Comparison of treatment effects during en-masse retraction of upper anterior teeth placed using mini-implants placed at infrazygomatic crest and interradicular sites: A randomized controlled trial.

INTRODUCTION: The objective of this prospective study was to examine the efficacy of posterior interradicular and infrazygomatic crest mini-implants for en-masse anterior retraction. METHODS: The 22 patients were divided into two groups. In group 1 (IZC n = 11), mini-implants were placed in the infrazygomatic crests and in group 2 (IR, n = 11), mini-implants were placed in the molar-premolar interradicular sites. Soft tissue, skeletal, and dental treatment effects between two groups were compared using lateral cephalometric measurements. RESULTS: The average angle between the cranial base and A point was 1.01 degrees (P = .004), and the linear distance between the upper incisor and A point was 2.67 to 5.2 millimetres (P = .00). In IZC group the maxillary incisor to the palatal plane moved upward by a mean of -5.20 mm (P = .059), whereas in IR group the incisor movement changed by -2.67 mm (P = .068). There was no significant difference between groups IZC and IR while comparing overall treatment changes on upper incisor position change, angle, and overjet. CONCLUSIONS: Mini-implants placed in between the molar and premolar as well as the infrazygomatic crest can withstand the deepening of the bite during retraction. Mini-implants in IZC are capable of causing intrusion of the anterior teeth and preventing intrusion of the molars, thereby providing absolute anchoring in all planes. Placement of the mini-implants in the infrazygomatic crest resulted in more linear retraction.

A finite element analysis of stress distribution with various directions of intermaxillary fixation using orthodontic mini-implants and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy.

OBJECTIVE: This finite element analysis (FEA) aimed to assess the stress distribution in the mandible and fixation system with various directions of the intermaxillary fixation (IMF) using mini-implants (MIs) and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy (BSSRO). MATERIALS AND METHODS: A total of nine mandibular advancement models were set according to the position of the MIs (1.6 mm in diameter, 8 mm in length) and direction of the IMF elastics (1/4 inch, 5 oz). Major and minor principal stresses in the cortical and cancellous bones, von Mises stresses in the fixation system (miniplate and monocortical screws), and bending angles of the miniplate were analysed. RESULTS: Compressive and tensile stress distributions in the mandible and von Mises stress distributions in the fixation system were greater in models with a Class III IMF elastic direction and a higher IMF elastic force than in models with a Class II IMF elastic direction and a lower IMF elastic force. The bending angle of the miniplate was negligible. CONCLUSIONS: Stress distributions in the bone and fixation system varied depending on the direction, amount of force, and position of IMF elastics and MIs. Conclusively, IMF elastics in the Class II direction with minimal load in the area close to the osteotomy site should be recommended.

Interdisciplinary treatment of mutilated dentition and transverse maxillary deficiency with microimplant-assisted rapid palatal expansion, microimplants, and dental implants.

OBJECTIVE: This case report demonstrates an interdisciplinary approach to treat a 26-year-old male patient with hyperdivergent Class II skeletal pattern, maxillary transverse deficiency, slight anterior open bite, and multiple hopeless teeth with root rests. CLINICAL CONSIDERATIONS: An interdisciplinary treatment was required for oral hygiene improvement, caries treatment, extraction of residual roots and hopeless teeth, maxillary expansion using microimplant-assisted rapid palatal expansion, improvement of skeletal and dental relationship using orthodontic microimplants, and prosthetic restorations with the aid of dental implants. CONCLUSION: Consequently, esthetic and functional occlusal rehabilitation was achieved. CLINICAL SIGNIFICANCE: Hyperdivergent Class II facial and skeletal patterns with multiple missing teeth can be effectively treated using orthodontic skeletal anchorage. In young adults, the transverse discrepancy can be resolved using MARPE, which is also useful for improving the sagittal and vertical relationships. In the case of multiple missing teeth, orthodontic treatment can provide the proper space to facilitate dental implants to achieve optimal esthetics and function.

