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Jayaprakash K, Nandish BT, Prabhu S. Impact of storage environments on the dimensional stability of irreversible hydrocolloid alginate impression used in dentistry. International J... Article · January 2014 CITATIONS

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Storage Environments and Dimensional Stability of Alginate Impression

ORIGINAL RESEARCH

Jayaprakash K is Lecturer, B T Nandish is Assistant Professor & Shama Bhat V is Professor & Head, Dept of Dental Materials, Yenepoya Dental College, Yenepoya University, Mangalore – 575018, Karnataka, India.

Impact of Storage Environments on the Dimensional Stability of Irreversible Hydrocolloid Alginate Impression used in Dentistry Kukkila Jayaprakash, Bantarahalli Thopegowda Nandish, Harish Kumar Shetty K, A Nityananda Shetty, Shama Bhat Voddya, Sudeendra Prabhu, Kishore Ginjupalli

Dr Harish Kumar Shetty K is Professor & Head, Dept of Conservative Dentistry, Yenepoya Dental College, Yenepoya University, Mangalore – 575018, Karnataka, India.

Background: Alginate impression material is widely used for recording accurate impressions to fabricate various oral appliances such as crowns, bridges, partial dentures and complete dentures. Alginate impressions are dimensionally unstable and hence it should be poured immediately to form exact cast. The impressions are sometimes sent to the nearby laboratories for making cast and models. For maximum dimensional stability, the cast should be poured immediately or it can be stored in lower concentration NaCl or K 2SO4 solutions during transport to distant laboratories.

A Nityananda Shetty is Professor, Department of Chemistry, National Institute of Technology Karnataka, Mangalore, Karnataka, India.

Objective: To evaluate the effect of various storage environments on the dimensional stability of irreversible hydrocolloid alginate impressions and to select a suitable medium for long time storage.

Sudeendra Prabhu is Reader, Dept of Oral Pathology, Yenepoya Dental College, Yenepoya University, Mangalore – 575018, Karnataka, India.

Materials and Methods: Alginate impression material is supplied in powder form and is mixed with distilled water and poured on cylindrical hollow plastic mold. After setting, the sample is removed, weighed and then stored for 24 hours in a) exposed to atmosphere at 28+2°C(60 +5% relative humidity), b) refrigeration at 8+2°C, c) refrigeration in closed plastic sachets at 8+2°C, d) humidity chamber at 28+2°C and 8+2°C (100% relative humidity), e) distilled water f) solutions of NaCl at three different concentration and h) solutions of K2SO4 at three different concentration. The dimensional stability is measured by weight loss method and ion released during syneresis and imbibitions in storage media by using ion selective electrode method.

Kishore Ginjupalli is Selection Grade Lecturer, Dept of Dental Materials, Manipal College of Dental sciences, Manipal, Karnataka, India.

Results: Alginate impressions were more stable at lower concentrations of NaCl & K 2SO4 and dimensional changes are less than +0.6%. At higher concentrations more syneresis occurs, hence causes shrinkage of impressions. Impressions stored in open atmosphere showed maximum dimensional change followed by refrigerated sample, closed plastic sachets in refrigerator, humidity chamber and distilled water.

Corresponding Author: Jayaprakash K E-mail: [email protected]

Conclusion: For maximum dimensional stability, the impression should be poured immediately with cast material or the impression can be stored 24 hours in lower concentrations NaCl or K2SO4 solutions during transport to distant laboratories. This can also be stored in humidity chamber or zip lock polythene sachets in refrigerator at 8+2°C up to 6 hours. This saves chair side time and helps to produce accurate results.

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Keywords: Irreversible hydrocolloid, model and cast, syneresis, imbibitions, ion release, pH, dimensional stability.

