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In vitro changes of hydroxyapatite coatings
K A Gross1, C C Berndt, D D Goldschlag
1Department of Materials Science, University of Technology, Sydney, Australia. Karlis.Gross@uts.edu.au
The International Journal of Oral & Maxillofacial Implants
|October 23, 1997
Summary
Hydroxyapatite coatings on dental implants degrade via dissolution. The amorphous phase degrades faster than the crystalline phase, especially in acidic conditions, potentially affecting bone bonding.
Area of Science:
- Biomaterials Science
- Dental Implantology
- Materials Degradation
Background:
- The stability of hydroxyapatite (HA) coatings on dental implants is crucial for osseointegration.
- HA coatings can contain both crystalline and amorphous phases, influencing their degradation behavior.
- Understanding coating degradation is essential for predicting implant longevity and performance.
Purpose of the Study:
- To investigate the degradation pathways of hydroxyapatite coatings with varying amorphous content.
- To compare the degradation rates of crystalline and amorphous phases under different conditions.
- To explore the potential impact of coating degradation on implant-tissue interactions.
Main Methods:
- Immersion of HA-coated implants in Ringer's solution to simulate physiological conditions.
- Exposure to a decreased pH environment to mimic infection conditions.
- Microscopic observation and chemical analysis to assess coating morphology and phase changes.
Main Results:
- Both crystalline and amorphous HA coatings degraded through cracking and dissolution in Ringer's solution.
- Precipitation of crystalline apatite occurred on the implant surface upon saturation.
- The amorphous phase of the HA coating showed preferential dissolution under acidic (low pH) conditions.
- Dissolution of the amorphous phase led to the exposure and liberation of crystalline segments.
Conclusions:
- The amorphous phase of hydroxyapatite coatings is more susceptible to degradation, particularly in acidic environments.
- Degradation mechanisms involve both dissolution and cracking, with subsequent surface modification by apatite precipitation.
- Morphological changes resulting from degradation may influence the rate of bone bonding and implant osseointegration.