Efficacy of the injectable platelet-rich fibrin (i-PRF) in gingival phenotype modification: a systematic review and meta-analysis of randomized controlled trials.

Background: Gingival phenotype (GP), comprising gingival thickness (GT) and keratinized tissue width (KTW), plays a crucial role in preserving the integrity of gingival and periodontal tissues, thereby enhancing their resistance to trauma and mechanical irritation. This systematic review and meta-analysis aimed to evaluate the current evidence about the changes in GT and KTW following the injection of injectable platelet-rich fibrin (i-PRF) in patients with thin GP.

Methods: A thorough search was conducted up to April 2024 across the following nine databases: The Cochrane Central Register of Controlled Trials (CENTRAL), PubMed^®, Scopus^®, Web of Science^®, Google Scholar, Trip, CINAHL via EBSCO, EMBASE via OVID, and ProQuest. This review covered parallel-group and split-mouth randomized controlled trials (RCTs) which investigated the changes in GT and KTW following i-PRF injection on the buccal anterior region in both jaws for individuals with thin GP. The risk of bias in the included studies was evaluated using Cochrane's tool (RoB 2), and the GRADE framework was utilized to assess the overall strength of evidence. Agreement between the authors was assessed using Cohen's kappa statistic.

Results: Seven RCTs were included in this review, five of which were appropriate for the quantitative synthesis of data. The meta-analysis showed a statistically significant increase in the GT in the i-PRF group at all assessment times compared to baseline (MD ranged from 0.12 mm to 0.38 mm). Regarding KTW, 4-time injections led to a significant increase in KTW after 3-month and 6-month follow-ups compared to baseline (MD = 0.31 mm, and MD = 0.37 mm, respectively). In contrast, 3-time injections yielded a non-significant increase in KTW after 1 and 3 months of follow-up (MD = 0.14 mm at both assessment times). The strength of evidence supporting these findings ranged from low to moderate. However, when comparing the i-PRF group and the i-PRF + microneedling (MN) group, the pooled estimate exhibited significant differences in the GT at both assessment times, with superiority for the MN + i-PRF group (MD = 0.04 mm after 3 months, MD = 0.11 mm after 6 months). In contrast, there were no statistically significant differences in KTW between the two comparisons (MD = 0.03 mm at both assessment times). The strength of evidence supporting these findings was moderate.

Conclusions: For patients with a thin GP, i-PRF administration resulted in a significant increase in GT at all assessment times compared to baseline. Regarding the KTW, the results varied depending on the number of injection sessions. When the injections were carried out four times, there was an observed increase in KTW, while repeating the intervention three times revealed a non-significant increase in KTW.

Protocol registration: The protocol was registered in the PROSPERO database (CRD42024543374) on 16 May 2024.

Level of evidence: According to the GRADE recommendations, the strength of evidence regarding the effect of i-PRF injection on GT and KTW ranged from low to moderate. The evidence strength for differences between the i-PRF group and the i-PRF + MN group in both GT and KTW was moderate. The overall quality of evidence for these outcomes is presented in Table 4.