6
Calculus
Table 6.1 Differences between supragingival and subgingival calculus.
| Supragingival calculus | Subgingival calculus | |
| Location | Coronal to gingival margin | Apical to gingival margin within gingival sulcus or periodontal pocket |
| Distribution | Adjacent to openings of salivary ducts:
lingual of mandibular incisors (sublingual duct)
buccal maxillary second molar (parotid duct)
|
No predilection for particular parts of mouthApproximal and lingual sites more affected than buccal sites |
| Appearance | Creamy-white colourMay become nicotine-stained in smoker | Brownish-black due to haemorrhagic elements from gingivalcrevicular fluid and black pigments from calcified anaerobic rods |
| Morphology | Undifferentiated morphology – amorphous deposit | Variable:
• ledges or rings around tooth, especially on the cementenamel junction
• on root surface(s) as crusty, spiny, nodular formations, thin veneers, fern-like arrangements, individual islands.
• supragingival on subgingival deposits
|
| Detection | Visible clinicallyDetection enhanced by air drying, which gives chalky appearance | By probing – tactile sensation enhanced by using ball end of WHO 621 probe.If deposit is located at entrance to pocket:
• it may be visible as dark shadow under the gingival margin;
• by directing air jet from three-in-one syringe at entranceto pocket it may be possible to retract the gingiva and see deposit directly.
Following gingival recession, subgingival deposit may become located supragingivally and be easily visibleRadio-opaque calculus ‘wings’ may be visible on approximal sites on radiographs
|
| Formation | Nucleation and crystal growth are heterogeneous Calcification is heterogeneousDeposit builds up in layers with variable mineral content in the layers | Nucleation and crystal growth are heterogeneousCalcification is more homogeneous (uniform) than supragingival calculusDeposit builds up in layers, each with similarly high mineral density |
| Mineral content and source | Mean of 37% by volume (range 16–51% in the different layers)Derived from saliva | Mean of 58% by volume (range 32–78% in the different layers) Derived from gingival crevicular fluid |
| Composition | 70–80% inorganic saltsMainly calcium, phosphate (lower ratio than subgingival calculus)Small amounts of magnesium, sodium, carbonate and fluoride.Regular distribution of fluorideTraces of other elementsOrganic matrix constitutes 15–20% of dry weight: protein (55%), lipid (10%) and carbohydrate | Greater concentration of calcium, magnesium and fluoride than in supragingival calculusHigher calcium to phosphorus ratio than in supragingival calculusIrregular distribution of fluori/> |
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