Xray - Midterm Learning Objectives 1-4, 6&8

Question 1

1.1 Outline the history surrounding the discovery of x-radiation.

Answer 1

Wilhelm Conrad Roentgen: became father of radiography in 1895 when he discovered X-rays.
- He noticed that one of the fluorescent plates at the far side of the room was glowing & realized that something coming from the Crookes tube was striking the fluorescent plate and causing it to glow. Placing various objects in the x-ray beam’s path, he produced images on the screen. He then went on to expose and produce images on photographic plates.

Dr. Otto Walkhoff - made the first dental xray, a radiography of the lower premolar. Exposure time was 25 minutes (today exposure time is 3/10 of a second)

Question 2

1.2 Define the key definitions of radiography basics.

Answer 2

1. Roentgen ray: An X-Ray named after Wilhelm Roentgen
2. Roentgenograph: An image produced on photosensitive film
3. X-Radiation (x-rays): A beam of energy that has the power to penetrate substances and record shadow images on receptors (photographic film or digital sensors)
4. Dental Radiograph - A photographic image produced on film by the passage of x-rays through teeth and related structures
5. Dental Radiography - The method of recording images of dental structures by the use of x-radiation
6. Dental Radiographer - Ther person who takes the radiograph by positioning, exposing, and processing dental photographic film/receptor.
7. Radiology - The science or study of radiation as used in medicine
8. Wavelength - The distance between two peaks of a wave in the same phase.
9. Frequency - The number of repetitions in a given period of time.

Question 3

1.3 List the properties of x-radiation.

Answer 3

X-rays have similar characteristics to that of light.

1. Appearance - X-rays are invisible energy that cannot be sensed (tasted, heard, felt, or smelled)
2. Charge - Xrays have no particles therefore they cannot have a charge.
3. Mass - Xrays have no mass, or weight.
4. Speed - Xrays travel at the speed of light (3.0 x 10^8m/s)
5. Wavelength - X-rays travel in waves and have short wavelengths with a high frequency
6. Path of travel - X-rays travel in straight lines and can be deflected, or scattered
7. Focusing capability - X-rays cannot be focused to a point and always diverge from a point
8. Penetrating Power - Xrays can penetrate liquids, solids & gases. The composition of the substances determines whether Xrays penetrate or pass through, or are absorbed
9. Absorption - Xrays are absorbed by matter; the absorption depends on the atomic structure of the matter and the wavelength of the xray
10. Ionization capability - x-rays interact with materials they penetrate and cause ionization
11. Fluorescence capability - Xrays can cause certrain substances to fluoresce or emit radiation in longer wavelengths (e.g. visible light and ultraviolet light)
12. Effect on receptor - Xrays can produce an image on a receptor
13. Effect on living tissues - Xrays cause biological changes in living cells

The shorter the wavelength and the higher the frequency, the more energy. Because X-rays have a short wavelength with a high frequency they have the energy required to penetrate many materials

Question 4

1.4 Describe the production of x-radiation.

Answer 4

Xray Production: Dental and medical X-rays are produced in an X-ray tube. Electrons are produced at the cathode end of an X-ray tube. When activated these electrons accelerate towards the positively charged anode. Here the high-speed electrons will collide with the anode to produce energy. Most of the energy is transformed into heat, but a small portion (1%) is converted into x-rays

Ionizing Radiation: X-rays are referred to as ionizing radiation as it has the capability of dislodging an electron from its orbit or creating an ion pair. Because X-radiation has the ability (energy) to do this; it is known as ionizing radiation. It is this ionizing effect of x-radiation that accounts for its potential for harmful biological effects. Cells can be damaged or killed by ionizing radiation

Exposure: is defined as a measure of ionization in the air produced by x-radiation. In order to produce dental x-rays, it is necessary to have: a source of electrons, a high voltage to accelerate the electrons, a target to stop the electrons

Roentgen (R) - is the unit of exposure ionization in the air. (does not describe what happens when radiation enters body tissues)

Radiation Absorbed Dose (rad) - the unit of absorbed dose of radiation by body tissues (radiation from an xray machine does not become a dose until it is absorbed)

Roentgen equivalent in humans (rem) - is not only the amount of a particular form of radiation absorbed but also includes the relative biological effect it has upon body tissues

1 R = 1 rad = 1 rem

Maximum permissible does (MPD) - for operators in daily contact with roentgen rays - should not be more than 5.0 rem per year - age of individual must also be considered (children and elderly are sensitive… repair mechanism is extremely low)

Question 5

1.5 Describe factors that affect the quantity and quality of the x-ray beam.

Answer 5

Factors Affecting the Penetrating Power of X-Radiation:

1. The wavelength of the rays: the shorter the wavelength, the more energy, and the greater the penetrating power. (Longer wave length = less energy, less penetrating power)
2. The distance from the source of the x-rays to the object; the shorter the distance, the grater the penetrating power. (The further the object = the lesser the penetrating power)
3. The density of the object to be penetrated. The less dense an object, the greater the penetrating power. Because of this factor radiographs can show the internal structures of objects. Enamel is less easily penetrated than pulp tissue and therefore when transposed the image appears different.

