Mitsuko Inoue

Morphological and Microleakage Studies of the Cavities Prepared by Er:YAG Laser Irradiation in Primary Teeth

OBJECTIVE The purposes of this study were to investigate cavity surfaces morphologically, and compare microleakage at cavities prepared by Er:YAG laser after composite resin restoration versus conventional mechanical treatment in human primary teeth in vitro. BACKGROUND DATA There have been few reports on microleakage at cavities prepared by Er:YAG laser irradiation. MATERIALS AND METHODS A total of 30 cavities (class V) in human primary teeth were used. Half of the cavities were prepared by an Er:YAG laser system at 300 mJ pulse energy and 4 Hz, and the other half were prepared with a high-speed diamond bur. Five cavities from each group were investigated by scanning electron microscopy (SEM) and histopathological examination. Remaining cavities were filled with a composite resin without an acid-etching technique and then subjected to microleakage test in 0.6% rhodamine B solution under thermocycling. RESULTS Microleakage (score: 2.45 +/- 1.07) at cavities prepared by laser was significantly less than that by bur (score: 1.30 +/- 0.95; p < 0.05). SEM observation showed that, compared with the relatively flat appearance of cavities prepared by bur, cavity margins prepared by laser were irregular but there was almost no smear layer at the cavity walls. CONCLUSION It can be concluded that cavity surfaces prepared by Er:YAG laser are irregular, but microleakage at cavities prepared by the laser after filling with composite resin is better than that by mechanical bur using the dye penetration method.

Importance of deletion of T at nucleotide 1559 in the tissue-nonspecific alkaline phosphatase gene in Japanese patients with hypophosphatasia.

Abstract. The tissue-nonspecific alkaline phosphatase (TNSALP) gene in four unrelated patients with hypophosphatasia was analyzed using polymerase chain reaction–single strand conformation polymorphism and the direct sequencing method. Of the participating patients, one had childhood-type and three had perinatal-type disease. All carried a deletion of T at cDNA number 1559, which causes a frameshift downstream from codon L503, as a heterozygote. In the childhood-type patient, an F310L mutation was detected in the opposite allele. Similarly, a perinatal-type patient carried a V365I mutation in the opposite allele. Mutations in the opposite alleles were not detected in the other two patients with perinatal-type disease. In addition, although both parents carried the deletion as a heterozygote in two families with childhood-type and perinatal-type disease, patients from those families were not homozygous for the deletion. Several single-nucleotide polymorphisms (SNPs) were also detected, which were shown to be useful for haplotype analysis. Allele frequency of the deletion among Japanese patients was 36% (10 of 28 alleles) but none occurred in Caucasian patients. These findings indicate that regardless of clinical type, deletion in the TNSALP gene occurs frequently among Japanese patients. Furthermore, haplotype analysis using SNPs suggested that the deletion might have derived from more than a single founder.

Regulation of Osteoclast Multinucleation by the Actin Cytoskeleton Signaling Network.

Although it is known that osteoclasts are multinucleated cells that are responsible for bone resorption, the mechanism by which their size is regulated is unclear. We previously reported that an actin‐rich superstructure, termed the zipper‐like structure, specifically appears during the fusion of large osteoclast‐like cells (OCLs). Actin cytoskeleton reorganization in osteoclasts is regulated by a signaling network that includes the macrophage colony‐stimulating factor (M‐CSF) receptor, a proto‐oncogene, Src, and small GTPases. Here, we examined the role of actin reorganization in the multinucleation of OCLs differentiated from RAW 264.7 cells using various pharmacological agents. Jasplakinolide, which stabilizes actin stress fibers, induced the development of small OCLs, and the Src inhibitor SU6656 and the dynamin inhibitor dynasore impaired the maintenance of the podosome belt and the zipper‐like structure. These inhibitors decreased the formation of large OCLs but increased the number of small OCLs. M‐CSF is known to stimulate osteoclast fusion. M‐CSF signaling via Src up‐regulated Rac1 activity but down‐regulated Rho activity. Rac1 and Rho localized to the center of the zipper‐like structure. Rho activator II promoted the formation of small OCLs, whereas the Rho inhibitor Y27632 promoted the generation of large OCLs. These results suggest that the status of the actin cytoskeleton signaling network determines the size of OCLs during cell fusion. J. Cell. Physiol. 230: 395–405, 2015.

