Miniscrew implants: The Aarhus anchorage system

A biomechanical investigation of miniscrews placed on a mandible for temporary anchorage; a patient-specific finite element analysis

Miniscrews are temporary skeletal anchorage devices that are widely used in orthodontic treatment, and their success depends on the placement area, angle, technique, and screw dimensions. This study aimed to investigate the effects of miniscrew lengths, insertion angles, and force directions on a mandible model consisting of teeth, cortical and cancellous bones. One Dental Volumetric Tomography (DVT) scan from a patient who had miniscrews were used for mandibular bone modeling to perform finite element analysis. The model variables included miniscrew lengths (6, 8, and 10 mm), insertion angles (-15°, 45°, 60°, and 90°), and force directions (30°, 45°, and 60°). The minimum and maximum stresses were calculated as 18.61 and 37.11 MPa at 6 mm and 10 mm, respectively. According to the insertion angles, the lowest stress was observed at 60°, while the highest stress was found at 15° in the ventral direction. At force directions, the lowest stress was at 60°, and the highest stress was at 45°. However, there were no significant differences in insertion angles and force directions. A statistically significant difference was determined in miniscrew length. As a result, the best result was calculated to be 6 mm inserted at a 60° angle, which could induce the lowest stress. Increasing the miniscrew length will increase the stress on the mandible. In addition, because of the higher force direction, stress decreases with shorter power arms.

Evaluation of safe areas for miniscrew use according to various skeletal anomalies with CBCT

OBJECTIVES

We aimed to determine safe areas to apply miniscrews in the interradicular region of the maxilla and mandible in individuals with various sagittal skeletal malocclusions.

MATERIALS AND METHODS

Cone beam-computed tomography images of 159 individuals were used. Individuals were divided into three groups: Class I, Class II, and Class III. In the sagittal plane, 3-6-9-mm apical sections were determined from the alveolar crest apex. The buccal cortical bone thickness, interradicular distance, and buccolingual bone distances were measured.

RESULTS

In the buccal cortical bone thickness, we observed statistically significant differences between the classes except for the 1-1 region in the maxilla and all regions and sections in the mandible (p < 0.05). The differences in the buccolingual bone distance between classes were statistically significant, except for the 3-mm and 6-mm sections in the 3-4 and 4-5 regions of the maxilla, the 9-mm sections in the 1-2 and 2-3 regions, the 6-mm and 9-mm sections in the 3-4 region, and the 6-mm section in the 4-5 regions of the mandible (p < 0.05). The differences in the interradicular bone distance were statistically significant between the classes in all regions and sections of the mandible except the 6-mm sections in the 1-2 region and in all sections of the maxilla except the 6-mm sections in the 3-4 region (p < 0.05).

CONCLUSIONS

We observed significant differences in the buccal cortical bone thickness, interradicular bone distance, and buccolingual bone distance among individuals.

CLINICAL RELEVANCE

Understanding the anatomy of interradicular regions and preventing complications.

The impact of immediate versus delayed mini-screw placement on alveolar bone preservation and bone density following tooth extraction: evidence from a canine model

The aim of this study was to evaluate the impact of mini-screw placement on the alveolar ridge using a split-mouth design. Twelve beagles underwent bilateral extraction of their lateral teeth. In the immediate group, a mini-screw was unilaterally placed approximately 3-4 mm below the alveolar crest of the extraction site on the experimental side. The delayed group received mini-screws six weeks after tooth extraction. On average, the dogs were sacrificed after 11 weeks, and the maxillary bones were excised and scanned using cone-beam computed tomography (CBCT). Histopathological examinations were conducted to assess inflammation and bone formation scores. The results showed that in the immediate group, bone height was significantly greater on the intervention side compared to the control side (p < 0.05), whereas there was no significant difference in the delayed group. In both groups, there was a significant increase in bone density around the mini-screws compared to the control sides (p < 0.05). Mini-screw insertion led to a significant enhancement of bone growth in both groups (p < 0.05), with no notable differences between the two groups. The mini-screws did not have any impact on bone inflammation or width. Overall, both immediate and delayed mini-screw placement in the extraction socket positively influenced bone dimensions, density, and histological properties. However, immediate insertion was more effective than delayed placement in preserving vertical bone height, despite delayed insertion resulting in higher bone density.

Bimaxillary Dentoalveolar Protrusion Case Treated with Anchorage by Buccally Implemented Mini-Implants Using a 3D-Printed Surgical Guide

The article presents a case of bimaxillary dentoalveolar protrusion treated by distalizing the upper and lower teeth, using anchorage from mini implants. A 16-year-old male patient presented with severe upper and lower incisor proclination with protruding lips and a convex profile, with a background of bimaxillary dentoalveolar protrusion. Instead of having four premolars extracted, retraction of the dentition was decided with absolute anchorage, provided by mini implants. In order to carry out the procedure in one stage, four mini-implants were inserted as close to the root of the 1st molars as possible. Implementation was facilitated by a surgical template which was created on a digital model and then 3D printed. Accurate placement was achieved and the case was successfully treated by significant uprighting of the incisors and retraction of the anterior dentition, closing the spaces in the upper and lower arch. Facial aesthetics were also improved. A digitally designed surgical guide was utilized in this case of bimaxillary dentoalveolar protrusion in order to facilitate the accurate placement of the mini implants which were used for a one-stage retraction of the dentition.

