The Lubricating Properties of Human Whole Saliva

We demonstrate the efficient boundary lubricating properties of human whole saliva (HWS) in a soft hydrophobic rubbing contact, consisting of a poly(dimethylsiloxane) (PDMS) ball and a PDMS disk. The influence of applied load, entrainment speed and surface roughness was investigated for mechanically stimulated HWS. Lubrication by HWS results in a boundary friction coefficient of μ ≈ 0.02, two orders of magnitude lower than that obtained for water. Dried saliva on the other hand results in μ ≈ 2–3, illustrating the importance of hydration for efficient salivary lubrication. Increasing the surface roughness increases the friction coefficient for HWS, while it decreases that for water. The boundary lubricating properties of HWS are less sensitive to saliva treatment than are its bulk viscoelastic properties. Centrifugation and ageing of HWS almost completely removes the shear thinning and elastic nature observed for fresh HWS. In contrast, the boundary friction coefficients are hardly affected, which indicates that the high-Mw (supra-)molecular structures in saliva, which are expected to be responsible for its rheology, are not responsible for its boundary lubricating properties. The saliva-coated PDMS surfaces form an ideal model system for ex-vivo investigations into oral lubrication and how the lubricating properties of saliva are influenced by other components like food, beverages, oral care products and pharmaceuticals.

[1]  R. Kusy,et al.  Resistance to sliding of orthodontic appliances in the dry and wet states: influence of archwire alloy, interbracket distance, and bracket engagement. , 2000, Journal of biomedical materials research.

[2]  G. V. Aken,et al.  Lubrication of oral surfaces by food emulsions: the importance of surface characteristics , 2006 .

[3]  Bradley S. Turner,et al.  Viscous fingering of HCI through gastric mucin , 1992, Nature.

[4]  H. Weenen.  Effects of structure breakdown on creaminess in semisolid foods , 2006 .

[5]  H. Olsson,et al.  A new device for measuring oral mucosal surface friction--reference values. , 1991, Scandinavian journal of dental research.

[6]  M. Levine,et al.  Lubrication and viscosity features of human saliva and commercially available saliva substitutes. , 1987, Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons.

[7]  M. Levine,et al.  Lubrication of saliva substitutes at enamel-to-enamel contacts in an artificial mouth. , 1996, The Journal of prosthetic dentistry.

[8]  Stefano Mischler,et al.  Effect of surface structure on frictional behaviour of a tongue/palate tribological system , 2006 .

[9]  M. Dickinson,et al.  Nanomechanics and morphology of salivary pellicle , 2006 .

[10]  Jason R. Stokes,et al.  Soft-tribology : Lubrication in a compliant PDMS-PDMS contact , 2007 .

[11]  A. Pedersen,et al.  Saliva and gastrointestinal functions of taste, mastication, swallowing and digestion. , 2002, Oral diseases.

[12]  Zhou Zhongrong,et al.  On the friction and wear behaviour of human tooth enamel and dentin , 2003 .

[13]  W. Schwarz.  The Rheology of Saliva , 1987, Journal of dental research.

[14]  G. Carpenter,et al.  The function of salivary proteins and the regulation of their secretion by salivary glands , 1998 .

[15]  A. Noble.  Astringency and Bitterness of Flavonoid Phenols , 2002 .

[16]  S. Challacombe,et al.  Patient preferences in a preliminary study comparing an intra-oral lubricating device with the usual dry mouth lubricating methods , 2002, British Dental Journal.

[17]  Caldwell,et al.  Mucin Adsorption to Hydrophobic Surfaces. , 2000, Journal of colloid and interface science.

[18]  T. Arnebrant,et al.  An in vitro study of initial adsorption from human parotid and submandibular/sublingual resting saliva at solid/liquid interfaces , 2001 .

[19]  K. Siebert,et al.  An alternate mechanism for the astringent sensation of acids , 2004 .

[20]  R. Wijk,et al.  The role of friction in perceived oral texture , 2005 .

[21]  T. Arnebrant,et al.  Adsorption of MUC5B and the role of mucins in early salivary film formation , 2002 .

[22]  M. Levine.  Salivary Macromolecules , 1993, Annals of the New York Academy of Sciences.

[23]  H. Olsson,et al.  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. , 1995, Acta odontologica Scandinavica.

[24]  T. Arnebrant,et al.  The effect of ionic surfactants on salivary proteins adsorbed on silica surfaces. , 1991, Acta odontologica Scandinavica.

