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High-quality dental radiographs are essential for accurate diagnosis and treatment planning. Even small changes in beam angle or patient positioning can affect the image and obscure important details. Taking X-rays at the correct angle with consistent technique captures a true representation of the anatomy and gives veterinarians the clarity they need to make confident clinical decisions.
At Advanced Animal Dentistry, Dr Aaron Forsayeth and specialist Dr Bec Tucker are deeply committed to improving oral health and supporting veterinarians in clinical practice. Accurate imaging is central to that work.
At times, we’ve been asked to review radiographs that don’t provide all the detail needed for a full assessment. This article explains the bisecting angle and how it guides many of the views needed in veterinary dentistry.
Parallel vs bisecting
There are two main approaches to veterinary dental imaging.
The parallel technique is the simpler option but applies only when the plate can sit directly alongside the tooth, which is possible for the mandibular premolars and molars.
In most other regions, the anatomy prevents this, and the bisecting angle is required instead.
“The bisecting angle takes some time to picture and apply, but once it clicks, dental radiography becomes quicker, easier and far more consistent.”
Understanding the bisecting angle
The bisecting angle technique is required when the plate cannot be positioned parallel to the tooth because of the jaw shape or limited access. It is used for the incisors and canines in both jaws, and for the maxillary premolar and molar teeth.
The X-ray beam is directed along an imaginary line that divides the angle between the tooth and the plate. This produces an image that reflects the tooth’s true length and width without distortion.
A helpful analogy is to imagine a tree and its shadow throughout the day. When the sun is low, the shadow appears longer, and when it is high, the shadow shortens. The point where the tree and the shadow are the same length represents the bisecting angle where the image is true to scale.
Many veterinarians are shown fixed angles to follow, but not the reasoning behind them. Without that foundation, it is hard to adapt the view when the plate cannot sit where it needs to or when the first image does not show what is required. The bisecting angle takes some time to picture and apply, but once the concept becomes clear, it often makes dental radiography quicker, easier and far more consistent.
“Even subtle changes in beam angle can dramatically affect image clarity — understanding the ‘why’ behind each view is key to accurate diagnosis.”
Other techniques in veterinary dental radiography
Understanding the bisecting angle also helps make sense of the other imaging techniques used in veterinary dentistry, each applied in different regions of the mouth depending on access and anatomy. Some areas allow direct placement of the plate, while others require alternative approaches to account for the position of the teeth, surrounding structures or the limits of the oral cavity.
Examples include:
Mandibular incisor and canine views
These require adjustments to account for the backward curve of the roots and the limited space available under the tongue.
Maxillary incisor views
Applied when the plate must sit rostral to the teeth, with beam angulation adjusted to avoid overlapping structures.
Maxillary canine views
Each canine is imaged separately because the root sits over adjacent premolars, requiring changes in angulation to avoid interference.
Maxillary premolar and molar views
Used when the palate restricts plate placement, and the zygomatic arch can obscure part of the image, so alternative angles are chosen to minimise obstruction.
Fourth premolar views in dogs
These often need a change in tube position to separate the mesial roots when they overlap in a standard view.
Fourth premolar views in cats
A modified approach is used to work around the zygomatic arch, and in some cases, an extraoral view offers clearer access when intraoral positioning is limited.
Patient factors influencing dental imaging
Dental radiography is also influenced by the patient in front of you. Skull shape is one of the biggest factors, as the relationship between the teeth, palate and mandible changes significantly between brachycephalic, mesocephalic and dolichocephalic breeds. These variations determine how much room there is to place the plate and how easily the view can be aligned.
Soft-tissue structures, such as the position of the tongue, the width of the cheeks, and the height of the palate, can all restrict access or alter the available angle. In smaller patients, the mouth may not open wide enough to position the plate exactly where you would like it to sit, which means the angle must be adjusted within the limits of the available space.
Movement and patient comfort are additional factors to consider. Even under anaesthesia, tension in the jaw or limited opening can make certain views harder to obtain. This is why dental imaging is never identical between patients and why each case requires a custom approach.
Building confidence in pet dental radiography
At Advanced Animal Dentistry, pet teeth and holistic oral health are our entire focus. Dental imaging is essential in the diagnosis and treatment of patients.
We understand how complex these views can be, but a solid understanding of the underlying principles makes the work more predictable and far less time-consuming in daily practice.
We are currently developing detailed resources that will walk through each technique in depth, and we have a companion article on common imaging pitfalls here. For tailored guidance or help interpreting your own radiographs, please contact our team. To refer a patient, complete the referral form here.
