SECTIONEDITOR
The presence and identification dental laboratories G. Lynn Barbara
of organisms
transmitted
to
Powell, D.D.S.,* Robert D. Runnells, D.D.S.,** A. Saxon, B.A.,*** and Brian K. Whisenant, B.S.****
University of Utah, School of Medicine, Salt Lake City, Utah The potential for infection of dental personnel in the office and dental laboratory by transmission of microorganisms between dentists’ offices and commercial dental laboratories does exist. Sixty-seven percent of all materials sent from dental offices to dental laboratories sampled in four cities were contaminated with bacteria of varying degrees of opportunistic pathogenicity. Dental o5ces and dental laboratories need to practice adequate infection control procedures to prevent possible cross-contamination. (J PROSTAET DENT 1990;64:236-7.)
A
11dental laboratories, defined as both in-practice and commercial laboratories, have been receiving increasing scrutiny from a number of investigators as potential sources for infectious disease cross-contamination. The potential for infection by transmission of microorganisms has prompted the U. S. Department of Health and Human Services’ and the American Dental Association2p3 to issue guidelines for cleaning, disinfecting, and handling impressions, dentures, and other items transmitted to and from dental offices and dental laboratories. Others have offered more specific instructions to minimize cross-contamination between personnel in dental offices, dental laboratories, and the patient.4p 5 As dental practitioners become more aware of the modes of transmission of pathogens, laboratory procedures have received increasing attention. According to the Centers for Disease Control,G “Blood and saliva should be thoroughly and carefully cleaned from material that has been used in the mouth (e.g., impression materials, bite registration), especially before polishing and grinding intra-oral devices. Contaminated materials, impressions, and intra-oral devices should also be cleaned and disinfected before being handled in the dental laboratory and before they are placed in a patient’s mouth.” Previous studies have reported that organisms are transmitted from impressions to casts7 and from dentures to pumice, where they continue to live.8 However, identification of the organisms that are actually transferred from the
Presented at the Society for Infection Control in Dentistry ing, San Francisco, Calif. *Associate Professor, Department of Pathology. **Clinical Assistant Professor, Department of Pathology.
***Senior ResearchSpecialist, Department of Pathology. ****Laboratory
Technician,
Department
of Pathology.
10/l/17396 THEJOURNALOFPROSTHETIC
DENTISTRY
meet-
dental office to the dental laboratories or the frequency of the presence of organisms has not been :reported. Whereas it is generally accepted that microbes are routinely transmitted from dentists’ offices to laboratories, this study was undertaken to establish a direct correlation between these dental facilities and to identify any organisms present.
METHODS
AND MATERIAL
Laboratories in four different geographic regions of the country (San Francisco, California; Houston, Texas; Denver, Colorado; and Salt Lake City, Utah) were chosen to be representive of patient profiles, types of organisms, dental practices, and dental laboratories. In each of the regions, dentures, impressions, and crowns were cultured on their arrival at dental la’boratories to determine the extent of viable organisms present on these items. The samples were taken before any disinfecting procedures were followed in the laboratory. A minimum of 20 bacterial samples from at least 20 separate items were obtained for each region for a total of 100 bacterial samples. Thirty viral samples, 10 from each city, were collected from three of the cities for the study. Sampling was conducted separately for bacterial and viral culturing. The dental items to be sampled were vigorously rubbed with sterile cotton swabs and the swabs were placed in Culturette (Marion Scientific, Ktmsas City, MO.) bacterial or viral transport tubes. Samples were transported under refrigeration at 3OC to the University of Utah Pathology Department in Salt Lake City, IJtah. All bacterial samples were processed within 12 hours and all viral samples within 24 hours after being obtained from the dental items. Standard microbiology laboratory methods and procedures of the University of Utah Department of Pathology were used to culture, incubate, and identify the organisms 235
POWELL
Table I. Representative summary of laboratory samples Sample
22 Impression 23 Crown
Microbiology
results
62 Complete denture
No growth Alpha-hemolytic Streptococcus species Staphylococcus species Alpha-hemolytic Streptococcus species Staphylococcus species Micrococcus species Staphyloccus species Two types of fungus Diphtheroids Bacillus species Pseudomonas species No growth Alpha-hemolytic Streptococcus species Neisseria species Enterobacter species (two species) Staphylococcus species Corynebacterium species Bacillus species No growth Staphylococcus species Alpha-hemolytic Streptococcus species Staphylococcus species
