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1.
Artigo em Inglês | MEDLINE | ID: mdl-33736907

RESUMO

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.

2.
Am J Orthod Dentofacial Orthop ; 159(4): 502-511, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33495061

RESUMO

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.


Assuntos
Maxila , Técnica de Expansão Palatina , Tomografia Computadorizada de Feixe Cônico , Humanos , Maxila/diagnóstico por imagem , Maxila/cirurgia , Dente Molar , Suturas
3.
Orthod Craniofac Res ; 2020 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-33277824

RESUMO

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 a 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 moderate 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.

4.
J Clin Pediatr Dent ; 44(4): 274-282, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-33167022

RESUMO

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.


Assuntos
Reposicionamento de Medicamentos , Má Oclusão de Angle Classe II , Adolescente , Cefalometria , Estudos Transversais , Humanos , Má Oclusão de Angle Classe II/diagnóstico por imagem , Má Oclusão de Angle Classe II/terapia , Mandíbula/diagnóstico por imagem , Prognóstico
5.
J Clin Pediatr Dent ; 44(5): 356-365, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-33181848

RESUMO

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.


Assuntos
Densidade Óssea , Tomografia Computadorizada de Feixe Cônico Espiral , Adolescente , Tomografia Computadorizada de Feixe Cônico , Feminino , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Estudos Retrospectivos
6.
Orthod Craniofac Res ; 2020 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-32599658

RESUMO

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.

7.
Korean J Orthod ; 50(3): 157-169, 2020 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-32475843

RESUMO

Objective: The aim of this retrospective study was to evaluate the pre- and postsurgical bone densities at alveolar and extra-alveolar sites following twojaw orthognathic surgery. Methods: The sample consisted of 10 patients (mean age, 23.2 years; range, 18.0-27.8 years; 8 males, 2 females) who underwent two-jaw orthognathic surgery. A three-dimensional imaging program (Invivo 5) was used with multidetector computed tomography images taken preand postoperatively (obtained 32.3 ± 6.0 days before surgery and 5.8 ± 2.6 days after surgery, respectively) for the measurement of bone densities at the following sites: (1) alveolar bone in the maxilla and mandible, (2) extra-alveolar sites, such as the top of the head, menton (Me), condyle, and the fourth cervical vertebrae (C4). Results: When pre- and postsurgical bone densities were compared, an overall tendency of decrease in bone density was noted. Statistically significant reductions were observed in the densities of cancellous bone at several areas of the maxillary alveolar bone; cortical and cancellous bone in most areas of the mandibular alveolar bone; cortical bone in Me; and cancellous bone in C4. There was no statistically significant difference in bone density in relation to the depth of the alveolar bone. In a comparison of the bone densities between groups with and without genioplasty, there was almost no statistically significant difference. Conclusions: Accelerated tooth movement following orthognathic surgery may be confirmed with reduced bone density. In addition, this study could offer insights into bone metabolism changes following orthognathic surgery, providing direction for further investigations in this field.

8.
Am J Orthod Dentofacial Orthop ; 157(4): 571-583.e16, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32241364

RESUMO

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.


Assuntos
Anodontia , Fechamento de Espaço Ortodôntico , Dente Pré-Molar , Humanos
9.
Angle Orthod ; 90(2): 224-232, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31638857

RESUMO

OBJECTIVES: To evaluate the condyle-fossa relationship in adolescents with various skeletal patterns using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: CBCT images obtained in 120 adolescent patients were used for this study. The patients were divided into 3 groups according to 3 criteria: (1) age (early, middle, and late adolescence); (2) facial height ratio or Jarabak quotient (hyperdivergent, normodivergent, and hypodivergent); and (3) ANB classification (Class I, Class II, and Class III). Temporomandibular joint space (TMJS: AS, anterior space; SS, superior space; PS, posterior space; MS, medial space; LS, lateral space), width and depth of the condyle (MLT, mediolateral thickness; APT, anteroposterior thickness), articular slope (ArS) and vertical height of the fossa (VHF) were measured and compared using CBCT. RESULTS: Differences in condyle-fossa relationships were not significantly different between male and female adolescents, but were significantly different (P < .05) between left and right sides. The mean values showed no statistical differences according to age and skeletal pattern. Most measurements in the sagittal view showed that SS was the greatest, and the mean ratio of AS to SS to PS was 1.00 to 1.27 to 1.19, respectively. The mean values of coronal MS and LS were not significantly different. CONCLUSIONS: There were almost no statistical differences in the TMJS in adolescents across various factors except between left and right sides.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Côndilo Mandibular , Articulação Temporomandibular , Adolescente , Feminino , Humanos , Masculino , Côndilo Mandibular/anatomia & histologia , Côndilo Mandibular/diagnóstico por imagem , Articulação Temporomandibular/anatomia & histologia , Articulação Temporomandibular/diagnóstico por imagem
10.
Am J Orthod Dentofacial Orthop ; 156(6): 808-817, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31784014

