RADIATION THERAPY OF HEAD AND NECK TUMORS

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RADIATION THERAPY OF HEAD AND NECK TUMORS

• Dr. Vinit Shah
• Junior Resident
• Prosthodontics
• FODS, KGMU

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Contents

• PART - I
• Introduction
• Physical principles
• Interaction of radiation and tissues
• Fractionation
• Brachytherapy
• Indications for treatment of head and neck
  tumours
• Use of prosthetic stents and splints during
  therapy
• Radiation effects
• Part - II
• Dental management dentulous patients
• Osteoradionecrosis
• Prosthetic management edentulous patients
• Implants in irradiated tissues
• Irradiation of existing implants
• Conclusion

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Introduction

• John Beumer III, Tohomas A. Curtis, and
  Russel Nishimura
• Radiation therapy is defined as the therapeutic
  use of ionizing radiation.
• Two categories of radiation
• Electromagnetic
• Particulate
• Electromagnetic wave of wavelength less than 1
  angstrom are called photons.
• They have 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)

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Interactions of Radiation and Tissues

• Radiation absorption by tissues
• Biologic effects
• Reoxygenation
• Repopulation
• Accelerated repopulation

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Radiation absorption by tissue
Direct ionizing
Indirect Ionizing
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INTERACTIONS OF RADIATION AND TISSUES

• When Charged particles have sufficient energy ,
  they are directly ionizing.
• ( pass through target matter, and disrupt the
  atomic structure by producing chemical and
  biological changes).
• Photons and neutrons (uncharged particle) are
  indirectly ionizing .(give up their energy to
  produce fast moving charged particles.)

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Biologic effect

• The primary effect of radiation is confined to
  the intranuclear structures such as DNA and
  mitotic apparatus.
• Damage to intranuclear structures may be
• 1. lethal
• 2. sublethal (may not be apparent
  until atleast one cellular division is
  attempted).
• If enough time passes between the sublethal event
  and cellular division, the damage may be
  corrected, process known as repair of sublethal
  damage.

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Reoxygenation

• The indirect action of photon beam on target
  tissues is dependent on the level of oxygenation
  concept known as reoxygenation.
• Anoxic tissues - 3 times more resistant to
  radiation effects
• oxygen organic free radicals organic
  peroxides
• This reaction leaves more hydroxyl free radical
  which can then interact with target molecules
  that would otherwise react with hydrogen to form
  inactive molecules of water.

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Redistribution

• The radiation effect on individual cells may
  vary according to the position they occupies in
  the cell cycle at the time of irradiation.
• More vulnerable during G1 and in mitotic
  phase
• Relatively radioresistant at the beginning
  and the end of DNA synthesis.
• Radiation given during these phases, increased
  cell killing, known as redistribution.

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Repopulation and accelerated repopulation

• In a given enough overall treatment time, cell in
  the irradiated tissue can proliferate and
  repopulate known as repopulation.
• It has been observed that any cytotoxic agent,
  including radiation, can trigger colonogenic
  surviving cells to divide faster than before.
  This is called accelerated repopulation.
• Estimated to occur about 4 weeks after the
  initiation of the treatment.
• Thus in order to keep pace with the more rapid
  growth of tumor cell, a more rapid delivery of
  treatment may be needed.

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Isoeffect Models

• Biologically Equivalent Treatment Schedules
• As dose increases, tissue changes become more
  profound and irreversible ? increased
  complications.
• Important variables
• Number of fractions
• Dose per fraction
• Total dose
• Time period

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FRACTIONATION

• Radiation therapy is delivered in the series of
  treatment or fractions.
• Conventional fractionation (in US)
• total dose - 6500 to 7200cGy
• daily fractions -180-200cGy
• period- 7weeks
• given Monday through friday

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FRACTIONATION

• Advantages
• Allows regular reoxygenation of the tumor during
  the course of treatment, making it more
  radiosensitive.
• Offers radiation to effect more tumor cells
  during the radiosensitive phase of their cell
  cycle.
• Normal cell seems to recover more completely
  between fractions from sublethal damage than do
  tumor cells.

