Rational
Socket preservation techniques are effective in mitigating the dimensional changes of the
alveolar socket that spontaneously occur after tooth extraction (Avila-Ortiz G, et al. 2019).
However, there is insufficient information regarding the type and quality of the newly formed
tissue at the extraction site before implant positioning.
Study design
This study is a three-arm multicentric randomized trial that will evaluate the bone healing
following ridge preservation of extraction sockets using two different combinations of
commercially available xenograft bone granules and collagen membranes available in the
market. Results will be compared to tissues obtained from spontaneous healing. A total of 45
participants (15 in each arm) is expected.
Study protocol
Patients, satisfying inclusion criteria and having signed study informed consent, will be
randomly allocated to three study groups, receiving the following treatments at the time of
tooth extraction:
Group A: grafting of postextraction socket with Dentsply Symbios Xenograft granules
covered with Dentsply Symbios pre-hydrated Collagen Resorbable Membrane (Test - Group A)
Group B: grafting of postextraction socket with Geistlich Bio-Oss Collagen and covering
with Geistlich Bio-Gide Collagen membrane (Active comparator - Group B)
Group C: no further treatment of the postextraction socket (spontaneous healing, Control
- Group C) After 6 months from the extraction, radiographic examinations will be
performed and the implant surgery will take place.
On the day of the surgery the width of keratinized mucosa at socked site will be registered.
Then, following loco-regional anesthesia, a soft tissue sample of 3 mm in diameter will be
obtained using a circular punch at the site intended to receive the implant. Subsequently, a
flap will be elevated. Using a trephine drill a 3 mm in diameter block of hard tissue with a
length of 5- 6 mm will be collected. The preparation of the implant site will be then carried
out until the desired diameter and length are reached for the insertion of the corresponding
implant. Torque at implant insertion will be registered.
Once the implant has been inserted, the healing abutment will be positioned and soft tissues
will be sutured with single sutures. The prosthetic rehabilitation will be completed after
osseointegration, approximately 3 months after the implant surgery.
Histological analysis of soft tissue and hard tissue biopsies
Tissue samples will be immediately fixed in formalin after collection. Histological analysis
will be performed on formalin-fixed paraffin-embedded tissue sections, to determine the
quantity and quality newly formed tissue and the remaining fraction of the implanted
biomaterials.
More specifically, the collected tissue biopsies will be fixed in 4% buffered formalin,
decalcified into ethylenediaminetetraacetic acid (EDTA) (if necessary), dehydrated and
included in paraffin. Serial sections, including the central portion of the biopsy, will be
prepared and colored in hematoxylin and eosin. Vascular structures will be identified by CD34
(Cluster of differentiation 34, hematopoietic progenitor cell antigen) antibody. Portions
occupied by mineralized bone (lamellar bone, trabecular bone), osteoid (partially mineralized
connective tissue matrix rich in collagen), bone marrow (adipocytes and vascular structures),
fibrous tissue (unorganized collagen fibers, cells and vessels), biomaterial granules and
residual tissue (unidentified tissue elements, preparation artifacts) will be characterized
by morphometric measurements performed according to the protocol described by Lindhe et al.
(Clin. Oral Impl. Res.2014;25:786-790). Soft tissues characterization will include the
analysis of the structural composition of epithelial and connective tissues, the
quantification of the amount micro-vessels in connective tissue, the definition of the
inflammatory cell types, and the collagen tissue content according to protocols described in
Tomasi et al. (J Clin Periodontol. 2016;43:816-24).
Data analysis and statistics
Data analysis will be aimed at detecting statistically significant differences in tissue
composition between the group A in respect to the most appropriate of the two remaining
groups (e.g. the percentage of bone tissue in the test group will be compared with that of
control group C while the percentage of residual biomaterial six months after implantation
will be compared with the active control B). Statistically significant differences with
p<0.05 will be considered.
Data normality will be verified with the Shapiro-Wilk test. Outcome variables for each of
three groups will be expressed by means of mean ± standard deviation for continuous variables
with normal distribution, or by means of median and value at the 25th and 75th percentile for
variables with non-normal distribution. Parametric or non-parametric statistical tests will
then be applied to compare between groups, according to data normality.