Maxillofacial Prosthetics: History to Modern Applications. Part 1 – Obturators
The role of the maxillofacial prosthodontist in the treatment of head and neck cancer patients is not well understood in the medical community. Frequently, dental professionals are called upon by physicians to provide advice regarding the complex needs of head and neck cancer patients. Most general dentists have had limited training in this area. The general dentist has the opportunity to provide the bridge between the physician and the maxillofacial prosthodontist, who can provide treatment information to both the general dentist and the physician. A better understanding of maxillofacial prosthodontics can clarify which patients should be referred to a maxillofacial prosthodontist for treatment.
Maxillofacial prosthetics is the branch of prosthodontics concerned with the restoration and/or replacement of the stomatognathic and craniofacial structures with prostheses that may or may not be removed on a regular or elective basis.1 Within maxillofacial prosthetics there are basically four broad areas of focus: 1) obturators; 2) speech and/or swallow prostheses; 3) mandibular resection prostheses; and 4) extraoral facial prostheses. Detailed historical reviews of obturator prostheses are available elsewhere.2,3 The aim of this article is to highlight milestones leading to the modern-day obturator prostheses. A discussion of conventional therapeutic processes will provide insight into the role of the general dentist in management of these challenging patients.
Maxillary defects can be congenital, the result of trauma, or the postoperative condition following surgical resection of a maxillary tumor. Regardless of the etiology, the clinical problems that must be overcome are identical. Because maxillectomy patients are missing a portion of the hard palate, speech is hypernasal, and swallow results in nasal regurgitation (food or fluid out of the nose). If the soft palate is involved, fluid or a food bolus cannot be properly propelled into the esophagus, swallow is difficult if not impossible, and speech is hypernasal.
Brief History of Obturators
Although the origin of the first maxillofacial prosthesis is uncertain, it is widely accepted that attempts to replace missing structures date to ancient times. According to Saul Bein,4 Demosthenes the Greek orator may have used pebbles to obturate a congenital cleft lip and palate. During the late 16th century, Ambrose Pare′5 is credited as the first to refer to “obturateurs” derived from the Latin word “obturo,” which means “stop up” (Figure 1). Over the centuries numerous examples of ingenious prostheses have appeared. A palatal obturator described by Pierre Fauchard6 in the early to mid 18th century was inserted into the palatal defect. Next, a pair of mechanical wings were made to contact the superior surface of the palate through a turnkey mechanism operated by the patient (Figure 2). It was not until the late 18th century that Delabarre7 used (clasps) similar to those found on modern removable partial dentures to retain an obturator (Figure 3). Between 1888 and 1903, Martin8 described an obturator that incorporated a rubber balloon-like bladder attached to the superior surface of the obturator. When inflated with water, the bladder engaged the maxillary defect and retained the prosthesis. During the 19th century, Alcock3 was the first to use a cast metal palate in an obturator. Prior to Alcock’s innovation, metallic reinforcement used in obturators originated from sheet metal cut and worked into usable shapes. Near the end of the 19th century vulcanite was widely accepted for use in maxillofacial prosthetics. In 1893, President Grover Cleveland was restored with a vulcanite obturator to close a defect resulting from surgical resection of a malignant maxillary tumor.9
Polymethyl methacrylate (PMMA) was first used as a denture base material in 1936 with the introduction of Veronite.10 One of the earliest references to the use of acrylic in the fabrication of maxillofacial prostheses appears in 1947. Lloyd11 suggested that methyl methacrylate has the advantages of light weight and adaptability through processing. For more than 80 years, methyl methacrylate has remained the dominant material for fabricating most removable dental prostheses, including maxillary obturators.
