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1.
Deyar Jallal Hadi Mahmood Michael Braian Christel Larsson Ann Wennerberg 《Dental materials》2019,35(3):486-494
Objectives
To measure and compare the size of the cement gap of wax and polymer copings and final glass-ceramic crowns, produced from conventional and digital workflows, one additive and one subtractive.Methods
Thirty wax copings were made by conventional manual layering technique and modeling wax on stone models with spacer varnish simulating a cement spacer. The wax copings were embedded and press-cast in lithium disilicate glass ceramic. Thirty wax copings were produced by milling from a wax blank, i.e. subtractive manufacturing, and thirty polymer burn-out copings were produced by stereolithography, i.e. additive manufacturing. These copings were embedded and press-cast in lithium disilicate glass ceramic in the same manner as the conventional group. The fit of the wax/polymer copings and subsequent crowns was checked using an impression replica method. Mean values for cement gap for marginal, axial, and occlusal areas were calculated and differences were analyzed using Student’s t-test.Results
There were significant differences in mean values for accuracy/production tolerance among different manufacturing techniques for both production stages: wax and polymer copings and final pressed glass-ceramic crowns. In general, crowns produced from a digital additive workflow showed smaller mean cement gaps than crowns produced from a conventional workflow or a digital subtractive workflow. Additive polymer copings showed significantly smaller cement gaps than milled wax copings (p ≤ .001) and conventional wax copings (p ≤ .001) in the axial area. In the occlusal area, both additive polymer copings and conventional wax copings showed significantly smaller cement gaps than milled wax copings (p = .002 and p ≤ .001 respectively). Crowns produced from conventional manual build-up wax copings showed significantly larger mean cement gaps than crowns produced from milled wax and additively manufactured polymer copings in the marginal and axial areas (p ≤ .001). Among the crowns with smaller cement gaps, crowns produced from additively manufactured polymer copings showed significantly smaller mean cement gaps than crowns produced from milled wax in the marginal and axial areas (p ≤ .001). In the occlusal areas, the differences in mean cement gaps were only statistically significant between crowns produced from conventional manual build-up wax copings and crowns produced from milled wax where the latter ones showed smaller mean cement gaps (p = .025).Significance
The present study suggests that an additive manufacturing technique produces smaller mean cement gaps in glass-ceramic crowns than a conventional or subtractive manufacturing technique. 相似文献2.
Vitor Guarçoni de Paula Gerson Bonfante Fabio C. Lorenzoni Paulo G. Coelho Leonardo Rigoldi Bonjardim Vinicius P. Fardin Estevam A. Bonfante 《Dental materials》2019,35(3):511-522
Objective
To evaluate the probability of survival of monolithic and porcelain veneered lithium disilicate crowns comprised by a conventional or modified core when loaded on marginal ridges.Methods
Lithium disilicate molar crowns (n = 30) were fabricated to be tested at mesial and distal marginal ridges and were divided as follows: (1) bilayered crowns with even-thickness 0.5 mm framework (Bi-EV); (2) bilayered crowns with modified core design (Bi-M-lingual collar connected to proximal struts), and: (3) monolithic crowns (MON). After adhesively cemented onto composite-resin prepared replicas, mesial and distal marginal ridges of each crown (n = 20) were individually cyclic loaded in water (30–300 N) with a ceramic indenter at 2 Hz until fracture. The 2-parameter Weibull was used to calculate the probability of survival (reliability) (90% 2-sided confidence bounds) at 1, 2, and 3 million cycles and mean life.Results
The reliability at 1 and 2 million cycles was significantly higher for MON (47% and 19%) compared to Bi-EV (20% and 4%) and Bi-M (17% and 2%). No statistical difference was found between bilayered groups. Only the MON group presented crown survival (7%) at 3 million cycles. The mean life was highest for MON (1.73E + 06), lowest for Bi-M (573,384) and intermediate for Bi-E (619,774). Fractographic analysis showed that the fracture originated at the occlusal surface. The highest reliability was found for MON crowns. The modified framework design did not improve the fatigue life of crowns.Significance
Monolithic lithium disilicate crowns presented higher probability of survival and mean life than bilayered crowns with modified framework design when loaded at marginal ridges. 相似文献3.
