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CAN UPPER LIP MOVEMENT RATIOS BE PREDICTED BEFORE MAXILLARY SURGERY?
UW14-159

George JM, Robinson W, Khambay BS

Introduction: Orthognathic surgery prediction planning involves correcting the skeletal
position and predicting the overlying soft tissue response based on historical ratios.
Objective: The aim was to evaluate the ratio of upper lip soft tissue movement to simulate
maxillary advancements in a group of patients with maxillary hypoplasia, using conformed
3D soft tissue meshes. Materials and Methods: A total of 25 patients with Class III
malocclusion were randomly selected. For each patient, 3D facial images were taken, using
stereophotogrammetry, at rest and with 3mm, 6mm and 9mm pre-fabricated spacers
beneath the upper lip. Following superimposition of each image on the rest image, the
movement of the complete upper lip surface in response to each spacer was determined.
Based on a pre-treatment cephalogram, upper lip thickness was also measured. Results:
Across all three spacers the mean ratio of upper lip movement to simulate maxillary
advancements was 0.83:1 (95% CI 0.80 to 0.86) with a wide range between 0.5 to 1.0. There
was no correlation between lip thickness and upper lip displacement. Conclusion: Upper
lip response to known simulated surgical maxillary advancements varies greatly between
individuals. The current practice of using a single ratio during prediction planning may not
be valid and “patient-specific” ratios are required.

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Poster presentation at the 38 Asia Pacific Dental Congress in Hong Kong on 17-19 June 2016
Dr Jaclyn @ Marilyn George
Tudan Dental Clinic
Tudan Health Clinic
Miri Sarawak Malaysia
Dr Wayne Robinson
The University of Hong Kong

Prof Dr Balvinder Khambay Singh
Orthodontic Department
Birmingham Dental School
University of BIrmingham

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