CLINICAL EFFICACY OF XENOGENEIC COLLAGEN MATRIX AS A COMPARATIVE ALTERNATIVE TO FREE GINGIVAL GRAFT IN AUGMENTING KERATINIZED MUCOSA WIDTH AROUND DENTAL IMPLANTS: A SYSTEMATIC REVIEW AND META-ANALYSIS

Abstract

Introduction: The literature has suggested that minimal keratinized mucosa width (KMW) around osseointegrated implants, less than 2mm, may lead to a higher incidence of peri-mucositis, inflammation around the implant, and in the longer-term lead to peri-implant disease (Moraschini et al., 2017). Therefore, procedures to augment keratinized tissue have become a standard in periodontal plastic surgery, aiming to prevent peri-mucositis and peri-implantitis. Since the late 1960s, clinicians have corrected a lack of keratinized tissue by transplanting autogenous free gingival grafts (FGGs), and connective tissue grafts (CTGs) (Nevins et al., 2011) from the patient’s palate. Possible alternatives to FGGs and CTGs are xenografts and allografts (Dragan et al., 2017). Clinical studies have demonstrated a xenogeneic collagen matrix (XCM) potential as a means of increasing the width of keratinized tissue around dental implants without the need for an autologous graft and second surgical site (Rokn et al., 2020), improving patient post-surgical experience and increasing the willingness of patients to opt for further treatment. Purpose: This systematic review aimed to determine the clinical efficacy of using a xenogeneic collagen matrix (XCM) to augment keratinized mucosa width (KMW) around implants as a comparative alternative to free gingival grafts (FGG). Materials and Methods: Articles that were published between 1990 to November 2022 were electronically searched in six databases and manually searched in major periodontology and oral implantology journals and grey literature. The eligibility criteria comprised of randomized controlled trials (RCTs) and non-randomized clinical studies that analyzed the clinical efficacy of XCM for augmenting KMW around dental implants in comparison to FGG. Six studies were identified for final inclusion in this review and were included in the meta-analysis. The continuous outcomes were expressed as standardized means for KMW and PDs with a confidence interval (CI) of 95%. Outcome measures were statistically evaluated at the subject level. A fixed-effects model was used to pool the results from more than one study. Results: Six studies published between 2016 and 2021 were included in this systematic review and meta-analysis. Results from all six included studies were homogenous in concluding that FGG provided a greater overall increase in mean gain of KMW when compared to XCM; three of the six studies found this difference to be statistically significant. However, XCM still produced an average increase in KMW (2.84mm) that was significant from baseline, and comparable to FGG gains (4.07mm) at 6 months. Other clinical parameters such as PDs, BOP and/or GI were found to be statistically and clinically comparable between the test and control groups, suggesting both materials can provide peri-implant stability and health. Four of the studies provided data on patient-reported outcome measures. All four studies noted that the use of FGG graft was perceived as more painful at 2 weeks follow-up compared to XCM, which were also found to be statistically significant. One study mentioned that there was also a statistically significant difference in willingness for retreatment in the XCM group (76%) compared to the FGG group (43%). Two studies observed tissue shrinkage from baseline and determined that after 6 months there appeared to be significantly more tissue shrinkage with the XCM group compared to FGG. Another study that observed shrinkage over 5 years found a statistically significant difference between XCM and FGG, with the test group showing increasingly more shrinkage over long-term healing. Conclusions: The use of XCM around integrated dental implants improved KMW and provided stable and periodontally healthy probing depths, GI, and BOP indices with rates comparable to those for FGG. This review revealed that FGG could result in an overall greater increase in KMW than XCM. However, both XCM and FGG have demonstrated an increase in KMW ≥2mm around dental implants and maintain peri-implant health. A limited number of randomized controlled trials have compared the performance of xenogeneic collagen matrices with free gingival grafts around dental implants at longer healing periods and are needed to determine the true long-term efficacy of XCM as a substitute.