Influence of the Computer-Aided Static Navigation Technique and Mixed Reality Technology on the Accuracy of the Orthodontic Micro-Screws Placement. An In Vitro Study

To analyze the effect of a computer-aided static navigation technique and mixed reality technology on the accuracy of orthodontic micro-screw placement. Material and methods: Two hundred and seven orthodontic micro-screws were placed using either a computer-aided static navigation technique (NAV), a mixed reality device (MR), or a conventional freehand technique (FHT). Accuracy across different dental sectors was also analyzed. CBCT and intraoral scans were taken both prior to and following orthodontic micro-screw placement. The deviation angle and horizontal deviation were then analyzed; these measurements were taken at the coronal entry point and apical endpoint between the planned and performed orthodontic micro-screws. In addition, any complications resulting from micro-screw placement, such as spot perforations, were also analyzed across all dental sectors. Results: The statistical analysis showed significant differences between study groups with regard to the coronal entry-point (p < 0.001). The NAV study group showed statistically significant differences from the FHT (p < 0.001) and MR study groups (p < 0.001) at the apical end-point (p < 0.001), and the FHT group found significant differences from the angular deviations of the NAV (p < 0.001) and MR study groups deviations (p = 0.0011). Different dental sectors also differed significantly. (p < 0.001) Additionally, twelve root perforations were observed in the FHT group, while there were no root perforations in the NAV group. Conclusions: Computer-aided static navigation technique enable more accurate orthodontic micro-screw placement and fewer intraoperative complications when compared with the mixed reality technology and conventional freehand techniques.

Influence of the Computer-Aided Static Navigation Technique on the Accuracy of the Orthodontic Micro-Screws Placement: An In Vitro Study

To analyze the influence of the computer-aided static navigation technique on the accuracy of placement of orthodontic micro-screws. One hundred and thirty-eight orthodontic micro-screws were randomly assigned to the following study groups: Group A. orthodontic micro-screw placement using a computer-aided static navigation technique (n = 69); B. orthodontic micro-screw placement using the conventional freehand technique (n = 69). In addition, the accuracy in the canine–premolar, premolar and molar sectors was analyzed in each study group. Cone-beam computed tomography and intraoral scans were taken both prior and subsequent to orthodontic micro-screw placement. The images were then uploaded using a 3D implant planning software, where the deviation and horizontal angles were analyzed using a multivariate linear model. These measurements were taken at the coronal entry point and apical endpoint between the planned orthodontic micro-screws. In addition, any complications resulting from micro-screw placement, such as spot perforations, were also analyzed in all dental sectors. The statistical analysis showed significant differences between the two study groups with regard to the coronal entry-point, apical end-point (p < 0.001) and angular deviations (p < 0.001) between the computer-aided static navigation technique and freehand technique study groups. Moreover, statistically significant differences were showed between the different dental sectors (p < 0.001). Additionally, twelve root perforations were observed at the conventional free hand technique study group while there were no root perforations in the computer-aided static navigation technique study group. The results showed that the computer-aided static navigation technique enables a more accurate orthodontic micro-screw placement with less intraoperative complications when compared with the conventional freehand technique.

Sex-, growth pattern-, and growth status-related variability in maxillary and mandibular buccal cortical thickness and density

Objective

The primary objective of this study was to quantitatively analyze the bone parameters (thickness and density) at four different interdental areas from the distal region of the canine to the mesial region of the second molar in the maxilla and the mandible. The secondary aim was to compare and contrast the bone parameters at these specific locations in terms of sex, growth status, and facial type.

Methods

This retrospective cone-beam computed tomography (CBCT) study reviewed 290 CBCT images of patients seeking orthodontic treatment. Cortical bone thickness in millimeters (mm) and density in pixel intensity value were measured for the regions (1) between the canine and first premolar, (2) between the first and second premolars, (3) between the second premolar and first molar, and (4) between the first and second molars. At each location, the bone thickness and density were measured at distances of 2, 6, and 10 mm from the alveolar crest.

Results

The sex comparison (male vs. female) in cortical bone thickness showed no significant difference (p > 0.001). The bone density in growing subjects was significantly (p < 0.001) lower than that in non-growing subjects for most locations. There was no significant difference (p > 0.001) in bone parameters in relation to facial pattern in the maxilla and mandible for most sites.

Conclusions

There was no significant sex-related difference in cortical bone thickness. The buccal cortical bone density was higher in females than in males. Bone parameters were similar for subjects with hyperdivergent, hypodivergent, and normodivergent facial patterns.

Abalakov: Posterior mandibular anchorage technique for orthodontic treatment

INTRODUCTION

Abalakov is a mountaineering technique consisting in drilling two holes that intersect to form a V in order to thread a rope through to make an anchorage point. This technique can be applied to orthodontic treatment and constitutes a posterior mandibular orthodontic anchorage.

TECHNICAL NOTE

The technique can be performed on its own during local anaesthesia or during surgery for the extraction of wisdom teeth. The posterior anchorage point is located in the ramus of the mandible. It consists in drilling two holes that intersect to form a V and then threading a steel wire through to make an anchorage point.

DISCUSSION

This technique is simple, inexpensive, fast and non-invasive, providing an anchorage system with immediate loading and which is not dependent on the quality of the bone.

Effects of cortical bone thickness and trabecular bone density on primary stability of orthodontic mini-implants

Background/purpose

Mini-implant screws are now routinely used as anchorage devices in orthodontic treatments. This study used synthetic bone models to investigate how the primary stability of an orthodontic mini-implant (OMI) as measured by resonance frequency (RF) is affected by varying cortical bone thickness and trabecular bone density.

