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risk approach is known as the directed or targeted approach where a particular subgroup of population are the target group or the high-risk approach where individuals consists the target group (Daly et al. 2002). The goal, in the whole-population approach is to control the determinants of incidence of caries at the whole population while in the risk approach, identifying groups or individuals with high susceptibility to caries in order to protect them Dentists and Preventive Oral Health Care is called for. The advantages and limitations of both high-risk and population strategies are summarized in the following table (Rose 1985): High-risk strategy Population strategy Advantages Intervention appropriate to individual Subject motivation Dentist motivation Cost-effective use of resources Benefit: risk ratio favourable Radical Large potential for population Behaviourally appropriate Disadvantages Difficulties and costs of screening Palliative and temporary; not radical Limited potential for both individual and population Behaviourally inappropriate Small benefit to individual Poor motivation of subject Poor motivation of dentist Benefit: risk ratio worrisome Table 1. Comparison of high-risk and population strategies 6. Caries-risk assessment In any preventive program, determining person's risk to develop that kind of disease would help professionals better manage patients preventively. Incorporation of risk assessment, as an important part of clinical decision making, into routine dental practice has been increasingly emphasised in recent years (American Dental Association 1995, Brad Rindal et al. 2006). The information gathered from caries risk assessment will be helpful in directing preventive and curative efforts according to patients' need, identifying the particular risk factors for each patient, and transferring this information to patient in order to encourage him/her for keeping recall appointments (Kidd and Nyvad 2003). Providing preventive measures and recall visits according to each individual’s need would ensure appropriate use of resources. Since patients with elevated caries risk require receiving especial preventive regimen to reduce elevated incidence and severity of caries while those with low caries risk needs no additional preventive interventions and should have extended recall intervals. (Brad Rindal et al. 2006). Caries risk assessment covers a variety of factors such as past caries experience, microbiological tests (salivary lactobacilli, mutans streptococci, and yeasts and salivary flow rate and buffer capacity), dietary habits, oral hygiene, and social factors (Hausen 2003). 6.1 How to do caries-activity assessment? Presence of active caries lesions (cavitated and/or non/cavitated) at the time of examination, is the strongest evidence for the prediction of future caries activity (Zero et al. 2001). There is no consensus on the definition of high caries activity; the following two criteria, however, might be indicative of high rate of caries progression in most populations: 1. Two or more lesion increment annually, and 2. Multiple active lesions in regions of mouth with high and rapid flow of saliva (lower incisors and buccal surfaces of upper molars) (Kidd and Nyvad 2003). Stage of development of the dentition is another important issue when estimating caries activity status. Risk sites in different stages of dentition over life are as follows: in children, occlusal surfaces of erupting permanent molars; in adolescents, proximal surfaces especially Oral Health Care – Prosthodontics, Periodontology, Biology, Research and Systemic Conditions 214 the distal surface of second premolars and the mesial surface of second molars; in adults and elderly, root surfaces which are difficult to be cleaned (Kidd and Nyvad 2003). 6.2 How to determine the risk factors? A risk factor is defined as "an environmental, behavioural, or biologic factor confirmed by temporal sequence, usually in longitudinal studies, which if present, directly increases the probability of a disease occurring, and if absent or removed, reduces the probability. Risk factors are part of causal chain, or expose the host to the causal chain. Once disease occurs, removal of a risk factor may not result in a cure." (Beck 1998). Caries risk factors are usually categorised as biological factors and social and demographic factors. Both of these risk factors can be detected by getting a medical and dental history. The following conditions that contribute to high caries activity should be considered in medical history: Dry mouth due to diseases like Sjögren's syndrome or radiotherapy in head and neck regions, using medications which interfere with salivary flow such as antidepressants or drugs which have sugar in their structure like some syrups or asthma inhalers. The following issues are informative in dental history: 1. A history of multiple restorations with frequent replacements is an important sign of high caries risk. 2. Questions about patient's oral hygiene activities like frequency and time of brushing and flossing, type of toothpaste, method of rinsing after brushing, use of mouthrinse. 3. Patient's diet: frequency of using sugary drinks or snacks. Sometimes asking patients to fill a diet sheet may provide further information than just a verbal enquiry. Social and demographic risk factors are not involved directly in the process of dental caries (Kidd and Nyvad 2003). Instead, these risk factors such as income, education and social environment will influence dietary and oral health related behaviours (Kidd and Nyvad 2003). 6.3 How to categorise patients based on their caries-activity status? After the information regarding caries activity gathered, patients will allocate to one of these categories: 1. Caries inactive or caries controlled: no active lesion or at maximum one presents, with no history of recent restoration. 2. Caries active but all relevant risk factors can potentially be changed: in this category, active lesions are present and patients experience two or more new/progressing/filled lesions in each year during past 2-3 years. These patients are able to control caries through changes in risk factors.