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Screw-Retained Versus Cement-Retained Restorations: Aesthetic Zone Options

of each must be taken into consideration in treating the spe-
cific case at hand. When properly executed, either restoration
can produce a viable and predictable definitive solution for
restoring single-unit implants for most situations.
Single-Tooth Screw-Retained Restorations
(Dr. Chandur Wadhwani)
Since the introduction of the cement-retained implant resto-
ration almost 25 years ago, there has been an increase in the
number of cemented single-unit restorations, with a move away
from the screw-retained alternative. Some studies report less
than 10% of implant restorations were screw-retained in gen-
eral practice.1 Cited disadvantages of screw retention relate to
aesthetics, economics, occlusal management, and lack of sim-
plicity. Also, dentists have been using cementation as a means of
attachment of prostheses for more than 100 years, so clinicians
are familiar with these materials and techniques.2,3 However,
controversy still exists as to the most appropriate restorative
retention means. Although there is no absolute way of restor-
ing the implant, screw retention still has many attributes and,
when possible, should be considered the optimal solution.
Clinical Methods
The screw-retained implant restoration can be aesthetic,
and the occlusion is easily controlled during the laboratory
manufacturing process. The major argument against using
screw-retained restorations is dealing with the screw access
hole. The 2 clinical cases shared here (Figures 1 to 5) show how
this can be readily and predictably achieved, using materials
and techniques available to all technicians. These cases also
exemplify the ability to fabricate and deliver a screw-retained
single crown with high aesthetic value. In both instances, a
porcelain plug was fabricated using pressed ceramics, a common
procedure used by many dental laboratory teams today. The
porcelain plug and the porcelain used on the restoration can
Screw-Retained Versus
Aesthetic Zone Options
Effective Date: 01/01/17 Expiration Date: 01/01/20
Dr. Schoenbaum is an associate clinical professor
in the division of constitutive and regenerative
sciences and the director of continuing dental
education at the University of California, Los
Angeles School of Dentistry. He is also in private
practice in Los Angeles. He can be reached at
(310) 267-3380 or via email at the following
Disclosure: Dr. Schoenbaum reports no disclosures.
Dr. Wadhwani is an adjunct assistant professor
in the department of restorative dentistry at the
Loma Linda University School of Dentistry, Loma
Linda, Calif. He is also in private practice limited
to prosthodontics in Bellevue, Wash. He can be
reached at (425) 453-1117 or via email at the
following address:
Disclosure: Dr. Wadhwani is the innovations
advisor for and has received a research grant
from Nobel Biocare. He has received lecture
honoraria from Nobel Biocare, Straumann,
Zimmer Biomet, Astra, and BioHorizons.
Use of a single-unit implant is a common treatment option in
the replacement of a missing tooth in the aesthetic zone. This
article focuses on the clinical decision making involved in the
selection of the restoration type as related to retention: screw-re-
tained versus cement-retained. The screw-retained restoration
is favored due to its ease of retrievability and lack of cement
(and the potential for cement induced). The cement-retained
restoration is favored due to its aesthetics in situations with
angled implants and lower incidence of porcelain failure. Both
authors agree that there is not one solution applicable to all clinical
scenarios, and that the distinct advantages and disadvantages
About the Authors
Figure 1.
making and
cast fabrication,
the cast
the lingual
inclination of
the implant.
be etched easily with hydrofluoric acid, and then
silane applied. This allows for resin bonding of
the 2 surfaces. Colors are easy to match and resin
options are available to provide an indiscernible
margin. This technique is similar to that used with
porcelain veneers on natural teeth.
Expected Outcomes
Although there is no ideal way to restore an
implant, and the aesthetic zone presents with
more issues due to angulation of dental implants,
screw retention still provides an excellent solution.
With more control, fewer materials, and improved
peri-implant health, it should be considered the ideal
restorative option.
Advantages and Limitations
The screw-retained implant restoration is considered
the traditional method of restoring a root-form implant
restoration and has been used for more than 50 years.
