Dimensional Changes of Soft and Hard Tissues Following Alveolar Ridge Preservation: Freeze-dried Bone Allograft vs. L-PRF Clot Covered With d-PTFE Membrane: A Randomized Clinical Trial
Phase: PHASE2
Conditions: Alveolar Bone Loss, Tooth Loss
Sponsor: University of Manitoba

Final version dated: 2 December 2018 
Volumetric changes of soft and hard tissues following alveolar ridge preservation: Freeze-
dried bone allograft vs. L-PRF clot covered with d-PTFE membrane. 
ID: B2017:125 NCT03331185 
Background 
One of the most important factors that allows for predictable prosthetically driven implant 
placement is adequate bone volume at the proposed implant site. The main purpose of alveolar 
ridge preservation is to maintain the dimensions of the alveolar ridge, to allow for bone 
formation, and reduce the rate of resorption during the healing phase following tooth 
extraction. The histological changes observed during the healing of a post extraction socket 
have been described in detail in multiple histologic studies1–4: The following sequence of events 
has been described in the literature: 
• Initial clot formation 
• Within 4-7 days the clot is gradually replaced by granulation tissue and subsequent 
angiogenesis initiated by endothelial cells. 
• Connective tissue gradually replaces the granulation tissue within 2 weeks. 
• The base of the socket undergoes initial osteoid calcification between days 7-10 with 
trabecular bone fill of two thirds of the socket by 6 weeks.  Osteoblastic activity is at its 
most pronounced at 4-6 weeks.  The process slows down at week 8.  
• Epithelial coverage of the socket starts at the 4th day and is complete after 4-5 weeks. 
Bone fill is complete after 16 weeks. 

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Depending on the amount of destruction due to pathology or trauma, the extraction socket can 
be classified using Elian’s simplified socket classification:5 
• Type I: The facial soft tissue and buccal plate of bone are at normal levels in relation to 
the cementoenamel junction of the pre-extracted tooth and remain intact 
postextraction. 
• Type II: Facial soft tissue is present but the buccal plate is partially missing following 
extraction of the tooth.  
• Type III: The facial soft tissue and the buccal plate of bone are both markedly reduced 
after tooth extraction.  
Extraction sockets with no adjunctive grafting at the time of extraction, will present twelve 
months post-operatively with approximately 1mm vertical bone loss and 50% width reduction 
of the alveolus. A recent study reported that in the esthetic zone, patients with a buccal wall of 
less than 1mm, presented with a median vertical bone loss of 62.3%, 8 weeks following an 
extraction6. When compared to extraction alone, alveolar ridge preservation has a statistically 
significant effect in limiting the loss of alveolar ridge height and width7–10.  Several modalities 
and combinations of augmentation materials have been used successfully in alveolar ridge 
preservation9,10.  Some of the modalities employed are various combinations of autogenous 
bone, xenografts, allografts and growth factors such as Platelet Rich Plasma (PRP), Leukocytic 
Platelet Rich Fibrin (L-PRF) and Recombinant Human Bone Morphogenic Protein 2 (rh-BMP2), 
all of which were combined with absorbable or non-absorbable membranes4,11.  The clinical 
application and benefit of these grafting materials have been researched at length in the 

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literature9,10. Multiple studies have shown, that when used for alveolar ridge preservation, L-
PRF reduced the amount of post operative pain, bone resorption and healing time in extraction 
sites12–15.  Leukocytic Platelet Rich Fibrin (L-PRF) is a concentrate of platelets and leukocytes 
within a fibrin clot that is derived from the patient’s own blood sample, when centrifuged at 
2700rpm for 12 minutes.  L-PRF has been shown to accelerate wound healing by stimulating 
angiogenesis and neutrophil migration as well as harness stem cells and growth factors16.  One 
study found that L-PRF presented with similar results when indirectly compared to bone 
substitutes17.  However, when systematically analyzing the literature, regarding different types 
of grafting materials, no material has produced superior results over the others when 
comparing changes in ridge height and width7,9.    
Hard tissue volumetric changes also affect the presence and location of keratinized gingiva3,9,18.  
As mentioned previously, alveolar ridge preservation is performed in an effort to maintain 
adequate ridge dimension for implant placement and the remaining amount of keratinized 
tissue at the prospective implant site, may have implications for future implant survival.  There 
is no consensus in the current literature regarding the optimal amount of keratinized tissue 
required to maintain long-term peri-implant soft tissue health.  Some studies have shown that 
the lack of keratinized mucosa did not have any adverse effects on soft tissue health and 
implant survival21,22.  In contrast, other studies have shown that implants with less than 2mm of 
keratinized mucosa, presented with increased plaque accumulation, higher rates of 
inflammation, increased risk of recession and attachment loss23,24.  Although no correlation was 
found between implant survival, probing depth, bone loss and the amount of keratinized tissue, 
an increase in plaque accumulation and peri-implant inflammation, especially in the presence 

