Comparison of zirconia and titanium implants after a short healing period. A pilot study in minipigs

Comparison of Microbiota in Zirconia and Titanium Implants: A Qualitative Systematic Review

BACKGROUND

In this systematic review, we examine the variations in microbiota on zirconia versus titanium implants, providing insights into their impact on dental health and outcomes. The ongoing discussion regarding whether to use zirconia or titanium for implants underscores the significance of microbiota colonization in determining the longevity and performance of implants.

METHODS

Research questions were formulated following the Participants, Intervention, Comparison, and Outcomes framework, and a PROSPERO protocol was registered. A thorough systematic search was carried out in PubMed, Embase, and Web of Science. Two reviewers independently assessed the reports against the Participants, Intervention, Comparison, and Outcomes criteria, including the inclusion and exclusion criteria. Risk of bias was assessed using the Quality Assessment Tool for In Vitro Studies (QUIN Tool).

RESULTS

Of the 2063 articles identified, 19 articles fulfilled the inclusion criteria and subjected to quality assessment. All of the included studies were in vitro research with low (31.5%) or moderate (36.8%) or high (31.5%) risk of bias and reported data from 2 implant abutments. Zirconia implants displayed a higher occurrence of Gram-negative bacteria, such as Tannerella, Aggregatibacter, and Porphyromonas. In contrast, titanium implants showed a greater prevalence of Gram-positive bacteria, including Streptococcus, Lactobacillus acidophilus, and Staphylococcus species.

CONCLUSION

According to the findings of the current study, both zirconia and titanium implants support the growth of different microorganisms. There were also differences in the quakity and the quantity of microorganisms detected on each material. These differences in microbial profiles indicate that the selection of implant material might impact the microbial ecosystem on the implant surface, potentially affecting clinical outcomes such as infection rates and the longevity of the implant.

Antibacterial Zirconia Surfaces from Organocatalyzed Atom-Transfer Radical Polymerization

Antibacterial coatings are becoming increasingly attractive for application in the field of biomaterials. In this framework, we developed polymer coating zirconia with antibacterial activity using the "grafting from" methodology. First, 1-(4-vinylbenzyl)-3-butylimidazolium chloride monomer was synthesized. Then, the surface modification of zirconia substrates was performed with this monomer via surface-initiated photo atom transfer radical polymerization for antibacterial activity. X-ray photoelectron spectroscopy, ellipsometry, static contact angle measurements, and an atomic force microscope were used to characterize the films for each step of the surface modification. The results revealed that cationic polymers could be successfully deposited on the zirconia surfaces, and the thickness of the grafted layer steadily increased with polymerization time. Finally, the antibacterial adhesion test was used to evaluate the antibacterial activity of the modified zirconia substrates, and we successfully showed the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa strains.

Effect of milled and lithography-based additively manufactured zirconia (3Y-TZP) on the biological properties of human osteoblasts

STATEMENT OF PROBLEM

Lithography-based additively manufactured (AM) zirconia has been used to fabricate dental implants and custom barriers for guided bone regeneration procedures. However, studies on the effect of AM zirconia on the biological properties of human osteoblasts are lacking.

PURPOSE

The purpose of this in vitro study was to compare the effect of milled and lithography-based AM zirconia on the biological properties of normal human osteoblasts (NHOsts), as well as to compare the chemical composition between the milled and lithography-based AM 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) zirconia.

MATERIAL AND METHODS

Three mol percentage yttria-stabilized tetragonal zirconia polycrystal disks (Ø6×2-mm) were fabricated using subtractive milling (Priti multidisc ZrO2 monochrome) (M group) and lithography-based additive manufacturing methods (LithaCon 3Y 210) (AM group) (n=10). NHOsts were exposed to different material extracts (1:1, 1:2, and 1:4) and cytotoxicity, cell migration, cell morphology, and cell attachment biological tests were completed. Additionally, for morphological and chemical analysis, a scanning electronic microscopy with energy-dispersive X-ray analysis (SEM/EDX) evaluation was completed. Data were analyzed by using 1-way ANOVA and the Dunnett test (α=.05).

RESULTS

Substantial cell attachment and spreading were observed in both material surfaces. The presence of zirconium was evident in both groups, although the percentage of zirconium in the AM group (64.7%) was slightly higher than in the M group (52.6%). When NHOsts were cultured in the presence of the different material eluates, the M and AM groups exhibited similar NHOst viability and migration rates when compared with untreated cells; no significant differences were found (P>.05).

CONCLUSIONS

The lithography-based AM zirconia tested showed adequate cytocompatibility without differences when compared with the milled zirconia (M group) specimens. Slight chemical element composition differences were found between milled and lithography-based AM zirconia.

A chlorogenic acid-chitosan complex bifunctional coating for improving osteogenesis differentiation and bactericidal properties of zirconia implants

Poor osteogenesis caused by limited bioactivity and peri-implantitis caused by bacterial colonization are the main challenges affecting the use of zirconia-based materials in dental implants. Accordingly, the development of a surface treatment method with an antibacterial effect and that promotes osteogenesis without damage to cells is crucial for yttrium-stabilized tetragonal zirconia (Y-TZP) implants. Herein, we have developed a functional surface modification strategy whereby a poly (ethylene imine)/hyaluronic acid /chitosan-chlorogenic acid (PEI/HA/CGA-CS) conjugate is deposited on a zirconia surface by the layer-by-layer (LBL) technique, enhancing its osteogenic differentiation and antibacterial activities. The results showed that the PEI/HA/CGA-CS coating improved the wettability of the zirconia surface and maintained stable release of CGA. The PEI/HA/CGA-CS functional coating was found to promote early cell adhesion, proliferation, differentiation, and calcification. The results of bacterial adhesion and activity tests showed that the coating effectively inhibits the proliferation and activity of Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) without impairing the biological activity of osteoblasts. In addition, we found that the PEI/HA/CGA-CS coating enhances the osteogenesis of MC3T3-E1 cells by promoting the protein expression of Nephronectin (NPNT) and activating the Wnt/β-catenin signaling pathway. The above results are of profound significance for the practical application of zirconia-based implants. DATA AVAILABILITY: Data will be made available on request.

