13 Intraoral Radiographic Precedures

Objectives Define the key words. Compare the three intraoral x-ray examinations. Identify the two intraoral techniques. List the five rules for shadow casting. Determine conditions that effect the selection of image receptor size.

Objectives Select the type and number of image receptor required for a full mouth survey. Explain horizontal and vertical angulation. Explain point of entry. List at least five contraindications for using the patient’s finger to hold the image receptor during exposure.

Objectives Explain the basic design of image receptor positioners/holders. Describe the proper patient seating position. Demonstrate a systematic and orderly sequence of the exposure procedure.

Key Words Angulation Bisecting technique Biteblock Bitewing radiograph Cone cut error Film holder Full mouth series (full mouth survey)

Key Words Horizontal angulation Identification dot Image receptor holder or positioner Intraoral Interproximal radiograph

Key Words Mean tangent Midsaggital plane Negative angulation Occlusal plane Occlusal radiograph Paralleling technique Periapical radiograph

Key Words Point of entry Positive angulation Rule of isometry Shadow casting Vertical angulation Vertical bitewing radiograph

Introduction Intraoral radiography consists of methods of exposing dental x-ray film, phosphor plates, or digital sensors within the oral cavity.

Introduction Producing diagnostic quality dental radiographs depends on knowledge of and attention to: Positioning the patient in the chair Selecting a film, phosphor plate, or digital sensor of suitable size Determining how the image receptor is to be positioned and held in place

Introduction Producing diagnostic quality dental radiographs depends on knowledge of and attention to: Setting the radiation exposure variables Aiming the position indicating device (PID)

Introduction Each of these steps have specific applications for each of the three types of intraoral examinations and when using the paralleling or the bisecting technique.

Intraoral Procedures Examinations Techniques Bitewing Periapical Occlusal Techniques Bisecting Paralleling

Figure 13-1 Full mouth series Figure 13-1 Full mouth series. The 20-film radiographic survey includes four bitewing radiographs and eight anterior and eight posterior periapical radiographs.

Figure 13-2 Periapical radiograph Figure 13-2 Periapical radiograph. Posterior periapical radiograph showing (1) extensive caries, (2) apical pathology, and (3) impacted third molar. Note the use of a size #2 film and the horizontal positioning of the long dimension of the film packet for imaging the posterior regions.

Figure 13-3 Periapical radiograph Figure 13-3 Periapical radiograph. Anterior periapical radiograph showing extensive periodontal involvement. Note the use of a size #1 film and the vertical positioning of the long dimension of the film packet for imaging the anterior regions.

Fundamentals of Shadow Casting Use the smallest possible focal spot on the target (source of radiation). The object (tooth) should be as far as practical from the target (source of radiation). The object (tooth) and the image receptor (film, phosphor plate, or digital sensor) should be as close to each other as possible.

Fundamentals of Shadow Casting The object (tooth) and the image receptor (film, phosphor plate, or digital sensor) should be parallel to each other. The radiation (central ray) must strike both the object (tooth) and the image receptor (film, phosphor plate, or digital sensor) at right angles (perpendicularly).

Fundamentals of Shadow Casting Bisecting technique — often not possible to position the image receptor parallel to the object, preventing the radiation from striking the object and the image receptor at right angles. Paralleling technique — the distance between the object and the image receptor is often greater than ideal in most regions of the oral cavity.

Figure 13-4 Principle of the paralleling technique Figure 13-4 Principle of the paralleling technique. Positioning the recording plane parallel to the long axis of the tooth and directing the x-ray beam perpendicular to both the recording plane and the long axis of the tooth produces an image with less distortion. (Courtesy of Dentsply Rinn.)

Figure 13-5 Principle of the bisecting technique Figure 13-5 Principle of the bisecting technique. The x-ray beam is directed perpendicular to the imaginary line that bisects the angle formed by the recording plane and the long axis of the tooth. Because the tooth is a three–dimensional object, the part of the object farthest from the recording plane is projected in an incorrect relationship to the parts closest to the recording plane. (Courtesy of Dentsply Rinn.)

The Radiographic Examination Occlusal radiographs: size #4 film or phosphor plate is used (for adults) Horizontal bitewing: size #3 film or phosphor plate (for adults) Bitewing and periapical radiographs: any of the three intraoral film, phosphor plates, or digital sensor sizes (#0, #1, #2) or any combination of these sizes (for adults, adolescents, and children)

The Radiographic Examination The size of the image receptor selected for use depends on: The age of the patient The size of the oral cavity The shape of the dental arches The presence or absence of unusual conditions or anatomical limitations

The Radiographic Examination The size of the image receptor selected for use depends on: The patient’s ability to tolerate placement of the image receptor The image receptor positioner or holder and technique used Image receptor number and size for a full mouth series of bitewing and periapical radiographs varies among practices.

Figure 13-6 Full mouth series Figure 13-6 Full mouth series. Drawing of 18-image full mouth survey includes 14 periapical and 4 bitewing radiographs.

Figure 13-7 Maxillary anterior image receptor placement Figure 13-7 Maxillary anterior image receptor placement. (A) Five-image survey. (B) Four-image survey. (C) Three-image survey.

Table 13-1 Standard Image Receptor Placements for Periapical Radiographs of a Full Mouth Series

Horizontal and Vertical Angulation Procedures Horizontal angulation Vertical angulation Positive Negative

Figure 13-8 Horizontal angulation Figure 13-8 Horizontal angulation. Horizontal angulation is determined by directing the x-ray beam directly through the interproximal spaces perpendicular to the mean tangent of theteeth. The image receptor must be positioned parallel to the teeth of interest so that the central ray will also strike the image receptor perpendicularly.

