Fernando Suarez - Periodontics

Biofilmformation 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. 14–16The shift from gram-positive to gram-negative bacteria occurs as subgingival plaquedevelops and is influenced by biofilm thickness and gingival crevicular fluid. The process of mineralization of biofilm into dental calculushas been suggested by Genco et al 16to 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. 17–28Major inorganic components of dental calculus are calcium, phosphorus, carbonate, sodium, magnesium, potassium, and trace elements such as fluoride and zinc. 16Moreover, four major crystalline forms can be noted within mature calculus, including hydroxyapatite, octacalcium phosphate (OCP), whitlockite (WHT), and brushite. 18,20,22On 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. 29Major differences in the characteristics of dental calculus exist depending on the location. Table 5-1summarizes the characteristics of both supragingival and subgingival calculus. 30

TABLE 5-1 Characteristics of supragingival and subgingival calculus *

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

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

In 1953, Zander explored the mechanisms of calculus attachment upon 50 freshly extracted teeth. 31Four main types of attachment were identified: (1) secondary cuticle, (2) direct attachment into irregularities of cementum, (3) penetration into cementum, and (4) mechanical retention in areas of resorption. In addition, various forms of combinations were also described ( Box 5-1). 31Types II (20%) and III (10%) were noted as the most frequent modalities of calculus attachment, and the cementoenamel junction (CEJ) was the favored site for calculus formation. 31

BOX 5-1 Mode of calculus attachment to cementum 31

Following Zander’s findings, multiple authors questioned specific types of calculus attachment and attempted to employ more sophisticated technology to test his conclusions. 19,32–40Notably, Canis et al rejected the possibility that microorganisms can penetrate the cementum surface and considered this phenomenon as an artifact due to superimposition of a detached cementum onto the tooth structure during sample preparation. 41These findings were confirmed using light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Defined as an apical extension of enamel usually toward a furcation, 1 enamel projections(also known as cervical enamel projections [CEPs]) are common anatomical variations where a definitive projection of enamel extends into the furcation area, preventing true attachment of periodontal ligament (PDL) fibers upon the root surface 7(Fig 5-1).

Fig 5-1 Classification of cervical enamel projections.

Early observations in dental anatomy described how the enamel dips into the furcation area of multirooted teeth in a tongue-like fashion. 42–48A landmark article by Masters and Hoskins examined extracted teeth with CEPs and suggested a grading system to determine the severity of these projections ( Box 5-2). 7The authors reported the prevalence of CEPs in mandibular and maxillary molars as 28.6% and 17%, respectively. In addition, clinical observations revealed that 90% of isolated furcation involvementswere associated with CEPs and mainly affected buccal furcation entrances. 7

BOX 5-2 Grading system for cervical enamel projections by Masters and Hoskins 7

A myriad of studies continued exploring the prevalence, incidence, and association between CEPs and furcation involvement ( Table 5-2). 7,49–55Variations within these investigations might arise from differences in tooth type, reason for tooth extraction (eg, caries, severe periodontitis, endodontic failure), and patient population. With the exception of Leib et al, 50most studies confirmed a positive correlation between CEPs and furcation defects. Notably, Hou and Tsai reported a high prevalence (63.2%) of furcation defects associated with CEPs and intermediate bifurcational ridges (IBRs) affecting primarily mandibular molars. 55

TABLE 5-2 Prevalence of enamel projections

FI, furcation involvement; IBR, intermediate bifurcational ridge.