Water Storage Period Research Articles

IN VITRO COMPARATIVE STUDY OF MODULUS OF ELASTICITY BETWEEN DENTINE SUBSTITUTE AND FLOWABLE COMPOSITE RESIN

Objectives: This study will analyze the modulus of elasticity of novel smart dentine replacement (SDR) and a flowable composite resin when used as a base material under composite restoration. Materials: 1. Smart Dentine Replacement (SDR) 2. X-flow (flowable composite) Methods: Forty eight specimens will be fabricated for elastic modulus test. The specimens will be divided into two groups, twenty four specimens of SDR and twenty four specimens of X-flow. Each group will be further divided according to the aging condition into three subgroups, each subgroup contain eight specimens. In which modulus of elasticity will be measured after 24 hrs and then measured after storage in distilled water for one month then measured after storage in distilled water for three months. Then the data will be statistically analysed. Results: Elastic modulus of both Surefil SDR and X-Flow increases with the increase in the storage period in distilled water. Conclusion: SDR has higher elastic modulus than X-Flow.

Is chlorhexidine-methacrylate as effective as chlorhexidine digluconate in preserving resin dentin interfaces?

ObjectivesThe aim of the current study was to evaluate the effect of 2% CHX and 2% CHX-methacrylate compared to the resin–dentin bonds created by a two-step etch-and-rinse adhesive system after 24h, 6min and 12min. MethodsMicrotensile bond strengths and interfacial nanoleakage within resin–dentin interfaces created by Adper Single Bond 2, with or without CHX or CHX-methacrylate pre-treatment for 30s on acid-etched dentin surfaces, were evaluated after 24h, 6min and 12min of storage in distilled water at 37°C. ResultsTwelve months of storage resulted in a significant decrease in microtensile bond strength in the control group, and significant increases in silver nanoleakage. In contrast, Single Bond 2+CHX, and to a greater extent CHX-methacrylate, significantly reduced the rate of deterioration of resin–dentin interfaces over the 12min water storage period, in terms of bond strength. ConclusionsSimilar to Single Bond 2+CHX, Single Bond+CHX-methacrylates reduced the degradation of resin-bonded interfaces over a 12 month storage period. Thus it can be concluded that Single Bond 2+CHX-methacrylate may be important to improve durability of bonded interfaces and therefore, prolong the life span of adhesive restorations. Clinical significanceAlthough CHX primers have been shown to enhance the durability of etch-and-rinse adhesives, that protection is lost after 2h. The use of CHX-methacrylate should last much longer since it may copolymerize with adhesive monomers, unlike CHX.

Influence of water storage on fatigue strength of self-etch adhesives

ObjectivesThe purpose of this study was to determine enamel and dentin bond durability after long-term water storage using self-etch adhesives. MethodsTwo single step self-etch adhesives (SU, Scotchbond Universal and GB, G-ӕnial Bond) and a two-step self-etch adhesive (OX, OptiBond XTR) were used. The shear bond strength (SBS) and shear fatigue strength (FS) of the enamel and dentin were obtained with and without phosphoric acid pre-etching prior to application of the adhesives. The specimens were stored in distilled water at 37°C for 24h, 6 months, and one year. A staircase method was used to determine the FS using a frequency of 10Hz for 50,000 cycles or until failure occurred. ResultsThe SBS and FS of enamel bonds were significantly higher with pre-etching, when compared to no pre-etching for the same water storage period. The FS of dentin bonds with pre-etching tended to decrease relative to no pre-etching at the same storage period. For the one year storage period, SU and GB with pre-etching showed significantly lower FS values than the groups without pre-etching. ConclusionsThe influence of water storage on FS of the self-etch adhesives was dependent on the adhesive material, storage period and phosphoric acid pre-etching of the bonding site. Clinical significancePhosphoric acid pre-etching of enamel improves the effectiveness of self-etch adhesive systems. Inadvertent contact of phosphoric acid on dentin appears to reduce the ability of self-etch adhesives to effectively bond resin composite materials.

