A clinical comparison between commercially available mucin- and CMC-containing saliva substitutes

Pinching dynamics, extensional rheology, and stringiness of saliva substitutes

Saliva substitutes are human-made formulations extensively used in medicine, food, and pharmaceutical research to emulate human saliva's biochemical, tribological, and rheological properties. Even though extensional flows involving saliva are commonly encountered in situations such as swallowing, coughing, sneezing, licking, drooling, gleeking, and blowing spit bubbles, rheological evaluations of saliva and its substitutes in most studies rely on measured values of shear viscosity. Natural saliva possesses stringiness or spinnbarkeit, governed by extensional rheology response, which cannot be evaluated or anticipated from the knowledge of shear rheology response. In this contribution, we comprehensively examine the rheology of twelve commercially available saliva substitutes using torsional rheometry for rate-dependent shear viscosity and dripping-onto-substrate (DoS) protocols for extensional rheology characterization. Even though most formulations are marketed as having suitable rheology, only three displayed measurable viscoelasticity and strain-hardening. Still, these too, failed to emulate the viscosity reduction with the shear rate observed for saliva or match perceived stringiness. Finally, we explore the challenges in creating saliva-like formulations for dysphagia patients and opportunities for using DoS rheometry for diagnostics and designing biomimetic fluids.

Randomized Double-Blind Placebo-Controlled Study of Salivary Substitute with Enzymatic System for Xerostomia in Patients Irradiated in Head and Neck Region

This study aims to compare whether the use of a salivary substitute including an enzymatic system clinically reduces the intensity of xerostomia, as well as exploring the impact that this has on the quality of life, in patients who had received radiotherapy in the head and neck (HNC) region. Forty patients who had completed radiotherapy treatment within 6 months to 1 year previously were allocated into an Enzymatic Spray group (n = 21) or a Placebo arm (n = 19). It should be noted that two patients in the Placebo arm declined to participate during phase 2 of the study. All patients were randomized and used both products three times a day for 30 days. For analysis, xerostomia grade, unstimulated (UWS) and stimulated (SWS) salivary flow rate, and quality of life through the University of Washington Quality of Life Questionnaire validated in Portuguese (UW-QoL) were assessed in two phases: Phase 1 (before the use of the products) and Phase 2 (after 30 days of using the products). All clinical data were collected from medical records. Analyzing the salivary substitute with the enzymatic system, an improvement in xerostomia complaints was observed 30 days after using the product; however, this difference was not statistically significant (p > 0.05). Regarding quality of life, no significant differences were observed in relation to the UW-QoL and saliva domain between the groups in the two phases of the study (p > 0.05). The salivary substitute with the enzymatic system may be effective in reducing radio-induced xerostomia symptoms; however, further research is necessary to evaluate the efficacy of this salivary substitute on oral health.

Could the use of saliva substitutes improve food oral processing in individuals with xerostomia? A systematic review

Xersotomia is associated with food avoidance and low nutritional assessment. This review seeks to document whether products called "saliva substitutes" or "artificial saliva" can really replace saliva in food oral processing. Pubmed and Science Direct were searched for articles using the keywords "saliva substitutes" and "artificial saliva." An advanced search was applied using the terms "xerostomia" and/or "food oral processing" and/or "eating" and/or "mastication" and/or "chewing" and/or "swallowing." The analysis methods and the inclusion criteria were documented in a protocol published in the International prospective register of systematic reviews (PROSPERO with the registration number CRD42019124585). The search included 43 articles, published between 1979 and 2017. Among the included studies, 17 were observational studies, 5 were pilot studies, 21 were crossover studies, and 14 of these studies were blinded. The Strobe score for the included articles varied from 7.5 to 20. The possible effects of the use of saliva substitutes on the ingestion function were poorly investigated. No evidence was based on physiological studies. It is unknown whether using a saliva substitute has an effect on the composition and rheological properties of the food bolus, on the lubrication of the oral and laryngeal mucosa or on both phenomena. Moreover, saliva substitutes were not formulated to improve food oral processing and most of them are flavored. New saliva substitutes and artificial saliva should be designed and formulated to improve food oral processing.

