Evaluation of Keratinized Tissue Augmentation Using Amnion/Chorion Allograft vs. Autogenous Connective Tissue in Implant Therapy: A Retrospective Study

doi:10.21203/rs.3.rs-4887714/v1

Download PDF

Research Article

Evaluation of Keratinized Tissue Augmentation Using Amnion/Chorion Allograft vs. Autogenous Connective Tissue in Implant Therapy: A Retrospective Study

https://doi.org/10.21203/rs.3.rs-4887714/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Objectives: Successful implant therapy must also ensure the integration of the soft tissues around the crown/abutment emergence profile. The existing literature does not consistently agree on the necessity of a minimal amount of keratinized tissue (KT), though it appears advantageous for the long-term stability and aesthetics of implants. The purpose of this clinical retrospective study is to compare the effectiveness of amnion/chorion membrane and autogenous subepithelial connective tissue in increasing the keratinized mucosa and maintaining it over a 5-year follow-up.

Methods: Twenty patients who had previously undergone implant surgery were included in the study. Ten patients had received the allograft (Group 1) and ten had received autogenous connective tissue (Group 2).An independent examiner retrospectively analyzed the patient records at 7, 15, and 60 days, and five years post-procedure. Data from these observations were collected and analyzed using SPSS Statistics, version 25. Descriptive statistical analysis was conducted.

Results: All patients exhibited an increase in KT. For Group 1, the mean KT width measurements were 1.27 ± 0.46 mm at the initial evaluation, increasing to 2.00 ± 0.38 mm, 2.80 ± 0.78 mm, 3.27 ± 0.80 mm, and 3.01 ± 0.68 mm at 7, 15, and 60 days post-surgery (with prosthesis delivery on day 60), and five years after prosthetic rehabilitation, respectively.

Conclusions: Within the limitations of this retrospective clinical study, both amnion/chorion and connective tissue show significant potential for KT expansion when used in conjunction with implant surgery. Considering the minimally invasive approach, focusing future research on the use of allografts or xenografts appears justified. Clinical Relevance: the use of allografts , due their low morbidity, and acceptable results should be considered as a viable option for soft tissues augmentations.

dental implants

peri-implant mucosa

biological width

soft tissues allograft

The success of a dental implant is closely tied to osseointegration, but the integration of the marginal soft tissue surrounding the implant is equally critical. The soft tissue around the implant, which can be either keratinized tissue (KT) or alveolar mucosa, is influenced by the surgical procedure performed during or after implant placement and alveolar bone resorption [1] together with appropriate management of the prosthetic restoration which might affect soft tissue morphology and proper hygienic maintenance.[2]

Despite ongoing debates regarding its role in the long-term success of implants, the presence of KT around implants has been recognized as beneficial for achieving esthetic outcomes [3], facilitating effective plaque control [4], and maintaining peri-implant tissue health over the long term [5].

Recent clinical studies have assessed the conditions of soft tissue around implants [4], finding that the presence or absence of KT does not significantly impact implant success rates or peri-implant tissue health. These results align with other research suggesting that with proper plaque control, the type of peri-implant mucosa has a minimal effect on the long-term survival of implants [6, 7]. However, maintaining oral hygiene around implant restorations can be more challenging without KT [8]. Additionally, a greater width of keratinized mucosa has been associated with better health of the implant supporting tissues, showing lower average alveolar bone loss and improved soft tissue health indices when KT is present [9]. Comparative studies also indicate that KT is important for reducing plaque accumulation, minimizing mucosal inflammation, and is linked to various immunologic factors [10, 11]. Conversely, insufficient KT around implants increases the risk of gingival recession and crestal bone loss, making adequate KT advantageous for both esthetic and stability purposes [12].