Materials and methods

Three synthetic cortical shells (thicknesses of 1, 2, and 3 mm) and three polyurethane foam blocks (densities of 40, 20, and 10 pound/cubic foot) were used to represent jawbones of varying cortical bone thicknesses and varying trabecular bone densities. Twenty-five stainless steel OMIs (2 × 10 mm) were sequentially inserted into artificial bone blocks to depths of 2, 4, and 6 mm. Five experimental groups of bone blocks with OMIs were examined by Implomates® RF analyzer. Statistical and correlation analyses were performed by Kruskal-Wallis test, Wilcoxon rank-sum test, and simple linear regression.

Results

As trabecular bone density decreased, RF decreased; as cortical bone thickness decreased, RF also decreased. Simple linear regression analysis showed highly linear correlations between trabecular bone density and RF (R² > 0.99; P < 0.0001) and between cortical bone thickness and RF (R² > 0.98; P < 0.0001).

Conclusion

The stability of an OMI at the time of placement is influenced by both cortical bone thickness and trabecular bone density. Both cortical bone thickness and trabecular bone density have strong linear correlations with RF.

Miniscrews failure rate in orthodontics: systematic review and meta-analysis

Background

Miniscrews in orthodontics have been mainly used for anchorage without patient compliance in orthodontic treatment. The literature has reported changing failure rates.

Objective

The aim of this review was to provide a precise estimation of miniscrew failure rate and the possible risk factors of the mechanically-retained miniscrews.

Search method

Electronic search in database was undertaken up to July 2017 through the Cochrane Database of Systematic Reviews, MEDLINE, Scopus, and Ovid. Additional searching for on-going and unpublished data, hand search of relevant journals and grey lietraure were also undertaken, authors were contacted, and reference lists screened.

Eligibility criteria

Randomised controlled trials (RCTs) and prospective cohort studies (PCSs), published in English were obtained, which reported the failure rate of miniscrews, as orthodontic anchorage, with less than 2 mm diameter.

Data collection and analysis

Blind and induplicate study selection, data extraction, and risk of bias assessment were undertaken in this research. Failure rates and relevant risk factors of miniscrews with the corresponding 95 per cent confidence intervals (CIs) were calculated by using the random-effects model. The heterogeneity across the studies was assessed using the I2 and Chi2 test. The risk of bias was assessed using Cochrane risk of bias and Newcastle-Ottawa Scale. Subgroup and sensitivity analyses were performed in order to test the robustness of the results in meta-analysis.

Results

The 16 RCTs and 30 PCSs were included in this research. Five studies were not included in the meta-analysis due to a lack of the statistical information needed to compute the effect sizes. About 3250 miniscrews from 41 studies were pooled in a random-effect model. The overall failure rate of miniscrews was 13.5 per cent (95% CI 11.5-15.9). Subgroup analysis showed that miniscrews 'diameter, length and design, patient age, and jaw of insertion had minimal effect on rate of miniscrews failure while the type of the gingivae and smoking had statistically significant effect.

Conclusion

Miniscrews have an acceptably low failure rate. The findings should be interpreted with caution due to high-level of heterogeneity and unbalanced groups in the included studies. High quality randomized clinical trial with large sample sizes are required to support the findings of this review.

A comparative histomorphological and micro computed tomography study of the primary stability and the osseointegration of The Sydney Mini Screw; a qualitative pilot animal study in New Zealand rabbits

Objective

The aim of this study was to assess the potential of improving orthodontic miniscrews’ (MSs) primary stability in vivo by evaluating the dispersion capacity of an injectable bone graft substitute (iBGS) through a newly designed hollow MS [The Sydney Mini Screw (SMS)] and its integration with the cortical and trabecular bone by using the femur and tibia in a New Zealand rabbit animal model.

Methods

In total, 24 MSs were randomly placed in each proximal tibia and femur of 6 New Zealand rabbits with an open surgery process. Aarhus MSs were used as controls and the effect of injection of iBGS was studied by implanting SMSs with and without iBGS injection. The dispersion of iBGS and the integration of the SMS were studied by using micro Computed Tomography (μCT) and histochemical analysis at two time points, 0 day and 8 weeks post-implantation.

Results

iBGS was successfully injected through the SMS and hardened in situ. After 8 weeks, μCT results revealed that the iBGS particles were resorbed and bone tissue was formed around the SMS and within its lateral exit holes.

Conclusions

This pilot animal study showed the high potential of the combined use of iBGS and SMS as a newly developed technique to promote the primary stability of MSs.

Resonance frequency analysis of miniscrew implant stability

This study used resonance frequency (RF) analysis to assess miniscrew implant (MSI) stability during wound healing in a sample of 68 patients (41 women, 27 men; mean age, 27.7 years). The 104 MSIs included 66 placements in the buccal shelf (BS; 2.0 × 12 mm) and 38 placements in interradicular (IR; 1.5 × 8 mm) sites. Thirteen (12.5%) of the MSIs failed. A new RF detection device was used to measure RF at baseline (T0) and at 3 (T1), 6 (T2), 9 (T3), 12 (T4), and 15 (T5) weeks after placement. A linear mixed-effects model was fitted to change in RF values. As compared with the BS group, the IR group had significantly lower RF values on the right side from T0 through T4 and on the left side from T0 through T2. Insertion site and time of visit were significantly associated with RF value. The effects of time of visit significantly differed between the BS and IR sites. Starting from T0, the MSIs placed at both sites had significantly lower RF values at all intervals, except for T0-T1. Future studies should examine how the present clinical protocols can optimize timing of MSI loading to maximize the success rate.

