In vitro fatigue tests and in silico finite element analysis of dental implants with different fixture/abutment joint types using computer-aided design models

Influence of connection design and material properties on stress distribution and fatigue lifetime of zygomatic implants: A finite element analysis

Zygomatic implants (ZIs) were developed as a graftless alternative to rehabilitate severely reabsorbed maxillae. This study aims to employ three-dimensional finite element analysis (FEA) to simulate the impact of external hexagonal implant connection (EHC) and internal hexagonal implant connection (IHC) on the stress distribution and fatigue lifetime within the ZI systems using parameters defined in ISO 14801:2016. Two ZI assemblies (Nobel Biocare and Noris Medical) were scanned in a micro-CT scanner and reconstructed using Nrecon software. Three-dimensional models were generated by Simpleware ScanIP Medical software. All models were exported to FEA software (ABAQUS) and subsequently to a fatigue analysis software (Fe-safe). A compressive 150 N load was applied at a 40° angle on the cap surface. A 15 Hz frequency was applied in the in silico cyclic test. The implant components had material properties of commercially pure grade 4 titanium (CPTi) and Titanium-6Aluminum-4Vanadium alloy (Ti64). Von Mises stress data, contour plots, and fatigue limits were collected and analyzed. EHC models exhibited higher peak stresses in implant components for both materials compared to IHC models. However, simulated bone support results showed the opposite trend, with higher stresses on IHCthan EHC models. The fatigue analysis revealed that assemblies with both designs exceeded ISO 14801:2016 number of cycles limits using Ti64, while CPTi groups exhibited comparatively lower worst life-repeats. In conclusion, ZIs with IHC were found to have a more homogeneous and advantageous stress distribution within both materials tested. Ti64 demonstrates a prolonged service life for both design connections.

Finite element analysis of non-ultraviolet and ultraviolet-irradiated titanium implants

AIM

The purpose of this study is to calculate von Mises stresses, von Mises strains, deformation, principal stresses and principal elastic strains of non-UV and UV-irradiated hybrid SLA (sandblasted, large-grit, acid-etched)-coated titanium implants.

MATERIALS AND METHODS

A cross-sectional analytical study was conducted at the Institute of Dentistry, CMH Lahore Medical College. Cone beam computed tomography (CBCT) data of One Hundred and Thirty Eight Dio Hybrid sandblasted and acid-etched implants of identical dimensions (10 mm in length and 4.5 mm in diameter) were allocated in the three groups. Control group A samples were not given UV irradiation, while groups B and C were given UVA (382 nm, 25 mWcm-2) and UVC (260 nm, 15 mWcm-2) irradiation, respectively. The CBCT data were analyzed using FEA (ANSYS software). CBCT images were taken before functional loading (8th week) and after functional loading (26th week). A 3-way ANOVA test was employed to see the difference between the three groups. Tukey test was utilized for multiple comparisons. p ≤ 0.05 was considered significant.

RESULTS

The control group exhibited the highest average values for maximum von Mises stress, von Mises strain, deformation, principal stress, and principal elastic strain in both the maxilla and mandible compared to the UV-irradiated groups. Additionally, these measures consistently displayed higher averages in the maxilla across all groups compared to the mandible. Particularly, the UVC-irradiated group demonstrated the lowest von Mises stresses around the implants compared to the UVA group.

CONCLUSION

Insignificant differences were observed between UVA- and UVC-irradiated implants in terms of principal stress, deformation, von Mises strain, and principal elastic strain. The only notable distinction was in von Mises stress, where the UVC-irradiated group exhibited lower von Mises stress around SLA-coated titanium implants.

Influence of Connector Design on Displacement and Micromotion in Tooth-Implant Fixed Partial Dentures Using Different Lengths and Diameters: A Three-Dimensional Finite Element Study