The optimal timing for soft tissue augmentation around implants remains unclear and depends on the specific clinical scenario. Early intervention may increase the likelihood of successful outcomes. The timing of treatment is typically categorized as: (1) before implant placement; (2) simultaneously with implant placement; (3) at the second-stage surgery; and (4) during the maintenance period when the implant is uncovered and loaded [13, 14]. The first three timing options generally offer more predictable results compared to post-loading protocols, as complications such as mucositis or peri-implantitis can arise when augmentation is needed after loading [15].

Recent reviews of soft tissue augmentation techniques have identified procedures aimed at enhancing peri-implant soft tissue. These include (1) KT width expansion using an apically repositioned flap (APPTF) or vestibuloplasty combined with a free gingival graft (FGG) or graft materials such as xenogenic (XCM) or allogenic (AMDA) tissues, and (2) soft tissue volume enhancement using autogenous subepithelial connective tissue grafts (SCTG) or soft tissue replacement grafts. Among these, APPTF combined with FGG is particularly notable, despite an associated increase in surgical time and patient morbidity. Both AMDA and SCTG are effective for soft tissue volume gain, with significant increases reported for all methods used [15].

The objective of this study is to retrospectively evaluate the stability of peri-implant soft tissues five years after augmentation using dehydrated de-epithelialized amnion/chorion membranes and autogenous subepithelial connective tissue grafts.

This retrospective study was conducted in full compliance with the Declaration of Helsinki and was approved by the University of Genoa Ethical Committee CERA (nr. 2024/64). Informed consent was obtained from all patients. Additional signed releases were collected for the use of patient images in the study.

A total of 20 patients, aged between 28 and 77 years and of mixed gender (12 males and 8 females), were included in the study. These patients, who did not have a history of chronic periodontitis, were treated at a private practice in Acqui Terme, Italy, in 2018. The study followed these inclusion criteria:

Non-smokers
Presence of at least 2 mm of keratinized tissue at the time of implant placement, second-stage surgery, or at any implant site where mucosal recession with a thin biotype was observed

Exclusion criteria included:

Poor oral hygiene or non-compliance with treatment
Presence of systemic diseases, compromised medical conditions, or immunosuppressive conditions contraindicating elective surgery or affecting healing
Use of antihypertensive, antilipemic, antiarrhythmic, or anticoagulant medications
Pregnancy or lactation
Inflammation at implant sites

Keratinized tissue width measurements were obtained using standardized digital image analysis softwares (CorelDRAW Graphics Suite 2023® and ImageJ®). An independent examiner, blinded to the treatment type, performed all the measurements. ( Fig. 1)

All patients received standardized oral hygiene instructions and underwent supragingival dental scaling one week prior to surgery. The same specialist (NDA) performed all treatments using 4.3x400 surgical head-worn loupes (KS, Carl Zeiss Vision, Jena, Germany). Patients were divided into two groups: Group 1 (n = 10) received an allograft, and Group 2 (n = 10) received an autogenous sub-epithelial connective tissue graft. The choice of graft material was determined by the operator based on clinical judgment. (Fig. 2a,b,c)

Surgical procedures were performed under local anesthesia using Articaine 2% with 1:100000 epinephrine. A full-thickness flap was created, and the graft material (allograft or autogenous) was placed and secured with PTFE sutures. The allograft membrane was left partially exposed during the healing period. Chlorhexidine mouth rinse was recommended post-operatively only for patients treated with autogenous grafts to avoid potential negative interactions with the protein content of the amnion/chorion membrane in the allograft group. (Fig. 3a,b) (Fig. 4a,b,c)

Antibiotic prophylaxis was administered as follows [16, 17]:

Amoxicillin + Clavulanic Acid 875 + 125mg, 2 grams 1 hour before surgery, or Azithromycin 500 mg at the same timing
Post-operative continuation with Amoxicillin + Clavulanic Acid 1 gram every 6 hours or Azithromycin 500mg for 2 additional days

Follow-up evaluations were conducted at 7, 15, and 60 days post-surgery.

Participants also received regular dental check-ups and professional oral hygiene treatments at six-month intervals during the follow-up period.

