Finite element simulation and statistical investigation of an orthodontic mini-implant's stability in a novel screw design

Optimization of primary screw stability in Trabecular bone using neural network-based models

BACKGROUND AND OBJECTIVE

Screw implant stability in bone is crucial to the success of many orthopaedic procedures, yet the relationship between screw design parameters and specific bone characteristics remains underexplored. This study aims to optimize screw designs to enhance primary stability by leveraging subject-specific bone data and advanced surrogate modelling techniques.

METHODS

In this study, 2880 screw pull-out simulations were conducted to assess primary screw stability by analysing pull-out stiffness and strength. The resulting dataset was used to develop surrogate models using multiple linear regression, random forest, and neural networks (NN). An optimization process was then applied to find optimal screw designs for 80 distinct trabecular bone specimens, in terms of inner diameter, pitch, and thread angle.

RESULTS

The models, trained with various input parameters, including bone morphological parameters and computed tomography images, promisingly predicted the results of the simulations. The prediction errors varied by model type, with multiple linear regression yielding approximately 12 % error, while non-linear machine learning models achieved lower errors, ranging between 2-6 %. The series of subsequent optimization tasks provided optimized screw designs showing statistically significant improvements in pull-out stiffness and strength compared to the average screw designs (approximately 16 and 14 %, respectively). This even though our study focused only on screw design parameters that generally have a smaller impact on stability compared to factors such as screw outer diameter and insertion depth.

CONCLUSIONS

Multiple linear regression models were found to be insufficient for generating optimized screw configurations, and more complex surrogate models, such as NN, are needed. It could be concluded that different trabecular bone morphologies can benefit from distinct optimal screw designs. The insights gained from this study could have implications for the development of patient-specific orthopaedic treatments.

Exploring the use, perceptions, and challenges of mini-implants in orthodontic practice: a survey study

The present study aims to explore and evaluate current practices among orthodontic specialists regarding the use of mini-implants, focusing on factors influencing usage decisions, experience in placement, perceptions of outcomes, and future perspectives of these devices in orthodontic practice. It seeks to explore the association between specialists' experience levels and their perceptions of mini implants, as well as the challenges encountered in their use. It is hypothesized that orthodontic specialists' perceptions and practices regarding the usage of mini implants are influenced by various factors, including their experience, training engagement, treatment outcomes, and preferences.

Material and methods

The study was conducted using an online, cross-sectional survey developed on the Survio platform to assess orthodontic specialists' perceptions of the clinical effectiveness and advantages of mini-implants in orthodontic treatments. The survey, consisting of 24 closed-ended questions in binary and multiple-choice formats, covered demographics, theoretical knowledge, clinical experience, and educational resources related to mini-implant use. Orthodontic specialists from Romania were invited to participate through the AREO association, and the survey was open for 12 weeks. Data collected from the survey were analyzed using descriptive statistics and multivariate logistic regression in SPSS software (Version 28), with a statistical significance threshold set at p < 0.05.

Results

through a comprehensive analysis of survey data, the study investigates factors influencing specialists' perceptions, challenges encountered in practice, training engagement, material preferences, treatment outcomes, and indications for mini-implant usage. Notable correlations and discrepancies between documented literature and orthodontists' responses in Romania regarding mini-implant indications are explored, shedding light on the diversity of applications in orthodontic procedures highlighting the significance of education, training, and technical support in enhancing mini-implant utilization. Strategies to address barriers and promote informed decision-making among orthodontists are discussed.

Conclusions

the study reveals diverse preferences and utilization patterns regarding mini-implants across different orthodontic procedures, reflecting the versatility and adaptability of these devices in addressing various clinical needs. By comparing documented literature with real-world practices, the study identifies both correlations and discrepancies, providing valuable insights into the practical application of mini-implants in orthodontic treatments.

Development and in vitro testing of an orthodontic miniscrew for use in the mandible

OBJECTIVE

Temporary anchorage devices (TADs) have been successfully used in the maxilla. However, in the mandible, lower success rates present a challenge in everyday clinical practice. A new TAD design will be presented that is intended to demonstrate optimization of the coupling structure as well as in the thread area for use in the mandible.

METHODS

Three TADs were examined: (A) Aarhus® system (68.99.33 A, Medicon, Tuttlingen, Germany), (B) BENEfit® orthodontic screw (ST-33-54209; PSM Medical, Gunningen, Germany) and (C) a new design with a two-part screw thread. The TADs were inserted into artificial bone blocks after predrilling to test primary stability. To test the fracture stability, the TADs were embedded in Technovit® 4004 (Heraeus Kulzer, Wehrheim, Germany) and torsional loaded at an angle of 90° until fracture. The threshold torque values occurring were recorded digitally. The statistical evaluation was carried out using the Kruskal-Wallis test with a post hoc test according to Bonferroni (p < 0.05).

