Influence of different restorative materials on lysozyme and amylase activity of the salivary pellicle in situ

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

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

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.

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

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

The dentin pellicle - A neglected topic in dental research

OBJECTIVE

All soft and solid surfaces exposed to the oral cavity are covered by an acquired pellicle. While the pellicle adsorbed on enamel is well researched, only limited data are available on the dentin pellicle. The purpose of the present review is to summarize studies considering the composition, structure and properties of the dentin pellicle and compare them with the current state of research on enamel pellicle.

METHODS

The literature search was conducted using Medline database and Google Scholar, including checking reference lists of journal articles by handsearching. Thereby, 19 studies were included in the present review.

RESULTS AND CONCLUSION

The dentin pellicle has a similar ultrastructure to the enamel pellicle, which is up to 1 μm thick depending on pellicle formation time and localization in the oral cavity. In contrast, due to the lack of studies on the dentin pellicle regarding its composition and properties, a comparison to the enamel pellicle is difficult. So far, only one study showed anti-abrasive properties and data on anti-erosive properties were controversial. Despite becoming more and more clinically relevant due to the increasing frequency of dentin exposure, the dentin pellicle is largely unexplored. For further investigations it is not only necessary to standardize dentin specimens, but also to assess fundamental research on dentin itself, as its complex morphology and composition may have a crucial influence on pellicle formation. Furthermore, a more detailed knowledge of the dentin pellicle may also reveal target sites for modification in favor of its protective properties.

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.

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

BACKGROUND

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

OBJECTIVES AND FINDINGS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Effect of amylase activity on mechanical properties of dental composite resin

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

Novel urethane-based polymer for dental applications with decreased monomer leaching

The aim of this study was to synthesize and characterize new multifunctional-urethane-methacrylate monomers to be used as the organic matrix in restorative dental composites, and evaluate the main physical-chemical properties of the resulting material. Bis-GMA (bisphenol-A-diglycidylmethacrylate) and GDMA (glycerol dimethacrylate) were modified by reacting the hydroxyl groups with isocyanate groups of urethane-methacrylate precursors to result in the new monomeric systems U-(bis-GMA)-Mod and U-(GDMA)-Mod, U=Urethane and Mod=Modified. The modifications were characterized by FTIR and ¹H NMR. The final monomeric synthesized system was used to prepare dental resins and composites. The physical-chemical properties were evaluated and compared with those of bis-GMA composites with varying filler contents or unfilled resins. U-(bis-GMA)-Mod and U-(GDMA)-Mod can be used to prepare dental restorative composites, with some foreseeable advantages compared with bis-GMA composites. One significant advantage is that these composites have the potential to be less toxic, once they presented a reduction of 50% in leaching of unreacted monomers extracted by solvent.

Changes of free radicals and digestive enzymes in saliva in cases with deficiency in spleen-yin syndrome

Objective

To explore the nature of deficiency in spleen-yin syndrome, which could provide scientific theoretical support and practical guidance for clinical Traditional Chinese Medicine (TCM) syndrome differentiation based on biology, and had a strong clinical significance.

Methods

Serum Cu and Zn were detected by atomic absorption spectrophotometer, serum vitamin E by high performance liquid chromatography, serum vitamin C by 2,4-Dinitrophenylhydrazine Colorimetry, total superoxide dismutase (SOD) and Cu and Zn-SOD by the xanthine oxidase method, and malondialdehyde (MDA) by the 2-thiobarbituric acid method (TBA). Total antioxidant capacity was detected by a colorimetry kit. Amylase Activity was detected by an automatic biochemical analyzer. Lysozyme was detected by lysozyme detection plate, the diameter of bacteriolysis circle was measured and the corresponding content of lysozyme was obtained from a table of standard curve values.

Results

No significant difference in total SOD and Cu, Zn-SOD was found between deficiency in spleen-yin group and normal group. However, such factors in deficiency in kidney-yin group were significantly lower than the other groups (P < 0.05). The MDA content in both deficiency in spleen-yin group and deficiency in kidney-yin group were significantly higher than that of normal group (P < 0.05), while the total antioxidant capacity was significantly lower than normal group (P < 0.05). The vitamin E content in deficiency in kidney-yin group was significantly lower than that in the other two groups (P < 0.05). No significant difference in the contents of vitamin C, Cu and Zn were observed in these groups. The Zn/Cu level in deficiency in kidney-yin group and the vitamin E level in deficiency in spleen-yin group decreased, but with no significant difference. Amylase activity in unit time in cases with deficiency in spleen-yin was lower than and had significant differences with that in normal cases, and higher than that in cases with deficiency in kidney-yin. The sectional velocity of saliva and the ratio of lysozyme in normal case group were significantly higher than other two groups, while deficiency in the spleen-yin group was significantly higher than the deficiency in kidney-yin group.

Conclusion

All the results indicated that the objective pathological mechanism between the deficiency in spleen-yin and deficiency in kidney-yin was different.

