A randomized clinical trial is set out to compare the effectiveness of two types of fixed retainer (multistranded stainless steel and PEEK types) in maintaining the stability of lower anterior teeth with less failure rate.

It is a multicenter randomized clinical trial with two arms parallel group. The patients will be randomly divided into two groups, group one: multistranded stainless steel fixed retainer will be used while, and group two PEEK fixed retainer will be used. An intra-oral scan, intra-oral swap and periodontal indices will be taken before starting the treatment (T0), after one month (T1), after 3 months (T2), and after 6 months (T3). Patient perception concerning the fixed retainer will be taken for the patients.

Inclusion Criteria:

• Age: 17-32 years.
• Patients with a score of 0-0.5 on Little's irregularity index in the lower arch.
• Patients treated with the pre-adjusted orthodontic appliance (both Extraction and non-extraction cases).
• Patients who have healthy periodontal condition

Exclusion Criteria:

• Patients treated with rapid maxillary expansion or surgically assisted rapid maxillary expansion.
• Patients with a cleft lip / and or palate.
• Patients with a deep overbite and traumatic parafunctional habits such as bruxism and clenching.
• Patients with carious, restored, fractured, or missing lower anterior teeth.
• Patients with medical health problems that may influence gingival health like uncontrolled type II diabetic patient, patients with hormonal disturbances or systemic drug administration that effect on oral health.
• Smokers