## 1 Introduction  
Periodontal disease (PD) consists of a chronic inflammatory destruction of tooth-supporting tissues caused by the action of specific anaerobic pathogens contained in dental plaque [1]. If not treated, PD can lead to tooth loss, as well as impaired quality of life, and important systemic inflammation [2].  
A strict correlation between diabetes and periodontal disease was assessed [3, 4]. In fact, periodontal disease is considered the sixth complication of diabetes [5]. Diabetic patients with concomitant periodontal disease generally have a worse glycemic control and a higher prevalence of diabetes-related complications [6]. It was also demonstrated that the glycemic control is strictly correlated with incidence and gravity of periodontal disease [7, 8], as well as that the treatment of PD is able to improve the metabolic control [9].  
Different pathogenetic mechanisms to explain how hyperglycemia could affect the periodontal status have been proposed, e.g., an excessive inflammatory response to infection, a decreased reparative reaction, and the action of advanced glycation end products. In addition, periodontal disease could affect glycemic control in diabetic patients through chronic inflammation [1]. On the basis of these considerations, PD should be carefully regarded as an important aspect of the clinical care of diabetic patients.  
Diabetes mellitus (DM) is mainly classified into two different types, type 1 and type 2 DM. Type 1 DM (T1 DM) is associated with the autoimmune destruction of pancreatic \(\beta\)-cells, resulting in the failure of insulin production, whereas type 2 DM (T2 DM) is characterized by PD. Hyperglycemia was mainly found in T2 DM patients [10], as it can be deduced considering previous literature [3]. Anyway, according to a recent systematic review [1], even T1 DM is related to the onset of PD, as the number of patients affected was twice as those of non-diabetic ones. Moreover, among T1 DM patients, PD seems to be more severe, with significant differences between subjects under glycemic control.  
Probiotics are living microorganisms that are able to exert a beneficial action on human health and are being used in recent years for the prevention and treatment of oral diseases like periodontitis. The strains generally used are _Bifidobacterium_ and _Lactobacillus_. According to the recent systematic review by [PERSON] et al., the use of probiotics seems to be beneficial for the improvement of some clinical periodontal parameters [11]. Notwithstanding their positive effects, several shortcomings on probiotics should be taken into consideration; specifically, the safety of live microorganisms should be carefully evaluated in cases of older and immunocompromised patients making use of them. Accordingly, the novel non-viable probiotics are named paraprobiotics (tyndallized probiotics). Their beneficial role is explained by the fact that they are inactivated microbial cells that do not present risks to the host thanks to their anti-inflammatory, antiproliferative, and antioxidant actions, with a regulation of adaptive and innate immune systems, and an antagonistic role against pathogens [12].  
The objective of the present report is to evaluate the effect of two domiciliary oral hygiene protocols on the periodontal clinical status as well as on the amount of glycosylated hemoglobin (HbA1c) in patients affected by T1 DM. In particular, a natural extracts-based toothpaste and probiotics-based agents have been chosen due to their wide diffusion among products for oral care.  
The first null hypothesis of the study is that no significant differences occur between the two groups considering the periodontal evaluation. The second null hypothesis is that no significant differences neither occur for the amount of HbA1c.