Biomechanical evaluation of the natural abutment teeth in combined tooth-implant-supported telescopic prostheses: a three-dimensional finite element analysis

Evaluation of two treatment concepts of four implants supporting fixed prosthesis in an atrophic maxilla: finite element analysis

BACKGROUND

Currently, oblique placement of long implants or the use of short implants to circumvent the maxillary sinus area and provide support for fixed prostheses are viable alternatives. The purpose of this study was to compare these two treatment concepts and ascertain which one exhibits superior biomechanical characteristics.

METHODS

Two different treatment concept models were constructed. The first one, LT4I, consisting of two mesial vertical implants positioned in lateral incisor regions and two distal tilted implants (45°) situated in second premolar regions of the maxilla. The second model, VS4I, includes two mesial vertical implants in lateral incisor regions and two vertically positioned short implants in second premolar regions. Numerical simulations were conducted under three loading types: firstly, oblique forces upon the molars; secondly, vertical forces upon the molars; thirdly, oblique forces upon the incisors. The maximum principal stress (σmax) and minimum principal stress (σmin) of the bone, as well as von Mises stress of the implants, were calcuated.

RESULTS

Under oblique loading on the molar, higher stress values in the bone were observed in LT4I group. Under vertical loading on molar, higher stress values in the bone were also observed in LT4I group. Furthermore, little difference was found between the two groups under oblique loading on the incisor.

CONCLUSION

Both treatment concepts can be applicable for edentulous individuals with moderate atrophic maxilla. Compared to tilted implants, short implants can transmit less occlusal force to the supporting tissues.

Additive Manufacturing of Polyhydroxyalkanoate-Based Blends Using Fused Deposition Modelling for the Development of Biomedical Devices

In the last few decades Additive Manufacturing has advanced and is becoming important for biomedical applications. In this study we look at a variety of biomedical devices including, bone implants, tooth implants, osteochondral tissue repair patches, general tissue repair patches, nerve guidance conduits (NGCs) and coronary artery stents to which fused deposition modelling (FDM) can be applied. We have proposed CAD designs for these devices and employed a cost-effective 3D printer to fabricate proof-of-concept prototypes. We highlight issues with current CAD design and slicing and suggest optimisations of more complex designs targeted towards biomedical applications. We demonstrate the ability to print patient specific implants from real CT scans and reconstruct missing structures by means of mirroring and mesh mixing. A blend of Polyhydroxyalkanoates (PHAs), a family of biocompatible and bioresorbable natural polymers and Poly(L-lactic acid) (PLLA), a known bioresorbable medical polymer is used. Our characterisation of the PLA/PHA filament suggest that its tensile properties might be useful to applications such as stents, NGCs, and bone scaffolds. In addition to this, the proof-of-concept work for other applications shows that FDM is very useful for a large variety of other soft tissue applications, however other more elastomeric MCL-PHAs need to be used.

Advanced method of rehabilitating edentulous Jaws: A review of telescopic denture

BACKGROUND

Edentulism conducts to a recognized impairment of oral function with both aesthetic and psychological changes. These patients suffer from a multiplicity of problems with their dentures, such as insufficient stability, retention and pain during mastication. The rehabilitation of a part edentulous patient can be established using a wide range of prosthetic treatment options. The overdenture treatment uses a removable total denture that overlies retained teeth, tooth roots, or dental implants. In the literature it was shown that patients with removable overdentures supported and retained either by tooth roots or implants have more predictable prosthodontic outcomes.

OBJECTIVE

The aim of this review is to provide an overview on the overdenture with a focus on the tooth-supported telescopic overdenture.

METHODS

The literature research was performed in the Scopus, Web of Science, and Pubmed electronic databases. Document type was limited to papers written in English, without time restrictions. The Review was recorded in the international PROSPERO (International Prospective Register of Systematic Reviews) database with the following number CRD42022326415.

RESULTS

A total of 256 articles published were found from electronic searches, Two independent reviewers carried out the screening and the selection process for the studies. First, duplicate citations were eliminated. Then, the two Authors independently screened the retrieved articles by title and abstract of each citation to determine its suitability for inclusion. Finally, 13 full-text articles satisfied the inclusion criteria.

