radiation and prosthodontics

1. Presented by
Rani Ranabhatt
JR II

2.  Most patients with head
and neck cancer will
receive radiotherapy at
some time during the
course of their disease.
 For some tumors
radiation is applied alone
whereas for others it is
used in combination with
surgery or chemotherapy

3.  Particularly carcinoma of nasopharynx, base of
tongue, soft palate, tonsillar fossa radiation
therapy is the treatment of choice because of
surgical morbidity, difficult access, and high risk
of regional lymph node involvement.
 Carcinoma of salivary gland and alveolar ridge
should be treated surgically followed by
radiotherapy due to potential for bony infiltration.

4.  Early carcinoma of glottic larynx and tongue are
equally well controlled by radiation or surgery
but radiation offer a better functional result
 Hard deeply infiltrated carcinoma of tongue are
less likely to be controlled by radiation. (Due to
fixation to the vocal cord)
( superficial / exophytic lesions have higher cure
rate with radiation than deeply infiltrated
lesions)

5.  Minimize the
postradiation
morbidities
associated with oral
function that affect
the patient’s quality
of life

6.  Radiation therapy is defined as the therapeutic
use of ionizing radiation.
 Two categories of radiation ;
Electromagnetic
Particulate
John Beumer III, Tohomas A. Curtis, and Russel Nishimura:
Radiation Therapy

7. Electromagnetic wave of wavelength less
than 1 angstrom are called photons.
-neither mass nor charge.
Measured in electron volt. eg x- rays and
gamma rays.
Particulate radiation have mass and are
charged negatively (electrons), positively (
protons, alpha particles) or are neutral
(neutrons)

8. Radiation absorption by tissue
Direct
ionizing
Indirect
Ionizing
Direct action results
when secondary
particles interact with
the target molecule ie
DNA
Indirect action results
from interaction with
water molecule which
in turn produces free
radical which reacts
with target molecule

9. Radiobiological
Principles
Reoxygenation Repopulation
Accelerated
repopulation
Anoxic tissue 3
times resistant to
radiation , due to
formation
nonrestorable
organic peroxides
Cells in the
irradiated tissue
can proliferate
and repopulate,
if given enough
overall treatment
times
Radiation triggers
clonogenic
surviving cells in
a tumor to divide
faster than before

10. 4 basic Radiation
Plans
1.7 to 2.0 Gy,
5 fractions per
week, upto 70
Gy
Reduction of
the no of
fractions with
an increase of
the daily
fraction. Eg. 2.5
Gy, 5 fractions
per week, upto
50 Gy
Increasing
both the no of
fractions and
the total dose.
Eg. 1.1Gy
twice a day, 5
days a week,
to 74 Gy
Hybrid of
hypo and
hyperfraction
ation
Conventional
fractionation
Hypofractionation
Hyperfractionation
Accelerated
fractionation

11. CONVENTIONAL
RADIOTHERAPY
1. Opposed
parallel fields
2. Oral stent or
shield
3. Facemask
4. Simulation and
inkmarks
INTENSITY MODULATED
RADIATION THERAPY
1. Delivered doses of
radiation are defined for
volumes (planning target
volumes)
2. PTV1 : cancer and
carcinomatous lymph
nodes
3. PTV2 : high risk lymph
nodes
4. PTV3 : subclimical
nodes
BRACHY THERAPY
1. Method of radiation
treatment by
radioactive sources
2. Radioisotopes –
irridium 192, cesium
137, and radium 226
3. Can be interstitial, intra
cavitary, or surface
application (molds)

13. These are used to optimize the delivery of radiation while
reducing the associated morbidity.
stents
shields
positionerscarriers
splints

14.  Used to rearrange tissue topography within the
radiation field and displace normal tissues outside the
radiation field.
Useful in;
 tongue and floor of
the mouth lesions.
 inferior positioning of tongue
and mandible enabling to lower the radiation field.
Goel A et al . Use of positioning stents in lingual carcinoma
patients subjected to radiotherapy. Int J Prosthodont 2010. 23;
450-52

15.  Interocclusal stent
prepared that extends
lingually from both occlusal
tables with a flat plate of
acrylic resin.
 Serves to depress the
tongue
 A hole is made in the
anterior horizontal segment
 Serves as an orientation
hole for reproducible
tongue position.

