Thesis
Lip changes following extraction and non-extraction orthodontic treatment: a cephalometric study
University of Iowa
Master of Science (MS), University of Iowa
Spring 2020
DOI: 10.17077/etd.005334
Abstract
Introduction: When deciding between extraction and non-extraction orthodontic treatment in patients where tooth crowding can be feasible managed with either approach, the so-called “borderline” patients, soft tissue profile changes should be considered. Studies have observed soft tissue profile changes as a result of retracting incisors during orthodontic treatment. This study investigates how the upper lip position changes with retraction or protraction of the upper incisors after orthodontic treatment. Lip changes resulting from upper incisor retraction or protraction were compared when the initial upper incisor crown position was anterior to or posterior to the anterior nasal spine (ANS). The results of this study suggest changes in the antero-posterior position of the upper lip after orthodontic treatment approximate a linear relationship to upper incisor movement over the range of incisor movement studied. The results also suggest that the relationship of upper incisor movement to upper lip movement does not significantly differ when the initial antero-posterior position of the upper incisor crown is anterior or posterior to ANS.
Materials and Methods: 60 adult patients with moderate to severe crowding were treated with fixed orthodontic appliances, 30 treated with tooth extractions and 30 treated without tooth extractions, were evaluated. Lateral cephalograms were taken at initial records and final records, digitized, and traced using a custom analysis on Dolphin Imaging Software. The custom analysis, [Iowa Lip Calculated] includes additional soft tissue points and provides measurements from calculated X and Y axes to analyze linear distances of lip changes with orthodontic treatment.
Results: As expected, there are significant differences in upper incisor horizontal movement between the extraction and non-extraction groups. On average, the non-extraction group showed an increase in upper incisor angulation by 6.77 degrees, while the extraction group showed a decrease in upper incisor angulation by 4.30 degrees. Significant differences in upper tooth and upper lip movement between the non-extraction group and the extraction group were detected at A/CEJ-U1 midpoint, U1 midpoint, and soft tissue A/U lip midpoint. Correlation analysis of all three variables (ST A/UL, ST A, and Upper Lip Point) for the retraction group with initial upper incisor positon posterior to ANS and the protraction group with the initial upper incisor position anterior to ANS showed significant positive correlation between upper incisor midpoint and the soft tissue variable. Scatter plot analysis of horizontal upper incisor crown movement and corresponding horizontal lip movement suggests a ratio of crown movement to lip movement approximating a 1:1 ratio. No difference in this relationship was apparent when patients with pre-treatment upper incisor crown positioned posterior to ANS were compared to patients with pre-treatment upper incisor crown positioned anterior to ANS.
Conclusion: Horizontal movement of the upper lip in response to horizontal movement of the upper incisor crown showed an approximately equivalent response, occurring in approximately a 1:1 ratio, crown movement to lip movement. Comparing patients whose upper incisor crowns were anterior to ANS prior to protraction or retraction to those with upper incisor crowns posterior to ANS prior to protraction or retraction showed no discernible difference in crown movement to lip movement ratio. We did not see significant differences in the relationship between tooth movement and lip movement at the various soft tissue landmarks.
Details
- Title: Subtitle
- Lip changes following extraction and non-extraction orthodontic treatment: a cephalometric study
- Creators
- Sydney Alexa Sherman
- Contributors
- Thomas E Southard (Advisor)Steven Marshall (Committee Member)Kyungsup Shin (Committee Member)Shankar Rengasamy Venugopalan (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Orthodontics
- Date degree season
- Spring 2020
- DOI
- 10.17077/etd.005334
- Publisher
- University of Iowa
- Number of pages
- ix, 64 pages
- Copyright
- Copyright 2020 Sydney Alexa Sherman
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 63-64).
- Public Abstract (ETD)
When patients have moderate to severe crowding of their teeth, extractions may be indicated in conjunction with orthodontic treatment. This can allow for better dental and facial harmony. Patients with crowded teeth often present with protruded lips and proclined front teeth.
It is important for orthodontists to consider how the lips and soft tissue profile will be affected with extraction or non-extraction treatment. The purpose of this study is to evaluate how specific areas of the lips and soft tissue profile change with backward or forward movement of the upper front teeth. This study also investigates how the soft tissue changes compared to the original position of the upper front teeth compared to the anterior nasal spine.
This study demonstrates that horizontal retraction of the upper lip was equivalent to horizontal retraction of the upper incisor, approximating a ratio of 1:1, upper incisor crown retraction to upper lip retraction. Horizontal protraction of the upper lip related similarly to upper incisor protraction, approximating a 1:1 ratio, upper incisor protraction to upper lip protraction. Upper lip movement when upper incisors were initially positioned posterior to the anterior nasal spine, appeared not to follow a 1:1 tooth movement to lip movement ratio. We did not see significant differences in the relationship between tooth movement and lip movement at the various soft tissue landmarks.
- Academic Unit
- Orthodontics; Craniofacial Anomalies Research Center
- Record Identifier
- 9983968397602771
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