CONCLUSION

Prostheses supported by Frictional telescopic crowns offer an effective treatment alternative for patients with Severely reduced dentitions who do not want implant treatment or complete dentures.

Finite Element Study of Stress Distribution with Tooth-Supported Mandibular Overdenture Retained by Ball Attachments or Resilient Telescopic Crowns

Objective The removable partial denture must keep health of the remaining teeth and the supporting tissues through the distribution of chewing forces on the abutment teeth and alveolar process.

This study aimed to evaluate stress distribution with canines-supported mandibular overdenture retained by two different attachment types: ball attachments or resilient telescopic crowns.

Materials and Methods Two 3-dimensional finite element models consisting of the cortical mandible bone, cancellous mandible bone, oral mucosa, canines, periodontal ligaments, the two attachment types, and overdenture were simulated. The models were imported into the mathematical analysis software Ansys Workbench V 15.0. All materials were considered to be homogeneous, isotropic, and linearly elastic. A vertical bilateral load of 120 N was applied to the central fossa of the first molars. The von Mises stress was calculated for canines, cortical, and cancellous bone.

Results The maximum von Mises stress of the ball attachments model was 35.61, 4.28, 7.82, and 1.29 MPa for canines, cortical alveolar bone of canines, cortical alveolar bone at the distal end of the overdenture, and cancellous alveolar bone of canines, respectively. The maximum von Mises stress of the resilient telescopic crowns model was 39.22, 4.74, 7.06, and 1.05 MPa for canines, cortical alveolar bone of canines, cortical alveolar bone at the distal end of the overdenture, and cancellous alveolar bone of canines, respectively.

Conclusion Resilient telescopic crowns distribute the stresses between canines, alveolar bone of canines, and overdenture supporting alveolar bone. Ball attachments transfer less stress to the canines and cortical alveolar bone of the canines, but more stress to the cancellous alveolar bone of canines and alveolar bone at distal end of the overdenture. Resilient telescopic crowns are preferred over ball attachment when the abutment teeth have good periodontal support.

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.

Assessment of Customized Alveolar Bone Augmentation Using Titanium Scaffolds vs Polyetheretherketone (PEEK) Scaffolds: A Comparative Study Based on 3D Printing Technology

Customized alveolar bone augmentation provides sufficient and precisely regenerated bone tissue for subsequent dental implant placement. Although some clinical cases have confirmed the successful use of the patient-specific polyetheretherketone (PEEK) scaffolds, the biomechanical property and osteogenic performance of the patient-specific PEEK scaffolds remain unclear. The objectives of this study were (1) to evaluate the space maintenance capacity and osteogenic performance of the patient-specific PEEK scaffolds for customized alveolar bone augmentation and (2) to compare the biomechanical properties of three-dimensionally printed titanium scaffolds and PEEK scaffolds. Both titanium scaffolds and PEEK scaffolds were designed and manufactured via additive manufacturing technology combined with computer-aided design (CAD). In three-point bending tests, the bending strength of the PEEK scaffold was about 1/3 that of the titanium scaffold. Accordingly, the equivalent strain value of the internal bone graft beneath the PEEK scaffold was about 3 times that beneath the titanium scaffold in finite element analysis, but the maximum deformations of both scaffolds were less than 0.05 mm. Meanwhile, in in vivo experiments, it is demonstrated that both scaffolds have similar space maintenance capacity and bone ingrowth efficiency. In conclusion, patient-specific PEEK scaffolds showed significantly lower biomechanical strength but comparable space maintenance and osteogenic properties to the titanium counterpart. Compared with traditional guided bone regeneration (GBR) surgery, both patient-specific PEEK and titanium scaffolds can achieve excellent osteogenic space maintenance ability. This study provides a preliminary basis for the clinical translation of the nonmetallic barrier membrane in customized alveolar bone augmentation.

