Evaluation of design parameters of osseointegrated dental implants using finite element analysis

A forecasting model for suitable dental implantation in canine mandibular premolar region based on finite element analysis

In recent years, dental implants have become a trend in the treatment of human patients with missing teeth, which may also be an acceptable method for companion animal dentistry. However, there is a gap challenge in determining appropriate implant sizes for different dog breeds and human. In this study, we utilized skull computed tomography data to create three-dimensional models of the mandibles of dogs in different sizes. Subsequently, implants of various sizes were designed and subjected to biomechanical finite element analysis to determine the optimal implant size. Regression models were developed, exploring the relationship between the average weight of dogs and the size of premolar implants. Our results illustrated that the regression equations for mean body weight (x, kg) and second premolar (PM2), third premolar (PM3), and fourth premolar (PM4) implant length (y, mm) in dogs were: y = 0.2785x + 7.8209, y = 0.2544x + 8.9285, and y = 0.2668x + 10.652, respectively; the premolar implant diameter (mm) y = 0.0454x + 3.3506, which may provide a reference for determine suitable clinical implant sizes for dogs.

Mechanical Integrity of All-on-Four Dental Implant Systems: Finite Element Simulation of Material Properties of Zirconia, Titanium, and PEEK

Background

Dental implants are critical for restoring functionality and aesthetics in patients with missing teeth. The all-on-four treatment concept utilizes four dental implants to support a full-arch prosthesis. Material choice for these implants plays a crucial role in the long-term success of the treatment, affecting everything from biomechanical stability to osseointegration and patient comfort.

Aim

The purpose of this study is to analyze the biomechanical performance of three different materials used in all-on-four dental implant designs through finite element analysis (FEA). The aim is to determine which material optimally balances stress and deformation under various loading conditions.

Objective

The main objective of this research is to evaluate the effects of stress, strain, and deformation on all-on-four dental implants made from titanium, zirconia, and polyether ether ketone (PEEK). The study seeks to identify which material demonstrates the best mechanical properties under simulated functional loads.

Methods

A 3D model simulating the dental implants integrated with cancellous and cortical bone was developed. Finite element analysis was conducted to assess the biomechanical performance of the implants made from titanium, zirconia, and PEEK. A perpendicular load of 100 N was applied to the tips of the implants, followed by an oblique load of 100 N at a 30-degree angle, to simulate different chewing forces.

Results

The deformation analysis indicated that implants made of zirconia exhibited significantly lower maximum and average deformation compared to those made from titanium and PEEK. Although PEEK implants showed lower maximum and average stress, they did not perform well in stress dissipation compared to zirconia. Similar patterns of stress and deformation were observed under both perpendicular and oblique loading conditions.

Conclusion

Zirconia implants outperformed titanium and PEEK in terms of deformation and stress distribution under simulated loading conditions. This suggests that zirconia could be a superior material for all-on-four dental implants, offering better mechanical stability and potentially enhancing the longevity and success of dental restorations. Further clinical trials are recommended to validate these findings and assess the long-term outcomes of zirconia-based implants.

Evaluation of Effect of Different Insertion Speeds and Torques on Implant Placement Condition and Removal Torque in Polyurethane Dense D1 Bone Model

The aim of this study was to evaluate the effect of two different insertion speeds at eight different insertion torque values ranging from 25 to 60 during implantation in a dense polyurethane (PU) D1 bone model on the placement condition and removal torque of dental implants. In this study, 50 pcf single-layer PU plates were used. In the study, a total of 320 implant sockets were divided into two groups, Group 1 (30 rpm) and Group 2 (50 rpm), in terms of insertion speed. Group 1 and Group 2 were divided into eight subgroups with 25, 30, 35, 40, 45, 50, 55 and 60 torques. There were 20 implant sockets in each subgroup. During the implantations, the implant placement condition and removal torque values were assessed. There was a statistically significant difference between the 30 and 50 rpm groups in terms of overall implant placement condition (p < 0.01). It was found that the removal torque values at 50 rpm were statistically significantly higher than those at 30 rpm (p < 0.01). This study showed that in dense D1 bone, the minimum parameters at which all implants could be placed at the bone level were 50 torque at 30 rpm and 40 torque at 50 rpm.

Biomechanical analysis of peri-prosthetic bone response to hybrid threaded zirconia dental implants: An in silico model

The biomechanical response of mandibular bone determines primary stability and concomitant osseointegration of dental implants. This study explores the impact of nature of loading and bone conditions on biomechanical response of hybrid threaded single-piece zirconia dental implants. To develop such understanding, three implants (SQ_V, V_BUT, and V_V), with different combinations of threads, square (SQ), buttress (BUT), and triangular (V), have been investigated. Finite Element Analysis (FEA) was carried out to simulate implantation at the molar position of mandible of varying densities under axial (≤500 N) and oblique (118.2 N) loadings. Patient-specific bone conditions (for a wider population) were considered by scaling the density and the elastic modulus of mandible to represent, 'weak', 'healthy', and 'strong' bone conditions. FEA results revealed that SQ_V and V_BUT implants exhibited a better biomechanical response without significant variation (<0.5%) in von Mises stress, regardless of bone density and axial loadings. These implants are predicted to perform with clinically acceptable factor of safety under investigated implantation scenarios, whereas V_BUT implant showed a larger variation (∼±12%). FEA simulation with oblique loading further validated such results. The 'weak' bone conditions resulted in maximum peri-implant microstrain, whereas 'strong and healthy' bone exhibited values close to the permissible range of physiological remodeling. The maximum micromotion (∼12.3 ± 6.2 μm for 'weak' bone) at bone-implant interface suggested that implant loosening and impaired osseointegration will not occur in any of selected virtual implantation cases. Both SQ_V and V_BUT implants will be considered further in implant development, involving manufacturing and product prototype validation. Taken together, the critical analysis of FEA results indicates a significant impact of bone density and distinct combinations of external threads on the biomechanical responses, in both the implant and the surrounding bone.

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.

Automated Remodelling of Connectors in Fixed Partial Dentures

In this study, an approach for automated parametric remodelling of the connector cross-sectional area in a CAD model of a given fixed partial denture (FPD) geometry was developed and then applied to a 4-unit FPD. The remodelling algorithm was implemented using Rhinoceros and the Grasshopper plugin. The generated CAD models were used to perform a finite element analysis with Ansys to analyse the stress distribution in an implant-supported 4-unit FPD for different connector designs. The results showed that the type of connector adjustment matters and that the resulting stress can be significantly different even for connectors with the same cross-sectional area. For tensile stresses, a reduction in the connector cross-sectional area from the gingival side showed the highest influence on each connector type. It can be concluded that the developed algorithm is suitable for automatic connector detection and adjustment.

