Placement and removal torque values of orthodontic miniscrew implants

Functionality testing of an innovative biomechanically optimized and surface-modified orthodontic mini-screw-a comparative study

PURPOSE

The failure rate of orthodontic mini-screws depends strongly on primary stability and, thus, on insertion torque. Further improvement regarding the failure rate might be achieved by modifying the surface coating. Therefore, the aim of the study was to investigate the stability of a newly designed and surface-modified orthodontic mini-screw in beagle dogs.

METHODS

Newly designed mini-screws coated either with DOTIZE® or DOTIZE®-copper (DOT GmbH, Rostock, Germany; each: n = 24) were inserted in the mandibles of eight beagle dogs for a duration of 8 months. Insertion and removal torque were measured. These data were compared to values generated by using the artificial bone material Sawbones® (Sawbones Europe AB, Malmö, Sweden). Experiments with and without torque limitation (each: n = 5) were run. The bone-to-implant contact rate and the amount of bone between the threads were examined. Statistical significance was set at P < 0.05.

RESULTS

The success rates of the in vivo study reached high levels with 95.3% for the DOTIZE-coated and 90.5% for the DOTIZE-copper-coated screws, whereas the insertion and removal torque did not differ between the coatings. During insertion, a torque limitation of 20 Ncm was necessary to ensure that the recommended limit was not exceeded. The insertion in Sawbones without torque limitation revealed a significantly higher torque compared to torque-limited insertion (18.2 ± 1.3 Ncm, 23.6 ± 1.3 Ncm). Bending occurred (n = 5) in the thread-free part of the mini-screw.

CONCLUSIONS

Surface coating might be able to improve the performance of orthodontic mini-screws. The study showed high success rates and stable mini-screws until the end of observation. Further investigations are necessary.

Success rate of infrazygomatic crest mini-implants used for en-masse retraction of maxillary anterior teeth in first premolar extraction cases: A three-dimensional comparative prospective clinical trial between adolescents and young adults

BACKGROUND

The purpose of this study was to compare the success rate of infrazygomatic mini-implants between adolescents and young adults.

METHODS

A total of 60 subjects of different age groups ie, (group I [adolescents]: 12-18 years, mean age: 14.9 ± 2.9 years; group II [young adults]: 19-25 years, mean age = 21.9 ± 3.1 years) were assessed in the study. En-masse retraction of maxillary anterior teeth was carried out with extraction of upper first premolars with infrazygomatic crest (IZC) mini-implants as anchorage units. Clinical parameters such as success rate, soft tissue thickness, maximum insertion torque, maximum removal torque, pain response, soft tissue response, and cone-beam computed tomography parameters such as embedded angulation, penetration depth, thickness of bone on buccal and palatal aspect of mini-implant, and peri-implant bone density were evaluated.

RESULTS

The success rate of IZC mini-implants in adolescents was found to be 96.6% and 98.3% in young adults respectively. There was no significant difference in success rate between the two groups. Intergroup comparison showed a significant difference (P < 0.05) in terms of maximum insertion torque, maximum removal torque, soft tissue thickness, cortical bone thickness, and peri-implant bone density values. Comparison between right and left side revealed a significant difference (P < 0.05) with regards to soft tissue response, soft tissue thickness, total bone thickness, cortical bone thickness, and peri-implant bone density.

CONCLUSIONS

There was no significant difference in the success rate of IZC mini-implants between adolescents and young adults. Thus, the use of IZC mini-implants can be recommended in adolescents for successful orthodontic treatment.

Alveolar Bone Microstructure Surrounding Orthodontic Anchor Screws with Plasma Surface Treatment in Rats

A lateral load was applied to anchor screws that had undergone surface treatment, and the structure, cellular dynamics, and quality of the bone surrounding anchor screws were analyzed to investigate the effect of this surface treatment on the peri-implant jawbone. In addition, bone microstructural characteristics were quantitatively evaluated for each site of loading on the bone around the anchor screw. Rats were euthanized after observation on days 3, 5, or 7, and bone quality analyses were performed. Bone-implant contact rate increased more rapidly at an early stage in the treated surface group than in the untreated surface group. Bone lacuna morphometry showed that the measured values adjacent to the screw at the screw neck on the compressed side (A) and at the screw tip on the uncompressed side (D) were significantly lower than those at the screw tip on the compressed side (B) and at the screw neck on the uncompressed side (C). Collagen fiber bundle diameter showed that the measured values adjacent to regions A and D were significantly higher than those at regions B and C. Anchor screw surface activation facilitates initial bone contact of the screw, suggesting that early loading may be possible in clinical practice.

Mechanical properties and biocompatibility of a novel miniscrew made of Zr70Ni16Cu6Al8 bulk metallic glass for orthodontic anchorage

The purpose of the present study was to fabricate a miniscrew possible for clinical application using Zr₇₀Ni₁₆Cu₆Al₈ bulk metallic glass (BMG), which has high mechanical strength, low elastic modulus, and high biocompatibility. First, the elastic moduli of Zr-based metallic glass rods made of Zr₅₅Ni₅Cu₃₀Al₁₀, Zr₆₀Ni₁₀Cu₂₀Al₁₀, Zr₆₅Ni₁₀Cu_17.5Al_7.5, Zr₆₈Ni₁₂Cu₁₂Al₈, and Zr₇₀Ni₁₆Cu₆Al₈ were measured. Zr₇₀Ni₁₆Cu₆Al₈ had the lowest elastic modulus among them. Then, we fabricated Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrews with diameters from 0.9 to 1.3 mm, conducted a torsion test, and implanted them into the alveolar bone of beagle dogs to compare insertion torque, removal torque, Periotest, new bone formation around the miniscrew, and failure rate compared with 1.3 mm diameter Ti-6Al-4 V miniscrew. The Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrew exhibited a high torsion torque even if the miniscrew had a small diameter. Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrews with a diameter of 1.1 mm or less had higher stability and lower failure rate than 1.3 mm diameter Ti-6Al-4 V miniscrews. Furthermore, the smaller diameter Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrew was shown, for the first time, to have a higher success rate and to form more new bone around the miniscrew. These findings suggested the usefulness of our novel small miniscrew made of Zr₇₀Ni₁₆Cu₆Al₈ BMG for orthodontic anchorage.

