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.

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.

Cobalt chromium alloys in fixed prosthodontics: Investigations of mechanical properties and microstructure.

STATEMENT OF PROBLEM: Cobalt chromium (Co-Cr) alloys possess beneficial mechanical properties because alloys, even in thin sections, can resist high mastication forces and exhibit an acceptable bond to the surface porcelain layer. Traditional manufacturing techniques of Co-Cr alloys such as casting have been replaced with newer fabrication techniques, such as milling, laser melting, and presintered milling. Despite scarce documentation, these new manufacturing techniques are being used to fabricate dental and implant constructions. PURPOSE: This in vitro study investigates the hardness, yield strength, elastic modulus, and microstructure of the most commonly used Co-Cr alloys for fixed prosthodontics based on manufacturing technique. In addition, this study investigates the effect of heat treatment on the mechanical properties and microstructure of these materials. MATERIAL AND METHODS: Five Co-Cr alloys were included (dumbbell and rectangular shaped) based on four manufacturing techniques: cast, milled, laser melted, and presintered milled. Commercially pure titanium grade 4 and titanium-6 aluminum-4 vanadium ELI (extra low interstitial) were included for comparison, and yield strength and elongation after fracture were evaluated. The specimens were tested for hardness using the Vickers test and for elastic modulus using a nondestructive impulse excitation technique. The microstructure of selected specimens was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS). RESULTS: The mechanical properties depend on the manufacturing technique used; the laser-melted and presintered Co-Cr specimens demonstrated the highest mechanical properties, followed by the milled and cast groups. Both the laser-melted and the presintered milled Co-Cr specimens showed smaller grain size compared with the cast and milled Co-Cr specimens. The titanium-6 aluminum-4 vanadium ELI demonstrated higher hardness and yield strength compared to commercially pure titanium grade 4. No major differences were observed for the selected materials regarding the mechanical properties and microstructural appearance after heat treatment. CONCLUSIONS: The laser melting and presintered milling techniques produced higher mechanical properties compared with the cast and milled Co-Cr. These findings were confirmed through microstructural analysis with respect to the grain size, precipitation, and number of pores.

Long-term performance of implants with moderately rough anodized surface supporting single-tooth restorations: A retrospective analysis with an up to 15-year follow-up.

OBJECTIVES: This retrospective study aimed to evaluate long-term clinical and radiologic performance of anodized surface implants supporting single implant restorations. MATERIALS AND METHODS: Patients who received at least one anodized surface implant for a single-tooth restoration between 2003 and 2004 in the Brånemark clinic (Göteborg, Sweden) were included in the study. The assessed outcomes included implant survival, biological and technical complications, as well as marginal bone levels (MBL) based on radiographs. Baseline data on patient demographics, implant placement, and surgery details were also collected. The cumulative survival rate (CSR) was calculated using the Kaplan-Meier survival analysis. RESULTS: The study included 97 patients with 129 implants. Mean patient age at the time of implant placement was 31.7 ± 16.4 years. All implants were placed in a two-stage approach with delayed loading. The last follow-up visit was on average 13.4 ± 4.8 years after implant insertion. Three implants failed, yielding the implant-level 15-year CSR of 97.4%. Majority of the implants had no biological (70.5%) nor technical (81.4%) complications. The mean MBL was -1.0 ± 0.7 mm (n = 101) at prosthetic placement and -1.8 ± 1.0 mm (n = 80) at the last follow-up, while the mean marginal bone loss (MBL) from prosthetic placement to last follow-up was 0.6 ± 1.1 mm (n = 65). CONCLUSIONS: Moderately rough anodized implants have shown favorable long-term outcomessingle-tooth indication, with high survival and a low rate of technical complications. Furthermore, long-term studies are needed to present longitudinal data on peri-implantitis.

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.

A retrospective clinical study of fixed tooth- and implant-supported prostheses in titanium and cobalt-chromium-ceramic: 5-9-year follow-up.

OBJECTIVES: The aim of this retrospective study was to evaluate the clinical outcome of fixed tooth- and implant-supported protheses manufactured in porcelain veneered cobalt-chromium (CoCr) or titanium with a follow-up period of 5-9 years. MATERIALS AND METHODS: This study included 63 patients with a total of 86 fixed dental protheses (FDPs) (53 implant-supported and 33 tooth-supported). In total, 67 were short-span FDPs (3-5 units) and 19 were long-span FDPs (6-12 units). The FDPs were evaluated using a modified version of the California Dental Association (CDA). RESULTS: The binary regression analysis indicated that neither CoCr nor titanium had a statistically significant effect on the odds of success or survival of either tooth- or implant-supported FDPs. However, the success of FDPs was negatively affected by greater FDP length and general tooth wear. The survival of FDPs was negatively affected by increased FDP longevity. CONCLUSIONS: This study found no statistically significant effect on the odds of success and survival outcomes for any combination of tooth-supported, implant-supported, porcelain-veneered CoCr, or porcelain-veneered titanium FDPs. As the number of FDPs was limited, the results should be interpreted with caution. CLINICAL RELEVANCE: This study shows that the choice between CoCr porcelain and titanium porcelain in fixed protheses did not have a statistically significant effect on the outcome.

