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11
MODIFICATIONS TO IMMEDIATE MOLAR IMPLANT PLACEMENT PROTOCOLS
188
bone regeneration with graft and barriers. However,
recent authors have shown that if the procedure to
place the IMI was planned to be apless, simpler
options are possible. For example, Hu et al26 managed
IMI placement in sites with varying degrees of buccal
dehiscence simply by densely packing xenograft particles under the buccal soft tissues and waiting 6 months
for bone healing. Sicilia-Felechosa et al27 used a similar
approach for buccal dehiscences, but rst placed and
stabilized with sutures either an autogenous connective tissue graft or AlloDerm (AbbVie) under the buccal
soft tissues.
Socket Shielding
Purpose of socket shielding
Socket shielding, intending to retain alveolar ridge
anatomy, is another approach recently suggested to
oer positive benets with IMI outcomes.28 e loss of
a tooth leads to profound changes of its alveolus that
may directly inuence the ability to place an implant.
e amount of resorption the alveolus will undergo
following tooth extraction is dicult to predict, but
it is generally held to be 50% or more by 1 year.29 e
main reason for this resorption is due to the “bundle
bone phenomenon.” Bundle bone is the thin (0.2- to
0.4-mm) layer of bone laid down by the developing
tooth bud when a tooth’s root system rst develops. It forms part of the periodontal ligament (PDL)
complex, and once the tooth is extracted, it quickly
resorbs because of the lack of function and loss of
blood supply from the PDL.
“Partial extraction therapy”28 is an umbrella term
for techniques where either the whole or part of the
root is left behind to help maintain the integrity of
the ridge. e technique of socket shielding, or the
root membrane technique,30 involves leaving a thin
shell of buccal tooth root and periodontal attachment
apparatus at the time of immediate implant placement
in order to maintain buccal alveolar ridge contour,
and it was rst studied as a concept in one dog.31 e
investigators sectioned the dog’s mandibular third and
fourth premolars and decoronated the distal aspect of
each crown to allow implant osteotomy preparation
toward the lingual and within the remaining distal
root structure. After osteotomy preparation, any
remaining proximal or lingual root remnants were
removed, leaving only a thin shell of intact tooth and
periodontium buccally and extending approximately
1 mm coronal to the buccal bone plate. Enamel matrix
derivative (Emdogain, Straumann) was applied to the
internal aspect of this buccal fragment, presumably to
encourage new cementum formation,32 followed by
placement of an immediate implant. Four implants
were placed, with two intentionally in direct contact
with the buccal root fragment and two not. Placement of 4-mm-long healing abutments then allowed
nonsubmerged site healing. After 4 months, specimens
were retrieved and examined by backscatter scanning
electron and light microscopy. With the two implants
intentionally installed in contact with the retained
shell of tooth, new cementum did in fact form at the
implant-to–tooth fragment interface. e removal
of the palatal or lingual portion of the root, including its root canal contents, apex, and any pathology,
FIG 11-5 (a to c) To avoid buccal plate thinning and unwanted shrinkage in alveolar ridge anatomy, it can be useful to do buccal onlay
grafting. is grafting can be as straightforward as placing xenograft particles in a pouch under the periosteum.
a b c
189
Socket Shielding
combined with the maintenance of the thin section of
buccal root and periodontium, was seen to maintain
and nourish the thin buccal plate and bundle bone.
Following this proof-of-principle study, investigators33
undertook clinical studies conrming at 5 years that
there were minimal changes in local ridge dimensions.
A large cohort retrospective study by Gluckman et
al34 conrmed the viability of the technique despite
limitations.35
e original socket shield was intended to contribute to esthetically pleasing immediate implants placed
in the anterior maxilla, and this has proved to be the
case.
However, the technique is highly technical and
likely not appropriate for use by the average clinician
without training. Nevertheless, with adequate experience, it has now been shown to be applicable with
IMI placement. e concept of the molar shield was
rst published by Schwimer36 and coworkers, showing
excellent maintenance and emergence of alveolar bone
and soft tissue morphology both clinically and radiologically. e thinness and curvatures of molar roots,
however, can make it dicult to resect the lingual or
palatal portions and to eliminate apical pathology. If
successful, the rewards are stunning. Contraindications include molars with marked curvatures in the
root, lack of buccal plate, periodontal attachment loss,
mobile roots, and inaccessible apical infection.
