1,720,988 research outputs found
The effect of zirconia surface treatment on bond strength of various cement systems
Get PDFOBJECTIVES: The aim of this in-vitro study is to evaluate the effect of different zirconia surface pretreatments, different cement types and the effect of accelerated aging on the adherence of bonding cements to zirconia.
MATERIALS AND METHODS: 64 zirconia 3Y-TZP tapered rings were pressed from TZ-3YSB-E zirconia powder, pre-treated with different surface treatments, then cemented to titanium abutment pins using 8 different cements: Maxcem Elite chroma (Kerr), TheraCem (Bisco), RelyX Unicem2 (3M ESPE), Multilink Automix (Ivoclar Vivadent), Panavia SA Cement Plus (Kuraray), Ceramir C&B (Doxa), CemEZ Universal (Zest Dental), and Bifix SE (VOCO). The partitally sintered zirconia specimens were divided according to design of experment (DOE). Zirconia surface treatments: 1) control group with no surface treatment, 2) airborne particle abrasion of fully sintered zirconia ring (FS-APA50), 3) airborne particle abrasion of partially sintered zirconia (PS-APA50), 4) tribochemical silica coating of fully sintered zirconia (FS-CoJet30), 5) tribochemical silica coating of partial sintered zirconia (PS-CoJet30), and 6) nano-structured alumina coating of fully sintered zirconia (NanoAl). Zirconia rings were subjected to post-treatment:1) control 24h incubation after cementing proceedure, and 2) accelerated aging . The pull-out axial tensile retention load was tested using an Instron Model 5566A. Multi factorial linear regression model (JMP Pro 15) was used for data analysis (α=0.05).
RESULTS: The retention force (N) of zirconia rings to titanium abutment pins was evaluated using a pull-out test. Four key factors were investigated in this study: zirconia surface pre-treatment, cement type, post-treatment and firing effect. There was a significant effect of zirconia surface pre-treatment on retention force (nano-structured alumina coating ≥ tribochemical abrasion = airborne-particle abrasion ≥ control). There was a significant effect of cement type on retention force [Multilink AM ≥ (Cem EZ = TheraCem = Panivia SA = RelyX Unicem2 = BiFix) ≥ Ceramir CB = Maxcem Elite]. There is a significant difference in retention strength to zirconia among post-treatment effect, with accelerated aging groups achieving slightly higher bond strength than 24h water storage groups.
CONCLUSIONS: Significant different retention loads were found among tested groups. Nano-structured alumina coating surface pre-treatment has significantly higher bond strength than other treatments. Some cement systems with functional monomer had significant higher bond strengths
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The effect of hydrofluoric acid etching on zirconia bond strength and surface properties
Get PDFOBJECTIVES: This in-vitro study aimed to evaluate the effect of hydrofluoric acid etching and airborne particle abrasion on zirconia bond strength, using three different types of cement. To assess the impact of hydrofluoric acid etching on zirconia surface roughness and investigate the effect of hydrofluoric acid etching on zirconia's surface topography, microstructure, and crystal structure.
MATERIALS AND METHODS: Crown-abutment simulation systems were constructed, using a custom-made zirconia tapered ring model and tapered titanium pin-abutments. Twelve groups were included in the study and classified according to the surface treatment and type of cement used. Each group had 10 specimens for a total of 120 test specimens. The fully sintered zirconia ring was alumina particle abrasion (APA) treated with a 50-μm alumina and/or etched with 9.5% HF acid, solution for 1 minute. The Ti pin was APA treated with 125-μm alumina. Three different types of cement were used: one RMGIC (GC FujiCem Evolve) and two resin composite types of cement (Panavia SA Universal and Panavia V5). A cementing jig was used to standardize the cementation process of the titanium pins to the zirconia rings. An Instron was used to obtain the retention load values.
The failure load between the zirconia ring and the titanium pin was determined using an axial pullout test and the values were statistically analyzed for the effects of etching treatment, APA treatment, and cement type using JMP Pro 16.
Zirconia-disk specimens were constructed using a custom-made disk model. Thirteen groups were included in the study and classified according to the hydrofluoric acid etching concentrations, consistencies, and timing used. Each group had 3 specimens. The total specimen size was thirty-nine specimens. Disks were polished and etched using 5% HF, 9.5% HF, and 40% HF acid etching concentrations, gel, and solution consistencies, and for 1 and 15 minutes of etching time. Disks were examined with an SEM, X-Ray diffractometer, and a profilometer for microstructure, crystallography, and surface roughness, respectively.
