Proteomic evaluation of acquired enamel pellicle during in vivo formation

Can the combination of proanthocyanidin and vitamin E or palm oil effectively protect enamel against in vitro erosive and abrasive challenges?

OBJECTIVES

This study aimed to assess the effect of proanthocyanidin, palm oil and vitamin E against erosive and erosive+abrasive challenges in vitro after enamel pellicle formation in situ.

METHODOLOGY

Bovine enamel blocks (n=84) were obtained and divided into the following treatment groups: negative control (NC) - deionized water; positive control (PC) - SnCl2/NaF/AmF-containing solution; palm oil (PO); 2% proanthocyanidin (P2); vitamin E (VitE); 2% proanthocyanidin+palm oil (P2PO); and 2% proanthocyanidin+vitamin E (P2VitE). For 5 days, one half of the sample from each group was subjected to erosion and the other half was subjected to erosion+abrasion. The acquired enamel pellicle (AEP) was pre-formed in situ for 30 minutes. The specimens were then treated in vitro with solutions (500 µl, 30s for each group). Subsequently, the blocks were left in the oral cavity for another hour to obtain the modified AEP. The blocks were immersed in 0.5% citric acid (pH=2.5) for 90s, 4×/day. AEP formation and treatment were carried out before the first and third erosive challenges, and after these challenges, abrasive cycles (15s) were performed on half of the samples. Enamel wear was quantified by profilometry and data were analyzed by two-way ANOVA and Tukey's test (p<0.05).

RESULTS

All groups showed higher wear when exposed to erosion+abrasion than when exposed to erosion alone (p=0.0001). PO, P2VitE, P2, and P2PO showed enamel wear similar to the PC group, but only PC, PO and P2VitE differed from the NC group. The other groups behaved similarly to NC.

CONCLUSION

It was concluded that the combination of proanthocyanidin and vitamin E was effective in reducing wear in the face of in vitro erosive and erosive+abrasive challenges.

Immunorecognition of Streptococcus mutans secreted proteins protects against caries by limiting tooth adhesion

INTRODUCTION

Childhood caries, a prevalent chronic disease, affects 60-90 % of children in industrialized regions, leading to lesions in both primary and permanent teeth. This condition precipitates hospital admissions, emergency room visits, elevated treatment costs, and missed school days, thereby impeding the child's academic engagement and increasing the likelihood of caries into adulthood. Despite multiple identified risk factors, significant interpersonal variability remains unexplained. The immune system generates a unique antibody repertoire, essential for maintaining a balanced and healthy oral microbiome. Streptococcus mutans is a primary contributor to the development of caries.

METHODS

Employing mass spectrometry, we investigated the S. mutans proteins targeted by antibodies in children both with and without caries, delineating a fundamental suite of proteins discernible by the immune systems of a majority of individuals. Notably, this suite was enriched with proteins pivotal for bacterial adhesion. To ascertain the physiological implications of these discoveries, we evaluated the efficacy of saliva in thwarting S. mutans adherence to dental surfaces.

RESULTS

Antibodies in most children recognized a core set of ten S. mutans proteins, with additional proteins identified in some individuals. There was no significant difference in the proteins identified by children with or without caries, but there was variation in antibody binding intensity to some proteins. Functionally, saliva from caries-free individuals, but not children with caries, was found to hinder the binding of S. mutans to teeth. These findings delineate the S. mutans proteome targeted by the immune system and suggest that the inhibition of bacterial adherence to teeth is a primary mechanism employed by the immune system to maintain oral balance and prevent caries formation.

CONCLUSIONS

These findings enhance our knowledge of the immune system's function in oral health maintenance and caries prevention, shedding light on how immunoglobulins interact with S. mutans proteins.

CLINICAL SIGNIFICANCE

Targeting S. mutans proteins implicated in bacterial adhesion could be a promising strategy for preventing childhood caries.

Acquired pellicle engineering with the association of cystatin and vitamin E against enamel erosion

OBJECTIVE

Evaluate CaneCPI-5 associated with Vitamin E in acquired enamel pellicle (AEP) engineering to prevent dental erosion.

METHODS

180 human enamel specimens were divided into 12 groups and treated with the following solutions: Cane+VitT and Cane+VitS- CaneCPI-5 + Vit E; Vit+CaneT and Vit+CaneS- Vit E + CaneCPI-5; VitT and VitS- Vit E; CaneT and CaneS- CaneCPI-5; ControlT and ControlS - AmF/NaF/SnCl2; WaterT and WaterS- Deionized water. Groups' name followed by "T" were first treated (200 μl; 2 min) and then incubated in human saliva (200 μl; 1 h) to form the AEP. For groups followed by "S", the AEP was formed and then treatment was applied. The erosive challenge consisted of immersion in 1% citric acid (1 min, 1x/day, for 3 days). The percentage of superficial hardness loss (%SHL) and the relative surface reflection intensity (%SRI) were subjected to normality and homogeneity tests, Shapiro-Wilk and Levene tests, respectively. Subsequently, the data were analyzed using two-way ANOVA, Tukey's test and Pearson's correlation (p < 0.005).

RESULTS

For%SHL and%SRI, water controls showed significantly lower protective capacity. Cane+VitT, Cane+VitS, and Vit+CaneS presented the lowest%SHL, and VitT and VitS did not differ from Vit+CaneT, but they were different from the other groups (p = 0.002). The greatest%SRI was found for the Cane+VitT, Vit+CaneT, VitT, Cane+VitS, Vit+CaneS, and VitS groups, which did not significantly differ. CaneT and ControlT, showed similar reflections compared to CaneS and ControlS.

CONCLUSION

CaneCPI-5 and Vitamin E demonstrated a synergistic protective effect against initial erosion.

CLINICAL SIGNIFICANCE

The results open up new possibilities for preventive approaches against erosion through the acquired pellicle engineering, with the combination of CaneCPI-5 and Vitamin E, which demonstrated to be more effective than commercial stannous mouthwash. Further research is warranted to explore the potential of this combination in diverse clinical settings.

Amyloid Fibrils Produced by Streptococcus sanguinis Contribute to Biofilm Formation and Immune Evasion

Bacterial surface proteins assembled into amyloids contribute to biofilm formation and host immune evasion. Streptococcus sanguinis, a pioneer colonizer of teeth commonly involved in cardiovascular infections, expresses about thirty-three proteins anchored to the cell wall by sortase A. Here, we characterized the production of amyloid in S. sanguinis strains differing in biofilm and immune evasion phenotypes and investigated the role of sortase A in amyloidogenesis. Amyloid was identified in biofilms formed by nine strains, using Congo red (CR) staining and cross-polarized light microscopy. Additionally, EGCG, an amyloid inhibitor, impaired biofilm maturation in a strain-specific fashion. The amounts of amyloid-like components quantified in culture fluids of nine strains using thioflavin T and fluorimetry negatively correlated with bacterial binding to complement-activating proteins (SAP, C1q), C3b deposition and rates of opsonophagocytosis in PMNs, implying amyloid production in immune evasion. The deletion of the sortase A gene (srtA) in strain SK36 compromised amyloid production and sucrose-independent biofilm maturation. The srtA mutant further showed increased susceptibility to C3b deposition and altered interactions with PMNs as well as reduced persistence in human blood. These findings highlight the contribution of amyloids to biofilm formation and host immune evasion in S. sanguinis strains, further indicating the participation of sortase A substrates in amyloidogenesis.

