The fate of marginal bone around axial vs. tilted implants : a systematic review

Aims: The use of tilted implants has recently gained popularity as a feasible option for the treatment of edentulous jaws by means of implant-supported rehabilitations without recurring to grafting procedures. The aim of this review was to compare the crestal bone level change around axially placed vs. tilted implants supporting fixed prosthetic reconstructions for the rehabilitation of partially and fully edentulous jaws, after at least 1 year of function. Materials and methods: An electronic search of databases plus a hand search on the most relevant journals up to January 2014 was performed. The articles were selected using specific inclusion criteria, independent of the study design. Data on marginal bone loss and implant survival were extracted from included articles and statistically analysed to investigate the effect of implant tilting, location, prosthesis type, loading mode and study design. The difference in crestal bone level change around axial vs. tilted implants was analysed using meta-analysis. Results: The literature search yielded 758 articles. A first screening based on titles and abstracts identified 62 eligible studies. After a full-text review, 19 articles (14 prospective and five retrospective studies) were selected for analysis. A total of 670 patients have been rehabilitated with 716 prostheses (415 in the maxilla, 301 in the mandible), supported by a total of 1494 axial and 1338 tilted implants. Peri-implant crestal bone loss after 1 year of function ranged from 0.43 to 1.13 mm for axial implants and from 0.34 to 1.14 mm for tilted implants. In spite of a trend for a lower bone loss around axial implants with respect to tilted ones at 12 months, as well as after 3 or more years of function, no significant difference could be found (P = 0.09 and P = 0.30, respectively). The location (maxilla vs. mandible), the loading mode (immediate vs. delayed), the restoration type (full vs. partial prosthesis) and the study design (prospective vs. retrospective) had no significant effect on marginal bone loss. Forty-six implants (18 axial and 28 tilted) failed in 38 patients within the first year of function. All failures except five occurred in the maxilla. After 12 months of loading, the survival rate of implants placed in the maxilla (97.4%) was significantly lower as compared to the mandible (99.6%). No prosthesis failure was reported. Conclusions: Tilting of the implants does not induce significant alteration in crestal bone level change as compared to conventional axial placement after 1 year of function. The trend seems to be unchanged over time even though the amount of long-term data is still scarce. The use of tilted implants to support fixed partial and full-arch prostheses for the rehabilitation of edentulous jaws can be considered a predictable technique, with an excellent prognosis in the short and mid-term. Further long-term trials, possibly randomised, are needed to determine the efficacy of this surgical approach and the remodelling pattern of marginal bone in the long term.