With the more recent advent of single-tooth replacement
with dental implants, screw retention can be considered
the optimal solution when dealing with the attachment
of the abutment and crown to the dental implant. This
option has distinct advantages, including the following:
l Health characteristics for the soft tissues: A 3-year study
was done to compare screw-retained with cement-retained
single-implant restorations, finding that the screw-retained
restorations provided improved peri-implant soft-tissue
health as compared to their cement-retained counterparts.4
More recent systematic reviews have further confirmed the
health benefit of using screw-retained implant restorations.5
Systematic reviews have also shown there to be fewer technical
complications with screw-retained implant supported
l Minimal number of components: A single-unit, screw-retained
restoration has the benefit of using fewer components, with
more controllable delivery of the restoration. The restoration
is an integral part of the abutment that connects directly to
the implant. Provided that the delivery steps and screw-down
forces (torque value) are strictly followed, there should be
no issues with occlusion being altered by the introduction
of cement, something that can easily occur within a crown
system. This also provides for more predictable retention of the
crown, and there is no permanent versus provisional retention
l In tight interocclusal height spaces, no minimum height
is required as compared to the axial wall height minimum
required with a cement-retained restoration. There is also no
requirement to modify the abutment form to improve retention
of the crown, since it is one unit.11-13
l A screw-retained restoration provides an easy and
predictable means of retrievability of the restoration, with no
guesswork for the screw access channel site. The crown can
be readily accessed, usually without damage. The integrity of
the crown is therefore maintained, keeping its original design
and strength for long-term success. Retrievablilty also allows
easy and direct access to the implant itself, should the implant
need advanced cleaning, evaluation, or repair as a result of peri-
implant disease.5
l The ability to remove and replace the restoration easily
allows for repair and adjustment (as required), without an
increased chance of permanent damage to the abutment
during removal, which could have an economic impact for the
l Screw retention is highly desired for provisional
restorations, providing better control during the fabrication
stages of the restoration. With fewer materials and fabrication
on a cast, there is less chance for contamination of the wound
site when fixing the restoration to the implant body. This makes
for easy adjustment of the restoration to allow for soft-tissue
Screw-Retained Versus Cement-Retained Restorations
Figure 2. (a) A UCLA-type cast abutment with addition of metal and porcelain restoration
was fabricated. (b) Crown and porcelain “plug” was etched with hydrofluoric acid, then
silane was applied for adhesive bonding.
Figure 3. (a) Cast with crown and plug evident. (b) Clinical presentation after
delivery and adhesive cementation of the restoration. The plug was almost
indistinguishable from the crown, complete control of the occlusion and
aesthetics have been achieved.
Screw-Retained Versus Cement-Retained Restorations
support and contouring between appointments,
as the retrieval of the provisional is much easier
to control.
l Screw-retained crowns can be easily made
aesthetic in most sites. Angulation issues, often
related to implant placement, can be avoided
with well-planned and well-executed surgery.
In situations where angulation issues cannot be
avoided (eg, the anterior maxilla), manufacturers
have developed novel off-axial implant screw
designs. These allow for up to 30° variation from
the long axis of the implant.14-16 Also, with a
screw designed single-tooth implant restoration,
there is no separate margin for the abutment-to-
crown interface, so aesthetics can be more easily
controlled. In situations where the implant depth
is shallow, an extra margin for the crown increases
the likelihood of a poor aesthetic outcome.
l Delivery of the restoration requires only
mechanical screw-in of the crown and sealing off
the screw access channel, with no cleanup of other
materials around the implant that could damage
either the implant surface or leave material within
the soft tissues.17,18
l The screw access channel can provide a means of locating
and affixing auxiliary radiographic devices to better monitor
implant bone health with radiographs, allowing for orthogonal
images that give direct comparison to the implant site and
surrounding mineralized tissues without distortion of the
true attachment site. Studies have shown that comparison of
images that are not truly standardized can result in misleading
information, with bone changes up to 4.8 mm measured when,
in reality, there was no difference at the measurement site.19,20
Single-Tooth Cement-Retained Restorations
(Dr. Todd Schoenbaum)
The controversy of implant crown retention generally
revolves around 4 key factors: durability of the restoration,
risk of peri-implantitis, aesthetics, and cost. The situation
is further complicated, since the restoration of implants
has moved into the mainstream, where clinicians without
appropriate training are attempting to restore implants using
principles gleaned from the restoration of natural teeth. This
has inevitably presented problems, primarily with the use of
cemented restorations when cement is left behind (up to 81%
of cases of peri-implantitis have been reported to involve excess
cement).21 However, note that cement is not the only cause of
inflammation, and bone loss around implants as such problems
can also appear with non-cemented restorations.5-7,22,23
The increasing popularity of cement-retained implant
restorations (one large lab reports that more than 80% of its
single-unit implant restorations are prescribed as cement-
retained) is due to several factors, as follows. The process of
delivering a cement-retained restoration is familiar to clinicians;
superficially, it seems no different than cementing a restoration
on a natural tooth. In some cases, the surgical doctor will even
place the definitive abutment and impression components,
thus allowing the restoring doctor to avoid handling screws and
torque wrenches. Angulation of the implant toward the facial
area (more common in the aesthetic zones) creates a relative
contraindication to screw-retained restorations due to the screw
access channel exiting through the facial, where it is difficult to
cover with acceptable long-term aesthetics. Some manufacturers
have addressed this problem with the use of special screws and
drivers that allow screw retention with up to 25° of angulation
correction with a screw access through the palatal.16 Traditional
cast gold screw-retained restorations have also decreased in
popularity due to the increasing (and volatile) cost of gold. Not
only do such restorations tend to be more expensive, but the
cost of gold presents very real and practical challenges for the
restoring clinician. Additionally, with the decreasing num ber of
Figure 4. (a) Molar restoration with the access site ideally located in center of occlusion
(rubber dam was used). (b) Plug, with red orientation mark on wax holder, ready for delivery.
