplification. The etiology of chronic TMJD is not known; however, female sex hormones have been identified as significant risk factors. Converging lines of evidence indicate that the junctional region between the trigeminal subnucleus caudalis (Vc) and the upper cervical spinal cord, termed the Vc/C1-2 region, is the primary site for the synaptic integration of sensory input from TMJ nociceptors. In this paper, the mechanisms behind the estrogen effects on the processing of nociceptive inputs by neurons in the Vc/C1-2 region reported by human and animal studies are reviewed. The Vc/C1-2 region has direct connections to endogenous pain and autonomic control pathways, which are modified by estrogen status and are suggested to be critical for somatomotor and autonomic reflex responses of TMJ-related sensory signals.

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  • Takanori Tsujimura, Makoto Inoue
    Type: review-article
    2020 Volume 62 Issue 2 Pages 156-159
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Swallowing has a vital function in airway protection and is the next step after mastication. Swallowing impairment, which is known as dysphagia, is frequently accompanied by pain. Previous clinical studies have shown that orofacial pain affects swallowing function. Thus, it was hypothesized that orofacial noxious inputs may modulate swallowing function. Previous studies using anesthetized animals has proposed that the facial skin-nucleus tractus solitarii (NTS), masseter muscle-NTS, lingual muscle-NTS, and lingual muscle-paratrigeminal nucleus-NTS pathways may be involved in the inhibition of swallowing caused by facial, masseter, and lingual pain. Moreover, the activation of gamma-aminobutyric acidergic NTS neurons is involved in the inhibition of the swallowing reflex following trigeminal noxious inputs. This review focused on the recent management of dysphagia, neural mechanisms of swallowing, and relationship between orofacial pain and swallowing function. This and other future studies in this field can provide a better understanding of both normal and impaired swallowing and can help develop a new approach to treat patients with dysphagia and orofacial pain.

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  • Ayano Katagiri, Takafumi Kato
    Type: review-article
    2020 Volume 62 Issue 2 Pages 160-164
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Neuropathic pain is characterized by sensory abnormalities, such as mechanical allodynia and heat hyperalgesia, associated with alteration in the peripheral and central nervous systems. After trigeminal nerve injury, phenotypic changes that involve the expression of calcitonin gene-related peptide occur in large- and medium-sized myelinated neurons; primary afferent neurons exhibit hyperexcitability because of neuron-glia interactions in the trigeminal ganglion. Increased nociceptive inputs from C- and Aδ-fiber and innocuous inputs from Aβ-fiber into the trigeminal spinal subnucleus caudalis (Vc) contribute to the phenotypic changes; further, they potentiate noxious information transmission in the ascending nociceptive pathways to the thalamus and parabrachial nucleus (PBN). It is noteworthy that C-fiber mediated nociceptive inputs can activate both the Vc-ventral posteromedial thalamic nucleus and Vc-PBN pathways, while mechanoreceptive fiber inputs specifically activate the Vc-PBN pathway. The Vc-PBN pathways project to the central nucleus of the amygdala (CeA) where affective behaviors are modulated. In addition, the PBN interacts with wakefulness-regulating neurons and hunger-sensitive neurons in the hypothalamus, suggesting that the Vc-PBN pathway can modulate sleep and appetite. Therefore, phenotypic changes in primary neurons and stimulus modality-specific activation of ascending nociceptive pathways to the PBN may exacerbate affective aspects of trigeminal neuropathic pain, including behavioral problems, such as sleep disturbance and anorexia, via the PBN-CeA-hypothalamus circuits.

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  • Yoshiki Imamura, Akiko Okada-Ogawa, Noboru Noma, Takahiro Shinozaki, K ...
    Type: review-article
    2020 Volume 62 Issue 2 Pages 165-169
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    Burning mouth syndrome (BMS) is one of the most frequently seen idiopathic pain conditions in a dental setting. Peri- and postmenopausal women are most frequently affected, and patients who experience BMS complain of persistent burning pain mainly at the tip and the bilateral border of the tongue. Recent studies have assessed whether BMS is a neuropathic pain condition, based on morphologic changes in biopsied tongue specimens, and whether there are abnormal pain responses in patients with this disease. Somatosensory studies have reported some abnormal findings in sensory and pain detection thresholds with inconsistency; however, the most distinct finding was exaggerated responses to painful stimuli. Imaging and electrophysiologic studies have suggested the possibility of dysregulation of the pain-modulating system in the central nervous system, which may explain the enhanced pain responses despite the lack of typical responses toward quantitative sensory tests. Basic studies have suggested the possible involvement of neuroprotective steroids, although the underlying mechanisms of this condition have not been elucidated. Experimental studies are looking for preferable supportive therapies for BMS patients despite the obscure pathogenesis.

