mauricio g. arau´jo socket grafting with the use of jan lindhe ......arau´jo & lindhe socket...
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Socket grafting with the use ofautologous bone: an experimental studyin the dog
Mauricio G. AraújoJan Lindhe
Authors’ affiliations:Mauricio G. Araújo, Department of Dentistry, StateUniversity of Maringá, Parana, BrazilMauricio G. Araújo, Jan Lindhe, Institute ofOdontology, The Sahlgrenska Academy at theUniversity of Gothenburg, Gothenburg, Sweden
Corresponding author:Mauricio G. AraújoRua Silva Jardim15/sala 0387013-010Maringá, ParanáBrazilTel.:/Fax: þ 55 44 3224 6444e-mail: [email protected]
Key words: alveolar socket, autogenous bone, graft, ridge preservation
Abstract
Background: Studies in humans and animals have shown that following tooth removal
(loss), the alveolar ridge becomes markedly reduced. Attempts made to counteract such
ridge diminution by installing implants in the fresh extraction sockets were not successful,
while socket grafting with anorganic bovine bone mineral prevented ridge contraction.
Aim: To examine whether grafting of the alveolar socket with the use of chips of
autologous bone may allow ridge preservation following tooth extraction.
Methods: In five beagle dogs, the distal roots of the third and fourth mandibular premolars
were removed. The sockets in the right or the left jaw quadrant were grafted with either
anorganic bovine bone or with chips of autologous bone harvested from the buccal
bone plate. After 3 months of healing, biopsies of the experimental sites were sampled,
prepared for buccal–lingual ground sections and examined with respect to size and
composition.
Results: It was observed that the majority of the autologous bone chips during healing had
been resorbed and that the graft apparently did not interfere with socket healing or
processes that resulted in ridge resorption.
Conclusion: Autologous bone chips placed in the fresh extraction socket will (i) neither
stimulate nor retard new bone formation and (ii) not prevent ridge resorption that occurs
during healing following tooth extraction.
Following tooth extraction (loss), the alveo-
lar ridge undergoes a marked change (Pie-
trokovski & Massler 1967; Schropp et al.
2003; Pietrokovski et al. 2007). During the
first year after tooth extraction, about 50%
of the bucco-lingual ridge dimension will be
lost (Schropp et al. 2003). Furthermore,
ridge reduction will become more pro-
nounced from a buccal than from a lin-
gual/palatal aspect (Pietrokovski & Massler
1967). It was suggested that the ridge di-
mensions could be preserved if implants
were placed in the fresh extraction socket
(Denissen et al. 2000; Paolantonio et al.
2001). The validity of this hypothesis was
refuted by Botticelli et al. (2004) and Sanz
et al. (2010), who in prospective studies
involving large numbers of subjects and
sites, clearly documented that also follow-
ing immediate implant placement (Type 1;
Hämmerle et al. 2004), the edentulous site
underwent substantial diminution.
Processes of hard tissue modeling and
remodeling following tooth extraction were
studied in the dog model (Cardaropoli et al.
2003; Araújo & Lindhe 2005). It was de-
monstrated that the socket was first occu-
pied by a coagulum that was replaced with
granulation tissue, provisional connective
tissue and woven bone. This immature
Date:Accepted 25 January 2010
To cite this article:Araújo MG, Lindhe J. Socket grafting with the use ofautologous bone: an experimental study in the dog.Clin. Oral Impl. Res. 22, 2011; 9–13.doi: 10.1111/j.1600-0501.2010.01937.x
c� 2010 John Wiley & Sons A/S 9
mailto:[email protected]
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hard tissue was subsequently replaced with
lamellar bone and marrow. During healing,
the height of the buccal bone wall was
substantially reduced. In addition, about
30% of the marginal portion of the alveolar
process of the extraction site was modeled
and lost (Araújo et al. 2008). In later
experiments using the same model, the
post-extraction socket was grafted with
Bio-Osss
collagen (Geistlich Pharma) and
healing was monitored in biopsies sampled
after 3 months (Araújo et al. 2008) or 6
months (Araújo & Lindhe 2009) of healing.
