14 The Periapical Examination-Paralleling Technique

Objectives Define the key words. Discuss the principles of the paralleling technique. List the advantages and disadvantages of the paralleling technique. Identify and be able to assemble and position image receptor holders for use with the paralleling techniques.

Objectives Explain the importance of achieving accurate horizontal and vertical angulation in obtaining quality diagnostic radiographs using the paralleling technique. Identify vertical angulation errors made when using the paralleling technique.

Objectives Demonstrate the image receptor positioning for maxillary and mandibular periapical exposures using the paralleling technique.

Key Words Bite block Embrasure External aiming device Film holder Image receptor holder or positioner Indicator ring

Introduction Because of its ability to produce superior diagnostic quality radiographs, the paralleling technique should be the technique of choice when exposing periapical radiographs.

Table 14-1 Advantages and Disadvantages of the Paralleling Technique

Fundamentals of Paralleling Technique The basic principles of the paralleling technique: The image receptor (film packet, phosphor plate, or digital sensor) is placed parallel to the long axis of the object (tooth) being radiographed. The central ray of the x-ray beam is directed to intersect both the image receptor and the object (tooth) perpendicularly.

Figure 14-1 Paralleling technique Figure 14-1 Paralleling technique. The x-ray beam is directed perpendicular to the recording plane of the image receptor, which has been positioned parallel to the long axis of the tooth.

Figure 14-2 Visible and actual long axis of the tooth Figure 14-2 Visible and actual long axis of the tooth. The root portion of the tooth should be taken into consideration to accurately locate the long axis of the tooth.

Figure 14-3 Comparison of the bisecting and paralleling methods Figure 14-3 Comparison of the bisecting and paralleling methods. With the bisecting technique, the image receptor is positioned adjacent to the tooth, making a target–image receptor distance of 8 in. (20.5 cm) acceptable. With the paralleling technique the image receptor is positioned near the center of the oral cavity, where it must be retained in a position parallel to the long axes of the teeth. This increased object–image receptor distance requires a longer (12 in./30 cm or 16 in./41 cm) target–image receptor distance to produce a quality radiograph.

Holding the Periapical Image Receptor in Position Image receptor holders designed for use with the paralleling technique usually have a long biteblock area for the purpose of achieving a parallel relationship between the recording plane of the image receptor and the long axes of the teeth and an L-shaped backing to help support the image receptor and keep it in position.

Figure 14-4 Paralleling image receptor holder. Anterior biteblock Figure 14-4 Paralleling image receptor holder. Anterior biteblock . The biting plane is at a right angle (900) with the backing plate. The patient bites down far enough out on the bite extension to keep the image receptor and teeth parallel.

Figure 14-5 Rinn XCP™. Note the external aiming device to assist with locating the correct angles and points of entry. The external aiming device eliminates the need to position the patient’s head precisely. (Courtesy of Dentsply Rinn.)

Figure 14-6 Flow Dental’s RAPD®. (Courtesy of Flow Dental.)

Figure 14-7 Dentsply Rinn’s Uni-GripAR® Figure 14-7 Dentsply Rinn’s Uni-GripAR®. Note the wireless digital sensor image receptor. (Courtesy of Dentsply Rinn.)

Figure 14-8 Dentsply Rinn’s Flip Ray™ Figure 14-8 Dentsply Rinn’s Flip Ray™. Note the film packet image receptor. (Courtesy of Dentsply Rinn.)

Figure 14-9 Flow Dental’s SUPA®. Note the film packet image receptor Figure 14-9 Flow Dental’s SUPA®. Note the film packet image receptor. (Courtesy of Flow Dental.)

Figure 14-10 Dentsply Rinn’s XCP-ORA®. (Courtesy of Dentsply Rinn.)

Figure 14-11 Long axes of the premolar and molar teeth.

Table 14-2 Summary of Steps for Acquiring Periapical Radiographs – Paralleling Technique

Table 14-2 (continued) Summary of Steps for Acquiring Periapical Radiographs—Paralleling Technique

Points of Entry Paralleling technique — locate by using the external aiming device of the image receptor positioner for directing the central ray at the image receptor.

Figure 14-13 Maxillary incisors exposure Figure 14-13 Maxillary incisors exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth with the biteblock inserted to its full length to position the image receptor back toward the region of the first molars to achieve parallelism with the long axes of the incisors. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary incisors radiograph.

Figure 14-14 Maxillary canine exposure Figure 14-14 Maxillary canine exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth with the biteblock inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve parallelism with the long axis of the canine. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary canine radiograph.

Figure 14-15 Maxillary premolar exposure Figure 14-15 Maxillary premolar exposure. (A) Diagrams show the relationship of image receptor and holder, teeth, and PID. As in all posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth with the biteblock inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve parallelism with the long axes of the premolars. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary premolar radiograph.

Figure 14-16 Maxillary molar exposure Figure 14-16 Maxillary molar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth with the biteblock inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve parallelism with the long axes of the molars. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary molar radiograph.

Figure 14-17 Mandibular incisors exposure Figure 14-17 Mandibular incisors exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth and PID. As in all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Mandibular incisors radiograph.

Figure 14-18 Mandibular canine exposure Figure 14-18 Mandibular canine exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Mandibular canine radiograph.

Figure 14-19 Mandibular premolar exposure Figure 14-19 Mandibular premolar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Mandibular premolar radiograph.

Figure 14-20 Mandibular molar exposure Figure 14-20 Mandibular molar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Mandibular molar radiograph.

Review: Chapter Summary The paralleling technique is the technique of choice when exposing periapical radiographs because of its ability to produce superior diagnostic-quality radiographs. A holding device with a long biteblock and L-shaped backing is required.

Review: Chapter Summary The four basic steps to exposing a periapical radiograph are placement, vertical angulation, horizontal angulation, and point of entry.

Recall: Study Questions General Chapter Review

Reflect: Case Study You have recently accepted a position in a general practice dental office. This week you discovered that the image receptor holding device for exposing a full mouth survey is the one pictured in Figure 14-9. You have always used the film-holding device pictured in Figures 14-13 through 14-20, and the new holder is unfamiliar to you.

Reflect: Case Study Based on what you have learned about image receptor holders designed for use with the paralleling technique, answer the following questions:

Reflect: Case Study Which technique is the new holder designed to be used with? How can you tell? How is the new holder similar to the one you have been using? Different? Which holder would it be best to know how to use? Why? What are the advantages/disadvantages of the new holder?

Reflect: Case Study What are the advantages/disadvantages of the holder you have been using? What is your recommendation for the practice? Should they continue to use this holder, or should they purchase the holder you are familiar with? Explain your answers.

Relate: Laboratory Application Proceed to Chapter 14, Laboratory Application, to complete this activity.