63 Rubber base impression
Enterobacter cloacae Staphylococcus species Alpha-hemolytic Streptococcus
24 Wax occlusion rim
25 Wax occlusion rim
26 Irreversible hydrccolloid 38 Crown 39 Denture
40 Wax jaw relation record 41 Impression 61 Partial denture
64 Artificial stone cast 65 Wax jaw relation record 92 Irreversible hydrocolloid 93 Impression 94 Stone cast 95 Reline
species No growth Alpha-hemolytic Streptococcus species Escherichia
coli
Alpha-hemolytic Streptococcus species Alpha-hemolytic Streptococcus species No growth Alpha-hemolytic Streptococcus species
Staphylococcusspecies 96 Complete denture
97 Complete denture
Alpha-hemolytic Streptococcus species Gamma-hemolytic Streptococcus species Klebsiella oxytoca Pseudomonas species (three
types)
from the samples. Controls were used to assure the aterility of the cotton swabs and reliability
of the techniques.
Samples were identified by number only and were used to identify
236
the type of items sampled, city, and organism
ET AL
found. No record was made of the office or patient from which the samples were obtained.
RESULTS Sixty-seven percent (67 of 100) of the items sampled showed the presence of bacteria. The identification of bacteria showed the presence of such organisms as Enterobacter cloacae, Escherichia coli, and Klebsiella oxytoca plus
many others. Representative samples are shown in Table I. None of the items sampled (0 of 30) demonstrated the growth or presence of viral contamination.
DISCUSSION This study confirms the need for dental laboratories and dentists to practice adequate infection control procedures for all dental items sent to or received from dental laboratories. Sixty-seven percent of the impressions, dentures, crowns, and wax occlusion rims sampled showed the presence of the microorganisms of varying pathogenicity. Since no attempt was made to identify items that had been disinfected by dentists before transfer to the commercial laboratories, it is presumed that some of the offices submitted items that had been treated with a disinfectant. If such a presumption is correct, the number of contaminated incoming items would be higher than 67% without such treatment. No samples showed the presence of viruses. However, this result should not be considered as validation that viruses are not transmitted on the materials tested. Because none of the 30 samples showed the presence of viruses, several possibilities exist: (1) no viruses were present on these samples; (2) the transport methods used did not allow the more fragile viral agents to survive; (3) current screening methods do not allow for growth and identification of all potential viruses; and (4) the number of transports and handling, from dentist to commercial laboratory to transport media to microbiologic laboratory, did not allow survival of the viruses. Further research is necessary to determine whether the development of better methods for handling viruses is necessary. Such research should include artificial
contamination
with viruses of items in dentists’
offices and subsequent tracing of such known contaminants from offices to the laboratories and back to the office.
SUMMARY Dental impressions, dentures, crowns, and wax occlusion rims received by commercial dental laboratories from different dental offices in four U.S. cities were sampled microbiologically for the presence of microorganisms. Sixty-seven percent of the samples showed the presence of bacteria of varying opportunistic pathogenicity, including the organisms Enterobacter cloacae, Klebsiella oxytoca, and Pseudamonas aerugenosa, which under the right circumstances, such as lacerations or cracks of the skin, could
result in an infection. Of concern, however, is that the presence of isolated organisms demonstrates the possibil-
AUGUST
1990
VOLUME
64
NUMBER
2
ORGANISMS
TRANSMITTED
TO LABORATORIES
ity of transmitting pathogens such as group A Streptococcus, Staphylococcus aureus, Mycobacterium tuberculosis, Chlamydia, and Mycoplasma from the dental patient to dental personnel. None of the samples showed the presence of viruses. This study confirms the need for dental laboratories and dental offices to practice adequate infection control procedures to prevent the possibility of cross-contamination by pathogenic microorganisms among patients, dental office, and dental laboratory personnel. REFERENCES 1. U.S. Department of Health and Human Services, Public Health Service. Recommended infection control practices for dentistry. MMWR 1986; 35:237-42. 2. Council on Dental Therapeutics, Council of Prosthetic Services, and
Dental Laboratory Relations. Guidelines for infection control in the dental office and the commercial dental laboratory. J Am Dent Assoc 1985;110:969-72.