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BRACYTHERAPY

• Method of radiation treatment in which sealed
  radioactive source is used to deliver the dose to
  a short distance by interstitial(direct insertion
  into tissue), intracavitary(placement within a
  cavity) or surface application(molds).
• (Boost for advanced tumors or primarily for
  small lesions)
• Most commonly used radioisotope in head and neck
  regions are iridium 192, cesium137 and radium
  226.
• Radiation sources may be form of needles, narrow
  tubes, wires or small beads.

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• Advantages
• Rapid decrease in dose with distance from
  radiation source (inverse square law).
• Thus a high radiation dose can be given to the
  tumor while sparing surrounding normal tissues.
• Also dose rate is low relative to external beam
  therapy, it can be considered a highly
  fractionated form of irradiation
• Thus continuous low dose irradiation tends to
  synchronize the cell cycle and allows sublethal
  damage repair.

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• Disadvantages
• Inhomogeneity.
• Requires the operator to have adequate technical
  and conceptual skills to achieve good dose
  distribution.
• Exposure to room personnel and to therapist
  specially with the use of radium needles.

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Indications for treatment of head and neck tumors

• Decision regarding the use of radiation and/or
  surgery for the control of primary lesion is a
  function of the location and extent of the tumor.
• 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.

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• Carcinoma of salivary gland and alveolar ridge
  should be treated surgically followed by
  radiotherapy due to potential for bony
  infiltration.
• 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)

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Prosthetic devices in Radiation Therapy

• These are used to optimize the delivery of
  radiation while reducing the associated
  morbitity.

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Positioning stents

• 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.
• (sparing to parotid gland more salivary
  output )

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• For dentulous patients.
• Interocclusal stent prepared that extends
  lingually from both occlusal tables with a flat
  plate ff 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.

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• For edentulous patients
• 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

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Per oral cone positioning device

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

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Shielding

• Helpful if patient is to receive unilateral dose
  of radiation.
• Useful in
• Buccal mucosa, skin and alveolar ridge.
• It has been reported that 1 cm thickness of
  Cerrobend alloy will prevent transmission of
  95of an 18 Mev electron beam radiation exposure
  to normal structures.

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• Lipowitz metal or cerrobend alloy is commonly
  used to shield.
• Cerrobend Alloy
• Low fusing alloy
• 50 bismuth
• 26.7 lead
• 13.3 tin
• 10 cadmium

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Recontouring tissues to simplify dosimetry

• 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.

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Positioning a radioactive source

• 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.

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Templates used in direct implantation

• Direct implantation of the radioactive source in
  the tumor.
• useful in
• Lesion of the tongue and anterior floor of the
  mouth.
• Used to position the source and also determine
  the proper depth of insertion.
• Once prosthesis is secured , tissue
  conditioning material is flowed over the implants
  to maintain them in proper position during the
  treatment period.

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Tissue bolus devices

• 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.
• This method optimizes the dosimetry by restoring
  tissue density throughout the defect and ensures
  uniform delivery of radiation and also protects
  friable healing tissue such as skin graft.

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• 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

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Radiation effects

• Oral mucous membrane
• Taste
• Olfaction
• Edema
• Trismus
• Salivary glands
• Bone
• Periodontium
• Teeth

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Radiation effects

• ORAL MUCOUS MEMBRANE-
• Initially an erythema appears, epithelium
  becomes thin, less keratinized, vascularity
  decreases and mucosa becomes more fibrotic
  leading to extensive ulceration and desquamation.
• 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.
• Soft palategt hypopharynxgt floor of the mouth gt
  buccal mucosagt base of the tonguegt dorsum of
  tongue
• Healing is rapid and usually complete in 2-3
  weeks.