Socket shielding procedure
A molar should be prepared for socket shielding as
shown in Fig 11-6. e authors recommend raising a
conservative ap to enable visualization of the buccal
bone crest (Figs 11-6a to 11-6c). Following decoronation, the root trunk is sectioned mesiodistally at
the level of the furcation using a long-shank, straight
diamond bur at high speed and with copious irrigation
(Figs 11-6d and 11-6e). e length and depth of cut
needed are determined from the pretreatment radiographs. is sectioning will allow separation of the
buccal from the lingual/palatal root portions. ereafter, a similar mesiodistal cut is made in the buccal
half of the rst cut (Fig 11-6f). e unwanted root
fragments are removed, leaving only the two future
socket shields, which then can be thinned and shaped
with the same long shank diamond bur18 (Figs 11-6g
and 11-6h). Next, a round 2-mm-diameter diamond
bur is used at high speed to reduce the crestal portion
of the two socket shields to bone level and create a
2-mm internal chamfer bevel to provide prosthetic
space for the crown margin (Figs 11-6i and 11-6j).
At this point, the root sockets should be meticulously curetted apically and rinsed vigorously using
sterile saline. One or more periapical radiographs
should be taken to verify that all endodontic root
FIG 11-6 (a to c) Both the mandibular second premolar and rst
molar in this patient were condemned with the plan to place immediate implants.
a b
c
11
MODIFICATIONS TO IMMEDIATE MOLAR IMPLANT PLACEMENT PROTOCOLS
190
FIG 11-6 (cont) (d) After decoronation, the
teeth are sectioned into buccal and lingual
halves. (e) Illustration of the rst cut. (f )
The second cut is made to separate the
buccal half into two pieces. (g) After removal
of the unwanted root fragments, the two
“shields” can be thinned further using a
long-shanked diamond pencil bur. The
remaining IRS can be seen to be type C.18
(h) e pencil bur is used to thin and shape
the buccal root shields. (i) A high-speed,
large-diameter round diamond bur is then
used to reduce the crestal portion of the two
socket shields to bone level and create a
2-mm internal chamfer bevel to provide
prosthetic space for the crown margin. (j)
e round bur is used to reduce the height
and create a chamfer in the two buccal
shields. (k) e two implants were successfully placed and stabilized. (l) Custom healing abutments were fabricated chairside to
isolate the peri-implant gaps and shape the
surrounding soft tissues during site healing.
No suturing of the tissues was needed. (m)
When the implants were ready for restoration, the soft tissue contours were seen
to have been maintained by the custom
healing abutments. (n) A clinical photograph at the time of insertion of the implant
restorations. (Illustrations courtesy of Dr
Ryan Noh, University of Toronto.)
d e f
g h
i
k
j
l
m n
191
IMI Placement and Risk of Interproximal Caries
canals and obturation material and granulation
tissue have been eradicated. Knowing this and that
there is absolutely no mobility of the buccal root
shields after checking their internal surfaces with a
sharp probe, the implant osteotomy preparation can
proceed. Wherever possible, the authors prefer to use
the osseodensication protocol described by Huwais
and Meyer
37
(see chapter 7).
After inserting the implants and verifying them
to have adequate stability (Fig 11-6k), the buccal
gaps between implant and shields were grafted with
a particulate bone allograft. Finally, custom transgingival healing abutments were prepared onto
PAEK (polyaryletherketone) temporary prosthetic
abutments, taking care to capture and support the
soft tissues with a aring emergence prole that
conformed to the socket circumference (Fig 11-6l;
see also chapter 12).
Explicit postoperative instructions are necessary.
