Dental caries and bacterial load in saliva and dental biofilm of type 1 diabetics on continuous subcutaneous insulin infusion

Abstract Objectives Since most of the studies evaluates diabetics on multiple daily injections therapy and continuous subcutaneous insulin infusion may help gain better metabolic control and prevent complications, the objective of this study was to evaluate the prevalence of dental caries, the unstimulated salivary flow rate and the total bacteria load, Streptococcus spp. levels and Lactobacillus spp. levels in saliva and supragingival dental biofilm of type 1 diabetics on insulin pump. Material and Methods Sixty patients with type 1 diabetes on insulin pump and 60 nondiabetic individuals were included. The dental caries evaluation was performed using ICDAS and the oral hygiene was assessed according to Greene and Vermillion Simplified Oral Hygiene Index. Unstimulated saliva and supragingival dental biofilm were collected. Total bacteria, Streptococcus spp. and Lactobacillus spp. was quantified by qPCR. Results Patients with type 1 diabetes had a higher prevalence of dental caries and filled and missing teeth when compared with the control group. These patients were associated with more risk factors for the development of dental caries, namely a lower unstimulated salivary flow rate and a higher bacterial load in saliva and dental biofilm. Conclusion Some risk factors related to dental caries were associated with type 1 diabetics. An early diagnosis combined with the evaluation of the risk profile of the diabetic patient is imperative, allowing the dental caries to be analyzed through a perspective of prevention and the patient to be integrated into an individualized oral health program.

Among the oral complications associated with type 1 diabetic patients are changes in the salivary flow rate and composition, dental caries, periodontal disease and oral candidiasis. There is also a higher prevalence of burning mouth syndrome, aspergillosis, lichen planus, geographic tongue, postsurgical infections, halitosis and benign parotid enlargement, as well as taste disorders 16 . However, most of the complications are not adequately represented in the literature.
Regarding dental caries, the results are controversial. Some authors reported a higher prevalence of dental caries in diabetic patients 1,21,23 , but others reported a similar 3,25 or even a lower prevalence 13

Results
Twenty-four men and thirty-six women, with a mean age of 34.63±12.91 years, were included in each group.
Regarding oral hygiene habits, no differences were found between groups. Most patients reported brushing their teeth at least twice a day and not using dental floss (Table 1).

Diabetics
Control p % n % n  Correlation between HbA 1 c and the number of decayed, missing and/or filled teeth/surfaces was not found (p>0.05). Likewise, no correlation was found between the time elapsed since the diagnosis of type 1 diabetes and the number of decayed, missing and/ or filled teeth/surfaces (p>0.05).
Regarding OHI-S, significant statistical differences between groups were not found (p=0.501). In the group of patients with diabetes, it was 1.66±1. 11  Moreover, no correlation was found between the time elapsed since the diagnosis of type 1 diabetes and the unstimulated salivary flow rate (rs=-0.154, p=0.239).
The diabetics had a higher salivary total bacterial load when compared with subjects of the control group. There were statistically significant differences between groups regarding salivary total bacteria load (p=0.036), Streptococcus spp. levels (p=0.050), and Lactobacillus spp. levels (p=0.050) (Figures 1 to 3).
Regarding the dental biofilm, samples from patients with type 1 diabetes also had a higher total bacterial load when compared with those in the control group. Statistically significant differences were found between groups for total bacteria load (p<0.001), Streptococcus spp. levels (p=0.011), and Lactobacillus spp. levels (p=0.007) (Figures 4 to 6).
No association was found between saliva and dental biofilm bacterial composition and HbA 1 c (p>0.05) or the time elapsed since the diagnosis of diabetes (p>0.05).
The patients with more than three decayed teeth (D 1-6 ) had a higher total bacterial load in saliva (p=0.042), a higher load of Streptococcus spp. in saliva (p=0.050) and in dental biofilm (p=0.042), and a higher load of Lactobacillus spp. in saliva (p=0.029) and in dental biofilm (p=0.044).  with the duration of the disease. Some authors 6,8,20 have also found a correlation between low salivary flow rate and poor metabolic control, but others 15,18,29 did not find these correlations in their studies. The different inclusion criteria, the reduced size of some samples (as well as the consequent creation of groups with few elements after stratification by metabolic control) may, nevertheless, justify the lack of statistically significant results of some studies.
The importance of the study of the oral hygiene habits is clear since they represent an essential causal factor for the accumulation of dental biofilm 30,33 . Although a significant proportion of studies attribute higher plaque levels to patients with type 1 diabetes 17,23,25 , the evaluation of the oral hygiene habits is not performed in the majority of them.
Studies evaluating the bacterial composition of the dental biofilm of patients with type 1 diabetes were not found. In this study, the results of the microbiological analysis revealed that patients with type 1 diabetes have a higher total bacterial load in the dental biofilm.
Moreover, a correlation between decayed, missing and/or filled teeth and the bacterial load in the dental biofilm was found, which demonstrates the importance of the dental biofilm as a risk factor for dental caries.
The correlation between the diabetics' metabolic control and the susceptibility to dental caries reported by some authors requires a careful interpretation. The results regarding this association are controversial and the multifactorial etiology of the studied pathologies and their complications make it difficult to interpret the obtained data. On the other hand, behavioral factors may also play a critical role in this association and should therefore be considered. Oral health may be included in general health care, which may determine that a patient who attributes little importance to their oral health is also a patient who does not adequately adhere to the treatment of diabetes.

Conclusions
An early diagnosis combined with the risk profile evaluation of the diabetic patient is imperative, allowing dental caries to be analyzed through a perspective of prevention. The clinician needs to know which risk factors for dental caries may be associated with patients with diabetes so that, after analysis, the patient can be integrated into an individualized oral health program, according to its risk profile.