Direct Anchorage Research Articles

Space Closure with Different Appointment Intervals: A Split-mouth Randomized Controlled Trial.

Canine retraction has been successful with various force systems and retraction techniques. The appointment interval for force reactivation in canine retraction along the archwire is 4-8 weeks. The aim was to evaluate the effect of different reactivation intervals on the rate of space closure. This split-mouth randomized clinical trial recruited 38 patients indicated for the first premolar extraction. Monthly digital models were acquired for 6 months. The first premolars were extracted, and temporary anchorage devices were placed for maximum anchorage control. The canines were retracted using elastomeric chains which were replaced every 2, 4, 6, or 8 weeks. The monthly rate of canine retraction was measured. The time to space closure was calculated. The secondary outcome was the mesial drift of the first molars. The Kaplan-Meier survival analysis and the Friedman test evaluated and compared the groups. There was no significant difference between the monthly canine retraction rate or the first molar mesial drift between the groups. The mean time to space closure was 5.74 months in the 2-week reactivation group, which was statistically less than the other groups. The 2-week reactivation interval may reduce time to space closure. Direct anchorage control with miniscrews limited anchorage loss significantly.

Unilateral mesialisation using Temporary anchorage device and segmental T loop – A case report

A temporary anchorage device is a device that is temporarily fixed to bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and which is subsequently removed after use. Use of mini implants is one of the innovative approach for complex tooth movements such as mesialisation. Space closure from distal to mesial is one of the most difficult orthodontic tasks. Tooth-borne anchorage limits the scale of tooth movement. Extraoral or intraoral appliances are used especially for unilateral space closure. As an alternative to conventional mesialization appliances, osseointegrated implants may be used for maximum anchorage in orthodontic treatment. The use of direct anchorage in the form of installed mini-implant that is connected to the teeth requiring horizontal movement causes low levels of strains on anchor unit comparing to the results that were registered during indirect anchorage with one or two anchor teeth. This report presents the case of removal of mesiodens and blocked out and fractured premolar and the space closure by unilateral mesialisation with the help of mini implants and loops.

Quantitative Evaluation of Pentraxin-3 in Peri-Miniscrew Implant Crevicular Fluid in Patients Undergoing Orthodontic Treatment: A Prospective Study.

To assess the levels of Pentraxin-3 (PTX3) in peri-miniscrew implant crevicular fluid (PMICF) before and after orthodontic force application Material and Methods: This study included 40 miniscrew implants (MSI) sites in 11 orthodontic patients with high arch discrepancy requiring first premolar extraction using maximum anchorage mechanics for the retraction of anterior teeth. After alignment, the en-masse anterior retraction was carried out using the MSI-supported direct anchorage method. PMICF was collected from the crevice of MSI using Periopaper strips 1.2µl (OraflowInc. USA) after one hour, 24 hours, and three weeks of MSI insertion and after one hour, 24 hours, seven days, three weeks, and six weeks of the force application. Samples were quantitatively analyzed for PTX3 levels through enzyme-linked immunosorbent assay (ELISA). The trend in the change of PTX3 levels was evaluated using the Wilcoxon signed-rank test. The mean concentration of PTX3 immediately after MSI insertion was 1.19 ng/ml, significantly higher than after 3 weeks after MSI insertion (0.72 ng/ml), which may correspond to the baseline. After loading, the mean PTX3 concentration increased significantly with the peak at 24 hrs (1.28 ng/ml), followed by a gradual decline till the completion of the study (0.5 ng/ml). After MSI insertion, a rise in PTX3 levels in PMICF suggests an underlying inflammatory process. The slow decline in PTX3 level and return to the baseline after loading suggests an adaptive bone response to the stimulus.

Factorial analysis of variables affecting bone stress adjacent to mini-implants used for molar distalization by direct anchorage—A finite element study

