CAD/CAM

[Anonymous]

Materials used
CAD/CAM technology has used metals such as titanium and titanium alloys, and ceramics such as aluminum
oxide or zirconium oxide for the fabrication of implant
abutments (12). The higher strength of these materials,
which can be shaped only with CAD/CAM systems, has
increased the longevity of these restorations and the demand between dentists recently. Some of these products
are: CEREC 3D® (Sirona Dental Systems) (CEREC
3D), Everest® (Everest) (13) and Lava® (LAVA) (14).
CAD/CAM Custom Implant Abutments
Most implant systems offer these kind of abutments (4).
The sequence begins introducing the patient informa-E143
Med Oral Patol Oral Cir Bucal. 2009 Mar 1;14 (3):E141-5. CAD / CAM dental systems in implant
tion in the software that employs CAD/CAM technology. The laboratory technician waxes the prosthesis
over the corresponding abutment and scans it. Then
this structure is adapted to the antagonist arch and to
the emergency profile. These data are transferred to the
CAM center and the designed abutment is then milled,
adding the ceramic later (4).
Nowadays, with the exception of the internal or external
hex, the abutment structure is designed following this
method. The current CAD softwares have databases
that allow to choose the abutment, or another option is
to scan and introduce it into the software to get the desired shape. Then the designed shape can be modified
according to instructions sent with the case. The digital information is transferred to a computer-controlled
milling machine and the abutment is milled from a solid
block of titanium alloy. The milled abutment is turned
to the cast to verify the fit and shape (10).
Commercially available CAD/CAM abutments systems
Cerec® (Sirona, Patterson Dental Co., Milwaukee, WI)
is an available system that allows the milling of ceramic
restorations at the dental office. The dentist can scan
the image from the patient mouth using an optical scanner, design the ceramic restorations and mill them at
the dental office. If diagnosis is thorough and accurate,
placing the implant and doing a definitive restoration in
1 appointment can be as predictable as the traditional
2 appointment technique (15). One of the most important disadvantages is that the dentist must purchase the
scanner machine, the milling units and softwares.
Ortorp et al. (16) show that the precision of fit between
cast and CNC-milled titanium implant frameworks for
the edentulous mandible was better than structures
made in a traditional process.
Atlantis® Abutments(Atlantis Components, Inc, Cambridge, MA), milled in titanium alloy, has been commercially available since the early the 1990s.
A single impresion or implant positioning index can be
made at the time of implant surgery, or it can be made in
a second stage, when a minor modification of the abutment will be necessary so that soft tissues will be healed.
A transfer coping is attached to the implants and an index
is fabricated orienting the transfer copings to the adjacent
teeth. This is sent to the laboratory together with full-arch
impressions. The laboratory incorporates the implant
analogs into the master cast using the transfer coping and
makes measurements directly on the cast. This determines
what degree of emergence profile is needed and the length
and shape of the abutments and the margins. The image
generated can be modified according to instructions sent
with the case. The file is transferred to a computer-controlled precision milling machine and the abutment is milled
from a solid block of titanium. The milled abutments are
returned to the treatment casts to verify proper shape, contour, and occlusal clearance (10).
Atlantis provides a second duplicate abutment to give
dentists the option of placing a provisional crown on
the first abutment and a definitive crown on the second.
Ensuing tissue recession during soft tissue healing may
necessitate hand modifications of the abutment margin
before crown fabrication (2).
Procera® (Nobel Biocare, Yorba Linda, CA), initially
developed for titanium and aluminum oxide copings for
convencional crowns, has recently added implant abutments to their line of CAD/CAM components (5).The
abutment made of commercially pure titanium elimininates concerns about the use of dissimilar metals and
about interfases between machined and cast components. As for natural abutments, the luting agent, the
height and convergence angle of the abutment influence
the retention of metal doping luted on titanium CAD/
CAM abutments. Specifically for CAD/CAM titanium
Procera® abutment the most retentive cement was zincphosphate, followed by polyurethane, polyurethane plus
vaseline, and zinc oxide-eugenol (17).
The Procera® system also allowed the production of
sintered alumina and zirconia abutments, which have
provided new opportunities for single-tooth esthetic
restorations. With this system, the abutment is virtually
designed by the local laboratory using a Procera digital
scanning system and software purchased from Nobel
Biocare. The information is ellectronically transmitted to a Procera facility where the virtual abutment is
milled and returned to the local laboratory. The dentist
has the option to receive both a CAD/CAM abutment
and CAD/CAM titanium or ceramic coping using this
same system (2).