Interim
acrylic
resin duplicate
3. Council on Dental Materials, Instruments, and Equipment: Council on
Dental Practice, Council on Dental Therapeutics. Infection control recommendations for the dental office and dental !.aboratory. J Am Dent Assoc 1988;116:241-8. Schaefer ME. Infection control in dental labors tory procedures. CDA 1985;13:81-4. Runnells RR. Infection control in the dental laboratory. Salt Lake City, Utah: Publishers Press, 1984. Centers for Disease Control. Recommendations for prevention of HIV transmission in health-care settings. MMWR 1987;36(Suppl 2S):8. 7. Leung RL, Schonfeld SE. Gypsum casts as a potential source of microbial cross-contamination. J PROSTHET DENT 1983;493210-1. 8. Williams N, Falkler W Jr, Hasler J, Romberg E. The persistence of contaminant bacteria in dental Iaboratory pumice [Abstract]. J Dent Res 1985;64:258. Reprint requests to: DR. G. LYNN POWELL DENT& EDUCATION, BLIK. 518 UNIVERSITY OF UTAH SALT LAKE CITY, UT 84112
removable
partial
dentures
W. Lance McKitrick, D.D.S.,* and David Dutko, D.D.S.** Indiana University, School of Dentistry, Indianapolis, Ind. Certain dental procedures require patients to be without their removable partial dentures. This can be a great inconvenience and psychologically difecult for some patients. This procedure permits duplicating existing removable partial dentures so that patients will not have to be without prostheses. (J PROSTHET DENT 1999$4:23740.)
D
uplicate complete dentures have been used for many years. l-l9 However, the use of duplicate removable partial dentures to meet the needs of partially edentulous patients has often been overlooked. As patients are undergoing dental treatment, procedures may be necessary that would be more acceptable to the patient if they had an interim prosthesis. These procedures may include: (1) making new retainers to fit an existing removable partial denture, (2) making new retainers and a new removable partial denture, (3) rebasing a removable partial denture, (4) repairing or relining that requires keeping the prosthesis for an extended period of time, and (5) preparatory phases of treatment before placement of an immediate complete denture. This article describes a procedure for making duplicate removable partial dentures. Some advantages of using this procedure to make a du-
*AnesthesiologyResident, Boston City Hospital, Boston University Medical School. **General practice, Victorville, Calif. 10/l/20007
TEE JOURNAL
OF PROSTHETIC
DENTISTRY
plicate removable partial denture are (1) it is a simple, adequately accurate, and fairly rapid procedure; (2) there is less inconvenience for the patient; (3) the prosthesis is easy to modify as treatment progresses; (4) existing occlusal relationships and tooth positions are easily duplicated; and (5) the patient has a spare prosthesis after placement of the definitive removable partial denture. Some disadvantages are that it may be necessary to make a reline impression in the old partial denture before proceeding and in some instances it may be more desirable to make an impression and a treatment partial denture.
PROCEDURE Modification of existing prosthesis Most removable partial dentures to be duplicated will have metal major connectors. Because the duplicate denture will be made in acrylic resin, it will be n.ecessaryto reinforce the major connector for strength. 1. Reinforce the existing metal major connector by adding W8x.
