Treatment planning of implants in the aesthetic zone.

Abstract

Aesthetic restoration of anterior teeth with implant supported restorations is one of the most difficult procedures to execute. Bone resorption following anterior tooth extraction often compromises gingival tissue levels for the implant restoration. In the last 10 years the focus has shifted from osseointegration, to creation of an implant borne restoration which is in harmony with the surrounding hard and soft tissue. Complete reconstruction of tooth and gingival related aesthetics remains the primary objective and in some instances can be very difficult to achieve.

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3
Treatment planning of implants in the aesthetic
zone
S. Jivraj1 and W. Chee2
Aesthetic restoration of anterior teeth with implant supported restorations is one of the most difficult procedures to execute.
Bone resorption following anterior tooth extraction often compromises gingival tissue levels for the implant restoration.
In the last 10 years the focus has shifted from osseointegration, to creation of an implant borne restoration which is in
harmony with the surrounding hard and soft tissue. Complete reconstruction of tooth and gingival related aesthetics
remains the primary objective and in some instances can be very difficult to achieve.
IN BRIEF
● Patients diagnosed with a lack of posterior support should be treatment planned for dental
implants to re-establish support.
● Sufficient restorative space must exist when treatment planning dental implants in posterior
quadrants.
● There are many advantages in designing posterior dental implant restorations to be
retrievable.
● Splinting of multiple posterior implants provides many benefits.

The predictability of aesthetic success depends
on the tissue loss present at the initiation of
treatment. The greater the amount of bone and
soft tissue loss, the more difficult it becomes
to produce an ideal aesthetic result. Single
tooth implants have a high degree of predict-
ability as the adjacent teeth can provide the
morphological substructure that is required to
restore natural gingival and papillary architec-
ture. Replacement of multiple missing teeth in
the aesthetic zone is challenging particularly
when the three dimensional architecture of the
existing bone and soft tissue is deficient. The
bony housing in this instance would require
augmentation to provide a configuration that
permits placement of implants in optimal posi-
tions which in turn would result in pleasing
aesthetics. The purpose of this article is to look
at the diagnostic factors that affect the predict-
ability of peri-implant aesthetics. Emphasis is
placed on those parameters which are critical
to overall treatment planning.
Marketing enquiries have identified aesthet-
ics as one of the major reasons why dentists use
dental implants in their surgeries. If we go by
that premise it is reasonable to speculate that the
aesthetic results provided with dental implants
should be similar to the aesthetics provided with
more conventional modes of therapy such as
fixed and removable partial dentures. However,
achieving aesthetics with implant restorations
is significantly more challenging than that with
conventional restorations. Diagnosis and appro-
priate treatment planning are critical in obtain-
ing a successful outcome. Many manufacturers
will identify their systems as aesthetic; from an
objective perspective components in themselves
are not aesthetic. There is not a single com-
ponent available from a manufacturer which
would be the ideal replacement for a maxillary
central incisor. Aesthetic outcomes are based
on many variables. It is not the specific implant
design, surface characteristics or type of abut-
ment that will guarantee an aesthetic result. It
is rather the time spent on data collection in
reaching a correct diagnosis that pays dividends
in terms of function and aesthetics.1
Root form cylindrical implants placed follow-
ing surgical techniques described by Branemark
et al. have proven to be a predictable method
for anchoring replacement teeth to the jaw
bone.2,3 Today clinicians can prescribe the use
of implants with the knowledge and confidence
that they will predictably integrate into the jaw
IMPLANTS
1. Rationale for dental implants
2. Treatment planning of implants in
posterior quadrants
3. Treatment planning of implants in
the aesthetic zone
4. Surgical guidelines for dental
implant placement
5. Immediate implant placement:
treatment planning and surgical
steps for successful outcomes
6. Treatment planning of the
edentulous maxilla
7. Treatment planning of the
edentulous mandible
8. Impressions techniques for
implant dentistry
9. Screw versus cemented implant
supported restorations
10. Designing abutments for
cement retained implant supported
restorations
11. Connecting implants to teeth
12. Transitioning a patient from
teeth to implants
13. The role of orthodontics in
implant dentistry
14. Interdisciplinary approach to
implant dentistry
15. Factors that affect individual
tooth prognosis and choices in
contemporary treatment planning
16. Maintenance and failures
1*Chairman, Section of Fixed Prosthodontics and Operative Dentistry,
University of Southern California School of Dentistry / Private
Prosthodontics Practitioner, Sherman Oaks and Torrance California; 2Ralph
W. and Jean L. Bleak Professor of Restorative Dentistry, Director of Implant
Dentistry at the University of Southern California School of Dentistry /
Private Prosthodontics Practitioner, Pasadena, California
*Correspondence to: Dr Sajid Jivraj, School of Dentistry, Rm. 4372 University
Park, University of Southern California, Los Angeles, CA 90089-0641, USA
Email: jivraj@usc.edu
Refereed Paper
© British Dental Journal 2006; 201: 13–23
DOI: 10.1038/sj.bdj.4813645
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bone. The successful integration of an implant,
however, is not sufficient to declare success;
implants placed in poor restorative positions
result in unaesthetic restorations that provide
little satisfaction for the clinician or the patient
(Figs 1-3). The above illustrations demonstrate
the complexity of implant use in aesthetic zones
and the importance of proper treatment plan-
ning prior to implant placement.
