Comparison of trueness and repeatability of facial prosthesis design using a 3D morphable model approach, traditional computer-aided design methods, and conventional manual sculpting techniques

STATEMENT OF PROBLEM

Manually sculpting a wax pattern of a facial prosthesis is a time-, skill-, and resource-intensive process. Computer-aided design (CAD) methods have been proposed as a substitute for manual sculpting, but these techniques can still require high technical or artistic abilities. Three-dimensional morphable models (3DMMs) could semi-automate facial prosthesis CAD. Systematic comparisons of different design approaches are needed.

PURPOSE

The purpose of this study was to compare the trueness and repeatability of replacing facial features with 3 methods of facial prosthesis design involving 3DMM, traditional CAD, and conventional manual sculpting techniques.

MATERIAL AND METHODS

Fifteen participants without facial defects were scanned with a structured light scanner. The facial meshes were manipulated to generate artificial orbital, nasal, or combined defects. Three methods of facial prosthesis design were compared for the 15 participants and repeated to produce 5 of each design for 2 participants. For the 3DMM approach, the Leeds face model informed the designs in a statistically meaningful way. For the traditional CAD methods, designs were created by using mirroring techniques or from a nose model database. For the conventional manual sculpting techniques, wax patterns were manually created on 3D printed full face baseplates. For analysis, the unedited facial feature was the standard. The unsigned distance was calculated from each of the several thousand vertices on the unedited facial feature to the closest point on the external surface of the prosthesis prototype. The mean absolute error was calculated, and a Friedman test was performed (α=.05).

RESULTS

The median mean absolute error was 1.13 mm for the 3DMM group, 1.54 mm for the traditional CAD group, and 1.49 mm for the manual sculpting group, with no statistically significant differences among groups (P=.549). Boxplots showed substantial differences in the distribution of mean absolute error among groups, with the 3DMM group showing the greatest consistency. The 3DMM approach produced repeat designs with the lowest coefficient of variation.

CONCLUSIONS

The 3DMM approach shows potential as a semi-automated method of CAD. Further clinical research is planned to explore the 3DMM approach in a feasibility trial.

IMproving facial PRosthesis construction with contactlESs Scanning and Digital workflow (IMPRESSeD): study protocol for a feasibility crossover randomised controlled trial of digital versus conventional manufacture of facial prostheses in patients with orbital or nasal facial defects

BACKGROUND

Facial prostheses can have a profound impact on patients' appearance, function and quality of life. There has been increasing interest in the digital manufacturing of facial prostheses which may offer many benefits to patients and healthcare services compared with conventional manufacturing processes. Most facial prosthesis research has adopted observational study designs with very few randomised controlled trials (RCTs) documented. There is a clear need for a well-designed RCT to compare the clinical and cost-effectiveness of digitally manufactured facial prostheses versus conventionally manufactured facial prostheses. This study protocol describes the planned conduct of a feasibility RCT which aims to address this knowledge gap and determine whether it is feasible to conduct a future definitive RCT.

METHODS

The IMPRESSeD study is a multi-centre, 2-arm, crossover, feasibility RCT with early health technology assessment and qualitative research. Up to 30 participants with acquired orbital or nasal defects will be recruited from the Maxillofacial Prosthetic Departments of participating NHS hospitals. All trial participants will receive 2 new facial prostheses manufactured using digital and conventional manufacturing methods. The order of receiving the facial prostheses will be allocated centrally using minimisation. The 2 prostheses will be made in tandem and marked with a colour label to mask the manufacturing method to the participants. Participants will be reviewed 4 weeks following the delivery of the first prosthesis and 4 weeks following the delivery of the second prosthesis. Primary feasibility outcomes include eligibility, recruitment, conversion, and attrition rates. Data will also be collected on patient preference, quality of life and resource use from the healthcare perspective. A qualitative sub-study will evaluate patients' perception, lived experience and preference of the different manufacturing methods.

