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Hard and Soft Tissue Evaluation of
Different Socket Preservation
Procedures Using Leukocyte and
Platelet-Rich Fibrin: A Retrospective
Clinical and Volumetric Analysis
Paolo De Angelis, DDS,
*
Silvio De Angelis, DDS,
y
Pier Carmine Passarelli, DDS,
z
Margherita Giorgia Liguori, DDS,
x
Paolo Francesco Manicone, DDS,
jj
and
Antonio D’Addona, DDS, MSc
{
Purpose: The extraction of a tooth is followed by hard and soft tissue changes that can compromise
implant placement. The aim of the present retrospective study was to compare the clinical and radio-
graphic outcomes of different ridge preservation procedures based on the use of leukocyte and
platelet-rich fibrin (L-PRF).
Materials and Methods: The study population consisted of all patients who had undergone surgery
from January 1, 2017 to January 1, 2018 for alveolar ridge preservation on single posterior teeth using 3
clinical protocols: L-PRF alone, L-PRF mixed with a bone xenograft, and bone xenograft alone. Clinical
and radiographic measures were recorded preoperatively and at 6 months postoperatively to determine
the horizontal and vertical ridge resorption.
Results: A total of 45 patients were included in the present study. All the surgeries were performed suc-
cessfully, and no intraoperative complications developed. The L-PRF group experienced significantly
greater horizontal and vertical bone resorption. The L-PRF plus bone xenograft group had less vertical
and horizontal bone resorption than the bone xenograft alone group. Statistically significant differences
in postoperative pain and wound healing were observed, with the bone xenograft alone group, in partic-
ular, having higher values for pain and experiencing delayed wound healing.
*Resident, Division of Oral Surgery and Implantology,
Department of Head and Neck, Oral Surgery, and Implantology
Unit, Institute of Clinical Dentistry, Fondazione Policlinico
Universitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro
Cuore, Rome, Italy.
yPrivate Practitioner, Private Dental Practice, Ascoli Piceno, Italy.
zResident, Division of Oral Surgery and Implantology,
Department of Head and Neck, Oral Surgery, and Implantology
Unit, Institute of Clinical Dentistry, Fondazione Policlinico
Universitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro
Cuore, Rome, Italy.
xPrivate Practitioner, Division of Oral Surgery and Implantology,
Department of Head and Neck Oral Surgery, and Implantology
Unit, Institute of Clinical Dentistry, Fondazione Policlinico
Universitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro
Cuore, Rome, Italy.
kProfessor, Division of Oral Surgery and Implantology,
Department of Head and Neck Oral Surgery, and Implantology
Unit, Institute of Clinical Dentistry, Fondazione Policlinico
Universitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro
Cuore, Rome, Italy.
{Department Head, Division of Oral Surgery and Implantology,
Department of Head and Neck Oral Surgery, and Implantology
Unit, Institute of Clinical Dentistry, Fondazione Policlinico
Universitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro
Cuore, Rome, Italy.
Conflict of Interest Disclosures: None of the authors have any
relevant financial relationship(s) with a commercial interest.
Address correspondence and reprint requests to Dr De Angelis:
Division of Oral Surgery and Implantology, Department of Head
and Neck, Institute of Clinical Dentistry, Fondazione Policlinico Uni-
versitario A. Gemelli IRCCS—Universit
a Cattolica del Sacro Cuore,
Largo Francesco Vito 1, Rome 00168, Italy; e-mail: dr.
paolodeangelis@gmail.com
Received March 7 2019
Accepted May 6 2019
Ó2019 American Association of Oral and Maxillofacial Surgeons
0278-2391/19/30535-X
https://doi.org/10.1016/j.joms.2019.05.004
1807
Conclusions: Within the limitations of the present retrospective study, the use of a bone xenograft alone
or L-PRF combined with a bone xenograft to perform alveolar ridge preservation procedures significantly
limited bone resorption.
Ó2019 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 77:1807-1815, 2019
The alveolar bone is a tissue strictly dependent on the
tooth and the periodontal ligament.
1
After tooth
extraction, hard and soft tissue changes should be
expected at the surgical site.
2,3
Also, even in the
absence of any complications developing during the
postoperative phase, it will not be possible to
maintain the preoperative bone volume.
1
The bundle
bone is the inner part of the alveolus,
2
and postopera-
tive changes will be triggered by its resorption, which
results from the loss of blood support deriving from
the periodontal ligament.
