Rate of viscosity changes in five salivary protein fractions following pH alterations

Abstract – The change of viscosity with time following alteration of pH was studied in five protein fractions isolated from human parotid saliva. The results indicate that sudden pH changes may cause rapid charge alterations leading to shock-like expansion or compression of the molecules. This quick reaction seems to be followed by more slowly proceeding conformational alterations probably involving folding, intermingling, and other types of chain interactions. The content of proline residues may influence the rate and extent of such conformational changes.     

Tissue pH and temperature regulate pulpal nociceptors

The TRPV1 receptor acts as a sensor for environmental changes in pH and temperature. Since many nociceptors express TRPV1, it is possible that local tissue-cooling may inhibit nociceptor activity via reduction of TRPV1 activation. The present study used isolated superfused rat dental pulp to test the hypothesis that capsaicin receptors are activated in inflamed tissue, as measured by alterations in neuropeptide release. We tested the hypothesis that alterations in the tissue temperature and pH of isolated superfused rat dental pulp regulate capsaicin-induced release of calcitonin gene-related peptide (CGRP). Application of capsaicin with increased proton concentration (i.e., lowered pH) produced a nearly two-fold increase in peak immunoreactive CGRP release, as compared with capsaicin applied at a pH of 7.4. Reduction in tissue temperature from 37 degrees C to 26 degrees C completely blocked the capsaicin effect. The study indicates that environmental stimuli regulate the activity of capsaicin-sensitive neurons innervating dental pulp, and these factors may be significant clinically in the development and amelioration of dental pain.     

Effects of pH values of hydrogen peroxide bleaching agents on enamel surface properties

This study investigated the influence of pH values of bleaching agents on the properties of the enamel surface. Sixty freshly extracted premolars were embedded in epoxy resin and mesiodistally sectioned through the buccal aspect into two parts. The sectioned slabs were distributed among six groups (n=10) and treated using different solutions. Group HCl was treated with HCl solution (pH=3.0) and served as a positive control. Group DW, stored in distilled water (pH=7.0), served as a negative control. Four treatment groups were treated using 30% hydrogen peroxide solutions with different pH values: group HP3 (pH=3.0), group HP5 (pH=5.0), group HP7 (pH=7.0), and group HP8 (pH=8.0). The buccal slabs were subjected to spectrophotometric evaluations. Scanning electron microscopy investigation and Micro-Raman spectroscopy were used to evaluate enamel surface morphological and chemical composition alterations. pH value has a significant influence on the color changes after bleaching (p<0.001). Tukey's multiple comparisons revealed that the order of color changes was HP8, HP7>HP5, HP3>HCl>DW. No obvious morphological alterations were detected on the enamel surface in groups DW, HP7, and HP8. The enamel surface of groups HCl and HP3 showed significant alterations with an erosion appearance. No obvious chemical composition changes were detected with respect to Micro-Raman analysis. Within the limitations of this study, it was concluded that no obvious morphological or chemical composition alterations of enamel surface were detected in the neutral or alkaline bleaching solutions. Bleaching solutions with lower pH values could result in more significant erosion of enamel, which represented a slight whitening effect.     

Function of gingival fibroblasts and periodontal ligament cells in the presence of methyl mercaptan.

OBJECTIVE: This study examined the effects of methyl mercaptan, a product of the bacterial putrefaction of protein in periodontal pockets, on the function of cells in culture. METHOD AND MATERIALS: Human gingival fibroblasts and periodontal ligament cells were exposed to a constant, continuous flow of methyl mercaptan in vitro. Control and test cultures were then examined for changes in intracellular pH, an event often associated with alterations in cellular function. Intracellular pH was determined by single-cell image analysis of cells loaded with a fluorescent, pH-sensitive dye. Periodontal ligament cells were also tested for changes in synthesis of total protein and fibronectin. RESULTS: Test cells exhibited a consistent decrease in intracellular pH following exposure to methyl mercaptan. Measurements of total protein production showed that test periodontal ligament cell cultures produced approximately 30% less protein than control cultures (P < 0.05). Western-blot analysis of fibronectin in medium demonstrated that abnormal monomeric fibronectins were a major protein in test, but not in control, cell cultures. CONCLUSION: Exposure to methyl mercaptan induced alterations in intracellular events that paralleled changes in extracellular matrix proteins. The observed changes in extracellular matrix proteins support the hypothesis that methyl mercaptan contributes to the progression of periodontal disease.     

