Oral cancer belongs to the group of head and neck cancers, and it represents any cancerous tissue in the oral cavity, regardless of being primarily oral lesion, tumor metastases or a distant tumor that has spread into the mouth from the adjacent area (1-3). Squamous cell carcinoma develops in 90% of cases and makes up 3% of all cancers in the United States. In 9% of cases, it is salivary glands cancer, or sarcoma, lymphoma, and metastases occur in only 1% of cases, usually from lung, breast, prostate and kidney (1-3). With regard to the gender, oral cancer is more common in men (4). Risk factors for oral cancer are alcohol, tobacco, or human papilloma virus, and ultraviolet radiation (2-5). Oral cancer therapy is usually aggressive and comprises surgical removal followed by radiotherapy and chemotherapy (6, 7). Maxillectomy is an appropriate surgical procedure which means that either a part or maxilla or the entire maxilla is removed in the process of surgical treatment of oral cancer (8). After surgical removal of cancerous tissue, a great tissue defect with oroantral communication remains, resulting in impaired function of chewing and swallowing, speech, esthetics, and generally impaired oral health related to quality of life. Therefore, in such patients it is necessary to perform appropriate prosthetic rehabilitation which can be additionally complicated by consequences of performed surgical, and radiation therapy such as trismus and limited mouth opening (10 to 15 mm or less) (9). Trismus begins shortly after radiotherapy, and therefore is necessary to start immediately with daily exercises of masticatory muscles using bite openers or a tongue blade. If physiotherapy is not carried out, trismus will become chronic with fibrosis of masticatory muscles. Limited mouth opening impairs masticatory function and prosthetic rehabilitation for such patients is a challenge for clinicians (9).
Traditional approach in the prosthetic rehabilitation of patients after surgical removal of oral cancer is fabrication of obturator (resection) prosthesis in order to close acquired resection cavity primarily on the hard palate, but also on contiguous alveolar and soft tissue structures (8). Some authors described the fabrication of obturator prosthesis retained on the remaining teeth, while others described the obturator prosthesis retained by implants (6, 10-14). The period of 6 months after surgical treatment, when tissue of resection cavity becomes dimensionally stabilized (first tissue swelling, and then shrinkage), is usually sufficient for the beginning of the fabrication of the obturator prosthesis. During this period, temporary obturator prosthesis could be fabricated in order to enable better masticatory function (9). According to Haug (13), a sufficient period for the beginning of fabrication of definitive obturator prosthesis is up to 3 months after surgery, or 3 months after radiotherapy. The extension of surgical resection and the number and position of the remaining teeth affect the form as well as the stability of obturator prosthesis. Apart from the retention of prosthesis on the remaining teeth, it is important to expand the prosthesis base over the remaining oral structures. Maximal extension of obturator prosthesis base transmits masticatory forces to the remaining part of the palate and alveolar ridge, thus reducing masticatory stress. Aramany classification of maxillary defects in 6 classes is based on the relationship between the position of resection cavity and the remaining retention teeth, and is very helpful in the planning of the obturator prosthesis framework design (15, 16).
The advantages of classic obturator prosthesis related to the obturator prosthesis retained on implants is relatively simple and faster fabrication, simple maintaining of oral hygiene, the ability to control possible tumor recurrence on resection cavity tissues, as well as lower price, which is very important among the patients of lower economic status. The aim of this paper was to present a fabrication of maxillary obturator prosthesis after surgical removal of maxillary squamous cell carcinoma with emphasis on simplicity and lower costs of this procedure.
Six months after surgical treatment of oral cancer, a 65 year old patient visited Department of Prosthodontics at Clinical Hospital Dubrava seeking for prosthodontic rehabilitation. During clinical examination, Kennedy Class 4 of maxillary dental arch was observed with remaining right first and second molars, and remaining left second molar. Resection cavity was located in the central part of the hard palate (class 3 according to Aramany classification), whereas the alveolar ridge and the soft palate were fully preserved (Figure 1). The mandible was partially edentulous but without abnormal tissue defects. Only the maxillary obturator prosthesis with metal framework (Co-Cr-Mo alloy, Wironit, Bego, Bremen, Germany) retained by Bonwill clasp on the right side, and by circumferential clasp on the left side was planned. Prosthetic treatment of the mandible was not planned due to the patient’s low socio-economic status.
Because of partially expressed trismus (the distance between the maxillary alveolar ridge in the central incisors area and incisal edges of mandibular central incisors was 35 mm), which occurred as a result of radiotherapy, it was impossible to make a precise one step impression of both, oral and resection cavity. Therefore, the two step impression technique was used. First step impression was made using irreversible hydrocolloid material (Aroma Fine III; GC Corp, Tokyo, Japan), and precisely captured alveolar ridge with remaining teeth, remaining part of the hard palate and only the entrance part of the resection cavity. The impression was poured in hard dental stone (Moldano, Heraeus Kulzer, Hanau, Germany), and the obturator prosthesis framework (Co-Cr-Mo alloy, Wironit, Bego, Bremen, Germany) was fabricated by standard procedure with certain modifications in design (Figure 2). Retentive mesh and dowels on obturator prosthesis framework (Figure 3) were added over the resection cavity to ensure retention for secondary impression material, as well as for the retention of a future acrylic resin bulb of the obturator. The obturator prosthesis framework engaged second left molar by circumferential clasp as well as first and second right molars by interdental Bonwill clasp.