A CBCT Evaluation of Esthetic Preference Regarding the Perceived Facial Attractiveness of Young Korean Female Adults with a Normal Skeletal Pattern.

The aim of this study was to determine the factors that affect esthetic preference regarding the perceived facial attractiveness of young Korean female adults with a normal skeletal pattern using cone-beam computed tomography (CBCT). After reorienting the CBCT images of 40 young Korean female adults, three-dimensional (3D) measurements were analyzed, and five 3D facial images were digitally constructed. A computer-based questionnaire was used to determine perceived facial attractiveness by scoring from 1 (very unattractive) to 10 (very attractive). Esthetic perception and the most influential facial view and component were examined and compared by orthodontists, general dentists, and laypeople to evaluate facial attractiveness. Compared to the unattractive group, the attractive group had significantly greater values for Pog-NB, L1SI-FH, U lip thickness, L lip-U lip, and Nasolabial angle, along with significantly lower values for U1SI-FH and Cant of U lip; the attractive group also had a more retruded U1MP (p < 0.01), L1MP (p < 0.01), U lip (p < 0.05), and L lip (p < 0.01) relative to N, as well as a more retruded U lip (p < 0.05) and L lip (p <0.001) relative to esthetic lines. Orthodontists and general dentists were more likely to consider the profile view. When evaluating facial attractiveness, orthodontists and laypeople more often focused on the lips and chin. When evaluating facial attractiveness, all evaluators showed a high esthetic preference for retroclination and retrusion of the incisors and lips, but there were some differences in how they perceived facial attractiveness. Therefore, the ultimate perception of facial attractiveness needs to be based on the esthetic perceptions of laypeople.

Biomechanical analysis of the maxillary molar intrusion: A finite element study.

INTRODUCTION: The purpose of this study was to analyze and clarify tooth movement when intruding the maxillary molars using intrusive forces between the maxillary first and second molars. METHODS: A finite element method was used to simulate the long-term orthodontic movement of the maxillary dentition by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. Intrusive forces of 2 N were applied buccally to the archwire between the maxillary first and second molars. Two different sized transpalatal arches (TPAs) (0.036-in and 0.06-in) and a gradually increased constriction bend and torque toward the posterior teeth were applied to prevent buccal tipping of the posterior teeth when intruding the maxillary posterior teeth. RESULTS: The whole maxillary dentition rotated clockwise as the intrusive force passed posteriorly to the center of resistance. Buccal crown tipping of the maxillary posterior teeth and lingual tipping of the maxillary incisors occurred. Their tipping decreased with a constriction bend and lingual crown torque and when a TPA was applied. CONCLUSIONS: Supplemental procedures such as a constriction bend and lingual crown torque and a TPA could effectively prevent the buccal crown tipping of the maxillary posterior teeth when intruding on them.

A cone-beam computed tomography evaluation of posterior available space in both arches relative to various skeletal patterns.

INTRODUCTION: This study aimed to evaluate the posterior available space (PAS) in both dental arches of adult patients with varying skeletal patterns using cone-beam computed tomography. METHODS: A sample of 114 adult patients (56 males and 58 females) was divided into 3 groups according to ANB angle and facial height ratio. Using C-mode cone-beam computed tomography images from these patients, maxillary PAS (MxPAS) and mandibular PAS (MnPAS) were measured in the distobuccal and palatal roots of the maxillary second molars and the distal roots of the mandibular second molars, respectively. The planes perpendicular to the tooth axes of the second molars in the coronal views and parallel to the posterior occlusal planes in the sagittal views were set at 3 heights of furcation, middle, and apex of the roots. For each plane, the shortest posterior distances from the roots to the inner and outer cortices were measured parallel to the furcation line connecting the furcations of the molars in the axial views. Posterior cortical bone thickness, defined as the distance from the inner cortex to the outer cortex, was measured. RESULTS: PAS was significantly greater in males than in females and in the maxilla than in the mandible (P <0.01). All MxPAS gradually increased from the furcation to the apex with significance (P <0.05), but there was no difference in MnPAS. MxPAS was significantly greater (P <0.05) in subjects with Class II and III malocclusion than subjects with Class I malocclusion, whereas MnPAS showed no difference. MxPAS showed no significant differences in facial height ratio, whereas MnPAS was significantly greater (P <0.05) at furcation in normovergent subjects than in others. Posterior cortical bone thickness was greater (P <0.001) in the mandible than in the maxilla. CONCLUSIONS: PAS was different according to sex and skeletal patterns. It would be helpful to evaluate PAS when distalizing the molars in either arch.