International Journal of Health and Rehabilitation Sciences

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Issue 1

Storage Environments and Dimensional Stability of Alginate Impression

INTRODUCTION Irreversible hydrocolloid alginate impression material is widely used in dentistry for recording impressions accurately to obtain a model for diagnostic purposes, treatment planning, fabrication of provisional prosthesis, custom trays etc1. The alginate impression materials are supplied in the powder form containing potassium or sodium alginate, calcium sulfate, tri-sodium phosphate, diatomaceous earth, potassium titanium fluoride, zinc oxide etc. When the powder is mixed with water a sol is formed through a reaction with sodium or potassium salts of alginic acid and calcium sulfate. After this chemical reaction alginic salts cross linked into a flexible matrix by replacement of the monovalent sodium and potassium ions by calcium ions 2,3. Alginate impressions are dimensionally unstable due to syneresis and imbibitions. Hence it should be poured immediately to form exact cast4. The factors affecting the dimensional instability of the alginate impression were studied by storing the impressions for two hours in solutions of gluteraldehyde (GA), NaClO, Na2SO4, CaCl2, ZnSO4, dilute 2% aqueous solutions of potassium sulfate and potassium chloride and recommended to use 2% aqueous solution of potassium sulfate for temporary stabilization. Dimensional changes of impressions are not only due to the immersions solutions but also to the impression components.5 The effects of storage conditions on the surface characteristics of irreversible hydrocolloids were studied. Diminution of detail clarity began rapidly upon storage in room air, at 30ºC and 100% relative humidity, and in water. Downward inversion of the impressions markedly slowed surface changes in open air and under cover of the bell jar. Solutions of K2SO4 or KCl did not produce appreciable surface changes until the storage time exceeded

24 hours. Loss of detail occurred after 30 minutes in gypsum water slurry. Similar changes were observed after 15 minutes in ZnSO4 solution. Alcohol and mineral oil produced alterations within 30 minutes. The effect of alcohol was much more severe than that of mineral oil. Sucrose solution caused only moderate changes after 24 hours6. In the present study the dimensional changes of alginate impression are measured in detail by preparing standardized cylindrical specimens and stored in sodium chloride and potassium sulfate solutions at three different concentration, distilled water and storage conditions such as kept in open atmosphere, refrigerator and humidity chamber at controlled temperature. This is intended to find the most suitable storage medium and condition for use in clinical practices.

MATERIALS AND METHODS In this study, Alginate impression material has been used, which is manufactured by Tropicalgin, lot A39979 (Italy), Sodium chloride, lot no- 193606.0527) (Merk) and potassium sulphate (lot no 7778-805) (MerkIndia). Alginate powder of 8gm weight was mixed with 23ml of distilled water (20°C) for 45 seconds and emptied into a cylindrical ring of 23mm diameter and same height and placed on the glass plate. After 6 minutes, it is carefully removed, washed with distilled water, wiped with blotting paper and weighed immediately. This procedure is adopted for various samples and six samples were prepared for each group, which were stored for 24 hours in a) exposed to atmosphere at 28+2°C (68%+5% relative humidity), b) kept open inside refrigerator at 8+2°C, c) kept closed in zip lock polythene sachet in refrigerator at 8+2°C, d) humidity chamber at temperature 8+2°C and 28+2°C (100%+5% relative humidity),

Table 1 Ion released and pH by the Alginate gel in Distilled water

25

Time (Hours)

Ion released (Unit for Na & K-milli mole/litre and unit for Ca mg/litre)

pH of the solution at 28°C

1

Na = 75, K = 1.4, Ca = 1.0

6.01

24

Na = 103, K = 3.6, Ca = 1.5

5.97

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International Journal of Health and Rehabilitation Sciences

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Storage Environments and Dimensional Stability of Alginate Impression

Mean dimensional change (%)

0 -2

0

10

20

30 Dimensional changes in room temperature (28±2°C) (%)

-4 -6

Dimensional changes in refrigerator at 8±2°C (%)

-8 -10

Dimensional changes with closed sachets in refrigerator at 8±2°C (%)

-12 -14 -16

Time (hours)

Figure 1 Mean dimensional change (%) Vs Time (hours) for specimens exposed to open atmosphere, kept open inside refrigerator and kept closed in zip lock polythene sachet inside refrigerator

0 Mean dimensional change (%)

-0.2 0

5

10

15

-0.4 -0.6 Dimensional changes in humidity chamber at 28±2°C. (%)

-0.8 -1

Dimensional changes in humidity chamber at 8±2°C

-1.2 -1.4 -1.6 -1.8 -2

Time (hours)

Figure 2 Mean dimensional change (%) Vs Time (hours) of specimen stored in humidity chamber at two different temperature

e) distilled water f) solutions of NaCl at different concentrations (0.05%, 2%, and 3%) and g) solutions of K2SO4 at different concentrations (0.02%, 0.2% and 1.0%). Dimensional changes were approximately measured by weight loss method as it is more related to clinical lab conditions. Graph is plotted by using the average values for each group. For theoretical considerations of syneresis and imbibitions, ions released were measured by selective electrode 26

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method and pH was measured by using pH meter.

