Osseointegration and Biocompatibility of Zirconia Implants

1. Research Article: Citation date: 2021/10/09 Osseointegration and Biocompatibility of Zirconia Implants 2021 Page | 1 Vladyslav Pereverzyev IISS Galileo Galilei Department How to cite: Pereverzyev, V. (2021) ‘Osseointegration and Biocompatibility of Zirconia Implants’, ResearchBerg Review of Science and Technology, 1(1), pp. 1–8. Received: 2021/08/06 Available online: 2021/10/09 This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Abstract For over three decades, zirconia ceramics have been used in orthopaedic surgery, and they were just recently brought into dentistry as a metal substitute for crown and bridge construction, as well as implant abutments. Both osseointegrative and biocompatibility characteristics of zirconium dioxide have been demonstrated in experiments. This study investigates whether zirconia dental implants are a viable substitute to titanium dental implants in terms of osseointegrative and biocompatibility characteristics. The findings of this study indicate that Zirconia dental implants provide greater osseointegration and soft tissue response than titanium dental implants, in addition to outstanding aesthetic outcomes. In addition, Zirconia has exhibited predicted osseointegration, cell metabolism, and favorable tissue response in in vivo experiments, with some findings obtained under loaded conditions. Our findings also show that the inflammatory response and bone loss caused by zirconia implants are significantly lower than those caused by titanium implants, suggesting that zirconia is a biocompatible material. Keywords: Biocompatibility, Implants, Osseointegration, Zirconia

2. Introduction Dental implants have become a recognized therapeutic method that has changed the notion of restoring lost teeth since their inception over 40 years ago (Babbush et al., 2010). Because Page | 2 of its outstanding biocompatibility and mechanical characteristics, commercially pure titanium has recently become the material of choice for producing dental implants. Modern dental implantology considers titanium implants to be the gold standard (Kubasiewicz-Ross et al., 2017). Because of its outstanding biocompatibility and mechanical properties, as well as their lengthy, detectable record of predictable clinical achievement, outstanding biocompatibility and mechanical characteristics, ability to osseointegrate, and the fact that titanium implants are convenient to produce, commercially pure titanium has recently become the material of preference for manufacturing dental implants. Titanium has a number of cosmetic drawbacks, particularly in periodontia with a thin biotype in the esthetically sensitive anterior region of the jaw(Smijs and Pavel, 2011). If a titanium implant is utilized in this situation, the mucosa in the implant's neck area may turn grey, limiting the overall treatment's effectiveness. Titanium implants may also necessitate further soft tissue augmentation operations, such as connective tissue grafting, which seeks to expand and thicken keratinized tissue. A less common, but conceivable, disadvantage is that titanium may be an allergy, causing it to spread not just within the surrounding tissues (as seen by increased amounts in the area of oral implants and regional lymph nodes), but also systemically (Guttenberg, 2012). Nonetheless, the titanium's gray color may be unfavorable and cause cosmetic issues, particularly if the soft tissue condition is poor and the dark color shows through the thin periimplant mucosa. Since 1988, zirconia has been utilized as a non-dental implant (total hip replacements). It has been shown to be inert to acids and bases in biological systems (Harianawala et al., 2016). Patients who have had allergic reactions to titanium can use it. The absence of periodontal ligament fibres causes the implant–bone contact to be weaker than that of natural dentition, therefore peri-implant tissue is oriented differently than periodontal tissue. Controlled surgical techniques, the quality of the bone where the implant is put, the bacterial environment, the health of the peri-implant gingiva, and functional loading are all important variables impacting the implant's healing and effectiveness (Harianawala et al., 2016). Zirconia, also known as zirconium oxide, is a natural mineral that may be found in igneous rocks such as granites and syenites. In the realm of dental implantation, zirconia is a popular

