Radiation Biology
Question 1. discuss in detail radiation effects on oral cavity.
or
Write note on radiation hazards of oral cavity.
or
Describe harmful effect of radiation on oral mucosa, taste buds, salivary glands, teeth and jaw bones.
or
Write in detail about radiation hazards in dentistry.
or
Describe in detail about the effect of radiation on mucosa, salivary gland and bone.
or
Write short answer on effect of radiation on salivary glands
Answer. Study of the effects of ionizing radiation on the living system is called as radiation biology.
Read And Learn More: Oral Radiology Question And Answers
Harmful Effect of Radiation in oral cavity/oral Mucosa
The oral cavity is irradiated during the course of healing of radiosensitive oral malignant tumors, e.g. squamous cell carcinoma.
Oral Mucosa
- Oral mucous membrane contains the basal layer of differentiating inter mitotic cells which are highly radiosensitive at the end of second week of therapy, the mucous membrane begins to show areas of redness and inflammation, this state is called as “Mucositis.”
- Asthetherapycontinuesthemucousmembranebreaksdown with the formation of white or yellow pseudomembrane.
- At the end of therapy, the mucositis is severe, painful leading to difficulty in talking, eating and swallowing.
- After termination of therapy, the healing may be complete after about two months, but the mucous membrane tends to become thin, atrophic and relatively avascular. Secondary infection by Candida albicans is very common complication.
- Patient is usually prone to oral ulcerations and unable to tolerate dentures.
Radiation Effects on Taste Buds
- Taste buds are sensitive to radiation even therapeutic dose of radiation causes degeneration of taste buds.
- Loss of taste sensation occurs during 2nd and 3rd week of therapy.
- Loss of taste sensation can be partial or complete.
- Posterior two-third of the tongue when irradiated affects the bitter and acid flavors.
- Anterior one-thirds of the tongue when irradiated affects sweet and salty flavors.
Radiation Effects on salivary Glands
- Parenchymal component of the gland is sensitive to radiation.
- Glands demonstrate progressive fibrosis, adiposis, loss of fine vasculature.
- There is marked decrease in salivary flow.
- The composition of saliva is affected.
- There is increased concentration of sodium, chloride, calcium, magnesium ions and proteins.
- Saliva losses its lubricating properties.
- Mouth becomes dry and tender due to xerostomia.
- pH of saliva is decreased which may initiate decalcification of enamel.
Radiation Effects on teeth
Adult teeth are resistant to the effects of radiation.
Radiation caries
- Involve mainly cementum and dentin at cervical lesion.
- Dark pigmentation of crown.
- Superficial lesion affect buccal, incisal, palatal and occlusal surfaces.
During development
- Before calcification: There is complete destruction of tooth bud which results in partial anodontia.
- Once calcification starts: Hypoplastic changes seen.
- During root development: Retardation or loss of root development.
After Eruption
Radiation caries: It is a form of rampant caries; it is secondary to the change in saliva.
Radiation Effects on Bone
- Marrow is replaced by bone marrow and fibrous connective tissue.
- Endosteum becomes atrophic.
- Bone becomes hypovascular hypocellular and hypomineralized.
- The complication following irradiation, i.e. “osteoradionecrosis”.
- Necrosis of bone may result in nonhealing ulcer which may occur after tooth extraction.
- Lack of osteoblastic and osteoclastic activity in endosteum.
- Mandible affects more than maxilla.
Question 2. discuss in detail biological effects of radiation on human tissue.
Answer. Biological effects of radiation are considered under the following headings:
Radiation On Human Tissue Classification 1
Somatic: Effect of radiation which occurs in exposed individuals during their lifetime is known as somatic effect. Except the reproductive cells, all cells in the body are somatic cells.Biological effects of ionizing radiation are divided into two categories, i.e.
- Stochastic effect: This effect includes the increase in probability of occurrence of biological effect with the increasing absorbed dose rather than its severity. They are the direct effect of dose.
- Non-stochastic effect or deterministic effect: In this effect severity increases with increase in the absorbed dose in affected individual.
Genetic: It is the effect, which is manifested in future generation of exposed individuals. Reproductive cells are the genetic cells.
Radiation On Human Tissue Classification 2
- Acute or immediate effect: These are the effects which appear shortly after the exposure due to large dosage.
- Chronic or long-term effects: These effects get evident after a long period of time.
Radiation On Human Tissue Somatic Effects
Effect of radiation which occurs in exposed individuals during their lifetime is known as somatic effect.
