IV. MULTIFACTORIAL CONCEPT OF CARIES ETIOLOGY Dental caries – a multifactorial disease – interplay of 3 primary factors plus time. Presence of bacteria and a suitable substrate on a tooth surface at a given time is not enough to cause caries. So, variations in caries incidence occur because of number of indirect factors ( CONTRIBUTING FACTORS ).

dental caries to occur : bacterial biofilm has to accumulate on a tooth surface. The bacteria within the biofilm metabolize dietary sugar substrates producing acids. acids, over time, lead to demineralization of the tooth tissue. Clinically, this is not the case. Some tooth surfaces that are frequently covered with plaque do not develop caries whereas other tooth surfaces covered with plaque in the same mouth develop caries .

Many other factors, such as: dietary habits, fluoride and saliva impact upon the disease process which is complex and dynamic in nature. From the earliest stage, continued demineralization can be stoped and lesion arrest is possible by simply disrupting the plaque biofilm on the surface of the tooth at regular intervals. Very early lesions which are not detected clinically may therefore not progress to clinically detectable white spot lesions.

CONTRIBUTING FACTORS - TOOTH 1. COMPOSITION OF TOOTH: - Structure & composition of a tooth determines initiation and rate of progression of caries. Surface enamel more mineralized than subsurface enamel and is more resistant to caries. It also accumulates more fluoride, zinc, lead ions than subsurface enamel. Therefore in initial carious lesions, the subsurface enamel shows marked demineralization even though the outer enamel is relatively intact.

2. MORPHOLOGIC CHARACTERISTICS: - Deep, narrow occlusal fissures or buccal and lingual pits predispose to caries as they tend to retain food and bacteria. Also enamel is quite thin at the base of such deep pits and fissures. Certain surfaces of teeth are more susceptible to decay like e.g. in mandibular 1st molars the likelihood of caries in descending order is occlusal, buccal, mesial, lingual and distal. The most susceptible teeth are mandibular 1st molars followed by maxillary 1st , mandibular and maxillary 2nd molars.

CONTRIBUTING FACTORS – TOOTH 3. POSITION: - Malaligned, rotated and abnormally situated teeth can be difficult to cleanse and are likely to trap food debris and bacteria. This, in susceptible persons is sufficient to cause dental caries.

CONTRIBUTING FACTORS - DIET 1.PHYSICAL FORM: - Very important factor responsible for difference between caries incidence of primitive and modern man. Already explained that diet of primitive man contained plenty of roughage which mechanically cleansed the teeth of any adhering to the teeth.

Also, the coarse nature of the diet induced early attrition of occlusal and proximal surfaces leading to reduction in food entrapment. Diet of modern man in contrast is soft and lacking in roughage. As a result, food sticks to teeth and is not cleansed mechanically.

2. CARBOHYDRATE CONTENT OF DIET: - Accepted all over as one of the most important factors in caries process. Observed that different ethnic populations have differing caries incidences – postulated that it could be due to difference in diet, especially carbohydrate content.

Diet of caries free ethnic races contain low amounts of carbohydrates, that too found in fruits and vegetables, while diet of caries prone westerners contains more carbohydrates due to intake of processed food. Exceptions – certain populations in India have a high carbohydrate content but are relatively caries free.

3. LIPID CONTENT OF DIET: - Understood that medium chain fatty acids and their salts have antibacterial effects at low pH. Mechanism of action not understood. Its potential as anticariogenic food needs more investigation (more study).

4. VITAMIN CONTENT OF DIET: - Only Vit D and Vit K appear to have some role in the caries process. Vit D deficiency can cause enamel hypoplasia which can make the tooth more susceptible to caries. Vit K has enzyme inhibiting action in carbohydrate degradation cycle. Can be utilized as an anticariogenic agent.

5. CALCIUM & PHOSHORUS CONTENT:- Available evidence indicates that there is no relation between dietary calcium and phosphorus and dental caries. 6. FLUORINE CONTENT: - While topical and water fluoridation has been known to be effective in caries control, dietary fluorine may have no role as it is unavailable metabolically.

CONTRIBUTING FACTORS – SALIVA 1. COMPOSITION: - Many inorganic and organic components of saliva have been investigated for anti cariogenic effects. However, results have been conflicting. In normal circumstances, saliva is supersaturated with calcium and phosphate ions w.r.t enamel hydroxyapatite. This not only prevents enamel from dissolving but even tends to precipitate apatite in the surface enamel of carious lesions.

2. pH OF SALIVA: - The “critical” pH at which the inorganic material of tooth begins to dissolve is about 5.5, since above this pH, saliva is supersaturated with Ca and Po4 ions. Although much has been discussed about buffering capacity of saliva, its relation with caries incidence is not so simple! Acid production during caries occurs at a localized site on tooth, which in initial stages at least, is covered by dental plaque. This plaque prevents a free exchange of ions.

3. QUANTITY OF SALIVA: - Caries incidence is significantly higher in people with less or no saliva flow, as is seen in cases of salivary gland aplasia and xerostomia. Continuous flow of saliva is required for mechanical removal of bacteria and food debris from the tooth surfaces.

4. VISCOSITY OF SALIVA: - Sound scientific evidence is lacking to support the view that viscous saliva is associated with high caries incidence as some studies have reported. The reverse has also been shown to be true in some other studies.

5. ANTIBACTERIAL PROPERTIES: - Saliva contains many antibacterial factors like lysozyme, lactoferrin, sialoperoxidase, bistatin, thiocyanate ion etc. However their efficacy has been doubtful as saliva always appears to contain bacteria capable of causing caries if carbohydrates are present.

CONTRIBUTING FACTORS – SYSTEMIC FACTORS 1. HEREDITY: - Racial tendency for high or low caries may be explained by heredity. However, local factors like change in dietary habits can change this tendency. Possible that caries tendency may be inherited through tooth form & structure. Prepared by Dr Sundeep S Bhagwath

2. PREGNANCY & LACTATION: - Commonly observed that during pregnancy, women tend to neglect their oral health owing to all her attention being diverted to that of care for the newborn. Thus increased caries incidence during pregnancy & lactation is more a problem of neglect !