Digital workflow for fabricating a verification device for all on four abutment

1. DENTAL TECHNIQUE
Digital workflow for fabricating a verification device
for an all-on-4 abutment: A dental technique
Seung-Mi Jeong, DDS, PhD,a
Young-Il Kim, DH,b
Xueyin An, DDS,c
and Byung-Ho Choi, DDS, PhDd
Immediate-loading protocols
for implant-supported pros-
theses have become a popular
approach for patients with
edentulism.1
The all-on-4
implant concept was intro-
duced to overcome anatomic
limitations and has been reported to have high success
rates.2-6
Four implants positioned between the mental
foramina provide for favorable immediate loading by
tilting the distal implant, resulting in reduced mechanical
stress in the prosthesis.7
Flapless implant surgery with a digital surgical guide
has gained popularity.8
The surgical procedure is mini-
mally invasive and straightforward, provides excellent
patient satisfaction, and reduces treatment time and
postoperative discomfort.9
Angled abutments have
usually been used for distal implants in computer-
guided flapless surgeries, with a long handle used as a
transfer device to place the abutment.10
However, the
length of the handles of the angled abutments produced
by most manufacturers is excessively long, requiring the
patient to open the mouth wide during the surgery.
Additionally, the long handle makes it difficult to place
the driver accurately from the distal side in the patient’s
mouth.
A verification device is commonly used to accurately
transfer the position of the angled distal abutment in the
edentulous patient’s mouth during computer-guided
surgery. However, the traditional verification device
needs to be fabricated on a cast, which takes time and
effort.10
With a traditional verification device, a distal
angled abutment with a hexagon connector cannot be
used because the device uses the abutment in the ante-
rior implant as a solid reference. If a substantial surgical
error does occur, a traditional verification device may lead
to the misfit of the distal angled abutment with a hexa-
gon connector.
The purpose of this technique article was to
describe a digital workflow for fabricating a verification
device to position the angled distal abutment with a
hexagon connector during computer-guided flapless
surgery.
TECHNIQUE
1. Import the scan standard tessellation language
(STL) file and the Digital Imaging and Communi-
cations in Medicine (DICOM) data acquired from
cone beam computed tomography (CBCT) into a
virtual implant planning software program (Implant
Studio; 3ShapeA/S) and merge the image of the STL
file with the DICOM data.
2. Plan the implant position preoperatively based on
the virtual alignment of teeth by using a virtual
implant planning software program (Implant Stu-
dio; 3ShapeA/S). Follow the direction of the anterior
a
Professor, Department of Dentistry, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
b
Researcher, Department of Dentistry, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
c
Graduate student, Department of Dentistry, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
d
Professor, Department of Dentistry, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
ABSTRACT
The all-on-4 implant concept has been used to overcome anatomic limitations and has been
reported to have high success rates. A verification device is commonly used to transfer the
position of the angled distal abutment accurately. This article describes a digital workflow for
fabricating a verification device to position the angled distal abutment with a hexagon
connection during computer-guided flapless surgery. (J Prosthet Dent 2020;-:---)
THE JOURNAL OF PROSTHETIC DENTISTRY 1

2. teeth and jaw anatomy for the 2 anterior implants.
Place 2 additional implants anterior to the mental
foramina, tilted distally less than 60 degrees. Adjust
the angle of the simulated angled abutment to 20 or
30 degrees (following the specifications of the
angled abutment provided by the manufacturer)
and adjust the implant position based on the
direction of the angled abutment to the optimal
position (Fig. 1). After implant planning, generate a
surgical template.
Obtain the STL file with the virtual implant position
from the implant planning software program and import
it to a denture planning software program (Dental Sys-
tem; 3ShapeA/S). Use a workaround and create a new
“order;” set the crown as “screw retained crown;” and
choose the abutment library provided by the manufac-
turer. Shape the abutment into a precylinder and
generate a crown on the abutment (Fig. 2). Place another
2 cantilever pontics anteriorly. Position the most anterior
pontic consistently with the anterior implant (Fig. 3).
Make the cantilevered pontics contact the gingiva
without pressure (Fig. 4).
3. Automatically generate a screwdriver access hole
through the crown in the same direction as the
implant and another screwdriver access hole for
which the angled abutment was generated by using
the hole function (Fig. 3).
4. Transfer the STL file of the device to the software
application of the 3D printer (DIO; 3D Printer
Probe) for printing with photopolymerized resin
(DIO; Dio navi-B&C).
5. Insert the precylinder with a sidewall opening
(Temporary Cylinder; DIO Inc) (Fig. 5) into the
coronal structure of the verification device (Fig. 6)
and connect it with the angled abutment to com-
plete the device (Fig. 7).
Figure 1. Implant position based on direction of angled abutment
adjusted to optimal position.
Figure 3. Anterior pontic crown positioned consistent with anterior
implant.
Figure 4. Bases of 2 cantilever pontic crowns contacting gingiva without
pressure.
Figure 2. Abutment shaped into precylinder and crown generated on
abutment.
2 Volume - Issue -
THE JOURNAL OF PROSTHETIC DENTISTRY Jeong et al

