In-vitro impact of insertion angle on primary stability of miniscrews

Effects of novel microimplant-assisted rapid palatal expanders manufactured by 3-dimensional printing technology: A finite element study

INTRODUCTION

The expansion effects of several new microimplant-assisted rapid palatal expanders (MARPEs) manufactured by 3-dimensional printing technology were evaluated by finite element analysis (FEA). The aim was to identify a novel MARPE suitable for treating maxillary transverse deficiency.

METHODS

The finite element model was established using MIMICS software (version 19.0; Materialise, Leuven, Belgium). First, the appropriate microimplant insertion characteristics were identified via FEA, and several MARPEs with the above insertion patterns were manufactured by 3-dimensional printing technology. Then, the stress distribution and displacement prediction of the 4 MARPEs and hyrax expander (model E) were evaluated via FEA: bone-borne (model A), bone-tooth-borne (model B), bone-mucous-borne (model C), bone-tooth-mucous-borne (model D).

RESULTS

Monocortical microimplants perpendicular to the cortical bone on the coronal plane resulted in better expansion effects. Compared with a conventional hyrax expander, the orthopedic expansion of each of the 4 MARPEs was far larger, the parallelism was greater, and the posterior teeth tipping rate was lower. Among them, the expansion effects of models C and D were the best; the von Mises peak values on the surfaces of the microimplants were smaller than those of models A and B.

CONCLUSIONS

This study may demonstrate that the 4 MARPEs obtained more advantageous orthopedic expansion effects than a hyrax expander. Models C and D obtained better biomechanical effects and had better primary stability. Overall, model D is the recommended expander for treating maxillary transverse deficiency because its structure acts like an implant guide and is beneficial for the accurate insertion of the microimplant.

Stress distribution for mandibular extra-alveolar anchorage at different angles and force magnitudes: a finite element study

The aim of this study was to evaluate the stress distribution in cortical and cancellous bones and within the screw when a stainless steel extra-alveolar screw (EA-S) is inserted into the retromolar region of the mandible using the finite element method (FEM). The stress values in the EA-S were highest at 60° with horizontal (shear) force and lowest at 90° with axial force. In the bones (cortical and cancellous), the stress value was greatest at 90° with horizontal force. Greater stability of the screw may be achieved by tilting it to the force when horizontal loads are applied.

Fixation Methods for Replacement Screws in Scaphoid Fractures: A Biomechanical Study

Purpose

To investigate the changes in biomechanical fixation of an initial and replacement headless compression screw by quantifying interfragmentary compression and shear displacement.

Methods

A bone model was created with 2 blocks of rigid polyurethane foam to simulate a fracture site. A 24-mm headless compression screw was inserted into the model at a perpendicular or oblique angle, removed, and replaced with the 22-mm screw. The 22-mm screw replaced the 24-mm screw in either the same or reverse direction of initial insertion. All 4 methods of initial and replacement screw fixation were trialed 15 times for a total of 60 trials. Two button load cells measured compression. A digital microscope recorded shear displacement. Statistical analysis was performed to determine the differences in compression and sheer between the initial and replacement screw for each angle and screw insertion group with a 2-sided paired Student t test.

Results

In comparison with the average compression force achieved by placement of the primary screw, there was a significant loss of average compression force when the secondary screw was placed in the same direction and perpendicular to the fracture plane (50 N, P < .001), in the reverse direction and perpendicular to the fracture plane (9 N, P = .049), and in the same direction and 60º to the fracture plane (11 N, P < .001). A significantly greater average shear displacement was noted for initial screw insertion at oblique compared with perpendicular orientations (0.03 mm, P < .001).

Conclusions

This study demonstrates loss of compression when replacing screws despite varying orientations. Additionally, shear displacement in obliquely placed screws increased compared with perpendicularly placed screws.

Clinical relevance

This study provided quantitative evidence to support the importance of establishing the correct screw length initially to avoid compression loss caused by replacing a primary screw.

