<strong>Objective:</strong> This study aimed to clarify the effect of trace elements on enamel erosion due to citric acid eliminating other factors that can affect enamel erosion.<strong> Method: <...<strong>Objective:</strong> This study aimed to clarify the effect of trace elements on enamel erosion due to citric acid eliminating other factors that can affect enamel erosion.<strong> Method: </strong>Forty enamel specimens were obtained by embedding bovine enamel blocks into a quick cure resin. Half of the enamel surface of the specimens was covered with nail varnish. The specimens were randomly divided into control (Ct), zinc (Zn), iron (Fe), and copper (Cu) groups and immersed in 1% citric acid solution, 1% citric acid solution with 10 mmol/L zinc, 1% citric acid solution with 10 mmol/L iron, or 1% citric acid solution with 10 mmol/L copper, respectively, at 37<span style="white-space:nowrap;">°</span>C for 5 h. After immersion, the demineralized lesion depth was measured using transverse microradiography (TMR) and compared between groups using one-way analysis of variance and Tukey’s test. <strong>Results: </strong>The lesion depth was significantly higher in the Zn (218.9 ± 88.5 μm) group than that in the Ct group (116.3 ± 22.1 μm) (p < 0.01). <strong>Conclusion:</strong> It was suggested that zinc has decalcification properties when consumed with citric acid, while iron and copper don’t have such properties.展开更多
Supernumerary tooth in the upper central incisor region is called mesiodens. Mesiodens causes serious complications such as displacement, retarded eruption, and rotation in the adjacent permanent incisors, inducing in...Supernumerary tooth in the upper central incisor region is called mesiodens. Mesiodens causes serious complications such as displacement, retarded eruption, and rotation in the adjacent permanent incisors, inducing inhibition of oral development. This report was aimed to provide epidemiology of mesiodens in Japanese children. Using dental record, panoramic radiographs and images of cone-beam computed tomography in 128 non-syndromic child patients, patients’ age at their first visit, gender composition, shape of mesiodens, position of mesiodens, posture of mesiodens, and age distribution of the patients based on each complication were investigated. In addition to the survey, patient age was compared between the groups with and without each complication. Patients’ age ranged 3 - 10 years old. Male-to-female ratio was approximately 3:1. Conical shape (75%) and inverted position (49%) were the most frequent among the patients. Displacement was the commonest complication. Age comparison indicated that patients with displacement or retarded eruption consulted the dentist younger than those without the complications. The present study provided etiology of mesiodens in Japanese children that will contribute to daily clinical practice in the field of pediatric dentistry.展开更多
As erosion has become one of the serious oral health problems, some fluoride-releasing dental materials have been developed to protect enamel from demineralization. The purpose of this study was to evaluate the antide...As erosion has become one of the serious oral health problems, some fluoride-releasing dental materials have been developed to protect enamel from demineralization. The purpose of this study was to evaluate the antidemineralization effect of PRG Barrier Coat<sup>®</sup> and FujiVII<sup>®</sup> (fluoride-releasing dental materials). Four square windows measuring 1 mm<sup>2</sup> were prepared on the labial enamel surface of each bovine tooth using masking tape and nail varnish. The first and second windows were half covered by fluoride-releasing material and control material, respectively, whereas the third and fourth windows were left untreated. All windows were immersed into 0.1 M lactic acid and 6wt% CM-cellulose (pH 4.5) at 38℃ for 21 days. Subsequently, the first and second windows were covered with nail varnish after removal of the materials, and the third and fourth windows were immersed into ultrapure water at 38℃ for 28 days after being half covered with fluoride-releasing and control materials, respectively. The following procedure was performed separately during evaluations of the fluoride-releasing materials, PRG Barrier Coat, and FujiVII<sup>®</sup>, using eight and six bovine teeth, respectively. The first, second, third, and fourth windows were classified into DM-PRG;Demineralized-PRG or DM-FujiVII;Demineralized-FujiVII, DM-TCM;Demineralized-traditional cement or DM-TGIC;De-mineralized-traditional glass ionomer cement, RM-PRG;Remineralized-PRG or RM-FujiVII;Re-mineralized-FujiVII, and RM-TCM;Remineralized- traditional cement or RM-TGIC;Remineral-ized-traditional glass ionomer cement, respectively. After nail varnish was removed, △Q values (mean ± SD) of the windows were measured using QLF-D and were compared between DM-PRG and DM-TCM, RM-PRG and RM-TCM, DM-FujiVII and DM-TGIC, and RM-FujiVII and RM-TGIC groups. △Q values of RM-PRG (-60 ± 44) and RM-FujiVII (-5.0 ± 10) were significantly higher than that of RM-TCM (-315 ± 193) and RM-TGIC (-56 ± 43), respectively. The fluoride releasing materials provided remineralization effects to bovine enamel.展开更多
Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study w...Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study were to compare the elution levels of aluminum and calcium from deciduous enamel into acidic artificial saliva, and determine whether the degree of aluminum elution reflects individual caries risk. One hundred and eleven extracted human deciduous teeth were collected. Concentrations of aluminum and calcium eluted from sound regions of enamel into artificial saliva (pH 6.2 or 5.5) were determined using atomic absorption spectrophotometry. One hundred and four and 108 available data samples were obtained for aluminum and calcium evaluation, respectively, and were compared based on the sex, tooth type, caries history, and the number of the donor’s carious teeth at each pH. Calcium elution was not affected by the sex;however, more aluminum was eluted from boys’ than from girls’ teeth at pH 5.5. The aluminum release depended on the tooth type, and was significantly higher in incisors than in molars at a pH of 5.5. In relation to the caries history, aluminum (at pH 5.5) and calcium (at pH 6.2) dissolved more from sound regions of the enamel of caries-experienced teeth than from the enamel of teeth without caries experience. Moreover, aluminum markedly dissolved from enamel in artificial saliva at both pH 6.2 and 5.5 when the donor had more carious teeth, regardless of the presence or absence of caries experience in the sampled teeth. There is a possibility that the rate of aluminum elution from enamel into acidic fluid reflects individual caries sensitivity.展开更多
Restoring natural forests after field abandonment is a land management objective that fosters the recovery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the aband...Restoring natural forests after field abandonment is a land management objective that fosters the recovery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the abandonment of an arable field that became dominated by a dwarf bamboo(Pleioblastus chino(Franch. et Sav.)Makino) and by kudzu(Pueraria lobata(Willd.) Ohwi).By permutation tests, the removal of competing vegetation(gap creation) significantly increased the survival of three seeded species of Fagaceae and of eight transplanted species. In contrast, intact vegetation prevented most individuals of all species from surviving for 1 year after planting. The lack of natural recruitment of Fagaceae in the nonseeded subplots indicated that seed limitation was a cause of the slow afforestation. Although litter accumulation in gaps at the time of seeding slightly increased survival for late-germinating Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino) Hatus. ex T. Yamaz. et Mashiba, the effect was not consistent among plots and was not statistically significant. Our results suggest that for successful afforestation using native trees in abandoned fields, it will be necessary to remove competitive native species to avoid severe limitations on microsite availability and that simultaneous tree establishment by seeding or transplanting should be implemented to accelerate the establishment of native tree species.展开更多
Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired.We investigated seedling survival of four transplant...Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired.We investigated seedling survival of four transplanted native tree species(Quercus myrsinifolia, Quercus serrata,Aphananthe aspera, and Rhus sylvestris) by experimentally manipulating the vegetation cover, which was mainly dominated by dwarf bamboo(Pleioblastus chino), and herbivore access to the planting sites on farmland that had been abandoned for 15 years at the start of the study. Few transplanted seedlings of any species survived under intact vegetation cover, irrespective of herbivore presence. In gaps in the vegetation cover, winter browsing by Japanese hare(Lepus brachyurus) damaged all species. However,lower browsing frequency and higher resprouting ability after grazing of the seedlings enabled both Quercus species to survive better than the other species. These results indicate that dwarf bamboo and the hare jointly limit the establishment of native trees in old fields. If active afforestation by transplanting seedlings at sites dominated by dwarf bamboo is planned, a combination of vegetation removal, selection of suitable species, and temporary seedling protection will be most effective.展开更多
