Cone-beam evaluation of pharyngeal airway space in adult skeletal Class II patients with different condylar positions

Objectives:To test the null hypothesis that there is no significant difference in pharyngeal airway space among adult skeletal Class II patients with different condylar positions using cone-beam computed tomography (CBCT).Materials and Methods:The CBCT records of 60 patients with skeletal Class II malocclusion (ANB angle ≥ 4°, Wits ≥ 0) were selected from the CBCT database. According to the condyle position, the patients were divided in three groups: anterior group (CD ≤ −12%), centric group (−12% ≤ CD ≤ +12%), and posterior group (CD ≥ +12%). Three-dimensional (3D) pharyngeal airway models were reconstructed using InvivoDental software 5.1.3. The volume and area of the pharyngeal airway space were measured in the 3D airway model.Results:The volume and area of the pharyngeal airway space in the centric group were significantly smaller than those in the posterior group (P < .01). The volume and area of the pharyngeal airway space were smallest in the anterior group and significantly increased in the centric and posterior groups (P < .001).Conclusions:The null hypothesis was rejected. Significant differences were noted in pharyngeal airway space among adult skeletal Class II patients with different condylar positions.     

Evaluation of mandibular volume classified by vertical skeletal dimensions with cone-beam computed tomography

Objective:To investigate the relationship between anteroposterior and vertical differences in maxillofacial morphology and mandibular volume.Materials and Methods:Subjects comprised 213 Japanese adults (84 males and 129 females) who were divided into three groups based on mandibular basal arch (ANB) and Wits, measured in a cephalometric analysis: Class I (−1° ≤ ANB < 4°,−1 mm ≤ Wits < 0 mm), Class II (ANB ≥ 4°, Wits ≥ 0), and Class III (ANB <−1°, Wits <−1 mm). Subjects were also divided into three groups based on the mandibular plane angle (Mp), as follows: hypodivergent (Mp < 23°), normodivergent (Mp  =  23–30°), and hyperdivergent (Mp > 30°) groups. Mandibular volume was measured from cone-beam computed tomographic images that were analyzed using Analyze™ image processing software and compared among the three groups in each classification.Results:No significant differences were noted in mandibular volume among Classes I, II, and III. An inverse relationship was found between mandibular volume and Mp, and a significant difference was noted in mandibular volume between the hypodivergent and hyperdivergent groups.Conclusions:In addition to two-dimensional analysis, such as lateral cephalometry, three-dimensional information such as volume, provided by cone-beam computed tomography, contributes to a more detailed assessment of maxillofacial morphology.     

Three-dimensional analysis of molar compensation in patients with facial asymmetry and mandibular prognathism

Objective:To evaluate the characteristic transverse dental compensations in patients with facial asymmetry and mandibular prognathism and to compare features of dental compensations between two types of mandibular asymmetry using 3-dimensional (3D) cone-beam computed tomography (CBCT).Materials and Methods:Seventy-eight adult patients with skeletal Class I (control group; n  =  33; 19 men and 14 women) or skeletal Class III with facial asymmetry (experimental group; n  =  45; 23 men and 22 women) were included. The experimental group was subdivided into two groups according to the type of mandibular asymmetry: translation type (T-type; n  =  20) and roll type (R-type; n  =  19). CBCT images were acquired before orthodontic treatment and 3D analyses were performed.Results:The transverse dental distance was significantly different between the two groups only at the palatal root apex of the maxillary first molar (P < .05). In the experimental group, the first molar axes were compensated significantly on both arches except the maxillary nondeviated side. The vertical molar heights were different between the two groups only on the maxillary arch (P < .001). The R-type showed greater mandibular ramal length difference and menton deviation than the T-type (P < .001). In the R-type, transverse compensation of the maxillary first molars was more obvious than with the T-type, which resulted in canting in the maxillary occlusal plane.Conclusions:Mandibular asymmetry with prognathism showed a characteristic transverse dental compensation pattern. The mandibular asymmetry type influenced the amount and direction of molar compensation on the maxillary arch.     

