Extra-short implants in the posterior region: a case series of single and multi-unit fixed prostheses

Aims: Anatomical and surgical conditions may require the use of implants with reduced length. This study reports a case series of patients treated with single or multi-unit fixed prostheses supported by 4-mm implants in the posterior region. The aim was to describe the success rate up to four years of loading, and the mechanical and biological complications. Materials and Methods: The sample consisted of all patients treated with prostheses supported by 4-mm implants at the Military Policlinic of Porto Alegre, Brazil, between the years 2015 and 2019. The patients were recalled for clinical examination and data collection: The type of prosthesis, maximum bite force, presence of bruxism, peri-implant bone level, and crown-implant ratio were recorded. Results: Eight patients with 19 implants place in pre-molar and molar region were examined. Eleven implants were rehabilitated with single crowns and 8 with splinted crowns. The implant survival rate was 100%, with a mean follow-up of 33.8 ± 10.6 months after surgery. There were 6 (2 non-splinted) cases of prosthetic screw loosening, resulting in a prosthetic complications rate of 27.3%, with an average follow-up of 28.6 ± 10.86 months after prosthesis installation. Conclusions: Within the study limitations, it can be concluded that 4-mm implants show high survival but also relevant occurrence of prosthetic complications.