Bicortical titanium screws for critical orthodontic anchorage in the mandible: a preliminary report on clinical applications

Class II Correction with Microimplant Supported Molar Distalization: A Report of Two Cases

Introduction

Orthodontic treatment of class II malocclusion with conventional treatment modalities can be challenging for the clinician. The use of microimplants to obtain absolute anchorage has become very popular in recent years especially in noncompliant patients. Microimplants are convenient, save time, and produce good treatment results with no need for patient cooperation. A special approach for class II correction with microimplant supported molar distalization has been developed by the authors and is illustrated through two clinical cases. Description. For each clinical case, 0.022” preadjusted brackets were bonded on both arches except on the maxillary first and second premolars with bands on the first and second molars. After leveling and alignment, a 0.017^” × 0.025^” stainless steel wire was fitted on the upper arch, and two microimplants were placed bilaterally between the maxillary second premolar and the first molar. Open coil springs were inserted in the upper archwire on both sides and compressed via a steel ligature on sliding hooks to the microimplants pushing distally simultaneously the first and second maxillary molars. En-masse retraction of the maxillary anterior teeth was then carried out on a 0.019^” × 0.025^” stainless steel closing loop archwire while the posterior segment was anchored to the microimplant with a steel ligature to the first premolar.

Results

Class I canine and molar relationship were achieved, and an ideal occlusion was established. Both ANB and FMA angles decreased by 1° due to the counterclockwise rotation effect of the maxillomandibular complex. Skeletal and dental results remained stable three years later.

Conclusion

Maxillary molar distalization using coils and buccal microimplants can be regarded as an effective technique in a relatively short time and might be considered a breakthrough in the treatment of class II malocclusions. Microimplants enable the clinician to perform a nonextraction treatment in noncompliant patients who would alternatively be treated only with extractions.

Maxillary Skeletal Expansion with Monocortical and Bicortical Miniscrew Anchorage: A 3D Finite Element Study

The aim of the present study is to use a 3D finite element analysis to investigate and compare the transverse displacement and stress distribution between stainless steel miniscrews and titanium alloy miniscrews used for monocortical and bicortical anchorage during miniscrew-assisted rapid maxillary expansions. Skull models were constructed to depict expansion after and before midpalatal suture opening at varying miniscrew insertion depths in four clinical scenarios: monocortical, monocortical deepening, bicortical, and bicortical deepening. Finite element analyses of miniscrew properties, including transverse displacement and von Mises stress distribution, were performed for each clinical scenario. Peri-implant stress was lesser in both bicortical anchorage models compared to both monocortical models. Transverse displacement in the coronal and axial planes was also greater and more parallel in both bicortical models compared to both monocortical models. Transverse displacement and peri-implant stress did not significantly differ between monocortical and monocortical deepening models or between bicortical and bicortical deepening models. From a biomechanical perspective, the bicortical deepening miniscrew anchorage is preferable to monocortical and monocortical deepening anchorage, because bicortical anchorage induces less stress on the peri-implant bone. Consequently, bicortical deepening anchorage should be considered the preferred option in challenging clinical scenarios in which strong anchorage is required for maxillary skeletal expansion.

Application of the Digital Workflow in Orofacial Orthopedics and Orthodontics: Printed Appliances with Skeletal Anchorage

As digital workflows are gaining popularity, novel treatment options have also arisen in orthodontics. By using selective laser melting (SLM), highly customized 3D-printed appliances can be manufactured and combined with preformed components. When combined with temporary anchorage devices (TADs), the advantages of the two approaches can be merged, which might improve treatment efficacy, versatility, and patient comfort. This article summarizes state-of-the-art technologies and digital workflows to design and install 3D-printed skeletally anchored orthodontic appliances. The advantages and disadvantages of digital workflows are critically discussed, and examples for the clinical application of mini-implant and mini-plate borne appliances are demonstrated.

Correlation between cortical bone thickness at mini-implant insertion sites and age of patient

Introduction:

Orthodontic mini-implants (MI) are a reliable alternative to provide temporary orthodontic anchorage. Prior to miniscrew insertion, the best approach would be to evaluate each possible insertion site and measure the cortical bone thickness, and verify whether it would provide adequate primary stability.

Objective:

This study aimed to evaluate the difference in cortical bone thickness in areas of mini-implants insertion in patients of different ages, by means of cone beam computed tomography (CBCT).

Methods:

The sample of this retrospective study was composed of 123 CBCT scans, which were used to measure cortical bone thickness in the buccal and palatal inter-radicular space in the mesial region of the first permanent molars. These measures were compared by using the Student’s t-test, ANOVA/Tukey tests, and Linear regression between male and female subjects, from 12 to 30 years old.

