Nanoceramics: Synthesis, Characterizations and Applications
145
4.1 Nanoceramics as Orthopaedic Implant Coatings
Implants are used to replace and restore the functions of diseased and/or damaged
hard tissues such as bone and teeth. A good artificial implant material should be
able to mimic the physical structure, chemical composition and biological function
of the natural bone. The increase in the life expectancy of people along with those
undergoing treatments for musculoskeletal disorders is on the rise every year. The
biological environment is harsh and it leads to loosening of the metal implants, corrosion in the physiological medium, inflammation, loosening, wear and/or tear debris,
autoimmune reactions and ultimately failure of implants in patients with traditional
metallic implants [69, 70]. Improving the bioactivity and corrosion resistance of the
implant material as well as facilitating faster bone-implant interface establishment
is crucial to avoid early implant failure and increase the lifetime of an implant.
Modifying the implant surface is a simple and cost-effective method to effect
osseointegration and increase the bioactivity of the implant. This can be done by
applying biocompatible coatings, modifying the surface topography or by removing
material from the existing surface to create new topography [71, 72]. Considering
the constraints in the physiological environment, nanoceramics is a suitable material
for different bone system-related applications such as dental, periodontal, cranial,
maxillofacial, spinal surgery etc. Applying nanoceramics in the form of coatings
over the implant surface is an effective methodology.
Numerous nano bioceramics have been developed and categorized based on their
activity. The first-generation bioceramics such as zirconia (ZrO 2 ), alumina (Al 2 O 3 ),
etc., had good mechanical properties but were bioinert [73]. Copper and silver incorporated ZrO 2 coatings were developed on pure Ti implant by magnetron sputtering.
The nanostructured coatings changed the structure of crystalline zirconia coating and
the incorporation of Cu and Ag improved the antibacterial resistance of the implant
material [74]. A thin layer of dense Al 2 O 3 was developed by micro-arc oxidation
method. The Al 2 O 3 layer exhibited good adhesion to the Ti implant, had high Vickers
hardness and it is suggested to be a preferred material for load-bearing applications
such as artificial hip joint [75].
The second-generation nano bioceramics were based on their chemical reactivity,
i.e., they had bioactivity. Bioactive ceramics can bond with the living bone without
having adverse reactions such as inflammation and toxicity [76]. The high reactivity
of this class of materials is the main advantage for being used in periodontal repair
and bone growth. Hydroxyapatite, silica-based bioactive glasses, etc., are the important second-generation bioceramics. Hydroxyapatite coatings were developed over
NaOH treated and untreated Ti-6Al-4 V by electrodeposition method and compared
with that of plasma-sprayed Hap coated Ti-6Al-4 V. The new bone area value for HAp
electrodeposited coating on alkali-treated material was highest at 12 weeks indicating
enhanced osseointegration in vivo [77]. A new family of glasses was formulated by
partially substituting CaO by MgO and Na 2 O by K 2 O. The glass was deposited on the
sample surface by a dip-coating method following by annealing. The glass coating’s
thickness was adjusted to be between 100–200 nm to have good adhesion and hence
145
4.1 Nanoceramics as Orthopaedic Implant Coatings
Implants are used to replace and restore the functions of diseased and/or damaged
hard tissues such as bone and teeth. A good artificial implant material should be
able to mimic the physical structure, chemical composition and biological function
of the natural bone. The increase in the life expectancy of people along with those
undergoing treatments for musculoskeletal disorders is on the rise every year. The
biological environment is harsh and it leads to loosening of the metal implants, corrosion in the physiological medium, inflammation, loosening, wear and/or tear debris,
autoimmune reactions and ultimately failure of implants in patients with traditional
metallic implants [69, 70]. Improving the bioactivity and corrosion resistance of the
implant material as well as facilitating faster bone-implant interface establishment
is crucial to avoid early implant failure and increase the lifetime of an implant.
Modifying the implant surface is a simple and cost-effective method to effect
osseointegration and increase the bioactivity of the implant. This can be done by
applying biocompatible coatings, modifying the surface topography or by removing
material from the existing surface to create new topography [71, 72]. Considering
the constraints in the physiological environment, nanoceramics is a suitable material
for different bone system-related applications such as dental, periodontal, cranial,
maxillofacial, spinal surgery etc. Applying nanoceramics in the form of coatings
over the implant surface is an effective methodology.
Numerous nano bioceramics have been developed and categorized based on their
activity. The first-generation bioceramics such as zirconia (ZrO 2 ), alumina (Al 2 O 3 ),
etc., had good mechanical properties but were bioinert [73]. Copper and silver incorporated ZrO 2 coatings were developed on pure Ti implant by magnetron sputtering.
The nanostructured coatings changed the structure of crystalline zirconia coating and
the incorporation of Cu and Ag improved the antibacterial resistance of the implant
material [74]. A thin layer of dense Al 2 O 3 was developed by micro-arc oxidation
method. The Al 2 O 3 layer exhibited good adhesion to the Ti implant, had high Vickers
hardness and it is suggested to be a preferred material for load-bearing applications
such as artificial hip joint [75].
The second-generation nano bioceramics were based on their chemical reactivity,
i.e., they had bioactivity. Bioactive ceramics can bond with the living bone without
having adverse reactions such as inflammation and toxicity [76]. The high reactivity
of this class of materials is the main advantage for being used in periodontal repair
and bone growth. Hydroxyapatite, silica-based bioactive glasses, etc., are the important second-generation bioceramics. Hydroxyapatite coatings were developed over
NaOH treated and untreated Ti-6Al-4 V by electrodeposition method and compared
with that of plasma-sprayed Hap coated Ti-6Al-4 V. The new bone area value for HAp
electrodeposited coating on alkali-treated material was highest at 12 weeks indicating
enhanced osseointegration in vivo [77]. A new family of glasses was formulated by
partially substituting CaO by MgO and Na 2 O by K 2 O. The glass was deposited on the
sample surface by a dip-coating method following by annealing. The glass coating’s
thickness was adjusted to be between 100–200 nm to have good adhesion and hence