Radiation On Human Tissue Somatic Stochastic Effect
- In these effects, probability of occurrence of change increases rather than the severity.
- Somatic stochastic effects are likely to occur and they are dose dependent.
- Threshold dose is no there for the stochastic effect.
- As body gets exposed to any amount of radiation, damaging effect can be induced.
- As low is the radiation dose less is the possibility of the cell to get damage.
- Example of this is radiation-induced cancer whose chances of occurrence increase due to greater exposure of a person or population to the radiation, this increases probability of cancer but not its severity.
Radiation On Human Tissue Non–stochastic Effects
- These are the effects which increase the probability of occurrence with increase in the radiation dose and consist of dose threshold below which the response cannot be seen.
- These effects occur specifically from high doses of radiation. Example is during radiotherapy procedure.
- Variousotherexamplesofnon-stochasticeffectsareulceration and desquamation of skin which leads to reddening of skin; damage to the connective tissue, blood vessels and glands; damage to alveolar bone; formation of cataract.
Radiation On Human Tissue Genetic Effects
- These effects are not appreciated in the person irradiated but are transferred to future generations.
- Genetic cells are the germ cells of reproductive organs. These cells get damage even in the very small doses.
- Radiation lead to fragmentation of chromosome as well as mutation in the genes of sexual cells and the mutant genes are passed onto next generation. Mutation indicates the change in gene of a cell.
- Due to mutation congenital abnormality in offspring of person irradiated may occur. Growth rate can also be diminished.
- Dose which causes doubling of all gene mutations is known as doubling dose.
- Damage can occur in any of the dominant or the recessive genes. Dominant effect is seen in the next generation while the recessive effect is seen after the several generations.
- Genetic damage is cumulative and is not repaired.
- Human embryo is most sensitive to radiation during 15–42 days of its term, so radiation is strictly avoided during the pregnancy.
- As human beings are exposed to heavy doses sterility occur in them.
- Beyond the age of reproduction, there is no genetic effect seen in human beings.
Radiation On Human Tissue Acute Effects
- Acute somatic effects are manifested in few hours to few days of acute irradiation and severity of effect depend on dose and dose rate.
- As per the latent period, effects are seen in minutes, days and weeks.
- Acute radiation effect is basically a short-term effect which occurs when large dose of radiation occur in short period of time, e.g. nuclear accident.
- These effects are not seen in dentistry as the diagnostic radiographs use 5 rad.
- Various examples of acute effects are:
- Skin: Excessive exposure can cause dermatitis. Repeated exposures leads to dryness of skin, erythema, thickening, desquamation and cracking of hands can also occur.
- Eyes: Radiation dose can lead to cataract and larger doses may detach retina.
- Nails: They get brittle, develop longitudinal fissures as well as ridges, finally nails get crumbled.
- Hair: Epilation of hairs occur by radiation. Hair loss can be permanent.
Radiation On Human Tissue Chronic Effects
- Chronic effects occur due to low level of irradiation for long time or by chronic irradiation.
- These effects to be manifested take years, decades or generations.
- Chronic effects depend on the extent of damage to the fine vasculature.
- Various examples of chronic effects are:
- Carcinoma: It is the earliest form of radiation-induced malignant tumor.
- Leukemia: It occurs due to primary or secondary radiation. Its incidence is seen in radiologists.
- Necrosis: It is commonly seen in the extracted socket after the radiation exposure.
Radiation On Human Tissue Pathogenesis of Chronic effect
Question 3. Write short note on consequences of unprotected radiation in major salivary gland.
Answer. Following are the consequences of unprotected radiation on major salivary gland:
- Parenchymal component of the gland is sensitive to radiation.
- Glands demonstrate progressive fibrosis, adiposis, loss of fine vasculature and simultaneous parenchymal degeneration.
- There is marked decrease in salivary flow.
- Composition of saliva is affected.
- There is increased concentration of sodium, chloride, calcium, magnesium ions and proteins.
- Saliva losses its lubricating properties.
- Mouth becomes dry and tender due to xerostomia.
- pH of saliva is decreased which may initiate decalcification of enamel.
- A compensatory hypertrophy of salivary gland may take place and the xerostomia may subside after 6–12 months after therapy. The xerostomia which persist beyond a year is less likely to show return to normal.
Question 4. Write short note on osteoradionecrosis.
Answer. Osteoradionecrosis is a radiation-induced pathologic process characterized by the chronic and painful infection and necrosis is accompanied by the late sequestration and sometimes permanent deformity.
