The Effect of Full Versus Partial Coverage Thermoformed Retainers in Dual Retention With a Lower Bonded Retainer, on Periodontal, Orthodontic, and Patient-Reported Outcomes: A Randomised Controlled Trial

After braces are removed, teeth may move back toward their original positions. Retainers are used to help keep teeth straight after orthodontic treatment. This study compares two types of clear removable retainers used together with a fixed wire retainer behind the lower front teeth. One retainer covers the entire inner surface of the teeth (full coverage), while the other covers only part of the inner surface (partial coverage).

The purpose of this study is to find out whether the two retainer designs differ in their effects on gum health, comfort, retainer breakages, stability of the orthodontic correction, comfort, and compliance. The findings from this study may help orthodontists choose the most suitable retainer design for future patients.

Participants in this study will receive a fixed wire retainer on the lower front teeth and upper and lower clear removable retainers. They will be randomly assigned to receive either the full coverage or partial coverage lower retainer. Participants will attend follow-up visits at 1 month, 3 months, and 6 months after starting retainer wear. At these visits, the orthodontist will examine the teeth, gums, and retainers, and participants will complete a short questionnaire about their experience wearing the retainer.

This study excluded participants who are pregnant or breastfeeding within the first 6 months, have uncontrolled medical conditions or gum disease, smoke or vape, require a Hawley retainer instead of a clear retainer, or have missing front teeth or certain jaw conditions.

Participants may benefit from receiving retainers, oral hygiene care, and regular monitoring of their teeth and gum health at no additional cost. Participants will also receive an oral care kit during the debond appointment and at the 3-month and 6-month review visits.

Possible risks include breakage of the retainers, which may require repair or replacement, gum problems if oral hygiene is not maintained, and slight tooth movement despite retainer use. If gum problems develop, appropriate cleaning and referral for further treatment may be provided. Replacement retainers required during the study period will be provided free of charge.