Typically, patients are prescribed a regimen of a 0.2%
chlorhexidine oral rinse twice daily for 2 weeks. Generally, systemic antibiotics are unnecessary and not
prescribed. A short checkup appointment is made
for the patient 48 hours postsurgery, and again at 2
weeks for removal of any sutures used. Assuming that
no adverse healing events are reported by the patient,
the implant should be ready for restoration (resonance
frequency value > 70) after approximately 3 months,
preferably with a screw-retained crown (Figs 11-6m
and 11-6n).
IMI Placement and Risk of
Interproximal Caries
Matching implant diameter to the mesiodistal space
of a molar extraction site, ie, the distance from the
implant’s coronal margin (implant-to-abutment interface) from the proximal surfaces of contiguous teeth
is a crucial consideration. us, Smith et al38 observed
that when the implant-abutment interface is placed
too far from an adjacent tooth root surface, an unusually high incidence of caries on this tooth is a risk,
likely due to frequent food impaction/collection. e
cited critical implant-tooth distance (ITD) was found
by the author to be 4 mm (Fig 11-7). Cases in which
the ITD was 4 mm or more showed a clinically and
statistically signicant jump in decay rates, with rates
continuing to rise as distance increased.
e distance from tooth to tooth as measured at the
alveolar crest across an edentulous molar site will vary
between arches and with the sex of the patient. For
example, mean mesiodistal widths of mandibular rst
molars have been recorded as 11.5 mm in men and
10.9 mm in women, while the same measurements
for mandibular second molars are 10.9 mm in men
and 10.1 mm in women.39 erefore, with typical
mandibular molar sites (mesiodistal width up to 11
mm) having type A or B septa, appropriate implant
diameters would be 4.5 to 6.0 mm. With a 6-mm-
diameter implant, the ITD would be approximately
2.5 mm from each adjacent tooth. On the other hand,
with type C septa or when mesiodistal width of the
site is signicantly greater than 11 mm, an implant
of wider diameter may be needed to reduce risk of
root caries. With some of these situations, an ultrawide-diameter implant (> 6 mm) can be helpful (Fig
11-8; see also chapter 8).
Rarely, the distance between the teeth on either
side of an IMI may be too great even for an ultrawide implant to allow the ITD to be less than 4 mm
on either side. In these cases, two narrower-diameter
implants placed in the root sockets and within the
acceptable ITD range may be preferable (Fig 11-9). e
FIG 11-7 ITD is measured horizontally at the level of the crest of
bone from the implant-abutment interface to the adjacent root
surface.
11
MODIFICATIONS TO IMMEDIATE MOLAR IMPLANT PLACEMENT PROTOCOLS
192
restoration then can be designed as either two premolars or as a “uted” molar with a cleansable gingival
embrasure between the two implants. If the implant
is to replace the terminal molar in the arch, it is more
important to place the implant within an acceptable
ITD to the tooth mesial to it than it is to place it in
the center of the socket.
Osseodensification for Indirect
Sinus Floor Elevation
As discussed elsewhere in this book (see chapter 7),
unlike traditional implant burs that remove bone in
order to create an osteotomy, osseodensication burs
run at high speed in reverse (ie, noncutting) mode,
creating osteotomies by compacting bone laterally and
apically. e autograft collected and pushed apically by
these burs can create a minor (2 to 3 mm), localized,
indirect sinus oor elevation not unlike that achievable with hand osteotomes,
40,41
but in a much less trau-
matic way for the patient and less stressful manner for
the clinician. However, the approach can be further
modied for sites requiring more than 3 mm of sinus
elevation using a well-tested protocol provided by the
manufacturer. Sites selected should have 4 to 5 mm of
residual subantral bone height measured from CBCT
scans. e surgery should be apless, as is usual with
IMI procedures. Following decoronation of the molar
crown at the level of the tooth’s furcation, the three
roots should be sectioned and removed individually.
e case shown is one with a maxillary rst molar
needing replacement (Figs 11-10a to 11-10c). After
extraction, a type A IRS suitable to receive an IMI
remained (Fig 11-10d). The plan was to place a
10-mm-long × 6-mm-diameter implant, meaning
that around 6 mm of sinus membrane elevation was
needed. Rather than initiating the osteotomy with a
pilot bur, the smallest diameter (2.0-mm) Densah bur
(Versah) was used in cutting mode (clockwise) to the
approximate depth of the sinus oor. e same bur
then was used in reverse (counterclockwise [CCW]
FIG 11-8 (a) An ultra-wide implant was used in this site to ensure appropriate ITD. (b) Use of an ultra-wide-
diameter implant will allow for an anatomically accurate molar restoration.
a b
FIG 11-9 Two 4.1-mm-diameter implants were placed at this
mandibular molar site in order not to exceed favorable ITD
distances.
