Thread Depth Research Articles

The effects of dental implant macrodesign on the success of prosthetic replacement

Currently dental implantation is widely used in the areas of denture defects during the orthopedic rehabilitation of the patients. The clinical success of the implantation-related prosthetic replacement depends on multiple factors, including the macrodesign of the implant (the specific features of its structure: the shape, the characteristics and the number of thread turns). However, there are not so many comparative clinical trials exploring the effects of the main characteristics of the implant on the success of prosthetic procedures. For the practical dentist, the problem of selecting the implant system remains topical, which is why the proposed review is focused on the effects of the dental implant macrodesign on the success of implantation. The search of publications was arranged in the PubMed and eLibrary search engines using the “dental implant”, “dental implant macro-design”, “number of dental implant turns” and “implant thread characteristics” search enquiries with focusing on the research works evaluating the effects of the main characteristics of the implant in terms of primary stability and osteointegration. Various geometric parameters of the implant were analyzed, such as the shape, the length, the diameter and the thread characteristics, with further evaluating their significance for optimal tension distribution, as well as the effects on bone remodeling during the process of osteointegration. The successful implantation is being achieved by synergetic combination of numerous factors. The majority of investigators adhere to the opinion that implants shall be selected individually for each specific case with taking into consideration the local and general factors. However, the characteristics of the implant thread and the number of its thread turns improve the primary stability and represent a prerequisite for successful osteointegration. The choice of implant thread construction plays an important role for a treatment result. It was shown that the macrodesign of the implant, specifically its shape (cone), its length and diameter, higher thread width and depth, lesser thread pitch and higher numbers of thread turns influence the primary stability. Specifically these characteristics, according to our opinion, assure the success of dental implantation.

Using optimization approach to design dental implant in three types of bone quality - A finite element analysis

Background/PurposeThe use of finite element (FE) analysis in implant biomechanics offers many advantages over other approaches in simulating the complexity of clinical situations. The aim of this study was to perform an optimization analysis of dental implants with different thread designs in three types of bone quality. Materials and methodsThe three-dimensional FE model of a mandibular bone block with a screw-shaped dental implant and superstructure was simulated. In the optimization analysis, the design variables included the thread pitch and the thread depth of the implant. The objective was to minimize the displacement of the implant to the target value. Three FE models with different bone qualities (D2: better bone quality; D3: ordinary bone quality; D4: poor bone quality) were created. ResultsThe FE results showed that the displacement of the implant and the stress of the cortical bone increased, while the Young's modulus of the cancellous bone decreased. In the D2 bone, changing the thread pitch and thread depth had little effect on cortical stress and implant displacement. However, in D3 and D4 bone, increasing thread depth reduced cortical stress by 40 % and implant displacement by at least 9 %. ConclusionAdjusted thread depth for D3 and D4 bone would reduce crestal bone stress and increase implant stability, but only a little alteration on crestal bone stress and implant stability for D2 bone.

The Effect of Increasing Thread Depth on the Initial Stability of Dental Implants: An In Vitro Study

Background: The long-term success of dental implants largely depends on achieving primary stability, previously described as crucial to obtaining osseointegration and immediate loading protocol requirements. Implant thread depths seem to be one of the key factors influencing primary stability, particularly in low-density bone. Insertion torque (IT) and resonance frequency analysis (RFA) are considered the most reliable tests to assess primary stability. The aim of this work was to evaluate how different thread depths of commercially available dental implants affect primary stability in low-density D3 bone. Materials and Methods: An in vitro study was carried out between February 2024 and March 2024. Twenty-four dental implants were divided into four groups (six implants each) according to their thread depths (Group A: 4 mm, Group B: 4.5 mm, Group C: 5 mm, Group D: 5.5 mm) and were inserted in D3-type artificial bone blocks. The main outcome variables were the IT and the Implant Stability Quotient (ISQ) measured in four different areas of the implant (buccal, lingual, mesial, and distal) with an Osstel® ISQ reader. Descriptive and inferential analyses of the data were performed, and the significance value was set at 5%. Results: A total of 24 implants were analyzed. The highest IT values were obtained in Group D, with a mean of 54.03 Ncm (standard deviation (SD) = 8.99), while the lowest measurements were observed in Group A (mean = 25.12; SD: 2.96 N.cm). The mean ISQ values were consistently higher in Group D for each analyzed area, with a mean of 70.13 N.cm (SD = 1.12). Conclusions: Taking into consideration the limitations of this in vitro study, greater thread depths seem to increase the primary stability of dental implants placed in soft bone. Furthermore, a positive correlation was observed between all IT and ISQ values, regardless of the thread depth.

