Indirect latex glove contamination and its inhibitory effect on vinyl ...

Indirect latex glove contamination and its inhibitory effect on vinyl polysiloxane polymerization Katsuhiko Kimoto, DDS, PhD,a Kinya Tanaka, DDS, PhD,b Minoru Toyoda, DDS, PhD,c and Kent T. Ochiai, DDSd Kanagawa Dental College, Kanagawa, Japan; UCLA School of Dentistry, Los Angeles, Calif; Division of Bioengineering, Surgical and Therapeutic Sciences, University of Southern California, Los Angeles, Calif Statement of problem. The inhibitory effect of indirect latex contamination on the polymerization of vinyl polysiloxane (VPS) impression material has been previously reported. However, the transfer of specific elements that cause inhibition has not been confirmed, nor has the removal of such contaminants been reported. Purpose. This study examined the surfaces of materials commonly used in restorative procedures that were contaminated by indirect latex glove contact and then evaluated for inhibition of polymerization of VPS. The effect of selected cleansing procedures was then studied. Material and methods. Four experimental groups (n = 8) were prepared: (1) clean vinyl gloves (control), (2) clean gingival retraction cords (control), (3) contaminated vinyl gloves, and (4) contaminated gingival retraction cord. Microscopic evaluation of the appearance and the characterization of surface particulate contamination were performed for each. Three cleansing protocols were then evaluated for efficacy in cleaning vinyl glove surfaces contaminated by latex contact (n = 10): (1) brushing with water, (2) brushing with soap/rinsing with water, (3) cleansing with rubbing alcohol. The subsequent degree of VPS polymerization inhibition was evaluated subjectively. A chi-square test was used for data analysis (a=.05). Results. Particulate sulfur elements and sulfur-chloride compounds were present on the contaminated substrates. None of the 3 cleansing procedures eliminated polymerization inhibition (P=.33). Residual elemental sulfur remained on all tested surfaces. Conclusion. Particulate sulfur and sulfur-chloride compounds were identified as the particulate contamination that resulted in polymerization inhibition of the tested VPS dental impression material. Removal of these contaminants from the tested vinyl gloves and gingival retraction cord was not possible with the 3 cleansing protocols tested in this study. (J Prosthet Dent 2005;93:433-8.)

CLINICAL IMPLICATIONS Particulate sulfur may be easily transferred from latex gloves to vinyl gloves and the gingival retraction cord and may not be readily removable by use of traditional surfactants or physical cleansing procedures.

F

or successful restorative dental treatment with cast restorations, impression materials must possess dimensional accuracy and predictable properties.1 Vinyl polysiloxane impression material (VPS) is a commonly used

a

Assistant Professor, Department of Oral and Maxillofacial Rehabilitation, Kanagawa Dental College. b Assistant Professor, Department of Oral and Maxillofacial Rehabilitation, Kanagawa Dental College. c Professor and Chairman, Department of Oral and Maxillofacial Rehabilitation, Kanagawa Dental College. d Lecturer, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA School of Dentistry; Clinical Associate Professor, Division of Bioengineering, Surgical and Therapeutic Sciences, University of Southern California.

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and readily available addition reaction silicone rubber. Partial or incomplete polymerization of an impression has a detrimental effect on the dimensional accuracy and surface definition of resultant casts used for restorative procedures.2 Inhibition of the polymerization reaction of VPS impression materials may occur with use of latex protective barriers such as gloves or rubber dam material.2-5 It has been proposed that sulfur as a reactive element may interfere with the silicone polymerization reaction.6 Further, elemental sulfur contained within latex gloves or rubber dam material may react with the chloroplatinic acid catalyst in VPS impression material.6-10 The sulfurcontaining chemical zinc diethyl dithiocarbamate used during latex glove fabrication is a preservative and THE JOURNAL OF PROSTHETIC DENTISTRY 433

