Clinical Assessment of Short (> 6 mm and ≤ 8.5 mm) Implants in Posterior Sites with an Average Follow-Up of 74 Months: A Retrospective Study

Purpose: To evaluate the survival and success rates of short (> 6 mm and ≤ 8.5 mm) implants after at least 2 years of functional loading. Implants were assessed using clinical parameters such as marginal bone loss (MBL), pocket depth (PD), keratinized mucosa width (KMW), bleeding on probing (BoP), and the peri-implant condition (mucositis or peri-implantitis). Any correlations between clinical parameters were analyzed. Materials and Methods: This observational and retrospective study included 114 posterior maxillary and mandibular implants placed in 27 women and 38 men with a mean age of 68.04 ± 9.07 years. Patients included in the study had received at least one short implant between 2001 and 2013, such that each implant was in occlusal function for at least 2 years by 2015. Patients with only long (≥ 10 mm) implants, patients with any systemic condition, and smokers were excluded from the study. PD, KMW, peri-implant condition, BoP, and MBL were the clinical parameters assessed in the study. Data on prosthesis type (single or splinted) and implant features were also obtained. All data were submitted to analysis via Mann-Whitney unpaired test, with a significance level of P < .05. Spearman correlation coefficient was also measured to verify the negative or positive correlation. Results: The mean follow-up time was 74.08 months, and mean implant success and survival rates were 87.63% and 94.74%, respectively. There were 6 implant failures (5.26%). A total of 66 (59.46%) prostheses were screw-retained implant-supported restorations, and 45 (40.54%) were cemented. A total of 93 (86.49%) short implants were splinted to another implant, and 15 out of 111 (13.51%) restorations were single implants. Keratinized mucosa was missing around 43 (39%) implants, whereas PD was measured to be between 0 and 3 mm in 64.86% of implants and ≥ 4 mm in 31.53% of implants. MBL was ≤ 1.5 mm in 71.17% of cases and > two-thirds the length of the implant in 2.71% of cases. Mucositis and peri-implantitis were found in 22.52% and 7.21% of implants, respectively. The correlation coefficient showed a positive result for PD and MBL (0.11; P = .368) and negative results for PD and KMW (–0.42; P = .002) and KMW and MBL (–0.19; P = .183). Conclusions: Within the limitations of this study, it is possible to conclude that short implants are a feasible treatment option for dental rehabilitation. They are considered an excellent alternative to complex procedures and have high survival rates after at least 2 years of follow-up, with compatible peri-implant local tissue response. Moreover, a significant negative correlation between KMW and PD was observed.