The functions of salivary acinar cells are regulated by the activation of receptors on their basolateral membranes and by subsequent intracellular signaling events, including increases in cytoplasmic Ca²⁺ ([Ca²⁺]_i) and cyclic AMP (cAMP) production. Ca²⁺ plays essential roles in fluid and electrolyte secretions from salivary acinar cells. A typical agonist-induced Ca²⁺ response in salivary acinar cells shows Ca²⁺ waves, in which the rise in [Ca²⁺]_i is initiated at the apical pole before spreading towards the basal region of the cell. Ca²⁺ responses with low concentrations of agonist often occur result in repetitive transient rises in [Ca²⁺]_i, which have been referred to as Ca²⁺ oscillations. These spatial characteristics of the Ca²⁺ signal are primarily determined by the distribution of the endoplasmic reticulum (ER) and inositol 1,4,5-trisphosphate (IP₃) receptors, which correspond to the major intracellular Ca²⁺ store and Ca²⁺ releasing channels, respectively. ER cisternae are densely packed in the entire basolateral region, whereas small ER vesicular structures are located in the apical region of acinar cells. This apparent paradox would be resolved if it could be shown that the small Ca²⁺-releasing ER elements in the apical region are connected to the main part of the ER in the basolateral area. Although the mitochondria are not considered to be a physiological Ca²⁺ store, accumulating evidence indicates that mitochondria play a significant role in the regulation of the spatial and temporal patterns of Ca²⁺ signals. The mechanism that is responsible for Ca²⁺ oscillations remain controversial. Two general models for Ca²⁺ oscillations have been proposed ; one explains Ca²⁺ oscillations generated by constant cytoplasmic IP₃ concentrations [IP₃]_i) and the other explains Ca²⁺ oscillations generated by oscillating [IP₃]_i. Quantitative measurements of [IP₃]_i using fluorescent IP₃ biosensors revealed two cell type-specific differences in IP₃ dynamics : non-fluctuating rises in [IP₃]_i and repetitive IP₃ spikes during Ca²⁺ oscillations. However, the repetitive IP₃ spikes are thought to be passive reflections of Ca²⁺ oscillations, and are unlikely to be essential for driving Ca²⁺ oscillations. Regarding the mechanism of Ca²⁺ oscillations, the importance of dual feedback effects of Ca²⁺ on IP₃Rs has been demonstrated experimentally, while the precise mechanism responsible for establishing these oscillations remains unclear. In addition to the necessity of continuing work on the mechanisms that control Ca²⁺ oscillations, an important challenge for the future will be to determine how these patterns of Ca²⁺ signaling systems function in specific cellular processes.

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Porphyromonas gingivalis has been implicated as an important pathogen in periodontitis. Hemagglutinins have been identified in the adhesion of P. gingivalis onto the gingival tissue cells and the attachment and lysis of erythrocytes to facilitate the uptake of iron, an essential nutrient for P. gingivalis. A 40-kDa outer membrane protein (OMP) gene has been cloned from P. gingivalis. Because the monoclonal antibody against recombinant (r) 40-kDa OMP inhibited the hemagglutinating activity and the polymeric form of the recombinant protein expressed hemagglutinating activity, the 40-kDa OMP is thought to be a hemagglutinin. Moreover, the immunodominant domain has been identified as “WPRVGQLFIALDQTLGIPGF”, designated as peptide C, using phage display epitome mapping. On the other hand, chicken yolk antibody (IgY) has been shown to prevent bacterial infection and thought to be a useful and safe antibody for passive immunotherapy. In this study, r40-kDa OMP was highly purified and hens were inoculated with it to produce IgY. The purified IgY reacted with r40-kDa OMP and the synthetic peptide C, and significantly inhibited the hemagglutinating activity of P. gingivalis. Thus, IgY may be useful in the development of passive immunization against periodontal diseases caused by P. gingivalis infection.

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The purpose of this study was to investigate the microflora and identify streptococci from the oral cavity of cats. Oral samples from 15 cats were cultured on BHI-YE agar for total organisms, and selective media for streptococci and mutans streptococci. The distribution and characterization of the isolates were studied. The predominant bacteria were gram-positive and -negative rods, accounting for approximately 46.8% and 44.6% on BHI-YE plates, respectively. On MS medium, commonly used for the detection of oral streptococci in humans, the cultivable bacteria comprised 36% of those on BHI-YE medium. The predominant bacteria were gram-negative rods on MS plates. Gram-positive cocci were detected at low levels of less than 1% on both media. The genus Streptococcus was found in 5 cats, at 0.0002-0.0082% of total cultured bacteria. The most isolates were identified as Streptococcus minor. As one isolate could not be identified by biochemical and genetic methods, it was suggested that it might be a new species. Mutans streptococci were not detected from the oral cavity of the cats.

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In pediatric dentistry, treatment is performed mainly for oral health care and prevention of caries. Fissure sealants are often used in clinical practice for prevention of dental caries. The prevention of caries in occlusal fissures is of practical importance, since pits and fissures are more susceptible to caries than any area. It is possible to debride pits and fissures using laser irradiation in order to remove the fissure contents without altering the shape and structure of the fissures. Although the adhesive strength of fissure sealant to enamel may grow weak when a laser is used, there have been no reports regarding the adhesive strength of enamel to fissure sealant after Nd-YAG laser irradiation with 1% TiO₂ suspension. Therefore, the authors investigated the tensile bond strength of a commercial fissure sealant applied after Nd-YAG laser irradiation in contact mode with a fiber diameter of 400 μm, 5 pps, laser tip output power of 300 mJ, and with the use of 1% TiO₂ suspension. It was revealed that lasers could react to an enamel surface without any special treatment like application of a black pigment to the surface of the tooth when Nd-YAG laser irradiation was performed. Also, the tensile bond strength of TeethmateF1^® to the enamel was lower after laser irradiation with 1% TiO₂ suspension, whereas that of Fuji III LC^® was stable. From the SEM images of the interfaces between the fissure sealant and enamel, it was found that the enamel surface was affected to a depth of approximately 20-30 μm by laser irradiation. It was revealed that when the fissure sealant was applied with laser irradiation, the laser should be precisely irradiated and the use of a glass-ionomer fissure sealant was more effective.