Providing an aesthetic outcome requires
understanding of the objective and subjective
criteria related to hard and soft tissue aesthetics.4
Both dental and gingival aesthetics act together
to provide a smile with harmony and balance.
The clinician must be aware of parameters relat-
ed to gingival morphology, form and dimension,
characterisation, surface texture and colour5
(Fig. 4). Ceramists can often produce restora-
tions to match adjacent teeth in terms of colour,
however if the surrounding tissues are not recon-
structed an aesthetic outcome is not likely (Fig.
5). The ultimate aim is for the implant restoration
to harmonise with the frame of the smile, face
and more importantly the individual.
Treatment planning must address hard and
soft tissue deficiencies and combine this with
precision in implant placement. Only with this
approach can implant restorations be indistin-
guishable from the adjacent teeth (Fig. 6).
Recreating what nature provided can be a
formidable challenge. The physiology of wound
healing after tooth extraction creates an unfa-
vourable soft tissue complex. The remaining
mucosa often recedes palatally and apically.
Often this results in a restoration that appears
long and this is compounded by the absence of
interdental papilla (Fig. 7).
The predictability of the aesthetic outcome
of an implant restoration is dependent on many
variables including but not limited to the fol-
lowing:
1) Patient selection and smile line
2) Tooth position
3) Root position of the adjacent teeth
4) Biotype of the periodontium and tooth shape
5) The bony anatomy of the implant site
6) The position of the implant.
1. Patient selection and smile line
Patients who are candidates for replacement
of an anterior tooth with an implant supported
restoration must understand the benefits of an
implant restoration. They must also understand
the additional length of time required for treat-
ment and additional costs that will be incurred.
The clinician must also understand the patient’s
desires. In most cases the patient’s primary
demand is an aesthetic tooth replacement; with
this in mind it is important to establish sound
clinical concepts with clearly defined param-
eters that lead to successful aesthetics with long
term stability of the peri-implant tissues.
The major indication for a single tooth
implant restoration is preservation (non prep-
aration) of one or more of the adjacent teeth
(Fig. 8), and reduction in the rate of alveolar
resorption. Additional indications would be res-
toration of a missing tooth to maintain a diaste-
ma and preservation of extensive fixed restora-
tions that are intact.
A patient’s aesthetic expectations must also
be evaluated together with their lip activity and
lip length. In an average smile 75-100% of the
maxillary incisors and the interproximal gingi-
va are displayed. In a high smile line additional
gingival tissue is exposed. Less than 75% of the
incisors are exposed in a low smile line (Figs
9-11).6 The clinician should be aware that the
patient who presents with unacceptable tooth
health, shade or position may not give a full
smile when asked. Previous photographs may
aid in determining the natural position of the
patient’s lip when smiling.
A high smile line poses considerable chal-
lenges when planning for implant supported
restorations in the aesthetic zone because the
restoration and gingival tissues are completely
displayed. In these types of clinical situations
maximal efforts towards maintaining peri-
implant tissue support throughout the planning,
provisional, surgical and restorative phases will
be required. An article later in the series will dis-
cuss soft tissue management with provisional
restorations.
The low smile line is a less critical situation
because the implant restoration interface which
will be hidden behind the upper lip. However
this cannot be assumed and the patient’s input
must be sought to confirm this. ‘The aesthetic
zone is where the patient thinks it is.’
2. Tooth position
The tooth needs to be evaluated in three planes
of space: apicocoronal, faciolingual and mesio-
distal. The existing tooth position will signifi-
cantly influence the presenting gingival archi-
tecture. In many instances teeth with a poor
prognosis are thoughtlessly extracted. These
teeth can significantly influence both the hard
and soft tissue configuration.
Apico-coronal On assessment of the apico-coro-
nal position of the tooth it may be more apical,
more coronal or ideal and mimic the level of the
adjacent gingival margin (Fig. 12). Numerous
authors have shown that following extraction
and insertion of an ovate pontic there is likely
to be up to 2 mm of gingival recession, and on
extraction and placement of an implant imme-
diately the migration of the gingival margin is
likely to approximate 1 mm.7,8
The implications this has from a practical
perspective are that if there is a hopeless tooth
positioned ideally or apically and this is extract-
ed, the gingival margin is likely to migrate api-
cally. Restoratively, long clinical crowns, pink
porcelain or visible metal margins will result,
compromising the aesthetic outcome. These
teeth can benefit from orthodontic extrusion
(Fig. 13) prior to extraction which will serve to
position the gingival level at a more harmoni-
ous level.9,10
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Facio-lingual In this dimension the tooth posi-
tion may present with different concerns. The
tooth may be positioned too far facially; this
often results in very thin or non existent labial
bone. These teeth are not good candidates for
orthodontic extrusion because of inadequate
underlying bone. Extraction of these teeth
results in significant vertical bone loss and col-
lapse of the gingival architecture. This type of
situation would benefit from bone augmenta-
tion procedures prior to implant placement. A
tooth positioned more lingually would benefit
from the presence of an increased amount of
facial bone. This situation is more favourable
prior to extraction since the resultant discrep-
ancy in the facial free gingival margin may be
minimal.9
Mesio-distal The proximity of the adjacent
teeth necessary to provide proximal support and
volume of interdental papillae should be evalu-
ated. Ideally the mesiodistal tooth width should
be equal to that of the contra lateral tooth so
that an aesthetic outcome can be achieved (Figs
14-15). Excess or deficiencies in this dimension
should be addressed through the use of ortho-
dontics, enameloplasty or restorations. For
patients with diastemas it is imperative that the
decision to maintain or close the space be made
prior to implant placement. If the patient refuses
the above options to close the space and insists
on closing the space with the implant restora-
tion there is a likelihood that a black triangle
may ensue. This results from inadequate support
from the adjacent tooth to maintain the papilla.
