2021 prosthodontics consideration for irradiated patient

Psychological consideration in maxillofacial patient:
Maxillofacial patients are classified according to the etiology into acquired, congenital &developmental. Patient with acquired maxillofacial defect are usually resulted from trauma or cancer, both of them were have normal anatomy &physiology but these are changed or impaired due to the trauma or cancer. Usually patients with small defect frequently appear more demanding &have higher expectation than patients with larger defect. Patients with cancer may face chemotherapy, radiotherapy, recurrence &more surgical procedure. Patient with congenital defects may understand that they are different from norm &they may face a knowledge that there may be genetic predisposition. Those patients usually face multiple surgeries, orthodontics &prosthodontics procedures over several years in an attempt for correction of the defect, again in cleft lip &palate patients you may expect variations from simple cleft lip with minimal loss of function to extensive bilateral cleft lip &palate with sever impairment in function. Patient with developmental defect may display some emotional response similar to patients with congenital defects.
Requirement of ideal materials used for facial prosthesis:
Prostheses can be made from a variety of materials, such as Poly(methyl) methacrylate, polydimethylsiloxane, &polyetherurethanes.
Ideal physical &mechanical properties:-
1. High elongation strength.
2. High tear strength.
3. Softness, compatible to the tissue.
4. High edge strength.
5. Translucent.
Ideal processing properties:-
1. Chemically inert after processing.
2. Long working time.
3. Ease of intrinsic &extrinsic coloring with commercially available colorant.
4. No color changes after processing, retain intrinsic &extrinsic colors .
5. Reusable mold.
Ideal biological properties:-
1. Biologically compatible.
2. Cleansable with disinfectant.
3. Color stability.
4. Resistance to the growth of the micro-organisms.
Prosthesis fixation:
These prostheses are retained with adhesives, tissue undercuts, or in some cases extra-oral osseointegrated implant. Facial &intraoral prostheses can be connected with magnets. The aesthetic result depends on the amount of tissue removed, type of reconstruction, morbidity adjunctive treatment, and the physical characteristics of the tissue base available to support &retain the prosthesis.
So prosthesis fixation may be:
1. Anatomic (teeth, alveolar ridge, residual hard palate, undercut)
2. Mechanical.
3. Magnets.
4. Implants.
5. Screw.
Primary factors that affect prosthetic success:
All prostheses must resist a variety of forces that may displace it &generate stress to the residual structure of the orofacial complex. Prostheses success is often dependent upon methods of compensation for diminished anatomic capacity for support, retention &stability of a prosthesis.
In order to achieve a favorable level of retention, remaining teeth &the remaining soft &hard tissues must be used to the optimal degree. This may be gained by:-
A. It is prudent to extend impressions as much as possible without interfering with movable tissue.
B. Border molding is performed whenever a prosthesis depends on tissue support whether that tissue is located within the defect or is part of the remaining structures.
C. In addition, close adaptation to the underlying tissue results in a thin fluid film between the prostheses &the tissue, the thinner the intervening fluid, the greater the prosthetic retention.
Frequently, the means of retention is used, &may encompass descriptive adjectives such as adjacent tissue, teeth, dental/craniofacial implants or a combination of such, thus appropriate terminology &classification of the prostheses in relation to the retention means are:-
1. Tissue retained maxillofacial prostheses.
2. Tooth retained maxillofacial prostheses.
3. Implant retained maxillofacial prostheses.
4. Tissue/implant retained maxillofacial prostheses.
Teeth are the greatest asset for providing retention of the obturator prosthesis. The amount of stress generated by the movement of the obturator may be great. The number, position, &periodontal status of the remaining teeth are the most critical factors in evaluating the amount of stress that remaining teeth may be able to absorb.
Support is the ability to resist displacement of the prosthesis towards the supporting structure. Remaining teeth, remaining edentulous areas &the postsurgical defect are the supporting tissues for prosthesis & prosthesis loads are generated through these tissues to the underlying supporting bone.
A. Since the tissue has limited capacity for displacement, the greater the surface area of tissue contact, the less the displacement of the prosthesis towards the tissue.
B. Maximum peripheral extension combined with an accurate adaptation to the remaining teeth, the residual ridges & the postsurgical site will provide the most favorable support for prosthesis.
Stability is the ability to resist displacement of the prosthesis by functional forces.
Adhesives enhance retention through optimizing interfacial force. The alteration in the normal structures results in diminished potential for support &retention. Since the majority of forces are not directed towards or away from the tissue, but generated at an angle to the tissue, it is stability that is tested most frequently in function.
An alternative method of prosthetic retention has been developed. Endosseous implants may be used to address the concerns of diminished support, retention &stability.
Use of similar implants in extra-oral sites is growing in popularity especially for the retention of auricular prosthesis and for bone anchored hearing aids.