3. bi-inert material. The zirconium substance is strong, comparable to metals, and matches the color of the teeth. Hydrothermal concentration is used to recover pure zirconia from baddeleyite, which contains tiny quantities of silica and iron as impurities. Zirconia levels in Baddeleyite range from 96.5 percent to 98.5 percent. Zirconia has a monoclinic structure at Page | 3 ambient temperature (Paul et al., 2020). Zirconia is found in its natural state as an oxide, which is purified and synthesised into a cubic structure at high temperatures, known as cubic crystal structure. As a result, it's also known as 'ceramic steel,' and as a single-piece implant, it has excellent biomechanical characteristics. Since 1989, zirconia has been utilized in dentistry, with the first fixed dental prosthesis being used in 1998. Zirconia phases are a kind of zirconia that comes in a variety of. The three phases of zirconia are (M) Monoclinic, (T) Tetragonal, and (C) Cubic (Luo et al., 2009). At room temperature, the purest Zirconia is monoclinic, and this stable phase lasts up to 1170°C. It will change from (M) Monoclinic to (T) Tetragonal at 2370° C when heated as described above. It will also convert to (C) Cubic if heated over 2370°C for an extended period of time. Osseointegration and tissue repose of zirconia implants In the lack of a connective tissue layer, osseointegration was previously characterized as direct contact of essential bone with the implant surface. The term direct structural and functional link between essential bone and the surface of a loaded implant was later added to the definition (Mavrogenis et al., 2009). The principle of osseointegration, a process of implant-bone contact that eventually leads to bone-to-implant anchorage, is directly connected to the success of endosseous implants. Because a biomaterial's surface topography has a significant influence on osseointegration, several chemical and physical surface modifications have been created to promote implant osseointegration. Increased surface roughness of dental implants led to better bone apposition and faster healing (Mavrogenis et al., 2009). The processes for osseointegration of metal implants are as follows (Liu et al., 2020): following the first surgical lesion, necrotic tissue is resorbed and unique matrix is generated to fill the gap between the bone and the implant through preparation of the implant bed. Primary bone healing, which is characterized by direct deposition of new bone at the contact, is required for excellent implant anchoring. Immediate implant stability and a small gap between implant and bone (less than 1 mm) are required for this. A blood coagula fills the gap between the implant and the bone in the early stages, attracting multipotent

4. mesenchymal cells from the arteries and the surroundings and recruiting cells for debridement. These cells move to the implant surface via the coagula (osteoconduction) and deposit a thin, afibrillar layer. They deposit a collagen matrix on over of this layer following differentiation to osteoblasts, and these structures are supplanted by woven bone after Page | 4 another 4-6 weeks, forming the link between the implant and neighboring bone. The neighboring implant is firmly implanted in the bone socket as the woven bone is reformed and replaced by lamellar bone over time. It appears to be a viable material for dental usage due to its chemical and material stability, great strength, and durability. Several studies have documented its effective use in dentistry for manufacturing endodontic posts for crown and bridge restorations (Tinschert et al., 2007). Zirconia has been recommended as a viable alternative to titanium for the production of dental implants, owing to its tooth-like appearance. The findings of this study demonstrate that zirconia implants with a modified surface appear to integrate into bone in the same way as titanium implants do. Because the osseointegration of zirconia implants has not been thoroughly explored, Depprich et al., (2008) aimed to evaluate the osseous healing of zirconia implants with titanium implants that have a roughened surface but otherwise comparable implant geometries. Twelve minipigs' tibias were implanted with 48 zirconia and titanium implants. After 1, 4, or 12 weeks, specimens containing the implants were analyzed using histological and ultrastructural methods. The zirconia and titanium surfaces have direct bone contact, according to histological findings. Histomorphometry revealed that titanium surfaces had somewhat better bone implant contact than zirconia surfaces. However, there was no statistically significant difference between the two groups. The findings of Depprich et al., (2008) showed that zirconia implants with changed surfaces had osseointegration that is equivalent to titanium implants. Plecko et al., (2012) showed that combining outstanding mechanical and osseointegrative characteristics, surface coating cobalt chrome implants with titanium or zirconium/titanium enhanced their total osseointegration and makes them very desirable material combinations for orthopedic implants. The maintenance of primary stability provided by rapid bone growth is a need for immediate or early loading of implants. The key to accelerating and enhancing new bone development is implant surface modification, which translates to larger bone–contact ratios and better RTQ resistance. The bone tissue response to novel zirconia implants with changed surfaces is compared to generally existing titanium dental implants and currently accessible zirconia implants by Kubasiewicz-Ross, Hadzik and Dominiak, (2018). Methods and materials. The experiment was conducted on a group of 1216-month-old minipigs. The mean bone-implant

