Generic Root Form
Component Terminology
CHAPTER
Carl E. Misch
3
A
n endosteal implant is an alloplastic material surgically inserted into a residual bony ridge primarily as
a prosthodontic foundation.1 The prefix endo means
“within,” and osteal means “bone.”2 The major subcategory of
endosteal implants covered in this text are root form implants.
The term endosseous also is used in the literature. Because the
term osseous also indicates bone, either term is acceptable.
However, endosteal, periosteal, and transosteal are preferred.
Root form implants are the design most often used in
restoration of the partial or completely edentulous patient.
The desire has always been to replace missing teeth with
something similar to a tooth. Root form implant history
dates back thousands of years and includes civilizations
such as the ancient Chinese, who 4000 years ago carved
bamboo sticks the shape of pegs and drove them into the
bone for fixed tooth replacement. The Egyptians, 2000 years
ago, used precious metals in a similar method, and a skull
was found in Europe with a ferrous metal tooth inserted
into a skull in similar fashion. Incas from Central America
took pieces of sea shells and tapped them into the bone to
replace missing teeth3 (Fig. 3-1). In other words, to replace
a tooth with an implant has always made sense. In reality,
if the lay public was given a choice to replace a missing
tooth with an implant or to grind down several adjacent
teeth and connect them to a bridge to replace a missing
tooth, making it harder to clean, and attempting to make
the adjacent teeth look similar to the condition before their
preparation, the implant would be the obvious choice.
Maggiolo4 introduced the more recent history of implant
dentistry in 1809 using gold in the shape of a tooth root. In
1887 Harris5 reported the use of teeth made of porcelain into
which lead-coated platinum posts were fitted. Many materials
were tested, and in the early 1900s Lambotte6 fabricated
implants of aluminum, silver, brass, red copper, magnesium,
gold, and soft steel plated with gold and nickel. He identified the corrosion of several of these metals in body tissues
related to electrolytic action. The first root form design that
differed significantly from the shape of a tooth root was the
Greenfield latticed-cage design in 1909, made of iridoplatinum.7 The surgery was designed to use a calibrated
trephine bur to maintain an inner core of bone within the
implant. The implant crown was connected to the implant
body with an internal attachment after several weeks.
Reports indicate this implant had a modicum of success.
32
Surgical cobalt chromium molybdenum alloy was introduced to oral implantology in 1938 by Strock8 when he
replaced a maxillary left incisor single tooth, an implant
that lasted more than 15 years. In 1946 Strock designed a
two-stage screw implant that was inserted without a permucosal post. The abutment post and individual crown
were added after complete healing.9 The desired implant
interface at this time was described as ankylosis, which may
be equated to the clinical term rigid fixation. The first submerged implant placed by Strock was still functioning
40 years later10 (Fig. 3-2).
Bone fusing to titanium was first reported in 1940 by
Bothe et al.11 Brånemark12 began extensive experimental
studies in 1952 on the microscopic circulation of bone marrow healing. These studies led to dental implant application
in early 1960; 10-year implant integration was established in
Figure 3-1
Implant dentistry is the second oldest discipline
in dentistry (oral surgery [exodontia] is the oldest). Implants date
back more than 4000 years, when the Chinese carved bamboo
stakes and hammered them into the bone for fixed tooth replacement. This mandible, dated AD 600, was found in Honduras. Inca
Indians carved sea shells into stakes and tapped them into the
bone, such as this jaw with three incisors implanted. Calculus formation on these three implants indicate this was not a burial ceremony, but a fixed, functional, and esthetic tooth replacement.
Generic Root Form Component Terminology
Figure 3-2
Al Strock, from Boston, Mass., invented a series
of two-stage endosteal implants in 1948. This patient received one
of these implants to replace a maxillary lateral incisor. The patient
presented in 1986 with the implant still in function 38 years later.
dogs without significant adverse reactions to hard or soft tissues. Studies in human beings began in 1965, were followed
for 10 years, and were reported in 1977. Osseointegration, as
first defined by Brånemark, denotes at least some direct contact of living bone with the surface of an implant at the light
microscopic level of magnification.13 The percentage of
direct bone-implant contact varies. The term osseointegration
has become a common term in the implant discipline,
which describes not only a microscopic condition but also a
clinical condition. A more generic term, osteointegration also
is used widely by the profession. To determine true osteointegration by the original definition, the implant must be
removed and evaluated under a microscope. In reality, rigid
fixation defines the clinical aspect of this microscopic bone
contact with an implant and is the absence of mobility with
1 to 500 g force applied in a vertical or horizontal direction.