RESUMO

INTRODUCTION: Patients with impacted maxillary canines typically endure long treatment time, and reliable pretreatment estimates of orthodontic treatment duration would be beneficial to patients and clinicians. The purpose of this study was to identify factors that affect the duration of forced eruption for impacted maxillary canines. METHODS: Data from treatment records and radiographic scans of 27 patients with 29 impacted and labially displaced maxillary canines (25 unilateral, 2 bilateral) were collected. The patients underwent surgical and orthodontic interventions to bring the canine into the dental arch. Linear and angular measurements between the cusp tip and various reference planes were made on 3-dimensional images. Measurements associated with dental follicle, bone density, and canine root length were also obtained. Data were analyzed using simple linear regression and stepwise regression analysis. RESULTS: A total of 29 treated canines moved into the arch over a period of 13.0 ± 8.3 months (range, 5-33 months). Simple regression analysis showed that the only significant factor, with duration of traction as the dependent factor, was pretreatment inclination of the canines toward the midsagittal plane; stepwise regression analysis indicated a strong direct correlation between the duration of traction and this factor. The other variables were not significantly associated with the duration of traction. CONCLUSIONS: The inclination of canines toward the midsagittal plane was found to be a reliable predictor of the duration of forced eruption for impacted maxillary canines.


Assuntos
Extrusão Ortodôntica , Dente Impactado , Dente Canino , Arco Dental , Humanos , Maxila
11.
Am J Orthod Dentofacial Orthop ; 156(5): 653-662, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31677674

RESUMO

INTRODUCTION: The aim of this study was to investigate 3-dimensional changes of the zygomaticomaxillary complex (ZMC) after mini-implant assisted rapid maxillary expansion (MARME). METHODS: A total of 15 pairs of cone-beam computed tomography 3-dimensional images taken before expansion (T0) and after expansion (T1) were analyzed by measuring changes in the coordinates of the landmarks of the ZMC. RESULTS: Changes in the x coordinates of the landmarks showed significant expansion (P <0.01) and greater expansion at the lower than upper portion of the ZMC (P <0.05) in the transverse dimension. All y coordinates of the landmarks except the jugal point (J) showed forward displacement (P <0.05), and the z coordinates of ANS, PNS, Alare, A, and ectocanine showed downward displacement (P <0.01) in the sagittal and vertical dimensions. Also, z coordinates of the landmarks that were closer to the midsagittal plane and in a more posterior portion of the ZMC displaced further downward (P <0.05). SNA and ANB angles increased (P <0.05 and P <0.001, respectively) and the SNB angle decreased (P <0.01). There was a significant correlation between changes in the x coordinates of the ectomolare and ectocanine and the amount of expansion measured from the center of resistance of the maxillary first molars (CR6; P <0.05). There was no significant correlation between the amount of CR6 expansion and changes in y and z coordinates of the landmarks. CONCLUSIONS: 3-Dimensional changes of the ZMC after MARME showed expansion in a pyramidal shape from the coronal view, downward and forward displacement from the sagittal view, and parallel palatal expansion from the axial view. These findings might be useful for understanding skeletal expansion patterns using MARME.


Assuntos
Maxila , Técnica de Expansão Palatina , Cefalometria , Tomografia Computadorizada de Feixe Cônico , Humanos , Imageamento Tridimensional , Maxila/diagnóstico por imagem , Dimensão Vertical
12.
Korean J Orthod ; 49(3): 188-193, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31149609

RESUMO

Objective: The aim of this finite element study was to clarify the mechanics of tooth movement in palatal en-masse retraction of segmented maxillary anterior teeth by using anchor screws and lever arms. Methods: A three-dimensional finite element method was used to simulate overall orthodontic tooth movements. The line of action of the force was varied by changing both the lever arm height and anchor screw position. Results: When the line of action of the force passed through the center of resistance (CR), the anterior teeth showed translation. However, when the line of action was not perpendicular to the long axis of the anterior teeth, the anterior teeth moved bodily with an unexpected intrusion even though the force was transmitted horizontally. To move the anterior teeth bodily without intrusion and extrusion, a downward force passing through the CR was necessary. When the line of action of the force passed apical to the CR, the anterior teeth tipped counterclockwise during retraction, and when the line of action of the force passed coronal to the CR, the anterior teeth tipped clockwise during retraction. Conclusions: The movement pattern of the anterior teeth changed depending on the combination of lever arm height and anchor screw position. However, this pattern may be unpredictable in clinical settings because the movement direction is not always equal to the force direction.