Boosting the performance of bolt-microtubular solid oxide fuel cells through surface pattern tuning

A number of bolt-microtubular anode supports (BMASs) are manufactured by winding the corresponding thin tapes on threaded rods of different thread pitches and depths, followed by co-lamination using isostatic press. Bolt-microtubular cells (BMCs) are also constructed on BMASs to investigate the effects of the created surface patterns on the cell performance and microstructure. The bolt-microtubular cell, whose anode support is patterned by using a threaded rod with 0.8 mm thread pitch and 0.4 mm thread depth, exhibits ∼92% higher maximum performance than that of the reference cell at 800 ºC under 0.3 NL/min hydrogen flow and stagnant air. The almost doubled performance is mainly due to the increase in anode-electrolyte and cathode-electrolyte interfacial areas by the surface patterns created. The cell is also subjected to a 200-h life test at 800 °C and 0.7 V and demonstrates a stable performance.

Biomechanical and Biological Properties of Stereolithography-Based 3D-Printed Zirconia Interference Screws for Anterior Cruciate Ligament Reconstruction

For effective anterior cruciate ligament (ACL) reconstruction, an interference screw (IFS) is employed to force transplantation of the ligament into the bone tunnel. In this study, IFSs were successfully designed and prepared, and the top tooth width, thread depth, and drive structure were parameterized with a forming accuracy of 80.0 ± 21.1 µm using SLA–3D printing technology. To improve the initial stability of ACL reconstruction, a biomechanical model was established, and the results were optimized through insertion torque and tensile testing. Consequently, the IFS with the top tooth width of 0.4 mm, thread depth of 0.8 mm, and hexagon drive, matching with the Φ8 mm bone tunnel, exhibits the best mechanical properties (maximum insertion torque of 1.064 ± 0.117 N m, ultimate load of 446.126 ± 37.632 N, stiffness of 66.33 ± 27.48 N/mm). Additionally, the ZrO2/PDA/RGD/Zn2+ bioactive coating was found to significantly improve the surface bioactivity of zirconia IFS. In conclusion, this study has significant implications for ACL reconstruction.

UNDERSTANDING THE BIOMECHANICAL RESPONSE OF PROGRESSIVE THREAD DENTAL IMPLANTS USING MULTI-SCALE FINITE ELEMENT ANALYSIS

Implant osseointegration is an important factor dictating its long-term efficacy in situ. Along with various biological factors, it is greatly influenced by the mechanical stimulus at the peri-implant bone. The present study aims to understand the biomechanical response of progressive thread dental implants using multi-scale-based finite element analysis employing macro and micro models of bone. μ-CT images of a cadaveric human mandible of its premolar region were obtained, along with CT scan of the same region to generate computational models. Total of six dental implants were designed having regular and progressive thread depths. Three different stages of healing of the bone-implant assembly were simulated parametrically. The biomechanical environment at the peri-implant bone was analyzed considering the 'Mechanostat' hypothesis. The obtained results revealed that bone strain is significantly higher during the initial healing phase when the bone is weakest. During this phase, implant stress and its displacement in both buccolingual and coronoapical directions are also noticeably higher. Also, displacements of progressive thread implants were lower in all the healing phases as compared to the implants with constant thread depth. The observations of this μ FEA study highlights the clinical applicability of a progressive thread dental implant as it generates larger functional surface area, thus engages higher trabeculae and therefore is suitable for weaker bone conditions. Furthermore, by comparing the stress values at bone and implant between the two bone models, the CT-based model having inhomogeneous material was deemed suitable as an alternative to computationally expensive μ FEA.

Analysis of the Effect of Thread Depth in Four Different Thread Designs on the Stress Distribution at the Implant-bone Interface Using Finite Element Analysis – A Comparative Three-Dimensional In vitro Study

