STEM and HRTEM studies of accumulated deposits on human tooth surface.

The aim of this study was to clarify the fine structure of accumulated deposits on the surface of teeth that are considered to affect the gloss of teeth. The study was carried out using, as specimens, human incisor teeth having gloss, which were extracted from teenage donors and those incapable of showing gloss even by brushing which were extracted from donors in their 50s. Thin longitudinal sections of tooth enamel with accumulated deposits on the surface were prepared by focused ion beam (FIB) milling, and the fine structure was analyzed using a scanning transmission electron microscope (STEM) and a high resolution transmission electron microscope (HRTEM). By FIB, thin longitudinal sections could be prepared from tooth enamel together with organic and inorganic substances accumulated on the surface without artifacts. The accumulated deposits on the surface of teeth having gloss were composed of organic substances. However, it was first revealed by STEM observation that the accumulated solid deposits on the surface of teeth having no gloss had a complicated structure wherein inorganic and organic substances coexisted. It is suggested that the organic substances contain proteins derived from saliva. The inorganic substances were spherical and needle-like hydroxyapatites (HAs). It is considered that amino acids constituting the proteins affected the nucleus formation and the crystal formation of HA. It is considered that the unevenness of the accumulated deposits existing on the surface of tooth enamel having no gloss causes the decrease in gloss of teeth due to diffuse reflection of light.

Assessment and management of halitosis.

Halitosis is an unpleasant condition that may be the origin of concern not only for a possible health condition but also for frequent psychological alterations which may lead to social and personal isolation. The most frequent sources of halitosis that exist in the oral cavity include bacterial reservoirs such as the dorsum of the tongue, saliva and periodontal pockets. Volatile sulphur compounds (VSCs) are the prominent elements of oral malodour. Genuine halitosis and pseudo-halitosis should be in the treatment realm of dental practitioners. Clinical Relevance: Halitosis can be a symptom of underlying systemic disease, therefore the exact diagnosis and its source (oral or non-oral) is important in the proper approach to its management.

Effect of time and pH on physical-chemical properties of orthodontic brackets and wires.

OBJECTIVE: To test the hypothesis that treatment time, debris/biofilm, and oral pH have an influence on the physical-chemical properties of orthodontic brackets and arch wires. MATERIALS AND METHODS: One hundred twenty metal brackets were evaluated. They were divided into four groups (n  =  30) according to treatment time: group C (control) and groups T12, T24, and T36 (brackets recovered after 12, 24, and 36 months of treatment, respectively). Rectangular stainless-steel arch wires that remained in the oral cavity for 12 to 24 months were also analyzed. Dimensional stability, surface morphology, composition of brackets, resistance to sliding of the bracket-wire set, surface roughness of wires, and oral pH were analyzed. One-way analysis of variance, followed by a Tukey multiple comparisons test, was used for statistical analysis (P < .05). RESULTS: Carbon and oxygen were shown to be elements that increased expressively and in direct proportion to time, and there was a progressive increase in the coefficient of friction and roughness of wires as a function of time of clinical use after 36 months. Oral pH showed a significant difference between group T36 and its control (P  =  .014). CONCLUSIONS: The hypothesis was partially accepted: treatment time and biofilm and debris accumulation in bracket slots were shown to have more influence on the degradation process and frictional force of these devices than did oral pH.

Calcium silicate coating derived from Portland cement as treatment for hypersensitive dentine.

OBJECTIVES: To evaluate the in vitro effectiveness on dentine permeability and dentine morphology of a calcium silicate treatment based on Portland cement (DSC). METHODS: The experimental treatment consisted of a calcium silicate paste based on Portland cement that was applied on dentine surface for 3 min. A professional re-mineralizing treatment (GC Tooth Mousse), two in office desensitizing agents (D/Sense Crystal, and By Sealant) and a commercial toothpaste Dentosan S were studied as comparison materials. All materials were applied accordingly with manufacturer directions on wet dentine. The quantitative changes in the hydraulic conductance i.e., permeability through tubules of dentine discs samples produced by treatment were quantified in vitro using a hydrostatic device working at 6.9 kPa. SEM/EDX analyses of dentine were carried out to obtain qualitative information on dentine morphology and surface deposits and to study their relationship with the hydraulic conductance. After treatment, each dentine sample was immersed in artificial saliva and permeability re-evaluated. Finally, each sample was exposed to 0.02 M citric acid solution and the final permeability was assessed. RESULTS: The experimental treatment and both oxalate-based products (D/Sense Crystal and By Sealant) significantly decreased dentine permeability and created crystals and precipitates on the dentine surface that reduced the diameter of dentinal tubules. Artificial saliva immersion and citric acid challenge increased dentine permeability and partially modified the treated surfaces. Dentosan S and GC Tooth Mousse treatments partially reduced dentine permeability and created small amount of precipitates that were removed by saliva immersion and citric acid exposure. EDX revealed the presence of calcium-rich layer after DSC experimental treatment. CONCLUSIONS: The application of the experimental calcium silicate paste and oxalate-based treatments was determined to be effective on dentine permeability reduction and tubules occlusion. The clinical use as desensitizing agent of materials derived from Portland cement as desensitizing agent should be considered for dentine hypersensitivity treatment.