The aim of this study was to investigate the stresses on mini-implant, cortical bone, and cancellous bone for maxillary molar distalization using an orthodontic implant in a finite element model for different angulations and depths of insertion.A three-dimensional finite element method was used to simulate overall orthodontic tooth movements by using ANSYS software. The maxillary bone and the molars were reproduced using CT scan images and conversion of the same into STL file was done. Finite element model was generated and the effect of forces was studied on the model for different depths and angulations of mini-implant insertions. The distalization force was exerted by an open-coil spring and the direct skeletal anchorage was provided by a mini-implant. Mini-implants were placed in depths of 5 mm, 7 mm, and 9 mm inside the bone and insertion angles of 30°, 60°, and 90°. Stresses on mini-implant and extent of stress on the surrounding bone were assessed by the software.1. Least stress was found when the mini-implant was inserted at an angle of 30°, as it is nearer to the stronger cortical bone. 2. As the length of the mini-implant increases, accompanied by the increase in the depth of insertion, a decrease in stress in the mini-implant, cortical bone, and cancellous bone was noticed.An increase in the insertion angle from 30° to 90° increases the stresses on both the implant and the cortical bone. A higher depth of thread in the bone helps in reducing the stress on the implant, cortical bone, and cancellous bone. This helps in improving the primary stability of the mini-implant and its life.

Different biomechanical effects of clear aligners in bimaxillary space closure under two strong anchorages: finite element analysis

BackgroundClear aligner (CA) treatment has been gaining popularity, but the biomechanical effects of CAs in bimaxillary dentition have not been thoroughly investigated. Direct and indirect strong anchorages are two common anchorage control methods, but the underlying biomechanical mechanism has not yet been elucidated. This study aimed to investigate the different biomechanical effects of CAs in closing the bimaxillary space under different anchorage controls, further instructing the compensation strategies design and strong anchorage choice in clinical practice.MethodsThree-dimensional (3D) bimaxillary models of different anchorage controls were created based on cone-beam computed tomography and intraoral scan data. Four first premolars were extracted using 3D modeling software. Finite element analysis was conducted to simulate the space closure process of the CAs.ResultsIn the two strong anchorage groups, the bimaxillary dentition presented different movement patterns during the space closure process, and the lower dentition was more vulnerable to elastic force. From the vertical view, direct strong anchorage with elastic force had the advantage of flattening the longitudinal occlusal curve and resisting the roller-coaster effects, whereas indirect strong anchorage could lead to a deep longitudinal occlusal curve. From the sagittal view, indirect strong anchorage with metallic ligaments had a greater instantaneous anchorage protection effect, particularly in the lower dentition, which reduced the mesial movement of the posterior teeth by nearly four times that of the direct anchorage group. In addition, indirect strong anchorage presented better anterior teeth torque/tipping control, while direct strong anchorage could aggravate lingual tipping of the upper central incisors. Due to the differences in anterior–posterior anchorage and arch shape, compared with the upper dentition, anchorage preservation and vertical control effects were amplified in the lower dentition.ConclusionsThe biomechanical effects of CAs differed between the two strong anchorage groups. Due to the differences in dentition morphology, anterior–posterior anchorage, and dental arch shape, CAs present different biomechanical effects in bimaxillary space closure. Orthodontists should consider the corresponding mechanical compensation according to specific anchorage control methods and dentitions.

Treatment of Palatally Displaced Canines Using Miniscrews for Direct or Indirect Anchorage: A Three-Dimensional Prospective Cohort Study on Tooth Movement Speed

Palatally impacted canines are usually challenging to treat in terms of both biomechanics and possible side effects. Different therapeutic approaches have been reported with or without the use of temporary anchorage devices, including the canine-first approach. Two groups of patients with palatally impacted canines were compared, observing their canine movement measured on consecutive CBCTs after three months of treatment. In the control group, impacted canines were treated with direct anchorage on miniscrews, and in the test group with indirect anchorage using a miniscrew-supported transpalatal arch. The primary outcome was the canine movement speed; the secondary outcome was the change in the root length of adjacent teeth. The median monthly apex speed was 1.05 mm in the control group (IR [0.74, 1.64]) and 0.72 mm in the test group (IR [0.27, 1.30]). The median monthly cusp displacement was 1.89 mm in the control group (IR [1.04, 2.84]) and 1.08 mm in the test group (IR [0.81, 1.91]). Approximately 50% of teeth adjacent to an impacted canine underwent a negative root length change of less than 1 mm in the majority of cases, but no significant differences were found in root length changes between groups. No statistically significant differences in the reported speeds were found, and no miniscrew failures were observed in either group.

Effects of Rigid and Nonrigid Connections between the Miniscrew and Anchorage Tooth on Dynamics, Efficacy, and Adverse Effects of Maxillary Second Molar Protraction: A Finite Element Analysis.

