Guidelines for Developinga Dental Laboratory

Infection-Control Protocol

Pius M. Kimondollo, MS. MDT, CDTAllied Health and Public ServicesSouthern Illinois tjniversityCarbondale, Illinois 62901

Guidelines for developing a dental laboratory infection-control protocol are discussed. A detailed outline ofinfection-control protocol regarding universal precautions,personal protective equipment, hepatitis B vaccination,environmental and surface cleaning and disinfection, andpersonnel training is presented, Int I Proslbodont1992:5:452-456.

E ven though published documentation regardingrisks faced by dental health care personnel

(DHCP) (ie. hepatitis B, herpes simplex II, andother infectious diseases) have existed for manyyears, the recognition of Acquired Immunodefi-ciency Syndrome (AIDS) as a disease in 1981 by ateam of physicians in California and the Center forDisease Control (CDC),^ has changed how infec-tion-control procedures are being practiced in boththe dental office and the dental laboratory.

The general public is concerned about potentialdevastating consequences that may occur if guide-lines for preventing the spread of infection in den-tistry are not followed by all DHCP, Certainly, thepublic has the right to expect the DHCP to doeverything possible to prevent cross-contamina-tion of infectious diseases through the dental officeor the dental laboratory.

All dental laboratories, both in-office and com-mercial, pose certain risks for cross-contaminationof infectious diseases common to dentistry. Thedental laboratory personnel (DLP) (owners andemployees) have the moral and legal responsibilityto prevent cross-contamination via Ihe dental lab-oratory. As members of the dental health care com-munity, DLP are in an ideal position to ensure thatall items (interocclusal registrations, impressionmaterials, intraoral devices, etc) received from the

dental office are decontaminated before they aredistributed to those who will complete the workrequired. Likewise, all items completed in the den-tal laboratory and returned to the dental officeshould be cleaned and disinfected before deliveryto the dental office and subsequent placement inthe patient's mouth.

An integral part of the dental laboratory plan forcontrolling cross-contamination is an infection-control protocol. Such a protocol is helpful instandardizing procedures and educating personnel.

This paper provides an outline of a laboratoryprotocol for practicing universal precautions, per-sonal protection, hepatitis B vaccination, environ-mental and surface cleaning and disinfection, andinfection-control training.

Universal Precautions

Universal precautions should be used by all DLPto prevent cross-contamination of infectious dis-eases through dental items (eg, interocclusal reg-istrations, impressions, intraoral devices) receivedin the laboratory from the dental office. All itemsreceived from the dentai office should be treatedas if they harbor microorganisms responsible forhepatitis B, the human immunodeficiency syn-drome, or other infectious diseases.'

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Personal Protective Equipment

Any DLP having the potential for occupationalexposure to blood-borne pathogens or other infec-tious diseases should be required to wear protec-tive equipment (eg, disposable or utility gloves,face masks, protective eye wear, laboratory coats).Appropriate personal protective equipment shouldbe made available to all laboratory personnel basedon the type of exposure expected.

Disposable Cloves

Disposable (ie, latex or vinyl) gloves should beworn by all laboratory personnel who have thepotential for direct hand-skin contact with bloodor other potentially infectious materials and bythose who unpack items hrought to the laboratoryfrom the dental office. Gloves should also be wornby personnel when packing completed productsfrom the laboratory to be delivered to the dentaloffice and subsequently placed into the patient'smouth. Used disposable gloves should be changedand disposed of appropriately after completion ofeach procedure.

Hands must be washed before wearing dispos-able gloves and after gloves have been removed.It is important to recognize that the warm and moistenvironment of the gloved hands encouragesmicroorganisms to multiply rapidly on the hands.When performing laboratory tasks such as unpack-ing items received from the dental office, pouringimpressions, and packing items to be delivered tothe dental office, DLP should wear disposablegloves.

Utility Cloves

Only reusable utility gloves, such as ncopreneor polynitrile gloves that are puncture resistant,should be worn by all laboratory personnel whencleaning and disinfecting equipment and surfaces(eg, sinks, pumice pans, laboratory pans, workbench tops, ultrasonic cleaners, bristle brushes, ragwheels, articulators, reusable base formers, face-bow transfers, mixing spatulas and bowls, lathes,handpieces, cast trimmers, grinding burs andstones, vibrators, immersible disinfectant con-tainers, quick polymerization units-pots) and whendisposing of trash. Reusable puncture-resistant util-ity gloves are excellent for handling contaminatedinstruments because they prevent accidental punc-ture or other types of injuries when sharp instru-ments are cleaned and protect hands fromchemical irritation. Hands must be considered con-

taminated after each cleanup, even when glovesare worn, and must be washed appropriately withantiseptic soap after glove removal. Reusable utilitygloves that have been used must be washed anddisinfected before they are stored. It is importantto inspect utility gloves for cracks, peels, tears,punctures, or any other signs of deteriorationbefore rinsing them.

