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Journal of Prosthodontics : Official... Dec 2021To assess the feasibility of manufacturing a dental crown with internal color gradient and graded structure design using additive manufacturing technology, a mandibular...
To assess the feasibility of manufacturing a dental crown with internal color gradient and graded structure design using additive manufacturing technology, a mandibular first molar was prepared and a monolayer dental crown with 1.5 mm uniform thickness was designed in a dental software (STL ). The monolayer crown design was sliced into multiple layers of 0.1 mm thickness and a design for a multilayer crown was obtained (STL ). A multilayer crown was manufactured with gradient color and graded structure using a material jetting printer. Different materials with different colors and properties were used and mixed in different ratios during manufacturing to achieve the prospected design. The feasibility of manufacturing such a crown was reported. This report confirms that multilayer dental crowns with internal gradient color and graded structure are possible when using a multimaterial jetting printer.
Topics: Color; Computer-Aided Design; Crowns; Dental Porcelain; Dental Prosthesis Design; Molar
PubMed: 34297467
DOI: 10.1111/jopr.13410 -
Journal of Esthetic and Restorative... Sep 2021To evaluate the optical, chemical, and mechanical properties of feldspathic porcelain after handling with different instrument materials.
OBJECTIVE
To evaluate the optical, chemical, and mechanical properties of feldspathic porcelain after handling with different instrument materials.
MATERIAL AND METHODS
Feldspathic porcelain was manipulated with different spatula compositions: metal spatula (MS), plastic spatula (PS), and glass spatula (GS) for the fabrication of 30 (n = 10) disks. Contrast ratio (CR), translucency parameter (TP), and surface Knoop microhardness (KHN) were measured. The color change (ΔE ) was evaluated using the CIEDE2000 system. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used for surface analysis. Data were analyzed using one-way ANOVA and Tukey test (P < 0.05).
RESULTS
All groups presented different morphological surfaces with higher presence of Al on the MS. PS group presented lower Al, Si, K than MS, and GS. Higher CR was observed for PS (0.734; P < 0.043), followed by MS (0.696; P < 0.043) and GS (0.65; P < 0.011). The highest TP (13.06) and KHN (386.27) were presented by GS (P < 0.001). MS and PS presented similar KHN results. The higher ΔE were found for plastic/metal comparison. Also, the L values for the MS group (67.49) were lower than the other groups.
CONCLUSION
The use of metal spatula promoted higher color alteration during feldspathic porcelain manipulation than did the other materials. Handling with glass instrument promoted higher microhardness than other spatula materials.
CLINICAL SIGNIFICANCE
The effect of the material used for ceramic handling on feldspathic porcelain properties is often ignored. This study shows that the handling spatula material must be carefully chosen to avoid inadvertent changes to the feldspathic porcelain restoration.
Topics: Ceramics; Dental Porcelain; Materials Testing; Microscopy, Electron, Scanning; Surface Properties
PubMed: 33045124
DOI: 10.1111/jerd.12665 -
Clinical Oral Investigations Mar 2022This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the...
OBJECTIVES
This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of maxillary molars with 2-mm deep proximal margins restored with MOD inlay.
METHODS
Fifty-two extracted human third molars were randomly assigned into four groups (n = 13): C; DME + C; R; and DME + R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step = 50 N; 20 Hz; initial load = 200 N). Fatigue failure loads and the number of cycles were analyzed with 2-way ANOVA and Tukey's test (p < 0.05) and Kaplan-Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, and homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion.
RESULTS
For fatigue, there was no difference for DME factor (p > 0.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p < 0.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups.
CONCLUSIONS
DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive.
CLINICAL SIGNIFICANCE
DME does not impair mechanical behavior. Resin composite inlays failed at higher loads but with a more aggressive failure mode.
Topics: Composite Resins; Dental Porcelain; Dental Stress Analysis; Humans; Inlays; Materials Testing; Molar; Stress, Mechanical
PubMed: 34643807
DOI: 10.1007/s00784-021-04219-6 -
Dental Materials Journal Jan 2023This review describes the development of ultra-high translucent zirconia (referred to as UHTZ) using new manufacturing technology and its characterization results. The... (Review)
Review
This review describes the development of ultra-high translucent zirconia (referred to as UHTZ) using new manufacturing technology and its characterization results. The development of UHTZ was primarily due to the adoption of two basic manufacturing technologies, "Cyclic CIP" and "Plus Y Technology". This manufacturing technology could provide stable processing characteristics, which improves chipping resistance during milling. Furthermore, the enlargement factor (processing coefficient) for UHTZ is smaller than those for conventional products. In general, the higher the light transmittance, the lower the flexural strength. Despite its extremely high translucency, the most significant feature of UTHZ is that its flexural strength is comparable to that of 5Y. Furthermore, UHTZ has higher chemical durability and uniform microstructure, which results in less wear on the opposing teeth and superior discoloration resistance. Therefore, UHTZ is a new option for inlay, onlay, and laminate veneer applications, where lithium disilicate glass ceramics has been widely used.
