Hydrocolloid Impression Material Research Articles

Effect of disinfection on irreversible hydrocolloid and alternative impression materials and the resultant gypsum casts

Many new products have been introduced and marketed as alternatives to traditional irreversible hydrocolloid materials. These alternative materials have the same structural formula as addition reaction silicone, also known as vinyl polysiloxane (VPS), impression materials. Currently, there is limited in vitro and in vivo research on these products, including on the effects of chemical disinfectants on the materials. The purpose of this study was to compare the effects of a spray disinfecting technique on a traditional irreversible hydrocolloid and 3 new alternative impression materials in vitro. The tests were performed in accordance with the American National Standards Institute/American Dental Association (ANSI/ADA) Specification Nos. 18 and 19. Under standardized conditions, 100 impressions were made of a ruled test block with an irreversible hydrocolloid and 3 alternative impression materials. Nondisinfected irreversible hydrocolloid was used as the control. The impressions were examined for surface detail reproduction before and after disinfection with a chloramine-T product. Type III and Type V dental stone casts were evaluated for linear dimensional change and gypsum compatibility. Comparisons of linear dimensional change were analyzed with 2-way ANOVA of mean ranks with the Scheffé post hoc comparisons (α=.05). Data for surface detail reproduction were analyzed with the Wilcoxon Signed-Rank procedure and gypsum compatibility with the Kruskal-Wallis Rank procedure (α=.05). The alternative impression materials demonstrated significantly better outcomes with all 3 parameters tested. Disinfection with chloroamine-T did not have any effect on the 3 alternative impression materials. The irreversible hydrocolloid groups produced the most variability in the measurements of linear dimensional change. All of the tested materials were within the ADA's acceptable limit of 1.0% for linear dimensional change, except for the disinfected irreversible hydrocolloid impression material. The alternative impression materials performed best for the parameters tested. Spray disinfection had no effect on the alternative impression materials.

Physical characteristic of brown algae (Phaeophyta) from madura strait as irreversible hydrocolloid impression material

Background: Brown algae is a raw material for producing natrium alginates. One type of brown algae is Sargassum sp, a member of Phaeophyta division. Sargassum sp could be found in Madura strait Indonesia. Natrium alginate can be extracted from Sargassum sp. The demand of alginate in Indonesia is mainly fulfilled from abroad, meanwhile Sargassum sp is abundantly available. Purpose: The purpose of study were to explore the potency of brown alga Sargassum sp from Madura strait as hydrocolloid impression material and to examine its physical characteristic. Methods : The methods of research including extraction natrium alginate from Sargassum sp, synthesis of dental impression material and the test of porosity, density, viscosity, and water content of impression material which fulfilled the standard of material used in clinical application in dentistry. Results: Extraction result of Sargassum sp was natrium alginate powder with cream colour, odorless, and water soluble. The water content of natrium alginate was 21.64% and the viscosity was 0.7 cPs. The best porosity result in the sample with the addition of trinatrium phosphate 4% was 3.61%. Density value of impression material was 3 gr/cm3. Conclusion: The research suggested that brown algae Sargassum sp from Madura strait is potential as hydrocolloid impression material, due to its physical properties which close to dental impression material, but still need further research to optimize the physical characteristic. Latar belakang: Alga coklat adalah sumber bahan baku material natrium alginat. Salah satu jenis alga coklat adalah Sargassum sp yang merupakan anggota divisi Phaeophyta. Sargassum sp dapat ditemukan di Selat Madura Indonesia. Natrium alginat dapat diekstraksi dari Sargassum sp. Kebutuhan akan bahan ini di Indonesia sebagian besar dipenuhi dari impor, padahal ketersediaan Sargassum sp di Indonesia sangat melimpah. Tujuan: Penelitian ini bertujuan untuk mengeksplorasi potensi alga coklat Sargassum sp dari Selat Madura sebagai bahan cetak hidrokoloid dan meneliti karakteristik fisiknya. Metode: Tahap pertama adalah ekstraksi natrium alginat dari Sargassum sp, tahap kedua yaitu sintesis bahan cetak gigi dan menguji karakteristik bahan seperti porositas, densitas, viskositas, kadar air, bahan cetak yang memenuhi standar bahan yang digunakan dalam aplikasi klinis bidang Kedokteran Gigi. Hasil: Hasil ekstraksi berupa natrium alginat bubuk dengan warna krem, tidak berbau, dan dapat larut dalam air. Kadar air natrium alginat sebesar 21,64% dengan viskositas 0,7 cPs. Porositas terbaik dalam sampel dengan penambahan trinatrium fosfat 4% yaitu 3,61%. Nilai densitas bahan cetak 3 gr/cm3. Kesimpulan: Penelitian ini menunjukkan bahwa alga coklat Sargassum sp dari Selat Madura memiliki potensi sebagai bahan cetak hydrocolloid kedokteran gigi karena memiliki karakter fisik yang mirip dengan bahan cetak kedokteran gigi, namun masih memerlukan penelitian lebih lanjut untuk mengoptimalkan karakter fisiknya.

