Comparison of Synthetic Bone Substitute and a Bovine-derived Xenograft in Horizontal Bone Augmentation

Inclusion Criteria: * Males and females, 18 years to 80 years of age * At least two missing teeth up to full edentulous arches. * Desiring implant supported restorations. * Both study implants should have a self-containing (2-wall) buccal dehiscence defect after oral implant placement (at least 3.0 mm / max. 5.0 mm defect in apico-coronal aspect to be measured from the boarder of the rough surface of the oral implant to the bottom of the defect). * At least 4mm of the implant, measured from the apical end to the lowest margin of the bone level, should be covered with bone. * Sufficient bone volume such that both oral implants will not encroach on vital structures and primary stability of the oral implant can be achieved; * Patients must be committed to the study and must sign informed consent. * Patient in good general health as documented by self assessment; * Full mouth plaque score of \<20%; Exclusion Criteria: * Any systemic medical condition that could interfere with the surgical procedure or planned treatment; * Current pregnancy or breast feeding/ lactating at the time of recruitment; * Physical handicaps that would interfere with the ability to perform adequate oral hygiene; * Alcoholism or chronically drug abuse causing systemic compromise. * Patients who smoke more than 20 cigarettes per day. * Conditions or circumstances, in the opinion of the investigator, which could represent a general contra-indication for surgical procedure or would prevent completion of study participation or interfere with analysis of study results, such as history of non-compliance, or unreliability * Lack of primary stability of 1 or both implant(s) at surgery, measured by hand testing. In this instance the patient must be withdrawn and treated accordingly. * Mucosal diseases such as erosive lichen planus * History of local radiation therapy. * Presence of osseous pathologies. * Presence of oral lesions (such as ulceration, malignancy) * Severe bruxing or clenching habits. * Local inflammation, including untreated periodontitis. * Bone surgery at the implant site(s) (bone grafts, guided tissue regeneration techniques for bone enhancement) prior to implant placement unless performed more than 6 months prior to implant placement. * Patients presenting clinical and radiological signs and symptoms of maxillary sinus disease. * Existing teeth in the residual dentition with untreated endodontic pathologies. * Patients with inadequate oral hygiene or unmotivated for adequate home care