1. Introduction
Implantology has revolutionized the field of dentistry, providing an effective and permanent solution to replacing missing teeth.
Dental implants are titanium or zirconium oxide devices surgically inserted into the jawbone to replace the roots of natural teeth. They provide a solid foundation for bridges, crowns and complete dentures. These devices offer a more natural feel and greater stability than removable dentures. They also maintain the integrity of the jaw by stimulating bone growth and preventing bone resorption. Dental implants can be designed to perfectly match the color, shape and size of natural teeth.
This therapeutic solution is aimed at a wide range of patients, including edentulous people, people suffering from the loss of one or more teeth and those who wish to replace traditional prostheses with more modern, stable and comfortable implants.
The use of cone beam computed tomography (CBCT) for precise implant planning, computer-assisted surgery for minimal and precise interventions and the use of high-quality biocompatible materials for optimal bone integration.
Today, hydroxyapatite-coated dental implants are widely used in clinical practice and provide patients with predictable and long-lasting results. With continued advancements in materials research and technology, it is likely that the use of hydroxyapatite-coated titanium in dental implantology will continue to increase, providing new opportunities to improve clinical outcomes and quality of life for patients.
The present work aims to study the nanostructure of titanium implants coated with hydroxyapatite, their clinical performance, as well as to compare them with conventional dental implants.
2. Materials and Methods
2.1. Identifying the Literature
To meet the objectives of our subject, two types of search strategies documentary have been summer used for this literature review.
2.2. Digital Research Strategy
First of all, this involves research using computer databases accessible via the Internet. We examined PubMed, which provides access to the MEDLINE bibliographic database. Other search engines examined: Google Scholar.
We used the keywords (Dental Implants, Titanium, Hydroxyapatite, Coating, Clinical Performance) to achieve targeted and precise research.
These terms were used in each database searched separately and cross-referenced to identify articles for analysis after inclusion.
- Dental Implants and Hydroxyapatite
- Dental Implants and Coating
- Dental Implants and Hydroxyapatite and Coating and Titanium and Clinical Performances
- Hydroxyapatite and Titanium
- Hydroxyapatite and Coating
2.3. Bottom-Up Approach
This search strategy gave us the opportunity to collect from the already pre-selected reference list a number of articles that would have gone unnoticed in electronic research of interest to our topic.
2.4. Inclusion Criteria
We admitted during our bibliographical research:
- Articles meeting the objectives of our research.
- Articles with a publication date between 2014 and 2024.
- Articles published in English.
2.5. Exclusion Criteria
We have eliminated and excluded any criterion opposing this selection.
3. Results (See Table 1)
Table 1. Representative table of selected articles.
Title of article |
Authors |
Year |
Bibliographic reference |
Investigations of titanium implants covered with hydroxyapatite layers |
B. Świeczko-Żurek, M. Bartmański |
2016 |
[1] |
Bioactive Surfaces vs. Conventional Surfaces in Titanium Dental Implants: A Comparative Systematic Review |
Nansi López-Valverde, Javier Flores-Fraile, Juan Manuel Ramírez, Bruno Macedo de Sousa, Silvia Herrero-Hernández Antonio López-Valverde |
2020 |
[2] |
A Review of Hydroxapatite and Its Use as a
Coating in Dental Implants |
Joo L. Ong & Daniel CN Chan |
2017 |
[3] |
A short view on nanohydroxyapatite as coating of
dental implants |
Javad Yazdani, Elham Ahmadian, Simin Sharifi, Shahriar Shahi, Solmaz Maleki Dizaj |
2018 |
[4] |
Clinical Outcome of Hydroxyapatite Coated, Bioactive Glass Coated, and Machined Ti6Al4V Threaded Dental Implant in Human Jaws: A short-term comparative study |
Surajit Mistry, Rajiv Roy, Biswanath Kundu,
Someswar Datta, Manoj Kuma, Abhijit Chanda, and Debabrata Kundu |
2016 |
[5] |
Retrospective clinical outcome of nanopolymorphic crystalline hydroxyapatite-coated and anodic oxidized titanium implants for 10 years |
Eiji Kato, Masahiro Yamada, Kaoru Sakurai |
2014 |
[6] |
Hydroxyapatite and Fluorapatite in Conservative Dentistry and Oral Implantology—A Review |
Kamil Pajor, Lukasz Pajchel and Joanna Kolmas |
2019 |
[7] |
Efficacy of Nano-Hydroxyapatite Coating On Osseointegration of Early Loaded Dental Implants |
Osama Alabed Mela, Mohamed Abdel-Monem
Tawfik, Wael Mohamed Ahmed Said Ahmed,
Fakhreldin Hassan Abdel-Rahma |
2022 |
[8] |
Surface modifications of endosseous dental implants by incorporation of roughness and hydroxyapatite coatings |
Fahd Ahmed, Haroon Rashid, Sadaf Farookhi, Vivek Verma, Yuliya Mulyar, Murai Khalifa, Zeeshan Sheikh |
2015 |
[9] |
The Influence of Nanostructured Hydroxyapatite Surface in the Early Stages of Osseointegration: A Multiparameter Animal Study in Low-Density Bone |
Suelen Cristina Sartoretto, Jose Calasans -Maia, Rodrigo Resende, Eduardo Câmara, Bruna
Ghiraldini, Fabio Jose Barbosa Bezerra, Jose Mauro Granjeiro, Monica Diuana Calasans-Maia |
2016 |
[10] |
The Soft Tissue Immunologic Response to
Hydroxyapatite-Coated Transmucosal Implant Surfaces: A Study in Humans |
Elisabeth AWJ De Wilde; Ryo Jimbo; Ann Wennerberg, Yoshihito Naito; Paul Coucke; Matthew S. Bryington; Stefan Vandeweghe; Hugo De Bruyn, |
