Improvement of an additively manufactured subperiosteal implant structure design by finite elements based topological optimization

Subperiosteal implants constructed with digital technology: A systematic review

STATEMENT OF PROBLEM

Atrophied jaw is a condition where there is insufficient bone quantity and quality. Several treatment plans are available for treating atrophied jaws, including subperiosteal implants.

PURPOSE

To evaluate the spectrum of subperiosteal implants for severely atrophied jaws using digital technology.

MATERIALS AND METHODS

An electronic and manual search was conducted in the PubMed, Scopus, and Google Scholar databases. Publications of cohort studies, case series, and case reports written in English without data restrictions that reported on subperiosteal implant management of patients with severely atrophied jaws in a completely and partially edentulous population.

RESULTS

A total of 26 articles, comprising 302 cases, were analyzed. In patients with severely atrophied jaws. The success rate was 87.7%, the surviving rate was 95.3%. The most common complications were biological, such as dehiscence and framework exposure. The rates of biologic complications were 11.5%, and the rates of prosthetic problems were 5.9%.

CONCLUSIONS

Subperiosteal implants designed and constructed using digital technology are a promising treatment in the short term. Attention should be directed to decrease the biological complication. Correct designing, implanting, fixing, and patient selection and maintenance are critical for the success of the treatment. Longer prospective studies with larger population are needed to view the effect on hard and soft tissue.

Mandibular Fixed Prosthesis With a 3D-Printed Subperiosteal Implant: A Case Report

This case report aims to present the successful restoration of the atrophic partially edentulous posterior mandible using custom-made subperiosteal implants. The fixed prosthesis restoration was achieved using computer-aided design and computer-aided manufacturing technologies and 3D metal printing methods. The partially edentulous 58-year-old patient expressed a preference not to undergo bone augmentation procedures. The patient with teeth in the anterior mandible was treated with 2 separate custom-made subperiosteal implants. A custom-made implant was fabricated from sintered titanium using machined subperiosteal implants with a universal external connection. Subperiosteal implants offer several advantages over conventional bone grafting plus intraosseous implant placement techniques, such as the simple, 1-step procedure for atrophic jaws, streamlining the treatment process and reducing the overall time involved. Treatments using subperiosteal implants can be an alternative solution for individuals with severely atrophic jaws. Longer term studies in a larger sample are warranted to corroborate previous reports.

Evaluation of Different Subperiosteal Implant Thicknesses on Mechanical Strength and Stress on Bone by Finite Element Analysis

Implants have always been within the interest of both clinicians and material scientists due to their places in reconstructive and prosthetics surgery. Excessive bone loss or resorption in some patients makes it difficult to design and manufacture the implants that bear the necessary loads to carry the final prosthetics. With this study; we tried to determine the minimum material thickness of the subperiosteal implants that can withstand the physiological forces. We have created a digital average bone structure based on actual patient data and designed different subperiosteal implants with 1, 1.5, and 2mm material thicknesses (M1, M2, M3) for this digital model. The designed implant models are subjected to 250 Newtons (N) of force, and the implant and bone are tested for the stress they are exposed to, the pressure they transmit to, and their mechanical strength with Finite Element Analysis with the physical parameters boot for the implant material and human bone. Results show us that under specific design parameters and thicknesses, the 1mm thickness design failed due to exceeding the yield stress limit of 415MPa with a 495,44MPa value. The thinnest implant showed plastic deformation and transmitted excessive forces, which may cause bone resorption due to residual stress. We determined that thinner subperiosteal implants down to 1.5mm that have the necessary material parameters for function and tissue support can be designed and manufactured with current technologies.

Enhancing oral function: A case report on mandibular overdenture utilization with custom-made subperiosteal implant

Subperiosteal implants, previously set aside because of complications, are now emerging again as effective treatments for severe mandibular atrophy, aided by recent improvements in digital dentistry. Traditional dentures in such cases often face challenges with support and retention, necessitating complex regenerative procedures. This paper presents a case report of a 54-year-old male patient with significant mandibular atrophy who received a custom-made subperiosteal implant, showcasing promising results. The implant was precisely designed utilizing computed tomography (CT) scans, a 3D-printed model, the selective laser melting (SLM) technique, and constructed with biocompatible Ti6Al4V material. This innovative approach offered a practical solution, resulting in high patient satisfaction and no complications over a year of use.