Microbiological Advances in Orthodontics: An Overview and Detailed Analysis of Temporary Anchorage Devices

Dental biofilm is the initiating factor of oral diseases, such as periodontitis and caries. Orthodontic treatment could alter the microbiome structure balance, and increase the risk of such diseases. Furthermore, fixed appliances can induce temporary changes in the microbiome community, and the changes that clear aligners bring are smaller by comparison. Temporary anchorage devices (TADs) are skeletal anchorages that are widely used in orthodontic treatment. Microorganisms affect the occurrence and development of inflammation surrounding TADs. At present, existing researches have verified the existence of plaque biofilm on the surface of TADs, but the formation of plaque biofilm and plaque composition under different stable conditions have not been fully understood. The development of high-throughput sequencing, molecular biology experiments, and metabonomics have provided new research ideas to solve this problem. They can become an effective means to explore the microbiome surrounding TADs.

Buccal bone thickness of posterior mandible for microscrews implantation in molar distalization

BACKGROUND

This study explored the inter-radicular space and buccal bone thickness of the posterior mandibular region to provide an appropriate miniscrew insertion site for lower dentition distalization.

METHODS

The cone-beam computed tomographic (CBCT) records of 63 subjects were collected. Buccal bone thickness (BBT) was measured at four sections: (I) the root of the second premolar(P₁); (II) the mesial root of the first molar(P₂); (III) the distal root of the first molar(P₃); (IV) the mesial root of the second molar(P₄). The narrowest inter-radicular space of the four sections was also detected. Both BBT and inter-radicular space were measured at 4 height levels, 2, 4, 6 and 8mm from the alveolar ridge.

RESULTS

The largest BBT was observed at the mesial root of the second molar at 6 and 8mm, demonstrating a thickness of 6.77±2.50mm and 7.46±1.94mm, respectively. It provided sufficient coverage for mini-implants inserted 10°-30° oblique to the root. Therefore, during distalization of the mandibular dentition, roots have sufficient space to bypass the inclined mini-implants on the lingual side, avoiding miniscrew-root contact. The width between the mesiodistal roots of the first molar was the smallest, showing 1.53±0.69mm and 2.13±0.65mm at 4 and 6mm. Miniscrews implanted in this region had an increased risk of root proximity.

CONCLUSIONS

The most appropriate insertion site at the mandibular buccal shelf was the mesial point of the second molar at 6-8mm from the alveolar ridge, and an insertion angle of 10°-30° was recommended to avoid miniscrew-root contact. CBCT analysis is recommended before implantation due to individual differences.

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.

Interradicular distance and alveolar bone thickness for miniscrew insertion: a CBCT study of Persian adults with different sagittal skeletal patterns

Background

This study aimed to assess the interradicular distance and alveolar bone thickness of Persian adults with different sagittal skeletal patterns for miniscrew insertion using cone-beam computed tomography (CBCT).

Methods

This cross-sectional study was conducted on maxillary and mandibular CBCT scans of 60 patients (18–35 years) in three groups (n = 20) of class I, II and III sagittal skeletal pattern. Anatomical and skeletal parameters were measured at 2, 4 and 6 mm apical to the cementoenamel junction (CEJ) by one examiner. The intra- and inter-class correlation coefficients were calculated to assess the intra, and interobserver reliability. Data were analyzed by ANOVA and Tukey’s test (alpha = 0.05).

Results

The intra- and interobserver reliability were > 0.9 for all parameters. The largest inter-radicular distance in the maxilla was between the central incisors (1–1) in classes I and III, and between premolars (4–5) in class II patients. The largest inter-radicular distance in the mandible was between molar teeth (6–7) in all three classes. The buccal cortical plate thickness was maximum at the site of mandibular first and second molars (6–7). The posterior maxilla and mandible showed the maximum thickness of cancellous bone and alveolar process. Wide variations were noted in this respect between class I, II and III patients.

Conclusions

The area with maximum inter-radicular distance and optimal alveolar bone thickness for miniscrew insertion varies in different individuals, depending on their sagittal skeletal pattern.

Effect of miniscrew insertion angle in the maxillary buccal plate on its clinical survival: a randomized clinical trial

INTRODUCTION

This study sought to assess the effect of miniscrew insertion angle (vertical and oblique) on its clinical survival under shearing forces in orthodontic patients undergoing canine retraction.

MATERIALS AND METHODS

In this split-mouth randomized controlled clinical trial, 50 miniscrews were placed bilaterally in 25 patients with 45° and 90° insertion angles relative to a line perpendicular to the occlusal plane distal to the maxillary first premolar extraction site. Allocation of insertion angles to the right/left side was random using the Random Allocation Software. The patients, clinician, and statistician were blinded to the allocation of miniscrews to the side of jaw. The patients were followed-up monthly for 6 months. The primary outcome was the clinical survival of miniscrews, which was evaluated at each follow-up session. The secondary outcomes were the miniscrew stability based on the Periotest value (PTV) and the level of pain experienced by patients at 1, 12, and 24 h, and 7 days after miniscrew placement using a visual analog scale (VAS). Data were analyzed using paired t-test, repeated measures ANOVA, and McNemar's test.