2014 |
[11] |
The biocompatibility of silver and hydroxyapatite coatings on titanium dental implants with human
primary osteoblast cells |
Ranj Nadhim Salaie, Alexandros Besinis, Huirong Le, Christopher Tredwin, Richard D. Handy |
2019 |
[12] |
In vivo biofunctionalization of titanium
patient specific implants with nano hydroxyapatite and other nano calcium phosphate coatings: A systematic review |
Alexander Bral, Maurice Y. Mommaerts |
2022 |
[13] |
In vitro assessment of the biological response of Ti6Al4V implants coated with hydroxyapatite microdomains |
Salvador Clavell, Martín de Llano, Carda; Gómez Ribelles, Vallés-Lluch |
2015 |
[14] |
Systematic Review of Current Dental Implant Coating Materials and Novels Coating Techniques |
Maria Xuereb, Josette Camilleri, Nikolai J. Attard, |
2020 |
[15] |
Effect of Induced Periimplantationitis on Dental Implants with and Without Ultrathin Hydroxyapatite Coating |
Marwa Madi, Osama Zakaria, Shizuko Ichinose, and Shohei Kasugai |
2019 |
[16] |
Hydroxyapatite coating techniques for Titanium Dental Implants—an overview |
Arati Sharma, BPKoirala |
2015 |
[17] |
Effects of a hydroxyapatite coating on the stability
of endosseous implants in rabbit tibiae |
Magdalena Łukaszewska-Kuska, Piotr Krawczyk, Agnieszka Martyla, Wiesław Hędzelek, Barbara Dorocka-Bobkowska |
2016 |
[18] |
Bio-implant as a novel tooth restoration loss |
Dong-Joon Lee, Jong-Min Lee, Eun-Jung Kim,
Takashi Takata, Yoshihiro Abiko, Teruo Okano,
David W. Green, Masaki Shimono & Han-Sung Jung |
2015 |
[19] |
Combined antibacterial and osteogenic in situ
effects of a bifunctional titanium alloy with
nanoscale hydroxyapatite coating |
Hua-Wei Liu, Dai-Xu Wei, Jiu-Zheng Deng,
Jian-Jin Zhu, Kai Xu, Wen-Hao Hu,
Song-Hua Xiao & Yong-Gang Zhou |
2015 |
[20] |
Microstructure and Wear Behavior of Ti
Reinforced HVOF Coating |
Szabo, ID Utu, I Hulka, l Bordeasu and I Mitelea |
2023 |
[21] |
Surface characterization and osteoblast response to a
functionally graded hydroxyapatite/
fluorohydroxyapatite/titanium oxide coating on
titanium surface by sol–gel method |
G. He, B. Guo, H. Wang, C. Liang, L. Ye, Y. Lin and X. Cai |
2019 |
[22] |
Immediate and early loading of hydrothermally
treated, hydroxyapatitecoated dental implants:
a 7-year prospective randomized clinical study |
A. Arghami, D. Simmons, J. St. Germain and P. Maney |
2017 |
[23] |
Randomized controlled clinical trial of 2 types of
hydroxyapatitecoated implants on moderate
periodontitis patients |
Hyun-Suk Kim, Pil-Young Yun, Young-Kyun Kim |
2018 |
[24] |
Preparation of Bone-Implants by Coating
Hydroxyapatite Nanoparticles on Self- formed
Titanium Dioxide Thin-Layers on Titanium Metal
Surface |
WPSL Wijesinghe, MMMGPG Mantilaka, KG
Chathuranga Senarathna, HMTU Herath, TN
Premachandra, CSK Ranasinghe, RPVJ Rajapakse, RMG Rajapakse, Mohan Edirisinghe, S. Mahalinga |
2018 |
[25] |
Production of hydroxyapatite layers on the plasma
electrolytically oxidized surface of titanium alloys |
Alex Lugovskoy, Svetlana Lugovskoy |
2014 |
[26] |
Nanoporous hydroxyapatite/sodium titanate bilayer
on titanium implants for improved osteointegration |
A. Carradò, F. Perrin-Schmitt, QV Le, M. Giraudel, C. Fischer, G. Koenigb, L. Jacominec, L. Behr, A. Chalome, L. Fiettee, A. Morlet, G. Pourroy |
2016 |
[27] |
Taking Hydroxyapatite-Coated Titanium Implants Two Steps Forward: Surface Modification Using
Graphene Mesolayers and a Hydroxyapatite-
Reinforced Polymeric Scaffold |
AM Fathi, MK Ahmed, M. Afifi, AA Menazea, and Vuk Uskokovic |
2020 |
[28] |
comparative study of zinc, magnesium,
strontiumincorporated hydroxyapatite-coated
titanium implants for osseointegration of
osteopenic rats |
Zhou-Shan Tao, Wan-Shu Zhou, Xing-Wen He, Wei Liu, Bing-Li Bai, Qiang Zhou, Zheng-Liang Huang, Kai-kai Tu, Hang Li, Tao Sun, Yang-Xun Lv, Wei Cui, Lei Yang |
2016 |
[29] |
Titanium Dental Implants: An Overview of Applied
Nanobiotechnology to Improve Biocompatibility
and Prevent Infections |
Rayane CS Silva, Almerinda Agrelli, Audrey N.
Andrade, Carina L. Mendes-Marques, Isabel RS
Arruda, Luzia RL Santos, Niedja F. Vasconcelos and Giovanna Machado |
2022 |
[30] |
Bioactivity and Mechanical Properties of
Hydroxyapatite on Ti6Al4V and Si (100)
Surfaces by Pulsed Laser Deposition |
Salizhan Kylychbekov, Yaran Allamyradov,
Zikrulloh Khuzhakulov, Inomjon Majidov Simran Banga, Justice ben Yosef, Liviu Duta and Ali Oguz Er |
2023 |
[31] |
Effect of Er: YAG Pulsed Laser-Deposited
Hydroxyapatite Film on Titanium Implants on M2
Macrophage Polarization In Vitro and
Osteogenesis In Vivo |
Lin Ma, Min Li, Satoshi Komasa, Shigeki Hontsu,
Yoshiya Hashimoto, Joji Okazaki and Kenji
Maekawa |
2023 |
[32] |
Vapor-Induced Pore-Forming Atmospheric
-Plasma- Sprayed Zinc-, Strontium-, and
Magnesium-Doped Hydroxyapatite Coatings on
Titanium Implants Enhance New Bone Formation—An In Vivo and In Vitro Investigation |
Hsin-Han Hou, Bor-Shiunn Lee, Yu -Cheng Liu, Yi-Ping Wang, Wei-Ting Kuo, I-Hui Chen,
Ai-Chia He, Chern-Hsiung Lai, Kuo-Lun Tung
and Yi-Wen Chen |
2023 |
[33] |
4. Discussion
4.1. Titanium and Its Alloys
Titanium, the ninth most common metal, was discovered by William Gregor in 1791. Low density (4.506g/cm3) and high strength (590 MPa) are some of the characteristic physical and chemical properties of the silver metal in its form pure. Titanium and its biocompatibility are obtained thanks to the oxide layer present on its surface. Under ambient conditions, TiO2 occurs in three crystalline forms:
- Rutile;
- Brookite;
- Anatase.
