On the wettability of soft tissues in the human oral cavity

In this study, the wettability of gingival surfaces in the human oral cavity was assessed by the measurement of intra-oral water contact angles. Intra-oral water contacts angles were measured in the morning prior to tooth brushing, immediately after tooth brushing and prior to and after lunch in order to reveal the influences of toothpaste and dietary components on the wettability of the gingiva. Within a group of 10 volunteers, gingival surfaces were hydrophobic, with water contact angles ranging from 72 to 79°, which is high as compared with other soft tissues in the human body. Gingival contact angles were not affected by most commercial toothpastes involved in this study, but decreased slightly to 65° after brushing with a hexametaphosphate containing toothpaste. During the day, however, the hydrophobicity readily recovered and after lunch contact angles on the gingival surfaces were higher than early in the morning, now ranging from 76 to 83°. It is generally known that soft tissues in the human body involved in adsorptive and exchange functions and requiring lubrication are more hydrophilic than tissues with more protective functions. This study shows that gingival surfaces classify as the most hydrophobic soft tissue in the human body, attesting to their important protective role in the oral cavity.