The effect of disinfectants on the surface quality of irreversible hydrocolloid impression material and gypsum cast

Objective: To evaluate the changes in the surface quality of irreversible hydrocolloid impression materialhydrogum following disinfection with 0.525% sodium hypochlorite, 0.2% Chlorehexidine Gluconate, and 4%Povidone Iodine.Methodology: Forty specimens of alginate impression materials hydrogum were fabricated according to theISO 1563 and were divided into four groups according to the method of solution dipping: group 1: Dip in0.525% sodium hypochlorite, group 2: Dip in 0.2% chlorhexidine gluconate, Group 3: Dip in 4% Povidone Iodine,Group 4: No treatment with any solution (control group). Then the specimens were poured in type II stone.Surface detail was determined using a stainless steel block in accordance with ISO 1563.Results: The results were subjected to Kruskal – Wallis non parametric test showed no statistical significantdifference in the effect of the disinfection solution on the surface detail quality (P – value 0.392, at p> 0.05).However, the surface quality of the specimens disinfected by sodium hypochlorite showed some degree oferosion or damage to the surface quality of the resultant cast, but the difference was not statisticallysignificant.Recommendations: make microbiological study to evaluate the effect of disinfectant solutions on differentmicroorganisms present in the oral cavity and evaluate the hardness of impression material following the useof disinfectant solutions.

A Study on Imbibition and Syneresis in Four Commercially Available Irreversible Hydrocolloid (Alginate) Impression Materials

ABSTRACT Purpose To evaluate imbibition and syneresis in four commercially available irreversible hydrocolloid (alginate) impression materials at different time intervals (10, 20 and 30 minutes). Materials and methods Eighty samples of four commercially available irreversible hydrocolloid (alginate) impression materials Algitex (DPI, Mumbai), Plastalgin (Septodont, Cedex, France), Zelgan 2002 (Dentsply), Finndent (Pyrex Polykem) were made. Twenty samples each of four irreversible hydrocolloid (alginate) impression materials were grouped into four groups (I, II, III and IV). Measured quantity of alginate powder and liquid was used to make samples. The samples were evaluated for imbibition and syneresis at different time intervals (i.e.10, 20, and 30 minutes) by weighing on electronic analytic balance. The data were analyzed using the one-way ANOVA, post hoc test and t-test. Results The statistical data revealed that imbibition within four groups of irreversible hydrocolloid (alginate) impression materials were not significant. Regarding syneresis there was insignificant difference between the four groups but within the group itself they showed significant difference between them depending upon the time interval. It was observed that Group I showed significant difference in syneresis at time interval of 10 to 20 minutes. Group II showed significant difference in syneresis at time interval of 10 to 30 minutes. Conclusion This study demonstrated that four groups of irreversible hydrocolloid (alginate) impression materials showed different rates of imbibition and syneresis at time interval of 10, 20 and 30 minutes depending upon molecular weight, calcium concentration and environmental conditions. How to cite this article Garg S, Mittal S, Bansal S, Kansal G. A Study on Imbibition and Syneresis in Four Commercially Available Irreversible Hydrocolloid (Alginate) Impression Materials. Int J Prosthodont Restor Dent 2012;2(1):1-4.