Revisiting the Complications of Orthodontic Miniscrew

Miniscrew has been used widely as an effective orthodontic anchorage with reliable stationary quality, ease of insertion and removal techniques, immediate or early loading, flexibility in site insertion, less trauma, minimal patient cooperation, and lower price. Nonetheless, it is not free of complications, and they could impact not only the miniscrew success rate but also patients’ oral health. In this article, literature was searched and reviewed electronically as well as manually to evaluate the complications of orthodontic miniscrew. The selected articles are analyzed and subcategorized into complications during and after insertion, under loading, and during and after removal along with treatment if needed according to the time. In addition, the noteworthy associated factors such as the insertion and removal procedures, characteristics of both regional and local anatomic structures, and features of the miniscrew itself that play a significant role in the performance of miniscrews are also discussed based on literature evidence. Clinicians should notice these complications and their related factors to make a proper treatment plan with better outcomes.

A Scoping Review about the Characteristics and Success-Failure Rates of Temporary Anchorage Devices in Orthodontics

This study synthesized the scientific evidence concerning the main characteristics of the Temporary Anchorage Devices (TADs) used in orthodontics and reported the success-failure rates during treatment. For that means, this scoping review collected articles from previous research. A complementary search was carried out in the databases PubMed-MEDLINE, Scopus, LILACS, and EMBASE, focusing on original studies published from 2010 to 2020. We analyzed the main characteristics of the publications. As a result, 103 articles were included. Most of the research was conducted among different groups, who needed TADs principally in the maxilla and an interradicular location between the second premolar and first molar. AbsoAnchor, Dentos Inc., Daegu, Korea, was the most used brand of TADs. The most common characteristics of the devices and biomechanics were a diameter and length of 1.6 mm and 8 mm, a self-drilled system, a closed technique for placement, immediate loading, and forces that ranged between 40 and 800 g. Of the studies, 47.6% showed success rates ≥90%. In conclusion, high success rates were found for TADs, and differences were found according to sociodemographic and clinical variables. The studies showed variability in methodological design, and scientific publications were concentrated in certain countries. We recommend further scientific research on TADs using more standardized designs.

Influence of late removal after treatment on the removal torque of microimplants

Objective

To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors.

Methods

The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque.

Results

The mean period of total in-bone stay of microimplants in the post-retention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4–5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively.

Conclusions

The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

Evaluation of clinical parameters for the stability of 2 types of miniscrews

INTRODUCTION

The purpose of this research was to compare insertion techniques and effects on mechanical and clinical parameters between 2 types of miniscrews.

METHODS

Forty-four consecutive patients whose orthodontic treatment involved the use of miniscrews (miniscrew A [MA] and miniscrew B [MB]) for anchorage were included in this study. Miniscrews were placed with predrilling or self-drilling; peak maximum insertion torque (MIT) and Periotest values were measured. Cone-beam computed tomography was performed after the insertion of miniscrews and root proximity determination; cortical bone thickness was also analyzed. Periotest values were measured after the application of orthodontic force.

RESULTS

Self-drilling produced higher Periotest values (P <0.01) for MA and higher MIT (P <0.01) for MB with closer root proximity (P <0.05). MB had higher MIT and Periotest values with drilling compared with MA (P <0.05); MB also showed closer root proximity (P <0.05). Successful miniscrews had lower MIT (P <0.05) for MB and lower Periotest values (P <0.01) for both MA and MB, with significantly more distant root proximity (P <0.01). Self-drilling produced higher Periotest values at the time of placement (P <0.01) and after 4 weeks (P <0.05) in MA. Drilling produced higher Periotest values for MB at the time of placement (P <0.05). MIT had positive correlations with Periotest values for MB with self-drilling (P <0.01) and with root proximity for MA with drilling (P <0.01). Periotest values had negative correlations with root proximity for MA and the MB group with drilling (P <0.01).

CONCLUSIONS

For miniscrews with larger diameters, higher MIT may result in more mobility (higher Periotest values). Drilling can avoid root contact and enhance primary stability, thus producing lower Periotest values.

Long-term evaluation of factors affecting removal torque of microimplants

Background

The current study aimed to evaluate factors affecting the long-term stability of microimplants using removal torque and the correlation between removal torque and clinical variables.

Materials and methods

This research evaluated 703 microimplants placed in 354 patients (mean age: 30.4 ± 12.1 years). The removal torque was evaluated according to various clinical variables including sex, age, placement site, microimplant size, and placement method (self-drilling versus pre-drilling). Pearson correlation and stepwise multiple linear regression analyses were performed to investigate different variables and their association with removal torque.

Results

The mean removal torque was significantly higher in the mandible (4.46 N cm) than in the maxilla (3.73 N cm). The values in the posterior teeth/retromolar areas were significantly higher than those in the anterior teeth area. There were no significant difference in terms of sex. Teenagers had a lower removal torque than older adults in the mandible, but not in the maxilla. Microimplants with a greater length and diameter, except for those with a greater diameter in the maxilla, was associated with a higher removal torque. Regardless of placement torque, the removal torque convergently reached approximately 4 N cm in both placement methods. The removal torque was significantly correlated with screw length in the self-drilling group and with diameter in the pre-drilling group.

Conclusions

Removal torque was related with placement site, age, placement method, and length and diameter of microimplants.

Effect of surface treatment on the mechanical stability of orthodontic miniscrews

OBJECTIVES

To provide collective quantitative evidence about the effect of surface treatments on the mechanical stability of orthodontic miniscrews (MSs).

MATERIALS AND METHODS

The study was registered in PROSPERO (No. CRD42020209652). The research question was defined according to the PICO (population, intervention, control, and outcomes) format. Various research databases were searched for animal and human studies on effects of surface treatment on the mechanical stability of MSs. Both prospective and retrospective in vivo clinical studies published in English were included. The risk of bias was assessed using SYRCLE's risk of bias tool for animal studies. The meta-analysis was conducted using RevMan 5.4.

RESULTS

A total of 109 articles were identified; 14 were included in the systematic review, and seven studies with sandblasting, acid etching (SLA) methods of surface treatment were included for meta-analysis. The number of study participants ranged from 6 to 24 (total n = 185), with a mean of 13.2. A total of 949 MSs were used with a mean of 67.8. The overall success rate for surface-treated MSs ranged from 47.9% to 100%. Forest plot of removal torque values showed significantly higher values for SLA surface-treated MSs compared with controls with a standard mean difference of 2.61 (95% confidence interval = 1.49-3.72, I2 = 85%). Forest plot of insertion torque showed a standard mean difference of -6.19 (95% confidence interval = -13.63-1.25, I2 = 98%, P = .10).

CONCLUSIONS

Surface treatment of MSs improved primary and secondary stability with good osseointegration at the bone-implant surface. However, significant heterogeneity across the studies included in the meta-analysis made it difficult to draw conclusions.

Influence of pre-drilling diameter on the stability of orthodontic anchoring screws in the mid-palatal area

PURPOSE

The aim of this study was to investigate the stability of orthodontic anchor screws (OASs) in the mid-palatal area according to pre-drilling diameter.

