The Clinical Problem
Dentofacial (dentoskeletal) deformities are characterized by an abnormal position of the maxilla and/or mandible and associated teeth that affect jaw function and facial aesthetics. These deformities are as follows ( Fig. 22.1 ):
- •
Class I—normal skeletal pattern, maxilla and mandible in an orthognathic relationship
Occlusal relationships are characterized by the mesiobuccal cusp of the maxillary first molar occluding with the mesiobuccal groove of the mandibular first molar; the maxillary canine occludes with the distal half of the mandibular canine and the mesial half of the mandibular first premolar.
- •
Class II—skeletal deformity characterized by a deficient mandible
- •
Class III—skeletal deformity characterized by a prognathic mandible
Class II and III occlusal relationships are characterized by the mesiobuccal cusps of the maxillary first molar being mesial and distal to the buccal groove of the mandibular first molar, respectively, as well as the distal surface of the mandibular canine being distal and mesial to the mesial surface of the maxillary canine, respectively.
In addition to anteroposterior jaw discrepancies, there are transverse jaw discrepancies, open bite or deep bite discrepancies, vertical (excess or deficient) deformities, and chin deformities—retrusive (retrogenia) or protrusive (progenia).
The Aesthetic Problem
Dentofacial deformities of the maxilla, mandible, and chin include overgrowth (hyperplasia), undergrowth (hypoplasia), and asymmetries. Facial aesthetics are compromised by the abnormal position of the maxilla, mandible, and chin.
Patients may appear to have an upper or lower jaw or chin that is too large or too small, which manifests within the dentition as a malocclusion (e.g., class I, II, III). There may be a lip incompetence, mentalis strain, gummy smile, underbite, overbite, poor neck-chin-throat morphology, sagging skin, submental redundancy, lack of malar projection, scleral show, ptotic nasal tip, everted lower lip, thin upper lip, and other facial aesthetic problems.
Surgical Preparation and Technique
Management and Treatment Options
A thorough cephalometric analysis assists the clinical and radiographic diagnostic evaluation and treatment of the malocclusion and skeletal deformity. The operative plan should be clinically driven with the aid of three-dimensional treatment planning and virtual surgical planning (VSP) considering functional and aesthetic concerns ( Fig. 22.2 ).
Surgical therapy is aimed at the correction of the specific individual patient deformity, with correction of the malocclusion, functional deficiency, and unaesthetic appearance. Surgical procedures include a maxillary Le Fort osteotomy ( Fig. 22.3 ), malar augmentation, mandibular sagittal split osteotomy ( Fig. 22.4 ), vertical ramus osteotomy, various other forms of ramus osteotomies (e.g., inverted L osteotomy), chin genioplasty procedures ( Fig. 22.5 ), and malar augmentation ( Fig. 22.6 ).
Treatment and Operative Techniques
Maxillary Surgery: Le Fort I Osteotomy
Using a proper surgical drape, with a nasal endotracheal tube secured while avoiding excessive alar pressure, a K-wire is placed at the soft tissue nasion as an external vertical reference point. Calipers are used to measure and record the vertical distance between the K-wire and orthodontic brackets at the central incisor.
A circumvestibular incision is made from the first molar to the first molar above the mucogingival junction. Subperiosteal dissection exposes the lateral maxilla, lateral nasal walls, piriform aperture, anterior nasal spine, infraorbital foramen, zygomatic-maxillary buttress, and posterior maxilla.
A reciprocating saw is used to create an osteotomy of the anterior maxillary wall. A straight osteotome completes the posterior osteotomy to the pterygoid plates, and a curved osteotome is used to separate the maxilla from the pterygoid plates. A nasal osteotome separates the nasal septum and vomer from the nasal crest of the maxilla. A single-guarded nasal osteotome separates the lateral nasal wall posteriorly toward the pyramidal process of the palatine bone.
For segmental maxillary surgery, interdental osteotomies are made with a saw. Next, the maxilla is downfractured. Tessier elevators are placed behind the posterior maxilla for mobilization.
The occlusal splint—intermediate (two-jaw surgery) or final (single-jaw surgery)—is used. The maxillomandibular complex is then passively positioned in a posterior-superior direction, seating the mandibular condyles. Anterior and posterior bony interferences are identified and reduced until the desired vertical dimension is achieved.
Rigid fixation is applied to the nasomaxillary and zygomatic-maxillary buttresses. Maxillomandibular fixation is released and, in single-jaw surgery, the occlusion is assessed for reproducibility. In the case of double-jaw surgery, the intermediate occlusion should be verified prior to mandibular surgery. An alar cinch suture may be applied to control the width of the alar base, and a V-Y (or double V-Y) advancement may be performed to increase lip prominence and provide lip support.
Mandibular Surgery—Bilateral Sagittal Split Osteotomy
A mucosal incision is made from the first molar to midway up the ascending ramus. Following subperiosteal dissection to the medial ramus and protection of the inferior alveolar neurovascular bundle, the medial osteotomy is made with a drill or saw and continued anteriorly along the ascending ramus, just medial to the mandibular buccal cortex to the external oblique ridge (first or second molar region).
The vertical osteotomy is made where the external oblique ridge blends with the body of the mandible, usually just between the first and second molar regions. The saw or drill cuts through the inferior border. Osteotomes are used to complete the mandibular split.
The interocclusal splint is inserted, and maxillomandibular fixation is applied. The condyle is seated passively into centric relation and fixation is applied. The occlusion is assessed for accuracy and reproducibility.
Genioplasty
A labial mucosal incision is made below the mucogingival junction between the canine teeth. The mentalis muscles are incised, leaving an adequate cuff for closure. Subperiosteal dissection to the inferior border of the mandible is carried out, identifying the mental nerves bilaterally.
After scoring the symphyseal midline, a reciprocating saw is used to cut through the anterior mandible. The osteotomy is completed.
Vertical augmentation by wedge ostectomy or vertical augmentation by bone grafting may be performed. The distal segment is positioned and rigid fixation is applied using bicortical screws or prebent plates.
The position of the chin is then reassessed. The wound is irrigated and closed in layers, and a postoperative chin dressing is applied.
Related posts:
Full access? Get Clinical Tree
