The impression is a necessary step for the orthodontic diagnosis. Digital impression has recently been introduced by means of intraoral optical scanners. To date, few studies have compared the conventional alginate impression with the digital impression with intraoral scanners. These studies have shown that digital impression could have some advantages in terms of satisfaction and less discomfort for the pediatric patient. Only one study is randomized and has analyzed patients between 10 and 17 years of age. There are, therefore, no randomized trials for patients under 10 years of age.

The objective of the study is to compare the conventional alginate impression with the digital impression of both dental arches in orthodontic patients between 6 and 10 years of age with a randomized crossover design. In particular, the preference, comfort, impression taking time and other subjective aspects will be analyzed. This is a monocentric, controlled, superiority, randomized, crossover, open study.

Inclusion criteria:

- Orthodontic patients between 6 and 10 years of age.

Exclusion criteria:

• Noncompliant patients
• patients with syndromes or systemic diseases
• patients suffering from cleft lip and palate. The patient will be asked which of the 2 dental arch impression procedures they prefer. In addition, patients will be provided with a questionnaire including VAS (Visual Analogue Scale) for comfort, pain, gag reflex and breathing difficulty. The VAS will consist of scales from 0 to 10.

As for the calculation of the sample size, this has been done by considering a null hypothesis for a proportion of 50% in the preference between the two treatments and an alternative hypothesis of 80%. For alpha set at 0.05, a power of 80% and a dropout rate of 10%, 24 patients are required.

Descriptive statistics will be performed for all variables (frequency and percentage for qualitative variables and mean and standard deviation for quantitative variables). For the primary endpoint variable, impression procedure preference, the test will be performed for one proportion and the 95% confidence interval will be calculated using the Clopper-Pearson method.

With regard to the secondary endpoint variables, duration of the procedure, comfort, pain, gag reflex, breathing difficulty, the 2 procedures will be compared with the t-test for paired data.

An Intention-To-Treat analysis will be performed. In case more than 5 deviations from the protocol will occur, a sensitivity analysis will also be performed per protocol.

Inclusion Criteria:

• Orthodontic patients between 6 and 10 years of age.

Exclusion Criteria:

• Noncompliant patients
• patients with syndromes or systemic diseases
• patients suffering from cleft lip and palate.