2. Attach large sprue formers (Periphery Wax, Columbus Dental, St. Louis, MO.) to the most distal polished surfaces of the prosthesis (Fig. l).i 237
The presence and identification dental laboratories G. Lynn Barbara
of organisms
transmitted
to
Powell, D.D.S.,* Robert D. Runnells, D.D.S.,** A. Saxon, B.A.,*** and Brian K. Whisenant, B.S.****
University of Utah, School of Medicine, Salt Lake City, Utah The potential for infection of dental personnel in the office and dental laboratory by transmission of microorganisms between dentists’ offices and commercial dental laboratories does exist. Sixty-seven percent of all materials sent from dental offices to dental laboratories sampled in four cities were contaminated with bacteria of varying degrees of opportunistic pathogenicity. Dental o5ces and dental laboratories need to practice adequate infection control procedures to prevent possible cross-contamination. (J PROSTAET DENT 1990;64:236-7.)
A
11dental laboratories, defined as both in-practice and commercial laboratories, have been receiving increasing scrutiny from a number of investigators as potential sources for infectious disease cross-contamination. The potential for infection by transmission of microorganisms has prompted the U. S. Department of Health and Human Services’ and the American Dental Association2p3 to issue guidelines for cleaning, disinfecting, and handling impressions, dentures, and other items transmitted to and from dental offices and dental laboratories. Others have offered more specific instructions to minimize cross-contamination between personnel in dental offices, dental laboratories, and the patient.4p 5 As dental practitioners become more aware of the modes of transmission of pathogens, laboratory procedures have received increasing attention. According to the Centers for Disease Control,G “Blood and saliva should be thoroughly and carefully cleaned from material that has been used in the mouth (e.g., impression materials, bite registration), especially before polishing and grinding intra-oral devices. Contaminated materials, impressions, and intra-oral devices should also be cleaned and disinfected before being handled in the dental laboratory and before they are placed in a patient’s mouth.” Previous studies have reported that organisms are transmitted from impressions to casts7 and from dentures to pumice, where they continue to live.8 However, identification of the organisms that are actually transferred from the
Presented at the Society for Infection Control in Dentistry ing, San Francisco, Calif. *Associate Professor, Department of Pathology. **Clinical Assistant Professor, Department of Pathology.
***Senior ResearchSpecialist, Department of Pathology. ****Laboratory
Technician,
Department
of Pathology.
10/l/17396 THEJOURNALOFPROSTHETIC
DENTISTRY
meet-
dental office to the dental laboratories or the frequency of the presence of organisms has not been :reported. Whereas it is generally accepted that microbes are routinely transmitted from dentists’ offices to laboratories, this study was undertaken to establish a direct correlation between these dental facilities and to identify any organisms present.
METHODS
AND MATERIAL
Laboratories in four different geographic regions of the country (San Francisco, California; Houston, Texas; Denver, Colorado; and Salt Lake City, Utah) were chosen to be representive of patient profiles, types of organisms, dental practices, and dental laboratories. In each of the regions, dentures, impressions, and crowns were cultured on their arrival at dental la’boratories to determine the extent of viable organisms present on these items. The samples were taken before any disinfecting procedures were followed in the laboratory. A minimum of 20 bacterial samples from at least 20 separate items were obtained for each region for a total of 100 bacterial samples. Thirty viral samples, 10 from each city, were collected from three of the cities for the study. Sampling was conducted separately for bacterial and viral culturing. The dental items to be sampled were vigorously rubbed with sterile cotton swabs and the swabs were placed in Culturette (Marion Scientific, Ktmsas City, MO.) bacterial or viral transport tubes. Samples were transported under refrigeration at 3OC to the University of Utah Pathology Department in Salt Lake City, IJtah. All bacterial samples were processed within 12 hours and all viral samples within 24 hours after being obtained from the dental items. Standard microbiology laboratory methods and procedures of the University of Utah Department of Pathology were used to culture, incubate, and identify the organisms 235
POWELL
Table I. Representative summary of laboratory samples Sample
22 Impression 23 Crown
Microbiology
results
62 Complete denture
