Hard Tissue Movement Research Articles

Masticatory function and three-dimensional facial morphology of soft tissues: One year after orthognathic surgery

ObjectiveDentofacial deformities (DFD) require orthodontic treatment, orthognathic surgery, and speech therapy for aesthetic and functional problems. This longitudinal study analyzed changes in masticatory function and three-dimensional (3D) facial soft tissue in patients with Class II and Class III DFD after orthognathic surgery. In addition, the study investigated the relationship between facial measurements, maximum bite force (MBF), and orofacial myofunctional status (OMS). DesignThe sample consisted of 46 participants, including 10 patients with Class II DFD, and 11 patients with Class III DFD. These groups were assessed before (T0) and 6 months (T1) after surgery. Twelve patients who completed the treatment protocol were evaluated 12 months post-surgery (T2). The patient groups were compared with each other and with a control group (CG) of 25 healthy subjects. The participants underwent MBF and clinical evaluation of OMS, including masticatory behavior, using a validated protocol. The 3D facial soft tissue was assessed using laser scanning. ResultsCompared to the CG, DFD patients showed reduced MBF, masticatory behavior, and OMS scores at T0. At T2, there was an improvement in MBF, masticatory, and OMS scores, but differences were observed compared to the CG. Changes in facial soft tissue followed the underlying hard tissue movement resulting from surgery, and reduction of vertical measurements contributed to improvements in masticatory function. ConclusionThese findings indicated that combined surgery, orthodontic treatment, and speech therapy can lead to a significant improvement in masticatory function and facial soft tissue in DFD patients, although not completely 12 months post-surgery.

Soft tissue movements after mandibular reconstruction using the vascularized iliac flap: patterns and predictions.

To investigate soft-to-hard tissue response following mandibular reconstruction and to develop a predictive model for projecting soft tissue movement. In this retrospective study, 18 patients receiving mandibular reconstruction using a vascularized iliac flap were enrolled. Various indicators for characterizing the movement of tissues were considered to identify the effective predictors for projecting soft tissue movements. Face-region-specific linear regression models for prediction were constructed and evaluated. The arithmetic mean of hard tissue movement in an extended area had the strongest correlation with the movement of the focal soft tissue, while the arithmetic mean in a regional area (Ram) was a more effective predictor. The linear regression model using Ram, global extrema and distances between them as the predictors performed the best in the lower margin of the face, with an average error of 1.51 ± 1.38mm. Soft tissue movement in the alveolar process was not correlated with the existence of dentition, only can be predicted by the soft tissue movement below it. The area of the masseter was strongly correlation with Ram, but no other factors. An accurate prediction of soft tissue movements in the lower margin and the alveolar process of the face can be achieved by considering hard tissue and adjacent soft tissue movements. No effective predictor in the masseter area was identified. We investigated the relationship between hard tissue movements and the soft tissue responses in the facial area. Through building predictive models for projecting postoperative soft tissue movements, we derive insights for the aesthetic outcome of face surgeries. This study was registered on the Chinese Clinical Trial Registry (registration number: ChiCTR2100054103).

Predictive modelling of freeway space utilising clinical history, normalised muscle activity, dental occlusion, and mandibular movement analysis

This study aimed to predict dental freeway space by examining the clinical history, habits, occlusal parameters, mandibular hard tissue movement, soft tissue motion, muscle activity, and temporomandibular joint function of 66 participants. Data collection involved video-based facial landmark tracking, mandibular electrognathography, surface electromyography of mandibular range of motion, freeway space, chewing tasks, phonetic expressions, joint vibration analysis, and 3D jaw scans of occlusion. This resulted in a dataset of 121 predictor features, with freeway space as the target variable. Six models were trained on synthetic data ranging from 500 to 25,000 observations, with 65 original observations reserved for testing: Linear Regression, Random Forest, CatBoost Regressor, XGBoost Regressor, Multilayer Perceptron Neural Network (MPNN), and TabNet. Explainable AI indicated that key predictors of freeway space included phonetics, resting temporalis muscle activity, mandibular muscle activity during clenching, body weight, mandibular hard tissue lateral displacements, and dental arch parameters. CatBoost excelled with a test error of 0.65 mm using 5000 synthetic data points, while a refined MPNN achieved the best performance with 25,000 synthetic data points and 121 unique predictors, yielding an absolute error of 0.43 mm on the 65 original observations.