Statistical analysis

Descriptive statistical analysis was used to get mean and standard deviations for KT width at all time points. In order to analyze the difference in mean KT width at all the different time points, repeated-measurement analysis of variance was performed. For all tests, the level of significance was set at P < .001 and the confidence interval (CI) was 95%. The software used for the analysis was the IBM SPSS Statistics for iOS, Version 25.0 (IBM Corp., Armonk, N.Y., USA).

During the 5-year observation period, no implant failures were reported among the study participants. All patients demonstrated an increase in the width of keratinized tissue (KT) over time.

For Group 1 (allograft), the mean KT width measurements were as follows: at baseline, the mean KT width was 1.27 ± 0.46 mm. At 7 days post-surgery, the mean KT width increased to 2.00 ± 0.38 mm. By 15 days post-surgery, the mean KT width further increased to 2.80 ± 0.78 mm. At 60 days post-surgery, coinciding with the time of prosthesis delivery, the mean KT width was 3.27 ± 0.80 mm. Five years post-prosthetic rehabilitation, the mean KT width was measured at 3.01 ± 0.68 mm.

These results indicate a statistically significant increase in KT width from the initial evaluation to all post-surgery time points (P < .001). The most substantial increase in KT width was observed between 7 days post-surgery and the time of prosthesis delivery at 60 days. This increase in KT width remained stable throughout the 5-year follow-up period.

Group 2 (autogenous sub-epithelial connective tissue) showed similar trends, with data reported in the corresponding table (Table 2). The gains in KT width for both groups were statistically significant (P < .001) and remained stable over the 5 years of observation.

Table 1

**Group 1 -** Mean keratinized tissue for each measurement time. SD is standard deviation.
Time	Mean (SD), mm
Initial	1.27 (0.46)
7 days postsurgery	2.00 (0.38)
15 days postsurgery
15 days postsurgery	2.80 (0.78)
60 days postsurgery/ prosthetic delivery	3.27 (0.80)
5 years after prosthetic delivery	3.01 (0.68)

Table 2. Group 2 - Mean keratinized tissue for each measurement time. SD is standard deviation.

Time	Mean (SD), mm
Initial	1.17 (0.43)
7 days postsurgery	1.87 (0.33)
15 days postsurgery
15 days postsurgery	2.30 (0.44)
60 days postsurgery/ prosthetic delivery	3.02 (0.72)
5years after prosthetic delivery	2.98 (0.56)

Table 3

Comparison of Keratinized Tissue (KT) at Each Measurement Time. Keratinized tissues width increase is noticeable from the initial first measure when compared to post surgical phases and it remains stable over the whole period of observation. Both groups consisted into 10 implants each.
Comparison of KT width (mm)	Group 1(10 implants) Mean difference (95% C.I.)	P-value	Group 2 (10 implants) Mean difference (95% C.I.)
Initial to 7 days postsurgery	–0.733 (–1.096, − 0.371)	< .001	–0.683 (–1.089, − 0.278)
Initial to 15 days postsurgery	–1.533 (–2.194, − 0.873)	< .001	–1.415 (–1.989, − 0.841)
Initial to prosthetic delivery	–2.000 (–2.599, − 1.401)	< .001	–1.923(–2.456, − 1.301)
7 days postsurgery to 15 days postsurgery	–0.800 (–1.414, − 0.186)	.008	–0.803 (–1.423, − 0.184)
7 days postsurgery to prosthetic delivery	–1.267 (–1.900, − 0.634)	< .001	–1.279 (–1.892, − 0.667)
15 days postsurgery to prosthetic delivery	–0.467 (–0.876, − 0.057)	.021	–0.433 (–0.799, − 0.067)
Initial to 5 years after prosthetic delivery	–1.836 (–2.326, − 1.347)	< .001	–1.811 (–2.245, − 1.378)

There is a trend shift in implantology from a functional focus on improving function to a greater emphasis on the aesthetics of the prosthetic part. [18]

This need cannot be addressed solely by prosthetic-driven implant placement; clinicians must consider both biological and aesthetic corrections of the soft tissue to provide a lifelike final prosthetic replacement.

