Long-term osseointegration of a laser ablated implant surface in a sheep model

• Introduction Osseointegration, the ability for an implant to be anchorage in bone tissue with a direct bone-implant contact and allowing for continual adaptive remodeling, is clinically used in different reconstructive fields, such as dentistry, orthopedics and otology. The latter uses a bone conducting sound processor connected to a skin-penetrating abutment that is mounted on a titanium implant placed in the temporal bone acting as a path transmission for the vibrations that are generated by the sound processor The success of the treatment relies on the bone healing and osseointegration, which could be improved by surface treatments. A laser-ablated implant surface has shown good ability to osseointegrate in the long bones of rabbits at both short- and long-term in the tibia and femur[1-2]. A lighter version of the implant surface showed a good osseointegration in short-term healing in the long bone[3], however, knowledge in the harder, denser bone of the skull is lacking. The aim of the current study was to evaluate the long-term (5 month) osseointegration in a sheep skull model, and compare the osseointegration of a laser-ablated implant surface with a machined implant. Experimental methods Standard implants from Oticon Medical (Askim, Sweden), either the Wide Ponto implants with a machined surface (figure 1A, C) or Ponto BHX implants with a laser-ablated surface (figure 1B, D) were used in the current study, both with a diameter of 4.5 mm and manufactured from c.p. titanium grade 4. The surfaces were evaluated by scanning electron microscopy (Ultra 55 FEG SEM, FEI company, The Netherlands). The surgical protocol consisted of implantation in the frontal bone of 8 female sheep. The implantation was performed with a full soft tissue flap, drilling was performed using the MIPS drill-kit (Oticon Medical AB, Sweden) with a successive enlargement of the hole (diameter 3.8 mm), prior installation of the implant (test and control altered between left and right side). After 5 months, the animals were scarified, biopsies including the implant and surrounding bone tissue were immersed in formalin, prior processing for histology using plastic embedded undecalcified ground sections. Histomorphometry was performed to quantify the bone-implant contact and bone area within the treaded area of the implant. Results and discussion The animals healed well and there were no signs of adverse events after implantation or at the time of sacrifice. The histomorphometry (Figure 2) showed large amount of bone tissue around both implant types with mean values of 75% of the threaded area occupied by bone for both implant types. Large amount of bone-implant contact was observed for both implant types, with mean values between 67-71% of the surface covered by bone. This is in agreement with previous long-term rabbit study where the large amount of bone growth was observed for both implant types. No difference in the amount of bone was observed at early time point using this type of surface while the biomechanics were largely improved [3], while earlier studies have shown that the improved biomechanical properties withstand with time [2]. The current results show that the laser-ablated surface induces similar healing as the well-known clinically used machined surface in skull bone. Conclusion The laser-ablated implant performs equally well at long term as the well documented, clinically used implant with machined surface. This, together with the improved early biomechanical anchorage [3], indicate a safe and efficient clinical potential. Acknowledgements We thank Dr Måns Eeg Olofsson and Dr Erik Renvall (Sahlgrenska University Hospital, Gothenburg, Sweden) and Dr Peter Monksfield (University Hospitals Birmingham, Birmingham, UK) for performing the surgeries and retrievals. This work was supported by Oticon Medical (Askim, Sweden). References 1. Brånemark R, Emanuelsson L, Palmquist A, Thomsen P. Bone response to laser-induced micro- and nano-size titanium surface features. Nanomed - Nanotechnol Biol Med 2011;7(2):220-7. http://dx.doi.org/10.1016/j.nano.2010.10.006 2. Palmquist A, Emanuelsson L, Brånemark R, Thomsen P. Biomechanical, Histological and Ultrastructural Analyses of Laser Micro- and Nano-structured Titanium implant after 6 months in rabbit. J Biomed Mater Res B 2011;97(2):289-98. http://dx.doi.org/10.1002/jbm.b.31814 3. Shah FA, Johansson ML, Omar O, Simonsson H, Palmquist A, Thomsen P. Laser-Modified Surface Enhances Osseointegration and Biomechanical Anchorage of Commercially Pure Titanium Implants for Bone-Anchored Hearing Systems. PLoS ONE 2016;11(6):e0157504 http://dx.doi.org/10.1371/journal.pone.0157504

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kirurgi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Surgery (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Cell- och molekylärbiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Cell and Molecular Biology (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinsk bioteknologi -- Biomaterialvetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Medical Biotechnology -- Biomaterials Science (hsv//eng)

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