METHODS

The success rate of 161 OASs (83 patients, φ2.0 mm, 6.0 mm in length) placed in a corresponding area to the mesial and distal borders of the first molar (mesial zone and distal zone) was assessed according to placement location and pre-drilling diameter (1.2 and 1.5 mm). Placement torque values from 73 OASs with a pre-drilling diameter of 1.2 mm were compared between success and failure groups.

RESULTS

The success rates of OASs pre-drilled with φ1.2 and 1.5 mm were 94.5% and 83.0%, respectively (P < 0.05); corresponding rates in the mesial zone were 100.0% and 77.3% (P < 0.005), and those in the distal zone were 89.2% and 88.6%, respectively. Placement torques of OASs predrilled with φ1.2 mm in the success and failure groups were 25.9 and 19.2 N·cm, respectively (P < 0.05).

CONCLUSION

A smaller pre-drilling diameter was associated with a higher success rate of OASs in the mid-palatal area, especially in the mesial zone. When pre-drilling diameter of 1.2 mm was used for φ2.0 mm OAS, greater placement torque was indicative of greater OAS stability.

Effect of Different Head Hole Position on the Rotational Resistance and Stability of Orthodontic Miniscrews: A Three-Dimensional Finite Element Study

The orthodontic miniscrew is driven into bone in a clockwise direction. Counter-clockwise rotational force applied to the implanted miniscrew can degrade the stability. The purpose of this three-dimensional finite element study was to figure out the effect of shifting the miniscrew head hole position from the long axis. Two miniscrew models were developed, one with the head hole at the long axis and the other with an eccentric hole position. One degree of counter-clockwise rotation was applied to both groups, and the maximum Von-Mises stress and moment was measured under various wire insertion angles from −60° to +60°. All Von-Mises stress and moments increased with an increase in rotational angle or wire insertion angle. The increasing slope of moment in the eccentric hole group was significantly higher than that in the centric hole group. Although the maximum Von-Mises stress was higher in the eccentric hole group, the distribution of stress was not very different from the centric hole group. As the positive wire insertion angles generated a higher moment under a counter-clockwise rotational force, it is recommended to place the head hole considering the implanting direction of the miniscrew. Clinically, multidirectional and higher forces can be applied to the miniscrew with an eccentric head hole position.

Comparison of one versus two maxillary molars distalization with iPanda: a finite element analysis

Background

The purpose of this study was to compare the stress distribution and displacement patterns of the one versus two maxillary molars distalization with iPanda and to evaluate the biomechanical effect of distalization on the iPanda using the finite element method.

Methods

The finite element models of a maxillary arch with complete dentition, periodontal ligament, palatal and alveolar bone, and an iPanda connected to a pair of midpalatal miniscrews were created. Two models were created to simulate maxillary molar distalization. In the first model, the iPanda was connected to the second molar to simulate a single molar distalization. In the second model, the iPanda was connected to the first molar to simulate “en-masse” first and second molar distalization. A varying force from 50 to 200 g was applied. The stress distribution and displacement patterns were analyzed.

Results

For one molar, the stress was concentrated at the furcation and along the distal surface in all roots with a large amount of distalization and distobuccal crown tipping. For two molars, the stress in the first molar was 10 times higher than in the second molar with a great tendency for buccal tipping and a minimal amount of distalization. Moreover, the stress concentration on the distal miniscrew was six times higher than in the mesial miniscrew with an extrusive and intrusive vector, respectively.

Conclusions

Individual molar distalization provides the most effective stress distribution and displacement patterns with reduced force levels. In contrast, the en-masse distalization of two molars results in increased force levels with undesirable effects in the transverse and vertical direction.

Stability of immediately loaded 3 mm long miniscrew implants: a feasibility study

Introduction:

Shorter miniscrew implants (MSIs) are needed to make orthodontics more effective and efficient.

Objective:

To evaluate the stability, insertion torque, removal torque and pain associated with 3 mm long MSIs placed in humans by a novice clinician.

Methods:

82 MSIs were placed in the buccal maxillae of 26 adults. Pairs of adjacent implants were immediately loaded with 100g. Subjects were recalled after 1, 3, 5, and 8 weeks to verify stability and complete questionnaires pertaining to MSI-related pain and discomfort.

Results:

The overall failure rate was 32.9%. The anterior and posterior MSIs failed 35.7% and 30.0% of the time, respectively. Excluding the 10 MSIs (12.2%) that were traumatically dislodged, the failure rates in the anterior and posterior sites were 30.1% and 15.2%, respectively; the overall primary failure rate was 23.6%. Failures were significantly (p= 0.010) greater (46.3% vs 19.5%) among the first 41 MSIs than the last 41 MSIs that were placed. Excluding the traumatically lost MSIs, the failures occurred on or before day 42. Subjects experienced very low pain (2.2% of maximum) and discomfort (5.5% of maximum) during the first week only.

Conclusions:

Shorter 3 mm MSIs placed by a novice operator are highly likely to fail. However, failure rates can be substantially decreased over time with the placement of more MSIs. Pain and discomfort experienced after placing 3 mm MSIs is minimal and temporary.

Can maxilla and mandible bone quality explain differences in orthodontic mini-implant failures?

Purpose: This study aimed to compare the risk of orthodontic mini-implant (OMI) failure between maxilla and mandible. A critical analysis of finite-element studies was used to explain the contradiction of the greatest clinical success for OMIs placed in the maxilla, despite the higher quality bone of mandible. Materials and Methods: Four tridimensional FE models were built, simulating an OMI inserted in a low-dense maxilla, control maxilla, control mandible, and high-dense mandible. A horizontal force was applied to simulate an anterior retraction of 2 N (clinical scenario) and 10 N (overloading condition). The intra-bone OMI displacement and the major principal bone strains were used to evaluate the risk of failure due to insufficient primary stability or peri-implant bone resorption. Results: The OMI displacement was far below the 50–100 µm threshold, suggesting that the primary stability would be sufficient in all models. However, the maxilla was more prone to lose its stability due to overload conditions, especially in the low-dense condition, in which major principal bone strains surpassed the pathologic bone resorption threshold of 3000 µstrain. Conclusions: The differences in orthodontic mini-implant failures cannot be explained by maxilla and mandible bone quality in finite-element analysis that does not incorporate the residual stress due to OMI insertion.

Characteristics and Dynamics of Full Arch Distalization Using Transpalatal Arches with Midpalatal and Interradicular Miniscrews as Temporary Anchorage Devices: A Preliminary Finite Element Analysis

INTRODUCTION

Miniscrews have proved quite effective in fixed orthodontic treatment. They can be placed in areas like palatal interradicular zones or midpalatal suture. Despite the value of these methods and their ever-increasing use, their characteristics are not assessed before when implanted in palatal interradicular areas or in the midpalatal suture. We aimed to assess, for the first time, the dynamics of full arch distalization using such miniscrews.