16.  Impressions
 Interocclusal record at
half/ two-thirds of
maximum opening
 Mounting
 Base plate wax
attached to mandibular
record base to form the
portion which will
depress the tongue.
 Occlusal index for
comfort and stability

17.  use to boost radiation over Small
superficial lesions (T1 or T2 in
sizes) in accessible locations in
the oral cavity.
 lesions like floor of mouth,
hard palate, soft palate, or
tongue.
(Spares vital adjacent tissues
such as mandible, teeth and
salivary gland.)

18.  unilateral dose of radiation.
 Buccal mucosa, skin and alveolar ridge.
 It has been reported that; 1 cm thickness of Cerrobend
alloy will prevent transmission of 95%of an 18 Mev
electron beam radiation exposure to normal structures.
Aggarwal et al. Radiation stents: Minimizing radiation-induced
complications. South Asian Journal

19.  Lipowitz metal or
cerrobend alloy or
Wood’s Metal is
commonly used to
shield.
 Low fusing alloy
 50% bismuth
 26.7% lead
 13.3% tin
 10% cadmium

20.  Use of a stent to flatten the lip and corner of the mouth,
thereby placing the entire lip in the same plane to
deliver uniform dosage of radiation.
Useful in;
 treating skin lesions
associated with upper and lower lips.

21. Radioactive source
(cesium132 or iridium 192).
Preloaded After loaded
 Preloaded (RS position within prosthesis prior to
carrier insertion) medical staffs receives some
exposure.
 After loading technique, isotopes are threaded into
the hollow tubing after the carrier is in
predesigned location reduces the radiation
exposure to medical staff.

22. Direct implantation of the
radioactive source in the
tumor.
useful in;
Lesion of the tongue and anterior
floor of the mouth, palatal
tumors
 Used to position the source
and also determine the proper
depth of insertion.

24.  Irregular tissue = uneven radiation dose
 A bolus is a tissue equivalent material placed directly
onto or into irregular tissue contours to produce a more
homogenous dose distribution.
commonly used materials are- saline, wax, acrylic
resins.
Singh BP et al. A simplified technique to fabricate tissue bolus device to
manage dose distribution in maxillectomy patient with orbital exenteration
journal of oral biology and craniofacial research(2013 ) 1 0 2 - 0 4

25.  Following orbital
exenteration and
maxillectomy
 Irregular contours and
air spaces
 Tissues at greatest risk of
radiation injury: skin
grafts, areas of thin
mucosa over bone and
brain tissue
Singh BP et al. A simplified technique to fabricate tissue bolus device to
manage dose distribution in maxillectomy patient with orbital exenteration
journal of oral biology and craniofacial research(2013 ) 10 2 - 0 4

26. Singh BP et al. A simplified technique to fabricate tissue bolus device to
manage dose distribution in maxillectomy patient with orbital exenteration
journal of oral biology and craniofacial research(2013 ) 10 2 - 0 4

27.  Oral mucous membrane
 Taste
 Olfaction
 Edema
 Trismus
 Salivary glands
 Bone
 Periodontium
 Teeth

28.  Pain and dysphagia resulting in
weight loss .
 Mucositis begins to appear
2-3 weeks after the start of
therapy
and reaches peak toward the
end of therapy.

