IRCT2017021722951N3.

Study name	Comparison of orthodontic treatment results stability and gingival health between Hawley and vacum‐formed retainers: randomized clinical trial
Methods	Study design: single‐centre, single‐blinded, 2‐armed, parallel, randomised, active‐control trial Country: Iran Duration of the follow‐up: time frame: before retainer delivery and 6 months after delivery Inclusion criteria  Completion of orthodontic treatment in a proper occlusion Indication of removable retainer Exclusion criteria The absence of several teeth and the need to replace them with prosthesis Patients with bruxism  Syndromic disease (lip and palate clefts, hemi‐facial microsomia)  Patients with allergy to acrylic resin  Patients with temporomandibular joint problems
Participants	The study aims to enrol and randomise 66 participants.
Interventions	Group 1 (experimental): clear plastic retainer with a thickness of 1 mm retainer Group 2 (experimental): clear plastic retainer with a thickness of 1.5 mm retainer Group 3 (active control): Hawley retainer
Outcomes	Primary outcomes Stability ‐ objective grading system method Gingival Index
Starting date	28 April 2017
Contact information	Principal Investigator: Dr Seyed Hossein Moslemzadeh Institution: Tabriz University of Medical Sciences, Iran Email: hmoslemzade@yahoo.com
Notes	Contacted study author, awaiting a response