Use of Cephalometric Analysis for Implant Placement in a Patient With an Edentulous Maxilla With a Severe Class III Intermaxillary Relationship

We often encounter patients who have intermaxillary discrepancy. Maxillary alveolar bone is usually resorbed from the labial side after extraction. Severe resorption of the maxilla can lead to a Class III intermaxillary relationship.1–3 We describe a patient with a totally edentulous maxilla who had a severe Class III intermaxillary relationship in the anterior region. Cephalometric analysis was used for planning treatment.4 

The patient was a 49-year-old man who was a nonsmoker. He was recommended to my clinic by another dentist and was first examined in May 1997. He complained of masticatory difficulty and the inability to wear a conventional denture. During the past 10 years, the patient had tried many dentures made by numerous dentists, but had not found suitable dentures. The patient claimed that using dentures had altered his pronunciation, causing him to feel strange when he spoke and making him feel uncomfortable at social events.

In the maxilla, 2 tooth roots remained. The relationship between the maxillary anterior region and the mandibular anterior teeth was severe Class III (Figure 1). In the mandible, there were 10 teeth between the second premolars (Figure 2). Panoramic and cephalometric radiographs were obtained (Figure 2). Cephalometric analysis of radiographs taken with the mandible in resting position showed that the angle of the upper anterior residual bone was +1 SD (FH plane), +2 SD (SN plane). The width of the alveolar bone was 6 mm at 10% magnification of the image.

There was no evidence indicating that the mandible should be rotated clockwise to improve the intermaxillary Class III relationship. If implants were inserted in the labio-palatal center of the anterior alveolar bone in the maxilla, the crown lengths of the lower anterior teeth would have to be reduced by 50% to obtain a normal overlap. Because the labio-lingual angle of the lower anterior teeth was within −1 SD, lingual angling with the use of prosthesis was not indicated5 (Table 1).

A surgical guide and a stent were made to determine the location of the implants in advance. Upper and lower impressions were taken, and the plaster models were mounted on an articulator.

Determining the occlusal vertical dimension is difficult.6–8 In some edentulous patients, the occlusal vertical dimension is unstable. In our patient, however, the occlusal vertical dimension was stable and could be easily determined. Multiple measurements of the occlusal vertical dimension on different days yielded similar results, which were consistent with those obtained by bite registration.

On the articulator, the crown lengths of lower anterior teeth were reduced by 50% to obtain a normal overlap. An upper complete denture with a normal anterior overlap was then made from clear resin. The location of the upper anterior artificial teeth was confirmed and used as a guide for surgery (Figure 3).

The relationship between the upper lip and the upper anterior artificial teeth was carefully checked to ensure there were no esthetic problems. A surgical guide was used during surgery to determine exact implant locations and directions. A surgical stent was made to position each initial drill hole (Figure 4).

First, the 2 remaining tooth roots were extracted from the maxilla before implant surgery. In July, 10 implants were placed in the maxilla, using the surgical guide and stent (Figure 5). To promote the formation of new bone in the anterior region, the guided bone regeneration technique was performed using autogenous bone-slurry harvested from 10 implant beds with an osseous collection filter. In October, a temporary maxillary full bridge was seated after reduction of the lower anterior teeth.

For the maxilla, an operator-removable (noncemented, screw-retained) full bridge was planned. First, a small section of the maxillary superstructure was made and placed in the patient's mouth to evaluate compatibility. Afterwards, self-curing resin cores were placed to facilitate soldering (Figure 6a and b). The soldered superstructure was again placed in the patient's mouth, and the fit was checked. The procedure was very complicated because poor alignment of even one screw would have adversely affected the passive fit of the entire superstructure. If this occurred, the entire procedure would have had to be repeated until the passive fit had been achieved.

In the molar region, conventional occlusal screws were used, but in the anterior region, horizontal screws inserted from the palatal side of the prostheses were used to maintain positive esthetics (Figure 6c, d, and e).9 

In December, a screw-retained maxillary full bridge, with a facing made from light cure hybrid hard resin (Artglass,10 Heraeus Kulzer Co), was placed (Figures 6f and 7). This type of bridge was selected because screw-retained superstructures and facing material can easily be repaired and rebuilt. In fact, in our patient the facing was rebuilt to improve the anterior emergence profile.

In the mandible, an apically positioned flap operation was performed in November to eliminate periodontal pockets and to obtain the proper clinical crown length of the lower anterior teeth.11 After the mucogingival flap was elevated, tooth debridement was performed, and the flap was repositioned apically to obtain a proper relative bone level (Figures 8 and 9).

In February 1998, a conventional mandibular full bridge was placed (Figures 10 and 11). On relaxed frontal view, the maxillary anterior teeth were esthetically appropriate relative to the upper labial position (Figure 10d).

On postoperative cephalometric X rays, the interincisal angle was 116.5 (−2 SD), the U-1 to FH plane angle was 114.0 (<+1 SD), the U-1 to SN plane angle was 112.5 (<+2 SD), the L-1 to occlusal angle was 25.0 (<+1 SD), and the L-1 to mandibular angle was 91.5 (<−1 SD) (Figure 12b). The location and angle of the anterior teeth were clinically acceptable.

Point A on X-ray film, after treatment by the GBR technique, had moved 3 mm anteriorly as compared its location before such treatment. Therefore, the SNA angle changed from 79.5 to 82.5. Consequently, the ANB angle (SNA – SNB difference) improved from −1.5 to +1.5 (Figure 12c).

The mandibular position did not change after treatment (Figure 12c). This outcome was favorable in terms of avoiding an increased risk of temporomandibular joint disorders.

After recovery, the patient could once again eat his favorite foods, speak without worrying about pronunciation, and not feel conscious about his appearance, owing to the improved esthetics of his mouth. The patient has remained satisfied for more than 5 years since the placement of the implant prostheses (Figures 13, 14, and 15).

Cephalometric diagnosis is usually used to evaluate natural teeth undergoing orthodontic treatment. Because the superstruc-ture in our patient more closely resembled natural teeth than conventional dentures, we used cephalometric diagnosis and found it to be a valid procedure that can be used to assess implant superstructures similarly to natural teeth. Cephalometric analysis is considered one technique that may be useful for planning implant therapy and evaluating its outcome.