摘要:

Surface prismatic and aprismatic human enamel and unpolished or diamond-polished specimens of bovine enamel, with test and control surfaces on each studied block, were immersed in phosphoric acid containing cola beverage (pH 2.6) and citric or malic acid containing sports drinks (pH 2.8 and 3.4, respectively) for 15–180 min. The specimens were then prepared and studied in a JEOL 35C scanning electron microscope. In human aprismatic surface enamel an irregular type of dissolution was observed, with severely affected areas adjacent to less affected ones. Prismatic human and bovine specimens showed a characteristic dissolution where initial erosion after 15 min immersion was seen to affect specifically the prism sheath areas. Longer immersion caused dissolution of enamel prism cores followed by interprismatic areas. In bovine enamel malic acid affected least the surface ultrastructure when compared with citric and phosphoric acids after 15–30 min of immersion, but thereafter no difference was observed between the acids in causing erosion. Diamond-polished enamel was found more liable to erosion than non-polished enamel. Thus, the structure of enamel greatly modified the progression of in vitro caused erosion, in particular in human tooth specim

ISSN:0008-6568    

DOI:10.1159/000261348

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Experiments with surface-softened synthetic hydroxyapatite show similar remineralization rates as surface-softened human enamel. The mineral gain with respect to time relates to parameters governing the precipitation of mineral in the specimens. A mathematical model regarding the mineral precipitation on the pore surface is fitted to the experimental values. We obtained comparable precipitation rates for apatite and tooth enamel. The geometry of the pores, however, proved to be different: a mostly tube-like pore structure must be attributed to demineralized enamel, while the synthetic hydroxyapatite specimens remineralize like a ramified, crack-like microstructure of pores.

ISSN:0008-6568    

DOI:10.1159/000261349

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The formation of calcium fluoride (CaF2) was measured on sound enamel (SE) and in caries-like enamel lesions (CL) after treatment in vitro with 2% neutral NaF or Duraphat®. The caries-like lesions were created by exposure to acidified gel at pH 4.5 within a 0.07-cm2 window punched in water-repellant tape. The same window area was used in series (n = 10) of SE or CL during the application of NaF for 1 or 5 min or for 18 h or Duraphat for 6 or 18 h. CaF2 was extracted with 1 MKOH for 24 h, and fluoride was determined by gas chromatography. The short-term applications of NaF produced only negligible amounts of CaF2 on SE. The amounts of CaF2 in CL after 5 min application of NaF corresponded to (mean ± SEM) 27 ± 2.0 μg F/cm2. More than half of this amount was observed after only 1 min exposure to the NaF solution. The quantities of CaF2 in CL were similar after 6 and 18 h application of Duraphat, amounting to 26 ± 2.2 and 31 ± 2.2 μg F/cm2, respectively, suggesting that the reaction was essentially terminated after 6 h. These amounts were only about one fourth of the quantity obtained after 18 h exposure to the NaF solution. Thus, the conventional 5-min treatment with NaF produced the same amount of CaF2 in CL as 6 or 18 h exposure to Du

ISSN:0008-6568    

DOI:10.1159/000261350

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

In the present work, hydrolysis reactions of sodium hexafluorosilicate (Na2SiF6) and sodium hexafluorostannate (Na2SnF6) were studied at various combinations of pH and calcium ion (Ca2+) concentrations using a quasi-constant composition titration method. Under high concentrations of hydrogen ion (H+) and Ca2+, the promoting effect of Ca2+ on the hydrolysis of Na2SiF6 was stronger than the inhibition effect of H+. However, the inhibition effect of H+ on the hydrolysis of Na2SnF6 was stronger than the promoting effect of Ca2+. Na2SiF6 and Na2SnF6 were found to have hydrolysis properties that may make them suitable for use with an acidic calcium phosphate solution in a topical fluoride treatment which forms dicalcium phosphate dihydrate as an intermediate.

