Guided Bone Regeneration Using Fixed vs Non-Fixed Resorbable Collagen Membranes

Horizontal Bone Gain

To compare the horizontal bone gain when grafting a mixture of xenograft and allograft (50/50) with non-fixed resorbable collagen membranes (control group) versus fixed resorbable collagen membranes (test group) in resorbed ridges requiring GBR to facilitate implant placement at 6 months. Along the 6 months, 3 Cone Beam Computed Tomography scans (CBCT) will be needed. At baseline (T1), the first CBCT will be taken before performing any surgical procedure to measure the initial width of the ridge. Immediately after the GBR (T2), a second CBCT scan will be taken, which will be useful to measure new ridge width in each group. Finally, at 6 month follow-up a third CBCT scan will be taken (T3) in order to assess the difference with T1 regarding amount of bone gain horizontally, and with T2 regarding horizontal dimensional stability of the grafted bone in each of the 2 groups.

Bone Width Gain

To compare the bone width gain between the test group and control group, 6 months after the horizontal GBR. A caliper will be used in order to evaluate and compare the bone width gain at T1, T2, and T3 between the Test and Control Groups. These measurements are performed intra-operatively before the Horizontal GBR (T1), immediately after (T2), and at 6 months (T3) at the time of implant placement. Measurements will be performed at 1cm, 3cm, and 5cm apical from the bone crest at the regenerated area.

Horizontal Dimensional Stability

To compare the horizontal dimensional stability of the augmented ridges between the test group and control group after 6 months. After the surgical procedure, a CBCT scan (T2) will be completed and the bone width will be assessed and compared with the bone width at 6 months postoperatively when a new CBCT scan (T3) will be completed before implant placement.

Post-surgical complications

To compare the post-surgical complications that may occur between the test group and control group throughout the period of healing and during the following 6 months. The complications will be evaluated using the Healing Complications Classification, as suggested by Fontana et al. 2011. The healing post-surgical complications are divided into four classes, according to the presence and extent of exposure, as well as the presence of a purulent exudate: * Class I: membrane exposure \<3mm, no purulent exudate * Class II: membrane exposure ≥3mm, no purulent exudate * Class III: membrane exposure with purulent exudate * Class IV: abscess, without membrane exposure

Patient's satisfaction

To compare patient's satisfaction regarding the post-operative pain and compare it between the test group and control group throughout the period of healing and during the following 6 months, through the use of a Visual Analogue Scale (VAS). It is a 10cm line with anchor statements on the left (no pain) and on the right (extreme pain). The patients will be asked to mark their average experience of discomfort and pain. The scores of the VAS will be obtained by measuring the distance in centimeters (0 to 10).

Histologic examination of the augmented bone at 6 months

To examine type of cells present after 6 months of procedure by performing histological examination to the sample harvested from the site with the use of an implant trephine drill. The histologic evaluation will be performed in order to evaluate the type of cells present at the site of augmentation