Case Presentation of Two Maxillectomy Patients Restored with Two-piece Hollow Bulb Obturator Retained using Two Different Types of Magnets.

Palatal defect can be repaired by reconstructive surgery and/or a dental prosthesis. We present prosthodontic rehabilitation of two partially edentulous patients, both with surgically induced palatal defect and explains how to achieve the goal for esthetics and phonetics. This also describes the fabrication of a hollow obturator by two piece method, which is simple and may be used as definitive obturator for maximum comfort of the patient. In both the above cases, since the mouth opening is restricted due to surgery, obturator prosthesis is given as two pieces retained with opposite poles of magnet, which facilitates the removal and insertion of the prosthesis.

INTRODUCTION

Malignancies are common in the oral region and are treated surgically. Surgical treatment creates anatomic defect that creates communication among the oral cavity, nasal cavity, and maxillary sinus. It is very difficult for the patient to perform various normal functions such as mastication, swallowing, and speaking. Speech becomes often unintelligible as a result of the marked defects in articulation and nasal resonance. Prosthodontic rehabilitation with obturator prosthesis restores the missing intraoral structures and acts as a barrier between the communications among oral and nasal cavities. Multidisciplinary treatment planning is essential to achieve adequate retention and function for the prosthesis.

Maxillary complete denture with a superiorly extended modified obturator provides a good chance to restore oral functions in patients with palatal defects. The patients’ skill and previous experience of denture wearing might have been important in their successful treatment. However, different patients present with unique problems and need to be treated individually.

CASE REPORTS

Case 1

A 55-year-old female patient reported to the Department of Maxillofacial Prosthodontics for the restoration of maxillary teeth and the associated structures, which were surgically resected 2 years back. On examination [Figure 1], Armany class I maxillary defect on the left side and patient had restricted mouth opening. Fabrication of two-piece hollow bulb obturator[1] was planned. First piece is the bulb, which was made hollow. Second piece was the denture part, fabricated over the bulb. Both the parts are approximated by magnets.

Figure 1

Case 1 – intraoral defect

Mandibular alginate (Algitex, DPI, India) impression was made. Impression of the defect portion was made with impression compound (Y-Dents, MDM Corporation, India) over which an alginate impression was made with stock tray. A secondary cast was poured with type 4 gypsum product [Figure 2]. Shell wax pattern of 2 mm thickness was fabricated in the defect side. Wax pattern for the lid to close the defect was fabricated. Both hollow bulb shell portion[2] and the lid portion were flasked, dewaxed, and processed with heat cure denture base resin (DPI Heat Cure, India). The bulb and lid were trimmed and polished. After verification of fit of bulb and lid intraorally, both were fused using chemically activated denture base resin and checked for air leak using water immersion methods [Figure 3].

Figure 2

Master cast

Figure 3

Secondary impression

After denture base fabrication, procedures such as occlusal rim adjustment, interocclusal record registration, denture try-in, and delivery of prosthesis with retentive clasps[3] were performed in the conventional manner for denture construction.[4] Proper palatal contour and peripheral seal were achieved.

Two pieces (hollow bulb piece and denture piece) were tried in patient mouth and fit verified. Since the vertical height of the bulb was more than the mouth opening of the patient, the obturator prosthesis was inserted as two separate pieces. The orientation and retention of two pieces intraorally could be done with opposite poles of magnets [Figure 4]. Magnets were incorporated into the denture base in the patient's mouth by using autopolymerizing resin [Figure 5]. The magnet used in Case 1 is 1 cm diameter uncoated neodymium magnet, where the magnet is directly exposed to oral cavity [Figure 6].

Figure 4

Final prosthesis

Figure 5

Final prosthesis – denture part and hollow bulb part

Figure 6

Intraoral view – hollow bulb part with magnet attachment

Case 2

A 50-year-old male patient reported to the department, with a 5-year-old acrylic obturator which was less retentive. On examination [Figure 7], he revealed Armany class 1 defect, missing left maxilla, and had restricted mouth opening. The existing denture showed short bulb portion and was less retentive. Treatment planned for a two-piece obturator with increased bulb height for more retention.

Figure 7

Case 2 – intraoral defect

Definitive impressions were made with impression compound in the defect area and the rest portion with alginate using stock tray. The prosthesis was fabricated in two pieces. First piece [Figure 8] was fabricated as hollow bulb. Second piece was fabricated as the maxillary denture [Figure 9] over the bulb. Both the pieces of obturator checked intraorally and fit verified. These two pieces were approximated using opposite poles of magnets of 1 cm diameter, stainless steel-coated neodymium magnets.

Figure 8

Intraoral view – hollow bulb part with magnet attachment

Figure 9

Intraoral view – denture part

Since the mouth opening was restricted, both the patients could remove and insert the obturator as two pieces [Figure 10], first insert the hollow bulb and then the denture part. The opposite poles of magnet attract each other and retain the prosthesis.

Figure 10

Final prosthesis – denture part and hollow bulb part

REVIEW

Patients reviewed after 1 year. Patient 1 with uncoated magnet revealed erosion of the magnet due to direct exposure of magnet into oral cavity and magnetic property was minimal. Patient 2 with stainless steel-coated magnet revealed unaffected magnets.

