Methods: 
transverse maxillary deficiency, TB, crossbite, Pain
Forty-two patients who met the eligibility criteria (aged 11-14 years, with
transverse maxillary deficiency, posterior crossbite, and presence of
maxillary first premolars and first permanent molars) were selected and
randomly divided into two groups: TBB GROUP (tooth-bone-borne expander),
treated with Hybrid Hyrax (12 females and 9 males, mean age 13.3 ± 1.3
years), and TB GROUP (tooth-borne expander), treated with Hyrax (5 females
and 16 males, mean age 13.3 ± 1.4 years). Pain and discomfort were assessed
in two times: after the first day of activation (T1) and four days after, by
means of the numerical rate scale and the instrument MFIQ (Mandibular
Functional Impairment Questionnaire). Descriptive statistics and the
Mann-Whitney test were used for comparison between groups and between sexes.
A 5% significance level was adopted. 