At the end of the synthesis, a heat treatment allows phase transitions. Brookite, arranged in an orthorhombic geometry, is the most difficult phase to obtain, while rutile and anatase are easily formed. The distortions between the octahedron formed by TiO6 are the reason why the rutile and anatase phases differ. Various techniques ranging from hydrothermal to electrochemical techniques are employed to create these structures. Therefore, the preferential formation of one of the predicted phases is caused by changes in the physicochemical parameters of the synthesis. Titanium and its alloys are considered non-toxic and even more biocompatible than cobalt-chromium and stainless steel in the dental industry. They are also compatible with CT and MRI scans and are used to make dentures and implants [30].
Titanium alloys have the following properties:
- Low elastic modulus,
- Thin,
- Biotolerance,
- Good corrosion resistance,
- Paramagnetic properties,
- High strength
- Strong tendency towards self-passivation.
Ti-6Al-4V is a titanium alloy commonly used for endoprosthesis, though its long-term use may release toxic elements, which will be deposited in the brain and cause cancerous reactions. To adress this, new alloys were developed that did not contain the toxic elements mentioned above and enhanced biocompatibility. These alloys exhibit a lower elastic modulus than other metallic biomaterials, though still higher than the elastic modulus of the bone, enhancing implant resistance to stress and bone tissue regeneration. Anatase is often associated with applications requiring osseointegration and is therefore most commonly used in dental implants [1] [30].
Titanium is currently the most widely used material for manufacturing dental implants, although ceramics and polymers are also available. There are six types of titanium for implants: four grades of commercially pure titanium (CPTi) with a purity of 98 to 99.6%, and two alloys (Ti-6Al-4V and Ti-6Al4V-Extra Low Interstitial alloys) with very weak interstitials. These categories are distinguished by their ductility, strength and corrosion resistance, linked to residual oxygen in the metal. CpTi Grade IV, with an oxygen content of 0.4%, is most commonly used for its mechanical strength [30].
4.2. Hydroxyapatite and Its Applications in Dental Implantology
4.2.1. Structure of Hydroxyapatite
Hydroxyapatite (HA) (Figure 1) is a mineral form of natural calcium apatite with the formula Ca5(PO4)3(OH).
Ca10(PO4)6(OH)2 is usually written to indicate that the crystal unit cell includes two elements [4].
Figure 1. Molecular structure of hydroxyapatite [4].
4.2.2. Applications in Dental Implantology
Hydroxyapatite has been used for many years as a coating for titanium implants (Figure 2 and Figure 3) and has achieved promising results [4].
According to some reports, HA is directly linked to bone, as there is no precise cause for this phenomenon more biological and clinical research is needed. Recently, nanotechnology has enabled the low-cost preparation of hydroxyapatite in micro and nano forms, increasing reactivity and surface area through “bottom-up” methods, as a result developping HA nano-cast dental implants that are capable of creating a chemical connection with the bone, promoting better bone integration and better biological fixation. However, controversies persist regarding HA-coated implants, with difficulties in correlating the properties of the coatings to their influence on bone formation and the long-term success and survival of the implants, due to limited data and variabilities between the studies reported on: [3] [4]
- The definition and duration of survival/success of the implant;
- The implant case and site selection;
- Surgeon experience, surgical protocols, post-operative regimens, recovery process;
- The characteristics of the coating and the prosthetic restoration.
Since 1981, efforts have been made to improve osseointegration and osteogenesis of dental implants by HA coatings, although these are more fragile compared to zirconium aluminum oxide ceramics, the hydroxyapatite has been studied for its use as a coating on metal implants, for its porous structure and resembles the inorganic structure of teeth and bone [9] [17].
Figure 2. Titanium implant coated with hydroxyapatite [6].
Figure 3. Dental implants (by Friadent ) coated with CaP by a plasma spray process (a: 10×, b: 1000× magnification; a : 1mm; b: 10 μm scale bars) [7].
In alkaline and neutral aqueous solutions, HA dissociates quite quickly. It was thought that the negative effects on bone formation were minimal; here, the release of unwanted metal ions is caused by the disruption of HA on the passive oxide layer of the titanium implant surface. According to the literature, HA-coated implants show better bone integration, reaching 75.9% after three months, compared to 45.7% for titanium metal implants, although after six months, there is no significant difference between ceramic coated and uncoated metal implants. It should also be noted that the HA coating helps create an additional interface between the bone surface and the implant, which could be a potential cause of failure. Nanocrystalline HA powders, used for coating, have improved synthesis capacity, increased surface area and better densification, reducing the synthesis temperature. Clinical studies have revealed that HA-coated titanium implants have greater longevity than uncoated ones [7] [9] (Figure 4).
![]()
Figure 4. Plasma-sprayed HA coating shows improvement in strength compared to uncoated porous titanium [7].
4.2.3. Synthesis of Hydroxyapatite
There are many ways in which hydroxyapatite can be synthesized. Here are the most common methods [7] [9]:
- Wet methods including precipitation method, hydrothermal techniques and calciumphosphate hydrolysis.
- Solid state reactions.
- Ultrasonic irradiation.
- Sol-gel method.
- Microwave irrigation.
- Chemical precipitation.
- Microemulsion.
