Effect of disinfectant agents on dimensional stability of elastomeric ...

Effect of disinfectant agents on dimensional stability of elastomeric impression materials Gelson Luís Adabo, DDS, PhD,a Elaine Zanarotti,b Renata Garcia Fonseca,b and Carlos Alberto dos Santos Cruz, DDS, PhDa São Paulo State University, Araraquara Dental School, Araraquara, São Paulo, Brazil Statement of problem. Difficulties in sterilizing impressions by traditional methods have led to chemical disinfection as an alternative, and some studies have shown that disinfectants may adversely affect impressions. Purpose. This study investigated the effect of disinfection methods on the dimensional stability of 6 elastomeric materials. Material and methods. Impression materials were submitted to the following treatments: immersion in 5.25% sodium hypochlorite solution for 10 minutes, immersion in 2% glutaraldehyde solution for 30 minutes, and no immersion (control). After treatments, impressions were poured, and respective stone casts were measured with a Nikon Profile projector and compared with the master model. Results. The elastomeric materials had different reproduction capacities, and the disinfecting treatments did not differ from the control. (J Prosthet Dent 1999;81:621-4.)

CLINICAL IMPLICATIONS Many contagious diseases such as AIDS, hepatitis, and many others can be prevented by practical control of infection in the dental office. Additional control procedures should be followed during the handling of dental impressions, such as disinfecting immediately after removal. In this study, immersion disinfection did not significantly alter on dimensional stability of elastomeric impression materials.

T

he function of dental surgeons as health professionals is to prevent disease in their field or, when disease sets in, to treat it. Concern about cross-infections strongly increased after the rapid evolution of AIDS and hepatitis B, leading the American Dental Association (ADA) to publish guidelines about the control of infection in dental offices and laboratories.1 Among these instructions, such as the use of gloves, caps, masks, eyeglasses, and sterilization of all dental materials, there is also concern about impressions, which, along with trays, are an important source of transmission between patients and dental laboratories. In a study on various impression materials, Gerhardt and Sydiskis2 observed that the materials differ widely in terms of absorption and retention of viruses. Thus, a specific disinfection procedure should be followed for each material. Similarly, Leung and Schonfeld3 reported that stone casts are potential sources of crossinfection and alerted dental professionals to the need to disinfect these casts. In a symposium on hepatitis, Crawford4 emphasized the importance of prevention of cross-contamination in Supported by National Council to Technologic Development and Research (CNPq) #300 816/89-8. aAssistant Professor of Dental Materials. bPostgraduate student, Department of Dental Materials and Prosthodontics. MAY 1999

dentistry. Many contagious diseases such as AIDS, hepatitis, herpes I and II, tuberculosis, and many others can be prevented by practical control of infection in the dental office. When 20 patients are seen per day, at least 1 active carrier may be seen per 7-day interval. Control of cross-infection is a process that consists of various stages such as identification of high risk populations by judicious anamnesis; use of a technical barrier consisting of masks, gloves, eyeglasses, and caps, both on the part of the professional and of his assistants; technique of disinfection and sterilization of instruments, surfaces, and equipment with disinfectant solutions (2% glutaraldehyde, sodium hypochlorite, quaternary ammonium compounds); and autoclaving and using an oven. In a review of infection control practices, Runnells5 stated that prosthetic work may expose professionals and technicians in the vicinity to certain contagious diseases such as AIDS, hepatitis, and tuberculosis. Thus, additional control procedures should be followed during the manufacture and handling of dental impressions and dentures, such as washing and disinfecting impressions immediately after removal. To issue guidelines regarding impression disinfection, the ADA determined the antimicrobial agents to be used for different impression materials and the time, dilution, and temperature needed for each agent’s optiTHE JOURNAL OF PROSTHETIC DENTISTRY 621

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Table I. Evaluated impression materials Code

M1 M2 M3 M4 M5 M6

Trade name

Composition

Manufacturer

Permlastic 3M Xantopren VL Provil L Extrude Wash Impregum F

PS PDS PDS PVS PVS PE

Kerr Manufacturing Co 3M Dental Products Bayer Pharmaceuticals Bayer Pharmaceuticals Kerr Manufacturing Co ESPE

City/state

Romulus, Mich. St Paul, Minn. France France Romulus, Mich. Seefeld, Germany

Table II. Mean values (µm) of the measurements of the stone casts for each experimental condition

T1 T2 T3

M1

M2

M3

M4

M5

M6

24,435.1 24,432.3 24,432.6

24,419.4 24,427.6 24,413.8

24,413.1 24,415.2 24,428.2

24,4343.1 24,429.5 24,430.3

24,421.1 24,428.2 24,407.0

24,445.2 24,436.1 24,455.8

Master model: 24,365 µm.