Short-term effects of microimplant-assisted rapid palatal expansion on the circummaxillary sutures in skeletally mature patients: A cone-beam computed tomography study.

INTRODUCTION: This study aimed to investigate the short-term effects on the circummaxillary sutures induced by microimplant-assisted rapid palatal expansion (MARPE) in skeletally mature patients. METHODS: Cone-beam computed tomography (CBCT) images of preexpansion (T0) and postexpansion (T1) of 23 patients (mean age, 20.9 ± 3.65 years) treated with MARPE were evaluated. The T0 and T1 CBCT images were reoriented and superimposed on the basis of the anterior cranial base, using OnDemand3D software (Cybermed, Seoul, Korea). Then, width changes of 9 circummaxillary sutures (frontonasal, frontomaxillary, frontozygomatic, nasomaxillary, zygomaticomaxillary, intermaxillary, midpalatal, zygomaticotemporal, and pterygopalatine sutures) were measured on 1 section of each patient's T0 and T1 CBCT images. In addition, correlation coefficients between changes in the midpalatal sutures, the amount of appliance activation, age, and the changes in other circummaxillary sutural widths were also calculated. RESULTS: Statistically significant (P <0.05) width increases were found in all 9 circummaxillary sutures. The changes in midpalatal suture at the maxillary central incisor level positively correlated with the intermaxillary sutures at the anterior nasal spine level, midpalatal sutures at the posterior nasal spine level, and frontomaxillary sutures (P <0.05). In addition, the changes in the midpalatal sutures at the posterior nasal spine level also positively correlated with the changes in the intermaxillary sutures at the anterior nasal spine level, frontomaxillary sutures, and medial pterygopalatine sutures (P <0.05). CONCLUSIONS: All 9 circummaxillary sutural widths increased in skeletally mature patients immediately after MARPE. The greatest increases in width were measured in the midpalatal sutures and the intermaxillary sutures, followed by the frontomaxillary sutures.

Class II Division 1 Adolescent Treatment with Twin Block and Fixed Orthodontic Appliances: 3-Dimensional Changes of the Temporomandibular Joint.

INTRODUCTION: Skeletal Class II division 1 malocclusions with a retrognathic mandible can be treated with Twin Block and fixed orthodontic appliances in growing adolescent patients. OBJECTIVE: The aim of this case report was to show successful treatment results following step-by-step procedures determined by visualizing the changes of the temporomandibular joint (TMJ) area using cone-beam computed tomography (CBCT) images. CASE REPORT: A 10-year, 8-month-old female adolescent with skeletal Class II division 1 (ANB, 6.2°), severe overjet (8.4 mm), and overbite (7.8 mm) was treated with Twin Block and fixed orthodontic appliances. After wearing an active plate for 4 months, a Twin Block appliance for 9 months, a retainer with an inclined plane for 13 months, and fixed orthodontic treatment for 17 months, her skeletal Class II was corrected. After 39 months of posttreatment retention, good treatment results were maintained with favorable occlusion and facial balance. Acceptable 3-dimensional changes of the TMJ area were identified using cone-beam computed tomography images. CONCLUSION: A female adolescent patient with skeletal Class II division 1 malocclusion, severe overjet and overbite, and mandibular retrusion was treated using Twin Block and fixed orthodontic appliances. Acceptable 3-dimensional changes in the TMJ area and 2-dimensional growth of the mandible were identified using CBCT and cephalometric images.

