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Biomedical subjects

I Kleinberg

Publications and source records attributed to I Kleinberg.

At least 19 recordsLinked to original sources
PubMed1992

Comparison of the effects of galactose and glucose on the pH responses of human dental plaque, salivary sediment and pure cultures of oral bacteria.

Comparisons made in dental plaque in vivo demonstrated that galactose produces a significantly smaller decrease in pH than does glucose. In vitro studies with plaque, salivary sediment and pure cultures of oral bacteria done in the absence of intraoral factors such as flowing saliva confirmed this lesser acidogenicity of galactose. Pure culture showed that most of the bacteria tested produce a moderate to large decrease with glucose but only a few do so with galactose; most produced a moderate to little or no pH response with this sugar. This suggested that the smaller decreases in pH seen in plaque in vivo with galactose were largely due to bacterial differences, basically that resident micro-organisms individually have less galactolytic than glucolytic capability. Variance in capability was attributed to differences in membrane transport processes and metabolic pathways normally available to bacteria for galactose and glucose catabolism. In the in vitro experiments, because plaque and sediment can produce base as readily as they can produce acid, the nitrogenous substrates identified earlier as major stimulants of base formation, urea and arginine, were concurrently examined for their attenuating effects on the galactose and glucose pH responses. These showed, consistent with its lesser acidogenicity, that galactose could be countered more readily in its ability to reduce the pH by either of these two base-forming substrates than could glucose. The effects were different with urea and with arginine, urea attenuation occurred sooner and arginine attenuation later in both plaque and sediment. The corresponding acid-base pH profiles for pure cultures were different.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1992

Use of multiple sensitivity measurements and logit statistical analysis to assess the effectiveness of a potassium-citrate-containing dentifrice in reducing dentinal hypersensitivity.

A potassium citrate-SMFP containing dentifrice was tested in a double-blind 8-week clinical trial on subjects with a history of dentinal hypersensitivity. A dentifrice containing SMFP but no potassium salt was used as the control and a 2nd test dentifrice containing potassium nitrate-SMFP was assessed at the same time. The sensitivity of the subjects was evaluated at 0, 3 and 8 weeks using electrical and tactile methods plus a 1-s air blast. The sensitivity scores for each subject at each examination were summarised as a proportion of the examined teeth deemed sensitive. Assessment of any effects of the dentifrices was via an analysis of covariance of the logit transformation of these proportions with the baseline value as the covariate. The use of this novel method of analysis had the advantage of taking into account changes in sensitivity of all of the teeth, both sensitive and non-sensitive, since electrical measurements indicated effects on both. Of the original 120 subjects, 111 completed the trial and the 3 dentifrice groups remained well balanced for age, sex and sensitivity. All 3 dentifrice groups showed statistically significant reductions in sensitivity over the 8 weeks. However, the potassium citrate-SMFP dentifrice was significantly more effective than either the control SMFP dentifrice, or the potassium nitrate-SMFP dentifrice, at reducing sensitivity after 3 weeks, and this difference plus further sensitivity reduction with all 3 dentifrices was observed after 8 weeks.

Adolescent↗
PubMed1992

Salivary and metabolic factors involved in oral malodor formation.

Saliva plays a central role in the formation of oral malodor. Such formation has as its basis bacterial putrefaction, the degradation of proteins, and the resulting amino acids by microorganisms. Saliva provides substrates that are readily oxidized and in the process facilitates oxygen depletion. This favors the reduced conditions conducive to production of odoriferous volatiles. At the same time, saliva is a major source of oxygen for the oral bacteria which generally is inhibitory of their formation. The pH is also critical to malodor development; acidity inhibits, whereas neutrality and alkalinity favor malodor production. Since the pH on oral mucosal surfaces where odor formation occurs is largely determined by the fermentative and putrefactive activities of the adhering bacteria, these acid-base processes are necessarily of major regulatory importance. Because oral malodor and periodontitis both involve excessive oral putrefaction, a better understanding of putrefaction could lead to more substantive methods of oral malodor treatment than exists today, as well as identifying new approaches to amelioration of the bacterial attack on the soft tissues leading to the destruction associated with periodontal disease.

