Caries in the Elderly

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Summary

Root Caries in the Elderly: Diagnosis and Management

Kenneth Shay DDS MS

The success of preventive dental measures that brought about the decline of toothlessness among Americans over age 65 has by definition expanded the number these individuals who are subject to dental and periodontal diseases in their seventh decades and beyond. The cumulative affect of a lifetime of subclinical episodes of inflammatory periodontal disease results in a nearly universal, measurable loss of periodontal attachment among adults over age 50 years, even those who have never been diagnosed with a destructive periodontal condition. Age-associated attachment loss followed by gingival recession results in growing prevalence and severity of root exposure with increasing age. The high carbonate hydroxyapatite of cementum and dentin demineralizes at a higher pH than enamel, making exposed root surface particularly susceptible to caries. Plaque control in older persons is commonly impaired by the presence of fixed and removable prostheses, tipped and rotated teeth, open gingival embrasures, and interproximal concavities; as well as by drug-induced xerostomia, impaired upper extremity mobility and manual dexterity, and diminished visual acuity. The new appearance of tooth surfaces with greater susceptibility to plaque colonization and demineralization in a generation that experiences compounding sources of interference to plaque control is responsible for the steady increase in root caries prevalence observed with advancing age.

The pathophysiology of root caries has similarities with but also differences from the processes and agents involved in caries initiating in enamel. Both begin with the colonization of the tooth surface by acidogenic microorganisms that metabolize simple dietary carbohydrates and excrete organic acids and a poly-sugar substance fostering adherence. The local drop in pH demineralizes crystallites of hydroxyapatite that may be remineralized when the carbohydrate source is exhausted and the pH of the environment reapproaches neutrality. Over time, when the net effect of demineralization predominates, proteinolytic plaque bacteria contribute to the further destruction of the tooth surface, resulting in cavitation.

The current approach to the systematic evaluation of attack patterns of root caries begins with the assumption that root caries cannot initiate in the absence of exposed root surface—a clinically reasonable but unproven belief. The number of exposed root surfaces increases with age, as does the percentage of them that have active and restored caries. Interproximal exposed root surfaces are the most likely to become carious, and maxillary root areas are more likely than mandibular. For at-risk surfaces in the maxilla, attack rates increase from posterior to anterior; the opposite trend is observed in the lower jaw. Detection of root caries relies on visual, tactile, and radiographic findings. Root areas that are carious may be undetectable visually, or they may appear more opaque than surrounding tissue, or slightly more pigmented. There is a variety of chemical approaches for enhancing the clinician’s ability to visually detect root caries but none is yet in common use. A sharp explorer that readily penetrates the tooth surface under light pressure has detected root caries, but the act of penetration may actually impair subsequent measures designed to foster remineralization. A blunted explorer can identify roughness and incipient cavitation but will fail to detect areas demineralized but uncavitated. Root caries detectable radiographically is so advanced that it will not escape visual and tactile detection, yet radiographs may nonetheless be helpful for assessing restorability and prognosis.

Approaches for managing root caries are still evolving but should always address both the restoration of the damaged tooth structure and mitigation of the factors that led to the disease. The management of incipient, non-cavitated lesions is accomplished successfully through repeated topical applications of high concentration fluoride. Small cavitated lesions may also be arrested in this manner, although the success rate is lower. Small cavitations may also be successfully treated through the recontouring of the tooth surface to prevent subsequent plaque entrapment. Restorative approaches for root caries are made challenging by uncertain extent of lesions, difficult access and isolation, atypical cavity preparations, and an absence of esthetic materials specifically designed for the purpose. Studies on restored root surfaces show higher rates of marginal failure than coronal restorations. Marginal integrity can be enhanced through a variety of approaches including dentinal bonding, phosphoric acid etching, use of a glass ionomer agent with subsequent, repeated fluoride application, and burnishing amalgam. Success rate of bonded restorations (composite, compomer, resin-modified glass ionomer, and glass ionomer) is improved through the incorporation of mechanical retention in cavity design and etching the preparation with phosphoric acid. Ease of cavity filling benefits from preparations that preserve a mortise form, even if one or more walls is initially carious. Placement of the apical margin within the sulcus may reduce failures as well. Full coverage restorations should be contoured to minimize plaque entrapment on adjacent root areas.

Because the incidence of root caries is the result of an equilibrium process that has tipped toward the progression of disease, management must include measures to tip the equilibrium toward oral health or any success will be short-lived. Management strategies include limiting the substrate, making the substrate more resistant to dissolution, limiting the numbers or pathogenicity of the causative organisms, enhancing plaque removal, and reducing plaque retention. Limitation of root exposure needs to be a primary goal of all adult dental care. Fluoride in drinking water, dentifrice, mouth rinse, topical gel, and varnish all foster development of a less-soluble fluoroapatite in the superficial areas of the root. Varnishes that incorporate thymol or chlorhexidine have proven effective at reducing oral bacterial load. Use of xylitol as a sugar substitute confers a sustained suppressive effect on caries progression for reasons that are still under discussion. Oral hygiene regimens for older individuals should be personalized and modified to be effective even in the face of reduced grip strength, altered shoulder and wrist motility, and widespread exposure of concave interproximal surfaces. Salivary flow rate and content that is adversely affected as a side effect of medications mandates education of the patient and prescribing provider in order to effect change.

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