Three-dimensional measurement and analysis of Mandibular Molar Distalization assisted by micro-implant anchorage combined with clear aligner.

Objective: To investigate the effect of micro-implant anchorage combined with a clear aligner on the efficiency of mandibular molar distalization and the protection of anterior teeth anchorage, provide reference for clinical scheme design. Methods: This is a prospective study. Seventeen patients who were treated in the Orthodontics Department of the Hospital of Stomatology affiliated to Fujian Medical University from 2019 to 2021 and used Invisalign clear aligners to move mandibular molars distally were included and divided into two groups according to anchorage types: Group-A and Group-B. Group-A (ten cases) were treated without micro-implant anchorage, while Group-B (seven cases) were treated with micro-implant anchorage nails for enhanced anchorage. The effect of micro-implant anchorage on crown and root distal movement of mandibular molars and the difference in three-dimensional movement between mandibular molars and mandibular central incisors were analyzed. Results: The crown distalization efficiency of mandibular first and second molars in Group-B was 68.66% and 71.02%, respectively, which were higher than those in Group-A(p<0.05). The mandibular central incisors in Group-A showed labial displacement and a small amount of elongation, while those in Group-B showed less anchorage loss(p<0.05). In Group-A, the crown was tilted in the distal direction and moved in the buccal direction during mandibular molar distalization(p<0.05). While in Group-B, the crown was tilted in the distal directio (p<0.05) and the mandibular second molar was depressed(p<0.05). Conclusion: In the process of mandibular molar distalization assisted by micro-implant anchorage combined with a clear aligner, better protects the anchorage of the mandibular central incisor and improves the efficiency of the molar crown distalization.

Comparison between effects of mini-implant anchorage and face-bow anchorage in orthodontics for children.

To study the values of mini-implant anchorage in orthodontics for children in the mixed dentition stage, 78 children in the mixed dentition stage who had accepted orthodontic treatment in our hospital from January 2020 to January 2021 were enrolled into this study. All children were treated with straight-wire appliance. According to their anchorages, children were divided into observation group and control group based on the random number table. Children in the control group used face-bow to control the anchorages and children in the observation group used mini-implants to control the anchorages. After treatment, the upper central incisor convex distance difference, inclination angle of the upper central incisor, displacement of the molar, gingival health, masticatory function, treatment effect and adverse reaction rate of children in two groups were compared. One year after treatment, compared with children in the control group, children in the observation group had smaller the upper central incisor convex distance difference, inclination angle of the upper central incisor, displacement of the molar, small scores of plaque index (PLI), bleeding index (BI) and gingival index (GI), stronger biting force and higher masticatory efficiency, lower adverse reaction rate during treatment, better treatment effect, higher satisfaction of orthodontic treatment. And differences of all the above indexes were statistically significant (p < 0.05). Mini-implant anchorages have good stability and directive force, and have certain values in orthodontics for children in the mixed dentition stage.

Experimental magnesium phosphate cement paste increases torque of trochanteric fixation nail advanced™ blades in human femoral heads.

BACKGROUND: The use of polymethylmethacrylate cement for in-situ implant augmentation has considerable disadvantages: it is potentially cytotoxic, exothermic and non-degradable. Therefore, the primary aim of this study was to develop a magnesium phosphate cement which meets the requirements for in-situ implant augmentation as an alternative. Secondly, this experimental cement was compared to commercial bone cements in a biomechanical test set-up using augmented femoral head blades. METHODS: A total of 40 human femoral heads were obtained from patients who underwent total hip arthroplasty. After bone mineral density was quantified, specimens were assigned to four treatment groups. A blade of the Trochanteric Fixation Nail Advanced™ was inserted into each specimen and augmented with either Traumacem™ V+, Paste-CPC, the experimental magnesium phosphate cement or no cement. A rotational load-to-failure-test (0° to 90°) was performed. FINDINGS: A conventional two-component magnesium phosphate cement failed in-situ implant augmentation consistently due to filter pressing. Only a glycerol-based magnesium phosphate paste was suitable for the augmentation of femoral head blades. While the blades augmented with Traumacem™ V+ yielded the highest maximum torque overall (22.1 Nm), the blades augmented with Paste-CPC and the magnesium phosphate paste also showed higher maximum torque values (15.8 and 12.8 Nm) than the control group (10.8 Nm). INTERPRETATION: This study shows for the first time the development of a degradable magnesium phosphate cement paste which fulfills the requirements for in-situ implant augmentation. Simultaneously, a 48% increase in stability is demonstrated for a scenario where implant anchorage is difficult in osteoporotic bone.