193
Osseodensification for Indirect Sinus Floor Elevation
mode) at 800 to 1,500 rpm to locate the sinus oor
with haptic feedback and then upfracture it, leaving
an intact sinus membrane (Figs 11-10e and 11-10f).
Osteotomy development is then continued in sequence
with Densah burs of 3-, 4-, and 5-mm diameter in
CCW mode, each entering the sinus domain 1 mm at
a time to a nal depth of 3 mm, all the while employing a modulating pressure and pumping motion with
the handpiece.
Sticky bone was prepared as the graft material by
combining the patient’s platelet-rich plasma with
particulate allograft material
23
(Fig 11-10g). is
e
f
FIG 11-10 (a) Residual bone height of the IRS ranged from 3.2 to 4.21 mm. (b) Type A IRS of 4.21-mm height was seen. (c) e lowest
measurement of residual IRS was measured as 3.32 mm. (d) e tooth roots were removed without raising a mucoperiosteal ap to
reveal a type A socket. (e) Osseodensication burs were used in reverse mode to propel autogenous bone shavings from the osteotomy
walls apically, ultimately upfracturing the sinus oor. (f) e initial osteotomy included intentional upfracture of the sinus oor, reaching
3 mm into the sinus domain without damaging the sinus membrane by driving autogenous bone shavings upward.
a b
c
d
11
MODIFICATIONS TO IMMEDIATE MOLAR IMPLANT PLACEMENT PROTOCOLS
194
biomaterial has the advantages of immediately sealing
any undetected minor membrane tears, having antiinammatory/antibacterial properties, and containing growth factors that promote vascular ingrowth
and osteogenesis. e sticky gelatinous preparation
was cut into small pieces, which were then packed into
the osteotomy one at a time and propelled apically
into the sinus domain using the 5.0-mm Densah bur
in CCW mode at 100 rpm and without irrigation (Fig
11-10h). While the bur propelled the graft material
apically, the actual bur tip was not allowed to pene-
trate more than 1 to 2 mm into the graft material,
after which the procedure was repeated with more
sticky bone. is sequence was repeated sucient
times to achieve the desired elevation of the sinus
membrane, which in this case was approximately 6
mm beyond the original sinus oor in order to receive
a 10-mm-long × 6-mm-diameter implant (Figs 11-10i
to 11-10r). Once inserted, the implant stability was
measured with resonance frequency analysis to be
75, as measured with an Osstell resonance frequency
device.
FIG 11-10 (cont) (g) Sticky bone was
created by mixing the patient’s venous
platelet-rich plasma with particulate
allograft.23 (h) Small bits of sticky bone
were added to the site and propelled
apically with the bur used in CCW mode
at 100 rpm without irrigation to elevate
the sinus oor to the desired level. (i)
Small bits of sticky bone were added in a
stepwise fashion and propelled apically
using the bur in reverse mode without
saline at 100 rpm. Never did the actual
bur tip penetrate more than 1 to 2 mm
beyond the sinus oor. (j) Once the sinus
membrane had been elevated approximately 6 mm, a 10-mm-long implant was
inserted. (k) Following implant placement, all gaps were lled with sticky bone
as a means of supporting the soft tissue
prole during site healing. (l) A chairside
customized abutment was used to shelter
the grafted gaps and support the healing
soft tissues.
j
g h
i
lk
195
Short Implants as IMIs
Short Implants as IMIs
While short threaded implants (≤ 7 mm) had a checkered history in the past,42 considerable evidence has
now accumulated to verify that with proper technique and implant design, implant length is rarely
a primary consideration43 since functional loading
primarily aects only the most coronal three to ve
threads regardless of implant length.44 Accordingly,
many implant manufacturers now oer short (6 to
8 mm) and even ultra-short (< 6 mm) implants for
use in replacing molars, particularly in the mandible, where proximity to the neurovascular canal is
a hazard.45 Many of these were originally oered as
“rescue” implants and were made with diameters of
5 mm or greater, generally for use at healed extraction
sockets.
