The effect of placement of glass fibers and aramid fibers on the fracture resistance of provisional restorative materials

The fracture resistance of provisional restorations is an important concern for the restorative dentist. The fracture resistance of a material is directly related to its transverse strength. Six specimens of similar dimensions were prepared from three resins (PMMA, PEMA and BIS acryl-composite). The resins were reinforced with glass and aramid fibers. The samples were tested immediately after the material set, following seven days of wet storage using three-point compression loading. The results were analyzed with an analysis of variance (ANOVA). Fracture resistance of the specimens was statistically different (p < 0.001) among the materials. Specimens reinforced with glass fibers showed higher transverse strength (149.82 MPa). The fiber reinforcement of resin materials increased the strength values (20-50%). Within the limitations of this study, the transverse strengths of PMMA, PEMA and BIS acryl-resin composites were improved after reinforcement with glass and aramid fibers.     

Mechanical property characterization of a novel directly-placed ceramic restorative material

PURPOSE: To compare, in vitro, the mechanical properties of a directly-placed ceramic restorative material (Doxadent) to glass-ionomer (Fuji IX), hybrid composite control (Z250) and amalgam control (Tytin). METHODS: Diametral tensile strength (DTS), compressive strength (CS), and Vickers hardness number (VHN) were measured for 10 specimens per group (n = 480 total) with time (1 hour, 24 hours, 1 week, 4 weeks). CS and DTS specimens were cylinders (4 x 8 mm). VHN specimens were disks (9.5 x 1 mm). Specimens were prepared following manufacturers' instructions, stored in deionized water (37 degrees C), and tested in 100% humidity (23 degrees C). CS and DTS specimens were loaded to failure (Instron, CHS = 0.5 mm/minute). VHN discs were indented. Data were analyzed using ANOVAand Tukey's test (P < 0.05) for pairwise comparisons of group means at each time. RESULTS: In CS and DTS, DoxaDent was weakest (P < 0.05) for all testing times except Fuji IX DTS at 1- and 4-week intervals. For VHN, DoxaDent was harder than glass-ionomer, better than composite except at 1 hour and less than amalgam. Except for VHN for Z250, all values improved from 1-24 hours. Based on current in vitro results, this novel restorative material does not yet equal composite or amalgam CS or DTS.     

The effect of fiber reinforcement on the fracture toughness and flexural strength of provisional restorative resins

STATEMENT OF PROBLEM: Fracture of provisional restorations is of concern, especially with long-span fixed partial dentures or areas of heavy occlusal stress. A number of different techniques for reinforcement of provisional restorations have been suggested; however, the effect of these techniques is largely unclear. PURPOSE: The aim of this study was to determine the fracture toughness and flexural strength of different types of provisional restoration resins reinforced with different commercially available fibers. MATERIAL AND METHODS: A total of 105 specimens were prepared in this study for each test; compact tensile specimens for the fracture toughness test and rectangular specimens for the flexural strength test. The specimens were divided into 3 groups according to the type of resin used, Jet, Trim, or Temphase (n=35), and then each group was divided into 7 subgroups (n=5) according to the type of fiber reinforcement, Construct, Fibrestick, Ribbond normal, Ribbond THM, Ribbond triaxial, or Fibrenet. Unreinforced specimens served as the control. Specimens were loaded in a universal testing machine until fracture. The mean fracture toughness (MPa.m(1/2)) and mean flexural strength (MPa) were compared by 1-way analysis of variance, followed by the Tukey standardized range test (alpha=.05). RESULTS: Fibrestick and Construct reinforcements showed a significant increase (P<.0001) in mean fracture toughness over unreinforced controls for all resins tested. Fibrestick increased the polymethyl methacrylate from 1.25+/-0.06 MPa.m(1/2) to 2.74+/-0.12 MPa.m(1/2); polyethyl methacrylate from 0.67+/-0.07 MPa.m(1/2) to 1.64+/-0.13 MPa.m(1/2); and bis-acryl from 0.87+/-0.05 MPa.m(1/2) to 1.39+/-0.11 MPa.m(1/2). Construct increased polymethyl methacrylate to 2.59+/-0.28 MPa.m(1/2); polyethyl methacrylate to 1.53+/-0.22 MPa.m(1/2); and bis-acryl to 1.30+/-0.13 MPa.m(1/2); however, there was no significant difference between Fibrestick and Construct reinforcements in the degree of reinforcement. Similarly the mean flexural strength values were significantly increased by different combinations of fiber and resin (P<.0001). CONCLUSION: The addition of fibers to provisional resin increased both fracture toughness and flexural strength.     

