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chapter 41

Notes part 2

QuestionAnswer
The paralleling technique is also referred to as l the extension-cone paralleling (XCP), right-angle, or long-cone technique.
The following basic rules must be followed when the paralleling technique is used: 1. Image receptor placement. The image receptor is placed in the mouth so that it includes the correct teeth for that projection.
The following basic rules must be followed when the paralleling technique is used 2. Image receptor position. The image receptor is positioned parallel to the long axis of the tooth. The image receptor, in the appropriate holder (positioning instrument), is placed away from the teeth and toward the middle of the mouth (Fig. 41.6).
The following basic rules must be followed when the paralleling technique is used 3. Vertical angulation. The central ray of the x-ray beam is directed perpendicular (at a right angle) to the image receptor and the long axis of the tooth.
The following basic rules must be followed when the paralleling technique is used 4. Horizontal angulation. The central ray of the x-ray beam is directed through the contact areas between the teeth (Fig. 41.7).
The following basic rules must be followed when the paralleling technique is used 5. Central ray. The x-ray beam is 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
GUIDELINES FOR FILM PLACEMENT The white side of the film always faces the teeth. • Anterior films are always placed vertically. • Posterior films are always placed horizontally.
GUIDELINES FOR FILM PLACEMENT The identification dot on the film is always placed in the slot of the film holder (dot in the slot). • The film holder is always positioned away from the teeth and toward the middle of the mouth.
GUIDELINES FOR FILM PLACEMENT • The film is always centered over the areas to be examined. • The film is always placed parallel to the long axis of the teeth.
GUIDELINES FOR SENSOR PLACEMENT • Use the paralleling technique and a sensor positioning device. • Place the sensor parallel to the teeth, but not necessarily against the teeth.
GUIDELINES FOR SENSOR PLACEMENT • For maxillary views, place the sensor at the midline of the palate. • For mandibular views, place the sensor more toward the tongue. • For mandibular molar views, make sure the bite block is fully inside the patient’s mouth.
GUIDELINES FOR SENSOR PLACEMENT • If the patient has difficulty closing, have the patient stabilize the arm of the holder with his or her finger. • Make sure the position indicator device (PID) is parallel to the arm of the holder and is directed at the center of the aiming ring.
GUIDELINES FOR SENSOR PLACEMENT • Use a cotton roll as a cushion between the sensor and tori. • For especially sensitive patients, foam cushions are made specifically for use with sensors, which can make placement much more comfortable.
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.
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/sensor, a total of seven to eight anterior placements are used in the paralleling technique: four maxillary exposures and three mandibular exposures
If size #2 film/sensor is used instead six anterior placements are needed: three maxillary and three mandibular exposures.
ANTERIOR EXPOSURE SEQUENCE FOR THE EXTENSION-CONE PARALLELING INSTRUMENTS 1. Assemble the anterior XCP instrument. 2. Begin with the maxillary right canine 3. Expose all maxillary anterior teeth from right to left. 4. End with the maxillary left canine (tooth #11).
ANTERIOR EXPOSURE SEQUENCE FOR THE EXTENSION-CONE PARALLELING INSTRUMENTS 5. Move to the mandibular arch. 6. Begin with the mandibular left canine (tooth #22). 7. Expose all mandibular anterior teeth from left to right. 8. Finish with the mandibular right canine (tooth #27).
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.
Always begin with the premolar view before the molar view
Premolar image receptor placement is easier for the patient... to tolerate than molar placement.
Premolar exposure is less likely to bring gag reflex.
With the paralleling technique, eight posterior image receptor placements are used four maxillary exposures and four mandibular exposures
The other method of exposing periapical views is the bisecting technique, also known as the bisecting-angle, bisection of the angle, or short-cone technique
The bisecting technique should be used only as an alternative method in special circumstances when it is not possible to use the paralleling technique.
bisecting technique special technique patients with very small mouths, children, and patients with low or flat palates.
bisecting technique places the film.... directly against the teeth making the film and the teeth not parallel, but at an angle.
With the bisecting technique, the angle formed by the long axes of the teeth and the film/image receptor is bisected into two equal parts, and the x-ray beam is directed perpendicular to the bisecting line
The major disadvantage of the disecting techique is dimensionally distorted.
Available types of image receptor holders for the bisecting technique include the following: • The bisecting-angle instrument (BAI: Dentsply Rinn) includes plastic bite-blocks, plastic aiming rings, and metal indicator arms.
Available types of image receptor holders for the bisecting technique include the following: The Stabe bite block is a disposable bite block that can be used with the paralleling technique or the bisecting technique. ]
With the bisecting technique, the scored front section is removed, and the image receptor is placed as close as possible to the teeth.
Angulation is the term used to describe the alignment of the central ray of the x-ray beam in the horizontal and vertical planes.
Angulation can be changed by moving the PID in a horizontal or a vertical direction.
BAI instruments with aiming rings dictate the proper PID angulation
In the bisecting technique, the angulation of the PID is critical
Horizontal angulation refers to he positioning of the tubehead and the direction of the central ray in a horizontal, or side-to-side, plane.
Horizontal angulation remains the same whether you are using the paralleling or the bisecting technique
With correct horizontal angulation the central ray is directed perpendicular to the curvature of the arch and through the contact areas of the teeth
Incorrect horizontal angulation results in overlapped (unopened) contact areas
A film with overlapped contact areas cannot be... used to examine the interproximal areas of the teeth
Created by: alejac0360
 

 



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