The design and characterisation of sinusoidal toolpaths using sub-zero bioprinting of polyvinyl alcohol

Sub-zero (°C) additive manufacturing (AM) systems present a promising solution for the fabrication of hydrogel structures with complex external geometry or a heterogeneous internal structure. Polyvinyl alcohol cryogels (PVA-C) are promising tissue-mimicking materials, with mechanical properties that can be designed to satisfy a wide variety of soft tissues. However, the design of more complex mechanical properties into additively manufactured PVA-C samples, which can be enabled using the toolpath, is a largely unstudied area. This research project will investigate the effect of toolpath variation on the elastic and viscoelastic properties of PVA-C samples fabricated using a sinusoidal toolpath. Samples were fabricated using parametric variation of a sinusoidal toolpath, whilst retaining the same overall cross-sectional area, using a sub-zero AM system. To mechanically characterise the samples, they were tested under tension in uniaxial ramp tests, and through dynamic mechanical analysis (DMA). The elastic and viscoelastic moduli of the samples are presented. No correlations between the parametric variation of the design and the Young's modulus were observed. Analysis of the data shows high intra-sample repeatability, demonstrated robust testing protocols, and variable inter-sample repeatability, indicating differences in the printability and consistency of fabrication between sample sets. DMA of the wavelength samples, show a frequency-dependent loss moduli. The storage modulus demonstrates frequency independence, and a large increase in magnitude as the sample increases to 3 wavelengths.

Application of hybrid SFLA-ACO algorithm and CAM softwares for optimization of drilling tool path problems

Abstract

In drilling process almost seventy percent time is spent in tool switching and moving the spindle from one hole to the other. This time travel is non productive as it does not take part in actual drilling process. Therefore, this non productive time needs to be optimized. Different metaheuristic algorithms have been applied to minimize this non productive tool travel time. In this study, two metaheuristic approaches, shuffled frog leaping algorithm (SFLA) and ant colony optimization (ACO) have been hybridized. In industry, the CAM softwares are employed for minimization of non productive tool travel time and it is considered that the path obtained by using the CAM softwares is the optimized path. However this is not the case in all problems. In order to show the contribution of the SFLA-ACO algorithm and to prove that results achieved through CAM softwares are not always optimized, hybrid SFLA-ACO algorithm has been applied to two drilling problems as case studies with the main objective of minimization of non productive tool travel time. The drilling problems which are taken from the manufacturing industry include ventilator manifold problem and lift axle mounting bracket problem. The results of hybrid SFLA-ACO algorithm have been compared with the results of commercially available computer aided manufacturing (CAM) software. For comparison purpose, the CAM softwares used are Creo 6.0, Pro E, Siemens NX and Solidworks. The comparison shows that the results of proposed hybrid SFLA-ACO algorithm are better than commercially available CAM softwares in both real world manufacturing problems.

Article highlights

Different optimization techniques are being used for optimization of drilling tool path problems. In this paper two techniques SFLA and ACO has been combined to form a hybrid SFLA-ACO algorithm and has been applied to the real world industrial problems.Two real world problems have been taken from the local manufacturing industries. In both the problems the objective is to optimize the tool traveling time through hybrid SFLA-ACO and compare it with CAM software.Four CAM softwares have been used for comparison purpose. The problems undertaken are solved through these CAM software and compared with the results of hybrid SFLA-ACO results. As result of comparison it is found that in both the problems the performance of hybrid SFLA-ACO algorithm remains outclass. This signifies that results of CAM software in case of optimization of drilling tool path are not always optimal and these can be improved by using different optimization techniques.

[Congenital thoracic deformities and 3D custom-made implants. New classification based on a series of 789 treated cases]

The authors present a new study on 789 cases of congenital thoracic malformations including 638 pectus excavatum and 151 Poland syndromes, according to a new classification which completes Chin's one. All these malformations were treated with silicone elastomer implants. The contribution of computer-aided design and manufacturing (CAD/CAM) since 2008 is essential. The one-stage surgical protocol is precisely described. The results are impressive, permanent, for life, and complications are rare. The authors evoke a common vascular etiopathogenesis theory at the embryonic stage and question the heavy techniques of invasive remodeling that are most often unjustified.

