Zirconia Discs Research Articles

Evaluation of microhardness and water sorption/solubility of dual-cure resin cement through monolithic zirconia in different shades.

Aim:The objective is to evaluate the effect of shades of monolithic zirconia on the microhardness and sorption/solubility of the underlying two dual-cured resin types of cement.Materials and Methods:Eighty samples of two dual-cured resin cement discs were polymerized under 60 monolithic zirconia discs in three shades and directly activated resin discs of cement were used as the control group (n = 10). After 24 h storage at 37°C in an incubator, Vickers microhardness and the sorption and solubility were measured.Statistical Analysis Used:Two-way ANOVA , one-way ANOVA, Independent t-test, Tukey's honestly significant difference, and Tamhane's T2 tests.Results:The mean microhardness of the Variolink N resin cements were significantly higher than Panavia SA ones (P < 0.001). Furthermore, Variolink N cements exhibited lower sorption/solubility than Panavia SA resin cements (both P < 0.05). The ceramic shade had a significant influence on the microhardness of both cements (P < 0.001) but had no significant effect on the sorption/solubility of resin cements (P > 0.05).Conclusion:Interposition of monolithic zirconia decreases the microhardness of resin cement especially Panavia SA. In Variolink N, by increasing the chroma saturation of ceramics, the microhardness decreased, however in Panavia SA, it was altered by the shades, but not in a specific pattern. For both cements, there were no statistical differences between the sorption/solubility of samples photo-cured under different shades. There was a reverse correlation between microhardness and water sorption/solubility of both cements.

Masking of High-Translucency Zirconia for Various Cores.

Various core materials with different shades affect the final color of high-translucency monolithic zirconia restorations. The blue core shows the greatest color difference in final zirconia restorations followed by metal, A3 dentin-shade resin core, and white core. The purpose of this study was to evaluate the masking ability of high-translucency monolithic zirconia for various core materials. A computer-aided design-computer-aided manufacturing system was used to design a zirconia disc with a diameter of 10 mm and a thickness of 1.0 mm. Four groups of cores (n=15 each) were fabricated with blue-colored dual-cure resin, white-colored dual-cure resin, A3 dentin-shade composite resin, and titanium block with 10-mm diameter and 5-mm thickness.Dual-cure, self-adhesive resin cement discs with a thickness of 25.0 ± 0.02 μm were fabricated. The color was measured using a handheld spectrophotometer. Color measurements of all specimens were performed on a white background. To assess the masking ability of zirconia, the difference between the values measured with zirconia on a white background and the values measured with zirconia on each of the four types of core material as a background with the cement specimens interposed (zirconia + cement + core) was determined. To enhance the optical connection between the specimens, distilled water was applied between each layer during each measurement.The results showed that the value of ΔE was highest for the blue core followed by metal, A3 dentin-shade resin core, and white-resin core. No significant differences were observed between the metal core and the A3 dentin-shade resin core or between the A3 dentin-shade resin core and the white core. The blue core had the significantly highest ΔE value based on Tukey's honest significant difference test.Different core materials affect the final color of high-translucency monolithic zirconia restorations. Thus, our study showed that the final color of high-translucency monolithic zirconia restorations could be affected by the type of core material used.

Effect of fabrication techniques on the optical properties of zirconia-based systems

Statement of problemHow the optical properties of zirconia restorations are affected by their differing processing techniques is unclear. PurposeThe purpose of this in vitro study was to evaluate the effects of 5 different fabrication techniques on the optical properties of zirconia-based systems, including the color difference between the corresponding shades (ΔE∗ab, ΔE00), translucency parameter, opalescence parameter, and fluorescence (ΔE∗ab-FL). Material and methodsSixty zirconia disks (IPS e.max ZirCAD) were prepared (0.5 ±0.01mm thick) and veneered by using different techniques (n=15): Group L – layering with fluorapatite ceramic; Group P – pressing with fluorapatite ceramic; Group CB – veneered with pressing followed by layering technique; Group CO – digitally veneered with lithium disilicate glass-ceramic; and Group FZ – prepared from monolithic zirconia (inCoris TZI) (n=15). All the specimens were set to 1.5 ±0.02 mm in thickness. Color measurements were made with a spectrophotometer. Data were statistically analyzed with 1-way ANOVA and the Tukey honestly significant difference, Kruskal-Wallis, Bonferroni (α=.05), Pearson, and Spearman correlation tests (α=.01). ResultsSignificant differences were found among the groups for all the optical parameters (P<.05). All the groups showed color differences higher than the perceptibility and acceptability thresholds for ΔE∗ab and ΔE00, except the P and FZ groups that showed values lower than the acceptability threshold (ΔE∗ab<2.7). Translucency parameter, opalescence parameter, and ΔE∗ab-FL values ranged between 5.77 and 9.95, between 4.72 and 7.07, and between 1.93 and 3.14, respectively. Strong positive correlations were found between ΔE∗ab and ΔE00, as well as between translucency parameter and opalescence parameter (P<.001). ConclusionsThe optical properties of the zirconia-based systems were significantly affected by the fabrication techniques even when the same nominal shade was used. Therefore, the color reproduction, translucence, opalescence, and fluorescence of the selected materials should be considered for acceptable color matching.