Mucogingival periodontal surgery can improve patient comfort during oral hygiene procedures and lead to better plaque control and less development of mucositis or peri-implantitis. A recent systematic review [15] concluded that implants with soft tissue augmentation showed a high survival rate and a relatively low incidence of peri-implantitis in the medium and long term. Similar to peri-implant tissue health, prosthetic aesthetics would also be enhanced by preventing the abutment or prosthetic margin from showing through the soft tissue. Despite the clinical success of autologous soft tissue [19], its use would increase morbidity due to the need for a second surgical site and increase patient discomfort and acceptance.

The present investigation's results indicate a similar behavior between autogenous connective tissue and the allograft over five years of observation. A systematic review published in 2021 [20] compared different approaches for peri-implant soft tissue augmentation, including studies using allografts and autogenous connective tissue. The review concluded that a bilaminar approach involving connective tissue or allografts achieved the highest mucosal thickness (MT) gain, while apically repositioned flaps (APF) combined with free gingival grafts (FGG) were most effective for increasing keratinized mucosa width (KMW). Our investigation's results align with these conclusions, although no significant difference was observed in the progressive reduction of soft tissue width. As described in the methods, only the bilaminar technique was the study's focus.

The allograft used in this study is a placental-derived amnion/chorion allograft membrane. Amnion/chorion tissue contains various growth factors, including epidermal growth factor, basic fibroblast growth factor, keratinocyte growth factor, transforming growth factor alpha, nerve growth factor, and hepatocyte growth factor, which may promote wound healing and tissue regeneration.[21] The amnion/chorion membrane has been utilized for socket preservation, guided tissue regeneration for periodontal and peri-implantitis defects, maxillary sinus augmentation, guided bone regeneration, and treatment of gingival recession,[22, 23] with high success rates in enhancing bone formation and tissue regeneration.

The mean keratinized tissue (KT) gained at the time of prosthetic delivery was 3.27 mm (P < 0.01) for allografts and 3.02 mm (P < 0.01) for connective tissue, remaining stable at 3.01 mm and 2.98 mm over five years. These results suggest that the presence of numerous growth factors in the allograft may contribute to the rapid growth and long-term maturation of peri-implant tissues.

It is also important to note that the width augmentation achieved immediately after surgery in both groups remained stable over five years, with mean differences of -1.836 mm and − 1.811 mm (P < 0.01) for allografts and connective tissue, respectively. This finding does not entirely align with existing evidence, except for a systematic review that focused solely on the stability of autogenous connective tissue grafts.[24] Patient interviews revealed good postoperative satisfaction, and clinical observations showed a good match of the surrounding implant tissue. A recent study by Prakasam et al. [25] compared amnion/chorion membranes with dense polytetrafluoroethylene membranes left intentionally exposed during ridge preservation procedures. They found that patients reported significantly lower postoperative VAS pain scores at amnion/chorion membrane-treated sites, potentially resulting in better quality bone for implant placement.

The preliminary findings published in a 2019 article [26] were corroborated by this retrospective study, suggesting that, despite the small number of included cases, allografts may represent a viable option for peri-implant soft tissue augmentations, demonstrating promising outcomes for enhancing keratinized tissue around implants.

Within the limitations of this retrospective clinical study, the procedures investigated seem to have an interesting potential for KT expansion when combined with implant surgery or after the implant placement. In a view a minimal invasive approaches it seems also reasonable to focus the research on the use of allografts or xenografts and these results, though limited in a small sample size, can be promising for future applications. The increase of keratinized tissue width in this study is surely consistent, comparing the initial millimeters to those measured three years after, but it is also important to notice the quality of the tissue, which in terms of texture and color reveals a complete ,full and stable maturation.

Institutional Review Board Statement

This study followed the Declaration of Helsinki with regard to medical protocol and ethics, and the University of Genoa Ethical Committee CERA (nr. 2024/64)

Informed Consent Statement: Informed consent was obtained from all subjects involved in the study and written informed consent has been obtained from the patient(s) to publish this paper” if applicable.