Nanoindentation tests to assess polymerization of resin-based luting cement

OBJECTIVE The optimal polymerization of resin-based luting cements plays a critical role in the long-term clinical success of dental prostheses and indirect restorations. This study investigated a mutual action between the conformational changes and mechanical properties of a dimethacrylate resin-based luting cement with and without pre-application of the acidic functional monomer 10-methacryloxydecyl dihydrogen phosphate. METHODS Degree of conversion in the luting cement was measured using conventional infrared spectrophotometry. Mechanical properties of the luting cements were also evaluated by quasi-static and dynamic nanoindentation tests. RESULTS The results of infrared spectrophotometry and nanoindentation testing were proportional in samples without functional monomer pretreatment. When considerable residual monomer remains within the final products, the mechanical properties of the resin-based luting cements could possibly be impaired. Although the apparent degree of conversion increased with a mixture of functional monomer, a reduction in the cross-linking polymer network may have resulted in the highest viscoelastic creep behavior of the luting cement. The time-dependent behaviors found in the nanoindentation tests likely resulted from linear polymerization chains of the functional monomer. SIGNIFICANCE The application of an acidic functional monomer may affect the viscosity of resin-based luting cements. Quasi-static or dynamic nanoindentation is a useful tool for assessing the polymerization qualities of resin composites.

Involvement of histaminergic inputs in the jaw-closing reflex arc

Histamine receptors are densely expressed in the mesencephalic trigeminal nucleus (MesV) and trigeminal motor nucleus. However, little is known about the functional roles of neuronal histamine in controlling oral-motor activity. Thus, using the whole-cell recording technique in brainstem slice preparations from Wistar rats aged between postnatal days 7 and 13, we investigated the effects of histamine on the MesV neurons innervating the masseter muscle spindles and masseter motoneurons (MMNs) that form a reflex arc for the jaw-closing reflex. Bath application of histamine (100 μM) induced membrane depolarization in both MesV neurons and MMNs in the presence of tetrodotoxin, whereas histamine decreased and increased the input resistance in MesV neurons and MMNs, respectively. The effects of histamine on MesV neurons and MMNs were mimicked by an H1 receptor agonist, 2-pyridylethylamine (100 μM). The effects of an H2 receptor agonist, dimaprit (100 μM), on MesV neurons were inconsistent, whereas MMNs were depolarized without changes in the input resistance. An H3 receptor agonist, immethridine (100 μM), also depolarized both MesV neurons and MMNs without changing the input resistance. Histamine reduced the peak amplitude of postsynaptic currents (PSCs) in MMNs evoked by stimulation of the trigeminal motor nerve (5N), which was mimicked by 2-pyridylethylamine but not by dimaprit or immethridine. Moreover, 2-pyridylethylamine increased the failure rate of PSCs evoked by minimal stimulation and the paired-pulse ratio. These results suggest that histaminergic inputs to MesV neurons through H1 receptors are involved in the suppression of the jaw-closing reflex although histamine depolarizes MesV neurons and/or MMNs.

Identification and functional analysis of the gene cluster for fructan utilization in Prevotella intermedia

Fructanase enzymes hydrolyze the β-2,6 and β-2,1 linkages of levan and inulin fructans, respectively. We analyzed the influence of fructan on the growth of Prevotella intermedia. The growth of P. intermedia was enhanced by addition of inulin, implying that P. intermedia could also use inulin. Based on this finding, we identified and analyzed the genes encoding a putative fructanase (FruA), sugar transporter (FruB), and fructokinase (FruK) in the genome of strain ATCC25611. Transcript analysis by RT-PCR showed that the fruABK genes were co-transcribed as a single mRNA and semi-quantitative analysis confirmed that the fruA gene was induced in response to fructose and inulin. Recombinant FruA and FruK were purified and characterized biochemically. FruA strongly hydrolyzed inulin, with slight degradation of levan via an exo-type mechanism, revealing that FruA is an exo-β-d-fructanase. FruK converted fructose to fructose-6-phosphate in the presence of ATP, confirming that FruK is an ATP-dependent fructokinase. These results suggest that P. intermedia can utilize fructan as a carbon source for growth, and that the fructanase, sugar transporter, and fructokinase proteins we identified are involved in this fructan utilization.