DISCUSSION

There is uncertainty regarding the best method of manufacturing facial prostheses in terms of clinical effectiveness, cost-effectiveness and patient acceptability. There is a need for a well-designed RCT to compare digital and conventional manufacturing of facial prostheses to better inform clinical practice. The feasibility study will evaluate key parameters needed to design a definitive trial and will incorporate early health technology assessment and a qualitative sub-study to identify the potential benefits of further research.

TRIAL REGISTRATION

ISRCTN ISRCTN10516986). Prospectively registered on 08 June 2021,  https://www.isrctn.com/ISRCTN10516986 .

Digital database for nasal prosthesis design with a 3D morphable face model approach

Designing nasal prostheses can be challenging because of the unpaired nature of the facial feature, especially in patients lacking preoperative information. Various nose model databases have been developed as a helpful starting point for the computer-aided design of nasal prostheses, but these do not appear to be readily accessible. Therefore, an open-access digital database of nose models has been generated based on a 3-dimensional (3D) morphable face model approach. This article describes the generation of the database, highlights steps for designing a nasal prosthesis, and points readers to the database for future clinical application and research.

Outcome measures in facial prosthesis research: A systematic review

STATEMENT OF PROBLEM

Facial prosthesis research uses a wide variety of outcome measures, which results in challenges when comparing the effectiveness of interventions among studies. Consensus is lacking regarding the most appropriate and meaningful outcome measures to use in facial prosthesis research to capture important perspectives.

PURPOSE

The purpose of the systematic review was to identify and synthesize outcome measures used in facial prosthesis research.

MATERIAL AND METHODS

Electronic searches were performed in 11 databases (including nonpeer-reviewed literature). The citations were searched, and expert societies were contacted to identify additional studies. Inclusion criteria comprised studies of participants with facial defects who required or had received prosthetic rehabilitation with an external facial prosthesis. Exclusion criteria comprised participants with ocular prostheses, case reports, case series with fewer than 5 participants, laboratory-based studies, and studies published before 1980. Study selection was performed independently by 2 reviewers. Discrepancies were resolved through discussion or by a third reviewer. Outcome measures were synthesized with a categorization approach based on the perspective, theme, and subtheme of the outcome measures. Quality assessment was performed with an appraisal tool that enabled evaluation of studies with diverse designs.

RESULTS

Database searching identified 13 058 records, and 7406 remained after duplications were removed. After initial screening, 189 potentially relevant records remained, and 186 full texts were located (98% retrieval rate). After full-text screening, 124 records were excluded. Citation searches and contact with expert societies identified 4 further records. In total, 69 articles (grouped into 65 studies) were included. Studies were categorized as per the perspective of their outcome measures, with the following findings: patient-reported (74% of studies), clinical indicators (34%), clinician-reported (8%), multiple viewpoints (6%), and independent observer-reported (3%). Patient-reported outcome measures included tools to assess satisfaction, quality of life, and psychologic health. Variability in the choice of outcome measures was evident among the studies, with many self-designed, unvalidated, condition-specific questionnaires reported. A greater number of outcome measure themes emerged over time; themes such as service delivery and health state utility have recently been evaluated.

CONCLUSIONS

Over the past 40 years, facial prosthesis research has focused on patient-reported outcome measures. Outcome measures relating to other perspectives have been used less frequently, although new themes appear to be emerging in the literature. Future research should use outcome measures with appropriate measurement properties for use with facial prosthetics.

Development of a 3D printable maxillofacial silicone: Part II. Optimization of moderator and thixotropic agent

STATEMENT OF PROBLEM

Conventionally, maxillofacial prostheses are fabricated by hand carving the missing anatomic defect in wax and creating a mold into which pigmented silicone elastomer is placed. Digital technologies such as computer numerical control milling and 3-dimensional (3D) printing have been used to prepare molds, directly or indirectly, into which a biocompatible pigmented silicone elastomer can be placed.

PURPOSE

The purpose of this in vitro study was to develop a silicone elastomer that could be 3D printed directly without a mold to create facial or body prostheses by varying its composition.