Results:

No significant difference was found in cortical bone thickness between sex, race and sagittal facial patterns. Significantly higher measurement values were observed in patients older than 12 years of age at all sites evaluated. The coefficient β at the adjusted linear regression analysis showed that at each increment in age, mean cortical thickness values increased by 0.06mm in the mandible, 0.03mm in the buccal region and 0.02mm in the palatal region of the maxilla.

Conclusions:

The increase in cortical bone thickness was positively associated with age; that is, the more advanced the patient’s age was, the less chance there was of failure due to primary stability.

3-D Evaluation of temporary skeletal anchorage sites in the maxilla

Background

The selection of temporary anchorage device (TAD) site can be a challenging task since one should not only consider the 2-D distances between roots, but also the entire 3-D space. Thus, the aim of this study was to evaluate the posterior maxillary region areas available for the insertion of temporary anchorage devices in reconstructed images from cone beam computed tomography (CBCT).

Material and Methods

Sample consisted of 72 patients with indication for orthodontic treatment, grouped into three distinct age groups: 11 to 14 years (age group 1), 15 to 19 years (age group 2) and aged 20 years or older (age group 3), which were further subdivided as to the type of malocclusion (Angle Class I, II and III). Orthopantomographic reconstructions and cross sections were obtained with the Dolphin Imaging software. The distance between the roots of maxillary teeth (canines, premolars and first molars) was determined at 5 mm of the cementoenamel junction, as well as the depth of bone availability at different insertion angles (90°, 75°, 60°, 45°). The influence of different angulations, age, and malocclusion on bone availability was evaluated by ANOVA, followed by the Bonferroni post-test. For the evaluation of the interaction of these factors, 2-way ANOVA was used.

Results

Bone availability was found to be poor between roots in the molar region. There was a reduction in bone availability with increasing age. With regard to angulations, greater bone availability was found in depth for 45° angulation in the canine and first premolar regions and for angulation of 75° or 90° in the molar region. However, there was no difference between bone availability in the region of the second premolars.

Conclusions

According to applied methodology it can be concluded that the region between canines and premolars accepts better vertical angular variations for TADs insertion.

Key words:Cone-Beam Computed Tomography, Orthodontic Anchorage Procedures.

Tomographic assessment of infrazygomatic crest bone depth for extra-alveolar miniscrew insertion in subjects with different vertical and sagittal skeletal patterns

OBJECTIVE

To evaluate bone availability at the infrazygomatic crest for extra-alveolar bone miniscrew insertion in subjects with different vertical and sagittal skeletal patterns.

SETTING AND SAMPLE POPULATION

Measurements of the infrazygomatic crest were performed on multislice computed tomography scans from 58 adults with different skeletal patterns.

MATERIALS AND METHODS

Infrazygomatic crest bone depth was measured at 4, 5 and 6 mm from the cementoenamel junction (CEJ) of the maxillary first molar at three different angles (60°, 70° and 80°) in the first molar occlusal plane. The sagittal and vertical skeletal patterns were determined. Analysis of variance followed by Tukey's post hoc test was used (P ≤ .05).

RESULTS

Bone depth was greater near the CEJ (8.7 ± 3.1 mm) and lower in the apical area (5.8 ± 2.7 mm). In Class II subjects, considering 6 mm from the CEJ, there was a significantly lower depth at the 80° angle (5.4 ± 2.5 mm) than at 60° (8.6 ± 3.5 mm; P = .007). In mesofacial subjects, considering 5 and 6 mm from the CEJ, bone depth was lower at 80° (5.7 ± 3.2 mm and 5.3 ± 2.5 mm) than at 60° considering 4 mm from the CEJ (P ≤ .019).

CONCLUSION

Bone availability was lower at the apical level, especially in Class II and mesofacial subjects. Therefore, when the planned insertion site is located in the apical direction, it is recommended to choose shorter miniscrews (2.0 x 12mm) and a smaller insertion angle (60°) and/or to plan a miniscrew bone insertion deep enough to allow bicortical fixation.

Knowledge of undergraduate dental students toward orthodontic skeletal temporary anchorage devices at Kuwait University

BACKGROUND

The introduction of skeletal Temporary Anchorage Devices (TADs) into orthodontics has provided orthodontists with reliable techniques of correcting anchorage problems. The objective of this study was to evaluate the knowledge of undergraduate dental students during their clinical years (fifth, sixth and seventh-year) at Kuwait University Faculty of Dentistry regarding the use of TADs.

METHODS

A printed structured questionnaire consisting of 21 questions was given to the undergraduate dental students of Kuwait University in the fifth (n = 22), sixth (n = 28) and seventh (n = 22)-years. It evaluated the level and source of information regarding orthodontic TADs.

RESULTS

The seventh-year dental students displayed the best degree of knowledge regarding the use of TADs and the clinical case management, compared with the sixth and fifth-year dental students. The significance of introducing the orthodontic TADs topic earlier in the orthodontic curriculum has been agreed upon by 42% of respondents. The total knowledge score showed a significant difference (χ2 = 40.3, p = 0.000), where the seventh year dental students had the best level of knowledge regarding the topic of TADs. Two-thirds (63.6%) preferred to introduce that topic during the sixth year.

