Analytical and ultrastructural studies of pellicle on primary teeth.

The pellicle on permanent enamel has been thoroughly studied. The aims of this study were to compare the chemical composition, rate of formation, and ultrastructural appearance of pellicle formed on deciduous enamel in children with those on permanent teeth. This was done by amino acid analyses, Auger analyses, and transmission electron microscopy. The amino acid composition of 2-h pellicle on deciduous and permanent enamel had an overall similar pattern, but the contents of serine, glycine, and tyrosine were statistically significantly different. An initially slower pellicle formation and a thinner 2-h pellicle without a globular structured second layer was observed on deciduous enamel. The results indicated therefore distinct differences in chemical composition, rate of formation, and ultrastructural appearance between pellicle on primary teeth and that on permanent teeth.

Caries development in fluoridated and non-fluoridated deciduous and permanent enamel in situ examined by microradiography and confocal laser scanning microscopy.

The aim of the study was to compare initial caries development in fluoridated and non-fluoridated deciduous and permanent enamel in situ. Enamel slabs were mounted in removable appliances and worn for 4 wks. Significantly larger lesions developed in deciduous than in permanent enamel when no topical fluorides were used. Fluoride mouthrinsing partly prevented lesion development in deciduous and completely in permanent enamel. Initial enamel caries not detected by microradiography can be visualized by CLSM (confocal laser scanning microscopy).

Fluoride release and uptake in vitro from a composite resin and two orthodontic adhesives.

The aim of this study was to investigate the fluoride release and uptake characteristics of a composite resin (Tetric) and two orthodontic adhesives (VP 862 and Saga Bond), with a type-II glass ionomer cement (Ketac Fil) as a control. Test specimens in 2 ml deionized water released fluoride over a period of 33 days. Ketac Fil released 54 and 15 times more fluoride than Tetric after 24 h and 1 month, respectively, whereas the two adhesives released amounts between these values. Specimen exposure to 1000-ppm NaF solution increased the 24-h fluoride release from all materials, with near pre-exposure levels reached after 2-3 days. Ketac Fil had a tendency to recharge not seen with the other materials. The ytterbium trifluoride filler in Tetric has a very low water solubility, and it is therefore suggested that the increases in fluoride release from Tetric after exposure to fluoride were most probably due to release of surface-retained fluoride.

Rate of pellicle formation in vivo.

The acquired enamel pellicle is thought to be the result of a selective adsorption of salivary proteins and to be involved in the protection of the enamel surfaces. The chemical composition of the 2-h acquired enamel pellicle is fairly well established. However, the rate of formation and the amino acid composition of the initially formed enamel pellicle have been little investigated. The aim of this study was therefore to examine the rate of pellicle formation and the amino acid composition of the initially formed enamel pellicle. Samples of human enamel surfaces were carried in the mouth for various periods of time (2.5 min to 10 h). Rate of pellicle formation was indicated as a function of oral exposure time and the time necessary to remove the proteinaceous film from the surfaces by argon ion sputtering. The chemical composition of the initially acquired pellicle was examined by amino acid analyses of pellicle material collected in vivo from enamel surfaces 15 min and 1 h after pumicing, respectively. The pellicle reached an initial thickness in about 2-3 min, at which level it stayed for about 30 min. The thickness of the acquired pellicle then increased to about three times the initial thickness and stayed at that level for the rest of the experimental period (10 h). Amino acid analyses of pellicle material collected after 15 min and after 1 h were different in that the amino acid profiles of the 15-min pellicle only contained traces of proline and arginine. It may be argued that the pellicle formation proceeds in two stages owing to the adsorption of protein aggregates and that the chemical compositions of the pellicles of the two stages differ.

A comparison of the anticaries effect on the primary dentition of two dentifrices containing 250 ppm and 1450 ppm fluoride.

The purpose of the study was to compare the anticaries effects of two dentifrices containing sodium fluoride with fluoride concentrations of 250 ppm and 1450 ppm on the primary dentition of kindergarten children. A total of 319 children participated in the study (155 in the low-fluoride and 164 in the high-fluoride group) and brushed their teeth daily under supervision in their kindergartens. The children were examined by one dentist trained according to the procedures of O'Mullane et al., and carious lesions were recorded at the cavitation level according to the WHO criteria. At the final examination after 22 months, the groups comprised 83 (low-fluoride group) and 89 (high-fluoride group) children. The differences in mean dmfs and dmft increments between the two groups were not statistically significant. In both groups about 57% of the children remained caries free. Excluding these children from the analyses, the mean dmfs increment was significantly lower in the high-fluoride group, but not the mean dmft increment. The mean dmfs increment excluding occlusal surfaces was significantly lower in the high-fluoride group.