Figure 5. (a) Crown delivered; note orientation mark that helped to locate plug. (b) Com-
pleted restoration. Occlusion controlled in laboratory, and high aesthetics for a screw-re-
tained restoration.
Screw-Retained Versus Cement-Retained Restorations
proper lab technician training programs, there are increasingly
fewer and fewer dental technicians who have been trained in the
fabrication of a cast screw-retained crown.24
Clinical Methods
Much of the reported problems with residual cement can
be managed by strictly following a few simple clinical
parameters: cement margins placed no deeper than 1.0 mm
subgingivally; presence of a robust and mature band of at least
2 mm of keratinized tissue; coating the emergence profile of
the abutment with petroleum jelly; and, the judicious use of a
semi-soluble cement.
l Margin placement: Margin position is the biggest
factor in controlling cement excess. Most implant systems
have various stock abutments to chose from, or custom
milled options are available. Selection of the abutment is
commonly, and mistakenly, done by opting for an abutment
that will be significantly below the gingiva in the mid-facial
area. This approach is problematic because, in partially
edentulous cases, the papilla is usually at least 3.0 mm higher
(Figure 6). Most stock abutments, even anatomically shaped
versions, are insufficient in compensating for this discrepancy.
This may result in a cement margin more than 4.0 mm deep
(subgingival) at the papilla, which is likely to result in retained
cement in the hands of even the most dedicated and skilled
clinicians. This problem is quite easily addressed through the
use of custom-milled abutments that allow the clinician to
prescribe how deep the margin is to be placed. Furthermore, the
use of a custom-milled zirconia abutment may allow the margins
to be placed in equigingival or even supragingival positions
(Figure 7). A balance must be struck between aesthetics and
the risk of retained cement. A clear correlation has been shown
between the depth of the margin and the amount of retained
cement.18 There is no biological or functional rationale for
placing margins subgingivally.
l Mature, robust gingiva: The peri-implant gingiva is a more
fragile structure compared to that around the natural dentition,
largely due to the lack of fiber insertion into the root surface.25
Figure 6. Stock abutments rarely meet
the aesthetic and biologic requirements
for cemented restorations in the aesthetic
zone. Commonly, the mesial and distal
margins are too deep (> 1.0 mm)
subgingivally to allow the clinician to ade-
quately remove any excess cement.
Figure 7. (a) Custom-milled zirconia abutments allow the clinician to prescribe margins that
are equigingival. (b) This allows a crown to be cemented with little danger of aesthetic
complications and minimal risk of cement induced peri-implantitis. (c) Cement was easily
removed from the equigingival/supragingival margins.
Figure 8. Cemented restorations should
only be utilized when a sufficient band
(> 2.0 mm) of mature, keratinized tissue
is present around the implant.
Figure 9. Petroleum jelly should be applied
to the emergence zone of the implant prior
to placement. This will help to ensure that
no cement is retained on the abutment
Figure 10. The challenge of locating the
screw access on cemented implant crowns
is easily mitigated by having the technician
place an opaque marker indicating the
location to drill, should the prosthesis need
to be removed at a future date.
Screw-Retained Versus Cement-Retained Restorations
Concern Screw-Retained Cement-Retained
Risk of
Advantage: Without any chance of residual cement,
the screw-retained restoration has not shown the
same levels of peri-implantitis.
Disadvantage: Cement left on the emergence of the abut-
ment is a significant cause of peri-implantitis. There is no
risk for this etiology with screw-retained restorations.
Porcelain Fracture30-32 Disadvantage: Due to the presence of an access
hole through the restoration, screw-retained PFM
restorations are weaker and more prone to fracture.
Advantage: Cemented implant crowns have shown
significantly less porcelain failure (4%) compared to
screw-retained (38%) at 5 years.
Ease of Retrieval33,34 Advantage: The screw channel is generally easily
identified and accessed should the restoration need
to be removed.
