Peri-Implant Soft-Tissue Augmentation Using Xenogeneic Collagen Matrices Versus Autogenous Connective Tissue Grafts in Single-Tooth Implants: a Systematic Review

Objectives: The aim of this systematic review was to evaluate and compare the clinical outcomes of peri-implant soft tissue augmentation using xenogeneic collagen matrices and autogenous subepithelial connective tissue grafts in single-tooth implant therapy. The review focused on key clinical parameters, including marginal bone loss, soft tissue thickness gain, mid-buccal recession, and aesthetic outcomes assessed by the pink aesthetic score.

Material and Methods: This systematic review was conducted following PRISMA guidelines. A comprehensive electronic search was performed in MEDLINE (PubMed), ScienceDirect, and the Cochrane Library for studies published between November 18, 2015, and November 18, 2025. Eligible studies included randomized controlled trials, prospective clinical trials, and cohort studies evaluating peri-implant soft tissue augmentation using xenogeneic collagen matrices compared with autogenous subepithelial connective tissue grafts. Study quality and risk of bias were assessed using the Joanna Briggs Institute Critical Appraisal Checklist.

Results: A total of 839 records were identified, of which six studies met the inclusion criteria. Both treatment modalities demonstrated favourable clinical outcomes. Marginal bone loss was generally limited, with no consistent statistically significant differences between groups, although one study reported greater bone loss in the xenogeneic group. Soft tissue thickness gain showed a trend favouring autogenous grafts. Mid-buccal recession data were limited but suggested slightly greater recession in the xenogeneic group. Aesthetic outcomes were comparable between groups.

Conclusions: Both treatment modalities are effective; however, autogenous grafts provide more consistent soft tissue thickness gain, while collagen matrices represent a viable alternative with comparable aesthetic and bone outcomes.

J Oral Maxillofac Res 2026;17(2):e2

doi: 10.5037/jomr.2026.17202

Accepted for publication: 29 June 2026

Keywords: bone resorption; collagen; connective tissue; dental esthetics; dental implants; endosseous dental implantation.

INTRODUCTION

Dental implants have become one of the most popular permanent solutions for tooth replacement worldwide, as they allow replacement of missing natural teeth with a high level of long-term function, stability, and patient comfort [1]. Over recent years, implant therapy has demonstrated high survival rates and predictable outcomes, making it a widely accepted treatment modality in both partially and fully edentulous patients [2]. The establishment and long-term maintenance of peri-implant soft tissue health plays a central role in the biological stability, aesthetic outcome, and overall success of implant-supported restorations [3]. Sufficient soft tissue quantity and thickness are related to greater implant resistance to mechanical trauma, reduced marginal bone loss (MBL), and better aesthetic integration [4]. Adequate peri-implant mucosal thickness has also been associated with improved tissue resilience, enhanced plaque control, and reduced susceptibility to recession [5]. In contrast, a thin peri-implant phenotype and the absence of sufficient attached keratinized mucosa have emerged as potential risk factors for MBL and reduced peri-implant aesthetics [6]. Clinical evidence suggests that thin peri-implant tissues may be less capable of withstanding functional loading and inflammatory challenges, potentially leading to crestal bone remodeling and soft tissue recession over time [7].

To overcome peri-implant soft tissue deficiencies, surgical procedures for soft tissue augmentation are often required to increase mucosal thickness, improve keratinized tissue width, and enhance long-term peri-implant stability [8]. Autogenous subepithelial connective tissue grafts (SCTGs), harvested from the palate, are known as the “gold standard” for peri-implant soft tissue augmentation due to proven efficacy and long-term clinical predictability [9]. SCTGs have demonstrated favourable outcomes in terms of increased soft tissue thickness, reduced mid-buccal recession, and improved aesthetic parameters [10]. However, harvesting autogenous grafts is associated with donor site morbidity, increased surgical time, postoperative discomfort, and limited tissue availability, which may affect patient acceptance and clinical decision-making [11]. Xenogeneic collagen matrices have been introduced as alternative graft materials for peri-implant soft tissue augmentation, functioning as three-dimensional matrices that support soft tissue integration and vascularization while eliminating the need for a secondary surgical site [12]. Although an increasing number of clinical studies have evaluated xenogeneic collagen matrices, the evidence regarding their effectiveness compared to autogenous SCTGs remains inconsistent, as some studies report comparable improvements in soft tissue thickness and aesthetic outcomes while concerns persist about their long-term ability to maintain peri-implant tissue stability [13]. Hence, the aim of this systematic review aimed to evaluate and compare the clinical outcomes of peri-implant soft tissue augmentation using xenogeneic collagen matrices and autogenous subepithelial connective tissue grafts in single-tooth implant therapy.