Some advantages of this technique are the possibility
of shorten the overall treatment time and the minimal
manipulation of the soft tissue (18). Heydecke et al. (19)
emphasizes the natural appearance using aluminum
oxide ceramic implant abutments and the minimal necessity of postproduction adjustments if we compare
with stock abutments. The accuracy of this system is reflected in the concept Teeth-in-an-hourTM (20) for immediate functional loading in maxilla using CAD/CAM
fixed prostheses manufactured from a block of milled
titanium through the protocol Procera Implant Bridge.
Procera abutment, after determining the precision of fit
(21), could be considered for universal application for
the most commonly used external-hexagon implant systems Branemark System (Nobel Biocare, Lifecore Restore (Lifecore Biomedical, Chaska, MN), Implant Innovations (3i) System, ImplaMed (Sterngold-IMplaMed,
Attleboro, MA) y Paragon Taper-Lock (Encino, CA).
There are some in vitro studies (22,23) which purpose
was to assess the precision at the implant interface of titanium, zirconia and alumina Procera abutments with a
hexagonal connection for single tooth restorations, suggesting Procera abutments showed less than 3 degrees of rotational freedom, what shows a stable screw joint
and may reduce the risk of screw loosening.
Encode® Restorative System (3i Implant Innovations
Inc, Palm Beach Gardes, Fla). The system consists of
a coded healing abutment and a CAD/CAM titanium
abutment. The proprietary healing abutment has three
notches that are codes that provide the information
about the implant hex position, the platform diameter,
and the soft tissue collar height, all of which are necessary to design the definitive abutment. A laser optical
scanner interprets these codes, and a custom abutment
is designed with special CAD software. The scanning
process is a white light scanner that scans the definitive casts of the healing abutment and the opposing
arch. The digital information is transformed to a solid
model. The proprietary software recognizes the codes
on the healing abutment and the designed abutment is
then milled from a solid titanium alloy block. Finally, a
cement-retained restoration is fabricated over the CAD/
CAM abutment in the dental laboratory (24).
Advantages of this system are (24): 1) it provides an anatomical emergente profile for the definitive abutment;
2) it provides the ability to correct an implant angle of
up to 30 degrees; 3) there is no need to wax or cast,
so laboratory time and cost are decreased; 4) it is easy
to use since there is an option not to make an implantlevel impression, and there is no need for intraoral abutment preparation. However, this technique does have its
disadvantages (24,25): 1) its use is limited to a specific
implant system (3i Implant Innovtions, Inc); 2) an interarch space of at least 6 mm and minimal distance of 2
mm between the implants are required; 3) ceramic abutments are not available; 4) specific mounting plates are
needed for mounting the final casts, 5) these abutments
cannot be used when there is less than 1 mm of soft tissue surrounding an implant or if one implant deviates
more than 30 degrees from other implants.
CAD/CAM surgical guides
Placement of dental implants requires precise planning that accounts for anatomic limitations and restorative goals. Diagnosis can be made with the assistance
of computerized tomographic scanning, but transfer
of planning to the surgical field is limited. Recently,
novel CAD/CAM techniques such as stereolithographic
rapid prototyping have been developed to build surgical guides in an attempt to improve precision of implant
placement (26,27). As a result of this technology, the
surgical guide permits accurate and consistent position
and orientation of the implants (28). Sarment et al. (26)
showed the advantage of this technique in a case-control study that compared the distances between planned
implants and actual osteotomies using a conventional
surgical guide or a stereolithographic surgical guide
(SurgiGuide; Materialise Medical, Glen Burnie, MD).
Using the surgical template, minimally invasive surgery
is performed without a flap, what is called transmucosal
implant placement, that shows reduced patient morbidity (29,30).
Then, the transference of the surgical planification from
the software to the patient using these guides facilitates
the production of a prostheses that will be delivered after surgery, achieving immediate functional loading to
the implants.
Conclusions
1 CAD/CAM technology applied to implant surgery allows the production of high resistance and high density
crowns, and the manufacture of implant abutments and
surgical guides.
2 A custom design, a perfect fit and a higher resistance
are the main characteristics of CAD/CAM implant abutments.
3 CAD/CAM surgical templates allow to transfer the
software planning to the surgical field.