Surface modifications of zirconia with plasma pretreatment and polydopamine coating to enhance the bond strength and durability between zirconia and titanium

The aim of this study was to assess the shear bond strength and durability between plasma-pretreated and polydopamine (PDA)-coated zirconia and titanium. Four groups were prepared according to the different surface treatments (untreated ZrO₂, plasma-pretreated ZrO₂, PDA-coated ZrO₂, and plasma-pretreated and PDA-coated ZrO₂ (PP+PDA-ZrO₂). The surface topography and roughness, contact angle, and elemental analysis of the coatings of the four groups were investigated, and the bond strength and durability of the specimens were evaluated based on shear bond strength and thermocycle tests. Physical and chemical characterization results confirmed that PDA coatings can be successfully formed on zirconia substrates. The roughness and hydrophilicity were significantly higher in the PP+PDA-ZrO₂ group_, which demonstrated better shear bond strength and durability between zirconia and titanium. The plasma pretreatment of zirconia substrates can enhance the stability of the PDA coating layer, and hybrid surface modifications can provide several bonding advantages for clinical use.

Early bone formation around immediately placed two-piece tissue-level zirconia implants with a modified surface: an experimental study in the miniature pig mandible

PURPOSE

To histologically examine early bone formation around transmucosal implants and to evaluate the influence of surface characteristics on early peri-implant bone healing using a miniature pig model. For this, commercially available dental implants with a rough zirconia (YTZP) surface were compared to surface-modified Ti control implants at 4 and 8 weeks after placement.

METHODS

Immediately following the extraction of six mandibular premolars, 20 two-piece, tissue-level, screw-shaped YTZP implants (Patent™ Standard Zirconia Implant ø4.1 × 11 mm) with a modified rough blasted before sintering surface were inserted in four adult miniature pigs. In addition, four titanium (Ti) tissue-level implants (Straumann® Standard RN ø4.1 × 10 mm Roxolid®) with a moderate surface (SLActive®), one per animal, were placed as control implants. A histological analysis was performed on the hard tissues after 4 and 8 weeks of transmucosal healing.

RESULTS

The results show a high rate of osseointegration of the test YTZP dental implants at 4 and 8 weeks following insertion. At 4 weeks, a bone-to-implant contact ratio (BIC) of 73.7% (SD ± 16.8) for the test implants (n = 10) and 58.5% for the first control implant was achieved. The second control implant had to be excluded from analysis. At 8 weeks, a BIC of 82.4% (SD ± 16.9) for the test implants (n = 9) and 93.6% (SD ± 9.1) (n = 2) for the control implant was achieved. No statistical difference was observed comparing 4 and 8 weeks YTZP data (p = 0.126).

CONCLUSIONS

The results indicate a predictable osseointegration of immediate zirconia implants with a modified YTZP implant surface and a high degree of BIC present at 4 weeks following insertion. After 8 weeks of healing both the zirconia implants and the Ti implants show a BIC indicating full osseointegration. Further studies involving a larger sample size with more time points are needed to confirm these results.

Surface Structure of Zirconia Implants: An Integrative Review Comparing Clinical Results with Preclinical and In Vitro Data

Background: The purpose of this review was to analyze and correlate the findings for zirconia implants in clinical, preclinical and in vitro cell studies in relation to surface structure. Methods: Electronic searches were conducted to identify clinical, preclinical and in vitro cell studies on zirconia implant surfaces. The primary outcomes were mean bone loss (MBL) for clinical studies, bone-to-implant contact (BIC) and removal torque (RT) for preclinical studies and cell spreading, cell proliferation and gene expression for cell studies. The secondary outcomes included comparisons of data found for those surfaces that were investigated in all three study types. Results: From 986 screened titles, 40 studies were included for data extraction. In clinical studies, only micro-structured surfaces were investigated. The lowest MBL was reported for sandblasted and subsequently etched surfaces, followed by a sinter and slurry treatment and sandblasted surfaces. For BIC, no clear preference of one surface structure was observable, while RT was slightly higher for micro-structured than smooth surfaces. All cell studies showed that cell spreading and cytoskeletal formation were enhanced on smooth compared with micro-structured surfaces. Conclusions: No correlation was observed for the effect of surface structure of zirconia implants within the results of clinical, preclinical and in vitro cell studies, underlining the need for standardized procedures for human, animal and in vitro studies.

The primary stability of two dental implant systems in low-density bone

Primary stability in low-density bone is crucial for the long-term success of implants. Tapered implants have shown particularly favourable properties under such conditions. The aim of this study was to compare the primary stability of tapered titanium and novel cylindrical zirconia dental implant systems in low-density bone. Fifty implants (25 tapered, 25 cylindrical) were placed in the anterior maxillary bone of cadavers meeting the criteria of low-density bone. The maximum insertion (ITV) and removal (RTV) torque values were recorded, and the implant stability quotients (ISQ) determined. To establish the isolated influence of cancellous bone on primary stability, the implantation procedure was performed in standardized low-density polyurethane foam bone blocks (cancellous bone model) using the same procedure. The primary stability parameters of both implant types showed significant positive correlations with bone density (Hounsfield units) and cortical thickness. In the cadaver, the cylindrical zirconia implants showed a significantly higher mean ISQ when compared to the tapered titanium implants (50.58 vs 37.26; P < 0.001). Pearson analysis showed significant positive correlations between ITV and ISQ (P = 0.016) and between RTV and ISQ (P = 0.035) for the cylindrical zirconia implants; no such correlations were observed for the tapered titanium implants. Within the limitations of this study, the results indicate that cylindrical zirconia implants represent a comparable viable treatment option to tapered titanium implants in terms of primary implant stability in low-density human bone.

The minipig intraoral dental implant model: A systematic review and meta-analysis

OBJECTIVES

The objective of this report was to provide a review of the minipig intraoral dental implant model including a meta-analysis to estimate osseointegration and crestal bone remodeling.

METHODS

A systematic review including PubMed and EMBASE databases through June 2021 was conducted. Two independent examiners screened titles/abstracts and selected full-text articles. Studies evaluating titanium dental implant osseointegration in native alveolar bone were included. A quality assessment of reporting was performed. Random-effects meta-analyses and meta-regressions were produced for bone-implant contact (BIC), first BIC, and crestal bone level.