Beyond dissolution: Xerostomia rinses affect composition and structure of biomimetic dental mineral in vitro

Xerostomia, known as dry mouth, is caused by decreased salivary flow. Treatment with lubricating oral rinses provides temporary relief of dry mouth discomfort; however, it remains unclear how their composition affects mineralized dental tissues. Therefore, the objective of this study was to analyze the effects of common components in xerostomia oral rinses on biomimetic apatite with varying carbonate contents. Carbonated apatite was synthesized and exposed to one of the following solutions for 72 hours at varying pHs: water-based, phosphorus-containing (PBS), mucin-like containing (MLC), or fluoride-containing (FC) solutions. Post-exposure results indicated that apatite mass decreased irrespective of pH and solution composition, while solution buffering was pH dependent. Raman and X-ray diffraction analysis showed that the addition of phosphorus, mucin-like molecules, and fluoride in solution decreases mineral carbonate levels and changed the lattice spacing and crystallinity of bioapatite, indicative of dissolution/recrystallization processes. The mineral recrystallized into a less-carbonated apatite in the PBS and MLC solutions, and into fluorapatite in FC. Tap water did not affect the apatite lattice structure suggesting formation of a labile carbonate surface layer on apatite. These results reveal that solution composition can have varied and complex effects on dental mineral beyond dissolution, which can have long term consequences on mineral solubility and mechanics. Therefore, clinicians should consider these factors when advising treatments for xerostomia patients.

Duration of effect of Biotène spray in patients with symptomatic dry mouth: A pilot study

OBJECTIVES

The objective of this study was to assess the duration of effect of a single dose of Biotène Moisturizing Spray on xerostomia compared to water spray.

STUDY DESIGN

This double-blind randomized controlled crossover trial compared the duration of effect of 2 agents on relieving xerostomia in adult patients recruited through convenience sampling. Following a xerostomia questionnaire, qualifying patients with an unstimulated whole saliva flow rate of ≤0.20 mL/min rated their baseline level of discomfort from oral dryness and received a single dose (3 sprays) of Biotène Moisturizing Spray or water (active control). Patients indicated their level of oral discomfort every 15 min and the precise time when relief ceased. After a minimum 48-h washout, patients repeated the exercise with the alternative product.

RESULTS

The baseline severity of discomfort from oral dryness among qualifying patients was significantly related to their level of hyposalivation (P = .001). The mean duration of effect of Biotène Moisturizing Spray was 27 ± 25 min, which was not significantly different from that for water (26 ± 25 min; P = .88; n = 25).

CONCLUSION

Biotène Moisturizing Spray and water spray had variable durations of effect averaging approximately 30 min. The results of this pilot study provide guidance regarding anticipated usage and dispensing needs for patients with objective xerostomia. ClinicalTrials.gov NCT03663231.

Dry mouth diagnosis and saliva substitutes-A review from a textural perspective

The aim of this review is to assess the objective and subjective diagnosis, as well as symptomatic topical treatment of dry mouth conditions with a clear focus on textural perspective. We critically examine both the current practices as well as outline emerging possibilities in dry mouth diagnosis and treatment, including a patent scan for saliva substitutes. For diagnosis, salivary flow rates and patient-completed questionnaires have proven to be useful tools in clinical practice. To date, objective measurements of changes in mechanical properties of saliva via rheological, adsorption, and tribological measurements and biochemical properties of saliva such as assessing protein, mucins (MUC5B) are seldom incorporated into clinical diagnostics; these robust diagnostic tools have been largely restricted to application in non-clinical settings. As for symptomatic treatments of dry mouth, four key agents including lubricating, thickening, adhesive, and moisturizing agents have been identified covering the overall landscape of commercial saliva substitutes. Although thickening agents such as modified celluloses, polysaccharide gum, polyethylene glycol, and so forth are most commonly employed saliva substitutes, they offer short-lived relief from dry mouth and generally do not provide boundary lubrication properties of real human saliva. Innovative technologies such as self-assembly, emulsion, liposomes, and microgels are emerging as novel saliva substitutes hold promise for alternative approaches for efficient moistening and lubrication of the oral mucosa. Their adoption into clinical practice will depend on their efficacies, duration of relief, and ease of application by the practitioners and patient compliance.

Salivary Gland Hypofunction and Xerostomia in Head and Neck Radiation Patients

BACKGROUND

The most manifest long-term consequences of radiation therapy in the head and neck cancer patient are salivary gland hypofunction and a sensation of oral dryness (xerostomia).

METHODS

This critical review addresses the consequences of radiation injury to salivary gland tissue, the clinical management of salivary gland hypofunction and xerostomia, and current and potential strategies to prevent or reduce radiation injury to salivary gland tissue or restore the function of radiation-injured salivary gland tissue.

RESULTS

Salivary gland hypofunction and xerostomia have severe implications for oral functioning, maintenance of oral and general health, and quality of life. Significant progress has been made to spare salivary gland function chiefly due to advances in radiation techniques. Other strategies have also been developed, e.g., radioprotectors, identification and preservation/expansion of salivary stem cells by stimulation with cholinergic muscarinic agonists, and application of new lubricating or stimulatory agents, surgical transfer of submandibular glands, and acupuncture.

