Overview of Oral and Facial Restoration and Rehabilitation
Rehabilitation is an essential phase of cancer care and should be considered from the time of diagnosis in a complete and comprehensive treatment plan. Surgical resections often create large defects accompanied by dysfunction and disfigurement, and radiation therapy produces significant morbidity and unique tissue-management problems. Speech, swallowing, control of saliva, and mastication can all be adversely affected. If these cosmetic and functional impairments are not corrected or minimized, the patient may be unable to resume a normal working and social life.
The primary objective of rehabilitation is the restoration of appearance and function. How successfully this is accomplished, depends upon both the judgment and skill of the therapist, and the post-treatment anatomic, physiologic, and psychological makeup of the patient.
Rehabilitation of the head and neck cancer patient requires a team approach, which includes many specialists. In addition to the surgeon, the dental oncologist and the prosthetic doctor, there are many other individuals involved as part of the restorative team. The clinical social worker sees the patient at the time of diagnosis, during primary cancer treatment, and during the long period of rehabilitation, to the help patient understand the process of treatment and to mobilize resources to cope with the situation. Nurses can provide support and comfort for the patient, give instruction on the care of the surgical defect or tracheostomy, and arrange for visiting nurse support when the patient returns home. As there may be conditions which alter eating habits, or skills, dietitians advise patients on obtaining proper nutrition. Occupational and physical therapists help retrain altered muscular systems, and the speech pathologist can help patients to adapt speech mechanisms to prosthetic appliances, and altered physiology. Dental hygienists provide prophylaxis and oral-health-care instruction.
Most tumors of the paranasal sinus, palatal epithelium, or minor salivary glands require surgical removal of a portion of the upper jaw, This is either a partial or total maxillectomy. A radical maxillectomy entails surgical resection of the entire maxilla to the midline. This is accomplished by an insicion through the cheek and the upper lip, allowing the tissue to be folded (reflected) back for access to the maxilla. A partial maxillectomy is less encompassing, and may be performed without the reflection of these external tissues (transorally). The amount of soft palate included in these resections varies, and depends on the need to obtain tumor-free margins (edges of the incision).
Defects created by surgery to remove cancerous tissues of the hard or soft palate may produce a variety of problems. For instance, hypernasality could make speech unintelligible. Chewing (mastication) may be difficult, particularly for the patient without natural teeth (edentulous patient). Because denture-bearing tissue surfaces are lost, it is difficult for the denture to seal completely around the edges, a key factor in holding it securely in place. Swallowing likely will become awkward, since food and liquid may be forced up into the nasal cavity and out the nose. The nasal mucous membranes become dried out (desiccated) by abnormal exposure to the oral environment, causing chronic irritation. Nasal and sinus secretions may collect in the defect area. Facial disfigurement can result from lack of midface bony support for the facial soft tissues, or the necessary surgical damage to a branch of the facial nerve. In some cases, extensive tumor invasion requires surgical removal of the eye.
Rehabilitation after surgical resection of the hard or soft palate is best accomplished prosthodontically. Customarily, a temporary prosthesis, known as an immediate surgical obturator, is placed at the time of surgery. This will provide closure of the surgical defect. During the healing period, this prosthesis is recontoured (relined) periodically to compensate for tissue changes which occur as a normal part of the healing process. When these tissues become well healed and dimensionally stable (usually 3 to 4 months after surgery), the final prosthesis is made.
The purpose of an obturator prostheses is to restore the physical separation between the oral and nasal cavities, thereby restoring speech and swallowing to normal, and to provide support to the lip and cheek. Inadequate retention of the obturator compromises stability. The remaining teeth, therefore, become extremely valuable in providing support, retention, and stability for these restorations.
It is essential that the prosthodontist examine and consult with the patient before surgery. The sequence of treatment should be explained to the patient, and diagnostic casts and appropriate radiographs should be obtained. With this information, the prosthodontist is ready to consult with the surgeon about the design and fabrication of the surgical obturator. Modifications in the surgical plan that may improve the prosthetic prognosis without adversely affecting tumor removal should be discussed at this time. Surgical considerations to improve the prosthetic outcome
The immediate surgical obturator
Immediate or early coverage of a palatal defect with an obturator is important. The obturator provides a matrix upon which the surgical packing can be placed, minimizes contamination of the wound in the immediate postoperative period, and enables the patient to speak and swallow effectively immediately after surgery.
