[Comparison of the virtual surgical planning position of maxilla and condyle with the postoperative real position in patients with mandibular protrusion]

OBJECTIVE

To compare the difference between virtual surgical planning (VSP) position and postoperative real position of maxilla and condyle, and to explore the degree of intraoperative realization of VSP after orthognathic surgery.

METHODS

In this study, 36 patients with mandibular protrusion deformity from January 2022 to December 2022 were included. All the patients had been done bilateral sagittal split ramus osteotomy (SSRO) combined with Le Fort Ⅰ osteotomy under guidance of VSP. The VSP data (T0) and 1-week postoperative CT (T1) were collected, the 3D model of postoperative CT was established and segmented into upper and lower jaws in CCMF Plan software. At the same time, accor-ding to the morphology of palatal folds, the virtual design was registered with the postoperative model, and the unclear maxillary dentition in the postoperative model was replaced. Then the postoperative model was matched with VSP model by registration of upper skull anatomy that was not affected by the operation. The three-dimensional reference plane and coordinate system were established. Selecting anatomical landmarks and their connections of condyle and maxilla for the measurement, we compared the coordinate changes of marker points in three directions, and the angle changes between the line connecting the marker points and the reference plane to analyze the positional deviation and the angle deviation of the postoperative condyle and maxilla compared to VSP.

RESULTS

The postoperative real position of the maxilla deviates from the VSP by nearly 1 mm in the horizontal and vertical directions, and the anteroposterior deviation was about 1.5 mm. In addition, most patients had a certain degree of counterclockwise rotation of the maxilla after surgery. Most of the bilateral condyle moved forward, outward and downward (the average distance deviation was 0.15 mm, 1.54 mm, 2.19 mm, respectively), and rotated forward, outward and upward (the average degree deviation was 4.32°, 1.02°, 0.86°, respectively) compared with the VSP.

CONCLUSION

VSP can be mostly achieved by assistance of 3D printed occlusal plates, but there are certain deviations in the postoperative real position of maxilla and condyle compared with VSP, which may be related to the rotation axis of the mandible in the VSP. It is necessary to use patient personalized condylar rotation axis for VSP, and apply condylar positioning device to further improve surgical accuracy.

[A long-term evaluation of periodontal phenotypes before and after the periodontal-orthodontic-orthognathic combined treatment of lower anterior teeth in patients with skeletal Angle class Ⅲ malocclusion]

OBJECTIVE

To evaluate the changes of periodontal phenotype (width of keratinized gingiva, thickness and height of alveolar bone) of lower anterior teeth in patients with skeletal class Ⅲ malocclusion before and after the periodontal-orthodontic-orthognathic combined treatment.

METHODS

In the study, 20 patients with skeletal class Ⅲ malocclusion (6 males and 14 females) completed the periodontal-orthodontic-orthognathic combined treatment were included from March 2017 to June 2022, with 39 central incisors, 40 lateral incisors and 40 canines. The mean age was (25.40±4.27) years (20-34 years). The mean follow-up time was (3.70±1.05) years from the beginning of periodontal corticotomy regenerative surgery (PCRS) to the end of the combined treatment. Cone-beam computed tomography (CBCT) was used to measure the thickness, area and height of alveolar bone by the same researcher, taken before the PCRS (T0), 6 months after the PCRS (T1), 12 months after the PCRS (T2), before the orthognathic surgery (T3), and after the periodontal-orthodontic-orthognathic combined treatment (T4). The periodontal clinical parameters were used to evaluate changes in the soft tissue by another researcher, measured before the PCRS (T0) and after the combined treatment (T4). Changes of soft and hard tissue were evaluated by the periodontal phenotype.

RESULTS

The width of keratinized gingiva increased significantly (all P < 0.001) in lower anterior teeth, the central incisors, lateral incisors and canines increased by (1.82±1.57) mm, (2.03±1.48) mm and (2.05±1.27) mm, respectively. The proportion of thick periodontal biotype in the central and lateral incisors increased significantly (all P < 0.001), while the changes of periodontal biotypes in the lower canines were not obvious. The thickness of labial alveolar bone of lower anterior teeth all increased significantly after periodontal corticotomy regenerative surgery and the combined treatment (all P < 0.001). The area of labial alveolar bone of lower anterior teeth also increased significantly after the combined treatment (all P < 0.001). The whole area of labial and lingual alveolar bone of central and lateral incisors increased (P < 0.001), while the whole area of canines remained the same. All The height of the alveolar bone increased (all P < 0.001) on the labial side after the treatment.

CONCLUSION

The periodontal phenotypes of lower anterior teeth were significantly improved after the periodontal-orthodontic-orthognathic combined treatment in patients with skeletal Angle class Ⅲ malocclusion. The improvement was long-termly stable, and the periodontal risk was reduced.

[Alveolar crest and relevant analysis of labial side of anterior teeth on skeletal Angle class III patients]

OBJECTIVE

To measure the distance from cemento-enamel junction (CEJ) to alveolar crest (AC) of labial side of anterior teeth on skeletal Angle class III patients under direct vision during periodontal bone augmentation surgery and to make relevant analysis to find the relevant factors.

METHODS

In the study, 46 skeletal Angle class III patients (10 males and 36 females) received periodontal bone augmentation surgery of anterior teeth were included, with 67 jaws (27 maxillae and 40 mandibles) and 400 anterior teeth (161 maxillary anterior teeth and 239 mandibular anterior teeth). The mean age was 23.65 years. Maxillary anterior teeth consisted of 54 central incisors, 53 lateral incisors and 54 canines. Mandibular anterior teeth consisted of 79 central incisors, 80 lateral incisors and 80 canines. CEJ-AC was measured in three sites (mesial sites, central sites and distal sites) by Williams periodontal probes during periodontal bone augmentation surgery under direct vision by the same researcher.