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• 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
• These changes make fabrication and tolerance of
  prosthesis difficult.

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Taste

• Taste bud shows signs of degeneration and
  atrophy at 1000 cGy and at cancericidal dose the
  architecture of taste bud is completely
  obliterated.
• 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

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Olfaction

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

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Edema

• Edema of tongue, buccal mucosa, submental and
  submandibular area is occasionally clinically
  significant.
• Apparent during the early postradiation period
  when scaring and fibrosis are common
• (Impairs patency of both lymphatic and
  venous channel resulting in obstruction.)
• Occasionally, edema reaches proportion which
  compromise tongue mobility, impairs salivary
  control, make denture utilization and speech
  articulation more difficult.

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Trismus

• Most noticeable following treatment of
  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

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Salivary gland

• 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.

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Bone

• 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.

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Periodontium

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

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Teeth

• Evidence in changes of crystalline structure of
  enamel, dentin, or cementum following RT is
  unclear.
• 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.
• Exposure
• before calcification completion - tooth bud may
  be damaged .
• At later stage of development - may arrest
  growth.

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Composition of oral flora

• Radiation field that include substantial portions
  of salivary glands leads to significant changes
  in the composition of oral flora.
• Increase in the population of streptococcus
  mutans, lactobacillus and actinomyces
  predisposing to dental caries.
• Brown has reported upto 100 fold increase in
  fungal populations.
• Post therapy candidiasis of corner of mouth and
  beneath prosthetic appliance is common.

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Contents

• PART - I
• Introduction
• Physical principles
• Interaction of radiation and tissues
• Fractionation
• Brachytherapy
• Indications for treatment of head and neck
  tumours
• Use of prosthetic stents and splints during
  therapy
• Radiation effects
• Part - II
• Dental management dentulous patients
• Osteoradionecrosis
• Prosthetic management edentulous patients
• Implants in irradiated tissues
• Irradiation of existing implants
• Conclusion

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Dental management dentulous patients

• Criteria for pre-radiation Extraction-
• Following factors should be considered before
  making decisions regarding extraction or
  retention of teeth.
• They are divided into 2 categories
• .Dental Disease Factors - Condition of residual
  dentition
• 
  -Dental compliance of patient
• Radiation Delivery Factors -Urgency of treatment
• 
  -Mode of therapy
• 
  - Radiation fields
• 
  -Mandible versus maxilla
• 
  - Dose to bone

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Condition of residual ridge

• Dentition in optimal condition (high risk dental
  procedures will not have to be performed in the
  post treatment period).
• Extraction of all teeth with questionable
  prognosis before radiation.
• Periodontal status in healthy condition.
  (Furcation involvement of mandibular molar teeth
  in the radiation field is ground for preradiation
  extraction) .

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Dental compliance of the patient

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

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Radiation delivery factors

• Urgency of treatment
• Mode of therapy
• Radiation fields
• Mandible versus maxilla
• Dose to bone

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Urgency of treatment

• The status and behavior of tumor may preclude
  pre-radiation dental extractions, since delay
  secondary healing could significantly compromise
  control of disease.
• 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.

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Mode of therapy

• 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.

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Radiation field

• 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.

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Mandible verses maxilla

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

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Dose to bone

• 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.

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Extraction of third molars

• 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.

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Surgical procedures

• Factors to be observed for extraction in the
  preradiation period for best results.
• 1. Radical alveoectomy should be performed,
  edges of the tissue flaps averted, and primary
  closure obtained .
• 2. Teeth should be removed in segments. (When
  individual teeth are extracted, closure is
  difficult to obtain without excessive tension on
  tissue flaps).

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• 3. Administration of antibiotics during the
  healing period Is effective when extraction
  results in excessive trauma.
• 4. 7 to 10 day for adequate healing before
  therapy is begun. Can be shortened or extended
  depending upon progress made by the patient.
• 5. Periosteum is the predominant source of
  vascularity and all efforts should be made to
  avoid mishandling it during surgical procedure.