In order to fabricate the prostheses, a stone model is made of the maxillary arch and the anterior portion of the soft palate. The obturator’s size is determined by the surgical boundaries of the resection, as indicated by the surgeon. In the patient who still has natural teeth, those in the path of the surgical resection are removed from the model. The obturator can now be made before the surgery, using self-curing plastics, and be ready for immediate insertion afterwards. If necessary, this first obturator can be altered at surgery by trimming it’s size, or by adding a temporary denture reline material. After surgery the prosthesis is wired to remaining teeth, alveolar ridge, or other available structures.
After the surgical packing is removed the prosthesis is recontoured with a temporary denture reline material. As healing progresses, the obturator is periodically relined and extended further into the defect, adaptation is improved, and anterior teeth are added as necessary to improve speech and esthetics. Three to five months after surgery, when healing and the related tissue changes are essentially complete, the final prosthesis is begun. Patients without natural teeth (edentulous) to use as fixation points for the obturator, often require a longer period of healing because the defect must be engaged more aggressively to maximize stability, support, and retention.
The definitive obturator prosthesis
Defects of the hard palate can be restored effectively with a denture prosthesis. Natural teeth greatly improve denture retention and stability of a maxillary prosthesis. When the denture is properly extended, speech, swallowing, mastication, and facial contour restoration can be accomplished. In it’s final contour, the obturator should extend maximally along the lateral wall of the defect. This high lateral extension not only increases retention and lateral stability, but also provides support for the lip and cheek. In some patients, extensions across the nasal aperture may be necessary to provide acceptable retention.
The placement of osseointegrated implants (More on dental implants) into the remaining bony structures, dramatically improves the function of an obturator prosthesis, particularly for edentulous patients. Implants can be placed, either during the surgical procedure to remove the malignant tissues, or at some appropriate time thereafter. These implants will allow mechanical attachment of the denture prosthesis to them, adding significant stability. For instance, implants may be splinted together with a bar in the mouth that mates to female snaps in the base of the denture, allowing the denture to be “clipped” in and out of the mouth. In patients with some remaining natural teeth, implants may still be used to augment the retention provided by these teeth. When the prosthesis is inserted and attached to the fixed implants, speech and swallowing are restored to normal limits. The tissue side of most prostheses require relining/recontouring within the first year because of slow, but continuous changes of the tissues on the periphery of the surgical defect.
The definitive soft palate prosthesis
Defects of the soft palate and velopharyngeal complex require different and more complex prosthetic treatment. Closure normally occurs when the soft palate comes into contact with the contracting lateral and posterior walls of the nasopharynx. When a portion of the soft palate or lateral pharyngeal wall is surgically removed, or when the soft palate is perforated, scarred, or neurologically impaired, complete closure cannot occur. Speech becomes hypernasal, and nominal swallowing is not possible. With a pharyngeal obturator, the patient may be able to re-establish this closing. A properly designed obturator will not interfere with breathing, impinge upon soft tissues during postural movements, or hamper the tongue during swallowing and speech.
The soft palate obturator remains in a fixed position in the nasopharynx and does not attempt to duplicate normal movements of the soft palate. The tissue side of the obturator remains level with the hard palate contour. During breathing and the production of nasal speech sounds, the space around the obturator reflects the potential for muscular contraction. During swallowing and the production of other speech sounds, this muscular network moves into contact with the stationary plastic obturator, establishing closure. A correctly constructed obturator will usually result in the return of normal speech and swallowing.
Disabilities resulting from tongue and mandibular resections include impaired speech articulation, difficulty swallowing, deviation of the mandible during functional movements, poor control of salivary secretions, and often cosmetic disfigurement. Consequently, these patients seldom return to presurgical levels of social function.
