Radiation prostheses/ dental crown & bridge courses

RADIATION
PROSTHESES
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

CONTENTS
INTRODUCTION
DEFINITION OF RADIATION THERAPY
INDICATIONS OF RADIATION THERAPY
TYPES OF RADIATION SOURCES IN R.T
MODALITIES OF RADIATION THERAPY
DOSIMETRY
 TYPES OF RADIATION PROSTHESES
SOME TECHNIQUES OF FABRICATION
REFERENCES
CONCLUSION

INTRODUCTION
Radiation therapy has been used with increasing
frequency in the recent years for the
management of neoplams of head and neck
region. A majority of patients with such tumors
will receive radiotherapy at some time during the
course of their treatment...In some tumours it is
preferred treatment, where as in others it is
employed in combination with surgery or
sometimes with chemotherapy.

WHAT IS RADIATION THERAPY?
According to JOHN BEUMER AND THOMAS
A.CURTIS,
Radiation therapy is defined as” the therapeutic
use of ionizing radiation in the management of
neoplasms of the body with out surgery or as an
adjunctive palliative treatment after surgery,
either in combination with or with out
chemotherapy”.

INDICATIONS OF RADIOTHERAPY
IN HEAD AND NECK LESIONS
1. Squamous cell carcinomas of soft palate, floor
of mouth, tongue, lips and buccal mucosa
2. Adenocarcinomas of salivary and mucous
glands
3. Primary lymphomas of nasopharynx, tonsils
4. Carcinomas of maxilla and mandible
5. Carcinomas of piriform sinus,subglottic area
etc..

WHAT ARE DIFFERENT TYPES OF
RADIATIONS USED FOR
RADIOTHERAPY?
1. ELECTROMAGNETIC WAVES of wavelengths
less than one amstrong (A0
) called PHOTONS.
 No mass and no charge
 Ex: x-rays, gamma rays
2. PARTICULATE RADIATIONS
 Have mass and charge
 Ex: electrons, protons, neutrons, alpha
particles , pi-mesons etc..

WHAT ARE THE DIFFERENT TYPES
OF RADIATION THERAPY
MODALITIES?
EXTERNAL RADIATION THERAPY
INTERSTITIAL /INTRACAVITARY RADIATION
THERAPY

EXTERNAL RADIATION THERAPY
Most common modality of radiation therapy.
Also called TELETHERAPY
Used to deliver high doses of radiation to tumors
that are located with in 6cms of skin surface.
When external radiotherapy is used the doses
are of order of 6500rads to 7500 rads for 6-7
weeks.

The following energy sources are used for
external radiation therapy
low energy x-rays (50 kev to 100 kev) which
are appropriate for treatment of small and
superficial tumors
Orthovoltage (200 kev to 250 Kev), which is
convenient for the treatment of superficial, but
thick tumors.
High energy photons (cobalt 60 and high
accelerator), which are used for all deeply
located tumors.

INTERSTITIAL RADIATION THERAPY
Also called BRACHYTHERAPY.
Used to deliver high doses of radiation over a
short distance for a short time period.
Used to deliver high doses (up to 20000rads) in
a relatively short time(10-15hrs)
Uses radioisotopes(Co60
,Cs137
,Ir 197
) positioned in
or close to the tumor

If radiation source is placed in a cavity it is called
intracavitary source or if it is inserted or
implanted directly into tissue its called
interstitial source.
Most commonly used interstitial sources are
needles, narrow tubes, wires or seeds
containing radioactive cesium, cobalt, gold or
iridium

HOW IS RADIATION THERAPY GIVEN?
Given in a series of treatments or fractions
called fractionation.
Most radiation therapists deliver external
curative radiation therapy for oral tumours in
about 30 fractions, spread over a 6-7 weeks
period.

DOSIMETRY
RAD (RADIATION ABSORBED DOSE)
It is a unit to measure the amount of energy
absorbed by tissues that are subjected to
radiation exposure.
1 RAD means 100 gms of energy is absorbed by
I gm of tissue.
ROENTGEN
It is the unit to measure the amount of
exposure to radiation.
it is based on absorption in air and not by
tissues.

