Inflammatory Response to Wear Particles: Comparisons Between Zirconia and Titanium In Vitro.

PURPOSE: To compare the inflammatory responses of peripheral blood mononuclear cells (PBMCs) subjected to titanium (Ti) and/or zirconia (Zr) particles while growing on Ti or Zr discs. MATERIALS AND METHODS: In total, 240 discs were fabricated at a size of 2 mm in height and 5 mm in diameter. Of the 240 discs, 120 discs were made of Ti (commercially pure [CP] grade 4), and 120 discs were made of Zr (3 mol% yttria-stabilized zirconia polycrystals [3Y-TZP]). The PBMCs were cultured on the two-disc materials, and particles with a size up to 20 mm Ti (99.5% Ti) and 0.1 to 0.2 mm Zr (3Y-TZP) were added to the cultures. The concentration levels of inflammatory cytokines in culture supernatants were measured through Bio-Plex assay (Bio-Rad Laboratories), and light microscopic analysis was performed to detect cell attachment and characterize particle shape and cell-particle interaction. RESULTS: The inflammatory responses of PBMCs were generally higher when cells were cultured on a Ti surface compared to a Zr surface. In addition, higher cytokine levels were seen when cells were cultured in the presence of Ti particles compared to Zr particles when no discs were used. However, there were only significantly increased levels for three cytokines (MCP-1, IFN-γ, and TNF-α) when particles were added to Ti discs. Higher release of neutrophil extracellular traps (NETs) from neutrophils were seen in presence of Zr particles compared to Ti particles. A reduction in cell death was observed in the presence of Zr particles compared to Ti particles and unstimulated control samples. CONCLUSIONS: The type of growth material and presence of particle affects PBMCs in vitro. Cells seeded on Ti discs and together with Ti particles generated higher levels of inflammatory cytokines compared to the Zr counterparts.

Aseptic Silk Ligatures Induce Bone Resorption Around Titanium Implants: A 12-week Pilot Study in Rabbits.

PURPOSE: Marginal bone resorption (MBR) around oral implants may sometimes be a selflimiting condition due to balancing immunological reactions against the utilized materials, rather than a progressive bacterial infection. Contrary to previous assumptions from ligature induced experimental peri-implantitis studies, our recent 8-week experiment showed that marginal ligatures per se trigger an inflammatory immune response, resulting in bone resorption around implants in absence of a plaque. The present study aims to investigate whether this inflammatory/immunological reaction attenuates or progresses toward implant failure after a longer healing time, 12 weeks. MATERIALS AND METHODS: Sterile silk ligatures were placed around the top of titanium (Ti) implants and compressed against the femoral cortical bone plate of 6 rabbits. A non-ligated implant was used as control. After 12 weeks of submerged healing, ground sections of implants and surrounding tissues were investigated with light microscopy. The marginal soft tissues were also analyzed using selected qPCR markers. RESULTS: Histologically, the ligatures were outlined by immune cells, including multinucleated giant cells (MNGC), with adjacent fibrous encapsulation and resorbed peripheral bone that contrasted from the osseointegrated non-ligated control implants. The difference in expression of qPCR markers was not significant, but >2-fold upregulation of markers CD11b, IL1b, ARG1, NCF1, CD4 and >2-fold downregulation of CD8 indicated a mild, focal inflammatory/immune response against the ligatures compared to controls, with upregulation of M1 and M2 macrophages, neutrophils and helper T-cells and downregulation of killer T cells. Further, the bone formation markers OC and ALPL were >2 fold down regulated, consistent with the lack of osseointegration of the ligatures, compared to control implants. CONCLUSIONS: Marginal silk ligatures per se trigger an inflammatory/immune response and aseptic bone resorption around oral implants. Compared to our previous 8-week study, the inflammatory reaction against the silk appears to attenuate with time, with only a mild persisting inflammation that may block osseointegration and instead maintains a fibrous tissue encapsulation type reaction. This may explain why traditional ligature experiments have required regular exchange of ligatures in order for the bone resorption to progress.

Inflammatory Gene Profile and Particle Presence in Peri-Implant Mucosa: a Pilot Study on 9 Patients.

