Non-destructive visualisation of protective proteins in the in situ pellicle

Mucins 5b and 7 and secretory IgA in the oral acquired pellicle of children with caries and caries-free children

OBJECTIVE

The objective of this study was to determine whether differences in the abundance of mucins 5b and 7 as well as secretory IgA exist in the oral acquired pellicle between children with active caries and caries-free children.

DESIGN

Pellicle formation was performed for 10 min in-situ on ceramic slabs in the oral cavity of children (5-7 years of age) with caries (n = 15) and without signs of caries (n = 13). Furthermore, unstimulated saliva was collected. Concentrations of Muc5b, Muc7 and sIgA were measured in desorbed pellicle eluates and in saliva.

RESULTS

Significantly larger concentrations of Muc5b, Muc7 and sIgA were detected in the pellicle obtained from children with caries compared to caries-free children. However, in the salivary samples concentrations of mucins Muc5b and Muc7 as well as sIgA did not differ significantly between the two groups.

CONCLUSIONS

All three pellicle components Muc5b, Muc7 as well as sIgA could be identified as potential biomarkers for early childhood caries with high sensitivity and specificity. This could contribute to a better understanding of the different caries susceptibility in children.

The salivary pellicle on dental biomaterials

The salivary pellicle, an adlayer formed by adsorption of salivary components on teeth and dental biomaterials, has direct consequences on basic outcomes of dentistry. Here, we provide an overview of salivary pellicle formation processes with a critical focus on dental biomaterials. We describe and critique the array of salivary pellicle measurement techniques. We also discuss factors that may affect salivary pellicle formation and the heterogeneity of the published literature describing salivary pellicle formation on dental biomaterials. Finally, we survey the many effects salivary pellicles have on dental biomaterials and highlight its implications on design criteria for dental biomaterials. Future investigations may lead to rationally designed dental biomaterials to control the salivary pellicle and enhance material function and patient outcomes.

Proteomic analysis of human dental pulp in different clinical diagnosis

OBJECTIVES

The present study aimed to identify proteins obtained from pulp tissue and correlate with each clinical diagnosis (healthy pulp, inflamed pulp, and necrotic pulp).

MATERIALS AND METHODS

A total of forty-five molars were used. Three biological replicas were evaluated. Lysis and sonication were used for protein extraction. Protein quantification was assessed by using the Bradford technique, and shotgun proteome analysis was performed by nanoUPLC-MS^E using a Synapt G2 mass spectrometer. Mass spectra data were processed using the Waters PLGS software, and protein identification was done using the human Uniprot database appended to the PLGS search engine.

RESULTS

A total of 123 different proteins were identified in all evaluated pulp conditions. Among these, 66 proteins were observed for healthy pulp, 66 for inflamed pulp, and 91 for necrotic pulp. Most protein identification was related to immune response, multi-organism process, platelet activation, and stress in inflamed pulp samples compared to healthy pulp. Proteins related to cellular component organization or biogenesis, developmental process, growth, immune response, multi-organism process, response to stimulus, signaling, stress, and transport were identified in cases of apical periodontitis compared to inflamed pulp.

CONCLUSIONS

The progression of the disease to inflamed pulp promoted a high abundance of proteins related to the immune system and stress. Comparing the necrotic pulp with inflamed pulp conditions, a high abundance of proteins was noticed related to metabolism, transport, and response between organisms.

CLINICAL RELEVANCE

This finding may assist in future studies of new markers, understanding of tissue engineering, and development of future products.

Vinegar inhibits the formation of oral biofilm in situ

Background

Vinegar has been recognized as an effective antimicrobial agent for long. This study intended to elucidate the effect of commercially available vinegar on in situ pellicle formation and existing 24-h biofilms.

Methods

In situ biofilm formation took place on bovine enamel slabs mounted in individual splints and exposed intraorally over 3 min and 24 h, respectively. After 5 s rinsing with vinegar, all samples were analyzed via fluorescence microscopy (FM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, salivary samples were collected and analyzed via FM. Samples with water rinsing served as controls.

