Artificial salivas: present and future

In Vitro Evaluation of Remineralization Potential of Five Toothpastes on Soft Drink-Eroded Human Enamel and Dentine

OBJECTIVE

The purpose of this in vitro study was to evaluate the potential remineralization of enamel and dentine erosion lesions after the application of five different toothpastes.

METHODOLOGY

A total of 104 enamel and dentine samples were prepared from maxillary third molars. Each group was divided according to the toothpaste application mode (topical = 56; brushing = 48) and the toothpaste used seven topical groups and six brushing groups (n = 8). The groups included negative control (NC), positive control (PC), Sensodyne Pronamel (SP), Regenerate (R), Regenerate with boosting serum (R+), Colgate Duraphat 5000 (CD), and tooth mousse (TM).

RESULTS

The statistical analysis showed significant surface microhardness (SMH) change. All enamel groups showed a significant decrease in SMH compared to NC for both application modes. However, no significance was recorded between test groups. Similar results were observed between dentine groups and their relevant controls for both application modes, except brushed R and R+ groups, which were insignificant to their NC. For topical groups, TM showed a significant increase in SMH. While R and R+ showed lower loss than SP and CD.

CONCLUSIONS

All tested agents offered a degree of remineralization in both enamel and dentine with no significant difference between agents in enamel groups while R, R+, and TM offered better results in dentine groups.

CLINICAL SIGNIFICANCE

 For dentine groups, similar findings were observed with superior tooth surface protection with the application of TM over other agents. Tooth surface remineralization was achieved when agents were either applied topically or brushed over the surface.

The effect of saliva substitute on the color stability of three different nanocomposite restorative materials after 1 month: An in vitro study

Context (Background):

The color stability of an esthetic material like composite resin may be hampered, due to the constant presence of oral microflora, saliva, and the frequent intake of food. However, as the oral cavity has a dynamic environment, the color stability of these restorative materials has been a challenge to dentistry.

Aim:

The aim of this study was to evaluate the effect of a saliva substitute (SS) on the color stability of three different nanocomposite restorative materials.

Materials and Methods:

A total of 66 disc-shaped samples of test materials were prepared using a polycarbonate mold measuring 15 mm diameter and 2 mm height and were randomly assigned to three groups of 22 samples each based on the test material used: Group I – Estelite Sigma Quick, Group II – Solare sculpt, and Group III – Beautifil II LS. They were further divided into two subgroups A and B with 11 samples each based on the immersion solutions, namely distilled water (DW) and saliva substitute (SS), respectively. The samples were immersed for 30 days. Baseline and post immersion color analysis were done with a spectrophotometer. The CIE L*a*b* values were measured and CIE ΔE values obtained were tabulated. Data were analyzed using the two-way-ANOVA test and Tukey's multiple post hoc test.

Results:

The mean color difference (ΔE) among the three different nanocomposite restorative materials ranged from 4.0 ± 0.26 to 10.62 ± 1.92. Group I showed the lowest color change (7.80 ± 0.55 and 4.00 ± 0.26), followed by Group III (8.59 ± 0.29 and 6.24 ± 0.66) and Group II (10.62 ± 1.92 and 6.85 ± 0.46) when immersed in SS and DW, respectively.

Conclusion:

All the specimens when immersed in SS showed greater discoloration than compared to the specimens immersed in DW. Group I showed greater resistance to color change compared to other groups.

Electron transfer studies of a conventional redox probe in human sweat and saliva bio-mimicking conditions

Modern day hospital treatments aim at developing electrochemical biosensors for early diagnosis of diseases using unconventional human bio-fluids like sweat and saliva by monitoring the electron transfer reactions of target analytes. Such kinds of health care diagnostics primarily avoid the usage of human blood and urine samples. In this context, here we have investigated the electron transfer reaction of a well-known and commonly used redox probe namely, potassium ferro/ferri cyanide by employing artificially simulated bio-mimics of human sweat and saliva as unconventional electrolytes. Typically, electron transfer characteristics of the redox couple, [Fe(CN)₆]^3−/4− are investigated using electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. Many different kinetic parameters are determined and compared with the conventional system. In addition, such electron transfer reactions have also been studied using a lyotropic liquid crystalline phase comprising of Triton X-100 and water in which the aqueous phase is replaced with either human sweat or saliva bio-mimics. From these studies, we find out the electron transfer reaction of [Fe(CN)₆]^3−/4− redox couple is completely diffusion controlled on both Au and Pt disc shaped electrodes in presence of sweat and saliva bio-mimic solutions. Moreover, the reaction is partially blocked by the presence of lyotropic liquid crystalline phase consisting of sweat and saliva bio-mimics indicating the predominant charge transfer controlled process for the redox probe. However, the rate constant values associated with the electron transfer reaction are drastically reduced in presence of liquid crystalline phase. These studies are essentially carried out to assess the effect of sweat and saliva on the electrochemistry of Fe^2+/3+ redox couple.