2种不同正颌术式对骨性Ⅲ类错畸形患者上气道形态的影响

目的： 建立骨性Ⅲ类错畸形患者正颌手术前、后上气道三维模型，比较不同正颌术式对骨性Ⅲ类错畸形患者上气道各截面积及容积的影响。方法： 28例骨性Ⅲ类错畸形患者经正颌-正畸联合会诊，制定手术方案，分为2组，实验A组（12例）为单纯双侧下颌支矢状劈开术（BSSRO）后退，即单颌手术组，实验B组（16例）为下颌骨BSSRO 后退 +上颌骨Le Fort I型截骨术前移，即双颌手术组。所有患者于正颌手术前（T1）和术后3个月（T2）分别行CT扫描，基于CT图像，应用Dolphin Imaging 11.7软件建立包含腭咽、舌咽和喉咽腔在内的上气道三维模型，测量、比较2组患者在正颌手术前、后的上气道各截面、腔隙的矢状径、冠状径、横截面积和容积改变的差异。采用SPSS 16.0 软件包进行统计学分析。结果： 在腭咽段，实验A组手术后各项数值均较术前减小；实验B组手术后除冠状径外，其余数值均较术前增大，且2组变化有显著差异（P<0.05）。在舌咽段及喉咽段，2组手术后数值均减小。在横截面积和容积方面，实验A组较实验B组减小更加明显，2组的减小量有显著差异（P<0.05）。结论： 与单颌手术相比，双颌手术对骨性Ⅲ类错畸形患者上气道形态的减小改变影响较小。     

Asymmetric dental arch treatment with Forsus fatigue appliances: Long-term results

Objectives:To investigate the treatment efficacy and follow-up stability of the asymmetric Forsus appliance by evaluating longitudinal changes in dental arch asymmetry on digital dental models from 21 patients.Materials and Methods:Maxillary and mandibular reference lines were used for measurements of intra-arch asymmetry at pretreatment (T1), posttreatment (T2), and 4.2 years after treatment (T3). Maxillary and mandibular measurements were performed relative to the dental midline and anterior reference line on digital dental models. To determine the amount of asymmetry between the Class I and Class II sides of a given arch, all maxillary and mandibular parameters were measured on each side of the model separately. Repeated-measures analysis of variance/paired sample t-tests were performed to evaluate dental arch asymmetries at the P < .05 level.Results:The alveolar transverse dimensions of the posterior segment of both arches were increased during treatment (P < .05) and remained stable during the retention period. Class II subdivision malocclusion was caused by distal positioning of the mandibular canine, premolars, and first molar on the Class II side (P < .05). Asymmetry was resolved by treatment with asymmetric Forsus appliances. The resolved asymmetry remained stable over the long term. There were no significant differences between T2 and T3 (P > .05).Conclusions:The asymmetric Forsus appliance can be used to treat dental arch asymmetry in patients with Class II subdivision malocclusions.     

Sagittal mandibular development effects on the dimensions of the awake pharyngeal airway passage

Objective:To test the hypothesis that sagittal mandibular development has no effects on the dimensions of the awake pharyngeal airway passage.Materials and Methods:Ninety-one subjects (age 15–25 years) with a normal vertical growth pattern of the mandible, normally positioned maxilla, and various sagittal mandibular developments were divided into three groups based on the sagittal mandibular development. Group I included 37 subjects who had a normally positioned mandible (76° ≤ angle between ‘S,’ ‘N,’ and ‘B’; it represents the antero-posterior position of the maxilla in relation to the anterior cranial base [SNB] ≤ 82°), Group II included 31 subjects in whom the mandible was retrognathic (SNB < 76°), and Group III included 23 subjects in whom the mandible was prognathic (SNB > 82°) in relation to the anterior cranial base. Lateral cephalograms were traced manually to evaluate the pharyngeal airway passage.Results:The length of the soft palate was significantly smaller in mandibular prognathism subjects than in subjects with mandibular retrognathism (P < .01). The thickness of the soft palate was significantly greater among subjects with mandibular prognathism than in subjects with normal (P < .01) and retrognathic (P < .001) mandibular development. The sagittal mandibular development had no effect on the dimensions of the nasopharyngeal and hypopharyngeal airway passage. The depth of the oropharynx was comparable among the subjects with normal and retrognathic mandibles but was greater (P < .001) among subjects with mandibular prognathism.Conclusions:The hypothesis is rejected. Sagittal mandibular development had significant effects on the dimensions of the awake pharyngeal airway passage.     