Morphological and compositional alterations of in vivo aged prefabricated pediatric metal crowns (PMCs).

OBJECTIVES: The purpose of the present study was to assess the morphological and elemental alterations of retrieved prefabricated metal crowns (PMCs) after intraoral exposure. METHODS: Seventeen in vivo aged stainless steel crowns (3M ESPE) were collected. The intraoral exposure time varied from 3 to 101 months. For every retrieved crown one new crown of the same type was used as a reference. The reference and in vivo aged crowns were examined by high-vacuum scanning electron microscopy and energy-dispersive X-ray microanalysis. The elemental composition between the as-received and in vivo aged crowns was statistically analyzed by t-test (a=0.05). RESULTS: In vivo aged crown surfaces demonstrated significantly morphological alterations with accumulation of amorphous intraoral integuments, biting imprints, wear and occlusal perforations. The results of microanalysis showed that there were no statistically significant differences in the elemental composition of the stainless steel crowns between the two conditions. SIGNIFICANCE: Under the conditions of the present study, retrieved prefabricated pediatric stainless steel crowns exhibit morphological changes mainly due to plastic deformation, without changes in elemental composition.

Rate of reformation of tongue coatings in young adults.

BACKGROUND: Reviewing the literature, no study on the rate of regrowth of tongue coatings after tongue cleaning was found. Therefore, the purpose of this study in young adults was to study the rate of reformation of tongue coatings after mechanical removal. MATERIAL AND METHODS: Thirty-five dental students participated in the present study. Following preparatory study instructions, baseline examinations were carried out followed by 3 days of observation. At baseline, tongue coating scores (prescraping) were obtained followed by tongue scrapings and determination of the wet weights of the coatings. A second tongue coating score was then obtained within 5 min of the first score (immediate post-scraping). The subjects returned for repeated tongue coating scores after 1 and 2 days and for final examination after 3 days, which included both tongue coating scores (prescraping and immediate post-scraping) and determination of the wet weights of the coatings. RESULTS: Prior to scraping the tongue at day 0 (baseline), mean tongue coating amounted to a surface extension of 33% of the entire dorsum of the tongue. Scraping the tongue reduced the score to 9%. On average, tongue coating scores had returned to baseline levels on day 2. The mean wet weights of tongue scrapings at days 0 and 3 were similar and amounted to 0.09 +/- 0.07 and 0.09 +/- 0.06 g, respectively. CONCLUSION: If tongue cleaning is to be recommended, the results of this study in dental students indicate that tongue cleaning should be performed on a daily basis.

Nitric oxide concentrations in saliva and dental plaque in relation to caries experience and oral hygiene.

The aim of the study was to determine the correlation of the antibacterial substance nitric oxide (NO) with dental caries in vivo. Salivary and dental plaque NO concentrations were analyzed by the Griess method in 11 subjects with high DMFT index and simplified oral hygiene index (OHI-S), 11 with low DMFT and OHI-S. Subjects with high DMFT and OHI-S had significantly higher NO concentrations in saliva (71.5 microM) and plaque (83.5 microM) than those with low DMFT and OHI-S (33.2 and 61.1 microM in saliva and plaque, respectively). Plaque NO concentrations were significantly higher than in saliva in both groups. NO production might be a host defense mechanism when dental caries increases or oral hygiene deteriorates.

Bacteria-binding plasma proteins in pellicles formed on hydroxyapatite in vitro and on teeth in vivo.

Previous studies on dental pellicle formation and bacterial adherence have focussed on saliva and its components. The tooth surface is, however, also exposed to the plasma-derived crevicular fluid. In the present study, (i). plasma proteins in in vitro and in vivo pellicles were examined using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting and image analysis and (ii). the adherence of periodontopathogenic bacteria to experimental plasma and saliva pellicles was examined using radio-labelled bacteria and liquid scintillation counting. The plasma components fibrinogen, fibronectin, albumin and IgG were incorporated from plasma in the experimental pellicle and mediated the adherence of Porphyromonas gingivalis, Fusobacterium nucleatum and Actinomyces naeslundii. These proteins were also readily detected in in vivo pellicles and were found to a higher extent in pellicles formed at the gingival part of the tooth surface than at the incisal part.

