Clinical and Histological Outcomes of Using Collagen Matrix or Soft Tissue Graft Around Implants

This was an interventional prospective randomized clinical trial (RCT) in parallel groups. The sample size is 35 patients who were randomly divided into two groups depending on the surgical intervention used. First group - patients underwent increasing the thickness of the mucous membrane using free connective tissue graft from tuberosity area of the upper jaw. Second group - patients used collagen matrix "Fibromatrix" (LLC "Cardioplant", Russia; registration in Russia 20/05/2019 No FSZ 2019/83671). In the postoperative period the value of soft tissue thickness gain, duration of surgery, severity of pain syndrome and quality of life were assessed. Also, after 3 months simultaneously with installation of gingiva formers biopsy specimens were sampled with mucotome in the area of the intervention followed by histomorphometric analysis of the obtained biopsies.

The aim of this research was to perform a comparative clinical and histomorphometric analysis of soft tissues in the area of soft tissue graft and collagen matrix transplantation. Thirty five patients diagnosed with partial absence of teeth were examined on the basis of the Department of Surgical Dentistry of the E.V. Borovsky Institute of Dentistry of I.M. Sechenov First Moscow State Medical University. Patients had a soft tissue thickness deficiency from the vestibular surface in the area of the planned dental implant placement which was an indication for its increase. All patients were randomly divided into two groups depending on method of soft tissue augmentation used. In 1 group (n=15) transplantation of a free connective tissue graft (CTG) from tuberosity area of the upper jaw was performed. In 2 group (n=20) collagen matrix "Fibromatrix" was used. According to gender and age characteristics both groups were comparable. Randomization of patients was carried out at the stage of surgical intervention as follows: after a dental implant placement and preparation of recipient's bed an envelope with a randomly assigned treatment method (using a connective tissue graft or a collagen matrix) was opened.

During the operation, incision was made along the top of the alveolar ridge within the defect; a full-thickness muco-periosteal flap was elevated. Traditional 2-stage dental implantation was performed according to surgical protocols of dental implant systems Ostem (Osstem Implant Co., Ltd., Korea; registration in Russia 05.09.2018 No FSZ 2018/7577). A free connective tissue graft was harvested in patients of the first group. Graft was fixed with a horizontal U-shaped suture to the buccal muco-periosteal flap. In second patients group a fragment of the collagen matrix "Fibromatrix" was fixed to the buccal muco-periosteal flap (LLC "Cardioplant", Russia; registration in Russia 20.05.2019 No № FSZ 2019/83671). For patients of all groups mobilization of the muco-periosteal flap conducted followed by suturing the wound tightly without tension with simple interrupted sutures.

In the early postoperative period the standard antibacterial and anti-inflammatory therapy in combination with the use of local antiseptics for daily care was prescribed. The stage of the implant uncovering with hilling abutments installation was carried out 3 months after the intervention. At this stage, a soft tissue fragment was taken using a mucotome in the area of the previously performed mucous membrane thickness increasing for subsequent histomorphometric analysis. In the study we used both conventional light microscopy (microscopy in the light field) and polarizing microscopy - to estimate the content of collagen fibers in preparations stained with picrosirius red. During a morphometric study we carried out a quantitative assessment of the characteristics of the epithelial layer, the basement membrane relative length (the ratio of the absolute length of the basement membrane to the length of the epithelial layer), the characteristics of the underlying connective tissue.

Eligibility Criteria:
Inclusion Criteria:

1. The presence of written informed consent of the patient to participate in the study;
2. The presence of an included defect (1 teeth) in the distal part of the lower jaw with a sufficient volume of bone tissue;
3. Deficiency of soft tissue thickness;
4. Adjacent teeth are without any of periodontal disease, namely the absence of periodontal probing depth \> 3 mm in any site of adjacent teeth;

6. Satisfactory level of oral hygiene, namely full mouth plaque score \< 20% and full mouth bleeding score \< 20%;

Non-inclusion criteria:

1. The presence of concomitant pathology in the stage of decompensation;
2. Hard smokers (more than 10 cigarettes per day);
3. Radio and chemotherapy in history over the past 5 years;
4. Pregnancy and breastfeeding;
5. Taking medications that affect the healing of soft tissues (nonsteroidal anti-inflammatory drug, steroid drugs).

Exclusion Criteria:

1. Patients with infections either periodontally or periapically;
2. Pregnantcy following entrance into the study;
3. Patients having poor oral hygiene or not wanting to carry out oral hygiene measures;
4. Subjects, who in the opinion of the investigator, for any reason will not be able to complete the study per protocol.