Antiseptic Hand Washing

All laboratory personnel should be required towash their hands with antiseptic soap before andafter putting on gloves and after completing eachlaboratory procedure that involves working withintraoral devices and/or cleaning and disinfectingintraoral devices, laboratory equipment, and sur-faces. The rationale for washing hands with anti-septic soap is to combat the tendency for increasedskin microbe replication during the period whengloves are worn. It is important to note that regularhandwashing with antiseptic soap helps to protectthe skin from pathogens.'

Face M^sks/Protective Eye Wear

Face masks and protective eye wear should beworn by any laboratory personnel who expectsplashes, spray, spatter, blood droplets or aerosols,and potential nose or mouth contamination. Theuse of face masks and protective eye wear shouldbe required when pouring impressions on a vibra-tor, grinding casts using a cast trimmer, using a latheand/or handpiece, and polishing with pumice onrotating rag wheels or bristle brushes. It is importantthat face masks be changed frequently becausemoisture promotes the growth of bacterial micro-organisms. Likewise, protective eye wear shouldbe routinely cleaned, disinfected, and dried after

Laboratory Coats

All laboratory personnel should wear laboratorycoats when performing tasks that involve spatter,spray, splashes, and blood droplets or aerosols—whenever there is potential for soiling. Laboratorytasks that require each individual to wear labora-tory coats include: trimming casts, pouring impres-sions, polishing, grinding, unpacking itemsreceived from the dental office, packing completeditems to be delivered to the dental office, andcleaning and disinfecting laboratory equipmentand surfaces.

It is important that laboratory personnel wear

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laboratory coats that cover street clothes. Addi-tionally, the laboratory coats should be removedin the laboratory: they sbould not be worn outside.The coats should also be stored appropriately andchanged at the first indication of soiling.

Hepatitis B Immunization

All laboratory personnel who have not been pre-viously vaccinated or have not had antibody testingrevealing immunity should receive hepatitis B virusimmunization. Such immunization is done at tberisk of the individual. It is recommended that tbeimmunizations consist of an initial dose followedby a second dose in 1 month, and a third dose at6 months (zero-one-six).'^ Additionally, immu-nized individuals should be tested 1 month aftercompleting the vaccine because one person out often does not respond. Repeating the immunizationhas produced immunity in most people.'=•" It isimportant that laboratory personnel be tested forantihepatitis B virus before receiving immunizationbecause if an individual is a carrier, that personcannot respond to the vaccine.''^

Cleaning and Disinfection

Effective cleaning and disinfection will help tomaintain a sanitary laboratory environment as wellas to minimize the potential for cross-contamina-tion of infectious diseases via the laboratory. Alllaboratory personnel must observe procedures thatmaintain a hygienic and sanitary environment. Util-ity gloves that are puncture resistant musí be wornto protect hands from contamination by pathogens.

Laboratory sanitation measures must include thefollowing areas: air ventilation and suction systems,equipment and instruments, and floors and sur-faces.

Air Ventilation/Suction Systems

Air ventilator filters and vacuum bags or suctionunit filters should be changed and/or cleaned reg-ularly to improve their effectiveness and efficiency.

Equipment/Instruments

Laboratory personnel should clean and disinfectequipment and instruments that have been con-taminated or have the potential for becoming con-tatninated by pathogens. Such laboratoryequipment and instruments include: grindinglathes and handpieces, ultrasonic units, packing

boxes, trash containers, utility gloves, pumice pans,laboratory pans, protective eye wear, vibrators, casttrimmers, articulators, facebow transfers, quickpolymerization units-pots, burs and stones, polish-ing rag wheels and bristle brushes, and mixingbowls and spatulas.

It should be noted that the present configurationof all laboratory lathes and handpieces does notlend itself to disinfection of both the internal andexternal surfaces. The American Dental Associationand tbe Center for Disease Control currently statethat handpieces should be heat sterilized, if pos-sible.«'-

Research data have sbown that external surfacesof laboratory lathes and handpieces can be disin-fected using surface-disinfecting chemicals. Labo-ratory personnel sbould follow the lathe andhandpiece manufacturers' instructions for propermaintenance, cleaning, disinfection, and compat-ibility witb disinfecting chemicals.

Generally, tbe following approach to laboratorylathe and handpiece cleaning and disinfection witha surface disinfectant should be followed:1. Thoroughly scrub the external portion of the

lathe and/or handpiece with detergent ordetergent disinfectant and rinse with water toremove adherent materials.

