Biomechanical stress and microgap analysis of bone-level and tissue-level implant abutment structure according to the five different directions of occlusal loads

Adding mechanobiological cell features to finite element analysis of an immediately loaded dental implant

Finite element analysis (FEA) has been used to analyze the behavior of dental materials, mainly in implantology. However, FEA is a mechanical analysis and few studies have tried to simulate the biological characteristics of the healing process of loaded implants. This study used the rule of mixtures to simulate the biological healing process of immediate implants in an alveolus socket and bone-implant junction interface through FEA. Three-dimensional geometric models of the structures were obtained, and material properties were derived from the literature. The rule of mixtures was used to simulate the healing periods-immediate and early loading, in which the concentration of each cell type, based on in vivo studies, influenced the final elastic moduli. A 100 N occlusal load was simulated in axial and oblique directions. The models were evaluated for maximum and minimum principal strains, and the bone overload was assessed through Frost's mechanostat. There was a higher strain concentration in the healing regions and cortical bone tissue near the cervical portion. The bone overload was higher in the immediate load condition. The method used in this study may help to simulate the biological healing process and could be useful to relate FEA results to clinical practice.

Influence of a new abutment design concept on the biomechanics of peri-implant bone, implant components, and microgap formation: a finite element analysis

BACKGROUND

A new two-piece abutment design consisting of an upper prosthetic component and tissue-level base has been introduced; however, the biomechanical behavior of such a design has not been documented. This study aimed to investigate the effect of a two-piece abutment design on the stress in the implant components and surrounding bone, as well as its influence on microgap formation.

METHODS

To simulate the implant models in the mandibular left first molar area, we established nine experimental groups that included three bone qualities (type II, III, and IV) and three implant-abutment designs (internal bone level, tissue level, and a two-piece design). After the screw was preloaded, the maximum occlusal (600 N) and masticatory (225 N) forces were established. Finite element analysis was performed to analyze the maximum and minimum principal stresses on the peri-implant bone; the von Mises stresses in the implants, abutments, bases, and screws, and the microgaps at the implant-abutment, implant-base, and base-abutment interfaces.

RESULTS

For all three loading methods, the two-piece abutment design and bone-level connection exhibited similarities in the maximum and minimum principal stresses in the peri-implant bone. The von Mises stresses in both screws and bases were greater for the two-piece design than for the other connection types. The smallest microgap was detected in the tissue-level connection; the largest was observed at the implant-base interface in the two-piece design.

CONCLUSIONS

The present study found no evidence that the abutment design exerts a significant effect on peri-implant bone stress. However, the mechanical effects associated with the base and screws should be noted when using a two-piece abutment design. The two-piece abutment design also had no advantage in eliminating the microgap.

Application in the analysis of the occlusal force of free-end missing tooth implant restoration with T-SCAN III

Introduction: The occlusal force of the teeth in the dental arch and the remaining adjacent natural teeth will change after implant restoration with a free-end missing tooth. This study intends to use the T-SCAN III scanner to collect dynamic quantitative data before and after the restoration of free-end implants and to explore the application of the T-SCAN III in redistributing the occlusal force of free-end implants.

Methods: In this study, 24 patients with free-end implant restoration were selected, and their occlusion was tested before, immediately after, and 3 months after implant restoration.

Results: In all 24 cases, the bite force of the first natural tooth adjacent to the implanted tooth after restoration changed from 19.12% ± 9.48%–12.93% ± 11.47% (p < 0.01). For additional data analysis, all cases were further subdivided by single implant and fixed bridge restorations. In 17 cases, there was a successful follow-up after 3 months. The percentage of the total bite force of dental arch with implant increased from 41.92% ± 10.78%–53.06% ± 10.71% (p < 0.01).

Discussion: This study shows that the free-end implant restoration protects the remaining natural teeth, and the patient’s missing dental arch bite force improves within 3 months of implant restoration.

The evaluation of stress on bone level and tissue level short implants: A Finite Element Analysis (FEA) study

PURPOSE

This study aimed to evaluate the difference between the stress level and distribution around the BL and TL short implants, and their surrounding structures, using finite element analysis.