Microscopic examinations of buccal–lin-
gual ground sections showed that place-
ment of the xenograft in the extraction
wound seemed to delay healing but also
counteract ridge contraction.
The use of autologous bone grafts from
intra- or extra oral donor sites has, for many
years, been regarded as the gold standard in
reconstructive surgery (e.g. Burchardt
1987; Goldberg & Stevenson 1987; Misch
1997; Hj�rting-Hansen 2002). However,
limited information is available regarding
the fate of autologous bone placed in alveo-
lar bone defects such as fresh extraction
sockets in humans (Becker et al. 1994,
1996). Jensen et al. (2006) studied healing
of standardized hard tissue defects that had
been prepared in the mandible of minipigs
and filled with grafts comprised of either
autologous bone chips, anorganic bovine
bone or synthetic b-tricalcium phosphate.Histological examination was performed in
biopsies sampled after 1, 2, 4 and 8 weeks
of healing. The authors reported that (i) all
defects regenerated with newly formed
bone but (ii) the bone substitutes seemed
to decelerate bone regeneration (in the early
phase) as compared with healing patterns
seen at sites augmented with the autolo-
gous bone chips.
The aim of the present experiment was
to evaluate whether grafting of the alveolar
socket with autologous bone might coun-
teract ridge resorption that occurs following
tooth extraction.
Material and methods
The research protocol was approved (State
University of Maringá, Brazil). Five beagle
dogs, about 1 year old, were used. The dogs
were anesthetized with intravenously
administered ketamine 10% (8 mg/kg,
Agener União, São Paulo, Brazil).
Sulcus incisions were made in the pos-
terior premolar region and small buccal–
lingual full-thickness flaps were elevated.
The third and fourth mandibular premolars
(3P3, 4P4) were hemi-sected. The canal of
the mesial root was reamed and filled with
gutta-percha.
In one quadrant, bone chips harvested
from the buccal surface of the mandible
using a sharp chisel were soaked in blood
and packed into the fresh sockets (auto-
graft). In the contra lateral quadrant, a
xenograft [a blend of granules of deprotei-
nized bovine bone (90%) and porcine col-
lagen fibers (10%); Bio-Osss
collagen;
Geistlichs
, Wolhusen, Switzerland] was
placed (xenograft) in a similar manner.
Three months after the grafting proce-
dure, the dogs were euthanized with an
overdose of ketamine and perfused,
through the carotid arteries, with a fixative
containing a mixture of 5% glutaraldehyde
and 4% formaldehyde (Karnovsky 1965).
The premolar sites, including the mesial
root and the distal socket area, were dis-
sected (Exacts
Apparatebeau, Norderstedt,
Hamburg, Germany). The tissue samples
were processed according to the methods
described by Donath & Breuner (1982) and
Donath (1988), dehydrated in ethanol, in-
filtrated with Technovits
7200 VLC resin
(Kulzer, Friedrichrsdorf, Germany), poly-
merized and sectioned (Exacts
Apparate-
beau). From each premolar site, four
sections were prepared, two sections from
the mesial root and two sections from the
healed socket. The sections were cut in the
buccal–lingual plane and were sampled
from the central area of either the root or
the socket. The sections were, by micro
grinding and polishing, reduced to a thick-
ness of about 25–30 mm and stained inLadewig’s fibrin stain.
Examinations
The histological examinations were per-
formed in a Leitz DM-RBEs
microscope
(Leica, Wetzlar, Germany) equipped with
an image system (Q-500 MCs
, Leica).
