scholarly journals Preliminary feasibility torque mechanical evaluation for 3D printed orthodontic springs with different parameters: invitro study

2020 ◽  
Author(s):  
Ahmed Othman ◽  
Steven Hartman ◽  
Dragan Ströbele ◽  
Jassin Arnold ◽  
Constantin von See
Keyword(s):  
Testing Machine ◽  
Control Group ◽  
3D Printer ◽  
Coil Design ◽  
Flexible Material ◽  
Universal Testing ◽  
Length Group ◽  
Cad Cam ◽  
3D Printed ◽  
Sydney Australia

Abstract Background: The purpose of the presented investigation is to evaluate the resulting torque on loaded 3D printed springs using different coil thickness and length.Methods: Specimens were designed and printed using the 3D printer MAX (Asiga, Sydney, Australia) with 3D printable, experimental, flexible material (Code:BM2008, GC, Tokyo, Japan). The specimens were divided into three groups according to spring coil design. Control group (n=18), length group (n=19) and thickness group (n=22). Groups were tested using a Sauter Machine for torque calculation (DB, Grindelwald, Switzerland) in conjunction with a universal testing machine (Zwick Z010, Ulm, Germany) for clock-wise and anti-clockwise testing. Statistical analysis was performed using the Steel-Dwass test to compare median values of the three groups in both testing directions (p<0.001). Results: The highest torque value was determined in the thickness group for both clockwise and anti-clockwise testing directions, achieving 44.00N/mm and 39.62N/mm respectively. The length group ranged from 21.65N/mm to 11.04N/mm in clockwise direction and from 18.04N/mm to 11.38N/mm in counter-clockwise testing. The control group ranged from 22.72N/mm to 17.18N/mm in the clock-wise direction while in the anti-clock wise testing it ranged from 21.34N/mm to 16.02N/mm.Conclusions: The amount of torque produced from the CAD/CAM springs is being affected by diameter more than the length design parameter in comparison to the control group. The values of the thickness group are significantly higher than those of the length group (P<0.001).

scholarly journals Torque Mechanical Evaluation for 3D Printed Orthodontic Springs with Different Parameters: Invitro Study

2020 ◽  
Author(s):  
Ahmed Othman ◽  
Steven Hartman ◽  
Dragan Ströbele ◽  
Jassin Arnold ◽  
Constantin von See
Keyword(s):  
Testing Machine ◽  
Control Group ◽  
3D Printer ◽  
Coil Design ◽  
Flexible Material ◽  
Universal Testing ◽  
Length Group ◽  
Cad Cam ◽  
3D Printed ◽  
Sydney Australia

Abstract Background: The purpose of the presented investigation is to evaluate the resulting torque on loaded 3D printed springs using different coil thickness and length. Methods: Specimens were designed and printed using the 3D printer MAX (Asiga, Sydney, Australia) with 3D printable, experimental, flexible material (Code:BM2008, GC, Tokyo, Japan). The specimens were divided into three groups according to spring coil design. Control group (n=18), length group (n=19) and thickness group (n=22). Groups were tested using a Sauter Machine for torque calculation (DB, Grindelwald, Switzerland) in conjunction with a universal testing machine (Zwick Z010, Ulm, Germany) for clock-wise and anti-clockwise testing. Statistical analysis was performed using the Steel-Dwass test to compare median values of the three groups in both testing directions (p<0.001). Results: The highest torque value was determined in the thickness group for both clockwise and anti-clockwise testing directions, achieving 44.00N/mm and 39.62N/mm respectively. For the thickness group values ranged from 21.28N/mm anti-clockwise to 44.00N/mm clockwise. The length group ranged from 21.65N/mm to 11.04N/mm in clockwise direction and from 18.04N/mm to 11.38N/mm in counter-clockwise testing. The control group ranged from 22.72N/mm to 17.18N/mm in the clock-wise direction while in the anti-clock wise testing it ranged from 21.34N/mm to 16.02N/mm. Conclusions: 3D printed springs are being affected by diameter than length as a design parameter compared to the control group. The thickness group values are statistically significant than the length group (P<0.001). Key words: CAD/CAM, 3D printing, Digital Orthodontics, Torque, Springs.