MATERIAL AND METHODS

Protocol and registration

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement for reporting systematic reviews [14]. This systematic review was registered in the PROSPERO register under the number CRD420261353341.

The protocol can be accessed at:

https://www.crd.york.ac.uk/PROSPERO/view/CRD420261353341

Focus question

The focus question was created according to the Patient, Intervention, Comparison, Outcome, and Study design (PICOS) framework as described in Table 1.

The focus question: “In adult patients undergoing single-tooth implant therapy with peri-implant soft-tissue deficiency, does peri-implant soft-tissue augmentation using xenogeneic collagen matrices, compared with autogenous SCTG, result in comparable MBL and peri-implant soft-tissue and aesthetic outcomes?”.

Types of publication

Only human studies published in English were included. Systematic reviews, case reports, meta-analyses, letters to the editor, and abstracts without full-text availability were excluded.

Information sources

An electronic search was conducted on the National Library of Medicine database (MEDLINE) through its online site PubMed, ScienceDirect database, and the Cochrane Library.

Types of studies

This review included randomized controlled trials, prospective and retrospective cohort studies, and cross-sectional studies.

Population

The population included adult patients (≥ 18 years) receiving single-tooth dental implants in the maxilla or mandible with peri-implant soft-tissue deficiencies requiring surgical soft-tissue augmentation.

Search strategy

According to the PRISMA guidelines [14] relevant research articles were identified through electronic database searches, including MEDLINE (PubMed), ScienceDirect, the Cochrane Library, covering studies published between November 18, 2015, and April 7, 2025. The keyword combinations used in the article search are presented in Table 2.

Inclusion criteria

• Studies involving adult patients (≥ 18 years) undergoing single-tooth implant therapy in the maxilla or mandible.

• Patients presenting with a peri-implant soft-tissue deficiency, such as thin soft-tissue phenotype, reduced mucosal thickness, or insufficient buccal soft-tissue volume.

• Studies evaluating peri-implant soft-tissue augmentation performed using a xenogeneic collagen matrix (e.g., porcine-derived or volume-stable collagen matrices).

• Studies including a comparison group treated with an autogenous SCTG.

• Studies reporting at least one of the following outcomes: MBL, soft-tissue thickness gain, width of keratinized tissue, mid-buccal marginal tissue recession, or PES.

• Randomized controlled trials, clinical trials, cohort studies, or cross-sectional studies.

• Studies including a minimum total sample size of at least 20 patients.

• Studies reporting a minimum follow-up duration of at least 3 months.

• Studies published in the English language within the predefined search period.

Exclusion criteria

• Studies involving animal models or in vitro experiments

• Case reports, case series, narrative reviews, systematic reviews, letters, or expert opinions.

• Studies including multiple implants, full-arch rehabilitations, or ridge augmentation procedures not related to peri-implant soft tissue.

• Studies evaluating soft-tissue augmentation without comparison between xenogeneic collagen matrices and autogenous SCTG.

• Studies with insufficient clinical or radiographic outcome data.

• Studies including medically compromised patients.

• Non-English publications.

Data extraction

The data was extracted independently from studies, based on the objectives and tasks of this study. The specific data items extracted are detailed below.

Selection process of articles

The research for this review was conducted in several stages. The initial step was to find articles using previously specified keywords (Table 2). Two reviewers (H.A. and D.S.) independently screened the records obtained from the systematic search. All subsequent database duplications were eliminated based on the titles and abstracts reading. Disagreements were resolved through discussion and consensus, with the involvement of a third reviewer (C.M.) when necessary. After full-text analysis, publications were evaluated for relevance and compliance with selection criteria. Only those that met these criteria were included in this review.

Inter-rater reliability in the abstract screening process was verified on 10% of publications using Cohen’s kappa (κ).

Data items

From each study, the following parameters were extracted: study and publication year, study design, total number of patients (control and test groups), mean age (or range), male/female ratio, duration of the longest follow-up (in months) presented in the article, total number of implants placed, type of implant, implant site of placement (maxilla/mandible, anterior/posterior), mid-buccal recession, soft tissue thickness gain (soft tissue thickness/mucosal thickness), pink aesthetic score (PES), MBL.

Risk of bias across studies

The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for quasi-experimental studies and JBI Critical Appraisal Checklist for randomized controlled trials [15] were used to assess the procedural quality of the studies that fulfilled the inclusion criteria. The specific questions evaluated are detailed in Tables 3 and 4. In both of the checklists, every criterion was given a rating of - “yes“, “no“, “unclear“, or “not applicable“. Methodological quality was categorized as follows: “high risk of bias”, when the study scored up to 49% of positive answers; “moderate risk of bias” when the study scored between 50 and 69% of positive answers; “low risk of bias” when the study reached more than 70% of favourable answers.

