Survival rates of ultra-short (<6 mm) compared with short locking-taper implants supporting single crowns in posterior areas: A 5-year retrospective study

Background Short and ultra-short implants represent a predictable treatment, in terms of implant survival, with patients presenting insufficient available bone volumes. Moreover, single crown restorations represent a gold standard in terms of oral hygiene. Purpose The aim of this retrospective study was to evaluate implant survival, marginal bone loss, and peri-implant complications in 333 locking-taper short and ultra-short implants. Materials and Methods Implants were placed in the maxillary and mandibular posterior regions of 142 patients. Clinical and radiographic examinations were performed at 5-year recall appointments. Results All implants placed consisted of 8.0-, 6.0-, and 5.0-mm length, 38.14%, 34.53%, and 27.33%, respectively. Three hundred thirty-two implants (one early failure) were rehabilitated with single crowns in 141 patients. In 45.48% of the implants the crown-to-implant ratio was >= 2, with a mean value of 1.94. Overall implant-based survival after 5 years of follow-up was 96.10%: 96.85%, 95.65%, and 95.60% for 8.0-, 6.0-, and 5.0-mm length implants, respectively (p = 0.82). Overall patient-based survival was 91.55%. Regarding crestal bone level variations, average crestal bone loss and apical shift of the "first bone-to-implant contact point" position were 0.69 and 0.01 mm, respectively. Setting the threshold for excessive bone loss at 1 mm, during the time interval from loading to follow-up, 28 implants experienced loss of supporting bone greater than 1 mm: 19 of them (67.85%) were surgically treated with a codified surgical regenerative protocol. After 60 months, a peri-implantitis prevalence of 5.94% was reported, with an overall implant success of 94.06%: 95.93%, 92.73%, and 93.10% for 8.0-, 6.0-, and 5.0-mm length implants, respectively (p = 0.55). Conclusion Long-term outcomes suggest that short and ultra-short locking-taper implants can be successfully restored with single crowns in the posterior area of the maxilla and mandible.