Aseptic Silk Ligatures Induce Bone Resorption Around Titanium Implants: A 12-Week Pilot Study in Rabbits

Area of Science:

• Dental Implantology
• Immunology
• Biomaterials Science

Background:

• Marginal bone resorption (MBR) around dental implants can be influenced by immunologic reactions to materials, not solely bacterial infection.
• Previous studies suggested ligatures induce progressive peri-implantitis, but the long-term immune response is less understood.

Purpose of the Study:

• To investigate if the inflammatory/immunologic reaction causing bone resorption around implants, triggered by ligatures, attenuates or progresses after 12 weeks.
• To determine if aseptic bone resorption is a self-limiting process.

Main Methods:

• Sterile silk ligatures were placed around titanium implants in rabbit femurs for 12 weeks of submerged healing.
• Control implants were nonligated.
• Histological analysis of ground sections and quantitative PCR (qPCR) analysis of marginal soft tissues were performed.

Main Results:

• Histology revealed immune cells, including multinucleated giant cells, fibrous encapsulation, and resorbed bone around ligated implants.
• qPCR showed a mild, focal inflammatory response with upregulated immune markers (CD11b, IL1β, ARG1, NCF1, CD4) and downregulated CD8.
• Bone formation markers (OC, ALPL) were downregulated, indicating impaired osseointegration.

Conclusions:

• Marginal silk ligatures induce aseptic bone resorption and an inflammatory/immune response around implants.
• The inflammatory reaction appears to attenuate over 12 weeks, resulting in fibrous encapsulation rather than continuous bone loss.
• This suggests that sustained bone resorption in ligature models may require repeated ligature exchange.