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vulcanizing accelerator.10 Latex gloves have been shown to cause complete polymerization inhibition of tested VPS materials.6,10 Sulfur has been suggested to be the major contributor to this inhibition.7 Indirect contact of VPS impression material with latex gloves has also been reported to influence the VPS polymerization reaction.2,4,5,11,12 Such indirect latex glove contamination has been reported to occur via vinyl gloves, gingival retraction cord, and periodontal scaling instruments.2,4,5,11 Speculation of indirect contact was discussed by Rosen et al,8 who indicated that an invisible yet active substance remaining on the surfaces of specimens previously touched by a latex glove could cause contamination of the silicone impression material. However, the presence of such transferred chemically active substances has not been previously documented. Methods to remove surface sulfur have been suggested,11,13 although any resulting improvement in VPS polymerization has not been documented. Previously recommended techniques for prevention of polymerization inhibition include switching to nonlatex vinyl barrier materials and cleaning and removing sulfur elements from contaminated surfaces.7,13 In addition to concerns about polymerization inhibition, the prevalence of latex skin sensitivity among health care workers has contributed to the elimination of latex in many medical and dental institutions.14-16 It has been reported that 6% to 12% of health care workers in the United States may have an immediate-type allergic reaction.15,16 Despite the risks of hypersensitivity, latex gloves remain popular because they are puncture resistant, durable, and satisfy most users relative to the continuing need for barrier protection in the clinical environment.17-20 Some researchers have reported that latex gloves demonstrate less defects in manufacture than nonlatex gloves and have suggested that latex gloves provide good protection from blood-borne pathogens.17 The purpose of this investigation was to examine the surface of vinyl gloves and gingival retraction cord materials previously in contact with latex gloves for particulate transfer and to identify any such contaminants. In addition to understanding the impact of identified contaminants on VPS polymerization, this study evaluated the feasibility of contaminant removal with several cleansing procedures commonly used in clinical practice.

MATERIAL AND METHODS Vinyl gloves and gingival retraction cord commonly used for restorative procedures were selected for contamination transfer testing. Clinical latex glove contamination was simulated using a 5-second light rubbing 434

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motion consistent with normal clinical manipulation of the specimen with a latex glove. Four experimental groups (n = 8) were prepared and classified as follows: (1) uncontaminated, clean vinyl gloves (Kenzmedico, Saitama, Japan) (control); (2) clean gingival retraction cord (TDZ Cord; BMD, Osaka, Japan) (control); (3) the same vinyl gloves after 5 seconds of rubbing contact with a latex glove (Kenzmedico); and (4) the same gingival retraction cord after 5 seconds of rubbing contact with the same latex glove. Qualitative analysis was performed on all specimen surfaces using x-ray fluorescence (XRF) spectroscopy (SEA5120; Seiko, Tokyo, Japan), operating with a molybdenum filament (tube at 45 kV, 1 mA, and low vacuum) (1021 torr). Elemental distribution was compared between each surface of the control and experimental groups. A separate qualitative analysis on the surfaces of the experimental groups was performed by scanning electron microscopy (SEM) (S-430; Hitachi, Tokyo, Japan), and an electron probe microanalysis (EPMA 8705; Shimazu, Kyoto, Japan).This was used to identify the chemical composition of these surfaces. The chemical composition was performed by color mapping microanalysis. Sample preparation was performed by arbitrary selection of 2 specimens from each experimental group of glove and retraction cord specimens. These were prepared for microanalysis by standardized specimen coating and embedment in epoxy resin (Epofix Kit; Struers A/S, Ballerup, Denmark). The epoxy-mounted specimens were prepared using 800-grit wet/dry silicone carbide paper (Maruto, Tokyo, Japan) prior to carbon coating and stereoscopic and elemental surface analysis. The cleansing effect on the surface of latexcontaminated vinyl gloves was evaluated for 3 cleaning protocols. Three protocols were selected, similar to traditional hand washing: (1) brushing with tap water (Belted brush; Ishimizu Brush, Tokyo, Japan) for 30 seconds, followed by drying with paper towel; (2) brushing with soap (Cationic detergent; Kao, Tokyo, Japan)/rinsing with water followed by towel drying, and (3) cleansing with cotton gauze saturated with alcohol (Ethanol 83%; Keneiseiyaku, Osaka, Japan) for 30 seconds. For each cleansing protocol (n = 10), VPS impression material was mixed with the proprietary mixing device (Exafine; GC, Tokyo, Japan) and dispensed into an open-top circular mold (2.0 cm in diameter, 1.0 cm high). This was placed in direct, sustained contact with the glove specimens from each of the cleaning protocols. The impression material specimens were allowed to polymerize for 5 minutes, removed, and evaluated for the degree of polymerization. The degree of polymerization was subjectively evaluated by 6 dental school faculty members, each with a minimum of 10 years of clinical experience. They were instructed in the use of an original assessment scale for polymerization completion that VOLUME 93 NUMBER 5

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Fig. 1. Elemental analysis with XRF spectroscopy and comparison of surfaces of restorative material contaminated by latex glove contact. A, Surface of vinyl gloves. B, Surface of vinyl gloves touched with latex glove. C, Surface of gingival retraction cord. D, Surface of gingival retraction cord touched with latex glove. Sulfur elements (S) present on surfaces of vinyl glove and gingival retraction cord contaminated by prior latex contact (arrow).