Size of the cross-section area of the edentulousridge
The profile of the ridge as well as the size of
the cross-section area of the edentulous
portion of the 3P3 and 4P4 sites were
determined in accordance with a method
described by Araújo et al. (2008). In brief,
the image of the profile of the alveolar
process that harbored the mesial root of
an experimental tooth site was divided into
three equally high portions. The size of
each of the apical, middle and marginal
portions was determined with a cursor
and expressed in mm2. The corresponding
measurements were then performed at the
edentulous, healed distal socket site. The
relative alteration of the size of the alveolar
process that had occurred in each dog after
tooth extraction was estimated by subtract-
ing the value obtained at the extraction site
from the corresponding value at the mesial
root site (for further details, see Araújo
et al. 2008).
Morphometric measurements
The composition of the alveolar process as
well as the newly formed tissue in the
edentulous distal socket site was deter-
mined using a point-counting procedure.
A lattice comprising 100 light points (mod-
ified from Schroeder & Münzel-Pedrazzoli
1973) was superimposed over the target
area and the percentage area occupied by
lamellar bone, newly formed bone (mainly
woven bone), BMUs (basal multicellular
units), bone marrow, provisional connec-
tive tissue and graft particles was deter-
mined (magnification �100).The mean values and standard deviations
of the different variables were calculated
using the dog as the statistical unit.
Results
In all experimental sites, healing was un-
eventful. After 3 months of healing, a
keratinized mucosa was observed to cover
the entrance of the edentulous part of all
premolar sites.
Gross histological findings
Sites with an autograft
A large portion of the central area of ex-
traction sites was occupied by bone mar-
row in which an island of newly formed,
mineralized bone could be observed (Fig. 1).
Remnants of non-vital bone chips (Fig. 2a
and b) were few in numbers, but occurred
in the entire part of the newly formed bone.
The graft particles had the nature of lamel-
lar bone and were frequently separated
Araújo & Lindhe � Socket grafting with the use of autologous bone
10 | Clin. Oral Impl. Res. 22, 2011 / 9–13 c� 2010 John Wiley & Sons A/S
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from the newly formed hard tissue by
reversal lines. A varying thick layer of
mainly woven bone was present in the
entrance region of the socket site. The
old buccal bone crest was located about
2 mm apical of its lingual counterpart in all
specimens.
Sites with a xenograft
The newly formed bone and provisional
connective tissue in socket sites that had
been filled with Bio-Osss
collagen harbored
large numbers of graft particles (Fig. 3).
The marginal and middle portions of the
site were comprised of newly formed wo-
ven and parallel-fibered bone. Bone mar-
row was observed mainly in the apical
portion of the site. Bio-Osss
particles pre-
sent within the bony housing were consis-
tently surrounded by parallel-fibered bone
or were in direct contact with multinu-
cleated cells (Fig. 4a and b). A fibrous
capsule surrounded particles of the bioma-
terial that were located in the mucosa
adjacent to the bone compartment of the
ridge. The old buccal bone crest was con-
sistently located about 1–2 mm apical of
the lingual crest.
Dimensions of the ridge
In all the experimental sites, the apical and
middle portion of the edentulous alveolar
process had dimensions similar to that of
the adjacent mesial root (Table 1). While
the marginal portion of sites grafted with
Bio-Osss
collagen had a cross-section area
that was similar in size to that of the
adjacent mesial root (þ3.6� 10.7%), thecorresponding portion of the sites grafted
with the autologous bone chips was mark-
edly smaller (� 25� 16.3%).
Composition of the alveolar process andthe healed socket
Alveolar process (Table 2)
The alveolar process that harbored the
autologous bone graft was comprised of
49.1� 6.6% old lamellar bone, 24.5� 3% newly formed bone, 20.7� 8.1%bone marrow, 4.4� 1.2% BMUs and1.4� 1.6% graft material.
The corresponding values obtained from
measurements in the Bio-Osss
grafted
sites were 54� 7.5% old lamellarbone, 18.1� 7% newly formed bone,10.5� 5.5% bone marrow, 4.1� 2.7%BMUs and 8.6� 2% graft material. Inaddition, sites grafted with the biomaterial
included 4.7� 2.5% provisional connec-tive tissue.