CONCLUSION

Many advances to manage salivary gland hypofunction and xerostomia induced by radiation therapy still only offer partial protection since they are often of short duration, lack the protective effects of saliva, or potentially have significant adverse effects. Intensity-modulated radiation therapy (IMRT), and its next step, proton therapy, have the greatest potential as a management strategy for permanently preserving salivary gland function in head and neck cancer patients.Presently, gene transfer to supplement fluid formation and stem cell transfer to increase the regenerative potential in radiation-damaged salivary glands are promising approaches for regaining function and/or regeneration of radiation-damaged salivary gland tissue.

Commercial Porcine Gastric Mucin Preparations, also Used as Artificial Saliva, are a Rich Source for the Lectin TFF2: In Vitro Binding Studies

Mucous gels (mucus) cover internal body surfaces. The secretory mucins MUC5AC and MUC6 and the protective peptide TFF2 are characteristic constituents of gastric mucus; TFF2 is co-secreted with MUC6. Herein, we investigated two commercial mucin preparations by FPLC and proteomics, because they are model systems for studying the rheology of gastric mucins. One preparation is also used as a saliva substitute, for example, after radiation therapy. We show that both preparations contain TFF2 (≈0.6 to 1.1 %, w/w). The majority of TFF2 is strongly bound noncovalently to mucin in a manner that is resistant to boiling in SDS. First overlay assays with ¹²⁵ I-labeled porcine TFF2 revealed that mucin binding is modulated by Ca²⁺ and can be blocked by the lectin GSA-II and the antibody HIK1083, both recognizing the peripheral GlcNAcα1→4Galβ1→R moiety of MUC6. TFF2 binding was also inhibited in the presence of Me-β-Gal but less so by the α anomer. TFF2 may play a role in the oligomerization and secretion of MUC6, the rheology of gastric mucus, and the adherence of gastric microbiota. TFF2 in artificial saliva may be of benefit. TFF2 might also interact with the sugar moiety of various receptors.

An ex vivo salivary lubrication system to mimic xerostomic conditions and to predict the lubricating properties of xerostomia relieving agents

Advances in medical research has resulted in successful treatment of many life-threatening infectious diseases as well as autoimmune and lifestyle-related diseases, increasing life-expectancy of both the developed and developing world. As a result of a growing ageing population, the focus has also turned on chronic diseases which seriously affect the quality of older patient life. Xerostomia (dry mouth) is one such condition, which leads to bad oral health and difficulty in consumption of dry foods and speech. Saliva substitutes are used to ease symptoms. However, they often don’t work properly and objective comparison of saliva substitutes to mimic natural salivary functions does not exist. The study thus aims to develop an ex vivo friction assay simulating dry mouth conditions and facilitating objective comparison of saliva substitutes. A reciprocating sliding tongue-enamel system was developed and compared to a PDMS (polydimethylsiloxane)-PDMS friction system. The tongue-enamel system, but not the PDMS-PDMS model, showed high mucin-containing saliva (unstimulated and submandibular/sublingual saliva) to give higher Relief than mucin-poor lubricants (water, parotid saliva, Dentaid Xeros) and correlated well (r = 0.97) with in vivo mouth feel. The tongue-enamel friction system mimicked dry mouth conditions and relief and seems suited to test agents meant to lubricate desiccated oral surfaces.

Effects of molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase

OBJECTIVES

To investigate the effects of the molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase in solution and on the hydroxyapatite surface.

DESIGN

Hyaluronic acids of four different molecular weights (10 kDa, 100 kDa, 1 MDa, and 2 MDa), hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used. Viscosity values of hyaluronic acids were measured using a cone-and-plate viscometer at six different concentrations (0.1-5.0 mg/mL). Enzymatic activities of lysozyme and peroxidase were examined by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus and oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein, respectively.

RESULTS

In solution assays, only 2 MDa-hyaluronic acid significantly inhibited lysozyme activities in saliva. In surface assays, hyaluronic acids inhibited lysozyme and peroxidase activities; the inhibitory activities were more apparent with high-molecular-weight ones in saliva than in purified enzymes. The 100 kDa-hyaluronic acid at 5.0 mg/mL, 1 MDa-one at 0.5 mg/mL, and 2 MDa-one at 0.2 mg/mL showed viscosity values similar to those of human whole saliva at a shear rate range required for normal oral functions. The differences among the influences of the three conditions on the enzymatic activities were not statistically significant.

CONCLUSIONS

High-molecular-weight hyaluronic acids at low concentration and low-molecular-weight ones at high concentration showed viscosity values similar to those of human whole saliva. Inhibitory effects of hyaluronic acids on lysozyme and peroxidase activities were more significant with high-molecular-weight ones on the surface and in saliva compared with in solution and on purified enzymes.

Mucins as multifunctional building blocks of biomaterials

Mucins glycoproteins are emerging as a multifunctional building block for biomaterials with diverse applications in chemistry and biomedicine.