4.3. Hydroxyapatite Coating Processes
For hydroxyapatite to be used as a dental implant coating, the following conditions must be met: crystallinity of 62%, phase purity of 95%, density of 2.98 g/cm3, a Ca/P ratio of 1.67 to 1.76, a cutting strength of more than 22 MPa and a tensile strength of more than 50.8 MPa [9].
The following figure shows the different methods used to coat implants with hydroxyapatite. (Figure 5)
Plasma spraying is a common method for applying hydroxyapatite coatings on implants. Studies have shown that the coating is prone to cracking and lack of adhesion. The temperatures required during the coating process can have negative effects on the prosthesis, such as a change in the crystal structure, the formation of a highly crystallized HA surface, and possible misorientation of the layer [9].
Figure 5. Some hydroxyapatite coating methods [9].
This method requires the application of an electrical charge to both the surface of the hydroxyapatite and the titanium implant. The electrically charged hydroxyapatite particles are attracted to the implant surface and deposit there, creating a uniform coating. The ceramic layers are produced using the electrophoretic deposition (EPD) technique. It is an electrochemical process that takes place in a colloidal environment. In this procedure, a titanium implant is immersed in a solution containing calcium and phosphate ions, which react on the surface of the implant to form hydroxyapatite [9] (Figure 6).
Figure 6. Electrophoretic equipment [1].
The process begins by dispersing the precursor particles in an aqueous or alcoholic solution, creating a colloidal suspension, also called sol. Subsequently, the addition of catalysts to the soil promotes polymerization reactions with hydrolysis and polycondensation, which form a gel (See Table 2). The dip coating method (DCM) involves well-controlled immersion. The DCM includes five different phases [9]
1) Immerse the pretreated titanium implant into the coating mixture at a specified rate.
2) Leave the implant immersed in the mixture for a while.
3) Remove the implant from the mixture, causing a film of liquid to form on the surface of the implant.
4) Drain the excess liquid to apply the new fixation to the implant surface.
5) Nanocrystalline hydroxyapatite can be synthesized using a variety of techniques, including hydrothermal, mechanochemical, precipitation, hydrolysis, and sol-gel.
This technique requires the use of a cathodic arc to vaporize the specific hydroxyapatite, which is then applied to the surface of the titanium implant. Electrochemical deposition is a process in which a solution containing the desired metal ion or its chemical complex can be electrolyzed to produce a thin, adherent layer of metal, oxide, or salt on the surface of a conductive substrate. By adjusting electrochemical deposition parameters such as pH, temperature and voltage as well as immersion time during the coating process, this technique can overcome the phase transition problems of HA coatings caused by PS and change the morphology of the HA coating [9].
This is a relatively new method that produces heterogeneous nucleation and crystal growth of the coating with tissue-like properties. To do this, the implant surface is pretreated with alkaline (NaOH) or acidic (HF or HCl) solutions or heat treatment. The substrate is then immersed in simulated body fluid (SBF) at a body temperature of 37 degrees Celsius and a physiological pH of 7.4. SBF should have an ionic concentration similar to that of human blood plasma. CaP-based coatings are deposited on the implant surface after several weeks of SBF [17].
It is a new method for obtaining dense nanostructured surface coatings on the surface of a titanium implant. The powder is dispersed in an aqueous or organic solvent and introduced axially to the combustion chamber of a high-speed oxy-combustion modified spray cloth. This is because traditional high-velocity oxygen spray (HVOF) processes are not suitable for producing nanoparticle coatings. The powder is processed as a suspension (in an aqueous or organic solvent) to solve problems associated with handling nanoparticle powders, and its delivery is facilitated by relatively simple thermal spraying techniques [17].
These are vacuum deposition techniques in which materials are vaporized or pulverized. Two physical processes can be used to generate steam:
1) Thermal evaporation: The material is heated until its vapor pressure exceeds ambient pressure.
2) Cathodic sputtering and ejection of neutral atoms, for example by moving an ion beam and sputtering a magnetron. It is very useful for the deposition of HA [17].
CVD and PVD are similar in the basic process of using steam and creating a thin film on a substrate. It does not produce vapor from a solid or liquid source in the vacuum chamber, which distinguishes it from PVD. Instead, vapors or gases are introduced into the chamber from an external source and, following a chemical reaction, are deposited on the substrate surface as non-solid volatiles in many directions. Unlike PVD, it is based on the chemical reaction of precursors in the gas phase [17].
It is a physical vapor deposition (PVD) method in which a high-power pulsed laser is focused in a vacuum chamber to target the material to be deposited. In this situation, a laser with high power density and narrow frequency bandwidth is used as the evaporation source for the desired material, and there are almost no restrictions on the material used. This method can be considered when other methods have failed to achieve deposition and have been used to synthesize nanotubes and nanopowders [17].
Table 2. The following table shows the advantage/disadvantage ratio of the different techniques used [9].
Technical |
Thickness |
Benefits |
Disadvantages |
Thermal spraying |
30 - 200 nm |
High deposit rate Low cost |
High temperatures Induces decomposition Rapid cooling produces amorphous
coatings |
Pulsed laser deposition |
0.05- 5 mm |
The coatings are crystalline amorphous
dense and porous |
sight technique |
Dynamic mixing
methods |
0.05 - 1.3 mm |
High adhesive strength |
sight technique Expensive Produces amorphous coatings |
Dip coatings |
0.05 - 0.5 mm |
Coatings are inexpensive and can be applied
quickly Can cover complex surfaces |
Requires high synthesis temperatures Thermal expansion fault |
Sol-gel |
<1 mm |
Used to cover complex shapes Low processing temperatures Cheap process because the coatings are very thin |
Some processes require controlled
amorphous processing Expensive raw materials |
Electrophoretic
deposition |
0.1 - 2.0 mm |
Uniform coating thickness Fast deposit rate Can be used to coat complex substrates |
Difficult to produce coatings without
cracks Requires high synthesis temperatures |
Biomimetic coating |
<30 mm |
Low processing temperatures Results in the formation of bone apatite Can take on complex shapes May incorporate bone growth stimulating
factors |
Time consumption Requires constant filling and pH of
stimulated body fluid |
Hot isostatic pressure |
0.2 - 2.0 mm |
Produces dense coatings |
Impossible to cover complex substrates High temperature required Thermal expansion fault Difference in elastic property Expandable Interaction of the encapsulated material |
Cathode sputtering |
0.5 - 3 mm |
Uniform coating thickness on flat substrates Dense coatings |
sight technique Expensive Time-consuming This technique produces amorphous
coatings |
4.4. Overall Clinical Performance of Hydroxyapatite-Coated Dental Implants
4.4.1. Representative Table
We compiled 18 studies (Table 3) from various authors who conducted research with the aim of exploring the clinical performance of HA-coated Ti dental implants and improving the osseointegration and biocompatibility of these devices.
