Water Storage Period Research Articles

Soil water regime estimated from the soil water storage monitored in time

During the vegetation season, the water storage in the soil aeration zone is influenced by meteorological phenomena and by the vegetated cover. If the groundwater table is in contact with the soil profile, its contribution to water storage must be considered. This impact can be either monitored directly or the mathematical model of the soil moisture regime can be used to simulate it. We present the results of monitoring soil water content in the aeration zone of the East Slovakian Lowland. The main problem is the evaluation of the soil water storage in seasons and in years in the soil profile. Until now, classification systems of the soil water regime evaluation have been mainly based upon climatological factors and soil morphology where the classification has been realized on the basis of indirect indicators. Here, a new classification system based upon quantified data sets is introduced and applied for the measured data. The system considers the degree of accessibility of soil water to plants, including the excess of soil water related to the duration for those characteristic periods. The time span is hierarchically arranged to differentiate between the dominant water storage periods and short-term fluctuations. The lowest taxonomic units characterize the vertical fluxes over time periods. The system allows the comparison of soil water regime taxons over several years and under different types of vegetative cover, or due to various types of land use. We monitored soil water content on two localities, one with a deep ground water level, one with a shallow ground water level. The profile with a shallow ground water level keeps a more uniform taxons and subtaxons of soil water regime due to the crop variation than the profile with a deep ground water level.

Effects of 6 Months of Aging in Water on Hardness and Surface Roughness of Two Microhybrid Dental Composites

This study assessed the effect of 6 months of aging in water on surface roughness and surface/subsurface hardness of two microhybrid resin composites. Filtek Z250 and Charisma were tested. Cylindrical specimens were obtained and stored in distilled water for 24 hours or 6 months, at 37 degrees C. For Knoop hardness evaluation, the specimens were transversely wet-flattened, and indentations were made on surface and subsurface layers. Data were submitted to three-way ANOVA and Tukey's test (alpha < or = 0.05). Surface roughness baseline measurements were made at 24 hours and repeated after 6 months of storage. Data were submitted to repeated measures ANOVA and Tukey's test (alpha < or = 0.05). Surface hardness (KHN, kg/mm(2)) means (+/- standard deviation) ranged from 55 +/- 1 to 49 +/- 4 for Z250 and from 50 +/- 2 to 41 +/- 3 for Charisma, at 24 hours and 6 months, respectively. Subsurface means ranged from 58 +/- 2 to 61 +/- 3 for Z250 and from 50 +/- 1 to 54 +/- 2 for Charisma, at 24 hours and 6 months. For both composites, the aged specimens presented significantly softer surfaces (p < 0.01). For the subsurface hardness, alteration after storage was detected only for Charisma, which presented a significant rise in hardness (p < 0.01). Z250 presented significantly harder surface and subsurface layers in comparison with Charisma. Surface roughness (Ra, mum) means ranged from 0.07 +/- 0.00 to 0.07 +/- 0.01 for Z250 and from 0.06 +/- 0.01 to 0.07 +/- 0.01 for Charisma, at 24 hours and 6 months, respectively. For both composites, no significant roughness alteration was detected during the study (p= 0.386). The 6-month period of storage in water presented a significant softening effect on the surfaces of the composites, although no significant deleterious alteration was detected for the subsurface hardness. In addition, the storage period had no significant effect on the surface roughness of the materials.

Histomorphologic characterization and bond strength evaluation of caries-affected dentin/resin interfaces: Effects of long-term water exposure