Rigid fixation is the clinical result of a direct bone interface
but also has been reported with a fibrous tissue interface.
No other person in recent history has influenced root
form implant concepts more than Brånemark. The documentation of past clinical case studies, research of surgery
and bone physiology, healing of soft and hard tissues, and
restorative applications from Brånemark’s laboratory were
unprecedented. Adell et al.13 published their 15-year clinical
case series report in 1981 on the use of implants in completely edentulous jaws. About 90% of the reported anterior
mandibular implants that were in the mouths of patients
after the first year were still in function 5 to 12 years later.
However, lower survival rates were observed in the anterior
maxilla. No implants were inserted into the posterior
regions of the mouth in the original clinical trials.
The use of dental implants to treat complete and partial
edentulism has become an integral treatment modality in
restorative dentistry.14-17 A 1990 survey indicated more than
90% of oral and maxillofacial surgeons, periodontists, and
prosthodontists and more than 50% of general dentists had
attended a professional development course on implants
during the preceding 3 years.18 The 1988 National Institutes
of Health consensus panel on dental implants recognized
that restorative procedures using implants differ from those
of traditional dentistry and stressed the necessity for
advanced education.19
33
Many practitioners are taught the use of a specific manufacturer’s implant system rather than the theory and comprehensive practice of implant dentistry. The increasing
number of manufacturers entering the field use trade names
for their implant components (often unique to a particular
system), and such names have proliferated to the point of
creating confusion. Several different terms or abbreviations
now exist that describe similar basic components.20-23
To make conditions worse, in the team approach to
implant treatment the widening referral base often requires
that the restoring practitioner be knowledgeable regarding
many implant systems. With the required knowledge of multiple systems and the lack of uniformity in component names,
communication is hampered among manufacturers, dentists,
staff, laboratory technicians, students, and researchers. In
addition, the incorporation of implant dentistry into the
curriculum of most predoctoral and postdoctoral programs
further emphasizes the need for standardization of terms
and components in implant dentistry.24 This chapter proposes a generic terminology, first introduced by Misch for
endosteal implants, that attempts to blend the continuity and
familiarity of many implant systems with established definitions from the Illustrated Dictionary of Dentistry and the glossaries of the Academy of Prosthodontics and the American
Academy of Implant Dentistry.1,2,25,26
GENERIC IMPLANT BODY
TERMINOLOGY
Root form implants are a category of endosteal implants that
are designed to use a vertical column of bone, similar to the
root of a natural tooth. Although many names have been
applied, the 1988 National Institutes of Health consensus
statement on dental implants and the American Academy of
Implant Dentistry recognize the term root form1,19 (Fig. 3-3).
The exponential growth of implant use over the last 20
years has been paralleled by an explosion of the implant
manufacturing field. Currently, more than 90 designs are
available, offering countless combinations of implant body
design, platform shapes, diameter, length, prosthetic connections, surface conditions, and interfaces.26-47
The most common root form design combines a separate
implant body and prosthodontic abutment to permit the
implant placement under the soft tissue during initial bone
healing. A second surgical procedure is required to uncover
the implant as a two-stage surgical approach, separated by
the hard tissue healing process. The design philosophy is to
achieve clinical rigid fixation that corresponds to a microscopic direct bone-to-implant interface without intervening
fibrous tissue occurring over any significant portion of the
implant body.
More recently, implant body designs with a permucosal
section have been developed to allow a one-stage (unsubmerged) approach. Also, the immediate load techniques are
reported more widely on two-piece and one-piece implant
designs.
