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iii
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A modified intraoral prosthesis for directing a radiation beam Stephen M. Parel, D.D.S.,* and Joe B. Drane, D.D.S.** The University o/Texas at Houston, M. D. Anderson Hospital and Tumor Institute and Dental Branch, Houston, Texas
Certain oral tumors can be treated by use of radiation therapy directed through an intraoral cone. In' such instances, the dentist may be called upon to construct a locating prosthesis which will direct the beam consistently and provide stability for the cone. 1-'~ This report describes a method for constructing a custom-fitted metal extension for the therapy cone a n d a means of incorporating this extension into a stabilizing prosthesis.
THE PROBLEM WITH STANDARD CONES Most intraoral cones used in radiation therapy range from 3 to 4 cm. in diameter and have flush or beveled ends. It is desirable in treating oral lesions for the end of the cone to be in contact with oral nmcosa within the entire perimeter of the treatment field. This is seldom possible due to the varied topography of the mouth (Fig. 1). When there is a space between the mucosa and the treatment cone, two things may occur. "First, normal tissues outside the radiation field may be irradiated. Second, the desired dose to the tumor field is diminished by an amount proportional to the square' of the distance between the end of the metal extension and the tissue (i6verse square rule) .4
CHOICE OF MATERIALS Any metal used in conjunction with a directed intraoral radiation beam should provide adequate shielding and be nontoxic. Lead shields were used intraorally by Brickner '~ as early as 1903. Others modified intraoral cones with lead sheets or cylinders for improved tissue shieldingf ''1° *Resident, Maxillofacial Prostheties, Tile University of Texas, Dental Branch and M. D. Anderson Hospital and Tumor Institute. **Professor, Maxillofacial Prosthetics, The University of Texas, Dental Branch; Director of Regional Maxillofacial Restorative Center, Clinical Surgeon (Prosthodontics), and Chief of Dental Service, M. D. Anderson HOSlfital and Tumor Institute.
666
Prosthesis /or directing a radiation beam
Voh,,,,e Number 33 6 'i:. ' . ~ . . _ .,.~~~.~ t ~
667
.
I
.
.
.
.
,
'
.
D
I RECT I O N
Fig. 1. Flush or beveled intraoral cones can rarely contact all mucosa surrounding a lesion. The result may be diminished beam intensity in the open regions and unwanted radiation to regions outside the treatment field.
However, there are hazards associated with the use of lead, mostly related to its high melting point (621 ° F.) and potential toxicity. ~' v, Several alloys that melt at lower temlx~ratures have been used in place of pure lead for intraoral shielding? 3' ~ In light of a review of these materials by Wallace, ~'~ Cerrobend ~ (a bismuth-tin alloy of read) was chosen. METHOD Tile following steps are followed in constructing a metal extension for a therapy cone and incorporating the extension into a stabilizing prosthesis. (1) Casts of tile patient's edentulous ridges are made, incorporating the lesion and as much surrounding tissue as possible (Fig. 2). (2) The casts are mounted on an articulator with a positional record at a vertical opening of tile jaws that is several millimeters less than maximum (Fig. 3). (3) The radiotherapist is consulted to determine the proposed radiation field and direction of the beam. (4) A plastic or metal forming tube is milled to a diameter whicll will allow it to fit snugly inside the metal treatment cone. (5) Two layers of baseplate wax are wrapped around the forming tube (Fig. 4). (6) By heating or adding wax to the baseplatc cylinder, a wax pattern is made which contacts tissue around the radiation field (Fig. 5). *Cerrobend, Cerro Copper and Brass Company, Stamford, Conn.
668
Parel and Drane
j.
Prosthet. Dent.
June, 1975
Gi): .......
;~,,?
) ,,
,
:-,
,
~'.
,
:
? :::)
Fig. 2. (A) The arrow indicates a small soft-palate squamous cell carcinoma. (B) The stone cast of the patient's mouth includes as much of the tissue surrounding the lesion as possible.
