Alveolar Ridge Preservation (ARP)
Introduction
Following tooth extraction, alveolar atrophy occurs in both horizontal and vertical dimensions, with a pronounced effect on the buccal site. While changes in bone height are moderate, horizontal reduction can reach up to 60% of the initial alveolar ridge width. Pooled estimates for mean horizontal and mid-facial vertical ridge resorption (non-molar sites) are:
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Clinically assessed: horizontal resorption is 2.7 mm (95% CI: 2.4–3.1), and vertical resorption is 1.7 mm (95% CI: 1.3–2.1).
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Radiographically assessed: horizontal resorption is 2.5 mm (95% CI: 2.0–3.1), and vertical resorption is 1.7 mm (95% CI: 0.4–2.9).
Approximately two-thirds of this reduction occurs within the first three months post-extraction (Couso-Queiruga et al., 2021). Alveolar ridge preservation has been introduced to reduce this resorption. A systematic review by Apaza-Bedoya and co-workers (2024) concluded that the application of a bone xenograft in combination with an absorbable sealing material resulted in a reduction in horizontal resorption of 62, 60 and 64%, respectively, at 1, 3, and 5 mm away from the alveolar crest.
The application of L-PRF significantly mitigates this resorption, reducing the need for additional bone regeneration procedures, such as those required for implant placement.
Protocol: step by step
step-by-step flow chart
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perform an atraumatic extraction (utilize root separation techniques),
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avoid flap elevation and releasing incisions,
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remove the pocket epithelium,
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remove all granulation tissue (preferably using a bur),
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prepare an envelope of 3-5 mm between the bone and the periosteum (blue arrows),
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rinse the socket with L-PRF exudate (for local disinfection),
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insert ≥ 3-5 L-PRF membranes/plugs and condense them in situ (using a graft condensor),
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cover/seal the socket with 2 L-PRF membranes (inserted in the previously prepared envelope),
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close with modified horizontal mattress sutures and extra sutures for a healing by secondary intention; complete wound closure is not required,
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optionally, create small perforations in socket wall for extra blood supply,
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prevent pressure on the wound (e.g., using an acid-etch crown).
Video: ARP in case of a nearly intact extraction socket: details
Start with an atraumatic extraction (consider root separation). Remove all pocket epithelium and granulation tissue using a bur. Preserve the inter-radicular bony septa. Prepare an envelope between the bony borders of the socket and the periosteum. Tightly pack several L-PRF plugs into the socket (optimal condensation). Seal the entrance to the socket with two layers of L-PRF membranes. Slide these membranes into the envelope created between the periosteum and bony socket borders, covering 3 to 5 mm of bone. Suturing is completed without any attempt to close the wound; its only purpose is to keep the L-PRF in the socket, allowing healing by secondary intention. Small perforations in the socket walls can improve the vascularization and optimize healing.
Video: ARP in case of a major buccal bone dehiscence (L-PRF only)
The buccal bony dehiscence must first be covered with at least a double layer of L-PRF membranes, extending 5 mm beyond its bony borders. The face portion of the inner L-PRF membrane should preferably be facing the bony dehiscence. L-PRF membranes are tightly packed into the socket and the bony dehiscence. The entrance to the socket is sealed with a double layer of L-PRF membranes. Suturing is completed without any attempt to close the wound; its only purpose is to keep the L-PRF in the socket (healing by secondary intention). Deeper sutures should not run over the bony dehiscence because they might push the L-PRF out of the socket; such sutures must be supported by bone. Small perforations in the socket walls can improve the vascularization, thereby optimizing the healing and bone formation.
Cases
(d = day, w = week, m = month, y = year)
1: ARP in case of buccal bone dehiscence (L-PRF only)
d 0: extraction of the first premolar with loss of the entire buccal bone plate (see bone curette).
d 0: 3D CBCT image indicating alveolar bone loss (no remaining buccal bone plate).
d 0: post-op CBCT, with an indication of where the L-PRF plugs have been positioned (L-PRF is not visible due to its low density; it is, in fact, only a blood clot).
d 0: socket filled with 4 L-PRF plugs and covered with a double layer of L-PRF membranes.
d 0: sagittal CBCT image.
m 4: clinical view on soft-tissue healing after removal of the provisional acid-etched crown.
d 0: suturing with modified horizontal mattress suture for healing by secondary intention.
d 0: cross-sectional image showing 7.7 mm residual bone height and a clear view of the lost integrity of buccal bone.
m 4: cross-section in the center of the socket, indicating good bone regeneration that is sufficient for proper implant insertion (red=initial bone, white=regenerated bone).
2: ARP in case of buccal bone dehiscence
d 0: sagittal CBCT image of the area of the first premolar, which needed to be extracted and where L-PRF has been applied.
d 7: suture removal and early healing; membranes become pink due to initial vascularization.
m 3: good soft-tissue healing.
m 3: a new sagittal CBCT image comfirmed early bone formation.
m 3: cross-section in socket center illustrating an optimal bone regeneration; the red line indicates the initial bone level, and the white line the location of the regenerated bone.
m 3: re-entry confirmed the bone regeneration, despite the absence of a buccal bone plate after tooth extraction; this was achieved without using a bone substitute.
m 3: during drilling, good bone density was observed.
m 3: the implant could be placed in an optimal position.
y 7: the intra-oral radiograph revealed a stable bone level.
