Frequency evaluation of different extraction protocols in orthodontic treatment during 35 years

BACKGROUND Studies that show frequencies of different orthodontic treatment protocols can be used as valuable parameters in the interpretation of treatment tendency with time. The purpose of this retrospective study was to evaluate all orthodontic treatment planning conducted at the Orthodontic Department at Bauru Dental School, University of São Paulo, Brazil, since 1973, in order to investigate extraction and non-extraction protocol frequencies selected at each considered period. METHODS The sample comprised 3,413 records of treated patients and was evaluated according to the protocol choice, divided into 10 groups: Protocol 0 (non-extraction); Protocol 1 (four first premolar extractions); Protocol 2 (two first maxillary and two second mandibular premolars); Protocol 3 (two maxillary premolar extractions); Protocol 4 (four second premolars); Protocol 5 (asymmetric premolar extractions); Protocol 6 (incisor or canine extractions); Protocol 7 (first or second molar extractions); Protocol 8 (atypical extractions) and Protocol 9 (agenesis and previously missing permanent teeth). These protocols were evaluated in seven 5-year intervals: Interval 1 (1973 to 1977); Interval 2 (1978 to 1982); Interval 3 (1983 to 1987); Interval 4 (1988 to 1992); Interval 5 (1993 to 1997); Interval 6 (1998 to 2002); Interval 7 (2003 to 2007). The frequency of each protocol was compared between the seven intervals, using the proportion test (P < 0.05). RESULTS The results showed that 10 protocol frequencies were significantly different among the 7 time intervals. CONCLUSIONS The non-extraction protocol frequency increased gradually with consequent reduction of extraction treatments. The four premolar extraction protocol frequency decreased gradually while the two maxillary premolar extraction protocol has maintained the same frequency of indications throughout time.