Background: Caries detection in school oral examinations insufficient accuracy. Objective: To evaluate advantages of introducing quantitative light-induced fluorescence-digital (QLF-D) in school oral examinations. Met...Background: Caries detection in school oral examinations insufficient accuracy. Objective: To evaluate advantages of introducing quantitative light-induced fluorescence-digital (QLF-D) in school oral examinations. Methods: Experiment No. 1. Early demineralized lesions in the upper and lower incisors and canines were visually inspected by three dentists and by QLF-D. The numbers of tooth planes with early demineralized lesions were compared between the methods. Experiment No. 2. Approximal demineralized lesions in molars were assessed by visual inspection, x-ray imaging, and QLF-D. The numbers of tooth planes with demineralized lesions were compared among the methods. Experiment No. 3. Plaque distribution was evaluated by QLF-D and a traditional staining method. The ratio of the diameter of plaque to tooth crown in the tooth axis direction in each method was calculated. The results were evaluated by Pearson’s correlation coefficient analysis and Bland-Altman plot. Results: Experiment No. 1. The three dentists found 0.67 tooth planes on average. QLF-D found 22 tooth planes with early demineralized lesions in the same samples. Experiment No. 2. Fourteen approximal tooth planes of molars were found to have demineralized lesions by x-ray imaging. QLF-D detected 71.4% of the tooth planes out of the 14, whereas visual inspection found 7.1%. Experiment No. 3. The Pearson’s correlation coefficient for the evaluations of plaque distribution between the QLF-D and traditional staining methods was 0.77 (P Conclusion: The results support introduction of QLF-D for use in school dental examinations.展开更多
As the prevalence of dental caries decreases, the diagnosis and treatment of initial mineral loss resulting in white spot lesions have been getting more and more important. Since dental CT provides computed tomography...As the prevalence of dental caries decreases, the diagnosis and treatment of initial mineral loss resulting in white spot lesions have been getting more and more important. Since dental CT provides computed tomography images of a tooth with radiation exposure similar to panoramic radiography, it will become possible in the near future to evaluate the enamel mineral density using CT in the same way as measurement of the bone mineral density. Such computed tomography images enable dentists to perform longitudinal, three-dimensional, and precise evaluation of the enamel mineral density before a demineralized lesion becomes detectable by any other traditional means. Despite their advantage, there are not enough reports on evalu- ation of the enamel mineral density using CT. This study evaluated the serial changes in mineral density in the earliest stage of enamel demineralization. Eight bovine enamel specimens were coated with nail varnish. On each specimen, 4 square windows measuring 1 mm2 were created. The specimens were incubated in lactic acid solution at 38?C. During incubation, the windows were covered by nail varnish one by one at 30, 60, and 90 minutes, respectively. At 120 minutes, the specimens were removed from the solution. After the nail varnish was removed, X-ray microradiography was performed using SKYSCAN1172 at settings of 100 kV and 100 μA. The mean Hounsfield unit values (HUV) of enamel in a non-window area and those in the window areas were calculated every 180 μm over a depth of 0 - 900 μm and analyzed by two-way ANOVA. Data were affected by the incubation time and depth from the enamel surface, and there was not interaction between the two factors. Considering the incubation time, HUV of the whole measured enamel (0 - 900 μm) in the non-window group was significantly higher than that of the other incubated groups. Considering the depth, HUV was decreased at 721 - 900 μm compared with that at 0 - 180 μm in the 30-minute-incubated group, and the decrease spread to 361 - 900 μm in the 60- and 90- minutes-incubated groups. HUV was additionally calculated at increments of 18 μm and compared within the 60-minute-incubated group, and changes in the mineral density at the boundary of the earliest demineralized lesion could be observed. This study demonstrated detailed mineral density changes in the earliest period of demineralization.展开更多
This study aimed to clarify the ability of the buffer systems of saliva to inhibit enamel demineralization after intake of an acid beverage. In the first experiment, titrable acidity tests were carried out. Ten millil...This study aimed to clarify the ability of the buffer systems of saliva to inhibit enamel demineralization after intake of an acid beverage. In the first experiment, titrable acidity tests were carried out. Ten milliliters of saliva stimulated by chewing gum base was obtained from 10 healthy adult subjects and the pH of each saliva sample was measured. The beverages used for the experiment were a carbonated soft drink (pH 2.2), a sports drink (pH 3.5), and 100% orange juice (pH 3.8). Distilled water adjusted to the pH of each saliva sample was used as a control. In the second experiment, the suppressive ability of saliva against enamel demineralization was quantitatively analyzed using quantitative light- induced fluorescence (QLF). Aliquots of stimulated saliva obtained from a subject were mixed with 15 ml of 100% orange juice in saliva:orange juice ratios of 1/30, 1/15, 1/10 and 1/5, and bovine teeth were soaked for 24 hours in the solutions. The △Q of the QLF analyses of the enamel was then measured. The lowest titrant volume which reduced the pH of the initial saliva (7.7 on average) to pH 5.4 was that of the orange juice. No relationship was found between the buffer capacity and the pH of the acid beverages. From the QLF measurement, the saliva-orange juice group showed a significantly decreased amount of enamel demineralization (p < 0.01 at 20% level) compared with the distilled water-orange juice group. In conclusion, saliva acts as a buffer to suppress enamel demineralization caused by low-pH beverages.展开更多