RESULTS

The following values were measured for the insertion torque: A: 33.7 ± 3.3 Ncm; B: 57.1 ± 8.4 Ncm; C: 34.2 ± 1.4 Ncm. There were significant differences between A-B and B-C. The measured values for the fracture strength were as follows: A: 46.7 ± 3.5 Ncm; B: 64.2 ± 5.1 Ncm; C: 55.4 ± 5.1 Ncm. Significant differences were found between all groups.

CONCLUSION

The adapted screw design has no negative influence on primary and fracture stability. Whether the design has a positive effect on the success rates in the mandible must be clarified in further clinical studies.

Optimization of thread configuration in dental implants through regulating the mechanical stimuli in neighboring bone

BACKGROUND AND OBJECTIVE

The threads, as the most critical component of dental implants, transfer the imposed occlusal loads to the adjacent bone. Moreover, regulation of the mechanical stimuli in the implant adjacent bone is crucial to maximize the bone-implant construct stability. An optimal thread design can be resulted when the distribution of mechanical stimuli within the bone, and at the implant-bone interface, lie in an advised confined range. In this work, with the goal of finding the optimal thread design, which can provide the maximum level of stability, the effects of thread parameters, namely, thread depth, thread width, and thread pitch, together with upper and lower thread angles, on maximum principal strain within the cortical and cancellous bone, and shear strain at the implant-bone interface, were investigated.

METHODS

In this study, the response surface methodology (RSM), due to the central composite design (CCD), was employed to obtain a set of 53 experiments. Following that, they were numerically simulated using the finite element method (FEM). The polynomial regression model was then used to predict the response functions based on the magnitude of thread parameters. The effectiveness of each thread parameter was also evaluated through statistical tools. Moreover, the non-dominated sorting genetic algorithm (NSGA-II) was performed to find the optimum dimensions of the thread.

RESULTS

Through comparing the results obtained from analyzing initial and optimized configuration of threads, it was shown that the latter causes a reduction in the maximum principal strains in cancellous and cortical bones by about 25% and 30%, respectively, which is in favor of making a higher quality bone, and thus greater stability in dental implant-bone construct. Moreover, the maximum shear strains at the implant-bone interface in different planes were reduced by about 40%, in the optimized thread, compared with the initial design.

CONCLUSIONS

The optimized design found in this study is a buttress thread with a fine pitch, but deep thread, which keeps the mechanical stimuli in a safe range to grant an acceptable level of stability.

How Does Orthodontic Mini-Implant Thread Minidesign Influence the Stability?-Systematic Review with Meta-Analysis

BACKGROUND

Clinical guidelines are lacking for the use of orthodontic mini-implants (OMIs) in terms of scientific evidence referring to the choice of proper mini-design. Thus, the present study aimed to investigate to what extent orthodontic mini-implant thread design influences its stability.

METHODS

Search was conducted in five search engines on 10 May. Quality assessment was performed using study type specific scales. Whenever possible, meta-analysis was performed.

RESULTS

The search strategy identified 118 potential articles. Twenty papers were subjected to qualitative analysis and data from 8 papers-to meta-analysis. Studies included were characterized by high or medium quality. Four studies were considered as low quality. No clinical studies considering the number of threads, threads depth, or TSF have been found in the literature.

CONCLUSIONS

Minidesign of OMIs seems to influence their stability in the bone. Thread pitch seems to be of special importance for OMIs retention-the more dense thread-the better stability. Thread depth seems to be of low importance for OMIs stability. There is no clear scientific evidence for optimal thread shape factor. Studies present in the literature vary greatly in study design and results reporting. Research received no external funding. Study protocol number in PROSPERO database: CRD42022340970.

Optimization Analysis of Two-Factor Continuous Variable between Thread Depth and Pitch of Microimplant under Toque Force

Microimplant, an anchorage device, is widely applied in clinical orthodontic treatment. Since tooth torque is required to be controlled during orthodontic tooth movement, a novel microimplant needs to be developed to apply better torque force during orthodontic. In this study, the optimal value ranges of thread depth and pitch under toque force were studied for choosing microimplant with relevant value ranges in clinical design from biomechanical perspective. Finite element analysis (FEA) and optimization design technology were used for accessing the optimal value ranges of thread depth and pitch under toque force. Thread depth (D) (0.1 mm to 0.4 mm) and pitch (P) (0.4 mm to 1 mm) were used as continuous variables, with the other parameters as constant, and the optimal value ranges were obtained by analyzing the tangent slope and sensitivity of the response curve. When a torque force of 6 Nmm was applied on the microimplant, the maximum equivalent stress (Max EQV) of cortical bone and maximum displacements (Max DM) of microimplant were analysis indexes. When 0.55 mm ≤ P ≤ 1 mm, the Max EQV of cortical bone was relatively smaller with less variation range. When 0.1 mm ≤ D ≤ 0.35 mm, the Max DM of microimplant was relatively smaller with less variation range. So in conclusion, the initial stability of microimplants with pitch 0.55 mm ≤ P ≤ 1 mm and thread depth 0.1 mm ≤ D ≤ 0.35 mm was better with the torque force applied.