Advanced tumors of the anterior two thirds of the tongue and floor of the mouth often require extensive resection of bone and soft tissue. The loss of large portions of the tongue prevents appropriate “valving” and/or interaction with the other oral structures. This loss of mobility combined with the loss of motor and sensory innervation leads to misarticulation of many speech sounds. Deglutition is less impaired, and most patients learn to swallow fairly efficiently. Tongue function is less affected if the resected portion is restored with either myocutaneous or free flaps. The myocutaneous flap restores bulk, prevents deviation of the mandible, and permits the reconstructed tongue to articulate more effectively with the palatal structures. Myocutaneous flaps, however, can become scarred and immobile. In contrast, tongues reconstructed with free flaps have the potential of supporting near normal speech and are less likely to become heavily scarred and immobile.
If much of the mandible is segmented and removed, the remaining functional mandibular segment will be retruded and deviated towards the surgical side at the vertical dimension of rest. When the jaw is opened this deviation increases. These factors, combined with impaired tongue function, may prevent effective mastication. The severity and permanence of mandibular deviation varies; some patients attend an acceptable intocclusal relationship without adjunctive therapy.
Resections of the tongue and mandible often obliterate portions of the lingual and buccal sulci so that a means of collecting and channeling secretions posteriorly no longer exists. In addition, the motor and sensory innervation of the lower lip on the resected side is often lost, impairing speech, eating, and control of saliva.
When removal of tumors in the anterior floor of the mouth requires that the mandible be resected anteriorly, and when mandibular continuity is not restored, the two remaining posterior fragments are pulled medially by the residual mylohoid muscles and superiorly by the muscles of mastication. Severe disfigurement and dysfunction result. Free flaps from the fibula can be used immediately to restore the lost hard and soft tissues, and most patients emerge with excellent function and acceptable appearance.
The nature and degree of the disabilities secondary to impaired tongue function after resection of lesions in the anterior floor of the mouth are proportional to the amount of tissue resected and to the nature of surgical closure. In most cases, motor control is unimpaired and the functional deficits depend on the degree of tongue mobility.
Surgical Closure And Initial Reconstructive Steps
If the surgical wound is closed primarily (primary closure) by suturing the edges of the wound together, the functional disabilities are compounded. The introduction of the myocutaneous flap in the late 1970s ameliorated some of the disabilities, and improved tongue mobility resulted in acceptable speech, swallowing and saliva control. The advantage of free-tissue transfers (free flaps) over musculocutaneous flaps is the improved blood supply, enhancing wound healing and flap survival. The fibula is the preferred donor site unless the soft-tissue deficit is unusually large. The osteotomized fibula provides sufficient length and bulk and bone. Osseointegrated implants can be placed to retain and support prosthesis.
Secondary Surgical Procedures
Vestibuloplasty, Tongue Release, and Skin Grafts
Vestibuloplasty and tongue release are of particular value when mandibular continuity has been maintained or restored. The creation of vestibules enables the patient to pool saliva more efficiently and allows for extension of denture flanges resulting in improved stability and retention . Creation of an attached keratinized mucosa on the ridge surface with either a skin graft or a palatal graft provides additional stability for a partial or complete denture. The patient’s appearance may also be improved because a prosthodontic restoration can now be molded to provide contour and support for the lower lip and cheek portions of the resected area. Improvement of speech is less noticeable in patients who lack tongue mobility.
Restoration of Mandibular Continuity
Surgically repairing mandibular discontinuity defects results in more normal mandibular movement patterns that enable an edentulous patient to exert force on both sides of the dental arch. This increases the stability of complete dentures. In dentulous patients a properly reconstructed mandible restores dental occlusion to normal and will partially alleviate deviation of the mandible.Free bone grafts. Reconstruction after extensive resection of oral malignancies with free grafts is difficult because of the lack of sufficient soft tissue to receive the graft, the decreased vascularity of the tissue bed secondary to radiation therapy and/or radical neck dissection, and the difficulty in achieving proper fixation of the graft during the healing period. The primary goals are to restore facial form, mandibular continuity and, in selected patients, appropriate volume and quality of bone should be provided for the placement of osseointegrated implants.
Autogenous graft sources for resected bone include iliac crest, rib, and clavicle. Most commonly the defects are restored either with particulate autogenous marrow housed in metal tray or with a block bone, both usually obtained from the iliac crest. The use of myocutaneous flaps for closure of the initial wound facilitates free-bone grafting of continuity defects by enhancing the volume and vascularity of the recipient soft tissue.
