Anette Carlén

Surface characteristics and in vitro biofilm formation on glass ionomer and composite resin.

In the initial stages of dental plaque formation, early colonizing bacteria bind to receptor structures in the pellicle, a proteinaceous film formed instantly after cleaning of the tooth surface. Dental restorative materials with surface characteristics different from the tooth might affect pellicle formation and the ability of bacteria to colonize the oral cavity. In this study (i) roughness and chemical composition of glass ionomer and composite resin surfaces before and after polishing, and (ii) the adsorption of salivary proteins and bacterial adherence to the pellicle-coated surfaces were examined. Compared with unpolished composite resin, unpolished glass ionomer had higher surface roughness, contained more inorganic, positively charged components, collected more proteins, and promoted better bacterial adherence. Polishing had the most pronounced effect on the composite resin, giving an enlarged and a rougher surface with a more inorganic character. Polishing the composite resin also led to increased biofilm formation.

Composition of Pellicles Formed in vivo on Tooth Surfaces in Different Parts of the Dentition, and in vitro on Hydroxyapatite

Saliva from the major salivary glands dominates different areas of the mouth. The parotid (PS) and submandibular/sublingual (SMS) saliva differ in their protein composition, and thus, the composition of pellicles formed in various parts of the dentition might vary. In this study, proteins incorporated in 60–min pellicles from the premolar and front regions of the mouths of 4 subjects were examined using sodium dodecyl sulphate–polyacrylamide gel electrophoresis and immunoblotting using antibodies to amylase, albumin, IgA, parotid saliva agglutinin, low molecular weight SMS mucin (MG2) and proline–rich proteins. Pellicles formed in vitro on hydroxyapatite using PS, SMS and whole saliva from the subjects were examined in a similar manner. The pellicles formed in vitro and in vivo showed a major difference in the appearance of albumin. Bands of albumin were clearly stained in the samples of in vivo pellicles but were not observed or hardly visible in Western blots from the experimental, in vitro pellicles. The sites in the dentition from which a specific protein was recovered could differ between the 4 individuals. The overall protein pattern of the pellicles showed, however, characteristics typical of the saliva which may prevail in the part of the mouth where the pellicles were formed. Thus, parotid saliva agglutinin, a receptor for Streptococcus mutans, was primarily found in the premolar part of the dentition. The mucin MG2, which may mediate the adherence of Streptococcus sanguis and Streptococcus oralis, was in no case clearly seen in pellicles from the premolar region of the upper jaw. The observed variations might be important to the establishment of microflora and tooth–related disease patterns in various parts of the dentition.

Agglutinin and Acidic Proline-rich Protein Receptor Patterns May Modulate Bacterial Adherence and Colonization on Tooth Surfaces

Bacterial binding to salivary proteins may in part account for individual differences in the colonization of tooth surface. High-motecular-weight glycoproteins, agglutinins, mediate S. mutans adherence, whereas acidic proline-rich proteins mediate adherence of other early-colonizing streptococci and Actinemyces. The aim of the present study was to examine the composition of adherence-related salivary proteins and dental plaque micro-organisms in three individuals with a low, moderate, and high capacity to mediate S. mutans adherence. The S. mutans (strain Ingbritt) binding activity resided with 300-kDa agglutinin which was six-fold more prevalent in the high S. mutans binding saliva compared with the low one. Binding to all three salivas was completely by a monoclonal anti-agglutinin antibody. The moderate S. mutans binding saliva was found to contain adherence-inhibiting components. Furthermore, the low and moderate S. mutant binding salivas mediated binding of A. naeslundii strain LY7 to a greater extent the saliva with high S. mutans binding. The A. naeslundii binding activity resided with the acidic proline-rich proteins (APRPS) and paralleled the relative content of 106- and 150-residue A-PRPS. Low A. naeslundii binding coincided with an almost two-fold higher ratio of 106/150 APRPs compared the high A. naestundii binding saliva. During conventional gel filtration, a degradation of the acidic, basic, and glycosylated proline-rich proteins was evident in the saliva with high S. mutatis and low A. naeslundii binding. This saliva donor had a comparably high rate of dental plaque formation, high counts of S. mutans, and low counts of other streptococci and Actinomyces.

