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94 Winter 2015 • Volume 30 • Number 4
Abstract
Retrievability of screw-retained restorations is a desirable clinical advantage.
However, implants planned for this type of restoration require precise place-
ment. When the long axis of an anterior implant is located toward the incisal
border or the buccal surface of the future crown, a cement-retained restoration
is normally indicated. This case report describes a new approach, in which a
screw-retained restoration is made possible when the exit of the screw channel
would normally compromise the esthetics. A newly developed abutment sys-
tem that allows alteration to the screw channel’s angulation up to 25 degrees
is introduced.
Key Words: screw-retained restoration, dental implant, angulated screw
channel, implant position, esthetic zone
AACD 2015–San Francisco is offering a “rapid-fire” lecture series featuring “The Next Generation.” Dr. Ochoa Durand will present:
Integrating Biological and Prosthetic Factors for Implant Placement in the Esthetic Zone and Dr. Stanley will discuss: The
Biomimetic Update: Biomimetic Implants & CAD/CAM Natural Restorations. Please join us on Friday, May 8, 2015, for this
event by registering at: aacd.com/registration.
Daniel Ochoa-Durand, DDS
Kyle G. Stanley, DDS
Sascha A. Jovanovic, DDS, MS
A New Approach for
Screw-Retained Restorations
Integrating Biological and Prosthetic Factors for Implant
Placement in the Esthetic Zone
5:03 pm, Feb 27, 2015
95
Journal of Cosmetic Dentistry
Ochoa Durand/Stanley/Jovanovic
96 Winter 2015 • Volume 30 • Number 4
Introduction
Dental implants in the esthetic zone remain one of
the most challenging treatment modalities. An ideal
outcome requires the establishment of optimal three-
dimensional bone-to-implant relationships and har-
mony with neighboring soft tissues.1-3 When the re-
quired mesiodistal, apico-coronal, and bucco-palatal
dimensions for implant placement are fulfilled, pre-
dictable esthetics can be achieved with either a screw-
or cement-retained restoration.4 However, the restor-
ative choice depends not only upon the clinician’s
preference but also is determined by the implant’s axis
in a sagittal view and its relationship with its future
type of restoration.5
Implants planned for screw-retained restorations
require extremely precise placement.6 The long axis of
the implant needs to be angulated in a slightly more
upright position to allow the screw channel’s exit to
be placed on the crown’s cingulum.4,7,8 However, mor-
phological changes on the alveolar ridge following a
tooth loss, coupled with the presence of a labial con-
cavity often limits the desired angulation for screw-
retained restorations in the anterior maxilla.5,9-11 Plac-
ing implants for screw-retained restorations within
the anatomical constraint can lead to the occurrence
of buccal fenestration, which may jeopardize the long-
term success of the restoration.5
When the angulation of the implant results in the
screw channel exiting from the buccal or incisal area
of the crown, a cement-retained restoration would
be indicated to preserve the esthetics of the restora-
tion. Cement-retained restorations often are preferred
due to less precision being required in surgical place-
ment, the ease of fabrication, and the familiarity of
the cementation procedures.8,12 However, difficulties
in removing excess cement and its possible sequelae
have been documented.13-15 Another drawback is the
difficulty in removing a cement-retained crown with-
out it being destroyed when complications arise and
removal of the restoration is necessary.16
The main advantage of a screw-retained restora-
tion is its retrievability without damaging the resto-
ration. Therefore, it is the preferred restoration of
choice if the desired angulation is attained.8,17 When
ideal implant axis is not achievable and cement res-
torations are to be used, several techniques have been
described to incorporate various dislodgment mecha-
nisms into the restorations.18-20 Alternatively, the use
of provisional cements that facilitate easy removal18
and the creation of location guides that allow for the
precise identification of the abutment’s screw channel
have been suggested.21-23 The use of lateral set, cross-
pinned, or lingual screws to avoid cement for the re-
tention of abutment supported crowns has also been
described.24-26 However, biological complications related to leakage of
bacteria from the crown abutment interface has been reported.27 Another
option is to use a newly developed abutment system that can alter the
screw channel’s angulation, resulting in its exit being located in an ideal
position. This is made possible with a newly designed screwdriver (Om-
nigrip, Nobel Biocare; Yorba Linda, CA) and fixation screw interface that
allows them to be able to engage up to an angulation of 25 degrees. This
case report discusses the use of this recent development, which may ex-
pand the indication range for screw-retained restorations.
Case Presentation
Guided Bone Regeneration
A 30-year-old female was referred for ridge reconstruction, placement,
and restoration of a single implant (Nobel Active NP 11.5 mm) at #9site
(Fig 1). Five months after the implant was placed simultaneously with
guided bone regeneration (GBR), it was determined that additional
hard and soft tissue augmentation procedures were required to ensure
the long-term stability of the implant and an optimal esthetic outcome
(Fig 2). GBR utilizing autogenous scrapings and xenograft (Bio-Oss,
Geistlich Pharma North America; Princeton, NJ), and resorbable col-
lagen membrane (Bio-Gide, Geistlich Pharma North America) was em-
ployed to cover the exposed implant threads and to augment the alveolar
contour (Figs 3-5). At the same appointment, an implant level impres-
sion was taken with polyvinylsiloxane impression material before flap
closure (Fig 6). Multiple connections and reconnections of abutments
have been shown to have a negative impact on marginal bone around an
implant site,28 which could lead to mid-buccal gingival recession or loss
of interdental papillae. Therefore, it was planned to deliver the definitive
abutment at the second stage, fulfilling the “one abutment, one time”
concept.29 The edentulous site was provisionalized with a fiber-reinforced
composite bridge to ensure that no transmucosal pressure was transmit-
ted to the grafted site.
