title: Rectangular collimation and radiographic efficacy in eight general dental practices in the West Midlands.
abstract: BACKGROUND
  Rectangular collimation is recommended in order to reduce radiation doses to patients. However, anecdotal reports suggest that it may result in more retakes, with a possible net increase in patient dosage.
  
  
  METHODS
  To test this hypothesis, eight general dental practitioners were recruited to participate in a project. Each took 25 pairs of bitewing radiographs of patients before and 25 after fitting rectangular collimators to their x-ray machines. Double-pack films were used so that duplicates could be examined. These were assessed by a consultant oral radiologist according to the National Radiographic Protection Board (NRPB) grading system for positioning and general film quality.
  
  
  RESULTS
  Initially, positioning quality was above the target level for six of the eight dentists; however, for all but one, this dropped after using rectangular collimation. General film quality was of a lower overall standard initially. Using rectangular collimation had an effect on general film quality but the direction and size of this varied among the dentists.
  
  
  CONCLUSIONS
  It was concluded that amongst the participating dentists, although numbers of retakes increased by 7%, there would be a net reduction in dosage to patients following rectangular collimation.
authors.affiliation: pthornley@blueyonder.co.uk
authors.forename: Peter H
authors.initials: PH
authors.lastname: Thornley
authors.forename: Dominic A
authors.initials: DA
authors.lastname: Stewardson
authors.forename: P G John
authors.initials: PG
authors.lastname: Rout
authors.forename: F J Trevor
authors.initials: FJ
authors.lastname: Burke
mesh_terms: D004739:England; D005792:General Practice, Dental; D006801:Humans; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D016300:Radiography, Bitewing / Q000295:instrumentation* / Q000592:standards