Partial-extraction therapy and dual-zone augmentation

Abstract

Recently, an aspect of partial-extraction therapy, the socket-shield technique, found its way into implant dentistry. This technique provides dimensional stability around an implant site without the use of any adjunctive biomaterials.

Full text

and the periodontal ligament. Since the average
thickness of the buccal bone in the aesthetic zone
is less than 1 mm [6], it hardly contains any well-
vascularized cancellous bone tissue. After an ex-
traction, no blood is supplied from the periodon-
tal ligament, so that the periosteum remains the
only one source of blood. For this reason, implants
should be placed without raising a ap.
Lee showed that lingualized apless implant
placement into fresh extraction sockets preserves
the buccal alveolar bone [7]. Gap augmentation
with a slowly resorbable bone substitute can com-
pensate for the bone-remodelling process [8,9].
Post-extraction implants placed in the palatal
aspect of the socket in a apless procedure with
gap augmentation have a lower risk of mid-facial
recession [10,11]. Additionally, immediate provi-
sionalization and custom healing abutments have
proven benecial for the long-term stability of the
marginal gingiva [5,12,13].
A further improvement can be achieved by per-
forming partial extraction therapy (PET), especially
when leaving a socket shield in place. The principle
is to prepare the root such that the buccal/facial
root section remains in situ, with its physiological
relation to the buccal bone plate intact.
The periodontal attachment of the root section
should remain vital and undamaged to prevent the
post-extraction socket remodelling otherwise to be
expected.
A frequently cited literature review dates from
2009 [4]. In 2015, another systematic review con-
cludes: “Immediate placement with immediate pro-
visionalization of dental implants in the aesthetic
zone results in excellent short-term treatment out-
comes in terms of implant survival and minimal
changes of peri-implant soft and hard tissue dimen-
sions” [5]. Over time it became clear that to achieve
a good aesthetic result, a post-extraction implant
should be placed on the palatal aspect of the socket
using a apless procedure, and the gap should be
augmented with a slowly resorbable bone substitute.
Blood is supplied to the buccal bone shield from
threes sources: cancellous bone, the periosteum
Immediate implant placement in the aesthetic zone
Partial-extraction therapy and
dual-zone augmentation
SNJEŽANA POHL, MD, DMD, EDA EXPERT FOR PERIODONTOLOGY AND IMPLANTOLOGY, RIJEKA, CROATIA
Studies have shown that the survival rate for implants placed in fresh extraction sockets is the same as that
for conventionally placed implants [1–3]. Although the success rates for both immediate and delayed im-
plant placement are comparable, the literature cautions us to expect recession of the facial gingiva following
immediate implant placement [1]. We should be aware that systematic reviews include studies regardless of
the surgical and prosthetic protocol used: ap procedures and apless procedures; buccal, central or palatal
implant positions; gap augmentation or no gap augmentation; primary wound closure or open healing.
1 I Initial situation. The right central incisor is hopeless.
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CASE STUDIES