Film-Forming Polymers for Inhibition of Hydroxyapatite Dissolution: A Screening Study

The aim of this study was to evaluate the effect of film-forming polymer solutions of different concentrations and pH values, either associated or not with sodium fluoride (F; 225 ppm F-), when applied during the initial stage of salivary pellicle formation, to prevent the dissolution of hydroxyapatite (HA), which was determined by the pH-stat method. Polyacrylic acid (PA), chitosan, sodium linear polyphosphate (LPP), polyvinyl methyl ether/maleic anhydride (PVM/MA), and propylene glycol alginate (PGA) were tested in three concentrations (lower, medium, and higher), two pH values (native or adjusted), and either associated or not with F. Distilled water, F, and stannous ion+fluoride (Sn/F; 225 ppm F- and 800 ppm Sn2+, as SnCl2) solutions were the controls, totalizing 63 groups. HA crystals were pretreated with human saliva for 1 min to allow pellicle formation, then immersed in the experimental solutions (1 min), and exposed to saliva for another 28 min. Subsequently, they were added to a 0.3% citric acid solution (pH = 3.8), connected to a pH-stat system that added aliquots of 28 μL 0.1 N HCl for a total reaction time of 5 min. Data were analyzed with one-way ANOVA and Tukey's tests (α = 0.05). For PA alone, the concentrations of 0.1% (native pH), 0.06%, and 0.08% (both pH adjusted) showed significantly lower HA dissolution than the negative control. PA concentrations of 0.1% and 0.08%, of both pH values, improved the effect of F against HA dissolution to a near-identical value as Sn/F. All solutions containing chitosan and LPP significantly reduced HA dissolution in comparison with the control. For chitosan, the concentration of 0.5% (in both pH values) improved the effect of F. LPP at 0.5% (native pH) and all associations of LPP with F outperformed the effect of F. Some PVM/MA solutions significantly reduced HA dissolution but PVM/MA could not improve the protection of F. PGA was incapable of reducing HA dissolution or improving F effect. It was concluded that chitosan, LPP, and some PA and PVM/MA solutions used alone were capable of reducing HA dissolution. Only PA, chitosan, and LPP were able to enhance fluoride protection, but for PA and chitosan, this was influenced by the polymer concentration.

The composition of the dental pellicle: an updated literature review

Background

The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation.

Methods

For this updated literature review, the PubMed database was searched for the dental pellicle and its composition.

Results

The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates.

Conclusions

The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.

Proteomic profile of the acquired enamel pellicle of children with early childhood caries and caries-free children

Acquired enamel pellicle plays an important role in the pathogenesis of early childhood caries (ECC), working as a protective interface between the tooth and the oral cavity. The aim of this cross-sectional in vivo proteomic study was to compare the acquired enamel pellicle protein profile of 3-5-year-old children with ECC (n = 10) and caries-free children (n = 10). Acquired enamel pellicle samples were collected and processed for proteomic analysis (nLC-ESI-MS/MS). In total, 241 proteins were identified. Basic salivary proline-rich protein 1 and 2, Cystatin-B, and SA were found only in the caries free group. When comparing caries free and ECC groups, lower protein levels were found in the caries free group for hemoglobin subunit beta, delta, epsilon, gamma-2, globin domain-containing protein and gamma-1, neutrophil defensin 3, serum albumin, protein S100-A8, and S100-A9. The proteins histatin-1, statherin, salivary acidic proline-rich phosphoprotein ½, proline-rich protein 4, submaxillary gland androgen-regulated protein 3B, alpha-amylase 1 and 2B were found at higher levels in the caries free group. The exclusive and the proteins found at higher levels in the caries free group might have protective functions that play a role in the prevention of caries, besides providing important insights to be evaluated in future studies for the possible development of new therapeutic strategies for ECC.

Proteomic profile of in situ acquired pellicle on tooth and restorative material surfaces

OBJECTIVES

To evaluate and compare the proteomic profile of acquired pellicle on smooth bovine tooth and tooth-coloured restorative materials, including resin composite (RC), glass ionomer cement (GIC), and casein phosphopeptide-amorphous calcium phosphate modified GIC (CPP-ACP GIC).

METHODS

Two-hour in situ pellicles on tooth/materials specimens mounted in oral appliances worn by ten healthy adults were investigated. Pellicle proteins and corresponding unstimulated whole saliva were quantitatively analysed through liquid chromatography-tandem mass spectrometry.

RESULTS

Significantly higher amounts of protein were adsorbed onto tooth surface than restorative materials tested (4.11 ± 0.69 vs. 2.54 ± 0.38/2.98 ± 0.80/3.01 ± 0.37 µg, RC/GIC/CPP-ACP GIC). From the ten participants, 1,444 (487-1,086/person), 1,454 (645-1,051/person), 1,731 (454-1,475/person), or 1,597 (423-1,261/person) pellicle proteins were detected at least once on bovine tooth, RC, GIC, or CPP-ACP GIC, respectively, and with 1,072 (304-793/person) salivary proteins identified. Comparative quantification revealed minor differences between tooth and restorative materials pellicle profiles. High inter-individual variations in pellicle protein composition were demonstrated. Compared to the salivary protein profile, 214/57 proteins showed significantly increased/decreased abundance in pellicle formed on at least one substrate (fold change > 3.325/fold change < 0.301). Gene Ontology enrichment analysis showed some pellicle proteins detected with increased affinity to tooth/material surface were identified as being related to "calcium-dependent protein binding" or "cell-cell adhesion mediator activity".

CONCLUSION

Similar protein quantity and composition was observed in 2 h in situ pellicles formed on different smooth restorative material surfaces. The proteomic profile of pellicles appeared distinct from that of the corresponding unstimulated whole saliva.

CLINICAL SIGNIFICANCE

Host backgrounds appeared more influential on the proteomic profile of the in situ acquired pellicle than the underlying substrate characteristics among systemically and orally healthy adults. Pellicle proteins preferentially adsorbed on tooth/materials were putatively associated with calcium ion homeostasis or host-microbiota interaction.

Caries Management-The Role of Surface Interactions in De- and Remineralization-Processes

BACKGROUND

Bioadhesion and surface interactions on enamel are of essential relevance for initiation, progression and prevention of caries and erosions. Salivary proteins on and within initial carious and erosive lesions can facilitate or aggravate de- and remineralization. This applies for the pellicle layer, the subsurface pellicle and for proteins within initial carious lesions. Little is known about these proteinaceous structures related to initial caries and erosion. Accordingly, there is a considerable demand for an understanding of the underlying processes occurring at the interface between the tooth surface and the oral cavity in order to develop novel agents that limit and modulate caries and erosion. Objectives and findings: The present paper depicts the current knowledge of the processes occurring at the interface of the tooth surface and the oral fluids. Proteinaceous layers on dental hard tissues can prevent or aggravate demineralization processes, whereas proteins within initial erosive or carious lesions might hinder remineralization considerably and restrict the entry of ions into lesions.

CONCLUSIONS

Despite the fact that organic-inorganic surface interactions are of essential relevance for de- and remineralization processes at the tooth surface, there is limited knowledge on these clinically relevant phenomena. Accordingly, intensive research is necessary to develop new approaches in preventive dentistry.