Fracture strength of orthodontic mini-implants

Objective:

This study aimed at evaluating the design and dimensions of five different brands of orthodontic mini-implants, as well as their influence on torsional fracture strength.

Methods:

Fifty mini-implants were divided into five groups corresponding to different manufactures (DEN, RMO, CON, NEO, SIN). Twenty-five mini-implants were subjected to fracture test by torsion in the neck and the tip, through arbors attached to a Universal Mechanical Testing Machine. The other 25 mini-implants were subjected to insertion torque test into blocks of pork ribs using a torquimeter and contra-angle handpiece mounted in a surgical motor. The shape of the active tip of the mini-implants was evaluated under microscopy. The non-parametric Friedman test and Snedecor’s F in analysis of variance (ANOVA) were used to evaluate the differences between groups.

Results:

The fracture torque of the neck ranged from 23.45 N.cm (DEN) to 34.82 N.cm (SIN), and of the tip ranged from 9.35 N.cm (CON) to 24.36 N.cm (NEO). Insertion torque values ranged from 6.6 N.cm (RMO) to 10.2 N.cm (NEO). The characteristics that most influenced the results were outer diameter, inner diameter, the ratio between internal and external diameters, and the existence of milling in the apical region of the mini-implant.

Conclusions:

The fracture torques were different for both the neck and the tip of the five types evaluated. NEO and SIN mini-implants showed the highest resistance to fracture of the neck and tip. The fracture torques of both tip and neck were higher than the torque required to insert mini-implants.

Facial Growth Patterns and Insertion Sites of Miniscrew Implants

INTRODUCTION

We aimed to evaluate the associations between the craniofacial growth pattern with interradicular distances (IRDs), cortical widths (CWs), and jaw heights (JHs). Also, we mapped safe zones for miniscrew implantation.

METHODS

Cone-beam computerized tomography data pertaining to 60 Class-I patients were divided into 3 growth groups: normal, horizontal, and vertical. IRDs and CWs were measured for bimaxillary canines to second molars, on buccal and lingual sides, at 3 transverse planes (1, 3, and 5 mm apically to the alveolar crest). JHs were measured in both jaws, between canines and second molars. The role of growth patterns and other variables were analyzed; also, safe zones were mapped with statistical substantiation.

RESULTS

IRDs were greater in the mandible, males, at points more distant from the ridge crest, and on the lingual side. Cortexes were thicker in the horizontal growth pattern, mandible, males, older patients, and lingual sides. JHs were greater in vertical growth pattern, mandible, and males.

CONCLUSIONS

The cortex might be thicker in patients with a horizontal growth pattern. The height might be greater in vertical growth pattern. IRDs might not be affected by growth pattern.

Three-dimensional finite element analysis of a newly designed onplant miniplate anchorage system

The purpose of this research was to evaluate the structural stress and deformation of a newly designed onplant miniplate anchorage system compared to a standard anchorage system. A bone block integrated with a novel miniplate and fixation screw system was simulated in a three-dimensional model and subjected to force at different directions. The stress distribution and deformation of the miniplate system and cortical bone were evaluated using the three-dimensional finite element method. The results showed that the stress on the plate system and bone was linearly proportional to the force magnitude and was higher when the force was in a vertical direction (Y-axis). Stress and deformation values of the two screws (screw 1 and 2) were asymmetric when the force was added along Y-axis and was greater in screw 1. The highest deformation value of the screws was 7.5148 μm, much smaller than the limit value. The load was decreased for each single miniscrew, and the ability of the new anchorage system to bear the load was also enhanced to some degree. It was suggested that the newly designed onplant miniplate anchorage system is effective, easily implanted and minimally invasive.

A custom made grid to guide placement of temporary anchorage devices

The use of implant anchorage has simplified orthodontic treatment by sparing us the need for patient compliance and the complexity of treatment. One of the most important factors affecting the success of interdental implants is preventing the damage to adjacent roots and periodontal ligament. The most common causes of root damage from mini-implant insertion are improper site selection and an inaccurate angle of drill penetration. We thereby present a custom made modified grid help in more accurate placement of temporary anchorage devices and guide the angle of drill penetration. The grid can be placed anywhere in the oral cavity (buccally, palatally, anteriorly or posteriorly) and it can be attached to the main arch wire, bracket or even on unbounded teeth. The measuring reference grid with two vertical guide arms is connected with a horizontal arm that will later be secured to the adjacent bracket at both ends. The grid includes small squares, which effectively upgrade the efficiency during the orthodontic implant placement. The two vertical guide arms help in maintaining the desired angulation while drilling indicating the mesial and distal root surface of the adjacent teeth.

In vivo determination of aluminum, cobalt, chromium, copper, nickel, titanium and vanadium in oral mucosa cells from orthodontic patients with mini-implants by Inductively coupled plasma-mass spectrometry (ICP-MS)

Miniscrews are used as orthodontic anchorage devices in the dentistry clinical practice but the in vivo metallic release from these structures has been not previously investigated. The aim of this study was to determine the content of Al, Co, Cr, Cu, Ni, Ti and V in oral mucosa cells of control subjects, patients under orthodontic treatment and with both, orthodontic treatment and miniscrew, in order to know the contribution of these mini-implants to the total metallic content. ICP-MS measurements revealed the following ascending order: Cr<Ni<Ti<Cu<Al, and Co and V were practically undetected. Significant differences in comparison to the control group were found for Cu in the orthodontic group, and for Ni in both, orthodontic and orthodontic+miniscrew groups. Potential correlations among metallic elements and with some clinical factors were also explored. These findings suggest that miniscrews do not increase significantly the metal release.