Disadvantage: Cement-retained restorations are more
difficult to retrieve because they require the clinician to
determine the approximate location of the screw access
and drill through porcelain rather than composite.
Screw Loosening5-7,22,23 Disadvantage: Many studies have shown an
increased propensity for screw loosening, the cause
of which is likely multifactorial and dependent on the
laboratory selection of components and handling.
Advantage: Abutment screw loosening has been shown to
be 6 times lower with cemented, single-unit implant crowns.
Loss of the
Disadvantage: Along with increased incidence of
loose screws, the crown is more likely to be lost.
Advantage: Crown loss has been shown to be 3 times lower
with cemented, single-unit implant crowns.
Interocclusal Distance
Advantage: Limited interocclusal distances can be
more readily restored with a screw-retained resto-
ration, though this is a complication generally best
resolved by improved implant placement or alter-
ation of the opposing dentition.
Disadvantage: Screw-retained restorations can be fabricated
in smaller interocclusal distances than that required for a
cement-retained restoration.
Aesthetics Disadvantage: The screw-retained restoration is
generally more difficult for the technician to create a
high level of aesthetics, particularly when adjacent
to other tooth-borne restorations.
Advantage: Most technicians can produce a more aesthetic
outcome with a cement-retained restoration. Additionally,
there is no screw access hole cover, which some find to be
aesthetically objectionable.
Angulation Correction Disadvantage: Though not a functional or biological
concern, implant angulations that have the screw
access through the facial surface are generally best
restored with a cemented restoration for aesthetic
reasons. New (and mostly untested) screw-retained
solutions do allow for angulation correction.
Advantage: Implants placed in the aesthetic zone
sometimes are angled toward the facial, which results
in a relative contradiction to screw-retained restorations
due to the access exiting through the facial surface of
the crown. Cement-retained restorations can resolve this
aesthetic issue.
Lab Costs Disadvantage: Screw-retained PFM restorations gen-
erally are the most expensive, and their costs fluc-
tuate with the costs of alloys. Future developments
with non-noble alloys and zirconia may mitigate this
Advantage: Lab costs for custom-milled abutments and
cemented implant restorations are constant and signifi-
cantly less than a cast gold alloy PFM restoration. They are
also not subject to short-term fluctuations in the cost of the
Table. Advantages and Limitations (For Single-Unit Implant Crowns)
Screw-Retained Versus Cement-Retained Restorations
No such connection exists with implants, and at best, a tenuous
hemi-desmosomal attachment has been found in some cases.
Largely, the fiber orientation around an implant is circular in
nature.26 This fibrous o-ring bundle around implants requires
sufficient time to develop and mature into a more dense and
robust configuration. When present, the o-ring helps to pro-
vide a barrier against the hydrostatic pressure of the cement. As
a general guideline, at least 2 mm of mature, robust, keratinized
tissue should be present when selecting a cemented implant
restoration (Figure 8). When the peri-implant tissue is imma-
ture or is lacking in keratinization, this seal is easily breached
by the cement. Such scenarios should be addressed through
soft-tissue augmentation, use of a screw-retained restoration,
or supragingival cement margins.
l Coating the abutment: The emergence profile of the abutment
should be coated with a separating medium prior to insertion
(Figure 9). Petroleum jelly (such as Vasoline) is applied circum-
ferentially to this area of the abutment in an effort to minimize
the adhesion of cement to this area. Some cements (many resin
cements) have a natural affinity for bonding to titanium and zir-
conia, which is good for retention of the restoration, but increases
the potential for cement-induced peri-implantitis.
l Judicious use of semi-soluble cements: The amount of cement
placed in the intaglio of the restoration should be kept to a
minimum. Various techniques have been developed to ensure
this. The most sophisticated of these techniques involves the
creation of a vinyl polysiloxane (VPS) analog replica onto
which the cement-filled crown is placed, then the excess
cement is removed, thus leaving only a bare minimum volume
of cement inside.27 Alternatively, cement can be brushed into
the restoration in a thin layer.28 The cement chosen should also
be semi-soluble in the oral environment, allowing any resid-
ual cement to be dissolved throughout time. The most soluble
cements are zinc oxide eugenol (ZOE)-based (such as Temp-
Bond [Kerr]) while the least soluble cements are resin-based.
Glass ionomer and resin-modified glass ionomer cements are
of moderate solubility.
Expected Outcomes
Cement-induced peri-implantitis is an avoidable problem.
There are significant advantages (Table) to the use of a cemented
implant restoration, so its use should not be dismissed outright.
