Anterior Mandible
The anterior mandible includes the area between the mental foramina and the chin. It is frequently utilized for implant placement or harvesting of autogenous block grafts. Both interventions carry the risk of perforation of the lingual bone cortex with su
- PDF / 1,824,925 Bytes
- 15 Pages / 595.28 x 790.87 pts Page_size
- 7 Downloads / 212 Views
The anterior mandible is generally defined as the part of the mandible rostral to the mental foramina, and hence, it is also called the interforaminal region (Fig. 20.1). The latter term is widely used in dental implantology, and it was introduced in the early phase of modern implant dentistry reflecting the concept of implant-borne removable, and later fixed, full mandibular prostheses (Almog et al. 2007) (Fig. 20.2). Another term frequently used to describe the anterior mandible is “symphysis.” By definition, the word “symphysis” in anatomy means the fibrocartilaginous fusion of two bones. As such, it is a misnomer for the anterior mandible since the mandible consists of a single bone, but embryologically forms from two halves that fuse and ossify early in life (Nyström and Ranta 2003). The symphysis has also been defined as the area bounded by distal imaginary vertical lines through the lower canine teeth (Goodday 2013). The chin (l: mentum) denotes the lower and most anterior portion of the mandible, and it is often the most forward skeletal part of the head (pogonion = most anterior point of the chin in midsagittal plane) (Fig. 20.3). The chin is the area where autogenous block grafts are frequently harvested or genioplastic surgeries and osteosynthesis of mandibular fractures are performed (Alatel and Al Majid 2012; Goodday 2013; Park et al. 2013). Usually, a bony and bilateral mental protuberance is present at the anterior lower border of the mandible. Above the chin is a slight concavity called the incisive fossa (Fig. 20.4). This area provides attachment for the bilateral mentalis muscle. Dissection of 14 cadaveric hemifaces found the origin of the mentalis muscle being located on average 18 mm above the inferior border of the mandible (Hazani et al. 2013). The fan-shaped muscle descends into the skin of the chin (Figs. 20.5, 20.6, 20.7, and 20.8), and it belongs to the lower group of the muscles of facial expression. It is innervated by the lower branches of the facial nerve (CN VII). The mentalis muscle provides the major vertical support of the lower lip and elevates the chin (Rubens and West 1989). Absence or malfunction of the mentalis muscle results in
20
the visibility of the lower incisor teeth, drooling, and denture instability (Zide and McCarthy 1989; Noia et al. 2012; Hur et al. 2013). In a dissection study of 20 Korean cadaveric heads, the upper fibers of the mentalis muscle were intermingled with the inferior margin of the orbicularis oris muscle in all specimens, and lateral fibers of the mentalis muscle joined the depressor labii inferioris muscle (Hur et al. 2013). Fibers of the mentalis muscle may also blend with the ipsilateral lower bundle of buccinator muscle fibers (D’Andrea and Barbaix 2006). The junction of the mentalis and orbicularis oris muscles forms the labiomental fold. If a significant overlap occurs, the fold is indistinct. If the orbicularis oris is narrow, the fold is high (Garfein and Zide 2008). Fat tissue is normally present deep to the mentalis and orbicularis oris mu
Data Loading...