METHODS

A 3D model of maxilla with all permanent dentition was created from a CT scan volume. Tissues were segmented and differentiated. Afterward, miniscrews and appliances were designed, and the whole model was registered within a finite element analysis software by assigning proper mechanical properties to tissues and orthodontic appliances. The full arches were distalized using transpalatal arches with miniscrews as anchorage devices (in two different models). The extents of stresses and patterns of movements of various elements (teeth, miniscrews, appliances, tissues) were estimated. Results and Conclusions. Comparing the two models, it is obvious that in both models, the stress distribution is the highest in the TPA arms and the head of the miniscrew where the spring is connected. In comparison with the displacement in the X-axis, the "mesial in" rotation is seen in the first molar of both models. But there is one exception and that is the "mesial out" rotation of the right second molar. In all measurements, the amount of movement in Model 2 (with palatal interradicular miniscrews) is more than that in Model 1 (with midpalatal miniscrew). In the Y-axis, more tipping is seen in Model 2, especially the anterior teeth (detorque) and the first molar, but in Model 1, bodily movement of the first molar is more evident. Along the Z-axis, the mesial intrusion of the first molar and the distal extrusion of this tooth can be seen in both models. Again, the displacement values are higher in the second model (with interradicular miniscrews). In comparison with micromotion and stress distribution of miniscrews, in Model 1, maximum stress and micromotion is observed at the head of the miniscrew where it is attached to the spring. Of course, this amount of micromotion increases over time. The same is true for Model 2, but with a lower micromotion. As for the amount of stress, the stress distribution in both miniscrews of both models is almost uniform and rather severe.

Maximum insertion torque loss after miniscrew placement in orthodontic patients: A randomized controlled trial

OBJECTIVES

To compare torque recordings of immediately loaded orthodontic miniscrews between insertion time and different post-placement timepoints (2 weeks, 4 weeks and removal time, respectively).

SETTING AND SAMPLE POPULATION

Parallel trial with an allocation ratio of 1:1. Eligibility criteria were needs of fixed orthodontic treatment, no systemic disease and absence of using drugs altering bone metabolism.

MATERIAL AND METHODS

Patients received miniscrews, 2.0 mm diameter and 10 mm length. All miniscrews underwent inter-radicular placement, and they were placed in the maxilla or in the mandible, palatally or buccally. No pre-drilling was performed. Miniscrews were loaded immediately after the insertion and were used for distalization, intrusion, extrusion, mesialization or indirect anchorage. Patients were randomly divided into three groups. For each patient, Maximum Insertion Torque (MIT) was evaluated at baseline. MIT was measured again after 2 weeks and after 4 weeks by tightening the screw a quarter of turn in Groups 1 and 2, respectively. At the end of the treatment, maximal removal torque was evaluated in Group 3. Torque variation with respect to insertion time was considered as the primary outcome. Baseline and longitudinal differences were tested using the linear mixed-effects (LME) model.

RESULTS

Forty seven patients and 74 miniscrews were followed up. An association existed between maximum insertion torque and the observation time. A torque decrease of 26.9% and 30% after 2 weeks was observed for mandibular and maxillary miniscrews, respectively. After 1 month, torque values were similar to the baseline records. The overall success rate was 79.7%. No serious harm was observed.

CONCLUSIONS

Maximum insertion torque undergoes a loss during the first 2 weeks, and its values may depend on the insertion site and the anchorage purpose. Removal torque value is almost the same as the initial torque after 1 month.

Mechanical and clinical evaluation of the effect of microscrew on root proximity and cortical bone thickness

BACKGROUND/OBJECTIVES

Primary stability is required for successful use of microscrew. This study investigated correlations among biomechanical, morphological, and clinical values in relationship to root contact and different placement locations.

MATERIALS/METHODS

Thirty-three microscrews were placed between the molars (n = 18) or in the body of the mandible (n = 15) in three pigs. Insertion torque, Periotest, resonance frequency analysis (RFA), and static and dynamic stiffness were measured. Cone beam computed tomography was performed before and after the insertion of microscrews. Interproximal microscrews were divided into root contacted microscrews (n = 9) and non-root contact microscrews (n = 9). Factorial analysis of variance was conducted, with significance set at P < 0.05.

RESULTS

A significant difference was observed between bodily and root contacted microscrews in Periotest, RFA, static and dynamic stiffness, Tanδ, and bone density (RFA, P = 0.045; all others, P < 0.001). A significant difference was observed between bodily and non-root contact microscrews in Periotest, RFA, and bone density (RFA, P = 0.025; all others, P < 0.001). A significant difference was observed in static (P = 0.01) and dynamic (P = 0.038) stiffness between microscrews with and without contact. Dynamic stiffness (P = 0.02) and Tanδ (P = 0.03) showed significant correlations with Periotest results only in bodily microscrews.

LIMITATIONS

Since a pig bone was used, some differences in the quality and quantity of the bone might be observed between humans.

CONCLUSIONS/IMPLICATIONS

Stiffness values distinguished between microscrews with and without contact. Periotest and RFA results indicated that bodily microscrews were more stable than interproximal microscrews. Periotest and RFA may be useful with large, microscrews and/or in thick cortical bone, but further investigation is required to determine the stability of interproximal microscrews.

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.

NP, Ahmed S, B. VN. Fracture Resistance of Commonly Used Self-drilling Mini-implants of Various Diameters

Context: Self-drilling mini-implants are commonly used in orthodontic treatment procedures, but there is limited information regarding their fracture resistance in areas of high-density bone without predrilling.

Aims: The objective of this study is to compare and evaluate the maximum insertion torque and fracture resistance of 3 commonly used self-drilling mini-implants in India, and to assess the influence of variation in diameter in torque generation.

Materials and methods: 90 mini-implants from 3 different manufacturers with 2 different diameters were drilled into acrylic blocks using a dial indicating torque screwdriver. All mini-implants were drilled at the rate of 20-30 rotations/min, implants were drilled until they fractured. Torque generated at the point of fracture is shown on the dial of the screwdriver. Measurements of the peak insertion torque value for each manufacturer were recorded separately.

Statistical analysis: Analysis of variance, post hoc Bonferroni test.

Results: Analysis of variance test showed a significant difference among all the manufacturers in both the diameters with P < .05. Implants of 1.6 mm diameter of Ancer group have the highest fracture resistance value when compared with the same diameter of JJ Orthodontics and SK Surgicals. Implants with higher diameter have more resistance than those with lower diameter.

