intraoraltecherrors学会看拍牙片.ppt

Intraoral Technique ErrorsThe following slides identify the most common errors seen when taking intraoral radiographs.Film Placement ErrorsAnterior-posterior placementVertical placement(too far above or below occlusal plane)Film tipping Poor film placement.(too ant.for PM,too post.for molar)APIncorrect film placementPremolar bitewing,too posteriorMolar bitewing,too anteriorFilm tippedFilm tippedFilm tipped(as patient closed,top edge of filmcaught palatal gingiva,forcing film down)1/4”of film beyond occlusalPatient not biting on biteblock(see next slide).Apices of incisors cut off.Patient not biting on biteblock ConeCutting X-ray beam not centered on film,leaving part of film unexposed.Unexposed part of film (below dotted line)ConeCutting(paralleling technique)Improper instrument assembly(ring upside down)(side view)Cone cuttingCone cutting(bisecting angle technique)(bitewing technique)ConeCutting Cone cutting Overlap(Incorrect horizontal angulation)Correct Horizontal AngulationX-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 AngulationfilmIf the x-ray beam is not perpendicular to the line connecting the buccal surfaces of the teeth,overlap between the buccal surface of one tooth and the lingual surface of the adjacent tooth occurs(see next slide).Overlap(incorrect horizontal)lingualbuccalOverlap of crowns(black arrows)and roots(red arrow)All contacts overlappedGeneralized overlapNot a technique error.Overlapped contact(arrow above)is caused by one of the molars being out of normal alignment;all other contact areas are open.Reversed FilmThe all-white side of the film should face the teeth.When placing the film in the biteblock of the paralleling instrument(periapical or bitewing),the all-white side of the film should face the ring.When using stick-on tabs for bitewings,the tabs should be placed on the all-white side of the film.Reversed film.The lead foil,which is embossed with a pattern and is normally behind the film when positioned properly,is now in front of the film,producing the tire-track pattern seen on the left side of the film.The film is also lighter than it should be.Vertical Angulation ErrorsResults in an image of the tooth that is longer or shorter than the actual tooth.Primarily seen when using the bisecting angle technique.Elongation ElongationNot enough vertical angulation.(The black arrow points to the end of tooth image;the white lines represent the actual length of the tooth).Foreshortening ForeshorteningToo much vertical angulation.(The arrow points to the end of the tooth;the white lines represent the actual length of the tooth).Double ExposureCaused by inadvertently using the same film to expose two different areas of the mouthDouble exposureDouble exposure Patient MovementResults 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.Patient or film movement.Patient may have opened mouth slightly during the exposure,allowing the film to move and creating the double image.(May be confused with double exposure).Patient movement(see explanation on previous slide).Failure to removeappliances,glassesFailure to remove glassesFailure to remove partial dentureMiscellaneous errorsExposure levelsoverexposure (too dark)underexposure (too light)just right Film bending Most frequently caused by placing the finger in an unsupported area while using the bisecting angle technique.Most obvious in canine region on this film,where root curves off of film.Note hypercementosis on root of second premolar(first premolar is missing).Excessive film softening(black lines)PIDBeam directed through top of thyroid collar.Beam blocked by collar;bottom of film unexposed.Finger in path of x-ray beam(arrow),between PID and film.Unnecessary Films (film 1 of 2)Premolar bitewing shows all teeth on right side film 2 of 2Molar bitewing not needed(edentulous area will be seen on periapical or pan)Bitewing of denture teeth.This film is unnecessary,unless you plan to restore these teeth.