RESULTS

125 out of 249 full-text articles were reviewed, 55 original studies were included. Quality of reporting was generally low, omissions included animal characteristics, examiner masking/calibration, and sample size calculation. The typical minipig model protocol included surgical extraction of the mandibular premolars and first molar, 12±4 wks post-extraction healing, placement of three narrow regular length dental implants per jaw quadrant, submerged implant healing and 8 wks of osseointegration. Approximately 90% of studies reported undecalcified incandescent light microscopy histometrics. Overall, mean BIC was 59.88% (95%CI: 57.43-62.33). BIC increased significantly over time (p<0.001): 40.93 (95%CI: 34.95-46.90) at 2 wks, 58.37% (95%CI: 54.38-62.36) at 4 wks, and 66.33% (95%CI: 63.45-69.21) beyond 4 wks. Variability among studies was mainly explained by differences in observation interval post-extraction and post-implant placement, and implant surface. Heterogeneity was high for all studies (I2 > 90%, p<0.001).

CONCLUSIONS

The minipig intraoral dental implant model appears to effectively demonstrate osseointegration and alveolar bone remodeling similar to that observed in humans and canine models.

Structural Characterization and Osseointegrative Properties of Pulsed Laser-Deposited Fluorinated Hydroxyapatite Films on Nano-Zirconia for Implant Applications

Standard zirconia implants used in restoration still present problems related to inertness and long-term stability. Various physicochemical approaches have been used to modify the implant surfaces to improve early and late bone-to-implant integration; however, no ideal surface modification has been reported. This study used pulsed laser deposition to deposit a fluorinated hydroxyapatite (FHA) film on a zirconia implant to create a biologically active surface. The film prepared was uniform, dense, and crack-free, and exhibited granular surface droplets; it also presented excellent mechanical strength and favorable biological behavior. The FHA-coated implant was implanted on the femur of Sprague-Dawley rats, and various tests and analyses were performed. Results show that the in vitro initial cell activity on the FHA-coated samples was enhanced. In addition, higher alkaline phosphatase activity and cell mineralization were detected in cells cultured on the FHA-coated groups. Further, the newly formed bone volume of the FHA-coated group was higher than that of the bare micro-adjusted composite nano-zirconia (NANOZR) group. Therefore, the FHA film facilitated osseointegration and may improve the long-term survival rates of dental implants, and could become part of a new treatment technology for implant surfaces, promoting further optimization of NANOZR implant materials.

A Clinical and Radiographic Evaluation of Zirconia Dental Implants: 10-Year Follow-Up

PURPOSE

The aim is to evaluate the survival and success rates, as well as the marginal bone loss (MBL) and periodontal indexes, of zirconia implants with 10-year follow-up.

MATERIALS AND METHODS

10 patients were selected and 26 one-piece zirconia implants were used for the rehabilitation of single tooth or partially edentulous ridge. After 10 years, a clinical-radiographic evaluation was performed in order to estimate peri-implant tissue health and marginal bone loss.

RESULTS

The survival and success rates were 100%. The average marginal bone loss from baseline to 120 months after surgery was 0.92 ± 0.97 mm.

CONCLUSION

One-piece zirconia dental implants are characterised by high biocompatibility, low plaque adhesion, and absence of microgap that can be related to the clinical success of these implants.

Zirconia vs. Titanium Dental Implants: Primary Stability In-Vitro Analysis

The present experimental trial uses two types of dental implants, one made of titanium (Ti₆A_l4V) and the other one of zirconia (ZrO₂), but both of identical design, to compare their stability and micro-movements values under load. One of each type of implant (n = 42) was placed into 21 cow ribs, recording the insertion torque and the resonance frequency using a specific transducer. Subsequently, a prosthetic crown made of PMMA was screwed onto each of the implants in the sample. They were then subjected to a static compression load on the vestibular cusp of the crown. The resulting micromovements were measured. The zirconia implants obtained a higher mean of both IT and RFA when compared with those of titanium, with statistically significant differences in both cases (p = 0.0483 and p = 0.0296). However, the micromovement values when load was applied were very similar for both types, with the differences between them (p = 0.3867) not found to be statistically significant. The results show that zirconia implants have higher implant stability values than titanium implants. However, the fact that there are no differences in micromobility values implies that caution should be exercised when applying clinical protocols for zirconia based on RFA, which only has evidence for titanium.

Titanium vs ceramic single dental implants in the anterior maxilla: A 12-month randomized clinical trial

OBJECTIVE

The aim of this randomized clinical trial was to compare ceramic and titanium implants with respect to the esthetic and clinical parameters, and patient-reported outcome measures (PROMs).

MATERIAL AND METHODS

Thirty patients received thirty implants (8-12 mm in length, 3.3 mm diameter, and a tissue level design) to replace single teeth in the anterior maxilla. Patients were randomly allocated to receive a ceramic or a titanium implant. Esthetic, clinical parameters, and PROMs were evaluated 18 months after surgery.

RESULTS

At 12 months post-final loading, there were no significant differences between groups with respect to esthetics. Mean Index Crown Aesthetic score was 6.31 (95% C.I. 4.59-8.04) and 6.07 (95% C.I. 4.21-7.93) for ceramic and titanium implants, respectively. The pink esthetic score (PES) was 7.81 (95% C.I. 6.90-8.73) for ceramic implants and 7.86 (95% C.I. 7.11-8.60) for titanium implants, with no significant differences between groups. No statistically significant differences were found for any of the other clinical parameters and PROMs.

CONCLUSIONS

Monotype ceramic implants have proven to be a good treatment option in the upper anterior sector, showing favorable esthetic results, being comparable to titanium implants. This clinical trial has been registered in clinical trials with the identifier CI_RCT_US16 and registration number NCT04707677. A retrospective registration of the clinical trial was carried out since registration was not mandatory on the date the study began.

