December 2007

Document Type


Degree Name



Dept. of Orthodontics


Oregon Health & Science University


Prevention of tooth relapse after orthodontic tooth alignment has been one of the greatest challenges within the field of orthodontics. Studies have found that following orthodontic treatment, it is not possible to accurately predict which patients will relapse and to what extent. Removable retainers rely on patient compliance to wear them continuously so teeth are held in place. The development and use of fixed retention takes away the need for patient compliance. The purpose for this study was to see if there is a difference in how an upper Hawley retainer and a fixed lingual retainer bonded to the upper central and lateral incisors hold teeth in place. Another purpose was to see if there are any differences in periodontal charting measurements between the two groups as the fixed retainer may interfere with oral hygiene. A random chart review from a private orthodontic practice and the OHSU orthodontic clinic was done to identify potential participants. Each group consisted of 25 subjects and had similar means for initial irregularity (9.0, Little's Index) and similar means for time in retention (41.8 months). To qualify, subjects had to be in retention for at least seven months and have before and after treatment dental study models available. Qualifying subjects were called by phone and asked to participate in this study. Each subject had a photograph and impression taken of their upper front six teeth. Little's index of irregularity was used to calculate tooth irregularity from the upper right canine to the upper left canine. Periodontal measurements (probing depths, bleeding on probing, gingival recession) around the upper incisors were measured with a periodontal probe. T-tests were run to evaluate if there was a difference between groups in how well the teeth have been held in place and for periodontal recordings. Regression analysis was done to see if there were relationships between time in retention and amount of relapse, initial irregularity and relapse, bleeding sites around the canines and bleeding sites around the central and lateral incisors, time in retention and number of bleeding sites, age and number of bleeding sites, time in retention and probing depths, age and probing depths. The acceptable P-value was set at 0.05 for all variables. ( 1.) No significant difference could be found for retention times or initial irregularity between the two groups. (2.) A significant difference was found between the Hawley and bonded groups for relapse. (3.) There was no significant relationship for time in retention and amount of relapse for the Hawley group or the bonded group. (4.) There was no significant relationship for initial irregularity and relapse. (5.) There was a significant difference in the number of bleeding points between the Hawley and the bonded groups. (6.) For the Hawley group, there was a significant positive relationship for bleeding on the canines and bleeding on the central and lateral incisors but not for the bonded group. (7.) There was no significant relationship for age and number of bleeding points, number of pockets and time in retention, age and number of pockets. (8.) No significant differences were found for the number of pockets (3 .5 and above), recession or age between the two groups. (9.) There was no evidence to show that the bonded maxillary retainer contributes to periodontal disease. (10.) The bonded maxillary retainer appears to be a good retainer to keep upper incisors in good alignment for many years.




School of Dentistry



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