Conclusions: The observed highest fracture resistance is 47 Ncm by Ancer and least fracture resistance is 16 Ncm by JJ Orthodontics. The values are higher than the torque required to place mini-implants intraorally. Ancer mini-implants have the highest peak fracture torque, thus more than SK Surgicals and JJ Orthodontics.

Maxillary molar distalization using conventional versus skeletal anchorage devices: A systematic review and meta-analysis

INTRODUCTION

The purpose of this study was to systematically review the evidence regarding conventional versus skeletal anchorage devices for molar distalization.

METHOD

An electronic search was conducted. Hand searching was done in the reference lists of included studies and some journals. Studies comparing conventional and skeletal anchorage for molar distalization in Angle class I or II malocclusions were assessed. Presence of periodontal disease, second or third molar extraction and application of tooth accelerating methods led to exclusion of studies. Generic-inverse variance approach was used for meta-analysis by use of the mean difference and random-effect model. Risk of bias was evaluated in included studies.

RESULTS

A total of 1996 articles were found; of which, 1991 were excluded. The mean amounts of molar distalization/tipping in skeletal anchorage and conventional anchorage groups were 5.35mm/8.44° and 4.25mm/8.31°, respectively, which were not significantly different. The mean amounts of premolar movement in skeletal anchorage and conventional anchorage groups were -0.96mm and +2.21mm, respectively, which was statistically significant (P=0.004). Duration of treatment in skeletal anchorage and conventional anchorage groups was 8.23 months and 7.95 months, respectively, which were significantly different (P=0.0001). Risk of bias was assessed to be high.

CONCLUSION

The conventional and skeletal anchorage devices were not significantly different in terms of the amount of molar distalization/tipping. However, the anchorage loss was lower in the skeletal anchorage group. The treatment time was shorter in the conventional anchorage group. More studies with proper design are required.

EFFECT OF BONE QUALITY ON INITIAL STABILITY OF ORTHODONTIC MINISCREWS

Purpose: This study investigated the effects of the contact percentage (BMC%) of three-dimensional (3D) bone-to-miniscrew specimens in relation to host bone quality on initial miniscrew stability. Furthermore, their correlations were evaluated.

Methods: Orthodontic miniscrews (1.6[Formula: see text]mm in diameter and 11[Formula: see text]mm in length) were inserted into four types of artificial bones to measure the maximum insertion torque value (ITV). The miniscrew and artificial foam bone specimens were also scanned using microcomputed tomography, and the obtained images were imported into Mimics software to reconstruct the 3D models and calculate the BMC%. The Kruskal–Wallis test, Wilcoxon rank-sum test with Bonferroni adjustment, and Spearman correlations were applied for statistical and correlation analyses.

Results and Conclusions: Inserting the orthodontic miniscrew into artificial foam bone exhibiting higher bone quality resulted in higher maximum ITV and BMC%. The initial implant stability, quantified using ITV, was strongly positively ([Formula: see text]) and correlated with BMC%, as measured from microcomputed tomography images.

Role of anatomical sites and correlated risk factors on the survival of orthodontic miniscrew implants: a systematic review and meta-analysis

Objectives

The aim of this review was to systematically evaluate the failure rates of miniscrews related to their specific insertion site and explore the insertion site dependent risk factors contributing to their failure.

Search methods

An electronic search was conducted in the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Knowledge, Scopus, MEDLINE and PubMed up to October 2017. A comprehensive manual search was also performed.

Eligibility criteria

Randomised clinical trials and prospective non-randomised studies, reporting a minimum of 20 inserted miniscrews in a specific insertion site and reporting the miniscrews’ failure rate in that insertion site, were included.

Data collection and analysis

Study selection, data extraction and quality assessment were performed independently by two reviewers. Studies were sub-grouped according to the insertion site, and the failure rates for every individual insertion site were analysed using a random-effects model with corresponding 95% confidence interval. Sensitivity analyses were performed in order to test the robustness of the reported results.

Results

Overall, 61 studies were included in the quantitative synthesis. Palatal sites had failure rates of 1.3% (95% CI 0.3–6), 4.8% (95% CI 1.6–13.4) and 5.5% (95% CI 2.8–10.7) for the midpalatal, paramedian and parapalatal insertion sites, respectively. The failure rates for the maxillary buccal sites were 9.2% (95% CI 7.4–11.4), 9.7% (95% CI 5.1–17.6) and 16.4% (95% CI 4.9–42.5) for the interradicular miniscrews inserted between maxillary first molars and second premolars and between maxillary canines and lateral incisors, and those inserted in the zygomatic buttress respectively. The failure rates for the mandibular buccal insertion sites were 13.5% (95% CI 7.3–23.6) and 9.9% (95% CI 4.9–19.1) for the interradicular miniscrews inserted between mandibular first molars and second premolars and between mandibular canines and first premolars, respectively. The risk of failure increased when the miniscrews contacted the roots, with a risk ratio of 8.7 (95% CI 5.1–14.7).

Conclusions

Orthodontic miniscrew implants provide acceptable success rates that vary among the explored insertion sites. Very low to low quality of evidence suggests that miniscrews inserted in midpalatal locations have a failure rate of 1.3% and those inserted in the zygomatic buttress have a failure rate of 16.4%. Moderate quality of evidence indicates that root contact significantly contributes to the failure of interradicular miniscrews placed between the first molars and second premolars. Results should be interpreted with caution due to methodological drawbacks in some of the included studies.

Electronic supplementary material

The online version of this article (10.1186/s40510-018-0225-1) contains supplementary material, which is available to authorized users.

Failure load and stress analysis of orthodontic miniscrews with different transmucosal collar diameter

Miniscrews have been introduced in orthodontics as temporary anchorage devices (TADs), in order to move the correct teeth and avoid other elements to slide toward a wrong direction. Moreover the ease of use of TADs encouraged clinicians to use miniscrews also for non-conventional purposes, as fixation in mandibular fracture, mini-implant supported temporary pontics, miniscrew-assisted rapid palatal expanders and distalizers. These applications develop higher forces, so TAD fracture can be an unwanted complication. Some authors analyzed torsional loads but no studies measured forces required to bend the screws and ultimate flexural strength. Accordingly, in the present report, Ti-6Al-4V TADs were mechanically evaluated. Seven different diameters of screws were tested: 1.3 mm (Aarhus Screw, Medicon), 1.5 mm (Spider Screw, HDC), 1.6 mm (Aarhus Screw, Medicon), 1.7 mm (Ortho Easy, Forestadent), 1.8 mm (Ortho Implant, 3 M), 1.9 mm (Spider Screw, HDC) and 2.0 mm (Storm, Kristal). The forces to bend the titanium TADs were measured at 0.1 mm, 0.2 mm magnitude of deflections and at maximum load (as peak before screw fracture) in air with a universal testing machine. Statistical analyses were performed. Both at 0.1 mm and at 0.2 mm deflections and at maximum load, the significantly highest forces were reported with 1.7, 1.8, 1.9, and 2.0 mm TADs. The lowest values were reported with 1.6, 1.5, and 1.3 mm mini-implants. No significant differences were reported between 1.6 mm and 1.7 mm screws. It was found that load values in N versus stress in MPa were not fully comparable when screws with small and larger diameter were compared. Therefore, when placing a miniscrew for applications that need maximum shear bending resistance, these results would be considered in order to reduce risk of unwanted fracture.

