Post-treatment stability after insertion of CAD/CAM fabricated or Conventional fixed orthodontic retainers: a two-year follow-up

Abstract

Objective Since relapse after orthodontic treatment and stability and failure of CAD/CAM fabricated and Conventional fixed retainers are widely discussed, this study investigated and compared two-year post-treatment stability after insertion of a CAD/CAM fabricated or Conventional fixed retainer in the lower jaw.

Materials and methods Digitized dental casts or intraoral scans of n = 60 patients were used for data acquisition. The patients were divided into two groups according to the retention protocol: CAD/CAM fabricated fixed retainer (n = 30, mean age 16.97 ± 5.74 years) and Conventional fixed retainer (n = 30, mean age 15.70 ± 4.19 years). The evaluation included established procedures for dental measurements of the mandible (Intercanine Distance and Little´s Irregularity Index) before orthodontic treatment, at the end of orthodontic treatment, when the fixed retainer was inserted and two years after the insertion of the fixed retainer. All retainers were inserted by the same practitioner. Complications were recorded. Statistics included Shapiro-Wilk-, T- and Friedman-Tests. The level of significance was set at p < 0.05.

Results In patients with Conventional fixed retainers the change of the Intercanine Distance between insertion of the fixed retainer and two years afterwards was significantly more pronounced than in patients with CAD/CAM fabricated fixed retainers (ICD: Δ CAD/CAMt1−t2: -0.03 ± 0.22 mm; Δ Conventionalt1−t2: 0.12 ± 0.29 mm). Stability of Intercanine Distance was less in patients with Conventional fixed retainers. The change of Little´s Irregularity Index was not significant between the groups. In two patients with a Conventional fixed retainer a bonding surface was renewed within the first three months.

Conclusions Within two years, CAD/CAM fabricated fixed retainers showed less relapse of Intercanine Distance and fewer complications than Conventional fixed retainers.

Clinical relevance Considering the amount of relapse and the differences in complications, CAD/CAM fabricated fixed retainers and Conventional fixed retainers are useful appliances for stabilization of treatment results with favorable stability. Fabrication of CAD/CAM based fixed retainers is aside from that timesaving compared to Conventional fixed retainers.