Facial soft-tissue shape changes after fixed edgewise treatment with premolar extraction in individual artificial-intelligence-classified facial profile patterns

ObjectiveTo examine the patterns of pretreatment facial soft tissue shape in orthodontic cases with premolar extraction using artificial intelligence (AI) and to investigate the corresponding changes.MethodsOne hundred and fifty-two patients who underwent orthodontic treatment with premolar extraction were enrolled. Lateral cephalograms were obtained before and after the treatment. For each record, the outlines of the nose-lip-chin profile and corresponding 21 cephalometric variables were extracted. The AI method classified pretreatment records into three subject groups based on the feature variables extracted from the outline. Dentoskeletal and soft tissue facial form changes observed after treatment were compared statistically (P < 0.05) between the groups using ANOVA. Multivariate regression models were used for each group.ResultsGroup 1 (n = 59) was characterized by Class II high-angle retrognathic mandible with an incompetent lip, group 2 (n = 55) by Class I malocclusion with retruded and thin lips, and group 3 (n = 38) by Class I malocclusion with an everted superior lip before treatment. The ratios of anteroposterior soft tissue to hard tissue movements in Group 1 were 56% (r = 0.64) and 83% (r = 0.75) for the superior and inferior lips, respectively, whereas those in Group 2 were 49% (r = 0.78) and 91% (r = 0.80), and 40% (r = 0.54) and 79% (r = 0.70), respectively, in Group 3.ConclusionsThe modes of facial form changes differed depending on the pre-treatment profile patterns classified by the AI. This indicates that the determination of the pre-treatment profile pattern can help in the selection of soft tissue to hard tissue movement ratios, which helps estimate the post-treatment facial profile with a moderate to high correlation.

Hard to Soft Tissue Profile Changes in Skeletal Class III Dentofacial Deformities After Maxillary Advancement and Mandibular Setback Orthognathic Surgery

Objective To correlate the sagittal hard tissue movement and soft tissue changes among patients with skeletal class III malocclusion following bimaxillary orthognathic surgery. Material and Methods Fifty-nine subjects with skeletal class III malocclusion treated consecutively with maxillary advancement and mandibular setback were assessed for skeletal and soft tissue linear changes using presurgical (T1) and post-treatment (T2) lateral cephalograms. Pearson’s correlation coefficient test was used to correlate hard and soft tissue parameters. Results The sagittal hard tissue movement and soft tissue changes for all the parameters assessed in maxilla and mandible showed statistically significant correlations. The ratios of changes for the maxillary protrusion [N-A (HP)] to horizontal subnasale (Sn), superior labial sulcus (Sls), and labrale superioris (Ls) were 0.574:1, 0.703:1, and 0.721:1 respectively. The ratio of horizontal labrale inferioris (Li), mentolabial fold (Mlf), and soft tissue (Pg′) to mandibular protrusion [N-B (HP)] were 0.992:1, 0.970:1, and 0.590:1 respectively and to chin protrusion [N-Pg (HP)] were 1.293:1, 1.252:1, and 1.001:1, respectively. The ratios were different for males and females in maxilla and mandible. Conclusion Sagittal hard tissue movement and soft tissue changes are significantly correlated. The soft tissue movement in the mandible were more proportionate compared to the maxilla. The sagittal hard tissue to soft tissues movement ratios were greater in maxilla and lesser at pogonion and mentolabial sulcus in females compared to males. The ratios obtained can be used for predicting postsurgical soft tissue changes.

Predicting masticatory muscle activity and deviations in mouth opening from non-invasive temporomandibular joint complex functional analyses.

