**Core Concept**
Esthetic fibre reinforced posts are a type of dental restoration used to replace missing teeth. They are made from a combination of resin and glass fibres, which provide strength and durability while mimicking the appearance of natural teeth. The main drawback of these posts is related to their mechanical properties.

**Why the Correct Answer is Right**
The main drawback of esthetic fibre reinforced posts is their lower flexural strength compared to metallic posts. This is because the fibres in the post are prone to fibre breakage under high stress, leading to a decrease in the post's ability to withstand occlusal forces. Additionally, fibre reinforced posts may not be suitable for teeth that require high restoration loads, such as molars or teeth with a large amount of remaining tooth structure.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because while esthetic fibre reinforced posts may be more expensive than metallic posts, this is not their main drawback.
* **Option B:** Incorrect because esthetic fibre reinforced posts are not necessarily more prone to corrosion than metallic posts.
* **Option C:** Incorrect because esthetic fibre reinforced posts are not necessarily more difficult to place than metallic posts.

**Clinical Pearl / High-Yield Fact**
When choosing between esthetic fibre reinforced posts and metallic posts, it's essential to consider the patient's oral health status, the location of the tooth, and the amount of remaining tooth structure. Fibre reinforced posts are generally recommended for anterior teeth or teeth with minimal restoration needs.

**Correct Answer: D. Lower flexural strength.**