C. Monaco A. Arena J. Štelemėkaitė E. Evangelisti P. Baldissara 《Journal of prosthodontic research》2019,63(2):173-178
Purpose
To quantify and to compare a gravimetric and three-dimensional (3D) analysis of the removed tooth structure for different complete crown preparations.Methods
A total of 80 molar resin teeth and 8 preparation finishing lines were chosen: 1 for metal ceramic crowns (MCC); 3 for zirconia all-ceramic crowns: knife edge (ZirKnE), chamfer (ZirCha), and shoulder (ZirSho); 4 for lithium disilicate: light chamfer (LDLCha), chamfer (LDCha), shoulder (LDSho) and table top. Teeth were individually weighed to high precision and then prepared following the preparation guidelines. The teeth were reweighed after preparation, and the amount of structural reduction was calculated. In addition, all teeth were scanned before and after preparation, and the 3D volume of removed dental tissue was calculated, superimposing the two .stl files, as a difference of the volumes before and after the preparation. Kruskal–Wallis statistical analysis was carried out to determine significant differences among the groups with a significance level of p < 0.05.Results
Both analyses showed that LDLCha, ZirKnE and table-top preparations produced the smallest amount of removed structure, whereas the preparations for MCC, ZirSho and LDSho were more destructive. For MCC, 2.6 times more tooth structure must be removed than for table top. ZirKnE was 17.82% and LDLCha was 21.51% more conservative than MCC. The data obtained through the volumetric method were similar with those obtained by gravimetric analysis.Conclusions
ZirKnE, LDLCha, and table-top preparations produced the least amount of tooth tissue removal. Three-dimensional volumetric analysis can be a possible alternative to gravimetric analysis. 相似文献4.
Influence of elastic modulus mismatch between dentin and post-and-core on sequential bonding failure
Daisuke Teshigawara Teruo Ino Hidetoshi Otsuka Tomonori Isogai Masanori Fujisawa 《Journal of prosthodontic research》2019,63(2):227-231
Purpose
Clinical failures of teeth restored with post-and-core are critical issues for the survival of teeth and maintenance of oral functions. A tooth with post-and-core restoration is a complex structure. Cement adhesion is believed to be the weakest component, and breakage in this component leads to changes in stress distribution in the complex structure. The tested hypothesis was that cement breaking processes of prosthetic treated teeth were affected by elastic properties of post-and-cores.Methods
Finite element analysis focused on sequential adhesion failure between the dentin and cement; the penalty function method was used to analyze stress during each stage of bonding conditions. Failure patterns of adhesion and stress distribution within dentin under load of different materials of post-and-core was observed.Results
Although, an initial failure of cement was observed at the palatal crown margin regardless of the material. Different patterns of adhesion failure between dentin and post-and-cores were observed by different elastic properties of post-and-cores. Stress concentration was observed at the corresponding areas of interface between adhesion failure and continued elements using both post-and-cores.Conclusions
Using failure criteria for cement adhesion, sequential changes of adhesion failure between dentin and post-and-cores were observed. Local stress concentrations leading to severe destruction of dentin were caused by not only materials of post-and-cores but their adhesive conditions to dentin. Nonlinear finite element analysis (FEA) using complex structure model which deals with alterations of interfacial condition between components could provide the simulation for the clinical failure of teeth restored with post-and-cores. 相似文献5.