Quantitative evaluation of maxillary interradicular bone with cone-beam computed tomography for bicortical placement of orthodontic mini-implants

INTRODUCTION

The purpose of this study was to propose a protocol for safe bicortical placement of mini-implants by measuring the interradicular spaces of the maxillary teeth and the bone quality.

METHODS

Cone-beam computed tomography data were obtained from 50 adults. Three-dimensional reconstructions and measurements were made with SimplantPro software (Materialise, Leuven, Belgium). For each interradicular site, the bone thicknesses and interradicular distances at the planes 1.5, 3, 6, and 9 mm above the cementoenamel junction were measured. Standard bone units were defined to evaluate the influences of bone density and the different placement patterns on the stability of the mini-implants.

RESULTS

The safe interradicular sites in the maxilla for bicortical placement of 1.5-mm-diameter mini-implants were in all planes between the first and second premolars, and between the second premolar and the first molar. The safe palatal sites were between the first and second molars, and the safe labial sites of the 9-mm plane were between the central incisors, and between the lateral incisor and the canine. The safe buccal sites of the 6- and 9-mm planes were between the first and second molars, and the safe buccal sites of the 3-, 6-, and 9-mm planes were between the canine and the first premolar. Most bone thicknesses were from 8 to 12 mm. The optimal placement angle between the second premolar and the first molar was 58°. Bicortical placement could have more standard bone units than unicortical placement in the maxilla.

CONCLUSIONS

Bicortical placement would be more stable in the maxilla. For the site between the molars, special care should be taken at a plane higher than 6 mm to prevent maxillary sinus penetration. The most favorable interradicular area in the maxilla was between the second premolar and the first molar.

Comparison of short-term effects between face mask and skeletal anchorage therapy with intermaxillary elastics in patients with maxillary retrognathia

INTRODUCTION

The aim of this study was to compare the short-term dental and skeletal effects of a face mask (FM) with those of skeletal anchorage (SA) therapy with intermaxillary elastics in prepubertal patients with skeletal Class III malocclusion.

METHODS

Fifty patients with skeletal Class III malocclusion and maxillary deficiency were divided into two groups. In the FM group, an FM was applied by a bite plate with a force of 400g for each side. In the SA group, mini-plates were placed between mandibular lateral incisors and canines, and mini-implants were inserted between maxillary second premolars and first molars. A bite plate was inserted into the upper arch, and Class III elastics were applied with a force of 200g between each mini-plate and mini-implant.

RESULTS

Mean treatment durations were 0.52±0.09 years for FM and 0.76±0.09 years for SA. After the treatment, statistically significant increases in SNA°, ANB°, A-y, 1-NA, SnGoGn°, Co-A, Co-Gn, and A-Nperp, and reductions in SNB° and FH┴N-Pg were observed in both groups, and these changes were similar in both groups. In the FM group, 1-NB decreased significantly, and in the SA group, it increased significantly (P < 0.05).

CONCLUSIONS

The undesired dentoalveolar effects of the FM treatment were eliminated with SA treatment, except with regard to lower incisor inclination. Favourable skeletal outcomes can be achieved by SA therapies, which could be an alternative to the extraoral appliances frequently applied to treat skeletal Class III patients with maxillary deficiency.

Effects of a newly designed orthodontic miniplate platform for elevating the miniplate over the gingiva: A 3-dimensional finite element analysis

INTRODUCTION

Miniplates are the treatment of choice for complex orthodontic and orthopedic problems. However, they require surgical placement and removal, and complications such as infection and mobility can occur. The aim of this finite element analysis was to investigate the effects of a newly designed miniplate platform to elevate the miniplate above the gingiva.

METHODS

A bone block was modeled in 3 dimensions, and 2 N of force was applied on miniplates in 2 scenarios. In scenario 1, the miniplate was fixed with 2 miniscrews on both ends; in scenario 2, miniplate platforms were first seated on the cortical bone surface with their spikes fully penetrating, and then the miniplate was fixed on top with 2 miniscrews.

RESULTS

The highest von Mises stress on the cortical bone decreased from 0.5 to 0.3 MPa when miniplate platforms were used. In scenario 2, the principal maximum stresses on the cortical bone around the miniscrews decreased from 0.42 and 0.48 MPa to 0.20 and 0.22 MPa, and the principal minimum stresses decreased from -0.45 and -0.48 MPa to -0.01 MPa.

CONCLUSIONS

Miniplate platforms used to elevate the miniplate lowered the stresses generated on cortical bone around the miniscrews by distributing the stresses on the cortical bone surface. Patients can clean the miniplate more readily because it is elevated above the soft tissues. Placing the miniplate platforms requires only removing the gingiva with a punch, and their removal does not require flap surgery.

Morphological evaluation of the active tip of six types of orthodontic mini-implants

OBJECTIVE

To morphologically evaluate the active tip of six different types of self-drilling mini-implants for orthodontic anchorage.

METHODS

Images of the active tips of the mini-implants were obtained with a Zeiss optical microscope Stemi 200-C, with magnification of 1.6X. The images of the surface were viewed with the Axio Vision program (Zeiss, Jena, Germany) to calculate linear and angular measures. Mini-implant morphology and the details of tips and threads were also evaluated through Scanning Electronic Microscopy (SEM) (JEOL, model JSM5800 LV - JEOL, Tokyo, Japan) with magnifications of 90X and 70X, respectively. The evaluation of the mini-implant taper shape was assessed using the formula: (b - a) / (2 x D).