Free vascularized flaps. A major advance in mandibular reconstruction has been the development of improved techniques in microvascular surgery, which allow for composite grafting of large volumes of tissue. In microvascular surgery, which allow for composite grafting of large volumes of tissue. In microvascular free-tissue transfer (free flaps), bone, muscle, connective tissue, and skin can be autogenously grafted and remain viable. The grafting can be accomplished simultaneously with resection of the tumor, with excellent results.
Numerous donor sites have been used. The radial forearm is favored for reconstruction of most extensive soft-tissue defects such as the tonsillar, partial-glossectomy, and floor-of-mouth defects. The composite fibula flap is the preffered donor site for most complex oro-facial-mandibular defects. Multiple osteotomies may be performed without devascularizing the bone segments to replicate the contour of the replaced mandible. Fibular thickness makes it an excellent recipient of osseointegrated implants.
Physiology Of Oral Function Following Tongue And Mandible Resection And Reconstruction
Even following successful reconstruction, functional deficits (deglutition, speech articulation, mastication efficiency) remain because of compromised motor and sensory control, inadequate tissue contour, and inadequate bulk of key tissues. Mastication efficiency is primarily dependent upon the quality of tongue function and the presence of a reasonable occlusal table adjacent to the sensate, functioning portion of the residual or reconstructed tongue. Articulation of speech is dependent upon tongue mobility and the presence of adequate tongue bulk. Patients with hemiglossectomy defects can learn to articulate and swallow effectively, if they can elevate their reconstructed tongue to interact with the palatal vault and maxillary dentition. More on dysphagia, speech, and eating issues.
Palatal Speech and Swallowing Aids
If the reconstructed tongue does not possess the ability to elevate sufficiently to interact with the palatal structures, an acrylic resin template is made to engage the palatal contours and/or maxillary dentition. Their surfaces can be modified with modeling plastic or tissue-conditioning material and eventually processed into acrylic resin.
Surgical Reconstruction of the Total Glossectomy Defects
With the development of free flaps, there has been an increased success in surgically reconstructing the tongue in total glossectomy patients. When these flaps are used, bulk should be limited, allowing room for total restoration of the mandibular dentition with a prosthesis. Palatal speech and swallowing aids may be quite useful in selected patients.
Mandibular Guidance Therapy
When mandibular continuity is not restored, correction of mandibular deviation includes inter-maxillary fixation, and mandibularly based or palatally based guidance restorations. The method of choice should be combined with well-organized mandibular exercise program.
Mandibular guidance therapy begins when the immediate postsurgical sequelae have subsided, usually in 2 to 3 weeks. Upon maximum opening, the mandible is displaced by hand as forcefully as possible towards the nonsurgical side. These movements tend to lessen scar contracture, reduce trismus, and improve maxillomandibular relationships. The earlier mandibular guidance therapy is initiated, the more successful the result. Unfortunately, those patients suffering the most severe mandibular deviations (because of extensive soft-tissue loss, tight wound closure, radiation therapy, and/or radical neck dissection) are most susceptible to postsurgical complications that delay mandibular guidance therapy.
If the mandible can be manipulated into an acceptable maxillomandibular relationship, but the patient lacks the neuromuscular control to bring the mandible into occlusion, a cast mandibular resection prosthesis is appropriate. This prosthesis consists of a removal partial denture framework with a metal flange extending 7 to 10 mm laterally and superiorly on the buccal aspect of the bicuspids and molars on the unresected side. This flange engages the maxillary teeth during mandibular closure, thereby directing the mandible into an appropriate intercuspal position. The partial denture framework must be stable and retentive to counteract the lateral forces generated on the flange during closure. The guidance flange is constructed of cast chrome-cobalt metal. Modifications can be made with acrylic resin.
A second design confines the guidance ramp and index to a maxillary prosthesis. This form of guidance prosthesis is indicated when severe deviation prevents manipulation of the mandible into acceptable occlusal contact. Maxillary guidance ramps are more adjustable than mandibular guidance ramps. They are usually constructed of acrylic resin with either cast or wrought-wire retainers, since they usually serve only temporarily until an acceptable occlusion can be established.
