Influence of the flexural modulus of prefabricated and experimental posts on the fracture strength and failure mode of composite resin cores

The purpose of this study was to evaluate the influence of flexural modulus of non-metal posts on the fracture strength and failure mode of composite resin cores. Thirty-two human premolars were divided into four groups: prefabricated glass fiber post with 1.0 mm diameter and composite resin core (Group PE1.0), that with 1.5 mm diameter and composite resin core (Group PE1.5), experimental post (flexural modulus; 4.25GPa) and composite resin core (Group EX), and preparation for abutment teeth only (Group NT). After a static loading test, the fracture strength and failure mode were recorded. Group NT (1670.81 N) showed higher fracture strength than Groups PE1.0 (866.44 N), PE1.5 (825.19 N) and EX (1075.63 N) (p<0.05). This study showed that the fracture strength of endodontically treated teeth restored with composite resin cores is not influenced by the flexural modulus of non-metal posts.     

Influence of airborne-particle abrasion on mechanical properties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts

STATEMENT OF PROBLEM: Controversy exists concerning the use of fiber-reinforced posts to improve bond strength to resin cement because some precementation treatments can compromise the mechanical properties of the posts. PURPOSE: The purpose of this study was to analyze the influence of airborne-particle abrasion on the mechanical properties and microtensile bond strength (MTBS) of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. MATERIAL AND METHODS: Flexural strength (delta(f)), flexural modulus (E(f)), and stiffness (S) were assessed using a 3-point bending test for glass fiber-reinforced and carbon fiber-reinforced resin posts submitted to airborne-particle abrasion (AB) with 50-microm Al(2)O(3), and for posts without any surface treatment (controls) (n=10). Forty glass fiber (GF) and 40 carbon fiber (CF) posts were submitted to 1 of 4 surface treatments (n=10) prior to MTBS testing: silane (S); silane and adhesive (SA); airborne-particle abrasion with 50-microm Al(2)O(3) and silane (ABS); airborne-particle abrasion, silane, and adhesive (ABSA). Two composite resin restorations (Filtek Z250) with rounded depressions in the lateral face were bilaterally fixed to the post with resin cement (RelyX ARC). Next, the specimen was sectioned with a precision saw running perpendicular to the bonded surface to obtain 10 bonded beam specimens with a cross-sectional area of 1 mm(2). Each beam specimen was tested in a mechanical testing machine (EMIC 2,000 DL), under stress, at a crosshead speed of 0.5 mm/min until failure. Data were analyzed by 2-way ANOVA followed by Tukey HSD test (alpha=.05). Failure patterns of tested specimens were analyzed using scanning electron microscopy (SEM). RESULTS: The 3-point bending test demonstrated significant differences among groups only for the post type factor for flexural strength, flexural modulus, and stiffness. The carbon fiber posts exhibited significantly higher mean flexural strength (P=.001), flexural modulus (P=.003), and stiffness (P=.001) values when compared with glass fiber posts, irrespective of surface treatment. An alteration in the superficial structure of the posts could be observed by SEM after airborne-particle abrasion. MTBS testing showed no significant effect for the surface treatment type; however, significant effects for post system factor and for interaction between the 2 factors were observed. For the carbon fiber post, the ABSA surface treatment resulted in values significantly lower than the S surface treatment. SEM analysis of MTBS-tested specimens demonstrated adhesive and cohesive failures. CONCLUSIONS: Airborne-particle abrasion did not influence the mechanical properties of the post; however, it produced undesirable surface changes, which could reduce the bond strength to resin cement. For the surface treatments studied, if silane is applied, the adhesive system and airborne-particle abrasion are not necessary.     

Flexural properties of fiber reinforced root canal posts.