Table 3. Representative table of the results of the selected articles.
Name of authors |
Purpose of the experiment |
Method |
Status |
Results |
López Valverde et al. [2] |
To evaluate the osseointegration
effectiveness of titanium (Ti) dental
implants using bioactive surfaces compared to that of Ti implants using conventional surfaces |
Following PRISMA guidelines, relying on the PICO framework for search strategy,
selection of independent reviews and
assessment using the Cochrane
Collaboration tool. |
Systematic review |
Bioactive surfaces on dental implants improve osseointegration. Bone-to-implant contact
surface area is higher for bioactive surfaces
compared to control implants. Certain coating biomolecules have an early impact of the
peri-implant on bone formation. |
Mistry et al. [5] |
Analysis and comparison of the clinical
results (osseointegration) of dental implants in hydroxyapatite, bioactive glass and
titanium alloy wire-machined in the human jaw bone after their implantation. |
Evaluations of the result up to 12 months after prosthetic rehabilitation based on different
clinical and radiological criteria. The use of
the laser profilometer to evaluate the surface roughness of the implants studied. |
In vivo |
Safety and osseointegration efficiency is
higher in bioactive glass coated implants than hydroxyapatite coated and machined
titanium implants. They can be used as an
alternative coating for dental implants. |
Madi et al. [16] |
To analyze the consequences of peri-
implantitis caused by ligation on dental
implants with and without hydroxyapatite (HA) coating. |
Histological examination of implants
containing surrounding tissues that were
inserted into the jaws of canines, with 4
surface treatments. The study of implant
surfaces and bone-to-implant contact (BIC) using scanning electron microscopy and
energy-dispersive X-ray spectroscopy. |
In vivo |
Histological analysis: Decrease in bone around the implant and extensive infiltration of
inflammatory cells into the surrounding soft
tissue. The BIC (Bone-to-implant contact) of
sputtered HA implants was highest (98.1%)
than machined implants (70.4%). The
disappearance after 28 weeks of the HA layer of cathode sputtering unlike plasma sputtering. |
Mela et al. [8] |
To analyze the performance of
nano-hydroxyapatite coating and bone
integration of early loaded dental
implants in the posterior jaw. |
In the Department of Oral and Maxillofacial Surgery of the Faculty of Dentistry of
Mansoura University in Egypt, carrying out
a clinical study on ten patients who need
twelve implants (root-shaped) with early
loading. |
In vivo |
Increase in the surface energy of titanium by the HAnano® coating combined with its
microtopography. |
Clavell et al. [14] |
Optimize HA coating times to stabilize
bone surfaces of Ti-6Al-4V samples and
evaluate cell adhesion and growth to
determine the effect of HA topographies
and identify the best acellular coating time
for development optimal biological. |
The method employed consists of proposing an in vitro ceramic coating, evaluating
optimal coating times, performing SEM and EDS analyses, as well as experimenting with human dental pulp stem cells. |
In vitro |
Treatment of titanium alloys with HA
coatings by simulated immersion of body
fluid and the formation of porous clusters of HA cauliflores on a flat coating, after 8 to 12 days. Change in the composition of the
ceramic layer initially into salts then apatites, with a Ca/P ratio comparable to that of
physiological hydroxyapatite. Short
incubation periods promote cell adhesion,
while long culture periods result in
hydroxyapatite deposition. |
Bral and Mommaerts. [13] |
To describe the best procedures for
increasing osseointegration in
cranio-maxillofacial surgery using nano
calcium phosphate coatings on
patient-specific titanium implants. |
A systematic review of the literature using a multiple database and a single reviewer was performed. Twenty-eight works composed of
twenty-five studies on animals and three on humans |
Systematic review |
Titanium implants coated with calcium
nanophosphate and hydroxyapatite improve osseointegration and implant fixation. While not all coating techniques improve
biofunctionalization. Implant
microroughness, coating thickness, calcium phosphate solubility, and nanotopography
contribute significantly to
biofunctionalization. However, additional
clinical studies are needed to confirm this. |
Świeczko et al. [1] |
To analyze how the electrophoretic method
is used to create hydroxyapatite coatings on
titanium alloys and evaluate the benefits of electrophoretic deposition (EPD) in
creating ceramic layers. |
Samples of Ti-6Al-4V and Ti1-3Zr1-3Nb
alloys were cut, polished and coated with
hydroxyapatite to conduct electrophoretic
studies. After applying a solution of
hydroxyapatite in ethyl alcohol, they were
heated at 500˚C for 20 minutes and
subjected to 60V of electricity for 7 minutes. The samples were analyzed using an
electron microscope and then immersed in bacterial liquid for 1 - 3 months to observe bacterial adhesion with a biological
microscope. |
In vitro |
Ti13Zr13Nb alloy was not associated with
bacteria and biofilms after 6 months, while
Ti-6Al-4V bond showed separated bacteria after 3 months and full biofilm coverage after 6 months. The EPD method quickly forms layers that can be controlled in thickness and morphology, and the hydroxyapatite coatings increase abrasion resistance and protect
against unwanted compounds. |
Kato et al. [6] |
To retrospectively analyze the 10-year