Oral Tissue Interactions and Cellular Response to Zirconia Implant-Prosthetic Components: A Critical Review

Background: Dental components manufactured with zirconia (ZrO₂) represent a significant percentage of the implant prosthetic market in dentistry. However, during the last few years, we have observed robust clinical and pre-clinical scientific investigations on zirconia both as a prosthetic and an implantable material. At the same time, we have witnessed consistent technical and manufacturing updates with regards to the applications of zirconia which appear to gradually clarify points which until recently were not well understood. Methods: This critical review evaluated the “state of the art” in relation to applications of this biomaterial in dental components and its interactions with oral tissues. Results: The physico-chemical and structural properties as well as the current surface treatment methodologies for ZrO₂ were explored. A critical investigation of the cellular response to this biomaterial was completed and the clinical implications discussed. Finally, surface treatments of ZrO₂ demonstrate that excellent osseointegration is possible and provide encouraging prospects for rapid bone adhesion. Furthermore, sophisticated surface treatment techniques and technologies are providing impressive oral soft tissue cell responses thus leading to superior biological seal. Conclusions: Dental devices manufactured from ZrO₂ are structurally and chemically stable with biocompatibility levels allowing for safe and long-term function in the oral environment.

Surface Modified Techniques and Emerging Functional Coating of Dental Implants

Dental implants are widely used in the field of oral restoration, but there are still problems leading to implant failures in clinical application, such as failed osseointegration, marginal bone resorption, and peri-implantitis, which restrict the success rate of dental implants and patient satisfaction. Poor osseointegration and bacterial infection are the most essential reasons resulting in implant failure. To improve the clinical outcomes of implants, many scholars devoted to modifying the surface of implants, especially to preparing different physical and chemical modifications to improve the osseointegration between alveolar bone and implant surface. Besides, the bioactive-coatings to promote the adhesion and colonization of ossteointegration-related proteins and cells also aim to improve the osseointegration. Meanwhile, improving the anti-bacterial performance of the implant surface can obstruct the adhesion and activity of bacteria, avoiding the occurrence of inflammation related to implants. Therefore, this review comprehensively investigates and summarizes the modifying or coating methods of implant surfaces, and analyzes the ossteointegration ability and anti-bacterial characteristics of emerging functional coatings in published references.

Evaluation of insertion torque and surface integrity of zirconia-coated titanium mini screw implants

INTRODUCTION

The aim of this study was to devise a modification of a temporary anchorage device (TAD) by coating titanium mini screw implants with yttrium stabilized zirconia and to evaluate the insertion torque and surface integrity of it.

METHOD

Five titanium implants (Absoanchor, Dentos, South Korea) from each of the four groups comprising of 6 SH 13-08, 6 SH 13 -10 cylindrical and 6 SH 1312-08, 6 SH 1312-10 tapered mini screw implants were selected to be in the experimental group (Zr Ti) of implants, wherein they were coated with yttrium stabilised zirconia using a RF/DC magnetron sputtering unit. One mini screw implant from each of the four groups remained without coating to serve as control (Ti). After the coating of the titanium mini screw implants, scanning electron microscope (SEM) study was performed to evaluate the thickness and uniformity of the coating obtained. The insertion torque of all implants were evaluated by inserting the implant into bone sample using a manual torque wrench (ADIN). The implants were retrieved from the bone sample and a post insertion SEM study was performed to evaluate any changes in the surface of the Zr-Ti and Ti implants. X-ray diffraction (XRD) analysis was done to confirm the presence of Zirconia in the implants from the experimental group.

RESULTS

There was no statistically significant difference between the insertion torque for the zirconia coated mini screw implants and the titanium mini screw implants, where the P value < 0.05 was considered as statistically significant. The values for insertion torque for Zr Ti cylindrical group of 8 mm length ranged from 19-20 N-cm and that for the tapered group of 8 mm length ranged from 15-17 N-cm. The insertion torque for the Zr Ti tapered group of 8 mm ranged from 21-22 N-cm and that of the tapered group ranged from 16-18 N-cm.The insertion torque values for the Ti cylindrical implant for length of 8 mm was 20 N-cm and 21 N-cm for length of 10 mm. The insertion torque values for the Ti tapered implant was 15N-cm for 8 mm length and 16N-cm for 10 mm length.

CONCLUSION

The Zirconia coating on the Titanium mini screw implants was of 2.6 µm in thickness. There was no statistically significant difference in the insertion torque of the Zirconia coated mini screw implants and the non-coated titanium mini screw implants which retained their structural integrity.

Bioactive glass coating on zirconia by vacuum sol-dipping method

In order to the preparation of biodegradable, bioactive and strongly adhered coating layer to the bioinert zirconia substrate, a bioactive glass (BG) was successfully coated on the zirconia plates. To achieve this goal, the zirconia plates dipped into the 45S5 BG sol in the vacuum chamber (vacuum sol-dipping method) followed by sintering to fabricate a strongly adhered BG coating on the zirconia plates. The parameters such as surface morphology and BG coating coverage ability on the zirconia plates have been assessed before and after coating with 45S5 BG. Phase structure of the BG coating based on the X-ray diffraction (XRD) result could be indexed as Na₄Ca₄(Si₆O₁₈). The interfacial adhesive strength between the zirconia substrate and BG coating layer was higher than the measured adhesive strength (55±7 MPa). The viability results approved the satisfying conclusion for the offered coating method on the zirconia substrates.

Safety and efficacy of a novel anodized abutment on soft tissue healing in Yucatan mini-pigs

BACKGROUND

It is well established that electrochemical anodization of implant surfaces contributes to osseointegration and long-term implant survival. Few studies have investigated its effect on soft tissue healing.

PURPOSE

To evaluate the safety and efficacy of a novel abutment surface prepared by electrochemical oxidation compared to commercially available machined titanium abutments.

MATERIALS AND METHODS

Twelve 16-19 months-old, Yucatan mini-pigs received three dental implants in each mandibular jaw quadrant. Each side was randomized to receive either an anodized or a machined titanium abutment. Titanium healing caps were placed on both abutments. Animals were euthanized at 6 and 13 weeks. Radiographic and histological analyses were performed.

RESULTS

No significant differences were observed histologically between groups in regard to inflammation, epithelium length, mucosal height, bone-to-implant contact, or bone density for any time point. Radiographically, crestal bone level change from baseline to 6 weeks was significantly lower for anodized than machined abutments (P = 0.046); no significant differences were observed at 13 weeks (P = 0.12).