-The use of endosseous implant support in maxillofacial defects can be complex. As seen in most maxillofacial prosthetic patients, alterations in normal anatomy reduce the opportunities for the clinician to place &restore endosseous implants. This situation occurs when supporting bone is lost due to surgical resection or when tissue is altered due to therapeutic modalities such as radiation.
-prosthetic designs &strategic implant placement must anticipate the functional demands of the prosthesis while also recognizing the dislodging forces applied to the prosthesis.
Sequence of treatment for pateints with intra-oral defect(maxilla or mandible):
1. Pre-operative stage.
2. Post-operative stage.
3. Definitive &follow-up stage.
? Pre-operative stage:
1. Close consultation : between the prosthodontics &surgeon (x-ray, study cast) to outline the defect location &size. The discussion involve the possible preservation of teeth &supporting structures that may be used for retention &stability of the prosthesis(obturator). A compromise is necessary &preservation of teeth &structures should not interfere with the surgical procedure to eliminate the disease.
2. Full dental treatment : for better oral hygiene which helps healing of surgical sight &successful of future prosthesis:
a. Hopeless teeth.
b. Filling of caries teeth (abutment for prosthesis).
c. Proper periodontal health care.
3. Construction of pre-operative obturator, surgical splint.
A temporary maxillofacial prosthesis inserted during or immediately following surgical or traumatic loss of a portion or all of one or both maxillary bones and contiguous alveolar structures (i.e. gingival tissue, teeth). It is secured either by palatal screw, suture or circumzygomatic wires. Old denture can be used as a surgical obturator but it might create some problems because the denture mostly not fit as before surgery therefore relining may help to improve patients’ acceptance and tolerance. It is mostly used for 10 days more or less depends on treatment plane.
This prosthesis is placed immediately after surgery to:
1. Serve as matrix for surgical pack –to be removed 3-10 days.
2. Eliminate the need for naso-gastric tube feeding.
3. Better hygiene for surgical sight –better healing.
4. Improve patient speech.
5. Better psychological status of patient.
6. Reduces the period of hospitalization.
Requirement:
1. Light weight.
2. Strong.
3. Easy to alter( addition, removal to fit the surgical splint).
4. Made from acrylic with or without teeth.
? Post-operative stage:
Construction of temporary(interim or transitional) post-operative obturator which is constructed from post-surgical impression cast which has a false palate and false ridge and generally no teeth. Every step of prosthesis construction must maximize prosthesis adaptation to enhance retention and stability to ensure optimum function, esthetic, occlusion, and correct jaw relations.
• The closed bulb extending into the defect area is hollow.
• The patient is usually seen every 2weeks because of the rapid soft tissue changes that occur within the defect during organization and healing of the wound.
• Correction of tissue-prosthesis relation can be made by relining.
• The temporary obturator will need to function comfortably for as long as 6months.
• The timing depending on the size of the defect, the progress of the healing, presence or absence of teeth.
• Used during the healing period of the surgical sight and the tissue conditioning material .
• Has the same advantage as surgical prosthesis.
• Constructed by obtaining a new post-operative impression or modification of the surgical prosthesis by adding teeth &clasp.
? Definitive stage:
• Construction definitive prosthesis(obturator)
• Construction after complete healing of surgical sight.
• Usually chrome-cobalt.
• Periodic follow-up.
Definitive obturator is a maxillofacial prosthesis that replace part or all of the maxilla and associated teeth lost due to surgery or trauma. It is made when it is deemed that further tissue changes or recurrence of tumor are likely and more permanent prosthetic rehabilitation can be achieved, it is intended for long term use.
There are several reasons for constructing a new definitive obturator:-
1. The periodic addition of interim lining material increases the bulk &weight of the obturator &this temporary material may become rough &unhygienic.
2. If teeth are included in the resection, the addition of anterior denture teeth to the obturator can be of great psychological benefit to the patient.
3. If retention &stability are inadequate, occlusal contact on the defect side ,may result in improvement of these aspects.
Approximately 6months after surgery consideration may be given to the construction of a definitive obturator prostheses, but this period may be extended depending on the case. It is constructed from the postsurgical maxillary cast. This obturator has a false palate, false ridge, teeth &closed bulb which is hollow. Changes associated with healing &remodeling will continue to occur in the border areas of the defect for at least 1 year. Dimensional changes are primarily related to the peripheral soft tissues rather than to bony support areas.
TREATMENT PLAN:
Primary impression: A gauze pack may be placed in the defect undercut area &the preliminary impression was made in a stock tray using irreversible hydrocolloid impression material as the tissues were in the healing phase, be careful because in certain cases alginate may be tear in the defect area during removal. Silicon impression material can be used. In some cases 2 compatible impression materials can be used in modified technique. The impression must extend as possible in the defected areas. The primary cast obtained was used to fabricate a custom tray for the definitive impression. Any undercuts may interfere with tray construction must be blocked. Relief areas must be determined also. Proper border molding is done on the non-defect side of the denture, by following the conventional methods of denture fabrication.
