Anatomy Monday: Anatomy on Mandibular Periapical Radiographs

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It’s been a while since I’ve updated anatomy seen on intraoral radiographs so I’m continuing with all the anatomy visible on mandibular periapical radiographs. Some of these were seen in the recent posts on canals and foramina but this will be the one stop spot for everything mandibular periapical radiographs. Here’s a list of all the anatomy in this post which you can click on to jump to the anatomy.

Starting from the midline and going posteriorly here we go. 🙂

Lingual Foramen

The lingual foramen is a term that applies to any foramen that opens on the lingual aspect of the mandible but for purposes of intraoral imaging the term is used when referring to the foramen or foramina that open in the midline of the mandible on the lingual side.  There can be up to 3 foramina in the midline on some patients. The multiple foramina are more commonly seen on cone beam CT (CBCT) imaging. It appears as a small very round (similar to a hole punch) radiolucent area in the midline of the mandible inferior to the apices of the central incisors.

A single lingual foramen presenting as a round radiolucent area in the midline of the mandible inferior to the apices of the central incisors.

Nutrient Canals / Vascular Canals

Nutrient canals are the accessory canals running throughout the mandible and maxilla. These canals are everywhere so theoretically they can be seen anywhere; however on 2D radiographs they are most commonly seen in the anterior mandible due to the thinness of the ridge in this location. They will appear as vertical (most common) or horizontal or really any direction radiolucent lines.

Nutrient canals presenting as multiple vertical radiolucent lines/bands in the anterior mandible.

Mental Ridge / Mental Triangle

The mental ridge is the inferior aspect of chin projected superiorly onto the mandible when an increased negative vertical angle has been used. It appears as two oblique thick radiopaque bands that that meet in the midline giving it the appearance of an inverted V or triangle shape.  

The mental ridge presenting as radiopaque inverted V in the anterior mandible.

Inferior Border of the Mandible

The inferior border of the mandible is exactly what it is – the inferior border of the mandible. This appears as a thick radiopaque border and can be seen in either the anterior or posterior aspects.

The inferior border of the mandible presenting as a thick radiopaque border in the anterior.
The inferior border of the mandible presenting as a thick radiopaque border in the posterior.

Mental Foramen

The mental foramen is an opening of the inferior alveolar nerve canal (mandibular canal). It opens on the facial of the mandible near the apex of the second premolar. It appears as a round to ovoid radiolucent area inferior to or superimposed over the apex of the second premolar. It can also been seen mesially up to the apex of the first premolar or distally to the mesial apex of the first molar.

Mental foramen presenting as an ovoid radiolucent area just mesial to the root of the second premolar.

Inferior Alveolar Canal / Mandibular Canal

The inferior alveolar canal is probably the first canal that comes to mind when people think of canals on intraoral radiographs. It appears as two radiopaque parallel lines with a radiolucent center running oblique and horizontally inferior to or superimposed over the roots of the mandibular posterior teeth. Note: sometimes only one radiopaque line is seen. If so, it is most commonly the inferior border of the canal.

The inferior alveolar canal presenting as two radiopaque parallel lines with a radiolucent center.

Mylohyoid Ridge

The mylohyoid ridge is the attachement of the mylohyoid muscle on the lingual aspect of the mandible about midway between the inferior border and crest of the alveolar ridge. It appears as an oblique radiopaque band near the roots/apices of the posterior teeth.

The mylohyoid ridge presenting as an oblique radiopaque band inferior to the apices of the posterior teeth.

Submandibular Salivary Gland Fossa

The submandibular salivary gland fossa is a fossa/indentation on the lingual aspect of the mandible inferior to the mylohyoid ridge where the submandibular salivary gland is positioned. It appears as a radiolucent area of bone inferior to the mylohyoid ridge to the inferior border of the mandible.

The submandibular salivary gland fossa presenting as a radiolucent area inferior to the mylohyoid ridge extending to the inferior border of the mandible.

External Oblique Ridge / External Oblique Line

The external oblique ridge appears a thick radiopaque line that runs obliquely as it descends and superimposes over the roots of the molars.

The external oblique ridge presenting as a thick radiopaque line running obliquely in the posterior mandible.

There is your overview of anatomy seen on intraoral mandibular periapical radiographs. I am in the process of making a video as well and hope to have it up within the next month.

If you have any questions or comments, please leave them below. Thanks and enjoy! 😀