A clinical pilot study of the time-dependent composition of tooth bleaching systems.

This pilot study was undertaken to determine the compositional changes in tooth bleaching materials as a function of time in vivo. Ten patients were recruited and two bleaching systems were used - one a paste and the other a gel. Each material was placed in a custom bleaching tray and worn by each patient for each of four times - 15, 30, 60 and 120 min. The material was collected and chemically analysed for water by Karl Fischer titration and titrated for carbamide peroxide by the US Pharmacopoeia method. The paste material contained 18.66% water as supplied, and after 2 h this rose to between 28.6 and 64.4%. The gel material contained 2.85% water as supplied, and after 2 h this was diluted to between 28.5 and 73.4%. There was considerable difference in saliva uptake by the custom tray between patients. Most water uptake usually occurred within the first 30 min. Peroxide concentrations decreased in an approximately linear manner with time. There was a significant difference between the materials from baseline to 30 min and thereafter (P < 0.0009). This pilot study is an effective technique for chemical evaluation of bleaching materials. The effect of saliva is an important factor to consider, and is one that has hitherto not always been appropriately emphasized.

Characterization of the immunologic responses to human in vivo acquired enamel pellicle as a novel means to investigate its composition.

Human acquired enamel pellicle is formed by molecules selectively adsorbed onto tooth surfaces. The present work describes the use of monoclonal antibody (mAb) technology as a novel approach to identify micro amounts of components present in pellicle. MAbs were obtained with reactivities against statherin, histatin, mucous glycoprotein 1(MGI), albumin, amylase and human immunoglobulins (Igs), indicating that these are pellicle components, which was further confirmed by immunoblotting. No mAbs against proline-rich proteins (PRPs), lysozyme, mucous glycoprotein 2 (MG2), carbonic anhydrase, lactoferrin or peroxidase were obtained, suggesting that these components are absent, present in low amounts, or exhibit low antigenicity. Further characterization of the binding epitopes of some of th e obtained anti-MGO, anti-statherin and anti-histatin mAbs were carried out and the biological relevance is discussed. The results open up the possibility that immunization with human pellicle and mAbs production can be employed to identify hitherto unknown constituents of pellicle.

The influence of a hexametaphosphate-containing chewing gum on the wetting ability of salivary conditioning films in vitro and in vivo.

OBJECTIVE: Adsorbed conditioning films of salivary components on dental enamel surfaces or pellicles form the interface between teeth and the oral environment. The wetting ability of salivary conditioning films dictates biological adhesion phenomena such as plaque formation, calcification and staining, and also influences mouth perception through effects on lubricity. This study assessed the effects of hexametaphosphate release from a chewing gum matrix on the wetting ability of salivary conditioning films in vitro and in vivo. METHODOLOGY: Results obtained for hexametaphosphate chewing gum were compared with those produced by hexametaphosphate-containing dentifrice, which has been clinically proven to have efficacy for stain removal and prevention and dental calculus prevention. RESULTS: Contact angle assessments revealed that hexametaphosphate dentifrice produced markedly hydrophilic conditioning films in vitro. Hexametaphosphate chewing gums had only minor effects on surface contact angles in vitro. However, in vivo intra-oral contact angle measurements on tooth surfaces in volunteers showed that both hexametaphosphate dentifrice and chewing gum produced more hydrophilic tooth surfaces. CONCLUSION: These results support the activity of hexametaphosphate on tooth surfaces delivered both from dentifrice and chewing gum forms.

Quantitative determination of salivary components in the pellicle on PMMA denture base material.

The formation of a salivary pellicle is a protective mechanism of the body for all surfaces in the oral cavity. The nature of the substrate may influence the composition of the pellicle. The aim of this study was to investigate the quantitative composition and individual variation of the salivary pellicle formed on denture base material (PMMA). Cylindrical specimens of PMMA were carried in the mouth and then desorbed with a 0.5-M sodium chloride solution. The solution was analysed for total protein, alpha-amylase, total proteases, protease inhibitors, secretory immunoglobulin A, immunoglobulin G, peroxidases, thiocyanate, lysozyme, and calcium content. All investigated salivary components could be found unequivocally in the desorption solution, indicating that a salivary pellicle had formed on the surface of the PMMA. Large coefficients of variation indicate large individual variations in the adsorbed amounts. The data also point to large intraindividual variations for the bound salivary components. Only the protease inhibitors revealed a strong positive correlation of the bound activity to the salivary activity. It is hypothesised that differences in the bound amounts of antimicrobial components might influence the microbial colonisation of denture bases and that protease inhibitors could be meaningful for the spread of the yeast Candida albicans from denture base material to the oral mucosa and thus might be an explanation for different susceptibility to denture base stomatitis.