Artificial Salivas: Present and Future

Modern technology has allowed us to understand better the functions of saliva and now provides a rationale for developing: (1) diagnostic reagents for monitoring oral and systemic health status and (2) replacement therapies for individuals with salivary dysfunctions. Several areas of dental research are directed at augmenting or enhancing both the quality and quantity of saliva for individuals with dry mouth. An “intrinsic” approach is being explored which utilizes medications such as pilocarpine and bromhexine to stimulate the salivary glands to produce more saliva. An “extrinsic” approach proposes to use topically applied artificial saliva. Studies in our laboratory have been directed toward developing artificial salivas which incorporate many of the protective features of “native” saliva. An ideal artificial saliva should be “long-lasting”, provide lubrication, inhibit colonization of microflora responsible for dental caries and gingivitis, and coat the oral soft tissues for protection against environmental insult and desiccation. Studies are currently under way to determine the structural requirements of salivary molecules responsible for these protective functions. Composite salivary molecules consisting of multiple biologically active or “functional domains” could then be designed and synthesized based upon primary sequence and conformational analyses, computer-assisted structural predictions, and in vitro testing. These supcrsalivary substances could then be used as saliva substitutes for targeting to selected oral surfaces to promote mineralization, hydration, and/or regulate microbial-mediated disease.

Biopolymeric Mucin and Synthetic Polymer Analogs: Their Structure, Function and Role in Biomedical Applications

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of biofunctional molecules (e.g., biogenic molecules, probes, nanoparticles), and its effect on bioavailability are well described in the literature. An alternate perspective is provided in this paper, presenting mucin’s complex network structure, and its interdependent functional characteristics in human physiology. We highlight the recent advances that were achieved through the use of mucin in diverse areas of bioengineering applications (e.g., drug delivery, biomedical devices and tissue engineering). Mucin network formation is a highly complex process, driven by wide variety of molecular interactions, and the network possess structural and chemical variations, posing a great challenge to understand mucin’s bulk behavior. Through this review, the prospective potential of polymer based analogs to serve as mucin mimic is suggested. These analog systems, apart from functioning as an artificial model, reducing the current dependency on animal models, can aid in furthering our fundamental understanding of such complex structures.

Cost-effectiveness landscape analysis of treatments addressing xerostomia in patients receiving head and neck radiation therapy

Head and neck (H&N) radiation therapy (RT) can induce irreversible damage to the salivary glands thereby causing long-term xerostomia or dry mouth in 68%-85% of the patients. Not only does xerostomia significantly impair patients' quality-of-life (QOL) but it also has important medical sequelae, incurring high medical and dental costs. In this article, we review various measures to assess xerostomia and evaluate current and emerging solutions to address this condition in H&N cancer patients. These solutions typically seek to accomplish 1 of the 4 objectives: (1) to protect the salivary glands during RT, (2) to stimulate the remaining gland function, (3) to treat the symptoms of xerostomia, or (4) to regenerate the salivary glands. For each treatment, we assess its mechanisms of action, efficacy, safety, clinical utilization, and cost. We conclude that intensity-modulated radiation therapy is both the most widely used prevention approach and the most cost-effective existing solution and we highlight novel and promising techniques on the cost-effectiveness landscape.

The oral cavity as a biological barrier system: design of an advanced buccal in vitro permeability model

An important area for future research lies in finding a drug delivery system across or into the oral mucosa. However, to design such systems, simplified biological models are necessary so that the mechanisms and/or interactions of interest can readily be studied. The oral epithelium is covered by a complex mucus layer, which enables exchange of nutrients and provides lubrication. However, it has been demonstrated that mucus has an impact on the mobility of nanoparticles and drug molecules. Thus, we aimed to develop an advanced buccal in vitro model for studying transport of nanoparticles, taking the mucus layer into account. First, animal mucins (porcine gastric, bovine submaxillary) were compared with natural human mucin regarding chemical and morphological structure. Second, an "external" mucus layer was prepared by a film method and deposited onto an oral cell line (TR 146), cultured on transwells®. Adherence of the mucin fibers was evaluated and the viability of the model was assessed. Nanoparticle transport studies were performed with this advanced in vitro model and an ex vivo diffusion system. The results revealed that porcine mucin is most similar to human natural mucin in chemical structure and morphology. Both the bovine and porcine mucin fibers adhered onto the oral cells: Due to the different morphology of bovine mucin, the viability of the oral cells decreased, whereas porcine mucin maintained the viability of the model for more than 48 h. Comparison of in vitro data with ex vivo data suggested reliability of the advanced buccal in vitro model. Additionally, it was demonstrated that the mucus layer in the oral cavity also acts as a strong barrier for the mobility of nanoparticles.

