Harold Baumgarten, DMD* • Roberto Cocchetto, DDS, MD† • Tiziano Testori, DDS, MD‡
Alan Meltzer, DMD, MScD§ • Stephan Porter, DDS, MSD, MS||
Pract Proced Aesthet Dent 2005;17(10):735-740 735
Following the exposure and restoration of two-piece dental implants, some change
in the vertical level of the peri-implant crestal bone height has been reported. This
change in crestal bone height has not, however, negatively impacted long-term
implant success. This article describes how the concept of platform switching is
incorporated into a new implant design as a means of reducing or eliminating the
occurrence of crestal bone loss. Preliminary observations from clinicians utilizing
this new implant design are herein presented.
Learning Objectives:
This article discusses an inflammatory mechanism involved in crestal bone loss
following implant restoration. Upon reading this article, the reader should:
• Be able to identify a mechanism involved in crestal bone loss following
implant exposure.
• Understand how the concept of platform switching as a means of reducing
or eliminating this occurrence is incorporated into a new implant design.
Key Words: implant, bone, resorption, platform switching
N O V E M B E R / D E C E M B E R B A U M G A R T E N
17
10
* Clinical Professor, Department of Periodontics, University of Pennsylvania, School of Dental
Medicine, Philadelphia, PA; private practice, Philadelphia, PA.
†Private practice, Verona, Italy.
‡Assistant Clinical Professor and Head of the Section of Implant Dentistry and Oral
Rehabilitation, Department of Odontology, Galeazzi Institute, Milan, Italy; private practice,
Como, Italy.
§Diplomate, American Academy of Periodontology; Associate Clinical Professor, Department
of Implant Dentistry, New York University College of Dentistry, New York, NY; private practice,
Voorhees, NJ.
||Private practice, West Palm Beach, FL, and Windsor, United Kingdom.
Harold Baumgarten, DMD,100 S. Broad Street, Philadelphia, PA 19110
Tel: 215-568-8130 • E-mail: hbaumgarten@4dentistry.com
Postrestorative reductions in crestal bone height around
endosseous dental implants have long been acknowledged
to be a normal consequence of implant therapy
involving two-stage hexed implants.1-4 Such remodeling
does not typically occur as long as the implant remains
completely submerged, but rather develops when an
abutment is connected during second-stage surgery,
when a two-stage implant is placed and connected to
an abutment in a one-stage procedure, or when an
implant is prematurely exposed to the oral environment
and bacteria.5
Research by Hermann, et al demonstrated that crestal
bone loss typically occurs approximately 2 mm apical
to the implant-abutment junction (IAJ).6 This position
appears to be constant, regardless of where the IAJ is
situated relative to the original level of the bony crest.6
The researchers also demonstrated that the addition of
a textured, bone-holding surface within 0.5 mm of the
IAJ fails to prevent bone resorption within 2 mm apical
to the IAJ.6
Investigations by various researchers offered explanations
on why the presence of the IAJ appears to trigger
resorption in the adjacent bone. Ericsson, et al found
histologic evidence of inflammatory cell infiltrate associated
with a 1-mm– to 1.5-mm–tall zone adjacent to
the IAJ.7 Berglundh and Lindhe concluded that approximately
3 mm of peri-implant mucosa is required to create
a mucosal barrier around a dental implant.8 This
suggests that crestal bone remodeling may occur to
create space when inadequate soft tissue height is present
so that a biological seal can be established, which
will isolate the crestal bone and protect it from the
oral environment.
These investigations have focused on implant
systems in which the diameter of the implant-seating
surface matches that of the abutment. This ubiquitous
design positions the abutment inflammatory cell infiltrate
in direct approximation to the crestal bone at the
time of abutment connection.
Platform Switching
The concept of “platform switching” refers to the use
of a smaller-diameter abutment on a larger-diameter
implant collar; this connection shifts the perimeter of
the IAJ inward toward the central axis (ie, the middle)
of the implant.5 Lazzara and Porter theorize that
the inward movement of the IAJ in this manner also
shifts the inflammatory cell infiltrate inward and away
from the adjacent crestal bone, which limits the bone
change that occurs around the coronal aspect.5
Crestal bone preservation has been reported on other
commercially available implant designs, purportedly
736 Vol. 17, No. 10
Practical Procedures & AESTHETIC DENTISTRY
Figure 4. Occlusal view of the sockets taken
after extraction. To avoid the risk of altering the
soft tissue profile, a flap was not reflected.
