Metabolic processes inside dental biofilms are likely to be influenced
by the velocity of the thin saliva film in contact with the biofilm.
In addition, in situ-grown biofilms are likely to behave
differently than in vitro biofilms. However, there is a lack of commercially
available flow-cells able to incorporate in situ samples
and adjust the saliva film to a match the oral cavity. Therefore, the
aim of this study was to design and 3D-print such a microfluidic
flow-cell. As a proof of concept, we studied pH developments
inside three 96 h biofilms under a stimulated saliva flow. The
microscope compatible flow-cell consists of an incoming port, outcoming port and a central bottomless impression for the in situ
sample. Sealing the flow-cell to a coverslip forms a bottom to the
flow-cell and creates a defined flow-space between the in situ sample
and the coverslip. The participant grew the in situ biofilms on
custom-made glass slabs fitted into a removable splint. The splint
was worn the entire time except during meals, and was immersed
in 10 % sucrose three times a day. Unsterile stimulated saliva and
4 % sucrose were used as flow medium, and the pH was analyzed
using the ratiometric dye C-SNARF-4. The results of this pilot
study showed that after 30 min of static conditions, pH ranged from
5.7 to 6.9, with differences both between fields of view (FOVs) and
between biofilms, confirming the presence of microenvironments.
After the onset of flow (5 mm/min), pH rose to neutral or
slightly alkaline values in all three biofilms. However, differences
between FOVs were still present. In conclusion, incorporating
flow is important when studying pH developments inside biofilms.