Stress-strain and fatigue life numerical evaluation of two different dental implants considering isotropic and anisotropic human jaw

Dental prostheses are currently a valid solution for replacing potential missing tooth or edentulism clinical condition. Nevertheless, the oral cavity is a dynamic and complex system: occlusal loads, external agents, or other unpleasant events can impact on implants functionality and stability causing a future revision surgery. One of the failure origins is certainly the dynamic loading originated from daily oral activities like eating, chewing, and so on. The aim of this paper was to evaluate, by a numerical analysis based on Finite Elements Method (FEM), and to discuss in a comparative way, firstly, the stress-strain of two different adopted dental implants and, subsequently, their fatigue life according to common standard of calculations. For this investigation, the jawbone was modeled accounting for either isotropic or anisotropic behavior. It was composed of cortical and cancellous regions, considering it completely osseointegrated with the implants. The impact of implants' fixture design, loading conditions, and their effect on the mandible bone was finally investigated, on the basis of the achieved numerical results. Lastly, the life cycle of the investigated implants was estimated according to the well-established theories of Goodman, Soderberg, and Gerber by exploiting the outcomes obtained by the numerical simulations, providing interesting conclusions useful in the dental practice.

The Impact of Implant Angulation on the Stress Distribution and Survival Rate of Implant-Supported Fixed Dental Prostheses: A Retrospective Study

Background Implant-supported fixed dental prostheses (FDPs) have become a reliable method for the rehabilitation of edentulous patients, offering improved contour, function, esthetics, and overall oral health. This retrospective study aimed to evaluate the impact of implant angulation on the stress distribution and survival rate of implant-supported FDPs using finite element analysis (FEA). Methods A retrospective cross-sectional design was employed, utilizing existing patient records and radiographic data. The study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for transparent and comprehensive reporting. Sample size calculation was based on a reference study, considering a standard deviation of 2.5 for stress distribution measurements and a minimum detectable effect size of 1.0. Data collection included demographic and clinical characteristics, implant selection and placement details, prosthetic design and fabrication, as well as stress distribution analysis using FEA. Results The study included a total of 307 participants who met the inclusion criteria. Demographic variables demonstrated a balanced gender distribution (p = 0.172), with 51.5% males and 48.5% females. Smoking status (p < 0.001) and income level (p = 0.026) were significantly associated with the research outcomes. Implant characteristics analysis revealed three main types: NobelReplace Select (53.6%), Straumann Bone Level (31.9%), and BioHorizons Tapered Internal (14.5%). Implant type (p < 0.001), length (p = 0.003), diameter (p = 0.019), and manufacturer (p < 0.001) were all found to have statistically significant associations with the research outcomes. Conclusion The findings of this retrospective study highlight the importance of implant angulation on the stress distribution and survival rate of implant-supported FDPs. The evaluation of stress distribution patterns and the analysis of implant characteristics provide valuable insights for optimizing implant design and placement strategies.

Relationship between thread depth and fixation strength in cancellous bone screw

BACKGROUND

Clarifying the effect of each parameter of screw design on its fixation strength is critical in the development of any type of screw. The purpose of this study was to clarify the relationship between the thread depth and fixation strength of metal screws for cancellous bone.

METHODS

Nine types of custom-made screws with the only changed variable being the thread depth were manufactured. Other elements were fixed at a major diameter of 4.5 mm, a thread region length of 15 mm, a pitch of 1.6 mm, and a thread width of 0.20 mm. The pull-out strength and insertion torque of each screw were measured for each of two foam-block densities (10 or 20 pcf). The correlation between the thread depth of the screw and the mechanical findings were investigated with single regression analysis.

RESULTS

Regardless of the foam-block density, the pull-out strength significantly increased as the thread depth increased from 0.1 mm to 0.4 mm; after that, the increase was more gradual (p < 0.01, respectively). The relationship between the thread depth and insertion torque was similar. In addition, the insertion torque tended to be more strongly affected by screw depth than the pull-out strength (2.6 times at 20 pcf and 1.4 times at 10 pcf).

CONCLUSIONS

The pull-out strength of 4.5-mm-diameter metal screws in a cancellous bone model was found to be biphasic, although linearly correlated with the change in screw depth in both phases. The boundary of the correlation was 0.4 mm regardless of the density of the bone model, with the effect of screw depth on pull-out strength beyond that being small in comparison.

Occlusion as a predisposing factor for peri-implant disease: A review article

BACKGROUND

The restoration of dental implants presents a unique challenge due to the intrinsic biomechanical differences between osseointegrated implants and natural teeth, and their subsequent responses to occlusal loading. However, controversy exists regarding the role that occlusion plays in the physiology of the peri-implant complex.

PURPOSE

To provide an overview of the scientific literature regarding occlusion as it relates to implant dentistry and peri-implant disease.

MATERIALS AND METHODS

This article presents a narrative review on occlusal loading and its potential effects on the peri-implant complex, as well as some generally accepted guidelines for occlusion in implant dentistry.

RESULTS AND CONCLUSIONS

Although there is strong evidence linking occlusal factors to mechanical complications of dental implants, the same cannot be said regarding biological complications. There is no clear scientific evidence on the relationship between occlusal overload and peri-implant disease. However, occlusal overload may be an accelerating factor for peri-implant disease in the presence of inflammation. As the biomechanical properties of dental implants differ from that of the natural dentition, modifications to classic concepts of occlusion may be necessary when dental implants are involved. Thus, clinical recommendations are proposed which function to minimize unfavorable occlusal forces on implant restorations and reduce the associated biological and mechanical complications.

How does dental implant macrogeometry affect primary implant stability? A narrative review

PURPOSE

The macrogeometry of a dental implant plays a decisive role in its primary stability. A larger diameter, a conical shape, and a roughened surface increase the contact area of the implant with the surrounding bone and thus improve primary stability. This is considered the basis for successful implant osseointegration that different factors, such as implant design, can influence. This narrative review aims to critically review macro-geometric features affecting the primary stability of dental implants.

METHODS

For this review, a comprehensive literature search and review of relevant studies was conducted based on formulating a research question, searching the literature using keywords and electronic databases such as PubMed, Embase, and Cochrane Library to search for relevant studies. These studies were screened and selected, the study quality was assessed, data were extracted, the results were summarized, and conclusions were drawn.

RESULTS

The macrogeometry of a dental implant includes its surface characteristics, size, and shape, all of which play a critical role in its primary stability. At the time of placement, the initial stability of an implant is determined by its contact area with the surrounding bone. Larger diameter and a conical shape of an implant result in a larger contact area and better primary stability. But the linear relationship between implant length and primary stability ends at 12 mm.

CONCLUSIONS

Several factors must be considered when choosing the ideal implant geometry, including local factors such as the condition of the bone and soft tissues at the implant site and systemic and patient-specific factors such as osteoporosis, diabetes, or autoimmune diseases. These factors can affect the success of the implant procedure and the long-term stability of an implant. By considering these factors, the surgeon can ensure the greatest possible therapeutic success and minimize the risk of implant failure.

Finite element analysis in implant dentistry: State of the art and future directions

OBJECTIVE

To discuss the state of the art of Finite Element (FE) modeling in implant dentistry, to highlight the principal features and the current limitations, and giving recommendations to pave the way for future studies.

METHODS

The articles' search was performed through PubMed, Web of Science, Scopus, Science Direct, and Google Scholar using specific keywords. The articles were selected based on the inclusion and exclusion criteria, after title, abstract and full-text evaluation. A total of 147 studies were included in this review.

