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PubMed1993

Effect of sucrose concentration on the cariogenic potential of pooled plaque fluid from caries-free and caries-positive individuals.

Pooled plaque samples were obtained from (1) coronal surfaces of two groups of caries-free (CF) subjects, (2) coronal 'white-spot' surface areas of a group of caries-positive (CP) subjects, and (3) exposed, sound root surfaces of root caries-free (RCF) and root caries-positive (RCP) subjects. The plaque samples were obtained before and 3 min after a 1 min rinse with a 0.5, 1, 2, 5 and 10% sucrose solution. Plaque fluid was then isolated from each plaque sample by centrifugation and analyzed for inorganic ions, organic acids, and pH values. With increasing sucrose concentration: (1) plaque fluid pH and the degree of saturation (DS) with respect to tooth mineral decreased; (2) the pH and DS values of CP and RCP samples were consistently lower than those of CF and RCF samples, respectively; (3) plaque fluid lactic acid concentrations increased and were consistently higher in the CP and RCP samples than in the CF and RCF samples, respectively, and (4) plaque fluid lactic acid concentrations leveled off between 1 and 5% sucrose; this occurred at lower sucrose concentrations with CP and RCP samples than with CF and RCF samples, respectively. RCP samples contained consistently higher levels of mutants streptococci than RCF samples. The chemical composition of plaque fluids, following sucrose exposure, were found to correlate well with caries history. The observed differences in lactic acid concentrations in samples from CF and CP subjects are discussed with regard to differences in microbiological composition and possible differences in plaque permeability to sucrose.

Adolescent↗

PubMed1994

Effect of xylitol and sorbitol in chewing-gums on mutans streptococci, plaque pH and mineral loss of enamel.

Seventeen subjects with more than 3 x 10(5) mutans streptococci per millilitre of saliva completed this randomised, cross-over study. Four different chewing-gums, containing: (1) 70% xylitol, (2) 35% xylitol + 35% sorbitol, (3) 17.5% xylitol + 52.5% sorbitol, and (4) 70% sorbitol, were tested. The participants used 12 pieces of each gum per day for 25 days. During the four experimental periods, they wore a removable palatinal plate containing two demineralised enamel samples, and brushed their teeth with a non-fluoridated toothpaste. The results showed that an increased concentration of xylitol in the gum resulted in a lower number of mutans streptococci in both saliva and dental plaque, although the decreases were only significant in the saliva samples (p < 0.01). The pH drop in plaque, measured in vivo after a 1-min mouthrinse with a 10% sorbitol solution, was least pronounced after the 70% xylitol gum and most pronounced after the 70% sorbitol gum period (p < 0.01). No significant differences were found after a mouthrinse with a 10% sucrose solution. All demineralised enamel samples lost mineral during the experimental periods. However, the lesion depth as well as the mineral loss values, assessed microradiographically, did not differ significantly between the four chewing-gums.

Adult↗

PubMed1994

Secondary caries in dentine around composites: a wavelength-independent microradiographical study.

Composite restorations are prone to develop secondary caries if a gap exists between tissue and restoration. The aim of this article was to quantify the effects of a fluoridating and non-F composite on secondary dentine caries in vitro as a function of time. The mineral loss in dentine was assessed in an artificial gap of 200 microns width at the composite/dentine interface; the samples were demineralised in a carboxymethylcellulose gel (pH = 5, 37 degrees C) for 8 weeks. Once a week the mineral content of the samples was determined using non-destructive wavelength-independent microradiography (WIM). After 8 weeks transversal microradiography (TMR) was done on the samples to investigate the mineral distribution of the dentine lesions. The WIM results show that the fluoride-releasing composite decreased the dentine demineralisation statistically significantly with respect of the non-F control by approximately 45%. The mineral loss values are found to be strictly proportional to time; the demineralisation reduction is expected to continue over extended periods of clinical relevance. The TMR results show that the fluoridating composite reduced the mineral loss values significantly with respect to the non-F control by approximately 55%, but had a negligible effect on the lesion depth values. This study indicates that WIM is an accurate and reliable technique to measure in vitro secondary dentine caries next to a composite restoration as a function of time.