Dental Plaque↗
PubMed1990

Oxygen uptake and its relation to pH in a human salivary system during fermentation of glucose.

Oxygen consumption by the mixed bacteria in salivary sediment was examined in relation to the decrease in pH that occurs when glucose at different concentrations (2.8 mM-1.68 M) was fermented in 4 h incubations at 37 degrees C. These experiments demonstrated that (i) the use of oxygen was extremely rapid, resulting in all cases in the PO2 decreasing within 1-2 min from atmospheric PO2 (approx. 20 kPa) to levels at or near zero; (ii) a period of about 30 min of reduced oxygen uptake consistently occurred after the initial PO2 drop, so long as salivary supernatant was present and the pH was allowed to fall; (iii) except for 11.2 mM glucose, the PO2 was kept at or near zero throughout each incubation with all glucose concentrations tested because of rapid oxygen consumption by the sediment bacteria--oxidizable substrates in the sediment and in added salivary supernatant contributed significantly to the prolonged oxygen depletion; (iv) the pH was important for determining the relative contributions of glucose and supernatant to the uptake of oxygen by the sediment bacteria and for observations (ii) and (iii). When the acids produced during aerobic degradation of glucose were tested for stimulation of oxygen uptake, L(+)lactic stimulated more rapid uptake than did D(-)lactic acid, whereas acetic and propionic acids showed none. These findings were in agreement with a metabolic scheme proposed earlier for aerobic degradation of glucose by the sediment microflora, and indicated where and how oxygen utilization might be involved in glucose fermentation.

Acetates↗
PubMed1990

Constituents of salivary supernatant responsible for stimulation of oxygen uptake by the bacteria in human salivary sediment.

The 10,000 g supernatant of wax-stimulated whole saliva was fractionated by gel filtration and its components were tested along with amino acids, small peptides and urea for their ability to stimulate this oxygen uptake, and for their effects on pH. Fractions containing the larger components, the proteins and large peptides, stimulated much less oxygen uptake than unfractionated supernatant, and caused a small decrease in pH. Analysis with anthrone indicated that both these effects were due mainly to the carbohydrate associated with these constituents. In contrast, fractions containing the remaining lower molecular-weight components stimulated substantial oxygen uptake and a rise in pH; both effects were like those seen with whole saliva supernatant. The oxygen effects were attributed mainly to certain amino acids and small peptides in the small molecular-weight fractions. Ornithine, arginine, proline and glutamic acid consistently stimulated oxygen uptake by the oral microflora in a test of 23 amino acids with the sediments of 13 subjects. Ornithine and arginine at the same time stimulated a significant rise in pH, whereas the other two amino acids showed no such effect. Variable and sometimes significant oxygen uptake was seen with alanine, aspartic acid, asparagine, glutamine and cysteine in 4-7 of the subjects; infrequent or no effects were seen with the remainder of the amino acids tested. There was some evidence to suggest that amino acid stimulation of oxygen uptake may be inducible. Urea had no effect on uptake but did contribute significantly to the pH rise. Small peptides containing those amino acids that could stimulate oxygen uptake also stimulated such uptake; peptides without such acids did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Oral malodor.

Explore the source record for details and available documents.

Amino Acids↗
PubMed1990

Methods of measuring tooth hypersensitivity.

Thermal, tactile, osmotic, and electrical stimuli, as well as exposure to air, can each elicit a painful response in individuals with hypersensitive teeth, and thus provide the basis for the different methods used to measure dentinal hypersensitivity. Tactile methods range from simple use of a sharp dental explorer to devices that can quantify the probing or scratching pressure exerted generally along the cementoenamel junction. Thermal methods involve flow of air or metal probes applied in different ways. Electrical stimulus is more complex and generally consists of progressive elevation of the magnitude of the stimulus until a sense of prepain rather than pain is felt. More than one method is usually needed in order to assess dentinal hypersensitivity, which has been estimated to affect one in every seven patients that visit a dental office.

