## 3 Results  
SEM images of some samples in the control and study groups are presented in Figure 1. In the control group, all of the samples showed a frank and wide opening of the dental tubules (Figure 1d), which confirmed the sensitive tooth model. In the study groups, obvious closure of the tubules by mineral depositions was observed, with different percentages of tubule occlusion being registered on the same sample or in different samples from the same group (Figure 1a-c). While most of the samples presented all the tubules partially occluded (as presented in Figure 1a,b), other samples presented completely unoccluded tubules beside partially occluded tubules. Mineral deposition on the dentin surface was also observed mostly on the samples in groups 1 and 2 (Figure 1a-c). Figure 1: SEM micrographs of dentin samples in study groups (**a-c**) and control group (**d**). (**a**) SEM image (2000\(\times\)) of a dentin sample in group 1 (score 1). (**b**) SEM image (2000\(\times\)) of a dentin sample in group 2 (score 1). (**c**) SEM image (2000\(\times\)) of a dentin sample in group 3 (score 2). (**d**) SEM image (2000\(\times\)) of a dentin sample in group 4 (score 5). SEM images on the dentin surface showing dentinal tubule occlusion with different scores in the study groups (group 1: Karex toothpaste, group 2: Biorepair Plus Sensitive toothpaste, and group 3: [PERSON]’s Biorepair toothpaste) and in the control group (group 4). Strong inter-examiner agreement on dentine tubule occlusion evaluated on SEM images was recorded (Kappa value of 0.961). The mean score values for dentin tubule occlusion and the number of samples specifically scored for tubule occlusion in each group are presented in Table 2. In group 3, the number of the samples with a score of 4 was higher than in groups 2 and 1. An equal number of samples with a score of 1 was recorded in groups 1 and 3 and an equal percentage of samples with a score of 3 was recorded in groups 2 and 3. The highest number of samples with a score of 2 was registered in group 1, followed by group 2 and 3, and the highest number of tubule closure with a score of 4 was obtained in group 3, followed by group 2 and group 1. Irrespective of the group, none of the samples in the study groups presented complete closure of dentinal tubules. The mean values of carbon, calcium, phosphorus, and oxygen ion concentration (wt%) are presented in Table 3. Carbon ion concentration in group 3 was significantly higher when compared to group 2 and group 1 (_p_ < 0.05, Table 4). Statistically significant results were also recorded when comparing carbon ion concentration in the study groups and the control group (_p_ < 0.05, Table 4). Significantly increased calcium ion concentration was recorded in the study groups when compared to the control group (_p_ < 0.05, Table 4). In group 3, significantly lower calcium concentration was observed when compared to group 2 (_p_ < 0.05, Table 4). Phosphorous ion concentration was significantly higher in the study groups when compared to the control group (_p_ < 0.05, Table 4). Significantly lower phosphorous ion concentration was recorded in group 3 when compared to group 1 and group 2 (_p_ < 0.05, Table 4). Oxygen ion concentration in the study groups was significantly higher when compared to the control group (_p_ < 0.05, Table 4). Also, statistically significant differences were recorded when comparing the values of tubule closure in the study groups and the control group (_p_ < 0.05, Table 4). There was no significant difference when comparing the values of dentin tubule occlusion in the study groups (_p_ values > 0.05, Table 4).