No growth Alpha-hemolytic Streptococcus species Staphylococcus species Alpha-hemolytic Streptococcus species Staphylococcus species Micrococcus species Staphyloccus species Two types of fungus Diphtheroids Bacillus species Pseudomonas species No growth Alpha-hemolytic Streptococcus species Neisseria species Enterobacter species (two species) Staphylococcus species Corynebacterium species Bacillus species No growth Staphylococcus species Alpha-hemolytic Streptococcus species Staphylococcus species
63 Rubber base impression
Enterobacter cloacae Staphylococcus species Alpha-hemolytic Streptococcus
24 Wax occlusion rim
25 Wax occlusion rim
26 Irreversible hydrccolloid 38 Crown 39 Denture
40 Wax jaw relation record 41 Impression 61 Partial denture
64 Artificial stone cast 65 Wax jaw relation record 92 Irreversible hydrocolloid 93 Impression 94 Stone cast 95 Reline
species No growth Alpha-hemolytic Streptococcus species Escherichia
coli
Alpha-hemolytic Streptococcus species Alpha-hemolytic Streptococcus species No growth Alpha-hemolytic Streptococcus species
Staphylococcusspecies 96 Complete denture
97 Complete denture
Alpha-hemolytic Streptococcus species Gamma-hemolytic Streptococcus species Klebsiella oxytoca Pseudomonas species (three
types)
from the samples. Controls were used to assure the aterility of the cotton swabs and reliability
of the techniques.
Samples were identified by number only and were used to identify
236
the type of items sampled, city, and organism
ET AL
found. No record was made of the office or patient from which the samples were obtained.
RESULTS Sixty-seven percent (67 of 100) of the items sampled showed the presence of bacteria. The identification of bacteria showed the presence of such organisms as Enterobacter cloacae, Escherichia coli, and Klebsiella oxytoca plus
many others. Representative samples are shown in Table I. None of the items sampled (0 of 30) demonstrated the growth or presence of viral contamination.
DISCUSSION This study confirms the need for dental laboratories and dentists to practice adequate infection control procedures for all dental items sent to or received from dental laboratories. Sixty-seven percent of the impressions, dentures, crowns, and wax occlusion rims sampled showed the presence of the microorganisms of varying pathogenicity. Since no attempt was made to identify items that had been disinfected by dentists before transfer to the commercial laboratories, it is presumed that some of the offices submitted items that had been treated with a disinfectant. If such a presumption is correct, the number of contaminated incoming items would be higher than 67% without such treatment. No samples showed the presence of viruses. However, this result should not be considered as validation that viruses are not transmitted on the materials tested. Because none of the 30 samples showed the presence of viruses, several possibilities exist: (1) no viruses were present on these samples; (2) the transport methods used did not allow the more fragile viral agents to survive; (3) current screening methods do not allow for growth and identification of all potential viruses; and (4) the number of transports and handling, from dentist to commercial laboratory to transport media to microbiologic laboratory, did not allow survival of the viruses. Further research is necessary to determine whether the development of better methods for handling viruses is necessary. Such research should include artificial
contamination
with viruses of items in dentists’
offices and subsequent tracing of such known contaminants from offices to the laboratories and back to the office.
SUMMARY Dental impressions, dentures, crowns, and wax occlusion rims received by commercial dental laboratories from different dental offices in four U.S. cities were sampled microbiologically for the presence of microorganisms. Sixty-seven percent of the samples showed the presence of bacteria of varying opportunistic pathogenicity, including the organisms Enterobacter cloacae, Klebsiella oxytoca, and Pseudamonas aerugenosa, which under the right circumstances, such as lacerations or cracks of the skin, could
result in an infection. Of concern, however, is that the presence of isolated organisms demonstrates the possibil-
AUGUST
1990
VOLUME
64
NUMBER
2
ORGANISMS
TRANSMITTED
TO LABORATORIES
ity of transmitting pathogens such as group A Streptococcus, Staphylococcus aureus, Mycobacterium tuberculosis, Chlamydia, and Mycoplasma from the dental patient to dental personnel. None of the samples showed the presence of viruses. This study confirms the need for dental laboratories and dental offices to practice adequate infection control procedures to prevent the possibility of cross-contamination by pathogenic microorganisms among patients, dental office, and dental laboratory personnel. REFERENCES 1. U.S. Department of Health and Human Services, Public Health Service. Recommended infection control practices for dentistry. MMWR 1986; 35:237-42. 2. Council on Dental Therapeutics, Council of Prosthetic Services, and
Dental Laboratory Relations. Guidelines for infection control in the dental office and the commercial dental laboratory. J Am Dent Assoc 1985;110:969-72.
