Evaluation of an automated superimposition method for computer-aided cephalometrics

ObjectivesTo evaluate a new superimposition method compatible with computer-aided cephalometrics and to compare superimposition error to that of the conventional Sella-Nasion (SN) superimposition method.Materials and MethodsA total of 283 lateral cephalometric radiographs were collected and cephalometric landmark identification was performed twice by the same examiner at a 3-month interval. The second tracing was superimposed on the first tracing by both the SN superimposition method and the new, proposed method. The proposed method not only relied on SN landmarks but also minimized the differences between four additional landmarks: Porion, Orbitale, Basion, and Pterygoid. The errors between the landmarks of the duplicate tracings oriented by the two superimposition methods were calculated at Anterior Nasal Spine, Point A, Point B, Pogonion, and Gonion. The paired t-test was used to find any statistical difference in the superimposition errors by the two superimposition methods and to investigate whether there existed clinically significant differences between the two methods.ResultsThe proposed method demonstrated smaller superimposition errors than did the conventional SN superimposition method. When comparisons between the two superimposition methods were made with a 1-mm error range, there were clinically significant differences between them.ConclusionsThe proposed method that was compatible with computer-aided cephalometrics might be a reliable superimposition method for superimposing serial cephalometric images.     

Longitudinal growth changes of the cranial base from puberty to adulthood: A Comparison of Different Superimposition Methods

Objective:To investigate the stability of cranial reference landmarks from puberty through adulthood and to compare the displacement of these landmarks among the superimposition methods of Björk, Ricketts, Steiner, and the proposed tuberculum sella-wing (T-W) reference line.Materials and Methods:The sample consisted of serial lateral cephalometric radiographs of 30 Class II division 1 patients taken at the pretreatment (T1; mean age, 11.98 years), posttreatment (T2; mean age, 15.32 years) and postretention (T3; mean age, 32.12 years) periods. All cephalometric radiographs were superimposed at the cranial base according to the overall superimposition methods of Björk, Ricketts, Steiner, and the T-W method. The horizontal and vertical displacements of cranial landmarks (nasion, wing, tuberculum sella, sella, basion, and pterygomaxillare) were assessed by paired t-test according to Björk''s structural method. One-way analysis of variance (ANOVA) was used for comparison of the displacement of cranial landmarks among the superimposition methods.Results:The tuberculum sella and wing were the most stable cranial landmarks of the cranial base. The stability of sella and pterygomaxillare points were somewhat questionable. Nasion and basion were highly variable. The displacements of all cranial landmarks were similar between the Björk and T-W methods in all study periods. Most of the cranial landmarks displaced similarly in the horizontal direction among the methods. Vertically, the behaviors of the cranial landmarks were frequently different.Conclusions:T-W is the most similar superimposition method to Björk''s structural method; thus, it is a reliable method for examining overall facial changes.     

Improved Lateral Cephalometric Superimposition Using an Automated Image Fitting Technique

Objective:To test the feasibility of automated lateral cephalometric radiograph (LCR) superimposition using an image fitting algorithm.Materials and Methods:Using radiopaque markers, we identified seven cephalometric landmarks on three dry skulls, took digital LCRs on each in several rotated positions, and used a custom software program (XRay3D) to automatically superimpose each rotated image on the initial image using an anterior cranial base reference. We measured superimposition error at each landmark and adjusted image brightness levels to simulate potential fitting error due to exposure variation.Results:The greatest mean error for 24 image rotation trials of less than 10° was less than 0.5 mm. Rotations of 10° or more were not reliably superimposed. Errors of 0.2–1.6 mm occurred for ±10% brightness but increased exponentially with further brightness alteration.Conclusion:Automated superimposition of LCRs, using this fitting technique, has great potential when rotation is less than 10° and brightness variation is less than 10%.     