Question 6

1.6 Explain various types of x-radiation.

Answer 6

Types of x-radiation produced:

1. Primary (beam) - consists of the useful rays projected from the tube target (rays of shorter wavelength). It is collimated and filtered to to remove less penetrating wavelengths.
2. Secondary - consists of rays reflected by objects that are in the path of x-rays (patient, dental unit). The primary beam interacts with matter creating secondary radiation. Secondary radiation will cause film fog - decrease diagnostic value.
3. Scatter - a form of secondary radiation that results from penetrating matter causing deflection in various directions. This is the radiation that is a concern to the operator and patient.
4. Stray - consists of rays that flow out from parts of the tube other than the window (due to faulty tube).

The denser the object/higher the absorption - the lighter the object appears on radiograph (due to the x-radiation not contacting the film emulsion - crystals are not energized leaving no latent image)

The less dense an object/the lower the absorption - the object appears darker/grayer on radiograph

Differential Absorption - Different tissue types absorb different amounts of x-radiation (soft tissue vs pulp)

Radiopaque - Tissues with high absorption of xradation, appear white

Radiolucent - Tissues with low absorption of xradiation appear dark

Question 7

2.1 Describe the biological effects of x-radiation on human tissue.

Answer 7

Any radiation exposure carries a potential for biological damage to the patient and operator, however slight. The penetration of the tissue by ionizing x-radiation has the capability to cause each living cell of the tissue to be altered in a mild or severe form, depending on the amount of exposure. Since the hazard increases with the amount of radiation, everything must be done to keep radiation doses “as low as reasonably achievable,” (ALARA principle). There is a level at which tissue will recover to its normal routine function

Effects of Radiation on Human Tissue:
All cells are sensitive to the effects of radiation. Irradiation of a living cell always alters the cell to some extent - can be damaged slightly, permanently, or even die as a result of exposure. This is determined by the quantity & quality of the radiation delivered to cell as well as the type of cell being irradiated. Different organs and body tissues respond differently to x-radiation: some are more sensitive to radiation than others. Within each specific organ or tissue, the immature or rapidly developing cells are much more sensitive than the mature cells

Genetic Cells - concerned with reproduction
Somatic Cells - all other cells, skin, hair, blood

Question 8

2.2 Describe the principles of personal radiation monitoring.

Answer 8

Radiation monitoring is the measuring of x-radiation that reaches the dental radiographer.

Monitoring is used to track radiation not protect the operator from exposure. 3 personal monitoring devices are:

Film badge (most common) - a badge that is to be clipped on the body as per the manufacturer’s direction. Tracked through your SIN. Consists of x-radiation-sensitive receptor which records exposure. Record of x-radiation tracked by Health Canada. In AB, we are required to wear!!

Pocket dosimeter - usually the size of a pen and can be read by the person wearing it

Thermo luminescent devices (LTD) - come i various forms; based on crystals that are energized through x-radiation that give off light when heated

Question 9

2.3 Outline patient and operator protection procedures for radiographic exposures - EXPLANATION OF EFFECTS OF XRADIATION ON PATIENT

Answer 9

Biological changes may be a temporary disruption or permanent irreversible damage. This change may be immediate latent (not immediately evident) and/or cumulative (accumulate over a lifetime).

Somatic - is exposure to radiation that causes a direct effect. Meaning the effect is not passed on to future generations. (effect on irradiated cells except for reproductive cells) - injury to the individual, reddening of skin, scales or ulcerations, nausea, loss of hair, cataracts, cancer, leukemia, shortening of life-span

Genetics - is the changing of the reproductive cells through radiation exposure. Can be transferred to succeeding generations via reproductive cells (sperm/ova) - injury to future generations, radiation-induced mutations

Latent period - lag time between the radiation exposure and the signs and symptoms of biological damage

-short term effects seen in minutes, days, months

-long term effects are identified years after original exposure

The harmful effects may also be lessened if the total exposure dose is given in fractionated doses over a period of time instead of all at once

• Localized radiation dose - is the localized exposure to a specific area. Repeated exposure to a given area will cause a cumulative effect. With each dose, cellular damage is increased. Cumulative effect depreciates over a period of time if the patient has not had further exposure. The tissues heal to a degree where they function normally but they do not return to their pre-irradiated state. It is this residual damage that accumulates.

Question 10

2.4 Discuss the principles of ALARA.

Answer 10

ALARA = as low as reasonably achievable

Concept states that all exposure to radiation must be kept to a minimum. To protect all, every possible method of reducing exposure to radiation should be employed to minimize risk.