Antimicrobial and Physicochemical Properties of Artificial Saliva Formulations Supplemented with Core-Shell Magnetic Nanoparticles

Saliva plays a crucial role in oral cavity. In addition to its buffering and moisturizing properties, saliva fulfills many biofunctional requirements, including antibacterial activity that is essential to assure proper oral microbiota growth. Due to numerous extra- and intra-systemic factors, there are many disorders of its secretion, leading to oral dryness. Saliva substitutes used in such situations must meet many demands. This study was design to evaluate the effect of core-shell magnetic nanoparticles (MNPs) adding (gold-coated and aminosilane-coated nanoparticles NPs) on antimicrobial (microorganism adhesion, biofilm formation), rheological (viscosity, viscoelasticity) and physicochemical (pH, surface tension, conductivity) properties of three commercially available saliva formulations. Upon the addition of NPs (20 µg/mL), antibacterial activity of artificial saliva was found to increase against tested microorganisms by 20% to 50%. NPs, especially gold-coated ones, decrease the adhesion of Gram-positive and fungal cells by 65% and Gram-negative bacteria cells by 45%. Moreover, the addition of NPs strengthened the antimicrobial properties of tested artificial saliva, without influencing their rheological and physicochemical properties, which stay within the range characterizing the natural saliva collected from healthy subjects.

Fluorescence Determination of Glutathione Using Tissue Paper-derived Carbon Dots as Fluorophores

Glutathione is an important antioxidant found in body fluids and tissues, which inhibit damage to essential cellular constituents caused by reactive oxygen species. The analysis of glutathione levels in biological systems is important in early clinical diagnosis. A novel, cost-effective synthetic strategy has been developed for the fluorescent probe ethylenediamine passivated carbon dots. Tissue paper was chosen as the carbon source for this "green one pot" synthesis. Glutathione could induce quenching of the fluorescence intensity of ethylenediamine passivated carbon dots through surface interactions, resulting from their aggregation. Based on this, a novel fluorescence sensor was fabricated for the determination of Glutathione in body fluids. A linear calibration graph was obtained in the range of 6.0 × 10^-7 to 5.0 × 10^-8 M with a detection limit of 1.74 × 10^-9 M. The developed sensor was successfully used for the determination of glutathione in artificial saliva samples.

Toward the Development of a Glucose Dehydrogenase-Based Saliva Glucose Sensor Without the Need for Sample Preparation

BACKGROUND

Strict glycemic control is known to be a vital key in the management of diabetes mellitus (DM). However, traditional methods face limitations in their efficacy due to the pain and invasiveness of needle pricking which often discourages DM patients from performing the required number of tests per day. Saliva glucose (SG) sensing has long been considered a noninvasive alternative to blood glucose monitoring for diabetes management, however the sample preparation and sensor detection limit have been deemed as challenges to overcome. Herein, we describe a preliminary clinical validation of a disposable SG sensor without any requirement for sample preparation.

METHODS

The sensor utilizes glucose dehydrogenase flavine-adenine dinucleotide (GDH-FAD) in conjunction with disposable screen printed electrodes to measure glucose levels in saliva collected directly from 9 healthy subjects. Cyclic voltammetry and amperometric-time (Amp-it) assays were used to develop calibration curves and test subjects. Sensor calibration was performed using simulated saliva at 6.5 pH and 37ºC.

RESULTS

The lower limit of detection was determined to be 0.11 mg/dL. A lag time of 15 minutes with a positive correlation between SG and BG levels was found, which agrees with literature results. The detected SG ranges from 2.38 to 3.40 mg/dL over a BG range of 90 to 143 mg/dL.

CONCLUSION

This is the first reported use of measuring SG with GDH-FAD without prior sample preparation. Upon optimization, the sensor has the potential to serve as a supplement to blood glucose monitoring.

Saliva: a Dynamic Proteome

The proteome of whole saliva, in contrast to that of serum, is highly susceptible to a variety of physiological and biochemical processes. First, salivary protein secretion is under neurologic control, with protein output being dependent on the stimulus. Second, extensive salivary protein modifications occur in the oral environment, where a plethora of host- and bacteria-derived enzymes act on proteins emanating from the glandular ducts. Salivary protein biosynthesis starts with the transcription and translation of salivary protein genes in the glands, followed by post-translational processing involving protein glycosylation, phosphorylation, and proteolysis. This gives rise to salivary proteins occurring in families, consisting of structurally closely related family members. Once glandular secretions enter the non-sterile oral environment, proteins are subjected to additional and continuous protein modifications, leading to extensive proteolytic cleavage, partial deglycosylation, and protein-protein complex formation. All these protein modifications occur in a dynamic environment dictated by the continuous supply of newly synthesized proteins and removal by swallowing. Understanding the proteome of whole saliva in an environment of continuous turnover will be a prerequisite to gain insight into the physiological and pathological processes relevant to oral health, and be crucial for the identification of meaningful biomarkers for oral disease.