Additional intraoral radiographs may change the judgment regarding the final position of orthodontic mini-implants

Objective:

This study aimed to assess if additional vertical bitewing (VBW) and/or occlusal (OC) radiographs may change initial judgment based only on periapical radiograph (PAR) about the final position of orthodontic mini-implants (OMI).

Methods:

Subjective and objective analyses were performed. Radiographic images of 26 OMI were divided into four groups: PAR, PAR+VBW, PAR+OC and ALL (PAR+VBW+OC). For subjective analysis, five observers were asked to assess if the position of OMI was favorable to its success, using questionnaires with a four-point scale for responses: 1= definitely not favorable, 2= probably not favorable, 3= probably favorable, or 4= definitely favorable. Each group containing sets of images was presented to them in four different viewing sessions. Objective evaluation compared horizontal distances between OMI tip and the root nearest to the device in PAR and VBW.

Results:

Most of observers (3 out of 5) changed their initial judgment based on PAR about OMI position when additional radiographs were analyzed. Differences between groups (i.e. PAR vs. PAR+VBW; PAR vs. PAR+OC; and, PARvs.ALL) were statistically significant for these observers. For those that changed their judgment about OMI position, confidence level could significantly increase, decrease or even be maintained, not indicating a pattern. There was no agreement for distances between OMI tip and the root nearest to the device in PAR and VBW.

Conclusion:

Considering the limitations of the study, it is concluded that additional radiographic images may change the judgement about OMI final position without necessarily increasing the degree of certainty of such judgment.

Effect of vertical placement angle on the insertion torque of mini-implants in human alveolar bone

Objective:

The aim of the present ex-vivo study was to evaluate the effect of the vertical placement angle of mini-implants on primary stability by analyzing maximum insertion torque (MIT).

Methods:

Mini-implants were placed in 30 human cadavers, inserted at either a 90° or 60° angle to the buccal surface of the maxillary first molar. Out of 60 self-drilling mini-implants used, half were of the cylindrical type and half were of the conical type. Primary stability was assessed by means of measuring the MIT. Data were subjected to analysis of variance (ANOVA) and Newman-Keuls tests. A significance level of 5% was adopted.

Results:

The MIT was higher for both mini-implant types when they were placed at a 90° angle (17.27 and 14.40 Ncm) compared with those placed at a 60° angle (14.13 and 11.40 Ncm).

Conclusions:

MIT values were differed according to the vertical mini-implant placement angle in the maxillary posterior area. Regardless of the type of mini-implant used, placement at a 90° angle resulted in a higher MIT.

Bone and cortical bone thickness of mandibular buccal shelf for mini-screw insertion in adults

OBJECTIVE

To analyze the buccal bone thickness, bone depth, and cortical bone depth of the mandibular buccal shelf (MBS) to determine the most suitable sites of the MBS for mini-screw insertion.

MATERIALS AND METHODS

The sample included cone-beam computed tomographic (CBCT) records of 30 adult subjects (mean age 30.9 ± 7.0 years) evaluated retrospectively. All CBCT examinations were performed with the i-CAT CBCT scanner. Each exam was converted into DICOM format and processed with OsiriX Medical Imaging software. Proper view sections of the MBS were obtained for quantitative and qualitative evaluation of bone characteristics.

RESULTS

Mesial and distal second molar root scan sections showed enough buccal bone for mini-screw insertion. The evaluation of bone depth was performed at 4 and 6 mm buccally to the cementoenamel junction. The mesial root of the mandibular second molar at 4 and 6 mm showed average bone depths of 18.51 mm and 14.14 mm, respectively. The distal root of the mandibular second molar showed average bone depths of 19.91 mm and 16.5 mm, respectively. All sites showed cortical bone depth thickness greater than 2 mm.

CONCLUSIONS

Specific sites of the MBS offer enough bone quantity and adequate bone quality for mini-screw insertion. The insertion site with the optimal anatomic characteristics is the buccal bone corresponding to the distal root of second molar, with screw insertion 4 mm buccal to the cementoenamel junction. Considering the cortical bone thickness of optimal insertion sites, pre-drilling is always recommended in order to avoid high insertion torque.

Comparative evaluation of insertion torque and mechanical stability for self-tapping and self-drilling orthodontic miniscrews - an in vitro study

Background

The aim of the present study was to evaluate the relationship between insertion torque and stability of miniscrews in terms of resistance against dislocation, then comparing a self-tapping screw with a self-drilling one.

Methods

Insertion torque was measured during placement of 30 self-drilling and 31 self-tapping stainless steel miniscrews (Leone SpA, Sesto Fiorentino, Italy) in synthetic bone blocks. Then, an increasing pulling force was applied at an angle of 90° and 45°, and the displacement of the miniscrews was recorded.

Results

The statistical analysis showed a statistically significant difference between the mean Maximum Insertion Torque (MIT) observed in the two groups and showed that force angulation and MIT have a statistically significant effect on miniscrews stability. For both the miniscrews, an angle of 90° between miniscrew and loading force is preferable in terms of stability.

Conclusions

The tested self-drilling orthodontic miniscrews showed higher MIT and greater resistance against dislocation than the self-tapping ones.

Electronic supplementary material

The online version of this article (doi:10.1186/s13005-017-0143-3) contains supplementary material, which is available to authorized users.

Intrusion of maxillary molar using mini-implants: A clinical report and follow-up at 5 years

This clinical report describes a straightforward alternative treatment for adult patients with extruded maxillary molars, who are reluctant to use fixed appliances and complex mechanics. The maxillary molar supereruption of a 57-year-old woman was treated using buttons bonded to the buccal and palatal surfaces of the molars, 2 mini-implants, and elastomeric chains. The intrusion was achieved in 5 months. The treatment stability was observed for 5 years after treatment.