The success of mandibular guidance therapy depends on the nature of the surgical defect, early initiation, and cooperation of the patient. Patients with extensive posterior base of tongue lesions, radical neck dissection, and radiation therapy are often unable to achieve functional intercuspal relationships. Mandibular guidance therapy is most successful when the resection involves minimal soft-tissue removal, or when defects are replaced with myocutaneous or fee flaps. Following mandibular guidance therapy, occlusal equilibration or selective crown placement may be required to achieve optimal interocclusal relationships.
Definitive Prosthetic Restoration
The outcome of removable prostheses for patients with resections of the tongue and mandible depends upon the function of the residual tongue. In some patients with poor tongue function, only appearance and oral competence can be improved, while in others with good tongue function, mastication is a reasonable objective.
Removable Partial Dentures
The usual principles of partial denture design and fabrication should be followed. Major connectors should be rigid; occlusal rests must be direct occlusal forces along the long axis of teeth; guiding planes should be employed to provide stability and bracing; retention must be within the limits of physiologic tolerance of the periodontal ligament of the abutment teeth; and maximum support should be gained from adjacent soft tissues. Retainers, minor connectors, and proximal plates should be designed so that they do not subject the remaining teeth to excessive lateral forces during function.
In patients with lateral discontinuity defects, it may not be possible to design a framework with retainers that disengage during function because of the altered patterns of force upon the prosthesis. Viewed from the frontal plane, the arc of closure of the mandible is angular rather than vertical, with forces of occlusion as the force of contracture on the unresected side is increased. The location of the fulcrum line of a partial denture is not easily determined because of the difficulty in predicting movement patterns of the prosthesis during function. The forces of occlusion are unilateral, so the axis of rotation (fulcrum line) of the partial denture deviates from the norm. By placing the occlusal rest on the mesial of the bicuspid that disengages during expression of an occlusal load in the distal extension area. However, a retainer can not be positioned in a retentive area on the opposite cuspid that disengages during occlusal function. Consequently, this retainer must either be placed on the height of contour, or it must be flexible so that an occlusal load will not subject the cupid to undue stress. All partial denture frameworks should be phsysiologically relieved.
After the partial denture casting has been fabricated, verified, and adjusted, an altered cast impression is obtained of the edentulous areas. Particular attention should be paid to the lingual extension on the unresected side, especially the polished surfaces, which provides additional retention and stability. Maximum extension of the denture base is always attempted. Coverage of the buccal shelf on the unresected side is essential to maximize support. Centric relation records are made and occlusal schemes developed that are consistent with the unilateral mandibular movement patterns of mandibulectomy patients.
Dentures for edentulous patients with discontinuity defects of the mandible may provide esthetic improvement by replacing teeth and improving lip and cheek contours, but unless the patient has extraordinary tongue control, mastication is generally not possible. A number of factors affect the patient’s ability to function with resection dentures (1) stability, support, and retention of the mandibular denture are compromised; (2) quality and quantity of saliva; (3) the angular pathway of mandibular closure, which induces lateral forces upon dentures, tending to dislodge them; (4) abnormal maxillomandibular relationships that may prevent ideal placement of the denture teeth over their supporting structures; and (5) impairment of motor and/or sensory control of the tongue, lip, and cheek, limiting the ability to control dentures during function. Implant-assisted resection dentures can overcome many of these difficulties, particularly those associated with compromised retention, stability, or support.
The status of the remaining tongue is probably the most important prognostic factor. If motor and/or sensory control are not significantly impaired, and the tongue can be moved in several directions, resection denture stabilization and control of the food bolus during function become possible. Paradoxically, immobility of the tongue often permits a more aggressive extension of the lingual flange on the nonsurgical side, aiding stability and retention. The position of the tongue is also an important prosthodontic prognosticator relative to obtaining a peripheral seal.
Mandibular resections extending to the midline have a poor prosthetic prognosis. If the resection is limited to the ramus-molar or cuspid regions anteriorly, the prosthetic prognosis is more favorable. In some of these patients remmants of the masseter or medial pterygoid muscle may remain attatched to the mandible, enabling the development of bilaterally balanced occlusion. These patients demonstrate more-normal envelopes of motion, and near-normal ridge relationships, allowing for more favorable distribution of forces during mastication and swallowing.