基于深度学习的二维头影测量定点分析系统的研究

目的 探讨基于深度学习的图像高斯金字塔和卷积神经网络方法,构建和训练一种高精准度的自动化二维头影测量标志点定位与分析系统模型。方法 收集2021年1月至12月期间本院所摄的400张年龄在18至50周岁且无牙列缺损的头颅侧位影像,在3D slicer（NIH美国）上完成每张44个牙颌和颅面软硬组织结构标志点的标注,并构建和训练基于图像高斯金字塔和卷积神经网络的自动化二维头影测量标志点定位和分析系统。结果 运用图像高斯金字塔和卷积神经网络方法能高精准获取44个牙颌和颅面的软硬组织结构标志点,在 2.0 mm、2.5 mm、3.0 mm、4.0 mm 精度范围内预测的平均准确率分别为 85.61 %、90.72 %、93.82 %、96.34 %;44个牙颌和颅面软硬组织结构标志点的平均误差为 1.22 mm,平均标准差为 1.27 mm;常见头影测量项目（ANB、SNA、SNB、ODI、APDI、FHI、FMA、MW）的平均预测准确率为 85.00 % 。结论 运用图像高斯金字塔和卷积神经网络方法能高精准获取牙颌和颅面的软硬组织结构标志点,并且对牙颌和颅面形态分析诊断具有良好的准确性,该技术将有助于推进自动化头影测量的临床运用。     

The relationship between 3D dentofacial photogrammetry measurements and traditional cephalometric measurements

Objectives:To determine the relationship between traditional cephalometric measurements and corresponding nonradiographic three-dimensional (3D) photogrammetry measurements.Materials and Methods:This was a cross-sectional study of 20 orthodontic patients (10 male and 10 female) who received lateral cephalometric radiographs and 3D dentofacial photogrammetric records with each subject serving as his or her own control for a total sample size of 40 images (20 per method). A 3D analysis that resembled a traditional cephalometric analysis was established using the eyes and natural head orientation as substitutes for the cranial base. Pearson correlation coefficients and multivariable linear regression plots were calculated to evaluate the relationship between the photogrammetry measurements and the cephalometric measurements.Results:The ANB angle, mandibular plane angle, lower anterior face height, upper incisor angle to SN, upper incisor angle to NA, and all measurements of lower incisor position and inclination had strong positive Pearson correlation coefficients with the corresponding 3D photogrammetry measurements (P < .004). Statistically significant regression plots demonstrated that cephalometric relationships between the jaws and incisor orientation can be predicted from corresponding 3D photogrammetry measurements.Conclusions:3D photogrammetry measurements relating the jaws to each other and incisor orientation has a strong positive correlation with corresponding traditional cephalometric measurements and can serve as cephalometric predictors. Capturing the eyes using 3D photogrammetry can obviate the need to expose the cranial base and allow limiting the radiographic field to the area of interest.     

Analysis of tooth movement in extraction cases using three-dimensional reverse engineering technology

Despite inherent errors, cephalometric superimpositions are currently the most widely used means for assessing sagittal and vertical tooth movements. The purpose of this study was to compare three-dimensional (3D) digital model superimposition with cephalometric superimposition. The material was collected from initial and final maxillary casts and lateral cephalometric radiographs of 30 patients (6 males, 24 females, mean age 17.7 years) who underwent orthodontic treatment with extraction of permanent teeth. Each pair of cephalograms was traced and superimposed according to Ricketts' four-step method. 3D scanning of the maxillary dental casts was performed using INUS dental scanning solution(R), which consists of a 3D scanner, an autoscan system, and 3D reverse modelling software. The 3D superimposition was carried out using the surface-to-surface matching (best-fit method) function of the autoscan system. The antero-posterior movement of the maxillary first molar and central incisor was evaluated cephalometrically and on 3D digital models. To determine whether any difference existed between the two measuring techniques, paired t-tests and correlation analysis were undertaken. The results revealed no statistical differences between the mean incisor and molar movements as assessed cephalometrically or by 3D model superimposition. These findings suggest that the 3D digital orthodontic model superimposition technique used in this study is clinically as reliable as cephalometric superimposition for assessing orthodontic tooth movements.     