Pellicle modification with natural bioproducts: Influence on tooth color under erosive conditions

Salivary pellicle was modified with bioproducts and we assessed the change in tooth color and the protection of enamel to erosion. Human enamel specimens were assigned to one of three solutions: grape seed extract or black tea (bioproducts), or deionized water (negative control); after which one half the specimens underwent erosive challenges. The specimens underwent 15 cycles involving salivary pellicle formation (10 min, 37°C), incubation in solution (2 min, 25°C), subsequent pellicle formation (90 min, 37°C). Half of the specimens was kept in a humid chamber and the other half was submitted to erosion (2 min, 1% citric acid). After 15 such cycles, the pellicle was removed. Tooth color and the surface reflection intensity were assessed after every five cycles and after pellicle removal. For non-eroded specimens, the exposure to bioproducts promoted significantly greater color change than the deionized water, with increases in yellow appearance. After pellicle removal, the color was similar in all non-eroded specimens. The bioproducts increased the surface reflection intensity over cycles. For the erosion-exposed specimens, erosion itself resulted in color change. Black tea and deionized water resulted in increased yellow appearance. Exposure to the bioproducts resulted in higher relative surface reflection intensity values over time, but only grape seed extract resulted in higher relative surface reflection intensity value at the time of pellicle removal. The bioproducts caused transient staining effect, which was reduced after pellicle removal. For enamel submitted to erosion, grape seed extract resulted in less color change and better protection of enamel against erosion than black tea or water.

Effect of Exo/Endogenous Prophylaxis Dentifrice/Drug and Cariogenic Conditions of Patient on Molecular Property of Dental Biofilm: Synchrotron FTIR Spectroscopic Study

(1) Objectives: This study is the first one to investigate the molecular composition of the dental biofilm during the exogenous and endogenous prophylaxis stages (use of dentifrice/drug) of individuals with different cariogenic conditions using molecular spectroscopy methods. (2) Materials and Methods: The study involved 100 participants (50 males and 50 females), aged 18–25 years with different caries conditions. Biofilm samples were collected from the teeth surface of all participants. The molecular composition of biofilms was investigated using synchrotron infrared microspectroscopy. Changes in the molecular composition were studied through calculation and analysis of ratios between organic and mineral components of biofilm samples. (3) Results: Based on the data obtained by synchrotron FTIR, calculations of organic and mineral component ratios, and statistical analysis of the data, we were able to assess changes occurring in the molecular composition of the dental biofilm. Variations in the phosphate/protein/lipid, phosphate/mineral, and phospholipid/lipid ratios and the presence of statistically significant intra- and inter-group differences in these ratios indicate that the mechanisms of ion adsorption, compounds and complexes arriving from oral fluid into dental biofilm during exo/endogenous prophylaxis, differ for patients in norm and caries development. (4) Conclusions: The conformational environment and charge interaction in the microbiota and the electrostatic state of the biofilm protein network in patients with different cariogenic conditions play an important role. (5) Clinical Significance: Understanding the changes that occur in the molecular composition of the dental biofilm in different oral homeostasis conditions will enable successful transition to a personalised approach in dentistry and high-tech healthcare.

A Mass Spectrometric Approach to the Proteomic Profiling of the Canis lupus familiaris Acquired Enamel Pellicle on Hydroxyapatite Discs

The acquired enamel pellicle (AEP) is a multi-protein film attached to the surface of teeth, which functions to lubricate the dental surface, form an anti-erosive barrier and exhibits antimicrobial properties. The initiation of AEP formation occurs within seconds of exposure to saliva, a biofluid rich in protein species. While there have been many publications on the formation of human AEP there is little research on the composition of canine AEP during its acquisition. The aim of these studies was to explore the composition of canine AEP formation, utilising hydroxyapatite (HA) discs as a tooth substitute matrix, over time. Qualitative and quantitative proteomics techniques using tandem mass tag labelled peptides and LC-MS/MS were used to follow the formation of canine AEP on hydroxyapatite discs over the course of an hour. Proteins adsorbed to the HA surface included highly abundant proteins in canine saliva, antimicrobial proteins, protease inhibitors and the buffering agent carbonic anhydrase. Greater understanding of the canine AEP deepens fundamental knowledge of the early processes driving bacterial colonisation of the tooth surface and subsequent plaque accumulation.

A systematic review of the proteomic profile of in vivo acquired enamel pellicle on permanent teeth

OBJECTIVES

To provide a comprehensive review on the proteomic profile of in vivo acquired enamel pellicle (AEP) formed on permanent teeth.

DATA/SOURCES

PubMed, EMBASE (Ovid) and Web of Science databases were searched for eligible studies (up to December 2020). Studies reporting mass spectrometry-based proteomic analysis of in vivo AEP were included. Risk of bias assessment was performed. Qualitative and quantitative proteomic data were extracted, integrated, then followed by bioinformatic analysis.

STUDY SELECTION

Eleven studies were included, involving 122 systemically and dentally healthy adults from four different research groups. Pooled AEP samples from study participants were the normal practice for all included studies. A total of 257/93/108/870 non-redundant proteins were detectable from the in vivo ≤ 5 min/10-min/60-min/2-h AEP samples, respectively. Fifteen "core in vivo 2-h AEP proteins", generally associated with immune and/or inflammatory responses, were consistently identifiable from all four research groups. Eight included studies conducted relative quantitative proteomic analysis, while no statistical analysis could be undertaken due to the inherent limitation of the relative quantification in the proteomics analyses of these studies.

CONCLUSIONS

A systematic review on adult in vivo AEP proteomic profile was undertaken. The results provide a comprehensive appreciation of the AEP proteome in healthy individuals from in vivo sampling. Further studies are warranted to clarify the biological role of AEP on oral health, particularly at an individual level.

CLINICAL SIGNIFICANCE

A comprehensive appreciation of the proteomic profile of in vivo AEP in healthy individuals is essential to further understand its functions in oral health and disease. The information generated also provides insights for future studies.

Vitamin E: A potential preventive approach against dental erosion-an in vitro short-term erosive study

OBJECTIVES

This study evaluated the in vitro effect of different components of palm oil on enamel in a short-term erosive challenge.

METHODS

The acquired enamel pellicle (AEP) was previously formed in situ for 2 h. Subsequently, the bovine enamel blocks were treated in vitro according to following solutions: G1-palm oil; G2-85% tocotrienol solution; G3-oily vitamin E; G4-oily vitamin A; G5-deionized water (negative control); G6-stannous-containing solution (Elmex® Erosion Protection Dental Rinse) (positive control). After application of the treatment solutions (500 µl, 30 s), the blocks were immersed in 0.5% citric acid (pH 2.4) during 30 s (initial erosion). The response variable was the percentage of surface hardness loss. Data were analyzed by one-way ANOVA and Fisher's Test (p < 0.05).

RESULTS

The positive control (G6), palm oil (G1) and oily vitamin E (G3) groups presented the lowest percentage of surface hardness loss, and were statistically different from the negative group (G5) (p < 0.05), and no differences were found between these three groups. The 85% tocotrienol solution (G2) and oily vitamin A groups (G4) were not different to the negative control group.

CONCLUSIONS

Stannous-containing positive control (Elmex® Erosion Protection), palm oil and oily Vitamin E were able to protect enamel against the erosive challenge performed in this in vitro study. In addition, vitamin E is probably the key ingredient of palm oil responsible for preventing enamel erosion.

CLINICAL SIGNIFICANCE

Vitamin E presented similar preventive effect to a commercial mouthwash stannous-containing solution (Elmex® Erosion Protection) against initial erosion and, it can be considered as a promising natural alternative for the formulations of solutions aiming to prevent erosive tooth wear.