Mitomycin-C suppresses mucus secretion in an ileal neobladder rat model

The aim of the present study was to investigate the mucus secretion status of mature goblet cells following the application of mitomycin-C (MMC) in ileal neobladder rat models. Bladder substitution models were established in Sprague Dawley rats, which had been divided into five groups, namely the control (sham), normal saline (NS), high-dose MMC (HMMC), low-dose MMC (LMMC) and dehydrated alcohol (DA) groups. To evaluate the total protein concentration and level of sialic acid following the therapy, urine from the rats in each group was collected on days 8, 11 and 14. In addition, to observe the variances between mucus secretion and the ileum goblet cells, immunohistochemistry and hematoxylin and eosin staining were conducted in the different groups on day 17. The results indicated that the ileal neobladder mucosas in the MMC groups were clearly undamaged, as compared with the DA group. Furthermore, the MMC and DA groups were shown to inhibit the proliferation of goblet cells. The concentration of protein and sialic acid in the LMMC group was found to be lower compared with the NS group, while the concentration in the HMMC group was considerably lower. In conclusion, HMMC was demonstrated to evidently reduce the mucin and sialic acid concentration in the urine, without visible damage to the ileal neobladder mucus membrane. Therefore, MMC may provide a novel therapeutic approach for the treatment of certain bladder conditions.

Influence of the lubricant and the alloy on the wear behaviour of attachments

OBJECTIVES

Wear of attachments leads to a loss of retention and reduces the function of overdentures. This study evaluated the retention force changes of an attachment system for overdentures. The influence of the lubricant and the alloy on wear constancy was examined.

METHODS

Cylindrical anchors of the Dalbo(®) -Z system were tested (Cendres+Métaux SA). Three groups of alloy-lubricant combinations were generated 1.Elitor(®) /NaCl-solution (EN) 2.Elitor(®) /Glandosane(®) aquadest. (EG) and 3.Valor(®) /Glandosane(®) /aquadest. (VG). Ten samples of each group were subjected to 10 000 insertion-separation cycles.

RESULTS

For the EN-group, this led to a large increase in retention force. The EG- and VG-group showed a constant decrease after an initial increase in retention force at the beginning of the wear simulation. The change of the alloy caused no statistically significant differences. The use of a more viscous lubricant reduced the retention force increase significantly.

CONCLUSIONS

The use of a lubricant which simulates clinical conditions is an absolute need for wear simulation because the retention force changes are influenced enormously. The change of the alloy at the Dalbo(®) -Z system did not influence the wear behaviour. As a slight decrease in retention force was recorded, it is useful for an attachment system to allow compensation with an adjustable matrix.

Managing the patient presenting with xerostomia: a review

AIMS

Patients complaining of a dry mouth can present themselves to various clinicians such as the primary care physician, dentists, otolaryngologists and/or oral surgeons. The aim of our review is to provide a systematic method of assessing and managing these patients based on current best evidence published in the literature.

METHODS

A literature search was performed on 20th April 2009 using MEDLINE and EMBASE using the terms dry mouth and xerostomia in combination with diagnosis, management, investigations and treatment.

RESULTS

There appears to be little correlation between patient symptoms and objectives tests of salivary flow. Therefore clinical management should be based on patient symptoms. There is good evidence to support that xerostomia is commonly associated with anticholinergic drugs, and altering such agents plays an important role in the management of these patients. In patients with residual salivary gland function, the use of salivary stimulants appears to be more beneficial than salivary substitutes.

CONCLUSION

Xerostomia can be debilitating and primarily affects the middle aged and elderly population. The most common causes of xerostomia include medications with anticholinergic properties, dehydration, diabetes and radiotherapy for head and neck cancer. Treatment of xerostomia essentially involves addressing the cause followed by salivary substitutes and/or salivary stimulants.

Mastication and swallowing: influence of fluid addition to foods

Introduction:

The production of sufficient saliva is indispensable for good chewing. Recent research has demonstrated that salivary flow rate has little influence on the swallowing threshold.

Objectives:

The hypothesis examined in the present study was that adding fluids to foods will influence chewing physiology.

Materials and Methods:

Twenty subjects chewed on melba toast, cake, carrot, peanut and Gouda cheese. They also chewed on these foods after addition of different volumes of water or α-amylase solution. Jaw muscle activity, number of chewing cycles until swallowing and chewing cycle duration were measured. Repeated measures analysis of variance was applied to test the null hypothesis that there would be no statistically significant difference among the results obtained for the various food types and fluids. Subsequently, contrasts were determined to study the levels of intra-subjects factors (food type and fluid volume). Linear regression was used to determine the changes in muscle activity and cycle duration as a function of the chewing cycles.

Results:

Fluid addition significantly decreased muscle activity and swallowing threshold for melba, cake and peanut (p<0.05). The effect of α-amylase in the solutions was similar to that of water (p>0.05). Doubling the volume of tap water had a greater effect.

Conclusions:

Fluid addition facilitated chewing of dry foods (melba, cake), but did not influence the chewing of fatty (cheese) and wet products (carrot). This study is relevant to improve patients’ life quality and the management of chewing and feeding disorders caused by hyposalivation.

