40 Questions
What is the study of the effects of ionizing radiation on living systems?
Radiobiology
Which of the following is a type of effect of radiation on tissues and organs?
Deterministic Effect
What is the result of DNA changes caused by radiation?
Mutations
What is the term for the effects of radiation that occur at low doses and have a random probability of occurrence?
Stochastic Effects
What is the term for the effects of radiation that occur at high doses and have a predictable outcome?
Deterministic Effects
What is the term for the short-term effects of radiation on the body?
Short-Term Effects
What is the term for the effects of radiation on the embryo or fetus?
Radiation Effects on Embryos and Fetuses
What is the term for the use of radiation to treat diseases in the oral cavity?
Radiotherapy
What is the typical duration of radiation therapy to the head and neck that can cause severe oral complications?
6 weeks
Which salivary gland is most radiosensitive?
Parotid gland
What is the typical outcome of a 60 Gy dose of radiation to the salivary glands?
Complete loss of saliva flow
What is xerostomia?
Dry mouth
What is the typical time course of oral complications after radiotherapy?
Most severe during the first few weeks, decreasing over time
What are the long-term risks of radiation therapy to the head and neck?
Lifelong oral complications
What is the dose range that the major salivary glands are sometimes unavoidably exposed to during radiotherapy for cancer in the oral cavity or oropharynx?
20 to 30 Gy
What is the effect of radiation therapy on taste and healing of mucositis?
Recovery of taste, healing of mucositis
What is a common complaint during the second or third week of radiotherapy?
Loss of taste acuity
Which flavors are more severely affected when the posterior two thirds of the tongue is irradiated?
Bitter and acid
What is the estimated decrease in taste acuity during radiotherapy?
By a factor of 1000 to 10,000
How long does it typically take for taste loss to recover after radiotherapy?
60 to 120 days
What is the primary cause of taste loss during radiotherapy?
Degeneration of taste buds
Which part of the tongue is responsible for detecting sweet and salt flavors?
Anterior third
What complication of radiotherapy can partly account for the reduction in taste acuity?
Hyposalivation
Is taste loss during radiotherapy reversible?
Yes, it is reversible
What is the characteristic of radiation caries that distinguishes it from other types of caries?
Rapid course and widespread attack
What is the best method of reducing radiation caries?
Daily application of a viscous topical 1% neutral sodium fluoride gel
What is a consequence of radiation caries on the periapical bone?
Increased risk of periapical inflammatory lesions
What is the effect of radiation therapy on the salivary glands?
Decreased flow and pH
What is a characteristic of teeth that have undergone radiation therapy?
They erupt, even if rootless
What is the relationship between the dose of radiation and the severity of damage to the tooth?
The severity of damage is directly proportional to the dose of radiation
What is the effect of radiation on the oral flora?
Increased growth of Streptococcus mutans, Lactobacillus, and Candida
What is the characteristic of the lesions that develop in patients with radiation caries?
They may progress around the teeth circumferentially
What is a characteristic of saliva in individuals with xerostomia?
Low concentration of Ca2+ ion
What is essential for patients undergoing radiation therapy to prevent radiation caries?
All of the above
What is the result of radiation on teeth, especially at doses greater than 30 Gy?
Flaking of enamel
Why are teeth with gross caries or periodontal involvement often extracted before irradiation?
To prevent radiation-induced damage to surrounding tissues
What is the primary damage to mature bone in the mandible or maxilla due to radiation?
Damage to the vasculature of the periosteum and cortical bone
What is the characteristic of the most common type of radiation caries?
Widespread superficial lesions on buccal, occlusal, incisal, and palatal surfaces
Why is patient cooperation in maintaining oral hygiene extremely important?
Because radiation caries is a lifelong threat
What is the minimum dose of radiation that can cause destruction of teeth, especially in areas of occlusal loading or stress?
30 Gy
Study Notes
Radiation Chemistry and Biology
- Radiobiology is the study of the effects of ionizing radiation on living systems.
- Ionizing radiation affects living systems through direct and indirect effects.
Direct and Indirect Effects
- Direct effects: radiation interacts with DNA, causing damage to cellular structures.
- Indirect effects: radiation interacts with water molecules, generating free radicals that damage cells.
Deterministic and Stochastic Effects
- Deterministic effects: effects of radiation on tissues and organs, often leading to cell death.
- Stochastic effects: random, long-term effects of radiation, including carcinogenesis and heritable effects.
Effects on Tissues and Organs
- Oral complications of radiotherapy include mucositis, taste loss, hyposalivation, and radiation caries.
- Salivary glands are radiosensitive, leading to xerostomia and alterations in saliva composition.
- Taste loss is reversible, but recovery takes 60-120 days.
Effects on Cells
- Radiation affects intracellular structures, including DNA, and disrupts cell replication.
Radiotherapy in the Oral Cavity
- Radiation therapy for cancer in the oral cavity or oropharynx often exposes salivary glands to 20-30 Gy.
- Parenchymal component of salivary glands is radiosensitive, leading to marked and progressive loss of saliva.
Radiation Caries
- Radiation caries is a rampant form of dental decay that may occur in individuals receiving radiotherapy.
- Causes of radiation caries include changes in salivary glands and saliva, including reduced flow, decreased pH, and altered flora.
- Daily application of 1% neutral sodium fluoride gel and excellent oral hygiene are essential in preventing radiation caries.
Osteoradionecrosis
- Susceptibility to osteoradionecrosis increases with radiation dose and duration.
- Radiation-induced damage to the vasculature of the periosteum and cortical bone leads to osteoradionecrosis.
This quiz covers the topics of radiation chemistry, deterministic effects on tissues and organs, and whole-body irradiation in biology.
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