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.

Patient factors related to early implant failures in the edentulous jaw: A large retrospective case-control study.

BACKGROUND: Dental implants provide anchorage for dental prostheses to restore functions for individuals with edentulous jaws. During the healing phase, proper osseointegration is required to prevent early implant failure. More knowledge is needed regarding factors related to early failure of dental implants. PURPOSE: The aim of the present study was to identify possible risk factors for early implant failure, with respect to anamnestic and clinical parameters. MATERIALS AND METHODS: All patients with edentulous jaws with early implant failure (n = 408) from one referral clinic were compared with a matched control group (n = 408) with no implant failure. Early implant failure was identified during the first year of prosthetic function. Matching was performed on age, gender, year of surgery, type of jaw, and type of implant surface. In addition, data on anamnestic and clinical parameters were collected. The data were analyzed with a multivariable logistic regression model using early implant failure as the binary outcome. RESULTS: Five anamnestic factors were statistically significant with respect to higher probability for early implant failure: systemic disease, allergies in general, food allergies, smoking, and intake of analgesic medication. Four clinical conditions (i.e., implants in the opposing jaw, low primary stability, reduced bone volume, and healing complications) were also related to higher probability for early implant failure. CONCLUSIONS: This study identified nine factors associated with early implant failure, several related to patient's general health. Further investigations are needed to fully understand the causality between the obtained variables and early implant failure.

Inflammatory Response to Cobalt-Chromium Alloys Fabricated With Different Techniques.

OBJECTIVES: To explore the in vitro cytokine expression of human peripheral blood mononuclear cells exposed to cobalt-chromium alloys, manufactured with different techniques, in comparison with commercially pure titanium grade 4 and titanium alloy grade 23. MATERIAL AND METHODS: Peripheral blood mononuclear cells (PBMC) were collected from 10 healthy blood donors and exposed to machine-ground coin-shaped: (a) cobalt-chromium (Co-Cr) specimens (n = 5) manufactured by four techniques, i.e. cast, milled, laser melted and presintered milled; (b) commercially pure titanium grade 4; and (c) titanium alloy grade 23. The cells were cultured for 4, 24 and 72 hours followed by investigations of pro- and anti-inflammatory cytokine release using Bio-Plex Pro™. RESULTS: In general, the PBMC produced significantly more cytokines when exposed to the cast and presintered milled Co-Cr materials compared to laser melted, milled Co-Cr and titanium materials. CONCLUSIONS: Within the limitation of the present study, it may be suggested that cast and presintered milled cobalt-chromium alloys provoke a stronger inflammatory response compared to milled and laser melted cobalt-chromium alloys and titanium materials.

Chemical Bonding to Novel Translucent Zirconias: A Mechanical and Molecular Investigation.

PURPOSE: To investigate direct bonding of a 10-MDP-based cement to two novel translucent yttria-stabilized tetragonal zirconia polycrystal ceramics (4Y-TZP, 5Y-TZP) and observe the influence of thermocycling on this bonding. MATERIALS AND METHODS: Powders of presintered and isostatically pressed 5Y-TZP, 4Y-TZP and 3Y-TZP were mixed with a 10-MDP-based cement (Panavia F 2.0), then stored in deionized water for 48 h at 37°C or thermocycled 10,000 times. Raman spectroscopy and Fourier-transform infrared spectroscopy were used to assess the presence of a functional group (PO32-) that could indicate bonding before and after thermocycling. X-ray photoelectron spectroscopy was used to identify the presence of the suspected Zr-O-P bond in the same specimens. A shear-bond strength (SBS) test was conducted based on ISO 29022:2013. RESULTS: Marked peaks assigned to the asymmetric vibrations of the PO32- functional group were observed in both zirconias before and after thermocycling. The binding energy corresponding to Zr-O-P interactions (531.5 eV) was masked by the aluminosilicate in the filler of the cement. Shear bond strengths were approximately 20 MPa after water storage and approximately 6 MPa after thermocycling. No differences were found between the control group and the translucent zirconias. CONCLUSION: Direct bonding of the 10-MDP-based cement to both 4Y-TZP and 5Y-TZP was highly plausible. Both 4Y-TZP and 5Y-TZP may be promising alternatives to glass-ceramic restorations.

Limited Effect of Cement Material on Stress Distribution of a Monolithic Translucent Zirconia Crown: A Three-Dimensional Finite Element Analysis.