Objectives To evaluate the longevity of sound (SD) and caries-affected dentin (CAD) bonds made with etch-and-rinse and self-etching adhesives after a 6-month water-storage period, using bond strength and morphological evaluations. Methods Extracted human molars with coronal carious lesions were selected. Flat surfaces of CAD surrounded by SD were bonded with etch-and-rinse (Adper Scotchbond 1) or with self-etching (Clearfil Protect Bond and AdheSE) adhesives. Trimmed resin–dentin bonded interfaces (1 mm 2) were stored in distilled water for 24 h or 6 months and subjected to microtensile bond strength (μTBS) evaluation. The quality of the dentin beneath fractured specimens was measured by Knoop microhardness (KHN). ANOVA and multiple comparisons tests were used ( P < 0.05). Fractographic analysis and interfacial nanoleakage evaluation were performed by scanning electron microscopy (SEM). Resin–dentin bonded sections (10 μm thick) were stained with Masson's trichrome and examined using light microscopy. Collagen exposure and adhesive penetration were examined qualitatively. Results μTBS to SD was significantly higher than that to CAD for all bonding agents. Bonds made with AdheSE were weaker than the other adhesives after 6-months storage regardless of the dentin substrate. CAD bonded specimens presented a significant μTBS decrease over time. Lower KHN was recorded in CAD compared to SD. An increase in the exposed collagen zone and a decrease in the quality of the adhesive infiltration were observed in CAD interfaces. Significance CAD bonded interfaces are more prone to hydrolytic degradation than SD bonds. Additionally, as compared to SD, there were remarkable differences in depth of demineralization, adhesive infiltration and interfacial bond strength with CAD.

Polymerization shrinkage and hygroscopic expansion of contemporary posterior resin-based filling materials—A comparative study

Objectives To investigate the polymerization shrinkage and hygroscopic expansion of contemporary posterior resin-based filling materials. Methods The densities of SureFil (SU), CeramXMono (CM), Clearfil AP-X (CF), Solitaire 2 (SO), TetricEvoCeram (TE), and Filtek P60 (FT) were measured using the Archimedes’ principle prior to and 15 min after curing for 20, 40 and 60 s and after 1 h, 24 h, 7 d, and 30 d storage at 37 °C in water. Volumetric changes (Δ V) in percent after polymerization and after each storage period in water were calculated from the changes of densities. Water sorption and solubility were determined after 30 d for all specimens and their curing times. Two-way ANOVA was calculated for shrinkage and repeated measures ANOVA was calculated for hygroscopic expansion ( p < 0.05). Results Δ V depended on filler load but not on curing time (SU ≈ −2.0%, CM ≈ −2.6%, CF ≈ −2.1%, SO ≈ −3.3%, TE ≈ −1.7%, FT ≈ −1.8%). Hygroscopic expansion depended on water sorption and solubility. Except for SU, all materials showed Δ V ≈ +1% after water storage. Conclusion Polymerization shrinkage depended on the type of resin-based filling material but not on curing time. Shrinkage was not compensated by hygroscopic expansion.

Ecological anomalies in the East China Sea: Impacts of the Three Gorges Dam?

In this study, we examined possible impacts of the Yangtze River Three Gorges Dam (TGD), the world largest hydroelectric construction, on the adjacent marine ecosystem of the East China Sea (ECS) during its initial water storage period. The TGD filled the first one-third of its storage capacity of 39 billion m 3 in 10 days in June 2003, causing an abrupt reduction in the river flow into the ECS. Noticeable changes in the microbial community structure including pico-sized autotrophs, heterotrophic bacteria and microbial diversity in the estuary and the ECS were observed 2 months later. Although causes for these changes could be multiple, the sudden decrease of river runoff and an ensuing intrusion of ECS ocean currents were postulated to be among the major ones.

Interfacial ultramorphology of single‐step adhesives: nanoleakage as a function of time

The aim of this study was to examine the effectiveness of single-step self-etching adhesives in preventing nanoleakage over a 90-day water-storage period, and analyse the ultramorphological characteristics of resin-dentin interfaces. Three single-step self-etching adhesives were evaluated: Adper Prompt L-Pop - LP (3M ESPE), iBond - iB (Heraeus Kulzer), and Clearfil Tri-S Bond - S3 (Kuraray). Bonded specimens were sectioned into 0.9-mm thick slabs and stored in water for 1, 60 or 90 days. After the storage periods, a silver tracer solution was used to reveal nanometer-sized spaces and evidence of degradation within resin-dentin interfaces. Epoxy resin-embedded sections were prepared, and the interfaces observed with the TEM. Nanoleakage patterns were compared among adhesives and storage periods using image analysis software. Data were statistically analysed by two-way anova and Tukey test. Nanoleakage was observed in all resin-dentin interfaces produced by the single-step self-etching adhesives. Results showed that LP presented the lowest silver deposition means at 1 day. However, after 60 and 90 days, the area of silver deposition significantly increased for LP. iB presented intense silver deposition after 1 day and a small increase after 90 days. S3 presented the lowest silver deposition means after 60 and 90 days of water-storage.