[25]  H. Olsson,et al.  The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. , 1991, Acta odontologica Scandinavica.

[26]  Ronald L. Davis,et al.  A Drosophila nonvisual arrestin is required for the maintenance of olfactory sensitivity. , 2006, Chemical senses.

[27]  J. Israelachvili,et al.  Thin Film Rheology and Tribology of Chocolate , 1997 .

[28]  I. Lakatos,et al.  Colloids Surfaces A: Physicochem , 1998 .

[29]  H. Olsson,et al.  Objective and subjective efficacy of saliva substitutes containing mucin and carboxymethylcellulose. , 1991, Scandinavian journal of dental research.

[30]  P. A. Raj,et al.  Statherin: a major boundary lubricant of human saliva. , 1991, Biochemical and biophysical research communications.

[31]  Jean-Xavier Guinard,et al.  Relation Between Parotid Saliva Flow and Composition and the Perception of Gustatory and Trigeminal Stimuli in Foods , 1997, Physiology & Behavior.

[32]  R. Wijk,et al.  MECHANISMS UNDERLYING THE ROLE OF FRICTION IN ORAL TEXTURE , 2006 .

[33]  Lei Shi,et al.  Biomimetic Surfaces of Biomaterials Using Mucin-Type Glycoproteins , 2000 .

[34]  Zhongrong Zhou,et al.  Friction and wear behavior of dental feldspathic porcelain , 2006 .

[35]  Hao Li,et al.  Wear behaviour of human teeth in dry and artificial saliva conditions , 2001 .

[36]  R. Wijk,et al.  Explaining perceived oral texture of starch-based custard desserts from standard and novel instrumental tests , 2006 .

[37]  P. Brockhurst,et al.  The dynamnic frictional resistance between orthodontic brackets and arch wires. , 1994, American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics.

[38]  T. Arnebrant,et al.  Intraoral Lubrication of PRP-1, Statherin and Mucin as Studied by AFM , 2004, Biofouling.

[39]  T. Arnebrant,et al.  On the Adsorption of Human Acidic Proline-rich Proteins (PRP-1 and PRP-3) and Statherin at Solid/liquid Interfaces , 2002 .

[40]  Mark W Rutland,et al.  Lubricating Properties of the Initial Salivary Pellicle — an AFM Study , 2003, Biofouling.

[41]  F. P. Bowden,et al.  The Friction and Lubrication of Solids , 1964 .

[42]  L. Tabak.  In defense of the oral cavity: structure, biosynthesis, and function of salivary mucins. , 1995, Annual review of physiology.

[43]  R P Kusy,et al.  Comparison of the frictional coefficients for selected archwire-bracket slot combinations in the dry and wet states. , 2009, The Angle orthodontist.

[44]  I. Norton,et al.  Oral behaviour of food hydrocolloids and emulsions. Part 1. Lubrication and deposition considerations , 2003 .

[45]  A. Soto-Rojas,et al.  The oral side of Sjögren syndrome. Diagnosis and treatment. A review. , 2002, Archives of medical research.

[46]  Seunghwan Lee,et al.  Porcine gastric mucin (PGM) at the water/poly(dimethylsiloxane) (PDMS) interface: influence of pH and ionic strength on its conformation, adsorption, and aqueous lubrication properties. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[47]  T. Axéll,et al.  Oral mucosal friction and subjective perception of dry mouth in relation to salivary secretion. , 1993, Scandinavian journal of dental research.

[48]  R. Wijk,et al.  Load dependency of the coefficient of friction of oral mucosa , 2007 .

[49]  P. Humbert,et al.  Friction coefficient and wettability of oral mucosal tissue: Changes induced by a salivary layer , 2006 .

[50]  L. Tabak,et al.  Artificial Salivas: Present and Future , 1987, Journal of dental research.

[51]  M. Malmsten,et al.  Mucin layers on hydrophobic surfaces studied with ellipsometry and surface force measurements , 1992 .

[52]  L. Tabak,et al.  Structural Aspects of Salivary Glycoproteins , 1987, Journal of dental research.

[53]  J. Vicente,et al.  Lubrication properties of non-adsorbing polymer solutions in soft elastohydrodynamic (EHD) contacts , 2005 .

[54]  R. Kusy,et al.  Effect of salivary viscosity on frictional coefficients of orthodontic archwire/bracket couples , 1995 .

[55]  C. Dawes,et al.  How Much Saliva Is Enough for Avoidance of Xerostomia? , 2004, Caries Research.