Roles of salivary proteins in the adherence of oral streptococci to various orthodontic brackets.

Knowledge of salivary pellicles on orthodontic brackets provides a better understanding of microbial adherence. The aim of this study was to analyze the effects of bracket pellicles on the adherence of Streptococcus gordonii and Streptococcus mutans. Bracket pellicles were formed by the incubation of 4 kinds of orthodontic brackets with unstimulated whole saliva for 2 hrs, and analyzed by electrophoresis, immunodetection, and amino acid analysis. Binding assays were then performed by the incubation of tritium-labeled streptococci with the pellicle-transfer blots and orthodontic brackets. The results showed that low-molecular-weight mucin, alpha-amylase, secretory IgA, acidic proline-rich proteins, and cystatins adhered to all kinds of brackets, though the amino acid composition of pellicles differed between bracket types. Some of these proteins increased the binding of S. gordonii to saliva-coated brackets. However, salivary pellicles decreased the binding of S. mutans. Collectively, salivary pellicles were found to play a significant role in the initial adhesion of oral streptococci to orthodontic brackets.

Preliminary evaluation of salivary pellicle on nickel-chromium alloy in vivo.

OBJECTIVE: The composition of the salivary interface (pellicle) between dental restorations and oral mucosa may be critical to the biocompatibility of the restoration. The purpose of this study was to examine the molecular composition of the salivary pellicle on nickel-chromium alloy in vivo. METHOD AND MATERIALS: The molecular components of nickel-chromium pellicle was examined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses. RESULTS: Only limited numbers of salivary proteins were found to participate in the formation of nickel-chromium pellicle in vivo. Salivary amylase and secretory immunoglobulin A were among the proteins identified in the pellicle. CONCLUSION: In vivo, nickel-chromium pellicle consists of selectively adsorbed salivary proteins. Because both salivary amylase and secretory immunoglobulin A are antimicrobial proteins, it is possible that they play a role in modulating the microbial flora on the nickel-chromium prosthesis.

The effect of unstimulated and stimulated whole saliva on extrinsic staining in vitro--a developmental method.

OBJECTIVES: To detect any differences in the propensity of unstimulated and stimulated, individual whole saliva to cause in vitro staining by chlorhexidine and tea. METHODS: Unstimulated and stimulated human saliva was collected on a daily basis and used to coat optically clear acrylic specimens. Specimens were subjected to an established chlorhexidine/tea staining model in vitro shown to correlate well with in vivo staining, and cycles repeated until an optical density of <2 was reached. RESULTS: Stain development increased incrementally with increasing cycles. Overall differences in chlorhexidine/tea staining were noted both between subjects and between unstimulated and stimulated saliva used. Mean staining for the subject group, at each cycle was always higher with unstimulated saliva compared to stimulated saliva and differences reached statistical significance at cycles 2-5. CONCLUSIONS: In vitro stain formation using unstimulated saliva from different individuals occurred at a faster rate and to a greater extent than when stimulated saliva from the same subjects was used, presumably reflecting differences in composition. Understanding the nature of these differences could provide fundamental information on the very poorly understood process of tooth staining.

Hexametaphosphate effects on tooth surface conditioning film chemistry--in vitro and in vivo studies.

These studies compared the effects of Crest Dual Action Whitening dentifrice with sodium hexametaphosphate and control commercial dentifrices on the surface chemistry of conditioning film-coated dental enamel in vitro and in vivo. Conditioning film chemistry was studied by measurements of film thickness, ability to wet the surface/surface energy, conditioning film chemical composition and zeta potential. Laboratory and in vivo studies demonstrated that brushing and chemical-only treatment of pellicle-coated enamel surfaces produced marked changes in surface chemistry. Brushing of surfaces with all commercial dentifrices significantly reduced pellicle film quantity. Effects on non-brushed areas, of significance in the clinical situation, were different for different dentifrices. For dentifrice chemical treatments, calcium phosphate surface active builders, such as pyrophosphate and hexametaphosphate, produced stronger effects than standard (non-tartar control) dentifrices, peroxide baking soda dentifrices and dentifrices formulated with carboxylate polymers, viz. Colgate Total with copolymer. Crest Dual Action Whitening hexametaphosphate dentifrice removed more pellicle conditioning film, produced a lower zeta potential, produced the largest changes in film composition and had the greatest impact on surface free energies of the tested dentifrices. Crest Dual Action Whitening dentifrice also produced lasting changes in the reacquisition of pellicle conditioning film, as established by in vitro cycling immersion studies. Crest Dual Action Whitening dentifrice produced stronger and more lasting effects on surface film chemistry than low molecular weight pyrophosphate (Crest Tartar Control) or other polymeric-based dentifrice systems (Colgate Total). These surface chemistries may contribute to the unique clinical actions of hexametaphosphate established in recently reported, randomized clinical studies of tartar control, stain prevention and stain removal effects.