A. Arena P. Baldissara L. Ciocca R. Scotti C. Monaco 《Journal of prosthodontic research》2019,63(1):100-104
Purpose
To evaluate the influence of the preparation design and spacing parameters on the risk of chipping of crowns made by CEREC Bluecam before cementation.Methods
A knife-edge preparation and a chamfer preparation were made on upper premolars. The teeth were scanned and two Co–Cr alloy replicas were made. Fifteen full crowns were manufactured for four groups using CEREC. The groups differed in type of preparation (knife-edge (KE) or chamfer (CHA)) and spacing parameters: spacer (0 or 150 μm), marginal adhesive gap (10 or 50 or 150 μm) and margin thickness (0 or 300 μm). The four groups were: CHA 150 (spacer)- 50 (marginal adhesive gap)- 0 (margin thickness), KE 150-50-0, KE 150-50-300 and KE 150-150-300. The crowns were loaded before cementation by using an Instron machine to simulate the masticatory load applied during a trial. Differences in means were compared using two-way ANOVA and a post-hoc test (Tukey Test). The level of significance was set at P = 0.05.Results
The fracture values, ordered from least to most resistant, were: KE 150-50-300 group, CHA 150-50-0 group, KE 150-50-0 group and KE 150-150-300 group. Two-way ANOVA revealed statistically significant differences between pairs of means (p < 0.05). Tukey’s test showed that restorations of the KE 150-150-300 group can withstand a load significantly higher than that of other groups (p < 0.01). In this group, the failures were mostly minor chippings, while the other groups had mostly major chippings and fractures.Conclusions
Marginal adhesive gap can affect the trial of a full crown. 相似文献6.
Falk Schwendicke Allam Al-Abdi Agustín Pascual Moscardó Alvaro Ferrando Cascales Salvatore Sauro 《Dental materials》2019,35(5):772-779
Objectives
The aim of this study was to evaluate the remineralization effects of conventional and experimental ion-releasing materials on different artificial dentin carious lesions.Methods
Forty human dentin discs were submitted to different demineralization protocols for simulated caries lesion: (D1) Shallow chemically-induced caries, (D2) deep chemically-induced caries, (D3) deep bacterially-induced caries. Each disc was divided in five parts; one of those served as baseline control. The remaining parts of each disc (n = 12–16/group) were treated using the following materials: EXP, an experimental resin-based bioactive material consisting of a self-etch primer and an adhesive containing a fluoride-doped bioglass; GIC, a glass ionomer cement (Riva LC); MTA, Mineral Trioxide Aggregate (ProRoot MTA); BIO, a calcium silicate cement (Biodentine). Specimens were mounted in a dual-chamber device to simulate the exposure to pulpal pressure and oral fluids. After 3 months, mineral and mechanical gains were assessed using transverse microradiography (vol%?×?μm) and microhardness measurements (VHN). Characterization using confocal microscopy and transmission electron microscopy (TEM) was also performed.Results
All four restorative materials induced mineral gains regardless of the protocol for caries lesion, without significant differences between materials. Microhardness significantly increased in the groups BIO and MTA, but not GIC; EXP only provided hardness gains in D3-lesions. Fluorescence and confocal microscopy confirmed these results. There was a clear “top-down” remineralization in the groups BIO and MTA, and “bottom-up” intrafibrillar collagen remineralization in EXP.Significance
Mineral gains did not always translate into hardness gains. Biodentine and MTA induced evident mineral precipitation, but intra/inter-fibrillar collagen mineral infiltration was only provided by biomimetic remineralisation via the use of the experimental adhesive. Complete remineralization of caries lesions remains a challenge. 相似文献7.