RESULTS

The average CEJ-AC of 400 anterior teeth was (2.21±1.48) mm. The average CEJ-AC of maxillary anterior teeth was (1.72±1.13) mm, more than (2.54±1.60) mm of mandibular anterior teeth (P<0.05). The average CEJ-AC of canines was (2.42±1.78) mm, more than (2.06±1.27) mm of central incisors or (2.16±1.32) mm of lateral incisors (P<0.05). The average CEJ-AC of central sites was (3.04±2.01) mm, more than (1.79±0.86) mm of mesial sites or (1.81±0.89) mm of distal sites (P<0.05). CEJ-AC of 233 anterior teeth was more than 2 mm, accounting for 58.25%, and 117 anterior teeth with dehiscence were found, accounting for 29.25%. Multilevel and multivariate Logistic regression showed age, jaw, tooth and site were the relevant factors to the position of alveolar crest.

CONCLUSION

The position of alveolar crest of skeletal Angle class III patients who received periodontal bone augmentation surgery was lower than that of the general population, causing periodontal risks during decompensation orthodontics therapy before orthognathic surgery. The position of alveolar crest was lower in older patients than in younger patients, in mandibular teeth than in maxillary teeth, in canines than in central incisors or lateral incisors, and in central sites than in mesial sites or distal sites of labial side, which showed much higher risk.

[Establishment of three-dimensional measurement methods of nasolabial soft tissue for patients with maxillary protrusion]

OBJECTIVE

To establish a series of three-dimensional measurement methods of nasolabial soft tissue for maxillary protrusion patients by using 3dMD camera, and to evaluate preoperative and postoperative changes of the nasolabial soft tissue.

METHODS

Three-dimensional facial photos of 30 female patients with maxillary protrusion [average age, (27.33±2.54) years] were taken by 3dMD camera preoperatively and at the end of postoperative 6 months or more. Then, 3dMD patient software was used to locate the selected landmarks at nasolabial region on the three-dimensional photos. Ten measurements, including soft tissue line distance, angle, curve distance and postoperative three-dimensional volume changes were measured twice with one week interval by 3 investigators, respectively. A standard consistency test calculated by the correlation coefficients (ICC) was performed between two sets of data (including all of the 10 measurements) for each investigator and among the three investigators to verify the repeatability.

RESULTS

The average maxillary incisor retraction distance of the 30 subjects was (5.13±0.99) mm, and the average follow-up time was (11.07±5.11) months. The standard consistency test was performed between the two sets of data for each investigator, and the correlation coefficients (ICC) of the 10 measurements were all over 0.8 for each investigator (P>0.05). The standard consistency test was performed among the three surveyors, with the result that the ICC of the width of the bilateral inner canthus, the height of the nose, the height of nasal tip, nasolabial angle, philtrum length, the curve height of upper vermilion and the height of upper lip were greater than 0.8 (P>0.05), and the ICC of the distance between SbalSbal, length of nasal dorsum and three-dimensional volume change of upper lip were 0.680, 0.627 and 0.528, respectively (P>0.05).

CONCLUSION

3dMD camera and 3dMD patient software can be used to measure and analyze the three-dimensional morphology of the nasolabial soft tissue for patients with maxillary protrusion preoperatively and postoperatively, and it is relatively accurate and reliable. However, the repeatability of three-dimensional positioning of the nasal tip point and the Sbal is slightly worse resulting in the lower value of the ICC of the distance between SbalSbal and length of nasal dorsum, as well as the upper lip three-dimensional volume change after the operation.

[Establishment of three-dimensional measurement methods of nasolabial soft tissue for patients with maxillary protrusion]

OBJECTIVE

To establish a series of three-dimensional measurement methods of nasolabial soft tissue for maxillary protrusion patients by using 3dMD camera, and to evaluate preoperative and postoperative changes of the nasolabial soft tissue.

METHODS

Three-dimensional facial photos of 30 female patients with maxillary protrusion [average age, (27.33±2.54) years] were taken by 3dMD camera preoperatively and at the end of postoperative 6 months or more. Then, 3dMD patient software was used to locate the selected landmarks at nasolabial region on the three-dimensional photos. Ten measurements, including soft tissue line distance, angle, curve distance and postoperative three-dimensional volume changes were measured twice with one week interval by 3 investigators, respectively. A standard consistency test calculated by the correlation coefficients (ICC) was performed between two sets of data (including all of the 10 measurements) for each investigator and among the three investigators to verify the repeatability.

RESULTS

The average maxillary incisor retraction distance of the 30 subjects was (5.13±0.99) mm, and the average follow-up time was (11.07±5.11) months. The standard consistency test was performed between the two sets of data for each investigator, and the correlation coefficients (ICC) of the 10 measurements were all over 0.8 for each investigator (P>0.05). The standard consistency test was performed among the three surveyors, with the result that the ICC of the width of the bilateral inner canthus, the height of the nose, the height of nasal tip, nasolabial angle, philtrum length, the curve height of upper vermilion and the height of upper lip were greater than 0.8 (P>0.05), and the ICC of the distance between SbalSbal, length of nasal dorsum and three-dimensional volume change of upper lip were 0.680, 0.627 and 0.528, respectively (P>0.05).

CONCLUSION

3dMD camera and 3dMD patient software can be used to measure and analyze the three-dimensional morphology of the nasolabial soft tissue for patients with maxillary protrusion preoperatively and postoperatively, and it is relatively accurate and reliable. However, the repeatability of three-dimensional positioning of the nasal tip point and the Sbal is slightly worse resulting in the lower value of the ICC of the distance between SbalSbal and length of nasal dorsum, as well as the upper lip three-dimensional volume change after the operation.