Following impressions, centric and lateral registrations and occlusal schemes should take into consideration the altered pattern of mandibular movements. Denture extensions can be verified with a disclosing wax, and excessive tissue displacement eliminated with the aid of pressure indicating paste.
Implant-Assisted Overlay Dentures
Patients with reasonable tongue bulk and mobility and with motor and sensory innervation intact on at least one side gain the most from implant-retained overlay prostheses. The tongue, then, is no longer required to control the denture, so it functions mainly to manipulate the food bolus during mastication and swallowing. If the patient’s speech is intelligible, the prognosis for effective bolus manipulation with an implant-retained prosthesis is good. More on the placement of dental implants in radiated patients.
In mandibular resection patients, if implants are to be placed into the mandible to retain and support an overlay prosthesis, consideration should be given to placing implants in the opposing maxilla. The unilateral occlusal forces and increased lateral forces generated during the chewing cycle tend to dislodge the upper denture. In addition, xerostomia may compromise the peripheral seal. Therefore, implants should be considered if the retention and stability of a conventional maxillary denture is marginal.
In most patients, the only implant sites available in the edentulous resected mandible are located in the symphyseal region. A minimum of two implants should be placed. However, more are desirable, if space allows, mainly for stability.
Implant success rates in bone grafts used to restore mandibular continuity defects have been encouraging. Free bone grafts demonstrate a homogenous calcification pattern that results in an excellent bone-implant interface, particularly with fibula free flaps. To date, of the 54 implants that have been placed at the University of California, Los Angeles, (UCLA) in fibula free flaps, 46 are in function; 2 have been buried because of improper positioning or angulation; 3 have failed; and 3 have not yet been placed into function. More on the surgical placement of dental implants, and their prosthetic restoration.
Surgical reconstruction and prosthodontic restoration both have limitations. The surgeon is limited by the availability of tissue, damage to the local vascular bed, and the need for periodic visual inspection of an oncologic defect. The prosthodontist is limited by the materials available for facial restoration, movable tissue beds, difficulties in retaining large prostheses, and a patient’s willingness to accept the result. The method of facial restoration should be considered before surgery and patients should participate in the decision making process with realistic expectations.
Surgical Reconstruction Versus Prosthetic Restoration
Surgical reconstruction of small facial defects is preferable. However, it is difficult for the surgeon to contour a facial component that is as effective in appearance as a well-made prosthesis. Osseointegrated implants in facial defects have changed patient perceptions about facial prostheses because of the retention achieved. Additionally, when a large resection is necessary and recurrence of tumor is realistic, it is advantageous to be able to monitor the surgical site closely, which a prosthesis permits. Even when surgical reconstruction is deemed possible, most surgeons prefer to wait at least one year before surgical construction. Also, surgical restoration of large defects is technically difficult and requires multiple procedures and hospitalizations, which may be further complicated if radiotherapy has been included.
Prosthetic Facial Restoration
The challenge to the prosthodontist is to fabricate an esthetically pleasing restoration. A conspicuous prosthesis may produce more anxiety and permit less social readjustment than a simple face bandage or eye patch. The most critical periods is the first 2 to 3 days after delivery. The patient must understand that a prosthesis has two different roles: for family, close friends, or business associates, it can only cosmetically replace the tissues excised; for the public at large, it generally provides enough concealment to render the reconstructed defect inconspicuous.
Materials Used for Facial Prostheses
Current materials all possess some undesirable characteristics. The materials most often used are the new silicone elastomers, which have achieved wide clinical acceptance. Adhesives are used to retain facial restorations. A major development has been the use of osseointegrated implants, resulting in extremely well-retained prostheses that permit vigorous physical activities.
A presurgical moulage can be very helpful, especially if a total rhinectomy or total auriculectomy is anticipated. Impressions of the defect are usually obtained with elastic impression materials, taking care not to displace the tissues being recorded. The contours of the prostheses are sculptured in wax, both on the cast and on the patient. Surface characteristics, appropriate contour, coloration, and margin placement are equally important factors. Processing the materials is complicated and requires special instrumentation. Special flasks are necessary for processing large prostheses.
Basic skin tones should be developed into a shade guide for each material. The base shade selected should be slightly lighter than the lightest skin tones of the patient, because as color is added the prosthesis will darken. Intrinsic coloration is long-lasting and is therefore preferred over trinsic application.