Effect of Microwave Disinfection Procedures on Torsional Bond Strengths of Two Hard Chairside Denture Reline Materials

This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). Cylindrical (30 x 3.9 mm) denture base specimens (n= 160) were stored in water at 37 degrees C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n= 10): Group 1 (G1)--tests performed after bonding; Group 2 (G2)--specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3)--specimens irradiated daily until seven cycles of disinfection; Group 4 (G4)-specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p= 0.05). For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days--138 MPa; 30 days--132 MPa), G3 (2 days--126 MPa; 30 days--130 MPa), and G4 (2 days--130 MPa; 30 days--137 MPa) were significantly higher (p < 0.05) than G1 (2 days--108 MPa; 30 days--115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days-73 MPa; 30 days--71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day--86 MPa; 30 days--90 MPa), G3 (2 days--82 MPa; 30 days--82 MPa), and G4 specimens (2 days--78 MPa; 30 days--79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study.

Dimensional stability of distances between posterior teeth in maxillary complete dentures

The aim of this study was to assess the displacement of posterior teeth in maxillary complete dentures stored in water at 37 degrees C. Twenty acrylic resin-based maxillary complete dentures were constructed with the anterior teeth arranged in normal overlap and the posterior teeth in Angle class I. Metallic pins were placed on the labial cusp of the first premolars (PM), and on the mesiolabial cusp of the second molars (M). The final acrylic resin pressing was made in a metallic flask with aid of the RS tension system, and polymerized in a moist-hot cycle at 74 degrees C for 9 hours. The dentures were deflasked after cooling in their own polymerizing water or after cooling in polymerizing water plus bench storage for 3 hours, and stored in water at 37 degrees C for periods of 7, 30, and 90 days. Following deflasking and after each storage period tested, the PM-PM (premolar to premolar), M-M (molar to molar), LPM-LM (left premolar to left molar), and RPM-RM (right premolar to right molar) distances were measured with an STM Olympus microscope, with an accuracy of 0.0005 mm. Collected data were submitted to ANOVA and Tukey's test (5%). There was no statistically significant difference for the PM-PM, M-M, and LPM-LM distances after all storage periods when the flask cooling methods were considered. With exception of the RPM-RM distance after the 30-days water plus bench storage period, the other distances remained statistically stable.

Effect of light-activation methods and water storage on the flexural strength of two composite resins and a compomer

The present study evaluated the flexural strength of three composite resins recommended for direct esthetic restorations: a polyacid modified composite (Dyract AP), a unimodal composite resin (Filtek Z250) and a hybrid composite resin (Point 4). The variation factors, apart from the type of composite resin, were the light activation method and the water storage period. The composite resins were light-cured in continuous mode (40 s, 500 mW/cm2) or in ramp mode (0-800 mW/cm2 for 10 s followed by 30 s at 800 mW/cm2) and stored for 24 hours or 30 days in distilled water at 37 degrees C. The data were analyzed by ANOVA and Tukey test for multiple comparisons (alpha = 0.05). The composite resin Z250 presented the highest mean flexural strength (166.74 MPa) and Dyract AP presented the lowest one (129.76 MPa). The storage for 30 days decreased the flexural strength in ramp mode (24 h: 156.64 MPa; 30 days: 135.58 MPa). The light activation method alone did not lead to different flexural strength values.