(7) A check is made with the therapist for fit and extension of the wax pattern. (8) The pattern is re-placed on the forming tube to assure a uniform inner diameter. (9) The metal cone tip is heated and brought in contact with the wax pattern on its forming tube. This will make a wax collar to guide placement of the cone and will provide a positive stop for the metal cone (Fig. 6). (10) The wax pattern is sprued twice with utility wax and invested in Gray investment. ~ (11 ) The wax pattern is eliminated by placing it il)-a standard denture boil-out tank with boiling water. (12) The Cerrobend is heated and poured into the warm flask through one of the sprue holes. (13) The casting is cooled and carefully recovered. The sprues and any flash or bubbles are removed with metal burs. (14) The casting is slotted with a separating disc to allow for retention of acrylic resin. (15) The acrylic resin sleeve is formed directly on the metal cone using aluminum foil for separation. (16) Tile casting and acrylic resin sleeve are approximated on the metal cone and attached with acrylic resin. (17) The sleeve-casting assembly is returned to the articulator and attached to the appropriate east with wax or modeling compound. (18) The sleeve and cast extension are incorporated into suitable record bases to stabilize and direct the cone (Fig. 7). *Gray investment, The Ransom & Randolph Company, Toledo, Ohio.
vol.,n,, :~3 Number 6
Prosthesis /or directing a radiation beam
669
Fig, 3, The casts are mounted at a vertical opening of the jaws that is several millimeters less than maximum opening possible. Fig. 4, Baseplate wax is adapted to a forming tube which conforms to the inner diameter of the treatment cone, Fig. 5, The wax pattern should contact mucosa entirely around the treatment field outlined by the radiation therapist. Fig, 6. A collar is made in the wax pattern using a heated treatment cone and the forming tube. This collar provides a positive stop for the treatment cone.
(19) The entire assembly is tried and adjusted in the patient's mouth before radiotherapy is begun (Figs. 8 and 9).
DISCUSSION T h e modified t r e a t m e n t cone-stent has several advantages over the conventional radiation stent. (1) T h e close proximity of the metal extension to the tissue a r o u n d the entire lesion limits radiation scatter and helps assure a m o r e constant bemn to the radiation field (Fig. 10). (2) I n a d v e r t e n t d a m a g e to oral and phm-yngeal structures can occur if tile t r e a t m e n t cone passes too far through a s t a n d a r d radiation stent. T h e modified cone extension provides a positive stop inside tim stent which will prevent such injury. (3) Collimation and dosimetric measurements are more consistent since the cone is inserted to tile same depth in l h e stent each time. (4) Structures outside tim field of radiation are consistently shielded or displaced with this prosthesis.
670
Parel and Drane
j. v,o.~tl~t. June,D~,t. 1975
Fig. 7. The completed prosthesis is attached to stabilizing baseplates.
Fig. 8. A sagittal radiograph indicates that the prosthesis is in place. The gold seed (arrow) indicates the top of the lesion. Fig. 9. The patient is undergoing treatment with the therapy unit in place.
Fig. 10. (A) The appearance of the palate four weeks after the start of treatment. Note the well-demarcated field of radiation. (B) The soft palate five weeks after completion of treatment at the beginning of scar tissue formation.
VoJ,,,,,, 3:~ Number 6
Prosthesis for directing a radiation b e a m
671
(5) T h e stent alone allows accurate p r e t r e a t m e n t visualization of the radiation field since unaffectdd tissue is displaced.
SUMMARY A m e t h o d of modifying fitted metal extension can nique. T h e final radiation beam for treating intraoral
an intraoral radiation cone has been presented. A custombe obtained either directly or indirectly using this techstent allows consistent and stable direction of a radiation lesions.
Appreciation is expressed to Dr. Richard E. Harrison, a resident in the Maxillofacial Prosthetics Department, and to Vince Sampiere of the Radiation Physics Department at M. D. Anderson Hospital and Tumor Institute.