The macroscopic body design can be a cylinder, thread,
plateau, perforated, solid, hollow, or vented; the surface can
be smooth, machined, coated, or textured. The designs are
available in submergible and nonsubmergible forms in a
variety of biocompatible materials. Three primary types of root
form endosteal implants are available based on design.26
34
DENTAL IMPL ANT PR OSTHETICS
Figure 3-3
Hundreds of different implant body designs are available in the world today.
These generally relate to three different categories: cylinder implants (top row), screw design
implants (middle row), or a combination (bottom row), which usually are pressed into position and
have a macro body design similar to a thread form. (Courtesy Charles English, Little Rock, AR.)
Cylinder (press fit) root form implants depend on a coating
or surface condition to provide microscopic retention and
bonding to the bone and usually are pushed or tapped into
a prepared bone site. They can be straight, tapered, or conical. Screw root forms are threaded into a bone site and have
macroscopic retentive elements for initial bone fixation.
These root forms may be machined, textured, or coated.
Three basic screw-thread geometries are V-thread, buttress
thread, and power (square) thread designs that are combined with different geometric shapes. Threaded implants
are now available in straight, tapered, conical tapered,
ovoid, and expanding designs. Combination root forms have
macroscopic features of the cylinder and screw root forms.
Micro or macro thread features, alternating thread pitch,
depth, and self-tapping features can be combined to create
a myriad of implant designs from which to choose. The
screw or combination root form designs also may benefit
from microscopic retention to bone through varied surface
treatment (machined, textured, etched, resorbable blast
medium [RBM]) and the addition of coatings or macroscopic
features such as baskets, vents, grooves, ledges, plateaux,
and fins.48-61 Root forms also have been described by their
means of insertion, healing, surgical requirements, surface
characteristics, and interface.20-23
IMPLANT BODY REGIONS
The implant body may be divided into a crest module
(cervical geometry), a body, and an apex (Fig. 3-4).
Crest module
Body
Apex
Figure 3-4
An implant body is the portion of the dental
implant that is designed to be placed into the bone to anchor
prosthetic components. The implant body has a crest module,
body, and apex.
Generic Root Form Component Terminology
Implant Body
A solid screw implant body design with a blunt apex offers
significant advantages to the practitioner with limited
experience or limited availability of different implant
systems. A solid screw is defined as an implant of a circular
cross section without any vents or holes penetrating the
implant body. A number of manufacturers provide this
design. The V-shaped threaded screw has a long history of
clinical use12,13; the most common thread outer diameter is
3.75 mm, with a 0.4 mm depth of thread and a crest module about 2 mm in height and crestal diameter of 4.1 mm.
The various lengths range from 7 to 20 mm; lengths from
10 to 16 mm are the most widely used. This design now is
offered in a variety of diameters (narrow, standard, wide) to
better answer the mechanical, esthetic, and anatomical
requirements in different areas of the mouth.62,63
A solid screw permits the preparation and placement of
the implant in dense cortical bone and in fine trabecular
bone. The surgery may be modified easily to accommodate
both extremes of bone density. The solid screw permits the
implant to be removed at the time of surgery if placement
is not ideal. A solid implant may perforate the inferior
border of the mandible, nares, or maxillary sinus without
inherent complication if the apex is smooth or blunted.
The solid screw may be plasma spray-coated with titanium
or hydroxyapatite to marginally increase the functional
surface area, microlock the bone, and take advantage of
biochemical properties related to the surface coating
(e.g., bone bonding or bone growth factors).
Manufacturers also may provide slightly smaller or larger
implant diameters for use in limited anatomical situations
or surgical complications. A solid screw also permits the
implant to be removed at the Stage II surgery if angulation
or crestal bony contours are not adequate for long-term
prosthesis success.
The functional surface area of a threaded implant is
greater than a cylinder implant by a minimum of 30% and
may exceed 500%, depending on the thread geometry. This
increase in functional implant surface area decreases the
stress imposed on the implant bone interface and also
depends on thread geometry.
