共查询到20条相似文献，搜索用时 31 毫秒
1.
Jovana Marjanovic Djordje N. Veljovic Jovana N. Stasic Tatjana Savic-Stankovic Branka Trifkovic Vesna Miletic 《Dental materials》2018,34(5):737-745
Objectives
To evaluate optical properties (color and translucency) of ‘sandwich’ restorations of resin-based composites and esthetically unfavorable dentin restoratives.Methods
Cylindrical ‘dentin’ specimens (8 mm in diameter and 2 mm thick, N = 5/group) were prepared using EverX Posterior (GC), Biodentine (Septodont), experimental hydroxyapatite (HAP) or conventional composites (Gradia Direct Posterior, GC; Filtek Z250 and Filtek Z500, 3M ESPE). Capping ‘enamel’ layers were prepared using composites (Gradia Direct Posterior, Filtek Z250 or Z550) of A1 or A3 shade and the following thickness: 0.6, 1 or 2 mm. Color (ΔE) and translucency parameter (TP) were determined using a spectrophotometer (VITA Easyshade Advance 4.0, VITA Zahnfabrik). Data were statistically analyzed using analysis of variance with Tukey’s post-hoc tests (α = 0.05).Results
TP was greatly affected by layer thickness, whilst ΔE depended on shade and layer thickness of the capping composite. HAP and Biodentine showed significantly lower TP and higher ΔE (deviation from ‘ideal white’) than composites (p < 0.05). Greater TP was seen in EverX_composite groups than in corresponding control groups of the same shade and thickness. TP of composites combined with Biodentine or HAP was below 2, lower than the corresponding control groups (p < 0.05). Within-group differences of ΔE were greatest in HAP_composite groups. EverX_Gradia and EverX_FiltekZ250 combinations showed the most comparable ΔE with the control groups.Significance
A 2 mm thick layer of composite covering dentin restoratives with unfavorable esthetics is recommended for a final ‘sandwich’ restoration that is esthetically comparable to a conventional, mono-composite control restoration. 相似文献2.
Farahnaz Nejatidanesh Ghazal Savabi Mehrak Amjadi Mahsa Abbasi Omid Savabi 《Journal of prosthodontic research》2018,62(4):462-467
Purpose
The aim of this clinical study was to compare the survival, modified California Dental Association (CDA) criteria, and periodontal parameters of laminate veneers made with Empress CAD and emax CAD over 60 months.Methods
One hundred and ninety seven ceramic laminate veneers were placed in 71 patients in a private practice. The restorations were made using CEREC AC Bluecam with Empress CAD and emax CAD blocks. Modified CDA guidelines were used to evaluate clinical performance of the restorations. Gingival and plaque indices, probing pocket depth, and bleeding on probing were also recorded. Patient’s satisfaction was assessed using visual analogue scale. Kaplan–Meier and Log rank test were used to analyze survival probability and success rate of the restorations. CDA rating of Empress CAD and emax CAD was compared with Log rank test (α = 0.05).Results
The survival rates of ceramic Empress CAD and emax CAD laminate veneers were 97.8 % and 100 % respectively (p = 0.13). The success rate of these veneers was 92.4 % for Empress CAD and 100 % for emax CAD (p < 0.05). Two Empress CAD laminate veneer failed because of fracture. Other restorations had very good or good CDA scores after 5 years. The periodontal parameters were not significantly different between first and fifth years except plaque index. The mean score of patients’ satisfaction was 95.5 ± 8.4.Conclusions
Chair-side computer-aided design/computer-aided manufacturing ceramic laminate veneers were clinically successful restorations with mean survival rate of 99.0 % and success rate of 96.4 % after 5 years. 相似文献3.
Doaa Taha Sebastian Spintzyk Christine Schille Ahmed Sabet Marwa Wahsh Tarek Salah Jürgen Geis-Gerstorfer 《Journal of prosthodontic research》2018,62(3):293-297
Purpose
The purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations.Methods
Root canal treated mandibular molars were divided into four groups (n = 8) and were prepared to receive Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) fabricated polymer infiltrated ceramic endocrowns (ENAMIC blocks). Group B2 represents teeth prepared with a butt joint design receiving endocrowns with 2 mm occlusal thickness and the same for group B3.5 but with 3.5 mm occlusal thickness. Group S2 represents teeth prepared with 1 mm shoulder finish line receiving endocrowns with 2 mm occlusal thickness and the same for group S3.5 but with 3.5 mm occlusal thickness. After cementation and thermal aging, fracture resistance test was performed and failure modes were observed.Results
Group S3.5 showed the highest mean fracture load value (1.27 ± 0.31 kN). Endocrowns with shoulder finish line had significantly higher mean fracture resistance values than endocrowns with butt margin (p < 0.05). However, the results were not statistically significant regarding the restoration thickness. Evaluation of the fracture modes revealed no statistically significant difference between the modes of failure of tested groups.Conclusions
For the restoration of endodontically treated teeth, adding a short axial wall and shoulder finish line can increase the fracture resistance. However, further investigations, especially the fatigue behavior, are needed to ensure this effect applies with small increases of restoration thickness. 相似文献4.