This is one of the most serious complications of radiation to head and neck seen frequently today because of better treatment modalities and prevention.
Factors Leading to osteoradionecrosis
- Irradiation of an area of previous surgery before adequate healing had taken place.
- Irradiation of lesion in close proximity to bone.
- Prolong oral hygiene and continued use of irritants.
- Poor patient’s corporation in managing irradiated tissues.
- Surgery in irradiated area.
- Failure to prevent trauma to irradiated bony areas.
Pathogenesis
Osteoradionecrosis Clinical Features
- Mandible is more commonly affected as compared to maxilla due to low vascularity. Mostly the posterior region of mandible is affected.
- Presence of trismus, pyrexia and halitosis.
- There is also presence of intermittent swelling with drainage of pus extraorally.
- Pain is severe which continue from weeks to months.
- Persistently draining sinuses are present.
- Bone exposure is the hallmark of osteoradionecrosis.
- As the bone become necrotic due to lack of supply of blood sequestrum is formed.
- Pathological fracture of bone is a common feature.
Osteoradionecrosis Treatment
- Debridement of necrotic tissue should be done along with removal of sequestrum.
- Administration of intravenous antibiotic and hyperbaric oxygen therapy are essential.
- Maintenance of oral hygiene is necessary.
Question 5. What are hazards of radiations? discuss how to get protection from the same.
or
Describe radiation protection measures.
or
Discuss in detail about various radiation protection measures.
or
Write in detail about radiation hazards.
Answer.
Hazards of Radiation
Radiation hazard on skin
The reaction of the skin to radiation may be categorized as:
- Early or acute signs:
- Increased susceptibility to chapping.
- Intolerance to surgical scrub.
- Blunting and leveling of finger ridges.
- Brittleness and ridging of finger nails.
- Late or chronic signs:
- Loosening of hair and epilation.
- Dryness and atrophy of skin, due to destruction of the sweat glands.
- Progressive pigmentation, telangiectasis and keratosis.
- Indolent type of ulcerations.
- Possibility of malignant changes in tissue.
Radiation hazard on Eyes
- Epilation of eyelashes.
- Inflammation, fibrosis and decreased flexibility of the eyelid.
- Damage to the lacrimal glands, leading to dryness.
- Ulceration of the cornea.
- Initiation of cataract formation from the periphery towards the center.
Radiation hazard on Ears
- Columnar epithelium of the middle ear may be desquamated.
- Edema of the mucosa and collection of sterile fluid in the middle ear, which leads to obstruction of the eustachian tube known as radiation otitis media.
- Deafness due to rupture of eardrums.
Radiation hazard on Reproductive system
- On Testicles:
- Suppression of germinal activity.
- Alteration in fertility.
- Functional changes in the offspring may be seen.
- On Ovary:
- The various cells respond differently to irradiation.
- Increase in frequency of hemangioma in children receiving dose of radiation in utero.
Radiation hazard in oral cavity
Oral Mucosa
- Oral mucous membrane contains the basal layer of differentiating inter-mitotic cells which are highly radiosensitive at the end of second week of therapy the mucous membrane begins to show areas of redness and inflammation, this state is called as “Mucositis.”
- As the therapy continues the mucous membrane breaks down with the formation of white or yellow pseudomembrane.
- At the end of therapy the mucositis is severe, painful leading to difficulty in talking, eating and swallowing.
- After termination of therapy, the healing may be complete after about two months, but the mucous membrane tends to become thin, atrophic and relatively avascular. Secondary infection by candida albicans is very common complication.
- Patient is usually prone to oral ulcerations and unable to tolerate dentures.
Effects on Taste Buds
- Taste buds are sensitive to radiation even therapeutic dose of radiation causes degeneration of taste buds.
- Loss of taste sensation occurs during 2nd and 3rd week of therapy.
- Loss of taste sensation can be partial or complete.
- Posterior two-third of the tongue when irradiated effects the bitter and acid flavors.
- Anterior one-third of the tongue when irradiated effects sweet and salty flavors.
Effects on Salivary Glands
- Parenchymal component of the gland is sensitive to radiation.
- Glands demonstrate progressive fibrosis, adiposis, loss of fine vasculature.
- There is marked decrease in salivary flow.
- The composition of saliva is affected.
- There is increased concentration of sodium, chloride, calcium, magnesium ions and proteins.
- Saliva losses its lubricating properties.
- Mouth becomes dry and tender due to xerostomia.
- pH of saliva is decreased which may initiate decalcification of enamel.
