Table 4.
Studies investigating mechanical properties of monolithic zirconia specimens/crowns after cycling loading, mechanical loading and various combinations of thermomechanical loading. Studies are presented in chronological order.
| Authors | Zirconia system | Test type /Aging test | Flexural strength change | m-ZrO2 content |
|---|---|---|---|---|
| Specimens | ||||
| Salihoglu-Yener et al. (2015) [129] | -ZirkonZahn | Flexural strength (piston-on-three balls), crosshead-speed 1 mm min−1 | Significant decrease only of unglazed zirconia. ZirkonZahn presented the highest strength with or without thermal cycling. | N/A |
| - Cercon | Thermal cycling (0-control, 1000, 3000, 5000 cycles, 5-55 °C, water). | |||
| – Ceramill | ||||
| Stawarczyk et al. (2016) [119] | - Zenostar | Flexural strength (4-Point Bending), crosshead-speed 1 mm min−1 | No significant change. All monolithic showed lower flexural strength values compared to the conventional zirconia. | N/A |
| - DD Bio ZX2 | Chewing simulator (100 N for 1.2 million times at 1.64 Hz) | |||
| - Ceramill Zolid | ||||
| - InCoris TZI | ||||
| - Ceramill ZI | ||||
| Munoz et al. (2017) [99] | - Prettau Anterior | Flexural strength (piston-on-three balls), crosshead-speed 1 mm min−1 | Significant reduction after M and H + M for Pretau Anterior. Significant reduction after M for the rest. Anterior zirconia had the lowest flexural strength | |
| - Prettau | - mechanical cyclic load (M) | |||
| - ICE Zirkon | - mechanical cyclic + hydrothermal (H + M) | |||
| -non-treated specimens (C). | ||||
| Crowns | ||||
| Johansson et al. (2014) [78] | - Z-CAD HTL | Flexural strength after thermocycling (5000 cycles, 5–55°, water), molar crowns, crosshead-speed 0,025 mm min−1. | The fracture strength of high translucent Y-TZP crowns is considerably higher than that of porcelain-veneered Y-TZP crown cores, porcelain-veneered high translucent Y-TZP crown cores and monolithic lithium disilicate crowns. | N/A |
| - NexxZr HT | ||||
| - Z-CAD HTL-veneered | ||||
| - NexxZr HT- veneered | ||||
| - NexxZr_ HS-veneered | ||||
| Lameira et al. (2015) [77] | - Lava Plus for monolithic crowns | Fracture strength, crowns (on bovine incisors) after thermocycling (2,500, 000 cycles, 80 N, 37 °C, artificial saliva) and loading in chewing simulator, crosshead-speed 0.5 mm min−1. | Monolithic crowns (polished and glazed) presented higher fracture strength than bilayer veneered crowns. No difference between polished and glazed monolithic crowns. | N/A |
| - Lava Frame for bi-layer crowns | ||||
| Nordahl et al. (2015) [131] | - Lava | Fracture toughness, 10° angulated molar crowns of varying thicknesses: 0.3, 0.5, 0.7, 1.0, and 1.5 mm, crosshead-speed 0,025 mm min−1 | Absence of non-aged specimens. There was no difference in strength between crowns of high- or low-translucency. The load at fracture decreased from thicker to thinner | N/A |
| - Lava Plus | Thermocycling of crowns (5000 cycles, 6-55 °C, water) | |||
| Bergamo et al. (2016) [128] | - Ceramill Zolid | Fracture test, molar crowns,crosshead-speed 1 mm min−1 | No significant change | Control: 4% |
| - Thermal fatigue (T): 104 cycles, 5–55 °C | Thermal fatigue:up to 4.5% | |||
| - Mechanical fatigue (M): 106 cycles, 70 N, 1.4-Hz, water, 37 °C | Mechanical fatigue: up to 8,9% | |||
| - Combination of M + T fatigue | Combination of mechanical and thermal fatigue: up to 8.3% | |||
| Mitov et al. (2016) [130] | Zeno Zr | Fracture toughness,molar crowns with various preparation designs (shoulderless, 0.4 mm and 0.8 mm chamfer), crosshead speed 0.5 mm min−1 | Autoclave + chewing simulation caused a significant decrease of the fracture load for all groups, but thermocycling did not. Circumferential shoulderless preparation had a significantly higher fracture | N/A |
| Steam autoclave 134 °C, 2 bar, 3 h + chewing simulation | ||||
| Thermocycling 5–55 °C, 5000 cycles, + chewing simulation | ||||