Influence of Er:YAG laser surface treatment on flexural and bond strengths to glass-infiltrated zirconia-reinforced ceramic.

To evaluate the effect of Er:YAG laser conditioning of a glass-infiltrated alumina-based zirconia-reinforced ceramic on its flexural strength and on bonding to a resin cement. Sixteen blocks (5 × 5 × 4mm) and 50 discs (Ø 12mm, 1mm thickness) of In-Ceram Zirconia (ICZ) obtained from CAD-CAM blocks were infiltrated with glass. For the microtensile bond strength (μTBS) test, all blocks were treated with aluminum oxide (AOX) and divided into 4 groups (n = 4): G1 (AOX), no combined surface treatment; G2 (ROC), tribochemical silica-coating; G3 (EY200), Er:YAG laser 200mJ/15Hz; and G4 (EY250), Er:YAG laser 250mJ/10Hz. The ceramic blocks were silanated and cemented with a resin cement (Panavia F2.0/Kuraray) to composite resin blocks and subjected to the μTBS test. For the flexural strength evaluation, the discs were divided into 5 groups (n = 10) as described above, in addition to a control group (G5 - CTRL, mirror-polished without further treatment). Each surface treatment was submitted to qualitative evaluation under SEM. One-way ANOVA (α = 5%) revealed the highest bond strength value for EY200 with no significant difference from ROC. The groups AOX and EY250 showed similar μTBS values that were statistically lower than those of EY200. For flexural strength, ROC was the only group with significantly lower values when compared with the CTRL. The use of Er:YAG laser at 200mJ/15Hz can be considered an innovative and effective alternative for surface conditioning of ICZ since it did not reduce the flexural strength of the ceramic and improved the resin cement bond to this substrate.

Effect of surface treatment with potassium hydrogen difluoride and ammonium hydrogen difluoride on bond strength between layered veneering porcelain and zirconia

ObjectivesThe purpose of this study was to show the effect of surface treatment of potassium hydrogen difluoride (KHF2) and ammonium hydrogen difluoride (NH4HF2) on the bonding of veneering porcelain to zirconia frameworks. Material and methodsTwo types of zirconia (Katana zirconia (3Y-TZP) and KZR-CAD Zr SHT (6Y-TZP)) were used as the adherend material. Cerabian ZR porcelain was fired to each type of zirconia disc (n = 11). Zirconia discs were prepared using the following surface treatment: no treatment (NT), alumina blasting (AB), KHF2 and NH4HF2. Coefficient of Linear Thermal Expansion (CTE) of each type of zirconia and veneering porcelain were measured. The specimens after surface treatment were analyzed with X-ray diffraction analysis (XRD). Shear bond strength was tested after 24 h water storage. The specimens were evaluated under scanning electron microscopy. ResultSignificant differences between CTE values of 6Y-TZP and veneering porcelain occurred as the temperature increased. The XRD analysis of the 3Y-TZP treated with AB, KHF2 or NH4HF2 demonstrated that 3Y-TZP becomes unstable and phase transformation occurs. In 3Y-TZP group, KHF2 and NH4HF2 groups exhibited higher shear bond strengths than AB and NT. In 6Y-TZP group, KHF2 groups showed higher shear bond strengths than NT, AB and NH4HF2. ConclusionHigh bond strength between zirconia and veneering porcelain can be achieved by a surface treatment with selected melted fluoride compounds.

