Effect of traction direction and pressure load on the palatal plate on retentive force.

BACKGROUND: Recently, a denture adhesive that is easy to clean and contain moisturizing ingredients have been developed for patients with dry mouth. Although the retentive force produced by conventional denture adhesives and oral moisturizers have been compared on models, no study has reported their comparison in the oral cavity. In this study, we aimed to clarify the effects of different directions of traction and loads at the time of pressure contact on the retentive force on a palatal plate made from a dentulous jaw model. METHODS: A palatal plate was fabricated with thermoplastic resin on a dentulous jaw model, and a loop-shaped traction device was attached to the centre of the palate. The test samples were a cream-type denture adhesive, a denture adhesive for dry mouth, an oral moisturizer, and a denture moisturizer. The specimens were applied to the inner surface of the plate, which was then mounted under vertical pressure. Then, the retentive force was measured, using a digital force gauge, while the plate was pulled in different directions and with different loads. RESULTS: No significant difference in retentive force was observed in any of the test samples when the direction of traction was between 45° and 60°. The retentive force of the denture adhesive for dry mouth was significantly higher with a direction of traction of 90° than that of 45° or 60°. The retentive force when oral moisturizer was used was significantly higher in the 90° traction direction than in the 45° direction. There was no significant difference between a force of 4.0 kgf or 5.5 kgf when using a denture adhesive for dry mouth. Comparing the four load size conditions, the larger the load, the higher was the retentive force. Similar results were obtained for the cream-type denture adhesive and denture moisturizer. Significantly higher retentive force was observed for larger loads when oral moisturizer was used. CONCLUSIONS: The results suggest that the direction of traction and the pressure load affect the retentive force on a palatal plate.

Changes in denture retention with denture adhesives and oral moisturizers for the oral cavity: an in vitro study.

BACKGROUND: It is difficult to maintain complete dentures during meals in place. This in vitro study aimed to assess changes in denture retention between rest and function using denture adhesives and oral moisturizers in an oral cavity model. METHODS: The following test samples were applied between the palatal plate and the edentulous jaw ridge model: denture adhesive, denture adhesive for dry mouth, oral moisturizer, and denture moisturizer. The retentive force was measured under two conditions: at rest while immersed in water and during function with a 2.5-kg load applied. The plate was pulled perpendicular to the occlusal plane and the retentive force was measured using a digital force gauge. RESULTS: Under dry conditions, denture adhesive for dry mouth and oral moisturizer had a significantly higher retentive force than denture adhesive and denture moisturizer. After 30 min of immersion in water, the retentive force of the denture adhesive increased while that of the oral moisturizer decreased. After 30 min of function, the retentive force of the denture adhesive and denture adhesive for dry mouth remained high, while that of the oral moisturizer and denture moisturizer significantly decreased. Between rest and function, the retentive force of the denture adhesive and denture adhesive for dry mouth was high, and that of the oral moisturizer was low. CONCLUSIONS: Immediately after use, denture adhesive for dry mouth exhibited high retentive force, but retention gradually decreased due to its water content.