Introduction Direct, rigid indirect, and nonrigid indirect absolute anchorages using temporary anchorage devices (TADs, mini-implants/miniscrews) can provide promising opportunities for challenging, yet common, orthodontic tooth movements such as molar protraction. Rigid rectangular wire and ligature wire are the most common methods of attaching a tooth to a miniscrew in indirect anchorages. We aimed to provide a comparison of the rigidity of the connecting wire in terms of stress on the miniscrew, the anchorage loss, and the risk of root resorption using finite element analysis (FEA). Methods The maxillary right second molar was protracted into the proximal space at a 150 g load (1) using direct absolute anchorage with a tapered miniscrew implanted between the premolar roots and using indirect absolute anchorage with the second premolar reinforced by the miniscrew through (2) a rigid stainless steel (SS) wire or (3) a nonrigid SS ligature wire (4) at different elastic moduli. Stresses and displacements of 4 models' elements were measured. The risk of external root resorption was evaluated. Results Connecting the tooth to the miniscrew using rigid full-size wire (model 2) compared to ligature (model 3) can give better control of the anchorage (using the ligature wire, the anchorage loss is 1.5 times larger than the rectangular wire) and may reduce the risk of root resorption of the anchorage unit. However, the risk of miniscrew failure increases with a rigid connection, although it is still lower than with direct anchorage. The miniscrew stress when using a ligature is approximately 30% of the rigid model using the rectangular wire. The miniscrew stress using the rectangular wire is approximately 82.4% of the miniscrew stress in the direct model. Parametric analysis shows that the higher the elastic modulus of the miniscrew-tooth connecting wire in the indirect anchorage, the less the anchorage loss/palatal rotation of the premolars/and the risk of root resorption of the anchorage teeth and instead the stress on the miniscrew increases. Conclusions Direct anchorage (followed by rigid indirect anchorage but not nonrigid) might be recommended when the premolars should not be moved or premolar root resorption is a concern. Miniscrew loosening risk might be the highest in direct anchorage and lowest in nonrigid indirect anchorage (which might be recommended for poor bone densities).

Biomechanical compensations during a stand-to-sit maneuver using transfemoral osseointegrated prostheses: A case series

BackgroundPatients with transfemoral amputation and socket prostheses are at a heightened risk of developing musculoskeletal overuse injuries, commonly due to altered joint biomechanics. Osseointegrated prostheses, which involve direct anchorage of the prosthesis to the residual limb through a bone anchored prosthesis, are a novel alternative to sockets yet their biomechanical effect is largely unknown. MethodsFour patients scheduled to undergo unilateral transfemoral prosthesis osseointegration completed two data collections (baseline with socket prosthesis and 12-months after prosthesis osseointegration) in which whole-body kinematics and ground reaction forces were collected during stand-to-sit tasks. Trunk, pelvis, and hip kinematics, and the surrounding muscle forces, were calculated using subject-specific musculoskeletal models developed in OpenSim. Peak joint angles and muscle forces were compared between timepoints using Cohen's d effect sizes. FindingsCompared to baseline with socket prostheses, patients with osseointegrated prostheses demonstrated reduced lateral trunk bending (d = 1.46), pelvic obliquity (d = 1.09), and rotation (d = 1.77) toward the amputated limb during the stand to sit task. This was accompanied by increased amputated limb hip flexor, abductor, and rotator muscle forces (d> > 0.8). InterpretationImproved lumbopelvic movement patterns and stabilizing muscle forces when using an osseointegrated prosthesis indicate that this novel prosthesis type likely reduces the risk of the development and/or progression of overuse injuries, such as low back pain and osteoarthritis. We attribute the increased muscle hip muscle forces to the increased load transmission between the osseointegrated prosthesis and residual limb, which allows a greater eccentric ability of the amputated limb to control lowering during the stand-to-sit task.