scholarly journals Preliminary feasibility torque mechanical evaluation for 3D printed orthodontic springs with different parameters: in vitro study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ahmed Othman ◽  
Steven Hartman ◽  
Dragan Ströbele ◽  
Jassin Arnold ◽  
von See
Keyword(s):  
Testing Machine ◽  
In Vitro Study ◽  
Control Group ◽  
Flexible Material ◽  
Length Group ◽  
Computer Aided ◽  
Cad Cam ◽  
3D Printed ◽  
Sydney Australia

Abstract Background The purpose of the presented investigation is to evaluate the resulting torque on loaded 3D printed springs using different coil thickness and length. Methods Specimens were designed and printed using the 3D printer MAX (Asiga, Sydney, Australia) with 3D printable, experimental, flexible material (Code:BM2008, GC, Tokyo, Japan). The specimens were divided into three groups according to spring coil design. Control group (n = 18), length group (n = 19) and thickness group (n = 22). Groups were tested using a Sauter Machine for torque calculation (DB, Grindelwald, Switzerland) in conjunction with a universal testing machine (Zwick Z010, Ulm, Germany) for clock-wise and anti-clockwise testing. Statistical analysis was performed using the Steel–Dwass test to compare median values of the three groups in both testing directions (p < 0.001). Results The highest torque value was determined in the thickness group for both clockwise and anti-clockwise testing directions, achieving 44.00 N/mm and 39.62 N/mm respectively. The length group ranged from 21.65 to 11.04 N/mm in clockwise direction and from 18.04 to 11.38 N/mm in counter-clockwise testing. The control group ranged from 22.72 to 17.18 N/mm in the clock-wise direction while in the anti-clock wise testing it ranged from 21.34 to 16.02 N/mm. Conclusions The amount of torque produced from the computer aided designing/computer aided manufacturing (CAD/CAM) springs is being affected by diameter more than the length design parameter in comparison to the control group. The values of the thickness group are significantly higher than those of the length group (P < 0.001).

Effect of Different Computer-aided Design/Computer-aided Manufacturing (CAD/CAM) Materials and Thicknesses on the Fracture Resistance of Occlusal Veneers

2018 ◽  
Vol 43 (5) ◽  
pp. 539-548 ◽  
Author(s):  
JP Andrade ◽  
D Stona ◽  
HR Bittencourt ◽  
GA Borges ◽  
LH Burnett ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Fracture Resistance ◽  
Testing Machine ◽  
Control Group ◽  
Computer Aided Manufacturing ◽  
Universal Testing ◽  
Computer Aided ◽  
Cad Cam ◽  
Aided Design

SUMMARY The aim was to evaluate, in vitro, the influence of different computer-aided design/computer-aided manufacturing (CAD/CAM) materials (IPS e.max CAD, Vita Enamic, and Lava Ultimate) and thicknesses (0.6 mm and 1.5 mm) on the fracture resistance of occlusal veneers. Sixty human third molars were prepared to simulate advanced erosion of the occlusal surface, and the teeth were randomly divided into six experimental groups (n=10) according to the material and thickness used to build the veneers. Ten sound teeth formed the control group. The veneers were adhesively luted and submitted to mechanical cyclic loading (1 million cycles at 200-N load). The fracture resistance test was performed in a universal testing machine. The failures were classified as “reparable” and “irreparable.” According to two-way analysis of variance and the Tukey test, the interaction (material × thickness) was significant (p=0.013). The highest fracture resistance was obtained for IPS e.max CAD at a 1.5-mm thickness (4995 N) and was significantly higher compared to the other experimental groups (p&lt;0.05). The lowest fracture resistance was obtained for Vita Enamic at 0.6 mm (2973 N), although this resistance was not significantly different from those for IPS e.max CAD at 0.6 mm (3067 N), Lava Ultimate at 0.6 mm (3384 N), Vita Enamic at 1.5 mm (3540 N), and Lava Ultimate at 1.5 mm (3584 N) (p&gt;0.05). The experimental groups did not differ significantly from the sound teeth (3991 N) (p&gt;0.05). The failures were predominantly repairable. The occlusal veneers of IPS e.max CAD, Vita Enamic, and Lava Ultimate, with thicknesses of 0.6 mm and 1.5 mm, obtained fracture resistances similar to those associated with sound teeth.

scholarly journals THE LABORATORY STUDY OF THE FLEXURAL STRENGTH OF REINFORCED BIS-ACRYLIC MATERIAL FOR PROVISIONAL FIXED RESTORATIONS