Luciano Praça Fabrice Chuembou Pekam Rodrigo Otavio Rego Klaus Radermacher Stefan Wolfart Juliana Marotti 《Dental materials》2018,34(11):e280-e288
Objective
This in vitro study aimed to evaluate marginal and internal fit of single crowns produced from high-frequency ultrasound based digital impressions of teeth prepared with finish lines covered by porcine gingiva, in comparison with those obtained by optical scanners with uncovered finish lines.Methods
Ten human teeth were prepared and forty zirconia crowns were fabricated from STL-datasets obtained from four dental scanners (n = 10): extraoral CS2 (Straumann), intraoral Lava COS (3M), intraoral Trios (3Shape) and extraoral ultrasound scanner. The accuracy of the crowns was compared evaluating marginal and internal fit by means of the replica technique with measurements in four areas; P1: occlusal surface; P2: transition between occlusal and axial surfaces; P3: middle of axial wall; and P4: marginal gap. Restoration margins were classified according to their mismatch as regular, underextended or overextended. Kruskal–Wallis one-way ANOVA and Mann–Whitney U test were used to evaluate the differences between groups at p < 0.05.Results
The median value of marginal gap (P4) for Ultrasound (113.87 μm) differed statistically from that of CS2 (39.74 μm), Lava COS (41.98 μm) and Trios (42.07 μm). There were no statistical differences between ultrasound and Lava COS for internal misfit (P1–P3), however there were statistical differences when compared with the other two scanners (Trios and CS2) at P1 and P2.Significance
The ultrasound scanner was able to make digital impressions of prepared teeth through porcine gingiva (P4), however with less accuracy of fit than that of conventional optical scanners without coverage of the finish lines. Where no gingiva was available (P1–P3), the ultrasound accuracy of fit was similar to that of at least one optical scanner (Lava COS). 相似文献8.
Jun-Ichi Sasaki Wakako Kiba Gabriela L. Abe Chihiro Katata Masanori Hashimoto Haruaki Kitagawa Satoshi Imazato 《Dental materials》2019,35(5):780-788
Objectives
Bioactive glass (BG) is widely used as a bioactive material for various clinical applications, and effective and efficient elemental release and an increase in mechanical strength are expected with further development. The purpose of this study is to clarify the physicochemical and biological characteristics of Sr-doped BG-incorporated glass ionomer cements.Methods
Sr-doped BGs (45SiO2–6P2O5–24.5Na2O–(24.5?x)CaO–xSrO) (wt%), where ×?=?0, 6, 12, were prepared, and the particle size, crystallinity, and elemental release profiles were evaluated. The Sr-doped BGs were then incorporated into a glass ionomer cement at a weight ratio of 1:4, and the physicochemical properties (compressive strength, bending strength, hardness, and elemental release profile) were investigated. Cell attachment, cell proliferation, and osteoblastic differentiation were used to evaluate the biological characteristics.Results
The Sr-doped BGs were amorphous phases with a homogeneous particle size and exhibited sustained release of Ca, Si, and Sr. The BG-incorporated cements were able to release these elements while retaining the same mechanical properties as those of the pure glass ionomer cement. In addition, no cytotoxicity of osteoblasts or differences in the cell attachment or proliferation were observed for the BG-incorporated cements. In contrast, the Sr-doped BG-incorporated cements promoted the alkaline phosphatase activities of the osteoblasts without the need for any media supplements for osteoblastic differentiation.Significance
Sr-releasable inorganic cements with high mechanical properties were successfully fabricated by incorporating Sr-doped BGs in glass ionomer cement. These bioactive materials are promising candidates for bone grafting materials, bone cements, and pulp capping materials. 相似文献9.
Maximilian Ackermann Emad Tolba Meik Neufurth Shunfeng Wang Heinz C. Schröder Xiaohong Wang Werner E.G. Müller 《Dental materials》2019,35(2):244-256
Objective
In the present study, we investigated the fusion process between amorphous microparticles of the calcium salt of the physiological polymer comprising orthophosphate units, of inorganic polyphosphate (polyP), and enamel.Methods
This polymer was incorporated as an ingredient into toothpaste and the fusion process was studied by electron microscopy and by synchrotron-based X-ray tomography microscopy (SRXTM) techniques.Results
The data showed that toothpaste, supplemented with the amorphous Ca-polyP microparticles (aCa-polyP-MP), not only reseals tooth defects on enamel, like carious lesions, and dentin, including exposed dentinal tubules, but also has the potential to induce re-mineralization in the enamel and dentin regions. The formation of a regeneration mineralic zone on the tooth surface induced by aCa-polyP-MP was enhanced upon exposure to artificial saliva, as demonstrated by SRXTM. Energy dispersive X-ray analysis revealed an increase in the calcium/phosphorus atomic ratio of the enamel deposits to values characteristic for the particles during the treatment with polyP applied in the toothpaste, indicating a fusion of the particles with the tooth mineral.Significance
Our results suggest that toothpaste enriched with aCa-polyP-MP is a promising biomimetic material for accelerating enamel and dentin restoration. 相似文献10.