MATERIAL AND METHODS

The room temperature vulcanizing silicone composition was divided into 2 components which were mixed 1:1 to initiate polymerization in the printer before printing began. Different types of moderators and thixotropic agents were used, and the base composition was varied to obtain 11 formulations. The specimens were printed and polymerized from these formulations and tested for tear and tensile strength and hardness. Ten readings of the specimens were recorded for tear and tensile strength and 6 for hardness. Results were analyzed using ANOVA (α=.05). Visual assessment of uncured printed specimens was undertaken for 5 formulations to assess any differences in their ability to hold their shape after printing.

RESULTS

The tear and tensile strength of the 11 formulations with varying moderators, thixotropic agents, and base compositions were statistically similar to each other (P>.05). Five of 11 formulations were chosen for the visual assessment as they had sufficient thixotropic agent to avoid slumping while printing. The specimens showed varied slumping behavior until they polymerized. The filler content was increased in the selected formulation, and the tear and tensile strength of the formulation was increased to 6.138 kNm^-1 and 3.836 MPa; these increases were comparable to those of commercial silicones currently used for the fabrication of facial prostheses.

CONCLUSIONS

The optimum combination of mechanical properties implies the use of one of the formulations as a suitable material for the 3D printing of facial prostheses.

Development of a 3D printable maxillofacial silicone: Part I. Optimization of polydimethylsiloxane chains and cross-linker concentration

STATEMENT OF PROBLEM

Conventionally, maxillofacial prostheses are fabricated by hand carving the missing anatomic defect in wax and creating a mold into which pigmented silicone elastomer is placed. Digital technologies such as computer numerical control (CNC) milling and 3-dimensional (3D) printing have been used to prepare molds directly or indirectly into which a biocompatible pigmented silicone elastomer is placed.

PURPOSE

The purpose of this in vitro study was to develop a silicone elastomer by varying composition that could eventually be 3D printed directly without a mold to create facial/body prostheses.

MATERIAL AND METHODS

The silicone was composed of polydimethylsiloxane (PDMS), filler, catalyst, and cross-linker. Four types of base silicone polymers were prepared with different PDMS molecular weight combinations with long, medium, and short chain length PDMS. The effect of the cross-linker (2.5% to 12.5%) content in these bases was assessed for the effect upon the mechanical properties of the elastomer. Ten readings were made for each formulation, and differences in the means were evaluated with a 2-way ANOVA (α=.05).

RESULTS

Variations in silicone composition resulted in hardness from 6.8 to 28.5 durometer, tensile strength from 0.720 to 3.524 kNm^-1 and tear strength from 0.954 to 8.484 MPa. Significant differences were observed among all formulations (P<.05). These formulations have mechanical properties comparable with the commercial silicones currently used for the fabrication of facial prostheses. The formulation with 5% cross-linker content and high content of long-chain PDMS chains with optimum mechanical properties was chosen for further development.

CONCLUSIONS

The optimum combination of mechanical properties implies the use of one of these formulations for further evaluation in a 3D printer capable of actively mixing and extruding 2-component, room temperature vulcanization silicone.

Development of a morphing technique for predicting the position and size of an artificial ear in hemifacial microsomia patients

PURPOSE

People with hemifacial microsomia may be missing an ear on the affected side of the face. The principal aim of the study was to develop a morphing technique and to determine whether it could be used to appropriately position an artificial ear, as well as to give an indication of prosthesis size in comparison with the natural ear. Comparisons also were made between the artificial ears being worn by the patients with their natural ears.

MATERIALS AND METHODS

Data from stereophotogrammetry images of the faces of 10 people were converted into stereolithographic format. Anthropometric points on the face and ear of the unaffected side were plotted. By a process of scaling, the distance between facial landmarks on the unaffected side was estimated for the affected side so as to identify where the morphed ear would be positioned once generated.

RESULTS

Generally, the morphed ears appeared to be in acceptable positions. There was a statistically significant difference between the position of the morphed and natural ears (P = .011), as well as the artificial and natural ears (P = .001), but this was unlikely to have any clinical implications. There were no significant differences among the sizes of the natural, morphed, and artificial ears (P = .072).