Combined Oral and Facial Defects
When the integrity of the oral cavity has been destroyed, food and air escape during swallowing; speech is often unintelligible; and saliva control is difficult. Additionally, it is extremely hard to adapt the margins of the prosthesis to maintain tissue contact during facial and mandibular movements. Retention of maxillary teeth or a portion of the hard palate improves the prosthetic prognosis. Placement of implants, as well as skin grafts to decrease tissue contraction and to create undercut areas for retention, also improve the prosthetic prognosis.
Patients will experience less depression if as many functions as possible are restored immediately after surgery with a temporary prosthesis. These functions include swallowing food (thereby eliminating the need for a nasogastric tube or gastrostomy), controlling saliva, and speaking. The oral portion of the temporary prosthesis is constructed of acrylic resin and formed so that contact is established with healthy tissues adjacent to the defect. Functional contact with the remaining portions of the lips allows the patient to effectively seal the oral cavity. Tissue-bearing surfaces of the prosthesis are relined with temporary denture reliner at frequent intervals to accommodate tissue changes.
In constructing a definitive midface prosthesis, a custom tray is used for the master impression. Movable portions of the defect are recorded with a thermoplastic material. Record bases are fabricated, and centric relation records enable casts to be mounted on an articulator. Osseointegrated implants, eyeglass frames, adhesives, straps, teeth, and engagement of defect undercuts supply retention. The finished restoration usually provides the patient with acceptable appearance and function.
The use of osseointegrated implants has significantly improved patient acceptance. The retention provided by implants makes it possible to fabricate large prostheses that rest on movable tissues. This enables the prosthodontist to fabricate thinner margins, which enhance esthetics by blending and moving more effectively with mobile tissues. Other benefits include elimination of the occasional skin reactions to skin adhesives, ease and enhanced accuracy of prosthesis placement improved patient comfort, and decreased daily maintenance, which also increases the life span of the facial prosthesis.
The implants must be positioned within the confines of the proposed facial prosthesis. In most patients it is desirable to sculpt a wax replica of the future prosthesis and to use this replica to fabricate a surgical template. This template is sterilized and used as a guide during surgery to ensure proper implant position and angulation.
The number and arrangement of implants and possible bone sites are determined. In most acquired defects, radiographic studies are not necessary. In large extensive defects, CT scans and three-dimensional models may be useful in evaluating potential bone sites and important adjacent structures. The health of soft tissues circumscribing osseointegrated implants is easier to maintain if these tissues are thin (less than 5mm in thickness) and attached to underlying periosteum. If the skin contains hair follicles or scar tissue from past reconstructive procedures, these tissues should be removed and placed with skin grafts.
Craniofacial implant fixtures are fabricated from pure titanium. They are available either 3 or 4-mm lengths, with a 5-mm diameter flange. The short lengths are designed to permit placement in areas with limited available bone. The flange facilitates initial stabilization of the implant and prevents penetration into interior components.
For ear defects, two or three implants are positioned posteriorly and superiorly to the ear canal. For nasal defects, the preferred fixture location is the anterior portion of the floor of the nose. Care should be taken to avoid the roots of the teeth in this area. For orbital defects, the preferred location is the lateral portion of the superior orbital rim.
Several attachment systems have been used to connect the facial prosthesis to the implants, such as bar-clips, magnets, and O-ring types. For auricular and nasal prostheses we prefer the bar-clip systems because they provide superior retention. We prefer magnetic retention for orbital prosthesis, because the ease of insertion of magnetically retained prostheses outweighs the possibilities of magnet corrosion and decreased retention over time.
The retentive system is designed to fit within the contours of the facial prosthesis as an acrylic resin substructure. It should posses sufficient surface area so that the bond between the substructure and the silicone prosthesis will not fail during insertion or removal of the prosthesis.
Success rates for auricular sites have exceeded 95% in most studies and few complications have been encountered. Success rates of the floor-of-nose sites are between 85 and 90% and are about the same as oral implants placed in the premaxillary segment. Of 130 fixtures inserted at UCLA, only 2 of 83 floor-of-nose and mastoid implants were lost; however, there were 19 of 47 frontal bone failures. Success rates are diminished if implant sites have been irradiated previously.