Camila da Silva Rodrigues Luís Felipe Guilardi Andressa Cargnelutti Follak Catina Prochnow Liliana Gressler May Luiz Felipe Valandro 《Dental materials》2018,34(9):e225-e235
Objective
To investigate the effect of intaglio surface adjustment of simplified lithium disilicate ceramic restorations adhesively cemented to a dentin-like material on its fatigue behavior.Methods
Ceramic discs (IPS e.max CAD) were prepared and an in-Lab simulation of machining roughness was performed by grinding with SiC paper (#60). Ceramic discs were divided into 4 groups according to the internal adjustment of the cementation surface: no adjustments (CTRL); adjustment with a medium (M), fine (F), or extra fine (FF) diamond bur. Dentin-like material discs were also produced. Ceramic disc intaglio surfaces were etched (5% hydrofluoric acid; 20 s) and received a silane coating. Dentin-like material discs were etched (10% hydrofluoric acid; 1 min) and received a primer coating. Pairs of ceramic/dentin-like material were adhesively cemented (Multilink Automix), and fatigue failure load tests were performed using the Staircase approach (250,000 cycles; 20 Hz). Roughness, topographic and fractographic analyses were performed. Statistical analyses were carried out through ANOVA tests.Results
All ground groups (M = 521.3 N; F = 536.9 N; FF = 676.2 N) presented lower fatigue failure load values than the control (1241.6 N).?M diamond bur created a rougher surface than F (Ra and Rz parameters). However, FF was similar to F and M for Ra, and similar to F for Rz.Significance
Bur adjustments on the intaglio surface of simplified lithium disilicate ceramic restorations greatly decreased the fatigue failure load even using an extra-fine diamond bur. Care should be taken when internal adjustments are needed. 相似文献5.
Ryota Okada Masaki Asakura Akihiro Ando Hirokazu Kumano Seiji Ban Tatsushi Kawai Jun Takebe 《Journal of prosthodontic research》2018,62(3):287-292
Purpose
The purpose of this study was to ascertain whether computer aided design/computer aided manufacturing (CAD/CAM) composite resin crowns have sufficient strength to withstand the bite force of the molar teeth. The null hypothesis was that the fracture strength of CAD/CAM composite resin crowns is lower than the average maximum bite force of the molar tooth.Methods
The crowns, which shape is the right maxillary first molar, were fabricated using four CAD/CAM blanks made of composite resins (Block HC: HC, KZR-CAD HR: HR, KZR-CAD HR2: HR2, Avencia Block: AVE) and one CAD/CAM blank made of lithium disilicate glass-ceramic (IPS e.max CAD: IPS), which was used as a control. Fracture strength of fabricated crowns bonded to metal abutment and biaxial flexural strength of the materials were evaluated.Results
The results of fracture strength test and biaxial flexural strength test showed different tendencies. The fracture strength of CAD/CAM composite resin crowns except HC ranged from 3.3 kN to 3.9 kN, and was similar to that of IPS (3.3 kN). In contrast, biaxial flexural strength of CAD/CAM composite resins ranged from 175 MPa to 247 MPa, and was significantly lower than that of IPS (360 MPa).Conclusions
All CAD/CAM composite resin crowns studied presented about 3–4 times higher fracture strength than the average maximum bite force of the molar tooth (700–900 N), which result leads to the conclusion that CAD/CAM composite resin crowns would have sufficient strength to withstand the bite force of the molar teeth. 相似文献6.