Upper airway changes after Xbow appliance therapy evaluated with cone beam computed tomography

Objective:To determine the treatment effects of the Xbow appliance on the upper airway dimensions and volume using cone-beam computed tomography (CBCT); to evaluate the cephalometric changes in the skeletal and dental structures of the skeletal Class II patients.Materials and Methods:The sample consisted of 25 Class II patients (11 male, 14 female) with a mean age of 11.1 ± 1.1 years. CBCT images were obtained at the beginning of the treatment (T0) and after the debonding of the Xbow (T1).Results:Changes in superior, middle, and inferior parts of the oropharynx in the retroglossal region and changes in the oropharyngeal airway volume were statistically significant (P < .05, P < .01). The differences favoring the Xbow for the changes in the direction of Class II correction included SNA, SNB, ANB, maxillary depth angles, and point A-NPg and Co-B distances. Data of the dental parameters showed palatal tipping and extrusion of the maxillary incisors, labial tipping of the mandibular incisors, and mesial movement and extrusion of the mandibular molars.Conclusions:Treatment with the Xbow appliance in Class II patients resulted in favorable increase in the oropharyngeal airway dimensions and volume. Further studies with larger study samples and with control groups are needed.     

Three-dimensional evaluation of changes in upper airway volume in growing skeletal Class II patients following mandibular advancement treatment with functional orthopedic appliances

Objectives:The aim of this study was to assess three-dimensionally the upper airway changes following functional appliance treatment in growing Class II patients.Materials and Methods:Pre-and post-treatment Cone beam computed tomography scans of 20 patients (age range: 9 to 12; mean: 11.4 ± 1.0 years) were retrieved from the list of patients previously treated with functional appliances in the Postgraduate Clinic at the Section of Orthodontics, Aarhus University, Denmark. Total and partial volumes of the upper airway (ie, lower nasopharynx, velopharynx, and oropharynx) were calculated. To rule out the effect of growth, the changes in the functional appliance group were compared to an age-matched Class I group of 18 patients (age range: 8 to 14; mean: 11.8 ± 1.4 years).Results:In the functional appliance group, all the partial and total volumes were significantly larger at the end of treatment when compared to the start of treatment (P < .003). On the other hand, when comparing the changes for the total and partial volumes of the upper airway in the functional appliance group with the Class I group, a statistical difference was seen only for the oropharynx (P = .022) and total volume (P = .025), with the functional appliance group showing a larger volume increment.Conclusions:An increase in the upper airway volume was found after treatment with functional appliances. This difference was mainly related to the changes at the oropharynx level, which differed significantly from what was observed in the Class I group.     

Comparison of condylar size among different anteroposterior and vertical skeletal patterns using cone-beam computed tomography

Objectives:To compare condylar size among different anteroposterior and vertical skeletal patterns using cone-beam computed tomography (CBCT).Materials and Methods:The study included 166 subjects (61 men, mean age: 27.2 ± 7.6 years; 105 women, mean age: 27.4 ± 9.2 years). The anteroposterior skeletal patterns of the subjects were classified into Classes I (−1° ≤ A point–nasion–B point angle [ANB] < 4°), II (ANB ≥ 4°), and III (ANB < −1°). The vertical skeletal patterns were classified into hypodivergent (mandibular plane [MP] ≤ 23°), normodivergent (23° < MP < 30°), and hyperdivergent (MP ≥ 30°) groups. The condylar length, height, and width were examined using CBCT images. Analysis of covariance was used to compare three condylar size measurements among the three anteroposterior groups and the three vertical groups using sex as a covariate. Both left and right sides were examined. Nine groups were further divided according to the anteroposterior and vertical groups, and two-way analysis of covariance (ANCOVA) was applied to estimate the composite effect of skeletal patterns in both directions.Results:Sex as a covariate showed statistical significance in most examinations. The condylar height on both sides had statistically different anteroposterior skeletal patterns (P < .001). The condylar width on both sides also had statistically different vertical skeletal patterns (P < .001). After adjusting for sex, the condylar height and width on both sides increased from Class II, Class I, and Class III. The condylar width on both sides increased from the hypodivergent group, the normodivergent group, and the hyperdivergent group. No composite effect of skeletal patterns in both directions was observed.Conclusions:Condylar height and width considerably differed among subjects with different anteroposterior or vertical skeletal patterns. The anteroposterior or vertical skeletal patterns independently affected the condylar size.     