Question 11

2.5 Apply quality assurance standards.

Answer 11

Quality Assurance - all dental facilities must develop/maintain an effective quality assurance program. (ineffective program can lead to poor-quality radiograms - impair diagnosis, increase costs, unnecessary exposure)

Quality Assurance DEFINED AS - the planned and organized actions necessary to provide adequate confidence that dental xray eqipment and related components reliably produce quality radiographs with minimum doses to all. Program includes periodic control tests, preventive maintenance procedures, administrative methods & training. Continuous assessment of the efficacy of the imaging service as means to initiate corrective action.

Question 12

2.6 Discuss legal issues that surround dental radiography.

Answer 12

Federal & State Regulations - established requirements for the safe use of xray equipment (Ex. Consumer-Patient Radiation Health & Safety Act)

Risk Management - refers to the policies and procedures that should be followed by the dental radiographer to reduce the chances of a patient taking legal action against the dental radiographer or the supervising dentist.

Informed Consent - persons have the legal right to make choices about the care received, including the opportunity to consent to or refuse treatment. Therefore before receiving treatment, the dental patient should be informed of the various aspects of the proposed treatment, including diagnostic procedures such as dental imaging

Liability - cording to state laws, dentists are legally accountable (liable) to supervise the performance of dental auxiliaries. Even though dental auxiliaries work under the supervision of a licensed dentist, auxiliaries are also legally liable for their own actions.

Malpractice Issues - Negligence in dental treatment occurs when the diagnosis made or the dental treatment delivered falls below the standard of care. The standard of care can be defined as the quality of care that is provided by dental practitioners in a similar locality under the same or similar conditions. Examples include the exposing of an incorrect number of images, lost or misplaced images, or nondiagnostic images requiring retakes.

Question 13

2.3 Outline patient and operator protection procedures for radiographic exposures - PROTECTION FOR PATIENT

Answer 13

• A DA must not perform any Xray procedures unless its been prescribed by the dentist responsible for patient

-Xray examination of a patient should be based on the history & clinical evaluation of the patient and should be to obtain diagnostic info

• Xray exams should only be preformed after a clinical examination & if there is a health benefit to patient

-possibility of performing non-radiographic exams should be considered first - confirm no previous xray images are available

• # of radiographic views should be kept to a minimum

-equipment must be maintained/monitored routinely through a quality assurance program and preventive maintenance - routine monitoring of the quality of radiographs to ensure they satisfy diagnostic requirements with minimal exposure

-all images captured must remain in patient’s record unless rejected (all rejected images must be collected for use during routine rejection/retake analysis

Lead apron and thyroid collar use:
-thyroid collar especially important for children (particularly sensitive)
-thyroid collar must be provided when it will not interfere with required diagonistic information
-use of lead apron not required for patient during routine dental xray procedures if all other recommendations to limit exposure are respected as the dose to patient ill not be significantly affected by abdominal shielding - great to use as aid for patient comfort (if fears of radiation)

Collimation - beam must be well collimated and aligned with patient’s head to restrict beam to area of diagnostic interest
-rectangular collimation must be used for intra-oral examinations (dose is reduced compared to circular)

Intra-Oral Examinations - a film/image receptor older with alignment device should be used
- a long cone (30 cm or longer) should be used
-focal spot-to-skin distance of 20cm is the min (long cone ensures this)
-E-Speed film or faster must be used (d-speed film not allowed)

Pregnancy:
-full consideration must be taken of the consequences of fetal irradiation
-should be deferred until after pregnancy - if essential, keep # of exposures to minimum
-level of radiation to the fetus from dental xrays is extremely low (abdomen not exposed)

Question 14

2.3 Outline patient and operator protection procedures for radiographic exposures - PROTECTION FOR OPERATOR

Answer 14

Any measure taken to protect the patient also protects the operator, but there are some “special” precautions to be observed by the operator.

1. Never hold films in the patient’s mouth during exposure.
2. Never stand in the direct path of the X-rays.
3. Stand as far as possible, at least 6 feet, from the source of radiation.
4. Never stay in an operatory to stabilize the tube head or PID during exposure.
5. Lead-lined walls and specially constructed partitions or lead screens afford excellent protection for the operator.
6. Utilize personnel monitoring devices for all staff members (dosimeter badges).
7. Routinely check all radiographic equipment to prevent “trouble” before it happens (quality assurance).
8. A periodic on-site survey will determine the output of the x-ray unit, radiation leakage, or any dangerous area by qualified radiation protection personnel.