ISSN:0008-6568    

DOI:10.1159/000261351

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Actinomyces viscosus WVU 627, Streptococcus oralis LPA-1 and Veillonella dispar OMZ 193 were cocultured on teeth in a model mouth for 66 h. Synthetic saliva containing bovine salivary glycoprotein supported bacterial growth, although the delivery of an intermittent nutrient supplement, containing 1% (w/v) glucose or sucrose, gave greater bacterial cell and viable counts. When Streptococcus mutans C67-1 was super-inoculated onto 24-hour mixed plaques, it became established under all regimens, but there was pronounced colonization resistance. With saliva only, the proportion of S. mutans at 66 h was < 0.5% of the total cultivable microflora. When a glucose supplement was delivered for 1 h every 6 h, S. mutans attained a final proportion of 2.4%. With sucrose, both S. mutans C67-1 and its non-cariogenic glucan-deficient mutant, C67-25, attained similar proportions of 15–20%. These experiments indicate how this model can be used to study the factors influencing colonizing ability and microbial interactions in biofilms under controlled condition

ISSN:0008-6568    

DOI:10.1159/000261352

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Streptococcus sobrinus is known to possess cariogenic properties in vitro. It can produce acid in large amounts and it has the capacity to adhere to enamel and other surfaces. However, most studies on cariogenicity have been performed with laboratory strains that have been subcultured over long periods of time. Therefore, the cariogenicity and acidogenicity of 9 fresh isolates of both S. sobrinus and Streptococcus mutans from human dental plaque were compared. The bacteria were inoculated into the oral cavity of rats. The rats were fed diet SSP 20/5, containing 20% sucrose and 5% glucose. After the experimental period of 42 days, the amount of caries was assessed and bacterial counts were determined using monoclonal antibodies. Four out of 9 S. sobrinus strains and 3 out of 9 S. mutans strains did not colonize the rats. Colonizing strains constituted 39–78% of the total anaerobic cultivable microflora. The numbers of advanced dentinal lesions in the fissures of the rats colonized with S. mutans were significantly lower than those colonized with S. sobrinus (p < 0.05). S. sobrinus produced acid more rapidly than S. mutans in a pH-stat system at pH values between 6.5 and 5.0 (p < 0.01). The results indicate that fresh isolates of S. sobrinus are more cariogenic in rats than fresh isolates of S. mutans. This is possibly due to differences in glycolytic properties of these two specie

ISSN:0008-6568    

DOI:10.1159/000261353

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Fluoride is the only extensively clinically proven means of reducing dental caries. Despite a large body of epidemiological data on the effectiveness of fluoride, delivered in the form of dentifrices, mouthrinses, drinking water, etc., the precise mode of action of fluoride is not completely understood. The purpose of this paper is to report an investigation of the link between oral fluoride levels and applied fluoride dose from dentifrices. Human salivary fluoride clearance studies and equilibrium baseline studies of fluoride in saliva and plaque have been carried out with dentifrices which contained 1,000, 1,500 and 2,500 μg fluoride per gram as sodium monofluorophosphate. After a single brushing with a fluoride dentifrice, salivary fluoride decreased in two distinct phases: an initial rapid phase which lasted for 40–80 min, depending on the individual, and a second slow phase lasting for several hours. The latter phase is believed to be due to fluoride released from an oral fluoride reservoir. During regular repeated use of the test dentifrices, the equilibrium baseline fluoride concentration, attained in both saliva and plaque between one application and the next, increased significantly compared with placebo values. Such elevated baseline fluoride concentrations also increased with increasing Na2FPO3 content of the dentifrices. The present work supports the concept that labile fluoride, stored in an oral fluoride reservoir at the time of treatment application, may maintain a prolonged protective effect against dental cari

ISSN:0008-6568    

DOI:10.1159/000261354

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

A comparison is described of three methods of preclinical assessment of potential anti-caries efficacy for topical fluoride treatments. Methods are compared using dentifrices containing 1,000, 1,500 and 2,500 ppm F as sodium monofluorophosphate (SMFP). These formulations have been shown elsewhere to give a statistically significant dose response of increasing anti-caries efficacy [Stephen et al., 1988]. An in situ enamel insert model, oral fluoride pharmacokinetics and F uptake to demineralised enamel are all shown to correlate with clinical efficacy for the test dentifrices studied.

ISSN:0008-6568    

DOI:10.1159/000261355

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The effects of hyposalivation on the induction of dental caries and on the oral microflora were examined in SPF Sprague-Dawley rats with or without inoculation of oral streptococci. Significant dental caries was induced in hyposalivated rats, irrespective of the infection with oral streptococci including Streptococcus mutans. In addition, bacteriological analyses demonstrated that the total number of lactobacilli increased significantly at the expense of the inoculated streptococci. These findings suggest that opportunistic infections may be induced in the oral cavity of hyposalivated rats and some acidogenic microorganisms including lactobacilli may promote the induction of dental caries.

ISSN:0008-6568    

DOI:10.1159/000261356

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000261357

出版商:S. Karger AG    

年代:1991

数据来源: Karger