Animals↗

PubMed1994

Influence of oral hygiene on early enamel caries.

For 548 children aged 4-16 years, mean (+/- SD) age 10.3 +/- 2.7 at visit 1, the dental status was recorded at four consecutive 6-monthly visits. Simultaneously oral hygiene was scored according to a modified patient hygiene performance (PHP) index after application of disclosing solution and before the dental examination. The following cariogenic changes could be observed: initiation (white spot formation), progression (cavitation), stabilisation and regression (disappearance of a white spot). The PHP score was examined in relation to these changes in smooth surfaces, as well as in fissures. For fissures when oral hygiene worsened, stabilisation of a white spot increased significantly. Also, regression of a white spot into sound enamel increased with poor oral hygiene, but the significance was only marginal. White spots turning into cavities, however, did not change with poor oral hygiene. It was speculated that under low oral hygiene conditions the remaining plaque of children receiving intensive fluoride treatment can bind fluoride to the fissure surfaces, thereby promoting enamel maturation concomitant with stabilisation and regression of white spots, which in an earlier study were also found to be dependent on posteruptive age.

Adolescent↗

PubMed1995

Comparisons of in vitro root caries models.

The purpose of this article is to compare various model systems for the production of in vitro root caries and to assess their ability to simulate the naturally occurring root caries process. Partially saturated buffer models and gel models were evaluated using polarized light microscopy and both qualitative and quantitative microradiography. All model systems showed very similar lesion formation when examined under polarized light. When microradiographs were compared, the systems which contained fluoride, showed clear radiopaque bands within the lesion. The bands, which occurred only in the presence of fluoride, appeared to be due to remineralization. When using an in vitro system that simulates the natural root caries process, it is imperative to understand the components of the particular model, as well as its limitations, and to be aware of the need for more than one evaluative technique.

Buffers↗

PubMed1995

Formation of phosphate-containing calcium fluoride at the expense of enamel, hydroxyapatite and fluorapatite.

During the caries process complex reactions involving calcium, phosphate, hydrogen and fluoride ions as main species take place. In this study the precipitation and dissolution reactions occurring in suspensions of enamel, hydroxyapatite (HAP) and fluorapatite (FAP) on addition of fluoride were investigated under well-defined conditions. pH and pF were monitored; calcium and phosphate concentrations were measured at selected times; the solid phases were examined by infra-red, X-ray diffraction and transmission electron microscopy. Precipitation of phosphate-containing calcium fluoride crystals, CaF2(P), can cause severe reduction in the calcium ion concentration and release of hydrogen ions from the precipitated phosphate. These reactions result in considerable dissolution of enamel, HAP and even of FAP. More of the added mineral dissolves with 50 mmol/l fluoride than with 10 mmol/l fluoride, mainly due to the greater reduction in calcium ion concentration. This work shows that phosphate-containing calcium fluoride is most likely an important compound to be considered in the caries process.

Animals↗

PubMed1995

Effects of caffeine intake during gestation and lactation on the acid solubility of enamel in weanling rats.

The purpose of this study was to evaluate the effects of dietary caffeine during gestation and lactation on the acid solubility of molar teeth of weanling rats. Nineteen pregnant dams were divided into two groups. The 9 dams in the control group were fed a 20% protein diet supplemented with caffeine (2 mg/100 g BW) throughout the experiment. At birth, 8 pups were randomly assigned to each dam. Pups were killed on day 22. The 1st and 2nd molars were removed from each pup's maxilla and mandible. Four randomly selected molars from each litter were placed in a chamber and bathed with a flow of acid solution and the amount of mineral dissolved from the enamel was determined. The results showed that the amount of dissolved Ca and Mg from enamel surfaces of 1st molars from rats in the caffeine group after exposure to acid was consistently greater than that of the non caffeine group. In the 2nd molars there was no significant difference between caffeine and noncaffeine groups. Scanning electron microscopy revealed an alteration of the enamel surface of the 1st molars of the caffeine group after acid exposure. These results indicate that caffeine intake during gestation and lactation would have a deleterious effect on dental enamel of 1st molars in newborn rats.

