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.

Effects of intrusion combined with anterior retraction on apical root resorption

This study evaluated the influence of intrusion mechanics combined with anterior retraction on root resorption of the maxillary incisors. A sample of 56 patients was divided into two groups: group 1 comprised 28 patients (12 females and 16 males), presenting with an increased overjet and deep overbite (6.48 and 4.78 mm, respectively) treated with reverse curve of Spee intrusion mechanics and group 2 comprised 28 patients (12 females and 16 males) with an increased overjet of 5.67 mm and a normal overbite of 1.12 mm. The initial mean ages for groups 1 and 2 were 13.41 and 13.27 years, respectively. Pre- (T1) and post- (T2) treatment periapical radiographs were used to evaluate root resorption. The groups were compared using the Mann-Whitney U-test. Correlation between root resorption and tooth movement was investigated with Spearman's correlation coefficient. The subjects in group 1 had statistically greater root resorption (P < 0.05) than those in group 2. The initial overbite severity and the amount of correction had significant positive correlations with root resorption (r = 0.324 and r = 0.320, respectively). The combination of anterior retraction with intrusive mechanics causes more root resorption than anterior retraction of the maxillary incisors alone.

Orthodontic treatment time in 2- and 4-premolar-extraction protocols

INTRODUCTION

The purpose of this study was to compare the treatment times of complete Class II malocclusions treated with 2- and 4-premolar-extraction protocols.

METHODS

Ninety-seven patients were selected and divided into 2 groups, according to the 2 extraction criteria. Group 1, treated with 2 maxillary premolar extractions, consisted of 49 patients (30 male, 19 female) with a mean age of 14.35 years. Group 2, treated with 4 premolar extractions, consisted of 48 patients (27 male, 21 female) with a mean age of 13.03 years. Treatment times of the groups were compared with the t test.

RESULTS

Treatment times were significantly shorter with the 2-premolar-extraction protocol compared with the 4-premolar-extraction protocol.

CONCLUSIONS

Treatment time will be shorter and the occlusal results more predictable with a 2-premolar-extraction protocol compared with 4 premolar extractions.