OBJECTIVES: Fiber-reinforced composite (FRC) root canal posts have been introduced to be used instead of metal alloys and ceramics. The aim of this study was to investigate the flexural properties of different types of FRC posts and compare those values with a novel FRC material for dental applications. METHODS: Seventeen different FRC posts of various brands (Snowpost, Carbopost, Parapost, C-post, Glassix, Carbonite) and diameters, (1.0-2.1 mm) and a continuous unidirectional E-glass FRC polymerized by light activation to a cylindrical form (everStick, diameter 1.5 mm) as a control material were tested. The posts (n=5) were stored at room's humidity or thermocycled (12.000 x, 5 degrees C/55 degrees C) and stored in water for 2 weeks before testing. A three-point bending test (span=10 mm) was used to measure the flexural strength and modulus of FRC post specimens. RESULTS: Analysis of ANOVA revealed that thermocycling, brand of material and diameter of specimen had a significant effect (p<0.001) on the fracture load and flexural strength. The highest flexural strength was obtained with the control material (everStick, 1144.9+/-99.9 MPa). There was a linear relationship between fracture load and diameter of posts for both glass fiber and carbon fiber posts. Thermocycling decreased the flexural modulus of the tested specimens by approximately 10%. Strength and fracture load decreased approximately 18% as a result of thermocycling. SIGNIFICANCE: Considerable variation can be found in the calculated strength values of the studied post brands. Commercial prefabricated FRC posts showed lower flexural properties than an individually polymerised FRC material.     

玻璃纤维预拉伸对增韧光固化树脂基桩力学性能的影响

目的 研究玻璃纤维预拉伸对自行研制的高强玻璃纤维增韧光固化树脂复合材料（FRC）桩力学性能的影响。方法 利用加载装置将高强玻璃纤维分别拉伸0%、0.5%、1.0%后,按60%体积比浸入自行配置的光固化树脂基质,采用压膜法制成玻璃纤维增韧树脂基齿科桩,三点弯曲测试各试样的弯曲模量、弯曲强度和弯曲载荷,测试结果进行统计学分析。使用扫描电子显微镜观察FRC桩横截面和断裂面的形态。结果 玻璃纤维拉伸率对FRC桩的力学性能影响有显著差异,其中拉伸率为1.0%的玻璃纤维制成的FRC桩综合性能最佳,弯曲模量(20.40±1.40) GPa,弯曲强度(573.38±29.45) MPa,弯曲载荷(180.42±5.88) N,与未预拉伸的玻璃纤维增韧的FRC桩有显著差异(P<0.05)。结论 玻璃纤维预拉伸对FRC桩有增韧效果。     

Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements

Davis P, Melo LSD, Foxton RM, Sherriff M, Pilecki P, Mannocci F, Watson TF. Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Eur J Oral Sci 2010; 118: 197–201. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aims of this study were to evaluate the flexural strength of two different types of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Forty glass methacrylate‐based fibre posts (GC Fiber Post) and 20 glass fibre inter‐polymerizing network posts (everStick POST) were divided into three groups. Group 1 contained 20 GC posts that were bonded to a dual‐cure composite cement (UnifilCore). Group 2 contained 20 Stick Tech posts that had adhesive applied (Scotchbond Multipurpose resin) and were bonded to a dual‐cure composite resin cement (RelyX Unicem). Group 3 contained 20 GC posts that were pretreated with a silane‐coupling agent before being treated with resin and composite, as in group 1. A 4‐point bend test was carried out to failure on all of the groups. Failure modes were determined using scanning electron microscopy. Pretreatment of the post surface with the silane‐coupling agent did not increase the flexural strength. The flexural strength of the Stick Tech post was significantly lower than the flexural strength of the GC post. The mode of failure for the GC Posts was adhesive, whereas the Stick Tech posts failed cohesively. Different flexural strengths and failure modes were observed among the two fibre post–resin systems.     

Effects of chemical surface treatments of quartz and glass fiber posts on the retention of a composite resin