Light irradiance through novel CAD–CAM block materials and degree of conversion of composite cements
Diogo Pedrollo Lise Annelies Van Ende Jan De Munck Kumiko Yoshihara Noriyuki Nagaoka Luiz Clovis Cardoso Vieira Bart Van Meerbeek 《Dental materials》2018,34(2):296-305
Objective
To assess light irradiance (LI) delivered by two light-curing units (LCU’s) and to measure the degree of conversion (DC) of three composite cements, when cured through different thicknesses of two novel CAD–CAM block materials.Methods
100-μm-thick films of a dual-curable composite cement (G-CEM LinkAce, GC), a light-curable flowable resin-based composite (RBC) (G-ænial Universal Flo, GC) and a micro-hybrid RBC (G-ænial Posterior, GC) were investigated as luting agents. Two ‘polymer–ceramic’ CAD–CAM blocks (Cerasmart, GC; Enamic, Vita Zahnfabrik) were sectioned in slabs with different thicknesses (1, 3 and 5 mm). LI at the bottom of the specimens was measured using a calibrated spectrometer, while being light-cured through the CAD–CAM block slabs for 40 s with a low- (±500 mW/cm2) or high- (±1,600 mW/cm2) irradiance LCU (n = 5). After light-curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 min, 10 min, 1 h and 24 h. LI data were statistically analyzed by Kruskal–Wallis followed by post-hoc comparisons, while a linear mixed-effect model was applied for the DC analysis. In addition, the CAD–CAM blocks ultrastructure was characterized upon argon-ion slicing using scanning transmission electron microscopy (STEM). Finally, light transmission (LT) through each CAD–CAM block material was assessed using a spectrophotometer.Results
Curing-light attenuation and DC were significantly influenced by thickness and type of the overlying material. LCU only had a significant effect on DC of the micro-hybrid RBC. DC significantly increased over time for all composite cements. CAD–CAM block structural analysis revealed a relatively small and homogenous filler configuration (mean filler size of 0.2–0.5 μm) for Cerasmart, while Enamic contained ceramic grains varying in shape and size (1–10 μm), which were interconnected by the polymer-based network. LT was much higher at a wavelength range of 300–800 nm for Cerasmart than for Enamic.Significance
Light-curable composite cements can be cured through a restoration up to 2.7-mm thickness, depending on the kind of CAD–CAM material. A high-irradiance LCU only has a limited effect on the maximum thickness of the polymer–ceramic CAD–CAM material that can be cured through. 相似文献7.
Katharina Debye Taskin Tuna Shaza Bishti Stefan Wolfart 《Journal of prosthodontic research》2018,62(4):416-421
Purpose
In implant dentistry, temporary restorations (TR) might often be required for up to one year. The aim of this in vitro study was to evaluate the long-time performance of four-unit TRs in the posterior region based on different materials and reinforcement methods.Methods
One hundred and forty four TRs were manufactured on 16 models simulating an oral situation of two missing posterior teeth. With a computer-aided-design/computer-aided-manufacturing (CAD/CAM) workflow, a TR was fabricated (CAD; Telio CAD), which served as a template for other subgroups. With a vacuum-formed template, unreinforced and reinforced TRs [glass fibres (g; EverStick); polyethylenefibres (p; Ribbond original) and TRs with increased connector area (c; 27.5–35 mm2)] were manufactured. Two different composite materials were used (C1: Luxatemp, C2: Protemp). Altogether, 16 subgroups with 8 specimens each were tested. After temporary luting (Temp Bond NE) and artificial-aging [1600 thermo-cycles (5–55 °C), 240,000 chewing-cycles (50 N)], all specimens were tested until fracture in a universal testing machine.Results
After artificial aging, mean fracture loads (N) were: (C1)201.2 ± 109.7, (C1c)1033.0 ± 173.1, (C1p)90.0 ± 40.0, (C1g)75.9 ± 25.9, (C2)108.6 ± 58.6, (C2c)1363.3 ± 148.6, (C2p)104.7 ± 54.7, (C2g)50.0 ± 0.0 and (CAD)232.5 ± 19.1. The one-factor ANOVA analysis showed significant differences for the factors temporary material (p < 0.047), reinforcement (p < 0.0001) and artificial-aging (p < 0.0001).Conclusions
The study indicated that both CAD/CAM TRs and TRs with increased connector areas are suitable for long-term use of one year. No enhancement of fracture load was observed for fibre-reinforced TRs except for the fact that fractured TRs were not totally separated. 相似文献8.