clinical results of HA-coated implants
(HA implants) by comparing them with the
same system implants with a titanium
oxidized anodic surface (Ti implants). |
Life table analysis was used to calculate the cumulative survival rate (CSR) of HA or Ti implants implanted in 183 patients (55 aged
12.4 years) over a twenty-year period. RCS differences were compared in each year
based on interval, gender, age and frequency of number of placements based on location and implant diameter for both implant
types. |
In vivo |
HA implants showed better long-term
stability at the upper molar site compared to Ti implants, with cumulative success rates of 89.9% and 77.7% respectively after 10 years. HA implants showed a preferential
distribution at the upper molar site and
tended to have a larger diameter than
Ti implants, with no notable variation in
RCS over the course of a year. |
Salaie et al. [12] |
improving the biocompatibility of Ag
NP-coated titanium dental implants
with surface-applied hydroxyapatite (HA) |
The experimentation involved coating a
medical titanium alloy with an Ag NP
surface for an antibacterial coating, then
adding a layer of hydroxyapatite for
biocompatibility. The coatings were
prepared and characterized, then osteoblast cells were cultured on these discs for seven days to assess their health and function. |
In vitro |
Silver and HA nanoparticles were successfully applied to implants, providing long-lasting coatings and slow release of silver over 7 days. Osteoblasts retained normal morphology and 70% viability with Ag-nHA, demonstrating superior biocompatibility to Ag-mHA or Ag alone. |
Sartoretto et al. [10] |
To analyze implant surface structure and
biomechanical, histomorphometric and
histological bone reactions to a novel
nanostructured hydroxyapatite surface
implanted in the iliac crest of sheep. |
This study compares three types of dental implants in female sheep aged 2 to 4 years. Thirty implants (n = 10/group): HAnano® coated (Epikut Plus®, SIN Implant System, Sao Paulo, SP, Brazil), SLActive (BLX®, Straumann, Basel, Switzerland) and TiUnite ( NobelActive®, Nobel Biocare, Gothenburg, Sweden) were analyzed for their
topography, insertion torque value, and
resonance frequency via electron
microscopy. Primary stability,
bone-to-implant contact and bone fraction were assessed after 14 and 28 days. |
In vivo |
The implant surfaces were similar, except for TiUnite®, which stood out. The average
insertion torques were 74 (±8.9) N/cm for
SLActive® and TiUnite®, and 72 (±8.3) N/cm for HAnano® (p > 0.05). All groups showed a significant increase in bone-to-implant
contact and bone fraction rates after four
weeks, reaching over 80% and approximately 60% respectively, with no significant
differences between groups. |
Łukaszewska-Kuska et al.
[18] |
endosseous titanium implants in rabbits
using a modified electrochemical method. |
Rabbit tibias were fitted with titanium
implants with HA coatings and controls with gritt-blasted Al2O3 surfaces. The
chemical composition, roughness and
morphology of the implants were
established. Implant stability tests were
carried out and Periotest ® (PTV) and
Implant Stabilization Coefficient (ISQ)
values were recorded for Osstell Mentor to assess their bone integration. |
In vivo |
Implant surface characteristics impact
implant stability, as shown by Osstell and Periotest measurements. The HA coating mentioned in this paper exhibited chemical and physical characteristics that appeared to favor osseointegration compared to grit -blast implants. |
Lee et al. [19] |
The aim is to demonstrate that different
human periodontal cells can be combined
on a titanium implant. |
The bio-implants, which are made of
hydroxyapatite-coated titanium screws, are used to coil cell sheets from immortalized human periodontal cells, which have been
transplanted into a mouse model used for
dental extractions. A stereomicroscope was
used to analyze the tissues by excising,
fixing, decalcifying and staining them. |
In vivo |
Over the course of 8 weeks, the bio-implant
promoted the formation of fibrous
connective tissue, blood vessels and bone
growth integrated into the alveolar bone base. The use of human cells allowed a partial
reconstruction of the natural dental
attachment complex, including cement, PDL and alveolar bone. Research has
demonstrated that periodontal tissues can be restored with cell sheets around the dental
implant, without the use of embryos. |
Liu et al. [20] |
Development of a dual-functional titanium
alloy with nano-hydroxyapatite coating for sustained release of HBD-3 and BMP-2,
providing protection against bacterial
infections in orthopedic and dental clinic,
while improving osteogenesis of implants
in titanium in dental and bone treatments. |
The method involved manufacturing HA-Ti using a dip coating technique, loading it
with HBD-3 and BMP-2, and evaluating the
encapsulation efficiency using specific
genetic markers. |
In vivo |
The bio-functional titanium alloy with
nano-hydroxyapatite coating enabled
sustained release of antimicrobial peptides
b- defensin 3 (HBD-3) and bone
morphogenetic protein2 (BMP-2). This
material inhibited the growth of
Gram-negative and Gram-positive bacteria after 7 days of incubation, with an absence of viable bacteria. Furthermore, it promoted the adhesion, proliferation and osteogenic
differentiation of human bone marrow
mesenchymal stem cells (hBMSCs) under the same conditions. |
Szabo et al. [21] |
Develop Al2O3-HA coatings by HVOF
sputtering to improve the wear resistance
and biocompatibility of titanium substrates.