Three-dimensional finite element study of mandibular first molar distalization with clear aligner.

OBJECTIVES: This study aimed to construct the finite element model of the mandibular first molar with the invisible appliance and explore the dentition movement characteristics of the mandibular first molar when using micro-implant anchorage and different initial positions of the first molar. METHODS: Models of the mandible, tooth, periodontal membrane, and invisible appliance were constructed using cone beam computed tomography (CBCT) data. The two groups were divided into the non-anchorage group and the micro-implant group (between the roots of the first molar and the second molar) based on whether the elastic traction of the micro-implant was assisted or not. The two groups were divided into the following conditions based on the starting position of the first molar: Working condition 1: the distance between the first molar and the second premolar was 0 mm; working condition 2: the distance between the first molar and the second premolar was 1 mm; working condition 3: the distance between the first molar and the second premolar was 2 mm; working condition 4: the distance between the first molar and the second premolar was 3 mm. The data characte-ristics of total displacement and displacement in each direction of dentition were analyzed. RESULTS: In the non-ancho-rage group, all the other teeth showed reverse movement except for the first molar which was moved distally. Meanwhile, in the micro-implant group, except for a small amount of mesial movement of the second molar in wor-king condition 1, the whole dentition in other working conditions presented distal movement and anterior teeth showed lingual movement, among which the distal displacement of the first molar in working condition 4 was the largest. With the change of the initial position of the first molar to the distal, the movement of the first molar to the distal, the premolar to the mesial, and the anterior to the lip increased, while the movement of the second molar to the mesial decreased. CONCLUSIONS: The micro-implant can effectively protect the anterior anchorage, increase the expression rate of molar distancing, and avoid the round-trip movement of the second molar. The initial position of the first molar movement is related to the amount of distancing and the remaining tooth movement.

Three-dimensional finite element study of mandibular first molar distalization with clear aligner / 华西口腔医学杂志

OBJECTIVES@#This study aimed to construct the finite element model of the mandibular first molar with the invisible appliance and explore the dentition movement characteristics of the mandibular first molar when using micro-implant anchorage and different initial positions of the first molar.@*METHODS@#Models of the mandible, tooth, periodontal membrane, and invisible appliance were constructed using cone beam computed tomography (CBCT) data. The two groups were divided into the non-anchorage group and the micro-implant group (between the roots of the first molar and the second molar) based on whether the elastic traction of the micro-implant was assisted or not. The two groups were divided into the following conditions based on the starting position of the first molar: Working condition 1: the distance between the first molar and the second premolar was 0 mm; working condition 2: the distance between the first molar and the second premolar was 1 mm; working condition 3: the distance between the first molar and the second premolar was 2 mm; working condition 4: the distance between the first molar and the second premolar was 3 mm. The data characte-ristics of total displacement and displacement in each direction of dentition were analyzed.@*RESULTS@#In the non-ancho-rage group, all the other teeth showed reverse movement except for the first molar which was moved distally. Meanwhile, in the micro-implant group, except for a small amount of mesial movement of the second molar in wor-king condition 1, the whole dentition in other working conditions presented distal movement and anterior teeth showed lingual movement, among which the distal displacement of the first molar in working condition 4 was the largest. With the change of the initial position of the first molar to the distal, the movement of the first molar to the distal, the premolar to the mesial, and the anterior to the lip increased, while the movement of the second molar to the mesial decreased.@*CONCLUSIONS@#The micro-implant can effectively protect the anterior anchorage, increase the expression rate of molar distancing, and avoid the round-trip movement of the second molar. The initial position of the first molar movement is related to the amount of distancing and the remaining tooth movement.

Torque recovery of the maxillary incisors with a modified double J retractor in a Class II division 2 case treated with clear aligners.