Interim
acrylic
resin duplicate
3. Council on Dental Materials, Instruments, and Equipment: Council on
Dental Practice, Council on Dental Therapeutics. Infection control recommendations for the dental office and dental !.aboratory. J Am Dent Assoc 1988;116:241-8. Schaefer ME. Infection control in dental labors tory procedures. CDA 1985;13:81-4. Runnells RR. Infection control in the dental laboratory. Salt Lake City, Utah: Publishers Press, 1984. Centers for Disease Control. Recommendations for prevention of HIV transmission in health-care settings. MMWR 1987;36(Suppl 2S):8. 7. Leung RL, Schonfeld SE. Gypsum casts as a potential source of microbial cross-contamination. J PROSTHET DENT 1983;493210-1. 8. Williams N, Falkler W Jr, Hasler J, Romberg E. The persistence of contaminant bacteria in dental Iaboratory pumice [Abstract]. J Dent Res 1985;64:258. Reprint requests to: DR. G. LYNN POWELL DENT& EDUCATION, BLIK. 518 UNIVERSITY OF UTAH SALT LAKE CITY, UT 84112
removable
partial
dentures
W. Lance McKitrick, D.D.S.,* and David Dutko, D.D.S.** Indiana University, School of Dentistry, Indianapolis, Ind. Certain dental procedures require patients to be without their removable partial dentures. This can be a great inconvenience and psychologically difecult for some patients. This procedure permits duplicating existing removable partial dentures so that patients will not have to be without prostheses. (J PROSTHET DENT 1999$4:23740.)
D
uplicate complete dentures have been used for many years. l-l9 However, the use of duplicate removable partial dentures to meet the needs of partially edentulous patients has often been overlooked. As patients are undergoing dental treatment, procedures may be necessary that would be more acceptable to the patient if they had an interim prosthesis. These procedures may include: (1) making new retainers to fit an existing removable partial denture, (2) making new retainers and a new removable partial denture, (3) rebasing a removable partial denture, (4) repairing or relining that requires keeping the prosthesis for an extended period of time, and (5) preparatory phases of treatment before placement of an immediate complete denture. This article describes a procedure for making duplicate removable partial dentures. Some advantages of using this procedure to make a du-
*AnesthesiologyResident, Boston City Hospital, Boston University Medical School. **General practice, Victorville, Calif. 10/l/20007
TEE JOURNAL
OF PROSTHETIC
DENTISTRY
plicate removable partial denture are (1) it is a simple, adequately accurate, and fairly rapid procedure; (2) there is less inconvenience for the patient; (3) the prosthesis is easy to modify as treatment progresses; (4) existing occlusal relationships and tooth positions are easily duplicated; and (5) the patient has a spare prosthesis after placement of the definitive removable partial denture. Some disadvantages are that it may be necessary to make a reline impression in the old partial denture before proceeding and in some instances it may be more desirable to make an impression and a treatment partial denture.
PROCEDURE Modification of existing prosthesis Most removable partial dentures to be duplicated will have metal major connectors. Because the duplicate denture will be made in acrylic resin, it will be n.ecessaryto reinforce the major connector for strength. 1. Reinforce the existing metal major connector by adding W8x.
2. Attach large sprue formers (Periphery Wax, Columbus Dental, St. Louis, MO.) to the most distal polished surfaces of the prosthesis (Fig. l).i 237
