Despite the growing diversity of materials used for mandibular fixed retainers, the evidence base remains inconclusive. In particular, conflicting findings have been reported regarding the bond failure of titanium retainers across different evaluation periods, including immediate and 12-month outcomes. Additionally, the emergence of 3D metal-printed retainers has not yet been matched by sufficient clinical evidence, with current data being limited and lacking long-term validation.

In recent years, CAD/CAM technology and 3D printing have introduced new possibilities in orthodontic practice, with expanding applications across various treatment modalities. Additive manufacturing, commonly known as 3D printing, enables the fabrication of objects through the sequential layering of material to produce precise three-dimensional structures. While orthodontists are already familiar with 3D-printed appliances such as clear aligners, the application of these technologies in fixed retention is still evolving. Recent studies have reported the fabrication of customized lingual retainers using CAD/CAM techniques, including nickel-titanium-milled retainers and zirconia bars designed for use as bonded mandibular fixed retainers.

Inclusion Criteria:

• Age ≥ 13 years
• Complete permanent dentition up to second molars
• Completed Class I orthodontic treatment and requiring a mandibular fixed -bonded retainer
• No sex predilection.

Exclusion Criteria:

• Enamel defects that may compromise bonding (e.g., hypoplasia, fluorosis)
• Poor oral hygiene
• Active dental or periodontal pathology at the site of intervention
• Lingual restorations on mandibular anterior teeth
• Poor compliance or inability to attend follow-up visits
• Psychological or medical conditions that may interfere with study participation