Topics: Materials Testing; Dental Porcelain; Ceramics; Zirconium; Flexural Strength; Surface Properties
PubMed: 36631076
DOI: 10.4012/dmj.2022-243 -
The Journal of Prosthetic Dentistry Jun 2022The influence of different glaze firing protocols and cooling on the behavior of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is unclear.
STATEMENT OF PROBLEM
The influence of different glaze firing protocols and cooling on the behavior of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is unclear.
PURPOSE
The purpose of this in vitro study was to investigate the influence of different glaze firing protocols on the abrasion resistance, surface roughness, microhardness, and brittleness index of CAD-CAM ceramics.
MATERIAL AND METHODS
Rectangular specimens of IPS e.max CAD (MAX), IPS Empress CAD (PRE), and CEREC Blocs (CER) were obtained and divided into 5 groups according to the glaze firing protocol (n=8): control (CO), 1 conventional glaze firing (GF), 2 conventional glaze firings (GF), 1 extended glaze firing (EG), and 2 extended glaze firings (EG). The coefficient of friction (μ) was determined with the pin-on-disk test, and specimens were analyzed with an optical interferometer to calculate volume loss and roughness. Vickers microhardness and the brittleness index were obtained with a microdurometer. Microhardness data were evaluated by 2-way ANOVA and the Sidak tests (α=.05). Data from other tests were assessed with nonparametric ANOVA and Bonferroni tests (α=.05).
RESULTS
Groups GF, EG, and EG of MAX and PRE and all groups of CER presented higher levels of coefficient of friction. Groups EG and EG of MAX and CER showed high volume loss and surface roughness. Groups EG and EG of MAX and PRE showed lower hardness, as did all groups of CER. MAX-CO and groups GF and EG of PRE showed a lower brittleness index (P<.05), while CER groups showed no significant differences (P>.05).
CONCLUSIONS
Ceramic specimens with conventional glaze firing presented less surface wear than those with extended glaze firing. The number of firings did not have a statistically significant influence.
Topics: Ceramics; Computer-Aided Design; Dental Porcelain; Materials Testing; Surface Properties
PubMed: 35469648
DOI: 10.1016/j.prosdent.2022.03.009 -
Dental Materials : Official Publication... Jan 2023To seek dentine analogue materials in combined experimental, analytical, and numerical approaches on the mechanical properties and fatigue behaviours that could replace...
OBJECTIVE
To seek dentine analogue materials in combined experimental, analytical, and numerical approaches on the mechanical properties and fatigue behaviours that could replace human dentine in a crown fatigue laboratory test.
METHODS
A woven glass fibre-filled epoxy (NEMA grade G10; G10) and a glass fibre-reinforced polyamide-nylon (30% glass fibre reinforced polyamide-nylon 6,6; RPN) were investigated and compared with human dentine (HD). Flexural strength and elastic modulus (n = 10) were tested on beam-shaped specimens via three-point bending, while indentation hardness (n = 3) was tested after fracture. Abutment substrates of G10, RPN and HD were prepared and resin-bonded with monolithic lithium disilicate crowns (n = 10), then subjected to wet cyclic loading in a step-stress manner (500 N initial load, 100 N step size, 100,000 cycles per step, 20 Hz frequency). Data were statistically analysed using Kruskal-Wallis one-way ANOVA followed by post-hoc comparisons (α = 0.05). Survival probability estimation was performed by Mantel-Cox Log-Rank test with 95% confidence intervals. The fatigue failure load (FFL) and the number of cycles until failure (NCF) were evaluated with Weibull statistics. Finite Element Models of the fatigue test were established for stress distribution analysis and lifetime prediction. Fractographic observations were qualitatively analysed.
RESULTS
The flexural strength of HD (164.27 ± 14.24 MPa), G10 (116.48 ± 5.93 MPa), and RPN (86.73 ± 3.56 MPa) were significantly different (p < 0.001), while no significant difference was observed in their flexural moduli (p = 0.377) and the indentation hardness between HD and RPN (p = 0.749). The wet cyclic fatigue test revealed comparable mean FFL and NCF of G10 and RPN to HD (p = 0.237 and 0.294, respectively) and similar survival probabilities for the three groups (p = 0.055). However, RPN promotes higher stability and lower deviation of fatigue test results than G10 in Weibull analysis and FEA.
SIGNIFICANCE
Even though dentine analogue materials might exhibit similar elastic properties and fatigue performance to human dentine, different reliabilities of fatigue on crown-dentine analogues were shown. RPN seems to be a better substrate that could provide higher reliability and predictability of laboratory study results.
