6
Surgical Anatomy and Local Anesthesia
Roya Afshar‐Mohajer and Babak Hamidi
Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, NY, USA
As dental surgeons, our main objective during the procedures we perform is to gain access to the underlying structures of the oral cavity. Whether the procedure is resective or regenerative in nature, we must be cognizant of what anatomic landmarks are present in our designated surgical site. The purpose of this chapter is to review some key anatomic landmarks that must be taken into consideration when planning a surgical procedure especially with regards to our incision, flap design, and tissue management.
The two key considerations when designing a flap is to understand the anatomy of the site and a clear goal and expected outcome. During periodontal surgery, our key objective is to have access to the underlying structures, namely, the roots and the bone. Our definitive incisions and flap reflection keeping in mind the anatomy as well as the blood supply (Figure 6.1) will lead to less tissue trauma and better tissue management. During these procedures we are often modifying the osseous architecture either in a resective manner or through regenerative modalities but ultimately leading to better hard and soft tissue contours. In turn this will lead to enhanced plaque control and long term maintenance (Rose).
To ensure an optimum outcome we must always practice atraumatic tissue techniques, which include making concise, smooth incisions with a sharp blade followed by careful flap reflection. During closure we want to avoid too much tension on a flap while suturing and making sure there is proper hemostasis. Ultimately these steps will help ensure ideal wound healing without complications.
Anatomic Landmarks
Mandible
The mandible or lower jaw is a u‐shaped bony structure that is made up of different components that are important for us to be cognizant not only in terms of giving local anesthesia prior to surgery but also for proper surgical planning. It is made up of the ramus and the body and contains foramen, ridges, and concavities we need to be aware of as well as the corresponding nerves and vessels running throughout (Table 6.1; Figure 6.2).
Periodontal surgery in the posterior mandible can most often be complicated by the presence of the external oblique ridge as well as when the temporal crest and anterior border of the ramus sharply abut the most terminal mandibular molar. This makes proper re‐contouring of the bone a challenge during osseous surgery or crown lengthening procedures (Figure 6.2).
The buccinator muscle, which attaches to the mandible along the molar teeth, may limit proper extension of the vestibule in the posterior mandible. This muscle forms a portion of the medial wall of the buccal space; therefore if it were damaged while elevating a buccal flap; the buccal space would be violated producing the possibility of an infection in the space. Since the buccal space communicates with the para‐pharyngeal space, potential danger of the spread of a buccal space infection into other spaces of the head and neck (Clarke) (Figure 6.2).
The mental foramen that is usually located inferior to apices of mandibular premolars may become a consideration during osseous surgery where there is correction infra‐bony defects or if there are muco‐gingival defects that may require apically positioning the buccal flap during surgery. Damage to the mental nerve could result in temporary or possibly permanent paresthesia of the lip and gingiva (Clarke) (Figure 6.3).
Figure 6.1 Arteries supplying the maxilla and mandible.
Table 6.1 Anatomy of the mandible.
| Anatomic feature | Characteristics |
|---|---|
| Alveolar process |
|
| Anterior border of the ramus |
|
| Coronoid process |
|
| Temporal crest |
|
| External oblique ridge |
|
| Mylohyoid ridge |
|
| Genial tubercule |
|
| Mental foramen |
|
Figure 6.2 Mandible.
Figure 6.3 Nerve innervation of the mandible.
While performing surgery on the lingual aspect of the mandible, we must be aware of the location of the lingual nerve, which can sometimes be positioned superficially in the area of the second and third molars. Also, anytime the attached gingiva is elevated on the lingual aspect of a mandible, or when there is a perforation in the mucosal on the floor of the mouth, the sublingual space may be violated. If there is an infection in this space it could lead to an elevation of the tongue and respiratory problems. Such an infection may spread into the para‐pharyngeal space or even produce cellulitis of the neck (Clarke).
The mentalis muscle may prevent the surgeon from adequately increasing the zone of attached gingiva or deepening the vestibule in the anterior mandible region. The elevation of this same muscle could violate the sub‐mental space.
Since the plate of bone overlying the facial and lingual root surfaces of the mandibular anterior teeth is usually quite thin, it may be beneficial to utilize a partial thickness flap; therefore, the periosteum and connective tissue would help prevent postoperative osseous and gingival defects over these roots (Clarke).
In the anterior lingual region, the possible obstacle would be the presence of an abnormally large or high genial tubercle, which may prevent osseous re‐contouring during periodontal surgery (Figure 6.2).
Anatomic Spaces
There are two categories of anatomical spaces or compartments are found in the head and neck:
- Spaces found within subcutaneous or submucosal connective tissues
- Spaces delineated by fascial membranes
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