Objectives: The purpose of this pilot study is to compare gene expression in mucosa around dental implants with zirconia abutment to titanium and investigate presence of particles in mucosa samples and on implant heads. Material and Methods: Ten patients with a single implant supported prosthesis connected to zirconia or titanium abutments were invited at the five-year control. A clinical examination and a survey on experience of function and appearance were conducted. A mucosa biopsy taken in close vicinity to the implant were analysed by real-time polymerase chain reaction (qPCR) and presence of particles in a scanning electron microscope/energy-dispersive X-ray spectroscope (SEM/EDX). Cytological smear samples were collected and analysed through inductively coupled plasma mass spectrometry (ICP-MS) to investigate presence of particles on implant heads. Results: In total, 9 patients participated in the study, five with titanium abutments and four with zirconia abutments. All patients were satisfied with function and aesthetics. Titanium and iron particles were detected in mucosa biopsies. The ICP - MS analysis demonstrated presence of zirconia and titanium. Several proinflammatory genes were upregulated in the zirconia abutment group. Conclusions: Around zirconia abutments a slight increase in proinflammatory response and amount of wear particles was seen as compared to titanium. Wear particles of titanium were present in all soft tissue samples, however zirconia particles only in the samples from implants heads/mucosa with zirconia abutments.

On the material dependency of peri-implant morphology and stability in healing bone.

The microstructural architecture of remodeled bone in the peri-implant region of screw implants plays a vital role in the distribution of strain energy and implant stability. We present a study in which screw implants made from titanium, polyetheretherketone and biodegradable magnesium-gadolinium alloys were implanted into rat tibia and subjected to a push-out test four, eight and twelve weeks after implantation. Screws were 4 mm in length and with an M2 thread. The loading experiment was accompanied by simultaneous three-dimensional imaging using synchrotron-radiation microcomputed tomography at 5 µm resolution. Bone deformation and strains were tracked by applying optical flow-based digital volume correlation to the recorded image sequences. Implant stabilities measured for screws of biodegradable alloys were comparable to pins whereas non-degradable biomaterials experienced additional mechanical stabilization. Peri-implant bone morphology and strain transfer from the loaded implant site depended heavily on the biomaterial utilized. Titanium implants stimulated rapid callus formation displaying a consistent monomodal strain profile whereas the bone volume fraction in the vicinity of magnesium-gadolinium alloys exhibited a minimum close to the interface of the implant and less ordered strain transfer. Correlations in our data suggest that implant stability benefits from disparate bone morphological properties depending on the biomaterial utilized. This leaves the choice of biomaterial as situational depending on local tissue properties.

Dental implant surface morphology, chemical composition, and topography following double wavelength (2780/940 nm) laser irradiation. An in vitro study.

OBJECTIVE: The aim of this in vitro study was to evaluate morphology alterations, chemical composition, and topography of moderately rough dental implants following double-wavelength laser irradiation. MATERIAL AND METHODS: Commercial-grade titanium dental implants representing different surface characteristics (Osseospeed [OS], TiUnite [TiU], and Roxolid SLActive [RS]) were used. Laser irradiation was performed using a computer-controlled robotic device with calibrated energy/power settings and deionized water spray. Micro-, nano-morphology surface alterations, chemical composition, and surface topography (Sa , Sds , Sdr ) in the test group (laser plus water), control group A (water only), and control group B (no treatment) were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and white light laser profilometer (Interferometry). RESULTS: SEM-evaluation revealed minor between-group differences in micro- and nano-morphology within each implant system. Significant overall differences in surface element content were observed between the test and control group B for all implant systems (p < .05). For the test compared with control group B, statistically significantly higher oxygen content was detected for OS and RS (p < .05), a corresponding significant difference was detected for carbon for TiU (p < .05). For RS, a significantly lower content of titanium and zirconium was detected within the test group (p < .05). A significant difference in topography between test and control group B was observed for OS (Sa : p = .039 and Sdr : p = .041) with the highest roughness value for control group B. CONCLUSIONS: Altered chemical composition and surface topography were observed for all implant surfaces compared with untreated control following double wavelength laser irradiation. A clinical evaluation of the impact of the altered surface composition following double wavelength laser irradiation on the ability to reosseointegrate appears warranted.