RESULTS

To date, the FE analysis of the bone-dental implant system has been investigated by analyzing several types of implants; modeling only a portion of bone considered as isotropic material, despite its anisotropic behavior; assuming in most cases complete osseointegration; considering compressive or oblique forces acting on the implant; neglecting muscle forces and the bone remodeling process. Finally, there is no standardized approach for FE modeling in the dentistry field.

SIGNIFICANCE

FE modeling is an effective computational tool to investigate the long-term stability of implants. The ultimate aim is to transfer such technology into clinical practice to help dentists in the diagnostic and therapeutic phases. To do this, future research should deeply investigate the loading influence on the bone-implant complex at a microscale level. This is a key factor still not adequately studied. Thus, a multiscale model could be useful, allowing to account for this information through multiple length scales. It could help to obtain information about the relationship among implant design, distribution of bone stress, and bone growth. Finally, the adoption of a standardized approach will be necessary, in order to make FE modeling highly predictive of the implant's long-term stability.

Optimization of stress distribution of bone-implant interface (BII)

Many studies have found that the threshold of occlusal force tolerated by titanium-based implants is significantly lower than that of natural teeth due to differences in biomechanical mechanisms. Therefore, implants are considered to be susceptible to occlusal trauma. In clinical practice, many implants have shown satisfactory biocompatibility, but the balance between biomechanics and biofunction remains a huge clinical challenge. This paper comprehensively analyzes and summarizes various stress distribution optimization methods to explore strategies for improving the resistance of the implants to adverse stress. Improving stress resistance reduces occlusal trauma and shortens the gap between implants and natural teeth in occlusal function. The study found that: 1) specific implant-abutment connection design can change the force transfer efficiency and force conduction direction of the load at the BII; 2) reasonable implant surface structure and morphological character design can promote osseointegration, maintain alveolar bone height, and reduce the maximum effective stress at the BII; and 3) the elastic modulus of implants matched to surrounding bone tissue can reduce the stress shielding, resulting in a more uniform stress distribution at the BII. This study concluded that the core BII stress distribution optimization lies in increasing the stress distribution area and reducing the local stress peak value at the BII. This improves the biomechanical adaptability of the implants, increasing their long-term survival rate.

Finite Element Analysis of a New Non-Engaging Abutment System for Three-Unit Implant-Supported Fixed Dental Prostheses

(1) Background: The stability of implants plays a significant role in the success of osseointegration. The stability of the connection between the fixture and the abutment is one of the critical factors affecting osseointegration. When restoring multiple, non-parallel, and splinted implants, achieving a passive fit can be complicated and challenging. A new EZ post non-engaging abutment system of the BlueDiamond^® (BD) implant allows a wide connection angle while achieving a passive prosthesis fit. This study aimed to confirm the new abutment system's clinical applicability by evaluating its biomechanical characteristics using finite element analysis (FEA). (2) Methods: The implant-supported fixed three-unit dental prostheses model was reproduced for two groups of AnyOne^® (AO) and BD implants using FEA. The loading conditions were a preload of 200 N in the first step and loads of 100 N (axial), 100 N (15°), or 30 N (45°) in the second step. (3) Results: The peak Von Mises stress (PVMS) value of the fixture in the BD group was more than twice that in the AO group. In contrast, the PVMS values of the abutment and abutment screws were lower in the BD group than in the AO group. The AO group revealed higher maximal principal stress (MPS) values than that of the BD group in the cortical bone, cancellous bone, and crown. The average stress of the outer surface of the abutment was lower in the AO group than in the BD group. The stress distribution for the inner surface of the fixture confirmed that the BD group displayed a lower stress distribution than the AO group under axial and 15° loads; however, the average stress was 1.5 times higher at the 45° load. The stress values of the entire surface where the cortical and cancellous bone were in contact with the fixture were measured. The AO group showed a higher stress value than the BD group in both cortical and cancellous bone. (4) Conclusions: In the AO group, the PVMS value of the fixture and the stress distribution at the contact surface between the fixture and the abutment were lower than those of the BD group, suggesting that the stability of the fixture would be high. However, due to the high stress in the fastening area of the abutment and abutment screw, the risk of abutment fracture in the AO group is higher than that of the BD group. Therefore, the new EZ post non-engaging abutment of the BD implant can be used without any problems in clinics, similar to the non-engaging abutment of the AO implant, which has been widely used in clinical practice.

Influence of bone morphology on the mechanobiological stimuli distribution of maxillary anterior labial bone: A biomechanical study

OBJECTIVE

This study intended to ascertain the dimensional effects of labial bone thickness and height on the mechanobiological stimuli distribution of maxillary anterior labial bone through biomechanical analysis.

MATERIAL AND METHODS

Twelve 3D finite element models of an anterior maxillary region with an implant were computer-simulated, including four levels of labial bone thicknesses (2, 1.5, 1.0, and 0.5 mm) and three levels of labial bone heights (normal, reduced by 1/3, reduced by 1/2). A 45° buccolingual oblique load of 100 N was applied to the implant restoration.

RESULTS

Equivalent stress and principal strain mainly concentrated on crestal bone around the implant neck. The maximum equivalent stress in bone decreased as labial bone mass decreased, while the maximum principal strain and the displacement of dental implant increased as labial bone mass decreased. No significant difference of these three indicators was observed, when the labial bone thickness changed in the range of 2.0-1.0 mm with sufficient labial bone height.

CONCLUSIONS

In terms of biomechanics, the thickness of labial bone plate was recommended ≥1 mm. Sufficient labial bone height was warranted to prevent the stability of the implants from being seriously affected. The labial bone heights were more effective than thicknesses on the mechanobiological stimuli response of the dental implant-bone system.

CLINICAL SIGNIFICANCE

For this 3D finite element study, the biomechanical responses under different bone mass conditions were explored, in order to predict the process of bone remodeling and provide valid clinical recommendations for the decision-making process regarding the choices of tissue augmentation for some specific esthetic implantation cases for future clinical applications.

Finite Element Analysis of the Stress Distribution Associated With Different Implant Designs for Different Bone Densities

PURPOSE

The main objective of this study was to investigate the influence of implant design, bone type, and abutment angulation on stress distribution around dental implants.

MATERIALS AND METHODS

Two implant designs with different thread designs, but with the same length and brand were used. The three-dimensional geometry of the bone was simulated with four different bone types, for two different abutment angulations. A 30° oblique load of 200 N was applied to the implant abutments. Maximum principal stress and minimum principal stresses were obtained for bone and Von misses stresses were obtained for dental implants.

RESULTS

The distribution of the load was concentrated at the coronal portion of the bone and implants. The stress distributions to the D4 type bone were higher for implant models. Increased bone density and increased cortical bone thickness cause less stress on bone and implants. All implants showed a good distribution of forces for non-axial loads, with higher stresses concentrated at the crestal region of the bone-implant interface. In implant types using straight abutments there was a decrease in stress as the bone density decreased. The change in the abutment angle also caused an increase in stress.

