The Use of a Porcine Collagen Matrix for the Prevention of Buccal Bone Wall Resorption During Implant Placement in the Aesthetic Zone.

Introduction: The need to restore lost teeth with dental implants is now a daily practice. In particular, treatments aimed at replacing lost teeth in the upper anterior aesthetic zone are particularly demanding, in terms of evaluating functional and aesthetic factors that influence the result. In order to successfully maintain the implants in the long term and to ensure aesthetics, there must be adequate dimensions of the alveolar crest and especially a satisfactory range of buccal bone in the area of placement. There are reports, that in areas with reduced width and thickness of soft tissues, there is a risk of resorption and further loss of buccal plate after implant placement which can lead to deterioration of aesthetics. For this reason soft tissue augmentation using soft tissue grafts may lead to a decrease in buccal bone resorption. According to the above, it would be of particular interest to investigate the possibility of using a material such as the collagen matrix as an alternative procedure for soft tissue augmentation, compared to the conventional use of a subepithelial connective tissue graft, which is associated with greater morbidity and complicates the surgical procedure.

So, the investigators designed a prospective, randomized controlled clinical trial of 6 months duration. The 36 participants will be periodontally healthy or periodontally treated patients, who seek treatment at the clinic of Periodontology and Implantology of the Department of Dentistry, Aristotle University Thessaloniki.The participants should have completed Step 1 and 2 of periodontal treatment at least 3 months before being enrolled. If periodontally healthy, they will have received a session of supragingival removal of deposits and they will be given oral hygiene instructions. Patients should need implant reconsruction in the upper anterior esthetic zone without need for a prior bone augmentation procedure to increase the dimensions of the bone substrate. After the initial clinical evaluation for the appropriateness of the case, a consent form will be signed by the participants and then the patients will be randomized to one of the three treatment groups.In the control group, 12 patients will undergo prosthetically guided implant placement without increasing soft tissue volume. In the first experimental group, the next 12 patients will receive prosthetically guided implant placement and simultaneous volume increase of the soft tissues with a collagenous matrix of porcine origin (Geistlich Fibro-Gide), while in the second experimental group (12 patients), the volume increase of the soft tissues will be performed with a subepithelial connective tissue graft from the palate.The evaluation of the therapeutic outcome will be based on (a) clinical parameters (bleeding on probing, plaque index, extent of keratinized gingiva), (b) measurement of soft tissue thickness with an ultrasound device (Pirop Ophthalmic Scanner, Echoson Company, Poland. A scan Probe 20MHz) (c) radiographic parameters (Cone Beam Computed Tomography immediately after dental implant placement and 6 months postoperatively) and (d) histological examination of the soft tissues during the exposure of the implants at 3 months.The tissue biopsy will be taken from the coronal part of the alveolar crest. Finally, the participants will be asked to complete a questionnaire to assess the experience and subjective perception and discomfort after surgical treatment.The re-assesment in 3 months will include exposing the dental implant and taking the tissue for biopsy. Finally, at 6 months postoperatively, the clinical parameters mentioned above will be evaluated, the thickness of the soft tissues will be measured with the ultrasound device and radiographic control with cone beam computed tomography to measure the thickness of the buccal bone plate.

Schedule and clinical procedures for both treatment groups:

First visit- Initial examination at least 3 months after the end of periodontal treatment Medical dental history Patient participation eligibility check - written consent - randomization Taking intraoral photographs Periodontontal chart recording: Pocket depth (PD), Clinical attachment loss (CAL), Bleeding on probing (BoP), Keratinized tissue width (KT), Soft Tissue Thickness (STH) with an ultrasound device, Buccal Bone Thickness (BBT) through bone sounding using a customized splint.

Taking a periapical radiograph in the area of interest with a parallel technique.

Repetition of oral hygiene instructions (Soft toothbrush Modified Bass technique, Interdental cleaning) Removal of supragingival deposits.

Second visit- Baseline Implant placement in experimental or control group. Modification of oral hygiene instructions - Post-operative instructions. Taking intraoral photographs Radiographic examination by Cone Beam Computed Tomography (CBCT)

Third visit (2 weeks after surgery) - Suture removal - Assessment of healing Removal of sutures Healing control Oral hygiene instructions Taking intraoral photographs Completing a questionnaire

Forth visit (3 months after placement of implants) - Second stage procedure the - Taking a piece of tissue for biopsy Surgical exposure of implant Obtain tissue for biopsy Oral hygiene instructions

Fifth visit (6 months after placement of the implants) - Radiographic examination Periodontal chart recording: Pocket depth (PD), Clinical attachment loss (CAL), Bleeding on probing (BoP), Keratinized tissue (KT), Measurement of Soft Tissue Thickness (STH) with ultrasound device and customized splint Radiographic screening by cone beam computed tomography (CBCT) to measure the Buccal Bone Thickness Repeat oral hygiene instructions Taking intraoral photographs

• Keratinized tissues [Срок оценки: 6 months]