Implant-Supported Single Crowns with Titanium or Zirconia Abutments: A Retrospective Up-to-5-year Follow-up Study.

PURPOSE: To compare the clinical outcomes of single implants with titanium (Ti) or zirconia (Zr) abutments after up to 5 years in function. MATERIALS AND METHODS: This study was a retrospective analysis on single implants with screw-retained abutments (Zr or Ti) covered with porcelain veneer placed between 2011 and 2013 at one referral specialist clinic. Clinical data from patient records were collected from 132 patients and 174 implants. Technical complications such as fractures, chipping, and abutment screw loosening were registered. Radiographs were analyzed comparing both annual bone loss and accumulated bone loss at 5 years. In 57 patients with 85 implants, the values of accumulated bone loss at 5 years were compared to baseline. RESULTS: Technical complications occurred in 16 (9%) of the implants, most often during the first year. The following complications were found: fracture of the abutment (n = 1); loosening of the abutment screws (n = 5); and chipping of the porcelain veneer (n = 11). Ti abutments had more complications than Zr abutments (79%). Of all the implants, 45% had an annual bone loss ranging between 0.05 and 2.15 mm, and 59% had an accumulated bone loss at 5 years ranging between 0.05 and 4.25 mm. Zr abutments had a statistically significantly higher amount of yearly and accumulated bone loss at 5 years. CONCLUSION: Abutment material affected marginal bone loss. The Zr group displayed statistically more bone loss both yearly and after 5 years compared to the Ti group. Technical complications were not affected by abutment material but were affected by age of the patient.

Review of PEEK implants and biomechanical and immunological responses to a zirconium phosphate nano-coated PEEK, a blasted PEEK, and a turned titanium implant surface.

PURPOSE: To investigate the biomechanical and immunological reactions to coated and non-coated blasted PEEK implants in vivo after 12 weeks and review the associated literature. METHODS: Two osteotomy sites were performed in each proximal tibia of 10 lop-eared rabbits (n= 4 per rabbit). Each rabbit received a randomly placed (1) blasted zirconium phosphate nano-coated PEEK- (nano-ZrP), (2) blasted PEEK- (PEEK) and (3) titanium implant (Ti) and an empty sham site. At 12 weeks, removal torque of all implants and biological investigation with qPCR was performed. The implant surfaces were analyzed prior to insertion with interferometry, SEM and XPS. RESULTS: The interferometry analysis showed that there was no difference in roughness for the uncoated PEEK compared to the ZrP coated PEEK implants. The titanium implants were considerably smoother (Sa= 0.23 µm) than the uncoated Sa= 1.11 µm) and ZrP coated PEEK implants (Sa= 1.12 µm). SEM analysis on the PEEK implants corroborated the interferometry results; no difference in structure between the uncoated vs. the ZrP coated PEEK was visible on the micrometer level. At higher magnifications, the ZrP coating was visible in the SEM as a thin, porous network. All tested implants displayed osseointegration with the highest RTQ for nano-ZrP (18.4 Ncm) followed by PEEK (14.5 Ncm) and Ti (11.5 Ncm). All implants activated the immune system, with elevated macrophage and M2 macrophage qPCR markers at 12 weeks compared to the sham site. CLINICAL SIGNIFICANCE: Nano-ZrP coating improves osseointegration of blasted PEEK implants at 12 weeks of follow-up. Osseointegration of titanium, PEEK and nano-ZrP PEEK is not a normal bone healing process, but rather a shield-off mechanism that appears to be regulated by the innate immune system.

High-resolution ex vivo analysis of the degradation and osseointegration of Mg-xGd implant screws in 3D.