In the second impression step, a precise impression of the resection cavity (Figure 4) was made. Condensation silicone impression material (Optosil/Xantopren, Heraeus Kulzer, Hanau, Germany) was placed on the obturator prosthesis framework which served as a tray, and inserted into the oral cavity. Despite trismus, and because of the appropriate design of obturator prosthesis framework, it was possible to make impression of the entire resection cavity as well as to remove it from the patient’s mouth. The stone cast was then modified; the part of the stone cast which corresponds to the entrance of resection cavity was cut out. Obturator prosthesis framework with silicon impression of the resection cavity was placed on the reduced stone cast. The adjacent impression was poured in dental stone (GC Fuji Rock, GC Europe, Leuven, Belgium) in order to produce definitive stone cast (Figures 5 and 6).
In the patient’s mouth, vertical and horizontal occlusal relationships were determined with interocclusal rest space of 3 mm at the physiologic rest position. After the artificial teeth were arranged (Figure 7), occlusion and esthetics were tested in the patient’s mouth.
The obturator prosthesis was finished by laboratory procedures using heat-curing acrylic resin (Probase Hot, Ivoclar Vivadent, Schaan, Liechtenstein), where both, acrylic base and acrylic bulb of the obturator (Figure 8), which covered retentive elements (mesh and dowels) on the obturator prosthesis framework, were fabricated.
In the next step, the obturator prosthesis was finished and polished. At insertion of obturator prosthesis (Figures 9 and 10) the accuracy of obturator prosthesis fit was verified, especially on the edges of the resection cavity. The occlusion was tested by articulation paper (Arti-Fol, Dr. Jean Bausch GmbH & Co. KG, Cologne, Germany), and the clasps were activated.
Hygiene instructions (especially for the obturator surgical site) were given to the patient in order to avoid possible infections due to microbial contamination of the obturator’s surface. Regular follow-up every 3 to 6 months, or as needed was recommended to the patient, with a remark on possible need for obturator prosthesis relining procedure due to the occurring bone and mucosal tissue changes.
An overall therapy of patients with oral cancer requires a multidisciplinary approach. It should include the maxillofacial surgeon, the oral surgeon, the oncologist, and the prosthodontist. Besides, the psychologist is often needed (1, 17). The aim of the prosthetic rehabilitation in the present case report was to fabricate appropriate obturator prosthesis in order to close communication with nasal cavity, replace lost bone tissue and teeth and improve oral function and esthetics. In addition, the aim was to accomplish this task at lowest cost. The prosthetic rehabilitation of patients with obturator prosthesis has the following advantages: fluid leakage into the nasal cavity and maxillary sinus is minimized; mastication, swallowing and speech with reduced or eliminated hipernasality are enabled due to separation between the oral and nasal cavity (13, 18, 19). The fabrication of the obturator prosthesis shortens the procedure time, and the resection cavity can be easily examined after removing the obturator prosthesis in order to detect tumor recurrence in time (13, 18).
Surgical reconstruction of resection cavity should not be of primary consideration for partially dentate patients with remaining teeth and palatal bone after surgical resection. For such patients, as well as for the patient presented in this case report, the fabrication of obturator prosthesis which functions similarly to removable partial dental prosthesis would be a good solution. The success of prosthetic rehabilitation with obturator prosthesis depends on the size and shape of dental arch after surgical removal of cancer as well as on the quality of the soft tissue covering the alveolar ridge and resection cavity. In cases with little or no preserved maxillary bone, the fabrication of the classic obturator prosthesis is more difficult, and the retention of obturator prosthesis on implants may be a good solution (10, 12, 20). Aramany classification (15, 16) of maxillary defects is very helpful in planning of the obturator prosthesis. In this clinical case, Aramany class 3 defect was present. The resection cavity was located in central part of the hard palate; however, not all the teeth in dental arch were preserved. The obturator prosthesis was retained by Bonwill clasps and circumferential clasps on the molars with retention arms positioned on the buccal surfaces and stabilization elements on the oral surfaces of the teeth. Due to the patient’s low socio-economic status, the remaining molars were not covered by crowns with rests. However, the locations and morphology of the teeth were satisfactory to establish retention of obturator prosthesis.
A serious problem associated with the prosthetic rehabilitation of a patient after radiotherapy is trismus or limited mouth opening. In addition to the clinical implications discussed throughout this paper, the aim of this paper was to present a two-step impression technique with emphasis on the simplicity of obturator prosthesis fabrication as well as on economic acceptability for the patients of low socio-economic status.
Depprich et al. (18) stated that acrylates (polymethyl methacrylate), silicone and titanium are commonly used materials for fabricating the obturator. Disadvantage of acrylates and silicones is in affinity to microorganisms’ contamination due to the surface porosity and roughness which can result in penetration of microorganisms into the interior of the obturator. Depending on the general health condition of the patient and pathogenicity of microorganisms, locally or even systemic infections can occur. In present clinical case obturator was made of heat-curing acrylic resin whose surface could be better polished thus facilitating hygiene and reduces the microorganisms’ accumulation. Sometimes, because of the vulnerability of resection cavity mucosa, it is necessary to use soft acrylates for obturator fabrication. In that case, obturator hygiene maintenance will be more difficult due to the surface porosity of the material. On the other hand, titanium has good biomechanical properties, it is biocompatible, low weight, corrosion resistant, nonallergic material, and its surface can be polished good. Disadvantage is that titanium is not easily to adjust or reline, and the price of such prosthetic appliance is higher (18).
Prosthetic rehabilitation after surgical removal of oral cancer is complex and challenging for prosthodontist. Trismus, as a complication after surgery and radiotherapy, complicates further prosthetic rehabilitation. Using the two-step impression technique it is possible to make an accurate impression of the denture-bearing area and the resection cavity, thus providing a good seating of obturator prosthesis, good retention, and adequate closure of the resection cavity. In prosthetic rehabilitation of such patients, it is important to search for simplified treatments which enable simple examination of resection cavity, and simultaneously, lower the costs in order to be acceptable to patients of low socio-economic status.