Figure 13-9 Vertical angulation Figure 13-9 Vertical angulation. Diagram showing patient sitting in the recommended position upright in dental chair with midsagittal plane perpendicular to and occlusal plane parallel with the floor. Zero angulation is achieved when the long axis of the PID is directed parallel with the floor. All angulations achieved with the PID pointed toward the floor are called positive, or plus angulations. All angulations achieved with the PID is pointed toward the ceiling are called negative, or minus angulations. Generally a positive angle is used for bitewing exposures and periapical exposures of the maxilla, and a negative angle is used for periapical exposures of the mandible.

Points of Entry The image receptor must be centered within the beam of radiation to avoid cone cut error, where a portion of the image is not recorded on the radiograph. The point of entry for the central ray should be in the middle for the image receptor.

Film Holders and Image Receptor Positioners Image receptor holders or positioners: Film holders; holders designed to position a phosphor plate or digital sensor Receptor holders or positioners hold the image receptor in place to expose intraoral radiographs.

Box 13-1 Contraindications for Using the Patient’s Finger to Hold the Film Packet, Phosophor Plate, or Digital Sensor in Place

Figure 13-10 Rinn XCP™ paralleling technique film holders Figure 13-10 Rinn XCP™ paralleling technique film holders. Color-coded rings and biteblocks assist with assembly of multiple parts. Note the mirror-image assembly of these posterior periapical film holders. Assembly A is used for exposures on the maxillary right and the mandibular left, whereas assembly B is used for exposures on the maxillary left and on the mandibular right.

Figure 13-11 Rinn XCP ORA™ (one ring and arm) positioning system Figure 13-11 Rinn XCP ORA™ (one ring and arm) positioning system. Color-coded pins on the metal arm match the colored inserts on the plastic ring. When matched with the appropriate biteblocks, it can be configured for exposures in all regions of the oral cavity with either film or digital sensors.

Figure 13-12 Stabe® (Dentsply Rinn) Figure 13-12 Stabe® (Dentsply Rinn). Bite extension required for use with the paralleling technique may be broken off for use with the bisecting technique.

Figure 13-13 Film holders. The extension arm and aiming ring of the Rinn XCP® (Dentsply Rinn) instrument may be combined with a (A) biteblock suitable for the paralleling technique or a (B) biteblock suitable for the bisecting technique.

Preparations and Seating Positions Unit preparation Patient preparation Patient seating position

Figure 13-14 Patient positioning Figure 13-14 Patient positioning. The patient is positioned with the head supported against the headrest with the (A) occlusal plane parallel to the floor and the (B)midsaggital plane perpendicular to the floor.

Figure 13-15 Head divided by midsagittal plane and occlusal plane Figure 13-15 Head divided by midsagittal plane and occlusal plane. The midsagittal plane (A–B) must be perpendicular to the floor, and the occlusal plane (C) must be parallel with the floor unless an image receptor with an external aiming device is used. The lines O–X and X–Y are the lines of orientation for the maxillary teeth, also known as the ala–tragus line. The apices of the roots of the maxillary teeth are located close to this line.

Sequence of Procedure Suggested sequence of image receptor placements: Maxillary anterior periapicals Mandibular anterior periapicals Maxillary posterior periapicals Mandibular posterior periapicals Anterior bitewings Posterior bitewings

Procedure 13-1 Procedure for exposing a full mouth series of radiographs

Procedure 13-1 (continued) Procedure for exposing a full mouth series of radiographs

Procedure 13-1 (continued) Procedure for exposing a full mouth series of radiographs

Review: Chapter Summary The three types of intraoral radiographic procedures are the bitewing, periapical, and occlusal surveys. Both the bisecting and the paralleling techniques are used to produce a shadow image of the tooth on the radiograph.

Review: Chapter Summary The size and number of image receptors used for exposure of a full mouth radiographic survey depends on several factors. The horizontal angulation is determined by directing the central rays of the x-beam perpendicular to the plane of the image receptor through the mean tangent of the embrasures between the teeth of interest.

Review: Chapter Summary With negative vertical angulation, the PID is pointing down toward the floor. With position vertical angulation, the PID is pointing up toward the ceiling. The point of entry is used to center the image receptor within the beam of radiation.

Review: Chapter Summary Film holders are designed for use with the paralleling or the bisecting technique or may be modified to use with both techniques. An exposure sequence is recommended to avoid error and be efficient.

Recall: Study Questions General Chapter Review

Reflect: Case Study The dentist has prescribed a full mouth series of periapical and bitewing radiographs for a patient who represents with several areas of decay and a suspected abscess. This oral health care practice uses an 18-image full mouth series configuration. Consider the following and write out your answers:

Reflect: Case Study Prepare a list of the specific periapical and bitewing radiographs you intend to expose. Include what size image receptor you will use and why, and which specific teeth must be imaged on each of the projections. Which radiographic technique for exposing periapical radiographs will you choose for this exam? Why?

Reflect: Case Study How will your patient be seated for the exposures? Why? Will you be using the patient’s finger or a holder to position the image receptor within the oral cavity? Explain your choice.

Reflect: Case Study Describe how the image receptor will be positioned in relation to the teeth and how you will be directing the central ray of the x-ray beam for the specific technique you plan to use.

Reflect: Case Study Summarize the steps you would take to locate the vertical and horizontal angulations. Prepare a sequence of exposures and explain your choice.

Relate: Laboratory Application Proceed to Chapter 13, Laboratory Application, to complete this activity.