The literature presents insufficient data evaluating the displacement and micromotion effects resulting from the combined use of tooth-implant connections in fixed partial dentures. Analyzing the biomechanical behavior of tooth-implant fixed partial denture (FPD) prothesis is vital for achieving an optimum design and successful clinical implementation. The objective of this study was to determine the relative significance of connector design on the displacement and micromotion of tooth-implant-supported fixed dental prostheses under occlusal vertical loading. A unilateral Kennedy class I mandibular model was created using a 3D reconstruction from CT scan data. Eight simulated designs of tooth-implant fixed partial dentures (FPDs) were split into two groups: Group A with rigid connectors and Group B with non-rigid connectors. The models were subjected to a uniform vertical load of 100 N. Displacement, strain, and stress were computed using finite element analysis. The materials were defined as isotropic, homogeneous, and exhibiting linear elastic properties. This study focused on assessing the maximum displacement in various components, including the bridge, mandible, dentin, cementum, periodontal ligament (PDL), and implant. Displacement values were predominantly higher in Group B (non-rigid) compared to Group A (rigid) in all measured components of the tooth-implant FPDs. Accordingly, a statistically significant difference was observed between the two groups at the FPD bridge (p value = 0.021 *), mandible (p value = 0.021 *), dentin (p value = 0.043 *), cementum (p value = 0.043 *), and PDL (p value = 0.043 *). Meanwhile, there was an insignificant increase in displacement values recorded in the distal implant (p value = 0.083). This study highlighted the importance of connector design in the overall stability and performance of the prosthesis. Notably, the 4.7 mm × 10 mm implant in Group B showed a displacement nearly 92 times higher than its rigid counterpart in Group A. Overall, the 5.7 mm × 10 mm combination of implant length and diameter showcased the best performance in both groups. The findings demonstrate that wider implants with a proportional length offer greater resistance to displacement forces. In addition, the use of rigid connection design provides superior biomechanical performance in tooth-implant fixed partial dentures and reduces the risk of micromotion with its associated complications such as ligament overstretching and implant overload, achieving predictable prognosis and enhancing the stability of the protheses.

Fatigue life prediction considering variability for additively manufactured pure titanium clasps

PURPOSE

This study aims to develop a numerical prediction method for the average and standard deviation values of the largely varied fatigue life of additively manufactured commercially pure titanium (CPTi grade 2) clasps. Accordingly, the proposed method is validated by applying it to clasps of different shapes.

METHODS

The Smith-Watson-Topper (SWT) equation and finite element analysis (FEA) were used to predict the average fatigue life. The variability was expressed by a 95% reliability range envelope based on the experimentally determined standard deviation.

RESULTS

When predicting the average fatigue life, the previously determined fatigue parameters implemented in the SWT equation were found to be useful after conducting fatigue tests using a displacement-controlled fatigue testing machine. The standard deviation with respect to stroke and fatigue life was determined for each clasp type to predict variability. The proposed prediction method effectively covered the experimental data. Subsequently, the prediction method was applied to clasps of different shapes and validated through fatigue tests using 22 specimens. Finally, the fracture surface was observed using scanning electron microscopy (SEM). Many manufacturing process-induced defects were observed; however, only the surface defects where the maximum tensile stress occurred were crucial.

CONCLUSIONS

It was confirmed that the fatigue life of additively manufactured pure titanium parts is predictable before the manufacturing process considering its variability by performing only static elasto-plastic FEA. This outcome contributes to the quality assurance of patient-specific clasps without any experimental investigation, reducing total costs and response time.

Biomechanical Fatigue Behavior of a Dental Implant Due to Chewing Forces: A Finite Element Analysis

The use of titanium as a biomaterial for the treatment of dental implants has been successful and has become the most viable and common option. However, in the last three decades, new alternatives have emerged, such as polymers that could replace metallic materials. The aim of this research work is to demonstrate the structural effects caused by the fatigue phenomenon and the comparison with polymeric materials that may be biomechanically viable by reducing the stress shielding effect at the bone-implant interface. A numerical simulation was performed using the finite element method. Variables such as Young's modulus, Poisson's coefficient, density, yield strength, ultimate strength, and the S-N curve were included. Prior to the simulation, a representative digital model of both a dental implant and the bone was developed. A maximum load of 550 N was applied, and the analysis was considered linear, homogeneous, and isotropic. The results obtained allowed us to observe the mechanical behavior of the dental implant by means of displacements and von Mises forces. They also show the critical areas where the implant tends to fail due to fatigue. Finally, this type of non-destructive analysis proves to be versatile, avoids experimentation on people and/or animals, and reduces costs, and the iteration is unlimited in evaluating various structural parameters (geometry, materials, properties, etc.).