Proteome difference among the salivary proteins adsorbed onto metallic orthodontic brackets and hydroxyapatite discs

The aim of this study was to investigate the atomic composition and the proteome of the salivary proteins adsorbed on the surface of orthodontic metallic bracket. For this, the atomic composition of orthodontic metallic brackets was analyzed with X-ray Photoelectron Spectroscopy (XPS). The acquired bracket pellicle was characterized after brackets were immersed in human whole saliva supernatant for 2 hours at 37°C. Hydroxyapatite (HA) discs were used as a control. Acquired pellicle was harvested from the HA discs (n = 12) and from the metallic brackets (n = 12). Proteomics based on mass spectrometry technology was used for salivary protein identification and characterization. Results showed that most of the proteins adsorbed on the surface of orthodontic metallic brackets and on the HA discs were identified specifically to each group, indicating a small overlapping between the salivary proteins on each study group. A total of 311 proteins present on the HA discs were unique to this group while 253 proteins were unique to metallic brackets, and only 45 proteins were common to the two groups. Even though most proteins were unique to each study group, proteins related to antimicrobial activity, lubrication, and remineralization were present in both groups. These findings demonstrate that the salivary proteins adsorbed on the bracket surface are dependent on the material molecular composition.

Analysing Complex Oral Protein Samples: Complete Workflow and Case Analysis of Salivary Pellicles

Studies on small quantity, highly complex protein samples, such as salivary pellicle, have been enabled by recent major technological and analytical breakthroughs. Advances in mass spectrometry-based computational proteomics such as Multidimensional Protein Identification Technology have allowed precise identification and quantification of complex protein samples on a proteome-wide scale, which has enabled the determination of corresponding genes and cellular functions at the protein level. The latter was achieved via protein-protein interaction mapping with Gene Ontology annotation. In recent years, the application of these technologies has broken various barriers in small-quantity-complex-protein research such as salivary pellicle. This review provides a concise summary of contemporary proteomic techniques contributing to (1) increased complex protein (up to hundreds) identification using minute sample sizes (µg level), (2) precise protein quantification by advanced stable isotope labelling or label-free approaches and (3) the emerging concepts and techniques regarding computational integration, such as the Gene Ontology Consortium and protein-protein interaction mapping. The latter integrates the structural, genomic, and biological context of proteins and genes to predict protein interactions and functional connections in a given biological context. The same technological breakthroughs and computational integration concepts can also be applied to other low-volume oral protein complexes such as gingival crevicular or peri-implant sulcular fluids.

Rinsing with Statherin-Derived Peptide Alters the Proteome of the Acquired Enamel Pellicle

Changes in the proteomic profile of the acquired enamel pellicle (AEP) formed for 3 min or 2 h after rinsing with a peptide containing the 15 N-terminal residues of statherin, with serines 2 and 3 phosphorylated (StatpSpS), were evaluated. Nine volunteers participated in 2 consecutive days. Each day, after professional tooth cleaning, they rinsed for 1 min with 10 mL of phosphate buffer containing 1.88 × 10-5 M StatpSpS or phosphate buffer only (control). The acquired pellicle formed on enamel after 3 min or 2 h was collected with electrode filter papers soaked in 3% citric acid. After protein extraction, samples were analyzed by quantitative shotgun label-free proteomics. In the 3-min AEP, 19 and 131 proteins were uniquely identified in the StatpSpS and control groups, respectively. Proteins typically found in the AEP were only found in the latter. Only 2 proteins (neutrophil defensins) were increased upon treatment with StatpSpS, while 65 proteins (among which are several typical AEP proteins) were decreased. In the 2-h AEP, 50 and 108 proteins were uniquely found in StatpSpS and control groups, respectively. Hemoglobin subunits and isoforms of keratin were only found in the StatpSpS group, while cystatin-C, cathepsin D, and cathepsin G, isoforms of heat shock 70 and protocadherin were exclusively found in the control group. In addition, 23 proteins were increased upon treatment with StatpSpS, among which are histatin-1, serum albumin, and isoforms of neutrophil defensin and keratin, while 77 were decreased, most of them were typical AEP proteins. In both evaluated periods, rinsing with StatpSpS profoundly changed the proteomic profile of the AEP, which might impact the protective role of this integument against carious or erosive demineralization. This study provides important insights on the dynamics of the protein composition of the AEP along time, after rinsing with a solution containing StatpSpS.

Preventive Applications of Polyphenols in Dentistry-A Review

Polyphenols are natural substances that have been shown to provide various health benefits. Antioxidant, anti-inflammatory, and anti-carcinogenic effects have been described. At the same time, they inhibit the actions of bacteria, viruses, and fungi. Thus, studies have also examined their effects within the oral cavity. This review provides an overview on the different polyphenols, and their structure and interactions with the tooth surface and the pellicle. In particular, the effects of various tea polyphenols on bioadhesion and erosion have been reviewed. The current research confirms that polyphenols can reduce the growth of cariogenic bacteria. Furthermore, they can decrease the adherence of bacteria to the tooth surface and improve the erosion-protective properties of the acquired enamel pellicle. Tea polyphenols, especially, have the potential to contribute to an oral health-related diet. However, in vitro studies have mainly been conducted. In situ studies and clinical studies need to be extended and supplemented in order to significantly contribute to additive prevention measures in caries prophylaxis.

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 profile of the acquired enamel pellicle of professional wine tasters with erosive tooth wear

The aim of this study was to compare the acquired enamel pellicle protein profile of professional wine tasters with mild and moderate erosive tooth wear. Twelve professional wine tasters participated (3 from a low tooth wear group; 9 from a high tooth wear group). Acquired enamel pellicle samples were collected and processed for proteomic analysis (nLC-ESI-MS/MS). The acquired enamel pellicle proteomic profile was different between the groups. The proteins found exclusively in the low tooth wear group were histatins 1 and 3 and mucins 7 and 21. When comparing the wear groups, proteins with higher levels in the low tooth wear group included neutrophil defensins (1 and 3), lysozyme C, lysozyme, myeloperoxidase, and squalene monooxygenase. In conclusion, the findings indicate that the proteins found at higher levels in the low tooth wear group and proteins exclusively found in the low tooth wear group might be protective and, therefore, could be good candidates for further studies regarding their potential to be added to dental products to protect professional wine tasters from extrinsic erosive tooth wear.

Acid tolerance in early colonizers of oral biofilms

Background

In caries, low pH drives selection and enrichment of acidogenic and aciduric bacteria in oral biofilms, and development of acid tolerance in early colonizers is thought to play a key role in this shift. Since previous studies have focussed on planktonic cells, the effect of biofilm growth as well as the role of a salivary pellicle on this process is largely unknown. We explored acid tolerance and acid tolerance response (ATR) induction in biofilm cells of both clinical and laboratory strains of three oral streptococcal species (Streptococcus gordonii, Streptococcus oralis and Streptococcus mutans) as well as two oral species of Actinomyces (A. naeslundii and A. odontolyticus) and examined the role of salivary proteins in acid tolerance development.

Methods

Biofilms were formed on surfaces in Ibidi® mini flow cells with or without a coating of salivary proteins and acid tolerance assessed by exposing them to a challenge known to kill non-acid tolerant cells (pH 3.5 for 30 min) followed by staining with LIVE/DEAD BacLight and confocal scanning laser microscopy. The ability to induce an ATR was assessed by exposing the biofilms to an adaptation pH (pH 5.5) for 2 hours prior to the low pH challenge.

Results

Biofilm formation significantly increased acid tolerance in all the clinical streptococcal strains (P < 0.05) whereas the laboratory strains varied in their response. In biofilms, S. oralis was much more acid tolerant than S. gordonii or S. mutans. A. naeslundii showed a significant increase in acid tolerance in biofilms compared to planktonic cells (P < 0.001) which was not seen for A. odontolyticus. All strains except S. oralis induced an ATR after pre-exposure to pH 5.5 (P < 0.05). The presence of a salivary pellicle enhanced both acid tolerance development and ATR induction in S. gordonii biofilms (P < 0.05) but did not affect the other bacteria to the same extent.