A cylinder implant design system offers the advantage of
ease of placement, even in difficult access locations. For
example, in the very soft D4 bone of the posterior regions
of the maxilla, a 70 : 1 handpiece, rather than a hand
wrench, is needed to insert a threaded implant design. Very
soft bone otherwise may be displaced during the hand
ratchet procedure, and the implant will not be rigid.
A cylinder implant may be pressed into the bone by hand
in hard or soft bone. The cylinder system also has some
benefits for the single-tooth implant application, especially
if the crown height of the adjacent teeth is large. Extenders
are needed for the screw implant placement in these situations, as well as additional armamentarium to insert the
cover screw of the implant. Cylinder systems also are easier
and faster to place because bone tapping is not required.
The speed of implant rotation during insertion and the
amount of apical force in implant insertion are also less
relevant.
However, most cylinder implants are essentially smoothsided and bullet-shaped implants that require a bioactive or
increased surface area coating for retention in the bone.
If these same materials were placed on a threaded design,
35
the surface area of bone contact would be more than
30% higher compared with the smooth cylinder design.
The greater the functional surface area of the bone implant
contact, the better the support system for the prosthesis. In
addition, if bone loss occurs around a coated implant, a
biological smear layer attaches to the coating. The contaminated coating often must be removed for the bone to
readapt to the implant. However, once the coating is
removed, the cylindrical implant primarily imposes shear
loading to the bone implant interface. Bone is 65% weaker
in shear force compared with compression. As a result,
future bone loss is even more likely. Once the surface is
decontaminated and bone is regenerated next to the implant,
the threaded implant still can transmit compression and
tensile forces to bone. Hence surgical correction of bone
loss has better prognosis with screw-type implants.
Crest Module
The crest module of an implant is that portion designed to
retain the prosthetic component in a two-piece system; it
also represents the transition zone from the implant body
design to the transosteal region of the implant at the crest
of the ridge. The crest module also may be designed to exit
the soft tissue in some implant systems (e.g., the ITI
implant system). The abutment connection area often has a
platform on which the abutment is set; the platform offers
physical resistance to axial occlusal loads. An antirotation
feature often is included on the platform (external hexagon) but may extend within the implant body (internal
hexagon, Morse taper, internal grooves). The implant body
has a macroscopic design (e.g., threads or large spheres),
whereas the crest module is often smoother to impair
plaque retention if crestal bone loss occurs. The apical
dimension of the crest module varies greatly from one
system to another (0.5 mm to 5 mm).
The platform features a coupling that is above or below
the crestal bone level. Nonrotational features are typically
part of this element. The classic connection above the platform is an external hexagon of dimensions varying with
manufacturers and implant diameter.
A high-precision fit of the external hexagon, flat-to-flat
dimension is paramount to the stability of the implant
body–abutment connection.62-66 Internal connections can
be of the internal hexagon or octagon type. Other geometrics include octagonal, cone screw, cylinder hexagon,
spline, cam tube, and pin slots. The connection is received
by slip-fit or friction-fit with butt or bevel joint. All aim at
providing a precise mating of the two components with
minimal tolerance. A multitude of patents have been filed
touting the merits of a particular design, and one can
expect the field will see more creative versions as the field
further expands.
Implant Collar
A cervical collar may be incorporated: its design varies from
straight to flared neck, beveled, reverse bevel, tapered,
smooth, surfaced, or microthreaded. Designs that incorporate a microscopic component into the implant bodies by
coatings with hydroxyapatite or titanium often have an
implant collar at the superior aspect of the crest module.
Prevention of hydroxyapatite exposure above the bone may
be one solution to decrease the potential bacterial liability.
36
DENTAL IMPL ANT PR OSTHETICS
From observations of a number of hydroxyapatite-coated
cylinder Integral implants exhibiting morbidity, Block and
Kent67 made recommendations to reduce complications,
including (1) caution in placing implants in thin bone or
extraction sites without adequate bony coverage or grafting
and (2) primary closure to prevent premature exposure and
possible bone loss. However, the amount of bone remodeling following implant placement is difficult to predict. The
inclusion of a metal collar allows functional remodeling to
occur to a more consistent region on the implant.68 Studies
on osseous healing around implants69,70 suggest that crestal
remodeling is limited to the smooth region of the collar.
