Richard J. Bibb

A comparison of plaster, digital and reconstructed study model accuracy

Objectives To evaluate the accuracy and reproducibility of a three-dimensional (3D) optical laser-scanning device to record the surface detail of plaster study models. To determine the accuracy of physical model replicas constructed from the 3D digital files. Design and setting A method comparison study using 30 dental study models held in the Orthodontic Department, School of Dentistry, Cardiff University. Materials and methods Each model was captured three-dimensionally, using a commercially available Minolta VIVID 900 non-contact 3D surface laser scanner (Konica Minolta Inc., Tokyo, Japan), a rotary stage and Easy3DScan integrating software (TowerGraphics, Lucca, Italy). Linear measurements were recorded between landmarks, directly on each of the plaster models and indirectly on the 3D digital surface models, on two separate occasions by a single examiner. Physical replicas of two digital models were also reconstructed from their scanned data files, using a rapid prototyping (RP) manufacturing process, and directly evaluated for dimensional accuracy. Results The mean difference between measurements made directly on the plaster models and those made on the 3D digital surface models was 0.14 mm, and was not statistically significant (P = 0.237). The mean difference between measurements made on both the plaster and virtual models and those on the RP models, in the z plane was highly statistically significant (P <0.001). Conclusions The Minolta VIVID 900 digitizer is a reliable device for capturing the surface detail of plaster study models three-dimensionally in a digital format but physical models of appropriate detail and accuracy cannot be reproduced from scanned data using the RP technique described.

Rapid manufacture of removable partial denture frameworks

Purpose – The aim of this study was to explore the application of rapid manufacturing (RM) to the production of patient specific, custom‐fitting removable partial denture (RPD) alloy frameworks. RPDs are metal frameworks designed to retain artificial replacement teeth in the oral cavity.Design/methodology/approach – The study was undertaken by applied case study. An RPD was designed using computer‐aided design software according to well‐established dental technology design principles, based on a digitally scanned cast produced from an impression of the patients mouth. The RPD design was then exported as an STL file in preparation for direct manufacture using selective laser melting. Dimensionally accurate frameworks were manufactured in 316L stainless steel and chromium‐cobalt alloy. These were assessed for accuracy of fit and function on the patient cast and on the patient in clinic.Findings – This successful case study demonstrates that an RM approach can produce fully functional, precisely fitting RPD...

The computer-aided design and rapid prototyping fabrication of removable partial denture frameworks

Abstract This study explores the application of computer-aided design and manufacture (CAD/CAM) to the process of electronically surveying a scanned dental cast as a prior stage to producing a sacrificial pattern for a removable partial denture (RPD) metal alloy framework. These are designed to retain artificial replacement teeth in the oral cavity. A cast produced from an impression of a patients mouth was digitally scanned and the data converted to a three-dimensional computer file that could be read by the computer-aided design (CAD) software. Analysis and preparation were carried out in the digital environment according to established dental principles. The CAD software was then used to design the framework and generate a standard triangulation language (STL) file in preparation for its manufacture using rapid prototyping (RP) methods. Several RP methods were subsequently used to produce sacrificial patterns, which were then cast in a chromium-cobalt alloy using conventional methods and assessed for accuracy of fit. This work demonstrates that CAD/CAM techniques can be used for electronic dental cast analysis, preparation, and design of RPD frameworks. It also demonstrates that RP-produced patterns may be successfully cast using conventional methods and that the resulting frameworks can provide a satisfactory fit.

The use of a reconstructed three-dimensional solid model from CT to aid the surgical management of a total knee arthroplasty: a case study

The use of a rapid prototyping method was utilised to produce a pre-operative solid model of the proximal tibia in a patient with a massive defect of the medial tibial plateau. The solid model was reconstructed from aligned sequential CT images of the knee. This was then used to determine the level of bone resection of the proximal tibia for the optimum placement of the tibial component of a total knee replacement. This technique gives the surgeon both the three-dimensional anatomical information needed to ascertain whether there is adequate bony support after cutting for the prosthesis, as well as a solid model on which to carry out the proposed surgery, before undertaking the procedure on the patient.

