We identified two prospective studies investigating the influence of type II diabetes on osseointegration. They are published by the same author but are independent studies from different years. In both studies, the patients included were stratified by HbA1c levels as well-controlled (HbA1c 6.1–8 %), moderately controlled (HbA1c 8.1–10 %), and poorly controlled (HbA1c ≥10 %).

The healthy control had HbA1c ≤6 %. Patients with poorly controlled diabetes have lower stability at the first 2 to 6 weeks. In the following weeks, stability reaches the baseline again, but reaching baseline takes two times the duration it needs in the healthy treatment group. Looking at the implant stability 1 year after implantation, there is no difference between the groups, not even to the poorly controlled HbA1c.

Diabetes and peri-implantitis

We found two prospective, two cross-sectional, and one retrospective study examining the influence of diabetes on peri-implantitis. The conclusions are quite heterogeneous. The study of Aguilar-Salvatierra started to evaluate 2 years after insertion and found that the number of patients suffering from peri-implant inflammation increases with elevated HbA1c values. The population was divided into well-controlled (HbA1c 6–8 %), moderately controlled (HbA1c 8–10 %), and poorly controlled (HbA1c >10 %), but there was no healthy control. The two cross-sectional studies yield an elevated relative risk for peri-implantitis of 1.9 and 4.1 caused by diabetes. The duration of these studies was 6 months to 5 years and 10 years, respectively. On the other hand, the retrospective study of Turkyilmaz showed no evidence of diminished clinical success 1 year after implantation, defined by negative bleeding on probing, no pathological probing depth, and a marginal bone loss of 0.3 ± 0.1 mm in a population of type II diabetics. The results in the prospective study of Gomez-Moreno show that elevated HbA1c causes more bone resorption after 3 years, but this effect is not significant.