Dimensional stability of irreversible hydrocolloid impression materials as a function of pouring time: A systematic review

Pouring time of irreversible hydrocolloid impressions differs depending on the brand and intended use, either of which may result in variable dimensional stability. The purpose of this study was to investigate the available literature on dimensional stability of irreversible hydrocolloid impression materials as a function of pouring time and disinfectant solutions used. Three electronic database searches (Medline, PubMed, and EMBASE) were conducted to identify in vitro peer-reviewed studies published in English between the early 1970s and October 2010. Selection criteria included in vitro studies, irreversible hydrocolloid as impression material, and storage time. Heterogeneity in the methodology of the selected studies precluded a meta-analysis. Of 62 initially selected studies only 18 were included. Traditional irreversible hydrocolloids were generally stable when poured immediately. However, stability decreased as time elapsed. New irreversible hydrocolloid substitutes appear to allow delay in pouring time and repouring of impressions without significant side effects. Shorter storage time of irreversible hydrocolloid impressions before pouring is desirable, although this may not be necessary for the extended-pour types. The lack of a standardized technique for studying the effect of storage condition, with or without the use of disinfectants, makes it difficult to make clear recommendations.

Microbiological Appraisal of Three Different Brands of Commercially Available Irreversible Hydrocolloid Impression Materials: An in vitro Study

To evaluate factory-sealed containers of three different commercially available irreversible hydrocolloid impression materials for their microbial contamination and the type of microorganisms present. Thirty-six measured samples were taken of each brand and placed on chocolate agar plates or in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated and identified using standard microbiological methods. The three brands contained viable microorganisms in 90% of the samples. Samples from the top, middle and bottom layers had approximately equal contamination frequencies. The concentration of organism varied from 25 to 74 CFUs per gram of contaminated sample. The samples contained viable microorganism which may be potentially dangerous to immunocompromised patients.

Efficacy of various spray disinfectants on irreversible hydrocolloid impression materials: An in vitro study

Most of the materials (casts, impressions, etc.) that are sent to the dental laboratories show the presence of numerous pathogenic microorganisms. All the spray disinfectants are not equally effective against these microorganisms. The aim was to compare the effectiveness of different spray disinfectants on irreversible hydrocolloid impressions and to find out the most effective dilution, contact time, and effect against each microorganism studied. The effects of four spray disinfectants, 5.25% sodium hypochlorite, 0.525% sodium hypochlorite, 1:213 (1 part in 213 parts of water) povidone iodine, and 2% glutaraldehyde along with control (distilled water) on irreversible hydrocolloid impressions contaminated with Staphylococcus aureus, Bacillus subtilis and Streptococcus viridans were studied. Sodium hypochlorite, 5.25%, showed 1-min exposure time which was able to effect a 4 log 10 reduction in bacterial counts against S. aureus and S. viridans followed by 0.525% sodium hypochlorite and 2% glutaraldehyde for 10 min. None were able to effect a 4 log10 reduction against B. subtilis. Sodium hypochlorite with a concentration of 5.25% was the most effective disinfectant and required the shortest contact time (1 min). Not all ADA-approved concentrations of surface disinfectants work equally well on irreversible hydrocolloid impression materials.

A randomized clinical trial to compare diagnostic casts made using plastic and metal trays

Virtually every prosthodontic rehabilitation involves making diagnostic casts for analysis and prosthesis fabrication. Frequently, these casts are produced using irreversible hydrocolloid (IH) impression materials in stock metal or plastic trays. However, it is unclear whether one technique produces a more accurate cast. The purpose of this randomized clinical trial was to compare the linear accuracy of diagnostic casts produced using IH with 1 of 3 different tray types: (1) perforated metal trays, (2) stock plastic trays, and (3) directed-flow stock plastic trays. All groups were compared to casts produced with custom trays and vinyl polysiloxane (VPS) impression materials, which were considered the control. Seven subjects participated in this trial. IH impressions were made in a random order using 1 of 3 tray types: stock plastic, perforated metal, or plastic directed flow. These were compared to VPS impressions using custom trays (control group). Each impression technique was repeated 3 times per subject, for a total of 84 observations. Impressions were disinfected and poured in a type IV stone. Linear accuracy of casts was measured using computer software analysis of scanned images of the casts at x30 magnification. Three linear measurements were made on each cast: second molar to second molar, right second molar to left first premolar, and left second molar to right first premolar. Measurements were compared among techniques using mixed-model analysis of variance to account for correlation among the multiple measurements made on each subject. Dunnett's adjustment for multiple comparisons with control was used (α=.05). For molar-to-molar and right second molar to the left first premolar measurements, there were no significant differences in linear dimensions between casts made from different trays. However, linear measurements from the left second molar to the right first premolar demonstrated significant differences for casts made with stock metal, directed-flow, and stock plastic trays compared to custom trays. In this group, casts produced by stock metal, directed-flow, and stock plastic trays differed from controls by 102, 68, and 71 um, respectively. Generally, casts made with plastic trays (stock plastic and directed flow) had values closer to those of custom trays than did casts made with metal trays. Impressions made with irreversible hydrocolloid produced casts that were significantly different in linear dimension than casts produced by custom trays and VPS impressions. These differences were not uniform, but varied by location on the cast.