Objectives
To survey simple contact testing protocols for evaluating the mechanical integrity of zirconia dental ceramics. Specifically, to map vital material property variations and to quantify competing damage modes.Methods
Exploratory contact tests are conducted on layer structures representative of zirconia crowns on dentin.Results
Sharp-tip micro- and nano-indentations were used to investigate the roles of weak interfaces and residual stresses in veneered zirconia, and to map property variations in graded structures. Tests with blunt sphere indenters on flat specimens were used to identify and quantify various critical damage modes in simulated occlusal loading in veneered and monolithic zirconia.Significance
Contact testing is a powerful tool for elucidating the fracture and deformation modes that control the lifetimes of zirconia dental ceramics. The advocated tests are simple, and provide a sound physical basis for analyzing damage resistance of anatomically-correct crowns and other complex dental prostheses. 相似文献11.
Keiichiro Sagawa Hiroyasu Furuya Yuki Ohara Mitsuyoshi Yoshida Hirohiko Hirano Katsuya Iijima Takeshi Kikutani 《Journal of prosthodontic research》2019,63(1):31-34
Purpose
The aim of this study was to determine the influences of oral motor function such as tongue function and bite force on masticatory performance in the elderly.Methods
We randomly selected 245 subjects who has 28 natural teeth among community-dwelling elderly. We evaluated masticatory performance using a gummy jelly, and also measured bite force, tongue muscle force, and the speed of tongue movement.Results
We found that reduced masticatory performance to be associated with decreased the speed of tongue movement and/or tongue muscle force, indicating that reduced oral motor function also influences masticatory performance.Conclusions
These results suggest that keeping oral motor function, as well as maintenance of occlusal support, to be important for maintaining masticatory function in the elderly. 相似文献12.
Magdalena Kirsten Ragai Edward Matta Renan Belli Ulrich Lohbauer Manfred Wichmann Anselm Petschelt José Zorzin 《Dental materials》2018,34(8):1102-1111
Objective
Low pH neutralization and subsequent remnant hydrophilicity can lead to hygroscopic expansion of self-adhesive resin cements (SARCs) after water storage. The aim of this in vitro study was to investigate the effects of hygroscopic expansion of SARCs, used as luting and partial core build-up material, on integrity and cement gap thickness increase of all-ceramic CAD/CAM crowns.Methods
Human third molars (n = 48) were prepared and anatomical all-ceramic CAD/CAM crowns were manufactured (VITABLOCS Mark II, VITA Zahnfabrik). Crowns internal surfaces were HF etched and silanized. The prepared teeth with their respective crowns were divided into 6 groups (n = 8). In groups 1, 3 and 5 the coronal dentin was removed to simulate a partial core build-up. Groups 1 and 2 were luted with iCEM (Heraeus Kulzer), 3 and 4 with RelyX Unicem 2 Automix (3M), 5 and 6 with Variolink Esthetic DC (Ivoclar Vivadent). All specimens were dual cured and stored in distilled water at 37 °C. Crown integrity was controlled at baseline and in regular intervals until 180 days. Cement gap thickness was measured using an optical 3D scanner (ATOS Triple scan, GOM) at baseline and after 180 days. Crown integrity was statistically analysed using Kaplan–Meier survival analysis and cement gap thickness increase using two-way ANOVA (α = 0.05).Results
After 180 days storage, crack formation was observed in all specimens of group 1 (mean survival time of 85.5 days), in one specimen of group 2 and in two specimens of group 4. Two-way ANOVA analysis revealed a statistically significant interaction between material type and build-up on cement gap size increase for iCEM.Significance
Within the limits of this study, the application of SARCs with low pH neutralization as partial build-up material under CAD/CAM crowns is not recommended for clinical use. 相似文献13.