CONCLUSIONS

The use of different implant threads and angled abutments affects the stress on the surrounding bone and implant. In addition, it was observed that a decrease in density in trabecular bone and a decrease in cortical bone thickness increased stress. This article is protected by copyright. All rights reserved.

Biomechanical Stress Analysis of Platform Switch Implants of Varying Diameters on Different Densities of Bone

Purpose

The purpose of this study was to evaluate and compare the strain developed in D2 and D3 types of bones on vertical loading by platform switch implants of different diameters.

Materials and Methods

Implants of diameters 3.25 mm, 4.2 mm, and 5.0 mm and of length 11.5 mm were taken and placed each on D2 and D3 bone models. Strain gauges were attached on the buccal and the lingual sides on each of these samples, and a vertical load of 190N was placed on the samples. The strain was recorded using a data logger. The data obtained was analysed using one-way ANOVA and post hoc Tukey test.

Results

In D2 and D3 bone models, 3.25 mm significantly showed greater bone strain values. The buccal side strain was higher irrespective of the implant diameter and density of bone.

Conclusion

Within the limitations of the study, it may be concluded that the narrow diameter implant produces greater strain than 4.2 and 5.0 mm diameter implants, respectively. The buccal side consistently produced higher bone strain values.

Comparison of Stress Distribution in Surrounding Bone during Insertion of Dental Implants on Four Implant Threads under the Effect of an Impact: A Finite Element Study

The design of an implant thread plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and stability in cancellous bone. The primary stability of a dental implant is determined by the mechanical engagement between the implant and bone at the time of implant insertion. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. Numerous factors influence load transfer at the bone-implant interface, for example, the type of loading, surface structure, amount of surrounding bone, material properties of the implant and implant design. The purpose of this study was to investigate the effects of the impact two different projectile of implant threads on stress distribution in the jawbone using three-dimensional finite element analysis.

Performance and service quality enhancement in a healthcare setting through lean six sigma strategy

Purpose

The article intended to excavate the Lean Six Sigma (LSS) deployment challenges, Critical Success Factors (CSF), tools and techniques, and managerial implications in an Indian healthcare setting.

Design/methodology/approach

The article illustrates a case study established using Action Research (AR) approach. Further, the case study is based on the Define, Measure, Analyze, Improve, Control (DMAIC) phases of LSS. The performance and service quality of the Endodontics department of a dental college attached to a hospital is enhanced and sustained through the LSS strategy.

Findings

The processing time of Root Canal treatment is reduced by determining the root causes for delay and implementing sustainable solutions. The structured deployment of the LSS strategy helped the Endodontics department to reduce the processing time from an average of 116 min–84 min. Thus, the process's sigma level is enhanced from 0.06 to 4.17 and assisted in sustaining the results.

Research limitations/implications

The case study's findings are based on the single AR carried out at an Endodontics department of a dental college hospital based on LSS strategies. Even though this study's results cannot be generalized, the deliverables of the case study can be used to develop the LSS roadmap for the dental colleges to enhance the service quality and safety of the patients.

Originality/value

The article provides step-by-step details for implementing LSS in dental college hospitals with critical analysis based on robust statistical tools and techniques. The case study provides evidence of the adoption of LSS in medical college education and provides the confidence to adopt the same through novice users. The study's findings may persuade the policymakers to add LSS in the medical education curriculum to reinforce safety and reduce errors in the healthcare system.

Three-Dimensional Finite Element Investigation into Effects of Implant Thread Design and Loading Rate on Stress Distribution in Dental Implants and Anisotropic Bone

Variations in the implant thread shape and occlusal load behavior may result in significant changes in the biological and mechanical properties of dental implants and surrounding bone tissue. Most previous studies consider a single implant thread design, an isotropic bone structure, and a static occlusal load. However, the effects of different thread designs, bone material properties, and loading conditions are important concerns in clinical practice. Accordingly, the present study performs Finite Element Analysis (FEA) simulations to investigate the static, quasi-static and dynamic response of the implant and implanted bone material under various thread designs and occlusal loading directions (buccal-lingual, mesiodistal and apical). The simulations focus specifically on the von Mises stress, displacement, shear stress, compressive stress, and tensile stress within the implant and the surrounding bone. The results show that the thread design and occlusal loading rate have a significant effect on the stress distribution and deformation of the implant and bone structure during clinical applications. Overall, the results provide a useful insight into the design of enhanced dental implants for an improved load transfer efficiency and success rate.

Influence of sequential opening/closing of interface gaps and texture density on bone growth over macro-textured implant surfaces using FE based mechanoregulatory algorithm

Intramedullary implant fixation is achieved through a press-fit between the implant and the host bone. A stronger press-fit between the bone and the prosthesis often introduces damage to the bone canal creating micro-gaps. The aim of the present investigation is to study the influences of simultaneous opening/closing of gaps on bone growth over macro-textured implant surfaces. Models based on textures available on CORAIL and SP-CL hip stems have been considered and 3D finite element (FE) analysis has been carried out in conjunction with mechanoregulation based tissue differentiation algorithm. Additionally, using a full-factorial approach, different combinations (between 5 µm to 15 µm) of sliding and gap distances at the bone-implant interface were considered to understand their combined influences on bone growth. All designs show an elevated fibrous tissue formation (10.96% at 5 µm to 29.38% at 40 µm for CORAIL based textured model; 11.45% at 5 µm to 32.25% at 40 µm for SP-CL based textured model) and inhibition of soft cartilaginous tissue (75.64% at 5 µm to 53.94% at 40 µm for CORAIL based model; 76.02% at 5 µm to 53.60% at 40 µm SP-CL based model) at progressively higher levels of normal micromotion, leading to a fragile bone-implant interface. These results highlight the importance of minimizing both sliding and gap distances simultaneously to enhance bone growth and implant stability. Further, results from the studies with differential texture density over CORAIL based implant reveal a non-linear complex relationship between tissue growth and texture density which might be investigated in a machine learning framework.

Comparative Analysis of Stress and Deformation between One-Fenced and Three-Fenced Dental Implants Using Finite Element Analysis

Finite element analysis (FEA) has always been an important tool in studying the influences of stress and deformation due to various loads on implants to the surrounding jaws. This study assessed the influence of two different types of dental implant model on stress dissipation in adjoining jaws and on the implant itself by utilizing FEA. This analysis aimed to examine the effects of increasing the number of fences along the implant and to compare the resulting stress distribution and deformation with surrounding bones. When a vertical force of 100 N was applied, the largest displacements found in the three-fenced and single-fenced models were 1.7469 and 2.5267, respectively, showing a drop of 30.8623%. The maximum stress found in the three-fenced and one-fenced models was 13.518 and 22.365 MPa, respectively, showing a drop of 39.557%. Moreover, when an oblique force at 35° was applied, a significant increase in deformation and stress was observed. However, the three-fenced model still had less stress and deformation compared with the single-fenced model. The FEA results suggested that as the number of fences increases, the stress dissipation increases, whereas deformation decreases considerably.

