Inclusion Criteria:  Systemically healthy Periodontally healthy or with stable treated periodontitis and good oral hygiene (Full Mouth Plaque Score (FMPS) and Full Mouth Bleeding Score (FMBS) ≤ 15%, measured at six sites per tooth) Need for one or two implants in the posterior mandible (maximum of three missing teeth). Enough bone availability to place an implant with a minimum diameter of 3.8 mm and at least 7 mm length. Non-smoker or smokers < 10 cig/day (self-reported). Ability to understand the study procedures and to comply with them to the entire length of the study.  Exclusion Criteria:  Subjects with uncontrolled systemic diseases (ASA type III). Subjects taking medications with immunosuppressors, bisphosphonates or high doses of corticosteroids; current drug or alcohol use or dependence that could interfere with adherence to study requirements. Pregnant or lactating women. Allergy to collagen or analgesics/anti-inflammatory non-steroid drugs. History of cancer requiring radiotherapy or chemotherapy during the last 5 years. Local inflammation (including untreated periodontitis) Severe bruxism or clenching habits. Any kind of bone augmentation performed on the implant site, with a healing period <6 months Less than 4 mm of keratinized mucosa Post-extraction sites with <12 weeks of healing Lack of primary implant stability assessed intrasurgically.