Enrichment of Acid-Associated Microbiota in the Saliva of Type 2 Diabetes Mellitus Adults: A Systematic Review.

It could conceivably be hypothesized that a link exists between an altered microbiota due to local hyperglycemia and the increased risk of caries in diabetes mellitus (DM). This systematic review aimed to perform a cross-study comparison into the salivary microbiota of adults with type 2 diabetes mellitus (T2D) compared to adults without T2D, particularly focusing on the abundance of acid-associated bacteria. This report follows PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Studies using next-generation sequencing and other molecular techniques are included. The methodological quality of individual studies was assessed using appropriate Joanna Briggs Institute tools. The certainty of the evidence considering the effect direction was evaluated using the GRADE approach. From 2060 titles retrieved, 12 were included in the data synthesis, totalling 873 individuals with T2D and controls evaluated across the literature. Weighted averages of blood glucose levels (HbA1c-fasting blood glucose) were 8.21%-172.14 mg/dL and 5.12%-84.53 mg/dL for T2D and controls, respectively. In most studies, the relative abundance of acidogenic and aciduric bacteria was higher in diabetics when compared to their normoglycaemic controls. Whilst the evidence certainty was very low, there was a consistent Proteobacteria depletion and Firmicutes enrichment in T2D. As for the acid-associated genera, there was consistent enrichment of Lactobacillus and Veillonela for T2D. Tannerella/T. forsythia was enriched in T2D saliva, but the certainty is low. Further well-designed cohorts are needed to clarify the distribution of acid-associated microorganisms in the saliva of adults with T2D and how this can be clinically manifested (PROSPERO = CRD42021264350).

Can hyperglycemia be associated with caries activity and root caries in adults?

AIMS: A previous meta-analysis showed that individuals with Type 2 diabetes mellitus (T2D) have a greater chance of developing both coronal caries and root caries than systemically healthy ones, which can be influenced by hyperglycemia per se. This study aimed to associate blood and salivary glucose levels with caries. METHODS: This research is a subset of a cross-sectional study. N = 39 individuals underwent a dental examination and salivary glucose, fasting blood glucose (FBG) and glycated hemoglobin (A1c) measurements. RESULTS: The prevalence of active coronal caries was 10.2%, and that of root caries was 20.5%. A1c and FBG averages were higher in individuals with root caries (9.75 ± 1.71 and 186.3 ± 62.5) than without (7.01 ± 2.23 and 115.1 ± 48.6; p < 0.05). Individuals with T2D showed weak correlation of salivary glucose and number of active coronal caries. Significant correlations were observed between salivary and blood glucose. There was relevance of A1c (0.53; CI=0.124-0.941; p = 0.01) and FBG (0.019; CI=0.006-0.033; p = 0.006) toward the increased number of root caries lesions, even after adjustment for salivary flow and age. CONCLUSION: Blood glucose levels are associated with an increased number of root caries in adults with or without T2D. In individuals with T2D, salivary glucose was correlated with active coronal caries. Additional studies are needed to support this association.

Enrichment of sulphate-reducers and depletion of butyrate-producers may be hyperglycaemia signatures in the diabetic oral microbiome.

Objectives: This study aimed to investigate oral microbial signatures associated with hyperglycaemia, by correlating the oral microbiome with three glycaemic markers. Potential association between clinical parameters and oral bacterial taxa that could be modulating the hyperglycaemic microbiome was also explored. Methods: Twenty-three individuals diagnosed with type 2 Diabetes Mellitus (T2D) and presenting periodontitis were included, as well as 25 systemically and periodontally healthy ones. Fasting blood glucose, glycated haemoglobin, salivary glucose, periodontitis classification, caries experience and activity and salivary pH were evaluated. The V4 region of the 16S rRNA gene was amplified from total salivary DNA, and amplicons were sequenced (Illumina MiSeq). Results: Hyperglycaemia was correlated with proportions of Treponema, Desulfobulbus, Phocaiecola and Saccharimonadaceae. Desulfobulbus was ubiquitous and the most enriched organism in T2D individuals (log2FC = 4). The Firmicutes/Bacteroidetes ratio was higher at alkali salivary pH than acidic pH. In the network analysis, Desulfobulbus was clustered in a negative association with caries-associated and butyrate-producing bacteria. Conclusion: The salivary microbiome is shaped by systemic hyperglycaemia, as well as changes in the salivary pH, which may be linked to local hyperglycaemia. The enrichment of predictive biomarkers of gut dysbiosis in the salivary microbiome can reflect its capacity for impairment of hyperglycaemia.

Salivary parameters of adults with diabetes mellitus: a systematic review and meta-analysis.

OBJECTIVE: Among the oral manifestations of diabetes mellitus (DM), salivary alterations stand out when considering that they can be linked to environmental changes that prompt other oral diseases. This study aimed to compare whether salivary parameters such as salivary flow, ionic composition, pH, and buffer capacity are altered in adults with DM. STUDY DESIGN: A literature search was performed in 8 databases and the gray literature. Observational and clinical studies with populations >30 years old were included. The methodological quality of individual studies was assessed, 7 meta-analyses were performed, and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach (protocol registered at PROSPERO-CRD42021214632). RESULTS: Of the 5,816 titles retrieved, 22 observational studies were included, representing a total of 1,202 individuals with DM and 946 normoglycemic control subjects. Individuals with DM had significantly lower unstimulated (mean difference [Md] = 0.13 mL/min; CI = 0.06-0.2; P = .0005) and stimulated (Md = 0.44 mL/min; CI = 0.13-0.75; P = .005) salivary flow rates, a lower pH when evaluated with electrodes (Md = 0.45; CI = 0.19-0.71; P = .0007), and a higher salivary urea (standard Md = 1.52; CI = 0.19-2.85; P = .03). No significant differences were found in the other parameters. CONCLUSIONS: Although the certainty of evidence was low because of the type of studies included, this review indicated salivary alterations in individuals with DM, such as hyposalivation, pH, and urea concentration.

Impact of detection criteria on coronal and root caries estimates in adults with and without type 2 diabetes mellitus.

OBJECTIVE: To compare caries prevalence and extent in adults with or without diabetes mellitus (DM) according to different caries detection criteria (WHO, ICDAS, and Nyvad). MATERIALS AND METHODS: A cross-sectional study was carried out including 122 individuals, 44 without DM and 78 with type 2 DM. Trained and calibrated examiners performed a visual-tactile inspection to record coronal and root caries lesions (weighted kappa > 0.7). Caries prevalence and extent were calculated according to the WHO (only cavitated lesions, missing and filled surfaces), ICDAS (all non-cavitated and cavitated lesions, missing and filled surfaces), and Nyvad (only active lesions, non-cavitated and cavitated). For root caries, lesions were classified as active or inactive. RESULTS: A significantly higher overall caries experience (DMF-S) was observed among patients with DM when the WHO (RR = 1.37; 95% CI = 1.09-1.71) and the ICDAS (RR = 1.32; 95% CI = 1.07-1.62) criteria were adopted. No difference between groups was found when the Nyvad criterion was used, although a low study power was observed in this comparison. Estimates for root caries showed a higher prevalence (PR = 2.65; 95% CI = 1.05-6.70) and risk (RR = 6.02, 95% CI = 1.81-20.00) of total D-S among diabetic patients. CONCLUSIONS: DM can predispose individuals to a higher number of root caries lesions, independently of their past caries experience. Missing teeth can overestimate caries extent in individuals with DM. CLINICAL RELEVANCE: Individuals with DM should be monitored for the prevention and control of root caries. It is recommended to splitting missing teeth from the caries estimates in studies involving adults, particularly diabetic ones.