THE CARIES PROCESS: A BRIEF OVERVIEW

There is a call to action for the profession of dental hygiene to employ the same standards in caries assessment, prevention, and subsequent management as we have in our treatment of periodontal disease. With the vast array of new and innovative products designed to assist both chairside and self-care protocols, we may emerge confident in having a strong impact on preventive intervention. The understanding of the mechanism of both the disease and its prevention is critical in counterbalancing the effects of today’s modern lifestyle. The need to intervene in the earliest stages of caries development cannot be overstated.

Dental caries is ranked as the most prevalent global disease even though we have witnessed a significant reduction during the past several decades. It is defined as a “dynamic disease process” which is caused by acids from bacterial metabolism diffusing into enamel and dentin creating dissolution of the tooth matrix. The disease itself is an infectious, communicable disease that, if left untreated, can lead to pain, infection, tooth loss, and cellulitis of significant proportion. The psychological trauma associated with emergency-based care, although not measurable, can be debilitating. The process of dental caries is now well understood and is not the enigma it once was. However, there has been debate about whether early caries turns into eventual cavitation, and whether the different types of caries are both comparable and predictive. The predominant bacteria implicated in the process is Streptococcus mutans, which is a gram-positive facultatively anerobic bacterium and an early colonizer in plaque biofilm. The microbe was initially isolated by J. Clarke in 1924. In addition to describing S mutans, he introduced the concept of microbial succession with different bacteria being dominant at different stages of the caries process. The clinical significance of this finding becomes essential in the development of a rational approach to risk assessment and the introduction of mechanisms of intervention.

Assessment, education, treatment, and prevention are all key components of addressing this disease successfully. One of the most critical factors is the recognition of the caries process being cyclic in nature and transitioning from demineralization to remineralization. This provides the dental hygienist with many opportunities to intervene in this dynamic process. Remineralization may be introduced with calcium and phosphate ions in conjunction with minimal amounts of fluoride facilitating a natural reparative process designed to rebuild stronger and less soluble structure than the original mineral.

The secondary challenge arises with the confrontation of making an evidence-based decision regarding product selection and treatment interventions both chairside as well as self-care recommendations. Fluoride selection falls into this category, given the immense and vast array of product availability. The ADA Council on Scientific Affairs has assisted our profession greatly by evaluating the collective body of scientific evidence as it pertains to the efficacy of professionally applied topical fluoride for caries prevention. The recommendations were published as a guide, rather than a requirement or regulatory statement, to assist the dental professional in the selection of an effective product. MedLine and the Cochrane Database of Systematic Reviews were both consulted for clinical studies and systematic reviews of professionally applied topical fluoride including gels, foams, and varnishes. The evidence was further graded and classified according to the strength of the recommendations as well as the highest category of evidence. There was clear, strong evidence to support the recommendation of fluoride varnish for prevention of caries in children and adolescents. New innovations in fluoride varnish have prompted a shift, with one of the most compelling rationales being the prolonged contact time that fluoride varnish provides.

The primary benefits of topical fluoride include inhibition of demineralization, enhancement of remineralization, and inhibition of bacterial enzymes. Low but slightly elevated levels of fluoride in saliva and plaque help prevent and reverse caries by inhibiting demineralization and enhancing remineralization.6 Remineralization may be further enhanced by providing calcium and phosphate in conjunction with minimal amounts of fluoride. This is due to the fact that fluoride acts as a catalyst and influences reaction rates with dissolution and transformation of various calcium phosphate mineral phases within tooth structure and reacts within the plaque adjacent to tooth surfaces. Continuous low levels of a slow release extended contact fluoride varnish containing both calcium and phosphate in a resin-modified glass ionomer applied to site-specific areas of demineralization provide further protection against demineralization and acid erosion.

Complimentary remineralization strategies may be employed in daily self-care regimens that are simple to incorporate into oral health practices. When the bacterial challenge is high and/or pH is lowered, there is a volatile oral environment that emerges. The added consideration of inadequate salivary flow to provide a buffering capacity further tips the scale towards demineralization. The remineralization process can be successfully integrated through the selection of remineralization toothpastes. Calcium and phosphate technologies such as the casein protein (CPP-ACP) as well as bioactive glasses containing NovaMin have been more recently developed to improve upon the earlier calcium phosphate products.

Recaldent (CPP-ACP) results in localization of CPP-ACP at the tooth surface by binding to dental plaque biofilm both in the microorganisms and in the extracellular matrix. Higher concentration fluoride toothpastes in combination with both calcium and phosphate have also been developed, producing favorable results when the dose response relationship was observed clinically. NovaMin is a sodium calcium phosphosilicate glass that releases calcium and phosphate ions in an aqueous environment such as saliva. Sodium ions are the driving mechanism that exchange with hydrogen cations allowing both calcium and phosphate ions to be released. The result is a rapid and continuous release and deposition of a natural crystalline hydroxyl-carbonate apatite layer that is chemically and structurally the same as tooth mineral.

Nature also provides a “secret weapon” to fight back effectively against the caries process, and that product is xylitol. Xylitol is a 5 carbon sugar alcohol or polyol that cannot be metabolized by S mutans resulting in starvation or inability to assist in the demineralization or dissolution of tooth structure. The American Academy of Pediatric Dentistry has recognized the benefits of caries strategies implementing xylitol. Their recommendations were based on the overwhelming clinical data which underlines the caries reduction effects of xylitol. Their goal was to “assist oral healthcare professionals make informed decisions about the use of xylitol-based products in caries prevention.”12 Studies suggest xylitol intake that consistently produces positive results ranged from 4 to 10 g per day divided into 3 to 7 consumption periods.