Dental Calculus Formation Rate: The Role of Salivary Proteome and Metaproteome

Abstract

Background: Dental calculus accumulation varies across individuals. While various factors contribute to its accumulation, the role of salivary composition remains underexplored. This study aims to compare individuals suffering from rapid rates of dental calculus formation rates with those having slow formation rates in terms of salivary electrochemical properties as well as its proteomic, metaproteomic and elemental composition.

Methods: A total of 26 patients with a history of dental calculus were recruited. Saliva samples were collected and evaluated for electrochemical properties as well as elemental, proteomic and metaproteomic composition. Patients were provided scaling treatment to remove all calculus. Six months after the dental cleaning patients were re-assessed for the presence of dental calculus. Based on the dental calculus formation rate participants were categorised into slow (57.7%) and rapid calculus formers (42.3%) that were then assessed for differences in salivary composition.

Results: Rapid calculus formers exhibited a more neutral zeta-potential and lower concentration of salivary calcium ions than their slow-forming counterparts. Proteomic analysis identified 895 proteins across all samples. Of these, 38 proteins were exclusive to the rapid formation group, while 24 proteins were specific to the slow group. The rapid group demonstrated augmented pathways related to cell binding (e.g., cytoskeletal regulation by Rho GTPase and integrin signalling), inflammatory mediation (e.g., chemokine and cytokine signalling) and neurodegenerative disorders (e.g., 5-Hydroxytryptamine degradation, Huntington's disease and Parkinson's disease) and significant enrichment in peptidase inhibitor activity. In contrast, the slow group demonstrated enrichment mainly in immune response. Metaproteomic analysis for salivary bacteria showed significant predominance of Streptococci in the rapid group and elevated levels of Rothia in the slow group.

Conclusion: The saliva of patients with rapid calculus formation rates differs from that of patients with slow rates of calculus formation in terms of electrochemical properties as well as proteomic, metaproteomic and elemental composition.

Keywords: dental calculus; human saliva; metaproteome; proteomics; salivary proteome; zeta potential.

FIGURE 1

Study flow chart.

FIGURE 2

(A) Venn diagram showing salivary proteins uniquely expressed with statistical significance in rapid and slow group or commonly expressed in both groups; (B) and (C) Gene Ontology (GO) enrichment analysis of cellular components, molecular functions, and biological processes for up‐regulated proteins in the rapid and slow groups. The number of proteins for respective terms is shown on the x‐axis.

FIGURE 3

Enrichment analysis of the Gene Ontology terms arising from proteins in both groups. Bar chart illustrating the distribution of the enriched pathways obtained from PANTHER. The value of −log₁₀ (Fisher's test p value) is shown.

FIGURE 4

(A) Heat tree analysis utilises a hierarchical structure of taxonomic disparities. Quantitative evaluation of these differences is achieved using the log₂ transformed ratio of median proportions, visualised through colour intensity. The total protein spectra counts dictate the branch size and node. Blue branches imply a higher bacterial expression in the rapid group whereas yellow branches signify the converse. (B) The bar plot depicts the differential abundance of phyla between the two groups, as assessed by two‐way ANOVA with multiple comparisons. Notably, a substantial up‐regulation of Firmicutes was observed in the rapid group.