2018 ◽  
Vol 14 (4) ◽  
pp. 121-126
Author(s):  
Олег Петрикас ◽  
Oleg Petrikas ◽  
Дмитрий Трапезников ◽  
Dmitry TRAPEZNIKOV ◽  
Эмилия Змеева ◽  
...  
Keyword(s):  
Mechanical Test ◽  
Testing Machine ◽  
Control Group ◽  
Test Results ◽  
Flexural Test ◽  
Routine Procedure ◽  
Universal Testing ◽  
Glass Fiber Reinforced ◽  
Cad Cam

Background. The use of provisional (interim, temporary) restorations has become a routine procedure in modern dentists after the end of the era of brazed-stamped bridges. The use of traditional acrylic plastics does not provide the necessary strength for the long-term functioning of provisional prostheses. Bis-acrylic materials have helped to eliminate some of the problems associated with traditional acrylic materials. However the disadvantage of bis-acryls is that they can break relatively easily when placed in areas of increased stress. The use of provisional prostheses, obtained by casting or CAD/CAM technology, undoubtedly solve problems, however, prosthetics are significantly more expensive. Another known and cheaper way is to harden polymers by reinforcing them. Objectives ― to study, when conducting a mechanical test, the fracture resistance of glass fiber-reinforced bis-acrylic composite beams. Methods. On a universal testing machine (three-point flexural test), 8 groups of samples were studied depending on the material — Re-fine Bright acrylic material (Yamahachi Dental MFG., CO., Japan), or Luxatemp bis-acrylic material (DMG) and Protemp 4 (3M ESPE), and also, the method of reinforcement of Protemp 4 with GlasSpan fiberglass tape (GlasSpan). The fracture strength (F) was calculated in MPa. Statistical differences between groups were determined using T-test. Results. Comparison of the fracture strengths results between the first control group (Protemp 4 bis-acrylic plastic without reinforcement) and other groups (glass tape reinforcement) revealed a significant hardening of Protemp 4 after reinforcement (p <0,05). Conclusions. The use of reinforcing glass tape with a full impregnation with an adhesive and a flowable composite increases the strength of Protemp 4 more than 2 times.

scholarly journals In-house 3D-printed surgical guides for osseous lesions of the lower jaw: an experimental study

2021 ◽  
Vol 26 (1) ◽  
Author(s):  
Lukas Postl ◽  
Thomas Mücke ◽  
Stefan Hunger ◽  
Oliver Bissinger ◽  
Michael Malek ◽  
...  
Keyword(s):  
Control Group ◽  
Head Model ◽  
Computer Assisted ◽  
3D Printer ◽  
Surgical Guide ◽  
Surgical Guides ◽  
Lower Jaw ◽  
Bony Lesion ◽  
3D Printed ◽  
Phantom Head

Abstract Background The accuracy of computer-assisted biopsies at the lower jaw was compared to the accuracy of freehand biopsies. Methods Patients with a bony lesion of the lower jaw with an indication for biopsy were prospectively enrolled. Two customized bone models per patient were produced using a 3D printer. The models of the lower jaw were fitted into a phantom head model to simulate operation room conditions. Biopsies for the study group were taken by means of surgical guides and freehand biopsies were performed for the control group. Results The deviation of the biopsy axes from the planning was significantly less when using templates. It turned out to be 1.3 ± 0.6 mm for the biopsies with a surgical guide and 3.9 ± 1.1 mm for the freehand biopsies. Conclusions Surgical guides allow significantly higher accuracy of biopsies. The preliminary results are promising, but clinical evaluation is necessary.

scholarly journals Flexible 3D Printed Molds for Educational Use. Digital Fabrication of 3D Typography

2019 ◽  
Vol 15 (13) ◽  
pp. 4 ◽  
Author(s):  
Alejandro Bonnet De León ◽  
Jose Luis Saorin ◽  
Jorge De la Torre-Cantero ◽  
Cecile Meier ◽  
María Cabrera-Pardo
Keyword(s):  
3D Modeling ◽  
Low Cost ◽  
Digital Fabrication ◽  
3D Printer ◽  
School Environments ◽  
Flexible Material ◽  
Educational Environments ◽  
3D Printers ◽  
3D Printed ◽  
The Subject