Topics: Humans; Ceramics; Reproducibility of Results; Nylons; Materials Testing; Surface Properties; Dental Stress Analysis; Dental Porcelain; Crowns; Dentin; Computer-Aided Design
PubMed: 36503862
DOI: 10.1016/j.dental.2022.11.020 -
Operative Dentistry May 2021This study aimed to characterize the surface topography, effect of polishing on surface roughness, residual stresses, and hardness in two glass-ceramic veneers....
This study aimed to characterize the surface topography, effect of polishing on surface roughness, residual stresses, and hardness in two glass-ceramic veneers. Fifty-two (52) upper incisors were collected, prepared, and scanned for ceramic veneers. Half of the teeth were restored with veneers made up of feldspathic ceramic (FE), and the other half with zirconia-reinforced lithium silicate ceramic (SZ). All the veneers were designed and milled using a CAD/CAM system and later cemented following the manufacturer's guideline. An optical microscope analyzed the topography of the specimens before and after polishing. The surface roughness was measured using the roughness meter (n=12) and the topographical analysis was carried out using an atomic force microscope (n=6). The residual stresses and Vickers' hardness were evaluated by the indentation method in a micro-hardness indenter (n=6). The surface roughness was analyzed using a three-way analysis of variance (ANOVA) followed by a post hoc Tukey test. The Student t-test was used to compare the residual stresses and hardness between the two ceramics. The topographical analysis revealed that both glass-ceramic veneers had similar percentages of specimens with cracks, before (34.6%) and after (42.3%) polishing. The surface roughness decreased after polishing (p<0.001), and the polishing smoothed out the surface of the veneers. The zirconia-reinforced lithium silicate veneer had a lower roughness as compared to the feldspathic one after polishing, while the residual stresses (p=0.722) and hardness (p=0.782) were statistically similar for both ceramic veneers.
Topics: Ceramics; Computer-Aided Design; Dental Porcelain; Humans; Materials Testing; Surface Properties
PubMed: 34251455
DOI: 10.2341/20-067-L -
Journal of Esthetic and Restorative... Sep 2023The aim of this study was to evaluate staining layer behavior applied to high-translucency zirconia (YZHT), feldspathic ceramics (FD), and zirconia-reinforced lithium...
PURPOSE
The aim of this study was to evaluate staining layer behavior applied to high-translucency zirconia (YZHT), feldspathic ceramics (FD), and zirconia-reinforced lithium silicate (ZLS) surfaces against different antagonists.
METHODS AND MATERIALS
Monolithic ceramic discs (n = 120) (ø 12 mm; thickness, 1.2 mm; ISO 6872) were obtained, 30 from YZHT and FD, and 60 from ZLS CAD/CAM blocks (staining layer applied before or after the crystallization procedure). The specimens were divided into 12 subgroups (n = 10) according to the antagonists: steatite, polymer-infiltrated ceramic, or zirconia. Mechanical cycling (1.5 × 10 cycles; 15 N; horizontal displacement, 6 mm; 1.7 Hz) and flexural strength tests (1 mm/min-1000 kg cell) were performed. The differences between final and initial roughnesses (Ra, Rz, and Rsm), the mass loss, and the flexural strength data were individually analyzed by two-way ANOVA and Tukey's test (α = 0.05).
RESULTS
The roughnesses of all ceramics did not present a statistically significant difference before wear simulation: Ra (p = 0.3348), Rz (p = 0.5590), and Rsm (p = 0.5330). After the wear simulation, the Ra parameter was not affected by an interaction between ceramic and antagonist (p = 0.595). The Rz and Rsm parameters were affected only by the antagonist pistons (both, p = 0.000). The ceramics used in this study showed statistically significant differences in mass loss after the wear test (p < 0.0001). The additional firing (2 steps) of the ZLS2 led to a higher lost mass quantity.
CONCLUSION
All ceramics presented similar initial roughnesses and similar roughnesses after the wear simulation. The zirconia antagonist showed better performance against ceramics with high crystalline content.
CLINICAL SIGNIFICANCE
It is clear that restorative materials must be carefully selected by dental practitioners according to indications, properties, and antagonists. The steatite antagonist, that is, an enamel analog, showed better performance against vitreous ceramics, while the zirconia antagonist showed better performance against ceramics with high crystalline content. Wear affects the surface roughnesses of the ceramics. Additional firing for the staining of the zirconia-reinforced lithium silicate ceramic led to a greater loss of mass.