RESULTS: HF acid-etching treatment significantly increased retention load compared to non-etched groups. There was no significant difference in retention load between APA-treated and non-APA-treated groups. Groups cemented with Panavia V5 showed a higher retention load compared to GC FujiCem Evolve and Panavia SA Universal. There was no significant difference in the surface roughness among the etched groups and the control groups. Roughening of the crystal boundaries with irregularities and pits was observed under SEM. As etching time and concentration increased the surface became rougher and
more irregular. There were no obvious crystal structure differences between the etched groups and non-etched groups.
CONCLUSIONS: Significantly different retention loads were found among tested groups. Hydrofluoric acid etching increases the bond strength of zirconia and titanium, using resin composite cement. Using hydrofluoric acid etching to pre-treat the zirconia surface may be an alternative approach to obtain sufficient bonding strength
Analysis of accuracy and mechanical properties of 3D-printed polymeric dental materials
No full textOBJECTIVES: The objective was to investigate the accuracy, storage stability, and
mechanical properties of 3D-printed polymeric dental materials.
MATERIALS AND METHODS: Three completely dentate models, two maxillary and one
mandibular each with their respective die, and three implant models were designed using
dental CAD software (3SHAPE DENTAL SYSTEM). A horseshoe-shaped solid base with
a posterior horizontal bar was utilized. The models were printed based on the
manufacturer's instructions for four weeks using six printers with the corresponding
recommended resin materials: Carbon M2 (DPR10), HeyGears A2D4K (Model HP
UV2.0), Stratasys J5 (MED610), Stratasys Origin One (DM200), Envision One (E-Model
LightDLP), and Asiga Pro4K (VeriModel) with a standard layer thickness of 50 μm
(N=72). The models were scanned after printing using Sirona inEOS X5 scanner, while the implant models were scanned using a CT scanner (GE Phoenix V|tome|x metrology edition). The full arch models were randomly assigned to three groups of storage conditions: cold environment (LT, 4 ± 1°C), hot and dry environment (HT, 50 ± 2°C), and
room temperature (RT , 25 ± 2°C, serving as the control). Each group was kept under the
designated conditions and scanned at 1, 2, 3, 4, and 8 weeks. The generated STL files were
imported into a 3D inspection software for comparison with the original STL files. Four
sets of reference points (central fossa of first premolars and central fossae of second molars)
were selected to determine six distances of inter-arch segments, from which the inter-arch
distance trueness and precision deviation were measured.
For the second part of the study, maxillary Lucitone Digital Print denture base (DB) (N=5),
maxillary Lucitone IPN 3D Premium anterior and posterior teeth (N=6), and maxillary
Keystone Keysplint Soft Clear occlusal splint (N=5) were printed using two printers
(Carbon M2, Asiga Max UV) with a standard layer thickness of 50 μm for denture base
and teeth, and 100 μm for the occlusal splint. The tolerance threshold was set to 50 μm for
Lucitone IPN and 100 μm for Lucitone DB and Keysplint Soft. In-tolerance percentage
and deviation RMS were obtained and analyzed with multivariate least square mean linear
regression using JMP Pro 17 (SAS, Cary, NC) to identify significant effects (α=0.05).
The third part investigated the mechanical properties of Lucitone DB and IPN using 2
printers (Carbon M2, Asiga Max UV) as follows: flexural strength (N=10) using a threepoint
bend test, fracture toughness (N=10), creep (N=5), Vickers hardness test (N=15),
surface roughness (N=15), while Shore A hardness (N=15) and tensile strength (N=10)
were performed for Keysplint Soft Clear. Data were analyzed using one-way and multivariate least square mean linear regression followed by Tukey’s HSD test using JMP Pro 17 (SAS, Cary, NC) to identify significant effects (α=0.05).
RESULTS: The in-tolerance percentage varied significantly among printers, with Carbon M2
(CAB) showing the highest values. Stratasys (J5) displayed the highest accuracy in term of
precision, while HeyGears A2D4K (HGS), Carbon M2 (CAB), and Stratasys (J5) exhibited
the highest accuracy in term of trueness. The inter-molar segment showed the highest
deviation. No significant difference was observed in in-tolerance percentage across
different print weeks except for week 2 in one printer (Stratasys Origin1). CAB exhibited
a higher in-tolerance percentage for the DB than Asiga Max UV (ASG), with the fitting
surface having the highest in-tolerance percentage. IPN anterior teeth had a higher intolerance
percentage than posterior teeth, with ASG showing a higher value than CAB. No
statistically significant difference was found in the in-tolerance percentage of Keysplint
Soft Clear between ASG and CAB. Resin printed using ASG demonstrated higher flexural
strength, Vickers hardness, and creep, while resin printer using CAB exhibited higher
fracture toughness, with no significant difference in surface roughness between the two
printers. Lucitone IPN had higher flexural strength and Vickers hardness, surface
roughness , and lower creep and fracture toughness than Lucitone DB. CAB Keysplint
Soft had higher tensile strength than ASG, with no statistically significant difference in
Shore A hardness between the two printers.