Conflicts of Interest:

The authors declare no conflict of interest

Funding:

no funds were allocated to this study

Author Contribution

“Conceptualization, N.D.A. P.P. ; methodology, N.D.A. P.P. M.M.; software, Z.H.K.; validation, N.D.A. M.M.; formal analysis, C.Y..; investigation, N.D.A.; resources, N.D.A. P.P.; data curation, D.B.; writing—original draft preparation, Z.H.K., C.Y. .; writing—review and editing, N.D.A., C.Y..; visualization, P.P. M.M..; supervision, M.M. ; project administration, M.M.;. All authors have read and agreed to the published version of the manuscript.”

Data Availability

The data that support the findings of this study are not openly available due to reasons of sensitivity and are available from the corresponding author upon reasonable request. Data are located in controlled access data storage at Genoa University

Wennstrom JL, Derks J (2012) Is there a need for keratinized mucosa around implants to maintain health and tissue stability? Clin Oral Implants Res 23(suppl 6):s136–s146
Canullo L, Menini M, Covani U, Pesce P (2020) Clinical outcomes of using a prosthetic protocol to rehabilitate tissue-level implants with a convergent collar in the esthetic zone: A 3-year prospective study. J Prosthet Dent 123:246–251
Fürhauser R, Florescu D, Benesch T, Haas R, Mailath G, Watzek G (2005) Evaluation of soft tissue around single-tooth implant crowns: The pink esthetic score. Clin Oral Implants Res 16:639–644
Roccuzzo M, Grasso G, Dalmasso P (2016) Keratinized mucosa around implants in partially edentulous posterior mandible: 10-year results of a prospective comparative study. Clin Oral Implants Res 27:491–496
Ladwein C, Schmelzeisen R, Nelson K, Fluegge TV, Fretwurst T (2015) Is the presence of keratinized mucosa associated with periimplant tissue health? A clinical cross-sectional analysis. Int J Implant Dent 1:11
Wennström JL, Bengazi F, Lekholm U (1994) The influence of the masticatory mucosa on the peri-implant soft tissue condition. Clin Oral Implants Res 5:1–8
Salvi GE, Lang NP (2004) Diagnostic parameters for monitoring peri-implant conditions. Int J Oral Maxillofac Implants 19(suppl):s116–s127
YeungSC.Biologicalbasisforsofttissue management in implant dentistry (2008) Aust Dent J 53(suppl 1):s39–s42
BouriAJr,BissadaN,Al-ZahraniMS,Fad-, doul F, Nouneh I (2008) Width of keratinized gingiva and the health status of the supporting tissues around dental implants. Int J Oral Maxillofacial Implants 23:323–326
ZigdonH,MachteiEE (2008) Thedimensionsof keratinized mucosa around implants affect clinical and immunological parameters. Clin Oral Implants Res 19:387–392
Boynueg ̆ri D, Nemli SK, Kasko YA (2013) Significance of keratinized mucosa around dental implants: A prospective comparative study. Clin Oral Implants Res 24:928–933
Kim BS, Kim YK, Yun PY et al (2009) Evalua- tion of peri-implant tissue response according to the presence of keratinized mucosa. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 107:e24–e28
Hürzeler MB, Weng D (1996) Periimplant tissue management: Optimal timing for an esthetic result. Pract Periodontics Aes- thet Dent 8:857–869
Bassetti M, Kaufmann R, Salvi GE, Sculean A, Bassetti R (2015) Soft tissue grafting to improve the attached mucosa at dental implants: A review of the literature and proposal of a decision tree. Quintes- sence Int 46:499–510