RESULTS

The following variables were measured: (1) active tip width, (2) major diameter of external thread, (3) minor diameter of internal thread and taper of the mini-implant, (4) number of threads and lead of the screw, (5) angle of thread, (6) flank width and (7) pitch width.

CONCLUSIONS

Mini-implants from different manufacturers presented active tips with different characteristics. Mechanical testing is necessary to correlate the analyzed characteristics aiming to determine the best performance.

Translational mini-screw implant research

It is important to thoroughly test new materials as well as techniques when these innovations are to be utilized in the human clinical situation. Translational research fills this important niche. The purpose of translational research is to establish the continuity of evidence from the laboratory to the clinic and in so-doing, provide evidence that the material is functioning appropriately and that the process in the human will be successful. This concept applies to the mini-screw implant; which, has been very successfully introduced into the orthodontic armamentarium over the last decade for application as a temporary anchorage device. The examples of translational research that will be illustrated in this paper have paved the way to ensure that clinicians have evidence to confidently utilize mini-screw implants in orthodontic practice. Needless to say, more studies are needed to ensure a safe, effective and efficient manner to practice orthodontics.

Retrieval analysis of immediately loaded orthodontic mini-implants: material and tissue characterization

OBJECTIVE

To investigate the morphological and compositional alterations of retrieved orthodontic mini-implants and the type of adjacent bone, in relation to loading period and anatomical region.

MATERIALS AND METHODS

Seventy orthodontic mini-implants (Aarhus: n = 35 and AbsoAnchor: n = 35) were placed in the maxilla and mandible of 33 orthodontic patients for anchorage purposes. All mini-implants were immediately loaded for a period specified by treatment plan. Fifty-nine mini-implants were retrieved (Aarhus: n = 29 and AbsoAnchor: n = 30) and examined by stereomicroscopy, reflection Fourier transform infrared microspectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Tissue samples adjacent to the implants were histologically examined to identify the bone type.

RESULTS

Changes in surface finish, formation of biological integuments, and compositional alterations mainly due to adsorption of proteinaceous material (rich in C, O, N, OH, NH, CH2/CH3, amide I, II, and III, and CH-OH) were identified in all mini-implants. In some cases, mineralized fragments were identified (rich in Ca, P, and Ca-P). In 25 out of the 59 histological sections examined, woven and lamellar bone types were detected. In 12 sections, only woven bone was detected, whereas in the residual 22, only lamellar bone was identified. A significant correlation was found between histological result and loading time but not between histology and region.

CONCLUSION

Morphological and elemental alterations were found for both types of mini-implant surfaces. An increase of the loading period increased the possibility of lamellar bone development around mini-implants.

Miniscrew implant applications in contemporary orthodontics

The need for orthodontic treatment modalities that provide maximal anchorage control but with minimal patient compliance requirements has led to the development of implant-assisted orthodontics and dentofacial orthopedics. Skeletal anchorage with miniscrew implants has no patient compliance requirements and has been widely incorporated in orthodontic practice. Miniscrew implants are now routinely used as anchorage devices in orthodontic treatment. This review summarizes recent data regarding the interpretation of bone data (i.e., bone quantity and quality) obtained by preoperative diagnostic computed tomography (CT) or by cone-beam computed tomography (CBCT) prior to miniscrew implant placement. Such data are essential when selecting appropriate sites for miniscrew implant placement. Bone characteristics that are indications and contraindications for treatment with miniscrew implants are discussed. Additionally, bicortical orthodontic skeletal anchorage, risks associated with miniscrew implant failure, and miniscrew implants for nonsurgical correction of occlusal cant or vertical excess are reviewed. Finally, implant stability is compared between titanium alloy and stainless steel miniscrew implants.

Miniscrew implants as temporary anchorage devices in orthodontics: a comprehensive review

In recent times, the use of miniscrew implants to obtain absolute anchorage has gained momentum in clinical orthodontics as rigid anchorage modality. Miniscrew implants offers many advantages when used as temporary anchorage devices like, easy placement and removal, immediate loading, can be used in a variety of locations, provide absolute anchorage, economic and requires less patient cooperation. This makes them as a necessary treatment option in cases with critical anchorage that would have otherwise resulted in anchorage loss if treated with conventional means of anchorage. The aim of this comprehensive review is to highlight the gradual evolution, clinical use, advantages and disadvantages of the miniscrew implants when used to obtain a temporary but absolute skeletal anchorage for orthodontic applications.

Volumetric measurement of root resorption following molar mini-screw implant intrusion using cone beam computed tomography

Objective

Molar intrusion by mini-screw implantation can cause different degrees of root resorption. However, most methods (2-D and 3-D) used for evaluating root resorption have focused on the root length without considering 3-D resorption. The purpose of this study was to volumetrically evaluate root resorption using cone beam computed tomography(CBCT) after mini-screw implant intrusion.

Materials and Methods

1. The volumes of 32 teeth were measured using CBCT and laser scanning to verify the accuracy of CBCT. 2. Twelve overerupted molars from adult patients were investigated in this study. After mini-screw implants were inserted into the buccal and palatal alveolar bones, 150 g of force was applied to the mini-screw implants on each side to intrude the molars. CBCT images of all patients were taken immediately prior to intrusion and after intrusion. The volumes of the roots were calculated using the Mimics software program. The differences between the pre-intrusion and post-intrusion root volumes were statistically evaluated with a paired-samples t-test. In addition, the losses of the roots were statistically compared with each other using one-way analysis of variance at the P<0.05 level.

