Mechanical response comparison in an implant overdenture retained by ball attachments on conventional regular and mini dental implants: a finite element analysis

Influence of dental implant/mini-implant design on stress distribution in overdentures: a systematic review

PURPOSE

Critically evaluate the existing literature and answer the question, "Does the dental implant/mini-implant design influence the stress distribution in prosthetic overdentures according to finite element analysis?".

METHODS

This systematic review was registered in the Open Science Framework (osf.io/2bquj) and followed the PRISMA protocols. The custom search strategy was applied to 4 databases. In vitro experimental studies that evaluated the influence of dental implant/mini-implant design on stress distribution in overdentures by FEM, without time and language restrictions, were included. The selection process was carried out in two stages by two reviewers independently. Risk of bias analysis was performed by a checklist of important parameters.

RESULTS

Sixty articles were evaluated by their title and abstract, four were selected for full reading, three were relevant, and nine were included by additional search. The 12 studies have a low risk of bias. The meta-analysis could not be performed due to the heterogeneity of the data (implant type, design variation, load intensity, and direction).

CONCLUSION

It can be inferred from the evaluated literature that design modifications influence the stress distribution, but as the FEM presents limitations inherent to the in vitro study, clinical trials are necessary to infer the effectiveness of the modifications. It should be noted that there is no consensus on which is the best thread design and that implants with a very narrow diameter are subject to the highest stress concentration.

Biomechanical comparison of different framework materials in mandibular overdenture prosthesis supported with implants of different sizes: a finite element analysis

BACKGROUND

The aim of this study is to evaluate the stresses on the supporting bone, implants, and framework materials under masticatory forces in mandibular overdenture prostheses modeled with different framework materials and different implant types, using the Finite Element Analysis (FEA).

METHODS

For the finite element modeling, two identical mandibular jaw models were created; one with two standard (diameter:4.1 mm/12 mm length) and the other with two mini-implants (diameter:2.4 mm/12 mm length) were placed in the canine teeth area. The polymethylmethacrylate (PMMA) denture was modeled upon them, supported by Cobalt Chromium alloy (CoCr), Poly-ether ether ketone (PEEK), and Zantex materials with framework. No framework was added as a control model; only PMMA overdenture prosthesis was modeled.

RESULTS

Regardless of the framework materials of the overdenture prostheses, the stress values ​​on mini-implants in all models yielded approximately two times higher results comparing to standard implants. More stress transmission was observed in the supporting bone and implants in the control prostheses and overdenture prostheses supported with respectively PEEK, Zantex, CoCr alloy frameworks, respectively. In the framework materials, more stress occurred on CoCr, Zantex and PEEK in that order.

CONCLUSION

In the light of this study, the use of mini-implants as an alternative to standard implants is not promising in terms of distribution and transmission of chewing stresses. As a framework material, standard rigid metal alloys were found to be more advantageous than polymer materials in terms of stress distribution.

Finite element analysis of dental implants with validation: to what extent can we expect the model to predict biological phenomena? A literature review and proposal for classification of a validation process

A literature review of finite element analysis (FEA) studies of dental implants with their model validation process was performed to establish the criteria for evaluating validation methods with respect to their similarity to biological behavior. An electronic literature search of PubMed was conducted up to January 2017 using the Medical Subject Headings “dental implants” and “finite element analysis.” After accessing the full texts, the context of each article was searched using the words “valid” and “validation” and articles in which these words appeared were read to determine whether they met the inclusion criteria for the review. Of 601 articles published from 1997 to 2016, 48 that met the eligibility criteria were selected. The articles were categorized according to their validation method as follows: in vivo experiments in humans (n = 1) and other animals (n = 3), model experiments (n = 32), others’ clinical data and past literature (n = 9), and other software (n = 2). Validation techniques with a high level of sufficiency and efficiency are still rare in FEA studies of dental implants. High-level validation, especially using in vivo experiments tied to an accurate finite element method, needs to become an established part of FEA studies. The recognition of a validation process should be considered when judging the practicality of an FEA study.

To what extent residual alveolar ridge can be preserved by implant? A systematic review

Background

It has been reported that the load for (or to) implant-supported restoration may lead to bone remodeling as bone resorption and/or formation. While many authors supported the process of bone resorption, others elaborated bone apposition and increasing bone density close and remote to implant body (or fixture). This may suggest the role of the implant to reserve alveolar ridge from physiologic/pathologic resorption. The aim of this systematic review was to predict to how extend dental implants can preserve the residual alveolar ridge based on previous clinical investigations.

Methods

This systematic review based on the retrospective and prospective studies, randomized clinical trial, and case reports. The process of searching for proposed articles included PubMed, Ovid, and Web of Science databases, with specific inclusion and exclusion criterion.

Results

A total 2139 citations were identified. After expunging the repeated articles between databases and application of exclusion and inclusion criteria, 18 articles were found to meet the topic of this systematic review. Many of the articles reported bone preservation with implant-assisted restorations, and the rest denoted noticeable bone apposition.

Conclusion

According to the published clinical studies, the behavior of bone remodeling around implant predicts a sort of residual alveolar bone preservation.

Long-Term Fatigue and Its Probability of Failure Applied to Dental Implants

It is well known that dental implants have a high success rate but even so, there are a lot of factors that can cause dental implants failure. Fatigue is very sensitive to many variables involved in this phenomenon. This paper takes a close look at fatigue analysis and explains a new method to study fatigue from a probabilistic point of view, based on a cumulative damage model and probabilistic finite elements, with the goal of obtaining the expected life and the probability of failure. Two different dental implants were analysed. The model simulated a load of 178 N applied with an angle of 0°, 15°, and 20° and a force of 489 N with the same angles. Von Mises stress distribution was evaluated and once the methodology proposed here was used, the statistic of the fatigue life and the probability cumulative function were obtained. This function allows us to relate each cycle life with its probability of failure. Cylindrical implant has a worst behaviour under the same loading force compared to the conical implant analysed here. Methodology employed in the present study provides very accuracy results because all possible uncertainties have been taken in mind from the beginning.

Early Loaded Single Implant Reinforced Mandibular Overdenture

Rehabilitating atrophied mandible with two-implant supported denture is a common treatment modality for implant retained removable overdenture in mandible. This paper aims to design a treatment modality where single implant reinforced overdenture is fabricated for a severely atrophied mandibular ridge with early loading protocol. Results of studies have shown that a single implant mandibular overdenture significantly increases the satisfaction and quality of life of patients with edentulism. Midline fracture of the prosthesis is the most common complication related to single implant and two-implant retained mandibular overdentures. To manage such complication, a thin metal mesh is used to reinforce the overdenture and also to make the prostheses lighter and cost effective as compared to conventional cast metal framework.