Short- and long-term in vitro study of the bonding of eight commercial adhesives to normal and deproteinized dentin

Objective. The aims of this study were to investigate the influence of deproteinization of dentin on the shear bond strength (SBS) mediated by eight dentin adhesives, and to evaluate the long-term durability of the SBSs. The hypotheses were that deproteinization of dentin would not affect the capacity for adherence, and that in contrast to the SBSs to collagen-rich surfaces, the SBSs to deproteinized surfaces would be stable during a 1-year period of storage in water. Material and Methods. Ground surfaces of human dentin were either rinsed with water (normal dentin) or treated with sodium hypochlorite (deproteinized dentin). The dentin surfaces were analyzed by Fourier transform-infrared spectroscopy (FT-IR) using horizontal attenuated total reflectance (HATR). In addition, the SBS to normal and deproteinized dentin treated with the adhesives was measured after 24 h or 1 year of storage in water. Results. The IR absorption peaks at approximately 1,640, 1,560, and 1,240 cm−1 were assigned to the collagen matrix and peaks at about 1,000 cm−1 were assigned to the phosphate group in hydroxyapatite. From the relative magnitude of the peaks, it was determined that the utilized deproteinization method was effective. Furthermore, the normal dentin group showed SBS values ranging from 10 to 39 MPa and the deproteinized dentin group showed SBS values ranging from 13 to 30 MPa. Conclusions. According to the statistical analysis, the results only partly supported the hypotheses: it was found that the influence on bond strength of deproteinization of dentin surfaces and the effect of 1 year of storage in water depended on the composition of the dentin adhesive.

Compressive strength of resin-modified glass ionomer restorative material: effect of P/L ratio and storage time

The aim of this study was to evaluate the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC. For each material, P/L ratio and storage time, 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. Data were submitted to ANOVA and Tukey's test (5%), and showed that the compressive strength of resin-modified glass ionomer cement was reduced when P/L ratio was reduced and that the storage in water had little influence on compressive strength.

Shear bond strength of adhesive systems to saliva-contaminated dentin

This study evaluated the shear bond strength of two adhesive systems: Scotchbond Multi-Purpose (SBMP) and Clearfil Liner Bond 2V (CLB2V) on different dentin surface conditions. Bovine incisors were collected and prepared according to the ISO’s (TR 11405) directions. The samples were divided into nine groups (n=10): 1- SBMP control group (without contamination); 2-SBMP: saliva contamination after priming; 3- SBMP: saliva contamination after bond application; 4-SBMP: saliva contamination after acid etching; 5-SBMP: as group 4 with re-etching after saliva contamination; 6-CLB2V control group (without contamination); 7-CLB2V: saliva contamination after priming; 8-CLB2V: saliva contamination after bond application; and, 9-CLB2V: saliva contamination before priming. After the storage period in water at 37o C, the samples were tested with an Instron testing machine, at crosshead speed of 0.5mm/min. The results were submitted to ANOVA (one way) and Tukey’s test at 5% significance level. For SBMP groups, the mean shear bond strengths were: 1 - 4.8 MPa, 2 - 5.0 MPa, 3 - 5.2 MPa, 4 - 6.6 MPa and 5 - 4.2 MPa. There was no statistical difference among groups tested. For CLB2V groups 6, 8, 9, the mean shear bond strengths were 8.0 MPa, 6.9 MPa and 8.8 MPa respectively and demonstrated no statistical differences. Group 7 (4.7 MPa) differed from all other groups except 8. Slight salivary contamination does not influence the shear bond strength of SBMP during any stage and slight salivary contamination influences the shear bond strength of CLB2V after priming step.

One‐Year Tensile Bond Strengths of Two Self‐Etching Primers to Bovine Enamel

The purpose of this study was to evaluate the enamel bond strengths of two self-etching primer systems and a total-etch self-priming adhesive system at 24 hours and after a 1-year period of storage in water at 37 degrees C. An experimental self-etching priming system (ABF, Kuraray Medical, Tokyo, Japan), Clearfil SE Bond (Kuraray), and One-Step (Bisco, Schaumburg, IL, USA) were used as the adhesive systems. Eleven bovine incisors stored frozen were ground with 600-grit SiC paper, bonded as recommended by the manufacturers, and restored with Clearfil AP-X (Kuraray) or Renew (Bisco). After 24 hours in water at 37 degrees C, the teeth were sectioned into 0.7 mm-thick slabs that were trimmed and tested for microtensile bond strength using a tabletop tester (EZ test, Shimadzu, Kyoto, Japan) at a crosshead speed of 1 mm/min. Alternate slices were either tested at 24 hours or kept in an incubator at 37 degrees C for 1 year prior to testing. The data were analyzed using paired t-test (p < .05). Differences in bond strengths were not significant at 24 hours. After 1 year, ABF and Clearfil SE Bond had significantly higher mean bond strengths than at 24 hours (p < .001). Enamel bond strengths of the total-etch two-step adhesive remained stable, and the bond strengths of the two self-etching primer systems increased with time. Although self-etching primers create a milder etching pattern than does phosphoric acid, the results of this study suggest that the ones evaluated in this study produce stable bond strengths over a 1-year period.

