Lower incisor changes following non-extraction orthodontic decompensation in Class III surgical cases


  • Nor Nadia Zakaria
  • Yasmin Kamarudin University of malaya
  • Kah Shin Ong
  • Zi Qing Koo




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).


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Author Biographies

Nor Nadia Zakaria

Department of Paediatric Dentistry and Orthodontics

Kah Shin Ong

Elective student 

Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia

Zi Qing Koo

Elective student

Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia


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Original/Research Article