Saliva as research material: Biochemical, physicochemical and practical aspects

Whole saliva is a complex mixture of proteins and other molecules which originate from several sources. The biochemical and physicochemical properties of saliva contribute to the numerous functions of saliva in, e.g., speech, maintaining oral and general health, and food processing. Interest in saliva has increased in the last few years for its potential to diagnose viral, bacterial and systemic diseases. The use of saliva as research material may pose particular problems due to its inherent variability and instability. This review describes practical aspects of salivary as research material with emphasis on protein biochemistry and physical chemistry.

Viscosity and wettability of animal mucin solutions and human saliva

OBJECTIVE

The purpose of this study was to compare viscosity and wettability between animal mucin solutions and human saliva.

MATERIALS AND METHODS

Human whole and glandular saliva, porcine gastric mucin, bovine submaxillary mucin, and a mucin-based saliva substitute were used. Viscosity was measured with a cone-and-plate digital viscometer, while wettability on acrylic resin and Co-Cr alloy was determined by the contact angle.

RESULTS

The viscosity of animal mucin solutions was proportional to mucin concentration, with the animal mucin solution of concentration 5.0 mg ml(-1) displaying similar viscosity to stimulated whole saliva. A decrease in contact angle was found with increasing animal mucin concentration. For the saliva samples tested, viscosity increased in the following order: stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. Contact angles of human saliva on the tested solid phases were inversely correlated with viscosity. Contact angles of human saliva on acrylic resin were much lower than those of animal mucin solutions and of those on Co-Cr alloy (P < 0.01).

CONCLUSIONS

The effectiveness of animal mucin solutions in terms of their rheological properties was objectively confirmed, indicating a vital role for mucin in proper oral function as well as the development of effective salivary substitutes.

Analysis of potential lubricants for in vitro wear testing

OBJECTIVES

A critical testing aspect for a reliable two-body wear simulation may be the lubricity condition. The main hypothesis tested in this study was that, over the experiment duration, the presence or absence of lubricants would provide to a composite similar wear rates to those observed under human saliva lubrication.

METHODS

Seventy specimens, fabricated from a minifill composite, were tested in a programmable logic controlled wear simulator with human saliva (HS), mucin-based artificial saliva (MC), carboxymethylcellulose-containing saliva (CM), deionized water (DW) or with no lubrication (UN). Wear depth was quantified at the end of 1000, 5000, 10,000 and 50,000 cycles and at each 50,000 through 250,000 cycles.

RESULTS

Over all the test period, UN led to the greatest wear. Initially, lubrication resulted in no significant differences among the wear rates. Subsequently, up to 50,000 cycles, depths of wear provided by HS and MC were still similar, being the lowest, whereas DW yielded greater wear than CM. Later, interposition of CM and HS resulted in equivalent wear. At 250,000 cycles, wear of the composite ranked as follows: MC<HS<CM<DW<UN. Regression analyses showed that for all lubricity conditions wear of the composite rose logarithmically with number of cycles.

SIGNIFICANCE

The role of the interposed lubricant was of importance for the wear testing. The present findings supported by studies on the lubricity ability of mucin-based artificial saliva, allowed to conclude that this preparation may be considered as a potential lubricant for in vitro wear test purposes.

The influence of product and oral characteristics on swallowing

The urge to swallow food could be triggered by a threshold level in both food particle size and lubrication of the food bolus. Thus, both oral physiology and product characteristics may influence the swallowing threshold. We quantified the swallowing threshold in a group of 266 healthy adult subjects (age 42 +/- 12 years) by counting the number of chewing cycles needed to prepare food for swallowing. The influence of oral physiology on the swallowing threshold was determined by measuring salivary flow rate, maximum bite force and masticatory performance. We used about 10 cm(3) of bread, toast, melba toast, breakfast cake, peanuts and cheese to determine the influence on the swallowing threshold of various food characteristics, e.g. hardness, moisture and fat. Furthermore, we tested the effect of buttering the bread, toast, melba toast and breakfast cake on the swallowing threshold. Salivary flow rates were significantly and negatively correlated with the number of chewing cycles of melba toast and breakfast cake. Hence, subjects with more saliva needed less chewing cycles for these dry products. Maximum bite force and masticatory performance had an influence on the swallowing threshold for the hard products only (carrot and peanut). Although significant, the correlation coefficients were less than 0.28. Thus, the oral physiology parameters explained less than 10% of the variance in the swallowing threshold. We found significantly different numbers of chewing cycles for the various foods, ranging from 17 for cake to 63 for carrot. Hard and dry products needed more chewing cycles until swallowing. Buttering the food significantly reduced the number of chewing cycles needed before swallowing. This was especially true for the dry products cake, melba toast and toast. Hard and dry products require more chewing cycles and longer time in mouth until swallowing for sufficient breakdown to take place and for enough saliva to be added to form a coherent bolus safe for swallowing. In spite of this, more saliva, higher maximum bite force and better masticatory performance were only weakly correlated with a smaller number of chewing cycles. Butter enhanced lubrication and bolus formation of dry products, thus reducing the number of chewing cycles until swallowing. In conclusion, product characteristics and to a lesser extent oral physiology significantly affect swallowing threshold.

