To the Editor The report by Dr Engebretson and colleagues¹ explored the effect of nonsurgical periodontal therapy (scaling and root planing) on glycemic control in persons with type 2 diabetes and chronic periodontitis. Given the high global prevalence of both diseases, the adverse effect of periodontal infection on blood glucose levels and diabetes complications,² and the improvements in levels of HbA_1c following clinically effective periodontal therapy reported in meta-analyses,³ the results of this multicenter RCT require careful review to ensure that the conclusions drawn are supported by the data. We identified important problems with the study design, execution, data interpretation, and reporting that we think render the conclusions inappropriate.