Methods: Thirty adult orthodontic patients of the Bernhard Gottlieb University Clinic in Vienna, Austria, were enrolled in this clinical trial and allocated by block randomization (size, 4) in a 1:1 ratio to either the treatment or the placebo group. Randomization was performed with software, and the allocations were concealed in sealed envelopes. Eligibility criteria included healthy adult patients with mesially directed orthodontic movement of the mandibular second molar into the extraction site of the mandibular first molar. The fixed orthodontic devices included active superelastic coil springs (200 cN) and TADs in the mandibular alveolar bone. Blinding was performed for the subjects and the outcome assessor. The treatment group received 1 shock-wave application with 1000 impulses at 0.19 to 0.23 mJ per square millimeter in the region of the TADs. The placebo group was treated with a deactivated shock-wave applicator and acoustic sham. The TADs positions were evaluated at placement and after 4 months. The reliability and precision of the impression process of the TADs were evaluated in an in-vitro model.

Results: Thirteen participants finished the investigation successfully in the treatment group but only 12 finished in the placebo group because 1 TAD loosened. The difference of the total TAD displacement for the 4-month time period between the placebo and treatment groups was 0.17 ± 0.95 mm (95% CI: -0.96, 0.62). No statistically significant difference between the 2 groups was found when sex was evaluated. Primary stability of the TADs as measured by placement torque, amount of tooth movement, and age of the patients did not influence displacement of the TADs. The reliability and precision of TAD impressions were confirmed. No unintended pernicious effects occurred after shock-wave treatment during the study period.

Conclusions: A single application of extracorporeal shock-wave treatment did not improve the stability of the TADs during orthodontic loading. Sufficient interradicular space should be provided to minimize the risk of periodontal and dental root defects.

Registration: This trial was registered at https://clinicaltrials.gov.

Protocol: The protocol was published before trial commencement, NCT01695928.

Funding: No funding or conflict of interest to be declared.