References 1. Santiago, A.: An Intraoral Stent for Direction of Radiation Beam Therapy, J. PROSTHET. DENT. 15: 938-941, 1965. 2. Rahn, A. O., and Boucher, L. J.: MaxiIlofaciaI Prosthetics, Philadelphia, 1970, W. B. Saunders Company. 3. Fletcher, G. H.: Textbook of Radiotherapy, Philadelphia, 1966, Lea & Febiger, Publishers, pp. 57-59. 4. Beder, O. E.: Surgical and Maxillofaeial Prosthetics, Seattle, 1959, The University of Washington Press, p, 25. 5. Brickner, W. M.: How to Secure the Best Skiagrams: Some Practical Points in Manipulation of Vacuum Tubes in Radiography and Radiotherapy, Int. J. Surg. 16: 303-306, 1903. 6. Martin, H. E.: Peroral X-Radiation in Treatment of Intra-Oral Cancer, Radiology 28: 527-532, 1937. 7. Merritt, E. A.: Roentgen Therapy of Cancer in Buccal Cavity and Cervix Uteri, Am. J. Roentgenol. 42: 418-422, 1939. 8. Castigliano, S. G., and Sklaroff, D. M.: Use of Precision Cones in Peroral Irradiation, Am. J. Roentgenol. 64: 968-973, 1950. 9. Dresser, R., and Dumas, C. E.: Radiation Treatment of Carcinoma of the Buccal Cavity, Am. J. Roentgenol. 36: 939-945, I936. I0. Ebenuis, B.: Peroral Roentgen Treatment of Malignant Tumors, Acta Radiol. 22: 194201, 1941. 11. Karzmark, C. J., and Huisman, P. A.: Melting, Casting and Shaping Lead Shielding Blocks: Method of Toxicity Aspects, Am. J. Roentgenol. Radium Ther. Nucl. Med. ! 14: 636-638, 1972. 12. Chisolm, J. J., Jr.: Lead Poisoning, Sci. Am. 224: 15-23, 1971. 13. Wallace, R. E.: A Comparison of Radiation Shielding Effects of Lead, Cerrohend, and Other Materials: A Research Report, M. D. Anderson Hospital and Tumor Institute, 1971. (Unpublished report.) 14. Aramanyi M. A., and Drane, J. B.: Radiation Displacement Prostheses for Dentulous Patients, J. PROSTHET. DENT. 27: 212-216, 1972. DR. PAREL V. A. HOSPITAL 7400 MERTON MINTER BLVD. SAN ANTONIO, TEXAS 78284 DR. DRANE CHIEF, DENTAL SER.VlCE,CP-723 M. D. ANDERSON HOSPITALAND TUMOR INSTITUTE TEXAS MEmCAL CENTER HOUSTON, TEXAS 77025
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A modified intraoral prosthesis for directing a radiation beam Stephen M. Parel, D.D.S.,* and Joe B. Drane, D.D.S.** The University o/Texas at Houston, M. D. Anderson Hospital and Tumor Institute and Dental Branch, Houston, Texas
Certain oral tumors can be treated by use of radiation therapy directed through an intraoral cone. In' such instances, the dentist may be called upon to construct a locating prosthesis which will direct the beam consistently and provide stability for the cone. 1-'~ This report describes a method for constructing a custom-fitted metal extension for the therapy cone a n d a means of incorporating this extension into a stabilizing prosthesis.
THE PROBLEM WITH STANDARD CONES Most intraoral cones used in radiation therapy range from 3 to 4 cm. in diameter and have flush or beveled ends. It is desirable in treating oral lesions for the end of the cone to be in contact with oral nmcosa within the entire perimeter of the treatment field. This is seldom possible due to the varied topography of the mouth (Fig. 1). When there is a space between the mucosa and the treatment cone, two things may occur. "First, normal tissues outside the radiation field may be irradiated. Second, the desired dose to the tumor field is diminished by an amount proportional to the square' of the distance between the end of the metal extension and the tissue (i6verse square rule) .4
CHOICE OF MATERIALS Any metal used in conjunction with a directed intraoral radiation beam should provide adequate shielding and be nontoxic. Lead shields were used intraorally by Brickner '~ as early as 1903. Others modified intraoral cones with lead sheets or cylinders for improved tissue shieldingf ''1° *Resident, Maxillofacial Prostheties, Tile University of Texas, Dental Branch and M. D. Anderson Hospital and Tumor Institute. **Professor, Maxillofacial Prosthetics, The University of Texas, Dental Branch; Director of Regional Maxillofacial Restorative Center, Clinical Surgeon (Prosthodontics), and Chief of Dental Service, M. D. Anderson HOSlfital and Tumor Institute.
666
Prosthesis /or directing a radiation beam
Voh,,,,e Number 33 6 'i:. ' . ~ . . _ .,.~~~.~ t ~
667
.
I
.
.
.
.
,
'
.