Amino acid composition of acquired enamel pellicle collected in vivo after 2 hours and after 24 hours.

The adsorption of salivary proteins to dental enamel during pellicle formation has been shown to be a specific process and dependent on the chemical composition of the surfaces. Most studies on the amino acid composition of the acquired enamel pellicle have, however, been performed on the "2-h-pellicle" under controlled experimental conditions. This may have eliminated some natural factors involved in pellicle formation. The aim of the present study was to investigate the effect of extended time of formation and diet on the pellicle formation. Pellicle material was collected from the same subject after 2 and after 24 h when food and beverages were avoided, and after 24 h with the intake of a normal diet. The collected pellicle materials were hydrolyzed and amino acid analyzed. The results showed that pellicle material collected after 24 h and fasting had a chemical composition similar to the "2-h-pellicle", whereas pellicle material collected after 24 h and a normal diet was different, indicating a dietary contribution to pellicle formation or a bacterial degradation of the pellicle.

Chemical analysis and scanning electron microscopy of acquired pellicle formed in vivo on stannous fluoride treated enamel.

Stannous fluoride (SnF2) has been shown to be an effective caries preventive agent. After topical treatment of enamel surfaces, two reaction products have been demonstrated to precipitate on the surfaces, a larger type of globules, probably a calcium fluoride like product, and a smaller type of globules, probably a tin phosphate. The aim of the present study was to examine the amino acid composition and the formation of the acquired pellicle on SnF2-treated enamel in vivo. The chemical composition was examined by amino acid analysis of pellicle material collected in vivo from SnF2-treated enamel surfaces. Pellicle formation was examined by scanning electron microscopy on SnF2-treated enamel fragments carried in the mouth for 2 h. The results showed that pellicle material was formed in abundant amounts and covered the globular surfaces following the SnF2 treatment. The chemical analyses showed amino acid profiles with high content of acidic and neutral amino acids. The profiles were different from known amino acid profiles obtained from analyses of pellicle material collected from untreated enamel surfaces.

Survival analysis of amalgam restorations in long-term recall patients.

The longevity of amalgam restorations in premolars and first and second molars in long-term recall patients has been calculated by means of survival analysis. The present retrospective longitudinal study includes information from 32 patients and their records over a time period of 17 years. The data were recorded by six dentists. The estimated time of 90% survival was 7 years. After 17 years the survival estimate decreased to 78%, indicating a favorable longevity of amalgam restorations in patients taken care of in an established recall system.

Effect of sodium lauryl sulfate on protein adsorption to hydroxyapatite in vitro and on pellicle formation in vivo.

Sodium lauryl sulfate (SLS) is widely used as a synthetic detergent in dentifrices. It has been shown to have high affinity for hydroxyapatite (HA), and the binding mechanism has been proposed to be electrostatic, involving the negative sulfate terminals of the SLS and the calcium sites on the HA. The binding of SLS to HA may thus well interfere with the protein adsorption to HA. The aim of the present study was to examine the effect of SLS on protein adsorption in vitro and on pellicle formation in vivo. The effect on protein adsorption was studied using ion exchange chromatography. The effect on pellicle formation was studied using enamel fragments carried in the mouth. The study showed that SLS-treated HA adsorbed less protein than untreated HA. Protein adsorbed to SLS-treated HA was more firmly bound to HA as compared to untreated HA. SLS-treated enamel fragments carried in the mouth showed a slower rate of pellicle formation than non-treated enamel.

Interindividual and longitudinal studies of amino acid composition of pellicle collected in vivo.

The formation of the acquired enamel pellicle is due to the adsorption of salivary proteins to the enamel surface. This adsorption is assumed to be specific and is dependent on the chemical characteristics of the surface. The aim of the present study was to investigate the consistency of the chemical composition of the acquired pellicle collected in vivo. Inter- and intraindividual differences in the chemical composition of pellicle material were examined during 2 yr in three different individuals. The amino acid profiles obtained from pellicle analyses were compared to hydrolyzed whole saliva collected at the same time as the pellicle material. The results showed that the amino acid composition of pellicle was consistent both between and within the individuals. The amino acid profiles obtained from the analyses of the saliva samples were different from the pellicle profiles, illustrating the selective nature of pellicle formation. This supports the contention that the adsorption of salivary proteins to dental enamel is a very specific process.