CONCLUSIONS

The novel anodized abutment showed a comparable effect on soft and hard tissue healing/remodeling and inflammation reaction to standard titanium abutments. Clinical studies should confirm these findings and explore the positive radiographic results observed at the early time point.

Zirconia surface modifications for implant dentistry

BACKGROUND

Zirconia has emerged as a versatile dental material due to its excellent aesthetic outcomes such as color and opacity, unique mechanical properties that can mimic the appearance of natural teeth and decrease peri-implant inflammatory reactions.

OBJECTIVE

The aim of this review was to critically explore the state of art of zirconia surface treatment to enhance the biological and osseointegration behavior of zirconia in implant dentistry.

MATERIALS AND METHODS

An electronic search in PubMed database was carried out until May 2018 using the following combination of key words and MeSH terms without time periods: "zirconia surface treatment" or "zirconia surface modification" or "zirconia coating" and "osseointegration" or "biological properties" or "bioactivity" or "functionally graded properties".

RESULTS

Previous studies have reported the influence of zirconia-based implant surface on the adhesion, proliferation, and differentiation of osteoblast and fibroblasts at the implant to bone interface during the osseointegration process. A large number of physicochemical methods have been used to change the implant surfaces and therefore to improve the early and late bone-to-implant integration, namely: acid etching, gritblasting, laser treatment, UV light, CVD, and PVD. The development of coatings composed of silica, magnesium, graphene, dopamine, and bioactive molecules has been assessed although the development of a functionally graded material for implants has shown encouraging mechanical and biological behavior.

CONCLUSION

Modified zirconia surfaces clearly demonstrate faster osseointegration than that on untreated surfaces. However, there is no consensus regarding the surface treatment and consequent morphological aspects of the surfaces to enhance osseointegration.

Current status of zirconia implants in dentistry: preclinical tests

PURPOSE

This systematic review aimed to provide an overview of zirconia implants as well as regarding the outcome of the implant-restorative complex in preclinical studies.

STUDY SELECTION

An electronic search of the literature prior to July 2017 was performed to identify all articles related to preclinical research on zirconia implants. The search was conducted using MEDLINE (National Library of Medicine) and PubMed without restrictions concerning the date of publication. The search terminology included: zirconia implant, osseointegration, bone-to-implant contact, soft tissue, histology, histomorphometry, surface modification, surface roughness, surface characteristics, and restoration (connecting multiple keywords with AND, OR).

RESULTS

Fifty-seven studies were finally selected from an initial yield of 654 titles, and the data were extracted. The identified preclinical studies focused on several aspects related to zirconia implants, namely biocompatibility, mechanical properties, implant design, osseointegration capacity, soft tissue response, and restorative options. Due to heterogeneity of the studies, a meta-analysis was not possible. The most frequently used zirconia material for the fabrication of implants is yttria-stabilized tetragonal zirconia polycrystal. The resistance-to-fracture for zirconia implants ranged between 516-2044N. The mostly investigated parameter was osseointegration, which is compared to that of titanium. A lack of evidence was found with other parameters.

CONCLUSIONS

Due to its good biocompatibility as well as favorable physical and mechanical properties, zirconia implants are a potential alternative to titanium implants. However, knowledge regarding the implant-restorative complex and related aspects is still immature to recommend its application for daily practice.

Hard and soft tissue responses to implant made of three different materials with microgrooved collar in a dog model

The objective of the present study was to assess hard and soft tissue around dental implants made of three different materials with microgrooves on the collar surface. Microgrooved implants were inserted in the mandibles of five male beagles. Implants were made of three kinds of material; titanium (Ti), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria partially stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃). The animals were euthanatized at three months after implantation, and harvested tissue was analyzed by means of histology. All kinds of implant were osseointegrated, and there were no significant differences in any histomorphometric parameters among the three groups of microgrooved implants made of different materials. Within the limitations of this study, implants with microgrooves integrated into the surrounding bone tissue, without statistically significant differences among the three tested materials, Ti, Y-TZP, and Ce-TZP/Al₂O₃.

Bone response to functionally loaded, two-piece zirconia implants: A preclinical histometric study

OBJECTIVE

To evaluate the bone response to a two-piece zirconia implant in comparison with a control titanium implant in the canine mandible 4 and 16 weeks after restoration.

MATERIAL AND METHODS

Zirconia and titanium implants were alternately placed bilaterally in healed mandibular molar and premolar sites of five canines. Full-ceramic single-tooth restorations were cemented after 6 weeks of transmucosal healing, allowing for full functional loading of the implants. Histologic and histometric analyses were performed on orofacial and mesiodistal undecalcified sections of the specimens obtained upon sacrifice after 4 and 16 weeks of functional loading. Bone-to-implant contact (BIC), multinucleated giant cells-to-implant contact (MIC), crestal bone level, and peri-implant bone density were histometrically assessed.

RESULTS

All 60 implants and 60 restorations were still in function after 4 and 16 weeks of loading in both test and control groups. No implant loss, no implant or abutment fracture, and no chipping of the restorations could be detected. Histometric analysis showed no statistically significant differences between zirconia and titanium implants in BIC, crestal bone level, and peri-implant bone density at both time points. Between 4 and 16 weeks, the crestal bone level around zirconia implants showed a small but statistically significant increase in its distance from the implant shoulder. MIC was very low on both implant types and both time points and decreased statistically significantly overtime.

CONCLUSION

The present two-piece zirconia implant showed a similar bone integration compared to the titanium implant with similar surface morphology after 4 and 16 weeks of loading.

Osseointegration of zirconia dental implants in animal investigations: A systematic review and meta-analysis

OBJECTIVE

To determine the osseointegration rate of zirconium dioxide (ZrO₂) dental implants in preclinical investigations.

DATA

Data on the osseointegration rate was extracted considering the bone to implant contact (BIC), removal torque analysis (RTQ) and push-in tests. Meta analyses were conducted using multilevel multivariable mixed-effects linear regression models. The Šidák method was used in case of multiple testing.

SOURCES

An electronic screening of the literature (MEDLINE/Pubmed, Cochrane Library and Embase) and a supplementary manual search were performed. Animal investigations with a minimum sample size of 3 units evaluating implants made of zirconia (ZrO₂) or its composites (ZrO₂>50vol.%) were included.