Conclusions

These findings suggest that factors such as surface contact, the presence of a salivary pellicle and sensing of environmental pH can contribute to the development of high levels of acid tolerance amongst early colonizers in oral biofilms which may be important in the initiation of caries.

Metaproteome and metabolome of oral microbial communities

The emergence of high-throughput technologies for the comprehensive measurement of biomolecules, also referred to as "omics" technologies, has helped us gather "big data" and characterize microbial communities. In this article, we focus on metaproteomic and metabolomic approaches that support hypothesis-driven investigations on various oral biologic samples. Proteomics reveals the working units of the oral milieu and metabolomics unveils the reactions taking place; and so these complementary techniques can unravel the functionality and underlying regulatory processes within various oral microbial communities. Current knowledge of the proteomic interplay and metabolic interactions of microorganisms within oral biofilm and salivary microbiome communities is presented and discussed, from both clinical and basic research perspectives. Communities indicative of, or from, health, caries, periodontal diseases, and endodontic lesions are represented. Challenges, future prospects, and examples of best practice are given.

Evaluating protein binding specificity of titanium surfaces through mass spectrometry-based proteomics

OBJECTIVES

To evaluate whether surface characteristics of different titanium modifications may influence the composition of the salivary pellicle on each surface by analyzing the salivary proteome through mass spectrometry-based proteomics.

MATERIALS AND METHODS

Titanium discs with three surfaces modifications (PT (machined titanium), SLA (sandblasted/large-grit/acid-etched), and SLActive (modified SLA)) were characterized (topography, chemistry, and energy) prior to being exposed to saliva for 2 h to form a protein pellicle. The resultant protein layer was retrieved and analyzed through mass spectrometry (nLC-ESI-MS/MS) to examine the surface specificity for protein binding, while the proteome profile of each surface was classified.

RESULTS

The proteome analysis showed that the salivary pellicle composition was more complex on rough surfaces (SLA and SLActive). Although variability in protein composition was observed between surfaces, most proteins were detected on more than one surface, indicating a limited surface specificity for protein binding. Additionally, the salivary pellicle formed on the SLActive presented a larger number of proteins associated with immune response, biological adhesion, and biomineralization.

CONCLUSIONS

Although topography, chemistry, and energy differed between the surfaces, they were not determinant to produce a salivary pellicle with high surface specificity. Also, we showed that several salivary proteins adsorbed on Ti surfaces are involved in biological functions important to the biointegration.

CLINICAL RELEVANCE

This study sheds light on the necessity for the development of bioactive surfaces that favors the formation of a specific protein layer that can enhance tissue response to assist the biointegration of dental implants.

Optimizing the formation of the acquired enamel pellicle in vitro for proteomic analysis

Saliva is the major contributor for the protein composition of the acquired enamel pellicle (AEP), a bacteria-free organic layer formed by the selective adsorption of salivary proteins on the surface of the enamel. However, the amount of proteins that can be recovered is even smaller under in vitro condition, due to the absence of continuous salivary flow.

Proteomic profile of the saliva and plasma protein layer adsorbed on Ti-Zr alloy: the effect of sandblasted and acid-etched surface treatment

Titanium-zirconium (Ti-Zr) alloy has been widely used as a biomaterial for implant devices, and it is commonly treated by sandblasting followed by acid etching (SLA) to improve biological responses. Although protein adsorption is the first biological response, the effect of this SLA treatment on the proteomic profile of proteins adsorbed from saliva and blood plasma has not been tested. In this study, the proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Streptococcus sanguinis was used to test whether the protein layer affects bacterial adhesion. SLA treatment affected the proteomic profile, showing exclusive proteins adsorbed from saliva (14) and plasma (3). However, both groups exhibited close patterns of intensity for common proteins, molecular functions and biological processes mediated by proteins. Interestingly, Ti-Zr_SLA showed higher bacterial adhesion (∼1.9 fold over) for the surface coated with plasma proteins. Therefore, SLA treatment of Ti-Zr alloy changed the proteomic profile, which may affect bacterial adhesion.

Physical-chemical interactions between dental materials surface, salivary pellicle and Streptococcus gordonii

Dental materials are susceptible to dental plaque formation, which increases the risk of biofilm-associated oral diseases. Physical-chemical properties of dental material surfaces can affect salivary pellicle formation and bacteria attachment, but relationships between these properties have been understudied. We aimed to assess the effects of surface properties and adsorbed salivary pellicle on Streptococcus gordonii adhesion to traditional dental materials. Adsorption of salivary pellicle from one donor on gold, stainless steel, alumina and zirconia was monitored with a quartz crystal microbalance with dissipation monitoring (QCM-D). Surfaces were characterized by X-ray photoelectron spectroscopy, atomic force microscopy and water contact angles measurement before and after pellicle adsorption. Visualization and quantification of Live/Dead stained bacteria and scanning electron microscopy were used to study S. gordonii attachment to materials with and without pellicle. The work of adhesion between surfaces and bacteria was also determined. Adsorption kinetics and the final thickness of pellicle formed on the four materials were similar. Pellicle deposition on all materials increased surface hydrophilicity, surface energy and work of adhesion with bacteria. Surfaces with pellicle had significantly more attached bacteria than surfaces without pellicle, but the physical-chemical properties of the dental material did not significantly alter bacteria attachment. Our findings suggested that the critical factor increasing S. gordonii attachment was the salivary pellicle formed on dental materials. This is attributed to increased work of adhesion between bacteria and substrates with pellicle. New dental materials should be designed for controlling bacteria attachment by tuning thickness, composition and structure of the adsorbed salivary pellicle.

Comparison of protein profiles of the pellicle, gingival crevicular fluid, and saliva: possible origin of pellicle proteins

Background

The pellicle, the acellular organic material deposited on the surface of tooth enamel, has been thought to be derived from saliva. In this study, protein compositions of the pellicle, gingival crevicular fluid, and saliva collected from healthy adults were compared to elucidate the origin of pellicle proteins.

Results

The pellicle, gingival crevicular fluid, and saliva from the parotid gland or mixed gland were collected; subsequently, protein expression in samples from the respective individual was compared by SDS-PAGE and mass spectrometry. Following SDS-PAGE, proteins in the major bands were identified by mass spectrometry. The band pattern of pellicle proteins appeared different from those of gingival crevicular fluid, or saliva samples. Using mass spectrometry, 13 proteins in these samples were identified. The relative abundance of the proteins was quantitatively analyzed using mass spectrometry coupled with stable isotope labeling and by western blot. Cystatin S and α-amylase detected in pellicle were enriched in saliva samples, but not in gingival crevicular fluid, by western blot, and their abundance ratios were high in saliva and low in gingival crevicular fluid when analyzed by stable isotope labeling. Serotransferrin, however, was found only in the pellicle and gingival crevicular fluid by western blot and its abundance ratio was low in saliva.

Conclusions

Our study revealed that the gingival crevicular fluid appears to contribute to pellicle formation in addition to saliva.

Development of a New Cell-Based Oral Model To Study the Interaction of Oral Constituents with Food Polyphenols

Some polyphenols have unpleasant taste properties such as astringency, which could interfere with consumers' choices. The knowledge on astringency mechanisms points that astringency is a complex phenomenon probably related to more than one physical-chemical mechanism. Thus, this work aims to develop a new and more realistic cell-based model containing human saliva, mucosa pellicle, and an oral cell line (HSC-3) to understand the oral molecular events that could contribute to the overall astringency perception. This model was then used to study the interactions with a food procyanidin fraction (PF) by HPLC. In general, the results revealed higher interaction (synergism) for the model with all the referred oral constituents (mucosa pellicle, salivary proteins, and HSC-3 cell line, HSCMuSp) when compared to the interaction with individual constituents, the PF + cells or PF + saliva. Regarding the procyanidins, a significant interaction was observed for the procyanidin monomer EcG, procyanidin dimers B7 and B2G, and trimer C1.