Question 15

2.3 Outline patient and operator protection procedures for radiographic exposures - SAFETY CODE 30

Answer 15

This Safety Code sets out principles and best practices to help ensure radiation protection for all individuals who may be exposed to radiation from dental X-ray equipment. It provides dental facilities with the necessary information to achieve the following principal objectives:

1. to minimize patient exposure to ionizing radiation in dental radiography, while ensuring the necessary diagnostic information is obtained;
2. to help ensure optimal protection of personnel operating dental X-ray equipment; and
3. to help ensure optimal protection of other personnel and the general public in the vicinity of areas where dental X-ray equipment is operated

Question 16

2.3 Outline patient and operator protection procedures for radiographic exposures - MPD (Maximum Permissible Dose)

Answer 16

The MPD is the maximum dose of radiation that the body can endure with little or no injury.

occupationally exposed - 50 MSv/year

pregnant occupationally exposed - 0.5 msv per month during pregnancy

Non-occupationally exposed - 1 mSv/year

Cumulative Occupational Dose - occupationally exposed workers must not exceed an accumulated lifetime radiation dose. An individual’s cumulative occupational effective dose must not exceed the worker’s age x 10mSv. (50 y.o = 50 x 10mSv = 500mSv)

Question 17

3.1: Describe components of x-ray machines and their function

Answer 17

Tube Head - from which the X-Rays are generated. Is the housing that contains the Xray tube. It consists of various components. Tube head is made of metal and lined with lead to protect actual xray tube and to prevent the escape of radiation in any direction except toward the position indicating device (PID). It is attached to the extension arm by means of a yoke. Can be rotated in two directions, vertically & horizontally.

Extension Arm - Allows positioning of the tube head. It is wall mounted. It is hollow to allow the passage of electrical wires from the control pane to xray tube head.

Control Panel - Contains the regulating devices. Mounted to the wall where it is electrically connected. Consists of indicator lights and activation buttons ex. ready lamp, tooth selection, and exposure times.

Question 18

3.2: Describe the basic principles of electricity specific to the production of x-radiation

Answer 18

Electrical current is the flow of electricity through a conductor which is required for the production of x-rays. The electrical current (circuit) is controlled by a transformer. The xray tube and transformers are housed in the tube head and one in the control panel.

Volt - is the unit used to measure electrical potential or work capacity. Since dental xrays operates at a very high voltage it is expressed in kilovolts. (1kV = 1000 volts)

Three transformers are: step-down (decreases the voltage to allow for heating of the filament), step-up (increases the voltage upon activation accelerating the electrons), & auto-transformer (maintains consistency of the current, to correct fluctuations.

Transformers - are necessary because the line voltage coming to most dental offices is 110 to 220 volts. The xray tube operates at varying voltages. The low-voltage transformer is used to reduce the current to 3-5 volts which is enough to heat the cathode filament and form the electron cloud.

The high-voltage transformer produces a voltage of 65,000 to 100,000 volts which is necessary to propel the electrons across the tube. The high-voltage current begins to flow when the activator button is depressed. When voltage is increased, the electrons travel faster and produce the strongest type of radiation. The highest voltage to which the current in the tube rises during exposure is called the kilovolt peak (kVp). (if Xray machine controls are set at 65,000 volts, the maximum xray energy produced during exposure is 65kVp). Higher kilovolt peak setting produces xrays with greater penetrating power (quality) - greater capacity to pass through matter.

Constant Potential (kVcp) is the maintaining of consistent energy (acceleration) of electrons

Ampere - is the unit of quantity of electrical current, or number of electrons flowing in an electrical circuit. Milliampere is used as only small current is required for dental xray. (1/1000 = 1mA) Most dental xrays operate at 10-15 mA.

The milliamperage regulator determines the number of X-rays produced by controlling the temperature of the tungsten coil. The higher the mA, the hotter the tungsten coil will become, and the greater will be the number of electrons produced in the electron cloud

Kilovoltage controls the speed of each electron while the milliamperage controls the number of electrons**

Timer - regulates the length of time the current will pass through the X-ray tube. All dental X-ray machines are required to be equipped with an exposure switch of the “deadman” type, which automatically terminates the exposure when the finger ceases to press the timer button. This makes it necessary to maintain firm pressure on the button during the entire exposure

Question 19

3.3 Describe mechanical reduction of x-radiation

Answer 19

The manufacturer installs two devices, which will reduce the total x-ray exposure to the patient, in the tube head.

Aluminum filter - placed in the path of the primary beam before it leaves the unit. Filter is added in increments of 0.5mm usually to an acquired thickness of 1.5-2.5mm. Only xrays with shorter wavelengths pass through filter. This way the longer wavelengths (not capable of exposing the film) are not received by patient.

Lead Collimator - collimates or restricts the size of the beam. The collimator is used to restrict the size/shape of the xray beam. Collimation of the primary beam reduces patient exposure and increases film quality by reducing amount of scattered radiation formed. Collimator is a lead disc that threads onto a fitting over the Porte of the tube head housing and shapes the x-ray beam. Center of disc has circular opening through which xrays pass. These X-rays comprise the useful beam or the central ray. The size of the useful beam is 2.75 inches in diameter.