| Bankoglu et al. (2017) [132] | Incoris TZI | Fracture toughness, molar crowns, crosshead-speed 0.5 mm min−1. | Absence of non-aged specimens. The highest resistance was observed for zirconia crowns. All specimens survived the mastication simulation. | N/A |
| Thermal and mechanical cycling 5000 cycles, 5°-55 °C, water | ||||
| Mechanical loading 100 N, 12 × 105 cycles. | ||||
| Sarıkaya et al. (2018) [87] | - Bruxzir | Fracture strength, crosshead speed 1 mm min−1 (crowns: force applied on buccal and lingual cusps, FPDs: force applied on occlusal connector area). | - No fractures during chewing simulation | N/A |
| - Incoris TZI | Aging: thermocycling (10,000 cycles /5–55 °C / dwell time = 60 s / transfer time = 10 s, | - Bruxzir crowns and FPDs presented significantly higher fracture strength compared to Incoris TZI | ||
| Dual axis chewing simulator with a total of 1,200,000 cycles. | - No significant difference in fracture strength of crowns and FPDs fabricated from Bruxzir | |||
| Weigl et al. (2018) [85] | Zirkon BioStar HT | Fracture strength, crosshead speed 1 mm min−1 | - All 0.5 mm crowns exceeded 900 N. | N/A |
| Aging: chewing simulation (1,200,000 cycles, 50 N, f = 1.6 Hz)) | − 0.2 mm adhesively cemented control crowns exceeded 900 N. | |||
| Thermal cycling (2 × 3000 between 5 °C and 55 °C, 2 minutes for each cycle) | ||||
| Elshiyab et al. (2018) [90] | -Zenostar Zr | Fracture strength, crosshead speed 1 mm min−1 | - Monolithic lithium disilicate crowns presented lower fracture strength compared to monolithic zirconia | N/A |
| - IPS e.max- CAD | Aging: fatigue by chewing simulation with 1.2 million cycles + thermal cycling at 5–55 °C in distilled water (5118 thermal cycles with 60 s dwell time for each cycle, 15 s pause time). | - All crowns presented a reduction in fracture strength following fatigue aging. | ||
| Yin et al. [89](2019) | A3 12 T, Liaoning Upcera, Benxi, China | Fracture strength, crosshead speed 1 mm min−1 | After polishing the crown presented higher fracture strengths than after adjustment of occlusal contact | Not calculated but observed in the diffraction patterns depending on the polishing method |
| Different polishing protocols were evaluated. Cementation using resin cement. | ||||
| Chewing simulation with cyclic loads between 2 and 300 N, frequency 1 Hz (100,000 cycles) | ||||
| Elsayed et al. (2019) [88] | - DD Bio ZX2 (3Y-TZP) | Fracture strength, lower molar crowns with minimum thickness 0.8 mm (buccal) and 1.0 mm (occlusal, lingual, and approximal), crosshead speed 0.5 mm min−1. | Significantly higher fracture strength was noted for 3Y-TZP compared to 5Y-TZP. | N/A |
| - DD cubeX2 HS (4Y-TZP) | chewing simulator for 1,200,000 cycles + simultaneous thermocycling between 5 °C and 55 °C. Vertical load of 49 N applied 2 mm buccal to the central fissure with a lateral movement of 0.3 mm towards the center | (3Y-TZP > 4Y-TZP > 5Y-TZP) | ||
| - DD cubeX2 (5Y-TZP) | ||||
| Fixed partial dentures | ||||
| Preis et al. (2012) [133] | - Cercon ht | Fracture strength, 3-unit FDPs after thermal cycling, crosshead-speed 1 mm min−1 | Similar strength of monolithic compared to veneered zirconia | |
| Alshahrani et al. (2017) [134] | - ICE Zirkon Translucent | Fracture strength, cantilevered frameworks after thermal cycling, crosshead-speed 1 mm min−1 | Increased occlusocervical thickness and decreased cantilever length allowed the cantilever to withstand higher loads. | N/A |
| Villefort et al. (2017) [135] | In-Ceram YZ | Fatigue limit after cycling loading (100,000cycles, 5 Hz frequency), 3-unit posterior FDPs | The glass/silica infiltration techniques in the monolithic zirconia bridges significantly increased the fatigue limits compared with the glazed control group | N/A |
| Control group (CTL) | ||||
| Silica sol-gel group (SSG) | ||||
| Glass-zirconia-glass group (GZG) | ||||
| Lopez-Suarez et al. (2017) [136] | Veneered FDPS: | Fracture strength, 3-unit FPDs after loading in chewing simulator, crosshead-speed 1 mm min−1. | Comparable fracture resistance of monolithic and veneered zirconia FDPs. | N/A |
| - Lava | ||||
| Monolithic FDPs: | ||||
| - Lava Plus | ||||