A patient with a Class II division 2 malocclusion is presented, illustrating the application of a modified double J retractor (DJR) and palatal miniscrews along with clear aligners to correct the malocclusion and normalize the incisor torque. In terms of incisor torque recovery, a nonextraction approach might be a good choice if the Class II correction could be successfully achieved with total arch distalization. When maxillary molar distalization was limited by anatomical boundaries, the treatment plan was changed to bilateral maxillary first premolar extractions, which led to even more retroclination of the maxillary incisors after space closure. Anterior interdental miniscrews were used to intrude the maxillary incisors. A modified DJR and palatal miniscrews were used to regain torque and achieve palatal root movement of the maxillary incisors. The treatment effects and biomechanical designs were evaluated for torque recovery of the retroclined maxillary incisors.

[Efficacy of vertical control by using mini-implant anchorage in maxillary posterior buccal area for Angle class â ¡ extraction patients].

OBJECTIVE: To investigate the efficacy of vertical control by using conventional mini-implant anchorage in maxillary posterior buccal area for Angle class Ⅱ extraction patients. METHODS: Twenty-eight Angle class Ⅱ patients [9 males, 19 females, and age (22.6±2.8) years] were selected in this study. All of these patients were treated by using straight wire appliance with 4 premolars extraction and 2 mini-implant anchorage in maxillary posterior buccal area. In this study, the self-control method was used to measure and analyze the lateral radiographs taken before and after orthodontic treatment in each case, the main cephalometric analysis items were related to vertical changes. The digitized lateral radiographs were imported into Dolphin Imaging Software (version 11.5: Dolphin Imaging and Management Solutions, Chatsworth, California, USA), and marked points were traced. Each marked point was confirmed by two orthodontists. The same orthodontist performed measurement on the lateral radiographs over a period of time. All measurement items were required to be measured 3 times, and the average value was taken as the final measurement result. RESULTS: Analysis of the cephalometric radiographs showed that, for vertical measurements after treatment, the differences of the following measurements were highly statistically significant (P < 0.001): SN-MP decreased by (1.40±1.45) degrees on average, FMA decreased by (1.58±1.32) degrees on average, the back-to-front height ratio (S-Go/N-Me) decreased by 1.42%±1.43% on average, Y-axis angle decreased by (1.03±0.99) degrees on average, face angle increases by (1.37±1.05) degree on average; The following measurements were statistically significant (P < 0.05): the average depression of the upper molars was (0.68±1.40) mm, and the average depression of the upper anterior teeth was (1.07±1.55) mm. The outcomes indicated that there was a certain degree of upper molar depression after the treatment, which produced a certain degree of counterclockwise rotation of the mandibular plane, resulting in a positive effect on the improvement of the profile. CONCLUSION: The conventional micro-implant anchorage in maxillary posterior buccal area has a certain vertical control ability, and can give rise to a certain counterclockwise rotation of the mandible, which would improve the profile of Angle Class Ⅱ patients.

Torque control of maxillary anterior teeth with the double J retractor and palatal miniscrews during en masse retraction.

A double J retractor (DJR) and palatal miniscrews were used to retract maxillary anterior teeth after failure of buccal posterior miniscrews. The line of action passing through the center of resistance of the maxillary anterior teeth and the moment generated by the palatal miniscrews via torquing springs successfully controlled the overbite and incisor torque during space closure. The DJR and palatal miniscrews work well with labial fixed appliances to address bimaxillary protrusion.

CBCT study on the safe location of palatal microscrew implant anchorage nail between maxillary first and second molars / 口腔疾病防治