As a result of this remodeling, the sulcular epithelium
migrates to the base of the implant collar. However, no significant differences in the probing depths between healthy
implants with and without coronal collars have been
noted69 probably because of the close adaptation of circular
fibers encircling the implant neck.71
Besides the possible prevention of hydroxyapatite exposure, an additional advantage of using a machined coronal
portion is the potential for an improved interface at the
abutment connection. Although the machined collar
region may provide this advantage, the collar contributes
little to the biomechanical support at the bony crest where
stresses are most severe; one must consider this factor in
treatment planning and prosthesis design. Therefore the
machined collar limited in height to 0.5 to 1 mm provides
the biological and abutment connection advantages and
limits the biomechanical disadvantage.
Prosthesis screw
Coping
Analog
A. Implant body
B. Abutment
A
Transfer coping
(abutment or implant body)
A. Indirect
B. Direct
A
B
B
Hygiene screw
Abutment
A. For screw retention
B. For cement retention
C. For attachment
A
B
C
Second-stage permucosal
extension or healing
abutment
First-stage cover screw
Implant body
GENERIC PROSTHETIC COMPONENT
TERMINOLOGY
Misch and Misch26 developed a generic language for
endosteal implants in 1992. This language is presented in an
order following the chronology of insertion to restoration
(Fig. 3-5). In formulating the terminology, five commonly
used implant systems in the United States were referenced.
Ten years later, the dramatic evolution of the U.S.
implant market has resulted in the complete disappearance
of some and the multiplication and mutation of others
through mergers and name changes. To make matters
worse, even if the company remained the same, changes in
the implant line and component design (dimensions or
connection types) may have taken place. A 1998 article
reported that in the U.S. alone the profession now has to
choose from more than 1300 implants and 1500 abutments
in various materials, shapes, sizes, diameters, lengths,
surfaces, and connections.62 More than ever, a common
language is needed. Just as in pharmacology in which the
multiplicity of pharmaceutical components makes it
impossible to list them all by proprietary names but by category, implant components still can be classified into broad
applications/indications categories, and the practitioner
should be able to recognize a certain component category
and know its indications and limitations.
At the time of insertion of the implant body or Stage I
surgery, a first-stage cover is placed into the top of the
implant to prevent bone, soft tissue, or debris from invading the abutment connection area during healing. If the
first-stage cover is screwed into place, the term cover screw
may be used.
Figure 3-5
Implant components most often have terms that
are different for each company. Misch and Misch26 published a
generic language that applies to any product. This language permits improved communication between referring doctors and
laboratories, which often must be familiar with several different
systems. (From Misch CE: Contemporary implant dentistry, ed 2,
St Louis, 1999, Mosby.)
After a prescribed healing period sufficient to allow a
supporting interface to develop, a second-stage procedure
may be performed to expose the implant or to attach a
transepithelial portion.25 This transepithelial portion is
termed a permucosal extension because it extends the implant
above the soft tissue and results in the development of
a permucosal seal around the implant. This implant component also is called a healing abutment because Stage II uncovery surgery often uses this device for initial soft tissue
healing (Figs. 3-6 and 3-7).
In the case of a one-stage procedure, the surgeon may
have placed the permucosal extension at the time of
implant insertion or may have selected an implant body
design with a cervical collar of sufficient height to be
supragingival. In the case of immediate load, the permucosal healing abutment may not be used at all if a temporary prosthesis is delivered on the day of surgery or may
be used until the suture removal appointment and the
Generic Root Form Component Terminology
Figure 3-6
The permucosal extension (PME) attaches to the
implant body and allows the soft tissue to heal and mature around
the future implant abutment. The PME may be the same size as the
crest module of the implant body (left) or slightly larger (right) and
helps develop the emergence contour of the implant crown.
37
temporary teeth delivery. The healing abutment is available
in multiple heights to accommodate soft tissue variations
and also can be straight or flared or anatomical to assist in
the soft tissue healing sculpture.