3,4
The dimensional
changes that occur during the healing phase will
cause a significant reduction in width that will be
greater than the loss in height.
Furthermore, the width reduction can reach 50% at
1 year in the premolar and molar areas, and 75% of the
final changes will usually occur within the first
3 months.
1,5
The postoperative hard and soft tissue
alterations can cause difficulties in implant
placement, especially when a prosthetically driven
and aesthetic rehabilitation is desired.
2,6
Therefore,
different regenerative procedures have been
proposed to counteract the hard and soft tissue
changes. These procedures have included the
flapless approach,
7,8
immediate implant placement,
9
and ridge preservation procedures using a combina-
tion of various surgical techniques and biomate-
rials.
7,8,10
Numerous ridge preservation procedures
with different degrees of success have been
described, including the use of autografts, allografts,
alloplasts, and xenografts, which can be combined
with resorbable or nonresorbable membranes.
11,12
However, no guidelines have been reported
regarding which type of biomaterial or surgical
procedure would be best.
10,13
Platelet concentrates have long been applied in
dentistry with the purpose of inducing tissue regener-
ation to take advantage of the supraphysiological
doses of autologous growth factors released.
13
Leuko-
cyte and platelet-rich fibrin (L-PRF) is created without
anticoagulants and was developed in 2001 as an
improved formulation of PRP to avoid the formation
of a fibrin clot and eliminate leukocytes from the final
blood concentrates.
13,14
L-PRF acts as an ideal
postextraction material by improving bone healing
and reducing the risk of infection. However, a
limited number of studies have been reported on
this subject; thus, the necessity exists to further
evaluate the outcomes of L-PRF use in
postextraction sockets.
13
The aim of the present study was to compare the
clinical and radiographic outcomes of different ridge
preservation procedures according to the use of
L-PRF within the first 6 months after tooth extraction.
Materials and Methods
The present study was designed as a retrospective
comparative study to evaluate different socket preser-
vation procedures performed before implant place-
ment. The study population consisted of all patients
who had undergone surgery from January 1, 2017 to
January 1, 2018 in a periodontal private practice for
alveolar ridge preservation on single posterior teeth
using 3 clinical protocols: L-PRF alone, L-PRF mixed
with a bone xenograft, and a bone xenograft alone.
Patients were preoperatively assigned to 1 of these 3
groups. The decision to perform 1 of these 3 protocols
was made after a discussion with the patient and a
review of their preoperative clinical and radiographic
evaluation data. Those patients who had refused to
receive a bone xenograft were treated using only
L-PRF. Those patients who had refused to undergo
blood collection were treated using only a bone xeno-
graft. Finally, those patients who had agreed to receive
a bone xenograft and who had undergone blood
collection were treated using L-PRF and a
bone xenograft.
The present study was conducted in private prac-
tice, and the medical devices evaluated had already
been approved for clinical use. All investigations
reported were performed in accordance with the
1975 Declaration of Helsinki, as revised in 2013, for
ethical approval. All the participants had provided
written informed consent after receiving explanations
of the study objectives and procedures. Because of the
retrospective nature of our study, the local institu-
tional review board had granted an exemption
in writing.
The inclusion criteria were as follows: 1) the need
for 1 or more extractions in the upper or lower
jaw, 2) the need for 1 or more implants in the upper
or lower jaw, 3) sufficient vertical and horizontal
bone dimensions, and 4) all extraction sites had adja-
cent teeth present. The diagnosed indications for
tooth extractions were caries, endodontic
1808 EVALUATION OF DIFFERENT SOCKET PRESERVATION PROCEDURES
complications (eg, root fracture), periodontitis, or
other prosthetic reasons. Only healthy patients with
adequate oral hygiene were included. The participants
were required to have a full-mouth plaque score and
full-mouth bleeding score less than 15%.
Patients with acute periodontal or periapical infec-
tions were excluded. In addition, patients were
excluded because of the following contraindications:
1) a general contraindication for bone augmentation
procedures and/or surgical treatment; 2) uncontrolled
periodontal disease; 3) immunosuppressant, cortico-
steroid, or bisphosphonate therapy; 4) a history of
malignancy, radiotherapy, or chemotherapy for malig-
nancy within the previous 5 years; 5) smoker; 6)
blood-related disease; and 7) an unwillingness to
return for the follow-up examinations. However,
patients with sites with a loss of the buccal or palatal
bone plate (<50% of the initial height) were included.