was developed by the authors. These observations were scored subjectively on a scale of 1 to 5 as follows: 1 = no polymerization, no viscosity change, no polymerization reaction; 2 = slight viscosity change, harder than premixed consistency, specimen viscosity soft, surface soft and wet; 3 = specimen viscosity hard, surface wet and not stable, visible surface distortion; 4 = hard polymerization, surface slightly wet, slightly recognizable surface distortion; 5 = complete polymerization, nonwet surface, no surface distortion noted. Interobserver reliability between the 6 clinicians was 100% when determining whether polymerization inhibition had occurred. Following the determination that complete polymerization had occurred, confirmation by surface resistance to instrumentation and contact by diamond probe (Micro Hardness Tester; Matsuzawa Seki, Tokyo, Japan) was performed. No further determination of polymerization inhibition was performed for the other conditions (1-4). Polymerization inhibition frequencies were determined for each cleaning technique. A chi-square test for independence (a=.05) was used to determine MAY 2005

whether significant relationships between clinically acceptable and unacceptable results for each cleaning technique were observed (Stat View software; Abacus Concepts, Berkeley, Calif). Lastly, spectroscopic XRF analysis was performed again, this time for 3 glove specimens of each of the cleaning protocols previously described. These surfaces were prepared, observed, photographed, and chemically identified by elemental composition.

RESULTS No sulfur particulates were identified on the clean vinyl glove or the gingival retraction cord specimens (Fig. 1, A and C). However, sulfur particulate elements were identified on the surfaces of both vinyl glove and gingival retraction cord specimens that had been in prior contact with the latex (Fig. 1, B and D). EPMA elemental analysis mapping identified the particulates, with red denoting the presence of elemental sulfur and yellow denoting the presence of sulfur-chloride (Fig. 2). The vinyl glove specimens were markedly 435


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Fig. 2. SEM observation and EPMA elemental analysis, mapping of gingival retraction cords and vinyl gloves following simulated contamination. A, SEM finding of vinyl glove contaminated by latex glove contact. B, EPMA analysis of vinyl glove contaminated by latex glove contact. Red color indicates sulfur element. Yellow color indicates sulfur-chloride compound (arrow). C, SEM finding of gingival retraction cord contaminated by latex glove contact. Arrows indicate particles on surfaces and within fibers of gingival retraction cord. D, EPMA analysis of gingival retraction cord contaminated by latex glove contact. Red color indicates sulfur element (arrows). Table I. Result of polymerization inhibition of VPS by 3 traditional cleaning protocols Unacceptable scores Cleaning method

(1)

Brushing with water 0 Brushing with soap/rinsing 0 with water Cleaning with rubbing alcohol 0

Clinically acceptable scores

(2)

(3)

(4)

(5)

0 0

7 6

3 4

0 0

0

3

6

1

P=.33 for chi-square test between clinically acceptable score (5) and unacceptable scores (1-4).

covered with elemental sulfur (Fig. 2, B, red color), and a layer of sulfur-chloride was detected on the surface (Fig. 2, B, yellow color, arrowheads). Particulate debris was also demonstrated as present on the gingival retraction cord specimens. The particulates were interspersed between the fibers in several areas and identified as a sulfur (Fig. 2, C and D). Polymerization inhibition frequency of VPS impression material occurred irrespective of the cleansing technique used. The resulting observations were collected and are reported in Table I. Polymerization inhi436

bition frequency was 100% after brushing with water and the soap/water rinse cleaning. Cleaning with alcohol resulted in polymerization inhibition in 90% of the specimens tested. A chi-square test for independence of these data showed no significant difference between clinically acceptable (score 5) and clinically unacceptable VPS polymerization (score 1-4) as a function of the evaluated cleaning techniques (P=.33). Subsequent XRF microscopy demonstrated the presence of residual sulfur on all vinyl surfaces that had been in prior contact with latex after all 3 cleansing protocols (Fig. 3).

