J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  22 
 

The Effect of Silver-Zinc Zeolite Incorporation on Some 

Properties of Condensation Silicone Impression Material 
 

Rehab A. Al-Azawi, B.D.S., H.D.D. (a) 

Widad A. Al-Naqash, B.D.S., H.D.D., M.Sc. (b) 

 

ABSTRACT 
Background: elastomeric impression materials are indicated when a high degree of accuracy is required, due to 

their excellent properties like details reproduction, dimensional stability and tear strength but with main two 

disadvantages those are their hydrophilicity as well as the absence of antibacterial activity. This study aimed to 

evaluate the effect of incorporation of 0.5% wt Ag-Zn zeolite into condensation silicone through the following tests; 

setting time, dimensional stability, reproduction of details, wettability, and hardness . 

Materials and methods: one hundred specimens were constructed of condensation silicone, divided into two groups 

for the first 50 specimens one0.5% by wt Ag -Zn zeolite was added, keeping the other fifty specimens without 

addition. Then each group further subdivided into five subgroups according to the conducted test. The tests 

performed were; setting time, dimensional stability, reproduction of details, hardness and wettability. 

Results: A statistically non-significant effect on the setting time and reproduction of details tests was observed, 

combined with a highly significant increase of wettability of condensation silicone after incorporation of 0.5% wt Ag-

Zn zeolite with non-significant increase of dimensional change of condensation silicone following incorporation of 

0.5% wt Ag-Zn zeolite. Hardness test results shoed statistically significant increase following the addition of Ag-Zn 

zeolite. 

Conclusion: Ag-Zn zeolite incorporated into condensation silicone, improved wettability which determine  the extent  

to  which  an  impression  material  replicates  the  structures  of  the  oral  cavity  and  production of bubble-free 

gypsum die. It also showed a statistically significant increase in the hardness of condensation silicone impression 

material, and had no effect on setting time, reproduction of details and dimensional stability. 

Key words: Condensation silicone impression materials, Antimicrobial agent, Ag- Zn Zeolite, wettability. (J Bagh Coll 

Dentistry 2016; 28(4):22-27) 

 

INTRODUCTION 
Elastomeric impression materials include a 

group of synthetically polymerized impression 

materials that are chemically cross-linked when 

set and could be stretched and recover to their 

original dimensions. There are three types based 

on the chemical backbone of polymer chains: 

polysulfide, polyether, and silicone; the 

condensation and addition (1). 

Condensation silicone impression materials are 

widely used nowadays is supplied in a two 

consistencies light and putty-like. The curing of 

this material involves a reaction of tri- and tetra-

functional alkyl silicates in the presence of 

stannous octoate as a catalyst. The material sets 

by cross-linking between terminal groups of the 

silicone polymers and the alkyl silicate to form a 

three-dimensional network, the ethyl alcohol as a 

byproduct. Its subsequent evaporation accounts 

for much of the contraction that takes place in the 

setting impression (1,2). 

Nowadays infection control takes interest in 

order to prevent cross infection between the 

patients and dental staff. The threat of infections 

could be transferred by blood, saliva, and/or 

plaque is a potential occupational risk as they 

include pathogenic microorganisms (3). 
(a)M.Sc. student. Department of Prosthodontics. College of 
Dentistry, University of Baghdad. 
(b)Professor. Department of Prosthodontics. College of Dentistry, 
University of Baghdad. 

The incorporation of zeolite as filler in 

polymers was reported in literatures and proved 

that it enhanced the antibacterial activity of these 

polymers. Silver ion exchanged zeolites have 

excellent antibacterial activity and therefore have 

a potential in the medical field to enhance 

antimicrobial properties.(4) 

The present study was conducted to assess the 

incorporation of Ag-Zn zeolite into condensation 

impression material and evaluate its effects on 

their properties 

 

MATERIALS AND METHODS 
One hundred specimens of condensation 

silicone were prepared, divided into two groups; 

fifty specimens control (without addition) and 

fifty experimental specimens (with addition of 

0.5% Ag-Zn zeolite) with fifty specimens, then 

each group was subdivided according to the test 

conducted; each subgroup containing ten 

specimens for each test.  