Synthesis of results

After extraction of the relevant data from articles, items and data were collected and arranged in tables.

Statistical analysis

Mendeley^® Reference Manager version 2.110.2 (Elsevier; London, UK) was used for reference management and organization of the cited literature. No statistical analysis or meta-analysis was performed due to the heterogeneity of the included studies. Inter-rater agreement between the two reviewers during the abstract and study selection process was quantified using Cohen’s kappa coefficient (κ).

RESULTS

Study selection and exclusion

A total of 839 records were initially identified through database search (Figure 1). After removal of 92 duplicate records, 747 total records remained for screening. Of these, 130 records were excluded because they were published more than 10 years prior, leaving 617 titles and abstracts for screening. Following titles and abstracts screening, 606 records were excluded due to irrelevance to the topic. Consequently, 11 full-text articles were assessed for eligibility.

The level of agreement between two independent reviewers (H.A. and D.S.) in selecting abstracts was κ = 0.85, indicating almost perfect agreement.

Study exclusion

After analysing the full-text articles, 5 studies [16-20] were excluded for the following reasons. Two studies [16,17] did not meet the predefined inclusion criteria. One study [19] was excluded due to an ineligible study design. One study [20] was excluded because it did not include a comparison with a xenogeneic collagen matrix. One study [18] was excluded because its population was not related to peri-implant soft tissue augmentation. Finally, six studies [21-26] met all criteria and were included in this systematic review.

Risk of bias in included studies

The methodological quality of the included studies was assessed according to study design using the JBI critical appraisal checklists. Quasi-experimental (non-randomized) studies were evaluated using the JBI checklist for quasi-experimental studies, while randomized controlled trials were appraised using the JBI checklist for randomized controlled trials. The detailed quality assessments for each study are presented in Tables 5 and 6.

Overall, all included studies [22-26] were judged to be of high methodological quality, with the exception of the quasi-experimental study by De Angelis et al. [21], which was classified as having moderate methodological quality.

Study characteristics

The demographic characteristics of the included studies are summarized in Table 7. A total of six clinical trials were included [21-26], comprising four randomized controlled trials and two prospective clinical trials. Overall, 239 patients were included in the analysis. For each study, the longest follow-up duration was selected for analysis.

Type of implant

All included studies used commercially available implant systems (Table 8). De Angelis et al. [21] used bone-level tapered implants in both test and control groups. Cosyn et al. [22] used Nobel Biocare^® (Nobel Biocare AB; Gothenburg, Sweden), while Puisys et al. [23] used Straumann^® BLX™ implant system (Straumann AG; Basal, Switzerland). Thoma et al. [24] did not record the implant system used in the study. De Angelis et al. [25] used either MIS^® (MIS Implants Technologies Ltd.; Bar-Lev, Israel) or Straumann^® (Institute Straumann AG; Basel, Switzerland), and Ashurko et al. [26] used Astra Tech Implant System™ (Dentsply Sirona; Mölndal, Sweden).

Type of graft

All included studies compared autogenous SCTGs with xenogeneic collagen matrices. In the control groups, SCTGs harvested from the palate were used in the studies by De Angelis et al. [21], Cosyn et al. [22], Thoma et al. [24], and De Angelis et al. [25], whereas Puisys et al. [23] and Ashurko et al. [26] reported CTGs obtained from the maxillary tuberosity.

In the test groups, all studies utilized porcine-derived collagen matrices, although different materials were applied. Geistlich Fibro-Gide^® (Geistlich Pharma AG; Wolhusen, Switzerland) was used in the studies by De Angelis et al. [21], Cosyn et al. [22], Thoma et al. [24], and Ashurko et al. [26], whereas Mucoderm^® (Botiss Biomaterials GmbH; Zossen, Germany) was used in the studies by Puisys et al. [23] and De Angelis et al. [25]. Although all collagen matrices were xenogeneic, variations in material composition and cross-linking properties contributed to methodological heterogeneity among the included studies.

Implant site of placement

Cosyn et al. [22] and Puisys et al. [23] reported implant placement exclusively in the anterior maxilla, focusing on single-tooth sites in the aesthetic zone. Ashurko et al. [26] investigated implants placed in the posterior mandible. De Angelis et al. [21] and De Angelis et al. [25] included implants placed in the maxilla and mandible without restriction to a specific region. In contrast, Thoma et al. [24] did not clearly specify the exact implant site of placement. Across all the studies included, implant placement was limited to single-tooth sites.

