Three-dimensional evaluation of dental decompensation and mandibular symphysis remodeling on orthodontic-surgical treatment of Class III malocclusion

Alveolar bone remodelling and stability of mandibular incisors in adult patients after orthodontic treatment with premolar extractions: A prospective follow-up study

OBJECTIVE

To evaluate alveolar bone remodelling and stability of mandibular incisors in adult orthodontic extraction patients.

MATERIALS AND METHODS

Cone-beam computed tomography images of 25 adult patients undergoing extraction were collected before orthodontic treatment (T1), after orthodontic treatment (T2), and after at least 1 year of retention (T3). The labial and lingual alveolar bone heights (ABH), thickness (ABT), and tooth movement of the mandibular incisors were measured during the retraction (T2-T1) and retention (T3-T2) periods. According to the tooth movement during the retention period, the mandibular incisors were further divided into stable and unstable groups, and the correlation between L1-BMe and stability was evaluated.

RESULTS

The labial and lingual ABHs significantly increased after orthodontic treatment and decreased during the retention period. The lingual ABH was 7.36 ± 2.27 mm at T2 and 5.37 ± 1.98 mm at T3, indicating a great bone remodelling capacity. The labial ABT exhibited a significant increase during orthodontic treatment and a slight decrease during the retention period, while the lingual ABT showed an opposite trend. During the retention period, the root apex moved labially into the alveolar bone housing. L1-BMe significantly increased during orthodontic treatment and decreased during the retention period. Compared to the stable group, lingual ABH and L1-BMe at T2 was significantly higher, and lingual ABT was smaller in the unstable group.

CONCLUSION

Post-treatment lingual alveolar bone defects of the mandibular incisors could recover to some extent during the retention period. There was a negative correlation between post-treatment L1-BMe and mandibular incisor stability.

Influence of differences in mandibular incisor inclination on skeletal stability after orthognathic surgery in patients with skeletal Class III malocclusion

OBJECTIVE

The preoperative inclination angle of mandibular incisors was crucial for surgical and postoperative stability while the effect of proclined mandibular incisors on skeletal stability has not been investigated. This study aimed to evaluate the effects of differences in presurgical mandibular incisor inclination on skeletal stability after orthognathic surgery in patients with skeletal Class III malocclusion.

METHODS

A retrospective cohort study of 80 consecutive patients with skeletal Class III malocclusion who underwent bimaxillary orthognathic surgery was conducted. According to incisor mandibular plane angle (IMPA), patients were divided into 3 groups: retroclined inclination (IMPA < 87°), normal inclination (87° ≤ IMPA < 93°) and proclined inclination (IMPA ≥ 93°). Preoperative characteristics, surgical changes and postoperative stability were compared based on lateral cephalograms obtained 1 week before surgery (T0), 1 week after surgery (T1), and at 6 to 12 months postoperatively (T2).

RESULTS

The mandible demonstrated a forward and upward relapse in all three groups. No significant differences in skeletal relapse were observed in the 3 groups of patients. However, the proclined inclination group showed a negative overbite tendency postoperatively compared with the other two groups and a clinically significant mandibular relapse pattern. Proclined IMPA both pre- and postoperatively was correlated with mandibular relapse.

CONCLUSION

Sufficient presurgical mandibular incisor decompensation was of crucial importance for the maintenance of skeletal stability in patients with skeletal Class III malocclusion who subsequently underwent orthognathic surgery.

How much should incisors be decompensated? periodontal bone defects during presurgical orthodontic treatment in class III double-jaw orthognathic surgery patients

INTRODUCTION

The aims of this study were to evaluate periodontal bone defects around the lower and upper incisors and to identify changes in the buccolingual inclination of the incisors during orthodontic decompensation in skeletal Class III orthognathic surgery patients.

MATERIALS AND METHODS

The sample consisted of 26 adults with skeletal Class III deformity who had undergone presurgical orthodontic treatment and orthognathic surgery. Lateral cephalograms obtained before orthodontic treatment and before surgery were used to determine the inclination and position changes of the incisors. Cephalometric measurements were taken using Dolphin Imaging 11.95. Three-dimensional images were generated from cone-beam computed tomography (CBCT) scans prior to surgery and used to detect periodontal bone defects, including fenestration (F) and dehiscence (D).

RESULTS

Intraclass correlation coefficients (ICC) were determined and the measurements showed high reproducibility. The cephalometric data showed normal distribution and there were no differences between genders in terms of cephalometric changes, dehiscence, fenestration, or coexistent (D-F/DF) formation. The patients presented maxillary incisor retroclination and mandibular incisor proclination, which was consistent with the tooth decompensation. CBCT assessment was performed for a total of 208 teeth; while 81 upper and 94 lower incisors had D-F/DF formation, 23 upper and 10 lower incisors were healthy. Statistically significant correlations were not found between the inclination degree of the incisors and D-F/DF formation.

CONCLUSIONS

Decompensation of incisors during presurgical orthodontic treatment increases the risk of periodontal defects. There is no linear relationship between the increase in the inclination degrees of incisors and D-F/DF formation.

Evaluation of the Predictability and Accuracy of Orthognathic Surgery in the Era of Virtual Surgical Planning

Virtual surgical planning allows orthognathic surgeons to design a surgical plan preoperatively and establish a personalized surgical protocol. This study aims to validate the predictability and accuracy of orthognathic surgery through a comparison of the three-dimensional (3D) models of the virtual planning and postoperative CBCT using free software (3D Slicer) on 40 patients who underwent bimaxillary orthognathic surgery. The distances of point A, point B, pogonion (Pog), and the first upper and lower molars, both in each axis (x, y, and z) and in the 3D space, were analyzed. The median of the distances in the mediolateral direction was the lowest, while the highest differences were found at point A and Pog in the anteroposterior direction (0.83 mm and 0.78 mm, respectively). Vertical differences were higher in the maxilla than in the mandible. In conclusion, we found that orthognathic bimaxillary surgery using virtual surgical planning was more accurate when positioning the bone segments in the mediolateral direction, using the information provided by the splint, as well as when positioning the mandible compared to the maxilla.