Discussion

1
78. Effect of brushing time and dentifrice dose
on orally retained fluoride in vivo JE
Creetha, DT Zerob, ML Bosmaa, A Butlera, RG
Guiberta, R Karwala, RJM Lyncha, M Northa, EA
Martinez-Mierb, C González-Cabezasb, SA
Kellyb a GlaxoSmithKline Consumer Healthcare,
St Georges Avenue, Weybridge, UK b Oral
Health Research Institute, Indiana University,
Indiana, USA.

• Overview
• This study shows that increasing brushing time
  and paste quantity increases the post-brushing
  reservoir of fluoride retained on the oral
  surfaces, indicating that these elements of
  brushing behaviour have the potential to
  influence the caries protection from fluoride.
• Introduction
• Creating a fluoride reservoir in the oral cavity
  (bound fluoride) is critical to its full
  caries-protective effect. Fluoride can promote
  remineralisation of early carious lesions in
  saliva, even at very low concentrations such as
  those found over the extended period after use of
  fluoridated dentifrices or mouthrinses1.
• To create an effective oral reservoir of
  fluoride post-brushing, brushing behaviour is
  important i.e. enough dentifrice must be used
  for enough time to deliver enough fluoride to the
  oral surfaces to exert an anticaries effect.
  Furthermore, this F- should not be removed by
  excessive rinsing after brushing. However, the
  effect of brushing time and paste quantity on
  fluoride concentration in saliva post-brushing
  has not been well-studied.
• The aim of this work was therefore to measure
• the effect of brushing time (30 seconds to 3
  minutes)
• the amount of dentifrice used (1.5 g or 0.5 g)
• on F- delivery to the oral cavity and
  post-brushing F- concentration in saliva.
• Data are presented on the effects of these
  behaviours on F- bound within the oral cavity
  after brushing, rather than merely dissolved in
  oral fluids, and include an exploratory analysis
  using a bi-phasic clearance model.
• Methods
• A randomized, single-centre, single-product,
  multi-use, six way crossover clinical study was
  performed involving 57 healthy subjects, aged
  25-65. The study measured F- delivery to the oral
  cavity and F- concentration in saliva over 2
  hours post-brushing, after different brushing
  regimens. This study also measured
  remineralisation of enamel in situ over the
  4-hour period post-brushing (results reported
  separately) so subjects wore an intra-oral
  appliance during the course of the experiment2.
• After a 2-day lead-in period on non-F-
  dentifrice, subjects brushed with an Aquafresh
  Flex soft, flat-trim toothbrush and Aquafresh
  Advanced dentifrice (1100 ppm F- as NaF). On
  separate occasions subjects brushed for 30, 45,
  60, 120 or 180 seconds with 1.5 g ( 0.05 g)
  dentifrice, or for 60 seconds with 0.5 g ( 0.05
  g) dentifrice.
• For each regime, subjects first brushed their
  occlusal tooth surfaces for 12 s to create a
  dentifrice slurry and then brushed their buccal
  tooth surfaces for the remainder of the time.
  For the 120 s and 180 s brushings only, subjects
  were allowed to expectorate within the brushing
  period. After brushing, subjects expectorated
  dentifrice slurry and then immediately rinsed
  with 10 mL of deionized water for 10 s.
  Unstimulated saliva samples were collected over 5
  min periods, starting at pre-brushing, 5 min ( 1
  min), 15 min ( 1 min), 30 min ( 1 min), 60 min
  ( 5 min) and 120 min ( 5 min) post-brushing.
  The concentration of fluoride was measured in all
  saliva samples, expectorate, rinse and toothbrush
  washings. Analysis of F- in saliva was conducted
  using a modification of the hexamethyldisiloxane
  (HMDS,) microdiffusion method3 as modified by
  Martinez-Mier et al.4
• The data were fitted to a bi-exponential
  equation, assuming two first-order F clearance
  processes, one rapid (unbound F), and one slow
  (bound F), in which bound F releases into
  unbound F5
• Fs A ? e-at B ? e-ßt (Eqn. 1)
• . where Fs is the concentration of F- in saliva
  at time t, and A and B represent the amount of F-
  initially bound (t0) in the rapid and slow
  clearance reservoirs respectively. The results
  were compared with a less-sophisticated estimate
  of bound F- achieved by summing areas of trapezia
  defined by the saliva clearance data between 30
  and 120 minutes post-brushing (AUC30-120min).

Figure 2. Effect of brushing time and dentifrice
quantity on AUC, calculated using the trapezium
method, between 30-120 min post-brushing (mean
s.e.)
Figure 3. Effect of brushing time and dentifrice
quantity on orally bound F-, (i.e. the B
parameter from the bi-exponential Eqn. 1)
Figure 1. Effect of brushing time and dentifrice
quantity on salivary F- concentration after
brushing (mean s.e.)