Biodegradable magnesium (Mg) alloys can revolutionize osteosynthesis, because they have mechanical properties similar to those of the bone, and degrade over time, avoiding the need of removal surgery. However, they are not yet routinely applied because their degradation behavior is not fully understood. In this study we have investigated and quantified the degradation and osseointegration behavior of two biodegradable Mg alloys based on gadolinium (Gd) at high resolution. Mg-5Gd and Mg-10Gd screws were inserted in rat tibia for 4, 8 and 12 weeks. Afterward, the degradation rate and degradation homogeneity, as well as bone-to-implant interface, were studied with synchrotron radiation micro computed tomography and histology. Titanium (Ti) and polyether ether ketone (PEEK) were used as controls material to evaluate osseointegration. Our results showed that Mg-5Gd degraded faster and less homogeneously than Mg-10Gd. Both alloys gradually form a stable degradation layer at the interface and were surrounded by new bone tissue. The results were correlated to in vitro data obtained from the same material and shape. The average bone-to-implant contact of the Mg-xGd implants was comparable to that of Ti and higher than for PEEK. The results suggest that both Mg-xGd alloys are suitable as materials for bone implants.

Wear particle release at the interface of dental implant components: Effects of different material combinations. An in vitro study.

OBJECTIVES: Particle generation from implant components caused by frictional wear affect the surrounding peri-implant tissues. The objective of this study was to evaluate the effect of combining implant and abutment materials on wear and particle release in a dynamical loading setup. METHODS: A customized dynamical loading machine was used to subject two implant materials (Titanium and Titanium- Zirconium alloy) paired with two different abutment materials (Titanium and Zirconia) to a cyclic loading set of 240.000 cycles (simulating 1 year of clinical use). The implant and abutment complex was immersed in corrosive liquid to collect particle debris and measure the release of corroded ions. Scanning electron microscopy was used to analyze signs of wear on the components after testing and evaluate the size and composition of particle debris. RESULTS: Wear signs were evident in all material couplings. Particle debris was found on top, inside the implants, and on the abutment heads. The particle size ranged between 0.6 and 16.9 µm, with larger particles composed of Ti. Smaller-sized particles were found in the container liquid ranging from 0.253 to 1.7 µm compared to inside the implants ranging from 3.25 to 95.3 µm. Larger particles were found inside Tizr implants compared to Ti implants. Low levels of ions released due to corrosion were found when measuring content in surrounding liquid. SIGNIFICANCE: Particle generation is evident when subjecting dental implant and abutment couplings in a dynamic loading setup. Internally connected implants hinder the release of larger particles to surrounding container liquid.

The use of implant-level connection in screw-retained fixed partial dentures: A 3-year randomised clinical trial.

OBJECTIVES: This randomised controlled trial compares the 3-year outcomes, that is, marginal bone-level (MBL) changes and clinical parameters, between an abutment-level (AL) and implant-level (IL) connection for implants with an internal conical connection (ICC) supporting a screw-retained fixed partial denture. MATERIAL AND METHODS: Fifty patients with 119 implants were randomly allocated to either the AL or IL group. Radiographic and clinical examinations were performed after one, two, and 3 years. A linear mixed model was used to evaluate the differences between groups. RESULTS: The MBL change was not significantly different between the groups at any point. The MBL was 0.12 ± 0.31 mm (AL) and 0.23 ± 0.26 mm (IL) after 1 year; 0.15 ± 0.34 mm (AL) and 0.17 ± 0.22 mm (IL) after 2 years; 0.18 ± 0.39 mm (AL) and 0.15 ± 0.21 mm (IL) after 3 years. The bleeding on probing was 43.44 ± 39.24% (AL) and 58.19 ± 41.20% (IL) after 1 year; 35.78 ± 39.22% (AL) and 50.43 ± 41.49% (IL) after 2 years; 51.27 ± 44.63% (AL) and 49.57 ± 37.31% (IL) after 3 years and was significantly different (p = .025) between 1 and 2 years. The probing depth showed a significant difference at each time point while the plaque was not significant between the groups. The overall technical, biological and prosthetic complication rates were 5.04%, 3.36%, and 16.00%, respectively. CONCLUSIONS: The MBL change was similar in the groups. The slight differences in the soft tissue complications between the groups are likely not of clinical relevance. An IL connection is considered to be a valid alternative to an AL set-up in ICC implants.

Quality Assessment of Five Randomly Chosen Ceramic Oral Implant Systems: Cleanliness, Surface Topography, and Clinical Documentation.