13.
Orthod Craniofac Res ; 22(4): 329-336, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31230415

RESUMO

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.


Assuntos
Dentição , Dente , Análise de Elementos Finitos , Dente Molar , Técnicas de Movimentação Dentária
15.
Am J Orthod Dentofacial Orthop ; 155(3): 388-397, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30826042

RESUMO

INTRODUCTION: The aim of this finite element study was to analyze and clarify the mechanics of tooth movement patterns for total distalization of the mandibular dentition based on force angulation. METHODS: Long-term orthodontic movement of the mandibular dentition was simulated by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. RESULTS: Displacement of each tooth was caused by movement of the whole dentition, elastic deflection of the archwire, and clearance gap between the archwire and bracket slot. The whole dentition was rotated clockwise or counterclockwise when the line of action of the force passed below or above the center of resistance. Elastic deflection of the archwire induced a lingual tipping of the anterior teeth. It became larger when increasing the magnitude of angulation. The archwire could be rotated within the clearance gap between the archwire and the bracket slot, and thereby the teeth tipped. CONCLUSIONS: Mechanics of total mandibular distalization was clarified. Selective use of force angulation with a careful biomechanical understanding can achieve proper distalization of the whole mandibular dentition.


Assuntos
Análise de Elementos Finitos , Má Oclusão de Angle Classe III/terapia , Mandíbula/fisiologia , Técnicas de Movimentação Dentária , Processo Alveolar/fisiologia , Fenômenos Biomecânicos , Módulo de Elasticidade , Humanos , Braquetes Ortodônticos , Fios Ortodônticos , Ligamento Periodontal/fisiologia
17.
J Clin Pediatr Dent ; 43(1): 56-63, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30289367

RESUMO

Treatment of horizontally and deeply impacted mandibular molars is challenging for both orthodontists and oral surgeons because of the limited access and anchorage control. We report on two patients who had horizontally and mesially impacted mandibular second molars (MM2s). Both patients were treated by a surgical orthodontic approach, and the crowns of the impacted teeth were brought into the arches by closed forced eruption. Mesially impacted MM2s were uprighted with orthodontic microimplants, inserted in the retromolar area, and then moved into their ideal position. The first patient was in an active growing stage, while the second patient was beyond the active growing stage. Therefore posterior available space (PAS) should be analyzed before treatment of impacted MM2s to prevent periodontal problems after uprighting of impacted teeth. If PAS is not enough for uprighting impacted MM2s, alternative treatment should be considered based on the stage of growth.


Assuntos
Técnicas de Movimentação Dentária , Dente Impactado , Assistência Odontológica , Humanos , Mandíbula , Dente Molar , Extrusão Ortodôntica , Dente Impactado/terapia
18.
Am J Orthod Dentofacial Orthop ; 154(3): 382-389, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30173841

RESUMO

INTRODUCTION: The aim of this study was to evaluate the bone density of mandibular condyles in adolescents with varying skeletal patterns using cone-beam computed tomography. The null hypothesis was that there is no difference in the bone density of mandibular condyles in adolescents across various facial height ratios, ANB angle classifications, sexes, and age categories. METHODS: We divided 120 adolescent patients, 56 boys and 64 girls, into 3 groups according to 3 criteria: (1) age (early, 10 to <14 years; middle, 14 to <17 years; late, 17 to <20 years); (2) facial height ratio or Jarabak quotient (hyperdivergent: facial height ratio, <62%; normovergent: facial height ratio, 62% to ≤65%; and hypodivergent: facial height ratio, >65%); and (3) ANB angle classification (Class I, 1° to ≤4°; Class II, (>4°); and Class III, <1°). The total, cortical, and cancellous bone densities were measured and compared on the axial slice with the largest mediolateral diameter of the mandibular condyle using C-mode cone-beam computed tomography. RESULTS: Cortical bone density increased as age increased and showed statistically significant differences between the early and middle (P = 0.041) and the early and late adolescent groups (P = 0.031). Condylar bone density increased as facial height ratio decreased, and cancellous bone density showed statistically significant differences between the hyperdivergent and hypodivergent groups (P = 0.038). The cortical, cancellous, and total bone densities increased as ANB angle increased and showed statistically significant differences between the Class II and Class III groups (P = 0.022, P = 0.006, and P = 0.003, respectively). CONCLUSIONS: The null hypothesis was rejected. Condylar bone density increased as facial height ratio decreased and ANB angle increased. These findings may be useful in predicting the vertical and horizontal skeletal growth patterns of growing adolescents.