It is important that the clinician discusses this
with the patient ahead of time so disappoint-
ment with the final outcome is avoided (Figs
16-17).
3. Root position of the adjacent teeth
Part of the diagnostic work up for patients
who need implants is a peri-apical radiograph,
as often root position will preclude placing of
implants. Many of these patients can benefit
from orthodontics to reposition malposed teeth.
If the patient illustrated in Figures 18 and 19
desired implant restorations to replace congeni-
tally missing maxillary lateral incisors, ortho-
dontic therapy would be necessary to move the
roots of the cuspid and central incisor to allow
room for ideal implant placement.
Teeth with root proximity also possess very
little interproximal bone; this thin bone creates
a greater risk of lateral resorption which will
decrease the vertical bone height after extrac-
tion or implant placement. When teeth are
present the use of orthodontics serves as a valu-
able adjunct to create space. This can be advan-
tageous for support of proximal gingival archi-
tecture.11,12
4. Biotype of periodontium and tooth shape
The position of the gingival tissue around a
tooth is determined by the connective tissue
attachment and by the bone level. Two differ-
ent periodontal biotypes have been described
in relation to the morphology of the interden-
tal papilla and the osseous architecture: the thin
scalloped periodontium and the thick flat peri-
odontium.13
The thin scalloped periodontium found in
less than 15% of cases is characterised by a deli-
cate soft tissue curtain, a scalloped underlying
osseous form and often has dehiscence and fen-
estrations and a reduced quantity and quality
of keratinised mucosa. Generally interproximal
tissue does not completely fill the space between
adjacent teeth. This form of gingiva reacts to
insults by receding facially and interproximal-
ly. As recession occurs and the inter-root bone
resorbs, the subsequent soft tissue loss compro-
mises the overall aesthetic result (Fig. 20).
The tooth form in this type exhibits a contact
point towards the incisal third essentially tri-
angular anatomic crowns and contact areas of
teeth that are small facio-lingually and apico-
coronally. Due to extreme taper of the roots the
bone interproximally tends to be thicker.
Characteristics of the soft tissue biotype will
play a prominent role in final planning for the
shoulder position of the implant. A thin biotype
with highly scalloped tissue will require the
implant body and shoulder to be placed more
palatal to mask any titanium show through.
When implants are placed toward the palate a
slightly deeper placement is required to allow
for proper emergence profile.
Combining previous factors in a patient with
a high lip line and a thin biotype is extreme-
ly difficult to treat. Patients who fit into these
treatment categories should be made aware of
the challenges involved in obtaining an aes-
thetic result before treatment begins.
The thick flat periodontal biotype is charac-
terised by a denser more fibrotic soft tissue cur-
tain, a flat thicker underlying osseous form and
an increased quantity and quality of attached
keratinised gingiva. This tissue often reacts
to insults by pocket formation. Flat gingiva is
associated with a tooth form that is more bul-
bous. Contact areas are located more toward the
middle third of the tooth; primarily square ana-
tomic crowns and contact areas that are wide
facio-lingually and apico-coronally (Fig. 21).
The tooth morphology appears to be cor-
related with the soft tissue quality. The trian-
gular tooth shape is associated with the scal-
loped and thin periodontium. The contact area
is located in the coronal third of the crown
underlining a long and thin papilla. The square
anatomic crown shape combines with a thick
and flat periodontium. The contact area is
located at the middle third supporting a short
and wide papilla.
Loss of interproximal tissue in the presence
of a triangular tooth form will display a wider
black triangle than in a situation when a square
tooth is present (Fig. 21). In some cases when the
adjacent teeth are to be restored the crown form
can be modified prosthetically to compensate
for partial interproximal tooth loss. The contact
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Fig. 1 (left) Intra oral photograph
of implant in poor position angled
labially and exiting the ridge too
coronally
Fig. 2 (right) Restoration fabricated
for implant in Figure 1; note length
of restoration compared to adjacent
teeth
Fig. 3 (left) Labial view of restoration
for implant on Figure 1 note poor
shape and form of the tooth dictated
by poor implant position
Fig. 4 (right) Restoration of implants
must satisfy objective and subjective
aesthetic criteria. There should be
sufficient inter-radicular space for
placement of the implant and sufficient
inter-tooth distance for fabrication of
an aesthetically pleasing restoration
Fig. 5 (left) Note ceramics of right
central incisor matches that of
the left central incisor, however
reconstruction of the deficient
hard tissue has not been achieved,
resulting in a restoration that does
not satisfy objective criteria of
aesthetics
Fig. 8 (right) A perfect indication
for a dental implant is non-
preparation of the adjacent teeth
Fig. 6 (right) Implant restoration on
left lateral incisor in harmony with
the existing hard and soft tissue
Fig. 7 (left) Wound healing
following extraction of a tooth can
result in apical and palatal migration
of the inter-dental papilla
Fig. 9 (left) Low smile line
Fig. 10 (right) Average smile line
Fig. 12 (right) The right lateral
incisor has been treatment planned
for an implant restoration. The level
of the soft tissues mimic that of the
contra lateral tooth
Fig. 11 (left) High smile line.
