Adhesion of oral streptococci to experimental bracket pellicles from glandular saliva

Managing oral biofilms to avoid enamel demineralization during fixed orthodontic treatment

Enamel demineralization represents the most prevalent complication arising from fixed orthodontic treatment. Its main etiology is the development of cariogenic biofilms formed around orthodontic appliances. Ordinarily, oral biofilms exist in a dynamic equilibrium with the host's defense mechanisms. However, the equilibrium can be disrupted by environmental changes, such as the introduction of a fixed orthodontic appliance, resulting in a shift in the biofilm's microbial composition from non-pathogenic to pathogenic. This alteration leads to an increased prevalence of cariogenic bacteria, notably mutans streptococci, within the biofilm. This article examines the relationships between oral biofilms and orthodontic appliances, with a particular focus on strategies for effectively managing oral biofilms to mitigate enamel demineralization around orthodontic appliances.

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.

Bio-Interactive Zwitterionic Dental Biomaterials for Improving Biofilm Resistance: Characteristics and Applications

Biofilms are formed on surfaces inside the oral cavity covered by the acquired pellicle and develop into a complex, dynamic, microbial environment. Oral biofilm is a causative factor of dental and periodontal diseases. Accordingly, novel materials that can resist biofilm formation have attracted significant attention. Zwitterionic polymers (ZPs) have unique features that resist protein adhesion and prevent biofilm formation while maintaining biocompatibility. Recent literature has reflected a rapid increase in the application of ZPs as coatings and additives with promising outcomes. In this review, we briefly introduce ZPs and their mechanism of antifouling action, properties of human oral biofilms, and present trends in anti-biofouling, zwitterionic, dental materials. Furthermore, we highlight the existing challenges in the standardization of biofilm research and the future of antifouling, zwitterated, dental materials.

THE ROLE OF NEW TECHNOLOGIES IN DEFINING SALIVARY PROTEIN COMPOSITION FOLLOWING PLACEMENT OF FIXED ORTHODONTIC APPLIANCES - BREAKTHROUGH IN THE DEVELOPMENT OF NOVEL DIAGNOSTIC AND THERAPEUTIC PROCEDURES

Human saliva is rich in proteins of variable functions (e.g., enzymes, immunoglobulins, cytokines) and origin (blood plasma, salivary glands, or oral microflora). Circadian dynamics, volume and composition (electrolytes, pH, protein, etc.) of secreted saliva vary with local and systemic physiological and pathophysiological conditions. Therefore, the composition of saliva, protein in particular, has been intensively investigated to identify the potential markers and/or mechanisms of systemic and local diseases. Proteomic techniques used for the analysis of biological fluids have enabled great advances in salivary protein stabilization (as the main precondition for their analysis) and detection of those found in saliva in very low concentrations, including small proteins and peptides. This review brings the main characteristics of current proteomic techniques such as liquid chromatography-mass spectrometry, two-dimensional electrophoresis-mass spectrometry, and surface-enhanced laser desorption ionization/time of flight/mass spectrometry. These techniques enable simultaneous identification of hundreds and thousands of protein molecules, as well as identifying those of a potential biological value in particular states. This literature review is focused on the state-of-the-art and possibilities offered by proteomic techniques in analyzing the effects of orthodontic appliances on salivary protein composition and searching for potential markers of therapeutic success/failure or for the molecules by which therapeutic effects are achieved.

Changes in tribological and antibacterial properties of poly(methyl methacrylate)-based 3D-printed intra-oral appliances by incorporating nanodiamonds