CONCLUSIONS

Morphing appears to offer a more precise way of planning the positioning and construction of an artificial ear on patients with hemifacial microsomia than traditional methods. Differences in facial shape on either side of the face may impact on the process. This requires further study.

The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing qualities of impressions that may lead to occlusal discrepancies with indirect restorations

There are few published studies that directly assess the quality of impressions for crowns and bridges in the UK. This paper considers aspects of impression quality with particular attention to factors causing potential occlusal discrepancies in the final restoration. To this end three dental laboratories were visited over a 3-month period. All impressions for conventional crown and bridgework that arrived on the days of the visits were examined and assessed against criteria defined on a custom-designed assessment form. A total of 206 impression cases were considered in this study. Flexible impression trays were used for 65% of working impressions. Their use was more common for NHS work than for private work. 31.9% of all alginate impressions examined were not adequately fixed to the tray. Visible contamination of impressions was not uncommon.

The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing the quality of the impressions of prepared teeth

The literature is limited in studies directly assessing the quality of impressions for crowns and bridges in the UK. The aim of the study was to assess the quality of impressions for conventional crown and bridgework received by commercial dental laboratories. Three dental laboratories were visited over a 3-month period. All impressions for conventional crowns and bridges that arrived on the days of the visits were examined prior to any laboratory processing. A total of 206 impression cases were examined and assessed against criteria laid out in a custom-designed assessment form. Defects were commonly found in the recording of prepared teeth. Overall, 44.2% of impression cases were unsatisfactory. NHS impressions were more than twice as likely to be unsatisfactory compared to private impressions. If the results of this survey are typical then the general quality of impressions for fixed crown and bridgework is unacceptable. This is particularly true for work completed under the NHS contract.

A comparison of three methods to evaluate the position of an artificial ear on the deficient side of the face from a three-dimensional surface scan of patients with hemifacial microsomia

PURPOSE

Patients with hemifacial microsomia may have a missing ear on the deficient side of the face. The fabrication of an ear for such individuals usually has been accomplished by directly measuring the ear on the normal side to construct a prosthesis based on these dimensions, and the positioning has been, to a large extent, primarily operator-dependent. The aim of the present study was to compare three methods, developed from the identification of landmarks plotted on three-dimensional surface scans, to evaluate the position of an artificial ear on the deficient side of the face compared with the position of the natural ear on the normally developed side.

MATERIALS AND METHODS

Laser scans were undertaken of the faces of 14 subjects with hemifacial microsomia. Landmarks on the ear and face on the normal side were identified. Three methods of mirroring the normal ear on the deficient side of the face were investigated, which used either facial landmarks from the orbital area or a zero reference point generated from the intersection of three orthogonal planes on a frame of reference. To assess the methods, landmarks were identified on the ear situated on the normal side as well as on the face. These landmarks yielded paired dimensional measurements that could be compared between the normal and deficient sides. Mean differences and 95% confidence intervals were calculated.

RESULTS

It was possible to mirror the normal ear image on to the deficient side of the face using all three methods. Generally only small differences between the dimensional measurements on the normal and deficient sides were observed. However, two-way analysis of variance revealed statistically significant differences between the three methods (P = .005).

CONCLUSIONS

The method of mirroring using the outer canthi was found to result in the smallest dimensional differences between the anthropometric points on the ear and face between the normally developed and deficient sides. However, the effects of the deformity can result in limitations in relation to achieving a precise alignment of the ear to the facial tissues. This requires further study.

Development of a stereophotogrammetry technique to assess facial change following surgery for head and neck cancer

A stereophotogrammetry technique is described that can be used to map the face following surgery for head and neck cancer. It enables the effects of obturators on facial form to be assessed and may have a wide variety of applications. Int J Prosthodont 2011;24:342-344.