Rapid prototyping technologies in soft tissue facial prosthetics: current state of the art

Purpose – Maxillofacial prosthetics is faced with increasing patient numbers and cost constraints leading to the need to explore whether computer‐aided techniques can increase efficiency. This need is addressed through a four‐year research project that identified quality, economic, technological and clinical implications of the application of digital technologies in maxillofacial prosthetics. The purpose of this paper is to address the aspects of this research that related to the application of rapid prototyping (RP).Design/methodology/approach – An action research approach is taken, utilising multiple case studies to evaluate the current capabilities of digital technologies in the preparation, design and manufacture of maxillofacial prostheses.Findings – The research indicates where RP has demonstrated potential clinical application and where further technical developments are required. The paper provides a technical specification towards which RP manufacturers can direct developments that would meet the...

Rapid manufacture of custom‐fitting surgical guides

Purpose – The computer‐aided design (CAD) and manufacture of custom‐fitting surgical guides have been shown to provide an accurate means of transferring computer‐aided planning to surgery. To date guides have been produced using fragile materials via rapid prototyping techniques such as stereolithography (SLA), which typically require metal reinforcement to prevent damage from drill bits. The purpose of this paper is to report case studies which explore the application of selective laser melting (SLM) to the direct manufacture of stainless steel surgical guides. The aim is to ascertain whether the potential benefits of enhanced rigidity, increased wear resistance (negating reinforcement) and easier sterilisation by autoclave can be realised in practice.Design/methodology/approach – A series of clinical case studies are undertaken utilising medical scan data, CAD and SLM. The material used is 316L stainless steel, an alloy typically used in medical and devices and surgical instruments. All treatments are p...

The custom-made titanium orbital floor prosthesis in reconstruction for orbital floor fractures.

This is the author’s version of a work that was accepted for publication in Journal of Oral and Maxillofacial Surgery. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/S0266435602002498

An investigation of three-dimensional scanning of human body surfaces and its use in the design and manufacture of prostheses

Abstract The capture of highly accurate data describing the complex surfaces of the human body may prove extremely useful in many medical situations. The data provide a method of measuring and recording changes to the surface of a patients soft tissue. The data may be applied to computer-controlled manufacturing techniques, such as rapid prototyping (RP). This enables accurate physical replicas of the patient topography to be produced. Such models may be used as an aid in the design and manufacture of prostheses. This paper describes an investigation aimed at identifying problems that may be encountered when scanning patients and describes the application of the resulting data in the design and manufacture of facial prostheses. The results of the experiment are presented together with a discussion of the accuracy and potential advantages afforded by this approach.

Development of a rapid prototyping design advice system

This paper describes the initial development of a computer based Rapid Prototyping Design Advice System. The system is intended to assist the designer or project manager, particularly those in small and medium sized companies, in planning the prototyping stage of product development. It provides the user with an efficient and user friendly development aid which uses information obtained from the user and Computer Aided Design data to recommend suitable rapid prototyping solutions.

Comparing additive manufacturing technologies for customised wrist splints

Purpose – The purpose of this paper is to compare four different additive manufacturing (AM) processes to assess their suitability in the context of upper extremity splinting. Design/methodology/approach – This paper describes the design characteristics and subsequent fabrication of six different wrist splints using four different AM processes: laser sintering (LS), fused deposition modelling (FDM), stereolithography (SLA) and polyjet material jetting via Objet Connex. The suitability of each process was then compared against competing designs and processes from traditional splinting. The splints were created using a digital design workflow that combined recognised clinical best practice with design for AM principles. Findings – Research concluded that, based on currently available technology, FDM was considered the least suitable AM process for upper extremity splinting. LS, SLA and material jetting show promise for future applications, but further research and development into AM processes, materials an...