Optical approach to the salivary pellicle

The salivary pellicle plays an important role in oral physiology, yet noninvasive in situ characterization and mapping of this layer remains elusive. The goal of this study is to develop an optical approach for the real-time, noninvasive mapping and characterization of salivary pellicles using optical coherence tomography (OCT) and optical coherence microscopy (OCM). The long-term goals are to improve diagnostic capabilities in the oral cavity, gain a better understanding of physiological and pathological processes related to the oral hard tissues, and monitor treatment responses. A salivary pellicle is incubated on small enamel cubes using human whole saliva. OCT and OCM imaging occurs at 0, 10, 30, 60 min, and 24 h. For some imaging, spherical gold nanoparticles (15 nm) are added to determine whether this would increase the optical signal from the pellicle. Multiphoton microscopy (MPM) provides the baseline information. In the saliva-incubated samples, a surface signal from the developing pellicle is visible in OCT images. Pellicle "islands" form, which increase in complexity over time until they merge to form a continuous layer over the enamel surface. Noninvasive, in situ time-based pellicle formation on the enamel surface is visualized and characterized using optical imaging.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Protective effect of the in situ pellicle on dentin erosion–an ex vivo pilot study

AIM

The acquired pellicle is well known as an anti-erosive proteinaceous layer on enamel, but its protective properties on dentin have not been investigated in detail until now. The aim of the present ex vivo study was to evaluate the erosive effects on pellicle coated dentin.

METHODS

Bovine dentin slabs were exposed to the oral cavity of one subject for 120 min for in situ pellicle formation. Subsequently, the slabs were incubated with HCl (pH 2.3) in vitro for 5 min and erosive calcium-release was measured photometrically. In addition, the acid treated specimens were evaluated by transmission electron microscopy (TEM). Pellicle free samples served as controls.

RESULTS

Calcium erosion from the pellicle coated dentin slabs amounted to 23.5+/-2.9 microg Ca/min (pellicle free samples: 32.2+/-4.2 microg Ca/min). The difference was statistically significant (p < or = 0.05). In pellicle coated as well as in uncoated dentin samples, TEM-evaluation showed a demineralised dentinal surface layer which thickness ranged between 3 and 6 microm. The pellicle itself was partially dissolved but not removed by hydrochloric acid treatment.

CONCLUSION

The protective properties of the acquired pellicle against an erosive challenge of the dentinal surface are limited. The dentinal pellicle functions like an ion permeable network rather than a barrier.

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

Several salivary anti-microbial and buffering components are part of the acquired in vivo pellicle. The purpose of the present in situ study was to visualise these proteins within the in situ formed pellicle and to investigate their distribution with respect to pellicle formation time and intra-oral localisation. Bovine enamel slabs were fixed on individual splints. They were carried by 6 subjects buccally and palatally in the region of the upper first molar teeth over 30 and 120 min, respectively, for in situ pellicle formation. After intra-oral exposure, enamel specimens were processed for transmission electron microscopy. Secretory immunoglobulin A (sIgA), lactoferrin, lysozyme, carbonic anhydrase (CA) I and II were visualised successfully in the in situ pellicle layer by gold immuno-labelling. All components were found to be distributed randomly within all layers of the pellicle. Significantly higher amounts of the proteins were detected after 120 min of formation time. Furthermore, significantly more labelled lactoferrin and lysozyme were found on buccal surfaces compared with palatal sites. For CA I, CA II and sIgA, no significant influence of the localisation was detected. All investigated anti-bacterial and buffering proteins are distributed randomly in the in situ formed pellicle layer and thus could contribute to its protective properties as an early defence barrier.

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

Amylase and lysozyme are components of the salivary pellicle, exposing considerable enzymatic activity in the immobilized state. The purpose of the present study was to elucidate the influence of different solid substrata on the amount and distribution of amylase and lysozyme exposed on the surface of the salivary pellicle formed in situ. Slabs of titanium, feldspar ceramic, and bovine enamel were fixed on the buccal sites of individual splints worn by three subjects for 3 or 30 min, respectively, to allow pellicle formation. Subsequently, slabs were removed from the splints and rinsed with running water. Detection of amylase and lysozyme was performed by FEI-SEM after gold-immunolabeling of the enzymes. Both enzymes were found to be distributed randomly at the pellicle surface. Irrespective of formation time and substratum, significantly more labeled lysozyme molecules (5.23 +/- 4.5 microm(-2)) were detected compared with amylase (3.4 +/- 2.9 microm(-2)). Neither the substratum nor the pellicle formation time had significant impact on the amount of the respective enzyme that could be detected. This study for the first time provides evidence, that amylase and lysozyme are exposed at the surface of the salivary pellicle formed in situ on titanium and ceramics. Both enzymes are distributed randomly on the surface of the pellicle, irrespective of the underlying substratum.