Dental and skeletal effects after total arch distalization using modified C-palatal plate on hypo- and hyperdivergent Class II malocclusions in adolescents

ObjectivesTo compare the dental and skeletal treatment effects after total arch distalization using modified C-palatal plates (MCPPs) on adolescent patients with hypo- and hyperdivergent Class II malocclusion.Materials and MethodsThe study group included 40 patients with Class II malocclusion (18 boys and 22 girls, mean age = 12.2 ± 1.4 years) treated with MCPPs. Fixed orthodontic treatment started with the distalizing process in both groups. Participants were divided into hypo- or hyperdivergent groups based on their pretreatment Frankfort mandibular plane angle (FMA) ≤22° or ≥28°, respectively. Pre- and posttreatment lateral cephalograms were digitized, and 23 variables were measured and compared for both groups using paired and independent t-tests.ResultsThe hyper- and hypodivergent groups showed 2.7 mm and 4.3 mm of first molar crown distalizing movement, respectively (P < .001). The hypodivergent group had a slight 2.2° crown distal tipping of first molars compared with 0.3° in the hyperdivergent group. After distalization, the FMA increased 3.1° and 0.3°, in the hypodivergent and hyperdivergent groups, respectively (P < .001). SNA decreased in the hypodivergent group, while other skeletal variables presented no statistically significant differences in the changes between the groups.ConclusionsThe hypodivergent group showed more distal and tipping movement of the maxillary first molar and increased FMA than the hyperdivergent group. Therefore, clinicians must consider vertical facial types when distalizing molars using MCPPs in Class II nonextraction treatment.     

Evaluation of the effects of skeletal anchoraged Forsus FRD using miniplates inserted on mandibular symphysis: A new approach for the treatment of Class II malocclusion

Objective:To evaluate the skeletal, dentoalveolar, and soft tissue effects of the Forsus Fatigue Resistant Device (FRD) appliance with miniplate anchorage for the treatment of skeletal Class II malocclusion.Material and Methods:The prospective clinical study group included 17 patients (11 girls and 6 boys; mean age 12.96 ± 1.23 years) with Class II malocclusion due to mandibular retrusion and treated with skeletal anchoraged Forsus FRD. After 0.019 × 0.025-inch stainless steel archwire was inserted and cinched back in the maxillary arch, two miniplates were placed bilaterally on the mandibular symphysis. Then, the Forsus FRD EZ2 appliance was adjusted to the miniplates without leveling the mandibular arch. The changes in the leveling and skeletal anchoraged Forsus FRD phases were evaluated by means of the Paired and Student''s t-tests using the cephalometric lateral films.Results:The success rate of the miniplates was found to be 91.5% (38 of 42 miniplates). The mandible significantly moved forward (P < .001) and caused a significant restraint in the sagittal position of the maxilla (P < .001). The overjet correction (−5.11 mm) was found to be mainly by skeletal changes (A-VRL, −1.16 mm and Pog-VRL, 2.62 mm; approximately 74%); the remaining changes were due to the dentoalveolar contributions. The maxillary and mandibular incisors were significantly retruded (P < .001).Conclusion:This new approach was an effective method for treating skeletal Class II malocclusion due to the mandibular retrusion via a combination of skeletal and dentoalveolar changes.     