Effect of a new resin inlay/onlay restorative material on cuspal reinforcement

Nine maxillary premolars were restored with composite resin inlays involving large intracoronal cavity preparations. Buccal and lingual bonded strain guages measured the cuspal flexure under a carefully controlled application of occlusal force. The intact tooth was compared with the corresponding preparation and final restoration. The preparation itself greatly reduced the coronal rigidity, but this was completely recovered in the restored tooth, within the functional force of 111 N. A stiffness ratio showed a 97% recovery. From the point of view of cuspal strength, this may mean that larger intracoronal restorations are feasible with this type of restoration. However, other factors, such as chairside time and complexity, and material properties, such as occlusal wear, have to be taken into consideration.     

Marginal accuracy of provisional restorative materials

Marginal integrity is an important quality in the provisional restoration. Previous studies on marginal integrity have presented conflicting results. In addition, newly available resins are making the selection of an accurate resin for provisional restorations difficult. The objective of this study was to evaluate the marginal accuracy of seven commercially available resins by using an established indirect technique, and to evaluate the effect of water absorption on polymerization shrinkage. Eight specimens of each material were tested under three conditions: immediately after polymerization, after 1 week of dry storage, and after 1 week of storage in room temperature water. Three materials, Duralay, Cold Pac, and Snap resins, produced statistically significantly superior marginal adaptation. Water absorption appeared to compensate for continued polymerization shrinkage.     

Effect of food-simulating liquids on the mechanical properties of provisional restorative materials

OBJECTIVES: The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the mechanical properties of provisional restorative materials. METHODS: Four provisional restorative materials were selected: (1) Dentalon Plus (DP), (2) Protemp II (PII), (3) Systemp C&B (SCB) and (4) Integrity (INTG). The specimens were fabricated in customized molds and each type was randomly divided into five groups (n = 10). The test groups were conditioned for 7 days at 37 degrees C as follows: water, 0.02 N citric acid, heptane and 75% ethanol in aqueous solution. Specimens in the control group were stored at room temperature in air. After conditioning, the flexural strength (FS) values were assessed using a universal testing machine (5 mm/min crosshead speed) and the fractured specimens were used for the determination of the Knoop hardness number (KHN) using a digital micro-hardness tester (100 gf/15 s). Kruskal-Wallis and Mann-Whitney U-tests were used for statistical analysis. RESULTS: In ethanol and heptane solutions, DP specimens were totally degraded, thus, FS/KHN for DP could not be measured. For all materials, the FS/KHN values were significantly lower than their control groups after conditioning in ethanol. After heptane conditioning, the decrease in FS for SCB and KHN for PII were statistically significant. After citric acid conditioning, KHN for PII and INTG were significantly higher than the controls and the decrease in FS for SCB and INTG were statistically significant. SIGNIFICANCE: The mechanical properties of provisional restorative materials are strongly influenced by food-simulating liquids.     

Mechanical properties of compomer restorative materials.