ABSTRACT Statement of Problem: Treatment with dental implants owes much of its success to the development and maintenance of an osseointegrated bone-implant interface. The development of this interface is influenced by various factors, of which implant thread design plays a dominant role. Purpose: The purpose of this study is to analyze the effect of thread depth in four different thread designs on the stress distribution at the implant-bone interface using three-dimensional finite element analysis. Materials and Methods: Four implant models with different thread shapes, namely V thread, square thread, buttress thread, and reverse buttress thread with an uniform thread depth of 0.4 mm were designed. These models were then placed in the mandibular first molar region. Force of 100 N was applied axially and at 45°angle to the implant. Von Mises stress was measured at the implant – Bone interface area and compared for the different designs. Results: The color plots obtained were studied and the maximum Von Mises stress was noted and tabulated for each condition. Stress distribution in the finite element models comes in the numerical values and in color coding. Maximum values of Von Mises stress are denoted by red color and minimum value by blue color. In between, the values are represented by bluish green, green, greenish yellow, and yellowish red in the ascending order of stress distribution. Conclusion: Thread design plays an important role in stress distribution in implant and bone. Varying Von Mises stress is seen at the cortical bone-implant and cancellous bone-implant interface. Clinical Implication: Successful osseointegration is necessary for implant success and thread design plays a very important role in osseointegration. Therefore, the selection of implants with proper thread design contributes greatly to the success of an implant-retained prosthesis.

Optimization of Pedicle Screw Parameters for Enhancing Implant Stability Based on Finite Element Analysis

ObjectiveTo improve the implant stability, the parameters including outer diameter, thread depth and pitch of pedicle screw were optimized by finite element analysis. MethodsThe insertion and pullout of pedicle screw were simulated by finite element analysis, and the precision of simulation was evaluated by comparing with mechanical tests. The influences of the parameters on the maximum insertion torque and maximum pullout force were analyzed by computational simulations including single-factor analysis and orthogonal experiment. ResultsThe simulation results agree with the mechanical tests. The influencing orders of the parameters on insertion torque and pullout force are both: outer diameter > pitch > thread depth. When the pilot hole diameter is 0.1 mm larger than the inner diameter of pedicle screw, the calculated Pearson correlation coefficient between the maximum insertion torque and maximum pullout force is r = 0.99. The optimized pedicle screw shows a maximum insertion torque of 485.16 N·mm and a maximum pullout force of 1726.33 N, which are 23.9% and 9.1% higher than those of standard screw, respectively. ConclusionsThe presently used models are feasible to evaluate the implant stability of pedicle screw. The maximum insertion torque and maximum pullout force of pedicle screw are highly correlated. The insertion torque and pullout force can be improved by increasing outer diameter and decreasing pitch. Beside the parameters of pedicle screw, the size of pedicle and bone mineral density are two considerable factors for a better implant stability.

Biomaterials and Clinical Application of Dental Implants in Relation to Bone Density-A Narrative Review.

Titanium has been the material of choice for dental implant fixtures due to its exceptional qualities, such as its excellent balance of rigidity and stiffness. Since zirconia is a soft-tissue-friendly material and caters to esthetic demands, it is an alternative to titanium for use in implants. Nevertheless, bone density plays a vital role in determining the material and design of implants. Compromised bone density leads to both early and late implant failures due to a lack of implant stability. Therefore, this narrative review aims to investigate the influence of implant material/design and surgical technique on bone density from both biomechanical and biological standpoints. Relevant articles were included for analysis. Dental implant materials can be fabricated from titanium, zirconia, and PEEK. In terms of mechanical and biological aspects, titanium is still the gold standard for dental implant materials. Additionally, the macro- and microgeometry of dental implants play a role in determining and planning the appropriate treatment because it can enhance the mechanical stress transmitted to the bone tissue. Under low-density conditions, a conical titanium implant design, longer length, large diameter, reverse buttress with self-tapping, small thread pitch, and deep thread depth are recommended. Implant material, implant design, surgical techniques, and bone density are pivotal factors affecting the success rates of dental implant placement in low-density bone. Further study is required to find the optimal implant material for a clinical setting's bone state.

Investigation on thread rolling processes of screws for intelligent thread rolling system

The traditional screw production equipment is very large, and many procedures need manual operation, which has a certain influence on the production of screws. In order to improvement the production efficiency, a new type of “Intelligent Thread Rolling System” is to be designed for the requirement. In this system, it is necessary to provide and transmit the relevant data for screw manufacturing, especially in the process of thread rolling. The thread plate design changes the traditional flat shape to become the curved shape. This paper has used the numerical model of the finite element method to calculate and simulate thread rolling process of thread plate of curved shape to understand the applicability. The results of relevant parameters on the thread rolling are obtained to compare with experimental data of Intelligent Thread Rolling System. Under certain test condition, the screw embryonal material can produce threads and cut off tails, but the created thread shape and depth are non-standard. The results are consistent with experimental data. The main reason is that the thread surface of thread plates of curved shape has not been redesigned. Due to the comparison and verification, the numerical parameters can be provided for the actual thread rolling operation of the ITRS. This is very helpful for the completion of the ITRS development.