Bioadhesive, rheological, lubricant and other aspects of an oral gel formulation intended for the treatment of xerostomia

Xerostomia is commonly known as 'dry mouth' and is characterised by a reduction or loss in salivary production. A bioadhesive gel for its localised treatment was formulated to help enhance the residence time of the product, based on the polymer Carbopol 974P. The bioadhesion of various formulations was evaluated on different mucosal substrates, as simulations of the oral mucosa of xerostomic patients. Depending on the type of model substrate used, the mechanism of bioadhesion could alter. When the rheology of various formulations was examined, changes in bioadhesion were more easily interpreted, as the presence of other excipients caused an alteration in the rheological profile, with a change from a fully expanded and partially cross-linked system to an entangled system. Improving the lubricity of the product was considered important, with optimum incorporation of vegetable oil causing a desirable lowering of the observed friction of the product. The final complex formulation developed also contained salivary levels of electrolytes to help remineralisation of teeth, fluoride to prevent caries, zinc to enhance taste sensation, triclosan as the main anti-microbial/anti-inflammatory agent and non-cariogenic sweeteners with lemon flavour to increase the palatability of the product while stimulating any residual salivary function.

The impact of saliva on patient care: A literature review

Decreased salivary flow results in a clinically significant oral imbalance that may manifest as increased caries, susceptibility to oral candidosis, altered taste sensation, or a host of other problems. This article reviews the role of saliva in oral health, highlights the causes and consequences of xerostomia, and outlines treatment modalities for patients with xerostomia. Journal articles were investigated through Medline, and relevant textbooks and handbooks were consulted. A summary of the literature pertinent to clinical prosthodontics is presented.

An in vitro mucosal model for prediction of the bioadhesion of alginate solutions to the oesophagus

This paper discusses the development of an in vitro model utilised to assess the adhesion of alginate solutions to porcine oesophageal tissue. The methodology involved the construction of retention apparatus onto which sections of tissue were mounted. Fluorescently labelled alginate solutions of known rheological profile were dispensed onto the tissue at a concentration of 2% w/v. A washing solution was applied at a specified rate to mimic saliva flow and the eluted material collected. Fluorimetric analysis allowed dose retention to be assessed as a function of time. The effect of the nature of the washing solution and the choice of alginate were investigated. It was found that after 30 min up to 20% of the applied alginate dose remained associated with the tissue, regardless of the alginate selected from the range examined. The nature of the washing medium did not have a significant effect on retention, irrespective of the inherent mucin concentration. Overall this study indicated that the technique presented offers a viable means of studying bioadhesion of liquids and also demonstrates that alginate solutions may have an application as bioadhesive agents for localisation within the oesophagus.

Asparagine-linked carbohydrate chains of inducible rat parotid proline-rich glycoprotein contain terminal beta-linked N-acetylgalactosamine

Rats treated with daily injection of DL-isoproterenol for 10 consecutive days (25 mg kg(-1) body weight) showed marked induction of a proline-rich glycoprotein (GPRP) of 220 kDa. Proteinase K digestion of GPRP produced a homogeneous glycopeptide with an average chemical composition as follows (residues per mol): Pro4, Glx3, Asx2, Gly1, His1, Thr1, Arg1, GlcNAc5, GalNac1, Man3, Gal2-3, and Fuc1. The structural analysis of the asparagine-linked carbohydrate unit was performed by methylation, periodate oxidation and enzymatic degradation. Methylation studies indicated that the three mannosyl residues were substituted at 1,2-, 1,2,4-, and 1,3,6-positions. Fucose, N-acetylgalactosamine, 1.5 residues of galactose and 0.35 residues of N-acetylglucosamine were terminally located and one galactose residue was 1,4-substituted. Approximately four of the 5 N-acetylglucosamine residues were substituted at 1,4-position and approximately 1 residue of N-acetylglucosamine was substituted at 1,4,6-positions. Periodate oxidation studies and exoglycosidase results were consistent with the methylation data. Based on the results of Smith degradation, methylation and sequential exoglycosidase digestions a triantennary oligosaccharide structure having terminal N-acetylgalactosamine in one of the branches is proposed for the major Asn-linked carbohydrate moiety of GPRP.