A comparison of prosthetic ear models created from data captured by computerized tomography, magnetic resonance imaging, and laser scanning

PURPOSE

To compare the dimensional measurements and surface topography of stereolithographic models generated from computerized tomography (CT), magnetic resonance imaging (MRI), and laser scanning (LS) data with the same subjects' natural ears and ear casts.

MATERIALS AND METHODS

Stereolithographic models were manufactured from images of the subjects' ears and ear casts recorded by CT, MRI, and LS, and dimensional measurements were compared. In the second part of the study, all stereolithographic models were CT scanned and reconstructed in an STL file format. A comparison of the surface topography of the CT, MRI, and LS model ears was made.

RESULTS

Intraclass correlation coefficients indicated that dimensions could be reliably measured on the CT, MRI, and LS stereolithographic models. A 2-way analysis of variance revealed no statistical differences between the various sources of data (P = .991). The smallest differences of surface topography were observed on the MRI/CT superimpositions.

CONCLUSION

The dimensional measurements on the stereolithographic models were similar to those from the original source. Only small differences were apparent between the surface topography of the CT, MRI, and LS models. MRI may be particularly appropriate to fabricate a prosthesis because it involves no radiation for the patient and internal form can be reproduced. The use of this technique in clinical practice requires further study.

A comparison between computerized tomography, magnetic resonance imaging, and laser scanning for capturing 3-dimensional data from a natural ear to aid rehabilitation

PURPOSE

To compare dimensional measurements on computer images generated from data captured digitally by 3 different methods to those obtained directly from natural ears and ear casts, so as to determine the optimal method of creating a computer-generated ear image.

MATERIALS AND METHODS

Magnetic resonance imaging (MRI) was used to obtain 3-dimensional (3D) data images of the normal ears of 14 subjects. Computerized tomography (CT) and laser scanning (LS) were used to obtain 3D data images from stone casts of the same ears. Dimensional measurements were recorded on 2 occasions between anthropometric landmarks on the subjects' natural ears, casts of the ears, and reconstructed ear images obtained by CT, MRI, and LS. The intraclass correlation coefficients and coefficients of repeatability were calculated. The means of the 2 measurements for each of the dimensions were analyzed using 2-way analysis of variance to determine whether there were differences between the methods of data collection.

RESULTS

The intraclass correlation coefficients indicated that dimensions could be reliably measured on the natural ears, casts, and CT, MRI, and LS images. The coefficients of repeatability were all of a small magnitude in relation to the overall dimensions studied. No statistical differences existed between the various sources of data (P = .866) (i.e., direct, cast, CT, MRI, and LS).

CONCLUSION

The 3 methods of imaging have generally resulted in dimensional measurements on the reconstructed images that are similar to those of the original source. These are considered appropriate for manufacturing 3D models that can be used to fabricate a prosthesis. However, other factors may also be important, such as shape, contour, and internal form, and these require further investigation.

A comparison between computerized tomography, magnetic resonance imaging, and laser scanning for capturing 3-dimensional data from an object of standard form

PURPOSE

The study's aim was to compare dimensional measurements on computer images generated from data captured digitally by 3 different methods of the surfaces of a plastic cube of known form to those obtained directly from the cube itself.

MATERIALS AND METHODS

Three-dimensional images were reconstructed of a plastic cube obtained by computerized tomography (CT), magnetic resonance imaging (MRI), and laser scanning. Digital calipers were used to record dimensional measurements between the opposing faces of the plastic cube. Similar dimensional measurements were recorded between the cube faces on each of the reconstructed images. The data were analyzed using a 2-way ANOVA to determine whether there were differences between dimensional measurements on the computer images generated from the digitization of the cube surfaces by the different techniques, and the direct measurement of the cube itself.

RESULTS

A significant effect of how the measurements were taken (ie, direct, CT, MRI, and laser scanning) on the overall variation of dimensional measurement (P < .0005) was observed. Post hoc tests (Bonferroni) revealed that these differences were due principally to differences between the laser-scanned images compared to other sources (ie, direct, CT, and MRI). The magnitude of these differences was very small, up to a maximum mean difference of 0.71 mm (Cl +/- 0.037 mm).