Electron-microscopic study on structural changes of mini-implants following fixed orthodontic treatment

In today's society, patients who turn to the orthodontist want final results in the shortest possible time, with maximum emphasis on smile aesthetics, dental alignment and facial harmony. In this regard, some procedures have emerged to accelerate the movement of teeth through the alveolar bone, thus shortening the duration of active treatment: corticotomy, application of mini-implants, etc. Of these methods, bone anchorage on mini-implants is increasingly popular among adult patients, as it is a versatile technique that ensures a stable, bony anchorage and more predictable final results. Compared to implantology in prosthodontics, which has a long history, mini- orthodontic implants emerged later in medical practice. In 1998, Shapiro and Kokich described for the first time the possibility of using dental implants for anchorage in orthodontic therapy. Odman J et al. (Upsala University, Sweden) applied implants to patients with partial edentulousness. The results were favorable, leading the authors to recommend the technique for adult partial edentulousness. Kanomi (1997) showed that a 1.2 mm diameter titanium mini- implant provides anchorage for the intrusion of the lower front teeth. After 4 months, the mandibular incisors were intruded by 6 mm without root resorption. Birte Melsen et al. (1998) introduced the use of zygomatic ligatures as anchorage in patients with partial edentulousness. To this they attached nickel-titanium springs for intrusion and retraction of maxillary incisors. Hugo de Clerk (2008) used 4 mini-implants (Bollard type) inserted into the infra-zygomatic crest in patients with Angle class III anomalies. He used 2 mini-implants with hooks in the chin area, and patients wore Class III 150 grams elastics on each side. This direct anchorage also has orthopedic effects, with clinicians achieving upper jaw advancement and correction of mandibular prognathism.

The Effectiveness of Conventional and Accelerated Methods of Orthodontic Traction and Alignment of Palatally Impacted Canines in Terms of Treatment Time, Velocity of Tooth Movement, Periodontal, and Patient-Reported Outcomes: A Systematic Review.

The objective of the current review was to evaluate the effectiveness of traditional and accelerated methods of palatally impacted canine's (PIC) traction in terms of treatment duration, velocity, periodontal, and patient-reported variables.An electronic search for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) published between January 1990 and October 2021 was conducted in nine databases. Five major orthodontic journals were hand searched for additional studies. The participants were patients with unilateral or bilateral PICs who received conventional or accelerated orthodontic treatment with fixed appliances. Cochrane’s risk of bias tool (RoB 2 tool) for RCTs and ROBINS-I tool for CCTs were used to assess the risk of bias. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) guidelines were used to assess the overall quality of the evidence.Nine articles (eight RCTs and one CCT) were included in this review (371 patients). There was no clarity in most studies about the possible effect of the mechanical traction method on treatment outcomes. The treatment duration decreased (about three to six months) when the open surgical method was used with traditional techniques and the traction velocity increased significantly (about 1-1.5 mm/month) when acceleration methods were used. No significant differences were found between the conventional intervention groups, as well as between the traditional and accelerated groups, in terms of most periodontal variables (p > 0.005).No significant differences were found in the pain levels associated with traditional PICs' traction when comparing different exposure methods in the short-term follow-up (1-10 days), while contradictory results were found in the pain incidence between these methods. The relationship between the pain/discomfort levels and the type of mechanical traction method was not evaluated. According to the GRADE, the quality of evidence supporting these findings ranged from low to very low.The combination of the open surgical technique with various designs of either superelastic wires or elastic traction means can lead to a reduction in the orthodontic treatment duration of PICs. The use of direct anchorage by miniscrews to move the PICs away from the adjacent teeth roots can lead to a reduction in root resorption and shorten the treatment duration. The evidence supporting these findings ranged from low to very low. The use of different types of mechanical means for conventional PICs' traction, with the use of open or closed traction techniques, does not lead to significant differences in periodontal outcomes between intervention groups. Contradictory results exist regarding the severity of the perceived pain in relation to the surgical exposure type, and the relationship between this variable and the mechanical traction method is still unclear. The use of accelerated methods for PICs' traction can lead to an increase in the velocity of traction movement with no significant differences in periodontal outcomes between accelerated and conventional methods. The evidence supporting these findings ranged from low to very low. More high-quality randomized CCTs are needed to establish good evidence in this field.The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42021274476) during the first stages of this review.

Evaluation of maxillary first molar rotation during direct miniscrew-supported maxillary canine retraction: a before-and-after study

BackgroundExtraction of the first premolar followed by canine retraction into the extraction space is a common treatment in orthodontics. Molar rotation occurs when they are used as anchorage units for the canine distalization. The aim of this single-arm clinical trial was to evaluate the maxillary first molar rotation during maxillary canine retraction with elastic power chains and direct miniscrew anchorage.ResultsThe mean difference between pre-retraction and post-retraction molar rotation was 1.89° ± 0.6 which was statistically insignificant.ConclusionThe use of miniscrews for direct anchorage can eliminate unwanted rotation of the maxillary first molars during canine retraction.Trial registration ClinicalTrials.gov, NCT04887974. Registered on May 6, 2021- Retrospectively registered https://clinicaltrials.gov/ct2/show/NCT04887974?id=NCT04887974&draw=2&rank=1.

