Establishing Ideal Occlusion to Achieve Esthetic and Functional Excellence - An Interdisciplinary Approach to Functional Esthetics

With the curve of Wilson viewed frontally, the posterior teeth in the maxillary arch have a buccal inclination. From the frontal view, the posterior teeth in the mandibular arch have a lingual inclination. A line drawn through the buccal and lingual cusp tips of the right and left posterior teeth produces a curved plane. The curvature is convex in the maxilla and concave in the mandible.

Viewed laterally, the curve of Spee is an imaginary line drawn through the buccal cusp tips of the posterior teeth (molars and premolars); a curved line following the plane of occlusion will be established that is convex for the maxillary arch and concave for the mandibular arch. These convex and concave lines match perfectly when the dental arches are placed in occlusion.

Much of the mandible movement is determined by the two temporomandibular joints (TMJs), which rarely function with identical simultaneous movements. Because most jaw movements are complex, with the centers of rotation constantly shifting, a flat occlusal plane will not permit simultaneous functional contact in more than one area of the dental arch. The occlusal planes of the dental arches are, therefore, curves in a manner that permits maximum use of tooth contacts during function.

The first case in this article illustrates the planes of occlusion in an adult (Figure 1) who has always functioned with her malocclusion. She was told she would need surgery to correct her skeletal discrepancy.

The patient, age 35 (Figure 1), presented with a Class II Division I malocclusion with a 6-mm anterior open bite. The open bite was present from the right second molar to the left second molar. The only contacts were on the distal occlusal surfaces of the second molars. There was moderate maxillary and mandibular crowding (Figure 2, Figure 3, Figure 4, Figure 5). The patient complained of soreness in both jaws. She presented with bilateral TMJ pain and had bilateral clicking of her joints on opening and closing. She stated that she had morning headaches every few days and her “jaws locked once.” The patient had had this malocclusion since childhood.

The patient presented with a straight-to-slightly concave facial profile, with a very strong tissue pogonion. Her soft-tissue chin was very prominent in both the profile and frontal views. She presented with lip competency and normal soft-tissue contours. Cephalometrically, the initial SNA relationship was 82º and SNB was 77º with an ANB difference of 5º before orthodontic treatment. The mandibular plane angle (GoGnSN) was 36º. Note the two planes of occlusion and the open bite present from second molar to second molar (Figure 5). Diagnosis is critical in this type of case because the mandibular position is being determined by the dentition. The critical diagnostic work-up for this patient was the evaluation of the occlusal planes: the curve of Spee and the curve of Wilson.

The mandible is a bone joined to the skull by ligaments and suspended in a muscular sling. When elevator muscles (masseter, medial pterygoid, and temporalis) are called on to function, their contraction raises the mandible so that contact is made and force is applied to the skull in three areas: the two TMJs and teeth. Because these muscles can provide heavy forces, there is a great potential for damage to occur at the three sites. This is obviously more severe if the patient presents with functional contacts on only the distal surfaces of the second molars.

Orthodontic treatment for this patient consisted of full edgewise appliances. The maxillary and mandibular right third molars were extracted to prevent binding in the mechanics used to correct this malocclusion. After extraction of the third molars, an activated maxillary quad helix appliance was inserted to correct the transverse discrepancy and improve the curve of Wilson of the maxillary arch (Figure 6). In the maxilla, 0.018 lever arm expansion arches were used for rotation and expansion of the second molars.

After correction of the transverse discrepancy, rotations, and maxillary and mandibular arch alignment, the maxillary buccal dentition was distalized into a Class I occlusion. Buccal-lingual coordination of the maxillary and mandibular arches was achieved. After 1 year of orthodontic treatment, the patient had no TMJ pain and felt smooth opening of her jaw with no clicking on opening and closing. Her headaches had disappeared.

Finishing the occlusion entailed an additional 5 months. Total active orthodontic treatment was 17 months. The edgewise appliances were removed, and maxillary and mandibular spring aligners were used for retention for approximately 2 years. Postretention evaluation presented a stable occlusion, and the patient had no symptoms (Figure 7, Figure 8 and Figure 9).

Posttreatment cephalometric analysis showed SNA was 82º and SNB was 80º with an ANB difference of 2º. The mandibular plane angle (GoGn-SN) was 30º. Note the mandibular plane position rotated counterclockwise to reduce the ANB difference from 5º to 2º. Posttreatment cephalometric radiograph revealed a clockwise forward rotation of the mandible, with complete elimination of the two planes of occlusion that were present before orthodontic treatment (Figure 10, Figure 11, Figure 12, Figure 13, Figure 14). The patient’s soft-tissue contours improved (Figure 15).

The second case illustrates a 30-year-old female (Figure 16) with distorted planes of occlusion presenting for presurgical orthodontic treatment. She had a severe Class II Division I malocclusion and a severe open bite and overjet. She presented with a retrognathic mandible as well as moderate maxillary and mandibular crowding. The maxilla had a V-shaped arch. She also presented with severe wear facets (Figure 17, Figure 18, Figure 19 and Figure 20) on her dentition from past bruxism, which indicated later pathologic joint degeneration with clockwise downward and backward rotation of the mandible (Figure 21 and Figure 22).