Objective@#Conebeam CT (CBCT) was used to measure the palatine between the maxillary first and second molars. The proximal and distal palatal widths of the maxillary first and second molar and the palatal mucosal thickness and bone tissue thickness when microscrew implant anchorage nail were implanted at different angles provided a reference for the clinical selection of microscrew implant placement.@* Methods@#The image data of 90 adult patients were selected as the research object, and the jaw bone was reconstructed by scanning. In maxillary palatine, selection of distances at 12 mm, 14 mm, 16 mm, and 18 mm from the palatal apex of maxillary first molar between the maxillary first and second molar were used as measurement, measured the proximal and distal palatal widths of maxillary first and second molar and the palatal mucosal thickness and bone tissue thickness when microscrew implant anchorage nails were implanted at 30 °, 45 °, 60 °, and 90 °. SPSS 26.0 software was used for one-way ANOVA and LSD pair comparison. @*Results@#The larger the angle of the microscrew implant anchorage nail was, the smaller the proximal and distal medial widths between the maxillary first and second molar, and the difference was statistically significant (P < 0.05). Compared with the 90° direction, the proximal and distal medial widths of the microscrew implant anchorage nail were larger in the 60° direction. The greater the angle of implantation, the smaller the mucosal thickness and the greater the bone tissue thickness, and the results showed a significant difference (P < 0.001). Compared with the direction of 30° and 45°, the mucosal thickness at the direction of 60° was smaller, and the bone tissue thickness was larger. The higher the position of the microscrew implant anchorage nail, the greater the width of the proximal and distal medial, and the difference was statistically significant (P < 0.05). Compared with the positions 12 and 14 mm from the palatal tip, the proximal and distal medial widths of the microscrew implant anchorage nail were larger. The higher the implant position was, the greater the mucosal thickness and the smaller the bone tissue thickness. The results showed a significant difference (P < 0.001). Compared with the position of 18 mm from the palatal tip of the maxillary first molar, the mucosal thickness was smaller and the bone tissue thickness was larger.@*Conclusion@#It is most appropriate to implant microscrew implant anchorage nail at least 10 mm in length in the direction of 60° at the palatal apex 16 mm from the maxillary first molar in palatine between the first and second molar.

Efficacy of vertical control by using mini-implant anchorage in maxillary posterior buccal area for Angle class Ⅱ extraction patients / 北京大学学报(医学版)

OBJECTIVE@#To investigate the efficacy of vertical control by using conventional mini-implant anchorage in maxillary posterior buccal area for Angle class Ⅱ extraction patients.@*METHODS@#Twenty-eight Angle class Ⅱ patients [9 males, 19 females, and age (22.6±2.8) years] were selected in this study. All of these patients were treated by using straight wire appliance with 4 premolars extraction and 2 mini-implant anchorage in maxillary posterior buccal area. In this study, the self-control method was used to measure and analyze the lateral radiographs taken before and after orthodontic treatment in each case, the main cephalometric analysis items were related to vertical changes. The digitized lateral radiographs were imported into Dolphin Imaging Software (version 11.5: Dolphin Imaging and Management Solutions, Chatsworth, California, USA), and marked points were traced. Each marked point was confirmed by two orthodontists. The same orthodontist performed measurement on the lateral radiographs over a period of time. All measurement items were required to be measured 3 times, and the average value was taken as the final measurement result.@*RESULTS@#Analysis of the cephalometric radiographs showed that, for vertical measurements after treatment, the differences of the following measurements were highly statistically significant (P < 0.001): SN-MP decreased by (1.40±1.45) degrees on average, FMA decreased by (1.58±1.32) degrees on average, the back-to-front height ratio (S-Go/N-Me) decreased by 1.42%±1.43% on average, Y-axis angle decreased by (1.03±0.99) degrees on average, face angle increases by (1.37±1.05) degree on average; The following measurements were statistically significant (P < 0.05): the average depression of the upper molars was (0.68±1.40) mm, and the average depression of the upper anterior teeth was (1.07±1.55) mm. The outcomes indicated that there was a certain degree of upper molar depression after the treatment, which produced a certain degree of counterclockwise rotation of the mandibular plane, resulting in a positive effect on the improvement of the profile.@*CONCLUSION@#The conventional micro-implant anchorage in maxillary posterior buccal area has a certain vertical control ability, and can give rise to a certain counterclockwise rotation of the mandible, which would improve the profile of Angle Class Ⅱ patients.

Clinical efficacy of counterclockwise rotating the functional occlusal plane using micro-implant anchorage.