Comparison of the efficacy of two-time versus one-time micro-osteoperforation on maxillary canine retraction in orthodontic patients: A split-mouth randomized controlled clinical trial

Micro-osteoperforation (MOP), a minimally invasive technique for accelerating the rate of orthodontic tooth movement has been research extensively, but with varied clinical results. To compare the efficacy of one-time versus two-time micro-osteoperforation on the rate of maxillary canine retraction, its influence on anchorage loss, canine angulation and the levels of interleukin (IL-1β) in gingival crevicular fluid (GCF). The split-mouth study included 16 patients in which the left and right sides were randomly allocated to the control side (one-time MOP) and experimental side (two-time MOP). MOP was performed on both sides distal to the maxillary canines and canine retraction was carried out using NiTi closed coil springs (150gm) and direct anchorage with miniscrew implants. The second MOP was performed on experimental side one month after the first MOP. The rate of canine movement was assessed using 3D model superimposition over a period of six months. The type of tooth movement, anchorage loss and levels of IL-1β were also evaluated. Sixteen patients (mean age, 17.87±3.34 years) were analysed for a rate of canine retraction, anchorage loss, and type of tooth movement, while 15 patients were analysed for IL-1β. The rate was significantly higher on two-time MOP side after two months (P<0.001). No statistical difference was found in anchorage loss and controlled tipping of canines was observed. The IL-1β levels immediately after 2nd MOP were significantly higher than 1st MOP (P<0.001). The two-time intervention of MOP is more efficacious than one-time MOP in accelerating tooth movement.

Biomechanics of mini-implants: analysis of the adverse effects of four clinical situations and proposed resolutions

The biomechanical adverse effects generated by our treatments must be considered among the failures of mini-implants, certainly excellent means of anchorage. The aim of this article was to illustrate and comment on mechanical adverse effects and to propose solutions. Four common clinical situations in vestibular technique are analyzed, decomposed three-dimensionally and solved. Maxillary incisor intrusion in direct traction (mini-implant between lateral incisors and canines in direct anchorage) can lead to a disto-labial rotation of the supporting teeth and an incisor flaring. Maxillary incisivo-canine retraction (mini-implant between 5 and 6 in direct anchorage) leads to a canine rotation, a clockwise rotation of the occlusal plane and a version of the adjacent teeth. The maxillary molar two-steps distalization (mini-implant between 5 and 6 with metal ligation to the canine) causes a rotation of the adjacent to the spring teeth, an incisor flaring and a molar disto-version. The protraction of a mandibular molar (mini-implant between 3 and 4 in direct anchorage) causes a disto-labial rotation, a lingual torque and a mesio-version of the molar as well as an incisor flaring and a clockwise rotation of the occlusal plan. The compensation bends on the adjacent teeth, the choice of the location and the type of mini-implant, the use of a power arms to get closer to the center of resistance are among the means of resolution. If mini-implants anchorage allows a significant quantitative effect, adverse effects should be considered individually with a three-dimensional biomechanical analysis.

Consideraţii privind osteointegrarea implanturilor dentare endoosoase

Implant osseointegration has not been accepted over time, considering that in fact the implant integration is performed only in the soft tissue of the host. For this reason, the implant has never been sufficiently integrated into the host tissue immediately after insertion. Experiments performed in Branemark laboratories in the early 1960s, with a new type of implant, which required a direct anchorage to bone tissue for clinical function, this anchorage was called osseointegration. It has been shown that it is possible to achieve direct osseointegration if the Branemark method is considered, which was published a few years later in the first clinical report. The authors of this article come up with new contributions that validate the implant osseointegration process. Inside this article we present our methodology for evaluating the osseointegration of endosseous implants: ESEM (environmental scanning electron microscope) studies of the implant-bone tissue interface.