Paula Fernanda Damasceno Silva Lais Rani Sales Oliveira Stella Sueli Lourenço Braga Cácia Signori Steve R. Armstrong Carlos José Soares Maximiliano Sérgio Cenci André Luis Faria-e-Silva 《Dental materials》2018,34(9):1289-1298
Objectives
This study aimed to develop a method to induce carious lesions in the pulpal floor dentin of a class II cavity preparation, and to determine the effects of this carious lesion on the biomechanical behavior of the dental composite restoration.Methods
The pulpal floor dentin of class I cavities in sound third molars were demineralised with acetic acid for 35 days followed by a 7-day exposure to pooled human saliva biofilm and demineralization was verified by micro-CT. Subsequently, the proximal walls were removed forming a class II cavity and the caries lesion was left intact or was completely removed prior to restoration with a bulk-fill dental composite (n = 10). Cuspal deflection was assessed by strain-gauge and micro-CT imaging. The presence of enamel cracks was assessed by transillumination before and after restoration, and again after 1,200,000 cycles of mechanical fatigue in a chewing simulator. Finally, resistance to fracture by axial compressive loading and failure mode was determined. Data were analyzed by 2-way repeated measures ANOVA, Fisher’s exact test, and t-test (α = 0.05).Results
The presence of carious lesions had no significant effect upon cuspal deflection, formation of enamel cracks, and fracture strength of the dental composite restorations. The restorative procedure increased the number of enamel cracks, which was not affected by mechanical cycling.Significance
Maintaining carious lesions does not affect the biomechanical behavior of class II restorations performed with bulk-fill dental composite. 相似文献9.
Michael Wendler Renan Belli Anselm Petschelt Daniel Mevec Walter Harrer Tanja Lube Robert Danzer Ulrich Lohbauer 《Dental materials》2017,33(1):99-109
Objective
Strength is one of the preferred parameters used in dentistry for determining clinical indication of dental restoratives. However, small dimensions of CAD/CAM blocks limit reliable measurements with standardized uniaxial bending tests. The objective of this study was to introduce the ball-on-three-ball (B3B) biaxial strength test for dental for small CAD/CAM block in the context of the size effect on strength predicted by the Weibull theory.Methods
Eight representative chairside CAD/CAM materials ranging from polycrystalline zirconia (e.max ZirCAD, Ivoclar-Vivadent), reinforced glasses (Vitablocs Mark II, VITA; Empress CAD, Ivoclar-Vivadent) and glass-ceramics (e.max CAD, Ivoclar-Vivadent; Suprinity, VITA; Celtra Duo, Dentsply) to hybrid materials (Enamic, VITA; Lava Ultimate, 3M ESPE) have been selected. Specimens were prepared with highly polished surfaces in rectangular plate (12 × 12 × 1.2 mm3) or round disc (Ø = 12 mm, thickness = 1.2 mm) geometries. Specimens were tested using the B3B assembly and the biaxial strength was determined using calculations derived from finite element analyses of the respective stress fields. Size effects on strength were determined based on results from 4-point-bending specimens.Results
A good agreement was found between the biaxial strength results for the different geometries (plates vs. discs) using the B3B test. Strength values ranged from 110.9 MPa (Vitablocs Mark II) to 1303.21 MPa (e.max ZirCAD). The strength dependency on specimen size was demonstrated through the calculated effective volume/surface.Significance
The B3B test has shown to be a reliable and simple method for determining the biaxial strength restorative materials supplied as small CAD/CAM blocks. A flexible solution was made available for the B3B test in the rectangular plate geometry. 相似文献10.
Satoshi Yamaguchi Renshirou Kani Kazuma Kawakami Manami Tsuji Sayuri Inoue Chunwoo Lee Wakako Kiba Satoshi Imazato 《Dental materials》2018,34(10):1578-1584
Objective
The aim of this study was to evaluate long-term fatigue behavior using an in vitro step-stress accelerated life test (SSALT), and to determine the crack initiation point using in silico finite element analysis for computer-aided designed and manufactured (CAD/CAM) molar crowns fabricated from three commercial CAD/CAM resin composite blocks: Cerasmart (CS; GC, Tokyo, Japan), Katana Avencia Block (KA; Kuraray Noritake Dental, Niigata, Japan), and Shofu Block HC (HC; Shofu, Kyoto, Japan).Methods
Fifty-one mandibular first molar crowns luted on a resin core die were embedded in acrylic resin and covered with a polyvinyl chloride tube. Single compressive tests were performed for five crowns. SSALT was conducted for 36 crowns using three profiles and reliabilities at 120,000 cycles, and a Weibull analysis was conducted. The maximum principal strain of each CAD/CAM resin composite crown model was analyzed by three-dimensional finite element analysis.Results
Fracture loads of CS and KA (3784 ± 144 N and 3915 ± 313 N) were significantly greater than that of HC (2767 ± 227 N) (p < 0.05). Fracture probabilities at 120,000 cycles were 24.6% (CS), 13.7% (KA), and 14.0% (HC). Maximum principal strain was observed around the mesiolingual cusps of CS and KA and the distobuccal cusp of HC.Significance
CAD/CAM resin composite molar crowns containing nano-fillers with a higher fraction of resin matrix exhibited higher fracture loads and greater longevity, suggesting that these crowns could be used as an alternative to ceramic crowns in terms of fatigue behavior. 相似文献11.
