intra-oral tech-errors学会看拍牙片.pptVIP

Foreshortening Foreshortening Too much vertical angulation. (The arrow points to the end of the tooth; the white lines represent the actual length of the tooth). Double Exposure Caused by inadvertently using the same film to expose two different areas of the mouth Double exposure Double exposure Patient Movement Results in a blurring or apparent double image of the teeth and surrounding structures. Slight movement of the tubehead, in the absence of patient movement, will not affect the images on the film. Patient movement. Images of all structures on film are blurred. * Intraoral Technique Errors The following slides identify the most common errors seen when taking intraoral radiographs. Film Placement Errors Anterior-posterior placement Vertical placement (too far above or below occlusal plane) Film tipping Poor film placement. (too ant. for PM, too post. for molar) AP Incorrect film placement Premolar bitewing, too posterior Molar bitewing, too anterior Film tipped Film tipped Film tipped (as patient closed, top edge of film caught palatal gingiva, forcing film down) 1/4” of film beyond occlusal Patient not biting on biteblock (see next slide). Apices of incisors cut off. Patient not biting on biteblock Cone Cutting X-ray beam not centered on film, leaving part of film unexposed. Unexposed part of film (below dotted line) Cone Cutting (paralleling technique) Improper instrument assembly (ring upside down) (side view) Cone cutting Cone cutting (bisecting angle technique) (bitewing technique) Cone Cutting Cone cutting Overlap (Incorrect horizontal angulation) Correct Horizontal Angulation X-ray beam directed perpendicular to a line connecting the buccal surfaces of the teeth (dotted line below). When using the paralleling instrument, the film should be parallel to this line. Incorrect Horizontal Angulation film If the x-ray beam is not perpendicular to the line connecting the buccal surfaces