Abstract
Titanium micro-scale topography offers excellent osteoconductivity and bone–implant integration. However, the biological effects of sub-micron topography are unknown. We compared osteoblastic phenotypes and in vivo bone and implant integration abilities between titanium surfaces with micro- (1–5 µm) and sub-micro-scale (0.1–0.5 µm) compartmental structures and machined titanium. The calculated average roughness was 12.5 ± 0.65, 123 ± 6.15, and 24 ± 1.2 nm for machined, micro-rough, and sub-micro-rough surfaces, respectively. In culture studies using bone marrow-derived osteoblasts, the micro-rough surface showed the lowest proliferation and fewest cells attaching during the initial stage. Calcium deposition and expression of osteoblastic genes were highest on the sub-micro-rough surface. The bone–implant integration in the Sprague–Dawley male rat femur model was the strongest on the micro-rough surface. Thus, the biological effects of titanium surfaces are not necessarily proportional to the degree of roughness in osteoblastic cultures or in vivo. Sub-micro-rough titanium ameliorates the disadvantage of micro-rough titanium by restoring cell attachment and proliferation. However, bone integration and the ability to retain cells are compromised due to its lower interfacial mechanical locking. This is the first report on sub-micron topography on a titanium surface promoting osteoblast function with minimal osseointegration.
Highlights
Titanium and titanium alloy have been widely used in the fields of orthopedic surgery and dentistry owing to their excellent mechanical properties, high corrosion resistance, and suitable biocompatibility [1,2,3]
Low-magnification scanning electron microscopy (SEM) images of the machined surface showed parallel traces formed during the concentric machining process (Figure 1g,j)
Low-magnification images of the sub-micro-rough surface showed no recognizable roughness with faintly machine traces (Figure 1i)
Summary
Titanium and titanium alloy have been widely used in the fields of orthopedic surgery and dentistry owing to their excellent mechanical properties, high corrosion resistance, and suitable biocompatibility [1,2,3]. To improve the biocompatibility of titanium, its osteoconductivity, various methods of surface modification have been developed to roughen titanium surfaces. For improved osseointegration of implants, researchers have assessed the impact of surface roughness at the micro-scale [12]. Surface roughness increases the surface area and triggers biological changes, such as the skeletal and morphological alteration of cells. These changes can affect planar cell polarity, as well as gene expression and the differentiation and maturation of osteoblasts [13,14]. Titanium surfaces with various micro-scale topographies developed to date have been shown to provide osteoblasts with structural mimetics and thereby biological cues to promote new bone formation [17]
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