Time Dependency of Non-Thermal Oxygen Plasma and Ultraviolet Irradiation on Cellular Attachment and mRNA Expression of Growth Factors in Osteoblasts on Titanium and Zirconia Surfaces.

Ultraviolet (UV) light and non-thermal plasma (NTP) are promising chair-side surface treatment methods to overcome the time-dependent aging of dental implant surfaces. After showing the efficiency of UV light and NTP treatment in restoring the biological activity of titanium and zirconia surfaces in vitro, the objective of this study was to define appropriate processing times for clinical use. Titanium and zirconia disks were treated by UV light and non-thermal oxygen plasma with increasing duration. Non-treated disks were set as controls. Murine osteoblast-like cells (MC3T3-E1) were seeded onto the treated or non-treated disks. After 2 and 24 h of incubation, the viability of cells on surfaces was assessed using an MTS assay. mRNA expression of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) were assessed using real-time reverse transcription polymerase chain reaction analysis. Cellular morphology and attachment were observed using confocal microscopy. The viability of MC3T3-E1 was significantly increased in 12 min UV-light treated and 1 min oxygen NTP treated groups. VEGF relative expression reached the highest levels on 12 min UV-light and 1 min NTP treated surfaces of both disks. The highest levels of HGF relative expression were reached on 12 min UV light treated zirconia surfaces. However, cells on 12 and 16 min UV-light and NTP treated surfaces of both materials had a more widely spread cytoskeleton compared to control groups. Twelve min UV-light and one min non-thermal oxygen plasma treatment on titanium and zirconia may be the favored times in terms of increasing the viability, mRNA expression of growth factors and cellular attachment in MC3T3-E1 cells.

EFFECT OF DIFFERENT SURFACE TREATMENTS ON BONDING OF ULTRA- TRANSLUCENT ZIRCONIA

Introduction: Introduction of ultra-translucent zirconia led to increase its indications for minimally invasive aesthetic restorations, therefore, it is important to test its adhesive potentiality. Objectives: Investigation of shear bond strength (SBS) of ultra-translucent zirconia to enamel after different surface treatments and examination of their effect on surface topography. Materials and methods: Thirty six ultra-translucent zirconia discs, (O5mm×3mm height) were divided into three groups (n=12): Control (C): as-sintered discs, Sandblasted discs (SB): discs were sandblasted by 110μm Al2O3 particles for 10 seconds, at 2.5 bar pressure, from 10mm distance, and Etched discs (ZE): discs were dipped into Zircos-E etching solution (BIO DEN CO, Korea) for thirty minutes in an ultrasonic cleaner. The surface topography of two randomly selected discs from each group were examined by scanning electron microscopy (SEM) for descriptive analysis, and the remaining discs were bonded to enamel surfaces of human central incisors for performing the SBS test. Statistical analysis of SBS results was done by Kruskal Wallis test and post hoc test with statistically significant results at (p < 0.05). Results: Morphological examination of (C) showed closely connected grains, (SB) showed a number of superficial irregularities, and shallow scratches, whereas (ZE) showed gross discontinuity of grain structure. The highest SBS value was recorded by (SB) (19.01±2.00 MPa) with insignificant difference from (ZE) (16.73± 2.13 MPa), and significant difference from (C) with the lowest SBS value (8.69±1.95 MPa). Conclusions: Etching of ultra-translucent zirconia using (Zircos-E) is a promising technique for improvement of resin bonding in comparison to control and sandblasted groups.

Effect of zirconia etching solution on the shear bond strength between zirconia and resin cement