CONCLUSION: Model dimension deviations were impacted by storage conditions and the
specific printer utilized, with high-temperature storage exhibiting the least stability.
However, no significant difference was noted between low and room temperature storage
conditions. Carbon M2 exhibited the highest level of accuracy. The of 3D-printed denture
bases and denture teeth varied across different printers. Conversely, no significant
difference in accuracy was observed for a soft occlusal splint between two printers.
Materials printed using different printers showed statistically significant different
mechanical properties
Mechanical properties of printable and machinable denture tooth material
Get PDFOBJECTIVES: The aim of this study was to compare and determine the mechanical properties of printed and machined provisional and definitive dental restorations. Specimens from various materials were obtained via different production techniques, additive or subtractive manufacture. These samples underwent various tests to examine properties including wear resistance and flexural strength.
METHODOLOGY: Five different materials were tested for wear resistance and flexural strength via three distinct procedures. The materials were from the following manufacturers: PAC-DENT (definitive printed material), BEGO (provisional printed material), DENTCA (provisional printed material), SHOFU (definitive machined material), and TELIO (provisional machined material). The specimens for each material were divided into subgroups of 12 specimens per test and prepared into specific dimensions in accordance with the parameters of the test. The first procedure was a wear test that examined a 3.5 mm in diameter pin-shaped specimen sliding on a ceramic substrate. The second test was a biaxial flexural strength test that examined disc-shaped specimens using a ball-on-three-ball fixture. The third test was a three-point bend flexural strength test that examined two different-sized rectangular bar specimens. The final test was a Vickers microhardness test that examined indentations made along the surfaces of the specimens. Sites of fracture, deformation, or wear were examined under scanning electron microscope (SEM). Results were analyzed via ANOVA, Tukey’s HSD test, and student t-test (α = 0.05).
RESULTS: The results of the wear test indicated that SHOFU and TELIO had a significantly greater rate of volume loss than the remaining materials. The results of the biaxial flexural strength test indicated that the TELIO group was significantly higher than the other materials with a mean value of 187.63 MPa. The three-point bend test on materials tested on a 10 mm support span indicated that the TELIO group once again showed significantly higher values than the remainders with a mean flexural strength of 149.80 MPa. However, on the 20 mm support span of the three-point bend test, PAC-DENT showed significantly higher flexural strength values of 140.47 MPa. SHOFU showed the highest mean hardness value of 71.60 Hv, which was significantly higher than other materials. SEM imaging and EDS analysis showed the existence of inorganic filler load in the SHOFU, PAC-DENT, and BEGO materials.
CONCLUSION: The results of the study rejected the proposed null hypothesis. The type and production method of a restorative material did indeed influence the resulting mechanical properties. The properties of wear resistance, flexural strength, and surface hardness that were tested all exhibited significant differences between the materials. Although differences were found between the individual materials themselves; when compared to the existing literature, it was found that the resulting mechanical properties values all fell within an acceptable range when compared to most commercially available products. This was crucial information, as it indicated that these materials would be practical and of use in a clinical setting. Further investigation is required for other factors which may affect the aforementioned mechanical properties, such as aging and fatiguing, which were not studied in this thesis
Evaluation of the bond strength of various denture teeth materials to conventional, CAD/CAM, and 3D printed denture bases
Get PDFOBJECTIVES: The aim of this in vitro study is to investigate the bond strength of recently introduced commercial denture teeth to denture base materials that are fabricated in different methods. The effect of thermocycling on shear bond strength was investigated.
MATERIALS AND METHODS: From high-impact pourable acrylic HIPA (Dentsply Sirona), Ivotion Base (Ivoclar Vivadent), Lucitone Digital Print (Dentsply Sirona), and Formlabs Denture Base (Formlabs) denture base materials, plate specimens were fabricated (15 mm × 15 mm × 2 mm). These base materials were bonded to Portrait IPN (Dentsply Sirona), Ivotion Dent (Ivoclar Vivadent), Lucitone Digital Value (Dentsply Sirona), and Formlabs Denture Tooth (Formlabs) tooth rods (3.5 mm × 6 mm) according to manufacturer instructions, respectively. For each material combination, 24 specimens were prepared and divided into 2 groups including control and aged. Bond strength was determined using shear bond test. Data were analyzed using two-way ANOVA followed by Tukey’s HSD test and Student’s t test (α=0.05).
