Failures in Single Extra-Short Implants (≤ 6 mm): A Systematic Review and Meta-analysis

The aim of this systematic review with meta-analysis was to compare the survival rate of single crowns supported by extra-short implants (≤ 6 mm) to those supported by conventional implants, with or without previous maxillary sinus augmentation. The proportion of failures was described according to the type of complication and follow-up periods. Materials and methods: Randomized and prospective clinical trials were selected from six databases and gray literature. The risk of bias was evaluated by Joanna Briggs Institute Critical Appraisal Checklist, and the certainty of the evidence was analyzed with Grading of Recommendations Assessment, Development, and Evaluation. Meta-analyses were processed with RevMan and MedCalc Statistical Software. Results: Single crowns supported by extra-short implants had a similar risk of failure to those supported by conventional implants, regardless of previous maxillary sinus augmentation (P > .05). Overall failure proportion of extra-short implants was 5.19%, but it varied according to follow-up (1.18% before loading, 1.56% at 12 months, 1.20% at 24 months, 2.10% at 48 months). Biologic failure complications were 37.90% for bleeding on probing, 22.45% for peri-implantitis, and 11.29% for infection. Prosthodontics failure complications were 14.88% for abutment failures and 14.73% for prosthetic screw loosening. Considering the risk of bias, most studies were classified at moderate risk. Conclusion: The risk of failure of single crowns supported by extra-short implants is similar to those supported by conventional implants, regardless of previous maxillary sinus augmentation or follow-up period. The most frequent biologic and prosthetic complications were bleeding on probing and abutment failures, respectively.