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===2. Bisecting Angle Technique===

===2. Bisecting Angle Technique===

[[File:Bisecting angle positioning.jpg|right|200px|thumb|Positioning for the bisecting angle technique using a dental xray generator.<small>''© Lisa Milella 2013''</small>]]

[[File:Bisecting angle positioning.jpg|right|200px|thumb|Positioning for the bisecting angle technique using a dental x-ray generator.<small>''© Lisa Milella 2013''</small>]]

[[File:Bisecting angle technique.jpg|right|200px|thumb|Bisecting angle technique: The cone of the dental xray generator is positioned at ninety degrees to a line (bottom spatula) that bisects the long axis of the film and the long axis of the tooth (top spatula) being radiographed.<small>''© Lisa Milella 2013''</small>]]

[[File:Bisecting angle technique.jpg|right|200px|thumb|Bisecting angle technique: The cone of the dental x-ray generator is positioned at ninety degrees to a line (bottom spatula) that bisects the long axis of the film and the long axis of the tooth (top spatula) being radiographed.<small>''© Lisa Milella 2013''</small>]]

When radiographing [[:Category:Teeth - Anatomy & Physiology|teeth]] other than the mandibular [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molars]] it is not anatomically possible to position the film parallel to the [[Enamel Organ#Root|tooth root]]. The bisecting angle technique uses a principle of geometry (the two sides of an isosceles triangle are equal in length) to prevent image elongation or foreshortening .

When radiographing [[:Category:Teeth - Anatomy & Physiology|teeth]] other than the mandibular [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molars]] it is not anatomically possible to position the film parallel to the [[Enamel Organ#Root|tooth root]]. The bisecting angle technique uses a principle of geometry (the two sides of an isosceles triangle are equal in length) to prevent image elongation or foreshortening.

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*The film should be placed intra-orally as close to the [[:Category:Teeth - Anatomy & Physiology|tooth]] as possible. (Usually this involves placing the cusp tip at the extreme outside (aboral) edge of the film, or even off the film if it is not important to include the [[Enamel Organ#Crown|crown]] in the radiograph. This leaves the largest possible surface area of the film available for the [[Enamel Organ#Root|roots]]).

*The film should be placed intra-orally as close to the [[:Category:Teeth - Anatomy & Physiology|tooth]] as possible. (Usually this involves placing the cusp tip at the extreme outside (aboral) edge of the film, or even off the film if it is not important to include the [[Enamel Organ#Crown|crown]] in the radiograph. This leaves the largest possible surface area of the film available for the [[Enamel Organ#Root|roots]]).

*The film should not be bent, because any curvature of the film will cause distortion of the image.

*The film should not be bent, because any curvature of the film will cause distortion of the image.

*The x-ray beam (tube-head) is positioned perpendicular (at a right angle) to an imaginary line that bisects the angle formed between the film and the [[Enamel Organ#Root|roots]] of the [[:Category:Teeth - Anatomy & Physiology|teeth]] being radiographed.<br>

*The x-ray beam (tube-head) is positioned perpendicular (at a right angle) to an imaginary line that bisects the angle formed between the film and the [[Enamel Organ#Root|roots]] of the [[:Category:Teeth - Anatomy & Physiology|teeth]] being radiographed.<br>

N.B. If the xray beam was directed perpendicular to the film then the image would be foreshortened. If the xray beam was directed perpendicular to the long axis of the [[:Category:Teeth - Anatomy & Physiology|tooth]], the image would be elongated.

N.B. If the x-ray beam was directed perpendicular to the film then the image would be foreshortened. If the x-ray beam was directed perpendicular to the long axis of the [[:Category:Teeth - Anatomy & Physiology|tooth]], the image would be elongated.

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Full-mouth radiographs describe a series of films where each [[:Category:Teeth - Anatomy & Physiology|tooth]] of the dentition is accurately depicted in at least one view. It is often recommended that all adult cats have full-mouth radiographs taken as part of the [[Oral Examination - Small Animal|oral and dental examination]]. [[Feline Odontoclastic Resorptive Lesions|Odontoclastic resorptive lesions]] are common in cats and clinical examination without radiography will only detect end-stage lesions.<br>

Full-mouth radiographs describe a series of films where each [[:Category:Teeth - Anatomy & Physiology|tooth]] of the dentition is accurately depicted in at least one view. It is often recommended that all adult cats have full-mouth radiographs taken as part of the [[Oral Examination - Small Animal|oral and dental examination]]. [[Feline Odontoclastic Resorptive Lesions|Odontoclastic resorptive lesions]] are common in cats and clinical examination without radiography will only detect end-stage lesions.<br>

==Recommended Views==

==Recommended Views==

'''Incisor view in the upper jaw''' - The film is placed with the incisor cusp tips along the short side of the film that has the dimple. The tube is positioned perpendicular to the film when viewed from the front and to bisect the angle when viewed from the side. Large-breed dogs may require a separate radiograph for the third [[Dental Formula - Dog#incisors|incisor teeth]], with the tube-head angled from slightly more lateral when viewed from the front.

