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 mouth Approximal and lingual sites more affected than buccal sites |
| Appearance | Creamy-white colour May become nicotine-stained in smoker |
Brownish-black due to haemorrhagic elements from gingival crevicular 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 clinically Detection 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 entrance
to 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 visible
Radio-opaque calculus ‘wings’ may be visible on approximal sites on radiographs |
| Formation | Nucleation and crystal growth are heterogeneous Calcification is heterogeneous Deposit builds up in layers with variable mineral content in the layers |
Nucleation and crystal growth are heterogeneous Calcification is more homogeneous (uniform) than supragingival calculus Deposit 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 salts Mainly calcium, phosphate (lower ratio than subgingival calculus) Small amounts of magnesium, sodium, carbonate and fluoride. Regular distribution of fluoride Traces of other elements Organic matrix constitutes 15–20% of dry weight: protein (55%), lipid (10%) and carbohydrate |
Greater concentration of calcium, magnesium and fluoride than in supragingival calculus Higher calcium to phosphorus ratio than in supragingival calculus Irregular distribution of fluori/> |
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