Transient thermal behavior of a water heater system driven by a heat pump

A dynamic model of a water heater system driven by a heat pump was designed to investigate transient thermal behavior of the system which was composed of a heat pump and a hot water circulation loop. Finite volume method was applied to describe the heat exchangers, and lumped parameter models were used to analyze the compressor and the hot water reservoir. Dynamic performances were evaluated as the hot water temperature changes for various sizes of the hot water reservoir. In order to compare the performance characteristics, time scale was normalized by the time constant determined from a quasi-steady state simulation of the system. From the simulation, the smaller size of the water reservoir was found to have larger transient performance degradation, and the larger size caused additional heat loss during the hot water storage period. Therefore, the reservoir size should be optimized in a design process to minimize both the heat loss and the performance degradation.

Strengthening effect of aluminum fluoride added to resin composites based on polyacid-containing polymer

Objectives. The study investigates the possible strengthening effect of aluminum ions liberated during long-time water storage of experimental resin composites containing a polymer with carboxylic acid groups. Methods. The organic part of the resin composites was formed by photopolymerization of methacrylate monomers. The monomer mixture was composed of UEDMA, HEMA or TEGDMA, and 0–40 mol% HEMAN (the adduct of HEMA and maleic anhydride). The filler part of the resin composites consisted of a conventional silanated glass filler and 1 or 5 wt% of AlF 3·3H 2O. The rupture strength and bending modulus were measured without water storage and after 1 month, 1 year, and 3 years of water storage at 37 °C of the resin composite. Results. The experimental composites that had been stored in water had lower rupture strength and modulus than the composites that were tested without water storage. Specimens containing 30 or 40 mol% HEMAN increased in strength, and specimens containing 20, 30, or 40 mol% HEMAN increased in modulus during the period of water storage. Depending on composition, values for strength and modulus obtained after 3 years of water storage was up to 50% higher than the values obtained after 1 month. Significance. The strengthening effect of aluminum fluoride may be interpreted as the result of increased crosslinking by aluminum ions and carboxylate groups. The results may serve as a basis for the improvement of the mechanical properties of polyacid-modified resin composites.

Storage effect on the shear bond strength of adhesive systems.

The purpose of this study was to evaluate the effects of storage (1 day, 3 months and 6 months) on the shear bond strength of five adhesive systems on bovine dentin substrate. One hundred and fifty bovine incisors were flattened until areas of a minimum of 5 mm in diameter were exposed. A round area of 4 mm in diameter was marked on the dentin to be treated with the following adhesive systems: Clearfil Liner Bond 2V (CLB2V), Scotchbond Multi Purpose Plus (SBMP), Optibond Solo (SOLO), Prime & Bond NT (PBNT) and Etch & Prime 3.0 (E&P). To perform the test, a composite restoration (Z100) was made in a cylindrical shape on the treated surface. After the storage period in distilled water at 37 degrees C, the samples were tested on an Instron testing machine. Results were submitted to ANOVA and Tukey's test at 5% significance level. SBMP, PBNT and E&P were statistically similar at all storage times (p > 0.05). CLB2V demonstrated the highest mean shear bond strength at 3 months which was not significantly different at 6 months (p > 0.05). In addition. CLB2V had the highest means at all times tested. SOLO had the lowest mean shear bond strength at 6 months, which was statistically lower than means at 3 months and 1 day (p < 0.05).