The percentage 0.5 % is chosen in this study as 

this percentage representing the minimum 

percentage as an effective bactericidal agent as 

proved by many authors (5,6). 

 

Physical and mechanical tests: 

1- Dimensional change test: 
The test block and ring mold were fabricated 

for this study (ADA/ANSI) specification no.19. 

Consisted of two parts; a circular stainless steel 



J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  23 
 

block, and a hollow stainless steel ring was used 

to retain and confine the impression material. 

Three vertical lines a 25 mm length and of 25 

μm, 50 μm and 75 μm width were engraved on the 

metal surface of the stainless steel block (line a 

50μm, line b 25 μm, and line c 75 μm).Two 

additional horizontal lines 25 mm apart from each 

other were engraved perpendicular to the 

previously marked lines, each have 50 μm width, 

(line d1 and d2) as in (fig. 1) 

 

Figure 1: The lines of the test mold: 

1 line a (50 um thick.), 2 line b(25 um thick.), 

3 line c (75 um thick.), 4 line d1(50 um thick), 

5 line d2 (50 um thick).(7) 
 

2-Reproduction of details test 
The same mold used for dimensional change 

test (fig. 1) was again used for this test. Following 

the separation and washing of the specimen an 

enter-estimation by three independent examiners 

was carried on to assess the reproduction of 

details by examining the continuity of the line b 

(25 µm) on the impression surface. Where line b 

is the smallest in diameter among the die lines, so 

if it is clearly reproduced the other larger lines 

would be already reproduced (8-10). 

 

3-Setting time test 
Vicat penetrometer has been used, with a 

needle of 3-mm diameter and a total weight of 

300g. A metal ring of8 mm high and diameter of 

16 mm was filled with newly mixed material and 

positioned on the penetrometer base. Then needle 

was applied to the surface of the impression 

material for 10 sec. and a reading was recorded. 

This step was repeated every 30 sec.  

The initial set is that time when the needle no 

longer penetrates the specimen completely to the 

bottom of the specimen. While the final set is the 

first of three non-maximum identical penetration 

readings (2). 

 

 

 

4-Wettability test: 
Wettability assessed by measuring the 

advancing contacting of liquid on the surface of 

the set impression material. Specimens were 

poured in cylindrical metal mould A drop of 

distilled water falling down above a set specimen 

and after one minute measure the angle between 

the surface of the drop and the surface of 

specimen by dino-litemicroscope (11). 

 

5- Hardness test: 

The specimens made for this test by using a 

cylindrical mold. Then the hardness of 

condensation silicone impression material was 

tested by shore A  hardness durometer instrument. 

This device was firmly grasped and insert it's 

indenter in the set specimen as shown in the 

(fig.2) the specimen was placed on a stable bench 

where the readings were recorded on the device 

screen. Two readings were obtained, the first 

represented  the  hardness  1.5  minutes  after  

setting, where  the second reading was for  the 

hardness after 2  hours.(12) 

Four specific  indentations were measured 

each time distributed it in a 90 ° manner at a 

location12 mm from any edge and at least 6 mm 

from any previous indent (the same selected area 

of each specimen), measurements followed 

ASTM D2240–05specification for Shore A 

hardness measurements. The average of the four 

readings in order to measure the whole surface of 

the specimen (13). 

 

Figure 2: Hardness sample with the sites of 

penetration 

 

RESULTS 
1- Dimensional change test: 

Mean values, number of specimens, standard 

deviation, t-test, and p-values of dimensional 

change test for control and experimental groups of 

1 

2 

3 
25mm 

4 

5 



J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  24 
 

condensation silicone are presented in table 1, 

table 2 and fig. 3. 

The results of dimensional test indicated non-

significant difference between experimental and 

control groups which exhibited a mean values -

0.877 and -0.917 respectively.   

 

Table 1: descriptive data of dimensional 

change test for control and experimental 

groups 
Group N Mean% SD 

Control 10 -0.917 0.47 

Experimental 10 -0.877 0.4 

 

Table 2: t-test and p-value for dimensional 

change test 
t-test p-value Sig. 