STATEMENT OF PROBLEM: Failure of a fiber post and composite resin core often occurs at the junction between the 2 materials. This failure process requires better characterization. PURPOSE: The purpose of this study was to evaluate the effect of 2 chemical solvents, hydrogen peroxide and methylene chloride, on the shear bond strength of quartz and glass fiber posts to a composite resin. MATERIAL AND METHODS: Twenty-four posts (3 +/-0.1 mm in length) were prepared for each quartz (LIGHT-POST (LP)) and glass fiber (Cytec blanco (CB)) post. Posts were horizontally embedded in acrylic resin with half of the post diameter exposed. The exposed surfaces were successively ground with 400-, 800-, and 1200-grit silicon carbide papers, to ensure uniform smoothness. The specimens were divided into 3 subgroups (n=8) representing different surface treatment techniques, including application of silane for 60 seconds (S), etching with hydrogen peroxide for 20 minutes (H), and etching with methylene chloride for 5 seconds (M). Silane-treated specimens served as controls. A dual-polymerized composite resin (Tetric EvoCeram) was placed in a polytetrafluoroethylene mold (30 x 2 mm) positioned upon the post specimens and polymerized for 20 seconds with a light-emitting diode (LED) polymerization unit. The specimens were stored in water at 37 degrees C for 24 hours. Shear bond strength values (MPa) of posts and composite resin cores were measured using a universal testing machine with a crosshead speed of 0.5 mm/min. Data were analyzed by 2-way analysis of variance (ANOVA). Post hoc Tukey intervals for comparison among the 2 post materials and 3 surface treatment techniques were calculated (alpha =.05). The effect of the chemical surface treatments on glass and quartz fiber post surfaces were examined with a scanning electron microscope (SEM). RESULTS: There were significant differences between the shear bond strength for LP and CB (P<.001). For all groups, the application of H showed the highest bond strength values. There was no significant difference between the S and M groups (P>.05). The SEM observations demonstrated that the fiber post surfaces were modified after chemical surface treatment techniques. CONCLUSIONS: The surface treatment of quartz and glass fiber posts with hydrogen peroxide significantly enhanced the shear bond strength of the composite resin tested due to its ability to dissolve the epoxy resin matrix used in each post. The lowest bond strength was obtained with M and S groups. Application of methylene chloride to the fiber post surfaces for 5 seconds was not effective in increasing the shear bond strength of the fiber post to composite resin.     

The flexural properties of fiber-reinforced composite with light-polymerized polymer matrix

PURPOSE: The aim of this study was to measure the flexural strength and the elastic modulus of composite resin with and without reinforcing fibers and to evaluate the reinforcing effect of various fibers. MATERIALS AND METHODS: A polyethylene fiber (Ribbond), a polyaramid fiber (Fibreflex), and three glass fibers (FibreKor, GlasSpan, Vectris) were used to reinforce composite resins. The flexural strength and elastic modulus of specimens in the three-point bending mode were measured using a universal testing machine at a cross-head speed of 1 mm/min after storage in water at 37 degrees C for 24 hours. All tests were carried out in a water bath at 37 degrees C. The data were analyzed using analysis of variance and the Sheffé test at P= 0.05. After testing, the fractured surface was evaluated using a scanning electron microscope at 50x, 500x, and 3,000x magnifications. RESULTS: Yield flexural strengths of nonreinforced resins were 48 to 56 MPa, and those of reinforced resins were 56 to 134 MPa. Ultimate flexural strengths of nonreinforced specimens were 96 to 119 MPa, and those of reinforced ones were 203 to 386 MPa. Elastic modulus of nonreinforced resin was 6 to 9 GPa, and fiber reinforcing increased the value to 9 to 15 GPa, while it had no effect in Ribbond. CONCLUSION: Most of the fibers used in this study increased both yield and ultimate flexural strengths of composite resins, with the exception of the yield strength of Vectris. GlasSpan, Fibreflex, and FibreKor were effective in reinforcing elastic modulus, while Ribbond had no effect on it. Unidirectional glass fibers and polyaramid fiber were effective in reinforcing both flexural strength and elastic modulus of composite resin.     

Three-point bending test of fiber posts.

Five different types of fiber posts (carbon fiber Composipost radio-opaque, quartz fiber Aestheti-Plus, carbon fiber Carbotech, glass fiber Light post, and silica fiber Snowpost) were submitted to a three-point bending test after being stored for 1 yr under three different conditions: dry storage at room temperature, storage in 37 degrees C water, and storage in bovine teeth that were endodontically treated and restored with composite resin. The posts were observed before and during the test by confocal microscopy. More voids were found within the Composipost radio-opaque than in other posts. Posts of all groups that were stored in water showed flexural strength values lower than posts that were stored dry. In all storage conditions, Carbotech posts showed higher flexural strength values than Composiposts and Snowposts, and Aestheti-Plus posts showed higher flexural strength values than Snowposts. Posts that were stored in bovine teeth showed flexural strength values similar to those of posts that were stored dry. It was concluded that fiber posts must not be in contact with oral fluids and that during the 1-yr storage in bovine teeth, they were sufficiently protected from this contact by the apical root canal filling and by the coronal composite resin filling.     