Erosion is one of serious oral health problems among Japanese children. Some dentists argue that brushing just after food/drink intake induces enamel abrasion. Objectives of this study were to evaluate amount of calci...Erosion is one of serious oral health problems among Japanese children. Some dentists argue that brushing just after food/drink intake induces enamel abrasion. Objectives of this study were to evaluate amount of calcium elution from bovine enamel due to single and short immersion into carbonated soft drink, to calculate depth of the eroded lesion, and to determine when to brush teeth after carbonated soft drink intake from the view point of preventing enamel abrasion. Four enamel specimens were made from each of eight bovine teeth. The specimens were covered by quick-cure resin except for enamel surfaces. The four specimens from each bovine tooth were classified into three, six, nine, and 12 minutes immersion (IM3, IM6, IM9, and IM12) groups and immersed separately in five mL of carbonated soft drink. After the immersion, the calcium concentration of the original drink and the drink samples were evaluated using atomic absorption spectrophotometry. The dimension of each enamel specimen was calculated using a planimeter. The amount of eluted calcium per unit area of the enamel specimen into each drink sample was obtained. The depth of the demineralized lesion was obtained by dividing the amount of calcium elution per unit area by the concentration of calcium in enamel and the specific gravity of enamel. The lesion depth of the IM3 group was significantly lower than those in the IM6, IM9, and IM12 groups. The mean lesion depth in the IM12 group which showed the deepest lesion depth was 0.21 μm. As conclusions, the erosive lesion depth due to intake of carbonated soft drink was much shallower than remineralized enamel surface of a white spot lesion which can be repaired in plaque fluid in a short time, suggesting such erosion hardly causes tooth wear, hence it was suggested that brushing teeth just after the intake was recommended.展开更多
Aims Faunal assemblage alterations due to anthropogenic impacts have changed herbivore-vegetation relationships in various ecosystems,but the influences of small vertebrates on revegetation processes remain unclear.In...Aims Faunal assemblage alterations due to anthropogenic impacts have changed herbivore-vegetation relationships in various ecosystems,but the influences of small vertebrates on revegetation processes remain unclear.In a peri-urban agricultural landscape in eastern Japan that lacks large ungulates but supports small generalist herbivores,fewer native seedlings have become established in thickets dominated by native dwarf bamboo,Pleioblastus chino(Franch.et Sav.)Makino.The mechanisms limiting tree seedling establishment are unknown.Our aim here was to evaluate the influence of interactions among the dwarf bamboo,its litter cover and small vertebrate herbivores on the micro-site conditions governing the establishment of native tree seedlings from different successional stages in an old field in temperate Japan.Methods First,seedling emergence and survival of seeded Pinus densiflora Siebold et Zucc.,Celtis sinensis Pers.,Aphananthe aspera(Thunb.)Planch.,Quercus serrata Murray,Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino)Hatus.ex T.Yamaz.et Mashiba were observed in a factorial design that accounted for the presence or absence of dwarf bamboo and its litter cover,as well as the exclu-sion or access of small vertebrate fauna,in 2009 and 2010.To identify small vertebrate herbivores that reduced the emergence or survival of tree seedlings in the first experiment,reseeding experi-ments using P.densiflora,C.sinensis,A.aspera and Q.myrsinifolia were conducted by video trapping in 2011 and video and still-cam-era trapping in 2012.Important Findings The abiotic conditions under the dwarf bamboo were lethal to early-to mid-successional P.densiflora,C.sinensis,A.aspera and Q.serrata but led to better survival-although spindly growth-of late-succes-sional Q.myrsinifolia and C.sieboldii.The main consumers and the plants they found palatable differed between the bamboo thickets and the intervening gaps.Predation by mice appeared to have severely limited the emergence of all species,particularly in the bamboo thick-ets but occasionally in the gaps,whereas litter cover slightly mitigated this limitation.However,bamboo litter cover reduced the emergence of P.densiflora in the gaps.Chinese bamboo partridge(Bambusicola thoracicus Temminck),an introduced game bird,selectively and severely fed on the cotyledons-and probably seeds-of A.aspera and moderately preyed upon those of P.densiflora in the gaps.Apparent consumption of seedlings in the gaps by the Japanese hare(Lepus brachyurus Temminck)suppressed the growth of all species but apparently did not severely affect emergence and survival.Thus,the net balance of positive and negative interactions at the bamboo thicket scale(i.e.the presence of dominant dwarf bamboo cover or intervening gaps and the herbivore behaviours in these two environments)and at the microsite level(i.e.litter cover)shapes the early establishment patterns of native tree seedlings,and this balance differs among tree seedling species.展开更多