Effect of one-year water storage on the surface microhardness of resin-modified versus conventional glass-ionomer cements

Objectives: Conventional and resin-modified glass-ionomer cements (GIC, RM-GIC) are available for clinical use as restorative materials or as liners and bases. This study was conducted to compare the effect of a 12-month storage period in water on the surface microhardness, measured in Vickers units (VH), between a GIC and a RM-GIC group and to determine if the addition of resins improved the GIC microhardness. Method: VH microhardness was assessed in three GIC: Ketac-Fil, Ketac-Molar and Ketac-Silver (KF, KM, KS) and three RM-GIC: Photac-Fil, Fuji II LC and Vitremer (PF, FU, VI) stored in distilled water at 37 °C for 12 months. Measurements were taken at 1, 7, 15, 30, 90, 180 and 365 days. The statistical evaluation was done by means of one-way analysis of variance (ANOVA) and Tukey's multiple comparison tests. Results: There are significant VH differences among the materials studied and within each material over storage time. GICs, except for KS, showed a higher VH throughout the study period. Among the RM-GIC, VI showed a significantly higher VH at 12 months than at 1 day. The VH of PF diminished in the final stage of the study, whereas that of FU stabilized. Significance: The results suggest that the addition of resins to the GIC did not appear to improve the surface microhardness of these materials. Furthermore, the surface microhardness of both the conventional and resin-modified glass-ionomers suffered variations over time. However, these materials should not be deemed inadequate for use in clinical applications. Probably, conventional and resin-modified GICs placed in the oral environment would not be affected to the same extent as in in vitro tests.

Hydration Characteristics of Portland Cement after Heat Curing: I, Degree of Hydration of the Anhydrous Cement Phases

The degree of hydration of the four major anhydrous cement phases in three U.K. portland cement mortars has been observed during the period of water storage at room temperature after an initial short-term heat cure. Such a heat cure at 85° or 100°C for 12 h generally accelerated the initial hydration of the four major anhydrous minerals in portland cement. Subsequent retardation of the degree of hydration of the alite, tricalcium aluminate, and ferrite phases was observed when these heat-cured mortars were stored at ambient temperature. General similarity but some differences in hydration behavior were observed between the three cements. The hydration of belite in the heat-cured mortars during storage at room temperature produced porous inner products that favored deposition of ettringite and reduced the risk of expansive ettringite formation. The substantial retardation in hydration of the aluminate-bearing phases, especially the ferrite phase, during the storage at room temperature raised the overall SO3/Al2O3 ratio of the cement hydrates formed, bringing about a potential for ettringite formation and hence the risk of expansion through delayed ettringite formation.

Tensile bond strengths of hard chairside reline resins as influenced by water storage.

Due to gradual resorption of the edentulous ridge bone, removable prostheses often require denture base relines to improve fit and stability. This research evaluated the bond strength between one heat-cured acrylic resin (Lucitone 550(R)) and two hard chairside reline resins, after two different periods of storage in water (50 h and 30 days). The bond strength was evaluated using a tensile test. The mode of failure, adhesive or cohesive, was also recorded. The results submitted to the Kruskal-Wallis test indicated that the highest tensile strengths were achieved with intact Lucitone 550(R) denture base resin in both periods of storage in water. After 50 h of storage in water, Duraliner II(R) reline material exhibited the highest bond strength to the denture base resin. After 30 days of storage in water, Duraliner II(R) reline resin demonstrated a significant reduction in adhesion, showing lower tensile bond strength than Kooliner(R) material. Both hard chairside reline materials failed adhesively across Lucitone 550(R) denture base resin, in both periods of time.

Deterioration of heat-cured mortars due to the combined effect of delayed ettringite formation and freeze/thaw cycles

The interaction between freeze/thaw (F/T) exposure and delayed ettringite formation (DEF) and their combined effect on the performance of heat-cured mortar specimens are reported. The results show that heat-cured mortar, not subject to F/T, starts to expand gradually after a long induction period ([approx]150 days). This period is shortened and the extent of the expansion is increased as a result of F/T exposure. The longer the period of water storage at 20 °C before F/T exposure, the greater the rate and extent of expansion immediately after F/T exposure and during the water storage period. The expansion observed in heat-cured mortars seems to be associated with delayed ettringite band formation. Mortar specimens that exhibit marked expansion show a corresponding decrease in strength and increase in oxygen gas permeability.