Effect of Chemical Materials on the Properties of Dental Stone

DR.AMER A.TAQA * MSC . PhD (Professor)NADA Z. MOHAMMED, MSC(Assistant Professor)

TARIK Y. KASSAB Bash DBs, MSC, (Professor)

ABSTRACT

Aims: To determine the effect of some chemical materials on the compressive strength and surface hardness of dental stone. Material: three types of chemical materials(rosin, nigella stavia oil and sodium lauryl sulfate)were incorporated into three kinds of type III

dental stone (Zeta, Elite and Dental stone) at four concentrations (0.5%, 1%, 1.5% and 2%).The collected data of compressive strength and surface hardness were subjected to

the descriptive analysis (mean and stander deviation), student T test(to evaluate the difference between standard and experimental groups) and one way analysis of

variance(ANOVA)(to show if there are significant differences among experimental groups). Also the FTIR was measured to show the effect of the additives on the chemical

structure of the stone. Results:revealed that the incorporation of these chemical materials into each type of dental stone resulted in changing their evaluated physical

properties;this change varies with the type, concentration of the added chemical material and type of dental stone being used. Conclusion:The highest values of compressive

strength and surface hardness were recorded with the addition of rosin in each of Zeta, Dental stone(at a concentration of 1%)and Elite stone(at a concentration of 1.5%).Also the

addition of nigella sativa stone oil increases in the compressive strength and surface hardness of Zeta and Dental stone when this materials added at a concentration of 1%

and at a concentration of 0.5%when it is added to Elite.

The compressive strength values were The compressive strength values were determined according to ADA determined according to ADA

specification No.25 (1975).specification No.25 (1975). A special A special split mold was used to prepare three split mold was used to prepare three

cylindrical specimens.cylindrical specimens. The compressive strength was determined

from the value of the maximum load at the point of specimen fracture

according to the following formula:

20 mm40

m

m

Compressive StrengthCompressive Strength

Load (Kg)

Area (cm²)

The Surface Hardness was evaluated with The Surface Hardness was evaluated with “microhardness tester”“microhardness tester”

Rockwell hardness test was used with Rockwell hardness test was used with minor load of 10 Kg and major load of 50 Kg minor load of 10 Kg and major load of 50 Kg

(El-Tannir and Imam, 1970; Combe and (El-Tannir and Imam, 1970; Combe and Smith, 1971; Kasier ana Nicholls, 1976; Smith, 1971; Kasier ana Nicholls, 1976;

Mohammed, 1983).Mohammed, 1983).

30

mm

20 mm

Initially, the indenter is placed under a static load of

a given magnitude (minor load), and the dial gauge is set at zero. The load is then

increased by a given amount (major load) and maintained

for a certain period. The depth of indentation is

measured after the major load is again reduced to the minor load (Phillips, 1982).

0

50

100

150

200

250

300

350

400 RosinNigella Stavia oilSodium Lauryl Sulfate

-ve Zeta Elite Dental +ve

control stone control

0

20

40

60

80

100

120 RosinNigella Stavia oilSodium Lauryl Sulfate

-ve Zeta Elite Dental +ve

control stone control

change the chemical composition of these stones and from comparing ir-spectra of those modified stones

with ir-spectra of rosin alone we can note the disappearing of some bands that present in ir-spectra

rosin specially at 2560, 1250, 1300, 1600 cm-¹ region .Also this figure shows new bands in the ir-spectra of these modified stone at 600, 500, 1450,

1550,3000,3200cm-¹region.

The ir-spectra of sodium lauryl sulphate show bands

at 450, 850, 1000, 1100, 1250, 1850, 2400, 2500 cm-¹region. Some of these bands disappear when

sodium lauryl sulphate mixed with each type of dental stone, especially at 850, 1100, 1250, 1850,

2400, 2500 cm-¹region.

Throughout comparing the ir-spectra chart of nigella stavia oil alone with the ir-spectra chart of the three

types of dental stone after the addition of nigella stavia oil), we can note the disappearing of some

bands at 1100, 1150, 1400, 1700, 2800, 2850 cm-¹region in negllia stavia oil spectra. And the

appearance of new bands at 600, 1600, 1850, 2100, 3400 cm-¹region in the modified stone spectra.

This increase in a compressive strength may be attributed to the This increase in a compressive strength may be attributed to the reduction: reduction:

in the water-powder ratio that achieved after the addition of these in the water-powder ratio that achieved after the addition of these chemical materials which indicate a denserchemical materials which indicate a denser

and to the effect of these additives on the chemical structure of the and to the effect of these additives on the chemical structure of the experimental dental stones.experimental dental stones.

material.El-Tannir and Imam (1969) reported that the basis of physical properties of gypsum is the function of the crystals structure and the

crystal rate of formation

However, there is a decrease in compressive strength with increasing the concentration of the added chemical materials); this may be partially

attributed to the action of the added chemical materials as an adulterant and to the reduction in the intercrystalline cohesion

(Anusavice, 1996).significant reduction in the compressive strength that is achieved after the significant reduction in the compressive strength that is achieved after the

addition of the sodium lauryl sulfate (despite the reduction in the water-addition of the sodium lauryl sulfate (despite the reduction in the water-powder ratio). powder ratio).

This was advocated by Mori and Yamane (1982) reported that the water-powder ratio alone dose not necessarily determine the strength of cast

gypsum. So this reduction in the compressive strength could be attributed to:

the reduction in the intercrystalline cohesion between the crystals

to the change in the chemical composition of these stones after the addition of these chemical materials.

The change in the surface hardness as a result of the incorporation of the chemical materials into the experimental dental stones is

recorded in terms of the change in the Rockwell hardness number.

In the present study, different types and concentrations of added the chemical materials render different results on the surface hardness

of the experimental dental stones. Improving the surface hardness of the experimental dental stones is achieved after the addition of rosin

and nigella stavia oil, while the addition of sodium lauryl sulfate resulted in the reduction of the surface hardness.

This was advocated by Craig( 1997) Surface hardness of gypsum products stated to be related to their compressive strength,

the higher the compressive strength, the higher being the hardness,

but disagreeing with Combe and Smith (1964) who reported that there is no clear relation detected between the values of

both hardness and compressive strength, since the conditions in the surface layer determine the former.

The effect of chemical additives used in this study on the hardness has been reported to correlate with the effect of

these chemicals on the compressive strength.

The differences in the examined properties of the dental stone related The differences in the examined properties of the dental stone related to the different chemical interactions between the added chemical to the different chemical interactions between the added chemical

materials and the calcium sulfate hemihydrate crystals. Incorporating materials and the calcium sulfate hemihydrate crystals. Incorporating of suitable chemical additives can produce dental stone with superior of suitable chemical additives can produce dental stone with superior mechanical properties. The highest values of compressive strength mechanical properties. The highest values of compressive strength and surface hardness were recorded with the addition of rosin into and surface hardness were recorded with the addition of rosin into

each of Zeta, Dental stone (at a concentration of 1%) and Elite stone each of Zeta, Dental stone (at a concentration of 1%) and Elite stone (at a concentration of 1.5%). Also the addition of nigella sativa stone (at a concentration of 1.5%). Also the addition of nigella sativa stone oil increases in the compressive strength and surface hardness of oil increases in the compressive strength and surface hardness of

Zeta and Dental stone when this materials added at a concentration of Zeta and Dental stone when this materials added at a concentration of 1% and at a concentration of 0.5%when it is added to Elite. 1% and at a concentration of 0.5%when it is added to Elite.