Predicting soft tissue changes after orthognathic surgery: The sparse partial least squares method

Objectives:To develop a prediction algorithm for soft tissue changes after orthognathic surgery that would result in accurate predictions (1) regardless of types or complexity of operations and (2) with a minimum number of input variables.Materials and Methods:The subjects consisted of 318 patients who had undergone the surgical correction of Class II or Class III malocclusions. Two multivariate methods—the partial least squares (PLS) and the sparse partial least squares (SPLS) methods—were used to construct prediction equations. While the PLS prediction model included 232 input variables, the SPLS method included a reduced number of variables generated by a handicapping algorithm via the sparsity control. The accuracy between the PLS and SPLS models was compared.Results:There were no significant differences in prediction accuracy depending on surgical movements, the sex of the subjects, or additional surgeries. The predictive performance with a reduced set of 34 input variables chosen using the SPLS method was statistically indistinguishable from the full set of variables with the original PLS prediction model.Conclusions:The prediction method proposed in the present study was accurate for a wide range of orthognathic surgeries. A reduced set of input variables could be selected through the SPLS method while simultaneously maintaining a prediction level that was as accurate as that of the original PLS prediction model.     

Testing a better method of predicting postsurgery soft tissue response in Class II patients: A prospective study and validity assessment

Objective:(1) To perform a prospective study using a new set of data to test the validity of a new soft tissue prediction method developed for Class II surgery patients and (2) to propose a better validation method that can be applied to a validation study.Materials and Methods:Subjects were composed of two subgroups: training subjects and validation subjects. Eighty Class II surgery patients provided the training data set that was used to build the prediction algorithm. The validation data set of 34 new patients was used for evaluating the prospective performance of the prediction algorithm. The validation was conducted using four validation methods: (1) simple validation and (2) fivefold, (3) 10-fold, and (4) leave-one-out cross-validation (LOO).Results:The characteristics between the training and validation subjects did not differ. The multivariate partial least squares regression returned more accurate prediction results than the conventional method did. During the prospective validation, all of the cross-validation methods (fivefold, 10-fold, and LOO) demonstrated fewer prediction errors and more stable results than the simple validation method did. No significant difference was noted among the three cross-validation methods themselves.Conclusion:After conducting a prospective study using a new data set, this new prediction method again performed well. In addition, a cross-validation technique may be considered a better option than simple validation when constructing a prediction algorithm.     

Long-term skeletal and profile stability after surgical-orthodontic treatment of Class II and Class III malocclusion

ObjectiveThe purpose of this perspective research was to study the long-term stability of skeletal, dentoalveolar and soft tissue after orthognathic surgery in subjects presenting with Class II and Class III malocclusions.MethodsThe available digitized cephalometric radiographs, including pretreatment (t₀), presurgery (t₁), a minimum of 12 months postsurgery (t₂) and at least 3 years after the orthosurgery treatment (t₃) were taken between 1998 and 2010. In Group 1 mandibular advancement and in Group 2 mandibular advancement and maxillary impaction surgery were performed for correction of Class II. In Group 3 maxillary advancement and in Group 4 surgical maxillary advancement with mandibular setback, for correction of Class III.ResultsIn all the phases mandibular length was shorter in Group 1, and the inferior third of the face was longer in Group 2. Before the surgery there was greater maxillary deficiency in Group 3 than Group 4 and mandibular length was longer in Group 4.ConclusionIn Groups 1 and 2, at retention phase, relapse occurred due to the increase in mandibular plane, whereas the surgeries performed in Groups 3 and 4 remained stable.     

Stability of skeletal Class II correction with 2 surgical techniques: the sagittal split ramus osteotomy and the total mandibular subapical alveolar osteotomy.