Figure 1. Diagram of the Certain Prevail implant.
Note implant body and implant collar taper to
the restorative platform for standard prosthetics.
Figure 2. Preoperative facial view of nonrestorable
fractured and carious central incisors.
Figure 3. Initial radiograph where the central
incisors had been endodontically treated and the
margins were fractured apical to the crestal bone.
attributed to microthreads at the coronal aspect of
the implant, connection designs, occlusal schemes, or
combinations thereof.9
In 1991, Implant Innovations, Inc. (3i, Palm Beach
Gardens, FL) introduced 5-mm– and 6-mm–diameter
implants with seating surfaces (ie, restorative platforms)
of the same dimensions. These large-diameter implants,
with a larger surface area, were intended to increase the
amount of bone-to-implant contact when placing shorter
implants in areas of limited bone height, such as under
the maxillary sinus or above the inferior alveolar canal.
The ability to increase the bone-to-implant contact by the
use of wide-diameter implants also enhanced the likelihood
of achieving primary stability in areas of poor-quality
bone. At the time of the wide-diameter implants’
introduction, no matching, similarly dimensioned prosthetic
components were available. Hence, clinicians
restored them with standard 4.1-mm abutments.
After a 5-year period, the typical pattern of crestal
bone resorption was not observed radiographically in
cases where platform switching was utilized. Lazzara
and Porter theorize that this occurred because shifting
the IAJ inward also repositioned the inflammatory cell
infiltrate and confined it within a 90° area that was not
directly adjacent to the crestal bone.
The ability to reduce or eliminate crestal bone loss
can result in significant aesthetic and clinical benefits.
In order to facilitate the practice of platform switching,
the Certain Prevail Implant (3i, Implant Innovations, Inc.,
Palm Beach Gardens, FL) has been developed. Its design
utilizes the Osseotite dual acid-etched surface, which
maximizes the contact of bone to implant. The performance
of the original Osseotite implant (an externalhexed,
parallel-walled, hybrid design) has been shown
in both in vitro and in vivo studies to perform differently
from machine-surfaced versions.10-14
The coronal aspect of the Certain Prevail Implant
is designed to be slightly wider than the diameter of the
straight-walled implant body, flaring out at approximately
a 30° angle and resulting in a collar diameter of 4.8 mm
(Figure 1). This expanded collar can provide better
engagement of the bone crest, better sealing of extraction
sockets, and better primary stability. The collar then
bevels back at a 15° angle to provide a color-coded
restorative platform with a diameter of 4.1 mm. Restoring
the 4.8-mm implant collar with the corresponding 4.1-
mm prosthetic component shifts the IAJ inward, moving
the inflammatory infiltrate away from the surrounding
bone. To achieve this effect and maintain adequate softtissue
depth, the implant should be placed crestally if
sufficient soft tissue height and/or interocclusal space
is present, or subcrestally if insufficient soft tissue height
and/or interocclusal space is present.
P P A D 737
Baumgarten
Figure 8. Occlusal view of implants with healing
abutments in place postoperation. The interdental
papillae were not disturbed during the surgery.
Figure 5. Clinical occlusal view of the surgical
guide in place. The planned implant placement
was identified by the holes in the surgical guide.
Figure 7. Periapical radiograph taken immediately
after implant placement. Note the vertical
height of the interimplant bone.
Figure 6. Clinical occlusal view of the implants in
place. Note that the interdental papillae were
maintained throughout the procedure.
Case Presentation
A 28-year-old male presented with nonrestorable maxillary
central incisors that had previously been treated
endodontically, and then were subsequently fractured by
trauma (Figures 2 and 3). The teeth were carefully
extracted and, with the aid of a surgical guide, two 5.0-
mm x 13-mm implants (ie, Certain Prevail, 3i, Palm Beach
Gardens, FL) were placed in a single-stage protocol
(Figures 4 through 8). The specific implant diameters and
lengths were selected by the clinician based on the size
and shape of the individual sockets. The implants were
placed in a flapless manner in order to protect the buccal
cortical plate from injury to the vascular supply, which
is often associated with a full-thickness flap. Moreover,
great care was taken to avoid touching the buccal plate
of the sockets during implant site preparation.
Healing abutments with 5-mm emergence profiles
and 4.1-mm restorative platforms were immediately placed
(Figures 9 and 10). The patient was then discharged with
antibiotic and anti-inflammatory prescriptions.
