**Question:** What is the effect of soft tissue liner under the denture on the residual ridge?

**Core Concept:** Soft tissue liners are materials placed between the denture base and the underlying oral tissues to improve the fit, comfort, and function of the denture. The residual ridge refers to the remaining alveolar bone supporting the denture after tooth loss.

**Why the Correct Answer is Right:**
Soft tissue liners are designed to adapt to the oral tissues, thus reducing pressure points and friction between the denture and the residual ridge. This results in improved denture retention, stability, and comfort. In turn, the soft tissue liner helps to distribute the forces exerted by the denture more evenly across the residual ridge, preventing excessive pressure on specific areas and reducing the risk of denture-related mucosal pathology (e.g., ulceration, inflammation) and alveolar bone resorption.

**Why Each Wrong Option is Incorrect:**
A. Residual ridge resorption is a process where the alveolar bone decreases in size due to the absence of tooth roots and the subsequent loss of periodontal ligament mechanoreceptors. Soft tissue liners do not directly affect residual ridge resorption, as they primarily address issues related to denture fit and comfort.

B. Soft tissue liners are intended to improve denture performance by reducing pressure points and friction, not to promote bone formation or regeneration.

C. The primary function of a soft tissue liner is to improve denture fit, stability, and comfort, rather than modify the shape or size of the residual ridge.

D. Soft tissue liners help to distribute denture forces more evenly across the residual ridge, preventing excessive pressure on specific areas and reducing the risk of denture-related mucosal pathology and alveolar bone resorption.

**Clinical Pearl:** The use of soft tissue liners under dentures is essential for long-term denture success and patient comfort, but they do not directly halt or reverse the process of residual ridge resorption. This process is primarily influenced by factors such as age, bone-supporting structures, and the type of denture used. Ensuring proper denture fit and distribution of forces on the residual ridge is crucial to minimize complications and maintain oral health.