Dentures feature clasps or crowns that grip natural teeth in the mouth, enabling the denture to function properly without dislodging. Complete dentures rely on atmospheric negative pressure and adhesive forces for retention. Specifically, the denture base forms a tight seal with the mucosa covering the alveolar ridge, creating a vacuum between them.Saliva between the baseplate and mucosa further creates adhesive force. The combined effects of atmospheric pressure and adhesive force constitute the retention of complete dentures.
This principle resembles overlapping two water-soaked glass plates: the vacuum and adhesive force formed between glass-water-glass cause the plates to adhere tightly, making separation difficult.According to physics principles, this atmospheric vacuum and adhesive force are proportional to the surface area of the glass plates. Therefore, a high and wide alveolar ridge has a larger surface area, generating greater atmospheric vacuum and adhesive force, resulting in better denture retention. Conversely, a low and flat alveolar ridge has a smaller surface area, producing weaker atmospheric vacuum and adhesive force, leading to poorer denture retention.It's no wonder some dentists are reluctant to treat such patients. However, the reality isn't entirely so. In clinical practice, it's common to observe that patients with favorable alveolar ridge conditions don't always experience good retention with their complete dentures, while patients with poor alveolar ridge conditions can sometimes achieve excellent retention.Furthermore, some patients wearing complete dentures experience the maxillary denture base splitting in half due to poor material quality. They drill several holes on either side of the fracture line, tie them together with thread, and continue wearing the denture. Among these patients, some simply skip the tying step and wear only one half of the denture, yet still manage to chew food.These phenomena cannot be explained by atmospheric negative pressure or adhesive force.