29.  After therapy, changes in tissues in
the field of therapy predispose to
tissue breakdown and delayed
healing
 Epithelium thin and less
keratinized
 Submucosa less vascular and
fibrotic
Prevention------frequent daily cleaning of teeth with soft brush , oral
rinses with combination of salt and sodium bicarbonate in water or dilute
solutions of hydrogen peroxide and water

30. Taste bud shows signs of
degeneration and atrophy at 1000
cGy
 Alteration in taste are discovered
during the second week and continue
throughout the course of treatment.
 Perception of bitter and acid flavors
are more impaired than salt and
sweet.
 Taste gradually return to normal
levels after therapy is completed.
 Xerostomia  decreased recovery of
taste

31.  Since the olfactory epithelium is high in nasal passage
and not included within the radiation field, the sense of
smell is less affected.

32.  Edema of tongue, buccal
mucosa, submental and
submandibular area
 Apparent during the early
postradiation period when
scaring and fibrosis are
common
(Impairs patency of both
lymphatic and venous
channel resulting in
obstruction.)
 .

33.  nasopharyngeal, parotid,
palatal and nasal sinus
tumors in which TMJ and
muscles of mastication are
in radiation field.
 Maximum mouth opening
may be reduced upto 10-
15mm.
 Treatment
 Exercise
 Dynamic bite openers

34.  Saliva changes in volume, viscosity, pH, inorganic
and organic constituents, predisposing to caries,
periodontal disease, impairment of taste acuity,
poor tolerance of prosthetic restoration, and
difficulty in swallowing.

35.  Bone is 1.8 times as dense as
soft tissue , thus, it absorbs a
large proportion of radiation
than does a comparable
volume of soft tissue.
 Mandible absorbs more than
maxilla because of increased
density, plus reduced
vascularity accounts for
increase incident of
osteoradionecrosis.

36.  Periodontal ligament
thickens and fibres
become disoriented.
 Exhibit decreased
cellularity and vascularity
 cementum capacity for
repair and regeneration is
also compromised.

37.  Pulp shows decrease in
vascular elements, with
accompanying fibrosis and
atrophy.
 Pulpal response to infection,
trauma, and various dental
procedures appears
compromised.
Level as low as 2500 cGy
can have marked effect on
tooth development.

38.  Radiation field that include substantial portions of
salivary glands leads to significant changes in the
composition of oral flora.
 Increased----streptococcus mutans, lactobacillus and
actinomyces predisposing to dental caries.
 Post therapy candidiasis of corner of mouth and
beneath prosthetic appliance is common.

39.  Criteria for pre-radiation Extraction-
Dental Disease
Factors
Condition of residual
dentition
Dental compliance of
patient
Radiation Delivery
Factor
•Urgency of treatment
•Mode of therapy
•
Radiation fields
•
Mandible versus maxilla
•
Dose to bone

40.  Dentition in optimal condition
 Extraction of all teeth with questionable
prognosis before radiation.
 Periodontal status in healthy condition.

41. Becomes difficult to maintain after treatment;
 reduced salivary output.
 Trismus,
 impaired motor functions,
 and surgical morbidities
(The patient’s oral hygiene at initial examination is
often a reliable indicator of future performance.)

42.  Urgency of treatment
 Mode of therapy
 Radiation fields
 Mandible versus maxilla
 Dose to bone

43. Fast proliferating tumors eg; palatal tumors .
 The dentist, radiation therapist and patient must
accept the risk of complications and must attempt
to maintain oral health at optimum level. Control
of tumor obviously is the most important
consideration.

44.  When external beam therapy is used in
combination with radioactive sources implanted(
brachytherapy) - dose to adjacent tissues is
reduced and more confined.
 When external radiation is the sole mean of
radiation delivery - close scrutiny of the dentition
is mandatory.

45.  Nasopharynx and posterior soft palate, (includes
both parotid glands) – xerostomia and
postradiation caries.
 Lateral tongue and floor of mouth, (encompass
the entire body of mandible ) - osteoradionecrosis
is high.
 Tonsillar, soft palate , or retromolar trigone
carcinomas, (major salivary glands and a
significant portion of body of mandible.) - caries
and osteoradionecrosis is high in this group.