The sockets were carefully cleaned and treated
using 1 of the following: L-PRF; L-PRF mixed with
a bone xenograft (L-PRF plus Bio-Oss; Geistlich
Pharma AG, Wolhusen, Switzerland); or bone xeno-
graft (Bio-Oss Collagen; Geistlich Pharma AG).
The patients’ age, sex, number and type of technical
and biological complications, and the aesthetic out-
comes were recorded. The baseline findings were
considered before tooth extraction. Every patient un-
derwent radiologic examinations before surgery to
allow for preoperative planning. A preoperative
cone-beam computed tomography (CT) scan was
also performed for evaluation of the bone height and
thickness of the cortical plates.
The primary outcomes measure was defined as the
dimensional changes in the ridge width and height at
6 months after the procedure. A cone-beam CT scan
was taken at 6 months postoperatively with a resolu-
tion of 100 mm (Orthophos XG 3D; Dentsply Sirona,
York, PA). The horizontal ridge width was measured
at 3 levels: 1, 3, and 5 mm below the most coronal
aspect of the crest (HW-1, HW-3, and HW-5, respec-
tively). Vertical resorption was assessed by measuring
the height of the alveolus at the midbuccal and midlin-
gual aspects.
The volumetric changes in the soft tissues were
assessed at baseline and at 6 months after surgery by
taking impressions of the site using A-silicone impres-
sion material (Persident; Coltene/Whaledent, Altst€
at-
ten, Switzerland). The site included 2 neighboring
teeth and the mucosa. Dental stone casts were fabri-
cated and optically scanned (inEos X5; Dentsply
Sirona). Next, the obtained files were imported into
a digital imaging software program.
The width of the keratinized tissue was assessed at
baseline and 6 months after the procedure. Also, the
plaque index (PI), gingival index, probing depth, and
bleeding on probing (BOP) were measured at the
tooth sites adjacent to the treatment areas to evaluate
soft tissue inflammation. The occurrence of adverse
events (eg, wound infection, exposure of the graft
and soft tissue dehiscence, necrosis) was recorded at
weeks 1, 2, and 3 and months 1, 3, and 6 after surgery.
The subjects’ overall postoperative pain was
assessed for the first 7 days using a visual analog scale
(VAS). The answers were recorded using a hash mark
on a non-numeric 100-mm line, with no pain marked
as 0 and the highest level of pain as 100. Wound heal-
ing was assessed using the Landry, Turnbull, and How-
ley index (HI). The score ranged from 1 to 5 points,
with 1 point indicating very poor healing and 5 points
indicating excellent healing. Recordings of the HI
were performed every 7 days for the first 3 weeks.
CLINICAL PROCEDURES
Before starting the surgical procedures, all the
subjects had undergone periodontal procedures to
establish adequate oral hygiene conditions. Teeth
were extracted under local anesthesia. A flapless
approach was performed as atraumatically as possible
using periotomes. After using periotomes, the teeth
were carefully extracted using extraction forceps. If
necessary, the teeth were sectioned to allow for atrau-
matic extraction. After tooth extraction, debridement
of the adjacent tooth surfaces, careful removal of gran-
ulation tissue with manual instruments, and rinsing
with sterile saline were performed.
Patient blood samples were obtained during surgery
but before tooth extraction. The blood samples were
collected and processed for L-PRF centrifugation. A to-
tal of 9 mL of whole blood without anticoagulants was
centrifuged using a sterile glass-coated plastic tube
(2700 rpm for 12 minutes; IntraSpin System; Intra-
Lock International, Boca Raton, FL). After centrifuga-
tion, each L-PRF clot was removed from the tube and
separated from the red element phase. Four L-PRF
clots were squeezed between a sterile glass plate and
a metal box to obtain L-PRF membranes that were
equal in size and thickness (Fig 1).
For the group of patients who received L-PRF mixed
with a bone xenograft, 2 PRF clots were placed in ster-
ile cups, cut into small pieces, and mixed with depro-
teinized bovine bone mineral (Geistlich Bio-Oss small
particles; Geistlich Pharma AG) at a ratio of 1 mem-
brane to 0.25 g of biomaterial (a 50:50 ratio). The
mixture obtained constituted an easy-to-use homoge-
neous graft material. Liquid fibrinogen was added to
the homogeneous mix and stirred gently for
10 seconds. The L-PRF mixed with the bone xeno-
graft was packed into the socket to at least the level
of the palatal/lingual bone plate (Fig 2).