Combined orthodontic and surgical treatment of severe Class II dentoskeletal deformities with the use of the bilateral sagittal split ramus osteotomy is a routine procedure in orthodontic practices. However, an alternative surgical technique, the total mandibular subapical alveolar osteotomy, could be used for the same purpose. The aim of this investigation was to compare the stability of the sagittal split ramus osteotomy with the total mandibular subapical alveolar osteotomy in the correction of dentoskeletal Class II malocclusions. Forty patients that exhibited Class II dentoskeletal relationships were included in the study. Twenty of these patients had mandibular advancement with the sagittal split ramus osteotomy; the remaining 20 patients had advancement of the whole lower alveolar segment with the total mandibular subapical alveolar osteotomy. The cephalograms studied were taken before the surgical procedure (T1 = 4 weeks before operation), immediately after the procedure (T2 = 10 days after surgery), and 1 year later (T3). The statistical analysis used to assess the results between and within the groups over the different time periods was the analysis of variance. The regression analysis was used to test the interdependence of soft tissue response to hard tissue movement. The results of this study show that both procedures are equally stable when correcting Class II malocclusions. This was proved by the stability of the correction of overjet, B point, and incisor-mandibular plane angle. There were no statistically significant differences between or within the groups in the position of these landmarks over time. There was a statistically significant change in the position of pogonion from T1 to T2 (P <.0028) between the groups, although at T3 this difference was not significant (P <.05). There were no significant changes in face height either within or between the groups over time. The hard/soft tissue interactions for the total mandibular subapical alveolar osteotomy were as follows: The lower lip advanced 60% to the incisor movement; soft tissue B' point responded with a 130% advancement in relation to the change in its hard tissue counterpart. Soft tissue pogonion advanced 90% in relation to the hard tissue landmark. The data suggest that the total mandibular alveolar osteotomy is the treatment of choice for the correction of severe dentoalveolar retrusive Class II malocclusion for which alteration of the mentolabial sulcus is desirable.     

A retrospective study of Class II mixed-dentition treatment

Objective:To consider the effectiveness of early treatment using one mixed-dentition approach to the correction of moderate and severe Class II malocclusions.Materials and Methods:Three groups of Class II subjects were included in this retrospective study: an early treatment (EarlyTx) group that first presented at age 7 to 9.5 years (n = 54), a late treatment (LateTx) group whose first orthodontic visit occurred between ages 12 and 15 (n = 58), and an untreated Class II (UnTx) group to assess the pretreatment comparability of the two treated groups (n = 51). Thirteen conventional cephalometric measurements were reported for each group and Class II molar severity was measured on the study casts of the EarlyTx and LateTx groups.Results:Successful Class II correction was observed in approximately three quarters of both the EarlyTx group and the LateTx group at the end of treatment. EarlyTx patients had fewer permanent teeth extracted than did the LateTx patients (5.6% vs 37.9%, P < .001) and spent less time in full-bonded appliance therapy in the permanent dentition than did LateTx patients (1.7 ± 0.8 vs 2.6 ± 0.7years, P < .001). When supervision time is included, the EarlyTx group had longer total treatment time and averaged more visits than did the LateTx group (53.1 ± 18. 8 vs 33.7 ± 8.3, P < .0001). Fifty-five percent of the LateTx extraction cases involved removal of the maxillary first premolars only and were finished in a Class II molar relationship.Conclusion:EarlyTx comprehensive mixed-dentition treatment was an effective modality for early correction of Class II malocclusions.     

Comparison of early treatment outcomes rendered in three different types of malocclusions

Objective:To evaluate the outcome of early treatment in Class I, II, and III malocclusions based on the reduction of weighted Peer Assessment Rating (PAR) scores.Materials and Methods:Two hundred thirty subjects (female = 105; male = 125) selected from 400 cases were divided into three groups based on their malocclusions (Class I, II, and III). The PAR index was evaluated prior to early treatment (T0), at the end of phase I (T1), and after completion of phase II therapy (T2). The reliability of overall PAR scores was assessed by Bland-Altman plot and intraclass correlation coefficient. The starting age, total weighted PAR scores and their changes after phase I and II treatments, treatment time, and the percentage of correction in the three different malocclusions were assessed by repeated-measures analysis of variance with post hoc analysis. The level of significance was set at P < .05.Results:More than 30% reduction of the weighted PAR scores and less than 10 points of the remaining weighted PAR scores were observed in all malocclusion groups at T1. The Class III group had the highest percentage of correction during phase I treatment.Conclusions:Early treatment effectively reduced the complexity of Class I, II, and III malocclusions and accounted for 57%, 64%, and 76% of the total correction, respectively, after phase I treatment, as indicated by an overall reduction in weighted PAR scores. The Class III group responded most favorably to early treatment followed by the Class II group.     