Multi-objective design optimization of dental implant geometrical parameters

In-silico investigations are becoming an integral part of the development of novel biomedical devices, including dental implants. Using computer simulations can streamline the process by tuning different geometrical and structural features, emphasizing the osseointegration of the implant design a priori, leading to the optimal designs in preparation for in-vivo trails. This research aims to elucidate the interrelationship between 12 geometrical variables that holistically define the shape of the implant. The approach to achieve optimality hinged on coupling the finite element analysis results with the fractional factorial design method. The latter was used to determine the most influential variables during the screening process, followed by the parameter optimization process using the response surface method, regarding four different objectives, namely: bone-implant contact area, volume of trabecular bone dead cells, volume of cortical bone dead cells, and axial displacement. This resulted in reducing the number of virtual experiments and substantially decreasing the computational cost without compromising the accuracy of the solution. It was found that the optimized values improved the performance significantly. The validity of all models was verified by comparing optimized responses with simulation results. A sensitivity analysis was performed on all five optimized models to address the effect of friction coefficient on the implant-bone joint interaction. It was shown that the mechanical behavior of implant-bone would be independent in higher friction coefficients. The significance of this study is demonstrated in determining the most effective and optimized values of all possible geometrical parameters considering their singular or interactive effects.

Collagen Fibres Orientation in the Bone Matrix around Dental Implants: Does the Implant's Thread Design Play a Role?

The aim of this study was to analyse the influence of different thread shapes of titanium dental implant on the bone collagen fibre orientation (BCFO) around loaded implants. Twenty titanium dental implants, divided for thread shapes in six groups (A–F) were analysed in the present study. All implants were immediately loaded and left in function for 6 months before retrieval. The parameters evaluated under scanning electron microscope were the thread width, thread depth, top radius of curvature, flank angle, and the inter-thread straight section. Two undecalcified histological sections were prepared from each implant. Birefringence analysis using circularly polarized light microscopy was used to quantitively measure BCFO. For groups A–F, respectively, transverse BCFO was 32.7%, 24.1%, 22.3%, 18.2%, 32.4%, and 21.2%, longitudinal BCFO was 28.2%, 14.5%, 44.9%, 33.1%, 37.7%, and 40.2%. The percentage differences between transverse and longitudinal orientation were 4.50% (A), 9.60% (B), −22.60% (C), −14.90% (D), −5.30% (E), and −19.00% (F). Following loading, the amount of transverse and longitudinal BCFO were significantly influenced by the thread shape. The greater flank angles and narrower inter-thread sections of the “V” shaped and “concave” shaped implant threads of groups A and B, respectively, promoted the predominance of transverse BCFO, compared to groups C-F (p < 0.05). A narrow inter-thread straight section promotes transverse BCFO, as do “V” shaped and “concave” shaped threads, which can thus be considered desirable design for implant threads.

Analysis of micromovements and peri-implant stresses and strains around ultra-short implants - A three-dimensional finite-element method study

Background:

Success of an implant depends on its placement in the bone and how well the stress and strain are distributed to the surrounding structures when occlusal force is applied to it. The size and shape of the implant plays an important role is the formation and distribution of stress and strains in the periodontium. Von Mises stresses and micromovements need to be evaluated while placing implants in D4 bone quality regions for a higher success rate.

Aim:

To evaluate the peri-implant Von Mises stresses, strains, and micromovements distribution in D4 bone quality around ultra-short implants of 5 mm length with varying diameters of 4 mm, 5 mm, and 6 mm.

Materials and Methods:

The finite element method was employed to make models replacing maxillary molars in D4 type bone that was missing. Implants that could be classified as ultrashort (5 mm) were used. These implants were of varying diameters of 4, 5, and 6 mm. In each model, the implant was subjected to a force of 100 N and analyzed. The force was applied in an oblique (45 degrees) and vertical direction (90°) to the long axis of the tooth. The models were made such that they simulated cortical and cancellous anisotropic properties of the bone. The models were then analyzed using the program ANSYS workbench version 12.1.

Results:

When all the three diameters were compared wide diameter, i.e., 6 mm threads had the least values of peri-implant von Mises stresses, strains, and micro-movements around them. When thread shapes were taken into consideration square micro thread created the most favorable stress parameters around them with minimum values of stress, strains, and micromovements.

Conclusion:

Ultrashort implants combined with a wide diameter and platform switched can be used in atrophic ridges or when there is a need for extensive surgery to prepare the implant site.

Finite Element Analysis of Dental Implants with Zirconia Crown Restorations: Conventional Cement-Retained vs. Cementless Screw-Retained

The present study was designed to compare the stress distributions in two restoration types of implants and the surrounding bone. The first restoration type was a conventional cement-retained zirconia crown, and the second was a novel cementless screw-retained zirconia crown with a base abutment. A three-dimensional finite element method was used to model the implants, restorations, and supporting bone. A comparative study of the two implants was performed under two masticatory loads: a vertical load of 100 N and a 30-degree oblique load of 100 N. Under both loading conditions, the maximum von Mises stress and strain values in the implant and supporting bone were higher in the conventional cement-retained restoration model than in the cementless screw-retained model. In terms of stress distribution, the cementless screw-retained zirconia crown with base abutment may be considered a superior restoration option compared to the conventional cement-retained zirconia crown.

Application of Lean Six Sigma in conservative dentistry: an action research at an Indian dental college

Purpose

The article evaluates the obstacles, lessons learned and managerial implications of deploying Lean Six Sigma (LSS) in a dental college hospital in India.

Design/methodology/approach

The work adopts the action research (AR) methodology to establish a case study, which is carried out using the LSS define–measure–analyze–improve–control (DAMIC) approach in a dental college. It uses LSS tools to enhance the productivity and performance of the Conservative Dentistry Department of a dental college and to unravel the obstacles and success factors in applying it to the education and healthcare sector together.

Findings

The root cause for high turn-around time (TAT) is ascertained using LSS tools and techniques. The effective deployment of the solutions to the root causes of variation assists the dental college to reduce the TAT of the Conservative Dentistry process from an average of 63.9 min–36.5 min (i.e. 42.9% improvement), and the process Standard Deviation (SD) was reduced from 2.63 to 2 min. This, in turn, raises the sigma level from 0.48 to 3.23, a noteworthy successful story for this dental college.

Research limitations/implications

While the results and recommendations of this research are focused on a single case study, it is to be noted that the case study is carried out with new users of LSS tools and techniques, especially with the assistance of interns. This indicates the applicability of LSS in dental colleges; thus, the adopted modality can be further refined to fit India's education and hospital sector together.

Originality/value

This article explains the implementation of LSS from an aspiring user viewpoint to assist dental colleges and policymakers in improving competitiveness. In addition, the medical education sector can introduce an LSS course in the existing programme to leverage the potential of this methodology to bring synergy and collaborative research between data-based thinking and the medical field based on the findings of this study. The most important contribution of this article is the illustration of the design of experiments (DOE) in the dental college process.

A randomized clinical study to compare implant stability and bone loss using early loading protocol in two implant systems with different design

Aims

The study compared changes in implant stability and bone loss of implants with different designs using early loading at 6 weeks.

Setting and Design

In vivo-comparative study.