Influence of Staining Solutions on Color Change and Enamel Surface Properties During At-home and In-office Dental Bleaching: An In Situ Study

The purpose of this in situ study was to evaluate the influence of staining solutions (coffee and cola) on the color change, microhardness, roughness, and micromorphology of the enamel surface during at-home and in-office dental bleaching. One hundred and thirty-five enamel bovine blocks were prepared to perform the evaluations. Fifteen volunteers used an intraoral appliance with nine enamel blocks for 15 days. The enamel blocks were randomly assigned among the different groups according to the three treatments: in-office bleaching with high hydrogen peroxide concentration (Opalescence Boost PF 40%, Ultradent) for 40 minutes in three sessions (first, eighth, and 15th days of treatment), at-home bleaching with low carbamide peroxide concentration (Opalescence PF 10%, Ultradent) for 60 minutes daily for 15 days, and a control group (no bleaching agent applied). The enamel blocks were immersed daily in different staining solutions (coffee or cola) for 30 minutes for 15 days or were not submitted to staining (control) to obtain a factorial scheme (3×3) of the dental bleaching treatment and staining solution (n=15). The microhardness analyses (Knoop), roughness evaluations (Ra), surface micromorphological observations, and color measurements (using the CIELAB system and the VITA Classical scale) were made before and after the bleaching treatments to assess immersion in staining solutions. Mixed model tests showed that there was a decrease in enamel microhardness after exposure to cola compared with coffee and the control group (p<0.0001) for both bleaching techniques. Roughness was higher for the cola groups (p<0.0001), and there was no significant difference between the coffee and the control groups. Generalized linear models showed that when no staining solution was applied, lighter color scores were found for the VITA Classical scale (p<0.0001). Without the staining solutions, there was an increase in luminosity (ΔL) (p=0.0444) for in-office bleaching. Lower values of Δa (p=0.0010) were observed when the staining solutions were not used. The Δb (p=0.3929) did not vary significantly between the bleaching agents, but when cola was applied, the values were significantly higher than for the control (p=0.0293). Higher values of ΔE (p=0.0089) were observed for in-office bleaching without staining solutions, while lower values of ΔE were observed for the in-office associated with coffee immersion. Regardless of whether being submitted to bleaching, the enamel stained with cola showed a decrease in microhardness, an increase in roughness, and changes in the micromorphology. The efficacy of the bleaching agents was greater when no staining solution (cola or coffee) was used, and in-office bleaching showed greater color change than the at-home bleaching technique.

Sialometry and concentration of phosphate and calcium in stimulated whole saliva and gingival crevicular fluid and its association with dental caries in schoolchildren

Introduction: The remineralizing properties of saliva contribute to maintain the physical and chemical integrity of the mineral structure of teeth, which protects it from the installation and evolution of dental caries. Objective: To relate sialometry, buffering capacity, calcium and phosphate concentration in whole stimulated saliva, and in gingival crevicular fluid with school children caries severity and activity. Materials and methods: We selected 36 schoolchildren aged 6 years: 18 with caries (International Caries Detection and Assessment System, ICDAS>1 group) and 18 without caries (ICDAS=0 group). The severity and activity of dental caries were diagnosed in the primary dentition: in the occlusal surface of molars and in the vestibular of the anterior teeth by ICDAS-II. Results: Caries in occlusal surface were more severe than in vestibular surface. The concentration of calcium in saliva and phosphate in healthy teeth gingival crevicular fluid were higher in the ICDAS>1 group. The concentration of calcium in gingival crevicular fluid was higher in the ICDAS=0 group than in the decayed teeth of the ICDAS>1 group. We found a statistically significant association between the frequency of active caries andthe concentration of phosphate in gingival crevicular fluid of teeth with caries, as well as between the severity of caries with buffering capacity and the concentration of phosphate in the gingival crevicular fluid of teeth with caries. Conclusion: We found an association between dental caries with buffering capacity and buccal calcium and phosphate.

Proteome analysis of the salivary pellicle formed on titanium alloys containing niobium and zirconium

The chemical composition of biomaterials can drive their biological responses; therefore, this in vitro study aimed to evaluate the proteomic profile of the salivary pellicle formed on titanium (Ti) alloys containing niobium (Nb) and zirconium (Zr). The experimental groups consisted of Ti35NbxZr (x = 5 and 10 wt%) alloys, and commercially pure titanium (cpTi); titanium aluminium vanadium (Ti6Al4V) alloys were used as controls. The physical and chemical characteristics of the Ti materials were analysed. The proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry. Bacterial adhesion (2 h) of mixed species (Streptococcus sanguinis and Actinomyces naeslundii) was investigated as colony-forming units (n = 6). This paper reports the finding that salivary pellicle composition can be modulated by the composition of the Ti material. The Ti35NbxZr group showed a significant ability to adsorb proteins from saliva, which can favour interactions with cells and compatibility with the body.

Proteomic Analysis of the Initial Oral Pellicle in Caries-Active and Caries-Free Individuals

PURPOSE

To 1) elucidate individual proteomic profiles of the 3-min biofilm of caries-active and caries-free individuals and 2) compare these proteomic profiles against the background of caries.

EXPERIMENTAL DESIGN

The initial oral pellicle of 12 caries-active and 12 caries-free individuals is generated in situ on ceramics specimens. The individual, host-specific proteomic profiles of this basic pellicle layer are analyzed by a chemical elution protocol combined with an elaborate mass spectrometry and evaluated bioinformatically.

RESULTS

A total of 1188 different proteins are identified. Additionally, 68 proteins are present in the profiles of all individuals, suggesting them as ubiquitously occurring base-proteins of the initial human pellicle. Thereof, the single profiles exhibit high inter-individual differences independent of their group affiliation, stating the initial pellicle to represent a rather "individual fingerprint". Quantitative analyses imply slight indication for 23 proteins potentially capable of counting for caries-specific biomarkers.

CONCLUSIONS AND CLINICAL RELEVANCE

The introduced protocol enables the individual analysis of minimal protein amounts and allows for highly precise characterizations and comparisons of individual proteomic profiles. The results contain a considerable higher extent of protein identifications and might serve as a base for future large scale analyzes to identify discrimination factors for the development of caries susceptibility tests.

Proteomic analysis of the acquired enamel pellicle formed on human and bovine tooth: a study using the Bauru in situ pellicle model (BISPM)

OBJECTIVES

The acquired enamel pellicle (AEP) is an organic film, bacteria-free, formed in vivo as a result of the selective adsorption of salivary proteins and glycoproteins to the solid surfaces exposed to the oral environment. Objective: This study aimed to compare the proteomic profile of AEP formed in situ on human and bovine enamel using a new intraoral device (Bauru in situ pellicle model - BISPM).

MATERIAL AND METHODS

Material and Methods: One hundred and eight samples of human and bovine enamel were prepared (4×4 mm). Nine subjects with good oral conditions wore a removable jaw appliance (BISPM) with 6 slabs of each substrate randomly allocated. The AEP was formed during the morning, for 120 minutes, and collected with an electrode filter paper soaked in 3% citric acid. This procedure was conducted in triplicate and the pellicle collected was processed for analysis by LC-ESI-MS/MS. The obtained mass spectrometry MS/MS spectra were searched against human protein database (SWISS-PROT).

