Sixty patients with partially edentulous posterior maxilla requiring a transcrestal sinus floor elevation technique to insert one implant will be selected. The purpose of this multi-center, prospective, double blind, and randomized investigation is to analyze a platform switched implant when placed at limited maxillary residual bone height with low bone density compared to a platform matching implant with or without bone graft material.

Approximately 60 subjects who require at least one posterior maxilla implant in the areas of the second pre-molars or (first or second) molars with 6 to 9 mm of crestal bone below the sinus floor, as determined on the computerized axial tomographic (CT) scan, will be recruited for the study. Subjects will receive dental implants to replace a missing tooth (second pre-molar or first/second molar) on one side of the maxillary arch. Each subject will receive one type of implant: platform switched (PS) or platform matching (PM). Each site will receive either a bone graft material composed of anorganic bovine bone mineralized (ABBM, Bio-Oss, Geistlich Pharma) or no graft material (collagen membrane used for wound healing (Collatape, Zimmer)). At implant placement surgery and post-surgical follow-ups, the treated site will be examined, clinically measured, and radiographs and photographs will be taken.

The central hypothesis is that the mean crestal bone level for the platform switched (test implants) implants will be superior to the mean crestal bone level for the platform matching (control implants) implants when placed in limited maxillary residual bone in the posterior regions, regardless of the use of bone graft material or collagen membrane.

Inclusion Criteria:

1. Subjects must have read, understood and signed an informed consent form.
2. Subjects must be 18 to 70 years of age.
3. Subjects must be able and willing to follow study procedures and instructions.
4. Subject must maintain good oral hygiene.
5. Subjects must have a single tooth missing in the pre-molar or molar region of the maxilla (ADA tooth positions 2-4 and 13-15; FDI tooth positions 15-17 and 25-27).
6. The mesio-distal distance of the tooth gap at bone level must be at least 6.8 mm to allow for placement of the Ø3.8 mm implant with a minimal distance of 1.5 mm from the implant shoulder to the adjacent tooth at bone level. A minimum of 7.8 mm of buccal-lingual ridge to allow 2 mm of buccal and lingual plate will be required.
7. No apical disorder/inflammation at the area of the implant site.
8. Residual bone height ranging from 6 to 9 mm.
9. The implant must penetrate at least 2 mm into the sinus on the mesial or distal sides.
10. Sufficient bone width in the edentulous region (≥ 6mm).
11. Subjects must be committed to the study and attend the required follow-up visits.

Exclusion Criteria:

1. Subjects with a systemic disease that would preclude dental implant surgery (e.g. serious internal medical problems, disorders of bone metabolism, uncontrolled bleeding disorders, weakened immune system, illness requiring periodic use of steroids, uncontrollable endocrine disorders, uncontrolled diabetes).
2. Subjects who have failed to maintain good plaque control.
3. Subjects with any contraindications for oral surgical procedures (e.g. inadequate wound healing capacity, poor oral hygiene, maxillary and mandibular growth not completed, xerostomia).
4. Subjects with mucosal diseases (e.g., erosive lichen planus) in the localized area around the study implant site.
5. Subjects presenting with maxillary sinus pathology.
6. Subjects with a history of local irradiation therapy in the head/neck region.
7. Subjects with severe bruxing, parafunctional habits, or temporomandibular joint dysfunction.
8. Subjects receiving, or having a history of receiving intravenous or subcutaneous antiresorptive agents associated with osteonecrosis of the jaw, such as bisphosphonates.
9. Oblique sinus floor (> 45 inclination).
10. Subjects with any untreated endodontic lesions or untreated periodontal disease.
11. Subjects who are heavy smokers (defined as >10 cigarettes per day or >1 cigar per day) or chew tobacco, including within 3 months prior to enrollment.
12. Subjects who have physical or mental handicaps that would interfere with the ability to perform adequate oral hygiene.
13. Subjects who are pregnant or intending to become pregnant during the duration of the study.
14. Subjects requiring bone augmentation or socket grafting prior to surgery.
15. Subject allergic to collagen or porcine derived products.
16. Subjects with 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.