Effect of proanthocyanidin incorporation into dental adhesive on durability of resin–dentin bond

BackgroundProanthocyanidin has shown to have beneficial effects on dentin bonding via its collagen cross-linking and protease inhibitory effects. ObjectiveThis study evaluated the effect of incorporation of 1–3% PA into a dental adhesive on durability of resin–dentin bond. Materials and methodsThe experimental adhesive was first formulated by combining 50wt% comonomer mixtures with 50wt% ethanol. PA was then added to the ethanol-solvated adhesive to yield three groups of adhesives at concentrations of 1.0wt%, 2.0wt% and 3.0wt%. The PA-free adhesive served as control. Flat dentin surfaces from forty extracted third molars were etched with 32% phosphoric acid and the specimens were randomly assigned to one of the four adhesive groups. Two layers of experimental adhesives were applied to etched dentin and light-cured for 20s after solvent evaporation. Composite build-ups were performed using Filtek Z250 (3M ESPE). The bonded teeth were divided into three subgroups for different methods of storage: (1) 24h indirect water exposure (IE), (2) 6 M IE and (3) 6 M direct water exposure (DE). After the designated period of water storage, the bonded teeth were sectioned into 0.9mm×0.9mm beams for bond strength testing. Bond strength data were evaluated by two-way ANOVA and Tukey׳s tests (α=0.05). Interfacial nanoleakage was examined using a field-emission scanning electron microscopy. Two-way ANOVA and Tukey׳s tests were used to examine the effects of PA concentration and water exposure on bond strength and percentage of nanoleakage (α=0.05). ResultsTwo-way ANOVA showed that the factors, water exposure and PA concentration had a significant effect on bond strength (p<0.001). Interaction between the two factors was also significant (p<0.001). Bond strength of all four adhesives decreased with PA concentrations and ageing. Type of water exposure had no effect on the bond strength of PA-incorporated adhesive; while direct water exposure significantly reduced the bond strength of PA-free adhesive. Conversely, the factors, water exposure and PA concentration showed a significant effect on nanoleakage percentage (p<0.001). Interaction between the two factors was not significant (p>0.05). ConclusionIncorporation of proanthocyanidin into a dental adhesive did not prevent resin–dentin bond degradation over time.

Initial and long-term bond strengths of one-step self-etch adhesives with silane coupling agent to enamel-dentin-composite in combined situation.

This study evaluated the effect of adding silane coupling agent on initial and long-term bond strengths of one-step self-etch adhesives to enamel-dentin-composite in combined situation. Cervical cavities were prepared on extracted molars and filled with Clearfil AP-X. After water-storage for one-week, the filled teeth were sectioned in halves to expose enamel, dentin and composite surfaces and then enamel-dentin-composite surface was totally applied with one of adhesive treatments (Clearfil SE One, Clearfil SE One with Clearfil Porcelain Bond Activator, Beautibond Multi, Beautibond Multi with Beautibond Multi PR Plus and Scotchbond Universal). After designed period, micro-shear bond strengths (µSBSs) to each substrate were determined. For each period of water-storage, additive silane treatments significantly increased µSBS to composite (p<0.001). On the other hand, they significantly decreased µSBS to dentin (p<0.001), although did not have adverse effect on µSBS to enamel (p>0.05). Moreover, the stability of µSBS was depended on materials and substrates used.

Methacrylate bonding to zirconia by in situ silica nanoparticle surface deposition