CONCLUSIONS

The senior (7th year) dental students had the best knowledge about the topic of TADs. Introducing the topic of TADs earlier in the undergraduate dental program will enhance the students' case-based learning setup. Hence, the early exposure to use of TADs will improve the students' clinical problem-solving and decision making skills during their undergraduate clinical years.

Autotransplanted premolars with incomplete root formation in a growing patient with multiple missing teeth

A boy aged 8 years 11-months with 4 missing teeth in his mandibular arch and with a skeletal Class II pattern was treated with autotransplantation of developing premolars from his maxillary arch with the aid of temporary skeletal anchorage devices. The active treatment duration was 25 months. After treatment, he had a normal occlusion, and his profile was improved. Posttreatment records at 12 months showed stable occlusion and successfully autotransplanted premolars.

Accuracy of fully guided orthodontic mini-implant placement evaluated by cone-beam computed tomography: a study involving human cadaver heads

OBJECTIVES

The aim of this study was to evaluate the accuracy of fully guided orthodontic mini-implant (OMI) placements supported by tooth- (TBGs) or gingiva-borne silicone guides (GBGs) based on virtually superimposed lateral cephalograms on virtual plaster models.

MATERIALS AND METHODS

Lateral cephalograms and corresponding plaster models were virtually superimposed for the planning of OMI positions; fully guided TBGs and GBGs were fabricated (each, n = 10). A total of 40 OMIs were inserted in a paramedian position into the palate of 20 human cadavers. Postoperative cone-beam computer tomographies (CBCTs) were carried out, and an accuracy evaluation was performed by comparing preoperative planning models and postoperative CBCTs. Deviations of the axis, tip, centre of the shoulder and vertical position of each of the implants were evaluated. Furthermore, the transfer accuracy measured by postoperative CBCT scans were compared with the accuracy determined using an intraoral scanner.

RESULTS

A significant deviation between TBGs (2.81° SD 2.69) and GBGs (6.22° SD 4.26) regarding implant angulation was evaluated (p = 0.005). Implant tip and implant shoulder deviations revealed no statistical differences between the guides. Accuracy values of oral scans regarding vertical deviations were significantly more inaccurate when compared with CBCTs (p < 0.001).

CONCLUSIONS

The accuracy of an OMI position can be significantly increased by using a guide extension over the teeth. Vertical implant positions presented the lowest deviations. Postoperative oral scans and CBCTs represent diverging accuracy measurements when compared with virtual planning.

CLINICAL RELEVANCE

Users must keep in mind that despite virtual planning deviations, inaccuracies of a few millimetres may occur.

An Umbrella Review of the Effectiveness of Temporary Anchorage Devices and the Factors That Contribute to Their Success or Failure

OBJECTIVES

New methodological approaches, such as the umbrella review, constitute an important pathway for synthesizing the scientific evidence provided from studies with a high level of evidence. This study aims to summarize the results on the effectiveness of temporary anchorage devices (TADs) and the factors that contribute to their success or failure during orthodontic treatment in patients of different age groups and to identify the gaps in knowledge based on analysis of the scientific literature.

METHODS

An umbrella review of systematic reviews and meta-analyses was performed. A quality evaluation and a descriptive analysis of the included studies were conducted. The study protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO: CRD42018094463).

RESULTS

Seventeen systematic reviews and meta-analyses were considered (10 descriptive and 7 with meta-analysis; 12 of high quality and 5 of moderate quality). Variability was observed in the type of intervention and the type of system (TADs). Most of the studies reported high success rates (≥90%), and just one systematic review indicated a low rate of success (≤56%) for the mini-screws. All the studies discussed several factors related to the success of the TADs. These factors were classified as device-related factors, patient-related factors, procedure-related factors, and orthodontic treatment-related factors. Conceptual and methodological gaps were observed when considering the data analysis, the terminology used, and the orthodontic protocols.

CONCLUSIONS

The results should be analysed cautiously because of several research gaps related to the methodological quality and the high heterogeneity of the original studies and because of the necessity to add several clinical and sociodemographic variables to enrich the data analysis.

Maxillary molar mesialization with the use of palatal mini-implants for direct anchorage in an adolescent patient

A unique clinical challenge presents when dealing with a compromised first permanent molar. A compelling treatment option for consideration is the removal of a nonrestorable first permanent molar, with the subsequent "replacement" through controlled mesial tooth movement of viable second and third molars. To reinforce the anchorage support associated with such a planned movement, indirect or direct implant-supported mechanics may be used. With the use of direct anchorage, orthodontic brackets are not required and space closure can be commenced immediately. In this article, we report the clinical procedure and design of direct-anchorage mechanics used for the successful closure of a maxillary first permanent molar space with the use of an implant-supported appliance (Mesialslider). Treatment was completed in just under 12 months, with successful mesial movement of the maxillary second and third molars without the need for the bonding of orthodontic brackets on the anterior dentition. The result was determined to be stable over a 3-year period.