Results

No statistically significant volume differences were observed between the physical (laser scanning) and CBCT measurements (P>0.05). The overerupted molars were significantly intruded (P<0.05), and the average intrusion was 3.30±1.60 mm. The differences between the pre-intrusion and post-intrusion root volumes were statistically significant for all of the roots investigated (P<0.05). The roots were sorted by volume loss in descending order as follows: mesiobuccal, palatal, and distobuccal. Statistical significance was achieved among the three roots. The average total resorption for each tooth was 58.39±1.54 mm³.

Conclusion

Volume measurement using CBCT was able to effectively evaluate root resorption caused by mini-screw intrusion. The highest volume loss was observed in the mesiobuccal root among the three roots of the investigated first molar teeth.

Failure rates and associated risk factors of orthodontic miniscrew implants: a meta-analysis

INTRODUCTION

Risk factors concerning orthodontic miniscrew implants have not been adequately assessed. In this systematic review, we summarize the knowledge from published clinical trials regarding the failure rates of miniscrew implants used for orthodontic anchorage purposes and identify the factors that possibly affect them.

METHODS

Nineteen electronic databases and reference lists of included studies were searched up to February 2011, with no restrictions. Only randomized controlled trials, prospective controlled trials, and prospective cohort studies were included. Study selection and data extraction were performed twice. Failure event rates, relative risks, and the corresponding 95% confidence intervals were calculated. The random-effects model was used to assess each factor's impact. Subgroup and meta-regression analyses were also implemented.

RESULTS

Fifty-two studies were included for the overall miniscrew implant failure rate and 30 studies for the investigation of risk factors. From the 4987 miniscrew implants used in 2281 patients, the overall failure rate was 13.5% (95% confidence interval, 11.5-15.8). Failures of miniscrew implants were not associated with patient sex or age and miniscrew implant insertion side, whereas they were significantly associated with jaw of insertion. Certain trends were identified through exploratory analysis; however, because of the small number of original studies, no definite conclusions could be drawn.

CONCLUSIONS

Orthodontic miniscrew implants have a modest small mean failure rate, indicating their usefulness in clinical practice. Although many factors seem to affect their failure rates, the majority of them still need additional evidence to support any possible associations.

Mini-implants in the anchorage armamentarium: new paradigms in the orthodontics

Paradigms have started to shift in the orthodontic world since the introduction of mini-implants in the anchorage armamentarium. Various forms of skeletal anchorage, including miniscrews and miniplates, have been reported in the literature. Recently, great emphasis has been placed on the miniscrew type of temporary anchorage device (TAD). These devices are small, are implanted with a relatively simple surgical procedure, and increase the potential for better orthodontic results. Therefore, miniscrews not only free orthodontists from anchorage-demanding cases, but they also enable clinicians to have good control over tooth movement in 3 dimensions. The miniplate type also produces significant improvements in treatment outcomes and has widened the spectrum of orthodontics. The purpose of this paper is to update clinicians on the current concepts and versatile uses and clinical applications of skeletal anchorage in orthodontics.

Thread shape factor: evaluation of three different orthodontic miniscrews stability

The thread shape factor (TSF) to evaluate the relationships between geometrical characteristics and mechanical properties of the temporary anchorage devices (TADs) has recently been introduced. This in vitro experimental study evaluated in 30 different tests with three TADs: ORTHOImplant (1.8 mm diameter and 10 mm length; 3M Unitek), Tomas (1.6 mm diameter and 10 mm length; Dentaurum), and Orthoeasy (1.7 mm diameter and 10 mm length; Forestadent). Scanning electron microscopy images were acquired for each TAD to measure the TSF; afterwards, the maximum insertion torque (MIT) was evaluated and thereafter pull-out tests on two differently designed organic bone analogs were carried out using a testing machine with a crosshead speed of 2 mm/minute being applied. One-way analysis of variance with group as factor was performed. Post hoc multiple comparisons Bonferroni test was used. Rank-transformed data were used when asymmetry of data was shown. To assess correlation between characteristics, load, and MIT, Spearman's rank correlation coefficient was used. A P-value of 0.05 was considered statistically significant. Significant direct correlations were found between TSF and depth and both load and MIT. Particularly, a correlation of 0.90 (P < 0.001) was found between depth and MIT for 2.2 mm cortical thickness. The authors conclude that MIT and maximum load values of pull-out test are statistically related to depth of the thread of the screw and to TSF.

Clinical factors correlated with the success rate of miniscrews in orthodontic treatment

Miniscrews offer a reliable alternative for anchorage during orthodontic treatment, particularly for non-cooperative patients or periodontal patients with alveolar bone loss. The study aims at assessing the correlation of various clinical indicators with the success or failure of miniscrews used for anchorage during orthodontic treatment. Thirty-four consecutive patients with a cumulative total of 82 miniscrews implanted participated in the study. Generalized Estimating Equations were used to assess the correlation of various factors with success rates. The miniscrew was considered the unit of analysis clustered within site and within patient. The overall success rate of miniscrews was 90.2%. For every additional miniscrew used in a patient's oral cavity, the success rate was reduced by 67%. Retromandibular triangle and palatal placement and in movable mucosa resulted in lower success rate. The miniscrew length and diameter were found to correlate with success rates. Orthodontic force applied on miniscrews for uprighting purposes showed a lower success rate than that used for retraction. This study revealed that miniscrews present high success rates. The number of miniscrews used per patient, the miniscrew site placement, the soft tissue type of placement, the miniscrew length and diameter as well as the orthodontic force applied on the miniscrew showed significant correlation with success rates.

