Detection of salivary α-amylase and lysozyme exposed on the pellicle formedin situ on different materials

Salivary Pellicle Formed on Dental Composites Evaluated by Mass Spectrometry-An In Situ Study

(1) Background: In the oral environment, sound enamel and dental restorative materials are immediately covered by a pellicle layer, which enables bacteria to attach. For the development of new materials with repellent surface functions, information on the formation and maturation of salivary pellicles is crucial. Therefore, the present in situ study aimed to investigate the proteomic profile of salivary pellicles formed on different dental composites. (2) Methods: Light-cured composite and bovine enamel samples (controls) were exposed to the oral cavity for 30, 90, and 120 min. All samples were subjected to optical and mechanical profilometry, as well as SEM surface evaluation. Acquired pellicles and unstimulated whole saliva samples were analyzed by SELDI-TOF-MS. The significance was determined by the generalized estimation equation and the post-hoc bonferroni adjustment. (3) Results: SEM revealed the formation of homogeneous pellicles on all test and control surfaces. Profilometry showed that composite surfaces tend to be of higher roughness compared to enamel. SELDI-TOF-MS detected up to 102 different proteins in the saliva samples and up to 46 proteins in the pellicle. Significant differences among 14 pellicle proteins were found between the composite materials and the controls. (4) Conclusions: Pellicle formation was material- and time-dependent. Proteins differed among the composites and to the control.

Bioadhesion on Textured Interfaces in the Human Oral Cavity-An In Situ Study

Extensive biofilm formation on materials used in restorative dentistry is a common reason for their failure and the development of oral diseases like peri-implantitis or secondary caries. Therefore, novel materials and strategies that result in reduced biofouling capacities are urgently sought. Previous research suggests that surface structures in the range of bacterial cell sizes seem to be a promising approach to modulate bacterial adhesion and biofilm formation. Here we investigated bioadhesion within the oral cavity on a low surface energy material (perfluorpolyether) with different texture types (line-, hole-, pillar-like), feature sizes in a range from 0.7–4.5 µm and graded distances (0.7–130.5 µm). As a model system, the materials were fixed on splints and exposed to the oral cavity. We analyzed the enzymatic activity of amylase and lysozyme, pellicle formation, and bacterial colonization after 8 h intraoral exposure. In opposite to in vitro experiments, these in situ experiments revealed no clear signs of altered bacterial surface colonization regarding structure dimensions and texture types compared to unstructured substrates or natural enamel. In part, there seemed to be a decreasing trend of adherent cells with increasing periodicities and structure sizes, but this pattern was weak and irregular. Pellicle formation took place on all substrates in an unaltered manner. However, pellicle formation was most pronounced within recessed areas thereby partially masking the three-dimensional character of the surfaces. As the natural pellicle layer is obviously the most dominant prerequisite for bacterial adhesion, colonization in the oral environment cannot be easily controlled by structural means.

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.

Functional biomedical materials derived from proteins in the acquired salivary pellicle

In the oral environment, the acquired salivary pellicle (ASP) on the tooth surface comprises proteins, glycoproteins, carbohydrates, and lipids. The ASP can specifically and rapidly adsorb on the enamel surface to provide effective lubrication, protection, hydration, and remineralisation, as well as be recognised by various bacteria to form a microbial biofilm (plaque). The involved proteins, particularly various phosphoproteins such as statherins, histatins, and proline-rich proteins, are vital to their specific functions. This review first describes the relationship between the biological functions of these proteins and their structures. Subsequently, recent advances in functional biomedical materials derived from these proteins are reviewed in terms of dental/bone therapeutic materials, antibacterial materials, tissue engineering materials, and coatings for medical devices. Finally, perspectives and challenges regarding the rational design and biomedical applications of ASP-derived materials are discussed.

Bioadhesion in the oral cavity and approaches for biofilm management by surface modifications

BACKGROUND

All soft and solid surface structures in the oral cavity are covered by the acquired pellicle followed by bacterial colonization. This applies for natural structures as well as for restorative or prosthetic materials; the adherent bacterial biofilm is associated among others with the development of caries, periodontal diseases, peri-implantitis, or denture-associated stomatitis. Accordingly, there is a considerable demand for novel materials and coatings that limit and modulate bacterial attachment and/or propagation of microorganisms.

OBJECTIVES AND FINDINGS

The present paper depicts the current knowledge on the impact of different physicochemical surface characteristics on bioadsorption in the oral cavity. Furthermore, it was carved out which strategies were developed in dental research and general surface science to inhibit bacterial colonization and to delay biofilm formation by low-fouling or "easy-to-clean" surfaces. These include the modulation of physicochemical properties such as periodic topographies, roughness, surface free energy, or hardness. In recent years, a large emphasis was laid on micro- and nanostructured surfaces and on liquid repellent superhydrophic as well as superhydrophilic interfaces. Materials incorporating mobile or bound nanoparticles promoting bacteriostatic or bacteriotoxic properties were also used. Recently, chemically textured interfaces gained increasing interest and could represent promising solutions for innovative antibioadhesion interfaces. Due to the unique conditions in the oral cavity, mainly in vivo or in situ studies were considered in the review.

CONCLUSION

Despite many promising approaches for modulation of biofilm formation in the oral cavity, the ubiquitous phenomenon of bioadsorption and adhesion pellicle formation in the challenging oral milieu masks surface properties and therewith hampers low-fouling strategies.

CLINICAL RELEVANCE

Improved dental materials and surface coatings with easy-to-clean properties have the potential to improve oral health, but extensive and systematic research is required in this field to develop biocompatible and effective substances.