Mechanical behavior of endodontically treated teeth: A three-dimensional finite element analysis using displacement vector

PURPOSE

This study aimed to analyze the effects of core materials, remaining tooth structures, and interfacial bonding on stress distribution in endodontically treated teeth using finite element analysis (FEA).

MATERIALS AND METHODS

Three-dimensional FEA was conducted using a reverse engineering technique based on maxillary premolars scanned by micro-computed tomography. Six models were generated with or without ferrules and with one of the following three abutment systems: metal core, resin core, or resin core with fiber posts. In each model, bonding and debonding were assumed in the dentin and surrounding structures: bonded and debonded models. The maximum principal stress values were recorded, and stress distribution of the entire restored teeth and dentin was generated. Furthermore, the distribution of the displacement vector of the debonded models was generated.

RESULTS

In comparing the bonded and debonded models, the debonded models showed larger values for tensile stresses than those in bonded models for all abutment models. The models without ferrules rotated around the center of the abutment, whereas those with ferrules did not show remarkable displacement in the analysis.

CONCLUSION

FEA assuming fracture of adhesive interface proved to be an effective method to clarify the significance of ferrules. It prevents stress concentration in dentin by reducing the rotation of the abutment, even when the adhesive fails.

Comparison of the fatigue life of pure titanium and titanium alloy clasps manufactured by laser powder bed fusion and its prediction before manufacturing

PURPOSE

In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion.

METHODS

Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps.

RESULTS

The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement.

CONCLUSIONS

Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.

Clinical performance of short and extrashort dental implants with wide diameter: A systematic review with meta-analysis

STATEMENT OF PROBLEM

Rehabilitation with wide-diameter reduced-length implants has become popular for patients with minimal vertical bone. However, a consensus on the benefits of this approach is lacking.

PURPOSE

The purpose of this systematic review with meta-analysis was to evaluate the influence of wide compared with regular diameter on the clinical performance of short (<10 mm) and extrashort (≤6 mm) dental implants used for rehabilitations with single crowns, fixed partial dentures, or both, in the posterior region.

MATERIAL AND METHODS

A search in 6 databases was conducted to select randomized controlled trials (RCTs) and nonrandomized controlled trials (N-RCTs). Five meta-analyses were performed, where the risk ratio (RR) was evaluated. The certainty of evidence was evaluated, and the risk of bias was determined from the Joanna Briggs Institute checklist.

RESULTS

Fourteen articles were included, 272 wide- and 478 regular-diameter implants. One study presented a low, 3 an unclear, and 11 a high risk of bias. Meta-analyses showed no statistical difference: implant survival, short dental implants in N-RCTs (up to 1 year - RR 1.01 [0.98; 1.03], 1 to 5 years - RR 1.01 [0.94; 1.08], more than 5 years - RR 1.01 [0.97; 1.06]), extrashort dental implants in N-RCTs (RR 1.04 [0.90; 1.20]), RCTs (RR 1.05 [0.88; 1.25]); implant success in N-RCTs (RR 1.01 [0.97; 1.05]); prosthesis success in N-RCTs (RR 1.01 [0.97; 1.05]).

CONCLUSIONS

Short and extrashort dental implants with a wide and regular diameter appear to be clinically appropriate options for implant-supported posterior restorations, with high survival, success, and prosthesis success rates.

Comparative analysis of the mechanical limits of resistance in implant/abutment set of a new implant design: An in vitro study

OBJECTIVE

The aim of the present in vitro study was to evaluate the resistance on quasi-static forces and in the fatigue mechanical cycling of a new implant design compared to two other conventional implant designs.

MATERIALS AND METHODS

Eighty-eight implants with their respective abutments were tested and distributed into four groups (n = 22 per group): Morse taper connection implant (MT group), conventional external hexagon implant (EH con group), new Collo implant of external hexagon with the smooth portion out of the bone insertion (EH out group), and new Collo implant of external hexagon with the implant platform inserted to the bone level (EH bl group). All the sets were subjected to quasi-static loading in a universal testing machine, and we measured the maximum resistance force supported by each sample. Another 12 samples from each group were submitted to the cyclic fatigue test at 4 intensities of forces (n = 3 per force): 80%, 60%, 40%, and 20%. The number of cycles supported by each sample at each force intensity was evaluated.

