CAD/CAM ear model and virtual
construction of the mold
Leonardo Ciocca, DDS, PhD,a Roberto Mingucci, PhD,b
Gianfranco Gassino, MD, DMD,c and Roberto Scotti, MD, DMDd
Alma Mater Studiorum University of Bologna, Bologna, Italy;
University of Turin, Turin, Italy
This article describes a technique to make an implant-retained maxillofacial prosthesis using CAD/CAM technology
and a rapid prototyping machine. The primary advantage of this technique is virtual 3-dimensional integration of the
defective surface with the mirrored and digitalized normal ear. Making an impression of the defective side is not neces-
sary, because only the position of the implants must be recorded to develop the bar for the retention of the prosthesis.
This procedure allows positioning of the ear straight onto the computer screen, eliminating the diagnostic waxing,
and the fabrication of the stone mold is not necessary because of the rapid prototyping process. (J Prosthet Dent
In a previous article,1 the authors agement is the base of the external (other than the one used for fabrica-
describe a technique using rapid pro- ear, which must fit perfectly onto the tion of the implant bar), trial waxing
totyping to fabricate a mirrored vol- defective side. To achieve this goal, the for the positioning of the ear, and the
ume of healthy ear for situations that wax pattern is developed and adapt- indirect fabrication of the stone mold.
necessitate ablative surgery of the ex- ed to the stone cast, but this makes This technique is useful both for con-
ternal ear. A recent report by Mardini it difficult to preserve the correct po- ventional mold fabrication (eliminat-
et al2 described a technique to obtain sition as previously determined on ing only the trial waxing), and for the
a further simplification of the mirror- the skin of the patient. The protocol completely automated method of
image wax pattern of an ear for the presented in this article describes a mold fabrication. The primary ad-
fabrication of an auricular prosthe- method of projecting the position of vantages of this technique include
sis using rapid prototyping technol- the new ear directly onto the personal allowing scanning of the existing ear
ogy involving computer-aided design computer (PC) screen and developing without making an impression, elimi-
and computer-aided manufacturing a wax pattern that can be transferred nation of the diagnostic waxing of the
(CAD/CAM). A review of the litera- into the mold for silicone processing. lost ear for positioning onto the skin,
ture identified several reports describ- As an alternative procedure, this pro- in relation to the skull of the patient
ing the manufacture of an ear pros- tocol also allows for fabrication of and the implants, and creation of the
thesis.3-16 Laser-scanning techniques the mold. Using the negative volume mold directly from the volume of the
and CAD/CAM systems have been of the scanned and mirrored healthy mirrored ear. The disadvantages of
used to design and develop auricular ear, and virtually adapting it to the this procedure are the technical skills
prostheses.17-18 scanned defective side surface, this necessary to use CAD/CAM equip-
However, the remaining problem protocol eliminates the need to make ment and the related costs of the lab-
to be solved in terms of virtual man- an impression of the defective side oratory equipment required to cre-
Presented at the International Society of Maxillofacial Rehabilitation/American Academy of Maxillofacial Prosthetics joint meeting,
Maui, Hawaii, October 2006.
Assistant Clinical Professor of Maxillofacial Prosthetics, Section of Oral and Maxillofacial Rehabilitation, Department of Oral Sci-
ence, Alma Mater Studiorum University of Bologna.
Professor and Dean, Department of Architecture and Urban Planning, Faculty of Engineering, Alma Mater Studiorum University of
Associate Professor, Section of Oral and Maxillofacial Implant Rehabilitation, University of Turin.
Dean and Professor of Prosthodontics, Section of Oral and Maxillofacial Rehabilitation, Department of Oral Science, Alma Mater
Studiorum University of Bologna.
Ciocca et al
340 Volume 98 Issue 5
ate the 3-dimensional (3-D) model, points, each one with 3-D point co- a transfer impression (Permadyne Ga-
including the 3-D scanner and rapid ordinates. rant 2:1, 3M ESPE, Seefeld, Germany)
prototyping machine. 8. Elaborate these digitalized ear of the craniofacial implants. Then
surfaces using software (Rapidform send the cast to the laboratory for
TECHNIQUE CAD, version 2006; INUS Technology, fabrication of the bar. Fabricate the
Inc, Seoul, Korea) to recombine, align, bar with at least a 1.5-mm distance
1. Place at least two 3-mm cranio- and blend the different surfaces into between the skin and the bar and a
facial implants (Vista Fix; Cochlear a single virtual model, eliminating the maximum cantilever length of 8 mm.
Americas, Englewood, Colo) in the surface abnormalities, remeshing the 11. Use a skin adhesive (Blom-
mastoid bone and wait for 3 to 4 organization of the triangulated mesh Singer Brush-on Silicone Skin Adhe-
months prior to the stage II surgical of points, and filling in the surface sive; InHealth Technologies) to adhere
exposure procedure. gaps that remain after data elabora- the same small spherical balls onto
2. Use a laser scanner (Minolta tion. the skin around the defect (Fig. 1).
VIVID 900; Minolta Co, Osaka, Ja- 9. To merge the 3-D point clouds, 12. Connect the bar to the im-
pan) connected to a personal com- locate the same 3-D points in each plants so that it can be scanned to-
puter (Asus, Pentium 4 - 2.8; ASUS- digital image and overlap the center gether with the skin of the defective
TeK Computer Inc, Taipei, Taiwan) to of each colored spherical pin with side. Then, develop the acrylic resin
acquire the 3-D spatial coordinates of the corresponding one in the other substructure that will be included in
the healthy ear with software (Polygon angled image scans and integrate all the silicone prosthesis to retain the
Editing Tool, version 1.03; Minolta measurements. bar clips used to connect the pros-
Co). Make the first measurement af- 10. On the defect side, manufac- thesis to the bar, using a CAD/CAM
ter positioning the patient in front of ture the metal bar (Cendres & Metaux design.
