## 3 Results
### Microstructural Analysis  
An intra-operator reliability analysis of the study variables was performed, obtaining an ICC = 0.996 for the tubular count variable, and an ICC = 0.988 for the tubular diameter variable, considering both values as an excellent degree of agreement [26]. We aimed to determine whether the distribution of the variables tubular count and diameter followed normal criteria, and found that although most of the variables followed a normal curve, the tubular count did not have a normal distribution in nine of the points studied, and the tubular diameter was observed at four of the points studied (\(p\) Shapiro-Wilk < 0.05). In the analysis of the detection of Calcium and Phosphorus, normality criteria were not met in most of the study points (\(p\) Shapiro-Wilk < 0.05). It was found that the type of tooth influenced the count or tubular density in the longitudinal cut pattern in the external (\(p\) value = 0.046), deep (\(p\) value = 0.032) and pulpal (\(p\) value = 0.028) dentin. The differences found in the average dentin or in the cross sections and in the variable tubular density were not statistically significant, so it was secondary to the type of cut of the dental tubules, and not an effect of the type of tooth. Due to this, the type of tooth was not differentiated in the analysis of the variables. The differences in the tubular count are not statistically significant in the longitudinal cut pattern or in the OI-control group comparison, neither between the three OI groups, excluding or not the control group (\(p\) value > 0.05) (Table 2). In the cross-sectional pattern, there are significant differences between control and OI groups in the external (\(p\) U Mann-Whitney = 0.003) and pulpal dentin (\(p\) U Mann-Whitney = 0.027), with a higher tubular density of the teeth with OI in external dentin and lower in pulpal dentin \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Tooth**} & \multicolumn{2}{c}{**Obtaining Age**} & \multicolumn{2}{c}{**Bisphosphonate**} & \multicolumn{2}{c}{**Genetic Mutation**} \\  & & **Incisor** & **Canine** & **Molar** & **Mean** & **SD*** & **Yes** & **No** & **CO1A1-COL1A2** & **Other** & **Unknown** \\ \hline \multirow{4}{*}{**Study (OI)**} & **OI-I** & 4 & 3 & 4 & 9.22 & 3.34 & 10 & 1 & 7 & 2 & 2 \\  & **OI-III** & 2 & 4 & 4 & 11.20 & 3.77 & 10 & - & 5 & 2 & 3 \\  & **OI-IV** & 3 & 1 & - & 7.44 & 1.54 & 4 & - & 2 & - & 2 \\  & **Total** & 9 & 8 & 8 & 9.73 & 3.49 & 24 & 1 & 14 & 4 & 7 \\ \hline \multirow{2}{*}{**Control sample**} & & 8 & 10 & 12 & 10.14 & 2.64 & - & 30 & - & - & - \\ \hline \hline \end{tabular}
* SD—standard deviation.  
\end{table} 
Table 1: Demographic description of the study sample. than healthy teeth (Table 2). Regarding OI types, statistically significant differences were found in the tubular count in outer or external dentin between healthy controls and OI-I, and in deep and middle dentin between OI-I and OI-III (\(p\) value < 0.05). The results suggest the existence of a higher overall tubular density and in the deep dentin in the subjects with OI-I compared to OI-III, in addition to a higher tubular count in the outermost dentin than the control group. The behavior of the tubular density in the dentin points studied was analyzed, and a similar curve was observed in the longitudinal cut pattern in the control group and the group with OI (\(p\) G-G = 0.611) and in the three OI types (\(p\) G-G= 0.36) (Figure 1) with an increase in the tubular count as the dentin approaches the pulpal tissue. Significant differences (\(p\) G-G < 0.001) were found between the outer dentin and the rest of the studied points, and between the medium and deep dentin.