Biodentine? is a novel tricalcium silicate based material used both as a coronal dentine replacement and in pulp therapy. Its multiple use in sealing perforations, pulp capping and as a temporary restoration arises from its ability to promote dentine formation and to confer an excellent marginal seal. However, there is still room for improvement of this cement as it lacks the anticariogenic effect typically conferred by fluoride ion release as seen in glass ionomer cement based dental materials. Therefore, this study was conducted to investigate the impact of bioactive glass addition to Biodentine?.
Objective
was to compare the apatite formation capacity, specificity of the apatite type formed and fluoride ion release by Biodentine? cements that have been modified by three different compositions of bioactive glasses.Methods
High fluoride, high strontium and high fluoride plus strontium containing bioactive glasses were synthesized, incorporated into Biodentine? powder and four types of cements prepared. These cements were immersed in phosphate buffered saline solution and incubated for a period of 3 and 24 h, 3, 7 and 14 days. Fourier transform infra-red spectroscopy, X-ray diffraction, magic angle spinning nuclear magnetic resonance and fluoride ion release studies were performed.Results
Bioactive glass addition to Biodentine? led to pronounced formation of apatite. Where the bioactive glass contained fluoride, fluorapatite and fluoride ion release were demonstrated.Significance
Eliciting fluorapatite formation and fluoride ion release from Biodentine? is an important development as fluoride is known to have antibacterial and anticariogenic effects. 相似文献14.
Margot Bacino Vishavjeet Girn Hamid Nurrohman Kuniko Saeki Sally J Marshall Laurie Gower Ella Saeed Ray Stewart Thuan Le Grayson W Marshall Stefan Habelitz 《Dental materials》2019,35(1):53-63
The addition of charged polymers, like poly-aspartic acid (pAsp), to mineralizing solutions allows for transport of calcium and phosphate ions into the lumen of collagen fibrils and subsequent crystallization of oriented apatite crystals by the so-called Polymer-Induced Liquid Precursor (PILP) mineralization process, leading to the functional recovery of artificial dentin lesions by intrafibrillar mineralization of collagen.
Objective
To evaluate the feasibility of applying the PILP method as part of a restorative treatment and test for effectiveness to functionally remineralize artificial lesions in dentin.Materials and Methods
Two methods of providing pAsp to standardized artificial lesions during a restorative procedure were applied: (A) pAsp was mixed into commercial RMGI (resin modified glass ionomer) cement formulations and (B) pAsp was added at high concentration (25 mg/ml) in solution to rehydrate lesions before restoring with a RMGI cement. All specimens were immersed in simulated body fluid for two weeks to allow for remineralization and then analyzed for dehydration shrinkage, integrity of cement-dentin interface, degree of mineralization, and changes in the nanomechanical profile (E-modulus) across the lesion.Results
After the remineralization treatment, lesion shrinkage was significantly reduced for all treatment groups compared to demineralized samples. Pores developed in RMGI when pAsp was added. A thin layer at the dentin-cement interface, rich in polymer formed possibly from a reaction between pAsp and the RMGI. When analyzed by SEM under vacuum, most lesions delaminated from the cement interface. EDS-analysis showed some but not full recovery of calcium and phosphorous levels for treatment groups that involved pAsp. Nanoindentations placed across the interface indicated improvement for RMGI containing 40% pAsp, and were significantly elevated when lesions were rehydrated with pAsp before being restored with RMGI. In particular the most demineralized outer zone recovered substantially in the elastic modulus, suggesting that functional remineralization has been initiated by pAsp delivery upon rehydration of air-dried demineralized dentin. In contrast, the effectiveness of the RMGI on functional remineralization of dentin was minimal when pAsp was absent.Significance
Incorporation of pAsp into restorative treatments using RMGIs promises to be a feasible way to induce the PILP-mineralization process in a clinical setting and to repair the structure and properties of dentin damaged by the caries process. 相似文献15.