The internal marginal gingiva of the extraction
socket was de-epithelialized using a diamond burr.
DE ANGELIS ET AL 1809
Next, a mucoperiosteal envelope was created by
detaching the soft tissues from the oral and buccal sides
of the alveolar ridge to insert 2 L-PRF membranes under
the periosteum and seal the socket from soft tissue
ingrowth (Fig 3). Finally, mattress sutures were placed
to stabilize the graft (5-0 polytetrafluoroethylene
[PTFE] sutures; Omnia S.p.A., Fidenza, Italy; Fig 4).
For the group treated with L-PRF alone, the mem-
branes were inserted into the alveolar socket and
gently compressed to at least the level of the palatal/
lingual bone plate. A mucoperiosteal envelope was
created, detaching the soft tissues from the oral and
buccal sides of the alveolar ridge to insert 2 L-PRF
membranes under the periosteum and seal the socket
from soft tissue ingrowth. Finally, mattress sutures
were placed to stabilize the graft (5-0 PTFE sutures;
Omnia S.p.A.).
For the bone xenograft alone group, deproteinized
collagen-coated bovine bone mineral (Geistlich Bio-
Oss Collagen; Geistlich Pharma AG). was packed into
the socket. Subsequently, the soft tissue borders of
the alveolus were de-epithelialized using a diamond
drill under copious irrigation with water. Finally,
mattress sutures were placed to stabilize the graft
(5-0 PTFE sutures; Omnia S.p.A.).
Antibiotic therapy with 1 g of amoxicillin was pre-
scribed every 12 hours for 6 days. The patients were
instructed to rinse every 8 hours with a 0.2% chlorhex-
idine mouth rinse and to take ibuprofen 600 mg every
12 hours for 3 days. All the patients returned at 7 and
14 days postoperatively for examination and at 21 days
for suture removal. The patients then followed their in-
dividual maintenance program according to their indi-
vidual periodontal and caries risk assessment. The
patients agreed not to wear any prostheses during
the healing period.
STATISTICAL ANALYSIS
Descriptive statistics were used to indicate the
mean, median, minimum, maximum, and standard
FIGURE 2. Leukocyte and platelet-rich fibrin mixed with the bone xenograft and packed into the socket.
De Angelis et al. Evaluation of Different Socket Preservation Procedures. J Oral Maxillofac Surg 2019.
FIGURE 3. Placement of 2 leukocyte and platelet-rich fibrin mem-
branes under the periosteum to seal the socket.
De Angelis et al. Evaluation of Different Socket Preservation Pro-
cedures. J Oral Maxillofac Surg 2019.
FIGURE 1. Leukocyte and platelet-rich fibrin clots squeezed be-
tween a sterile glass plate and a metal box.
De Angelis et al. Evaluation of Different Socket Preservation Pro-
cedures. J Oral Maxillofac Surg 2019.
1810 EVALUATION OF DIFFERENT SOCKET PRESERVATION PROCEDURES
deviation values for each treatment group. The data
were analyzed using 1-way analysis of variance (Statis-
tical Package for the Social Sciences, version 10, soft-
ware; IBM Corp., Armonk, NY). A Pvalue of < 0.05
was selected to indicate statistical significance.
Results
A total of 45 patients were included in the present
study. Of the 45 patients, 15 each were included in
the 3 groups. In the L-PRF group, the mean patient
age was 51.2 13.2 years, and 10 were women and
5 were men. In the L-PRF plus bone xenograft group,
the mean patient age was 52.4 16.6 years, and 7
were women and 8 were men. Finally, in bone xeno-
graft only group, the mean patient age was
47.7 9.1 years, and 9 were women and 6 were
men. The teeth in the present study were extracted
because of crown or root fractures in 26 patients
(58%), trauma in 4 (9%), destructive carious lesions
in 10 (22%), endodontic complications in 3 (7%),
and external root resorption in 2 (4%). All the surgeries
were successfully performed, and no intraoperative
complications were recorded. None of the patients
had presented with biological complications or signs
of periapical radiolucency at 6 months after surgery.