D
I RECT I O N
Fig. 1. Flush or beveled intraoral cones can rarely contact all mucosa surrounding a lesion. The result may be diminished beam intensity in the open regions and unwanted radiation to regions outside the treatment field.
However, there are hazards associated with the use of lead, mostly related to its high melting point (621 ° F.) and potential toxicity. ~' v, Several alloys that melt at lower temlx~ratures have been used in place of pure lead for intraoral shielding? 3' ~ In light of a review of these materials by Wallace, ~'~ Cerrobend ~ (a bismuth-tin alloy of read) was chosen. METHOD Tile following steps are followed in constructing a metal extension for a therapy cone and incorporating the extension into a stabilizing prosthesis. (1) Casts of tile patient's edentulous ridges are made, incorporating the lesion and as much surrounding tissue as possible (Fig. 2). (2) The casts are mounted on an articulator with a positional record at a vertical opening of tile jaws that is several millimeters less than maximum (Fig. 3). (3) The radiotherapist is consulted to determine the proposed radiation field and direction of the beam. (4) A plastic or metal forming tube is milled to a diameter whicll will allow it to fit snugly inside the metal treatment cone. (5) Two layers of baseplate wax are wrapped around the forming tube (Fig. 4). (6) By heating or adding wax to the baseplatc cylinder, a wax pattern is made which contacts tissue around the radiation field (Fig. 5). *Cerrobend, Cerro Copper and Brass Company, Stamford, Conn.
668
Parel and Drane
j.
Prosthet. Dent.
June, 1975
Gi): .......
;~,,?
) ,,
,
:-,
,
~'.
,
:
? :::)
Fig. 2. (A) The arrow indicates a small soft-palate squamous cell carcinoma. (B) The stone cast of the patient's mouth includes as much of the tissue surrounding the lesion as possible.
(7) A check is made with the therapist for fit and extension of the wax pattern. (8) The pattern is re-placed on the forming tube to assure a uniform inner diameter. (9) The metal cone tip is heated and brought in contact with the wax pattern on its forming tube. This will make a wax collar to guide placement of the cone and will provide a positive stop for the metal cone (Fig. 6). (10) The wax pattern is sprued twice with utility wax and invested in Gray investment. ~ (11 ) The wax pattern is eliminated by placing it il)-a standard denture boil-out tank with boiling water. (12) The Cerrobend is heated and poured into the warm flask through one of the sprue holes. (13) The casting is cooled and carefully recovered. The sprues and any flash or bubbles are removed with metal burs. (14) The casting is slotted with a separating disc to allow for retention of acrylic resin. (15) The acrylic resin sleeve is formed directly on the metal cone using aluminum foil for separation. (16) Tile casting and acrylic resin sleeve are approximated on the metal cone and attached with acrylic resin. (17) The sleeve-casting assembly is returned to the articulator and attached to the appropriate east with wax or modeling compound. (18) The sleeve and cast extension are incorporated into suitable record bases to stabilize and direct the cone (Fig. 7). *Gray investment, The Ransom & Randolph Company, Toledo, Ohio.
vol.,n,, :~3 Number 6
Prosthesis /or directing a radiation beam
669
Fig, 3, The casts are mounted at a vertical opening of the jaws that is several millimeters less than maximum opening possible. Fig. 4, Baseplate wax is adapted to a forming tube which conforms to the inner diameter of the treatment cone, Fig. 5, The wax pattern should contact mucosa entirely around the treatment field outlined by the radiation therapist. Fig, 6. A collar is made in the wax pattern using a heated treatment cone and the forming tube. This collar provides a positive stop for the treatment cone.
(19) The entire assembly is tried and adjusted in the patient's mouth before radiotherapy is begun (Figs. 8 and 9).
DISCUSSION T h e modified t r e a t m e n t cone-stent has several advantages over the conventional radiation stent. (1) T h e close proximity of the metal extension to the tissue a r o u n d the entire lesion limits radiation scatter and helps assure a m o r e constant bemn to the radiation field (Fig. 10). (2) I n a d v e r t e n t d a m a g e to oral and phm-yngeal structures can occur if tile t r e a t m e n t cone passes too far through a s t a n d a r d radiation stent. T h e modified cone extension provides a positive stop inside tim stent which will prevent such injury. (3) Collimation and dosimetric measurements are more consistent since the cone is inserted to tile same depth in l h e stent each time. (4) Structures outside tim field of radiation are consistently shielded or displaced with this prosthesis.