A quantitative approach to predict expected muscle activity and mandibular movement from non-invasive hard tissue assessments remains unexplored. This study investigated the predictive potential of normalised muscle activity during various jaw movements combined with temporomandibular joint (TMJ) vibration analyses to predict expected maximum lateral deviation during mouth opening. Sixty-six participants underwent electrognathography (EGN), surface electromyography (EMG) and joint vibration analyses (JVA). They performed maximum mouth opening, lateral excursion and anterior protrusion as jaw movement activities in a single session. Multiple predictive models were trained from synthetic observations generated from the 66 human observations. Muscle function intensity and activity duration were normalised and a decision support system with branching logic was developed to predict lateral deviation. Performance of the models in predicting temporalis, masseter and digastric muscle activity from hard tissue data was evaluated through root mean squared error (RMSE) and mean absolute error. Temporalis muscle intensity ranged from 0.135 ± 0.056, masseter from 0.111 ± 0.053 and digastric from 0.120 ± 0.051. Muscle activity duration varied with temporalis at 112.23 ± 126.81 ms, masseter at 101.02 ± 121.34 ms and digastric at 168.13 ± 222.82 ms. XGBoost predicted muscle intensity and activity duration and scored an RMSE of 0.03-0.05. Jaw deviations were successfully predicted with a MAE of 0.9 mm. Applying deep learning to EGN, EMG and JVA data can establish a quantifiable relationship between muscles and hard tissue movement within the TMJ complex and can predict jaw deviations.

Effect of maxillary distraction osteogenesis and LeFort-1 advancement orthognathic surgery on soft-tissue thickness and anterior soft-tissue to hard-tissue movement ratios among patients with complete unilateral cleft lip and palate

Objectives: The objective of this study was to compare the soft-tissue thickness and anterior soft-tissue to hard-tissue movement ratios in patients with unilateral cleft lip and/or palate (UCLP) following maxillary distraction osteogenesis using rigid external distractor device and maxillary advancement at LeFort I level using lateral cephalograms. Material and Methods: This retrospective study was conducted on 20 patients with UCLP who underwent either LeFort I maxillary advancement or maxillary distraction osteogenesis. Non-syndromic patients with complete UCLP anomalies and skeletal class III patterns due to maxillary hypoplasia were included in the study. The patients with a pre-surgical negative overjet of ≥5 mm were treated by maxillary distraction osteogenesis, while a negative overjet of &lt;5 mm was managed with maxillary advancement orthognathic surgery. The growth completion in all the patients was assessed using the cervical vertebrae maturation index (CS 6) on a lateral cephalogram. The lateral cephalograms taken before surgery at (T0) and after a minimum interval of six months (T1) of surgery were assessed for changes in soft-tissue thickness and hard-tissue to soft-tissue movement ratios among the two groups. Paired t-test was used to compare the mean values obtained within the same group at two different time intervals. Unpaired t-test was used to compare mean values between the Groups 1 and 2. Pearson’s correlation coefficient (r) test was used to assess the associations between the mean changes in hard- and soft-tissue variables. Results: Group 1 showed significantly greater maxillary advancement compared to Group 2 with a mean difference of 5.80 mm at Point A and 7.65 mm at the upper incisal edge. Soft-tissue thickness decreased significantly after advancement in Group 1 at subnasale (P &lt; 0.05), labrale superius, stomion, and labrale inferius (P &lt; 0.01) and at subnasale (P &lt; 0.05), stomion and labrale inferius (P &lt; 0.01) in Group 2. There was a significantly strong correlation between the hard- and soft-tissue movement in sagittal plane in both Group 1 and Group 2. In Groups 1 and 2, a statistical highly significant strong positive correlation was found between vertical change in dU1 to soft-tissue dLs and dStms. In Group 2, a statistical highly significant strong positive correlation was found between vertical change in dA to soft-tissue dC and dStms. Conclusion: The soft-tissue thickness reduced in patients with UCLP after maxillary advancement in both groups. The soft tissue followed the hard tissue in both groups. There was a greater downward movement of the maxillary base and soft-tissue lengthening in Group 1 compared to Group 2.

Facial and mandibular landmark tracking with habitual head posture estimation using linear and fiducial markers.

This study compared the accuracy of facial landmark measurements using deep learning-based fiducial marker (FM) and arbitrary width reference (AWR) approaches. It quantitatively analysed mandibular hard and soft tissue lateral excursions and head tilting from consumer camera footage of 37 participants. A custom deep learning system recognised facial landmarks for measuring head tilt and mandibular lateral excursions. Circular fiducial markers (FM) and inter-zygion measurements (AWR) were validated against physical measurements using electrognathography and electronic rulers. Results showed notable differences in lower and mid-face estimations for both FM and AWR compared to physical measurements. The study also demonstrated the comparability of both approaches in assessing lateral movement, though fiducial markers exhibited variability in mid-face and lower face parameter assessments. Regardless of the technique applied, hard tissue movement was typically seen to be 30% less than soft tissue among the participants. Additionally, a significant number of participants consistently displayed a 5 to 10° head tilt.