It is essential for 3D-printed intra-oral appliances to be able to withstand the mechanical and microbial insult existent in the harsh environment of the oral cavity. Poly(methyl methacrylate) (PMMA)-based appliances are widely used in dentistry. Hence, the present study aimed to evaluate the role of nanodiamonds (NDs) as fillers to enhance the resistance to friction and wear. Using a solution-based mixing technique, 0.1 wt% ND was incorporated into the PMMA, and specimens were 3D-printed for tribological and bacterial analysis. The control specimens without ND fillers were tested against specimens with both amine-functionalized NDs (A-ND) and pure non-functionalized NDs (ND). The surface hardness test revealed a statistically significant increase in the Vickers micro-hardness (p < 0.001) in the nanocomposite groups. There was a significant reduction in the coefficient of friction (COF) (p < 0.01) in both the ND and A-ND nanocomposites compared to the stainless steel (SS) counter surfaces. However, for titanium (Ti)-based specimens, the COF of the control group was similar to that of A-ND but lower than that of ND. The wear resistance evaluation revealed that both the ND and A-ND groups displayed enhanced resistance to surface loss in comparison to the controls for both SS and Ti counter-surfaces (p < 0.001). Furthermore, both A-ND and ND exhibited significantly enhanced resistance to the formation of Streptococcus mutans biofilms after 48 h (p < 0.01) compared to the control group. Hence, we concluded that the addition of 0.1 wt% ND in the PMMA-based resin for 3D printing resulted in significant improvement in properties such as COF, wear resistance, and resistance to S. mutans, without any notable impact associated with the functionalization of the NDs.

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.

Saliva-coated titanium biosensor detects specific bacterial adhesion and bactericide caused mass loading upon cell death

Bacteria adhering to implanted medical devices can cause invasive microbial infections, of e.g. skin, lung or blood. In dentistry, Streptococcus gordonii is an early oral colonizer initiating dental biofilm formation and also being involved in life-threatening infective endocarditis. To treat oral biofilms, antibacterial mouth rinses are commonly used. Such initial biomaterial-bacteria interactions and the influence of antibacterial treatments are poorly understood and investigated here in situ by quartz crystal microbalance with dissipation monitoring (QCM-D). A saliva-coated titanium (Ti) biosensor is applied to analyze possible specific signal patterns indicating microbial binding mechanisms and bactericide-caused changes in bacterial film rigidity or cell leakage caused by a clinically relevant antibacterial agent (ABA), i.e., a mouth rinse comprising chlorhexidine (CHX) and cetylpyridinium chloride (CPC). Apparent missing mass effects during the formation of microscopically proven dense and vital bacterial films indicate punctual, specific binding of S. gordonii to the saliva-coated biosensor, compared to unspecific adhesion to pure Ti. Coincidentally to ABA-induced killing of surface-adhered bacteria, an increase of adsorbed dissipative mass can be sensed, contrary to the prior mass-loss. This suggests the acoustic sensing of the leakage of cellular content caused by bacterial cell wall rupturing and membrane damage upon the bactericidal attack. The results have significant implications for testing bacterial adhesion mechanisms and cellular integrity during interaction with antibacterial agents.

Photocatalytic antibacterial effects on TiO2-anatase upon UV-A and UV-A/VIS threshold irradiation

Photocatalysis mediated by the anatase modification of titanium dioxide (TiO2) has shown antibacterial effects in medical applications. The aim of this study was to investigate the possibility of expanding the excitation wavelengths for photocatalytic antibacterial effects from ultraviolet (UV) into the visible light range. After deposition of salivary pellicle and adhesion of Streptococcus gordonii on anatase, different irradiation protocols were applied to induce photocatalysis: ultraviolet A (UV-A) > 320 nm; ultraviolet/visible (UV-A/VIS) light > 380 nm and > 390 nm; and VIS light 400-410 nm. A quartz crystal microbalance with dissipation (QCM-D) tests and microscopic examination were used to observe the photoinduced antibacterial effects. Salivary pellicle could be photocatalytically decomposed under all irradiation protocols. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only. Wavelengths above 380 nm show promise for in situ therapeutic antifouling applications.

Inhibition of initial bacterial adhesion on titanium surfaces by lactoferrin coating

Because dental implant abutments are located at transmucosal sites, their surface should inhibit bacterial accumulation to prevent peri-implantitis. The authors examined the effects of human lactoferrin (LF), an antibacterial protein present in saliva, as an antibacterial coating on the titanium surface and evaluated its effects before and after mucin-containing artificial saliva (AS) incubation. In the control group, titanium disks were soaked in distilled water, whereas in the LF group, titanium disks were soaked in LF solution to coat the disks. In the control-AS and LF-AS groups, half of the control and LF disks were incubated with AS. To confirm LF adsorption, the fluorescence intensity of fluorescein isothiocyanate-labeled LF was measured. The LF and LF-AS groups showed significantly higher intensity than the control and control-AS groups (P < 0.01). There was no significant difference between the LF and LF-AS groups (P > 0.05). The amount of adhered Streptococcus gordonii significantly increased by incubation with AS (P < 0.01) and significantly decreased by adsorption of LF (P < 0.01). There was no interaction between the two factors, LF adsorption and AS incubation (P = 0.561). These results suggest that the adsorbed LF inhibited bacterial adhesion following AS incubation. According to qualitative LIVE/DEAD analysis, viable bacteria appeared to be decreased in the presence of LF and SEM observation indicated that altered morphologies increased in LF and LF-AS groups. These results suggest that the adsorbed LF remained on the titanium surface after incubation with AS, and the remaining LF inhibited bacterial adhesion and exhibited bactericidal effects. Therefore, the adsorption of LF on the abutment material appears to be effective in preventing peri-implantitis.