Marginal bone loss

MBL was reported in four of the included studies (Table 8). Cosyn et al. [22] reported mean MBL values of 0.72 mm in the test group and 0.34 mm in the control group (P = 0.001). Puisys et al. [23] reported mesial bone loss values of 0.1 (SD 0.21) mm in the test group and 0.2 (SD 0.22) mm in the control group (P = 0.035), and distal bone loss values of 0.2 (SD 0.26) mm and 0.2 (SD 0.17) mm (P = 1.000). Thoma et al. [24] reported MBL values of 0.5 (SD 0.7) mm in the test group and 0.4 (SD 0.4) mm in the control group (P = 0.772). De Angelis et al. [25] reported mean MBL values of 0.53 (SD 0.35) mm in the test group and 0.47 (SD 0.36) mm in the control group (P = 0.419).

Mid-buccal recession

Mid-buccal recession was reported in two studies (Table 8). Cosyn et al. [22] reported a mean recession of 0.91 mm in the test group and 0.16 mm in the control group (P < 0.001). De Angelis et al. [25] reported mid-buccal recession values of 0.81 (SD 0.35) mm in the test group and 0.56 (SD 0.4) mm in the control group with significant difference between the groups (P = 0.021). The remaining studies did not provide quantitative data on mid-buccal recession.

Soft tissue thickness gain

Soft tissue thickness gain was reported in five of the included studies (Table 8). De Angelis et al. [21] reported occlusal thickness gains of 0.68 (SD 0.15) mm in the test group and 0.9 (SD 0.16) mm in the control group, while buccal thickness gain was 1.16 (SD 0.25) mm and 1.35 (SD 0.34) mm with statistically significant difference between the two groups for the occlusal side (P < 0.0008), while the difference between the groups did not differ significantly for the buccal side (P = 0.136). Cosyn et al. [22] reported thickness gains of 0.85 mm in the test group and 1.15 mm in the control group (P = 0.054). Thoma et al [24] reported gain of 0.3 (SD 1.1) of test group and 0.5 (SD 1) mm of control group (P = 0.752). De Angelis et al. [25] reported gains of 0.66 (SD 0.31) mm in buccal aspect in the test group and 1.16 (SD 0.41) mm in buccal aspect in the control group (P < 0.001). Ashurko et al. [26] reported soft tissue thickness gains of 1.11 (SD 0.44) mm in test group and 1.43 (SD 0.81) mm in the control group (P = 0.0459).

Pink aesthetic score

All included studies reported aesthetic outcomes using the PES (Table 8). De Angelis et al. [21] reported a mean PES of 8 (SD 0.94) in the test group and 8.29 (SD 0.92) in the control group at 6 months, with no statistically significant difference between groups (P > 0.05). Cosyn et al. [22] reported mean PES values of 10.59 in the test group and 10.47 in the control group at 3 months, also without a statistically significant intergroup difference (P > 0.05). Puisys et al. [23] reported mean PES values of 12.1 (SD 1.39) in the test group and 12.9 (SD 1.27) in the control group at 12 months, with no statistically significant difference between groups (P > 0.05). Thoma et al. [24] reported mean PES values of 11 in the test group and 11 in the control group at 60 months, with no statistically significant difference between groups (P > 0.05). De Angelis et al. [25] reported PES values of 7.8 (SD 0.96) in the test group and 8.15 (SD 1.86) in the control group at 12 months, again without a statistically significant difference (P > 0.05). Ashurko et al. [26] reported PES values of 9.17 in the test group and 11.86 in the control group at 6 months, with statistically significant difference between groups (P < 0.001).

DISCUSSION

This literature review evaluated the clinical outcomes of peri-implant soft tissue augmentation using xenogeneic collagen matrices compared with autogenous SCTGs in adult patients undergoing dental implant therapy. Six studies [21-26] were included and analysed (Tables 7 and 8). Each study comprised a group treated with a collagen matrix and a group treated with an SCTG. A comparative assessment of mid-buccal recession, soft tissue thickness gain, PES, and MBL changes was performed to determine the differences between them.

Mid-buccal recession was evaluated in two of the six included studies [22,25]. Both studies reported higher numerical recession values in the xenogeneic collagen matrix group compared with the SCTG group (Table 8). These findings are consistent with Cairo et al. [27], who reported significantly greater peri-implant mucosal thickness gain with SCTGs than with a volume-stable collagen matrix after 12 months of follow-up. Because increased peri-implant soft tissue thickness has been associated with improved tissue stability and a lower susceptibility to recession, these findings may partly explain the slightly greater mid-buccal recession observed in the xenogeneic collagen matrix groups in the present review. Nevertheless, as only two studies evaluated mid-buccal recession, definitive conclusions regarding material superiority for mid-buccal recession cannot be drawn.