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Post radiation disease

• 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.

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Treatment of severe post radiation disease

• If the dose to bone locally is below 5500cGy,
  conventional therapies for tooth or teeth in
  question can be employed, including root planning
  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.

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• 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 .

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Endodontic therapy as alternative treatment to
PRE

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

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Osteoradionecrosis

• 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.
• The dose to bone is probably the best predictor
  of risk .

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• In a study by Morrish, in which dose to bone was
  calculated on all patients, mandibular bone
  necrosis developed in 85 of dentulous patients
  who received 7500cGy or more to bone.
• None of the patients who received less than
  6500cGy to mandibular bone develop necrosis.

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Treatment options

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

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• Hyperbaric oxygen
• 2.4 atmospheres with
  100oxygen
• Stimulates neovascular proliferation in
  marginally necrotic tissues , enhances
  fibroblastic prolifiration, enhances the
  bactericidal activity of white blood cells and
  increases production of bone matrix.
• Marx stated that hyperbaric oxygen is a
  valuable therapeutic modality not only in
  treatment of osteoradionecrosis but, also, in
  preventing osteoradionecrosis.

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• Marx protocol for treatment of
  osteoradionecrosis
• Stage I- Osteoradinecrosis but without
  pathological fracture, orocutaneous fistula or
  radiographic evidence of bone resorption to the
  inferior border of mandible.
• 2.4 atmospheres, 100oxygen 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

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• 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.

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• 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.

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• Contraindications to Hyperbaric oxygen
• Persistent tumor
• Optic neuritis
• Active viral disease states
• Untreated pneumothorax
• Complications include barotrauma of ear,
  temporary myopia and in rare instances pulmonary
  fibrosis .

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Soft tissue necrosis

• Non neoplastic mucosal ulceration occurring in
  the postradiation field and which does not expose
  bone. Occurs most often following treatment with
  interstitial implants and peroral cone modalities
  .
• Most of these necrosis 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.
• A tumor recurrence usually presents with
  irregular indurated margins whereas soft tissue
  necrosis present with regular , non indurated
  margins

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Prosthetic management- edentulous patients

• 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.

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• 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.

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• Examination
• 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,
• Appearance of oral mucous membranes,
  scarring and fibrosis at tumor site, degree of
  trismus, presence and nature of lymphodema, and
  status of salivary function.

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• Impression
• Conventional border molding, using custom
  tray and modeling plastic is advocated for making
  impression.
• In xerostomia ,thin coating of
  petrolatum may be applied over the soft modeling
  plastic to avoid sticking to dry mucosa.
• Peripheral seal is virtually impossible
  to obtain in these patients because of
  curtailment of salivary flow. Efforts should be
  to gaining stability and support rather than
  retention
• Edema of floor of mouth and tongue (radical
  neck dissection), will limit the extent of the
  lingual flange.

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• vertical dimension
• Consideration for reduce vertical dimension of
  occlusion.
• Reducing the vertical dimension may limit
  the extent of the forces applied to the
  supporting mucosa and bone during a forceful
  closure.
• In patients with clinically significant
  trismus, entrance of bolus is more easily
  accomplished by increasing the interocclusal
  space.

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• Occlusal
  form
• Lingualised or monoplane occlusal schemes.
• In arranging posterior teeth, careful
  attention should be directed toward attaining 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.

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• Delivery and post insertion
• Occlusal discrepancies caused by processing
  errors should be eliminated prior to removing the
  dentures from the cast. After removal any rough
  projections on tissue surface should be
  smoothed..
• Instructions concerning removal of
  prosthesis if soreness develops, the necessity
  for periodic return visits, and initial limited
  use of prosthesis are provided.

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Implants in irradiated tissues

• 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 gt 5000 cGy

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Irradiation of existing implants

• 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

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Conclusion

• 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 patients quality of life.

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