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Original article
  • Ryutaro Kohashi, Takahiro Shinozaki, Naohiko Sekine, Kosuke Watanabe, ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 170-174
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Burning mouth syndrome (BMS) is classified into idiopathic orofacial pain conditions. Although central and peripheral neuropathic mechanisms are believed to be involved, the etiology remains to be fully elucidated. The present study examined temporal brain responses to an ongoing hot stimulus to investigate the pain modulating system in patients with BMS. The thermal stimulation sequence comprised baseline (32°C, 40 s) to warm (40°C, 32 s) to baseline (32°C, 40 s) to hot (49°C, 32 s), which was repeated four times using a Peltier thermode. These warm and hot stimuli were applied on the right palm and right lower lip in two separate sessions. Functional magnetic resonance imaging data were acquired by recording echo-planar images with a block design. Brain activity induced by purely hot stimulation (49°C vs. 40°C) applied to the palm was more pronounced than that induced by lip stimulation and in patients with BMS compared with controls. Comparison of brain activity between the first 16 s and second 16 s of the stimulus revealed pronounced time-dependent facilitation in patients with BMS during lip stimulation. These findings indicate that the pain modulating system in patients with BMS is dysregulated and that the brain in BMS is highly sensitized to pain information originating from the trigeminal system.

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  • Jihua Guo, Xiaole Wang, Jun Jia, Rong Jia
    Type: research-article
    2020 Volume 62 Issue 2 Pages 175-179
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS
    Supplementary material

    Head and neck cancer collectively is one of the most common cancer types in the world. Oral squamous cell carcinoma (OSCC) is the most common subtype of head and neck cancer. SRSF3 is a proto-oncogene and is overexpressed in patients with OSCC. However, the relationship between SRSF3 expression and the clinical outcomes of patients with head and neck cancer remains unclear. By using the cBioPortal for Cancer Genomics, a public online tool originally developed at Memorial Sloan Kettering Cancer Center (New York, NY, USA), it was revealed that patients with head and neck cancer with an underexpression of SRSF3 showed better overall and disease-/progression-free survival rates. Moreover, 227 genes were found to be significantly coexpressed with SRSF3 in head and neck cancer. Then, in combination with the analysis of a previous splice-array dataset that included significantly changed genes after the silencing of SRSF3, four potential target genes of SRSF3 were identified. RBMX and HNRNPL were further confirmed to be target genes of SRSF3. Moreover, the underexpression of RBMX was determined to be significantly associated with a favorable overall survival rate among patients, while patients with an underexpression of both SRSF3 and RBMX is a subgroup of individuals with better prognoses than all other patients. These results suggest that the underexpression of SRSF3 and that of its target RBMX can be used as potential biomarkers to predict favorable overall survival among head and neck cancer patients.

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  • Steffi Baxter, Marie Jablonski, Michael Hülsmann
    Type: research-article
    2020 Volume 62 Issue 2 Pages 180-183
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    This study aimed to evaluate the prevalence of internal symmetry (the number and morphology of root canals) in the mandibular incisors using cone beam computed tomography (CBCT). A total of 302 CBCT scans involving 1,208 mandibular incisors were evaluated using the Vertucci’s classification regarding the number and configuration of root canals. The central mandibular incisors exhibited two root canals in 22.6% of patients and lateral incisors in 24.3% of patients. Most teeth (76.4%) had a type I configuration (a single root canal, 1-1), 21.7% had type II (2-1), 1.1% had type V (1-2), and 0.8% had type IV (2-2). Teeth with a type-III configuration (1-2-1) were not found. In total, 17.5% of patients had a symmetric appearance of the two-canalled central mandibular incisors and 20.5% had a bilateral appearance of the two-canal lateral incisors. Moreover, in 12.3% of the patients, all four incisors showed two root canals. The highest degree of symmetry was found in incisors that had one root canal (central incisors: 217 of 302, lateral incisors: 229 of 302), followed by type 2-1 incisors (central incisors 50, lateral incisors 58). The influence of sex and age on the prevalence of symmetries was not significant. Concluding, the internal anatomy of the mandibular incisors cannot not be sufficiently predicted from the root canal anatomy of the contralateral tooth. Thorough clinical and radiographic inspection of each tooth remains mandatory to address the internal anatomy of the mandibular incisors correctly.