Statement of problemThe bond between resin cement and zirconia is essential to the long-term retention of a zirconia crown. However, it is unclear if the existing methods provide a long-term bond between resin cement and zirconia. PurposeThe purpose of this in vitro study was to evaluate the effects of a zirconia etching solution on the shear bond strength between zirconia and resin cement. Material and methodsSixty yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) disks (Ø8×5 mm) were divided into 4 groups (n=15). Each group was then treated with 1 of the following methods: airborne-particle abraded with 50-μm Al2O3 (AA); etched with zirconia etching solution (ZES); airborne-particle abraded with 50-μm Al2O3 and then etched with ZES (AA-ZES); etched with ZES and then airborne-particle abraded with 50-μm Al2O3 (ZES-AA). Sixty composite resin cylinders (Ø2.3×2.4 mm) were luted to the zirconia disks with a self-adhesive resin cement under constant load and then light-polymerized for 40 seconds. Specimens were stored in a 37 °C incubator in distilled water for 24 hours and then thermocycled for 1000 cycles between 5 °C and 55 °C. A universal testing machine with a crosshead speed of 0.5 mm/min was used to measure the shear force (N). The shear bond strength (MPa) was then calculated. One-way ANOVA was used to compare the mean shear bond strength among the groups (α=.05). The failure mode was evaluated by using light microscopy at ×90 magnification and categorized as an adhesive, cohesive, or mixed failure. ResultsMean ±standard deviation shear bond strength for AA, ZES, AA-ZES, and ZES-AA groups were 9.9 ±2.6, 8.9 ±2.9, 9.6 ±3.9, and 11.0 ±2.3 MPa, respectively. There was no significant difference among the treatment groups (P>.05). ConclusionsA zirconia etching solution did not significantly improve the shear bond strength between zirconia and resin cement compared with airborne-particle abrasion with Al2O3.

Impact of sintering procedure and clinical adjustment on color stability and translucency of translucent zirconia

Statement of problemChairside and laboratory adjustments of translucent monolithic zirconia restorations sintered by short cycles are inevitable. Therefore, the optical properties of these materials should be evaluated under conditions similar to those in the oral environment. PurposeThe purpose of this in vitro study was to evaluate the color stability and the translucency changes of translucent monolithic zirconia after the sintering procedure, simulated clinical adjustment, and coffee thermocycling. Material and methodsEighty monolithic zirconia disks (diameter: 10 mm; thickness: 1 mm) were milled from 4 zirconia brands (Zolid FX Preshaded, Zolid FX White, DD Cubex2, and DD Bio ZX2). Two sintering procedures (standard or speed) were performed for each zirconia brand. The color coordinates and the translucency after sintering, clinical adjustment, and after 5000 cycles in a coffee solution were analyzed with a reflectance spectrophotometer, and the translucency parameters and contrast ratio were measured. The color differences and the translucency variations were calculated for each tested variable and statistically analyzed with 2-way ANOVA and pairwise comparison (α=.05). ResultsBoth clinical adjustment procedure and coffee thermocycling had significant influence on color differences (P<.001). For translucency, 2-way ANOVA showed a significant interaction between sintering procedure and zirconia brand after coffee thermocycling (P<.001) while no significant interaction was recorded after the clinical adjustment procedure (P=.247). For all evaluated groups, the translucency parameter values decreased after either clinical adjustment procedure or coffee thermocycling (P<.001). For tested zirconia, group DD Cubex2 showed higher translucency parameter regardless of the variables tested. ConclusionsThe color and the translucency of the translucent zirconia can be affected by the type of the zirconia brand and the sintering protocol. Furthermore, the color and the translucency were affected by both the clinical adjustment procedure and the coffee thermocycling, but not beyond the clinically acceptable limit of the color difference.Clinical Implications

The Effect of Aging on the Roughness and Bacterial Adhesion of Lithium Disilicate and Zirconia Ceramics.