Evaluating mandibular symphysis bone density according to various skeletal patterns with CBCT.

OBJECTIVE: The aim of this retrospective study was to evaluate the bone density (BD) at the mandibular symphysis according to horizontal and vertical patterns using cone-beam computed tomography (CBCT). SETTING AND SAMPLING: Three hundred nineteen untreated adults with a mean age of 24 years. MATERIALS AND METHODS: CBCT images were converted into the lateral cephalometric images, and tracings were performed for categorizing the patients based on skeletal features. Cortical BDs at B point, pogonion (Pog), genion (Ge) and menton (Me), and cancellous BDs of the mandibular symphysis were measured using CBCT images. Statistical analyses were performed to evaluate the effects of horizontal and vertical skeletal patterns on BDs. RESULTS: Females exhibited higher BD than males at the Me, Pog, Ge (P < .001). Hyperdivergent skeletal pattern showed significantly higher cortical BD than normovergent and hypodivergent skeletal patterns at Me (P < .001). Normovergent skeletal pattern showed significantly higher cortical BD than hypodivergent skeletal patterns at Me (P = .001). Class II skeletal pattern showed significantly higher cortical BD than Class I and III skeletal patterns at Me (P < .001) and Ge (P < .05). Class I skeletal pattern showed significantly higher mean cortical BD than Class III skeletal pattern at B point (P = .025). Cancellous BD was higher in Class III and hypodivergent skeletal patterns than others but showed no statistical significance. CONCLUSIONS: Significant differences were identified across various skeletal patterns. Several mandibular symphyseal landmarks showed statistically significant differences in BD at Me, B point and Ge, with Me having the most statistically significant findings.

Cortical bone thickness and bone density effects on miniscrew success rates: A systematic review and meta-analysis.

OBJECTIVE: To systematically review the effects of cortical bone thickness (CBT) and bone mass density (BMD) on miniscrew success rates. METHODS: MEDLINE, the Cochrane Library and Scopus were searched up to June 2020. Of a total of 5734 articles, seven studies were finally selected for the review. RESULTS: The overall mean success rate weighted by the number of miniscrews was 87.21% (89.87% in the maxilla and 79.24% in the mandible). There was a significantly higher success rate for miniscrews placed in the maxilla compared with those in the mandible (P < .05). CBT showed small positive effect on the success rate of the miniscrews although it failed to reach a statistical significance. The cortical BMD had a minimal effect on the success of the miniscrews. The cancellous BMD demonstrated a very strong effect on the success of the miniscrews in the maxilla, whereas it showed a moderately negative effect in the mandible. LIMITATIONS: Because of the small number and clinical heterogeneity of the included studies, the results should be interpreted with caution. Further randomized clinical studies with a large sample size are recommended.

A CBCT Evaluation of Midpalatal Bone Density in Various Skeletal Patterns.

The purpose of this study was to evaluate midpalatal bone density (BD) by using cone-beam computed tomography (CBCT) according to gender, age, and vertical and horizontal skeletal patterns. CBCT images from 126 subjects (64 females and 62 males) were reoriented and analyzed in order to attain BD values at the midpalatal suture. Four age groups were used for classification (adolescence, 10 ≤ early < 14 years, 14 ≤ middle ≤ 17 years, and 17 < late ≤ 21 years; adult > 21 years). Vertical skeletal pattern categories were differentiated by the Frankfort horizontal line to mandibular plane angle (hypodivergent < 22°, 22° ≤ normovergent ≤ 28°, and 28° < hyperdivergent). Horizontal skeletal pattern differentiation was defined by ANB angle (Class III < 0°, 0° ≤ Class I ≤ 4°, and 4° < Class II). Females showed significantly higher BD than males (p < 0.001). As age increased, BD increased significantly (p < 0.001). There were no significant differences between vertical skeletal patterns. Class II showed significantly less BD than Class III (p < 0.05). With this information, clinicians can better understand BD trends of the midpalatal suture and, thus, better understand our patient's anatomy and potential hurdles in successful treatment.