46.  Osteoradionecrosis in maxilla is rare -
conservative approach is justified. BETTER
BLOOD SUPPLY
 Almost all osteoradionacrosis occur in mandible -
more aggressive approach is advocated,
Particularly mandibular molars (common site of
osteoradionecrosis). when they are in radiation
beam.

47.  For tissues treated to the high level of `tolerance,
more aggressive program of extracting teeth prior
to therapy is indicated .
 The type of tumor will also dictate the radiation
levels used in treatment. Eg;- Hodgkin's disease -
4000 to 4500 cGy,
-Squamous cell carcinoma of oral cavity-6500 to
8500cGy.

48.  Extraction of impacted
mandibular third molars prior to
radiation is not advocated for
most patients. (create large
defects requiring prolonged
periods for healing).
 Patients with partially erupted
mandibular third molars
represent a particularly difficult
and perplexing problem because
of risk of pericoronities.
Operculectomy is useful in
selected cases.

49.  Radical alveoectomy should
be performed, edges of the
tissue flaps everted, and
primary closure obtained .
 Teeth should be removed in
segments.
 Antibiotic coverage
 7-10 days healing prior to
radiotherapy

50.  The risk of bone necrosis secondary to dental
extractions in postradiation period has been
debated by many clinicians.

 Following definitive course of radiation therapy -
vascular changes in bone and oral mucosa impair
blood supply and predispose to tissue breakdown
and secondary infections of bone and soft tissue.
Best indicator of potential risk is the
radiation dose to bone in the area of the dentition
being considered for removal.

51.  If the dose to bone locally is below 5500cGy,
conventional therapies for tooth or teeth in
question can be employed, including root planing
and curettage, crown lengthening and root canal
therapy. However, Periodontal flap surgery is not
recommended.
 When tumor dose exceeds 6500cGy, options are
dependant upon the radiation treatment modality
used.

52.  If the dental infection involved the molar region
adjacent to implant in absence of exposed bone,
dental extractions are employed only as last resort.
 Endodontic therapy is recommended in order to
maintain mucosal integrity.
 If the infection is periodontal and/ or into the
bifurcation area following the root canal therapy,
the crown can be amputated , thereby providing
access for oral hygiene to this area .
 If the implant increases the dose in these regions
above 5500cGy, hyperbaric oxygen maybe
considered .

53. Difficulties;
o Rubber dam isolation is complicated by minimal
coronal tooth structure and risk of tissue trauma
and resultant bone exposure.
o Oropharyngeal reflexes compromised , translating
into greater risk for aspiration of files.
o Trismus and small pulp canals make the access for
instrumentation and filling difficult.

54.  Is not primarily an infectious
process, it is exposure of bone
within radiation treatment
volume of 3 months or longer
in duration.
 It may progress to intractable
pain and pathological fracture
of mandible, often accompanied
by orocutaneous fistula and
requiring resection of major
portion of mandible.

55.  mandibular bone necrosis developed in 85%
of dentulous patients who received 7500cGy
or more to bone.

56.  Osteoradionecrosis associated with external beam;
 -
 ,
Dose less than
6500cGy and
localized exposure
Dose to bone above 6500cGy
and exposure extends beyond
the mucogingival junction, or
in association with teeth
If external beam dose to
the bone is below
5500cGy
local irrigation and
packing of idoform
gauze, impregnated
with tincture of
benzoin.
-hyperbaric oxygen combined
with surgical sequestrectomy
should be considered.
conservative therapy are
excellent,

57. Hyperbaric oxygen ;
2.4 atmospheres with 100%oxygen
Stimulates neovascular proliferation in marginally
necrotic tissues , enhances fibroblastic
proliferation, enhances the bactericidal activity of
white blood cells and increases production of bone
matrix.