Quantitative analysis of S. mutans and S. sobrinus cultivated independently and adhered to polished orthodontic composite resins

In orthodontics, fixed appliances placed in the oral cavity are colonized by microorganisms.

OBJECTIVE

The purpose of this study was to quantitatively determine the independent bacterial colonization of S. mutans and S. sobrinus in orthodontic composite resins.

MATERIAL AND METHODS

Seven orthodontic composite adhesives for bonding brackets were selected and classified into 14 groups; (GIm, GIs) Enlight, (GIIm, GIIs) Grengloo, (GIIIm, GIIIs) Kurasper F, (GIVm, GIVs) BeautyOrtho Bond, (GVm, GVs) Transbond CC, (GVIm, GVIs) Turbo Bond II, (GVIIm, GVIIs) Blugloo. 60 blocks of 4x4x1 mm of each orthodontic composite resin were made (total 420 blocks), and gently polished with sand-paper and ultrasonically cleaned. S. mutans and S. sobrinus were independently cultivated. For the quantitative analysis, a radioactive marker was used to codify the bacteria (³H) adhered to the surface of the materials. The blocks were submerged in a solution with microorganisms previously radiolabeled and separated (210 blocks for S. mutans and 210 blocks for S. sobrinus) for 2 hours at 37 ºC. Next, the blocks were placed in a combustion system, to capture the residues and measure the radiation. The statistical analysis was calculated with the ANOVA test (Sheffè post-hoc).

RESULTS

Significant differences of bacterial adhesion were found amongst the groups. In the GIm and GIs the significant lowest scores for both microorganisms were shown; in contrast, the values of GVII for both bacteria were significantly the highest.

CONCLUSIONS

This study showed that the orthodontic composite resin evaluated in the GIm and GIs, obtained the lowest adherence of S. mutans and S. sobrinus, which may reduce the enamel demineralization and the risk of white spot lesion formation.

Adhesion of Streptococci to various orthodontic composite resins

BACKGROUND

This investigation aimed to determine quantitatively the adhesion of Streptococcus mutans and Streptococcus sobrinus to orthodontic composite resins that were tested simultaneously using radio-markers.

METHODS

Seven orthodontic composite resins were classified into seven groups: BeautyOrtho Bond (GI), Blugloo (GII), Enlight (GIII), Grengloo (GIV), Kurasper F (GV), Transbond CC (GVI) and Turbo Bond II (GVII). Thirty 4 x 4 x 1 mm blocks of each orthodontic composite resin were made (a total of 210 blocks). Both Streptococcus species were cultivated independently. For the quantitative analysis, radioactive markers were used to codify the bacteria ((3) H for Streptococcus mutans and (14) C for Streptococcus sobrinus). The blocks were submerged in a solution with microorganisms previously radiolabelled for 2 hours at 37 °C in constant movement. The blocks were placed in a combustion system to quantify the Streptococcus adhering to the surface of the materials by capturing the residues and measuring the radiation.

RESULTS

Significant differences in bacterial adhesion were found among the groups. The lowest significant scores for both microorganisms were observed in GIII.

CONCLUSIONS

The orthodontic composite resin evaluated in GIII exhibited the lowest adhesion of Streptococcus mutans and Streptococcus sobrinus, which may reduce enamel demineralization and the risk of white spot lesion formation.