'''Incisor view in the upper jaw''' - The film is placed with the incisor cusp tips along the short side of the film that has the dimple. The tube is positioned perpendicular to the film when viewed from the front and to bisect the angle when viewed from the side. Large-breed dogs may require a separate radiograph for the third [[Dental Formula - Dog#incisors|incisor teeth]], with the tube-head angled slightly more laterally when viewed from the front.

'''Left and right view for each of the canines of the upper jaw''' - Size 4 (occlusal) film in dogs is helpful to avoid missing the [[Enamel Organ#Root|root]] apex. Size 2 film can be used in cats and small dogs. The film is placed horizontally in the mouth with the canine cusp tip on the outside, rostral corner of the film. The tube is positioned to bisect the angle when viewed from the side, and angled laterally from a dorsovental (DV) position when viewed from the front. This projects the [[Enamel Organ#Root|root]] tip to the opposite corner of the film from the cusp tip.

'''Left and right view for each of the canines of the upper jaw''' - Size 4 (occlusal) film in dogs is helpful to avoid missing the [[Enamel Organ#Root|root]] apex. Size 2 film can be used in cats and small dogs. The film is placed horizontally in the mouth with the canine cusp tip on the outside, rostral corner of the film. The tube is positioned to bisect the angle when viewed from the side, and angled laterally from a dorsovental (DV) position when viewed from the front. This projects the [[Enamel Organ#Root|root]] tip to the opposite corner of the film from the cusp tip.

'''Left and right [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxillary]] [[Dental Formula - Dog#Premolars|premolar]] and [[Dental Formula - Dog#Molars|molar]] views''' - The first to third [[Dental Formula - Dog#Premolars|premolars]] are often included on one image, and a separate radiograph is made of the fourth [[Dental Formula - Dog#Premolars|premolar]]. On small dogs, it may be possible to include all the [[Dental Formula - Dog#Premolars|premolars]] on a single radiograph. On cats the [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molar]] can be included in one image. The tube is positioned to bisect the angle when viewed from the front and perpendicular to the film and alveolar ridge when viewed from the top or side. Tube-shift can be performed to separate superimposed structures on the image. The alveolar arch curves medially behind the [[Dental Formula - Dog#Premolars|premolars]] in most dogs. The tube is positioned to bisect the angle when viewed from rostrolateral (from the mesial contact surface of the tooth), and perpendicular to the film, the [[Dental Terminology|buccal]] surface of the [[Dental Formula - Dog#Molars|molars]] and alveolar ridge when viewed from the top.

'''Left and right [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxillary]] [[Dental Formula - Dog#Premolars|premolar]] and [[Dental Formula - Dog#Molars|molar]] views''' - The first to third [[Dental Formula - Dog#Premolars|premolars]] are often included on one image, and a separate radiograph is made of the fourth [[Dental Formula - Dog#Premolars|premolar]]. On small dogs, it may be possible to include all the [[Dental Formula - Dog#Premolars|premolars]] on a single radiograph. On cats the [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molar]] can be included in one image. The tube is positioned to bisect the angle when viewed from the front and perpendicular to the film and alveolar ridge when viewed from the top or side. Tube-shift can be performed to separate superimposed structures on the image. The alveolar arch curves medially behind the [[Dental Formula - Dog#Premolars|premolars]] in most dogs. The tube is positioned to bisect the angle when viewed from rostrolateral (from the mesial contact surface of the tooth), and perpendicular to the film, the [[Dental Terminology|buccal]] surface of the [[Dental Formula - Dog#Molars|molars]] and alveolar ridge when viewed from the top.

'''Mandibular incisor and canine view''' - One radiograph can include all the [[Dental Formula - Dog#Incisors|incisor teeth]] in dogs and all [[Dental Formula - Cat|incisor and mandibular canine teeth]] in cats. The film is placed with the incisor cusp tips along the short side of the film. The tube is positioned perpendicular to the film when viewed from the front and to bisect the angle when viewed from the side. For larger dogs one radiograph can include the apices of both [[Dental Formula - Dog#Canines|canine teeth]]. The positioning is similar to that for the mandibular incisors but angled slightly more [[Dental Terminology|ventrodorsally]]. The tube is positioned to bisect the angle when viewed from the side. For dedicated radiographs of one canine tooth (for example, during endodontic treatment) and to prevent superimposition of the first [[Dental Formula - Dog#Premolars|premolar tooth]], the tube can be angled from slightly lateral rather than perpendicular when viewed from the front.

'''Mandibular incisor and canine view''' - One radiograph can include all the [[Dental Formula - Dog#Incisors|incisor teeth]] in dogs and all [[Dental Formula - Cat|incisor and mandibular canine teeth]] in cats. The film is placed with the incisor cusp tips along the short side of the film. The tube is positioned perpendicular to the film when viewed from the front and to bisect the angle when viewed from the side. For larger dogs one radiograph can include the apices of both [[Dental Formula - Dog#Canines|canine teeth]]. The positioning is similar to that for the mandibular incisors but angled slightly more [[Dental Terminology|ventrodorsally]]. The tube is positioned to bisect the angle when viewed from the side. For dedicated radiographs of one canine tooth (for example, during endodontic treatment) and to prevent superimposition of the first [[Dental Formula - Dog#Premolars|premolar tooth]], the tube can be angled slightly laterally rather than perpendicular when viewed from the front.

