Mini-implant placement under existing removable partial dentures decreased the mobility of remaining teeth in a randomized controlled 3-year clinical trial

Objectives: Longitudinal stability values of teeth after strategic implant insertion under existing removable partial dentures (RPD) are lacking. This explorative evaluation of a 3-year randomized controlled trial on strategic min-implants (MI) aims to estimate the stability changes of the remaining teeth and the tooth survival rates under different MI loading conditions. Materials and methods: Partially edentulous study participants of a university clinic and three private practices with inadequately supported RPDs received strategic MIs (diameter 1.8–2.4 mm). According to the randomization the MIs were either immediately loaded in group A or delayed loaded in group B. The longitudinal changes of Periotest values (PTV) for teeth were compared between groups using mixed models adjusted by sex, age, jaw, tooth site, center, and baseline PTVs. The tooth survival was estimated with Kaplan-Meier analyses and group differences were analyzed using Cox regression. Results: Altogether 232 MIs were placed under 48 mandibular and 31 maxillary RPDs with a total of 255 remaining teeth in both jaws. The initial median PTV of 9.5 in group A and 8.0 in group B decreased to 5.0 in group A and 2.0 in group B at the 3-year follow-up. In the fully adjusted model the tooth mobility reduction revealed 5.3 PTV units (95% CI: 3.5–7.2) in group A and 7.6 PTV units (95% CI: 5.4–9.9) in group B without inferiority of any group (P = 0.122). The 3-year tooth survival rates were 88% in group A versus 92% in group B without relevant group differences (P = 0.338). Conclusion: Strategic MIs under existing RPDs in persons with severe reduced dentitions decreased the mobility of the remaining teeth independent from implant loading modus. Further tooth loss can emerge despite of relieving the remaining dentition by the MIs. Statement of clinical relevance: Mini-implants as supplementary abutments can restabilize loose teeth in jaws with RPDs and unfavorable tooth distributions. Clinical trial registration: German Clinical Trials Register (Deutsches Register Klinischer Studien, DRKS-ID: DRKS00007589, www.germanctr.de), January 15th, 2015.