41. Intraoral Imaging

Intraoral Imaging

Learning Outcomes

On completion of this chapter, the student will be able to achieve the following objectives:

• Pronounce, define, and spell the Key Terms.

• Describe how to prepare a patient for dental imaging.

• Name the two primary types of projections used in an intraoral technique, and describe the differences.

• Explain the advantages and disadvantages of the paralleling and bisecting techniques.

• Explain the basic principle of the paralleling technique.

• Explain why an image receptor holder is necessary with the paralleling technique.

• State the five basic rules of the paralleling technique.

• Label and identify the parts of the Rinn XCP instruments.

• Explain the recommended vertical angulation for all bitewing exposures.

• Explain the basic rules for the bitewing technique.

• Describe the appearance of opened and overlapped contact areas on a dental image.

• Explain the procedural principles of the bisecting technique.

• Identify the image receptor size used in the bisecting technique.

• Describe the result of correct vertical angulation.

• Describe the result of incorrect vertical angulation.

• Identify the types of image receptor holders that can be used with the bisecting technique.

• Explain the technique for exposing occlusal radiographs.

• Describe techniques for managing the patient with a hypersensitive gag reflex.

• Describe techniques for managing patients with physical and mental disabilities.

Performance Outcomes

On completion of this chapter, the student will be able to meet competency standards in the following skills:

Electronic Resources

imageAdditional information related to content in Chapter 41 can be found on the companion Evolve Web site.

imageand the Multimedia Procedures DVD

Key Terms

Angulation Alignment of central ray of x-ray beam in horizontal and vertical planes.

Bisecting (bisection of the angle) technique Intraoral technique of exposing dental images.

Bitewing Type of image used for interproximal examination.

Central ray X-ray at center of beam.

Contact area Area of the mesial or distal surfaces of a tooth that touches adjacent tooth in the same arch.

Crestal bone Coronal portion of alveolar bone found between the teeth.

Developmental disability Impairment of mental or physical functioning that usually occurs before adulthood and lasts indefinitely.

Diagnostic quality Referring to images with the proper structures and necessary density, contrast, definition, and detail for diagnostic purposes.

Interproximal Between two adjacent surfaces.

Intersecting Cutting across or through.

Long axis of the tooth Imaginary line dividing the tooth longitudinally (vertically) into two equal halves.

Occlusal technique Used to examine large areas of the upper or lower jaw.

Parallel Moving or lying in the same plane, always separated by the same distance.

Paralleling technique Intraoral technique of exposing periapical and bitewing images.

Perpendicular Intersecting at or forming a right angle.

Physical disability Impairment in certain function(s) of the body, such as vision, hearing, or mobility.

Positioning instrument Device used to hold the image receptor in place during exposure.

Right angle Angle of 90 degrees formed by two lines perpendicular to each other.

It is possible for every dental assistant to be successful in producing quality dental images that are free from distortion, have the correct density and contrast, and can be used for the detection of dental disease. You can create such images by carefully following the steps in image receptor placement, exposure, and processing (Fig. 41-1).

Your patients will come in a variety of sizes, physical and mental abilities, types of dentitions, and personalities. Often, you will take x-rays on patients with special needs. For example, you will explain x-rays to a 6-year-old patient differently than you will to an adult. Your technique will vary depending on whether you are using digital sensors, phosphor storage plates (PSPs) or conventional dental film. In addition, you will have to modify your technique if your patient has a palate that is very high and narrow, or your patient may have a sensitive gag reflex. This chapter provides guidelines about various situations you are likely to encounter in your career.

Even the most skilled operators can make errors; the ability to recognize errors and to know the steps to take to prevent their recurrence is most important. This chapter explains common technique errors and how to prevent them. In addition, you will learn to recognize and use normal anatomical landmarks in mounting radiographs.

Full-Mouth Survey

No dental examination can be complete without dental images, and, in almost all cases, the full-mouth survey is the preferred technique.

An intraoral full-mouth survey (FMX) contains both periapical and bitewing images. The bitewing image shows the upper and lower teeth in occlusion. Only the crowns and a small portion of the root are seen. This view is used for detecting interproximal decay, early periodontal disease, recurrent decay under restorations, and the fit of metallic fillings or crowns (Fig. 41-2). The periapical image shows the entire tooth from occlusal surface or incisal edge to about 2 to 3 mm beyond the apex to show the periapical bone. This view is used to diagnose pathologic conditions of the tooth, root, and bone, as well as tooth formation and eruption (Fig. 41-3). Periapicals are essential in endodontics and in oral surgical procedures.

For the average adult, a full-mouth series consists of 18 to 20 images—generally, 14 periapical views and 4 to 6 bitewing views. The number may vary, however, depending on the dentist’s preference and the number of teeth present. For example, for the patient without teeth, 14 periapical views are enough to cover the edentulous arches; bitewings are not necessary. For the patient with a full dentition, the number of periapical views varies depending on whether the paralleling or the bisecting technique is used.

The anterior area is the region in which the number of images varies. Variables include the size of the sensor, if you are using digital, and the technique used (Fig. 41-4, A). When using dental film and the bisecting technique, three anterior views are taken on each arch (maxillary and mandibular) with size #2 film. For the paralleling technique, three or four size #1 films would be used on each arch (Fig. 41-4, B).

Intraoral Imaging Techniques

Whether using conventional film, digital sensors, or PSPs, two basic techniques can be used to obtain periapical images: the paralleling technique and the bisecting (bisection of the angle) technique. The American Academy of Oral and Maxillofacial Radiology and the American Association of Dental Schools recommend use of the paralleling technique because it provides the most accurate image with the least amount of radiation exposure to the patient. In some situations, however, such as a small mouth, a shallow palate, or tori, the operator may need to use the bisecting technique. This chapter provides step-by-step procedures on how to produce diagnostic-quality images with both techniques (Fig. 41-5).