Dentin Sensitivity↗
PubMed1989

Incidence of selected ureolytic bacteria in human dental plaque from sites with differing salivary access.

Saliva is the main source of urea in the human mouth and may be responsible for the predilection of ureolytic bacteria for certain tooth sites. As a test of this hypothesis, the ureolytic bacteria, Haemophilus parainfluenzae, Actinomyces naeslundii, Actinomyces viscosus and coagulase-negative oral staphylococci, were enumerated in supragingival plaque from various sites in each of 10 subjects. The sites sampled included the maxillary and mandibular incisors (chosen because the lower incisors are more exposed to the submandibular-sublingual secretion than the upper) and the maxillary and mandibular molars (the upper molars being closer to the source of parotid saliva). After dispersion of the plaque samples in saline, subsamples of each suspension were plated on appropriate selective media and other subsamples were taken for nitrogen analysis to measure the amount of plaque sampled. H. parainfluenzae that used urea was present in the largest numbers, A. viscosus was next and A. naeslundii and coagulase-negative staphylococci were least. The staphylococci and H. parainfluenzae were more numerous from mandibular than from maxillary incisors and from maxillary than mandibular molars, a pattern which suggests that salivary access favours their selection. The numbers of A. viscosus and A. naeslundii were not related to salivary access: A. viscosus was most numerous from the maxillary incisors, possibly because this site is normally the most acidic of the four studied and A. viscosus is strongly acidogenic and aciduric; the incidence of A. naeslundii had no relationship with site.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1989

Arginolytic and ureolytic activities of pure cultures of human oral bacteria and their effects on the pH response of salivary sediment and dental plaque in vitro.

Thirty-nine different microorganisms commonly found in supragingival plaque and salivary sediment were screened for their ability to raise the pH by producing base from arginine, lysylarginine and urea. Only Actinomyces naeslundii and Staphylococcus epidermidis showed significant pH-rise activity with all three compounds. Eleven bacteria demonstrated such activity with arginine and lysylarginine but not with urea. Only one, Actinomyces viscosus, produced a pH-rise with urea but not with the two arginine compounds. The remaining 26 bacteria showed little or no base-forming activity with any of the three test substrates. The ability of the different oral bacteria to produce base (especially from urea) was a less universal function than their ability to produce acid from fermentable carbohydrate. Substituting pure cultures of arginolytic or non-arginolytic bacteria for portions of the mixed bacterial populations of plaque or sediment in test incubations containing glucose and arginine altered their ability to produce pH-fall-pH-rise responses shaped like those of the Stephen curve in vivo. In general, addition of arginolytic bacteria made these in vitro pH responses less acidic, whereas addition of non-arginolytic bacteria made the responses more acidic. Because of the relatively high arginolytic activity of the plaque harvested in this study, the effect of adding non-arginolytic bacteria was more readily seen than the converse. Similar changes in levels of ureolytic microorganisms and incubation with glucose and urea had little effect on sediment or plaque being able to produce a pH-fall-pH-rise type of response. When increasing proportions of the mixed bacteria in salivary sediment were replaced with the highly cariogenic Lactobacillus casei or Streptococcus mutans, the pH minimum became slightly more acidic and then slightly more alkaline, whereas the pH-rise became progressively and significantly less. Thus arginolytic bacteria have a different and greater effect on shaping the pH response of plaque or sediment than ureolytic bacteria. A large change in the proportions of arginolytic or non-arginolytic microorganisms may be needed to make a plaque microflora potentially non-cariogenic or cariogenic, respectively.

Arginine↗
PubMed1989

Acid-base pH curves in vitro with mixtures of pure cultures of human oral microorganisms.