Effect of amylase activity on mechanical properties of dental composite resin

The purpose of this study was to investigate the effect of amylase activity on the mechanical properties of three dental composite resin (Filtek Z350; Filtek Z250 and Polofil Supra). The specimens were immersed in amylase solution at four different activities (25, 50, 100 and 200 KIU/L) with an artificial saliva solution (AS) as a control. The flexural strength (FS) and elastic modulus (EM) were determined in a three-point bending test after immersion for periods up to 12 months. In addition, surface roughness and surface morphology also determined. The FS of Filtek Z350 reaching the lowest level of 67.86 MPa after AS immersion for one year. There was a general trend for FS to decrease following immersion in AS for all the tested materials. However, the amylase groups did not undergo a significant decrease in FS and EM, and there was a slight increase in FS and EM for Polofil Supra.

Adherence of Streptococcus sanguinis and Streptococcus mutans to saliva-coated S-PRG resin blocks

This in vitro study performed elemental analysis of the ions absorbed into the salivary coat covering the surfaces of S-PRG resin blocks and assessed the adherence of Streptococcus sanguinis and Streptococcus mutans to these saliva-coated S-PRG resin blocks. Elemental analysis of ions absorbed into the salivary coat of resin blocks exposed to the saliva was performed using an inductive coupled plasma atomic emission spectrometer and the fluoride electrode method. Quantitative adherence of radio-labeled test bacteria to the resin blocks was determined. As the results, the saliva-coated S-PRG resin showed significantly greater amounts of absorbed B, Al, Si, Sr, and F than the saliva-coated unfilled resin. It was of particular significance that the salivary coating of the S-PRG resin reduced the adherence of S. mutans to this resin. However, in the case of S. sanguinis, no significant difference in adherence could be recognized between saliva-coated S-PRG resin and saliva-coated unfilled resin.

Visualization of adherent micro-organisms using different techniques

The visualization and quantification of adherent bacteria is still one of the most relevant topics in microbiology. Besides electron microscopic techniques such as transmission electron microscopy, scanning electron microscopy and environmental scanning electron microscopy, modern fluorescence microscopic approaches based on fluorogenic dyes offer detailed insight into bacterial biofilms. The aim of the present review was to provide an overview of the advantages and disadvantages of different methods for visualization of adherent bacteria with a special focus on the experiences gained in dental research.

The composition of enamel salivary films is different from the ones formed on dental materials

This study utilized two-dimensional gel electrophoresis (2DE) to illustrate the compositional differences between in vitro salivary conditioning films (denoted pellicles) formed on human enamel as well as on the dental materials titanium and poly(methyl methacrylate). The salivary pellicles were formed by immersing each surface in individual tubes containing small volumes of freshly collected whole saliva. Saliva remaining in the tubes after the pellicle formation for 2 h was visualized by means of 2DE and silver staining. The results showed that the protein patterns in 2DE of the liquid phase of saliva left after the exposure to the respective surfaces, regarding proteins <100 kDa in size, were different depending on the surface used. Several protein groups and/or individual proteins were shown to be distinct for each surface used.

Impact of the in situ formed salivary pellicle on enamel and dentine erosion induced by different acids

OBJECTIVE

To investigate and compare the protective impact of the in situ formed salivary pellicle on enamel and dentine erosion caused by different acids at pH 2.6.

METHODS

Bovine enamel and dentine samples were exposed for 120 min in the oral cavity of 10 healthy volunteers. Subsequently, enamel and dentine pellicle-covered specimens were extraorally immersed in 1 ml hydrochloric, citric or phosphoric acid (pH 2.6, 60 s, each acid n=30 samples). Pellicle-free samples (each acid n=10) served as controls. Calcium release into the acid was determined by atomic absorption spectroscopy. The data were analysed by two-way ANOVA and Tukey's test (alpha=0.05).

RESULTS

Pellicle-covered samples showed significantly less calcium loss compared to pellicle-free samples in all acid groups. The mean (SD) pellicle protection (% reduction of calcium loss) was significantly better for enamel samples [60.9 (5.3)] than for dentine samples [30.5 (5.0)], but revealed no differences among the acids.

CONCLUSION

The efficacy of the in situ pellicle in reducing erosion was 2-fold better for enamel than for dentine. Protection of the pellicle was not influenced by the kind of acid when enamel and dentine erosion was performed at pH 2.6.

Peptide profile of human acquired enamel pellicle using MALDI tandem MS

The present study proposes a strategy for human in vivo acquired enamel pellicle (AEP) peptidome characterisation based on sequential extraction with guanidine and TFA followed by MALDI-TOF/TOF identification. Three different nanoscale analytical approaches were used: samples were subjected to tryptic digestion followed by nano-HPLC and mass spectrometry (MS and MS/MS) analysis. Undigested samples were analysed by LC-MS (both linear and reflector modes) and LC-MS/MS analysis, and samples were subjected to nano-HPLC followed by on-plate digestion and mass spectrometry (MS and MS/MS) analysis. The majority of the identifications corresponded to peptide/protein fragments of salivary protein, belonging to the classes: acidic PRPs, basic PRPs, statherin, cystatins S and SN and histatin 1 (all also identified in intact form). Overall, more than 90 peptides/proteins were identified. Results clearly show that peptides with acidic groups are enriched in the TFA fraction while peptides with no acidic or phosphate groups are prevalent on the guanidine extract. Also, phosphorylated peptides were observed mainly on the TFA fraction. Fragments present in the AEP show a predominance of cleavage points located at Arg, Tyr and Lys residues. Obtained data suggest that proteolytic activity could influence AEP formation and composition.