Animals↗

PubMed1995

Ultrastructural change of enamel exposed to a normal pulsed Nd-YAG laser.

The ultrastructural changes of the enamel surface occurring due to normal pulsed Nd-YAG laser irradiation were examined by scanning electron microscopy. The melted and recrystallized enamel in the lased enamel surface was observed. A coalescence of enamel globules was caused by 10 pulses of laser irradiation. In the case of excessively repeated irradiation (3 applications of 10 pulses), new particles of enamel crystal were produced which had a larger size than the original and measured about 0.2-1.0 microns in diameter. In some portions, large-sized hexagonal particles were also observed. In fractured surfaces of enamel, the shapes of the new particles of enamel crystal varied and included granules, needles and columns. The column structure had various appearances such as being well packed, along with piled granules and hollow columns, as well as having intercrystal or intracrystal voids. It was suggested that a distinctive polygonal column shape of more than 2 microns in length might be formed in the process of homogeneous melting at high temperatures followed by uniform cooling and contraction. The recrystallized layer demonstrated significant acid resistance but was a little fragile. These results greatly support the hypothesis that a larger crystal size may cause acid resistance in enamel exposed to pulsed laser.

Crystallization↗

PubMed1996

The influence of mineral loss on the auto-fluorescent behaviour of in vitro demineralised dentine.

The aim of this study is to investigate the influence of demineralisation on the fluorescent properties of dentine. The fluorescence emission at 529 nm due to 515 nm excitation of in vitro demineralised lesions was determined with a micro-Raman spectroscope as a function of location. Results were compared with the mineral loss profiles of the same lesions measured by microradiography. The root surfaces of 6 in vitro demineralised human third molars (lactic acid CMC gel, pH 5; six groups: 0, 4, 7, 14, 18 and 21 days) were used in the experiment. Thin slices of +/- 130 microns were cut perpendicular to the tooth axis. The fluorescence scans corresponded to mineral loss profiles. Confocal microscope images showed increasing fluorescence with increasing mineral loss. From these results it is concluded that this mineral loss causes an increase in auto-fluorescence by a factor of at least 10, therefore the chromophore causing this green fluorescence must be organic in nature. De-quenching or modification of this fluorophore due to the demineralisation process is probably the cause for the increase of the green fluorescence.

Dentin↗

PubMed1996

Histological validation of electrical resistance measurements in the diagnosis of occlusal caries.

Diagnosis of occlusal caries is difficult from visual and radiographic examination. The use of electrical resistance measurement has been described previously and reported to be a potentially sensitive alternative technique. This is possibly due to the decreased resistance of carious pits and fissures. The aim of this study was to validate a prototype electrical caries monitor for the diagnosis of caries in pits and fissures in vitro using a microfocal radiographic technique. Thirty discrete sites were investigated in 10 extracted molar teeth. Electrical resistance measurements were recorded at each site and thick sections (approximately 0.65 mm) prepared for microfocal radiography. Microfocal radiography indicated that six sites were sound, 10 had enamel caries and 14 dentine caries. At a resistance value of 2.2 M(OMEGA), below which a site was regarded as carious and above which it was regarded as sound, electrical resistance measurements proved sensitive (92%) and specific (100%). Quantification of mineral content indicated that mineral loss in enamel may influence resistance measurement more than lesion depth.

Adult↗

PubMed1996

A method to monitor dental demineralisation in vitro.

This paper presents an in vitro method for monitoring the progression of dental hard tissue demineralisation using consecutive, standardised radiographs. Reliability and factors affecting the reproducibility of this method were established by replicate measurements and comparison to histological evaluation. Whereas assessment of the extent of the lesions by measuring linear distances was highly reproducible, reproducibility of measurements of the central depth of a lesion is affected by the superficial extension and the surrounding hard tissue. Radiographic imaging underestimates the extent of demineralisation as compared to histological analysis.

Disease Progression↗

PubMed1996

Preparation and measurement of artificial enamel lesions, a four-laboratory ring test.

