**9. Methods and materials: Part I**

#### **9.1 Selection of subjects**

From a population of 2,296 patients treated in the graduate orthodontic clinic at the University of Michigan School of Dentistry (UMSD) between 1997 and 2004, 350 patient records were selected randomly using a random number sequence. Inclusion criteria for record selection consisted of patients who:


#### **9.2 Chart abstraction**

Data collection from de-identified patient charts included gender and age at initiation of orthodontic treatment, and treatment variables such as extraction therapy and comprehensive treatment time. Comprehensive treatment time was defined as the period between initiation of full fixed appliance therapy and removal of all active fixed appliances. Initial oral hygiene score, frequency of oral hygiene discussion, oral hygiene instruction and fluoride application and/or rinse were recorded from progress notes in the chart.

#### **9.3 Photography**

Intraoral pre-treatment (initial) and post-treatment (final) photographs of each patient were taken as part of standard orthodontic recordkeeping procedures. All photographs, stored as 35 mm slides, were taken in the Clinical Photography Department at the UMSD by two professional photographers utilizing a standardized intraoral photography procedure. Individual slides were scanned into digital format using a Nikon Slide Feeder SF-200 (S) and Super Coolscan 4000 ED scanner. Scanned images were enlarged 325% and imported into an individual Microsoft PowerPoint presentation for each patient.