Fabrication of a mandibular implant-retained overdenture using an existing subperiosteal implant: A clinical report

A 64-year-old edentulous woman with a mandibular fracture received a subperiosteal implant for fracture fixation and dental rehabilitation. However, the ball abutments were submerged by the soft tissue because they were too short. Therefore, we designed a connector to lengthen the attachment and achieve adequate stability and retention for the overdenture.

Clinical performance of additively manufactured subperiosteal implants: a systematic review

PURPOSE

The aim of this study was to assess implant survival and complications rate of modern subperiosteal implants (CAD designed and additively manufactured).

METHODS

A systematic review was conducted using three electronic databases; Medline (Pubmed), Cochrane library, and SCOPUS, following the PRISMA statement recommendations to answer the PICO question: "In patients with bone atrophy (P), do additively manufactured subperiosteal implants (I), compared to subperiosteal implants manufactured following traditional approaches (c), present satisfactory implant survival and complication rates (O)? The study was pre-registered in PROSPERO (CRD42023424211). Included articles quality was assessed using the "NIH quality assessment tools".

RESULTS

Thirteen articles were finally selected (5 cohort studies and 8 case series), including 227 patients (121 female / 106 male; weighted mean age 62.4 years) and 227 implants. After a weighted mean follow-up time of 21.4 months, 97.8% of implants were in function (5 failures reported), 58 implants (25.6%) presented partial exposure, 12 patients (5.3%) suffered soft tissue or persistent infection. Fracture of the interim prosthesis was reported in 8 of the155 patients (5.2%) in which the use of a provisional prosthesis was reported. A great heterogeneity was found in terms of study design and methodological aspects. For this reason, a quantitative analysis followed by meta-analysis was not possible.

CONCLUSIONS

Within the limitations of this study, modern additively manufactured subperiosteal implants presented a good survival in the short-time, but a noticeable number of soft-tissue related complications were reported. Further studies are needed to assess the clinical behavior in the medium- and long-term.

Custom-made Subperiosteal Implants: A Finite Element Analysis on Monoblock and Dual Implant Systems in Atrophic Maxilla

This study aims to investigate and compare the stress distribution, displacement, and bone loading of monoblock and dual custom-made subperiosteal implant systems in atrophic maxilla using finite element analysis (FEA). A total of 11 patients with insufficient bone tissue for conventional implant treatment were included in the study. Customized subperiosteal implant designs were generated using the 3D average models obtained from patients' computed tomography (CT) scans. Two different models were produced: a monoblock that covered the entire maxillary bone and a dual implant system where two mirror-imaged implants covered the left and right halves of the maxillary bone separately. We have calculated residual stress values formed on the implant models and jaw bone models separately. In addition, the highest displacement values formed on the implants and the highest stress values formed on abutment parts have also been observed in this study. Results showed that the stresses formed on implants that are under the mastication forces were significantly lower than the yield strength of the selected material, indicating that plastic deformation would not occur under static load. The dual implant geometry demonstrated a substantial reduction in stress compared to the monoblock structure. The highest von Mises stress values for the monoblock implants ranged from 131 MPa to 206 MPa, while those for the dual structure ranged from 124 MPa to 178 MPa. The highest residual stress values on the upper jawbone were observed in the M6 implant model, and the lowest was seen in the M1 and M3 models at 12 MPa. Displacement values under static load showed that loads on the implant would be below 0.21 mm. In conclusion, custom subperiosteal implants are a viable treatment option for patients with insufficient bone tissue for conventional implants. Dual implant systems were found to have lower stress and displacement values compared to monoblock structures, indicating a potential advantage in clinical use. However, mono implants may have benefits in cases of immediate teeth loading due to their ability to absorb and distribute occlusal forces better.

Comparison of Two Types of Patient Specific Implants (PSI) and Quad Zygoma Implant (QZI) for Rehabilitation of Post-COVID Maxillary Mucormycosis Defect (PCMMD): Finite Element Analysis

Introduction

The residual post-COVID maxillary mucormycosis defect (PCMMD) were extensive, due to unilateral or bilateral maxillectomies. The Goal of rehabilitation of PCMMD is to deliver a prosthetically driven reconstruction. FEA was to evaluate the biomechanical response of PSI struts (PSI 1), PSI Screw retained (PSI 2) and QZI to masticatory load on virtual simulation to improve accuracy and enhance the design.