The impact of dendrimer-grafted modifications to model silicon surfaces on protein adsorption and bacterial adhesion

In the oral cavity, omnipresent salivary protein films (pellicle) mediate bacterial adhesion and biofilm formation on natural tissues as well as on artificial implant surfaces, which may cause serious infectious diseases like periimplantitis. The purpose of this in vitro study was to investigate the adsorption/desorption behaviour of human saliva on model surfaces grafted with polyamidoamine (PAMAM) dendrimer molecules compared to self-assembled monolayers (SAMs) exhibiting the same terminal functions (-NH(2), -COOH) by two complementary analytical methods. Furthermore, the role of saliva conditioning of PAMAM and analogous SAM modifications on the adhesion of Streptococcus gordonii DL1, an early oral colonizer, was investigated. In contrast to SAMs, PAMAM-grafted surfaces showed reduced streptococcal adherence in the absence of pre-adsorbed saliva similar to the level obtained for poly(ethylene glycol) (PEG) coatings. Moreover, coatings of PAMAM-NH(2) maintained their bacteria-repellent behaviour even after saliva-conditioning. As a general outcome, it was found that lower amounts of protein adsorbed on PAMAM coatings than on analogous SAMs. Since this study demonstrates that covalently bound PAMAM dendrimers can modulate the oral bacterial response, this approach has significant potential for the development of anti-adhesive biomaterial surfaces that are conditioned with proteinaceous films.

Surface Characteristics of Orthodontic Materials and Their Effects on Adhesion of Mutans streptococci

Objective: To test the hypothesis that there are no significant differences in the adhesion of mutans streptococci (MS) to various orthodontic materials based on their surface characteristics.

Materials and Methods: Surface roughness (SR) and surface free energy (SFE) characteristics were investigated for nine different orthodontic materials (four orthodontic adhesives, three bracket raw materials, hydroxyapatite blocks, and bovine incisors) using confocal laser scanning microscopy and sessile drop method. Each material, except the bovine incisors, was incubated with whole saliva or phosphate-buffered saline for 2 hours. Adhesion assays were performed by incubating tritium-labeled MS with each material for 3 or 6 hours.

Results: Orthodontic adhesives had higher SFE characteristics and lower SR than bracket materials. Orthodontic adhesives showed a higher MS retaining capacity than bracket materials, and MS adhesion to resin-modified glass ionomer and hydroxyapatite was highest. Extended incubation time increased MS adhesion, while saliva coating did not significantly influence MS adhesion. SFE, specifically its dispersive and polar components, was positively correlated with MS adhesion, irrespective of saliva coating.

Conclusions: The hypothesis is rejected. This study suggests that SFE characteristics play an important role in the initial MS adhesion to orthodontic materials.

Photocoupling of fibronectin to titanium surfaces influences keratinocyte adhesion, pellicle formation and thrombogenicity

OBJECTIVES

Coating of implant surfaces with biomolecules can influence basic host responses and enhance subsequent tissue integration. The biological factors have to be immobilized on the implant material. Human fibronectin (Fn) was used as a model protein and covalently coupled to titanium (Ti) surfaces via silanization and an anthraquinone linker. The impact on several aspects of initial host/biomaterial interactions (keratinocyte adhesion, platelet interactions and pellicle formation) was studied.

METHODS

Coupling efficiency was characterized by immunological techniques. The effects of coupled Fn on initial host/biomaterial interactions were assessed. Cell adhesion and spreading were investigated by fluorescent staining, pellicle formation by an acoustic sensor system (quartz crystal microbalance with dissipation, QCM-D), and platelet adhesion as one parameter mediating the inflammatory response by scanning electron microscopy (SEM) and immunological assays.

RESULTS

Coupling efficiency was related to irradiation time used for photochemical coupling of the UV-activated anthraquinone to the silanized Ti surface. With an optimized protocol, the amount of Fn coupled to the surface could be almost doubled compared to standard dip-coating methods. On the anthraquinone-coupled Fn coatings, cell adhesion and spreading of human keratinocytes was significantly enhanced. Online detection of pellicle formation revealed strong reversibility of saliva protein adhesion on Fn coated surfaces compared to the pure Ti surface. Furthermore, the Fn coated Ti showed a low thrombogenicity.

SIGNIFICANCE

This study suggests that anthraquinone-coupled biological coatings may be useful for biofunctionalization of Ti dental implants by enhancement of soft tissue re-integration (restoration of the epithelial seal) combined with diminished pellicle formation.