Retrospective Study of Short Versus Standard Posterior Implants and Analysis of Implant Failure Risk Factors.

PURPOSE To compare the clinical and radiographic outcomes of short implants (≤ 8 mm) vs standard implants (> 8 mm, < 10 mm) and to uncover risk factors influencing implant failure in short implants. MATERIALS AND METHODS Short and standard implants were compared in the aspect of survival rates, biologic and mechanical complications, and marginal bone loss. To analyze risk factors of implant failure in short implants, several variables were taken into consideration, including sex, age, time interval, arch, implant brand, additional surgery, prosthesis material, restoration, smoking status, and crown-root ratio. RESULTS Three hundred twenty-one short implants and 136 standard implants were retrospectively followed up from 12 to 104 months with an average of 40 months (3.33 years) in short implants and 34 months (2.83 years) in standard implants. The survival rates of short implants were 95.6% at the implant-based analysis and 94.9% at the patient-based analysis, and rates of 96.3% and 94.0%, respectively, were calculated for standard implants. No statistically significant differences were observed between short and standard implants with respect to survival rate, complications, or marginal bone loss. The failure rates were 4.2% for implants and 5.4% for patients in total implants with an average of 38 months (3.17 years). In analyzing risk factors of short implants for survival rate, single short implants resulted in a higher failure rate compared with splinted short implants, while no significant variable was found in standard implants. CONCLUSION Short implants tend to be a reliable alternative in atrophic posterior regions. Splinted prostheses were more ideal for short implant restorations.