Assuntos
Densidade Óssea , Tomografia Computadorizada de Feixe Cônico , Imageamento Tridimensional , Má Oclusão/diagnóstico por imagem , Côndilo Mandibular/diagnóstico por imagem , Adolescente , Feminino , Humanos , Masculino , Valor Preditivo dos Testes , Dimensão Vertical , Adulto Jovem
19.
Am J Orthod Dentofacial Orthop ; 154(1): 108-114, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29957307

RESUMO

INTRODUCTION: The 2-fold purpose of this study was to evaluate the effects of acid etching and calcium chloride immersion on removal torque and the bone-cutting ability of orthodontic mini-implants (OMIs). METHODS: For the removal torque part of the study, 3 types of OMIs (titanium alloy) were evaluated in a rabbit model: OMIs with acid surface etching with and without calcium chloride immersion (ECG and EG, respectively) and a control group (CG), in which the OMIs had an untreated, machined surface. We inserted 126 OMIs (42 OMIs per type) into both tibias of 21 male rabbits (5 months of age) with body weights of 3.0 to 3.5 kg. Removal torque was evaluated after 1, 4, and 7 weeks. To determine the OMIs' bone-cutting ability, total insertion time to place an OMI 6 mm into artificial bone was measured (6 OMIs per group). RESULTS: Removal torque values for the EG (3.97 ± 0.52 Ncm) and ECG (4.21 ± 0.44 Ncm) were statistically and significantly higher than those of the CG (3.02 ± 0.53 Ncm) 1 week after implantation (P <0.05). The ECG (6.54 ± 0.50, 6.61 ± 0.66 Ncm) showed the highest removal torque value followed by the EG (5.68 ± 0.58, 5.89 ± 0.70 Ncm) and CG (3.43 ± 0.62, 3.38 ± 0.54 Ncm) at 4 and 7 weeks after implantation (P <0.05). Removal torque did not change over time with the CG, but with the ECG and EG, it was significantly higher in weeks 4 and 7 than in week 1 (P <0.05). Total insertion time was significantly greater for the EG than for the ECG and CG (P <0.05). CONCLUSIONS: Treating OMIs with a calcium chloride solution improved the initial bone reaction by preventing contamination of the implant surface, and increasing the surface roughness of OMIs by acid etching enhanced their stability without decreasing the bone-cutting ability compared with OMIs without surface treatment.


Assuntos
Condicionamento Ácido do Dente , Cloreto de Cálcio/farmacologia , Implantes Dentários , Animais , Remoção de Dispositivo , Masculino , Procedimentos de Ancoragem Ortodôntica , Coelhos , Propriedades de Superfície , Torque
20.
Korean J Orthod ; 48(1): 3-10, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29291183

RESUMO

Objective: The purpose of this study was to predict the optimal bending angles of a running loop for bodily protraction of the mandibular first molars and to clarify the mechanics of molar tipping and rotation. Methods: A three-dimensional finite element model was developed for predicting tooth movement, and a mechanical model based on the beam theory was constructed for clarifying force systems. Results: When a running loop without bends was used, the molar tipped mesially by 9.6° and rotated counterclockwise by 5.4°. These angles were almost similar to those predicted by the beam theory. When the amount of tip-back and toe-in angles were 11.5° and 9.9°, respectively, bodily movement of the molar was achieved. When the bend angles were increased to 14.2° and 18.7°, the molar tipped distally by 4.9° and rotated clockwise by 1.5°. Conclusions: Bodily movement of a mandibular first molar was achieved during protraction by controlling the tip-back and toe-in angles with the use of a running loop. The beam theory was effective for understanding the mechanics of molar tipping and rotation, as well as for predicting the optimal bending angles.

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