This in vitro study was designed to compare bacterial adhesion to zirconia versus lithium disilicate crowns after artificial aging. Seventy-five discs were tested in this study: 25 Cr-Co base metal discs (control), 25 zirconia discs, and 25 lithium disilicate discs. Each sample was polished and glazed appropriately. The discs were subjected to 1000 thermal cycles between 5 and 55°C, whereby samples stayed in the bath for 20 seconds, at each temperature. Then, 10 µL of Streptococcus sanguinis suspension was placed on the discs. The samples were scanned for surface roughness before and after aging, and after incubation. Sp and Sa were measured with a confocal, visible light disk-scanning system (Sa expresses the difference in height of each point compared to the arithmetical mean of the surface. Sp is the height of the highest peak within the defined area). Optical density of the discs was evaluated by a spectrophotometer. One-way ANOVA was performed to assess differences after aging and incubation. Statistical analysis showed significant differences (p = 0.02) in surface roughness between the Cr-Co base metal, zirconia and lithium disilicate before and after aging. The mean Sa was 0.36 ± 0.12 µm, 0.638 ± 0.24 µm, and 1.23 ± 0.42 µm, respectively. Lithium disilicate had the highest surface roughness values. There was a significant difference (p = 0.001) after incubation. The mean and standard deviation surface roughness of Cr-Co base metal, zirconia and lithium disilicate were 0.99 ± 0.49 µm, 1.40 ± 0.46 µm, and 2.44 ± 1.21 µm, respectively. While no significant differences were found in the accumulation of S. sanguinis between zirconia and lithium disilicate, there was a significant difference (p = 0.02) in the optical density between these 2 test groups and the control group (metal). The optical density of metal (0.94 ± 0.15) was higher than for lithium disilicate (0.74 ± 0.10) and zirconia (0.75 ± 0.08). There was no statistical difference in bacterial adherence between lithium disilicate and zirconia. Dental crown materials differed significantly in terms of surface roughness and bacterial adhesion between Cr-Co base metal and zirconia and lithium disilicate. After aging and bacterial adherence, the zirconia discs had the smoothest surface, with similar bacterial accumulation as lithium disilicate; suggesting that lithium disilicate may be less sensitive to bacterial adhesion than zirconia.

Femtosecond Ti: Sa ultra short-pulse laser irradiation effects on the properties and morphology of the zirconia surface after ageing

Femtosecond pulses from a Ti:Sapphire laser were used to irradiate specimens of yttria-stabilised (35% mol) tetragonal zirconia (Y-TZP) with the purpose of studying the effects of the irradiations on their surface properties and morphology after ageing. Zirconia disks were divided into eight groups (n = 32) according to their surface treatment and subsequent ageing: Control: no treatment; sandblasting: Al2O3 sandblasting 50 μm; and ultrashort laser pulses irradiation with 25 μJ pulses, considering two different scanning steps based on the width between two grooves. These groups were duplicated and submitted to ageing. The surfaces were analysed using scanning electron microscopy (SEM), and X-ray diffraction. A finite element analysis, a biaxial flexure test, as well as fractographic and Weibull analyses, were performed. The strengths of the disks were statistically different for the treatment factor, and the principal stresses seemed to be concentrated at the centre of the specimens, as predicted by the computer simulations. Ageing decreased the strengths for all groups and increased the Weibull modulus for the laser group with the 40 μm-width between two grooves. The sandblasting group presented the highest monoclinic phase peak. Although the most significant strength was found within the sandblasting group, the phase transformation was favourable to the laser groups. The Weibull modulus was higher for the laser group with the 60 μm-width between two grooves, confirming the highest homogeneity of its failure distribution. Regardless of the surface treatment, strength was decreased with ageing in all groups. The femtosecond Ti:Sa ultra-short pulse laser irradiation can be suggested as an alternative to the gold standard sandblasting in long-term Y-TZP zirconia rehabilitations, such as crowns and veneers.

Shear Bond Strength of the Metal Bracket to Zirconium Ceramic Restoration Treated by the Nd: YAG Laser and Other Methods: An In Vitro Microscopic Study.

Introduction: Providing reliable bonding of the bracket base and the zirconia surface is required to apply orthodontic force. The purpose of this scientific experiment was to evaluate the efficacy of three different methods of surface preparation for Zirconia, including surface roughening, sandblasting and the Nd: YAG laser, in the shear bond strength (SBS) of the orthodontic brackets. Methods: Fifty-four discs of zirconia were divided into three groups of 18: A) Hydrofluoric acid etching, B) sandblasting, and C) Nd: irradiation using the power of 1.5 W for 10 seconds. After bonding the brackets, the samples were slowly thermo-cycled (1000 times) for 24 hours. The SBS test was performed by a universal testing machine at a head speed of 0.5 mm/min. The adhesive remnant index (ARI) was scored at a magnification of 10 in the stereo microscope. All data were collected and analyzed using the variance, Kruskal-Wallis, Tukey, Don, and Weibull tests (α = 0.05). Results: The HF acid etching group (6.11± 0.94 MPa) had the highest SBS, which was followed by the laser group (6 ± 0.61 MPa) and the sandblast group (3.1080 ± 0.82 MPa). There was a significant statistical difference between the laser and HF groups and the sandblast group (P < 0.05) and no significant difference between the HF group and the laser group (P = 0.03). Conclusion: Based on the obtained bond strength, the Nd: YAG laser with a power of 1.5 W could be a substitute treatment method for the HF acid-etching.