Effect of various pH values, ionic strength, and temperature on papain hydrolysis of salivary film

Stimulated human whole saliva (WS) was used to study the dynamics of papain hydrolysis at defined pH, ionic strength, and temperature with the view of reducing an acquired pellicle. A quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency caused by enzyme hydrolysis of WS films, and the hydrolytic parameters were calculated using an empirical model. The morphological and conformational changes of the salivary films before and after enzymatic hydrolysis were characterized by atomic force microscopy (AFM) imaging and grazing-angle Fourier transform infrared (GA-FTIR ) spectra, respectively. The characteristics of papain hydrolysis of WS films were pH-, ionic strength-, and temperature-dependent. The WS films were partially removed by the action of papain, resulting in thinner and smoother surfaces. The infrared data suggested that hydrolysis-induced deformation did not occur on the remnants of salivary films. The processes of papain hydrolysis of WS films can be controlled by properly regulating pH, ionic strength, and temperature.     

Developmental-specific expression and immunoreactivity of keratins during odontogenesis in rat embryos

The enamel organ of the mammalian dental primordium undergoes a precise sequence of differentiation. To correlate this differentiation with tissue-specific markers we analysed the keratin protein composition and immunoreactivity of incisor primordia from the earliest stage of odontogenesis to the neonatal period. Throughout the enamel organ synthesized a characteristic subset of keratin proteins, and the expression of one specific keratin marked the onset of the cap stage. Interestingly, the immunoreactivity of the ameloblastic keratins against polyclonal antibodies increased with progressive odontogenesis, suggesting that cytokeratin filaments may undergo post-translational or conformational alterations during assembly within differentiating enamel-organ cells.     

Alterations of p16/CDKN2, p53 and ras genes in oral squamous cell carcinomas and premalignant lesions

Exons 1–3 of the p16/CDKN2 gene, exons 4–9 of the p53 gene and exons 1 and 2 of H-, K- and N- ras genes were screened for mutations by a combination of immunohistochemistry and single-strand conformational polymorphism (SSCP) analyses of polymerase chain reaction products from human surgical samples of both frank oral squamous cell carcinomas and premalignant lesions. The samples included 20 squamous cell carcinomas. 10 epithelial dysplasias and 10 epithelial hyperplasias. No identifiable gene mutations were detected in any of the dysplasias or hyperplasias, while 2 (10%) deletions and 2 (10%) mutations of p16/CDKN2, along with 5 (25%) p53 mutations were found in the advanced carcinomas, yielding characteristic p16/CDKN2 and p53 changes. A mutation in the K- ras gene was found in single carcinoma and dysplastic samples. From the data, it can be argued that p16/CDKN2 and p53 mutations are relatively late occurrences in human oral tumorigenesis and that genetic alterations of the ras genes may not play a significant role in squamous neoplasia.     

Thermally enhanced conformational relaxation during electrochemical oxidation of polypyrrole

Oxidation of polypyrrole which was previously prepolarized at highly negative potentials is limited by the ability of polymeric chains to undergo conformational changes. As is well known, polymeric chains can vary their conformational state only when some energetic requirements are fulfilled. This allows the study of how conformational relaxation processes associated with electrochemical doping in conducting polymers are affected by changes in the experimental conditions used. In this work, the influence of temperature on the rate of conformational relaxation in polypyrrole is evaluated, on the basis of our electrochemical relaxation model. The comparison between experimental data and theoretical predictions from the model allows the activation energy ΔH* for the conformational changes associated with polypyrrole doping to be obtained, together with the evolution of structural and electrochemical features of the polymer with the temperature. A new technique of electrochemical thermocurrents is proposed to obtain information about interactions between polymer, solvent and ions.     

The effects in vitro of zinc released from dental restorative materials

Summary. Zinc at the levels released from several dental restorative materials was toxic to both fibre-blasts and macrophages, and so appears to be an important factor in the cytotoxicity in vitro of these materials. The toxicity of zinc to fibroblasts was less at high and low pH, but alterations in pH caused a substantial reduction in cell numbers, accompanied by alterations in cell membrane permeability. With macrophages, zinc had a significant effect at all pH values tested and there was little alteration in cell numbers with pH. No evidence was found for the role of zinc in stabilizing either cell or lysosomal membranes. However, as in vivo zinc is readily adsorbed by dentine, it is unlikely to cause toxic effects.     

Effect of different bleaching systems on the ultrastructure of bovine dentin

Abstract –  The aim of this study was to evaluate in vitro the effect of different in-office bleaching systems on the surface morphology of bovine dentin. Thirty tooth fragments measuring 4 × 4mm, containing enamel and dentin, were obtained from the crowns of extracted bovine incisors. Samples were subjected to simulated intracoronal bleaching techniques using conventional (Opalescence Endo^® and Whiteness Super Endo^®) and light-activated systems (Opalescence Xtra^® and Whiteness HP Maxx^®). Controls were treated with either sodium perborate mixed with 10% hydrogen peroxide or no bleaching agent. The samples were observed under SEM and the recorded images were evaluated for topographic alterations. The ultrastructural alterations of dentin observed in this study varied greatly between groups according to the products used. Higher pH products (Whiteness HP Maxx^® and Opalescence Xtra^®) associated with in-office techniques yielded better maintenance of dentin ultrastructure. Apparently, both low pH and hydrogen peroxide oxidation play a role in altering the ultrastructure of dentin during internal dental bleaching. The use of alkaline products with reduced time of application (in-office techniques) may decrease such morphological alterations.     