<p class="0abstract"><span lang="EN-US">One of the drawbacks of using 3D printers in educational environments is that the creation time of each piece is high and therefore it is difficult to manufacture at least one piece for each student. This aspect is important so that each student can feel part of the manufacturing process. To achieve this, 3D printers can be used, not to make pieces, but to make the molds that students use to create replicas. On the other hand, for a mold to be used to make several pieces, it is convenient to make it with flexible material. However, most used material for 3D printers (PLA) is very rigid. To solve this problem, this article designs a methodology that allows the use of low-cost 3D printers (most common in school environments) with flexible material so that each mold can be used to manufacture parts for several students. To print flexible material with low-cost printers, it is necessary to adapt the machine and the print parameters to work properly. This article analyzes the changes to be made with a low cost 3D printer and validates the use of molds in school environments. A pilot test has been carried out with 8 students of the subject of Typography, in the School of Art and Superior of Design of Tenerife. During the activity, the students carried out the process of designing a typography and creating digital molds for 3D printing with flexible material. The designs were made using free 3D modeling programs and low-cost technologies.</span></p>

scholarly journals Fully-customized distraction assembly for maxillofacial distraction osteogenesis: a novel device and its experimental accuracy verification

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Sang-Hoon Kang ◽  
Hye-Jin Tak ◽  
Ha-Won Park ◽  
Jin-Ung Kim ◽  
Sang-Hwy Lee
Keyword(s):  
Distraction Osteogenesis ◽  
Reference Points ◽  
Assembly System ◽  
Control Group ◽  
Novel Device ◽  
Mandibular Distraction Osteogenesis ◽  
Distraction Device ◽  
Cad Cam ◽  
3D Printed ◽  
Group 1

Abstract Background A new distraction osteogenesis assembly system comprising a fully customized CAD/CAM-based fixation unit and ready-made distraction unit was developed. The aim of this study was to introduce our new distraction system and to evaluate its accuracy level in a sampled mandibular distraction osteogenesis. Methods Our system consists of a fully customized CAD/CAM-based fixation plate unit with two plates for each moving and anchoring part, and a ready-made distraction unit with attachment slots for fixation plates. The experimental distractions were performed on 3D-printed mandibles for one control and two experimental groups (N = 10 for each group). All groups had reference bars on the chin region and teeth to measure distraction accuracy. The control group had the classical ready-made distraction system, and experimental groups 1 and 2 were fitted with our new distraction assembly using a different distractor-positioning guide design. All distracted experimental mandibles were scanned by CT imaging, then superimposed on a 3D simulation to get their discrepancy levels. Results The measured 3D distances between the reference landmarks of the surgical simulations and the experimental surgeries for the three groups were significantly different (p < 0.0001) by statistical analysis. The errors were greater in the control group (with a total average of 19.18 ± 3.73 mm in 3D distance between the simulated and actual reference points) than those in the two experimental groups (with an average of 3.68 ± 1.41 mm for group 1 and 3.07 ± 1.39 mm for group 2). The customized distraction assembly with 3D-printed bone plate units in group 1 and 2, however, did not show any significant differences between simulated and actual distances (p > 0.999). Conclusion Our newly-developed distraction assembly system with CAD/CAM plate for the distraction osteogenesis of the mandible produced a greater level of accuracy than that of a conventional distraction device. The system appears to address existing shortcomings of conventional distraction devices, including inaccuracy in vector-controlled movement of the system. However, it also needs to be further developed to address the requirements and anatomical characteristics of specific regions.

scholarly journals Pengaruh penambahan hidroksiapatit terhadap porositas dan compressive strength basis resin akrilik heat-curedEffect of hydroxyapatite addition towards porosity level and compressive strength of heat-cured acrylic resin base

2020 ◽  
Vol 32 (2) ◽  
pp. 91
Author(s):  
Chaterina Diyah Nanik Kusumawardani ◽  
Ronaldo Triputro Chondro ◽  
Ivan Andrian ◽  
Rima Parwati Sari
Keyword(s):  
Compressive Strength ◽  
Testing Machine ◽  
Acrylic Resin ◽  
Load Cell ◽  
Control Group ◽  
Porosity Level ◽  
Universal Testing ◽  
White Spots ◽  
Sem Imaging ◽  
One Way Anova