PURPOSE: The literature shows that the performance of densely sintered zirconia single crowns seems to be unaffected by the cement material. The purpose of this study was to evaluate the effects of various cement materials on the stress distribution in a monolithic translucent zirconia crown. MATERIALS AND METHODS: A crown-cement-dentin complex was modeled. Six cements were evaluated: zinc phosphate, glass-ionomer, resin-modified glass-ionomer, dual-cure resin, calcium aluminate-based, and a theoretical or conceptual cement with mechanical properties close to those of dentin (ie, monoblock cement). RESULTS: While varying stress concentrations were found within the cements, the stress concentrations in the crown and dentin were consistent irrespective of cement material. CONCLUSION: Within the limitations of this study, it can be concluded that cement material had a negligible effect on stress distribution in the monolithic zirconia crown.

Associations Between Early Implant Failure, Patient Age, and Patient Mortality: A 15-Year Follow-Up Study on 2,566 Patients Treated with Implant-Supported Prostheses in the Edentulous Jaw.

PURPOSE: The aim of this study was to report the distribution of patients with early implant failures after implant treatment in the edentulous jaw with regard to age at surgery and association with patient mortality over a 15-year period. MATERIALS AND METHODS: All consecutively treated patients treated in the edentulous jaw at a single specialist clinic from 1986 to 1997 were included and followed up for 1 year for implant failures and for 15 years with regard to patient mortality. Patients were arranged into age groups, and life tables for patients and reference groups of patients with comparable age (based on national population data) were calculated. Log rank test was used to test differences in patient survival between those with reported early implant failures and those with no early failures. Mantel-Haenszel chi-square test was used to test association between proportions of implant failures and age groups. RESULTS: A total of 55 patients were excluded because they were not living in Sweden (nonresidents/emigrated). Altogether, 2,566 patients were included, with a mean age of 65 years (SD: 11). Of these, 988 patients were deceased during the 15 years of follow-up (38%), and 291 presented an early implant failure (11.3%), most of them before prosthesis placement (72%). Patients with early implant failures presented higher mortality rates than patients with no failures (P < .05), and failure rates decreased consistently from younger to higher age groups (P < .05). CONCLUSION: Patients in the younger age groups showed an increased mortality compared with the reference group (P < .05) and a higher prevalence of early failures compared with older patients (P < .05). Older patients showed an opposing pattern of lower mortality compared with reference groups of comparable age (P < .05), but both younger and older patients with early failures showed a higher mortality compared to patients with no failures (P < .05).

Laminin Coating Promotes Calcium Phosphate Precipitation on Titanium Discs in vitro.

OBJECTIVES: The objective of this study was to investigate the effect of a laminin coating on calcium phosphate precipitation on three potentially bioactive titanium surfaces in simulated body fluid. MATERIAL AND METHODS: Blasted titanium discs were prepared by alkali and heat treatment (AH), anodic oxidation (AO) or hydroxyapatite coating (HA) and subsequently coated with laminin. A laminin coated blasted surface (B) served as a positive control while a blasted non coated (B-) served as a negative control. Surface morphology was examined by Scanning Electron Microscopy (SEM). The analysis of the precipitated calcium and phosphorous was performed by Energy Dispersive X-ray Spectroscopy (EDX). RESULTS: The thickness of the laminin coating was estimated at 26 Å by ellipsometry. Interferometry revealed that the coating process did not affect any of the tested topographical parameters on µm level when comparing B to B-. After 2 weeks of incubation in SBF, the alkali-heat treated discs displayed the highest calcium phosphate deposition and the B group showed higher levels of calcium phosphate than the B- group. CONCLUSIONS: Our results suggest that laminin may have the potential to be used as a coating agent in order to enhance the osseoinductive performance of biomaterial surfaces, with the protein molecules possibly functioning as nucleation centres for apatite formation. Nevertheless, in vivo studies are required in order to clarify the longevity of the coating and its performance in the complex biological environment.

Onlay and inlay bone grafts with platelet-rich plasma: histologic evaluations from human biopsies.

PURPOSE: The aim of the present study was to histomorphometrically evaluate biopsies from 1) sinus inlay bone grafts prepared with or without platelet-rich plasma (PRP) and 2) onlay bone grafts in the anterior maxilla with particulate bone and PRP or block bone without PRP after 3 months. MATERIALS AND METHODS: Biopsies were retrieved with a trephine drill, and samples were processed in laboratories to result in nondecalcified cut and ground sections. Light microscopic measurements of total bone area, new bone, number of vessels, and vessel area were performed at 3 regions in each sample. Calculations of ratios of new bone to total bone and vessel area to total area were performed. RESULTS: There was a tendency toward higher mean values for total bone area percentage and area of newly formed bone in the PRP-treated inlay biopsies. However, there was no measurable effect on vessel formation in the PRP-treated inlay samples compared with untreated inlay samples. Particulate and PRP-treated onlay bone biopsies showed higher mean values in all measured parameters compared with block bone samples; however, no differences were statistically significant. CONCLUSION: PRP treatment may favor bone formation in grafted bone, and further research is needed to describe the outcome of PRP treatment and grafting techniques in the maxilla.