F.O. Abu-Izze G.F. Ramos A.L.S. Borges L.C. Anami M.A. Bottino 《Dental materials》2018,34(9):1401-1409
Objective
The goal of this study was to investigate the fatigue life, failure modes, and stress distribution of partial ultrafine restorations for posterior teeth in different ceramics.Methods
Sixty standard tabletop preparations in epoxy resin G10 received lithium-silicate-based zirconia-reinforced (ZLS) or hybrid ceramic (PIC) restorations in 0.5- or 1-mm thickness bonded with resin cement. The same cycling protocol was applied for all specimens, which consisted of 5000 cycles at 200 N, followed by 450-N cycles until the specimens’ fracture or the suspension of the test after 1.5 × 106 cycles. Axial load was carried out with a 4 Hz frequency in Biocycle V2 equipment (Biopdi, São Carlos, SP), with samples immersed in water. The presence of cracks and/or fractures was checked every 2.5 × 105 cycles, and the survival analysis was performed with the number of cycles in which each specimen failed. All specimens were evaluated by stereomicroscopy and scanning electron microscopy (SEM). After data tabulation, Kaplan–Meier and Mantel–Cox (log-rank test) analyses were performed, followed by multiple pairwise comparison, all with a significance level of 5%, and Weibull analysis. Through three-dimensional finite element analysis, stress distribution and maximum principal stresses in the posterior occlusal veneers were evaluated by comparison of different types of substrate (G10, enamel/dentin, enamel), thicknesses, and ceramic materials.Results
Zirconium-reinforced lithium silicate restorations with 0.5-mm thickness (ZLS.5) showed lower fatigue strength compared with that of 1.0-mm hybrid ceramic restorations (PIC1), and both were similar to other restorations (PIC.5 and ZLS1) (log-rank test, χ2 = 11.2; df = 3; p = 0.0107 < 0.05). ZLS groups presented random defects that culminated in fracture, whereas PIC groups presented defects that increased with mechanical fatigue after some cycling time. Stereomicroscope images show radial cracks due to the translucency of the material. There was no damage caused by the applicator. MPS (maximum principal stress) distributions were similar for the different substrate types, but the highest modulus of elasticity showed slightly lower stress concentration.Significance
PIC is more likely to be used in thinner thickness than indicated by the manufacturer, with fatigue strength similar to that of thicker ZLS restorations. 相似文献12.
Objective
The objective of the present study is to understand the role of yttria stabilized zirconia (YSZ) in achieving the desired spectrum of clinically relevant mechanical properties (hardness, elastic modulus, fracture toughness and brittleness index) and chemical solubility of mica glass ceramics.Methods
The glass–zirconia mixtures with varying amounts of YSZ (0, 5, 10, 15 and 20 wt.%) were ball milled, compacted and sintered to obtain pellets of glass ceramic-YSZ composites. Phase analysis was carried out using X-ray diffraction and microstructural characterization with SEM revealed the crystal morphology of the composites. Mechanical properties such as Vickers hardness, elastic modulus, indentation fracture toughness and chemical solubility were assessed.Results
Phase analysis of sintered pellets of glass ceramic-YSZ composites revealed the characteristic peaks of fluorophlogopite (FPP) and tetragonal zirconia. Microstructural investigation showed plate and lath-like interlocking mica crystals with embedded zirconia. Vickers hardness of 9.2 GPa, elastic modulus of 125 GPa, indentation toughness of 3.6 MPa·m1/2, and chemical solubility of 30 μg/cm2 (well below the permissible limit) were recorded with mica glass ceramics containing 20 wt.% YSZ.Significance
An increase in hardness and toughness of the glass ceramic-YSZ composites with no compromise on their brittleness index and chemical solubility has been observed. Such spectrum of properties can be utilised for developing a machinable ceramic for low stress bearing inlays, onlays and veneers. 相似文献13.