Experimental investigation of novel internal thread fabrication: A drill thread milling

In this study, a novel method for fabricating internal threads called drill thread milling (DTM) was experimentally investigated. DTM is a fabrication process that combines drilling and thread milling into a single process, thereby eliminating the need for a pilot hole and making it a viable alternative to existing methods. To optimize the DTM process, the characteristics of DTM must first be understood. In this study, the machining characteristics of DTM were examined using a variety of materials and machining parameters. The results were then compared with those obtained using the tapping method. During the experiments, the machining force and vibration were recorded, and the results indicated that DTM required less machining time than did the tapping method. However, DTM exhibited an additional periodic components in the machining force, which could resulted in chatter. In certain materials, a tool offset was required to pass the thread gauge, indicating substantial tool deflection occurred during the machining process. The examination of the resulting threads revealed that, for the same thread depth, DTM required a shallower hole than that required in the tapping method.

Experimental study on the tensile performance of a large-diameter UHPC grouted sleeve with thread

An ultra-high-performance concrete (UHPC)-grouted sleeve with a large-diameter seamless steel pipe with threads and bolts was designed. To study the mechanical properties of this grouted sleeve, various factors, such as the grouts type, rebar, thread, and bolts, were considered to conduct a uniaxial tensile test on the grouted sleeve specimens. The bonding performance of the grouted sleeve under a combination of various factors was studied, and its working mechanism was discussed. The results showed that the failure modes of the test sleeve specimens included rebar fracture, rebar slip and grouts slip. The G1 (UHPC without basalt fibre) grouted sleeve showed the best bonding performance and bearing capacity. Bolts and inner wall threads of the sleeve improved the grouts–sleeve bond strength. However, the level of improvement was related to the bolt location, thread spacing and depth. The closer the bolt position was to the elastic section of the sleeve port, the more significant the bond performance improved. The thread could provide mechanical bite force. The greater the thread depth were, the greater the mechanical bite force; nevertheless, there was a threshold. Based on the thick-walled cylinder theory, the calculation model for stress on the sleeve surface was obtained; these calculations were used to analyse the stress–strain law on the sleeve surface.

Improving dental implant stability by optimizing thread design: Simultaneous application of finite element method and data mining approach

Lack of knowledge regarding the optimal design of thread configuration in dental implants, which can offer a satisfactory level of stability in the implant-bone construct, is a significant challenge in the field of dental biomechanics. The purpose of this finite element analysis study was to identify the optimal thread design by investigating the effects of thread parameters such as thread depth (TD), thread width (TW), and thread pitch (TP), as well as upper (α) and lower (β) thread angles, on the maximum principal stress in cancellous and cortical bone, maximum von Mises stress in the dental implant, and maximum shear stress at the implant-bone interface. A finite element model of an alveolar bone segment with a dental implant was developed. The Latin hypercube sampling method was used to generate a dataset of virtual experiments, which were analyzed by using the decision tree method to identify suitable thread designs that minimize mechanical stimuli. Additionally, the effectiveness of thread parameters on stress levels in the bone, implant, and their interface were assessed. The results of this study, verified by comparison with previous literature, indicated that TD, TW, and upper thread angle were the most effective parameters in promoting implant stability. By analyzing the decision trees, optimum ranges for all the thread parameters were determined as follows: 0.25<TD<0.34, 0.25≤TW≤0.28, 0.8≤TP≤0.88, 66.2≤α≤80, and β≤65.4, which led to the V-shape thread design.

Evaluation of two implant-supported fixed partial denture abutment designs: Influence on screw surface characteristics.