In vitro Evaluation of Calcium Phosphate Precipitation on Possibly Bioactive Titanium Surfaces in the Presence of Laminin.

OBJECTIVES: The aim of the present study was to evaluate calcium phosphate precipitation and the amount of precipitated protein on three potentially bioactive surfaces when adding laminin in simulated body fluid. MATERIAL AND METHODS: BLASTED TITANIUM DISCS WERE PREPARED BY THREE DIFFERENT TECHNIQUES CLAIMED TO PROVIDE BIOACTIVITY: alkali and heat treatment (AH), anodic oxidation (AO) or hydroxyapatite coating (HA). A blasted surface incubated in laminin-containing simulated body fuid served as a positive control (B) while a blasted surface incubated in non laminin-containing simulated body fuid served as a negative control (B-). The immersion time was 1 hour, 24 hours, 72 hours and 1 week. Surface topography was investigated by interferometry and morphology by Scanning Electron Microscopy (SEM). Analysis of the precipitated calcium and phosphorous was performed by Energy Dispersive X-ray Spectroscopy (EDX) and the adsorbed laminin was quantified by iodine ((125)I) labeling. RESULTS: SEM demonstrated that all specimens except for the negative control were totally covered with calcium phosphate (CaP) after 1 week. EDX revealed that B- demonstrated lower sum of Ca and P levels compared to the other groups after 1 week. Iodine labeling demonstrated that laminin precipitated in a similar manner on the possibly bioactive surfaces as on the positive control surface. CONCLUSIONS: Our results indicate that laminin precipitates equally on all tested titanium surfaces and may function as a nucleation center thus locally elevating the calcium concentration. Nevertheless further studies are required to clarify the role of laminin in the interaction of biomaterials with the host bone tissue.

Evaluations of bone tissue integration to pure and alloyed titanium implants.

PURPOSE: This study was performed for comparisons of tissue integration to commercially pure (CP) and titanium-6-aluminum-4 vanadium (Ti-6-Al-4V) implants using various existing three-dimensional biomechanical and two-dimensional histomorphometrical techniques, and to monitor the loosening torque during in vivo removal torque (RTQ) test with a novel unit not used before in a pilot study in rabbits. MATERIALS AND METHODS: The implants were topographically characterized and inserted in femurs and tibiae of five rabbits (in total 40 implants, 20 per group). After 16 weeks, the implant integration was biomechanically evaluated by: (1) resonance frequency test, and (2) peak RTQ test and the graph from the monitoring curve. Biopsies of the implants in situ were processed to undecalcified cut and ground sections followed by light microscopical quantifications. Shear strength calculations were performed. RESULTS: Significantly higher mean value of RTQ (p = .01) and shear strength tests (p = .03) were observed for the CP titanium implants compared to Ti-6-Al-4V implants. The monitoring curve from the RTQ test demonstrated no differences in the shape or form that could provide further information about the differences in the implant-to-bone attachment. CONCLUSIONS: The CP titanium implants showed increased RTQ and shear strength values compared to the Ti-6-Al-4V implants. The new tool of monitoring the RTQ curve could not demonstrate differences between the two materials. The exact influence of the implant materials on the surrounding tissues needs to be further investigated.

Failure to induce supracrestal bone growth between and around partially inserted titanium implants using bone morphogenetic protein (BMP): an experimental study in dogs.

The effect of bone morphogenetic protein on supracrestal bone growth around partially inserted implants in a dog model is described. The lower premolar teeth (P1, P2, P3 and P4) were extracted on both sides of the mandible in six dogs. At a surgical exposure 12 weeks later, two 10-mm turned titanium implants were partially inserted, approximately 15 mm apart, in the areas of the P1 and P3 in each side of the mandible, allowing five threads to protrude from the bone crest. A titanium mesh was fastened to the coronal aspect of the two fixtures and the space beneath the mesh was filled with bone morphogenetic protein (S300 BMP) in combination with an insoluble bone matrix carrier, or with the carrier alone. The mesh was covered with an ePTFE membrane. Thus, a space for potential bone formation was created between the two implants. The surgical flaps were coronally positioned and secured with vertical mattress sutures. After 16 weeks of healing, biopsy specimens were retrieved and examined histologically. Bone was not formed around the protruding implants or in the created space between the implants in any case. The carrier was incompletely resorbed. We conclude that supracrestal bone growth beyond the crestal limit with or without BMP in such a large space as in this experimental design may not be possible.