Nasolabial soft tissue changes associated with posterior maxillary movement following anterior segmental osteotomy in skeletal Class II patients: A case series

ObjectiveThis study investigated the relationship between the external nasal morphology and hard tissue movement in patients who underwent anterior segmental maxillary osteotomy (ASMO) to correct maxillary protrusion correction. MethodsThe study enroled patients with an overjet ≥ 5 mm, and an ANB ≥ 2° who underwent ASMO with or without Le Fort I osteotomy. Linear and angular measurements were performed on computed tomography images obtained preoperatively and one year post-surgery. ResultsThe movement of the maxilla at U1 was 6.7 ± 2.9 mm backward and 1.9 ± 2.0 mm upward. Tooth axis inclination of U1 (∠U1 to FH) increased 5.5 ± 6.1°. The nasolabial angle significantly increased from 90.0 ± 16.8° to 101.0 ± 13.2°. No significant differences were observed in alar base width or nasal tip angles. The change of ∠U1 to FH and the backward movement of U1 were relevant factors influencing the change of nasolabial angle. ConclusionsThis study provides insights into the relationship between external nasal morphology and posterior movement of the anterior maxillary segment after ASMO surgery. These findings are significant for predicting post-operative patient profiles.

Do Patients Detect Changes in Breathing After Orthognathic Surgery?

Orthognathic surgery addresses facial aesthetics and function in patients with dentofacial deformities. It is associated with changes in upper airway volume (UAV). If changes in UAV are perceived by asymptomatic patients is unclear. The purpose was to measure associations between changes in UAV and patient-reported benefits using patient-reported outcome measures. A sample presenting dentofacial deformities without reported breathing problems undergoing orthognathic surgery was retrospectively studied. Patients aged 18-30years with 12-month follow-up were included. Patients with systemic disease, drug abuse, mental health disorder, or temporomandibular joint dysfunction were excluded. The predictor variable was changes in UAV measured in 3-dimensional computed tomography. Subjects were grouped into increased or decreased UAV. The primary outcome variable was changes in health-related quality of life measured with Oral Health Impact Profile 49 (OHIP-49). Weight, height, age, sex, and sub-scaled OHIP-49 were registered. Cephalometric measurements of hard tissue movements were recorded. Mean, standard deviation, and a level of statistical significance at P<.05 were used. Differences in OHIP-49 were compared using unpaired t-test. The correlation between covariates and outcomes was analyzed using the Spearman's rank test. Analysis of covariance between the predictor and outcome, adjusted for covariates (body mass index), was performed. Fifty-four subjects with a mean age of 20.89years and 52% males were enrolled. The mean change in UAV was 0.12cm3 (standard deviation [SD] 9.21, P=.93) with a mean absolute deviation of 7.28cm3 (SD 5.54). The mean change in OHIP-49 score was 20.93 (SD 28.90). Twenty-seven (50%) subjects had increased UAV (7.4cm3, SD 6.13) and the other had decreased (-7.17cm3, SD 5.01) (P=.01). At follow-up, equal levels of mean OHIP-49 score were found, but because of a baseline difference (15.74, P=.048), the subjects with and without increased UAV improved in OHIP-49 score 13.04 (SD 30.53) and 28.81 (SD 25.33), respectively (P=.04). Because equal levels of OHIP-49 score at follow-up, changes in UAV could not be associated with patient-reported health-related quality of life. Patient-reported outcome measure evaluations of orthognathic surgical treatment for airway obstruction should be performed in patients with a perceived impairment.

Soft Tissue Movement in Orthognathic Surgery: Does Pre-Operative Soft Tissue Thickness Affect Movement Change?