ObjectiveThis study introduces an innovative method to enhance adhesion of methacrylate-based cements to yttria-stabilized zirconia (Y-TZP) by means of a silica-nanoparticle deposition process. MethodsTwo alkoxide organic precursors, tetraethyl-orthosilicate (TEOS) and zirconium tert-butoxide (ZTB) were diluted in hexane at different concentrations in order to obtain several experimental materials to enhance deposition of a SiOx reactive layer to Y-TZP. This deposition was attained via sintering alkoxide precursors directly on pre-sintered zirconia (infiltration method—INF) or application on the surface of fully sintered zirconia (coating method—COA). Untreated specimens and a commercial tribochemical silica coating were also tested as controls and all the treated Y-TZP specimens were analyzed using SEM-EDX. Specimens were bonded using silane, adhesive and dual-cure luting cement and submitted to shear bond strength test after different water storage periods (24h, 3-, 6- and 12-months). ResultsSEM-EDX revealed Y-TZP surface covered by silica nanoclusters. The morphology of silica-covered Y-TZP surfaces was influenced by sintering method, employed to deposit nanoclusters. High bond strength (MPa) was observed when using COA method; highest TEOS percentage achieved the greatest bond strengths to Y-TZP surface (36.7±6.3 at 24h). However, bonds stability was dependent on ZTB presence (32.9±9.7 at 3 months; 32.3±7.1 at 6 months). Regarding INF method, the highest and more stable resin–zirconia bond strength was attained when using experimental solutions containing TEOS and no ZTB. Both sintering methods tested in this study were able to achieve a bonding performance similar to that of classic tribochemical strategies. SignificanceThis study demonstrates that it is possible to achieve a reliable and long-lasting bonding between yttria-stabilized zirconia ceramic and methacrylate-based cements when using this novel, simple, and cost-effective bonding approach.

Bond strength of novel CAD/CAM restorative materials to self-adhesive resin cement: the effect of surface treatments.

To evaluate the effect of different surface treatments on the microtensile bond strength (μTBS) of novel CAD/CAM restorative materials to self-adhesive resin cement. Two types of CAD/CAM restorative materials (Vita Enamic [VE] and Lava Ultimate [LU]) were used. The specimens were divided into five groups in each test according to the surface treatment performed; Gr 1 (control; no treatment), Gr 2 (sandblasted [SB]), Gr 3 (SB+silane [S]), Gr 4 (hydrofluoric acid [HF]), and Gr 5 (HF+S). A dual-curing self-adhesive resin cement (Bifix SE [BF]) was applied to each group for testing the adhesion after 24 h of storage in distilled water or after 30 days using the μTBS test. Following fracture testing, specimens were examined with a stereomicroscope and SEM. Surface roughness and morphology of the CAD/CAM restorative materials were characterized after treatment. Data were analyzed using ANOVA and Tukey's test. The surface treatment, type of CAD/CAM restorative material, and water storage periods showed a significant effect on the μTBS (p<0.001). For the LU/BF system, there was no significant difference in the bond strength values between different surface treatments (p>0.05). On the other hand, for the VE/BF system, surface treatment with HF+S showed higher bond strength values compared with SB and HF surface treatments (p<0.05). Surface roughness and SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments. The effect of surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement is material dependent. The VE/BF CAD/CAM material provided higher bond strength values compared with the LU/BF CAD/CAM material.

Study of evaporation and seepage losses from farm pond in saline area

Farm ponds have traditionally been used as an economical and efficient way to retain water for livestock, watering and irrigation. Water harvesting through farm pond and utilization of conserved water for cultivated field is very crucial for promoting sustainable agriculture in Saline Area. The traditional concept of locating dug out structures at strategic locations was revived and promoted as farm ponds. To overcome the drought prone situation in drought affected districts of Vidarbha, constructions of number of dug out type ponds (water storage structures) for harvesting of excess rain water on farmers field is the best option available and is being implemented since last three years. Research Concluded evaporation and seepage loss component from unlined dug out type farm pond was found to be 58.82 and 12.60 cm, respectively during three months of water storage period (October to December). The evaporation component in Lined Black polyethylene was found to be in the range of 19.51 to 24.60 per cent of storage period. The one protective irrigation using harvested in runoff water in dug out farm ponds resulted in increases in the dry land productivity of Cotton and Gram crops to 47 to 55 per cent and 43 to 58 per cent, respectively.

Effect of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin

ObjectivesThe aim of this research was to investigate the effects of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin. MethodsPMMA powder was applied after heat treatment at 100°C for 2h (code: HT100) or 130°C for 2h (code: HT130). The test specimens were fabricated from autopolymerizing resin to investigate the flexural properties of denture base resin cross-linked with methacrylated dendrimer, the surface microhardness of PMMA beads, and the thickness of the swollen layer of PMMA beads. The specimens were autopolymerized, and all specimens were stored in 37°C water for 24h. Half of the specimens were immersed in 37°C water for an additional 6 months (water storage period: 24h and 6 months). The flexural strength and flexural modulus (n=10/group) were measured with a three point bending test. Statistical analysis was performed using ANOVA and the Newman–Keuls test at a significance level of 0.05. ResultsHeat treatment and the water storage period had a significant effect on flexural strength. The flexural strength of HT130 showed significantly higher values than in other groups. The surface microhardness of PMMA beads of HT130 showed a significantly greater microhardness than other groups. The thickness of a swollen layer of PMMA beads of HT100 and HT130 was significantly decreased. ConclusionsThe flexural strength and the surface microhardness were increased after heat treatment at 130°C. The thickness of a swollen layer of PMMA beads was decreased after heat treatment.

