Table 5 -. Data obtained from articles included.

	Dacre,26 1985	Germeç et al,23 2008	Germec-Cakan et al,24 2010	Ileri et al,25 2012
Study type	Retrospective	Randomized prospective	Randomized prospective	Retrospective
n / sex	8F/8M	11F/2M	11F/2M	13F/7M
Mean age (years)	15.0 ± 2.7	17.8 ±2.4	17.8 ± 2.4	14.3 ± 2.9
Treatment type	IE	NE = Air rotor wear (AIR) from mesial of 1st molar to mesial of 1st molar	NE = Air rotor wear (AIR) from mesial of 1st molar to mesial of 1st molar	IE
Statistical analysis	Dahlberg’s formula Snedecor’s F ratio T-test	Wilcoxon test Mann-Whitney U test Dahlberg’s formula T-test	Wilcoxon test Mann-Whitney U test Dahlberg’s formula	ANOVA Tukey HSD Mann-Whitney U test
Treatment duration (years)	1.8 ± 1.4	ND	17.0 ± 4.6	1.6 ± 0.9
Author’s conclusion	Overjet and overbite increased mildly after incisor extraction with clinical significance varying from patient to patient. Posterior occlusion was not affected.	In determining treatment for borderline Class I patients the following should be considered: Treatment duration with premolar extraction, AIR limitations (enamel thickness, tooth morphology, convexity of the proximal surface), and in facial changes resulting from growth.	In Class I borderline patients with moderate crowding the extraction of premolars with minimum anchorage does not result in a narrower arch. Furthermore, in treatments without extraction both the intercanine width and the arch perimeter are preserved.	Treatments without extraction yield better results than those involving extraction of 4 first premolars, or extraction of incisors in Class I patients with moderate to severe crowding. Tooth size discrepancy should be considered to ensure satisfactory interdigitation of upper and lower teeth.

F = females; M = males; IE = incisor extraction; NE = nonextraction (interproximal wear); ND = not declared.