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Biomedical subjects

F Lagerlöf

Publications and source records attributed to F Lagerlöf.

At least 37 records · Page 2Linked to original sources
PubMed1990

Automatic pH-cycling caries model applied on root hard tissue.

The development of a caries lesion is a dynamic process that includes frequently alternating periods of de- and remineralization, a process for which no in vitro models currently exists. The aim of this study was to develop a model which could repeatedly generate identical pH versus time curves over extended periods of time. To test the model demineralization studies on cementum/dentin were performed. Cementum/dentin blocks were repeatedly subjected to de- and remineralizing solutions delivered by a computerized pump system connected to a pH-meter and a recorder. pH versus time curves similar to those produced in plaque after carbohydrate intake were generated 18 times during 15 h followed by a remineralizing period of 9 h every day for 16 days. The intra-day and inter-day variation of the pH-cycling model were found to be low. The mineral change of the blocks was followed by 125I absorptiometry and the transmission through the blocks during the experimental period increased in average by 1.4 +/- (SE) 0.18%. Microradiographic analysis of the transversal sections of the blocks confirmed the development of lesions resembling root caries.

Absorptiometry, Photon↗
PubMed1990

Root hard-tissue demineralization rate measured by 125I absorptiometry: comparison with lesion-depth measurements.

The aim of the present study was to compare demineralization of root hard tissue, monitored by 125I absorptiometry, with lesion-depth measurements under polarized light microscopy. The intact roots of ten human molars, which had not been exposed to the oral environment, were divided into 39 cementum/dentin blocks and exposed to a buffer solution of pH 4.5 containing 2.2 mmol/L calcium and inorganic phosphate. After demineralization for 3.5, 7, 14, and 21 days, transmission measurements by 125I absorptiometry were performed, and one block from each tooth was taken out of the solution for lesion-depth measurement. The results showed a high degree of correlation (r = 0.952) between lesion depth and change in transmission, with a more rapid increase initially in both variables. A linear relationship with the square root of time was found. Conversion of transmission data to lesion-depth data was possible when this caries model system was used on cementum dentin blocks.

Absorptiometry, Photon↗
PubMed1989

Influence of flow rate, pH and plasma fluoride concentrations on fluoride concentration in human parotid saliva.

In two separate studies the influence of some physiological factors on salivary fluoride excretion was investigated. In the first study, parotid saliva, at two predetermined flow rates, and capillary blood were sampled after ingestion of 1 mg fluoride. In the second study, parotid saliva was collected at five different flow rates, starting 1 h after ingestion of 5 mg fluoride. Capillary blood was sampled throughout the experiment. The first study showed that parotid saliva and plasma fluoride concentrations were closely correlated (r = 0.81). The mean parotid salivary and plasma fluoride concentration ratio (S/P ratio) +/- SD ranged from 0.29 +/- 0.11 to 0.65 +/- 0.15. The fractions of the ingested fluoride dose excreted from one parotid gland were 0.08 and 0.18% at flow rates of 0.25 +/- 0.02 and 0.49 +/- 0.06 ml/min, respectively. The second study showed that at the mean basal plasma fluoride concentration of 0.65 +/- 0.18 mumol/l the mean S/P ratio was 0.55 +/- 0.24. At a plasma fluoride concentration ranging from 3.5 to 11.6 mumol/l the S/P ratio was 0.73 +/- 0.15. Thus the S/P ratio was influenced by the plasma fluoride concentration, but not by variations in parotid salivary flow rate or pH.

Adult↗
PubMed1989

Effect of flow rate on tissue plasminogen activator activity in human parotid saliva.

Parotid saliva from 10 healthy volunteers was collected at rest and at constant flow rates of 0.25, 0.5 and 1.0 ml/min, and its tissue plasminogen activator (tPA) activity assayed on fibrin plates containing plasminogen. In unstimulated salivas the median tPA activity was 0.26 (range 0.03-2.0) IU/ml. During the first 15 min of stimulation, a continuous decrease in tPA activity was found at the three flow rates; thereafter a steady state was obtained. No significant differences in activity were found between the three rates. The initial decrease was on average 0.15 IU/ml, and the activity during the steady state was 38% of the prestimulatory level. Thus, stimulation with citric acid causes a significant decrease in tPA activity of parotid saliva but this decrease, as well as the reduction rate, appears to be independent of flow rate.

Adult↗
PubMed1989

Studies on fluoride excretion in human whole saliva and its relation to flow rate and plasma fluoride levels.