Michel Lehmensiek Haitham Askar Fredrik Brouwer Uwe Blunck Sebastian Paris Falk Schwendicke 《Dental materials》2018,34(12):e317-e323
Objective
Secondary caries lesions next to direct restorations are associated with the restoration material and the integrity of the tooth-restoration-interface (presence of interfacial gaps) as well as the application of masticatory forces. It remains unclear if this is true for indirect restorations. We aimed to evaluate secondary lesions next to conventionally-cemented partial gold (PG) and adhesively-cemented partial ceramic (PC) restorations, placed with or without interfacial gaps.Methods
In human molars, standardized two-surfaced cavities were prepared. Four groups (restoration material + cementation strategy) were compared: (1) gold + glass ionomer cement (Degudent/Ketac Cem), (2) lithium disilicate ceramic + self-adhesive resin cement (IPS e.max Press/RelyX Unicem 2), (3) lithium disilicate ceramic + self-etch adhesive + resin cement (IPS e.max Press/Adhese Universal/Variolink Esthetic DC), (4) lithium disilicate ceramic + etch-and-rinse adhesive + resin cement (IPS e.max Press/Syntac/Variolink Esthetic DC). Half of the restorations received a simulated interfacial gap (mean gap height was 237 μm), while the other half did not (n = 12/group). Specimens were submitted to a Lactobacillus rhamnosus-monospecies-biofilm-model with concomitant cyclic loading for 10 days. Mineral loss (ΔZ) of enamel-surface-lesions (ESL) and dentin-wall-lesions (DWL) was analyzed using transversal microradiography.Results
For ESL, neither the presence of an interfacial gap nor the restoration material nor the cementation strategy had a significant influence on ΔZ (p > 0.05/Generalized Linear Modelling). For DWL, ΔZ was significantly higher beneath restorations with interfacial gaps (p = 0.003/GLM); the restoration material and cementation strategy did not have a significant influence (p > 0.05).Significance
The presence of interfacial gaps, but not the restoration material or cementation strategy determined secondary caries lesions next to indirect restorations in vitro. 相似文献14.
Andressa B. Venturini Catina Prochnow Gabriel K.R. Pereira Rodrigo D. Segala Cornelis J. Kleverlaan Luiz Felipe Valandro 《Dental materials》2019,35(4):534-542
Objective
To evaluate the fatigue failure load, number of cycles until failure, and survival probability of adhesively cemented materials with different microstructures (glass-, hybrid- and resin-ceramic) used to manufacture CAD/CAM monolithic restorations.Methods
Disc-shaped specimens (n = 15; Ø = 10 mm; thickness = 1.0 mm) were produced from CAD/CAM blocks as follows: feldspathic (FEL); leucite (LEU); lithium disilicate (LD); zirconia-reinforced lithium silicate (ZRLS); polymer-infiltrated ceramic network (PICN); and resin nanoceramic (RNC). Adhesive cementation was performed onto epoxy discs (dentin analogue- Ø = 10 mm; thickness = 2.5 mm). The cemented assemblies were subjected to fatigue testing using a step–stress approach (400 N–2200 N; step-size of 200 N; 10,000 cycles per step; 1.4 Hz). Fatigue data were analyzed using Kaplan–Meier and Mantel–Cox (log-rank) tests (p < 0.05) and Weibull statistical analysis. Fractographic analysis was also performed.Results
All RNC specimens survived the fatigue test (100% probability of survival at 2200 N; 100,000 cycles) and presented occlusal deformation in response to loading, while all other tested materials failed in distinct loading steps with radial cracks starting from the bonding surface. LD (1146.7 N; 47,333) and ZRLS (1013.3 N; 40,666) materials obtained the highest fatigue failure loads and cycles until failure, meanwhile all PICN specimens failed during the first step (0% probability of survival at 400 N; 10,000). FEL had similar Weibull modulus to LD and ZRLS and higher than LEU for both load and number of cycles outcomes.Significance
The microstructure of adhesively cemented glass-, hybrid- and resin-ceramic CAD/CAM restorative materials influence their response during fatigue testing, which aids in suggesting the best clinical indications. 相似文献15.
