الفهرس 
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Abstract
This study was carried to clinically compare between the efficiency of metallic and non- metallic bonded lingual retainers. A sample of 32 patients randomly selected from patients who finished comprehensive orthodontic treatment with a fixed appliance.
All subjects were selected from the Orthodontic Department outpatient clinic, Faculty of Dentistry, Ain Shams University. All subjects aged from 20- 25 years; were treated with full fixed appliances; had class I molar and canine relationship; with no history of posterior cross-bite; or abnormal habits (attrition, abrasion, erosion or bruxism); no interproximal enamel reduction or circumferential supracrestal fiberotomy were performed; all subjects were free from any dental abnormalities and all had good oral hygiene.
Patients were divided into two main groups Group I Metallic retainer subdivided into sub-group IA-(twist flex) and sub-group IB (Braided wire); for the Group II Non-metallic [Fiber reinforced composite] it was subdivided into sub-group IIA(Fiber glass reinforced composite ) consisting of a three-layer
Summary and conclusions
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fiber-glass band, 2 mm wide, especially developed for post-orthodontic retainers and sub-group IIB (Polyethylene fiber reinforced composite) consisting polyethylene erephthalate woven fibers which have undergone various treatments to completely clean the ribbon and improve adhesion of the composite.
For every patient, orthodontic study models and intra oral photographs were taken each visit before bonding retainers and at 3 months intervals for a period of 1year. Model analysis was carried out manually with an electronic caliper with an accuracy of 0.01 mm.
Success rate and survival time were calculated and cast analysis was carried out for the following variables [Irregularity index, inter-canine width, inter-premolar width, inter-molar width and arch length]
The collected data were tabulated and statistically analyzed using Statistical Package for Social Science (SPSS) version 20.
The obtained results of the current study led to the following conclusions:
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1. All types of bonded fixed retainers were able to maintain inter-canine width and irregularity index 1 year in retention and the changes recorded were non-statistically significant.
2. Polyethylene fiber reinforced composite retainer showed to be superior to metallic retainers (twist flex and braided) in both success rate and maintenance of inter-canine width and irregularity index.
3. Glass fiber reinforced composite retainer showed the least success rate.
4. Inter-molar width showed a statistically significant decrease over time.
Inter-premolar width showed a statistically significant decrease over time.