American Journal of Orthodontics and Dentofacial Orthopedics
Original articleKeys to Class II correction: A comparison of 2 extraction protocols
Section snippets
Material and methods
The sample includes 54 growing extraction patients treated by 2 private practice orthodontists. The treatment mechanics used included Tweed directional force mechanics, headgears, and Class II elastics or Saif springs. Archwires and sometimes headgears were used to derotate the maxillary first molars. Sliding and frictionless (closing loops) mechanics were used for space closure on a 19 × 25-in stainless steel archwire. High-pull J-hook headgears were used to retract maxillary anterior teeth.
Results
There were no statistically significant T1 between-group differences for SNA, SNB, ANB, MPA, maxillary TSALD, and mandibular TSALD (Table II). Both treatment groups exhibited Class II maxillomandibular relationships (ANB, 5.52°) and normodivergent (MPA, 34.5°) skeletal patterns. There were statistically significant (P <0.05) differences in IMPA, L1:NB, and L1:Apg at T1.
The SNA, SNB, ANB, and MPA angles showed no statistically significant between-group treatment differences in the treatment
Discussion
Historically, the teeth most commonly extracted for orthodontic treatment have been the 4 first premolars. Maxillary and mandibular first premolars extractions are recommended in patients with Class II Division 1 malocclusion with protrusive lips.13 Nance14 was among the first to suggest extracting second premolars to limit incisor and lip retraction. Second premolar extractions provide an alternative in patients with mild crowding, acceptable incisor position, and relatively acceptable
Conclusions
This study evaluated horizontal and vertical incisor and molar movements in normodivergent patients with Class II Division I malocclusion with 4/4 or 4/5 extraction patterns. The following conclusions can be drawn:
- 1.
The mandibular incisors are retracted significantly more after mandibular first than mandibular second premolar extractions.
- 2.
The mandibular first molars migrate mesially significantly more after mandibular second than mandibular first premolar extractions.
Neither extraction pattern
Acknowlegments
The authors thank Drs Jimmy Boley and James L. Vaden for providing the patients.
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Cited by (0)
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.
This research was partially funded by the Robert E. Gaylord Endowed Chair in Orthodontics.