8 - Quality Assurance and Infection Control

7/28/2019 8 - Quality Assurance and Infection Control

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Final lecture 1 31-March-2013

Quality Assurance and Infection Control

The reference for this lecture is the textbook: Dental Radiography: Principles and Techniques.

Chapter 10 covers Quality Assurance; Chapter 15 covers Infection Control.

Quality Assurance

Quality assurance is mainly a plan of action to ensure a diagnostic X-ray facilitywill constantly produce high-quality images with minimal radiation exposure to the

patient and personnel (so radiation protection is a part of quality assurance). This plandepends upon professional judgment and standards, which differ among specialties (eachspecialty has its own standards).

It might also be defined as regular testing to detect equipment malfunctions, or anyvariables affecting image quality.

For dentistry, diagnostic images must permit the detection of caries, periodontal problems, and periapical pathosis.

There are quality assurance kits , which are collections of devices for quality assurancethat are sold together that are used for regular maintenance of X-ray equipment. Theyare expensive, however, and if you can't (or don't want to) buy them, you can ask for help from a technician who has this kit and whose job it is to inspect X-ray equipment.

By checking your equipment regularly you benefit greatly; you improve diagnosis, youreduce exposure, and you save time.

Quality Control Tests

We have quality control tests for dental X-ray equipment, supplies, and film processing.Some must be done daily; others must be done weekly, others monthly and others yearly.(Check the table).

You need to have a book in your clinic, it is called retake book. If you want to retake

any image recorded in a book, you write the reason for the retake in order not to do thismistake again.


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Equipment and Supplies

Dental X-ray Machines A quality assurance kit contains many devices to monitor the machine; a dosimeter tomonitor X-ray output, kilovoltage meter to monitor kilovoltage, and others for milliamperage linearity, half-value layer, timer accuracy, focal spot size, beamalignment and tubehead stability.

The little timer-accuracy testing devicemeasures the number of impulses.

A beam-alignment test is performed byexposing four numbered films simultaneouslyto make sure the diameter is n o more than 2.7.

Dental X-ray Film

A simple test: fresh film test unwrap a new unexposed film from a newly-

opened box and process it properly using freshchemicals. The film must appear clear with aslight blue tint (because of emulsion).An


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outdated film is usually foggy (cloudy) due to inappropriate storage conditions or exposure to radiation. Fogged films should not be used.

You can use this test if you're buying films from any suppliers and you want to make surethe films are really new.

Screens and Cassettes

Intensifying screens should be checked for dirt and scratches. They should be cleanedmonthly.

Cassette holders must be examined for worn closures, light leaks, warping, and adequatefilm-to-screen contact.

* Film-to-screen contact test ,

1. You place a film in the cassette holder,2. Place a wire mesh on top of the cassette,3. Expose it at a target-film distance of 40 inches using 10 mA, 70 kVp, and 15

impulses (memorize these numbers!).4. Process the exposed film,5. View it on a viewbox in a dimly-lit room at a distance of 6 feet.

If there is no proper contact between the screen and the film, it will have different areasof darkness (indicating a light leak), and so the image will not be uniform.

Wire mesh image in case of no proper contact exhibits varying densities while in case of good film contact it exhibits a uniform density.

Viewbox Equipment

The viewbox must accommodate the size of the film. So if you have a white area onyour viewbox (if the view box is larger than the film) you must cover it before viewingyour film.

The viewbox should also have adequate lighting in order for you to see the imagesclearly. A viewbox must be cleaned.

Film Processing

Darkroom Lighting

The darkroom must be checked every six months for light leaks, processing solutions,and safelighting.

This is done by simply going into the darkroom, looking at doors, keyholes, and cracks


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to check if there is any light coming in. Light leaks must be correcting with weather stripping or black tape before proceeding with film processing.

# Safelighting test

The coin test is used to make sure that the safelight issafe; in which a coin is placed on an unwrapped,unexposed film, the safelight is turned on for 3-4minutes, and then the film is processed. If the light is notsafe, the film will be fogged except for the area under the coin; because it will be masked by the coin. If thesafelight is safe, there will be no exposure, and after

processing, the film will be completely blue. If a

positive coin test is persistent, white-light leaks should be looked for (through cracks, under-door spaces,keyholes...), or the safelight's position, filter, and bulbwattage. Panoramic films are used in this test becausethey're more sensitive than intraoral films.