三种复合树脂与玻璃纤维桩的微拉伸强度研究

目的：3种复合树脂材料与玻璃纤维桩微拉伸粘结强度的对比研究。方法：45个Parapost玻璃纤维桩随机分为3组，分别用3种不同的复合树脂：可乐丽菲露AP-X^TM、Ceram—X、ParaCore双重固化复合树脂桩核材料粘固制成桩核样本，制备好的样本切割成截面为1．0mm×1．0mm的条状试件用于微拉伸强度测试。结果：ParaCore与Ceram—X的微拉伸粘结强度显著高于AP-X^TM（P〈0．05），ParaCore和Ceram—X与纤维桩的微拉伸粘结强度没有显著性差异（P〉0．05）。结论：ParaCore与Ceram-X与玻璃纤维桩的粘结性能较好，适于临床塑核使用。     

The effect of sandblasting on adhesion of a dual-cured resin composite to methacrylic fiber posts: microtensile bond strength and SEM evaluation

OBJECTIVES: To evaluate the influence of different surface treatments on the microtensile bond strength of a dual-cured resin composite to fiber posts. METHODS: Thirty-two glass methacrylate-based fiber posts (GC Corp.) were used in the study. Posts were divided into two groups, according to the surface pretreatment performed. Group 1: sandblasting (Rocatec-Pre, 3M ESPE). Group 2: no pretreatment. In each of the two groups posts received three types of additional "chair-side" treatments. (1) Silane application (Monobond S, Ivoclar Vivadent); (2) adhesive application (Unifil Core self-etching bond, GC); (3) no treatment was performed. A dual-cured resin composite (Unifil Core, GC) was applied on the posts to produce cylindrical specimens. Specimens were cut to obtain microtensile sticks that were loaded in tension at a cross-head speed of 0.5mm/min until failure. The morphology of the post/composite interface and the post surface morphology were evaluated under SEM. Statistical analysis was performed with two-way ANOVA and Tukey test for post hoc comparisons (p<0.05). RESULTS: Post surface pretreatment did not prove to be a significant factor in post-composite bond strength (p=0.08), whereas "chair-side" treatment modalities and the interaction between pretreatment and treatment showed a significant influence on bond strength (p<0.001). When no "chair-side" treatment was performed, bond strength was significantly higher on sandblasted posts. Additional adhesive application resulted in significantly lower bond strength on sandblasted posts. When no pretreatment was performed, silane application resulted in higher bond strength than adhesive application. CONCLUSIONS: Sandblasting may give an increase in microtensile strength to methacrylate-based glass fiber posts, eliminating the need for additional "chair-side" treatments. Reducing the number of clinical steps could contribute to simplify the clinical procedures.     

Flexural properties of endodontic posts and human root dentin.

OBJECTIVES: To evaluate the flexural modulus and flexural strength of different types of endodontic post in comparison with human root dentin. METHODS: Three different types of fiber-reinforced composite (FRC) posts and three metal posts each comprising 10 specimens (n=10) and 20 dentin bars were loaded to failure in a three-point bending test to determine the flexural modulus (GPa) and the flexural strength (MPa). Three randomly selected fiber posts of each group were evaluated using a scanning electron microscope (SEM) to illustrate the differences in mode of fracture. Data were subjected to a one-way ANOVA to determine significant differences between groups and the Bonferroni t-test multiple comparison was applied to investigate which mean values differed from one another with significance levels of P<0.05. RESULTS: The flexural modulus recorded for the dentin bars was 17.5+/-3.8 GPa. The values for posts ranged from 24.4+/-3.8 GPa for silica fiber posts to 108.6+/-10.7 GPa for stainless steel posts. The flexural strength for dentin was 212.9+/-41.9 MPa, while the posts ranged from 879.1+/-66.2 MPa for silica fiber posts to 1545.3+/-135.9 MPa for cast gold posts. The ANOVA test analysis revealed significant differences between groups (P<0.05) for flexural modulus and flexural strength mean values. SIGNIFICANCE: FRC posts have an elastic modulus that more closely approaches that of dentin while that for metal posts was much higher. The flexural strength of fiber and metal posts was respectively four and seven times higher than root dentin.     