Five of the six included studies [21,22,24-26] evaluated soft tissue thickness gain, and all reported greater numerical gains in the SCTG group than in the xenogeneic collagen matrices group. Although not all intergroup differences reached statistical significance, the overall trend consistently favoured the SCTG group. These findings suggest that while xenogeneic collagen matrices can increase peri-implant soft tissue thickness, SCTGs appear to produce a more pronounced effect.

These findings are supported by the systematic review and meta-analysis conducted by Ashurko et al. [13], who reported that xenogeneic collagen matrices are less effective than autogenous SCTGs in increasing peri-implant soft tissue thickness. Similarly, Tavelli et al. [28], in a network meta-analysis, demonstrated that connective tissue grafting remains the most effective approach for peri-implant soft-tissue phenotype modification. Together, these reports reinforce the concept that SCTGs provide superior and more predictable volumetric soft-tissue augmentation around dental implants.

Beyond volumetric changes, aesthetic outcomes represent another critical parameter when evaluating peri-implant soft tissue augmentation procedures. Fürhauser et al. [29] originally introduced the PES, which evaluates multiple peri-implant soft tissue parameters, including the mesial and distal papilla, soft-tissue level and contour, alveolar process deficiency, and soft-tissue colour and texture. This composite index therefore reflects not only the vertical mucosal level but also the overall harmony of the peri-implant soft tissue complex.

In the present analysis, all included studies [21-26] assessed PES, and most reported no statistically significant differences between xenogeneic collagen matrices and SCTGs. Only Ashurko et al. [26] demonstrated significantly higher PES values in the control group. Overall, these findings suggest that both treatment modalities are generally capable of achieving comparable aesthetic outcomes in dental implant therapy. The similarity in PES values observed in the present review may reflect the multifactorial nature of aesthetic success around dental implants. Wang et al. [30] reported that aesthetic outcomes are influenced not only by the grafting material but also by factors such as baseline soft tissue phenotype, implant positioning, surgical technique, and prosthetic contour.

Regarding MBL, four of the included studies [22-25] evaluated radiographic bone level changes. Only one study [22] reported significantly greater bone loss in the xenogeneic collagen matrix group, whereas the remaining investigations demonstrated no statistically significant intergroup differences. Overall, MBL values in both groups remained limited and within physiological remodelling ranges, suggesting that peri-implant soft tissue augmentation with either xenogeneic collagen matrices or SCTGs does not negatively compromise peri-implant hard tissue stability. These findings are consistent with the systematic review by Thoma et al. [31], who reported that soft tissue augmentation procedures do not result in increased MBL compared with control conditions and may even contribute to improved peri-implant tissue stability. Taking together, the available evidence indicates that no consistent or clinically meaningful differences in MBL exist between the treatment modalities. Although isolated studies reported statistically significant intergroup differences, the magnitude of bone level changes was small and remained within clinically acceptable limits, suggesting comparable short-term outcomes with respect to marginal bone stability.

Limitations

Several limitations should be considered when interpreting the findings of this review. First, the included studies presented heterogeneity in follow-up periods (3 to 60 months), which limits direct comparison of outcomes and may reflect different stages of tissue remodelling rather than long-term stability.

Second, outcome reporting was inconsistent across studies. Mid-buccal recession was reported in only two studies and MBL in four, while soft tissue thickness was measured using different reference points, restricting direct quantitative comparisons.

Additionally, variability in implant systems, surgical protocols, and implant placement sites (anterior maxilla, posterior mandible, or both jaws) may have influenced the outcomes. Finally, all studies evaluated single-tooth implants, limiting the generalizability of the findings to multiple-implant or full-arch restorations.

CONCLUSIONS

Xenogeneic collagen matrices and autogenous subepithelial connective tissue grafts demonstrated comparable outcomes regarding marginal bone loss, with bone level changes remaining minimal.

Both materials improved peri-implant soft tissue conditions; however, autogenous subepithelial connective tissue grafts generally resulted in greater soft tissue thickness gain and tended to provide better mid-buccal tissue stability.

Aesthetic outcomes, assessed using the pink aesthetic score, were largely comparable between xenogeneic collagen matrices and subepithelial connective tissue grafts, indicating that both approaches can achieve satisfactory aesthetic results in single-tooth implant therapy.

ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS

The authors received no specific grants from funding agencies or financial support for this work. The authors report no conflicts of interest related to this study.

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