Effects of bicortical anchorage on pterygopalatine suture opening with microimplant-assisted maxillary skeletal expansion.

INTRODUCTION: The objectives of this study were to evaluate the effects of bicortical engagement by microimplants with maxillary skeletal expanders on pterygopalatine sutures opening and to analyze the postexpansion skeletal changes associated with it. METHODS: Eighteen subjects treated with maxillary skeletal expanders were examined for pterygopalatine suture openings. Eight subjects who showed no evidence of the suture opening were assigned to the nonsplit group (NG), whereas 10 subjects with opened sutures were assigned to the split group (SG). Preexpansion and postexpansion cone-beam computed tomography images were superimposed for each group, and the changes in the 2 groups were compared. Finally, cone-beam computed tomography volumes were reoriented along the axis of each microimplant to check the bicortical engagement of the 4 microimplants. RESULTS: There was a significant correlation between the bicortical engagement of the orthodontic microimplants and the pterygopalatine suture opening (P = 0.0003). In the NG, the average amount of transverse expansion measured at the center of resistance of the maxillary first molars, anterior nasal spine, and posterior nasal spine (PNS) was 4.33 mm, 2.22 mm, and 1.58 mm, respectively, whereas the transverse expansion in the SG was 5.29 mm, 2.21 mm, and 2.46 mm, respectively. The magnitude of transverse expansion at PNS was significantly higher in the SG than in the NG (P = 0.036). The PNS also showed a significant anterior displacement in the SG (0.89 mm) compared with the NG (0.06 mm) (P = 0.033). CONCLUSIONS: Bicortical microimplant anchorage is essential for pterygopalatine suture opening in microimplant-assisted maxillary skeletal expansion, which may result in further skeletal expansion and forward movement in the posterior part of the palatomaxillary complex.

Hemimandibular hyperplasia treatment with condylectomy and orthodontic camouflage treatment using miniplate.

A 13-year-old growing female patient presented with hemimandibular hyperplasia of the right side, Class III hypodivergent skeletal pattern, and severe facial asymmetry. Corrective surgery was deferred until her growth had been completed. When the patient was 16 years old, a low condylectomy was performed on the hyperplastic side of her mandible to prevent its progressive condylar hyperplasia, while simultaneous orthodontic camouflage treatment was performed with the intrusion of the maxillary right posterior teeth using temporary skeletal anchorage devices without additional orthognathic surgery. A low condylectomy caused anterior and lateral open bite after the downward and backward movement of the chin, which improved Class III appearance. The intrusion of the maxillary right posterior teeth followed by compensating extrusion of the mandibular posterior teeth contributed to improve the patient's facial asymmetry with correction of the transverse occlusal plane and lip canting. After 30 months of treatment, an acceptable esthetic outcome and functional occlusion were achieved. The treatment results were well maintained for 1-year retention.

Biomechanical analysis for total mesialization of the maxillary dentition: A finite element study.

INTRODUCTION: The purpose of this study was to analyze and clarify tooth movement during mesialization of the whole maxillary dentition with various force angulations (FAs). METHODS: A finite element method was used to simulate the long-term orthodontic movement of the maxillary dentition by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. A mesial force of 3 N was applied to the maxillary second molar at 5 different FAs (-30°, -15°, 0°, 15°, and 30°) to the occlusal plane. RESULTS: At an FA of 28°, the line of action of the force passed through the center of resistance of the maxillary whole dentition. With all FAs, the central incisors and molars tipped labially and mesially, respectively. The tipping angles gradually decreased as the FAs shifted from -30° to 30°. The molars tipped lingually with FAs of -30° and -15°, whereas they tipped buccally with FAs of 0°, 15°, and 30°. The molars tended to rotate mesiolingually more as the angle of force increased toward an FA of 30°. The occlusal plane rotated counterclockwise with FAs of -30°, -15°, and 0°, whereas it rotated clockwise with FAs of 15° and 30°. With an FA of 30°, buccal tipping and mesiolingual rotation of the molars, and the change in the occlusal plane angle decreased when the transpalatal arch (TPA) was fixed to the first molars and decreased, even more when the TPA was fixed to the second molars rather than the first molars, when a thicker TPA was used, and when the TPA was fixed to both molars rather than a single molar. CONCLUSIONS: There was a correlation between tooth movement during mesialization of the whole maxillary dentition and the angle at which the force was applied.