PURPOSE: After some initial setbacks in the 1970s, ceramic implants seem to be a promising alternative to titanium implants. Since the surface of an implant system represents the interface to surrounding biologic structures, the study focuses on cleanliness and surface topography. Clinical documentation of the corresponding systems completes the picture and allows a better evaluation of zirconia implant systems. MATERIALS AND METHODS: Five different ceramic implant systems were selected randomly and purchased via blind-shopping: Z5s (Z-Systems), ZiBone (COHO), W implant (TAVDental), ceramic. implant (vitaclinical), and BioWin!/Standard Zirkon Implantat (Champions-Implants/ZV3 system). Three samples of each implant system underwent scanning electron microscopy (SEM) imaging and elemental analysis (EDS). Where appropriate, subsequent Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was performed to identify the chemical nature of impurities. Surface topography was evaluated, and a search for clinical trials in the PubMed database, on the websites and by written request to each dental implant manufacturer, was performed. RESULTS: Surfaces of Champions implants (ZV3) and Z-Systems implants were relatively clean, whereas the other investigated surfaces of vitaclinical, TAV Dental, and ZiBone implants all displayed organic contaminations on their surfaces. Four of the investigated ceramic implants showed a moderately rough implant surface. Only the vitaclinical ceramic.implant had minimal surface roughness. Three ceramic designs-vitaclinical, ZV3, and Z-Systems-had clinical trials documented with up to 3 years of follow-up and results varying between 82.5% and 100% survival. TAV Dental W and ZiBone implant systems lacked properly conducted clinical recording of results. CONCLUSION: The results of this study showed that it is technically possible to produce zirconia implants that are largely residue-free. On the other hand, the variety of significant residues found in this analysis raises concerns, as contamination may lead to undesirable biologic effects. The lack of clinical studies in peer-reviewed journals does not seem to be relevant for the approval of marketing, nor does the lack of surface cleanliness. In the authors' opinion, a critical analysis of these aspects should be included in a more stringent future analysis prior to the marketing of oral implant systems.

Multimodal ex vivo methods reveal that Gd-rich corrosion byproducts remain at the implant site of biodegradable Mg-Gd screws.

Extensive research is being conducted on magnesium (Mg) alloys for bone implant manufacturing, due to their biocompatibility, biodegradability and mechanical properties. Gadolinium (Gd) is among the most promising alloying elements for property control in Mg alloy implants; however, its toxicity is controversial. Investigating Gd behavior during implant corrosion is thus of utmost importance. In this study, we analyzed the degradation byproducts at the implant site of biodegradable Mg-5Gd and Mg-10Gd implants after 12 weeks healing time, using a combination of different imaging techniques: histology, energy-dispersive x-ray spectroscopy (EDX), x-ray microcomputed tomography (µCT) and neutron µCT. The main finding has been that, at the healing time in exam, the corrosion appears to have involved only the Mg component, which has been substituted by calcium and phosphorus, while the Gd remains localized at the implant site. This was observed in 2D by means of EDX maps and extended to 3D with a novel application of neutron tomography. X-ray fluorescence analysis of the main excretory organs also did not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy happened during degradation. STATEMENT OF SIGNIFICANCE: Gadolinium is among the most promising alloying elements for property control in biodegradable magnesium alloy implants, but its toxicity is controversial and its behavior during corrosion needs to be investigated. We combine 2D energy dispersive x-ray spectroscopy and 3D neutron and x-ray tomography to image the degradation of magnesium-gadolinium implants after 12 weeks of healing time. We find that, at the time in exam, the corrosion has involved only the magnesium component, while the gadolinium remains localized at the implant site. X-ray fluorescence analysis of the main excretory organs also does not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy has happened during degradation.

Fixed full-arch maxillary prostheses supported by four versus six implants with a titanium CAD/CAM milled framework: 3-year multicentre RCT.