Clinical trial of a mucin-containing oral spray for treatment of xerostomia in hospice patients

Thirty-five hospice patients complaining of dry mouth entered a double-blind, single-phase placebo-controlled trial of a mucin-containing oral spray (Saliva Orthana) for the relief of xerostomia. The sprays were administered ad libitum for two weeks by the patients themselves, with nursing help as necessary. A detailed history and examination were undertaken, together with collection of microbiological specimens, at entry and after seven and 14 days of spray usage, respectively. Thirty-one patients were available for follow-up at seven days and 26 patients after 14 days. Relief of oral dryness during the day was reported by 9/15 patients on Saliva Orthana and 10/16 patients on placebo by day 7, with a similar degree of improvement maintained to day 14. The corresponding figures by day 7 for relief of dryness at night were 8/15 for Saliva Orthana and 8/16 for placebo. There were no statistically significant differences between those on active and those on placebo spray for any of the oral symptoms recorded. Neither spray had any major impact on the oral microflora. However, the majority of patients in both treatment groups wished to continue using a mouth spray at the end of their involvement in the trial. Whilst the data from this study provide no evidence for increased benefit of a mucin-containing spray over a mucin-free placebo among xerostomic hospice patients, it is clear that both sprays provided worthwhile symptomatic relief of oral dryness for many of the participants.

Lubrication of saliva substitutes at enamel-to-enamel contacts in an artificial mouth

Mechanisms of salivary lubrication can be quantitatively measured by a reduction in the coefficient of friction. It is important that lubrication be assessed under the conditions of the oral cavity to properly assess lubrication regimes. The relative lubricity of three artificial salivas and two controls were assessed at a bovine enamel interface in an artificial mouth with a range of conditions that approximate oral function. Statistical analysis indicated that the enamel lubricity of sodium dodecylsulfate (SDS) and Oracare-D saliva substitutes were different from the other saliva substitutes and water. The low friction with Oracare-D and SDS saliva substitutes was because of resident amphipaths adsorbed at the enamel interface. Amphipaths adsorbed on enamel may provide a reduction in interocculsal friction and its resulting complications for patients with xerostomia.

Short-term contamination of luting cements by water and saliva

OBJECTIVES

The aim of this study was to determine the effect of water, artificial saliva and natural saliva on the hardening process of three dental luting cements.

METHODS

Cement samples, 1 mm thick and 5 mm in diameter, were subjected to various storage conditions in an oven maintained at 37 degrees C. Some samples were aged in 100% humidity or water for up to 1 wk. The other samples were covered with water, artificial saliva or natural saliva at various times after mixing. The Knoop hardness values of the cement surfaces were measured. Differences between groups were evaluated with an ANOVA followed by a Tukey multiple comparison at the 5% level of significance. The hardness ratio of the contaminated samples was calculated using the 30 min mean KHN of the samples aged in 100% humidity as the divisor.

RESULTS

The glass ionomer samples were significantly harder (48.3 +/- 3.8) than the zinc phosphate (38.9 +/- 7.5) or composite cements (35.4 +/- 10.2) after 1 wk in 100% humidity storage condition. When immersed in water, the hardness of both the glass ionomer and the zinc phosphate decreased to almost half that of the specimens stored in 100% humidity (26.2 +/- 2.7 and 16.9 +/- 2.5, respectively). Contamination decreased the hardness of zinc phosphate and glass ionomer (hardness ratio, water contamination at 5 min: 0.39 +/- 0.10 and 0.52 +/- 0.12, respectively) but had very little effect on the composite. Overall, water had a greater softening effect than artificial or natural saliva on the cements.

SIGNIFICANCE

In light of these results, glass ionomer cement should be protected from water and saliva for the first 15 min after mixing.

Lubrication of human and bovine enamel compared in an artificial mouth

Bovine enamel has been a good model for human enamel across a broad range of studies. The present work sought to consider if bovine enamel would be a suitable substitute for human enamel in experiments on simulated oral lubrication. Enamel samples of the same size were prepared from bovine and human teeth for use as maxillary and mandibular elements in a miniature artificial mouth. Sliding speeds from 1.99 to 7.84 mm/s and occlusal forces of 3.8-19.5 N were used. Water and four solutions consisting of a mucin-rich fraction, a statherin-rich fraction, 3[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate and sodium dodecyl sulphate were evaluated. The high correlations between widely different lubricants on the two enamel substrates gives confidence in the use of bovine enamel as a model for human enamel in salivary lubrication studies. Knoop hardness indentations on enamel samples were combined with friction data and calculations of the true contact area to give a method for the indirect determination of surface shear. The calculated surface shear value was compared with published values obtained by punch shear testing.

Preventing the ITU syndrome or how not to torture an ITU patient! Part 2

Admission to an intensive therapy unit (ITU) has been described as a 'necessary evil' (Barrie-Shevlin 1987), and some of the 'tortures' described in Part I of this article (Dyer 1995) may be an inevitable result of ITU care. This does not mean that the development of the ITU syndrome should be regarded as inevitable. Many potential causes of the syndrome can be avoided or at least ameliorated. Some suggested means of preventing the syndrome include designing ITUs with windows (Keep et al 1980), use of noise reducing materials when building ITUs (Hopkinson 1994, Topf & Davis 1993), using noise level as a criterion when purchasing equipment (Dracup 1988) or using remote telemetry for monitoring (Fisher & Moxham 1984). These would undoubtedly be beneficial but they are not practical propositions for nurses who wish to improve psychological care in the short term. For this reason, this article, concentrates mainly on immediately applicable, relatively cost-free interventions. Methods of preventing the syndrome should begin, whenever possible, before admission and should continue throughout the patients' stay. The main emphasis should be placed on prevention, but early detection and treatment of problems should also be given high priority. If a patient exhibits symptoms of psychological disturbance physical causes should be considered, but at the same time the ITU syndrome should be suspected and attempts made to alleviate possible causes of this. Nurses play a vital role in any attempts to alleviate problems and in 'humanising' the technical ITU environment (Ashworth 1987, Mackellaig 1990).(ABSTRACT TRUNCATED AT 250 WORDS)