Effect of silica coating and silanization on flexural and composite-resin bond strengths of zirconia posts: An in vitro study

STATEMENT OF PROBLEM: The bond strength of composite resin cores to the smooth surface of prefabricated zirconia-based ceramic posts is problematic because it might not be sufficient to ensure stability of the post-and-core system. It is also not clear whether any alteration of the post surface to provide additional mechanical or chemical retention would compromise flexural strength of the posts. PURPOSE: This study tested the effect of a tribochemical treatment on the bond strength (BS) between zirconia-based ceramic posts and composite resin and on the flexural strength (FS) of the posts. MATERIAL AND METHODS: For the BS test, 2 groups of specimens (n = 10) were prepared as follows: In the experimental (E) group, zirconia-based ceramic posts (Cosmopost), 21 mm long and 1.7 mm in diameter, were treated with a tribochemical silica coating and silanization system (Rocatec). For the control (C) group, zirconia-based ceramic posts were used as supplied by the manufacturer. For the 2 groups, posts were centered and vertically positioned in a metal mold, and composite resin (Tetric Ceram) was polymerized around the posts to form rings (6 mm diameter x 4 mm height). All specimens were positioned in a universal testing machine, and a load was applied axially on the protruding heads of posts in a shear push-out mode test until bond failure (MPa). Fracture mode was assessed as cohesive, cohesive/adhesive, or adhesive. Following this, the FS of the posts was measured in MPa using a 3-point bending test. Data were recorded and statistically analyzed using the Student t test for both tests (alpha = .01). RESULTS: Mean fracture load values +/- SDs for the BS test were 28.1 +/- 2.3 MPa and 8.9 +/- 3.97 MPa for the E and C groups, respectively. The mean FS values were 1544.9 +/- 214.1 MPa and 844.8 +/- 50.8 MPa for the E and C groups, respectively. The tribochemically treated posts exhibited significantly higher values for both bond strength to composite resin and resistance to fracture when compared to posts in the control group (P < .001). Fracture analysis showed 100% cohesive/adhesive fractures for group E specimens and 100% adhesive fractures for group C specimens. CONCLUSIONS: The use of a tribochemical silica coating process and silanization on zirconia-based ceramic posts increased both the bond strength to composite resin as well as the fracture strength of posts.     

吸水对充填复合树脂抗弯性能的影响

目的：研究吸水对充填复合树脂抗弯强度和弹性模量的影响。方法将混合型前牙充填复合树脂(GDA)和通用型充填复合树脂(GCK)根据ISO FDIS 4049：1999标准制备为大小(25±2)mm ×(2±0.1)mm ×(2±0.1)mm的柱状试件,分为GDA1,GDA30,GDA90,GDA150,GCK1,GCK30,GCK90,GCK150共8组,每组13个样本。分别放入(37±1)oC的去离子水中浸泡1天、30天、90天、150天。利用三点弯曲实验测量并计算试件的三点抗弯强度和挠曲弹性模量。在体视显微镜和扫描电子显微镜下观察断面形貌。结果 GDA30和GCK30组分别与GDA1和GCK1组相比,抗弯强度的差异均无统计学意义。 GDA90及GDA150组的抗弯强度随浸水时间延长而逐渐降低,差异具有统计学意义;GCK90及GCK150组与GCK1组抗弯强度的差异具有统计学意义,但GCK90及GCK150组之间抗弯强度的差异无统计学意义。 GDA及GCK不同浸水时间的各组之间,其弹性模量的差异无统计学意义。结论在浸水150天的有限时间内,吸水会使充填复合树脂GDA和GCK的抗弯强度降低,但不会影响其弹性模量。     

The static strength and modulus of fiber reinforced denture base polymer.