RESULTS

The three groups of implants with external hexagon connection had similar maximum strength values of the sets (p > 0.05). Meanwhile, samples from the MT group showed the highest resistance values in comparison to the other three groups (p < 0.05). In the fatigue test, the Collo out group supported a smaller number of cycles that led to the fracture than the other 3 groups proposed at loads of 80%, 60%, and 40%, and only at the load value of 20% all groups had the same performance.

CONCLUSIONS

Within the limitations of the present in vitro study, the results showed that the new Collo implant performs better when installed at bone level.

Biomechanical evaluations of the long-term stability of dental implant using finite element modeling method: a systematic review

PURPOSE

The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM).

MATERIALS AND METHODS

A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here.

RESULTS

By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling.

CONCLUSION

Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

Fatigue Resistance of Cast-on Implant Abutment Fabricated with Three Different Alloys

OBJECTIVES

 This study aimed to evaluate fatigue resistance of cast-on implant abutment using three alloys.

MATERIALS AND METHODS

 Forty specimens of implant-supported crowns were prepared; Group 1 (TA) stock titanium abutments, Group 2 (GS) abutment cast with 40% gold alloy, Group 3 (GP) abutment cast with palladium alloy, and Group 4 (CN) abutment cast with nickel-chromium alloy. Specimens were cyclic loaded at 20 Hz, starting from 200 N (5,000 cycles), followed by stepwise loading of 400, 600, 800, 1,000, 1,200, 1,400, 1,600, and 1,800 N (30,000 cycles/step). Specimens were loaded until failure or reached 245,000 cycles.

STATISTICAL ANALYSIS

 The withstand cycles were analyzed using one-way analysis of variance and Weibull survival analysis. Fracture surfaces were examined using scanning electron microscopy.

RESULTS

 The results of withstand cycles were TA (189,883 ± 22,734), GS (195,028 ± 22,371), GP (187,662 ± 22,555), and CN (200,350 ± 30,851). The statistical analysis showed no significant difference between the groups (p = 0.673).

CONCLUSION

 Although CN has higher Weibull characteristic strength which means greater durability, its lower Weibull modulus demonstrated less structural reliability. Consistent failures at implant fixture level were also found in CN group.

Investigation of the Type of Angled Abutment for Anterior Maxillary Implants: A Finite Element Analysis

PURPOSE

The optimal abutment material and design for an angled implant-abutment connection in the esthetic zone is unclear. The purpose of this finite element analysis (FEA) study was to compare different abutment models by evaluating the stress values in the implant components and strain values on the simulated bone around an anterior maxillary implant with different angled abutment models and loading conditions.

MATERIALS AND METHODS

One Ø3.5×12-mm implant was placed in 3D FEA models representing the anterior left lateral segment of the maxilla. Three different contemporary implant models were created with 17° or 25° angled abutments (Ti base abutment, zirconia abutment, and titanium abutment) and 3D-modeled. The implant abutment model was an angled Ti base abutment (TIB), an angled zirconia abutment (ZIR), or an angled titanium abutment (TIT). Vertical and oblique loads of 100 N for the central incisors were applied as boundary conditions to the cingulum area and incisal area in a nonlinear FEA.

RESULTS

The TIB model resulted in reduced stress conditions. According to the von Mises stresses occurring on the screw, abutment, crown, and implant, especially under oblique loads, the TIB model was exposed to less stress than the ZIR or TIT models. Strain values in simulated cortical and trabecular bones were obtained lower in the TIB model.

CONCLUSIONS

When a standard implant was placed in the esthetic zone at an increased angle, the implants, abutments, and screws had more unfavorable stress levels; therefore, using a Ti-base abutment may reduce stress. The amount of contact surface of the implant with the simulated cortical bone is also an important factor affecting stress and strain.