The incorporation of alumina into these
coatings significantly increases the
durability of titanium |
The methodology involved the use of a
high-velocity oxygen fuel (HVOF) thermal spray process for coating deposition,
scanning electron microscopy (SEM) and
X-ray diffraction techniques for
identification of microstructure and phase, measuring surface roughness and
determining sliding wear using a pin on the disk tribometer. |
In vitro |
Al2O3-HA coatings significantly improve the wear resistance of the titanium substrate, with the presence of alumina improving the wear
resistance by approximately 2 - 3 times. The
structure of hydroxyapatite has not
undergone significant changes, which is
important for the restoration of bone tissue. |
He et al. [22] |
Improving the performance of common
titanium and its alloys, with regard to their
bioactivity and their speed of
osseointegration, in the field of
orthopedic implants. |
A functional triple-layer coating, consisting
of a porous outer layer of hydroxyapatite
(HA), an intermediate fluoro -HA layer
(FHA) and an inner layer of titanium oxide
(TiO2), was developed on a titanium
substrate using a multi-step sol-gel method. Using X-ray diffraction, the presence of
anatase TiO2 and apatite crystallization was noted in the coating. |
In vitro |
Electron microscopy revealed strong bonding
of the ~2 mm thick coating, with good
adhesion resistance. Tests showed excellent biological compatibility and osteoblasts with
better proliferation and ALP activity than
pure titanium or HA coatings. |
Yazdani et al. [4] |
To examine the impact of
nano-hydroxyapatite on osseointegration
of titanium implants by conducting a
literature review, analyzing implant and
nanotechnology data, evaluating the ability of HA nanoparticles to bind to tissues
dental, determining the long-term stability of the HA/bone interface and identifying needs for future research on the
cell-substrate interface to optimize
implants. |
The methodology used in the study involved a literature review using electronic databases and MeSH keywords to collect relevant
literature published in English on the effect of nano-hydroxyapatite on osseointegration of implants. titanium, without any
limitation on the publication date. Data
regarding titanium implants,
nanotechnology, nano-hydroxyapatite,
osseointegration and cell attachment were
collected and reviewed. |
Literature review |
Hydroxyapatite coatings for dental materials have shown improved bone tissue integration to the coating implant surfaces. The release of calcium and phosphate ions from HA coatings as a result of degradation and dissolution may play a role in accelerating bone adaptation to these surfaces. The degree of crystallinity of HA plays a key role in the initial cellular interaction with implant surfaces. |
Kylychbekov et al. [31] |
The use of pulsed laser sputtering makes it
possible to study the effects of substrate
temperature on the properties of
hydroxyapatite (HA) coatings applied to
Ti6Al4V and Si(100) surfaces. The analyzes
focus on the structural, mechanical and
bioactive properties of the coatings, taking
into account the deposition temperature
and the ablation process. |
The Si(100) and Ti6Al4V surfaces received
HA coatings. The substrate temperature
varied from room temperature to 800˚C.
The depositions were carried out in Ar/H2O
environments and under vacuum.
Structural and morphological variations
were analyzed by X-ray diffraction,
scanning electron microscopy and atomic
force microscopy. The shrinkage method
was used to evaluate the adhesion of the
coatings to the substrates. |
In vitro |
The coatings crystallize uniformly at
increasing temperatures, but above 700˚C,
protein adsorption and adhesion properties
degrade. Tests show that crystallinity,
influenced by deposition conditions, is
crucial to coating performance. However, the morphostructural, mechanical and bioactive properties deteriorate above 700˚C. |
Ma et al. [32] |
To study the effect of a hydroxyapatite layer deposited on titanium implants with a
pulsed erbium-doped yttrium and
aluminum laser on the polarization of
M2 type macrophages in vitro and on
osteogenesis in vivo |
In vitro and in vivo experiments to evaluate
the effect of a laser-applied hydroxyapatite
layer on titanium implants. Titanium plates
and screws were coated with hydroxyapatite
and polarization by M2 macrophages,
osteogenic properties and osseointegrative
activity were evaluated. |
In vitro/In vivo |
Erbium-doped hydroxyapatite-coated
titanium implants improve hard tissue
differentiation, M2 macrophage polarization, and bone formation, providing improved
osseointegration and long- term clinical
success |
Hou et al. [33] |
multidoped HA coatings on titanium discs
and implants to improve both osteogenesis
and antibacterial properties against
Porphyromonas gingivalis and Prevotella
nigrescens |
Human embryonic palatal mesenchymal
cells were analyzed for mRNA and protein
levels of osteogenesis-related genes
(COL1A1, DCN, TNFRSF11B, SPP1).
Antibacterial properties against
Porphyromonas gingivalis and Prevotella
nigrescens have been studied. Histological examination and CT scan assessed bone
formation in rats |
In vivo |
ZnSrM-HA group showed the best results
in stimulating the expression of key mRNAs and proteins and exhibited significant bone growth. Additionally, ZnSrMg-HA and
Zn-HA groups were found to be effective against P. gingivalis and P. nigrescens. A
porous coating of ZnSrMg-HA with
VIPF-APS could be innovative for coating
titanium implants and preventing bacterial
infections. |
4.4.2. Table of Figures (see Figures 7-12)
Name of authors |
Figures |
Łukaszewska-Kuska et al. [18] |
Figure 7. Implant stability test with an Ostell device. Measurements were made in 2 directions, with the instrument parallel and perpendicular to the longitudinal axis of the tibia. Mean ISQ values were recorded [18]. |
Figure 8. Testing implant stability with a periotest. The measurements were made at the same point from the rolled abutment to the implants. During measurements, the Periotest handle was always kept perpendicular to the abutment axes [18]. |
Figure 9. Values of the stability coefficient of HA-coated and sandblasted implants at the time of implantation and after 2 weeks of healing. Each value is a mean ± standard deviation (SD). Statistically significant differences were observed for measurements between the time of implantation and the time of sacrifice for HA-coated implants (p = 0.006), while for Al2O3 coated implants there were had an increase in ISQ values, not significant (p = 0.15). [18] |
Figure 10. Periotest values of HA-coated and sandblasted implants at the time of implantation and after 2 weeks of healing. Each value is a mean ± standard deviation (SD). Statistically significant differences were observed between measurements between the time of implantation and the time of animal sacrifice for the Al2O3 sandblasted implants (p = 0.01) and for the implants coated with a HA coating (p = 0.04). [18] |
by Liu et al. [20] |
Figure 11. A biofunctional titanium alloy with a nano-hydroxyapatite coating (HBD þ BMP/HA-Ti), which enables sustained simultaneous release of the natural antimicrobial peptide human b-defensin 3 (HBD-3) and bone morphogenetic protein-2 (BMP-2). It shows combined antibacterial and osteogenic effects for potential application in clinical dental and bone therapy. [20] |
He et al. [22] |
Figure 12. Electron microscopy scanning the morphology of osteoblasts cultured on the TiO2/FHA/HA coating after (a) 1 day; (b) 3 days; (c) 5 days and (d) 7 days. [22] |
4.4.3. Clinical Performance Aspects of Hydroxyapatite-Coated Ti Dental Implants
From the results of this compilation we have raised several aspects of the clinical performance of Ti dental implants coated with hydroxyapatite:
- Improved osseointegration: Results show significantly improved bone-to-implant contact compared to untreated or conventional surfaces, as hydroxyapatite-coated surfaces appear to promote better bone integration. This indicates better stability and anchoring of the implants in the surrounding bone [2] [4] [5] [8] [13] [18] [31]-[33].