Minor gland and whole saliva in postmenopausal women using a low potency oestrogen (oestriol)

Many women undergo hormone replacement therapy in order to relieve menopausal and postmenopausal symptoms. Oral discomfort is common among these symptoms and studies have shown that the stimulated whole saliva flow rate is increased after combined oestradiol and progesterone replacement therapy. There is, however, no data regarding the effect of other oestrogens or of oestrogen alone on whole and minor gland saliva. In the present study, the flow rate from minor salivary glands (buccal, labial and palatal) and the secretion rate and buffer capacity of whole saliva was examined in 18 postmenopausal women (61-76 years) prior to, and during 1 year of a low potency oestrogen (oestriol) use. The ability of whole saliva to aggregate and mediate bacterial adherence as well as subjective feelings of dry mouth was also examined. For comparison, the same variables were examined in nine peri- and postmenopausal, non-medicated women (reference group, 53-61 years). During hormone treatment, the labial saliva flow was significantly increased and the complaints of dry mouth reduced. Increased stimulated whole saliva flow was seen in both the hormone and reference groups. This was also true for the stimulated whole saliva buffer capacity, which was increased parallel to the flow rate. The secretion rates were generally lower in the hormone group compared to the reference group throughout the study period. Except for stimulated whole saliva, statistical analysis at baseline revealed no age-related reduction of the saliva flow rates. The ability of whole saliva to mediate aggregation of Actinomyces naeslundii was significantly decreased after hormone treatment. Thus, the present findings indicate that a low dose oestrogen (oestriol) may affect the flow rate of labial salivary glands and the bacterial aggregation activity of whole saliva.

An update on minor salivary gland secretions

In this article, the literature on minor salivary gland secretion rates, composition, and function is reviewed. Measurements of the minor salivary gland secretion rates and composition are complicated, and the secretions display large biological variability. Despite this, some characteristics of these secretions have been found repeatedly in independent investigations. Minor gland saliva varies between different oral sites. Buccal saliva flow is higher than labial saliva flow, which in turn is usually higher than the palatal gland secretion rate. It is generally agreed that minor gland saliva is important for the whole saliva composition, and especially for the secretory immunoglobulin A and mucins. The secretion from these glands seems also important for subjective feelings of dry mouth and general wellbeing. Further research is essential for understanding the role of these secretions for oral, as well as for general, health.

Monoclonal Antibodies Against a High-molecular-weight Agglutinin Block Adherence to Experimental Pellicles on Hydroxyapatite and Aggregation of Streptococcus mutans

High-molecular-weight (HMW) glycoproteins, agglutinins, in parotid saliva induce the aggregation of S. mutans and mediate binding of the bacteria to saliva-coated hydroxyapatite (SHA). Two types of monoclonal antibodies (mAb) directed against, respectively, protein and carbohydrate epitopes on the agglutinin have been reported to inhibit the aggregation of S. mutans. In this study, the mAbs were tested for their ability to block aggregation and adherence to SHA of S. mutans serotype c mediated by parotid, submaxillary, and whole saliva from three subjects. Both types of antibody inhibited the adherence and aggregation in a dose-dependent manner. However, individual variations were noted for the effects of the antibodies. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent immunoblotting with the antibodies revealed a > 300 kDa agglutinin component in all types of saliva and in the proteins desorbed from SHA. The degree of staining of this component in immunoblots of the salivas and the desorbates seemed to be paralleled by the rates of aggregation and adherence, respectively. Thus, our results indicate that the adherence to SHA as well as the aggregation of S. mutans serotype c is primarily mediated by structurally related, HMW glycoproteins in parotid, submaxillary, and whole saliva.

Protein characterisation of salivary and plasma biofilms formed in vitro on non-corroded and corroded dental ceramic materials.

Dental ceramics are generally regarded as low-adhesive materials. Different ceramics may, however, differ in composition and physico-chemical surface properties, which may be changed after corrosion. The aim of this study was to examine the adsorption of proteins onto specimens of different ceramic materials after the incubation in saliva and plasma before and after in vitro corrosion. In addition, the topography of the biofilm was examined by AFM. Surface-bound proteins were desorbed and analysed by polyacrylamide gel electrophoresis (PAGE) and immunoblotting using antibodies to saliva and plasma proteins. Silver-stained gels indicated differences in the adsorption of proteins. Differences in surface roughness at the nanometer level did not, however, seem to be correlated to the protein adsorption. After corrosion, unchanged or increased protein staining was generally seen in the gels and Western blots. The reactions for salivary amylase and proline-rich proteins varied between the different materials. Albumin and fibrinogen were identified in samples from all materials tested. Fibronectin and in specific IgA were more sparsely seen. No saliva but all plasma proteins were identified in the alumina and yttria-stabilised zirconia samples and reduced protein reactions were obtained after corrosion.