Background: The aim of this study was to examine whether the thickness of the preoperative soft tissue affects the degree of soft tissue movement relative to the hard tissue movement after orthognathic surgery. Methods: This is a retrospective examination of lateral cephalometric X-rays of patients who underwent orthognathic surgery in single medical center, during a 5-year period. Demographic and operative data were collected. Soft tissue thickness was measured in preoperative cephalometric X-ray, followed by superimposition of postoperative (&gt;6 months) cephalometric X-rays by overlapping fixed bony points. Results: In the upper jaw, there was a decrease in the relative movement of soft tissue with an increase in the initial thickness in surgeries performing advancements up to 5 mm (r = −0.288). In mandibular advancements, there was a clear decrease in soft tissue movement ratio with an increase in the initial soft tissue thickness (r = −0.418), while there was no correlation in mandibular setback cases (r = 0.062). The same correlation between the decrease in relative soft tissue movement and the increase in initial soft tissue thickness was found in advancement genioplasty (r = −0.411). Conclusion: This research shows a general pattern of decrease in relative movement of soft tissue in orthognathic surgery correlated to an increase in its initial thickness.

The Influence of Three Root Canal Irrigation Methods on PostThe Influence of Three Root Canal Irrigation Methods on PostOperative Pain “Randomized Clinical Trial”

Introduction: Facial soft tissue changes in relation to hard tissue movements after orthognathic surgery cases is always of concern to patients , surgical and orthodontics teams. The aim of the present study was to assess facial soft tissue changes and stability using 3D facial laser scanner after orthognathic surgery Le Forte I maxillary impaction in excessive gingival display patients. Methods: The subjects consisted of 12 patients with skeletal vertical maxillary excess (VME) causing an aesthetic concern to the patients in the form of “Gummy smile”, who underwent LeFort I osteotomy with maxillary impaction, Three-dimensional images of the patients were acquired with a 3D laser scanner preoperatively and postoperatively. The changes in facial soft tissue were detected using a colour coded map for analysis. Results: Significant change was recorded in the upper lip, alar base, nasolabial fold and nasal tip areas, without specification of this change in direction. Conclusions: The 3D images captured using the laser scanner in this study can be a useful tool for communication with both patients and professionals but cannot be relied upon solely for accurate analysis of the facial soft tissue changes. The colour coded map analysis cannot be relied upon solely as a method of analysis as it lacks an important aspect of the change which is the direction.

Three-dimensional changes in the location of soft tissue landmarks following bimaxillary orthognathic surgery.

We sought to determine the amount of three-dimensional (3D) movement of soft tissue landmarks in patients who underwent bimaxillary orthognathic surgery. We recruited 28patients (11women and 17men), who had received one-piece Le FortI osteotomy with maxillary advancement and impaction, and bilateral sagittal split ramus osteotomy for mandibular setback. The 3D images were acquired 1-7days before surgery and at least 6months after surgery using stereophotogrammetry. We recorded 50 coordinate measurements and correlated the movements between soft and hard tissues. Paired samples t‑test, independent samples t‑test, and Pearson's correlation analysis were used for statistical analysis. Patients' ages ranged from 17-31years (mean 20.4 ± 3.0years). The mean advancement and impaction of the maxilla was 4.7 ± 1.2 and 2.2 ± 1.0 mm, respectively. The mean setback of the mandible was 4.2 ± 1.6 mm. Menton (Me) moved significantly closer to the midsagittal plane, and the bilateral alare (Al) and alar curvature (Ac) moved laterally. In addition, pronasale (Prn), bilateral Al, Ac, subnasale (Sn), subspinale (Ss), labiale superior (Ls), sublabiale (Sl), pogonion (Pog), and Me moved upwards. The bilateral cheek bone (Cbp), Al, Ac, Prn, Sn, Ss, Ls, and stomion (Sto) moved forward. Li, Sl, Pog, and Me moved backward. Interestingly, poor correlation was found between soft tissue landmarks and hard tissue movements. We observed 3D coordinate changes in several soft tissue landmarks in the middle and lower thirds of the face. The results of this study may be useful for estimating postoperative changes in similar patients.

Three-Dimensional Analysis of Soft and Hard Tissue Changes following Orthognathic Surgery