Ten years of miniscrew use in a U.S. orthodontic residency program

Orthodontic miniscrews have become popular not only because they can provide an absolute form of anchorage, but also because they can reduce the required patient compliance when compared with traditional orthodontic anchorage. The objective of this study was to examine success rates of miniscrews placed by orthodontic residents and to evaluate which factors may affect insertion outcomes. The sample consisted of 109 consecutive miniscrews placed in 60 patients (27 males and 33 females). Miniscrews were placed at 4 different insertion sites (anterior palate [n=31], palatal alveolar process [n=25], maxillary buccal alveolar process [n=15], and mandibular buccal alveolar process [n=38]). Analysis of variance tests were used to evaluate the influence of insertion sites and anchorage type (direct vs indirect) on the success rate. The overall success rate for miniscrews was 72.5%. The success rate was 83.9% in the anterior palate, 76% in the palatal alveolar process, 60% in the maxillary buccal alveolar process, and 65.8% in the mandibular buccal alveolar process. The success rate was significantly higher in indirect anchorage (84.2%) compared with direct anchorage (58.8%). Palatal miniscrews were more successful than buccal miniscrews. Indirect anchorage mechanics had a higher success rate than direct anchorage mechanics.

Nanostructured pencil graphite electrodes for application as high power biocathodes in miniaturized biofuel cells and bio-batteries

This work describes a simple method for the fabrication of an enzymatic electrode with high sensitivity to oxygen and good performance when applied as biocathode. Pencil graphite electrodes (PGE) were chosen as disposable transducers given their availability and good electrochemical response. After electrochemical characterization regarding hardness and surface pre-treatment suited modification with carbon-based nanostructures, namely with reduced graphene, MWCNT and carbon black for optimal performance was proceeded. The bioelectrode was finally assembled through immobilization of bilirubin oxidase (BOx) lashed on the modified surface of MWCNT via π–π stacking and amide bond functionalization. The high sensitivity towards dissolved oxygen of 648 ± 51 µA mM−1 cm−2, and a LOD of 1.7 µM, was achieved for the PGE with surface previously modified with reduced graphene (rGO), almost the double registered for direct anchorage on the bare PGE surface. Polarization curves resulted in an open circuit potential (OCP) of 1.68 V (vs Zn electrode) and generated a maximum current density of about 650 μA cm−2 in O2 saturated solution.

Orthopaedic osseointegration: Implantology and future directions.

Osseointegration (OI) is the direct anchorage of a metal implant into bone, allowing for the connection of an external prosthesis to the skeleton. Osseointegration was first discovered in the 1960s based on the microscopic analysis of titanium implant placed into host bone. New bone was observed to attach directly to the metal surface. Following clinical investigations into dentistry applications, OI was adapted to treat extremity amputations. These bone anchored implants, which penetrate the skin and soft tissues, eliminate many of the challenges of conventional prosthetic sockets, such as poor fit and suspension, skin breakdown, and pain. Osseointegrated implants show promise to improve prosthesis use, pain, and function for amputees. The successful process of transcutaneous metal integration into host bone requires three synergistic systems: the host bone, the metal implant, and the skin-implant interface. All three systems must be optimized for successful incorporation and longevity of the implant. Osseointegration begins during surgical implantation of the metal components through a complex interplay of cellular mechanisms. While implants can vary in design-including the original screw, press fit implants, and compressive osseointegration-they face common challenges to successful integration and maintenance of fixation within the host bone. Overcoming these challenges requires the understanding of the complex interactions between each element of OI. This review outlines (a) the basic components of OI, (b) the science behind both the bone-implant and the skin-implant interfaces, (c) the current challenges of OI, and (d) future opportunities within the field.

Two distalization methods compared in a novel patient-specific finite element analysis.

Orthodontic mini-implants aid in the correction of distocclusions via direct anchorage (pull from mini-implant to teeth) and indirect anchorage (teeth pulled against other teeth anchored by the mini-implant). The aim of this study was to compare stress levels on the periodontal ligament (PDL) of maxillary buccal teeth in direct and indirect distalization against orthodontic mini-implants and accounting for individual variation in maxillary anatomy and biomechanical characteristics of the compact bone. A 3D model of the maxilla containing the different components (teeth, PDL, trabecular and cortical bones) was generated from a computed tomographic scan. Cortical bone was divided into several areas according to previously defined zones. Bone stiffness and thickness data, obtained from 11 and 12 cadavers, respectively, were incorporated into the initial model to simulate the individual cortical bone variation at the different locations. Subsequently, a finite element analysis was used to simulate the distalization modalities. Stresses at the buccal, palatal, mesial, and distal surfaces were significantly different between adjacent teeth under stiffness but not thickness variation. In both distalization modalities, low or no significant correlations were found between stress values and corresponding cortical bone thicknesses. High significant and inverted correlations were observed at the first molar between stress amounts and cortical bone stiffness (direct modality: -0.68<r<-0.72; indirect modality: -0.80<r<-0.82; P<0.05). With the use of a novel finite element approach that integrated human data on variations in bone properties, findings suggested that cortical bone stiffness may influence tooth movement more than bone thickness. Significant clinical implications could be related to these findings.

