Читать книгу Periodontics - Fernando Suarez - Страница 87

Biofilm formation is a progressive and dynamic process that facilitates bacterial attachment to tooth structures through van der Waals forces, glycocalyx, and lectin-like receptors within a salivary pellicle and negative surface charges mediated by teichoic acid of gram-positive bacteria.^14–16 The shift from gram-positive to gram-negative bacteria occurs as subgingival plaque develops and is influenced by biofilm thickness and gingival crevicular fluid. The process of mineralization of biofilm into dental calculus has been suggested by Genco et al¹⁶ to undergo four theoretical processes: booster mechanism, epitaxic concept, inhibition theory, and transformation theory.

The inorganic and organic composition of dental calculus have been extensively explored.^17–28 Major inorganic components of dental calculus are calcium, phosphorus, carbonate, sodium, magnesium, potassium, and trace elements such as fluoride and zinc.¹⁶ Moreover, four major crystalline forms can be noted within mature calculus, including hydroxyapatite, octacalcium phosphate (OCP), whitlockite (WHT), and brushite.^18,20,22 On the other hand, proteins (50%–60%), carbohydrates (12%–20%), and lipids (10%–15%) represent about 15% to 20% of the dry weight of mature supragingival plaque.²⁹ Major differences in the characteristics of dental calculus exist depending on the location. Table 5-1 summarizes the characteristics of both supragingival and subgingival calculus.³⁰

TABLE 5-1 Characteristics of supragingival and subgingival calculus*

	Supragingival	Subgingival
Location	Coronal to gingival margin	Apical to gingival margin
Color	Yellow/white	Brown/black
Distribution	Adjacent to salivary duct openings	Randomly around the oral cavity
Composition	Low concentration of Ca, Mg, F, Sr, and ZnHigh concentration of carbonate and Mn	High concentration of Ca, Mg, and FLower concentration of carbonateMore irregular distribution of F
Mineral content and source	Average of 37% from saliva by volume	Average of 58% from gingival crevicular fluid by volume
Crystal type	Mostly OCP and hydroxyapatite	Mostly WHT
Formation	Heterogenous nucleation and crystal growthMore variable calcification	Heterogenous nucleation and crystal growthMore homogenous calcification
Microorganisms	More filamentous, faster growing	Less filamentous, slower growing
Morphology	Heterogenous with small needle-shaped (100 nm), large-ribbon-like and bundle/rosettes (1–50 nm) crystals	Several crystal types (< 50 nm): spiny, crusty, nodular, ledge/ring, individual islands, smooth veneers and finger/fern-like
Pathogenic potential	Little evidence	Associated with periodontal disease

*Adapted and modified from Roberts-Harry and Clerehugh.³⁰

Ca, calcium; Mg, magnesium; F, fluoride; Sr, strontium; Zn, zinc; Mn, manganese; Na, sodium.