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of poor oral hygiene or limited access, it still remains a concern regarding the long term peri-
implant tissue health.  There is limited evidence in the literature investigating the amount of 
keratinized soft tissue available, following ridge preservation with freeze-dried bone allograft 
(FDBA) and dense polytetrafluoroethylene (d-PTFE) membrane19,20.  To the best of our 
knowledge, no studies exist in the current literature evaluating the amount of keratinized soft 
tissue following ridge preservation with L-PRF and d-PTFE membrane.  
Another factor that has not been taken into consideration is informed consent and patient 
preference. A recent study analyzed patient preferences to dental grafts and demonstrated 
that the highest rate of refusal of grafts was for allografts (20%) followed by xenografts (15%), 
due to ethical, personal or religious considerations25.  Clinicians have been presented with the 
dilemma where a patient rejects the use of allografts and xenografts allowing only for the use 
of alloplastic materials or autologous grafts.  Harvesting autologous grafts may necessitate the 
need for a second  site surgery, can be seen as unnecessarily invasive and my lead to an 
increased rate of morbidity. An alloplastic graft is a synthetic bone substitute with 
osteoconductive properties only and carries no risk of disease transmission26.  Cost, potential 
for allergic reaction, and patient preference may negate the use of alloplasts.  A more 
conservative and cost effective approach may be to proceed with venipuncture and subsequent 
production of a suitable grafting material, L-PRF, from the patient’s blood.  To the best of our 
knowledge, when reviewing the literature regarding volumetric changes following alveolar 
ridge preservation, there were no direct comparative studies evaluating the efficacy of L-PRF to 
other grafting materials. 

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Research question 
What is the effect of an L-PRF clot covered with a d-PTFE non-absorbable membrane on the 
hard and soft tissue volumetric changes in ridge preservation procedures when compared to 
FDBA covered by a d-PTFE non-absorbable membrane. 
 
Participants 
Patients of the Graduate Periodontics Clinic, College of Dentistry, University of Manitoba that 
require extraction of either molar or premolar teeth and subsequent ridge preservation from 
…2017 to December 2018 and have signed the consent form. Patients will receive initial 
periodontal examination and treatment if necessary.   
Inclusion Criteria:  
• Male or female, 22 years and over.  
• Subjects with molars or premolars indicated for extraction. 
• Patients that present with a post extraction class I and II socket (<30% bone loss on the 
buccal or lingual plate, measured from the most coronal aspect of intact bone to the 
most apical aspect of the defect divided by the measurement from the most apical 
aspect of the defect to the apex of the socket x 100). 
• Patients presenting with the need for single extractions. 

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• Patients with general good health that does not have a condition contra-indicating 
routine dental treatment, extraction and implant placement.  
• Patients that are compliant with the research protocol and methods.   
• Patients that have read, understood and signed an informed consent form. 
Exclusion Criteria:  
• Patients younger than 22 years 
• Extraction and ridge preservation indicated for teeth other than premolars and molars. 
• Patients that present with a post extraction class III socket (>30% bone loss on the 
buccal or lingual plate, measured from the most coronal aspect of intact bone to the 
most apical aspect of the defect divided by the measurement from the most apical 
aspect of the defect to the apex of the socket x 100) 
• Patients deemed eligible for immediate implant placement following extraction and 
intra-operative assessment by the attending supervisor. 
• Patients that present with an oral-antral communication, post extraction. 
• Patients that present with the need for multiple, adjacent extractions.  
• Patients with coagulation disorders, on corticosteroids, uncontrolled diabetes mellitus, 
or any systemic disease where periodontal surgery is contraindicated and healing may 
be compromised. 
• Pregnant and nursing women. 
• Patients with any contact hypersensitivity to the related materials used in the study. 
• Heavy tobacco users, >10 cigarettes per day.  
• Patients unwilling to sign consent or follow the protocol of the study.   

Final version dated: 2 December 2018 
 
 
 
Proposed method 
The study will take place at the Graduate Periodontics Department, College of Dentistry, 
University of Manitoba and will be for a total of at least 8 visits over a study period of 4 months.  
Randomization will be achieved using computerized randomization scheme. Each participant 
will be assigned to one of two groups and allocated by means of sealed envelope opened on 
the day of surgery communicated to the surgeon during the surgery by the independent 
examiner (JT). Participants will be block-randomized for each of the 5 operators for balance. 
Group A (control): Extraction followed by ridge preservation with freeze-dried bone allograft 
covered with d-PTFE membrane. 
Group B (test): Extraction followed by ridge preservation with L-PRF clot covered with d-PTFE 
membrane. The surgical procedure will be performed by one of all the calibrated periodontics 
residents (CS, JB, DR, JC, BW). Patients will be followed for 2 weeks post-operatively by the 
same resident to monitor the healing process and to assess for any complications.  
Visit 1: Following full examination and treatment planning, patients requiring extraction, socket 
preservation and implant treatment that meet the inclusion criteria, will be eligible to 
participate.  Once deemed eligible and the patient is interested in the study, the patient will be 
provided with the complete protocol, consent forms, as well as potential risks and benefits of 