RESULTS Findings of the present study reveal, the linear dimensional changes (%) of sample stored in open atmosphere at 28+2°C, refrigerator at 8+2°C, closed plastic sachets in refrigerator at 8+2°C. Maximum syneresis occured at lab temperature followed by refrigerator at 8+2°C,

International Journal of Health and Rehabilitation Sciences

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Storage Environments and Dimensional Stability of Alginate Impression closed plastic sachets in refrigerator at 8+2°C (Figure 1). The dimensional changes in 100% relative humidity chamber at different temperature and more negative dimensional change (i.e. syneresis) at higher temperature are shown in Figure 2. The linear dimensional change in distilled water is more than that occurs in lower concentration of 0.02% NaCl and 0.05% of K2SO4 (Figure 3). At lower concentration, NaCl and K2SO4 give smaller

positive dimensional change (i.e. imbibition). But at higher concentration the percentage of dimensional change is more i.e. it shows more decrease in weight (syneresis) as indicated by negative values in the graph (Figure 4 & 5). The pH of the solution and ion released by alginate gel stored in distilled water at 1 hour and 24 hours is shown in the Table 1.

DISCUSSION Exposure of impressions to air during

0.8 Mean dimensional change (%)

0.6 0.4 0.2 0 -0.2 0

10

20

30

-0.4

Dimensional changes in distilled water (%)

-0.6 -0.8 -1 -1.2

Time (hours)

Figure 3 Mean dimensional change (%) Vs Time (hours) of specimen stored in distilled water

Mean dimensional change (%)

1 0.5 0 0

10

20

Dimensional changes in 0.2% NaCl solution (%)

-0.5 -1

Dimensional changes in 1.0% NaCl solution (%)

-1.5 -2

30

Dimensional changes in 0.02% NaCl solution (%)

Time (hours)

Figure 4 Mean dimensional change (%) Vs Time (hours) of specimen stored in NaCl solutions at three different concentration

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Storage Environments and Dimensional Stability of Alginate Impression storage in open atmosphere, results in loss of water and accompanying increase in ion concentrations (probably K+, Na+, Ca+2and SO42 ). The temperature and moisture plays a major role in syneresis as indicated by more dimensional changes in the samples stored in open air and in humidity chamber at lab temperature and which is lesser at lower temperature in humidity chamber. Loss of weight is more on refrigerator at 8+2°C compared to same conditions in humidity chamber, since the volume, enclosing the sample is less with later case. The sample stored in airtight sachets is more stable than that stored in refrigerator directly, indicated by less volume of

The effects of storage in NaCl and K2SO4 salt solutions can be understood by Hofmeister or lyotropic series in which ions of metallic salts can be arranged in order of their decreasing ability to precipitate lyophilic substances from colloidal dispersion (anion order: SO4-2 >C2H3O2- > Cl->NO3->ClO3->I>CNS; cation order: Mg+2 >Ca+2 >Sr+2 >Ba+2>Li+ >Na+ >K+).6 As the coagulation power/extent of coagulation/precipitation of gel is high (because of high concentration of ions/electrolytes), volume will decrease and thus shrinkage takes place. Although dimensional changes can be slowed by certain storage conditions, the importance of immediate pouring cannot be

Mean dimensional Change (%)

1 0.5 0 0

10

20

Dimensional changes in 2 % K2SO4 solution (%)

-0.5 -1

Dimensional changes in 3% K2SO4 solution (%)

-1.5 -2

30

Dimensional changes in 0.05% K2SO4solution (%)

Time (hours)

Figure 5 Mean dimensional change (%) Vs Time (hours) of specimen stored in K2SO4 solutions at three different concentration

air sachets, getting saturated more quickly. In distilled water initially expands, because of the absorption of water to reach equilibrium. After few hours negative effect (decrease in weight) indicates that, heavier components from the gel are substituted with lighter constituents (H+ ions) of water. The decrease in pH of distilled water during storage indicates the release of H+ ions from the gel into the solution. After one hour storage in distilled water, Na, K, Ca ions are lost and positive dimensional change (increase in weight/expansion) indicates the excess water absorbed by reversible hydrocolloids. 28

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overlooked. Temporary surface stabilization can be achieved by immersion in dilute aqueous solution of 0.02% NaCl and 0.05% of K2SO4 for 24 hours and also in humidity chambers and zip lock polythene sheets in refrigerator at low temperature up to 6 hours which shows minimal dimensional changes ±0.5%. Linear dimensional changes for these materials were within the limits of the ANSI/ADA specification7. Long term storage in all conditions other than 0.02% NaCl 0.05% of K2SO4, shows more dimensional changes which are clinically significant. Further studies need to be carried out to find out exact methods of volume changes, ion release in various storage media at different time and

International Journal of Health and Rehabilitation Sciences

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Storage Environments and Dimensional Stability of Alginate Impression factors affecting the dimensional changes of alginate gel.