of 46 implants placed immediately after extraction
using the socket-shield technique [18]. He reported
a 100 per cent survival rate.
Case 1: Socket-shield technique
A 25-year-old female patient presented with a right
central incisor that was non-restorable due to cervi-
cal decay (Figs. 1 to 3). The patient had good inter-
proximal bone levels; all socket walls were present.
There were some asymmetries of the gingival mar-
gins: On the right central incisor, the gingiva level
was more coronal compared to the adjacent central
incisor (see Fig. 1).
It was decided to replace the failing incisor with
an implant-supported crown. To preserve as much
hard and soft tissue as possible, an immediate post-
extraction implant was to be placed in combination
with partial-extraction therapy.
After the crown had been hemisected (Fig. 4), the
tooth was dissected in a mesiodistal direction, and
the palatal and apical portions of the root were re-
moved (Fig. 5). The vestibular socket shield was
levelled to one millimetre above the buccal bone.
Aminimal ap was raised to shape the coronal part
of the socket shield to smooth any sharp edges
(Fig.6).
There are contraindications to the socket shield
technique, such as periodontitis, root resorption
and tooth mobility. The procedure is time-consum-
ing and technically rather challenging. If there is a
contraindication or if the socket shield fails during
preparation, dual-zone augmentation is a possible
alternative for achieving a highly aesthetic result.
Dual-zone augmentation includes peri-implant hard
as well as soft-tissue augmentation.
The socket-shield technique
In 2010, Hürzeler published an animal experimental
study and a case report entitled “The socket-shield
technique: A proof-of-principle report” [14]. One
critical factor for buccal bundle-bone resorption
is the loss of periodontal ligament. The resorption
of the buccal bundle bone can be avoided by leav-
ing a buccal root segment in place (socket-shield
technique), as the biological integrity of the buccal
perio dontium (bundle bone) remains untouched.
In the last six years, several clinical studies have
demonstrated the potential of buccal root reten-
tion (socket-shield technique) in combination with
immediate implant placement to avoid signicant
changes in ridge shape after tooth extraction [15–
17]. Siormpas published two- to ve-year follow-ups
3 I Occlusal view prior to tooth extraction.2 I Preoperative CBCT showing root decay.
The buccal bone wall is present.
4 I The crown is hemisected. There is some
root resorption.
5 I The root is separated in a mesiodistal
direction. The palatal part of the root with
the apex is taken out.
6 I A socket shield is prepared 1 mm above
the buccal bone crest.
CASE STUDIES
67

tissue on the implant site. The CBCT taken one year
after implant placement illustrates very well main-
tained buccal bundle bone (Fig. 14). Figures15 and
16 show zirconium coping on a hybrid abutment.
The sagittal view shows a natural emergence prole
(Fig. 17). The pressable ceramic crown immediately
after insertion is to be seen in Figure 18.
A 4.1 × 13 mm implant (Semados RSX; Bego,
Bremen, Germany) was placed in a 3D comfort zone
(Figs. 7 to 9). Since the insertion torque was 40 N·cm
and the ISQ was 70, it was decided to restore it with
an immediate provisional crown (Fig. 10).
Five months after the rst (and only) surgery,
the hard and soft tissue were very well preserved
(Figs.11 and 12). Figure 13 shows an occlusal view
with a provisional crown in situ. The intentional re-
tention of the facial aspect of the root preserved the
7 I An implant (4,1 × 13 mm, Bego Semados RSX) is placed in a ap-
less procedure.
8 I Occlusal view showing the implant placed in the palatal aspect of
the socket with some contact with the socket shield.
11 I Five months after surgery, the papillae are well maintained.
9 I Postoperative radiograph.
12 I The occlusal view shows no dierence in horizontal ridge volume
between the implant site and the adjacent tooth.
10 I The provisional crown is placed on the same day.
68
CASE STUDIES

and Salama[20,21]. The provisional restoration can
then act as a “prosthetic socket seal” to protect,
contain and maintain the blood clot and bone-graft
material during the healing phase.
Tarnow, Chu and Salama also proved that hard-
and soft-tissue grafting at the time of implant
placement in combination with a contoured heal-
ing abutment or a provisional restoration result in
the smallest amount of ridge contour change. This
concept is called “dual-zone augmentation”.
Dual-zone augmentation
Bone-zone augmentation between the implant and
the socket wall reduces dimensional changes of
the ridge after tooth extraction. A further improve-
ment can be achieved by soft-zone augmentation.
Araújo and coworkers showed that xenograft parti-
cles can be incorporated into the soft-tissue prole
without any inammatory reaction [19]. These in-
corporated particles provide substance to increase
the soft-tissue prole as described by Tarnow, Chu
13 I Occlusal view with provisional crown.
15 I Hybrid abutment, occlusal view, …
17 I … and prole view.
14 I CBCT one year after
implant insertion.
16 I … frontal view, …
18 I Screw-retained pressable-ceramic crown immediately after insertion.
Prosthodontics: DrJagoda Berber Torbarac, Rident Clinic.
CASE STUDIES
69