MILLICURIE
It is the unit of activity of radioactivity material.
1 mCi = 3.7 x 107
disintegrations/sec
NSD ( NOMINAL SINGLE DOSE)
The normal tissue tolerance in head and neck
has been in range of 1800 rets (radiation
therapeutic equivalents)

WHAT IS RADIATION PROSTHESIS?
ANY DEVICE ARTIFICIALLY FABRICATED
THAT AIDS IN THE EFFICIENT
ADMINISTRATION OF RADIOTHERAPY TO
THE AFFECTED AREAS AND THEREBY
HELPS IN LIMITING THE POST THERAPY
MORBIDITY.

WHAT ARE VARIOUS TYPES OF
RADIATION PROSTHESES?
Radiation carriers
Radiation shielding stents
Radiation cone positioners
Bolus compensators
Position maintaining device
Displacing stents
Dosimeter positioning stent

I. RADIATION CARRIERS
DEFINITION by GPT 8:
 radiation carrier is an ancillary prosthesis
used to administer radiation to confined areas by
means of capsules, beads or needles of
radiation emitting materials such as radium or
cesium. Its function is to hold the radiation
source securely in the same location during the
entire period of treatment.
syn - CARRIER PROSTHESIS,
INTRACAVITY APPLICATOR,
INTRACAVITY CARRIER,
RADIATION APPLICATOR,
RADIUM CARRIER,

Used in brachytherapy
Used to carry the radiation sources close to
the site of treatment (intracavitary) or directly
into the tumor (interstitial)
TYPES:
Preloaded carriers
After loaded carriers
RADIATION CARRIERS

Both the types of radiation carriers are used in
treatment of accessible superficial oral lesions
like palatal and buccal mucosal lesions
After loaded carriers are usually
advantageous compared to preloaded
carriers as the radioactive sources are placed
after the carrier is in position, hence minimizing
the radiation exposure to personnel handling,
positioning and securing such devices.
RADIATION CARRIERS

PRELOADED RADIATION CARRIERS

AFTER LOADED RADIATION CARRIERS

II. RADIATION SHIELD/STENT
radiation shield is an intraoral ancillary
prosthesis designed to shield adjacent tissues
from radiation during orthovoltage treatment of
malignant lesions of the head and neck region—
Syn- LEAD SHIELD,
TONGUE PROTECTOR

Used to shield the vital structures adjacent to
radiation therapy sites from excess dosage of
radiation.
Mostly used to protect tongue, salivary glands
and opposite side of mandible, when buccal
mucosa, skin and alveolar ridge of one side are
being treated.
Low melting alloys like CERROBEND, Pb-Bi-
Sn , LIPOWITZ are used as shielding materials.
RADIATION SHIELD/STENT

Lead alone is not suitable for shielding because
its melting temperature is in excess of 6000
F,and hence it cannot be poured into prosthesis
in molten state.
Cerrobend alloy is mostly preferred than lead
as it melting temperature is 1400
F and hence it
can be melted and poured into the cavity
prepared in prosthesis with out adversly
affecting methyl methacrylate.
A recently developed compound named WR-
2712,have a property of selectively protecting
the healthy cells and not the malignant cells

METHOD OF FABRICATION
FOR DENTULOUS PATIENTS:
impressions made for maxilla and mandible with
alginate
When obtaining the mandibular impression,
dental modeling compound is used to displace
the tongue away from the tray on the side for
which the stent is to be fitted.
Casts obtained
If the tongue was not displaced properly while
making the impression, the mandibular cast
must be trimmed so that a 1cm space is created
between the tongue and alveolar ridge.

3 or 4 strips of baseplate wax are softened and
placed between the teeth, and a bite recorded to
form occlusal index.
Casts with occlusal index mounted on suitable
articulator, with incisal pin opened to 2-3 mms.
A wax rim of 1-2 cms thick is prepared to fit into
the lingual space created by reduction of cast or
obtained in the impression.
Softened wax is placed inside the cast and
articulator closed so that a ring outline form can
be moulded.

Wax pattern is invested and processed into
methyl methacrylate to obtain a stent that is
finished ,polished and further refined if
necessary.
Cerrobend alloy is melted at 1400
F and poured
into cavity prepared in the prosthesis
When pouring the stent around a corner it is
advisable to utilize clay to block out curved
section and pour one straight section at a time.
A layer of wax or auto polymerizing methyl
methacrylate should be added to the exposed
surface of alloy to prevent back scatter.

FOR EDENTULOUS PATIENTS:
The stent can be made by duplicating the
patient’s existing dentures or by making
maxillary and mandibular impressions and
mounting on the cast.
The shield is then attached on the lingual side of
the maxilla and mandible as previously
described.