A finite element analysis of the optimal bending angles in a running loop for mesial translation of a mandibular molar using indirect skeletal anchorage

OBJECTIVES

To estimate the optimal bending angles in the running loop for mesial translation of a mandibular second molar using indirect skeletal anchorage and to clarify the mechanics of tipping and rotating the molar.

METHODS

A three-dimensional finite element model was developed for predicting tooth movement, and a mechanical model based on the beam theory was constructed for clarifying the force systems.

RESULTS

When using a running loop without bends, the molar tipped mesially 14.4° and lingually 0.6°, rotated counterclockwise 4.1°, and the incisors retracted 0.02 mm and intruded 0.05 mm. These angles were about the same as those estimated by the beam theory. When the amount of tip back and toe-in angles was 11.0°, mesial translation of the molar was achieved, and incisors retracted 0.10 mm and intruded 0.30 mm.

CONCLUSIONS

Mesial translation of a mandibular second molar without any significant movement of anterior teeth was achieved during protraction by controlling the tip back and toe-in angles and enhancing anterior anchorage with the combined use of a running loop and indirect skeletal anchorage.

Success rates of a skeletal anchorage system in orthodontics: A retrospective analysis

OBJECTIVES

To evaluate the premise that skeletal anchorage with SAS miniplates are highly successful and predictable for a range of complex orthodontic movements.

MATERIALS AND METHODS

This retrospective cross-sectional analysis consisted of 421 bone plates placed by one clinician in 163 patients (95 female, 68 male, mean age 29.4 years ± 12.02). Simple descriptive statistics were performed for a wide range of malocclusions and desired movements to obtain success, complication, and failure rates.

RESULTS

The success rate of skeletal anchorage system miniplates was 98.6%, where approximately 40% of cases experienced mild complications. The most common complication was soft tissue inflammation, which was amenable to focused oral hygiene and antiseptic rinses. Infection occurred in approximately 15% of patients where there was a statistically significant correlation with poor oral hygiene. The most common movements were distalization and intrusion of teeth. More than a third of the cases involved complex movements in more than one plane of space.

CONCLUSIONS

The success rate of skeletal anchorage system miniplates is high and predictable for a wide range of complex orthodontic movements.

Comparison of Anchorage Pattern under Two Types of Orthodontic Mini- Implant Loading During Retraction in Type A Anchorage Cases

INTRODUCTION

The orthodontic mini-screws are the mainstay of direct skeletal anchorage which requires minimal compliance and provides maximal anchorage control. However, the timing of initiation of orthodontic loading of these mini-screws is not clearly established in the available studies.

AIM

The purpose of this study was to determine the reciprocal effects on mini-screw implant with immediate loading in comparison to that of delayed loading during retraction.

MATERIALS AND METHODS

The prospective clinical study included a sample of 25 orthodontic patients in the age range of 18-25 years. All the cases were of bi-maxillary proclination with Type-A anchorage demands. All the first premolars were indicated for extraction. A split mouth technique for each patient was utilized by loading mini-implant immediately after its placement on one side and the opposite side implant was loaded after a time lag of two weeks post-insertion. Retraction force of 150g was applied for three months on each side. The displacement of the head and tail of the implant, molar anterior tooth retraction was measured on Orthopantomograph (OPG) taken at T1 (initial) and T2 (after three months). A grid method with each 1mm magnified to 500 pixels was superimposed on OPG and the relative displacements were evaluated. Student's unpaired 't' test was used for comparison between left and right side and paired 't' test for the parameters on the same side. The p-value equal to or less than 0.05 was taken as statistically significant.

RESULTS

The mean displacement of head of the implant on the immediate loading is 0.57mm where as the tail exhibited 0.75 mm. The head and tail of the implant on the delayed loading displaced by 0.35mm and 0.38mm respectively, on an average when data was analysed. Significant difference between the two types of loading was noted.

CONCLUSION

Delayed loading is beneficial as compared to immediate loading during extraction space closure.

Are assessments of damping capacity and placement torque useful in estimating root proximity of orthodontic anchor screws?

INTRODUCTION

Placement torque and damping capacity may increase when the orthodontic anchor screws make contact with an adjacent root. If this is the case, root contact can be inferred from the placement torque and damping capacity. The purpose of this study was to verify the detectability of root proximity of the screws by placement torque and damping capacity. For this purpose, we investigated the relationship among placement torque, damping capacity, and screw-root proximity.