Design of a randomized controlled double-blind crossover clinical trial to assess the effects of saliva substitutes on bovine enamel and dentin in situ

Background

Hyposalivation is caused by various syndromes, diabetes, drugs, inflammation, infection, or radiotherapy of the salivary glands. Patients with hyposalivation often show an increased caries incidence. Moreover, hyposalivation is frequently accompanied by oral discomfort and impaired oral functions, and saliva substitutes are widely used to alleviate oral symptoms. However, preference of saliva substitutes due to taste, handling, and relief of oral symptoms has been discussed controversially. Some of the marketed products have shown demineralizing effects on dental hard tissues in vitro. This demineralizing potential is attributed to the undersaturation with respect to calcium phosphates. Therefore, it is important to modify the mineralizing potential of saliva substitutes to prevent carious lesions. Thus, the aim of the present study was to evaluate the effects of a possible remineralizing saliva substitute (SN; modified Saliva natura) compared to a demineralizing one (G; Glandosane) on mineral parameters of sound bovine dentin and enamel as well as on artificially demineralized enamel specimens in situ. Moreover, oral well-being after use of each saliva substitute was recorded.

Methods/Design

Using a randomized, double-blind, crossover, phase II/III in situ trial, volunteers with hyposalivation utilize removable dentures containing bovine specimens during the experimental period. The volunteers are divided into two groups, and are required to apply both saliva substitutes for seven weeks each. After both test periods, differences in mineral loss and lesion depth between values before and after exposure are evaluated based on microradiographs. The oral well-being of the volunteers before and after therapy is determined using questionnaires. With respect to the microradiographic analysis, equal mineral losses and lesion depths of enamel and dentin specimens during treatment with SN and G, and no differences in patients' experienced oral comfort after SN compared to G usage are expected (H₀).

Discussion

Up to now, 14 patients have been included in the study, and no reasons for early termination of the trial have been identified. The design seems suitable for determining the effects of saliva substitutes on dental hard tissues in situ, and should provide detailed information on the oral well-being after use of different saliva substitutes in patients with hyposalivation.

Trial registration

ClinicalTrials.gov ID. NCT01165970

Clinical management of salivary gland hypofunction and xerostomia in head-and-neck cancer patients: successes and barriers

The most significant long-term complication of radiotherapy in the head-and-neck region is hyposalivation and its related complaints, particularily xerostomia. This review addresses the pathophysiology underlying irradiation damage to salivary gland tissue, the consequences of radiation injury, and issues contributing to the clinical management of salivary gland hypofunction and xerostomia. These include ways to (1) prevent or minimize radiation injury of salivary gland tissue, (2) manage radiation-induced hyposalivation and xerostomia, and (3) restore the function of salivary gland tissue damaged by radiotherapy.

A systematic review of salivary gland hypofunction and xerostomia induced by cancer therapies: management strategies and economic impact

PURPOSE

This systematic review aimed to assess the literature for management strategies and economic impact of salivary gland hypofunction and xerostomia induced by cancer therapies and to determine the quality of evidence-based management recommendations.

METHODS

The electronic databases of MEDLINE/PubMed and EMBASE were searched for articles published in English since the 1989 NIH Development Consensus Conference on the Oral Complications of Cancer Therapies until 2008 inclusive. For each article, two independent reviewers extracted information regarding study design, study population, interventions, outcome measures, results, and conclusions.

RESULTS

Seventy-two interventional studies met the inclusion criteria. In addition, 49 intensity-modulated radiation therapy (IMRT) studies were included as a management strategy aiming for less salivary gland damage. Management guideline recommendations were drawn up for IMRT, amifostine, muscarinic agonist stimulation, oral mucosal lubricants, acupuncture, and submandibular gland transfer.

CONCLUSIONS

There is evidence that salivary gland hypofunction and xerostomia induced by cancer therapies can be prevented or symptoms be minimized to some degree, depending on the type of cancer treatment. Management guideline recommendations are provided for IMRT, amifostine, muscarinic agonist stimulation, oral mucosal lubricants, acupuncture, and submandibular gland transfer. Fields of sparse literature identified included effects of gustatory and masticatory stimulation, specific oral mucosal lubricant formulas, submandibular gland transfer, acupuncture, hyperbaric oxygen treatment, management strategies in pediatric cancer populations, and the economic consequences of salivary gland hypofunction and xerostomia.

Saliva substitutes for the treatment of radiation-induced xerostomia--a review

GOAL

The aim of this review is to summarize the in vitro and in vivo evidence on the performance of contemporary saliva substitutes in the treatment of xerostomia and hyposalivation caused by radiation therapy for head and neck malignancies.

METHODS

A literature search was conducted during July to September 2008 in PubMed, using the query terms "saliva substitute", "saliva substitute and xerostomia", "artificial saliva", and "artificial saliva and xerostomia"; for clinical studies, only studies in patients suffering from radiation-induced xerostomia have been included in the review.