文摘<strong>Objective:</strong> This study aimed to clarify the effect of trace elements on enamel erosion due to citric acid eliminating other factors that can affect enamel erosion.<strong> Method: </strong>Forty enamel specimens were obtained by embedding bovine enamel blocks into a quick cure resin. Half of the enamel surface of the specimens was covered with nail varnish. The specimens were randomly divided into control (Ct), zinc (Zn), iron (Fe), and copper (Cu) groups and immersed in 1% citric acid solution, 1% citric acid solution with 10 mmol/L zinc, 1% citric acid solution with 10 mmol/L iron, or 1% citric acid solution with 10 mmol/L copper, respectively, at 37<span style="white-space:nowrap;">°</span>C for 5 h. After immersion, the demineralized lesion depth was measured using transverse microradiography (TMR) and compared between groups using one-way analysis of variance and Tukey’s test. <strong>Results: </strong>The lesion depth was significantly higher in the Zn (218.9 ± 88.5 μm) group than that in the Ct group (116.3 ± 22.1 μm) (p < 0.01). <strong>Conclusion:</strong> It was suggested that zinc has decalcification properties when consumed with citric acid, while iron and copper don’t have such properties.
文摘Supernumerary tooth in the upper central incisor region is called mesiodens. Mesiodens causes serious complications such as displacement, retarded eruption, and rotation in the adjacent permanent incisors, inducing inhibition of oral development. This report was aimed to provide epidemiology of mesiodens in Japanese children. Using dental record, panoramic radiographs and images of cone-beam computed tomography in 128 non-syndromic child patients, patients’ age at their first visit, gender composition, shape of mesiodens, position of mesiodens, posture of mesiodens, and age distribution of the patients based on each complication were investigated. In addition to the survey, patient age was compared between the groups with and without each complication. Patients’ age ranged 3 - 10 years old. Male-to-female ratio was approximately 3:1. Conical shape (75%) and inverted position (49%) were the most frequent among the patients. Displacement was the commonest complication. Age comparison indicated that patients with displacement or retarded eruption consulted the dentist younger than those without the complications. The present study provided etiology of mesiodens in Japanese children that will contribute to daily clinical practice in the field of pediatric dentistry.
文摘As erosion has become one of the serious oral health problems, some fluoride-releasing dental materials have been developed to protect enamel from demineralization. The purpose of this study was to evaluate the antidemineralization effect of PRG Barrier Coat<sup>®</sup> and FujiVII<sup>®</sup> (fluoride-releasing dental materials). Four square windows measuring 1 mm<sup>2</sup> were prepared on the labial enamel surface of each bovine tooth using masking tape and nail varnish. The first and second windows were half covered by fluoride-releasing material and control material, respectively, whereas the third and fourth windows were left untreated. All windows were immersed into 0.1 M lactic acid and 6wt% CM-cellulose (pH 4.5) at 38℃ for 21 days. Subsequently, the first and second windows were covered with nail varnish after removal of the materials, and the third and fourth windows were immersed into ultrapure water at 38℃ for 28 days after being half covered with fluoride-releasing and control materials, respectively. The following procedure was performed separately during evaluations of the fluoride-releasing materials, PRG Barrier Coat, and FujiVII<sup>®</sup>, using eight and six bovine teeth, respectively. The first, second, third, and fourth windows were classified into DM-PRG;Demineralized-PRG or DM-FujiVII;Demineralized-FujiVII, DM-TCM;Demineralized-traditional cement or DM-TGIC;De-mineralized-traditional glass ionomer cement, RM-PRG;Remineralized-PRG or RM-FujiVII;Re-mineralized-FujiVII, and RM-TCM;Remineralized- traditional cement or RM-TGIC;Remineral-ized-traditional glass ionomer cement, respectively. After nail varnish was removed, △Q values (mean ± SD) of the windows were measured using QLF-D and were compared between DM-PRG and DM-TCM, RM-PRG and RM-TCM, DM-FujiVII and DM-TGIC, and RM-FujiVII and RM-TGIC groups. △Q values of RM-PRG (-60 ± 44) and RM-FujiVII (-5.0 ± 10) were significantly higher than that of RM-TCM (-315 ± 193) and RM-TGIC (-56 ± 43), respectively. The fluoride releasing materials provided remineralization effects to bovine enamel.
