The goal of this clinical trial is to compare two different tunneling surgical technique in treatment of gingival recession using two different materials.

Participants will be divided into four groups according to the treatments they'll be given.

Comparative Evaluation of laterally Closed Tunnel (LCT) Technique and Modified Coronally Advanced Tunnel (MCAT) Technique in the treatment of isolated gingival recession: Randomized controlled clinical trial.

Proposal Submitted in Partial Fulfillment of the Requirements of Doctor of philosophy Degree in Oral Medicine and Periodontology BY Ahmed Mohamed El-Bana B.D.S, MSC (Mansoura University, 2014) Assistant lecturer at Oral Medicine, Periodontology, Oral Diagnosis and Radiology Department 2021

Gingiva represents one of the important defense barriers of the periodontium and any alteration of its conditions may result in detrimental effects on the stability of the periodontium. Gingival recession is a common mucogingival problem that is associated with apical migration of the gingival margin and exposure of the root surface.Various factors are associated with increased incidence of gingival recession such as plaque-induced inflammation, violation of the biological width of the gingiva, aggressive teeth brushing and high frenulum attachment.

Various surgical techniques were described for the treatment of gingival recession from which, the coronally advanced flap (CAF) is one of the most commonly used techniques for root coverage of miller class I, II. Many modifications of CAF have been used to get the best treatment outcomes. The CAF can be used alone or in combination with connective tissue graft [CTG], platelet rich fibrin , enamel matrix derivative or any other regenerative materials. Various systematic reviews have reported the efficacy of CAF as the gold standard protocol for gingival recession treatment especially if used with CTG.

Tension free healing is the main goal to get the ideal results of gingival recession correction, which was difficult to achieve with a coronal displacement of the tunnel. In addition, the vestibular depth distortion was related to the procedures due to tissue tension. Therefore new clinical approaches are warranted to be more predictable and to minimize the post-operative complications.

Recently, mucogingival surgeries have been extremely improved with many advanced surgical techniques to be minimally invasive and to get better outcomes for complex recession defects that are associated with soft and hard tissue defects.

The split-flap approach using tunneling technique is one of the approaches used to treat gingival recession. However, it was associated with a lot of difficulties and risks of flap perforation and graft necrosis during the healing process.To overcome such limitations, a modification of the techniques has been adopted as modified coronally advanced tunneling (MCAT) which can be either full orpartial thickness tunnel followed by displacing and moving the tissue in a coronal direction. The results of MCAT are predictable regarding the mean root coverage and recession depth reduction. The outcomes were also improved after using sub epithelium connective tissue graft (SCTG) under the tunnel to augment the keratinized attached gingiva and yield more stable outcomes on the long term basis.

Laterally closed tunnel technique (LCT) is a minimally invasive novel technique proposed by Sculean and Allen in 2018 for the management of isolated gingival recession. Tunneling instruments and micro blades are used to create a pouch that extends apically beyond the mucogingival junction and also extends mesially and distally away from the recession defect to dissect and separate the muscles and collagen fibers to allow lateral tissue displacement without tension or vestibular distortion.

Although the SCTG is the gold standard soft tissue graft and is associated with complete root coverage and ideal esthetics and maturation, it was associated with many tissue morbidities and healing complications. SCTG needs second surgical site which may be not accepted by many patients. Therefore many regenerative alterative tissue substitutes have been tested and investigated to be used in recession coverage surgeries instead of SCTG.

Mucoderm or porcine-derived collagen matrix has been used in many studies as an alternative to connective tissue graft CTG as a soft tissue grafting material for volume augmentation and gingival phenotype modification. Furthermore, it acts as a seeding scaffold on which cells can grow and differentiate into gingival fibroblasts. It has been investigated in many studies around teeth and dental implants with predictable outcomes.

Aim of the study

The objective of the current study is to compare two different surgical tunneling techniques: the laterally closed tunnel (LCT) and modified coronally advanced tunnel (MCAT) in the treatment of deep isolated gingival recession defects using subepithelial connective tissue graft (SCTG) and porcine derived collagen matrix (MUCODERM).

Material and methods

A total of 80 patients with isolated mandibular gingival recession defects will be selected from the outpatient clinic of the Department of Oral Medicine and Periodontology Department, Faculty of Dentistry, Mansoura University. The patients will be informed about the treatment protocol that they will receive and the steps that will be done. This includes the possible effects or risks, and other treatment options according to the rules of the ethical committee of the faculty of dentistry, Mansoura University. The subjects must understand this explanation in broad terms. The subjects must be legally competent to give written consent before performing any required steps.

Patient grouping:

All patients will receive perfect professional non-surgical periodontal therapy in form of scaling and root planning and oral hygiene instructions will be given to the patients. Pre-operative periapical x-ray on the area of interest to confirm the integrity of the interproximal bone.The participants were randomly assigned by the toss of a coin into four treatment groups.

Group I It will Include 20 patients and they will be treated with the [LCT] and SCTG. Group II It will Include 20 patients and they will be treated with the [LCT] and MUCODERM.

Group III It will Include 20 patients and they will be treated with the MCAT and SCTG. Group IV It will Include 20 patients and they will be treated with the MCAT and MUCODERM.

Surgical procedure Surgical sites were accurately assessed for each patient. An aseptic field was required for all surgical procedures using povidine iodine. Local anesthesia using 4% articane with 1:100.000 epinephrine was applied for buccal infiltration injection of 1.5 ml and palatal infiltration injection of 0.3 ml. Inferior alveolar nerve block and Lingual nerve block were used for mandibular posterior segment.