Question 20

3.4: Describe digital imaging systems and associated dental management software

Answer 20

3 Types of Digital Imaging:
1. Direct Digital Imaging - a sensor is used in place of a film but sensor works like an exposed film. Digital imaging reduces radiation exposure from 50 to 80%, less than the fastest E-speed film

2. Indirect Digital Imaging - a film based radiograph is required. The radiographs are then scanned or photographed. The recreated image is compromised in quality as it is a copy
3. Storage Phosphor Imaging - uses as reusable imaging plate instead of a sensor. The phosphor-coated plate is similar to an intensifying screen. After exposure, the plate is electronically processed (scanned with a laser). This system is not as efficient.

Question 21

3.6: Explain image enhancement functions associated with software programs

Answer 21

Digital radiography allows the dentist or dental assistant to change the contrast (lighter to darker), enlarge images, place color enhancements, and so forth. It also allows for immediate and effective patient communication.

All xray software systems will have these functions. It will be up to the operator to learn these functions and how to operate them effectively within the different operating systems.

Computer software allows the dental radiographer to digitally enhance images. An image may have any of the following features enhanced:

Contrast
Brightness
Image size (zoom)
Sharpness
Inversion (white to black and black to white)
Pseudocolor alteration

Question 22

4.1: Describe composition and types of radiographic imaging receptors

Answer 22

An image receptor is an object that records the information created by X-rays. There are currently three main kinds of dental image receptors available:

1. Traditional Xray Films - have been adapted in size, emulsion, film speed, and packaging for dental uses. Most packets contain one film, although two films per packet are available in the event a duplicate is required
2. Phosphor Plates (PSP) - are digital imaging receptors that require processing through an electronic processor. The latent image will appear on the computer and the phosphor plate may be reused
3. Direct imaging sensors - are digital imaging receptors that do not require processing because the image appears immediately on the computer screen after exposure

Latent Image - On traditional films & PSPs, the transposed image is not visible; therefore it is called the latent image. These types of dental imaging require some form of processing to turn the latent image into the visible image.

Question 23

4.2: Identify various receptor sizes used to make periapical, occlusal and bitewing exposures

Answer 23

Intraoral receptors are placed inside the mouth (intraorally) during the xray exposure. There are four main sizes of intraoral receptors. Size 0, 1, 2, and 4 (also known as occlusal).

The size of patient as well as the type of intraoral radiograph being performed will determine the size of receptor that is used.

Size 0 = Pediatric bitewings & PA
Size 1 - adult anterior or mixed dentition BW/PA
Size 2 - Adult posterior BW/PA
4 - Occlusal images

Question 24

4.3: Describe the quality control conditions for storing and handling of dental image receptors

Answer 24

Protection and Storage of Traditional Film:
dental films are extremely sensitive to light, moisture, high temperatures, chemical fumes, and stray radiation. Storage area should be cool & dry (50 to 70 F) Older films should be used first (check date on box). Ideally, should be refrigerated & used by date on box. Only a small amount of film should be kept in operatory - will prevent age/film fog.

Right after exposure, the film is removed from the patients mouth, wiped with a tissue and dropped in a container outside of the operatory. Storing them outside the op protects the exposed film from additional exposure while others are being done. (Must be 6 feet away or behind barrier wall). Aftter all exposures are made, the films are then to be processed.

Protection & Storage of Phosphor Plates:
- are not as light sensitive as traditional film. But if an image is on the PSP, light exposure to the phosphor (blue) side will cause the image to fade over time. Phosphor side must be hidden from light/processed as soon as possible.

Protection & Storage of Direct Digital Sensors:
-are not light sensitive. But to increase their longevity they should be stored in a way that decreases the risk of being dropped and kinking of the wires.

Question 25

6.1: Describe the principles of intra-oral radiographic technique with periapical, bitewing and occlusal radiographs

Answer 25

Principles of Shadow Casting are…

1. Xray should be emitted from the smallest source (target or focal spot) possible:
   - to produce an image with sharp detail, we need an Xray beam with parallel rays. the smaller the point at which xrays are generated, the more parallel the rays will be.
   - smaller focal spot = the better the detail
   -focal spot size is determined by manufacturer
2. The distance from the xray source (focal spot to target) to the object should be long as possible:
   -added distance results in an image with less magnification and a sharper outline
   -this occurs because the xrays that interact with the film are straighter/less divergent.
   -straighter photons display a more accurate shadow/image on film

The distance between the object (oral structure) and the film should be as short as possible:
- placing the film as close to the object as possible decreases distortion by reducing magnification.
-as the distance increases, the image becomes larger & fuzzier
-however, keeping in mind your patient’s anatomy & comfort zone

the film & the long axis of the object should be parallel:
- a film not parallel to the to long axis of tooth will display magnigication and distortion

The xray should be directed perpendicular to the film:
-if not, the image will be distorted on the film
-image would appear shorter than actual structure, or a stretched out structure.