Results

Vinegar caused destruction of the pellicle. Compared to the control group, vinegar rinsing reduced the outer globular layer of the pellicle (p < 0.001), and resulted in formation of subsurface pellicle. Also, vinegar rinsing could reduce bacterial viability and disrupt the 24-h biofilm. Total bacteria amount of saliva samples decreased remarkably (p < 0.001) after vinegar rinsing within 30 min. Reduction of bacterial viability was observed even 120 min after vinegar rinsing in both biofilm and saliva sample (p < 0.001).

Conclusion

This in situ study reveals that rinsing with vinegar for only 5 s alters the pellicle layer resulting in subsurface pellicle formation. Furthermore, vinegar rinsing will destruct mature (24-h) biofilms, and significantly reduce the viability of planktonic microbes in saliva, thereby decreasing biofilm formation.

Activity and distribution pattern of enzymes in the in-situ pellicle of children

OBJECTIVE

This study investigated, for the first time, pellicle enzymes with respect to their activity, distribution and fluorescence pattern in children with different caries experience.

DESIGN

In-situ pellicles were collected from 41 children (aged 4-6 years) with different caries status; 17 of them were caries-free (dmf = 0), 12 had dental restorations but no current caries (dmf ≥ 2) and 12 had at least two carious lesions (dmf ≥ 2). Bovine enamel samples were fixed on individual upper jaw braces for pellicle formation. After 30 min of intraoral exposure, the pellicle and saliva samples were analysed for the activities of amylase, lysozyme, peroxidase and glucosyltransferase (GTF). The distribution of these enzymes, including GTF-isoforms B, C and D, and the pellicle ultrastructure were examined by gold-immunolabelling and transmission electron microscopy (TEM). Furthermore, interactions between pellicle enzymes and adherent bacteria were visualised using combined fluorescence and immunofluorescence labelling.

RESULTS

There were no significant differences in the pellicle enzyme activities between the study groups. TEM analysis revealed the absence of GTF C and D in the pellicle of caries-active children. Amylase, peroxidase and GTF-isoforms showed a random distribution within the pellicle layer; lysozyme was found in the form of clusters. A similar ultrastructural pattern was observed for all subjects. Fluorescence labelling technique enabled visualisation of all enzymes, except for GTF B.

CONCLUSION

Pellicle enzyme activities and ultrastructure are not associated with children's caries status. Further investigation is needed to assess the influence of individual GTF-isoforms on caries susceptibility in children.

Is it really penetration? Part 2. Locomotion of Enterococcus faecalis cells within dentinal tubules of bovine teeth

OBJECTIVE

The aim of the present vitro study was to examine the question whether devitalized Enterococcus faecalis (E. faecalis) cells can migrate into dentinal tubules and if that process takes place in a time-dependent manner.

DESIGN

Sixty bovine root canals were incubated with devitalized and vital streptomycin-resistant E. faecalis strains after root canal enlargement (size 80, taper .02) with 3% NaOCl solution. Incubation times 7, 14, 21, 28, 35, and 42 days. Samples were processed for analysis by scanning electron microscopy (SEM) and DAPI (4',6-diamidino-2-phenylindole) staining. The penetration depth was calculated with the measurement tool of the Axio Vision program (Zeiss, Jena, Germany). Statistical analysis was performed by Kruskal-Wallis (α = 0.05) and Mann-Whitney U test (p < 0.05).

RESULTS

Devitalized E. faecalis strains were able to migrate into dentinal tubules. The total number and penetration depth of devitalized E. faecalis cells was lower compared to the vital suspension of E. faecalis. It was noted, that bacterial penetration was not common to all of the dentinal tubules in the vital E. faecalis control and especially in the devitalized control. The migration took place in a time-dependent migration characteristic.