The abutment is the portion of the implant that supports
or retains a prosthesis or implant superstructure.25 A superstructure is defined as a metal framework that fits the
implant abutment(s) and provides retention for a removable
prosthesis1 (e.g., a cast bar retaining an overdenture with
attachments) or provides the framework for a fixed prosthesis.
Three main categories of implant abutment are described,
according to the method by which the prosthesis or superstructure is retained to the abutment: (1) an abutment for
screw retention uses a screw to retain the prosthesis or superstructure; (2) an abutment for cement retention uses dental
cement to retain the prosthesis or superstructure; and (3) an
abutment for attachment uses an attachment device to retain a
removable prosthesis (such as O-ring attachment) (Figs. 3-8
to 3-10). Many manufacturers classify the prosthesis as fixed
Abutment for
cement
Angled
abutment
Profile
abutment
One-piece
abutment
Figure 3-7
An intraoral view of eight second-stage permucosal extensions that were inserted into the implant bodies.
Figure 3-9
Abutment for cement retention may be one
piece (far left) or two pieces, which are retained by a separate
abutment screw.
O-ring abutment
Abutment for screw
Figure 3-8
An abutment for screw retention is used for a
screw-retained bar or fixed prosthesis. (Courtesy BioHorizons,
Birmingham, Ala.)
Figure 3-10
Abutment for attachment is used for removable
prostheses that are implant retained. These may be used for complete dentures and/or partial dentures.
38
DENTAL IMPL ANT PR OSTHETICS
whenever cement retains the prostheses, fixed/removable
when screws retain a fixed prosthesis, and removable when
the restoration can be removed by the patient. This description implies that only screw-retained prostheses may be
removed. The description is not accurate because the dentist also may remove a fixed-cemented prosthesis. Hence the
generic language in this chapter separates prostheses into
fixed or removable as does traditional prosthetics. The abutment may be screwed or cemented into the implant body,
but this aspect is not delineated within the generic terminology. Each of the three abutment types may be classified
further as straight or angled abutments, describing the axial
relationship between the implant body and the abutment.
An abutment for screw retention uses a hygiene cover screw
placed over the abutment to prevent debris and calculus
from invading the internally threaded portion of the abutment during prosthesis fabrication between prosthetic
appointments.
The paucity of abutment design of a decade ago has been
replaced by a plethora of options. The expansion of implant
dentistry, its applications for esthetic dentistry, and the
creativity of manufacturers in this competitive market are
responsible for the explosion of implant abutment styles
available today. In the abutment for cement category, the
doctor may choose from one- and two-piece abutments,
University of California—Los Angeles (UCLA) type (plastic
castable, machined/plastic cast to cylinder, gold sleeve
castable), two-piece esthetic, two-piece anatomical, twopiece shoulder, preangled (several angulations), or telescopic mullable ceramic (Figs. 3-9, 3-11, and 3-12). The
abutment for screw category also has been enlarged with
one- and two-piece overdenture abutments of different
contours and heights.
An impression is necessary to transfer the position and
design of the implant or abutment to a master cast for
prosthesis fabrication. A transfer coping is used in traditional
prosthetics to position a die in an impression25 (Fig. 3-13).
Most implant manufacturers use the terms transfer and coping
to describe the component used for the final impression.
Figure 3-11
On a custom abutment, porcelain may be built
between the crown margin and the abutment-to-implant position.
This buildup allows the crown margin to be above the bone, yet
the subgingival region has pink or tooth-colored porcelain and a
customized shape to improve esthetics.
Figure 3-12
A customized abutment with tooth-colored
ceramic and ideal emergence profile from the implant body. If the
tissue shrinks in the future, the crown will appear longer, but the
titanium color of the abutment will not be evident.
Therefore a transfer coping is used to position an analog in
an impression and is defined by the portion of the implant
it transfers to the master cast, either the implant body transfer coping or the abutment transfer coping.
Two basic implant restorative techniques are used to
make a master impression, and each uses a different design
transfer coping, based on the transfer technique performed.
An indirect transfer coping uses an impression material
requiring elastic properties.25 The indirect transfer coping is
screwed into the abutment or implant body and remains in
place when the set impression is removed from the mouth.