By following the above criteria, this popular and effective resto-
ration can be utilized with minimal risks and predictable out-
comes. There is no “one-solution-for-all” implant restoration option in
the aesthetic zone, but through the stringent adherence to proper
clinical protocols, any significant risk can be mitigated.22
Cemented implant restorations for single units have been
well documented to be significantly less prone to porcelain fail-
ure, screw loosening, and loss of the crown.5-7,22,23 It has also been
shown that for single-unit implant crowns, rates of implant loss
and bone loss greater than 2.0 mm are equivalent between screw-
and cement-retained restorations. Instances of peri-implantitis
vary markedly between papers. This is due to a lack of a cohesive
standard on what is and is not peri-implantitis-retained subgin-
gival cement. This is clearly an etiological factor in inflammation
around implants; however, so too are porosity of castings or lay-
ered porcelains, loose abutments, and poor fitting castings. One
histological study looked at bone loss around various abutment
materials, concluding that full-cast gold restorations produced
more than 1.0 mm more bone and soft-tissue loss as compared to
titanium.29 However, when a casting was made onto a titanium
interface (rather than a casting that formed the interface), the
loss was insignificant. This is likely due to the presence of greater
gaps and roughness in a fully cast interface, rather than the gold
alloy itself. This illustrates the importance of a precision fit at the
implant-abutment junction. Unfortunately, this is a lab issue
and something out of the control of the clinician. Most dental
lab technicians are using the appropriate components provided
by the manufacturer with a titanium insert, but some attempt to
save on the cost of components by skipping this part and casting
the interface in its entirety, or they sometimes improperly divest
the casting with abrasive blasting techniques, which damage the
abutment interface.
Porcelain fracture is arguably a minor complication in
implant dentistry, but with some studies showing as much as
38% porcelain failure at 5 years for screw-retained restorations
versus 4% for cement-retained,30 it can become a very real bur-
den on the restoring clinician. Nevertheless, a crown with a hole
through it is significantly less durable, no matter the material,
than one with an intact surface.31,32 The risk of porcelain fracture
can depend in large part on the skill and knowledge of the dental
technician who designs the framework and applies the layering
porcelain. However, it is difficult to know how this can be quan-
tified preoperatively, especially when labs often have multiple
technicians. Alternatively, cemented restorations can be fabri-
cated with newer “enhanced” porcelains (such as lithium disili-
cate) that have very consistent and reliable strength and fracture
toughness values.
Much is often made of the fact that screw-retained resto-
rations are “retrievable,” while cement-retained restorations are
not. To retrieve a screw-retained restoration, one simply identi-
fies the screw access cover (usually a discolored composite), drills
through it, removes the screw cover material, and unscrews the
Screw-Retained Versus Cement-Retained Restorations
restoration. For cement-retained restorations, the process is iden-
tical with 2 minor caveats: the location to drill is not obvious,
and it will be porcelain, not a composite resin, that will be drilled
through.33 In most situations, the location of the screw access
can be identified with radiographs and a basic understanding of
implant angulation. During fabrication of the restoration, the
location of this access can also be marked with an opaque por-
celain stain (Figure 10).34 Once the location is identified, drilling
through porcelain to gain access is only slightly more time con-
suming (depending on the material).F
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... 5 TABLO 1: Siman tutuculu ve vida tutuculu implant destekli protezlerin avantaj ve dezavantajları. 7,11 lan simanlar ile ilgili birçok çalışma olmasına rağmen implant destekli restorasyonlarda simanların metal veya seramik abutmentlara bağlanmasıyla ilgili çalışmalar sı- nırlıdır. İmplantüstü protezlerin simantasyonunda kul- lanılacak simanın tercihi ile ilgili yapılan çalışmalarda, araştırma protokollerinde ve kullanılan sistemlerdeki farklılıklar nedeniyle birbiriyle çelişkili sonuçlar elde edilmiştir. ...
... Hekimler kişiye özel abutmentlar sayesinde protezin bitim sınırlarını istedik- leri gibi ayarlayabilirler. 7 Daimi simanlar arasında seçim yapılırken, artık si- manın uzaklaştırılmasının kolay olması ve Ti abutment- ların da hasar görmemesi dikkate alınmalıdır. Yapılan bir çalışmaya göre simanların temizlenme sırası en ko- laydan en zora çinko fosfat, cam iyonomer ve rezin si- manlar şeklindedir. ...
... yerleştirmeden önce abutment çıkış profilinin ol- duğu bölgeye vazelin uygulanmasının abutment yüze- yinde herhangi bir siman artığı kalmamasına yardımcı olacağını bildirmiştir. 7 Retraksiyon ipleri artık simanın implant çevresin- deki bölgelere kaçmasına engel olmak için kullanılabilir. Fakat simanın iplere yapışabileceği ve bunu temizleme- nin de zorluklara sebep olabileceği unutulmamalıdır. ...