Protein adsorption to hydroxyapatite and to calcium fluoride in vitro and amino acid analyses of pellicle formed on normal enamel and on calcium-fluoride-covered enamel in vivo.

Fluoride treatment of enamel has been reported to result in the formation of a layer of a CaF2-like material on the enamel surface. Protein adsorption to enamel is a specific process dependent on the nature of the surface, and little is known about protein adsorption to CaF2. Albumin and lysozyme were adsorbed to hydroxyapatite (HA) and CaF2 powder in vitro, and protein adsorption patterns constructed. In vivo pellicle was collected from three volunteers from fluoride-treated enamel and from normal enamel, and the amino acid compositions analyzed separately. The results showed that CaF2 took up small amounts of proteins as compared with HA. When the CaF2 was pretreated with a phosphate buffer, pH 6.8, the protein adsorption increased markedly. The amino acid analyses showed no major differences in the amino acid compositions between pellicle collected from CaF2-covered enamel and pellicle collected from normal enamel. This lack of difference is presumably due to the adsorption of phosphate ions to the CaF2 crystals and hence changed surface properties.

Effect of pyrophosphate on protein adsorption to hydroxyapatite in vitro and on pellicle formation in vivo.

This study showed that pyrophosphate (PP) desorbed an acidic protein (albumin) from hydroxyapatite (HA) more effectively than phosphate and that HA pretreated with PP took up markedly less protein than untreated HA. The protein which adsorbed to PP-treated HA was more loosely bound than that adsorbed to untreated HA. In vivo experiments showed that pellicle formed more slowly on PP-treated etched enamel than on untreated controls. The possible clinical implications of these findings are discussed.

Chemical and morphological studies of the acquired pellicle formed subgingivally on dentin in vivo.

The morphological appearance and chemical composition of the subgingival pellicle were studied, using Auger analysis and scanning and transmission electron microscopy. A pellicle was formed on pieces of dentin (2 X 2 X 1 mm), prepared from freshly extracted teeth after root planing. The dentin slabs were inserted for 2 h into healthy gingival sulci. Control slabs cemented supragingivally were used for comparison. The results confirmed the presence of an organic film on the surface of all slabs. Auger analysis of the organic film showed the presence of Ca in the supragingival integument but not in the subgingival integument. The subgingival pellicle was in all cases thicker than the supragingival pellicle. The transmission and scanning electron microscopy observations confirmed the presence of a film essentially free of bacteria on the subgingival specimens and also indicated a possible morphological difference between the supra- and sub-gingival pellicle.

Effect of sucrose rinses on bacterial colonization on amalgam and composite.

The effect of sucrose rinses on the bacteriology of early plaque on enamel, amalgam and composite was investigated. Three test persons rinsed with a 15% sucrose solution every hour for 12 h prior to the insertion of the test materials. Round disks of amalgam and composite were carried on the buccal surfaces of the upper molars for 2 1/2 h. Sucrose rinses were found to have an effect both on plaque composition and on the amount of plaque on composite, but not no enamel or on amalgam. A small increase in the number of Streptococcus mutans as well as a general increase in the number of bacteria were found.

Is sulphated blood-group substance in pancreas a factor in cystic fibrosis?

The present study showed that the pancreas of two monkey species contained sulphated blood-group substance. Such strongly anionic molecules are known to bind calcium, and their solutions form gels in the presence of cations. It is suggested that such a mechanism may be involved in cystic fibrosis.

Furfurals in chlorhexidine-discolored pellicle.

The purpose of the present study was to investigate the possible presence of furfurals in chlorhexidine-discolored pellicle. Pellicle material was scraped off teeth and hydrolyzed in sulfuric acid and the hydrolysate then extracted with ether and examined by thin layer chromatography and gas chromatography-mass spectrometry. The presence of furaldehyde in discolored pellicle was demonstrated by these methods. There were also indications of hydroxymethyl furfuraldehyde in the thin layer chromatograms.

Chemical analysis of a sulphated macromolecule isolated from rabbit submandibular gland.

Chemical analysis of a sulphated macromolecule isolated from the rabbit submandibular gland showed that about 70 per cent of the dry weight could be accounted for in terms of amino acids of which the acidic amino acids, proline and alanine were the most abundant. Total carbohydrate was 11%. Galactose was the main neutral sugar but galactosamine, glucosamine, neuraminic acid, glucose and mannose could also be demonstrated. Sulphate accounted for 1,4%. No uronic acid was found. The data indicate that the sulphated macromolecule from the rabbit gland is in fact a sulphated glycoprotein.