OBJECTIVES: Partial fiber reinforcements have been employed to strengthen dentures both during repair and in the manufacturing process. The reinforcing fibers can be evenly distributed in the denture base polymer or alternatively fiber-rich phase in the denture base polymer can form a separate structure. The aim of this study was to determinate static three-point flexural strength and modulus of denture base polymer that had been reinforced with different fiber reinforcements. METHODS: The test specimens (3 x 5 x 50 mm) were made of auto-polymerized denture base polymer and reinforced with different fiber reinforcements. The test groups were: (A) no fibers; (B) non-impregnated polyethylene fibers; (C) light-polymerized monomer impregnated glass fibers; (D) porous polymer preimpregnated glass fibers and (E) light-polymerized monomer-polymer impregnated glass fibers. The fibers were oriented parallel to the long axis of the specimen and embedded into the denture base resin on the compression side (n=7) or tension side (n=7). Dry specimens were tested with three-point static flexural strength test set-up at crosshead speed of 5 mm/min. RESULTS: The statistical analysis by two-way analysis of variance showed that the brand and the location of the fiber reinforcements significantly influenced the flexural strength (p<0.0001). However, the location of the fiber reinforcements did not influence the flexural modulus (p<0.722). SIGNIFICANCE: The results suggest that impregnated and preimpregnated fibers reinforce denture base polymer more than non-impregnated fibers. Fiber reinforcements placed on the tensile side resulted in considerably higher flexural strength and flexural modulus values compared with same quantity of fibers placed on the compression side.     

Influence of fiber type and wetting agent on the flexural properties of an indirect fiber reinforced composite

STATEMENT OF PROBLEM: Different fiber types are available for reinforcing composite restorations. Little information exists regarding optimal fiber type/bonding agent combinations. PURPOSE: This in vitro study examined the influence of storage time and 2 fiber wetting agents on the flexural properties of an indirect dental composite reinforced by 3 fiber types. MATERIAL AND METHODS: Three types of fiber (ultra-high molecular weight polyethylene, Kevlar, and Glass fiber) were used to reinforce samples of an indirect composite (Artglass) prepared to test flexural properties. Each fiber type was used to prepare 3 groups of 10 specimens after fiber wetting with an unfilled or a filled resin bonding agent. All fibers were weighed to an accuracy of 0.01 mg to standardize the amount of fiber placed in the base (tensile side) of the specimen preparation mold (2 x 2 x 25 mm). Fiber-reinforced samples wetted with the unfilled resin were stored for 24 hours before flexural testing, whereas separate groups of fiber-reinforced samples wetted with the filled resin were tested after both 24 hours and 6 months storage in water at 37 degrees C. Two additional groups of unreinforced composite control specimens (10 samples per group) were prepared, one for each of the 2 storage times, resulting in 11 groups total. Mean flexural strengths (MPa) and flexural modulus (GPa) values were determined in a 3-point bend test at a crosshead speed of 1 mm/min by use of a universal testing machine. Comparisons between means were performed with 2- and 1-way analysis of variance tests (alpha=.01) to demonstrate the influence of storage time, fiber wetting agent, and fiber type on the flexural properties of the indirect dental composite tested. RESULTS: Significant increases (124% to 490%) in mean flexural strength (P<.01) were found for all fiber-reinforced groups in comparison to the unreinforced controls at both storage time intervals. The silane containing unfilled bonding agent gave the greatest reinforcing effect (364%) when used with the glass fiber material. After 6 months storage in water, a significant decline (28%) occurred in the mean flexural strength of the glass fiber-reinforced specimens (P<.01) when the filled bonding agent was used. CONCLUSION: Within the limitations of this study, the choice of fiber type and wetting agent was shown to have a significant positive influence on the flexural properties of the fiber-reinforced composite. When used with the silane containing unfilled bonding agent, the glass fiber increased the mean flexural strength of the unreinforced indirect composite by 364%.     

Comparison of the push-out strength of two fiber post systems dependent on different types of resin cements

The purpose of this study was to compare the push-out strength of glass fiber posts dependent on the resin cement. One hundred human teeth were divided into five groups (n = 20). Two glass fiber post systems (DT Light SL (DTSL) and RelyX Fiber Post (RF)) were used. DTSL posts were cemented with one "etch & rinse" system (ER) or one of three self-adhesive resin cements (SA). The RF posts were cemented with RelyX Unicem. Afterwards, half of the specimens were thermocycled (TC; 5°C/55°C, 5,000 cycles). All specimens were cut into disks (thickness, 2 mm). The push-out test was performed (crosshead speed, 1 mm/min), fracture types were determined (×25 and ×40 magnification), and statistical analysis was performed (one-way analysis of variance (ANOVA), Scheffe test, p < 0.05). One-way ANOVA showed a significant influence of the resin cement on the push-out strength of the glass fiber posts before thermocycling (p < 0.001). After TC, no significant differences were detected. Microscopic evaluation showed mainly adhesive failures between post and cement for ER or mixed fractures for SA. The bond strength of adhesively cemented glass fiber posts is not dependent on the type of resin cement after TC. The use of SA can lead to bond strength values comparable to ER. Self-adhesive resin cements could be used just as well as resin cements with "etch & rinse" adhesive systems for the cementation of glass fiber posts.     