Cement-retained implant-supported fixed prostheses are widely used for restoring missing teeth in the last 20 years. In comparison to screw-retained restorations, cement-retained implant- supported prostheses show some complications, such as difficulty in retrieving the restoration and biocompatibility of cement. For that reason, the clinicians should consider several important factors when using cement-retained restorations. It is clear that there are insufficient guidelines based on evidence-based clinical data to recommend a certain type of cement when restoring implant supported prostheses. Therefore, biocompatibility and radiographic characterics of the cement, retrievability of prosthesis and residual cement formation must be taken into consideration when selecting appropriate cement. In addition, cement-retained implant supported prosthesis require more attention to the removal of excess cement so that any associated peri-implant complications can be avoided. Siman tutuculu implant destekli sabit protezler, son yirmi yıldır dişsiz bölgelerin tedavisinde yaygın olarak kullanılmaktadır. Siman tutuculu implant destekli protezlerde vida tutuculu restorasyonlara kıyasla, restorasyonun ilk haline geri getirilmesindeki zorluklar ve simanın biyouyumluluğu gibi bazı sorunlar görülmektedir. Bu nedenle, klinisyenler siman tutuculu restorasyonları kullanırken bazı önemli faktörleri dikkate almalıdır. İmplant destekli protezlerin simantasyonunda belirli bir simanı önermek için kanıta dayalı klinik verilerin yetersiz olduğu görülmektedir. Bu nedenle, uygun siman seçiminde, simanın biyouyumluluğu, radyografik özellikleri, protezin ilk haline geri getirilebilmesi ve artık siman oluşumu dikkate alınmalıdır. Ayrıca, siman tutuculu implant destekli protezlerde artık simanın uzaklaştırılması esnasında çok daha titiz çalışılması implant çevresinde oluşabilecek komplikasyonların önlenmesi açısından da önemlidir.
Full-text available
The esthetic outcome of implant-supported restorations is affected by the implant position. A well-placed implant will allow appropriate contours of the restoration and together with an adequate volume of soft tissue will result in a functional and esthetic restoration. When a screw-retained restoration is anticipated, an implant that is angled too far facially would be esthetically unacceptable. In 2004, an abutment called the Dynamic Abutment (Talladium International Implantology) became commercially available. This abutment can allow a deviation of the restoration screw access angle to the implant angle of up to 28 degrees while allowing a screw-retained restoration to be connected directly to the platform of the implant. The purpose of this article was to describe the components, technique, and clinical use of this abutment. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
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Purpose: To assess the survival outcomes and reported complications of screw- and cement-retained fixed reconstructions supported on dental implants. Materials and methods: A Medline (PubMed), Embase, and Cochrane electronic database search from 2000 to September 2012 using MeSH and free-text terms was conducted. Selected inclusion and exclusion criteria guided the search. All studies were first reviewed by abstract and subsequently by full-text reading by two examiners independently. Data were extracted by two examiners and statistically analyzed using a random effects Poisson regression. Results: From 4,324 abstracts, 321 full-text articles were reviewed. Seventy-three articles were found to qualify for inclusion. Five-year survival rates of 96.03% (95% confidence interval [CI]: 93.85% to 97.43%) and 95.55% (95% CI: 92.96% to 97.19%) were calculated for cemented and screw-retained reconstructions, respectively (P = .69). Comparison of cement and screw retention showed no difference when grouped as single crowns (I-SC) (P = .10) or fixed partial dentures (I-FDP) (P = .49). The 5-year survival rate for screw-retained full-arch reconstructions was 96.71% (95% CI: 93.66% to 98.31). All-ceramic reconstruction material exhibited a significantly higher failure rate than porcelain-fused-to-metal (PFM) in cemented reconstructions (P = .01) but not when comparing screw-retained reconstructions (P = .66). Technical and biologic complications demonstrating a statistically significant difference included loss of retention (P ≤ .01), abutment loosening (P ≤ .01), porcelain fracture and/or chipping (P = .02), presence of fistula/suppuration (P ≤ .001), total technical events (P = .03), and total biologic events (P = .02). Conclusions: Although no statistical difference was found between cement- and screw-retained reconstructions for survival or failure rates, screw-retained reconstructions exhibited fewer technical and biologic complications overall. There were no statistically significant differences between the failure rates of the different reconstruction types (I-SCs, I-FDPs, full-arch I-FDPs) or abutment materials (titanium, gold, ceramic). The failure rate of cemented reconstructions was not influenced by the choice of a specific cement, though cement type did influence loss of retention.