In Silico Finite Element Analysis of the Foot Ankle Complex Biomechanics: A Literature Review

Computational approaches, especially finite element analysis (FEA), have been rapidly growing in both academia and industry during the last few decades. FEA serves as a powerful and efficient approach for simulating real-life experiments, including industrial product development, machine design, and biomedical research, particularly in biomechanics and biomaterials. Accordingly, FEA has been a "go-to" high biofidelic software tool to simulate and quantify the biomechanics of the foot-ankle complex, as well as to predict the risk of foot and ankle injuries, which are one of the most common musculoskeletal injuries among physically active individuals. This paper provides a review of the in silico FEA of the foot-ankle complex. First, a brief history of computational modeling methods and finite element (FE) simulations for foot-ankle models is introduced. Second, a general approach to build an FE foot and ankle model is presented, including a detailed procedure to accurately construct, calibrate, verify, and validate an FE model in its appropriate simulation environment. Third, current applications, as well as future improvements of the foot and ankle FE models, especially in the biomedical field, are discussed. Finally, a conclusion is made on the efficiency and development of FEA as a computational approach in investigating the biomechanics of the foot-ankle complex. Overall, this review integrates insightful information for biomedical engineers, medical professionals, and researchers to conduct more accurate research on the foot-ankle FE models in the future.

Biomechanical effects of dental implant diameter, connection type, and bone density on microgap formation and fatigue failure: A finite element analysis

BACKGROUND AND OBJECTIVE

Understanding fatigue failure and microgap formation in dental implants, abutments, and screws under various clinical circumstances is clinically meaningful. In this study, these aspects were evaluated based on implant diameter, connection type, and bone density.

METHODS

Twelve three-dimensional finite element models were constructed by combining two bone densities (low and high), two connection types (bone and tissue levels), and three implant diameters (3.5, 4.0, and 4.5 mm). Each model was composed of cortical and cancellous bone tissues, the nerve canal, and the implant complex. After the screw was preloaded, vertical (100 N) and oblique (200 N) loadings were applied. The relative displacements at the interfaces between implant, abutment, and screw were analyzed. The fatigue lives of the titanium alloy (Ti-6Al-4V) components were calculated through repetitive mastication simulations. Mann-Whitney U and Kruskal-Wallis one-way tests were performed on the 50 highest displacement values of each model.

RESULTS

At the implant/abutment interface, large microgaps were observed under oblique loading in the buccal direction. At the abutment/screw interface, microgap formation increased along the implant diameter under vertical loading but decreased under oblique loading (p < 0.001); the largest microgap formation occurred in the lingual direction. In all cases, the bone-level connection induced larger microgap formation than the tissue-level connections. Moreover, only the bone-level connection models showed fatigue failure, and the minimum fatigue life was observed for the implant diameter of 3.5 mm.

CONCLUSIONS

Tissue-level implants possess biomechanical advantages compared to bone-level ones. Two-piece implants with diameters below 3.5 mm should be avoided in the posterior mandibular area.

Study on statics and fatigue analysis of dental implants in the descending process of alveolar bone level

Alveolar bone atrophy can directly cause a decrease in bone level. The effect of this process on the service life of dental implants is unknown. The aim of this study was to determine the failure forms of the two-piece dental implants in the descending process of alveolar bone level, and the specific states of the components during the failure process. The CAD software SolidWorks was used to establish the model of alveolar bone and dental implants in this article. The finite element analysis was used to analyze the statics of the dental implants in the host oral model. The finite element analysis results showed that the stress concentration point of the implant and abutment in the implant system has changed greatly during the descending process of alveolar bone level, and indirectly increased the fatigue life of the same fatigue risk point. At the same time, the dental implants were tested in vitro in the descending process of alveolar bone level. Then, the fracture of the implant system was scanned by scanning electron microscope. The fatigue test results proved the finite element analysis hypothesis the central screw first fractured under fatigue and then caused an overload break of the implant and abutment.

Fatigue Design of Dental Implant Assemblies: A Nominal Stress Approach

Fatigue is the most common mechanical failure type in dental implants. ISO 14801 standardizes fatigue testing of dental implants, providing the load-life curve which is most useful for comparing the fatigue behavior of different dental implant designs. Based on it, many works were published in the dental implant literature, comparing different materials, component geometries, connection types, surface treatments, etc. These works are useful for clinicians in order to identify the best options available in the market. The present work is intended not for clinicians but for dental implant manufacturers, developing a design tool that combines Finite Element Analysis, fatigue formulation and ISO 14801 experimental tests. For that purpose, 46 experimental tests were performed on BTI INTERNA® IIPSCA4513 implants joined with INPPTU44 abutments by means of INTTUH prosthetic screws under three different tightening torque magnitudes. Then, the load case was reproduced in a FE model from where the nominal stress state in the fatigue critical section was worked out. Finally, Walker criterion was used to represent accurately the effects of mean stress and predict fatigue life of the studied dental implant assembly, which can be extended to most of the products of BTI manufacturer. By means of this tool, dental implant manufacturers will be able to identify the critical design and assembly parameters in terms of fatigue behavior, evaluate their influence in preliminary design stages and consequently design dental implants with significantly better fatigue response which in turn will reduce future clinical incidences.