Unfortunately, a technique has not yet been devised that meets these requirements

Question 26

6.1: Advantages & Disadvantages of Direct Digital

Answer 26

The advantages of digital radiography are:
-Instant image
-Decrease in time for processing
-Improved grayscale through image enhancement
-Reduced radiation
-Capability for electronic transmission
-Patient education
-No need for processing chemicals

The disadvantages are:
-Overhead
-Debate over the quality of an image
-Infection control (unable to sterilize sensor)
-Bulkiness of the sensor (patient comfort)
-Concerns about legal implications as the original can be modified.

Question 27

6.2: Outline the diagnostic value of the periapical and bitewing radiograph

Answer 27

Bitewings/Interproximal Radiographs:
-show the crowns of the teeth and the alveolar crests of both the maxillary & mandibular arches on the same film.
-greatest value is it reveals caries in the earliest stages that are not clinically evident
-also reveals changes in the pulp, overhanging restorations, improperly fitted crowns, recurrent decay beneath restorations, and loss of alveolar bone

Periapical exposure:
-typically used to view a specific tooth/teeth or area of the patient’s mouth.
-placement of receptor must be very accurate to ensure all required structures are visible on the radiograph
-PAs are required to assess the entire tooth, the crown the root and surrounding tissues.

Question 28

6.3: Describe the basic principles of the paralleling technique.

Answer 28

-The paralleling technique has also been referred to as the right angle or long cone technique.

-Research confirms that the Paralleling Technique displays the most accurate image with the least amount of radiation exposure to the patient

-the use of a film-holding device that aligns the x-ray beam perpendicular to the film is recommended

• is preferred by most dentists because it minimizes distortion of the radiographic image and reduces the x-radiation dose to the patient’s head and neck area
• film is placed parallel to the long axis of the tooth. The film must be positioned away from the lingual surface of the tooth in most areas. Paralleling is achieved by placing the film as parallel as possible to the long axis of the tooth while taking into consideration the anatomical features. The central ray is then directed so it is perpendicular to the long axis of the tooth being exposed.
• difficulty with paralleling technique is film placement with a shallow roof of mouth creating discomfort

Question 29

6.4: Describe the conditions leading to successful use of the paralleling technique

Answer 29

Successful use of the long-cone technique depends on maintaining certain conditions:

1. The film plane must be flat and positioned so that it covers the necessary teeth.
2. The film must be parallel to the long axis of the teeth.
3. In all areas, except the mandibular molars, the film must be positioned away from the lingual surface of the teeth and located in the deeper areas of the mouth to cover the apices of the teeth.
4. The face of the open cone must be kept parallel to the film plane by adjusting both the vertical and horizontal angulations. In this way, the central ray is directed perpendicularly to the film plane.
5. The cone must be directed so that all of the film is covered by the x-ray beam.

Question 30

6.5: Demonstrate the production of diagnostically acceptable periapical and bitewing radiographs using the XCP

Answer 30

• A film holder is ideal for the correct parallel placement of the film.
• many film holders have external markers the “locator ring” to help position the PID exactly over the film
• Rinn XCP (Extension Cone Paralleling) film holders are the type we use at SAIT
  -Stabe styrofilm bite blocks and snap-a-ray film holders are also commonly used.

The advantages of the X-Tension Cone Paralleling (XCP) technique are:

1. Simplicity - Eliminates the need for predetermined angulation and positioning of the patient’s head.
2. Adaptability - Can be used in most offices regardless of space limitations, by rotating the chair and/or the patient’s head.
3. Reliability - Anatomic accuracy of tooth size, length of canals, etc., is assured.
4. Results - Radiographs that reproduce anatomic structures in their normal size and relationship, free of distortion with minimal superimposition of the zygomatic shadow, and exhibiting maximum detail definition.

Question 31

6.5: Demonstrate the production of diagnostically acceptable periapical and bitewing radiographs using the XCP - placement of a film holder in the patient’s mouth

Answer 31

The following suggestions will further facilitate the placement of a film holder in the patient’s mouth (Robinson, 2024):

Always soften the corners of the film that contact soft tissue: this contributes greatly to patient comfort.

When exposing the maxillary anterior teeth, place the film deep in the mouth: this allows the film to parallel the teeth as much as possible. The patient will bite on the end of the bite-block. Make two-point contact before asking the patient to close on the bite-block.