Processing Equipment Automatic Processor

The automatic processor can be checked by processing two films, one of which isexposed to light. After processing, one must be dark (the exposed one), the other must belight (the unexposed film). Otherwise, the processor is not working well.

Processing Solutions

Developer strength and fixer strength must be checked. Processing solutions must bereplenished daily and changed every 3 to 4 weeks as recommended by the manufacturer.

Developer Strength

There are three tests used to check for developer strength:

Reference film

It is a film that is processed under ideal conditions (ideal exposure, fresh chemicals,correct duration and temperature) and kept to compare to radiographs processed daily. Amatched density means that daily radiographs are good. If the daily radiograph is lighter than the reference radiograph, this means the developer is weak or cold. If they're darker,the developer solution is too concentrated or too warm.


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Stepwedge radiographs

A stepwedge is an aluminum block that has multiple graduated thicknesses.Different thicknesses result in different densities on a radiograph. So a stepwedgeradiograph will give an image of adjacent bands of different shades (black, shades of

gray, and white), corresponding to different thicknesses of aluminum in the stepwedge.

This radiograph can be used as a reference film. Compared to other films, if there is adifference of more than two densities (two steps), the solution must be changed. If thefilms are darker than the reference stepwedge film, the developer solution is hot or concentrated. If they are lighter, the developer solution is cold or weak.

Using fresh chemicals, twenty films are usually exposed, but only one is processed. Theremaining 19 films are processed one film per day. Then compare the density of the

daily stepwedge radiograph with the standard one.

An unmatched density by more than two steps on the stepwedge the developer solutionis depleted.

Normalizing device

It can be used to monitor the developer strength and film density. It has one slot for exposing the film, beneath a copper plate. After processing, the film is inserted into

another slot and compared with numbered densities on the device. Fixer strength

Test: clearing test.An unexposed film is unwrapped and immediately placed in the fixer solution. If it

becomes white (clear) in 2-3 minutes, the fixer is working properly; if it doesn't, the fixer solution is depleted.

Operator Competence

The X-ray technician must be competent in taking radiographs; because retakingradiographs means exposing the patient to additional radiation. A retake log must bekept to record all retakes and their reasons to avoid them in the future.

As a student, you can do the simple tests listed above. It is good to have a sense of whata machine (or processing solution) malfunction is, and correct it whenever possible, or

call the technician to do it.


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Infection Control

Standard infection control measures must be followed to minimize the potential of patient-to-doctor, patient-to-patient, and doctor-to-doctor disease transmission. Youshould assume that every patient is an infection risk. A source of infection.

Patients' saliva, blood, and mucous membranes are considered to be potentiallyinfectious. The same infection control proced ures are used for all patients. These arecalled standard precautions .

Infection Control Terminology

Pathogen : a microorganism capable of causing disease.

Antiseptic : a substance used to decrease the number of microorganisms.

Asepsis : the absence of microorganisms.

Blood-borne pathogens : pathogens that are transmitted by blood.

Disinfection: decreasing the number of pathogens but not killing all of them.

Sterilization : killing all microorganisms.

Exposure incident: any incident that exposes the dental professional to infectiousmaterials during procedures like radiography or applying local anesthesia.

Infectious waste : waste that is contaminated with blood or other products of the body(like sharps and gloves).

Occupational exposure: exposure during work.

Parenteral exposure: exposure due to injury by a contaminated sharp object (like aneedle).

Guidelines for Infection Control Practices

Protective Attire and Barrier Technique

Protective clothing must be changed daily. Powder-free gloves must be used in order notto artifact-free radiographs. Gloves must always be worn during intraoral exposures.Long-sleeve gowns and protective eyewear must be worn whenever contamination is

anticipated. ( While taking intraoral radiographs, the patient's gag reflex my causehim/her to vomit. Patient may (inadvertently) spit on you; so you should protect your

face. )


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Hand washing and Care of Hands

The dental professional must always wash his/her hands before and after gloving, beforeand after each patient, and after touching contaminated surfaces with plain soap for routine dental procedures. Wearing gloves is not a substitute for washing hands . Alcohol

or any disinfectant may be used.

Fingernails should be short and clean. Rings and watches are to be removed.

