Statement of problem: Volumetric resorption of the alveolar ridge often occurs following tooth extraction in both horizontal and vertical directions. There is a specific lack of evidence for alveolar ridge reconstruction at molar and premolar sites with severe bone resorption. Purpose. This randomized and controlled trial aimed to use three dimensional and linear analyses to evaluate volumetric changes of the alveolar bone following alveolar ridge reconstruction (ARR) at molar and premolar sites with severe bone resorption as compared with non-assisted socket healing be implant placement. Material and Methods: A total of 31 patients (15 males and 16 females) with more than 50% of hard tissue loss in one or more socket walls were recruited and randomized into either a test group (ARR after extraction using deproteinized bovine bone mineral with 10% collagen (DBBM-C) and platelet-rich fibrin (PRF) with a resorbable collagen membrane) or a control group (natural healing after extraction). Then, the clinical, linear, volumetric implant-related and patient-reported outcomes were analyzed after a 4-month healing process. Results: Linear bone assessments revealed significantly greater gains of ridge width in the test group (25% in the mesial, mid-facial and distal aspects) and less reduction of vertical bone ridge than in the control group (P＜0.05). Furthermore, volumetric bone remodeling was significantly higher in the test group (ARR=35.1±34.9%, control=14.2±12.8%, P＜0.05). Patient-reported discomfort and keratinized mucosal changes were comparable between groups. Conclusions: Alveolar ridge reconstruction with a combination of DBBM-C, PRF, and a resorbable membrane at posterior sites with severe socket wall deficiency (＞ 50% bone loss) is a safe and more capable therapeutic method when compared with natural healing and non-assisted sockets. Clinical implications: Collectively, our analyses demonstrated that alveolar ridge reconstruction represents an efficient method to maintain and augment crestal bone at posterior extraction sites with severe bone defects when assessed after four months of healing.