Saliva mediated adherence, aggregation and prevalence in dental plaque of Streptococcus mutans, streptococcus sanguis and actinomyces spp. in young and elderly humans

Salivary components in the pellicle mediate bacterial adherence to the tooth. Such components may also aggregate bacteria in saliva and prevent them becoming established in dental plaque. In the present study, the adherence and aggregation of Streptococcus mutans strain Ingbritt, S. sanguis strain 10556 and Actinomyces viscosus-strain 19246 mediated by parotid and whole saliva from groups of young and elderly people were examined. Significant differences were found between test strains, salivary secretions and age groups. S. sanguis 10556 and A. viscosus 19246 generally adhered more strongly than S. mutans Ingbritt, which adhered better to pellicles from parotid saliva than from whole saliva Strain 19246 bound in higher numbers to parotid saliva pellicles from elderly compared to young individuals. Strain 10556 adhered better to whole saliva than parotid saliva pellicles, and the difference was significant among the young individuals, indicating reduced adherence ability in elderly whole saliva. The streptococci were aggregated by parotid and whole saliva, and S. sanguis aggregation was less with whole saliva from the elderly than from the young participants. Besides a correlation between whole saliva aggregation of S. mutans and proportions of bacteria in plaque, no correlations were found for the individual binding properties of saliva and prevalence of bacteria in vivo. However, the level of saliva-mediated adherence in vitro was in the following order: S. mutans. Actinomyces S sanguis, which corresponded to their isolation frequency in plaque. These findings emphasize the importance of initial adherence to salivary receptors in bacterial colonization on teeth. Further studies are needed to reveal if individual patterns in the in vitro binding characteristics of saliva lead to variation of colonization in vivo.

Dental Plaque pH and Micro-organisms during Hyposalivation

We have previously reported that minor gland and whole saliva flow rates and salivary proteins showed differences in individuals with primary Sjögren’s syndrome or head and neck radiation therapy, compared with controls (Eliasson et al., 2005). We now hypothesize that pH and number of acidogenic micro-organisms in dental plaque as well as saliva buffering capacity also differ in these individuals. Plaque pH was measured by the microtouch method up to 60 min after a sucrose rinse. Plaque collected from the same sites was analyzed for counts of total and acidic micro-organisms. Compared with their controls, the irradiated group but not the Sjögren’s syndrome group displayed significantly lower plaque pH, increased numbers of lactobacilli and Candida species, as well as reduced buffering capacity. Stepwise regression tests suggested that the buccal minor-salivary-gland secretion rate in the test groups and counts of mutans streptococci in the controls were of significant importance for dental plaque pH.

Inhibition of Streptococcus mutans Adherence by Means of Surface Hydrophilization

Derivatives of polyalkylene oxide (PAO) were examined for their ability to inhibit adherence of 3H-labeled cells of Streptococcus mutans to hydroxyapatite (HA) and to plastic surfaces treated with buffer or parotid saliva from two individuals. Pellicles formed on HA with saliva from the two subjects were distinct in their binding capacity. One saliva promoted and the other saliva reduced adherence, as compared with the buffer control (BHA). Three of the PAO compounds effectively hindered binding of bacteria to BHA. However, on saliva-treated HA (SHA) the inhibition was not as effective. One compound, a phosphated polypropylene glycol, was potent in inhibiting adherence both to BHA and to the plastic surfaces treated with either buffer or saliva. However, treatment of HA with this compound followed by saliva incubation only gave a limited reduction in the number of bacteria binding. Evidently, salivary constituents are capable of interacting also with the PAOtreated surface. When 14C-labeled hydrophilizing agent was used, it was shown that the PAO was not replaced by salivary molecules. Instead, the components of the saliva that mediate the binding of bacteria seemed capable of adhering directly to the PAO layer.