Biomechanical analysis for total distalization of the maxillary dentition: A finite element study.

INTRODUCTION: This study aimed to identify the tooth movement patterns relative to various force angulations (FAs) when distalizing the total maxillary dentition. METHODS: Long-term orthodontic movement of the maxillary dentition was simulated by accumulating the initial displacement of teeth produced by elastic deflection of the periodontal ligament using a finite element analysis. Distalization forces of 3 N were applied to the archwire between the maxillary canine and first premolar at 5 different FAs (-30°, -15°, 0°, 15°, and 30°) to the occlusal plane. RESULTS: Maxillary incisors and molars showed lingual and distal tipping at all FAs, respectively. At a force angulation of 30°, almost bodily distalization of the total maxillary dentition occurred, but incisors showed considerable lingual tipping because of the effect of clearance gap (0.003-in, 0.022 × 0.025-in bracket slot, 0.019 × 0.025-in archwire) and elastic deflection of the archwire. Medial displacement of the maxillary anterior teeth occurred because of lingual tipping during distalization. The occlusal plane rotated clockwise at all FAs because of extrusion of the maxillary incisors and intrusion of the maxillary second molars, and the amounts decreased as FA increased. CONCLUSIONS: Tooth movement patterns during distalization of the total maxillary dentition were recognized. With an understanding of the mechanics, a proper treatment plan can be established.

Craniomaxillofacial Changes Using High-Pull J-Hook Headgear and Mini-Implant Anchorage in Adolescents: A Structural Superimposition Method.

OBJECTIVE: The aim of this study was to compare the craniomaxillofacial changes when using high-pull J-hook headgear (HPJH) and mini-implants (MIs) as maxillary anchorage in adolescents. STUDY DESIGN: 40 female adolescents with dentoalvolar protrusion were divided into 2 groups; the HPJH group (n=20) and the MI group (n=20). Lateral cephalograms taken before treatment (T0) and after anterior tooth retraction (T1) were superimposed on the stable structures and then craniomaxillofacial changes were evaluated. RESULTS: The cranial base angle, SNB, and facial angle decreased in the HPJH group but increased in the MI group. ANB decreased more in the MI group than in the HPJH group. Mandibular plane angle increased in the HPJH group but decreased in the MI group. Facial height index increased in the MI group while it showed no change in the HPJH group. Mandibular true rotation occurred clockwise in the HPJH group and counterclockwise in the MI group. Maxillary central incisors were intruded and retracted more in the MI group than in the HPJH group. Maxillary first molars were extruded in the HPJH group and were intruded in the MI group. Maxillary first molars were protracted more in the HPJH group than in the MI group. Mandibular central incisors were retracted more in the HPJH group than the MI group. Mandibular first molars were extruded more in the MI group than in the HPJH group. CONCLUSION: More favorable craniomaxillofacial changes occurred in the MI group than in the HPJH group.

The congenitally missing second premolar: Space closure. A viable option.

Many treatment options are available to address the problem of missing second premolars. Extraction of retained deciduous second molars and subsequent space closure are often appropriate because this option alleviates the need for implants or other restorations. This article describes the conventional orthodontic closure of unilateral and bilateral congenitally missing second premolar spaces after the extraction of retained deciduous second molars.