CONCLUSIONS

Devitalized E. faecalis cells are still able to migrate into the dentinal tubules due to possible electrokinetic and osmotic processes. Thereby, increased exposure times lead to a time-dependent penetration characteristic.

CLINICAL RELEVANCE

Since devitalized bacteria can migrate as well into dentinal tubules, the presence of bacteria within dentinal tubules cannot be interpreted as a failure of tested preparation regimens.

Is it really penetration? Locomotion of devitalized Enterococcus faecalis cells within dentinal tubules of bovine teeth

OBJECTIVE

The aim of the present study was to evaluate the penetration characteristics of devitalized and vital E. faecalis cells into root dentinal tubules.

DESIGN

Thirteen root canals were incubated with devitalized (4days, 7days, 14days, 28days) and vital (28days) E. faecalis strains (streptomycin-resistant strains) after root canal enlargement (size 80, taper 0.02) with 3 % NaOCl solution. The smear layer was intentionally removed with 20 % EDTA before inoculation. Samples were processed for analysis by scanning electron microscopy (SEM) and DAPI (4',6-diamidino-2-phenylindole) staining. DAPI was conducted for fluorescence microscopic visualization of the bacterial penetration into dentinal tubules. The penetration depth was calculated with the measurement tool of the Axio Vision program (Zeiss, Jena, Germany).

RESULTS

Devitalized E. faecalis strains were able to penetrate into dentinal tubules of the root canal. Apikal penetration depths of the devitalized cells were 100.67μm±26.54μm after 7days, 230.67μm±111.5μm after 14days and 266.5μm±92.63μm after 28days of incubation. The total number and penetration depth of E. faecalis cells was lower compared to a vital suspension of E. faecalis (1002.45μm) after 28days. It was noted that bacterial penetration was not common to all of the dentinal tubules in the vital E. faecalis control and especially in the devitalized control.

CONCLUSIONS

Increased exposure times of devitalized bacteria into root canals lead to an increased number of penetrated dentinal tubules as well as to a deeper penetration.

Enzymology and Ultrastructure of the in situ Pellicle in Caries-Active and Caries-Inactive Patients

Aim: The present study aimed to evaluate the impact of caries activity on the key enzymes and the ultrastructure of the in situ pellicle. Methods: Pellicle formation was performed on bovine enamel slabs. Intraoral exposure (3, 30, and 120 min) was accomplished by 14 caries-active (DMFS: 22.7 ± 12.1) and 13 caries-inactive (DMFS: 1.5 ± 1.8) individuals. The enzyme activities (lysozyme, peroxidase, α-amylase, glycosyltransferase [GTF]) in the in situ pellicle and resting saliva of all participants were analyzed directly after oral exposure. In addition, a simultaneous visualization of these enzymes, extracellular glucans, and adherent bacteria was carried out. Fluorescent patterns were analyzed with fluorescence labeling and 4′,6-diamidino-2-phenylindole/concanavalin A staining. In addition, the distribution of GTF B, C, and D and the ultrastructure of the pellicle were examined by gold immunolabeling and transmission electron microscopy with selected samples. Results: Enzyme activities of amylase, peroxidase, lysozyme, and GTF were detected on all enamel slabs in an active conformation. Neither exposure time nor caries activity had an impact on the enzyme activities. Gold immunolabeling indicated that the pellicle of caries-active subjects tends to more GTF D molecules. The pellicles of caries-inactive and -active individuals revealed a similar ultrastructural pattern. Conclusion: The enzyme activities as well as the pellicle's ultrastructure are of high similarity in caries-active and -inactive subjects. Thereby, oral exposure time has no significant influence. This reflects a high uniformity during the initial phase of bioadhesion (3-120 min) concerning enzymatic functions. However, there is a tendency towards more GTF D in caries-active individuals.

