This study aims at demonstrating the effect of erythritol and xylitol lozenges on preventing the new caries lesions and the possible remineralization effect of both polyols on incipient caries lesions.

Rationale: Several polyols (xylitol, sorbitol, erythritol) have been shown to act as excellent sugar substitutes, especially for in-between meals food products. Most commonly they are used in chewing gums, but the recent field trials also show a clear effectiveness of xylitol lozenges. Although sorbitol is metabolized at a slower rate than sucrose and not at all by most microorganisms, it can be fermented at a slow rate by all of the mutans streptococci including S. mutans while xylitol and erythritol are considered to be non-acidogenic. It has been demonstrated in some studies that xylitol reduces to a greater extent caries rate than sorbitol, however, the scientific committee on medicinal products is of the opinion that no clear data support the concept that xylitol possesses specific effects in vivo which validate a superiority claim over other polyols.

Objective: It is believed that the benefits of sugar-free gums may be twofold; 1) decreased lactic acid production and increased salivary flow potentially leading to an increased buffering of acids in plaque and 2) increased supersaturation of saliva with the mineral ions as well as enhanced clearance of sugars from the mouth. Thus sugar substitution and salivary stimulation could, it has been argued, be equally responsible for the noncariogenicity of sugar-free chewing gum. By comparing long term effects of several polyols, on possible remineralization effect on incipient caries lesions and on preventing the new caries lesions in comparison with sorbitol,the study will help demonstrate the superiority of erythritol and eventually xylitol over sorbitol and will help demonstrate the role of sugar substitutes, beyond saliva stimulation-mediated oral benefits on dental caries prevention.Sorbitol lozenges are used as a positive control. The saliva and plaque sample analyses would reveal the possible mechanisms of the expected caries preventive effects.

Study design: This is a double-blind, parallel, randomized, controlled study in primary school children around Tartu city. The allocation of the children into three groups will be based on classrooms for the practical reasons. The classrooms will be randomly allocated into the intervention and control groups. The study will last three years. During the first 2 years, the two intervention groups will consume either xylitol or erythritol-containing lozenges and the control group will be provided with sorbitol-containing tablets Then, there will be two options, depending on the effects on caries prevention after 2 years feeding with the polyols and depending on the SD of the caries incidence,. If the SD >2, the groups will not be spilt up as the power of the study would not be high enough to see any statistical effect. In this case, during the third experimental year, groups will stop eating polyol-containing lozenges and tablets to assess the lasting preventive effects of the polyol. If the SD<2 , the groups will be spilt up into two sub-groups, where one sub-group will stop eating polyols-containing lozenges to assess the lasting effect of polyol on caries prevention and the other sub-group will continue consuming the polyol-containing lozenges to assess the long-term effect of polyol intake on caries prevention.

Study population: The classrooms of 1st and 2nd primary schoolchildren (n=450) will be randomly allocated into two intervention groups (erythritol and xylitol) and into one positive control group (sorbitol. The list of the 1st and 2nd graders classrooms will be used as a sample frame. The allocation of the classrooms will be based on the random numbers generated by a computer.

Intervention: The test products will be distributed to the pupils in all (erythritol, xylitol, and sorbitol) groups three times a day during the school days (about 200/year) by the teachers.

Main study parameters/endpoints: All children will be clinically examined at the beginning of the trial, one -, two - and three years after the baseline examinations. All the surfaces of the mixed dentition (primary and permanent teeth) will be examined. The mean annual incipient and dentinal caries increment will be calculated. The teeth (FT) and surfaces (FS) restored or extracted because of caries during the study period will be calculated and included in the caries experience indices (dmft/DMFT). The plaque and saliva samples will be collected in each examination.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: There will be clinical examinations and plaque sample collection of the study subjects four times in this study. Each examination will take about 15 min. No risks for the pupils can be expected from these examinations. The children will be given a toothbrush and toothpaste every 6 months. After the study examinations, pupils will be driven to a museum by bus.

Inclusion Criteria:

• Children who's parents have signed and returned informed consent form

Exclusion Criteria:

• Any eating disorder
• Refuse to continue