Materials and Methods

Forty subjects were selected and divided randomly by sealed envelope method in Group X and Group A for early loading for missing single posterior tooth in mandible. Implants in Group X had flared crest module and buttress thread design, whereas implants in Group A had parallel crest module and V-shaped thread design. All subjects were evaluated by Ostell for implant stability at the interval of baseline, 6 weeks, 3 months, and 6 months. ImageJ software was used for measurement of crestal bone loss in intraoral periapical radiographs at the interval of 6 weeks, 3 months, and 6 months.

Statistical Analysis Used

Unpaired t test, repeated ANOVA, Tukey post hoc test.

Results

The mean bone loss values of Group X at predetermined interval were 1.51 ± 0.20 mm, 2.11 ± 0.21 mm and 2.13 ± 0.21 mm. The mean bone loss values of Group A were 1.79 ± 0.16 mm, 2.92 ± 0.23 mm and 2.95 ± 0.23 mm. The mean bone loss was statistical significant (P < 0.05) at 6 weeks, 3 months and 6 months. It was highly significant in Group A at 6 months (P < 0.001).

Conclusions

It was concluded that Group X implants design showed better implant stability and less bone loss when compared to Group A implants design.

Can barb thread design improve the pullout strength of bone screws?

AIMS

To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws.

METHODS

Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared.

RESULTS

The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure.

CONCLUSION

Bone screws with a reverse buttress thread design will significantly increase the pullout strength. Cite this article: Bone Joint Res 2021;10(2):105-112.

Evaluation of stability of three different mini-implants, based on thread shape factor and numerical analysis of stress around mini-implants with different insertion angle, with relation to en-masse retraction force

Objectives:

Assess the stability of three different mini-implants, based on thread shape factor (TSF), and evaluate stresses at the mini-implant site and surrounding cortical bone on application of retraction force, at two different insertion angles.

Methods:

Mini-implants of three different diameters (M1 - Orthoimplant, 1.8mm), (M2 - Tomas, 1.6mm) and (M3 - Vector TAS, 1.4mm) and length of 8mm were used. Using scanning electronic microscopy, the mean thread depth, pitch and relationship between the two (TSF) were calculated. The mini-implants were loaded into a synthetic bone block and the pull-out strength was tested. One way ANOVA and Tukey post-hoc tests were used to compare the pull-out strength of mini-implants. P values < 0.05 were considered statistically significant. Finite element models (FEM) were constructed with insertion angulation at 90° and 60°, with retraction force of 150 g. The results were analyzed using ANSYS software.

Results:

Statistically significant difference was found among all the three mini-implants for thread depth and pitch (< 0.001). Statistically significant higher pull-out force value was seen for Orthoimplant. The stress distribution level in mini-implant and surrounding bone was observed to be smaller for Orthoimplant.

Conclusion:

Orthoimplant mini-implants have more favorable geometric characteristics among the three types, and less stress with 90°angulation.

Design optimization of implant geometrical characteristics enhancing primary stability using FEA of stress distribution around dental prosthesis

The main objective of this study was to investigate the influence of implant geometrical characteristics: diameter, length and thread's pitch, on stress distribution around dental prosthesis. A set of numerical simulations using FEM were conducted and responses surfaces were generated. With the aim of optimizing the equivalent stresses responses; desirability function approach was adopted to solve this multi-objective problem. Results showed that implant diameter had most significant influence on generated stresses and high concentration of stresses were identified in the lower part of the implant. This study is helpful in choosing the optimal dental implant for clinical application.

Influence of Implant Dimensions in the Resorbed and Bone Augmented Mandible: A Finite Element Study

Aims:

The scope of this study was to analyze the influence of clinically feasible implant diameter and length on the stress transmitted to the peri-implant bone in the case of a resorbed and bone augmented mandible through finite element analysis.

Settings and Design:

The study was carried out in silico.

Subjects and Methods:

Resorbed and bone-augmented 3D models were derived from in vivo cone-beam computed tomography scans of the same patient. Corresponding implant systems were modeled with the diameter ranging from 3.3 to 6 mm and length ranging from 5 to 13 mm, and masticatory loads were applied on the abutment surface.

Statistical Analysis Used:

None.

Results:

In the bone augmented ridge, maximum stress values in the peri-implant region drastically decreased only when using implants of a diameter of 5 mm and 6 mm. Implants up to 4 mm in diameter led to comparable stress values with the ones obtained in the resorbed ridge, when using the larger implants. The increase of length reduced stress in the resorbed mandible, whereas in the bone augmented model, it led to small variations only in implants up to 4 mm in diameter.

Conclusions:

It was concluded that bone augmentation provides the optimal framework for clinicians to use larger implants, which, in turn, reduces stress in the peri-implant region. Diameter and length play an equally important role in decreasing stress. Implant dimensions should be carefully considered with ridge geometry.

Influence of Connection Type and Platform Diameter on Titanium Dental Implants Fatigue: Non-Axial Loading Cyclic Test Analysis

Two-pieces dental implants must provide stability of the implant-abutment-interface. The connection type and platform diameter could influence the biomechanical resistance and stress distribution. This study aims to evaluate the fatigue for different types of connections, external and internal, and different platform diameters. Three implant designs with the same length were used: (a) external hexagon/narrow platform; (b) internal double hexagon/narrow platform; (c) internal octagon/regular platform. A fatigue test was developed to establish the number of cycles needed before fracture. A 30º oblique load with a sinusoidal function of fatigue at a frequency of 15 Hz and 10% stress variation was applied to each system. The fatigue load limit (FLL) for design (a) was 190 N, being the nominal-curvature-moment (NCM) = 1.045; FLL = 150 N, with a NCM = 0.825 for (b), and FLL = 325 N, with a NCM = 1.788 for (c). The platform diameter affects the FLL, obtaining lower FLL on a narrow platform. The connection type interferes with the implant walls’ width, especially in narrow implants, making internal connections more unstable at this level. Long-term clinical studies to assess the restoration’s success rate and survival are mandatory.

Finite Element Analysis of the Stress Field in Peri-Implant Bone: A Parametric Study of Influencing Parameters and Their Interactions for Multi-Objective Optimization

The present work proposes a parametric finite element model of the general case of a single loaded dental implant. The objective is to estimate and quantify the main effects of several parameters on stress distribution and load transfer between a loaded dental implant and its surrounding bone. The interactions between them are particularly investigated. Seven parameters (implant design and material) were considered as input variables to build the parametric finite element model: the implant diameter, length, taper and angle of inclination, Young’s modulus, the thickness of the cortical bone and Young’s modulus of the cancellous bone. All parameter combinations were tested with a full factorial design for a total of 512 models. Two biomechanical responses were identified to highlight the main effects of the full factorial design and first-order interaction between parameters: peri-implant bone stress and load transfer between bones and implants. The description of the two responses using the identified coefficients then makes it possible to optimize the implant configuration in a case study with type IV. The influence of the seven considered parameters was quantified, and objective information was given to support surgeon choices for implant design and placement. The implant diameter and Young’s modulus and the cortical thickness were the most influential parameters on the two responses. The importance of a low Young’s modulus alloy was highlighted to reduce the stress shielding between implants and the surrounding bone. This method allows obtaining optimized configurations for several case studies with a custom-made design implant.