2. Thoroughly spray or wipe lathe and/or band-piece with absorbent material (eg, disposablepaper towels) saturated witb a surface disin-fectant that is recommended by tbe manu-facturers. Allow at least a 10-minute contacttime and then rinse with water and dry. Makecertain that tbe surface-disinfecting chemicalbeing recommended by the latbe and/orhandpiece manufacturers is being registeredwith the EPA and is accepted by tbe ADA.^-^

3. Depending on tbe lathe and/or handpiece,apply lubrication before use (follow manufac-turer's instructions).

4. Use plastic wrap, aluminum foil, or othermaterials impervious to water to cover thecleaned and wiped lathe and/or handpiece.Replace the cover after each use.

Floors/Surfaces

Tbe laboratory personnel sbould be required toclean and disinfect floors and other surfaces (eg,workbench tops, sinks) wben they have obviouslybeen contaminated (eg, when there is a spill ofpotentially infectious materials, after unpackingitems received in tbe laboratory from the dentaloffice, or alter packing items to be delivered to tbedental office).

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, Dentai t.abüratorv In feet ion-Control Protocol

Generally, all surfaces should be cleaned anddisinfected at the end of each work day. Othersignificant infection-control practices that shouldbe observed by each laboratory personnel include:

1, Using disposable overgloves when answeringa telephone call if interrupted while perform-ing a task requiring glove wearing

2, Refraining from eating, drinking, applying cos-metics or lipbalm, and handling contact lensesat prohibited areas in the dental laboratory orwork areas where there is potential for occu-pational exposure

3, Using stone that has not been poured againstan impression to make slurry water

4, Mixing polishing pumice with antiseptic liquidsoap

5, Using puncture-resistant utility gloves toretrieve items immersed in disinfecting solu-tion. Avoid using disposable gloves becausedisinfecting solutions cause deterioration ofglove material, resulting in minute tears orpunctures in the gloves during laboratory pro-cedures, thereby contaminating the hands

6, Refraining from placing the ceramic brush inthe mouth when building ceramic restorations

7, Refraining from using saliva to polish a waxpattern

8, Replacing contaminated pumice after eachuse when polishing prosthesis repairs

9, Replacing expired disinfecting solutionaccording to the manufacturer's instructions

10, Using separate pumice pans for polishingrepaired and new prostheses as indicated

11. Using spray bottles instead of gauze and otherapplicators to carry disinfecting solutionswhen cleaning and disinfecting surfaces (Therationale for using spray bottles is to allow thedisinfectant to better penetrate equipmentcrevices. Additionally, spray bottles protectthe disinfectant solution from being inacti-vated or absorbed by costly gauzes, dispos-able paper towels, or sponges,)

12. Diluting disinfecting solutions with water fol-lowing the manufacturer's instructions to pre-vent impairment of the c leaning anddisinfecting efficacy

13, Using mechanical shell blaster only on disin-fected dental items

It is important that universal precautions for pre-vention of cross-contamination of infectious dis-eases are used by each individual performing thetask of cleaning and disinfecting floors and/or othersurfaces. It is also important to use effective dis-infecting chemicals that have the ability to pene-trate and preclean contaminated surfaces. Such

surface-disinfecting chemicals include iodophors,phenolics, chlorine solutions, and glutaraldehydesthat are available in a myriad of formulations andtrade names.

Disinfecting chemicals should indicate on thelabel that they kill Mycobaclerium tuberculosis.This is significant because the tubercle bacillus isan intracellular bacterial parasite that presents asevere challenge to chemical disinfectants used indental offices and laboratories and is considered tobe the next most-resistant microorganism afterbacterial endospores,'"" The mycobacterium tub-erculocidal action assures that the product is anintermediate or higher-level disinfectant and thatit will destroy all pathogens potentially threateningto dentistry.

Disinfecting chemicals should also possess thefollowing additional characteristics:1, The widest possible antimicrobial spectrum2, A rapidly lethal action on all vegetative forms

and spores of bacteria and fungi, protozoa,and viri

3, Activity in the presence of organic matter suchas blood, sputum, and feces and compatibilitywith soaps, detergents, and other chemicalsencountered in use

4, A noncorrosive nature, especially with regardto instruments, equipment, and other metallicsurfaces (the disinfectant also should not alterthe integrity of impression materials, eg, dentalstones)

5, A residual effect to combat pathogens ontreated surfaces

6, Ease of use7, A pleasant odor8, Affordability

Biohazard Labels-Symbols

Any infectious waste or potentially contaminatedmaterials and equipment, such as trash bags andcontainers, should be identified with biohazardlabels and/or symbols.

