Background and purpose: The aim of this study was to investigate the relationship between the implant survival rates and the length and diameter in disabled veterans attending Qazi Tabatabai Dental Clinic, Tehran, Iran during 2000-2010.

Materials and methods: A retrospective study was conducted in 181 disabled veterans referring to Qazi Tabatabai Clinic. They received 1,255 implants from three different manufacturers including 3i (Riverside drive, Palm Beach, Gardens, F1, USA), Xive (Friadent GmbH, Mannheim, Germany), and BH (Goteborg, Sweden). The length of implants was classified as short (8-10 mm), medium (11-13 mm), and long (14-15 mm), and the diameter was classified as narrow, regular, and wide. The data analysis was performed using the R statistical software. To evaluate the impacts of the implant length and diameter on its survival rate, the frailty parametric model, with exponential distribution as baseline hazard and gamma distribution as frailty was used.

Results: The mean age and injury rate of the patients were 49.47±5.61 years and 42.98%, respectively. In addition, the estimated medians of survival time for 3i, Xive, and BH implants were 76.15, 79.06, and 77.94 months, respectively. There was no significant difference between the survival rate and type of implant (P=0.353). Regarding the implant length, the 3i implant with with long length (14-15 mm) and the Xive implant with medium length (11-13 mm) had the lowest (88%) and highest success rates (97.8%), respectively. According to the frailty model, the higher length and diameter in 3i and Xive implants were associated with higher failure rates; but this condition was not observed in BH implants.

Conclusion: We found a significant relationship between implant failure and short length implants. However, no relationship was observed between failure of implant and its diameter.