[CAD/CAM assisted facial epithesis: Clinical and technical aspects]

The face is an important part of the human body from an anatomical, functional, aesthetic and psychosocial point of view. It can be the site of several mutilations resulting from trauma, treatment of neoplasms and congenital malformations. The plastic facial prosthesis is therefore indicated to restore these facial deformities and to compensate for the various consequences. Recently, digital technologies have shown an increasing impact on the future of maxillofacial rehabilitation. Computer-aided design and manufacturing technique enabled practitioners to acquire numerical data, perform three-dimensional reconstructions, and then materialize and manufacture the facial epithesis through various manufacturing processes, by addition or subtraction. The aim of this article is to describe, through a clinical case, the steps of realization of a nasal epithesis by CAD/CAM, in a patient who underwent a surgical exeresis of the nasal pyramid following a squamous cell carcinoma. Thus, the clinical and technical aspects are highlighted, as follows, the taking of the impression, the materials used, the set-up and the make-up, as well as the software and the useful concepts for the computer-assisted realization of a facial plastic prosthesis of the nasal epithesis type. Our therapy will also focus on the interest of the multidisciplinary approach in Maxillofacial Prosthodontics.

Implant rehabilitation of edentulous maxilla in digital dentistry: A case report utilizing CAD/CAM technologies

The replacement of missing teeth utilizing dental implants and digital dental technologies has gained significant popularity in daily clinical practice over the last decade. Partially dentate patients present more anatomical references to guide the implant position and prosthetic reconstruction as compared to completely edentulous arches. Therefore, the management of edentulous maxilla using implant digital dentistry represents a challenging clinical situation where a thorough treatment plan is paramount to achieve a final prosthetic result that meets both functional and esthetic requirements. This case report discusses the oral rehabilitation of an edentulous maxilla and partially dentate mandible using a digital workflow for both the surgical and prosthetic phases of the implant therapy. Protocols for clinical assessment, treatment planning, and restorative management are described to provide a predictable and prosthetic-driven treatment for implant-supported prostheses.

In silico non-linear dynamic analysis reflecting in vitro physical properties of CAD/CAM resin composite blocks

PURPOSE

The aim of this study was to assess the validity of in silico models of three-point bending tests to reflect in vitro physical properties obtained from three commercially available computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks and demonstrate notchless triangular prism analysis with those properties.

MATERIAL AND METHODS

Three types of commercially available CAD/CAM resin composite blocks were used: Cerasmart 300 (CS300; GC, Tokyo, Japan), Katana Avencia P Block (AP; Kuraray Noritake Dental, Tokyo, Japan), and KZR CAD HR3 Gamma Theta (GT; Yamakin, Osaka, Japan). In vitro/in silico three-point bending tests were conducted to obtain elastic modulus and fracture strain for non-linear dynamic finite element analysis (n = 10/each). Fractured surfaces of specimens after in vitro NTP tests were observed, and the fracture toughness of each CAD/CAM resin composite was obtained by in silico NTP analysis.

RESULTS

Both in vitro and in silico load-displacement curves obtained from three-point bending tests were significantly correlated (p < 0.05). The elastic moduli of CS300, AP, and GT were 8.0 GPa, 10.0 GPa, and 9.0 GPa, respectively. The fracture toughness values obtained from in silico NTP analysis of CS300, AP, and GT were 5.057 MPa m^1/2, 4.193 MPa m^1/2, and 4.880 MPa m^1/2, respectively. There was no significant difference in the length of the stable region among the three CAD/CAM resin composites (p = 0.09).

CONCLUSIONS

The in silico approach established in this study showed acceptable reflection of in vitro physical properties and will be useful for assessing fracture toughness related to the longevity of CAD/CAM resin composites without wastage of materials.

Combined application of virtual surgery and 3D printing technology in postoperative reconstruction of head and neck cancers

Background

The complex anatomy of the head and neck creates a formidable challenge for surgical reconstruction. However, good functional reconstruction plays a vital role in the quality of life of patients undergoing head and neck surgery. Precision medical treatment in the field of head and neck surgery can greatly improve the prognosis of patients with head and neck tumors. In order to achieve better shape and function, a variety of modern techniques have been introduced to improve the restoration and reconstruction of head and neck surgical defects. Digital surgical technology has great potential applications in the clinical treatment of head and neck cancer because of its advantages of personalization and accuracy.

Case presentation

Our department has identified the value of modern digital surgical techniques in the field of head and neck surgery and has explored its utility, including CAD/CAM technology and VR technology. We have achieved good results in the reconstruction of head and neck surgical resection defects.

Conclusion

In this article, we share five typical cases from the department of head and neck surgery where the reconstruction was performed with the assistance of digital surgical technology.