Effect of large incisor retraction on upper airway morphology in adult bimaxillary protrusion patients: Three-dimensional multislice computed tomography registration evaluation

Objective:To evaluate, using multislice computed tomography (MSCT), the morphologic changes in the upper airway after large incisor retraction in adult bimaxillary protrusion patients.Materials and Methods:Thirty adult patients with bimaxillary protrusion had four first premolars extracted, and then miniscrews were placed to provide anchorage. A CT scan was performed before incisor retraction and again posttreatment. Three-dimensional (3D) reconstruction of the pre- (T1) and post- (T2) CT data was used to assess for morphological changes of the upper airway. A paired t-test was used to compare changes from T1 to T2. The relationship among the three variables (upper incisor retraction amount, upper airway size, and hyoid position) was analyzed by Pearson correlation coefficient.Results:The amounts of upper incisor retraction at the incisal edge and apex were 7.64 ± 1.68 mm and 3.91 ± 2.10 mm, respectively. The hyoid was retracted 2.96 ± 0.54 mm and 9.87 ± 2.92 mm, respectively, in the horizontal and vertical directions. No significant difference was observed in the mean cross-sectional area of the nasopharynx (P > .05) between T1 and T2, while significant differences between T1 and T2 were found in the mean cross-sectional areas of the palatopharynx, glossopharynx, and hypopharynx (P < .05); these mean cross-sectional areas were decreased by 21.02% ± 7.89%, 25.18% ± 13.51%, and 38.19% ± 5.51%, respectively. The largest change in the cross-sectional area is always noted in the hypopharynx. There was a significant correlation among the retraction distance of the upper incisor at its edge, the retraction distance of the hyoid in the horizontal direction, and the decrease of the hypopharynx.Conclusion:Large incisor retraction leads to narrowing of the upper airway in adult bimaxillary protrusion patients.     

Pharyngeal airway space,hyoid bone position and head posture after orthognathic surgery in Class III patients

Objective:To determine the effect of orthognathic surgery on pharyngeal airway in Class III patients and to (1) compare the results of different surgical techniques, (2) determine the change at the position of the hyoid bone, and (3) evaluate the craniocervical posture changes related to pharyngeal airway change.Materials and Methods:Forty-eight Class III adult patients were included in the study to assess airway space after orthognathic surgery. Nine patients were treated with maxillary advancement, seven patients were treated with mandibular set back, and 32 patients were treated with bimaxillary surgery. Cephalometric records were taken before treatment, after surgery, and about 1 year after surgery (at the end of the treatment).Results:No differences were determined at the position of hyoid bone and craniocervical posture. Nasopharyngeal area was significantly increased in all groups (P < .05). Oropharyngeal area and SPSS and IPS parameters were significantly decreased after mandibular set back operation (P < .05). In bimaxillary and maxillary advancement groups, PPS parameter was significantly increased (P < .01), and IPS parameter was significantly decreased (P < .05). No differences were detected at oropharyngeal and hypopharyngeal areas in bimaxillary and maxillary advancement groups.Conclusion:Different surgical procedures have different effects on pharyngeal airway space.     

Three-dimensional evaluation of soft tissue change gradients after mandibular setback surgery in skeletal Class III malocclusion

Objective:To evaluate whether mandibular setback surgery (MSS) for Class III patients would produce gradients of three-dimensional (3D) soft tissue changes in the vertical and transverse aspects.Materials and Methods:The samples consisted of 26 Class III patients treated with MSS using bilateral sagittal split ramus osteotomy. Lateral cephalograms and 3D facial scan images were taken before and 6 months after MSS, and changes in landmarks and variables were measured using a Rapidform 2006. Paired and independent t-tests were performed for statistical analysis.Results:Landmarks in the upper lip and mouth corner (cheilion, Ch) moved backward and downward (respectively, cupid bow point, 1.0 mm and 0.3 mm, P < .001 and P < .01; alar curvature-Ch midpoint, 0.6 mm and 0.3 mm, both P < .001; Ch, 3.4 mm and 0.8 mm, both P < .001). However, landmarks in stomion (Stm), lower lip, and chin moved backward (Stm, 1.6 mm; labrale inferius [Li], 6.9 mm; LLBP, 6.9 mm; B′, 6.7 mm; Pog′, 6.7 mm; Me′, 6.6 mm; P < .001, respectively). Width and height of upper and lower lip were not altered significantly except for a decrease of lower vermilion height (Stm-Li, 1.7 mm, P < .001). Chin height (B′-Me′) was decreased because of backward and upward movement of Me′ (3.1 mm, P < .001). Although upper lip projection angle and Stm-transverse projection angle became acute (Ch_Rt-Ls-Ch_Lt, 5.7°; Ch_Rt-Stm-Ch_Lt, 6.4°, both P < .001) because of the greater backward movement of Ch than Stm, lower lip projection angle and Stm-vertical projection angle became obtuse (Ch_Rt-Li-Ch_Lt, 10.8°; Ls-Stm-Li, 23.5°, both P < .001) because of the larger backward movement of Li than labrale superius (Ls).Conclusions:Three-dimensional soft tissue changes in Class III patients after MSS exhibited increased gradients from upper lip and lower lip to chin as well as from Stm to Ch.     