Training Programs

All laboratory personnel should be required toattend infection-control training at the time of ini-tial employment and annually thereafter, A recordindicating name, date of training, clinician, andcontent covered should be maintained in the per-sonnel file.

It is recommended that the content covered inthe training session(s) include some if not all of thefollowing information:

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1, An explanation of the contents of llie "Occu-pational Exposure to Blood-borne Pathogens"

2, An explanation of the dangers and symptomsof blood-borne diseases

3, An explanation of the modes of transmissionof blood-borne pathogens

4, An outline of the dental laboratory infection-control program (DLICP)

5, A guideline for determining the tasks and pro-cedures that may involve occupational expo-sure to blood-borne pathogens and otherpotentially infectious materials in the dentallaboratory

6, An explanation of the practices that will pre-vent or reduce exposure to blood-borne path-ogens and other infectious diseases, includingappropriate engineering controls, work prac-tices, and personal protective equipment

7, Information on the types, proper use, location,removal, and handling of decontaminationand/or disposal of personal protective equip-ment

8, An explanation of the basis for tbe selectionof personal protective matenals and equip-ment

9, Information on the hepatitis B vaccine, includ-ing the efficacy, safety, and benefits of vac-cination for protection (The purpose of thisinformation is to encourage all laboratory per-sonnel to be vaccinated as part of the dentallaboratory's effort to lower the incidence ofdiäease transmitted by occupational expo-sure,]

Summary and Conclusion

A guideline has been presented for developingeffective laboratory infection-control protocol thatis comprehensive enough for any sized dental lab-oratory. All dental laboratories should have infec-t ion control in place. It is the laboratory'sresponsibility to reduce occupational exposure toblood-borne pathogens, as well as to protect itspersonnel and the spread of pathogens to the den-tal office personnel through dental items deliveredfrom the laboratory.

The laboratory infection-control protocol is con-sidered effective only when it supports use of uni-versal precaut ions and disseminat ion of

information regarding varied infectious diseases toall laboratory personnel. Because the developmentof a laboratory infection-control protocol is adynamic process, appropriate review should beconducted annually and improvements should bemade when necessary. Additionally, periodicupdates should be made whenever significantchanges occur regarding laboratory tasks and/orprocedures, materials, and disinfecting chemicals.

These developmental guidelines should provehelpful to dental laboratory owners, managers, orother individuals charged with the responsibility ofdeveloping a laboratory infection-control protocol.

References

1, Center for Disease Control, Update: Universal proceduresfor prevention of transmission of HIV, hIBV, and otherbloodborne pathogens in bealth care setting. MorbidityMortality Weekiy Rep 1988;37:377,

2, Center for Disease Control, Guidelines for Prevention ofTransmission of HiV and HBV lo Healthcare and Public5afety Workers. Atianta, US Department of Health andHuman Services, 19fi9, pp 1-12.

3, Underhili TE, Terezhalniy GT, Cottone JA. Prevention ofcross-contamination in the dental environment, ContEduc DenM986;7:260-269.

4, Occupational Safety and Healtb Administration (OSHA).Enforcement of Procedures for Exposure to HBV and HIV.OSHA Instruction CPL2-2-44B, 1990,

5, Center for Disease Control, Suboptimal response to hep-atitis B vaccine given by injection into the buttocks. Mor-bidity Mortality Weekly Rep 1985;34:I05-n3,

6, Immunization Practices Advisory Committee (iPAC), Hep-atitis B Vaccine: Update on HB Prevention, MorbidityMortality Weekly Rep ]987;36:353-365,

7, Szmuness WR, Goodman A: Passive-active immunizationagainst hepatitis B immunogenicity studies in adult Amer-icans, í.anceM98l:I:575-.S77,

B, Center for Disease Control, Recommended infection con-trol practices for dentistry. Morbidity Mortality Weeklyifep1986;35:237-242,

9. American Dental Association Council on Dental iVlateriais,Instruments, and Equipment; Dental Practice; and DentaiTherapeutics, infection controi recommendations for den-tai office and dental iaboratory. / Am Dent Assocl988;I16:24]-248.

10. Immunization Practices Advisory Committee (iPAC), Mea-sles prevention: Recommendations of tbe ImmunizationPractices Advisory Committee, Morbidity MortalityWeekly Rep ]989;38:sl9,

11, Center for Disease Control. Recommendations for pre-venting transmission of infection with buman T-lympho-tropic virus type Ill/lympbadenopatby-associated virus inthe workplace. Morbidity Mortality Weekly Rep198S;34:682-686, 691-695,

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