Influence of Calcium Phosphate and Apatite Containing Products on Enamel Erosion

For the purpose of erosion prevention the present study aimed to compare the efficacy of two biomimetic products and a fluoride solution to optimize the protective properties of the pellicle. After 1 min of in situ pellicle formation on bovine enamel slabs, 8 subjects adopted CPP-ACP (GC Tooth Mousse), a mouthwash with hydroxyapatite microclusters (Biorepair), or a fluoride based mouthwash (elmex Kariesschutz) for 1 min each. Afterwards, samples were exposed in the oral cavity for 28 min. Native enamel slabs and slabs exposed to the oral cavity for 30 min without any rinse served as controls. After oral exposure, slabs were incubated in HCl (pH values 2, 2.3, and 3) for 120 s and kinetics of calcium and phosphate release were measured photometrically; representative samples were evaluated by SEM and TEM. The physiological pellicle reduced demineralization at all pH values; the protective effect was enhanced by fluoride. The biomimetic materials also reduced ion release but their effect was less pronounced. SEM indicated no layer formation after use of the different products. However, TEM confirmed the potential accumulation of mineral components at the pellicle surface. The tested products improve the protective properties of the in situ pellicle but not as effectively as fluorides.

Effect of CPP/ACP on initial bioadhesion to enamel and dentin in situ

The present in situ study investigated the influence of a preparation containing CPP/ACP (caseinphosphopeptide-amorphous calcium phosphate) (GC Tooth mousse) on initial bacterial colonization of enamel and dentin. Therefore, pellicle formation was performed in situ on bovine enamel and dentin specimens fixed to individual upper jaw splints worn by 8 subjects. After 1 min of pellicle formation GC Tooth mousse was used according to manufacturer's recommendations. Rinses with chlorhexidine served as positive controls. Specimens carried without any rinse served as negative controls. After 8 h overnight exposure of the splints, bacterial colonization was quantified by fluorescence microscopy (DAPI and BacLight live/dead staining). Additionally, the colony forming units (CFU) were determined after desorption. Furthermore, the effects on Streptococcus mutans bacteria were tested in vitro (BacLight). There was no significant impact of CPP/ACP on initial bacterial colonization proved with DAPI and BacLight. Determination of CFU showed statistical significance for CPP/ACP to reduce bacterial adherence on enamel. The in vitro investigation indicated no antimicrobial effects for CPP/ACP on Streptococcus mutans suspension. Under the chosen conditions, CPP/ACP (GC Tooth mousse) had no significant impact on initial biofilm formation on dental hard tissues. The tested preparation cannot be recommended for biofilm management.

New Insights into the Composition and Functions of the Acquired Enamel Pellicle

The acquired enamel pellicle (AEP) is a thin acellular film that forms on tooth surfaces upon exposure to the oral environment. It consists predominantly of salivary proteins, but also includes non-salivary-derived proteins, carbohydrates, and lipids. Since it is the interface between teeth and the oral environment, the AEP plays a key role in the maintenance of oral health by regulating processes including lubrication, demineralization, and remineralization and shaping the composition of early microbial flora adhering to tooth surfaces. Knowledge of the 3D structure of the AEP and how that correlates with its protective functions may provide insight into several oral pathological states, including caries, erosion, and periodontal disease. This review intends to update readers about the latest discoveries related to the formation, ultrastructure, composition, and functions of the AEP, as well as the future of pellicle research, with particular emphasis on the emerging role of proteomic and microscopy techniques in oral diagnosis and therapeutics.

A comprehensive method for determination of fatty acids in the initial oral biofilm (pellicle)

The acquired pellicle is a tenacious organic layer covering the surface of teeth, protecting the underlying dental hard tissues. Lipids account for about one quarter of the pellicle's dry weight and are assumed to be of considerable importance for their protective properties. Nevertheless, only preliminary information is available about the nature of lipids in the pellicle. Gas chromatography coupled with electron impact ionization mass spectrometry was used to establish a convenient analytical protocol in order to obtain a qualitative and quantitative characterization of a wide range of FAs (C(12)-C(22)). In situ biofilm formation was performed on bovine enamel slabs mounted on individual splints carried by 10 subjects. A modified Folch extraction procedure was adopted to extract the lipids from the detached pellicle, followed by transesterification to fatty acid methyl esters using methanol and concentrated hydrochloric acid. Tridecanoic and nonadecanoic acid were used as internal standards suitable and reliable for robust, precise and accurate measurements. The present study demonstrates, for the first time, a procedure based on a combination of innovative specimen generation and convenient sample preparation with sensitive GC-MS analysis for the determination of the fatty acid profile of the initial oral biofilm.