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As the popularity of cement-retained implant prosthetics grows, so, too, does the need for retreatment. The predictable removal of cement-retained implant crowns has often proven difficult due to a multitude of variables, including locating the access and stripped screws. The techniques discussed in this article address these issues, thus simplifying the retreatment process.
Dental implant restorations may be either screw-retained or cemented onto an abutment. While each method has its advantages and disadvantages, cemented restorations are commonly used in the maxillary arch, usually because of esthetic concerns. Available bone in the anterior maxilla dictates the placement of the implant, which may result in a facially positioned screw-access opening. Still, a growing volume of literature states that periimplant soft tissues respond more favorably to screw-retained crowns than cement-retained crowns. This clinical report outlines a treatment with a new method of fabricating a custom abutment-crown combination for a screw-retained restoration. The technique allows the channel for the screw to be placed at an angle other than parallel to the implant body. In this case, the practitioner may choose either a screw-retained or cement-retained implant restoration, where previously only a cemented restoration was possible.
Purpose: To identify the influence of fixed prosthesis type on biologic and technical complication rates in the context of screw versus cement retention. Furthermore, a multivariate analysis was conducted to determine which factors, when considered together, influence the complication and failure rates of fixed implant-supported prostheses. Materials and methods: Electronic searches of MEDLINE (PubMed), EMBASE, and the Cochrane Library were conducted. Selected inclusion and exclusion criteria were used to limit the search. Data were analyzed statistically with simple and multivariate random-effects Poisson regressions. Results: Seventy-three articles qualified for inclusion in the study. Screw-retained prostheses showed a tendency toward and significantly more technical complications than cemented prostheses with single crowns and fixed partial prostheses, respectively. Resin chipping and ceramic veneer chipping had high mean event rates, at 10.04 and 8.95 per 100 years, respectively, for full-arch screwed prostheses. For "all fixed prostheses" (prosthesis type not reported or not known), significantly fewer biologic and technical complications were seen with screw retention. Multivariate analysis revealed a significantly greater incidence of technical complications with cemented prostheses. Full-arch prostheses, cantilevered prostheses, and "all fixed prostheses" had significantly higher complication rates than single crowns. A significantly greater incidence of technical and biologic complications was seen with cemented prostheses. Conclusion: Screw-retained fixed partial prostheses demonstrated a significantly higher rate of technical complications and screw-retained full-arch prostheses demonstrated a notably high rate of veneer chipping. When "all fixed prostheses" were considered, significantly higher rates of technical and biologic complications were seen for cement-retained prostheses. Multivariate Poisson regression analysis failed to show a significant difference between screw- and cement-retained prostheses with respect to the incidence of failure but demonstrated a higher rate of technical and biologic complications for cement-retained prostheses. The incidence of technical complications was more dependent upon prosthesis and retention type than prosthesis or abutment material.
Purpose: The probability of survival of implant-supported prostheses may be affected by the interplay between different implant diameters supporting screwed or cemented crowns. The purpose of this study was to investigate the effect of implant diameter and prosthesis retention system on the reliability and failure modes of single crowns. Materials and methods: Internal-hexagon implants were divided into six groups (n = 21 each) according to implant diameter (3.3, 4.0, or 5.0 mm) and crown retention system (screwed or cemented). Abutments were torqued to the implants, and crowns were then fixed and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for missions of 50,000 cycles at 100, 150, and 200 N were calculated. Failure analysis was performed. Results: Cemented systems presented higher reliability than screwed ones, except between 3.3-mm-diameter cemented and screwed systems at a load of 100 or 150 N. Failure modes were restricted to the abutment screw and varied with implant diameter only in the cement-retained groups. Conclusion: Higher reliability was observed for cement-retained crowns and implants of larger diameter compared to screw-retained and smaller diameter. Failure modes differed between groups.
OBJECTIVE: The purpose of this prospective clinical study was to evaluate peri-implant soft-tissue conditions and esthetic fulfillment during a 3-year follow-up period following prosthetic rehabilitation. MATERIAL AND METHODS: As part of a prospective multi-center study, 152 ITI dental implants were placed in 80 patients in the maxillary anterior region. Fifty-nine crowns (38.82%) were cement retained, while 93 (61.18%) crowns were screw retained. At loading and 3, 6, 12 and 36 months post-loading, modified plaque index (MPI), sulcus bleeding index (SBI), keratinized mucosa (KM), gingival level (GL), and esthetic fulfillment were recorded. RESULTS: All patients completed the study and no complications were reported. While statistically not significant at all time points, cement-retained crowns seemed to present a worsening trend in MPI and SBI scores. Interestingly, screw-retained crowns seemed to present an opposite picture, their MPI and SBI scores improved over time. While plaque accumulation, prophylaxis and depth of crown margin significantly affected levels of sulcus bleeding, prophylaxis alone played a key role in reducing plaque accumulation. No soft tissue recession was observed in either cement-or screw-retained crowns up to 3 years post-loading. Esthetic fulfillment survey revealed that patients did not have a preference for crown types; however, dentists favored cement-retained over screw-retained crowns.
