Aims: To evaluate the effect of different water types on the water powder ratio of dental gypsum products. Materials and Methods: In this study five types of water (distilled, tab, slurry, de-ionized and well water) were used to be mixed with two types of dental gypsum products (plaster and stone). Results: Results showed a statistically significant difference at p ≤ 0.05 in water powder ratio of gyp-sum products when mixed with different types of water that used in this study . Conclusions: Water requirement of gypsum product varies in respect to the type of water used to be mixed with. The most pronounce decrease in water requirement of dental gypsum products was achieved with slurry water.
ABSTRACT
Aims: To evaluate the effect of different water types on the water powder ratio of dental gypsum products. Materials and Methods: In this study five types of water (distilled, tab, slurry, de-ionized and well water) were used to be mixed with two types of dental gypsum products (plaster and stone). Results: Results showed a statistically significant difference atp≤ 0.05 in water powder ratio of gypsum products when mixed with different types of water that used in this study . Conclusions: Water requirement of gypsum product varies in respect to the type of water used to be mixed with. The most pronounce decrease in water requirement of dental gypsum products was achieved with slurry water. Key words: types of water, water powder ratio and gypsum product.
Taqa AA. Mohammed NZ. Alomari AW. The Effect of Different Water Types on The Water Powder Ratio of Dental Gypsum Products.Al-Rafidain Dent J. 2012; 12(1): 142-147. Received:16/9/2010Sent to Referees:21/9/2010Accepted for Publication:22/12/2010
INTRODUCTION
Gypsum materials are popular as a die material because of ease of use, low cost, compatibility with most impression mate- rials and appropriate setting expansion and familiarity.(1-3)
Water powder ratio is an important fac- tor in the quality of gypsum materials,(4,5) many experimental attempts to improve mechanical properties of dental stone are oriented mainly towards the decrease of gauging water requirement. (6-11) Accurate compassion of gypsum properties should be undertaken while all materials are mixed to the same consistency.(12) The principal difference among gypsum prod- ucts is in the physical shape and nature of the calcium sulfate crystals makes it poss- ible to obtain the same consistency with less excess water with dental stone and high stone than with model plaster.(13-15) Although particle size and the total surface area are the chief factors in determining the amount of gauging water, the particle size distribution, grinding of the particles and adhesion between particles of hemi- hydrate are also a factor in determining the amount of water requirement.(16-19)
MATERIALS AND METHODS
1: Materials:
Materials used in this study can be clas- sified into:First: Dental gypsum prod- ucts; two types of dental gypsum products used in this study (plaster and stone). Two types of plaster (Al-Ahliya Co. for gypsum industries Ltd, and Al-Alaf Co. for gyp- sum industries Ltd ) and two types of stone (Elite, Zhermack SPA-45021Badia Poesine, Italy and Dental stone China Me- heco co.P.R. China).
Second: Mixing water; five types of mix- ing water has been used in this study( dis- tilled water, tab water, slurry water, de- ionized water and well water( AL- Rashe- dia well water)).The distilled water was used to prepare the control specimen to study the effect of other types of water on the water requirement of dental gypsum products used in this study.
2: Methods: Water analysis was done in the Nenava environmental center analysis department (Table 1).
Table (1): Chemical analysis of four water types
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Mixing procedure employed in the preparation of the test specimens followed the ADA specification No. 25 of gypsum products (1975).(20) The mixing water temperature was maintained at 25°C. Me- chanical mixer (Degussa AG, Germany) with vacuum for mechanical mixing for 20 seconds. The preparation of test specimens and test procedures were conducted under laboratory environment of 25 ± 2.0 and a relative humidity of 50 ± 10%.