Mechanical Assessment of Fatigue Characteristics between Single- and Multi-Directional Cyclic Loading Modes on a Dental Implant System

Mechanical testing based on ISO 14801 standard is generally used to evaluate the performance of the dental implant system according to material and design changes. However, the test method is difficult to reflect on the clinical environment because the ISO 14801 standard does not take into account the various loads from different directions during chewing motion. In addition, the fracture pattern of the implant system can occur both in the horizontal and the vertical directions. Therefore, the purpose of this study was to compare fatigue characteristics and fracture patterns between single directional loading conditions based on the ISO 14801 standard and multi-directional loading condition. Firstly, the static test was performed on five specimens to derive the fatigue load, and the fatigue load was chosen as 40% of the maximum load measured in the static test. Subsequently, the fatigue test was performed considering the single axial/occlusal (AO), AO with facial/lingual (AOFL) and AO with mesial/distal (AOMD) directions, and five specimens were used for each fatigue loading modes. In order to analyze the fatigue characteristics, the fatigue cycle at the time of specimen fracture and displacement change of the specimen every 500 cycles were measured. Field emission scanning electron microscopy (FE-SEM) was used to analyze the fracture patterns and the fracture surface. Compared to the AO group, the fatigue cycle of the AOFL and AOMD groups showed lower about five times, while the displacement gradually increased with every 500 cycles. From FE-SEM results, there were no different surface morphology characteristics among three groups. However, the AOMD group showed a vertical slip band. Therefore, our results suggest that the multi-directional loading mode under the worst-case environment can reproduce the vertical fracture pattern in the clinical situation and may be essential to reflect on the dental implant design including connection types and surface treatments.

Classification of the journal category "oral surgery" in the Scopus and the Science Citation Index Expanded: flaws and suggestions

Objectives

The aim of this study was to evaluate the journal category “oral surgery” in Scopus and in the Science Citation Index Expanded (SCIE).

Materials and Methods

The Journal of Oral and Maxillofacial Surgery (JOMS), The Journal of the Korean Association of Oral and Maxillofacial Surgeons (JKAOMS), and The Journal of Prosthodontic Research (JPR) were selected from the Scopus list of journals as oral surgery journals. Maxillofacial Plastic and Reconstructive Surgery (MPRS) was selected from PubMed as a Scopus oral surgery title. From these titles, 10 recently published articles were collected and used for reference analysis.

Results

The percentage of citations from oral surgery journals was 26.7%, 24.5%, and 40.1% for JKAOMS, MPRS, and JOMS, respectively. In total, 1.1% of JPR's citations were from oral surgery journals and significantly fewer from other journals (P<0.001). The percentage of citations from dentistry journals excluding oral surgery journals was 11.9%, 34.4%, and 15.8% for JKAOMS, MPRS, and JOMS, respectively. For JPR, 80.6% of citations were from dentistry journals and significantly more were from other journals (P<0.001).

Conclusion

Selected samples revealed that JPR is incorrectly classified as an oral surgery journal in Scopus. In addition, the scientific interaction among JKAOMS, MPRS, and JOMS was different to JPR in the reference analysis.