Objectives: The authors conducted a study to determine the types, outcomes, risk factors and esthetic assessment of implants and their restorations placed in the general practices of a practice-based research network. Methods: All patients who visited network practices three to five years previously and underwent placement of an implant and restoration within the practice were invited to enroll. Practitioner-investigators (P-Is) recorded the status of the implant and restoration, characteristics of the implant site and restoration, presence of peri-implant pathology and an esthetic assessment by the P-I and patient. The P-Is classified implants as failures if the original implant was missing or had been replaced, the implant was mobile or elicited pain on percussion, there was overt clinical or radiographic evidence of pathology or excessive bone loss (> 0.2 millimeter per year after an initial bone loss of 2 mm). They classified restorations as failures if they had been replaced or if there was abutment or restoration fracture. Results: The authors enrolled 922 implants and patients from 87 practices, with a mean (standard deviation) follow-up of 4.2 (0.6) years. Of the 920 implants for which complete data records were available, 64 (7.0 percent) were classified as failures when excessive bone loss was excluded from the analysis. When excessive bone loss was included, 172 implants (18.7 percent) were classified as failures. According to the results of univariate analysis, a history of severe periodontitis, sites with preexisting inflammation or type IV bone, cases of immediate implant placement and placement in the incisor or canine region were associated with implant failure. According to the results of multivariate analysis, sites with preexisting inflammation (odds ratio [OR] = 2.17; 95 percent confidence interval [CI], 1.41-3.34]) or type IV bone (OR = 1.99; 95 percent CI, 1.12-3.55) were associated with a greater risk of implant failure. Of the 908 surviving implants, 20 (2.2 percent) had restorations replaced or judged as needing to be replaced. The majority of P-Is and patients were satisfied with the esthetic outcomes for both the implant and restoration. Conclusions: These results suggest that implant survival and success rates in general dental practices may be lower than those reported in studies conducted in academic or specialty settings. Practical implications: The results of this study, generated in the private general practice setting, add to the evidence base to facilitate implant treatment planning.
The effect of managing the screw access channels of zirconia implant abutments in the esthetic zone has not been extensively evaluated. The purpose of this study was to determine the effect of an insert placed within the screw access channel of an anterior zirconia implant abutment on the amount of cement retained within the restoration-abutment system and on the dislodging force. Thirty-six paired zirconia abutments and restorations were fabricated by computer-aided design and computer-aided manufacturing and were divided into 3 groups: open abutment, with the screw access channel unfilled; closed abutment, with the screw access channel sealed; and insert abutment, with a thin, tubular metal insert projection continuous with the screw head and placed into the abutment screw access channel. The restorations were cemented to the abutments with preweighed eugenol-free zinc oxide cement (TempBond NE). Excess cement was removed, and the weight of the cement that remained in the restoration-abutment system was measured. Vertical tensile dislodging forces were recorded at a crosshead speed of 5 mm/min after incubation in a 37°C water bath for 24 hours. The specimens were examined for the cement flow pattern into the screw access channel after dislodgement. Data were analyzed with ANOVA, followed by multiple comparisons by using the Tukey honestly significant difference test (α=.05). The mean (standard deviation) of retentive force values ranged from 108.1 ±29.9 N to 148.3 ±21.0 N. The retentive force values differed significantly between the insert abutment and both the open abutment (P<.05) and closed abutment groups (P<.01). Distinct patterns of cement failure were noted. The weight of the cement that remained in the system differed significantly, with both open abutment and insert abutment being greater than closed abutment (P<.05). Modifying the internal configuration of the screw access channel of an esthetic zirconia implant abutment with a metal insert significantly affected both the cement retained within the abutment itself and the retention capabilities of the zirconia restoration cemented with TempBond NE cement.
A radiograph positioning device was developed to fit with commercially available film holders and implant systems. The device is indexed to the dental implant body and the adjacent dentition by using an implant placement driver and polyvinyl siloxane occlusal registration material. By fitting the device to a conventional film holder, accurate orthogonal radiographs can monitor changes in bone architecture and prosthetic misfit. © 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.