RESULTS

The clinical survival rate of miniscrews placed at 90° and 45° angles was 76% and 88%, respectively. This difference was not statistically significant (P = 0.375). No significant difference was noted between the two groups regarding the PTV or the pain score either (P > 0.05).

CONCLUSION

Clinically, the insertion angle of miniscrews (90° versus 45° relative to a line perpendicular to the occlusal plane) has no significant effect on the miniscrew survival rate or stability during orthodontic treatment.

TRIAL REGISTRATION

This trial was registered at www.irct.ir ( IRCT20190901044659N1 ).

PROTOCOL

The protocol was published after trial commencement.

[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.

A Custom-Made Orthodontic Mini-Implant-Effect of Insertion Angle and Cortical Bone Thickness on Stress Distribution with a Complex In Vitro and In Vivo Biosafety Profile

BACKGROUND

Orthodontic mini-implant failure is a debatable subject in clinical practice. However, the most important parameter to evaluate the success rate of mini-implant is the primary stability, which is mainly influenced by cortical bone thickness (CBT) and insertion angle.

MATERIALS AND METHODS

Three-dimensional finite element models of the maxilla were created and a custom-made, self-drilling, tapered mini-implant was designed. For the pull-out test, 12 simulations were performed, sequentially increasing the thickness of the cortical bone (1, 1.5 and 2 mm) and the insertion angle (30°, 60°, 90°, 120°). For the force analysis, 24 simulations were performed using an experimental orthodontic traction force of 2 N both in the horizontal and vertical axis.

RESULTS

Insertion angle and CBT have significant impact on force reaction values (p < 0.05). Cortical bone stress had the lowest value when the mini-implant had a 30° insertion angle and the highest value when the implant had a 120° insertion angle, while the CBT was 1 mm. Cortical bone stress had the lowest value with an insertion angle of 90° and the highest value when the implant was inserted at an angle of 30°, while the CBT was 2 mm independent of the force direction. Regarding the biosafety profile of the mini-implant alloy, the present results reveal that the custom-made mini-implant presents good biocompatibility.

CONCLUSIONS

When the CBT is reduced, we recommend inclined insertion while, when the CBT is appropriate, perpendicular insertion is advised.

Influence of bone density, screw size and surgical procedure on orthodontic mini-implant placement - part B: implant stability

This in vitro study aimed to investigate the influence of bone density, implant size, and surgical procedure on the primary stability (PS) of orthodontic mini-implants (OMIs). In total, 640 OMIs of various sizes (2.0 × 7, 2.3 × 7, 2.0 × 11 and 2.3 × 11 mm) were inserted in the artificial bone of different densities (D1-D4). Placement was performed with an insertion angle of 90° or 60° to the bone surface and in 320 cases without predrilling, which resulted in 64 groups. PS was measured on the basis of implant stability quotient (ISQ) and insertion torque (IT). With regard to all possible influencing parameters, the mean PS differed between 39.20 and 60.00 (ISQ), and 10.00 and 39.00 Ncm (IT). The effect of OMI size and surgical procedure was dependent on bone quality. For example, implant size had less effect in high-density bone and was stronger with decreasing density. Overall, implant length had a greater influence than the diameter, and a high correlation was found among both PS measurement techniques. Therefore, a suitable choice of implant size and surgical protocol with regard to bone density can positively influence PS. In principle, ISQ and IT are suitable for measuring OMI stability.

Anatomical consideration for optimal position of orthodontic miniscrews in the maxilla: a CBCT appraisal

BACKGROUND

Orthodontic miniscrews are commonly used as temporary anchorage devices. Bone thickness and bone depth are important factors when placing miniscrews. There are no studies to assess the maxillary bone thickness for optimum miniscrew placement in a Saudi population.

OBJECTIVE

Assess the proximity of the maxillary sinus and nasal cavity in areas where miniscrews are usually inserted using cone beam computed tomography (CBCT).

DESIGN

Retrospective, cross-sectional.

