Evaluations of miniscrew type-dependent mechanical stability

Upper Midline Correction Using the Mesial-Distalslider

AIM

The purpose of the present study is the three-dimensional (3D) analysis of molar and incisor movements that occur during the correction of the upper midline deviation by using the Mesial-Distalslider appliance.

MATERIALS AND METHODS

A total of 20 consecutive patients (12 women and 8 men; mean age 19.6 ± 11.1 years) were selected from the Orthodontic Department of Heinrich-Heine University of Düsseldorf. To correct the upper midline deviation (>2 mm), the patients were treated with asymmetric mechanics (mesialization on one side and distalization on the contralateral side) with the aid of Mesial-Distalslider. Dental casts were taken for each patient before (T0) and after the treatment (T1). The casts were 3D digitized and the models were superimposed on the palatal anterior region. Three-dimensional molar movements and sagittal incisor movements (proclination and retroclination) were assessed for T0 and T1.

RESULTS

At the end of the treatment, the total movements of the molars resulted in 4.5 ± 2.2 mm (antero-posterior direction), -0.4 ± 2.4 mm (transverse direction) and 0.3 ± 0.9 mm (vertical direction) on the mesialization side, and -2.4 ± 1.7 mm (antero-posterior direction), -0.5 ± 1.5 mm (transverse direction) and 0.2 ± 1.4 mm (vertical direction) on the distalization side. Incisor displacement was 0.9 mm ± 1.7 (mesialization side) and 0.6 mm ± 0.7 (distalization side).

CONCLUSION

The Mesial-Distalslider appliance could be considered a valuable tool in orthodontic treatment for upper midline correction. Within the limits of a retrospective study, asymmetric molar movements appeared possible without clinically relevant anchorage loss.

Success rates of single-thread and double-thread orthodontic miniscrews in the maxillary arch

AIM

There is limited research on the clinical performance of double-thread orthodontic miniscrews. This study aimed to compare the stability of double-thread and single-thread orthodontic miniscrews and identify the potential associations between patient-related and location-related factors with miniscrew stability.

METHODS

This retrospective cohort study involved 90 orthodontic miniscrews (45 single-thread, 45 double-thread) with identical dimensions (8 mm length, 1.6 mm diameter). The screws were inserted in various locations within the upper jaw of 83 patients (54 females, 29 males; mean age = 15.1 ± 2.4 years). Failure was defined as excessive mobility or loss of miniscrew after placement. The data recorded were patient age, gender, insertion site, side of insertion (buccal or lingual), duration of force application, and failure occurrence.

RESULTS

The overall success rate within the sample was 92.2%. Double-thread miniscrews exhibited a significantly higher success rate than single-thread miniscrews (P = 0.049), with 97.8% and 86.7% success rates, respectively. Gender, age, insertion location, and side of insertion did not show significant associations with failure (P > 0.05). Log-rank analysis revealed a significant difference between the two groups (P = 0.046), indicating a higher probability of survival for the double-thread design.

CONCLUSIONS

The overall success rate of orthodontic miniscrews was high in the present sample. Double-thread miniscrews placed in various locations within the maxillary arch demonstrated superior stability and survival rates compared to their single-thread counterparts. Therefore, double-thread miniscrews may be preferred when bone quality is inadequate, such as in young patients.

The effect of different orthodontic mini-implant brands and geometry on primary stability (an in vitro study)

Background

In orthodontic procedures, mini-implants are routinely used as temporary anchorage devices. Early failure is primarily attributed to a variety of issues, which are mostly connected to the quality and geometry of the screw that lead to insufficient primary stability.

Objectives

To evaluate the primary stability of different sizes and brands of orthodontic mini-implants by optimizing the insertion torque value (ITV) and to clear out which one has the greatest primary stability among the most widely used mini-implants by orthodontists.

Methods

Eighty-two self-drilling mini-implants from three different brands with different sizes were used (Optimus Ortho System (Osteonic made in Korea), Smart anchor (GNI made in Korea) (1.4 × 6, 1.6 × 8 and 1.8 × 10mm) and Morelli (made in Brazil) (1.5 × 6, 1.5 × 8 and 1.5 × 10mm), made from (Ti 6Al 4V). All were drilled at a 60° angle on Sixty artificial bone blocks made from polyurethane foam with a digital torque meter device (Orthonia, Jeil made in Korea), pullout strength (tensile force) was measured with a universal testing machine to find out the best brand and size in the mean of primary stability. Data were analyzed using SPSS Version 25 and JMP Pro Version 16 software using the One-way ANOVA test, the Post hoc and Tukey HCD tests.