The purpose of this study was to measure the compressive strength, flexural strength, microhardness, and surface roughness of three compomers (Compoglass, Dyract, and Hytac) and compare the values to the ones obtained for a resin-modified glass-ionomer cement (Vitremer) and a resin composite (Z100). All materials were handled according to the manufacturers' instructions. There was a significant difference (P < 0.01) among Vitremer, Hytac and Z100 composite with regard to yield strength. Vitremer values were lower than for Hytac, which were lower than for Z100. The yield strength values for Compoglass and Dyract were significantly lower than for Hytac and Z100 composite and significantly higher than for Vitremer (P < 0.01). There was no significant difference in the strain at yield among Vitremer, Hytac, and Z100, but their values were significantly higher than for Compoglass and Dyract (P < 0.01). The flexural strength data displayed a significant difference between Vitremer and Hytac (P < 0.05). Z100 was significantly stronger than the other products tested. The values of strain at break for Vitremer, Hytac, and Z100 were significantly lower than for Compoglass and Dyract (P < 0.01). The compressive strength results showed significantly higher values for Dyract, Compoglass, and Hytac than for Vitremer (P < 0.01). Z100 displayed higher values than the other products tested (P < 0.01). Hytac strength was significantly higher than for Dyract (P < 0.01). The microhardness of Compoglass and Dyract was not significantly different (P < 0.05). Hytac displayed microhardness values higher than for Vitremer, Compoglass, and Dyract (P < 0.01). However, all products tested showed values significantly lower than for Z100 (P < 0.01). The surface roughness values for Compoglass, Dyract, Hytac, and Z100 were not significantly different. Vitremer displayed a significantly higher value than Dyract, Hytac, and Z100 (P < 0.05).     

三种暂时冠桥树脂材料的力学性能研究

目的比较3种暂时冠桥树脂材料的力学性能,为临床选用材料提供实验参考。方法 3种被测试材料分别为半永久冠桥树脂材料LuxaCrown、普通冠桥树脂材料Protemp 4和MB自凝塑料。参照标准推荐的模具分别制备用于弯曲强度和弯曲模量测试用的条状试样(2.0mm×2.0mm×25mm),用于压缩强度测试用的圆柱状试样(直径4.0mm,高8mm)和用于断裂韧性测试的单边缺口梁试样(5.0mm×2.5mm×25mm,缺口深度2.5mm),每种材料制备各10个试样。在拉力试验机上以1.0mm/min的加载速度进行测试。结果 3种材料(LuxaCrown、普通冠桥树脂材料Protemp 4、MB自凝塑料)的弯曲强度分别为(110.35±10.94) MPa、(97.21±11.59) MPa、(49.43±11.63) MPa,弯曲模量分别为(2.46±0.17) GPa、(2.24±0.15) GPa、(2.09±0.19) GPa,压缩强度分别为(303.22±14.13) MPa、(279.21±12.54) MPa、(214.87±12.43) MPa,断裂韧度分别为(1.30±0.12)...     

牙科用玻璃纤维增强复合树脂的研究

目的：研究玻璃纤维增强丙烯酸树脂的力学性能。方法：将Ｅ玻璃纤维按６１．９７％、７２．６０％、７７．６８％（重量比）,与丙烯酸树脂制成单向玻璃纤维增强复合材料,并测试其弯曲强度、弯曲模量和面内剪切强度。结果：随着纤维比例的提高,复合材料的弯曲强度有显著性增加（Ｐ＜０．０５）,达（１３２９．４６±８５．１３）ＭＰａ。７２．６０％组和７７．６８％组与６１．９１％组相比,弯曲模量提高非常显著（Ｐ＜０．０１）,达（３４．０６±３．５８）ＧＰａ;面内剪切强度降低非常显著（Ｐ＜０．０１）,为（５３．５２±４．６２）ＭＰａ。结论：玻璃纤维对丙烯酸树脂的弯曲性能具有增强作用。     

Mechanical and optical properties of monolithic CAD-CAM restorative materials

Statement of problem

Achieving natural tooth appearance with sufficient mechanical strength is one of the most challenging issues of computer-assisted design and computer-assisted manufacturing (CAD-CAM) materials. However, limited evidence is available regarding their optical and mechanical properties for proper and evidence-based material selection in clinical practice.