Aim

To validate and compare the Biomechanical benefit of the PSI struts, PSI Screw retained, QZI in a case of rehabilitation of post-COVID maxillary mucormycosis defect (PCMMD) by FEA study.

Methodology

The result of stress to masticatory load on virtual simulation for (1) Maximum and minimum stress (Von Mises stress); (2) the Displacement (in three positions) and (3) the Deformation (Plastic strain) was compared on virtual simulation for PSI 1 and PSI 2 and QZI.

Conclusion

The FEA and comparative evaluation of PSI 1, PSI 2 and QZI showed a good resistance to displacement. The stress and strain values are low and acceptable. In comparison QZI shows more stress in the anterior region.

The atrophic edentulous alveolus. A preliminary study on a new generation of subperiosteal implants

The aim of this cohort case series is to present a new subperiosteal implant device that uses CAD-CAM technologies together with 3D metal printing capabilities to produce direct bone-anchored dental prosthetic solutions for the management of atrophic edentulous alveolus and jaws. The clinical experience of 21 subperiosteal devices implanted over a 4-year period is presented. The results of this study showed 14 of the 21 cases were successful (66.7%), while 7 cases had complications including exposure of the metal frame (5 cases), mobility of the device (1 case) and 1 case failed for reasons unrelated to the device. Four of the 7 cases were successfully salvaged resulting in an overall success rate of 85.7% (18 /21 cases). This study supports the use of fully customized subperiosteal jaw implants as a simple and reliable alternative for dental rehabilitation of atrophic edentulous cases which would otherwise require bone grafts for conventional fixed dental implant solutions. With more research, the clinical potential for this device is significant as it not only avoids the need for complex and lengthy reconstructive jaw surgery but also allows for the placement of immediate prosthetic teeth at the time of implantation.

Submodelling approach to screw-to-bone interaction in additively manufactured subperiosteal implant structures

Thanks to new digital technologies, complex cases of severe maxillary atrophy may now be treated with additively manufactured subperiosteal implant structures (AMSISs). However, there are few studies addressing this topic and most of them focus on the mechanical behaviour of the AMSIS itself without considering its interaction with the maxilla bone. The aim of this study is to provide a methodology based on finite element analysis (FEA) to evaluate the effect of interaction between the maxilla bone and the screws fixing the AMSIS. The mechanical performance of an AMSIS was examined via a FEA based on submodelling. Significant differences were encountered in displacements and reaction forces when bone-screw interaction was considered. Stress in the cortical layer was found to be close to the maximum strength while the trabecular layer seems to have no effect on the results; stresses in the AMSIS are lower than the fatigue stress limit. Finally, the comparison of stresses between models with and without osseointegration shows how stresses drop once osseointegration is complete. The proposed submodelling approach considerably reduces the computational effort and enables both a detailed model of the interaction between the thread of the screws and the bone and an accurate evaluation of displacement and stress fields on the interface. The results have shown that stresses in the cortical bone are highly affected by the initial geometry of the thread inside the bone, which demonstrates the importance of modelling the effect of the thread.

Biocompatibility of Subperiosteal Dental Implants: Effects of Differently Treated Titanium Surfaces on the Expression of ECM-Related Genes in Gingival Fibroblasts

INTRODUCTION

Titanium alloys currently are the most used material for the manufacture of dental endosseous implants. However, in partially or totally edentulous patients, varying degrees of maxillary bone resorption usually occur, making the application of these devices difficult or even impossible. In these cases, a suitable alternative is offered by subperiosteal implants, whose use is undergoing a revival of interest following the introduction of novel, computer-assisted manufacturing techniques. Several procedures have been developed for the modification of titanium surfaces so to improve their biocompatibility and integration with bone. Information is, however, still incomplete as far as the most convenient surface modifications to apply with subperiosteal implants, in which an integration with soft mucosal tissues is just as important.

OBJECTIVES

The present study aimed at evaluating whether different treatments of titanium surfaces can produce different effects on the viability, attachment, and differentiation of gingival fibroblasts, i.e., the cell type mainly involved in osteointegration as well as the healing of soft tissues injured by surgical procedures, in order to verify whether any of the treatments are preferable under these respects.

