Laser-Modified Surface Enhances Osseointegration and Biomechanical Anchorage of Commercially Pure Titanium Implants for Bone-Anchored Hearing Systems

Abstract

Osseointegrated implants inserted in the temporal bone are a vital component of bone-anchored hearing systems (BAHS). Despite low implant failure levels, early loading protocols and simplified procedures necessitate the application of implants which promote bone formation, bone bonding and biomechanical stability. Here, screw-shaped, commercially pure titanium implants were selectively laser ablated within the thread valley using an Nd:YAG laser to produce a microtopography with a superimposed nanotexture and a thickened surface oxide layer. State-of-the-art machined implants served as controls. After eight weeks’ implantation in rabbit tibiae, resonance frequency analysis (RFA) values increased from insertion to retrieval for both implant types, while removal torque (RTQ) measurements showed 153% higher biomechanical anchorage of the laser-modified implants. Comparably high bone area (BA) and bone-implant contact (BIC) were recorded for both implant types but with distinctly different failure patterns following biomechanical testing. Fracture lines appeared within the bone ~30–50 μm from the laser-modified surface, while separation occurred at the bone-implant interface for the machined surface. Strong correlations were found between RTQ and BIC and between RFA at retrieval and BA. In the endosteal threads, where all the bone had formed de novo, the extracellular matrix composition, the mineralised bone area and osteocyte densities were comparable for the two types of implant. Using resin cast etching, osteocyte canaliculi were observed directly approaching the laser-modified implant surface. Transmission electron microscopy showed canaliculi in close proximity to the laser-modified surface, in addition to a highly ordered arrangement of collagen fibrils aligned parallel to the implant surface contour. It is concluded that the physico-chemical surface properties of laser-modified surfaces (thicker oxide, micro- and nanoscale texture) promote bone bonding which may be of benefit in situations where large demands are imposed on biomechanically stable interfaces, such as in early loading and in compromised conditions.

Clinical evaluation of a new laser‐ablated titanium implant for bone‐anchored hearing in 34 patients: 1‐year experience

“…[Kruyt et al submitted at O&N, under review] This was also found in pre‐clinical animal testing of this implant; however, removal torque measurements showed a 153% higher biomechanical anchorage of the laser‐modified implants. This underlines that ISQ might not reliably reflect actual osseointegration and that this implant might be beneficial for using in high‐risk patients.…”

“…4.2 |Comparisons with other studies laser-modified implants 8. This underlines that ISQ might not reliably reflect actual osseointegration and that this implant might be beneficial for using in high-risk patients.…”

“…This implant is, in contrast to currently used implants, selectively laser‐ablated within the thread valley. Combined with modified chemical properties, this has shown improved biomechanical anchorage in pre‐clinical animal testing . In our clinical practice, before this implant is tested in patients with a higher risk of implant loss, it first has to be proven effective to use in healthy adults.…”

“…Combined with modified chemical properties, this has shown improved biomechanical anchorage in pre-clinical animal testing. 8 In our clinical practice, before this implant is tested in patients with a higher risk of implant loss, it first has to be proven effective to use in healthy adults. This study, therefore, assesses retrospectively the performance of the new laser-ablated implant by reviewing implant survival, stability and soft tissue tolerability in healthy adults 1 year after surgery.…”

Clinical, radiological, and gene expression analyses in smokers and non‐smokers, Part 2: RCT on the late healing phase of osseointegration

“…Here, we show that the overall MBL was significantly greater in smokers compared with non‐smokers as early as 90 days following implant installation. On the basis of experimental data and the fluctuation of ISQ values during healing in humans, it is likely that the greatest bone remodeling occurs during this very early time phase. Albeit speculative, the increased MBL in smokers during this early time phase might be related to different bone homeostasis in smokers, resulting in a net imbalance between the anabolic and catabolic pathways, favoring bone resorption.…”