摘要:

One of the predominant bacteria in early dental plaque, Streptococcus mutans 25 × 106), free fructose and oligosaccharides were formed from sucrose. The enzyme had a pH optimum at 6.0, optimal activity around 40° C and isoelectric point at pH 4.2. Iodoacetamide, cysteine, Tris and sodium fluoride in a concentration of 0.05 m had no effect on the enzyme activity. The enzyme was totally inhibited by 0.1 mM Hg++ and to about 40% by 1 mM Pb++, Ag+, Ni++ and Cu++. EDTA in a concentration of 1 mM reduced the over-all activity of the enzyme by 75% and specifically interfered with the synthesis of levan. Most divalent cations could restore the activity of the enzyme in the presence of EDTA. The properties of this streptococcal levansucrase were similar to those previously described for levansucrases from Aerobacter levanicum and Bacillus subtilis. The finding, that EDTA interfered with the synthesis of levan, may give new possibilities in elucidating the mechanism of this enzyme reactio

ISSN:0008-6568    

DOI:10.1159/000259632

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

The influence of drastic dietary carbohydrate restriction on the occurrence of Strep. mutans, Strep. sanguis and iodophilic polysaccharide-producing bacteria in the dental plaque of 6 subjects was studied. During a carbohydrate-free period of 17 days, the percentage that Strep. mutans constituted of the total cultivable flora decreased to a very low or undetectable level, while simultaneously the percentage Strep. sanguis increased. The percentage IPS-producing bacteria was also lower during this period. Reinstitution of the normal diet, after periods of added glucose and sucrose to the carbohydrate-free diet, resulted in a return of Strep. sanguis to its original proportions and of Strep. mutans and the IPS-producers to levels that were significantly higher and slightly higher respectively than before the experiment. During the study an inverse relationship between the occurrence of Strep. mutans and Strep. sanguis was observed.

ISSN:0008-6568    

DOI:10.1159/000259633

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

Twelve male mice, 3 weeks old, were caged together with caries-active hamsters and the twin brothers of the mice served as controls. The hamsters harboured Streptococcus mutans and Streptococcus salivarius in their mouths, while neither of these streptococcal species could be recovered from the mice at the beginning of the experiment. At the end of the experiment after nine weeks Strep. mutans could be isolated in a high number from the mouth of six mice reared in the company of hamsters. Five of these mice had a moderate caries activity (2–19 lesions) while one was caries-free. Of the six mice from which Strep. mutans was not recovered, one mouse had five caries lesions while the other five animals were caries-free. In the 12 control mice Strep. mutans could not be isolated and only one animal had one caries lesion. This experiment demonstrates the transfer of Strep. mutans from hamster to mouse and a possible relation between the presence of Strep, mutans and caries activity in the mous

ISSN:0008-6568    

DOI:10.1159/000259634

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

The purpose of the present study was to develop a method for short-term caries trials in man, using an experimental model already employed in periodontal research. Twelve students were given prophylaxis and instruction to practice meticulous oral hygiene until Plaque Index and Gingival Index approached zero. The carious state of the bucco-gingival enamel areas, excluding molars, was evaluated using a dissection microscope. The cleaned and dried tooth surfaces were scored according to the Caries Index system. During a period of 23 days without oral hygiene 6 participants performed 9 daily mouthrinses with 10 ml of a 50% sucrose solution. At the termination of this period the sucrose group demonstrated a higher mean Caries Index and a greater number of new early lesions than the six control subjects. The mean Plaque Index scores were higher in the sucrose group, whereas the Gingival Index scores were similar for both groups. Smears of plaque showed no significant differences in the percentage distribution of various types of microorganisms. After 30 days of oral hygiene and daily mouthrinses with 0.2 % NaF, fair agreement was found between the Caries Index scores of the two groups. Similar observations were made after a second hygiene and fluoride period. The results demonstrate that it is possible to produce detectable carious alterations within 23 days by abolishment of oral hygiene and frequent sucrose additions and that these alterations are reversible.