To compare screw surface characteristics between hemi-engaging and non-engaging implant-supported fixed partial denture (FPD) designs after cyclic loading. Twenty-four implants measuring 4.3 × 10mm were mounted on acrylic resin blocks. Specimens were divided into two groups. An experimental group included twelve 3-unit FPD with a hemi-engaging design; a control group included twelve 3-unit FPDs with the conventional design of two non-engaging abutments. Both groups were subjected to two types of cycling loading (CL), first axial loading, and then lateral loading at 30°. Load was applied to the units one million times (1.0 × 106 cycles) for each loading axis. Data on screw surface roughness in three locations and screw thread depth were collected before (BL) and after (AL) each loading type. Screw surface roughness was measured in μm using a mechanical digital surface profilometer and optical profiler. To evaluate screw thread depth in μm, an upright optical microscope Axio-imager 2 was used. To confirm readings made from the optical microscope, four random samples were selected from each group for scanning electron microscopy (SEM) analysis. The effect of cyclic loading was evaluated by averaging values across the two screws within each specimen, then calculating difference scores (DL) between BL and AL (DL = AL - BL). Additional difference scores were computed between the non-engaging screws in each experimental group specimen, and one randomly selected non-engaging screw in each control specimen. This difference was referred to as the non-engaging DL. Statistical significance was assessed using Mann-Whitney U tests (α = 0.05). Comparisons of DL and non-engaging DL by loading type revealed one significant difference regarding surface roughness at the screw thread. Significantly greater mean changes were observed after axial loading compared to lateral loading regarding both DL (axial M = -0.36 ± 0.08; lateral M = -0.21 ± 0.09; U = 20; p = 0.003) and non-engaging DL (axial M = -0.40 ± 0.22; lateral M = -0.21 ± 0.11; U = 29; p = 0.013). No significant differences in screw surface roughness in other sites or thread depth were found between the experimental and control abutment designs in DL or in non-engaging DL. No significant differences were found for DL (axial U = 13, p = 0.423; lateral U = 9, p = 0.150;) or non-engaging DL (axial U = 13, p = 0.423; lateral U = 18, p = 1.00). Results suggest that overall, changes in screw surface physical characteristics did not differ between hemi-engaging and non-engaging designs after evaluating screw surface roughness and thread depth before and after axial and lateral cyclic loading.

Dental balance in the arcs for the implants: a concise systematic review

The teeth together perform the functions of mastication, protection, and support of related soft tissues, help in the articulation of words, and are an important factor in the aesthetics of the face. The macro geometry of the implant provides influences on osseointegration. In this sense, the various isolated characteristics (thread type, thread pitch, thread depth, face angle) must be studied so that the implant geometry can balance the compressive stress and tensile stress and produce a minimum shear force. The present study aimed to carry out a concise systematic review of the main considerations of dental balance in the arches in implant dentistry. Thus, knowledge of the direction of the teeth is of great importance in clinical implant dentistry for the correct installation of implants, which are very important for maintaining the balance of forces exerted by masticatory muscles (masseter muscle, temporal muscle, medial pterygoid muscle). In addition to this, the evaluation of the amount and density of bone available in the patient's edentulous site. It was concluded that the optimized aesthetic positioning of the implant presents numerous factors for the good aesthetic performance of an implant-supported prosthesis. The main conditions of the soft tissues, the amount of bone, and the location and inclination of the placed implant can be cited as the main ones. The correct positioning of the implant is linked to the location and axial inclination of the implant, aiming to favor the emergence profile and aesthetic contours of the prosthesis. The ideal location for the implant would be the one assumed by the lost tooth root. Also, the location of the height of the cervical portion of this implant concerning the adjacent teeth is important for determining the prosthetic space available for making the restoration, as well as its emergence profile and the biological space of the surrounding soft tissues.

Pull-out behavior and damage assessment of core concrete of Full-scale prestressed High-strength hollow square piles

Prestressed high-strength (PHS) hollow square piles have been used recently to improve the ability of structural foundations to resist uplift loads, and the connection between PHS hollow square pile and upper cap is often in the form of core concrete. The main purpose of this paper is to study the effect of the internal thread of the pile wall on the pull-out behavior of core concrete. For this reason, pull-out tests of the core concrete of full-scale PHS hollow square piles were carried out. And the influence of core concrete type, core concrete length, thread length, and thread depth on the pull-out bearing capacity of core concrete was discussed. Simultaneously, acoustic emission technology was used for damage monitoring in the whole process to characterize the progressive failure behavior of piles. The results show that the gain of ultimate pull-out bearing capacity caused by an increase in the core concrete length is highly dependent on the form of the inner wall of the pile. In addition, under the same core concrete length, the ultimate pull-out bearing capacity of core concrete with appropriate thread pitch (P) and thread depth (D) are increased by 79%, which means P/D should be considered in the optimal design of internally threaded PHS hollow piles. The test results also prove the great potential of UHPC for improving the pull-out behavior and safety of core concrete.