Table III. Analysis of variance Source of variation

Sum of squares

df

Mean square

F ratio

Significance

Material Treatment Interaction Residue Total

17,626.094 1.878 6,664.1889 14,691.90 171,208.06

5 2 10 162 179

3525.2189 0.9389 666.41889 906.88827

3.887 0.001 0.735

.0024 .9990 .6909

mal performance.1 In another publication, the ADA noted that immersion in a disinfectant improves the wettability of polysulfide but may adversely affect hydrophilic addition reaction silicones.6 In view of the need to control infection in dental offices and dental laboratories, the purpose of this study was to determine the effect of 2 methods for the disinfection of impressions obtained with 6 elastomers. The materials used in this study represent the types that exist on the Brazilian market (polysulfide, addition silicone, condensation silicone, and polyether).

MATERIAL AND METHODS Six impression materials were used (Table I), and all materials were of a light consistency, except the polyether supplied in a regular consistency only. A total of 180 impressions were obtained from a master model (Columbia Dentoform Corp., New York, N.Y.) representing an upper arcade. Reference points for the measurements were the cusp tip of the left canine and the cusp tip of the distobuccal cusp of the first left maxillary molar. Individual acrylic resin trays were manufactured for the impressions. Trays were perforated and, for Permlastic and Impregum, painted with adhesive pro622

vided by the manufacturer. After preparation of individual trays, the materials were manipulated according to manufacturer instructions and impressions obtained by the 1-step technique directly on the master model. After removal and careful inspection, impressions were subjected to 1 of the following disinfecting treatments, based on ADA recommendations: T1: no treatment with a disinfectant solution, with the impressions being simply left to stand on the work bench for 30 minutes (control group) T2: immersion in 5.25% sodium hypochlorite solution (Soda Clorada/Inodon, Porto Alegre, Brazil) for 10 minutes, followed by standing on the work bench for 20 minutes T3: immersion in 2% glutaraldehyde solution (Glutaron, Rio Química Ltda, Rio de Janeiro, Brazil) for 30 minutes. After the resting period, impressions were immediately poured with type IV die stone (Durone, Dentsply, Petrópolis, Brazil). The impression was separated from the stone cast 1 hour after pouring and readings were taken 24 hours later. Each measurement was read 3 times with a Nikon Profile projector (Nikon Corporation, Tokyo, Japan) with 1 µm sensitivity between the reference points and then the average was calculated. VOLUME 81 NUMBER 5

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Table IV. Multiple range analysis of the material factor

Table V. Multiple range analysis of the material treatment

Material

Treatment

Quantity

Measurement

Homogeneous groups

30 30 30 30 30 30

24,418.333 24,418.700 24,420.267 24,431.300 24,433.433 24,445.533

X X X XX XX X

M5 M3 M2 M4 M1 M6

Standard error: 5.498.

The examiner did not have any knowledge regarding what treatments the casts had received before making measurements. The data were submitted to analysis of variance and multiple range analysis for material and treatment with Statgraphics 7.0 software (Statistical Graphics Corp, Rockville, Md.).

RESULTS Table II shows the mean values of the measurements of the stone casts for each experimental condition (in µm). Statistical analysis of the original data (Table III) revealed significant differences in material behavior, but there were no differences in terms of the disinfection treatment (Tables III and V) or material × treatment interaction (Table III). Data regarding the material factor were submitted to the multiple range analysis (Table IV), which showed that the stone casts obtained from impressions made with M6 material (Impregum) were significantly different from those obtained from impressions made with materials M5 (Extrude), M3 (3M impression material), and M2 (Xantopren VL). Materials M1 (Permlastic) and M4 (Provil) produced casts statistically identical to the remaining ones (M6, M5, M3, and M2).