Group I-Ⅱ: laterally closed tunnel technique [LCT]

Using a microblade [swan Morton] an internal beveled intrasulcular incisions will be made at the circumferential gingival margin of the affected tooth.

Then specially designed tunneling instruments [devmed] will be used through the sulcular incision to create a pouch. The pouch will be extended apically beyond the mucogingival line and extended mesially and distally from the recession defect undermining all the submucosal tissues.

All fibers should be removed in all directions to ensure optimal tissue mobility without tension.

A microsurgical blade will be used at the inner surface of the pouch till sufficient tissue release will be achieved.

Tissue forceps will be used to approximate the mesial and distal margin of the gingiva at the pouch margin.

Perfect root planning will be performed at the denuded root surface to remove the necrotic cementum.

Subsequently, palatal anesthesia will be given to harvest palatal SCTG using deepithelialized free gingival graft (FGG) technique to get a 1 to 1.5 mm thick connective tissue graft.

After harvesting the graft, it will be placed at the prepared pouch after root surface biomodification using EDTA gel 24% for 2 minutes and copious rinsing with saline solution.

SCTG will be pulled using single or mattress sutures and the graft will be fixed mesial and distal at the inner part of the pouch using resorbable suture material [Vicryl suture], then the graft will be sutured around the neck of the CEJ by sling suture 6/0 polypropylene.

Finally, the margin of the pouch will be adapted close to each other over the graft and sutured together using simple interrupted suturing to get complete or partial coverage of the grafted root surface.

In patients with MUCODERM, after the pouch preparation the collagen matrix will be trimmed to a size suitable for the recession defect then it will be soaked in sterile saline solution for 5 to 10 minutes to allow collagen expansion.

After saturation, the MUCODERM will be inserted into the pouch and sutured in the same way as SCTG.

Patients will be instructed not to brush the surgical site for 14 days and will be ensured to use 0.1% chlorhexidine mouth rinse twice daily for 1 minute each, they will resume brushing after 14 days from the surgery.

Palatal sutures will be removed after 7 days from the surgery, while the sutures at the surgical site will be removed between 14 to 21 days post-surgery. At that time the patients will be instructed to use an ultra-soft toothbrush at the surgical site. Recall professional teeth cleaning will be scheduled 1, 3, 6 months postoperatively.

Group Ⅲ-Ⅳ Modified coronally advanced tunnel technique [MCAT]

The MCAT will be used to treat a single isolated recession defect as the following:

A microsurgical blade [swan Morton] will be used to perform supraperiosteal sulcular incisions at the buccal gingiva of the affected tooth.

Supraperiosteal incisions will be extended to the mucosal level beyond the MGJ to allow sufficient tissue mobility and release.

A Specially designed tunneling knifes with special angles will be used to avoid flap perforation.

The tunnel will be extended in all directions around the recession defect to create a sufficient pouch for connective tissue graft stabilization.

The interdental papilla tunneling adjacent to the defect will be a critical step for technique success. Full thickness tunnel preparation at the papillary region will be done and the papilla will be completely detached from the underlying periosteal layer using mini elevator to avoid tearing.

Then perfect root planning will be performed at the denuded root surface to remove the necrotic cementum at the accessible recession defect.

Subsequently palatal anesthesia will be given to harvest palatal SCTG using deepitheliailized free gingival graft (FGG) technique to get 1 to 1.5 mm thick connective tissue graft.

After harvesting the graft, it will be placed at the prepared pouch after root surface biomodification using EDTA gel 24% for 2 minutes and copious rinsing with saline solution.

SCTG will be pulled using single or mattress sutures and the graft will be fixed mesial and distal at the inner part of the pouch using resorbable suture material [Vicryl suture], then the graft will be sutured around the neck of the CEJ by sling suture 6/0 polypropylene.

After SCTG adaptation, the entire gingival complex will be moved in coronal direction using vertical mattress suture anchored apically at the palatal gingiva.

In patients with porcine-derived collagen matrix( MUCODERM), after the pouch preparation, the collagen matrix will be trimmed to size suitable for the recession defect then it will be soaked in sterile saline solution for 5 to 10 minute to allow collagen expansion.

After saturation the MUCODERM will be inserted into the pouch and sutured in the same wayas SCTG.

Patients will be instructed not to brush the surgical site for 14 days and will be ensured to use 0.1% chlorhexidine mouth rinse twice daily for 1 minute each, they will resume brushing after 14 days from the surgery.

Palatal sutures will be removed after 7 days from the surgery, while the sutures at the surgical site will be removed between 14 to 21 days post-surgery. At that time the patients will be instructed to use ultra-soft toothbrush at the surgical site. Recall professional teeth cleaning will be scheduled 1, 3, 6 months post operatively.

Clinical assessment The following parameters will be measured at the start of the study as well as 3 months and 6 months after the surgery.

Recession depth RD Pink esthetic score PES Root coverage esthetic score RES The mean Root Coverage %RC Gingival Index GI Clinical attachment level CAL Pocket depth PD Keratinized tissue width KTW

Inclusion Criteria:

• No systemic diseases or Pregnancy.
• Smoking < 10 cigarettes/day.
• Full mouth plaque score <15%.
• Full mouth bleeding score <15%.
• Presence of isolated gingival recession defect >2 mm in depth
• No interproximal attachment loss.
• No history of previous mucogingival surgeries.

Exclusion Criteria:

• Sever interproximal alveolar bone loss.
• Pregnancy and lactation.
• Heavy smokers.
• Uncontrolled diabetic patients.
• Immunocompromised patients.
• Prosthetic crown at the experimental site.
• Teeth with cervical caries or abrasion.
• Presence of infection or gingival abscess related to the surgical area.
• Bad oral hygiene.