Stability of surgically assisted rapid palatal expansion with and without retention analyzed by 3-dimensional imaging

Introduction: Surgically assisted rapid palatal expansion (SARPE) is the procedure of choice for treatment of adults with transverse maxillary deficiency greater than 7 mm. There is no consensus about the dentoskeletal effect of an orthodontic retainer on the outcome of SARPE. Our objective was to assess the effectiveness of an orthodontic retainer on dentoskeletal stability.

Methods: Ninety digitized dental casts of 30 adults undergoing SARPE were divided into 2 groups-no retention (n = 15) and retention (n = 15)-and assessed. The dental casts were obtained at 3 checkpoints: (1) 7 days on average before SARPE (preoperatively), (2) 4 months after expansion, and (3) 10 months after expansion was completed. The retention patients received a transpalatal arch just after expander removal, at checkpoint 2. The transpalatal arch was kept for 10 months after completion of the expansion (checkpoint 3 and end of the study). The dental casts were scanned with a Vivid 9i 3D laser scanner (Konica Minolta, Wayne, NJ). The distances measured were premolar and molar intercusp distances, premolar and molar intercervical distances, premolar and molar inter-WALA (Will Andrews and Lawrence Andrews) ridge distances, and palate height at the maxillary first molar.

Results: The planned maxillary expansion was within the expected amount (P <0.05). Palatal height at the 4-month checkpoint decreased by 0.79 mm (4.38%) (P <0.001) and again at the 10-month checkpoint by 0.38 mm (0.98%) (P >0.05) but not significantly in both groups. The premolar intercusp distance had a relapse at checkpoint 3 of 1.84 mm (7.18%) (P <0.001) in the no-retention group. Both groups had average relapses of 0.95 mm in the premolar intercervical distances, of 0.88 mm in the premolar inter-WALA ridge distances, of 1.04 mm in the molar intercusp distances, of 0.74 mm in the molar intercervical distances, and of 0.84 mm in the molar inter-WALA ridge distances (P <0.05) at checkpoint 3.

Conclusions: The analysis of relapse in both groups suggests that the use of a transpalatal arch as a retaining device does not improve dento-osseous stability.