Results

There were significant differences between the pullout strength of different sizes for the GNI and OSTEONIC brands, while for the MORELLI brand there were no significant differences between the three different sizes considering ITV (10Ncm) whereas for ITV (20Ncm) there was a significant difference between the different sizes for the pullout of all three brands. GNI was the best brand for all the selected sizes with ITV (10Ncm) and size 1.4 × 6 for ITV (20Ncm), whereas OSTEONIC sizes 1.6 × 8 and 1.8 × 10 were the best for ITV (20Ncm) in term of primary stability.

Conclusion

GNI screws were demonstrated higher primary among the three widely used brands followed by OSTEONIC for size 1.6 × 8 and 1.8 × 10 while MORELLI was the least resistant to dislodgement for the two torque insertion values 10 N/cm and 20 N/cm.

Comparison of mechanical stability of mini-screws with resorbable blasting media and micro-arc oxidation surface treatments under orthodontic forces: An in vitro biomechanical study

INTRODUCTION

The aim of this study was to compare the primary stability of mini-screws with different surface treatments such as resorbable blasting media (RBM) and micro-arc oxidation (MAO) under in vitro orthodontic forces.

MATERIAL AND METHODS

Thirty-six self-drilling TiAl6V4-ELI grade 23 titanium alloy 1.6×8mm mini-screws were inserted into polyurethane foam blocks and divided into three groups according to surface properties: machine surface (MS), RBM-treated, and MAO-treated. An orthodontic force of 150g was applied to the mini-screws using NiTi coils. Maximum insertion torque (MIT) and maximum removal torque (MRT) were measured with a digital torque screwdriver during insertion and removal. For each mini-screw, stability measurements were made with the Periotest M device at day 0 and weeks 1, 2, 4, 8, and 12.

RESULTS

Significant differences in MIT were observed between all groups in pairwise comparisons (P<0.001) with the highest value in the MAO-treated group and the lowest in the MS group. The mean MRT values differed in all three groups (P=0.001). In pairwise comparisons of MRT, only the difference between MS group and RBM-treated group was significant. The highest value was observed in the RBM-treated group, while the lowest value was observed in the MS group. Periotest values were significantly higher in the MAO-treated group than the RBM-treated group at weeks 8 and 12. A positive significant correlation was found between MIT and MRT in all groups. No significant correlation was found between MIT, MRT and Periotest values in all groups.

CONCLUSION

RBM-treated group was significantly higher than the MS group in MIT and MRT values. According to Periotest values, RBM-treated group was found to be significantly more stable than the MAO-treated group at weeks 8 and 12. Therefore, RBM surface treatment was found to be more favourable than other surfaces to increase success rate in clinical applications.

Effect of cutting flute design features on primary stability of immediate implant placement and restoration: a dynamic experimental analysis

Self-tapping implants with self-cutting flutes may influence primary stability, especially for the immediate implant placement and restoration protocol in which implants are affixed to the bone in the apical portion. Screw geometry differs between brands, and the effect of apical design on its clinical outcomes remains unclear. This study is aimed at investigating the influence of cutting flute shape (spiral, straight, and without flute) on primary stability by using a dynamic experimental test. Six types of dental implants were designed using computer-aided design and computer-aided manufacturing technology, consisting of three types of cutting flute shapes along with two types of screw features. A dynamic mechanical test was performed using a cyclic loading scheme. The mechanical behaviors of resistance to lateral load (RLL), maximum force, and energy dissipation were compared between groups. In the dynamic test, implants without cutting flute also exhibited higher values in RLL, maximum force, and energy dissipation. The aggressive thread implant with straight flute displayed higher RLL and had a significantly higher values in RLL (p = 0.033) at the threshold point of bone-implant interface breakdown. The implants without cutting flutes exhibited higher primary stability. Straight flute design would improve RLL for aggressive thread implant.

