Bone-hydroxyapatite interface in retrieved hydroxyapatite-coated titanium implants: a clinical and histologic report

Area of Science:

• Biomaterials Science
• Dental Implantology
• Materials Science

Background:

• Hydroxyapatite coatings are widely used on dental implants to enhance osseointegration.
• Understanding the long-term stability and biological interaction of these coatings is crucial for clinical success.

Purpose of the Study:

• To investigate the interface between retrieved hydroxyapatite-coated implants and surrounding bone after 12 months of functional loading.
• To analyze the chemical and structural integrity of the hydroxyapatite coating in situ.

Main Methods:

• Retrieval of two hydroxyapatite-coated implants due to abutment fracture after 12 months of loading.
• Preparation of thin ground sections for light microscopy.
• Microprobe chemical analysis using scanning electron microscopy with energy-dispersive X-ray analysis and cathodoluminescence.

Main Results:

• Close bone-to-coating contact observed with no interfacial gaps.
• Evidence of hydroxyapatite coating thickness reduction in some areas.
• Detached hydroxyapatite particles were found embedded within newly formed bone.
• Chemical analysis revealed a reduced calcium:phosphorus ratio at the interface in cathodoluminescent areas.

Conclusions:

• While hydroxyapatite coatings promote initial bone apposition, long-term loading may lead to coating degradation.
• The presence of detached particles and altered chemical composition suggests potential challenges for long-term implant stability.
• Further research is needed to optimize hydroxyapatite coating formulations for enhanced durability.