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  • Bingyu Zhu, Qi Jiang, Guoying Que, Zhuo Dai, Yingfang Wu
    Type: research-article
    2020 Volume 62 Issue 2 Pages 184-188
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS

    Oral submucous fibrosis (OSF) is a serious, potentially malignant oral disorder. It is histopathologically characterized by chronic inflammation and atrophic epithelium accompanied by the accumulation of collagen fibers in the lamina propria. The molecular mechanisms leading to atrophic epithelium remain poorly understood. Therefore, the present study investigated the role of autophagy and apoptosis in atrophic epithelium in OSF. The expression of Caspase-3 and autophagy-related proteins (LC3 and P62) in OSF epithelial tissues was quantified by immunohistochemistry. The analysis demonstrated that, compared with normal oral mucosal tissues, autophagy and apoptosis increased with the progression of OSF. Flow cytometry and Western blotting showed that arecoline induces apoptosis in human oral keratinocytes (HOKs) in a time-dependent manner in vitro. Arecoline-induced autophagy was confirmed by transmission electron microscopy and Western blotting. When chloroquine was used as an inhibitor of autophagy, the apoptosis rate and Caspase-3 expression decreased compared with the use of arecoline alone. Thus, autophagy and apoptosis may be involved in atrophic epithelium in OSF, and arecoline-induced autophagy promotes apoptosis in HOKs.

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  • Shingo Kasai, Satoru Onizuka, Sayaka Katagiri, Taiji Nakamura, Tomoya ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 189-196
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 04, 2020
    JOURNALS FREE ACCESS

    Studies suggest that analysis of gingival crevicular fluid (GCF) is useful for evaluating periodontal status. In this study, clinical variables related to tooth mobility, and multiple cytokine levels in proximate GCF, were measured at four time points during initial periodontal treatment: before treatment (baseline), after supragingival scaling, after occlusal adjustment, and after scaling and root planing (SRP); 20 teeth from 13 patients with periodontitis were included. Baseline interleukin (IL)-10 level in GCF was significantly higher around teeth that showed substantial improvement in periodontal epithelial surface area (PESA) after SRP than around teeth without PESA improvement. IL-3 and IL-16 levels in GCF at baseline were significantly higher around teeth with a periodontal inflamed surface area (PISA) of 0 mm2 after SRP than around teeth without PISA improvement. In addition, baseline IL-7, IL-11, and IL-12p40 levels in GCF were significantly lower around teeth with decreased mobility after occlusal adjustment than around teeth without decreased mobility. These results suggest that pre-treatment cytokine levels in GCF are useful in predicting the effects of initial periodontal treatment.

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  • Keitaro Satoh, Kaori Satoh, Yoshie Imaizumi-Ohashi, Mika Yokoi-Hayakaw ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 197-201
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Magnetic resonance imaging (MRI) was used to observe growth of the mandibular condyle, mandibular fossa, and articular disc as a single unit. Changes in each component’s relative position and size were observed using 7-tesla MRI. Mandibular condyle chondrocytes’ growth was evaluated with immunohistochemistry, using the expression of zinc transporter ZIP13. Three-dimensional T1-weighted (T1w) MRI was used to obtain images of the TMJ of Sprague Dawley rats at 4-78 days old (P4-78) with a voxel resolution of 65 μm. Two-dimensional T1w MR images were acquired after a subcutaneous injection of the contrast reagent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The T1w MR images showed that the mandibular condyle was located posterior to the mandibular fossa until P20; however, it then moved to a location underneath the mandibular fossa. In the Gd-DTPA enhanced images, the articular disc was identified as a region with lower signal intensity from P20. The number of ZIP13-positive chondrocytes at P6 was larger than the number at P24. In conclusion, the mandibular condyle with cartilage and disc grows on the posterior side of the mandibular fossa until P20, which was the weaning age. Then, the condyle fit into the mandibular fossa and completed the functional unit.