Efficacy of Different Surface Treatments on the Bond Strength of Resin cement to Zirconia Ceramic

Purpose: The plan for this study was to anatomise the effect of alternative surface treatments to enhance bonding to zirconia. Materials and Methods: forty discs of zirconia (Prettau,zircon zhan, Italy) were prepared using Isomet 4000 precision Saw then discs were divided into 5 groups. Group 1, control; Group2, zirconia discs were treated with50-mm Al2O3 particles; Group 3, zirconia discs were received hand grinding; Group 4, zirconia discs were treated by a CO2 laser and Group 5, zirconia discs were treated using ERYAG laser. Composite resin discs were constructed and cemented to zirconia samples with panavia cement. For the bond strength test, a universal testing machine was used. Results: the highest shear bond strength was recorded for (Hand grinding) group (2) while the lowest mean value was recorded for control group (1). Conclusions: Treatment of Zirconia Surfaces with hand grinding or sandblasting increased shear bond strength. Treatment of Zirconia with CO2 and ERYAG lasers increased shear bond strength of zirconia, with the CO2 laser being higher than ERYAG laser.

Initial curing characteristics of composite cements under ceramic restorations.

To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks. Portions of mixed cement, either G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) or ResiCEM (Shofu), were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a 100-µm film thickness using a microscopy cover glass. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered zirconia disk (0.5-mm thick zirconia with a 1.0-mm thick veneering ceramic) for 40 sec using two light-curing units (G-Light Prima 2, GC; PenCure, Morita). Per experimental group, 5 tests were conducted to measure DC in self-cure and dual-cure mode (n=5). FTIR spectra of the composite cement films were acquired to determine DC every min up to 30 min. DC of the composite cements was statistically compared using two-way repeated-measures ANOVA (α=0.05). For all cements investigated, the self-curing mode resulted in significantly lower DC at 10, 20 and 30 min than the light-curing mode. When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCem (Shofu), while not for Panavia V5 (Kuraray Noritake) and G-CEM LinkForce (GC). Self-curing slows down polymerization but does not reach for all composite cements the highest (light-cured) DC. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements.

Biofilm formation on metal alloys, zirconia and polyetherketoneketone as implant materials in vivo.

This study investigated biofilm formation on discs of metal alloys, zirconia and polyetherketoneketone in vivo. Sixteen healthy volunteers conducted two runs of 24hr each wearing an intraoral splint with 15 discs representing five different materials (gold-based [EL] and silver-based [PA] noble metal alloys; zirconia [ZR]; polyetherketoneketone [PEKK]; titanium zirconium alloy [TiZr]). Safranin staining assays and colony-forming unit (CFU) counts were conducted. Linear mixed-effects models were used to compare materials, and geometric mean ratios with 95% confidence interval were calculated with the level of significance set at α=0.05. Less biofilm mass and lower CFU counts were found on PA and EL, while ZR and PEKK developed similar levels as the reference material TiZr alloy. Compared with PA, biofilm mass was 1.5 times higher for EL (p=.004), 1.7 times higher for PEKK (p<.001), 2.2 times higher for TiZr (p<.001) and 2.4 times higher for ZR (p<.001). The culturing method confirmed these results for EL and PA with lower CFU compared to TiZr. The biomass staining technique and cell culturing correlated for EL and PA. Silver-based noble alloy and gold-based high noble alloy demonstrated the least biofilm formation indicating a potential clinical use as material for implant components in the transmucosal compartment. Zirconia and Polyetherketoneketone revealed similar results as the reference material titanium zirconium alloy used in commercially available titanium dental implant.