When exposing the maxillary posterior teeth, place the bite-block in the mouth so that the upper edge of the film is at the highest part of the palate. Angle the bite-block up to the occlusal surfaces of the teeth. Hold in position and ask the patient to close on the bite- block.

When placing the film for the lower anterior teeth, compress the tongue back in the mouth with the bite-block while placing the film in position. (Having the patient close his mouth in a protrusive manner may aid you in this procedure). Make two-point contact before asking the patient to close on the bite-block.

When placing the film for the lower posterior teeth, the film may be placed close to the lingual surfaces and still be parallel to the long axis of the teeth. Insert indicator in the inside holes of plastic bite-block.

To ensure patient comfort and stability of the XCP instrument, a cotton roll on the opposing arch should be used. Use orthodontic elastics to secure cotton roll to plastic bite block.

The bite-block may take an uneven position in the mouth when the patient closes IF THEY ARE MISSING TEETH. To maintain an even plane, use a cotton roll to replace the missing teeth.

Tilt - For maxillary, tilt the film holder as you place it into the patient’s mouth, try not to touch any tissues until the film is in proper position. The same procedure is used for mandibular exposures except for the posterior teeth when the cheek and tongue must be contacted during film placement.

Position - when still tilted, carefully position it exactly in line with the teeth you a capturing. Remember central ray must be directed through the teeth to center of film.

Relax - Relax your grip on handle as the patient closes - allowing the film to move itself into best position for patient. Patient must close firmly.

Bitewings - survey can be made with two to eight films using the appropriate size. Anterior exposures are rarely made because its easier to detect caries thru visual observation. Film can be placed vertical or horizontal. The goal is to obtain bite-wings with no overlapping of the interproximal contacts since the primary purpose is to obtain clear view of contact ears

Question 32

6.6: Demonstrate the correct application of the bisecting angle technique as an alternative technique for exposing

Answer 32

Bisecting Angle technique is another method that can be used to expose peri-apical films
-technique for the radiographic exposure of peri-apical films is a technique whereby the central ray (CR) of the x-ray beam is directed at right angles to an imaginary line which bisects the angle formed by the long axis of the tooth or teeth being examined and the plane in which the film is positioned behind the tooth or teeth

-The patient must be positioned with the occlusal plane of the arch being examined parallel to the floor and the mid-sagittal plane perpendicular to the floor.
-The film must be placed against the lingual surface of the tooth being examined (film is not parallel to the tooth).
-An angle is formed where the film contacts the tooth.
-The operator must visualize a line that divides in half, or bisects, the angle formed by the film and the tooth.
-The operator must then direct the central ray of the x-ray beam perpendicular to the imaginary bisector.
-Then, the central ray must be directed between the contacts of the teeth.
-Finally, the film must be centered in the circle of radiation.

• If we direct CR at a right angle to the film - resulting image will be shorter
• if we direct the CR at a right angle to the long axis of tooth, the image will be longer

Question 33

6.6: Demonstrate the correct application of the bisecting angle technique as an alternative technique for exposing - Commercially available intra oral film holders

Answer 33

1. RINN Bisecting Angle Instrument (BAI) - These instruments, similar to the RINN XCP film holders (bite blocks, aiming rings, and indicator arms), have been designed to assist in determining vertical and horizontal angulations and prevent cone-cutting.
2. Stabe Bite-Block -For use with the BA technique, the scored section is removed and the film is placed as close to the teeth as possible.
3. Eezee-Grip (Snap-A-Ray) - Place the “dot edge” of a size two film into the teeth of the holder and secure the film with the sliding lock. The front of the film should face the wide part of the holder. Place the “dot edge” of a size two film into the teeth of the holder and secure the film with the sliding lock. The front of the film should face the wide part of the holder.

Question 34

6.7: Produce diagnostically acceptable PA, BW and occlusal radiographs as exposed on mannequins - OCCLUSAL

Answer 34

Maxillary:

1. For an adult, a size #4 film and a child size #2 film are recommended.
2. Adjust the headrest so that the patient’s head is upright and the maxillary arch parallel to the floor, and place a lead apron.
3. Set the control panel to bring the extension arm in close to the patient.
4. Place the film with the tube side towards the area being radiographed (maxilla) with the orientation allowing for maximum anatomical coverage. Ask the patient to gently occlude.
5. Confirm the ID dot is placed anteriorly and the film is centered.
6. Bisect the angle between the teeth and the film.
7. Center the tubehead (+65 degrees) over the film with the CR perpendicular to the bisected angle.
8. Confirm patient is still, and expose the film.

Mandibular:

1. For an adult, a size #4 film and for a child, a size #2 film is recommended.
2. Slightly recline the patient and place the lead apron.
3. Set the control panel and bring the extension arm in close to the patient.
4. Place film with the tube side towards the area being radiographed (mandible) with the orientation allowing form maximum anatomical coverage. Ask the patient to gently occlude.
5. Confirm the ID dot is placed anteriorly and the film is centered.
6. Bisect the angle between the teeth and the film.
7. Center the tubehead (90 degree angle to the film) with the CR perpendicular to the bisected angle.
8. Confirm patient is still, exposed the film.