-0.2 0.84 NS 

 

 
 

Figure 3: Bar chart of dimensional change 

for condensation silicone 
 

2-reproduction of details 

The results of reproduction of details test are 

listed in table 3, showed the similarity in 

descriptive data for both groups; control and 

experimental.  

 

Table 3: reproduction of details results for 

the control and experimental groups. 
Group N Satisfactory Unsatisfactory 

Control 10 100% 0% 

Experimental 10 100% 0% 

 

3- Wettability 

Mean values, number of specimens, standard 

deviation, t-test, and p-values of wettability test, 

are presented in tables 4, 5 and fig4. 

The results indicated very clear and highly 

significant difference between means of the 

experimental (62.27) and control (72.84) groups. 

 

Table 4: Descriptive data of wettability test 

for control and experimental groups. 
Group N Mean° SD 

Control 10 72.84 1.28 

Experimental 10 62.27 2.38 

 

Table 5: t-test and p-value for wettability test 
t-test p-value Sig. 

12.346 0.00 HS 

 

 
 

Figure 4: Bar chart for wettability test. 
 

4-Setting time test:  
Mean values, number of specimens, standard 

deviation, t-test, and p-values of setting time test, 

are presented in table 6, table 7 and fig. 5. 

These results indicated a similar mean values 

for both groups; experimental and control, which 

is (216 seconds).  

 

Table 6: Descriptive data of setting time test 

for control and experimental groups 
Group N Mean(sec) SD 

Control 10 216 12.64 

Experimental 10 216 12.64 

 

Table 7: t-test and p-value for setting time 

test 
t-test p-value Sig. 

0.00 1 NS 

 

 
 

Figure 5: Bar chart for setting time test. 

0.85
0.86
0.87
0.88
0.89

0.9
0.91
0.92

cond_contr cond_exp

dimensional_change

56
58
60
62
64
66
68
70
72
74

cond_contr cond_exp

wettability

0

50

100

150

200

250

cond_contr cond_exp

setting_time_seconds



J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  25 
 

5-Hardness test: 

A– After 1.5 minute: 

Mean values, number of specimens, standard 

deviation, t-test, and p-values of hardness test at 

1.5 minute, are presented in table 8,table 9 and 

fig. 6. 

 
Figure 6: Bar chart for hardness at 90 

second 
 

Their results indicated a non-significant 

difference between experimental and control 

means which are 16.62 and 16.14 respectively  

 

Table 8: Descriptive data of hardness test at 

90 sec. for control and experimental groups. 
Group N Mean(°) SD 

Control 10 16.14 1.58 

Experimental 10 16.62 0.94 

 

Table 9: t-test and p-value for hardness test 

at 90 sec. 
t-test p-value Sig. 

-0.595 0.42 NS 

 

B-Hardness test at 2 hour  

Mean values, number of specimens, standard 

deviation, t-test, and p-values of hardness test at 

1.5 minute, are presented in table 10, table 11 and 

fig. 7.  

The results indicated very clear and highly 

significant difference between means of the 

experimental and control groups, which are; 35.04 

and 31.39 respectively.   

 

Table 10: Descriptive data of hardness test at 

2hr. for control and experimental groups. 
Group N Mean(°) SD 

Control 10 31.39 1.77 

Experimental 10 35.04 0.78 

 

Table 11: t-test and p-value for hardness test 

at 2hr. 
t-test p-value Sig. 

-0.82 0.00 HS 

 

 

 
 

Figure 7: Bar chart for hardness at 2 hour 
 

DISSCUSION 
Zeolite was selected as a vehicle for 

antimicrobial cations because of its 

characteristics, including prolonged antimicrobial 

activity, non-toxicity and lack of odor or flavor (14-

16). 

Zeolite type X was used in this study due to 

the fact that zeolite X has got an excellent ionic 

conductivity as well as superior hydrophilicity. As 

zeolite X has low Si/Al ratio where the cation 

concentration, ion exchange capacity and 

hydrophilicity are inversely proportional to that 

ratio (15-17) 

Hydrophilicity is a beneficial attribute to 

prevent air bubbles formation within gypsum 

replica (18). 