3. DISCUSSION
An immediate function concept for the edentulous
mandible was presented in a previous report with a
clinical follow-up (All-on-4; Nobel Biocare AB). The
protocol used a surgical guide for the positioning of 4
implants to provide favorable biomechanical prosthetic
support. Advantageous load conditions made it possible
to use an interim acrylic resin prosthesis, delivered
within 2 hours of surgery.7
The traditional verification
device, proposed by Brånemark, was used with angled
nonhexagon abutments. However, if an angled non-
hexagon abutment is used, it is difficult to reposition the
abutment when the screw is loose. In addition, it is
difficult to use a prefabricated angled abutment with a
long handle in a distally titled implant as it requires a
wide mouth opening and does not allow the driver to
place the distal implants.
The anterior abutment is used as a reference for a
traditional verification device, with no allowance for
surgical errors. If the surgical error is large, it may be
difficult to place the angled distal abutment with the
traditional verification device. The verification device
described in this article uses an anterior hole in the
mucosa as the position reference, which is generated by
using a punch drill for the anterior implant and 2
cantilever pontic crowns contacting the mucosa without
pressure, with the mucosa also providing support for the
transfer device. Contrary to the traditional verification
device with a solid reference, the new transfer device
could accommodate larger 3D surgical errors because of
the flexibility of the mucosa.
The verification device described in this article has a
driver insertion path, and the driver was inserted in
advance in the verification device. This facilitates
tightening the distal angled abutment from the distal
side of the mouth. In addition, for the immediate
loading protocol, the tightening torque of the abutment
screw is directly associated with screw loosening.11
However, when the bone quality is low, applying a
tightening torque with a torque wrench may cause the
implant to rotate and fail to obtain the required torque.
Another advantage of the verification device is that
when applying the tightening torque to the screw in a
clockwise direction, a force in the opposite direction can
be generated by holding the anterior cantilever pontic
crowns of the verification device, and the screw of the
abutment can be applied with sufficient tightening
torque by using the torque wrench.
SUMMARY
This article describes a digital workflow for fabricating a
verification device to position the angled distal abutment
with a hexagon connector during a computer-guided
flapless surgery. In this technique, the optimal position
of implants and angled abutment is preselected by using
the virtual implant planning software program. There-
fore, a cast is not needed to provide information on
implant position to fabricate the verification device, and
the whole process is performed digitally.
Figure 5. Precylinder with sidewall opening.
Figure 6. Precylinder with sidewall opening inserted into coronal
structure of verification device.
Figure 7. Verification device.
- 2020 3
Jeong et al THE JOURNAL OF PROSTHETIC DENTISTRY

4. REFERENCES
1. Bidra AS. A device to improve fabrication of a conversion prosthesis for
immediate loading of dental implants. J Prosthet Dent 2019;121:557-60.
2. Esposito M, Grusovin MG, Maghaireh H, Worthington HV. Interventions for
replacing missing teeth: different times for loading dental implants. Cochrane
Database Syst Rev 2013;28:CD003878.
3. Schnitman PA, Wöhrle PS, Rubenstein JE, DaSilva JD, Wang NH. Ten-
year results for Brånemark implants immediately loaded with fixed
prostheses at implant placement. Int J Oral Maxillofac Implants 1997;12:
495-503.
4. Balshi TJ, Wolfinger GJ. Immediate loading of Brånemark implants
in edentulous mandibles: a preliminary report. Implant Dent 1997;6:
83-8.
5. Randow K, Nilner K, Petersson A, Petersson A, Glantz PO. Immediate
functional loading of Brånemark dental implants. An l8-month clinical
follow-up study. Clin Implant Dent Relat Res 1999;10:8-15.
6. Ericsson I, Randow K, Nilner K, Peterson A. Early functional loading of
Brånemark dental implants: 5-year clinical follow-up study. Clin Implant
Dent Relat Res 2000;2:70-7.
7. Malo P, Rangert B, Nobre M. All-on-4 immediate-function concept with
Brånemark System® implants for completely edentulous maxillae: a
1-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7:
88-94.
8. Albiero AM, Quartuccio L, Benato A, Benato R. Accuracy of computer-guided
flapless implant surgery in fully edentulous arches and in edentulous arches
with fresh extraction sockets. Implant Dent 2019;28:256-64.
9. Kupeyan HK, Shaffner M, Armstrong J. Definitive CAD/CAM-guided pros-
thesis for immediate loading of bone-grafted maxilla: a case report. Clin
Implant Dent Relat Res 2006;8:161-7.
10. Jivraj S, editor. Graftless solutions for the edentulous patient. Springer:
Cham; 2018. p. 121.
11. Choi BH, Jeong SM. Digital flapless implantology. Jisung Pub Co: Seoul;
2015P151.
Corresponding author:
Dr Byung-Ho Choi
Department of Dentistry
Yonsei University Wonju College of Medicine
162 Ilsandong, Wonju
REPUBLIC OF KOREA
Email: choibh@yonsei.ac.kr
Copyright © 2020 by the Editorial Council for The Journal of Prosthetic Dentistry.
https://doi.org/10.1016/j.prosdent.2020.01.007
4 Volume - Issue -
THE JOURNAL OF PROSTHETIC DENTISTRY Jeong et al