RESULTS: Lucitone Digital Print (Dentsply Sirona) bonded to Lucitone Digital Value (Dentsply Sirona) and Ivotion Base (Ivoclar Vivadent) bonded to Ivotion Dent (Ivoclar Vivadent) exhibited significantly higher bond strength to high-impact pourable acrylic HIPA (Dentsply Sirona) bonded to Portrait IPN (Dentsply Sirona) and Formlabs Denture Base (Formlabs) bonded to Formlabs Denture Tooth (Formlabs) (p < 0.0001). Each paired Student’s t-test showed that thermocycling treatment decreased the shear bond strength of the Formlabs materials significantly (p < 0.0001).
CONCLUSION: The application of monomer and conditioning agents improved bond strength between denture base and denture tooth material regardless of the fabrication method. Thermocycling had an adverse effect on bond strength for all materials
Evaluation of the mechanical and physical properties of 3D-printed resin materials
Get PDFOBJECTIVES: This in vitro study aims to compare and evaluate the mechanical properties of different 3D-printed resin materials. Determine the impact of 3D printer type on the mechanical properties. Investigate the filler percentage by weight for each resin material.
MATERIALS AND METHODS: Eight resin materials were tested for flexural strength, flexural modulus, microhardness, fracture toughness, and wear resistance. Resin materials: Rodin Sculpture (RS), BEGO VarseoSmile Crown Plus (BVS), Desktop Health Flexcera Smile Ultra Plus (DHF), SprintRay Crown (SRC), SprintRay Ceramic Crown (SCC), Saremco Crowntec (SC), Myerson Trusana (MT), PacDent Ceramic Nanohybrid (PAC). 3D printer Asiga Max and Ackuretta SOL were used to print 12 specimens from each material to compare three-point flexural strength in bar-shape, biaxial flexural strength in disc-shape, fracture toughness in single edge V-notched beam, wear resistance in pin-shape. Three discs shape specimens from each material were used to compare the Vickers microhardness. The filler percentage by weight of each material is determined by Ash burning and Solvent extraction. The microstructure of a polished disc from each material was examined under a scanning electron microscope (SEM), and the elemental composition was investigated by Energy Dispersive Spectrometry (EDS). Results were analyzed using ANOVA, regression of least square means (α = 0.05), Tukey HSD test, Pearson correlation coefficient, and Student’s t-test.
RESULTS: The flexural strength test results, utilizing the three-point method, reveal significant differences among the materials tested. The highest average was recorded in SCC at 160 MPa, while the lowest was found in SRC at 84.4 MPa. The flexural modulus also exhibited significant differences, with the highest average observed in SCC, BVS, RS, SRC, DHF, SC, and MT, measuring 7.8, 6.2, 6.0, 5.8, 4.9, 4.5, and 3.0 GPa, respectively. The resin materials with the highest biaxial flexural strength were DHF 217 MPa and MT 200 MPa, with no significant distinction between them and different from the remaining materials. SCC demonstrated a notably higher average value in Vickers microhardness 44 HVN, while DHF exhibited a significantly lower value of 15.58. The Fracture toughness test presented no significant differences between DHF, MT, and SCC, with values of 2.28, 2.27, and 2.11 MPa.m0.5, respectively, exceeding the remaining materials. In the wear test, DHF and MT had a significantly higher weight loss rate of 29.25 and 27.18 mg/million cycle, respectively. In contrast, MT's height loss rate of 2.02 mm/million cycle was the only significantly higher difference from other materials. The data indicates that the printer type does not significantly affect biaxial flexural strength. At the same time, Asiga exhibited significantly higher values in three-point flexural strength, flexural modulus and hardness tests. In contrast, the SOL printer demonstrated higher values in fracture toughness than Asiga. The ash and solvent extraction methods revealed that SCC had the highest filler percentage by weight, while MT had the lowest. SEM imaging showed the existence of filler particles in all materials, with PAC containing the largest particles and MT containing the smallest. DHF was the only resin material that contained exclusively spherical shape filler particles. EDS analysis disclosed the elemental composition of each material with a higher percentage in Silica, Oxygen, Barium, Titanium, and Ytterbium.