Effect of Different Implant Designs on Strain and Stress Distribution under Non-Axial Loading: A Three-Dimensional Finite Element Analysis

Implant design evolved alongside the development of implant therapy. The purpose of this finite element analysis (FEA) study was to analyze the influence of different implant designs on the stress and strain distribution to the implants and surrounding bone. Three implant designs with the same length and diameter were used. The three-dimensional geometry of the bone was simulated with a cortical bone of three different thicknesses and two medullar bone densities: low density (150 Hounsfield units) and high density (850 Hounsfield units). A 30° oblique load of 150 N was applied to the implant restoration. Displacement and stress (von Mises) results were obtained for bone and dental implants. The strain and stress distributions to the bone were higher for the tissue-level implant for all types of bone. The maximum principal strain and stress decreased with an increase in cortical bone thickness for both cancellous bone densities. The distribution of the load was concentrated at the coronal portion of the bone and implants. All implants showed a good distribution of forces for non-axial loads, with higher forces concentrated at the crestal region of the bone–implant interface. Decrease in medullar bone density negatively affects the strain and stress produced by the implants.

Finite element analysis of narrow dental implants

Narrow-diameter implants (NDIs) traditionally have been associated to higher rates of failure in comparison with regular-diameter implants (RDIs) and wide-diameter implants (WDIs), since they generate a more unfavorable stress distribution in peri-implant bone. However, it is well known that the load sharing effect associated with prostheses supported by multiple implants (also called splinted prostheses) affords mechanical benefits. The present study involves finite element analysis (FEA) to determine whether the risks linked to NDIs could be mitigated by the mechanical advantages afforded by the splinting concept. For this purpose, a three-dimensional (3D) model of a real maxilla was reconstructed from computed tomography (CT) images, and different implants (NDIs, RDIs and WDIs) and prostheses were created using computer-aided design (CAD) tools. Biting forces were simulated on the prostheses corresponding to three different rehabilitation solutions: single-implant restoration, three-unit bridge and all-on-four treatment. Stress distribution around the implants was calculated, and overloading in bone was quantified within peri-implant volumes enclosed by cylinders with a diameter 0.1mm greater than that of each implant. The mechanical benefits of the splinting concept were confirmed: the peri-implant overloaded volume around NDIs splinted by means of the three-unit bridge was significantly reduced in comparison with the nonsplinted condition and, most importantly, proved even smaller than that around nonsplinted implants with a larger diameter (RDIs). However, splinted NDIs supporting the all-on-four prosthesis led to the highest risk of overloading found in the study, due to the increase in compressive stress generated around the tilted implant when loading the cantilevered molar.

A Comparison of Photoelastic and Finite Elements Analysis in Internal Connection and Bone Level Dental Implants

This study is a contribution to our understanding of the mechanical behaviour of dental implants through the use of the finite element and the photoelastic methods. Two internal connection and bone level dental implants with different design have been analysed (M-12 by Oxtein S.L., Zaragoza, Spain, and ASTRA, from Dentsply Sirona, Charlotte, NC, USA), evaluating the stress distribution produced by axial stresses and a comparison has been established between them, as well as between the two methods used, in order to validate the adopted hypotheses and correlate the numerical modelling performed with experimental tests. To load the implant in laboratory testing, a column was placed, such that the loading point was about 9.3 mm from the upper free surface of the resin plate. This column connects the implant with the weights used to define the test load. In turn, support for both plates was achieved by two 6 mm bolts 130 mm apart and located on a parallel line with the resin (flush with the maximum level of the implant), at a depth of 90 mm. The results obtained with both methods used were similar enough. The comparison of results is fundamentally visual, but ensures that, at least in the range of forces used, both methods are similar. Therefore, the photoelastic method can be used to confirm in a real way the virtual conditions of the finite element models, with the implications in the investigation of dental implants that this entails.

Finite element analysis of a one-piece zirconia implant in anterior single tooth implant applications

This study evaluated the von Mises stress (MPa) and equivalent strain occurring around monolithic yttria-zirconia (Zir) implant using three clinically simulated finite element analysis (FEA) models for a missing maxillary central incisor. Two unidentified patients' cone-beam computed tomography (CBCT) datasets with and without right maxillary central incisor were used to create the FEA models. Three different FEA models were made with bone structures that represent a healed socket (HS), reduced bone width edentulous site (RB), and immediate extraction socket with graft (EG). A one-piece abutment-implant fixture mimicking Straumann Standard Plus tissue level RN 4.1 X 11.8mm, for titanium alloy (Ti) and Zir were modeled. 178 N oblique load and 200 N vertical load were used to simulate occlusal loading. Von Mises stress and equivalent strain values for around each implant model were measured. Within the HS and RB models the labial-cervical region in the cortical bone exhibited highest stress, with Zir having statistically significant lower stress-strain means than Ti in both labial and palatal aspects. For the EG model the labial-cervical area had no statistically significant difference between Ti and Zir; however, Zir performed better than Ti against the graft. FEA models suggest that Ti, a more elastic material than Zir, contributes to the transduction of more overall forces to the socket compared to Zir. Thus, compared to Ti implants, Zir implants may be less prone to peri-implant bone overloading and subsequent bone loss in high stress areas especially in the labial-cervical region of the cortical bone. Zir implants respond to occlusal loading differently than Ti implants. Zir implants may be more favorable in non-grafted edentulous or immediate extraction with grafting.

Effects of occlusal forces on the peri-implant-bone interface stability

The occlusal forces and their influence on the initiation of peri-implant bone loss or their relationship with peri-implantitis have created discussion during the past 30 years given the discrepancies observed in clinical, animal, and finite element analysis studies. Beyond these contradictions, in the case of an osseointegrated implant, the occlusal forces can influence the implant-bone interface and the cells responsible for the bone remodeling in different ways that may result in the maintenance or loss of the osseointegration. This comprehensive review focuses on the information available about the forces transmitted through the implant-crown system to the implant-bone interface and the mechano-transduction phenomena responsible for the bone cells' behavior and their interactions. Knowledge of the basic molecular biology of the peri-implant bone would help clinicians to understand the complex phenomenon of occlusal forces and their effects on the implant-bone interface, and would allow better control of the negative effects of mechanical stresses, leading to therapy with fewer risks and complications.

Influence of Implant Length and Associated Parameters Upon Biomechanical Forces in Finite Element Analyses: A Systematic Review

PURPOSE

The aim of this systematic review is to provide an overview of finite element analyses comparing standard and short dental implants concerning biomechanical properties and to detect the most relevant parameters affecting periimplant stress concentrations.

MATERIAL AND METHODS

After screening the literature and assessment of studies, 36 studies were included in this review.

RESULTS

Eighty-three percent of the studies state that short dental implants have to bear higher stress concentrations compared with standard length implants. At the same time, 44% of articles note that implant diameter can be considered a more effective design parameter than implant length to reduce stress concentrations and to avoid an overload of periimplant bone. Regardless of implant dimension, in all studies, the highest stress concentrations are found in the cortical section around the upper part of the implant.