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  • Paolo G. Arduino, Alessio Gambino, Marco Cabras, Veronica Sciannameo, ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 202-205
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    Oral biopsy is a common surgical practice. To date, few authors have described the healing of mucosal wounds following oral biopsy. The aim of the present single-center, prospective, randomized, controlled study is to evaluate the differences between two chlorhexidine (CHX) mouthrinses and a treatment-free approach in the immediate postoperative period following oral mucosal biopsy. 354 patients were included in this study and were randomly allocated to three groups: A) CHX 0.12% mouthrinse (twice daily, 10 mL rinse for 30 s), B) CHX 0.20% mouthrinse (twice daily, 10 mL rinse for 30 s), and C) no topical treatment. 118 patients were treated in group A and 115 in group B; 121 received no therapy in group C, reporting the greatest improvement in related symptoms. Outcome variables included the age, gender, site and size of lesions, visual analog score (VAS), Oral Health Impact Profile questionnaire (OHIP-14), and number of painkillers taken during the first week post-surgery. Use of a CHX 0.12% mouthrinse exhibited the poorest outcome. On the other hand, best clinical healing was found for patients treated with CHX 0.20%. These findings suggest that regardless of its concentration, CHX was found to be ineffective in reducing related symptoms, whereas CHX 0.20% can be recommended to facilitate enhanced healing.

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  • Ryota Nomura, Hiroaki Inaba, Saaya Matayoshi, Sho Yoshida, Yuki Matsum ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 206-211
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    Mouth rinses are a useful supplementary tool for the prevention of oral infectious diseases. Although the antimicrobial effects of mouth rinses have been investigated, there are few studies focusing on the comparison of the effects among various oral bacterial species. In the present study, the inhibitory effect of a commercial mouth rinse, “ConCoolF,” and each of its major components, chlorhexidine gluconate, ethanol, and green tea extract, on multiple species of oral bacteria were investigated. Inhibition of bacterial growth was observed in all cariogenic streptococcal species with different genera, serotypes, and strains isolated from different countries when either the complete mouth rinse or chlorhexidine gluconate were used. However, no growth inhibition was observed when the bacteria were exposed to ethanol or green tea extract. Interestingly, growth inhibition was greatly reduced in non-cariogenic streptococci compared with cariogenic streptococci. In addition, both the mouth rinse and chlorhexidine gluconate inhibited the biofilms formed by both Streptococcus mutans (S. mutans) and Porphyromonas gingivalis (P. gingivalis), among which the inhibitory effect against S. mutans was higher than that against P. gingivalis. These results suggest that a mouth rinse containing chlorhexidine gluconate, ethanol, and green tea extract, or chlorhexidine gluconate alone, exhibits antimicrobial activity against several oral bacteria species, having greater activity against pathogenic bacteria.

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  • Shinji Usami, Yosuke Yamazaki, Maki Yuguchi, Yuichi Namba, Hirofumi Ka ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 212-216
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    The morphogenesis of long bones is a multistep process that generates a variety of genetically defined forms. The tarsometatarsal (TMT) long bone morphology in birds develops through lateral fusion of three initially independent periosteal bone cylinders (BCs). Previous studies have clarified the histological details and chronology of the changes occurring during development. The present study investigated the temporospatial distribution of osteogenic and osteoclastic cells in the embryonic chicken using histochemistry for alkaline phosphatase and tartrate-resistant acid phosphatase, with particular reference to the radial growth of BCs and their subsequent fusion process. Osteogenic cells were localized preferentially in the periosteum of radially growing BCs, leaving open cancellous spaces in the BC wall. Osteoclasts observed later than embryonic day 10 were localized preferentially in the endosteal surface, and therefore the radial growth of BCs resulting from osteoblast activity was accompanied by endosteal resorption by osteoclasts, with progressive enlargement of the bone marrow spaces. During BC fusion, trabecular bridges were formed by periosteal osteogenic cells, with removal of the bone septum by endosteal osteoclasts. These findings suggest that fusion of BCs in the embryonic chicken is mediated by cellular events constituting ordinary long bone development, and not through a defined mechanism specific for fusion.