Sliver and zinc ion as the cations of choice to 

be used in this study because they proved to 

possess strong antibacterial and antifungal activity 
(19,20). The concentration of 0.5 % selected in this 

study was optimized as this percentage 

representing the minimum percentage as an 

effective bactericidal agent (5,6). 

The results of dimensional change test in this 

study shows that the incorporation of Ag-Zn 

zeolite into condensation silicone because a non-

significant change in the dimensional change of 

condensation silicone, this could be due to that the 

zeolite slightly decreases the evaporation of 

ethanol as by product. Another explanation is that 

it could be due to that the condensation silicone 

already contain silica in its basic ingredients in a 

percentage between (35-70%)  so the added 0.5% 

by wt well probably has no sensible effects on 

condensation properties (12,21). 

Concerned with reproduction of details test it 

was noticed that the experimental group of 

condensation silicone showed almost identical 

results with those of control group, as an 

explanation it could be due to the small particles 

of incorporated zeolite in a range of (0.5–1µm) 

which was in accordance with the requirements of 

ADA/ANSI specification no. 19 for elastomeric 

impression material (7,8,21). Also it could be due to 

15.8
16

16.2
16.4
16.6
16.8

cond_contr cond_exp

hardness_90seconds

28

30

32

34

36

cond_contr cond_exp

hardness_2hours



J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  26 
 

the small percentage of Ag-Zn zeolite 

incorporated (22). Another explanation is that may 

be due to an increase in the hydrophilicity of the 

impression material as a result of incorporation of 

zeolite. As the hydrophilicity increased the 

reproduction of details enhanced (1). 

The wettability test results showed a highly 

significant increase in wettability of the 

experimental groups for condensation silicone in 

comparison to its control group. This increase of 

wettability could be explained by hygroscopic 

property of zeolite (23-25). 

The setting time results experimental and 

control groups for condensation silicone had 

nearly the same mean values of setting time test 

which was statistically non-significant. This may 

be contributed to the fact that only small 

percentage as well as small particle size (in range 

of 0.5-1µm) of the Ag-Zn zeolite incorporated 

into experimental material (21,22,24). 

The results of hardness test showed that the 

hardness after 1.5 min. of setting exhibit a 

statistically non-significant increase but with 

highly significant increase after 2 hours of setting 

time. Generally, zeolite incorporation may 

increase the hardness values of the material, and 

this increase in hardness was directly proportional 

to the increases in concentration of incorporated 

Ag-Zn zeolite (25). 

As an explanation that it could be attributed to 

the randomly distributed particles of a hard 

material into impression material matrix. Other 

explanation; it could be due to that zeolite is 

mainly composed of silica  with small particle 

size and high surface area leading to better 

interfacial adhesion of the test material (25). 

 

REFERENCES 
1. Anusavice KJ, Shen C, Rawls HR. Phillips’ science of 

dental materials.12th ed. St. Louis: Saunders, Elsevier 

Inc.; 2013. pp.153. 

2. Craig RG, Powers JM. Restorative dental 
materials.12th ed. St. Louis: Elsevier; 2006. pp.291. 

3. Samra RK, Bhide SV. Efficacy of different 
disinfectant systems on alginate and addition siliconee 

impression materials of indian and international 

origin: A comparative evaluation. J Indian Prosthodont 

Soc 2010; 10(3):182–9. 

4. Kamişoğlu K, Aksoy EA, Akata B, Hasirci N, Baç N. 
Preparation and characterization of antibacterial 

zeolite–polyurethane composites. J Appl Polymer Sci 

2008; 110: 2854–61. 

5. Mutneja P, Raghavendraswamy KN, Gujjari AK. 
Flexural strength of heat cure acrylic resin after 

incorporation of different percentage of Sliver-zinc 

zeolite an in-vitro study. IJCI 2012; 4(4): 25-31. 

6. Kawahara K, Tsuruda K, Morishita M, Uchida M. 
Antibacterial effect of silver-zeolite on oral bacteria 

under anaerobic condition. Dent Mater 2000; 16: 452-

5. 

7. American National Standardization Institute / 
American Dental Association, Specification No.19 for 

elastomeric impression material. 2004. Chicago IL: 

ANSI/ADA. 