Inter-implant distance and buccal bone thickness for a novel implant design: a preclinical study

ObjectivesThis study assessed bone height between novel tapered implants at different inter-implant thread peak (TP) distances, and the impact of TP distance from outer buccal bone (BB) on marginal bone levels (MBL).Materials and MethodsFully tapered implants with 0.5-mm thread depth and TP diameter 1 mm wider than the shoulder diameter were placed in healed ridges of minipigs. On one side, four implants were placed with inter-implant TP distances of 1, 2, or 3 mm corresponding to inter-implant implant shoulder distances of 2, 3, and 4 mm respectively. Three implants were placed on the other side with TP distances to outer BB of > 1 mm, 0.5–1 mm, or < 0.5 mm. After 12 weeks, (a) first bone-to-implant contact (fBIC), total BIC, bone area-to-total area (BATA), and coronal bone height between implants (Bi ½ max) for inter-implant distance, and (b) fBIC, BIC, and perpendicular crest to implant shoulder (pCIS) for BB were evaluated.ResultsNo significant differences in bone healing and inter-implant bone height were noted for any of the TP distances. BB resorption was significant when TP distance to outer BB was < 0.5 mm. However, fBIC was lowest with TP to outer BB of 1.75 mm.ConclusionsInter-implant bone height between adjacent implants can be maintained even at an inter-implant TP distance as low as 1 mm. A minimum TP to outer BB distance of 0.75 mm is required for predictable maintenance of MBL.Clinical relevanceInter-implant distance and BB thickness are clinically relevant and require preclinical research to clarify concepts.

Nonsurgical cleaning potential of deep-threaded implants and titanium particle release: A novel in vitro tissue model.

To measure the efficiency of three cleaning modalities on two implant designs with similar diameters but different thread depths as well as the presence of titanium particles. Sixty dyed implants (30 × 4.8 apically tapered (ATAP) and 30 × 5.0 fully tapered (FTAP)) were fixed in plastic models. The horizontal bone defects were surrounded with porcine soft tissue. Three instrumentation modalities were used to clean for 150 s: Curette (CUR), ultrasonic scaler (US), and air powder waterjet device (APWJ) with erythritol powder. Afterward, implants were photographed and scanning electron microscopic (SEM) images were taken. Titanium in the soft tissues was quantified in dissolved samples and histologically confirmed. For ATAP and FTAP implants, the percentage of the cleaned surface was 26.4 ± 3.0 and 17.1 ± 2.4% for CUR, 33.7 ± 3.8% and 28.1 ± 2.3% for US, and 45.5 ± 4.1% and 24.7 ± 3.8% for APWJ, respectively. SEM images showed significant implant surface changes, especially after instrumentation with CUR and US, whereas APWJ had little to no effect. Most titanium residues were found after cleaning ATAP implants with CUR (152.0 ± 75.5), followed by US (89.5 ± 73.8) and APWJ (0.3 ± 0.8). For the FTAP implants, respective values accounted for 129.5 ± 58.6 μg and 67.0 ± 14.4 μg for CUR and US, respectively. No titanium residues were detected on ATAP with APWJ. Based on in vitro data, erythritol-powered APWJ still appears to be the most efficient and gentle cleaning method. All three instruments, however, were found to have unprocessed areas depending on different implant designs, hence, clinical relevance for non-surgical approaches remains challenging and warrants further improvement.

Test on compressive performance of hollow concrete filled circular steel tube connected by thread through inner lining tube

A method of lengthening the steel tube of concrete-filled circular steel tube by inner lining tube and threaded connection is proposed. Taking the length, depth and position of the thread as the basic parameters, 12 hollow concrete-filled circular steel tube specimens connected by thread through inner lining tube are designed, and the axial compression test is carried out. The axial compressive loading-longitudinal compressive displacement curves, axial compressive loading -strain of steel tube curves and failure mode of the specimens are analyzed, and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens are studied. The results show that the axial compressive loading-displacement curves of the specimen can be divided into linear elastic stage, elasto-plastic stage and descending stage. The bearing capacity and stiffness of the specimens connected by thread through inner lining tube are basically the same as those of the unconnected specimen or the specimen connected by weld. In the range of parameters studied of this paper, bearing capacity and stiffness of the specimens connected at end section by thread through inner lining tube are higher than those of the specimens connected at middle section by thread through inner lining tube, and the axial compressive bearing capacity and stiffness of the specimen increase with the increase of thread length and depth. Based on the comparison between the calculation results calculated by existing formulas of the axial compression bearing capacity of hollow concrete-filled circular steel tube and the test results of specimens connected by thread through inner lining tube, the calculation method of the bearing capacity of hollow concrete-filled circular steel tubes connected by thread through inner lining tube are suggested.

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

Background and objectiveThe 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. MethodsIn 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. ResultsThrough 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. ConclusionsThe 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.