The baseline clinical parameters were comparable
among all 3 groups, with no statistically significant dif-
ferences (P> .05). At 6 months postoperatively, a sta-
tistically significant reduction in BOP and PI was
recorded in all groups compared with the baseline
evaluation (P< .05). The statistical comparison of clin-
ical parameters revealed no significant differences
among the 3 groups (P> .05). No statistically signifi-
cant differences in the postoperative width of the ker-
atinized mucosa were observed among the 3 groups
(P> .05). The bone volume of all sites allowed for
placement of the planned implants.
The change in the horizontal ridge width from
baseline to 6 months after surgery was statistically
significant in all 3 groups analyzed at HW-1, HW-3,
and HW-5 (P< .05). However, the L-PRF group expe-
rienced significantly greater horizontal width resorp-
tion, with a mean change at HW-1 of 2.8 0.31 mm.
The L-PRF plus bone xenograft group, with a mean
FIGURE 4. Sutures placed to stabilize the graft.
De Angelis et al. Evaluation of Different Socket Preservation Pro-
cedures. J Oral Maxillofac Surg 2019.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
123456789101112131415
Patients
Mean postoperative change at HW-1
PRF
B
PRF+B
FIGURE 5. Mean change in the horizontal ridge width measured 1 mm below the most coronal aspect of the crest (HW-1).
De Angelis et al. Evaluation of Different Socket Preservation Procedures. J Oral Maxillofac Surg 2019.
DE ANGELIS ET AL 1811
change of 1.05 0.23 mm, experienced less width
resorption than did the bone xenograft group
(mean change, 1.12 0.28 mm). However, the dif-
ference was not statistically significant (P= .44;
Fig 5). The L-PRF group had also had significantly
greater horizontal width resorption at HW3 and
HW5 (P< .05; Fig 6).
The differences in the vertical ridge changes of the
buccal and lingual/palatal plates from baseline to
6 months after surgery were statistically significant
in all 3 groups (P< .05). However, the L-PRF group
experienced significantly greater vertical ridge resorp-
tion of the buccal and lingual/palatal plates, with a
mean change of 2.24 0.66 mm and
1.54 0.53 mm, respectively. The L-PRF plus bone
xenograft group had less vertical resorption on the
buccal and lingual/palatal plates, with a mean change
of 0.58 0.25 mm and 0.42 0.48 mm, respectively.
However, no statistically significant difference was
observed in the lingual/palatal plate (P< .05) or in
the buccal bone plate in the bone xenograft group
(P> .05; Figs 7, 8). A statistically significant
difference in the soft tissue thickness was observed
in the group treated with the L-PRF alone, with the
patients in this group showing greater
thickness (P< .05).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1 2 3 4 5 6 7 8 9 101112131415
Patients
Mean postoperative change at HW-3
PRF
B
PRF+B
FIGURE 6. Mean change in the horizontal ridge width measured 3 mm below the most coronal aspect of the crest (HW-3).
De Angelis et al. Evaluation of Different Socket Preservation Procedures. J Oral Maxillofac Surg 2019.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
123456789101112131415
Patients
Mean postoperative change at MB
PRF
B
LPRF+B
FIGURE 7. Mean vertical change measured at the midbuccal aspect.
De Angelis et al. Evaluation of Different Socket Preservation Procedures. J Oral Maxillofac Surg 2019.
1812 EVALUATION OF DIFFERENT SOCKET PRESERVATION PROCEDURES
Statistically significant differences in postoperative
pain sensation were observed at days 2, 3, 4, and 5
(P< .05). The bone xenograft group, in particular,
had greater pain scores on the VAS. Statistically signif-
icant differences in postoperative wound healing were
observed for the first 3 weeks in the L-PRF and L-PRF
plus bone xenograft groups, with a trend found to-
ward a greater degree of healing in both groups
compared with the bone xenograft group (P< .05).
In the bone xenograft group, 2 cases of delayed heal-
ing were noted.
Discussion
The results of the present study have demonstrated
that the use of L-PRF combined with a bone xenograft
resulted in significantly better clinical and radio-
graphic outcomes compared with those obtained
using only L-PRF or a bone xenograft.
Socket preservation procedures aim to minimize the
resorption of the ridge and maximize bone regenera-
tion within the alveolus to facilitate implant placement
in a prosthetically driven position or to maintain an
acceptable ridge contour in areas of aesthetic
concern.