The colour and contour of the
restorations and associated hard and
soft tissues becomes very visible to
the observer
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Fig. 13 (left) Immediate extraction
of the right lateral incisor would
result in apical migration of the
soft tissue. Orthodontic extrusion
will allow the clinician to position
the tissue more coronally so that on
extraction there is a margin of error
Fig. 14 (right) The mesio-distal
width of the tooth requiring
replacement must equal that of the
contra lateral tooth
Fig. 16 (right) Excessive mesiodistal
space in the region of the tooth
requiring an implant restoration
Fig. 15 (left) Implant restoration
replacing the right central incisor
Fig. 17 (left) Implant restoration in
the region of the right central incisor.
Note absence of interdental papilla as
a result of inadequate support of the
soft tissue by the restoration
Fig. 18 (right) Clinical presentation
of patient with congenitally missing
maxillary lateral incisors post
orthodontic treatment
Fig. 19 (left) Radiograph of patient
in Figure 18 revealing that there is
insufficient inter radicular space for
implants
Fig. 20 (right) Biotype 1
periodontium; note thin and
scalloped tissue
Fig. 21 (left) Biotype 2
periodontium, not thick and flat
tissues
Fig. 22 (right) Loss of interproximal
soft tissue in the presence of a
triangular tooth form can result in
unsightly black triangles
Fig. 23 (left) Over contour of the
implant restoration as it emerges
from the free gingival margin can
result in apical migration of the soft
tissues
Fig. 24 (right) A diagnostic wax
up can highlight the deficiency of
the hard and soft tissue and can
indicate to the surgeon how much
augmentation is required
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cervically reducing the volume of the interden-
tal space.
The presenting tooth shape will also influ-
ence the implant restoration shape. The implant
restoration should mimic its contra lateral nat-
ural tooth coronal to the free gingival margin.
However, apical to the free gingival margin, the
implant restoration will not be an anatomic rep-
lica. A delicate balance must be developed that
provides adequate support of the gingival archi-
tecture yet does not provide excessive pressure.
Ideally the facial contour should be slightly
flatter than the contra lateral natural tooth to
minimise apical displacement of the free gingi-
val margin after insertion (Fig. 23).14
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BRITISH DENTAL JOURNAL VOLUME 201 NO. 1 JUL 8 2006
area of the prosthetic tooth is positioned more
5. Bony anatomy of the implant site
For successful aesthetic restoration of implants,
the bony housing must have a three dimen-
sional configuration that permits placement of
an implant in a restoratively ideal position.15 If
the bony anatomy is inadequate, a bone graft-
ing procedure may be required to enhance the
site. When these situations are encountered the
patient must be made to understand that a suc-
cessful outcome will involve replacing more
than just a ‘missing tooth’. The patient must also
understand that the missing hard and soft tissue
architecture will need to be rebuilt so that opti-
mum aesthetics can be achieved.
The definitive implant restoration needs to be
surrounded by a hard and soft tissue environment
which is in harmony with the surrounding denti-
tion. It is not only the amount of bone and soft tis-
sue present prior to implant surgery but the preci-
sion of surgical execution which leads to an overall
favorable outcome. Several key analyses need to
be performed prior to commencing with implant
placement. A diagnostic wax up highlighting tis-
sue deficiencies and final tooth positioning can
assist in the planning process (Fig. 24).
Facio-lingual ridge anatomy should be eval-
uated to determine if there is sufficient crest
width to house the implant. Deficient alveolar
crest width will require a bone augmentation
procedure to allow the implant to be placed
in the ideal position (Fig. 25). Clinical sound-
ing techniques or sophisticated radiographic
techniques such as tomograms or CT scans can
assist in diagnosing deficiencies in this dimen-
sion (Figs 26 and 28).
Mesio-distal space should be equal to that of
the contra lateral tooth; excess or deficiencies
in this dimension need to be addressed through
orthodontics, enameloplasty or restoration
either prior to or after implant placement.
The most critical dimension remains the
apicocoronal dimension; deficiencies in this
dimension can result from periodontal disease,
trauma, atrophy and infection. Vertical grafting
is complex and the site may require several sur-
geries to achieve an optimal configuration. The
most efficient method to evaluate this dimen-
sion is through the use of a diagnostic template
highlighting the proposed gingival margin of
the implant restoration.
Two anatomic structures are important in
determining predictability of soft tissues after
implant placement. The first is the height and
thickness of the facial bony wall and the second
is the bone height of the alveolar crest in the
interproximal areas.
Height and thickness of facial bony wall
The position of the osseous crest is an important
predictor for gingival levels. Kois,16 in a survey
of 100 patients, classified patients as having
high, normal or low crests. This was based on the
vertical distance of the osseous crest to the free
gingival margin. The greater the distance from
the osseous crest to the free gingival margin the
greater the risk of tissue loss after an invasive
procedure. Kois proposed that if the total vertical
distance of the total dentogingival complex on
the mid facial aspect is 3 mm, a slight apical loss
of tissue up to 1 mm is anticipated after extrac-
tion and immediate implant placement. Greater
or lesser than 3 mm indicates the change will be
relatively negligible to more than 1 mm. Measur-
ing the distance from the free gingival margin to
the osseous crest prior to extraction is an impor-
tant diagnostic predictor of the anticipated final
position of the free gingival margin.