Prosthetic treatment of the irradiated patient
The risk of developing an osteoradionecrosis is minimal in patients who have been edentulous for some time before undergoing head and neck radiation therapy. The risk of bone necrosis increases in those patients who have teeth removed just before or after radiotherapy. More on osteoradionecrosis (ORN).
Timing of denture placement
Empirical recommended insertion times have ranged up to three years. In our study of 92 patients who were edentulous before the onset of cancer, prostheses were inserted, on an average, 15 months after radiation was completed; 45 patients received dentures within 6 months. None of the 92 developed a denture-related osteoradionecrosis. This data and our clinical experience indicate that dentures can be fabricated soon after completion of radiation therapy in most patients. If the radiation fields cover little of the mandibular denture-bearing surface, dentures can be inserted as soon as the mucositis resolves. An irregular mandibular ridge, especially in a patient whose mandible was wholly within the radiation field, may prompt the clinician to defer dentures indefinitely.
In summary, for edentulous patients who were experienced denture wearers before radiotherapy, there is little risk of developing significant complications from wearing dentures. For those who had teeth extracted within the radiation field before radiotherapy and were not experienced denture wearers, the risk of bone necrosis is higher. Therefore, placement of dentures depends upon patient needs, the status of the mucosal and bony wearing surfaces, and the amount and fields of radiation. Some patients in this group may never be candidates for complete dentures.
Prosthodontic procedures Complete Dentures
Boggy mucosa with prominent telangiectasia and fibrosis implies that prosthodontic restorations will be poorly tolerated, and mucosal integrity is at risk. In the case of floor-of-mouth lesions, it may be prudent to somewhat limit extension of the mandibular-lingual flange. Scar tissue is most unyielding, and the slightest overextention can result in a mucosal perforation and perhaps lead to bone or soft-tissue necrosis.
Excessive trismus is occasionally observed in patients whose radiation field includes the temporo-mandibular joint and muscles of mastication. If there is trismus, it may be necessary to reduce the vertical dimension of occlusion. This will make intake of food easier and may reduce the forces exerted on the supporting mucosa during closure. Xerostomia and viscous saliva compromise retetntion as well as increase friction at the denture mucosa interface, causing mucosal irritation. Here the use of a denture adhesive powder is recommended to facilitate retention. Patients with mandibular ridges having severe bilater undercuts, mandibular tori, or excessive ridge resorption with little attached mucosa are poor candidates for complete dentures after radiation therapy.
Conventional border molding using a custom tray and modeling plastic is advocated. If xerostomia is particularly profound, a thin coating of petroleum may be applied over the soft modeling plastic to prevent its sticking to dry mucosa. Displacement of the tissues of the floor of the mouth in an attempt to obtain peripheral seal is not advocated. Efforts in developing the lingual flange should be directed toward gaining stability and support rather than retention. The elastic impression materials are most suitable in refining the impression.
The completed impressions are boxed and poured in dental stone. Conventional record bases are prepared and used to determine the vertical dimension of occlusion. The usual methods of determining vertical dimension (phonetics, closest speaking distance, swallowing, neuromuscular perception, and recording vertical dimension at rest) and centric relation apply. Wax, plaster, and zinc oxide paste are suitable media for obtaining the final registrations. Graphic recording devices can likewise be employed successfully.
On a theoretical basis, we favor monoplane occlusal schemes with bilateral balance obtained with posteriorly situated balancing ramps. In arranging posterior teeth, there should be proper buccal horizantal overlap to avoid tongue and cheek biting. When using anatomic posterior teeth, bilateral balance during function is mandatory.
Delivery and Postinsertion Care
Eliminate occlusal discrepancies before removing processed dentures from their casts. Pressure-indicating paste is used to identify areas of excessive pressure, and disclosing wax is useful in verifying extension of denture flanges. Remount on a suitable articulator with new maxillomandibular records taken at the time of delivery. Instructions are provided about removing dentures if soreness develops, limiting denture use initially during mastication, and not wearing them during sleeping hours. During the first week, 24- and 48- hour recall appointments are recommended. Commercial denture cleansers are effective tools for removing plaque deposits and food particles from denture surfaces. Careful follow-up is essential for denture adjustments and to minimize necrosis and infections.