Comparison of splinted and non-splinted superstructures of three implants placed in a mandibular distal extension model with missing teeth using modal analysis

This study evaluated the effects of two types of superstructures (splinted crown and non-splinted crown) on four vibration characteristics (natural frequency, damping ratio (DAR), vectors in antiphase, maximum displacement (MDP)) by using modal analysis. These structures were fabricated on three implants placed in the mandibular free-end defect model. After placing three implants on a mandibular distal extension model with missing teeth, the three-unit splinted and non-splinted crowns were designed on the CAD software. Subsequently, the zirconia disc was milled using a milling machine to produce the superstructures (n = 5). After establishing four measurement points on each crown of the prostheses, a vibration was applied to the mandible model with an impact hammer, and the transfer function of each measurement point was identified. Using the modal analysis software, the natural frequency and damping ratios were calculated from the transfer function, modal shapes at each natural frequency were observed, and maximum displacement that takes into account the lateral force during mastication was simulated. The t-test was performed for each of the averaged values of natural frequency, maximum displacement, and damping ratio (p < 0.05). Mann-Whitney U test was performed on the average of the number of vectors in antiphase (p < 0.05). The mean natural frequency was significantly higher in the splinted crown (758.2 ± 2.8 Hz) than that in the non-splinted crown (752.8 ± 3.7 Hz) (P = 0.047). The mean damping ratio was not significantly different for the splinted (3.3 ± 0.2%) and non-splinted crowns (3.2 ± 0.3%) (P = 0.535). The average number of vectors in antiphase was significantly smaller in the non-splinted crown (4.4 ± 0.9) than in the splinted crown (10 ± 2.5) (P = 0.008). The mean value of the maximum displacement was significantly smaller in the splinted crown (6.7 ± 1.1 μm) than that in the non-splinted crown (7.3 ± 0.6 μm) (P = 0.048). Within the limitations of this study, the vibration characteristics of the superstructures differed between designs with splinted and non-splinted crowns. Crown splinting increased the rigidity and natural frequency and decreased the MDP. However, the higher number of vectors in antiphase indicated more twists in the superstructures during vibration. The non-splinted crowns showed a lower natural frequency and a greater maximum displacement; however, they comprised fewer vectors in antiphase, indicating that the twist during vibration was less than that observed with the splinted crowns. Thus, our results suggest that crown splinting reduces the deformation of the superstructure, implants, and the surrounding tissues in comparison to the deformation observed when no splinting is performed.

Glow Discharge Plasma Treatment on Zirconia Surface to Enhance Osteoblastic-Like Cell Differentiation and Antimicrobial Effects.

Peri-implantitis is the pathological condition of connective tissue inflammation and the progressive loss of supporting bone around dental implants. One of the primary causes of peri mucositis evolving into peri-implantitis is bacterial infection, including infection from Porphyromonas gingivalis. Enhancing the surface smoothness of implants helps to prevent P. gingivalis adhesion to the implant’s surface. Interaction analyses between bacteria and the surface roughness of zirconia (Zr) discs subjected to a glow discharge plasma (GDP) treatment compared with non-plasma-treated autoclaved control Zr discs were done. Examinations of the material prosperities revealed that the GDP-treated Zr group had a smoother surface for a better wettability. The GDP-treated Zr discs improved the proliferation of the osteoblast-like cells MG-63, and the osteoblastic differentiation was assessed through alkaline phosphatase detection and marker gene bone sialoprotein (Bsp) and osteocalcin (OC) induction. Scanning electron microscopy demonstrated a relatively low P. gingivalis adhesion on GDP-treated Zr disks, as well as lower colonization of P. gingivalis compared with the control. Our findings confirmed that the GDP treatment of Zr discs resulted in a significant reduction of P. gingivalis adhesion and growth, demonstrating a positive correlation between surface roughness and bacteria adhesion. Therefore, the GDP treatment of Zr dental implants can provide a method for reducing the risk of peri-implantitis.

Comparison between novel strength-gradient and color-gradient multilayered zirconia using conventional and high-speed sintering