CONCLUSION

All 3 methods of imaging would be of value in further studies, not only for the fabrication of complex shapes such as prosthetic ears, but also for other facial prostheses.

A preliminary study to investigate the potential of plasma screen technology in small group teaching for dental undergraduates

AIM

This preliminary study was devised to ascertain whether students considered that they had an adequate view of demonstrated procedures, while observing these directly at the workbench, or indirectly on a remote plasma screen. In addition, this study sought to identify whether the students observing remotely believed that they had been disadvantaged by the inability to question the demonstrator during the demonstration.

METHODS

Seventeen students divided into two groups observed a live demonstration of a laboratory technical procedure either at the workbench, or remotely at a plasma screen with the aid of video cameras. They subsequently observed a second demonstration with the roles reversed. Questionnaires were used to obtain the students' views of their ability to see and interact with the demonstrator.

RESULTS

The responses of the students observing the demonstration at the plasma screen indicated that (they felt that) they were able to see the demonstration more clearly than those observing at the workbench. Those observing at the plasma screen first, in particular indicated this. The majority of students acknowledged their inability to ask questions while observing at the plasma screen. There was overwhelming support for the idea that the plasma screen should be used to complement the demonstration at the workbench.

CONCLUSION

Plasma screen technology has considerable potential as a teaching tool for small groups of students, where it can afford significantly superior views of practical procedures. The students considered that the plasma screen would be best employed to provide close-up views to supplement a live demonstration. When used remotely, the apparatus may be used more satisfactorily if videoconferencing technology is also employed to facilitate interaction with the demonstrator.

Identifying the position of an ear from a laser scan: the significance for planning rehabilitation

Laser scanning techniques are used to plan the construction of prosthetic ears as dimensional measurements between anthropometric points can be accurately measured on a screen image. The aim of this study was to determine if these techniques could be used to assess the position of ears on the face. Computer-generated images were created from laser scans of 20 subjects. Frames of reference were constructed by locating a series of anthropometric points on the face from which three orthogonal planes were constructed. A central reference point was identified at the intersection of the three orthogonal planes. Dimensional measurements were made between anthropometric points on the ear and the reference planes. The differences between anthropometric points and the reference planes on the left and right sides of the face were small. It was possible to describe the location of points three-dimensionally with respect to a central reference point. The development of frames of reference and a central reference point would appear to offer many advantages in the assessment and description of ear position for patients requiring reconstruction with prostheses.

The contribution of imaging and digitised data to mandibular reconstruction and implant stabilised occlusal rehabilitation: a case report

Different methods are recommended for the surgical reconstruction of the resected mandible. The advantages for implant stabilised prostheses in restoring the occlusion are recognised but few papers provide adequate data to identify the successful outcome of treatment. The literature is reviewed and the advantages of imaging together with the use of digitised data is highlighted by a case requiring rehabilitation with enhanced planning methods.

A comparison between videotaped and live demonstrations, for the teaching of removable partial denture procedures

AIM

This study was devised to test the effectiveness of videotaped demonstrations as opposed to live demonstrations, to small groups of undergraduate dental students. The outcome was assessed by comparing the students' understanding of the clinical and laboratory technical stages of the altered cast impression technique, which is used in the construction of removable partial dentures.

METHOD

31 students watched a series of videotaped demonstrations and 30 received a similar series of live demonstrations. The altered cast procedure was divided into 5 distinct stages, each of which was assessed with the aid of agreed criteria, initially by the students and then by 2 staff assessors and these results were compared. The students were subsequently asked to rate how helpful the videotaped or live demonstration had been on a 5-point scale.

RESULTS

The live demonstration group showed better agreement between the students' assessment and the assessors' assessment of the quality of the work for the first part of the clinical stage. There was no difference in the groups' assessment of the final outcome of this clinical stage and the subsequent laboratory technical stages. Students who observed the live demonstrations indicated higher scores for its helpfulness in performance of all the stages of the technique, when compared to those who had observed a videotaped demonstration.

