Lower incisor changes following non-extraction orthodontic decompensation in Class III surgical cases
Keywords:Orthognathic, decompensation, Class III malocclusion, lower incisor angle, Li-APo, prediction
The amount of incisor decompensation during pre-surgical orthodontics may affect the outcome of Class III orthognathic cases. The purpose of this study was to assess the lower incisor changes post-orthodontic decompensation in Class III surgical cases and to investigate the amount of crowding as a predictive factor. This was a retrospective study reporting on 22 Class III orthognathic cases. The lower incisor angulation (LIA) and distance of the lower incisor edge to the A-Pogonion line (Li-APo) were measured on pre-treatment and pre-surgical lateral cephalograms whereas crowding was measured on digitised pre-treatment study models. Pearson’s correlation (p <0.05) was used to assess the correlation of crowding with LIA and Li-APo changes, and prediction of the lower incisor decompensation was conducted using linear regression analysis. Results showed lower incisors were retroclined at 79.84° ± 7.08° and positioned ahead of APo line by 6.52 mm ± 2.97 mm at the start of treatment. Pre-surgical LIA and Li-APo were found to increase following orthodontic decompensation to 90.43° ± 5.96° and 10.34 mm ± 3.25 mm, respectively. There was a moderate positive correlation (r = 0.592) between crowding and Li-APo changes which was statistically significant, p value = 0.004, and had a strong predictor with 31.8% predictability. However, LIA showed a weak correlation (r = 0.329) with crowding and was not statistically significant (p = 0.135). Li-APo changes during orthodontic decompensation can be predicted with 31.8% predictability using the formula; Li-APo change = 2.064 + 0.503 (crowding).
2. Kim SJ, Kim KH, Yu HS, Baik HS. Dentoalveolar compensation according to skeletal discrepancy and overjet in skeletal Class III patients. Am J Orthod Dentofacial Orthop. 2014;145(3):317-24.
3. Capelozza Filho L, Martins A, Mazzotini R, da Silva Filho OG. Effects of dental decompensation on the surgical treatment of mandibular prognathism. Int J Adult Orthodon Orthognath Surg. 1996;11(2):165-80.
4. McIntyre GT. Treatment planning in Class III malocclusion. Dent Update. 2004;31(1):13-20.
5. Hussain SS, Ashraf B, Khan SQ. Relationship of dental crowding to tooth size and arch dimensions in class I normal & class I malocclusion sample. Pak Oral Dental J. 2014;34(4).
6. Hassan MS. Cephalometric Norm for Malay. Universiti Malaya. 1998. (unpublished)
7. Adnan and Hussain. Cephalometric Norm for Chinese and Indian. Universiti Malaya. 1998. (unpublished)
8. Suja AG, Babu EC, Presanth SS. Assessment of dental crowding. Int J Basic Appl Med Sci. 2014;4(1):52-55.
9. Evans JD. Straightforward Statistics for the Behavioral Sciences. Thomson Brooks/Cole Publishing Co; 1996.
10. Koo TK, Li MY. A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research. J Chiropr Med. 2016;15(2):155-63.
11. O'Higgins EA, Kirschen RH, Lee RT. The influence of maxillary incisor inclination on arch length. Br J Orthod. 1999;26(2):97-102.
12. O'Higgins EA, Lee RT. How much space is created from expansion or premolar extraction? J Orthod. 2000;27:11-13.
13. Troy BA, Shanker S, Fields HW, Vig K, Johnston W. Comparison of incisor inclination in patients with Class III malocclusion treated with orthognathic surgery or orthodontic camouflage. Am J Orthod Dentofacial Orthop. 2009;135(2):146-e1.
14. Miloro M, Ghali GE, Larson P, Waite P. Peterson's Principles of Oral and Maxillofacial Surgery. 3rd ed. Connecticut: People’s Medical Publishing House; 2011.
15. McNeil C, McIntyre GT, Laverick S. How much incisor decompensation is achieved prior to orthognathic surgery? J Clin Exp Dent. 2014;6(3):e225.
16. Ahn HW, Baek SH. Skeletal anteroposterior discrepancy and vertical type effects on lower incisor preoperative decompensation and postoperative compensation in skeletal Class III patients. Angle Orthod. 2011;81(1):64-74.
17. Allais D, Melsen B. Does labial movement of lower incisors influence the level of the gingival margin? A case–control study of adult orthodontic patients. Eur J Orthod. 2003;25(4):343-52.
18. Choi YJ, Chung CJ, Kim KH. Periodontal consequences of mandibular incisor proclination during presurgical orthodontic treatment in Class III malocclusion patients. Angle Orthod. 2015;85(3):427-33.
19. Melsen B, Allais D. Factors of importance for the development of dehiscences during labial movement of mandibular incisors: a retrospective study of adult orthodontic patients. Am J Orthod Dentofacial Orthop. 2005;127(5):552-61.
20. Johnston C, Burden D, Kennedy D, Harradine N, Stevenson M. Class III surgical-orthodontic treatment: a cephalometric study. Am J Orthod Dentofacial Orthop. 2006;130(3):300-9.
21. Ricketts RM. The Keystone Triad. Am J Orthod Dentofacial Orthop. 1964;50(4):244-64.
22. Julku J, Hannula M, Pirilä-Parkkinen K, Tolvanen M, Pirttiniemi P. Dental arch effects after early and later timed cervical headgear treatment—a randomized controlled trial. Eur J Orthod. 2019;41(6):622-30.
23. Durão AP, Morosolli A, Pittayapat P, Bolstad N, Ferreira AP, Jacobs R. Cephalometric landmark variability among orthodontists and dentomaxillofacial radiologists: a comparative study. Imaging Sci Dent. 2015;45(4):213-20.
24. Chen YJ, Chen SK, Chung-Chen Yao J, Chang HF. The effects of differences in landmark identification on the cephalometric measurements in traditional versus digitized cephalometry. Angle Orthod. 2004;74(2):155-61.
- The Faculty of Dentistry, Universiti Malaya holds the copyright of the published manuscript including all its components such as supplementary information, graphical contents and raw data without any restrictions.
- The author grant the Faculty of Dentistry, University of Malaya assignable and sub-licensable right, unlimited in time and territory, to copy-edit, reproduce, publish, distribute, transmit, make available and store the Article, including abstracts thereof, in all forms of media of expression now known or developed in the future, including pre- and reprints, translations, photographic reproductions and extensions.
- After acceptance for publication in Ann Dent UM, the author(s) have the right to use any of its components in whole or in part for academic purposes such as, presentation in scientific conferences and seminars.