Stress and Deformation Characteristics of Rock-Fill Dam with Asphalt Concrete Core Wall Founded on Deep Overburden

Abstract: The stress and deformation of rock-fill dam with asphalt concrete core wall founded on deep overburden is calculated and analyzed by Duncan E-ν model and double-yield-surface model through three-dimensional finite element method. The stress and deformation of dams in water storage period is compared by the two models, the results show that the deformation distribution of dam core via two different models are coincide one another. The horizontal displacement and vertical displacement of rock-fill dam with asphalt concrete core wall by double-yield-surface model is smaller than which by Duncan E-ν model in the period of water storage. Furthermore, the horizontal displacement and vertical displacement by double-yield-surface model, which are close to the practical test data through the deformation via two models are in good agreement. The analysis of core-wall stress via double-yield-surface model is more reasonable than the Duncan E-ν model. The analysis result of resisting hydraulic fracturing of core dams by DuncanE-ν model is coincide which of core dams by double-yield-surface model.

Back Analysis on Deformation of Concrete Faced Rockfill Dam Based on Prototype Monitoring

Material properties, calculation models and parameters are the main factors affect the simulation results of concrete face rockfill dams. According to the Baixi project, a 3D numerical model was built including the concrete face, filled rock, rock foundation and peripheral joint. Then, based on the deformation monitoring data during the construction and water storage period, the Duncan E-B model parameters were back analyzed. Finally, the sedimentation of dams, stress and strain of concrete face was simulated, and the actual working performance of concrete face and filled rock was studied.

Effect of Three Gorges Reservoir on River-Connected Lakes in Central Yangtze River

As a very critical indicator of the health of the lake, water level of the river-connected lakes is influenced by both watershed inflows and the mainstream. Lakes connected to the Yangtze River has showed big differences since the impoundment of the TGR in 2003, as the hydrological regime in central Yangtze River has changed a lot. In order to grasp the effect of the TGR on the river-connected lakes, based on the water level data of four typical stations in Poyang Lake during the water release operation and storage period before and after the impoundment, the variation of water level is compared and discussed. It is shown that water level of Poyang Lake has undergone changes. In the water release operation stage, the average water level is higher, but in the storage period from late September to October, the average water level of the lake lower than before. In addition, it is pointed out that the extent is gradually reduced from north to south, as the max influence water level is about 1.5 meters and the average influence water level is about 0.6 meters in Hukou station. However, considering the time since the dam n period has not been long, the reservoir effect still needs to be further assessed based on long-term monitoring.

Effects of solvent drying time and water storage on ultimate tensile strength of adhesives

Simplified adhesives are a blend of monomers with solvents that are expected to evaporate before light curing. The aim of the present study was to evaluate the effects of drying time and water storage on the ultimate tensile strength (UTS) of three adhesives: Adper Single Bond 2 (ASB), One-Step Plus (OSP) and Clearfil S(3) Bond (CSB). Dumbbell-shaped samples from each adhesive were prepared in three groups: (a) air drying prior to light curing; (b) no drying equal to active air drying; and (c) 3-h drying. Each group was further divided into two subgroups of no storage or 7days' water storage, prior to the UTS measurement (n=10). Material, drying-time, and storage had a significant effect on UTS, and the interactions of the factors were also significant (P<0.05). OSP showed a higher evaporation rate under passive air drying, and OSP and CSB showed higher UTS values compared to ASB (P<0.05). Air drying improved UTS in OSP and CSB, but not in ASB. Likewise, water storage only affected the UTS of OSP and CSB. The effects of air drying and water storage period on UTS are material dependent. Whenever solvent evaporation improved the UTS of adhesive, water storage decreased it. The all-in-one self-etching adhesive can maximize its best properties when the solvent is dried for an extended period.