ISSN:0008-6568    

DOI:10.1159/000259635

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

The prolonged prophylactic effect of three years’ daily supervised toothbrushing with a 0.22% sodium fluoride effect dentifrice was studied in 113 schoolchildren. During the trial the number of new carious surfaces in the test group (57 children) was smaller than in the control group (56 children); the difference was 20% in the first year, 34% in the second, and 48% in the third. The numerical reduction found was largest for the proximal lesions. During the first two years after the end of the trial the test group showed a 13% reduction of caries. This was due mainly to a difference in caries increment on buccal surfaces. This means that no persistent prophylactic effect of great practical value could be demonstrate

ISSN:0008-6568    

DOI:10.1159/000259636

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

Pastes of different abrasives were prepared by mixing pumice, zirconium silicate (zircate), levigated alumina and insoluble metaphosphates (IMP) with water. Measurements of the amount of enamel worn off after polishing for 30 seconds with the pastes and a rotating rubber cup showed loss of a 3 or more micron thick layer from use of the zircate, pumice and levigated alumina paste and loss of less than one micron from the IMP paste. Fluoride pastes prepared by mixing the abrasives with a solution containing 4% NaF, 0.1 m phosphate and having a pH of 4.6 were tested for stability and uptake of fluoride by intact enamel. The pastes of pumice, zircate and levigated alumina increased in pH and approached neutral pH within 24 hours, while the IMP paste maintained a low pH. The uptake of fluoride from the pastes without abrasive action was pH dependent and was greatest from the IMP paste. Enamel polished with the pastes showed only a a slight gain in F. Marked deposition of F was obtained in enamel polished for 30 sec with a paste containing 0.2 m aluminum nitrate and then exposed to the fluoride solutions. The findings in the study elucidate the action of fluoride prophylaxis pastes on enamel and are in support of routine use of fluoride pastes in dental practice.

ISSN:0008-6568    

DOI:10.1159/000259637

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

In a previous investigation of fluoride retention after mouth-washing a group of adults retained more fluoride than children in spite of more complete expectoration of the children. It therefore appeared possible that certain oral structures, such as calculus deposits and silicate fillings as well as intact enamel might have taken up important quantities of fluoride. In the present study an attempt was made to assess the magnitude of the storage in the tooth surfaces and to determine to what extent dental calculus and silicate fillings moderate this uptake. By the aid of 18F the uptake was studied in vitro in surfaces of intact enamel, calculus deposits and silicate fillings exposed to sodium fluoride solutions and in vivo after mouth-rinses in the following groups of patients: 1. patients with all teeth missing, 2. patients where single intact teeth with calculus deposits were to be extracted, and 3. patients where single teeth were to be extracted. Both in vitro and in vivo studies showed that the uptake in the tooth-crowns is responsible for only a small fraction of the total fluoride loss. This uptake is 5.5 and 8.5 times higher in silicate fillings and dental calculus, respectively, than in intact enamel. The fluoride uptake of the total intact enamel surfaces after mouth-washing can be calculated to only about 1% of the total fluoride retention. Retention probably takes place by direct absorption in the oral mucosa and by involuntary swallowing.

ISSN:0008-6568    

DOI:10.1159/000259638

出版商:S. Karger AG    

年代:1970

数据来源: Karger

摘要:

The selenium concentration of enamel from samples of human teeth was determined by a method of neutron activation analysis. The samples, weighing approximately 100 mg were irradiated in a reactor at a thermal neutron flux of 1.2 × 1012 n/cm2/sec for 1 hour for 81Se and for one week for 75Se. The selenium activity was measured after radiochemical separation. The samples analysed were obtained in Manchester and in Edinburgh. The mean level of selenium found in the teeth from Edinburgh was 0.830 ppm and the range 0.213–1.96 ppm. In the teeth from Manchester the mean level was 0.914 ppm and the range from 0.274 ppm–2.08

ISSN:0008-6568    

DOI:10.1159/000259639

出版商:S. Karger AG    

年代:1970

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000259640

出版商:S. Karger AG    

年代:1970

数据来源: Karger