Long-term soft tissue changes after orthodontic and surgical corrections of skeletal class III malocclusions

OBJECTIVE: To evaluate long-term soft tissue changes after orthodontic and surgical corrections of skeletal Class III malocclusions. MATERIALS AND METHODS: Postoperative cephalometric radiographs at 1 year and at 5 years or more after treatment were digitized for 92 patients who had surgical correction of their Class III problem by LeFort I maxillary advancement (n = 48), mandibular setback (n = 12), or a combination of the two procedures (n = 32) and for 25 patients who received orthodontic treatment only. RESULTS: For all groups, the mean changes were quite small. For most measurements, fewer than 20% of patients experienced long-term changes from 2 mm to 4 mm, and fewer than 10% experienced long-term changes greater than 4 mm. CONCLUSIONS: A smaller percentage of surgically treated Class III patients showed long-term soft tissue changes than did surgically treated Class II patients, but compared with both Class II patients and untreated adults they experienced greater long-term forward projection of the soft tissue chin.     

Treatment outcomes of growing Class II Division 1 patients with varying degrees of anteroposterior and vertical dysplasias, Part 1. Cephalometrics.

The purpose of this retrospective study was to evaluate the differences in orthodontic treatment outcomes for 5 groups of growing Class II Division 1 patients with various anteroposterior and vertical skeletal dysplasias. Pretreatment and posttreatment cephalograms of 100 patients were evaluated for soft and hard tissue treatment effects and differences between groups. Changes from pretreatment to posttreatment differed between groups in correction of overjet and change in ANB angle (P <.05). Those with the largest skeletal dysplasias had the greatest skeletal correction but also retained the largest ANB angles posttreatment. Additional correction was achieved through dentoalveolar change with the greatest uprighting of maxillary incisors occurring in patients who initially were the most severely affected (P <.05); this effect was accompanied by an increase in nasolabial angle. All groups had similar changes in mandibular incisor positions, and final positions of the mandibular incisors did not differ between groups. Compared with norms, Z angles and facial contour angles showed discrimination between the most and least severely affected patients based on combined anteroposterior and vertical dysplasias (P <.05). However, there were no clear-cut divisions between the groups, especially with regard to soft tissue cephalometric outcomes. Further evaluation of profile esthetics follows in Part 2. We conclude that conventional orthodontic therapy successfully corrects Class II Division 1 malocclusions in growing patients through a combination of skeletal and dentoalveolar changes, with the greatest changes occurring in patients who initially have the most severe skeletal dysplasias.     

Long-Term Dentoskeletal Effects and Facial Profile Changes Induced by Bionator Therapy

Objective:To evaluate the long-term skeletal and soft tissue changes induced by the bionator in Class II subjects.Materials and Methods:The treatment sample consisted of 20 Class II patients (6 males and 14 females) treated consecutively with the bionator. The sample was evaluated at T1, start of treatment; T2, end of bionator therapy; and T3, long-term observation (including fixed appliances). Mean age at the start of treatment was 10 years 2 months (T1); at posttreatment, 12 years 4 months (T2); and at long-term follow-up, 18 years 11 months (CS 6). The control group consisted of 20 subjects (8 males and 12 females) with untreated Class II malocclusions. Lateral cephalograms were analyzed at the three time points for all groups. Student''s t-tests were used for comparisons of starting forms, and of the T1–T2 and T1–T3 changes between groups.Results:The bionator group showed significant, favorable T1–T2 changes both at the skeletal and dentoalveolar levels. The vertical dimension was increased. Significant modifications were assessed for the soft tissues as well. The treated group showed a final improvement in soft tissue pogonion of about 2.5 mm. Significant mandibular changes were noted in the treated group, with a net average 3.3 mm long-term increase in mandibular length compared with untreated Class II controls.Conclusions:This study suggests that bionator treatment of Class II malocclusion maintains favorable results over the long-term with a combination of skeletal, dentoalveolar, and soft tissue changes.     