After 3 days, two 4.1-mm customizable abutments
(ie, GingiHue Posts, 3i, Palm Beach Gardens, FL), prepared
by the dental technician on the master cast were
inserted into the internal interface of the implants and
torqued to 20 Ncm (Figures 11 through 14). These titanium
abutments have a gold-nitride coating that eliminates
graying of the marginal gingival tissue. Two acrylic
provisional crowns were then luted to the abutments with
temporary cement and adjusted out-of-occlusal contact,
following the protocol of immediate nonocclusal loading
(Figure 15).15 An intraoral radiograph was taken (Figure
16), and the patient was instructed to avoid loading
the crowns for any purpose for at least eight weeks.
Gentle brushing with a toothpaste containing chlorhexidine,
was recommended.
Following a 2-month healing period (Figure 17),
clinical osseointegration was confirmed and two metalceramic
crowns were placed. The prognosis for maintenance
of the interdental papillae was excellent.
The definitive crowns were constructed on duplicate
abutments made from a surgical index at the time of
implant placement.
No additional implant-level impression procedure
was required due to the technical prosthetic protocol,
which allowed the construction of the definitive crowns
Figure 9. Radiograph of the two implants with the
4-mm–diameter healing abutments in place. Note that the
implant restorative platforms were subcrestal.
Figure 12. Two provisional crowns splinted together on the
prepared implant abutments.
Figure 10. Occlusal view of master cast with soft tissue
replicated in resilient material. The implant restorative platforms
are color coded to simplify the restorative process.
Figure 11. View of the prepared abutments on the model.
Platform switching is a design feature of the Certain
Prevail Implant.
738 Vol. 17, No. 10
Practical Procedures & AESTHETIC DENTISTRY
on a duplicated model and their subsequent delivery
chairside (Figures 18 and 19).
Discussion
Clinical observation of the bone-preserving effects of
platform switching has been ongoing for more than a
decade. This procedure has been used by a number of
clinicians successfully around the world.
The procedure requires that the “switch” be in place
from the day the implant is uncovered or exposed to the
oral cavity in either a one- or two-stage approach. It cannot
be utilized after the establishment of the biologic
width around a conventional implant-abutment interface
configuration to regain crestal bone height. Potential
applications include situations where a larger implant is
desirable, but the prosthetic space is limited, in the aesthetic
zone; where preservation of the crestal bone can
lead to improved aesthetics; and where shorter implants
must be utilized.
It is important to note that sufficient tissue depth
(approximately 3 mm or more) must be present to accommodate
an adequate biologic width. In the absence of
sufficient soft tissue, bone resorption will likely result,
regardless of the implant geometry.16-19 This sometimes
requires that the implant platform be placed below the
bone crest to obtain adequate tissue depth. Additionally,
sufficient ridge width (ie, a minimum of 6.8 mm) must be
present to accommodate the flared 4.8-mm implant collar.
Case selection and management, however, may influence
the clinical outcome and radiographic evidence of
crestal bone preservation.
While bone preservation has been observed for
some time as a result of the use of a standard-diameter
abutment on a wider-diameter implant, the potential for
confusion has existed for clinicians who have attempted
to employ this strategy while using standard components.
Laboratories and restorative dentists are accustomed to
working with matching-diameter implants and abutments.
The color-coordinated scheme of the Certain Prevail
Implant has been designed to ensure that the diameter
of the implant-seating surface and the restorative platform
of the abutment match, minimizing the possibility
of confusion at the time of component selection, dentallaboratory
processing, and prosthetic selection.
Figure 13. View of the peri-implant soft tissues and
implant restorative platforms three days after placement.
Note advanced healing of the soft tissues.
Figure 14. Facial view of the prepared abutments in place.
Their gold-colored titanium nitride coating helps to mask
the metallic color of the titanium abutments.
Figure 15. Facial view of the provisional crowns immediately
after cementation. The peri-implant soft tissues will
adapt to the provisional crown contours.
Figure 16. Radiograph at abutment connection, three days
after implant placement. The implant restorative platforms
of the abutments and implants are subcrestal.
P P A D 739
Baumgarten
Conclusion
Preliminary evidence suggests that the anticipated bone
loss that occurs around two-stage hexed implants
may be reduced or eliminated when implants are
restored with smaller-diameter abutments, a practice
termed platform-switching.5 A new implant design
has been developed that facilitates this practice,
and initial clinical observations indicate the preservation
of crestal bone results. Definitive clinical trials are
currently underway.