58. Marx protocol for treatment of
osteoradionecrosis;
 Stage I- Osteoradionecrosis but without
pathological fracture, orocutaneous fistula or
radiographic evidence of bone resorption to the
inferior border of mandible.
2.4 atmospheres, 100%oxygen for 90
minutes for 30 treatments.
End of 30 treatments improvement
20 treatments are added.
No clinical improvement non- responder
and advanced to stage II

59.  Stage II- Surgical sequestrectomy, wound closed
primarily in 3 layers over a base of bleeding bone.
Additional 10 hyperbaric treatments wound
dehisces
non -responder and advanced to stage III.
Stage II Nonresponder with orocutaneous
fistula, pathologic fracture or radiographic
evidence of bone resorption to inferior border of
mandible are considered stage III patients.

60.  Stage III- Nonvital mandibular bone are resected
transorally with the aid of tetracycline fluorescence
under ultraviolet light. External fixation of
mandibular segment, orocutaneous fistulae closed
and soft tissue deficits restored with local or
distant flaps.
 Another 10 hyperbaric treatments are given and
the patient is advanced to stage IIIR.
 Stage IIIR- Ten weeks after resection, the
mandible is reconstructed with bone grafts , using
transcutaneous exposure. Mandibular fixation is
achieved and maintained for 8 weeks.
 10 hyperbaric treatments are given
postoperatively.

61.  following treatment with interstitial implants and peroral
cone modalities .
 occurs within 1 year after completion of radiation therapy.
 Intense local discomfort is a clinical symptom that is
sometimes useful in differentiating this lesion from
persistent disease.


62.  If the radiation fields cover little of denture bearing
surfaces (eg; nasopharyngeal carcinoma ),
dentures can be inserted as soon as mucositis
resolves.
 Most prosthodontists advised the construction of
dentures be deferred for at least 1year after
radiation therapy had been completed.

63. The status of the residual ridge is an important
clinical factors to be carefully appraised.
 Regular/ irregular mandibular ridge
 Denture base should ensure distribution of
pressure as widely and as equally as possible.
 Occlusal scheme should be to minimize lateral
movement of mandibular denture base.
2 groups of people
1. One already a denture wearer
2. Another new denture wearer

64.  Information of site of the
tumor, mode of therapy
employed, total dose ,dates
of treatment, radiation
fields, tumor response and
prognosis for disease control
should collected.
 Oral examination,

65.  Conventional border molding, using
custom tray and modeling plastic
 In xerostomia---- apply thin coating of petrolatum
 Efforts should be to gaining stability and support rather
than retention
 thermoplastic waxes
 Polysulfide

66. Consideration for reduced vertical dimension of
occlusion.
In patients with clinically significant trismus,
entrance of bolus is more easily accomplished
by increasing the interocclusal space.

69. Lingualised or monoplane occlusal schemes.
 attain a proper buccal horizontal overlap.
 Some clinicians use only 3 posterior teeth, 1
bicuspid and 2 molars in order to avoid
trauma to the posterior buccal mucosa.

70.  Pressure indicating paste
 Disclosing wax
 Clinical remount
 24 and 48 hour follow up
 Leave dentures out at
night

71.  Irradiation predisposes changes
in bone, skin, mucosa which
affect the predictability of
Osseointegrated implants.
 Careful consideration to risk of
osteoradionecrosis
 Osseointegration is impaired in
bone that has received > 5000
cGy

72.  Results in backscatter.
 Dose is increased about 15% at
1mm from the implant
 It is recommended that all
abutments and superstructures be
removed prior to radiation.
 Skin/mucosa closed over implant till
healing is complete

73.  Intensity Modulated Radiation Therapy
(IMRT)
 Cyberknife
 Tomotherapy
 Stereotactic radiosurgery

74.  The cancer patient who is to receive curative
doses of radiation to the head and neck
presents an interesting challenge to the
dentist.
 Dental management of the irradiated patient
is a serious undertaking since the standard
of care has an effect on the patient’s quality
of life.