Influence of dentifrices and dietary components in saliva on wettability of pellicle-coated enamel in vitro and in vivo.

In vitro salivary pellicles were found to be less hydrophobic by water contact angles than clinically formed pellicles. In this study, water contact angles were measured on enamel coated with pellicles adsorbed from reconstituted human whole saliva (RHWS) and after exposure to dentifrices or dietary components. In addition, adhesion of Streptococcus oralis J22 to pellicles formed from RHWS with minor amounts of milk added and after exposure to dentifrices was studied. Exposure of RHWS-pellicles to milk or salad oil yielded an increase in the hydrophobicity of in vitro pellicles to values observed in vivo, but a decrease was seen after exposure to a sugar solution. Pellicles formed from saliva with 0.4% milk added attracted less S. oralis cells than pellicles formed in the absence of milk components. Exposure of pellicles formed from saliva with milk added to various dentifrices had a variable effect on bacterial adhesion: markedly lower numbers of adhering S. oralis were found for a dentifrice with NaF, but exposure to dentifrices containing SnF2 or hexametaphosphate showed slightly increased adhesion. In summary, dietary components have influence on the hydrophobicity of enamel pellicles, while combinations of dietary components and dentifrices certainly influence the adhesiveness of the pellicles. The effects of dietary components on pellicle conditioning film should be taken into consideration in research on the development of ingredients to control intraoral surface chemistry and microbiology, as well as in the development of oral products.

Electron-microscopic demonstration of proline-rich proteins, statherin, and histatins in acquired enamel pellicles in vitro.

Proline-rich proteins (PRPs), histatins, and statherin are salivary proteins that exhibit high affinities for hydroxyapatite surfaces. In vitro experiments with parotid submandibular/sublingual or whole saliva have shown these proteins to adsorb selectively to tooth surfaces. This investigation focuses on the histo-morphological identification of PRPs, histatins, and statherin in acquired enamel pellicles. Synthetic hydroxyapatite or bovine enamel were exposed to glandular secretions, and whole saliva and pellicle precursor proteins were identified immunohistologically by electron microscopy. Results obtained by back-scattered scanning electron microscopy showed these proteins to be present in pellicles. Pellicles displayed a distinct structure consisting of a sponge-like meshwork of microglobules. Interconnections between structural elements were identified in submandibular/sublingual and whole saliva pellicles only. Transmission electron microscopy of pellicles formed on bovine enamel surfaces revealed a tendency for preferential localization of precursor proteins within the protein film. Since the data showed the presence of pellicle precursors in pellicles derived both from glandular secretions and from whole saliva, it is likely that PRPs, histatins, and statherin are integral components of acquired enamel pellicles in vivo.

Compositional analysis of human acquired enamel pellicle by mass spectrometry.

Relatively little is known about the formation of the acquired enamel pellicle other than that it involves the selective adsorption of specific proteins from oral fluids. Previous studies on the identification of pellicle components have relied largely on immunological or enzymatic detection and have been hampered by the fact that only minute quantities of pellicle can be removed from tooth surfaces. The present work describes an improved method of harvesting pellicle that combines mechanical and chemical removal; this approach was used to investigate systematically the desorption of in vitro pellicle components with different solutions. Eleven major in vitro pellicle proteins were identified by using a combination of electrophoretic separation and matrix-assisted laser desorption/ionization-reflectron time-of-flight mass spectrometry. A similar analysis of in vivo-formed pellicle revealed the presence of intact statherin, lysozyme, albumin and amylase. Further analysis of in vivo pellicle by liquid chromatography-electrospray ionization mass spectrometry suggested the presence of numerous low molecular-weight fragments of precursor proteins. The protein composition of in vitro whole-salivary pellicle adsorbed to hydroxyapatite and that of in vivo enamel pellicle differed for proline, the result of a reduction in the content of acidic proline-rich proteins in the in vivo samples. Unique features of the oral environment such as enzymatic activities or mineral surface properties may account for these differences between in vivo and in vitro pellicle formation.