Flexural properties and impact strength of denture base polymer reinforced with woven glass fibers.

OBJECTIVES: The present investigation was undertaken to determine the reinforcing effect of woven glass fibers on deflection, flexural strength, flexural modulus and impact strength of acrylic denture base polymer. METHODS: Three silanized or unsilanized woven glass fibers were used. Specimens were made by heating the denture cure resin dough containing glass fibers, which were sheathed in the dough. Specimens with four different thicknesses and of five different types were made, incorporating the glass fiber. Three-point flexural test and flywheel type impact test were employed to determine the flexural properties and impact strength. RESULTS: When specimens contained unsilanized glass fiber, the flexural strength in specimens of 1 and 2 mm thickness and the impact strength in specimens of 2 mm thickness were higher than those of specimens without glass fiber (p < 0.01). On the contrary, the flexural strength and deflection in specimens reinforced with silanized glass fiber of 1 mm thickness were significantly higher (p < 0.01, p < 0.05) than those of unreinforced specimens. Further, the impact strength in specimens reinforced with silanized glass fiber of 2 mm thickness was significantly higher (p < 0.01) than that of unreinforced specimens. Statistically significant differences were found in the flexural strength (p < 0.05) and in the impact strength (p < 0.01) when specimens of 4 mm thickness were reinforced with two or three unsilanized glass fibers. SIGNIFICANCE: The reinforcement with glass fiber was effective in thin specimens, and the reinforcing effect increased with the increase of the number of glass fibers in the case of thick specimens.     

预浸润玻璃纤维强化复合树脂的力学性能

大学口腔医院　修复科;2.北京大学口腔医院　材料教研室,北京100081) [摘要]　目的　研究预浸润玻璃纤维对不同复合树脂的强化效果。方法　制作Sinfony和belleGlass两种复合树脂的加入和不加预浸润玻璃纤维的标准试件(25 mm×2 mm×2 mm),于(37±1)℃的蒸馏水环境中保存24 h后,在万能力学试验机上测试弯曲强度和弹性模量。结果　Sinfony复合树脂加入纤维后弯曲强度和弹性模量显著提高,分别为(555·76±67·31)MPa和(12·59±3·06)GPa,较不加玻璃纤维试件平均提高了4·9和2·5倍(P=0);belleGlass复合树脂加入纤维后弹性模量有提高,为(14·10±2·88)Gpa,较不加玻璃纤维试件平均提高了0·9倍(P=0),而弯曲强度提高不明显。结论　预浸润玻璃纤维可以显著提高复合树脂的力学性能,但对不同复合树脂的强化效果有明显差别。     

Diametral tensile strength of composite core material with cured and uncured fiber posts

The aim of this study was to determine the influence of different types of posts and post head designs on the fracture resistance of a composite resin core material using the diametral tensile strength (DTS ). Seventy-five disc specimens were prepared using a composite core and prefabricated glass fiber posts and were divided into four test groups and one control group (n=15). The use of fiber posts reduced the DTS of the composite core material; the DTS value of the control material was significantly higher (p=0.05) than all of the test groups.     

Evaluation of flexural resistance of a denture base acrylic resin reinforced with glass fiber and with composite resin

The objective of this study was to evaluate the flexural strength of denture base resin reinforced with glass fibers and with a laboratorial composite resin. Group G1 was formed with specimens made of acrylic resin. Group G2 was formed with the same acrylic resin but reinforced with a glass-fiber system, and G3 was reinforced with the composite resin. A flexural strength test was performed in all groups (n=10). The mean value for the G1 was 86.70 MPa +/- 6.48, for G2 it was 86.60 MPa +/- 15.01 and for G3 it was 108.90 + 11.03. The addition of glass fiber did not increase the flexural strength however the use of a resin-based composite produced significant reinforcement.