Patient and miniscrew implant factors influence the success of orthodontic miniscrew implants

Data sourcesMedline via PubMed, Scopus and Web of Science databases were searched from January 2003 to March 2015 limited to human studies published in English. Manual searches for the relevant reference lists and a grey literature search via Google Scholar were also conducted.Study selectionProspective and retrospective studies about the stability of miniscrew implants (MIs) used for orthodontic anchorage into the posterior buccal region were considered. Two review authors independently assessed titles and abstracts, and evaluated full manuscripts for the meta-analysis.Data extraction and synthesisThe outcome measure was the success rate of MIs which had to be explicitly reported in order to enable its computation as odds ratios with regards to patient factors (age (years), < 20 vs. ≥ 20; sex, male vs. female; jaw of insertion, maxilla vs. mandible) and MI factors (length, < 8 mm vs. ≥ 1.4 mm; diameter, ≤ 1.4 mm vs. > 1.4 mm). The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS). The meta-analysis was expressed as combined OR and heterogeneity was evaluated (Cochran Q and I²). Subgroup meta-analysis was conducted based on study design, study quality and MIs sample size. Publication bias analysis (Begg's and Eggar's tests) and sensitivity analysis were performed.ResultsSeventeen non-randomised studies, five prospective and 12 retrospective, were included. Significantly higher success rates were observed for the maxillary MIs (14 studies odds ratio (OR), 2.32; 95% CI, 1.81-4.08), older patients (six studies OR, 1.59; 95% CI, 1.14-2.22), and for longer MIs (four studies OR, 0.56 (1/0.46= 2.17); 95% CI, 0.26-0.20) and MIs with larger diameter (four studies OR, 0.62 (1/0.62= 1.61); 95% CI, 0.40-0.97), whereas there was no difference observed between male and female patients (13 studies OR, 1.18; 95% CI, 0.92-1.51). All subgroups acquired homogeneity except for the components of study design regarding the jaw of insertion.ConclusionsThe results of this meta-analysis based on non-randomised clinical studies showed that jaw of insertion, age, MI length and MI diameter are critical risk factors to the success of MIs, whereas sex was not influential.Source of FundingThe Basic Science Research Program of the National Research Foundation of Korea was stated as the source of funding.

Torque ratio as a predictable factor on primary stability of orthodontic miniscrew implants

OBJECTIVE

To evaluate the torque ratio (TR) as a predictable factor on primary stability of orthodontic miniscrews.

DESIGN

Fifty-eight orthodontic patients (17 men, 41 women; mean age, 21.9 years) with a total of 112 titanium miniscrews of 3 different diameters were subjected. Maximum insertion torque (MIT) and maximum removal torque (MRT) were measured by a digital torque checker at the screw placement. Four weeks after the placement, the stable screw was recorded as a success. Multiple logistic regression analysis was performed to estimate the influence of each clinical variable on success.

RESULTS

Success rates were 82.1% to 89.5%, and there were no significant differences in the 3 types of miniscrews. MIT and MRT showed a positive correlation but did not affect the success rates of miniscrews directly. On the contrary, TR was significantly higher in the success group than in the failure group. In multiple regression analysis, age, TR, and screw proximity had a significant influence on the miniscrew success.

CONCLUSIONS

TR might be related with the miniscrew success rates, and it can be used as a predictable factor on primary stability of orthodontic miniscrew implants. Miniscrew implants should be replaced if MRT is significantly lower than MIT at placement surgery.

Effectiveness of methods for detaching orthodontic implants likely to fracture upon rotational torque - an animal study

Orthodontic implants may fracture at the cortical bone level upon rotational torque. The impacted fragment can be detached by a range of methods, which are all more or less time-consuming and injurious to the cortical bone. The aim of this study was to compare three different methods for detaching an orthodontic implant impacted in cortical bone. Health Sciences University of Hokkaido animal ethics committee approved the study protocol. Orthodontic titanium-alloy (Ti-6Al-4 V) implants were placed bilaterally on the buccal side of the mandible of beagle dogs. Subsequently, the implants were detached using either a low-speed handpiece with a round bur, alternatively by use of a low-power or a high-power ultrasonic instrument. In the first experiment, 56 orthodontic implants were placed into the dissected mandible from 7 animals. The methods for detachment were compared with respect to time interval, as well as associated undesirable bone loss as appraised by use of cone-beam computed tomography. In experiment two, 2x2 implants were placed bilaterally in the mandible of 8 animals and subsequently detached by manual rotational torque, and the described three methods for detachment. The implant socket was investigated histologically as a function of removal method immediately after removal, and after 1, 3 and 8 weeks and contrasted with the healing of the socket of the implant that was detached by manual rotational torque. Statistical significance was appraised by the use of non-parametric Kruskal-Wallis one-way analysis of variance. The method using the low-power ultrasonic required significantly longer removal time versus the two other methods, i.e. high-power ultrasonic and low-speed handpiece with a round bur (p < 0.02). The amount of undesirable bone loss was substantially larger with low-speed handpiece with a round bur compared to the two ultrasonic methods (p < 0.05). Bone formation after 3 weeks of healing was more complete following the use of low or high-power ultrasonic instrument in comparison with a low-speed handpiece rotary instrument method. Orthodontic implants likely to fracture upon rotational torque or impacted fractured fragments should be detached preferably with an ultrasonic instrument, because of less associated bone loss and more rapid bone healing compared to the use of a low-speed handpiece rotary instrument.

Evaluation of the surface characteristics of anodic oxidized miniscrews and their impact on biomechanical stability: An experimental study in beagle dogs

INTRODUCTION

In this study, we aimed to assess the surface characteristics and the biomechanical stability of miniscrews with an anodic oxidized surface compared with machined surface miniscrews in beagle dogs.

METHODS

Self-drilled, titanium-aluminum-vanadium alloy miniscrews with an anodic oxidized surface (n = 48) or a machined surface (n = 48) were placed into the mandibles of 12 beagle dogs. The surface characteristics of both types of miniscrews were analyzed before implantation with scanning electron microscopy and atomic force microscopy. Insertion torque was measured during placement of all 96 miniscrews. Half of the implants in each group (24 specimens per subgroup) received 200 to 250 g of tensile force for 3-week or 12-week loading periods. Removal torque was measured in 12 specimens of each subgroup, and bone-implant contact and bone volume were quantified in the other 12 specimens of each subgroup.

RESULTS

Atomic force microscopy measurements demonstrated that the anodic oxidized surface miniscrews had significantly higher roughness parameters than did the machined surface miniscrews (P < 0.001). The 2 types of miniscrews were not significantly different in insertion and removal torque values or in bone-implant contacts and bone volumes, regardless of the loading period.