CONCLUSION: The results demonstrate significant differences in the tested materials' flexural strength, flexural modulus, biaxial flexural strength, Vickers microhardness, fracture toughness, and wear rates. Even though there are significant differences in some of the mechanical properties of the printer type, it is small and might not have an effect clinically. A strong correlation exists between filler percentage with flexural modulus r = 0.83, biaxial flexural strength r = 0.60, microhardness r = 0.73, and wear resistance r= 0.82. There is a low correlation between filler percentage with fracture toughness r= 0.41, with no correlation with flexural strength in the three-point test. Filler particle percentage highly affects the mechanical properties of 3D printed resin materials. These findings could be valuable in selecting appropriate materials for specific applications
Mechanical and optical properties of machined, printed, and conventional dental polymers
Get PDFOBJECTIVE: This study aims to compare the flexural strength and color stability of conventional, machined, and printed dental polymers. Secondarily, the effects of aging, fatigue, coffee, distilled water, and UV light on the color stability and flexural strength of the different dental polymers will be evaluated.
MATERIALS AND METHODS: Sixty disks 14mm in diameter and 2mm in thickness were fabricated from each of the following polymers: Jet Tooth Shade (Lang Dental), ProTemp (3M-ESPE), Telio CAD Temp (Ivoclar Vivadent), Vita CAD Temp (Vita), Temporary CB (FormLab), Dentca (Dentca), and Bego VarseoSmile Crown Plus (Bego). The sixty disks from each polymer were then divided into the six following groups: no treatment, thermocycling, fatigue, thermocycling and coffee, distilled
water and finally UV Light. Prior to any treatment, the color coordinates CIE L*a*b*, were registered first. The non-treated groups were fractured using the Instron Universal Testing Machine to obtain flexural strength values.
Thermocycling consisted of placing the specimens in 30 seconds 5°C water and then 30 seconds in 55°C water for 5,000 cycles. Fatigue testing consisted of cyclic
loading the disk specimens by calculating 60% of the mean load to failure from the non-treated group and subjecting them to 50,000 cycles. The third group was placed under thermocycling for 1,500 cycles and then placed in coffee for 15 days. Another group was placed in distilled water for 15 days. Finally, the UV light treatment consisted of exposing the disk specimens to UV light for ten hours over the course of five days. After treatment, the color coordinates were recorded again and fractured using the Instron Universal Testing Machine. The data was analyzed
for any statistically significant differences using ANOVA with a<0.05.
RESULTS: The flexural strength values were highest for Telio CAD Temp, that was affected only by UV light via a statistical analysis. ProTemp was second highest followed by Bego VarseoSmile Crown Plus, Dentca, Temporary CB, Vita CAD Temp and finally Jet Tooth Shade. Color differences were highest for Dentca followed by Jet Tooth Shade, ProTemp, Telio CAD Temp, Temporary CB and finally Vita CAD Temp. UV light and thermocycling/ coffee had the highest impact.
CONCLUSION: Telio CAD Temp had the highest overall flexural strength and was resistant to all post fabrication treatments except for UV light. ProTemp had the second highest overall flexural strength but was susceptible to multiple post fabrication treatments like distilled water, fatigue, and aging. The printed specimens had flexural strength values lower in the middle range of all tested materials. In terms of treatment, UV light and coffee/thermocycling had the biggest impact on the overall color stability values. Powder and Liquid based PMMA had the lowest overall flexural strengths
Effect of the GentleWave System on dentin microhardness and sealer penetration: an in vitro study
Get PDFThis study investigates the impact of the GentleWave (GW) System on dentin hardness and sealer penetration in root canal treatment, aiming to assess its potential advantages over conventional techniques. Conventional instrumentation can alter root canal anatomy, necessitating irrigation methods that minimize mechanical impact. The GW System, utilizing multisonic energy to activate irrigation solutions, has been lauded for its advantages in bacterial reduction, superior debris removal, and minimal dentin erosion.
Samples (n=10) were randomly assigned to three groups: control (Group C), traditional root canal treatment (Group T), and GW with minimal instrumentation (Group G). Following irrigation and obturation with AH Plus sealer and gutta percha using cold lateral compaction, transverse slices were obtained at 2-, 5-, and 8-mm distances from the apex. Assessment methods included microhardness testing and scanning electron microscopy (SEM).
Vickers Test results revealed significant differences in hardness values, with Group C exhibiting the highest and Group T the lowest values. In terms of sealer penetration, Group G demonstrated significantly higher penetration than Group T overall (p = 0.004). When considering slice locations, no significant differences were observed in the coronal sections. However, in the middle and apical thirds, Group T exhibited significantly lower sealer penetration levels (p = 0.02).
These findings suggest that the GW System maintains dentin hardness while promoting enhanced sealer penetration compared to traditional root canal treatment methods. By preserving dentin integrity and facilitating deeper sealer penetration, the GW System may contribute to improved treatment outcomes and long-term success rates in root canal therapy. These results support the adoption of innovative irrigation techniques, such as the GW System, in clinical practice to optimize patient care and treatment efficacy
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