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It has been well documented that 1,25(OH)₂D₃ regulates the synthesis of collagen, however, little is known about its effect on the quality of collagen. Most recently, we have demonstrated that 1,25(OH)₂D₃ upregulates the expression of specific isoforms of lysyl hydroxylases (LHs) and lysyl oxidases (LOXs) in murine osteoblastic cell line, MC3T3-E1 cells resulting in specific collagen cross-linking pattern (1). However, at present, it is not clear whether or not this is a generalized effect or cell type specific. In order to address this, we investigated the effects of 1,25(OH)₂D₃ on gene expression of LHs and LOXs and the extent of lysine (Lys) hydroxylation of collagen using an fibroblastic cell line, NIH3T3 cells. The effect was compared to controls where cells were treated with cholecalciferol (VD₃) or ethanol (Et-OH). When compared to the controls, gene expressions of LH1 and LH2 were upregulated and LOXL2 was markedly upregulated by 1,25(OH)₂D₃ at 48 hours of culture. The extent of Lys hydroxylation of collagen was only slightly higher in the 1,25(OH)₂D₃ treated group. This study indicates that 1,25(OH)₂D₃ regulates the expression of collagen modifying enzymes in fibroblastic cells in a similar manner as osteoblastic cells but the extent of the effects could vary depending on the cell types.

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The differentiation and functions of osteoclasts are regulated by the receptor activator of nuclear factor kappa beta (RANK) and its ligand (RANKL). The present study was designed to identify the expression of RANK/RANKL in the event of root resorption provoked by excessive orthodontic force and also to explore the biological mechanism of the RANK/RANKL system in regulating odontoclastogenesis in root cementum. Thirty male Wistar rats were subjected to orthodontic force of 100 g to induce a mesially tipping movement of the left mandibular first molars. The contralateral molars served as intraindividual controls. The rats were sacrificed after 3, 7, or 10 days. The mandibular body surrounding the molars was harvested and serial sections of 6-μm thickness were cut. Immunohistochemical assays were conducted to localize the expression of RANK/RANKL proteins and histomorphological examination was undertaken to identify cellular response in cementum, periodontal ligament, and alveolar bone during root resorption. Root resorption in cementum occurred at the sites corresponding to compression of the periodontal ligament, indicated by increased numbers of multinucleated osteoclasts and odontoclasts. Immunoreaction against RANKL became stronger in osteoblasts, osteoclasts, odontoclasts, and fibroblasts of the periodontal ligament from Day 3 onwards. The number of positively immunoreactive cells against RANK also increased significantly over Days 3, 7, and 10 (p<0.01). The RANK/RANKL system is responsible for transducing the heavy mechanical loading signals into an odontoclastic episode in root resorption.

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The virulence of a large mucoid-form colony of Streptococcus mutans strain ZO-1 serotype c on Mitis Salivarius agar and its revertants were investigated. In rat caries experiments, the caries score of ZO-1 was very high, similar to that of the Streptococcus mutans reference strain. Their revertants appeared in the ZO-1 strain infected group in an in vivo experiment. The frequency range of the revertants varied from 0.1-62.5% (average : 21.9%). The ability to form plaque from sucrose was similar in ZO-1 and revertant strains compared with the S. mutans reference strain. Acid production in all test strains was similar. The production of polysaccharides from sucrose of the ZO-1 strain mainly involved water-soluble fructan, however, revertants did not produce as much fructan as the ZO-1 strain. The soluble and insoluble glucan synthesis of ZO-1 and the revertants were similar to those of the S. mutans reference strain. In in vivo experiments, the caries scores of revertant strain infected group was similar to that of reference strain of S. mutans infected group. The mucoid-form colony did not appear from the revertant infected group. The mucoid-form ZO-1 and its revertant strains exhibited a cariogenic potenial similar to the S. mutans reference strain.

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Oral lesions associated with human immunodeficiency virus (HIV) are often the first overt clinical features of HIV infection. Reports of HIV-associated herpes zoster infection with alveolar bone necrosis and spontaneous tooth exfoliation are extremely rare, with only four cases reported in the literature. The exact mechanism of osteonecrosis induced by herpes zoster infection remains uncertain. An altered oral environment, decreased host immunity, or immune reconstitution inflammatory syndrome (IRIS) could further compromise the viable periodontal status, leading to alveolar bone necrosis and tooth exfoliation. We report a case of herpes zoster infection involving two divisions of the trigeminal nerve in an HIV-seropositive patient who further manifested with mandibular and maxillary osteonecrosis and spontaneous mandibular and maxillary tooth exfoliation. The occurrence of such infection in immunosuppressed individuals, its etiopathogenesis, and associated clinical features are briefly reviewed and discussed.

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Recurrence of ameloblastoma in the soft tissue is a rare entity. We present a case in which recurrence occurred 20yrs after radical excision of the lesion. We hypothesize that seeding of cells in the soft tissue would have occurred by intraoperative contamination leading to recurrence. The case highlights the importance of long-term follow up of all cases of multicystic ameloblastoma and also demonstrates the need for follow-up after excision of dentigerous cyst and unicystic ameloblastoma due to their unpredictable nature and time intervals between recurrences even after aggressive treatment by radical excision.

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