METHODOLOGY

The human immortalized gingival fibroblast (CRL-4061 line) were cultured in the presence of titanium specimens previously treated with five different procedures for surface modification: (i) raw machined (Ti-1); (ii) electropolished (Ti-2); (iii) sand-blasted acid-etched (Ti-3); (iv) Al Ti Color™ proprietary procedure (Ti-4); and (v) anodized (Ti-5). At different times of incubation, viability and proliferation of cells, was determined along with the changes in the expression patterns of ECM-related genes involved in fibroblast attachment and differentiation: vinculin, fibronectin, collagen type I-alpha 1 chain, focal adhesion kinase, integrin β-1, and N-cadherin. Three different experiments were carried out for each experimental point. The release from fibroblasts of endothelin-1 was also analyzed as a marker of inflammatory response. The proliferation and migration of fibroblasts were evaluated by scratch tests.

RESULTS

None of the five types of titanium surface tested significantly affected the fibroblasts' viability and proliferation. The release of endothelin-1 was also not significantly affected by any of the specimens. On the other hand, all titanium specimens significantly stimulated the expression of ECM-related genes at varying degrees. The proliferation and migration abilities of fibroblasts were also significantly stimulated by all types of titanium surface, with a higher-to-lower efficiency in the order: Ti-3 > Ti-4 > Ti-5 > Ti-2 > Ti-1, thus identifying sandblasting acid-etching as the most convenient treatment.

CONCLUSIONS

Our observations suggest that the titanium alloys used for manufacturing subperiosteal dental implants do not produce cytotoxic or proinflammatory effects on gingival fibroblasts, and that sandblasting acid-etching may be the surface treatment of choice as to stimulate the differentiation of gingival fibroblasts in the direction of attachment and migration, i.e., the features allegedly associated with a more efficient implant osteointegration, wound healing, and connective tissue seal formation.

Custom-made additively manufactured subperiosteal implant

Subperiosteal implants were introduced in the last century. Poor clinical results led those implants to be progressively abandoned. Recently, several Authors suggested a revival of subperiosteal implants as an alternative to regenerative procedures. The purpose of this study was to describe the clinical application of custom-made additively manufactured subperiosteal implant for fixed prosthetic rehabilitation of edentulous maxilla. Plaster models of the upper and the lower arch were scanned, as well as the mock-up. Digital Imaging and Communications in Medicine data obtained from cone beam computed tomography were processed through the thresholding procedure. The design of the subperiosteal implant was drawn on the stereolithographic model and scanned. Once the digital project of the subperiosteal implant was completed, it was sent to additive manufacturing. After the surgery, the patient was strictly monitored for up to 2 years. The outcomes were assessed based on the incurrence of biological and mechanical complications, postoperative complications, and implant survival. The patient did not suffer from postoperative complications. Neither biological nor mechanical complications occurred during the follow-up period. At the end of the study, the implant was still in function. Custom-made subperiosteal implants could be considered as an alternative to regenerative procedures for the rehabilitation of severe bone atrophy. Further studies are needed in the future to confirm the positive outcome.

Additively manufactured metallic biomaterials

Metal additive manufacturing (AM) has led to an evolution in the design and fabrication of hard tissue substitutes, enabling personalized implants to address each patient's specific needs. In addition, internal pore architectures integrated within additively manufactured scaffolds, have provided an opportunity to further develop and engineer functional implants for better tissue integration, and long-term durability. In this review, the latest advances in different aspects of the design and manufacturing of additively manufactured metallic biomaterials are highlighted. After introducing metal AM processes, biocompatible metals adapted for integration with AM machines are presented. Then, we elaborate on the tools and approaches undertaken for the design of porous scaffold with engineered internal architecture including, topology optimization techniques, as well as unit cell patterns based on lattice networks, and triply periodic minimal surface. Here, the new possibilities brought by the functionally gradient porous structures to meet the conflicting scaffold design requirements are thoroughly discussed. Subsequently, the design constraints and physical characteristics of the additively manufactured constructs are reviewed in terms of input parameters such as design features and AM processing parameters. We assess the proposed applications of additively manufactured implants for regeneration of different tissue types and the efforts made towards their clinical translation. Finally, we conclude the review with the emerging directions and perspectives for further development of AM in the medical industry.