Influence of Anatomical Factors Upon Root Coverage

• Pre-surgical treatment: Initial periodontal therapy will be performed 1 month prior to surgery. Patients will receive a pre-surgical prophylaxis, oral hygiene instructions and elimination of toothbrushing traumatic technique, if needed. They will be taught to use a toothbrush of medium hardness applying Roll brushing technique.

• Surgical treatment: In brief description, CAF+CTG treatment will be performed by starting with two vertical releasing incisions lateral to the teeth to be treated and split-full-split thickness flap will be raised beyond the MGJ. The periosteum will be cut, and a blunt dissection into the vestibular lining mucosa will be carried out to eliminate muscle tension so that the mucosal flap can be passively positioned above the level of CEJ on the tooth. The papillae adjacent to the involved teeth will be de-epithelialized and the exposed root surfaces will be treated with pre-conditioning EDTA (Straumann PrefGel®) for 2 minutes. CTG of 1mm in thickness will be harvested from the posterior palate by means of disepithelization of a free gingival graft (22), cut to the exact size of the defect, and placed over the dehisced defect, sutured to the interdental papillae (7-0 Polyglactin 910, Vycril, Ethicon, Johnson and Johnson, New Brunswick, NJ, USA) and subsequently covered with CAF. Sling sutures will be placed to stabilize the flap in a coronal position about 1-2 mm above the CEJ (6-0 Polypropylene, Prolene, Ethicon, Johnson and Johnson, New Brunswick, NJ, USA), followed by interrupted sutures to close the releasing incisions.

Patients will be instructed to avoid any mechanical trauma or tooth brushing in the surgical sites for 2 weeks. Analgesic medication (ibuprofen) will be prescribed as required and patients will be instructed to rinse with Chlorhexidine three times per day for 2 weeks. Sutures will be removed after 14 days. Two weeks after surgery, patients will resume mechanical tooth cleaning with a soft toothbrush. Patients will be recalled at 1, 3 and 6 months for professional oral hygiene procedures.

• Post-surgical instructions and infection control: Patients will be instructed to avoid any mechanical trauma or tooth brushing in the surgical sites for 2 weeks. Analgesic medication (ibuprofen) will be prescribed as required and patients will be instructed to rinse with Chlorhexidine 0.12% two times per day for 2 weeks. Sutures will be removed after 14 days. Two weeks after surgery, patients will resume mechanical tooth cleaning with a soft toothbrush. Patients will be recalled at 1, 3 and 6 months for professional oral hygiene procedures.

• Data collection: A guidebook will be prepared to systematize the procedures for sample and data collection. The data will be later transferred to a computerized database (Epidata®, Odense, Denmark, Europe).

A) Sociodemographic data An interview will be conducted during the pre-surgical visit to obtain information regar- ding age, sex, medical history, use of medication, exposure to tobacco, pregnancy and previous periodontal surgeries.

B) Clinical measurements Probing depth (PD) and keratinized tissue width (KTW) will be measured using a periodontal probe (PCP UNC 15, Hu-Friedy, Chicago, IL, USA). KTW will be measured at the most apical point in the GM to the mucogingival junction at the mid-buccal site to the nearest millimeter. KTT will be measured 1.5mm and 3mm apical to the GM using an injection needle, perpendicular to the tissues surface and a silicon stop over the gingival surface and fixed with a cyanoacrylic adhesive (23). Clinical attachment level will be calculated as REC + PD.

C) Digital measurements All patients will be scanned and their models will be digitalized with an optical 3D measurement system (3Shape, Erlangen, Germany) creating surface tessellation language (STL) files while a bilateral retractor is placed in the mouth and teeth are held lightly in occlusion. The acquired data will be transferred into a digital imaging software (3Shape Trios®, Erlangen, Germany) in which patient name will be substituted for a random ID number in order to anonymize the data. Baseline and corresponding follow-up scans of each clinical case will be then virtually superimposed and matched into one common coordinate system (Geomagic, 3D Systems, Research Triangle Park, NC, USA) using the tool Control X. By using the buccal surfaces of the concerned teeth as reference points for the superpositioning of the different time points (pre-operative and post-operative), this approach will allow for precise evaluation of dimensional soft tissue alterations over time by a blinded examiner. Vestibular depth will be measured from the GM to the point of greatest concavity of the mucobuccal fold.

The digital linear and volumetric measurements and assessment will be performed by a single, calibrated examiner for the surgical. The examiner will be trained on 15 casts with gingival recessions who will not be included in this study. This examination will be repeated 24 h later; differences of ≤0.5 mm in at least 90% of the cases will be considered to be acceptable.

The following measurements will be taken:

All clinical measurements and volumetric evaluations of the soft will be performed at baseline, 3 months and at 6 months after surgery.