文摘Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study were to compare the elution levels of aluminum and calcium from deciduous enamel into acidic artificial saliva, and determine whether the degree of aluminum elution reflects individual caries risk. One hundred and eleven extracted human deciduous teeth were collected. Concentrations of aluminum and calcium eluted from sound regions of enamel into artificial saliva (pH 6.2 or 5.5) were determined using atomic absorption spectrophotometry. One hundred and four and 108 available data samples were obtained for aluminum and calcium evaluation, respectively, and were compared based on the sex, tooth type, caries history, and the number of the donor’s carious teeth at each pH. Calcium elution was not affected by the sex;however, more aluminum was eluted from boys’ than from girls’ teeth at pH 5.5. The aluminum release depended on the tooth type, and was significantly higher in incisors than in molars at a pH of 5.5. In relation to the caries history, aluminum (at pH 5.5) and calcium (at pH 6.2) dissolved more from sound regions of the enamel of caries-experienced teeth than from the enamel of teeth without caries experience. Moreover, aluminum markedly dissolved from enamel in artificial saliva at both pH 6.2 and 5.5 when the donor had more carious teeth, regardless of the presence or absence of caries experience in the sampled teeth. There is a possibility that the rate of aluminum elution from enamel into acidic fluid reflects individual caries sensitivity.
文摘Restoring natural forests after field abandonment is a land management objective that fosters the recovery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the abandonment of an arable field that became dominated by a dwarf bamboo(Pleioblastus chino(Franch. et Sav.)Makino) and by kudzu(Pueraria lobata(Willd.) Ohwi).By permutation tests, the removal of competing vegetation(gap creation) significantly increased the survival of three seeded species of Fagaceae and of eight transplanted species. In contrast, intact vegetation prevented most individuals of all species from surviving for 1 year after planting. The lack of natural recruitment of Fagaceae in the nonseeded subplots indicated that seed limitation was a cause of the slow afforestation. Although litter accumulation in gaps at the time of seeding slightly increased survival for late-germinating Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino) Hatus. ex T. Yamaz. et Mashiba, the effect was not consistent among plots and was not statistically significant. Our results suggest that for successful afforestation using native trees in abandoned fields, it will be necessary to remove competitive native species to avoid severe limitations on microsite availability and that simultaneous tree establishment by seeding or transplanting should be implemented to accelerate the establishment of native tree species.
文摘Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired.We investigated seedling survival of four transplanted native tree species(Quercus myrsinifolia, Quercus serrata,Aphananthe aspera, and Rhus sylvestris) by experimentally manipulating the vegetation cover, which was mainly dominated by dwarf bamboo(Pleioblastus chino), and herbivore access to the planting sites on farmland that had been abandoned for 15 years at the start of the study. Few transplanted seedlings of any species survived under intact vegetation cover, irrespective of herbivore presence. In gaps in the vegetation cover, winter browsing by Japanese hare(Lepus brachyurus) damaged all species. However,lower browsing frequency and higher resprouting ability after grazing of the seedlings enabled both Quercus species to survive better than the other species. These results indicate that dwarf bamboo and the hare jointly limit the establishment of native trees in old fields. If active afforestation by transplanting seedlings at sites dominated by dwarf bamboo is planned, a combination of vegetation removal, selection of suitable species, and temporary seedling protection will be most effective.