TECHNIQUE OF FABRICATION OF
TONGUE SHIELDING STENT
BY
STEVEN .C.RAMBACH, D.D.S,
J .FEMING, D.D.S
(J PROSTHET DENT 1983;49(3);389-392)

III. RADIATATION CONE
LOCATOR/POSITIONER
radiation cone locator is an ancillary prosthesis
used to direct and reduplicate the path of
radiation to an oral tumor during a split course of
irradiation.
Syn-
CONE LOCATOR,
DOCKING DEVICE

Used to position the peroral cones in a constant
position , thereby directing the radiation beam
consistently over the lesion to be treated and
also protecting the adjacent healthy structures
from irradiation.
Used in the treatment of superficial lesions
involving anterior floor of mouth, hard and soft
palate.
RADIATATION CONE LOCATOR/POSITIONER

RADIATATION CONE LOCATOR/POSITIONER

TECHNIQUE OF FABRICATION OF
RADIATION CONE POSITIONER
BY
GORDON .J. MAHANNA,.D.D.S,
JOHN .R. EVANHOE,.D.D.S
RONALD .A,D.D.S
(J PROSTHET DENT1994;71,600-2)

IV. TISSUE BOLUS
COMPENSATORS
These prostheses helps in treatment of
superficial lesions of face with irregular contours.
Due to irregularities in lesion, some areas with in
field may be untreated, while others may
develop isolated hotspots.

BOLUS is a tissue equivalent material placed
directly onto or into irregularities, that help in
converting irregular tissue contours into flat
surfaces perpendicular to the central axis of
ionizing beam, thereby more accurately aid in
homogenous distribution of radiation.
Most commonly used materials for bolus are
tissue conditioners, water, saline, waxes and
acrylic resin.

TISSUE BOLUS COMPENSATORS

TECHNIQUE FOR FABRICATION OF A
BALLOON RETAINING STENT TO
RETAIN A BALLOON TISSUE BOLUS
IN AN ORO-CUTANEOUS DEFECT
BY
RICHARD.H. MIYAMOTO,D.D.S
TERENCE.J.FLEMING,D.D.S,
(J PROSTHET DENT 1992;68:115-7)

V. POSITION MAINTAINING DEVICE
Used to precisely position structures to be
treated in a fixed and repeatable positions for
multiple treatment sessions.
Used to position movable structures mostly like
tongue, soft palate etc..

POSITION MAINTAINING DEVICE

TONGUE POSITION MAINTAINING DEVICE

Patient head positioning stent

VI. DISPLACING STENTS
Used to move/displace and thereby protect the
vital structures from the field of radiation.
Mostly used in the treatment of lesions involving
the mandibular alveolus, buccal mucosa and
posterolateral borders of tongue
Separates the mandible from the maxilla, thus
sparing the maxilla from the effects of irradiation.

DISPLACING STENTS

VII. DOSIMETER POSITIONING STENT
Dosimeter is a device used to calculate the
amount of dosage required for a lesion.
Lithium fluoride capsule are mostly used as a
dosimeter for accurate and efficient means of
determining the dosage locally.
These stents are useful in positioning the
dosimeter appropriately

DOSIMETER POSITIONING STENT

Use of computer tomography for
fabrication of a custom brachytherapy
carrier-A clinical report
( J prosthet dent 2003;89:15-18)

CONCLUSION
Radiation therapy has been a boon to the
medical profession in the treatment of patients
with malignant conditions. we, the
Prosthodontists can become a great helping
hand to the oncologists and radiation therapists
in improving the quality of the treatment with
these prostheses, there by preventing lot of post
irradiation morbidity. This way by having a
thorough knowledge of these appliances, we can
improve the quality of life of patients undergoing
radiation therapy.

REFERENCES
John Beumer III/Thomas A. curtis/David N.Firtell,
Maxillofacial rehabilitation (prosthodontic and surgical
considerations), The C.V.Mosby Company , edn-1979
White and Pharaoh, oral radiology, principles and
interpretations,5th
edn
Jpd 1983;49(3);389-92
Jpd 1987;58(5):620-22
Jpd 1990;63(6):665-70
Jpd 1991;65(6):370-4
Jpd 1992;68:115-7
Jpd 1994;71:600-2
Jpd 2000;83:119-21
Jpd 2003; 89:15-8

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