RESULTS AND CONCLUSION

Fifty-two studies met the inclusion criteria and were allotted either to the in vitro topics "viscosity", "lubrication", "wetting properties", "antimicrobial effects", and "enamel and dentin de- and remineralization", or to the in vivo topics "clinical acceptance" or "influence on plaque formation and oral mucosa and microflora". The findings suggest that there are significant differences in the performance of various saliva substitutes concerning the review parameters, yet indicate that further in vitro and in vivo studies on the properties of saliva substitutes are necessary.

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.

Influences of animal mucins on lysozyme activity in solution and on hydroxyapatite surfaces

The purpose of this study was to investigate the influence of animal mucins on lysozyme activity in solution and on the surface of hydroxyapatite (HA) beads. The effects of animal mucins on lysozyme activity in solution were examined by incubating porcine gastric mucin (PGM) or bovine submaxillary mucin (BSM) with hen egg-white lysozyme (HEWL) or salivary samples. HA-immobilised animal mucins or lysozyme were used to determine the influence of animal mucins on lysozyme activity on HA surfaces. Lysozyme activity was determined by turbidity measurement of a Micrococcus lysodeikticus substrate suspension. Protein concentration was determined by ninhydrin assay. PGM inhibited the activity of HEWL and salivary lysozyme in solution. The amount of inhibition was dependent on mucin concentration, incubation time and temperature, and the structural integrity of the mucin. The inhibition of salivary lysozyme activity by PGM was greater in submandibular/sublingual saliva than in parotid saliva. The inhibition of lysozyme activity by PGM was markedly dependent on pH. However, BSM did not inhibit the in-solution lysozyme activities of HEWL and clarified saliva. Both PGM and BSM bound to HA surfaces, and HA-adsorbed animal mucins increased the subsequent adsorption of lysozyme. When HA beads were exposed to a mixture of HEWL and PGM or BSM, lysozyme activity on the HA surfaces was significantly increased. The results suggest that animal mucins affect lysozyme activity, and the effects are different on HA surfaces compared with in solution. Further research is needed to determine the effect of animal mucins on lysozyme activity in vivo.

Radiation-related damage to dentition

Because of typical tissue reactions to ionising radiation, radiotherapy in the head and neck region usually results in complex oral complications affecting the salivary glands, oral mucosa, bone, masticatory musculature, and dentition. When the oral cavity and salivary glands are exposed to high doses of radiation, clinical consequences including hyposalivation, mucositis, taste loss, trismus, and osteoradionecrosis should be regarded as the most common side-effects. Mucositis and taste loss are reversible consequences, usually subsiding early post-irradiation, whereas hyposalivation is commonly irreversible. Additionally, the risk of rampant tooth decay with its sudden onset and osteonecrosis is a lifelong threat. Thus, early, active participation of the dental profession in the development of preventive and therapeutic strategies, and in the education and rehabilitation of patients is paramount in consideration of quality-of-life issues during and after radiotherapy. This Review focuses on the multifactorial causes of so-called radiation caries and presents possible treatment strategies to avoid loss of dentition.

Prevention and treatment of the consequences of head and neck radiotherapy

The location of the primary tumor or lymph node metastases dictates the inclusion of the oral cavity, salivary glands, and jaws in the radiation treatment portals for patients who have head and neck cancer. The clinical sequelae of the radiation treatment include mucositis, hyposalivation, loss of taste, osteoradionecrosis, radiation caries, and trismus. These sequelae may be dose-limiting and have a tremendous effect on the patient's quality of life. Most treatment protocols to prevent these sequelae are still based on clinical experience, but alternatives based on fundamental basic and clinical research are becoming more and more available. Many of these alternatives either need further study before they can be incorporated into the protocols commonly used to prevent and treat the radiation-related oral sequelae or await implementation of these protocols. In this review, the various possibilities for prevention and/or treatment of radiation-induced changes in healthy oral tissues and their consequences are discussed.

Role of saliva in the maintenance of taste sensitivity

Saliva is the principal fluid component of the external environment of the taste receptor cells and, as such, could play a role in taste sensitivity. Its main role includes transport of taste substances to and protection of the taste receptor. In the initial process of taste perception, saliva acts as a solvent for taste substances; salivary water dissolves taste substances, and the latter diffuse to the taste receptor sites. During this process, some salivary constituents chemically interact with taste substances. For example, salivary buffers (e.g., bicarbonate ions) decrease the concentration of free hydrogen ions (sour taste), and there are some salivary proteins which may bind with bitter taste substances. Another effect of saliva on taste transduction is that some salivary constituents can continuously stimulate the taste receptor, resulting in an alteration of taste sensitivity. For example, the taste detection threshold for NaCl is slightly above the salivary sodium concentrations with which the taste receptor is continuously stimulated. In contrast, saliva protects the taste receptor from damage brought about by dryness and bacterial infection, and from disuse atrophy via a decrease in transport of taste stimuli to the receptor sites. This is a long-term effect of saliva that may be related to taste disorders. These various effects of saliva on the taste perception differ depending on the anatomical relationship between the taste buds and oral openings of the ducts of the salivary glands. Many taste buds are localized in the trenches of the foliate and circumvallate papillae, where the lingual minor salivary glands (von Ebner's glands) secrete saliva. Taste buds situated at the surface of the anterior part of the tongue and soft palate are bathed with the mixed saliva secreted mainly by the three major salivary glands.