The indirect transfer coping is parallel-sided or slightly
tapered to allow ease in removal of the impression and
often has flat sides or smooth undercuts to facilitate reorientation in the impression after removal. A direct transfer
coping usually consists of a hollow transfer component,
often square, and a long central screw to secure it to the abutment or implant body and may be used as a pickup impression coping. After the impression material is set, the direct
transfer coping screw is unthreaded to allow removal of the
impression from the mouth. Direct transfer copings take
advantage of impression materials having rigid properties
and eliminate the error of permanent deformation because
they remain within the impression until the master model
is poured and separated (Fig. 3-14).
An analog is something that is analogous or similar to
something else.25 An implant analog is used in the fabrication
of the master cast to replicate the retentive portion of the
implant body or abutment (implant body analog, implant
abutment analog). After the master impression is obtained, the
corresponding analog (e.g., implant body or abutment for
screw) is attached to the transfer coping and the assembly is
poured in stone to fabricate the master cast (Figs. 3-15, 3-16,
and 3-17).
A prosthetic coping is a thin covering,25 usually designed
to fit the implant abutment for screw retention and serve as
the connection between the abutment and the prosthesis
or superstructure. A prefabricated coping usually is a metal
Generic Root Form Component Terminology
39
Type of restoration
Single-tooth restoration
Ball-top
screw
Multiple-unit restoration
Directtransfer
coping
screw
Straight
abutment
for cement—
hexed
Closed-tray technique
Directtransfer—
hexed
Ball-top
screw
Indirect
impression
coping—
nonhexed
Directtransfer
coping
screw
Directtransfer—
nonhexed
Straight abutment
for cement—hexed
Open-tray technique
One-piece
abutment
for cement—
nonhexed
Closed-tray technique
Open-tray technique
Color-code scheme
Blue
5.0 mm
Green
4.0 mm
Yellow
3.5 mm
O-Ring O-Ring abutment
abutment
analog
Indirect analog
Figure 3-13
An indirect transfer (far left and center ) is inserted into an implant body or
abutment for screw retention and a closed tray impression is made. The impression is removed
and the transfers are connected to an analog and reinserted into the impression. A direct impression transfer (far right ) uses an open tray to make the impression. The direct transfer coping
screw must be unthreaded before the impression is removed from the mouth. (Courtesy
BioHorizons, Birmingham, Ala.)
Figure 3-14
These eight maxillary implants are connected
to two-piece indirect impression transfers, which engage the hexagon of the implant platform. A closed-tray impression is made, and
the indirect transfer copings are unthreaded from the implant bodies, connected to implant body analogs, and reinserted into the
impression before pouring of the cast.
Implant analog
Figure 3-15
O-ring abutment analog
Analogs may represent an abutment for
screw retention, an implant body (left ), and/or an abutment for
attachment (right ).
40
DENTAL IMPL ANT PR OSTHETICS
regardless of the implant system used; the term is descriptive of the function of the component rather than its proprietary name.
References
Figure 3-16 An indirect closed-tray impression in a
“customized” impression tray, which also is related to the incisal
edge of the patient to the laboratory technician. The indirect
impression transfers have been attached to implant body analogs
and reinserted into the closed-tray impression.
Figure 3-17
The impression in Figure 3-16 is mounted
against the opposing arch (with a bite registration not pictured).
In this particular system the indirect transfer coping may be a oneor two-piece component. A one-piece component does not
engage the hexagon and does not transfer the position of the
antirotational hexagon from the mouth to the model. The twopiece indirect transfer does allow the transfer. The laboratory can
remove the indirect transfer copings, insert the abutments for
cement retention, and prepare them before making a transition
prosthesis. Some dentists also will make a metal casting for the
final restoration on this model.
component machined precisely to fit the abutment. A
castable coping usually is a plastic pattern cast in the same
metal as the superstructure or prosthesis. A screw-retained
prosthesis or superstructure is secured to the implant body or
abutment with a prosthetic screw (see Table 2-1).
A generic terminology has been developed to facilitate
the communication between implant team members,
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