Zygoma implant-supported prosthetic rehabilitation of a patient with a maxillary defect

Abstract

This clinical report describes the successful management of a patient who underwent extensive resection of a maxillary cancer, by introduction of a maxillary obturator prosthesis using zygoma implants. The patient was a 57-year-old man with cancer of the upper anterior gingiva. The maxillary bone in the affected region had been extensively excised by radical surgery. Owing to loss of teeth retaining the denture, the existing prosthesis was unstable, and the patient experienced severe speech and mastication disorders. Four zygoma implants (two on each side), and two conventional dental implants (one each at both maxillary tuberosities) were used as denture retainers. The obturator prosthesis was stabilized by the implants, and the patient’s oral function improved. High-level compatibility between the implant and surrounding tissue was obtained by mucosal regeneration around the implant. The results suggest that the combination of zygoma and conventional dental implants improves postoperative oral function by facilitating retention of the obturator prostheses.

Severe maxillary defects resulting from surgical resection of oral neoplasms are associated with major difficulties in restoring oral function, such as mastication, speaking and swallowing, and impaired facial esthetics. In such cases, conventional dental implants have been used to improve the stability and retention of maxillofacial prosthetic obturators and to restore oral function . Implant placement and the subsequent prosthetic treatment often become difficult following resection of maxillary cancer because of a lack of bone tissue in the areas where conventional dental implants can be placed, and extensive loss of soft tissues including the gingiva, mucosa and muscle.

The zygoma implant was developed for edentulous patients with insufficient bone mass for dental implants . This implant is fixed in the zygoma so it is considered beneficial for maxillary defects after resection of cancer . The application of zygoma implants in maxillary defects is associated with various problems, including deficiency of bone tissue, loss of soft tissue and overloading of the zygoma and implant.

This clinical report describes the successful management of a patient with maxillary cancer who underwent extensive maxillary resection, followed by the introduction of a maxillary obturator prosthesis using zygoma implants.

Case report

The patient was a 57-year-old Japanese man, who was diagnosed with cancer of the upper incisor gingival region in July 1994. He underwent preoperative radiation therapy of 40 Gy, followed by left radical neck dissection, right supraomohyoid neck dissection, bilateral maxillary resection, and a split thickness skin graft from the thigh to the bilateral buccal region. A maxillary prosthetic obturator, with bilateral second molars used as abutments, was placed postoperatively. The patient had difficulty wearing the obturator prosthesis after the bilateral upper molars were lost, and returned in April 2006. The maxillary defect included the alveolar bone, hard palate, and nasal septum between the bilateral first molars, and extended vertically to the frontal wall of the maxillary sinus ( Fig. 1 ), which corresponded to Class 2b in the classification of maxillary defects by B rown et al. . An extensive skin graft, transplanted from the thigh during tumor resection, was observed in the bilateral buccal region. Owing to the loss of abutment teeth, the patient was not able to wear the obturator prosthesis, and experienced an articulation disorder and serious masticatory dysfunction. The patient’s masticatory function was assessed using an evaluation sheet for chewing function ( Table 1 ) in complete denture wearers . The chewing function score was 15, indicating that the patient was only able to chew food items in class 5, such as tofu and boiled eggplant, which can be eaten without chewing. Because the maxillary prosthetic obturator could not be retained with conventional treatment, zygoma and conventional dental implants were inserted into the maxillary tuberosity region as retainers to restore occlusion. The surgery was performed in May 2006. The surgical area extended from the anterior wall of the bilateral maxillary sinus to the zygomatic bone ( Fig. 2 A ). The inferior and inner borders of the zygomatic bone were marked under general anesthesia, followed by placement of two zygoma implants (Zygoma Fixture; NobelBiocare, Göteborg, Sweden) into each side of the zygomatic bone (35 and 40 mm long), and Brånemark System Mark III TiUnite implants (Nobelbiocare, Göteborg, Sweden), 4 mm in diameter and 10 mm long in the bilateral maxillary tuberosity region ( Fig. 2 B and C). Considering that zygoma implants could not be fixed in the alveolar bone because of the loss of bilateral maxillary bone, and because the frontal bone of the maxillary sinus was relatively thick (approximately 1 mm), the zygoma implants were placed in the zygomatic bone crossing the frontal wall of the maxillary sinus, so that sufficient retention could be achieved. Since the implant body surface was exposed on both the buccal and maxillary sinus sides in the frontal wall area of the maxillary sinus, iliac cancellous bone segments were grafted inside the maxillary sinus and on the surface of the frontal wall of the maxillary sinus to cover the exposed implant surface ( Fig. 2 D). The cancellous bone harvesting and the implant surgery were performed simultaneously, and a standardized surgical procedure with an anterior approach was used for harvesting the iliac crest grafts .

Fig. 1
Preoperative three-dimensional computed tomography data showing the loss of maxillary bone between the bilateral molars.

Table 1
Assessment of chewing function in complete denture wearers, based on food intake questionnaire method. This case showed recovery of masticatory function, at a level similar to that in patients wearing complete dentures with excellent retention, stability, and fit. ○: Easy to chew; ▵: difficult to chew; ×: impossible to chew. Chewing factor score: number of ○/20 × 100.
Class Food Before treatment After treatment
1 Whole apple × ×
Chewing gum ×
Dried shell ligament ×
Dried cuttlefish × ×
2 Fresh ear shell × ×
Hard pickled radish ×
Hard cracker ×
Hard biscuit ×
3 Pickled radish ×
Peanuts ×
Beef steak ×
Rice-cake cubes ×
4 Burdock ×
Potato chips ×
Boiled fish paste (kamaboko) ×
Artificially grown soybean ×
5 Boiled carrot
Boiled potato
Boiled eggplant
Bean curd (Tofu)
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Feb 7, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Zygoma implant-supported prosthetic rehabilitation of a patient with a maxillary defect
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