To evaluate the therapeutic effect of using micro-implant anchorage (MIA) to rotate the functional occlusal plane (FOP) counterclockwise. Forty skeletal class Ⅱ high-angle patients who had completed orthodontic treatment were enrolled, including 20 patients treated with MIA orthodontic system (MIA group) and the other 20 patients treated with traditional sliding straight wire appliance (control group). Cephalometric measurements on the lateral cranial radiographs before and after treatment were performed, all acquired data were statistically analyzed with SPSS 26.0. At the end of treatment, MIA group obtained better effect of FOP and mandibular plane counter-clockwise rotation than the control group. In the MIA group, the average change of FOP-frankfort horizontal plane (FH), FOP-SN and mandibular plane angle (MP-FH) angle was -4.5(-7.3, -3.7)°, (3.3)° and -1.7(-3.0, -0.9)°, respectively. In the control group, the average change of FOP-FH, FOP-SN and MP-FH angle was -0.1(-4.1, 3.0)°, (-0.1±5.1)° and -0.4(-2.4, 0.7)°, respectively. There was significant difference between the change of the two groups (all <0.05). Compared with the traditional sliding straight wire appliance, counterclockwise rotation of FOP can be more effectively reversed by using MIA orthodontic system, and the MP-FH can be reduced as well.

The Role of Power Arm by Combined Use of Clear Aligner and Miniscrew in En-Masse Retraction of Maxillary Anterior Teeth / 医用生物力学

Objective To investigate the role of Power Arm in en-masse retraction of maxillary anterior teeth using clear aligner (CA) and micro-implant anchorage (MIA). Methods The three-dimensional (3D) model of maxillary anterior teeth by combined use of CA and MIA was established, and the 6 mm-height Power Arm, was attached to the canine or appliance. The initial displacement and the maximum von Mises stress of periodontal ligament under three loading conditions were analyzed, namely the force was loaded by CA+150 g retraction force at canine, CA+150 g retraction force on Power Arm at appliance, CA+150 g retraction force on Power Arm at canine. Results In sagittal direction, the crown and root displacement difference of maxillary central incisor was 129, 129, 133 μm，respectively. The crown displacement of the maxillary first molar was -23.3, -23.5, -26.8 μm, respectively. The maximum von Mises stress of periodontal ligament in central incisor was 48.4, 72.6, 40.0 kPa, respectively, and that of the first molar was 5.3, 10.5, 5.8 kPa, respectively. Conclusions It can not be testified that retraction of the 6 mm-height Power Arm at canine or appliance with 5 mm-height mini-screw has more advantages than retraction of the canine directly for more favorably controlling the torque of incisors, saving anchorage of posterior teeth and decreasing von Mises stress of the periodontal ligament.

Clinical efficacy of counterclockwise rotating the functional occlusal plane using micro-implant anchorage / 浙江大学学报·医学版

To evaluate the therapeutic effect of using micro-implant anchorage (MIA) to rotate the functional occlusal plane (FOP) counterclockwise. Forty skeletal class Ⅱ high-angle patients who had completed orthodontic treatment were enrolled, including 20 patients treated with MIA orthodontic system (MIA group) and the other 20 patients treated with traditional sliding straight wire appliance (control group). Cephalometric measurements on the lateral cranial radiographs before and after treatment were performed, all acquired data were statistically analyzed with SPSS 26.0. At the end of treatment, MIA group obtained better effect of FOP and mandibular plane counter-clockwise rotation than the control group. In the MIA group, the average change of FOP-frankfort horizontal plane (FH), FOP-SN and mandibular plane angle (MP-FH) angle was -4.5(-7.3, -3.7)°, (3.3)° and -1.7(-3.0, -0.9)°, respectively. In the control group, the average change of FOP-FH, FOP-SN and MP-FH angle was -0.1(-4.1, 3.0)°, (-0.1±5.1)° and -0.4(-2.4, 0.7)°, respectively. There was significant difference between the change of the two groups (all <0.05). Compared with the traditional sliding straight wire appliance, counterclockwise rotation of FOP can be more effectively reversed by using MIA orthodontic system, and the MP-FH can be reduced as well.

Occlusal reconstruction of a patient with ameloblastoma ablation using alveolar distraction osteogenesis: a case report.

