title: The use of lithium as a marker for the retention of liquids in the oral cavity after rinsing.
abstract: OBJECTIVE
  The aim of this study was to validate the use of lithium as a marker to indicate the retention of simple liquids in the oral cavity and use this to determine how much liquid is retained in the oral cavity following 30 s of rinsing.
  
  
  METHODS
  This is a validation study in which saliva was spiked with known concentrations of lithium. Twenty healthy participants then rinsed their mouths with either water or a 1 % w/v carboxymethylcellulose (CMC) solution for 30 s before expectorating into a collection cup. Total volume and concentration of lithium in the expectorant were then measured, and the percentage of liquid retained was calculated.
  
  
  RESULTS
  The mean amount of liquid retained was 10.4 ± 4.7 % following rinsing with water and 15.3 ± 4.1 % following rinsing with 1 % w/v CMC solution. This difference was significant (p < 0.01).
  
  
  CONCLUSIONS
  Lithium was useful as a marker for the retention of liquids in the oral cavity, and a value for the amount of water and 1 % w/v CMC solution remaining in the oral cavity following a 30-s rinse was established.
  
  
  CONCLUSIONS
  The present study quantifies the retention of simple fluids in the oral cavity, validating a technique that may be applied to more complex fluids such as mouth rinses. Further, the application of this method to specific population groups such as those with severe xerostomia may assist in developing effective saliva substitutes.
authors.affiliation: New Zealand's National School of Pharmacy, University of Otago, PO Box 56, Dunedin, 9054, New Zealand, sara.hanning@otago.ac.nz.
authors.forename: Sara M
authors.initials: SM
authors.lastname: Hanning
authors.forename: Jules A
authors.initials: JA
authors.lastname: Kieser
authors.forename: Martin M
authors.initials: MM
authors.lastname: Ferguson
authors.forename: Malcolm
authors.initials: M
authors.lastname: Reid
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Medlicott
mesh_terms: D006801:Humans; D018020:Lithium Compounds / Q000008:administration & dosage*; D009055:Mouth; D014867:Water
chemical_list: D018020:Lithium Compounds; D014867:Water