A sparse principal component analysis of Class III malocclusions

Objectives:To identify the most characteristic variables out of a large number of anatomic landmark variables on three-dimensional computed tomography (CT) images. A modified principal component analysis (PCA) was used to identify which anatomic structures would demonstrate the major variabilities that would most characterize the patient.Materials and Methods:Data were collected from 217 patients with severe skeletal Class III malocclusions who had undergone orthognathic surgery. The input variables were composed of a total of 740 variables consisting of three-dimensional Cartesian coordinates and their Euclidean distances of 104 soft tissue and 81 hard tissue landmarks identified on the CT images. A statistical method, a modified PCA based on the penalized matrix decomposition, was performed to extract the principal components.Results:The first 10 (8 soft tissue, 2 hard tissue) principal components from the 740 input variables explained 63% of the total variance. The most conspicuous principal components indicated that groups of soft tissue variables on the nose, lips, and eyes explained more variability than skeletal variables did. In other words, these soft tissue components were most representative of the differences among the Class III patients.Conclusions:On three-dimensional images, soft tissues had more variability than the skeletal anatomic structures. In the assessment of three-dimensional facial variability, a limited number of anatomic landmarks being used today did not seem sufficient. Nevertheless, this modified PCA may be used to analyze orthodontic three-dimensional images in the future, but it may not fully express the variability of the patients.     

Surgical prediction of skeletal and soft tissue changes in treatment of Class II

IntroductionThe purpose of this study was to study the treatment outcomes and the accuracy of digital prediction and the actual postoperative outcome with Dolphin program on subjects presenting Class II malocclusions.MethodsForty patients underwent surgical mandibular advancement (Group 1) and 40 underwent combined surgery of mandibular advancement and maxillary impaction (Group 2). The available pre surgical (t₁) and a minimum of 12 months post surgical (t₂) cephalometric radiographs were digitized. Predictive cephalograms (t₃) for both groups were traced.ResultsAt all times evaluated, Group 1 displayed a shorter mandibular length and Group 2 had a longer lower face. In both groups the surgical interventions (t₂) were greater than initially predicted. There was no significant difference between groups with regards to overjet, overbite and soft tissue measurements.ConclusionsIn both groups surgeries were more extensive than planned. Facial convexity and the distance of the lips to cranial base presented similar values between t₂ (post surgical) and t₃ (predicted).     

Treatment effects of the mandibular anterior repositioning appliance in patients with Class II skeletal malocclusions

Objective:To examine the changes produced by the mandibular anterior repositioning appliance (MARA) appliance and compare the treatment effects to an untreated Class II control group.Materials and Methods:Thirty consecutively treated patients were matched with an untreated control group. Lateral cephalograms were taken at T1, 5 months pre-MARA (CVMS 2.7); T2, immediately after MARA removal and prior to placement of full fixed edgewise appliances (CVMS 4.2); and T3, at least 2 years after MARA removal and completion of edgewise treatment (CVMS 5.4). The mean age of the MARA patients was 11.9 years for boys and 10.8 years for girls. Repeated-measures analysis of variance (ANOVA) was used to assess if the samples were morphologically comparable at the outset and to test if there were significant differences between the groups for the various increments of change. Given a significant ANOVA, the source of the difference was explored via Tukey-Kramer tests.Results:Restriction of maxillary growth and no significant mandibular growth were observed with the MARA appliance. The Class II correction was obtained mainly by slight maxillary molar distalization and intrusion, in addition to mesial migration of the lower molars and flaring of the lower incisors. No vertical effect was observed with this appliance.Conclusion:The MARA appliance was effective in the treatment of Class II malocclusions. Restriction of maxillary growth and dentoalveolar changes in the maxillary and mandibular arches were responsible for the correction of the Class II malocclusion. Significant mandibular growth did not contribute to this correction.     

Correction of class II malocclusion by combined sagittal ramus and subapical body osteotomy.

The complete mandibular subapical osteotomy has been presented as a method for correction of Class II malocclusions. At this point, it holds some promise as a solution to the skeletal relapse seen in the surgical correction of Class II malocclusions with use of other techniques. The procedure is a straight-forward combination of the sagittal osteotomy as described by Obwegeser and the subapical osteotomy as described by K?le. Further investigation into the versatility of this procedure is recommended.     