Pendahuluan: Resin akrilik heat cured (HC) merupakan pilihan utama bahan sebagai basis gigi tiruan. Hidroksiapatit (HAP) adalah molekul kristalin yang sudah banyak digunakan di kedokteran gigi. Penelitian terdahulu membuktikan bahwa HAP mampu mengurangi monomer sisa pada resin akrilik HC, yang akan mengurangi juga porositas resin akrilik tersebut. Berkurangnya porositas resin akrilik, diharapkan akan meningkatkan kekuatan mekanik resin akrilik tersebut. Tujuan penelitian menganalisis pengaruh penambahan hidroksiapatit terhadap porositas dan compressive strength resin akrilik HC. Metode: Jenis penelitian eksperimental laboratoris. Sampel penelitian 20 resin akrilik HC berbentuk silindris (6x3mm), dibagi menjadi 4 kelompok. Kelompok kontrol (tanpa penambahan HAP), kelompok HAP 2%, kelompok HAP 5%, dan kelompok HAP 10%. Permukaan sampel diteliti menggunakan SEM untuk porositasnya. Penghitungan compressive strength sampel menggunakan Universal Testing Machine (load cell 300kg/mm2). Hasil: Uji one-way ANOVA dan Tukey-HSD menunjukkan perbedaan signifikan (p<0,05) antara kelompok kontrol (90±13,5MPa) dengan 5%HAP (105±4,3MPa) dan 10%HAP (113±10,2MPa), begitu pula antara 2%HAP (96±8,4MPa) dengan 10%HAP. Uji SEM menunjukkan tidak adanya reaksi kimia antara HAP dan resin akrilik HC. Tampak pula bercak putih tersebar tidak merata pada permukaan sampel akrilik di kelompok-kelompok perlakuan. Bercak putih ditemukan meningkat sebanding dengan peningkatan konsentrasi HAP, dengan diameter yang semakin besar. Simpulan: Penambahan HAP pada basis resin akrilik HC mampu menurunkan tingkat porositas dan meningkatkan nilai compressive strength. Penurunan tingkat porositas meningkat seiring dengan penambahan HAP. Compressive strength yang paling tinggi didapatkan pada basis resin akrilik heat cured dengan penambahan 10% hidroksiapatit.Kata kunci: Compressive strength, uji SEM, resin akrilik heat cured, hidroksiapatit. ABSTRACT Introduction: Heat-cured acrylic resin has been commonly used as a denture base, whereas hydroxyapatite (HAP) is a crystalline molecule widely used in the field of dentistry. Previous research has been proofed that HAP could reduce the residual monomer of heat-cured acrylic resin, which will reduce the porosity level in advance, so it was expected for better mechanical properties. This research was aimed to analyse the effect of HAP addition towards the porosity level and compressive strength of heat-cured acrylic resin. Methods: An experimental laboratory research was conducted towards 20 cylindrical samples (6 x 3 mm) of heat-cured acrylic resins, which were divided into four groups: Control group (without HAP addition), 2% HAP addition group, 5% HAP addition group, and 10% HAP addition group. Compressive strength was tested using Universal Testing Machine (load cell of 300kg / mm2). Each sample surface porosity was observed using the scanning electron microscope (SEM). Results: One-way ANOVA and Tukey-HSD tests results showed significant differences (p < 0.05) between compressive strength in the control group (90 ± 13.5 MPa) compared to 5% (105 ± 4.3 MPa) and 10% HAP addition group (113 ± 10.2 MPa), significant differences were also shown between the 2% (96±8.4MPa) and 10% HAP addition group. SEM imaging showed that there was no chemical reaction between HAP and heat-cured acrylic resin. It showed uneven white spots in acrylic sample’s surface in all treatment groups. Those white spots were likely to be found more in the higher concentration of HAP, so did the diameter of white spots was also found more in the higher concentration. Conclusion: The addition of hydroxyapatite to the base of heat-cured acrylic resin can reduce the level of porosity and increase the compressive strength value. The decrease in the porosity level increases with the addition of hydroxyapatite. The highest compressive strength is obtained with the addition of 10% hydroxyapatite.Keywords: Compressive strength, SEM imaging, heat-cured acrylic resin, hydroxyapatite.

scholarly journals Effect of beverages on surface properties of resin-based sealants

2017 ◽  
Vol 16 ◽  
pp. 1-7
Author(s):  
Bruna Genari ◽  
Vicente Castelo Branco Leitune ◽  
João Henrique Macedo Saucedo ◽  
Susana Maria Werner Samuel ◽  
Fabrício Mezzomo Collares
Keyword(s):  
Bond Strength ◽  
Testing Machine ◽  
Resin Cement ◽  
Control Group ◽  
Resin Cements ◽  
Universal Testing ◽  
Halogen Light ◽  
Significant Difference ◽  
Tooth Surfaces ◽  
Light Curing