Impacts and Implications of Major Changes Caused by the Three Gorges Dam in the Middle Reaches of the Yangtze River, China

The impoundment of the Three Gorges Dam (TGD) has disturbed the hydrological regime downstream and has directly affected the relationship between the Yangtze River and Dongting Lake. To trace the realistic and potential impacts, this paper examined the changes of the channel morphology and sedimentology caused by the TGD through a field survey on the channel cross-sections and then analyzed the impact on lake water level through BP neural networks. The possible impacts on inundation patterns in lake wetlands were studied based on the lake basin DEM. The results indicate that drastic sediment decline and severe channel erosion are putting considerable pressure on the river and lake. Changing river channels are evident in some monitoring cross-sections. Dongting Lake, for the first time, changed from trapping to supplying net sediment to the Yangtze River. During the water storage periods of the TGD, the water level decreased 2.03 m in 2006 and 2.11 m in 2009 at the outlet of the lake, with extreme decreases up to 3.30 m and 3.02 m, respectively. These changes have inevitably induced alterations in the inundation patterns of the lake wetlands, which in turn have disturbed the ecological function of lake wetlands as habitats for both migratory birds and aquatic fish. The serious droughts in Dongting Lake recent years were largely connected with the above changes. Therefore, proper attention should be paid to this occurrence.

Effect of Silver Diamine Fluoride on Microtensile Bond Strength to Dentin

The aim of this in vitro study was to investigate the effect of the cariostatic and preventive agent silver diamine fluoride (SDF) on the microtensile bond strength of resin composite to dentin. Forty-two caries-free, extracted molars were flattened occlusally and apically using a diamond saw, and the exposed occlusal dentin was polished with a series of silicon carbide papers, all under water irrigation. The teeth were then randomly divided into six groups of seven teeth each that were treated as follows: 1) Peak SE self-etch bonding agent; 2) 12% SDF + Peak SE; 3) 38% SDF + Peak SE; 4) Peak LC etch-and-rinse bonding agent; 5) 12% SDF + Peak LC; and 6) 38% SDF + Peak LC. Four-millimeter buildups of Amelogen Plus were incrementally placed on all teeth; after a 24-hour storage period in distilled water, the specimens were sectioned perpendicular to the adhesive interface to produce beams of cross-sectional surface area measuring approximately 1 mm(2). The beams were placed on a microtensile testing machine, which utilized a single-speed pump motor and force gauge at 20 kgf × 0.01 second to record maximum tensile force before failure occurred. Two-way analysis of variance and post hoc Tukey tests were performed to compare the effects of the SDF on microtensile bond strength, with statistical significance set at α = 0.05. None of the experimental groups treated with different concentrations of SDF showed a significant difference in bond strength compared to the control groups, and there was no significant difference in bond strength between self-etch and etch-and-rinse groups. However, the effect of SDF on self-etch bonded teeth compared to etch-and-rinse bonded teeth was statistically significant (p=0.0363), specifically at the 12% concentration. SDF does not adversely affect the bond strength of resin composite to noncarious dentin.

Effect of three prophylaxis methods on surface roughness of giomer

Plaque and stains are removed by prophylaxis methods from tooth surfaces. Since prophylaxis methods can have a detrimental effect on the surface finish of restorations, the aim of this in vitro study was to investigate the effect of three prophylaxis methods, including pumice with rubber cup, pumice with brush, and air-powder polishing device (APD) on the surface roughness of giomer. Sixty four cylindrical giomer (Beautifil II, Shofu) samples with a diameter of 6 mm and a height of 2 mm were used. Subsequent to a 3-month period of storage in distilled water at 37°C, the samples were randomly divided into four groups of 16. In group 1 (control), no prophylaxis procedure was carried out. In groups 2 to 4 the samples were exposed to pumice with rubber cup, pumice with brush, and APD prophylaxis methods, respectively. The surface roughness of the samples was measured using a profilometer and the effect of different prophylaxis methods on surface topography was characterized by atomic force microscopy (AFM). All data were analyzed by one-way ANOVA and Duncan's post hoc test at a significance level of P < 0.05. There were statistically significant differences in surface roughness among the groups (P < 0.0005). Furthermore, in pairwise comparisons there were statistically significant differences between all the groups (P < 0.05). The roughest surfaces, in descending order, were observed with the use of APD, pumice with brush, and pumice with rubber cup. The use of different prophylaxis methods resulted in an increased surface roughness of giomer compared with the control group. APD prophylaxis exerted the most detrimental effects on the surface of giomer.

Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers' instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage, decreasing thereafter.

Effect of polymerisation techniques on residual monomer amount released from different acrylic resins

The purpose of this study was to investigate the influence of different polymerisation methods (heat, auto-, injection moulding and microwave) with curing processes (conventional, short- and long-term terminal boiled heat polymerisation and room temperature polymerisation) in combination with varied water storage periods (24 h, 7 and 30 days) on the residual methyl methacrylate (MMA) contents of different dental acrylic resins. Twelve discs were fabricated for each denture base material. Specimens were immersed immediately in separate light proof glass bottles containing 20 mL 75% ethanol and 25% deionised water. Residual monomer (MMA) which eluted from acrylic resins was analysed with high performance liquid chromatography. Data were analysed by two-way analysis of variance and Tukey honestly significant difference tests. The MMA monomer amount eluted from autopolymerised acrylic resin groups (p<0·01) was higher than that from the other groups. Microwave polymerised acrylic resin showed the lowest residual monomer amount compared to the other acrylic resins (p<.01).

Crystal growth by restorative filling materials

This study examined the activity and ability of materials to mineralize teeth in gaps, simulating microleakage between the materials and teeth. Three restorative materials (two glass ionomer cements and a compomer) were used in this study. Cured disks of restoratives were placed over flat human tooth surfaces (enamel and dentin), separated by a standardized 20-μm interfacial space, and stored in water for 24 h or 1 yr. After the water-storage period, the materials were detached from the teeth and the opposing surfaces were examined by scanning electron microscopy (SEM) and electron probe micro analysis (EPMA).Hemispherical-shaped precipitations, composed of minute semicircle plate-like crystals, were observed by SEM on the enamel surface after 1 yr of water storage for glass ionomer cement. The amount of crystal growth with the chemical-cured type of glass ionomer cement was greater than with the dual-cured type of glass ionomer cement. However, there was no crystal formation in the compomer. Moreover, no structural changes were observed on dentin surfaces for any material in water after 1 yr. The elements detected in the crystals by EPMA were calcium (Ca), phosphorus (P), and aluminum (Al). The two glass ionomer cements tested have the ability to induce crystals whose composition might be derived from cured glass ionomers.

Fractographic analysis, accuracy of fit and impact strength of acrylic resin

This study evaluated accuracy of fit, impact strength, types and morphology of fractures of a microwave acrylic resin polymerized with a cycle alternative to that recommended by the manufacturer. Onda Cryl was polymerized according to the manufacturer's instructions (MC), 3 min at 360 W, 4-min pause, and 3 min at 810 W; and with an alternative cycle (AC) of 6 min at 630 W. Accuracy of fit was measured at 3 points at the right (A) and left (B) ridge crests and at the midline (C) on the posterior palatal seal for each denture base (n = 10/group). The measurements were taken immediately after finishing and after 30-day storage in water. The impact strength test (Charpy method) was performed with a 40 kJ/cm load (n = 20/group). Fractographic analysis was accomplished for all fragments and the fracture types were characterized by means of their morphology, crack propagation angles and microstructure. Accuracy of fit data were analyzed by ANOVA, impact strength and radius values were compared by the t test, and the fractographic analysis data, by the Wilcoxon Mann-Whitney test. The significance level was fixed at p < 0.05. No statistical differences were found between the two cycles of polymerization used. However, after the 30-day storage period in water, the denture bases showed better fit (P < .05). Most of the fractures were classified as brittle (MD: 70%, AC: 80%). Based on the results of this study, it could be concluded that both polymerization cycles are adequate to polymerize the denture resin studied.