OBJECTIVES: This RCT compares marginal bone level (MBL) change and the clinical parameters after a 3-year function in maxillary implant-supported fixed complete dentures (FCDs) treated with four-implants (4-I) or six-implants (6-I). MATERIAL AND METHOD: Three centres treated 56 patients with 280 implants allocated to the 4-I or 6-I group. Radiographic and clinical examinations were performed. The primary outcome was to investigate MBL change between the groups. RESULTS: Implant survival rates were 100% and 99% in the 4-I and 6-I groups, respectively. Considering the clustering effects, the MBL change was not significantly different between the groups over the 3-year follow-up. The MBL in the 4-I group was 0.30 ± 0.50 mm at baseline, 0.24 ± 0.31 mm at 1 year and 0.24 ± 0.38 mm at 3 years. In the 6-I group, MBL was 0.14 ± 0.32 mm at baseline, 0.16 ± 0.35 mm at 1 year and 0.12 ± 0.26 mm at 3 years. There was a statistically significant difference between the groups at BL and 3Y. No significant differences between the groups were reported for clinical parameters at each time point as well as in between the visits. The technical and biological complications rates were 1.6% and 6.0%, respectively. Prosthetic complications affected 25 FCDs (47.2%). CONCLUSION: Marginal bone level change revealed a stable condition in the 3-year period in the two groups. Few technical and biological complications occurred apart from the chipping/fracture of the prosthetic teeth. Four-implant is a feasible solution if the rehabilitation is oriented towards the most cost-effective treatment and towards avoiding bone augmentation procedures. Clinicians have to consider the potential required visits for prosthetic maintenance.

Cobalt-chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness.

OBJECTIVE: To investigate the metal ion release, surface roughness and cytoxicity for Co-Cr alloys produced by different manufacturing techniques before and after heat treatment. In addition, to evaluate if the combination of materials affects the ion release. METHODS: Five Co-Cr alloys were included, based on four manufacturing techniques. Commercially pure titanium, CpTi grade 4 and a titanium alloy were included for comparison. The ion release tests involved both Inductive Coupled Plasma Optical Emission Spectrometry and Inductive Coupled Plasma Mass Spectrometry analyses. The surface analysis was conducted with optical interferometry. Cells were indirectly exposed to the materials and cell viability was evaluated with the MTT (3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) method. RESULTS: All alloys showed a decrease of the total ion release when CpTi grade 4 was present. The total ion release decreased over time for all specimens and the highest ion release was observed from the cast and milled Co-Cr alloy in acidic conditions. The cast and laser-melted Co-Cr alloy and the titanium alloy became rougher after heat treatment. All materials were within the limits of cell viability according to standards. SIGNIFICANCE: The ion release from Co-Cr alloys is influenced by the combination of materials, pH and time. Surface roughness is influenced by heat treatment. Furthermore, both ion release and surface roughness are influenced by the manufacturing technique and the alloy type. The clinical implication needs to be further investigated.

Immediate Loading of Single Implants, Guided Surgery, and Intraoral Scanning: A Nonrandomized Study.

PURPOSE: To compare clinical and esthetic outcomes between immediately loaded single implants placed with and without a fully guided surgical procedure. MATERIALS AND METHODS: Patients with a missing maxillary tooth (second premolar to second premolar) were considered for inclusion in this 1-year prospective nonrandomized study. Exclusion criteria were general health contraindications for oral surgery besides the need for bone grafting or ridge augmentation. One group received digital implant planning, fully guided surgery, and immediate loading (DIL). The other group received freehand surgery and immediate loading (IL). Outcome measures were implant survival, marginal bone loss, soft tissue changes, papilla index, pink and white esthetic scores (PES and WES, respectively), and patient-reported outcome measures (PROMs). RESULTS: Two of 21 implants failed in the DIL group soon after placement, resulting in a 1-year implant survival rate of 90.5%, while no implants failed in the IL group. Significantly higher papilla index scores and lower soft tissue changes were found for the DIL group compared to the IL group. No differences were found after 1 year regarding marginal bone loss, PES, WES, or PROMs. CONCLUSION: Within the limitations of this study, immediate loading in combination with fully guided surgery might negatively affect implant survival. Immediate loading, fully guided surgery, and a digital workflow appear to have a positive effect on early soft tissue adaptation.

An Imbalance of the Immune System Instead of a Disease Behind Marginal Bone Loss Around Oral Implants: Position Paper.

