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Effect of upper premolar extractions on the position of the upper lip
1School of Dentistry, The University of Melbourne, Australia.
Background:
It has been suggested that Class II division 1 malocclusions treated with extractions result in detrimental changes in the facial profile. This study investigates changes in the position of the upper lip following upper arch extractions only.
Objective:
To investigate changes in the position of the upper lip following extraction of the upper first premolars and retraction of the upper incisors.
Methods:
The sample consisted of 35 Class II division 1 patients with overjets of least 5 mm whose malocclusions were corrected with upper first premolar extractions and full fixed appliances. Twelve patients in the sample had overjets > or = 9 mm. There were no extractions in the lower arch. Pre- and post-treatment lateral cephalograms were used to determine the changes in the position of the upper lip.
Results:
At the end of treatment the upper lip was 0.46 mm less protrusive than at the start of treatment. In patients with overjets > or = 9 mm the upper lip was approximately 1 mm less protrusive at the end of treatment (Mean pre- and post-treatment difference: 0.92 mm). There were no significant gender differences in the positions of the upper lip.
Conclusion:
Minimal changes occur in the position of the upper lip following extraction of the upper premolars and retraction of the upper incisors. Factors other than the position of the upper incisors may determine the post-treatment position of the upper lip.