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.

Oral care for patients with cancer: a review of the literature

Mouth care is an integral part of nursing practice. However, it has become a ritualistic and banal activity, a topic of conflicting advice and subjective conclusions from sporadic research. Rarely do experts teach it, and it frequently is delegated to the most junior members of the nursing staff. Many cancer treatments result in unavoidable oral toxicity, and the significant prevalence of oral complications in oncology makes mouth care a particular priority for cancer nurses. The confusion and conflict that surrounds best nursing practice in relation to delivering appropriate mouth care should be redressed. This review article details pertinent research to date regarding oral care, with an aim to clarify intervention options, and to identify and promote best nursing practice.

The efficacy of Xialine in patients with xerostomia resulting from radiotherapy for head and neck cancer: a pilot-study

Changes in subjective sensations due to xerostomia before and after administration of Xialine, a xanthan gum-based saliva substitute, were evaluated in 30 patients with radiation-induced xerostomia using the QLQ-H&N35. Xerostomia in general decreased with both Xialine and placebo to almost the same degree. A trend was seen for Xialine to improve problems with speech and senses.

A comparison of artificial saliva and pilocarpine in the management of xerostomia in patients with advanced cancer

This was a crossover study comparing a mucin-based artificial saliva (Saliva Orthana) and pilocarpine hydrochloride (Salagen) in the management of xerostomia in patients with advanced cancer. The pilocarpine was found to be more effective than the artificial saliva in terms of mean change in visual analogue scale scores for xerostomia (P = 0.003). Furthermore, more patients reported that it had helped their xerostomia, and more patients wanted to continue with it after the study. However, the pilocarpine was found to be associated with more side-effects than the artificial saliva (P < 0.001). These side-effects were usually reported as being mild. Of the patients who used both treatments, 50% preferred the artificial saliva, and 50% preferred the pilocarpine. The commonest reason for preferring the artificial saliva was the fact that it was a spray, rather than a tablet.

Role of submandibular and sublingual saliva in maintenance of taste sensitivity recorded in the chorda tympani of rats

1. To evaluate the role of saliva in the maintenance of taste sensitivity, the activities in the rat chorda tympani innervating taste buds in the anterior part of the tongue were analysed. The effects of chronic extirpation of the submandibular and sublingual salivary glands were tested and compared with results after chronic oral administration of artificial saliva. 2. Removal of the salivary glands sharply decreased chorda tympani responses to four different taste stimuli by 7 days post-desalivation, while a stable response to cold water was observed by at least 28 days. 3. This selective decrease in taste responses was considerably recovered by 7-day-oral injection of artificial saliva (containing NaHCO3, KCl and/or mucin) or distilled water. However, the injection of the salt-containing artificial saliva induced significantly larger sucrose and smaller NaCl, HCl and quinine responses than did the injection of distilled water. 4. In our salivary manipulations, an alteration in the number of the functional sweet receptors was suggested by the cross-adaptation technique using NaHCO3, whereas sensitivity to the epithelial sodium transport blocker, amiloride, was stable in the NaCl response. 5. Salivary water and electrolytes which may participate in forming the external environment of the taste receptor cells modulated taste sensitivity in the chorda tympani.

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.

Evaluation of in vitro properties of films of saliva substitutes in contact with different surfaces. A comparative study with instruments for measurements of friction and rheologic properties

An instrument based on friction measurement has been developed to evaluate oral mucosal dryness objectively. The purpose of this study was to compare the friction instrument with instruments measuring in vitro rheologic properties. Measurements were performed against steel and irreversible hydrocolloid after application of different concentrations of aqueous solutions of carboxymethylcellulose and chitosan lactate. The results of the measurements were logical, with inversely proportional values for the friction instrument as compared with values obtained using the instrument measuring rheologic properties; that is, increased viscosity led to decreased friction values.