CONCLUSION For maximum dimensional stability, theoretically the cast should be poured immediately. If it is not possible the impression can be stored in 0.02% NaCl or 0.05% of K2SO4, solutions for about 24 hours, facilitating the shifting to distant laboratories from the clinics. This can also be stored in humidity chamber or zip lock polythene sachets in refrigerator at 8+2°C up to 6 hours. These have additional benefit of increasing surface hardness of the gypsum cast. The concentrations of these storage solutions will depend on various products and water powder ratio, which may be further studied in detail.

CONFLICTS OF INTEREST None declared

NOTE This article was presented in National seminar on “Emerging trends in chemical sciences” held on 14th to 16th February 2013 at Mangalore, Karnataka, India.

REFERENCES 1. Swartz MI, Richard D, Norman, Gilmore HW, Phillips RW. Studies on syneresis and imbibition in reversible hydrocolloid. J Dent Res. 1957;36(3):472-478. 2. Imbery TA, Nehring J, Janus C, Moon PC. Accuracy and dimensional stability of extendedpour and conventional alginate impression materials. J Am Dent Assoc. 2010; 141(1):32-9. 3. Rodrigues SB, Agusto CR, Leitune VCB, Samuel SMW, Collares FM. Influence of delayed pouring on irreversible hydrocolloid properties. Braz oral res. 2012;26(5):404-9. 4. Gilmore HW, Phillips RW, Swartz MI. The effect of residual stress and water change on the deformation of hydrocolloid impression materials. J Dent Res 1958;37(5):816-823. 5. Saito S, Ichimaru T, Araki Y. Factors affecting dimensional instability of alginate impressions during immersion in the fixing and disinfectant solutions. Dent Mater J. 1998;17(4):294-300. 6. Civjan S, Huget FE, Laszlo B, Simon D. Surface characteristics of alginate impressions. J Pros Dent. 1972;28(4):573-578. 7. Nassar U, Hussein B, Oka A, Carey JP, Mir CF. Dimensional accuracy of 2 irreversible hydrocolloid alternative impression materials 29

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with immediate and delayed pouring. J Can Dent Assoc. 2012;78:c2. 8. Bradna P, Cerna D. Impact of water quality on setting of irreversible hydrocolloid impression materials. J Pros Dent. 2006;6(6):443-448. 9. C.M. Fellowsa, Thomas B. Determination of bound and unbound water in dental alginate irreversible hydrocolloid by nuclear magnetic resonance spectroscopy. Dent mater J. 2009;25:486–493. 10. Walkera MP, Burckhardb J, Mittsc DA, Williams KB. Dimensional change over time of extended-storage alginate impression materials. Angle Orthod. 2010;80(6):1110-5. 11. Muzaffar D, Ahsan SH, Afaq JA. Dimensional changes in alginate impression during immersion in a disinfectant solution. J Pak Med Assoc. 2011;61(8):756-9. 12. Hiraguchi H, Kaketani M. Effect of immersion disinfection of alginate impressions in sodium hypochlorite solution on the dimensional changes of stone models. Dent Mater J. 2012;31(2):280–286. 13. Funda B, Nuran Y, Zeynep D. Thermal and PH changes, and dimensional stability in irreversible hydrocolloid impression material during setting. J Dent Mater. 2002; 21(2):200-209. 14. Skinner EW, Pones CE. Syneresis in hydrocolloids. J Am Dent Assoc. 1946;33:12531260. 15. Koshi RE. Comparative study of selected alginate materials and devices. J Am Dent Assoc. 1977;94:713-716. 16. Rodrigues SB, Augusto CR, Leitune VCB, Samuel SMW, Collares FM. Influence of delayed pouring on irreversible hydrocolloid properties. Braz Oral Res. 2012;26(5):404-409. 17. Hondrum OS, Fernandez R. Effects of long term storage on the properties of an alginate impression material. J Pros Dent. 1997;77(6): 601-606.

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