Lippo Lassila Filip Keulemans Eija Säilynoja Pekka K. Vallittu Sufyan Garoushi 《Dental materials》2018,34(4):598-606
Objective
The aim was to evaluate the effect of short glass-fiber/filler particles proportion on fracture toughness (FT) and flexural strength (FS) of an experimental flowable fiber-reinforced composite (Exp-SFRC) with two methacrylate resin formulations. In addition, we wanted to investigate how the fracture-behavior of composite restorations affected by FT values of SFRC-substructure.Methods
Exp-SFRC was prepared by mixing 50 wt% of dimethacrylate based resin matrix (bisGMA or UDMA based) to 50 wt% of various weight fractions of glass-fiber/particulate filler (0:50, 10:40, 20:30, 30:20, 40:10, 50:0 wt%, respectively). FT and FS were determined for each experimental material following standards. Specimens (n = 8) were dry stored (37 °C for 2 days) before they were tested. Four groups of posterior composite crowns (n = 6) composed of different Exp-SFRCs as substructure and surface layer of commercial particulate filler composite were fabricated. Crowns were statically loaded until fracture. Failure modes were visually examined. The results were statistically analysed using ANOVA followed by post hoc Tukey’s test.Results
ANOVA revealed that ratio of glass-fiber/particulate filler had significant effect (p < 0.05) on tested mechanical properties of the Exp-SFRC with both monomer systems. Exp-SFRC (50 wt%) had significantly higher FT (2.6 MPam1/2) and FS (175.5 MPa) (p < 0.05) compared to non-reinforced material (1.3 MPam1/2, 123 MPa). Failure mode analysis of crown restorations revealed that FT value of the substructure directly influenced the failure mode.Significance
This study shows that short glass-fibers can significantly reinforce flowable composite resin and the FT value of SFRC-substructure has prior importance, as it influences the crack arresting mechanism. 相似文献16.
Michael Wendler Renan Belli Diana Valladares Anselm Petschelt Ulrich Lohbauer 《Dental materials》2018,34(6):910-921
Objectives
Chemical and mechanical degradation play a key role on the lifetime of dental restorative materials. Therefore, prediction of their long-term performance in the oral environment should base on fatigue, rather than inert strength data, as commonly observed in the dental material’s field. The objective of the present study was to provide mechanistic fatigue parameters of current dental CAD/CAM materials under cyclic biaxial flexure and assess their suitability in predicting clinical fracture behaviors.Methods
Eight CAD/CAM materials, including polycrystalline zirconia (IPS e.max ZirCAD), reinforced glasses (Vitablocs Mark II, IPS Empress CAD), glass-ceramics (IPS e.max CAD, Suprinity PC, Celtra Duo), as well as hybrid materials (Enamic, Lava Ultimate) were evaluated. Rectangular plates (12 × 12 × 1.2 mm3) with highly polished surfaces were prepared and tested in biaxial cyclic fatigue in water until fracture using the Ball-on-Three-Balls (B3B) test. Cyclic fatigue parameters n and A* were obtained from the lifetime data for each material and further used to build SPT diagrams. The latter were used to compare in-vitro with in-vivo fracture distributions for IPS e.max CAD and IPS Empress CAD.Results
Susceptibility to subcritical crack growth under cyclic loading was observed for all materials, being more severe (n ≤ 20) in lithium-based glass-ceramics and Vitablocs Mark II. Strength degradations of 40% up to 60% were predicted after only 1 year of service. Threshold stress intensity factors (Kth) representing the onset of subcritical crack growth (SCG), were estimated to lie in the range of 0.37–0.44 of KIc for the lithium-based glass-ceramics and Vitablocs Mark II and between 0.51–0.59 of KIc for the other materials. Failure distributions associated with mechanistic estimations of strength degradation in-vitro showed to be useful in interpreting failure behavior in-vivo. The parameter Kth stood out as a better predictor of clinical performance in detriment to the SCG n parameter.Significance
Fatigue parameters obtained from cyclic loading experiments are more reliable predictors of the mechanical performance of contemporary dental CAD/CAM restoratives than quasi-static mechanical properties. 相似文献17.
Makiko Takashima Yoshiaki Arai Atsushi Kawamura Katsumi Uoshima 《Journal of prosthodontic research》2018,62(3):365-369
Purpose
This study analyzed risk factors for post-loading implant loss in cases of implant-supported prostheses applied to edentulous jaws of Japanese patients.Methods
In total, 245 dental implant fixtures placed in 54 edentulous jaws of 46 patients performed at Niigata University Hospital were retrospectively analyzed. Kaplan–Meier curves were used to estimate the cumulative survival rate (SR) of implants, and multiple Cox regression analysis was used to identify predictive factors of implant loss. The following risk factors for implant failure were examined: age, sex, survival time, implant length, implant location, smoking habit, bone density, bone augmentation, opposing dentition, loading period, and type of final restoration. The Cochran–Mantel–Haenszel test was used to examine difference in survival curves of the extracted predictors.Results
Sixteen implants failed during the observation period (SR = 92.8 %). Multiple Cox regression analysis revealed that male sex [hazard ratio (HR) = 16.1; p = 0.007] and use of maxillary removable restorations (HR = 12.7; p < 0.000) were risk factors for implant failure. Other factors had no significant effect on implant failure. The SR of implants for males (SR = 86.9 %) was significantly lower than that for females (SR = 99.1 %). The SR of implants for maxillary removable restorations (SR = 76.4 %) was significantly lower than for maxillary fixed restorations (SR = 99.1 %) and mandibular fixed restorations (SR = 97.8 %).Conclusions
Maxillary implants with removable restorations and male sex were risk factors for implant failure among Japanese edentulous patients. 相似文献18.
