Chapters 19 & 20: The Paralleling Technique & The Bisecting Technique

Vocabulary flashcards covering key principles, distances, errors, and angulations for both the Paralleling Technique and the Bisecting Technique in periapical radiography.

Paralleling Technique

A periapical radiographic procedure where the image receptor is placed parallel to the long axis of the tooth, and the central ray of the x-ray beam is directed perpendicularly to both.

Bisecting Technique

A periapical radiographic method where the central ray of the x-ray beam is directed perpendicular to the imaginary bisector dividing the angle formed by the long axis of the tooth and the image receptor.

Imaginary Bisector

The line dividing the angle formed between the long axis of the tooth and the plane of the image receptor into two equal parts.

Target-to-Image Receptor Distance (Paralleling)

The distance between the radiation source and the receptor, ideally $16\text{ inches}$ ($41\,cm$) or at least $12\text{ inches}$, used to compensate for the increased tooth-to-receptor distance and minimize image magnification.

Target-to-Image Receptor Distance (Bisecting)

The distance between the radiation source and the receptor, typically $8\text{ inches}$ ($20.5\,cm$), recommended to limit magnification and distortion when the receptor is placed close to the tooth.

Excessive Vertical Angulation (Paralleling)

A vertical alignment error in the paralleling technique that results in cutting off the incisal or occlusal edges of the teeth on the radiograph.

Inadequate Vertical Angulation (Paralleling)

A vertical alignment error in the paralleling technique that results in cutting off the root apices of the teeth on the radiograph.

Foreshortening

An image distortion error occurring in the bisecting technique caused by excessive vertical angulation, making teeth appear shorter than their actual length.

Elongation

An image distortion error occurring in the bisecting technique caused by inadequate (insufficient) vertical angulation, making teeth appear longer than their actual length.

Cone-Cut Error

An exposure error resulting from an incorrect point of entry where the primary x-ray beam fails to fully encompass the centered image receptor.

Horizontal Angulation

The side-to-side alignment of the PID to direct central rays perpendicular to the interproximal spaces (embrashures) or mean tangent, preventing contact overlap.

Indicator Ring

An external aiming device on receptor holders that must be slid along the extension arm as close to the patient's skin as possible without touching, aiding precise PID alignment.

Bisecting Receptor Holder Support Backing

A backing plate on a bisecting positioner that slants at an angle of $105^\circ$, allowing the receptor to rest in close proximity to the lingual surfaces of the teeth.

Facial Landmarks for Bisecting Point of Entry

Anatomical reference points on the face used to guide PID entry points, requiring the patient's midsagittal plane to be perpendicular to the floor and occlusal plane parallel to the floor.

Vertical Angulation for Maxillary Incisors (Bisecting)

The recommended vertical angulation of $+40^\circ$ with the PID directed downward.

Vertical Angulation for Maxillary Canines (Bisecting)

The recommended vertical angulation of $+45^\circ$ with the PID directed downward.

Vertical Angulation for Maxillary Premolars (Bisecting)

The recommended vertical angulation of $+30^\circ$ with the PID directed downward.

Vertical Angulation for Maxillary Molars (Bisecting)

The recommended vertical angulation of $+20^\circ$ with the PID directed downward.

Vertical Angulation for Mandibular Incisors (Bisecting)

The recommended vertical angulation of $-15^\circ$ with the PID directed upward.

Vertical Angulation for Mandibular Canines (Bisecting)

The recommended vertical angulation of $-20^\circ$ with the PID directed upward.

Vertical Angulation for Mandibular Premolars (Bisecting)

The recommended vertical angulation of $-10^\circ$ with the PID directed upward.

Vertical Angulation for Mandibular Molars (Bisecting)

The recommended vertical angulation of $-5^\circ$ with a slight upward tilt of the PID.