Five volunteers participated in two separate experiments where whole saliva was collected without stimulation or with stimulation by chewing on paraffin wax. The saliva was collected continuously for 120 min after ingestion of 1 mg fluoride as NaF. Blood was collected at intervals throughout the experiments. The results showed that the concentration of fluoride in whole saliva mirrored the fluoride concentration in plasma, but at a lower level. Variations in salivary flow rate (0.34 +/- 0.15 ml/min for unstimulated and 1.06 +/- 0.28 ml/min for stimulated) did not affect the salivary fluoride concentration. The amount of fluoride excreted into stimulated whole saliva was significantly correlated with the salivary flow rate, with a correlation coefficient of 0.98. The fraction of the ingested fluoride dose recovered in whole saliva within 2 h was 0.05 +/- 0.02 and 0.18 +/- 0.09% for the unstimulated and the stimulated whole saliva, respectively.

Administration, Oral↗
PubMed1989

Studies on fluoride concentrations in human submandibular/sublingual saliva and their relation to flow rate and plasma fluoride levels.

Submandibular/sublingual saliva and blood were collected from five subjects after ingestion of 1 mg fluoride as NaF. An individual collection device, made from a silicone impression material, was used to collect the saliva in 10-minute samples, before and during 2 hr after the fluoride intake. In two separate experiments on each individual, submandibular/sublingual saliva was collected continuously at different flow rates: without stimulation and with gustatory stimulation. Blood was also collected at intervals throughout the experiments. The concentration of fluoride in the submandibular/sublingual saliva was less than that in the plasma but independent of salivary flow rate. The ratio between the saliva and plasma fluoride concentrations at the peak of the mean plasma fluoride concentrations was 0.55 +/- 0.13 and 0.69 +/- 0.11 in the experiments on unstimulated and stimulated salivary, flow rate, respectively. The total amount of the ingested fluoride dose that was excreted through the submandibular/sublingual glands during 130 min was highly correlated with the salivary flow rate. The fraction of the ingested fluoride dose excreted in 2 hr was 0.04 +/- 0.02% in the unstimulated saliva and 0.15 +/- 0.09% in the stimulated saliva.

Fluorides↗
PubMed1988

Effect of fluoride addition on ionized calcium in salivary sediment and in saliva.

Fluoride was added in increments to pooled whole saliva. The ionized calcium concentration was determined in the saliva and the salivary sediment after centrifugation. The maxima of the ion product with respect to calcium fluoride were for salivary sediment and saliva found at 15 mmol/l and 25 mmol/l of fluoride, respectively. The study indicated that calcium fluoride may precipitate in the plaque matrix during and after topical application of fluoride.

Calcium↗
PubMed1988

Effect of sodium lauryl sulfate on the deposition of alkali-soluble fluoride on enamel in vitro.

There are indications that sodium lauryl sulfate may reduce the cariostatic effect of fluoride when present together with sodium monofluorophosphate during topical application. The aim of the present study was to examine the in vitro deposition of alkali soluble fluoride on enamel during topical application with sodium fluoride in combination with sodium lauryl sulfate. It was found that increasing amounts of lauryl sulfate decreased the amount of alkali soluble fluoride deposited on the enamel. The amount of fluoride deposited from toothpaste supernatants was less than that from aqueous solutions of NaF with the same concentration of fluoride. Enamel pieces, pretreated with sodium lauryl sulfate showed a reduced deposition of alkali-soluble fluoride after incubation in a fluoride solution. It was also observed that the presence of lauryl sulfate increased the solubility of CaF2 in water.

Administration, Topical↗
PubMed1988

Effects of inorganic orthophosphate and pyrophosphate on dissolution of calcium fluoride in water.

Calcium and fluoride release from excess solid calcium fluoride was monitored for 15-30 min in aqueous solutions containing various concentrations of inorganic orthophosphate and pyrophosphate. Low concentrations of these ions (1-10 mumol/L) considerably inhibited the rate of dissolution of calcium fluoride. This inhibition was pH-dependent, being reduced at pH values below 5. It is suggested that a reduced calcium fluoride dissolution rate, in the presence of phosphate, can account for the relatively slow loss of calcium fluoride from dental enamel observed in recent clinical studies. It also appears that calcium fluoride coated with phosphate may provide a pH-controlled slow release of fluoride that may be of clinical significance and a major component of the cariostatic mechanism of topically applied fluoride.

Calcium Fluoride↗
PubMed1988

In vitro root caries progression measured by 125I absorptiometry: comparison with chemical analysis.