Preventing the ITU syndrome or how not to torture an ITU patient! Part I

Staff working in intensive therapy units (ITUs) have known about the 'ITU syndrome' for many years. In spite of this the syndrome continues to occur. It is suggested that one of the reasons for this continued occurrence is that ITU staff place a lower priority on psychological care than they do on physical care. In this paper the potential seriousness of the ITU syndrome is emphasised by describing it as a form of torture. Publications from Amnesty International which describe methods of psychological torture are provided to support this suggestion. The analogies between psychological torture and ITU care are explored, and this is followed by consideration of ways of reducing the incidence of the syndrome and a suggested method of auditing an ITU in order to identify potential problem areas.

Quantifying the strength of bacterial adhesive interactions with salivary glycoproteins

We adapted an assay that has been used to estimate the strength of eukaryotic cell-cell and cell-extracellular matrix adhesive interactions (McClay et al., 1981) to quantify the strength of bacterial (streptococci, fusobacteria, actinomyces) interactions with salivary receptors. Bacteria are centrifuged onto human submandibular/sublingual or parotid-saliva-coated microtiter wells. Plates are sealed with pressure-sensitive, double-sided tape which allows them to be inverted and centrifuged again. The force required to remove the bacteria from the coated wells is a direct measure of the adhesive strength of the interaction(s) being disrupted. The bacteria-saliva adhesive forces we detected ranged from 1.6 x 10(-8) dynes (Streptococcus sanguis 72-40) to > 1.1 x 10(-7) dynes (Actinomyces viscosus T14 V). These forces were in the range to withstand the shear stress produced by salivary flow, which we calculated as approximately 6.1 x 10(-7) dynes.

Salivary gland dysfunction: causes, symptoms, treatment

The three most common known causes of salivary gland dysfunction are medication usage, radiation therapy and Sjogren's syndrome. Current therapeutic options to treat salivary dysfunction are limited. Clinical considerations as well as the outlook for individuals experiencing salivary dysfunction are discussed.

Development of artificial salivas

Salivary research is at a critical crossroads regarding the clinical application of basic knowledge. Studies by numerous salivary researchers over the last 5 years using advanced technologies (e.g., protein chemistry, molecular biology, and biophysics) have demonstrated that the structural requirements for salivary function are quite complex. Nevertheless, several patterns or principles have evolved. First, the majority if not all salivary molecules are multifunctional. Second, the conformation of a molecule is an important factor in biological activity. Third, many molecules have overlapping functions (e.g., mucins and amylase interact with viridans streptococci; statherin and proline-rich proteins are involved in mineralization). Thus, saliva has "built-in" compensatory or redundant properties. Nevertheless, it must be determined which molecule is more potent or effective with respect to a particular function. Fourth, salivary molecules may be "amphifunctional". In other words, the different functions of a single molecule may be protective or potentially harmful depending on the intraoral site of action. Examples of amphifunctional molecules are amylase and statherin. Fifth, functional relationships may exist between different salivary components. The principles mentioned above can provide experimental strategies for the design and synthesis of a first generation of salivary substitutes that can be topically applied to oral surfaces. These molecules should be used to combat microbial mediated diseases and occlusal disharmony in subjects with normal salivary flow as well as those with xerostomia. In general, these substitutes should be long-lasting, biocompatible, biodegradable, and provide specific protective qualities that can be targeted to selected intraoral sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of human salivary histatin and cystatin/histatin chimeric cDNAs in Escherichia coli

We have previously constructed recombinants encoding the full-length and truncated forms of cystatin-SN and expressed these in the Escherichia coli expression system pGEX-2T, which expresses foreign sequences as fusion proteins with glutathione S-transferase (GST). Recombinant cystatins were produced and purified in large quantities. The full-length recombinant cystatin-SN exhibited comparable biological activity and secondary structure to natural cystatin, validating the use of the full-length and mutant recombinant proteins for structure-function studies of salivary molecules. In this study, we have expressed histatin-1 cDNA in the pGEX-3X vector and cystatin-SN/histatin-1 or cystatin-SN/histatin-3 chimeric cDNAs in the pGEX-2T vector. Gene splicing by overlap extension (SOE), a PCR-based method, was used for generating the chimeric cDNAs. Each construct was analyzed by DNA sequencing, which showed the correct junctions and reading frames between the GST/histatin-1 and the GST/cystatin/histatin cDNAs. Expression of histatin and cystatin/histatin chimeras was induced by IPTG and the production of the fusion proteins monitored by SDS-PAGE/Coomassie blue staining and in the case of the GST/cystatin/histatin fusion proteins, also by Western blot using anti-cystatin antibody. The results of these studies showed that we have successfully constructed recombinants encoding the individual and chimeric salivary molecules and efficiently expressed these in E. coli expression system pGEX. Purification and characterization of recombinant histatin and cystatin-histatin hybrid proteins are presently ongoing.