METHODS

The placement torque, damping capacity, and root proximity of 202 screws (diameter, 1.6 mm; length, 8.0 mm) were evaluated in 110 patients (31 male, 79 female; mean age, 21.3 ± 6.9 years). Placement torque was measured using a digital torque tester, damping capacity was measured with a Periotest device (Medizintechnik Gulden, Modautal, Germany), and root contact was judged using cone-beam computed tomography images.

RESULTS

The rate of root contact was 18.3%. Placement torque and damping capacity were 7.8 N·cm and 3.8, respectively. The placement torque of screws with root contact was greater than that of screws with no root contact (P <0.05; effect size, 0.44; power, <0.8). Damping capacity of screws with root contact was significantly greater than that of screws with no root contact (P <0.01; effect size, >0.5; power, >0.95).

CONCLUSIONS

It was suggested that the damping capacity is related to root contact.

Root proximity and stability of orthodontic anchor screws

This study aimed to investigate a causal relationship between the stability of orthodontic anchor screws (screws) and the degree of their proximity to the root (root proximity) using mobility test device (Periotest) and cone-beam computed tomography (CBCT). In total, 165 (diameter 1.6 mm; length 8 mm) screws in 58 patients (average age, 24.4 ± 8.5 years) were evaluated. After screw placement, CBCT was used for diagnostic imaging of the area around the site. Root proximity was evaluated and categorized into three groups: A, no contact; B, single contact; and C, multi-contact. The Periotest value was used to assess screw stability. The screw failure rate according to root proximity significantly differed between categories A and C. In addition, failure rate significantly differed between mandibular screws with and without root contact. Periotest values in categories A and C were significantly higher in the mandible than in the maxilla. Mandibular screws had greater mobility than maxillar screws, even when the screw avoided root contact. The lower stability of mandibular screws with root contact might be related to their greater mobility.

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.

The Benefit System and its scope in contemporary orthodontic protocols

Currently, the alveolar process is the most preferred insertion site for orthodontic mini-implants. However, due to the varying bone quality and the risk of root contact, the survival rate of implants inserted in the alveolar ridge still needs improvement. Other regions, such as the anterior palate and the mental region provide much better conditions for temporary anchorage device (TAD) insertion since the amount and quality of the available bone are far superior. Mini-implants with different types of abutments and connectors allow the construction of versatile and cost efficient appliances for a large variety of orthopedic and orthodontic applications. Utilizing TAD’s in the anterior palate and the mental region eliminates the risk of root injury and takes the implants out of the path of tooth movement. The design of the interchangeable abutment system provides the orthodontist with a skeletal anchorage system that integrates easily into clinical practice and allows treatment of cases that were difficult or impossible to treat previously.

Finite Element Analysis of Bone Stress for Miniscrew Implant Proximal to Root Under Occlusal Force and Implant Loading

Because of the narrow interradicular spaces and varying oral anatomies of individual patients, there is a very high risk of root proximity during the mini implants inserting. The authors hypothesized that normal occlusal loading and implant loading affected the stability of miniscrew implants placed in proximity or contact with the adjacent root. The authors implemented finite element analysis (FEA) to examine the effectiveness of root proximity and root contact. Stress distribution in the bone was assessed at different degrees of root proximity by generating 4 finite element models: the implant touches the root surface, the implant was embedded in the periodontal membrane, the implant touches the periodontal surface, and the implant touches nothing. Finite element analysis was then carried out with simulations of 2 loading conditions for each model: condition A, involving only tooth loading and condition B, involving both tooth and implant loading. Under loading condition A, the maximum stress on the bone for the implant touching the root was the distinctly higher than that for the other models. For loading condition B, peak stress areas for the implant touching the root were the area around the neck of the mini implant and the point of the mini implant touches the root. The results of this study suggest that normal occlusal loading and implant loading contribute to the instability of the mini implant when the mini implant touches the root.

A 2-year outcome audit of a versatile orthodontic bone anchor

This study examined complications leading to, or possibly leading to, treatment failure, related to the use of the orthodontic bone anchor (OBA). The OBA is a potential means of providing absolute anchorage and consists of a base-plate fixed with mono-cortical screws, a neck piercing the soft tissues, and a coronal part with conventional orthodontic hooks, tubes or slots. The investigation took the form of a single centre prospective registry at a supra-regional teaching hospital. Eighteen patients (average age 21 years) had one to four OBAs placed between January 2000 and February 2002. Altogether 35 OBAs were placed. Follow-up took place until April 2004. Reasons for placing the OBAs were noted together with any associated complications during the follow-up period. Twenty-three OBAs have been removed so far, four prematurely (one of them before it was taken into use, due to a change of treatment plan enforced by loss of the contralateral OBA). Nineteen were removed as planned after completion of the intended tooth movements. Common (but minor) complications included granulations, acute gingivitis and gingival recession. Light mobility of the OBA was also noted in some cases, but without clinical repercussions. The OBA can be loaded directly, at the level of the orthodontic archwire or more occlusally. It can be placed at any site at the circumference of the jaws, given good quality and thickness of the bony wall. Conventional biomechanical techniques can be applied. However, the failure rate (premature loss of OBA) of 8.6% is considered high, and has necessitated changes in the hardware and protocol.