Pure cultures of microorganisms commonly found in supragingival plaque were incubated alone and in combinations to determine the bacterial contribution to the pH-fall-pH-rise that is the central characteristic of the Stephan-curve pH change seen in plaque in vivo after brief exposure to a sugar solution. To avoid the complicating conditions of saliva flow and plaque diffusion, experiments were done with bacterial suspensions in incubations in vitro. In an initial experimental series where each microorganism was incubated only with glucose, all but a few produced the initial pH fall. Some also showed a subsequent small, sharp rise in the pH which then quickly levelled off; this was due to metabolism of endogenous substrate accumulated by most microorganisms during their growth in culture. When arginolytic and non-arginolytic bacteria were each then incubated with both glucose and arginine present (the glucose substrate to stimulate a pH fall and the arginine to stimulate a pH rise), the non-arginolytic gave a progressively more acidic pH response with progressive increase in the cell concentration, whereas the arginolytic bacteria produced a much smaller and variable pH decrease with similar cell concentration increase. Mixing pure cultures of either arginolytic or non-arginolytic bacteria gave acid-base pH responses similar to those of their respective pure cultures, whereas mixing arginolytic with non-arginolytic bacteria resulted in an approximate averaging of their different curves. The organisms present in highest proportion in a mixture had the greatest effects. The outcome of mixing the most numerous streptococcal and actinomyces species found normally in supragingival plaque indicated that the well-established difference in the acidity level of the Stephan pH response of caries-active and caries-inactive plaques could be due to differences in the proportions of their arginolytic and non-arginolytic members.

Arginine↗
PubMed1985

Clearance of glucose and sucrose from the saliva of human subjects.

The ability of 20 healthy people to clear test solutions of sucrose (0.73 M) and glucose (1.4 M) from the mouth was examined. Both sugars were cleared within 20 min in a two-step manner. Rapid clearance occurred between 0 and 6 min; much slower clearance occurred thereafter. It took 7.2 min with glucose and 6.3 min with sucrose for the saliva-sugar concentration to fall to 1 mg/ml. Salivary flow, stimulated during sugar exposure, decreased in a two-step pattern similar to sugar clearance. Evidently, clearance was dependent on the rate of flow of saliva which took about 1 h to return to its resting flow level. Comparison of the pattern of sugar clearance to the Stephan curve (the rapid pH fall followed by a slow pH rise seen after rinsing with sugar solutions) indicated that the pH-fall phase of the curve occurs during the initial period of rapid sugar clearance and salivary flow, and the pH-rise phase occurs during the subsequent period of slower clearance and slow saliva flow. Comparison with the data of Swenander-Lanke (1957) [Acta odont. scand. 15, 3-156], indicated that the clearance of sugar solutions also reflects the clearance of sugar-containing solid foods from the mouth.

Adult↗
PubMed1985

Oral effects of sugars and sweeteners.

Increasingly, sweeteners are being used in the diets of caries-prone individuals to reduce sugar intake. Such substitution deprives the bacteria in the dental plaque of the sugars many of them use to produce the acids that cause demineralization of tooth tissue and development of the caries lesion. Sweeteners are particularly effective replacements for dietary sugars because they also stimulate the flow of saliva which can, through several mechanisms, prevent demineralization and even bring about remineralization of already demineralized enamel, dentine or cementum. More saliva means that more of its nitrogen-containing substances will reach the dental plaque where they can be degraded by plaque bacteria and thus produce base and the alkaline conditions that are conducive to a shift from tooth demineralization to tooth remineralization. At the same time, the additional saliva brings to the plaque more calcium and phosphate ions, the necessary ingredients for the remineralization process. At alkaline pH, saliva also provides a source of easily solubilized calcium phosphate that, in association with salivary carbohydrate protein, becomes part of the dental plaque. Because it is dissolved by acid more easily than is the calcium phosphate of the tooth, plaque calcium phosphate acts as a substitute for the tooth tissues when periods of acid attack occur following sugar ingestion. It is proposed that diagnostic tests be developed that can conveniently determine the acid-base and demineralization-remineralization potentials of different dental plaques and that these tests be used to determine the extent to which sugars in the diets of caries-active individuals be replaced with sweeteners.

Bacteria↗