SD	Standard deviation
ES	Epidemiological survey
CS	Cross-Sectional study
LS	Longitudinal study
Nr.	Number of subjects
Sch.Ch.	Schoolchildren
Ch.	Children
Pat.	Patients
Pat. rec.	Patient records
Clin. Exam.	Clinical examination
OPT	Orthopantomogram
Interv.	Interviews
Quest.	Questionnaires
IOTN	Index of Orthodontic Treatment Need
DAI	Dental Aesthetic Index
ICON	Index of Complexity, Outcome and Need
ANGLE	Angle classification
BJÖRK	Björk’s method
Y	Years
Class I “normal occlusion”	Angle Class I normal molar occlusion with well aligned dental arches without any anomalies.
Class I malocclusion	Angle Class I molar occlusion but with an anomaly
Class II	Angle Class II malocclusion
Class II, 1	Angle Class II,1 malocclusion
Class II, 2	Angle Class II,2 malocclusion
Class III	Angle Class III malocclusion
FTP	Flush distal plane second deciduous molars
DS	Distal step second deciduous molars
MS	Mesial step second deciduous molars
M	MINORs item
T	Total
NC	Noncomparative study
C	Comparative study
%	Percentage, noted as noted in the article; in most of the cases, two decimals are reported, and if not possible, one or no decimals are reported