The literature included to this review is very heterogeneous concerning the investigated objects, methods, and conclusions. Diabetes is a group of metabolic diseases in which there are high blood sugar levels over a prolonged period. When looking at the complications and side effects resulting from diabetes, it is important to know which type of diabetes the patient suffers from, if there is any therapy, which kind of therapy, the grade of glycemic control, and duration of the disease. The previously described micro- and macroangiopathies develop with the duration and repetitions of elevated glycemic periods. In most studies, these information are missing and there is only a dichotomy classification of diabetes or healthy. Most studies include patients with well-controlled diabetes, and there is no or little effect on implant survival. Many authors conclude that prospective long-time studies are needed to answer the issues. On the other hand, it would be non-ethical to observe patients with poor glycemic control, because health-threatening systemic side effects developed.

Analyzing the available studies, we conclude as follows:

Dental implants are safe and predictable procedures for dental rehabilitation in diabetics. The survival rate of implants in diabetics does not differ from the survival rate in healthy patients within the first 6 years, but in the long-term observation up to 20 years, a reduced implant survival can be found in diabetic patients. Patients with poorly controlled diabetes seem to have delayed osseointegration following implantation. After 1 year, there is no difference between diabetic and healthy individuals, not even to the poorly controlled HbA1c. Therefore, we recommend avoiding immediate loading of the implants. In the first years after implant insertion, there seems to be no elevated risk of peri-implantitis; but in the long-term observation, peri-implant inflammation seems to be increased in diabetic patients. Therefore, a risk-adapted dental recall is helpful to detect early signs of gingivitis, which can easily be treated by dental/implant cleanings to avoid serious peri-implant infection. We found some hints that good glycemic control improves osseointegration and implant survival. Therefore, and to avoid other long-term side effects, the practitioner should ask for the HbA1c and if necessary improvement of antidiabetic therapy should be aimed. In the literature, we found no evidence that bone augmentation procedures like guided bone regeneration and sinus lifts have a higher complication and failure rate in patients with well- to fairly well-controlled diabetes. To improve implant survival and reduce postoperative complications, supportive therapy consisting of prophylactic antibiotics and chlorhexidine mouth rinse is recommended.