Healed socket sites (Table 3)
The newly formed tissue and the remaining
graft material that occupied the post-extrac-
tion socket augmented with autologous bone
chips was comprised of 57.2� 8.6% miner-alized bone, 38.3� 10.9% bone marrow,2.9� 2.8% BMUs and 1.9� 1.9% non-vital bone chips.
The corresponding values for the Bio-Osss
collagen sites were 43.1� 10% for miner-alized bone, 16� 7.6% for bone marrow,2� 2.2% for BMUs, 4.7� 2.5% for provi-sional connective tissue and 24.4� 3.7%for Bio-Oss
s
particles.
Discussion
Sockets grafted with autologous bone ex-
hibited a healing pattern that had many
features in common with those described
Fig. 1. Microphotograph of a buccal–lingual section
representing an experimental site after 3 months of
healing. The fresh extraction socket was grafted
with autologous bone chips. The lingual bone wall
is wider than the buccal wall. Note the area of
mineralized bone residing in the bone marrow. The
socket entrance is occupied by a bridge of miner-
alized hard tissue. B, buccal bone wall; L, lingual
bone wall; BM, bone marrow. Ladewig fibrin stain;
original magnification �16.
Fig. 2. Higher magnification of newly formed bone. Note the presence of non-vital autologous bone chips
(asterisk) that are delineated by a dark-stained reversal line (a). The same detail presented in polarized light (b).
The autologous bone chips are made of lamellar bone and are in direct contact with woven and parallel-fibered
bone (b). Ladewig fibrin stain; original magnification �100.
Fig. 3. Microphotograph of a buccal–lingual section
representing an experimental site after 3 months of
healing. The fresh extraction socket was grafted
with Bio-Osss
collagen. The xenograft particles
(blue stain) are embedded in newly formed bone
and some provisional connective tissue. Note that
the biomaterial occupies a large portion of the socket
entrance. Bio-Osss
particles can also be seen in the
mucosa of the ridge. B, buccal bone wall; L, lingual
bone wall; BM, bone marrow. Ladewig fibrin stain;
original magnification �16.
Araújo & Lindhe � Socket grafting with the use of autologous bone
c� 2010 John Wiley & Sons A/S 11 | Clin. Oral Impl. Res. 22, 2011 / 9–13
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for non-grafted post-extraction sites (Car-
daropoli et al. 2003; Araújo & Lindhe
2005; Araújo et al. 2008) Thus, in the
current study as well as in the previous
experiments, the sockets – after 3 months
of healing – had become filled with similar
amounts of mineralized bone (mainly wo-
ven bone) and marrow. This indicates that
the autograft material used in the present
study apparently failed to enhance healing
and/or to stimulate hard tissue formation
in the socket.
The mineralized bone in the grafted sites
harbored chips of non-vital autologous
bone. The chips (particles) were never ob-
served in the bone marrow but only within
the newly formed bone from which they
were consistently separated by well-
defined, often undulating reversal lines.
This suggests that the autologous bone
graft during the early, inflammatory phase
of healing had been exposed to osteoclastic
activity and that, as a consequence, after 3
months, comparatively few graft particles
remained in the socket site.
In the present study, it was furthermore
noted that in sites grafted with autologous
bone, there was pronounced resorption of
the buccal bone wall and also a marked
reduction (�25%) of the marginal portionof the ridge. Similar amounts of buccal wall
reduction (about 2 mm) and ridge diminu-
tion (�30%) were reported for non-graftedsites by Araújo & Lindhe (2005), Araújo
et al. (2008).
In other words, despite the fact that the
autogenous bone used in the current ex-
periment may have delivered an osteogenic
as well as an osteoconductive stimulus
(Burchardt 1987) to the fresh extraction
socket and although the gold standard for
bone grafting may include the use of auto-
genous hard tissue from, e.g., intra-oral
donor sites (for a review, see Hj�rting-
Hansen 2002), in the current model, this
type of graft material failed to prevent ridge
contraction.