Newly defined landmarks for a three-dimensionally based cephalometric analysis: A retrospective cone-beam computed tomography scan review

Objectives:To identify two novel three-dimensional (3D) cephalometric landmarks and create a novel three-dimensionally based anteroposterior skeletal measurement that can be compared with traditional two-dimensional (2D) cephalometric measurements in patients with Class I and Class II skeletal patterns.Materials and Methods:Full head cone-beam computed tomography (CBCT) scans of 100 patients with all first molars in occlusion were obtained from a private practice. InvivoDental 3D (version 5.1.6, Anatomage, San Jose, Calif) was used to analyze the CBCT scans in the sagittal and axial planes to create new landmarks and a linear 3D analysis (M measurement) based on maxillary and mandibular centroids. Independent samples t-test was used to compare the mean M measurement to traditional 2D cephalometric measurements, ANB and APDI. Interexaminer and intraexaminer reliability were evaluated using 2D and 3D scatterplots.Results:The M measurement, ANB, and APDI could statistically differentiate between patients with Class I and Class II skeletal patterns (P < .001). The M measurement exhibited a correlation coefficient (r) of −0.79 and 0.88 with APDI and ANB, respectively.Conclusions:The overall centroid landmarks and the M measurement combine 2D and 3D methods of imaging; the measurement itself can distinguish between patients with Class I and Class II skeletal patterns and can serve as a potential substitute for ANB and APDI. The new three-dimensionally based landmarks and measurements are reliable, and there is great potential for future use of 3D analyses for diagnosis and research.     

Evaluation of deep learning and convolutional neural network algorithms accuracy for detecting and predicting anatomical landmarks on 2D lateral cephalometric images: A systematic review and meta-analysis

IntroductionCephalometry is the study of skull measurements for clinical evaluation, diagnosis, and surgical planning. Machine learning (ML) algorithms have been used to accurately identify cephalometric landmarks and detect irregularities related to orthodontics and dentistry. ML-based cephalometric imaging reduces errors, improves accuracy, and saves time.MethodIn this study, we conducted a meta-analysis and systematic review to evaluate the accuracy of ML software for detecting and predicting anatomical landmarks on two-dimensional (2D) lateral cephalometric images. The meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for selecting and screening research articles. The eligibility criteria were established based on the diagnostic accuracy and prediction of ML combined with 2D lateral cephalometric imagery. The search was conducted among English articles in five databases, and data were managed using Review Manager software (v. 5.0). Quality assessment was performed using the diagnostic accuracy studies (QUADAS-2) tool.ResultSummary measurements included the mean departure from the 1–4-mm threshold or the percentage of landmarks identified within this threshold with a 95% confidence interval (CI). This meta-analysis included 21 of 577 articles initially collected on the accuracy of ML algorithms for detecting and predicting anatomical landmarks. The studies were conducted in various regions of the world, and 20 of the studies employed convolutional neural networks (CNNs) for detecting cephalometric landmarks. The pooled successful detection rates for the 1-mm, 2-mm, 2.5-mm, 3-mm, and 4-mm ranges were 65%, 81%, 86%, 91%, and 96%, respectively. Heterogeneity was determined using the random effect model.ConclusionIn conclusion, ML has shown promise for landmark detection in 2D cephalometric imagery, although the accuracy has varied among studies and clinicians. Consequently, more research is required to determine its effectiveness and reliability in clinical settings.     

