Abstract
Purpose: A 3–5 mm apical anchorage length is commonly accepted to achieve primary stability in immediate implant placement and restoration (IIPR). However, this linear criterion overlooks the variability of current implant designs. Therefore, the main objective was to use digital technologies to evaluate the endosseous surface of the implant when the apical anchorage is 3 mm using digital technologies. Methods: Fifty implants meeting defined inclusion criteria (13 mm length, internal connection, 3.3–4.2 mm occlusal diameter) were analyzed. 3D models were processed to calculate total surface area (TSA), functional surface area (FSA; excluding cutting flutes), and cylindrical surface area (CSA) for full implants and their apical 3 mm portions. Comparisons used paired t-tests or Wilcoxon signed-rank tests. This study is purely digital and includes no in vitro or clinical validation. Results: FSA was 7 % (SD 5 %) smaller than TSA for full implants and 19 % (SD 15 %) smaller for the apical portions (p < 0.001). Apical FSA ranged from 14.37 to 50.24 mm2, averaging 17 % of total FSA. Compared to CSA, FSA was 7 % (SD 10 %) larger for full implants and 38 % (SD 19 %) smaller for the apex (p < 0.001). Conclusions: A fixed 3 mm apical anchorage does not reflect functional surface area availability reliably. Apical FSA varies substantially by implant design, highlighting the need to consider apical geometry during planning. Clinical implications: Rather than relying solely on linear anchorage depth, clinicians should consider apical implant design and its influence on functional surface area as one of several factors guiding implant selection and drilling protocol adaptation in IIPR.