**Core Concept**
Resin ionomer restorative materials are a type of dental restorative material used for filling teeth. They are composite materials that combine resin and glass powder, providing both mechanical strength and fluoride release. This unique combination makes them an attractive option for restorations, especially in non-load bearing areas.

**Why the Correct Answer is Right**
The correct answer is one that does not align with the properties of resin ionomer restorative materials. Resin ionomers are known for their fluoride release, which helps prevent secondary caries and promotes oral health. They also have good mechanical strength, making them suitable for load-bearing applications. Additionally, resin ionomers have a low thermal conductivity, which helps reduce thermal sensitivity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because resin ionomers are indeed known for their ability to release fluoride ions, which is a key property of this material.
**Option B:** This option is incorrect because resin ionomers do have good mechanical strength, making them suitable for various clinical applications.
**Option C:** This option is incorrect because resin ionomers have a low thermal conductivity, which helps reduce thermal sensitivity in patients.

**Clinical Pearl / High-Yield Fact**
One key advantage of resin ionomer restorative materials is their ability to release fluoride ions, which helps prevent secondary caries and promotes oral health.

**Correct Answer: D.**