Thread shape, cortical bone thickness, and magnitude and distribution of stress caused by the loading of orthodontic miniscrews: finite element analysis

Cortical bone thickness is assumed to be a major factor regulating miniscrew stability. We investigated stress distribution in two miniscrews with different thread shapes (type A and B) and in cortical bone of three different thicknesses using three-dimensional (3D) finite element (FE) models. More specifically, 3D FE models of two different miniscrews were created and placed obliquely or vertically into a cylindrical bone model representing different cortical bone thicknesses. When force was applied to the miniscrew, the stress distribution on the screw surface and in the peri-implant bone was assessed using FE methodology. Miniscrew safety was evaluated using a modified Soderberg safety factor. Screw head displacement increased with a decrease in cortical bone thickness, irrespective of screw type. The smallest minimum principal stresses on the screw surfaces remained constant in type A miniscrews on changes in cortical bone thickness. Minimum principal stresses also appeared on the cortical bone surface. Lower absolute values of minimum principal stresses were seen in type A miniscrews when placed vertically and with upward traction in obliquely placed type B miniscrews. Both miniscrews had acceptable safety factor values. Taken together, orthodontists should select and use the suitable miniscrew for each patient in consideration of bone properties.

Bone quality affects stability of orthodontic miniscrews

The objective of this study was to evaluate the effect of bone–miniscrew contact percentage (BMC%) and bone quality and quantity on orthodontic miniscrew stability and the maximum insertion torque value (ITV). Orthodontic miniscrews of five different dimensions and several bovine iliac bone specimens were used in the evaluation. Miniscrews of each dimension group were inserted into 20 positions in bovine iliac bone specimens. The experiment was divided into three parts: (1) Bone quality and quantity were evaluated using cone-beam computed tomography (CBCT) and microcomputed tomography. (2) The 3D BMC% was calculated. (3) The ITVs during miniscrew insertion were recorded to evaluate the stability of the orthodontic miniscrews. The results indicated that longer and thicker miniscrews enabled higher ITVs. CBCT was used to accurately measure cortical bone thickness (r = 0.939, P < 0.05) and to predict the bone volume fraction of cancellous bone (r = 0.752, P < 0.05). BMC% was significantly influenced by miniscrew length. The contribution of cortical bone thickness to the ITV is greater than that of cancellous bone structure, and the contribution of cortical bone thickness to BMC% is greater than that of cancellous bone structure. Finally, the higher is BMC%, the greater is the ITV. This study concludes that use of CBCT may predict the mechanical stability of orthodontic miniscrews.

Mechanical stability of orthodontic miniscrew depends on a thread shape

Background/purpose

Primary stability of orthodontic miniscrew system is of great importance in maintaining stable anchorage during a treatment period. Thus, this study aimed to examine whether the thread shape of orthodontic miniscrew had an effect on its mechanical stability in bone.

Materials and methods

Three different types of miniscrews (type A and B with a regular thread shape; type C with a novel thread shape) were placed in artificial bone block with different artificial cortical bone thickness of 1.5, 2.0 and 3.0 mm. Values of maximum insertion torque (MIT), removal torque (RT), torque ratio (TR), screw mobility, static stiffness (K), dynamic stiffness (K∗) and energy dissipation (tan δ) ability were assessed for each miniscrew system.

Results

The MIT, RT, TR and K of type C miniscrew were significantly greater than those of type A and B miniscrews when the miniscrews were placed in the thinner artificial bone. Furthermore, the TR value of type C miniscrew was more than 1, indicating the MRT value was larger than the MIT value in the novel miniscrew. The values of K∗ and tan δ were almost similar among the three types of miniscrews.

Conclusion

The miniscrew with a novel thread shape showed a higher initial stability compared to those with a regular thread shape. Thus, in order to obtain a sufficient initial stability, it is important to select the type of screw thread that is appropriate for the thickness of the cortical bone.

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.

The effects of cortical bone thickness and miniscrew implant root proximity on the success rate of miniscrew implant: A retrospective study

OBJECTIVE

To investigate the effects of cortical bone thickness (CBT), miniscrew implant root proximity (MRP) and other related factors on the success rate of miniscrew implant (MSI).