ObjectivesTo investigate and compare the mechanical and optical properties of novel strength- and color-gradient multilayered zirconia and the impact of conventional and high-speed sintering. Materials and methodsFollowing zirconia materials were analyzed and compared: the high-speed sintered Katana Zirconia Block STML (4Y-TZP, KZC), the conventionally sintered Katana Zirconia Disc STML (4Y-TZP, KZL) and IPS e. max ZirCAD Prime (5Y-TZP/3Y-TZP, EZL). As control group acted the crystallized lithium disilicate ceramic IPS e. max CAD (ELC). Monolithic single molar crowns were fabricated and half of them were aged in a chewing simulator with human enamel antagonists (1.2 × 106 cycles, 50 N, lateral movement of 0.7 mm, 5/55 °C). The fracture load was tested in a universal testing machine (N = 96/n = 12). The two-body wear was determined using 3D matching of pre- and post-scans (N = 48/n = 12). Translucency (N = 36/n = 10) was evaluated with UV/Vis spectrophotometer. Data was analyzed using Kolmogorov-Smirnov test, one-way ANOVA followed by post-hoc Scheffé test, unpaired t-test and Weibull analysis (p < 0.05). ResultsZirconia groups showed higher fracture load than ELC (p ≤ 0.001). Initially, all zirconia materials ranged in the same values (p > 0.05). After chewing simulation, EZL showed higher fracture load than KZC (p < 0.001) and KZL (p = 0.043). Zirconia materials showed no material loss, whereas the ELC showed the volumetric wear of 0.334 ± 0.34 mm3 and vertical wear of 0.155 ± 0.07 mm. Enamel antagonist wear ranged in the same values (p = 0.083-0.906). The translucency values within each zirconia material showed significant differences between the enamel and the dentin layers (p < 0.001). ConclusionsThe novel strength and color-gradient multilayered zirconia showed higher mechanical properties than lithium disilicate ceramic. The high-speed sintering of zirconia showed neither a negative impact on the fracture load nor on the two-body wear. However, the optical properties and the reliability of zirconia is lower than those of highly translucent lithium disilicate ceramic.

Biofilm formation on zirconia and titanium over time-An in vivo model study.

The aim of this study was to evaluate volume, vitality and diversity of biofilms on the abutment materials zirconia and titanium as a function of time using an in vivo model for the biofilm formation. The development of biofilms on zirconia and titanium grade 4 test specimens in the human oral cavity over time was analysed. After pretreatment, a total of 96 titanium and 96 zirconia discs were fixed on 12 composite splints, which were worn by 12 volunteers. After 6hr, 24hr, 3days and 5days, biofilms on 48 specimens of each material were analysed with confocal laser scanning microscopy (CLSM). The microbiota composition on the other 48 test specimens was examined using full-length 16S sequence analysis. Statistical analysis was performed by SPSS and R, and level of significance was set at 0.05. Confocal laser scanning microscopy analysis of the biofilms revealed significant changes in volume over time on zirconia and titanium. The material did not significantly influence the volume or live/dead ratio at the individual time points. The composition of the microbiome was influenced by the age of the biofilm, but not by the material of the test specimen. The most frequently found bacteria were Streptococcus spp., followed by Neisseria spp., Rothia spp., Haemophilus spp., Gemella spp. and Abiotrophia spp. On both materials, the quantity and diversity of the microbiome increased over time. Apart from a slight difference in Veillonella abundance at one time point, there were no significant differences between zirconia and titanium.

Shear bond strength of cemented zirconia-reinforced lithium silicate ceramics (Celtra Duo) with two surface treatments (in vitro study)

Enhance the bonding of cement to ceramic surface with a variety of ceramic surface modifications have been established. Air-abrasion using alumina particles, hydrofluoric acid has been shown to provide micromechanical interlocking at the ceramic-resin interface. The aim of the present study was to evaluate the effect of two surface treatments; acid etching and sandblasting; on the shear bond strength of cemented newly introduced zirconia-reinforced lithium silicate ceramics following thermocycling. Methods: 24 discs of Zirconia- reinforced glass ceramics (Celtra Duo) were tested using 10% hydrofluoric acid for 20 s (control group) and 50 µm aluminum oxide for 60 s at 10 mm distance from the nozzle tip of sandblasting machine. Subsequent to the surface treatments, both groups were salinized and cemented to composites background discs using self-adhesive dual cure resin cement (BisCem). All sample were subjected to 2500 thermal cycle shear bond strength and failure mode was evaluated. The results of the t-test indicated that the bond strength value is significantly influenced by the surface treatment method. It was found that hydrofluoric acid group recorded statistically significantly higher shear bond strength mean value (10.81 MPa) than aluminum oxide sandblasting group (7.76 MPa) as indicated by t-test (t = 2.9, p = 0.0109 < 0.05). Conclusion: failure mode showed a relation between the bond strength and the failure type mixed failure showed with higher bond valves and cohesive failure accompanied with lowest bond strengthen values. The shear bond strength of zirconia reinforced lithium silicate (Celtra Duo) ceramic cemented to resin cement was affected by the type of surface treatment.