12,15
The application of a slowly resorbing
grafting material could counteract, to some extent,
the ridge resorption, and that combined with L-PRF
seems to be an ideal example of guided tissue
engineering because it will act as an autologous
blood-derived scaffold.
16
Platelets are the first cells re-
cruited to the site of injury and have generally been
considered to be important in the wound healing pro-
cess. However, Bielecki et al
17
observed that the rates
of wound re-epithelialization, collagen synthesis, and
angiogenesis and the level of growth factors were
nearly identical for thrombocytopenic mice compared
with control mice. These results suggest that other
cells, such as leukocytes, have a role in the wound
healing process.
17
The L-PRF has strong fibrin poly-
merization, with leukocytes, especially lymphocytes,
enmeshed in the dense fibrin matrix.
17
These cells
are beneficial, not only because of their immune and
antibacterial potential, but also because they are the
mainstay of the wound healing process.
17
The ratio-
nale for using L-PRF is the delivery of blood compo-
nents at an early stage of healing, which diminishes
the noxious phases, regulates inflammation, promotes
vascularization, provides a matrix for cells, and
improves the regeneration of tissue and bone.
18
After
centrifugation, the L-PRF clot will contain nearly all
platelets and more than 50% of the leukocytes (most
of the lymphocytes) from the initial blood sample.
18-
20
In vitro studies revealed that L-PRF progressively
releases a significant amount of growth factors,
including transforming growth factor-b1, platelet-
derived growth factor AB, vascular endothelial growth
factor, insulin-like growth factor, matrix glycoproteins
(ie, thrombospondin-1, fibronectin, vitronectin), and
sequences of cytokines for at least 7 days.
18-20
In
addition, L-PRF is able to stimulate for at least
28 days the proliferation of different cell lines,
including bone cells (ie, fibroblasts,
prekeratinocytes, preadipocytes, osteoblasts,
mesenchymal stem cells).
18-20
L-PRF has many applications; however, clear proto-
cols are necessary to compare the outcomes and stan-
dardize all the parameters, such as the number of clots
used, amount of blood taken to prepare L-PRF, type of
centrifuge used, and centrifugation protocol.
20,21
The
different protocols of centrifugation allow us to obtain
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
1 2 3 4 5 6 7 8 9 101112131415
Patients
Mean postoperative change at ML
PRF
B
PRF+B
FIGURE 8. Mean vertical change measured at the midlingual aspect.
De Angelis et al. Evaluation of Different Socket Preservation Procedures. J Oral Maxillofac Surg 2019.
DE ANGELIS ET AL 1813
various types of platelet concentrates such as PRP,
L-PRF, advanced platelet-rich fibrin (A-PRF), and inject-
able platelet-rich fibrin, all of which have specific
behaviors. Although the standard L-PRF is centrifuged
at 2700 rpm for 12 minutes, the A-PRF is centrifuged at
a slower speed (1500 rpm for 14 minutes). The slower
speed results in an increase in platelet cell numbers
and an enhanced presence of neutrophilic granulo-
cytes in the distal part of the clot, which might
contribute to the differentiation of monocytes into
macrophages.
16,22
Macrophages are able to increase
osteoblast differentiation and play a key role in
promoting biomaterial integration and new bone
formation.
22
Kobayashi et al
23
investigated the growth
factors released over time, with the results indicating
that PRP demonstrated the ability to release signifi-
cantly greater levels of growth factors very early in
the healing process. In contrast, the use of PRF and
A-PRF resulted in a more gradual release of growth fac-
tors for up to 10 days, with A-PRF showing signifi-
cantly greater growth factor release over time, which
could be clinically beneficial.
23
A systematic review by Tan et al revealed that the
horizontal dimensional reduction (3.79 0.23 mm)
was greater than the vertical reduction
(1.24 0.11 mm, 0.84 0.62 mm, and
0.80 0.71 mm) at the buccal, mesial, and distal sites,
respectively, at 6 months after tooth extraction. The
proportion of vertical dimensional change was 11 to
22% at 6 months, and the proportion of horizontal
dimensional change was 32% at 3 months and 29 to
63% at 6 to 7 months.
24
The L-PRF group revealed a mean vertical bone loss
of 19.9% for the buccal bone plate and 14.6% for the
lingual/palatal bone plate. The horizontal dimensional
change at HW1 was 38.3%. The L-PRF plus bone xeno-
graft group had smaller dimensional changes in the
horizontal (18.9%) and vertical (11.42%) dimensions.