DISCUSSION Measurements of the stone casts obtained from the different elastomers were slightly larger than the measurement of the master model (24,365 µm), with a 0.21% change for material M5 (Extrude), 0.22% for M3 (3M), 0.23% for M2 (Xantopren VL), 0.27% for M4 (Provil), 0.28% for M1 (Permlastic), and 0.33% for M6. Although these percentage alterations are small, they demonstrate that not even the best impression materials can fully reproduce the molded area and suggest that these differences should be considered when preparing indirect restorations executed on these casts. When the mean values for the stone casts were compared on the basis of the disinfecting treatment factor, the results of analysis of variance were confirmed, which proved to be nonsignificant (Tables III and V). These data indicate that the disinfecting treatment did not cause any change in the elastomers compared with the control group. MAY 1999

T1 T2 T3

Quantity

Measurement

Homogeneous groups

30 30 30

24,427.800 24,427.933 24,428.050

X X X

Standard error: 3.887.

The material × disinfectant interaction, as stated earlier, did not reveal any statistically significant differences, demonstrating that there was no interference of one factor with the other. This result is in agreement with studies in the literature that used the most varied media and times of immersion. For example, Tullner et al7 did not observe any negative effect after immersing polysulfide, polyether, and addition reaction silicone impressions in iodophor, 5.25% sodium hypochlorite, or neutral 2% glutaraldehyde. Similar results were obtained by Langenwalter et al8 who studied the same materials immersed in iodophor, sodium hypochlorite, glutaraldehyde or twice deionized water, or exposed to room air for 10 minutes. Similarly, Matyas et al9 concluded that there was no adverse effect of the various disinfecting media on the different impression materials. The same results were obtained by Merchant and Herrera10 in a study of polysulfides immersed in different disinfecting solutions for 30 minutes and also by Herrera and Merchant11 in a study on the dimensional stability of disinfected polysulfide, polyether, or addition silicone. Rios et al12 used longer immersion times (60 minutes) and did not detect any dimensional changes when investigating the dimensional stability of 2 polyethers and an addition reaction silicone disinfected by immersion in chlorine compounds, 2% neutral glutaraldehyde, 3.5% neutral glutaraldehyde, and distilled water. Other disinfecting systems, Hygojet/MD 520 and Impresept, were studied by Kern et al.13 The first was a glutaraldehyde and ammonium chloride spray (storage in a chamber for 10 minutes) and the second a glutaraldehyde and glyoxal solution (immersion system). When the 2 systems were applied for the same period (10 minutes), they did not cause clinically significant effects. Minagi et al14 also observed that silicones were insensitive to immersion in glutaraldehyde, presenting less than 0.03% dimensional changes, although the authors warn that these small differences should be compensated for in the casting process. However, others have demonstrated adverse effects of elastomer immersion in disinfecting solutions. Thouati et al15 observed that elastomer immersion in 5.25% sodium hypochlorite solution for 30 minutes caused expansion of the impressions, whereas immersion in quaternary ammonia and aldehyde solution did not cause significant dimensional changes. Johnson et al,16 among others, warn that polyether is particularly sensitive to immersion and that disinfection by immer623

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sion is contraindicated for this material. Merchant17 also warns that polyether should be disinfected for short periods with the disinfectants accepted by the ADA, which in turn recommends immersion not exceeding 30 minutes. Owens and Goolan18 recommend that polyethers should not be immersed for periods exceeding 5 hours, because they may expand. Care should also be taken with condensation reaction silicone impressions, which may contract because of the loss of subproducts. When sterilization is imperative, as in the case of patients with HIV or hepatitis, the best option is the use of an addition silicone. This had also been observed by Johansen and Stackhouse,19 who concluded that only addition reaction silicone remained stable after immersion in a glutaraldehyde solution for 16 hours, whereas polysulfide and condensation reaction silicone contracted both in a dry environment and in immersions, and polyether contracted in a dry environment and expanded in a humid environment. Another feature discussed is the possible effect of disinfection of the impression on the stone cast produced from it. Davis and Power20 concluded that immersion of the impressions in glutaraldehyde for 30 minutes did not provoke significant dimensional changes in addition reaction silicone or polyether, although humidification of both materials occurred. However, Lepe et al21 stated that both silicones and polyether are relatively hydrophobic and can be disinfected for more than 18 hours without an effect on humidification. They observed that materials suffered some mass loss, especially polyether. In a study on the effect of disinfection on the surface texture of the resulting stone casts, Peutzfeldt and Asmussen 22 observed that some disinfectant/impression combination may provoke changes in the surface texture of the stone, so that the ideal disinfectant should be determined for each impression material. It is important to draw attention to the fact that dimensional changes were determined only in 1 plane. Three-dimensional studies should be performed to determine the security of the disinfectant treatment.