RESULTS

Results: The use of BISPM allowed the collection of enough proteins amount for proper analysis. A total of 51 proteins were found in the AEP collected from the substrates. Among them, 15 were common to both groups, 14 were exclusive of the bovine enamel, and 22 were exclusive of the human enamel. Proteins typically found in the AEP were identified, such as Histatin-1, Ig alpha-1, Ig alpha 2, Lysozyme C, Statherin and Submaxillary gland androgen-regulated protein 3B. Proteins not previously described in the AEP, such as metabolism, cell signaling, cell adhesion, cell division, transport, protein synthesis and degradation were also identified.

CONCLUSIONS

Conclusion: These results demonstrate that the proteins typically found in the AEP appeared in both groups, regardless the substrate. The BISPM revealed to be a good device to be used in studies involving proteomic analysis of the AEP.

Salivary functions in mastication, taste and textural perception, swallowing and initial digestion

Saliva exerts multiple functions in relation to the initial digestive processes taking place in the upper parts of the gastrointestinal tract. Ingestion of food and beverages, in turn, is a strong stimulus for secretion of saliva with a differential composition depending on the neuronal stimulation pattern. This review paper provides insight into the mechanisms by which saliva acts in relation to taste, mastication, bolus formation, enzymatic digestion and swallowing. Also, the protective functions of saliva including maintenance of dental and mucosal integrity will be discussed as they indirectly influence the digestive process. The final part of this study focuses on the implications of xerostomia and salivary gland dysfunction on gastrointestinal functions.

Novel Two-Component System of Streptococcus sanguinis Affecting Functions Associated with Viability in Saliva and Biofilm Formation

Streptococcus sanguinis is a pioneer species of teeth and a common opportunistic pathogen of infective endocarditis. In this study, we identified a two-component system, S. sanguinis SptRS (SptRS _Ss ), affecting S. sanguinis survival in saliva and biofilm formation. Isogenic mutants of sptR_Ss (SKsptR) and sptS_Ss (SKsptS) showed reduced cell counts in ex vivo assays of viability in saliva compared to those of parent strain SK36 and complemented mutants. Reduced counts of the mutants in saliva were associated with reduced growth rates in nutrient-poor medium (RPMI) and increased susceptibility to the deposition of C3b and the membrane attach complex (MAC) of the complement system, a defense component of saliva and serum. Conversely, sptR_Ss and sptS_Ss mutants showed increased biofilm formation associated with higher levels of production of H₂O₂ and extracellular DNA. Reverse transcription-quantitative PCR (RT-qPCR) comparisons of strains indicated a global role of SptRS _Ss in repressing genes for H₂O₂ production (2.5- to 15-fold upregulation of spxB, spxR, vicR, tpk, and ackA in sptR_Ss and sptS_Ss mutants), biofilm formation, and/or evasion of host immunity (2.1- to 11.4-fold upregulation of srtA, pcsB, cwdP, iga, and nt5e). Compatible with the homology of SptR _Ss with AraC-type regulators, duplicate to multiple conserved repeats were identified in 1,000-bp regulatory regions of downstream genes, suggesting that SptR _Ss regulates transcription by DNA looping. Significant transcriptional changes in the regulatory genes vicR, spxR, comE, comX, and mecA in the sptR_Ss and sptS_Ss mutants further indicated that SptRS _Ss is part of a regulatory network that coordinates cell wall homeostasis, H₂O₂ production, and competence. This study reveals that SptRS _Ss is involved in the regulation of crucial functions for S. sanguinis persistence in the oral cavity.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

Investigating the association between stress, saliva and dental caries: a scoping review

BACKGROUND

This scoping review addressed the question 'what do we know about stress-related changes in saliva and dental caries in general population?'

METHODS

The review was conducted using electronic searches via Embase, MEDLINE, PsycINFO, CINAHL and WoS. All published human studies with both observational and experimental designs were included. Two reviewers independently reviewed eligible articles and extracted the data. The studies' quality was assessed using the Effective Public Health Practice Project Quality Assessment Tool.

RESULTS

Our search identified 232 reports, of which six were included in this review. All six studies were conducted in children and used salivary cortisol as stress marker. The studies varied by design, types of stressors, children's caries experience, methods of saliva collection. Four studies reported a positive association between saliva cortisol levels and caries (p < 0.05) while the other two reported no association (p > 0.05). The quality of the included studies was weak to moderate.

CONCLUSIONS

There is lack of evidence about an association between stress-related changes in saliva and caries. Well-designed longitudinal studies with rigorous measurement technics for stress, saliva and dental caries are necessary. This will help to generate new insights into the multifactorial etiology of caries and provide evidence for a rational method for its control.

Changes in the Proteomic Profile of Acquired Enamel Pellicles as a Function of Their Time of Formation and Hydrochloric Acid Exposure

Objective: Changes in the protein profile of acquired enamel pellicles (AEP) formed in vivo over different time periods were evaluated after the application of hydrochloric acid (HCl). Methods: Nine subjects were submitted to dental prophylaxis with pumice. After 3 or 120 min, the teeth were isolated with cotton rolls and 50 μL of 0.1 M HCl (pH 1.0), 0.01 M HCl (pH 2.0), or deionized water were applied on the buccal surface of the teeth for 10 s. The AEP was then collected using an electrode filter paper presoaked in 3% citric acid. After protein extraction, the samples were submitted to reverse-phase liquid chromatography coupled to mass spectrometry (nano LC-ESI-MS/MS). Label-free quantification was performed (Protein Lynx Global Service software). Results: A total of 180 proteins were successfully identified in the AEP samples. The number of identified proteins increased with the time of pellicle formation. Only 4 proteins were present in all the groups (isoforms of IgA, serum albumin, and statherin). The greatest number of proteins identified uniquely in one of the groups was obtained for the groups treated with HCl after 2 h of pellicle formation (approx. 50 proteins). Conclusion: Proteins resistant to removal by HCl, such as serum albumin and statherin, were identified even in the short-term AEP. In addition, 120-min pellicles present many proteins that are resistant to removal by HCl. This suggests an increase in protection against intrinsic acids with the time of pellicle formation, which should be evaluated in future studies.

Protein Profile of the Acquired Enamel Pellicle after Rinsing with Whole Milk, Fat-Free Milk, and Water: An in vivo Study

This study detected changes in the protein profile of the acquired enamel pellicle (AEP) formed in vivo after rinsing with whole milk, fat-free milk, or water. Nine subjects in good oral condition took part in the study. The acquired pellicle was formed in the morning, for 120 min, after prophylaxis with pumice. Following this, the volunteers rinsed with 10 mL of whole milk, fat-free milk, or deionized water for 30 s, following a blinded crossover protocol. After 60 min, the pellicle was collected with filter paper soaked in 3% citric acid and processed for analysis by liquid chromatography-electrospray ionization tandem mass spectrometry. The obtained tandem mass spectrometry spectra were searched against a human protein database (Swiss-Prot). The proteomic data related to protein quantification were analysed using the PLGS software. A total of 260 proteins were successfully identified in the AEP samples collected from all groups. Forty-nine were common to all 3 groups, while 72, 62, and 49 were specific to the groups rinsing with whole milk, fat-free milk, and water, respectively. Some were typical components of the AEP, such as cystatin-B, cystatin-SN, isoforms of α-amylase, IgA and IgG, lysozyme C, protein S100 A78, histatin-1, proline-rich protein 27, statherin, and lactotransferrin. Other proteins are not commonly described as part of the AEP but could act in defence of the organism against pathogens. Distinct proteomic profiles were found in the AEP after rinsing with whole or fat-free milk, which could have an impact on bacterial adhesion and tooth dissolution. The use of fat-free milk could favourably modulate the adhesion of bacteria to the AEP as well as biofilm formation when compared with whole milk.