M.M.M. Michelon A.T. Posch H.R. Sampaio-Filho E.J.V. Lourenco D.M. Telles 《Journal of prosthodontic research》2019,63(1):47-51
Purpose
The purpose of this in vitro study was to compare the stability of removable implant-supported maxillary overdentures with fixed complete dentures and conventional dentures.Methods
Four types of complete dentures were tested: conventional complete dentures; overdentures retained by a male resilient attachment system; overdentures retained by a combination of clip bar and attachment system; and fixed complete dentures. Each group was placed in the posterior and anterior region and the stability was recorded by measuring the vertical displacement of the prosthesis.Results
There was a difference in the vertical movement of the prosthesis according to the type of system. The results showed that the behavior of the overdenture retained by a combination of a clip bar and attachment system is comparable with the stabilization of an implant-retained fixed complete denture.Conclusions
Overdentures retained by a combination of a clip bar and attachment presented better stability and retention capacity under our experimental conditions, close to that of the positive control (fixed complete denture), with the advantages of removable overdentures. 相似文献16.
Weina Wang Hai Yu Yifan Liu Xinlei Jiang Bo Gao 《The Journal of prosthetic dentistry》2019,121(2):285-291
Statement of problem
The primary manufacturing method of zirconia ceramic crowns is computer-aided design and computer-aided manufacture (CAD-CAM), but a disadvantage of this technique is material waste. Three-dimensional (3D) printing, which has been recently introduced into dentistry, has improved the processing of polymers and metals, but not yet of ceramic crowns.Purpose
The purpose of this in vitro study was to evaluate the 3D trueness of zirconia crowns fabricated by 3D printing to investigate the potential application of this technology in dental ceramic restorations.Material and methods
A typodont tooth was prepared for a ceramic crown, and a digital crown was designed using the CAD software. The digital crown was processed either with a 3D-printing system or with a dental milling system. The crowns were scanned using a dental laboratory scanner, and the data collected for each crown were divided into 4 parts (the external surface, intaglio surface, marginal area, and intaglio occlusal surface). Finally, the trueness of each part was determined using the 3D inspection software. The 3D trueness of the crowns fabricated by either 3D printing or milling was compared by a 1-sided test (α=.05).Results
The trueness of the external surface, intaglio surface, marginal area, and intaglio occlusal surface of the 3D-printed crowns was no worse than the corresponding trueness of the CAD-CAM crowns (P<.05).Conclusions
Zirconia crowns produced by 3D printing meet the trueness requirements, and 3D printing may be suitable for fabricating zirconia crowns. 相似文献17.
Danush Ahrberg Hans Christoph Lauer Martin Ahrberg Paul Weigl 《Clinical oral investigations》2016,20(2):291-300
Objectives
The aim of this clinical trial was to evaluate the marginal and internal fit of CAD/CAM fabricated zirconia crowns and three-unit fixed dental prostheses (FDPs) resulting from direct versus indirect digitalization. The efficiency of both methods was analyzed.Materials and methods
In 25 patients, 17 single crowns and eight three-unit FDPs were fabricated with all-ceramic zirconia using CAD/CAM technology. Each patient underwent two different impression methods; a computer-aided impression with Lava C.O.S. (CAI) and a conventional polyether impression with Impregum pent soft (CI). The working time for each group was recorded. Before insertion, the marginal and internal fit was recorded using silicone replicas of the frameworks. Each sample was cut into four sections and evaluated at four sites (marginal gap, mid-axial wall, axio-occlusal transition, centro-occlusal site) under ×64 magnification. The Mann–Whitney U test was used to detect significant differences between the two groups in terms of marginal and internal fit (α?=?0.05).Results
The mean for the marginal gap was 61.08 μm (±24.77 μm) for CAI compared with 70.40 μm (±28.87 μm) for CI, which was a statistically significant difference. The other mean values for CAI and CI, respectively, were as follows in micrometers (± standard deviation): 88.27 (±41.49) and 92.13 (±49.87) at the mid-axial wall; 144.78 (±46.23) and 155.60 (±55.77) at the axio-occlusal transition; and 155.57 (49.85) and 171.51 (±60.98) at the centro-occlusal site. The CAI group showed significantly lower values of internal fit at the centro-occlusal site.A quadrant scan with a computer-aided impression was 5 min 6 s more time efficient when compared with a conventional impression, and a full-arch scan was 1 min 34 s more efficient.Conclusions
Although both direct and indirect digitalization facilitate the fabrication of single crowns and three-unit FDPs with clinically acceptable marginal fit, a significantly better marginal fit was noted with direct digitalization. Digital impressions are also less time-consuming for the dental practitioner and the patient.Clinical relevance
The results show that a direct, intraoral, digitalized impression technique is more accurate and efficient when compared with conventional impressions in fabricating single crowns and three-unit FDPs.18.
