Bone Immune Response to Materials, Part II: Copper and Polyetheretherketone (PEEK) Compared to Titanium at 10 and 28 Days in Rabbit Tibia

Abstract

Osseointegration is likely the result of an immunologically driven bone reaction to materials such as titanium. Osseointegration has resulted in the clinical possibility to anchor oral implants in jaw bone tissue. However, the mechanisms behind bony anchorage are not fully understood and complications over a longer period of time have been reported. The current study aims at exploring possible differences between copper (Cu) and polyetheretherketone (PEEK) materials that do not osseointegrate, with osseointegrating cp titanium as control. The implants were placed in rabbit tibia and selected immune markers were evaluated at 10 and 28 days of follow-up. Cu and PEEK demonstrated at both time points a higher immune activation than cp titanium. Cu demonstrated distance osteogenesis due to a maintained proinflammatory environment over time, and PEEK failed to osseointegrate due to an immunologically defined preferential adipose tissue formation on its surface. The here presented results suggest the description of two different mechanisms for failed osseointegration, both of which are correlated to the immune system.

Osteoimmunology drives dental implant osseointegration: A new paradigm for implant dentistry

“…Interestingly, recent results on bone immune response to titanium implant showed the activation of CD4+ T cells, while the phenotype of CD8+ T cells is suppressed. Therefore, these findings also indicate an adaptive immune response around Titanium [ 30 , 31 ]. Nevertheless, it unknown whether lymphocytes make an acquired immunity participation in the process or if it remains within the innate immunity limits [ 18 ].…”

“…On the other hand, modulation of the M1/M2 balance of macrophages is important in wound healing, regeneration and osseointegration [ 2 , 5 ]. In fact, a balanced M1/M2 macrophage ratio-correlates with M2-associated bone growth at the peri-implant niche at post-implant day (PID) 10 [ 30 , 31 ]. During fracture healing, M2 macrophages participate in both the resolution phase of inflammation and in the homing of mesenchymal stem cells (MSCs) [ 32 , 33 ].…”

“… Biological event M1/M2 relationship Predominant macrophage phenotype Proinflammatory environment Ref. Osseointegration Balance M2 (−) [ 2 , 30 , 31 , 57 , 111 ] Loosening of implants Unbalanced M1 (+) [ 29 ] Epimorphic regeneration Balance M2 (−) [ 5 , 5 , 36 ] Fracture repair Balance M2 (−) [ 34 , 35 ] Bone resorption Unbalanced M1 (+) [ 44 ] …”

Hydroxyapatite-incorporation improves bone formation on endosseous PEEK implant in canine tibia

“…11 Fibrous tissue encapsulation instead of direct bone contact occurs around PEEK implants more frequently than titanium implants. 12 The phenomenon is mostly attributed to the chemical inertness and hydrophobic nature of PEEK. The bioinert surface of PEEK is related to reduced osteoblastic differentiation of progenitor cells and production of an inflammatory environment that favors cell death via apoptosis and necrosis.…”

Are Oral Implants the Same As Teeth?

“…Today we are aware of our misinterpretations. Trindade et al [18,19] published two papers in this volume with evidence that titanium is not at all inert; the material causes clearly observable immune reactions in the tissue. Other biomaterials such as Poly-ether-ether-ketone, covered by Han et al [20] in this volume, displayed significantly greater immune reactions than did titanium [19].…”