D9 Transportation Intervention

Topic

Transport interventions modify substance flows within the oral system to improve the patient's transport balance. Key transport interventions include dental sealants, saliva substitutes and stimulants, controlled drug-release systems, and fluoride varnishes, each targeting a specific flow within the oral system.

Dental sealants serve two functions depending on where they are applied: when they occlude exposed dentinal tubules, they reduce the dentin permeability responsible for tooth sensitivity; when they occlude the pits and fissures of molars, they prevent biofilm bacteria and their substrates from accumulating in these grooves, thereby preventing the development of dental caries in those areas.

The reduction in dentin permeability achieved by dental sealants is proportional to the fraction of dentinal tubules the sealant successfully occludes: the greater the fraction of tubules occluded, the lower the remaining dentin permeability available for an external stimulus to shift dentinal fluid and trigger tooth sensitivity.

Saliva substitutes and stimulants—such as pilocarpine or cevimeline—increase the salivary flow available in the mouths of patients with xerostomia; saliva substitutes externally replace missing saliva, whereas saliva stimulants act on the patient's own salivary glands to induce increased saliva production.

Saliva stimulants act on the muscarinic receptors of the glandular acini—the same acini whose function determines basal salivary flow. By activating these muscarinic receptors, the stimulant increases salivary flow in a dose-dependent manner; that is, the higher the administered dose of the stimulant, the greater the resulting increase in salivary flow. Controlled drug-release systems—such as devices containing chlorhexidine or tetracycline—are placed directly into the periodontal pocket to maintain a local drug concentration that is far higher and more sustained than what could be achieved with a mouthwash or a tablet; this ensures the local concentration within the pocket remains above the minimum level required to control bacteria for an extended period.

When diffusion is the mechanism controlling drug release from these systems, the cumulative amount of drug released does not increase in direct proportion to time; instead, it increases in proportion to the square root of elapsed time—a pattern of behavior also observed in diffusion-controlled processes within other dental tissues.

Fluoride varnishes act as a fluoride reservoir applied to the tooth, slowly releasing fluoride ions into the enamel over time rather than delivering the entire dose at once. Thus, dental sealants, saliva substitutes and stimulants, controlled drug-release systems, and fluoride varnishes each modify—in their own way—specific substance flows that define the transport equilibrium of the oral system described earlier.

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