Prognostic Indicators for Anterior Mandibular Repositioning in Adolescents with Class II Malocclusion: A Cross-Sectional Cephalometric Study.

OBJECTIVE: To investigate the cephalometric changes following anterior repositioning of the mandible for predicting the treatment effects in Class II adolescent patients. STUDY DESIGN: Lateral cephalograms of 28 patients (ANB > 4°) were taken in centric occlusion (CO) and edge-to-edge bite (EtoE) before orthodontic treatment. The patients were classified into two groups according to their mandibular plane angle [MPA; low MPA (LMPA) ≤ 28° and high MPA (HMPA) > 28°]. Cephalometric changes of hard and soft tissues were measured and analyzed with an x-y cranial base coordinate system. RESULTS: For CO to EtoE, there were no significant cephalometric changes between HMPA and LMPA, but the horizontal ratio of soft to hard tissue pogonion (H-Pog'/H-Pog) change was significantly greater with LMPA than with HMPA while the vertical ratio (V-Pog'/V-Pog) showed vice versa. For CO to EtoE, MPA showed significant correlations with H-Pog'/H-Pog and V-Pog'/V-Pog. Y-axis angle, V-Pog'/V-Pog and H-Pog'/H-Pog can be used as good tools to discriminate between HMPA and LMPA. CONCLUSION: Cephalometric findings for CO to EtoE may be useful in predicting the vertical and horizontal changes of hard and soft tissues with the treatment of growing adolescents having various vertical skeletal patterns of Class II malocclusion.

A Retrospective CBCT Study of the Relationship between Mandibular Symphysis Bone Density and Mandibular Growth Direction.

OBJECTIVE: The objective of this retrospective study was to investigate the relationship between mandibular symphysis bone density (BD) and mandibular growth direction in adolescent patients by facilitating the measurement of cortical and cancellous BDs at the mandibular symphysis using cone beam computed tomography (CBCT). STUDY DESIGN: 224 adolescent patients (98 males and 126 females) were categorized by sex, age, and mandibular growth direction. Cortical and cancellous BDs were measured along with a sagittal slice at multiple locations. RESULTS: Females exhibited higher cortical BD than males at menton (Me, P =0.002). Patients with a posterior growth direction exhibited a higher cortical BD than those with anterior and normal growth direction at Me (P <0.021, P <0.001, respectively), pogonion (Pog, P =0.037, P =0.037, respectively) and genion (Ge, P =0.007, P =0.008, respectively). Patients with a posterior growth direction exhibited a higher cortical BD than those with anterior growth direction at B point (P =0.009). CONCLUSIONS: Significant differences in BD were identified across anthropometric categories. These findings may be useful in determining mandibular growth direction in adolescents.

Biomechanical analysis for total mesialization of the mandibular dentition: A finite element study.

OBJECTIVES: To clarify the mechanics of tooth movement in mesialization of the whole mandibular dentition when changing the force angulation. SETTING: A finite element method was used to simulate long-term movements of the whole mandibular dentition. MATERIAL AND METHODS: Tooth movement was simulated by accumulating the initial displacement, which was produced by elastic deformation of the periodontal ligament. Mesial forces of 3 N were applied to the second molar bracket at -30°, -15°, 0°, 15° and 30° to the occlusal plane. RESULTS: The whole dentition and occlusal plane were rotated depending on the direction of the force with respect to the centre of resistance (CR). At a force angulation of -30°, the line of action of the force passed near the CR, and the whole dentition translated without rotation of the occlusal plane. The second molar tipped buccally due to a clearance gap between the archwire and bracket slot. When increasing a force angulation from -30°, the line of action of the force passed above the CR, and thereby, the occlusal plane rotated clockwise. This rotation of the whole dentition induced tipping of the individual teeth. Buccal tipping of the molar due to an elastic deformation of the archwire was prevented by using a lingually pre-bent archwire. CONCLUSIONS: Careful selection of force angulation and biomechanics is essential to obtain proper tooth movement in total mesialization of the mandibular dentition.