Effects on Teeth
Adult teeth are resistant to the effects of radiation.
Radiation Caries
- Involve mainly cementum and dentin at cervical lesion.
- Dark pigmentation of crown.
- Superficial lesion affects buccal, incisal, palatal and occlusal surfaces.
During Development
- Before calcification: There is complete destruction of tooth bud which results in partial anodontia.
- Once calcification starts: Hypoplastic changes seen.
- During root development: Retardation or loss of root development.
After Eruption
Radiation caries: It is a form of rampant caries; it is secondary to the change in saliva.
Effects on Bone
- Marrow is replaced by bone marrow and fibrous connective tissue.
- Endosteum becomes atrophic.
- Bone becomes hypovascular hypocellular and hypomineralized.
- The complication following irradiation, i.e. “osteoradionecrosis”.
- Necrosis of bone may result in nonhealing ulcer which may occur after tooth extraction.
- Lack of osteoblastic and osteoclastic activity in endosteum.
- Mandible affects more than maxilla.
Acute Radiation syndrome
When the whole body is exposed to low or moderate doses of radiation, a very characteristic change are seen known as acute radiation syndrome. This can be followed by death within a month. If an individual survive, it can show late somatic changes which are:
- Prodromal syndrome (1 to 2 Gy): Shortly after exposure patient may develop nausea, vomiting, diarrhea and anorexia.
- Latent period: It is a period of apparent well being, the extent of which is dose related. Symptoms follow the latent period when the individuals are exposed in the lethal range (approximately 2–5 Gy) or the supralethal range (more than 5 Gy).
- Bone marrow (hemopoietic) syndrome {2 to 7 Gy): Here severe damage may be caused to the circulatory system. The bone marrow being radiosensitive, results in fall in the number of granulocytes, platelets and erythrocytes. Clinically, this is manifested as lymphopenia, granulocytopenia and or hemorrhage due to thrombocytopenia and anemia due to depletion of the erythrocytes.
- Gastrointestinal syndrome (7 to 15 Gy): This causes extensive damage to the gastrointestinal tract, leading to anorexia, nausea, vomiting, severe diarrhea and malaise. Injury to the basal cell epithelial cells of the intestines causes denuded mucosal surfaces, leading to loss of plasma and electrolytes, hemorrhage and ulcerations leading to diarrhea, dehydration and loss of weight. Finally, leading to septicemia unusually leading to death.
- Cardiovascular and central nervous system syndrome (more than 50 Gy): This produces death within one or two days. Individuals show intermittent stupor, incoordination, disorientation and convulsions suggestive of extensive damage to the nervous system.
Protection from hazards of Radiation
Protection of Patient
- X-ray machine: Good machines of reputed companies should be used.
- Selection of film: F- and E-speed films are used as they are of good quality and are highly sensitive. E speed films or Ekta speed films reduce exposure to 40%.
- Focal spot film distance: Longer is the focal spot film distance decrease is in the exposed tissue volume.
- Source skin distance: Increase in the source skin distance reduces the size of beam and reduces the volume of tissue irradiation which decreases the patient dose.
- Filtration: Low energy X-ray beam is removed by the filtration. As these X-rays do not contribute to the image formation they should be removed before they reach to the patient as they lead to the radiation exposure.
- X-ray collimation: It prevent the scattering. Beam should be collimated so that it is not more than 7 cm in diameter at the face of patient. Rectangular collimators should be preferred as they reduce the amount of tissue radiation.
- Intensifying screen: Use of rare earth screen decreases dosage for extraoral films.
- Grid: Grid decreases the fogginess of film due to the secondary radiation, this reduces the need for repeating the film.
- Kilovoltage: Operation of X-ray unit should be done at 60 to 90 kVp. X-ray beam of low kilovoltage leads to the higher patient doses, mainly to skin.
- Position-indicating devices: A 12 to 16 inches long position indicating device reduces exposure to patient as compared to short position indicating device. Open ended, circular or rectangular lead-lined cylinders are preferred to direct the X-ray beam.
- Lead aprons should be used who have lead content equivalent to 0.25 mm aluminum which is to be worn by patient during taking the radiograph.
- Thyroid collars should be weared to protect thyroid gland from radiation.
- Film-holding devices: They stabilize the X-ray film in mouth and so the hands of patient are not exposed to radiation.
- RVG: It decreases the dose of radiation required in IOPA.
Protection of the operator
- Operator should not hold X-ray film in mouth of patient at the time of exposure.
- Operator should not stabilize the X-ray machine at the time of exposure.