CONCLUSIONS On the basis of the methods used, the following results were drawn: 1. There was a significant difference among the elastomers used. The M2, M3, and M5 materials exhibited better approximation of the master model dimension than the M6 material. The M1 and M4 materials did not differ significantly from the others. 2. For the treatment factor, no significant difference was observed between the control group (no immersion) and the disinfecting treatments with 5.25% sodium hypochlorite solution and 2% glutaraldehyde solution. 624

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3. The interaction between material and treatment was not significant. REFERENCES 1. ADA Council on Scientific Affairs and ADA Council on Dental Practice. Infection control recommendations for the dental office and the dental laboratory. J Am Dent Assoc 1996;127:672-80. 2. Gerhardt DE, Sydiskis RJ. Impression materials and virus. J Am Dent Assoc 1991;122:51-4. 3. Leung RL, Schonfeld S. Gypsum cast as a potential source of microbial cross-contamination. J Prosthet Dent 1983;49:210-1. 4. Crawford JJ. State of the art: practical infection control in dentistry. J Am Dent Assoc 1985;110:629-33. 5. Runnels RR. An overview of infection control in dental practice. J Prosthet Dent 1988;59:625-9. 6. Councils on Dental Materials, Instruments and Equipment prepared at the request of the council by PL Fan, PhD. Disinfection of impressions. J Am Dent Assoc 1991;122:110. 7. Tullner JB, Commette JA, Moon PC. Linear dimensional changes in dental impressions after immersion in disinfectant solutions. J Prosthet Dent 1988;60:725-8. 8. Langenwalter EM, Aquilino SA, Turner KA. The dimensional stability of elastomeric impression materials following disinfection. J Prosthet Dent 1990;63:270-6. 9. Matyas J, Dao N, Caputo AA, Lucatorto FM. Effects of disinfectants on dimensional accuracy of impression materials. J Prosthet Dent 1990;64: 25-31. 10. Merchant VA, Herrera SP, Dwan JJ. Marginal fit of cast gold MO inlays from disinfected elastomeric impressions. J Prosthet Dent 1987;58:276-9. 11. Herrera SP, Merchant VA. Dimensional stability of dental impressions after immersion disinfection. J Am Dent Assoc 1986;113:419-22. 12. Rios MP, Morgano SM, Stein RS, Rose L. Effects of chemical disinfectant solutions on the stability and accuracy of the dental impression complex. J Prosthet Dent 1996;78:356-62. 13. Kern M, Rathmer RM, Strub JR. Three-dimensional investigation of the accuracy of impression materials after disinfection. J Prosthet Dent 1993; 70:449-56. 14. Minagi S, Kohada A, Akagawa Y, Tsuru H. Prevention of acquired immunodeficiency syndrome and hepatitis B. Part III: disinfection of hydrophilic silicone rubber impression materials. J Prosthet Dent 1990; 64:463-5. 15. Thouati A, Deveaux E, Iost A, Behin P. Dimensional stability of seven elastomeric impression materials immersed in disinfectants. J Prosthet Dent 1996;76:8-14. 16. Johnson GH, Drennon DG, Powell GL. Accuracy of elastomeric impressions disinfected by immersion. J Am Dent Assoc 1988;116;525-30. 17. Merchant VA. Update on disinfection of impressions, prosthesis, and casts. ADA 1991 guidelines. J Calif Dent Assoc 1992;20:31-5. 18. Owen CP, Goolam R. Disinfection of impression materials to prevent viral cross contamination: a review and protocol. Int J Prosthodont 1993;6: 480-94. 19. Johansen RE, Stackhouse JA. Dimensional changes of elastomers during cold sterilization. J Prosthet Dent 1987;57:233-6. 20. Davis BA, Powers JM. Effect of immersion disinfection on properties of impressions materials. J Prosthodont 1994;3:31-4. 21. Lepe X, Johnson GH, Berg JC. Surface characteristics of a polyether and addition silicone impression materials after long-term disinfection. J Prosthet Dent 1995;74:181-6. 22. Peutzfeldt A, Asmussen E. Effect of disinfecting solutions on surface texture of alginate and elastomeric impressions. Scand J Dent Res 1990;98: 74-81.

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