Kinnbein

Kinnbein is a nonstandard term that may be used in informal German to refer to the bone beneath the chin. In formal anatomy there is no bone officially named kinnbein; the chin area is part of the mandible, the lower jaw bone. When people speak of a “chin bone” they are describing the anterior part of the mandible, notably the mental region and the menton, the point at the tip of the chin.

Anatomy: The mandible is a single U‑shaped bone that forms the lower jaw. It consists of a horizontal body (corpus mandibulae) with a midline symphysis where the two halves fuse, and two vertical rami. The chin is produced by the anterior portion of the body and presents the mental protuberance (menton). On the external surface there is a mental foramen near the premolar region, through which the mental nerve exits to supply the chin and lower lip. The internal surface has various muscle and ligament attachments and features such as genial tubercles. The mandible bears the lower dental arch and supports the teeth.

Development and variation: The mandible develops from two embryonic elements that typically fuse at the mandibular symphysis during early childhood. The appearance and projection of the chin vary with age, sex, and genetic factors and may be altered by dental status, orthodontic treatment, or cosmetic procedures. In discussions, the menton is usually referred to rather than implying a distinct separate bone.

Clinical relevance: Fractures of the chin are common in facial trauma and are part of mandibular fracture patterns. Diagnosis relies on clinical examination and imaging, including X‑rays or CT scans. Treatments aim to restore occlusion and facial contour, and may involve reductions or fixation of the mandible.