METHODS

Two different study models were constructed: BL model and TL model. Two dental implant systems (ITI (Straumann, Waldenburg, Switzerland) and NTA Short) with a diameter of 4.1 mm and 4 mm and with a length of 6 mm were used in this study. In each model, implants were placed in the mandibular 1st molar region. The von Mises stress and maximum principal (tensile) and minimum principal (compressive) stresses were evaluated.

RESULTS

The highest stress values recorded in the BL implants (von Mises: 342.77 MPa), in the peri‑implant bone around the BL implants (maximum principal stress: 114.1 MPa), as a result of oblique loading, and overall stress values were found to be higher in the BL model. However, these measured values appeared to be low to cause a fracture, when considering the yield strengths of the materials and bone.

CONCLUSIONS

The stress values were higher in the BL model, but not high enough to cause failure. Short implants could be an effective method of treatment for patients unsuitable for advanced surgical techniques.

Automated vector analysis to design implant-supported prostheses: A dental technique

The prosthesis loading force is an important factor for dental implant survival. Even if adequate osseointegration of the dental implant has been achieved, if the occlusal forces are not correctly distributed, lateral torque can be generated causing high stress on surrounding tissues. The stress value of implant prostheses could be different whether the direction of load is vertical or oblique, affected by the shape of the occlusal surface. When an implant-supported prosthesis is designed with a dental computer-aided design software program, the average vectors from each occlusal contact point can be visualized. If the visualized vector generates lateral torque, the occlusal surface design can be modified before finalizing the design. The described technique uses automated vector analysis to enable visualization of the occlusal vector to improve prosthesis design, optimizing occlusal forces.

Mechanical, Chemical, and Biological Properties of 3D-Printed Abutments: A Systematic Review

Aim:

A systematic review of the methods of 3D printing and the materials used so far for the manufacture of abutments was performed to evaluate whether their clinical use is indicated through the mechanical, chemical, and biological analyses carried out.

Materials and Methods:

An electronic search conducted by three independent reviewers was carried out in the PubMed, Web of Science, Cochrane Library, Science Direct, and Lilac databases. The inclusion criterion was researching articles in English that contained as subject the manufacturing of abutments through 3D printing/additive manufacturing. Any meta-analyses, reviews, book chapters, abstracts, letters, conferences papers, and studies without abutments printed were excluded.

Results:

We found 780 references, which after applying the exclusion criteria resulted in the final inclusion of seven articles for review. The studies had a high heterogeneity, showing different materials and methodologies to manufacture abutments, which makes a comparison between them difficult, and for this reason it was not possible to carry out a meta-analysis with the data found.

Conclusions:

Even with the limitations found in the present research, it is possible to conclude that printed abutments have adequate mechanical, chemical, and biological properties that can indicate their clinical use. 3D printing presents high accuracy and speed and can produce customized abutments according to each case.

Fractal Dimension as a Tool for Assessment of Dental Implant Stability-A Scoping Review

A lot of modalities for assessing implant stability are available for clinicians, but they fail to assess trabecular changes as they are solely dependent on the operator's skills. The use of Fractal Dimension (FD) has evolved to be used as a measure for trabecular changes depicting implant stability before and after implant placement. The objective of this systematic review was to qualitatively analyse the available scientific literature describing the use of FD as a tool to measure implant stability on the basis of trabecular changes. An electronic search in PubMed, Web of Science and Scopus was carried out using relevant keywords, such as: fractal dimension; fractal analysis; dental implants; implant stability; osseointegration, etc. Studies reporting the use of FD as a tool to measure implant stability were included and subjected to qualitative analysis using ROBINS-I and Cochrane risk of bias assessment criteria. Fourteen studies were included in this review. Results showed that FD was found to be used solely as a measure of implant stability in seven studies, out of which six studies showed an increment in FD values. The majority of studies concluded with a statistical correlation between FD and respective other assessment methods used. FD may not serve as a sole indicator of implant stability; however, it can be used as an adjunct to conventional methods along with additional fractal factors.