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the study.   
Visit 2:  Confirmation of all relevant forms are signed. Clinical photographs taken and 
requisition for standardized CBCT filled out. 
Visit 3: Review of medical history and changes recorded.  Anesthesia will be achieved with 
either infiltration or block anesthesia depending on site. Anesthetic agent used will be 
Lidocaine 2% with 1:100 000 epinephrine. Keratinized tissue is measured on the buccal and 
lingual with UNC 15 probe from the gingival margin to the mucogingival junction.  Atraumatic 
extraction technique is recommended to allow for minimal disturbance of the soft and hard 
tissue architecture3,5.  The technique requires initial severing of the cervical gingival fibers with 
a periotome, then, once the gingival fibers have been completely severed, the PDL is severed by 
incrementally advancing the blade apically around the circumference of the root into the PDL 
space up to two thirds of the root distance towards the apex27. In the case of multi-rooted 
teeth, the crown is amputated with a high-speed hand piece, surgical bur and copious 
irrigation, taking care not to damage the adjacent soft and hard tissues.  Following amputation 
of the crown, the roots are then sectioned into separate entities followed by the use of the 
periotome as described above. Roots can further be mobilized with luxators followed by 
delivery with extraction forceps, taking care to leave the surrounding soft and hard tissues as 
intact as possible.  Irrigation with saline and curettage of the socket with hand instruments to 
remove all granulation and infected tissue is performed after extraction.  The socket walls are 
then assessed and the socket width measured with a periodontal probe.  If there is >30% bone 
loss caused by trauma, dehiscence or fenestrations in any of the socket walls, the patient will 
be exited from the study.  Patients exited from the study, depending on the extent of the 

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defect, will at the time proceed with ridge preservation or guided bone regeneration. For 
eligible patients, a randomized numbered envelope assigned to them is opened to determine 
the type of alveolar ridge preservation procedure.  Group A: Full thickness mucoperiosteal 
pouch is created up to ~3mm apical of the bony crest of the socket with a periosteal elevator.  
The socket is incrementally filled with mineralized cortical freeze-dried bone allograft and 
condensed.  Group B: Full thickness mucoperiosteal pouch is created up to ~3mm apical of the 
bony crest of the socket with a periosteal elevator followed by venipuncture of the antecubital 
vein with 21G needle and collection of 4-6 vials (10ml each) of venous blood without any 
additive or anticoagulant. The vials are centrifuged for 12 minutes at 2700 rpm.  Once 
centrifugation is complete, L-PRF specimens are collected and compressed into L-PRF clots.  The 
socket is gently rinsed with saline and incrementally filled with the clots and condensed.  
Following socket fill, both groups will have the grafts covered by a dense 
polytetrafluoroethylene membrane. The membrane is trimmed and adapted with the borders 
tucked 2-3mm below the mucoperiosteal pouch.  The soft tissues and membrane are stabilized 
with 5/0 PTFE sutures, one horizontal mattress suture and one cross suture, without an attempt 
at primary closure.  The patient is then assessed for hemostasis and provided with written and 
verbal post-operative instructions.  Patients will be instructed to avoid mechanical plaque 
control of the area and instructed to stay on a soft diet for 7 days post-operatively. Patients will 
be provided with Chlorhexidine 0.12% to rinse twice daily for 30 seconds during the first week 
of healing.  Participants are encouraged to contact the operator if they have any problem at any 
time.  The patients also receive post-operative medication: Amoxicillin 500mg P.O Q8H for 7 
days or in the case of penicillin allergy, Clindamycin 150mg P.O Q6H for 7 days.  The patients 