The effect of different salivary calcium concentrations on the erosion protection conferred by the salivary pellicle

Different proportions of mineral ions in saliva can influence the protective effect the salivary pellicle provides against dental erosion. To investigate the effect of different calcium concentrations in human saliva on the protection against enamel erosion, enamel specimens were divided into 8 treatment groups: humid chamber (Ctrl); whole mouth stimulated human saliva (HS); artificial saliva containing different calcium concentrations (AS_low, AS_medium, AS_high); and dialysed human saliva containing different calcium concentrations (DS_low, DS_medium, DS_high). The specimens underwent 4 cycles of incubation in the treatment group followed by an erosive challenge. Surface hardness and calcium release were measured during the cycling process. All DS groups exhibited significantly higher enamel surface softening than HS and the corresponding AS groups. Among the DS groups, the surface softening was significantly higher in DS_low than in DS_high. No significant differences were found within the AS or DS groups regarding calcium release. The results of this study indicated that erosion protection conferred by saliva depends on an interplay between salivary proteins and ions. While both proteins and ions have a positive effect on their own, the combination of the two can lead to different degrees of protection or even negative effects, depending on the relative concentrations.

Influence of saliva on the oral microbiota

Saliva plays a major role in determining the composition and activity of the oral microbiota, via a variety of mechanisms. Molecules, mainly from saliva, form a conditioning film on oral surfaces, thus providing receptors for bacterial attachment. The attached cells use saliva components, such as glycoproteins, as their main source of nutrients for growth. Oral bacteria work sequentially and in a concerted manner to catabolize these structurally complex molecules. Saliva also buffers the pH in the biofilm to around neutrality, creating an environment which is conducive to the growth of many oral bacteria that provide important benefits to the host. Components of the adaptive and innate host defences are delivered by saliva, and these often function synergistically, and at sublethal concentrations, so a complex relationship develops between the host and the resident microbiota. Dysbiosis can occur rapidly if the flow of saliva is perturbed.

Advances of Proteomic Sciences in Dentistry

Applications of proteomics tools revolutionized various biomedical disciplines such as genetics, molecular biology, medicine, and dentistry. The aim of this review is to highlight the major milestones in proteomics in dentistry during the last fifteen years. Human oral cavity contains hard and soft tissues and various biofluids including saliva and crevicular fluid. Proteomics has brought revolution in dentistry by helping in the early diagnosis of various diseases identified by the detection of numerous biomarkers present in the oral fluids. This paper covers the role of proteomics tools for the analysis of oral tissues. In addition, dental materials proteomics and their future directions are discussed.

Polymicrobial Biofilm Studies: From Basic Science to Biofilm Control

Microbes rarely exist as single species planktonic forms as they have been commonly studied in the laboratory. Instead, the vast majority exists as part of complex polymicrobial biofilm communities attached to host and environmental surfaces. The oral cavity represents one of the most diverse and well-studied polymicrobial consortia. Despite a burgeoning field of mechanistic biofilm research within the past decades, our understanding of interactions that occur between microbial members within oral biofilms is still limited. Thus, the primary objective of this review is to focus on polymicrobial biofilm formation, microbial interactions and signaling events that mediate oral biofilm development, consequences of oral hygiene on both local and systemic disease, and potential therapeutic strategies to limit oral dysbiosis.

Intermicrobial Interactions as a Driver for Community Composition and Stratification of Oral Biofilms

The oral cavity is accessible to microorganisms, and biofilms are present throughout on hard and soft tissues. The shedding of epithelial cell layers is usually effective for controlling biofilm development on soft tissues. Innate immune mechanisms are not so effective against biofilms on tooth surfaces, and oral hygiene measures such as brushing and flossing are required for the periodic removal of dental plaque. Even with good oral hygiene, microbial communities accumulate on teeth in areas that are protected from mechanical abrasion forces. Changes in the composition of these biofilms are associated with oral diseases such as dental caries or periodontitis. Newly formed biofilms and more mature dental plaque each have a level of spatial organization in the horizontal and vertical planes. Communities are shaped by many varied interactions between different species and genera within the biofilm, which include physical cell-cell associations known as coaggregation, interspecies signaling, secretion and turnover of antimicrobial compounds and the sharing of an extracellular matrix. Central to these interactions is the selection for metabolic synergies and it is becoming clear that the ability of communities to extract the maximum energy from the available metabolites is a potent driver for biofilm structure and stratification. This review discusses recent advances in our understanding of intermicrobial interactions in oral biofilms and the roles that they play in determining the spatial organization of biofilm communities.

Application of Plant Extracts for the Prevention of Dental Erosion: An in situ/in vitro Study

OBJECTIVES

Antiadherent and antibacterial effects of certain plant extracts have been proven to be beneficial in preventive dentistry. In the present in situ/in vitro crossover study, the impact of plant extracts rich in polyphenols on the erosion-protective properties of the in situ pellicle was evaluated.

METHODS

Individual splints were prepared for 12 subjects for intraoral exposure of bovine enamel specimens. Following formation of a 1-min pellicle, watery plant extracts (leaves of the wild form of Ribes nigrum, the wild form of Origanum as well as a combination of both) were administered for 10 min in situ. Alternatively, a mouth rinse with fluorides (Elmex Kariesschutz) was performed for 1 min. After further oral exposure for 19/28 min, respectively, slabs were removed and incubated with HCl in vitro over 120 s (pH 2, 2.3, 3). The resulting calcium and phosphate release was quantified photometrically. Slabs with and without a 30-min in situ pellicle served as controls. The modification of pellicle ultrastructure was evaluated by transmission electron microscopy (TEM).

RESULTS

Plant extracts modulated the erosion-protective properties of the native in situ pellicle in all test groups in a pH-dependent manner. The combination of R. nigrum leaves and Origanum enhanced the protective properties of the pellicle at all pH values; the administration of this preparation was comparable, yet superior, to the effect of the fluoridated mouth rinse. TEM images indicated that rinsing with R. nigrum leaves/Origanum yielded a distinctly thicker and more electron-dense pellicle.

CONCLUSION

The combination of certain plant extracts offers a novel approach to the complementary prevention of dental erosion.

Saliva as the Sole Nutritional Source in the Development of Multispecies Communities in Dental Plaque

Dental plaque is a polymicrobial biofilm that forms on the surfaces of teeth and, if inadequately controlled, can lead to dental caries or periodontitis. Nutrient availability is the fundamental limiting factor for the formation of dental plaque, and for its ability to generate acid and erode dental enamel. Nutrient availability is also critical for bacteria to grow in subgingival biofilms and to initiate periodontitis. Over the early stages of dental plaque formation, micro-organisms acquire nutrients by breaking down complex salivary substrates such as mucins and other glycoproteins. Once dental plaque matures, dietary carbohydrates become more important for supragingival dental plaque, and gingival crevicular fluid forms the major nutrient source for subgingival microorganisms. Many species of oral bacteria do not grow in laboratory monocultures when saliva is the sole nutrient source, and it is now clear that intermicrobial interactions are critical for the development of dental plaque. This chapter aims to provide an overview of the key metabolic requirements of some well-characterized oral bacteria, and the nutrient webs that promote the growth of multispecies communities and underpin the pathogenicity of dental plaque for both dental caries and periodontitis.