文摘Background: Caries detection in school oral examinations insufficient accuracy. Objective: To evaluate advantages of introducing quantitative light-induced fluorescence-digital (QLF-D) in school oral examinations. Methods: Experiment No. 1. Early demineralized lesions in the upper and lower incisors and canines were visually inspected by three dentists and by QLF-D. The numbers of tooth planes with early demineralized lesions were compared between the methods. Experiment No. 2. Approximal demineralized lesions in molars were assessed by visual inspection, x-ray imaging, and QLF-D. The numbers of tooth planes with demineralized lesions were compared among the methods. Experiment No. 3. Plaque distribution was evaluated by QLF-D and a traditional staining method. The ratio of the diameter of plaque to tooth crown in the tooth axis direction in each method was calculated. The results were evaluated by Pearson’s correlation coefficient analysis and Bland-Altman plot. Results: Experiment No. 1. The three dentists found 0.67 tooth planes on average. QLF-D found 22 tooth planes with early demineralized lesions in the same samples. Experiment No. 2. Fourteen approximal tooth planes of molars were found to have demineralized lesions by x-ray imaging. QLF-D detected 71.4% of the tooth planes out of the 14, whereas visual inspection found 7.1%. Experiment No. 3. The Pearson’s correlation coefficient for the evaluations of plaque distribution between the QLF-D and traditional staining methods was 0.77 (P Conclusion: The results support introduction of QLF-D for use in school dental examinations.
文摘As the prevalence of dental caries decreases, the diagnosis and treatment of initial mineral loss resulting in white spot lesions have been getting more and more important. Since dental CT provides computed tomography images of a tooth with radiation exposure similar to panoramic radiography, it will become possible in the near future to evaluate the enamel mineral density using CT in the same way as measurement of the bone mineral density. Such computed tomography images enable dentists to perform longitudinal, three-dimensional, and precise evaluation of the enamel mineral density before a demineralized lesion becomes detectable by any other traditional means. Despite their advantage, there are not enough reports on evalu- ation of the enamel mineral density using CT. This study evaluated the serial changes in mineral density in the earliest stage of enamel demineralization. Eight bovine enamel specimens were coated with nail varnish. On each specimen, 4 square windows measuring 1 mm2 were created. The specimens were incubated in lactic acid solution at 38?C. During incubation, the windows were covered by nail varnish one by one at 30, 60, and 90 minutes, respectively. At 120 minutes, the specimens were removed from the solution. After the nail varnish was removed, X-ray microradiography was performed using SKYSCAN1172 at settings of 100 kV and 100 μA. The mean Hounsfield unit values (HUV) of enamel in a non-window area and those in the window areas were calculated every 180 μm over a depth of 0 - 900 μm and analyzed by two-way ANOVA. Data were affected by the incubation time and depth from the enamel surface, and there was not interaction between the two factors. Considering the incubation time, HUV of the whole measured enamel (0 - 900 μm) in the non-window group was significantly higher than that of the other incubated groups. Considering the depth, HUV was decreased at 721 - 900 μm compared with that at 0 - 180 μm in the 30-minute-incubated group, and the decrease spread to 361 - 900 μm in the 60- and 90- minutes-incubated groups. HUV was additionally calculated at increments of 18 μm and compared within the 60-minute-incubated group, and changes in the mineral density at the boundary of the earliest demineralized lesion could be observed. This study demonstrated detailed mineral density changes in the earliest period of demineralization.
文摘This study aimed to clarify the ability of the buffer systems of saliva to inhibit enamel demineralization after intake of an acid beverage. In the first experiment, titrable acidity tests were carried out. Ten milliliters of saliva stimulated by chewing gum base was obtained from 10 healthy adult subjects and the pH of each saliva sample was measured. The beverages used for the experiment were a carbonated soft drink (pH 2.2), a sports drink (pH 3.5), and 100% orange juice (pH 3.8). Distilled water adjusted to the pH of each saliva sample was used as a control. In the second experiment, the suppressive ability of saliva against enamel demineralization was quantitatively analyzed using quantitative light- induced fluorescence (QLF). Aliquots of stimulated saliva obtained from a subject were mixed with 15 ml of 100% orange juice in saliva:orange juice ratios of 1/30, 1/15, 1/10 and 1/5, and bovine teeth were soaked for 24 hours in the solutions. The △Q of the QLF analyses of the enamel was then measured. The lowest titrant volume which reduced the pH of the initial saliva (7.7 on average) to pH 5.4 was that of the orange juice. No relationship was found between the buffer capacity and the pH of the acid beverages. From the QLF measurement, the saliva-orange juice group showed a significantly decreased amount of enamel demineralization (p < 0.01 at 20% level) compared with the distilled water-orange juice group. In conclusion, saliva acts as a buffer to suppress enamel demineralization caused by low-pH beverages.