Complete mechanical characterization of an external hexagonal implant connection: in vitro study, 3D FEM, and probabilistic fatigue

The aim of this study was to fully characterize the mechanical behavior of an external hexagonal implant connection (ø3.5 mm, 10-mm length) with an in vitro study, a three-dimensional finite element analysis, and a probabilistic fatigue study. Ten implant-abutment assemblies were randomly divided into two groups, five were subjected to a fracture test to obtain the maximum fracture load, and the remaining were exposed to a fatigue test with 360,000 cycles of 150 ± 10 N. After mechanical cycling, all samples were attached to the torque-testing machine and the removal torque was measured in Newton centimeters. A finite element analysis (FEA) was then executed in ANSYS® to verify all results obtained in the mechanical tests. Finally, due to the randomness of the fatigue phenomenon, a probabilistic fatigue model was computed to obtain the probability of failure associated with each cycle load. FEA demonstrated that the fracture corresponded with a maximum stress of 2454 MPa obtained in the in vitro fracture test. Mean life was verified by the three methods. Results obtained by the FEA, the in vitro test, and the probabilistic approaches were in accordance. Under these conditions, no mechanical etiology failure is expected to occur up to 100,000 cycles. Graphical abstract ᅟ.

Micro finite element analysis of dental implants under different loading conditions

Osseointegration is paramount for the longevity of dental implants and is significantly influenced by biomechanical stimuli. The aim of the present study was to assess the micro-strain and displacement induced by loaded dental implants at different stages of osseointegration using finite element analysis (FEA). Computational models of two mandible segments with different trabecular densities were constructed using microCT data. Three different implant loading directions and two osseointegration stages were considered in the stress-strain analysis of the bone-implant assembly. The bony segments were analyzed using two approaches. The first approach was based on Mechanostat strain intervals and the second approach was based on tensile/compression yield strains. The results of this study revealed that bone surrounding dental implants is critically strained in cases when only a partial osseointegration is present and when an implant is loaded by buccolingual forces. In such cases, implants also encounter high stresses. Displacements of partially-osseointegrated implant are significantly larger than those of fully-osseointegrated implants. It can be concluded that the partial osseointegration is a potential risk in terms of implant longevity.

Validation of finite-element simulations with synchrotron radiography - A descriptive study of micromechanics in two-piece dental implants

State-of-the art, two-piece dental implants made from titanium alloys exhibit a complex micromechanical behavior under dynamical load. Its understanding, especially the formation of microgaps, is of crucial importance in order to predict and improve the long-term performance of such implants. Microgap formation in a loaded dental implant with a conical implant-abutment connection can be studied and quantified by synchrotron radiography with micrometer accuracy. Due to the high costs and limited access to synchrotron radiation sources, alternative approaches are needed in order to depict the microgap formation. Therefore, synchrotron radiography is used in this article to validate a simple finite element model of an experimental conical implant design. Once validated, the model is in turn employed to systematically study the microgap formation developed in a variety of static load scenarios and the influence of the preload of abutment screw on the microgap formation. The size of the microgap in finite element analysis (FEA) simulations is consistent with that found in in-vitro experiments. Furthermore, the FE approach gives access to more information such as the von-Mises stresses. It is found that the influence of the abutment screw preload has only a minor effect on the microgap formation and local stress distribution. The congruence between FE simulations and in-vitro measurements at the micrometer scale underlines the validity and relevance of the simple FE method applied to study the micromovement of the abutment and the abutment screw preload in conical implant-abutment connections under load.

Assessment of automatic segmentation of teeth using a watershed-based method

OBJECTIVE

Tooth 3D automatic segmentation (AS) is being actively developed in research and clinical fields. Here, we assess the effect of automatic segmentation using a watershed-based method on the accuracy and reproducibility of 3D reconstructions in volumetric measurements by comparing it with a semi-automatic segmentation(SAS) method that has already been validated.

METHODS

The study sample comprised 52 teeth, scanned with micro-CT (41 µm voxel size) and CBCT (76; 200 and 300 µm voxel size). Each tooth was segmented by AS based on a watershed method and by SAS. For all surface reconstructions, volumetric measurements were obtained and analysed statistically. Surfaces were then aligned using the SAS surfaces as the reference. The topography of the geometric discrepancies was displayed by using a colour map allowing the maximum differences to be located.

RESULTS

AS reconstructions showed similar tooth volumes when compared with SAS for the 41 µm voxel size. A difference in volumes was observed, and increased with the voxel size for CBCT data. The maximum differences were mainly found at the cervical margins and incisal edges but the general form was preserved.

CONCLUSION

Micro-CT, a modality used in dental research, provides data that can be segmented automatically, which is timesaving. AS with CBCT data enables the general form of the region of interest to be displayed. However, our AS method can still be used for metrically reliable measurements in the field of clinical dentistry if some manual refinements are applied.