Regarding resonance frequency analysis, the values are related to bone quality and quantity as well as the exposed implant height above the alveolar crest, which depends on the type of implant and insertion technique [55,56,57]. Our results (primary stability in the maxilla 66.9 ± 8.9 ISQ units and in the mandible 72.5 ± 11.1 ISQ units; secondary stability in the maxilla 66.4 ± 10.0 ISQ units and in the mandible 73.0 ± 9.7 ISQ units) are comparable with the results from Becker and co-authors (standard-length implants): primary stability 72.1 ISQ units and secondary stability 72.6 ISQ units [58]. These values are marginally lower than those of short implants inserted only in the posterior mandible (79.0 ISQ units) [12]. Other authors measured in the posterior maxilla 68.2 ISQ units (6-mm implants) [15]. Altogether, our mean results (Fig. 2a, b) represent high stability values [34]. Huré and co-authors [47] measured in their animal study the following stability values (expandable implant of ≥ 10-mm length): for primary stability, 53.6 ± 3.0 ISQ units, and for secondary stability (3 months after insertion), 59 ± 4.5 ISQ units. The evaluation of stability values during the osseointegration period was not possible in our trial due to submerged healing. The question, whether the level of implant stability achieved at insertion can be maintained during the early healing period, remains. This should be analysed separately for all bone types in front of the known lowest stability values at 3–4 weeks after placement for all bone types [59,60,61] and the recent attempts of immediate [14] or early (6 weeks) functional loading of other short implant systems [28]. In relation to the results by McCullough and Klokkevold [62], who found that the macrothread design appears to play a positive role in implant stability in the early healing period, this can also be assumed for the employed implant system. Additionally, with regard to the results by Marković and co-authors [61], a critical stability drop down due to bone remodeling after bone condensing (implant site preparation and/or using expandable implants) should not be suspected; the opposite can be expected. The authors analysed the implant stability (4.1 × 10-mm screw implant) in the posterior maxilla in vivo depending on the implant site preparation (bone condensing vs. bone drilling) and confirmed that, after bone condensing, significantly higher implant stability results were achieved, immediately after implant insertion as well as during the whole observation period of 6 weeks. Especially in the third week in both groups, the following results were measured: 66.7 ± 1.64 vs. 57.1 ± 1.45 (p < 0.001). [61]. In the present study, we measured in the posterior maxilla 66.3 ± 10.4 ISQ units for primary stability and 66.9 ± 12.0 ISQ units for secondary stability, respectively.