Height of bony crest in the interproximal area
The interproximal bony crest plays a critical
role in the presence or absence of peri-implant
papillae. A clinical study around teeth12 meas-
ured the distance from the interproximal con-
tact to the vertical height of bone and observed
how frequently the interproximal space would
be filled completely by soft tissue. When the
contact point to the bone was 3-5 mm, papilla
always filled the space. When the distance was
6 mm papilla was absent 45% of the time and
with a distance of 7 mm, papilla did not fill the
space 75% of the time. A difference of 1-2 mm
is significant in obtaining soft tissue aesthetics.
This has been confirmed with implant support-
ed restorations.17 Kan et al.18 have also shown
that the height of peri-implant papillae in single
tooth gaps is independent of the proximal bone
level next to the implant but is dependent on
the interproximal bone height of the adjacent
teeth. From a diagnostic perspective sounding
from the tip of the papilla to the interproximal
bone crest of the adjacent tooth would be an
important predictor (Figs 29-30). If this distance
is 5 mm or less there is an increased likelihood
that the interproximal tissues will be predict-
ably maintained following implant placement
and restoration. If the distance is greater than
5 mm the papilla cannot be predictably main-
tained after surgical intervention (Figs 30, 31).
6. Implant position
Aesthetic implant placement is driven by both a
restorative and biological philosophy. Aestheti-
cally the implant should be placed to satisfy
the parameters of contour so that the restora-
tion is pleasing. Biologically it should be placed
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to allow maintenance of both hard and soft
tissue architecture. If the tooth to be replaced
has not yet been removed, several determina-
tions should be made prior to the extraction.9,10
Immediately placing the implant after extrac-
tion helps to shorten the treatment time and
may reduce the amount of ridge width reduc-
tion that accompanies tooth extraction. In addi-
tion, if bone deficiencies are present, orthodon-
tic eruption of the tooth prior to extraction can
help to increase the amount of hard and soft tis-
sue in the future implant site.19-21
The need for precision in implant placement
varies according to each individual case. For
example, in the edentulous mandible there is need
for precision only in the facio-lingual direction.
The need for precision increases in the partially
edentulous jaws according to the teeth treated
and the positions of the neighbouring and oppos-
ing teeth. The most challenging is the anterior
maxilla where a malposition of less than a 1 mm
can jeopardise the overall treatment outcome.
In most situations involving a single anterior
implant restoration, the aesthetic considerations
are more important than functional considera-
tions. As such axial loading is not as critical as
it is with posterior implant restorations. Implant
position is critical to the final aesthetic outcome
and needs to be considered in all three dimen-
sions and in relation to the adjacent teeth. Mis-
alignment of the implant in the prosthetic space
can have adverse aesthetic consequences.
Apico-coronal placement
Apicocoronal positioning appears to be the most
critical aspect. Deficient tissue in this dimen-
sion can result from several factors. This type
of tissue needs to be addressed during treatment
planning. Because of the complexity of vertical
hard and soft tissue grafting these patients are
placed in a high risk group.
Most often tooth loss is followed by bone loss
of minor or major importance. It is necessary to
evaluate the discrepancy between the bone level at
the proposed implant site and the level at the adja-
cent teeth. Too large a difference represents a risk
to both periodontal and peri-implant tissue health.
Facing this, the surgeon should consider recon-
structing the ridge prior to implant placement.
The apico-coronal positioning of the implant
is the vertical discrepancy between the occlusal
surface of the implant and the peaks of the bony
septa proximal to the adjacent teeth, the most
pleasing aesthetic result occurs when this dis-
crepancy is minimal.
To obtain appropriate apicocoronal position-
ing of the implant, a diagnostic wax up needs to
be completed and from this a surgical guide is
made. The emergence profile and the shape of
the restoration are reproduced on the guide to
verify the implant positioning on placement.
A maxillary central incisor measures on
average 7-8 mm mesiodistally and 6 mm facio-
lingually at the emergence from the soft tissue.
A 4.0 mm the implant needs to be placed 3-4
mm apical to the gingival margin of the contra
lateral tooth to allow the restoration to emerge
with a natural profile. A vertical distance of 3-4
mm is needed for gradual transition from the 4
mm diameter of the implant platform to the 7-8
mm dimension at the gingival margin. If a lat-
eral incisor is being replaced the implant would
not have to be placed so apically since the aver-
age diameter of the crown at the gingival mar-
gin is 5 mm and less room is required for transi-
tion (Figs 33-37).
There are also situations in which there is
excess tissue height and these require attention
as well. In these types of patients a bone scallop-
ing procedure is required to allow placement of
the implant shoulder in a subgingival position,
once again the most efficient way to examine
this is through a surgical guide highlighting the
proposed gingival margin.
Errors in apico-coronal implant placement
can have serious aesthetic and biomechanical
implications. An implant placed too coronally
will not allow adequate transition from the head
of the implant to the point where the restoration
exits from the free gingival margin. The restora-
tion will look short in comparison to the con-
tra lateral tooth. The only prosthetic ‘bailout’
for this type of situation is to provide a ridge-
lapped restoration with contours that are pleas-
ing to the observer’s eye (Figs 38-39).