Staff Protection

Immunization by vaccination is critical for dental professionals. All should get HepatitisB vaccines. A booster must be used in case of injury.

Sterilization and Disinfection of I nstruments

The type of instruments dictates whether we have to sterilize or disinfect instruments:

Critical instruments (instruments that penetrate soft tissue or bone) must be sterilized.

Semicritical instruments (instruments that contact but do not penetrate soft tissue or

bone, like film-holding instruments and bite blocks placed in the patient's mouth) mustundergo sterilization or high-level disinfection before reuse.

Noncritical instruments (instruments that do not contact mucous membranes) aredisinfected.

Clean (sterile, disinfected, aseptic) materials should not contact contaminated materials,and vice versa. This is the key to following infection control procedures correctly. For example, after placing a film in a patient's mouth, the operator's hands are contaminated,

and should not be used, for example, to answer a phone call. Cleaning and Disinfection of Dental Unit and Surfaces

Intermediate-level or low-level disinfectants can be used for these purposes.

Infection Control in Dental Radiography

There are different measures followed before exposure, during exposure, after exposure,and for processing. Barrier technique, re-golving technique, or two-person technique

must be used.


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Barrier Technique

Any surface that will come in contact with your hand must be covered with a barrier.Barriers must be changed between patients. However, in limited facilities, this might bedifficult. Barriers are very important for surfaces that cannot be sterilized.

Re-gloving Technique

In this technique, when the operator's gloves become contaminated, he/she must get ridof them and wear another pair. The film is placed in the patient's mouth, and new glovesare worn to orient the cone, close the door, and press the exposure button.

Two-person Technique

This technique is basically working with a partner while taking radiographs. One person

will put the film in the patient's mouth and removes it after exposure; the other points thecone, closes the door, and presses the exposure button.

Infection Control Procedures Used Before Exposure

Preparing the chair (the working area)

Everything must be covered (barrier technique) because it will come in contact with

your hands or the patient. While preparing films and holders, the working area must be prepared. Nothing should be placed on a bench without a towel or plastic barrier underneath it. The machine should also be covered with barriers.

Also, films can be covered by specific barriers. Once the film is removed from the patient's mouth, the barrier can be torn and the film will come down uncontaminated,and can then be taken to the darkroom for processing in new gloves.

Preparing the patient

The operator should adjust the chair, the headrest, and the lead apron.

Preparing the radiographer

The operator washes his/her hands, and wears gloves, masks, and eyewear.

Infection Control Procedures Used During Exposure

Exposed films must be dried and then collected in disposable containers.

In case of interruption during exposure (as in responding to a phone call), gloves should be removed, and hands washed before leaving.


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Infection Control Procedures Used After Exposure

Contaminated items should be disposed of, film-holding devices must be sterilized, andhands should be washed, and the patient is asked to remove the lead apron. The barriersare removed and the surfaces are disinfected.

After exposure, film holders must be put in plastic bags for sterilization. A clean cupshould be prepared in which the film is to be put. After that, the gloves should beremoved. A towel is sprayed by disinfectant, and then used to wipe the X-ray equipment.

Infection Control Procedures Used for Processing

With clean hands (after removing the gloves) the cup is taken to the darkroom, where

new gloves are worn. The working area in the darkroom must be prepared: a towel or plastic barrier is placed on the bench, because the films are contaminated. The films areopened (slowly) to get rid of other things (wrapping, lea\d foil, and black paper) and thefilms are placed in the machine with clean bare hands.

In a daylight loader, there are 'sleeves' in which the operator should put his/her hands toopen the film inside the box and drop it (there is a glass window that permits theoperator to see the prepared working area). The film is put into the film feed slot with

bare hands. The film is dispensed in a container labeled with the patient's name.

In case you have barriers after finishing taking the film, you can get the film off, andtransport it clean to the cup, so this will make everything easy for you because you are

dealing with clean film, gloves, etc. you will not worry about contamination. When we put our hands in the sleeves, the hands must be without gloves in order to prevent itscontamination, also when we want to get our hands out of the sleeves, they must be


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without gloves.

If you are using digital systems you have to put barriers and you have to swap it withmaterials indicated by the manufacturer, if disinfection is required you have to spray thedisinfectant then use a towel.

The End

Done by: Abdullah khasawneh

Checked by: Sawsan Jwaied

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8 - Quality Assurance and Infection Control