Catina Prochnow Andressa Borin Venturini Luís Felipe Guilardi Gabriel Kalil Rocha Pereira Thiago Augusto Lima Burgo Marco Cícero Bottino Cornelis Johannes Kleverlaan Luiz Felipe Valandro 《Dental materials》2018,34(9):e255-e263
Objectives
To evaluate the effects of the etching with different hydrofluoric acid (HF) concentrations on the cyclic load-to-failure of machined lithium disilicate crowns cemented to dentin analogue material.Methods
Pairs of dentin analogue prosthetic preparations and lithium disilicate ceramic crowns with simplified and standardized designs were machined (n = 18). The preparations were etched with 10% HF (60 s), followed by primer application. The intaglio surface of the ceramic crowns was treated as follows: non-etched (control, CTRL); or etched for 20 s with different HF concentrations — 3% (HF3), or 5% (HF5), or 10% (HF10). A silane coating was then applied onto the treated ceramic surfaces, and they were adhesively cemented to the preparations. To perform the fatigue tests (staircase approach), a hemispheric stainless-steel piston (Ø = 40 mm) applied cyclic loads in the center of the crowns under water (initial load: 720 N; step-size: 70 N; cycles: 500,000; frequency: 20 Hz). Additionally, topographic, fractographic, and fractal analyses were carried out. The fatigue data were analyzed using the Dixon and Mood method.Results
Although the topographic and fractal analyses depicted the action of HF etching altering the superficial complexity and topography, the preponderant topography pattern was established by machining on CAD/CAM. All groups showed similar CLf (in N) (CTRL = 805.00 ± 91.23; HF3 = 781.25 ± 29.87; HF5 = 755.00 ± 154.49; HF10 = 833.75 ± 100.74).Significance
Etching with different HF acid concentrations did not promote a deleterious effect on the cyclic load-to-failure of machined lithium disilicate crowns. 相似文献19.
Dan L. Romanyk Ysidora Torrealba Martinez Sydney Veldhuis Nyssa Rae Yilan Guo Slobodan Sirovica Garry J.P. Fleming Owen Addison 《Dental materials》2019,35(1):98-104
Objective
The fabrication of all-ceramic restorations using Computer Aided Design and Computer Aided Manufacturing (CAD–CAM) most commonly involves subtractive machining which results in strength-limiting, surface and sub-surface damage in the resultant prosthesis. The objective was to explore how clinically relevant machining-process variables, and material variables, affect damage accumulation in lithium silicate glass-ceramics.Methods
Three commercial lithium silicate glass-ceramics (IPS e.max® CAD, Celtra® Duo and Vita Suprinity®) were selected. For each material, two groups of disk-shaped specimens were fabricated (n = 15), using a CAD–CAM process, creating surfaces equivalent to those generated for a dental restoration, or alternatively, using a highly controlled laboratory process generating disk-shaped test specimens with a consistent polished surface. Bi-axial flexure strength (BFS) was determined in a ball-on-ring configuration and fractographic analyses performed. For each material BFS was correlated with machining sequence and with surface roughness.Results
BFS was significantly influenced by material substrate (p < 0.01) and by fabrication route (p < 0.01). A significant factorial interaction (p < 0.01) identified that the magnitude of changes in BFS when comparing the two specimen fabrication routes, was dependent on substrate type. The polished control specimens exhibited a significantly increased BFS when compared with the CAD–CAM counterparts for all materials. IPS e.max® CAD and Celtra® Duo showed a 44 and 46% reduction in mean BFS for the CAD–CAM specimens when compared with the polished counterparts, respectively. In contrast, Vita Suprinity® showed the least disparity in mean BFS (21%) but the greatest variance in BFS data.Significance
All CAD–CAM specimens showed evidence of machining introduced damage in the form of median and radial cracks at sites either coincident with, or peripheral to the failure origin. Subtractive machining introduced significant strength limiting damage that is not eliminated by heat treatments applied for either microstructure development (IPS e.max® CAD and Vita Suprinity®) or annealing/crack blunting (Celtra® Duo). 相似文献20.
Magdalena Kirsten Ragai Edward Matta Renan Belli Ulrich Lohbauer Manfred Wichmann Anselm Petschelt José Zorzin 《Dental materials》2018,34(8):1102-1111