Five Months Post-GBR
Five months after the GBR procedure (Fig 7), second stage surgery was
performed and the definitive zirconia abutment (Nobel Procera ASC)
was delivered and torqued to 35 Ncm. If the screw channel’s angulation
of the abutment were to follow the long axis of the implant, the available
space would be insufficient for an ideal porcelain thickness at the incisal
border of the definitive crown (Figs 8 & 9). The design of the Omnigrip
screwdriver and fixation screw interface from this abutment system al-
lows them to engage up to an off-axis angulation of 25 degrees, thereby
altering the screw channel’s angulation to an ideal position. Furthermore,
the abutment margin was designed to be located at the gingival level to
better facilitate the removal of excess cement of the definite crown.
A connective tissue graft harvested from the palate was placed into a
buccal pouch at the #9 site to optimize soft tissue contour, and a provi-
sional crown was temporarily cemented onto the abutment (Fig 10).
Implants planned for screw-retained restorations
require extremely precise placement.
97
Journal of Cosmetic Dentistry
Figure 2: Ridge contour site #9 after implant placement..
Figure 3: Bone loss around implant, #9. Figure 4: Placement of bone graft material around implant, #9.
Figure 5: Placement of barrier membrane. Figure 6: Implant level impression.
Ochoa Durand/Stanley/Jovanovic
Figure 1: Preoperative occlusal view of site #9.
98 Winter 2015 • Volume 30 • Number 4
Figure 8: Master cast with abutment.
Figure 9: Clinical screw and abutment. Figure 10: Front view of provisional restoration #9 after second stage
surgery and soft tissue grafting.
e main advantage of a screw-retained restoration is its
retrievability without damaging the restoration.
Figure 7: Fiber-reinforced composite bridge, #9.
99
Journal of Cosmetic Dentistry
After soft tissue maturation was complete and the color of
the final restorations was confirmed, an all-ceramic restoration
(IPS e.max ZirCAD/IPS e.max Ceram, Ivoclar Vivadent; Schaan,
Liechtenstein) with a screw channel exit in the palatal surface
was cemented onto the zirconia abutment. The screw channel
was then sealed with polytetrafluoroethylene tape and covered
with composite resin. Tooth #10 was also prepared to receive a
porcelain veneer to improve the harmony of the anterior teeth
(Figs 11-13). After the delivery of the restorations, final x-rays
were taken showing adequate interproximal bone height be-
tween #8 and #9. Follow up at three months demonstrated
complete papilla fill interproximally and adequate buccal soft
tissue contour (Figs 16-18).
Figure 11: Crown and veneer for #10.
Figure 12: Screwdriver for final torque of abutment.
Figure 13: Maxillary frontal view of abutment.
Figure 14: Maxillary frontal view of cemented all-ceramic
restorations.
Figure 15: Postoperative radiograph, #9.
Ochoa Durand/Stanley/Jovanovic
100 Winter 2015 • Volume 30 • Number 4
Summary
Predictable esthetics on implant-supported anterior restora-
tions can be achieved either with cement- or screw-retained
restorations. When cement-retained restorations are used, tech-
niques and methods to ease their future retrieval must be con-
sidered and planned in advance. When the esthetics are com-
promised by the screw channel’s exit, the use of the abutment
system demonstrated here may overcome this issue. Further
studies are needed to validate the long-term success of the de-
scribed implant abutment system.
Acknowledgments
The authors thank Sean Park, MDC (Gardena, CA), for his labo-
ratory work and assistance with case documentation; and Wendy
Wang, BDS (London, UK), for her revisions to the manuscript.
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Dr. Ochoa-Durand is a resident in the Implant Dentistry Depart-
ment at NYU College of Dentistry. He owns a private practice
in Lima, Peru.
Dr. Stanley is an adjunct faculty member with the Herman
Ostrow School of Dentistry of USC, Los Angeles, California. He
owns and operates a private group practice in Beverly Hills,
California.
Dr. Jovanovic is an instructor at Loma Linda University in Loma
Linda, California, and a course director at UCLA Center for
Continuing Dental Education in Los Angeles. He also is founder
and director of gIDE Global Institute for Dental Education in
Los Angeles
Disclosures:
Dr. Ochoa Durand did not report any disclosures.
Dr. Stanley receives an honorarium for lecturing from Nobel
Biocare. He did not receive any financial remuneration for co-
authoring this article.
Dr. Jovanovic is a consultant for Nobel Biocare and receives
lecture fees for some presentations. He did not receive any
financial remuneration for co-authoring this article.
An ideal outcome requires the establishment
of optimal three-dimensional bone-to-
implant relationships and harmony with
neighboring soft tissues.