Change in salivary levels of chromogranin A in children by hearing dental air turbine noise

Abstract Dental fear in children can be a psychological barrier for maintenance of oral health, thus it is important to objectively evaluate the responses to stress stimuli produced during dental treatments. In this study, we analyzed the stress responses of 15 preschool (3- to 6-year) and 22 school-aged (6- to 12-year) children to dental air turbine noise by measuring salivary levels of chromogranin A (CgA), a marker of psychological stress. Salivary CgA was significantly increased during exposure to the noise in the school-aged subjects, especially in those who had previously experienced tooth excavation, while there was no significant difference in CgA levels before and during noise exposure in those without such experience. In the preschool children, the noise did not induce increased secretion of CgA even in those with previous excavation experience. In addition, the levels of dental fear were assessed using a dental subscale of childrens fear survey schedule (CFSS-DS), while reactions during dental care were scored according to the Frankl Behavior Rating scale. In the school-aged children, change in salivary CgA level was not correlated with CFSS-DS ( r =0), while there was a weak negative correlation with Frankl score ( r =−10.202). Our results indicate that air turbine noise causes psychological stress in school-aged children, especially in those who have previously received dental treatments.

The characteristics of the deciduous dental arch form of children in Changchum-city, China

Abstract It is important to know racial differences in the characteristics of the dental arch form from the view point not only of dental interests but also of anthropology. We got an opportunity to investigate the status of oral condition of children living in the Changchum-city, Jilin Province in China. The size and the form of the deciduous dental arch were measured using plaster casts prepared from the impressions taken at the time of oral examination. The same measurement was conducted using the dental plaster cast of the Japanese children and the size and shape of the dental arch were compared between the Japanese and the Chinese children. The subjects were the Chinese children who had the Hellman IIA dentition lining in Changchum-city. The average age of the Chinese children was 9 years and 4 months and that of the Japanese children was 4 years and 1 month. The measurement results showed that the Chinese children were bigger than Japanese children in every measurement items. As for the dental arch form, Japanese children had a U-shaped arch form with wider width in the front part of the dental arch. On the other hand, the Chinese children had a half-circle-shape arch form that the front arch width was not so wide but that of the back was wide.

A study of prevalence of caries and oral health behavior in Japanese children with cleft lip and palate

Abstract The aims of this study were to investigate the condition of dental caries in 1–4 years old Japanese children with cleft lip and/or palate, and also to examine the relationships between age, location of the cleft, oral health behavior of cleft children and the incidence of dental caries. The study was carried out through a dental examination of a sample of children and a questionnaire to their parents which included questions about infant feeding practices, frequency of consumption of specific drinks and childrens frequency of tooth brushing. A sample of 116, 1–4 years old Japanese children (58 boys and 58 girls) with oral clefts referred to the Department of Pediatric Dentistry Clinic, Showa University, after receiving surgical treatment, participated in this study. Results indicated that the prevalence of caries in cleft children was related to patient age, location of clefts and oral health behavior. A higher level of dental caries was recognized in children with cleft lip and alveolus/palate than in those with cleft lip alone. Incidence of caries increased with patient age. Children who had been fed in a determined time were less affected than those who had been fed at will. Incidence of caries was also high in the children who ingested drinks with sugar than in those who did not. The results of this study suggest that it is important to improve the oral health behavior of cleft children to minimize the risk of caries. Moreover, children with clefts and their parents should as early as possible undergo a preventive program to ensure preservation of primary dentition.

Streptococcus mutans sortase catalyzes cell wall anchoring of WapA and FruA

Abstract Previous studies using a sortase-deficient mutant (SrtA − mutant-) of Streptococcus mutans have demonstrated that the sortase (SrtA) catalyzes cell wall anchoring of the surface protein antigen PAc, a dextranase and a glucan-binding protein C. In this study, cell wall anchoring of a wall-associated protein antigen A (WapA) and an exo- β -D-fructosidase (FruA) in S. mutans was examined by Western blot analysis with a specific antiserum. In the SrtA − mutant, FruA and WapA were not bound to the cell wall but were secreted into the culture supernatant. In contrast, in the wild type, both proteins were associated with the cell wall of S. mutans . Biological properties of the SrtA − mutant were examined by determination of fructan fermentation and adherence to a smooth surface. Both the SrtA − mutant and the wild type retained the ability to ferment levan. In addition, adherence to a smooth surface of the SrtA − mutant was as extensive as that of the wild-type 109c when sucrose was present. However, in the absence of sucrose, the adhesion of the SrtA − mutant remarkably decreased as compared with that of the wild type. These results suggest that SrtA catalyzes anchoring of WapA and FruA to the cell wall in S. mutans and that surface proteins anchored by SrtA are involved in the initial adhesion of S. mutans to smooth surface. In addition, it was shown that both cell wall-anchored and extracellular FruA are related to the degradation of extracellular fructan as a nutrient source.