DISCUSSION

Lack of support, retention, and stability are common prosthodontic treatment problems for patients who have had a maxillectomy. Factors that affect the prosthetic prognosis for these patients are the size of defect, number of remaining teeth, amount of remaining bony structure, quality of existing mucosa, radiation therapy, and patient's own ability to adapt to the prosthesis. For patients who receive a unilateral maxillectomy, saving as many of the remaining teeth as possible could be critically important for successful prosthesis design and function.[5] Remaining structures are subjected to continuous stresses from such large, heavy obturator, jeopardizing the health of the tissues, and compromising patient function and comfort. To reduce the weight of the prosthesis, the bulb portion of the obturator is generally hollowed after it has been processed into acrylic resin. A hollow maxillary obturator may reduce the weight of the prosthesis by up to 33%, depending on the size of the maxillary defect.

The use of magnets has been popular in dentistry.[6] In maxillofacial prosthodontics,[7] they have been used for decades to reconstruct large defects with the help of multiple component prostheses. Javid,[8] in 1971, constructed an extensive prosthesis for both extraoral and intraoral aspects connected with magnets. Hence, mutually attractive forces of paired magnets were used as retentive aid for sectional dentures, maxillofacial prostheses, obturators, and complete dentures. One of the earliest magnets is paired Alnico. It is a permanent magnet alloy of iron, cobalt, nickel, and aluminum.

In the late 1960s, another permanent magnet in which cobalt was alloyed with samarium (Co5 Sm) was introduced. This has twice the magnetic field strength of Co-Pt and the strongest of the Alnico alloys. Another alloy based on neodymium-iron-boron (Nd-Fe-B) became available in the 1980s for dental applications. Both Co5 Sm and Nd-Fe-B[9] are termed as rare earth (RE) magnets because they are rare from the standpoint of extraction. Both are excellent for dental applications because of their small size and relatively high retentive capacity.[10] However, they are brittle and have low corrosion resistance. In spite of encapsulating them in stainless steel, titanium, or palladium, if these coating materials wear out, they cause deleterious effects on the tissues and this may be increased in the presence of bacteria such as Streptococcus sanguinis.

A magnet has poor corrosion resistance in the oral fluids, especially the uncoated ones. Both the RE magnets are brittle and are susceptible to corrosion. They corrode rapidly in saliva and the presence of bacteria enhances corrosion of Nd-Fe-B magnets. These corrosive products have been found to have cytotoxic effects on the tissues. Hence, they should be encapsulated before placement in the oral cavity. Stainless steel and titanium have been the most commonly used materials but polymeric materials also have been used. However, continuous wearing of these coating materials leads to the exposure of the magnets. It was found by Gillings[11] that a metal of 0.0015” thick wore through after about only six months. The pitting corrosion of stainless steel also occurs in the oral environment. To overcome these problems, other coating materials such as titanium and chromium nitrides have been used to prevent wear. The pole pieces used currently are 0.25 mm thick and have a life span of about at least 10 years before perforation.

Angelini et al[12] in 1991, the electrochemical properties, corrosion tendencies and reactivity of Co2Sm and Ne-Fe-B magnet to oral environment revealed the necessity to improve surface coating. Drago[13] in 1991 reported that the edges of all magnetic implants used in various clinical prosthodontic procedures showed evidence of tarnish and somewhat corroded, thus significantly affecting the useful lifespan of intraoral magnets.

In a detailed study, Kitsugi et al.[14] in 1992 concluded that although the corrosive activity of the Nd-Fe-B magnet was higher than that of Co5 Sm magnet, it was necessary to seal both the magnets for dental use.

Riley et al.[15] suggest that the magnets have to be encapsulated in any of the materials mentioned earlier. They observed that if the coating wears out, the magnet would come in contact with saliva, which can corrode the magnet. Corrosion rate can increase in the presence of bacteria like S. sanguinis. Thus, life span of the magnet may decrease. Furthermore, coated magnets have been found to produce no effect on human dental pulp, gingival or osteoblasts or blood flow. Only uncoated magnet has cytotoxic effects on the cells. Oral mucosal fibroblasts are most sensitive to effects of these RE magnets.

Although magnets are potentially very helpful, there are a number of problems that severely affect their performance. One of the common problems is dramatic reduction in force if magnets are not ideally aligned to one another. In addition, Haoka et al.[16] suggested that magnets corrode badly in the mouth and a robust coating is required to protect them. Overall magnetic force system is a total force system with a favorable benefit to risk ratio.

The insertion and removal of an obturator in large maxillary defects with or without trismus are difficult. Obturator is fabricated in two pieces, which are approximated together by various techniques, namely, silicone cover, embedded magnets, and press studs.[17] This article describes rehabilitation of large maxillary defects with two pieces (a maxillary plate and a bulb component) and are approximated by magnets. Prosthetic rehabilitation of large maxillary defects with two-piece obturators offers the possibility of adequate oral rehabilitation by fabricating light weight prosthesis, which is easy to use. The bulb extends to the undercut areas of the defect enhancing the facial contour and retention. It facilitates easy examination of underlying tissues, recreation of the anatomic barrier between the oral and nasal cavities, and restoration of the function and esthetics. Thus, it adds to the quality of life.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.