Problems can also result when implants are
placed too apical. Clinically if an implant is
placed too apically with excessive countersink-
ing procedures an unnecessary amount of bone
loss will occur (Fig. 40). Because this bone loss
takes place circumferentially it will affect not
only the proximal bone structure but also the
height of the facial bone wall and can lead to
undesirable soft tissue contours.22
A practical problem in placing an implant
too deep is access for instrumentation. Making
an impression of a deeply place implant can be
a difficult experience (Fig. 41). The soft tissue
tends to collapse, there is tissue impingement
when trying to locate the head of the implant
and seating is difficult to evaluate. This is spe-
cific to external hex systems.
If an implant is placed too deep a screw
retained restoration is the treatment of choice.
The literature shows that removing all the
cement when an implant is placed so deep can
prove to be a difficult endeavor. Agar et al.23
found that when six experienced investigators
were asked to remove cement there was a sur-
prising amount of cement left behind, these can
lead to serious soft tissue complications.
Mesio-distal placement
Improper mesiodistal positioning of implants can
also have a substantial effect on the generation of
interproximal papillary support as well as on the
osseous crest of the adjacent tooth. An implant
should be placed 1.5-2 mm from an adjacent
tooth placement too close to the adjacent tooth
can cause resorption of the interproximal alve-
olar crest to the level of that on the implant.24
With this resorption comes a reduction in pap-
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BRITISH DENTAL JOURNAL VOLUME 201 NO. 1 JUL 8 2006
Fig. 25 (left) A deficient alveolar
crest will not allow the implant to
be placed in an ideal position. There
will be insufficient bony housing to
accommodate the fixture
Fig. 26 (right) Clinical slide of
inadequate bucco-lingual width for
implant placement
Fig. 27 (left) Bone augmentation of
the site pictured in Figure 26
Fig. 28 (right) Ideal implant
placement; note adequate ridge
contours
Fig. 30 (right) Black triangles are
likely to result between the implant
restoration and adjacent teeth
Fig. 29 (left) If attachment of
adjacent teeth is deficient it is
unlikely that the interdental papilla
will be maintained
Fig. 32 (right) Radiograph of Figure
31, the right lateral incisor has been
treatment planned for an implant
restoration. Due to attachment loss
on the adjacent canine it is unlikely
that the interproximal papilla will be
maintained
Fig. 31 (left) Diagnostic sounding
of the bone interproximally is a good
clinical indicator in predicting post
treatment papilla levels
Fig. 33 (left) Ideal implant
placement for central incisor.
Implant should be placed 3-4 mm
apical to the existing free gingival
margin. Adequate room is required
for transition from the head of
the implant to the point where
the restorations exits the free
gingival margin. Note minimal bone
discrepancy between the implant and
the adjacent teeth
Fig. 34 (right) Laboratory slide
depicting ideal implant placement
and transition required
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Fig. 35 (left) Occlusal view of
implant restoration shown in
Figure 34
Fig. 36 (right) Lateral view of
implant restoration in Figure 34
showing fill of interproximal soft
tissue
Fig. 37 (left) Facial view of implant
restoration in Figure 34 showing
aesthetic harmony
Fig. 38 (right) Placement of an
implant too shallow will result in
inadequate space for transition and a
short restoration in length
Fig. 40 (right) Too deep an
implant placement can result in
biomechanical problems. Note
level of the bone around implant
in relation to the adjacent teeth.
This deep a placement can result in
fistula formation and constant post
operative maintenance problems
Fig. 39 (left) A prosthetic bailout
for too shallow implant placement
is to ridge lap the restoration onto
the tissues
Fig. 42 (right) Ideal implant
placement should be palatal to an
imaginary line that outlines the
curvature of the teeth. (Modified
from Parel S M, Sullivan D Y)28
Fig. 41 (left) Too deep an implant
placement can result in soft
tissue collapse and difficulty in
instrumentation
Fig. 44 (right) The restoration for
the implant placement in Figure 43
would require an excessive facial
cantilever
Fig. 43 (left) Too palatal an implant
placement
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Poor embrasure form and emergence profile will
result in a restoration with a long contact zone
and compromised clinical outcomes.
The loss of crest height on adjacent teeth is
caused by bone saucerisation routinely found
around the implant shoulder in implants. This
has two dimensions: a horizontal and vertical.
Radiographs only demonstrate the horizon-
tal aspect of bone saucerisation; the proximal
bone saucerisation measures 1-1.5 mm from
the implant surface. This distance needs to be
respected on implant placement to prevent ver-
tical bone loss on adjacent teeth.25
22
BRITISH DENTAL JOURNAL VOLUME 201 NO. 1 JUL 8 2006
illary height. Restorative problems exist as well.
Facio-lingual placement
• The crest width needs to be examined to
determine the presence or absence of bone
atrophy.
• Placement will vary depending on the mech-
anism of retention of the final restoration
(screw retained vs. cement retained).
• Deficient alveolar crest width may require
augmentation so that the implant can be posi-
tioned in the correct facio-lingual position.
Computerised tomographic scan techniques
are useful in assisting to determine width. The
amount of bone available should be at least 1
mm greater than the implant diameter on each
side. Hence a 4 mm diameter implant would
require 6 mm of bone. The single implant placed
in the maxillary anterior region should be situ-
ated palatal to an imaginary line that outlines
the curve of the arch formed by the facial sur-
faces of the adjacent teeth (Fig. 42).26
Implants placed too palatal complicate devel-
opment of hygienic contours. Biomechanical
complications can also arise as a result of can-
tilever forces on the screw joint of external hex
systems (Figs 43-45). Implants are often mis-
takenly placed too facial. This error results in
excessive resorption of the supporting osseous
structure resulting in a restoration that will
appear long in comparison to the contra-lateral
tooth. Placement of a restoration such as this in
the aesthetic zone is certainly unlikely to meet
the patient’s desires (Figs 46-47).