PURPOSE: The purpose of this paper is to present evidence that supports the notion that the primary reason behind marginal bone loss and implant failure is immune-based and that bacterial actions in the great majority of problematic cases are of a secondary nature. MATERIALS AND METHODS: The paper is written as a narrative review. RESULTS: Evidence is presented that commercially pure titanium is not biologically inert, but instead activates the innate immune system of the body. For its function, the clinical implant is dependent on an immune/inflammatory defense against bacteria. Biologic models such as ligature studies have incorrectly assumed that the primary response causing marginal bone loss is due to bacterial action. In reality, bacterial actions are secondary to an imbalance of the innate immune system caused by the combination of titanium implants and ligatures, ie, nonself. This immunologic imbalance may lead to marginal bone resorption even in the absence of bacteria. CONCLUSION: Marginal bone loss and imminent oral implant failure cannot be properly analyzed without a clear understanding of immunologically caused tissue responses.

Analysis of the bone ultrastructure around biodegradable Mg-xGd implants using small angle X-ray scattering and X-ray diffraction.

Magnesium alloys are increasingly researched as temporary biodegradable metal implants in bone applications due to their mechanical properties which are more similar to bone than conventional implant metals and the fact that Magnesium occurs naturally within the body. However, the degradation processes in vivo and in particular the interaction of the bone with the degrading material need to be further investigated. In this study we are presenting the first quantitative comparison of the bone ultrastructure formed at the interface of biodegradable Mg-5Gd and Mg-10Gd implants and titanium and PEEK implants after 4, 8 and 12 weeks healing time using two-dimensional small angle X-ray scattering and X-ray diffraction. Differences in mineralization, orientation and thickness of the hydroxyapatite are assessed. We find statistically significant (p < 0.05) differences for the lattice spacing of the (310)-reflex of hydroxyapatite between titanium and Mg-xGd materials, as well as for the (310) crystal size between titanium and Mg-5Gd, indicating a possible deposition of Mg within the bone matrix. The (310) lattice spacing and crystallite size further differ significantly between implant degradation layer and surrounding bone (p < 0.001 for Mg-10Gd), suggesting apatite formation with significant amounts of Gd and Mg within the degradation layer. STATEMENT OF SIGNIFICANCE: Biodegradable Magnesium-based alloys are emerging as a viable alternative for temporary bone implant applications. However, in order to understand if the degradation of the implant material influences the bone ultrastructure, it is necessary to study the bone structure using high-resolution techniques. We have therefore employed 2D small angle X-ray scattering and X-ray diffraction to study the bone ultrastructure surrounding Magnesium-Gadolinium alloys as well as Titanium and PEEK alloys at three different healing times. This is the first time, that the bone ultrastructure around these materials is directly compared and that a statistical evaluation is performed. We found differences indicating a possible deposition of Mg within the bone matrix as well as a local deposition of Mg and/or Gd at the implant site. DATA AVAILABILITY STATEMENT: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

Osseointegration effects of local release of strontium ranelate from implant surfaces in rats.