'''Lateral canine and rosral (mesial) mandibular [[Dental Formula - Dog#Premolars|premolars]]''' - The mandibular canine and rostral [[Dental Formula - Dog#Premolars|premolar]] teeth are adjacent to the symphysis, requiring the film to be placed along the floor of the mouth, on top of the [[Tongue - Anatomy & Physiology|tongue]] to avoid the frenulum preventing the film being placed correctly. The tube is positioned to bisect the angle when viewed from the front, and perpendicular to the film when viewed from the side or top.

'''Lateral canine and rostral (mesial) mandibular [[Dental Formula - Dog#Premolars|premolars]]''' - The mandibular canine and rostral [[Dental Formula - Dog#Premolars|premolar]] teeth are adjacent to the symphysis, requiring the film to be placed along the floor of the mouth, on top of the [[Tongue - Anatomy & Physiology|tongue]] to avoid the frenulum preventing the film being placed correctly. The tube is positioned to bisect the angle when viewed from the front, and perpendicular to the film when viewed from the side or top.

'''Lateral view of the distal [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molar]] teeth of the mandible''' - This is the one region in which parallel technique can routinely be used. The film is placed into the space between the [[Tongue - Anatomy & Physiology|tongue]] and the lingual surface of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandicle (mandibula)|mandible]], positioned apically so the cusp tip is level with the top of the film. The tube is positioned perpendicular to the plane of the tooth [[Enamel Organ#Root|roots]] and to the film.

'''Lateral view of the distal [[Dental Formula - Dog#Premolars|premolars]] and [[Dental Formula - Dog#Molars|molar]] teeth of the mandible''' - This is the one region in which parallel technique can routinely be used. The film is placed into the space between the [[Tongue - Anatomy & Physiology|tongue]] and the lingual surface of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandicle (mandibula)|mandible]], positioned apically so the cusp tip is level with the top of the film. The tube is positioned perpendicular to the plane of the tooth [[Enamel Organ#Root|roots]] and to the film.

==Tube Shift==

==Tube Shift==

Structures that are superimposed can be separated on the radiograph by shifting the tube-head in the third axis while maintaining the bisecting angle in the plane that includes the axis of the [[Enamel Organ#Root|root]] and the edge (plane) of the film . For example, when making a radiograph of the [[Dental Formula - Dog#Premolars|premolar]] region, the tube-shift redirects the x-ray beam to a [[Dental Terminology|mesial-to-distal or distal-to-mesial]] direction while maintaining the bisecting angle position when viewed from the front of the patient (transverse plane). Shifting the tube [[Dental Terminology|mesially]] (mesiobuccal to distopalatal beam) moves objects that are closer to the tube-head distally on the radiograph image and objects that are closer to the film mesially. <br><br>

Structures that are superimposed can be separated on the radiograph by shifting the tube-head in the third axis while maintaining the bisecting angle in the plane that includes the axis of the [[Enamel Organ#Root|root]] and the edge (plane) of the film. For example, when making a radiograph of the [[Dental Formula - Dog#Premolars|premolar]] region, the tube-shift redirects the x-ray beam to a [[Dental Terminology|mesial-to-distal or distal-to-mesial]] direction while maintaining the bisecting angle position when viewed from the front of the patient (transverse plane). Shifting the tube [[Dental Terminology|mesially]] (mesiobuccal to distopalatal beam) moves objects that are closer to the tube-head distally on the radiograph image and objects that are closer to the film mesially. <br><br>

Conversely, when the tube-head is shifted distally (distobuccal to mesiopalatal beam), objects that are closer to the tube-head will move mesially on the radiograph, while objects closer to the film will move distally on the radiograph. In other words, objects on the radiograph that move the same direction that the tube was shifted are on the [[Dental Terminology|palatal/lingual]] side, while objects that move the opposite direction from which the tube was shifted are on the [[Dental Terminology|buccal/labial]] side. A helpful acronym to remember this relationship is the '''SLOB rule''', which stands for '''Same Lingual Opposite Buccal'''.

Conversely, when the tube-head is shifted distally (distobuccal to mesiopalatal beam), objects that are closer to the tube-head will move mesially on the radiograph, while objects closer to the film will move distally on the radiograph. In other words, objects on the radiograph that move the same direction that the tube was shifted are on the [[Dental Terminology|palatal/lingual]] side, while objects that move the opposite direction from which the tube was shifted are on the [[Dental Terminology|buccal/labial]] side. A helpful acronym to remember this relationship is the '''SLOB rule''', which stands for '''Same Lingual Opposite Buccal'''.

   

   

[[Category:Intra-Oral Radiography]]

[[Category:Intra-Oral Radiography]]

[[Category:To Do - Dentistry preMars]]

[[Category:To Do - Mars Check]]