Slurry water was prepared by placing the dental cast made from plaster (mixed with plaster specimens) or from stone cast (mixed with stone specimens) in water for
72 hours. Slurry water was standardized for saturation with help of complex metric titration test.(3,21,22) The water-powder ra- tio was measured by using modified vicat apparatus (Mumboldt MFG co, Chicaco, U.S.A ). Three hundred grams of test sam- ple were added to a known volume of 4% sodium citrate in distilled water and then mixed mechanically with vacuum. The mixture was then poured into the ring mold (vibrated slightly to remove air bub- bles) and then it was struck level with spa- tula at the top of the mold. The conical plunger of the modified vicat apparatus was wiped clean with a moist cloth before each determination, and then it lowered to the surface of the sample. The scale was read then the plunger released quickly by opening the thumbscrew. After the plunger settled, the scale was read again. The dif- ference in scale reading was millimeters of penetration. Determinations were made at 7, 8, 9 minutes after the start of the mix. Three penetrations averaged for each de- termination. The average of three determi- nations (9 penetrations) was taken as a measure of consistency. The water-powder ratio that gives the consistency specified in Table (2) was used as a correct water- powder ratio for that sample (ADA speci- fication No.25, 1975). (20)
Table (2): Testing Consistency
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*Cone penetration depth (35gm) total weight. **Cone penetration depth (100gm) total weight.
ADA specification No. 25 (1975)
RESULTS
The mean and standard deviation of water powder ratio of gypsum products mixed with different types of water were listed in the Table (3). This table reveals that the water requirement of each type of gypsum
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For both dental stone and plaster spe- cimens increase in their water powder ra- tio was noted in Table (3) when they mixed with de-ionized water. The most pronounced increase in the water powder ratio of both plaster and stone specimens was achieved with well water.
One way analysis of variance (ANO-
VA) revealed that their was a statistically significant difference at p≤0.05 on the ef- fect of water type on the water require- ment of all gypsum products that is used in this study at f=78.56, f=37.83, f=24, f=24 for Al-Ahlia, Al-Alaf, Elite stone and Dental stone respectively (Table 4).
Table (4): One Way ANOVA of the Effect Different Water Types on Water Powder ratio of Gypsum Products
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Duncan multiple comparison rang test for the effect of different types of water on the water requirement of elite stone and dental stone (Figure 1) revealed that their were statistically significant differences atp≤ 0.05 on the water requirement of elite stone and dental stone when mixed differ- ent types of water that used in this study.
Duncan's multiple range test Figure(2) revealed that their were a statistically sig- nificant differencesp≤ 0.05 among the effect of water types used in this study on the water requirement of Al-Ahlia plaster and Al-Alaf plaster . Except that there was no statistically significant difference in water requirement of Al-Alaf plaster when mixed with tab or de-ionized water Figure (2).
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Figure (1): Duncan Multiple Rang Test for the Effect of Different Water Types on The Water Powder Ratio of Elite Stone and Dental Stone
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Figure (2): Duncan Multiple Rang Test for the Effect of Different Water Types on The Water Powder Ratio Al-Ahlia plaster and Al-Alaf plaster
DISCUSSION
Calcium sulphate hemihydrates (gyp- sum) is an ionic solid and is therefore es- sentially hydrophilic. The surface interac- tions play an appreciable part in determin- ing the water requirement ; this can act through changing the condition of the grains and forces between the grains.(16,23)
Analysis of the mean and standard deviation Table (3) reveales that slurry water produces the most pronounce de- crease in the water powder ratio of both stone and plaster specimens. This can be explained according to the crystallization theory.(15,24-26) Increasing the nucleolus of crystallization (calcium sulfate dihydrate) that present in slurry water enhances the wetting of gypsum crystals by water and thereby decreasing their water powder ra- tio.(21,22)
According to this study, a decrease in water powder ratio of stone specimens was noted when mixed with tab water as com- pared with that when it mixed with distill- ed water Table (3). Tab water contains large amount of calcium carbonate ions (CaCO3) Table (1) and this salt highly soluble in water and make tab water as soft water ; this means that salt makes tab water easy dispense between the particles of stone powder( it provides sites for nuc- leation of the newly formed dehydrate) (21) and there by decrease their water powder ratio.
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- Quote paper
- Amer Taqa (Author), Nada Z. Mohammed (Author), Alia'a W Alomari (Author), 2010, The Effect of Different Water Types on The Water Powder Ratio of Dental Gyp-sum Products, Munich, GRIN Verlag, https://www.grin.com/document/209000