References
1. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The longterm
efficacy of currently used dental implants: A review and
proposed criteria of success. Int J Oral Maxillofac Impl
1986;1(1):11-25.
2. Smith DE, Zarb GA. Criteria for success of osseointegrated
endosseous implants. J Prosthet Dent 1989;62(5):567-572.
3. Bengazi F, Wennestrom JL, Lekholm U. Recession of the soft tissue
margin at oral implants: A 2-year longitudinal prospective
study. Clin Oral Implants Res 1996;7(4):303-310.
4. Morris HF, Ochi S. The influence of implant design, application,
and site on clinical performance and crestal bone: A multicenter,
multidisciplinary clinical study. Dental Implant Clinical
Research Group (Planning Committee). Implant Dent 1992;1(1):
49-55.
5. Lazzara RJ, Porter SS. Platform switching: A new concept in
implant dentistry for controlling post-restorative bone levels.
Accepted for Publication, 2006 Int J Perio Rest Dent.
6. Hermann JS, Schoolfield JD, Nummikoski PV, et al. Crestal bone
changes around titanium implants: A methodologic study comparing
linear radiographic with histometric measurements. Int J
Oral Maxollofac Impl 2001;16(4):475-485.
7. Ericsson I, Persson LG, Berglundh T, et al. Different types of inflammatory
reactions in peri-implant soft tissues. J Clin Periodontol
1995;22(3):255-261.
8. Berglundh T, Lindhe J. Dimension of the periimplant mucosa.
Biologic width revisited. J Clin Periodontol 1996;23(10):
971-973.
9. Morris HF, Winkler S, Ochi S, Kanaan A. A new implant
designed to maximize contact with trabecular bone: Survival to
18 months. J Oral Implantol 2001;27(4):164-173.
10. Lazzara RJ, Testori T, Trisi P, et al. A human histologic analysis
of Osseotite and machined surfaces using implants with two
opposing surfaces. Int J Periodont Rest Dent 1999;19:117-129.
11. Khang W, Feldman S, Hawley CE, Gunsolley J. A multicenter
study comparing DAE and machined-surfaced implants in various
bone qualities. J Periodontol 2001;72(10):1384-1390.
12. Bain CA, Weng D, Meltzer A, et al. A meta-analysis evaluating
the risk for implant failure in patients who smoke. Compend
Cont Educ Dent 2002;23(8):695-699, 702, 704.
13. Stach RM, Kohles SS. A meta-analysis examining the clinical survivability
of machined-surfaced and Osseotite implants in poorquality
bone. Implant Dent 2003;12(1):87-96.
14. Feldman S, Boitel N, Weng D, et al. Five-year survival distributions
of short-length (10 mm or less) machined-surfaced and
Osseotite implants. Clin Implant Dent Relat Res 2004;6(1):
16-23.
15. Cocchetto R, Vincenzi G. Delayed and immediate loading of
implants in the aesthetic zone: A review of treatment options.
Pract Proced Aesthet Dent 2003;15(9):691-698.
16. Todescan FF, Pustiglioni FE, Imbronito AV, et al. Influence of the
microgap in the peri-implant hard and soft tissues: A histomorphometric
study in dogs. Int J Oral Maxillofac Impl 2002:17(4):
467-472.
17. Hermann JS, Cochran DL, Nummikoski PV, Buser D. Crestal bone
changes around titanium implants. A radiographic evaluation of
unloaded nonsubmerged and submerged implants in the canine
mandible. J Periodontol 1997;68(11):1117-1130.
18. Herman J, Buser D, Schenk R, et al. Biologic width around oneand
two-piece titanium implants. A histomorphometric evaluation
of unloaded nonsubmerged and submerged implants in the
canine mandible. Clin Oral Impl Res 2001;12:559-571.
19. Gaucher H, Bentley K, Roy S, et al. A multi-centre study of
Osseotite implants supporting mandibular restorations: A 3-year
report. J Can Dent Assoc 2001;67(9):528-533.
Figure 17. Clinical view of the soft tissue healing eight
weeks after implant placement. The underlying bone supports
the interdental papillae.
Figure 19. Postoperative facial view of the definitive
restoration in place. The final crowns were splinted for
greater stability at the request of the patient, who had had
the provisionals splinted.
740 Vol. 17, No. 10
Practical Procedures & AESTHETIC DENTISTRY
Figure 18. Radiograph of the definitive restoration. Note
minimal remodeling of the interproximal bone and the
absence of bone loss relative to restorative platforms.
No hay comentarios:
Publicar un comentario