Success and complication rate of miniscrew assisted non-surgical palatal expansion in adults - a consecutive study using a novel force-controlled polycyclic activation protocol

Abstract

Introduction: Bone-borne miniscrew assisted palatal expansion (MAPE) is a common technique to improve maxillary transverse deficiency in young adolescents. Adult patients usually present a challenge, as they often require additional surgical assisted maxillary expansion (SARPE). There is still no clear statement about non-surgical expansion in adult patients using this technique. The aim of this study was to evaluate the success and complication rate of non-surgical palatal expansion in adults utilizing MAPE with a novel force-controlled polycyclic expansion protocol (FCPC).

Methods: This consecutive study consisted of 33 adult patients with an average age of 29.1 ± 10.2 years (min. 18 years, max. 58 years), including one dropout patient. First, four miniscrews were inserted and after 12-weeks latency, the expander was placed and the FCPC protocol was applied (MAPE group). In case of missing expansion, a SARPE was performed (SARPE group). After maximum expansion, a cone beam CT was made and widening of the midpalatal suture was measured. The outcome variables were successful non-surgical expansion and, with sample size power above 80%, the odds of failed non-surgical expansion and associated complications were evaluated. The primary predictor variable was age. Statistical analysis was performed using R (Version 3.1) to calculate power, to construct various models for measuring the odds of requiring surgical intervention/complications, and others.

Results: Successful non-surgical expansion was achieved in 27 patients (84.4%), ranging from 18 to 49 years. Mean age differed significantly between both groups (26.8 ± 8.2 years vs. 41.3 ± 9.9 years; p < 0.001). Mean expansion at the anterior and posterior palate for the MAPE group was 5.4 ± 1.5 mm and 2.5 ± 1.1 mm, respectively. Among these subjects' complications were observed in 18.5%. Age significantly increased the odds of complications (p = 0.019).

Conclusions: 1. The success rate of MAPE among individuals aged 18 to 49 years was 84.4%. 2. A V-shaped expansion pattern in the antero-posterior dimension was mostly observed. 3. Complications were significantly associated with age. 4. A careful expansion protocol seems to be beneficial to prevent unfavorable results in adult patients.

Trial registration: Consecutive cohort study, Review Board No. EK-2-2014/0016.

Keywords: Adult patients; Bone-borne; Complication; MAPE; MARPE; Maxillary expansion; Miniscrew; Non-surgical; Success.

Fig. 1

a-k Example of maxillary expansion with a MICRO-4 device in a 33.8 y a M4 and M5 positions for the orthodontic miniscrews b After placement, both screws on each side were connected with alastic chains. c This serves as a bridge to cover the screw heads with light curing resin to assure stability during 3 months of osseo-integration d MICRO-4 device with small hex nut e Initial occlusal x-ray f After reaching maximum opening of the jackscrew, the MICRO4 expander was removed and the small hex nut exchanged against a wider one g The same device was reinserted to continue the expansion procedure without the need of appliance reconstruction (in this case the right M5 orthodontic miniscrew needed to be relocated and the expander slightly adapted) h Final occlusal x-ray after expansion stop i Two year retention with bone-borne TPA. The orthodontic miniscrews in position M5 removed after insertion of TPA

Fig. 2

Force-controlled polycyclic expansion protocol (FCPC): force control by measuring the applied force at the end of the activating wrench. This is done by the patient twice a day with less than 500 cN turning power allowed

Fig. 3

Measurements on CBCT after maximum of non-surgical expansion at the anterior and posterior palate. The nasopalatine foramen (white bracket) and the greater palatine foramina on both sides (white line) were references for measurements

Fig. 4

Minor deformation of mini screw as seen in 4 patients in the present study