45,46
e present authors have used both short
and ultra-short threaded implants frequently, initially
in healed extraction sites, but more recently as IMIs.
Several sample IMI cases will be shown.
Case 1
A rst example involved a patient needing replacement of his left maxillary right second premolar and
rst and second molars (Fig 11-11a). e three teeth
FIG 11-10 (cont) (m) e immediate postoperative radiograph of the implant and abutment. (n) A CBCT image of the implant imme-
diately after placement. A well-circumscribed dome of sticky bone can be seen holding up the sinus membrane. (o) e soft tissue prole
after 3 months of site healing. (p) A photograph of the denitive restoration. (q) An occlusal image of the screw-retained implant crown.
(r) e radiograph of the restored implant.
q r
o p
n
m
11
MODIFICATIONS TO IMMEDIATE MOLAR IMPLANT PLACEMENT PROTOCOLS
196
were removed using apless surgery, and three immediate implants were placed (Figs 11-11b and 11-11c),
the two molar implants being short Dentium Superline implants (7 mm long × 6 mm diameter). No gap
grafting was done, and the implants were left with
healing caps rather than healing abutments. Healing was uneventful, and after 3 months, the molar
implants were used to support a two-unit xed partial
denture, while the premolar implant received a single
crown (Figs 11-11d and 11-11e).
Case 2
e second example is of a single hopeless maxillary
rst molar (Fig 11-12a). While minimal subantral bone
height remained, the socket walls were all intact, and
the septum was type B (Fig 11-12b). erefore it was
decided to place an IMI with dimensions 5 × 5 mm
(Fig 11-12c). e immediate postoperative radiograph
of this implant can be seen in Fig 11-12d. No transcrestal sinus grafting was used, and while large periimplant gaps remained, these were left ungrafted. A
healing cap rather than a healing abutment was used,
and healing by secondary intention was uneventful
(Fig 11-12e). e implant was successfully restored,
but the patient has not yet been available for a current
image of the restored implant.
FIG 11-11 (a) Both of these molars and the second premolar
presented with advanced periodontal destruction. (b) Using
flapless surgery, three immediate implants were placed.
(c) Dentium Superline implants of 7-mm length and 6-mm
diameter were used as IMIs to replace the two molars. (d)
e two restored short implants are seen here after 1 year
in function. (e) A periapical radiograph of the two short
implants replacing the molars. Both implant apices appear
to have breached the sinus oor.
a b
c
d
e
197
Short Implants as IMIs
Case 3
A third case involved a patient requiring the replacement of his maxillary right rst and second premolars
and rst and second molars (Fig 11-13a). Immediate
implants were planned for all four sites. MegaGen
Rescue implants (5 × 5 mm) were selected for the
two molar sites, as there was very limited subantral
bone height (Figs 11-13b and 11-13c). Healing caps
only were used. No gap grafting was done, and the
soft tissue margins were secured with sutures. As can
be seen in the postoperative radiograph (Fig 11-13d),
both implant apices penetrated through the sinus
oor, but the implants were stable (Fig 11-13e).
a
b
c d e
FIG 11-12 (a) e maxillary right rst molar was deemed hopeless. (b) After removing the tooth remnants, a type B IRS was seen. (c)
e implant was stabilized by the IRS, and no gap grafting was needed. (d) An immediate postoperative radiograph of the implant. (e)
By 3 weeks, the peri-implant gaps showed advanced healing by secondary intention.
FIG 11-13 (a) All four posterior teeth in this quadrant were hopeless. (b) All four sites received immediate implants. (c) No gap grafting
was performed. (d) An immediate postoperative radiograph shows that the two molar sites received ultra-short, ultra-wide threaded
implants. (e) A panoramic radiograph of the completed case after 1 year in function.
a b c
d e