Transversal microradiography is the most widely accepted method used to study changes in mineral content profiles. In spite of its widespread use, relatively little information is available on its validity and reproducibility. Following the recommendation of the Consensus Conference on Intraoral Model Systems, this study was designed to explore reproducibility of lesion analysis within a laboratory and comparability of analysis among various laboratories. Incipient enamel lesions were produced by four research groups using both a common ('standard') and a local ('preferred') protocol. Sections were produced by each group and allocated to 'mixed' bags of specimens, which were analysed by the groups. With the chosen scheme some sections were analysed six times by the same group (as an internal reference standard) while others were analysed by all four groups. The data for the mineral content profiles were expressed as the integrated mineral loss (IML) value and lesion depth. The results showed the lesions produced with the standard protocol to be in the range 2,000-3,000 vol% mineral x microns for IML. The IML of the lesions produced with the preferred protocol varied between 1,800 and 6,300 vol% mineral x microns. Variation in IML values could be attributed to the biological variation between lesions, but also to time (of microradiograph production) and measurement effects, calibration of the magnification of the specimens, and the parameters used in the algorithm to calculate IML. Some of these parameters also affected the lesion depth. It is advised to standardise (or at least report) the method of calculation of IML, and to include a reference lesion between analyses in a longitudinal study as an internal standard. With the data produced, it was calculated that the number of lesions required to differentiate between preventive treatments varied substantially among laboratories. The recommendations given will improve the power of the screening methods for caries-preventive agents for which microradiography is an essential analytical method.

Analysis of Variance↗

PubMed1996

In vitro and intra-oral investigations into the cariogenic potential of human milk.

The acidogenic and cariogenic potential of plain and supplemented human and bovine milk was determined by pH tests and with intra-oral experiments. Human milk produced a lower pH than bovine milk and bovine milk with a 2% lactose supplement. Human milk caused greater softening of enamel than bovine milk in the intra-oral tests. This could be modified by supplementing with calcium and phosphorus to the levels present in bovine milk.

Analysis of Variance↗

PubMed1997

Determination of plaque pH changes within the trough of an in situ appliance used to study mineral changes in early carious lesions.

Plaque pH was measured using a glass combination pH microelectrode of plaque deposits lining the trough of an intra-oral appliance which contained single sections of human teeth with artificial enamel lesions. Plaque exposure to a 10% sucrose solution produced significantly lower plaque pH levels than a solution of sorbitol gum extract. The subsequent flow of saliva over the plaque/pH electrode interface resulted in a significant and rapid increase in pH. Repeat experiments, using deionised water instead of saliva, demonstrated no increase in pH at the plaque/electrode interface. This system may provide a convenient method of producing plaque suitable for repeated pH analysis in intimate association with artificial enamel lesions. This may permit further study of the relationship between plaque acidogenicity, salivary buffering capacity and mineral change within the incipient enamel lesion.

Adult↗

PubMed1997

The effect of airflow on site-specific electrical conductance measurements used in the diagnosis of pit and fissure caries in vitro.

There has been renewed interest in the electronic diagnosis of occlusal caries using measurement of conductance or impedance. One of two previously manufactured electronic caries detectors (the Vanguard electronic caries detector, Massachusetts Manufacturing Corporation, Cambridge, Mass., USA) had a probe tip with an integral air supply. Airflow is essential for removing superficial moisture and preventing surface conduction to the gingival margin. The aim of this study was to determine the effect of airflow on electronic diagnosis of occlusal caries using a prototype electronic caries meter (ECM II. LODE, Groningen, The Netherlands) fitted with a flow meter. Stable conductance readings were taken at 76 discrete sites on 32 extracted teeth with no visible signs of cavitation, at 3 airflows: 5, 7.5 and 10 litres/min. The stable conductance scale was a continuous scale from -0.45 to 13.25 and set by the manufacturer. Histological validation was carried out on macroradiographs of sections cut to include each sample site. The histological picture was compared with the stable conductance readings taken at various airflows. Sensitivity and specificity were calculated using different conductance readings to differentiate sound and carious sites, and receiver operating characteristic (ROC) curves constructed. Of the sites, 32% had enamel and dentine caries and 33% had enamel caries. The ROC curves showed airflow to be highly relevant. An airflow of 5 litres/min was shown to be inadequate and led to large numbers of false-positive diagnoses. A minimum airflow of 7.5 litres/min was required to achieve optimum sensitivity (92%) and specificity (87%) for dentine caries diagnosis.