Three-dimensional positional assessment of glenoid fossae and mandibular condyles in patients with Class II subdivision malocclusion

Objectives:To test the null hypotheses that the positions of the glenoid fossae and mandibular condyles are identical on the Class I and Class II sides of patients with Class II subdivision malocclusion.Materials and Methods:Retrospective three-dimensional (3D) assessments of the positions of the glenoid fossae and mandibular condyles were made in patients with Class II malocclusion. Relative to a fiducial reference at the anterior cranial base, distances from the glenoid fossae and condyles were calculated in pretreatment cone beam computed tomographic scans of 82 patients: 41 with Class II and 41 with Class II subdivision malocclusions. The 3D distances from glenoid fossae to sella turcica in the X (right-left), Y (anterior-posterior), Z (inferior-superior) projections were calculated.Results:Patients with Class II malocclusion displayed a symmetric position of the glenoid fossae and condyles with no statistically significant differences between sides (P > .05), whereas patients with Class II subdivision showed asymmetry in the distance between the glenoid fossae and anterior cranial base or sella turcica (P < .05), with distally and laterally positioned glenoid fossae on the Class II side. (P < .05). Male patients had greater distances between glenoid fossae and anterior cranial fossae (P < .05). The condylar position relative to the glenoid fossae did not differ between the two malocclusion groups nor between males and females (P > .05).Conclusions:The null hypotheses were rejected. Patients with Class II subdivision malocclusion displayed asymmetrically positioned right- and left-side glenoid fossae, with a distally and laterally positioned Class II side, although the condyles were symmetrically positioned within the glenoid fossae.     

Assessment of asymmetry in a normal occlusion sample and asymmetric patients with three-dimensional cone beam computed tomography: A study for a transverse reference plane

Objective:To characterize symmetrical features of patients with facial asymmetry and thus to find the most reliable horizontal reference lines easily used in three-dimensional images. The hypothesis was that there is a difference in the location of bilateral landmarks of the upper skull between the normal occlusion sample and skeletal Class III patients with asymmetry.Materials and Methods:Group 1 (normal occlusion sample) was composed of 20 Korean adults with normal occlusion and no noticeable asymmetry. Groups 2 through 4 were selected from patients who were diagnosed as skeletal Class III malocclusion and grouped according to the extent of asymmetry (group 2: symmetric mandible, no maxillary cant; group 3: asymmetric mandible, no maxillary cant; group 4: asymmetric mandible, more than 4 mm maxillary cant measured at maxillary first molars). Three-dimensional cone beam computed tomography images were taken before treatment, and bilateral landmarks of the skull were located and their vertical and horizontal differences compared.Results:No statistically significant difference was noted in the position of bilateral landmarks between groups, except for AG (P < .05). AG showed significant differences in vertical dimension (P < .001) and in horizontal dimension (P < .0001) between groups. The mean of the difference was clearly greatest at FM.Conclusions:The hypothesis is rejected. All groups had a similar pattern of asymmetry in the upper third of the face. Therefore, the transverse reference line of the bilateral Z or orbitale may be used even in patients with severe asymmetry of the maxilla with reference to the clinical photos.     