However, none of the procedures used in the 3 groups
in the present study were able to entirely compensate
for the alterations that occurred after tooth extrac-
tion.
7,8,15
The soft tissue changes demonstrated a
gain in thickness at 6 months on the buccal and
lingual aspects in all 3 groups. The horizontal
dimensional changes in the hard and soft tissue were
more substantial than were the vertical changes
during the observation period of 6 months. The
bone dimensional changes have not been the only
parameters investigated in reported data. In a study
by Hauser et al,
11
L-PRF membranes placed in the
socket were associated with improved alveolar bone
healing and better preservation of the bone volume
and architecture, with a greater degree of bone tissue
quality. Furthermore, L-PRF can remain exposed in the
oral cavity, creating accelerated tissue cicatrization by
its function in immune control, circulating stem cell
trapping, angiogenesis, and wound-covering epitheli-
alization.
11
Thus, L-PRF can be used to create a regen-
eration room sealed from the oral cavity, which avoids
an open healing state and the loss of biomaterials. Jung
et al
25
hypothesized that open healing after an alveolar
ridge preservation procedure could affect the out-
comes negatively. Data comparing socket seal surgery
have rarely been reported.
26
Brkovic et al
27
compared
the effects of applying an adjunctive resorbable dense
collagen membrane to bone substitutes. However,
they found no significant differences in the horizontal
and vertical changes after 9 months.
27
Meloni et al
26
compared the use of a porcine collagen matrix with
that of an epithelial connective tissue graft, with
similar outcomes found. However, the investigators
noted that the use of a membrane allowed for simplifi-
cation of the treatment for both patients and surgeons
by avoiding the need to harvest from the palate.
26
Bar-
one et al
28
reported that less vertical resorption
occurred using a flapped approach with a resorbable
membrane and primary closure versus a flapless
approach with a resorbable membrane left exposed.
Mean vertical bone changes of 0.6 mm 0.7 mm
and 1.1 mm 0.9 mm were recorded for the flapped
and flapless approach, respectively.
28
Furthermore,
the secondary wound healing with the flapless
approach appeared to be slower than the primary
healing with the flapped approach, despite the pres-
ence of the 2 release incisions.
28
The investigators sup-
posed the existence of a negative effect of secondary
closure related to the difficulty in cleaning the postex-
traction area with an exposed membrane in place,
which probably played a role in the greater resorp-
tion.
28
These results have been confirmed by those
from the present study. We showed that the use of
L-PRF to seal the socket promoted healing, reducing
the discomfort perceived by the patients, and avoiding
the harvesting procedures and the use of a membrane,
which were substituted for by the use of these autolo-
gous and bioactive matrices. Another important aspect
of L-PRF is related to the presence of high concentra-
tions of leukocytes, which prevent pathogens from
infiltrating. Therefore, L-PRF can be placed into the
extraction sockets, which will limit the rate of compli-
cations and infections.
22,29
Furthermore, L-PRF used as
an adjunct to a bone graft will enhance the graft
volume without interfering with bone maturation.
30
A systematic review and meta-analysis by Avila Ortiz
showed that flap elevation, the use of a membrane,
and the application of a xenograft or an allograft can
contribute to enhancing the outcomes, especially for
midbuccal and midlingual height preservation. Never-
theless, a certain degree of ridge volume loss should be
expected, although alveolar ridge preservation could
result in the maintenance of sufficient bone volume
to place an implant in an ideal restorative position,
1814 EVALUATION OF DIFFERENT SOCKET PRESERVATION PROCEDURES
avoiding other ancillary implant site development
procedures.
31
Clinical studies are required to evaluate
and compare the use of L-PRF and different bone graft
material combinations for bone regeneration proced-
ures.
32
The limitations of the present study included
the lack of randomization, low number of included pa-
tients, and the absence of a histological analysis.
Future studies should account for these limitations.
In conclusion, within the limitations of our study,
we have shown that the use of a bone xenograft alone
or the use of L-PRF combined with a bone xenograft
for performing alveolar ridge preservation procedures
significantly limited bone resorption. Furthermore,
the use of L-PRF alone or combined with a bone xeno-
graft resulted in less postoperative discomfort and
pain and better postoperative progress and healing
for the patients.
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DE ANGELIS ET AL 1815