Question 35

6.8: Identify the characteristics of an exposing error and technique for correction - ERRORS IN EXPOSING

Answer 35

1. Incorrect Film Placement
   - Correct placement of film is most critical step
   -Memorizing the criteria for proper position (FMS) is essential.
   - These guidelines help minimize film position errors: a) the distal surface of cuspid should be visible in any bicuspid view. b) the third molar region should be visible in the molar view
   c) When exposing a specific tooth, the tooth of interest should be centered
2. Elongation
   -most frequent error by beginners
   -when the image of tooth is longer than reality
   -caused by insufficient vertical angulation (too shallow) of the tube head
   -Paralleling the open face of the cone (PID) with the film will ensure correct vertical angulation
3. Foreshortening
   - opposite of elongation
   -image of tooth is shorter than reality
   -caused by too much vertical angulation (too steep)
4. Horizontal Overlap
   -Improper selection of the horizontal angulation will result in overlapping of contact areas
   -occurs when central rays are not directed through the contact points parallel to the interproximal surfaces
5. Cone Cutting
   - caused by failure of the central ray to expose entire film
   -film will have a cresent-shaped clear area.
   -happens when xray beam is not directed at center of film
6. Film Bending
   -gross bending or creasing of film causes image distortion
   -localized to the “bent” area, elongation occurs
   -only roots of tooth appear distorted while crowns remain relatively true
   -usually caused by improper film placement, must be placed deep in the mouth for all exposures except mandi posteriors
   -bend/creases will have black lines on it when processed
7. Reversed Film
   -sensitive side of film must face xray tube
   -when exposed on the wrong side, the xrays must pass through the lead foil packaging which inhibits some rays from reaching the film
   -resulting film will lack density
   -overall image is lighter/weaker than normal
   -HERRINGBONE patter appears due to embossed pattern on lead foil backing
8. Improper Film Selection
   -can cause array of issues
   - if too small, tooth of interest may be missing
   if too large, patient may not accept the film comfortably
   -correct size is that which will cover area of interest & be comfortable
9. Double Image
   -when the film is moved slightly during exposure
   -image is doubled or has shadowy appearance
   -instruct patient to hold the film securely in exact position placed
10. Double Exposure
    -results when an already exposed film is placed back into the mouth & re-exposed
    -appearance is dark/double imaged
    -be careful to separate exposed & unexposed films
11. Saliva Leak
    -when film is bent too sharply, or left in patients mouth too long the seal around edge of the packet may break allowing saliva to leak in the film
    -causes surrounding black envelope to adhere to the film, black paper will ream stuck to film
12. Blurred Image
    -usually caused by movement of patient’s head, film, or PID/tube head during exposure
    -caution patient to sit still while the exposure is made
13. Incorrect Instrument Assembly
    -always look through the locator wring to make sure the film is centered in the right
14. Overexposure (dark image) / Underexposure (light image)
    -overexposure occurs when exposure time is too long or too short
    -usually caused by incorrect tooth selection on control panel
15. Blank Film / No image
    -usually results when no x-rays are generated in the tube during what you thought was the exposure time
    -make sure unit is plugged in securely/functioning properly
    -partial image can result from the lead apron in the path of xray beam
16. Superimposed images
    -failure to remove an appliance from the patients mouth before exposure will result in the superimposition of these structures over the areas exposed

Question 36

6.8: Identify the characteristics of an exposing error and technique for correction - PANORAMIC ERRORS

Answer 36

1. Metal Objects
   - if not removed from patients head/neck area, they will appear on the resulting films and obscure diagnosis
   - lead apron must be placed carefully so it does not cause a large unexposed area on the film
2. Occlusal film too low
   - the roots of the lower anterior will be placed out of the focal trough & will appear foreshortened & blurred. The palate will form an occlusal plane exaugurated “smile”
3. Occlusal plane too high
   - the upper anterior roots are placed out of the focal trough and will appear blurred and foreshortened
   -the hard palate will form an occlusal plane “frown”
4. Slumped posture
   -the spinal cord will be superimposed over the anterior area of the mouth
   - patients with very heavy bone/neck structure may present spinal cord shadow even if properly positioned - may be necessary to increase kVP 5-10
5. Midsagittal plane not centered
   -unequal left-right magnification results
   -If the bite guide is not used, the upper and lower anterior crowns will appear overlapped and blurred.
   -If the patient’s chin is not on the chin rest, the lower border of the mandible will be located too high within the film

Question 37

8.1 Differentiate between conventional film and indirect digital receptors.