- Operator should not stand in the path of primary radiation.
- Operator should have to stand behind a lead barrier which consists of 0.5 mm lead equivalent during the exposure.
- Operator should stand 6 feet away from primary X-ray beam.
- Operator should have radiation exposure monitored by personal monitoring devices or film badges.
- Operator should work on the rotation of duties, to avoid accidental exposure.
- The maximum permissible dose for whole body exposure per year for occupationally exposed individual is 5 rem. It should be noted that operator should not go above the range of maximum permissible dose.
Protection of other Persons
- Persons who are needed should stay in the room.
- Conch shell design of operatory area is recommended for protection of people in the surrounding areas.
- X-ray tube is away from doorways to avoid the accidental exposure.
- Monitoring of the radiation exposure to room and adjacent office premises is done.
- Walls of X-ray shooting room consists of either the barium plaster or the increased thick walls which consists of additional layer of bricks.
- Displaying of warning signs and caution should be done.
- Regular radiation surveys should be carried out at regular intervals to detect the amount of radiation exposure
Question 6. describe in detail about hazards of radiation of oral cavity and add a note on radiation protection.
Answer.
Hazards of Radiation of oral cavity
Oral Mucosa
- Oral mucous membrane contains the basal layer of differentiating inter mitotic cells which are highly radiosensitive at the end of second week of therapy the mucous membrane begins to show areas of redness and inflammation, this state is called as “Mucositis.”
- As the therapy continues the mucous membrane breaks down with the formation of white or yellow pseudomembrane.
- At the end of therapy, the mucositis is severe, painful leading to difficulty in talking, eating and swallowing.
- After termination of therapy, the healing may be complete after about two months, but the mucous membrane tends to become thin, atrophic and relatively avascular. Secondary infection by Candida albicans is very common complication.
- Patient is usually prone to oral ulcerations and unable to tolerate dentures.
Hazards of Radiation of oral cavity Effects on Taste Buds
- Taste buds are sensitive to radiation even therapeutic dose of radiation causes degeneration of taste buds.
- Loss of taste sensation occurs during 2nd and 3rd week of therapy.
- Loss of taste sensation can be partial or complete.
- Posterior two-third of the tongue when irradiated effects the bitter and acid flavors.
- Anterior one-third of the tongue when irradiated effects sweet and salty flavors.
Hazards of Radiation of oral cavity Effects on salivary Glands
- Parenchymal component of the gland is sensitive to radiation.
- Glands demonstrate progressive fibrosis, adiposis, loss of fine vasculature.
- There is marked decrease in salivary flow.
- The composition of saliva is affected.
- There is increased concentration of sodium, chloride, calcium, magnesium ions and proteins.
- Saliva losses its lubricating properties.
- Mouth becomes dry and tender due to xerostomia.
- pH of saliva is decreased which may initiate decalcification of enamel.
Hazards of Radiation of oral cavity Effects on teeth
Adult teeth are resistant to the effects of radiation.
Hazards of Radiation of oral cavity Radiation Caries
- Involve mainly cementum and dentin at cervical lesion.
- Dark pigmentation of crown.
- Superficial lesion affects buccal, incisal, palatal and occlusal surfaces.
During Development
- Before calcification: There is complete destruction of tooth bud which results in partial anodontia.
- Once calcification starts: Hypoplastic changes seen.
- During root development: Retardation or loss of root development.
After Eruption
Radiation caries: It is a form of rampant caries; it is secondary to the change in saliva.
Effects on Bone
- Marrow is replaced by bone marrow and fibrous connective tissue.
- Endosteum becomes atrophic.
- Bone becomes hypovascular hypocellular and hypomineralized.
- The complication following irradiation, i.e. “osteoradionecrosis”.
- Necrosis of bone may result in nonhealing ulcer which may occur after tooth extraction.
- Lack of osteoblastic and osteoclastic activity in endosteum.
- Mandible affects more than maxilla.
Radiation Protection
Radiation protection is divided into three parts, i.e.
- Protection of patient from radiation
- Protection of operator from radiation
- Protection of other persons from radiation
Protection of Patient
- X-ray machine: Good machines of reputed companies should be used.
- Selection of film: F- and E-speed films are used as they are of good quality and are highly sensitive. E speed films or Ekta speed films reduce exposure to 40%.
- Focal spot film distance: Longer is the focal spot film distance decrease is in the exposed tissue volume.
- Source skin distance: Increase in the source skin distance reduces the size of beam and reduces the volume of tissue irradiation which decreases the patient dose.