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  • Andrea Toffoli, Ludovica Parisi, Roberta Tatti, Andrea Lorenzi, Robert ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 217-221
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    Titanium surface characteristics, including microtopography, chemical composition, and wettability, are essential features to achieve osseointegration of dental implants, but the choice of a particular surface topography is still a debated topic among clinicians. An increased level of implant surface hydrophilicity has been demonstrated to ameliorate osseointegration and shorten healing times. The aim of this work is to develop and test a suitable thermal-based method to enhance titanium surface wettability without modifying other characteristics of the implant surface. For this function, titanium discs with different surface topography have been thermally treated by testing different temperatures and excluding those that led to evident chromatic and morphological modifications. The selected surface gain in wettability after the treatment was assessed through contact angle measurement, chemistry modifications through x-ray photoelectron spectroscopy (XPS) analysis, and microtopography through scanning electron microscopy (SEM). Results showed a great enhancement in hydrophilicity on the tested surfaces without any other modification in terms of surface chemical composition and topography. A possible limitation of this method could be the persistent, although relatively slow, biological aging of the surfaces after the treatment. The present findings indicate that the described treatment could be a safe and effective method to enhance dental titanium hydrophilicity and thus its biological performance.

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  • Yusuke Miyake, Osamu Shimizu, Hiroshi Shiratsuchi, Takaaki Tamagawa, M ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 222-225
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    The present study was done to develop a useful experimental model for analysis of the effects of physiologically active substances on atrophy and regeneration of salivary gland acinar cells. Resection wounds (diameter, 3 mm) were made in the submandibular glands of 8-week-old Wistar rats (n = 24) for histochemical examination on Days 3, 5, 7, 10, 14, and 21 after implantation of a gelatin-based hydrogel sheet. The results showed that the sheet had nearly disappeared by Day 10. Regions around the resection wounds were classified as normal, atrophic, or necrotic. In atrophic regions, acinar cells atrophied after resection, and few acinar cells were observed on Day 7. On Days 5-7, striated and granular ducts resembled duct-like structures. On Day 10, newly formed acinar cells were confirmed by increased periodic acid-Schiff staining, and a greater number of mature cells was present thereafter. In necrotic regions, acinar and ductal cells were destroyed, and scattered enucleated acinar cells and duct-like structures were present, on Day 3; newly formed acinar cells were observed on Day 10. Thus, the experimental model demonstrated atrophy and regeneration of the submandibular gland and enabled analysis of the effects of sustained release of physiologically active substances contained within an implanted sheet.

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  • Junko Shimomura-Kuroki, Tomoko Nashida, Yukio Miyagawa, Takao Morita, ...
    2020 Volume 62 Issue 2 Pages 226-230
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Early detection of oral disease is important to reduce its severity and increase the likelihood of successful treatment. This study aimed to perform a quantitative assessment of the saliva components as a first stage of the research to screen oral homeostasis. Here, saliva secretions collected from children were evaluated, and their constituents were analyzed to investigate the potential correlations between the buffering capacity and a range of salivary factors. Subjects aged 3-16 years in the primary, mixed, or permanent dentition stage, were selected for this study. The following salivary factors were analyzed: flow rate, total protein, total sugar quantifications, and constituent analyses using RT-PCR and western blotting. The associations between each factor and the buffering capacity were then analyzed using multiple regression analysis. Flow rate, BPIFA2 RNA level, histatin 1 and BPIFB1 protein levels as well as female sex were positively associated with buffering capacity. In contrast, total sugar concentration and MUC7 RNA levels showed a negative relationship with the buffering capacity. Some of these constituents may indicate oral homeostasis and are therefore potential biomarkers of oral health status. These results suggest that the analyses of the correlations between oral homeostasis and salivary factors are an effective strategy for identifying the susceptibility to oral diseases.