Disinfection procedures: Their efficacy and effect on dimensional accuracy and surface quality of an irreversible hydrocolloid impression material

Objectives This study investigated the antibacterial efficacy and effect of 0.55% ortho-phthalaldehyde (Cidex OPA ®) and 0.5% sodium hypochlorite (NaOCl) on the dimensional accuracy and surface quality of gypsum casts retrieved from an irreversible hydrocolloid impression material. Methods A simulated clinical cast and technique was developed to compare the dimensional accuracy and surface quality changes of the test gypsum casts with controls. Dimensional accuracy measurements were completed between fixed points using a travelling microscope under low angle illumination at a magnification of ×3. Surface quality changes of “smooth” and “rough” areas on the cast were evaluated by means of optical profilometry. The efficacy of the disinfection procedures against Pseudomonas aeruginosa was evaluated by determining the number of colony forming units (cfu) recovered after disinfection of alginate discs inoculated with 1 × 10 6 cfu for defined intervals. Results The dimensional accuracy of the gypsum casts was not significantly affected by the disinfection protocols. Neither disinfectant solution nor immersion time had an effect on the surface roughness of the “smooth” area on the cast, however, a significant increase in surface roughness was observed with increasing immersion time for the “rough” surface. Complete elimination of viable Pseudomonas aeruginosa cells from alginate discs was obtained after 30 and 120 s immersion in Cidex OPA ® and NaOCl, respectively. Conclusions Immersion of irreversible hydrocolloid impressions in Cidex OPA ® for 30 s was proved to be the most effective disinfection procedure.

An in vitro investigation into the physical properties of irreversible hydrocolloid alternatives

A number of manufacturers have introduced new products that are marketed as alternatives to irreversible hydrocolloid impression materials. However, there is a paucity of laboratory and clinical research on these products compared to traditional irreversible hydrocolloid. The purpose of this study was to evaluate the detail reproduction, gypsum compatibility, and linear dimensional change of 3 recently introduced impression materials designed as alternatives to irreversible hydrocolloid. The tested materials were Position Penta Quick, Silgimix, and AlgiNot. An irreversible hydrocolloid impression material, Jeltrate Plus Antimicrobial, served as the control. The parameters of detail reproduction, gypsum compatibility, and linear dimensional change were tested in accordance with ANSI/ADA Specifications No. 18 and 19. The gypsum compatibility was tested using a type III stone (Microstone Golden) and a type IV stone (Die-Keen Green). The data were analyzed using the Kruskal-Wallis rank test and the Mann-Whitney U test (α=.05). The test materials demonstrated significantly (P<.001) better detail reproduction than the control material. Silgimix exhibited the best compatibility with Microstone, whereas AlgiNot and Position Penta Quick exhibited the best gypsum compatibility with Die-Keen. An incompatibility was observed over time between the Jeltrate control material and the Microstone gypsum material. For linear dimensional change, the mean dimension of the control material most closely approximated the distance between the lines on the test die, but it exhibited the greatest variability in measurements. All of the test materials exhibited linear dimensional change within the ADA's accepted limit of 1.0%. The 3 new impression materials exhibited better detail reproduction and less variability in linear dimensional change than the irreversible hydrocolloid control. Gypsum compatibility varied with the brand of gypsum used, with an incompatibility identified between the control material (Jeltrate Plus Antimicrobial) and Microstone related to surface changes observed over time.