Corrosion behaviour of dental metals and alloys in different media

The corrosion tendencies of metals are related with their position in the electromotive series. These electrode potential degrees may change due to the compositions of the alloys, the surrounding media, or due to alterations in the composition because of recurrent casting. Therefore in this research, the electrode potentials and their changes over a period of time were measured in different pH media simulating the oral electrochemical conditions in vitro. The surface structure of the first and second castings of 29 different dental metals and alloys were examined under a scanning electron microscope and their composition in percentage weight was calculated by the Energy-dispersive X-ray Analysor system. Further the current–potential curves of the dental alloys were found by the potentiodynamic method in three different solutions and, in addition, the changes of corrosion potentials over time were also determined. The corrosion rates, corrosion potentials, their changes over time and their cathodic Tafel slopes were determined. All alloys tested showed ion leakage in corrosive media. Titanium exhibited the least, but alloys with tin and cobalt content displayed the greatest corrosion tendencies. Alloys with iron and copper corroded in the acid media, conversely alloys containing chromium, nichel and molybdenum proved to be resistant to corrosion. The recurrent castings were also corrosion resistant.     

PH effects on experimental wound healing of human fibroblasts in vitro

The aim of the present study was to examine to what extent pH affects human fibroblast repopulation of an experimental wound in vitro laying special emphasis on cell migration, DNA synthesis, and alterations in cell morphology. Wounds were simulated in vitro by partially scraping off monolayers of human embryonic diploid lung fibroblast and human periodontal ligament fibroblast-like cells respectively. The wounded monolayers were cultured at pHs ranging from 7.2 to 8.4. The experiments were evaluated by autoradiography as well as light and scanning electron microscopic techniques. A significant, approximately linear, decrease was noted both in cell migration into and DNA synthesis in the experimental wounds as a result of pH increase. The surviving cells in the wounds showed cytoplasmatic vacuoles and blebbing at pH levels above 7.8. Clinical implications of these results for endodontic calcium hydroxide treatment are that hydroxyl ions, diffusing through root dentin, may interfere with vital cell functions necessary for healing on the root surface.     

A study on changes in caries risk and microbial flora with the placement of edgewise appliance

The aim of this study was to evaluate the changes of caries risk and oral microbial flora in the patients having edgewise appliance. Forty-two patients treated at the Orthodontic Clinic of Niigata University Hospital participated. Using a caries risk examination kit by Bio Medical Laboratory (BML, Tokyo), stimulated saliva test was performed to investigate the salivary flow rate, pH of saliva, buffer capacity, and the levels of lactobacilli. Modified Mitis–Salivarius–Bacitracin (MSB) agar plates were used to detect and count Streptococcus mutans and S. sobrinus. Furthermore, the members of commensal bacteria and transient bacteria in aerobic culture medium were examined in salivary level to investigate the alterations in oral microbial flora. The number of mutans streptococci and lactobacilli decreased after 1 month of treatment, and then increased to reach the initial level at 3 months. While the amount of plaque increased and saliva pH deteriorated after the onset of treatment, the salivary flow rate improved. The number of transient bacteria showed a tendency toward an increase. These results demonstrate that both caries risk and oral microbial flora balance possibly change with the placement of appliances. Therefore, caries risk test should be performed before and during orthodontic treatment to monitor alterations in intraoral environment of the orthodontic patients not to cause an iatrogenic caries.     

Evaluation of pH changes in inflammation of the subcutaneous air pouch lining in the rat, induced by carrageenan, dextran and Staphylococcus aureus

The lowering of tissue pH in inflammation is generally accepted as the important mechanism for the failure of local anaesthesia in inflamed tissues. However, studies relating to pH changes in inflammation are scant in the literature and more importantly the findings are inconsistent. The purpose of this study is therefore to re-evaluate the pH changes using more reliable models of inflammation and pH measurement techniques. Wistar rats were used in the study. The inflammatory model used was based on the air pouch granuloma technique. Carrageenan, dextran and staphylococcus aureus were used as irritants and the pH measurements were made with a miniaturised glass tissue pH electrode designed by Roche. Results showed only a small lowering of pH in inflammation, of the order of about 0.5 pH unit. It may be possible that even such a small pH reduction would affect the buffer capacity of the tissues rendering the local anaesthetics less effective, but this needs to be confirmed with further studies.     