SETTING

Department of maxillofacial radiology in a Saudi dental school.

PATIENTS AND METHODS

Using CBCT images, we measured the distance between the maxillary sinus and nasal cavity to the palatal bone, buccal intra-radicular and infrazygomatic crest areas. Mean values (SD) were compared at various locations, including by gender, and correlation with age was calculated.

MAIN OUTCOME MEASURE

Mean bone thickness at commonly used sites for orthodontic miniscrew placements in the maxilla. Secondary outcome was the insertion angle in the infrazygomatic crest area.

SAMPLE SIZE

CBCT images of 100 patients (50 males and 50 females).

RESULTS

The mean (standard deviation) age for the sample was 25.4 (6.5) years with no significant difference between males and females. In the palate, the distance to the nasal cavity and maxillary sinus was greater anteriorly and decreased significantly posteriorly (P<.001). Buccally, the interdental bone depth was significantly greater between the second premolar and first molar (11.96 mm) compared to between the central and lateral incisors (7.53 mm, P<.001). The mean bone thickness of the infrazygomatic crest area at a 45° insertion angle was 4.94 mm compared to 3.90 at a 70° insertion angle (P<.001). No correlation was found between age and bone thickness.

CONCLUSION

The distance to the nasal cavity and maxillary sinus was greater in the anterior than posterior areas. There is minimal risk of injuring the maxillary sinus or nasal cavity using the buccal approach. Caution is needed when placing miniscrews in the infrazygomatic crest area.

LIMITATIONS

Cross-sectional study from one center; hence, findings cannot be generalized to other populations.

CONFLICT OF INTEREST

None.

Effects of size and insertion angle of orthodontic mini-implants on skeletal anchorage

INTRODUCTION

The primary aim of this in vitro study was to compare the insertion torque (IT) and anchorage force (AF) values of 4 different sizes of orthodontic mini-implants with 2 different angles. The second aim was to evaluate the relationship between IT and AF values under different diameter, length, and insertion angle variables.

METHODS

A total of 160 mini-implants, including 20 implants in each group, with 4 different sizes (1.6 × 8 mm, 1.6 × 10 mm, 2.0 × 8 mm, and 2.0 × 10 mm) at 2 different angles (70° and 90°), were inserted into bovine iliac bone segments. The IT and AF values leading to 1.5 mm deflection were compared. The correlations between IT and AF values under different variables were also analyzed.

RESULTS

The mini-implants with greater diameter and length showed greater IT and AF values (P <0.05). The IT and AF values of mini-implants inserted at 70° angle were significantly greater than those of mini-implants inserted at 90° angle (P <0.001). Significant correlations were found between IT and AF values in all variables.

CONCLUSIONS

The diameter, length, and insertion angle of orthodontic mini-implants have significant effects on IT and AF values. Insertion angle and diameter of mini-implants are more effective than implant length on skeletal anchorage. Significant correlations are present between IT and AF values of mini-implants regardless of their diameters, lengths, and insertion angles.

Distance to alveolar crestal bone: a critical factor in the success of orthodontic mini-implants

Background

To evaluate the success rate of orthodontic mini-implant (MI) in relation to implant characteristics, mainly implant distance to alveolar crestal bone (AC) and root proximity (RP) to adjacent teeth.

Methods

Two hundred sixty MIs (209 in maxilla, 51 in mandible) were categorized into success (n = 229) and failure (n = 31) groups. Distances from MI to the most adjacent tooth (DT) and to AC level (DC) were measured on periapical radiographs taken with the orthoradial projection technique. Appropriate statistical tests (chi-square, t test, logistic regression) were applied.

Results

DC measurements were statistically significantly greater in the success group (7.46 ± 1.7 mm) compared to 3.43 ± 0.81 mm in the failure group. Root proximity was not associated with miniscrew failure. Patient age, mini-implant site, and DC were significant predictors of mini-implant failure (p < 0.001), which decreased significantly with increasing age (Coef = − 0.345; p = 0.013) and when the mini-implant was placed between premolars (p = 0.028) or between premolar and first molar (p = 0.045). The probability of failure also decreased with increasing DC distance (Coef = − 3.595; p < 0.001).

Conclusion

The distance to alveolar crest was strongly associated with long-term stability. More apical placement of the MI from the crest would be compatible with a denser and thicker bucco-lingual/palatal bone level.