Change in soft tissue in relation to that in hard tissue following orthognathic surgery was evaluated. Twenty-five patients were enrolled in the study. The diagnosis in all was jaw deformity (maxillary retrusion and mandibular protrusion) and all underwent a Le Fort I osteotomy and bilateral sagittal splitting ramus osteotomy. Three-dimensional (3D) computer-aided design (CAD) models (polygon models) of the hard and soft tissue of the maxilla and mandible were constructed and superimposed. Reference points were established on the pre- and postoperative hard and soft tissues. Specific elements of each reference point were divided into X, Y, and Z components, respectively, and the distances in each direction and 3D distance (normal distance) measured. The Wilcoxon signed-rank test was used to determine differences in the mean values for the distance moved of each element as the error between pre- and postoperatively. The results revealed statistically significant differences in the Y-direction in the maxilla and the X- and Z-directions in the mandible. A significant difference was also observed in the 3D distances of the maxilla and mandible. Little evidence was found of linearity between the amount of hard and soft tissue movement in the X- and Z-directions in the maxilla. This means that 3D movement in the maxilla was masked more by changes in the morphology of the soft tissue than in the mandible, making it less evident. The results of this study suggest that the 3D analysis method used enables changes in hard and soft tissues to be understood qualitatively, and that it can be used in diagnosis and treatment in orthognathic surgery. It may also be useful in simulation of morphological change in soft tissue.

Study of soft tissue changes in the upper lip and nose after backward movement of the maxilla in orthognathic surgery.

ObjectivesThis study evaluates soft tissue changes of the upper lip and nose after maxillary setback with orthognathic surgery such as Le Fort I or anterior segmental osteotomy.Materials and MethodsAll 50 patients with bimaxillary protrusion and skeletal Class II malocclusion underwent Le Fort I or anterior segmental osteotomy with backward movement. Soft and hard tissue changes were analyzed using cephalograms collected preoperatively and 6 months postoperatively.ResultsCluster analysis on the ratios shows that 2 lines intersected at 4 mm point. Based on this point, we divided the subjects into 2 groups Group A (less than 4 mm, 27 subjects) and Group B (more than 4 mm, 23 subjects). Also, each group was divided according to changes of upper incisor angle (≥4°=A1, B1 or <4°=A2, B2). The correlation between A and B groups for Aʼ/ANS and Ls/Is (P<0.001) was significant; Aʼ/A (P=0.002), PRN/A (P=0.043), PRN/ANS (P=0.032), and St/Is (P=0.010). Variation of nasolabial angle between the two groups was not significant. There was no significant correlation of vertical movement and angle variation.ConclusionThe ratio of soft tissue to hard tissue movement depends on the amount of posterior movement in the maxilla, showing approximately two times higher rates in most of the midface when posterior movement was greater than 4 mm. The soft tissue changes caused by posterior movement of the maxilla were little affected by angular changes of upper incisors. Interestingly, nasolabial angle showed a different tendency between A and B groups and was more affected by incisal angular changes when horizontal posterior movement was less than 4 mm.

Three-dimensional evaluation of treatment results of the Alt-RAMEC and facemask protocol in growing patients

The aim of this retrospective study was to evaluate the skeletal, dental, and soft tissue effects of the alternating rapid maxillary expansions and constrictions (Alt-RAMEC) protocol combined with afacemask in prepubertal patients. The study group (mean age 9.74 ± 1.46 years) consisted of 20 patients with classIII malocclusion characterized by maxillary retrognathism. They were treated with afacemask for 7months following a 9‑week Alt-RAMEC protocol. Cone-beam computed tomography (CBCT) records and three-dimensional (3D) photographs taken before (T0) and after the protraction and retention period (T1) were evaluated. The study group was compared with awell-matched control group of 16untreated patients (mean age 9.44 ± 0.79years) with the same malocclusion. The records for the control group included cephalometric radiographs and 3D photographs. In the study group, significant forward movements of Apoint (3.49 mm), nasal (2.91 mm) and zygomatic bones were achieved. Intermolar, internasal, and interzygomatic widths increased. Soft tissue points followed the hard tissue movements, apart from band pog. In the control group, A(0.97 mm), B(1.69 mm), Pog, and bpoints presented forward movement. Significant differences were found regarding the forward movement of the maxilla between the groups. The Alt-RAMEC/facemask protocol was effective not only in the maxillary region but also in the midface.

Evaluation of Palatal Rugae Following Orthopedic Treatment Using Rapid Maxillary Expander and Facemask

The purpose of this study was to determine whether the palatal rugae could be used as an appropriate reference area for serial model superimposition following Rapid maxillary expansion(RME) and facemask treatment.&lt;br/&gt;A total of 52 pediatric patients who had undergone RME and facemask treatment were selected. Palate and palatal rugae in the pre- and post- treatment casts from the patients were measured.&lt;br/&gt;In spite of dentoalveolar changes occurred by RME and facemask, anteroposterior changes in palate and palatal rugae were not significant. Anatomical changes of palate and palatal rugae were mostly shown in the transverse dimension. The soft tissue of the palatal rugae stretches in adaptation to hard tissue movement. Among the evaluated landmarks, the medial point of the third palatal rugae seemed to be the most stable.&lt;br/&gt;The observed alterations in the palatal rugae demonstrated the potential of medial points of third palatal rugae as a reference point in model superimpositions to evaluate dental movement within the maxillary arch following RME and facemask treatment.