Considerations for multiple implants
Patients with extended edentulous spaces present
greater anatomic and aesthetic challenges mak-
ing it even more difficult to obtain an aesthetic
result with certainty. Following extraction and
wound healing of two adjacent teeth, the ensuing
apical and facio-lingual resorption results in an
edentulous segment which is flattened. The same
diagnostic considerations need to be addressed as
when looking at single tooth edentulous sites. The
aim prior to implant placement is to have a three-
dimensional configuration of hard and soft tissue
which will allow placement of implants in an ideal
position. The placement of two missing central
incisors poses an additional challenge. Follow-
ing surgical placement an additional peri-implant
bone remodelling takes place. In the frontal plane
two processes occur: one between the implant
and the adjacent natural tooth and one between
the two adjacent implants. On the tooth implant
side the predictability of the interdental papilla is
governed by the height of the interproximal bone
crest of the tooth. If this height is favourable there
is good certainty that the interdental papilla will
be maintained following implant placement. The
bone crest between the two implants is likely to
undergo further resorption in an apical direction;
this is accompanied by a loss of interimplant soft
tissue which in the case of multiple edentulous
sites will result in black triangles between the
adjacent restorations.
Many clinicians have sought after the ideal
implant distance required to maintain the inter-
dental papilla. Tarnow and colleagues11 per-
formed a radiographic study to address this
clinical problem. Radiographic measurements
were taken at a minimum of one or three years
after implant exposure. All radiographs were
taken with a paralleling technique.
Radiographs were computer scanned imaged
and magnified for measurement. The following
measurements were taken:
1. Lateral distance from the crest of the inter-
implant bone to the implants
2. Vertical crestal bone loss
3. Distance between the implants at the implant/
abutment interface.
When implants were placed too close togeth-
er the bone remodelling overlapped to a great
degree and consequently resulted in loss of ver-
tical bone height which subsequently had soft
tissue implications.
When implants were placed 3 mm and greater,
lateral bone loss from the adjacent implants did
not overlap with minimal resultant crestal bone
loss. They concluded that it is more difficult to
create or maintain papilla between two adjacent
implants than it is between an implant and a nat-
ural tooth. Their recommendation was that when
two implants are placed adjacent to each other in
the aesthetic zone, a minimum of 3 mm of bone
should be retained between them at the implant/
abutment level (Figs 48-49). This particular study
addressed bone loss between the implants. It
should be remembered that the bone saucerisa-
tion has two dimensions — a horizontal and a ver-
tical. Radiographs only demonstrate the horizon-
tal aspect of bone saucerisation. Bone loss occurs
circumferentially around the implant and when
two implants are placed adjacent to each other
facial bone loss also occurs (Figs 50-51). This has
implications in terms of stability of the facial gin-
gival margin. If the implants are placed too far
forward there will be less facial bone and this will
ultimately result in apical migration of the free
gingival margin (Fig. 52). Placement of adjacent
implants is also critical for restorative contours;
placing implants too close together makes it dif-
ficult for the laboratory technician to fabricate
restorations with pleasing aesthetic contours.
Tarnow and colleagues27 also performed
a study to determine the height of the soft tis-
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23
sue to the crest of the bone between two adja-
cent implants. This was done independent of
the location of the contact point. They looked
at 136 inter-implant papillary heights in 33
patients by eight examiners. A standardised
periodontal probe was used and placed from the
height of the papilla to the crest of the bone.
What they found was that the mean height of
papilla between two adjacent implants was 3.4
mm with a range of 1-7 mm.
Although this was a retrospective study
and there were many variables such as opera-
tor, implant type, placement and so forth it did
give us information that soft tissue between two
adjacent implants in the aesthetic zone is not
a predictable procedure, and when treatment
planning, the patient must be aware of this or
alterations must be made in the treatment plan
to provide an aesthetic result.
Recreating interdental papilla between two
adjacent implants is a formidable task. Restora-
tively, clinicians alter the position of the contact
point to give the illusion of papilla. The thin spi-
cule of bone remaining between the implants may
be sufficient to maintain the papilla during the
first few years of the restorations service. How-
ever, there are no clinical studies with long term
results presented to date to illustrate the predict-
ability of papilla between two adjacent implants.
Another clinically challenging situation is
replacement of a maxillary canine and adjacent
lateral incisor. This becomes clinically more
challenging because the edentulous space is
smaller and the inter-implant soft tissue tends
to be less voluminous. Consideration in this
instance should be given to placement of a
single implant in the canine region and canti-
levering a lateral incisor from it. Placement of
the implant should follow all the principles dis-
cussed previously in the article.