STUDY SELECTION

The search provided 4577 articles, and finally 54 investigations were included and analyzed. Fifty-two studies included implants made from zirconia, 4 zirconia composite implants and 37 titanium implants. In total, 3435 implants were installed in 954 animals.

CONCLUSIONS

No significant influence of the evaluated bulk materials on the outcomes of interest could be detected. When comparing different animal models, significant differences for the evaluated variables could be found. These results might be of interest for the design of further animal investigations.

Is zirconia a viable alternative to titanium for oral implant? A critical review

PURPOSE

Titanium based implant systems, though considered as the gold standard for rehabilitation of edentulous spaces, have been criticized for many inherent flaws. The onset of hypersensitivity reactions, biocompatibility issues, and an unaesthetic gray hue have raised demands for more aesthetic and tissue compatible material for implant fabrication. Zirconia is emerging as a promising alternative to conventional Titanium based implant systems for oral rehabilitation with superior biological, aesthetics, mechanical and optical properties. This review aims to critically analyze and review the credibility of Zirconia implants as an alternative to Titanium for prosthetic rehabilitation.

STUDY SELECTION

The literature search for articles written in the English language in PubMed and Cochrane Library database from 1990 till December 2016. The following search terms were utilized for data search: "zirconia implants" NOT "abutment", "zirconia implants" AND "titanium implants" AND "osseointegration", "zirconia implants" AND compatibility.

RESULTS

The number of potential relevant articles selected were 47. All the human in vivo clinical, in vitro, animals' studies were included and discussed under the following subheadings: Chemical composition, structure and phases; Physical and mechanical properties; Aesthetic and optical properties; Osseointegration and biocompatibility; Surface modifications; Peri-implant tissue compatibility, inflammation and soft tissue healing, and long-term prognosis.

CONCLUSIONS

Zirconia implants are a promising alternative to titanium with a superior soft-tissue response, biocompatibility, and aesthetics with comparable osseointegration. However, further long-term longitudinal and comparative clinical trials are required to validate zirconia as a viable alternative to the titanium implant.

Thirty Years of Translational Research in Zirconia Dental Implants: A Systematic Review of the Literature

Thirty years of transitional research in zirconia (Zr) ceramics has led to significant improvements in the biomedical field, especially in dental implantology. Oral implants made of yttria-tetragonal zirconia polycrystals (Y-TZP) because of their excellent mechanical properties, good biocompatibility, and esthetically acceptable color have emerged as an attractive metal-free alternative to titanium (Ti) implants. The aim of the review was to highlight the translation research in Zr dental implants that has been conducted over the past 3 decades using preclinical animal models. A computer search of electronic databases, primarily PubMed, was performed with the following key words: "zirconia ceramics AND animal trials," "ceramic implants AND animal trials," "zirconia AND animal trials," "zirconia AND in vivo animal trials," without any language restriction. However, the search was limited to animal trials discussing percentage bone-implant contact (%BIC) around zirconia implants/discs. This search resulted in 132 articles (reviews, in vivo studies, and animal studies) of potential interest. We restricted our search terms to "zirconia/ceramic," "bone-implant-contact," and "animal trials" and found 29 relevant publications, which were then selected for full-text reading. Reasons for exclusion included the article's not being an animal study, being a review article, and not discussing %BIC around Zr implants/discs. Most of the studies investigated BIC around Zr in rabbits (30%), pigs (approximately 20%), dogs, sheep, and rats. This review of the literature shows that preclinical animal models can be successfully used to investigate osseointegration around Zr ceramics. Results of the reviewed studies demonstrated excellent %BIC around Zr implants. It should be noted that most of the studies investigated %BIC/removal torque under nonloading conditions, and results would have been somewhat different in functional loading situations because of inherent limitations of Zr ceramics. Further trials are needed to evaluate the performance of Zr ceramics in clinical conditions using implants designed and manufactured via novel techniques that enhance their biomechanical properties.

Silicon Nitride (Si3N4) Implants: The Future of Dental Implantology?

For decades titanium has been the preferred material for dental implant fabrication, with mechanical and biological performance resulting in high clinical success rates. These have been further enhanced by incremental development of surface modifications aimed at improving speed and degree of osseointegration and resulting in enhanced clinical treatment options and outcomes. However, increasing demand for metal-free dental restorations has also led to the development of ceramic-based dental implants, such as zirconia. In orthopedics, alternative biomaterials, such as polyetheretherketone or silicon nitride, have been used for implant applications. The latter is potentially of particular interest for oral use as it has been shown to have antibacterial properties. In this article we aim to shed light on this particular biomaterial as a future promising candidate for dental implantology applications, addressing basic specifications required for any dental implant material. In view of available preclinical data, silicon nitride seems to have the essential characteristics to be a candidate for dental implants material. This novel ceramic has a surface with potentially antimicrobial properties, and if this is confirmed in future research, it could be of great interest for oral use.

Zirconia implants and peek restorations for the replacement of upper molars

Background

One of the disadvantages of the zirconia implants is the lack of elasticity, which is increased with the use of ceramic or zirconia crowns. The consequences that could result from this lack of elasticity have led to the search for new materials with improved mechanical properties.

Case presentation

A patient who is a 45-year-old woman, non-smoker and has no medical record of interest with a longitudinal fracture in the palatal root of molar tooth 1.7 and absence of tooth 1.6 was selected in order to receive a zirconia implant with a PEEK-based restoration and a composite coating. The following case report describes and analyses treatment with zirconia implants in molars following a flapless surgical technique. Zirconia implants are an alternative to titanium implants in patients with allergies or who are sensitive to metal alloys. However, one of the disadvantages that they have is their lack of elasticity, which increases with the use of ceramic or zirconia crowns. The consequences that can arise from this lack of elasticity have led to the search for new materials with better mechanical properties to cushion occlusal loads. PEEK-based restoration in implant prosthetics can compensate these occlusal forces, facilitating cushioning while chewing.

Conclusion

This procedure provides excellent elasticity and resembles natural tooth structure. This clinical case suggests that PEEK restorations can be used in zirconia implants in dentistry.

