**Question:** Over extension of the posterior border of the denture causes:

A. Temporomandibular joint (TMJ) dysfunction
B. Incidence of carious lesions
C. Excessive pressure on the lingual and vestibular surfaces
D. Soft tissue ulceration

**Core Concept:** Dentures are removable dental prostheses used to replace missing teeth and adjacent tissues. Proper denture design, fit, and adjustment are essential to ensure optimal patient comfort, function, and aesthetics. Over extension of the posterior border of the denture refers to the denture extending beyond the natural contour of the residual ridge, potentially leading to various oral complications.

**Why the Correct Answer is Right:**

Correct Answer: C. Excessive pressure on the lingual and vestibular surfaces

The correct answer is related to the consequences of over-extending the posterior border of the denture. When a denture has an excessively long posterior border, it puts excessive pressure on the lingual (tongue side) and vestibular (oral cavity side) surfaces, leading to discomfort, ulceration, and tissue irritation. This may cause pain, difficulty in speech, and impaired mastication.

**Why Each Wrong Option is Incorrect:**

A. Temporomandibular joint (TMJ) dysfunction: While dentures can indirectly affect TMJ function due to altered mandibular movement, the specific cause mentioned here is incorrect. TMJ dysfunction is primarily related to malocclusion, inadequate denture base thickness, or poorly designed occlusion, not posterior denture extension.

B. Incidence of carious lesions: Over-extended dentures are more prone to traumatic ulceration rather than caries formation. Trauma-induced ulceration may lead to secondary bacterial colonization and infection, but carious lesions are caused by dental plaque accumulation and biofilm formation, typically in areas of poor oral hygiene.

C. Excessive pressure on the lingual and vestibular surfaces: As mentioned earlier, denture pressure on these areas causes tissue irritation, ulceration, and discomfort, which is the correct rationale behind this option.

D. Soft tissue ulceration: While denture-related ulceration can be present, this option does not address the specific issue of denture over-extension, making it an incorrect answer.

**Clinical Pearl:**

In clinical practice, it is crucial to ensure an appropriate fit and contour of the posterior border of the denture to avoid complications like ulceration, tissue irritation, and impaired function. Regular denture adjustments and patient education on oral hygiene are essential for long-term oral health and denture longevity.