Evaluation of soft tissue changes around the lips after bracket debonding using three-dimensional stereophotogrammetry

Objective:To evaluate the changes in soft tissue around the lips after orthodontic bracket debonding using three-dimensional (3-D) stereophotogrammetry.Materials and Methods:3-D facial images of 20 subjects (10 men and 10 women; mean age, 26.81 ± 7.23 years) were taken with a white light scanner before and after debonding the labial brackets. Two images acquired from each subject were superimposed, and 15 soft tissue landmarks around the lips were plotted and analyzed. Statistical analysis was performed using both paired and independent t-tests (P < .05).Results:There were no significant changes in position of any landmark on the x (left-right)- or y (vertical)-axes after removal of the brackets. However, the landmarks in the oral commissures and lower lip (LLP, −0.55 mm; Li, −0.44 mm; Ch-L, −0.56 mm, all P < .05) on the z (anteroposterior)-axis showed statistically significant differences. There were no significant positional changes of most landmarks on the x-, y-, or z- axes after bracket removal among the various genders and lip thicknesses.Conclusions:There was a slight retrusion in the oral commissure and lower lip areas after debonding, but no changes were found in the upper lip area. This study showed that 3-D stereophotogrammetry can be useful in evaluating facial soft tissue changes in orthodontic patients.     

Effect of the presence of orthodontic brackets on intraoral scans

ObjectivesThe need for intraoral scanning in the presence of brackets has increased for monitoring tooth movement during orthodontic treatment. The purpose of this study was to evaluate the effect of orthodontic brackets bonded to tooth surfaces on intraoral scans.Materials and MethodsIntraoral scans were performed in 30 patients using both iTero and Trios scanners before and after bonding of the brackets. The two sets of intraoral scans of each patient and intraoral scans with and without brackets were superimposed using a best-fit algorithm, and three-dimensional (3D) surface analysis was performed. In each superimposition, discrepancies in the 3D axes and arch-width measurements in the incisor and molar regions were compared. In addition, the range of distortion around the brackets was evaluated on the cross sections of each superimposition.ResultsThe overall discrepancies between the intraoral scans with and without brackets were within 0.30 mm. The arch-width discrepancies in the molar region were greater than those in the incisor region, but the differences were not statistically significant (P = .972 for iTero; P = .960 for Trios). The cross sections of the superimposed intraoral scans with and without brackets showed that the deviations were within 0.40 mm in the horizontal section and within 0.35 mm in the vertical section around the brackets.ConclusionsThe results of this study indicate that the accuracy of intraoral scans, even in the presence of brackets, is clinically acceptable, and the regions beyond 0.50 mm around the brackets should be used for superimposition on images without brackets.     

Orthognathic surgery outcome analysis: 3-dimensional landmark geometric morphometrics

Traditional cephalometric analysis of 2-dimensional (2D) landmarks has been limited to distances, indices, and angles. Quantitative results vary depending on what baseline is chosen. Geometric morphometric techniques, such as Procrustes superimposition, assume all landmarks carry equivalent information. Using these methods, landmark coordinates (x, y, z) facilitate comparison of patients and "normative"shapes and assessment of pre- to postoperative outcomes. Pre- and postoperative lateral and frontal cephalograms and stereophotograms were taken of a 48-year-old Caucasian man and a 38-year-old Caucasian woman. Coordinates of 3D hard tissue landmarks were collected directly from scanned cephalograms, and 3D soft tissue landmarks were collected onscreen. Procrustes superimpositions of pre- and postoperative 3D craniodental landmark coordinates and 3D soft tissue coordinates were made, and scatter plots were created to show the surgical shape change separately for each patient. Procrustes superimposition of the preoperative and "normative craniodental data (18-year-old male and female Bolton standards) provided both qualitative and quantitative evaluations of the patients, allowing a better determination of the required treatment. Unlike traditional baseline-dependent methods, Procrustes shape analysis produces a single useful measure of surgical shape change or comparison to normative shape.     