Final impression of the defect area is made in rubber base impression materials. Sectional trays or double trays technique can be used but this might complicate the procedure .A master cast is procured out of it and the borders are outlined for the record bases. The undercuts on the sides of the defect are blocked with wax and also, the internal part of the cavity is painted with a thin layer of wax before making the acrylic record bases.

Digital impression laser surface scanning was applied to acquired three-dimensional imaging data of the patient’s facial defect. Transferred to a CAD/CAM interactive program in computer system for image processing produced a model for fabrication of the facial prosthesis.
Jaw relation record is made by a conventional method, an attempt must made to compensate for the loss of facial support on the defect side to improve the esthetics. Minimal block out should be made because excessive block out result in unstable record base. Improve esthetic by an attempt to compensate for the loss of facial support on the defect side. Estimation of the occlusal plane &wax level is difficult in most of the cases due to the tissue scar &block out procedure. The record jaw relation was transferred to a semi-adjustable articulator. Teeth are selected &arranged according to principles. It is advisable to choose cuspless teeth (monoplane occlusion) may allow for freedom in movement & give a negative overlap especially on the surgical site.
Verification of jaw relation &esthetic try in: Waxed up dentures are tried and checked for retention, stability and comfort in the mouth. It must ensure that there is simultaneous contact of posterior teeth at centric relation position. Adjust the occlusal plane &teeth alignment, scars &asymmetry of the face due to surgery may require some modifications &extra-care. The patient approval regarding esthetics must also obtain.
Flasking: The wax up denture is flasked &dewaxed, finally during the procedure, a layer of acrylic in dough stage should be packed to the walls of the defect. The center space is filled with salt &an acrylic lid is placed over which acrylic is packed as for a conventional denture. The obturator is cured &retrieved. A small perforation is made in cured bulb of the obturator &salt is flushed out using water in a syringe &the perforation is seated with autopolymerizing resin.
Insertion: all the border must be adjust, use of pressure indicating paste to check for the pressure areas that must be removed. Jaw relation &occlusion must be checked; remounting of the prosthesis for occlusal adjustment, premature occlusal contact must be eliminated to have smooth occlusion. The patient must be instructed that mastication might be difficult in early time &it is better to use a non-surgical side; soon the patient will adapt &tolerate the limitations. Adhesives may be given but concentrate about its used. Give instruction to the patient to maintain good oral hygiene.
Design of maxillary obturator:
Depend on :1. Size 2. Location (defect). 3. Number &position of the remaining teeth.
General principles in designing of maxillary obturator:
1. Maximum clasping of remaining teeth with multiple occlusion rest (for retention &stability).
2. Maximum tissue coverage.
3. Maximum use of favorable undercut in the defect region.
4. Flat occlusion to eliminate deflective occlusion.
5. Hallow obturator (bulb) in case of large defect.
PROSTHODONTICS TREATMENT FOR IRRADIATED PATIENTS:
Radiotherapy is a common primary or surgical adjuvant treatment for cancer of the head &neck. While the radiotherapy is effective in destroying residual cancer cells, the side effects to adjacent tissues are well documented. The bone forming cells, osteoblasts &osteocytes, within the direct path of irradiation are damaged &killed in bone, reducing the capacity for new bone synthesis. The periosteum loses cellularity &vascularity with impairment of osteoid formation. Osteoclast continue resorption after radiotherapy, patients who have had radiation therapy in or above oral cavity should be carefully evaluated prior to prosthetic service, since the duration , methods, &dosage of radiation effect the soft &hard tissues. The use of radiation stent may reduce the side effect. The amount &viscosity of saliva is an important determinant of prosthodontics success. Compromised salivary function leads to more friction at the denture mucosal interface &more mucosal irritation. Retention of CD may be compromised because of diminished salivary quantity &change quality, such as the increased film thickness of the scanty &more mucinous saliva.
? Factors that should be taken in consedration in denture or partial construction for irradiated patient:
1. Evaluation of psychological status &general health.
2. Tumor is under control.
3. Red, inflamed, edematous mucosa, one year after therapy is contraindicated for prosthetic treatment(unhealthy denture foundation).
4. Avoidance of pre-prosthetic surgery(tori, bony spicules)due to low body resistance &slow repair mechanism which may lead to osteradionecrosis.
5. Rubber base is material of choice for impression ,zinc oxide eugenol is contra-indicated (eugenol is irritant).
6. Good occlusion without disharmony.
7. Wetting of mouth with artificial saliva(due to xerostomia will help in decreasing friction &improve retention.