A correlation between the PPD of the peri-implant tissue and lesion progression has been reported, similar to that seen with periodontitis [27]. Probing around the implant is useful for evaluating soft tissue inflammation and is considered reproducible [36]. Examination of peri-implant bleeding is reported to have higher diagnostic accuracy than probing around natural teeth [37]. However, because measurement results differ depending on the shape of the superstructure and because bleeding can occur even if peri-implant tissue is healthy, implant probing is not completely established as a method to distinguish between healthy and inflamed sites [37, 38]. As in natural teeth, we consider that peri-implant BoP should be assessed after checking for sulcus bleeding. The results of this study, especially the correlation between PPD and BoP, suggest that implant probing is useful for evaluating peri-implant tissue.

In this study, we measured clinical parameters at only one point during the maintenance period. Further investigation is needed with attention not only to the amount of parameter change over time but also to bone resorption on radiological images.