Evaluation of an automated superimposition method based on multiple landmarks for growing patients

ObjectivesTo determine if an automated superimposition method using six landmarks (Sella, Nasion, Porion, Orbitale, Basion, and Pterygoid) would be more suitable than the traditional Sella-Nasion (SN) method to evaluate growth changes.Materials and MethodsSerial lateral cephalograms at an average interval of 2.7 years were taken on 268 growing children who had not undergone orthodontic treatment. The T1 and T2 lateral images were manually traced. Three different superimposition methods: Björk''s structural method, conventional SN, and the multiple landmark (ML) superimposition methods were applied. Bjork''s structural method was used as the gold standard. Comparisons among the superimposition methods were carried out by measuring the linear distances between Anterior Nasal Spine, point A, point B, and Pogonion using each superimposition method. Multiple linear regression analysis was performed to identify factors that could affect the accuracy of the superimpositions.ResultsThe ML superimposition method demonstrated smaller differences from Björk''s method than the conventional SN method did. Greater differences among the cephalometric landmarks tested resulted when: the designated point was farther from the cranial base, the T1 age was older, and the more time elapsed between T1 and T2.ConclusionsFrom the results of this study in growing patients, the ML superimposition method seems to be more similar to Björk''s structural method than the SN superimposition method. A major advantage of the ML method is likely to be that it can be applied automatically and may be just as reliable as manual superimposition methods.     

Reliability and reproducibility of three-dimensional cephalometric landmarks using CBCT: a systematic review

Objective

: The aim of this study was to review the reliability and reproducibility of 3D-CBCT (cone beam computed tomography) cephalometric landmark identification.

Methods

: Electronic databases (Pubmed, Scopus, Web of Science) were searched for papers published from 1998 to October 2014. Specific strategies were developed for each database, with the guidance of a librarian. Two reviewers independently analyzed the titles and abstracts for inclusion. The articles that met the inclusion and exclusion criteria were selected for full-text reading, and the selected articles went through methodological quality evaluation. After the exclusion of repeated articles, the titles of the remaining ones were read and 1,328 of them were excluded. The abstracts of 173 articles were read, of which 43 were selected, read in full and submitted to the inclusion and exclusion criteria. Fourteen articles or studies with reliable methodology and reproducibility remained. The data were collected, organized into figures and analyzed for determination of the reliability and reproducibility of the three-dimensional cephalometric landmarks.

Results

: Overall, the landmarks on the median sagittal line and dental landmarks had the highest reliability, while the landmarks on the condyle, porion and the orbitale presented lower levels of reliability. Point S must be marked in the multiplanar views associated with visualization in 3D reconstruction. Further studies are necessary for evaluating soft tissue landmarks.     

Palatal volume and area assessment on digital casts generated from cone-beam computed tomography scans

Objectives:The objective of this study was to develop a reproducible method to measure the change of palatal volume and area through superimposition using maxillary expansion digital cast models.Materials and Methods:A total of 10 pre- and 10 postexpansion dental cast models were scanned by the same cone-beam computed tomography machine. Superimposition was performed using a fully automated surface-best fit of the palatal surfaces on the digital cast models. A gingival plane, identified only once on superimposed casts, and a distal plane with the lateral closing border and the palatal surface were used to localize this selection of air. Area and volume were calculated for pre- and postexpansion records. Pre- and postexpansion palatal volume and area were measured by the main investigator and three different observers for inter- and intra-observer reproducibility assessment.Results:The level of intra- and inter-observer agreement was very strong (intraclass correlation coefficients ≥ 0.953; P value < .0001) for all measurements.Conclusions:Palatal volume and area measurements based on the proposed superimposition are reproducible and can be used reliably.     

