Evaluation of Using Different Screwed Abutment Height

Evaluation of Straumann Bone Level Tapered® Implants Using Screwed Abutment Height in Partially Edentulous Patients: a Randomized Controlled Clinical Trial

A prospective randomized controlled clinical trial will be conducted. Study groups will be assigned as described above. The patients will be randomly divided into two groups in order to study the influence of prosthetic screw abutment in marginal bone loss (MBL) around Bone Level Tapered implants (BLT® Roxolid® SLActive® guided implants, Straumann Dental Implant System, Institut Straumann AG, Basel, Switzerland).

48 patients will be selected with partial edentulism in the maxilla or mandible, requiring two dental implants in the posterior areas (molars and premolars).

Each patient will be randomly allocated in one of the two groups: test group (n=36) or control group (n=12) and all the implants will be placed by residents of the International Master in Oral Surgery and Master in Periodontics of the same University.

Study groups

Group 1: Two stage approach (cover screw in first surgery and healing abutment in second surgery) (12 patients)

Group 2: One stage approach (healing cap over trans-epithelial abutments) (36 patients).Two subgroups according to different trans-epithelial height abutment:

• Subgroup 2.1: Screw-retained abutment of 1 mm height (18 patients)
• Subgroup 2.2: Screw-retained abutment of 2.5 mm height (18 patients)

Clinical Parameters and Outcomes

• Three-dimensional volumetric changes in hard and soft tissues (Cone-beam computed tomography superposed with digital cast models).
• Marginal bone level (MBL) change: Standardized intraoral periapical x-rays will be taken on the day of surgery, 4, 6, 12, 24 and 36 months following surgery.
• Probing depth, bleeding on probing and keratinized mucosa width will be measured in the follow-up visits in 3 different points in buccal (Mesial, center and distal).
• VAS Scale: The visual analog scale or visual analog scale (VAS).

Inclusion Criteria:

1. Signed informed consent
2. Overall, healthy subjects
3. Females and males of at least eighteen-years
4. Requiring a minimum of two implants (molar and/or premolar teeth)
5. Adequate oral hygiene (less than 15% FMPS)
6. Able to follow instructions and attend a regular compliance
7. Enough bone to place a standard implant of 4.1 mm diameter.

Exclusion Criteria:

1. Acute local infection
2. Occlusal overload with parafunctional activity (assessed clinically)
3. Large occlusal discrepancies
4. Untreated periodontal disease assessed by Socransky et al. parameters (≥2mm clinical attachment loss in two consecutive visits within 1 year)
5. Smokers (more than 10 cigarettes/day)
6. Drug and/or alcoholic dependencies
7. Medical conditions contraindicating implant surgery
8. History of head and/or neck radiation
9. Bisphosphonate therapy