Flexural strength of a provisional resin material with fibre addition

The effect of fibre addition on the flexural strength of a resin was studied. A provisional material (ALIKE^®; GC America Inc.) was used as the control and resinous matrix. Silane treated glass fibre was selected for the reinforcing treatment. In order to determine the geometric influence on the strength, ordered fibres (1 w/o) were immersed within a resinous matrix in four different locations. In addition, randomly dispersed fibres, 5 mm in length, were blended at 1 w/o up to 8 w/o with acrylic powder and moulded into rectangular specimens (34 mm × 9 mm × 8 mm) with P : L = 2 : 1. Ten specimens were prepared for each group. A three‐point flexural test was run using a span of 25 mm at a rate of 5 mm/min. The strength values were collected and analysed with ANOVA and Scheffe tests. The strengths of the specimens with orientated fibre addition ranged from 49·4 (s.d. = 5·7) to 64·5 (6·7) MPa and the control was 54·3 (4·0) MPa. In the dispersed groups, the strengths obtained ranged from 55·9 (5·9) to 87·3 (7·9) MPa. The results disclosed that inclusion of orientated fibres horizontally on the tension side of the specimens significantly improved the flexural strength compared with the control ( P < 0·05). An optimal strength was obtained in the group of provisional resin containing 5 w/o dispersed fibre. Incorporation of glass fibres significantly improved the flexural strength of the resin and the dispersed method is more efficient than the orientated inclusion method.     

Mechanical properties of two restorative reinforced glass-ionomer cements

This study investigated the mechanical properties (hardness, compressive and diametral tensile strength) of two restorative reinforced glass-ionomer cements (GC Fuji IX GP and Miracle Mix). The mechanical properties of the two cements were compared after 1 day, 1 week and 1 month storage in distilled water at 37 degrees C. Hardness testing (VHN) was carried out with a digital microhardness tester (load = 50 g, dwell time = 30 s) and compressive/diametral tensile strength testing (MPa) was conducted based upon British Standard Specification for Glass-Ionomer Cements (BS 6039: 1981). Results were analysed using analysis of variance (ANOVA)/Scheffe's test and independent samples t-test (P < 0.05). Mechanical properties generally increased with time for both cements. Hardness at 1 day was significantly lower than that at 1 week and 1 month. No significance difference in compressive and diametral tensile strengths was observed between the different time intervals. After 1 month storage in water, no significant difference in hardness and compressive strength was observed between Fuji IX and Miracle. The diametral tensile strength of Fuji IX was, however, significantly greater than that of Miracle Mix at all time intervals. Fuji IX GP may serve as a potential substitute for Miracle Mix.     

暂时冠桥材料挠曲强度的体外研究

目的体外对比2种甲基丙烯酸酯类和3种bis-acryl类暂时冠桥材料的挠曲强度.方法依据ISO40492000标准,制作25mm×2 mm×2 mm条状试样,人工唾液中37℃保存24 h后,在万能力学实验机上三点加荷测定试样挠曲强度.结果5种材料挠曲强度值排序QuickResin＜Protemp Ⅱ＜Curefast＜Luxatemp＜Protemp 3 Garant.QuickResin、Protemp Ⅱ和Curefast之间没有统计学差异(P＞0.05).Protemp 3 Garant挠曲强度值高于Luxatemp(P＜0.05),他们均高于前三者(P＜0.05).结论bis-acryl类材料较甲基丙烯酸酯类材料强度好,但是早期bis-acryl类材料强度一般.临床医生应根据不同的病人选用合适的暂时冠桥材料.     

Evaluation of surface finish and polish of eight provisional restorative materials using acrylic bur and abrasive disk with and without pumice

This study evaluated the effects of two finishing techniques and pumice polishing on the surface roughness of eight different provisional materials. Provisional materials included polymethylmethacrylate-based Alike, Snap, Trim and Jetand composite-based provisional materials Temphase, Protemp 3 Garant, Luxatemp and Integrity. Baseline surface roughness was measured by a profilometer, then the provisional materials were finished using extra fine acrylic burs or medium abrasive disks. The surface roughness of each sample was measured following finishing using a profilometer as previously stated. Each surface was then polished with pumice and the surface roughness was measured again. The data were analyzed using repeated measures of ANOVA and Bonferroni pairwise comparisons (alpha = 0.05). The results indicated that with composite provisional materials, the unfinished surfaces are smoother than with bur or abrasive-disk finished surfaces. Pumice application did not smooth the surface finish for all materials. The different types of provisional materials required different finishing techniques to produce the smoothest finishes.     

Mechanical properties of a new facial prosthetic material

The tensile strength, tear resistance, and hardness of four silicone elastomers were compared. Results suggest that Cosmesil has improved mechanical properties over commonly used facial prosthetic silicone elastomers.