Prosthodontic Rehabilitation of Patients with Double Crown and Locator Attachment - Retained Overdentures Supported by a Combination of Natural Tooth and Strategic Implants: Case Series

Prosthetic rehabilitation of edentulous patients and patients with one or two own teeth can be established by different treatment modalities. The most commonly used in the treatment of these patients is conventional complete denture or removable partial denture. However, due to increasing problems with this type of therapy, such as insufficient retention, stability, comfort and pain during mastication, it is suggested an overdenture supported by two natural teeth or implants. We will present series of clinical reports. In two clinical cases patients came to the dental office because of the impossibility of wearing lower partial denture, and in one case patient had problems with the upper partial denture. After clinical examination and radigraphic analysis, in all patients, dental implants were implanted. In first case there were implanted two dental implants in the region 41 and 43, in second case it was region 33, and in third case implanatiton is performed in the region of 14, 11, 21. Prosthetic rehabilitation was done after 3-months bone oseointegration period. The treatment consisted in the production of double crowns and overdentures that are retained with locator attachment. This design of the denture significantly improves the quality of patient’s life (the dentures are stable, chewing is improved, the feeling of thermal sensations of food and drink is present, the feeling of taste is complete, and the psychological patient becomes safer).

Biomechanical Analysis of Various Reconstructive Methods for the Mandibular Body and Ramus Defect Using a Free Vascularized Fibula Flap

Several different methods exist for reconstructing the mandibular body and ramus defect with the use of a free vascularized fibula flap, but none have adequately addressed the long-term mechanical stability and osseointegration. The aim of this study is to compare the biomechanics of different surgical methods and to investigate the best approach for reconstructing the mandibular body and ramus defect. Five finite element models based on different reconstructive methods were simulated. Stress, strain, and displacement of connective bone sections were calculated for five models and compared. The models were printed using a 3D printer, and stiffness was measured using an electromechanical universal testing machine. The postoperative follow-up cone beam computed tomography (CBCT) was taken at different time points to analyze bone mineral density of connective bone sections. The results showed that the “double up” (DU) model was the most efficient for reconstructing a mandibular body and ramus defect by comparing the mechanical distribution of three sections under vertical and inclined loading conditions of 100 N. The stiffness detection showed that stiffness in the DU and “double down” (DD) models was higher compared with the “single up” (SU), “single down” (SD), and “distraction osteogenesis” (DO) models. We used the DU model for the surgery, and postoperative follow-up CBCT showed that bone mineral density of each fibular connective section increased gradually with time, plateauing at 12 weeks. We conclude that a free vascularized fibula flap of the DU type was the best approach for the reconstruction of the mandibular body and ramus defect. Preoperative finite element analysis and stiffness testing were shown to be very useful for maxillofacial reconstruction.

Clinical outcomes of rigid and non-rigid telescopic double-crown-retained removable dental prostheses: An analytical review

PURPOSE

The objective of this literature review was to analyze the cumulative survival rates (CSRs) of rigid and non-rigid double-crown-retained removable dental prostheses.

MATERIALS AND METHODS

Screening of the literature published from January 1995 to December 2019 was performed by using electronic data base (Pubmed) and manual search. The CSRs of rigid and non-rigid double crown removable dental prostheses were investigated.

RESULTS

A total of 403 articles were reviewed and 56 relevant articles of them were selected. Subsequently, 25 articles were included for data extraction. These articles were classified according to rigid and non-rigid type double crowns and further subdivided into teeth, implants, and teeth-implant combination types. The CSRs of rigid type double crown ranged from 68.9% to 95.1% of 5 to 10 years in tooth abutments, 94.02% to 100% over a 3-year mean observation periods in implant abutments, and 81.8% to 97.6% in tooth-implant combination. Non-rigid type double crowns had various CSR ranges from 34% to 94% maximum during 10 years observation in teeth abutment. The CSRs of non-rigid type had over 98% in implant abutments, and ranged from 85% to 100% in tooth-implant combination.

CONCLUSION

The CSRs of double crowns varies according to types. With accurate evaluation of the remaining teeth and plan of the strategic implant placement, it could be successful treatment alternatives for partially or completely edentulous patients.