One-Piece Zirconia Ceramic versus Titanium Implants in the Jaw and Femur of a Sheep Model: A Pilot Study

Reports have documented titanium (Ti) hypersensitivity after dental implant treatment. Alternative materials have been suggested including zirconia (Zr) ceramics, which have shown predictable osseointegration in animal studies and appear free of immune responses. The aim of the research was to investigate the bone-to-implant contact (BIC) of one-piece Zr, compared with one-piece Ti implants, placed in the jaws and femurs of domestic sheep. Ten New Zealand mixed breed sheep were used. A One-piece prototype Ti (control) and one Zr (test) implant were placed in the mandible, and one of each implant (Ti and Zr) was placed into the femoral epicondyle of each animal. The femur implants were submerged and unloaded; the mandibular implants were placed using a one-stage transgingival protocol and were nonsubmerged. After a healing period of 12 weeks, %BIC was measured. The overall survival rate for mandibular and femur implants combined was 87.5%. %BIC was higher for Zr implants versus Ti implants in the femur (85.5%, versus 78.9%) (p = 0.002). Zirconia implants in the mandible showed comparable %BIC to titanium implants (72.2%, versus 60.3%) (p = 0.087). High failure rate of both Zr and Ti one-piece implants in the jaw could be attributed to the one-piece design and surface characteristics of the implant that could have influenced osseointegration. Further clinical trials are recommended to evaluate the performance of zirconia implants under loading conditions.

The evaluation of prepared microgroove pattern by femtosecond laser on alumina-zirconia nano-composite for endosseous dental implant application

Ceramic dental materials, especially alumina (20 %vol)-yttrium stabilized tetragonal zirconia poly crystal (A-Y-TZP20), have been considered as alternatives to metals for endosseous dental implant application. For increasing the bone-to-implant contact as well as the speed of bone formation, a new surface modification can be effective. The aim of this study was to design microgroove patterns by femtosecond laser on A-Y-TZP20 nano-composite disks for endosseous dental implant application. The phase composition and the morphology of the A-Y-TZP20 nano-composite samples were characterized using X-ray diffraction and Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy techniques. Statistical analysis was submitted to Kolmogorov-Smirnov test and Student's t test for independent variables, with a 5 % significance level. EDAX analysis revealed a significant decrease in the relative content of contaminants like carbon (p < 0.05) in laser surface-treated group as compared to non surface-treated group. X-ray diffraction did not show any change in the crystalline structure induced by laser processing. It was concluded that the femtosecond laser is a clean and safe method for surface modification of A-Y-TZP20.

Evaluation of stress distributions occurring on zirconia and titanium implant-supported prostheses: A three-dimensional finite element analysis

STATEMENT OF PROBLEM

Titanium implants have been successfully used to support fixed dental prostheses. Zirconia implants have been suggested as support for crowns, but information on their use to support partial fixed dental prostheses is limited.

PURPOSE

The purpose of this finite element study was to evaluate the maximum principal, minimum principal, and von Mises stresses and their distributions on zirconia and titanium implant-supported, partial fixed dental prostheses located in the anterior maxillary region.

MATERIAL AND METHODS

Zirconia and titanium implants (4 mm in diameter and 11. 5 mm in length) and prostheses made from 2 different materials (lithium disilicate and zirconia) were simulated, and 4 models were generated: Titan-IPS, Titan-Lava, Zircon-IPS, and Zircon-Lava. The maxillary bone was modeled as type 3 bone. The load was applied obliquely (534 N) and horizontally (76.5 N), and the stress values and distributions were examined.

RESULTS

Under horizontal loading, stresses generated on the cortical bone in the Zircon models were lower than those in the Titan models. Under oblique loading, stress values were similar in the same implant material and stress type. For all types of stress among the models, the stress values that occurred on the trabecular bone were found to be similar under both horizontal and oblique loading. The maximum stress values on the bones, implants, cores, and veneers did not exceed the strength of the structures.

CONCLUSIONS

Different stress values resulted from the different implant types. The prosthetic materials did not change the stress distributions in bone.

Osteoblast integration of dental implant materials after challenge by sub-gingival pathogens: a co-culture study in vitro

Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium (Ti), titanium-zirconium (TiZr) alloys and zirconia surfaces. Monoculture studies with either U2OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2OS osteoblasts were favourable on all materials. Adhering U2OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from TiZr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.

Histological analysis of loaded zirconia and titanium dental implants: an experimental study in the dog mandible

OBJECTIVE

To assess whether or not peri-implant soft tissue dimensions and hard tissue integration of loaded zirconia implants are similar to those of a titanium implant.

MATERIALS AND METHODS

In six dogs, two one-piece zirconia implants (VC, ZD), a two-piece zirconia implant (BPI) and a control one-piece titanium implant (STM) were randomly placed. CAD/CAM crowns were cemented at 6 months. Six months later, animals were killed and histomorphometric analyses were performed, including: the level of the mucosal margin, the extent of the peri-implant mucosa, the marginal bone loss and the bone-to-implant contact (BIC). Means of outcomes variables were calculated together with their corresponding 95% confidence intervals.

RESULTS

In general, the mucosal margin was located coronally to the implant shoulder. The buccal peri-implant mucosa ranged between 2.64 ± 0.70 mm (VC) and 3.03 ± 1.71 mm (ZD) (for all median comparisons p > 0.05). The relative marginal bone loss ranged between 0.65 ± 0.61 mm (BPI) and 1.73 ± 1.68 mm (ZD) (buccal side), and between 0.55 ± 0.37 mm (VC) and 1.69 ± 1.56 mm (ZD) (lingual side) (p > 0.05). The mean BIC ranged between 78.6% ± 17.3% (ZD) and 87.9% ± 13.6% (STM) without statistically significant differences between the groups (p > 0.05).

CONCLUSIONS

One- and two-piece zirconia rendered similar peri-implant soft tissue dimensions and osseointegration compared to titanium implants that were placed at 6 months of loading. Zirconia implants, however, exhibited a relatively high fracture rate.

Zirconia in dental implantology: A review

Background:

Titanium has been the most popular material of choice for dental implantology over the past few decades. Its properties have been found to be most suitable for the success of implant treatment. But recently, zirconia is slowly emerging as one of the materials which might replace the gold standard of dental implant, i.e., titanium.