3: ARP: healing sequence
d 0: L-PRF application after the extraction of a first molar.
d 4: suture removal; soft-tissue has already started wound closure.
d 17: nearly complete wound closure; the underlying membrane is still intact.
d 23: complete wound closure, but with a remaining soft-tissue crater.
d 6: 30% of the wound is closed, and the L-PRF membranes are still intact.
m 3: the soft-tissue crater has completely disappeared.
Courtesy Nelson Pinto
Data:
RCTs illustrating benefits when applying L-PRF (studies ≥ 2 m follow-up)
Abbreviations: RCT = randomized controlled trials, Subjects: n = number, ♀ = female, ♂ = male; Treatment: PrH = primary healing; SeH = secondary healing, c = control group, T = test group, (..) = number of patients/sites, L-PRF = leukocyte- and platelet-rich fibrin (acronym as mentioned in the paper: A = advanced, CGF = concentrated growth factor); cl = clot; pl = plug; m = membrane.
Conclusion
From the fifteen RCTs, fourteen, involving 408 patients and 528 sockets, examined the effects of L-PRF on alveolar bone resorption (ABR) using a variety of parameters. Eleven studies reported statistically significant reductions in ABR in both horizontal and vertical dimensions when L-PRF was used [e.g., using proportional horizontal ABR data: 75% less (Hauser et al. 2013); 56% less (Temmerman et al. 2016); 47% less (Alzahrani et al. 2017); 38% less (Ivanova et al. 2019); 33% less (Alsayed et al. 2020); 61% less (Canellas et al. 2020); 55% less (Ma et al. 2021); 75% less (Al Kassar & Heshmeh 2023); 88% less (Assadi et al. 2023); and 46% less Jouliq et al. 2023), or significantly more socket fill (89 vs. 80%; 95 vs. 63%; 85 vs. 68%)]. One study found L-PRF to be superior only in reducing vertical height resorption (Rodrigues et al. 2023). Two studies, however, failed to find any statistically significant differences (Wang et al. 2022, Abad et al. 2023). The effectiveness of L-PRF appears to depend on the specific treatment strategy employed (for more information, see Siawasch et al. 2025a). Several studies also reported improved bone quality and/or a higher relative proportion of bone in histological sections, all favoring L-PRF.
Important Notice
Clinical experience:
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L-PRF plugs/membranes are clearly superior to clots.
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Apply at least 3 L-PRF plugs/membranes per socket.
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Proper condensation of membranes/plugs in the socket is crucial.
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Always seal the entrance to the socket by applying membranes in the envelope.
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Ensure optimal blood supply within the socket by creating small perforations.
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Avoid raising a flap; there is no need for a primary wound closure.
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Prevent any pressure on the healing site (e.g., using an acid-etched crown instead of a temporary spoon denture).
Additional Benefits:
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The use of L-PRF will improve the patient-reported outcome measures (PROMs), including reduced pain and less post-extraction bleeding, and lead to a faster soft-tissue healing.
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It is a flapless approach (less pain, easier procedure).
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Wound closure is not necessary, which means no changes to the position of the mucogingival border or the vestibulum.
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The procedure will result in a naturally healed bone of better quality and without "residual" bone substitute.
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L-PRF plugs/membranes can also serve as hemostatic agents.
Open Issues:
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What is the best approach in case of multiple neighboring extraction sockets: using a slow resorbing barrier membrane, a GBR approach, ... ?
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Under what conditions is a slow-resorbing barrier membrane preferred (e.g., large non-contained defect, ...)?
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What is the ideal number of L-PRF plugs/membranes per extraction socket?
Unfortunately, there is a lack of studies directly comparing the above-mentioned strategies.
Failures: disappointing results have been observed:
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In sockets with limited blood supply.
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In sockets where the bony walls were overheated due to deep subgingival use of piezo-instruments without adequate cooling.
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After the early loss of L-PRF matrices (sutures should not push out/displace the graft); the entrance to the socket must be properly sealed.
Is the use of L-PRF in extraction socket of impacted third molar beneficial?
The benefits of an L-PRF application in the extraction socket of impacted mandibular third molars have been examined in a recent systematic review (Siawasch et al. 2025b). A detailed analysis revealed significant heterogeneity between studies, likely due to variability in protocols [extraction technique, number of L-PRF matrices, type of matrix (membrane/clot/plug)], applied parameters, and/or timing of follow-up visit(s). The application of L-PRF mostly resulted in statistically significant reductions of postoperative sequelae [lower pain intensity (10/17 papers), reduced consumption of analgesics (3/5 papers), less postoperative edema (8/17 papers), and a lower incidence of trismus (6/9 papers) and alveolar osteitis (7/13 papers)]. Additionally, it was associated with faster soft tissue healing (6/7 papers), and both qualitatively (10/15 papers) and quantitatively better bone healing (5/10 papers). A minority of studies reported significant differences in periodontal parameters distal to the second molar.
Interesting references
Several videos and/or cases on this webpage are discussed more in detail in the following book: Quirynen M & Pinto N 2022. Leukocyte- and Platelet-Rich Fibrin in Oral Regenerative Procedures. Quintessence Publishing;
ISBN: 978-1-78698-105-9