Abstract:
Gummy smile is one of the esthetic problems in conventional orthodontic
treatment. Its appearance may result from skeletal and dental imbalances arising from
multiple etiologic factors. The purpose of this study was to identify the soft tissue,
skeletal and dental variables that could produce effects on improved or non-improved
gummy smile before and after using the Edgewise orthodontic technique. Gummy
smile samples (65 females) were divided into 2 groups using definite criteria as 35
improved (13 skeletal type I and 22 skeletal type II) and 30 non-improved (12 skeletal
type I and 18 skeletal type II) gummy smiles after orthodontic treatment. Pre- and
post-treatment lateral cephalometric radiographs of those two groups were analyzed.
Independent t-test, Mann-Whitney U test, Pair t-test, Wilcoxon match-pairs signedranks
test and ANCOVA were calculated in this study. The findings were as follows:
1. Skeletal type I female patients with non-improved gummy smiles had more
retroclined upper incisors, more backward movement in mandibular position, more
posterior rotation of mandibular plane, longer upper anterior face height, while the
improved gummy smile group had a more decreased facial index after treatment.
2. Non-improved gummy smile, skeletal type II female patients still presented
more protrusive upper lip prominences related to skeletal convexity, while the
improved group had reduced facial index measurements.
3. Both improved and non-improved gummy smile patients with skeletal type
I and II demonstrated vertical maxillary excess before treatment and this parameter
still remained after treatment. Non-improved gummy smile patients of both skeletal
types had more vertical maxillary excess, more decrease in mandibular position,
increased upper anterior face height, while the improved group showed more of a
decrease in facial index and increase in upper posterior dental height.
These findings suggest that there are some soft tissue, skeletal and dental
variables that may be influenced in unpleasing gummy smile appearance. The extreme
parameters that orthodontists should be aware of are very retroclined upper incisors,
posterior rotation of mandible and the increase of facial index following orthodontic
treatment.