Comparative Study of Inflammatory and Fibrotic Reactions Induced by Silicone Implants with Different Hardness.

Background: Silicone nasal implants have been widely used in rhinoplasty. However, research on the correlation between implant hardness and the development of fibrosis and inflammation is lacking. This study investigated how the hardness of silicone implants influences fibrosis and inflammation through an experimental investigation.

Methods: Three types of nasal silicone implants with varying hardness levels were implanted bilaterally on the backs of 15 Wistar rats. Ten weeks post-implantation, clinical aspects, such as differences in immune reactions and formation of peri-implant capsules were analyzed. The intra-tissue response of the host was assessed by qRT-PCR using 11 markers. Specific markers were investigated by immunohistochemical (IHC) staining. Pathological grading was performed to investigate inflammation and fibrosis in the peri-implant tissues. Quantification and statistical analysis of these parameters were conducted to derive scores for intergroup comparisons.

Results: Histological analysis of the 45 capsules obtained revealed lower levels of fibrosis and acute inflammation in the group with lower hardness. This result was confirmed by IHC staining. Hematoxylin and eosin staining showed that the capsule thickness was less in the low-hardness group. Additionally, inflammation resolved quickly in the low-hardness group, and mature fibrotic tissue was observed.

Conclusions: When silicone implants are stably positioned within the body, less-rigid implants exhibit lower inflammatory or fibrotic responses. This is directly related to the adverse effects associated with capsule formation. These findings contribute to our understanding of the behavior of heterotopic materials in the nasal dorsum and their effects on the skin and soft tissue envelope.