670
Parel and Drane
j. v,o.~tl~t. June,D~,t. 1975
Fig. 7. The completed prosthesis is attached to stabilizing baseplates.
Fig. 8. A sagittal radiograph indicates that the prosthesis is in place. The gold seed (arrow) indicates the top of the lesion. Fig. 9. The patient is undergoing treatment with the therapy unit in place.
Fig. 10. (A) The appearance of the palate four weeks after the start of treatment. Note the well-demarcated field of radiation. (B) The soft palate five weeks after completion of treatment at the beginning of scar tissue formation.
VoJ,,,,,, 3:~ Number 6
Prosthesis for directing a radiation b e a m
671
(5) T h e stent alone allows accurate p r e t r e a t m e n t visualization of the radiation field since unaffectdd tissue is displaced.
SUMMARY A m e t h o d of modifying fitted metal extension can nique. T h e final radiation beam for treating intraoral
an intraoral radiation cone has been presented. A custombe obtained either directly or indirectly using this techstent allows consistent and stable direction of a radiation lesions.
Appreciation is expressed to Dr. Richard E. Harrison, a resident in the Maxillofacial Prosthetics Department, and to Vince Sampiere of the Radiation Physics Department at M. D. Anderson Hospital and Tumor Institute.
References 1. Santiago, A.: An Intraoral Stent for Direction of Radiation Beam Therapy, J. PROSTHET. DENT. 15: 938-941, 1965. 2. Rahn, A. O., and Boucher, L. J.: MaxiIlofaciaI Prosthetics, Philadelphia, 1970, W. B. Saunders Company. 3. Fletcher, G. H.: Textbook of Radiotherapy, Philadelphia, 1966, Lea & Febiger, Publishers, pp. 57-59. 4. Beder, O. E.: Surgical and Maxillofaeial Prosthetics, Seattle, 1959, The University of Washington Press, p, 25. 5. Brickner, W. M.: How to Secure the Best Skiagrams: Some Practical Points in Manipulation of Vacuum Tubes in Radiography and Radiotherapy, Int. J. Surg. 16: 303-306, 1903. 6. Martin, H. E.: Peroral X-Radiation in Treatment of Intra-Oral Cancer, Radiology 28: 527-532, 1937. 7. Merritt, E. A.: Roentgen Therapy of Cancer in Buccal Cavity and Cervix Uteri, Am. J. Roentgenol. 42: 418-422, 1939. 8. Castigliano, S. G., and Sklaroff, D. M.: Use of Precision Cones in Peroral Irradiation, Am. J. Roentgenol. 64: 968-973, 1950. 9. Dresser, R., and Dumas, C. E.: Radiation Treatment of Carcinoma of the Buccal Cavity, Am. J. Roentgenol. 36: 939-945, I936. I0. Ebenuis, B.: Peroral Roentgen Treatment of Malignant Tumors, Acta Radiol. 22: 194201, 1941. 11. Karzmark, C. J., and Huisman, P. A.: Melting, Casting and Shaping Lead Shielding Blocks: Method of Toxicity Aspects, Am. J. Roentgenol. Radium Ther. Nucl. Med. ! 14: 636-638, 1972. 12. Chisolm, J. J., Jr.: Lead Poisoning, Sci. Am. 224: 15-23, 1971. 13. Wallace, R. E.: A Comparison of Radiation Shielding Effects of Lead, Cerrohend, and Other Materials: A Research Report, M. D. Anderson Hospital and Tumor Institute, 1971. (Unpublished report.) 14. Aramanyi M. A., and Drane, J. B.: Radiation Displacement Prostheses for Dentulous Patients, J. PROSTHET. DENT. 27: 212-216, 1972. DR. PAREL V. A. HOSPITAL 7400 MERTON MINTER BLVD. SAN ANTONIO, TEXAS 78284 DR. DRANE CHIEF, DENTAL SER.VlCE,CP-723 M. D. ANDERSON HOSPITALAND TUMOR INSTITUTE TEXAS MEmCAL CENTER HOUSTON, TEXAS 77025
