Definitions in Dentistry Part 2

PLAQUES
Solid, elevated, flat-topped, plateau like lesions that cover a fairly large area, they may arise from papules that join together.
Eg: psoriasis ,chronic eczematous dermatitis

WHEALS
Wheals are raised flesh colored or erythematous papules or plaques that are transient lesions . Wheals generally last than 24hrs ,during which they may change shape and size.
Eg:urticaria, angioedema

SCALES
Derive from the outer layer of epidermis, which is imperceptibly shed daily.
Eg:ichthyosis, seborrheic dermatitis and psoriasis.

CRUSTS[SCABES]
Dried secrtions of the body. Eg. blood , serum or other dried exudate.
Eg: Bloody crusts in Erythyma Multiforme, infected insect bites, impetigo.

EROSIONS
Is a shallow moist ,red lesions often caused by rupture of vesicles or bullae as well as trauma, representing a loss of covering epithelium down to and involving stratum germinativum but without any loss of deeper structures.
Eg: erosive lichen planus, traumatic erosions

ULCERS
Is a break or discontinuity in the surface epithelium of mucus membrane or skin due to pathologic processes with degeneration of connective tissue cells. The base of ulcer may be necrotic, granular, purulent or covered with mucous.
Eg:traumatic ulcer, tubercle’s ulcer

FISSURES
Fissures are linear ulcers or cracks in the skin.
Eg: eczema of finger.

PURPURA
Reddish to purple flat lesions caused by blood from vessels leaking into subcutaneous tissue. Eg. Thrombocytopenic purpura

PETECHIAE
Petechiae are purpuric lesions of 1cm or 2cm in diameter.

ECCHYMOSIS
Ecchymosis are purpuric lesions of more than 2cm in diameter.

Hematoma
Hematoma is a large clot resulting from blood released into the tissue from a ruptured blood vessels.

SINUS
Sinus is a blind epithelized tract which connects a pathological cavity to the epithelial surfaces.

FISTULA
It is a communicating track between a hollow viscus and the skin{external fistula} and between the two hollow viscera {internal fistula}.the track is lined granulation tissue.

RADIOLOGY
That branch of the health sciences dealing with radioactive substances and radiant energy and with the diagnosis and treatment of disease by means of both ionizing (eg: X-rays) and non – ionizing (eg: Ultra sound radiation)

Radiotherapy
Is the treatment of disease by ionizing radiation

Interstitial radiotherapy:
That administrated with radioactive element contained in devices inserted directly into the tissues

RADIOLUCENT
Permitting the passage of roentgen rays or other forms of radiant energy with little attenuation. Radiolucent areas appear dark on the exposed film

RADIO-OPAQUE
not penetrable by x-ray or other forms of radiant energy radio opaque appear light or white on the exposed film.

RADIOGRAPHIC CONTRAST: is defined as the difference in densities between various regions on a radiographs.
RADIOGRAPHIC DENSITY: it is the overall degree of darkening of the dental x-ray film.

ATOMIC NUMBER :The number of protons in the neutrons in the nucleus of an atom.
ATOMIC MASS NUMBER: sum of number of protons and number of neutrons in an atom.
ISOTOPES: atoms with same atomic number but with different atomic mass numbers.
RADIOISTOPES:isotopes with unstable nuclie which undergo radioactive disintegration.
IONISATION:
the process of converting atoms into ions.
RADIATION:
transmission of energy through space and matter.
ACUTE RADIATION SYNDROME:
when whole body is exposed to low or moderate doses of radiation, there are characteristic changes called as acute radiation syndrome.
RADIATION BIOLOGY:
Is the study of the effects of ionizing radiation on living system.
DOSIMETRY :Determing the quantity of radiation exposure or dose is termed dosimetry.
DOSE:dose is used to describe the amount of energy absorbed per unit mass at the site of interest.
EXPOSURE:is a measure of radiation based on its ability to produce ionization in air under standard conditions of temperature and pressure.

SPEED
is the amount of radiation required to produce a radiographic film of standard density.
SHARPNESS
Sharpness is the degree to which the image reveals the differential at density boundaries
RESOULTION
Resolution or resolving power is the ability of a radiographs to record separate structures that are close together.
IMAGE CLARITY:
Image clarity is the overall appearance of a radiographs and the clinicians subjective judgment of its appearance.

FILTRATION
The passage of a liquid through a filler, accomplished by gravity
Pressure ,or vacuum (Suction) In radiology: the use of solid screen usually made of metal (aluminum, copper, tin, lead etc) to absorb beta particles and Photons of longer wavelengths.

Collimation
Collimation means to shape an x-ray beam usually by the use of a metallic barrier with an aperture in the middle.

Reduces patient exposure

Increases film quality

GRID
Grid is defined as that radiographic accessory which when placed between the patient and the film, as close as possible to the latter, helps in reducing the scattered radiation.

INTENSIFYING SCREEN
Intensifying screen are those radiographic axcillaries which use the principle of fluorescence to obtain a better image with lesser amount of x-ray exposure.

X-RAY FILM
X-ray film is a type of photographic film that is composed of two principal components.
Emulsion:sensitive to x-rays and visible light and records the radiographic image
Base:supporting material onto which the emulsion is coated.

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