MATERIALS AND METHODS

Four hundred and five MSIs placed in 171 patients were analysed in this retrospective study. The primary predictor variables were CBT and MRP at MSI insertion sites. The predictor variables also included patient, location, MSI design and procedure related factors. The outcome variable was the survival of MSI. The differences in measurement data between success group and failed group were evaluated by the analysis of variance and independent samples t tests. Patient, location, MSI design and procedure related factors associated with the MSI prognosis were analysed by survival analysis with Cox proportional hazard regression model. The P value was set at .05. And the survival curves of independent factors were plotted.

RESULTS

The overall success rate of MSI was 82.7%. The age of MSI host, CBT, interdental root distance (IRD) and MRP at MSI sites showed no significant differences between failed group and success group. CBT and insertion jaws were independent prognosis factors screened out by Cox proportional hazard regression model. Failure risk (hazard ratio) of MSI with CBT <1 mm was 4.72. The failure risk in the mandible was 3.80 times as high as that in the maxilla.

CONCLUSION

Inadequate CBT (<1 mm) contributed to the failure of MSI. MSI placed in the maxilla showed better prognosis compared to the mandible. MRP had no significant effect on the prognosis.

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.

[The experimental study of a Russian orthodontic mini-screw]

BACKGROUND

The aim of this research is the experimental study measuring stability of the orthodontic miniscrews «Turbo» designed in Russia in comparison with its foreign analogues, namely, «Vector Tas» (USA) and «BioRay» (Taiwan).

MATERIAL AND METHODS

Four self-drilling orthodontic miniscrews of each manufacturer, i.e. «Vector Tas», USA, (10-mm length, 2-mm diameter), «BioRay», Taiwan, (10-mm length, 2-mm diameter), «Turbo», Russia, (9-mm length, 2-mm diameter), a total of 12 items, were inserted into native pig mandible sample. Their stability was estimated by torques using a dynamometer (Zahoransky AG, Germany) and «Periotest» device («Periotest M», Germany). This experiment was conducted in native pig mandible sample immediately after the screws' placement and in 7 days after loading at an angle 70°.

RESULTS

After application of a load, the decreased torque values and increased Periotest values were registered in all orthodontic miniscrews.

CONCLUSION

Orthodontic miniscrews «Turbo» designed in Russia are slightly inferior to «VectorTas» miniscrews and superior to «BioRay» miniscrews in primary stability and stability after 7 days under loading.

Mechanical Evaluation of the Stability of One or Two Miniscrews under Loading on Synthetic Bone

The aim of the present study was to evaluate the primary stability of a two-miniscrew system inserted into a synthetic bone and to compare the system with the traditional one. Forty-five bi-layered polyurethane blocks were used to simulate maxillary cancellous and cortical bone densities. Samples were randomly assigned to three groups—one-miniscrew system (Group A, N = 23), two-miniscrew system (Group B, N = 22) and archwire-only (Group C, N = 10). A total of 67 new miniscrews were subdivided into Group A (23 singles) and Group B (22 couples). 30 mm of 19″ × 25″ archwires were tied to the miniscrew. The load was applied perpendicularly to the archwire. Maximum Load Value (MLV), Yield Load (YL) and Loosening Load (LL) were recorded for each group. The YL of Group B and C had a mean value respectively of 4.189 ± 0.390 N and 3.652 ± 0.064 N. The MLV of Group A, B and C had a mean value respectively of 1.871 ± 0.318N, of 4.843 ± 0.515 N and 4.150 ± 0.086 N. The LL of Group A and B had a mean value respectively of 1.871 ± 0.318 N and of 2.294 ± 0.333 N. A two- temporary anchorage device (TAD) system is on average stiffer than a one-TAD system under orthodontic loading.

Thread shape affects the stress distribution of torque force on miniscrews: a finite element analysis

This study aimed to investigate the effect of miniscrews thread shape on the stress distribution receiving a torque load. Seven thread shapes (S,V1,V2,B1,B2,R1,R2) models were constructed and a 6 Nmm-torque load was applied. The order of maximum equivalent stress (EQV) value was V1 > V2 > B1 > R1 > R2 > B2 > S. The order of maximum displacement of miniscrew (Max DM) value was S > B2 > R1 = V1 > B1 > V2 > R2. Model R2 may be the most appropriate thread shape affording a torque force.