Xerostomia: the missing diagnosis?

Xerostomia is a distressing condition which may be associated with a number of specific diseases, iatrogenically induced following the administration of drugs or radiotherapy, or the result of inflammatory processes affecting salivary gland tissue. In this article epidemiological background is briefly reviewed and aetiological conditions associated with xerostomic states are summarized. The oral sequelae of xerostomia are discussed and approaches to diagnosis demonstrated. Treatment of xerostomia is basically supportive and the main elements are presented.

Sjogren's syndrome: oral and dental considerations

Patients with Sjogren's syndrome have many oral health needs. Due to the extensive oral involvement, dentists may be the first to recognize this condition. Characteristics and treatment options for this disorder are discussed and three case histories are presented.

Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study

Two new saliva stimulants: V6 and a mucin containing chewing gum were tested in this placebo-controlled double-blind crossover study. Forty-three patients (mean age 63 yr) complaining of dry mouth participated. The products were administered in a randomized order, and used for 2 wk each. The effect was evaluated by interviews and by determining changes in stimulated and unstimulated saliva flow rates. A positive effect was reported by 64%, 44%, and 26% of the patients using the mucin chewing gum, V6, and the placebo, respectively. More than 2/3 of the patients found the mucin chewing gum efficient at various times and situations. Sixty-one percent of the patients preferred the mucin chewing gum, 21% V6, and 5% the placebo product. Fifty percent of the patients had an increase in unstimulated salivary secretion rate from all products after 14 days regular use indicating a long-term effect.

Effects of combined hydrochlorothiazide and amiloride versus single drug on changes in salt taste and intake

Hydrochlorothiazide stimulates salt intake without altering salivary or gustatory function. Amiloride reportedly reduces salivary sodium levels and salt taste. It was hypothesized that these unintended drug actions would be attenuated by concurrent use of these 2 diuretics. Normotensive adults (n = 23) were administered placebo for 2 weeks, active combination drug Moduretic for 4 weeks, and placebo again for 2 weeks in a double-blind protocol. Salivary flow, gustatory function and sodium intake were monitored at the end of each period, together with selected physiologic measures (i.e., plasma aldosterone, plasma renin activity, body composition, blood pressure and heart rate). No significant changes were observed for salivary flow, salt taste or sodium intake. These findings indicate that amiloride and hydrochlorothiazide used in combination can reduce drug effects that may compromise the efficacy of either drug when used alone.

Cystatins--inhibitors of cysteine proteinases

The cystatin superfamily of proteins, derived from a common ancestor, is comprised of a diverse group of potent cysteine proteinase inhibitors and antibacterial/viral agents grouped into several families. This review concentrates on family 2 cystatins, namely, the human salivary cystatins and cystatin C. Emphasis is given to their physicochemical and functional properties at both the protein and the molecular level. The role of cystatins in disease processes, including those in the oral cavity, is also discussed. Finally, future directions for cystatin research in oral biology are presented.

Large-scale purification and characterization of the major phosphoproteins and mucins of human submandibular-sublingual saliva

The major components of human submandibular-sublingual saliva (HSMSL) are mucins, amylases, cystatins, proline-rich proteins and statherin. Structure-function studies of these molecules have been hampered by the small amounts of purified materials that can be isolated from human secretions. The present study describes an integrated purification protocol for the large-scale preparation of many of these molecules. To dissociate partially heterotypic complexes among salivary molecules, HSMSL was initially fractionated into four pools by gel filtration with 6 M-guanidine hydrochloride. Subsequent fractionation of these four pools by gel-filtration and ion-exchange chromatography resulted in the purification of high- and low-Mr mucins, neutral and acidic cystatins, acidic and basic proline-rich proteins and statherin. Many variants or isoforms of these salivary molecules have been identified and biochemically characterized. Biochemical studies indicated that the low-Mr mucin exists as two isoforms which vary in their sialic acid to fucose ratios. Three isoforms of acidic cystatin S were characterized which differ in their phosphate content. Two isoforms of a basic proline-rich peptide were identified; the smaller peptide was a truncated form missing the first seven amino acids.

A new assessment in vitro of human salivary lubrication using a compliant substrate

The lubrication effect of salivary secretions was assessed in terms of separating a rigid object from a compliant substrate. There was little difference among the various secretions of a single donor. The viscosity of salivas increased as a function of time. Neither the friction testing nor viscometry provided an adequate model of the tissue-coating function ascribed to saliva.