Three-dimensional soft tissue changes according to skeletal changes after mandibular setback surgery by using cone-beam computed tomography and a structured light scanner

BackgroundTo evaluate the three-dimensional (3D) changes after mandibular setback surgery (MSS) in skeletal Class III malocclusion using cone-beam computed tomography (CBCT) and a structured light-based scanner.MethodsTwenty-eight adult Korean patients with skeletal Class III malocclusion treated by MSS were evaluated. CBCT and facial scan images were recorded one week before and six months after surgery. To use an identical 3D coordinate system, superimposition was performed, and nine skeletal and 18 soft tissue landmarks were identified. Changes in the landmarks and correlation coefficients and ratios between hard and soft tissue changes were evaluated. Paired t test and Pearson’s correlation test were performed.ResultsAfter MSS, the amount of transverse correction was 2.45 mm; mandibular setback, 5.80 mm; and vertical reduction, 1.64 mm at the menton, on average. In the transverse axis, there were significant changes and correlations in the lips and chin and an increasing gradient of ratios from the lower lip to the chin. In the anteroposterior axis, the lower lip and chin moved backward significantly and showed notable correlation with hard tissue movement. In the vertical axis, significant upward movement was observed in the landmarks related to the chin, but only lower facial height was significantly decreased.ConclusionsSoft tissue changes according to hard tissue movement after MSS exhibited a distinct pattern of an increasing gradient from the lips to the chin in a transverse aspect.

Understanding Predictability Error in Orthognathic Surgery

Orthognathic surgery aims to improve the facial aesthetics while maintaining stable jaw form and function. Lateral cephalometry provides objective data used in pre-op mock surgery to predict movement of the maxilla and mandible during orthognathic procedures. A prospective cohort study was conducted on 30 adult orthognathic surgery patients. Mock jaw surgery predicted two-dimensional (horizontal and vertical) linear movement of maxilla and mandible. Operative procedures performed were bilateral sagittal split osteotomy and Le Fort I osteotomy. Seven-day pre-op cephalogram (T1) was compared to 7th day post-op cephalogram (T2) to assess hard tissue movement of point A (maxilla) and point B (mandible) using Cartesian (X-Y) plane. The difference between predicted values to the 7th day post-op outcome results was statistically insignificant (p value less than 0.001). Planning in orthognathic surgery using digitized two-dimensional cephalometric tracings and mock jaw surgery produces predictable results.

Three-dimensional region-based study on the relationship between soft and hard tissue changes after orthognathic surgery in patients with prognathism.

Both deep understanding and reliable prediction of postoperative soft tissue changes are crucial for planning orthognathic surgery. Instead of estimating soft tissue responses by measuring individual landmark changes, this study aimed to investigate the relationship (ratio) between soft and hard tissue movements in different facial regions through three-dimensional cone-beam computed tomography (CBCT). Preoperative and postoperative CBCT images were superimposed using the surface registration method on the basis of the cranial base, and 10 facial regions of interest were defined. Region-based volumetric subtractions between the preoperative and postoperative segments were performed. The volumetric differences and surface of each region were used to estimate the average movement. Correlation and regression analyses were performed to examine the relationships between the corresponding soft and hard tissue movements. An overall pattern of facial soft tissue movement was observed in patients with prognathism who underwent orthognathic surgery. The experiment results have shown that mean ratios for the average soft-to-hard tissue movements in the facial regions varied, which may not exactly be similar to the published reports because of the population biocharacteristics and study methods, but the trend is in agreement with the previous studies. Additionally, the prediction capability of the regression model was significantly high, ranging from 0.786 to 0.857, in upper lip, upper vermilion, and chin regions, thus demonstrating that the skin outline changes in these critical regions could be reliably predicted from the underlying bone movements. These results could likely be applied in future soft tissue simulation in orthognathic surgery.