Miniscrews: a simple alternative for complex treatments

The use of mini-implants has already considerably changed the way we plan and perform a large number of orthodontic treatments to the point where, today, we can envisage taking a fresh look at some of our "classical" treatment options. This article will describe a number of clinical cases drawn from several years' experience of working with miniscrews. We present first a brief flashback and an overview of the different indications for micro-implants followed by four case studies presenting treatments which, without miniscrews, would have been treated by much more aggressive approaches.

A Novel Rat Model of Orthodontic Tooth Movement Using Temporary Skeletal Anchorage Devices: 3D Finite Element Analysis and In Vivo Validation

The aim of this animal study was to develop a model of orthodontic tooth movement using a microimplant as a TSAD in rodents. A finite element model of the TSAD in alveolar bone was built using μCT images of rat maxilla to determine the von Mises stresses and displacement in the alveolar bone surrounding the TSAD. For in vivo validation of the FE model, Sprague-Dawley rats (n = 25) were used and a Stryker 1.2 × 3 mm microimplant was inserted in the right maxilla and used to protract the right first permanent molar using a NiTi closed coil spring. Tooth movement measurements were taken at baseline, 4 and 8 weeks. At 8 weeks, animals were euthanized and tissues were analyzed by histology and EPMA. FE modeling showed maximum von Mises stress of 45 Mpa near the apex of TSAD but the average von Mises stress was under 25 Mpa. Appreciable tooth movement of 0.62 ± 0.04 mm at 4 weeks and 1.99 ± 0.14 mm at 8 weeks was obtained. Histological and EPMA results demonstrated no active bone remodeling around the TSAD at 8 weeks depicting good secondary stability. This study provided evidence that protracted tooth movement is achieved in small animals using TSADs.

Revisiting the stability of mini-implants used for orthodontic anchorage

BACKGROUND/PURPOSE

The aim of this study is to comprehensively analyze the potential factors affecting the failure rates of three types of mini-implants used for orthodontic anchorage.

METHODS

Data were collected on 727 mini-implants (miniplates, predrilled titanium miniscrews, and self-drilling stainless steel miniscrews) in 220 patients. The factors related to mini-implant failure were investigated using a Chi-square test for univariate analysis and a generalized estimating equation model for multivariate analysis.

RESULTS

The failure rate for miniplates was significantly lower than for miniscrews. All types of mini-implants, especially the self-drilling stainless steel miniscrews, showed decreased stability if the previous implantation had failed. The stability of predrilled titanium miniscrews and self-drilling stainless steel miniscrews were comparable at the first implantation. However, the failure rate of stainless steel miniscrews increased at the second implantation. The univariate analysis showed that the following variables had a significant influence on the failure rates of mini-implants: age of patient, type of mini-implant, site of implantation, and characteristics of the soft tissue around the mini-implants. The generalized estimating equation analysis revealed that mini-implants with miniscrews used in patients younger than 35 years, subjected to orthodontic loading after 30 days and implanted on the alveolar bone ridge, have a significantly higher risk of failure.

CONCLUSION

This study revealed that once the dental surgeon becomes familiar with the procedure, the stability of orthodontic mini-implants depends on the type of mini-implant, age of the patient, implantation site, and the healing time of the mini-implant. Miniplates are a more feasible anchorage system when miniscrews fail repeatedly.

Finite element analysis of mandibular molar protraction mechanics using miniscrews

BACKGROUND/OBJECTIVES

The aim of this study was to determine the most desirable force system to achieve molar protraction from an interdental miniscrew minimizing side-effects. Several iterations of force delivery were simulated through variations in the height of a miniscrew, length of a molar extension arm, and incorporation of a lingual force.

MATERIALS/METHODS

A three-dimensional mesh model of the right posterior segment of the mandible was developed from cone beam computed tomography data from a patient missing a first molar. Protraction appliances were constructed using computer-aided design software and integrated with finite element software. After mesh generation, a total of 80 loading conditions were simulated by altering the extension arm length (2-10mm), miniscrew height (0-8mm), and magnitude of protraction force from the lingual side (0-1.5 N). A constant labial force of 1 N was used in all models.

RESULTS

As the length of the extension arm increased, mesial tipping decreased, rotation decreased, and buccolingual inclination remained the same without lingual traction force. Lingual traction reduced rotation but increased tipping. Similar trends were observed in all situations despite of the height of the miniscrew.