Anchorage reinforcement with miniscrews and molar blocks in adolescents: A randomized controlled trial

Anchorage can be reinforced in many ways. Due to the variety of anchorage concepts, only a few general conclusions can be drawn. Therefore, more research is needed to investigate specific concepts with specific indications. The objective of this trial was to compare the anchorage capacities of miniscrews and molar blocks. This randomized controlled trial was conducted on 2 parallel arms. The trial was conducted at the Public Dental Service Orthodontic Clinic in Gävle, Sweden. Participants were adolescents who needed orthodontic treatment with a fixed appliance, extraction of the maxillary first premolars, and anchorage reinforcement. In group A, miniscrews were used as direct anchorage during space closure. In group B, molar blocks were used as anchorage reinforcement during leveling and alignment and space closure. The primary outcome was loss of anchorage assessed as maxillary first molar movement. Random allocation was maintained with a simple randomization stratified by sex. The observer was blinded to the allocations during the measurements. Forty participants each were randomized to groups A and B. Results were analyzed on an intention-to-treat basis, meaning that all participants, successful or not, were included in the analysis. Group A showed a mean anchorage loss of 1.2mm during leveling and alignment. During space closure with miniscrews, no significant anchorage loss was found. Group B showed mean anchorage losses of 1.4mm during leveling and alignment and 2.4mm during space closure. No serious harms were detected. The first molar rotation, torque, and tipping showed different characteristics during the treatment phases. Miniscrews can be recommended for anchorage reinforcement. Depending on the need for anchorage reinforcement, miniscrews can be inserted at the beginning of treatment or when space closure starts. Molar blocks cannot be recommended for anchorage reinforcement. This trial was registered at www.clinicaltrials.gov (NCT02644811). The protocol was published after trial commencement. This trial received funding from the Center for Research and Development, Uppsala University/Region Gävleborg; Thuréus Foundation for the Promotion of Dental Science; and the Swedish Dental Associations Scientific Funds.

Mandibular anterior intrusion using miniscrews for skeletal anchorage: A 3-dimensional finite element analysis.

Deepbites can be corrected by intrusion of mandibular anterior teeth. Direct anchorage with miniscrews simplifies complex tooth movements; however, few studies have reported their use for mandibular anterior intrusion. The purpose of this study was to evaluate, by means of the finite element method, initial tooth displacement and periodontal stress distribution using various mandibular anterior intrusion mechanics. Miniscrews were used as skeletal anchorage devices. Cone-beam computed tomography scans were used for 3-dimensional reconstruction of the mandible and the mandibular anterior dentition. Models included the 4 incisors with or without the canines. After all surroundingperiodontal and bony structures were determined brackets, segmental archwires, and miniscrews were added. Finite element studies were performed to assess initial tooth displacement and periodontal stress distribution with multiple intrusion force vectors. Changes in the location of the miniscrews and loading points on the archwire created 14 scenarios. Minimum buccolingual displacements, a uniform distribution of periodontal stress, and overall group intrusion for both 4-tooth and 6-tooth scenarios were best achieved when applying distointrusive vectors. The highest peaks of periodontal stress were observed when the force was directed at the corners of the segmental archwire. It was found that, in addition to distointrusive vectors, 4 loading points on the archwire were necessary for pure intrusion and uniform distribution of periodontal stress in the 6-tooth scenarios. The simulations in this study suggest that group intrusion of all 6 mandibular anterior teeth might be achieved by applying distointrusive vectors. Inserting a pair of miniscrews distal to the canine roots, 1 screw per side, and directing 4 loading points on the archwire generates uniform periodontal stress distribution and minimum buccolingual displacements. Local conditions, such as narrow bone width and attached gingiva level, play significant roles in the clinical viability of the proposed virtual scenarios.