CONCLUSION

Both teaching methods developed a similar level of understanding of the principles behind the exercise, although the students preferred the live demonstrations. A carefully produced videotaped demonstration can be a useful alternative to a live demonstration in teaching the short and clear cut technique selected for this study.

Laser scanning of the ear identifying the shape and position in subjects with normal facial symmetry

The objective of the present study was to discover if dimensional measurements of the ear could be determined with a laser scanning technique and whether or not the location of landmarks of the ear could be reliably measured with respect to those on the midline of the face. Computer-generated images were created from laser scans of 20 subjects. Dimensional measurements were made between landmarks on the ear and face. Differences between repeated dimensional measurements of the ear were very small, as were those measurements made between landmarks on the ear to the midline of the face. Differences between dimensions of the left and right ears were observed, but were of a small magnitude. The results suggest that the dimensions of the ear and its position with respect to landmarks in the midline of the face can be reliably measured on normal subjects and that laser scanning is a useful technique for planning and monitoring facial reconstruction of the ear.

Fabrication of a wax ear by rapid-process modeling using stereolithography

PURPOSE

The purpose of this article is to describe an automated technique that creates a mirror-image wax model of the contralateral ear using a rapid prototyping technique, which allows precise positioning and adaptation to the deficient side of the face.

MATERIALS AND METHODS

Magnetic resonance images (MRI) are taken of the face and then digitized and reformatted into a 3-dimensional image. The image of the normal ear is extracted, mirrored, and positioned onto the image of the deformed side of the face. The digitized data, when used in conjunction with stereolithography, produces a photopolymerized resin model ear. A model wax ear is created by pouring molten wax into a silicone mold of the resin model ear.

RESULTS

A model wax ear of identical dimensions, shape, and internal contouring as the contralateral normal ear is created. The technique allows the undersurface of the model wax ear to be precisely positioned against the surface contours of the deformed side of the face in 1 patient.

CONCLUSION

The use of stereolithography from MRI scan data is a suitable technique for producing a model wax ear that fits the deformed side of the face. The 3-dimensional computer image of the face may also be used to plan the position (level and protrusion) of the ear.

Laser scanning for the identification of repeatable landmarks of the ears and face

OBJECTIVE

To determine whether or not landmarks of the ears and face could be reliably identified using a laser scaning system.

DESIGN

A single centre study with two assessors jointly agreeing the siting of the landmarks on the ear on two separate occasions from an original laser scanned image.

SETTING

University based research study in London, UK.

SUBJECTS

20 subjects, 11 males, 9 females, aged 16-24 years with normal facial development.

MAIN OUTCOME MEASURES

Differences were determined between the locations of landmarks on the two occasions studied. Differences were assessed for the x, y and z co-ordinates of each point.

RESULTS

The mean difference between the two sitings of 21 landmarks ranged between 0 and 0.85 mm in the x, y and z axes. With a small number of exceptions, the differences were not statistically significant. The three-dimensional mean differences between the two sitings of each landmark ranged between 1 and 2.5 mm. Coefficients of repeatability ranged between 1.6 and 7.0 mm.

CONCLUSIONS

Landmarks of the ears and face from a laser scanned image can be sited consistently by two assessors. Since the landmarks can be located it should be possible to evaluate dimensional measurements of the ear and its position on the face.

Locating angulated abutments: a technical note

A simple laboratory-made acrylic resin guide offers rapid location of angulated abutments after the healing abutments are removed. An impression recording the relation of the implants to the dental arch enables the choice of abutments to be made in the laboratory. The precise position and angulation of each abutment can be transferred to the mouth.

Results of treatment of 20 patients with implant-retained auricular prostheses

A prospective study of 20 patients receiving rehabilitation for a missing external ear revealed the failure of three flanged implants in a total of 60 placed for the support of a prosthesis and 10 for retention of a bone-anchored hearing aid. Factors limiting an optimal outcome were health of the cutaneous cuff around the abutments, bonding of the silicone ear to the acrylic-resin substructure, and the ability to minimize disfigurement of a congenitally deformed face.