This study aims to compare the clinical performance of 4 mm short implants supporting cross-arch fixed reconstructions in the edentulous mandible either with a combination of two short implants as distal support and two implants of conventional length placed in the interforaminal region, or with a combination of four short implants as distal support and two interforaminal implants of conventional length.

This is a post-market, multi-center, prospective, open, randomized controlled clinical study. The total study duration for each patient should be 36 ± 2 months.

Roxolid Standard Plus Implants, 4 mm, Ø 4.1 mm, SLActive will be placed in positions 36/46 or 35/45, 36/46.

Roxolid Standard Plus Implants, Ø 4.1 mm, SLActive, in lengths of 10, 12 and 14 mm will be placed in positions 33/43.

In total 10 visits per patient are scheduled in this study. Implant survival, implant success, prosthetic survival and success, and adverse events (AEs) will be assessed.

All products are CE-(Conformité Européenne, meaning European Conformity) marked and used within its intended use.

Two centers in Switzerland and Northern Ireland will participate. The study and any amendments will be performed according to International Organization for Standardization (ISO) 14155:2011, local legal and regulatory requirements and conform to the Declaration of Helsinki (last revision Fortaleza 2013)

Inclusion Criteria:

• Males and females with at least 18 years of age (including 18 years)
• Subject must have voluntarily signed the informed consent, are willing and able to attend scheduled follow-up visits, and agree that the encoded data will be collected and analyzed
• Fully edentulous (latest extraction in the mandible should be performed at least 12 weeks before implant placement) that can be restored with a complete denture
• Atrophic jaw bone in the posterior area, sufficient bone height and width to permit insertion of four short implants, 4 mm in regions of the first molar and second premolar on both sides and two standard length implants in the canine region

Exclusion Criteria:

• Patients with inadequate bone volume and/or quality
• Uncontrolled systemic disease that would interfere with dental implant therapy (e.g. uncontrolled diabetes)
• Any contraindications for oral surgical procedures
• History of local irradiation therapy in the head / neck area
• Patients who smoke >10 cigarettes per day or tobacco equivalents, chew tobacco or have ≥ 20 pack years
• Medical conditions requiring chronic high dose steroid therapy or high dose anti-resorptive treatment
• Subjects who have undergone administration of any investigational device within 30 days of enrollment in the study
• Conditions or circumstances, in the opinion of the investigator, which would prevent completion of study participation or interfere with analysis of study results, such as history of non-compliance or unreliability
• Cognitive impairment that would interfere with the ability to perform adequate oral hygiene (assessed by the Ottawa 3DY scale)
• Patients with chronic pain
• Patients with HIV and/ or Hepatitis infection
• Severe bruxing or clenching habits
• Patients with inadequate oral hygiene or unmotivated for adequate home care (Denture Plaque Index (DPI) ≥ 5)
• Patients with drug or alcohol abuse
• Patients with allergies or hypersensitivity to chemical ingredients of titanium-zirconium alloy
• Major simultaneous augmentation procedures. Dehiscence of a vertical distance of more than 3 mm
• A woman who is pregnant or planning to become pregnant at any point during the study duration

Secondary Exclusion Criteria:

• Patients with inadequate bone volume and/or quality