Protocol for the prevention and treatment of oral sequelae resulting from head and neck radiation therapy

In addition to the desired antitumor effects, head and neck radiation therapy induces damage in normal tissues that may result in oral sequelae such as mucositis, hyposalivation, radiation caries, taste loss, trismus, soft-tissue necrosis, and osteoradionecrosis. These sequelae may be dose-limiting and have a tremendous effect on the patient's quality of life. Current policies to prevent these sequelae primarily are based on clinical experience and show great diversity. A protocol for the prevention and treatment of oral sequelae resulting from head and neck radiation therapy, based on fundamental research and data derived from the literature, is presented. The protocol is particularly applicable in centers with a dental team. This team should be involved at the time of initial diagnosis so that a successful preventive regimen is an integral part of the overall cancer treatment regimen.

The condition of the oral mucosa in institutionalized elderly patients before and after using a mucin-containing saliva substitute

The purpose of this investigation was to evaluate whether the condition of the oral mucous membrane and the mouth comfort of the elderly could improve using a mucin-containing saliva substitute. In total, 52 patients were examined before and after a 60-day treatment period, with mucin-containing saliva substitute given three times a day before meals. The patients were examined with regard to weight, oral mucosa condition, the duration of meals, eating and swallowing. Before the treatment period the prevalence of stomatitis was 90.4% and oral candidosis was 80.8% compared to 15.4% and 5.8% respectively after the treatment period. The pH increased significantly. Artificial mucin-containing saliva substitute seems to be an adequate treatment of stomatitis and oral candidosis in elderly patients.

A clinical comparative trial of saliva substitutes in radiation-induced salivary gland hypofunction

Use of saliva substitutes may become necessary to manage xerostomia when no means of stimulating saliva production is effective. Few clinical trials have compared products that may act as salivary substitutes. Patients' preference of products depended on effect duration, lubrication, taste, delivery system, and cost. Many patients did not continue with the use of the products studied, and instead chose to rely on frequent use of water. Clinical trials of the products are recommended before prescription to indicate what may be the best choice for the individual patients.

Increased mucin levels in submandibular saliva from mice following repeated isoproterenol treatment

Mucin decreases with age in the submandibular glands of mice and can be restored by chronic administration of isoproterenol. Mice were given repeated injections of isoproterenol to determine if the increase of mucin in the submandibular gland leads to elevated levels of mucin in the submandibular saliva. Mucin was significantly elevated in both the gland and the saliva after isoproterenol. Gland contents of mucin and the concentration of mucin in their salivas were positively correlated for both the isoproterenol (p = 0.01) and the control group (p less than 0.01).

Objective and subjective efficacy of saliva substitutes containing mucin and carboxymethylcellulose

The lubrication properties of mucin and carboxymethylcellulose (CMC)-containing saliva substitutes and water were evaluated in a double-blind trial. After mouthrinsing with the substitutes, the patients answered a questionnaire (subjective effect) and the change of oral mucosal friction was measured with a probe (objective effect). Mucin and CMC-containing saliva substitutes showed almost the same objective effects, with changed friction values of about 15 min, which was more than twice as long as for water. Both water and the two saliva substitutes relieved the symptoms of dry mouth to some extent but they did not have a sufficiently long-lasting effect.

pH measurements with an ion sensitive field effect transistor in the mouth of patients with xerostomia

A transistor pH electrode (ion sensitive field effect transistor), placed in the upper dentures of eleven xerostomia patients and five healthy volunteers, was used to register pH changes in five-, six- and seven-day-old dental plaque. A mouth rinse with a 10% sucrose solution caused a pH fall of about three decades. A significant difference in duration of critical plaque pH was observed: in xerostomia patients, a 10% longer period of pH less than 5.7 was registered during 60 min following a sucrose rinse. Normal oral functions were not influenced by the denture with an integrated electrode. This method is usable for plaque pH registration in xerostomia patients.

Evaluation of some electrical methods for objective assessment of oral mucosal dryness

The aim of this study was to evaluate different electrical methods (resistance, capacitance and polarization resistance) for clinical and objective registration of dryness of the oral mucosa. Measurements were performed in the buccal and in the lip mucosa before and every 30 min after injection of 1.0 ml methylscopolamine nitrate submucosally in the labial sulcus in 10 healthy subjects. For comparison, a dental mirror sliding test was used. About 1 h after injection, all three methods showed statistically significant decreases of values in the buccal as well as the lip mucosa except for polarization resistance, which showed such a difference only in the buccal mucosa. The deviations from initial values in the individual subject showed no agreement between measurements with the electrical instruments and oral mucosal dryness assessed with the mirror test. Neither was there any agreement between values registered with the three electrical methods. It seems that these electrical methods are not suitable for registration of individual variations in oral mucosal dryness.

Analysis of mucin as raw material and in a saliva substitute by isotachophoresis

An isotachophoretic method is presented for the analysis of the glycoprotein mucin as raw material. The assay is also used for the mucin assay in the saliva substitute Saliva Orthana.