Topics: Humans; Dental Porcelain; Lithium; Dentists; Materials Testing; Professional Role; Ceramics; Zirconium; Silicates; Surface Properties; Computer-Aided Design
PubMed: 37203879
DOI: 10.1111/jerd.13067 -
Clinical Oral Investigations Nov 2022To evaluate the wear resistance and abrasiveness of monolithic CAD/CAM ceramics.
OBJECTIVES
To evaluate the wear resistance and abrasiveness of monolithic CAD/CAM ceramics.
MATERIALS AND METHODS
Rectangular-shaped specimens (12 mm × 6.5 mm × 1.5 mm) were sectioned from the following CAD/CAM blocks (n = 10); partially crystallized lithium disilicate (PLD), experimental fully crystallized lithium disilicate (FLD), zirconia-reinforced lithium silicate (ZLS), super-translucent monolithic zirconia (SMZ), and ultra-translucent monolithic zirconia (UMZ). Silicon carbide papers were used to mechanically flatten and polish the surfaces. PLD specimens were subjected to a combined crystallization/glazing firing cycle. Ceramic specimens were mounted to the wear device and tested for 200,000 cycles against human premolars at 20 N force and 2 mm sliding distance. Artificial saliva was used as a lubricant. The teeth were scanned using micro-CT before and after the wear test and the generated models were overlapped to determine the volumetric tooth loss. Before and after the test, specimens' weights and surface roughness (R) values were measured, and the differences were calculated. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were utilized for microstructural and chemical analysis. Statistical analysis was performed using one-way ANOVA or an equivalent test for non-parametric results. Significance level was set at P ≤ 0.05.
RESULTS
The type of ceramic material affected the ceramic and antagonist wear rates (P < 0.001). PLD and ZLS had the highest ceramic and antagonist wear, whereas UMZ and SMZ demonstrated the lowest wear values. The FLD group showed comparable antagonist wear and significantly less ceramic wear than PLD and ZLS.
CONCLUSIONS
Monolithic zirconia demonstrated the best wear resistance and least abrasiveness to the antagonist. The experimental lithium disilicate was more wear-resistant than other glass-ceramic groups.
CLINICAL RELEVANCE
Monolithic zirconia is wear-resistant and gentle on the antagonist. In contrast, glass-ceramics are more abrasive to enamel.
Topics: Humans; Mastication; Materials Testing; Surface Properties; Dental Porcelain; Zirconium; Ceramics; Computer-Aided Design
PubMed: 35819543
DOI: 10.1007/s00784-022-04611-w -
The Journal of Prosthetic Dentistry Jan 2022Data concerning the mechanical properties of the newly developed lithium disilicate ceramic HS10PC are lacking.
STATEMENT OF PROBLEM
Data concerning the mechanical properties of the newly developed lithium disilicate ceramic HS10PC are lacking.
PURPOSE
The purpose of this in vitro study was to investigate the flexural strength (FS), Martens hardness (HM), indentation modulus (E), fracture load (FL), and wear resistance (WR) of HS10PC compared with those of the established glass-ceramics IPS e.max Press and IPS Empress Esthetic.
MATERIAL AND METHODS
Four pressable glass-ceramics were examined: HS10PC (estetic ceram ag), IPS e.max Press low translucency (LT) and high translucency (HT; Ivoclar Vivadent AG), and IPS Empress Esthetic (ES; Ivoclar Vivadent AG). For each material, a total of 85 specimens were fabricated. Specimens were subdivided into 4 groups for FS (n=30), HM, E (n=10), and FL measurement according to the Voss test after artificial aging in an autoclave (n=15), artificial aging in a mastication simulator (n=15), and no artificial aging (n=15). In addition, WR (n=10) was measured after 240 000, 600 000, and 1 200 000 masticatory cycles. Data were statistically analyzed using the global univariate ANOVA, the Scheffé post hoc and paired t tests, and Weibull distribution (α=.05).
RESULTS
HT showed the highest FS, while ES presented the lowest FS of all groups (P<.001). ES showed lower values for HM (P<.001), E (P<.001), and FL for specimens treated in an autoclave and mastication simulator (P<.001) compared with all other groups. An increase in the wear of the ceramic and enamel antagonist between 240 000 and 1 200 000 masticatory cycles was observed for all groups (P<.001). After 1 200 000 masticatory cycles, HS10PC presented less wear of the ceramic than the other 3 materials (P=.003).
CONCLUSIONS
The newly developed lithium disilicate ceramic HS10PC showed comparable results with the established IPS e.max Press for FS, HM, E, FL, and WR. Lithium disilicate ceramics presented higher mechanical results than the leucite-reinforced ES, with all the ceramics showing similar results for the WR of the enamel antagonist.
Topics: Ceramics; Dental Porcelain; Esthetics, Dental; Flexural Strength; Materials Testing; Surface Properties
PubMed: 33168175
DOI: 10.1016/j.prosdent.2020.06.027