1.Lower incisor changes following non-extraction orthodontic decompensation in Class III surgical cases
Nor Nadia Zakaria ; Yasmin Kamarudin ; Ong Kah Shin ; Koo Zi Qing
Annals of Dentistry 2021;28(1):15-22
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 presurgical 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).