3D stereophotogrammetric image superimposition onto 3D CT scan images: the future of orthognathic surgery. A pilot study

The aim of this study was to register and assess the accuracy of the superimposition method of a 3-dimensional (3D) soft tissue stereophotogrammetric image (C3D image) and a 3D image of the underlying skeletal tissue acquired by 3D spiral computerized tomography (CT). The study was conducted on a model head, in which an intact human skull was embedded with an overlying latex mask that reproduced anatomic features of a human face. Ten artificial radiopaque landmarks were secured to the surface of the latex mask. A stereophotogrammetric image of the mask and a 3D spiral CT image of the model head were captured. The C3D image and the CT images were registered for superimposition by 3 different methods: Procrustes superimposition using artificial landmarks, Procrustes analysis using anatomic landmarks, and partial Procrustes analysis using anatomic landmarks and then registration completion by HICP (a modified Iterative Closest Point algorithm) using a specified region of both images. The results showed that Procrustes superimposition using the artificial landmarks produced an error of superimposition on the order of 10 mm. Procrustes analysis using anatomic landmarks produced an error in the order of 2 mm. Partial Procrustes analysis using anatomic landmarks followed by HICP produced a superimposition accuracy of between 1.25 and 1.5 mm. It was concluded that a stereophotogrammetric and a 3D spiral CT scan image can be superimposed with an accuracy of between 1.25 and 1.5 mm using partial Procrustes analysis based on anatomic landmarks and then registration completion by HICP.     

Reliability of different three-dimensional cephalometric landmarks in cone-beam computed tomography: A systematic review

Objectives:Conventional two-dimensional (2D) cephalometric radiography is an integral part of orthodontic patient diagnosis and treatment planning. One must be mindful of its limitations as it indeed is a 2D representation of a vaster three-dimensional (3D) object. Issues with projection errors, landmark identification, and measurement inaccuracies impose significant limitations, which may now be overcome with the advent of cone-beam computed tomography (CBCT). A systematic review of the reliability of different 3D cephalometric landmarks in CBCT imaging was conducted.Materials and Methods:Electronic database searches were administered until October 2017 using PubMed, MEDLINE via OvidSP, EBMR and EMBASE via OvidSP, Scopus, and Web of Science. Google Scholar was used as an adjunctive search tool.Results:Thirteen articles considering CBCT scans of human subjects from preexisting data sets were selected and reviewed. Most of the studies had methodological limitations and were of moderate quality. Because of their heterogeneity, key data from each could not be combined and were reported qualitatively. Overall, in 3D, midsagittal plane landmarks demonstrated greater reliability compared with bilateral landmarks. A minimum number of dental landmarks were reported, although most were recommended for use.Conclusions:Further research is required to evaluate the reliability of 3D cephalometric landmarks when evaluating 3D craniofacial complexes.     

Evaluation of two-dimensional lateral cephalogram and three-dimensional cone beam computed tomography superimpositions: a comparative study

Superimposition of radiographic imaging is used to evaluate patient growth and the effects of surgical and/or orthodontic treatment. The purpose of this study was to compare the outcomes of superimposition between two-dimensional (2D) and three-dimensional (3D) superimpositions. 2D lateral cephalograms were generated from the initial and final cone beam computed tomography scans (CBCT) of 18 patients and superimposed. Both 3D CBCT and 2D CBCT generated lateral cephalograms were oriented to the Frankfort horizontal plane and superimposed according to the American Board of Orthodontics recommendations. Changes in landmark position were quantified from the resulting superimposition outcomes via linear measurements made with Dolphin software. Differences between the two methods were analyzed using paired t-tests. Measurements were repeated twice for 10 randomly selected scans to assess reliability by intra-class correlation coefficient (ICC) analysis. Intra-examiner reliability was high for all measurements (ICC > 0.84). Agreement between 2D and 3D superimposition outcomes, as measured by P-values, was low for ANS (P = 0.026), B-point (P < 0.001), ST Upper lip (P = 0.019), U1 tip (P = 0.010), and U1 apex (P = 0.026). 2D measurements were significantly higher than 3D measurements for ANS, B-point, ST Upper lip, U1 tip, and U1 apex. Findings indicated that both methods of superimposition (2D and 3D) are highly reliable. Statistical differences between 2D and 3D superimposition outcomes were below the threshold of clinical significance.     

