共查询到5条相似文献，搜索用时 15 毫秒
1.
Roberto E. Campos Paulo César F. Santos Filho Osmir Batista de O. Júnior Gláucia M.B. Ambrosano Cristina Alves Pereira 《The Journal of prosthetic dentistry》2018,119(1):166-174
Statement of problem
Bond strength (BS) values from in vitro studies are useful when dentists are selecting an adhesive system, but there is no ideal measuring method.Purpose
The purpose of this in vitro study was to investigate the influence of the evaluation method in the BS between dentin and composite resin.Material and methods
Molars with exposed superficial dentin (N=240) were divided into 3 groups according to the test: microtensile (μTBS), microshear (μSBS), and micropush-out (μPBS). Each one was subdivided into 4 groups according to the adhesive system: total etch, 3- and 2-step; and self-etch, 2- and 1-step). For the μPBS test, a conical cavity was prepared and restored with composite resin. An occlusal slice (1.5 mm in thickness) was obtained from each tooth. For the μSBS test, a composite resin cylinder (1 mm in diameter) was built on the dentin surface of each tooth. For the μTBS test, a 2-increment composite resin cylinder was built on the dentin surface, and beams with a sectional area of 0.5 mm2 were obtained. Each subgroup was divided into 2 (n=10) as the specimens were tested after 7 days and 1 year of water storage. The specimens were submitted to load, and the failure recorded in units of megapascals. Original BS values from the μTBS and μSBS tests were normalized for the area from μPBS specimens. Original and normalized results were submitted to a 3-way ANOVA (α=.05). The correlation among mechanical results, stress distribution, and failure pattern was investigated.Results
Significant differences (P<.05) were found among the adhesive systems and methods within both the original and normalized data but not between the storage times (P>.05). Within the 7 days of storage, the original BS values from μTBS were significantly higher (P<.001) than those from μPBS and μSBS. After 1 year, μSBS presented significantly lower results (P<.001). However, after the normalization for area, the BS values of the μTBS and μPBS tests were similar, and both were higher (P<.001) than that of μSBS in both storage times. In the μSBS and μTBS specimens, cohesive and adhesive failures were observed, whereas μPBS presented 100% of adhesive failures. The failure modes were compatible with the stress distribution.Conclusions
The storage time did not affect the results, but differences were found among the adhesives and methods. For comparisons of bond strength from tests with different bonding areas, the normalization for area seemed essential. The microshear bond test should not be used for bond strength evaluation, and the microtensile test needs improvement to enable reliable results regarding stress concentration and failure mode. The micropush-out test may be considered more reliable than the microtensile in the bond strength investigation, as demonstrated by the uniform stress concentration and adhesive failure pattern. 相似文献2.
Marcela G. Borges Carlos J. Soares Thaís S. Maia Aline A. Bicalho Tarsis P. Barbosa Henara L. Costa Murilo S. Menezes 《The Journal of prosthetic dentistry》2019,121(5):868.e1-868.e8
Statement of problem
Posterior composite restorations may be negatively affected by acidic and colored drinks. Little information is available about the effect of acidic drinks on bulk-fill composite resins.Purpose
The purpose of this in vitro study was to investigate the effect of acidic drinks on the different properties of conventional and bulk-fill composite resins.Material and methods
A conventional composite resin and 2 representative bulk-fill composite resins were used to prepare disk-shaped specimens. The degree of conversion (DC) was monitored by spectroscopy (n=5). The specimens were divided into 5 groups: control, artificial saliva, acai juice, red wine, and Coca-Cola and were maintained for 30 days of challenge (3 periods of 15 min/d). Surface topography parameters were measured by interferometry (n=5). Elastic modulus (E) and Vickers hardness (VH) were determined by microhardness dynamic indentation (n=5). Diametral tensile strength (DTS) was determined at 0.5 mm/min (n=5). Shade matching was evaluated by using the Vitapan Classic Shade Guide. The DC, Sa, Ssk, Sku, Sdq, and DTS were statistically analyzed using 2-way ANOVA, followed by the Tukey HSD tests. E and VH were statistically analyzed by 3-way ANOVA, followed by Tukey HSD tests (α=.05). Shade matching was analyzed with the Kruskal-Wallis test.Results
DC values were similar for the immediate evaluation and after 24 hours, regardless of the composite resin (P<.05). All surface topography parameters increased significantly after the acidic drinks and were greatest for Coca-Cola. The E, VH, and DTS decreased significantly for all composite resins tested (P<.05). Acai juice and red wine produced more surface staining than Coca-Cola.Conclusions
Acidic drinks negatively influenced the physical and mechanical properties of conventional and bulk-fill composite resins. 相似文献3.
4.
Francesco Saverio Ludovichetti Flávia Zardo Trindade Gelson Luis Adabo Luca Pezzato Renata Garcia Fonseca 《The Journal of prosthetic dentistry》2019,121(5):866.e1-866.e8
Statement of problem
The effect of clinical adjustments on the strength of cemented computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials under aging challenge is unclear.Purpose
The purpose of this in vitro study was to assess the surface roughness and fracture resistance (with or without mechanical aging) of cemented CAD-CAM monolithic materials submitted to grinding and polishing procedures.Material and methods
Disks of Lava Ultimate, Vita Enamic, crystallized Vita Suprinity, and IPS e.max CAD were analyzed for roughness after polishing by using silicon carbide papers (Lava Ultimate and Vita Enamic) or glazing (IPS e.max CAD and Vita Suprinity) (control), after grinding by using 30-μm grit diamond rotary instruments, and after grinding and polishing by using a polishing kit. For fracture resistance, a simplified trilayer model consisting of a restorative disk, an epoxy resin disk, and a steel ring was used. The bonded trilayer disks received the same treatments described for the roughness analysis. Half of the specimens underwent mechanical aging for 1×106 cycles. All specimens were loaded until failure. The Weibull modulus was calculated.Results
The IPS e.max CAD and Vita Suprinity showed the highest roughness after grinding and the lowest at baseline. For the Lava Ultimate and Vita Enamic, polishing provided lower roughness than at baseline. Grinding, followed or not by polishing, and mechanical aging did not adversely affect the fracture resistance or the reliability of the materials.Conclusions
Polishing did not recover the initial surface roughness of the glass-ceramic materials. Fracture resistance was not affected by grinding, followed or not by polishing, even after mechanical aging. 相似文献5.
Karla G.F. Gomes Natália S. Faria Walter R. Neto Vivian Colucci Erica A. Gomes 《The Journal of prosthetic dentistry》2018,119(1):97-102