CONCLUSIONS

The height of the miniscrew is not as critical in affecting tooth movement during mandibular second molar protraction as the length of the extension arm. The most ideal force system in the model appeared to be the longest extension arm (10mm) with the addition of a lingual force of half or equal magnitude of the labial force.

Effect of different sterilization modes on the surface morphology, ion release, and bone reaction of retrieved micro-implants

OBJECTIVE

To compare as-received and sterilized micro-implants in order to assess the prospects of reusing them.

MATERIALS AND METHODS

Forty micro-implants from a single manufacturing lot were used in the study. Thirty were retrieved from patients after successful service in their mouth and with no signs of failure. The retrieved micro-implants were divided into three groups, according to method of sterilization: autoclave, gamma radiation, or ultraviolet radiation. All groups were subjected to scanning electron microscope analysis for surface morphology assessment. The specimens were immersed in a standard simulated body-fluid solution kept at 37°C in an incubator; the solution was then withdrawn at 24 hours and 30 days to evaluate aluminum and vanadium ion release by atomic absorption spectrophotometer in parts per billion. The micro-implants were then surgically implanted into the tibia of rabbits for a 1-month healing period, and the bone-implant blocks were processed for routine histologic examination.

RESULTS

This study revealed that sterilized micro-implants had altered surface topography, different ion release values, and different histologic cell reactions than the as-received micro-implants.

CONCLUSIONS

Within the limitations of this study, it can be concluded that retrieved self-drilling micro-implants have tip sharpness variations that require correction before insertion by bone drilling. The autoclave-sterilized micro-implants showed better histologic results than micro-implants sterilized by gamma or ultraviolet rays.

Effect of healing time on bone-implant contact of orthodontic micro-implants: a histologic study

Objectives. This study aimed to evaluate the effect of immediate and delayed loading of orthodontic micro-implants on bone-implant contact. Materials and Methods. Sixty four micro-implants were implanted in dog's jaw bone. The micro-implants were divided into loaded and unloaded (control) groups. The control group had two subgroups: four and eight weeks being implanted. The loaded group had two subgroups of immediate loading and delayed (after four weeks healing) loading. Loaded samples were subjected to 200g load for four weeks. After sacrificing the animals micro-implants and surrounding tissues were observed histologically. Bone-implant contact ratios (BIC) were calculated and different groups' results were compared by three-way ANOVA. Results. Mean survival rate was 96.7% in general. Survival rates were 96.7%, 94.4% and 100% for control, immediate and delayed loaded groups, respectively. BIC values were not significantly different in loaded and control groups, immediate and delayed loading groups, and pressure and tension sides. Mandibular micro-implants had significantly higher BIC than maxillary ones in immediate loading, 4-weeks control, and 8-weeks control groups (P = 0.021, P = 0.009, P = 0.003, resp.). Conclusion Immediate or delayed loading of micro-implants in dog did not cause significant difference in Bone-implant contact which could be concluded that healing time had not significant effect on micro-implant stability.

Does cortical thickness influence the primary stability of miniscrews?: A systematic review and meta-analysis

OBJECTIVE

To investigate whether there is evidence to support the association between cortical thickness (CtTh) and the primary stability of mini-implants (MI).

MATERIALS AND METHODS

A search was performed including articles published until September 2013. The inclusion criteria comprised observational clinical studies conducted in patients who received monocortical MI for orthodontic anchorage and in vivo or ex vivo experimental studies performed to evaluate the primary stability of MI, studies that evaluated the association between CtTh and MI primary stability, CtTh measurement performed numerically, and MI primary stability evaluated by implant stability quotient value, Periotest value , pull-out strength, or insertion torque. Studies conducted exclusively in artificial bone or finite elements were excluded.

RESULTS

Abstract and title reading identified 15 possible articles to be included. After reading the complete text, three were excluded. One article was found by hand searching and another excluded for an overlapping sample. Finally, 12 articles were selected. A positive correlation was found between primary stability and CtTh when studies that evaluated primary stability through PS were grouped (r  =  .409) and when studies that evaluated stability in humans were grouped (r  =  .338).

CONCLUSIONS

There is a positive association between MI primary stability and CtTh of the receptor site. However, there is still a lack of well-designed clinical trials.

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.

[Combined use of Beneslider and lingual braces, mechanical aspects and procedures]

Over the last years, a tendency to prefer purely intra-oral appliances with minimal need for patient cooperation is noticed if upper molars should be distalized. Unfortunately, most of the conventional devices for non-compliance upper molar distalization produce unwanted side effects such as anchorage loss. To minimize or eliminate anchorage loss, mini-screws attracted a great attention in recent years because of minimal surgical invasiveness and low cost. Using the anterior palate as an insertion site, the failure rate is extremely low, there is no risk of root damage and the appliances are out of the path of tooth movement. Based on comprehensive clinical documentation, the rational and practical applications of the Beneslider in combination with lingual braces are presented. By this procedure, extractions in the upper arch and reactive forces in the lower arch resulting in a protrusion of the incisors can be avoided with an invisible treatment appliance.