Technological advances in nontraditional orthodontics

New technological advances have helped the orthodontic profession progress in traditional and surgical methods of treatment. The profession has seen transitions from traditional braces to self-ligating brackets, lingual braces, removable aligners, and more advanced technology, which have helped to address concerns that include but are not limited to better diagnostics, anchorage control, length of treatment, and esthetics. An increase in the number of adult patients seeking orthodontic treatment and the need for a timely efficient care will continue to drive technology and the use of cone beam computed tomography, miniscrews, piezocision, distraction osteogenesis, and bioengineering.

Northcroft lecture: how has the spectrum of orthodontics changed over the past decades?

Three aspects have had a significant impact on orthodontics during the last few decades: the appliances being used, the anchorage being used and finally the distribution of patients being treated. Firstly, the marketing of appliances is increasingly leading the orthodontist to outsource important aspects of treatment such as wirebending and bracket positioning. Brackets and wires are being presented as the solution to all problems and metaphysical terms such as 'intelligent design,' 'working brackets' and 'intelligent wires' are dominating advertising and reducing the impact of evidence-based treatment approaches. Secondly, the introduction of skeletal anchorage has potentially widened the spectrum of orthodontics, allowing for treatments that could not be done with conventional appliances. Biomechanical knowledge is, however, mandatory if we agree that the system should not be abused. Thirdly, the orthodontic population comprises an increasing number of adult patients, many of whom are characterized by a degenerated dentition. The treatment of these patients requires a thorough knowledge not only of biomechanics but also of the reaction of the periodontal tissues to various types of loading. They can be treated only with custom-made appliances adapting the force systems and magnitude to the patient-specific treatment goal. In summary, the orthodontic world is being split between 'appliance-driven fast-food orthodontics' where the results to a large extent are dependent on both growth and function and 'orthodontist-driven' 'slow-food' treatments attempting to push the limits of the possible in relation to complicated problems and reversal of degeneration in adult patients. The latter treatments are performed with individualized appliances adapting the force system to the patient. This paper will attempt to summarize the bearing of these factors on present orthodontics.

Optimizing anterior en masse retraction with miniscrew anchorage

In severely protrusive patients, skeletal anchorage from miniscrew is often used to avoid anchorage loss with preferred miniscrew location near centre of resistance (Cres) of posterior teeth. Biomechanical requirement for directing retraction force towards Cres of posterior teeth demands the insertion of miniscrew in loose mucosa, where risk of infection and failure increases. In addition, undesirable biomechanical side effects on anterior and posterior segments may be possible in all three planes, when continuous arch sliding mechanics are installed with miniscrew anchorage. This paper describes technique of molar-stabilizing power arm (MSPA) for simultaneous intrusion and retraction of anteriors with miniscrew placement at attached gingiva between 1st molar and 2nd premolar. Advantages of this technique include (i) the need of miniscrews placement in loose mucosa apically near the Cres of the posterior teeth is eliminated, (ii) the risk of infection and miniscrew failure is lowered since the miniscrew is placed in attached gingiva rather than the loose mucosa, and (iii) by adjusting vertical length or replacing MSPA, alteration of the retraction force vector is possible in all three planes; thus, need of removal and repositioning of the miniscrew (e.g., in correction of occlusal cant) can be eliminated.

[Mapping mini-implant anatomic sites in the area of the maxillary first molar with the aid of the NewTom 3G® system]

INTRODUCTION

The goal of our study was to construct a map of the implant sites in the region of the attached gingiva around the maxillary first molars that would be appropriate locations for placement of miniscrews to serve as orthodontic anchorage.

METHOD

We conducted 58 radiographic examinations with the NewTom 3G(®) cone beam technique. For each interdental space, between upper second bicuspids and first molars (5/6) and between upper first and second molars (6/7), we studied the mesio-distal width and depth of bucco-lingual bone at two different levels, L1 and L2, that corresponded to the lower and upper limits of the attached gingiva in the general population.

RESULTS

The widths of the interdental spaces varied very little between L1 and L2 and their variances were comparable. At the level of the 5/6 space, the interdental widths displayed a Gaussian distribution, which made it possible for us to determine the confidence intervals at the two borders of attached gingiva as a function of age: IC(99%) of L1 = [2.045 ; 3.462] from 12 to 17 years or [1.594 ; 2.519] from 18 to 24 or [1.613 ; 2.5] from 25 to 48 years and IC(99%) of L2 = [2.37 ; 3.69] from 12 to 17 years or [1.5 ; 2.613] from 18 to 24 or [1.546 ; 2.619] from 25 to 48 ans. The interdental depths increased in an apical direction and their variance diminished. Even if the adequacy of the Gaussian law is less reliable in the sagittal plane, we find a greater consistency in depths in the spaces around 5/6 that allows us to establish very precise confidence levels: IC(99%) of L1 = [9.213; 10.575] and IC(99%) of L2 = [10.295; 11.593].

CONCLUSION

The mesial areas of the first molars constitute safe zones for implantation of miniscrews with a maximum of 2-2.3 mm for 12 to 17 years old or 1.5-1.6 mm for 18 to 48 year olds and of a maximum of 9-10 mm in length whether the attached gingival level is strong or feeble. The distal areas of the first molars, because of their great variability, require an individualized radiographic study before any mini/screw can be placed.