BACKGROUND: Numerous studies have reported the beneficial effects of strontium on bone growth, particularly by stimulating osteoblast proliferation and differentiation. Thus, strontium release around implants has been suggested as one possible strategy to enhance implant osseointegration. AIM: This study aimed to evaluate whether the local release of strontium ranelate (Sr-ranelate) from implants coated with mesoporous titania could improve bone formation around implants in an animal model. MATERIALS AND METHODS: Mesoporous titania (MT) thin coatings were formed utilizing the evaporation induced self-assembly (EISA) method using Pluronic (P123) with or without the addition of poly propylene glycol (PPG) to create materials with two different pore sizes. The MT was deposited on disks and mini-screws, both made of cp Ti grade IV. Scanning electron microscopy (SEM) was performed to characterize the MT using a Leo Ultra55 FEG instrument (Zeiss, Oberkochen, Germany). The MT was loaded with Sr-ranelate using soaking and the drug uptake and release kinetics to and from the surfaces were evaluated using quartz crystal microbalance with dissipation monitoring (QCM-D) utilizing a Q-sense E4 instrument. For the in vivo experiment, 24 adult rats were analyzed at two time points of implant healing (2 and 6 weeks). Titanium implants shaped as mini screws were coated with MT films and divided into two groups; supplied with Sr-ranelate (test group) and without Sr-ranelate (control group). Four implants (both test and control) were inserted in the tibia of each rat. The in vivo study was evaluated using histomorphometric analyses of the implant/bone interphase using optical microscopy. RESULTS: SEM images showed the successful formation of evenly distributed MT films covering the entire surface with pore sizes of 6 and 7.2 nm, respectively. The QCM-D analysis revealed an absorption of 3300 ng/cm2 of Sr-ranelate on the 7.2 nm MT, which was about 3 times more than the observed amount on the 6 nm MT (1200 ng/cm2). Both groups showed sustained release of Sr-ranelate from MT coated disks. The histomorphometric analysis revealed no significant differences in bone implant contact (BIC) and bone area (BA) between the implants with Sr-ranelate and implants in the control groups after 2 and 6 weeks of healing (BIC with a p-value of 0.43 after 2 weeks and 0.172 after 6 weeks; BA with a p-value of 0.503 after 2 weeks, and 0.088 after 6 weeks). The mean BIC and BA values within the same group showed significant increase among all groups between 2 and 6 weeks. CONCLUSION: This study could not confirm any positive effects of Sr-ranelate on implant osseointegration.

On the Cleanliness of Different Oral Implant Systems: A Pilot Study.

(1) Background: This paper aimed to compare the cleanliness of clinically well-documented implant systems with implants providing very similar designs. The hypothesis was that three well-established implant systems from Dentsply Implants, Straumann, and Nobel Biocare were not only produced with a higher level of surface cleanliness but also provided significantly more comprehensive published clinical documentation than their correspondent look-alike implants from Cumdente, Bioconcept, and Biodenta, which show similar geometry and surface structure. (2) Methods: Implants were analyzed using SEM imaging and energy-dispersive X-ray spectroscopy to determine the elemental composition of potential impurities. A search for clinical trials was carried out in the PubMed database and by reaching out to the corresponding manufacturer. (3) Results: In comparison to their corresponding look-alikes, all implants of the original manufacturers showed-within the scope of this analysis-a surface free of foreign materials and reliable clinical documentation, while the SEM analysis revealed significant impurities on all look-alike implants such as organic residues and unintended metal particles of iron or aluminum. Other than case reports, the look-alike implant manufacturers provided no reports of clinical documentation. (4) Conclusions: In contrast to the original implants of market-leading manufacturers, the analyzed look-alike implants showed significant impurities, underlining the need for periodic reviews of sterile packaged medical devices and their clinical documentation.

Aseptic Ligatures Induce Marginal Peri-Implant Bone Loss-An 8-Week Trial in Rabbits.

The clinical value of ligature-induced experimental peri-implantitis studies has been questioned due to the artificial nature of the model. Despite repeated claims that ligatures of silk, cotton and other materials may not induce bone resorption by themselves; a recent review showed that the tissue reaction toward them has not been investigated. Hence, the current study aimed to explore the hard and soft tissue reactions toward commonly used ligature materials. A total of 60 dental implants were inserted into the femur (n = 20) and tibia (n = 40) of 10 rabbits. The femoral implants were ligated with sterile 3-0 braided silk in one leg and sterile cotton retraction chord in the other leg. The tibial implants were ligated with silk or left as non-ligated controls. All wounds were closed in layers. After a healing time of 8 weeks, femoral (silk versus cotton) and proximal tibial (silk versus non-ligated control) implants were investigated histologically. Distal tibial (silk versus non-ligated control) implants were investigated with real time polymerase chain reaction (qPCR). The distance from the implant-top to first bone contact point was longer for silk ligated implants compared to non-ligated controls (p = 0.007), but did not vary between cotton and silk. The ligatures triggered an immunological reaction with cell infiltrates in close contact with the ligature materials, adjacent soft tissue encapsulation and bone resorption. qPCR further demonstrated an upregulated immune response toward the silk ligatures compared to non-ligated controls. Silk and cotton ligatures provoke foreign body reactions of soft tissue encapsulation type and bone resorption around implants in the absence of plaque.