Long-term clinical outcomes in short (6 mm) versus standard (8.5 mm) implants: a retrospective cohort study

The aim of this study was to evaluate long-term clinical outcomes in short (6 mm) and standard implants (8.5 mm) and to identify clinical and prosthetic factors associated with marginal bone loss (MBL). In this retrospective cohort study, 84 implants (39 short, 45 standard) were placed in 73 patients between 2012 and 2021. Clinical and radiographic parameters, including marginal bone loss (MBL), crown–implant ratio (CIR), abutment height, insertion depth, emergence profile, and emergence angle, were recorded. MBL was compared between short and standard implant, and its associations with patient-, implant-, and prosthesis-related factors were analyzed. Statistical analyses included t-tests, Mann–Whitney U tests, Spearman’s correlation, and linear mixed-effects models (p < 0.05). The mean follow-up period was 6.52 ± 2.81 years. No significant difference in MBL was observed between standard (0.12 ± 0.07 mm) and short implants (0.05 ± 0.08 mm, p > 0.05). Short implants showed a significantly higher CIR than standard implants (1.96 ± 0.05 vs. 1.41 ± 0.05, p < 0.001), although CIR was not significantly associated with MBL. Insertion depth was positively associated with MBL (r = 0.372, p < 0.001). Within the limitations of this retrospective study, in sites with limited vertical bone height where short implants were indicated, long-term marginal bone loss was comparable to that observed in sites restored with standard implants placed in sites with sufficient bone height. Insertion depth, rather than implant length alone, was associated with marginal bone loss. When appropriate surgical and prosthetic protocols are applied, short implants may serve as a reliable treatment option in sites with limited vertical bone height.