BACKGROUND: Ameloblastoma is one of the most common benign odontogenic neoplasms. Its surgical excision has the potential to lead to postoperative malocclusion. In this case report, we describe the successful interdisciplinary orthodontic treatment of a patient with ameloblastoma who underwent marginal mandibulectomy. CASE PRESENTATION: A woman of 20-year-old was diagnosed with ameloblastoma, and underwent marginal mandibulectomy when she was 8 years of age. She had an excessive overjet (11.5 mm) and a mild open bite (- 1.5 mm) with a severely resorbed atrophic edentulous ridge in the area around the mandibular left lateral incisor, canine and first premolar. An alveolar bone defect associated with tumor resection was regenerated by vertical distraction osteogenesis (DO). Subsequently, 3 dental implants were placed into the reconstructed mandible. Orthodontic treatment using implant-anchored mechanics provided a proper facial profile with significantly improved occlusal function. The occlusion appeared stable for a 7-year retention period. CONCLUSIONS: These results suggest that surgically assisted and implant anchored-orthodontic approaches might be effective for the correction of such malocclusions.

Three-Dimensional Finite Element Analysis on En-Masse Retraction of the Maxillary Anterior Teeth With Quantitative Combined Loading Control.

This study aims to elucidate the biomechanical effects of combined loading of maxillary anterior and posterior implants using the sliding method on en-masse retraction of the anterior teeth and to quantify the loading ratio (LR) of anterior and posterior implants to achieve controlled retraction of the maxillary anterior teeth. A three-dimensional finite element model of the maxilla-upper dentition appliance was constructed. Implants were placed on the distal (A) and mesial (B) sides of the lateral incisors as well as on the mesial (C) side of the first molar and different amounts of force were loaded between the implants using 2- or 5-mm traction hooks. The labiolingual movement of the anterior teeth was recorded and the relationship between the LR of the implants and the movement of the central incisors was evaluated. With 2-mm traction hooks, the central incisors exhibited a translation tendency during retraction at lower A/C and B/C LR and labial or lingual crown inclination at higher values. With 5-mm traction hooks, the central incisors, lateral incisors, and canine teeth exhibited a labial crown inclination. The results of this study suggest that 2-mm traction hooks can cause labial crown inclination, translation tendency during retraction, or lingual crown inclination of the central incisors due to alterations in the LR of the anterior and posterior implants. The central incisors only exhibited labial crown inclination during combined loading of the anterior and posterior implants when 5-mm traction hooks were used.

Biomodulation of an implant for enhanced bone-implant anchorage.

Aseptic loosening of implants is the major cause for revision surgery. By modulating the bone-implant interface, early bone-implant anchorage could be improved. Implant surface manipulation by the addition of osteopromotive molecules locally and systemically to promote implant integration has been described with limited success. This study describes a novel approach by making the implant capable of biologically modulating its surroundings. It was hypothesized that the early implant fixation would improve by filling the interior of the implant with a carrier providing spatio-temporal release of bone active drugs with known osteogenic effect. The implant consisted of a threaded polyether ether ketone (PEEK) hollow chamber with holes at the bottom. The implant was filled with a calcium sulphate (CaS)/hydroxyapatite (HA) carrier, delivering two bone active molecules; zoledronic acid (ZA) and bone morphogenic protein-2 (BMP-2). At first, a rat abdominal muscle pouch model indicated a sustained in-vivo release of both 125I-rhBMP-2 (57%) and 14C-ZA (22%) from the CaS/HA carrier over a period of 4-weeks. The biomodulated implant was then inserted in the proximal tibia in rats with the following experimental groups: G1) Empty implant, G2) Implant + CaS/HA, G3) Implant + CaS/HA + ZA and G4) Implant + CaS/HA + ZA + rhBMP-2. Significantly higher bone volume (BV) was seen around the implant in groups G3 (3.3 ±â€¯0.7 mm3) and G4 (3.1 ±â€¯0.7 mm3) compared to the control (1.3 ±â€¯0.4 mm3) using micro-computed tomography and qualitative histology. Group G3, also exhibited significantly higher pull-out force and absorbed energy when compared to the control group G1. These findings indicate that a low dose of ZA alone, released in a controlled manner from within a fenestrated implant is enough to improve implant anchorage without the need of adding rhBMP-2. This simple method of using a fenestrated implant containing a ceramic carrier releasing bone active molecules improved bone anchorage and could clinically reduce prosthetic failure. STATEMENT OF SIGNIFICANCE: Aseptic loosening remains as a major cause for implant revisions and early reaction of surrounding bone to the prosthesis is important for longevity. A novel approach to enhance early bone-implant anchorage is presented. The implant is filled with a carrier providing controlled release of bone active molecules. In an animal model, a calcium sulphate (CaS)/hydroxyapatite (HA) carrier was used to provide a spatio-temporal release of bone morphogenic protein-2 (BMP-2) and zoledronic acid (ZA). Significantly better bone-implant integration was achieved using ZA alone, thereby eliminating the need for adding BMP-2. The developed method of implant biomodulation holds potential to prevent implant loosening and is an alternative to prosthetic coatings or systemic drug treatment. Importantly, all constituents are approved for clinical use.