the laser scanner. SA, Biel/Bienne, Switzerland) to be 13. Repeat steps 2 through 8 of this
3. Randomly position at least supported by implants prior to laser protocol on the skin of the patient to
three 2.5-mm-diameter colored balls scanning the tissue surface. First make obtain a virtual 3-D image of the de-
(Ballpin; Gruppo Buffetti SpA, Milan,
Italy) onto the healthy ear using a skin
adhesive (Blom-Singer Brush-on Sili-
cone Skin Adhesive; InHealth Tech-
nologies, Carpinteria, Calif ). Record
the volume of the external healthy ear
straight onto the skin of the patient
(without making an impression) with
the laser scanner (Minolta VIVID 900;
4. As an alternative to step 2, use a
stone cast of the healthy ear instead.
Develop a stone cast of the healthy
ear using conventional techniques.3
Randomly position the cast of the ex- 1 Pin system on defective side.
isting ear on a platform with colored
pins (Ballpin; Gruppo Buffetti SpA)
(diameter of 2.5 mm) around it, as
described by Ciocca et al.1
5. Place the patient in 4 random
positions and make 4 laser measure-
ments of the surface from different
angles to detect all undercuts.
6. Record these patterns with the
laser scanner software (Polygon Edit-
ing Tool, version 1.03; Minolta Co).
7. Represent the surface of the
scanned healthy ear with 4 clouds (the
entire number of the 3-D points rep-
resenting a volume surface) of 50,000 2 Digitalized image after laser scan of skin.
The Journal of Prosthetic Dentistry Ciocca et al
November 2007 341
fective side (Fig. 2), and develop the determine the correct position in re- 17. Virtually design, on the PC, the
final STL file of the defective side. lation to the face of the patient (Fig. acrylic resin substructure in relation
14. Mirror the 3-D image of the 3). to the bar dimensions and the mir-
healthy ear to create a pattern of the 16. Once the STL file of the exter- rored ear thickness, to obtain a sepa-
lost ear. nal ear has been developed, represent rate structure from the entire prosthe-
15. Using CAD elaboration, su- it as a negative volume and transform sis. Prototype the resin substructure
perimpose the two 3-D images of the this pattern into a new STL file for the alone (not connected with the base
healthy ear and the defective side, and mold design (Fig. 4). of the mold) and position it into the
3 Integration of external mirrored ear with laser-scanned 4 Virtual mold.
skin of defective side.
5 CAD/CAM fabrication of substructure. A, Laser-scanned bar and defective side. B, Computer-assisted design of
substructure. C, CAD of mold with separate substructure. D, CAM of mold: substructure is separate and perfectly
positioned onto prototyped bar in mold.
Ciocca et al
342 Volume 98 Issue 5
mold before silicone processing using
the scanned bar on implants in the
base of the defective side (Fig. 5).
18. Process the STL file using the
computer system (Z Printer 310; Z
Corp, Burlington, Mass) to manu-
facture the mold in a single step. Us-
ing the computer system and layers
of sealant (Z Corp Sealant; Z Corp)
with layers of resin powder (Z Corp
Powder; Z Corp), develop the entire
volume of the mold through layer-by-
19. Allow 60 minutes for the acryl-
ic resin to polymerize.
20. Extract the cast from the pow-
der and then coat the surface of the
cast with the epoxy resin (Renlam M-
1; Fuchs SpA, San Giuliano Milanese,
Italy) to further harden the mold. A
21. To correctly position the acryl-
ic resin substructure in the final mold,
use as a positional landmark the pro-
totyped bar previously scanned on
the defective side (see step 12) (Fig. 5,
D). Do this in the same manner as for
a conventional stone mold, for which
the resin substructure is positioned
onto the metal bar before process-
ing the silicone. Insert the connect-
ing structure onto the prototyped
bar, to precisely place it onto the 3-D
mold base (Fig. 6, A). Adhere it with B
an adhesive (496; Loctite Italia SpA, 6 A, Cast with processed silicone. B, Bar retainers.
22. Complete conventional sili-
cone (VST-30; Factor II, Lakeside,
Ariz) processing procedures3 to ob-
tain the definitive prosthesis, as for a
conventional stone mold processing
(Fig. 6, B).
23. Use a spectrophotometer to
determine the intrinsic color of the
ear (SpectroShade Office; MHT SpA,
24. Apply extrinsic colors (Extrin-
sic; Factor II Inc) and use silicone
adhesive (A-564; Factor II Inc) as a
sealant. Finally, apply the matting dis-
persion liquid (MD-564; Factor II Inc) 7 Definitive prosthesis.
mixed with the silicone dispersion liq-
uid (TS-564; Factor II Inc) to provide
a matte appearance to the prosthesis
The Journal of Prosthetic Dentistry Ciocca et al