CONCLUSIONS

Unaffected of bone quality, implant diameter is found to play a key role to minimize periimplant stress concentrations. Concerning stress reduction implant length gains increasing relevance with decreasing bone density. Furthermore, splinting of short implants constitute an appropriate tool to avoid crestal overloading.

Optimized Dental Implant Fixture Design for the Desirable Stress Distribution in the Surrounding Bone Region: A Biomechanical Analysis

The initial stability of a dental implant is known to be an indicator of osseointegration at immediate loading upon insertion. Implant designs have a fundamental role in the initial stability. Although new designs with advanced surface technology have been suggested for the initial stability of implant systems, verification is not simple because of various assessment factors. Our study focused on comparing the initial stability between two different implant systems via design aspects. A simulated model corresponding to the first molar derived from the mandibular bone was constructed. Biomechanical characteristics between the two models were compared by finite element analysis (FEA). Mechanical testing was also performed to derive the maximum loads for the two implant systems. CMI IS-III active (IS-III) had a more desirable stress distribution than CMI IS-II active (IS-II) in the surrounding bone region. Moreover, IS-III decreased the stress transfer to the nerve under the axial loading direction more than IS-II. Changes of implant design did not affect the maximum load. Our analyses suggest that the optimized design (IS-III), which has a bigger bone volume without loss of initial fixation, may minimize the bone damage during fixture insertion and we expect greater effectiveness in older patients.

Impact of Different Titanium Implant Thread Designs on Bone Healing: A Biomechanical and Histometric Study with an Animal Model

Threads of dental implants with healing chamber configurations have become a target to improve osseointegration. This biomechanical and histometric study aimed to evaluate the influence of implant healing chamber configurations on the torque removal value (RTv), percentage of bone-to-implant contact (BIC%), bone fraction occupancy inside the thread area (BAFO%), and bone and osteocyte density (Ost) in the rabbit tibia after two months of healing. Titanium implants with three different thread configurations were evaluated: Group 1 (G1), with a conventional “v” thread-shaped implant design; Group 2 (G2), with square threads; and Group 3 (G3), the experimental group with longer threads (healing chamber). Ten rabbits (4.5 ± 0.5 kg) received three implants in each tibia (one per group), distributed in a randomized manner. After a period of two months, the tibia blocks (implants and the surrounding tissue) were removed and processed for ground sectioning to evaluate BIC%, BAFO%, and osteocyte density. The ANOVA one-way statistical test was used followed by the Bonferoni’s multiple comparison test to determine individual difference among groups, considering a statistical difference when p < 0.05. Histometric evaluation showed a higher BAFO% values and Ost density for G3 in comparison with the other two groups (G1 and G2), with p < 0.05. However, the RTv and BIC% parameters were not significantly different between groups (p > 0.05). The histological data suggest that the healing chambers in the implant macrogeometry can improve the bone reaction in comparison with the conventional thread design.

Finite Element Analysis of Novel Separable Fixture for Easy Retrievement in Case with Peri-Implantitis

Peri-implantitis is a common complication following dental implant placement, which may lead to bone loss and fixation failure. With the conventional fixture, it is difficult to perfectly clear-up the infection. To solve this, we have designed a separable fixture of which the top part is replaceable. This study aimed to compare the structural and biomechanical stability of the separable and conventional fixture. A single surgical model corresponding to the first molar in a virtual mandible model and conventional/separable implants were reproduced to compare the biomechanical characteristics of the implants using finite element analysis (FEA). The loading condition was 200N preload in the first step, and 100N (Axial), 100N (15°), and 30N (45°) in the second step. The stress distribution on the cortical bone in the separable implant was lower than the conventional implant. In particular, the Peak von Mises Stress (PVMS) values of the separable implant under lateral load was found to be about twice as low as that of the conventional implant. In this study, we suggest that the separable implant has an equivalent biomechanical stability compared to the conventional implant, is easy to retrieve in the case of peri-implantitis, and has an excellent initial stability after the surgery when used in stage 2.

Unravelling the effect of macro and microscopic design of dental implants on osseointegration: a randomised clinical study in minipigs

Several dental implants are commercially available and new prototype design are constantly being fabricated. Nevertheless, it is still unclear what parameters of the design affect most the osseointegration of dental implants. The purpose of this study is to assess the effects of the microscopic and macroscopic design of dental implants in the osseointegration by comparing three macroscopic designs (Straumann tissue level (STD), essential cone (ECD) and prototype design (PD)) and six surface treatments. A total of 96 implants were placed in 12 minipigs. The implant stability quotient (ISQ), was assessed at the time of implantation, as well as at 2, 4 and 8 weeks. Histomorphometric and statistical analyses were conducted at the different sacrifice times, being 2, 4 and 8 weeks, to analyse the bone to implant contact (BIC), the bone area density (BAT) and the density of bone outside the thread region (ROI). The macroscopic design results showed higher ISQ values for the ECD, whereas the histomorphometric analysis showed higher ossoeintegration values for the STD. Regarding the microscopic design, both Sandblasted plus acid etching (hydrochloric/sulphuric acid) in a nitrogen atmosphere (SLActive) and Shot-blasted or bombarded with alumina particles and posterior alkaline immersion and thermal treatment (ContacTi) showed superior results in terms of osseointegration and reduced the osseointegration times from 8 weeks to 4 weeks compared to the other analysed surfaces. In conclusion, each of the macroscopic and microscopic designs need to be taken into account when designing novel dental implants to enhance the osseointegration process.

Evaluation of bone stimulation by different designs of microthreaded implants in enhancing osseointegration: An in vivo animal study supported by a numerical analysis

BACKGROUND

An optimal shape of the thread design of the implants is required for equal distribution of stresses to the surrounding bone matrix and for stimulation and promotion of bone remodeling.

PURPOSE

The study was construed with the aim of histomorphometric evaluation of bone stimulation generated by different microthread designed implants in enhancing osseointegration, and to assess the pattern of stress dissipation through a two-dimensional finite element analysis.

MATERIALS AND METHODS

Computer Aided Designing of two type of microthreads, one V-shaped and the other Power-shaped microthreaded dental implants with only microthreads all along body of the implant from the neck to the apex was made and 30 implant prototypes were milled. Two-dimensional finite elemental analysis (FEA) was carried out to assess the pattern of stress distribution in the bone around these implant designs and for In vivo study 24 implant prototypes were placed in rabbits tibia and femur, out of which 12 were with V-shaped microthreads and the other 12 were with Power-shaped microthreads. Histomorphometric analysis was carried out of the sections obtained from the enbloc specimen retrieved from the sacrificed rabbits.

RESULTS

FEA showed less stress around the V-shaped microthreaded implant model when compared to Power-shaped microthreaded implant model. Hitomorphometry showed statistical significance difference in new bone volume (BV) and Total BV for V-shaped microthreaded prototype implant.

CONCLUSIONS

V-shaped microthreaded dental implant design can be preferred over Power-shaped microthreaded dental implant for proper stress distribution and for promoting osseointegration.