CONCLUSIONS

Anodic oxidized miniscrews have different surface roughness profiles but no clinically significant superiority in biomechanical stability compared with machined surface miniscrews.

Fracture resistance of commonly used self-drilling orthodontic mini-implants

OBJECTIVE

To investigate the fracture resistance of six commonly used self-drilling orthodontic mini-implants by comparing their respective fracture torques during insertion.

MATERIALS AND METHODS

Ninety self-drilling mini-implants from six manufacturers (Aarhus, Dual-Top, OrthoEasy, Tomas-pin, Unitek, and VectorTAS), with diameters ranging from 1.4 to 1.8 mm, were inserted into acrylic blocks using a custom-made insertion device. Insertion torques were measured using a 6-degree-of-freedom load cell fixed to the base of the acrylic blocks, and peak torques experienced at the time of fracture for each of the mini-implants were recorded. One-way analysis of variance (α  =  .05) was used to compare the fracture torques among the six different groups.

RESULTS

Statistical analysis revealed significant differences (P < .05) in the peak fracture torques among mini-implant groups. Mean fracture torques ranked as follows: Unitek (72 Ncm) > Tomas-pin (36 Ncm) > Dual-Top (32 Ncm) ≈ VectorTAS (31 Ncm) > OrthoEasy (28 Ncm) > Aarhus (25 Ncm), with significant differences found between all manufacturers, except for Dual-Top and VectorTAS.

CONCLUSIONS

Mini-implants tested showed a wide range of torque at fracture depending on the manufacturer, with only a weak correlation between mini-implant diameter and fracture resistance. This torque should be considered at the time of mini-implant insertion to minimize the risk of implant fracture, especially in areas of high-density bone without predrilling.

Stability of smooth and rough mini-implants: clinical and biomechanical evaluation - an in vivostudy

OBJECTIVE

To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability.

METHODS

Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance.

RESULTS

There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference.

CONCLUSIONS

MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques.

The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity

BACKGROUND

Orthognathic surgery with presurgical and postsurgical orthodontic treatment is the most widely accepted method for the correction of skeletal or dentoalveolar malocclusion. However, recent advancements in presurgical orthodontic simulations and postsurgical orthodontic treatments using miniscrews have shown remarkable stability and control of the occlusion after orthognathic surgery. Thus, we have adopted a surgery-first orthognathic approach without presurgical orthodontic treatment, based on a novel presurgical simulation process using a dental model. We hypothesized that this treatment modality will be feasible for skeletal class III dentofacial deformity patients.

MATERIALS AND METHODS

This prospective study investigated intervention outcomes in 24 standard and 32 surgery-first approaches for patients with skeletal class III dentofacial deformity. The patients underwent orthognathic surgery between December 2007 and July 2010. In the surgery-first approach, a dental model was created and a novel preoperative orthodontic simulation of the standard presurgical orthodontic treatment was performed to determine the final occlusion between the maxilla and mandible. Changes in cephalometric landmarks were compared between the standard and surgery-first groups in the preoperative, immediate postoperative, and postoperative periods. The Student t test, Kruskal-Wallis test, and a linear mixed model were used for statistical analysis.

RESULTS

The follow-up period ranged from 12 to 36 months (average, 20.5 months). The average age of the patients was 22.4 years, with 16 male and 40 female patients. We found that a surgery-first approach without presurgical orthodontic treatment is possible and can give similar results to standard orthognathic surgery. The statistical analysis showed that changes in skeletal cephalometric landmarks were similar between the surgery-first and standard approach groups, according to each period. However, the cephalometric landmarks relating to the dental component showed changes between treatment groups at different time points but similar final values. This suggests that the benefits of postsurgical orthodontic treatment after the surgery-first approach could be similar to those obtained via the standard approach.

CONCLUSIONS

The surgery-first orthognathic approach without presurgical orthodontic treatment was found to be predictable and applicable to treat class III dentofacial deformities, and we recommend consideration of the technique as an effective alternative for treating this condition.

Insertion angle of orthodontic mini-implants and their biomechanical performance: finite element analysis

AbstractObjectiveThe aim of this study was to assess the stresses and strains generated after the application of two types of forces (traction of 200 gf and torsion of 20 N.cm) in two types of orthodontic mini-implants inserted at different (45° and 90° to the cortical bone) angles.Material and methodthree-dimensional models of two brands of mini-implant (SIN – Sao Paulo, Brazil, and RMO – South Korea) were exported and analyzed by finite element analysis (FEA). Analyses were performed on simulations of cortical bone, cancellous bone and the screw.ResultFEA analysis showed that RMO mini-implants had greater elastic deformation when subjected to tensile and torsional forces when compared with SIN mini-implants. For both trademarks and insertion angles tested, there was greater cortical bone deformation, but with the greatest strain located on the mini-implant. Tension on the mini-implant was located in its transmucosal profile region.ConclusionWhen comparing the two brands of mini-implants by FEA, it is fair to conclude that that the larger number of threads and their greater angle of inclination resulted in less resistance to deformation and induced a higher level of tension in the mini-implant and cortical bone when subjected to forces, especially when inserted at an angle of 45º to the cortical bone.

Miniscrew implant fracture and effects of such retained tip on dentin-pulp complex: a histological report

Miniscrew implants provide an excellent orthodontic anchorage. Besides the clinical benefits, miniscrew implants cause minor discomforts and in certain instances poses problematic complications. Damage to the adjacent tooth structure is the most feared complication of miniscrew implant placement, while fracture of miniscrew implants is the rarest. Miniscrew fracture could occur either during its placement or during its removal. An unusual case report is presented of a miniscrew implant tip fracture following root contact while attempting to remove it. This report highlights the effect of such miniscrew implant fracture on the dentin-pulp complex. The present case is probably the first to give direct histological evidence in humans that a miniscrew fracture or a retained miniscrew implant tip along the dentin/cementum without obvious miniscrew implant penetration could elicit pulp changes. Therefore this case report emphasizes the fact that prior to placing miniscrew implant, clinicians should have acquired proper training and adequate skills in terms of MSI placement and management of fractured MSI.

Dental extrusion with orthodontic miniscrew anchorage: a case report describing a modified method

In recent years, the skeletal anchorage through miniscrews has expanded the treatment options in orthodontics (Yamaguchi et al., 2012). We hereby present a modified method for tooth extrusion for cases where crown-lengthening surgery is contraindicated for aesthetic reasons. This modified method uses three orthodontic appliances: a mini-implant, an orthodontic wire, and a bracket. The aim of this case report was to increase the length of the clinical crown of a fractured tooth (tooth 23) by means of an orthodontic extrusion with the modified method of Roth and Diedrich.