Experimental and clinical assessment of three-dimensional cephalometry: A systematic review

ObjectivesThis study provides a systematic review of the current scientific literature on three-dimensional (3D) cephalometry. The null hypothesis was that 3D cephalometry is an accurate and reproducible diagnostic technique. To examine this hypothesis, the following three research questions were proposed: 1) What is the accuracy of 3D cephalometric measurements compared to in vitro measurements? 2) What is the intra- and inter-observer reliability of the selection of 3D cephalometric landmarks? 3) What is the reproducibility of the linear and angular measurements?MethodsA comprehensive database search was performed, using Medline, the Cochrane Central Register of Controlled Trials, Web of Science and Google Scholar. The titles and abstracts obtained from the search were screened and evaluated by two observers according to the inclusion and exclusion criteria.ResultsThe evaluation process yielded 21 articles. A high level of agreement (<1 mm) between the in vitro measurements and those obtained from 3D cephalometry was observed and some landmarks provided highly reproducible results. However, the linear (0.04–7.49 mm) and angular (0.99–9.30°) measurements differed greatly.ConclusionsThe null hypothesis was rejected. This study indicates critical points regarding 3D cephalometry and provides guidance for future research in this field.     

Long-term skeletodental stability of mandibular symphyseal distraction osteogenesis: Tooth-borne vs hybrid distraction appliances

Objective:To evaluate and compare the long-term skeletodental stability of mandibular symphyseal distraction osteogenesis (MSDO) achieved with the use of tooth-borne vs. hybrid distraction appliances.Materials and Methods:Posttreatment and follow-up orthodontic records were collected for 33 patients. The 14 patients who underwent distraction with a tooth-borne appliance had a mean follow-up of 5.08 years. The 19 patients who underwent distraction with a hybrid appliance had a mean follow-up of 6.07 years. Records included intraoral photographs, study models, postero-anterior cephalometric radiographs, and lateral cephalometric radiographs. Total changes of 16 measurements were analyzed to compare patients who underwent the tooth-borne vs. the hybrid distraction.Results:Both groups shared several similar and significant (P < .05) changes from posttreatment to follow-up records. Cast analysis showed a decrease in intercanine width and arch length and an increase in irregularity index. The postero-anterior cephalometric radiograph showed an increase in the width of the interincisal apices. The lateral cephalometric radiograph showed a decrease in the MP-L1 angle. The only statistically significant difference between the two appliances was the intercentral incisor contact point.Conclusion:Changes found are consistent with those found in untreated and orthodontically treated individuals over time. The long-term changes in the current patient sample can be determined to be expected and acceptable. MSDO is a viable treatment option with the use of either a hybrid or tooth-borne appliance.     

Soft tissue profile changes after setback genioplasty in orthognathic surgery patients

PurposeThe aim of this study was to assess the soft tissue/hard tissue ratio after setback genioplasty for a more precise surgical prediction.Patients and methodsThe surgical records of 22 patients with skeletal class III malocclusion who underwent orthodontic-surgical treatments were analyzed retrospectively. All patients had undergone bimaxillary orthognathic procedures with setback genioplasties. Lateral cephalometric tracings at four time points, T0, T1, T2, and T3, were superimposed to analyze the horizontal and vertical changes of the hard and soft tissues at eight reference points in the lower face.ResultsThe thickness of the soft tissue was statistically significantly increased 1 year after the operation. Analysis showed that the horizontal movements of the soft and hard tissue were significantly correlated in the horizontal direction with ratios of 0.9:1 at the lip, B-point, 0.7:1 at the Pogonion, and 1:1 at the menton. The vertical movements were not statistically correlated except for the B-point. The chin setback independently made by genioplasty was also analyzed and the horizontal ratio was 1.1:1 at the menton.ConclusionsConsidering the soft tissue thickening and the soft/hard tissue ratios, the soft tissue profile of the chin can be predicted more precisely after setback genioplasty. Setback genioplasty can be used to effectively and reliably correct horizontal chin protrusion.