DISCUSSION Although there are some concerns about the use of latex gloves, the gloves remain prevalent in clinical practice because of previously described attributes of puncture resistance, durability, and user satisfaction.17-20 The presence of latex in the clinical dental setting remains, despite prior recommendations for removal. Previous reports have established that latex gloves can impair the polymerization of selected VPS impression materials.2-10 However, the extent and the chemical source of the inhibition of the polymerization reaction VOLUME 93 NUMBER 5

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Fig. 3. Elemental analysis of vinyl glove surfaces following attempted cleansing of latex contamination using 3 techniques. Elemental analysis demonstrated residual particulate sulfur following cleansing attempts. There was residual sulfur on vinyl glove surfaces following all cleansing procedures (arrow). A, Brushing with water. B, Brushing with soap/rinsing with water. C, Rubbing alcohol.

have not been specifically identified. The presence of free sulfur residue in latex gloves has been suggested as the causative mechanism underlying this inhibition. Elemental analysis of the gloves and retraction cord examined in this study demonstrated the transfer of particulate sulfur to the surfaces of vinyl gloves and gingival retraction cord after brief contact with latex. The particulate nature of the demonstrated contaminants is not discernible with the naked eye. Traditional methods of hand washing or cleaning with or without surfactant did not result in particulate removal. This study addressed only brief contact with a single latex glove as a primary source for potential contamination. Other possible sources of latex contamination such as latex rubber dam material were not addressed in this study. Browning et al13 suggested that that the polymerization inhibition of VPS impression material might be reduced or eliminated by mechanical decontamination with toothbrush cleansing of gingival, tooth, and palatal surfaces prior to impression procedures. The present study suggests that such procedures may be unsuccessful on the surface of vinyl gloves. The presence of transferred particulate sulfur was demonstrated on the cleaned vinyl gloves. Elemental analysis identified these particulates as sulfur-chloride. The results of cleansing procedures studied in this investigation call into question the ability to effectively debride items previously contaminated with sulfurchloride compounds due to latex contact. Following latex glove use, the immediate replacement of latex gloves by vinyl gloves may seem clinically appropriate for the prevention of possible contamination and inhibition of VPS impression material polymerization, yet there remains a high potential for indirect contamination based on particulate transfer. In the present study, the degree of VPS polymerization inhibition was evaluated subjectively using a 5-point scale MAY 2005

developed by the authors. Beyak and Chee21 reported inhibition of VPS polymerization as either a polymerization or nonpolymerization condition. However, the authors note that polymerization inhibition may not always be readily observed throughout an entire impression arch. Subtle surface changes or localized areas of an impression material inhibition within a full arch impression might be easily hidden or missed on clinical observation. It was noted that conditions 1 through 4 of the 5-point scale described are polymerization conditions that are clinically unacceptable for restorative dental procedures or requirements. Slight variations in clinical observations that might be reported for the first 4 conditions were not considered a liability to reporting accuracy. Condition 5, representative of complete polymerization, is the only polymerization condition acceptable for clinical use. In the present study, the degrees of polymerization inhibition that were found were all within the clinically unacceptable VPS polymerization score range of 1 to 4. Based on the stereoscopic findings of this study, the indirectly transferred small particulate contaminants from latex gloves were not found to be removable by any of the cleaning methods evaluated. The clinical removal of invisible, microscopic, trace contaminants from the clinical field does not appear possible. Cleansing attempts may not reduce the potential for inhibition of VPS impression material polymerization caused by sulfur contaminants. Gauze or brush rubbing, with or without surfactant, cannot remove the trace elements demonstrated to be present following contamination with sulfur-containing materials. It has been previously recommended that techniques for prevention of polymerization inhibition include use of nonlatex vinyl barrier materials and additional procedures to clean and remove the sulfur elements from 437


contaminated surfaces.7,13 Unless contact with latex is avoided, such cleaning efforts may be unsuccessful. The particulate nature of the identified sulfur-chlorides makes removal difficult, if not impossible, for the clinical setting. The risk of contaminant transfer from latex via brief indirect contact suggests that it may be prudent to completely avoid contact with latex in any area in which VPS will be used. Although vinyl barrier materials have relative disadvantages to latex material in the areas of puncture resistance, durability, and stretch resistance, the exclusive use of such nonallergenic, nonlatex barriers and materials may be necessary during restorative dental procedures that involve VSP impression materials. Elemental sulfur and sulfur-chloride compounds were analyzed qualitatively as candidate elements that inhibit polymerization in this experiment. However, the specific quantitative analysis of these elements was not performed. Sulfur and sulfur-chloride elements have been shown to be a source of VPS inhibition. Should VPS remain a common dental impression material, other barrier materials made of noncontaminating materials with desirable physical properties and costs similar to latex should be developed.

CONCLUSIONS Within the limitation of this in vitro study, the following conclusions can be drawn: 1. The transfer of residual elemental sulfur and sulfur-chloride compounds to vinyl gloves and retraction cord was demonstrated after brief contact with a specific latex glove. 2. These contaminants were not readily removable from vinyl surfaces with the traditional cleaning techniques tested or rubbing alcohol. 3. The polymerization inhibition observed under these experimental conditions appears directly related to the transfer of the identified sulfur compounds.