5. contact (BIC) of the zirconia trial implants was 41.44 percent, according to Kubasiewicz- Ross, Hadzik, and Dominiak (2018). In specifically, the BIC percent for M1 was 39.72 percent, M2 was 43.97 percent, and M3 was 40.63 percent; for ceramic and titanium control implants, the BIC percent was 49.63 percent and 27.77 percent, respectively. There were no Page | 5 statistically significant disparities between the BIC values for implants in any of the groups, according to the intra-group analysis. The findings of the threaded region, the neck, and the apex, however, indicated statistically significant differences in all of the groups when BIC was analyzed for various parts of the same implant. Conclusions. Their findings show that zirconia implants with changed surfaces have osseointegration characteristics similar to titanium implants. The bone tissue reactivity to zirconia implants with three distinct surface modifications was compared to the oxidized titanium surface in order to maximize osseointegration in terms of toughness and speed in a study by Rocchietta et al., (2009). A total of 18 rabbits were utilized, with 143 implants. A total of 123 threaded zirconia ceramic implants with three distinct surface topographies were tested, with 20 modified titanium oxide implants serving as controls. After three weeks, each rabbit was killed after receiving eight implants. Histology and the removal torque test (RTQ) were carried out. 16 out of 18 rabbits finished the trial with a total of 110 implants, according to Rocchietta et al., (2009). In terms of interfacial shear strength as measured by the RTQ, no statistical significance was seen between the chemically changed implants and the topographically modified zirconia implants. The bone- to-implant interaction between the zirconia implants and the control oxidized implants had no statistical significance. Additional particular chemical alterations of topographically modified zirconia implants do not appear to improve bone-to-implant contact or boost interfacial shear strength, according to the findings. Biocompatibility of zirconia implants Biocompatibility refers to a biomaterial's ability to perform its intended function in relation to a medical therapy without causing any inflammatory, allergic, immune, or toxic consequences in the recipient of that therapy, but rather generating the most suitable advantageous cellular or tissue reaction in that specific situation, and enhancing the clinically relevant performance of that therapy. Metal ceramic restorations have an allergic reaction caused by some metal alloys, which has led to an increase in the need for more biocompatible ceramic implants for restorations. The level of cytotoxicity of metal alloys, on the other hand, is highly dependent on the type of