Finite element analysis of torque control efficiency of a homemade four-curved auxiliary arch for anterior teeth / 口腔疾病防治

Objective @#To analyze the initial displacement of the upper central incisor and stress distribution of periodontal ligament under different torque values of upper incisors under the action of a four-curved auxiliary arch to provide a reliable basis for the safety of clinical application of four-curved auxiliary arches.@*Methods @# A three-dimensional finite element model for torque control of upper anterior teeth with a homemade quadrilateral auxiliary arch was established. Four different states were analyzed: molar ligation without extraction space (group A), microimplant ligation without extraction space (group B), molar recovery with extraction space closure (group C) (the adductive traction force was set at 115 g) and microimplant recovery with extraction space closure (group D) (the adductive traction force was set at 115 g). When four types of torque (0.5 N, 1.0 N, 1.5 N, and 2.0 N) were applied. The initial displacement of upper central incisors and the stress distribution of periodontal ligament in 16 groups (A1-A4, B1-B4, C1-C4, D1-D4) were observed.@*Results @#Under different conditions, as the strength of the four-curve auxiliary arch increases, the maxillary anterior teeth has crown labial inclination and a root lingual inclination. The displacement of the incisor tip increases with the increase in the loading force of the torque auxiliary arch, and the displacement of the incisor root apex increases as the force increases. The difference in incisor-apex displacement distance in A1-A4, B1-B4, C1-C4, D2 and D4 groups increased as the torque force increases, while the difference between the D3 group and D1 and D2 groups decreased slightly. The stress of the cervical periodontal ligament of the upper central incisor did not exceed the stress of the periodontal ligament in the following groups: A1, A2, B1, B2, B3, C1, C2, D1, and D2. The stress of the lip side of the upper central incisor did exceed the stress of the periodontal ligament in the following groups: A3, A4, B4, C3, C4, D3, and D4. In other words, when using the four-curved auxiliary arch as an implant anchorage, the force applied in the absence of extraction space should not exceed 1.5 N, and the force applied in the adduction of extraction space should not exceed 1.0 N. When using the nonimplant anchorage, the force applied in the absence of extraction space and the adduction of extraction space should not exceed 1.0 N. In addition, the range of force should not exceed the maximum stress of the periodontal ligament in the cervical region such that the effective and safe torque movement can be achieved. Under other stress conditions, the stress of the labial and cervical periodontal ligament of the upper central incisor exceeded the stress value (2.6 × 10-2MPa). The stress value of periodontal ligament was 2.6 × 10-2MPa in all groups.@*Conclusion@#A four-curved auxiliary arch has a significant effect on the upper anterior teeth, and the use of microimplants can better control root movement such that the crown of upper central incisors cannot be excessively lip inclined.

