19 AUG 2020 · RADIATION PHYSICS Cathode Both made of tungsten * Anode  Xray produced at anode by an effect called BRHAMSTALUNG effect or CHRACTERISTIC EFFECT (interaction of high speed with tungsten nuclei)

19 AUG 2020 · FLITER  Filters away the low energy x-rays  Made of Aluminium  From x-ray cone COLLIMATOR  Absorbs X-rays in unwanted direction  Made of lead  Circular tube  Rectangular collimator is best due to less patient exposure = 7mm diameter QN

19 AUG 2020 · LESS EXPOSURE FACTOR FOR PATIENT  Decrease current decrease Time  Increase KVP (potential) (kilovolt potential) If Kvp increased – speed of e increses and more energy photons are formed, thus penetrate the body creating images INTENSIFYING SCREENS Decreases patient exposure , but decreases film contrast ∴ contraindicated intraorally (IOPA) - made of rare earth material QN FACTORS DECREASING XRAY EXPOSURE TO TRACHEA Lead apron Thyroid collar Position — distance rule  6 feet away position ** (5 ft for cephalometry)  How to increase the image quality – increase the distance between object & the cone**  90° - 130° angle ALARA – As Low As Reasonably Achievable

19 AUG 2020 · C/F SEEN INTRA ORALLY — AS AFTER EFFECT OF RADIATION 1. Mucositis – inflammation of mucosa 2. Radiation caries – mainly due to radiation injury to parotid gland, causing smooth surface caries due to xerostomia 3. c/f – — blackish discolouration of crown --- affects labial + lingual surface of all teeth +cervical third — patient also gives h/s of cancer – suspect radiation therapy Rx – 1% NaF every day QN Preventive method done soon after radiation

19 AUG 2020 · TYPES OF RADIOGRAPHY IOPA  Intra – oral periapical radiograph  Function – to determine o Working length o Periapical pathosis QN o External root resorption  Commonly used size – size 2  In anterior teeth – proximal caries – IOPA is used QN  If improper horizontal angulation – OVERLAPPING PROXIMAL SURFACES

19 AUG 2020 · BISECTING ANGLE  The film is placed as close as possible to the surface.  Central ray is directed perpendicular to the imaginary bisector.  Advantage – shorter exposure time, more patient acceptance cos we don’t need a beam aligner ring.  Disadvatage – image distortion/ magnification is possible. Angulation problems maybe, coz beam aligner right. PARALELLING BEAM  It is easy to place using a film holder.  Central ray is perpendicular to both recptor & long axis of the tooth.  To maintain the parallelism between the object & the film, - INCREASE TARGET TO OBJECT DISTANCE *  Advantage – more accurate & Simplicity (no extra calculations required)  Disadvantages – patient discomfort.

19 AUG 2020 · BITE WING  Function – proximal caries** best detected by bitwing – post (whereas anterior proximal caries best – IOPA) ***  Vertical angulation for a bitewing radiograph is: 10 degree downward.  Determination of 2° caries  Crest of interdental bone  Incorrect horizontal angulation will lead to overlapping of proximal surface of teeth

19 AUG 2020 · OCCLUSAL  Commonly used in right angled technique  Function to determine o Mesiodense o Mandibular tori o Sialolithiasis in Submandibular duct o (other sialolithiasis best detected by – radiography)  It is the only radiograph can be done intraorally in TRISMUS cases QN

19 AUG 2020 · OPG  ORTHOPANTAMOGRAM  Most commonly used for dental implants QN ( BEST is CBCT )  ANATOMICAL LANDMARKS o Mental foramen – radiolucency at the apex of premolar o Zygoma – J shaped radio opacity at 1st or 2nd max molar o Sinus lining o Mandibular canal o Vertebrae – cervical o Styloid process o Ear lobe o Hyoid ERRORS IN OPG HEAD placed ———— ———— APPEARANCE a) Anterior to focal trough ** Blur and narrow b) Posterior to focal trough Blur and Magnified

19 AUG 2020 · HEAD tilted ————————— APPEARANCES a) Downward smiling appearance to OPG  Rx – tilt chin up*** b) Upward reverse curve / flat curve in OPG  Rx – tilt chin DOWN*** TONGUE – a) OBSCURES THE APICES OF MAX TEETH – SO MUST BE PLACED ON THE PALATE TO AVOID THIS !**