Radiation from a 125I source and a non-image-forming detector was used for non-destructive measurements of root caries progression. Blocks were cut parallel to the cementum surface of unexposed human roots. These blocks were then individually demineralized in under-saturated calcium phosphate solutions over an 84-hour period. In order for the in vitro root surface demineralization to be followed, the changes in transmission (delta T) through the blocks were measured, by 125I absorptiometry, eight times during the course of the experiment. Chemical analyses of the calcium output (delta Ca) from the blocks into the demineralizing solutions were also performed, and the rate of demineralization (Vdem) was calculated from these values. The precision of 125I absorptiometry was calculated from 176 duplicate transmission measurements, and the coefficient of variation was found to be 0.20%. The correlation coefficient between delta T and total delta Ca for each of 22 cementum/dentin blocks ranged between r = 0.934 and r = 0.998. The progression of root hard-tissue lesions observed by these two methods and by the calculated Vdem was found to be proportional to the square and cubic roots of time. The study shows that 125I absorptiometry can be used for continuous non-destructive measurements of root hard-tissue demineralization in vitro.

Calcium↗
PubMed1988

Dissolution of calcium fluoride in human saliva.

The dissolution behavior of calcium fluoride in saliva was investigated. Chemically pure calcium fluoride (200 mg) was equilibrated in 10 ml of either saliva or distilled water for 3 weeks or repeatedly exposed, at 15-min intervals, to 10 ml of fresh solutions of saliva, distilled water, or phosphate- or calcium-containing solutions. Calcium fluoride dissolved more readily in water than in saliva. The study confirmed that exposure to saliva caused formation of a dissolution-limiting layer and that this layer consists of surface-adsorbed phosphates and showed in addition that the dissolution rate was continuously reduced with time of exposure to saliva or phosphate buffer. Calcium fluoride-like material, formed on enamel by treatment with 2% NaF solution, was shown by scanning electron microscopy to have higher stability in saliva than in water after 3 weeks' incubation.

Calcium↗
PubMed1987

The diluting effect of saliva on the sucrose concentration in different parts of the human mouth after a mouth-rinse with sucrose.

Saliva at four buccal sites [between the upper (UC) and lower (LC) central incisors, and between the upper (UM) and lower (LM) second premolar and first molar], and also whole saliva, was collected from 10 subjects at 0.5, 2.5, 5.5 and 10.5 min after a rinse with 10 ml of 0.3 mol/l sucrose solution. After 0.5 min, unstimulated salivary flow rate was inversely correlated with sucrose concentration in whole saliva (p less than 0.05). Sucrose concentration decreased faster at LC than at other sites. Sucrose dilution at UC and LC was inversely correlated (p less than 0.05) with salivary flow rate at times after 0.5 min. At 10.5 min, the sucrose concentration at all sites was significantly correlated (p less than 0.05) with the salivary flow rate.

Adult↗
PubMed1987

Physiological factors influencing salivary clearance of sugar and fluoride.

The salivary clearance of sugar and fluoride is influenced by several physiological factors not yet fully investigated or understood. There are reasons to believe that these factors influence both the acid production by sugar fermentation in the dental plaque and the cariostatic action of fluoride on the enamel surface and its immediate environment. This paper presents theoretical and experimental considerations of physiological factors which influence the kinetics of sugar and fluoride in the oral cavity.

Fluorides↗
PubMed1985

The effects of different concentrations of sucrose, fructose, and glucose on pH changes by Streptococcus mitior in an artificial mouth.

The aim of this study was to determine the effects of the initial sucrose (S) concentration, as well as those of fructose (F), glucose (G), and invert sugar (F/G), on the pH developed by a layer of S. mitior, to represent dental plaque, in an artificial mouth which simulates the process of oral sugar clearance. At S, F. G, and F/G concentrations of 2% and with normal oral sugar clearance rates, the bacteria produced a smaller pH fall from S than from the other sugars; at initial concentrations of 20%, however, the differences were not significant. With constant S concentrations of 0.5-35%, the minimum pH reached was 4.03 +/- 0.14 (S.D.); with S concentrations of 50% and above, slightly but significantly higher values (4.41 +/- 0.34) occurred. However, with normal sugar clearance, the pH fall was much less than with a constant concentration and was dependent on the S concentration over the range of 0-10%, but was independent at higher concentrations. Exposure of the bacteria to S for as short a period as two min during normal sugar clearance gave a nearly maximum pH fall. This suggests that rinsing the mouth with water more than two min after consumption of sucrose in liquid form will have very little effect in reducing the pH fall in dental plaque. A more appropriate method for reducing acid formation by dental plaque would be consumption of a salivary stimulant which would increase the flow rate and buffer capacity of the saliva.

Acids↗