8. Johnson GH, Lepe X, Aw TC. The effect of surface 
moisture on detail reproduction of elastomeric 

impressions. J Prosthet Dent 2003; 90: 354-64. 

9. Petrie CS, Walker MP, O’Mahony AM, Spencer P. 
Dimensional accuracy and surface detail reproduction 

of two hydrophilicvinyl polysiloxane impression 

materials tested under dry, moist, and wet conditions. J 

Prosthet Dent 2003; 90: 365-72. 

10. Katyayan PA, Kalavathy N, Katyayan M. Dimensional 
accuracy and detail reproduction of two hydrophilic 

vinyl polysiloxane impression materials tested under 

different conditions. Indian J Dent Res 2011; 22: 881-

2. 

11. Zgura L, Beica T, Mitrofan IL, Mateias CG, Pirvu D,  
Patrascu I. Assessment of the impression materials by 

investigation of the hydrophilicity. Dig J Nanomater 

Bios 2010; 3: 749-55. 

12. Powers JM, Sakaguchi RL. Craig’s Restorative dental 
materials.13th ed. Philadelphia: Mosby Co.; 2012. 

13. ASTM International D2240–05. Standard test method 
for durometer hardness. 2010. West Conshohocken, 

PA. 

14. Zhang Y, Zhong S, Zhang M, Lin Y. Antibacterial 
activity of silver-loaded zeolite A prepared by a fast 

microwave-loading method. J Mater Sci 2009; 44: 

457–62. 

15. Matsuura T, Sato AY, Okamoto K, Ueshige M, 
Akagawa Y. Prolonged antimicrobial effect of tissue 

conditioners containing silver-zeolite. J Dent Mater 

1997; 25: 373–7. 

16. Bekkum HV, Flanigen EM, Jansen JC. Introduction to 
zeolite science and practice. Amsterdam: Elsevier; 

1991. pp.58. 

17. Čejka J, Bekkum H, Corrma A, Schűth F. Introduction 
to zeolite science and practice. 3rd Revised ed. St. 

Louis: Elsevier; 2007. 

18. Forch R, Schonherr H, Tobias A. Surface design: 
applications in bioscience and nanotechnology. Wiley-

VCH; 2009.  

19. Nikawa H, Yamamoto T, Hamada T, Rahardjo MB, 
Murata H, Nakanoda S. Antifungal effect of zeolite-

incorporated tissue conditioner against Candida 

albicans growth and/or acid production. J Oral 

Rehabil 1997; 24: 350–7. 

20. Abe Y, Ueshige M, Akagawa TM. Cytotoxicity of 
antimicrobial tissue conditioners containing silver-

zeolite. Int J Prosthodont 2003; 16:141-4. 

21. Azeez ZA, Hattor NA. The effect of incorporation of 
prepared Ag-Zn zeolite on some properties of heat 

polymerized acrylic denture base materials. J Bagh 

Coll Dentistry 2015: 27(1): 63-9. 

22. Nakanoda S, Nikawa H, Hamada T, Yamamoto T, 
Nakamoto T. The material and antifungal properties of 

antibiotic zeolite incorporated acrylic resin.J Jpn 

Prosthodont Soc1995; 39: 926. 

23. Kaali P, Pérez-Madrigal MM, Strömberg E, Aune R E, 
Czél G, Karlsson S. The influence of Ag+, Zn2+ and 

Cu2+ exchanged zeolite on antimicrobial and long 

term in vitro stability of medical grade polyether 

polyurethane. EXPRESS Polymer Lett 2011; 

5(12):1028–40. 



J Bagh College Dentistry                Vol. 28(4), December 2016                           The Effect of 
   

Restorative Dentistry  27 
 

24. Park YJ, Kim HO, Kim MK, Han HS, Song HJ, Vang 
MS. Effects of zeolite filler in surfactant-containing 

silicone rubber impression materials. 86th IADR, 2008.  

25. Bussaya R. The development of rubber compound 
based on natural rubber and ethylene propylene die ne 

monomer for playground rubber material. A master 

thesis, Kasetsart University, 2007. 

 

mailto:yjpark@chonnam.ac.kr