Combined use of miniscrews and clear aligner for en-mass retraction of maxillary anterior teeth: A finite element analysis / 实用口腔医学杂志

Objective: To evaluate the biomechanical effects of combined use of miniscrew and clear aligner in different kinds of loading condition on the en-mass retraction of maxillary anterior teeth. Methods: 3 D finite element models of the maxillary bone with miniscrews and clear aligner were reconstructed using the method of reverse engineering with CBCT data of an adult patient who had maxillary first premolars extracted. The orthodontic force was loaded by (1) clear aligner, (2) clear aligner and 1. 47 N force of retraction at appliance and (3) clear aligner and 1. 47 N force of retraction at canine, respectively. Results: Under the working condition of (1), (2) and (3), in sagittal direction, the displacement difference of crown and root of the maxillary central incisor was 1. 12 E-02 mm, 1. 29 E-02 mm and 9. 62 E-03 mm respectively, the displacement of the first molar crown was-2. 49 E-02 mm, -2. 09 E-02 mm and-2. 00 E-02 mm respectively; in vertical direction, extrusion of the maxillary central incisor was 1. 77 E-03 mm, 2. 93 E-03 mm and 6. 53 E-04 mm respectively. Conclusion: The working condition (3) is more advantageous to control the torque of incisors and to save the anchorage of posterior teeth, and more effective to control the extrusion of the incisors.

CBCT study of the alveolar bone remodeling after retraction of the maxillary incisors assisting with micro-implant anchorage in maxillary protrusion adults / 口腔疾病防治

Objective@# To study the remodeling of alveolar bone after retraction of the maxillary incisors assisting with micro-implant anchorage in adult patients with maxillary protrusion by CBCT.@*Methods@#Forty patients who were treated with extraction of the maxillary first premolars with microimplant anchorage meeting the inclusion criteria were selected. The CBCT data before and after treatment were collected, and the Dolphin Imaging 3D measurement software was used to measure and analyze the height and thickness of the alveolar bone of the 80 upper central incisors and the 80 lateral incisors.@*Results @#After retraction of the incisors assisting with microimplant anchorage, the labial alveolar bone height of the maxillary central incisors decreased (0.11 ± 0.33) mm, and the lingual alveolar bone height of the maxillary central incisors decreased (0.85 ± 1.23) mm. The labial alveolar bone height of the maxillary lateral incisors decreased (0.18 ± 0.42) mm, and the lingual alveolar bone height of the maxillary lateral incisors decreased (1.13 ± 1.14 ) mm. The reduction in the lingual alveolar bone height was greater than that of the labial side, and the difference was statistically significant (P < 0.05). The labial alveolar bone thickness of the maxillary central incisors increased (the root cervix, the root media and the root apex), and the difference was statistically significant (P < 0.001). The labial alveolar bone thickness of the maxillary lateral incisors also increased (P < 0.05), while the lingual alveolar bone thickness and the total alveolar bone thickness of the maxillary central and lateral incisors decreased (P < 0.001). @*Conclusion@#In adults with maxillary protrusion, the microimplant was used to assist the reduction of the anterior teeth. The alveolar bone height of the maxillary incisors was reduced, and the palatal alveolar bone height decreased more than that of the labial side. The alveolar bone of the labrum was thickened, and the palatal alveolar bone thickness and the total alveolar bone thickness of the maxillary incisors were reduced after treatment.

Bone remodeling and mechanobiology around implants: Insights from small animal imaging.

Anchorage of orthopedic implants depends on the interfacial bonding between the implant and the host bone as well as on the mass and microstructure of peri-implant bone, with all these factors being continuously regulated by the biological process of bone (re)modeling. In osteoporotic bone, implant integration may be jeopardized not only by lower peri-implant bone quality but also by reduced intrinsic regeneration ability. The first aim of this review is to provide a critical overview of the influence of osteoporosis on bone regeneration post-implantation. Mechanical stimulation can trigger bone formation and inhibit bone resorption; thus, judicious administration of mechanical loading can be used as an effective non-pharmacological treatment to enhance implant anchorage. Our second aim is to report recent achievements on the application of external mechanical stimulation to improve the quantity of peri-implant bone. The review focuses on peri-implant bone changes in osteoporotic conditions and following mechanical loading, prevalently using small animals and in vivo monitoring approaches. We intend to demonstrate the necessity to reveal new biological information on peri-implant bone mechanobiology to better target implant anchorage and fracture fixation in osteoporotic conditions. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:584-593, 2018.