Relationship Between Pterygomaxillary Notches and Maxillary Anterior Teeth

Selection of the appropriate size of maxillary anterior teeth in complete dentures may be difficult, as there is no universally accepted method that can be used reliably. The aim of this study was to investigate whether there is a relationship between the total mesiodistal width of the six maxillary anterior teeth and the interpterygomaxillary notch distance. One hundred and ten maxillary impressions were made on dental students (67 women, 43 men; 19 to 22 years old) using stock tray and irreversible hydrocolloid impression material. The mesiodistal width of the six maxillary anterior teeth and the distance of the interpterygomaxillary notch were measured by digital caliper on stone casts (on two separate occasions by two independent observers). The results were analyzed using correlation regression tests. The mean mesiodistal width of the six maxillary anterior teeth was 46.02 (+/-2.8) mm, and the mean distance of the interpterygomaxillary notch was 42.38 (+/-3.47) mm. A significant correlation was found between mesiodistal width of the maxillary anterior teeth and the interpterygomaxillary notch distance (p= 0.003; r = 0.28). Standardized coefficient was found to be low (28%) to predict the appropriate size of maxillary anterior teeth. Total mesiodistal width of the maxillary anterior teeth correlated with the distance between pterygomaxillary notches; however, measurement of the interpterygomaxillary notch could not be used for tooth selection reliably due to the low standardized coefficient. Within the limitations of this study, the interpterygomaxillary notch distance is not useful for the selection of six maxillary anterior teeth in edentulous patients.

Accuracy and dimensional stability of extended-pour and conventional alginate impression materials

The authors conducted a study to determine if two irreversible hydrocolloid impression materials (Cavex ColorChange, Cavex Holland BV, Haarlem, Netherlands; Jeltrate Plus Antimicrobial Dustless Alginate Impression Material, Dentsply Caulk, Milford, Del.) stored for five days were dimensionally accurate. The authors modified Ivorine teeth (Columbia Dentoform, Long Island City, N.Y.) on a Dentoform model (1560 series model, Columbia Dentoform) to allow measurements of tooth and arch width. They made impressions and generated casts immediately and at five additional times. They recorded tooth and arch widths on the casts and compared the measurements with those for the standard model. Compared with measurements for the model, the greatest measured difference in casts was 0.003 inches for Cavex ColorChange (extended-pour alginate) and 0.005 inches for Jeltrate Plus Antimicrobial Dustless Alginate Impression Material (conventional alginate). The percentage of dimensional change ranged from -0.496 to 0.161 percent for the extended-pour alginate and from -0.174 to 0.912 percent for the conventional alginate. Results of analysis of variance and paired t tests indicated that when generated immediately and at day 5, casts produced from both impression materials were not statistically different from the standard model (P < .05). When stored properly, both alginate materials can produce accurate impressions at day 5 for diagnostic casts and for fabrication of acrylic appliances.

Comparative study of intermaxillary relationships of manual and swallowing methods

This study compared the mandibular displacement from three methods of centric relation record using an anterior jig associated with (A) chin point guidance, (B) swallowing (control group) and (C) bimanual manipulation. Ten patients aged 25-39 years were selected if they met the following inclusion criteria: complete dentition (up to the second molars), Angle class I and absence of signs and symptoms of temporomandibular disorders and diagnostic casts showing stability in the maximum intercuspation (MI) position. Impressions of maxillary and mandibular arches were made with an irreversible hydrocolloid impression material. Master casts of each patient were obtained, mounted on a microscope table in MI as a reference position and 5 records of each method were made per patient. The mandibular casts were then repositioned with records interposed and new measurements were obtained. The difference between the two readings allowed measuring the displacement of the mandible in the anteroposterior and lateral axes. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) among the three methods for measuring lateral displacement (A=0.38 +/- 0.26, B=0.32 +/- 0.25 and C=0.32 +/- 0.23). For the anteroposterior displacement (A=2.76 +/- 1.43, B=2.46 +/- 1.48 and C=2.97 +/- 1.51), the swallowing method (B) differed significantly from the others (p<0.05), but no significant difference (p>0.05) was found between chin point guidance (A) and bimanual manipulation (C). In conclusion, the swallowing method produced smaller mandibular posterior displacement than the other methods.

Self-disinfecting irreversible hydrocolloid impression material

Self-disinfecting irreversible hydrocolloid impression material

Alginate impressions: A practical perspective

The choice of an impression material for a particular situation depends on the treatment being provided, operator preference, and so on. Even with the introduction of more advanced and more accurate rubber base impression materials, irreversible hydrocolloid impression materials have stood the test of time. This article gives a detailed perspective of how best to make alginate impressions.