- Filtration: Low energy X-ray beam is removed by the filtration. As these X-rays do not contribute to the image formation they should be removed before they reach to the patient as they lead to the radiation exposure.
- X-ray collimation: It prevent the scattering. Beam should be collimated so that it is not more than 7 cm in diameter at the face of patient. Rectangular collimators should be preferred as they reduce the amount of tissue radiation.
- Intensifying screen: Use of rare earth screen decreases dosage for extraoral films.
- Grid: Grid decreases the fogginess of film due to the secondary radiation, this reduces the need for repeating the film.
- Kilovoltage: Operation of X-ray unit should be done at 60 to 90 kVp. X-ray beam of low kilovoltage leads to the higher patient doses, mainly to skin.
- Position-indicating devices: A 12 to 16 inches long position indicating device reduces exposure to patient as compared to short position indicating device. Open ended, circular or rectangular lead-lined cylinders are preferred to direct the X-ray beam.
- Lead aprons should be used who have lead content equivalent to 0.25 mm aluminum which is to be worn by patient during taking the radiograph.
- Thyroid collars should be weared to protect thyroid gland from radiation.
- Film-holding devices: They stabilize the X-ray film in mouth and so the hands of patient are not exposed to radiation.
- RVG: It decreases the dose of radiation required in IOPA..
Protection of the operator
Operator should not hold X-ray film in mouth of patient at the time of exposure.
Operator should not stabilize the X-ray machine at the time of exposure.
Operator should not stand in the path of primary radiation.
Operator should have to stand behind a lead barrier which consists of 0.5 mm lead equivalent during the exposure.
Operator should stand 6 feet away from primary X-ray beam.
Operator should have radiation exposure monitored by personal monitoring devices or film badges.
- Operator should work on the rotation of duties, to avoid accidental exposure.
- The maximum permissible dose for whole body exposure per year for occupationally exposed individual is 5 rem. It should be noted that operator should not go above the range of maximum permissible dose.
Protection of other Persons
- Persons who are needed should stay in the room.
- Conch shell design of operatory area is recommended for protection of people in the surrounding areas.
- X-ray tube is away from doorways to avoid the accidental exposure.
- Monitoring of the radiation exposure to room and adjacent office premises is done.
- Walls of X-ray shooting room consists of either the barium plaster or the increased thick walls which consists of additional layer of bricks.
- Displaying of warning signs and caution should be done.
- Regular radiation surveys should be carried out at regular intervals to detect the amount of radiation exposure
Question 7. Write short note on radiation caries.
Answer. Radiation caries occurs in the patients who receive radiation therapy in head and neck region.
- Such patient has got caries because they suffer from loss of salivary gland function which leads to xerostomia. This xerostomia leads to the rampant tooth destruction which is known as radiation caries.
- Destruction in radiation caries start at the cervical region and aggressively approach the entire tooth which causes loss of complete crown and only the root fragments left in the jaw.
- In radiograph, the radiation caries appear as dark radiolucent shadow which appear at the neck of teeth and is more apparent towards mesial and distal surfaces.
- Clinically radiation caries is of three types, i.e.
- Type 1: Involving cementum and dentin in cervical areas. Lesion progresses around the tooth circumference and causes amputation of crown.
- Type 2: Generalized superficial lesion attacking buccal, occlusal, incisal and palatal surfaces of teeth.
- Type 3: Dark pigmentation of crown.
Radiation Caries Treatment
- Daily apply viscous topical 1% neutral sodium fluoride gel in custom made trays.
- Dietary sucrose is avoided and cariogenic foods should be restricted.
- Affected tooth should be restored and oral hygiene should be maintained.
Question 8. Write in detail about radiolysis of water.
Answer.
Radiolysis of Water
- Human tissues have 85% of water, on irradiation most of its energy will initially get deposited in the water and only small proportion is taken up by bone, skin etc.
- When water molecules get irradiated, ionization takes place as H2O losses an electron and become H2O+
- H2O → H2O+ + e–
- Electron can be captured by another H2O molecule to produce negative molecule
- H2O + e– → H2O–
- This completes the formation of an ion pair.
- Stability of molecule is maintained till now, this comes under the physical changes.
- Chemical change follows as mentioned:
- H2O+ → H+ + OH+
- H2O– → H– + OH–
- Free radicals have an odd electron which is the highly reactive entities.
- These have the lifetime of one microsecond and attack most of the organic substances. Free radicals can react with proteins, carbohydrates, hormones and enzymes which causes their breakdown.
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