## **Core Concept**
The question pertains to the historical development and surface modification of dental implants, specifically focusing on hydroxyapatite coating. Hydroxyapatite, a form of calcium apatite with the formula Ca₅(PO₄)₃(OH), is a naturally occurring mineral form of calcium apatite, which is a key component of bones and teeth. Its application in dental implants aims to enhance biocompatibility and osseointegration.

## **Why the Correct Answer is Right**
The introduction of hydroxyapatite coating on dental implants was a significant advancement in implant dentistry, aiming to improve the integration of implants with the surrounding bone. This coating promotes osseoconduction, allowing bone cells to grow onto and integrate with the implant surface. The correct answer, . **Branemark**, is associated with pioneering work in dental implantology. However, it was **Leite and coworkers** and others who explored various surface modifications, but **Per-Ingvar Branemark** is renowned for his work on titanium implants. Yet, specific introduction of hydroxyapatite coating is more accurately attributed to **De Groot** and others in the 1980s.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Without specific names provided in the query, it's challenging to directly refute incorrect options. Generally, though, incorrect options in questions about historical developments in dental implantology might include researchers not directly associated with hydroxyapatite-coated implants or those whose contributions were in different areas.
- **Option B:** Similarly, without details, one assumes this option does not directly relate to the introduction of hydroxyapatite coatings.
- **Option D:** This option would be incorrect based on the accurate attribution of hydroxyapatite coating introduction.

## **Clinical Pearl / High-Yield Fact**
A significant clinical pearl is that hydroxyapatite-coated dental implants are used to enhance osseointegration, particularly in cases where the bone density is poor. This coating can significantly improve the long-term success of dental implants by promoting bone growth around the implant.

## **Correct Answer:** . **De Groot**