Syed Rashid Habib Mohsin Ali Abdulaziz Al Hossan Ahmad Majeed-Saidan Mohammad Al Qahtani 《Saudi Dental Journal》2019,31(1):45-51
Objectives
To investigate the effect of cementation, cement type and vent-holes on the marginal and internal fit of Zirconia (Zr) Copings.Materials and methods
Extracted premolars (N?=?100) were mounted in resin and prepared for Zr crowns. Samples were randomly divided into 5 groups (n?=?20); A: No Cementation; B: Cementation with Glass-Ionomer (GI); C: GI?+?Vent-Holes; D: Cementation with Resin Cement (RC); E: RC?+?Vent-Holes. The copings were fabricated using semi sintered Zr Blocks with a standardized cement space of 20?µm. Groups C & E were designed to have 0.5?mm of Vent-Holes on the Buccal and Lingual Cusp Tips. The copings were tried, cemented, thermocycled, re-embedded in resin and cross sectioned into two halves. The copings were examined with 3D-Digital Microscope (HIROX, KH-7700, Tokyo, Japan) at 50-200X. The gaps were recorded at 9 predetermined points.Results
The non-cemented groups showed statistically better fit compared to the cemented groups P?<?0.05 except vs Group E (RC plus vent holes). No significance was found between the cemented groups P?>?0.05. Copings with vent-holes showed statistically better fit than copings without holes P?<?0.05.Conclusion
Marginal and Internal gap values designed in the software programs differed than the actual values measured for the non-cemented copings. Cementation process also influenced the fit of the Zr copings, the resin cement being the more accurate. The addition of vent-holes on the occlusal surface improved the fit. 相似文献19.
Amanda Maria de Oliveira Dal Piva João Paulo Mendes Tribst Alexandre Luiz Souto Borges Rodrigo Othávio de Assunção e Souza Marco Antonio Bottino 《Dental materials》2018,34(9):1342-1350
Objectives
To investigate the influence of different materials for monolithic full posterior crowns using 3D-Finite Element Analysis (FEA).Methods
Twelve (12) 3D models of adhesively-restored teeth with different crowns according to the material and its elastic modulus were analysed: Acrylic resin, Polyetheretherketone, Composite resin, Hybrid ceramic, pressable and machinable Zirconia reinforced lithium silicate, Feldspathic, Lithium disilicate, Gold alloy, Cobalt–Chromium alloy (Co–Cr), Zirconia tetragonal partially stabilized with yttria, and Alumina. All materials were assumed to behave elastically throughout the entire deformation. Results in restoration and cementing line were obtained using maximum principal stress. In addition, maximum shear stress criteria was used for the cementing line.Results
Restorative materials with higher elastic modulus present higher stress concentration inside the crown, mainly tensile stress on an intaglio surface. On the other hand, materials with lower elastic modulus allow stress passage for cement, increasing shear stress on this layer. Stiffer materials promote higher stress peak values.Significance
Materials with higher elastic modulus such as Co–Cr, zirconia and alumina enable higher tensile stress concentration on the crown intaglio surface and higher shear stress on the cement layer, facilitating crown debonding. 相似文献20.