A Self-Disinfecting Irreversible Hydrocolloid Impression Material Mixed with Chlorhexidine Solution

To examine the antibacterial effect and several physical properties of an irreversible hydrocolloid impression material mixed with chlorhexidine solution. The experimental irreversible hydrocolloid specimens were prepared and allocated into four groups (Group0.1 g/L, Group0.2 g/L, Group0.5 g/L, Group1.0 g/L) according to the concentrations of chlorhexidine solution used as the mixing liquid. Specimens mixed with distilled water served as a control. The antibacterial effect, three-dimensional accuracy, flowability, and setting time were tested. Statistical analysis was performed using a one-way analysis of variance and a Tukey test, which was used for multiple comparisons (alpha=.05). Zones of growth inhibition were observed around the test specimens, but not around the control specimens, and there were significant intergroup differences in the diameters of the inhibition zones. In the accuracy test, no significant differences (P>.05) were detected among all the measurements for all groups, and the accuracy was clinically acceptable. Also, no significant differences in the flowability (P=.987) and setting time (P=.103) were detected. Chlorhexidine self-disinfecting irreversible hydrocolloid impression material can exhibit varying degrees of antibacterial activity without influencing the three-dimensional accuracy, flowability, and setting time.

Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials

This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37 degrees C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate--389 CFU/g; Jeltrate Plus--516 CFU/g; Jeltrate Chromatic--135 CFU/g; Hydrogum--1,455 CFU/g; Kromopan--840 CFU/g; and Greengel--59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

次亜塩素酸ナトリウム溶液による寒天・アルジネート連合印象の消毒が歯型の寸法精度に及ぼす影響 : 市販印象材による検討

次亜塩素酸ナトリウム溶液による寒天・アルジネート連合印象の消毒が歯型の寸法精度に及ぼす影響 : 市販印象材による検討

Dimensional Accuracy of Stone Dies Obtained from Agar/Alginate Combined Impressions Disinfected by Sodium Hypochlorite : Comparison of Commercially Available Hydrocolloid Impression Materials

Dimensional Accuracy of Stone Dies Obtained from Agar/Alginate Combined Impressions Disinfected by Sodium Hypochlorite : Comparison of Commercially Available Hydrocolloid Impression Materials

Impact of water quality on setting of irreversible hydrocolloid impression materials

Setting of irreversible hydrocolloid impression materials is based on the ionic reaction between carboxylic groups and calcium ions and may, therefore, be affected by ionic species present in the mixing water. The impact of this phenomenon on the clinical performance of these materials has not been well documented. The purpose of this study was to compare the setting behavior of irreversible hydrocolloid impression materials when mixed with tap and distilled water, and to determine the impact of typical cations present in tap water and their concentrations on the setting process. Six brands of irreversible hydrocolloid impression materials (Kromopan 100, Xantalgin Select FS, Alginoplast, Elastic Plus, Ypeen, and Ypeen Premium) were mixed with tap and distilled water (control) according to manufacturers' recommendations. Elastic Plus was also mixed with aqueous solutions containing various concentrations of NaCl, CaCl(2), and AlCl(3) to determine the role of typical cations on setting. Using a controlled shear stress oscillatory rheometer, time changes of storage (G') and loss (G'') moduli during setting were measured at 23 degrees C and used to determine the working and setting times and rigidity of set impression materials. The sample size (n=3) for each material/mixing system was increased to 8 to increase reliability of measurements in systems where the effect of mixing water was low or variance of results was high. The data were analyzed (alpha=.05) using a t test (tap water), a 1-way ANOVA, a Tukey post hoc test (shear stress), and a nested ANOVA and Fisher Least Significant Difference post hoc analysis (cation and cation concentration). Statistical analysis showed significant (P<.001) acceleration in the setting rate for Kromopan 100, the working time of which was shorter with tap water by 23.4 seconds and the setting time, by 32.8 seconds. Similar significant reductions (in seconds) in both working and setting times, respectively, were found with Xantalgin Select FS (12.0, P<.001 and 23.6, P<.002), Alginoplast (24.3, P<.001 and 44.7, P<.005), and Elastic Plus (23.0, P<.001 and 22.0, P<.002), when compared with the same materials mixed with distilled water. At the same time, the rigidity of the set impression materials mixed with tap water increased by approximately 10%. With Ypeen Premium, the setting time decreased significantly by 20.0 seconds (P<.001) with tap water, while the working time and rigidity did not change. The setting behavior of Ypeen was not significantly affected by water quality. Acceleration of the setting reactions and increase in impression rigidity depended (P<.001) primarily on concentration and valency of cations present in mixing water. Setting of irreversible hydrocolloid impression materials can be significantly accelerated when tap water with high water hardness is used for mixing or when the mixing water contains higher concentrations of cations such as Na(+), Ca(2+), and Al(3+).