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  • Shiho Shimizu, Yosuke Nakatani, Masayuki Kurose, Hiroki Imbe, Nobuyuki ...
    Type: research-article
    2020 Volume 62 Issue 2 Pages 231-235
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: February 19, 2020
    JOURNALS FREE ACCESS

    Psychophysical stress can cause neural changes that increase nociception in the orofacial region, particularly the masseter muscle (MM). The nucleus raphe magnus (NRM), which is located in the brain stem, serves the crucial role of regulating nociception through descending modulatory pain control. However, it remains unclear if neural activities in the NRM are affected under psychophysical stress conditions. This study conducted experiments to assess (1) whether neural activity, indicated by Fos expression in an NRM that has experienced MM injury, is affected by the stress of repeated forced swim tests (FST); and (2) whether the selective serotonin reuptake inhibitor fluoxetine administered daily after an FST could affect the number of Fos-positive neurons in the NRM. Results revealed that the stress from repeated FSTs significantly increased the number of Fos-positive neurons in an NRM that had been affected by MM injury. Fluoxetine inhibited increases in the number of Fos-positive neurons in the NRM that occurred as a result of FSTs, but this was not observed in sham rats. These findings indicate that the stress from FSTs could increase nociceptive neural activity in an NRM that has experienced MM injury. This could be due, in part, to changes in serotonergic mechanisms.

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Short Communication
  • Qingxiao Chen, Shengjie Lin, Ji Wu, Peijun Lyu, Yongsheng Zhou
    Type: Short Communication
    2020 Volume 62 Issue 2 Pages 236-238
    Published: 2020
    Released: March 28, 2020
    [Advance publication] Released: March 11, 2020
    JOURNALS FREE ACCESS

    Qualified diagrams of removable partial denture (RPD) designs created by dentists provide technicians with clear and dynamic information. Generating RPD design in the clinical decision support system (CDSS) can be achieved by producing the RPD design in a textual format and then transferring the design onto diagrams. The drawing of RPD diagrams automatically and efficiently for the given textual designs is still under investigation. A new workflow consisting of three major steps is developed to produce and visualize two-dimensional RPD design diagrams. Annotations and orientations of teeth are established from the base maps in the first step, and built-in rules are then incorporated to describe the variations caused by the interactions of the RPD components. Finally, the software draws each component using a series of curve functions. To validate the performance of the software, 112 RPD clinical design plans are randomly selected as inputs for the software, and the outputs are independently verified by experienced clinicians. The proposed methods are proven to be efficient and accurate and thus can be used to improve clinical quality.

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  • Erika Matsumura, Kanji Nohara, Nobukazu Tanaka, Nami Fujii, Takayoshi ...
    Type: Short Communication
    2020 Volume 62 Issue 2 Pages 239-241
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    Polypharmacy in elderly persons living at home or in a nursing home is an issue. In the field of dentistry, strategies to reduce polypharmacy must be promoted; however, there is insufficient basic data on medications received by elderly persons with dysphagia living at home or in a nursing home. The subjects were 106 elderly persons with dysphagia living at home or in a nursing home. Based on their medical records, the presence of disease and number/type of drugs being administered were investigated. Stroke, dementia, and hypertension were common. The mean number of drugs per person was 6.3 (minimum: 0, maximum: 15). Drugs for digestive ulcers were the most frequently prescribed medication, followed by hypotensive drugs, anti-parkinsonism drugs, and other central nervous drugs. Fifty-nine patients (52.8%) had taken drugs that may cause dysphagia, and 19 (17.9%) had taken drugs that may cause aspiration. Of the subjects, 68.9% had taken ≥5 drugs, demonstrating polypharmacy in elderly persons with dysphagia living at home or in a nursing home. Many drugs that may cause dysphagia or aspiration had been prescribed, suggesting the importance of dentists’ reducing polypharmacy from the viewpoint of swallowing.

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Case Report
  • Hidemichi Kihara, Kyoko Takafuji, Wataru Hatakeyama, Kenta Oriso, Akih ...
    Type: case-report
    2020 Volume 62 Issue 2 Pages 242-244
    Published: 2020
    Released: March 28, 2020
    JOURNALS FREE ACCESS

    When the sinus is enlarged, it may be necessary to elevate the floor of the maxillary sinus using the crestal or lateral approach. This report presents a case where sinus floor elevation was performed using tricalcium phosphate (TCP) plates supported by implant bodies, and only the blood clot was present around the implant bodies. Cone-beam computed tomography images, taken one year after the lateral approach, revealed the presence of a TCP-like radio-opacity, which almost disappeared after two years. About seven years after the surgery, the patient’s superstructure and occlusion were stable. Furthermore, the grafted TCP was completely absorbed, and the implant body appeared to be in good condition, with no signs of bone resorption around the implant.

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