Factors Controlling the Formation of Salivary Films
Condition: Healthy
Study type: Observational

Summary: 
      The aim of this study is to determine how different ingredients which are found in food and
      other consumer products affect the ability of saliva to form surface films.

      Saliva forms a protective film on the surfaces inside the mouth. This film affects the way we
      consume and digest food and protects our teeth and other surfaces inside the mouth from
      disease and decay. It is not well known how this film forms, or which components in everyday
      life affect formation of the film, and therefore its protective properties.

      Samples of saliva will be collected from apparently healthy volunteers. The properties of the
      film (thickness, density, strength, protein composition) will be studied in the laboratory
      under controlled conditions. The effects of common ingredients in foods and other products
      such as proteins, emulsifiers, preservatives and surfactants on the formation and properties
      of the film will be determined.

      The results of this study will help us to understand how different ingredients can change the
      properties of saliva that may affect the way that we sense and digest food, and the ability
      of saliva to protect against decay and infection. This could, in the future lead to new ideas
      for developing:healthy foods (e.g. lower fat) that taste better, or more effective dental
      care products.
    

Detailed description: 
      The aim of this study is to determine the physical and biochemical mechanisms responsible for
      the formation and structure development (in vitro) of the salivary mucous film and the impact
      of common ingredients found in food or oral hygiene products.

      Saliva forms a film or pellicle on oral surfaces which serves as a protective barrier and
      lubricates the oral tissues during food consumption. However, it also provides the primary
      site for bacterial attachment and the build up of plaque. Therefore the physical and
      molecular structure of the salivary film is important for how we sense and taste food, how
      food is broken down in the mouth, and its effectiveness as a protective barrier. Much is
      known about the composition of saliva, but very little is known about the composition and
      structure of the salivary film or pellicle. We believe that the film formation and its
      physical properties, such as viscosity and strength are the result of complex interactions
      between different proteins within saliva, and with other components such as calcium and other
      salts, food components such as proteins and emulsifiers, and active compounds found in oral
      hygiene products such as preservatives and surfactants. This study will determine how the
      salivary film forms, its molecular composition and which other critical components affect its
      ability to form a stable, protective barrier. This knowledge will hopefully, in the future
      contribute to strategies to design healthier foods and more effective oral hygiene
      treatments.

      The physical properties of saliva are not stable as the proteins tend to aggregate following
      secretion, which affects the length of time the film formation can be studied (ex vivo).
      Therefore we need to use fresh human saliva samples collected from healthy volunteers using a
      defined protocol to ensure sample quality, and assess them within four hours of collection.
      Saliva will be collected (either whole mouth or parotid), taken to the laboratory and allowed
      to form films on model surfaces, representative of those found in the mouth. The rate of
      formation, strength, thickness and mass of the films will be studied using a range of
      physical methods. The protein content and composition will also be determined to identify the
      components responsible for various stages of film formation. Then, the influence of
      environmental conditions such as pH, calcium and salt will be determined. Finally, we will
      determine how the films interact with external components found in food and oral hygiene
      products such as proteins, emulsifiers, preservatives and surfactants. Although we are not
      studying the effects of dietary intervention on saliva properties, we want to determine the
      underlying mechanisms responsible for film formation and break down. Paired T-tests will be
      used to compare parotid with whole mouth saliva from the same volunteers. Two sample T-tests
      will be used for comparison of similar measurements on samples from different volunteers.
      Diagnostic checks on results will be performed to check whether transformations are required
      to meet normality assumptions.

      Two types of saliva samples will be collected: Whole Mouth Saliva (WMS) and Parotid Saliva
      (PS). The saliva will be stored at 4ºC (WMS may also be centrifuged at 2700xg for 20 minutes
      at 5°C to remove aggregates) and used within 4 hours of collection, as protein aggregation
      begins immediately after secretion, affecting the film formation properties, as determined in
      previous work. A range of physical techniques will be employed to determine the rate and
      extent of film formation, as well as the thickness, mass and rheological properties, under
      the different solution conditions and in the presence and absence of added ingredients as
      described above. Protein concentration and composition will also be determined. This will
      enable improved experimental design (e.g. normalising protein concentration) to improve the
      quality of the results. The results will be used to inform the design of further studies with
      other centres of expertise in order to understand the impact on in vivo behaviour of the
      salivary film and, for example the sensory perception of foods and the role of saliva on
      digestion of food structures.
    

Intervention name(s): Saliva sample collection
Intervention type(s): Other
Intervention description(s): Collection of either whole mouth saliva or parotid saliva. Whole mouth saliva is collected through stimulation by inert gum. Parotid saliva is collected by using a Lashley cup placed over the parotid duct and stimulated by a fruit sweet.
Other intervention name(s): Whole mouth saliva; Parotid saliva
Sampling method: Non-Probability Sample
Study population: 
        Apparently normal healthy volunteers from the local community able to donate saliva
        samples.
      
Keywords: saliva; food; sensory; oral health; film; pellicle