Quantifying faces three-dimensionally in orthodontic practice

PurposeThe purpose of this study was to formulate and demonstrate a method for quantifying and visualizing the three-dimensional (3-D) configuration of the soft tissues of the face at rest to facilitate a quantitative and instantaneous understanding of a patient's static facial form characteristics.Materials and methods3-D facial images of 200 Japanese adult volunteers at rest were recorded using a 3-D photogrammetric system. For each participant, a wire mesh fitting was conducted based on the assignment of landmarks to each 3-D facial image. This method generated 6,017 points on the wire mesh (i.e., the nodes of the fitted mesh). For each point, the mean and standard deviation were calculated and used for patient evaluation. The system performance was exemplified with three orthodontic patients with skeletal Class II and III malocclusions and laterotrusion.ResultsThree patients with severe skeletal Class II and III deformities and laterotrusion were evaluated with the proposed method.ConclusionA clinical method for practitioners to quantify and visualize the soft tissues of a patient's face in 3 dimensions has been presented with clinical applications and considerations. This method allows practitioners to evaluate how patients' facial characteristics differ from normative faces.     

Incisor inclination changes produced by two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions

Objective:To compare the changes in incisor inclination between two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions.Materials and Methods:Among Class II malocclusion patients a total of 38 consecutive patients treated with the Xbow appliance and later with full brackets (XB) were compared to 36 consecutive patients treated with Forsus connected to the archwire while on full brackets (FO). Evaluated cephalometric variables were overjet, overbite, skeletal Class II, lower incisor inclination, and upper incisor inclination. Factors that were analyzed were gender, treatment type, age at start of treatment (T1), and treatment length. Independent t-tests, χ², multiple analysis of variance, and Pearson correlations were applied.Results:No differences in incisor inclination between both treatment protocols were identified. At T1 no statistical difference for any cephalometric variable was demonstrated with regard to gender and treatment type. Gender was also not associated with a different treatment time or age at T1. The mean treatment time was 24.2 months for XB and 30.2 months for the FO group (P  =  .037). XB patients averaged 10 fewer months of fixed edgewise appliances compared to FO patients. Neither gender nor treatment type had any influence on the changes of the evaluated dependent variables between T1 and the end of treatment. Lower incisors proclined more the longer the treatment (P  =  .005). Both overjet and upper incisor inclination were affected by age at T1 (P  =  .001 and P  =  .014, respectively).Conclusions:Both compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions appear to generate the same amount of incisor inclination. Large variability was identified.     

A preliminary report of a new design of cast metal fixed twin-block appliance

Abstract

The present paper describes a cast metal fixed twin-block appliance utilized to correct a Class II malocclusion, which is designed for full-time wear. The object of the present paper is to achieve rapid functional correction of Class II malocclusions by transmitting favourable occlusal forces to inclined planes which are cemented to the posterior teeth. In the meantime, pre-adjusted fixed edgewise appliances can be placed on the anterior teeth to correct their malpositions. This new functional appliance design may shorten the total treatment duration and reduce the need for patient compliance.     

Cranial base characteristics in anteroposterior malocclusions: A meta-analysis

Objective:To investigate cranial base characteristics in malocclusions with sagittal discrepancies.Materials and Methods:An electronic search was performed in PubMed, Embase, Web of Science, and the Cochrane Library. A fixed- or random-effect model was applied to calculate weighted mean difference with 95% confidence intervals (CIs) according to statistical heterogeneity. Outcome measures were anterior, posterior, and total cranial base length and cranial base angle. Sensitivity analysis and publication bias were conducted.Results:Twenty studies that together included 1121 Class I, 1051 Class II, and 730 Class III cases qualified for the final analysis. Class III malocclusion demonstrated significantly reduced anterior (95% CI: −1.74, −0.53; P < .001 vs Class I; 95% CI: −3.30, −2.09; P < .001 vs Class II) and total cranial base length (95% CI: −3.33, −1.36; P < .001 vs Class I; 95% CI: −7.38, −4.05; P < .001 vs Class II). Further, Class II patients showed significantly greater anterior and total cranial base length than did Class I patients (95% CI: 0.51, 1.87; P < .001 for SN; 95% CI: 2.20, 3.30; P < .001 for NBa). Cranial base angle was significantly smaller in Class III than in Class I (95% CI: −3.14, −0.93; P < .001 for NSBa; 95% CI: −2.73, −0.68; P  =  .001 for NSAr) and Class II malocclusions (95% CI: −5.73, −1.06; P  =  .004 for NSBa; 95% CI: −6.11, −1.92; P < .001 for NSAr) and greater in Class II than in Class I malocclusions (95% CI: 1.38, 2.38; P < .001 for NSBa).Conclusions:This meta-analysis showed that anterior and total cranial base length and cranial base angle were significantly smaller in Class III malocclusion than in Class I and Class II malocclusions, and that they were greater in Class II subjects compared to controls.     