Self-adhesive, dual-polymerizing resin cements require no treatment to the prepared tooth surfaces before cementation. Aim: The aim of this study was to evaluate the influence of curing mode on bond strength (BS) of three cementing systems to bovine dentin. Methods: The buccal enamel surfaces of 50 bovine incisors were removed to expose dentin and to flat the surface. The teeth were divided into five groups (n=10), which consisted of two resin cements (Multilink and Clearfil SA Cement) that were tested in dual- (halogen light for 40 s) and self-cured modes, and a control (RelyX ARC). Two cylinders of resin cements (1.0 mm X 0.75 mm) were prepared on each bonded dentin surface. After 24h at 37oC, resin cylinders were subjected to micro-shear testing in a universal testing machine (4411/Instron - 0.5 mm/min). Data were statistically analyzed by two-way ANOVA, Tukey and Dunnett`s test (5%). Results: Multilink showed higher BS than those observed on Clearfil SA. Light-curing resulted in higher BS for both Multilink and Clearfil SA. When Multilink was light-cured, no significant difference on BS was demonstrated between it and RelyX ARC. Conclusions: The highest BS values were obtained in control group and light-cured Multilink resin cement.

scholarly journals Influence of time and hydration (ageing) on flexural strength of Yttrium stabilized Zirconia polycrystals (Y-TZP) fabricated with different CAD-CAM Systems

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
Khulud A Al Aali ◽  
Saad Alresayes ◽  
Aasem M Alhenaki ◽  
Fahim Vohra ◽  
Tariq Abduljabbar
Keyword(s):  
Flexural Strength ◽  
Testing Machine ◽  
Control Group ◽  
Stabilized Zirconia ◽  
Cad Cam ◽  
Group 3 ◽  
Group 2 ◽  
Cam Systems ◽  
Ageing Duration ◽  
Group 1

Objectives: To evaluate the effect of time and hydration (ageing) on flexural strength of yttrium-stabilized zirconia polycrystals (Y-TZP) zirconia fabricated from three different materials. Methods: This in-vitro study was performed from June to September 2019. Y-TZP bars, measuring 2 x 3 x 20 mm were prepared and sintered from three different materials, Group-1: LAVA™ Zirconia (3M™ ESPE, US) (control) Group-2: Vita In-Ceram YZ (VITA, Germany) and Group-3: Aadva™ Zirconia (Zr) (GC Advanced technologies Inc.). 30 zirconia bars per group were prepared using sectioning of blocks with isomet saw. Followed by sintering in furnaces for recommended temperature cycles. One side of bars were polished and beveled for flexural testing. Groups of specimens were divided into subgroups of 3 (n=10) based on the ageing (distilled water in the incubator at 37ºC) durations (48 Hrs and two and half years). Ten specimens in each material groups were not aged (controls). Samples were exposed to a static force in a three-point bend test using a universal instron-testing machine until fracture. Scanning electron microscopic assessment was performed for fractured specimens for ageing. Data was analyzed using ANOVA and Tukey post hoc test. Results: The mean flexural strength at baseline for Group-1: LAVA™ Zirconia, group (632.7 ± 136.5 MPa) 2: Vita In-Ceram YZ (1036.3 ± 229.6 MPa), and Group-3: Aadva™ Zirconia (1171.3 ± 266.3 MPa) were significantly different. Group-2 and Group-3 specimens showed higher strength compared to Group-1 specimens, irrespective of the ageing duration (p<0.05). Analysis of pooled data for flexural strength for materials by aging period (baseline, after 48 hours and after 2 and ½ years) showed that there was significant reduction of strength with increasing duration (p<0.05). Conclusions: Y-TZP showed variations in flexural strength depending on the material type. Ageing duration exhibited significant influence on the flexural strength of Y-TZP when comparing no ageing to two and half years. Vita In-Ceram YZ and Aadva Zirconia (Zr) showed higher and clinically acceptable flexural strength outcomes. doi: https://doi.org/10.12669/pjms.37.3.3996 How to cite this:Al-Aali KA, Alresayes S, Alhenaki AM, Vohra F, Abduljabbar T. Influence of time and hydration (ageing) on flexural strength of Yttrium stabilized Zirconia polycrystals (Y-TZP) fabricated with different CAD-CAM Systems. Pak J Med Sci. 2021;37(3):---------.   doi: https://doi.org/10.12669/pjms.37.3.3996 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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