- Reduction of infections: Some coatings, such as those that combine silver nanoparticles with hydroxyapatite, show a slow, prolonged release of silver, which can help prevent bacterial infections around dental implants [1] [31] [33].
- Increased Biocompatibility: It appears that hydroxyapatite coatings promote better adhesion, proliferation and differentiation of bone cells, which contributes to a favorable cellular response and better integration of implants with surrounding bone tissues [12] [20] [31] [32].
- Long-term durability and stability: According to long-term studies, hydroxyapatite-coated implants may provide superior long-term survival and stability compared to uncoated implants. These results are essential to guarantee the long-term success of implant -prosthetic treatments [7] [16] [21] [31].
- Reduced risk of inflammatory reactions: Hydroxyapatite coatings can help prevent inflammatory reactions around implants by promoting better integration with bone tissue and reducing unwanted immune response [12] [20] [33].
- Potential for tissue regeneration: Certain coatings, such as those that combine human periodontal cells with hydroxyapatite, have the potential for periodontal tissue regeneration, offering therapeutic prospects for reconstruction of the tooth attachment complex and tissue regeneration periodontal [19] [20] [31] [33].
4.5. Comparision with Conventional Dental Implants Not Coated
with Hydroxyapatite
Hydroxyapetite-coated implants present several advantages over conventional implants, particularly in osseointegration and long-term performance. The following overview outlines key differences and similarities between the two:
- Effectiveness of osseointegration: Dental implants with bioactive surfaces show potential for improvement over conventional surfaces, according to limited studies [2] [5].
- Bone-implant contact surface: HA-coated implants provide a more favorable bone-implant contact surface than conventional implants, with a statistically significant distinction [2].
- Favorable effect on osseointegration: Some bioactive coatings have demonstrated a positive effect on osseointegration by influencing bone formation around the dental implant [2].
- Long-term survival: HA-coated implants showed a higher cumulative survival rate up to 8 years after placement, particularly at the upper molar site, although no significant differences were observed after 10 years [6] [23].
Clinical studies have also shown that the lifespan of an implant coated with an HA layer is much longer than that of the implant without a layer [7].
- Effective alternative: Bioactive glass implants may be as effective as HA-coated titanium implants in achieving osseointegration, providing an alternative to conventional implants [5] [24].
- Risk of peri-implantitis: Implants fully coated with HA do not appear to significantly increase the risk of peri-implantitis compared to implants partially coated with HA [24].
- Biocompatibility: Implants coated with nano-hydroxyapatite present biocompatibility similar to conventional implants, according to studies carried out [11] [15].
Hydroxyapatite-coated implants show potential benefits in osseointegration and long-term survival compared to conventional implants, although additional studies are needed to confirm these findings and fully evaluate their clinical effectiveness.
4.6. Future Prospects
Thanks to their ability to promote rapid and effective osseointegration, Ti-HA dental implants represent a major advance in the field of restorative odontology and implantology. Here are some perspectives for future implants:
- Improved surface properties: Research focuses on optimizing the surface microstructure of HA-coated implants to improve cell adhesion and accelerate osseointegration. More biologically reactive surfaces can be obtained using sophisticated methods such as plasma or laser processing [26].
- Nano-coatings: Using HA nano-coatings on titanium implants can improve bone integration and release substances that promote bone healing and growth in a controlled manner. Nanocoatings can also improve the durability and corrosion resistance of implants [27].
- Biofunctionalization: Adding peptides or proteins that specifically promote bone cell adhesion and proliferation to implant surfaces can increase the efficiency of osseointegration. This could allow treatment to be tailored to the unique needs of each patient [29].
Models for computer-assisted surgical prediction and planning: The increased use of computer-assisted surgical planning (CAOS) to optimize implant positioning and the creation of predictive models to evaluate the success of osseointegration based individual patient characteristics could improve clinical outcomes [18].
- 3D printing technology: 3D printing allows the creation of personalized implants that perfectly adapt to each patient’s bone geometry, which can improve bone integration and reduce healing time [25].
- Long-term tracking and monitoring technologies: Creating technologies that can monitor the integrity and function of implants in real time could enable rapid intervention if problems arise, thereby increasing the long-term durability of implants [28].
These ideas are based on a deep understanding of the biological interactions between the implant-bone interface as well as technological advances in materials and engineering. They could significantly improve outcomes for patients who need dental implants in terms of functionality, comfort and aesthetics.
5. Conclusions
In this work, we review advances in the field of dental implantology, particularly the use of hydroxyapatite (HA)-coated titanium implants and their impact on improving clinical performance. According to research, these implants offer better osseointegration and biocompatibility, allowing a stronger bond between the implant and the bone. This improvement is essential for patients requiring dental reconstructions, as it provides a better quality of life through reliable and durable solutions. During our study, HA-coated implants were shown to promote faster recovery and reduce the risk of postoperative complications compared to conventional titanium implants. This difference represents a significant evolution in the practice of dental implants and provides patients and professionals with a safer and more effective option. Despite the obvious benefits, obstacles still need to be overcome, particularly regarding the cost and accessibility of these modern technologies.
Additional research is therefore necessary to optimize these implants, reduce their cost and make them more accessible to a wider population. Furthermore, it is important to deepen the understanding of the biological mechanisms underlying the improved osseointegration of HA-Ti implants in order to develop innovative strategies to further improve their performance.
This work highlights the importance of interdisciplinary collaboration in dental implant research by combining the efforts of biomaterials, biology, engineering and clinical dentistry to advance our understanding and skills in this area.
This research is expected to contribute to significant advances in the design and use of dental implants, improving the health and well-being of patients around the world. Remember that continued research and innovation are necessary to address remaining challenges and make these advanced solutions more accessible.
Conflicts of Interest
The authors declare no conflicts of interest.