REFERENCES 1. Shillingburg H, Hobo S, Whitsett L, Jacobi R, Brackett S. Fundamentals of fixed prosthodontics. 3rd ed. Chicago: Quintessence; 1997. p. 281–307. 2. Kahn RL, Donovan TE, Chee WW. Interaction of gloves and rubber dam with a poly(vinyl siloxane) impression material: a screening test. Int J Prosthodont 1989;2:342-6. 3. Neissen LC, Strassler H, Levinson PD, Wood G, Greenbaum J. Effect of latex gloves on setting time of polyvinylsiloxane putty impression material. J Prosthet Dent 1986;55:128-9.

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4. Chee WW, Donovan TE, Kahn RL. Indirect inhibition of polymerization of a polyvinyl siloxane impression material: a case report. Quintessence Int 1991;22:133-5. 5. Kahn RL, Donovan TE. A pilot study of polymerization inhibition of poly (vinyl siloxane) materials by latex gloves. Int J Prosthodont 1989; 2:128-30. 6. Noonan JE, Goldfogel MH, Lambert RL. Inhibited set of the surface of addition silicones in contact with rubber dam. Oper Dent 1985;10:46-8. 7. Cook WD, Thomasz F. Rubber gloves and additional silicone materials. Current note no. 64. Aust Dent J 1986;31:140. 8. Rosen M, Touyz LZ, Becker PJ. The effect of latex gloves on setting time of vinyl polysiloxane putty impression material. Br Dent J 1989;166:374-5. 9. Peregrina A, Land MF, Feil P, Price C. Effect of two types of latex gloves and surfactants on polymerization inhibition of three polyvinylsiloxane impression materials. J Prosthet Dent 2003;90:289-92. 10. Causton BE, Burke FJ, Wilson NH. Implications of the presence of dithiocarbamate in latex gloves. Dent Mater 1993;9:209-13. 11. de Camargo LM, Chee WW, Donovan TE. Inhibition of polymerization of polyvinyl siloxanes by medicaments used on gingival retraction cords. J Prosthet Dent 1993;70:114-7. 12. Chee WW, Donovan TE. Polyvinyl siloxane impression materials: a review of properties and techniques. J Prosthet Dent 1992;68:728-32. 13. Browning GC, Bromme JC Jr, Murchison DF. Removal of latex glove contaminants prior to taking poly (vinylsiloxane) impressions. Quintessence Int 1994;25:787-90. 14. ADA Council on Scientific Affairs. The dental team and latex hypersensitivity. J Am Dent Assoc 1999;130:257-64. 15. Hamann CP, Turjanmaa K, Rietschel R, Siew C, Owenby D, Gruninger SE, et al. Natural rubber latex hypersensitivity: incidence and prevalence of type I allergy in the dental professional. J Am Dent Assoc 1998; 129:43-54. 16. Tarlo SM, Sussman GL, Holness DL. Latex sensitivity in dental students and staff: a cross-sectional study. J Allergy Clin Immunol 1997; 99:396-401. 17. Korniewicz DM, Garzon L, Seltzer J, Feinleib M. Failure rates in nonlatex surgical gloves. Am J Infect Control 2004;32:268-73. 18. Murray CA, Burke FJ, McHugh S. An assessment of the incidence of punctures in latex and non-latex dental examination gloves in routine clinical practice. Br Dent J 2001;190:377-80. 19. Hollaus PH, Lax F, Janakiev D, Wurnig PN, Pridun NS. Glove perforation rate in open lung surgery. Eur J Cardiothorac Surg 1999;15:461-4. 20. Wong PS, Wright JE, White PA. Perforation of gloves. BMJ 1992; 304:1311. 21. Beyak BL, Chee WW. Compatibility of elastomeric impression materials for use as soft tissue casts. J Prosthet Dent 1996;76:510-4. Reprint requests to: DR KATSUHIKO KIMOTO DEPARTMENT OF ORAL AND MAXILLOFACIAL REHABILITATION KANAGAWA DENTAL COLLEGE 82 INAOKA-CHO YOKOSUKA KANAGAWA 238-8580 JAPAN Fax: 81-46-822-8861 E-MAIL: [email protected] 0022-3913/$30.00 Copyright Ó 2005 by The Editorial Council of The Journal of Prosthetic Dentistry.

doi:10.1016/j.prosdent.2005.02.015

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