Materials and Methods:

Literature was searched to retrieve information about zirconia dental implant and studies were critically analyzed. PubMed database was searched for information about zirconia dental implant regarding mechanical properties, osseointegration, surface roughness, biocompatibility, and soft tissue health around it. The literature search was limited to English language articles published from 1975 to 2015.

Results:

A total of 45 papers met the inclusion criteria for this review, among the relevant search in the database.

Conclusion:

Literature search showed that some of the properties of zirconia seem to be suitable for making it an ideal dental implant, such as biocompatibility, osseointegration, favourable soft tissue response and aesthetics due to light transmission and its color. At the same time, some studies also point out its drawbacks. It was also found that most of the studies on zirconia dental implants are short-term studies and there is a need for more long-term clinical trials to prove that zirconia is worth enough to replace titanium as a biomaterial in dental implantology.

Novel zirconia surface treatments for enhanced osseointegration: laboratory characterization

Purpose. The aim of this study was to evaluate three novel surface treatments intended to improve osseointegration of zirconia implants: selective infiltration etching treatment (SIE), fusion sputtering (FS), and low pressure particle abrasion (LPPA). The effects of surface treatments on roughness, topography, hardness, and porosity of implants were also assessed. Materials and Methods. 45 zirconia discs (19 mm in diameter × 3 mm in thickness) received 3 different surface treatments: selective infiltration etching, low pressure particle abrasion with 30 µm alumina, and fusion sputtering while nontreated surface served as control. Surface roughness was evaluated quantitatively using profilometery, porosity was evaluated using mercury prosimetry, and Vickers microhardness was used to assess surface hardness. Surface topography was analyzed using scanning and atomic force microscopy (α = 0.05). Results. There were significant differences between all groups regarding surface roughness (F = 1678, P < 0.001), porosity (F = 3278, P < 0.001), and hardness (F = 1106.158, P < 0.001). Scanning and atomic force microscopy revealed a nanoporous surface characteristic of SIE, and FS resulted in the creation of surface microbeads, while LPPA resulted in limited abrasion of the surface. Conclusion. Within the limitations of the study, changes in surface characteristics and topography of zirconia implants have been observed after different surface treatment approaches. Thus possibilities for enhanced osseointegration could be additionally offered.

An Overview of Zirconia Dental Implants: Basic Properties and Clinical Application of Three Cases

Due to the possible aesthetic problems of titanium implants, the developments in ceramic implant materials are increasing. Natural tooth colored ceramic implants may be an alternative to overcome aesthetic problems. The purpose of this article is to give information about the basic properties of dental zirconia implants and present 3 cases treated with two-piece zirconia implants. Two-piece zirconia dental implants, 4.0 mm diameter and 11.5 mm in length, were inserted into maxillary incisor region. They were left for 6 months to osseointegrate. Panoramic and periapical radiographs were obtained and examined for bone-implant osseointegration. During the follow-up period the patients were satisfied with their prosthesis and no complication was observed.

Osseointegration of short titan implants: A pilot study in pigs

Reduced vertical bone level in the implantation area is often considered one of the limiting factors before implant insertion. Inserting implants of reduced length might be useful in order to avoid vertical bone augmentation prior to implantation. To the present day, no official guidelines exist as to the optimal length for these implants. It is nevertheless well known that the stability of an implant depends primarily on its osseointegration, which could otherwise be influenced by modifying implant surface texture. The aim of our study was to evaluate osseointegration in correlation with implant length and surface texture. Three different variations of titan implants (n=5) were compared: two types, each with an acid-etched and ceramic blasted surface, were inserted in the upper jaw of adult female minipigs at different lengths (tioLogic ST Shorty, 5mm length; tioLogic ST, 9mm length) and were compared to a control group (tioLogic ST, 9mm length, ceramic blasted surface). Eight weeks after unloaded healing, bone tissue specimens containing the implants were processed, stained with Masson-Goldner-trichrome and analyzed histologically. Regardless of implant length and surface texture, new bone formation with no signs of inflammation could be detected in the area of the threads. Implants with a modified surface showed no statistically significant difference in bone-implant-contact (BIC) (tioLogic ST Shorty, 56.5%; tioLogic(©)ST; 77.2%), but a statistically significant difference could be found, when the 9mm implants were compared to the control group (BIC 48.9%). Surface modification could positively influence osseointegration as well as contribute to overcoming the adverse effects of length reduction.

A Pig Model for the Histomorphometric Evaluation of Hard Tissue Around Dental Implants

This study aimed to evaluate the frontal bone of Swiss Domestic pigs as an animal model for the histologic-histomorphometric examination of bony tissue around dental implants. We inserted SLA surface implants 4.1 mm in diameter and 10 mm in length into the frontal bones of 9 Swiss-Domestic pigs. Histologic and histomorphometric studies were conducted on the undecalcified sections. Histologic examinations showed that the specimens contain a sufficient amount of bone to provide homogenous bone coverage for standard diameter dental implant placement. The mean bone to implant contact was 61.9% ± 8.7%. Other histomorphometric parameters revealed the regular trabecular architecture at this site. Pigs' frontal bone appears to be a suitable animal model in short-term dental implant studies because it provides a sufficient amount of bone and favorable bone microarchitecture.

A single-tooth, two-piece zirconia implant located in the anterior maxilla: a clinical report

It can be difficult to achieve a natural appearance in the anterior region with implant-supported restorations because metal components may show through the soft tissue. Zirconia implants, therefore, should be considered as an alternative treatment for improved esthetics. The goal of this clinical report was to evaluate a new 2-piece zirconia implant system for the maxillary anterior region. A 2-piece zirconia dental implant was placed in the maxillary left lateral incisor position and left in place for 6 months to osseointegrate. Panoramic and periapical radiographs were examined for bone-implant osseointegration. The plaque control record (PCR), bleeding on probing (BOP), and probing depth (PD) were measured after the cementation of the definitive restoration and a 6-month follow-up period. The PCR, BOP, and PD values were compared and the marginal bone level was also evaluated by making standardized periapical radiographs. The results showed that over the 6-month follow-up period, the marginal area was healthy and presented no bleeding on probing, no plaque accumulation, and no change in periimplant marginal bone level.