高位头帽-口外弓肌激动器治疗Ⅱ类高角儿童患者前、后的上气道变化

目的： 研究生长发育高峰期Ⅱ类高角错畸形患者矫形治疗前、后上气道的变化。方法： 收集并拍摄23例生长发育高峰期患者经高位头帽-口外弓肌激动器矫形治疗前（T1）、矫形治疗后（T2）的锥形束CT（CBCT），将T1和T2的CBCT数据导入Minics17.0软件中进行测量。采用SPSS22.0软件包中的配对t检验对安氏Ⅱ类儿童患者矫形治疗前、后上气道的变化进行分析。结果： 患者经矫形治疗后，上气道总容积、腭咽容积、喉咽容积、舌咽容积，软腭尖平面、会厌尖平面上气道的横截面积和口咽段最小横截面积，软腭尖、会厌尖平面的矢状径、横径的变化均具有统计学意义（P<0.05）；上气道形态在软腭尖平面趋于圆形（P<0.05），而在会厌顶平面无显著变化（P>0.05）。结论： 高位头帽-口外弓肌激动器矫形治疗使下颌骨发育不足的高角儿童患者上气道容积增大，通气量增加，呼吸功能改善。     

Age-Related Long-Term Posttreatment Occlusal and Arch Changes

Objective:To evaluate differences in long-term postretention changes between adolescents and adults.Materials and Methods:The sample included 96 subjects, 51 adolescents and 45 adults (14.2 ± 0.8 and 21.5 ± 6.8 years of age, respectively, at the end of treatment) retained for 3 years and followed approximately 16 years post treatment, who were randomly selected from two private practices. Prior to treatment, 38 and 58 had Class I and Class II malocclusions, respectively.Results:With the exception of adult midlines, all of the occlusal variables (overjet [0.50–0.77 mm], overbite [0.85–0.95 mm], the maxillary incisor irregularity [0.69–0.80 mm], the mandibular incisor irregularity [0.85–1.50 mm] and the PAR score [0.86–1.92 points]) showed significant increases over time. Adolescents consistently showed greater increases of the occlusal variables than adults, with mandibular incisor irregularity and the PAR index attaining statistically significant (P < .05) levels. Arch length and mandibular intercanine width showed statistically significant decreases over time in both groups; maxillary intercanine and intermolar widths did not change significantly. Overjet increased significantly more in Class II patients than in Class I patients, whereas Class I patients showed significantly greater decreases in mandibular intermolar width than Class II patients.Conclusions:Over the 16-year posttreatment period, adolescents showed significantly greater increases in mandibular incisor irregularity, and the PAR index than adults. Treated Class I patients demonstrated less increase in overjet and greater decreases in mandibular intermolar width than Class II patients.     

Class II subdivision treatment with the Forsus Fatigue Resistant Device vs intermaxillary elastics

Objective:To compare the effectiveness of comprehensive fixed appliance treatments implemented in combination with Forsus or intermaxillary elastics in Class II subdivision subjects.Materials and Methods:Twenty-eight Class II subdivision patients were allocated to two groups using matched randomization: Forsus group (mean age, 14.19 ± 1.02 years) and elastics group (mean age, 13.75 ± 1.16 years). Patients received fixed appliance therapy in combination with either Forsus or intermaxillary elastics. The study was conducted on lateral cephalograms and digital models acquired before orthodontic treatment and 10–12 weeks after the fixed appliances were removed.Results:The treatment phase comprising the use of Forsus (4.53 ± 0.91 months) was significantly shorter compared with elastics application (6.85 ± 1.08 months). This was also true for comparing duration of overall comprehensive treatment in both groups. Extrusion and palatal tipping of maxillary incisors and clockwise rotation of the occlusal plane were greater in the elastics group (P < .05). The mandibular incisors were proclined in both groups (P < .001), but no significant difference was observed between groups (P > .05). The mandibular incisors showed intrusion in the Forsus group and extrusion in the elastics group; the difference between groups was significant (P < .05). Overbite was decreased in both groups (P < .001) in similar amounts. Improvement in overjet, mandibular midline deviation, and correction of molar relationship on the Class II side were greater in the Forsus group (P < .05).Conclusion:Forsus is more effective for correcting Class II subdivision malocclusion in a shorter treatment period with minimal patient compliance required.