Nanostructured severe plastic deformation processed titanium for orthodontic mini-implants

Titanium mini-implants have been successfully used as anchorage devices in Orthodontics. Commercially pure titanium (cpTi) was recently replaced by Ti-6Al-4V alloy as the mini-implant material base due to the higher strength properties of the alloy. However, the lower corrosion resistance and the lower biocompatibility have been lowering the success rate of Ti-6Al-4V mini-implants. Nanostructured titanium (nTi) is commercially pure titanium that was nanostructured by a specific technique of severe plastic deformation. It is bioinert, does not contain potentially toxic or allergic additives, and has higher specific strength properties than any other titanium applied in medical implants. The higher strength properties associated to the higher biocompatibility make nTi potentially useful for orthodontic mini-implant applications, theoretically overcoming cpTi and Ti-6Al-4V mini-implants. The purposes of the this work were to process nTi, to mechanically compare cpTi, Ti-6Al-4V, and nTi mini-implants by torque test, and to evaluate both the surface morphology and the fracture surface characteristics of them by SEM. Torque test results showed significant increase in the maximum torque resistance of nTi mini-implants when compared to cpTi mini-implants, and no statistical difference between Ti-6Al-4V and nTi mini-implants. SEM analysis demonstrated smooth surface morphology and transgranular fracture aspect for nTi mini-implants. Since nanostructured titanium mini-implants have mechanical properties comparable to titanium alloy mini-implants, and biocompatibility comparable to commercially pure titanium mini-implants, it is suggestive that nanostructured titanium can replace Ti-6Al-4V alloy as the material base for mini-implants.

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.

[Improvement of mini-implant stability in orthodontics]

Orthodontists are continuing to increase the use of mini-implants as a source of skeletal anchorage. However, the relatively high 16.4% rate of their failures remains a problem. An analysis of articles in the literature on the loss of mini-implants shows that larger size anchorage screws and plates inserted in the anterior and median regions of the hard palate are highly stable and, accordingly, contribute to a high rate of optimum orthodontic outcomes. It is the reliability of the mini-implant/skeletal structure couple that is the principal factor in this success. With mini-implants whose heads possess internal threads, orthodontists can attach different types of stable, screwed-in abutments. And with long plates with specifically designed perforations splinting two mini-implants together, orthodontists can further increase the stability of this artificial anchorage. By employing a system with pre-fabricated components orthodontists can quickly create skeletal anchorage adaptable to the mechanics of different techniques.

Combined orthodontic temporary anchorage devices and surgical management of the alveolar ridge augmentation using distraction osteogenesis

PURPOSE

Distraction osteogenesis is used to increase the vertical and transverse bone volume of the alveolar ridge and requires 3-dimensional vector controls. Temporary anchorage devices (TADs) may be inserted into the transported segment, enabling distraction vector control by exerting orthodontic force. The authors' aim was to describe a combined orthodontic surgical technique involving vertical alveolar distraction using TADs.

MATERIALS AND METHODS

Four patients who presented with extensive anterior alveolar ridge bone loss combined with the incisors and canines underwent treatment according to a combined surgical orthodontic protocol, including presurgical orthodontic preparation and a preimplantation surgical augmentation stage involving vertical distractor insertion. During the active vertical alveolar distraction process, 3 TADs were inserted. Intraoral orthodontic elastics were attached to the main orthodontic archwire exerting multidirectional forces to control the vertical distraction vector. After 4 to 5 months of vector controlling and active bone molding, the TADs were removed.

RESULTS

Anterior alveolar ridge augmentation using distraction osteogenesis was achieved. The application of TADs for better anterior segment curvature enabled dental implant insertion, ideal positioning, and restoration.

CONCLUSIONS

A combined surgical orthodontic management protocol involving vertical alveolar distraction osteogenesis for augmentation purposes using TADs enables improved alveolar ridge volume and architecture for the preimplantation stage.

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.

Evaluation of the palatal bone for placement of orthodontic mini-implants in Japanese adults

Mini-implants are increasingly being used for orthodontic anchorage in the palate. The anatomical structure of the jaw must be properly evaluated prior to use; however, there are a few research reports providing basic data regarding the palate. Bone thickness was measured and bone morphology evaluated in the palates of Japanese people. The palates of five Japanese adult cadavers and 15 skulls were examined. The samples were imaged and measured using the micro-CT system. In the mid-palatine suture region, the cortical bone had a complex mesh-like structure and was thicker than surrounding areas. Cortical bone thickness varied depending on the site. The mid-palatine suture region is an ideal site for mini-implant insertion; however, because bone and cortical bone thickness markedly decrease in the lateral region, careful attention should be paid when inserting mini-implants in the mid-palatine suture.