6. dental alloy utilized in metal ceramic restoration manufacturing. In general, zirconia-based ceramics are chemically inert substances that cause no harmful effects in the body. Because ceramic prostheses have finely refined surfaces, they can make touch with the gum tissue and help maintain the gingival architecture. The smoothness of the ceramics prevents plaque Page | 6 build-up, resulting in a suitable surface for gingival tissues. Zirconia-based materials have been correlated with excellent cell adherence and no harmful systemic responses. Particles from zirconia breakdown at low temperatures or manufacturing processes, on the other hand, might be liberated, triggering an immune-mediated localized inflammatory response. To assess the biocompatibility of zirconia, several in vitro experiments were performed on osteoblasts, fibroblasts, lymphocytes, monocytes, and macrophages (Hisbergues, Vendeville and Vendeville, 2009). Zirconia had no cytotoxic impact on osteoblasts and enabled them to synthesize a variety of important and structural proteins, allowing them to elaborate the extracellular matrix. Because zirconia has no pseudo-teratogenic impact, it is biocompatible. Because of its improved wettability, laser modified zirconia demonstrated greater adherence to osteoblasts. Zirconia does not cause irritation in any form. Sharanraj et al., (2020) describe the results of in-vitro experiments performed on cell culture on zirconia biomaterial used in dental implants using both direct contact and extraction methods to assess toxicity. In the work, the L929 cell line was used to test tissue biocompatibility in vitro (mouse fibroblast). The toxicity of Zirconia specimens was determined in vitro by calculating the proportion of viability in a cell-cultured medium. The active cell functions with mitochondrial dehydrogenases were measured using an MTT system, which is a simple technique that yields accurate and precise findings. The findings of a biocompatibility in-vitro test using both Direct and Extraction techniques revealed that Zirconia has the greatest cell growth rate of 93.17 percent and has zero-grade cytotoxicity. Zirconia has good cosmetic qualities, in that the color of the implant matches the color of the teeth. As a result, Zirconia is a better choice for implant material than other metals. All titanium or zirconium coated materials, as well as combinations thereof, were shown to be biocompatible in investigation by Plecko et al., (2012). Conclusion Dental implants are quickly emerging the treatment of choice for missing tooth restoration. Not only do they allow for tooth replacement, but they also restore function and appearance to a level that is difficult to achieve with other types of dental restorations.

7. An ideal implantation situation is one in which the implant is readily and securely integrated into the surrounding neighboring tissues in the shortest amount of time feasible, and the wound heals as quickly as possible, restoring and replacing the damaged one. However, in reality, implantation done under normal conditions has resulted in a variety of detrimental Page | 7 impacts due to surrounding adjacent tissue issues such as tissue overgrowth, improper bonding of the implant with tissue, implant fracture inside, and in some serious cases, the implant may have to be completely removed from the body. The implantation should be completed in the shortest amount of time feasible. The biocompatibility of zirconia was investigated using a variety of in vitro experiments. Zirconia was found to have no cytotoxic impact on osteoblasts and to have no pseudo- teratogenic effect, making it biocompatible. Standard clinical practice must be followed to avoid implant failure. Only stable materials should be used for implantation; if unstable materials are used, there is a higher risk of implant failure. Stable materials are less likely to react with surrounding tissue and have a low harmful effect on the body. They also improve biological characteristics and are highly biocompatible. When designing an implant, computer modeling and Finite Element Analysis (FEA) should be used in conjunction with simulation to gain a better knowledge of the maximum stress and strain values that induce implant failure. Following implant manufacturing, both mechanical and biological tests should be done in order to suggest it for clinical use or the intended purpose. References: Babbush, C. A. et al. (2010) Dental Implants-E-Book: The Art and Science. Elsevier Health Sciences. Depprich, R. et al.(2008) ‘Osseointegration of zirconia implants compared with titanium: an in vivo study’, Head & face medicine, 4(1), pp. 1–8. Guttenberg, S. A. (2012) Cosmesis of the mouth, face and jaws. John Wiley & Sons. Harianawala, H. et al.(2016) ‘Biocompatibilityof zirconia’, Journal of Advanced Medical and Dental Sciences Research, 4(3), p. 35. Hisbergues, M., Vendeville, S. and Vendeville, P. (2009) ‘Zirconia: Established facts and perspectives for a biomaterial in dental implantology’, Journal of Biomedical Materials Research Part B: Applied Biomaterials: An Official Journal of The Society for Biomaterials, The Japanese Society for Biomaterials, and The Australian Society for Biomaterials and the Korean Society for Biomaterials, 88(2), pp. 519–529. Kubasiewicz-Ross, P. et al.(2017) ‘Zirconium: The material of the future in modern implantology.’, Advances in clinical and experimental medicine: official organ Wroclaw Medical University, 26(3), pp. 533–537. Kubasiewicz-Ross, P., Hadzik, J. and Dominiak, M. (2018) ‘Osseointegration of zirconia implants with 3 varying surface textures and a titanium implant: A histological and micro-CT study’,

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