Currently, a patient diagnosed with oral cancer and treated with a maxillary resection will be provided with a surgical obturator fabricated prior to surgery or shortly thereafter. This obturator typically is made of one of the materials currently used for denture base fabrication on a cast generated using current impression techniques. The surgical defect will change drastically during the first weeks to months following surgery and require frequent modification. The surgical obturator is replaced with an intermediate obturator at such time when the most drastic changes have occurred and it is no longer practical to modify the initial obturator. The intermediate obturator will allow the patient to function during the prolonged healing period, which may continue for a number of months depending on the individual patient. When modifications to the intermediate obturator become less frequent and less extensive a definitive obturator will be fabricated. The time from surgical obturator to definitive obturator can easily span one year. The patient will continue to be seen for follow-up to monitor for recurrence of disease and to assess the fit of the definitive prosthesis.
On the Horizon
Making an accurate impression of a large defect, particularly one that extends to include the orbit, continues to challenge the profession. The defect can be so complex and extensive that sectional impression techniques are necessary. A multi-piece impression tray permits the completed impression to be dismantled and removed from the oral cavity and defect in separate sections. The impression may then be reassembled in the dental laboratory using paired magnets or a key and keyway indexing system, prior to casting.
Modern technology may provide better solutions for replicating extensive maxillary defects during prosthesis fabrication. Computerized tomography/magnetic resonance (CT/MRI) imaging techniques hold promise for providing a method of generating 3-dimensional computer models.12,13 Computer-aided design and computer-aided manufacturing (CAD/CAM) methods can then be used to fabricate the definitive prosthesis using one of the many currently available rapid manufacturing (RM) processes.14,15 The goal is to fabricate a more accurate prosthesis in less time. As an added advantage, since the information is contained in an STL file, the prosthesis can be modified, as tissue changes occur without necessarily remaking an impression.
Role of the General Dentist
Tang16 discussed the role of general dentists in maxillofacial prosthetics, stating that they face three questions: 1) what part does the general dentist play in diagnosis; 2) to whom does the general dentist refer the maxillofacial patient; and 3) what is the role of the general dentist in the treatment of maxillofacial patients?
Many oral cancers are detected by the general dentist. According to the American Cancer Society,17 an estimated 40,250 new cases of oral and pharyngeal cancer were expected in 2012. Incidence rates for this type of cancer have decreased since 1992 by about 1% annually. Unfortunately, according to this report, recent studies have shown that incidence is increasing for oral cancer associated with human papilloma virus (HPV). Early detection is critical. The 5-year survival rate for early detection is 75% compared to 20% for late detection.18
Restoration of extensive defects of the oral cavity is certainly within the purview of trained maxillofacial prosthodontists. In this instance, the role of the general dentist is one of partnering with the specialist in providing appropriate care. While the fabrication of the prosthesis may be accomplished by the maxillofacial specialist, the general dentist may opt to provide supportive therapy and follow-up care. In this case, it is advisable for the general dentist to view the maxillofacial prosthodontist as a resource for information regarding the unique considerations in appropriate patient management.
As Tang16 points out, not all maxillofacial defects are extensive. A small defect of the hard palate or perhaps even at the junction of the hard and soft palate may require a slight modification of what would be a conventional removable partial denture. Care must however be taken to avoid the inadvertent intrusion of impression material into the maxillary sinus. Here again, the maxillofacial specialist is a resource for information.
Given the dramatic difference in 5-year survival rates between early and late detection, it is incumbent on the dental profession to be on heightened alert for early detection and appropriate management of oral cancer. As discussed here, the dental profession has always played an integral role in the treatment of oral cancer. Over the centuries, knowledgeable dentists have devised ingenious prosthetic devices to restore form and function lost due to maxillofacial defects. The profession will continue to devise new techniques and incorporate superior materials to improve outcomes for maxillofacial patients.
ABOUT THE AUTHOR
Gregory J. Paprocki, DDS
Course Director, Staff Instructor, University of Tennessee, College of Dentistry, Memphis, Tennessee
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Read Part 2 of this series, "Maxillofacial Prosthetics: History to Modern Applications. Part 2 – Speech and Swallow Prostheses"