## 2 Materials and Methods
### Statistical Analysis  
Data were collected using Microsoft Office Excel spreadsheets (Microsoft, Redmond, WA, USA). Statistical analyses were performed using SigmaPlot 14.0 software (Systat, Palo Alto, CA, USA). \(p\)-value \(\leq\) 0.05 was considered statistically significant. Sample size was calculated for the association of risk factors and differences in palatal morphology between the two groups. A dedicated sample-size calculation tool was used to differentiate the impacted canine and control group with chi-square and \(t\)-tests. Assuming a power of the test of 0.80 and a level of statistical significance at 0.05 (alpha), the study would require a total of 42 participants to reach the level of statistical significance for differences in morphology of maxilla and a total of 30 participants to obtain statistically significant difference in odds of impaction when considering intraoral conditions.  
The experimental group and the control groups were described using descriptive statistics. To test for differences between them, the variables were analyzed for normal distribution using the Shapiro-Wilk test. In the case of a non-normal distribution, the non-parametric version of the statistical test was used.  
Differences between the sexes were tested using the chi-square test; differences between the groups in terms of age and skeletal maturity were tested using the Student \(t\)-test.  
The chi-square test and [PERSON]'s exact test were used to compare the frequency of intraoral disorders such as deep bite, hypoplastic lateral incisor, rotation of the neighbouring tooth, or intraocclusion of the deciduous tooth between the experimental group and the control group. Odds ratios (OR) with 95% confidence intervals (CI) were determined. The relationship was represented graphically in a bar chart. The symbol * indicates a \(p\)-value \(\leq\) 0.05.  
Morphological characteristics (palatal surface, projection area, and palatal volume) of the maxilla between the groups were compared using the Mann-Whitney test and the \(t\)-test. The results are shown graphically in a box plot. The center box represents the interquartile range, the dotted line the sample mean, and the solid line the median. The whiskers represent the 5 th and 95 th percentiles of the sample.  
To evaluate local factors that might be associated with impaction, the experimental group was further stratified, and impacted teeth were compared with non-impacted maxillary amines. The chi-square test was used to compare the effects of the presence of a persistent deciduous tooth on the probability of impaction. The Mann-Whitney test was used to compare the angle of the canine axis.  
Impacted canines requiring surgical exposure were compared with impacted canines treated by non-surgical means. The risk of the need for surgical exposure was compared. The influence of the presence of a persistent deciduous tooth was tested with a chi-square test, and the odds ratio for the need for surgical exposure was calculated. Univariate logistic regression was used to model the relationship between the need for surgical intervention and canine axis angle.  
The relationship between maxillary morphological characteristics, skeletal maturity, and intraoral factors was tested with linear regression and a Mann-Whitney test to exclude possible interactions between the variables.