In comparison with sockets that had
been filled with autologous bone, the Bio-
Osss
collagen-grafted sites exhibited a de-
layed healing pattern (Table 3). Thus, in
xenograft-treated sites, there was less
mineralized bone (43.5 vs. 57.2%), a smal-
ler proportion of bone marrow (16 vs.
38.3%) and a substantial amount of re-
maining provisional connective tissue (14
vs. 0%). This conclusion of a delayed
healing in Bio-Osss
-grafted sites is in
agreement with observations made pre-
viously (Artzi et al. 2004; Jensen et al.
2006) and from experiments using the ex-
traction socket model (Araújo et al. 2008,
2010; Araújo & Lindhe 2009). In a recent
experiment, Araújo et al. (2010) studied
the dynamics of Bio-Osss
incorporation in
extraction wounds and concluded that be-
fore new bone could form in the augmented
site, the biomaterial had to be exposed to a
‘‘surface cleaning’’ that was associated
with the presence of TRAP-positive multi-
nucleated cells, i.e. osteoclasts. This is in
agreement with the proposal by Jensen
et al. (2006) i.e. that the multinucleated
cells present adjacent to particles of Bio-
Osss
in a healing hard tissue wound ‘‘had
more the function of macrophages, i.e. to
clean the graft surface and thereby prepare
Fig. 4. Higher magnification of newly formed bone surrounding Bio-Osss
particles. The newly formed bone is
laid down in the provisional connective tissue and on the surface of the xenograft (a). The same detail presented
in polarized light (b). The hard tissue present on the surface of the biomaterial is comprised of woven bone and
parallel-fibered bone (b). Ladewig fibrin stain; original magnification �100.
Table 1. Mean relative alteration (% change in comparison with the tooth site� SD) of thesurface area (mm2) of the apical middle and apical third of the edentulous alveolar ridge
Area Autologous bone (%) Bio-Osss
collagen (%)
Coronal � 25 � 16.3 þ 3.6 � 10.7Middle þ 3.1 � 8 þ 6.4 � 5.4Apical þ 2.3 � 3.7 þ 6.1 � 4.4
þ , a relative increase of the cross-section area; � , a relative decrease of the cross-section area.
Table 2. Volumetric data describing the overall composition (%� SD) of the alveolarprocess in the grafted and non-grafted extraction sites
Autologous bone (%) Bio-Osss
collagen (%)
Lamellar bone 49.1 � 6.6 54 � 7.5Woven bone 24.5 � 3 18.1 � 7Bone marrow 20.7 � 8.1 10.5 � 5.5BMUs 4.4 � 1.2 4.1 � 2.7Connective tissue 0 � 0 4.7 � 2.5Graft particles 1.4 � 1.6 8.6 � 2
BMU, bone multicellular units.
Table 3. Volumetric data describing the composition (%� SD) of the newly formed tissuein the healed extraction sockets
Autologous bone (%) Bio-Osss
collagen (%)
Mineralized bone 57.2 � 8.6 43.1 � 10Bone marrow 38.3 � 10.9 16 � 7.6BMUs 2.9 � 2.8 2 � 2.2Connective tissue 0 � 0 4.7 � 2.5Graft particles 1.9 � 1.9 24.6 � 3.7
BMU, bone multicellular units.
Araújo & Lindhe � Socket grafting with the use of autologous bone
12 | Clin. Oral Impl. Res. 22, 2011 / 9–13 c� 2010 John Wiley & Sons A/S
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it for deposition of newly formed bone.’’ In
the studies by e.g. Jensen et al. (2006) and
Araújo et al. (2010), the biomaterial was
apparently not engaged in the processes of
modeling/remodeling. Thus, a large num-
ber of Bio-Osss
particles remained in the
newly formed tissue (Jensen et al. 1996,
2005, 2006; Piattelli et al. 1999; Artzi et al.
2004).
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c� 2010 John Wiley & Sons A/S 13 | Clin. Oral Impl. Res. 22, 2011 / 9–13