The treatment plan included immediate implant
placement for the left central incisor, a pressable-
ceramic crown for the right central incisor and ve-
neers for the two lateral incisors.
The left central incisor was extracted as atrau-
matically as possible (Fig. 22). All socket walls
were present. After thorough debridement, the
implant site was prepared in the palatal aspect
of the socket. Biological drilling as described by
Anitua was performed (50 rpm without irrigation)
Case 2: Dual-zone augmentation
A 35-year-old healthy female patient, a non-smoker,
presented with a left central incisor that was failing
due to external root resorption (Fig. 19). The other
incisors exhibited unaesthetic llings and chipping
(Fig. 20). The patient had a high smile line (Fig. 21).
The treatment goal was to replace the left cen-
tral incisor with an implant-supported crown and
to preserve the papilla and the level of the facial
gingival margin.
19 I Pre-treatment radiograph showing
external root resorption of the left central
incisor.
20 I Pre-treatment photograph showing incisors with wear and
unaesthetic llings.
21 I The smile line is high.
22 I The left incisor is removed in a apless procedure. 23 I Situation immediately after implant insertion (4,5 × 13 mm,
Bego Semados RSX); dual-zone augmentation.
70
CASE STUDIES

Following osseointegration of the implant, a
provisional crown was placed and left in place for
another three months (Fig. 26). An impression was
taken, the cast was scanned and a zirconia abut-
ment was designed. The abutment was milled in
Bego Medical (Fig. 27). Pressable-ceramic crowns
were cemented onto the implant and the adjacent
central incisor. Both lateral incisors received veneers
(Figs. 28 and 29). Figure 30 shows the radiograph
taken after crown cementation.
to collect autologous bone particles. A 4,5 × 13 mm
implant (Semados RSX; Bego) was inserted with
40 N·cm of insertion torque.
The gap between the socket wall and the implant
body was augmented with a mixture of two-thirds
autologous bone particles and one-third of a xeno-
graft material (Bego Oss). The same mixture was
used to augment the space between the healing
abutment and the soft tissue (Fig. 23).
Prior to implant placement, a provisional Maryland
bridge was prepared. The pontic was designed to
shape the peri-implant soft tissue (Figs. 24 and25).
24 I A Maryland bridge is inserted as a temporary restoration. 25 I Postoperative radiograph.
26 I After osseointegration of the implant, a provisional crown is
produced.
27 I Zirconia abutment milled in Bego Medical. The adjacent teeth
are treated with a crown and veneers.
28 I Situation immediately after denitive cementation
of the implant crown and veneers.
29 I Occlusal view immediately after prosthetic rehabili-
tation.
30 I Radiograph
after implant/pros-
thetic rehabilitation.
CASE STUDIES
71

Conclusion
Implants placed in fresh extraction sockets of type
one (all socket walls present) have the same survival
rates as conventionally placed implants. Mid-facial
recession can be avoided if the implant is placed lin-
gually in a apless procedure and the gap is lled
with a slowly resorbable bone substitute.
Immediate provisionalization and dual-zone aug-
mentation are known to be key factors for minimiz-
ing hard- and soft-tissue volume changes.
Recently, an aspect of partial-extraction therapy,
the socket-shield technique, found its way into im-
plant dentistry. This technique provides dimension-
al stability around an implant site without the use
of any adjunctive biomaterials.
The references are available at www.teamwork-media.de/literatur
Contact address
Snježana Pohl, MD, DMD
Poliklinike Rident
Franje Čandeka 39
Rijeka 51000 · Croatia
snjezana.pohl@rident.hr
Eighteen months after the implant/prosthetic
treatment, the peri-implant hard tissue was stable
(Fig. 31). The CBCT scan showed the bone volume to
have been preserved (Fig. 32). Both the papillae and
the marginal gingiva were well maintained (Fig. 33).
A close-up image showed a highly aesthetic out-
come (Fig. 34). On a scale of 1 to 10, the patient
rated the outcome a resounding 10 (Fig. 35).
31 I Radiograph 18 months after treatment showing a
stabile peri-implant situation.
32 I CBCT 18 months after treatment showing well-
maintained buccal bone.
33 I Clinical situation 18 months after treatment.
35 I Clinical situation 18 months after treatment.
34 I Close-up showing pleasing peri-implant soft tissue.
72
CASE STUDIES