Twin-block矫治Ⅱ类错He 12例分析

目的：定量评价双He垫矫治器(Twin-block)对生长期安氏Ⅱ类Ⅰ分类错He患者的颌骨及牙槽骨的影响。方法：12例10～12岁安氏Ⅱ类错He患者，用Twin-block进行矫治，治疗结果与11例未经治疗的10～12岁安氏Ⅱ类错He患者比较。观察时间为12个月。采用团体t检验进行组间比较。结果：Twin-block治疗组，覆盖和磨牙关系均得到改善，覆盖的减小主要是由于上切牙的远中移动，及下颌骨的向前生长；磨牙关系的矫正，下颌骨的生长与牙槽骨的变化各占50％作用。下颌骨长度(Ar-Gn)比对照组增加2．29mm，后面高(Ar-Go)与前下面高(ANS-Me)均有增加，分别为2．28mm与2．58mm，未观察到不利的垂直向生长。结论：Twin-block能有效减小前牙覆盖，矫正磨牙关系，改善软组织侧貌。并增强Ⅱ类错He患者下颌骨的生长。     

Class II correction in orthodontic patients utilizing the Mandibular Anterior Repositioning Appliance (MARA)

Objectives:To evaluate skeletal and dentoalveolar changes produced by the Mandibular Anterior Repostioning Appliance (MARA) in the treatment of Class II malocclusion in adolescent patients.Materials and Methods:Lateral cephalograms of 24 patients, mean age 12.40 years, with a Class II malocclusion consecutively treated with MARA were compared with a historical control group. Changes were evaluated using the Pancherz superimposition and grid analysis pre- and posttreatment. Independent sample t-test, Mann-Whitney U-test, and Pearson correlation coefficient analysis were performed.Results:Significant differences were seen between the treatment and control groups during the 12 month period. Improvement in Class II relationship in the MARA group resulted from skeletal and dentoalveolar changes. There was a 7-mm molar correction and a 4.7-mm overjet reduction. There was also an increase in the mandibular base of 3.3 mm with the lower molar and incisor coming forward 2.6 mm and 2.2 mm, respectively. No significant headgear effect was shown on the maxilla. The maxillary incisor position remained unchanged, whereas the molar distalized 1.8 mm. The anterior lower facial height had an overall increase of 2.2 mm.Conclusions:The MARA was successful in achieving a Class I molar relationship and reducing the overjet in Class II malocclusions. This was the result of both skeletal and dentoalveolar changes.     

Bimaxillary Protrusion in the Caucasian: A Cephalometric Study of the Morphological Features

Abstract

The skeletal morphology of bimaxillary dental protrusion has been investigated in a comparative cephalometric study. Because this is considered a subset of Class I malocclusions, the null hypothesis is that there should be no significant skeletal differences between this group and a Class I control group.

There were 30 Caucasians in each group with no bias for age and sex differences between them. Eighteen radiographic landmarks were identified from which 33 skeletal, dental and soft tissue parameters were computed. The bimaxillary group had an average interincisal angle of 115° versus the controls 135°, and showed the following morphological features which persisted over a 5-year growth period: 1. A shorter posterior cranial base.

2. A longer and more prognathic maxilla.

3. Similar mandibular dimensions and prognathism.

4. A mild Class II skeletal pattern.

5. A smaller upper and posterior face height.

6. Diverging facial planes.

7. A procumbent soft tissue profile with a low lip line.

These findings indicate that there is a distinctive difference between the underlying skeletal patterns found in the two groups.