文摘Erosion is one of serious oral health problems among Japanese children. Some dentists argue that brushing just after food/drink intake induces enamel abrasion. Objectives of this study were to evaluate amount of calcium elution from bovine enamel due to single and short immersion into carbonated soft drink, to calculate depth of the eroded lesion, and to determine when to brush teeth after carbonated soft drink intake from the view point of preventing enamel abrasion. Four enamel specimens were made from each of eight bovine teeth. The specimens were covered by quick-cure resin except for enamel surfaces. The four specimens from each bovine tooth were classified into three, six, nine, and 12 minutes immersion (IM3, IM6, IM9, and IM12) groups and immersed separately in five mL of carbonated soft drink. After the immersion, the calcium concentration of the original drink and the drink samples were evaluated using atomic absorption spectrophotometry. The dimension of each enamel specimen was calculated using a planimeter. The amount of eluted calcium per unit area of the enamel specimen into each drink sample was obtained. The depth of the demineralized lesion was obtained by dividing the amount of calcium elution per unit area by the concentration of calcium in enamel and the specific gravity of enamel. The lesion depth of the IM3 group was significantly lower than those in the IM6, IM9, and IM12 groups. The mean lesion depth in the IM12 group which showed the deepest lesion depth was 0.21 μm. As conclusions, the erosive lesion depth due to intake of carbonated soft drink was much shallower than remineralized enamel surface of a white spot lesion which can be repaired in plaque fluid in a short time, suggesting such erosion hardly causes tooth wear, hence it was suggested that brushing teeth just after the intake was recommended.
文摘Aims Faunal assemblage alterations due to anthropogenic impacts have changed herbivore-vegetation relationships in various ecosystems,but the influences of small vertebrates on revegetation processes remain unclear.In a peri-urban agricultural landscape in eastern Japan that lacks large ungulates but supports small generalist herbivores,fewer native seedlings have become established in thickets dominated by native dwarf bamboo,Pleioblastus chino(Franch.et Sav.)Makino.The mechanisms limiting tree seedling establishment are unknown.Our aim here was to evaluate the influence of interactions among the dwarf bamboo,its litter cover and small vertebrate herbivores on the micro-site conditions governing the establishment of native tree seedlings from different successional stages in an old field in temperate Japan.Methods First,seedling emergence and survival of seeded Pinus densiflora Siebold et Zucc.,Celtis sinensis Pers.,Aphananthe aspera(Thunb.)Planch.,Quercus serrata Murray,Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino)Hatus.ex T.Yamaz.et Mashiba were observed in a factorial design that accounted for the presence or absence of dwarf bamboo and its litter cover,as well as the exclu-sion or access of small vertebrate fauna,in 2009 and 2010.To identify small vertebrate herbivores that reduced the emergence or survival of tree seedlings in the first experiment,reseeding experi-ments using P.densiflora,C.sinensis,A.aspera and Q.myrsinifolia were conducted by video trapping in 2011 and video and still-cam-era trapping in 2012.Important Findings The abiotic conditions under the dwarf bamboo were lethal to early-to mid-successional P.densiflora,C.sinensis,A.aspera and Q.serrata but led to better survival-although spindly growth-of late-succes-sional Q.myrsinifolia and C.sieboldii.The main consumers and the plants they found palatable differed between the bamboo thickets and the intervening gaps.Predation by mice appeared to have severely limited the emergence of all species,particularly in the bamboo thick-ets but occasionally in the gaps,whereas litter cover slightly mitigated this limitation.However,bamboo litter cover reduced the emergence of P.densiflora in the gaps.Chinese bamboo partridge(Bambusicola thoracicus Temminck),an introduced game bird,selectively and severely fed on the cotyledons-and probably seeds-of A.aspera and moderately preyed upon those of P.densiflora in the gaps.Apparent consumption of seedlings in the gaps by the Japanese hare(Lepus brachyurus Temminck)suppressed the growth of all species but apparently did not severely affect emergence and survival.Thus,the net balance of positive and negative interactions at the bamboo thicket scale(i.e.the presence of dominant dwarf bamboo cover or intervening gaps and the herbivore behaviours in these two environments)and at the microsite level(i.e.litter cover)shapes the early establishment patterns of native tree seedlings,and this balance differs among tree seedling species.
