Monte Carlo simulation of reasons for early failure of implants: effects of two risk factors.

We have estimated the joint effects of two important risk factors on early failure of implants and then ranked all quoted risks by importance. We made a systematic search of published papers listed in PubMed, Web of Knowledge, Scopus, and Cochrane Central up to March 2018, and identified a total of 437 records. Eight studies met the inclusion criteria, in which seven significant risk factors for early failure were selected and used to build a conceptual simulation model. Selected risk factors were: "male sex", "smoking", "quality of bone", "short implants", "wide implants", "adjacent teeth", and "periodontitis". Based on these risk factors, all two-factor combinations that accounted for a total of 21 areas of greatest risk were created. We made a Monte Carlo simulation with 10 000 iterations and a sensitivity analysis to evaluate the estimates of these risks and to identify those that had the most influence on the model of early failure. The outcomes of the Monte Carlo simulation model showed that the SRS values of the combinations of these risks had different ranges of effects and probabilities of the early risk of failure. As a result, the most sensitive areas of greatest risk were "smoking and periodontitis", the second "short implants and periodontitis", and the third "smoking and short implants". The least sensitive combination of risks for early failure was "wide implants and male sex". This is to our knowledge the first study that has illustrated the contributions of various combinations of risk factors to early failure of implants. "Smoking and periodontitis" was thought to be associated with the greatest risk of early failure.