Replacement of several missing teeth with
implants allow for the use of fixed partial den-
tures and the opportunity to use ovate pontics to
help support the soft tissue and give an illusion
of papillae. The authors have encountered many
situations where one implant per tooth philoso-
phy is espoused to. This can be particularly det-
rimental in the aesthetic zone. The literature is
quite clear that maintaining papillae between
implants is not predictable. Even with the advent
of scalloped type implants there are no long
term studies showing papilla maintenance. For
an aesthetic outcome it is more predictable to
place implants away from each other so that the
intervening soft tissue can be sculpted to give
the illusion of papilla. One common error often
published in the literature is placement of four
implants to replace lateral incisor to lateral inci-
sor. This philosophy of implant placement will
not yield an aesthetic outcome (Fig. 55). Place-
ment of two implants in both lateral incisor
regions and fabrication of a fixed partial den-
ture sculpting the intervening tissue with ovate
pontics is likely to produce an illusion of papilla
which will be more pleasing to the observer’s eye
(Fig. 56). This placement philosophy can also be
reserved for extended edentulous spans where
aesthetics is of paramount importance (Figs 57-
58). Placement of implants in multiple edentu-
lous spaces must follow the same principles as
for single tooth situations; placement must fol-
low appropriate diagnosis and treatment plan-
ning, which includes a diagnostic wax up and
fabrication of a surgical guide to facilitate
implant placement. If these techniques are not
followed it is all too easy to easy to find implants
in the wrong position where prosthetic strategies
have to be used to satisfy the patient’s demand
for aesthetics. In situations like these patient
expectations are unlikely to be met (Fig. 59-61).
CONCLUSION
When a patient has a missing anterior tooth and
desires replacement, a decision must be made
by the dentist and patient as to the method of
replacement. Common choices would include a
conventional fixed partial denture, a resin bond-
ed fixed partial denture or an implant borne res-
toration. Each has its advantages and disadvan-
tages. The conventional fixed partial denture has
the advantages of being an established treatment
procedure, of having predictable aesthetics, and
being expedient. It has the disadvantage of requir-
ing preparation of adjacent teeth and potential
risk for periodontal and pulpal tissue. The resin
bonded partial denture has the advantages of pre-
serving tooth structure, having predictable aes-
thetics and reduced cost. It has the disadvantages
of being technique sensitive for the dentist and
technician and often losing retention which may
lead to decay. Implants used to replace missing
teeth in the aesthetic zone have many advantages
from preservation of unrestored adjacent teeth,
halting the resorption of edentulous spaces and
providing support. However, at present it has the
disadvantages of long treatment time, requiring
a provisional restoration during implant integra-
tion, requiring surgical placement of the implant,
requiring surgical uncovering of the implant,
requiring a provisional after the implant is
uncovered and having a higher cost. Much effort
is being directed at shortening the treatment time
and making delivery of the service more time
efficient. Immediately loading implants is one
direction that many researchers and clinicians are
taking. However, the parameters to when imme-
diately loading implants is possible have not
been established and until that time, immediately
loading implants must be made on an individual
and case by case basis, taking into account all
the factors that affect loading of the initially non
osseointegrated implants.
Even with all the disadvantages listed, the
implant supported single tooth restoration can
be successfully executed when all the factors
discussed in this article are addressed. When
one or more of the adjacent teeth are unrestored
or in need of only a minor restoration, the single
tooth implant should be considered the restora-
tion of choice.
1. Sullivan R M. Perspective on aesthetics in implant dentistry.
Compendium 2001; 22: 685-692.
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BRITISH DENTAL JOURNAL VOLUME 201 NO. 1 JUL 8 2006
Fig. 45 (left) Profile of restoration
in Figure 44 illustrating a
biomechanical and hygienic
compromise
Fig. 46 (right) Too facial an implant
placement
Fig. 48 (right) When implants are
placed 3 mm and greater apart the
bone loss from the adjacent implants
does not overlap resulting in minimal
crestal bone loss. (Modified from
Tarnow et al.)11
Fig. 47 (left) Too facial an implant
placement will result in facial bone
resorption and apical migration of the
soft tissue. The resulting restoration
will appear long in comparison to the
contra lateral tooth
Fig. 49 (left) When implants are placed
too close together, bone loss from
adjacent implants overlaps resulting
in additional loss of the crestal bone.
(Modified from Tarnow et al.11)
Fig. 51 (left) Ideal implant
theoretically will maintain the
interproximal peak of bone, however
there are no long term studies to
support this
Fig. 50 (right) Bone loss is
circumferential around the implants.
When implants are placed too close
together the vertical and horizontal
components of bone loss compromise
the peak of the interproximal bone
and thus the resulting soft tissues
Fig. 52 (right) If implants are place
too facial this will compromise the
thickness of the facial bony plate
which can eventually resorb. This
will result in apical migration of the
soft tissue
Fig. 54 (right) Implants placed
too close together will result in
compromised restorative contour
Fig. 53 (left) Ideal implant
placement will allow fabrication of
restorations with ideal contours
Fig. 56 (right) It is easier to develop
illusion of papilla between an
implant and an adjacent pontic.
Implant placement philosophy should
take advantage of such techniques
Fig. 55 (left) Placement of adjacent
implants compromises the inter
implant peak of bone resulting in
resorption and soft tissue loss
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Fig. 57 (left) Clinical slide showing
Implant placement so that illusion of
papilla can be developed
Fig. 58 (right) Facial view of slide in
Figure 57
Fig. 59 (left) Laboratory slide
illustrating facial placement of
implants
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incisor. This is likely the occurrence
of placement without a surgical
guide
Fig. 61 Facial view of slide in Figure
60 depicting interproximal implant
placement in the region of the right
lateral incisor, this is likely to result
in absence of interproximal soft
tissue
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