Air Movements↗

PubMed1997

Effect of a fluoridated toothpaste on lesion development in plaque-filled dentine grooves: an intra-oral study.

Fluoride can inhibit caries at plaque-retention sites, but some studies indicate that fluoride is less effective in fissures than on smooth surfaces. To study the efficacy of fluoridated toothpastes at plaque-retention sites, an intra-oral model was used with bovine coronal dentine discs, in which grooves of two different widths were sawn. The discs were mounted in the partial prostheses of 31 participants divided into two groups. One group brushed with a non-fluoridated toothpaste and a second with a paste containing 1,000 ppm fluoride as NaF. After 3 months, the specimens were retrieved and from each a thin section was taken for microradiographic analysis. Lesions which developed in the grooves resembled natural lesions in terms of the presence of a surface layer and the mineral content profiles. Extensive lesions followed the direction of the dentinal tubules. The mineral loss was quantified half-way into and at the base of the grooves and ranged from 0 to 20,000 vol% x microns. Analysis of variance showed that the mineral loss was significantly influenced by the treatment and the width of the grooves (p < 0.001). In the broad grooves the average mineral loss was 19% smaller in the fluoride group than in the non-fluoride group, in the narrow grooves this value was 7%. Taking the two treatment groups together, the average mineral loss was largest half-way into the broad grooves (4,921 vol% x microns) and smallest at the base of the narrow grooves (2,289 vol% x microns). The results with this new intra-oral model indicate that the dimensions of small grooves in dentine, and thus their accessibility, determine not only their susceptibility to caries but also the protective effect of a fluoridated toothpaste.

Adult↗

PubMed1997

In situ relationship between sucrose exposure and the composition of dental plaque.

The aim of this study was to analyze the composition of dental plaque according to sucrose exposure. Twelve adult volunteers took part in this crossover study done in four phases of 28 days each. For each phase of the study, an acrylic resin appliance containing four human dental enamel blocks was constructed for each volunteer. A 20% sucrose solution was dripped onto the enamel blocks from 0 to 8 times/day. The volunteers were randomly assigned to the treatments. During the experimental period all the subjects used fluoride-free dentifrice, refrained from brushing the enamel blocks and drank water fluoridated at 0.70 ppm F. After each phase the concentrations of fluoride (F), calcium (Ca), phosphorus (P) and total carbohydrate were determined in dental plaque. Statistical analyses showed that frequent sucrose exposure significantly (p < 0.05) reduced the F, Ca and P concentrations in dental plaque, but increased the alkali-soluble carbohydrate concentration. The results suggest that the cariogenicity of dental plaque formed in the presence of sucrose cannot be attributed only to its higher porosity, but the lower inorganic concentration may also be important.

Adult↗

PubMed1997

Protective effect of hexetidine against in vitro bacterial demineralisation of bovine enamel and dentin in the presence of fluoride.

Bovine enamel and dentin specimens were overlaid with acidogenic Streptococcus mutans suspensions in agarose. In this model, the minimal demineralisation-inhibiting concentrations (MDIC) of hexetidine was determined in the presence of fluoride. A commercially available mouthwash containing 0.1% (2.9 mmol/l) hexetidine was diluted serially and added to the bacterial suspensions together with 0, 5.3, or 26.3 mumol/l fluoride (NaF). After 22 h of incubation at 37 degrees C the bacterial suspensions were removed and assessed for calcium and lactate. The results showed significant inhibitory effects of hexetidine on the demineralisation of the enamel specimens with a MDIC between 15 and 31 mumol/l hexetidine. In the presence of fluoride, approximately fourfold higher concentrations of hexetidine were needed for a significant additional protection of the enamel. No synergistic effect between hexetidine and fluoride was observed. For the demineralisation of the dentin specimens, the MDIC of hexetidine had a value between 31 and 61 mumol/l. At both these concentrations the dentin specimens were relatively less protected in the presence than in the absence of fluoride, and some synergistic effect between hexeditine and fluoride was observed.

Animals↗