Evaluation of pH changes in inflammation of the subcutaneous air pouch lining in the rat, induced by carrageenan, dextran and staphylococcus aureus

The lowering of tissue pH in inflammation is generally accepted as the important mechanism for the failure of local anaesthesia in inflamed tissues. However, studies relating to pH changes in inflammation are scant in the literature and more importantly the findings are inconsistent. The purpose of this study is therefore to re-evaluate the pH changes using more reliable models of inflammation and pH measurement techniques. Wistar rats were used in the study. The inflammatory model used was based on the air pouch granuloma technique. Carrageenan, dextran and staphylococcus aureus were used as irritants and the pH measurements were made with a miniaturised glass tissue pH electrode designed by Roche. Results showed only a small lowering of pH in inflammation, of the order of about 0.5 pH unit. It may be possible that even such a small pH reduction would affect the buffer capacity of the tissues rendering the local anaesthetics less effective, but this needs to be confirmed with further studies.     

Burning mouth syndrome

In spite of the normal clinical appearance of the oral mucosa, BMS subjects do have demonstrated changes in sensory perception and salivary factors in addition to alterations in psychologic features. Although some of these changes may be suggestive of a peripheral or central dysfunction of small afferent nerve fibres, the extent of this alteration and its cause both remain unclear. The existence of changes other than psychologic, however, do weaken the proposition that BMS has a primarily psychogenic origin and suggests instead that future research should address the question of other organic changes in BMS.     

Acidity of glass ionomer cements during setting and its relation to pulp sensitivity

Recent findings regarding pulp sensitivity to luting glass ionomer cements have aroused controversy as to the cause of the problem. Contributing factors may include chemical irritation from the material and leakage. The pH changes during setting were determined for three glass ionomer cements, a zinc phosphate cement, and a polycarboxylate cement. The data showed that the glass ionomer luting cements may show lower pH values for longer times than the other cements. This initial acidity, involving a prolonged period at pH below 3, coupled with cytotoxicity of other ingredients, may lead to damaging effects on the pulp when manipulation of the material and tooth preparation and cementation procedures are less than ideal.     

Altered autophagy and sympathetic innervation in salivary glands from high-fat diet mice

Objectiveto investigate the effects of a high fat diet (HFD) on salivary glands in vivo, in a mouse model. In particular, whether it will induce the appearance of fat cells in salivary glands, alterations related to autophagy, mTOR pathway and sympathetic innervation.Design27 adult female ICR mice were separated in six groups. Three groups fed with (HFD) containing 55% fat, for one, two and three month and another three groups fed with normal diet (2.7% of fat), for the same time periods. The submandibular glands and liver were dissected and part homogenized for protein analyses and part fixed in formalin for histological analyses.ResultsAfter three months the HFD fed mice total body weight fold change increased compared to controls. The Oil Red O staining showed no fat cells deposit in salivary gland however a large increase was observed in liver after three months of HFD. Adiponectin levels were significantly decreased in the HFD group after three months. The group fed with HFD for three months showed increased conversion of the LC3 autophagy marker in salivary gland. mTOR showed no activation regarding the time point studied. Tyrosine hydroxylase significantly decreased after two and three month of HFD.ConclusionHFD caused several changes after three months however the earliest change was noticed after two months regarding sympathetic innervation. This suggests neural alteration may drive other diet induced changes in salivary glands. These early changes may be the starting point for longer term alterations of salivary glands with alterations in diet.     

Radiographic findings in 224Ra-caused dental resorptions.

Dental resorptions as a delayed effect of Thorium X (224Ra) were observed in four patients. The radiographic findings showed distinct and representative patterns. Apparently, the observed changes are typical for delayed alterations related to 224Ra-specific disturbances in the alveolar process. Degenerative and inflammatory reactions may also be involved in the pathogenesis.     

Antiplaque potential of topical stannous fluoride.

Sterile enamel samples treated by topical application of 10% stannous fluoride were incubated with S mutans and S sanguis respectively and with a mixed culture to which L casei had been added. The results were compared with sterile nonfluoridated enamel samples subjected to the same procedures. The parameters compared were postincubation pH values, bacterial concentrations on the surfaces, and enamel surface alterations. Stannous fluoride treated samples consistently yielded higher pH readings than nonfluoridated samples; the concentration of microorganisms adhering to the surfaces was conspicuously reduced on the pretreated enamel when compared by scanning electron microscopy to untreated samples, as were enamel surface alterations. These findings lend support to other recent investigations which have shown that fluorides act in several ways to inhibit cariogenesis in addition to reducing hydroxyapatite solubility.