Paralleling Technique

The paralleling technique is also known as the extension-cone paralleling (XCP), right-angle, or long-cone technique. To use the paralleling technique competently, you must understand the terminology, including parallel (Fig. 41-6), intersecting, perpendicular, right angle, long axis of the tooth (Fig. 41-7), and central ray, in addition to the five basic rules.

Five Basic Rules

The following basic rules must be followed when the paralleling technique is used:

Image receptor placement. The image receptor must be placed in the mouth, so that it will cover the correct teeth to be examined.

Image receptor position. The image receptor must be positioned parallel to the long axis of the tooth. The image receptor, in the appropriate holder (positioning instrument), must be placed away from the teeth and toward the middle of the mouth (Fig. 41-8).

Vertical angulation. The central ray of the x-ray beam must be directed perpendicular (at a right angle) to the image receptor and the long axis of the tooth.

Horizontal angulation. The central ray of the x-ray beam must be directed through the contact areas between the teeth (Fig. 41-9).

Central ray. The x-ray beam must be centered on the image receptor to ensure that all areas are exposed. Failure to center the x-ray beam results in a partial image, or cone cut (Fig. 41-10).

Patient Preparation

The patient who is having dental images taken should be seated after the room has been prepared and infection control procedures completed. See Procedure 41-1.

Exposure Sequence for Image Receptor Placement

You should plan an exposure sequence, or a definite order, for periapical image receptor placement when you are exposing images. When working with dental film without a planned exposure sequence, you are more likely to omit an area or to expose the same area twice. This does not occur as easily when using direct digital imaging because the image most recently exposed appears on the computer screen.

Anterior Exposure Sequence

When exposing periapical views with the paralleling technique, always start with the anterior teeth (canines and incisors) for the following reasons:

When using a size #1 film, a total of seven or eight anterior placements are used in the paralleling technique: four maxillary exposures and three mandibular exposures (Fig. 41-11). Some operators will choose to expose four maxillary and four mandibular anterior views. If size #2 film or small sensors are used instead, six anterior placements are needed: three maxillary and three mandibular exposures. The authors recommend the use of #1 film or the smallest sized sensor for the anteriors.

The recommended anterior exposure sequence for the Rinn XCP instruments (Dentsply Rinn, Elgin, Illinois) is as follows:

PROCEDURE 41-2  imageimage

Assembling the XCP (Extension-Cone Paralleling) Instruments


Equipment and Supplies

Procedural Steps

Anterior Assembly

Posterior Assembly

No wasted movement or shifting of the position indicator device (PID) occurs when you work from right to left in the maxillary arch, and then from left to right in the mandibular arch. You may find an exposure sequence that works better for you. The most important thing is to always use the same sequence. This allows you to keep track of the last exposure if you are interrupted (Procedure 41-3).

PROCEDURE 41-3  imageimageimageimage

Producing Full-Mouth Radiographic Survey Using Paralleling Technique


Equipment and Supplies

Procedural Steps

Preparation Before Seating Patient

Prepare the operatory with all infection control barriers.
Purpose: Any object that is touched and was not covered with a barrier must be disinfected after the patient is dismissed.

Determine the number and type of images to be exposed through a review of the patient’s chart, directions from the dentist, or both.

For films or PSPs, label a paper cup with the patient’s name and the date. Place it outside the room where the x-ray machine will be used.
Purpose: This is the transfer cup for storing and moving exposed films or PSPs.

Turn on the x-ray machine and check the basic settings (kilovoltage, milliamperage, exposure time).

Wash and dry your hands.

Dispense the desired number of films or PSPs, and store them outside the room where the x-ray machine is being used.
Purpose: To prevent fogging caused by scatter radiation.

Additional Preparation Requirements for Digital Technologies

Positioning Patient

Seat the patient comfortably in the dental chair, with the back in an upright position and the head supported.

Ask the patient to remove eyeglasses and bulky earrings.
Purpose: These objects may cause radiopaque images to be superimposed over the dental images.


Ask the patient to remove prosthetic appliances or objects from the mouth.
Note: Always wear gloves when handling a prosthetic appliance.

Position the patient so that the occlusal plane of the jaw being x-rayed is parallel to the floor when the mouth is open.

Drape the patient with a lead apron and a thyroid collar.

Wash and dry hands, and put on clean examination gloves.

Open the package, and assemble the sterile film sensor–holding instruments.
Purpose: Allowing the patient to observe you washing your hands, putting on clean gloves, and opening the sterile package of instruments assures the patient that appropriate infection control measures are being taken.
Note: When using dental film, the white side of the film always faces the tube. When using PSPs, follow the specifc manufacturer’s instructions to determine which side faces the tube.

Maxillary Canine Exposure

Insert the #1 image receptors vertically into the anterior bite-block.


Position the image receptors with the canine and the first premolar centered. Position image receptors as far posterior as possible.

With the film-holding instrument and image receptors in place, instruct the patient to close the mouth slowly but firmly.

Position the localizing ring and the position indicator device (PID); then press the exposure button.
Note: The image of the lingual cusp of the first premolar is usually superimposed on the distal surface of the canine because of the curvature of the maxillary arch. This contact area must be “opened” on the view of the premolar region.

Maxillary Central/Lateral Incisor Exposure

Mandibular Canine Exposure

Jan 8, 2015 | Posted by in Dental Nursing and Assisting | Comments Off on 41. Intraoral Imaging
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