Targeted immobilisation of lysozyme in the enamel pellicle from different solutions

Mouthwashes containing protective enzymes are required especially for patients suffering from xerostomia. The present study aimed to investigate the possibilities of modulating the immobilisation of lysozyme in the in situ pellicle layer. In situ formed pellicles were incubated in vitro for 10 min with various enzymatic buffer solutions containing lysozyme and additive enzymes such as transglutaminase or trypsin as well as polyphenolic compounds (cistus tea). After the rinses, the pellicle samples were incubated in collected whole saliva or in desorption solutions for 0, 20 and 40 min and the enzyme activities were measured. Furthermore, accumulation of lysozyme in the pellicle was visualised in ultrathin sections of the pellicle using the gold immunolabelling technique and transmission electron microscopy. Hen egg white lysozyme was accumulated in the in situ pellicle tenaciously. Up to 2.8-fold higher activities than in controls were observed. The addition of transglutaminase did not enhance the immobilisation of lysozyme activity, whereas the polyphenolic compound had no adverse effect. Accumulation of lysozyme in the acquired pellicle was confirmed by gold immunolabelling. Targeted and tenacious immobilisation of lysozyme in the acquired pellicle is possible. Poylphenolic compounds might be a relevant additive for mouthwashes containing lysozyme.

Bacterial colonization of enamel in situ investigated using fluorescence in situ hybridization

Oral biofilms are one of the greatest challenges in dental research. The present study aimed to investigate initial bacterial colonization of enamel surfaces in situ using fluorescence in situ hybridization (FISH) over a 12 h period. For this purpose, bovine enamel slabs were fixed on buccal sites of individual splints worn by six subjects for 2, 6 and 12 h to allow biofilm formation. Specimens were processed for FISH and evaluated with confocal laser-scanning microscopy, using probes for eubacteria, Streptococcus species, Veillonella species, Fusobacterium nucleatum and Actinomyces naeslundii. The number of adherent bacteria increased with time and all tested bacterial species were detected in the biofilm formed in situ. The general percentage composition of the eubacteria did not change over the investigated period, but the number of streptococci, the most frequently detected species, increased significantly with time (2 h: 17.7±13.8 %; 6 h: 20.0±16.6 %; 12 h: 24.7±16.1 %). However, ≤1 % of the surface was covered with bacteria after 12 h of biofilm formation in situ. In conclusion, FISH is an appropriate method for quantifying initial biofilm formation in situ, and the proportion of streptococci increases during the first 12 h of bacterial adherence.

Validation of mechanically-assisted sodium dodecyl-sulphate elution as a technique to remove pellicle protein components from human enamel

The salivary film, denoted the pellicle, formed on oral surfaces is of great importance for oral health and comfort. The present study describes mechanically-assisted sodium dodecyl sulphate (SDS) elution of the in vivo pellicle formed on human enamel and visualisation of the desorbed pellicle proteins using two-dimensional gel electrophoresis (2-DE). To verify this removal of the pellicle, a combined mechanical and surfactant procedure was additionally performed on an in vitro pellicle formed on human enamel, and the effectiveness was validated by mechanical removal in combination with HCl. As indicated by protein quantitation and one dimensional gel electrophoresis, rubbing with polyamide fibre pellets soaked in a 0.5% SDS solution was optimal for completely removing the adsorbed proteins from the enamel surface, and yet provided separation of the proteins by 2-DE to enable identification in future studies.