Her diagnostic work-up is as follows:

The patient had a long litany of dental treatment. Initially, the patient developed TMJ problems when she was 16 years old and began treatment with splint therapy. She had previous orthodontics with four first bicuspid extractions. At age 25, she developed a TMJ closed-lock situation and began splint therapy again. She subsequently had bilateral TMJ arthrocentesis and later had bilateral TMJ arthroscopy. At age 29, she began developing significant changes in her profile with the mandible becoming significantly retruded, developing an anterior open bite and occluding only on her left second molars. She had significant TMJ pain and myofascial pain with major difficulties with mastication. Her diet consisted of extremely soft to liquid foods only. She was significantly disabled because of her pain and jaw dysfunction.

Presurgical orthodontic treatment was to align, level, and correct the V-shaped maxillary arch. The maxillary lateral incisor roots were tipped mesially and the cuspid roots tipped distally to make room for interdental osteotomies. Correction of the curve of Wilson was achieved with a quad helix to correct the lingual version of the posterior dentition and create a buccal inclination.

The mandibular arch was aligned and leveled. The lower anterior teeth were stripped approximately 2 mm to keep them from flaring and help correct for the tooth size discrepancy. Presurgical edgewise orthodontic treatment was completed in 8 months.

The surgical procedures included reconstructing the TMJs and advancing the mandible using custom-fitted total joint prostheses (TMJ Concepts system, TMJ Concepts, https://www.tmjconcepts.com)^1-10 (Figure 23 and Figure 24). This prosthesis system allows reconstruction of the TMJ and in this case, advancement of the mandible in a counterclockwise rotation. The prostheses were placed through small incisions around the ear and below the angle of the mandible. Multiple osteotomies also were performed on the maxilla to advance it forward. The maxillary surgery was done from inside the mouth, and small bone plates were placed to hold the upper jaw in its new position. The maxilla was advanced forward 10 mm at the incisor tips, mandibular incisors advanced forward 17 mm, and pogonion (chin) advanced forward 28 mm.

Because of the resorption of her mandibular condyles, the mandible had moved posteriorly. This caused a significant decrease in her oropharyngeal airway. Prior to surgery, the airway dimension was 3 mm; however, the surgery opened her airway space to a normal 11 mm postsurgery. In addition, she had reduction turbinectomies and a nasal septoplasty to achieve a good functional nasal airway posttreatment. Fat grafts were harvested from the abdomen to place around the articulating portion of the bilateral total joint prostheses to enhance function. Postsurgery, her jaws were not wired together and she was able to function and move her jaws immediately.

The initial healing phase took approximately 4 months for the new bone to grow in and develop around the surgical areas where osteotomies were performed. For the first 4 months, the patient maintained a relatively soft diet. After 4 months, she began a more regular diet. The overall healing took approximately 1 year. At 1 month postsurgery, the orthodontics reinitiated to finalize the occlusion was completed in 6 months. Following completion of the orthodontics and retention, the restorative dentistry was completed to establish an ideal functional occlusion with proper cusp-to-fossa relations and buccal-lingual coordination (Figure 25, Figure 26 and Figure 27).

At 1 year postsurgery, she was pain-free with an incisal opening of 55 mm and excursion movements of more than 3 mm in each direction. She had a good stable occlusion and normal diet. The patient is now 4½ years postsurgery and continues to do well (Figure 28 and Figure 29).

Internal derangement^11-16 has often been implicated as a major factor for condylar resorption. Studies have shown internal derangement may cause minimal morphologic changes in one patient, whereas in another patient, severe condylar changes with the same level of internal derangement severity may be observed. Systemic etiologic factors have been investigated in aggressive condylar resorption.

Aggressive condylar resorption is multifactorial and has been described in the dental literatures extensively. Arnett et al^17,18 describe three groups of factors that may contribute to condylar resorption:

Wolford and others^19,20 reported condylar resorption favor women over men, and many investigators have implied a prominent systemic factor for the pathogenesis of this disease might be related to the sex hormones. A recent study by Gunson et al²¹ associated oral contraceptive pills and abnormal menstrual cycles in women displaying low serum 17b-estradiol as a major factor in progressive condylar resorption.

Two females presented with nonfunctional open-bite malocclusions displaying distorted curve of Wilson and curve of Spee with minimal tooth contacts and histories of TMJ symptoms of varying degrees. The differential diagnosis and treatment were presented.

Michael G. Arvystas, AB, DMD
Professor of Orthodontics
Montefiore Medical Center
Albert Einstein College of Medicine
New York, New York

Diplomate
American Board of Orthodontics

Private Practice
New York, New York
Denville, New Jersey

Larry M. Wolford, DMD
Clinical Professor
Department of Oral and Maxillofacial Surgery
Texas A&M University Health Science Center
Baylor College of Dentistry
Dallas, Texas