Stefanini M, Barootchi S, Sangiorgi M, Pispero A, Grusovin MG, Mancini L, Zucchelli G, Tavelli L (2023) Do soft tissue augmentation techniques provide stable and favorable peri-implant conditions in the medium and long term? A systematic review. Clin Oral Implants Res. ;34 Suppl 26:28–42. 10.1111/clr.14150. PMID: 37750532
Canullo L, Troiano G, Sbricoli L, Guazzo R, Laino L, Caiazzo A, Pesce P (2020) The Use of Antibiotics in Implant Therapy: A Systematic Review and Meta-Analysis with Trial Sequential Analysis on Early Implant Failure. Int J Oral Maxillofac Implants 35(3):485–494
Caiazzo A, Canullo L, Pesce P Consensus Report by the Italian Academy of Osseointegration on the Use of Antibiotics and Antiseptic Agents in Implant Surgery. Int J Oral Maxillofac Implants 2021 Jan-Feb ;36(1):103–105. 10.11607/jomi.8264
Canullo L, Menini M, Covani U, Pesce P (2020) Clinical outcomes of using a prosthetic protocol to rehabilitate tissue-level implants with a convergent collar in the esthetic zone: A 3-year prospective study. J Prosthet Dent 123:246–251
Bassetti RG, Stähli A, Bassetti MA (2017) Scu- lean A. Soft tissue augmentation around osseointergrated and uncovered dental implants: A systematic review. Clin Oral Invest 21:53–70
Tavelli L, Barootchi S, Avila-Ortiz G, Urban IA, Giannobile WV, Wang HL (2021) Peri-implant soft tissue phenotype modification and its impact on peri-implant health: A systematic review and network meta-analysis. J Periodontol 92(1):21–44 Epub 2020 Aug 9. PMID: 32710810
Koob TJ, Rennert R, Zabek N et al (2013) Bio- logical properties of dehydrated human amnion/chorion composite graft: Implications for chronic wound healing. Int Wound J 10:493–500
Holtzclaw D, Tofe R (2017) An updated primer on the utilization of amnion-chorion al- lografts in dental procedures. J Implant Adv Clin Dent 9:16–37
Nevins M, Aimetti M, Parma-Benfenati S, De Angelis N, Yu YH, Kim DM (2016) Mar-Apr;36(2):171-7 Treatment of Moderate to Severe Buccal Gingival Recession Defects with Placental Allografts. Int J Periodontics Restorative Dent. 10.11607/prd.2587. PMID: 26901295
Bakkali S, Rizo-Gorrita M, Romero-Ruiz MM, Gutiérrez-Pérez JL, Torres-Lagares D, Serrera-Figallo MÁ (2021) Efficacy of different surgical techniques for peri-implant tissue preservation in immediate implant placement: a systematic review and meta-analysis. Clin Oral Investig 25(4):1655–1675. 10.1007/s00784-021-03794-yEpub 2021 Jan 29. PMID: 33515121
Hassan M, Prakasam S, Bain C, Ghonei- ma A, Liu SS (2017) A randomized split-mouth clinical trial on effectiveness of amnion-chorion membranes in alveolar ridge preservation: A clinical, radiologic, and morphometric study. Int J Oral Maxillo- fac Implants 32:1389–1398
Angelis ND, Kassim ZH, Frosecchi M (2019) Antonio Signore Expansion of the Zone of Keratinized Tissue for Healthy Implant Abutment Interface Using De-epithelialized Amnion/Chorion Allograft. Int J Periodontics Restor Dent 39(3):e83–e88. 10.11607/prd.3757

No competing interests reported.

Download PDF

Editor assigned by journal
12 Aug, 2024
Submission checks completed at journal
12 Aug, 2024
First submitted to journal
09 Aug, 2024

You are reading this latest preprint version

Evaluation of Keratinized Tissue Augmentation Using Amnion/Chorion Allograft vs. Autogenous Connective Tissue in Implant Therapy: A Retrospective Study

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials and Methods

3. Results

4. Discussion

5. Conclusions

Declarations

Institutional Review Board Statement

Funding:

Author Contribution

Data Availability

References

Additional Declarations

Supplementary Files

Status:

Version 1