Final version dated: 2 December 2018 
will also receive a VAS questionnaire evaluating the post-operative pain 1 and 7 days following 
surgery as well as a supply of 20 tabs, Ibuprofen 400mg P.O Q6H PRN.  Intra-oral photographs 
will be taken pre-, intra- and post-operatively.  A CBCT will be taken within 72 hours of the 
surgery. 
Visit 4:  7 days post-op: Sutures will be removed if deemed suitable. The VAS questionnaire will 
be collected and remaining tablets of pain medication collected and recorded.   Oral hygiene 
instructions will be reviewed and a soft post surgical brush will be provided. Intra-oral 
photographs of the site will be taken. 
Visit 5:  14 days post-op: Sutures will be removed if they were not removed during the previous 
visit.  Oral hygiene instructions will be reviewed. Intra-oral photographs of the site will be 
taken. 
Visit 6:  6 weeks post op: d-PTFE membrane will be retrieved and discarded using tissue 
forceps.  Upper and lower alginate impressions will be taken for the manufacture of a surgical 
guide. Oral hygiene instructions will be reviewed. Intra-oral photographs of the site will be 
taken. 
Visit 7:  11 weeks post op:  Second CBCT will be taken with surgical guide.  The image obtained 
will be used to analyze and compare the ridge dimensions to those obtained at baseline as well 
as for surgical implant planning.  
Visit 8: 12 weeks post op: Medical history review. Intra-oral photographs of the site will be 
taken. Soft tissue measurement with periodontal probe and floss spanned over edentulous site 
from buccal to lingual mucogingival junction will be performed and recorded.  Implant 
placement will be done as per standard procedure.  A 2.5mm diameter trephine drill will be 

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used to harvest a bone core for histologic analysis. The bone core will be immediately 
submerged in a solution of 10% neutral buffered formalin.  The selection of the implant system 
will depend on the surgical and restorative needs of each individual case. Osteotomies and 
implant placement will be done following the manufacturer’s protocol. A final peri-apical 
radiograph will be obtained to verify correct implant position and angulation. If adequate 
primary stability is achieved and one-stage approach is feasible, a healing abutment will be 
placed. Depending on the buccal bone and soft tissue thickness, ancillary soft tissue 
augmentation, bone augmentation or combination of these procedures may be indicated.  If a 
two-stage procedure is indicated, a cover screw will be placed and the implant will be 
submerged. At the end of the appointment, written and verbal post-operative instructions will 
be given to the patients. The patient will be followed up and referred to the restorative dentist 
as per standard procedure. 
Data Collection 
CBCT measurements will be performed by the primary investigator (JB) after extraction (visit 3) 
and before implant placement (visit 7) with the use of i-Dixel image capturing software.  The 
DICOM files will be exported to 3D analysis software, Invivo by Anatomage, to superimpose the 
two images using static anatomical landmarks as reference points, and measuring the 
difference between baseline (Visit 3) and post-healing (Visit 7)28. Buccal bone plate thickness 
would be measured at 1, 3 and 5mm from the bone crest, as well as bucco-lingual width at 1, 3 
and 5 mm from the bone crest.  Vertical measurements would be measured from the buccal 
and lingual bone crest to the apex of the socket.  KT measurements will be compared to 
baseline and implant placement visit.  Objective and subjective post-operative pain experience 

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will be compared between the two groups using data from VAS questionnaires and tablet 
counts of remaining medication. 
Statistical methods 
Sample size was calculated assuming an alpha of .05, two tailed test, with a power estimate 0.8 
which resulted in sample estimates of 42 subjects.  The study will be blinded at the level of data 
assessment. The primary outcome will be the volumetric changes in soft and hard tissue for the 
two proposed methods.  Secondary outcomes will be reported patient discomfort from the VAS 
questionnaire between the two groups as well as evaluation of the amount of vital bone 
formed after the healing phase by means of histologic analysis of bone samples taken from the 
2 groups at the time of the implant surgery visit. To compare groups at T1 and T2, independent 
samples t-tests were used. Equal variances were not assumed and the significance levels were 
corrected as such. In addition, a non-parametic MannWhitney U test was also used. To test for 
differences at time 1 vs time 2, within and between groups, a linear mixed model was used with 
restricted maximum likelihood (REML) approach.  Spearman correlations reported to indicate 
relationship between Plate (T1) and Width (T2) measurements for 1, 3 and 5mm.  
Risks 
Extraction and alveolar ridge preservation may have a risk of membrane exposure, post-
operative bleeding, infection, swelling, pain and discomfort from the surgical site for both 
groups.  
 

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Potential benefits 
If L-PRF is proved to be equal or better in terms of alveolar ridge preservation, resulting in 
faster healing time and less discomfort, it would be of benefit to the patient due to a more 
comfortable and faster post operative healing phase, reduced costs compared to the purchase 
of grafting materials, less risk of graft rejection as well as providing the patient with a viable 
option should personal preference dictate that no synthetic, xeno- or allografts be used.  
Consent Process 
Patients of the Graduate Periodontics Clinic that require extraction, ridge preservation and 
subsequent implant placement, will be asked personally to volunteer. Those showing interest 
will be provided with a summary of the research study including a consent form to read and 
sign should they wish to partake.  
Data security 
All data will be recorded based on the participant’s number assigned once the consent form is 
signed. Each patient’s name and contact information will be kept locked in a secure place at the 
Graduate Periodontics Clinic. The results of the study may be published or presented in public 
forums; however the participants’ name will not be used or revealed.  
 
 
 
 

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